Passivating defects and optimizing interfaces to boost the comprehensive performance of carbon-cathode hole-transport-layer-free CsPbI 2 Br solar cells via an ionic liquid

A carbon-cathode hole-transport-layer-free CsPbI 2 Br perovskite solar cell exhibits reduced defect density in the CsPbI 2 Br layer due to treatment with an ionic liquid ([BMIM][OTF]), resulting in an enhanced power conversion efficiency of 15.39%.