Preparation of nanoporous TiO2 electrodes using different mesostructured silica templates and improvement of the photovoltaic properties of DSSCs

Nanoporous TiO2 (NP-TiO2) was synthesized using different mesostructured silica templates such as SBA-15, KIT-6, and MSU-H, which have highly ordered pore or well-connected inner-network structures. NP-TiO2 has a large surface area and a dye-adsorption capability 1.5 times greater than that of nanocrystalline TiO2 (NC-TiO2). We have investigated dye-sensitized solar cells (DSSCs) with bilayer TiO2 electrodes, which were prepared by applying a coating of NP-TiO2 onto an NC-TiO2 film. The photocurrent (J(sc)) and fill factor (FF) for the DSSC with the bilayer TiO2 electrode were greatly improved. The solar energy conversion efficiency (eta(eff)) also increased over 15% compared with a DSSC with a monolayer NC-TiO2 electrode. For the DSSC with the bilayer TiO2 electrode, the charge recombination and dye-regeneration processes, which were studied by transient absorption spectroscopy, were slower and faster, respectively, than those of the DSSC with an NC-TiO2 electrode.