Test method for the adhesion between the tco layer and the seed metal layer of a battery cell

Abstract

The application provides a test method for the bonding force between a TCO layer and a seed metal layer of a battery piece, and relates to the technical field of photovoltaics. The test method comprises the following steps: removing the seed metal layer outside a first region by adopting a chemical etching method to obtain a seed metal layer covering only the first region; and then testing the bonding force between the seed metal layer and the TCO layer by adopting a tensile test device. The first region is a region for forming a grid line structure. The test method provided by the application can effectively and accurately test the bonding force between the seed metal layer and the TCO layer.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and more specifically, to a method for testing the bonding strength between the TCO layer and the seed metal layer of a solar cell. Background Technology

[0002] Currently, in order to reduce the cost of forming the grid structure, the common practice is to "first deposit a seed metal layer on the TCO layer of the solar cell, and then electroplate copper grid lines on the seed metal layer" instead of the traditional process of "screen printing silver paste on the TCO layer to form grid lines".

[0003] If the bonding force between the seed metal layer and the TCO layer is poor, it will affect the conductivity between the seed metal layer and the TCO layer, which in turn will affect the current collection of the copper grid lines; it will also affect the contact resistance between the TCO layer and the copper grid lines, which will lead to poor electrical performance and conversion efficiency of the solar cells. In severe cases, it may even lead to a large number of tensile failures in the solar cells.

[0004] However, since the thickness of both the seed metal layer (only about 100-200 nm) and the TCO layer (only about 100 nm) is relatively thin, directly using a tensile testing device to test the bonding force between the seed metal layer and the TCO layer can easily lead to damage to the seed metal layer. Furthermore, since the seed metal layer and the TCO layer have the same area, directly using a tensile testing device to test the bonding force between the seed metal layer and the TCO layer will also result in an inability to effectively and accurately test the bonding force between the seed metal layer and the TCO layer, which is not conducive to avoiding situations such as poor electrical performance or conversion efficiency of the prepared solar cells in advance. Summary of the Invention

[0005] The purpose of this application is to provide a method for testing the bonding force between the TCO layer and the seed metal layer of a solar cell, which aims to effectively and accurately test the bonding force between the seed metal layer and the TCO layer.

[0006] This application provides a method for testing the adhesion between the TCO layer and the seed metal layer of a solar cell, comprising: removing the seed metal layer outside a first region by chemical etching to obtain a seed metal layer covering only the first region; and then testing the adhesion between the seed metal layer and the TCO layer using a tensile testing device. The first region is the area used to form the grid line structure.

[0007] This application first removes the seed metal layer outside the region used to form the grid structure (i.e., the first region), so that the remaining seed metal layer (i.e., the seed metal layer in the first region) forms a protruding structure on the surface of the TCO layer that is consistent with the shape of the grid structure. This makes it clear that there is a boundary between the TCO layer and the seed metal layer along the width or length direction of the cell, which facilitates the peeling between the TCO layer and the seed metal layer. This allows the surface of the seed metal layer in the first region to be used as a connection point for a tensile testing device. This helps to avoid the seed metal layer from being easily damaged when directly testing the bonding force between the seed metal layer and the TCO layer using a tensile testing device. It also helps to effectively and accurately test the bonding force between the seed metal layer and the TCO layer.

[0008] In an optional embodiment of this application, the method for removing the seed metal layer outside the first region includes: covering the seed metal layer with photosensitive emulsion, exposing the first region on the surface of the seed metal layer, developing and removing the photosensitive emulsion outside the first region; and then sequentially removing the seed metal layer outside the first region and the photosensitive emulsion within the first region.

[0009] The above method can effectively remove the seed metal layer outside the first region.

[0010] Optionally, the thickness of the photosensitive emulsion covering the surface of the seed metal layer is 5-10 μm.

