Tri-functional Nb2O5 nano-islands are deposited on indium tin oxide (ITO) transparent conductive layer on a plastic sheet (ITO PEN) as the anode substrate for a dye-sensitized solar cell by spin-coating a niobium precursor solution and heating at 150 degrees C for 10 min. The films are characterized by means of time of flight secondary ion mass spectrometry (TOF/SIMS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), small angle X-ray diffraction (SAXRD), electrochemical impedance spectroscopy (EIS), four-probe meter and current-voltage curves. It was found that the Nb2O5 coating exhibits at least three functions, including suppressing interfacial recombination, improving TiO2 film adhesion and lowering sheet resistance of the ITO PEN film; these functions are all beneficial to photovoltaic performance in a dye-sensitized solar cell. Finally, a plastic dye-sensitized solar cell with this Nb2O5-treated photoanode was fabricated, and a remarkable improvement of power conversion efficiency (PCE), from 5.19% to 5.81% was demonstrated. (C) 2013 Elsevier B.V. All rights reserved.