Abstract
When photoactive molecules interact strongly with confined light modes, new hybrid light–matter states may form: the polaritons. These polaritons are coherent superpositions of excitations of the molecules and of the cavity photon. Recently, polaritons were shown to mediate energy transfer between chromophores at distances beyond the Förster limit. Here we explore the potential of strong coupling for light-harvesting applications by means of atomistic molecular dynamics simulations of mixtures of photoreactive and non-photo-reactive molecules strongly coupled to a single confined light mode. These molecules are spatially separated and present at different concentrations. Our simulations suggest that while the excitation is initially fully delocalized over all molecules and the confined light mode, it very rapidly localizes onto one of the photoreactive molecules, which then undergoes the reaction.
Highlights
E fficient excitation energy transfer, in which a photon is absorbed in one part of the system but utilized in another, is a key process in both natural and artificial light harvesting.[1,2]
Whereas the transfer usually occurs via the well-established Förster or Dexter mechanisms,[3,4] recent experiments[5−8] and theories[9−12] suggest that strong coupling of donor and acceptor molecules with a single confined light mode in an optical cavity can mediate the transfer, even at distances beyond which the Förster mechanism can operate.[7]
Strong coupling between N molecules and confined light leads to formation of N + 1 hybrid light-matter states that are coherent superpositions of excitations in each of the molecules and of the confined light mode[19,20]
Summary
Whereas only one molecule eventually uses that energy for the reaction (Figure 1b). Light can be efficiently confined between the mirrors of a Fabry-Peŕ ot optical cavity[23] or on the surface of metallic nanoparticles supporting a localized surface plasmon resonance (LSPR).[24,25] Because in our simulations the details of the actual structure for confining light are irrelevant,[21] our results will be valid for both types of light confinement. The simulated cavities contained up to 1000 rhodamines and 10 HBT molecules in spatially separate layers, as in previous experiments.[7] Both rhodamine and HBT layers were simultaneously coupled to the second confined light mode of the cavity with energy ħωc = 4.13 eV (Figure 1a). In these simulations, the excitation is initially delocalized over all molecules but rapidly localizes onto one of the HBT molecules These results, presented in the SI and summarized, suggest that the variations have little effect on the efficiency of the excitation energy-transfer process under strong coupling. The acceptor of the excitation energy undergoes proton transfer, photovoltaic applications would aim for electron transfer instead Via nanofabrication, such photo-oxidation reactions can be made to occur inside an optimal chemical environment, shielded from the other photoactive molecules, thereby preventing radiation damage or recombination.
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