Journal article

Functionalized Graphene Sheets as a Versatile Replacement for Platinum in Dye-Sensitized Solar Cells

Several techniques for fabricating functionalized graphene sheet (FGS) electrodes were tested for catalytic performance in dye-sensitized solar cells. By using ethylcellulose as a sacrificial binder, and partially thermolyzing it, we were able to prep. electrodes which exhibited lower effective charge transfer resistance (<1 Ω·cm2) than the thermally decompd. chloroplatinic acid electrodes traditionally used. This performance was achieved not only for the triiodide/iodide redox couple, but also for the two other major redox mediators used in dye-sensitized solar cells, based on cobalt and sulfur complexes, showing the versatility of the electrode. Dye-sensitized solar cells using these functionalized graphene sheet electrodes had efficiencies (η) equal to or higher than those using thermally decompd. chloroplatinic acid electrodes in each of the three major redox mediators: I (ηFGS = 6.8%, ηPt = 6.8%), Co (4.5%, 4.4%), S (3.5%, 2.0%). Through an anal. of the thermolysis of the binder and composite material, we detd. that the high surface area of an electrode, as detd. by nitrogen adsorption, is consistent with but not sufficient for high performing electrodes. Two other important considerations are that (a) enough residue remains in the composite to maintain structural stability and prevent restacking of functionalized graphene sheets upon the introduction of the solvent, and (b) this residue must not disperse in the electrolyte.


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