[0011] The thickness of the photosensitive emulsion covering the surface of the seed metal layer is 5-10 μm, which helps to effectively improve the accuracy of the seed metal layer formed in the first region. If the thickness of the photosensitive emulsion covering the seed metal layer is too thin, it may cause the photosensitive emulsion to not be effectively covered in some areas due to local minor unevenness on the surface of the seed metal layer, which is not conducive to the subsequent accurate formation of the seed metal layer in the first region.

[0012] Optionally, the exposure operation uses laser exposure with a laser energy density of 50-100 mJ / cm². 2 .

[0013] The exposure process uses laser exposure, with a laser energy density of 50-100 mJ / cm². 2 This can improve the accuracy of the pattern formed by exposure corresponding to the first region, which is beneficial to effectively improve the accuracy of the seed metal layer formed in the first region.

[0014] In an optional embodiment of this application, the step of testing the bonding force between the seed metal layer and the TCO layer using a tensile testing device includes: attaching a welding rod to the surface of the seed metal layer, connecting the welding rod to the tensile testing device, and then testing the bonding force between the seed metal layer and the TCO layer.

[0015] In an optional embodiment of this application, the minimum distance from the welding electrode to the edge of the first region is ≤0.1mm.

[0016] Optionally, the welding electrode has at least a portion located at the edge of the first region.

[0017] The above-described configuration allows the edge of the seed metal layer to be directly subjected to the force from the tensile testing device, facilitating a tendency for the TCO layer and the seed metal layer to peel off from each other. Compared to the method where the welding rod is connected to the middle of the entire first region, the above configuration helps to avoid the situation where the seed metal layer in the middle of the first region is damaged due to the force from the tensile testing device acting directly on the middle of the seed metal layer in the first region, thus making it impossible to accurately obtain the bonding force data between the seed metal layer and the TCO layer.

[0018] In an optional embodiment of this application, the welding rod is welded to the area on the surface of the seed metal layer used to form the main grid lines in the grid line structure.

[0019] The above setup allows the bonding strength test results to more accurately reflect the impact on the conductivity between the seed metal layer and the TCO layer.

[0020] In an optional embodiment of this application, the welding rod is connected to the surface of the seed metal layer to form the intersection area of ​​the main gate line and the sub-gate line in the gate line structure.

[0021] The above setup allows the bonding strength test results to more accurately reflect the impact on the conductivity between the seed metal layer and the TCO layer.

[0022] In an optional embodiment of this application, the welding rod is connected to the area on the surface of the seed metal layer used to form PAD points, and the number of welding rods is 4-8, with one welding rod connected to one area on the seed metal layer used to form PAD points.

[0023] The above setup allows the test results of the bonding force between the TCO layer and the seed metal layer to better reflect the influence on the conductivity between the seed metal layer and the TCO layer. It also avoids the situation where the accuracy of the test results is affected by the poor welding force of some welding rods, which is conducive to improving the accuracy of the test of the bonding force between the TCO layer and the seed metal layer.

[0024] In an optional embodiment of this application, the welding rod is welded to the surface of the seed metal layer. The welding rod is a copper welding rod with a tin layer on its surface, and the welding temperature is 260-300°C.

[0025] The welding rod is a copper welding rod with a tin layer on its surface. The copper material as the base material can improve the mechanical strength of the entire welding rod and facilitate effective bonding force testing. The welding temperature is 260-300℃, which enables effective welding and fixing between the seed metal layer and the tin layer of the welding rod.

[0026] In an optional embodiment of this application, the tensile speed of the tensile testing device is 280-320 mm / min.

[0027] The tensile testing device has a tensile speed of 280-320 mm / min, which helps to further improve the accuracy of testing the bonding force between the TCO layer and the seed metal layer, and also helps to further avoid the seed metal layer from being damaged due to excessive tensile speed.

[0028] In an optional embodiment of this application, the step of testing the bonding force between the seed metal layer and the TCO layer using a tensile testing device further includes: first covering the surface of the seed metal layer with flux and drying the flux, and then connecting the welding rod.

