Electrode structure for tco surfaces and method of making same

Abstract

The present application provides an electrode structure for a TCO surface and a preparation method thereof, and solves the problems of high production cost caused by consumption of a large amount of expensive low-temperature conductive silver paste during preparation of a high-efficiency heterojunction cell, and technical difficulties in reducing silver paste consumption and refining metal wires. The second transition layer, the first transition layer and the conductive layer are sequentially constructed on the TCO surface, the contact resistance between the grid lines and the surface of the cell can be effectively reduced by setting the first transition layer and the second transition layer, and finally a high-efficiency heterojunction cell is obtained. At the same time, through research verification, the interval distance between each high-conductivity wire body, and the thickness of the first transition layer and the second transition layer are determined, which not only saves the use of low-temperature silver paste, but also avoids the process complexity problem caused by the patterning and electroplating process, and has low cost.

Description

Technical Field

[0001] This invention relates to an electrode structure and its preparation method, specifically to an electrode structure for TCO surfaces and its preparation method. Background Technology

[0002] With the rapid development of the photovoltaic market at home and abroad, the production of high-efficiency and low-cost solar cells has become an inevitable direction for the photovoltaic market. Among them, heterojunction cells are considered to be the next generation of mainstream cell technology.

[0003] For traditional crystalline silicon solar cells, silver paste is typically printed using screen printing, followed by high-temperature sintering to remove the organic phase of the silver paste, causing the silver powder to melt and sinter together on the surface, forming highly conductive metal grid lines. However, the fabrication process for high-efficiency heterojunction solar cells is more specialized, requiring low-temperature processes throughout. This necessitates the use of more expensive low-temperature conductive silver paste. Furthermore, since heterojunction solar cells are bifacial, their silver paste consumption is almost twice that of traditional single-sided solar cells. This makes silver paste a key factor hindering the industrialization of heterojunction solar cells, and reducing silver paste consumption and refining the metal grid lines remain technically challenging. Summary of the Invention

[0004] This invention addresses the high production costs of high-efficiency heterojunction solar cells due to the large amount of expensive low-temperature conductive silver paste required for their fabrication, and the technical difficulties in reducing silver paste consumption and refining metal wires. It provides an electrode structure for TCO surfaces and its fabrication method.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] An electrode structure for a TCO surface is characterized in that it includes a conductive layer and a first transition layer and a second transition layer disposed sequentially from top to bottom on the TCO surface.

[0007] The conductive layer comprises a plurality of highly conductive wires that are parallel to each other;

[0008] The first transition layer includes a plurality of parallel first conductors. The first conductors are made of a welding material composed of one or more conductive metals, or a conductive gel material composed of one or more conductive particles and an adhesive. The thickness of the first transition layer is 1-40 μm. Each highly conductive wire is respectively disposed inside each of the first conductors.

[0009] The second transition layer includes a plurality of parallel second conductors, each of which is a single-layer or multi-layer structure formed of one or more conductive metals, and the thickness of the second transition layer is 10-500 nm; each first conductor is respectively disposed on the upper surface of each second conductor.

[0010] Each second conductor is disposed on the surface of the TCO, and the spacing between each second conductor is 0.5-2 mm.

[0011] Furthermore, the material of the highly conductive wire body is copper, aluminum, or silver;

[0012] The second conductor is a single-layer or multi-layer structure formed by one or more conductive metals selected from copper, zinc, lead, aluminum, nickel, tin, and chromium.

[0013] Furthermore, the first conductor is a conductive gel material composed of one or more conductive particles and an adhesive selected from silver, carbon, copper, tin, and lead.

[0014] Alternatively, the first conductor may be a welding material composed of one or more conductive metals selected from tin, silver, copper, lead, bismuth, zinc, and nickel.

