Highly Stable CsPbBr 3 @Cs 4 PbBr 6 Perovskite Fluorescent Nanomaterials for White Light‐Emitting Diodes

ABSTRACT Although halide perovskite nanocrystals exhibit excellent photoelectric properties, their inherent instability greatly limits their practical applications. Here, we report a novel self‐assembly strategy to synthesize highly stable CsPbBr 3 @Cs 4 PbBr 6 perovskite fluorescent nanomaterials in a single step by using 4,4′‐azo (4‐cyanoglutaric acid, CA) and oleylamine (OAm) as ligands, with HBr introduced during the preparation process to create a Br‐rich reaction environment. Specifically, the ligands CA and OAm are anchored to the surface of the composite and then effectively improve their optical properties. Interestingly, because of the protective effect of Cs 4 PbBr 6 , the as‐synthesized CsPbBr 3 @Cs 4 PbBr 6 micromaterials demonstrate excellent solution stability, photostability, and thermal cycling stability. Moreover, the combined effects of the reduction in particle size of CsPbBr 3 @Cs 4 PbBr 6 and the decomposition of CsPbBr 3 into CsBr and PbBr 2 are found to induce an initial increase and subsequent decrease in its luminescence intensity in polar media. The as‐synthesized perovskite luminescent materials, when combined with Gd 2 O 3 :Eu red phosphor and Ba 2 Sr(PO 4 ) 2 :1% Eu 2+ blue phosphor, form a white light‐emitting diode (WLED) device that exhibits outstanding luminous properties. This work not only provides a novel approach for the stable synthesis of perovskite luminescent nanoparticles but also lays a foundation for their application in LED technologies.