Oligo(ethylene Glycol)-Incorporated NDI-Based Polymers for Aqueous-Processable Electron Transporting Layers in Organic Solar Cells
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초록
내용
In this work, two naphthalene diimide (NDI)-based n-type polymers, P(NDIDEG-T) and P(NDITEG-T), incorporated with different lengths of oligoethylene glycol (OEG) side chains are used as electron transporting layers (ETLs). By depositing the OEG-attached ETLs on PM6:Y6 with eco-friendly water-ethanol co-solvents, a maximum power conversion efficiency (PCE) of 15.20% was achieved, which is higher than that of the conventional PFN ETL (PCE= 14.12%). In addition, the ETLs show much superior thickness-insensitive features compared to PFN, exhibiting PCEs of ~11% at 50 nm. Furthermore, while the devices based on the OEG-based ETLs present good storage stability maintaining more than 80% of the initial PCEs after 200 h, the PFN counterparts retain only 40% of the initial value during the same timeframe. Our study suggests that the utilization of nonionic OEG side chains can be an effective strategy to design eco-friendly and stable ETLs having good charge extraction/transport properties.