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

ABSTRACT 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 cm 2 module achieving a high PCE of 17.63 %. Thus, this study provides an effective molecular design strategy toward highly efficient, stable, and scalable OSCs.