Electroluminescent Properties of WLEDs With the Structures of Ce:YAG Single Crystal/Blue Chip and $\hbox{Sr}_{2}\hbox{Si}_{5} \hbox{N} _{8}$ : $\hbox{Eu}^{2+} $ /Ce:YAG Single Crystal/Blue Chip

In this work, evidence for matching blue chips with Ce:YAG single crystal phosphor is given. Forward current ( I f) and red phosphor were investigated and discussed to improve the electroluminescent properties of WLEDs using Ce:YAG single-crystal phosphors. Optimum forward current of such a device is chosen at above 45 mA. The structure of Sr 2 Si 5 N 8 : Eu 2+ phosphor/Ce:YAG single crystal/blue chip enormously improved the color temperature and color rendering index. This method can be a solution to achieve warm white light. The chromaticity of this structure with the color temperature of 5629 K and color rendering index of 77.1 is (CIE x, CIE y) = (0.3296, 0.3369) closely meeting the demand for ideal white light for general lighting (0.33, 0.33), but the luminous efficiency ( ηL) is lower at 81.04 lm/W in comparison to that of the Ce:YAG single crystal/blue chip structure at 94.55 lm/W.