Phase Field Modeling of Growth Behaviors of Polycrystalline Silicon
Date Issued
2007
Date
2007
Author(s)
Chen, Peng
DOI
en-US
Abstract
In photovoltaic industry, polycrystalline silicon (poly-Si) is widely used as the material to manufacture the solar cell. However, the energy conservation of the solar cell is usually affected by the grain boundary density in the poly-Si due to the grain boundary will act as the photo-carrier in the cell. Thus, to decrease the grain boundary density is crucial to produce good quality poly-Si for solar cell. In general, the crystal growth environment will affect the quality of the crystal, and the computational simulation is used for studying the growth dynamics of the crystal.
In this thesis, we combine the polycrystalline phase field model proposed by Warren et al., with the highly anisotropic surface energy phase field model proposed by Eggleston et al. to study the growth behaviors of the polycrystalline silicon under different undercooling of the melt. According to the experimental observations from Fujiwara et al, when the undercooling is low enough, the (111) silicon will be the dominant orientation in the polycrystalline silicon. As the undercooling becomes much higher, the (100) will be the dominant orientation. To explain the behaviors, the mechanism of the grain selection between grains is the key to elucidate the whole problem.
According to Fujiwara et al., when the undercooling is low enough, the effect of the surface energy will dominate the grain selection mechanism. For the higher undercooling case, Atwater et al. explained that the kinetics effect will dominate the growth. In our simulations, we can reproduce the similar growth behaviors and morphologies from the experiments. Beside, from our qualitative analysis of the growth behaviors, the mechanism of the grain selection is mainly caused by the competition between the effect of the surface energy and the kinetic effect, and the undercooling serves as a factor to control the relative strength of the kinetic effect. In explaining the competitive growth behaviors of silicon, our conclusion shows good agreement with the explanations by Fujiwara et al. and Atwater et al.
Subjects
相場模式
熔體生長
多晶矽
晶體競爭生長機制
Phase-Field Model
Melt Growth
Polycrystalline Silicon
Competitive Growth Mechanism
SDGs
Type
thesis
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