Research On Fabrication And Properties Of Graphene Based Counter Electrode For Dye-sensitized Solar Cells

In the typical dye-sensitized solar cells(DSSCs), Pt-loaded conducting glass has been widely employed as the standard counter electrode(CE) for DSSCs due to its high catalytic activity and excellent conductivity. However, the poor stability and high cost of Pt means an alternative to be required for the further development of CEs for DSSCs. Graphene, which is a novel two-dimensional material with a single-layer hexagonal lattice of carbon atoms, is being expected to be a promising material as CE for DSSC due to its excellent electron mobility, high reactivity for triiodide reduction and high electrochemical stability under prolonged potential cycling. Due to the strong π-π interaction between the large basal planes, the main barrier hindering the development of DSSCs with GNs as CE is that GNs tend to easily aggregate during the process of fabricating the graphene-based CE, which greatly reduces the surface area and the chance of active defective sites interacting with the electrolyte at the edges of graphene, weakening the electrocatalytic properties of graphene. To over the aggregations and enhance the electrocatalytic activity, an idea about the hybrid nanostructure CEs consisting of GNs and other nanomaterials to enhance their electrocatalytic activity was proposed. Based on this idea, several parts are as follows:Using the pulsed laser equipment, the high quality graphene nanosheets have been synthesized. The CEs with different morphologies of Ag nanoparticles and graphene nanosheets were fabricated by changing the different concentration of Ag NO3. And the effect on the electrocatalytic properties was analysized by the electrochemical characterization. As a result, the electrocatalytic activity of graphene was enhanced due to the insertion of Ag nanoparticles into the layers of graphene.Through the hydrothermal method, the Zn O nanorods with one dimension were synthesized on the FTO substrates, and the Zn O nanorods have the wurtzite hexagonal phase. The graphene nanosheets were coated on the the top surface of ZnO nanorods by spin coating method, and the morphologies of graphene caused by the Zn O nanorods was analysized by the SEM. When a small amount of graphene was coated on the ZnO nanorods, the edges of graphene were exposed and inhanced the electrocatalytic activity of graphene. Meanwhile, the one dimension Zn O nanorods as the channels fast the transportation of charge.The high quality graphene foam with three dimension was fabricated on the Ni foam by chemical vapor deposition. The graphene nanosheets with different sizes have been spin coated on the surfaces of graphene foam, demonstrating that the three dimension graphene foam is benifical to reduce the aggregations of graphene nanosheets, increasing the chance of the active sites interacting with the electrolyte and the resistance of charge transportation. The DSSCs with this hybrid CE has the conversion efficiency of 7.70%.