Synthesis and Properties of Thieno[3,2‐b]thiophene Derivatives for Application of OFET Active Layer

A series of thieno3,2‐b]thiophene derivatives having styryl groups were synthesized via short steps and characterized by UV–vis absorption spectra and cyclic voltammetry. Based on these results, we found that the introduction of long chain alkyl groups to the terminal styryl groups leads to narrower HOMO–LUMO gaps and higher HOMO energy levels than the unalkylated styryl substituted molecules. Organic field–effect transistor (OFET) devices using these derivatives as the active layer were fabricated by a vacuum deposition process. It was demonstrated that these devices showed a relatively high hole mobility up to 3.5 × 10⁻² cm²/Vs. These devices also showed a good stability, namely their mobilities did not decrease over 100 days in air. Therefore, these facts suggested that the introduction of long‐chain alkylated styryl groups is an effective way to improve the hole mobilities in OFETs. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:25–35, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21059