CsPbBr3 nanocrystals prepared by high energy ball milling in one-step and structural transformation from CsPbBr3 to CsPb2Br5

All-inorganic halide perovskite nanocrystals (NCs) are generally prepared by liquid phase method with the help of volatile organic solvents, inert gas protection and complex organometallic precursors. Herein, a simple, efficient and green method based on all-solid-state mechanochemical synthesis is proposed to prepare CsPbBr3 NCs. NCs with excellent performance can be prepared by grinding raw materials CsBr and PbBr2 through high energy ball milling, and prepared NCs show good stability in ethanol and living conditions. Interestingly, CsPbBr3 NCs prepared by ball milling have a sudden increase in their fluorescence intensity dispersed in water. After soaking for 8 h, CsPbBr3 NCs have been almost entirely transformed into CsPb2Br5 NCs. The fluorescence intensity of samples is 80 times of that before soaking, and absolute PL quantum yield (PLQY) of samples increases significantly by up to 92%. These results provide a strong evidence for the current debate about whether CsPb2Br5 emits light and propose a deeper understanding about structural transition from orthorhombic CsPbBr3 to tetragonal CsPb2Br5, which is of great significance to the application of CsPb2Br5 in optoelectronic devices. This will provide a new idea for the synthesis and transformation of halide perovskites.