Xylenol orange (3,3'-bis[N,N-di (carboxymethyl)aminomethyl]-o-cresolsulfonephthalein), which is a water-soluble dye of the triphenylmethane group, was tested for a dye-sensitized solar cell. The observed short-circuit current (2.2 mA cm(-2)) was compared with the theoretical value (3.8 mA cm(-2)) which was estimated from the radiation spectrum of light source and the absorption spectrum of adsorbed dye on TiO2. The overall energy efficiency was 1.3%. The addition of 0.5 M water in the electrolyte did not show a bad effect. A molecule of xylenol orange occupied 1.48 nm(2) of the TiO2 surface. The roughness factor of the utilized TiO2 electrode was 630. (C) 2004 Elsevier B.V. All rights reserved.