Anion exchange promoting non-impurities enables conformable and efficient inverted perovskite solar cells

Abstract

Two-step sequential deposition is promising for controlling the crystallization and growth of compact perovskites by separating the deposition of PbI₂ and organic salt. Furthermore, thermally evaporated PbI₂ has the potential for application in textured surfaces. However, the performance of inverted perovskite solar cells by the two-step sequential deposition lags far behind the counterpart fabricated by the one-step deposition from a precursor solution. Herein, we provide insight into anion exchange in a sequential thermal evaporation-solution process for high-quality perovskite films. The exchange process promotes mass transport and the penetration of organic compounds into evaporated PbI₂, optimizes phase purity, and enables a homogeneous halide distribution with inhibited phase segregation. The device fabricated by evaporated-PbI₂ as the bottom layer following the solid-solution interdiffusion process yielded a high efficiency of 24.43% (certified 24.18%), which is the highest for inverted perovskite solar cells based on evaporated PbI₂. On incorporating the scalable blading process for solid-solution interdiffusion, the device exhibited an efficiency of up to 22.22%. The resulting conformable and scalable cells maintained 95% of the initial efficiency after operation for 682 h under one sun illumination. This anion-exchange strategy provides instructive significance for future large-area and monolithic perovskite–silicon tandem cells.