Polycrystalline silicon ingot and production method thereof

Abstract

The invention provides a production method of a polycrystalline silicon ingot, comprising: laying common seed crystal at the bottom center of a crucible to form a first seed crystal layer, and laying seed crystal with high-density crystal defect at the bottom of the crucible approximate to the sidewall of the crucible to form a second seed crystal layer; placing molten silicon material on the first seed crystal layer and the second seed crystal layer, and controlling the temperature of the bottom of the crucible so that the first and second seed crystal layers are not completely melted; controlling a heat field in the crucible to from a degree of supercooling, controlling the temperature in the crucible to rise gradually in a direction upwardly perpendicular to the bottom of the crucible to form a temperature gradient so that the melted silicon material crystallizes and solidifies, and annealing and cooling to obtain polycrystalline silicon ingot after complete crystallization.The silicon crystal density and impurity content of an edge area of the silicon ingot can be effectively reduced, and overall quality of the silicon ingot can be effectively improved.The invention also provides the polycrystalline ingot prepared using the method.

Description

technical field [0001] The invention relates to the field of polycrystalline silicon ingots, in particular to a polycrystalline silicon ingot and a preparation method thereof. Background technique [0002] At present, in the casting polycrystalline market, high-efficiency polycrystalline silicon wafers occupy a major position. High-efficiency polycrystalline casting mainly includes two methods: full-melt method and semi-melt method. After the material is melted, it nucleates and crystallizes on the seed crystal to form a polycrystalline silicon ingot. [0003] However, due to factors such as poor thermal conductivity of the crucible and unstable crystallization direction in the corner area of ​​the polycrystalline silicon ingot produced by the existing polycrystalline silicon casting method, the density of crystal defects in the edge area of ​​the silicon ingot is relatively high, resulting in the silicon ingot in this area. The conversion efficiency of the solar cell is lo...

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Problems solved by technology

[0003] However, due to factors such as poor thermal conductivity of the crucible and unstable crystallization direction in the corner area of ​​the polycrystalline silicon ingot produced by the existing polycrystalline silicon casting method, the density of crystal defects in the edge area of ​​the silicon ingot is relatively high, resulting in the silicon ingot in this area. The conversion efficiency of solar cells is low; in addition, the edge area of ​​the polycrystalline silicon ingot is polluted by the quartz crucible, the melt convection during the crystallization process is poor, and the impurity content in this area is high, which leads to the reduction of electrical properties.

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