Method for electroplating copper and tin grid lines on solar cell

Abstract

The invention relates to the technical field of solar cell manufacturing, and discloses a method for electroplating copper and tin grid lines on a solar cell, which comprises the following steps of: S1, copper electroplating: putting a cell piece on an electroplating tool, and putting the cell piece into a copper liquid tank for electroplating copper layers on a P surface and an N surface; wherein a very-low-frequency power supply is adopted. And S2, cleaning the copper liquid on the battery piece. S3, tin electroplating: the battery piece after the copper liquid is cleaned is placed in a tin liquid tank for electroplating tin layers on the P surface and the N surface; wherein a very-low-frequency power supply is adopted. And S4, cleaning the tin liquid on the battery piece. And S5, the cleaned battery piece is taken out, and grid line electroplating is completed. The very-low-frequency power supply is used for replacing a silicon controlled rectifier direct-current power supply, and self-developed voltage and current parameters are matched, so that the compactness and the conductivity of the HDT high-efficiency single-crystal heterojunction solar cell on an electroplated metal grid line film layer are improved, and the conversion efficiency of a cell piece is improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell manufacturing, in particular to a method for electroplating copper and tin grid lines applied to HDT high-efficiency single-crystal heterojunction solar cells. Background Art

[0002] HDT high-efficiency single-crystal heterojunction solar cells have high photoelectric conversion efficiency and excellent performance. In order to further improve the performance of solar cells, it is necessary to electroplate metal conductive grid lines (copper, tin) on the surface of the cell to reduce resistance loss and increase the output power of the cell. At present, HDT high-efficiency single-crystal heterojunction solar cells usually use thyristor DC power supplies for electroplating when electroplating conductive grid lines. However, this electroplating method has large gaps between metal ions during ion plating, and is easily oxidized / corroded in the air. Therefore, this electroplating method performs poorly in providing conductive effects. The main reason is the presence of peaks and troughs during electroplating, as well as the influence of the quality of the thyristor DC power supply itself. This problem leads to poor density and conductivity of the electroplated metal grid lines. The specific analysis is as follows:

[0003] Peak and trough phenomenon: Since the thyristor DC power supply has peak and trough phenomena when working, the current fluctuates greatly, which affects the stability of the electroplating process and the quality of the electroplating layer.

[0004] Influence of its own quality: The performance, stability and life of the thyristor DC power supply are affected by its manufacturing process, component quality and other factors. Low-quality thyristor DC power supply may cause unstable current during the electroplating process, thus affecting the quality of the electroplating layer.

[0005] Large gaps between metal ions: When using a thyristor DC power supply for electroplating, due to the unstable current, the gaps formed when metal ions are deposited on the battery surface are large (700nm~1090um), which affects the density and conductivity of the electroplating layer.

[0006] Easy to oxidize / corrode: Due to the large gaps between metal ions in the electroplating layer, the electroplated metal grid lines are more easily oxidized or corroded in the air, further reducing the conductivity of the electroplating layer and the output power of the battery.

[0007] Therefore, it is necessary to provide a new electroplating method to improve the electroplating quality of the conductive grid lines of HDT high-efficiency single-crystal heterojunction solar cells, enhance their density and conductivity, and improve the conversion efficiency of the cells. Summary of the invention

[0008] To solve the above problems, the present invention provides a method for electroplating copper and tin grid lines on solar cells, which uses a very low frequency power supply to replace a thyristor direct current power supply and is combined with self-developed voltage and current parameters, thereby solving the peak and trough problems existing in the thyristor direct current power supply, improving the compactness and conductivity of the electroplated metal grid line (copper, tin) film layer of the HDT high-efficiency single crystal heterojunction solar cell, and improving the conversion efficiency of the battery cell.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The invention discloses a method for electroplating copper and tin grid lines for solar cells, the method comprising the following steps:

[0011] S1. Copper electroplating: Place the cell on the electroplating tooling and put it into the copper liquid tank to electroplate the copper layer on the P side and N side; a very low frequency power supply is used.

[0012] S2. Cleaning copper solution: After the copper electroplating is completed, the battery cell is placed in a cleaning solution for cleaning.

[0013] S3, electroplating tin: the battery cell after cleaning the copper liquid is placed in the tin liquid tank to electroplating tin layer on the P side and N side; a very low frequency power supply is used.

[0014] S4. Cleaning tin solution: After the tin electroplating is completed, the battery cell is placed in a cleaning solution for cleaning.

[0015] S5. Take out the cleaned battery cell and complete the gate line electroplating.

[0016] Furthermore, the frequency of the very low frequency power supply is 12KHZ.

