Effect of the Push–Pull Electronic Structure of Nonfullerene Acceptor Molecules on the Interfacial Charge Dynamics in Heterojunction Organic Solar Cells

Nonfullerene acceptor (NFA) molecules have attracted significant attention in high-efficient heterojunction organic solar cells (OSCs) due to their push-pull electronic structures. Herein, using a universal quantum model for an organic donor/acceptor interface composed of a polymer donor and an NFA molecule, effect of the NFA molecular electron push and pull ability on the interfacial charge dynamics in the case of donor excitation is focused on. It is confirmed that energy and charge transfer coexist and compete during the interfacial charge dynamics, by which an interfacial hybrid state is created, and the quantitative correlations of the generation rates for different component states (e.g., donor exciton, acceptor exciton, and charge transfer state) with the NFA molecular electron push and pull ability are separately clarified. It is found that, by strengthening the NFA molecular electron push ability, competition between charge and energy transfer presents a nonmonotonous behavior; by strengthening the electron pull ability, charge transfer is always promoted and energy transfer is inhibited. This study provides a microscopic understanding for the interfacial charge dynamics modulated by tuning the NFA molecular push-pull electronic structure and thus sheds light on further improving the performance of heterojunction OSCs by rational designs of NFA molecules.