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Preparation and microstructural characteristics of solar-grade multicrystalline silicon by directional solidification in an axial magnetic field

Published online by Cambridge University Press:  22 November 2019

Xiao-Hui Chen Open the ORCID record for Xiao-Hui Chen [Opens in a new window] ,
Senlin Rao  and
Fayun Zhang
Xiao-Hui Chen*
Affiliation:
School of Mechanical and Electrical Engineering, Xinyu University, Xinyu 338004, People’s Republic of China; and Key Laboratory of University in Jiangxi for Silicon Materials, Xinyu 338004, People’s Republic of China
Senlin Rao
Affiliation:
School of New Energy Science and Engineering, Xinyu University, Xinyu 338004, People’s Republic of China; and Key Laboratory of University in Jiangxi for Silicon Materials, Xinyu 338004, People’s Republic of China
Fayun Zhang*
Affiliation:
School of New Energy Science and Engineering, Xinyu University, Xinyu 338004, People’s Republic of China; and Key Laboratory of University in Jiangxi for Silicon Materials, Xinyu 338004, People’s Republic of China
*
a)Address all correspondence to these authors. e-mail: chenxiaohui058@163.com
b)e-mail: zfyabc@126.com
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Abstract

Solar-grade multicrystalline silicon ingots as raw material for solar cells were obtained from upgraded metallurgical silicon by directional solidification in an axial magnetic field. The influence of preparation technology on the microstructural characteristics of silicon ingots was investigated. Governing equations were used to simulate the silicon fluid flow and thermal fields during directional solidification. The results show that appropriately increasing melt temperature and/or decreasing pulling-down rate can be conductive to the growth of a coarse columnar grain. Meanwhile, the axial magnetic field promotes the formation of low-energy ∑3 twin boundaries and reduces the dislocations and impurities, where the total concentration of major metal impurities is with a mean of 0.459 ppmw in the range of 1/9 to 8/9 of height along the growth direction. It is shown from the simulation results that suppressing silicon melt flow in both radial and azimuthal directions and reducing the growth rate in the edge regions contribute to the formation of a flat solid–liquid interface, which is more consistent with the experimental results. Moreover, the formation mechanism of the twins and removal mechanism of the impurities were discussed.

Keywords

solar cellsmulticrystalline silicondirectional solidificationaxial magnetic fieldmicrostructural characteristics
Type
Article
Information
Journal of Materials Research , Volume 34 , Issue 23 , 16 December 2019 , pp. 3931 - 3945
Copyright
Copyright © Materials Research Society 2019 

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