High-Performance Nanoporous TiO2/La2O3 Hybrid Photoanode for Dye-Sensitized Solar Cells

An organic lanthanum solution was prepared and used for modifying the nanoporous TiO2 photoanode for dye-sensitized solar cells (DSSCs). The preliminary characterization results demonstrate that La2O3 was formed on the surface of the TiO2 photoanodes. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses suggest that La3+ was introduced into the TiO2 nanocrystalline, while, the scanning electron microscopy (SEM) and tunnelling electron microscopy (TEM) characterizations suggest that a thin La2O3 layer forms on surface of the TiO2 nanostructure. The La2O3 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 coordination bonding between the dye molecules and the lanthanide. The bonding can also facilitate the electron transfer between the dye molecules and TiO2 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 La3+-modified film.