Improvement of the contact resistance between ITO and pentacene using various metal-oxide interlayers

Ultra-thin Al2O3, Ta2O5, and TiO2 films were deposited on the indium tin oxide (ITO) surfaces in organic thin film transistors using the atomic layer deposition (ALD) process at room temperature, and the contact resistance was significantly improved with the increase of the dielectric constant of the interlayer. The electronic band diagrams of the pentacene/ITO structures after ALD treatment on ITO surface with various metal-oxides were measured using in situ ultra-violet photoelectron spectroscopy during the step-by-step deposition of pentacene, and these results explained the decrease of the hole injection barriers and the resulting improvement of the contact resistance between pentacene/ITO interface.