A free-standing aligned-carbon-nanotubes/nanocomposite foil as efficient counter electrode for dye solar cells

A novel free-standing and flexible counter electrode for dye solar cells has been developed by conveniently transferring a vertically aligned carbon nanotubes forest onto an oxygen-plasma-treated flexible, free-standing and conductive nanocomposite foil. Vertically aligned carbon nanotubes were first grown onto an aluminium foil by chemical vapour deposition and then transferred to the nanocomposite surface by hot pressing. The most meaningful electrochemical parameters have been quantitatively analyzed by means of electrochemical impedance spectroscopy and cyclic voltammetry in order to elucidate how the implementation of the anisotropic carbon nanotubes top layer impacts on the ultimate catalytic performances of the plate. Such an engineered counter electrode is able to guarantee a fast and effective reduction of the iodide-based electrolyte as well as to provide a solar conversion efficiency that is comparable with a typical Pt/TCO-coated rigid counter electrode. A photocurrent density higher than 13.36 mA/cm2 along with a solar conversion efficiency of 7.26 % have been reported for the dye solar cell mounting a counter-electrode based on a vertically aligned carbon nanotubes implanted onto a conductive nanocomposite plate.