Research On Preparation And Properties Of SiN/a-Si/poly-Si/NiTi Thin Films For Solar Cell

In this thesis, summarized the present status and future development of semiconductor materials for solar cell applications, based on the properties of Si-based materials, SiN/a-Si/poly-Si/NiTi multilayer films were deposited by RF magnetron sputtering process. The microstructure, surface characteristics, optical and mechanical properties of the multilayer films were invesitgated by XRD, SEM, EDS, AFM, UV-Vis and scratch test methods.At first, the NiTi films were deposited on the quartz glass substrate and then the amorphous Si films were deposited on NiTi films by RF magnetron sputtering. The influences of main processing parameters of magnetron sputtering, such as substrate temperature, input power and gas pressure, on the film thickness, microstructure and surface characteristics, optical and mechanical properties of amorphous Si films were thoroughly investigated. The optimized deposition parameters of amorphous Si films were obtained, namely substrate temperature: 400℃, input power: 100-150W, gas pressure: 1.0Pa, Ar flowrate ratio: 10sccm, depositing time: 1h. Excellent surface characteristics, optical and mechanical properties were exhibited with these parameters.Secondly, based on the optimized deposition parameters, a-Si/NiTi, a-Si/Ti and a-Si films were deposited by RF magnetron sputtering. According to the principle of metal induced crystallization (MIC), the effect of different annealing conditions on the crystallization characterization, optical and mechanical properties of these films were explored. The results indicate that the Si begins to crystallize at 600℃. The crystallinity, as well as grain size of Si, is increased; the optical and mechanical properties are also increased with increasing annealing temperature. Meanwhile, the crystallization mechanism of NiTi induced crystallization was discussed.Finally, by combining the principle of energy bandgap theory and optical absorption principle of semiconductor materials as well as thermal annealing technology, a novel structure of"amorphous-polycrystalline"SiN/a-Si/poly-Si/NiTi films were fabricated. The results indicate that the optical and mechanical properties are increased because of multilayered structure and SiN antireflection coating.