Long‐Lived Charge‐Transfer State and Interfacial Lock in Double‐Cable Conjugated Polymers Enable Efficient and Stable Organic Solar Cells

Abstract The donor/acceptor (D/A) interfaces in bulk heterojunction (BHJ) organic solar cells (OSCs) critically govern exciton dissociation and molecular diffusion, determining both efficiency and stability. Herein, we design a double‐cable conjugated polymer, SC‐1F, to insert into a physically‐blended D/A system to optimize the interface. We have found that SC‐1F spontaneously segregates to the interface through favorable miscibility and heterogeneous nucleation with the acceptor. Its long‐lived charge‐transfer (CT) state with a lifetime of >3 ns enhances charge generation efficiency in the PM6:BTP‐eC9 blend, boosting the power conversion efficiency (PCE) from 19.00% to 20.12%. More importantly, the double‐cable nature of SC‐1F enables it to be simultaneously miscible with donor and acceptor so as to act as the interfacial lock to prevent their self‐aggregation under thermal treatment. Therefore, the PM6:BTP‐eC9:SC‐1F‐based solar cells provided a high T 80 of 2175 h compared to a T 80 of 530 h based on PM6:BTP‐eC9 under 65 °C treatment. Notably, SC‐1F‐based device demonstrates exceptional storage and thermal stability, with a T 80 lifetime exceeding 10 000 h. These results demonstrate the superior advantage of double‐cable conjugated polymers as the third component to achieve efficient and stable OSCs.