Synthesis of Silica-Coated Cs₄PbBr₆ and Cs₄Pb(Br_0.4I_0.6)₆ Quantum Dots with Long Lifetime and Enhancement in Quantum Efficiency for WLEDs Applications: Lightings with High CRI and Displays with Wide Color Gamut

To focus on developing white light-emitting diodes (WLEDs) for lightings with high color rendering index (CRI), low correlated color temperature (CCT), and the displays with wide color gamut, inorganic perovskite quantum dots (QDs) such as CsPbX₃ (X = C1, Br, I) were the promising candidate owing to the excellent optoelectronic properties such as high quantum efficiency, narrow emission wavelengths, and tunable emission spectrum. Nevertheless, the CsPbBr₃QDs in the form of powders or films had a poor air stability and severe decline of quantum efficiency. Therefore, in this article, a new idea was proposed that 0-D green-red perovskite QDs powders such as Cs₄PbBr₆ and Cs₄Pb(Br_0.4I_0.6)₆ with improved quantum efficiency and long lifetime were first developed by silica-coated method and crystal phase transition in low-temperature synthesis. The quantum efficiency in green Cs₄PbBr₆ powders could be significantly enhanced from 31.41% to 45.87% and red Cs₄Pb(Br_0.4I_0.6)₆ powders was 22.79%. Moreover, the as-prepared perovskite QD powders and commercial YAG phosphors combined with blue chips were applied to high-quality WLEDs for lightings and displays. More importantly, the as-fabricated wide Commission Internationale de l'Eclairage (CIE) color gamut WLEDs for displays possessed 115% National Television System Committee (NTSC) coverage rate and luminous efficiency of 51 lm/W under 20-mA driving current. On the other hand, the constructed WLEDs for high-power lightings would generate a warm white light with a luminous efficiency of 38 lm/W, extremely high CRI of 92.8, and low CCT of 3828 K under 350 mA. Hence, the proposed green-red perovskite QD powders had outstanding potential applications in WLEDs.