Photo‐Induced Phase Segregation in Mixed Halide Perovskite Structures and Various Methods of Suppression

ABSTRACT Halide perovskites are promising for optoelectronic applications thanks to their excellent properties. However, in mixed halide perovskites, photo‐induced phase segregation remains a major challenge, causing compositional instability and reducing device performance. In this study, we review the dynamic behavior of phase segregation in mixed‐halide perovskite thin films under various external stimuli. Through spectroscopic and structural analyses, we explain the evolution and kinetics of segregated domains and examine the influence of compositional ratio and environmental conditions. Furthermore, we propose and evaluate effective strategies to suppress phase segregation, thereby improving the photostability of the materials. These findings offer fundamental insights into the intrinsic mechanisms of phase segregation governing halide ion migration and present feasible approaches for enhancing the operational stability of devices based on halide perovskite materials.