Composite corrosion inhibitor etching liquid as well as preparation method and application thereof

Abstract

According to the composite corrosion inhibitor etching liquid and the preparation method and application thereof, a composite corrosion inhibition system composed of the first corrosion inhibitor and the second corrosion inhibitor is introduced into an acid etching system, and selective removal of a copper seed layer under different etching conditions is achieved; according to the composite corrosion inhibition system, the corrosion defect of the surface of a copper electrode can be remarkably reduced, the surface appearance can be improved, the lateral corrosion depth can be reduced, and meanwhile complete etching of a residual copper seed layer in a non-electrode area is not affected. The two types of nitrogen-containing heterocyclic corrosion inhibitors generate a synergistic adsorption effect on the copper surface by utilizing the molecular structure and adsorption behavior difference to form a compact and stable composite protection layer, so that the synergistic regulation and control on the overall corrosion rate and the local lateral corrosion behavior are realized. The composite corrosion inhibitor etching liquid has the advantages of being good in etching uniformity, remarkable in lateral erosion inhibition effect, wide in process window and suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of composite corrosion inhibitor preparation technology, and more specifically, to a composite corrosion inhibitor etching solution, its preparation method, and its application. Background Technology

[0002] In recent years, heterojunction with an intrinsic thin layer (HJT) solar cells have gradually become one of the important development directions in the photovoltaic field due to their advantages such as excellent surface passivation performance, high photoelectric conversion efficiency, and low-temperature manufacturing processes. Regarding metal electrode materials for these cells, copper is considered an ideal candidate material to replace traditional silver electrodes because of its low resistivity, abundant resources, and significantly lower cost compared to silver. By using electroplating processes to fabricate copper grid lines, not only can the manufacturing cost of solar cells be effectively reduced, but narrower electrode linewidths can also be achieved, thereby reducing front-side shading losses and further improving the overall conversion efficiency of the cell.

[0003] Currently, the metal electrode fabrication process for copper grid heterojunction solar cells typically involves multiple steps, including copper seed layer deposition, patterning, electroplating thickening, and seed layer etching back. The main purpose of the seed layer etching back process is to remove the residual copper seed layer outside the electrode area after electroplating, thus forming a metal electrode structure with good selectivity. This etching back process generally employs wet etching, using a chemical etching solution to remove the copper seed layer. However, in actual production, due to the isotropic etching characteristics of wet etching, while the etching solution etches the copper seed layer vertically, it often inevitably causes lateral erosion, resulting in significant side etching (also known as "undercutting") at the bottom of the copper electrode. This side etching problem easily leads to defects such as pinholes and pits on the copper electrode surface, weakening the adhesion between the copper electrode and the underlying cell substrate. This not only affects the stability of the electrode structure but may also adversely impact the electrical performance and long-term reliability of the cell.

[0004] In existing technologies, the industry commonly uses an acidic etching solution system composed of potassium persulfate composite salt (KHSO5·0.5KHSO4·0.5K2SO4) and concentrated sulfuric acid (H2SO4) for the etching back process of copper seed layers. This type of etching solution has good chemical stability in acidic environments and can effectively remove the copper seed layer, so it is widely used in related processes. However, in practical applications, this etching system still has the problem of insufficient precision in etching rate control: when the etching rate is high, it often aggravates the side etching phenomenon of copper electrodes; while when the etching rate is reduced to suppress side etching, it may lead to incomplete removal of the residual copper seed layer, affecting the subsequent battery performance and yield.

[0005] Therefore, in the seed layer etching process of copper grid heterojunction solar cells, how to ensure that the residual copper seed layer can be fully and thoroughly removed while effectively suppressing the lateral etching and bottom side etching of the copper electrode during the etching process, thereby reducing corrosion defects on the electrode surface, improving the integrity of the electrode structure and the overall performance of the cell, remains one of the key technical problems that urgently need to be solved in this field. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a composite etching inhibitor solution to solve the problems of strong isotropic etching, severe lateral etching, and easy undercutting and surface defects of copper electrodes in the process of removing residual copper seed layers in existing acid etching systems.

