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 CsPbBr 3 NCs. NCs with excellent performance can be prepared by grinding raw materials CsBr and PbBr 2 through high energy ball milling, and prepared NCs show good stability in ethanol and living conditions. Interestingly, CsPbBr 3 NCs prepared by ball milling have a sudden increase in their fluorescence intensity dispersed in water. After soaking for 8 h, CsPbBr 3 NCs have been almost entirely transformed into CsPb 2 Br 5 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 CsPb 2 Br 5 emits light and propose a deeper understanding about structural transition from orthorhombic CsPbBr 3 to tetragonal CsPb 2 Br 5 , which is of great significance to the application of CsPb 2 Br 5 in optoelectronic devices. This will provide a new idea for the synthesis and transformation of halide perovskites.