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13 September 2007 Synthesis of bis-silylated oligothiophenes for solution-processable organic field effect transistors
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A series of bis-dimethyl-n-octylsilyl end-capped oligothiophenes consisting of two to six thiophene units have been synthesized using palladium-catalyzed Stille coupling reactions. These oligothiophenes have been characterized by 1H-, 13C-NMR and high resolution mass spectrometry. The UV-vis spectral data indicate that these silyl end-capped oligothiophenes have longer conjugation lengths as evidenced by the higher λmax values than the corresponding unsubstituted thiophene oligomers. The thermal analyses indicate that the bis-silylated oligothiphenes show lower melting point (DSi-4T = 80°C; DSi-5T = 115°C; DSi-6T = 182°C) than the corresponding dialkylated thiophene oligomers by 100°C and hexamer DSi-6T exhibits a liquid crystalline mesophase at 143°C. The α,ω-bis(dimethyl-n-octylsilyl)oligothiophenes have a remarkably high solubility in chloroform which are comparable to the corresponding α,ω-dihexyloligothiophenes. The remarkably increased solubility by these silyl end groups leads the bis-silylated oligothiophenes to be applicable to solution processable devices for thin film transisitor (TFT) by utilizing a spin coating technique. We fabricated devices by spin-coating α,ω-bis(dimethyloctylsilyl)sexithiophene DSi-6T from chlorobenzene, toluene, chloroform onto device test structures. But the OFETs using DSi-6T solved in chloroform produced the transistor behavior. The hexamer DSi-6T, showed promising behavior as a solution-deposited semiconductor, with mobility up to 0.014 cm2V-1s-1.
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Jung Hei Choi, Dae Won Cho, Sung-Ho Jin, Chung Kun Song, and Ung Chan Yoon "Synthesis of bis-silylated oligothiophenes for solution-processable organic field effect transistors", Proc. SPIE 6658, Organic Field-Effect Transistors VI, 665818 (13 September 2007);


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