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Method for preparing high-purity polycrystalline silicon under action of electric field and fused salt

A polycrystalline silicon and molten salt technology, applied in the growth of polycrystalline materials, chemical instruments and methods, single crystal growth, etc., can solve the problems of easy reaction with molten silicon liquid, difficult to avoid electrodes, etc., to enhance the impurity removal effect, The effect of reducing the cutting length and reducing the impurity concentration

Inactive Publication Date: 2012-10-03
上海太阳能电池研究与发展中心
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method is suitable for large-scale production, but the graphite electrode is in direct contact with the silicon liquid, and it is easy to react with the molten silicon liquid. It is difficult to prevent impurities in the electrode from entering the silicon liquid, thereby affecting the purification effect.

Method used

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  • Method for preparing high-purity polycrystalline silicon under action of electric field and fused salt
  • Method for preparing high-purity polycrystalline silicon under action of electric field and fused salt

Examples

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Embodiment 1

[0033] Example 1 as figure 1 In the method of adding molten salt shown, a flat cathode electrode 9 is set at the inner bottom of the crucible 1, and then 2.4Kg of high-density molten salt 4 is added to the crucible. The high-density molten salt uses CaO-SiO with a mass ratio of 3:3:4. 2 -CaF 2 , and then add 10Kg silicon material 2 above the molten salt. Above the silicon material 2, a flat anode electrode 8 is set at a distance from the surface of the silicon material, and the position of the flat anode electrode can be adjusted by a lifting device (in figure 1 not pictured). The flat anode electrode 8 is connected to the positive pole of the DC power supply 7 with the wire 6, and the flat cathode electrode 9 is connected to the negative pole. The flat anode electrode 8 and the flat cathode electrode 9 are made of high-purity graphite, and the wire 6 is made of high-purity molybdenum wire. When arranging the electrodes, pay attention to make the direction of the electric ...

Embodiment 2

[0037] Embodiment 2: with figure 1 In the way of adding molten salt shown, the high-density molten salt 4 uses SiO with a mass ratio of 17:2:1 2 -Al 2 o 3 -K 2 O, the addition amount is 2.4Kg, and the small-density molten salt 3 adopts Si with a mass ratio of 1:6:4 3 N 4 -KCl-MgCl 2 , the add-on is 2.5Kg, the silicon material add-on is 10Kg, all the other steps are with embodiment 1.

Embodiment 3

[0038] Embodiment 3: with figure 1 The method of adding molten salt is shown as an example. The high-density molten salt 4 uses BaCO with a mass ratio of 10:3:4. 3 -SiO 2 -MgF 2 , the addition amount is 2.6Kg, and the small-density molten salt 3 adopts SiO with a mass ratio of 3:4:3 2 -NaHCO 3 -KCl. Add-on amount is 2.4Kg, silicon material add-on amount is 10Kg, all the other steps are the same as embodiment 1. Examples 2 and 3 also obtained high-purity polysilicon ingots.

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Abstract

The invention discloses a method for preparing high-purity polycrystalline silicon under the action of electric field and fused salt. The method specially comprises the steps that: in the growth process of directionally condensed crystals of polycrystalline silicon, a fused salt layer is arranged between a silicon solution and an electrode so as to separate the electrode from the silicon solution, impurities in the silicon solution fast shift towards the electrode under the action of the electric field, and can react with fused salt so as to be absorbed when arriving at the boundary of the fused salt and the silicon solution, and the fused salt layer protects the electrode from being corroded by the silicon solution. By the method, not only can the electrode be prevented from being polluted by the silicon solution, but also the impurity removal capability of the directional solidification process and the utilization rate of a silicon ingot can be improved.

Description

technical field [0001] The invention relates to the preparation of high-purity polysilicon materials, specifically a method for preparing high-purity polysilicon under the action of an electric field and molten salt. Background technique [0002] As the main raw material of silicon-based solar cells, polysilicon is in increasing demand with the rapid development of the photovoltaic industry. The current (improved) Siemens method is the main method for producing high-purity polysilicon. Although the polysilicon obtained by this method has high purity, it has disadvantages such as high energy consumption, high production cost, environmental pollution, large investment scale, and long construction period. In order to further reduce production costs, some new technologies and methods for preparing solar-grade polysilicon have been developed rapidly in recent years. Among many new processes, directly purifying metallurgical-grade industrial silicon to solar-grade silicon through...

Claims

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Application Information

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IPC IPC(8): C30B30/02C30B11/00
Inventor 褚君浩徐璟玉蒋君祥熊斌丁杰戴宁
Owner 上海太阳能电池研究与发展中心
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