  Transport phenomena in organic, self-assembled molecular J-aggregates have
long attracted a great deal of attention due to its potential role in designing
novel organic photovoltaic devices. A large number of theoretical and
experimental studies have been carried out describing excitonic energy transfer
in J-aggregates under the assumption that excitons are induced by a coherent
laser-light source or initialized by a localized excitation on a particular
chromophore. However, these assumptions may not provide an accurate description
to assess the efficiency of J-aggregates, particularly as building blocks of
organic solar cells. In natural conditions, J-aggregates would be subjected to
an incoherent source of light (as is sunlight), which would illuminate the
whole photosynthetic complex rather than a single molecule. In this work, we
present the first study of the efficiency of photosynthetic energy transport in
self-assembled molecular aggregates under incoherent sunlight illumination. By
making use of a minimalistic model of a cyanine dye J-aggregate, we demonstrate
that long-range transport efficiency is enhanced when exciting the aggregate
with incoherent light. Our results thus support the conclusion that
J-aggregates are indeed excellent candidates for devices where efficient
long-range incoherently-induced exciton transport is desired, such as in highly
efficient organic solar cells.
