Three-dimensional graphene networks and reduced graphene oxide nanosheets co-modified dye-sensitized solar cells

Graphene assisted dye-sensitized solar cells (DSSCs) have drawn increasing attention because of their high performances. However, two bottlenecks (the high defect density and the discontinuous structure) of the widely adopted reduced graphene oxide (RGO) nanosheets bring about that the practical photovoltaic properties are far inferior to the theoretical prediction values. Therefore, three-dimensional graphene networks (3DGNs) of high quality have been employed to modify DSSCs to avoid the above mentioned problems. However, a close contact between the graphene basal plane and TiO2 particles in the resulting photoanode is difficult to achieve due to the absence of surface functional groups of the 3DNG. In this study, the RGO nanosheets and 3DGNs co-modified DSSCs are prepared, and the advantages from these two modifiers can give full play to their synergy. The added RGO nanosheets enhance the electron transport ability at the interfaces between graphene, TiO2 and conductive substrate. After optimizing the reduction degree and mass fraction of the RGO nanosheets, the power conversion efficiency of the resulting DSSC reaches 7.68%, which is much higher than those cases of using the 3DGNs (or RGO nanosheets) as modifier alone.