We have investigated effects of the solvent polarity of a polymeric insulator on field-effect mobility in a pentacene used thin-film transistor (TFT). In our work, we used a poly(4-vinylphenol) (PVP) as a gate insulator to dissolve three different solvents. As the solvent polarity of the PVP solution is increased, the field-effect mobility is dramatically increased by a factor of five (from 0.30 cm(2)/Vs to 1.51 cm(2)/Vs). We found that an increase of polar solvents in polymeric insulators results in improved electrical properties in the organic TFTs. (C) 2013 Elsevier Ltd. All rights reserved.