Method and device for reducing oxygen content of monocrystalline silicon

Abstract

The invention provides a method and device for reducing the oxygen content of monocrystalline silicon, and the method comprises the steps: electrically connecting a metal conductor with the positive electrode of a power supply, and electrically connecting the prepared monocrystalline silicon with the negative electrode of the power supply; the metal conductor and the monocrystalline silicon are inserted into an electrolyte for electrolysis, and in the electrolysis process, oxygen elements in the monocrystalline silicon and hydrogen ions in the electrolyte form water, so that the content of the oxygen elements in the monocrystalline silicon is reduced to a certain extent, and the risk that concentric circles exist at the ends of the cell pieces is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal silicon manufacturing, and particularly to a method and device for reducing the oxygen content in single crystal silicon. Background Art

[0002] In solar cells, single crystal silicon is mainly prepared by the Czochralski method. Among them, single crystal silicon has high requirements for defects. However, due to the quartz crucible, during the formation of single crystal silicon, it is contaminated by the quartz crucible, and there is inevitably a situation where the oxygen content is too high, which is reflected in the cell end as a risk of concentric circles.

[0003] Therefore, how to reduce the oxygen content in single crystal silicon is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0004] To solve the above problems, the inventor found the cause of the problem through research and formed a solution.

[0005] In a first aspect, the present invention provides a method for reducing the oxygen content in single crystal silicon. The method for reducing the oxygen content in single crystal silicon includes:

[0006] Electrically connect a metal conductor to the positive electrode of a power supply, and electrically connect the prepared single crystal silicon to the negative electrode of the power supply;

[0007] Insert the metal conductor and the single crystal silicon into an electrolyte for electrolysis, and after the electrolysis is completed, take out the single crystal silicon;

[0008] Wherein, the electrolyte contains hydrogen ions, and during the electrolysis process, the oxygen element in the single crystal silicon forms water with the hydrogen ions.

[0009] Further, in the above method for reducing the oxygen content in single crystal silicon, inserting the metal conductor and the single crystal silicon into the electrolyte for electrolysis includes:

[0010] Insert the metal conductor into the electrolyte based on a first preset depth, and insert the single crystal silicon into the electrolyte based on a second preset depth, and perform electrolysis based on a first preset electrolysis parameter;

[0011] After the electrolysis is completed based on the first preset electrolysis parameter, control the single crystal silicon to sink at a preset speed and perform electrolysis based on a second preset electrolysis parameter.

[0012] Further, in the above method for reducing the oxygen content in single crystal silicon, the first preset electrolysis parameter at least includes:

[0013] A first energization voltage, a first energization current, and a first energization duration;

[0014] The second preset electrolysis parameter at least includes:

[0015] The second energization voltage, the second energization current, and the second energization duration.

[0016] Furthermore, in the method for reducing the oxygen content of single crystal silicon described above, the first energization voltage is greater than the second energization voltage;

[0017] The first energization current is greater than the second energization current.

[0018] Furthermore, in the method for reducing the oxygen content of single crystal silicon described above, the preset speed is a preset proportion of the total length of the single crystal silicon sinking per minute.

[0019] Furthermore, in the method for reducing the oxygen content of single crystal silicon described above, the metal conductor is copper and the electrolyte is hydrochloric acid.

[0020] Furthermore, in the method for reducing the oxygen content of single crystal silicon described above, the concentration of the copper is greater than or equal to 99%;

[0021] The concentration range of the hydrochloric acid is 5% to 10%.

[0022] Furthermore, in the method for reducing the oxygen content of single crystal silicon described above, the temperature range of the electrolyte is 60° to 90°.

[0023] In a second aspect, the present invention provides a device for reducing the oxygen content of single crystal silicon. The device for reducing the oxygen content of single crystal silicon includes:

[0024] A power supply, wherein the negative electrode of the power supply is used for electrically connecting with the prepared single crystal silicon;

[0025] A metal conductor, electrically connected with the positive electrode of the power supply;

[0026] An electrolytic container, which has an electrolyte inside, and the metal conductor and the single crystal silicon are inserted into the electrolyte for electrolysis;

[0027] Wherein, the electrolyte contains hydrogen ions, and during the electrolysis process, the oxygen element in the single crystal silicon forms water with the hydrogen ions.

[0028] Furthermore, the device for reducing the oxygen content of single crystal silicon described above further includes:

[0029] A motion mechanism, fixedly connected with the single crystal silicon;

[0030] A controller, electrically connected with the motion mechanism, and used for controlling the motion mechanism to move based on a preset speed so as to drive the single crystal silicon to sink.