[0015] Accordingly, the present invention provides a method for preparing the above-mentioned electrode structure for TCO surface, characterized by comprising the following steps:

[0016] S1, at least one second transition layer prefabricated layer with a total thickness of 10-500 nm is prepared on the entire surface of the TCO using the same conductive metal as the second transition layer material;

[0017] S2, using electroplating or hot-dip plating methods, each first conductor is respectively wrapped onto the surface of each highly conductive wire body to obtain multiple conductive assemblies;

[0018] S3, using hot-press welding, each conductive assembly obtained in step S2 is arranged in parallel on the upper surface of the second transition layer preform prepared in step S1 at intervals of 0.5-2mm to obtain an electrode preform, wherein the lower surface of the first conductor in the conductive assembly is in contact with the upper surface of the second transition layer preform.

[0019] S4, chemically etch the electrode preform to remove the area in the second transition layer preform that is not covered by the conductive assembly.

[0020] Furthermore, in step S3, the temperature of the hot-press welding is 20-250℃, and the pressure is 0.01-3MPa.

[0021] The present invention also provides another electrode structure for TCO surfaces, which is characterized in that it includes a conductive layer, a first transition layer and a second transition layer disposed sequentially from top to bottom on the TCO surface;

[0022] The conductive layer comprises a plurality of highly conductive wires that are parallel to each other, with a spacing of 0.5-2 mm between each highly conductive wire.

[0023] The first transition layer includes a plurality of parallel first conductors. The first conductors are made of a welding material composed of one or more conductive metals, or a conductive gel material composed of one or more conductive particles and an adhesive. The thickness of the first transition layer is 1-40 μm. Each highly conductive wire is respectively disposed inside each of the first conductors.

[0024] The second transition layer includes a plurality of parallel second conductors, each of which is a single-layer or multi-layer structure formed of one or more conductive metals, and the thickness of the second transition layer is 10-500 nm; each first conductor is respectively disposed on the upper surface of each second conductor.

[0025] Each of the second conductors is disposed on the surface of the TCO.

[0026] Furthermore, the material of the highly conductive wire body is copper, aluminum, or silver;

[0027] The second conductor is a single-layer or multi-layer structure formed by one or more conductive metals selected from copper, zinc, lead, aluminum, nickel, tin, and chromium.

[0028] The first conductor is a conductive gel material composed of one or more conductive particles and an adhesive selected from silver, carbon, copper, tin, and lead.

[0029] Alternatively, the first conductor may be a welding material composed of one or more conductive metals selected from tin, silver, copper, lead, bismuth, zinc, and nickel.

[0030] Corresponding to the second electrode structure of the present invention, the present invention also provides a method for preparing the above-mentioned electrode structure for TCO surface, which is characterized by including the following steps:

[0031] S1, at least one second transition layer prefabricated layer with a total thickness of 10-500 nm is prepared on the entire surface of the TCO using the same conductive metal as the second transition layer material;

[0032] S2, using electroplating or bonding methods, each first conductor is arranged in parallel on the upper surface of the second transition layer prefabricated layer prepared in step S1 at intervals of 0.5-2mm;

[0033] S3, using an adhesive method, each highly conductive wire body is fixed to each first conductor to obtain an electrode preform;

[0034] S4, chemically etch the electrode preform to remove the area in the second transition layer preform that is not covered by the first conductor.

[0035] Further, in step S3, the bonding specifically involves bonding under pressure at 0.01-3 MPa and 20-250°C.

[0036] Furthermore, in step S4, the chemical corrosion solution is composed of one or more of the following components: hydrochloric acid, phosphoric acid, sulfamic acid, ammonia, hydrogen peroxide, sodium hydroxide, surfactant, and ferric chloride, and the chemical corrosion temperature is 5-60℃.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. This invention relates to an electrode structure for TCO surfaces, which sequentially constructs a second transition layer, a first transition layer, and a conductive layer on the TCO surface. By setting the first and second transition layers, the contact resistance between the grid lines and the cell surface can be effectively reduced, ultimately resulting in a high-efficiency heterojunction cell. Simultaneously, research and verification have determined the spacing between the highly conductive wires and the thicknesses of the first and second transition layers, ensuring that the electrode structure of this invention maximizes the performance of the heterojunction cell while also considering fabrication feasibility. Compared to existing metallization methods, this method eliminates the need for low-temperature silver paste and avoids the complexities of patterning and electroplating processes, resulting in lower costs.

