Sputtered Nb2O5 as a novel blocking layer at conducting Glass/TiO2 interfaces in dye-sensitized ionic liquid solar cells

The preparation of a novel Nb2O5 blocking layer deposited between fluorine-doped tin oxide (FTO) and nanocrystalline TiO2 layer and its application for dye-sensitized ionic liquid solar cell have been studied. The Nb2O5 blocking layer prepared by the sputtering method on FTO has been characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and X-ray photoelectron spectroscopy. Thin Nb2O5 films work as a potential blocking layer between FTO and TiO2 nanocrystalline film in ionic liquid electrolyte cells, improving V-oc and finally giving a better conversion efficiency of dye-sensitized TiO2 solar cells. The remarkable improvements of V-oc and the fill factor for the dye-sensitized solar cells suggest that such a thin Nb2O5 layer is an effective blocking layer at FTO and TiO2 interface, contributing to the suppression of recombination processes between unidirectional transporting electron and redox electrolytes in the process of TiO2 photoelectron conversion systems. SEM and CV reveal that the Nb2O5 blocking layer is electronic blocking rather than morphological blocking at the FTO/nanoTiO(2) interface, which may give another direction on the suppression of charge recombination during photoelectron conversion process.