Toshihiro Kikuchi

Organic Thin-Film Transistor from a Pentacene Photoprecursor

Organic thin-film transistors were successfully fabricated by the spin-coating method using a photo-precursor of pentacene, 6,13-dihydro-6,13-ethanopentacene-15,16-dione. After spin coating the soluble precursor, irradiation with visible light gave a pentacene film. A good mobility of 0.34 cm2 V-1 s-1 and a high on/off ratio of 2.0×106 were achieved by treatment of the insulator surface with methyl silsesquioxane and by deposition of pentacene from the precursor with visible light irradiation (>300 nm) and mild heat treatment (110–120 °C). In this case, small grains of pentacene crystals existed in the loosely ordered pentacene mesophase, in which pentacene molecules aligned vertically. Not only the grains of pentacene crystals but also the loosely packed pentacene phase played an important role in the field-effect transistor (FET) performance.