Fabrication of organic thin film transistor based on the ink-jet printed electrodes of nano silver particles

In this work, we here developed a conductive ink which contains silver nano-particles from which the electrodes for organic thin film transistor were directly patterned by ink-jet printing. Nano-sized silver panicles having ∼ 20 nm diameter was used for the direct metal printing. Silver conductive ink was printed on the heavily doped n-type silicon wafer with 200-nm thick thermal SiO₂ layer as a substrate. To achieve a high line resolution and smooth conductive path, the printing conditions such as the inter-drop distance, stage moving velocity and temperature of the pre-heated substrates were optimized. After the heat-treatment at temperatures of about 100 ∼ 300 °C for 30 min, the printed silver patterns exhibit metal-like appearance and the conductivity. To fabricate a coplanar type TFTs, an active material of semiconducting oligomer, which was dissolved in a proper solvent, was deposited between the ink-jet printed silver electrodes by solution process. The output and transfer characterization was measured in air. The OTFT with the ink-jetted source/drain electrodes show a mobility of 1.3 × 10^-3 cm ² V^-1 s^-1 in the saturation regime and on/off current ratio over 10³ and a threshold voltage of about-13 V.