Solvent engineering improves efficiency of lead-free tin-based hybrid perovskite solar cells beyond 9%

Here, we report on the effect of different antisolvent dripping on film morphology and charge recombination of mixed formamidinium-methylammonium tin iodide (FA_0.75MA_0.25SnI₃) as a light absorber in perovskite solar cells. N,N-dimethyl methanamide (DMF) and dimethyl sulfoxide (DMSO) were used as the mixed solvent in the perovskite precursors together with tin fluoride (SnF₂) as an additive. Diethyl ether (DE), toluene (TL), and chlorobenzene (CB) were employed as antisolvents for comparison. Our results show that CB as an antisolvent leads to a dense and uniform Sn-based perovskite film. The maximum power conversion efficiency of our Sn-based perovskite solar cell achieves 9.06% (9.02%) under forward (reverse) voltage scan under AM 1.5G 100 mW/cm² illumination. The encapsulated cells show good long-Term stability with a75% of their initial efficiency retained over a period of 30 days of storage. Our work suggests the promising potential to further improve the performance of Pb-free Sn-based perovskite solar cells.