Ambipolar transport in solution-deposited pentacene transistors enhanced by molecular engineering of device contacts

We report ambipolar transport in bottom gold contact, pentacene field-effect transistors (FETs) fabricated by spin-coating and thermally converting its precursor on a benzocyclobutene/SiO2 gate dielectric with chemically modified source and drain electrodes. A wide range of aliphatic and aromatic self-assembled thiolate monolayers were used to derivatize the electrodes and all enhanced electron and hole currents, yet did not affect the observable thin film morphology. Hole and electron mobilities of 0.1–0.5 and 0.05–0.1 cm2 / V s are achieved, though the threshold for electron transport was >80 V. These ambipolar FETs are used to demonstrate inverters with gains of up to 94.