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 significantly superior to a bare 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.