Dr Wei Zhang

Associate Professor in Energy Technology
+44 (0)1483 688707
24 ATI 02


University roles and responsibilities

  • NPL academic leadership team

    My qualifications

    National University of Singapore

    Affiliations and memberships

    Member of EPSRC Peer Review College
    Member of Royal Society of Chemistry
    Member of American Chemical Society
    Associate Member of SUPERGEN SuperSolar Hub
    Fellow of the Higher Education Academy

    Business, industry and community links


    Research interests

    Research projects

    Research collaborations



    Postgraduate research supervision

    Completed postgraduate research projects I have supervised




    D. Luo, W. Yang, Z. Wang, A. Sadhanala, Q. Hu, R. Su, R. Shivanna, G. F. Trindade, J. F. Watts, Z. Xu, T. Liu, K. Chen, F. Ye, P. Wu, L. Zhao, J. Wu, Y. Tu, Y. Zhang, X. Yang, W. Zhang,* R. H. Friend, Q. Gong, H. J. Snaith,* R. Zhu.* Enhanced photovoltage for inverted planar heterojunction perovskite solar cells. Science 360 (6396), 1442-1446 (2018).

    Dongtao Liu, Deying Luo, Affan N Iqbal, Kieran WP Orr, Tiarnan AS Doherty, Zheng-Hong Lu, Samuel D Stranks*, Wei Zhang*. Strain analysis and engineering in halide perovskite photovoltaics. Nature Materials 20, 1337–1346 (2021).

    Aobo Ren, Hao Wang, Wei Zhang*, Jiang Wu*, Zhiming Wang, Richard V Penty, Ian H White. Emerging light-emitting diodes for next-generation data communications. Nature Electronics 4, 559–572 (2021).

    H. Li, W. Zhang*Perovskite Tandem Solar Cells: From Fundamentals to Commercial DeploymentChemical Reviews 120, 18, 9835–9950 (2020).

    D. Luo, R. Su, W. Zhang,* Q. Gong, R Zhu.* Minimizing non-radiative recombination losses in perovskite solar cellsNature Reviews Materials, 5, 44–60(2020).

    W. Zhang, G. E. Eperon, H. J. Snaith*. Metal halide perovskites for energy applications. Nature Energy 1, 16048 (2016).

    W. Zhang, M. Saliba, D. T. Moore, S. K. Pathak, M. T. Hörantner, T. Stergiopoulos, S. D. Stranks, G. E. Eperon, J. A. Alexander-Webber, A. Abate, A. Sadhanala, S. Yao, Y. Chen, R. H. Friend, L. A. Estroff, U. Wiesner, H. J. Snaith*. Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells. Nature Communications 6, 6142 (2015).

    W. Zhang, S. Pathak, N. Sakai, T. Stergiopoulos, P. K. Nayak, N. K. Noel, A. A. Haghighirad, V. M. Burlakov, D. W. deQuilettes, A. Sadhanala, W. Li, L. Wang, D. S. Ginger, R. H. Friend, H. J. Snaith*. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells. Nature Communications 6, 10030 (2015).

    THOMAS WEBB, STEPHEN SWEENEY, WEI ZHANG (2021)Device Architecture Engineering: Progress toward Next Generation Perovskite Solar Cells, In: Advanced functional materials31(35)2103121

    Over the past decade perovskite solar cells (PSCs) have quickly established themselves as a promising technology boasting both high efficiency and low processing costs. The rapid development and success of PSCs is a product of substantial research effort addressing compositional engineering, thin film fabrication, surface passivation and interfacial treatments. Recently, engineering of the device architecture has entered a renaissance with the emergence of several new bulk and graded heterojunction structures. These structures promote a lateral approach to the development of single-junction PSCs affording new opportunities in light management, defect passivation, carrier extraction and long-term stability. Following a short overview of the historic evolution of PSC architectures, we offer a detailed discussion of the promising progress of the recently reported perovskite bulk heterojunction (BHJ) and graded heterojunction (GHJ) approaches. To enable better understanding of these novel architectures, a range of approaches to characterizing the 2 architectures are presented. Finally, an outlook and perspective are provided offering insights into the future development of PSC architecture engineering.

    Jing Zhang, James Mcgettrick, Kangyu Ji, Jinxin Bi, Thomas Webb, Xueping Liu, Dongtao Liu, Aobo Ren, Yuren Xiang, Bowei Li, Vlad Stolojan, Trystan Watson, Samuel D. Stranks, Wei Zhang (2023)Fast and Balanced Charge Transport Enabled by Solution-Processed Metal Oxide Layers for Efficient and Stable Inverted Perovskite Solar Cells, In: Energy & environmental materials (Hoboken, N.J.) Wiley

    Metal oxide charge transport materials are preferable for realizing long-term stable and potentially low-cost perovskite solar cells (PSCs). However, due to some technical difficulties (e.g., intricate fabrication protocols, high-temperature heating process, incompatible solvents, etc.), it is still challenging to achieve efficient and reliable all-metal-oxide-based devices. Here, we developed efficient inverted PSCs (IPSCs) based on solution-processed nickel oxide (NiOx) and tin oxide (SnO2) nanoparticles, working as hole and electron transport materials respectively, enabling a fast and balanced charge transfer for photogenerated charge carriers. Through further understanding and optimizing the perovskite/metal oxide interfaces, we have realized an outstanding power conversion efficiency (PCE) of 23.5% (the bandgap of the perovskite is 1.62 eV), which is the highest efficiency among IPSCs based on all-metal-oxide charge transport materials. Thanks to these stable metal oxides and improved interface properties, ambient stability (retaining 95% of initial PCE after 1 month), thermal stability (retaining 80% of initial PCE after 2 weeks) and light stability (retaining 90% of initial PCE after 1000 hours aging) of resultant devices are enhanced significantly. In addition, owing to the low-temperature fabrication procedures of the entire device, we have obtained a PCE of over 21% for flexible IPSCs with enhanced operational stability.

    R Guo, Yan Zhao, Q Deng, Yongshang Zhang, Zhiheng Wu, Yanyan Duan, Wei Zhang, Yonglong Shen, Guosheng Shao (2022)Energy level matching between transparent conducting electrodes and the electronic transport layer to enhance performance of all-inorganic CsPbBr3 solar cells, In: Vacuum200 Elsevier Ltd

    Perovskite solar cells (PSCs) have become a promising research direction in photovoltaic field, where the evolution of the transparent conductive oxides (TCOs) electrodes, a vital part of photovoltaic devices, has played a distinctive role in their development. To date, the indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) have been widely used as TCOs in state-of-the-art PSCs. However, the energy level matching between the TCO electrodes and the electron transport layers (ETLs) are usually ignored. Herein, Ta doped SnO2 (TTO) films have been prepared by the high target utilisation sputtering (HiTUS) technology, which exhibited the lowest resistivity of 7.8 × 10−4 Ω cm and the average transmittance in the visible light region over 85%. A maximum power conversion efficiency (PCE) with 6.48% was achieved when the TTO films as the bottom electrodes in CsPbBr3 PSCs, higher than that of PSCs based on FTO (5.36%). Especially, the open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) were all enhanced, which were attributed to the suitable energy level matching between the TCOs and ETLs layers and their low interface roughness. This work demonstrates the band structure of the TCOs and ETL layers and the roughness of TCOs have more important influence on the PCE of PSCs under the similar optical and electrical properties of TCOs condition. •Ta doped SnO2 films show the resistivity of 7.8 × 10−4 Ω cm and transmittance of 85%.•The films were used as TCOs in CsPbBr3 solar cell, which showed PCE of 6.48%.•The band structure of TCOs has an important influence on the efficiency of PSCs.

    JINXIN BI, JING ZHANG, PAVLOS GIANNAKOU, Toshan Wickramanayake, XUHUI YAO, MANMAN WANG, XUEPING LIU, MAXIM SHKUNOV, WEI ZHANG, YUNLONG ZHAO (2022)A Highly integrated flexible photo-rechargeable system based on stable ultrahigh-rate quasi-solid-state zinc-ion micro-batteries and perovskite solar cells, In: Energy Storage Materials51pp. 239-248 Elsevier B.V

    Miniaturized flexible photo-rechargeable systems show bright prospects for wide applications in internet of things, self-powered health monitoring and emergency electronics. However, conventional systems still suffer from complex manufacturing processes, slow photo-charging and discharging rate, and mismatch between photovoltaic and energy storage components in size, mechanics and voltage, etc. Here, we demonstrate a facile inkjet printing and electrodeposition approach for fabricating a highly integrated flexible photo-rechargeable system by combining stable and ultra-high-rate quasi-solid-state Zn-MnO2 micro-batteries (ZMBs) with flexible perovskite solar cells (FPSCs). In particular, Ni protective layer is first introduced into ZMBs to stabilize battery configuration and facilitate enhanced electrochemical performance. The optimized ZMB exhibits ultrahigh volumetric energy density of 148 mWh cm−3 (16.3 μWh cm−2) and power density of 55 W cm−3 (6.1 mW cm−2) at the current density of 400 C (5 mA cm−2), enabling them comparable with the state-of-the-art micro-batteries or supercapacitors fabricated by conventional methods. The embedded FPSCs show excellent photovoltaic performance, sufficient to charge ZMBs and create a self-charging system capable to offer energy autonomy in miniaturized wearable electronics. The integrated systems can achieve an ultrafast photo-charging within 30 s, with sufficient energy to power other functional electronics (e.g., LED bulb and pressure sensor) for tens of minutes. This prototype offers a promising scheme for next-generation miniaturized flexible photo-rechargeable systems.

    Victoria Ferguson, Bowei Li, Mehmet O Tas, Thomas Webb, Muhammad T Sajjad, Stuart A. J Thomson, Zhiheng Wu, Yonglong Shen, Guosheng Shao, José V Anguita, S. Ravi P Silva, Wei Zhang (2020)Direct Growth of Vertically Aligned Carbon Nanotubes onto Transparent Conductive Oxide Glass for Enhanced Charge Extraction in Perovskite Solar Cells, In: Advanced materials interfaces7(21)2001121

    Vertically aligned carbon nanotubes (VACNTs) present an exciting avenue for nanoelectronics due to their predetermined orientation and exceptional transport capabilities along the tube length, with the potential to be employed in a variety of optoelectronic applications. However, growth of VACNTs using conventional chemical vapor deposition (CVD) methods requires elevated temperatures (>720 °C) and therefore, the suitability of commonly used transparent conductive oxide (TCO) glasses, such as fluorine‐doped tin oxide (FTO) and indium‐tin oxide (ITO), as the substrates for nanotube growth are limited by their temperature‐sensitive nature. Here, the successful growth of multi‐walled VACNTs directly onto commonly used TCO glasses, FTO and ITO, using the photo‐thermal chemical vapor deposition (PTCVD) growth method is reported. The benefit of reflection, within the infrared region, of the TCO substrate and the effect of surface roughness on the growth of VACNTs is investigated. The application of VACNTs on ITO in inverted planar perovskite solar cells is investigated, which shows superior charge transfer, larger grain sizes in the perovskite film, and a champion device efficiency approaching 16%. Vertically aligned carbon nanotubes are grown directly onto temperature‐sensitive transparent conductive oxide glass; the morphology, quality and electrical properties are analyzed and used to fabricate optimized patterned carbon nanotube forest films which are used in perovskite solar cells to improve charge extraction resulting in a champion efficiency approaching 16%.

    Wei Zhang, JUERONG LI, Xianghuan Meng, Zhiheng Wu, Yanyan Duan, R Guo, Weidong Xiao, Yongshang Zhang, Yukun Li, Yonglong Shen, Guosheng Shao (2022)Pinning Bromide Ion with Ionic Liquid in Lead-Free Cs2AgBiBr6 Double Perovskite Solar Cells, In: Advanced functional materials32(25) Wiley

    Lead-free Cs2AgBiBr6 double perovskite has received widespread attention because of its non-toxicity and high thermal stability. However, intrinsic bromide ion (Br-) migration limits continuous operation of Cs2AgBiBr6-based perovskite solar cells (PSCs). Herein, an operational and simple strategy is carried out to improve the power conversion efficiency (PCE) and long-term stability of Cs2AgBiBr6-based PSCs by introducing 1-butyl-1-methylpyrrolidinium chloride (BMPyrCl) and 1-butyl-3-methylpyridinium chloride (BMPyCl) ionic liquids (ILs). The higher binding energy between Br- in Cs2AgBiBr6 and cation in IL containing pyrrole can inhibit Br- migration effectively, thereby reducing film defects and improving energy level matching. The optimized PCE of 2.22% is obtained for hole transport layer-free, carbon-based PSC, which hardly degrades at 40% +/- 5% relative humidity and 25 degrees C for 40 days. This work highlights an effective method to mitigate the halide migration in Cs2AgBiBr6 perovskite, thus providing an effective route in promoting the development of lead-free double PSCs.

    Yan Zhao, Quanrong Deng, Ruxin Guo, Zhiheng Wu, Yukun Li, Yanyan Duan, Yonglong Shen, Wei Zhang, Guosheng Shao (2020)Sputtered Ga-Doped SnOxElectron Transport Layer for Large-Area All-Inorganic Perovskite Solar Cells, In: ACS applied materials & interfaces12(49)pp. 54904-54915 ACS

    The scalability processing of all functional layers in perovskite solar cells (PSCs) is one of the critical challenges in the commercialization of perovskite photovoltaic technology. In response to this issue, a large-area and high-quality gallium-doped tin oxide (Ga-SnOx) thin film is deposited by direct current magnetron sputtering and applied in CsPbBr3 all-inorganic PSCs as an electron transport layer (ETL). It is found that oxygen defects of SnOx can be remarkably offset by regulating oxygen flux and acceptor-like Ga doping level, resulting in higher carrier mobility and suitable energy level alignment, which is beneficial in accelerating electron extraction and suppressing charge recombination at the perovskite/ETL interface. At the optimal O2 flux (12 sccm) and Ga doping level (5%), the device based on sputtered Ga-SnOx ETL without any interface modification shows a power conversion efficiency (PCE) of 8.13%, which is significantly higher than that of undoped SnOx prepared by sputtering or spin coating. Furthermore, a PCE of 5.98% for a device with an active area of 1 cm2 is obtained, demonstrating great potential in fabricating efficient and stable large-area PSCs.

    Rui Su, Zhaojian Xu, Jiang Wu, Deying Luo, Qin Hu, Wenqiang Yang, Xiaoyu Yang, Ruopeng Zhang, Hongyu Yu, Thomas P Russell, Qihuang Gong, Wei Zhang, Rui Zhu (2021)Dielectric screening in perovskite photovoltaics, In: Nature Communications122479 Nature Publishing Group UK

    The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap ~1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation. Performance of perovskite photovoltaics is greatly affected by undesirable defects that contribute to non-radiative losses. Here, the authors mitigate these losses by doping perovskite with KI to alter the dielectric response, thus defect capturing probability, resulting in inverted device with PCE of 22.3% and low voltage loss.

    Deying Luo, Rui Su, Wei Zhang, Qihuang Gong, Rui Zhu (2019)Minimizing non-radiative recombination losses in perovskite solar cells, In: Nature Reviews Materials5pp. 44-60 Nature Research (Springer Nature)

    Photovoltaic solar cells based on metal halide perovskites have gained considerable attention over the past decade because of their potentially low production cost, earth-abundant raw materials, ease of fabrication and ever-increasing power conversion efficiencies of up to 25.2%. This type of solar cells offers the promise of generating electricity at a more competitive unit price than traditional fossil fuels by 2035. Nevertheless, the best research cell efficiencies are still below the theoretical limit defined by the Shockley-Queissier theory owing to the presence of non-radiative recombination losses. In this Review, we analyse the predominant pathways that contribute to non-radiative recombination losses in perovskite solar cells, and evaluate their impact on device performance. We then discuss how non-radiative recombination losses can be estimated through reliable characterization techniques, and highlight some notable advances in mitigating these losses, which hint at pathways towards defect-free perovskite solar cells. Finally, we outline directions for future work that will push the efficiency of perovskite solar cells towards the radiative limit.

    Dongtao Liu, Deying Luo, Affan N Iqbal, Kieran W. P Orr, Tiarnan A. S Doherty, Zheng-Hong Lu, Samuel D Stranks, Wei Zhang (2021)Strain analysis and engineering in halide perovskite photovoltaics, In: Nature materials20pp. 1337-1346 Nature Research

    Halide perovskites are a compelling candidate for the next generation of clean-energy-harvesting technologies owing to their low cost, facile fabrication and outstanding semiconductor properties. However, photovoltaic device efficiencies are still below practical limits and long-term stability challenges hinder their practical application. Current evidence suggests that strain in halide perovskites is a key factor in dictating device efficiency and stability. Here we outline the fundamentals of strain within halide perovskites relevant to photovoltaic applications and rationalize approaches to characterize the phenomenon. We examine recent breakthroughs in eliminating the adverse impacts of strain, enhancing both device efficiencies and operational stabilities. Finally, we discuss further challenges and outline future research directions for placing stress and strain studies at the forefront of halide perovskite research. An extensive understanding of strain in halide perovskites is needed, which would allow effective strain management and drive further enhancements in efficiencies and stabilities of perovskite photovoltaics.

    Xiaoyu Yang, Deying Luo, Yuren Xiang, Lichen Zhao, Miguel Anaya, Yonglong Shen, Jiang Wu, Wenqiang Yang, Yu‐Hsien Chiang, Yongguang Tu, Rui Su, Qin Hu, Hongyu Yu, Guosheng Shao, Wei Huang, Thomas P Russell, Qihuang Gong, Samuel D Stranks, Wei Zhang, Rui Zhu (2021)Buried Interfaces in Halide Perovskite Photovoltaics, In: Advanced Materials (Weinheim)33(7)2006435

    Understanding the fundamental properties of buried interfaces in perovskite photovoltaics is of paramount importance to the enhancement of device efficiency and stability. Nevertheless, accessing buried interfaces poses a sizeable challenge because of their non‐exposed feature. Herein, the mystery of the buried interface in full device stacks is deciphered by combining advanced in situ spectroscopy techniques with a facile lift‐off strategy. By establishing the microstructure–property relations, the basic losses at the contact interfaces are systematically presented, and it is found that the buried interface losses induced by both the sub‐microscale extended imperfections and lead‐halide inhomogeneities are major roadblocks toward improvement of device performance. The losses can be considerably mitigated by the use of a passivation‐molecule‐assisted microstructural reconstruction, which unlocks the full potential for improving device performance. The findings open a new avenue to understanding performance losses and thus the design of new passivation strategies to remove imperfections at the top surfaces and buried interfaces of perovskite photovoltaics, resulting in substantial enhancement in device performance.

    Min Jiang, Fei Wang, Fan Yang, Hao He, Jian Yang, Wei Zhang, Jiayan Luo, Jiao Zhang, Chaopeng Fu (2022)Rationalization on high-loading iron and cobalt dual metal single atoms and mechanistic insight into the oxygen reduction reaction, In: Nano energy93106793 Elsevier Ltd

    Rational design of single-atom catalysts (SACs) with high metal loadings is essential to enhance the sluggish kinetics of oxygen reduction reactions in metal-air batteries and proton-exchange membrane fuel cells (PEMFCs). Herein, an effective plasma engineering strategy to construct Fe/Co dual single atoms densely dispersed on porous nitrogen-doped carbon nanofibers (Fe, Co SAs-PNCF) with a high mass loading of 9.8 wt% is proposed without any acid leaching. The electrocatalyst exhibits superior ORR performances in both alkaline and acidic media (e.g., Eonset = 1.04 V and E1/2 = 0.93 V). The N3-Fe-Co-N3 moieties are identified to be the main active sites by X-ray absorption spectroscopy (XAS) and density functional theory calculations. The in situ XAS and Raman spectroscopy quantitively reveal the decrease in oxidation states of Fe/Co and the increase in bond lengths of the Fe-N/Co-N in the N3-Fe-Co-N3 during the ORR. Benefitting from the high loading of single atoms and enhanced activity, the Fe, Co SAs-PNCF endows the Al-air batteries and PEMFCs with excellent discharge performances, demonstrating promising practical applications. [Display omitted] •The atomic N3-Fe-Co-N3 dual sites with a high mass loading of 9.8 wt% are achieved.•The mass loading is linearly correlated with the defect degree.•Dual single atom sites are confirmed by AC-STEM and X-ray absorption spectroscopy.•In situ XAS and Raman reveal that the N3-Fe-Co-N3 plays an active role for ORR.

    JING ZHANG, Xiangang Hu, HUI LI, Kangyu Ji, BOWEI LI, XUEPING LIU, YUREN XIANG, Pengxiang Hou, Chang Liu, Zhiheng Wu, Yonglong Shen, Samuel D. Stranks, S RAVI PRADIP SILVA, HUIMING CHENG, WEI ZHANG (2021)High-Performance ITO-Free Perovskite Solar Cells Enabled by Single-Walled Carbon Nanotube Films, In: Advanced Functional Materials2104396 Wiley

    The unprecedented advancement in power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) has rendered them a promising game-changer in photovoltaics. However, unsatisfactory environmental stability and high manufacturing cost of window electrodes are bottlenecks impeding their commercialization. Here, a strategy is introduced to address these bottlenecks by replacing the costly indium tin oxide (ITO) window electrodes via a simple transfer technique with single-walled carbon nanotubes (SWCNTs) films, which are made of earth-abundant elements with superior chemical and environmental stability. The resultant devices exhibit PCEs of ≈19% on rigid substrates, which is the highest value reported to date for ITO-free PSCs. The facile approach for SWCNTs also enables application in flexible PSCs (f-PSCs), delivering a PCE of ≈18% with superior mechanical robustness over their ITO-based counterparts due to the excellent mechanical properties of SWCNTs. The SWCNT-based PSCs also deliver satisfactory performances on large-area (1 cm2 active area in this work). Furthermore, these SWCNT-based PSCs can retain over 80% of original PCEs after exposure to air over 700 h while ITO-based devices only sustain ≈60% of initial PCEs. This work paves a promising way to accelerate the commercialization of ITO-free PSCs with reduced material cost and prolonged lifetimes.

    Mozhgan Yavari, Xueping Liu, Thomas Webb, K D G Imalka Jayawardena, Yuren Xiang, Stefanie Kern, Steven Hinder, Thomas J Macdonald, S Ravi P Silva, Stephen J Sweeney, Wei Zhang (2021)A synergistic Cs2CO3ETL treatment to incorporate Cs cation into perovskite solar cells: Via two-step scalable fabrication, In: Journal of Materials Chemistry C Materials for optical and electronic devices9(12)pp. 4367-4377 Royal Society of Chemistry

    Triple cation CsFAMA perovskite films fabricated via a one-step method have recently gained attention as an outstanding light-harvesting layer for photovoltaic devices. However, questions remain over the suitability of one-step processes for the production of large-area films, owing to difficulties in controlling the crystallinity, in particular, scaling of the frequently used anti-solvent washing step. This can be mitigated through the use of the two-step method which has recently been used to produce large-area films via techniques such as slot dye coating, spray coating or printing techniques. Nevertheless, the poor solubility of Cs containing salts in IPA solutions has posed a challenge for forming triple cation perovskite films using the two-step method. In this study, we tackle this challenge through fabricating perovskite films on a caesium carbonate (Cs2CO3) precursor layer, enabling Cs incorporation within the film. Synergistically, we find that Cs2CO3 passivates the SnO2 electron transport layer (ETL) through interactions with Sn 3d orbitals, thereby promoting a reduction in trap states. Devices prepared with Cs2CO3 treatment also exhibited an improvement in the power conversion efficiency (PCE) from 19.73% in a control device to 20.96% (AM 1.5G, 100 mW cm−2) in the champion device. The Cs2CO3 treated devices (CsFAMA) showed improved stability, with un-encapsulated devices retaining nearly 80% efficiency after 20 days in ambient air.

