Synergetic Strategy for Highly Efficient and Super Flexible Thick‐film Organic Solar Cells

Efficient organic solar cells (OSCs) equipped with thick-film active layers and high flexibility are of great significance for industrial preparation and practical applications. Herein, a ternary strategy coupled with a functional additive is employed to obtain efficient thick-film flexible OSCs. A novel polymer donor PBB1-F with good planarity is synthesized as a third component to optimize photon capture and molecular stacking. Meanwhile, a high dielectric constant polyarene ether (PAE) functional additive with strong adhesion not only greatly improves exciton dissociation efficiency, but also acts as locking cage-like for effective enhancement of the mechanical stability of active layer. As a result, the PM6:PBB1-F:Y6-BO-4Cl and PM6:PBB1-F:BTP-eC9 based ternary OSCs with PAE exhibit an efficiency of 17.91% and 18.51% under rigid thin-film state, and perform better under thick-film state of rigid (16.40% and 16.84%) and flexible (14.78% and 14.95%). Under the protection of the polymers, tight entanglement and cage-like PAE adhesion, the elongation at break of the active layer increases by more than fourfold (27.3%), and gives a super flexible thick-film OSCs that maintains more than 90% performance after 1000 bending cycles with a diameter of 10 mm. Overall, this work provides a new feasible scheme to effectively solve thickness sensitivity and flexibility issues in the context organic photovoltaic applications.