Tin-coated copper grid line and preparation method and application thereof

Abstract

The invention relates to the field of solar cell preparation, in particular to a tin-coated copper grid line and a preparation method and application thereof. The invention provides a preparation method of a tin-coated copper grid line. The preparation method comprises the following steps: performing ink-jet printing on a mask region of a metal seed layer of an initial solar cell to form a mask layer with the height of h1; the contact angle between the ink droplet and the surface of the metal seed layer is 90-150 degrees after the ink droplet is solidified on the metal seed layer; an initial copper grid line with the height of h2 is formed on the grid line area through copper electroplating with the mask layer as protection, tin electroplating is carried out after # imgabs0 #, and then a tin-coated copper grid line is formed. According to the preparation method provided by the invention, the outer side of the copper grid line can be coated with tin in a tin electroplating manner before the mask layer is removed, and the production cost is relatively low.

Description

Technical Field

[0001] The invention relates to the field of solar cell preparation, and in particular to a tin-clad copper grid line and a preparation method and application thereof. Background Art

[0002] With the development of the photovoltaic industry, the industrialization preparation technology of solar cells is becoming more and more diversified, and the preparation cost is becoming lower and lower. At present, the photovoltaic grid line manufacturing process uses the screen printing silver electrode process, which consumes a large amount of silver paste, and the cost of silver paste is relatively expensive. Because the electroplating copper technology has the following advantages: low cost; the conductivity of the prepared copper grid line is better than the grid line prepared by silver paste, so the electroplating copper technology is considered to be the most potential manufacturing process for realizing the preparation of photovoltaic grid lines without silver. In the prior art, before forming the copper grid line by the electroplating copper process, a mask layer with a corresponding pattern of the grid line needs to be formed on the initial solar cell. After the copper grid line is formed, due to the characteristics of copper itself being easy to oxidize and having poor weldability, a tin layer needs to be plated on its surface. In the prior art, tin electroplating is often used to tin the surface of the copper grid line before the mask layer is removed. However, since the side wall of the copper grid line is adjacent to the mask layer, only the top surface of the copper grid line will be attached with a tin layer during the tin electroplating process. As the mask layer is removed in the subsequent process, the side wall of the copper grid line will still be exposed, and the copper grid line still has the risk of being oxidized in the air. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that it is difficult to avoid oxidation of the copper grid line when tin is applied to the surface of the copper grid line by tin electroplating before the mask layer is removed, thereby providing a tin-clad copper grid line and its preparation method and application.

[0004] The scheme adopted by the present invention is as follows:

[0005] The present invention provides a method for preparing a solar cell with a tin-clad copper grid line, comprising the following steps:

[0006] 1) forming a metal seed layer on at least one side of the surface of an initial solar cell; the surface of the metal seed layer has a mask area;

[0007] 2) performing inkjet printing on the mask area of ​​the metal seed layer to form a mask layer with a height of h1; wherein the contact angle between the ink droplets sprayed from the nozzles toward the mask area and the surface of the metal seed layer after solidification on the metal seed layer is 90-150°;

[0008] 3) The area on the surface of the metal seed layer not covered by the mask layer is the gate line area, and an initial copper gate line with a height of h2 is formed on the gate line area by copper electroplating with the mask layer as protection, wherein:

[0009] ​It can be understood that the initial solar cell is a cell to be made into a grid line; the cell to be made into a grid line can be a heterojunction cell (HJT cell) to be made into a grid line or a back contact cell (BC cell) to be made into a grid line;

[0010] Preferably, the method of forming the metal seed layer is selected from chemical vapor deposition or physical vapor deposition;

[0011] And / or, the thickness of the metal seed layer is 50nm-1000nm;

[0012] And / or, the material of the metal seed layer is selected from copper.

[0013] Preferably, in step 2), the height of the mask layer is 25-40 μm;

[0014] And / or, in step 2), the ink drop material is selected from a hot melt material, wherein the hot melt material has fluidity at a temperature greater than or equal to 50°C and a viscosity of 0.1 mPa·S to 20 mPa·S; and when at a temperature less than or equal to 25°C, the hot melt material is solid or fluid, and when it is a fluid, the viscosity of the hot melt material is greater than 10000 mPa·S.

[0015] Preferably, the hot melt material is selected from one or more of acrylate, rosin ester resin, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax, and ethylene-vinyl acetate copolymer wax.

[0016] Preferably, in step 3), the current density in the copper electroplating is 3-7ASD, and the electroplating time is 400-1000s.

