Altered Stability and Degradation Pathway of CH₃NH₃PbI₃ in Contact with Metal Oxide

Degradation in CH3NH3PbI3 (MAPbI3), when in contact with commonly used metal oxide transport layer materials in optoelectronic devices, is examined experimentally and theoretically. On the basis of the decomposition temperature, the interfacial stability decreases in the following order: MAPbI3 + TiO2 ∼ MAPbI3 alone > MAPbI3 + SnO2 > MAPbI3 + NiO, consistent with thermodynamic data. When MAPbI3 contacts NiO or SnO2, experimental results unequivocally show interfacial decomposition occurs at a lower temperature than bulk decomposition and produces different degradation products. Density functional theory calculations reveal an altered reaction pathway on oxide surfaces and elucidate the difference between NiO and TiO2. These findings pinpoint the importance of understanding the interaction between halide perovskite and other materials used in a device to achieve intrinsically stable devices.