Sub-Nanometer ZnS Shell-Controlled Warm-to-Cool White Color-Tunable CuGaS2 Quantum Dots for White Light-Emitting Diodes

Abstract

CuGaS₂ (CGS) quantum dots (QDs) have garnered significant attention as white light-emitting materials for lighting and display applications, especially owing to their white color emission characteristics, arising from their broad photoluminescence (PL) and multiple recombination centers. However, a synthetic strategy for balancing the charge carriers in multiluminescent centers remains unresolved. Herein, we report white light-emitting CGS/ZnS/ZnS/ZnS (CGS/3ZnS) QDs with a broad-band PL property, which exhibits dual internal band centers. We adopt ZnS shell engineering with sub-nanometer thickness growth to balance the carrier distributions of CGS defect states, enabling the precise tuning of wide PL spectral bands. Additionally, the relative intensities of two PL band centers are controlled by adjusting the shell formation temperature, thus enabling fine-tuning of warm and cool white light emission. A series of white light-emitting CGS/3ZnS QDs is applied as the emission layer of an electroluminescence device, which results in white light emission with a maximum luminance of 1,285 cd/m², an external quantum efficiency of 1.72%, high color rendering indices from 87 to 92, and highly tunable correlated color temperatures ranging from 5,900 to 18,200 K. This achievement provides guidance for the development of emerging white light sources.