Monodisperse and brightly luminescent CsPbBr₃/Cs₄PbBr₆ perovskite composite nanocrystals

The microscale composite structure strategy of embedding CsPbBr₃ nanocrystals (NCs) in the microscale Cs₄PbBr₆ matrix (CPB₁₁₃/CPB₄₁₆) has successfully demonstrated its ability to resolve the fluorescence quenching of perovskite NCs in the solid agglomeration state due to the loss of quantum confinement. Unfortunately, the controllable synthesis of monodisperse nanoscale composites with bright emission in the solid state remains a great challenge. Here, we present for the first time a novel supersaturated recrystallization process to controllably synthesize monodisperse CPB₁₁₃/CPB₄₁₆ composite NCs with bright emission in the solid form, where CsPbBr₃ NCs were uniformly embedded in the nano hexagonal Cs₄PbBr₆ matrix. The existence of 2-methylimidazole (MeIm) not only can control the composition rate of CsPbBr₃ to Cs₄PbBr₆, the size and dispersity of CsPbBr₃ in the composite NCs but can also help controllably obtain the monodisperse and hexagonal Cs₄PbBr₆ matrix. The as-prepared composite structure can effectively prevent CsPbBr₃ fluorescence quenching and make the composite NCs have a high photoluminescence quantum yield (PLQY) of 83%. In addition, we obtained tunable blue to red emitting composite NCs by varying the halide salts.