Electrophoretic deposition and compression of titania nanoparticle films for dye-sensitized solar cells

Cathodic electrophoretic deposition (EPD) of commercially available TiO₂ nanocrystals (P-25 and P-90, Degussa) for the formation of nanoporous electrodes for dye-sensitized solar cells (DSSCs) is reported. Thick, uniform, adherent TiO₂ films were obtained from alcoholic suspensions prepared in two steps: first, nanoparticles were treated in an alcoholic suspension with a small amount of acetylacetone; second, the obtained suspension was mixed with a EPD "charging solution" with small additives of iodine, acetone and water. A modified mechanical compression technique was employed to the electrophoretically deposited films to vary the porous structure and thickness of TiO₂ layers. By applying non-polar volatile organic liquids to fill the pores of dry TiO₂ films before compression, we obtained a substantial improvement in the quality of the pressed films. The fabrication of multilayer electrodes enabled us to obtain TiO₂ films with a thickness up to 25 μm and the photoelectric conversion efficiency up to 8.5% under 1 sun illumination.