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Liquid Crystal-Gated-Organic Field-Effect Transistors with In-Plane Drain–Source–Gate Electrode Structure

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posted on 14.01.2015, 00:00 by Jooyeok Seo, Sungho Nam, Jaehoon Jeong, Chulyeon Lee, Hwajeong Kim, Youngkyoo Kim
We report planar liquid crystal-gated-organic field-effect transistors (LC-g-OFETs) with a simple in-plane drain–source–gate electrode structure, which can be cost-effectively prepared by typical photolithography/etching processes. The LC-g-OFET devices were fabricated by forming the LC layer (4-cyano-4′-pentylbiphenyl, 5CB) on top of the channel layer (poly­(3-hexylthiophene), P3HT) that was spin-coated on the patterned indium–tin oxide (ITO)-coated glass substrates. The LC-g-OFET devices showed p-type transistor characteristics, while a current saturation behavior in the output curves was achieved for the 50–150 nm-thick P3HT (channel) layers. A prospective on/off ratio (>1 × 103) was obtained regardless of the P3HT thickness, whereas the resulting hole mobility (0.5–1.1 cm2/(V s)) at a linear regime was dependent on the P3HT thickness. The tilted ordering of 5CB at the LC-P3HT interfaces, which is induced by the gate electric field, has been proposed as a core point of working mechanism for the present LC-g-OFETs.