Light-Induced Degradation of CH₃NH₃PbI₃ Hybrid Perovskite Thin Film

Abstract

The stability of CH 3 NH 3 PbI 3 was investigated by observing the degradation in a coevaporated film irradiated by a blue laser in ultrahigh vacuum. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to investigate the effects of irradiation on the surface. The core levels of CH 3 NH 3 PbI 3 were observed to shift toward a higher binding energy (BE) during the irradiation, suggesting that the surface became more n-type. A new metallic Pb component in the XPS spectrum appeared after 120 min of irradiation, indicating that the film had started to decompose. The decomposition saturated after about 480 min of irradiation when the ratio of metallic Pb to total Pb was about 33%. Furthermore, the film was no longer continuous after irradiation, as the elements gold and oxygen from the substrate were detected by XPS. SEM images also show a roughened surface after irradiation. The results strongly indicate that CH 3 NH 3 PbI 3 is sensitive to the laser irradiation and that the light induced decomposition is a self-limiting process.