A method for etching the copper seed layer of a copper grid heterojunction solar cell, the etching solution and its application

Abstract

This application belongs to the field of battery technology and discloses a method for etching the copper seed layer of a copper-grid heterojunction solar cell, an etching solution, and its application. The etching solution consists of dilute sulfuric acid solution, ozone, and water, with the concentration of the dilute sulfuric acid solution being 0.6%-10% and the ozone concentration being 10-30 ppm. The solar cell containing the copper seed layer or the silicon wafer of a heterojunction solar cell containing an ITO film is completely immersed in the etching solution and etched at room temperature to remove the copper seed layer from the surface of the silicon wafer. The etching solution described in this technical solution is used to remove the copper seed layer in copper-grid heterojunction solar cells. It has a simple composition, and the waste liquid after etching is a copper sulfate solution with no harmful byproducts, making it environmentally friendly. The ozone is generated on-site from air or oxygen, and the sulfuric acid concentration is extremely low, reducing the cost of chemical solutions by more than 60% and resulting in extremely low overall operating costs. This system causes very little damage to transparent conductive films such as ITO and SnO2, and the sheet resistance and film thickness change rate can be controlled within 3%, ensuring the performance of the solar cell. Compared with other oxidant etching solutions, it avoids the etching capacity decay defects caused by oxidant decomposition.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a method for etching the copper seed layer of a copper grid heterojunction battery, an etching solution, and its application. Background Technology

[0002] In the photovoltaic industry, copper electroplating technology for heterojunction cells is a key alternative to high-cost silver paste. This technology includes a crucial step of seed layer etching, which aims to precisely remove the copper seed layer in non-grid areas without damaging the underlying transparent conductive oxide film. Currently, the industry commonly uses traditional etching solutions such as persulfate and sulfuric acid / hydrogen peroxide. These etching solutions have inherent drawbacks: firstly, they rely on chemical oxidants, and their etching efficiency drops rapidly as the copper ion concentration increases, leading to frequent solution replacements and high costs; secondly, the resulting waste liquid contains high concentrations of copper ions and other pollutants, classifying it as hazardous waste, with cumbersome treatment processes and significant environmental pressure.

[0003] Therefore, developing a green etching technology that reduces pollution at the source, consumes less chemical solution, and maintains high etching performance has become an urgent need for the photovoltaic industry.

[0004] Based on this, a copper seed layer etching method, etching solution and its application for copper grid heterojunction batteries were studied and developed. Summary of the Invention

[0005] The purpose of this application is to provide a method for etching the copper seed layer of a copper grid heterojunction battery, an etching solution, and its application. The etching solution uses dilute sulfuric acid and ozone as the etching solution for the copper seed layer of the copper grid heterojunction battery. The composition is simple, and the etching waste liquid is a pure copper sulfate solution. Copper can be recovered through simple neutralization precipitation or electrolysis, with almost no harmful byproducts. This eliminates the generation of complex hazardous waste at the source. Furthermore, the etching solution does not contain corrosive ions such as chloride ions, and the etching reaction is mild and controllable. This system causes extremely low damage to transparent conductive films such as ITO and SnO2, and the sheet resistance and film thickness change rate can be controlled within 3%. This solves the technical problems of low etching efficiency and cumbersome processing due to the high concentration of copper ions in the etching waste liquid in existing etching methods.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: In one aspect, embodiments of this application provide a copper seed layer etching solution for a copper grid heterojunction battery, which is composed of dilute sulfuric acid solution, ozone gas and water, wherein the concentration of dilute sulfuric acid solution is 0.6%-10% and the concentration of ozone is 10-30ppm.

[0007] The copper seed layer etching solution for copper-grid heterojunction solar cells described in this invention uses a low-concentration sulfuric acid aqueous solution as the liquid phase and ozone gas dissolved and dispersed therein as the sole effective oxidizing component. Ozone gas has a long lifetime and high interfacial area in acidic aqueous solutions. During its spontaneous contraction and rupture, it can generate hydroxyl radicals with extremely high oxidation potential in situ. These radicals can rapidly oxidize copper to soluble divalent copper ions, which then react with sulfate ions to form copper sulfate, thereby achieving clean etching of the copper layer of the solar cell.

