Powder Methodology—An Effective Way to Suppress Sn 2+ Oxidation in Narrow Bandgap Pb‐Sn Perovskite

Abstract Lead–tin halide perovskites are of significant merits due to their suitability for tandem solar cell fabrication and for lowering the environmental impact. However, the substantial disparity in the crystallization of tin‐ and lead‐based perovskites, coupled with the tendency of Sn 2+ to oxidize rapidly, poses hurdles and rise in defect concentration. Here, the study proposes a cost‐effective and facile route to synthesize lead–tin halide perovskite microcrystals. The perovskite formulation and the thin films deposited from lead–tin halide perovskite microcrystal exhibit an improved stability of Sn 2+ against environmental humidity conditions compared to their precursor‐based counterparts. The device fabricated with FAPb 0.5 Sn 0.5 I 3 microcrystal measures a power conversion efficiency of 18.55% with an open‐circuit voltage of 800 mV, coupled with low‐cost precursors and lead mitigation protocols.