The morphological properties of TiO2 nanotube heavily influence the performance of dye-sensitized solar cell using TiO2 nanotube-array as the photoanode. We report an efficient trimming method of fabricating 18.8 mu m TiO2 nanotube-arrays with sidewall thicknesses ranged from 23 nm to 12 nm. With the photoanode of thin-wall nanotube-array, the photocurrent density of the dye-sensitized solar cell increased from 13.0 mA/cm(2) to 16.2 mA/cm(2) when the thickness of the sidewall was thinned down from 23 nm to 14 nm. Electrical impedance spectroscopy showed a significant difference of internal electrical characteristics between the solar cells with the as-prepared and with thin-wall nanotube-arrays. The thinning of the sidewall of the nanotubes had little influence on the diffusion of the electrons; the improvements in photocurrent density are the result of the more efficient infiltration of electrolyte into wider voids between neighboring thin-wall nanotubes. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.099202jes] All rights reserved.