[0008] Optionally, in the copper seed layer etching solution of the copper grid heterojunction battery, the ozone gas is generated by oxygen through corona discharge.

[0009] Optionally, in the etching solution for the copper seed layer of the copper gate heterojunction battery, the dilute sulfuric acid solution is obtained by diluting 50% concentrated sulfuric acid.

[0010] Secondly, this application provides a method for preparing a copper seed layer etching solution for a copper grid heterojunction solar cell. At room temperature, a 0.6%-10% dilute sulfuric acid solution and a 10-30 ppm ozone solution are simultaneously injected into a dissolving tank. The dilute sulfuric acid solution and ozone continuously dissolve within the tank, with a circulation flow rate of 20-100 L / min. The ozone and dilute sulfuric acid solution are fully dissolved, yielding the final product. The dissolving tank can be an ozone acid solution dissolving tank.

[0011] Optionally, ozone is prepared by an ozone generator, which may be an ozone generator.

[0012] Optionally, the ozone generator is a high-concentration plate ozone generator, and the dissolution tank is a 400L process tank.

[0013] Optionally, the ozone is generated by corona discharge of oxygen through a high-concentration plate ozone generator.

[0014] Thirdly, this application provides an etching solution for etching the copper seed layer of a copper grid heterojunction solar cell. The etching solution removes the ink on the surface of the solar cell containing the copper seed layer. After the copper seed layer is exposed, or after the heterojunction solar cell containing the ITO film is completely immersed in the etching solution, the etching is performed at room temperature to remove the copper seed layer on the surface of the solar cell silicon wafer.

[0015] Optionally, the battery cell containing a 100nm copper seed layer is immersed in an etching solution, and the time to completely remove the copper seed layer is less than or equal to 1 minute.

[0016] Fourthly, this application provides an application of a copper seed layer etching solution for copper grid heterojunction solar cells, which is mainly used for etching the copper seed layer of heterojunction solar cell copper electroplating and photovoltaic electroplating products.

[0017] The present invention has the following beneficial effects: 1) The copper seed layer etching solution for copper grid heterojunction batteries described in this application has a simple composition, containing only sulfuric acid, ozone and water. The waste liquid after etching is a pure copper sulfate solution, which can be recovered by simple neutralization precipitation or electrolysis. There are almost no harmful by-products, eliminating the generation of complex hazardous waste from the source. Using this etching solution to remove the copper seed layer of batteries is green and environmentally friendly.

[0018] 2) In the etching solution preparation method of the technical solution described in this application, ozone is prepared on-site from air or oxygen, the sulfuric acid concentration is extremely low, the consumption cost of the solution is reduced by more than 60% compared with the traditional system, and the overall operating cost is extremely low.

[0019] 3) The copper seed layer etching solution of the copper grid heterojunction battery described in this application does not contain corrosive ions such as chloride ions, and the reaction during the etching process is mild and controllable. As a result, the system causes very little damage to transparent conductive films such as ITO and SnO2, and the sheet resistance and film thickness change rate can be controlled within 3%.

[0020] 4) In the copper seed layer etching solution of the copper grid heterojunction battery described in the application, the ·OH free radicals generated by the ozone system have a stronger oxidation ability than hydrogen peroxide and persulfate, and the continuous supply of ozone ensures the stability of the oxidation ability, avoiding the problem of etching ability decay caused by the decomposition of hydrogen peroxide and other oxidants. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the preparation process of a copper seed layer etching solution for a copper grid heterojunction solar cell as described in this application. Figure 2 This is a comparison chart of the light transmittance of solar cells after they have been treated with etching solution. Figure 3 These are comparison images of the copper seed layer residue after the solar cells have been treated with etching solution. Figure 4 This is a comparison chart showing the changes in the corrosion of gate lines by different etching solutions; Figure 5 These are comparative cross-sectional images of the copper electrode of the battery cell after removing the residual copper seed layer with different etching solutions. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The embodiments of this application will be described in detail below with reference to the accompanying drawings and specific examples and application scenarios.

