Construction of highly luminescent CdTe/CdS@ZnS-SiO₂ quantum dots as conversion materials toward excellent color-rendering white-light-emitting diodes

Highly red-luminescent N-acetyl-l-cysteine-stabilized CdTe/CdS@ZnS-SiO₂ quantum dots (QDs) were successfully synthesized in the aqueous phase via a promising microwave strategy for the first time; they were prepared by coating SiO₂ layers doped with ZnS-like clusters on CdTe/CdS core/shell QDs. Owing to the effective passivation of the coating CdS shell and ZnS-SiO₂ layer, the as-prepared QDs show high photoluminescence, good optical stability, and low biotoxicity. Moreover, the outermost SiO₂ layer endows the QDs with excellent silicone compatibility. The structures and photoluminescence properties of the CdTe/CdS@ZnS-SiO₂ QDs were well studied by various characterizations. For their practical applications, we explored the promising red-luminescent QDs as novel red phosphors to fabricate two types of white-light-emitting diodes (WLEDs), a low-power surface-mounted device and a high-power device. Both of the devices produce bright white light with remarkable color rendering. Especially, the color-rendering index (CRI) of the high-power device even reaches up to 91.9, suggesting the great potential of the highly red-luminescent QDs for solid-state lighting systems with high CRI.