State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
ACS Appl Mater Interfaces. 2017 Oct 11;9(40):35427-35436. doi: 10.1021/acsami.7b10675. Epub 2017 Sep 29.
Herein, we report the synthesis and characterization of a series of [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-based asymmetric conjugated molecules, that is, 2-(5-alkylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-Tn, in which T and n represent thiophene and the number of carbons in the alkyl group, respectively). All of the molecules with n ≥ 4 show mesomorphism and display smectic A, smectic B (n = 4), or smectic E (n > 4) phases and then crystalline phases in succession upon cooling from the isotropic state. Alkyl chain length has a noticeable influence on the microstructures of vacuum-deposited films and therefore on the performance of the organic thin-film transistors (OTFTs). All molecules except for 2-(thiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-ethylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed OTFT mobilities above 5 cm V s. 2-(5-Hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene and 2-(5-heptylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene showed the greatest OTFT performance with reliable hole mobilities (μ) up to 10.5 cm V s because they formed highly ordered and homogeneous films with diminished grain boundaries.
在此，我们报告了一系列基于[1]苯并噻吩并[3,2-b][1]苯并噻吩（BTBT）的不对称共轭分子的合成和表征，即 2-(5-烷基噻吩-2-基)[1]苯并噻吩并[3,2-b][1]苯并噻吩（BTBT-Tn，其中 T 和 n 分别代表噻吩和烷基中的碳原子数）。所有 n ≥ 4 的分子均表现出介晶性，并在冷却至各向同性态时依次显示出近晶 A、近晶 B（n = 4）或近晶 E（n > 4）相和结晶相。烷基链长对真空沉积薄膜的微结构有明显影响，因此对有机薄膜晶体管（OTFT）的性能有影响。除了 2-(噻吩-2-基)[1]苯并噻吩并[3,2-b][1]苯并噻吩和 2-(5-乙基噻吩-2-基)[1]苯并噻吩并[3,2-b][1]苯并噻吩外，所有分子的 OTFT 迁移率均高于 5 cm V s。2-(5-己基噻吩-2-基)[1]苯并噻吩并[3,2-b][1]苯并噻吩和 2-(5-庚基噻吩-2-基)[1]苯并噻吩并[3,2-b][1]苯并噻吩具有最大的 OTFT 性能，可靠的空穴迁移率（μ）高达 10.5 cm V s，因为它们形成了高度有序和均匀的薄膜，减少了晶粒边界。
