C60‐Terminated Acceptor Boosts Efficiency and Stability in Organic Solar Cells via Interfacial Manipulation

ABSTRACT With the rapid development of the A‐D‐A type non‐fullerene electron acceptors (NFAs), organic solar cells (OSCs) have exhibited remarkable progress in the last decade, with power conversion efficiency (PCE) reaching 21%. However, compared with the traditional inorganic Si photovoltaics, OSCs still show inferior PCE and operational stability, hindering its commercialization. By substituting the indanone structured end groups of cutting‐edge NFA L8‐BO with C 60 cage, this work prepares a novel C 60 terminated acceptor–donor–acceptor (A–D–A) type electron acceptor, C 60 ‐L8BO‐C 60 . Compared with the traditional spherical fullerene PC 61 BM, C 60 ‐L8BO‐C 60 exhibits significantly improved miscibility with both polymer donors and NFAs, enabling it to tune the donor/acceptor interfacial interactions and suppress their phase separation under device operation. As the results, by incorporating 5% of C 60 ‐L8BO‐C 60 as a guest component, increased exciton dissociation efficiency with suppressed carrier recombination is received, leading to a maximum efficiency of 20.6% (certified PCE of 20.25%) in a D18:L8‐BO:C 60 ‐L8BO‐C 60 based device. The university of C 60 ‐L8BO‐C 60 in enhancing the efficiency and stability is also verified in a range of polymer:non‐fullerene systems, and delivering a significantly improved operational T 80 lifetime of 200% (270 to 815 h) under a standardized ISOS‐L‐3 harsh stability measurement (65 ± 5°C, 65 ± 10% RH, one‐sun illumination).