[0031] One or more of the above technical solutions of the present invention have at least one or more of the following beneficial effects:

[0032] When implementing the technical solution of the present invention, after preparing monocrystalline silicon, the monocrystalline silicon is electrically connected to the negative electrode of the power supply as the cathode, and a metal conductor is used as the anode and electrically connected to the positive electrode of the power supply. Then, the metal conductor and the monocrystalline silicon are inserted into the electrolyte for electrolysis, so that the oxygen element in the monocrystalline silicon reacts with the hydrogen ions in the electrolyte to form water, thereby reducing the content of oxygen element in the monocrystalline silicon to a certain extent and reducing the risk of concentric circles existing at the battery chip end. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Referring to the accompanying drawings, the disclosure of the present invention will become more readily understood. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, the reference numerals in the drawings are used to represent corresponding components, where:

[0034] Figure 1 is a schematic flow chart of a method for reducing the oxygen content in monocrystalline silicon according to an embodiment of the present invention;

[0035] Figure 2 is a schematic structural diagram of a device for reducing the oxygen content in monocrystalline silicon according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be made with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] In the description of the present invention, terms such as "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include at least one of such features. In addition, in the present invention, unless otherwise clearly defined and limited, terms such as "connected" and "coupled" should be understood in a broad sense. For example, they can be directly connected or indirectly connected through an intermediate medium, and can be the internal connection or interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] During the process of preparing monocrystalline silicon by the Czochralski method, due to the pollution of the quartz crucible, it can combine with vacancies to form microdefects or form oxygen precipitates, such as SiO 2, which leads to induced defects. When reflected at the cell end, there is a risk of concentric circles. As a kind of defect, concentric circles will not only reduce the conversion efficiency of monocrystalline silicon cells, but also cause degradation of photovoltaic modules, thereby reducing the yield rate of photovoltaic modules.

[0039] Therefore, to solve the above technical problems, the present invention provides the following technical solutions:

[0040] Figure 1 is a schematic flow chart of a method for reducing the oxygen content of monocrystalline silicon according to an embodiment of the present invention. As Figure 1 shown, the method for reducing the oxygen content of monocrystalline silicon may specifically include steps 101 to 102.

[0041] Step 101: Electrically connect the metal conductor to the positive electrode of the power supply, and electrically connect the prepared monocrystalline silicon to the negative electrode of the power supply;

[0042] In a specific implementation process, monocrystalline silicon can be prepared by the Czochralski method, and a specific implementation process can be as follows:

[0043] a. Put high-purity virgin polysilicon into a quartz crucible;

[0044] b. Put in a certain amount of master alloy fragments of phosphorus-silicon alloy;

[0045] c. The virgin polysilicon and the master alloy fragments are melted and mixed at high temperature to obtain molten silicon liquid;

[0046] d. Insert a seed crystal with a single crystal structure into the molten silicon liquid and slowly lift it;

[0047] e. The atoms on the surface of the molten silicon liquid will cool and solidify on the seed crystal and completely replicate the single crystal structure of the seed crystal. This process continues continuously, and by controlling parameters such as temperature and pulling speed, it grows into a silicon rod with a certain diameter.

[0048] After preparing the monocrystalline silicon, the prepared monocrystalline silicon can be connected to the negative electrode of the power supply, and the monocrystalline silicon is used as the cathode. And a prepared metal conductor can be connected to the positive electrode of the power supply, and the metal conductor is used as the anode. Among them, the purity of the metal conductor is as high as possible. The metal conductor can be copper, and its concentration is greater than or equal to 99%.

[0049] Step 102: Insert the metal conductor and the monocrystalline silicon into the electrolyte for electrolysis, and after the electrolysis is completed, take out the monocrystalline silicon.

[0050] In a specific implementation process, a required amount of electrolyte can be pre-placed in the electrolytic container. Among them, the electrolyte contains hydrogen ions, such as dilute hydrochloric acid, with a concentration range of 5% to 10% and a temperature range of 60° to 90°. Insert the metal conductor and single-crystalline silicon into the electrolyte and apply electricity for electrolysis. So that, during the electrolysis process, the oxygen element in the single-crystalline silicon forms water with the hydrogen ions, thereby achieving the purpose of removing the oxygen element in the single-crystalline silicon. After the electrolysis is completed, take out the single-crystalline silicon, wash it with pure water and dry it to obtain a single-crystalline silicon with a lower oxygen content.

[0051] Specifically, the chemical equation during electrolysis is as follows:

[0052] Anodic reaction:

[0053] Copper is used as the anode and undergoes an oxidation reaction during electrolysis, being dissolved into the electrolyte to generate copper ions Cu 2+ :

[0054] Cu - 2e - →Cu 2+ ;

[0055] Cathodic reaction:

[0056] Single-crystalline silicon is used as the cathode and undergoes a reduction reaction during electrolysis, thereby removing a certain amount of oxygen content:

[0057] SiO 2 +4H + +4e - →Si + 2H 2 O;

[0058] The overall reaction is as follows:

[0059] Cu + SiO 2 +4HCl → Cu Cl 2 +Si + 2H 2 O.