[0017] Preferably, in step 3), an initial copper gate line with a height of h2 is formed on the gate line area by copper electroplating with a mask layer as protection, wherein:

[0018] Preferably, in step 3), the line width of the initial copper grid line is 15-25 μm.

[0019] Preferably, in step 3), the current density in the tin electroplating is 1.3-3ASD, and the electroplating time is 100-250s.

[0020] Preferably, after forming the tin-clad copper grid line, the process further includes sequentially removing the mask layer and the metal seed layer not covered by the tin-clad copper grid line.

[0021] The present invention also provides a tin-clad copper grid line, which is prepared by the above-mentioned preparation method.

[0022] The present invention also provides a solar cell sheet, comprising the tin-clad copper grid wire prepared by the above-mentioned preparation method.

[0023] The technical solution of the present invention has the following advantages:

[0024] The present invention provides a method for preparing a tin-clad copper grid line, comprising the following steps: 1) forming a metal seed layer on at least one side of an initial solar cell; the surface of the metal seed layer has a mask area; 2) performing inkjet printing on the mask area of ​​the metal seed layer to form a mask layer with a height of h1; wherein, during inkjet printing, the ink droplets sprayed from the nozzles to the mask area solidify on the metal seed layer, and the contact angle with the surface of the metal seed layer is 90-150°; 3) the area on the surface of the metal seed layer not covered by the mask layer is a grid line area, and an initial copper grid line with a height of h2 is formed on the grid line area by copper electroplating with the mask layer as protection, wherein, Then, tin electroplating is performed to form tin-clad copper grid lines.

[0025] The inventors found in their research that after a metal seed layer is formed on the surface of the initial solar cell, a mask layer is formed by inkjet printing in the mask area of ​​the metal seed layer. When the contact angle between the ink droplet and the surface of the metal seed layer during the inkjet printing process is 90-150°, and the height ratio of the initial copper grid line formed in the subsequent copper electroplating process to the mask layer is When the mask layer is removed, a small gap can be generated between the initial copper grid line and the mask layer. In the subsequent tin electroplating process, the tin layer can be deposited and grown in the above gap and on the top surface of the initial copper grid line to form a tin layer that fully wraps the top surface and side wall of the initial copper grid line, forming a tin-clad copper grid line. The present invention can use tin electroplating to tin the outer side of the copper grid line before removing the mask layer, and the production cost is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is an optical micrograph of the initial copper grid line prepared in Example 1 of the present invention;

[0028] Figure 2 is an optical micrograph of a portion of the initial copper grid lines after tin electroplating in Example 1 of the present invention;

[0029] Figure 3 This is an optical micrograph of the initial copper grid line prepared in Comparative Example 1 of the present invention;

[0030] Figure 4 This is an optical micrograph of the initial copper grid line prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0032] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0033] Example

[0034] A method for preparing a solar cell with a tin-clad copper grid line comprises the following steps:

[0035] 1) forming a metal seed layer on at least one side of the surface of an initial solar cell; the surface of the metal seed layer has a mask area;

[0036] 2) performing inkjet printing on the mask area of ​​the metal seed layer to form a mask layer with a height of h1; wherein the contact angle between the ink droplets sprayed from the nozzles toward the mask area and the surface of the metal seed layer after solidification on the metal seed layer is 90-150°;

[0037] 3) The area on the surface of the metal seed layer not covered by the mask layer is the gate line area, and an initial copper gate line with a height of h2 is formed on the gate line area by copper electroplating with the mask layer as protection, wherein: Then, tin electroplating is performed to form tin-clad copper grid lines.

[0038] After a metal seed layer is formed on the surface of the initial solar cell, a mask layer is formed in the mask area of ​​the metal seed layer by inkjet printing. When the contact angle between the ink droplet and the surface of the metal seed layer during the inkjet printing process is 90-150°, and the height of the initial copper grid line formed in the subsequent copper electroplating process and the mask layer is greater than When the mask layer is removed, a tiny gap can be created between the initial copper grid line and the mask layer. In the subsequent tin electroplating process, the tin layer can be deposited and grown in the above gap and on the top surface of the initial copper grid line to form a tin layer that fully wraps the top surface and side walls of the initial copper grid line, forming a tin-clad copper grid line. The present application can use tin electroplating to tin the outer side of the copper grid line before removing the mask layer, and the production cost is relatively low.

[0039] In one embodiment, the initial solar cell is an initial solar cell for which grid lines are to be manufactured.

[0040] In one embodiment, the method of forming the metal seed layer is selected from chemical vapor deposition or physical vapor deposition;

[0041] In a specific embodiment, the thickness of the metal seed layer is 50nm-1000nm; for example, 100nm, 200nm, 500nm or 800nm;

[0042] In a specific embodiment, the material of the metal seed layer is selected from copper.

