Tin( iv ) dopant removal through anti-solvent engineering enabling tin based perovskite solar cells with high charge carrier mobilities

Abstract

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. 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 Sn 4+ dopants, through engineering the anti-solvent method for Sn-based perovskites. Using a Cs 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb 0.5 Sn 0.5 I 3 perovskite, charge carrier mobilities of 32 ± 3 cm 2 V −1 s −1 (the highest reported for such systems through the optical-pump terahertz probe technique) together with ∼28 mA cm −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.