Fully 3D modeling of a laboratory-scale DSS
The casting technique is widely used for producing multi-crystalline
silicon for solar cells (SCs). Crystallization front dynamics during casting
of silicon ingots (CSi) and flow characteristics in the melt affect the
quality of the multi-crystal, in particular, the dislocation density in
crystal grains, growth shape of grains, the content and uniformity of
impurities in silicon ingot. Below, 3D unsteady analysis of melt convection
in a squared mould, coupled with the calculation of the crystallization front
shape is illustrated.
3D features of the flow in CSi are due to moderate temperature gradients
along the melt free surface and in the melt, which appeared to be
sufficient to generate velocity fluctuations of about 1 cm/s in the large
melt volume. It has been found that the flow in squared moulds can be
essentially asymmetric, which is illustrated in Fig.2. In a cross section,
a stable large vortex can appear for a long time changing the geometry
of the crystallization front. However, it is mixing by intermediate scale flow
structures that is mostly observed in the melt and contributes to better
uniformity of impurities.
Advanced 2D and 3D modeling of Directional Solidification of multi-crystalline silicon ingots (UNDER CONSTRUCTION)
Detailed 3D heat transfer modeling of a Directional Solidification System is discussed in consulting section of the site.
Example of 2D unsteady modeling of DS of mc-Si
Verification of crystallization front predictions for DS m-Si
Figure ... Crystallization front profiles: comparison of experiment by SAS (left) and simulation results (right). Vertical cut of the ingot is 250x700x700 mm. Data is published in the paper: Y. Y. Teng et al., Proceedings of PVSEC-18 conference
Predictions of impurity segregation
Figure ... From “The carbon distribution of growing multicrystalline silicon ingot during the directional solidification process” by Ying-Yang Teng, Jyh-Chen Chen, Chung-Wei Lu, Chi-Yung Chen; IWMCG-6, Poster Number PVM 3
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