An organic lanthanum solution was prepared and used for modifying the nanoporous TiO(2) photoanode for dye-sensitized solar cells (DSSCs). The preliminary characterization results demonstrate that La(2)O(3) was formed on the surface of the TiO(2) photoanodes. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses suggest that La(3+) was introduced into the TiO(2) nanocrystalline, while, the scanning electron microscopy (SEM) and tunnelling electron microscopy (TEM) characterizations suggest that a thin La(2)O(3) layer forms on surface of the TiO(2) nanostructure. The La(2)O(3) layer is able to alleviate the electron recombination as a passivation layer. Though the slight decrease in surface areas were induced by the surface modification, the dye loading were maintained, which can be attributed to the formation of strong co-ordination bonding between the dye molecules and the lanthanide. The bonding can also facilitate the electron transfer between the dye molecules and TiO(2) conduction band. Consequently, the open circuit potential and short circuit current were boosted significantly and the overall energy conversion efficiency of the DSSCs was remarkably improved from 6.84% for the control film to 9.67% for the La(3+)-modified film.
© 2012 American Chemical Society