    Bowei Li, Yuren Xiang, K.D.G. Imalka Jayawardena, Deying Luo, Zhuo Wang, Xiaoyu Yang, John F. Watts, Steven Hinder, Muhammad T. Sajjad, Thomas Webb, Haitian Luo, Igor Marko, Hui Li, Stuart A.J. Thomson, Rui Zhu, Guosheng Shao, Stephen J. Sweeney, S. Ravi P. Silva, Wei Zhang (2020)Reduced bilateral recombination by functional molecular interface engineering for efficient inverted perovskite solar cells, In: Nano Energy105249 Elsevier

    Interface-mediated recombination losses between perovskite and charge transport layers are one of the main reasons that limit the device performance, in particular for the open-circuit voltage (VOC) of perovskite solar cells (PSCs). Here, functional molecular interface engineering (FMIE) is employed to retard the interfacial recombination losses. The FMIE is a facile solution-processed means that introducing functional molecules, the fluorene-based conjugated polyelectrolyte (CPE) and organic halide salt (OHS) on both contacts of the perovskite absorber layer. Through the FMIE, the champion PSCs with an inverted planar heterojunction structure show a remarkable high VOC of 1.18 V whilst maintaining a fill factor (FF) of 0.83, both of which result in improved power conversion efficiencies (PCEs) of 21.33% (with stabilized PCEs of 21.01%). In addition to achieving one of the highest PCEs in the inverted PSCs, the results also highlight the synergistic effect of these two molecules in improving device performance. Therefore, the study provides a straightforward avenue to fabricate highly efficient inverted PSCs.

    K.D.G.I. Jayawardena, R. M. I. Bandara, M. Monti, E. Butler-Caddle, T. Pichler, H. Shiozawa, Z. Wang, S. Jenatsch, S. J. Hinder, M. G. Masteghin, M. Patel, H.M. Thirimanne, W. Zhang, R.A. Sporea, J. Lloyd-Hughes, S.R.P. Silva (2019)Approaching the Shockley-Queisser limit for fill factors in lead-tin mixed perovskite photovoltaics, In: Journal of Materials Chemistry A8(2)pp. 693-705 The Royal Society of Chemistry

    The performance of all solar cells is dictated by charge recombination. A closer to ideal recombination dynamics results in improved performances, with fill factors approaching the limits based on Shockley–Queisser analysis. It is well known that for emerging solar materials such as perovskites, there are several challenges that need to be overcome to achieve high fill factors, particularly for large area lead–tin mixed perovskite solar cells. Here we demonstrate a strategy towards achieving fill factors above 80% through post-treatment of a lead–tin mixed perovskite absorber with guanidinium bromide for devices with an active area of 0.43 cm2. This bromide post-treatment results in a more favorable band alignment at the anode and cathode interfaces, enabling better bipolar extraction. The resulting devices demonstrate an exceptional fill factor of 83%, approaching the Shockley–Queisser limit, resulting in a power conversion efficiency of 14.4% for large area devices.

    Zhiheng Wu, Yongshang Zhang, Yonglong Shen, Wei Zhang, Guosheng Shao (2020)Heater-Free and Substrate-Independent Growth of Vertically Standing Graphene Using A High-Flux Plasma-Enhanced Chemical Vapor Deposition, In: Advanced Materials Interfaces Wiley

    Vertically standing graphene (VSG) films have demonstrated various appealing functionalities on the basis of excellent electrical/thermal conductivity and electrochemical/catalytic properties, owing to their unique morphology, preferable orientation of the basal planes, and adequate defects as effective catalytic sites. Most fabrication processes for VSG suffer from the disadvantage of high processing temperature, difficulty in structural control, or poor scalability, which limits their many potential applications. Herein, a scalable high‐flux plasma‐enhanced chemical vapor deposition system is designed, with streamlined magnetic field to enable high and uniform ion density over a spatially extended plasma flux, which facilitates large‐area deposition of structurally tuned VSG independent of substrate materials without additional heating, for the first time. The orientation, density, and the degree of order for the as‐fabricated VSG can be tailored through adjusting the plasma environment, which in turn affects crystallization mechanisms. Such low‐temperature synthesized VSG films are demonstrated as high‐performance anode in sodium ion batteries, achieving a high capacity retention of 86% after 2000 cycles at a current density of 1 A g−1. It is expected that the current VSG films would have great potential for electrochemical applications that request catalytic sites together with favorable conductivity for ions and electrons.

    Hui Li, Wei Zhang (2020)Perovskite Tandem Solar Cells: From Fundamentals to Commercial Deployment, In: Chemical Reviews American Chemical Society

    Multi-junction (tandem) solar cells (TSCs) consisting of multiple light absorbers with considerably different band gaps show great potential in breaking the Shockley–Queisser (S–Q) efficiency limit of a single junction solar cell by absorbing light in a broader range of wavelengths. Perovskite solar cells (PSCs) are ideal candidates for TSCs due to their tunable band gaps, high PCE up to 25.2%, and easy fabrication. PSCs with high PCEs are typically fabricated via a low temperature solution method, which are easy to combine with many other types of solar cells like silicon (Si), copper indium gallium selenide (CIGS), narrow band gap PSCs, dye-sensitized, organic, and quantum dot solar cells. As a matter of fact, perovskite TSCs have stimulated enormous scientific and industrial interest since their first development in 2014. Significant progress has been made on the development of perovskite TSCs both in the research laboratories and industrial companies. This review will rationalize the recent exciting advancement in perovskite TSCs. We begin with the introduction of the historical development of TSCs in a broader context, followed by the summary of the state-of-the-art development of perovskite TSCs with various types of device architectures. We then discuss the strategies for improving the PCEs of perovskite TSCs, including but not limited to the design considerations on the transparency of perovskite absorbers and metal electrodes, protective layers, and recombination layers (RLs)/tunnel junctions (TJs), with a particular focus on the band gap tuning and thickness adjustment of active layers. We subsequently introduce a range of measurement techniques for the characterization of perovskite TSCs. We also cover other core issues related to the large-scale applications and commercialization. Finally, we offer our perspectives on the future development of emerging photovoltaic technologies as the device performance enhancement and cost reduction are central to almost any type of solar cell applied in the perovskite TSCs.

    Ruxin Guo, Junmin Xia, Hao Gu, Xuke Chu, Yan Zhao, Xianghuan Meng, Zhiheng Wu, Jiangning Li, Yanyan Duan, Zhenzhen Li, Zhaorui Wen, Shi Chen, Yongqing Cai, Chao Liang, Yonglong Shen, Guichuan Xing, Wei Zhang, Guosheng Shao (2023)Effective defect passivation with a designer ionic molecule for high-efficiency vapour-deposited inorganic phase-pure CsPbBr3 perovskite solar cells, In: Journal of materials chemistry. A, Materials for energy and sustainability11(1)pp. 408-418 Royal Soc Chemistry

    While caesium lead bromide (CsPbBr3) is promising for highly stable perovskite solar cells (PSCs), the usual solution-based methods require tedious multistep spin coating processes, which imposes a practical barrier against scaling up to large areas for industrial exploitation. Although sequential vapour deposition (SVD) can meet commercial requirements, these films are limited by high trap density and impure phases, resulting in poor performance of PSCs. Here, we obtained low-trap density and effectively phase-pure CsPbBr3 films (grain size > 3 mu m, trap density < 4 x 10(15) cm(-3)) by systematic defect and phase management. With the identification of a molecular ionic liquid from theoretical simulation, we find that such a designer molecule can form multiple bonding interactions with the perovskite phase. This results in significantly enhanced crystallization of the CsPbBr3 phase, and more importantly, effective passivation of well recognized Cs- and Br-vacancy defects. CsPbBr3 PSCs with simplified architecture using carbon as electrodes without hole transport layer (HTL) achieved highest power conversion efficiency (PCE) of up to 11.21% for small area devices (0.04 cm(2)) and 9.18% for large area devices (1 cm(2)). The unencapsulated devices exhibited excellent long-term stability, maintaining over 91% of the initial PCE after 100 days in ambient air at a humidity of similar to 55%. This work also provides a valuable approach to process phase-pure, low-defect, and large-area inorganic CsPbBr3 perovskite films for efficient and stable optoelectronic devices.

    Min Jiang, Jian Yang, Wei Zhang, Lin He, Jiao Zhang, Chaopeng Fu, Baode Sun (2020)Space-confined synthesis of CoNi nanoalloy in N-doped porous carbon frameworks as efficient oxygen reduction catalyst for neutral and alkaline aluminum-air batteries, In: Energy Storage Materials27pp. 96-108 Elsevier

    Exploring efficient and stable non-precious metal electrocatalysts for oxygen reduction reaction in neutral and alkaline solutions is of great importance for metal-air batteries. Herein, an efficient and stable electrocatalyst with CoNi nanoalloy (10-20 nm) uniformly embedded in porous N-doped carbon framework (CoNi-NCF) for neutral and alkaline primary Al-air batteries is prepared and studied. The CoNi-NCF electrocatalyst shows superior ORR performance in terms of half-wave potential of 0.91 V in 0.1 M KOH solution and 0.64 V in 3.5 wt% NaCl solution, outperforming those of the commercial Pt/C catalyst. Supported by in situ electrochemical Raman spectra and density functional theory calculations, the rich dual active sites of CoNi nanoalloy and porous N-doped carbon contributes to the outstanding ORR performance. Impressively, when employed as a cathode catalyst in both aqueous and solid flexible Al-air batteries, the CoNi-NCF-based Al-air batteries show the highest discharge performance, long-time durability and high flexibility, demonstrating the promising potential for practical application.

    Ruxin Guo, Yan Zhao, Yongshang Zhang, Quanrong Deng, Yonglong Shen, Wei Zhang, Guosheng Shao (2021)Significant performance enhancement of all-inorganic CsPbBr3 perovskite solar cells enabled by Nb-doped SnO2 as effective electron transport layer, In: Energy & environmental materials (Hoboken, N.J.) Wiley

    All-inorganic CsPbBr3-based perovskite solar cells (PSCs) have attracted great attention because of their high chemical and thermal stabilities in ambient air. However, the short-circuit current density (Jsc) of CsPbBr3-based PSCs is inadequate under solar illumination because of the wide bandgap, inefficient charge extraction and recombination loss, leading to lower power-conversion efficiencies (PCEs). It is envisaged that in addition to narrowing the bandgap by alloying, Jsc of the PSCs could be enhanced by effective improvement of electron transportation, suppression of charge recombination at the interface between the perovskite and electron transporting layer (ETL), and tuning of the space charge field in the device. In this work, Nb-doped SnO2 films as ETLs in the CsPbBr3-based PSCs have been deposited at room temperature by high target utilization sputtering (HiTUS). Through optimizing the Nb doping level alone, the Jsc was increased by nearly 19%, from 7.51 to 8.92 mA·cm−2 and the PCE was enhanced by 27% from 6.73% to 8.54%. The overall benefit by replacing the spin-coated SnO2 with sputtered SnO2 with Nb doping was up to 39% increase in Jsc and 62% increase in PCE. Moreover, the PCE of the optimized device showed negligible degradation over exposure to ambient environment (T ˜ 25 °C, RH˜45%), with 95.4% of the original PCE being maintained after storing the device for 1200 h.

    Bowei Li, Yuren Xiang, Imalka Jayawardena, Deying Luo, John Watts, Steven Hinder, Hui Li, Victoria Ferguson, Haitian Luo, Rui Zhu, S. Ravi P. Silva, Wei Zhang (2020)Tailoring Perovskite Adjacent Interfaces by Conjugated Polyelectrolyte for Stable and Efficient Solar Cells, In: Solar RRL4(5)2000060 Wiley

    Interface engineering is an effective means to enhance the performance of thin‐film devices, such as perovskite solar cells (PSCs). Herein, a conjugated polyelectrolyte, poly[(9,9‐bis(3′‐((N,N‐dimethyl)‐N‐ethyl‐ammonium)‐propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)]di‐iodide (PFN‐I), is used at the interfaces between the hole transport layer (HTL)/perovskite and perovskite/electron transport layer simultaneously, to enhance the device power conversion efficiency (PCE) and stability. The fabricated PSCs with an inverted planar heterojunction structure show improved open‐circuit voltage (Voc), short‐circuit current density (Jsc), and fill factor, resulting in PCEs up to 20.56%. The devices maintain over 80% of their initial PCEs after 800 h of exposure to a relative humidity 35–55% at room temperature. All of these improvements are attributed to the functional PFN‐I layers as they provide favorable interface contact and defect reduction.

    Xueping Liu, Deying Luo, Zheng-Hong Lu, Jae Sung Yun, Michael Saliba, Sang Il Seok, Wei Zhang (2023)Stabilization of photoactive phases for perovskite photovoltaics, In: Nature reviews. Chemistry7(7)pp. 462-479

    Interest in photovoltaics (PVs) based on Earth-abundant halide perovskites has increased markedly in recent years owing to the remarkable properties of these materials and their suitability for energy-efficient and scalable solution processing. Formamidinium lead triiodide (FAPbI )-rich perovskite absorbers have emerged as the frontrunners for commercialization, but commercial success is reliant on the stability meeting the highest industrial standards and the photoactive FAPbI phase suffers from instabilities that lead to degradation - an effect that is accelerated under working conditions. Here, we critically assess the current understanding of these phase instabilities and summarize the approaches for stabilizing the desired phases, covering aspects from fundamental research to device engineering. We subsequently analyse the remaining challenges for state-of-the-art perovskite PVs and demonstrate the opportunities to enhance phase stability with ongoing materials discovery and in operando analysis. Finally, we propose future directions towards upscaling perovskite modules, multijunction PVs and other potential applications.

    Bowei Li, Wei Zhang (2023)Ink engineering for slot-die coated perovskite solar cells and minimodules, In: JPhys Energy5(3)032002 IOP Publishing Ltd

    The power conversion efficiencies of perovskite solar cells (PSCs) have approached 26% for single-junction and 33% for multi-junction cells. Thus, various scalable depositions are studied to improve the manufacturability of PSCs for market entry. Of all types, slot-die coating is a promising technique thanks to its excellent compatibility with versatile systems. However, the complicated ink chemistry and film formation are major obstacles to scaling up devices. In this review, we systematically discuss ink engineering in the fabrication of slot-die-coated PSCs and perovskite minimodules, covering all functional layers that are processed using solution-based means. We then summarize a range of strategies to improve ink compatibility with slot-die coating, focusing on how to optimize the ink formulation to achieve high-quality films. Finally, we highlight the existing challenges and potential avenues for further development of slot-die-coated devices.

    THOMAS WEBB, Xueping Liu, Robert J. E. Westbrook, Stefanie Kern, Muhammad T. Sajjad, Sandra Jenatsch, K. D. G. Imalka Jayawardena, Withanage Hashini Kawshika Perera, Igor Marko, Sanjayan Sathasivam, Bowei Li, MOZHGAN YAVARI, David J. Scurr, Morgan R. Alexander, Thomas J Macdonald, Saif A. Haque, Stephen Sweeney, Wei Zhang (2022)A Multifaceted Ferrocene Interlayer for Highly Stable and Efficient Lithium Doped Spiro-OMeTAD-based Perovskite Solar Cells, In: Advanced energy materials12(26)2200666 Wiley

    Over the last decade, 2,2 '',7,7 ''-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9 '-spirobifluorene (spiro-OMeTAD) has remained the hole transporting layer (HTL) of choice for producing high efficiency perovskite solar cells (PSCs). However, PSCs incorporating spiro-OMeTAD suffer significantly from dopant induced instability and non-ideal band alignments. Herein, a new approach is presented for tackling these issues using the functionality of organometallocenes to bind to Li+ dopant ions, rendering them immobile and reducing their impact on the degradation of PSCs. Consequently, significant improvements are observed in device stability under elevated temperature and humidity, conditions in which ion migration occurs most readily. Remarkably, PSCs prepared with ferrocene retain 70% of the initial power conversion efficiency (PCE) after a period of 1250 h as compared to only 8% in the control. Synergistically, it is also identified that ferrocene improves the hole extraction yield at the HTL interface and reduces interfacial recombination enabling PCEs to reach 23.45%. This work offers a pathway for producing highly efficient spiro-OMeTAD devices with conventional dopants via addressing the key challenge of dopant induced instability in leading PSCs.

    Jing Zhang, Wei Zhang, Huiming Cheng, Ravi Silva (2020)Critical review of recent progress of flexible perovskite solar cells, In: Materials Today Elsevier

    Perovskite solar cells (PSCs) have emerged as a ‘rising star’ in recent years due to their high-power conversion efficiency (PCE), extremely low cost and facile fabrication techniques. To date, PSCs have achieved a certified PCE of 25.2% on rigid conductive substrates, and 19.5% on flexible substrates. The significant advancement of PSCs has been realized through various routes, including perovskite composition engineering, interface modification, surface passivation, fabrication process optimization, and exploitation of new charge transport materials. However, compared with rigid counterparts, the efficiency record of flexible perovskite solar cells (FPSCs) is advancing slowly, and therefore it is of great significance to scrutinize recent work and expedite the innovation in this field. In this article, we comprehensively review the recent progress of FPSCs. After a brief introduction, the major features of FPSCs are compared with other types of flexible solar cells in a broad context including silicon, CdTe, dye-sensitized, organic, quantum dot and hybrid solar cells. In particular, we highlight the major breakthroughs of FPSCs made in 2019/2020 for both laboratory and large-scale devices. The constituents of making a FPSC including flexible substrates, perovskite absorbers, charge transport materials, as well as device fabrication and encapsulation methods have been critically assessed. The existing challenges of making high performance and long-term stable FPSCs are discussed. Finally, we offer our perspectives on the future opportunities of FPSCs in the field of photovoltaics.

    Min Jiang, Chaopeng Fu, Ruiqi Cheng, Wei Zhang, Tongyao Liu, Ruibin Wang, Jiao Zhang, Baode Sun (2020)Integrated and Binder-Free Air Cathodes of Co3Fe7 Nanoalloy and Co5.47N Encapsulated in Nitrogen-Doped Carbon Foam with Superior Oxygen Reduction Activity in Flexible Aluminum-Air Batteries, In: Advanced Science2000747 Wiley Open Access

    All-solid-sate Al-air batteries with features of high theoretical energy density, low cost, and environmental-friendliness are promising as power sources for next-generation flexible and wearable electronics. However, the sluggish oxygen reduction reaction (ORR) and poor interfacial contact in air cathodes cause unsatisfied performance. Herein, a free-standing Co3Fe7 nanoalloy and Co5.47N encapsulated in 3D nitrogen-doped carbon foam (Co3Fe7@Co5.47N/NCF) is prepared as an additive-free and integrated air cathode for flexible Al-air batteries in both alkaline and neutral electrolytes. The Co3Fe7@Co5.47N/NCF outperforms commercial platinum/carbon (Pt/C) toward ORR with an onset potential of 1.02 V and a positive half-wave potential of 0.92 V in an alkaline electrolyte (0.59 V in sodium chloride solution), which is ascribed to the unique interfacial structure between Co3Fe7 and Co5.47N supported by 3D N-doped carbon foam to facilitate fast electron and mass transfer. The high ORR performance is also supported by in-situ electrochemical Raman spectra and density functional theory calculation. Furthermore, the fabricated Al-air battery displays good flexibility and delivers a power density of 199.6 mW cm−2, and the binder-free and integrated cathode shows better discharge performance than the traditionally slurry casting cathode. This work demonstrates a facile and efficient approach to develop integrated air cathode for metal-air batteries.

    Wenqiang Yang, Rui Su, Deying Luo, Qin Hu, Feng Zhang, Zhaojian Xu, Zhiping Wang, Jialun Tang, Zhao Lv, Xiaoyu Yang, Yongguang Tu, Wei Zhang, Haizheng Zhong, Qihuang Gong, Thomas P. Russell, Rui Zhu (2019)Surface modification induced by perovskite quantum dots for triple-cation perovskite solar cells, In: Nano Energy67104189 Elsevier

    Organic-inorganic hybrid perovskite solar cells are regarded as the most promising new-generation photovoltaic technology, owing to their high power conversion efficiencies and low cost. However, surface imperfections of perovskite films impede improvement in device performances, since surface imperfections can introduce undesired energy losses under sunlight illumination. Here, we show that the incorporation of zero-dimensional perovskite quantum dots into three-dimensional perovskite films can heal surface imperfections in perovskite films. Introducing perovskite quantum dots also leads to a more uniform surface topography and potential, along with an improved crystal quality of the triple-cation perovskite films, benefiting charge carrier kinetics between the perovskite films and the charge extraction layers. Ultimately, we achieve a power conversion efficiency exceeding 21% in triple-cation perovskite solar cells.

    Ehsan Rezaee, Wei Zhang, S. Ravi P Silva (2021)Solvent Engineering as a Vehicle for High Quality Thin Films of Perovskites and Their Device Fabrication, In: Small (Weinheim an der Bergstrasse, Germany)2008145 Wiley

    Organic–inorganic halide perovskite solar cells (PSCs) have shown a significant growth in power conversion efficiencies (PCEs) during last decade. Progress in device architecture and high-quality perovskite film fabrication has led to an incredible efficiency over 25% in close to a decade. Developments in solution-based thin film deposition techniques for perovskite layer preparation in PSCs provide low cost and ease of process for their manufacturing, making them a potential contender in future solar energy harvesting technologies. From small area single solar cells to large area perovskite solar modules, solvents play crucial roles in thin film quality and therefore, the device performance and stability. A comprehensive overview of solvent engineering toward achieving the highest qualities for perovskite light absorbing layers with various compositions and based on different fabrication processes is provided in this review. The mechanisms indicating the essential roles a solvent, or a solvent mixture can play to improve the crystallinity, uniformity, coverage and surface roughness of the perovskite films, are discussed. Finally, the role of solvent engineering in transferring from small area laboratory scale PSC fabrication to large area perovskite film deposition processes is explored.

    Bowei Li, Jun Deng, Joel A. Smith, Pietro Caprioglio, Kangyu Ji, Deying Luo, James D. McGettrick, K. D. G. Imalka Jayawardena, Rachel Kilbride, AOBO REN, Stephen Sweeney, Steven John Hinder, Jinxin Bi, S Ravi Pradip Silva, Wei Zhang, THOMAS WEBB, Igor Marko, Xueping Liu, YUREN XIANG, Joshua Dean Reding, HUI LI, Shixuan Du, D. G. Lidzey, Samuel D. Stranks, Trystan M. Watson, H. J. Snaith (2022)Suppressing Interfacial Recombination with a Strong-Interaction Surface Modulator for Efficient Inverted Perovskite Solar Cells, In: Advanced energy materials Wiley

    Successful manipulation of halide perovskite surfaces is typically achieved via the interactions between modulators and perovskites. Herein, it is demonstrated that a strong-interaction surface modulator is beneficial to reduce interfacial recombination losses in inverted (p-i-n) perovskite solar cells (IPSCs). Two organic ammonium salts are investigated, consisting of 4-hydroxyphenethylammonium iodide and 2-thiopheneethylammonium iodide (2-TEAI). Without thermal annealing, these two modulators can recover the photoluminescence quantum yield of the neat perovskite film in contact with fullerene electron transport layer (ETL). Compared to the hydroxyl-functionalized phenethylammonium moiety, the thienylammonium facilitates the formation of a quasi-2D structure onto the perovskite. Density functional theory and quasi-Fermi level splitting calculations reveal that the 2-TEAI has a stronger interaction with the perovskite surface, contributing to more suppressed non-radiative recombination at the perovskite/ETL interface and improved open-circuit voltage (V-OC) of the fabricated IPSCs. As a result, the V-OC increases from 1.11 to 1.20 V (based on a perovskite bandgap of 1.63 eV), yielding a power conversion efficiency (PCE) from approximate to 20% to 21.9% (stabilized PCE of 21.3%, the highest reported PCEs for IPSCs employing poly[N,N ''-bis(4-butylphenyl)-N,N ''-bis(phenyl)benzidine] as the hole transport layer, alongside the enhanced operational and shelf-life stability for unencapsulated devices.

    BOWEI LI, Wei Zhang (2022)Improving the stability of inverted perovskite solar cells towards commercialization, In: Communications materials3(1)pp. 1-13 Springer Nature

    Inverted perovskite solar cells (IPSCs) have great potential for commercialization, in terms of compatibility with flexible and multijunction solar cells. However, non-ideal stability limits their entry into the market. To shed light on the unstable origins of IPSCs, an analysis of recent research progress is needed. Here, we systematically discuss the stability of IPSCs, including each functional layer, interface and entire device, and consider environmental and operational stressors. We summarize a range of strategies for improving device stability and discuss the significance of stability test protocols. Finally, we highlight the shortcomings of current approaches for stability improvement and assessment, and provide recommendations for improving the stability of IPSCs. Inverted perovskite solar cells are promising for real-world energy harvesting, but suffer from issues with environmental stability. This Review discusses current understanding of stability in these devices and recent attempts to improve stability, as well as future directions that might enable their market roll-out.

