Adapting the Forster theory of energy transfer for modeling dynamics in aggregated molecular assemblies

The remarkable efficiencies of solar energy conversion attained by photosynthetic organisms derive partly from the designs of the light-harvesting apparatuses. The strategy employed by nature is to capture sunlight over a wide spectral and spatial cross section in chromophore arrays, then funnel the energy to a trap (reaction center). Nature's blueprint has inspired the conception of a diversity of artificial light-harvesting antenna systems for applications in solar energy conversion or photonics. Despite numerous, wide-ranging studies, truly quantitative predictions for such multichromophoric assemblies are scarce because Forster theory in its standard form often seems to fail. We report here a new framework within which energy transfer in molecular assemblies can be modeled quantitatively using a generalization of Forster's theory. Our results show that the principles involved in optimization of energy transfer in confined molecular assemblies are not revealed in a simple way by the absorption and emission spectra because such spectra are insensitive to length scales on the order of molecular dimensions.