The Preparation Of One-dimensional Heterostructure Photoelectrodes And The Investigation Of Their Photoelectric Conversion Properties

With the rapid development of economy and technology, traditional energy sources are rapidly consuming and the environment is subjected to the corresponding damage. Therefore, the development of new type of green energy becomes an important goal currently. The solar energy on the surface of the earth has many advantages including green ,safety ,long service life and a wide range of applications.So solar energy is the clean energy we need to develop and utilize urgently, and is also expected to become the largest target energy sources of mankind. Semiconductor photoelectric materials can be used as carriers of utilizing solar energy to realize the photoelectric conversion. ZnO and TiO2 have become the semiconductor photoelectric materials which are studied most because they have many significant advantages including widely sources, low cost, high electron mobility and high optical activity. However, due to their wide band gap, they mainly absorb the ultraviolet light and cannot effectively use visible light, resulting in the low total efficiency of ZnO and Ti02 photoelectrodes, so they are restricted in the practical applications. Therefore, we can use semiconductor materials with narrow band gap to modify ZnO and TiO2 to build heterostructure in nanometer scale or use organic dye to sensitize ZnO and Ti02 to form a composite system, which can make full use of visible light in the main part of the solar spectrum and improve the photoelectric conversion efficiency of the photoelectrode under visible light.One-dimensional Fe2O3/TiO2 and BiOI/TiO2/ZnO composite photoelectrodes were designed and prepared in this paper. The photocurrent technique , photovoltaic technique and the test of flat band potential were carried out to investigate the photoelectric conversion performance, and the transport mechanism of photogenerated charge was explored. Specific research work includes:1. TiO2 nanorod (NR) arrays, Fe2O3 nanofilm and one-dimensional Fe2O3/TiO2 nanocomposite photoelectrodes were prepared by hydrothermal method respectively on the fluorine doped tin oxide (FTO) conductive glass. The amount of Fe2O3 was adjusted to choose the optimum photoelectric performance of the composite photoelectrodes. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV-vis diffuse reflection spectrum were used to analyze the morphology of the materials. The photocurrent, photovoltic and water oxidation experiments were carried out under simulated light illumination, and the photoelectric conversion performance of the photoelectrode was studied.Through contrast test , photoelectric conversion efficiency of Fe2O3/TiO2 based solar cell reached 0.2086% ,the short circuit current reached 1.84 mA/cm2 and open circuit voltage was 0.44 V, which proves that Fe2O3/TiO2 photoelectrode has the optimum photoelectric performance. The transport mechanism of photogenerated charge was explored according to the test of flat band potential and energy band structure.2. ZnO NR arrays and TiO2 NR arrays were prepared by hydrothermal method respectively on FTO conductive glass, and then TiO2/ZnO NR arrays was prepared by chemical deposition method on the ZnO nanorods. At last, the above three samples were sensitized by BiOI through chemical deposition method to prepare BiOI/ZnO and BiOI/TiO2 and BiOI/Ti02/ZnO photoelectrodes. XRD, FESEM and UV-vis diffuse reflection spectrum were used to analyze the morphology of the above six samples. The tests of photocurrent, photovoltage and water splitting were carried out simulated light illumination. The test results of the above six samples were compared,proving BiOI/TiO2/ZnO based solar cell has best photoelectric conversion performance reaching 0.1173% , short circuit current reached 1.84 mA/cm2 , which proves that BiOI/Ti02/ZnO photoelectrode has the optimum photoelectric performance.Water oxidation experiment shows that the BiOI/TiO2 photoanode has the lowest initial voltage, the photocurrent of BiOI/TiO2/ZnO photoanode is the highest, further proving that BiOI/TiO2/ZnO has excellent photoelectric properties under visible light. In addition, the theory of photoelectric effect was carried on the preliminary discussion according to the flat band potential.