The Application Of Graphene-based Materials In Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs), a new way of utilization of solar energy, have attracted tremendous attentions recently due to the advantanges such as low cost, high efficiency, excellent stability as well as convenient fabrication. Counter electrodes (CEs) represent an important part of DSSCs which function as electron collections and catalyst for the reduction of I3-. Pt is the mostly widely used CE matetials owing to its high conductivity and high reduction capability of13’. However, the less avalibility, high cost, poor corrosion-resistance to electrolyte of Pt make the wide untilization of Pt as CEs impossible. As such, the development of low cost and easy accessible alternave to Pt remians a great challenge.Recently, many kinds of carbon nanomaterials such as activated carbon,carbon black, carbon nanotubes, graphene and fullerene, have been evaluated as CEs for DSSCs. Among all, graphene emerges as a potential candidate that can replace Pt as CE for DSSC assotiated with unique strucutre and extraordinary properties. In this work, Boron-doped graphene (BG) and Boron, Nitrogen-codoped graphene (B,N-G) have been successfully synthesized and their performance as CEs for DSSCs have been intensively investigated. The main results are shown as follow:BG have synthesized by thermal annealing the mixture containing graphite oxide (GO) and B2O3which serve as carbon source and boron source respectively. BGs have inherited the lamellar strucutre of graphene and the surfaces of BGs have been decorated with wrinkles and folds. When evaluated as CEs for DSSCs, BGs delivers a much better performace than that of G mainly resulted form higher conductivity and more active sites. The improved performance may associated with doped B atoms which can modulate the distribution of electrons. On the other hand, the doped B atoms may create more active sites. The content of B can be easily tuned by changing the mass ratio of GO and B2O3. When the mass ratio of B2O3and GO is set as1:2, the corresponding BGs show the best performance with conversion efficiency of6.73%B,N-G has been successfully synthesized by thermal annealing of GO nanosheets grafting with ionic liquid (1-aminopropyl-4-methylimidazolium tetrafluoroborate) served as B source and N source. The two-dimensional strucuture has been well maintained after the procedure mentioned above. Not only the electron distrubtion and active aites can be modulated by codoping of B and N atoms, but also they may have synergistic effect. When evaluated as CE for DSSCs, B,N-G delivers performance superior to that of Pt CE and strucutre obtained by annealing at1200℃can give rise to conversion efficiency as high as8.08%.