| Because of rapidly growing market demands for display and alternatives to conventional lighting sources (incandescent light bulb), a tremendous emphasis is being placed on white LEDs as the most promising illuminating sources. Despite the rapid progress of white LEDs, the commercial InGaN/YAG:Ce3+phosphor is not able to produce white light with satisfactory color-rendering-index and high luminescence efficiency. In recent years, there is an increasing special interest in development of high-performance luminescent materials capable of converting the near-UV light to multi-color visible emissions.Rare earth ions with high color purity and stability play an extremely important role in solid luminescence materials. The rare-earth ions have unfilled4fn electron configurations, the electrons in4f shell are shielded from the crystalline environment by the outer filled5s2and5p6orbits. As a result, the rare earth ions have abundant electron energy levels, long-lifetime excitation state, more than two hundred thousand energy transitions channels and its emission spectra cover from infrared, visible to ultraviolet range. Zinc Oxide (ZnO) is a direct wide-gap (3.37eV) semiconductor with n-type conductivity. ZnO’s exciton binding energy (60meV) is much larger than that of GaN (25meV) and has stronger absorption in the UV region. As the third generation of semiconductor functional materials, ZnO has become the hot spot in the domestic and foreign research due to its special photoelectric performance and potential application. The rare earth doped ZnO fluorescent film has good electrical conductibility, thermal conductivity, uniformity, and combination well with substrate, leading to high temperature and large current resisting, so the preparation of the fluorescent films are of great significance for the application of some kinds of display device. If efficient energy transfer from the ZnO host to the Re3+can be obtained, Re3+-doped ZnO would be a promising candidate for new light-conversion materials with strong UV absorption, high color purity, stability and high luminescence efficiency, which is desired in advanced display and lighting, such as full-color flat panel display, field emission displays.In addition, YAG (Y3A15O12, yttrium aluminum garnet) belonged to cubic system have garnet structure, optical homogeneity, Unique refraction and Chemcial Properties Stability. YAG is an widely applied luminous and laser host material. As YAG doped rare earth luminescent ceramic has good heat conduction, transmission, chemical stability, mechanical behavior, it can overcome light scattering of the mixture of fluorescent powder and silicone rubber, poor cooling and easy to aging. YAG fluorescence ceramic replacing the mixture of fluorescent powder and silicone rubber improve thermal and optical properties of LED effectively.In our work, undoped and Eu3+, Tb3+co-doped ZnO thin films, ZnO and ZnO:Eu3+luminescent material and YAG doped Ce, Cr fluorescent ceramics were prepared by different methods. Luminous mechanism and effect of the structural change resulted from doping content were investigated by Fluorescence Spectrometer (PL) and X-Ray Diffractomer (XRD). The effects of substrate, substrate temperature, doping and deposit time on structure and morphology of ZnO thin films were investigated by X-Ray Diffractomer (XRD). The energy transfer mechanism between the host and rare earth ion is discussed.First, ZnO and ZnO:Eu3+luminescent material were prepared by spin coating method on Anodic Alumina Oxide (AAO)Template, which were analyzed through scanning electron microscopy and spectrophotometer. SEM shows that the pore size of AAO template is between100nm-300nm, the AAO template spin coated ZnO or ZnO:Eu3+appear layer structure, part pores disappear and then indeed are filled by zinc oxide. The PL shows that ultraviolet emission peak and the characteristic emission peak of Eu3+(5D0-7F2) appear respectively, but the green light emission band from defects level transition of zinc oxide disappear. It reveals that the structure of ZnO has been improved obviously.Second, undoped and Eu3+, Tb3+co-dope ZnO thin films were deposited by radio frequency (RF) magnetron sputtering technique on different substrates and under different conditions. The effects of substrate, substrate temperature doping and deposit time on structure and morphology of ZnO thin films were investigated by X-Ray Diffractomer (XRD).Experimental results indicate that the films prepared on glass and quartz substrate have a preferred orientation along the c-axis at300℃, an hour sputtering and at ambient temperatures, half an hour sputtering respectively, whereas the films prepared on silicon substrate have a preferred orientation along the (103)-axis at300℃and an hour sputtering. The results of this study have certain reference significance for preparation of ZnO films with high quality.Third, Ce and Cr doped YAG fluorescent ceramics were fabricated by high temperature solid-state method. Luminous mechanism and effect of the structural change resulted from doping content were investigated by Fluorescence Spectrometer (PL) and X-Ray Diffractomer (XRD). Experimental results indicate that there is no observable hybrid phase in the XRD patterns of Ce, Cr doped YAG, but the impacts of ions’(Ce, Cr) doping on inter-planar distance was discussed in detail. The red emission peak of Cr3+in emission spectrum originates from2E-4A2transition and the energy transfer exists between Ce3+and Cr3+. |
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