Fabrication And Property Of The AZO/Cu₂O Heterojunction Solar Cell

With the development of economy and society, the environment pollution and ecosystem destruction become more and more serious induced by the consumption of the more and more fossil energy, therefore, it is necessary to explore and make use of the clean energy with non-polluting and renewable. As an inexhaustible clean energy, the solar energy has attracted a great attention, expecially the solar cell device which convert light energy into electrical energy. At present, the commercial solar cell based on silicon, cadmium telluride and copper indium gallium selenide have been commercialized. However, the high price, low efficiency and complicated technology have become the bottlenecks that restrict the popular application. It is a reasonable and reliable solution to explore a new-type solar cell with low cost, high efficiency and no pollution. In this paper, the solar cell based on the AZO/Cu2O heterojunction was fabricated by preparing Cu2O layer upon AZO with the electrochemical deposition method, and the interface controlling, structure optimization of the solar cell was systematically investigated. The main contents of the paper are illustrated as follows.Firstly, the ZnO nanoflowers structure has been successfully synthesized. The ZnO nanoflowers structure was successfully synthesized on Cu foil by thermal evaporation method and the effects of the gas flow ratio between oxygen and argon on structure and property of the ZnO nanoflowers were further studied. The results show that when the oxygen/argon gas flow ratio is 1:250, the ZnO nanoflowers contain uniform size and morphology with best flower structure. As the oxygen atmosphere decreasing, the ratio of the length to diameter of the ZnO nanorods on the ZnO nanoflowers decreases and the photoluminescence in visible region become from a wave packet into a broad peak. The defect photoluminescence related to the oxygen vacancy defects increase and related to the zinc vacancy defects decrease. Ultimately, a possible growth model of the ZnO nanoflower was proposed.Secondly, the performance of the AZO/Cu2O heteroj unction solar cell with different preferred crystal orientation of the Cu2O has been investigated. The Cu2O with preferred crystal orientation of (100), (110) and (111) have been successfully synthesized with the electrochemical deposition method by controlling the bath pH.And the AZO/Cu2O hetero junction solar cell has been constructed subsequently.Through testing and analysing on the optoelectronic properties of them, only the solar cell constructed with Cu2O (111) exhibits well-defined rectifying behavior and good photoelectric conversion efficiency. We thought that it may be ascribed to the AZO/Cu2O (111) heterojunction solar cells have the optimized energy band structure.Thirdly, the interface of the AZO/Cu2O heterojunction solar cell has been optimized by the intrinsic ZnO layer. The AZO/ZnO/Cu2O heterojunction solar cell has been fabricated by inserting ZnO buffer layer between AZO and Cu2O. And the performance of solar cell affected by annealing time of the ZnO buffer layer has been investigated. The performance of the solar cell improved obviously after annealing the ZnO buffer layers. When the annealing time prolonged, the short circuit current and conversion efficiency gradually increased, while the open circuit voltage and fill factor decreased. The best solar cell was obtained by annealing 2h at 500 ℃, in which the open circuit voltage is 152.89 mV, the fill factor is 0.35 and the conversion efficiency is 0.15%.Finally, a new-type solar cell based on AZO/ZnO NWs/PbS QDs/Cu2O has been constructed and investigated carefully. In this type solar cell, we make use of the PbS quantum dots which contained the advantage of the strong absorption properties in visible range. The open circuit voltage of the AZO/ZnO NWs/PbS QDs/Cu2O heterojunction solar cell increased 11%, comparing that of the AZO/ZnO NWs/Cu2O heterojunction solar cell.