Hao Mengmeng, Bai Yang, Zeiske Stefan, Ren Long, Liu Junxian, Yuan Yongbo, Zarribi Nasim, Cheng Ningyan, Ghasemi Mehri, Chen Peng, Lyu Miaoqiang, He Dongxu, Yun Jung-Ho, Du Yi, Wang Yun, Ding Shanshan, Arming Ardalan, Meredith Paul, Liu Gang, Cheng Hui-Ming, Wang Lianzhou (2020) Ligand-assisted cation-exchange engineering for high-efficiency colloidal Cs1?xFAxPbI3 quantum dot solar cells with reduced phase segregation,Nature Energy
The mixed caesium and formamidinium lead triiodide perovskite system (Cs1?xFAxPbI3) in the form of quantum dots (QDs) offers a pathway towards stable perovskite-based photovoltaics and optoelectronics. However, it remains challenging to synthesize such multinary QDs with desirable properties for high-performance QD solar cells (QDSCs). Here we report an effective oleic acid (OA) ligand-assisted cation-exchange strategy that allows controllable synthesis of Cs1?xFAxPbI3 QDs across the whole composition range (x = 0?1), which is inaccessible in large-grain polycrystalline thin films. In an OA-rich environment, the cross-exchange of cations is facilitated, enabling rapid formation of Cs1?xFAxPbI3 QDs with reduced defect density. The hero Cs0.5FA0.5PbI3 QDSC achieves a certified record power conversion efficiency (PCE) of 16.6% with negligible hysteresis. We further demonstrate that the QD devices exhibit substantially enhanced photostability compared with their thin-film counterparts because of suppressed phase segregation, and they retain 94% of the original PCE under continuous 1-sun illumination for 600 h.