    W. Hashini K. Perera, Mateus G. Masteghin, Hongjae Shim, Joshua L. Ryan, Steven J. Hinder, Jae S. Yun, Wei Zhang, K. D. G. Imalka Jayawardena, S Ravi Pradip Silva (2023)Modification of Hydrophobic Self-Assembled Monolayers with Nanoparticles for Improved Wettability and Enhanced Carrier Lifetimes Over Large Areas in Perovskite Solar Cells, In: Solar RRL Wiley

    The development of perovskite solar cells (PSCs) with low recombination losses, at low processing temperatures is an area of growing research interest as it enables compatibility with roll-to-roll processing on flexible substrates as well as with tandem solar cells. The inverted or p-i-n device architecture has emerged as the most promising PSC configuration due to the possibility of using low temperature processable organic hole transport layers and more recently, self-assembled monolayers such as, [4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid (Me-4PACz). However, devices incorporating these interlayers suffer from poor wettability of the precursor leading to pin hole formation and poor device yield. Here, we demonstrate the use of alumina nanoparticles (Al2O3 NPs) for pinning the perovskite precursor on Me-4PACz, thereby improving the device yield. While similar wettability enhancements can also be achieved by using poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]dibromide (PFN-Br), a widely employed surface modifier, the incorporation of Al2O3 NPs results in significantly enhanced Shockley-Read-Hall recombination lifetimes exceeding 3 μs, which is higher than those on films coated directly on Me-4PACz and on PFN-Br modified Me-4PACz. This translates to a champion power conversion efficiency of 19.9% for PSCs fabricated on Me-4PACz modified with Al2O3, which is a ∽20% improvement compared to the champion device fabricated on PFN-Br modified Me-4PACz.

    Mingyue Han, Yingrui Xiao, Chao Zhou, Yuxuan Yang, Xiaoxue Wu, Qi Hu, Xi Jin, Wei Zhang, Jin-Song Hu, Yan Jiang (2023)Recent advances on two-dimensional metal halide perovskite x-ray detectors, In: Materials futures2(1)012104 IOP Publishing
    Xueping Liu, THOMAS WEBB, Linjie Dai, Kangyu Ji, Joel A. Smith, Rachel Kilbride, MOZHGAN YAVARI, Jinxin Bi, AOBO REN, Yuanyuan Huang, Zhuo Wang, Yonglong Shen, Guosheng Shao, Stephen Sweeney, Steven John Hinder, HUI LI, D. G. Lidzey, Samuel D. Stranks, Neil C Greenham, Wei Zhang, S Ravi Pradip Silva (2022)Influence of halide choice on formation of low‐dimensional perovskite interlayer in efficient perovskite solar cells Wiley

    Recent advances in heterojunction and interfacial engineering of perovskite solar cells (PSCs) have enabled great progress in developing highly efficient and stable devices. Nevertheless, the effect of halide choice on the formation mechanism, crystallography and photoelectric properties of the low-dimensional phase still requires further detailed study. In this work, we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts, clarifying the effect of anions on the formation of quasi2D/3D heterojunctions. To demonstrate the importance of halide influences, we employ novel neo-pentylammonium halide salts with different halide anions (neoPAX, X = I, Br or Cl). We find that regardless of halide selection, iodide-based (neoPA)2(FA)(n-1)PbnI(3n+1) phases are formed above the perovskite substrate, while the added halide anions diffuse and passivate the perovskite bulk. In addition, we also find the halide choice has an influence on the degree of dimensionality (n). Comparing the three halides, we find that chloride-based salts exhibit superior crystallographic, enhanced carrier transport and extraction compared to the iodide and bromide analogs. As a result, we report high power conversion efficiency in quasi-2D/3D PSCs, which are optimal when using chloride salts, reaching up to 23.35% and improving long-term stability.

    M. T. Hörantner, Wei Zhang, M. Saliba, K. Wojciechowski, H. J. Snaith (2015)Templated microstructural growth of perovskite thin films via colloidal monolayer lithography, In: Energy and Environmental Science8(7)pp. 2041-2047 Royal Society of Chemistry

    Organic–inorganic metal halide perovskites have led to remarkable advancements in emerging photovoltaics with power conversion efficiencies (PCEs) already achieving 20%. In addition to solar cells, these perovskites also show applicability for lasing and LED applications. Here, we control perovskite crystal domain size and microstructure by guiding the growth through a highly ordered metal oxide honeycomb structure, which we form via colloidal monolayer lithography. The organic–inorganic perovskite material fills the holes of the honeycomb remarkably well leading to fully controlled domain size with tuneable film thickness. The honeycomb region is predominantly transparent, whereas the perovskite crystals within the honeycomb are strongly absorbing. We fabricate semi-transparent perovskite solar cells to demonstrate the feasibility of this structuring, which leads to enhanced open-circuit voltage and fill factor in comparison to unstructured partially dewet perovskite thin films. We achieve power conversion efficiencies of up to 9.5% with an average visible transmittance through the active layer of around 37%. The controlled microscopic morphology of perovskite films opens up a wide range of possible investigations, from charge transport optimization to optical enhancements and photonic structuring for photovoltaic, light emitting and lasing devices.

    Wei Zhang, Rui Zhu, Xi-Zhe Liu, Bin Liu, Seeram Ramakrishna (2009)Conjugated polymer-sensitized solar cells based on electrospun TiO2 nanofiber electrode, In: International Journal of Nanoscience08(01-02)pp. 227-230 World Scientific Publishing

    When conjugated polymer is used as dye sensitizer in dye-sensitized solar cell (DSSC), the device performance is usually limited by the poor penetration of conjugated polymer into the network formed by TiO2 nanoparticles. In this regard, we develop a novel photoanode composed of electrospun TiO2 nanofibers. Scanning electron microscopy (SEM) reveals the uniformity of the calcined TiO2 nanofibers. X-ray diffraction (XRD) analysis indicates that the calcined TiO2 nanofibers are polycrystalline and composed of pure anatase phase TiO2 grains. To demonstrate the application of the synthesized nanofibers in electronic devices, DSSCs are fabricated and investigated under illumination with AM 1.5 (100 mW cm-2) simulated sunlight. The initial results demonstrate the great potential of using conjugated polymer as the dye sensitizer for devices with TiO2 nanofiber electrode.

    James M. Ball, Samuel D. Stranks, Maximilian T. Hörantner, Sven Hüttner, Wei Zhang, Edward J. W. Crossland, Ivan Ramirez, Moritz Riede, Michael B. Johnston, Richard H. Friend, Henry J. Snaith (2015)Optical properties and limiting photocurrent of thin-film perovskite solar cells, In: Energy and Environmental Science8(2)pp. 602-609 Royal Society of Chemistry

    Metal-halide perovskite light-absorbers have risen to the forefront of photovoltaics research offering the potential to combine low-cost fabrication with high power-conversion efficiency. Much of the development has been driven by empirical optimisation strategies to fully exploit the favourable electronic properties of the absorber layer. To build on this progress, a full understanding of the device operation requires a thorough optical analysis of the device stack, providing a platform for maximising the power conversion efficiency through a precise determination of parasitic losses caused by coherence and absorption in the non-photoactive layers. Here we use an optical model based on the transfer-matrix formalism for analysis of perovskite-based planar heterojunction solar cells using experimentally determined complex refractive index data. We compare the modelled properties to experimentally determined data, and obtain good agreement, revealing that the internal quantum efficiency in the solar cells approaches 100%. The modelled and experimental dependence of the photocurrent on incidence angle exhibits only a weak variation, with very low reflectivity losses at all angles, highlighting the potential for useful power generation over a full daylight cycle.

    Ye Zhang, Mingzhen Liu, Giles E. Eperon, Tomas C. Leijtens, David McMeekin, Michael Saliba, Wei Zhang, Michele de Bastiani, Annamaria Petrozza, Laura M. Herz, Michael B. Johnston, Hong Lin, Henry J. Snaith (2015)Charge selective contacts, mobile ions and anomalous hysteresis in organic–inorganic perovskite solar cells, In: Materials Horizons2(3)pp. 315-322 Royal Society of Chemistry

    High-efficiency perovskite solar cells typically employ an organic–inorganic metal halide perovskite material as light absorber and charge transporter, sandwiched between a p-type electron-blocking organic hole-transporting layer and an n-type hole-blocking electron collection titania compact layer. Some device configurations also include a thin mesoporous layer of TiO2 or Al2O3 which is infiltrated and capped with the perovskite absorber. Herein, we demonstrate that it is possible to fabricate planar and mesoporous perovskite solar cells devoid of an electron selective hole-blocking titania compact layer, which momentarily exhibit power conversion efficiencies (PCEs) of over 13%. This performance is however not sustained and is related to the previously observed anomalous hysteresis in perovskite solar cells. The “compact layer-free” meso-superstructured perovskite devices yield a stabilised PCE of only 2.7% while the compact layer-free planar heterojunction devices display no measurable steady state power output when devoid of an electron selective contact. In contrast, devices including the titania compact layer exhibit stabilised efficiency close to that derived from the current voltage measurements. We propose that under forward bias the perovskite diode becomes polarised, providing a beneficial field, allowing accumulation of positive and negative space charge near the contacts, which enables more efficient charge extraction. This provides the required built-in potential and selective charge extraction at each contact to temporarily enable efficient operation of the perovskite solar cells even in the absence of charge selective n- and p-type contact layers. The polarisation of the material is consistent with long range migration and accumulation of ionic species within the perovskite to the regions near the contacts. When the external field is reduced under working conditions, the ions can slowly diffuse away from the contacts redistributing throughout the film, reducing the field asymmetry and the effectiveness of the operation of the solar cells. We note that in light of recent publications showing high efficiency in devices devoid of charge selective contacts, this work reaffirms the absolute necessity to measure and report the stabilised power output under load when characterizing perovskite solar cells.

    Hang Hu, Binghai Dong, Wei Zhang (2017)Low-toxic metal halide perovskites: opportunities and future challenges, In: Journal of Materials Chemistry A5(23)pp. 11436-11449 Royal Society of Chemistry

    Over the past few years, lead halide perovskites have emerged as a class of dominant semiconductor materials in the photovoltaic (PV) field with an unprecedented sharp enhancement of power conversion efficiencies (PCEs) up to 22.1%, as well as in other promising optoelectronic applications due to their extraordinary and unique properties. However, the lead toxicity and long-term stability of these lead-based perovskites have raised considerable concerns for their real applications. Exploration of potentially low-toxic metal halide perovskite materials becomes one of the significant pivotal challenges in this century for PV, optoelectronic, and other unexplored applications. In this review, we summarize the recent progress on the development of low-toxic metal halide perovskites with a particular focus on their structures and properties, and discuss their potential applications in PV and optoelectronic devices. Moreover, we suggest current challenges and future research directions with the goal of stimulating further research interest and potential applications.

    Zhaosheng Xue, Wei Zhang, Xiong Yin, Yueming Cheng, Long Wang, Bin Liu (2012)Enhanced conversion efficiency of flexible dye-sensitized solar cells by optimization of the nanoparticle size with an electrophoretic deposition technique, In: RSC Advances2(18) The Royal Society of Chemistry

    To optimize the conversion efficiency of plastic dye-sensitized solar cells fabricated by the electrophoretic deposition technique, anatase TiO2 nanoparticles of various sizes from 10 nm to 27 nm have been synthesized via a simple hydrothermal process. The obtained TiO2 nanoparticles have been characterized by X-ray diffraction and high resolution transmission electron microscopy, which confirmed that the synthesized nanoparticles are in the pure anatase phase. Rigid devices based on D149-sensitized TiO2 particles with a size of 19 nm showed the highest conversion efficiency of 7.0% among the four different devices, which was measured under illumination of AM 1.5G, 100 mWcm−2. The effect of the particle size on the photovoltaic performance of DSSCs has been systemically studied using photoelectrochemical characterizations, including intensity modulated photocurrent spectroscopy and intensity modulated photovoltage spectroscopy. The good photovoltaic performance for 19 nm TiO2 is ascribed to the good dye loading, an efficient electron transport and the high charge collection efficiency in the photoanode. Moreover, plastic DSSCs based on 19 nm TiO2 presented a conversion efficiency of 6.0% (AM 1.5G, 100 mWcm−2) under optimized conditions, showing about a 20% enhancement in the conversion efficiency as compared to that based on commercial Degussa P25 TiO2 (5.2%). These results demonstrate that optimization of the TiO2 nanoparticle size for devices fabricated using the EPD technique is an alternative method to achieve highly efficient plastic dye-sensitized solar cells.

    Yang Zhou, Zi-Jun Yong, Wei Zhang, Ju-Ping Ma, Aditya Sadhanala, Ya-Meng Chen, Bo-Mei Liu, Yi Zhou, Bo Song, Hong-Tao Sun (2017)Ultra-broadband optical amplification at telecommunication wavelengths achieved by bismuth-activated lead iodide perovskites, In: Journal of Materials Chemistry C5(10)pp. 2591-2596 Royal Society of Chemistry

    It is extremely difficult to achieve hybrid halide perovskite semiconductors with luminescence at wavelengths longer than 1.0 μm, because of the inherent limitation of their band gaps. We show herein that solution-processable, Bi-activated, high-quality MAPbI3 films can be adopted as a new gain medium operating in the whole telecommunication window of 1260–1625 nm. Additionally, the structural and optical properties of Bi doped MAPbI3 have been investigated. The results indicate that the NIR PL originates from the structural defects induced by Bi. Finally, we accomplished optical amplification in the whole telecommunication window by using Bi-doped MAPbI3 films, which represents the first work where such a performance is attained among lead halide perovskites and Bi-doped photonic films. This work opens up exciting possibilities of using perovskite semiconducting materials as gain media for optical amplifiers and lasers operating in the telecommunication window.

    Jacob Tse-Wei Wang, Zhiping Wang, Sandeep Pathak, Wei Zhang, Dane W. deQuilettes, Florencia Wisnivesky-Rocca-Rivarola, Jian Huang, Pabitra K. Nayak, Jay B. Patel, Hanis A. Mohd Yusof, Yana Vaynzof, Rui Zhu, Ivan Ramirez, Jin Zhang, Caterina Ducati, Chris Grovenor, Michael B. Johnston, David S. Ginger, Robin J. Nicholas, Henry J. Snaith (2016)Efficient perovskite solar cells by metal ion doping, In: Energy and Environmental Science9(9)pp. 2892-2901 Royal Society of Chemistry

    Realizing the theoretical limiting power conversion efficiency (PCE) in perovskite solar cells requires a better understanding and control over the fundamental loss processes occurring in the bulk of the perovskite layer and at the internal semiconductor interfaces in devices. One of the main challenges is to eliminate the presence of charge recombination centres throughout the film which have been observed to be most densely located at regions near the grain boundaries. Here, we introduce aluminium acetylacetonate to the perovskite precursor solution, which improves the crystal quality by reducing the microstrain in the polycrystalline film. At the same time, we achieve a reduction in the non-radiative recombination rate, a remarkable improvement in the photoluminescence quantum efficiency (PLQE) and a reduction in the electronic disorder deduced from an Urbach energy of only 12.6 meV in complete devices. As a result, we demonstrate a PCE of 19.1% with negligible hysteresis in planar heterojunction solar cells comprising all organic p and n-type charge collection layers. Our work shows that an additional level of control of perovskite thin film quality is possible via impurity cation doping, and further demonstrates the continuing importance of improving the electronic quality of the perovskite absorber and the nature of the heterojunctions to further improve the solar cell performance.

    Tomas Leijtens, Giles E. Eperon, Alex J. Barker, Giulia Grancini, Wei Zhang, James M. Ball, Ajay Ram Srimath Kandada, Henry J. Snaith, Annamaria Petrozza (2016)Carrier trapping and recombination: the role of defect physics in enhancing the open circuit voltage of metal halide perovskite solar cells, In: Energy & Environmental Science9(11)pp. 3472-3481 Royal Society of Chemistry

    One of the greatest attributes of metal halide perovskite solar cells is their surprisingly low loss in potential between bandgap and open-circuit voltage, despite the fact that they suffer from a non-negligible density of sub gap defect states. Here, we use a combination of transient and steady state photocurrent and absorption spectroscopy to show that CH3NH3PbI3 films exhibit a broad distribution of electron traps. We show that the trapped electrons recombine with free holes unexpectedly slowly, on microsecond time scales, relaxing the limit on obtainable open-circuit voltage (VOC) under trap-mediated recombination conditions. We find that the observed VOCs in such perovskite solar cells can only be rationalized by considering the slow trap mediated recombination mechanism identified in this work. Our results suggest that existing processing routes may be good enough to enable open circuit voltages approaching 1.3 V in ideal devices with perfect contacts.

    Wenzhe Li, Wei Zhang, Stephan Van Reenen, Rebecca J. Sutton, Jiandong Fan, Amir A. Haghighirad, Michael B. Johnston, Liduo Wang, Henry J. Snaith (2016)Enhanced UV-light stability of planar heterojunction perovskite solar cells with caesium bromide interface modification, In: Energy and Environmental Science9(2)pp. 490-498 Royal Society of Chemistry

    Interfacial engineering has been shown to play a vital role in boosting the performance of perovskite solar cells in the past few years. Here we demonstrate that caesium bromide (CsBr), as an interfacial modifier between the electron collection layer and the CH3NH3PbI3−xClx absorber layer, can effectively enhance the stability of planar heterojunction devices under ultra violet (UV) light soaking. Additionally, the device performance is improved due to the alleviated defects at the perovskite-titania heterojunction and enhanced electron extraction.

    Wei Zhang, Giles E. Eperon, Henry J. Snaith (2016)Metal halide perovskites for energy applications, In: Nature Energy1(6)16048 Nature Publishing Group

    Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications.

    W. Qiu, T. Merckx, M. Jaysankar, C. Masse de la Huerta, L. Rakocevic, Wei Zhang, U. W. Paetzold, R. Gehlhaar, L. Froyen, J. Poortmans, D. Cheyns, H. J. Snaith, P. Heremans (2016)Pinhole-free perovskite films for efficient solar modules, In: Energy and Environmental Science9(2)pp. 484-489 Royal Society of Chemistry

    We report on a perovskite solar module with an aperture area of 4 cm2 and geometrical fill factor of 91%. The module exhibits an aperture area power conversion efficiency (PCE) of 13.6% from a current–voltage scan and 12.6% after 5 min of maximum power point tracking. High PCE originates in pinhole-free perovskite films made with a precursor combination of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I.

    Miguel Anaya, Wei Zhang, Bruno Clasen Hames, Yuelong Li, Francisco Fabregat-Santiago, Mauricio E. Calvo, Henry J. Snaith, Hernán Míguez, Iván Mora-Seró (2016)Electron injection and scaffold effects in perovskite solar cells, In: Journal of Materials Chemistry C5(3)pp. 634-644 Royal Society of Chemistry

    In spite of the impressive efficiencies reported for perovskite solar cells (PSCs), key aspects of their working principles, such as electron injection at the contacts or the suitability of the utilization of a specific scaffold layer, are not yet fully understood. Increasingly complex scaffolds attained by the sequential deposition of TiO2 and SiO2 mesoporous layers onto transparent conducting substrates are used to perform a systematic characterization of both the injection process at the electron selective contact and the scaffold effect in PSCs. By forcing multiple electron injection processes at a controlled sequence of perovskite–TiO2 interfaces before extraction, interfacial injection effects are magnified and hence characterized in detail. An anomalous injection behavior is observed, the fingerprint of which is the presence of significant inductive loops in the impedance spectra with a magnitude that correlates with the number of interfaces in the scaffold. Analysis of the resistive and capacitive behavior of the impedance spectra indicates that the scaffolds could hinder ion migration, with positive consequences such as lowering the recombination rate and implications for the current–potential curve hysteresis. Our results suggest that an appropriate balance between these advantageous effects and the unavoidable charge transport resistive losses introduced by the scaffolds will help in the optimization of PSC performance.

    Haoxin Wang, Wei Zhang, Biyi Wang, Zheng Yan, Cheng Chen, Yong Hua, Tai Wu, Linqin Wang, Hui Xu, Ming Cheng (2023)Modulating buried interface with multi-fluorine containing organic molecule toward efficient NiO -based inverted perovskite solar cell, In: Nano energy111108363
    Guiqiang Wang, Jiarun Chang, Jiayu Bi, Wei Zhang, Fanning Meng (2022)Organic Additive Engineering to Grow High‐Quality Inorganic CsPbX 3 Perovskite Films for Efficient and Stable Solar Cells, In: Solar RRL6(11)

    Inorganic CsPbX 3 (X: Br, I, or their mixture) perovskite solar cells have gained widespread attention due to their superior stability and the steadily increased conversion efficiency. Inorganic CsPbX 3 perovskite for solar cell application are usually fabricated by the solution‐processing method. The nature of solution‐processing method and the rapid crystal growth of perovskite lead to the formation of a wide range of defects within CsPbX 3 perovskite films, which deteriorate the performance and stability of CsPbX 3 devices. Recently, organic additive engineering has been demonstrated to be an effective strategy for improving the perovskite quality. Herein, the recent progress of organic additive engineering to grow high‐quality inorganic CsPbX 3 perovskite films for high‐performance solar cells is summarized. The role of organic additives in the formation of inorganic CsPbX 3 perovskite films and their effect on the performance of corresponding perovskite solar cells are discussed. In addition, some issues of organic additive engineering that should be deeply understood are summarized, and the research trend on organic additive engineering for further improving the performance of CsPbX 3 devices is suggested.

    Zi-Yang Xia, Wei Zhang, Cheng Chen, Hao-Xin Wang, Lin-Qin Wang, Ya-Wei Miao, Xing-Dong Ding, Li-Cheng Sun, Ming Cheng (2023)Improving performance of Cs2AgBiBr6 solar cell through constructing gradient energy level with deep-level hole transport material, In: Rare metals42(9)pp. 3004-3012 Nonferrous Metals Soc China

    The valence band offset between Cs2AgBiBr6 and hole transport layer (HTL) is approximately 1.00 eV, which results in high energy loss and is identified as one of the bottle necks of Cs2AgBiBr6 perovskite solar cell (PSC) for achieving high power conversion efficiency (PCE). To tackle this problem, we propose the optimization of the energy level alignment by designing and synthesizing novel deep-level hole transport materials (HTMs). The sole introduction of deep-level HTMs successfully reduces the valence band offset between Cs2AgBiBr6 and HTL, but induces the increased valence band offset at HTL/Au interface, limiting the PCE improvement. To further solve the problem and improve the PCE, the gradient energy level arrangement is constructed by combining the newly developed deep-level HTM 6,6'-(3-((9,9-dimethyl-9H-fluoren-3-yl)(4-methoxyphenyl)amino)thiophene-2,5-diyl)bis(N-(9,9-dimethyl-9H-fluoren-2-yl)-N,9-bis(4-methoxyphenyl)-9H-carbazol-3-amine) (TF) with 2,2',7,7'-tetrakis(N,N'-di-pmethoxyphenylamine)-9,9-spirobifluorene (Spiro-OMeTAD). Through optimization, an impressive PCE of 3.50% with remarkably high open-circuit voltage (V-oc) and fill factor (FF) is achieved, qualifying it among the best pristine Cs2AgBiBr6 PSCs.

