Composite nanocrystalline SnO2 thin films layered with a polyimide sensitizer to which is attached a Ru(bpy)(3)(2+) derivative were prepared by spin-coating. Photophysical and electrochemical properties of such composite films, when formulated as polymer-modified electrodes, are described. Excitation spectra of both composite films and of the dissolved polymer indicate substantial ground-state aggregation of the pendent ruthenium(II) complexes. Because of high loading of the pendent ruthenium(II) complex in the composite, high adsorptivity by the dye is attained. A maximum incident photon-to-photocurrent conversion efficiency (IPCE%) of 16% was observed upon monochromatic photosensitization at 460 nm.