The preparation of nano-composites as gate dielectric film was carried out by blending nano TiO(2) particles and PI or PVP to enhance the capacitance of the gate dielectric. When concentration of nano TiO(2) particles less than 4 vol.% was well dispersed in PI, PVP slurry due to the presence of the dispersant, a nano-composite film with a homogeneous distribution of nano-TiO(2) particles in PI, PVP matrix and low roughness was obtained after curing at 180 degrees C, resulting in a low leakage current density of the nano-composite film and a high on/off ratio of the TFT device. A strong correlation between the morphology and the electrical properties of the nano-composite gate dielectric film reflected in OTFT device performance was observed. Since the higher capacitance and less vacant space between pentacene grains with slight surface roughness of the gate dielectric film when pentacene was deposited on a nano-composite gate dielectric film, the mobility and the threshold voltage of TFT were noticeably improved. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.