CN101302012A

CN101302012A - Purification process of photovoltaic silicon for solar cell

Info

Publication number: CN101302012A
Application number: CNA2007101071201A
Authority: CN
Inventors: 黄东; 赵晓江; 潘振宇
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-08
Filing date: 2007-05-08
Publication date: 2008-11-12

Abstract

The invention provides a technology for purifying polycrystalline silicon used for a solar cell. Along with the increment of temperature, either a solid body or a fusant can perform a series of chemicophysical actions in the process of melting metallic silicon. Along with the change of the temperature, impurities in the metallic silicon can generate fusion, dephlegmation and other phenomena in different degrees, which have important influences on melting loss, quality and purity of the metallic silicon. Fusing coefficient and dephlegmation coefficient of each element in the metallic silicon are different, which is the fundamental reason to the changes of the polycrystalline silicon. During the process of purifying the polycrystalline silicon, controlled fusion and directional solidification are performed to the impurities in fused silicon, thereby effectively removing certain detrimental impurities. The method mainly solves the technical problems of effectively removing Fe (iron), Al (aluminium), Ca (Calcium) and other impurities in the metallic silicon, and improving the purity of silicon, thereby meeting the purity requirement of the solar cell on the silicon.

Description

Purification process of photovoltaic silicon for solar cell

Affiliated technical field:

The present invention relates to the purifying technique of a kind of photovoltaic silicon for solar cell (polysilicon) material. this material is applied to electronics proprietary material and solar cell power generation field.

Solar cell is a kind of device of human use's sun power, and it utilizes the photovoltaic special efficacy sunlight directly should be transformed into electric energy, has only when solar light irradiation and just generates electricity, and therefore, must have a store battery to store electric power.At present, in the photocell commonly used a kind of be silion cell, its photoelectric transformation efficiency can reach 11%-16%.Photovoltaic effect abbreviates photovoltaic effect as, refers to that illumination makes the phenomenon that produces potential difference between the different sites of inhomogeneos semiconductor or semi-conductor and metallic combination.Photovoltaic silicon is the important intermediates in the solar energy industry chain, is the base mateiral of information technology and new forms of energy industry.

Background technology:

Photovoltaic silicon (polysilicon) purifying technique, remove U.S. AsiMi, SGS and MEMC company and adopt the silane decomposition purifying technique, account for the nearly 20% of total amount, all the other each companies are " Siemens process method-hydrogen reduction of trichlorosilane ", account for 80% of total amount, occupy dominant position.

The Siemens Method purifying technique is to be invented by Siemens in later stage nineteen fifties, gains the name thus.Continuous improvement surplus 50 year, technical maturation, reliable.But Siemens Method technology mainly is to take into account with production technology with electronics to be used for producing photovoltaic silicon.Need to use toxic gas-chlorine and explosion hazard gases-hydrogen to reduce in the purification process of this technology and produce high-purity polycrystalline (photovoltaic silicon), need the chlorine of a whole set of complex and expensive, the retrieving arrangement of hydrogen in the equipment, destroy environment to avoid above-mentioned toxic gas in air, to discharge.At present, China does not grasp the recovery and utilization technology of toxic gas in this technology as yet, and western countries carry out blockade on new techniques to China.

Summary of the invention:

No matter Pure Silicon Metal along with the rising of temperature, is solid or melt in fusion process, all a series of physics chemical action can take place.Along with variation of temperature, the impurity in the Pure Silicon Metal can produce phenomenons such as in various degree fusion, fractional condensation, this melting loss to Pure Silicon Metal, quality and purity important influence.The fusing coefficient of each element is different with segregation coefficient in the Pure Silicon Metal, is the fundamental cause that photovoltaic silicon composition changes.In the process that photovoltaic silicon is purified, the impurity in the molten silicon there are control fusion and directional freeze, can remove some detrimental impurity effectively.

The technical problem that the present invention mainly solves is effectively to remove Fe in the Pure Silicon Metal (iron), Al (aluminium), Ca impurity such as (calcium), improves the purity of silicon, so that reach the purity requirement of silicon for solar cell.

