Mechanically robust and air-processed all-polymer solar cells enabled by siloxane-modified monothiophene

초록

The practical deployment of organic solar cells (OSCs) is hindered by their humidity-sensitive processing and poor mechanical durability. Here, a siloxane-modified monothiophene (Br-Th-SiO) additive is developed to simultaneously tackle the both challenges in OSCs without polymer structural modification. Br-Th-SiO preferentially localizes in side-chain-rich regions, forming a siloxane-mediated entanglement network that stabilizes morphology evolution under humid conditions while effectively dissipating mechanical stress, yielding a continuous and resilient fibrillar network. Consequently, green solvent processed polymer PM6:PY-IT-based OSCs retain high power conversion efficiencies (PCEs) of 19.16% and 18.72% when processed in nitrogen glovebox and air with 90% relative humidity, respectively, with an outstanding open-circuit voltage (V-OC) of 0.94 V. Remarkably, the additive enhances mechanical robustness, increasing the crack-onset strain from similar to 10% to similar to 20%. Flexible devices retain > 96% of their initial PCE after 1000 bending cycles, while intrinsically stretchable devices maintain similar to 90% of the initial PCE after 400 stretching cycles at 20% strain. This work provides a practical and scalable additive strategy toward air-processable and mechanically durable organic photovoltaics for flexible and wearable applications.

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