Top-contact organic thin-film transistors with improved mobility and turn-on voltage

Abstract

Top-contact organic thin-film transistors were prepared on indium-tin-oxide-coated glass substrates. The pentacene phase structure exhibited smooth surface and high-quality crystalline thin films that varied with deposition parameters. The organic thin-film transistor devices were characterised using X-ray diffraction, atomic force microscopy and semiconductor parametric test system (HP 4156B). In the experiments, the mobility of 0·093 cm2 V−1s−1 and threshold voltage of −3·29 V, Ion/Ioff ratio = 3·9×106 and subthreshold slope = 1·39 V per decade were obtained when a lower-to-medium deposition rate (0·05 nm s−1) was employed. The improved performance was attributed to the smooth surface and high-quality crystalline thin film. An adequate deposition rate was therefore an effective method to improve the device characteristics. In addition, the mobility was dramatically increased from 0·007 to 0·1 cm2 V−1s−1 when the pentacene film deposition rate was reduced from 0·1 to 0·025 nm s−1.