The reduced graphene oxide (RGO) counter electrodes were prepared by drop casting method and followed by heat treatment. The as-prepared RGO counter electrodes were used as substitution for Pt counter electrode in dye-sensitized solar cells (DSSCs). The effects of hydrazine hydrate in graphene oxide (GO) suspension on the performance of RGO counter electrodes were investigated. The cyclic voltammetry ( CV) and electrochemical impedance spectroscopy (EIS) measurements revealed that a moderate amount of hydrazine hydrate can enhance the catalytic activity of the RGO film toward the reduction of I-3(-) and decrease the sheet resistance of the film. The efficiency (eta) of DSSC based on the RGO counter electrodes with optimum addition of hydrazine hydrate increased from 1.826% to 2.622% under a simulated solar illumination of 100 mW cm(-2) (AM 1.5). (C) 2014 Elsevier B.V. All rights reserved.