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ACS Appl Mater Interfaces. 2017 Oct 11;9(40):35427-35436. doi: 10.1021/acsami.7b10675. Epub 2017 Sep 29.

Asymmetric Conjugated Molecules Based on [1]Benzothieno[3,2-b][1]benzothiophene for High-Mobility Organic Thin-Film Transistors: Influence of Alkyl Chain Length.

He K1,2, Li W1, Tian H1, Zhang J1, Yan D1, Geng Y1,3,4, Wang F1.

Author information

1
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
2
University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
3
School of Materials Science and Engineering and Tianjin Key Laboratory of Molecular Optoelectronic Science, Tianjin University , Tianjin 300072, P. R. China.
4
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300072, P. R. China.

Abstract

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 cm2 V-1 s-1. 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 cm2 V-1 s-1 because they formed highly ordered and homogeneous films with diminished grain boundaries.

KEYWORDS:

asymmetric; mobility; morphology; organic semiconductors; organic thin-film transistors

PMID:
28937211
DOI:
10.1021/acsami.7b10675

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