A Thiophene-Based Anchoring Ligand and Its Heteroleptic Ru(II)-Complex for Efficient Thin-Film Dye-Sensitized Solar Cells

Authors

  • Amaresh Mishra,

    Corresponding author
    1. Institute of Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
    • Institute of Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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  • Nuttapol Pootrakulchote,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland
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  • Mingkui Wang,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland
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  • Soo-Jin Moon,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland
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  • Shaik M. Zakeeruddin,

    Corresponding author
    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland
    • Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland.
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  • Michael Grätzel,

    Corresponding author
    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland
    • Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015, Switzerland.
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  • Peter Bäuerle

    Corresponding author
    1. Institute of Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
    • Institute of Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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Abstract

A novel heteroleptic RuII complex (BTC-2) employing 5,5′-(2,2′-bipyridine-4,4′-diyl)-bis(thiophene-2-carboxylic acid) (BTC) as the anchoring group and 4,4′- dinonyl-2,2′-bipiridyl and two thiocyanates as ligands is prepared. The photovoltaic performance and device stability achieved with this sensitizer are compared to those of the Z-907 dye, which lacks the thiophene moieties. For thin mesoporous TiO2 films, the devices with BTC-2 achieve higher power conversion efficiencies than those of Z-907 but with a double-layer thicker film the device performance is similar. Using a volatile electrolyte and a double layer 7 + 5 μm mesoporous TiO2 film, BTC-2 achieves a solar-to-electricity conversion efficiency of 9.1% under standard global AM 1.5 sunlight. Using this sensitizer in combination with a low volatile electrolyte, a photovoltaic efficiency of 8.3% is obtained under standard global AM 1.5 sunlight. These devices show excellent stability when subjected to light soaking at 60 °C for 1000 h. Electrochemical impedance spectroscopy and transient photovoltage decay measurements are performed to help understand the changes in the photovoltaic parameters during the aging process. In solid state dye-sensitized solar cells (DSSCs) using an organic hole-transporting material (spiro-MeOTAD, 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene), the BTC-2 sensitizer exhibits an overall power conversion efficiency of 3.6% under AM 1.5 solar (100 mW cm−2) irradiation.

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