    Zhisheng Lv, Changxian Wang, Changjin Wan, Renheng Wang, Xiangyu Dai, Jiaqi Wei, Huarong Xia, Wenlong Li, Wei Zhang, Shengkai Cao, Feilong Zhang, Haiyue Yang, Xian Jun Loh, Xiaodong Chen (2022)Strain-Driven Auto-Detachable Patterning of Flexible Electrodes, In: Advanced materials (Weinheim)34(30)2202877pp. e2202877-n/a Wiley

    Flexible electrodes that are multilayer, multimaterial, and conformal are pivotal for multifunctional wearable electronics. Traditional electronic circuits manufacturing requires substrate-supported transfer printing, which limits their multilayer integrity and device conformability on arbitrary surfaces. Herein, a "shrinkage-assisted patterning by evaporation" (SHAPE) method is reported, by employing evaporation-induced interfacial strain mismatch, to fabricate auto-detachable, freestanding, and patternable electrodes. The SHAPE method utilizes vacuum-filtration of polyaniline/bacterial cellulose (PANI/BC) ink through a masked filtration membrane to print high-resolution, patterned, and multilayer electrodes. The strong interlayer hydrogen bonding ensures robust multilayer integrity, while the controllable evaporative shrinking property of PANI/BC induces mismatch between the strains of the electrode and filtration membrane at the interface and thus autodetachment of electrodes. Notably, a 500-layer substrateless micro-supercapacitor fabricated using the SHAPE method exhibits an energy density of 350 mWh cm(-2) at a power density of 40 mW cm(-2), 100 times higher than reported substrate-confined counterparts. Moreover, a digital circuit fabricated using the SHAPE method functions stably on a deformed glove, highlighting the broad wearable applications of the SHAPE method.

    Linlin Duan, Changyao Wang, Wei Zhang, Bing Ma, Yonghui Deng, Wei Li, Dongyuan Zhao (2021)Interfacial Assembly and Applications of Functional Mesoporous Materials, In: Chemical reviews121(23)pp. 14349-14429

    Functional mesoporous materials have gained tremendous attention due to their distinctive properties and potential applications. In recent decades, the self-assembly of micelles and framework precursors into mesostructures on the liquid-solid, liquid-liquid, and gas-liquid interface has been explored in the construction of functional mesoporous materials with diverse compositions, morphologies, mesostructures, and pore sizes. Compared with the one-phase solution synthetic approach, the introduction of a two-phase interface in the synthetic system changes self-assembly behaviors between micelles and framework species, leading to the possibility for the on-demand fabrication of unique mesoporous architectures. In addition, controlling the interfacial tension is critical to manipulate the self-assembly process for precise synthesis. In particular, recent breakthroughs based on the concept of the "monomicelles" assembly mechanism are very promising and interesting for the synthesis of functional mesoporous materials with the precise control. In this review, we highlight the synthetic strategies, principles, and interface engineering at the macroscale, microscale, and nanoscale for oriented interfacial assembly of functional mesoporous materials over the past 10 years. The potential applications in various fields, including adsorption, separation, sensors, catalysis, energy storage, solar cells, and biomedicine, are discussed. Finally, we also propose the remaining challenges, possible directions, and opportunities in this field for the future outlook.

    Qiao Chen, Shan Sun, Hengwei Lin, Zhongjun Li, Aiguo Wu, Xiaohong Liu, Fu-Gen Wu, Wei Zhang (2021)Supra-Carbon Dots Formed by Fe3+-Driven Assembly for Enhanced Tumor-Specific Photo-Mediated and Chemodynamic Synergistic Therapy, In: ACS applied bio materials4(3)pp. 2759-2768 Amer Chemical Soc

    We herein report a facile method to fabricate a multifunctional cancer theranostic nanoplatform via Fe3+-driven assembly of photosensitizer (chlorine e6, Ce6)-decorated red emissive carbon dots (Ce6-RCDs). The as-prepared Supra-CDs (i.e., CD clusters; also termed as Fe-Ce6-RCDs) are found to not only retain the intrinsic photosensitization, fluorescence (FL), and photothermal properties of the Ce6-RCDs component but also be endowed with the chemodynamic therapy (CDT) function by the introduced Fe(3+)via the Fenton reaction that can specifically occur in tumor sites. The suitable size (similar to 36 nm) of the Supra-CDs enables enhanced tumor accumulation, thus achieving significantly improved FL imaging-guided anticancer performance by combining photodynamic, photothermal, and chemodynamic therapeutic modalities. More interestingly, the multi-subcellular structure (including nucleolus and cytoplasm)-targeting capacity of the Supra-CDs further enhances their therapeutic outcomes. This work not only develops a Fe3+-mediated self-assembly approach to construct a multifunctional cancer theranostic nanoplatform but also emphasizes the ion-interference role of the Fe3+-mediated CDT in anticancer nanomedicines.

    Zhen Huang, Yan Sun, Zhe Zhang, Zishu Zhou, Bowen Liu, Jingxian Zhong, Wei Zhang, Gang Ouyang, Junran Zhang, Lin Wang, Wei Huang (2020)Tunable excitonic properties in two-dimensional heterostructures based on solution-processed PbI2 flakes, In: Journal of materials science55(24)pp. 10656-10667 Springer Nature

    We investigate the manifestations of band structure engineering in few-layer PbI2-based heterostructures by probing their tunable optical properties. First, we have successfully prepared atomically thin flakes from PbI2 solution by two distinct approaches. A drop-casting of PbI2 solution onto various substrates followed by a simple heating process yields abundant flakes with different thickness and regular shape. Mechanical exfoliation of PbI2 bulk crystals, obtained from a low-temperature recrystallization process of PbI2 solution, also gives ultrathin PbI2 flakes of high quality. Moreover, these PbI2 flakes are employed to construct various van de Waals heterostructures. A significant enhancement of photoluminescence in MoSe2 interfaced with PbI2 was observed at different laser excitation intensity, due to the forming of type-I band alignment. Type-I band alignment can also be investigated in MoS2/PbI2 heterostructure, while type-II band alignment is built-in WSe2/PbI2 heterostructure. These results demonstrate that the strong interfacial coupling between PbI2 and other two-dimensional semiconductors can modulate their band alignment, and as a result, the exciton properties noticeably, which provides new insights of building a designer heterostructure device at the atomic level.

    Qiushi Wang, Junhong Li, Wei Zhang, Huiling Zheng, Ridong Cong (2021)Synthesis, and photoluminescence and magnetic properties of Tb-doped AlN single-crystalline nanobelts, In: Journal of luminescence236118089 Elsevier B.V

    Tb doped AlN (AlN:Tb) nanobelts were prepared by in situ doping of Tb using a plasma-assisted arc discharge method. The structure, composition and morphology of the doped nanobelts were studied by means of X-ray diffraction, scanning and transmission electron microscopy and X-ray photoelectron spectroscopy, revealing that Tb ions have been introduced into the lattice of wurtzite-structured AlN nanobelts. The AlN:Tb nanobelts exhibit distinct emission peaks corresponding to intra-4f electron transitions of Tb3+ ions, and room temperature ferromagnetism, which make AlN:Tb nanobelts an excellent candidate for applications in future solid light-emitting diodes and spintronic nanodevices. •The Tb doped AlN nanobelts were fabricated using modified arc discharge method.•The Tb doped AlN nanobelts exhibit an intensive green emission.•The Tb doped AlN nanobelts exhibit ferromagnetism at room temperature.

    Wei Zhang, Luis K. Ono, Jiamin Xue, Yabing Qi (2022)Atomic Level Insights into Metal Halide Perovskite Materials by Scanning Tunneling Microscopy and Spectroscopy, In: Angewandte Chemie (International ed.)61(5)e202112352pp. e202112352-n/a Wiley

    Metal halide perovskite materials (MHPMs) have attracted significant attention because of their superior optoelectronic properties and versatile applications. The power conversion efficiency of MHPM solar cells (PSCs) has skyrocketed to 25.5 %. Although the performance of PSCs is already competitive, several important challenges still need to be solved to realize commercial applications. A thorough understanding of surface atomic structures and structure-property relationships is at the heart of these remaining issues. Scanning tunneling microscopy (STM) and spectroscopy (STS) can be used to characterize the surface properties of MHPMs, which can offer crucial insights into MHPMs at the atomic scale. This Review summarizes recent progress in STM and STS studies on MHPMs, with a focus on the surface properties. We provide understanding from the comparative perspective of several different MHPMs. We also highlight a series of novel phenomena observed by STM and STS. Finally, we outline a few research topics of primary importance for future studies.

    Qiushi Wang, Junhong Li, Wei Zhang, Min Zhong (2020)Plasma-Assisted Synthesis of Bicrystalline ZnS Nanobelts with Enhanced Photocatalytic Ability, In: Electronic materials letters16(2)180pp. 180-187 Korean Inst Metals Materials

    ZnS nanobelts have been synthesized by a reaction of Zn and S powders using the simple arc discharge method. The products were characterized using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, as well as energy-dispersive X-ray spectrometer. The results reveal that the ZnS nanobelts exhibit bicrystalline nanostructure. The roles of ion bombardment and plasma species in the growth of bicrystalline ZnS nanobelts are discussed. The ZnS nanobelts exhibit strong emission peaked at 516 nm under a 373 nm UV light excitation and excellent photocatalytic ability for degradation of methylene blue. This work represents a new strategy to synthesize bicrystalline nanostructures for design of optoelectronic nanodevices and photocatalysts. Graphic

    Wang Ren, Ying Zhang, Wen Yong Liang, Xiu Pei Yang, Wei Dong Jiang, Xiao Hong Liu, Wei Zhang (2021)A facile and sensitive ratiometric fluorescence sensor for rapid visual monitoring of trace resorcinol, In: Sensors and actuators. B, Chemical330129390 Elsevier B.V

    •The proposed fluorescence method can easily differentiate trace RS from its isomers.•The ratiometric sensor enabled RS to trigger the change of fluorescence color.•RS as low as 5.0 nM can be directly identified with the naked-eye within 2 min.•The ratiometric fluorescence sensing for RS was facile, rapid, and sensitive. Visual detection is favorable for the field monitoring and routine analysis of environmental pollutants. Specially, the change of fluorescent color instead of fluorescence brightness is particularly convenient for the visual monitoring. In this study, a facile, rapid and sensitive ratiometric fluorescence sensor is developed for visual discrimination of trace resorcinol (RS) from its isomers and analogues. Specific coupling reaction between RS and dopamine (DA) generates fluorescent azamonardine (AZMON) within 2 min, and the blue fluorescence intensity increases with the RS concentration. Furthermore, after red light-emitting Au nanoclusters (AuNCs) are added into the mixture of RS and DA, the fluorescence signal at 656 nm keeps unchanged, and the fluorescence intensity at 460 nm is positively correlated with RS concentration. Moreover, the increasing concentration of RS triggers the obvious change of fluorescent color from red to blue based on the red background fluorescence of AuNCs, and RS as low as 5.0 nM can be directly identified with naked eye. Herein, the reference signal of AuNCs facilitates the ratiometric and visual sensing of RS. The proposed sensor has been successfully applied to determination of RS in real water samples, and is convenient for the routine analysis and field monitoring of trace RS.

    Xiao-Hong Liu, Shan Jiang, Lin Chang, Wei Zhang (2020)Recent research progress of non-noble metal based surface-enhanced Raman scattering substrates, In: Wuli xuebao69(19)190701

    Surface-enhanced Raman scattering (SERS) is of great importance in analytical science, the noble-metal such as gold and silver are widely used in SERS research and applications. However, noble-metal based substrates are hampered in practical application. As for comparison, the Non-noble metal especially the semiconductor materials are the emerging SERS research frontier. Non-noble metal (such as C, Ti, Zn, Cu, Mo, W, etc.) nanomaterials based SERS substrate have been widely studied and applied due to their superior stability, selectivity, biocompatibility and low cost comparing to noble metal materials. As the chemical enhancement dominate its total SERS signals, it also provides an ideal platform for the investigation of chemical enhancement mechanism. In this review, we explored the development of non-noble metal SERS substrates, focusing on its enhancement mechanism and SERS performance of different materials as well as the future development direction.

    Jingxian Zhong, Yan Sun, Bowen Liu, Chao Zhu, Yang Cao, Encheng Sun, Kaiyue He, Wei Zhang, Kan Liao, Xiaoyong Wang, Zheng Liu, Lin Wang (2021)Thickness dependent properties of ultrathin perovskite nanosheets with Ruddlesden–Popper-like atomic stackings, In: Nanoscale13(45)pp. 18961-18966

    Ruddlesden–Popper perovskites possess a rich variety of multiple phases due to their mixed organic cations and variable layer numbers. However, the direct observation of these phases and their optical performance in ultrathin nanosheets, have rarely been reported. Here we demonstrate, through a one-pot CVD synthesis method to incorporate MA + and NMA + cations into PbI 2 simultaneously, that the stackings of Ruddlesden–Popper phases with a distribution of a number of layers 〈 n 〉 can be produced within a single perovskite nanosheet. As featured by the micro-, time-resolved and temperature-dependent photoluminescence measurements, the optical properties are highly dependent on the nanosheet thickness.

    Hongwei Zhang, Zhisheng Lv, Qinghua Liang, Huarong Xia, Zhiqiang Zhu, Wei Zhang, Xiang Ge, Pei Yuan, Qingyu Yan, Xiaodong Chen (2020)Highly Elastic Binders Incorporated with Helical Molecules to Improve the Electrochemical Stability of Black Phosphorous Anodes for Sodium-Ion Batteries, In: Batteries & supercaps3(1)pp. 101-107 Wiley

    Black phosphorus has aroused attention as an attractive anode for sodium-ion batteries, because of its high theoretical capacity. Nevertheless, its practical application is hindered by the large volume expansion, which results in rapid capacity decay. Herein, we report that this challenge can be addressed by using an elaborately designed binder for the phosphorus-based electrodes. The incorporation of amylose molecules with helical structures endows the linear polyacrylic acid polymer binders with extraordinary stretchability and elasticity under 400 % strain. When it is applied as a binder for black-phosphorus-based anodes for sodium-ion batteries, the adhesion between the electrode and the current collector is much stronger (2.95 N) than that of the polyvinylidene difluoride (PVDF) binder based one (1.90 N). The electrode delivered a capacity as high as 1280 mAh g(-1) at 200 mA g(-1) after 300 cycles, which is better than the electrode with PVDF binder. Impressively, even after 1000 cycles, the electrode with our binder exhibits a capacity retention of 80 %. Our work sheds light on the significance of the rational design of effective binders and provides a new strategy to further improve the electrochemical performance of phosphorus-based materials for battery applications, which can be added on directly to other new electrode materials development strategies.

    Jiayu Bi, Jiarun Chang, Miao Lei, Wei Zhang, Fanning Meng, Guiqiang Wang (2022)Thiourea-Assisted Facile Fabrication of High-Quality CsPbBr3 Perovskite Films for High-Performance Solar Cells, In: ACS applied materials & interfaces14(43)pp. 48888-48896 Amer Chemical Soc

    Inorganic CsPbBr3 perovskite solar cells have attracted widespread attention recently because of their decent efficiency and good ambient stability. Nevertheless, the fabrication of high-quality CsPbBr3 perovskite via the conventional solution-processing strategy still faces great challenges because the solubility of CsBr in the conventional solvent is poor. Here, we develop a facile thiourea-assisted two-step spin-coating process to fabricate a CsPbBr3 perovskite film with high phase purity and crystallinity and enlarged crystal grains. Thiourea is introduced into the PbBr2 layer during the first-step spin-coating process, which promotes the wettability of the PbBr2 layer and produces the space for growing large perovskite grains. The green high-concentration CsBr/H2O solution is adopted at the second -step spin-coating process, enabling enough CsBr to be deposited by a facile one-step process. By optimizing the content of thiourea, a compact CsPbBr3 perovskite film with a smooth surface, large grains, and high phase purity and crystallinity is formed. Consequently, the fabricated perovskite solar cell with the architecture of FTO/TiO2/ CsPbBr3 film/carbon exhibits a superior performance with a high efficiency of 9.11%. In addition, the unencapsulated device preserves over 90% of its initial efficiency after storage at ambient conditions for 45 days.

    Wenjun Liu, Mengli Liu, Xu Chen, Tao Shen, Ming Lei, Jiangang Guo, Huixiong Deng, Wei Zhang, Chaoqing Dai, Xiaofei Zhang, Zhiyi Wei (2020)Ultrafast photonics of two dimensional AuTe2Se4/3 in fiber lasers, In: Communications physics3(1)15 Springer Nature

    Two dimensional materials can exhibit unique optical properties, making them interesting for new photonic devices and laser sources. Here, the strong optical nonlinearity of AuTe2Se4/3 is exploited to achieve a femtosecond infra-red laser with high stability. The exploration of promising nonlinear optical materials, which allows for the construction of high-performance optical devices in fundamental and industrial applications, has become one of the fastest-evolving research interests in recent decades and plays a key role in the development and innovation of optics in the future. Here, by utilizing the optical nonlinearity of a recently synthesized, two dimensional material AuTe2Se4/3 prepared by the self-flux method, a passively mode-locked fiber laser operating at 1557.53 nm is achieved with 147.7 fs pulse duration as well as impressive stability (up to 91 dB). The proposed mode-locked fiber laser reveals superior overall performance compared with previously reported lasers which are more widely studied in the same band. Our work not only investigates the optical nonlinearity of AuTe2Se4/3, but also demonstrates its ultrafast photonics application. These results may stimulate further innovation and advancement in the field of nonlinear optics and ultrafast photonics.

    Yuanjing Meng, Wei Zhang, Zili He, Chongqing Liu, Jie Gao, Muhammad Akbar, Rui Guo, Shuaitong Zhou, Yuan Ji, Xunying Wang, Yang Yang (2021)Partially reduced Ni0.8Co0.15Al0.05LiO2-δ for low-temperature SOFC cathode, In: International journal of hydrogen energy46(15)pp. 9874-9881 Elsevier Ltd

    Nowadays, Ni0.8Co0.15Al0.05LiO2-δ (NCAL) has been increasingly applied into the solid oxide fuel cell (SOFC) field as a promising electrode material. Here, the performances of NCAL cathode were investigated for low-temperature SOFCs (LT-SOFCs) on Ce0.8Sm0.2O2-δ (SDC) electrolyte. After on-line reduction of NCAL for 30 min, the partially reduced NCAL, i.e., NCAL(r), was employed as the new cathode and its performances were also investigated. The area specific resistances of NCAL and NCAL(r) cathodes on SDC electrolyte are 7.076 and 1.214 Ω cm2 at 550 °C, respectively. Moreover, NCAL(r) exhibits the activation energy of 0.46 eV for oxygen reduction reaction (ORR), which is much lower than that of NCAL (0.88 eV). The fuel cell consisted of NCAL electrodes and SDC electrolyte shows an open circuit voltage (OCV) of 0.95 V and power output of 436 mW cm−2 at 550 °C. After cathode on-line optimization, the cell's OCV and power output are significantly increased to 1.01 V and 648 mW cm−2, which mainly attributed to the accelerated ORR and decreased electrode polarization resistance. These results demonstrate that NCAL(r) is a promising cathode material for LT-SOFCs. [Display omitted] •Partially reduced NCAL was applied as the novel cathode material.•ORR mechanism for NCAL and NCAL(r) cathodes were investigated.•The fuel cell's OCV and Pmax were enhanced to 1.01 V and 648 mW cm−2 at 550 °C.•NCAL(r) showed better ORR activity than NCAL with a lower Ea of 0.46 eV.

    Linlin Duan, Chin‐Te Hung, Jinxiu Wang, Changyao Wang, Bing Ma, Wei Zhang, Yuzhu Ma, Zaiwang Zhao, Chaochao Yang, Tiancong Zhao, Liang Peng, Di Liu, Dongyuan Zhao, Wei Li (2022)Synthesis of Fully Exposed Single‐Atom‐Layer Metal Clusters on 2D Ordered Mesoporous TiO2 Nanosheets, In: Angewandte Chemie (International ed.)61(43)e202211307pp. e202211307-n/a

    A sulfhydryl monomicelles interfacial assembly strategy is presented for the synthesis of fully exposed single‐atom‐layer Pt clusters on 2D mesoporous TiO2 (SAL‐Pt@mTiO2) nanosheets. This synthesis features the introduction of the sulfhydryl group in monomicelles to finely realize the controllable co‐assembly process of Pt precursors within ordered mesostructures. The resultant SAL‐Pt@mTiO2 shows uniform SAL Pt clusters (≈1.2 nm) anchored in ultrathin 2D nanosheets (≈7 nm) with a high surface area (139 m2 g−1), a large pore size (≈25 nm) and a high dispersion (≈99 %). Moreover, this strategy is universal for the synthesis of other SAL metal clusters (Pd and Au) on 2D mTiO2 with high exposure and accessibility. When used as a catalyst for hydrogenation of 4‐nitrostyrene, the SAL‐Pt@mTiO2 shows a high catalytic activity (TOF up to 2424 h−1), 100 % selectivity for 4‐aminostyrene, good stability, and anti‐resistance to thiourea poisoning under relatively mild conditions (25 °C, 10 bar). Fully exposed single‐atom‐layer Pt clusters on 2D mesoporous TiO2 nanosheets have been synthesized by a universal sulfhydryl monomicelles interfacial assembly strategy. The resultant catalyst shows unique chemical state and nanostructures, enabling a high catalytic activity, selectivity, poison tolerance and stability for the hydrogenation of 4‐nitrostyrene.

    Guiqiang Wang, Miao Lei, Weinan Dong, Jieqiong Liu, Wei Zhang (2020)Hierarchical Porous Carbon Arrays Derived from Directly Carbonizing Carex Meyeriana for Counter Electrodes of High-Efficiency Dye-Sensitized Solar Cells, In: Energy & fuels34(7)8905pp. 8905-8910 Amer Chemical Soc

    Hierarchical porous carbon arrays (HPCAs) are facilely produced by directly carbonizing Carex meyeriana through a self-activated and self-template process. The morphology analysis and nitrogen sorption measurements reveal that the obtained HPCAs have a large specific surface area and unique hierarchical pore structure comprising macropore channel arrays and micropores and mesopores developed on the wall of macropore channels. The HPCA electrodes are subsequently prepared by depositing HPCAs to the fluorine-doped tin oxide conductive substrate. Electrochemical tests demonstrate that the HPCA electrode shows a superior electrocatalytic activity for the regeneration of the I-/I-3(-) electrolyte. The superior electrocatalytic activity of HPCA electrodes is mainly due to the combined effect of unique hierarchical pore architecture and large surface area, which facilitates the electrolyte diffusion and provides the abundant effective electrocatalytic active sites. Under 1 sun illumination, the HPCA electrode-based dye-sensitized solar cell displays a gratifying conversion efficiency of 6.45%, which is close to that based on commonly used Pt electrodes.

    Li Wang, Wenfei Liang, Shenglan He, Mengjiao Liu, Yan Zhao, Wei Zhang, Yuanfu Chen, Xin Lai, Jian Bi, Daojiang Gao (2020)Realization of superior electrochemical performances for ZnMoO4 anode material through the construction strategy of 3D flower-like single crystalline, In: Journal of alloys and compounds816152673 Elsevier B.V

    3D flower-like single crystalline ZnMoO4 microcrystals have been constructed via a facile one-step hydrothermal process. The influences of reaction time and reaction temperature on phase purities and morphologies of ZnMoO4 microcrystals have been investigated in detail. The results illustrate that 3D flower-like single crystalline ZnMoO4 microcrystals with mesoporous architecture can be obtained after being hydrothermal treated at 150 °C for 12 h, which can enhance the stability of structure and facilitate the diffusion of lithium ions. When applied as lithium-ion batteries anode materials, they can deliver a high discharge capacity of 514.9 mAh g−1 at a current rate of 1 C after 500 cycles with nearly 92% capacity retention based on the discharge capacity of 2nd cycle. Most importantly, they also present superior electrochemical performances even at high rates (the capacities of 316.2 and 216.9 mAh g−1 even after 2000 cycles at very large current rate of 5 and 10 C, respectively). The electrochemical results further confirm that 3D flower-like single crystalline ZnMoO4 microcrystals possess high capacity, good rate capability and superior cyclic stability. Our work may provide an effective and facile strategy to control the microstructures and boost the electrochemical performances for transition metal molybdate electrode materials. [Display omitted] •3D flower-like single crystalline ZnMoO4 is constructed by a facile hydrothermal strategy.•The effects of time and temperature on microstructures of ZnMoO4 were investigated.•ZnMoO4 exhibits superior cyclic stability and outstanding rate capability.•Excellent electrochemical performances are due to the unique architecture.

