NH_4Cl-Modified ZnO for High-Performance CsPbIBr_2 Perovskite Solar Cells via Low-Temperature Process

摘要

Recently, the thermally stable and facilely fabricated inorganic CsPbIBr_2 perovskitesolar cells (PSCs) have attracted tremendous attention where the electrontransport layer (ETL) is vital. However, the typical sintering temperature forthe widely used electron transport material, that is, TiO_2, is more than 400℃,elevating the cost and hindering the application. Due to high electron mobilityand low fabrication temperature, ZnO becomes a desirable alternative for TiO_2,as the ETL in CsPbIBr_2 PSCs, albeit with low open-circuit voltage (Voc). Herein,this work introduces a trace of NH4Cl to the sol–gel-derived ZnO precursor todecrease the work function of the ZnO film, tune the surface morphology of theperovskite 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 micronsizeand high-crystallinity grains are obtained. More importantly, for the optimalNH4Cl-modified ZnO, a shining improvement in V_(oc) from 1.08 to 1.27 V booststhe 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 lowfabrication temperature of 160 ℃. In addition, the NH4Cl-modified ZnO ETLreduces the severe hysteresis and increases the device stability significantly.