Synthesis of color-tunable Cu–In–Ga–S solid solution quantum dots with high quantum yields for application to white light-emitting diodes

Synthesis and application of I–III–VI type Cu–In–Ga–S (CIGS) quantum dots (QDs) with varied In : Ga ratios to a white light-emitting diode (LED) are reported. The band gap and emission energies of CIGS QDs are found to be systematically higher with increasing Ga content as a result of an appropriate formation of CIS–CGS solid solution. ZnS shell-capped QDs of the CIGS/ZnS core–shell emit quite tunable wavelengths of 520–578 nm with exceptionally high photoluminescence quantum yield of 72–83%, depending on the composition. By combining highly fluorescent CIGS/ZnS QDs as color converters with a blue-emitting LED, efficient white QD-based LEDs with high luminous efficacies of 69.1–75.0 lm W−1 at a forward current of 20 mA are fabricated. A white QD-LED with an enhanced color rendering property is further developed by choosing and blending two kinds of CIGS/ZnS QDs, and its electroluminescent properties are characterized in detail as a function of applied current.