An explanation for the high stability of polycarboxythiophenes in photovoltaic devices—A solid-state NMR dipolar recoupling study

M. Bierring, J.S. Nielsen, Ana Siu, N.C. Nielsen, Frederik C Krebs

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Continuous operation of a polymer photovoltaic device under accelerated conditions for more than 1 year has been demonstrated (8760h at 72 degrees C, 1000Wm(-2), AM 1.5, under vacuum). Formation of hydrogen-bonded networks is proposed to be responsible for the long lifetime and high stability observed in photovoltaic devices employing polythiophene substituted with carboxylic-acid moieties under oxygen free conditions. H-1 and C-13 solid-state NMR, IR, and ESR spectroscopy of unmodified and isotopically labeled polythiophenes were studied. Distances between the isotopically labeled carboxylic acid carbon atoms were measured by C-13 solid-state magic-angle-spinning (MAS) NMR using symmetry-based double-quantum (2Q) dipolar recoupling. This revealed the presence of C-13-C-13 distances of 3.85 angstrom, which correspond to the C-C distance in hydrogen-bonded carboxylic acid dimers. In spite of the presence of carboxylic groups in the polymer as demonstrated by C-13 CP/MAS NMR and IR spectroscopy, the absence of carboxylic protons in solid state H-1 NMR spectra indicate that they are mobile. We link the extraordinary stability of this system to the rigid nature, cross-linking through a hydrogen-bonded network and a partially oxidized state. (c) 2007 Elsevier B.V. All rights reserved.
    Original languageEnglish
    JournalSolar Energy Materials & Solar Cells
    Volume92
    Issue number7
    Pages (from-to)772-784
    ISSN0927-0248
    DOIs
    Publication statusPublished - 2008

    Bibliographical note

    This work was supported by the Danish Strategic
    Research Council (DSF 2104-05-0052), the Danish
    National Research Foundation, the Danish Natural
    Science Research Council, and the Danish Biotechnology
    Instrument Centre (DABIC).

    Fingerprint Dive into the research topics of 'An explanation for the high stability of polycarboxythiophenes in photovoltaic devices—A solid-state NMR dipolar recoupling study'. Together they form a unique fingerprint.

    Cite this