Preparation Of Zno Nanowires And Its Applications In Sensitized Solar Cells

As a clean and renewable energy, solar energy is helpful to achieve the sustainable development of human society, but the efficient utilization and proper storage of solar energy is an important issue to be addressed in the future. The dye-sensitized solar cells was considered as one of the most promising new type of solar cell for the next generation due to its simple manufacturing process, lower cost and environmental friendship. Generally, TiO2 nanoparticles were used for the photoanode of sensitized solar cells, but poor contact between TiO2 nanoparticles and the low electron mobility of TiO2 resulte in the lower conversion efficiency of sensitized solar cell. Because ZnO nanowires has higher electron mobility, direct transport passway for electron, a wealth of raw materials and simple preparation process, sensitized solar cells based on ZnO nanowires have better application prospect. In this paper, we fabricated high aspect radio of ZnO nanowires as photoanode by chemical bath deposition (CBD) method and used CdS quantum dots and organic dye rose Bengal sensitized ZnO nanowires to assemble sensitized solar cell. After that, the structure and morphology of ZnO nanowires and the photoelectric properties of sensitized solar cells were systemically characterized. The details of our results are as follows:1. We prepared ZnO seed layers on the ITO conductive glass substrate by laser molecular beam epitaxy (LMBE) method, and then the ZnO nanowires were grown on the ZnO seed layers by chemical bath deposition (CBD) method. In order to obtain high aspect ratio of ZnO nanowires, parameters of processing ZnO nanowires were systematically investigated, including the crystallinity of ZnO seed layers, PEI concentration, water bath temperature and growth time. The results show that ZnO nanowires were vertically grown on ITO substrate and hexagonal wurtzite structure when the ZnO seed layers had c-axis preferred orientation. Moreover, we obtained ZnO nanowires with aspect ratio of 20.56 at the PEI concentration of 4.5mmol/L, the water bath temperature of 95 ℃, and the growth time of 9h.2. CdS quantum dot were deposited on ZnO nanowires by successive ionic layer adsorption and reaction (SILAR) method, which were assembled into sensitized solar cells. We explore that the times of CdS SILAR cycles and different aspect ratio of ZnO nanowires affect on the performance of solar cells. The research shown that with the times of CdS SILAR cycles increased from 2 to 16, the efficiency of solar cells increased first and then decreased. With the increase of aspect ratio of ZnO nanowires, number of CdS quantum dot adsorbed on ZnO nanowires increased and the absorption range of solar spectrum became wide and then the conversion efficiency of solar cell was improved. When the times of CdS SILAR cycles were 12 and the aspect ratio of the ZnO nano wire was 20.78, the solar cell could achieve the best photoelectric conversion efficiency of 0.401%.3. Rose Bengal were sensitized ZnO nanowires by direct adsorption (DA) method, and assembled into sensitized solar cells. Effect of the concentration of rose Bengal and different aspect ratio of ZnO nanowires on photoelectronic properties of dye sensitized solar cells was studied. The research found that when rose bengal concentration was 0.2mmol/L and the aspect ratio of ZnO nanowires was 20.78, solar cells could achieve the best performance, then short circuit current of 3.043mA/cm2, the open circuit voltage for 0.406V, fill factor of 0.341, photoelectric conversion efficiency of 0.421%.4. In order to broaden the absorption range of solar spectrum and make up for the defects caused by the single sensitization, CdS and rose Bengal co-sensitized ZnO nanowires solar cells was prepared. Compared with the photoelectronic properties of CdS or rose Bengal sensitized solar cells, we found that the CdS and rose Bengal co-sensitized ZnO nanowires can improve the short-circuit current and photoelectric conversion efficiency of solar cells, and the conversion efficiency were increased by 28% and 22%.