Top Contact Organic Thin Film Transistors with Ink Jet Printed Metal Electrodes

Abstract

Ink jet printing conductive metal nanopastes have been studied in research on printed circuit boards and passive components. This technique provides a manufacturing method that can replace more expensive processes, such as lithography or metal evaporation. In this paper, we demonstrated a printed silver top-contact source-drain electrodes on bottom-gate organic thin film transistors (OTFTs). The soluble conjugated polymer, regioregular poly(3-hexylthiophene) (RR-P3HT), was used as the active channel material. To increase electric transport efficiency by tuning the surface hydrophibic characteristics, a buffer layer, V2O5, between organic semiconductor and printed electrodes, was introduced to resolve the incompatibility of these two layers. The results indicated the printed Ag on V2O5 film is hydrophilic (contact angle ∼10°), different with that on P3HT only (hydrophibic, contact angle about 65°). High hydrophilic surface of V2O5 led to self-aligning behavior of patterned Ag nanopastes and is helpful to get a flat film. This study also compares the characteristics of OTFTs to traditionally evaporated electrodes and to ink jet printed source-drain electrodes, in order to analyze the mechanism action of the buffer layer and its related process differences.