Fabrication of dispersible graphene flakes using thermal plasma jet and their thin films for solar cells

Graphene has generated tremendous interest over the past decade because of its extraordinary properties and potential applications. In this work, dispersible graphene flakes were successfully fabricated via a one-step process using a thermal plasma jet system. The graphene flakes fabricated by injection of ethylene gas as a carbon source (500 sccm) were very pure, contained no oxygen, and were few layered. Although their average size was larger than 100 nm, they were well-dispersed in organic solvents by sonication. The production rate based on the collected amount was approximately 1.5 g/h. As a representative application, thin films of the graphene flakes were fabricated on fluorine-doped tin oxide (FTO) glass using three deposition techniques. The resulting dye-sensitized solar cell with a graphene flake/FTO counter electrode exhibited a power conversion efficiency of 9.03%, which was similar to the efficiency of the solar cell with a conventional Pt/FTO counter electrode. Therefore, our graphene flake/FTO electrode could be used as a substitute for the conventional Pt/FTO counter electrode for DSSCs as graphene flakes are much less expensive than Pt. In addition to this specific application, dispersible graphene could be used in the fabrication of composites as well as various energy storage, sensor, and electronic devices.