Multithiophene-based fused-ring electron acceptors (MFREAs) have demonstrated remarkable performance not only in organic solar cells

but also in other optoelectronic devices owing to their extended near-infrared absorption. However

an insufficient electrostatic potential (ESP) difference with the donor results in a weak intermolecular electric field (IEF)

which leads to low exciton dissociation efficiency. In addition

the narrow bandgap causes substantial energy loss (Eloss)

thereby restricting the open-circuit voltage. To address these problems

we developed two novel MFREAs

6TFIC-C11-4F and 6TFIC-C11-4Cl

which were developed from the typical molecule 6TIC-4F via central-core side-chain fluorination and terminal chlorination. Although core fluorination slightly attenuated the intramolecular charge transfer (ICT) effect

this strategy significantly increased the overall average ESP value

strengthening the donor-acceptor IEF

thereby facilitating exciton dissociation. Terminal chlorination enhanced the ICT effect

resulting in a red-shifted absorption spectrum and stronger IEF. Notably

6TFIC-C11-4F exhibited increased intermolecular interactions and reduced π–π stacking distances

leading to better charge transport. As a result

the PM6:6TFIC-C11-4F device achieved a decent power conversion efficiency of 13.32%

significantly outperforming the PM6:6TIC-4F device (10.52%). In addition

the PM6:6TFIC-C11-4Cl device demonstrated reduced Eloss and a higher short-circuit current density

validating the potential of central-core side-chain fluorination and terminal chlorination in designing high-performance MFREAs.