Data mining using experimental data and information generated from theoretical calculations is proposed to study dye-sensitized solar cells, which are complex systems. This method led to new knowledge about the influence of imidazole derivatives as additives in an electrolytic solution on the cell performance. It was found that the solar energy conversion efficiency is strongly correlated to the Mulliken charge of the carbon atom at position 4 in the imidazole group. This result indicates that data mining assisted by theoretical calculations should facilitate the rate that cell performance is improved. (c) 2006 Elsevier B.V. All rights reserved.