Molecular design of dithieno[3,2-b:2′,3′-d]thiophene via core functionalization and alkyl substitution for high-performance organic field-effect transistors

초록

In this study, we report the design, synthesis, and characterization of three new dithieno[3,2-b:2′,3′-d]thiophene (DTT)-based small-molecular organic semiconductors (OSCs) featuring extended π-conjugated backbones via ethynyl linkages. To elucidate the role of side-chain engineering on charge-transport behavior, three derivatives, 2-([2,2′-bithiophen]-5-ylethynyl)-6-octyldithieno[3,2-b:2′,3′-d]thiophene (1), 2-octyl-6-((5′-octyl-[2,2′-bithiophen]-5-yl)ethynyl)dithieno[3,2-b:2′,3′-d]thiophene (2), and 2-((5′-(2-ethylhexyl)-[2,2′-bithiophen]-5-yl)ethynyl)-6-octyldithieno[3,2-b:2′,3′-d]thiophene (3), were synthesized with systematically varied alkyl-chain configurations. To characterize the developed DTT compounds as OSCs, bottom-gate/top-contact organic field-effect transistors (OFETs) were fabricated using the solution-shearing technique on PS-brush-modified SiO2 substrates. Among the investigated materials, compound 2, which incorporates linear octyl chains on both sides, achieved superior electrical performance with a hole mobility of 0.11 cm2 V−1 s−1 and a current on/off ratio exceeding 107, which could be ascribed to the highest crystallinity and the most favorable film morphology among the three derivatives. These results highlight that the combined control of backbone conjugation and side-chain architecture represents a fundamental design approach to attaining superior DTT-based organic semiconductors. © 2026 Elsevier Ltd

키워드