[0007] To overcome the shortcomings of the prior art, the present invention provides a composite etching inhibitor solution, comprising the following components: Oxidizing agent: Potassium persulfate compound salt; Acid: Concentrated sulfuric acid; Composite corrosion inhibitor: Composed of a first corrosion inhibitor and a second corrosion inhibitor, wherein the first corrosion inhibitor is a nitrogen-containing heterocyclic compound that can form a covering adsorption film on the copper surface, and the second corrosion inhibitor is a nitrogen-containing heterocyclic compound that can preferentially adsorb onto highly active sites on the copper surface; Solvent: Deionized water.

[0008] Compared with existing technologies, the composite etching inhibitor of this invention has the following advantages: By introducing two types of etching inhibitors with different adsorption behaviors and action scales into the potassium persulfate-sulfuric acid system, the etching inhibitor of this invention achieves synergistic regulation of the etching behavior of copper electrodes. The first etching inhibitor molecule has a large planar conjugated structure, enabling stable adsorption on the copper crystal surface through nitrogen-containing coordinating groups, forming a continuous and dense covering adsorption film, thereby macroscopically reducing the overall corrosion rate of the copper surface. The second etching inhibitor has a smaller molecular weight and faster diffusion rate, preferentially adsorbing onto highly reactive sites such as grain boundaries, defects, and sidewall edges on the copper surface, providing a pinning-like protection for the initiation of lateral etching, effectively inhibiting the occurrence and spread of lateral etching. In this invention, the two etching inhibitors work synergistically on the copper surface, strengthening the covering adsorption film at highly reactive sites, forming a denser and more stable composite protective layer. This ensures the continuous etching capability of the oxidant on the residual copper seed layer in non-electrode areas while significantly reducing lateral etching and undercutting phenomena in the copper grid area. Based on the above mechanism, the present invention can effectively reduce corrosion defects on the surface of copper electrode while the copper seed layer is fully and selectively removed, improve the surface morphology and adhesion performance of the electrode, and achieve a precise balance between etching efficiency and side corrosion suppression. This solves the technical problem in the prior art that it is difficult to completely remove the residual seed layer and that it is difficult to simultaneously address the severe side corrosion of the copper electrode.

[0009] In one possible implementation, the first corrosion inhibitor is selected from one of methylbenzotriazole, o-phenanthroline, and 5-methylbenzimidazole; the second corrosion inhibitor is selected from one of imidazole, pyridine, and pyrazole.

[0010] Compared with existing technologies, the above-mentioned technical solution enables different corrosion inhibitor components in the composite corrosion inhibitor to form a well-defined and synergistic adsorption system on the copper surface. The first corrosion inhibitor (including methylbenzotriazole, o-phenanthroline, and 5-methylbenzimidazole) typically has a large planar conjugated structure and multiple nitrogen-containing coordination sites, which can stably adsorb on the copper crystal surface and form a protective film, thereby reducing the overall corrosion rate of the copper surface. The second corrosion inhibitor (imidazolium, pyridine, and pyrazole) has a small molecular weight and strong diffusion ability, which can preferentially reach and adsorb on highly reactive sites such as grain boundaries, defects, steps, and sidewall edges on the copper surface, forming a targeted protection for the initiation area of ​​lateral etching. This embodiment combines the above two types of specifically selected corrosion inhibitors with different adsorption characteristics to simultaneously enhance the overall protection of the copper surface and the protection of local key sites, suppressing the occurrence and expansion of lateral etching, and achieving a synergistic balance between selective removal of the copper seed layer and significant reduction of copper electrode lateral etching.

[0011] In one possible implementation, the mass ratio of the first corrosion inhibitor to the second corrosion inhibitor is (4-6):1.

