| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 105 === White light-emitting diodes (WLEDs) have been widely used in different lighting systems around the world because of their high brightness, low power consumption, high durability and environmental protection. In order to improve the WLEDs color rendering index (CRI), must add red-light phosphors rich red spectral area. Nitride phosphor is a red phosphors commonly used in WLED devices. However, the human eye is almost impossible to detect more than 650 nm red light. Fluoride phosphors with narrow spectral emission and the appropriate peak wavelength of 630 nm, moreover, no yellow-green light absorption can be effectively avoided in the components of the spectrum of re-absorption of energy consumption, based on the above advantages, fluoride phosphors has great potential applied to WLEDs system. However, the commercially fluoride phosphors K2SiF6:Mn4+ (KSF) lacks the spectral contribution of the positive red light at 620 nm in the emission spectrum. Therefore, the spectral modification of the fluoride phosphors are still important direction. At present, it is pointed out that with the additional zero phonon emission spectrum can be obtained by the distortion of the fluoride phosphors structure, which is a positive red light band at 620 nm to further enhance its red spectral contribution.
In this study, the red fluoride phosphors with high quantum efficiency and zero-phonon radiation was synthesized by chemical co-precipitation method. The crystal structure was analyzed by X-ray diffractometer. The relationship between the crystal structure and its electron transition process was discussed. To understand its radiation spectrum and zero-phonon radiation mechanism. The theoretical step of fluoride was obtained by theoretical calculation, and the transition process of the experimental spectrum was compared. In this study, we also measured the spectral lifetime of the powder in different environments, observed the trend of the zero-phonon line, and analyzed the mitigation process of the fluoride phosphors. In addition, we tried to adjust the main structure of the fluoride phosphors. The control of the zero-phoneme radiation intensity, and ultimately the synthesis of fluoride phosphors used in white light-emitting diodes, and with the commercial KSF phosphor powder comparison, the performance of its device can be seen by the additional zero phonon red light contribution, can effectively enhance the white light device color rendering and its Luminous efficacy of radiation (LER) of the lighting performance.
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