Layer-by-layer degradation method for profiling MAPbI 3 thin films by a fast photo-oxidative process using high-energy UV irradiation

Abstract

With their exceptional efficiency, ease of processing, and compatibility with large-scale deposition methods, hybrid halide perovskite solar cells have emerged as promising candidates for advanced photovoltaic devices in next-generation technologies. Halide hybrid perovskite materials are known to undergo degradation when exposed to light in the presence of oxygen, leading to the decomposition and volatilization of degradation products. In this study, we propose a novel characterization method based on layer-by-layer stripping of perovskite using high-energy ultraviolet radiation under an ambient environment through simultaneous monitoring of the transmittance spectrum of the sample in the visible range. This approach enables the spatial characterization ofthe intrinsic degradation rate throughout the thickness of the sample in approximately one hour. Furthermore, it allows monitoring the spatial homogeneity of the film by a developed model that interprets the evolution of the spectrum. Thin films of MAPbI3 containing a stoichiometric excess of PbI2 were examined using this method, verifying the existence of a surface layer associated with partial segregation of PbI2 and establishing that it has greater degradation resistance. As a powerful feature, our method allows us to determine whether the PbI2 excess is beneficial or detrimental to the stability of MAPbI3 films. In summary, the proposed characterization technique represents a simple and efficient method for monitoring the homogeneity and susceptibility to degradation ofperovskite materials in photovoltaic applications.