Sr _0.95 Zn _0.05 Se:Eu ²⁺ and CdSe/ZnS nanocrystals hybrid phosphors for enhancing color rendering index of white light emitting diode

In this study, the yellow emitting cubic structure of Sr _0.95 Zn _0.05 Se:Eu ²⁺ phosphors were prepared by high temperature solid state reaction. The Sr _0.95 Zn _0.05 Se:Eu ²⁺ phosphors exhibited strong excitation intensity under 400-460 nm region, and broad band emission appeared at around 545-600 nm due to the d-f transition of Eu ²⁺. To enhance the red emission, HDA/TOP/TOPO capped CdSe/ZnS NCs were synthesized via fast nucleation and slow growth method. The narrow emission peak was located at 615 nm with 69% of high quantum yield. Bright white emission was generated by combining a 460 nm InGaN LED chip with CdSe/ZnS NCs and Sr _0.95 Zn _0.05 Se:Eu ²⁺ hybrid phosphors. The fabricated white LEDs showed warm white light with acceptable CIE chromaticity coordinate variation from (0.343, 0.255) at 20 mA to (0.335, 0.250) at 50 mA. The addition of CdSe/ZnS NCs contributed to the extension of white light spectrum by supplement of the red region. The color rendering index was largely enhanced from 41.7 to 79.7 compared to the Sr _0.95 Zn _0.05 Se:Eu ²⁺ based phosphors white LED.