    Feng Huo, Wenqiong Li, Yuhang Liu, Xiaohong Liu, Chong-Yew Lee, Wei Zhang (2021)Review of long wavelength luminescent carbon-based nanomaterials: preparation, biomedical application and future challenges, In: Journal of materials science56(4)pp. 2814-2837 Springer US

    Carbon-based luminescent nanomaterials have attracted much attention in the biomedical field. Compared to traditional photoluminescent materials (such as rare earth-based semiconductors and organic dyes), they have excellent biocompatibility, low toxicity, excellent optical stability and site-targeting properties in addition to their low cost and environmentally friendly features. Carbon dots, a typical carbon-based luminescent material, have great application potential in biomedicine, biological imaging and optoelectronics. Actual biological imaging, however, uses low-level photon scattering and light absorption to avoid self-fluorescence by the target tissues, requiring the light waves to have strong tissue penetration ability. Long wavelength (red and near-infrared) is known to have strong tissue penetration. However, carbon dots in the long wavelength region give a low quantum yield. Thus, obtaining long wavelength-emitting carbon dots with high quantum yield is a big challenge in practical bioimaging and phototherapy. In this paper, recent progress in the development of long wavelength, strongly luminescence-emitting carbon dots, the mechanisms and methods to regulate their optical properties and improve their quantum yield are reviewed. Recent applications of carbon dots in biosensing, bioimaging and therapy are described. Finally, the future challenges and prospects of long wavelength carbon-based luminescent materials are discussed. Graphic abstract

    Nanxiang Wang, Wenhui Ji, Lan Wang, Wanxia Wu, Wei Zhang, Qiong Wu, Wei Du, Hua Bai, Bo Peng, Bo Ma, Lin Li (2022)Overview of the structure, side effects, and activity assays of l-asparaginase as a therapy drug of acute lymphoblastic leukemia, In: RSC medicinal chemistry13(2)pp. 117-128

    l-Asparaginase (l-ASNase is the abbreviation, l-asparagine aminohydrolase, E.C. is an enzyme that is clinically employed as an antitumor agent for the treatment of acute lymphoblastic leukemia (ALL). Although l-ASNase is known to deplete l-asparagine (l-Asn), causing cytotoxicity in leukemia cells, the specific molecular signaling pathways are not well defined. Because of the deficiencies in the production and administration of current formulations, the l-ASNase agent in clinical use is still associated with serious side effects, so controlling its dose and activity monitoring during therapy is crucial for improving the treatment success rate. Accordingly, it is urgent to summarize and develop effective analytical methods to detect l-ASNase activity in treatment. However, current reports on these detection methods are fragmented and also have not been systematically summarized and classified, thereby not only delaying the investigations of specific molecular mechanisms, but also hindering the development of novel detection methods. Herein, in this review, we provided a detailed summary of the l-ASNase structures, antitumor mechanism and side effects, and current detection approaches, such as fluorescence assays, colorimetric assays, spectroscopic assays and some other assays. All of them possess unique advantages and disadvantages, so it has been difficult to establish clear criteria for clinical application. We hope that this review will be of some value in promoting the development of l-ASNase activity detection methods.

    Lina Zhang, Xinyu Liu, Xing Zhang, Wei Zhang, Jinwen Ma, Qiushi Wang, Shi Su (2023)Sulfur-doped Sn3O4 nanosheets for improved photocatalytic performance, In: Journal of alloys and compounds961170904 Elsevier B.V

    Sn3O4 has shown great potential in photocatalytic water purification and energy conversion. However, it is still suffering from limited visible light-harvesting ability and sluggish charge-carrier separation. Nonmetal heteroatom doping is considered as an effective strategy to regulate the electronic structure and improve the photocatalytic performance. Herein, S-doped Sn3O4 was synthesized by a simple hydrothermal method using L-cysteine as sulfur source. It was found that the hierarchical flower-like structure of Sn3O4 would be destructed gradually by sulfur (S) doping. Nevertheless, the as-obtained S(1%)-doped Sn3O4 exhibits remarkable improved photocatalytic degradation performance of azo-dye methyl orange (MO) and antibiotic metronidazole (MTZ). S doped on the lattice of Sn3O4 can narrow the band bap to enhance sufficient photoadsorption, facilitate separating the charge carriers and producing the predominant active species (O2·-) compared with pristine Sn3O4 photocatalyst, resulting in the enhancement of MO/MTZ photogradation activity. This work demonstrates a simple route for S doping in Sn3O4 and provide guidance for the controllable design and synthesis of high-efficient photocatalysts by nonmetal heteroatom doping. •S-doped Sn3O4 photocatalyst was fabricated by a one-step hydrothermal process.•The structure and morphology of S-doped Sn3O4 photocatalyst were characterized.•The S-doped Sn3O4 exhibits remarkable improved photocatalytic degradation performance of MO and MTZ.•S dopant narrows the band bap to enhance sufficient photoadsorption, improves separating the charge carriers.

    Tong Tong, Yuquan Gan, Weisheng Li, Wei Zhang, Haizeng Song, Hehe Zhang, Kan Liao, Jie Deng, Si Li, Ziyue Xing, Yu Yu, Yudi Tu, Wenhui Wang, Jinlian Chen, Jing Zhou, Xuefen Song, Linghai Zhang, Xiaoyong Wang, Shuchao Qin, Yi Shi, Wei Huang, Lin Wang (2023)Boosting the Sensitivity of WSe2 Phototransistor via Janus Interfaces with 2D Perovskite and Ferroelectric Layers, In: ACS nano17(1)pp. 530-538 American Chemical Society

    Hybrid systems have recently attracted increasing attention, which combine the special attributes of each constitute and create interesting functionalities through multiple heterointerface interactions. Here, we design a two-dimensional (2D) hybrid phototransistor utilizing Janus-interface engineering, in which the WSe2 channel combines light-sensitive perovskite and spontaneously polarized ferroelectrics, achieving collective ultrasensitive detection performance. The top perovskite (BA2(MA)3Pb4I13) layer can absorb the light efficiently and provide generous photoexcited holes to WSe2. WSe2 exhibit p-type semiconducting states of different degrees due to the selective light-operated doping effect, which also enables the ultrahigh photocurrent of the device. The bottom ferroelectric (Hf0.5Zr0.5O2) layer dramatically decreases the dark current, which should be attributed to the ferroelectric polarization assisted charge trapping effect and improved gate control. As a whole, our phototransistors show excellent photoelectric performances across the ultraviolet to near-infrared range (360–1050 nm), including an ultrahigh ON/OFF current ratio > 109 and low noise-equivalent power of 1.3 fW/Hz1/2, all of which are highly competitive in 2D semiconductor-based optoelectronic devices. In particular, the devices show excellent weak light detection ability, where the distinguishable photoswitching signal is obtained even under a record-low light intensity down to 1.6 nW/cm2, while showing a high responsivity of 2.3 × 105 A/W and a specific detectivity of 4.1 × 1014 Jones. Our work demonstrates that Janus-interface design makes the upper and lower interfaces complement each other for the joint advancement into high-performance optoelectronic applications, providing a picture to realize the integrated engineering on carrier dynamics by light irradiation, electric field, interfacial trapping, and band alignment.

    Lei Yang, Yuping Li, Wei Zhang, Yanlei Liu, Jiacheng Cao, Yang Cao, Jusheng Bao, Zhiwei Wang, Lin Wang, Xiao Huang (2022)Promoting optoelectronic properties of Cs2AgBiBr6 nanocrystals by formation of heterostructures with BiOCl nanosheets, In: Chemical communications (Cambridge, England)58(56)pp. 7765-7768 Royal Soc Chemistry

    Lead halide perovskite nanocrystals and their heterostructures have achieved substantial advances in optoelectronics; however, their inherent material instability and lead toxicity have driven research on alternative material systems. Herein, solution-processable heterostructures composed of lead-free double perovskite Cs2AgBiBr6 nanocrystals and BiOCl nanosheets were prepared through a colloidal synthesis method. Defect states were present in BiOCl and benefited carrier generation, recombination and transport in Cs2AgBiBr6. As a result, the light emission of the Cs2AgBiBr6 nanocrystals was greatly enhanced at low temperatures, and the photodetector based on the Cs2AgBiBr6/BiOCl heterostructure exhibited a much improved on-off ratio compared to the device based on Cs2AgBiBr6 alone. Our work highlights the complex nature and impact of two-dimensional heterostructure assembly on the optoelectronic properties of lead-free double perovskites and demonstrates their great potential toward environmentally friendly optoelectronic devices.

    Among various types of alternative energy devices, solid oxide fuel cells (SOFCs) operating at low temperatures (300‐600°C) show the advantages for both stationary and mobile electricity production. Proton‐conducting oxides as electrolyte materials play a critical role in the low‐temperature SOFCs (LT‐SOFCs). This review summarizes progress in proton‐conducting solid oxide electrolytes for LT‐SOFCs from materials to devices, with emphases on (1) strategies that have been proposed to tune the structures and properties of proton‐conducting oxides and ceramics, (2) techniques that have been employed for improving the performance of the protonic ceramic‐based SOFCs (known as PCFCs), and (3) challenges and opportunities in the development of proton‐conducting electrolyte‐based PCFCs. Protonic ceramic fuel cells have attracted the increased attention in the last 20 years. This review summarizes progress in proton‐conducting solid‐oxide electrolytes for low temperature protonic ceramic fuel cells.

    Kangwei Xu, Supeng Pei, Wei Zhang, Zhiyue Han, Panpan Guan, Li Wang, Yecheng Zou, Han Ding, Xiaojuan Ma, Caidi Xu, Feng Liu, Yongming Zhang (2023)Ce (III)-terephthalic acid metal-organic frameworks as highly efficient ·OH radical scavengers for fuel cells and investigation of its antioxidation mechanism, In: Materials today energy31101195 Elsevier Ltd

    Herein, in order to relieve the chemical degradation of perfluorosulfonic acid (PFSA) membranes without decreasing their proton conductivity, Ce (III)-terephthalic acid metal-organic frameworks (Ce-TPA MOFs) with efficient ·OH radical scavenging efficiency are designed via coordinating the organic antioxidant ligand (TPA) with inorganic radical scavenger (Ce ions). Ce-TPA MOFs with a different weight ratio of 0.5, 1.0, or 2.0% was introduced in PFSA matrix to produce composite membranes. On the one hand, the hydrophilic groups of Ce-TPA MOFs caused better water absorption, which promoted the proton conduction to some extent. Also, the presence of the redox Ce3+/Ce4+ couple, oxygen vacancy, and TPA molecules in Ce-TPA MOFs scavenging ·OH radical together via synergy effect. The optimum peak power density of the PFSA/Ce-TPA1.0 composite membrane at 75 °C under 80% relative humidity was 1086 mW/cm that of pristine PFSA membrane was only 1032 mW/cm. Furthermore, PFSA/Ce-TPA1.0 composite membrane experienced the decay of only 0.31 mV/h during 96 h operation under the same conditions, whereas that of pristine PFSA membrane was 2.20 mV/h. Thus, the PFSA/Ce-TPA membrane was a potential candidate for proton exchange membrane fuel cells. [Display omitted] •Improve chemical durability of the proton exchange membrane by doping with Ce (Ⅲ)-terephthalic acid metal-organic frameworks (Ce-TPA MOFs).•Ce-TPA MOFs can eliminate ·OH radical by the synergy effect of terephthalic acid and redox Ce3+/Ce4+ couple.•Introduction of Ce-TPA MOFs to proton exchange membrane led to improved power density.•Optimized composite membrane (0.31 mV/h) showed much lower open-circuit voltage degradation than pristine perfluorosulfonic acid (2.20 mV/h).

    Yan Sun, Yao Yin, Mike Pols, Jingxian Zhong, Zhen Huang, Bowen Liu, Jinqiu Liu, Wei Wang, Hongguang Xie, Guixiang Zhan, Zishu Zhou, Wei Zhang, Pengcheng Wang, Chenyang Zha, Xiaohong Jiang, Yinjie Ruan, Chao Zhu, Geert Brocks, Xiaoyong Wang, Lin Wang, Jianpu Wang, Shuxia Tao, Wei Huang (2020)Engineering the Phases and Heterostructures of Ultrathin Hybrid Perovskite Nanosheets, In: Advanced materials (Weinheim)32(34)2002392pp. e2002392-n/a Wiley

    Low-dimensional perovskites have gained increasing attention recently, and engineering their material phases, structural patterning and interfacial properties is crucial for future perovskite-based applications. Here a phase and heterostructure engineering on ultrathin perovskites, through the reversible cation exchange of hybrid perovskites and efficient surface functionalization of low-dimensional materials, is demonstrated. Using PbI(2)as precursor and template, perovskite nanosheets of varying thickness and hexagonal shape on diverse substrates is obtained. Multiple phases, such as PbI2, MAPbI(3)and FAPbI(3), can be flexibly designed and transformed as a single nanosheet. A perovskite nanosheet can be patterned using masks made of 2D materials, fabricating lateral heterostructures of perovskite and PbI2. Perovskite-based vertical heterostructures show strong interfacial coupling with 2D materials. As a demonstration, monolayer MoS2/MAPbI(3)stacks give a type-II heterojunction. The ability to combine the optically efficient perovskites with versatile 2D materials creates possibilities for new designs and functionalities.

    Zhaohua Zhu, Chao Zhu, Lei Yang, Qian Chen, Linghai Zhang, Jie Dai, Jiacheng Cao, Shaoyu Zeng, Zeyi Wang, Zhiwei Wang, Wei Zhang, Jusheng Bao, Lijuan Yang, Yang Yang, Bo Chen, Chunyang Yin, Hong Chen, Yang Cao, Hao Gu, Jiaxu Yan, Nana Wang, Guichuan Xing, Hai Li, Xiaoyong Wang, Shaozhou Li, Zheng Liu, Hua Zhang, Lin Wang, Xiao Huang, Wei Huang (2022)Room-temperature epitaxial welding of 3D and 2D perovskites, In: Nature materials21(9)pp. 1042-1049 NATURE PORTFOLIO

    Formation of epitaxial heterostructures via post-growth self-assembly is important in the design and preparation of functional hybrid systems combining unique properties of the constituents. This is particularly attractive for the construction of metal halide perovskite heterostructures, since their conventional solution synthesis usually leads to non-uniformity in composition, crystal phase and dimensionality. Herein, we demonstrate that a series of two-dimensional and three-dimensional perovskites of different composition and crystal phase can form epitaxial heterostructures through a ligand-assisted welding process at room temperature. Using the CsPbBr3/PEA(2)PbBr(4) heterostructure as a demonstration, in addition to the effective charge and energy transfer across the epitaxial interface, localized lattice strain was observed at the interface, which was extended to the top layer of the two-dimensional perovskite, leading to multiple new sub-bandgap emissions at low temperature. Given the versatility of our strategy, unlimited hybrid systems are anticipated, yielding composition-, interface- and/or orientation-dependent properties. Heterostructures combine the unique properties of each constituent, improving the efficiency and stability of perovskite-based optoelectronic devices, yet the films suffer from poor compositional and structural uniformity. Here, the authors demonstrate a ligand-assisted welding process to fabricate a series of epitaxial 2D and 3D perovskite heterostructures.

    Guiqiang Wang, Jieqiong Liu, Miao Lei, Wei Zhang, Ge Zhu (2020)Optimizing the substrate pre-heating and post-annealing temperatures for fabricating high-performance carbon-based CsPbIBr2 inorganic perovskite solar cells, In: Electrochimica acta349136354 Elsevier

    Carbon-based CsPbIBr2 inorganic perovskite solar cells (PSCs) have emerged as one of the most promising photovoltaic devices owing to their excellent stability and simple fabrication process. Nevertheless, the efficiency of state-of-the-art carbon-based CsPbIBr2 PSCs is far from satisfactory due to the poor quality of CsPbIBr2 perovskite film. Herein, we prepare the high-quality CsPbIBr2 perovskite film through a one-step spin-coating method by optimizing both the substrate pre-heating temperature and the post-annealing temperature. The optimization of the substrate pre-heating and post-annealing temperatures greatly improves the coverage and crystallinity of CsPbIBr2 perovskite films, leading to enhanced light harvest and suppressed charge recombination. With the CsPbIBr2 perovskite film prepared at the optimized substrate pre-heating and post-annealing temperatures, the fabricated carbon-based CsPbIBr2 PSC with a simple structure of FTO/TiO2/CsPbIBr2/carbon exhibits a gratifying conversion efficiency of 8.10% with a high open-circuit voltage of 1.27 V. Moreover, the fabricated carbon-based CsPbIBr2 PSC without any encapsulation shows an excellent long-term stability under ambient condition. (c) 2020 Elsevier Ltd. All rights reserved.

    Junyi Feng, Guanzhao Wen, Rong Hu, Jun Peng, Hong Lu, Ningjiu Zhao, Xianshao Zou, Wei Zhang (2023)The Role of Energy Offsets on Charge Photogeneration Dynamics in Y-Series Molecules-Based Polymer Solar Cells, In: Solar RRL7(16)2300372

    Recent research has revealed that low-energy offset polymer solar cells (PSCs) are capable of a power conversion efficiency of over 19%. However, it is unclear how energy offsets and the charge photogeneration process are correlated. Herein, the effect of energy offsets on charge photogeneration dynamics for Y-series molecules (Y5, Y6, Y10, and BTP-4F-12)-based PSCs with the variations of the lowest unoccupied molecular orbital energy offsets (ΔELUMO) of 0.11–0.42 eV and the highest occupied molecular orbital energy offsets (ΔEHOMO) of 0.08–0.23 eV utilizing steady-state and time-resolved spectroscopies is studied. The steady-state measurement shows that the probability of photoluminescence quenching via energy transfer for the donor exciton reduces with the increasing ΔELUMO. It is found that even in PM6:Y6 with the highest ΔELUMO, ≈18% of PM6 exciton dissociated via the path of “energy transfer first and then hole transfer,” manifesting the energy transfer also plays a vital role in the process of exciton dissociation. Furthermore, it is found that the PM6 exciton can efficiently dissociate under the ΔELUMO of 0.11 eV. After photoexcitation of the Y-series molecule acceptors, the exciton dissociation efficiency enhances with the increase of ΔEHOMO. Besides, the higher energy offsets, the lower charge recombination rate in the ultrafast timescale has been found from the transient absorption measurement. These findings reveal that energy offsets are important for charge photogeneration and recombination in an ultrafast timescale for Y-series molecule-based PSCs, which may shed light on the design of high-performance PSCs.

    Dongli Lu, Wei Zhang, Lars Kloo, Liubov Belova (2021)Inkjet-Printed Electron Transport Layers for Perovskite Solar Cells, In: Materials14(24)7525 Mdpi

    Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO2, SrTiO3, and SnO2 were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO2 and SrTiO3 nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO3-based devices, mixed mesoporous SrTiO3/TiO2 ETLs were also investigated. In addition, inkjet-printed SnO2 thin films were fabricated by using a cosolvent system and the effect of the SnO2 ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO2 and SrTiO3 ETLs, the SnO2-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.

    Wei Zhang, Hao Chen, Lina Zhang, Shan Zhang, Enlai Dong, Jinwen Ma, Shichong Xu, Haibo Li, Guiqiang Wang (2020)A facile hydrothermal approach for the deposition of CaIn2S4 hierarchical nanosheet films for photocatalytic application, In: Journal of alloys and compounds821153545 Elsevier B.V

    In this paper, CaIn2S4 films with vertically aligned and interconnected hierarchical nanosheets were directly fabricated on tin-doped indium oxide (ITO) substrate via a facile hydrothermal process with no additional directing agent. The crystal structure, morphology and optical properties of the obtained CaIn2S4 films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–vis spectra. The results revealed the successful synthesis of uniform CaIn2S4 hierarchical nanosheet films on ITO substrate with a whole thickness of about 3 μm and an average nanosheet thickness of about 20 nm, with the band gap of 2.17 eV. A possible mechanism for the formation of CaIn2S4 films in hydrothermal process has been proposed. The CaIn2S4 hierarchical nanosheet films exhibited a photocurrent density of approximate 0.2 mA cm−2 at 0.82 V (vs. NHE) in a neutral solution. In addition, the CaIn2S4 films also exhibited superior photocatalytic activity for methyl orange and 1-naphthol. This study provided a green and facile method for the synthesis of high-quality CaIn2S4 films applied in photocatalytic water splitting and photodegradation of organic pollutant. •Hierarchical nanosheet CaIn2S4 films were fabricated by a hydrothermal process.•The CaIn2S4 films exhibited good PEC performance in a neutral solution.•The CaIn2S4 films demonstrated good MO and 1-naphthol degradation activity.•The structural and morphological properties of CaIn2S4 films were characterized.

    Wei Zhang, Yun Hang Hu (2023)Recent progress in design and fabrication of SOFC cathodes for efficient catalytic oxygen reduction, In: Catalysis today409pp. 71-86 Elsevier

    Solid oxide fuel cells (SOFCs) are highly promising energy conversion devices. However, the performance and efficiency of current SOFC devices are still limited by inadequate oxygen reduction activity in the cathode, which has been recognized as a great challenge for SOFCs to achieve high power output at low operating temperatures. This has stimulated intensive efforts to develop more efficient cathodes for enhanced catalytic oxygen reduction. This article reviews recent advances in design and fabrication of cathodes for efficient SOFCs, with emphasis on (1) engineering cathode microstructures, (2) fabrication techniques to prepare cathode layers, and (3) strategies to address segregation and poisoning issues.

    Ziyang Xia, Wei Zhang, Cheng Chen, Yawei Miao, Xingdong Ding, Linqin Wang, Mengde Zhai, Ming Cheng (2022)Low-cost star-shaped hole-transporting materials with isotropic properties and its application in perovskite solar cells, In: Dyes and pigments207110695 Elsevier Ltd

    The development of new hole-transporting materials (HTMs) with high hole mobility, suitable molecular configuration and low cost is of profound significance for the enhancement of the photovoltaic performance of perovskite solar cells (PSCs) and the advancement of industrialization. In this work, we have designed and synthesized a highly efficient and low-cost HTM of star-shaped carbazole (MPTCZ-FNP), which has isotropic, multi-channel hole transport properties. As the results show, MPTCZ-FNP has suitable energy levels, good hole transport properties, good film formation and hydrophobicity. According to the results, the efficiency of the mesoporous n-i-p structured PSCs prepared using MPTCZ-FNP material is up to 20.27%, which is higher than that of the traditional HTM Spiro-OMeTAD of 18.35%. Therefore, the present work has designed and synthesized a three-dimensional star-shaped HTM, which provides a reference for the design of subsequent highly efficient HTMs. •A low-cost star shaped hole transporting material MPTCZ-FNP is reported.•MPTCZ-FNP presented high hole mobility and suitable energy level arrangement.•The MPTCZ-FNP based perovskite solar cell obtains efficiency of 20.27%.

    Ping Zhang, Lina Zhang, Enlai Dong, Xing Zhang, Wei Zhang, Qiushi Wang, Shichong Xu, Haibo Li (2021)Synthesis of CaIn2S4/TiO2 heterostructures for enhanced UV–visible light photocatalytic activity, In: Journal of alloys and compounds885161027 Elsevier B.V

    •CaIn2S4/TiO2 nanocomposites were fabricated by a two-step hydrothermal process.•The structure and morphology of CaIn2S4/TiO2 heterostructures were characterized.•The CaIn2S4/TiO2 heterostructures exhibited efficient MO degradation activity.•The possible Z-scheme photocatalytic reaction mechanism was revealed. Semiconductor heterostructures are regarded as an efficient way to improve the photocatalytic activity. Herein, novel Z-scheme CaIn2S4 (CIS)/TiO2 heterostructures photocatalysts were synthesized by a simple two-step hydrothermal approach. Compared with single phase nanostructures of TiO2 and CIS, the CIS/TiO2-0.05 g nanocomposites exhibited efficient and stable photocatalytic activity, with 97% of methyl orange (MO) decomposed within 30 min under UV–visible light irradiation. In addition to increased broad light absorption, the outstanding photocatalytic performance is mainly attributed to intimate contact and matched energy band positions between CIS and TiO2, which efficiently produce more active electrons and holes, reduce the photogenerated electron-hole recombination, and boost photoinduced charge carrier transfer. The possible Z-scheme mechanism for the photocatalytic reaction in the system was reasonably proposed. This work would arouse an increasing interest in designing more Z-scheme heterojunction photocatalysts with high efficiency for the application of photodegradation.

