NH4Cl‐Modified ZnO for High‐Performance CsPbIBr2 Perovskite Solar Cells via Low‐Temperature Process

Recently, the thermally stable and facilely fabricated inorganic CsPbIBr 2 perovskite solar cells (PSCs) have attracted tremendous attention where the electron transport layer (ETL) is vital. However, the typical sintering temperature for the widely used electron transport material, that is, TiO 2 , is more than 400 °C, elevating the cost and hindering the application. Due to high electron mobility and low fabrication temperature, ZnO becomes a desirable alternative for TiO 2 , as the ETL in CsPbIBr 2 PSCs, albeit with low open‐circuit voltage ( V oc ). Herein, this work introduces a trace of NH 4 Cl to the sol–gel‐derived ZnO precursor to decrease the work function of the ZnO film, tune the surface morphology of the perovskite film, and thus suppress the density of trap states in the CsPbIBr 2 films. Consequently, full‐coverage and pure‐phase CsPbIBr 2 films consisting of micron‐size and high‐crystallinity grains are obtained. More importantly, for the optimal NH 4 Cl‐modified ZnO, a shining improvement in V oc from 1.08 to 1.27 V boosts the champion CsPbIBr 2 PSCs to obtain a power conversion efficiency of 10.16%, which is the highest value reported among pure‐CsPbIBr 2 PSCs under a low fabrication temperature of 160 °C. In addition, the NH 4 Cl‐modified ZnO ETL reduces the severe hysteresis and increases the device stability significantly.