堆积硅料的阶跃分布孔隙率对准单晶铸锭过程籽晶熔化的影响

摘要/Abstract

摘要： 本文针对光伏太阳能用准单晶硅铸锭系统的硅料熔化过程进行了数值模拟研究,尤其是孔隙率阶跃分布的堆积硅料熔化过程对籽晶熔化的影响。研究结果表明:堆积硅料孔隙率呈轴向阶跃分布有利于降低籽晶的熔化比例;籽晶的熔化界面形状主要受下层孔隙率影响,在特定的平均孔隙率范围内,上下两层孔隙率差异较小时,孔隙率的轴向阶跃分布对籽晶的熔化界面形状影响较小;当籽晶的熔化比例相近时,平均孔隙率越小,籽晶的熔化界面形状越平缓,越有利于籽晶边缘区域的保留;当平均孔隙率一定时,下层孔隙率越小越有利于籽晶边缘区域的保留。堆积硅料区域孔隙率呈径向阶跃分布会使籽晶的熔化界面形状发生畸变,内层孔隙率的逐渐增大会使籽晶的熔化界面形状由“凸”逐渐转变为“凹”,外层孔隙率不大于内层孔隙率时籽晶可以得到有效保留;内外两层孔隙率差值越小,籽晶的熔化比例越小。籽晶的熔化比例分布在不同轴向阶跃分布孔隙率下呈现一定的中心对称性,而在不同径向阶跃分布孔隙率下呈现一定的周期性,孔隙率均匀分布时的籽晶熔化界面形状优于其他情况。在实际工况条件下,可以根据由不同孔隙率分布条件下获取的籽晶熔化状态数据绘制的等值线图对堆积硅料区域的孔隙率分布进行合理配置。

关键词: 准单晶硅铸锭, 阶跃分布孔隙率, 籽晶熔化, 堆积硅料, 界面形状, 熔化状态

Abstract: This paper presents numerical studies of the melting process of stacked silicon with step porosity distribution, specifically its effect on seed crystal melting during quasi-single crystalline silicon casting for photovoltaic applications. The results show that an axial step porosity distribution in stacked silicon leads to a reduced melting ratio of the seed crystal. And the interface shape after seed crystal melting is mainly determined by the porosity at the lower part of the stacked silicon. In a specific range of the porosity, the axial step porosity distribution has little effect on the interface shape when the porosity difference between the upper and lower parts is small. For the situation with a similar melting ratio in the seed crystal, the interface shape of the seed crystal is flatter for a smaller average porosity. For the situation with a constant average porosity, a smaller porosity in the lower part of the stacked silicon is beneficial to the retention of the edge area of the seed crystal. The radial step porosity distribution dramatically influences the interface shape after seed crystal melting. As the porosity in the inner part of the stacked silicon increases, the interface shape changes from convex to concave after the seed crystal melting. To effectively retain the seed crystal, it is preferred to have the porosity in the outer part of the stacked silicon smaller than that of the inner part. And the size of the melting ratio of the seed crystal is directly related to the difference between the porosity at the outer and inner parts. The smaller the difference between the porosity at the outer and inner parts is, the smaller the melting ratio of seed crystals is. The melting ratio of seed crystal with axial step porosity distribution exhibits a certain symmetry, while that with radial step porosity distribution shows a certain periodicity. The interface shape after seed crystal melting is better under the uniform porosity distribution than others. Under the actual working conditions, the porosity distribution in the stacked silicon can be reasonably configured according to the contour map drawn by the melting state data of seed crystals obtained under different porosity distribution conditions. These findings provide guidelines for the optimal design of silicon stacking for the casting process.

Key words: quasi-single crystalline silicon casting, step porosity distribution, seed crystal melting, stacked silicon, interface shape, melting state

中图分类号:

O78
TQ127.2

孙英龙, 郑丽丽, 张辉. 堆积硅料的阶跃分布孔隙率对准单晶铸锭过程籽晶熔化的影响[J]. 人工晶体学报, 2023, 52(10): 1745-1757.

SUN Yinglong, ZHENG Lili, ZHANG Hui. Effect of Step Porosity Distribution of Stacked Silicon on Seed Crystal Melting During Quasi-Single Crystalline Silicon Casting Process[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2023, 52(10): 1745-1757.

