Singlet fission and triplet-triplet annihilation for covalently linked systems have been experimentally observed and reported, but theoretical characterization of the corresponding electronic couplings and rates of such processes remain a challenge. With the fragment excitation difference scheme with restricted active space spin-flip configuration interaction, we investigated three covalently-linked pentacene dimers via a phenyl group in an ortho-, meta- and para- arrangements. The results showed that the singlet fission/TTA couplings are enhanced when two chromophores are covalently linked. The population of charge-transfer excitions was also increased in the enhanced coupling cases.  With Fermi's golden rule, both the estimated singlet fission and triplet-triplet annihilation rates are in line with experimental results. Our approach allows an analysis of through-bond versus through-space singlet fission in the full electronic wavefunctions. The interaction of Frenkel and charge-transfer excitons will be discussed in this presentation.

Charge-transfer excitons and Frenkel excitons in linked pantacene dimers: Influences for singlet fission and triplet-triplet annihilations

256th National Meeting (2018)

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