[0012] Compared with the prior art, by limiting the mass ratio of the first corrosion inhibitor to the second corrosion inhibitor to (4-6):1, a reasonable match can be achieved between the covering and protective effect of the first corrosion inhibitor and the site-specific inhibition effect of the second corrosion inhibitor in the composite corrosion inhibitor system. When the proportion of the first corrosion inhibitor is too low, it is difficult to form a continuous and stable covering adsorption film on the copper surface, resulting in insufficient overall corrosion inhibition effect. When the proportion of the second corrosion inhibitor is too low, it is difficult to effectively inhibit the lateral corrosion initiation at highly active sites such as grain boundaries and sidewalls. By controlling the mass ratio of the two to the range of (4-6):1, this embodiment enables the second corrosion inhibitor to fully occupy the highly active sites, while the first corrosion inhibitor forms a dense and continuous covering layer on this basis, thereby constructing a stable composite adsorption structure at the microscopic level. This avoids excessive inhibition of the etching rate and significantly reduces lateral corrosion and undercutting phenomena, thus achieving the technical effect of balancing etching controllability and electrode integrity.

[0013] In one possible implementation, the concentration range of each component in the composite etching inhibitor solution is as follows: Potassium persulfate compound salt: 15-25 g / L; Concentrated sulfuric acid: 8-12 g / L; First corrosion inhibitor: 0.2-0.3 g / L; Second corrosion inhibitor: 0.04-0.06 g / L.

[0014] Compared with the prior art, this embodiment uses the above-mentioned concentration range. The concentrations of potassium persulfate composite salt and concentrated sulfuric acid ensure that the etching solution has sufficient oxidative etching ability for the residual copper seed layer in the non-electrode area. The concentrations of the first and second corrosion inhibitors ensure that they can form an effective composite adsorption protective layer on the copper electrode surface. As mentioned above, if the concentration of the corrosion inhibitor is too low, it is difficult to form a stable adsorption film, and the side corrosion inhibition effect is limited. If the concentration of the corrosion inhibitor is too high, it may excessively inhibit the etching reaction and affect the removal efficiency of the residual seed layer. The above-mentioned concentration range enables the etching solution to effectively inhibit the lateral corrosion and undercutting of the copper electrode surface while ensuring the etching efficiency, thereby obtaining a more stable and repeatable process effect.

[0015] In one possible implementation, the concentrations of each component in the composite etching inhibitor solution are as follows: Potassium persulfate compound salt: 20 g / L; Concentrated sulfuric acid: 10 g / L; First corrosion inhibitor: 0.25 g / L; Second corrosion inhibitor: 0.05 g / L.

[0016] Compared with the prior art, this embodiment further adopts the specific concentration ratio determined above as a preferred embodiment, and further optimizes the matching relationship between etching rate and corrosion inhibition effect under actual production conditions. Under the specific ratio above, the etching solution has a stable and controllable removal ability for the residual copper seed layer. At the same time, the composite corrosion inhibitor forms a dense and uniform adsorption protective layer on the copper electrode surface, effectively inhibiting the occurrence of side etching and undercutting. Under this concentration condition, corrosion defects on the copper electrode surface are significantly reduced, the side etching width is significantly reduced, and the flatness and integrity of the electrode surface are significantly improved.

[0017] The second technical problem this invention aims to solve is to provide a method for preparing a composite etching inhibitor solution, thereby addressing the issues of uneven dispersion of the etching inhibitor, poor system stability, and difficulty in achieving a synergistic etching inhibition effect in existing etching solution preparation processes. This invention provides a method for preparing the composite etching inhibitor solution, comprising the following steps: Under stirring conditions, concentrated sulfuric acid is slowly added to deionized water and mixed thoroughly. Add potassium persulfate complex salt to the obtained solution and stir until completely dissolved; Then add the second corrosion inhibitor and stir until completely dissolved; Finally, add the first corrosion inhibitor and stir until completely dissolved to obtain the composite corrosion inhibitor etching solution.