[0025] Example 1: like Figure 1 As shown, a copper seed layer etching solution for a copper grid heterojunction battery is composed of dilute sulfuric acid solution, ozone and water, wherein the concentration of dilute sulfuric acid solution is 0.6% and the concentration of ozone is 10ppm.

[0026] A method for preparing a copper seed layer etching solution for copper grid heterojunction solar cells is as follows: Ozone is generated from oxygen through corona discharge using a high-concentration plate ozone generator. Specifically, oxygen is ionized into oxygen atoms and other radicals by a high-frequency, high-voltage electric field, and these radicals combine with oxygen molecules to form ozone. For the dilute sulfuric acid solution preparation: 50% concentrated sulfuric acid is diluted to a concentration of 0.6% and injected into the process tank. Simultaneously, ozone gas with a concentration of 10 ppm, generated by an ozone generator or ozone host, is introduced. At room temperature, the ozone gas and dilute sulfuric acid solution continuously dissolve in a dissolution tank. The circulation flow rate in the dissolution tank is controlled at 20-100 L / min to ensure complete dissolution of the ozone and dilute sulfuric acid solution, resulting in an ozone-sulfuric acid mixed etching solution.

[0027] Example 2: An etching solution for the copper seed layer of a copper grid heterojunction battery is composed of dilute sulfuric acid solution, ozone and water, wherein the concentration of dilute sulfuric acid solution is 10% and the concentration of ozone is 30ppm.

[0028] A method for preparing a copper seed layer etching solution for a copper grid heterojunction solar cell is as follows: Ozone is generated from oxygen through corona discharge using a high-concentration plate ozone generator. Specifically, oxygen is ionized into oxygen atoms and other radicals by a high-frequency, high-voltage electric field, and these radicals combine with oxygen molecules to form ozone. For the dilute sulfuric acid solution preparation: 50% concentrated sulfuric acid is diluted to a concentration of 10% and injected into the process tank. Simultaneously, ozone gas with a concentration of 30 ppm, generated by the ozone generator, is introduced. At room temperature, the ozone and dilute sulfuric acid solution continuously dissolve in the dissolution tank. The circulation flow rate in the dissolution tank is controlled at 20-100 L / min to ensure complete dissolution of the ozone and dilute sulfuric acid solution, resulting in an ozone-sulfuric acid mixed etching solution.

[0029] Example 3: An etching solution for the copper seed layer of a copper grid heterojunction battery is composed of dilute sulfuric acid solution, ozone and water, wherein the concentration of dilute sulfuric acid solution is 8% and the concentration of ozone is 20ppm.

[0030] A method for preparing an etching solution for the copper seed layer of a copper-grid heterojunction solar cell is as follows: Ozone is generated from oxygen through corona discharge using a high-concentration plate-type ozone generator. Specifically, oxygen is ionized into oxygen atoms and other radicals by a high-frequency, high-voltage electric field, and these radicals combine with oxygen molecules to form ozone. For the preparation of the dilute sulfuric acid solution, 50% concentrated sulfuric acid is diluted to an 8% concentration and injected into the process tank. Simultaneously, ozone gas with a concentration of 30 ppm, generated by the ozone generator (ozone main unit), is introduced. At room temperature, the ozone and dilute sulfuric acid solution continuously dissolve in a dissolution tank. The circulation flow rate in the dissolution tank is controlled at 20-100 L / min to ensure complete dissolution of the ozone and dilute sulfuric acid solution, resulting in an ozone-sulfuric acid mixed etching solution, i.e., an etching solution for the copper seed layer of a copper-grid heterojunction solar cell. The dissolution tank is an ozone acid solution dissolution tank.

[0031] The ozone generator, ozone acid solution dissolution tank, process tank, and pump that transports the diluted sulfuric acid solution in the process tank to the ozone acid solution dissolution tank involved in the above embodiments are all existing technology structures. Their structures and working principles are existing technology and are not the main innovation of this invention, so they will not be described in further detail.

