Influence of the Electron Transport Layer on the Performance of Perovskite Solar Cells under Low Illuminance Conditions.

Owing to the tunable band gap of metal-halide perovskite compounds, perovskite solar cells (PSCs) are promising energy-harvesting devices for indoor applications. Since the electron transport layer (ETL) plays a critical role in the performance of PSCs, selecting a suitable ETL is important for improving the performance of PSCs. Here, we compared the characteristics of PSCs employing TiO 2 and SnO 2 , which are widely used as ETLs in PSCs, under low illuminance conditions. Electrochemical impedance spectroscopy revealed that PSCs employing SnO 2 as the ETL exhibited lower charge transfer resistance than those employing TiO 2 in low light intensity environments. Consequently, SnO 2 -based PSCs showed a higher power conversion efficiency of 27.7% than that of TiO 2 -based PSCs (22.5%) under 1000 lx white LED illumination. Space-charge-limited current measurements have shown that the defect density of ETLs strongly affects the performance of PSCs, especially under low illuminance conditions. We believe that this report provides an effective strategy for selecting appropriate ETLs for indoor applications of PSCs.