[0018] Compared with existing technologies, the preparation method of the composite corrosion inhibitor etching solution of this invention has the following advantages: In existing technologies, the preparation of corrosion inhibitor etching solutions often fails to rationally design the order of addition of acid, oxidant, and different types of corrosion inhibitors, which can easily lead to insufficient dissolution of the corrosion inhibitor, excessively high local concentration, or insufficient intermolecular interactions, thereby affecting the stability of the etching solution and its corrosion inhibition effect on the copper surface; while the preparation method of this invention, by sequentially adding concentrated sulfuric acid, potassium persulfate composite salt, second corrosion inhibitor, and first corrosion inhibitor to deionized water under stirring conditions, first stabilizes the acidic environment and oxidation system. The process involves first dissolving and uniformly dispersing a second corrosion inhibitor with a smaller molecular weight and stronger diffusion ability, and then adding a first corrosion inhibitor with covering adsorption properties. This facilitates the formation of a stable coexistence system between the two types of corrosion inhibitors in the solution. The preparation method of this invention ensures the full dissolution and uniform distribution of each component in the preparation sequence from a technical principle perspective. This provides a foundation for the subsequent formation of a dense and synergistic composite adsorption protective layer on the copper surface, improves the stability, repeatability, and actual corrosion inhibition effect of the etching solution, and solves the technical problems of large fluctuations in etching solution performance and difficulty in stably inhibiting lateral corrosion in the prior art.

[0019] Another technical problem to be solved by the present invention is to provide an application of the composite etching inhibitor etching solution to solve the problems of severe side etching of copper electrodes and difficulty in controlling bottom cutting in the existing wet etching process.

[0020] To overcome the shortcomings of the prior art, the present invention provides an application of a composite etching inhibitor in the removal of the seed layer of a copper grid heterojunction solar cell, comprising the following steps: A1: Etching process: The solar cell with copper seed layer is immersed in the etching solution and etched for 90±10 seconds at 20±10℃. A2: Rinsing treatment: Rinse the etched battery cells with deionized water until there is no residual etching solution on the surface; A3: Drying process: The rinsed solar cells are dried to obtain solar cells with the copper seed layer completely removed.

[0021] Compared with existing technologies, the application of the composite etching inhibitor of this invention has the following advantages: In existing wet etching processes for copper seed layers, the etching solution typically exhibits significant isotropic etching characteristics. While removing residual copper seed layers in non-electrode areas, it easily causes lateral erosion of the copper grid line body, leading to intensified undercutting, increased electrode surface defects, and consequently weakening the adhesion between the electrode and the substrate, thus affecting battery performance. This invention, by applying the composite etching inhibitor to the seed layer removal process of copper grid heterojunction solar cells, allows the etching solution to maintain necessary etching capacity in non-electrode areas while effectively suppressing lateral erosion and undercutting propagation during the etching process through the synergistic adsorption protective layer formed on the copper electrode surface by the first and second etching inhibitors. This application scheme achieves a balance between sufficient removal of residual copper seed layers and protection of the copper electrode structural integrity through the synergistic effect of the chemical etching system and the etching inhibition protection mechanism, thereby solving the technical problem in existing technologies where it is difficult to simultaneously achieve etching efficiency and lateral erosion suppression.

[0022] In one possible implementation, in step A1, the etching process is performed at 25°C for 90 seconds.

