Hydrogen Bond-Enabled Carbon Dot-Based Network for Efficient Inverted Organic Solar Cells with Prolonged Photoelectrical-Mechanical-Moist Stability

Achieving long operational stability is critical for advancing high-performance organic solar cells (OSCs) towards commercialization. Designing a charge transport layer with optimal electrical-physical-chemical compatibility is a pivotal strategy. Herein, we demonstrate an electron transport layer (ETL) by incorporating in-situ fluorinated carbon dots (FCDs) in a coherent polymer to construct the crystallinity-enhanced FCD network (netFCD) via strong hydrogen bonding. Uniquely, netFCD-based ETLs offer very strong electrical and mechanical contact with their all-sided (cathode and active layer) interfaces. The reduced basicity feature of netFCD prevents unexpected interfacial reactions with non-fullerene acceptors. Meanwhile, netFCD-based ETLs enable barrier-free devices with high electron mobility and hole blocking. Using the strategically designed netFCD with the interesting features as “all-in-one” ETL, the inverted OSCs (i-OSCs) achieve 20.01% PCE (Certified PCE: 19.78%). The OSCs maintained 85% of their initial PCE after 1800 hours of operation under 80 ± 5% humidity while the flexible i-OSCs realized 95% of the initial PCEs after 10,000 bending cycles, advancing the operational (i.e., photoelectrical), mechanical, and environmental stability in OSCs with different structures. This work contributes to developing not only feasible bulk-to-interface interlayer designs but also green and low-cost materials to promote OSCs as sustainable and green energy sources. Long-lasting organic solar cells require transport layers stable in electrical, mechanical and chemical aspects. Cui et al. fabricated a fluorinated carbon dot/polymer electron transport layer, which delivers high efficiency together with excellent humidity and bending stability.