High-Performance Planar Perovskite Solar Cells with Negligible Hysteresis Using 2,2,2-Trifluoroethanol-Incorporated SnO2

An efficient electron transport layer (ETL) between the perovskite absorber and the cathode plays a crucial role in obtaining high-performance planar perovskite solar cells (PSCs). Here, we incorporate 2,2,2-trifluoroethanol (TFE) in the commonly used tin oxide (SnO2) ETL, and it successfully improves the power conversation efficiency (PCE) and suppresses the hysteresis of the PSCs: the PCE is increased from 19.17% to 20.92%, and the hysteresis is largely reduced to be almost negligible. The origin of the enhancement is due to the improved electron mobility and optimized work function of the ETL, together with the reduced traps in the perovskite film. In addition, O2 plasma is employed to treat the surface of the TFE-incorporated SnO2 film, and the PCE is further increased to 21.68%. The concept here of incorporating organic small molecules in the ETL provides a strategy for enhancing the performance of the planar PSCs.