The main technological route that the present invention takes is as follows:

1, by 4N HIGH-PURITY SILICON → sun power photovoltaic silicon, mainly by the physical method of directional freeze, the solid phase silicon and the liquid-phase silicone velocity of transformation of control silicon melt (1500 ℃-1600 ℃) help the condition that impurity is separated out thereby create one from silicon.

2, according to the segregation coefficient of different impurities, accurate controlled temperature, the effect of segregation of application impurity is separated impurity in liquid-phase silicone, carry out the impurity separation thereby reach with directional solidification process, improves silicon purity.

This technology is present domestic blank, and the someone develops as yet.Compare with other similar technologies and to have following characteristics:

A. simple to operate.

B. do not use toxic gas

C. there are not waste residue, waste gas, waste water, environment friendly and pollution-free

D. facility investment is few, is 1/10th of other facility investments.

Embodiment:

The present invention utilizes the different segregation coefficients and the proportion of metallic element, with condensing of different temperature range control elements, thereby element is separated, and makes impurity drop to the bottom or rises to the top, reaches the purpose that impurity elimination is purified.

Further specify implementation process of the present invention as follows in conjunction with Figure of description:

Step 1,

Solid 4N HIGH-PURITY SILICON (160 kilograms) is put into special plumbago crucible, insert by in the computer-controlled purification furnace.This purification furnace is the double-deck hollow closed structure of stainless steel, the heating in medium frequency mode.

Step 2,

In body of heater, inject protective gas-argon gas, and make it to inject, discharge, keep circulation, to guarantee in the stove being anaerobic state from venting port by gas injection port.

Step 3,

Between the double-deck hollow layer of purification furnace, inject recirculated water, with coupled computer to temperature controlling in the stove.

Step 4,

Temperature in the stove was heated to 1600 ℃ gradually in 9 hours, so that the fusion of solid HIGH-PURITY SILICON is a liquid.

Step 5,

Temperature reaches 1600 ℃ in stove, and solid HIGH-PURITY SILICON (1410 ℃ of fusing points) is when becoming liquid, and harmful element Fe wherein (1535 ℃ of iron fusing points), Al (660.37 ℃ of aluminium fusing points), Ca (839 ℃ of calcium fusing points) etc. are fused liquid.Kept temperature 2 hours, so that Fe (iron proportion is 7.86g/ml), Al (aluminum ratio heavily is 2.7g/ml) sedimentation downwards, Ca (calcium proportion is 1.49g/ml) upwards suspends; And Si (silicon proportion is 2.33g/ml) is in fused liquid stage casing.

Step 6,

Stop heating,, upwards reduce temperature gradually from crucible bottom by computer control.The method that realizes is that crucible bottom is equipped with a water pond, and the temperature of the cooling circulating water in the water pond, flow are by computer control.

Step 7,

From crucible bottom begin the from bottom to top directional freeze of liquid gradual slow because temperature begins to reduce this moment.

Step 8,

In 10-12 hour with stove in temperature reduce to normal temperature gradually from 1600 ℃, solid phase silicon generates.

Step 9,

With epidermis (impure part) excision around the cooled silicon ingot, keep the high middle portion of silicone content and be sun power photovoltaic silicon.

Claims

1. purification process of photovoltaic silicon for solar cell.It is characterized in that: 1500 ℃ of-1600 ℃ of temperature, utilize the effect of segregation of impurity that the detrimental impurity in the molten silicon is separated with silicon in liquid state, reach the purpose that impurity elimination is purified.

2. purification process of photovoltaic silicon for solar cell according to claim 1 is characterized in that: temperature in the stove was heated to 1600 ℃ gradually in 9 hours, so that the fusion of solid HIGH-PURITY SILICON is a liquid.By computer control, upwards reduce temperature gradually from crucible bottom.The method that realizes is that crucible bottom is equipped with a water pond, and the temperature of the cooling circulating water in the water pond, flow are by computer control.