| Conversion of solar energy is one of the most effective way to solve the energy crisis and environment pollution nowdays. Various solar cells converting the solar energy to clean electricity have attracted much attention of researchers around the world. Due to the simplified preparation process, low cost of raw materials, high theoretical efficiency, designability of the devise, quantum dot-sensitized solar cells (QDSCs) are viewed as promising photoelectric conversion devises. For the moment, the conversion efficiency of QDSCs is above6%, however it is still difficult for commercialized application in large scale. One-dimensional nanomaterials can provide shorter electron transport path, facilitating the transport of the electron in the nanomaterials. Ordered nanoarray materials is beneficial for the diffusion and transfer of the species on the surface of electrodes and can provide large specific surface area. So, one-dimensional nanoarray materials applied in QDSCs is expected to further improve the conversion efficiency of the device.In this thesis, densely aligned ultralong rutile TiO2nanorod array films were grown on transparent conducting FTO substrates, chemically etched to change the morphology of TiO2nanorod arrays. Then the etched TiO2nanorod array films were used as a photoanode in the CdS/CdSe quantum dot-sensitized solar cells. On the other hand, the Co9S8hollow nanoneedle arrays were fabricated on the conducting FTO substrates, and then applied as counter electrodes in QDSCs. The main results achieved in this work are listed as following:1. Ultralong rutile TiO2nanorod arrays were grown on the conducting FTO substrates by hydrothermal method, chemically etched in hydrochloric acid. The CdS and CdSe quantum dots were deposited on TiO2nanorod arrays by successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD), respectively. Systematical investigations were conducted to verify the effect of etching condition on the morphology of TiO2nanorod arrays. The feature of growth of CdSe quantum dot on TiO2nanorod arrays was investigated. The experimental results showed that the chemical etching treatment greatly enhanced the specific surface area of TiO2nanorod arrays. There is an optimal number of CdSe quantum dot for QDSCs, and longer TiO2nanorod (>10μm) makes for better performance of QDSCs. An optimized conversion efficiency of2.66%with a short circuit current density (Jo)17.22mA/cm2was achieved, which was up to now the highest Jo of the QDSCs based on CdS/CdSe quantum dot sensitized TiO2nanorod arrays.2. The ordered Co(CO3)0.35Cl0.2(OH)1.10-1.74H20nanoneedle arrays were grown on FTO substrates by the chemical bath deposition, and then transformed to Co9S8hollow nanoneedle arrays by hydrothermal method. The TiCl4treatment of the FTO substrates improved adhesion between the Co9S8hollow nanoneedle arrays films and the FTO substrates. Several micrometers long of Co9S8nanoneedle arrays films was fabricated on FTO substrates for the first time. Systematical investigations were performed to identify the process of solid Co(C03)0.35Cl0.2(OH)1.10·1.74H20nanoneedle converting to Co9S8hollow nanoneedle. Then the Co9S8hollow nanoneedle array films as counter electrodes were applied in QDSCs. Our experimental results showed that Co9S8hollow nanoneedle was formed by the Kirkendall effect, annealing treatment increase the degree of crystallinity of the Co9S8hollow nanoneedle films and strengthen the electrocatalytic activity to the polysulfide redox couple in the electrolyte. A conversion efficiency of3.72%was achieved of QDSCs with annealed Co9S8hollow nanoneedle array film counter electrodes, while QDSCs with Pt counter electrodes just showed a conversion efficiency of2.12%. |
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