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

Abstract

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 co-ordination 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.