Reduced V OC Losses Through Fullerene‐Doping in the Roll‐to‐Roll Printed Organic Solar Cells

ABSTRACT Large‐area printed organic solar cells (OSCs) are promising in various applications but often suffer from open‐circuit voltage ( V OC ) losses and relatively poor device performance compared to spin‐coated devices. This work demonstrates that PC 61 BM addition can effectively solve this problem. This reveals that PC 61 BM doping enhances the crystallinity of printed films and reduces the phase purity in the blend, ultimately resulting in a reduction in V OC losses. As a result, the device performance shows a significant improvement in the gravure printed device, while for the spin‐coated device, PC 61 BM doping has little impact. Moreover, this strategy exhibits good universality in different photoactive systems, including PM6:BTP‐eC9, PM6:BTP‐BO‐4Cl, and PM6:L8‐BO. With this strategy, the 1 cm 2 device and 21.6 cm 2 flexible module give an efficiency of 13.74% and 13.21%, respectively.