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

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 C₆₀ cage, this work prepares a novel C₆₀ terminated acceptor-donor-acceptor (A-D-A) type electron acceptor, C₆₀-L8BO-C₆₀. Compared with the traditional spherical fullerene PC₆₁BM, C₆₀-L8BO-C₆₀ 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 C₆₀-L8BO-C₆₀ 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:C₆₀-L8BO-C₆₀ based device. The university of C₆₀-L8BO-C₆₀ in enhancing the efficiency and stability is also verified in a range of polymer:non-fullerene systems, and delivering a significantly improved operational T₈₀ 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).