High Resolution X-ray Photoelectron Spectroscopy Study on Stability of MAPbBr₃ Single Crystal

Organic-inorganic halide perovskites have emerged as a promising semiconductor family because of their remarkable performance in optoelectronic devices. However, the stability of perovskites remains a critical issue. Here, we quantitatively and systematicly investigated the in-situ cleaved MAPbBr₃ single crystal degradation processes in X-ray, N₂, O₂ and H₂O environments. The crystals were monitored by high resolution X-ray photoelectron spectroscopy with careful control of the exposure time and pressure. The detailed electronic structure and compositional changes of the crystal were tracked throughout different exposures, which provided insights into various degradation mechanisms. About 10% of the surface MAPbBr₃ degraded into metallic lead under X-ray, while N₂ can protect the sample from X-ray for 9 hours under the same condition. The crystal was not sensitive to pure O₂, but was susceptible to H₂O. A reaction threshold of ~10⁸ Langmuir was found. Below it, H₂O only acted as an n-type dopant; above it, the crystal began to decompose. These observations highlight possible future directions to improve the material stability by environmental control.