[0060] Based on the above chemical equation, for the prepared single-crystalline silicon, some SiO 2 in the single-crystalline silicon can be reduced to Si after electrolysis, reducing the oxygen content to a certain extent.

[0061] In the method for reducing the oxygen content of single-crystalline silicon in this embodiment, after the single-crystalline silicon is prepared, the single-crystalline silicon is electrically connected to the negative electrode of the power supply as the cathode, and a metal conductor is used as the anode and electrically connected to the positive electrode of the power supply. Then, the metal conductor and the single-crystalline silicon are inserted into the electrolyte for electrolysis, so that the oxygen element in the single-crystalline silicon reacts with the hydrogen ions in the electrolyte to form water, thereby reducing the content of the oxygen element in the single-crystalline silicon to a certain extent and reducing the risk of concentric circles existing at the battery chip end.

[0062] In a specific implementation process, the single-crystal silicon prepared by the Czochralski method is usually in a rod-like structure, and the oxygen content in different parts thereof is different. Among them, the oxygen content at the head position is the highest, followed by the middle part, and the lowest at the tail. Therefore, in order to balance the electrolysis rate and electrolysis energy consumption, the present invention also provides the following technical solutions:

[0063] Insert the metal conductor into the electrolyte based on a first preset depth, and insert the single-crystal silicon into the electrolyte based on a second preset depth. Electrolyze based on the first preset electrolysis parameters, and after completing electrolysis based on the first preset electrolysis parameters, control the single-crystal silicon to sink at a preset speed, and electrolyze based on the second preset electrolysis parameters. Wherein, the first preset electrolysis parameters at least include: a first energization voltage, a first energization current, and a first energization duration; the second preset electrolysis parameters at least include: a second energization voltage, a second energization current, and a second energization duration. The first energization voltage is greater than the second energization voltage; the first energization current is greater than the second energization current.

[0064] That is to say, the single-crystal silicon can be divided into a head, a middle part, and a tail. Insert the length corresponding to the head as the second preset depth into the electrolyte, and electrolyze with a relatively large energization voltage and energization current to increase the electrolysis speed. After electrolyzing the head of the single-crystal silicon for the first energization duration, the oxygen content of the head of the single-crystal silicon decreases, while the oxygen content of the middle part and the tail of the single-crystal silicon is relatively lower than that of the head of the single-crystal silicon. Therefore, in order to save energy, a relatively small energization voltage and energization current can be used, and the entire single-crystal silicon is gradually sunk at a preset speed. Wherein, the preset speed is a preset ratio of the total length of the single-crystal silicon sunk per minute. For example, the preset speed can be 1 / 30 of the length of the crystal bar sunk per minute. In this way, by reducing the energization current and energization voltage, the energy consumption in the entire electrolysis process is relatively small, and after electrolyzing for the first energization duration, the oxygen content of the head of the single-crystal silicon has decreased. After reducing the energization current and energization voltage, the total time of the entire electrolysis process will not increase much.

[0065] Furthermore, the present invention also provides a device for reducing the oxygen content of single-crystal silicon.

[0066] Figure 2 is a schematic structural diagram of a device for reducing the oxygen content of single-crystal silicon according to an embodiment of the present invention, as Figure 2As shown in the figure, the device for reducing the oxygen content in single crystal silicon may include a power supply 11, a metal conductor 12, and an electrolytic cell 13. Among them, the negative electrode of the power supply 11 is used to be electrically connected to the prepared 2, and the positive electrode of the power supply 11 is electrically connected to the metal conductor 12. The inside of the electrolytic cell 13 is filled with an electrolyte. The metal conductor 12 and the 2 can be inserted into the electrolyte, and electricity is passed through for electrolysis. Among them, the electrolyte contains hydrogen ions. During the electrolysis process, the oxygen element in the 2 forms water with the hydrogen ions, so as to achieve the purpose of reducing the oxygen content in the 2.

[0067] In a specific implementation process, the metal conductor 12 is copper, and the electrolyte is hydrochloric acid. The concentration of the copper is greater than or equal to 99%; the concentration range of the hydrochloric acid is 5% to 10%. The temperature range of the electrolyte is 60° to 90°.

