This study examined the photoelectric conversion efficiency of the dye-sensitized solar cell (DSSC) when the surface of a nanometer-sized TiO2 film, which was prepared using the solvothermal method, was modified by five acid compounds. The TiO2 film exhibited an anatase structure with an average particle size in the range of 10-15 nm, and the maximum absorption band was shown in the UV-visible spectrum around 360 nm. The surface colors of the carboxylic acid-modified TiO2 films were changed to light or dark with differing energy conversion efficiencies. Particularly, the conversion efficiency was considerably enhanced from approximately 6.25% for the non-modified TiO2 film to approximately 7.50% for the film treated by acetic acid of 1.0 mole, with the N719 dye under 100 mW/cm2 of simulated sunlight. FT-IR analysis of the films after N719 dye adsorption confirmed that the IR spectrum of the modified TiO2 showed a sharp and strong band at 500 cm^(-1), which was assigned to a metal-O bond, due to the formation of a new Ti-O bond between the O of COO. and the Ti atom, which was relatively weaker in the non-modified TiO2. Furthermore, these results were in agreement with an electrostatic force microscopy (EFM) study showing that the electrons were transferred rapidly to the surface of the acetic acid-modified TiO2 film, compared with that on the nonmodified TiO2 film.