Core-shell nanoporous electrode for dye sensitized solar cells:: the effect of the SrTiO3 shell on the electronic properties of the TiO2 core

A nanoporous TiO2 electrode coated with a thin SrTiO3 layer was synthesized for photoelectrochemical applications. Introduction of this core-shell electrode to a dye sensitized solar cell increased the open circuit photovoltage while reducing the short circuit photocurrent in comparison with a cell containing the standard noncoated TiO2 electrode. The photovoltage increases is more significant than the photocurrent reduction resulting in a 15% improvement of the overall conversion efficiency of the solar cell. The performance of the TiO2-SrTiO3 core-shell electrode in the dye sensitized solar cell was analyzed by several methods including photocurrent-voltage correlation, spectro-electrochemistry, dark current measurement, IPCE, and photovoltage spectroscopy. The results indicate that the SrTiO3 layer shifts the conduction band of the TiO2 in the negative direction rather than forming energy barrier at the TiO2/electrolyte interface as found for similar coating by other materials. The shift of the TiO2 bands is attributed to a surface dipole that is induced by the SrTiO3 coating.