The photonic energy bands of the inverse-opal solar cell were calculated. The finite difference time domain method was applied to the analysis of both hexagonal closest packed (hcp) and face-centered cubic (fcc) structures of the TiO2-electrolyte photonic crystal. The electrolyte, which filled the calculated photonic crystals, was set as an acetonitrile system. The calculated photonic energy bands were compared with the experimental scattering spectra. (C) 2007 Elsevier B.V. All rights reserved.