A method for preparing a metal electrode of a heterojunction solar cell

Abstract

The application discloses a kind of heterojunction solar cell metal electrode preparation methods, including dry method preparation selective seed layer, wet preparation protective layer, selective plating functional structure preparation, electrochemical deposition method preparation metal conducting layer and oxidation-resistant layer;In the present application, the seed layer prepared by dry method and the protective layer prepared by wet method are annealed to form a selective plating protective film and a reduction layer without seed layer, which can improve the adhesion of the copper electrode, avoid electrode grid, and does not require the use of full-area seed layer preparation;Without the preparation of complex pattern mask, the preparation process is simplified, the edge problem of electroplated copper electrode is treated at the same time, and subsequent stripping process is not required, which is beneficial to improve the yield of the battery;In addition, this process improvement is suitable for simplifying the preparation process of heterojunction battery electroplated copper electrode.

Description

Technical Field

[0001] This invention belongs to the field of heterojunction solar cell technology, and particularly relates to a method for preparing metal electrodes for heterojunction solar cells. Background Technology

[0002] The low-temperature silver paste used in heterojunction solar cells accounts for over 30% of the total cost, representing the largest portion of non-silicon costs and a significant factor hindering the industrialization of heterojunction solar cells. The annealing temperature of the low-temperature paste does not exceed 250℃, resulting in poor electrode conductivity (resistivity of approximately 6–10 Ω·m) and significantly higher power losses compared to conventional cells. In contrast, copper metallized electrodes exhibit lower wire resistance (1.7 Ω·m) and superior conductivity. Furthermore, copper grid lines can be made thinner than silver grid lines, leading to less light-shielding loss during copper plating, effectively improving carrier collection. Simultaneously, the internal density and uniformity of the electroplated copper electrode, without significant voids, effectively reduces ohmic losses in the cell electrodes. Therefore, copper plating technology is considered the most promising breakthrough for the industrialization of heterojunction solar cells.

[0003] Because direct electroplating of metals onto oxide layers results in poor adhesion and easy detachment, copper electrode deposition in heterojunction solar cells requires addressing three issues: 1. Selective copper metal deposition; 2. Good adhesion to TCO; 3. Edge defects in heterojunction cells caused by chemical electrodeposition. Therefore, a metal seed layer needs to be introduced between the transparent conductive film layer and the metal electrode to improve contact characteristics. Currently, the industrial process for preparing electroplated copper electrodes consists of two steps: patterning and metallization. Patterning: After preparing the ITO layer, a full-area seed layer is prepared using PVD, followed by the preparation of an organic mask. After drying, exposure, and development, the pattern on the photoresist or photoresist can be revealed through development. Metallization: Copper grid lines are prepared on the seed layer by electroplating, followed by zinc plating or the use of an antioxidant to create a protective layer. Finally, the mask and copper seed layer are removed to expose the original ITO. Subsequent processes include annealing or photoinjection. While the contact problem between the metal electrode and the ITO layer has been largely solved, it has brought new problems. Due to the complexity and long processing time of the copper electroplating process, corrosion at the battery edges is prone to occur, resulting in low battery yield and potential copper grid line detachment, making it unsuitable for large-scale mass production.

[0004] Later technologies simplified the patterned mask process, eliminating the need for subsequent stripping processes. However, the preparation of metal electrode masks required additional and more complex methods. Furthermore, the use of wet electrochemical reduction for the prepared copper electrode seed layer could lead to gate detachment issues in the copper electrode.

[0005] like Figure 1 and 2 The image shows the prior art. Figure 2The diagram illustrates the fabrication process of metal electrodes for heterojunction solar cells in the prior art: a- heterojunction cell substrate with transparent conductive film; b- Ni layer seed layer fabricated on the heterojunction cell substrate; c- photosensitive adhesive coated on the heterojunction cell substrate to form an electroplating mask; d- chemical plating to form a metal conductive layer at the exposed seed layer of the heterojunction cell substrate; e- chemical plating to form a metal anti-oxidation layer Sn layer; f- stripping and washing away the photosensitive adhesive coated on the heterojunction cell substrate; g- stripping and washing away the seed layer on the heterojunction cell substrate.

[0006] Therefore, a method for preparing metal electrodes for heterojunction solar cells was developed to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to design a method for preparing metal electrodes for heterojunction solar cells in order to solve the above-mentioned problems.

[0008] The present invention achieves the above objectives through the following technical solutions:

[0009] A method for fabricating a metal electrode for a heterojunction solar cell includes the following steps:

[0010] S1. Dry preparation of selective seed layers; selective seed layers are prepared on both sides of the heterojunction battery substrate;

[0011] S2. Wet preparation of protective layer: The heterojunction battery substrate treated in step S1 is immersed in a functional solution for surface wetting, forming a uniform anti-reflection protective layer on the surface of the heterojunction battery.

