The Preparation And Optical Properties Of YAG Fluorescent Materials For White LED

White light-emitting diodes (W-LEDs), as a new generation solid-state lighting source substitute for incandescent or fluorescent lamps,have attracted significant attention in lighting applications because of their excellent merits, including low energy consumption, a long lifespan and energy saving features. Currently, most current W-LEDs structures,which are generated by the combination of a blue InGaN chip and yellow-emitting Y3Al5O12:Ce3+ (Ce:YAG) phosphors dispersed in an organic resin or silicone, which are coated on the LED chip. This way has some drawbacks. Under the condition of high temperature, the property of the phosphor becomes weak and the organic binders undergoes yellow and age, which affects the W-LEDs properties and deteriorates the lifetime of LEDs devices, especially in the high-power LED application.Hence, the fluorescent materials, such as Ce:YAG single crystal and Ce:YAG glass ceramic with high performance via excellent thermal properties and optical properties, are needed for high-power LEDs to be suitable for general use.In this paper, the two kinds of YAG fluorescent materials with excellent optical properties, which are prepared by their optimized processes, have been investigated in detail. The materials based W-LEDs exhibit excellent thermal properties, which can meet the requirement of the high-power LED devices. Importantly, the structure, optical properties and thermal properties are studied through a series of characterization methods. The main conclusions are summarized as follows:1. The high-quality of Ce,Gd:YAG single crystal through the optimized proportion of Ce/Gd has been successfully grown by the Czochralski method. The result of XRD indicates that the Ce and Gd ions do not cause any significant changes in the host structure. The optical performances are investigated through fluorescence spectra. Finally, the LED device is fabricated by combining the single crystal wafer with a blue LED chip, yields a luminous efficacy of 144.11 1m/W. More importantly, the as-grown single crystal exhibits excellent thermal stability.2. A planar phosphor glass composite, has been successfully fabricated by Ce:YAG phosphor/glass thick film tape-casted on an ultrathin heat-resistance optical glass substrate. The properties of composite are investigated through XRD, SEM, decay curves and fluorescence spectra. The photoelectric parameters of W-LED devices are studied with different conditions such as phosphor contents, the thickness and the film position. Notably, an optimum performance W-LED with a luminous efficacy of 108.45 lm/W, a correlated color temperature of 5408 K and a color rendering index of 70.0 is fabricated under an optimized condition. Moreover, this composite exhibits a luminous efficacy loss of only 7.35% when it is heated to 433K, indicating that the material possesses better thermal stability, which could have potential applications in high-power W-LEDs.