▎ 摘　　要

Hybrid organic-inorganic metal halide perovskites have been considered as promising materials for boosting the performance of photovoltaics and optoelectronics. Reduced-dimensional condiments and tunable properties render two-dimensional (2D) perovskite as novel building blocks for constructing micro-/nanoscale devices in high-performance optoelectronic applications. However, the stability is still one major obstacle for long-term practical use. Herein, we provide microscale insights into the degradation kinetics of 2D CH3NH3PbI3 (MAPbI(3)) perovskite and CH3NH3PbI3/graphene heterostructures. It is found that the degradation is mainly caused by cation evaporation, which consequently affects the microstructure, light-matter interaction, and the photoluminescence quantum yield efficiency of the 2D perovskite. Interestingly, the encapsulation of perovskite by monolayer graphene can largely preserve the structure of the perovskite nanosheet and maintain reasonable optical properties upon exposure to high temperature and humidity. The heterostructure consisting of perovskite and another 2D impermeable material affords new possibilities to construct high-performance and stable perovskite-based optoelectronic devices.