title: Comparison of electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb, Ge, Zr-added TiO2 composite electrodes.
abstract: Electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were examined to disclose the effects of partial substitution of Ti atom by the other metals in the composite electrodes. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were prepared by sol-gel process using laurylamine hydrochloride as a template for the formation of micellar precursors yielding well-defined mesoporous nanocrystalline structures, as in the cases of the formation of silica and titania tubules and nanoparticles by the templating mechanism. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were characterized by transmission electron microscopy, BET surface area analysis, X-ray diffraction analysis, Raman spectroscopy, and impedance measurements. The TiO2 anatase nanocrystalline structure is retained after doping a small amount (5 mol %) of Nb, Ge, or Zr into the TiO2 structure, suggesting the homogeneous distribution of the doped metals with replacing Ti atom by the doped metal. The power conversion efficiency of the porphyrin-sensitized solar cells increases in the order Zr-added TiO2 (0.8%) < Nb-added TiO2 (1.2%) < TiO2 (2.0%) < Ge-added TiO2 cells (2.4%) under the same conditions. The improvement of cell performance of the Ge-added TiO2 cell results from the negative shift of the conduction band of the Ge-added TiO2 electrode. The Ge-added TiO2 cell exhibited a maximum power conversion efficiency of 3.5% when the porphyrin was adsorbed onto the surface of the Ge-added TiO2 electrode with a thickness of 4 microm in MeOH for 1 h.
authors.affiliation: Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan. imahori@scl.kyoto-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori
authors.forename: Shinya
authors.initials: S
authors.lastname: Hayashi
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Umeyama
authors.forename: Seunghun
authors.initials: S
authors.lastname: Eu
authors.forename: Akane
authors.initials: A
authors.lastname: Oguro
authors.forename: Soonchul
authors.initials: S
authors.lastname: Kang
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matano
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Shishido
authors.forename: Supachai
authors.initials: S
authors.lastname: Ngamsinlapasathian
authors.forename: Susumu
authors.initials: S
authors.lastname: Yoshikawa