Abstract
Interface defects are crucial to improve the perovskite solar cell stability. This study investigates and determines the suitable electron transport layer (ETL) for Sn-based perovskite solar cells. The investigation finds that carriers capture cross-sectional area greatly impacts photovoltaic performance, and the optimum value is 1 x 10(-25) cm(2). A low trap density of 10(12) cm-2 does not play a significant role, but an interface defect density of 10(17) cm-2 located near the valence band edge at the ETL/absorber interface has the most detrimental effect. In structure, defect states (E-t) near the valence band edge of PCBM/CH3NH3SnI3/NiO and WO3/CH3NH3SnI3/NiO devices have a higher destructive impact compared to TiO2/CH3NH3SnI3/NiO. The study also finds that absorber bulk defects and the interface defects in the ETL/absorber layer are the most sensitive to device performance. This detrimental impact on cell performance can be avoided by reducing the capture cross-sectional area and maintaining a low trap density.