Enhancing the performance of organic thin-film transistors using a novel photoalignment method

This study first demonstrated the feasibility of using the photoalignment method to adequately control the structural anisotropy of pentacene films, which are active semiconducting layers, in thin-film transistors (TFTs) with conspicuous anisotropic electrical characteristics. The photoaligned pentacene films were characterized with respect to structure and morphology using x-ray diffraction, atomic force microscopy and Raman scattering. Compared to the uncontrolled pentacene films, a maximum 25-times increase in field-effect mobility (up to 0.82 cm²/Vs) is achieved in the photoaligned pentacene-based TFTs by aligning pentacene orientation parallel to the current flow direction using a photoaligned polyimide layer. Mobility anisotropic ratios ranging between 2.7 -8.3 for the current flow parallel and perpendicular to the alignment of the photoaligned pentacene films have been observed for photoaligned pentacene-based TFTs.