[0039] 2. The first conductor in this invention can take two forms. At the same time, corresponding preferred conductive materials for the two forms are provided, making the structure of this invention more flexible and allowing for reasonable selection according to actual conditions.

[0040] 3. This invention provides two methods for preparing electrode structures, which can be achieved by hot pressing or bonding. The two methods also differ in the preparation sequence. Both methods can achieve the preparation of grid lines and the export of surface charge of heterojunction cells. Moreover, the entire production process is simple, fast, and low in cost. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of one embodiment of the electrode structure of the present invention used on a TCO surface;

[0042] Figure 2 This is a schematic flowchart of an embodiment of the method for preparing an electrode structure for a TCO surface according to the present invention;

[0043] Figure 3 This is a schematic flowchart of Example 2 of the method for preparing the electrode structure for TCO surface according to the present invention.

[0044] Wherein: 1-TCO, 2-Second transition layer, 3-First transition layer, 4-Conductive layer, 5-First conductor, 6-Second conductor, 7-Electrode preform, 8-Second transition layer preform, 9-Highly conductive wire body. Detailed Implementation

[0045] 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 embodiments of the present invention, and not all embodiments. 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.

[0046] Existing heterojunction solar cells all have a transparent conductive layer 4 (TCO1) on their surface, and an electrode needs to be fabricated on the TCO1 to collect current. Due to the need to control the contact resistance between the electrode and the TCO1, two main electrode schemes are currently adopted: 1) Screen printing silver paste and drying to prepare silver grid lines. The silver grid lines prepared by this process have low conductivity, approximately 5-7 times that of pure silver wire, because they are not sintered. Furthermore, low-temperature silver paste is more expensive than ordinary silver paste, and the amount of silver consumed by bifacial heterojunction cells is more than twice that of conventional solar cells, significantly increasing the manufacturing cost of heterojunction solar cells; 2) Fabricating grid lines through electroplating. This scheme generally requires pre-preparing a seed layer on the TCO1 surface, creating a mask pattern through coating or photolithography, electroplating copper electrodes on the exposed areas, and finally removing the mask layer and seed layer by wet etching. This scheme has a more complex process flow and also presents pollution problems.

[0047] This invention constructs a novel electrode structure, using other base metal materials instead of silver paste as the grid lines. Different types of coatings can be selected as needed, offering greater diversity. The conductive assembly, consisting of the first conductor 5 and the highly conductive wire body 9, is fixed to the second transition layer prefabricated layer 8 via thermo-press welding, or the highly conductive wire body 9 is fixed to the first conductor 5 via adhesive bonding, resulting in the electrode prefabricated product 7. The portion of the second transition layer prefabricated layer 8 not covered by the first conductor 5 is then etched away via chemical etching, achieving the fabrication of the grid lines and the discharge of surface charge from the heterojunction cell. Simultaneously, the first transition layer 3 and the second transition layer 2 not only fix the conductive layer 4 to the TCO1 surface but also help reduce the contact resistance between the metal grid lines and the TCO1, thus obtaining a highly efficient heterojunction cell. Compared to existing metallization methods, this invention eliminates the need for silver paste, avoids the complexities of patterning and electroplating processes, reduces pollution, and offers a simple, fast, and low-cost production process.

[0048] Example 1

[0049] An electrode structure for a TCO surface includes a conductive layer 4, a first transition layer 3, and a second transition layer 2 disposed sequentially from top to bottom on the TCO1 surface.

