The Impact of Measurement Atmosphere on the Ion Migration in Mixed-halide Perovskites

Perovskite light-emitting diodes (PeLEDs) face challenges toward commercialization due to their poor operational stability. The migration of mobile ions under electric fields is considered a critical cause of device degradation. Reliably measuring ion migration is therefore crucial for understanding the aging mechanisms. However, former studies in this direction did not fully consider the possible impact of the experimental conditions (e.g., atmosphere) on ion migration, compromising the reliability of findings. In this work, the ion migration processes in mixed-halide perovskites under various atmosphere are carefully investigated utilizing wide-field photoluminescence (PL) microscopy. Two predominant mechanisms, charge trapping and ion migration, are identified to be accountable for the stable emission and rapid PL degradation under electric fields in dry nitrogen and ambient air, respectively. Further, a connection between phase segregation and ion migration in mixed-halide perovskites is revealed, with an increased bromine content corresponding to more severe ion migration. This work underscores the critical role of the atmosphere, particularly humidity, in facilitating ion migration in perovskites. It clarifies some of the distinct ion migration behaviors in mixed-halide perovskites. These findings contribute to an improved understanding of the origin of ion migration in perovskite semiconductors.