Geometrical implication of ion transporters employing an ellipsoidal hollow structure in pseudo-solid electrolytes

We demonstrate facilitated ion transport in oligomer electrolytes by introducing TiO₂ hollow particles of ellipsoidal and spherical shapes. It was found that the TiO₂ hollow particles of ellipsoidal shape are much more effective in constructing ionic diffusion paths for the Grotthuss mechanism, resulting in highly enhanced diffusion coefficients of ions such as I^- and I₃^- in oligomer electrolytes. Compared to the hollow spheres of the TiO₂ component, the ellipsoidal hollow particles of the TiO₂ component provide 11% larger ionic diffusion coefficients, because of their geometry with a relatively small diffusion resistance. Since the facilitated ion transport can render fast redox reactions at both photo and counter electrodes, the solid state dye-sensitized solar cells employing oligomer electrolytes based on the TiO₂ hollow ellipsoids exhibit highly improved photovoltaic performances including highly improved energy-conversion efficiency without destabilizing the cell.