SiO2 Aerogel Templated, Porous TiO2 Photoanodes for Enhanced Performance in Dye-Sensitized Solar Cells Containing a Ni(III)/(IV) Bis(dicarbollide) Shuttle

High-area photoanodes consisting of silica aerogels, overcoated by atomic-layer-deposited TiO2, were fabricated on transparent conducting oxide platforms for their use in dye-sensitized solar cells (DSCs) in a similar fashion as previously described. These films were characterized by scanning electron microscopy, X-ray diffraction, diffuse reflectance spectroscopy, gas adsorption, and light and dark electrochemical impedance measurements. The use of aerogel-templated photoanodes in DSCs with a Ni(III/IV) bis(dicarbollide) redox shuttle results in a greater than 2-fold enhancement in photocurrent densities, in comparison to similar cells containing photoanodes constructed from TiO2 nanoparticles. This improvement in photocurrent is attributed to a combination of improved electron transport, increased recombination resistance across the TiO2/electrolyte interface, and increased light scattering within the aerogel films. As a result, DSC charge collection efficiencies with this comparatively fast exchanging outer-sphere redox couple are improved in the TiO2 aerogel templated photoanode.