POLYMERIC FIELD-EFFECT TRANSISTORS USING ORIENTED POLYMERS

Anisotropic charge carrier mobility in oriented conjugated polymers has been investigated. Mobility in thin films of undoped polythiophene polymers is measured using a field effect transistor. Thin polymer films, thickness 300-500 angstrom, supported on polyethylene are stretch oriented to various elongations, at maximum 4.5 times. The film is put onto the transistor substrate parallel or perpendicular to the conduction channel. The film can be lifted and put down again, perpendicular to the first orientation, enabling us to measure the mobility anisotropy. The anisotropy increases with increasing orientation, reaching values of 4. A simple model, describing the polymer chains as stiff rods along which charge transport occurs, gives a good agreement with observed results.