Fabrication of Organic Thin Film Transistor Based on the Ink-Jet Printed Electrodes of Nano Silver Particles
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Fabrication of Organic Thin Film Transistor Based on the Ink-Jet Printed Electrodes of Nano Silver Particles Dongjo Kim, Sunho Jeong, Sul Lee, Bong-Kyun Park, and Jooho Moon Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-ku, Seoul, 120-749, Korea, Republic of
ABSTRACT 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 particles 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 200nm 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 ℃ 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 cm2 V-1 s-1 in the saturation regime and on/off current ratio over 103 and a threshold voltage of about -13 V. INTRODUCTION In the electronic industry, the fabrication of conductive tracks is inevitable and traditionally photolithographic and electroless techniques are widely adopted in the printing circuit board (PCB) industry for manufacturing its conductive circuits. However, this method is not only time consuming but also very complicated and expensive, because many steps are required to construct one layer of the circuit [1,2]. Moreover, the conventional electroplating and etching processes also produce large quantities of chemical waste. Therefore, there is an industrial need for direct digital printing to simplify the processes and to reduce manufacturing costs. Furthermore, ink jet printing technique is desirable to fabricate onto polymeric or similar temperature-sensitive substrates by solution-based printing process and the development of a solution-based process on a flexible substrate would allow reel-to-reel fabrication, which is an extremely inexpensive way to mass-produce circuits since it eliminates conventional photolithography and complex substrate processing including vapor phase deposition and etching. For these reasons, the ink jet printing as convenient and fast processing techniques to fabricate conductive lines has attracted more and more attention in recent years. There has been also growing interest in organic thin-film transistors (OTFTs) because of their potential applications in flexible, low-cost integrated circuits, such as smart cards, RF identification tags, and d
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