Zn_xCd_1−xS quantum dots–based white light-emitting diodes

Abstract

In this study, two kinds of colloidal ternary semiconductor white light-emitting quantum dots (WQDs), Zn(0.5)Cd(0.5)S and Zn(0.8)Cd(0.2)S, are prepared and used as nanophosphors in a UV light-emitting diode (UV-LED) pumping device. When the weight ratio of Zn(0.5)Cd(0.5)S WQDs is 9.1 wt. % in silicone and the drive current is set at 20 mA, the chromaticity coordinates (CIE), correlated color temperature (CCT), color rendering index (CRI), and luminous efficiency are (0.43,0.37), 2830 K, 90, and 0.94 lm/W, respectively. On the other hand, under the same weight ratio in silicone, the CIE, CCT, CRI, and luminous efficiency of Zn(0.8)Cd(0.2)S WQDs are (0.36,0.33), 4240 K, 86, and 4.12 lm/W, respectively. Based on the above results, we can conclude that WQDs-based LED can be obtained by controlling the compositions of Zn(x)Cd(1-x)S QDs due to the coexistence of band-edge and surface state emission.