Numerical Study of the Thermal and Flow Fields during the Growth Process of 800 kg and 1600 kg Silicon Feedstock

Thi Nguyen,Bruce Hsu,Chieh Hu,Jyh Chen,Ray Yang,Yen Huang,Huang Lin,Michael Yang,Andy Yu,Chun Chen

doi:10.3390/cryst7030074

Abstract

Two-dimensional (2D) transient numerical simulations are performed to investigate the evolution of the thermal and flow fields during the growth of multi-crystalline silicon ingots with two different silicon feedstock capacities, 800 kg and 1600 kg. The simulation results show that there are differences in the structure of the melt flow. In the 1600 kg case, there is a reduction in the concavity of the crystal-melt interface near the crucible wall and an increase in the convexity of the interface at higher solidification fractions. Moreover, the Voronkov ratios, which are indicative of the formation of defects, become lower during the solidification process.

Highlights

Nowadays, multi-crystalline silicon solar cells hold the highest market share worldwide.To increase productivity and lower production costs, increasing attention is being paid to the development of techniques for growing larger-sized mc-Si crystals using the photovoltaic (PV) industry.Control of the temperature distribution and flow within the melt is very important for the growth of large-sized ingots due to their effects on impurity transport and defect formation during the growth process
The flow pattern will significantly led to an increase in the temperature gradient inside the melt and, the intensity of the upper affect the distribution of impurities along the c-m interface during the growth process
The flow pattern will significantly affect the distribution of impurities along strength and smaller size of the resultant buoyancy vortex (2) helped to reduce the impurity the c-m interface during the growth process

Summary

Introduction

Multi-crystalline silicon (mc-Si) solar cells hold the highest market share worldwide.To increase productivity and lower production costs, increasing attention is being paid to the development of techniques for growing larger-sized mc-Si crystals using the photovoltaic (PV) industry.Control of the temperature distribution and flow within the melt is very important for the growth of large-sized ingots due to their effects on impurity transport and defect formation during the growth process. Teng et al [1] analyzed the effects of the flow pattern and the crystalline front on the carbon distribution during the growth of a 250 kg mc-Si ingot at different solidification fractions. Their results showed that the structure of the flow in the melt changed at different solidification fractions, with two main vortices, which affected the homogeneity of the carbon content. The appearance of two main convection cells in the bulk melt has been reported [2,3,4]

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Conclusion