[0029] The above setup effectively improves the bonding effect between the welding rod and the seed metal layer, and helps to further improve the accuracy of testing the adhesion between the TCO layer and the seed metal layer.

[0030] Optionally, a method of coating the surface of the seed metal layer with flux includes immersing the battery cell in flux. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating the testing process for the bonding strength between the TCO layer and the seed metal layer of a solar cell, as provided in an embodiment of this application, is shown.

[0033] Figure 2 A cross-sectional schematic diagram of the battery cell provided in an embodiment of this application is shown.

[0034] Figure 3 This illustration shows a cross-sectional view of a photosensitive emulsion coating on a seed metal layer, as provided in an embodiment of this application.

[0035] Figure 4 This illustration shows a cross-sectional schematic diagram of the exposure of a first region on the surface of a seed metal layer, as provided in an embodiment of this application.

[0036] Figure 5 This is a schematic cross-sectional view of the battery cell after removing the photosensitive adhesive outside the first region, as provided in an embodiment of this application.

[0037] Figure 6 This illustration shows a cross-sectional view of a battery cell after removing the seed metal layer outside the first region, as provided in an embodiment of this application.

[0038] Figure 7 This illustration shows a cross-sectional view of a battery cell after the photosensitive adhesive in the first region has been removed, according to an embodiment of this application.

[0039] Figure 8 A schematic diagram of the structure provided in this application, showing a welding electrode connected to a seed metal layer, is shown.

[0040] Figure 9 It shows Figure 8 Enlarged view of point A in the middle.

[0041] Icons: 100 - Solar cell; 101 - First region; 102 - Second region; 110 - Seed metal layer; 120 - TCO layer; 130 - Doped layer; 140 - Intrinsic amorphous silicon layer; 150 - N-type silicon wafer substrate; 160 - Photosensitive adhesive; 170 - Solder rod. Detailed Implementation

[0042] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having”, and any variations thereof, in the specification and the foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0044] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] In the description of the embodiments of this application, the technical terms such as "middle", "length", "width", and "thickness" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0047] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "connection" and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can also refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0048] Since the seed metal layer is generally formed on the TCO layer by vapor deposition, the seed metal layer completely covers the TCO layer (i.e., the area of ​​the seed metal layer is equal to the area of ​​the TCO layer).

[0049] The inventors discovered that because the seed metal layer of the solar cell is only about 100-200 nm thick and the TCO layer is only about 100 nm thick, and the area of ​​the seed metal layer is equal to that of the TCO layer, if the connection point of the tensile testing device is directly placed on the surface of the seed metal layer, and the tensile testing device applies a force to the seed metal layer away from the TCO layer, since there is no clear boundary between the seed metal layer and the TCO layer along the tensile direction, the tensile force applied by the tensile testing device will cause a gap between the seed metal layer and the TCO layer. The seed metal layer is difficult to peel off. Under the tensile force applied by the tensile testing device, the seed metal layer is damaged before it shows any tendency to peel off. This makes it difficult to effectively and accurately test the bonding force between the TCO layer and the seed metal layer. Furthermore, since the seed metal layer and the TCO layer have the same area, directly using a tensile testing device to test the bonding force between the seed metal layer and the TCO layer will also result in an inability to effectively and accurately test the bonding force between the seed metal layer and the TCO layer. This is not conducive to avoiding situations such as poor electrical performance or conversion efficiency of the prepared solar cells in advance.

[0050] Therefore, this application provides a method for testing the bonding strength between the TCO layer and the seed metal layer of a solar cell. Figure 1 This application provides a flowchart illustrating the testing process for the bonding strength between the TCO layer and the seed metal layer of a solar cell, as illustrated in an embodiment of this application. Please refer to [link / reference]. Figure 1 The testing methods for the bonding strength between the TCO layer and the seed metal layer of the solar cell include:

[0051] S10, the seed metal layer 110 outside the first region 101 is removed by chemical etching to obtain a seed metal layer 110 that only covers the first region 101.

