Improving Stability of CIS/ZnS-Based White Light-Emitting Diodes by Silica Coating

Abstract

Cadmium-free quantum dots (QDs) have been investigated for replacement cadmium-based QDs because of highly toxicity for humans and environmental such as CuInS2/ZnS (CIS/ZnS) core/shell QDs that exhibit tunable emission wavelength and very broad emission spectrum. It often used in solid state lighting and white light-emitting diodes (WLEDs). This work reports on the synthesis of CIS/ZnS core/shell QDs using dodecanethiol (DDT) and zinc stearate as a precursor to form ZnS shell. Moreover, for improving the device stability, we coated SiO2 on CIS/ZnS QDs surface. The crystal structure was analysis by transmission electron microscopy (TEM) and powder X-ray diffractometer (PXRD). The result shows that the emission wavelength of CIS/ZnS is 534 nm and with a high quantum yield (QY) of 107 %. The color rendering index (CRI), correlated color temperature (CCT) and luminous efficacy of SiO2-coated WLED are 73, 4764 K, and 95 lmW−1, respectively. Moreover, high stability of SiO2-coated WLED can be obtained. The result indicates that CIS/ZnS@SiO2 QDs have great potential to development of further WLED application.