Ta doping for an enhanced efficiency of TiO2 nanotube based dye-sensitized solar cells

Ta doped TiO2 nanotube layers were fabricated by anodization of different Ti–Ta alloys with Ta contents of 0.03, 0.1 and 0.4 at.%. For all layers well defined nanotubular structures could be formed. The layers were then characterized in dye-sensitized solar cells. Under optimized conditions, that is for a 0.1 at.% Ta alloy, the solar cell efficiency could be enhanced by 25% compared to non-doped TiO2 nanotubes. Intensity modulated photocurrent spectra (IMPS) and intensity modulated photovoltage spectra (IMVS) measurements performed with the solar cells indicate that the beneficial effect is due to suppression of recombination effects.

► Self-organized Ta doped TiO2 nanotube arrays can be grown on Ti–Ta alloys.
► Doped TiO2 nanotubes show a higher solar cell conversion efficiency than pure TiO2 nanotubes.
► The beneficial effect is caused by suppression of electron recombination effects.