[0050] The conductive layer 4 comprises multiple parallel, highly conductive wire bodies 9, with a spacing of 0.5-2 mm between each wire body 9. This spacing should not be too large or too small. If the spacing is too small, it will significantly increase the processing difficulty and affect the battery efficiency of the heterojunction cell. If the spacing is too large, it will affect the current collection. The highly conductive wire bodies 9 are generally made of highly conductive materials such as copper, aluminum, and silver. The conductive layer 4 is primarily used to collect and conduct the current generated on the battery surface.

[0051] The first transition layer 3 includes multiple parallel first conductors 5. The first conductors 5 can be made of a welding material composed of one or more conductive metals such as tin, silver, copper, lead, bismuth, zinc, and nickel, or a conductive gel material composed of one or more conductive particles and an adhesive such as silver, carbon, and copper. Each highly conductive wire body 9 is fixed to each of the first conductors 5. The first transition layer 3 is used to connect each highly conductive wire body 9 and each of the second conductors 6 in the second transition layer 2, and to achieve a relatively low contact resistance compared with the conductive layer 4 and the second transition layer 2. The thickness of the first transition layer 3 is 1-40 μm.

[0052] The second transition layer 2 includes multiple parallel second conductors 6. Each second conductor 6 is a single-layer structure formed of one or more conductive metals. Each first conductor 5 is fixed to the upper surface of each second conductor 6. Each second conductor 6 is attached to the TCO1 to connect the first transition layer 3 and the TCO1, achieving a relatively low contact resistance between the first transition layer 3 and the TCO1. In other embodiments of the present invention, the second conductor 6 can also be a multi-layer structure larger than a single layer. The number of layers can be adjusted according to the bonding strength requirements. When the second conductor 6 is a multi-layer structure, the materials of each layer can be the same or different. The thickness of the second transition layer 2 is 10-500 nm. If the thickness of the second transition layer 2 is less than 10 nm, it will affect the long-term stability of the electrode structure. If the thickness is greater than 500 nm, it will affect the battery and increase unnecessary costs.

[0053] As a preferred embodiment of the electrode structure for a TCO surface according to the present invention, it includes a second transition layer 2, a first transition layer 3, and a conductive layer 4, which are sequentially fixed on the TCO surface from bottom to top. The second transition layer 2 is made of nickel and has a thickness of 200 nm. The first transition layer 3 is made of tin-lead alloy and has a thickness of 10 μm. The conductive layer 4 is made of high-purity copper, and the spacing between the highly conductive wires 9 in the conductive layer 4 is 1 mm. Performance testing was conducted on a battery with this electrode structure, and it was verified that the battery efficiency is comparable to that of the current method using silver paste, but the cost is significantly reduced¹.

[0054] This invention addresses the aforementioned electrode structure for TCO surfaces by designing two different preparation methods, which are illustrated by the following two examples:

[0055] like Figure 2 Accordingly, a method for preparing an electrode structure for a TCO surface is provided, comprising the following steps:

[0056] S1, using chemical plating, a second transition layer prefabricated layer 8 with a total thickness of 10-500nm is prepared on the entire surface of TCO1 using the same conductive metal as the second transition layer 2.

[0057] S2, using screen printing, each first conductor 5 is printed parallel to the surface of the second transition layer prefabricated layer 8 at intervals of 0.5-2mm. The material of the first conductor 5 is carbon-containing conductive adhesive.

[0058] S3, each highly conductive wire body 9 is fixed to each first conductor 5 by an adhesive method to obtain an electrode preform 7. During adhesive bonding, pressure is applied at 190°C and the pressure is 0.5MPa.

[0059] S4, chemically etch the electrode preform 7 to remove the area in the second transition layer preform 8 that is not covered by the first conductor 5.

