Sol–Gel Synthesis of Thermally Stable and Waterproof Silica-Coated CsPbBr₃ Nanocrystals for White Light-Emitting Diodes

CsPbBr 3 nanocrystals have attracted extensive attention due to their excellent photoluminescence (PL) properties, but the intrinsic structural instability limits their application in various optoelectronic devices. In order to alleviate this intractable problem, CsPbBr 3 nanocrystals were embedded in a noncrystalline SiO 2 matrix via a simple sol–gel process. The obtained green-emitting CsPbBr 3 @SiO 2 composites show a slight red shift of emission peaks with an increasing CsPbBr 3 concentration. The most luminous 4%CsPbBr 3 @SiO 2 exhibits a PL quantum yield of 41.5% (excited at 460 nm) and good thermal stability. Besides, it still retains 73.7% of the initial PL intensity after being placed in water for 30 days. Finally, a white LED device is fabricated by combining a blue LED chip with 4%CsPbBr 3 @SiO 2 and Eu 2+:CaAlSiN 3 phosphor, which exhibits bright white light (a luminous efficacy of 28.5 lm/W, a correlated color temperature of 5213 K, and a color-rendering index of 65.3) with 117% of the NTSC color gamut.