An exemplary organic semiconductor copolymer includes a polymeric repeat structure having a polythiophene structure and an electron accepting unit. The electron accepting unit has at least one electron-accepting heteroaromatic structure with at least one electron-withdrawing imine nitrogen in the heteroaromatic structure or a thiophene-arylene comprising a C.sub.2-30 heteroaromatic structure. Methods of synthesis and electronic devices incorporating the disclosed organic semiconductors, e.g., as a channel layer, are also disclosed.