The Impact of X‐Ray Radiation on Chemical and Optical Properties of Triple‐Cation Lead Halide Perovskite: from the Surface to the Bulk

Understanding the effects of X‐rays on halide perovskite thin films is critical for accurate and reliable characterization of this class of materials, as well as their use in detection systems. In this study, advanced optical imaging techniques are employed, both spectrally and temporally resolved, coupled with chemical characterizations to obtain a comprehensive picture of the degradation mechanism occurring in the material during photoemission spectroscopy measurements. Two main degradation pathways are identified through the use of local correlative physico‐chemical analysis. The first one, at low X‐Ray fluence, shows minor changes of the surface chemistry and composition associated with the formation of electronic defects. Moreover, a second degradation route occurring at higher fluence leads to the evaporation of the organic cations and the formation of an iodine‐poor perovskite. Based on the local variation of the optoelectronic properties, a kinetic model describing the different mechanisms is proposed. These findings provide valuable insight on the impact of X‐rays on the perovskite layers during investigations using X‐ray based techniques. More generally, a deep understanding of the interaction mechanism of X‐rays with perovskite thin films is essential for the development of perovskite‐based X‐ray detectors and solar for space applications. Mixed halide perovskites are exposed to X‐rays during X‐ray photoelectron spectroscopy (XPS) for different exposure times. Degradation patterns are analyzed via advanced photoluminescence (PL) imaging techniques allowing for the localization of defects and evidence of an emissive I‐poor phase. Correlation between surface chemical analysis and bulk/surface luminescence observation provide insightful knowledge on the degradation of perovskite layers under X‐ray radiation.