Two-Dimensional CoS Nanosheets Used for High-Performance Organic-Inorganic Hybrid Solar Cells

Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PE-DOT:PSS) is one of the most popular hole-transporting materials in organic-Si hybrid solar cells. However, the inferior sheet resistance and the low work function of the PEDOT:PSS layer hinder the power conversion efficiency (PCE) of the devices. Here, two-dimensional cobalt sulfide (CoS) nanosheets with a low sheet resistance and higher work function are blended into the PEDOT:PSS films in order to enhance the device performance. By tuning the morphology and concentration of CoS nanosheets in the PEDOT:PSS films, a lower recombination rate at the organic-inorganic interfaces and improved hole-transporting ability can be achieved simultaneously, yielding a PCE of 11.2% under simulated air mass 1.5 solar irradiation at 100 mW cm(-2). The scanning Kelvin probe microscopy, the ultraviolet photoelectron spectroscopy, four-probe sheet resistance measurement, and the transient electrical output characterization were used to study the origin of performance improvements in devices with CoS nanosheets blended in PEDOT:PSS films.