A series of dithieno[2,3-b:3′,2′-d]thiophene (DTT; 1) derivatives were synthesized and characterized. Facile, one-pot [2 + 1] and [1 + 1 + 1] synthetic methods of DTT were developed, which enabled the efficient realization of a new DTT-based semiconductor series for organic thin-film transistors (OTFTs). These DTTs are end-functionalized with perfluorophenyl (FP-), perfluorobenzoyl (FB-), benzoyl (B-), 2-naphthylcarbonyl (Np-), 2-benzothiazolyl (BS-), 2-thienylcarbonyl (T-), and 2-(5-hexyl)thienylcarbonyl (HT-) groups. The molecular structures of DFP-DTT (3), DFB-DTT (4), FBB-DTT (5), DB-DTT (6), and DNp-TT (7) were determined via single-crystal X-ray diffraction. Our studies reveal that the majority of these carbonyl-containing derivatives exhibit p-channel transport with hole mobilities of up to 0.01 cm2/Vs for DB-DTT and DBS-DTT, while perfluorobenzoyl and perfluorophenyl-substituted compounds exhibit n-channel transport with mobilities up to 0.002 cm2/Vs for DFB-DTT, 0.03 cm2/Vs for FBB-DTT, and 0.07 cm2/Vs for DFP-DTT, rendering the latter the DTT derivative currently having the highest electron mobility in OTFT devices. Within this family, the carrier mobility values are strongly dependent upon the semiconductor growth temperature and the dielectric surface treatment.