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

Halide perovskite nanocrystals (NCs) including CsPbBr 3 as the most typical composition , have attracted widespread attention due to their excellent photovoltaic properties . However, CsPbBr 3 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 CsPbBr 3 NCs with an average particle size of ∼1.8 nm on the surface of Cs 4 PbBr 6 support through adjusting Cs/Pb molar ratios (1−10). Interestingly, CsPbBr 3 /Cs 4 PbBr 6 powders with Cs/Pb ratio = 7 exhibit an ultra-high quantum yield of ∼98 %. Accordingly, the photoluminescence intensity of CsPbBr 3 /Cs 4 PbBr 6 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 CsPbBr 3 /Cs 4 PbBr 6 heterojunction structure. Subsequently, CsPbBr 3 /Cs 4 PbBr 6 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 CsPbBr 3 /Cs 4 PbBr 6 -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 CsPbBr 3 /Cs 4 PbBr 6 heterojunctions .