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 TiO2 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.