Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour

Efficiencies of organic-inorganic lead halide perovskite solar cells (PSCs) have significantly increased in recent years, but instability issues impede their further development and application. Previous studies reported that volatile species (for example, iodine, I 2) were generated when perovskites were subjected to moisture, oxygen, light illumination, applied electric field, and thermal stress (all of which are relevant to the operation of PSCs in practical applications). Here we show that I 2 vapour causes severe degradation of MAPbI 3 (MA: CH 3 NH 3 +) perovskite, due to chemical chain reactions. Furthermore, I 2 vapour could also induce degradation of other iodide-based perovskites, such as FAPbI 3 (FA: HC(NH 2) 2 +) and FA 0.8 Cs 0.2 PbI 3. The results reveal a universal degradation factor for iodide-based perovskite by I 2. As the release of I 2 is nearly inevitable during practical applications, this work suggests that MAPbI 3 may not be suitable for long-term stable solar cells and it is imperative to develop other types of perovskite material to achieve stable PSCs.