Bandara R. M. I., Jayawardena K. D. G. I., Adeyemo S. O., Hinder S. J., Smith J. A., Thirimanne H. M., Wong N. C., Amin F. M., Freestone B. G., Parnell A. J., Lidzey D. G., Joyce H. J., Sporea R. A., Silva S. R. P. (2019) Tin(iv) dopant removal through anti-solvent engineering enabling tin based perovskite solar cells with high charge carrier mobilities,Journal of Materials Chemistry C
Royal Society of Chemistry
We report the need for careful selection of anti-solvents for Sn-based perovskite solar cells fabricated through the commonly used anti-solvent method, compared to their Pb-based counterparts. This, in combination with the film processing conditions used, enables the complete removal of unwanted Sn4+ dopants, through engineering the anti-solvent method for Sn-based perovskites. Using a Cs0.05(FA0.83MA0.17)0.95Pb0.5Sn0.5I3 perovskite, charge carrier mobilities of 32 ± 3 cm2 V?1 s?1 (the highest reported for such systems through the optical-pump terahertz probe technique) together with ?2 short circuit current densities are achieved. A champion efficiency of 11.6% was obtained for solvent extraction using toluene (an 80% enhancement in efficiency compared to the other anti-solvents) which is further improved to 12.04% following optimised anti-solvent wash and thermal treatment. Our work highlights the importance of anti-solvents in managing defects for high efficiency low bandgap perovskite materials and develops the potential for all-perovskite tandem solar cells.