Fabrication of porous TiO₂ films using a spongy replica prepared by layer-by-layer self-assembly method: Application to dye-sensitized solar cells

In this study, we report the fabrication of the anatase TiO₂ films with high porosity using a new spongy replica which prepared by layer-by-layer self-assembly technique. The scanning electron microscope photographs revealed that the spongy replica has an extremely porous microstructure and high surface area. Moreover, this porous replica was easily fabricated from a very flat film through the action with silver acetate solution. This method facilitated the porous TiO₂ films with a high surface area. Additionally, by this method, a necking between the TiO ₂ films was strong and the amount of loaded dye was increased, so that the increase of forward electron transfer between the TiO₂ films on the surface and the TiO₂ films on the substrate. By using the fabricated porous TiO₂ films as the photoelectrode for dye-sensitized solar cell, the improvement of the photocurrent-voltage characteristic was achieved, resulting in an energy conversion efficiency of Eff = 2.66% with the thickness of approximately 5 μm.