Preparation Of Stannate Composite Photoanode By Two-step Method And Its Properties

With the rapid development of social economy, energy and environment problems had become a bottleneck for the sustainable development of the global economy. The survival environment was tested with the scarcity of traditional energy and serious environmental pollution. So, the alternative energy with the characteristics of non-pollution and sustainability was born. As the safest, green and ideal energy, solar energy was the leading, and making photovoltaic solar cells was the most important and effective way to utilize solar energy. Since 1991, Dye Sensitized Solar Cells (DSSCs) has caused the research interests for the simple preparation technology, rich in raw materials, high theoretical conversion efficiency and non-pollution. In order to further improve the conversion efficiency and explore the new types of photoanode, the stannate composite photoanode and the related systems had been prepared in this paper; various methods had been employed to study the relationships between structures, morphologies and properties. The research work includes the following several aspects:1. The experiment conditions and parameters to prepare the Zn2SnO4 composite photoanode were explored by the solide state method. The optimum condition had been founded by selecting the raw materials, grinding time, reaction time and temperature in the low temperature:Zn(NO3)2·6H2O, SnCl4·5H2O and NaHCO3 were the raw materical, and they were ground for 60 min at room temperature. And then, a further reaction was proceed under 60? keeping for 6 h. Finally, the sample was sintered at 500? for 2 h. The photoanode showed a better crystal structure and dispersion without particle agglomeration, and had a good photoelectric conversion efficiency (PCE) with 4.58%.2. The two-step solid state reaction was employed to prepare C-ZnO/SnO2 composite photoanode for the first time. First, the low heat solid state reaction was used to prepare different precursors; second, the mild sintering was adopted to obtain different photoanodes, including ZnO, SnO2, S-ZnO/SnO2 and C-ZnO/SnO2. The structures and morpholigies of the photoanode films were measured by the SEM and surface area analuzer. It had been demonstrated that the C-ZnO/SnO2 photoanode showed the best mesporous structure with a uniform distribution of nanoparticles, and the biggest surface area. The device based on the C-ZnO/SnO2 photoanode displayed the significant advantages in the aspects of restraining electron recombination, expediting elcetron transfer and extending electron lifetime via the analysis of EIS, and it showed the best performance of 5.36%. Two-step solid state reaction with the characteristics of simple operation, convenient, high production rate and environmental protection could simplify the preparation of photoanode materials, and it had provided an important reference to obtain the efficient DSSCs.3. A double-layer ZnO/ZnO-SnO2 photoanode film was designed and studied. First, ZnO nanorod array (Z) was prepared by hydrothermal method; second, ZnO-SnO2 nanoparticles was prepared by solid state method and used as the scattering layer. The ZnO/ZnO-SnO2 (ZZS) photoanode film was obtained after the sintering process. It had been found that the double-layer film showed a good interface bonding state and light scattering or capturing property by the analysis of SEM and UV-vis diffuse reflection. Owing to the increased surface area by the upper ZnO-SnO2 mesporous layer (ZS), the dye adsorption capacity had been improved. The structure of nanorod array could provide a fast chanel for the electron transfer, which would decreased the transmission path and recombination of the carrier. So, the PCE with 5.10% had been obtained for the double-layer ZnO/ZnO-SnO2 photoanode.4. The BaSnO3 photoanode was prepared:first, the precursor was obtained by the simple co-precipitation method; and second, the BaSnO3 photoanode material was gained by the high temperature sintering. In addition, the citric acid was used to optimize the preparation process. As a result, the photoanode material showed a good dispersion and uniformity without serious aggregation and the performance of the cell has been improved after the optimizing. When the amount of citric acid was 10%, the highest PCE with 2.81% had been received.