High‐Performance and Environmentally Stable Planar Heterojunction Perovskite Solar Cells Based on a Solution‐Processed Copper‐Doped Nickel Oxide Hole‐Transporting Layer

An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated. Perovskite solar cells based on using Cu-doped NiOx HTL show a remarkably improved power conversion efficiency up to 15.40% due to the improved electrical conductivity and enhanced perovskite film quality. General applicability of Cu-doped NiOx to larger bandgap perovskites is also demonstrated in this study.