A design methodology for phosphor mixtures for tunable spectrum LEDs

ABSTRACT Spectrum tuning in phosphor converted white light emitting diodes (pc-WLED) is done by mixing powders of phosphor compounds (with different emission wavelengths) in different weight ratios. In this paper, a new methodology for designing unique full spectrum phosphor mixtures (with fixed weight ratios of different emission phosphor) has been presented that could provide a wide range of pc-WLED spectrum. This is done by optimizing the excitation and emission spectra of the phosphor compounds used in the mixture. A unique phosphor mixture comprising of Eu2+ and Ce3+-Na1+ activated compounds of SrGa2S4, CaGa2S4, SrS, CaS and CaF2 was used to produce full spectrum warm, neutral and cool white LEDs with color temperatures between 2500 K and 7500 K and with color rendering index exceeding 95.