TiO2 nanopowders are synthesized using a hydrothermal process under various conditions. Effects of several hydrothermal conditions are investigated such that the TiO2 nanopowders having optimized size, surface area, crystallinity, and yield are used for the fabrication of photoanodes. The obtained TiO2 photoanodes are subjected to oxygen plasma treatments for various times. As-synthesized and plasma-treated photoanodes are then assembled into dye-sensitized solar cells. The plasma-treated photoanodes exhibit different concentrations of surface C–OH and oxygen vacancies, depending on the plasma treatment times. This leads to dye-sensitized solar cells having different conversion efficiencies. The use of plasma treatment can enhance the cell conversion efficiency by more than 24%. The effects of the photoanode surface condition on the performance of photoanode are discussed. Copyright © 2012 John Wiley & Sons, Ltd.