Electroplating method of heterojunction solar cell silicon wafer

Abstract

The invention relates to an electroplating method of a heterojunction solar cell silicon wafer, and relates to the photovoltaic field. According to the technical scheme, the dependence of an existing process on a copper seed layer is broken through, the conductive fiber layer is introduced to replace a traditional cathode contact mode, and the conductive fiber layer can directly extend into a mask opening groove with the width of only 5-50 microns by utilizing the flexibility and fine characteristics of the conductive fiber to be in direct conductive contact with the transparent conductive oxide TCO layer, so that the conductive effect is improved. Therefore, the problems of high cost, low efficiency and poor stability in the prior art are synchronously solved. In addition, the process of cleaning the copper seed layer is omitted, the cost is reduced, discharge of copper-containing wastewater for cleaning the copper seed layer is avoided, and the method is environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to an electroplating method for silicon wafers used in heterojunction solar cells. Background Technology

[0002] Compared to screen printing low-temperature silver paste technology, electroplating copper for generating grid electrodes on heterojunction (HJT) cells offers the advantage of lower production costs. Early electroplating techniques involved directly contacting the negative electrode of the power source with the total conductive core (TCO) at both ends of the HJT cell using clamps such as spring clips. Due to the poor conductivity of the TCO, copper initially forms near the negative electrode clamp, meaning it grows first at the two ends of the HJT cell and then gradually moves towards the center, resulting in a thicker copper plating at the ends compared to the center. To overcome this problem, a copper sublayer method was introduced for electrode generation on HJT cells, thus preventing the copper grid lines at the ends from being thicker than those in the center.

[0003] See Figure 4 The actual electroplating process using the copper seed layer method to generate electrodes is roughly as follows: The outermost layer of the upper and lower surfaces of the HJT cell is a transparent conductive film TCO110. A copper seed layer 120 is coated on the TCO110 layer outside the HJT cell silicon wafer, and an insulating layer 130 is coated on the copper layer 120. Then, according to the grid electrode pattern of the HJT cell, grooves are cut in the insulating layer 130 to form grid grooves 140. The width of the grid grooves 140 is about 10 micrometers. Various fixtures are used to bring the negative electrode of the electroplating power supply into contact with the two ends of the HJT cell (not shown in the figure) for electroplating. After electroplating, the insulating layer 130 is first cleaned off, and then the copper seed layer 120 below the insulating layer 130 is cleaned.

[0004] However, the process of cleaning the copper sublayer 120 can lead to the following two situations: Firstly, insufficient cleaning: The copper seed layer 120 is not cleaned properly, which affects the light-receiving area of ​​the battery and thus affects the battery efficiency. Secondly, over-cleaning: After the copper seed layer 120 is cleaned, the TCO110 part is cleaned, which affects the passivation and conductivity of the battery, and thus affects the battery efficiency. Furthermore, both of these situations present challenges in the treatment of copper-containing wastewater. Summary of the Invention

[0005] The purpose of this invention is to provide an electroplating method for silicon wafers of heterojunction solar cells, which solves the problems existing in the prior art, eliminates the step of cleaning the copper seed layer, reduces costs, and avoids the discharge of copper-containing wastewater from cleaning the copper seed layer, thus being environmentally friendly.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An electroplating method for a heterojunction solar cell silicon wafer, comprising: A first insulating layer and a second insulating layer are respectively disposed on the outside of the first transparent conductive oxide layer and the second transparent conductive oxide layer of the heterojunction solar cell silicon wafer, and opening slots are provided on both the first insulating layer and the second insulating layer. When the heterojunction solar cell silicon wafer is electroplated on the second surface, the conductive fiber layer with free conductive fibers on the surface is used as the cathode and contacts the first insulating layer. The free conductive fibers present on the surface of the conductive fiber layer extend into the opening groove of the first insulating layer and make conductive contact with the first transparent conductive oxide layer.

[0007] In some embodiments, the method further includes: When the heterojunction solar cell silicon wafer moves along the first direction to perform second surface electroplating, the opening groove of the second insulating layer contacts the electroplating solution in the electroplating tank, so that the second transparent conductive oxide layer can contact the electroplating solution. After the second surface of the heterojunction solar cell silicon wafer is electroplated, a copper protrusion is formed in the opening groove of the second insulating layer. The copper protrusion is used for current conduction from the heterojunction solar cell silicon wafer.

