Graphene-based nanohybrid materials as the counter electrode for highly efficient quantum-dot-sensitized solar cells

Dry plasma reduction is an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic AuPt nanoparticles (NPs) on a graphene nanoplatelets (GC)-coated layer under atmospheric pressure at a low temperature and without using any toxic reductants. The NPs with an average size of about 2 nm were stably and uniformly hybridized on the surface of reduced graphene nanoplatelets (RGC) after co-reduction of metal precursor ions and GC to metal atoms and RGC, respectively. Quantum-dot-sensitized solar cells exploiting AuNP/RGC, PtNP/RGC and bimetallic AuPtNP/RGC counter electrodes (CEs) exhibited power conversion efficiencies of 2.7%, 3.0% and 4.5%, respectively. The efficiencies are comparable to that of device with a conventional Au-sputtered CE (3.6%). The effect is ascribed to high electrochemical catalytic activity and high electrical conductivity of developed nanohybrid materials.