Synthesis, Photophysics, and Electroluminescence of Mesogen-Jacketed 2D Conjugated Copolymers Based on Fluorene−Thiophene−Oxadiazole Derivative

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• 作者：Qian Yang ; Hao Jin ; Yiding Xu ; Ping Wang ; Xiaochao Liang ; Zhihao Shen* ; Xiaofang Chen ; Dechun Zou ; Xinghe Fan* ; Qifeng Zhou*
• 刊名：Macromolecules
• 出版年：2009
• 出版时间：February 24, 2009
• 年：2009
• 卷：42
• 期：4
• 页码：1037-1046
• 全文大小：335K
• 年卷期：v.42,no.4(February 24, 2009)
• ISSN：1520-5835

文摘

A novel monomer 3-{2,5-bis[(4-hexadecyloxy-phenyl)-1,3,4-oxadiazole]phenyl}-2,5-dibromothiophene (MJTO) was copolymerized with 9,9′-dioctylfluorene to generate a series of new conjugated copolymers (PFT0.1, PFT0.5, PFT1, PFT5, PFT10, PFT25, and PFT50) by Suzuki coupling reaction. They were characterized by molecular weight determination, ¹H NMR, elemental analysis, TGA, DSC, UV−vis absorption, emission spectroscopy, and cyclic voltammetry. The copolymers exhibited high decomposition temperatures reaching 417 °C and high T_g values reaching 145 °C. The photophysical properties were greatly influenced by the content of the MJTO monomer. The copolymers in solution and film states of PFT25 and PFT50 showed two distinct absorption peaks corrresponding to absorptions from the electron-transport side chain and the hole-transport backbone, respectively, instead of a single peak when MJTO content was below 10.79%. The copolymers in solution with MJTO content below 10.79% shared similar emission spectra, whereas PFT25 and PFT50 showed absolutely different emission that red-shifted a lot. In the film state, the emission spectra gradually red-shifted when the MJTO content increased. The HOMO and LUMO energy levels were both lower than those of PF, which resulted in better electron injection and transport but still blue-green emission. Light-emitting diode devices were fabricated with a configuration of ITO/PEDOT−PSS/polymer/Ca (20 nm)/Al (70 nm) for all polymers. Among those devices, PFT5 attained brightness of 5558 cd/m² and current efficiency of 0.39 cd/A, which proved that the introduction of a proper ratio of the novel thiophene−oxadiazole comonomer to PF could largely improve its EL properties.