ABSTRACT
Conical intersections (CoIns) of multidimensional potential energy surfaces are ubiquitous in nature and control pathways and yields of many photo-initiated intramolecular processes. Such topologies can be potentially involved in the energy transport in aggregated molecules or polymers but are yet to be uncovered. Here, using ultrafast two-dimensional electronic spectroscopy (2DES), we reveal the existence of intermolecular CoIns in molecular aggregates relevant for photovoltaics. Ultrafast, sub-10-fs 2DES tracks the coherent motion of a vibrational wave packet on an optically bright state and its abrupt transition into a dark state via a CoIn after only 40 fs. Non-adiabatic dynamics simulations identify an intermolecular CoIn as the source of these unusual dynamics. Our results indicate that intermolecular CoIns may effectively steer energy pathways in functional nanostructures for optoelectronics.
ABSTRACT
A new class of acceptor-substituted S,N-heteropentacenes is developed for vacuum-processed organic solar cells, providing encouraging power conversion efficiencies of up to 6.5%. Atomic force microscopy (AFM) investigations give a direct correlation between the blend film morphology and the photovoltaic parameters, such as short-circuit current density (JSC ) and fill factor (FF).
