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

Abstract

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.