Internal reference electrode in dye sensitized solar cells for three-electrode electrochemical characterizations

A new design of dye-sensitized solar cells that contains an internal reference electrode enables detailed electrochemical characterization of the cells at the practical operating configuration. A thin insulating gap splits the nanoporous TiO₂ electrode in twin halves, one serving as the active electrode in the solar cell and the other one as a photoreference that maintains the open circuit potential. This configuration allows separation of the two components of the cell potential, that of the photoactive electrode and that in the counter electrode, while maintaining the practical sandwich configuration. Analysis of efficient solar cells shows that the contributions of the counter electrode to the energy losses are larger than expected. By intentionally decreasing the counter electrode quality, we observed a modification of the photocurrent at the same effective electrode potential. This result is explained in terms of the coupling between the hole collection efficiency at the counter electrode and the recombination currents at the active electrode.