Dimeric Acceptors Enable over 20% Efficiency Organic Solar Cells via Electron‐Deficiency Engineering of Quinoxaline Linkers

ABSTRACT

Dimeric acceptors attract intense interest in organic solar cells (OSCs) for their well‐defined structures and solution processability, yet the electronic role of the linking unit, particularly in electron‐deficient heteroarenes, remains largely unexplored. Here, we establish the quinoxaline skeleton as a versatile and tunable linking unit and accordingly have designed and synthesized three dimers, namely WD1, WD2, and WD4. By systematically changing the substituents with 4‐methoxyphenyl, methyl, and 4‐fluorophenyl groups on the quinoxaline‐based linkers, their optoelectronic properties can be precisely adjusted. Among the three quinoxaline‐based dimers, the most electron‐deficient variant WD4, which bears a 6,7‐difluoro‐2,3‐bis(4‐fluorophenyl)quinoxaline linking unit, exhibits superior optoelectronic properties. Consequently, the devices with PM6:WD4 as the active layer obtained a power conversion efficiency (PCE) of 17.95% with excellent stability, and the PM6:L8‐BO:WD4 ternary devices deliver an impressive PCE of 20.15%. This work demonstrates that fine‐tuning the electron delocalization of dimeric linking units represents a straightforward strategy to simultaneously boost efficiency and stability, offering a clear molecular design blueprint for next‐generation oligomeric acceptors.