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

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‐FAPbI3) microcrystals (MCs) is synthesized using retrograde solubility‐driven crystallization. Additionally, methylammonium lead bromide (MAPbBr3) and cesium lead iodide (δ‐CsPbI3) MCs are prepared through a sonochemical process, employing low‐grade PbX2 (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 FAPbI3, MAPbBr3, and CsPbI3 MCs. Upon analysing phase stability, a phase transition in FAPbI3 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 FAPbI3 and MAPbBr3 MCs with varying concentrations of CsPbI3. 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. [ABSTRACT FROM AUTHOR]