| Abstract:In order to deal with the global energy crisisi and enviroment pollution, research and development on the enviroment-friendly and energy efficient materials has become the main goal for material chemistry scientists. Because of its energy efficiency, enviromental frindness, high luminace efficiency and long life time, the solid state light (SSL) including LED and OLED, has been considered as the new generation lighting to repalce the convential incandescent lamp and fluorescent lamp.For the purpose of fabricated white SSL device with high color rendering index (CRI), proper correlated color temperature (CCT) and high luminence efficency, a seril of highly efficient phosphors have been synthesized in this study. Firstly, the connections between the phosphor performance, the preparation methods, and the phosphors crystal growth process have been studied. And then, the energy transition principles of the activator ions as well as the energy tranfer model between activator ions and matrix have been discussed. All the prepared phosphor samples have been fabricated into a white LED or white OLED devices in the end, the relationship between the phosphor performance and white light emitting device performance have been investigated. The follow conclusions were obtained:(1) YAG:Ce phosphor has been prepared by high temperature solid state reaction (SSR) method, co-precipitation approach and impinging stream (IS) method, respecitively. The obtained samples all shown two strong excitation peaked at345nm and460nm, which attributed by the transition2F5/2-5D and2F7/2-5D, respectively. An emission band peaked at550nm agree with the un-absorb blue emittiing from the chips produced white light emitting. The difference between these three methods is that the luminous intensity and dispersion properties, sample obtained by IS method demonstrated best performance among them, with relative intensity of about10,000, and best dispersion. And also IS method preparing perferct YAG csrystal at the lowest temperature of1200℃, the YAG crystal growth process agree with the Ostwald ripenning process. The particle size and size distrubution could be control by the size classification process and secondary calcining process. White LED devices were fabricited by the obtained phosphor samples successfully, the device fabricited by the IS methods sample shows best performance with CRI of85, CCT of7560K, CIE coordinates of (0.315,0.325), and the luminous efficiency of80.7lm/W, among them.(2) Rice shape Sr2Ce04:Sm3+phosphor with perfect crystal morphology and good dispersion has been synthesis by hydrothermal method. The phosphor sample shown a broad emission band between400nm600nm wavelenght and peak at466nm, which corresponds to the Ce4+-O2-chatge transfer (CT) energy transmission. Three emission band p.eaked at567.5nm,609.5nm and654.5nm, attributed to the transition of4G(4)5/2to the6H5/2,6H7/2,6H9/2level, respectively. The luminescent properties of the fabricated decices could ajust by changing the concentration of doped Sm ion. The best luminescent performace were CIE coordinates of (0.331,0.309), CRI of90K, CCT of5560K, and the luminous efficiency of32lm/W, at the doping concentration of1.0mol%; Single phased white emittiing phosphor Ba3LiMgV3O12:Eu3+with the same crystal structure of Ba3V2O8and particle size of3-5μm was prepared by high temperature SSR mothod. The obtained sample show very broad emission band between400and600nm, with peak of500nm, attributed to the transition of3T2-1A1and3T1-1A1in VO43-matrix. The excitation band peaked at343nm and side peaked at287nm, which corresponded to the transition of the1A1-3T1and1A1-3T2. After doped Eu ion to the matrix, three emission peakes at593,613and655nm, original from the transition of5D0-7F1,5D0-7F2,5D0-7F3, respectively. The best luminescent performace is CIE coordinates of (0.312,0.321), CRI of89, CCT of6600K, and the luminous efficiency of36lm/W, at the doping concentration of0.05mol%. Single phased white emittiing phosphor Sr2V2O7:Eu3+with perfect crystal structure at the temperture of800℃with charge compensation of Li2CO3the by SSR method. The charge compensation and doped Eu ion did not change the crysture of Sr2V2O7. The obtained sample has an excitation band between250-390nm, corresponded to the transition of3T2-1A1and3T1-1A1in VO43-matrix. Three emission distrubuted at red light region is the typical emission from the Eu ion. The best luminescent performace was CIE coordinates of (0.320,0.325), CRI of91, CCT of6126K, and the luminous efficiency of33lm/W, at the doping concentration of1.0mol%. In all, single phased phosphor fabricated LED device have better performance in CRI and CCT, close in CIE coordinate, and poor in luminous efficiency than that of YAG:Ce phosphor. One of the reason the the lower luminous efficiency for the near UV chips than the blue light emitting chips. Howerver, the results obtained in this study was better than others.(3) Nitride-based red emitting phosphor Sr2Si5N8:Eu2+with hexagonal structure, similar with crystal structure of Sr2Si5N8, has been prepared by SSR method. The phosphor sample shows excitation band between300-500nm and emission broad band between550-700nm. An efficient blue emitting OLED was obtain by blue phosphorescent material with the structure of ITO/m-MTDATA (30nm)/a-NPB (20nm)/mCP (10nm)/mCP:FIrpic (30nm,10/TPBi (40nm)/LiF/Al, which shown good stability at different current densities. The Sr2Si5N8:Eu2+phospphor color conversion layer (CCL) fabricated with optimized OLED-2become white OLED with the structure of CCL/glass substrate/ITO/m-MTDATA (30nm)/a-NPB (20nm)/mCP (10nm)/mCP:FIrpic (30nm,10/TPBi (40nm)/LiF/Al. The optimized condition for CCL prepared was phosphor doping concentration of50wt%at the spin speed of1500rpm. In the end, the obtained white OLED device illustrated CIE coordinates of (0.32,0.34), very close to the ideal white point (0.33,0.33), and the luminous efficiency of11.26lm/W, obviously better than the white OLED fabricated in other way.In all, many approaches could achieve efficiency white SSL, inorganic chip combined with inorganic phosphors or OLED combined with inorganic phosphors. High electro-optical conversion efficiency and properly distubute the the photon energy in differnet wavelength, which depand on the damand properities of the decivce, are two important items for all case. |
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