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

Papadopoulos I, Álvaro-Martins MJ, Molina D, McCosker PM, Keller PA, Clark T, Sastre-Santos Á, Guldi DM (2020)

Publication Type: Journal article

Publication year: 2020

Journal

DOI: 10.1002/aenm.202001496

Abstract

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).

Authors with CRIS profile

Involved external institutions

Miguel Hernández University of Elche (UMH) / Universidad Miguel Hernández de Elche Spain (ES) University of Wollongong (UOW) Australia (AU)

How to cite

APA:

Papadopoulos, I., Álvaro-Martins, M.J., Molina, D., McCosker, P.M., Keller, P.A., Clark, T.,... 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. https://dx.doi.org/10.1002/aenm.202001496

MLA:

Papadopoulos, Ilias, et al. "Solvent-Dependent Singlet Fission in Diketopyrrolopyrrole Dimers: A Mediating Charge Transfer versus a Trapping Symmetry-Breaking Charge Separation." Advanced Energy Materials (2020).

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