[0008] In some embodiments, the conductive fiber layer is made of graphite felt; or, the conductive fiber layer is made of polymer conductive fibers.

[0009] In some embodiments, the conductive fiber layer is a sheet-like conductive fiber layer; or, the conductive fiber layer is a cylindrical conductive fiber layer.

[0010] In some embodiments, the width of the opening groove is 5-50 micrometers.

[0011] In some embodiments, an anode is provided in the electroplating tank, the anode is connected to the positive terminal of a power source, and the negative terminal of the power source is connected to the conductive fiber layer.

[0012] In some embodiments, an anode is provided in the electroplating tank, the anode is connected to the positive terminal of a power source, the negative terminal of the power source is connected to the cathode, and the cathode is connected to the conductive fiber layer.

[0013] In some embodiments, the heterojunction solar cell silicon wafer is moved along a first direction by support conveying rollers mounted in the electroplating tank.

[0014] In some embodiments, illumination is provided above or below the heterojunction solar cell silicon wafer for photo-induced assisted electroplating of the heterojunction solar cell silicon wafer.

[0015] In some embodiments, the method further includes: After the second surface of the heterojunction solar cell silicon wafer is electroplated, the heterojunction solar cell silicon wafer is flipped over; The conductive fiber layer is placed on the flipped second insulating layer, and the free conductive fibers on the surface of the conductive fiber layer make conductive contact with the copper protrusions formed in the opening groove of the second insulating layer. At this time, the first insulating layer is immersed in the electroplating solution of the electroplating tank, and the side of the first transparent conductive oxide layer close to the first insulating layer can contact the electroplating solution. After the first surface of the heterojunction solar cell silicon wafer is electroplated, the copper protrusion is also formed in the opening groove of the first insulating layer.

[0016] The beneficial effects of the technical solution provided by this invention include at least the following: This technical solution breaks through the reliance on copper seed layers in existing processes. By introducing a conductive fiber layer to replace the traditional cathode contact method, the flexibility and fineness of the conductive fibers allow them to directly extend into mask openings only 5-50 micrometers wide, directly engaging with the transparent conductive oxide (TCO) layer. This simultaneously solves the problems of high cost, low efficiency, and poor stability in existing processes. Furthermore, it eliminates the need for cleaning the copper seed layer, reducing costs and avoiding the discharge of copper-containing wastewater, thus being environmentally friendly. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0018] Figure 1 A flowchart illustrating an exemplary embodiment of the present invention is shown.

[0019] Figure 2 The diagram illustrates the electroplating process of a heterojunction solar cell silicon wafer provided by an exemplary embodiment of the present invention.

[0020] Figure 3 The diagram shows a schematic of a cylindrical conductive fiber layer provided in an exemplary embodiment of the present invention.

[0021] Figure 4 The diagram illustrates the electroplating process for heterojunction solar cell silicon wafers provided by the prior art. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 A flowchart illustrating an exemplary embodiment of the electroplating method for a heterojunction solar cell silicon wafer provided by the present invention is shown. Figure 2 The diagram illustrates an electroplating process for a heterojunction solar cell silicon wafer according to an exemplary embodiment of the present invention. The electroplating method for the heterojunction solar cell silicon wafer includes: Step S1: A first insulating layer 2 and a second insulating layer 3 are respectively provided on the outer side of the first transparent conductive oxide layer 11 and the second transparent conductive oxide layer 12 of the heterojunction solar cell silicon wafer 1, and an opening groove 4 is provided on both the first insulating layer 2 and the second insulating layer 3. Step S2: When performing the second surface electroplating on the heterojunction solar cell silicon wafer 1, the conductive fiber layer 5 with free conductive fiber filaments 51 on the surface is used as the cathode and contacts the first insulating layer 2. In step S3, the free conductive fibers 51 present on the surface of the conductive fiber layer 5 extend into the opening groove 4 of the first insulating layer 2 and make conductive contact with the first transparent conductive oxide layer 11.

