Effects of Organic Cations on Carrier Transport at the Interface between Perovskites and Electron Transport Layers in (FA,MA)SnI₃ Solar Cells

Abstract

Charge extraction at carrier transport layers adjacent to perovskites is crucial for the optimization of perovskite solar cells. In particular, Sn-perovskites with no lead elements are known to struggle from charge extraction. Here, we report the effects of organic ligands such as FA and MA (FA = HC(NH2)2+; MA = CH3NH3+) on charge separation at the interface between electron transport layers and perovskites. TiO2 mesoporous covering the tin-perovskites show significant changes in the electronic structure and built-in potentials according to the ratio of FA to MA. Through a local probe with potential and current mapping, charge transport has been intensively examined. The best cell in this study is obtained as 5.37% at FA/MA = 3:1 with only iodine at the halide sites. Even though the value itself is not comparable with lead halides, it could pave a new direction to improve lead-free perovskite solar cells.