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-IV 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 69.1-75.01m 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.