Synthesis Of Graphene-based Composites And Its Application As Counter Electrodes In Dye-sensitized Solar Cells

The unique structure of graphene endows it superexcellent properties. As a new two-dimensional material, graphene has wide application prospects in the field of sensors, super-capacitors, lithium-ion batteries, solar cells and other electrochemical, which opens up new areas of research in materials science. In this thesis, we obtained reduced graphene (RGO) by reducing graphite oxide (GO). Then RGO solids were used as precursors to prepare graphene nanocomposites by different methods, and the electrical properties of the composites were also studied. After fabricating nanocomposites films based DSSCs, the effect-mechanism of energy conversion efficiency of the DSSCs was investigated. The dissertation is mainly focused on:1. An improved method for preparation of graphene oxide (GO) and reduced graphene (RGO) by our group. XRD analysis demonstrated that the distance of the GO sheets was about0.87nm, and TEM microphotograph showed that there were a large number of complete few-layer GO sheets, the surfaces were very smooth. FT-IR showed the presence of abundant benzene carboxylic, hydroxyl and epoxide groups in the basal planes of GO.2. We prepared low Pt loading graphene composites by one-step and two-step reduction process in graphene dispersions respectively. Cyclic voltammetry (CV) and electrical impedances analysis (EIS) indicated that the composites had high electrocatalytic activity toward the reduction of iodide/triiodide. We deposited Pt/RGO-composite films on FTO substrates by drop-casting and the films were applied as counter electrodes (CEs) of DSSCs. The energy conversion efficiency of the Pt/RGO CEs based DSSCs was0.91%lower than the Pt CEs based Cells.3. We prepared the PPy-PSS/RGO composites by in-situ polymerization. The composites were characterized by FT-IR, TEM and SEM measurements. A series of products were synthesized by changing the ratio of Py monomer and RGO. The composites films for DSSCs were also prepared by drop-casting. The PPy-PSS/RGO electrodes had an enhanced electrocatalytic activity for iodide/triiodide redox reaction, thus improving the performance of the DSSCs based on these electrodes. The energy conversion efficiency of the PPy-PSS/RGO CEs based DSSCs was1.82%lower than the Pt based Cells.