Theory of Energy Transfer in Organic Nanocrystals

Abstract: Recent experiments have shown that highly efficient energy transfer can take place in organic nanocrystals at extremely low acceptor densities. This striking phenomenon has been ascribed to the formation of exciton polaritons thanks to the photon confinement provided by the crystal itself. We propose an alternative theoretical model that accurately reproduces fluorescence lifetime and spectrum measurements in these systems without such an assumption. Our approach treats molecule-photon interactions in the weak-coupling regime, and describes the donor and acceptor population dynamics by means of rate equations with parameters extracted from electromagnetic simulations. The physical insight and predictive value of our model also enables us to propose nanocrystal configurations in which acceptor emission dominates the fluorescence spectrum at densities orders of magnitude lower than the experimental ones.