[0032] The etching solution obtained in any of Examples 1-3 above is used to etch the copper seed layer of the photovoltaic cell. The specific method is as follows: After electroplating a copper seed layer of approximately 100 nm thickness, the ink on the surface of the silicon wafer was removed, exposing the copper seed layer and the 100 nm thick ITO film. The heterojunction silicon wafer was then completely immersed in the etching solution prepared in Example 1 and etched at room temperature. Observation and sheet resistance testing determined that the copper seed layer on the surface of the silicon wafer was completely removed within 2 minutes, exposing the complete ITO film underneath.

[0033] Post-etching cell performance testing: 1) After immersing the copper grid line blue film of the experimental sample into the etching solution for 2 minutes, the etched ITO film was tested. The transmittance in the visible light region did not decrease. The sheet resistance changed. The sheet resistance was 34.8 before entering the etching solution and 35 after 2 minutes of etching. The results show that the etching solution does not damage the ITO film. 2) Immerse the copper seed sheet of the experimental sample after 100nm in the etching solution until the copper seed layer is completely removed, and record the seed layer removal time. The copper seed layer removal time is less than 1min.

[0034] 3) After removing the ink layer from the copper grid cell, immerse it in ozone sulfuric acid etching solution for 1 minute to remove the surface copper seed layer and observe whether there is side etching on the grid line surface morphology.

[0035] Comparison test of etching effects of different etching solutions: 1. Light transmittance comparison test: The same batch of 100nm thick copper seed layer solar cells were immersed in existing persulfate oxidant KH5SO4 / H2SO4, hydrogen peroxide H2O2 / H2SO4, and O3 / H2SO4 solutions (i.e., the copper gate heterojunction solar cell copper seed layer etching solution described in Example 1) under the same etching conditions, with complete immersion for the same time of 1 minute. The results are as follows. Figure 2 As shown.

[0036] Results analysis: After treating the copper seed layer of the battery cell with the copper grid heterojunction battery copper seed layer etching solution described in this embodiment, the transmittance did not decrease.

[0037] 2. Comparison test of copper seed layer removal effect: The same batch of 100nm thick copper seed layer solar cells were immersed in KH5SO4 / H2SO4, H2O2 / H2SO4, and O3 / H2SO4 solutions respectively for 1 minute, and the seed layer removal effect was observed. Figure 3 As shown.

[0038] Results analysis: Within the same time frame of 1 minute, H2O2 / H2SO4 and O3 / H2SO4 had the same copper removal effect, completely removing the copper seed layer, while KH5SO4 / H2SO4 left some copper seed layer residue.

[0039] It can be seen that the copper seed layer of the 100nm copper seed layer solar cell can be completely removed. The time required for the KH5SO4 / H2SO4 potassium persulfate sulfuric acid mixed concentrate, the H2O2 / H2SO4 hydrogen peroxide sulfuric acid mixed concentrate, and the O3 / H2SO4 ozone sulfuric acid mixed concentrate are 2 min, 1.2 min, and 1 min, respectively.

[0040] 3. Tests on the changes in corrosion of battery grid lines by different etching solutions: Experimental Samples: Battery cells coated with a 100nm thick copper seed layer. Surface ink was removed to expose the seed layer. The batch of cells was then subjected to copper removal in three different solutions: KH5SO4 / H2SO4, H2O2 / H2SO4, and O3 / H2SO4. The removal effects were as follows: Figure 4 As shown, It can be seen that after the three copper removal solutions were removed, the surface of the cell grid lines and the copper seed layer of the ITO layer could be completely removed, and there was no obvious difference on the grid line surface.

[0041] Cross-sectional images of the copper electrode of the solar cell after removing the residual copper seed layer using three different etching solutions are shown below. Figure 5As shown, the bottom side etching of the gate line is relatively mild compared to other etching solutions. The bottom side etching of potassium persulfate etching solution is 1-2 μm, the bottom side etching of hydrogen peroxide etching solution is 1-1.5 μm, and the bottom side etching of ozone-sulfuric acid etching solution is less than 1 μm.

