Room-temperature saturation recrystallization of CsPbBr3/Cs4PbBr6 heterojunction structure with quantum yield of ∼98 % for backlight displays and wearable devices

Abstract

Halide perovskite nanocrystals (NCs) including CsPbBr₃ as the most typical composition, have attracted widespread attention due to their excellent photovoltaic properties. However, CsPbBr₃ NCs encounter the serious problem of instability and luminescent quenching when removing protection from their colloidal solution. Herein, a facile room-temperature saturation recrystallization process is employed to form CsPbBr₃ NCs with an average particle size of ∼1.8 nm on the surface of Cs₄PbBr₆ support through adjusting Cs/Pb molar ratios (1−10). Interestingly, CsPbBr₃/Cs₄PbBr₆ powders with Cs/Pb ratio = 7 exhibit an ultra-high quantum yield of ∼98 %. Accordingly, the photoluminescence intensity of CsPbBr₃/Cs₄PbBr₆ powders with Cs/Pb ratio = 7 is greatly enhanced by about 2900-fold higher than the sample with a Cs/Pb ratio of 1 due to the formation of CsPbBr₃/Cs₄PbBr₆ heterojunction structure. Subsequently, CsPbBr₃/Cs₄PbBr₆ powders are encapsulated in a SBA-15 mesoporous silica and calcined at 700ºC to improve water-resistance properties, which can keep stable in water for more than 100 days. These CsPbBr₃/Cs₄PbBr₆-SBA-15 composites show potential applications in white light-emitting diodes, display light sources, and flexible luminescent films in the field of wearable devices. This work provides a facile way to achieve ultra-high quantum yield through the formation of CsPbBr₃/Cs₄PbBr₆ heterojunctions.