[0012] S3. Preparation of selective electroplating functional structure: The heterojunction cell obtained in step S2 is annealed to form a surface anti-reflection and selective electroplating protective layer, exposing the seed layer and forming a selective electroplating structure.

[0013] S4. Electrochemical deposition method is used to prepare the metal conductive layer and the antioxidant layer; the conductive layer and the antioxidant layer are prepared sequentially on the seed layer by electroplating.

[0014] The beneficial effects of this invention are as follows:

[0015] The seed layer prepared by the dry method and the protective layer prepared by the wet method, after annealing, together form a selective electroplating protective film and an anti-reflection layer in areas without a seed layer. This can improve the adhesion of the electroplated copper electrode, prevent electrode delamination, and eliminate the need for full-area seed layer preparation. It also eliminates the need for complex pattern mask preparation, simplifying the preparation process. At the same time, it addresses the edge problems of the electroplated copper electrode and eliminates the need for subsequent stripping processes, which is beneficial to improving the yield of the cell. In addition, this process improvement is suitable for simplifying the preparation process of electroplated copper electrodes for heterojunction cells. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the basic structure of a heterojunction solar cell in the prior art.

[0017] Figure 2 This diagram illustrates the fabrication process of metal electrodes for heterojunction solar cells in existing technologies. In this diagram: a - heterojunction cell substrate with a transparent conductive thin film; b - preparation of a full-area seed layer on the heterojunction cell substrate; c - coating the heterojunction cell substrate with photosensitive adhesive to form an electroplating mask; d - electroless plating to form a metal conductive layer at the exposed seed layer of the heterojunction cell substrate; e - electroless plating to form a metal anti-oxidation layer; f - stripping and washing away the photosensitive adhesive coating on the heterojunction cell substrate; g - stripping and washing away the seed layer on the heterojunction cell substrate.

[0018] Figure 3 This is a schematic diagram of the basic structure of the heterojunction battery in this invention;

[0019] Figure 4 This is a schematic diagram of the structure of the metal electrode of the heterojunction solar cell in this invention;

[0020] Figure 5 This is a schematic diagram of the fabrication process of the metal electrode of the heterojunction solar cell in this invention; wherein, a- a heterojunction cell substrate with a transparent conductive thin film; b- a selective seed layer is prepared on the heterojunction cell substrate; c- a protective layer is formed on the heterojunction cell substrate; d- the metal seed layer is exposed by low-temperature annealing of the heterojunction cell substrate to form a selective electroplating structure; e- a metal conductive layer is formed by electroless plating; f- a metal anti-oxidation layer is formed by electroless plating.

[0021] Figure 6 This is a schematic flowchart of the method for preparing heterojunction solar cell metal electrodes according to the present invention.

[0022] In the figure: 1-N-type silicon; 2-intrinsic amorphous silicon; 3-N-type amorphous silicon; 4-P-type amorphous silicon; 5-transparent conductive film; 6-metal electrode; 61-seed layer; 62-conductive layer; 63-antioxidant layer; 7-protective layer; 8-photosensitive adhesive. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to 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 this invention.

[0027] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0028] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] like Figure 6 As shown, a method for fabricating a metal electrode for a heterojunction solar cell includes the following steps:

[0031] S1. Dry preparation of selective seed layer 61; Selective seed layer 61 is prepared on both sides of the heterojunction battery substrate;

[0032] The selective seed layer 61 is prepared by a physical method, which can be laser transfer, physical vapor deposition, magnetron sputtering, or inkjet printing.

[0033] The metal seed layer 61 used in the selective seed layer 61 preparation uses a paste made of one or more of nickel, copper, aluminum, silver, chromium, gold, tin, and indium, and contains a binder, which is zinc glass or borate. The binder is used to enhance the adhesion between the conductive paste and the substrate.

[0034] The selective seed layer 61 has a height of 1μm-5μm and a width of 1μm-10μm;

[0035] S2. Wet preparation of protective layer 7: The heterojunction battery substrate treated in step S1 is immersed in a functional solution to wet the surface and form a uniform anti-reflection protective layer 7 on the surface of the heterojunction battery.

[0036] The functional solution is a precursor containing SiO2 or TiO2; in some embodiments, a SiO2 solution with a concentration of 40 μg / L, a soaking time of 20 min, and a temperature of 40 °C is preferred; the SiO2 on the battery surface can form surface anti-reflection in areas without grid lines, thereby improving battery efficiency.