    Hanrui Su, Wei Zhang, Yun Hang Hu (2022)Carbonate-superstructured solid fuel cells with hydrocarbon fuels, In: Proceedings of the National Academy of Sciences - PNAS119(41)e2208750119pp. e2208750119-e2208750119

    A basic requirement for solid oxide fuel cells (SOFCs) is the sintering of electrolyte into a dense impermeable membrane to prevent the mixing of fuel and oxygen for a sufficiently high open-circuit voltage (OCV). However, herein, we demonstrate a different type of fuel cell, a carbonate-superstructured solid fuel cell (CSSFC), in which in situ generation of superstructured carbonate in the porous samarium-doped ceria layer creates a unique electrolyte with ultrahigh ionic conductivity of 0.17 S⋅cm −1 at 550 °C. The CSSFC achieves unprecedented high OCVs (1.051 V at 500 °C and 1.041 V at 550 °C) with methane fuel. Furthermore, the CSSFC exhibits a high peak power density of 215 mW⋅cm −2 with dry methane fuel at 550 °C, which is higher than all reported values of electrolyte-supported SOFCs. This provides a different approach for the development of efficient solid fuel cells.

    Rui-Qing Li, Suyuan Zeng, Bin Sang, Chaozhuang Xue, Konggang Qu, Yu Zhang, Wei Zhang, Guangyu Zhang, Xinghui Liu, Jie Deng, Olivier Fontaine, Yachao Zhu (2023)Regulating electronic structure of porous nickel nitride nanosheet arrays by cerium doping for energy-saving hydrogen production coupling hydrazine oxidation, In: Nano research16(2)pp. 2543-2550 Tsinghua University Press

    Water electrolysis for energy-efficient H 2 production coupled with hydrazine oxidation reaction (HzOR) is prevailing, while the sluggish electrocatalysts are strongly hindering its scalable application. Herein, we schemed a novel porous Ce-doped Ni 3 N nanosheet arrays grown on nickel foam (Ce-Ni 3 N/NF) as a remarkable bifunctional catalyst for both hydrogen evolution reaction and HzOR. Significantly, the overall hydrazine splitting system can achieve low cell voltages of 0.156 and 0.671 V at 10 and 400 mA·cm −2 , and the system is remarkably stable to operate over 100 h continuous test at the high-current-density of 400 mA·cm −2 . Various characterizations prove that the porous nanosheet arrays expose more active sites, and more excellent diffusion kinetics and lower charge-transfer resistance, therefore boosting catalytic performance. Furthermore, density functional theory calculation reveals that the incorporation of Ce can effectively optimize the free energy of hydrogen adsorption and promote intrinsic catalytic activity of Ni 3 N.

    Xiaohui Jing, Lin Chang, Lixia Shi, Xiaohong Liu, Yuan Zhao, Wei Zhang (2020)Au Film-Au@Ag Core-Shell Nanoparticle Structured Surface-Enhanced Raman Spectroscopy Aptasensor for Accurate Ochratoxin A Detection, In: ACS applied bio materials3(4)2385pp. 2385-2391 Amer Chemical Soc

    As a powerful toxin that could cause fatal death, the detection of ochratoxin A (OTA) has gained much attention in the fields of environmental and food sciences. In this study, an internal standard (IS) aptasensor was synthesized through a facile and scalable method to enhance the sensitivity and quantativity of OTA detection. The substrates were formed through hybridization of modified aptamers on Au@Ag core-shell nanoparticles (NPs) and Au films at a silicon surface. Incorporated with 4-ATP and 4-NTP as an internal standard, OTA recognition of such aptamers could cause NP release and signal losses. Utilizing the strong peaks at 1078 and 1335 cm(-1), which represent 4-ATP and 4-NTP, respectively, the intensity ratio of I-1078/I-1335 could delegate the OTA concentration in a ratiometric manner. Therefore, the highest ratio of I-1078/I-1335 represents the lowest concentration of OTA, and a lower ratio means a higher OTA concentration. Quantitatively, the high consistency for OTA detection was achieved through correction of signal losses by IS references with an R-2 of 0.993 and RSD of 0.94%, and the OTA detection limit of 5 pM was achieved. Herein, such an IS aptasensor provides a reliable and scalable detection platform for various molecules in a continuous and high-throughput manner and holds great promise in future quantitative SERS measurements.

    Jie Deng, Wei Zhang, Xu Dai, Yu Yu, Zhifeng Li, Wei Wang, Lin Wang, Jing Zhou, Xiaoshuang Chen (2022)Nonmonotonic wavelength dependence of the polarization-sensitive infrared photoresponse of an anisotropic semimetal, In: Nanoscale14(19)pp. 7314-7321

    Layered semimetals with in-plane anisotropy are promising for advanced polarization-sensitive infrared detection. The investigation of the polarization-dependent photoresponse of semimetals over the whole visible-to-long-wave-infrared range and revealing the physical connection between their optoelectronic properties, optical properties, and electronic band structures is required, but there have been very few studies of this kind. In this work, we conducted a thorough investigation on the polarization-dependent infrared photoresponse of WTe over the visible-to-long-wave-infrared range and discovered a textbook-like perfect consistency between the wavelength-dependent polarization-sensitive photoresponse and the anisotropic dielectric constant mainly affected by interband transitions near the Weyl point. It is revealed that the polarization sensitivity and the responsivity both vary non-monotonically with the wavelength. This phenomenon is attributed to the polarization selective excitation of interband transitions associated with asymmetrically distributed electron orbitals around the Weyl points. Concerning the infrared detection properties of WTe , a maximum responsivity of 0.68 mA W is obtained under self-powered operation. The power dependence of the photoresponse is linear, and the response time is around 14 μs. This work would provoke further studies about the anisotropic photoresponse associated with the transitions even closer to the Dirac or Weyl points, and it provides an approach to select the right semimetal for the right wavelength range of infrared polarization detection.

    Shan Jiang, Lin Chang, Jie Luo, Jianfa Zhang, Xiaohong Liu, Chong-Yew Lee, Wei Zhang (2021)Fabrication of a honeycomb-like bimetallic SERS substrate for the detection of triphenyltin chloride, In: Analyst (London)146(20)6170pp. 6170-6177

    Triphenyltin chloride (TPhT) is an organotin compound that causes intensive toxicological risk to the environment and humans. A detection method with high sensitivity and stability is therefore desired to better detect TPhT. In this study, a novel SERS substrate was prepared by sputtering an ultra-thin Au layer on a honeycomb-like silver nanoarray fabricated via the nanosphere lithography method. The ultra-thin Au layer was formed by sputtering the intermittent Au nanoparticles on the silver nanoarray, resulting in bimetallic coupling with dramatically increased hotspots and extremely high SERS enhancement with an analytical enhancement factor (AEF) of 6.08 × 10 9 using Rhodamine 6G (R6G) as the probe molecule. Based on density functional theory (DFT) simulations, the Raman characteristic peaks of TPhT at 999 cm −1 and 655 cm −1 were selected for TPhT detection. The AEF of the SERS substrate HC5-AgAu was calculated to be 3.38 × 10 6 with the detection concentration of TPhT down to 10 −10 M. The as-prepared honeycomb-like silver–gold bimetallic SERS substrate demonstrated great stability and sensitivity for TPhT detection, which might also be applied in monitoring many other environmental pollutants.

    Jieqiong Liu, Miao Lei, Wei Zhang, Guiqiang Wang (2020)A multifunctional CuSCN interlayer in carbon electrode-based CsPbIBr(2)all-inorganic perovskite solar cells for boosting the efficiency and stability, In: Sustainable energy & fuels4(8)pp. 4249-4256 Royal Soc Chemistry

    Carbon electrode-based all-inorganic perovskite solar cells (PSCs) without hole-transport materials are attracting extensive interest due to their low cost, simple fabrication process, and high stability. Nevertheless, the conversion efficiency of carbon electrode-based PSCs is far from satisfactory owing to serious charge recombination at the inorganic perovskite/carbon interface, which mainly derives from the mismatched energy level between the inorganic perovskite film and carbon layer. Herein, a hydrophobic CuSCN film is introduced into carbon electrode-based CsPbIBr(2)all-inorganic PSCs as a multifunctional interlayer between the CsPbIBr(2)perovskite film and carbon electrode to form a favorable interfacial energy level alignment and protect the CsPbIBr(2)perovskite from ambient moisture. It is found that introducing a CuSCN interlayer can not only enhance the hole extraction and suppress the charge recombination in carbon electrode-based CsPbIBr(2)all-inorganic PSCs, but also improve the stability of the cell. Moreover, the very strong interaction between SCN(-1)and Pb(2+)remarkably reduces the surface defects of the CsPbIBr(2)perovskite film. Consequently, the device with the CuSCN interlayer displays an improved power conversion efficiency of 7.30% in comparison with 5.19% for the device without the CuSCN interlayer and an excellent long-term stability under the ambient conditions.

    Xing Wu, Yixuan Wu, Shichu Peng, Liangang Xiao, Zijie Xiao, Wei Zhang, Guoxing Ren, Yonggang Min, Yi Liu (2023)Layer‐by‐Layer‐Processed Organic Solar Cells with 18.02% Efficiency Enabled by Regulating the Aggregation of Bottom Polymers, In: Solar RRL7(11)2300136

    The fabrication of organic solar cells (OSCs) by a layer‐by‐layer (LBL) method has attracted growing attention in recent years. As already known, the pre‐aggregates of conjugated polymers in solution have a profound impact on their microstructure morphology in films. Herein, by simply controlling the solution temperature and annealing processes, the pre‐aggregation behavior of D18 polymer in solution can be fine‐tuned and the microstructure of D18 bottom layer is well manipulated. The optimized D18 bottom layer can effectively regulate L8‐BO upper‐layer‐forming suitable networks for efficient charge transportation. In addition, a vertical phase separation with a special D/D:A/A structure ( P ‐i‐N‐type component distribution) is also formed. As a result, compared to the 16.43% power conversion efficiency (PCE) of the bulk heterojunction devices, such control enables bilayer OSC devices based on the polymer D18 and L8‐BO to deliver an enhanced PCE of 18.02% with simultaneously improved short‐circuit current density, open‐circuit voltage, and fill factor. It is also demonstrated in these results that the LBL deposition process utilizing the pre‐aggregation of polymer and its fiber‐network‐forming ability is a very promising approach to improve charge dynamics, suppress carrier recombination, and fabricate highly efficient OSCs.

    Bin Liu, Huiliang Sun, Jin-Woo Lee, Jie Yang, Junwei Wang, Yongchun Li, Bangbang Li, Meng Xu, Qiaogan Liao, Wei Zhang, Dongxue Han, Li Niu, Hong Meng, Bumjoon J. Kim, Xugang Guo (2021)Achieving highly efficient all-polymer solar cells by green-solvent-processing under ambient atmosphere, In: Energy & environmental science14(8)pp. 4499-4507 Royal Soc Chemistry

    All-polymer solar cells (all-PSCs) exhibiting superior device stability and mechanical robustness have attracted considerable interest. Emerging polymerized small-molecule acceptors (PSMAs) have promoted the progress of all-PSCs exceeding a power conversion efficiency (PCE) of 14%. However, most of the all-PSCs are processed with halogenated solvents that are hazardous towards humans and the environment. Herein, halogen-free processing solvents of CS2, 1,2,4-TMB and o-XY are utilized for producing eco-friendly and highly efficient all-PSCs. In particular, o-XY solvent-processed all-PSCs achieve a high PCE of 15.6%, which is among the highest values in green-solvent-processed all-PSCs to date. Detailed investigations reveal that such enhancement is mainly attributed to the optimal blend morphology and polymer crystalline structures, which is resulted from aggregated structures of polymers formed in o-XY. Importantly, o-XY-processed-all-PSCs are successfully fabricated in ambient conditions, affording a high PCE approaching 15.0%. This work highlights the importance of green solvent strategy in controlling the polymer aggregated structures and blend film morphology of all-PSCs, paving the way towards high-performance and eco-friendly all-PSCs for practical applications.

    Shuaixing Li, Jianghua Wu, Binxi Liang, Luhao Liu, Wei Zhang, Nasrullah Wazir, Jian Zhou, Yuwei Liu, Yuefeng Nie, Yufeng Hao, Peng Wang, Lin Wang, Yi Shi, Songlin Li (2022)Antiferromagnetic alpha-MnTe: Molten-Salt-Assisted Chemical Vapor Deposition Growth and Magneto-Transport Properties, In: Chemistry of materials34(2)pp. 873-880 Amer Chemical Soc

    Antiferromagnetic (AF) materials are attracting increasing interest for research in magnetic physics and spintronics. Here, we report a controllable synthesis of room-temperature AF alpha-MnTe nanocrystals (Ne ' el temperature similar to 307 K) via the molten-salt-assisted chemical vapor deposition method. The growth kinetics are investigated regarding the dependence of flake dimension and macroscopic shape on growth time and temperature. The high crystalline quality and atomic structure are confirmed by various crystallographic characterization means. Cryogenic magneto-transport measurements reveal anisotropic magnetoresistance (MR) response and complicated dependence of MR on temperature, owing to the subtle competition among multiple scattering mechanisms of thermally excited magnetic disorders (magnon drag), magnetic transition, and thermally populated lattice phonons. Overall positive MR behavior with two transitions in magnitude is observed when out-of-plane external magnetic field (B) is applied, while a transition from negative to positive MR response is recorded when in-plane B is applied. The rich magnetic transport properties render alpha-MnTe a promising material for exploiting functional components in magnetic devices.

    Jinfa Chang, Guanzhi Wang, Wei Zhang, Yang Yang (2022)Atomically dispersed catalysts for small molecule electrooxidation in direct liquid fuel cells, In: Journal of energy chemistry68pp. 439-453 Elsevier

    Direct liquid fuel cells (DLFCs) have received increasing attention because of their high energy densities, instant recharging abilities, simple cell structure, and facile storage and transport. The main challenge for the commercialization of DLFCs is the high loading requirement of platinum group metals (PGMs) as cat-alysts. Atomically dispersed catalysts (ADCs) have been brought into recent focus for DLFCs due to their well-defined active sites, high selectivity, maximal atom-utilization, and anti-poisoning property. In this review, we summarized the structure-property relationship for unveiling the underlying mechanisms of ADCs for DLFCs. More specifically, different types of fuels used in DLFCs such as methanol, formic acid, and ethanol were discussed. At last, we highlighted current challenges, research directions, and future outlooks towards the practical application of DLFCs.(c) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

    Yuehui Yan, Heng Dai, Jiankun Li, Chuang Wang, Wei Zhang, Ge zhu (2023)Narrow-band green-emitting Cs3ZnCl5: Mn2+ phosphors with abnormal thermal quenching, In: Journal of luminescence258119821 Elsevier B.V

    Compounds with Cs3CoCl5 structure usually exhibit a large Debay temperature with a large band gap, which has been considered as new host materials for WLED application. Oxide materials of the Cs3CoCl5 structure have great luminescence characteristics, thus it is more worthwhile to research Cl-based materials with higher electronegativity. Here, an Mn2+ activated Cs3ZnCl5 narrow band green emitting phosphor was developed and investigated in detail. Ternary alkaline chloride Cs3ZnCl5 was successfully prepared by a coprecipitation method. XRD refinement, SEM and XPS have proved the successful preparation of Cs3ZnCl5: 6%Mn2+ with a single phase. The electronic structure investigation clearly states that Cs3ZnCl5 has a large band gap with Eg∼4.467 eV. The Cs3ZnCl5: 6%Mn2+ phosphor can also generate green light with a peak wavelength of 525 nm and a fullwidth at half-maximum (FWHM) of 47 nm when excited by blue light at 451 nm. The luminescent property, as well as the concentration-dependent emission decay behavior of Cs3ZnCl5: 6%Mn2+ at room temperature, were studied. Over the temperature range of 30–120 °C, the thermal quenching performance of Cs3ZnCl5: 6%Mn2+ was investigated, and the related mechanism was discussed through thermoluminescence analysis. Electron traps transmit energy to the Mn2+ luminescence center after 120 °C, which will increase the emission intensity. Finally, a blue light-pumped white LED was constructed using this phosphor in combination with commercially available red phosphors. The findings above suggested that Cs3ZnCl5: 6%Mn2+ could be served as a potential green-emitting phosphor for white light-emitting diodes. •The Cs3ZnCl5: Mn2+ phosphors are successful prepared.•The abnormal thermal quenching have been discussed in detail.•The Cs3ZnCl5: Mn2+ phosphors have a green emitting at 525 nm.•The Cs3ZnCl5: Mn2+ phosphors can be used in WLEDs.

    Barbora Laskova, Marketa Zukalova, Ladislav Kavan, Alison Chou, Paul Liska, Wei Zhang, Liu Bin, Pavel Kubat, Elham Ghadiri, Jacques E. Moser, Michael Grätzel (2012)Voltage enhancement in dye-sensitized solar cell using (001)-oriented anatase TiO2 nanosheets, In: Journal of Solid State Electrochemistry16(9)pp. 2993-3001 Springer Verlag

    A nanocrystalline TiO2 (anatase) nanosheet exposing mainly the (001) crystal faces was tested as photoanode material in dye-sensitized solar cells. The nanosheets were prepared by hydrothermal growth in HF medium. Good-quality thin films were deposited on F-doped SnO2 support from the TiO2 suspension in ethanolic or aqueous media. The anatase (001) face adsorbs a smaller amount of the used dye sensitizer (C101) per unit area than the (101) face which was tested as a reference. The corresponding solar cell with sensitized (001)-nanosheet photoanode exhibits a larger open-circuit voltage than the reference cell with (101)-terminated anatase nanocrystals. The voltage enhancement is attributed to the negative shift of flatband potential for the (001) face. This conclusion rationalizes earlier works on similar systems, and it indicates that careful control of experimental conditions is needed to extract the effect of band energetic on the current/voltage characteristics of dye-sensitized solar cell.

    T Kreouzis, R Baldwin, M Shkunov, I McCulloch, M Heeney, W Zhang (2005)High Mobility Ambipolar Charge Transport in a Cross-Linked Reactive Mesogen at Room Temperature, In: Applied Physics Letters87(17)
    R Sheng, MT Hörantner, Z Wang, Y Jiang, Wei Zhang, A Agosti, S Huang, X Hao, A Ho-Baillie, M Green, HJ Snaith (2017)Monolithic Wide Band Gap Perovskite/ Perovskite Tandem Solar Cells with Organic Recombination Layers, In: Journal of Physical Chemistry C121(49)pp. 27256-27262 American Chemical Society

    We demonstrate a monolithic tandem solar cell by sequentially depositing a higher-bandgap (2.3 eV) CH3NH3PbBr3 sub-cell and a lower-bandgap (1.55 eV) CH3NH3PbI3 sub-cell bandgap perovskite cells, in conjugation with a solution-processed organic charge carrier recombination layer, which serves to protect the underlying sub-cell and allows for voltage addition of the two sub-cells. Owing to the low-loss series connection, we achieve a large open-circuit voltage of 1.96 V. Through optical and electronic modelling, we estimate the feasible efficiency of this device architecture to be 25.9 %, achievable with integrating a best-in-class CH3NH3PbI3 sub cell and a 2.05 eV wide bandgap perovskite cell with an optimised optical structure. Compared to previous reported all-perovskite tandem cells, we solely employ Pb-based perovskites, which although have wider band gap than Sn based perovskites, are not at risk of instability due to the unstable charge state of the Sn2+ ion. Additionally, the bandgap combination we use in this study could be an advantage for triple junction cells on top of silicon. Our findings indicate that wide band gap all-perovskite tandems could be a feasible device structure for higher efficiency perovskite thin-film solar cells.

    Samuel D. Stranks, Pabitra K. Nayak, Wei Zhang, Thomas Stergiopoulos, Henry J. Snaith (2015)Formation of Thin Films of Organic-Inorganic Perovskites for High-Efficiency Solar Cells, In: Angewandte Chemie International Edition54(11)pp. 3240-3248 Wiley

    Organic–inorganic perovskites are currently one of the hottest topics in photovoltaic (PV) research, with power conversion efficiencies (PCEs) of cells on a laboratory scale already competing with those of established thin-film PV technologies. Most enhancements have been achieved by improving the quality of the perovskite films, suggesting that the optimization of film formation and crystallization is of paramount importance for further advances. Here, we review the various techniques for film formation and the role of the solvents and precursors in the processes. We address the role chloride ions play in film formation of mixed-halide perovskites, which is an outstanding question in the field. We highlight the material properties that are essential for high-efficiency operation of solar cells, and identify how further improved morphologies might be achieved.

    Michael Saliba, Kwan Wee Tan, Hiroaki Sai, David T. Moore, Trent Scott, Wei Zhang, Lara A. Estroff, Ulrich Wiesner, Henry J. Snaith (2014)Influence of Thermal Processing Protocol upon the Crystallization and Photovoltaic Performance of Organic–Inorganic Lead Trihalide Perovskites, In: The Journal of Physical Chemistry C118(30)pp. 17171-17177 American Chemical Society

    We investigate the thermally induced morphological and crystalline development of methylammonium lead mixed halide perovskite (CH3NH3PbI3–xClx) thin films and photovoltaic device performance with meso-superstructured and planar heterojunction architectures. We observe that a short rapid thermal annealing at 130 °C leads to the growth of large micron-sized textured perovskite domains and improved the short circuit currents and power conversion efficiencies up to 13.5% for the planar heterojunction perovskite solar cells. This work highlights the criticality of controlling the thin film crystallization mechanism of hybrid perovskite materials for high-performing photovoltaic applications.

    Miguel Anaya, Gabriel Lozano, Mauricio E. Calvo, Wei Zhang, Michael B. Johnston, Henry J. Snaith, Hernán Míguez (2014)Optical Description of Mesostructured Organic–Inorganic Halide Perovskite Solar Cells, In: The Journal of Physical Chemistry Letters6(1)pp. 48-53 American Chemical Society

    Herein we describe both theoretically and experimentally the optical response of solution-processed organic–inorganic halide perovskite solar cells based on mesostructured scaffolds. We develop a rigorous theoretical model using a method based on the propagation of waves in layered media, which allows visualizing the way in which light is spatially distributed across the device and serves to quantify the fraction of light absorbed by each medium comprising the cell. The discrimination between productive and parasitic absorption yields an accurate determination of the internal quantum efficiency. State-of-the-art devices integrating mesoporous scaffolds infiltrated with perovskite are manufactured and characterized to support the calculations. This combined experimental and theoretical analysis provides a rational understanding of the optical behavior of perovskite cells and can be beneficial for the judicious design of devices with improved performance. Notably, our model justifies the presence of a solid perovskite capping layer in all of the highest efficiency perovskite solar cells based on thinner mesoporous scaffolds.

    W Zhang, MK Lei, S Silva, L Johnson (2012)The effect of plasma modification on the sheet resistance of nylon fabrics coated with carbon nanotubes, In: Applied Surface Science258(20)pp. 8209-8213 Elsevier

    Low-pressure oxygen and argon plasmas were used to pre-treat nylon fabrics, and the modified fabrics, together with the raw fabrics, were subsequently coated with single walled carbon nanotubes (SWCNTs) by a dip-drying process. Scanning electron microscopy (SEM) and Raman spectroscopy analyses indicated the attachment of SWCNTs onto nylon fabrics. After the coating with SWCNTs, the plasma modified fabrics exhibited sheet resistance of as low as 2.0 kΩ/sq. with respect to 4.9 kΩ/sq. of the raw fabrics, presumably owing to the increase of fibre surface roughness incurred by the plasma modification, which is evidenced by SEM analyses. Fourier transform infrared spectroscopy (FTIR) analysis indicates the incorporation of oxygen functionalities on fibre surfaces in the plasma modification. This is responsible for the variation of the electrical conductance of SWCNT-coated fabrics with the type of plasma and the duration of plasma ablation. © 2012 Elsevier B.V. All rights reserved.

