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 solution-processable 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-alignmentinduced charge-transport anisotropy.