| As the fourth generation of "green lighting", white LEDs have attracted researchers’attention and become one of the important research points due to their advantages, such as energy saving, environmental protection, high efficiency, short response time, long service life, easy packaging and so on. Currently, the realization of white LED is mainly through the combination of chip and phosphors. Although the white LED technology has been developed greatly, and has been applied in many fields, but there are still two problems to be solved:(1) the organic matrix aging due to the huge heat of chip; (2) the color rendering index is not high enough. In traditional methods, the phosphors is directly coated with resin/silica hybrid on the chip of LED. The operation temperature of LED chips increases dramatically, causing an ageing and yellowing of organic resin or silicone, which consequently results in the unreliability of white LED modules and the weakly optical properties. It is a good idea to use phosphors in the inorganic matrix to replace the organic phosphor materials. So far, the white LEDs fabricated by a blue chip and yellow phosphor(YAG:Ce3+) generate low CRI white light due to the lack of the red region, which limits its application in the field of interior lighting and medical treatment. The addition of green/red phosphors has a significant effect on improving CRI to 80 or more.In view of the above problems, this paper presents the research idea of phosphor glass prepared by SPS solid phase sintering method, the specific research works are as follows:(1) This paper demonstrates that by applying spark plasma sintering (SPS), green phosphor in silica glass could be fabricated directly from mixtures of commercial LuAG:Ce3+ phosphor and self-synthesized mesoporous SiO2 (SBA-15) powders at 1050℃ within 100℃/min sintering rate and 3 min holding time, exhibiting high transparency. The results of XRD and ESEM show that the phosphor is distributed uniformly in the glass matrix. The relative quantum yield is 83% with a strong absorption peak at 470nm and a green emission peak at 520nm.(2) The red phosphor glass materials were prepared by same sintering method with red (CaAlSiN3:Eu2+) phosphors and SBA-15 powders, exhibiting different wavelength range with different red phosphors. From the results of ESEM and XRD, the red phosphor can be distributed in the glass matrix uniformly, but the partial lattice diffraction peaks are changed because of a certain extent interface reaction with mesoporous SiO2. The strong absorption peak at 470nm was still observed, while the emission peak was varied with the corresponding red phosphors.(3) Finally, the composite phosphor glasses were prepared by mixing various color phosphors with SBA-15 powder in different proportions, and the microstructure and optical properties were analyzed. Composite phosphor glass with different proportions of phosphors were excited at 470nm, emitting fluorescence with different wavelength peaks, increasing the the half high width and augmenting the light region coverage range. The blue LED chip and the sample of composite phosphor glass with a certain proportion of phosphors were packaged by COB to fabricate the white LED device. The highest CRI is 88.2 tested by HSP 3000 spectrum analyzer with a driving power of 36 V/140 mA, reaching the international advanced level. |
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