An atomistic description of donor-acceptor interfaces

Modeling charge generation and transport dynamics in organic semiconductors benefits greatly from an atomistic description of bulk-heterojunction microstructure. Using virtual site coarse-grained molecular dynamics, we are able to simulate the donor-acceptor interface of a PM6:Y6 blend. By comparing PM6:Y6 to other non-fullerene systems, we show that molecules with push-pull design have preferential moiety contacts at bulk-heterojunction interfaces, which are influenced by molecular design choices. Tracking close contacts between acceptor molecules, we also extract the connectivity of Y6 throughout the blend, which is higher compared with other systems. Differences in moiety contacts within different regions of the blend offer an explanation to the improved connectivity. Still, some clusters of Y6 molecules in the PM6-rich region are disconnected from the acceptor domains, which highlights an area for improvement in controlling the microstructure of donor-acceptor blends.