Joint Effects of Exciton–Exciton and Exciton–Photon Couplings on the Singlet Fission Dynamics in Organic Aggregates

The optical microcavities and plasmonic arrays have emerged as new ways to manipulate and control the molecular properties by exploiting radiation–matter coupling. Here, the time-dependent wave-packet diffusion method is extended to investigate the influence of the optical microcavity on the singlet fission (SF) dynamics in organic aggregates. The results from a model system show that the photon–exciton coupling can dramatically attenuate the dependence of SF rates on molecular packing mode and there is an optimal photon–exciton coupling at which the SF rate reaches its maximum, and the cavity effect becomes less obvious as the modulatory role of charge-transfer states on SF dynamics is incorporated. The possible mechanism is assigned to the joint effect of photon–exciton and exciton–exciton interactions on initial singlet exciton distribution. Furthermore, we simulate the SF dynamics of a realistic pentacene dimer with a medium-strength (VPE= 100 meV) and strong (VPE= 300 meV) photon–exciton couplings. The numerical results verify that SF rates are susceptible to VPE.