Uniform CH₃NH₃PbI_3-xBr_x film for efficient planar perovskite solar cells via facile PbBr₂ pre-coating layer treatment

Organometal halide perovskite solar cells (PSCs) have demonstrated exceptional, unparalleled progress in solar cell performance by optimizing the perovskite film morphology, composition, interfaces, and charge collection efficiency. In this work, a PbBr₂ pre-coating layer (PCL) was employed to effectively fabricate a relatively uniform composition perovskite film with large crystal sizes and no voids. We demonstrated that carrier recombination is reduced and charge collection is improved by the interface and interior passivation in PSCs fabricated with PCL process, which leads to a striking enhancement in open-circuit voltage and short circuit current. As a result, a promising power conversion efficiency of 17.38%, showing more than 10% enhancement over the reference devices, was realized in the passivated invert planar PSCs with negligible hysteresis and stable photocurrent output. This study gives a novel compositional passivation process to produce high-efficiency halide PSCs with improved process reproducibility.