Enhancement of Open-Circuit-Voltage of Dye-Sensitized Solar Cells by Using Organic Dye Sensitizers and TiO2 and ZnO Electrodes Doped with Mg

  • Dr Shinji Iwamoto, Department of Energy and Hydrocarbon Chemistry, Graduated School of Engineering, Kyoto University, Japan
  • Mr Yohei Sazanami, Department of Energy and Hydrocarbon Chemistry, Graduated School of Engineering, Kyoto University, Japan
  • Mr Takeaki Kadota, Department of Energy and Hydrocarbon Chemistry, Graduated School of Engineering, Kyoto University, Japan
  • Dr Masashi Inoue, Department of Energy and Hydrocarbon Chemistry, Graduated School of Engineering, Kyoto University, Japan
  • Mr Teruhisa Inoue, Nippon Kayaku Co.,Ltd., Japan
  • Mr Takayuki Hoshi, Nippon Kayaku Co.,Ltd., Japan
  • Mr Koichiro Shigaki, Nippon Kayaku Co.,Ltd., Japan
  • Mr Masasyoshi Kaneko, Nippon Kayaku Co.,Ltd., Japan

    • Dye-sensitized solar cells (DSSCs) are potential photovoltaic devices with high efficiency, which can be fabricated with low costs. As the electrodes of DSSCs, TiO2 and ZnO are usually used. In this study, addition of Mg to TiO2 and ZnO electrodes were examined to improve the open-circuit-voltage (Voc).
    Mg-doped titanias with the anatase structure (Mg(x)-TiO2, where x is Mg/Ti charged ratio) were prepared by the thermal reaction of mixtures of titanium tetraisopropoxide and magnesium acetate tetrahydrate in 1,4-butanediol. XRD, XPS, and XANES analyses indicated that Mg2+ ions were incorporated in the anatase structure for the products of x ≤ 0.2.
    As the amount of Mg added increased, the absorption edges of the products were gradually shifted to the lower wavelength side, indicating the increase in the band gap energy. The flat band potentials of Mg(x)-TiO2 electrodes estimated from the Mott-Schottky analysis were shifted to the negative potential side by Mg-modification; for instance, -0.73, -0.91, and -1.00 V (vs. Ag/AgCl), for the non-modified TiO2, Mg(0.1)-TiO2, and Mg(0.2)-TiO2, respectively.
    In Figure 1, photovoltaic properties of DSSCs using Mg(x)-TiO2 electrodes are shown. Using Mg(x)-TiO2 electrodes, higher Voc values were obtained. Especially, quite a high Voc, 0.99 V, was obtained with an acrylic acid organic dye (NKY-003) having a higher LUMO level than N719.
    Mg-doped zinc oxides were synthesized by thermal reaction of zinc acetate dehydrate and magnesium acetate tetrahydrate in 1,4-butanediol, and the products were characterized by several methods. An increase in Voc using the Mg-doped ZnO electrodes was also observed.