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 U cm 2 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 carbongraphene nanocomposites were stable.

Graphene-based cathodes for liquid-junction dye sensitized solar cells: Electrocatalytic and mass transport effects

“…(Note that this composite shows two charge M a n u s c r i p t transfer resistances in series [67].) Similar bimodal impedance spectrum was also reported for GNP in a composite with pyrolyzed poly(acrylonitrile) [129].…”

Graphene Nanoplatelets Doped with N at its Edges as Metal‐Free Cathodes for Organic Dye‐Sensitized Solar Cells

“…Their electrocatalytic activities are not comparable to Pt for the conventional I − /I 3 − redox couple, but graphene-based CEs outperformed the conventional Pt CEs in the Co-based mediators that have been reported. [ 11,12,[23][24][25] Moreover, nitrogen-doped carbon nanomaterials have demonstrated high electrocatalytic performance due to the high charge polarization stemming from the difference in electronegativity between carbon ( χ = 2.55) and nitrogen ( χ = 3.04), leading to enhanced catalytic activity and charge-transfer properties. [ 11,[26][27][28][29][30][31][32][33][34] We were able to demonstrate that nitrogen-doped graphene nanoplatelets that were prepared via a tedious wetchemical process [ 32 ] displayed high-performance in DSSCs.…”

Transparent graphene-based counter-electrodes for iodide/triiodide mediated dye-sensitized solar cells

“…8 The electroactivity of graphene is induced by lattice defects and attached oxygen-functional groups 8,12 but a sufficient high electrical conductivity should also be maintained. 6 Only just now have graphene-based CEs been proved to match and even surpass Pt as the premier catalytic material for DSCs but in different redox couple systems (ferrocene 13 or cobalt 14,15 ). Nevertheless such results have not been obtained yet for the I3 − /I − redox couple electrolyte.…”