CsPbBr3/Cs4PbBr6 heterostructure solids with high stability and photoluminescence for white light-emitting diodes

Cesium lead halide perovskite crystals have attracted widespread attention due to their excellent photoelectric properties. However, their intrinsic instability and the photoluminescence quantum yield (PLQY) sharply dropped in the solid-state limit their practical applications. Besides, the current synthesis strategies either need a variety of ligands, or an anti-solvent, which will result in potential environmental risks. Herein, we address the above issues simultaneously by embedding CsPbBr3 in a large bandgap Cs4PbBr6 matrix by high-speed mechanical mixing without using any ligands and highly toxic anti-solvent. Changing the molar ratio of PbBr2/CsBr, centrifugation time, and the solution concentration, the optimized CsPbBr3/Cs4PbBr6 show a high PLQY of up to 79%. In addition, mechanistic studies show that the origin of green luminesce of CsPbBr3/Cs4PbBr6 microcrystals is closely related to the CsPbBr3 inclusion theory, but not to the Br vacancy theory, in which CsPbBr3 embedded in Cs4PbBr6 to form a CsPbBr3/Cs4PbBr6 heterostructure. By taking advantage of the heterostructure, the photostability and thermostability of CsPbBr3/Cs4PbBr6 are significantly enhanced. In addition, the high optical and temperature/humidity-stable performances of CsPbBr3/Cs4PbBr6 are verified by applying them to white LEDs (WLEDs). The electroluminescence intensity of WLEDs remains 70% of the original one after being stored in a chamber with high temperature and high humidity (85 °C/RH 85%) for 40 h, and the device displays luminous efficiency of 74.5 lm/W at 20 mA. This result provides a solid foundation for their scale applications in lighting, displays, and other optoelectronic and photonic devices.