[0017] Furthermore, in the step S1, the voltage of the electroplated copper P surface is set to DC: 30-35V, the current is set to 5-12A, the voltage of the N surface is set to 30-35V, the current is set to 2.6-8A, and the electroplating time is 40-50 minutes.

[0018] Furthermore, the voltage of the copper electroplating P side is set to 35V, the current is set to 12A, the voltage of the N side is set to 35V, the current is set to 2.6A, and the electroplating time is 45 minutes.

[0019] Furthermore, in step S3, the voltage of the electrotin-plated P surface is set to DC: 6V, the current is set to 3-4.5A, the voltage of the N surface is set to 6V, the current is set to 1.6-3A, and the electroplating time is 10-15 minutes.

[0020] Furthermore, the voltage of the tin-plated P side is set to 6V, the current is set to 4.2A, the voltage of the N side is set to 6V, the current is set to 1.6A, and the electroplating time is 10 minutes.

[0021] Furthermore, in the S1 copper electroplating step, before placing the battery cell in the copper liquid tank for copper electroplating, preliminary cleaning is performed first. The preliminary cleaning method is: placing the battery cell in deionized water for cleaning for 15 to 20 seconds, and then treating it in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

[0022] Furthermore, in step S2 of cleaning the copper solution and step S4 of cleaning the tin solution, the cleaning method is: placing the battery cell in deionized water for cleaning for 15 to 20 seconds, and then treating it in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

[0023] Furthermore, the solution contained in the copper liquid tank includes metal phosphor copper balls, copper sulfate solution and additives; the solution contained in the tin liquid tank includes phosphor tin balls, stannous methyl xanthate, methyl sulfonic acid solution and additives.

[0024] Furthermore, the cell is a HDT high-efficiency single-crystal heterojunction solar cell.

[0025] The benefits of the present invention are:

[0026] The present invention improves the compactness and conductivity of the electroplated metal grid line by using a very low frequency power supply for electroplating, and effectively improves the conversion efficiency of the solar cell. Under the same electroplating conditions, the conversion efficiency of the cell is increased by more than 0.158%, and better coating quality and product reliability are obtained. This method saves manpower and material resources, and improves production efficiency, and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the process flow chart of this embodiment.

[0028] Figure 2 This is a gap diagram of electroplating metal copper ions using a thyristor DC power supply.

[0029] Figure 3 This is a gap diagram of electroplating metal copper ions using a very low frequency 12KHZ power supply. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, the present invention discloses a method for electroplating copper and tin grid lines for solar cells, the method comprising the following steps:

[0032] S2. Preliminary treatment: Place the HDT high-efficiency single crystal heterojunction solar cell onto the electroplating hanger, then place the hanger in deionized water for cleaning for 15 to 20 seconds, and then treat it in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

[0033] S2, copper electroplating: put the tooling into the copper liquid tank to electroplate copper layers on the P side and N side. The copper liquid includes metal phosphor copper balls, copper sulfate solution and additives; the power supply used is a very low frequency power supply, and the very low frequency power supply adopts a 12KHZ frequency. When electroplating the copper grid line, the very low frequency pulse power supply parameters are matched, the voltage of the P side is set to DC: 30~35V, the current is set to 5~12A, the voltage of the N side is set to DC: 30~35V, the current is set to 2.6~8A, and both sides are electroplated at the same time, and the electroplating time is 30~45 minutes. In this embodiment, the voltage of the electroplated copper P side is set to 35V, the current is set to 12A, the voltage of the N side is set to 35V, the current is set to 2.6A, and the electroplating time is 45 minutes.

[0034] S3, cleaning copper solution: After the copper electroplating is completed, the battery cell is placed in deionized water for cleaning for 15 to 20 seconds, and then treated in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

[0035] S4, electroplating tin: Place the battery cell after cleaning the copper liquid in a tin liquid tank to electroplate the tin layer on the P side and N side. The tin liquid includes phosphorus tin balls, stannous methyl yellow acid, methyl sulfonic acid solution and additives. The power supply used is a very low frequency power supply, and the very low frequency power supply adopts a frequency of 12KHZ. When electroplating the tin grid line, with the very low frequency pulse power supply parameters, the voltage of the P side is set to DC: 6V, the current is set to 3~4.5A, the voltage of the N side is set to DC: 6V, the current is set to 1.6~3A, and the two sides are electroplated at the same time, and the electroplating time is 10~15 minutes. In this embodiment, the voltage of the electroplated tin P side is set to 6V, the current is set to 4.2A, the voltage of the N side is set to 6V, the current is set to 1.6A, and the electroplating time is 10 minutes.

