Correlated Pair States Formed by Singlet Fission and Exciton-Exciton Annihilation

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Abstract

Singlet fission to form a pair of triplet excitations on two neighboring molecules and the reverse process, triplet-triplet annihilation to upconvert excitation, have been extensively studied. Comparatively little work has sought to examine the properties of the intermediate state in both of these processes-the bimolecular pair state. Here, the eigenstates constituting the manifold of 16 bimolecular pair excitations and their relative energies in the weak-coupling regime are reported. The lowest-energy states obtained from the branching diagram method are the triplet pairs with overall singlet spin |X1〉 ≈ 1[TT] and quintet spin |Q〉 ≈ 5[TT]. It is shown that triplet pair states can be separated by a triplet-triplet energy-transfer mechanism to give a separated, yet entangled triplet pair 1[T⋯T]. Independent triplets are produced by decoherence of the separated triplet pair. Recombination of independent triplets by exciton-exciton annihilation to form the correlated triplet pair (i.e., nongeminate recombination) happens with 1/3 of the rate of either triplet migration or recombination of the separated correlated triplet pair (geminate recombination).

Original languageEnglish (US)
Pages (from-to)12699-12705
Number of pages7
JournalJournal of Physical Chemistry A
Volume119
Issue number51
DOIs
StatePublished - Dec 24 2015

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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