We have significantly enhanced the energy conversion efficiency of the dye-sensitized solar cells based on TiO2 nanotube membranes by filling TiO2 nanoparticles in the channels. By filling approximately 10 wt.% of TiO2 nanoparticles to the membrane weight in the channels of the membrane, the energy conversion efficiency was improved from 5.2% to 6.3%, a 21% enhancement. By treating with TiCl4 after filling TiO2 nanoparticles in the channels, the efficiency was enhanced from 5.2% to 7.3% (a 40% enhancement). The efficiency enhancement is due to an increase in the total available surface area for dye adsorption. (C) 2011 Elsevier B. V. All rights reserved.