[0036] S5. Cleaning the tin solution: After the tin electroplating is completed, the battery cell is placed in deionized water for cleaning for 15 to 20 seconds, and then treated in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

[0037] S6. Take out the cleaned cell and complete the gate line electroplating

[0038] Table 1: Comparison of various test indicators of cells using the original electroplating process and the electroplating process of this embodiment

[0039]

[0040] The original cells 1 to 8 represent the finished cells that use the original process of thyristor DC power supply to electroplate metal grid lines; the modified cells 1 to 8 represent the finished cells that use the very low frequency power supply of this embodiment with the self-developed voltage and current parameters to electroplate metal grid lines. Except for the difference in process, the equipment and external conditions used are the same. Isc (A) is the short circuit circuit, Voc (V) is the open circuit voltage, FF (%) is the fill factor, Eff (%) is the conversion power, and Pmpp (W) is the power.

[0041] from Figure 2 , Figure 3 It can be seen that by using the improved VLF power supply electroplating process, the gap between metal copper ions is reduced from 704.2nm to 1094nm to 297.1nm to 765.1nm. As can be seen from Table 1, the conversion efficiency (Eff) of the cell is increased by more than 0.158%, and better coating quality and product reliability are obtained. This method not only saves manpower and material resources, but also improves production efficiency, and has high practical value.

[0042] In summary, the present invention uses a very low frequency power supply to replace the thyristor DC power supply, and is equipped with self-developed voltage and current parameters to improve the compactness and conductivity of the electroplated metal grid line, and effectively improve the conversion efficiency of the solar cell. Under the same electroplating conditions, the compactness of the electroplated metal grid line film layer of the HDT high-efficiency single crystal heterojunction solar cell is improved.

[0043] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for electroplating copper and tin grid lines in solar cells, characterized in that: The method comprises the following steps: S1. Electroplating copper: Place the cell on the electroplating tooling and put it into the copper liquid tank to electroplating copper layer on the P side and N side; a very low frequency power supply is used; S2, cleaning copper solution: after the copper electroplating is completed, the battery cell is placed in a cleaning solution for cleaning; S3, electroplating tin: placing the battery cell after cleaning the copper liquid in a tin liquid tank to electroplating tin layers on the P side and N side; using a very low frequency power supply; S4, cleaning tin solution: after the tin electroplating is completed, the battery cell is placed in a cleaning solution for cleaning; S5. Take out the cleaned battery cell and complete the gate line electroplating.

2. The method for electroplating copper and tin grid lines in solar cells according to claim 1, characterized in that: The frequency of the very low frequency power supply is 12KHZ.

3. The method for electroplating copper and tin grid lines in solar cells according to claim 1, characterized in that: In the step S1, the voltage of the copper electroplating P surface is set to DC: 30-35V, the current is set to 5-12A, the voltage of the N surface is set to 30-35V, the current is set to 2.6-8A, and the electroplating time is 30-45 minutes.

4. The method for electroplating copper and tin grid lines in solar cells according to claim 3, characterized in that: The voltage of the copper electroplating P side was set to 35V, the current was set to 12A, the voltage of the N side was set to 35V, the current was set to 2.6A, and the electroplating time was 45 minutes.

5. The method for electroplating copper and tin grid lines in solar cells according to claim 1, characterized in that: In the step S3, the voltage of the electrotin-plated P surface is set to DC: 6V, the current is set to 3-4.5A, the voltage of the N surface is set to 6V, the current is set to 1.6-3A, and the electroplating time is 6-10 minutes.

6. The method for electroplating copper and tin grid lines in solar cells according to claim 5, characterized in that: The voltage of the electrotin-plated P side was set to 6V, the current was set to 4.2A, the voltage of the N side was set to 6V, the current was set to 1.6A, and the electroplating time was 10 minutes.

7. The method for electroplating copper and tin grid lines for solar cells according to claim 1, characterized in that: In the S1 copper electroplating step, before placing the battery cell in the copper liquid tank for copper electroplating, preliminary cleaning is first performed. The preliminary cleaning method is: placing the battery cell in deionized water for cleaning for 15 to 20 seconds, and then treating it in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

8. The method for electroplating copper and tin grid lines on solar cells according to claim 1, characterized in that: In step S2 of cleaning the copper solution and step S4 of cleaning the tin solution, the cleaning method is: placing the battery cell in deionized water for cleaning for 15 to 20 seconds, and then treating it in 10 to 20% dilute sulfuric acid for 15 to 20 seconds.

9. The method for electroplating copper and tin grid lines in solar cells according to claim 1, characterized in that: The solution contained in the copper liquid tank includes metal phosphor copper balls, copper sulfate solution and additives; the solution contained in the tin liquid tank includes phosphor tin balls, stannous methyl xanthate, methyl sulfonic acid solution and additives.

10. The method for electroplating copper and tin grid lines in solar cells according to claim 1, characterized in that: The cell is a HDT high-efficiency single-crystal heterojunction solar cell.

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