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Solvent-Dependent Singlet Fission in Diketopyrrolopyrrole Dimers: A Mediating Charge Transfer versus a Trapping Symmetry-Breaking Charge Separation

Journal Article


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Abstract


  • © 2020 The Authors. Published by Wiley-VCH GmbH Three diketopyrrolopyrrole (DPP) dimers, linked via different dithienylphenylene spacers, ortho-DPP (o-DPP), meta-DPP (m-DPP), and para-DPP (p-DPP), are synthesized, characterized, and probed in light of intramolecular singlet fission (i-SF). Importantly, the corresponding DPP reference (DPP-Ref) singlet and triplet excited state energies of 2.22 and 1.04 eV, respectively, suggest that i-SF is thermodynamically feasible. The investigations focus on the impact of the relative positioning of the DPPs, and give compelling evidence that solvent polarity and/or spatial overlap govern i-SF dynamics and efficiencies. Polar solvents make the involvement of an intermediate charge transfer (CT) state possible, followed by the population of 1(T1T1) and subsequently (T1 + T1), while spatial overlap drives the mutual interactions between the DPPs. In o-DPP, the correct balance between polar solvents and spatial overlap leads to the highest triplet quantum yield (TQY) of 40%. Notable is the superimposition of CT and triplet excited states, preventing an accurate TQY determination. For m-DPP, poorer spatial overlap correlates with weaker CT character and manifests in a TQY of 11%. Strong CT character acts as a trap and prevents i-SF, as found with p-DPP. The DPP separation is decisive, enabling a symmetry-breaking charge-separated state rather than CT formation, shutting down the formation 1(T1T1).

UOW Authors


  •   Papadopoulos, Ilias (external author)
  •   Álvaro-Martins, Maria (external author)
  •   Molina, Desire (external author)
  •   McCosker, Patrick (external author)
  •   Keller, Paul
  •   Clark, Timothy (external author)
  •   Sastre-Santos, Angela (external author)
  •   Guldi, Dirk (external author)

Publication Date


  • 2020

Citation


  • Papadopoulos, I., Álvaro-Martins, M. J., Molina, D., McCosker, P. M., Keller, P. A., Clark, T., Sastre-Santos, A. & Guldi, D. M. (2020). Solvent-Dependent Singlet Fission in Diketopyrrolopyrrole Dimers: A Mediating Charge Transfer versus a Trapping Symmetry-Breaking Charge Separation. Advanced Energy Materials,

Scopus Eid


  • 2-s2.0-85091736748

Ro Full-text Url


  • https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2720&context=smhpapers1

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers1/1686

Place Of Publication


  • Germany

Abstract


  • © 2020 The Authors. Published by Wiley-VCH GmbH Three diketopyrrolopyrrole (DPP) dimers, linked via different dithienylphenylene spacers, ortho-DPP (o-DPP), meta-DPP (m-DPP), and para-DPP (p-DPP), are synthesized, characterized, and probed in light of intramolecular singlet fission (i-SF). Importantly, the corresponding DPP reference (DPP-Ref) singlet and triplet excited state energies of 2.22 and 1.04 eV, respectively, suggest that i-SF is thermodynamically feasible. The investigations focus on the impact of the relative positioning of the DPPs, and give compelling evidence that solvent polarity and/or spatial overlap govern i-SF dynamics and efficiencies. Polar solvents make the involvement of an intermediate charge transfer (CT) state possible, followed by the population of 1(T1T1) and subsequently (T1 + T1), while spatial overlap drives the mutual interactions between the DPPs. In o-DPP, the correct balance between polar solvents and spatial overlap leads to the highest triplet quantum yield (TQY) of 40%. Notable is the superimposition of CT and triplet excited states, preventing an accurate TQY determination. For m-DPP, poorer spatial overlap correlates with weaker CT character and manifests in a TQY of 11%. Strong CT character acts as a trap and prevents i-SF, as found with p-DPP. The DPP separation is decisive, enabling a symmetry-breaking charge-separated state rather than CT formation, shutting down the formation 1(T1T1).

UOW Authors


  •   Papadopoulos, Ilias (external author)
  •   Álvaro-Martins, Maria (external author)
  •   Molina, Desire (external author)
  •   McCosker, Patrick (external author)
  •   Keller, Paul
  •   Clark, Timothy (external author)
  •   Sastre-Santos, Angela (external author)
  •   Guldi, Dirk (external author)

Publication Date


  • 2020

Citation


  • Papadopoulos, I., Álvaro-Martins, M. J., Molina, D., McCosker, P. M., Keller, P. A., Clark, T., Sastre-Santos, A. & Guldi, D. M. (2020). Solvent-Dependent Singlet Fission in Diketopyrrolopyrrole Dimers: A Mediating Charge Transfer versus a Trapping Symmetry-Breaking Charge Separation. Advanced Energy Materials,

Scopus Eid


  • 2-s2.0-85091736748

Ro Full-text Url


  • https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2720&context=smhpapers1

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers1/1686

Place Of Publication


  • Germany