Molecular Design of Dimeric Acceptor Enables Binary Organic Solar Cells with 19.78% Efficiency and Enhanced Stability.

The development of organic solar cells (OSCs) with high efficiency and stability is highly desirable to facilitate its commercial applications. Although dimeric acceptors with distinctive advantages have been widely studied, high-performance binary OSCs based on such molecules have rarely been achieved. In this work, a new dimeric acceptor (DY-FL) is constructed by simultaneously optimizing the linking sites and units, as well as the building blocks. Thanks to the effective molecular design, DY-FL provides improved molecular stacking for fibrous morphology with favorable exciton/charge dynamics. Consequently, DY-FL-based binary OSCs render a superior power conversion efficiency (PCE) of 19.78%, representing a record-breaking efficiency for binary OSCs based on dimeric acceptors. Importantly, DY-FL-based devices display significantly enhanced operational stability under external stimuli such as light and heat, in comparison to their small molecule acceptor (Y-F)-based counterpart. These findings highlight the significance of building blocks and linking modes, providing insight into the effective molecular design strategy of dimeric acceptors for state-of-the-art OSCs.