CVD-grown TiO2 particles as light scattering structures in dye-sensitized solar cells

Chemical vapour deposition (CVD) at atmospheric pressure, using TiCl4 as a precursor, was used to grow nanostructured TiO2 films on glass substrates. At relatively low temperatures (similar to 245 degrees C) and using relatively high reactant concentrations, different nano-morphologies of TiO2 were formed simultaneously, such as spheres, nanowires and mesoporous structures. The TiO2 spheres were successfully applied as light-scattering particles in dye-sensitized solar cells, either by direct deposition onto electrodes in the reactor, or by preparation of a printing paste from the deposited particles. For dye-sensitized solar cells using the organic dye D35 as sensitizer and a cobalt-complex based redox electrolyte, a solar cell efficiency of 4.4% was obtained using a 5 mu m transparent mesoporous TiO2 layer. Addition of a 5 mu m light-scattering CVD-particle film increased the efficiency by 22% to 5.4%, which was similar to the result obtained with an equally thick commercially available light-scattering film (5.3%). Longer electron lifetime was found using CVD-based films, which is attributed to the presence of more traps in the bulk of the material.