[0043] In one embodiment, in step 2), the mask layer obtained by inkjet printing has a height of h1, and h1 is 25-40 μm; for example, 25 μm, 30 μm, 35 μm, 40 μm;

[0044] In one embodiment, in step 2), the ink drop material is selected from a hot melt material, wherein the hot melt material has fluidity at a temperature greater than or equal to 50°C and a viscosity of 0.1 mPa·S to 20 mPa·S; and when the temperature is less than or equal to 25°C, the hot melt material is solid or fluid, and when it is a fluid, the viscosity of the hot melt material is greater than 10000 mPa·S.

[0045] In a specific embodiment, the hot melt material may be one or more of acrylate, rosin ester resin, C11-C22 alkyl acid, polypropylene wax, microcrystalline wax, polyethylene wax, and ethylene-vinyl acetate copolymer wax.

[0046] In one embodiment, in step 3), the copper electroplating current density is 3-7ASD, and the electroplating time is 400-1000s; for example, the current density is 5ASD, and the electroplating time is 720s.

[0047] In a specific embodiment, in step 3), the initial copper grid line height is h2, wherein,

[0048] when When the gap between the initial copper grid line and the mask layer will be too small, which is not conducive to the subsequent tin electroplating; when When the gap between the initial copper grid line and the mask layer is too large, it is easy to cause the final tin-clad copper grid line to be wider, resulting in a large shading area of ​​the grid line, thereby affecting the conversion efficiency of the battery cell.

[0049] The inventors have found in their research that when the height ratio of the initial copper grid line to the mask layer is between 1 / 2 and 3 / 4, the formed copper-clad tin grid line has an ideal tin layer thickness and light shielding area.

[0050] In a specific embodiment, in step 3), the line width of the initial copper grid line is 15-25 μm; for example, 15 μm, 20 μm or 25 μm.

[0051] In a specific embodiment, in step 3), the current density in the tin electroplating is 1.3-3ASD, and the electroplating time is 100-250s; for example, the current density in the tin electroplating is 2ASD, and the electroplating time is 200s.

[0052] In a specific embodiment, the method further includes a process of sequentially removing the mask layer and the metal seed layer not covered by the tin-clad copper gate line after forming the tin-clad copper gate line.

[0053] In a specific embodiment, the mask layer is removed by dissolving it with a mixed solution of diethylene glycol butyl ether and alkali; the alkali is selected from sodium hydroxide or potassium hydroxide.

[0054] In a specific embodiment, the metal seed layer material is copper, and the process of removing the metal seed layer not covered by the tin-clad copper grid line is to use CuCl 2 The removal is carried out by etching method using alkaline etching solution / sulfuric acid and hydrogen peroxide.

[0055] Example 1

[0056] This embodiment provides a method for preparing a tin-clad copper grid line, comprising the following steps:

[0057] 1) forming a copper seed layer with a thickness of 200 nm on the surface of the initial solar cell by physical vapor deposition, and then performing inkjet printing on the mask area surface of the copper seed layer to form a mask layer, wherein the inkjet printing material is polypropylene wax, wherein the contact angle between the ink droplet and the mask area surface is 100-110°, and the mask layer thickness is 25 μm;

[0058] 2) forming an initial copper gate line on the gate line area by copper electroplating with the mask layer as protection, wherein the copper electroplating solution includes copper sulfate (concentration of 200 g / L), sulfuric acid (concentration of 70 g / L), sodium chloride (70 mg / L), and water, the electroplating current density is 5 ASD, the electroplating time is 720 s, and the initial copper gate line formed by electroplating (the height of the initial copper gate line is about 15 μm) is as follows Figure 1 As shown;

[0059] 3) Tin electroplating is performed on part of the initial copper grid lines, wherein the plating solution of the tin electroplating includes stannous methanesulfonate (concentration is 25 g / L), methanesulfonic acid (concentration is 200 g / L), and water, the electroplating current density is 2ASD, the electroplating time is 200 s, and the copper-clad tin grid lines (such as Figure 2 shown);

[0060] This embodiment only shows that a gap is generated between the initial copper grid line and the mask layer, so that a tin layer can be deposited on the side wall of the initial copper grid line.

