Sunlike Full-Spectrum Electroluminescent White Light-Emitting Diodes Based on Cu(In,Ga)S₂ Quantum Dots Coated with Multiple ZnS Shells

It is promising to develop next-generation indoor and outdoor flexible electroluminescent light sources, as thin as wallpaper, by converting electric energy into light directly based on semiconductor quantum dots (QDs). This work reports a sunlike full-spectrum electroluminescent white light-emitting diode (WLED) fabricated by spin-coating the mixture of yellow-green, red, and blue QDs at once, adopting the device structure of ITO/PEDOT:PSS/PVK(PTAA)/Mixed QDs/ZnO:Mg (AP-ZnO)/Al(Ag). The yellow-green and red QDs are prepared by coating three-layer ZnS shells on the CuInS₂ cores, which are synthesized using sulfur powder and dodecanethiol (DDT) as sulfur source, respectively. The blue QDs are prepared by coating three-layer ZnS shells on ZnCuGaS₂ cores. The photoluminescence quantum yield (PLQY) of the yellow-green, red, and blue QDs is 82%, 89%, and 83%, respectively. The WLED emits warm white light with a color temperature of 3000 K, chromaticity CIE (0.4228, 0.4287), and color rendering index (CRI) Ra 92.4. The electroluminescence spectrum of the device, whose similarity to the solar spectrum reaches 91.7% in the wavelength region of 450-700 nm, is rich in the red component and poor in the blue component, showing great potential for future healthy lighting applications.