Effect of Argon Flow on Oxygen and Carbon Coupled Transport in an Industrial Directional Solidification Furnace for Crystalline Silicon Ingots

Xiaofang Qi,Wenjia Su,Lijun Liu,Wencheng Ma,Yiwen Xue

doi:10.3390/cryst11040421

Xiaofang Qi, Wenjia Su + Show 3 more

Open Access

https://doi.org/10.3390/cryst11040421

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Journal: Crystals	Publication Date: Apr 14, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: Jiangsu University, Xi'an Jiaotong University

Abstract

Transient global simulations were carried out to investigate the effect of argon flow on oxygen and carbon coupled transport in an industrial directional solidification furnace for quasi-single crystalline silicon ingots. Global calculation of impurity transport in the argon gas and silicon melt was based on a fully coupled calculation of the thermal and flow fields. Numerical results show that the argon flow rate affects the flow intensity along the melt–gas surface, but has no significant effect on the flow patterns of silicon melt and argon gas above the melt–gas surface. It was found that the evaporation flux of SiO along the melt–gas surface decreases with the increasing argon flow rate during the solidification process. However, the net flux of oxygen atoms (SiO evaporation flux minus CO dissolution flux) away from the melt–gas surface increases with the increasing argon flow rate, leading to a decrease in the oxygen concentration in the grown ingot. The carbon concentration in the grown ingot shows an exponential decrease with the increase of the argon flow rate, owing to the fact that the dissolution flux of CO significantly decreases with the increasing argon flow rate. The numerical results agree well with the experimental measurements.

Highlights

Quasi-single crystalline silicon ingots grown by the seeded directional solidification (DS) technique are one of the main materials for solar cells, and have lower cost and a less favorable crystalline structure compared to the monocrystalline silicon
Considering that the extreme ones, 5 and 70 L/min, are rarely used in the real industrial DS process for quasi-single crystalline silicon ingots, only the middle three cases were analyzed and presented in order to control the length of the paper
L/min, are rarely used in the real industrial DS process for quasi‐single crystalline silicon ingots, only the middle three cases were analyzed and presented in order to control the length of the paper

Summary

Introduction

Quasi-single crystalline silicon ingots grown by the seeded directional solidification (DS) technique are one of the main materials for solar cells, and have lower cost and a less favorable crystalline structure compared to the monocrystalline silicon. Considerable research has been carried out to control the oxygen and carbon concentrations and transport during the DS process, such as hot-zone design of furnace and optimization of operating parameters The former method is dedicated to the configuration or the material of the local components, such as gas flow guidance device [5,6,7,8,9], graphite heaters [10,11], crucible cover [12,13,14] and heat exchanger block [15], to control. After obtaining the global thermal and flow fields, coupled oxygen and carbon transport in the whole furnace based on five major chemical reactions [16,19]. The boundary conditions for the impurity species transport in the silicon and argon gas regions are as follows:.

Effect on Heat Transfer

Effect

Oxygen

Conclusions