Ambient air synthesis of multi-layer CVD graphene films for low-cost, efficient counter electrode material in dye-sensitized solar cells

Abstract

Graphene holds great promise as a substitute counter electrode (CE) material to replace the conventional Pt in dye-sensitized solar cells (DSSCs). However, lengthy chemical processing with hazardous chemicals, high production cost and the poor quality of the graphene flakes produced impedes their utilization as a CE material in DSSCs. Herein, we demonstrate a low-cost synthesis of multi-layer graphene films using a thermal chemical vapour deposition (CVD) process in an ambient-air environment without expensive compressed gases while using a renewable source namely soybean oil. Utilization of our low-cost graphene film in DSSCs exhibits excellent electrocatalytic activity and high electrical conductivity, and thus delivers superior photovoltaic (PV) efficiency compared to the devices fabricated with graphene films produced from commonly adopted chemical methods. Even though no additional treatments such as heteroatom doping are applied, our low-cost graphene showed great promise in DSSCs. Further enhancement in the efficiency of our multi-layer graphene film based DSSCs is readily achievable by applying simple functional treatments (for example SOCl2). Finally, material cost analysis of our multi-layer graphene film compared to commercial Pt electrode suggests that we can reduce the CE material cost by five fold, making our CVD graphene film a realistic option for application in commercial DSSC systems.