Enhancing the Intrinsic Stability of Nonfullerene Acceptors through Dimerization via Ring-locking Strategy†

The power conversion efficiencies (PCEs) of non-fullerene acceptor (NFA)-based organic solar cells (OSCs) have undergone an exciting development in recent years, but the poor intrinsic stability of exocyclic ethylene bridges in NFAs poses a significant challenge to their commercialization. In this work, we propose a new pyran-locking strategy that can stabilize the exocyclic ethylene bridge connecting the strong electron-deficient 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile end group, based on which two dimerized NFAs (ITBIC-F and TBTBIC-F) with an A-D-π-A-π-D-A structure have been successfully synthesized with significantly improved chemical and photochemical stabilities in comparison with traditional NFAs without the ring-locked structure. The ITBIC-F and TBTBIC-F -based OSCs not only achieve promising PCEs of 13.03% and 10.01%, respectively, but also show good device stability; the ITBIC-F-based unencapsulated devices can retain 75% and 62% of their initial PCEs, respectively, under continuous heat (85 °C) and light irradiation (LED, 100 mW·cm^–2) in a nitrogen atmosphere.