Disentangling X-Ray and Sunlight Irradiation Effects Under a Controllable Atmosphere in Metal Halide Perovskites

Metal halide perovskites are versatile materials for photovoltaic and optoelectronic applications owing to their adjustable bandgap and emission properties. Nevertheless, a drawback is their photo-structural-chemical instability. Herein, structural and optical responses of metal halide perovskite films, exploiting in situ X-ray and visible light stimuli under dry and humid atmospheres, are correlated. It shows that the interplay of the physical parameters responsible for sample evolution depends in a nontrivial way on the nature of the excitation, radiation power density, and moisture conditions. Two perovskite samples demonstrate the relevance of each composition. They are resilient under a dry atmosphere, but the presence of water or oxygen molecules in the ambient air leads to structural and optical changes under irradiation. However, the sample reaction depends on the photons' excitation energy and power density to be effective. Under a dry atmosphere, the halide segregation involving Br and I atoms does not occur for the low-power density of X-ray and sunlight excitations. On the contrary, under the ambient air atmosphere, compound stability depends on sample composition, which relates to defects and traps, and the excitation source. Herein, the probe's relevance to perovskites' photoinduced structural and optical responses is highlighted.