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Title: Organic materials for application in electroluminescent devices
Other Titles: You ji dian zhi fa guang cai liao
Authors: Wong, Oi Yan (黃愛恩)
Department: Dept. of Physics and Materials Science
Degree: Master of Philosophy
Issue Date: 2004
Publisher: City University of Hong Kong
Subjects: Electroluminescent devices -- Materials
Electroluminescent display systems
Light emitting diodes
Notes: CityU Call Number: TK7871.89.L53 H83 2004
Includes bibliographical references.
Thesis (M.Phil.)--City University of Hong Kong, 2004
xv, 140 leaves : ill. (some col.) ; 30 cm.
Type: Thesis
Abstract: Organic light-emitting devices (OLEDs) operate on the principle of converting electrical energy into light, a phenomenon known as electroluminescence (EL). They exploit the properties of certain organic materials that emit light upon excitation and subsequent relaxation. This is a new technology for flat panel displays and being actively studied at many laboratories around the world. For a full color display, the three preliminary colors (red, green and blue) or white color emission are necessary. The aim of our research is to improve the EL efficiency and performance in all the three preliminary colors of RGB devices through proper materials design. Several potential series of blue host emitter, blue dopant emitter, intramolecular charge transfer (ITC) compounds with red and green emissions, were synthesized and used as the active emissive m"ateria1s in OLEDs. As the quantum efficiency of the device using fluorescent emitters is limited by the theoretical ratio of singlet excitons (25%) to triplet excitons (75%) upon electron-hole recombination from electrical excitation. Phosphorescence devices can make use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. A new tris-ortho-cyclometalated compound of iridium based on the pinene substituted 2- phenylpyridine was synthesized and characterized. This novel green phosphorescence material has a very high quantum yield of 0.71 in solution and a relative short triplet lifetime of 0.33 μs in solid. Self-quenching was significantly reduced in this iridium compound even at very high concentrations by the sterically hindered pinene spacer in the phosphor molecule . In addition, white emitting OLED was also studied. Through these studies, some new ideas on the design of chemical structures are discussed.
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