离心铸造太阳电池硅片液态成形机制的研究

LIQUID FORMING MECHANISM FOR CENTRIFUGAL CASTING OF SOLAR CELL SILICON SHEET

为了将离心铸造技术成功地移植到低成本超薄多晶太阳电池硅片的成形工艺上，提出了ＥＬＣＣ技术的硅片液态成形方法，即将铸模型腔预热至硅熔点以上温度，过热的硅液被浇注到型腔后，在离心力的作用下始终保持液态充型。这种成形机制易于实现厚度小于１ｍｍ的硅片的完整成形，而且对模具转速、硅液过热度等要求较低。采用该方法，硅片的成形与结晶不会同时发生，可以在硅片液态成形后，采用定向凝固的方法获得粗大的定向柱晶组织，提高硅片的光伏性能。采用理论分析、计算机模拟与工艺实验相结合的方法，对ＥＬＣＣ技术硅片液态成形机制进行了研究，为进一步对硅片凝固过程组织控制的研究奠定基础。

The Electromagnetic Levitation melt Centrifugal Casting(ELCC)technology,which is based on the centrifugal casting and characterized by the containerless melting such as the electromagnetic levitation melting,is a kind of new hi technology for directly preparing the low cost solar cell silicon wafer.The centrifugal casting has been widely sued in the metal casting processing for producing the circle,case or pipe casting.In order to transplant the centrifugal casting to the silicon wafer processing,the liquid forming mechanism for centrifugal casting of solar cell silicon wafer is proposed.This means that preheating the mold cavity up to the temperature of silicon melting point and then pouring the superheating molten silicon into the cavith.The liquid silicon is pushed into the cavity by the centrifugal force.This method is easy to form the complete silicon wafer with less than 1 mm thickness and,has low the spinning rate of the mold and the superheating degree of the molten silicon.Moreover,with this method,the shaping and the crystallization of the silicon wafer will not happen at same time.Thus,when the silicon wafer is formed under liquid state,the directional solidification technique could be used to obtain the coarse directional columnar crystal microstructure,which is beneficial to the photovoltaic property of the silicon wafer. With the theoretical analysis,the computer simulation and the process experiment methods,this paper studies the liquid forming mechanism of silicon wafer for ELCC technology and makes provision for further research on the solidification microstructure control of the silicon sheet.