The synthesis of 2,6-dialkylphenyldithieno[3,2-b:2′,3′-d]thiophene derivatives and their applications in organic field-effect transistors

2,6-Dialkylphenyldithieno[3,2-b:2′,3′-d]thiophene derivatives (DPCn–DTT) were synthesized and characterized. Effect of alkyl groups on optical characteristics, electrochemical properties, film-forming ability, and field-effect performance was studied. The four compounds DPCn–DTT show almost the same energy levels of the highest occupied molecular orbits and optical energy gaps, but they exhibit different charge carrier transport characteristics. The thin film transistors based on DPC1–DTT with the shortest alkyl groups (methyl groups) show the highest mobility of 0.54 cm2 V−1 s−1. Substrate temperature and surface modification of the SiO2 insulators have a remarkable effect on field-effect performance. High-quality microribbons of DPC8–DTT with octyl groups were prepared by a solution-phase self-assembly process. Single crystal field-effect transistors based on an individual DPC8–DTT microribbon exhibit a high mobility of 1.1 cm2 V−1 s−1 with a current on/off ratio of 6.5 × 104.

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► Dialkylphenyldithieno[3,2-b:2′,3′-d]thiophenes were synthesized as organic field-effect materials.
► Organic field-effect transistors were fabricated and a high mobility up to 0.54 cm2 V−1 s−1 was obtained.
► Single crystal micro/nano ribbons were prepared by a solution-phase self-assembly process.
► Single crystal field-effect transistors based on an individual microribbon were fabricated.