Mechanistic Insights into Photochemical Reactions on CH₃NH₃PbBr₃ Perovskite Nanoparticles from Single‐Particle Photoluminescence Spectroscopy

Abstract Metal halide perovskites have attracted considerable attention in applications such as photovoltaic cells and light‐emitting diodes. The performance and durability of perovskite devices are significantly dependent on the nature of structural defects, but the underlying mechanisms of structure‐related photochemical reactions are not yet fully elucidated. This study demonstrates that the photoluminescence (PL) from individual perovskite nanoparticles (NPs) can be utilized to resolve the different trapping pathways of the photogenerated charges, and hence, obtain a correlation between the pathways. PL deactivation and activation were observed and mainly attributed to nonradiative Auger recombination by the trapped charges and the passivation of surface traps by oxygen, respectively. Single‐particle spectroelectrochemical techniques were further employed to explore the possible origin of the effective charge trap states and the reversibility of redox events under electrical bias. Consequently, this study unravels the complex effects of the structural defects on the charge carrier dynamics in perovskites.