[0023] Compared with existing technologies, under the condition of 25°C and 90 seconds of treatment, potassium persulfate composite salt can stably release oxidation capacity in an acidic environment, achieving uniform and controllable removal of residual copper seed layer in non-electrode areas. Furthermore, the adsorption state of the composite corrosion inhibitor on the copper electrode surface remains stable, avoiding insufficient adsorption of corrosion inhibitor due to excessively low temperature, and also avoiding damage or desorption of the protective layer caused by excessively high temperature or etching time. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the undercut value after corrosion without corrosion inhibitor in Example 3; Figure 2 This is a schematic diagram of the undercut value after corrosion by the corrosion inhibitor in Example 3. Detailed Implementation

[0025] First, those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0026] This invention provides a composite etching inhibitor solution, comprising the following components: Oxidizing agent: Potassium persulfate compound salt; Acid: Concentrated sulfuric acid; Composite corrosion inhibitor: Composed of a first corrosion inhibitor and a second corrosion inhibitor, wherein the first corrosion inhibitor is a nitrogen-containing heterocyclic compound that can form a covering adsorption film on the copper surface, and the second corrosion inhibitor is a nitrogen-containing heterocyclic compound that can preferentially adsorb onto highly active sites on the copper surface; Solvent: Deionized water.

[0027] As a preferred embodiment, the first corrosion inhibitor is selected from one of methylbenzotriazole, o-phenanthroline, and 5-methylbenzimidazole; the second corrosion inhibitor is selected from one of imidazole, pyridine, and pyrazole.

[0028] As a preferred embodiment, the mass ratio of the first corrosion inhibitor to the second corrosion inhibitor is (4-6):1.

[0029] As a preferred embodiment, the concentration range of each component in the composite etching inhibitor is as follows: Potassium persulfate compound salt: 15-25 g / L; Concentrated sulfuric acid: 8-12 g / L; First corrosion inhibitor: 0.2-0.3 g / L; Second corrosion inhibitor: 0.04-0.06 g / L.

[0030] As a preferred embodiment, the concentrations of each component in the composite etching inhibitor solution are as follows: Potassium persulfate compound salt: 20 g / L; Concentrated sulfuric acid: 10 g / L; First corrosion inhibitor: 0.25 g / L; Second corrosion inhibitor: 0.05 g / L.

[0031] This invention provides a method for preparing the composite etching inhibitor solution, comprising the following steps: Under stirring conditions, concentrated sulfuric acid is slowly added to deionized water and mixed thoroughly. Add potassium persulfate complex salt to the obtained solution and stir until completely dissolved; Then add the second corrosion inhibitor and stir until completely dissolved; Finally, add the first corrosion inhibitor and stir until completely dissolved to obtain the composite corrosion inhibitor etching solution.

[0032] This invention provides an application of the composite etching inhibitor in the removal of the seed layer of a copper grid heterojunction solar cell, comprising the following steps: A1: Etching process: The solar cell with copper seed layer is immersed in the etching solution and etched for 90±10 seconds at 20±10℃. A2: Rinsing treatment: Rinse the etched battery cells with deionized water until there is no residual etching solution on the surface; A3: Drying process: The rinsed solar cells are dried to obtain solar cells with the copper seed layer completely removed.

[0033] As a preferred embodiment, in step A1, the etching process is performed at 25°C for 90 seconds.

[0034] In the composite etching solution of the present invention, the first and second etching inhibitors exert their etching effects on the copper surface through different adsorption characteristics and modes of action. The first etching inhibitor is a nitrogen-containing heterocyclic compound with a planar conjugated structure. Its molecular structure contains both benzene rings and imidazole rings. Under acidic etching environment, it can coordinate with copper atoms through nitrogen atoms on the imidazole ring, thereby adsorbing on the copper crystal surface in a flat manner to form a relatively dense and hydrophobic adsorption film. This adsorption film can cover the copper surface over a large area and act as a physical and chemical barrier against acidic media and oxidizing components in the etching solution, thereby significantly reducing the overall corrosion rate of copper. However, due to the relatively large molecular structure, its diffusion and adsorption kinetics are relatively slow, and its adsorption stability and specificity at highly reactive sites such as copper grain boundaries, defects, and steps are relatively limited.

