The impact of linker on the photovoltaic performance of helical perylene diimide based non-fullerene acceptors

Linking two or more perylene diimide (PDI) directly together and/or with congested spacers at the N-position, alpha-or bay-region is a robust strategy for constructing high-performance non-fullerene acceptors (NFAs). On the other hand, ethylene fused PDI dimer (PDI2) has emerged as alternative building blocks to the parent PDI in con-structing NFAs owing to the built-in twisted configuration, outstanding optoelectronic properties, concise gram -scale synthesis and so forth in recent years. In line with the parent PDI, tailoring PDI2 by dimerization, trime-rization as well as by introduction of heteroatoms can also result in enhanced photovoltaic performance. However, to the best of our knowledge, most of the modifications occurred at the bay region of PDI2. In this contribution, two PDI2 dimers namely P2-P2, P2-C6-P2 are constructed by using hydrazine and 1,6-hexanedi-amine as linkers at imide positions. The photovoltaic performance of these two NFAs as well as the parent PDI2 were evaluated using commercially available PM6 as the electron donor. The two PDI2 dimers show superior photovoltaic performances compared with PDI2 and P2-C6-P2 gives the best power conversion efficiency (PCE) of 8.03% among these three NFAs. These results argue that modification at the imide groups is also a robust strategy for constructing high-performance PDI2-based NFAs and the choice of linkers plays a vital role in device performance.