The effect of iron(III) p-toluenesulfonate hexahydrate (Fe(PTS)(3)) concentration on the formation and patternability of poly(3,4ethylenedioxythiophene) (PEDOT) films on (3-aminopropyl)trimethoxysilane (APS) monolayer was investigated. Low deposition rate yielded highly conductive and very smooth PEDOT films. However, the spin-coated oxidants in low Fe(PTS)(3) concentrations were susceptible to moistures, leading to the poorly patterned PEDOT films. Increasing Fe(PTS)(3) concentration enabled the fine patterning of the films. The fabricated thin film transistors with PEDOT electrodes formed on 30 wt.% Fe(PTS)(3) revealed the saturation mobility of 0.16 cm(2)/V s and subthreshold slope of 0.5 V/decade. The obtained low contact resistance was 12 K Omega cm. possibly due to the negligible interface morphological discontinuity at the pentacene-PEDOT interface. (c) 2010 Elsevier B.V. All rights reserved.