Organic thin-film transistors (OTFTs) with various buffer layers between the active layer and source/drainelectrodes were investigated. The structure was polyethylene terephthalate/indium-tin oxide/poly(methyl methacrylate) (PMMA)/pentacene/buffer layer/Au (source/drain). V2O5, 4,4', 4.-tris{N,(3-methylpheny)-Nphenylamino}-triphenylamine (m-MTDATA) and m-MTDATA-doped V2O5 films were utilized as buffer layers. The electrical performances of OTFTs in terms of drain current, threshold voltage, mobility and on/off current ratio have been determined. As a result, the saturation current of-40 mu A is achieved in OTFTs with a 10% m-MTDATA-doped V2O5 buffer layer at a VGS of-60 V. The on/off current ratio reaches 2 x 105, which is approximately double of the device without a buffer layer. The energy band diagrams of the electrode/buffer layer/pentacene were measured using ultra-violet photoelectron spectroscopy. The improvement in electrical characteristics of the OTFTs is attributable to theweakening of the interface dipole and the lowering of the barrier to enhance holes transportation from the source electrode to the active layer. (C) 2013 Elsevier B.V. All rights reserved.