Cost‐Effective Synthesis Method: Toxic Solvent‐Free Approach for Stable Mixed Cation Perovskite Powders in Photovoltaic Applications

Abstract Organometallic lead halide perovskite powders have gained widespread attention for their intriguing properties, showcasing remarkable performance in the optoelectronic applications. In this study, formamidinium lead iodide (α‐FAPbI 3 ) microcrystals (MCs) is synthesized using retrograde solubility‐driven crystallization. Additionally, methylammonium lead bromide (MAPbBr 3 ) and cesium lead iodide (δ‐CsPbI 3 ) MCs are prepared through a sonochemical process, employing low‐grade PbX 2 (X = I & Br) precursors and an eco‐friendly green solvent (γ‐Valerolactone). The study encompasses an analysis of the structural, optical, thermal, elemental, and morphological characteristics of FAPbI 3, MAPbBr 3 , and CsPbI 3 MCs. Upon analysing phase stability, a phase transition in FAPbI 3 MCs is observed after 2 weeks. To address this issue, a powder‐based mechanochemical method is employed to synthesize stable mixed cation perovskite powders (MCPs) by subjecting FAPbI 3 and MAPbBr 3 MCs with varying concentrations of CsPbI 3 . Furthermore, the performance of mixed cation perovskites are examined using the Solar Cell Capacitance Simulator (SCAPS‐1D) software. The impact of cesium incorporation in the photovoltaic characteristics is elucidated. All mixed cation absorbers exhibited optimal device performance with a thickness ranging between 0.6–1.5 µm. It's worth noting that the MCPs exhibit impressive ambient stability, remaining structurally intact and retaining their properties without significant degradation for 70 days of ambient exposure.