Fabrication Of Inverse Opal Photonic Crystal Photoelectrode And The Investigation Of Their Photoelectrochemical Properties Under Visible Light

Fossil fuels, such as oil, are facing rapid resource depletion, on the contrary, the growth of global energy demand increased rapidly. Therefore, new energy was needed to satisfy the future global need for energy sources. As an effective way of using solar energy, solar cells has attracted widespread interest because its potentiality to solve energy shortage. Dye sensitized solar cells (DSSCs) is more suitable for practical use because of their low-cost and environmental friendly. However, lower utilization of solar energy and lower photoelectric conversion efficiency needed to be solved. Narrowband semiconductors, such as CdSe, were a kind of new dye which have a wide light absorption range in the solar spectrum. Therefore when narrowband semiconductor was assembled onto the photoelectrode, the absorption of the photoelectrode could be enhanced effectively. In order to load more dyes onto photoelectrode, new nano structures were designed becasuse they possessed larger specific surface area. Inverse opal photonic crystal has not only large surface area but also the ability to controll the propagation of light. The combined effect of the photonic band gap and slow photo, the inverse opal photonic crystal can enhance the interaction of light and the dye. If CdSe was prepared with the structrue of inverse opal photonic crystal and loaded on photoelectrode, the photoelectric conversion efficiency of DSSC could be enhanced further. In this thesis, several works have been done as follows:(1) The TiO2inverse opal photonic crystal was prepared via the liquid-phase deposition. A3D inverse opal photonic crystal structure was obtained when the activation time was10min and the deposition time was20min. The average diameter of the hollow spheres was around200nm, and the center of the photonic band gap was about500nm. A photocurrent density of0.4mA cm-2was achieved under2mW/cm2ultraviolet light illumination with0V bias potential (vs. SCE), which was8fold higher than that of TiO2film.(2) The TiO2inverse opal photonic crystal was prepared via the liquid-phase deposition.The photonic band gap of inverse opal photonic crystal prepared from193nm,225nm and260nm polystyrene microsphere was420nm,500nm and680nm respectively. CdSe nanoclusters with well-defined crystallinity have been assembled onto TiO2inverse opal photonic crystal by photo-assisted electrodeposition method, and formed a new nanocrystal sensitized photoelectrode. The photocurrent density of TiO2/CdSe-PC was higher than that of TiO2/CdSe-NC under100mW/cm2visible light illumination with0V bias potential (vs. SCE). The photocurrent density of TiO2/CdSe-PC prepared from260nm polystyrene microsphere was the highest, which was2.5fold higher than that of TiO/CdSe-NC.The SPV and IPCE spectra indicated the same results. The excellent photoelectrochemical performance of TiO2/CdSe-260was obtained under the combined effects of photonic band gap effect and slow photon effect.(3) The CdSe inverse opal photonic crystal was prepared via electrochemical deposition. Compared with galvanostatic electrochemical depositions and potentiostatic deposition, potentiostatic electrochemical depositions was the optimum to fabricate CdSe inverse opal photonic crystal. A3D inverse opal photonic crystal structure was obtained when the potential was-0.65V, the electrolytes contained of0.3M CdNO3、0.3mM NaSeO3, and the deposition time was3h. The average diameter of the hollow spheres was around190nm,the center of the photonic band gap was about425nm. A photocurrent density of5.5mA/cm2was achieved under100mW cm2visible light illumination with0V bias potential (vs. SCE), which was10fold higher than that of CdSe film.The above results illuminated that CdSe, the narrow bandgap semiconductor, could expand the light response range. The well-designed photonic crystal nanostructure could enhance the absorption of photoelectrode and light utilization, as the phtonic band gap effect and slow photon effect efficiently intensified the absorption of light. These studies provide a feasible approach to design a high photoelectrochemical abilitive photoelectrode, which would promote the application of photoelectrode in the solar cells.