Improved photostability of mixed-cation perovskite microplatelets fabricated by a chemical vapor deposition method

Promising performances have been demonstrated for photovoltaic and light-emitting devices based on perovskite absorbers. However, to further fulfill this promise, the photo-instability that has long been observed in them must be overcome. In this work, ordinary CsPbBr3 and mixed cation FAxCs1_xPbBr3 perovskite microplates are synthesized by a chemical vapor deposition method. Under continuous intensive ultraviolet (UV) irradiation of 100 W/cm2, the photoluminescence (PL) of pristine CsPbBr3 quickly quenches within 10 minutes due to the vacancy assisted ion migration. Whereas, the PL of mixed cation FAxCs1_xPbBr3 perovskite maintains 80% of its original intensity after similar UV irradiation for 25 minutes. The narrower PL bandwidth, higher PL quantum yield, and longer PL lifetime reveal the reduced defect traps in the FAxCs1_xPbBr3. Therefore, the improved photostability of the mixed cation FAxCs1_xPbBr3 perovskite benefits from the suppressed ion migration due to the reduced density of halide vacancy. This work provides a promising approach to prepare photostable perovskites, which will promote their applications in optoelectronic devices.