Synthesis of CoFe₂O₄/graphene composite as a novel counter electrode for high performance dye-sensitized solar cells

A novel nanocomposite of CoFe₂O₄ nanoparticles with graphene nanosheet (CoFe₂O₄/GN) is prepared as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). The size of CoFe₂O₄ nanoparticles is about 3 nm, and the influence of CoFe₂O₄ on the electrochemical properties of graphene is studied. The CoFe₂O₄ nanoparticles anchored on graphene nanosheets can serve as spacers to prevent graphene aggregations and thereby provide efficient diffusion pathways and more active surface area for electrolyte molecules. Also, the CoFe₂O₄ nanoparticles with substantial catalytic activity accelerate the reduction of triiodide. Meanwhile the graphene improves charge transfer during the catalytic process. Compared with CoFe₂O₄, graphene, and Pt electrodes, the CoFe₂O₄/GN electrode displays higher catalytic activity because of its minimal charge transfer resistance. The DSSCs fabricated with CoFe₂O₄/GN demonstrate an improved photoelectric conversion efficiency of 9.04% in comparison to Pt electrodes (6.54%). This study suggests that CoFe₂O₄/GN can replace expensive Pt electrodes for large-scale fabrication of low cost and high efficiency DSSCs.