The Preparation And Luminescence Properties Of Ce:YAG Phosphor Glass For White LED

The development of white-light-emitting diodes(white-LEDs)is quite a promising field of research,which has gained enormous interest from scientists and engineers.LEDs offer superior properties over currently commercialized lighting such as incandescent and fluorescent lamps in terms of energy-saving,high efficiency,long lifetime and environmentally friendly features.Currently,a blue In Ga N chip combined with yellow Ce:YAG phosphors mixed with silicone or an organic resin is still the dominant technique for fabricating commercial white LEDs.Such silicones or organic resins are likely to deteriorate and turn yellow under long-term exposure to high temperature,which is ascribed to their poor thermal conductivity and low thermal stability,leading to a degradation in the LE and shifting of the chromaticity.The need to solve these proplems gives rises to transparent glass ceramic remote phosphors,taking advantage of their short preparation period,low cost,high physical and chemical stability,high thermal conductivity,high transparence,simple packaging,and excellent optical properties.The Ce:YAG glass ceramics with excellent optical properties have been studied for W-LEDs in this paper.Transparent Ce:YAG glass ceramics are prepared though two different methods,the optimum condition the optimized technology process of glass ceramic with high optical properties are obtained.Notably,the glass ceramic based W-LEDs possess better optical properties than the commercial W-LEDs and demonstrates an excellent thermal stability,and which have desirablepotential for application in the high powered W-LEDs.In addition,the structural,micro-structures and optical properties of glass ceramics are systematically investigated with the help of X-ray diffraction,scanning electron microscopy,optical absorption and luminescence spectra.The main research results have been summarized as follow:1.The transparent Ce:YAG glass ceramics were prepared though frozen sorbet method.The Pb/Si molar ratio dependence of the structural,micro-structures and optical properties of glass ceramics was studied.In addition,the glass ceramics were utilized to fabricate a white LED device,the Ce3+ concentration and thickness dependence of colourimetry parameters(including luminous efficacy and chromaticity coordination)were discussed in detail.Notably,a LE of 97 lm/W,a CCT of 5561 K and a CRI of 69.3,are achieved at the Ce3+ concentration of 0.6 mol% and a thickness of 1 mm.2.Transparent YAG The transparent Ce:YAG glass ceramics were prepared though “ Phosphor in Glass(PiG)Method”.The transparent Ce:YAG PiGs were fabricated using a one-step melt-quenching method with a relative low sintering temperature.The quality of the as-prepared products(structural,morphological and optical properties)was comparable to those of the PiG samples prepared using a two-step meltquenching method.Furthermore,the luminescence spectra of the PiGs with different phosphor concentration and sintering temperature/time was measured.And the phosphor concentration and thickness dependence of colourimetry parameters were studied in detail.Notably,we fabricated a high-performance white LED with high luminous efficacy(125 lm/W),low correlated colour temperature(4329 K)and colour rendering index of68,and the PiG material exhibits a good thermal stability.Therefore,the present transparent phosphor glass will have desirable potential for application in the high powered W-LEDs.