Effective Control of the Growth and Photoluminescence Properties of CsPbBr/CsPbBr Nanocomposites by Solvent Engineering.

Metal halide perovskites exhibit small exciton binding energy, which leads to a low electron-hole capture rate for radiative recombination and accordingly decreases the luminescence efficiency. Reducing the thickness of the perovskite film or the size of the perovskite crystal is found to be an effective method to spatially confine the electrons and holes to promote the bimolecular radiative recombination. Here, we fabricate CsPbBr/CsPbBr nanocomposites, applicable for light emission diodes, by a simple self-assembly method. We effectively reduce the critical size of the CsPbBr nanocrystals in the CsPbBr/CsPbBr nanocomposites by adding a certain amount of dimethyl sulfoxide into the perovskite precursor solution. Accordingly, the photoluminescence quantum yield of the CsPbBr/CsPbBr nanocomposites increased from 56 to 91% due to the quantum size effect. In situ observation of the growth of CsPbBr/CsPbBr nanocomposites reveals that the reduction of the CsPbBr crystal size is due to the change of the chemical reaction speed during the two-step growth process of the CsPbBr/CsPbBr nanocomposites.