Spectral Optimization of Phosphor-Coated White LEDs for Color Rendering and Luminous Efficacy

An optimization model for luminous efficacy of a correlated color temperature tunable phosphor-coated white (pc-W) light-emitting diode (LED) consisting of a blue LED, the phosphors, and a red LED, including down-conversion energy loss, has been developed under the constraint of the designated color rendering index. The optimized peak wavelength and full-width at half-maximum of each color component, as well as photometric and colorimetric performances of the pc-W LEDs for maximizing the luminous efficacy under various color rendering indices at a correlated color temperature of 2700 to 6500 K were presented. It has been found that the luminous efficacy for the tetrachromatic pc-W LED is higher than that for the trichromatic pc-W LED under good color rendering.