Electrophoretic deposition of graphene nanosheets: A suitable method for fabrication of silver-graphene counter electrode for dye-sensitized solar cell

Abstract

Dye-sensitized solar cell (DSSC) was fabricated by a suitable counter electrode (CE) based on graphene nanosheets in order to facilitate electrochemical reduction of triiodide in organic medium. Graphene oxide (GO) nanosheets were deposited at fluorine doped tin oxide (FTO) glass substrate by electrophoretic deposition (EPD) technique as an easy short-time method. Then GO nanosheets were converted to electrochemically reduced graphene oxide (ERGO) nanosheets by chronoamperometery technique. Graphene nanosheet-based electrode was modified by silver nanoparticles and was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray elemental mapping (MAP) and atomic force microscopy (AFM) studies. Also, the electrochemical behaviors of as-prepared electrodes were investigated by cyclic voltammetry method where electrodes fabricated by graphene-silver nanohybride (Ag/ERGO/FTO) presented the highest current density and the lowest peak-to-peak separation in comparison to bare FTO, GO/FTO and ERGO/FTO electrodes in iodine electrolyte medium. Moreover, electrochemical impedance spectroscopy (EIS) was applied to investigate the electrocatalytic capability of the modified electrode both in I3−/I− electrolyte and as a symmetrical dummy cell which represented relatively lower charge transfer resistance. Finally, the fabricated DSSC containing Ag/ERGO/FTO CE represented suitable photovoltaic characteristic parameters (Voc=0.8V, jsc=29.04mAcm−2 and η=4.24%) under simulated light of AM1.5G (1000Wm−2) compared to Pt-based DSSC (Voc=0.66V, jsc=19.54mAcm−2 and η=6.08%). Furthermore, the high conductivity of the cells was evaluated by EIS during the applying different biases.