Amide-Based Cathode Interfacial Layer with Dual-Modification Mechanisms Enables Stable Organic Solar Cells with High Efficiency Achieving 20%

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The cathode interfacial layers (CILs) play a critical role in the performance and long-term stability of the organic solar cells (OSCs). While amine-based CILs have been successful in reducing the work function of metal electrodes, they can also promote the decomposition of acceptor materials, compromising the stability of OSCs. To address this challenge and further improve device performance, we have innovatively designed and synthesized amide-functionalized perylene diimide (PDI)-Leu-am as a dopant-free CIL molecule. Notably, PDI-Leu-am effectively mitigates acceptor decomposition, significantly improving the photostability and thermal stability of OSCs. Moreover, it demonstrates dual-modification capabilities at the active layer/cathode interface, facilitating electron extraction from the active layer while lowering the electrode's work function. Encouragingly, this dual modification mechanism effectively refined the Ohmic contact, leading to a remarkable power conversion efficiency (PCE) up to 20%. This breakthrough opens up promising avenues for the practical deployment of OSCs and lays a robust foundation for the development of high-performance, enduring, and cost-efficient interface materials.