| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 103 === New thio-alkyl (SR) substituted bithiophene (BST)-based semiconductors, end-capped with the dithienothio-phen-2-yl (DTT) group, are fabricated for organic field effect transistors (OFETs) via solution-shearing process. The molecular structure of DDTT-BST-6 (SR= SC6H13) is determined by single-crystal X-ray diffraction and exhibits a typical herringbone packing. The BST building block core demonstrated a highly coplanar structure via the intramolecular S(C6H13)∙∙S(thiophenyl) interaction. In contrast, DDTT-BST-14 (SR= SC14H29) exhibits highly aligned microribbon crystal and the molecular structure of DDTT-BST-14 infer to strain from herringbone to brick-like packing in solid state characterized by grazing incident wide angle X-ray diffraction (GIWXD) and electron diffraction (ED). DDTT-BST-6 exhibits the hole mobility of 0.07 cm2 V-1 s-1 whereas DDTT-BST-14 has a highest mobility up to 1.7 cm2 V-1 s-1. For comparison, the alkyl substituted bithiophene (BT) derivative (DDTT-BT; R=C14H29) was prepared, and exhibited a relatively low device performance (~10-8 cm2 V-1 s-1). These results indicate that the intramolecular S··S interaction of DDTT-BST not only enhance backbone coplanarity but induce crystal alignment to promote the path of charge transport, and thus the DDTT-BST have an enhanced electrical properties for high performance solution-processed OFETs applications.
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