Well-dispersed CoS nanoparticles on a functionalized graphene nanosheet surface: a counter electrode of dye-sensitized solar cells.

With a facile electrophoretic deposition and chemical bath process, CoS nanoparticles have been uniformly dispersed on the surface of the functionalized graphene nanosheets (FGNS). The composite was employed as a counter electrode of dye-sensitized solar cells (DSSCs), which yielded a power conversion efficiency of 5.54 %. It is found that this efficiency is higher than those of DSSCs based on the non-uniform CoS nanoparticles on FGNS (4.45 %) and built on the naked CoS nanoparticles (4.79 %). The achieved efficiency of our cost-effective DSSC is also comparable to that of noble metal Pt-based DSSC (5.90 %). Our studies have revealed that both the exceptional electrical conductivity of the FGNS and the excellent catalytic activity of the CoS nanoparticles improve the conversion efficiency of the uniformly FGNS-CoS composite counter electrode. The electrochemical impedance spectra, cyclic voltammetry, and Tafel polarization have evidenced the best catalytic activity and the fastest electron transport. Additionally, the dispersion condition of CoS nanoparticles on FGNS plays an important role for catalytic reduction of I3 (-) .