Gas Quenching‐Mediated Crystallization for Optoelectronic‐Grade Pb–Sn Perovskite Films

The fabrication of narrow‐bandgap (NBG) Pb–Sn perovskites, with bandgaps typically around 1.1–1.3 eV, is often challenging due to issues related to repeatability, stability, and rapid crystallization kinetics. While Sn–Pb perovskites offer advantages such as defect tolerance and lower toxicity, they are also prone to inhomogeneous crystallization. Sn‐based component of perovskite crystallizes much faster than the Pb‐based component, leading to poor film coverage, pinholes, and rough morphologies. In this study, we employed gas quenching (GQ) instead of the commonly used antisolvent (AS) quenching to address the rapid crystallization issue. GQ approach resulted in slower crystallization and improved film quality. Besides, GQ produced more reproducible results compared to AS quenching. Devices fabricated using the GQ method also demonstrated better performance with higher open‐circuit voltage ( V OC ) values. Specifically, devices prepared with the AS method achieved a power conversion efficiency (PCE) of 18.3%, whereas those using the GQ method reached a PCE of 19.1%. This improvement in efficiency combined with enhanced reproducibility, the simplicity, and environmental friendliness of the GQ approach underscores its advantage for processing NBG Pb–Sn mixed perovskite films. Therefore, the GQ method holds significant potential for application in the fabrication of NBG Pb–Sn perovskite solar cells.