Efficient Surface Treatment to Improve Contact Properties of Inkjet-Printed Short-Channel Organic Thin-Film Transistors

Abstract

In this paper, we report contact properties of fully inkjet-printed organic thin-film transistors (OTFTs) with various channel lengths and their improvement by introducing an organo-compatible interlayer between the organic channel and inkjet-printed metallic contacts. To realize all-inkjet-printed OTFTs, a highly conductive metal-organic precursor type silver ink, poly(4-vinylphenol), chlorosilane-terminated polystyrene (PS) and 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene) solutions were printed by using a commercial piezoelectric inkjet-printer for gate and source/drain (S/D) electrodes, a gate dielectric layer, an interface engineering layer, and a semiconductor layer, respectively. Especially, since the contact resistance more dominantly affects a carrier injection property as channel length gets short, a short-channel length of 7 mu m was formed by using 1 picoliter volume ink cartridge to investigate effects of the organo-compatible interlayer obviously. To evaluate contact properties of the inkjet-printed short-channel OTFTs, transmission line method and Y-function method analyses were used for various channel lengths and low drain-to-source voltage (V-DS) regime of -5 V, respectively. The contact properties between inkjet-printed silver S/D electrodes and TIPS pentacene semiconductor were drastically enhanced showing contact resistance lowered by an order of magnitude and a good linearity at low V-DS regime after inserting an end-functionalized PS layer.