Orientation control of pentacene molecules and transport anisotropy of the thin film transistors by photoaligned polyimide film

Abstract

The authors report preferential in-plane molecular orientation and charge transport anisotropy in pentacene thin film transistors achieved by using a photoaligned polyimide film with large in-plane anisotropy. Polarized infrared absorption spectra indicated that the molecular plane normal of the pentacene preferentially aligned along the average orientation direction of the underlying polyimide backbone structure. Atomic force microscope images showed that the alignment of the polyimide backbone structure significantly modified the pentacene growth process and remarkably increased the grain size. The charge carrier mobility along the polyimide alignment direction was about twice of that perpendicular to it.