Uniform incorporation of two-dimensional BiOBr into perovskite crystals and films to enhance photoluminescence

The all-inorganic perovskite nanocrystals are promising luminescent materials for optoelectronic devices. However, it is still a challenge to prepare perovskite nanocrystals with high luminescence. Herein, a synthesis method was developed for the uniform incorporation of ultra-thin BiOBr nanosheets into perovskite crystals at both body-embedding and surface-passivating positions. The micron-scale green-emitting phosphors composed of Cs4PbBr6 nanocrystals and BiOBr nanosheets are prepared. The crystal structure of Cs4PbBr6 nanocrystals can remain almost unchanged although prepared from different PbBr2 concentrations. The luminescence mechanism of Cs4PbBr6 is discussed. The Cs4PbBr6@BiOBr submicron phosphors can be dispersed in DMSO solvent without disintegration and dissolution, which are used as seeds of the CsPbBr3 film growth. The CsPbBr3 films with Cs4PbBr6@BiOBr doped exhibit pure optical characteristics of CsPbBr3, indicating that Cs4PbBr6 is converted to CsPbBr3 during the film preparation process. Furthermore, these Cs4PbBr6@BiOBr phosphors are mixed with CaAlSiN3: Eu red-emitting commercial phosphors to make white LEDs (WLEDs). Overall, this study provides a revealing insight into a kind of composite material constructed with halide perovskite and bismuth halide oxide.