White Led Research And Preparation Of Rare Earth Doped Yag Phosphors

In recent years, WLEDs are extensively used in the fields such as lighting, display because of its distinguished advantages, i.e. high efficiency, energy saving, environment friendliness with the development of the semiconductor technology. These advantages are enormously significant in the realization of harmonica between human beings and nature and the sustainable development of our society. WLEDs are mainly realized by the method of phosphor converted LED chips, in which YAG:Ce3+phosphor and GaN based blue LEDs are usually combined to produce white light. That all of the commercialized products adopt this way makes the phosphor as a key factor in the WLED technology. However, nowadays, most of the WLED phosphor patents including YAG based ones are controlled by only a few famous foreign companies. There is still a long way to go for us to improve the efficiency and overcome the gap between them.In our research, two methods namely solid state reaction and co-precipitation are investigated to synthesize different rare earth elements doped YAG phosphors. And some useful parameters are optimized and derived for reference. During the investigation, TG-DSC, XRD and SEM are adopted to analyze the crystallizing temperature, crystal structure, phase and morphology of the production powder. Compared the two methods, in co-precipitation, the precursors are got by reaction in solution, so the material cations are mixed in nanometer scale uniformity, while, in solid state reaction, the material oxides are only mixed in micrometer scale. Thus, the atoms’diffusion distances during the crystallizing reaction for the co-precipitation precursor are shorter than solid reaction materials. But the solid reaction method is simpler and easier for industrialization.Gd3+, Ga3+and V3+are co-doped with Ce3+in YAG crystal structure, and their excitation spectral and phosphor luminescent (PL) spectral are investigated. The results indicate that these dopants can shift the peak of the PL spectral and some of them (i.e. Ga3+, V3+) will strengthen the intensity of the emission. Finally, some samples are coated on power blue LED chips, and the influence of different processes on the luminescent efficiency are discussed. And we get the conclusion such as sifting and twice reducing calcine can refine the production and improve the efficiency. Some samples we got have already reached over95percent of comparing sample of Hongda.