Coupled chromophores can undergo photophysical processes that are unavailable to a monomer.  These processes include exciton fission and annihilation, both of which are relevant to advanced photovoltaics.  We have investigated the excited-state dynamics of carotenoids in a variety of assemblies.  The systems include (1) self-assembled aggregates of thousands of molecules, (2) small multimers of carotenoids, and (3) covalently-bound dimers.  Our probes of these systems include time-resolved absorption and resonance Raman spectroscopy, along with steady-state methods.  Yields of singlet fission have been found in the range of 50-200 percent.  Correlations between structure and the triplet yields are emerging from these studies.  Annihilation of excitons is often prompt, and reflects the triplet excited-state energy levels.  These findings for the carotenoid assemblies will be discussed in the context of solar energy conversion, as well as the complementary role of photoprotection in excess-light conditions.

Lessons from carotenoid assemblies for exciton fission, and their connection to solar energy conversion

246th National Meeting (2013)

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