High‐Quality Sequential‐Vapor‐Deposited Cs₂AgBiBr₆ Thin Films for Lead‐Free Perovskite Solar Cells

Lead‐free double perovskites have been demonstrated as promising alternatives to solve the toxicity and stability issues in conventional lead trihalide perovskites. However, different solubility of components in the precursors hinders fabrication of double perovskite films with commonly used solution procedures. Here, for the first time, the authors successfully prepared double perovskite Cs 2 AgBiBr 6 thin films throughout a sequential‐vapor‐deposition procedure. The obtained thin films with pure double perovskite phase show large grain sizes, uniform, and smooth surface properties. In addition, the high‐quality vapor‐deposited Cs 2 AgBiBr 6 films exhibit a photoluminescence (PL) lifetime of 117 ns, indicative of significant potential in photovoltaic applications. The resulting solar cells with planar device structure show an optimized power conversion efficiency of 1.37%, which can be maintained at 90% after 240 h of storage under ambient condition. Our results demonstrate the feasibility of employing vapor deposition technique to fabricate high‐quality double perovskite thin films, which paves the way for further development of various optoelectronic devices based on these promising lead‐free semiconductors.