An upconversion NaYF_4:Yb~(3+),Er~(3+)/TiO_2 core-shell nanoparticle photoelectrode for improved efficiencies of dye-sensitized solar cells

摘要

Novel upconversion NaYF_4:Yb~(3+),Er~(3+)/TiO_2 core-shell nanopartides (NPs) are synthesized and used to prepare the photoelectrode (PE) of dye-sensitized solar cells (DSSCs). The morphology, structure, pho-toluminescence characterization of the NaYF_4:Yb~(3+),Er~(3+)/TiO_2 core-shell NPs and the photoelectric performance, alternating current impedance spectroscopy of DSSCs are characterized using transmission electron microscopy, X-ray diffraction, upconversion luminescence (UCL) spectrofluorimetry and electrochemistry. Compared with the pure TiO_2 PE or the NaYF_4:Yb~(3+),Er~(3+) upconversion NPs and TiO_2 simply mixed prepared PE as the volume ratio of the core-shell structure, the DSSCs with the upconversion core-shell PE show a greater photovoltaic efficiency. The energy conversion efficiency of the DSSCs with a NaYF_4:Yb~(3+),Er~(3+)/TiO_2 PE is 23.1% higher than with a pure TiO_2 PE and 99.1% higher than with a mixed PE using the same conditions. This enhancement is due to the UCL core extending the spectral response range of DSSCs to the infrared region and their particular shell structure, retaining its semiconductor character. This method represents a novel approach to increase the efficiencies of DSSCs.