Hyperbranched small-molecule electrolyte as cathode interfacial layers for improving the efficiency of organic photovoltaics

Small-molecule electrolytes (SMEs) have attracted increasing interests owing to their intrinsic advantages, such as high repeatability, easy purification and well-defined structures. Interfacial engineering plays crucial roles in enhancing the power conversion efficiency (PCE) of polymer solar cells (PSCs). Through a green route one-step reaction with nonhalogen solvent, we reported the design and synthesis of one novel hyperbranched SME PNSO₃Na as cathode interfacial layer (CIL). Owing to containing seven moles butyl sulfonate sodium, hyperbranched SMEs PNSO₃Na CIL can form interfacial dipoles, tune the interfacial energy alignment, realize environment-friendly water/alcohol processing, induce the upper active layer to form order morphology and enhance the PCE of PSCs. Based on P3HT–PC₆₁BM active layer, the PCE of the device based on PNSO₃Na CIL was dramatically enhanced from 0.8 to 3.7% compared to the bare ITO device.