TiO₂-coated nanoporous SnO₂ electrodes for dye-sensitized solar cells

This paper describes the synthesis and characterization of a core-shell nanoporous electrode consisting of an inner SnO₂ matrix and a thin shell of TiO₂. The coating is characterized as a very thin rutile TiO₂ layer whose conduction band level is located between the levels of bare SnO₂ and TiO₂. The TiO₂ shell acts as an energy barrier at the electrode-electrolyte interface, thus slowing the interaction between the electrons in the electrode and the electrolyte ions. When applied in a dye-sensitized solar cell, the coated electrode is significantty superior to a bate SnO₂ electrode. The increase of all cell parameters improves the conversion efficiency by a factor of 2.2. The combination of improved electron collection efficiency with respect to bare SnO₂ and a more positive conduction band with respect to bare TiO₂ should make dyes having a relatively positive excited-state potential usable in dye-sensitized systems.