聯噻吩(bithiphene)為核心及接上不同側鏈長度的硫碳鏈(thio-alkyl)取代基(BST)，並以頭尾端接上雙噻吩並噻吩基團(dithienothiophen-2-yl; DTT)的新型有機小分子半導體DDTT-BST，透過剪切力塗佈(solution-shearing)製作有機場效應電晶體元件。在BST中心上因為分子內的硫··硫作用力會呈現高度平面性的結構，DDTT-BST-6 (SR=SC6H13)的結構排列藉由單晶繞射分析為典型的魚骨狀(herringbone)排列。而DDTT-BST-14 (SR=SC14H29)藉由剪切力塗佈後呈現高度一致性的微緞帶狀(microribbon)晶體且分子結構排列藉由低掠角廣角X光繞射(GIWXD)及電子繞射圖譜(ED)分析可推論從原本魚骨狀排列扭轉成類磚狀(brick-like)排列。在元件電性的表現上，DDTT-BST-6的電洞遷移率為0.07 cm2 V-1 s-1，而DDTT-BST-14最高電洞遷移率達1.7 cm2 V-1 s-1 。為了和DDTT-BST相比較，長碳側鏈基取代的bithiophene (BT)衍伸物 (DDTT-BT; R=C14H29) 製備其電晶體元件，其元件特性相對於共平面性佳的DDTT-BST有顯著上的差異，電洞遷移率只有10-8 cm2 V-1 s-1。以上結果表明DDTT-BST分子內的硫··硫作用力不只可以增強結構共平面性，也可以使溶液法製作晶體有高度一致性進而促進電荷傳遞，可應用於溶液製程之高效能有機場效應電晶體元件上。;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.