[0035] The second corrosion inhibitor is a nitrogen-containing heterocyclic compound with a small molecular weight. Its small molecular size and rapid diffusion allow it to quickly reach the copper surface in the early stages of etching, preferentially adsorbing onto high-energy active sites such as grain boundaries, defects, and sidewall edges within the copper crystal. These sites are typically the starting points for lateral and side-wall corrosion during the etching process. The second corrosion inhibitor effectively inhibits localized corrosion reactions at these active sites through chemical adsorption of nitrogen atoms in its ring structure with copper, thereby reducing the initiation and spread of side-wall corrosion. However, due to the small molecular size of the second corrosion inhibitor, the adsorption layer it forms is relatively thin, limiting its ability to suppress the overall corrosion rate when used alone.

[0036] When the first and second corrosion inhibitors coexist in a composite form in this invention, they form a synergistic adsorption and synergistic corrosion inhibition effect on the copper surface. The second corrosion inhibitor first rapidly occupies the highly active sites on the copper surface, playing a "preferential passivation" role in the lateral corrosion initiation area. Subsequently, the first corrosion inhibitor undergoes large-area adsorption on the relatively flat copper crystal surface, forming a continuous covering protective layer. At the same time, the molecules of the two types of corrosion inhibitors may interact through intermolecular forces such as π-π stacking and hydrogen bonding, so that the covering adsorption film and the adsorption structure at the highly active sites are coupled with each other, ultimately forming a dense, stable composite adsorption protective layer with fewer defects on the copper surface. This invention, through the above-mentioned synergistic mechanism, ensures that the residual copper seed layer in the non-electrode area can be effectively removed while significantly inhibiting the lateral erosion and undercutting phenomenon in the copper electrode area, thereby achieving a balance between etching efficiency and lateral corrosion inhibition.

[0037] The following are embodiments incorporating specific data to further elaborate on the technical solution of the present invention: Example 1 This embodiment provides a composite etching inhibitor and its preparation method. The composite etching inhibitor is prepared by the method, which includes the following steps: A1: Etching Process In this embodiment, the specific formulation of the composite etching inhibitor is as follows: Potassium persulfate compound salt: 15 g / L; Concentrated sulfuric acid: 8 g / L; First corrosion inhibitor: o-phenanthroline: 0.20 g / L; Second corrosion inhibitor: pyridine, 0.04 g / L; The solvent is deionized water.

[0038] Solar cells that have completed the copper electroplating process and have residual copper seed layers on their surface are immersed in the above-mentioned etching solution and etched at 20°C for 80 seconds. Through this etching process, the residual copper seed layer in the area outside the copper electrode is removed.

[0039] A2: Rinsing treatment After the etching process is completed, the battery cell is removed and thoroughly rinsed with deionized water until no etching solution remains on the surface of the battery cell, so as to prevent the etching solution from continuing to act on the surface of the copper electrode.

[0040] A3: Drying treatment After rinsing, the solar cells are dried using conventional methods to obtain copper grid heterojunction solar cells with the copper seed layer completely removed.

[0041] Example 2 Based on Example 1, this embodiment uses another set of first and second corrosion inhibitors to further verify the process adaptability of the composite corrosion inhibitor etching solution under different concentrations and corrosion inhibitor combinations: A1: Etching Process In this embodiment, the specific formulation of the composite etching inhibitor is as follows: Potassium persulfate compound salt: 25 g / L; Concentrated sulfuric acid: 12 g / L; First corrosion inhibitor: methylbenzotriazole: 0.30 g / L; Second corrosion inhibitor: pyrazole: 0.06 g / L; The solvent is deionized water.

[0042] Solar cells that have completed the copper electroplating process and have residual copper seed layers on their surface are immersed in the above-mentioned etching solution and etched at 30°C for 100 seconds. Through this etching process, the residual copper seed layer in the area outside the copper electrode is removed.

[0043] A2: Rinsing treatment After the etching process is completed, the battery cell is removed and thoroughly rinsed with deionized water until no etching solution remains on the surface of the battery cell, so as to prevent the etching solution from continuing to act on the surface of the copper electrode.

