Preparation of Nb2O5 coated TiO2 nanoporous electrodes and their application in dye-sensitized solar cells

The preparation of a new bilayer nanoporous wide band gap semiconductor electrode and its application for solar cells are reported. This new electrode consists of an inner nanoporous TiO2 matrix covered with a thin layer of ca. 2-3 nm Nb2O5. The results presented in this study show that this Nb2O5 layer forms an inherent energy barrier at the electrode-electrolyte interface. This barrier reduces the recombination rate of the photoinjected electrons with their counter holes. A comparison of two similar dye-sensitized solar cells (DSSCs) that differ only in their nanoporous electrodes shows that the solar cells made from the new electrode are superior to the standard cells with respect to all parameters. This superiority measured with many cells results in a 35% increase of the overall conversion efficiency from 3.6 to 5.0%. Optimization of the coating process and the characterization of the coating effects are described.