Streamlined One-Step Dimerization of Small-Molecule Acceptors for High-Performance Organic Solar Cells

Achieving both high power conversion efficiency (PCE) and long-term operational stability remains a formidable challenge for organic solar cells (OSCs). Dimeric small-molecule acceptors (DSMAs), constructed by linking small-molecule acceptor (SMA) subunits, have recently emerged as promising candidates. However, their conventional synthesis via Stille coupling necessitates multistep reactions, rendering large-scale, low-cost preparation impractical. Herein, we report a streamlined direct dimerization strategy that efficiently constructs core-linked DSMAs through the condensation of bromoacetyl groups with diamine subunits, obviating the need for expensive palladium catalysts and toxic organotin reagents. By systematically varying the linking units, we synthesized a series of DSMAs with precisely tunable optical and electronic properties, demonstrating the generality of the approach. Such a direct dimerization approach effectively resolves the long-standing trade-off between cost-effective synthesis and high photovoltaic performance. Consequently, the best-performing device delivers a record-high PCE of 20.15%, while maintaining outstanding photostability. Collectively, this work provides a versatile blueprint for the cost-effective synthesis of stable, high-performance DSMAs, effectively bridging the gap between molecular design and practical OSC scalability.