Study On Application Of Carbon Nano-tubes As Counter Electrodes In Solar Cells

Dye-sensitized solar cells（DSSCs） is a new type of photoelectric chemical solar cell withsimple preparation procedure, low cost, stable performance and environmental friendly,which make it has a good application prospect and commercial value. DSSCs has developedvery quickly in the last two decades since it firstly came into being in1991. DSSCs has threemain parts: dye sensitized nanocrystalline TiO₂electrode, electrolyte （I-/I3-） and counterelectrode. Currently, a layer of platinum coated on transparent conducting oxide substrate isused widely as counter electrode in DSSCs. DSSCs attracts more and more attention due to itslow cost and higher photoelectric conversion efficiency, while the use of noble metal catalystplatinum is obviously not an economy way for mass production. Carbonaceous materials arequite attractive to replace platinum due to their high electronic conductivity, corrosionresistance towards I2, high reactivity for triiodide reduction and low cost.Carbon counter electrode of the dye-sensitized solar cells were prepared by the methods ofelectro-deposition, screen printing, pulling and doctor blading with carbon nanotubes（CNTs）,activated carbon, carbon black, graphite as raw materials. Electro-deposition was the mainpreparation method in this research. The best electrode materials and the best electrochemicaldeposition process parameters were obtained through the observation of surface morphologyand resistance testing of carbon films, and the performance testing of assembled cells.The experimental results showed that the CNTs counter electrodes of DSSCs prepared byelectro-deposition method exhibited excellent photoelectric property with an overallconversation efficiency of3.77%when the applied voltage was20V, deposition time was10min and bath temperature was65℃. When carbon materials were used as the raw materialsof counter electrodes for DSSCs the specific surface area, particle shape, pore structure,organization arrangement and conductivity of carbon materials had a great influence on theperformance of the DSSCs. By comparison of different carbon materials, the CNTs filmsshowed the best photoelectric conversion efficiency of5.87%in the DSSCs due to its uniquetube-like structure, good electrical conductivity, heat transfer performance and environmental tolerance. Compared with screen printing, doctor blading and pulling method,electro-deposition method had the advantages of simple process, easy operation, the thicknessand the adhesion of the CNTs film could be controlled and the carbon films prepared byelectro-deposition method could be used circularly in DSSCs, which made it have a brightprospect.