Constructing an n/n+ homojunction in a monolithic perovskite film for boosting charge collection in inverted perovskite photovoltaics

A simple heterovalent metal halide surface treatment enables formation of n/n⁺ perovskite homojunction, which enlarged built-in electric field and accelerated charge extraction at the perovskite/C₆₀ interface, achieving a high efficiency of 22.2%.