Titania-based Gratzel-type solar cells were fabricated by the use of polyene dyes with various transition dipole moments. in the dye having the largest transition dipole among the samples, an aggregate was readily formed through dispersive interaction, and the photocurrent was increased when the dye concentration or the light intensity was lowered. This observation was ascribed to the suppression of the singlet-triplet annihilation reaction. In the dye having the smallest transition dipole, there was no sign of aggregate formation, and the photocurrent was decreased when the dye concentration or the light intensity was lowered. (c) 2006 Elsevier B.V. All rights reserved.