Development and Characterization of Solution-Processable Dithieno[3,2-b : 2',3'-d]thiophenes Derivatives with Various End-capped Groups for Organic Field-Effect Transistors

Abstract

In this paper, four organic materials based on dithieno[3,2-b : 2',3'-d]thiophene (DTT) core structure with end-capping groups (phenyl and thienyl) and linker (acetylenic and olefinic) between DTT-core and end-capping groups were synthesized and characterized as solution-processable organic semiconductors (OSCs) for organic field-effect transistors (OFETs). Thermal, optical, and electrochemical properties of the corresponding materials were determined. Next, all DTT-derivatives were coated by solution-shearing method, and the thin-film microstructures and morphologies were investigated. To investigate the electrical performance of four newly synthesized DTT-derivatives, bottom-gate/top-contact OFETs were fabricated and characterized in ambient condition. It was found that substitution of acetylenic for olefinic linkers between DTT-cores and end-capping groups enhanced device performance. Especially, the resulting OFETs based on the compound containing phenylacetylene exhibited the highest hole mobility of 0.15 cm² /Vs and current on/off ratio of ∼10⁶ , consistent with film morphology and texture showing long range interconnected crystalline grains and strong diffraction peaks.

Keywords: dithieno[3,2-b : 2’,3’-d]thiophene; organic field-effect transistor; organic semiconductors; solution-process.