TY - JOUR
T1 - Correlated Pair States Formed by Singlet Fission and Exciton-Exciton Annihilation
AU - Scholes, Gregory D.
PY - 2015/12/24
Y1 - 2015/12/24
N2 - 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).
AB - 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).
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U2 - 10.1021/acs.jpca.5b09725
DO - 10.1021/acs.jpca.5b09725
M3 - Article
C2 - 26595530
AN - SCOPUS:84952944040
SN - 1089-5639
VL - 119
SP - 12699
EP - 12705
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 51
ER -