[0026] In this embodiment, a first insulating layer 2 and a second insulating layer 3 are respectively provided on the outer sides of the first transparent conductive oxide layer 11 and the second transparent conductive oxide layer 12 of the heterojunction solar cell silicon wafer 1. These layers isolate the non-electroplated areas of the two TCO layers, preventing metal from being mistakenly deposited due to erosion by the electroplating solution. At the same time, opening grooves 4 are provided on both insulating layers to reserve channels for subsequent conductive structure docking, ensuring that only the target TCO layer area can participate in electroplating. The conductive fiber filaments 51 of the conductive fiber layer 5, which serves as the cathode, extend into the opening grooves 4 of the first insulating layer 2 and make conductive contact with the first transparent conductive oxide layer 11. This can replace the traditional copper seed layer to realize the current path, eliminating the seed layer preparation process and reducing costs. Furthermore, the flexibility and fine performance of the conductive fiber filaments 51 are adapted to the tiny opening grooves, ensuring stable contact with the TCO layer, providing reliable current support for electroplating, and ensuring electroplating quality.

[0027] Optionally, the first insulating layer 2 and the second insulating layer 3 include, but are not limited to, photoresist (photosensitive adhesive), polyimide (PI) film, silicon oxide (SiO2) or silicon nitride (SiN). x All of these can meet the requirements of insulation, fine opening processing, resistance to electroplating solution corrosion, and subsequent removability.

[0028] Furthermore, the method also includes: when the heterojunction solar cell silicon wafer 1 moves along the first direction to perform second surface electroplating, the opening groove 4 of the second insulating layer 3 contacts the electroplating solution 61 of the electroplating tank 6, so that the second transparent conductive oxide layer 12 can contact the electroplating solution 61; after the second surface electroplating of the heterojunction solar cell silicon wafer 1 is completed, a copper protrusion 7 is formed in the opening groove 4 of the second insulating layer 3, and the copper protrusion 7 is used for current conduction of the heterojunction solar cell silicon wafer 1.

[0029] In the embodiments of this application, see Figure 2 When the heterojunction solar cell silicon wafer 1 moves along the first direction for second surface electroplating, the second insulating layer 3 is immersed in the electroplating solution 61 in the electroplating tank 6. The insulating layer's properties protect the non-opening areas of the second transparent conductive oxide layer 12, preventing accidental deposition of the electroplating solution 61. Simultaneously, the side of the second transparent conductive oxide layer 12 closest to the second insulating layer 3 contacts the electroplating solution 61, creating conditions for the formation of copper protrusions 7 within the opening groove 4. After the second surface electroplating is completed, copper protrusions 7 are formed within the opening groove 4 of the second insulating layer 3. These copper protrusions 7 can directly serve as the current-carrying structure of the heterojunction solar cell silicon wafer 1, replacing the traditional current-carrying method that relies on a copper seed layer, ensuring efficient current transmission.

[0030] In some embodiments, the conductive fiber layer 5 is made of graphite felt; or, the conductive fiber layer 5 is made of polymer conductive fibers.

[0031] In some embodiments, the width of the opening slot 4 is 5-50 micrometers.

[0032] In this embodiment, the conductive fiber layer 5 is made of graphite felt or polymer conductive fibers, both of which possess good conductivity and flexibility, enabling stable current transmission and adapting to the insertion requirements of the opening slot 4, thus providing a high-quality substrate for the conductive fiber filaments 51 to contact the transparent conductive oxide layer. Simultaneously, the relatively fine diameter of the conductive fiber filaments 51 in the graphite felt or polymer conductive fibers, combined with the 5-50 micrometer width of the opening slot 4, reduces the light-blocking area.

[0033] In some embodiments, such as Figure 2 As shown, the conductive fiber layer 5 is a sheet-like conductive fiber layer. The conductive fiber layer 5 is in parallel contact with the heterojunction solar cell silicon wafer 1. During electroplating, the conductive fiber layer 5 and the heterojunction solar cell silicon wafer 1 move horizontally, vertically, or in a circular motion along the first direction.

