Study of UV excited white light-emitting diodes for optimization of luminous efficiency and color rendering index

Wavelength down-converted white-light sources excited by near ultraviolet light-emitting diodes require specific phosphor properties in order to generate high-quality white light (namely, light with good color rendition and stability of color coordinate). Simulation and experimental results are discussed, with particular emphasis on the spectral distribution property of red phosphor required to realize high values of luminous efficiency and color rendition. A peak wavelength of 610 nm and an FWHM of 80 nm for the spectral power distribution were proposed, and co-doped phosphate materials were synthesized successfully. This can contribute to a whitelight source with a luminous efficiency of 45 lm/W and color rendering index greater than 90 at a color temperature of 5600 K and an operational current of 20 mA.