Characterization of graphene-oxide-based composite structures as counter electrodes for dye-sensitized solar cells

Graphene oxide (GO) was synthesized by using a "top-down" approach with the Hummers method; 2-dimensional (2-D) GO sheets were obtained starting from bulk graphite. The GO sheets were cut into nanoparticles by using ultrasonic dispersion in deionized water. The GO nanoparticle solution was deposited on fluorine-doped tin-oxide glass by using electrophoretic deposition (EPD). We applied the deposition current and voltage by using the results of cyclic voltammetry. The EPD process was monitored during the deposition times by using real-time chronoamperometery. The deposited GO films showed over 80% transmittance at 550 nm in spite of the composite structure consisting of porous particles and 2-D sheets. We prepared GO-based composite structures as counter electrodes for dye-sensitized solar cells. From the results of the electrochemical impedance spectroscopy, the electron transfer in the composite counter electrode was better than that of the graphite or the platinum. Also, the energy conversion efficiency was enhanced to 6.02% by using the suggested GO counter electrodes.