[0052] In this application, the solar cell 100 includes a TCO layer 120 and a seed metal layer 110 covering the surface of the TCO layer 120; and the areas of the TCO layer 120 and the seed metal layer 110 are equal.

[0053] In this application, the first region 101 is the region used to form the grid line structure.

[0054] As an example, the method for removing the seed metal layer 110 outside the first region 101 includes: first covering the seed metal layer 110 with a photosensitive emulsion 160 (i.e., a negative emulsion) that can undergo a cross-linking reaction after exposure and is insoluble in the developer; exposing the first region 101 on the surface of the seed metal layer 110; developing to remove the photosensitive emulsion 160 outside the first region 101; and then sequentially removing the seed metal layer 110 outside the first region 101 and the photosensitive emulsion 160 inside the first region 101 to obtain a seed metal layer 110 that only covers the surface of the first region 101 of the TCO layer 120.

[0055] Figure 2 This paper shows a cross-sectional schematic diagram of the battery cell 100 provided in an embodiment of this application. Figure 3 This illustration shows a cross-sectional view of a photosensitive emulsion 160 covering a seed metal layer 110, as provided in an embodiment of this application. Figure 4 This illustration shows a cross-sectional view of the first region 101 of the surface of the seed metal layer 110 exposed according to an embodiment of this application. Figure 4 The arrows in the image represent the laser used for exposure. Figure 5 This illustration shows a cross-sectional view of the battery cell 100 after removing the photosensitive adhesive 160 outside the first region 101, as provided in an embodiment of this application. Figure 6 This illustration shows a cross-sectional view of the battery cell 100 after removing the seed metal layer 110 outside the first region 101, as provided in an embodiment of this application. Figure 7 This illustration shows a cross-sectional view of the battery cell 100 after removing the photosensitive adhesive 160 from the first region 101, as provided in the embodiments of this application (i.e., a cross-sectional view of the battery cell 100 with the seed metal layer 110 covering only the surface of the first region 101 of the TCO layer 120); wherein Figure 4 The area indicated by the dashed line is the first region, 101.

[0056] Please see Figures 2 to 5 In this application, the photosensitive adhesive 160 located in the first region 101 is exposed, so that the photosensitive adhesive 160 in the first region 101 undergoes a cross-linking polymerization reaction after exposure, and thus becomes insoluble in the developing solution; while the photosensitive adhesive 160 outside the first region 101 is not exposed and can be dissolved in the developing solution. The developing process removes the photosensitive adhesive 160 outside the first region 101, thereby exposing the seed metal layer 110 outside the first region 101, which is convenient for subsequent etching to remove the seed metal layer 110 outside the first region 101 while retaining the seed metal layer 110 inside the first region 101.

[0057] Please see Figure 6 and Figure 7 This application utilizes an exposure and development technique for forming a grid line structure by electroplating and a film removal and etch process to first remove the seed metal layer 110 located outside the first region 101 and then remove the photosensitive emulsion 160 inside the first region 101, thereby obtaining a seed metal layer 110 that only covers the surface of the first region 101 of the TCO layer 120.

[0058] Since the seed metal layer 110 outside the region used to form the gate structure (i.e., the first region 101) is removed, the remaining seed metal layer 110 (i.e., the seed metal layer 110 within the first region 101) forms a protrusion structure on the surface of the TCO layer 120 that conforms to the shape of the gate structure (e.g., Figure 7As shown, along the width or length direction of the cell 100, there is a clear boundary between the TCO layer 120 and the seed metal layer 110, which facilitates the peeling between the TCO layer 120 and the seed metal layer 110. This allows the surface of the seed metal layer 110 in the first region 101 to serve as a connection point for a tensile testing device. This helps to avoid the seed metal layer 110 from being damaged when the tensile testing device is used to test the bonding force between the seed metal layer 110 and the TCO layer 120 directly. It also helps to effectively and accurately test the bonding force between the seed metal layer 110 and the TCO layer 120.

