In-situ spectroscopic insights into electrochemical degradation and surface passivation of CsPbBr₃ perovskite layers

Halide perovskites are promising materials for next-generation solar-driven chemistry. To fully exploit their potential under electrochemical conditions, it is essential to understand how electrolyte contact and applied potentials influence their structural and photophysical properties. In this study, the role of CsPbBr₃ perovskite layer composition was investigated by tracking photophysical responses under different applied biases. Using in-situ spectroelectrochemical techniques, including voltage-dependent absorption and spatially/time-resolved photoluminescence, we monitored the behavior of immersed CsPbBr₃ active layers. The results revealed both irreversible transformations and surface ligand effects, such as precursor reformation, oxidation, and defect passivation by residual ligands originating from the precursor nanoparticles. These findings highlight the complex interplay between perovskite composition and electrochemical environment, providing important insight into the stability and interfacial charge-transfer characteristics of perovskite layers for practical solar-to-chemical energy conversion.