| The application of solar energy is the key way to solve the energy and the environment issues, which are two sever problems in our society. However, so far, the main energy consumption is still dependent on oil, gas and other traditional energy sources, and the usage of solar energy is only 0.17%. Therefore, the methods of the development and utilization of solar energy requires further constant exploration and breakthroughs. Among the methods, the conversion of solar energy to electricity and chemical energy are two essential ways. Here, in this thesis, we mainly focused on the dye-sensitized solar cell which converts solar energy to electricity, and photoelectrochemical water splitting which converts solar energy to chemical energy.In the configuration of dye-sensitized solar cells, the photoanode is the key component, which is usually made up by one type of semiconductors sensitized to dye molecular, such as the traditional TiO2 nanoparticles photoanode. However, there are two main restrictions for this photoanode. On the one hand, the electron mobility of TiO2 is relatively low which hinder the transportation of photo-carries. On the other hand, a large amount of interfaces among the TiO2 nanoparticles lead to a big chance of the recombination. As a result, these two disadvantages will greatly decrease the power conversion of efficiency in dye-sensitized solar cell. To abbreviate these problems, we firstrly developed some candidate semiconductor nanomaterials for TiO2, such as ZnO and SnO2. Then, we employed core-shell structure to reduce the recombination on the interfaces. Finally, we designed one dimensional nanomaterial, such as nanowires and nanotubes to construct the high electron pathway in the photoanode.(1)We synthesized ZnO nanoaggregate-TiO2 heterojuntion structure and applied it as the photoanode in DSSCs. In this structure, the light absoraption has been greatly enhanced because of the aggregate structure. In addition, the unstability of ZnO has been restricted by the TiO2 coating layer. Finally, the power conversion efficiency of ZnO aggregate-TiO2 core-shell structure is higher than that of the commercialrized ZnO nanoparticles. However, the power conversion efficiency of ZnO based electrode is still too low due to the reactioin between ZnO and the electrolyte.(2) Instead of TiO2 and ZnO, we applied SnO2 as the active material in DSSCs. Here, we developed a SnO2 nanowire/nanotube-TiO2 core-shell heterojunction structure by the conmbiation of electrospinning and solution based method. This is the first time to report of synthesis SnO2 nanotubes by electrospinning method. The power conversion efficiency of SnO2 nanotube-TiO2 core-shell structure is 5.11% which is higher than that of P25 electrode(5.04%).(3) To further increase the photoelectrochemical performance, we optimized the fabrication conditions and developed a branched ultrafine SnO2 nanowire-TiO2 core-shell heterojunction structure. This structure combines the advantages of fast electron transport, slow interfacial electron recombination and large specific surface area together. Therefore, the short-circuit current, the opencircuit voltage and the fill factor have been increased compared to those of P25 electrode, respectively. The efficiency is as high as 7.11%.(4) Photoelectrochemical water splitting device has similar configuration with dye-sensitized solar cells, and suffers similar problems. Here, we designed a multi-heterojuntion structure of SnO2/TiO2/CdS as the photoanode in photoelctrochemical water splitting. It was found that this novel structure showed improved hydrogen conversion efficiency, which maybe attributed to the synergestic effects from both the electron transportation and light absorption.In brief, based on our research and rational design, the transportation of photo-carries was remarkably improved and simultaneously the chance of their recombination was effectively restrained. Here, we believe that this research can further promote the development of photoelectrochemical devices. |
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