| As a non-stoichiometric semiconductor, with a direct band gap around 2.09 eV, Cu2O has a high absorption coefficient in the visible region and the utilization efficiency of sun light by Cu2O thin films can reach 20% in theory. Cu2O attracted researchers’attention for a long time, owing to its potential applications in the development and application of the new thin-film batteries materials, photocatalytic and photoelectrochemical areas. ZnO is generally an n-type semiconductor, with a wide band gap of 3.4 eV, an exciton binding energy of 60 meV and a high electron mobility of 120cm2/V·s. These features make ZnO, like GaN, a candidate for applications to blue and ultra-violet optical devices. And ZnO has become a kind of important material in the dye sensitized solar cells anode. Thanks to the low cost, non-toxic and various preparation methods character of ZnO/Cu2O constituents. The ZnO/Cu2O heterojunction has been fabricated and used in semiconductor optoelectronic devices for a long time. In this thesis, we prepared the cuprous oxide films, ZnO nanorod array films and Cu2O/ZnO nanorod array composite films by potentiostatic deposition and characterization of their properties.The main conclusions obtained in this work were listed as follows:(1) Cu2O thin films were successfully deposited onto FTO conductive glass substrates by potentiostatic deposition. The electrolytes were Cu(Ac)2 and NaAc aqueous solution and the pH values of the electrolytes were modulated by adding acetic acid. The influence of the preparation on the properties of the thin films was studied. The results showed that when the pH of the solution was increased, the grain size of Cu2O became smaller which was opposite to the trend of the diffusion coefficient of Cu2+. With the pH of the solution increasing, the energy gap of Cu2O, reduction potential(Cu2O/Cu2+) and the solution concentration polarization gradually increased. When the deposition temperature was increased, the energy gap and the carrier concentration of Cu2O gradually increased. When the temperature was 50℃, the diffraction peaks of (111) and (200) were the strongest and the energy gap was 2.18eV closest to block Cu2O band gap value. When the deposition potential gradually increased to the negative direction, the crystallinity and carrier concentration of Cu2O. The energy gap was first increased and then decreased with the deposition potential gradually increased from -0.1V to -0.4V. When the deposition potential was -0.4V, there were copper impurities in thin film which reduced the energy gap of the Cu2O film. In addition, the preparation of semiconductor thin films were n-type semiconductor under different conditions in the acidic system.(2) Cu2O thin films were successfully deposited onto FTO conductive glass substrates by potentiostatic deposition. The electrolytes were cupric sulfate solution and the pH values of the electrolytes were modulated by adding NaOH solution, lactic acid as complexing agent. The influence of the preparation on the properties of the thin films was studied. The results showed that when the pH of the solution was increased, the energy gap and the flat band potential of the Cu2O films decreased. The photoelectric conversion efficiency was first increased and then decreased with increasing of the pH. When the pH was 11, the largest photoelectric conversion efficiency is 1.36%. When the deposition temperature was increased, the diffraction peaks intensity were first increased and then decreased. The reduction potential of Cu2O/Cu2+, deposition current and IPCE of Cu2O films were increased. When the deposition temperature was 60℃, there was the largest IPCE of 29%. The IPCE was under 5% in other temperature conditions. When the deposition potential gradually increased to the negative direction, the photoelectric conversion efficiency and the current density increased of Cu2O films were increased. In addition, the preparation of semiconductor thin films were p-type semiconductor under different conditions in the alkalic system.(3) ZnO thin films were successfully deposited onto FTO conductive glass substrates by potentiostatic deposition. The electrolytes were zinc nitrate and methenamine solution. ZnO/Cu2O heterojunctions were successfully deposited onto ZnO thin films. The electrolytes were cupric sulfate solution and the pH values of the electrolytes were modulated by adding NaOH solution, lactic acid as complexing agent. The influence of the preparation on the properties of the thin films was studied. The results showed that when the deposition potential gradually increased to the negative direction, the energy gap of ZnO films were increased, which was opposite to the trend of the flat band potential. The photoelectric conversion efficiency was first increased and then decreased with the deposition potential gradually increased to the negative direction. When the deposition potential was-1V, the largest photoelectric conversion efficiency is 0.976%. With the increase of concentration of Zn2+, the diffraction peak of (002) crystal plan was gradually enhanced and the flake ZnO grains were increased gradually. When the deposition potential gradually increased to the negative direction, the diffraction peak of ZnO/Cu2O heterojunctions were enhancement, the Cu2O grains became denser and smaller, the thickness of ZnO/Cu2O heterojunction film was increased and the photoelectric conversion efficiency increased to 1.61%. With the increasing of pH, the Cu2O grains became larger, the thickness of ZnO/Cu2O heterojunction film was increased and the photoelectric conversion efficiency increased to 2.33%. |
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