Influence of Crucible Thermal Conductivity on Crystal Growth in Solidification Process

by Redthermo - 2020-01-08

Photovoltaics (PV) power generation is developing rapidly and the annual growth rate of PV installations is 44% during the past 10 years. Silicon-wafer based PV technology accounts for more than 90% of the total production and among them, 60% is multi-crystalline silicon (mc-Si). Directional solidification (DS) is the main method for manufacturing mc-Si ingots for solar cells. Complex heat and mass transport characteristics can influence the crystal growth of silicon ingots significantly. In this paper, we choose an industrial DS furnace that can produce 450kg ingots to numerically study the effects of thermal conductivity of thermal analysis crucible on silicon crystal growth.

through experiments, Transient global simulations were carried out in the DS process to investigate the influence of crucible thermal conductivity on heat transfer and silicon crystal growth. It is found that increasing the thermal conductivity can decrease the melting and growing time, which means that large thermal conductivity is helpful for saving both production time and electrical energy. However, high-temperature gradient and locally concave melt crystal interface under the condition of large thermal conductivity are likely to cause high thermal stress and dislocation propagation. Therefore, crucibles with large and small thermal conductivity at the bottom and sidewalls respectively should be used.