Nanostructured Electrodes Improve the Fill Factor of Organic Photovoltaics

In this study, we demonstrate that suboptical-wavelength nanostructured electrodes (NEs) improve fill factor (FF) in organic photovoltaic devices without compromising open-circuit voltage or short-circuit current. We attribute this improvement to efficient charge collection by the NEs, which reduce recombination in low-mobility organic semiconductors. NEs increase the FF of planar heterojunction devices with boron subphthalocyanine chloride (SubPc)/C₆₀ from 28% to 40%. Optical simulations and external quantum efficiency measurements show that improved charge collection, rather than light trapping, is the mechanism for device improvement. Our findings suggest that NEs can be optimized for a given material set to improve FF performance, which is important for improving organic photovoltaic power conversion efficiency.