Optimum strategy for designing a graphene-based counter electrode for dye-sensitized solar cells

Abstract

In this study, we developed a cost-effective method to enhance the electro-catalytic activity and conductivity of graphene-based counter electrodes (CEs) by diminishing the oxygen content in graphene nanoplatelets (GNPs) through dry plasma reduction (DPR). As a result, the efficiency of dye-sensitized solar cells (DSCs) based on GNPs with an average surface area of 750 m(2)/g treated by DPR was enhanced by 15% over that of devices with pristine graphene oxide electrodes. The next step in the design strategy for improving DSC performance suggested the immobilization of platinum nanoparticles (PtNPs) on the electrode surface through DPR. DSCs based on the newly developed CEs had an increase in efficiency by 50.3% over that of the Pt-free device, and by 10.4% over the efficiency of state-of-the-art DSCs. The introduction of PtNPs on the surface of a CE through DPR along with removal of the oxygen functional groups from the surface of the GNP electrode reduces the charge-transfer resistance at the electrolyte/CE interface and the diffusion impedance of triiodide ions. PtNPs hybridization on the surface of CE facilitates the electron conductivity in the PtNPs/CE structure by creating a conductive network in the sp(3) phase for charge carriers delocalized in a sp(2) matrix. (C) 2014 Elsevier Ltd. All rights reserved.