TiO₂ nanocrystals shell layer on highly conducting indium tin oxide nanowire for photovoltaic devices

We demonstrated a highly efficient conducting indium tin oxide (ITO) core-TiO₂ nanocrystals shell nanowire array for a photoelectrode in dye-sensitized solar cells with regard to light harvest and charge collection. The TiO₂ shell layer, consisting of anatase nanocrystals of ∼2 nm, were successfully formed on a single crystalline ITO nanowire prepared via a vapor transport method using repetitive TiCl₄ aqueous solution treatments at 50°C. We found that the nanocrystal size and number of Cl ^- ions remaining on the formed shell layer critically influence the dye loading properties. Moreover, these factors can be controlled by means of a post-annealing process. We also found that the dye loading and the back electron transport from the conductive ITO nanowire to the electrolyte mainly determine the final cell performance. The proposed double-shell layer structure consisting of dense and porous layers showed significantly improved cell performance.