Effect of air exposure on metal/organic interface in organic field-effect transistors

We report the effect of air exposure on charge injection process through the metal/organic interface in organic field-effect transistors. Pentacene-based field-effect transistors and metal-insulator-semiconductor capacitors having gold or copper contact were fabricated without exposing to air. An air exposure caused remarkable improvement on the electrical characteristics of the devices, particularly on the contact resistance and frequency response characteristics. Measurements of photoelectron yield spectroscopy revealed that natural oxidation significantly shifted the work function of contact metal and thus charge injection efficiency was improved. This result provides critical insights on control of desirable metal/organic interface in organic electronics devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3599056]