Layer-by-Layer Electrodeposited Reduced Graphene Oxide-Copper Nanopolyhedra Films as Efficient Platinum-Free Counter Electrodes in High Efficiency Dye-Sensitized Solar Cells

Abstract

Efficient and low-cost platinum-free counter electrodes consisting of reduced graphene oxide (rGO) and copper nanopolyhedra (Cu) were fabricated on indium tin oxide (ITO) glass using a layer-by-layer electrochemical deposition. The structure and morphology of the as-fabricated counter electrodes were confirmed by X-ray diffraction, field-emission electron microscopy, and Raman spectroscopy. rGO-Cu-modified ITO electrodes, with different rGO loadings, were applied as catalytic counter electrodes in dye-sensitized solar cells (DSSCs) with an electrodeposited ZnO nanorod array as the photoanode. The current density−voltage curves and transient photocurrent measurements illustrate that the power conversion efficiency of the ZnO nanorod photoanode is significantly improved by the formation of rGO on the counter electrode. On the basis of electrochemical impedance spectroscopy, it is determined that the increased electrocatalytic activity of the rGO-Cu counter electrode is due to an enhanced conductivity of the counter electrodes. The maximum conversion efficiency is obtained for the rGO-Cu counter electrode with 0.5 mg ml−1 of rGO and has one and one half the efficiency achieved using a counter electrode modified only with Cu nanopolyhedra.