Thiocyanate-Free Ru(II) Sensitizers with a 4,4′-Dicarboxyvinyl-2,2′-bipyridine Anchor for Dye-Sensitized Solar Cells

Authors

  • Kuan-Lin Wu,

    1. Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
    2. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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  • Wan-Ping Ku,

    1. Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
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  • Sheng-Wei Wang,

    1. Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
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  • Aswani Yella,

    1. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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  • Yun Chi,

    Corresponding author
    1. Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan
    • Yun Chi, Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan

      Pi-Tai Chou, Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan.

      Mohammad K. Nazeeruddin, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

      Michael Grätzel, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

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  • Shih-Hung Liu,

    1. Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan
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  • Pi-Tai Chou,

    Corresponding author
    1. Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan
    • Yun Chi, Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan

      Pi-Tai Chou, Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan.

      Mohammad K. Nazeeruddin, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

      Michael Grätzel, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

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  • Mohammad K. Nazeeruddin,

    Corresponding author
    1. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
    • Yun Chi, Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan

      Pi-Tai Chou, Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan.

      Mohammad K. Nazeeruddin, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

      Michael Grätzel, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

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  • Michael Grätzel

    Corresponding author
    1. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
    • Yun Chi, Department of Chemistry and Low Carbon, Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan

      Pi-Tai Chou, Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan.

      Mohammad K. Nazeeruddin, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

      Michael Grätzel, Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

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Abstract

A new class of thiocyanate-free Ru(II) sensitizers with 4,4′-dicarboxyvinyl-2,2′-bipyridine anchor and two trans-oriented pyrid-2-yl pyrazolate (or triazolate) functional chromophores is synthesized, characterized, and evaluated in dye-sensitized solar cells (DSCs). Despite their enhanced red response and absorptivity when compared to the parent sensitizer TFRS-2 that possesses standard 4,4′-dicarboxyl-2,2′-bipyridine anchor and shows the best conversion efficiency of η = 9.82%, the newly synthesized carboxyvinyl-pyrazolate sensitizers, TFRS-11TFRS-13, exhibit inferior performance characteristics in terms of short-circuit current density (JSC), open-circuit voltage (VOC), and power conversion efficiency (η), the latter being recorded to be in the range 5.60–7.62%. The reduction in device efficiencies is attributed to a combination of poor packing of these sensitizers on the TiO2 surface and less positive ground-state oxidation potentials, which, respectively, increase charge recombination with I3 in electrolytes and impede the regeneration of sensitizers by I anions. The latter obstacle can be circumvented in part by the replacement of the pyrazolates with triazolates, forming the TFRS-14 sensitizer, which exhibits an improved JSC, VOC, and η of 16.4 mAcm−2, 0.77 V, and 9.02%, respectively.

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