Polymerized Small‐Molecule Acceptor as an Interface Modulator to Increase the Performance of All‐Small‐Molecule Solar Cells

Abstract Modulating the morphology of all‐small‐molecule organic solar cells (ASM‐OSCs) has proved to be a considerable challenge in the context of efficient exciton dissociation and charge transport. Regulating the morphology of ASM‐OSCs is a great challenge due to the low viscosity of the small molecules, which tend to form large domain sizes and loose molecular packing, especially in the interfacial region. Here, a polymerized small‐molecule acceptor (PJ1) is introduced as an interface modulator to strengthen the interfacial molecular interactions in a high‐efficiency system, consisting of a novel small molecule donor (ZR‐TT) and a widely used acceptor (Y6). Optimized ASM‐OSCs exhibit a power conversion efficiency (PCE) of 14.33% without any additives. A small amount of PJ1 effectively condenses the morphology, enhances the crystallinity of the blend, and decreases the domain sizes. Upon 3% PJ1 addition in the blends, the accelerated hole transfer and the enhanced charge transport ultimately lead to an increased PCE of 15.54% with improved short circuit current and fill factor. Notably, the generality of this interfacial modulator strategy is proved by using PJ1 in three other ASM‐OSCs and using another polymerized host acceptor, PYT‐F‐o.