Inkjet-printed polymer thin-film transistors: Enhancing performances by contact resistances engineering

In this paper, we demonstrate how to enhance polymer thin-film transistors (PTFTs) performances made by low-cost inkjet printing technique. Indeed, in PTFTs, contact resistances between semiconducting conjugated polymers (SCPs) and Source and Drain (S&D) contacts may dominate the transport properties of such electronic devices. Here, we report measurements of these parasitic resistances for several couples of (i) SCPs, as active material, and (ii) electrodes, as S&D contacts, in bottom-contact inkjetted PTFTs. The differences in PTFT performances are discussed upon these contact resistance. For this, we evaluate the performances of several inkjetted couples of SCP/S&D compared to devices with evaporated metal-based S&D. By this way, we show that inkjet printing is a suitable low-cost technique to dispense polymers and inorganic nanoparticles for direct-writing of PTFTs. A significant reduction in the contact resistance R-C was achieved when inkjetted Pedot:Pss-based S&D electrodes are used instead of evaporated metal-based S&D electrodes. The improved efficiency of charge carrier injection is assumed to be due to the formation of a p-doped interfacial layer at the interface between the SCP and the S&D electrodes. All these results pave the way towards flexible electronics applications by using inkjetted polymers both for electrodes and semiconducting active layer on flexible plastic substrate. (C) 2008 Elsevier B.V. All rights reserved.