Separation and Recovery of Refined Si from Al-Si Melt by Modified Czochralski Method.

Jingwei Li,Jian Shi,Yinhe Lin,Boyuan Ban,Woochul Yang,Guicheng Liu,Juncheng Li,Jian Chen

doi:10.3390/ma13040996

Abstract

Separation of refined silicon from Al–Si melt is still a puzzle for the solvent refining process, resulting in considerable waste of acid and silicon powder. A novel modified Czochralski method within the Al–Si alloy is proposed. After the modified Czochralski process, a large amount of refined Si particles was enriched around the seed crystalline Si and separated from the Al–Si melt. As for the Al–28%Si with the pulling rate of 0.001 mm/min, the recovery of refined Si in the pulled-up alloy (PUA) sample is 21.5%, an improvement of 22% compared with the theoretical value, which is much larger 1.99 times than that in the remained alloy (RA) sample. The content of impurities in the PUA is much less than that in the RA sample, which indicates that the modified Czochralski method is effective to improve the removal fraction of impurities. The apparent segregation coefficients of boron (B) and phosphorus (P) in the PUA and RA samples were evaluated. These results demonstrate that the modified Czochralski method for the alloy system is an effective way to enrich and separate refined silicon from the Al–Si melt, which provide a potential and clean production of solar grade silicon (SoG-Si) for the future industrial application.

Highlights

With the aggravation of environmental pollution and energy shortage, the development of clean and green energy, especially solar energy, is being increasingly emphasized all over the world
It is necessary to remove the impurities from the metallurgical grade silicon (MG-Si) and obtain high purity silicon for higher photovoltaic conversion efficiency
Czochralski process, large amounts of refined silicon particles were enriched around the seed

Summary

Introduction

With the aggravation of environmental pollution and energy shortage, the development of clean and green energy, especially solar energy, is being increasingly emphasized all over the world. The main material for solar cells is crystalline silicon, which accounts for more than 90% of the total cost [1,2]. Impurities in solar grade silicon (SoG-Si) can seriously decrease the efficiency of photovoltaic conversation [3,4]. It is necessary to remove the impurities from the metallurgical grade silicon (MG-Si) and obtain high purity silicon for higher photovoltaic conversion efficiency. 90% of Si-based solar cells globally are produced by the Siemens method [2]. The Siemens method as the main technology is not environmentally friendly, resulting in considerable pollution. In order to obtain low energy consumption and clean production, and improve the removal efficiencies of impurities, a series of purification methods of SoG-Si from MG-Si, such as solvent refining [5,6], Materials 2020, 13, 996; doi:10.3390/ma13040996 www.mdpi.com/journal/materials

Methods

Discussion

Conclusion