A Universal Hydrogen Bond Strategy Enable Highly Efficient, Mechanically Robust, and Thermally Stable Organic Solar Cells

Abstract Organic solar cells (OSCs) combining robust mechanical properties, high photovoltaic efficiency, and long‐term operational stability are crucial for their practical applications. Here, small molecule bisphenol A (BPA) is introduced into the D18:L8‐BO active film. The hydroxy groups of the BPA molecule are found form strong hydrogen bonds with the fluorine (F) atom in D18 as well as both F and carbonyl group in L8‐BO, reinforcing intermolecular interactions. This hydrogen bonding interaction enhances the intermolecular packing and aggregation of both donor and acceptor, promotes the phase separation, and optimizes film morphology. As a result, the power conversion efficiency (PCE) of the devices increases from 18.4% to 19.3%. Moreover, the BPA induced hydrogen bonding forms a 3D interpenetrating network that facilitates the stress energy dissipation during mechanical deformations, resulting in the improved stretchability from 6.5% to 21.3%. Besides, this compact hydrogen bond network inhibits the diffusion and crystallization of small molecule acceptors under thermal aging, thereby stabilizing the film morphology and improving device stability. The ubiquitous of the hydrogen bonding strategy is further validated by similar improvements in the PM6:Y6 blend system. The work highlights the important role of hydrogen bonding in concurrently enhancing the mechanical properties, photovoltaic performance, and morphology stability of OSCs.