Controlling Water for Enhanced Homogeneities in Perovskite Solar Cells with Remarkable Reproducibility

Two-step sequential deposition of perovskite films is proven efficient and compatible with large-scale production. Nevertheless, its critically regulated environmental humidity often remains a burden, hindering its applications in reproducible fabrication of perovskite solar cells (PSCs). Herein, by introducing a water ethyl acetate (W-EA) solution treatment before annealing, improved perovskite crystallinity and homogeneity in FA_0.95-xMA_xCs_0.05PbI₃ films without additional composition regulation is achieved. In situ Grazing-incidence Wide-angle X-ray Scattering experiments highlighted accelerated crystallization kinetics in W-EA-treated films, leading to high-quality perovskite formation. PSCs based on this method reached an optimal power conversion efficiency of 25.01% and demonstrated enhanced moisture resistance, retaining 88% efficiency after 1000 h in ambient conditions. This W-EA treatment simplifies the fabrication process, greatly reducing the need for controlled humidity, and offers insights into the role of water in perovskite film crystallization, with significant implications to produce high-performance PSCs.