Dimeric Acceptors Featuring an Electron-Rich Fused-Ring Linker Enable High-Efficiency and Stable Organic Solar Cells...

Organic solar cells (OSCs) are a promising renewable energy technology; however, balancing the power conversion efficiency (PCE) with long-term stability remains challenging. Herein, we report two novel dimerized small-molecule acceptors (DSMAs), GSNS-EH and GSNS-C8, that feature electron-rich planar pyrrolodithiophene bridges with tailored side chains. The optimized acceptor, GSNS-EH, with a branched 2-ethylhexyl chain, exhibited enhanced crystallinity and molecular ordering, reduced non-radiative losses, and improved blend morphology when incorporated into the PM6:BTP-eC9 host system as a third component. The resulting ternary OSC exhibited a PCE of 20.26 %, which is among the highest values reported for DSMA-based ternary devices. Moreover, the GSNS-EH-based cell exhibited exceptional operational stability, maintaining 86.7 % of its initial PCE after 1430 h of maximum power point tracking under high humidity (85 % ± 10 %) and 97.2 % after 1460 h at 85°C. The excellent scalability of this approach is demonstrated by a 15.6 cm² module achieving a high PCE of 17.63 %. Thus, this study provides an effective molecular design strategy toward highly efficient, stable, and scalable OSCs.