Trends in the electronic and geometric structure of non-fullerene based acceptors for organic solar cells

We constructed a database of 80 high performing non-fullerene electron acceptors and studied the common electronic and geometric properties in search of unifying design rules. We discovered that, without exception, all high performing materials are characterized by very low gap between LUMO and LUMO+1 orbitals, a feature that is consistent with microscopic models and seems to be true for all classes of compounds considered. We also confirmed that non-planarity of the acceptor is beneficial but not for all classes of acceptors. We suggested that by building similar databases and keeping it up to date it will be possible to identify statistically meaningful structure-property relations.