White LED Based on YAG : Ce,Gd Phosphor and CdSe–ZnS Core/Shell Quantum Dots

Core/shell CdSe-ZnS quantum dots (QDs) with a peak emission wavelength of 618 nm and size of ~ 5.5 nm were synthesized by thermal deposition approach. High photoluminescence efficiency with a quantum yield of more than 48% has been achieved. Red-shift of a peak emission wavelength from 532 to 568 nm was realized by doping Gd³⁺ ions into the YAG : Ce³⁺ to substitute some Y³⁺ ions. To compensate the poor color rendering index (CRI) of the YAG : Ce-based white light-emitting diode (LED) due to the lack of red spectral component, CdSe-ZnS QDs were blended into YAG : Ce³⁺ , Gd³⁺ phosphors. Prominent spectral evolution has been achieved by increasing the content of QDs. White LED combining a blue LED with the blends of phosphor and QDs with a weight ratio of 1:1, has been demonstrated with an improved CRI value of 90.