参考文献

[1] MA X, ZHENG L L, ZHANG H, et al. Thermal system design and optimization of an industrial silicon directional solidification system[J]. Journal of Crystal Growth, 2011, 318(1): 288-292.
[2] GAO B, NAKANO S, HARADA H, et al. Reduction of polycrystalline grains region near the crucible wall during seeded growth of monocrystalline silicon in a unidirectional solidification furnace[J]. Journal of Crystal Growth, 2012, 352(1): 47-52.
[3] MA W C, ZHONG G X, SUN L, et al. Influence of an insulation partition on a seeded directional solidification process for quasi-single crystalline silicon ingot for high-efficiency solar cells[J]. Solar Energy Materials and Solar Cells, 2012, 100: 231-238.
[4] YU Q H, LIU L J, MA W C, et al. Local design of the hot-zone in an industrial seeded directional solidification furnace for quasi-single crystalline silicon ingots[J]. Journal of Crystal Growth, 2012, 358: 5-11.
[5] BLACK A, MEDINA J, PIÑEIRO A, et al. Optimizing seeded casting of mono-like silicon crystals through numerical simulation[J]. Journal of Crystal Growth, 2012, 353(1): 12-16.
[6] MA X, ZHENG L L, ZHANG H. System design and hot zone optimization of monocrystalline silicon directional solidification furnace for PV application[J]. Journal of Crystal Growth, 2014, 385: 28-33.
[7] LI Z Y, LIU L J, ZHANG Y F, et al. Preservation of seed crystals in feedstock melting for cast quasi-single crystalline silicon ingots[J]. International Journal of Photoenergy, 2013: 1-7.
[8] 李早阳, 刘立军, 余庆华. 准单晶硅铸锭过程中种晶的保存及其界面的控制[A].第八届中国太阳级硅及光伏发电研讨会[C].上海, 2012.
LI Z Y, LIU L J, YU Q H. Preservation of seed crystal and control of seed-melt interface during quasi-single crystalline silicon casting process[A].8th China SoG Silicon and PV Power Conference[C]. Shanghai, 2012 (in Chinese).
[9] 贾存龙. 独立控制隔热环对籽晶保护作用分析[J]. 河南科技, 2014(17): 74-75.
JIA C L. Analysis of protective effect of independent control heat insulation ring on seed crystal[J]. Journal of Henan Science and Technology, 2014(17): 74-75 (in Chinese).
[10] 余庆华, 刘立军, 钟根香, 等. 准单晶硅铸锭过程中凝固界面形状的控制[J]. 工程热物理学报, 2013, 34(3): 505-508.
YU Q H, LIU L J, ZHONG G X, et al. Control of solidification front shape during quasi-single crystalline silicon casting process[J]. Journal of Engineering Thermophysics, 2013, 34(3): 505-508 (in Chinese).
[11] 张运锋, 孟庆超, 刘磊, 等. 多晶硅铸锭过程中的籽晶熔化控制[J]. 电子技术与软件工程, 2017(15): 115.
ZHANG Y F, MENG Q C, LIU L, et al. Seed melting control in polycrystalline silicon ingot process[J]. Electronic Technology & Software Engineering, 2017(15): 115 (in Chinese).
[12] 孟庆超, 张运锋, 刘磊, 等. 准单晶硅铸锭过程中固液相变界面形状的控制[J]. 太阳能学报, 2015, 36(7): 1545-1549.
MENG Q C, ZHANG Y F, LIU L, et al. Melt-solid interface shape control in the casting process for quasi-single crystalline silicon ingots[J]. Acta Energiae Solaris Sinica, 2015, 36(7): 1545-1549 (in Chinese).
[13] 孙英龙, 郑丽丽, 张辉. 准单晶硅铸锭过程中加热功率及硅料堆积孔隙率对籽晶熔化的影响[J]. 人工晶体学报, 2022, 51(9/10): 1755-1768.
SUN Y L, ZHENG L L, ZHANG H. Effect of heating power and porosity of stacked silicon on seed crystal melting during quasi-single crystalline silicon casting process[J]. Journal of Synthetic Crystals, 2022, 51(9/10): 1755-1768 (in Chinese).