A low-cost counter electrode of ITO glass coated with a graphene/Nafion® composite film for use in dye-sensitized solar cells

Carbon black (CB), multi-walled carbon nanotube (MWCNT), and graphene (GN) were examined as catalytic films on the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). GN exhibits the best performance among these materials for the corresponding cell. A composite film of GN/Nafion® was next used as the catalytic film on the CE of a DSSC. Nafion® is demonstrated to be an excellent dispersant for inhibiting the aggregation of GN. A solar-to-electricity conversion efficiency (η) of 8.19% was achieved for the DSSC sensitized by TBA(Ru[(4-carboxylic acid-4′-carboxylate-2,2′-bipyridine)(4,4′-bis(5-(hexylthio)-2,2′-bithien-5′-yl)-2,2′-bipyridine)(NCS)2]), i.e., CYC-B11 dye, which was synthesized by our group, after the optimization of the composition of GN/Nafion®, and an η of 8.89% was exhibited for the cell with a sputtered-Pt (s-Pt) film on its CE under the same conditions. The significance of the cell with the composite film of GN/Nafion® lies in the fact that the expensive Pt is avoided in this case, thereby the cost of the pertinent DSSC was greatly reduced, even though its η (8.19%) is slightly smaller than that of the cell with the s-Pt film (8.89%).