[0037] S3. Preparation of selective electroplating functional structure: The heterojunction cell obtained in step S2 is annealed to form a surface anti-reflection and selective electroplating protective layer 7, so that the seed layer 61 is exposed to form a selective electroplating structure.

[0038] The annealing atmosphere is at least one of air, hydrogen, nitrogen, and argon, and the annealing temperature range is 120℃-200℃.

[0039] S4. Electrochemical deposition method is used to prepare metal conductive layer 62 and antioxidant layer 63; conductive layer 62 and antioxidant layer 63 are sequentially prepared on seed layer 61 by electroplating; specifically, conductive layer 62 is deposited on the surface of seed layer 61 by bipolar pulse electroplating.

[0040] Conductive layer 62 is a copper layer, prepared by an electrochemical method using copper sulfate as the solution. The electroplating voltage is 1V-50V, and the electroplating current is 1A / dm². 2 -5 A / dm 2 ;

[0041] Antioxidant layer 63 is a tin layer, prepared by an electrochemical method using tin sulfamate as the solution. The electroplating voltage is 1V-10V, and the electroplating current is 0.1A / cm. 2 -5 A / cm 2 .

[0042] like Figure 3 and 4 As shown, the specific structure of the fabricated heterojunction solar cell metal electrode 6 is illustrated, as follows: Figure 5The diagram illustrates the entire fabrication process: a- heterojunction battery substrate with transparent conductive film 5; b- selective seed layer 61Ni layer fabricated on heterojunction battery substrate; c- SiO2 protective layer 7 formed on heterojunction battery substrate; d- low-temperature annealing of heterojunction battery substrate to expose metal seed layer 61Ni layer, forming a selective electroplating structure; e- electroless plating to form metal conductive layer 62Cu layer; f- electroless plating to form metal antioxidant layer 63Sn layer. In this process, the two ends of N-type silicon 1 are intrinsic amorphous silicon 2, and the outer sides of the two intrinsic amorphous silicon 2 layers are N-type amorphous silicon 3 and P-type amorphous silicon 4, respectively. The outer sides of N-type amorphous silicon 3 and P-type amorphous silicon 4 are both transparent conductive films 5. A protective layer 7 is formed on the outer side of the transparent conductive film 5. The first end of seed layer 61 is connected to the transparent conductive film 5, and the first end of seed layer 61 is connected to the first end of conductive layer 62. Antioxidant layer 63 covers the seed layer 61, the sides of conductive layer 62, and the second end of conductive layer 62.

[0043] 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 technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a metal electrode for a heterojunction solar cell, characterized in that, Includes the following steps: S1. Dry preparation of selective seed layers; selective seed layers are prepared on both sides of the heterojunction battery substrate; S2. Wet preparation of protective layer: The heterojunction battery substrate treated in step S1 is immersed in a functional solution for surface wetting, forming a uniform anti-reflection protective layer on the surface of the heterojunction battery; the functional solution is a precursor containing SiO2 or TiO2. S3. Preparation of selective electroplating functional structure: The heterojunction cell obtained in step S2 is annealed to form a surface anti-reflection and selective electroplating protective layer, exposing the seed layer and forming a selective electroplating structure; the annealing atmosphere is at least one of air, hydrogen, nitrogen, and argon, and the annealing temperature range is 120℃-200℃. S4. Electrochemical deposition method is used to prepare the metal conductive layer and the antioxidant layer; the conductive layer and the antioxidant layer are prepared sequentially on the seed layer by electroplating.

2. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, In step S1, the selective seed layer is prepared by a physical method.

3. The method for fabricating a heterojunction solar cell metal electrode according to claim 2, characterized in that, Selective seed layer preparation methods include laser transfer, physical vapor deposition, magnetron sputtering, or inkjet printing.

4. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, The metal seed layer raw material used in the selective seed layer preparation is at least one of nickel, copper, aluminum, silver, chromium, gold, tin, and indium.

5. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, The metal seed layer raw material used in the selective seed layer preparation contains a binder, which is zinc glass or borate.

6. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, The selective seed layer has a height of 1 µm-5 µm and a width of 1 µm-10 µm.

7. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, In step S4, the conductive layer is a copper layer, which is prepared by an electrochemical method using copper sulfate as the solution. The electroplating voltage is 1 V-50 V, and the electroplating current is 1 A / dm². 2 -5 A / dm 2 .

8. The method for fabricating a heterojunction solar cell metal electrode according to claim 1, characterized in that, In step S4, the antioxidant layer is a tin layer, which is prepared by an electrochemical method. The solution is tin aminosulfonate, the electroplating voltage is 1 V-10 V, and the electroplating current is 0.1 A / cm²-5 A / cm².

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