A process for fabricating a thin film transistor comprising: (a) forming a gate dielectric; (b) forming a layer including a substance comprising a fluorocarbon structure; and (c) forming a semiconductor layer including a thiophene compound comprising one or more substituted thiophene units, one or more unsubstituted thiophene units, and optionally one or more divalent linkages, wherein the layer contacts the gate dielectric and is disposed between the semiconductor layer and the gate dielectric.