Highly red-luminescent N-acetyl-l-cysteine-stabilized CdTe/CdS@ZnSSiO2 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 ZnSSiO2 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@ZnSSiO2 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.