Effect of phase transition on SiO₂-coated CsPbBr₃/Cs₄PbBr₆ quantum dots: Air-stability and quantum efficiency improvement

To develop white light-emitting diodes (WLEDs) with wide color gamut for displays, compared with nitride-based phosphors and traditional core-shell quantum dots (QDs) such as CdSe, InP, CuInS₂, all-inorganic perovskite QDs CsPbX₃ (X = Cl, Br, I) were more promising luminescent materials due to tunable wavelength, narrow emission spectrum and high quantum efficiency. However, when QDs were made into solid form (powders or films), poor air-stability and drastic decrease of quantum efficiency would be observed in CsPbBr₃. These drawbacks would restrict their practical applications. To resolve these issues, in this paper, we proposed a new concept that zero-dimensional perovskite QDs powders Cs₄PbBr₆ with outstanding quantum efficiency and long lifetime up to three months could be successfully prepared via silica-coated method and crystal phase transition in low-temperature synthesis. This phenomenon of phase transition would be discussed in detail and the quantum efficiency could be improved from 31.41% to 45.87%. Moreover, green LEDs with high color purity of 92% and luminous efficiency of 88.59 lm/W could also be achieved by using this material. Therefore, our proposed perovskite QDs powders Cs₄PbBr₆ had extreme potential for displays applications.