Platinum and Transparent Conducting Oxide Free Graphene-CNT Composite Based Counter-Electrodes for Dye-Sensitized Solar Cells

Abstract

Graphene nano-sheets were prepared from natural graphite by a simple high shear exfoliation technique in suspension form and in bulk quantity. The structural properties of the graphene thus prepared were characterised by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and dynamic light scattering. BYK-multi-walled carbon nanotubes (MWCNT) paste was infused into the graphene solution. UV-Vis spectroscopy was performed to know the concentration of both graphene and CNT solution. Glass microslides were used to be coated with used to be coated with the graphene-MWCNT solution and surface morphology was studied by field emission scanning electron microscopy. The study of morphology showed that the CNT’s provide better connectivity across the graphene flakes. Sheet resistance was measured by the van der Pauw method. An optimum concentration for CNT was found out for lowest sheet resistance. 3-Aminopropyl triethoxysilane (APTES) was added into the graphene-CNT composite paste to achieve better adhesion. Cell assembling was done using TiO₂ coated photo-anodes, tri-iodide/iodide electrolyte solution and the graphene-CNT-APTES based counter-electrodes. APTES improves the adhesion and was able to reduce the cell-cost.