TiO2 FILMS WITH VARIOUS CRYSTAL STRUCTURES FOR SINGLE AND BILAYER PHOTOANODES OF DYE-SENSITIZED SOLAR CELLS

Phase pure and composite TiO 2 nanopowders exhibiting various crystal structures (anatase, rutile and brookite) are used as photoanode in dye-sensitized solar cells. The nanopowders are deposited in paste form onto a conducting oxide glass using doctor blade method in single layer and bilayers. The highest solar efficiency achieved by the single layer photoanode composed of > 99 wt % anatase crystals was 2.86 %. The solar efficiency of 4.93 % has been harvested via bilayer photoanode built by applying a layer consisting 55 wt % anatase and 45 wt % rutile phase nanoparticles on top of the layer composed of a mixture of > 99 wt % anatase crystals. The improved photovoltaic performance is attributed to anatase dominated bottom layer which facilitates electron charge generation with high surface area and charge transport by proper crystal structure as well as synergistic effect of binary phase content of the photoanodes. The porous structure of top layer enhances diffusion of the I − /I 3 −  electrolyte in the bilayer TiO 2  photoanode.