Preparation Of Microcrystalline Silicon Thin Films And Studies Of Their Photoelectrical Properties

At present, the energy crisis and environmental pollution attracted the attention of people all over the world, the green energy has been a hot topic of discussion. It is one of effective ways to solve confused problem in application of solar energy. The low cost in fabrication and the preparation of cell could be complete in the process of deposition are advantages for thin-film solar cell with respect to other solar cell. Compared with the traditional amorphous crystalline silicon solar cell, the microcrystalline silicon solar cell has the stable performance, it can extent the spectrum of absorption to infrared region. So it is a good material in solar cell. The microcrystalline silicon which has the perfect performance, not only can enhance the conversion efficiency of solar cell, but also can improve the stability of the material greatly. The study is a long process, for μc-Si:H thin films could show the ideal growth condition under which conditions, and how to optimize to exhibit the excellent optical and electrical properties. The research on μc-Si:H started early abroad, and it began at2000years domestic, so this technology is more mature. But there are still some phenomenons and mechanisms not to be-explained clearly. The author would launch his study in these aspects.The Microcrystalline silicon films were prepared by Radio Frequency plasma-enhanced chemical vapor deposition (RF-PECVD). By the means of X-ray diffraction, Raman spectroscopy, UV-visible light transmission spectrum, the infrared Fourier absorption spectra et al to characterize the properties of microcrystalline silicon thin film and research the effects of deposition parameters on structural properties, the optical properties and electrical properties in the process of the preparation of microcrystalline silicon. And the effects of deposition time on characterization and properties of the film materials were also discussed. At the same time, the properties of microcrystalline silicon thin film after traditional annealing treatment were analysed simply.1. By means of PECVD technology to prepare the microcrystalline silicon thin films. The film material was prepared under conditions of200℃substrate temperature,2.5cm electrode distance,100sccm total gas flow,0.7%silane concentration,400pa deposition pressure and130w radio frequency powers by debugging these deposition parameters. Using the X-ray diffraction spectrum to characterize structure of the material, the result shows the three characteristic peaks of the microcrystalline silicon.2. During the growth of the microcrystalline silicon thin film, it showed the thin films would exhibit longitudinal inhomogeneity. Due to the different measurement depth, at the characterizing of materials by X-ray diffraction and Raman spectroscopy, it will cause some miscalculation. More sensitive Raman spectroscopy to determine the crystalline fraction, XRD could get a better result to determine overall crystalline phase. Effective means to improve the deposition time is a way to more fully understand the properties of materials.3. Studied the effect of density of the high radio frequency power in the microcrystalline silicon growth process to the change of the grain size and evolution of the surface topography under conditions of a low substrate temperature and a high deposition pressure. And it showed that the growth of the microcrystalline silicon thin film as small grain cluster like, micro-cavity appeared in the films,with the high energy ion bombardment, the surface showed nonuniform.4. By the deployment of silane concentration and substrate temperature in the process of microcrystalline silicon preparation, it found a matching relationship between the two parameters based the surface diffusion mode theory. When the diffusion coefficient of ion is adapted to the activity of surface reaction, it would promote the deposition rate and the crystallization. According to the test of the optical and electrical properties of the microcrystalline silicon thin films, the experiment confirmed that the optical and electrical properties are affected by the crystal phase fraction. There was a contrary trend between the optical band gap and crystal phase fraction, and the change of conductivity was opposite to the crystal phase fraction.5. Applying the traditional annealing method to anneal the amorphous silicon which deposited by RF-PECVD to prepare the microcrystalline silicon thin film. And simply discuss the effect of annealing on properties of the film materials.