Singlet Fission Dynamics Under Strong Light-Matter Coupling

Polaritons are unique hybrid light-matter states that offer an alternative way to manipulate chemical processes and change material properties. In this talk I will discuss our recent work focusing on how strong light-matter coupling can influence singlet fission dynamics in molecular materials.¹ Recent interest in singlet fission has been driven by its potential capacity to overcome the Shockley-Queisser limit for the efficiency of single junction solar cells. This is becuase in this process, a multiexcitonic state (TT) splits into two uncoupled triplets, therefore, a single photon triggers two electron hole-pairs. Although previous theoretical work has shown that singlet fission can benefit from polaritonic states,² a recent experiment did not obtain significant differences between cavity and non-cavity singlet fission dynamics.³In this talk I will discuss our results where we find that state mixing speeds up the dynamics in cavities when the lower polariton is close in energy to the multiexcitonic triplet-pair state. I will also show that this effect is more pronounced in non-conventional singlet fission materials in which the energy gap between the bright singlet exciton and the multiexcitonic state is large. In this case, the dynamics is dominated by the polaritonic modes and not by the bare-molecule-like dark states. I will also connect recent experimental observations to our results.<br/>¹C. Climent, D. Casanova, J. Feist, FJ. Garcia-Vidal, arXiv:2110.02173 (2021)<br/>² L. A. Martinez-Martinez, M. Du, R. F. Ribeiro, S. Kena-Cohen, J.Yuen-Zhou, J. Phys. Chem. Lett., 9, 1951 (2018)<br/>³ B. Liu, V. M. Menon, M. Y. Sfeir. ACS Photonics, 7, 2292 (2020)