Dynamic Disulfide-Linked Dimeric Acceptors for High-Efficiency and Mechanically Robust Organic Solar Cells

The practical application of organic solar cells (OSCs) in wearable electronics requires simultaneous improvements in efficiency, stability, and mechanical robustness. In this study, we developed a disulfide-linked dimeric acceptor, DY-SS, by integrating an exchangeable dynamic covalent linkage into the backbone of a photoactive acceptor, representing, to our knowledge, the first photoactive material framework containing exchangeable dynamic covalent linkages. DY-SS acts as an energetic and morphological regulator, reducing non-radiative energy loss, modulating crystallization kinetics, and enhancing molecular packing coherence. Consequently, the ternary devices achieve a high PCE of 20.40%, compared with 19.64% for the binary control, accompanied by a 1.62-fold extension of the T₈₀ thermal lifetime. In the presence of trace thioctic acid, thermally activated disulfide exchange enables the formation of an adaptive covalent network, which promotes stress dissipation and markedly improves film toughness and yielding a markedly increased crack-onset strain of 16.07% (3.89-fold over the binary control) and a 7.54-fold enhancement in toughness. Notably, the toughened flexible OSCs demonstrate unprecedented mechanical durability, retaining 91.1% of their initial efficiency even after 10⁵ bending cycles under the extreme condition of a 1 mm bending radius (vs. 82.1% for the control). This work provides a dynamic-bond-containing molecular design strategy for efficient and mechanically robust OSCs.