Highly efficient CsPbBr3 perovskite nanocrystals induced by structure transformation between CsPbBr3 and Cs4PbBr6 phases

With the fast development and extensive investigations of halogen atom-based perovskite quantum dots (QDs), the perovskite family of compounds (e.g., Cs4PbBr6 perovskite nanocrystals (PNCs)) has gradually drawn researchers’ attention. Recently, research studies have focused on the chemical transformation between “nonluminous” Cs4PbX6 PNCs and luminescent CsPbX3 QDs. Herein, a new method has been implemented to enable CsPbBr3 (113-structure) QDs gradually to transform into Cs4PbBr6 (416-structure) PNCs by adding ZnBr2 as a revulsive for the detection of the obvious fluorescence enhancement and the deep mechanism behind this transformation. Characterization of their morphological, optical, and physicochemical properties reveals that the fluorescence quantum yields of the remaining CsPbBr3 QDs still remain higher almost up to 99% owing to the reduction of the nonradiative process and the process of “Survival of the fittest” that occurred in the CsPbBr3 QDs, in which the good quality and stable CsPbBr3 QDs are retained, while the unstable CsPbBr3 QDs with poor quality are decomposed to ripen into the 416-structure. Simultaneously, we observed the precise luminous peak position of the ultraviolet fluorophore 416-structure Cs4PbBr6 PNCs and found that the strong green fluorescence comes from CsPbBr3 QDs exclusively. Finally, green light-emitting diodes based on CsPbBr3 QDs with enhanced fluorescence are successfully developed, which implies their tremendous potential in photoelectric devices in the future.