[0059] It should be noted that, in other feasible embodiments, the method for removing the seed metal layer 110 outside the first region 101 includes: firstly covering the seed metal layer 110 with a photosensitive emulsion 160 (i.e., positive emulsion) that is insoluble in the developer solution before exposure but readily soluble in the developer solution; exposing the photosensitive emulsion 160 outside the first region 101 on the surface of the seed metal layer 110; developing to remove the photosensitive emulsion 160 outside the first region 101; and then sequentially removing the seed metal layer 110 outside the first region 101 and the photosensitive emulsion 160 inside the first region 101 to obtain a seed metal layer 110 that only covers the surface of the first region 101 of the TCO layer 120.

[0060] As an example, please refer to Figure 2 The solar cell 100 has an N-type silicon wafer substrate 150, an intrinsic amorphous silicon layer 140, a doped layer 130, a TCO layer 120 and a seed metal layer 110 stacked sequentially.

[0061] Furthermore, in this application, the seed metal layer 110 is made of copper.

[0062] In this application, the thickness of the photosensitive emulsion 160 covering the surface of the seed metal layer 110 is 5-10 μm, which effectively improves the accuracy of the seed metal layer 110 subsequently formed in the first region 101. If the thickness of the photosensitive emulsion 160 covering the seed metal layer 110 is too thin, it may lead to a situation where the photosensitive emulsion 160 cannot be effectively covered in some areas due to local minor unevenness on the surface of the seed metal layer 110, which is not conducive to the subsequent accurate formation of the seed metal layer 110 located in the first region 101.

[0063] In this application, the exposure operation uses laser exposure, and the laser energy density is 50-100 mJ / cm². 2 This can improve the accuracy of the pattern corresponding to the first region 101 formed by exposure, which is beneficial to effectively improve the accuracy of the seed metal layer 110 formed in the first region 101 in the subsequent process.

[0064] In this application, a weakly alkaline solution is used for the developing operation, and the developing temperature is 25-35°C. Under these conditions, the photosensitive emulsion outside the first region 101 can be effectively removed, which is beneficial for subsequently improving the precision of the seed metal layer 110 formed in the first region 101.

[0065] Furthermore, the weakly alkaline solution is a sodium carbonate solution with a mass concentration of 10-15 g / L.

[0066] In this application, a back-etching solution containing sulfuric acid and hydrogen peroxide is used to remove the seed metal layer 110 located outside the first region 101. The mass concentration of sulfuric acid in the back-etching solution is 8-15 g / L, the mass concentration of hydrogen peroxide in the back-etching solution is 15-30 g / L, and the temperature of the back-etching solution is 25-35°C. Under the above conditions, the seed metal layer 110 located outside the first region 101 can be effectively removed.

[0067] In this application, a stripping solution containing a strongly alkaline solute is used to remove the photosensitive emulsion 160. The mass concentration of the strongly alkaline solute in the stripping solution is 25-50 g / L, and the temperature of the stripping solution is 40-60℃. Under these conditions, the photosensitive emulsion 160 can be effectively removed.

[0068] As an example, the strongly alkaline solute can be sodium hydroxide or potassium hydroxide, etc.

[0069] S20, a welding rod is attached to the surface of the seed metal layer 110, and a tensile testing device is used to test the bonding force between the seed metal layer 110 and the TCO layer 120.

[0070] Figure 8 This illustration shows a schematic diagram of the structure of the welding electrode 170 connected to the seed metal layer 110 according to an embodiment of this application. Figure 9 It shows Figure 8 Please refer to the enlarged view at point A in the middle. Figure 8 and Figure 9 In this application, the welding electrode serves as the connection point between the tensile testing device and the seed metal layer 110 in the first region 101, so that the bonding force between the seed metal layer 110 and the TCO layer 120 can be effectively tested by means of the tensile testing device.

