| As a novel solid state light source, the white light emitting diode hasmany advantages in high efficiency, superior lifetime, non-polluting, fastresponse, etc. Due to the requirements of "Green Illumination", whitesLEDs have been developed and widespread rapidly by the promotion ofnational policies in recent years, which are expected to be a goodcandidate for incandescent lamps or fluorescent lamps and regarded asthe "fourth-generation light Source". According to the LED’ structure andprinciple, luminescence materials is a essential part in the fabrication ofWhite LED, which can directly affects the Photoelectric parameters ofLED devices with its performance and different packaging methods.Therefore, the research on luminescence materials for White LED has animportant practical significance and application prospects.In this thesis, Ce:YAG single crystal and Ce,Mn:YAG single crystalwere prepared by Czochrolski Method, and the performances of rare earthions/transition metal ions doped single crystal were characterized byXRD, absorption spectra and fluorescence spectra, etc. Furthermore, thephotoluminescence behavior and energy transfer mechanism wereespecially analyzed. In addition, study on best doping concentration anddoping ratio in Ce,Mn:YAG are also included. The different packagingmethods were discussed, trying to determine the effect factors of LEDPhotoelectric parameters.(l)Focus on solving the problem of pure phase synthesis and CrystalGrowth technology, explore a stable and reliable crystal growth process.In this paper,[111] oriented YAG single crystal was used as a seed. We discussed the influence on the crystal growth of thermal fields,atmosphere, pulling speed and rotate speed, and finally obtained highquality single crystal which about O30mm in diameter with highcrystallinity. The experiment results show that the rare earth/transitionmetal ions doping did not change the crystalline phase of YAG.(2)Theabsorption spectrum of Ce:YAG and Ce,Mn:YAG singlecrystal indicate that: All single crystal prepared in this paper can beeffectively excited by the460nm blue light, match well with blue chipsfor White LED. The emission spectrum usually composite by multipleemission peaks, and the broad emission bands are due to the emission ofthe dopant ions corresponding energy level transition. In contrast withCe:YAG single crystal, Mn ions play a luminescent center added inspectrum which expand the half height width of the mission peakredshifts.(3)Theoptical performance of Ce,Mn:YAG single crystal withdifferent doping concentration were studied, we found that in YAG matrixthe best doping molar ratio of Mn and Ce ions is2:1, the best dopingconcentration of Mn and Ce ions is CeO.93%, MnO.72%. It is worthnoting that there is no direct relationship between doping molar ratio anddoping concentration, an ideal fluorescent material need to be selected onan appropriate dopant concentration with suitable doping ratio. In thisthesis, the best single crystal is Ceo.o28,Mnoinous.o36:YAG, the best lumefficacy value of0.5mm-thick Ce,Mn:YAG single crystal plate fabricatedWhite LED is114.7691m/W under20mA drive current, which havereached industry standard, can be directly applied to the daily life.(4)Differentpackaging methods was taken and the influence factorsof Photoelectric parameters was discussed in the research work.According to the analysis results, the combination of influencing factorsoptimization were executed. In addition, the adjustable photoelectricproperties of White LED under different crystal plate and drive currentwere also measured, the results show that a thickness of0.5mm YAGsingle crystal plate and low drive current are suitable with the matchingof blue chip. Moreover, the cost analysis of YAG crystal growth wastaken in this paper, to provide a reference for the industrial production. |
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