Ultra high luminous efficacy of white Zn_xCd_1-xS quantum dots-based white light emitting diodes

In this study, the colloidal ternary Zn_xCd_1-xS (x = 0.5 and 0.8, named as Zn_0.8 and Zn_0.5) white quantum dots (WQDs) have been prepared and used to form WQDs-based white light emitting diodes (WLED) with three different encapsulation types (convert, remote and conformal type). Moreover, acyclic-based UV curing polymer was used to incorporate with WQDs. The optical properties of Zn_x WQDs-based WLEDs including Commission Internationale de l'Eclairage (CIE) chromaticity coordinates, correlated color temperature (CCT), color rendering index (CRI) and luminous efficacy can be tuned by controlling the compositions, blending content of Zn_x WQDs and encapsulated methods. The optimum result for Zn_0.8 and Zn_0.5-based WLEDs can be observed in the remote type with the CIE, CRI, CCT and luminous efficacy under 20 mA of (0.34, 0.32), 87, 5000 K and 11.93 lm/W and (0.40, 0.37), 86, 3400 K and 2.76 lm/W, respectively. The higher luminous efficacy and stability of WLEDs can be obtained due to use an acyclic-based UV curing polymer, high QY of WQDs and suitable encapsulated method. The results also have exhibited the potential applications of Zn_x WQDs as nanophosphors in WLEDs.