Vacuum‐Deposited Organic Solar Cells with over 10% Efficiency and Device Lifetime over 2 Years Enabled by Fluorinated Donor

Abstract The simultaneous improvement of efficiency and stability of small‐molecule organic solar cells (SMOSCs) for commercialization remains a challenging task. Herein, two novel donor–acceptor–acceptor (D–A–A)‐configured small‐molecule donors, DTDCPB‐F and DTDCPB‐Cl, with F‐substituted and Cl‐substituted 2,1,3‐benzothiadiazole as the central A group, are synthesized and characterized. The influences of fluorination and chlorination on the optoelectronic properties, molecular packing, and photovoltaic performance are systematically investigated. The fluorinated DTDCPB‐F exhibits stronger and broader optical absorption as well as stronger intermolecular interactions and more compact packing, compared to its chlorinated analog DTDCPB‐Cl. Consequently, vacuum‐deposited SMOSCs based on DTDCPB‐F: C 70 show a remarkable power conversion efficiency (PCE) of 10.43%, surpassing that of the DTDCPB‐Cl: C 70 (8.03%). Notably, the PCE of 10.43% for DTDCPB‐F: C 70 based device is the record efficiency for single‐junction vacuum‐deposited SMOSCs. Furthermore, DTDCPB‐F: C 70 devices demonstrate outstanding stability in terms of storage, light‐soaking, and thermal stability. In particular, the DTDCPB‐F: C 70 based device maintains 92% of its initial PCE over 2 years (800 days) of storage in a nitrogen‐filled glove box. These results demonstrate that fluorination is an effective approach to construct small‐molecule donors for achieving highly efficient and stable vacuum‐deposited SMOSCs.