Strong-Coupling Modification of Singlet-Fission Dynamical Pathways

TL;DR

This paper explores how strong light-matter coupling within optical cavities can modify the pathways and efficiency of singlet-fission in organic dimers, revealing potential for enhanced or suppressed triplet yields depending on system parameters.

Contribution

It introduces a theoretical model showing how cavity-induced resonance conditions can control singlet-fission pathways and yields, including the use of polaritons to enhance triplet formation.

Findings

Cavity coupling can suppress or enhance triplet yields in singlet-fission.

Modified resonance conditions affect the passage through intermediate states.

Using the upper polariton can significantly increase triplet yield under certain conditions.

Abstract

We investigate theoretically the influence of strong light-matter coupling on the initial steps of the photo-triggered singlet-fission process. In particular we focus on intra-molecular singlet fission in a TIPS-pentacene dimer derivative described by a vibronic Hamiltonian including the optically active singlet excited states, doubly excited and charge transfer states, as well as the final triplet-triplet pair state. Quantum dynamics simulations of up to four dimers in the cavity indicate that the modified resonance condition imposed by the cavity strongly quenches the passage through the intermediate charge transfer and double-excitation states, thus largely reducing the triplet-triplet yield in the bare system. Subsequently, we modify the system parameters and construct a model Hamiltonian where the optically-active singlet excitation lies below the final triplet-triplet state such that the yield of the bare system becomes insignificant. In this case we find that using the upper polariton as the doorway state for photo-excitation can lead to a much enhanced yield. This pathway is operative provided that the system is sufficiently rigid to prevent vibronic losses from the upper polariton to the dark-states manifold.