A mechanistic investigation of moisture-induced degradation of methylammonium lead iodide

Applied Physics Letters, Volume 117, Issue 25, December 2020. We performed in situ x-ray diffraction (XRD) experiments on an inorganic–organic hybrid perovskite, CH3NH3PbI3 (MAPbI3), during its interaction with moisture to understand the degradation mechanism. Although the degradation of inorganic–organic hybrid perovskite is an important factor hampering their development as solar cell materials, understanding of the degradation process is currently limited. The moisture-induced degradation mechanism was revealed by the temperature dependence of the in situ XRD pattern sequences and first-principles calculations based on the nudged elastic band method. The combination of experimental and computational data suggests that the MAPbI3 crystal spontaneously changes into the MAPbI3 mono-hydrate crystal once water molecules activated with an energy of more than ∼0.6 eV penetrate the (100) outer surface of the MAPbI3 lattice. These findings have important implications for the development of more robust inorganic–organic hybrid perovskites as light absorbing layers in solar cells and other applications.