Synthesis of nitrogen and sulfur co-doped reduced graphene oxide by hydrothermal method for fabrication of cathodes in dye-sensitized solar cells

Carbon-based materials have been known as non-metal electrocatalysts with both high performance and low cost for the reduction at the cathode of dye-sensitized solar cells (DSSCs). In this work, nitrogen and sulfur co-doped reduced graphene oxide (NSG) materials were synthesized via using graphene oxide (GO) as a precursor with reducing agent thiourea as the source of providing heteroatoms. Furthermore, NSG materials were extensively prepared via hydrothermal treatment with the investigation of different mass ratios of GO to thiourea. To study the impact of the quantity of reductant on the properties of NSG, reduced graphene oxide (rGO) was prepared by reducing GO with ascorbic acid as a reference sample. Moreover, NSG and rGO cathodes were both prepared by drop-casting method, while platinum (Pt) cathodes were fabricated using commercial Pt paste by screen-printing method. The DSSCs based on NSG cathodes with ratio of GO to thiourea of 1:10 exhibited an efficiency of 7.21 %, which was similar to commercial DSSCs Pt (7.44 %), proving that the judicious heteroatom doping of GO might introduce a potential candidate for increasing performance of DSSCs.