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

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.