[0061] Comparative Example 1

[0062] This comparative example provides a method for preparing a copper grid line, comprising the following steps:

[0063] 1) forming a copper seed layer with a thickness of 200 nm on the surface of the initial solar cell by physical vapor deposition, and then performing inkjet printing on the mask area surface of the copper seed layer to form a mask layer, wherein the inkjet printing material is polypropylene wax, wherein the contact angle between the ink droplet and the mask area surface is 100-110°, and the mask layer thickness is 25 μm;

[0064] 2) forming an initial copper gate line on the gate line area by copper electroplating with the mask layer as protection, wherein the copper electroplating solution includes copper sulfate (concentration of 200 g / L), sulfuric acid (concentration of 70 g / L), sodium chloride (70 mg / L), and water, the electroplating current density is 1.5 ASD, the electroplating time is 720 s, and the copper gate line formed by electroplating (the height of the initial copper gate line is about 5 μm) is as follows Figure 3 As shown;

[0065] The initial copper grid line did not generate a gap with the mask layer, and no subsequent tin electroplating process was performed.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing a solar cell with a copper grid line, comprising the following steps:

[0068] 1) forming a copper seed layer with a thickness of 200 nm on the surface of the initial solar cell by physical vapor deposition, and then performing inkjet printing on the mask area surface of the copper seed layer to form a mask layer, wherein the inkjet printing material is polypropylene wax, wherein the contact angle between the ink droplet and the mask area surface is 70-80°, and the mask layer thickness is 25 μm;

[0069] 2) forming an initial copper gate line on the gate line area by copper electroplating with the mask layer as protection, wherein the copper electroplating solution includes copper sulfate (concentration of 200 g / L), sulfuric acid (concentration of 70 g / L), sodium chloride (70 mg / L), and water, the electroplating current density is 5 ASD, the electroplating time is 720 s, and the initial copper gate line formed by electroplating (the height of the initial copper gate line is about 15 μm) is as follows Figure 4 As shown;

[0070] The initial copper grid line did not generate a gap with the mask layer, and no subsequent tin electroplating process was performed.

[0071] from Figure 1-Figure 4It is not difficult to see that only when the ink droplet has a specific contact angle with the mask area and the copper grid line is within a certain range, a gap will be formed between the formed copper grid line and the mask layer, and tin-clad copper grid lines will be formed during subsequent tin electroplating.

[0072] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a tin-clad copper grid line, characterized in that: The steps include: 1) forming a metal seed layer on at least one side of the surface of an initial solar cell; the surface of the metal seed layer has a mask area; 2) performing inkjet printing on the mask area of ​​the metal seed layer to form a mask layer with a height of h1; wherein the contact angle between the ink droplets sprayed from the nozzles toward the mask area and the surface of the metal seed layer after solidification on the metal seed layer is 90-150°; 3) The area on the surface of the metal seed layer not covered by the mask layer is the gate line area, and an initial copper gate line with a height of h2 is formed on the gate line area by copper electroplating with the mask layer as protection, wherein: Then, tin electroplating is performed to form tin-clad copper grid lines.

2. The preparation method according to claim 1, characterized in that: The method of forming the metal seed layer is selected from chemical vapor deposition or physical vapor deposition; And / or, the thickness of the metal seed layer is 50nm-1000nm; And / or, the material of the metal seed layer is selected from copper.

3. The preparation method according to claim 1, characterized in that: In step 2), the height of the mask layer is 25-40 μm; And / or, in step 2), the ink drop material is selected from a hot melt material, wherein the hot melt material has fluidity at a temperature greater than or equal to 50°C and a viscosity of 0.1 mPa·S to 20 mPa·S; and when at a temperature less than or equal to 25°C, the hot melt material is solid or fluid, and when it is a fluid, the viscosity of the hot melt material is greater than 10000 mPa·S.

4. The preparation method according to claim 1, characterized in that: In step 3), the current density in the copper electroplating is 3-7ASD, and the electroplating time is 400-1000s.

5. The preparation method according to claim 1, characterized in that: In step 3), an initial copper gate line with a height of h2 is formed on the gate line area by copper electroplating with a mask layer as protection, wherein:

6. The preparation method according to claim 1, characterized in that: In step 3), the line width of the initial copper grid line is 15-25 μm.

7. The preparation method according to claim 1, characterized in that: In step 3), the current density in the tin electroplating is 1.3-3ASD, and the electroplating time is 100-250s. 。 8. The preparation method according to claim 1, characterized in that: After forming the tin-clad copper grid line, the process also includes sequentially removing the mask layer and the metal seed layer not covered by the tin-clad copper grid line.

9. A tin-clad copper grid wire, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. A solar cell, characterized in that: The invention comprises a tin-clad copper grid line prepared by the preparation method according to any one of claims 1 to 8.

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