Singlet Fission (SF), the phenomenon where an initial photo-excited singlet state spontaneously evolves into a correlated triplet state that can then decorrelate into two triplets, offers a rich landscape of challenges to theoretical simulations. We will describe our efforts towards mapping the reactive pathways relevant to designing promising chromophores for use in organic photovoltaic devices. In particular, we discuss the differing mechanisms intermolecular and intramolecular SF uncovered through high-level electronic structure studies. We also discuss the use of semi-emprical theory to arrive at a simple design rule that allows us to identify SF-active chromophores that absorb intensely in the visible region making them suitable for use in solar light harvesting devices. Finally, we discuss a strategy to compute nonradiative reaction rates that allow us to study recombination rates for the correlated triplet state produced through SF. By mapping out the key vibronic modes in the system, we demonstrate it is possible to uncover design strategies for slowing down the recombination rates while leaving the SF rates relatively unchanged.

Theoretical studies of singlet fission: Reaction rates and mechanisms

ACS Spring Meeting 2021

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