Improvement of mass transport of the [Co(bpy)3](II/III) redox couple by controlling nanostructure of TiO2 films in dye-sensitized solar cells.

Mass transport of the [Co(bpy)(3)](II/III) redox electrolyte is found to strongly depend on porosity and pore size of mesoporous TiO(2) films. Photocurrent density is improved by nearly two times with increasing the porosity from 0.52 to 0.59 despite 23% decreased dye loading. Optimized nanostructure sensitized with MK-2 dye shows efficiency of 5.5% at 1 sun.