Microwave-assisted exfoliation method to develop platinum-decorated graphene nanosheets as a low cost counter electrode for dye-sensitized solar cells

Abstract

Graphene nanosheets (GNs) are prepared from natural graphite by a simple ecofriendly microwave-assisted exfoliation technique. The as prepared GNs are decorated with platinum (Pt) nanoparticles by a simple chemical reduction method and used as a low-cost counter electrode (CE) material for dye-sensitized solar cells (DSSCs). Structure and morphology of the prepared GNs and Pt-decorated GNs (Pt–GNs) are evaluated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies. The electrochemical behavior of GNs and Pt–GNs are compared with std. Pt using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies. These studies indicate that the Pt–GNs-based counter electrode offered superior electrocatalytic activity towards the I⁻/I₃⁻ redox mediator with enhanced charge transfer rate and exchange current density at the electrode/electrolyte interface over std. Pt and GNs-based counter electrodes. DSSCs are fabricated with std. Pt, GNs and Pt–GNs to determine the photovoltaic performance under 1 Sun illumination (100 mW cm⁻², AM 1.5). It is found that the cell fabricated with 1 wt% Pt-decorated GNs as counter electrode showed an 11% improvement in photovoltaic cell efficiency compared with the cell assembled with std. platinum and other reported graphene–Pt-based composites as counter electrodes.