Efficiency‐Enhanced Scalable Organic Photovoltaics Using Roll‐to‐Roll Nanoimprint Lithography

Abstract Light‐trapping nanostructures have for decades been researched as a route to enhance the performance of organic solar cells (OSCs). Whereas the power conversion efficiencies (PCEs) of OSCs have reached above 18 %, industrially compatible devices made by scalable processing in air, using only nontoxic solvents and materials, have shown significantly lower performance values. Although light‐trapping nanostructures may improve this, the methods for integrating the nanostructures are typically not compatible with industrial scale up. In this work, scalable, industrially compatible, nonfullerene‐based OSCs are developed with integrated light‐trapping nanostructures at the back electrodes in the devices. The OSCs are made by using scalable roll‐to‐roll (R2R) and sheet‐to‐sheet (S2S) processes and the nanostructures are made by using roll‐to‐plate (R2P) nanoimprint lithography. A fully scalable solution is thereby developed for industrially compatible nanostructured OSCs. The nanostructured devices show enhancements in PCE up to 25 % compared to reference cells, owing to an enhancement in the short‐circuit current density (15 %) by enhanced absorption, and improved charge carrier extraction leading to an enhancement in the fill factor (7 %). Optical modeling is utilized to verify the optical effect of the nanostructures. The best devices attain a PCE of 6.5 %, which is the highest reported efficiency for air‐processed slot‐die coated ITO‐free flexible PBDB‐T : ITIC devices, here using nontoxic solvents.