Inkjet Printed PEDOT:PSS-based Source/Drain Electrodes for Organic Thin Film Transistors

Abstract

Printed electronics in recent years have attracted considerable attention because fabrication of electronic devices by printing method not only enables large area and volume manufacturing of devices but also reduces the process complexity and fabrication cost quite significantly. Hence, deploying printing method to fabricate organic electronic devices which are crucial for next generation flexible electronics and bio-electronic devices can combine the benefits and attributes of both printing technology and organic electronics. The current research demonstrates inkjet printing of electrically conducting poly (3, 4-ethylenedioxythiphene)-poly(styrenesulfonate) (PEDOT:PSS) to fabricate the source and drain electrodes for pentacene-based organic thin film transistors (OTFTs). The devices were fabricated on a highly doped silicon (n++Si) wafer in top contact bottom gate geometry. The n++Si wafer acted as the bottom gate whereas thermally grown silicon dioxide, vacuum deposited pentacene and inkjet printed PEDFOT:PSS were used as gate insulator, semiconductor and source/drain electrodes, respectively. So, the inkjet printing parameters for the top source/drain electrodes were carefully optimized to obtain a minimum channel length of ∼100 µm and width of ∼600 µm. Thus a channel width to length ratio of 6:1 was achieved. Device performance was tested using source measurement units. The field effect hole mobility, on-off ratio and threshold voltage for these devices were found to be ∼0.02 cm² V⁻¹ s⁻¹, ∼10⁴ and ∼−12 V, respectively.