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In this letter, phosphor-converted white light-emitting diodes (pc-WLEDs) were fabricated using two separated phosphor layers (B&G up/R down) that combine three color phosphors (blue, green, and red) with near-ultraviolet LED chips. The pc-WLEDs have a high color rendering index (CRI) and a tunable color temperature. Regarding the spectra of the phosphors, the CRI value increased with the increasing percentage of overlapping area between the spectra deconvoluted from the electroluminescence spectrum of the pc-WLED. By controlling the thickness of the phosphor layers, the pc-WLEDs with high CRI values and various color temperatures can be obtained. The correlated color temperature and the CRI value of the optimized pc-WLED were 4606 K and 93.8, respectively. [ABSTRACT FROM PUBLISHER]

Y2.95Al5O12{:}{\0.05Ce}^3+ phosphors were synthesized via the solid-state reaction method using fluxes of H3BO3 and BaF2. The thermal stability and luminescence of Y2.95Al5O12{:}{\0.05Ce}^3+ prepared with 6 wt% BaF2 flux additive (Sample II) were compared with those of Y2.95Al5O12{:}{\0.05Ce}^3+ prepared with 7 wt% H3BO3 flux additive (Sample I). The crystallinity of Sample I was found to be better than that of Sample II. This difference in crystallinity, which led to a difference in thermal stability, is well explained by the presence of defects. Moreover, Sample I, Sample II, and commercial Y3Al5O12{:}{\Ce}^3+ phosphors were coated onto 450-nm chips for the fabrication of white light-emitting diodes (WLEDs). The luminous efficacy (@ 350 mA) of Sample-I-based (68.98 lm/W) and commercial-Y3Al5O12{:}{\Ce}^3+-based (70.87 lm/W) WLEDs was lower than that (77.2 lm/W) of the Sample-II-based WLED due to the powder morphology of the phosphors. [ABSTRACT FROM PUBLISHER]