[0044] A3: Drying treatment After rinsing, the solar cells are dried using conventional methods to obtain copper grid heterojunction solar cells with the copper seed layer completely removed.

[0045] Example 3: This embodiment also provides a composite etching inhibitor and its preparation method. Taking a copper grid heterojunction solar cell as an example, the etching inhibitor containing the composite etching inhibitor is used to remove the residual copper seed layer during the preparation of the copper electrode, so as to verify the actual effect of the composite etching inhibitor in inhibiting the side corrosion of the copper electrode and improving the surface morphology of the electrode.

[0046] A1: Etching Process In this embodiment, the specific formulation of the composite etching inhibitor is as follows: Potassium persulfate compound salt: 20 g / L; Concentrated sulfuric acid: 10 g / L; First corrosion inhibitor: 5-methylbenzimidazole: 0.25 g / L; Second corrosion inhibitor imidazole: 0.05 g / L; The solvent is deionized water.

[0047] Solar cells that have completed the copper electroplating process and have residual copper seed layers on their surface are immersed in the above-mentioned etching solution and etched at 25°C for 90 seconds. Through this etching process, the residual copper seed layer in the area outside the copper electrode is selectively removed.

[0048] A2: Rinsing treatment After the etching process is completed, the battery cell is immediately removed and thoroughly rinsed with deionized water until no etching solution remains on the surface of the battery cell, so as to prevent the etching solution from continuing to act on the surface of the copper electrode.

[0049] A3: Drying treatment After rinsing, the solar cells are dried using conventional methods to obtain copper grid heterojunction solar cells with the copper seed layer completely removed.

[0050] Technical effectiveness verification: After the above etching process, the copper electrode of Example 3 was used as the test object to characterize the surface condition and lateral etching of the copper electrode of this example. The results are as follows: 1) Improved corrosion on copper electrode surface Compared to acidic etching solutions without added corrosion inhibitors, the copper electrode surface treated with the composite corrosion inhibitor etching solution of this embodiment is smoother, and corrosion defects are significantly reduced. The water contact angle is used as a characterization indicator. After etching without corrosion inhibitor, the contact angle between the copper electrode surface and water is 46.5°. After etching with the composite etching solution of this embodiment, the contact angle between the copper electrode surface and water is increased to 75.5°.

[0051] The above results show that the corrosion level of the copper electrode surface is significantly reduced and the surface smoothness is significantly improved.

[0052] 2) Significantly reduced copper electrode side etching (undercutting) Comparing the etching effects of the acidic etching solution without corrosion inhibitor and the composite corrosion inhibitor etching solution of this embodiment, the undercut value of the copper electrode changed significantly, such as... Figure 1 , Figure 2 As shown: After etching without corrosion inhibitor, the undercut value is 4.08 μm (17.78 − 13.70). After etching with the composite etching inhibitor solution of this embodiment, the undercut value was reduced to 0.18 μm (15.69 −15.51).

[0053] The above results show that the composite etching inhibitor used in this embodiment can significantly suppress the lateral etching of the copper electrode during the etching process while ensuring the full removal of the residual copper seed layer. This further proves that the etching solution using the composite etching inhibitor of the present invention can effectively balance the contradiction between the complete removal of the copper seed layer and the suppression of lateral etching of the copper electrode in the copper grid heterojunction solar cell seed layer back etching process, significantly improve the surface quality of the copper electrode, and has good process stability and application value.

