Influence of synthesis atmosphere on the properties and stability of MAPbI2Br and CsPbI2Br perovskite films

Systematic comparison of argon vs. air synthesis atmospheres reveals material-dependent effects on hybrid MAPbI 2 Br and all-inorganic CsPbI 2 Br films. • Argon-synthesized perovskite films exhibit superior crystallinity, uniform grain morphology, and enhanced light absorption. • Air processing induces distinct behaviors: it promotes decomposition in MAPbI 2 Br but enables beneficial surface passivation in CsPbI 2 Br, delaying its phase transition. • The air ambient stability of MAPbI 2 Br surpasses that of CsPbI 2 Br regardless of synthesis atmosphere, attributed to its more favorable Goldschmidt tolerance factor from the larger A -site cation. This study systematically compares the microstructure, optoelectronic properties, and ambient stability of hybrid MAPbI 2 Br and all-inorganic CsPbI 2 Br thin films processed in an inert argon atmosphere versus ambient air. Films prepared in argon exhibit better crystallinity, more uniform grain morphology, and stronger light absorption. For the air-synthesized samples, A-CsPbI 2 Br shows improved stability and delayed phase transition compared to A-MAPbI 2 Br, which is attributed to surface passivation. Among the argon-synthesized samples, G-MAPbI 2 Br demonstrates better air stability due to its high crystalline quality and fewer defects, whereas G-CsPbI 2 Br is highly prone to degradation in air, likely due to the lack of surface passivation. Regardless of the synthesis atmosphere, the ambient stability of MAPbI 2 Br surpasses that of CsPbI 2 Br, owing to a more favorable tolerance factor provided by the larger A -site cation. These findings highlight the crucial roles of both synthesis atmosphere and material composition in governing the properties and stability of halide perovskites.