Self-assembled composite thin film counter electrode of cobalt sulfide/functionalized graphene for dye-sensitized solar cells

Cobalt sulfide/functionalized graphene (CFG) composite thin film counter electrode has been obtained via a self-assembly method based on the electrostatic interactions between ion and graphene with charge. Consequently, without the aid of rigorous equipments and polyelectrolytes, the functionalized grapheme with opposite charge can be directly assembled to form graphene thin films in an aqueous environment, then the cobalt cation and sulfur anion adsorb on the graphene film to form cobalt sulfide nanoparticle. Due to the good dispersion of CoS nanoparticle, which is facilitated by functional groups on graphene, the DSSC with CFG electrode generates comparable power conversion efficiency (5.37%) to that of the Pt electrode (5.68%).