Repackaging energy through downconversion (1 to 2) and/or upconversion (2 to 1) can boost solar energy conversion efficiencies by 30% or more.  In organic semiconductors, the Frenkel character of the excitons leads to separate singlet and triplet bands, providing an ideal set of energy levels for both processes.  Singlet exciton fission produces a spin-entangled triplet pair that undergoes complicated dynamics after the fission event, including decoherence, spin relaxation, diffusion, and eventually energy release.  Monte Carlo modeling of triplet diffusion and recombination shows that simple kinetic models fail to capture the complexity of these dynamics, especially at early times.  Nonequilibrium spin state distributions can play an important role in both the ultimate triplet yield and the observation of experimental quantities like delayed fluorescence.  We describe experimental efforts to enhance diffusion by measuring triplet dynamics in organic melts.  We will also describe efforts to transform triplet excitons produced by singlet fission into other forms using energy transfer to inorganic semiconductors like silicon and heterogeneous approaches to enhance spin-orbit coupling and couple the triplet energy out as photons. <br/>

What happens to triplet excitons after singlet fission?

253rd National Meeting (2017)

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