[0034] In some embodiments, such as Figure 3 As shown, the conductive fiber layer 5 is a cylindrical conductive fiber layer. After contacting the heterojunction solar cell silicon wafer 1, the conductive fiber layer 5 moves relative to it. For example, the heterojunction solar cell silicon wafer 1 moves horizontally along the first direction, while the conductive fiber layer 5 rotates at a certain position with the same linear velocity. Simultaneously, after contacting the first insulating layer 2, the free conductive fibers 51 present on the surface of the conductive fiber layer 5 extend into the opening groove 4 of the first insulating layer 2 and make conductive contact with the first transparent conductive oxide layer 11. It is worth mentioning that... Figure 3 The surface of the cylindrical conductive fiber layer 5 contains free conductive fiber filaments 51 (the portion other than the opening groove 4). The conductive fiber filaments 51 are only schematically shown.

[0035] In some embodiments, Figure 3 The cylindrical conductive fiber layer 5 can be composed of a round rod and a conductive fiber layer, that is, the conductive fiber layer is wrapped around the outer periphery of the round rod.

[0036] In some embodiments, see Figure 2 An anode 8 is provided in the electroplating tank 6. The anode 8 is connected to the positive terminal of the power supply 9, and the negative terminal of the power supply 9 is connected to the conductive fiber layer 5.

[0037] In some embodiments, see Figure 2 An anode 8 is installed in the electroplating tank 6, and the anode 8 is connected to the positive terminal of the power supply 9. Not shown in the figure, the negative terminal of the power supply 9 is connected to the cathode, and the cathode is connected to the conductive fiber layer 5.

[0038] In this embodiment, the anode 8 is connected to the positive electrode and can serve as the current inflow end, maintaining the stability of the copper ion concentration in the electroplating solution 61. The conductive fiber layer 5 is connected to the negative electrode (or connected to the negative electrode through the cathode) and carries a negative charge, which can attract the positive metal ions in the electroplating solution 61 to move towards the vicinity of the transparent conductive oxide layer and deposit, ensuring the smooth formation of the copper protrusion 7 in the opening groove 4.

[0039] In some embodiments, see Figure 2 The heterojunction solar cell silicon wafer 1 moves along the first direction via the support conveying rollers 10 mounted in the electroplating tank 6.

[0040] Optionally, illumination is provided above or below the heterojunction solar cell silicon wafer 1 to perform photo-induced assisted electroplating on the heterojunction solar cell silicon wafer 1.

[0041] Furthermore, the method also includes: after the second surface of the heterojunction solar cell silicon wafer 1 is electroplated, the heterojunction solar cell silicon wafer 1 is flipped over; a conductive fiber layer 5 is placed on the flipped second insulating layer 3, and the free conductive fiber filaments 51 on the surface of the conductive fiber layer 5 are in conductive contact with the copper protrusions 7 formed in the opening groove 4 of the second insulating layer 3; at this time, the first insulating layer 2 is immersed in the electroplating solution 61 of the electroplating tank 6, and the side of the first transparent conductive oxide layer 11 close to the first insulating layer 2 can contact the electroplating solution 61; after the first surface of the heterojunction solar cell silicon wafer 1 is electroplated, copper protrusions 7 are also formed in the opening groove 4 of the first insulating layer 2.

[0042] In this embodiment, after the second surface is electroplated, it is flipped over and the conductive fiber layer 5 is placed on the second insulating layer 3, so that its fiber bundle 51 contacts the formed copper protrusion 7. The high conductivity of copper is used to replace the additional conductive structure to ensure that the current path is stable during the electroplating of the first surface. At the same time, the first insulating layer 2 is immersed in the electroplating solution 61, so that the side of the first transparent conductive oxide layer 11 close to the first insulating layer 2 contacts the electroplating solution. Finally, copper protrusions 7 are formed on both sides of the heterojunction solar cell silicon wafer 1, ensuring that the current output structure on both sides is symmetrical.

[0043] It is understandable that after both sides of the heterojunction solar cell silicon wafer 1 are electroplated, the first insulating layer 2 and the second insulating layer 3 are removed.

[0044] In this embodiment, the insulating layer has completed its mission of isolating non-target areas during the electroplating stage. After removal, the copper protrusions 7 in the two side opening slots 4 can be fully exposed, making them functional structures that directly participate in current conduction, so as to facilitate subsequent docking with component interconnects (such as solder strips).

