A thin film transistor composed of: (a) a semiconductor layer including a thiophene compound, wherein the thiophene compound comprises one or more substituted thiophene units, one or more unsubstituted thiophene units, and optionally one or more divalent linkages; (b) a gate dielectric; and (c) a layer contacting the gate dielectric disposed between the semiconductor layer and the gate dielectric, wherein the layer comprises a substance comprising a fluorocarbon structure.