Pseudohalide Functional Additives in Tin Halide Perovskite for Efficient and Stable Pb-Free Perovskite Solar Cells

The progress of tin-based halide perovskite solar cells (Sn-HaPSCs) is obstructed by their poor stability arising from tin oxidation. Herein, we introduced phenethylammonium thiocyanate (PEASCN) as a pseudohalide functional additive into an FASnI3 perovskite film to improve the optoelectronic properties. This approach is found to be effective for the suppression of Sn oxidation and formation of a compact and larger grain film with a higher degree of crystallinity. The device with the PEASCN additive improved the device efficiency from 4.52% (for pristine Sn-HaP) to 9.65% with a significant increase of VOC from ∼0.411 to 0.667 V and superior device stability. The device analysis revealed that the PEASCN additive has improved the optoelectronic properties coupled with a higher diffusion potential and suppression of bulk and interface defects in the Sn-HaPSC. This work corroborates that the incorporation of a pseudohalide-based functional additive in FASnI3 is propitious for better film formation, passivation of detrimental surface chemistry, and defects at the interface and in the bulk.