Singlet fission is a process where an initially excited state creates two excitations. While it has potential to increase yields in next generation photovoltaics, it is a rare relaxation pathway that occurs in a relative handful of compounds. To date, the efficiency of singlet fission has been measured to be much faster in molecular crystals than it has been in their covalent analogs. In this talk, I will discuss our work to generalize a Frenkel-exciton model, typically used to describe the spectroscopy of J-aggregates, to describe collective features of singlet fission. This model suggests that, in crystals, the difference in exciton localization between the initial singlet state and the dark final state leads to doubly excited states that can be separated by several unit cells, and therefore less prone to geminate recombination. These states, born under optical selection rules, exhibit quantum entanglement that is a novel feature of the two-particle final state. The resulting correlation may impact carrier extraction efficiencies.

Singlet fission in the condensed phase: Special features of molecular crystals

248th National Meeting (2014)

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