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Pyridine-N-Oxide 2-Carboxylic Acid: An Acceptor Group for Organic Sensitizers with Enhanced Anchoring Stability in Dye-Sensitized Solar Cells

Authors

  • Bianca Cecconi,

    1. Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 13, 50019 Sesto Fiorentino (FI) (Italy)
    2. Current address: Department of Materials Science, University of Milan-Bicocca, Building U5, Via R. Cozzi 53, 20125 Milan (Italy)
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  • Dr. Alessandro Mordini,

    1. Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 13, 50019 Sesto Fiorentino (FI) (Italy)
    2. Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI) (Italy), Fax: (+39) 055-4573571
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  • Dr. Gianna Reginato,

    1. Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI) (Italy), Fax: (+39) 055-4573571
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  • Dr. Lorenzo Zani,

    1. Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI) (Italy), Fax: (+39) 055-4573571
    2. Institute of Organic Synthesis and Photoreactivity (CNR-ISOF), Via P. Gobetti 101, 40129 Bologna (Italy)
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  • Prof. Dr. Maurizio Taddei,

    1. Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro 2, 53100, Siena (Italy)
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  • Dr. Fabrizia Fabrizi de Biani,

    1. Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro 2, 53100, Siena (Italy)
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  • Dr. Filippo De Angelis,

    1. Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Institute of Molecular Science and Technology (CNR-ISTM), Via Elce di Sotto 8, 06123 Perugia (Italy)
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  • Gabriele Marotta,

    1. Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Institute of Molecular Science and Technology (CNR-ISTM), Via Elce di Sotto 8, 06123 Perugia (Italy)
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  • Dr. Paolo Salvatori,

    1. Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Institute of Molecular Science and Technology (CNR-ISTM), Via Elce di Sotto 8, 06123 Perugia (Italy)
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  • Dr. Massimo Calamante

    Corresponding author
    1. Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 13, 50019 Sesto Fiorentino (FI) (Italy)
    2. Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI) (Italy), Fax: (+39) 055-4573571
    • Department of Chemistry “U. Schiff”, University of Florence, Via della Lastruccia 13, 50019 Sesto Fiorentino (FI) (Italy)

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Abstract

A D-π-A organic dye carrying a pyridine-N-oxide 2-carboxylic acid anchoring group (BC1) was synthesized together with two analogs lacking the N-oxide (BC2) or the carboxylic acid moiety (BC3). The distribution and energy of their molecular orbitals was determined, and modelling of their spectroscopic properties was performed through a TD-DFT computational study. The photo- and electrochemical properties of the dyes were assessed together with their desorption kinetics from nanocrystalline TiO2. In solution, the absorption spectra of dyes BC1 and BC3 were red-shifted compared with BC2, with the maximum absorption wavelength influenced by the dye protonation level. The 2-substituted carbonitrile dye BC3 was not adsorbed on the titania surface. On the other hand, the pseudo-first order desorption rate constants of BC1 and BC2 suggest that BC1 was removed from TiO2 more slowly than BC2 a reference cyanoacrylate dye, demonstrating that simultaneous use of the N-oxide and the carboxylic acid anchoring functions enhanced the stability of the dye/semiconductor assembly. When used as a photosensitizer for dye-sensitized solar cells, the photovoltaic performance of BC1 was better than BC2, which corresponds to approx. 66 % of that recorded with the reference dye.

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