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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.63: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Active layer thickness dependence in flexible P3HT field-effect transistors — •Benedikt Gburek and Veit Wagner — Jacobs University Bremen, School of Engineering and Science, Campus Ring 8, 28759 Bremen, Germany

Applications of organic electronics require cheap and fast production methods on e.g. flexible and transparent devices. Following these goals, organic field-effect transistors (OFETs) in top-gate architecture are produced on flexible and transparent plastic (PET) foils as device substrate. The organic semiconductor, regio-regular poly-(3-hexylthiophene) (rr-P3HT), and the gate insulator, poly-methylmethacrylate (PMMA), are deposited wet-chemically under atmospheric conditions. Comparably high charge carrier mobility of 0.02 cm^2/(Vs) was determined at -40 V gate-source voltage in devices with 300 nm insulator thickness in the linear regime. Unlike the severe degradation of uncapped P3HT transistors, our device characteristics remain stable for several months due to the encapsulation with the PMMA gate insulator. Plastic devices fabricated in this way were used to analyze the dependence of the charge carrier mobility on the thickness of the P3HT layer. The mobility was found to be low for thin layers of several nm and to increase strongly with increasing layer thickness. For sufficiently large thickness, i.e. beyond 15 nm, the mobility remains constant. Thickness dependent charge transport properties were analyzed by fitting theoretical models. Beside gate voltage dependent mobility also contact resistance - a crucial point for further miniaturization of devices - was taken into account.