Binder-Free Graphene Organogels as Cost-Efficient Counter Electrodes for Dye-sensitized Solar Cells

Abstract

Graphene organogels (GOGs) filled with organic electrolytes may function as high-activity, low-cost electrodes for energy conversion and storage devices such as Li ion batteries, supercapacitors, and dye-sensitized solar cells (DSSCs), because of their ideal electron-transport and ion-diffusion pathways through an interconnected 3D porous framework self-assembled from highly conductive and high-specific-area graphene sheets. Here, graphene hydrogels prepared by a modified hydrothermal method are converted into organogels with a specific surface area up to ∼1298m2g−1 by a simple solvent-exchange approach, and pressed onto titanium meshes to form GOG films as economical, wearable counter electrodes for DSSCs. Without optimizing TiO2 photoanodes, GOG-based DSSCs show a markedly enhanced short-circuit current density (16.34mAcm−2) and thus an impressive power conversion efficiency of 7.2%, higher than those using graphene aerogels (11.6mAcm−2, 5.9%) and commercial Pt films (10.2mAcm−2, 5.9%) as counter electrodes under otherwise identical conditions. The improved efficiency is ascribed to a substantial reduction in charge-transfer resistance and series resistance, which is correlated with the high conductivity and high specific area of GOGs.