Dual Liquid Rubber Matrix Based Highly Efficient and Mechanically Robust Layer‐by‐Layer Organic Solar Cells

ABSTRACT Developing organic solar cells (OSCs) simultaneously possessing high efficiency and robust mechanical properties is one of crucial tasks to ensure their operational reliability and applicability for emerging wearable devices. However, enhancing their mechanical properties without compromising the electrical properties of high‐performance active materials remains a challenge. This work presents a method that overcomes this limitation by embedding a dual liquid rubber (DLR) matrix consisting of tetra‐fluorophenyl azide and penta‐fluorophenyl end‐capped polybutadienes, PFFA and PFF, into layer‐by‐layer (LBL) films, which enables by a finely controlled film morphology built on strong noncovalent interactions and azide cross‐linking chemistry. The resulting LBL film demonstrates a significantly improved stretchability and reduced stiffness of the active layer, with a crack initiation strain that is approximately eight times higher than that of pristine film. The potential of the DLR strategy is demonstrated in PM6:L8‐BO flexible solar cells with a power conversion efficiency of 17.7%, which is among the highest efficiencies for flexible OSCs to date. More importantly, the DLR strategy also enables significant bending durability of flexible LBL OSCs that retain 84.2% of their initial performance after 5000 bending cycles. This design concept offers a new strategy for achieving highly efficient and stretchable LBL OSCs.