Time-resolved study of laser-induced phase separation in CsPb(I_xBr_1-x)₃ perovskite under high pressure

Mixed-halide perovskites have attracted extensive interest with their broadly tunable bandgap and optoelectronic properties, which makes them ideal candidates for various solar cells and light-emitting diodes. However, the mixed-halide perovskites often encounter phase separation and degradation under light illumination, which prevents them from many optoelectronic applications. The study on the underlying mechanism and the controlling of the phase separation is crucial to improve the tailored properties for practical applications. Here, we report our systematical investigations of the time-resolved photoluminescence shift and crystal structure evolution on the nanocrystalline CsPb(IxBr1-x)(3) perovskite under intense laser illumination and found the increasing contribution of bromine-rich phase over time. Furthermore, we subject the nanocrystalline CsPb(IxBr1-x)(3) perovskite to a quasi-hydrostatic pressure environment and observed that the phase separation slows down quickly with increasing pressure and can be totally suppressed at a rather mild pressure below 0.2 GPa. These findings suggest the light-induced separation of the crystalline structure, and their optoelectronic properties can be largely suppressed, which provides a useful approach to overcome the problem caused by the intense light applications.