[0071] In this application, welding electrode 170 is welded to the surface of seed metal layer 110. The welding electrode is a copper welding electrode with a tin layer on its surface, and the welding temperature is 260-300℃. The copper material, as the base material, improves the overall mechanical strength of the welding electrode and facilitates effective bonding strength testing. The welding temperature of 260-300℃ ensures effective welding and fixation between the seed metal layer 110 and the tin layer of the welding electrode.

[0072] It should be noted that in other feasible embodiments, the welding electrode 170 can be connected to the surface of the seed metal layer 110 in other ways, such as by bonding.

[0073] Furthermore, after removing the seed metal layer 110 outside the first region 101 in sequence, flux is first applied to the surface of the seed metal layer 110 and then dried before connecting the welding rod. This arrangement effectively improves the bonding effect between the welding rod and the seed metal layer 110, and further enhances the accuracy of testing the adhesion between the TCO layer 120 and the seed metal layer 110.

[0074] Furthermore, the drying time for the flux can be 1-3 hours.

[0075] As an example, a method for coating the surface of the seed metal layer 110 with flux includes immersing the battery cell 100 in the flux. Further, the battery cell 100 is immersed in the flux for 5-15 minutes.

[0076] It should be noted that this application does not limit the type of flux.

[0077] In this application, the minimum distance between the welding electrode 170 and the edge of the first region 101 is ≤0.1mm. It is understood that the edge of the welding electrode 170 may extend beyond the edge of the first region 101, or the edge of the first region 101 may extend beyond the edge of the welding electrode 170, as long as the minimum distance between the welding electrode 170 and the edge of the first region 101 is ≤0.1mm.

[0078] Furthermore, at least a portion of the welding electrode 170 is located at the edge of the first region 101. This arrangement allows the edge of the seed metal layer 110 to be directly subjected to the force from the tensile testing device, facilitating a tendency for the TCO layer 120 and the seed metal layer 110 to peel off from each other. Compared to the arrangement where the welding electrode 170 is connected to the middle of the entire first region 101, this arrangement helps to avoid the situation where the force from the tensile testing device directly acts on the middle of the seed metal layer 110 in the first region 101, causing the seed metal layer 110 in the middle of the first region 101 to be easily damaged, making it impossible to accurately obtain the bonding force data between the seed metal layer 110 and the TCO layer 120.

[0079] In this application, since the first region 101 is the region for forming the gate structure, welding the electrode to the region on the surface of the seed metal layer 110 for forming the main gate line in the gate structure can further enable the results of subsequent bonding force tests to more accurately reflect the influence on the conductivity between the seed metal layer 110 and the TCO layer 120.

[0080] It should be noted that, in this application, the area used to form the gate line structure refers to: an area on the seed metal layer 110 that corresponds to and has the same shape as the gate line structure pattern, or an area on the seed metal layer 110 that corresponds to the gate line structure pattern but has a size slightly larger than the size of the gate line structure pattern.

[0081] Furthermore, such as Figure 8 and Figure 9 As shown, the welding rod 170 is connected to the surface of the seed metal layer 110 in the intersection area of ​​the main gate line and the sub-gate line in the gate line structure. This arrangement allows the test results of the bonding force between the TCO layer 120 and the seed metal layer 110 to better reflect the impact on the conductivity between the seed metal layer 110 and the TCO layer 120.

[0082] Furthermore, the welding rod 170 is connected to the area on the surface of the seed metal layer 110 used to form PAD points (i.e., the second region 102, indicated by the dashed box in the figure). There are 4-8 welding rods 170, with one welding rod 170 connected to each second region 102 on the seed metal layer 110. This arrangement allows the test results of the bonding force between the TCO layer 120 and the seed metal layer 110 to better reflect the influence on the conductivity between the seed metal layer 110 and the TCO layer 120. It also avoids the situation where the accuracy of the test results is affected by the poor welding force of some welding rods 170, thus improving the accuracy of the test results on the bonding force between the TCO layer 120 and the seed metal layer 110.

[0083] As an example, the second region 102 has dimensions of 1mm × 0.8mm, and the diameter of the welding rod is 0.28-0.36mm.