[0042] It is evident that using perozonosulfuric acid etching solution can effectively slow down the lateral corrosion of copper electrodes in solar cells by acidic corrosive agents, and can also improve the corrosion inhibition capability of copper electrodes, providing selective adsorption protection for copper grid lines of silicon-based solar cells.

[0043] 4. Comparative test of copper seed layer removal efficiency: Control group 1: KH5SO4 / H2SO4; Comparative group 2: H2O2 / H2SO4; Experimental group: O3 / H2SO4 (prepared using Example 1 or the etching solution described).

[0044] The 100nm thick copper seed layer solar cells were completely immersed in the etching solutions described in the control group 1, control group 2, and experimental group, respectively. After immersion for 1 minute, the copper removal was observed and compared, as shown in Table 1 below: Table 1. Battery cell performance parameters. It is evident that the performance parameters of the solar cells did not decrease after treatment in the experimental group, control group 1, and control group 2.

[0045] 5. Comparison test of etching solution dosage: Under the same test conditions, comparing the removal efficiency of the copper seed layer, the amount of etching solution used in the experimental group and control groups 1-2 after etching the battery cells is shown in Table 2 below: Table 2 Comparison of etching solution dosage It is evident that by adopting the O3 / H2SO4 etching solution system, the amount of chemical reagents used is reduced by 60%-75%, demonstrating a significant advantage in resource conservation. The waste liquid treatment of the O3 / H2SO4 system is also simpler, highlighting the concept of green chemistry and providing an innovative solution for the sustainable development of copper electroplating technology.

[0046] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. An etching solution for the copper seed layer of a copper grid heterojunction battery, characterized in that, It consists of a dilute sulfuric acid solution, ozone, and water. The concentration of the dilute sulfuric acid solution is 0.6%-10%, and the concentration of the ozone is 10-30 ppm.

2. The copper seed layer etching solution for a copper grid heterojunction battery according to claim 1, characterized in that, Ozone is produced by the corona discharge of oxygen.

3. The copper seed layer etching solution for a copper grid heterojunction battery according to claim 1, characterized in that, The dilute sulfuric acid solution is obtained by diluting 50% concentrated sulfuric acid.

4. The method for preparing the etching solution according to any one of claims 1-3, characterized in that, At room temperature, a 0.6%-10% dilute sulfuric acid solution and a 10-30ppm ozone solution are simultaneously injected into a dissolving tank. The dilute sulfuric acid solution and ozone continue to dissolve in the dissolving tank, and the circulation flow rate in the dissolving tank is 20-100L / min. The ozone and dilute sulfuric acid solution are fully dissolved, and the solution is obtained.

5. The method for preparing a copper seed layer etching solution for a copper grid heterojunction solar cell according to claim 4, characterized in that, Ozone is obtained by using an ozone generator.

6. The method for preparing a copper seed layer etching solution for a copper grid heterojunction solar cell according to claim 5, characterized in that, The ozone generator is a high-concentration plate ozone generator, and the dissolution tank is a 400L process tank structure.

7. The method for preparing a copper seed layer etching solution for a copper grid heterojunction solar cell according to claim 6, characterized in that, The ozone is generated by corona discharge of oxygen through a high-concentration plate ozone generator.

8. An etching solution according to any one of claims 1-3 or an etching solution obtained by any one of claims 4-7, used for etching the copper seed layer of a copper grid heterojunction solar cell, characterized in that, Remove the ink from the surface of the solar cell containing the copper seed layer, and after the copper seed layer is exposed, or if the heterojunction solar cell wafer containing the ITO film is completely immersed in the etching solution, allow it to stand at room temperature for etching to remove the copper seed layer from the surface of the solar cell wafer.

9. The method for etching the copper seed layer of a copper grid heterojunction solar cell according to claim 8, characterized in that, When a battery cell containing a 100nm copper seed layer is immersed in an etching solution, the time to completely remove the copper seed layer is less than or equal to 1 minute.

10. A copper seed layer etching method for copper grid heterojunction solar cells is applied to copper electroplating of heterojunction solar cells and copper seed layer etching of photovoltaic electroplating products.

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