Polariton-assisted Singlet Fission in Acene Aggregates

TL;DR

This paper explores how strong light-matter interactions in microcavities can modify exciton quantum yields in acenes, revealing potential for improved organic photovoltaic efficiency through polariton-assisted singlet fission.

Contribution

It develops a kinetic model showing polaritonic effects can enhance or reduce exciton yields in acenes, including cases where poor candidates like hexacene outperform better ones like pentacene.

Findings

Polaritons can increase exciton yields in acenes.

Hexacene can outperform pentacene in microcavities.

Relaxation processes influence polariton photochemistry.

Abstract

Singlet fission is an important candidate to increase energy conversion efficiency in organic photovoltaics by providing a pathway to increase the quantum yield of excitons per photon absorbed in select materials. We investigate the dependence of exciton quantum yield for acenes in the strong light-matter interaction (polariton) regime, where the materials are embedded in optical microcavities. Starting from an open-quantum-systems approach, we build a kinetic model for time-evolution of species of interest in the presence of quenchers and show that polaritons can decrease or increase exciton quantum yields compared to the cavity-free case. In particular, we find that hexacene, a typically poor singlet-fission candidate, can feature a higher yield than cavity-free pentacene when assisted by polaritonic effects. Similarly, we show that pentacene yield can be increased when assisted by polariton states. Finally, we address how various relaxation processes between bright and dark states in lossy microcavities affect polariton photochemistry. Our results also provide insights on how to choose microcavities to enhance similarly related chemical processes.