[0084] In this application, the tensile testing device has a tensile speed of 280-320 mm / min, which is beneficial to further improve the accuracy of testing the bonding force between the TCO layer 120 and the seed metal layer 110, and also helps to further avoid the seed metal layer 110 from being damaged due to excessive tensile speed.

[0085] In summary, the test method for the bonding force between the TCO layer and the seed metal layer of the solar cell provided in this application can ensure that there is a clear boundary between the TCO layer and the seed metal layer along the width or length direction of the solar cell, which facilitates the peeling between the TCO layer and the seed metal layer. This method helps to avoid the seed metal layer from being easily damaged when directly testing the bonding force between the seed metal layer and the TCO layer using a tensile testing device, and thus helps to effectively and accurately test the bonding force between the seed metal layer and the TCO layer.

[0086] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for testing the bonding strength between the TCO layer and the seed metal layer of a solar cell, characterized in that, The testing method includes: The seed metal layer outside the first region is removed by chemical etching to obtain a seed metal layer that only covers the first region; then, a tensile testing device is used to test the adhesion between the seed metal layer and the TCO layer. Wherein, the first region is the region used to form the grid line structure; the method for removing the seed metal layer outside the first region includes: covering the seed metal layer with a photosensitive emulsion that can undergo a cross-linking reaction after exposure and is insoluble in the developing solution; exposing the first region on the surface of the seed metal layer; developing and removing the photosensitive emulsion outside the first region; and then sequentially removing the seed metal layer outside the first region and the photosensitive emulsion within the first region; or, covering the seed metal layer with a photosensitive emulsion that is insoluble in the developing solution before exposure but is easily soluble in the developing solution after exposure; exposing the photosensitive emulsion outside the first region on the surface of the seed metal layer; developing and removing the photosensitive emulsion outside the first region; and then sequentially removing the seed metal layer outside the first region and the photosensitive emulsion within the first region.

2. The test method according to claim 1, characterized in that, The thickness of the photosensitive emulsion covering the surface of the seed metal layer is 5-10 μm.

3. The test method according to claim 1 or 2, characterized in that, The exposure operation employs laser exposure, and the energy density of the laser is 50-100 mJ / cm². 2 .

4. The test method according to claim 1, characterized in that, The step of testing the bonding force between the seed metal layer and the TCO layer using the tensile testing device includes: attaching a welding rod to the surface of the seed metal layer, connecting the welding rod to the tensile testing device, and then testing the bonding force between the seed metal layer and the TCO layer.

5. The test method according to claim 4, characterized in that, The minimum distance from the welding rod to the edge of the first region is ≤0.1mm.

6. The test method according to claim 5, characterized in that, The welding electrode has at least a portion located at the edge of the first region.

7. The test method according to claim 4, characterized in that, The welding electrode is attached to the area on the surface of the seed metal layer used to form the main grid lines in the grid structure.

8. The test method according to claim 7, characterized in that, The welding rod is connected to the surface of the seed metal layer to form the intersection area of ​​the main grid line and the sub-grid line in the grid line structure.

9. The test method according to claim 8, characterized in that, The welding rod is connected to the area on the surface of the seed metal layer used to form PAD points. The number of welding rods is 4-8, and one welding rod is connected to one area on the seed metal layer used to form the PAD point.

10. The test method according to claim 4, characterized in that, The welding rod is welded to the surface of the seed metal layer. The welding rod is a copper welding rod with a tin layer on its surface. The welding temperature is 260-300℃.

11. The test method according to claim 4, characterized in that, The tensile testing device has a tensile speed of 280-320 mm / min.

12. The test method according to claim 4, characterized in that, The step of testing the bonding force between the seed metal layer and the TCO layer using the tensile testing device further includes: first covering the surface of the seed metal layer with flux and drying the flux, and then connecting the welding rod.

13. The test method according to claim 12, characterized in that, The method of coating the surface of the seed metal layer with the flux includes: immersing the battery cell in the flux.

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