Pressure-Induced Selective Amorphization of CsPbBr3 for the Purification of Cs4PbBr6

Abstract

Lead halide perovskites have been of great interest due to their promising optoelectronic applications. While solution-based synthetic methods have been well developed, they often form mixtures of perovskites having several different phases, which cannot be easily purified by conventional purification methods. Here we report a high-pressure purification method of 0D Cs4PbBr6 perovskite containing a trace of 3D CsPbBr3. The synthesized 0D Cs4PbBr6 perovskites exhibit strong photoluminescence at lambda(peak) = similar to 520 nm because of the trace amount of CsPbBr3 embedded in the Cs4PbBr6. With the application of high pressure (20 GPa), the crystalline CsPbBr3 phase turns amorphous, while the crystal structure of Cs4PbBr6 is retained without change. Almost 95% of the CsPbBr3 phase can be removed by one cycle of compression (1 atm to 20 GPa, and to 1 atm). Due to the removal of CsPbBr3, Cs4PbBr6 perovskites which originally show strong green fluorescence become nonfluorescent after one cycle of compression.