Chromaticity-tunable phosphor-in-glass for long-lifetime high-power warm w-LEDs

The commercially dominant phosphor-converted illumination white light-emitting-diodes (w-LEDs) generally suffer from red deficiency and the poor thermal stability of the organic encapsulants, resulting in cool white light, luminous degradation and chromatic aberration for the embedded YAG:Ce3+ phosphors after long-term working. Aiming to solve these problems, herein, a chromaticity-tunable robust phosphorin- glass (PiG) inorganic color converter was successfully fabricated by co-sintering YAG:Ce3+, Mn2+, Si4+ phosphor particles and the innovatively-designed TeO2-B2O3-ZnO-Na2O-Al2O3 low-melting precursor glass. At first, the spectrally-modified YAG:Ce3+, Mn2+, Si4+ phosphor was prepared by doping Mn2+ as the red emitter and doping Si4+ as the charge compensator through a solid-state reaction route. Then, the YAG:Ce3+, Mn2+, Si4+ powder was incorporated into a specifically prepared precursor glass to form the PiG composite at 550 degrees C. Owing to the density and the refractive index matches for the phosphor particles and the glass matrix, the particle dispersion in PiG is quite homogeneous and the adverse light-scattering is depressed. The high-power warm w-LED was constructed by coupling a PiG plate with an InGaN blue chip. Remarkably, the chromaticity coordinate of such a w-LED can be well tuned to follow along the Planckian locus with the correlated color temperature evolving from cool white (5541 K) to warm white (3050 K) and a color rendering index around 70, under a driving current of 350 mA. Moreover, the PiG-based warm w-LED presents much superior thermal stability to the traditional phosphor-in-silicone (PiS)-based one. This work highlights the practical applications of the PiG luminescent material in the long-lifetime high-power warm w-LEDs.