Enhanced efficiency in dye-sensitised solar cells using a TiO2-based sandwiched film as photoanode

A multi-layered film with a TiO2-based nanotubes/nanoparticles/nanotubes sandwich structure has been developed to increase light-harvesting efficiency by enhancing light scattering. Compared to a double-layered film of nanotubes/nanoparticles, the sandwiched film exhibited greatly improved light-absorption properties. An obviously improved total energy-conversion efficiency of 6.11% was obtained in the sandwiched film, which is 27.3, 46.1 and 213% higher than those of the double-layered film, nanoparticle film and nanotube film, respectively. A possible mechanism for the enhancement of light harvesting in the sandwiched film is proposed, whereby the observed enhancement is owing to effective scattering by the bottom layer and reflection of escaped light by the top layer.