Spherical rutile TiO2 particles (14-20 nm) and their corresponding well-defined round clusters (500-600 nm) were obtained by using a cationic surfactant cetyltrimethylammonium bromide (CTAB). The surfactant was employed in two stages, i.e., in the hydrolysis of TiCl4 and then in the precipitation of the corresponding Ti(IV) polymers at approximately 46 degrees C. On the other hand, without CTAB in the hydrolyzing solution, irregular clusters consisting of typical ellipsoidal TiO2 particles were produced. The advantage of such spherical rutile TiO2 particles and clusters was examined in terms of photovoltaic characteristics of a dye-sensitized solar cell (DSSC). Significantly higher overall solar energy conversion efficiency was obtained for a DSSC using the film of these spherical rutile TiO2 particles, compared with that of a cell using a TiO2 film of ellipsoidal particles. A mechanism for the formation of these spherical rutile particles and clusters is proposed. (C) 2008 Elsevier Ltd. All rights reserved.