[0045] In summary, this technical solution overcomes the reliance on copper seed layers in existing processes. By introducing a conductive fiber layer to replace the traditional cathode contact method, the flexibility and fineness of the conductive fibers allow them to directly extend into mask openings only 5-50 micrometers wide, directly engaging with the transparent conductive oxide (TCO) layer. This simultaneously solves the problems of high cost, low efficiency, and poor stability in existing processes. Furthermore, it eliminates the need for cleaning the copper seed layer, reducing costs and avoiding the discharge of copper-containing wastewater, thus being environmentally friendly.

[0046] In the embodiments disclosed in this invention, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this invention according to the specific circumstances.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electroplating method for silicon wafers used in heterojunction solar cells, characterized in that, include: A first insulating layer and a second insulating layer are respectively disposed on the outside of the first transparent conductive oxide layer and the second transparent conductive oxide layer of the heterojunction solar cell silicon wafer, and opening slots are provided on both the first insulating layer and the second insulating layer. When the heterojunction solar cell silicon wafer is electroplated on the second surface, the conductive fiber layer with free conductive fibers on the surface is used as the cathode and contacts the first insulating layer. The free conductive fibers present on the surface of the conductive fiber layer extend into the opening groove of the first insulating layer and make conductive contact with the first transparent conductive oxide layer.

2. The electroplating method for heterojunction solar cell silicon wafers according to claim 1, characterized in that, The method further includes: When the heterojunction solar cell silicon wafer moves along the first direction to perform second surface electroplating, the opening groove of the second insulating layer contacts the electroplating solution in the electroplating tank, so that the second transparent conductive oxide layer can contact the electroplating solution. After the second surface of the heterojunction solar cell silicon wafer is electroplated, a copper protrusion is formed in the opening groove of the second insulating layer. The copper protrusion is used for current conduction from the heterojunction solar cell silicon wafer.

3. The electroplating method for heterojunction solar cell silicon wafers according to claim 1, characterized in that, The conductive fiber layer is made of graphite felt; or, the conductive fiber layer is made of polymer conductive fibers.

4. The electroplating method for heterojunction solar cell silicon wafers according to claim 1, characterized in that, The conductive fiber layer is a sheet-like conductive fiber layer; or, the conductive fiber layer is a cylindrical conductive fiber layer.

5. The electroplating method for heterojunction solar cell silicon wafers according to claim 1, characterized in that, The width of the opening groove is 5-50 micrometers.

6. The electroplating method for heterojunction solar cell silicon wafers according to claim 2, characterized in that, An anode is provided in the electroplating tank. The anode is connected to the positive terminal of the power supply, and the negative terminal of the power supply is connected to the conductive fiber layer.

7. The electroplating method for heterojunction solar cell silicon wafers according to claim 2, characterized in that, An anode is provided in the electroplating tank. The anode is connected to the positive terminal of the power supply, the negative terminal of the power supply is connected to the cathode, and the cathode is connected to the conductive fiber layer.

8. The electroplating method for heterojunction solar cell silicon wafers according to claim 2, characterized in that, The heterojunction solar cell silicon wafer moves along a first direction via support conveying rollers mounted in the electroplating tank.

9. The electroplating method for heterojunction solar cell silicon wafers according to claim 2, characterized in that, The heterojunction solar cell silicon wafer is illuminated above or below for photo-induced assisted electroplating.

10. The electroplating method for heterojunction solar cell silicon wafers according to claim 2, characterized in that, The method further includes: After the second surface of the heterojunction solar cell silicon wafer is electroplated, the heterojunction solar cell silicon wafer is flipped over; The conductive fiber layer is placed on the flipped second insulating layer, and the free conductive fibers on the surface of the conductive fiber layer make conductive contact with the copper protrusions formed in the opening groove of the second insulating layer. At this time, the first insulating layer is immersed in the electroplating solution in the electroplating tank, and the side of the first transparent conductive oxide layer close to the first insulating layer can contact the electroplating solution. After the first surface of the heterojunction solar cell silicon wafer is electroplated, the copper protrusion is also formed in the opening groove of the first insulating layer.

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