A chlorinated thiophene flexible-bridged dimeric acceptor for stable organic solar cells with 19.6% efficiency

Abstract

Organic solar cells (OSCs) have garnered significant attention as next-generation green energy technologies due to their flexibility, lightweight, and solution-processable fabrication. Despite recent breakthroughs achieving power conversion efficiencies (PCEs) exceeding 20%, the long-term stability of OSCs limits their applicability and commercial viability. Inspired by the efficient and stable dimeric acceptors of the CH8 series, we designed a novel dimeric acceptor (CH8-10) by incorporating the 1,6-bis(3-chlorothiophen-2-yl)hexane linker between acceptor units. Owing to efficient charge carrier transport and charge collection, PM6:CH8-10-based binary devices achieve a remarkable PCE of 18.8%. Further incorporation of the small-molecule acceptor L8-BO-X as a third component optimized morphology and charge transport, boosting the PCE to 19.6%. The devices also exhibited exceptional thermal stability, retaining approximately 94% of their initial PCE after 1000 hours at 65 °C. Leveraging the flexible molecular design, we fabricated flexible OSCs (FOSCs) that delivered a champion PCE of 17.0% along with outstanding mechanical flexibility (retaining 90% of their initial PCE even after 1000 bending cycles). This work demonstrates a feasible strategy for designing dimeric acceptors that simultaneously achieve high efficiency, thermal stability, and mechanical flexibility, advancing the development of commercially green energy systems.