Highly efficient CsPbBr perovskite nanocrystals induced by structure transformation between CsPbBr and CsPbBr phases

With the fast development and extensive investigations of halogen atom-based perovskite quantum dots (QDs), the perovskite family of compounds ( e.g. , Cs 4 PbBr 6 perovskite nanocrystals (PNCs)) has gradually drawn researchers' attention. Recently, research studies have focused on the chemical transformation between "nonluminous" Cs 4 PbX 6 PNCs and luminescent CsPbX 3 QDs. Herein, a new method has been implemented to enable CsPbBr 3 (113-structure) QDs gradually to transform into Cs 4 PbBr 6 (416-structure) PNCs by adding ZnBr 2 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 CsPbBr 3 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 CsPbBr 3 QDs, in which the good quality and stable CsPbBr 3 QDs are retained, while the unstable CsPbBr 3 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 Cs 4 PbBr 6 PNCs and found that the strong green fluorescence comes from CsPbBr 3 QDs exclusively. Finally, green light-emitting diodes based on CsPbBr 3 QDs with enhanced fluorescence are successfully developed, which implies their tremendous potential in photoelectric devices in the future. The structure transformation from CsPbBr 3 to Cs 4 PbBr 6 perovskite nanocrystals induced fluorescence enhancement was detected and applied in the LED devices.