Solution-processable dithieno[3,2-b:2′,3′-d]thiophene derivatives for organic thin-film transistors and complementary-like inverters

Solution-processable dithieno[3,2-b:2′,3′-d]thiophene (DTT) derivatives, 2,6-bis(phenylethynyl)dithieno[3,2-b:2′,3′-d]thiophene (BP-Et-DTT) and 2,6-bis(thiophen-2-ylethynyl)dithieno[3,2-b:2′,3′-d]thiophene (BT-Et-DTT) were synthesized and characterized as organic semiconductors for organic thin-film transistors (OTFTs). Thermal, optical, and electrochemical properties of the DTT-based semiconductors were investigated. The solution-sheared thin films based on DTT derivatives exhibited p-channel characteristics as an active layer in organic thin-film transistors. The highest hole mobility was 0.32 cm² V⁻¹s⁻¹ based on BP-Et-DTT thin films. The thin films exhibited micrometer-sized crystalline fiber structures which were aligned along the shearing direction, resulting in fiber-alignment-induced charge-transport anisotropy. Furthermore, bulk heterojunction (BHJ) ambipolar transistors were fabricated with an optimized blending ratio of BP-Et-DTT and the representative n-channel semiconductor, PDIFCN₂. Complementary-like inverters were fabricated based on the two identical ambipolar transistors, resulting in moderate voltage gains of up to 16.