Degradation changes in the crystal and electronic structure of lead iodide perovskite

The degradation of CH₃NH₃PbI₃ powder and films following exposure to air and X-ray radiation was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Our findings revealed significant differences in the states of PbI₂ and PbO between the films and the powder, as indicated by the energy positions of the Pb 4f and C 1s peaks. Additionally, a reduction in both the mass and size of the crystals suggests ongoing degradation processes.