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

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).