One-step conversion of CsPbBr3 into Cs4PbBr6/CsPbBr3@Ta2O5 core–shell microcrystals with enhanced stability and photoluminescence

Abstract

It is well known that surface passivation and modification are efficient approaches to improve the photoluminescence and stability of perovskites. Although CsPbBr₃ nanocrystals (NCs) could be embedded into a Cs₄PbBr₆ matrix to enhance the photoluminescence property, the limited stability will hinder their applications. It still remains a challenge to convert CsPbBr₃ to Cs₄PbBr₆ in one step with surface modification by using oxide on a single-particle level. Herein, the process of conversion from CsPbBr₃ to Cs₄PbBr₆/CsPbBr₃ microcrystals (MCs) by a ligand-assisted supersaturated recrystallization (LASR) method has been studied. To improve its stability, CsPbBr₃ has been successfully converted into monodisperse Cs₄PbBr₆/CsPbBr₃@Ta₂O₅ core–shell MCs through a facile one-step sol–gel method at room temperature. Compared with Cs₄PbBr₆/CsPbBr₃, Cs₄PbBr₆/CsPbBr₃@Ta₂O₅ has better light stability and thermal stability. Cs₄PbBr₆/CsPbBr₃@Ta₂O₅ MCs display great enhancement in photoluminescence quantum yield (PLQY) (up to 94.7%) and photoluminescence lifetime (up to 67.8 ns). Furthermore, the luminous efficiency of the WLED device based on Cs₄PbBr₆/CsPbBr₃@Ta₂O₅ (31.9 lm W⁻¹) is twice that of the WLED device fabricated by Cs₄PbBr₆/CsPbBr₃ (15.2 lm W⁻¹).