Abstract
The preservation of seed crystals is important for the casting of quasi-single crystalline (QSC) silicon ingots. We carried out transient global simulations of the feedstock melting process in an industrial-sized directional solidification (DS) furnace to investigate key factors influencing seed preservation. The power distribution between the top and side heaters is adjusted in the conventional furnace for multicrystalline silicon ingots and in the evolved furnace with a partition block for QSC silicon ingots. The evolution of the solid-liquid interface for melting and the temperature distribution in the furnace core area are analyzed. The power distribution can influence the temperature gradient in the silicon domain significantly. However, its effect on seed preservation is limited in both furnaces. Seed crystals can be preserved in the evolved furnace, as the partition block reduces the radiant heat flux from the insulation walls to the heat exchange block and prevents the heat flowing upwards under the crucible. Therefore, the key to seed preservation is to control radiant heat transfer in the DS furnace and guarantee downward heat flux under the crucible.
Highlights
Quasi-single crystalline (QSC) silicon ingots have been popular in photovoltaic applications recently because of their lower manufacturing cost, higher throughput, and higher conversion efficiency for solar cells [1]
The QSC silicon ingot is cast by directional solidification (DS) technology evolved from the conventional DS method for multicrystalline silicon ingots [2]
We numerically investigate the effects of power distribution and partition block design on seed preservation in the melting process
Summary
Quasi-single crystalline (QSC) silicon ingots have been popular in photovoltaic applications recently because of their lower manufacturing cost, higher throughput, and higher conversion efficiency for solar cells [1]. It is necessary to investigate factors that could affect seed preservation during feedstock melting for growing single crystals and reducing costs. Ma et al [1], Yu et al [3], Black et al [4], and Gao et al [5] numerically investigated heat and mass transport in the crystal growth process They provided advice for controlling the temperature distribution, growth rate, solid-liquid interface shape, and impurity transport and for improving ingot quality. Witting et al [8], Tachibana et al [9], and Tsuchiya et al [10] tried to establish the mechanisms of defect generation in the QSC silicon ingots These studies are helpful for understanding the casting process and improving the quality of QSC silicon ingots. We numerically investigate the effects of power distribution and partition block design on seed preservation in the melting process
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