Small diameter TiO2 nanotubes vs. nanopores in dye sensitized solar cells

Highly ordered nanoporous and nanotubular TiO2 geometries can be anodically grown on Ti substrates in fluoride containing ethylene glycol electrolytes using different water contents. Here we fabricate 1 μm thick layers consisting of arrayed tubes or pores with an open diameter of 15 nm. We compare these small diameter structures to classical 100 nm diameter TiO2 nanotubes for their application in Grätzel-type solar cells. The results show clearly that a small diameter nanotube geometry significantly enhances the solar cell conversion efficiency.

► Three types of self ordered TiO2 structures are compared for use in DSSCs.
► TiO2 nanotubes of smaller diameter show a significantly enhanced light conversion efficiency.
► Nanotubes are clearly superior over comparable ordered porous structures (electron transport, dye loading).