| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系研究所 === 100 === Nowadays, the white light emission diode (LED) most adopts blue chips to excite yellow phosphor. However, uneven phosphor coating results in the phenomenon of uneven color distribution. In order to get higher quality of white light source, the thesis proposes a novel structure of phosphor coating. It adopts ultrasonic spray pyrolysis to doped YAG:Ce3+ phosphor into zinc oxide (ZnO:YAG) to discuss about the crystal structure and luminescence properties of fluorescent material.
The results of the experiment show that undoped ZnO appears in the structure of hexagonal plate. It indicates an excellent crystalline along the (002) preferred orientation. With the increasing doping concentration, it would change the growth mechanism of ZnO:YAG films. Then, it results in accelerating lateral growth rate of hexagonal plate. It''s the phenomenon of deflection of hexagonal plate. As the doping concentration increasing gradually, the degree of deflection would get much bigger. It results in ZnO:YAG film appearing in the structure of nanoflower. According to the XRD patterns, the increasing doping concentration would make the crystal quality deterioration and make FWHM larger.
Photoluminescence measurements revealed that ZnO is with stronger near-band-edge and peak value is about 380nm. As the doping percentage increasing, the defect exciting of ZnO and the luminescence of YAG:Ce3+ get increasing as well. The luminescence of YAG:Ce3+ emitted green due to the electron from excited state of 5d to ground state of 4f.
The results of the absorption spectrum show the absorption energy gap of ZnO would get red shift with the increasing doping concentration. Because of the defect density increasing with the doping concentration as well, it results in poor luminescence properties.
The n-ZnO:YAG/p-Si devise is made. The characteristic of ohmic contact from the electrode of Ni/Ag alloy on the p-Si substrate. The I-V is with the rectifying behavior and the starting voltage (Vth) is about 5V. According to PL, we can observe that the peak value of YAG:Ce3+ , and it would appear in the purple-white light after excited.
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