[0068] For the device for reducing the oxygen content in the 2 of this embodiment, after the 2 is prepared, the 2 is used as the cathode and electrically connected to the negative electrode of the power supply 11, and the metal conductor 12 is used as the anode and electrically connected to the positive electrode of the power supply 11. Then, the metal conductor 12 and the 2 are inserted into the electrolyte for electrolysis, so that the oxygen element in the 2 reacts with the hydrogen ions in the electrolyte to form water, thereby reducing the content of oxygen element in the 2 to a certain extent and reducing the risk of concentric circles existing at the battery cell end.

[0069] In a specific implementation process, the device for reducing the oxygen content in the 2 may further include a motion mechanism (not shown in the figure) and a controller (not shown in the figure). Among them, the motion mechanism is fixedly connected to the 2; the controller is electrically connected to the motion mechanism.

[0070] In a specific implementation process, the metal conductor 12 can be inserted into the electrolyte based on a first preset depth, and the 2 can be inserted into the electrolyte based on a second preset depth, and electrolysis is carried out based on a first preset electrolysis parameter; after the electrolysis is completed based on the first preset electrolysis parameter, the controller controls the motion mechanism to move based on a preset speed to drive the 2 to sink based on a preset speed, and electrolysis is carried out based on a second preset electrolysis parameter. Among them, the first preset electrolysis parameter at least includes:

[0071] A second energization voltage, a second energization current, and a second energization duration. The first energization voltage is greater than the second energization voltage; the first energization current is greater than the second energization current.

[0072] In this way, by reducing the energization current and the energization voltage, the energy consumption during the entire electrolysis process is relatively small. And after the electrolysis for the first energization duration, the oxygen content at the head of the 2 has been reduced. After reducing the energization current and the energization voltage, the time taken for the entire electrolysis process will not increase much.

[0073] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easily understood by those skilled in the art that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A method for reducing the oxygen content of single crystal silicon, characterized in that: include: Electrically connecting the metal conductor to the positive electrode of a power source, and electrically connecting the prepared single crystal silicon to the negative electrode of the power source; inserting the metal conductor and the single crystal silicon into an electrolyte to perform electrolysis, and after the electrolysis is completed, taking out the single crystal silicon; The electrolyte contains hydrogen ions, and during the electrolysis process, the oxygen elements in the single crystal silicon form water with the hydrogen ions.

2. The method for reducing the oxygen content of single crystal silicon according to claim 1, characterized in that: Inserting the metal conductor and the single crystal silicon into an electrolyte for electrolysis, comprising: Inserting the metal conductor into the electrolyte at a first preset depth, inserting the single crystal silicon into the electrolyte at a second preset depth, and performing electrolysis based on first preset electrolysis parameters; After the electrolysis is completed based on the first preset electrolysis parameters, the single crystal silicon is controlled to sink based on a preset speed, and electrolysis is performed based on second preset electrolysis parameters.

3. The method for reducing the oxygen content of single crystal silicon according to claim 2, characterized in that: The first preset electrolysis parameters at least include: a first power-on voltage, a first power-on current, and a first power-on duration; The second preset electrolysis parameters at least include: a second energizing voltage, a second energizing current, and a second energizing time period.

4. The method for reducing the oxygen content of single crystal silicon according to claim 3, characterized in that: The first power-on voltage is greater than the second power-on voltage; The first power-on current is greater than the second power-on current.

5. The method for reducing the oxygen content of single crystal silicon according to claim 2, characterized in that: The preset speed is a preset ratio of the total length of the silicon monocrystalline that sinks per minute.

6. The method for reducing the oxygen content of single crystal silicon according to any one of claims 1 to 5, characterized in that: The metal conductor is copper, and the electrolyte is hydrochloric acid.

7. The method for reducing the oxygen content of single crystal silicon according to claim 6, characterized in that: The copper concentration is greater than or equal to 99%; The concentration of the hydrochloric acid ranges from 5% to 10%.

8. The method for reducing the oxygen content of single crystal silicon according to any one of claims 1 to 5, characterized in that: The temperature of the electrolyte ranges from 60° to 90°.

9. A device for reducing the oxygen content of single crystal silicon, characterized in that: include: A power source, wherein a negative electrode of the power source is used to be electrically connected to the prepared single crystal silicon; a metal conductor, electrically connected to the positive electrode of the power source; An electrolysis container having an electrolyte inside, wherein the metal conductor and the single crystal silicon are inserted into the electrolyte for electrolysis; The electrolyte contains hydrogen ions, and during the electrolysis process, the oxygen elements in the single crystal silicon form water with the hydrogen ions.

10. The device for reducing the oxygen content of single crystal silicon according to claim 9, characterized in that: Also includes: A motion mechanism, fixedly connected to the single crystal silicon; The controller is electrically connected to the motion mechanism and is used to control the motion mechanism to move based on a preset speed to drive the single crystal silicon to sink.

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