Bending-stability Interfacial Layer as Dual Electron Transport Layer for Flexible Organic Photovoltaics

The flexibility of organic photovoltaics(OPVs)has attracted worldwide attention in recent years.To realize the bending-stability of OPVs,it is necessary to put forward the bending-stability of interfacial layer.A novel bendable composite is explored and successfully applied as an electron transport layer(ETL)for fully-flexible OPVs.We incorporated poly(vinylpyrrolidone)(PVP)into conjugated electrolytes(CPE)to composite a bendable ETL for high-performance OPVs devices.Fortunately,the devices based on PVP-modified CPE exhibited better device performances and more excellent mechanical properties of bendability.The fullerene-free OPVs based on PM6:IT-4 F with CPE@PVP as ETLs yield the best power conversion efficiency(PCE)of 13.42%.Moreover,a satisfying efficiency of 12.59%has been obtained for the fully-flexible OPVs.As far as we know,this is one of the highest PCE for fully-flexible OPV based PM6:IT-4 F system.More importantly,the flexible OPVs devices can retain more than 80%of its initial efficiency after 5000 bending cycles.Furthermore,among various curvature radii,the mechanical properties of the device based on CPE@PVP are superior to those of the device based on bare CPE as ETL.These findings indicate that the functional flexibility of CPE as a cathode interfacial layer is an effective strategy to fabricate high-performance flexible devices in the near future.