Carbon–graphene nanocomposite cathodes for improved Co(ii/iii) mediated dye-sensitized solar cells

Abstract

Cobalt-based electrolytes have significantly advanced the tunability and performance of dye-sensitized solar cells. The typically used platinum cathodes are expensive and non-optimal for cobalt complexes, motivating the search for replacements. Graphene nanopowders are a viable alternative but they are mechanically unstable as catalysts due to their poor substrate adhesion. Here we report a new type of carbon–graphene nanocomposite that maintains the catalytic performance of graphene with enhanced adhesion via a conductive carbon matrix. These nanocomposites were synthesized by carbonizing mixtures of graphene nanoplatelets with a carbon-source, poly(acrylonitrile). The resulting materials had tunable performance with a low charge transfer resistance of ∼1 Ω cm2 using as little as 20% graphene. Dye-sensitized solar cells fabricated with these carbon–graphene nanocomposites had enhanced fill factors and enhanced power conversion efficiencies as compared to platinum cathodes. Accelerated mechanical aging led to the complete detachment of graphene-only electrodes whereas carbon–graphene nanocomposites were stable.