Ambipolar organic thin-film transistors using C_(60)/pentacene structure: Characterization of electronic structure and device property

摘要

We fabricated ambipolar organic thin-film transistors (OTFTs) using C_(60) and pentacene. The electronic structure of the interface was investigated by using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy. The magnitude of the interface dipole and the band bendings at the interface was determined, and the complete energy level diagram for C_(60) on pentacene (C_(60)/pentacene) was obtained. The lowered band offsets, due to the enhanced charge redistribution in C_(60)/pentacene relative to pentacene on C_(60), are favorable for the ambipolar OTFTs. The measured field-effect mobilities were 0.017 cm~2/V s and 0.007 cm~2/V s for the p-channel and the n-channel operations, respectively. The threshold voltages were -2 V for the p channel and 15.6 V for the n channel, comparable to those of unipolar OTFTs using C_(60) or pentacene.