| Organic light-emitting diodes (OLEDs), which have high potential as the most ideal andpotential display technology in the21stcentury, possess many advantages, e.g., self-emission, fastresponse, full solid device, full-color, easy fabrication, high efficiency, wide view-angle, ultrathinthickness. To realize full-color displays, high performance red, green, and blue light-emittingmaterials are required. In contrast to red and green emitters, only a few blue emitters showapplication potential but much inferior performance in efficiency, stability and color purity. Thehighly efficient blue light-emitting materials can be used as not only emissive layer in OLEDs, butalso host materials for efficient blue and white light source. Among the promising blue emitters,fluorene and its derivatives which have an aromatic biphenyl structure with wide energy gap in thebackbones and high luminescent efficiency have drawn much attention of materials chemists anddevice physicists. However, a major problem in using these kinds of materials in OLEDs is theundesirable lower energy emission band, turning the pure blue emission to blue-green color, due tothe form of the excimer, the result of the chain aggregation. In order to improve this problem,covalently incorporating electron-donating and electron-withdrawing groups onto the polymerbackbone is an effective way to enhance the charge injection/transport and suppressaggregation/excimer formation. So nine different fluorene derivatives have been synthesized, theoptical performance of this fluorene derivatives were also measured in this work.In chapter one, the blue emitting materials of fluorene was summarized. The significance andresearch routes on this thesis were outlined.In chapter two, four new fluorene derivatives,2,7-bis(4-fluorophenyl)-fluorene,2,7-bis(3-cyanophenyl)-fluorene,2,7-bis(3,5-bis(trifluoromethyl)phenyl)-fluorene and2,7-bis(3-nitrophenyl)-fluorene was synthesized and characterized by X-ray single crystal diffraction,1HNMR, FT-IR spectra and elemental analysis. At the same time, the UV-Vis absorption andfluorescence spectra of those four new fluorene derivatives, in CH2Cl2solution as well as in filmwere also discussed. Studies have shown that those new fluorene derivatives exhibit deep-bluefluorescence differently under UV excitation except2,7-bis(3-nitrophenyl)-fluorene. Thefluorescence quantum yield of2,7-bis(4-fluorophenyl)-fluorene,2,7-bis(3-cyanophenyl)-fluoreneand2,7-bis(3,5-bis(trifluoromethyl)phenyl)-fluorene in CH2Cl2solution are0.59,0.62and0.60. In chapter three, four new fluorene derivatives,2,7-bis(4-fluorophenyl)-9,9-diethyl-fluorene,2,7-bis(3-cyanophenyl)-9,9-diethyl-fluorene,2,7-bis(3,5-bis(trifluoromethyl)phenyl)-9,9-diethyl-fluorene and2,7-bis(3-nitrophenyl)-9,9-diethyl-fluorene was synthesized and characterized by X-ray single crystal diffraction,1H NMR, FT-IR spectra and elemental analysis. At the same time, theUV-Vis absorption and fluorescence spectra of those four new fluorene derivatives, in CH2Cl2solution as well as in film were also discussed. The results show that those new fluorenederivatives exhibit deep-blue fluorescence differently under UV excitation except2,7-bis(3-nitrophenyl)-9,9-diethyl-fluorene. In CH2Cl2solution the fluorescence quantum yield of2,7-bis(4-fluorophenyl)-9,9-diethyl-fluorene,2,7-bis(3-cyanophenyl)-9,9-diethyl-fluorene,2,7-bis(3,5-bis(trifluoromethyl)phenyl)-9,9-diethyl-fluorene are0.61,0.64and0.62.In chapter four, a new fluorene derivative,2,2`7,7`-Tetrapyridine-9,9`-spirobifluorene wassynthesized and characterized by1H NMR, FT-IR spectra and elemental analysis. At the same time,the UV-Vis absorption and fluorescence spectra of this new fluorene derivative were alsodiscussed. The results show that this new fluorene derivative exhibit deep-blue fluorescence inCH2Cl2solution as well as in film under UV excitation. The fluorescence quantum yield of2,2`7,7`-Tetrapyridine-9,9`-spirobifluorene in CH2Cl2solution is0.65.In chapter five, systemic conclusions and outlooks for the whole work were given. |
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