    Simone Guarnera, Antonio Abate, Wei Zhang, Jamie M. Foster, Giles Richardson, Annamaria Petrozza, Henry J. Snaith (2017)Improving the Long-Term Stability of Perovskite Solar Cells with a Porous Al2O3 Buffer Layer, In: The Journal of Physical Chemistry Letters6(3)pp. 432-437 American Chemical Society

    Hybrid perovskites represent a new paradigm for photovoltaics, which have the potential to overcome the performance limits of current technologies and achieve low cost and high versatility. However, an efficiency drop is often observed within the first few hundred hours of device operation, which could become an important issue. Here, we demonstrate that the electrode’s metal migrating through the hole transporting material (HTM) layer and eventually contacting the perovskite is in part responsible for this early device degradation. We show that depositing the HTM within an insulating mesoporous “buffer layer” comprised of Al2O3 nanoparticles prevents the metal electrode migration while allowing for precise control of the HTM thickness. This enables an improvement in the solar cell fill factor and prevents degradation of the device after 350 h of operation.

    Vlad Stolojan, L McCafferty, Simon King, Wei Zhang, S Haq, Ravi Silva (2015)Decoration of multiwalled carbon nanotubes with protected iron nanoparticles, In: Carbon84pp. 47-55 Elsevier

    A method to simultaneously synthesize carbon-encapsulated magnetic iron nanoparticles (Fe-NPs) and attach these particles to multi-walled carbon nanotubes (MWCNT) is presented. Thermal decomposition of cyclopentadienyliron dicarbonyl dimer [(C5H5)(2)Fe-2(CO)(4)], over a range of temperatures from 250 degrees C to 1200 degrees C, results in the formation of Fe-NPs attached to MWCNT. At the same time, a protective carbon shell is produced and surrounds the Fe-NPs, covalently attaching the particles to the MWCNT and leading to resistance to acid dissolution. The carbon coating varies in degree of graphitisation, with higher synthesis temperatures leading to a higher degree of graphitisation. The growth model of the nanoparticles and subsequent mechanism of MWCNT attachment is discussed. Adsorption potential of the hybrid material towards organic dyes (Rhodamine B) has been displayed, an indication of potential uses as a material for water treatment. The material has also been electrospun into aligned nanocomposite fibres to produce a soft magnetic composite (SMC) with future applications in sensors and fast switching solenoids.

    David T. Moore, Hiroaki Sai, Kwan W. Tan, Detlef-M. Smilgies, Wei Zhang, Henry J. Snaith, Ulrich Wiesner, Lara A. Estroff (2015)Crystallization Kinetics of Organic–Inorganic Trihalide Perovskites and the Role of the Lead Anion in Crystal Growth, In: Journal of the American Chemical Society137(6)pp. 2350-2358 American Chemical Society

    Methylammonium lead halide perovskite solar cells continue to excite the research community due to their rapidly increasing performance which, in large part, is due to improvements in film morphology. The next step in this progression is control of the crystal morphology which requires a better fundamental understanding of the crystal growth. In this study we use in situ X-ray scattering data to study isothermal transformations of perovskite films derived from chloride, iodide, nitrate, and acetate lead salts. Using established models we determine the activation energy for crystallization and find that it changes as a function of the lead salt. Further analysis enabled determination of the precursor composition and showed that the primary step in perovskite formation is removal of excess organic salt from the precursor. This understanding suggests that careful choice of the lead salt will aid in controlling crystal growth, leading to superior films and better performing solar cells.

    W Zhang, SRP Silva (2010)Raman and FT-IR studies on dye-assisted dispersion and flocculation of single walled carbon nanotubes, In: SPECTROCHIM ACTA A77(1)pp. 175-178 PERGAMON-ELSEVIER SCIENCE LTD

    Aqueous suspensions of single walled carbon nanotubes (SWCNTs) were prepared with the aid of dye molecules to form thermodynamically stable colloidal systems. By adding sodium chloride electrolyte, SWCNTs flocculated and settled out due to the destabilization of colloidal systems initiated by the increase in ionic strength. The dye molecules were removed by heat treatment at 300 degrees C for 5 h following washing with water. Raman spectroscopy was used to monitor the whole procedure. The resulting spectra confirm the non-deconstructive dispersion and flocculation of SWCNTs and the complete removal of the dye molecules; Fourier transform infrared spectroscopy also confirms this. (c) 2010 Elsevier B.V. All rights reserved.

    W Zhang, SRP Silva (2012)Alter the sheet resistance of carbon nanotube-coated cellulose fabric with argon plasma pretreatment, In: MICRO & NANO LETTERS7(8)pp. 850-853 INST ENGINEERING TECHNOLOGY-IET
    D Luo, W Yang, Z Wang, A Sadhanala, Q Hu, R Su, R Shivanna, G Trindade, John Watts, Z Xu, T Liu, K Chen, F Ye, P Wu, L Zhao, J Wu, Y Tu, Y Zhang, X Yang, Wei Zhang, R Friend, Q Gong, H Snaith, R Zhu (2018)Enhanced photovoltage for inverted planar heterojunction perovskite solar cells, In: Science360(6396)pp. 1442-1446 American Association for the Advancement of Science

    The highest power conversion efficiencies (PCEs) reported for perovskite solar cells (PSCs) with inverted planar structures are still inferior to those of PSCs with regular structures, mainly because of lower open-circuit voltages (Voc). Here we report a strategy to reduce nonradiative recombination for the inverted devices, based on a simple solution-processed secondary growth technique. This approach produces a wider bandgap top layer and a more n-type perovskite film, which mitigates nonradiative recombination, leading to an increase in Voc by up to 100 millivolts. We achieved a high Voc of 1.21 volts without sacrificing photocurrent, corresponding to a voltage deficit of 0.41 volts at a bandgap of 1.62 electron volts. This improvement led to a stabilized power output approaching 21% at the maximum power point.

    W Zhang, CW Wu, YY Tan, SRP Silva (2012)Functionalisation of nylon with carbon nanotubes to make thermally stable fabric and wearable capacitor, In: MICRO & NANO LETTERS7(3)pp. 193-195 INST ENGINEERING TECHNOLOGY-IET
    W Zhang, YY Tan, C Wu, SRP Silva (2012)Self-assembly of single walled carbon nanotubes onto cotton to make conductive yarn, In: Particuology10(4)pp. 517-521 Elsevier

    A simple, economical and scalable technique is demonstrated to make conductiveyarn. Singlewalledcarbonnanotubes (SWCNTs) are non-covalently functionalized with dye (Acid Red 91) and dispersed in water; while cottonyarn is treated with poly (ethylene imine). When the resulting yarn is immersed in the SWCNT dispersion, SWCNTs self-assemble onto the yarn due to electrostatic forces between the functionalized nanotubes and yarn. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicate the assembly of carbonnanotubes. The SWCNT functionalized yarn exhibits reasonable electrical conduction behaviour and are then used to make chemiresistors. The electrical resistance of the chemiresistors used as sensors increases on exposure to ammonia gas, which can be explained in terms of electron transfer between gas molecules and SWCNTs.

    Lioz Etgar, Wei Zhang, Stefanie Gabriel, Stephen G. Hickey, Md K. Nazeeruddin, Alexander Eychmüller, Bin Liu, Michael Grätzel (2012)High Efficiency Quantum Dot Heterojunction Solar Cell Using Anatase (001) TiO2Nanosheets, In: Advanced Materials24(16)pp. 2202-2206 Royal Society of Chemistry

    This is the first report of using anatase TiO2 nanosheets with exposed (001) facets in a high-efficiency PbS quantum dot/TiO2 heterojunction solar cell. The TiO2 nanosheets have higher conduction band, and surface energy compared to normal anatase (101) TiO2 nanoparticles. This PbS QD/TiO2 heterojunction solar cell produces power conversion efficiency of 4.7% which is one of the highest reported in literature.

    Wei Zhang, R. Zhu, S. Ramakrishna (2011)Low-Cost Fabrication of TiO2 Nanorod Photoelectrode for Dye-sensitized Solar Cell Application, In: AUSTRALIAN JOURNAL OF CHEMISTRY64(9)pp. 1282-1287 CSIRO PUBLISHING

    One-dimensional nanostructured semiconductor oxides that can provide a direct electron conduction pathway have received increasing attention as photoelectrodes in dye-sensitized solar cells. In this study, a facile and cost-effective method to produce high-quality TiO2 nanofibres is developed based on an electrospinning technique. In particular, poly(ethylene oxide) was selected and proved to be an excellent matrix polymer for electrospinning owing to its low decomposition temperature, wide availability, and environmental friendliness. In addition to obtaining TiO2 nanofibres with well-controlled morphology and pure anatase, the TiO2 grain size could be easily tuned by changing the preparation conditions. Based on the synthesized TiO2 nanofibres, dye-sensitized solar cells were fabricated and a high energy conversion efficiency of 6.44 % was achieved under illumination with air mass 1.5 (100 mW cm–2) simulated sunlight, which demonstrates the great potential of the synthesized TiO2 nanofibres as efficient photoelectrode material for low-cost dye-sensitized solar cells.

    Michael Saliba, Wei Zhang, Victor M. Burlakov, Samuel D. Stranks, Yao Sun, James M. Ball, Michael B. Johnston, Alain Goriely, Ulrich Wiesner, Henry J. Snaith (2015)Plasmonic-Induced Photon Recycling in Metal Halide Perovskite Solar Cells, In: Advanced Functional Materials25(31)pp. 5038-5046 WILEY-V C H VERLAG GMBH

    Organic–inorganic metal halide perovskite solar cells have emerged in the past few years to promise highly efficient photovoltaic devices at low costs. Here, temperature-sensitive core–shell Ag@TiO2 nanoparticles are successfully incorporated into perovskite solar cells through a low-temperature processing route, boosting the measured device efficiencies up to 16.3%. Experimental evidence is shown and a theoretical model is developed which predicts that the presence of highly polarizable nanoparticles enhances the radiative decay of excitons and increases the reabsorption of emitted radiation, representing a novel photon recycling scheme. The work elucidates the complicated subtle interactions between light and matter in plasmonic photovoltaic composites. Photonic and plasmonic schemes such as this may help to move highly efficient perovskite solar cells closer to the theoretical limiting efficiencies.

    Wei Zhang, Michael Saliba, Samuel D. Stranks, Yao Sun, Xian Shi, Ulrich Wiesner, Henry J. Snaith (2013)Enhancement of Perovskite-Based Solar Cells Employing Core–Shell Metal Nanoparticles, In: Nano Letters13(9)pp. 4505-4510 American Chemical Society

    Recently, inorganic and hybrid light absorbers such as quantum dots and organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured organometal halide perovskite solar cells incorporating core–shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.

    RJ Baldwin, T Kreouzis, M Shkunov, M Heeney, W Zhang, I McCulloch (2007)A comprehensive study of the effect of reactive end groups on the charge carrier transport within polymerized and nonpolymerized liquid crystals, In: JOURNAL OF APPLIED PHYSICS101(2)ARTN 0pp. ?-? AMER INST PHYSICS
    Wei Zhang, Rui Zhu, Bin Liu, Seeram Ramakrishna (2012)High-performance hybrid solar cells employing metal-free organic dye modified TiO2 as photoelectrode, In: Applied Energy90(1)pp. 305-308 Elsevier

    High-performance TiO2–polythiophene hybrid solar cells are reported. Metal-free organic dye (D102) is employed to modify the TiO2/polythiophene interface. Results indicate that interfacial engineering and dye engineering are crucial for device performance.

    Zsolt Podolyak, B. Cederwall, X. Liu, O. Aktas, A. Ertoprak, W. Zhang, C. Qi, E. Clement, G. de France, D. Ralet, A. Gadea, A. Goasduff, G. Jaworski, I. Kuti, B.M. Nyako, J. Nyberg, M. Palacz, R. Wadsworth, J.J Valiente-Dobon, H. Al-Azri., A. Atac Nyberg, T. Back, G. de. Angelis, M. Doncel, J. Dudouet, A. Gottardo, M. Juardo, J. Ljunvall, D. Mengoni, D.R Napoli, C.M Petrache, D. Sohler, J. Timar, D. Barrientos, P. Bednarczyk, G. Benzoni, B. Birkenbach, A.J Boston, H.C Boston, I. Burrows, L. Charles, M. Ciemala, F.C.L Crespi, D.M Cullen, P. Desesquelles, C. Domingo-Pardo, J. Eberth, N. Erduran, S. Erturk, V. Gonzalez, J. Goupil, H. Hess, T. Huyuk, A. Jungclaus, W. Korten, A. Lemasson, S. Leoni, A. Maj, R. Menegazzo, B. Million, R.M Perez-Vidal, Zsolt Podolyak, A. Pullia, F. Recchia, P. Reiter, F. Saillant, M.D Salsac, E. Sanchis, J. Simpson, O. Stezowski, Ch. Theisen, M. Zielinska (2020)Isospin properties of nuclear pair correlations from the level structure of the self-conjugate nucleus 88Ru, In: Physical Review Society American Physical Society

    The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide 88 44Ru44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in 88Ru were populated via the 54Fe(36Ar; 2n )88Ru fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. The observed -ray cascade is assigned to 88Ru using clean prompt - -2-neutron coincidences in anti-coincidence with the detection of charged particles, conrming and extending the previously assigned sequence of low-lying excited states. It is consistent with a moderately deformed rotating system exhibiting a band crossing at a rotational frequency that is significantly higher than standard theoretical predictions with isovector pairing, as well as observations in neighboring N > Z nuclides. The direct observation of such a ____delayed" rotational alignment in a deformed N = Z nucleus is in agreement with theoretical predictions related to the presence of strong isoscalar neutron-proton pair correlations.

    Wei Zhang, Rui Zhu, Feng Li, Qing Wang, Bin Liu (2011)High-Performance Solid-State Organic Dye Sensitized Solar Cells with P3HT as Hole Transporter, In: Journal of Physical Chemistry C115(14)pp. 7038-7043 American Chemical Society

    Solid-state dye sensitized solar cells (SDSCs) with a power conversion efficiency of 3.85% have been fabricated using an organic indoline dye D131 as the sensitizer and poly(3-hexylthiophene) (P3HT) as the hole transporter, which represent one of the most efficient SDSCs using polymeric hole transporter. UV−vis and the incident photon-to-current conversion efficiency (IPCE) spectra indicate that P3HT almost only acts as the hole transporter to regenerate oxidized D131 and has little contribution to the photocurrent. Impedance spectroscopy is further employed to investigate charge transport and recombination kinetics in these cells. The electron diffusion length (Ln) is found to be obviously larger than TiO2 film thickness, resulting in efficient charge collection. However, the hole conductivity in P3HT is 1 order of magnitude lower than electron conductivity in TiO2, leading to relatively poor fill factors. This work represents the first systematic study of charge transport and recombination in SDSCs using conjugated polymer hole transporter, which sheds light on understanding the operation of highly efficient solid-state devices.

    Wei Zhang (2019)Nanomaterials in Dye-Sensitized Solar Cells, In: Feng Gao (eds.), Advanced Nanomaterials for Solar Cells and Light Emitting Diodespp. 69-95 Elsevier Inc

    Exploring clean and renewable energy resources is a key driver for the sustainable development of human society. Among the various clean energy techniques, photovoltaic (PV) solar cells present an ideal solution that can ultimately solve the energy problem without too much environmental burden. Dye-sensitized solar cells (DSSCs) are a promising third-generation PV technology that takes advantages of low material cost and relatively high performance. The compatibility of fabrication processes with the flexible substrates and roll-to-roll production greatly enhances the promise of DSSCs toward industrial applications. Several key parameters for their commercialization, such as device efficiency and long-term stability, have been rigorously evaluated through academic and industrial collaborations, which give us more confidence in the bright future of this new technology. During the advancement of DSSCs, nanomaterials play a key role in device performance enhancement and the development of new concepts. In this chapter, we will rationalize these exacting achievements regarding the innovations of nanomaterials at various length scales for DSSC applications, and discuss the prospective pathways toward highly efficient and stable DSSCs for their real applications.

    Wei Zhang, Yueming Cheng, Xiong Yin, Bin Liu (2011)Solid-State Dye-Sensitized Solar Cells with Conjugated Polymers as Hole-Transporting Materials, In: Macromolecular Chemistry and Physics212(1)pp. 15-23 Wiley-VCH Verlag

    DSCs are a promising alternative to conventional silicon-based solar cells owing to their low cost and relatively high efficiency. However, the utilization of a liquid electrolyte containing the iodine/iodide redox couple in traditional DSCs brings practical problems for their long-term application, which leads to rapid development of SDSCs based on inorganic p-type semiconductors or organic HTMs. In this review, we summarize the current research on SDSCs using conjugated polymer as HTM. Special attention is paid to understand the effects of polymer HTM structure and deposition process on SDSC performance. The limiting factors for SDSC energy conversion efficiency are discussed and strategies to improve device performance are proposed.

    Wei Zhang, R. Zhu, L. Ke, X. Liu, B. Liu, S. Ramakrishna (2017)Anatase Mesoporous TiO2 Nanofibers with High Surface Area for Solid-State Dye-Sensitized Solar Cells, In: SMALL6(19)pp. 2176-2182 WILEY-V C H VERLAG GMBH

    Mesoporous nanofibers (NFs) with a high surface area of 112 m2/g have been prepared by electrospinning technique. The structures of mesoporous NFs and regular NFs are characterized and compared through scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies. Using mesoporous TiO2 NFs as the photoelectrode, solid-state dye-sensitized solar cells (SDSCs) have been fabricated employing D131 as the sensitizer and P3HT as the hole transporting material to yield an energy conversion efficiency (η) of 1.82%. A Jsc of 3.979 mA cm−2 is obtained for mesoporous NF-based devices, which is 3-fold higher than that (0.973 mA cm−2) for regular NF-based devices fabricated under the same condition (η = 0.42%). Incident photon-to-current conversion efficiency (IPCE) and dye-desorption test demonstrate that the increase in Jsc is mainly due to greatly improved dye adsorption for mesoporous NFs as compared to that for regular NFs. In addition, intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy (IMVS) measurements indicate that the mesopores on NF surface have very minor effects on charge transport and collection. Initial aging test proves good stability of the fabricated devices, which indicates the promise of mesoporous NFs as photoelectrode for low-cost SDSCs.

    Wei Zhang, Rui Zhu, Xizhe Liu, Bin Liu, Seeram Ramakrishna (2009)Facile construction of nanofibrous ZnO photoelectrode for dye-sensitized solar cell applications, In: Applied Physics Letters95(4) AIP Publishing

    A facile method to prepare nanofibrous ZnO photoelectrodes with tunable thicknesses by electrospinning is reported. A “self-relaxation layer” is formed spontaneously between ZnO nanofibers and fluorine-doped SnO 2 (FTO) substrate, which facilitates the release of interfacial tensile stress during calcination, resulting in good adhesion of ZnO film to FTO substrate. Dye-sensitized solar cells (DSSCs) based on the nanofibrous ZnO photoelectrodes are fabricated and an energy conversion efficiency of 3.02% is achieved under irradiation of AM 1.5 simulated sunlight with a power density of 100 mW cm −2, which shows good promise of electrospun nanofibrous ZnO as the photoelectrode in DSSCs.

    Q Hu, L Zhao, J Wu, K Gao, D Luo, Y Jiang, Z Zhang, C Zhu, E Schaible, A Hexemer, C Wang, Y Liu, Wei Zhang, M Grätzel, F Liu, TP Russell, R Zhu, Q Gong (2017)In-Situ Dynamic Observations of Perovskite Crystallization and Microstructure Evolution Intermediated from [PbI6]4- Cage Nanoparticles, In: Nature Communications815688 Nature Publishing Group

    Hybrid lead halide perovskites have emerged as high-performance photovoltaic materials with their extraordinary optoelectronic properties. In particular, the remarkable device efficiency is strongly influenced by the perovskite crystallinity and the film morphology. Here, we investigate the perovskites crystallization kinetics and growth mechanism in real time from liquid precursor continually to the final uniform film. We utilize some advanced in-situ characterization techniques including synchrotron-based grazing incident X-ray diffraction to observe crystal structure and chemical transition of perovskites. The nano-assemble model from perovskite intermediated [PbI6]4- cage nanoparticles to bulk polycrystals is proposed to understand perovskites formation at a molecular- or nano-level. A crystallization-depletion mechanism is developed to elucidate the periodic crystallization and the kinetically trapped morphology at a mesoscopic level. Based on these in-situ dynamics studies, the whole process of the perovskites formation and transformation from the molecular to the microstructure over relevant temperature and time scales is successfully demonstrated.

    Wei Zhang, Sandeep Pathak, Nobuya Sakai, Thomas Stergiopoulos, Pabitra K. Nayak, Nakita K. Noel, Amir A. Haghighirad, Victor M. Burlakov, Dane W. deQuilettes, Aditya Sadhanala, Wenzhe Li, Liduo Wang, David S. Ginger, Richard H. Friend, Henry J. Snaith (2015)Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells, In: Nature Communications6 Nature Publishing Group

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I−, and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.

    I McCulloch, C Bailey, K Genevicius, M Heeney, M Shkunov, D Sparrowe, S Tierney, W Zhang, R Baldwin, T Kreouzis, JW Andreasen, DW Breiby, MM Nielsen (2006)Designing solution-processable air-stable liquid crystalline crosslinkable semiconductors, In: PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES364(1847)pp. 2779-2787 ROYAL SOC
    Victoria Ferguson, S. Ravi P. Silva, Wei Zhang (2019)Carbon Materials in Perovskite Solar Cells: Prospects and Future Challenges, In: Energy and Environmental Materials2(2)pp. 107-118 Wiley

    Metal halide perovskite solar cells are emerging candidates for next‐generation thin‐film photovoltaic devices with the potential for extremely low fabrication cost and high power conversion efficiency. Perovskite solar cells have demonstrated a rapid development in device performance over the last decade, from an initial 3.81% to a most recently certified 24.2%, though the challenges of long‐term stability and lead toxicity still remain. Carbon materials, ranging from zero‐dimensional carbon quantum dots to three‐dimensional carbon black materials, are promising candidates for the enhancement of both efficiency and stability of perovskite solar cells, offering unique advantages for incorporation into various device architectures. In this review article, we present a concise overview of important and exciting advancements of perovskite solar cells that incorporate different dimensions of carbon material in their device architectures in an effort to simultaneously improve device performance and long‐term stability. We also discuss the major advantages and potential challenges of each technique that has been developed in the most recent work. Finally, we outline the future opportunities toward more efficient and stable perovskite solar cells utilizing carbon materials.

    L Zhao, D Luo, J Wu, Qiang Huang, Wei Zhang, Ke Chen, T Liu, L Liu, Y Zhang, F Lui, T Russell, HJ Snaith, R Zhu, Q Gong (2016)High-Performance Inverted Planar Heterojunction Perovskite Solar Cells Based on Lead Acetate Precursor with Efficiency Exceeding 18%, In: Advanced Functional Materials26(20)pp. 3508-3514 Wiley

    Organic–inorganic lead halide perovskites are emerging materials for the next-generation photovoltaics. Lead halides are the most commonly used lead precursors for perovskite active layers. Recently, lead acetate (Pb(Ac)2) has shown its superiority as the potential replacement for traditional lead halides. Here, we demonstrate a strategy to improve the efficiency for the perovskite solar cell based on lead acetate precursor. We utilized methylammonium bromide as an additive in the Pb(Ac)2 and methylammonium iodide precursor solution, resulting in uniform, compact and pinhole-free perovskite films. We observed enhanced charge carrier extraction between the perovskite layer and charge collection layers and delivered a champion power conversion efficiency of 18.3% with a stabilized output efficiency of 17.6% at the maximum power point. The optimized devices also exhibited negligible current density–voltage (J–V) hysteresis under the scanning conditions.

