Impact of Linking‐Site on Photovoltaic Performance of Giant Molecular Acceptors Containing N‐Type Linker

Abstract Connecting small molecule acceptors through conjugated or nonconjugated linker to form giant molecular acceptors (GMAs) represents a strategic approach to enhancing the morphological stability of organic solar cells (OSCs). In this study, we employed benzothiadiazole (BT) as a typical n ‐type linker to design and synthesize two GMAs through linking‐site isomerization: i‐BT‐DY and o‐BT‐DY. Compared to i‐BT‐DY, o‐BT‐DY exhibits enhanced crystallinity and a more favorable face‐on orientation but lower electron mobility. This can be well explained by theoretical calculations, as i‐BT‐DY demonstrates a delocalized LUMO distribution and significantly stronger intramolecular super‐exchange coupling (43.7 meV versus 22.2 meV for o‐BT‐DY). Additionally, i‐BT‐DY also exhibits a stronger and red‐shifted absorption. Combining these attributes, the PM6: i‐BT‐DY blend achieved an impressive power conversion efficiency (PCE) of 18.86%. The PCE can be further increased to 19.49% in ternary blend. As expected, OSCs based on both i‐BT‐DY and o‐BT‐DY exhibit exceptional long‐term photostability (T85% >1000 hours). This work deepens our understanding of how n ‐type linkers at different linking sites influence the performance of GMAs, concluding that intramolecular interaction, rather than intermolecular, are the primary factor affecting charge transport in these acceptors. Additionally, it also highlights the potential of n ‐type linker GMAs as ternary components for OSCs.