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Bisquinoxaline-Fused Porphyrins for Dye-Sensitized Solar Cells

Authors

  • Prof. Hiroshi Imahori,

    Corresponding author
    1. Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan), Fax: (+81) 75-383-2571
    2. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
    3. Fukui Institute for Fundamental Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-8103 (Japan)
    • Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan), Fax: (+81) 75-383-2571
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  • Hiroaki Iijima,

    1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
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  • Hironobu Hayashi,

    1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
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  • Yuuki Toude,

    1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
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  • Prof. Tomokazu Umeyama,

    1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
    2. PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
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  • Prof. Yoshihiro Matano,

    1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)
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  • Seigo Ito

    1. Department of Electrical Engineering and Computer Sciences, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan)
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Abstract

5,10,15,20-Tetrakis(2,4,6-trimethylphenyl)-6′-carboxylquinoxalino[2,3-b]quinoxalino[12,13-b′]porphyrinatozinc(II) (ZnPBQ) is synthesized to evaluate the effects of π elongation of quinoxaline-fused porphyrins on the optical, electrochemical, and photovoltaic properties. ZnPBQ showed an intensified Soret band as well as red-shifted Soret and Q bands relative to 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)-6′-carboxylquinoxalino[2,3-b]porphyrinatozinc(II) (ZnPQ), demonstrating the improved light-harvesting property of ZnPBQ. The optical and electrochemical HOMO–LUMO gaps were consistent with those estimated by DFT calculations. The photovoltaic properties were compared under optimized conditions, in which a sealed device structure with TiCl4-treated, TiO2 double layers was used. The ZnPBQ cell exhibited a relatively high power conversion efficiency (η) of 4.7 %, which was smaller than that of the ZnPQ cell (η=6.3 %). The weaker electronic coupling between the LUMO of ZnPBQ and conduction band (CB) of TiO2 or more tilted geometry of ZnPBQ on the TiO2 surface may result in the low electron injection/charge collection efficiency as well as the low incident photon-to-current efficiency (IPCE) for the ZnPBQ cell (maximum IPCE=56 %) relative to the ZnPQ cell (maximum IPCE=75 %), leading to the lower η value of the ZnPBQ cell than that of the ZnPQ cell. In addition, the open-circuit potential of the ZnPBQ cell also slightly decreased with the effect of charge recombination from the electrons injected into the CB of TiO2 to I3.

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