    A McGlashon, KS Whitehead, DDC Bradley, AJ Campbell, W Zhang, M Heeney, DM Smilgies, M Shkunov, K Genevicius, A Amassian, GG Malliaras, A Amassian (2017)Spectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystals, In: Current Applied Physics

    3′-methyl-(5,5′′-bis[3-ethyl-3-(6-phenyl-hexyloxymethyl)-oxetane])-2,2′:5′,2′′-terthiophene (5T(Me)Ox) is a solution processable small molecule semiconductor displaying smectic-C and nematic liquid crystal phases. The pendant oxetane group can be polymerized in situ in the presence of a suitable photoacid at concentrations ≥1% by weight. Spin-coated films of pure 5T(Me)Ox and 5T(Me)Ox doped with the soluble photoacid were characterized by absorption and photoluminescent spectroscopy. Thick pristine films showed absorption and emission from a crystalline phase. Thin monolayer (

    W Zhang, X Zuo, D Zhang, C Wu, SRP Silva, S Ravi Pradip Silva (2016)Cr3+ substituted spinel ferrite nanoparticles with high coercivity, In: NANOTECHNOLOGY27(24)ARTN 24570 IOP PUBLISHING LTD
    Wei Zhang, Miguel Anaya, Gabriel Lozano, Mauricio E. Calvo, Michael B. Johnston, Hernán Míguez, Henry J. Snaith (2015)Highly Efficient Perovskite Solar Cells with Tunable Structural Color, In: Nano Letters15(3)pp. 1698-1702 American Chemical Society

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold within the photoactive layer of an opaque perovskite solar cell following a bottom-up approach employing inexpensive and scalable liquid processing techniques. The photovoltaic devices presented herein show high efficiency with tunable color across the visible spectrum. This now imbues the perovskite solar cells with highly desirable properties for cladding in the built environment and encourages design of sustainable colorful buildings and iridescent electric vehicles as future power generation sources.

    Wei Zhang, Zhen Fang, Mingjuan Su, Mark Saeys, Bin Liu (2009)A Triphenylamine-Based Conjugated Polymer with Donor-π-Acceptor Architecture as Organic Sensitizer for Dye-Sensitized Solar Cells, In: Macromolecular Rapid Communications30(18)pp. 1533-1537 Wiley-VCH Verlag

    A conjugated polymer containing an electron donating backbone (triphenylamine) and an electron accepting side chain (cyanoacetic acid) with conjugated thiophene units as the linkers has been synthesized. Dye-sensitized solar cells (DSSCs) are fabricated utilizing this material as the dye sensitizer, resulting a typical power conversion efficiency of 3.39% under AM 1.5 G illumination, which represents the highest efficiency for polymer dye-sensitized DSSCs reported so far. The results show the good promise of conjugated polymers as sensitizers for DSSC applications.

    Julien Warnan, Yann Pellegrin, Errol Blart, Fabrice Odobel, Wei Zhang, Bin Liu, Veluru Jagadeesh Babu, Seeram Ramakrishna (2011)Application of Poly(3-hexylthiophene) Functionalized with an Anchoring Group in Dye-sensitized Solar Cells, In: Macromolecular rapid communications32(15)pp. 1190-1194 Wiley-VCH Verlag

    A series of three poly(3-hexylthiophene) functionalized either with a cyanoacetic acid (CA) or a rhodanine-3-acetic acid anchoring groups were synthesized and characterized. The TiO2 based dye-sensitized solar cells have been fabricated and performances were tested. We show that shorter chain length (15 thiophene units) linked to CA binding group gives good performances as Jsc, Voc, FF and η(%) were 6.93(mA · cm−2), 0.65(V), 0.67 and 3.02%, respectively. A maximum IPCE of ≈50% at 500 nm was recorded with a liquid electrolyte, under AM 1.5 simulated solar irradiance.

    Xizhe Liu, Wei Zhang, Satoshi Uchida, Liping Cai, Bin Liu, Seeram Ramakrishna (2010)An Efficient Organic-Dye-Sensitized Solar Cell with in situ Polymerized Poly(3,4-ethylenedioxythiophene) as a Hole-Transporting Material, In: Advanced Materials22(20)pp. E150-E155 Wiley

    In situ polymerized PEDOT is used as hole-transporting material to fabricate dye-sensitized solar cells (DSSCs) with an average efficiency of 6.1% (under 100 mW cm−2 AM1.5 illumination) using organic D149 dye as the sensitizer. By comparing with Z907-based devices, the excellent light response of D149-sensitized DSSCs is attributed to the broad light absorption, low photoelectron recombination, and good polymer penetration.

    Wei Zhang, Michael Saliba, David T. Moore, Sandeep K. Pathak, Maximilian T. Hörantner, Thomas Stergiopoulos, Samuel D. Stranks, Giles E. Eperon, Jack A. Alexander-Webber, Antonio Abate, Aditya Sadhanala, Shuhua Yao, Yulin Chen, Richard H. Friend, Lara A. Estroff, Ulrich Wiesner, Henry J. Snaith (2015)Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells, In: Nature Communications6

    To date, there have been a plethora of reports on different means to fabricate organic– inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.

    Guy L. Whitworth, Jonathan R. Harwell, David N. Miller, Gordon J. Hedley, Wei Zhang, Henry J. Snaith, Graham A. Turnbull, Ifor D. W. Samuel (2016)Nanoimprinted distributed feedback lasers of solution processed hybrid perovskites, In: Optics Express24(21)pp. 23677-23684 Optical Society of America

    Hybrid perovskite materials have considerable potential for light emitting devices such as LEDs and lasers. We combine solution processed CH3NH3PbI3 perovskite with UV nanoimprinted polymer gratings to fabricate distributed feedback (DFB) lasers. The lead acetate deposition route is shown to be an effective method for fabricating low-loss waveguides (loss coefficient ~6 cm-1) and highly compatible with the polymer grating substrates. The nanoimprinted perovskite exhibited single-mode band-edge lasing, confirmed by angle-dependent transmission measurements. Depending on the excitation pulse duration the lasing threshold shows a value of 110 μJ/cm2 under nanosecond pumping and 4 μJ/cm2 under femtosecond pumping. We demonstrate further that this laser has excellent stability with a lifetime of 108 pulses.

    Lijing Zhang, Maximilian T. Hörantner, Wei Zhang, Qingfeng Yan, Henry J. Snaith (2016)Near-neutral-colored semitransparent perovskite films using a combination of colloidal self-assembly and plasma etching, In: Solar Energy Materials and Solar Cells160pp. 193-202 Elsevier

    Organo-lead-halide perovskite based solar cells have achieved remarkable advancements in power conversion efficiencies (PCEs) in recent years. Given their attractive properties, possible applications for perovskites are wide ranging and among others, particularly appealing for building integrated photovoltaics (BIPVs). In this study, patterned perovskite films were successfully fabricated based on a microsphere lithography SiO2 honeycomb scaffold template, which was derived by a combination of air-water interface self-assembly and O2 plasma etching. These patterned perovskite films exhibited near-neutral-color and tunable semitransparency, which meet the requisites of semitransparent solar cells for BIPVs application. O2 plasma etching of the microsphere template could effectively improve the active layer average visible transmission (AVT), and the existence of the SiO2 nanoscaffold effectively smoothed the internal trade-off of active layer AVT and device PCE. Solar cell devices fabricated with these optimized patterened perovskite films yielded a maximum PCE of 10.3% with relatively high active layer AVT of 38%. This nanoscaffold patterned perovskite opens up a new strategy for design and fabrication of functional photoelectric device based on organo-lead-halide perovskite.

    Ke Chen, Qin Hu, Tanghao Liu, Lichen Zhao, Deying Luo, Jiang Wu, Yifei Zhang, Wei Zhang, Feng Liu, Thomas P. Russell, Rui Zhu, Qihuang Gong (2016)Charge-Carrier Balance for Highly Efficient Inverted Planar Heterojunction Perovskite Solar Cells, In: Advanced Materials28(48)pp. 10718-10724 Wiley

    The charge-carrier balance strategy by interface engineering is employed to optimize the charge-carrier transport in inverted planar heterojunction perovskite solar cells. N,N-Dimethylformamide-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and poly(methyl methacrylate)-modified PCBM are utilized as the hole and electron selective contacts, respectively, leading to a high power conversion efficiency of 18.72%.

    Sai Bai, Nobuya Sakai, Wei Zhang, Zhiping Wang, Jacob T.-W. Wang, Feng Gao, Henry J. Snaith (2016)Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites, In: Chemistry of Materials29(1)pp. 462-473 American Chemical Society

    Metal halide perovskites have been demonstrated as one of the most promising materials for low-cost and high-performance photovoltaic applications. However, due to the susceptible crystallization process of perovskite films on planar substrates and the high sensitivity of the physical and optoelectronic nature of the internal interfaces within the devices, researchers in different laboratories still experience poor reproducibility in fabricating efficient perovskite solar cells with planar heterojunction device structures. In this methods paper, we present detailed information on the reagents, equipment, and procedures for the fabrication of planar perovskite solar cells in both “regular” n-i-p and “inverted” p-i-n architectures based on one-step solution-processed methylammonium lead triiodide (MAPbI3) perovskite films. We discuss key parameters affecting the crystallization of perovskite and the device interfaces. This methods paper will provide a guideline for the reproducible fabrication of planar heterojunction solar cells based on MAPbI3 perovskite films. We believe that the shared experience on MA-based perovskite films and planar solar cells will be also useful for the optimization process of perovskites with varied compositions and other emerging perovskite-based optoelectronic devices.

    MM Ramli, W Zhang, SRP Silva, SJ Henley (2012)Dye-assisted dispersion of single-walled carbon nanotubes for solution fabrication of NO2 sensors, In: AIP ADVANCES2(3)ARTN 0pp. ?-? AMER INST PHYSICS
    Deying Luo, Lichen Zhao, Jiang Wu, Qin Hu, Yifei Zhang, Zhaojian Xu, Yi Liu, Tanghao Liu, Ke Chen, Wenqiang Yang, Wei Zhang, Rui Zhu, Qihuang Gong (2017)Dual-Source Precursor Approach for Highly Efficient Inverted Planar Heterojunction Perovskite Solar Cells, In: Advanced Materials29(19)1604758 Wiley

    The highest efficiencies reported for perovskite solar cells so far have been obtained mainly with methylammonium and formamidinium mixed cations. Currently, high-quality mixed-cation perovskite thin films are normally made by use of antisolvent protocols. However, the widely used “antisolvent”-assisted fabrication route suffers from challenges such as poor device reproducibility, toxic and hazardous organic solvent, and incompatibility with scalable fabrication process. Here, a simple dual-source precursor approach is developed to fabricate high-quality and mirror-like mixed-cation perovskite thin films without involving additional antisolvent process. By integrating the perovskite films into the planar heterojunction solar cells, a power conversion efficiency of 20.15% is achieved with negligible current density–voltage hysteresis. A stabilized power output approaching 20% is obtained at the maximum power point. These results shed light on fabricating highly efficient perovskite solar cells via a simple process, and pave the way for solar cell fabrication via scalable methods in the near future.

    Wei Zhang, Chengwei Wu, S. Ravi P. Silva (2018)Proposed use of self-regulating temperature nanoparticles for cancer therapy, In: Expert Review of Anticancer Therapy18(8)pp. 723-725 Taylor & Francis

    The concept of magnetic induction of hyperthermia was first proposed by Gilchrist et al. in 1957. The physics is based on the simple principle that when exposed to an alternating magnetic field, the magnetic media can transform the electromagnetic energy to thermal energy, causing the temperature increase of any surrounding media or tissue. In biological tissue, normal cells usually possess higher heat resistance and resilience to temperature than tumor cells. As such, cancerous cells can be selectively destroyed by increasing the local temperature of the tissue to a desired temperature range (42–46°C), while ensuring healthy cells are unharmed.

    M Wang, W Zhang, J Wang, D Wexler, SD Poynton, RCT Slade, H Liu, B Winther-Jensen, R Kerr, D Shi, J Chen (2013)PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments, In: ACS APPLIED MATERIALS & INTERFACES5(23)pp. 12708-12715 AMER CHEMICAL SOC
    W Zhang, SRP Silva (2010)Reversible functionalization of multi-walled carbon nanotubes with organic dyes, In: SCRIPTA MATER63(6)pp. 645-648 PERGAMON-ELSEVIER SCIENCE LTD

    Multi-walled carbon nanotubes can be dispersed in water via the formation of adducts with dyes; this process may be qualitatively monitored by the visual observation of colour variations of dye solutions. Atomic force microscopy images corroborate evidence for attachment of dyes on nanotubes. Laser Raman and Fourier transform infrared spectroscopies suggest intimate electronic interactions between nanotubes and dyes. The dyes can be successfully exfoliated from the nanotubes by thin layer chromatography, showing the reversible nature of the process. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    W Zhang, Y Zhao, V Malgras, Q Ji, D Jiang, R Qi, K Ariga, Y Yamauchi, Jia Liu, J-S Jiang, M Hu (2016)Synthesis of Monocrystalline Nanoframes of Prussian Blue Analogues by Controlled Preferential Etching, In: Angewandte Chemie International Edition55(29)pp. 8228-8234 Wiley

    Metal cyanide coordination compounds are recognized as promising candidates for broad applications because of their tailorable and adjustable frameworks. Developing the nanostructure of a coordination compound may be an effective way to enhance the performance of that material in application-based roles. A controllable preferential etching method is described for synthesis of monocrystalline Prussian blue analogue (PBA) nanoframes, without the use of organic additives. The PBA nanoframes show remarkable rate performance and cycling stability for sodium/lithium ion insertion/ extraction.

    James A. Dawson, Andrew J. Naylor, Christopher Eames, Matthew Roberts, Wei Zhang, Henry J. Snaith, Peter G. Bruce, M. Saiful Islam (2017)Mechanisms of Lithium Intercalation and Conversion Processes in Organic–Inorganic Halide Perovskites, In: ACS Energy Letters2(8)pp. 1818-1824 American Chemical Society

    Organic-inorganic halide perovskites are attracting extraordinary attention in the field of energy materials. The reaction of hybrid lead halide perovskites with Li metal has been recently proposed for a number of potential applications. However, the mechanisms for Li uptake in such materials, such as intercalation and conversion, are still unknown. Using a combina-tion of density functional theory, electrochemical and diffraction techniques, we consider Li intercalation and conversion reactions in CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3. Our simulations suggest that conversion reactions with Li are far more energetically preferable in these materials than Li intercalation. Calculations confirm the formation of Pb metal as a result of Li conversion in all three materials, and this is supported by an X-ray diffraction analysis of CH3NH3PbBr3. The results of this study provide fresh insights into lithium and halide perovskite reactions that will hopefully drive further explo-ration of these materials for a wider variety of energy applications.

    Henry J. Snaith, Antonio Abate, James M. Ball, Giles E. Eperon, Tomas Leijtens, Nakita K. Noel, Samuel D. Stranks, Jacob Tse-Wei Wang, Konrad Wojciechowski, Wei Zhang (2014)Anomalous Hysteresis in Perovskite Solar Cells, In: The Journal of Physical Chemistry Letters5(9)pp. 1511-1515 American Chemical Society

    Perovskite solar cells have rapidly risen to the forefront of emerging photovoltaic technologies, exhibiting rapidly rising efficiencies. This is likely to continue to rise, but in the development of these solar cells there are unusual characteristics that have arisen, specifically an anomalous hysteresis in the current–voltage curves. We identify this phenomenon and show some examples of factors that make the hysteresis more or less extreme. We also demonstrate stabilized power output under working conditions and suggest that this is a useful parameter to present, alongside the current-voltage scan derived power conversion efficiency. We hypothesize three possible origins of the effect and discuss its implications on device efficiency and future research directions. Understanding and resolving the hysteresis is essential for further progress and is likely to lead to a further step improvement in performance.

    D deQuilettes, Wei Zhang, V Burlakov, D Graham, T Leijtens, A Osherov, V Bulović, H Snaith, D Ginger, S Stranks (2016)Photo-induced halide redistribution in organic–inorganic perovskite films, In: Nature Communications711683pp. 1-9 Nature Publishing Group

    Organic–inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced ‘brightening’ of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.

    Liping Cai, Hoi Nok Tsao, Wei Zhang, Long Wang, Zhaosheng Xue, Michael Grätzel, Bin Liu (2013)Organic Sensitizers with Bridged Triphenylamine Donor Units for Efficient Dye-Sensitized Solar Cells, In: Advanced Energy Materials3(2)pp. 200-205 Wiley

    Bridged triphenylamine was chosen as the donor unit for metal-free organic sensitizers in dye-sensitized solar cells (DSSCs). The easily constructed alkene linkage between the donor and the spacer improves the molecule's delocalization and causes a large red shift in its absorption peaks. Planarization of the donor and the use of alkene linkage have proven powerful in extending the red light response of the sensitizer, leading to a significant enhancement in photocurrent density of the device. As a result, devices sensitized with target sensitizers LC-2 (η = 7.51%) and LC-3 (η = 8.00%) exhibited more than 70% efficiency increase over devices sensitized with the reference sensitizer LC-1 (η = 4.44%).

    Yuren Xiang, Yameng Cao, Wenqiang Yang, Rui Hu, Sebastian Wood, Bowei Li, Qin Hu, Fan Zhang, Jujie He, Mozhgan Yavari, Jinlai Zhao, Yunlong Zhao, Jun Song, Junle Qu, Rui Zhu, Thomas P Russell, S. Ravi P Silva, Wei Zhang (2021)Laser‐induced recoverable fluorescence quenching of perovskite films at a microscopic grain‐scale, In: Energy & environmental materials (Hoboken, N.J.) Wiley

    Understanding the fundamental properties of metal halide perovskite materials is driving the development of novel optoelectronic applications. Here, we report the observation of a recoverable laser-induced fluorescence quenching phenomenon in perovskite films with a microscopic grain-scale restriction, accompanied by spectral variations. This fluorescence quenching depends on the laser intensity and the dwell time under Auger recombination dominated conditions. These features indicate that the perovskite lattice deformation may take the main responsibility for the transient, show a new aspect to understand halide perovskite photo-stability. We further modulate this phenomenon by adjusting the charge carrier recombination and extraction, revealing that efficient carrier transfer can improve the bleaching resistance of perovskite grains. Our results provide future opportunities to attain high-performance devices by tuning the perovskite lattice disorder and harvesting the energetic carriers.

    Bowei Li, Victoria Ferguson, S. Ravi P. Silva, Wei Zhang (2018)Defect Engineering towards Highly Efficient and Stable Perovskite Solar Cells, In: Advanced Materials Interfaces5(22)1800326 Wiley

    Metal halide perovskite solar cells are emerging candidates amongst the next-generation thin-film photovoltaic devices with extremely low fabrication cost and high power conversion efficiency. Defects (both in the bulk material and at the interfaces) are recognized as one of the most fundamental reasons for the compromised device performance and long-term stability of perovskite solar cells. In this review article, the authors analyze the possible origins of the defects formation in metal halide perovskites, followed by the rationalization of various approaches being utilized to reduce the density of defects. The authors demonstrate that defect engineering, including adding dopants in the precursor solutions, interface passivation, or other physical treatments (thermal or light stress), is an essential way to further boost the device performance and enhance their long-term stability. The authors note that although the exact mechanisms of defect elimination in some approaches are yet to be elucidated, the research on defect engineering is expected to have enormous impact on next wave of device performance optimization of metal halide perovskite solar cells toward Shockley–Queisser limit.

    AOBO REN, Hao Wang, WEI ZHANG, Jiang Wu, Zhiming Wang, Richard V. Penty, Ian H. White (2021)Emerging light-emitting diodes for next-generation data communications, In: Nature Electronics4pp. 559-572 Nature Research

    The continuing development of consumer electronics, mobile communications and advanced computing technologies has led to a rapid growth in data traffic, creating challenges for the communications industry. Light-emitting diode (LED)-based communication links are of potential use in both free space and optical interconnect applications, and LEDs based on emerging semiconductor materials, which can offer tunable optoelectronics properties and solution-processable manufacturing, are of particular interest in the development of next-generation data communications. Here we review the development of emerging LED materials—organic semiconductors, colloidal quantum dots and metal halide perovskites—for use in optical communications. We examine efforts to improve the modulation performance and device efficiency of these LEDs, and consider potential applications in on-chip interconnects and light fidelity (Li-Fi). We also explore the challenges that exist in developing practical high-speed LED-based data communication systems.

    Perovskite solar cells, which represent the promise of future generation photovoltaic technology with the lowest cost and highest efficiency, have evoked widespread scientific and industrial interest. Through rational device architecture design, materials interface engineering as well as processing technique optimization, a recorded efficiency around 18% has been attained, showing great potential for commercialization to compete with traditional silicon solar cells. Although the device performance of perovskite solar cells improves unprecedently fast in last two years, the basic properties of metalorganic halide perovskite, MAPbX3 (X=Cl, Br, I), such as the role of cation and anion, for example, are still not well understood. Most of research focuses on the perovskite band gap tuning by changing the ratio of either anions (Br to I) or cations (FA to MA). However, up to date, the effect of anion in percursor solution on the perovskite crystal growth and film formation has not been well studied yet, which is highly likely to correlate with the device performance. In addition, there is a long debate on the existence and role of Cl in mixed-halide perovskite and the results from varied groups employing different characterization techniques are quite controversial. Fully understanding of these questions is critically important for the advancement of perovskite solar cell technology in the next few years. In this work, the effect of anion was systematically studied and we found that anion in precursor solution has great influence on the perovskite crystal growth and film formation. By materials engineering, both film morphology and processing time are greatly improved, which leads to enhanced performance in plannar heterojunction devices.

    Metal halide perovskites have emerged as a class of semiconductor materials with unique optical and electrical properties which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has now been boosted up to a certified 22.1% within a few years. Obtaining high-quality perovskite thin films is the key step toward high performance photovoltaic and optoelectronic devices. The quality of the thin films is higly dependenent on the perovskite precursors and fabrication methods. Among various fabrication techinques, solution processing is still the most favorable as it relies on inexpensive deposition equipment and enables tuning the crystallization and composition of the perovskite thin film. In this talk, we briefly introduce the one-step solution processing of ultrasmooth, highly crystalline and pinhole free perovskite thin films through lead acetate based precursors, discuss the mechanism of perovskite crystallization and thin film formation as compared to other non-halide precursor routes, explore their energy related applications, and finally discuss current challenges of this method and possible solutions, with the aim of stimulating potential new fabrication techniques and applications.

    I McCulloch, M Coelle, K Genevicius, R Hamilton, M Heckmeier, M Heeney, T Kreouzis, M Shkunov, W Zhang (2008)Electrical properties of reactive liquid crystal semiconductors, In: JAPANESE JOURNAL OF APPLIED PHYSICS47(1)pp. 488-491
    W Zhang, S Ravi, P Silva (2011)Application of carbon nanotubes in polymer electrolyte based fuel cells, In: Reviews on Advanced Materials Science29(1)pp. 1-14

    Polymer electrolyte based fuel cells (PEFCs) are always in the forefront of fuel cell revolution. Recently a wide variety of application of carbon nanotubes (CNTs) in PEFC components has been exploited. The impetus is to improve the PEFC performance by taking advantages of CNTs' extraordinary physical, chemical and electronic properties. Herein, we briefly review these efforts with an attempt to obtain a better understanding on the role of CNTs in PEFCs, and this article is structured as the following: the contribution of CNTs is first addressed in terms of improving the mechanical strength and proton conductivity of polymer electrolyte membrane; their role in electrocatalysis is then discussed with respect to facilitating the utilization of noble metal catalysts (platinum) and exploring the platinum-free catalysts; the consideration of CNTs as hydrogen storage materials is also highlighted. Based on the literatures studied, CNTs demonstrate great potential as multifunctional materials in improving PEFC performance.

    Metal halide perovskites have emerged as a new class of semiconductor materials enabling a broad range of energy-related applications including photovoltaics, light-emission and solar energy storage devices. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has now been boosted up to a certified 22.1% within a few years. Obtaining high-quality perovskite thin films is the key step toward high performance photovoltaic and optoelectronic devices. The quality of the thin films is higly dependenent on the perovskite precursors and fabrication methods. Among various fabrication techinques, solution processing is still the most favorable as it relies on inexpensive deposition equipment and enables tuning the crystallization and compostion of the perovskite thin film. In this talk, we briefly introduce the fabrication of ultrasmooth, highly crystalline and pinhole free perovskite thin films through lead acetate based precursors, analyse the perovskite crystallization kinetics and thin film formation as compared to other non-halide precursor routes, explore their energy related applications, and finally discuss current challenges of this method and possible solutions, with the aim of stimulating potential new fabrication techniques and applications.

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