Exciton bandwidths and exciton transport are difficult to control by material
design. We showcase the intriguing excitonic properties in an organic semi-
conductor material with specifically tailored functional groups, in which
extremely broad exciton bands in the near-infrared-visible part of the elec-
tromagnetic spectrum are observed by electron energy loss spectroscopy and
theoretically explained by a close contact between tightly packing molecules
and by their strong interactions. This is induced by the donor–acceptor type
molecular structure and its resulting crystal packing, which induces a
remarkable anisotropy that should lead to a strongly directed transport of
excitons. The observations and detailed understanding of the results yield
blueprints for the design of molecular structures in which similar molecular
features might be used to further explore the tunability of excitonic bands and
pave a way for organic materials with strongly enhanced transport and built-in
control of the propagation direction.