Mesoporous TiO₂ Microbead Electrodes for Cobalt-Mediator-Based Dye-Sensitized Solar Cells

Light scattering, porosity, surface area, and morphology of TiO₂ working electrode can affect the power conversion efficiency of dye -sensitized solar cells dramatically. Here mesoporous TiO₂ microbeads were tested as working electrode in dye-sensitized solar cells based on cobalt tris-bipyridine electrolyte. Power conversion efficiencies up to 6.4% were obtained with D35 dye adsorbed onto the light-scattering microbeads. Electron transport, studied using small light perturbation methods, was found to be significantly faster in the microbead films than in standard mesoporous TiO₂ films. This was attributed to the favorable assembly of nanocrystals in the microbeads, which can increase the electron diffusion coefficient in the conduction band. Electron lifetimes were similar in both types of film. While solar cell performance of microbead films was comparable to that of standard mesoporous films in acetonitrile-based electrolytes, a significant improvement was found when the more viscous 3-methoxypropionitrile was used as solvent for electrolyte