Earth Abundant Silicon Composites as the Electrocatalytic Counter Electrodes for Dye-Sensitized Solar Cells

Earth abundant silicon compounds, including Si3N4, SiO2, SiS2, and SiSe2, were introduced as the electrocatalytic materials for the counter electrodes (CE) in dye-sensitized solar cells (DSSCs). Among these silicon-based materials, Si3N4, SiS2, and SiSe2 were applied in DSSCs for the first time. In the presence of a conducting binder, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT: PSS), various silicon-based composites (Si3N4/PEDOT:PSS, SiO2/PEDOT:PSS, SiS2/PEDOT:PSS, and SiSe2/PEDOT:PSS) were successfully coated on the ITO substrates via a simple drop-coating process. In a composite film, silicon-based nanoparticles provided attractive electrocatalytic ability and plenty of electrocatalytic active sites for the triiodine ion (I3(-)) reduction. PEDOT: PSS not only acted as a good conducting binder for silicon-based nanoparticles, but also provided a continuous polymer matrix to increase the electron transfer pathways. By adjusting the weight percent (1-5 wt %) of the silicon-based nanoparticles (Si3N4, SiO2, SiS2, and SiSe2) with respect to the weight of PEDOT: PSS, the composite films containing 5 wt % Si3N4 (denoted as Si3N4-5) and 5 wt % SiSe2 (denoted as SiSe2-5) both reached excellent electrocatalytic abilities and rendered the good cell efficiencies (η) of 8.2% to their DSSCs. It can be said that both Si3N4-5 and SiSe2-5 are promising electrocatalytic materials to replace the rare and expensive Pt (η = 8.5%).