[0054] Further comparative verification through the above embodiments shows that the composite etching agent provided by the present invention can stably achieve selective removal of the copper seed layer under different combinations of etching agents and different etching conditions. While ensuring that the residual copper seed layer in the non-electrode area is fully etched, it effectively inhibits the lateral erosion and undercutting phenomenon in the copper electrode area. After introducing a composite etching system composed of a first etching agent and a second etching agent, the corrosion defects on the copper electrode surface are significantly reduced, the surface morphology is smoother, the hydrophilicity is significantly reduced, and the lateral etching depth is greatly reduced. This fully demonstrates that the composite etching agent of the present invention has good etching stability and process adaptability under actual process conditions. The present invention utilizes the synergistic adsorption effect of two types of nitrogen-containing heterocyclic etching agents with different molecular structures and adsorption behaviors on the copper surface. The second etching agent preferentially passivates the highly active sites on the copper surface and inhibits the initiation of lateral etching, while the first etching agent forms a continuous covering protective film on the copper crystal surface. This results in the construction of a dense and stable composite adsorption protective layer on the copper surface, achieving synergistic control of the overall corrosion rate and local lateral etching behavior. Compared with existing etching systems with a single corrosion inhibitor or no corrosion inhibitor, this invention effectively solves the problems of severe side etching and difficulty in achieving both surface quality and quality during the back etching of the seed layer of copper grid heterojunction solar cells without significantly reducing etching efficiency. It has the advantages of good etching uniformity, significant side etching suppression effect, wide process window and suitability for industrial application.

[0055] In the description of this invention, the references to "one embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite etching inhibitor solution, characterized in that, Includes the following components: Oxidizing agent: Potassium persulfate compound salt; Acid: Concentrated sulfuric acid; Composite corrosion inhibitor: Composed of a first corrosion inhibitor and a second corrosion inhibitor, wherein the first corrosion inhibitor is a nitrogen-containing heterocyclic compound that can form a covering adsorption film on the copper surface, and the second corrosion inhibitor is a nitrogen-containing heterocyclic compound that can preferentially adsorb onto highly active sites on the copper surface; Solvent: Deionized water.

2. The composite etching inhibitor solution according to claim 1, characterized in that, The first corrosion inhibitor is selected from one of methylbenzotriazole, o-phenanthroline, and 5-methylbenzimidazole; the second corrosion inhibitor is selected from one of imidazole, pyridine, and pyrazole.

3. The composite etching inhibitor solution according to claim 1, characterized in that, The mass ratio of the first corrosion inhibitor to the second corrosion inhibitor is (4-6):

1.

4. The composite etching inhibitor according to claim 1, characterized in that, The concentration ranges of each component in the composite etching inhibitor are as follows: Potassium persulfate compound salt: 15-25 g / L; Concentrated sulfuric acid: 8-12 g / L; First corrosion inhibitor: 0.2-0.3 g / L; Second corrosion inhibitor: 0.04-0.06 g / L.

5. The composite etching inhibitor according to claim 1, characterized in that, The concentrations of each component in the composite etching inhibitor are as follows: Potassium persulfate compound salt: 20 g / L; Concentrated sulfuric acid: 10 g / L; First corrosion inhibitor: 0.25 g / L; Second corrosion inhibitor: 0.05 g / L.

6. A method for preparing the composite etching inhibitor solution according to any one of claims 1-5, characterized in that, Includes the following steps: Under stirring conditions, concentrated sulfuric acid is slowly added to deionized water and mixed thoroughly. Add potassium persulfate complex salt to the obtained solution and stir until completely dissolved; Then add the second corrosion inhibitor and stir until completely dissolved; Finally, add the first corrosion inhibitor and stir until completely dissolved to obtain the composite corrosion inhibitor etching solution.

7. The application of the composite etching inhibitor solution according to any one of claims 1-5, characterized in that, The application refers to the use of the composite etching inhibitor solution in the removal of the seed layer of a copper grid heterojunction solar cell, including the following steps: A1: Etching process: The solar cell with copper seed layer is immersed in the etching solution and etched for 90±10 seconds at 20±10℃. A2: Rinsing treatment: Rinse the etched battery cells with deionized water until there is no residual etching solution on the surface; A3: Drying process: The rinsed solar cells are dried to obtain solar cells with the copper seed layer completely removed.

8. The application of the composite corrosion inhibitor etching solution according to claim 7, characterized in that, In step A1, the etching process is performed at 25°C for 90 seconds.

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