【作者】 刘杰；

【导师】 罗玉峰；

【作者基本信息】 南昌大学 ， 精密仪器及机械， 2016， 硕士

【摘要】 太阳能是一种十分具有发展前景的可再生能源,具有无限制和无污染的特点,是解决能源和环境两大难题的有效方法。在太阳能电池领域中,多晶硅太阳能电池因为其低成本高效率的优势占据了重要的地位。多晶硅定向凝固铸锭技术是生产多晶硅太阳能电池的工艺中至关重要的环节。本文运用基于有限元方法的COMSOL Multiphysics软件,对多晶硅定向凝固过程的热场进行了全局瞬态模拟,分析了多晶硅铸锭炉顶部加热器与侧部加热器的垂直距离h分别为60 mm、150 mm和300 mm时,对多晶硅熔化以及结晶阶段的影响。结果表明:h为60 mm时硅料熔化所需时间最长,而h为150 mm和300 mm时硅料熔化时间与其相比分别要少34 min和60 min。对于结晶期间的固液界面,h为60 mm时固液界面接近于平面,有利于多晶硅晶体生长;h增加为150 mm时固液界面中间区域凸起程度增加,但并不十分明显;而h为300mm时固液界面呈现明显的凸形,会降低多晶硅锭的质量。本文还利用数值模拟技术对静态磁场下多晶硅定向凝固过程进行了一系列二维数值模拟,分别研究了横向磁场、轴向磁场和勾形磁场这三种场静态磁场对多晶硅定向凝固过程中熔体对流的影响。模拟分别在线圈电流设为0 A、10 A、20 A、30 A和40 A的情况下进行。结果表明:三种静态磁场均能有效的抑制熔体对流,其中轴向磁场主要抑制熔体水平方向的速度,横向磁场主要抑制熔体垂直方向的速度,勾形磁场对熔体水平方向和垂直直方向的速度都有抑制作用。当电流从0 A增加到40 A时,轴向磁场使得熔体最大流速减小了47.5%,横向磁场使得熔体最大流速减小了53.8%,而勾形磁场使得熔体最大流速减小了58.3%。可见,三种静态磁场中,勾形磁场对熔体对流的抑制作用最大。研究还发现,勾形磁场能够减小固液界面的曲率,改善杂质径向分布的均匀性。更多还原

【Abstract】 Solar energy as a great development prospects renewable energy, with unlimited and non-polluting characteristics, is an effective method to solve two major problems of energy and the environment. In the field of solar cells, multi-crystalline silicon solar cells occupy an important position for its advantages of low cost and high efficiency. The directional solidification casting technology of multi-crystalline silicon plays a vital important role in the process of production of multi-crystalline silicon solar cell.The transient global simulations of the directional solidification process for multi-crystalline silicon were carried out by COMSOL Multiphysics which is the software based on finite element method. The vertical distance between the top and side heater of the furnace for multi-crystalline silicon ingot was set to 60 mm, 150 mm and 300 mm to investigate its effect on multi-crystalline silicon melting and crystallization. It was found that the melting time is longest while the distance is 60 mm. When the distance is 150 mm and 300 mm, the melting time is respectively less than 34 min and 60 min compared with the situation that the distance is 60 mm. For the solid-liquid interface during crystallization, when the distance is 60 mm, the solid-liquid interface is similar to plane which is conducive to the growth of multi-crystalline silicon. While the distance is 150 mm, the central region of solid-liquid interface become more convex, but it is not very obvious. While the distance is 300 mm, the solid-liquid interface is obviously convex which is harmful to the quality of multi-crystalline silicon ingot.A series of two-dimensional numerical computations were conducted by numerical simulation technology to investigate the effects of three kinds of static magnetic field, including axial magnetic field, transverse magnetic field and cusp-shaped magnetic field, on the process of the directional solidification of multi-crystalline silicon. Numerical calculations were carried out when the current of coils were respectively set as: 0 A, 10 A, 20 A, 30 A and 40 A. The results showed that the three kinds of static magnetic field can effectively inhibit the melt convection,the axial magnetic field mainly inhibits the speed of melt in the horizontal direction,transverse magnetic field mainly inhibits the rate of melt in the vertical direction, cusp magnetic field can inhibit melt convection in both vertical direction and vertical direction. When the current increases from 0 A to 40 A, the axial magnetic field reduces the maximum flow velocity by 47.5%, the transverse magnetic field reduces the maximum flow velocity by 53.8%, while the cusp-shaped magnetic field reduces the maximum flow velocity decreases by 58.3%. It shows that cusp-shaped magnetic field has the biggest inhibitory effect on the melt convection among three kinds of static magnetic field. It is also found that cusp-shaped magnetic field can reduce the curvature of solid-liquid interface and improve the uniformity of radial distribution of impurities.更多还原