[0060] Example 2

[0061] like Figure 1 An electrode structure for a TCO surface, differing from Embodiment 1, includes a conductive layer 4 and a first transition layer 3 and a second transition layer 2 sequentially disposed from top to bottom on the TCO1 surface. Each highly conductive wire body 9 is correspondingly disposed inside each of the first conductive bodies 5.

[0062] like Figure 3 The present invention also proposes a method for preparing an electrode structure according to Embodiment 2, a method for preparing an electrode structure for a TCO surface, comprising the following steps:

[0063] S1, a second transition layer prefabricated layer 8 with a total thickness of 10-500 nm is prepared on the entire surface of TCO1 using a conductive metal of the same material as the second transition layer 2 through chemical plating. Chemical plating is a preferred method; in other embodiments of the present invention, magnetron sputtering or thermal evaporation can also be used.

[0064] S2, using a hot-dip plating method, each first conductor 5 is hot-dip plated onto the surface of each highly conductive wire body 9 to obtain multiple conductive assemblies.

[0065] S3, using hot-press welding, the conductive assemblies obtained in step S2 are arranged parallel to each other on the upper surface of the second transition layer preform 8 prepared in step S1 at intervals of 0.5-2 mm to obtain the electrode preform 7. During hot-press welding, the hot-press temperature is 190℃ and the pressure is 0.5MPa.

[0066] S4, use a chemical etching solution to chemically etch the electrode preform 7 to clean the area in the second transition layer preform 8 that is not covered by the conductive assembly.

[0067] Based on research on metallization technology and process parameter design of heterojunction cells, this invention proposes a novel electrode structure that leverages the high aspect ratio and low contact resistance of metal gates to achieve high photoelectric conversion efficiency in heterojunction cells. This structure significantly reduces processing costs while ensuring cell performance and also meets environmental protection requirements.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrode structure for the surface of a heterojunction cell (TCO), characterized in that: It includes a conductive layer (4), and a first transition layer (3) and a second transition layer (2) disposed sequentially from top to bottom on the surface of TCO (1); The conductive layer (4) includes a plurality of parallel, highly conductive wire bodies (9); The first transition layer (3) includes a plurality of parallel first conductors (5), the first conductors (5) are made of a welding material composed of one or more conductive metals, and the thickness of the first transition layer (3) is 1-40 μm; each highly conductive wire body (9) is respectively disposed inside each first conductor (5); The second transition layer (2) includes a plurality of parallel second conductors (6), each second conductor (6) being a single-layer or multi-layer structure formed of one or more conductive metals, and the thickness of the second transition layer (2) is 10-500 nm; each first conductor (5) is respectively disposed on the upper surface of each second conductor (6); Each second conductor (6) is disposed on the surface of TCO (1), and the spacing between each second conductor (6) is 0.5-2 mm; By using electroplating or hot-dip plating, each first conductor (5) is respectively wrapped on the surface of each highly conductive wire body (9) to obtain multiple conductive assemblies.

2. The electrode structure for the TCO surface of a heterojunction solar cell according to claim 1, characterized in that: The material of the highly conductive wire body (9) is copper, aluminum or silver; The second conductor (6) is a single-layer or multi-layer structure formed by one or more conductive metals selected from copper, zinc, lead, aluminum, nickel, tin, and chromium.

3. The electrode structure for the TCO surface of a heterojunction solar cell according to claim 1 or 2, characterized in that: The first conductor (5) is a welding material composed of one or more conductive metals selected from tin, silver, copper, lead, bismuth, zinc, and nickel.

4. A method for preparing an electrode structure for a TCO surface in a heterojunction solar cell as described in any one of claims 1-3, characterized in that, Includes the following steps: S1, at least one second transition layer prefabricated layer (8) with a total thickness of 10-500nm is prepared on the entire surface of TCO(1) using the same conductive metal as the second transition layer (2); S2, by electroplating or hot-dip plating, each first conductor (5) is respectively wrapped on the surface of each highly conductive wire body (9) to obtain multiple conductive assemblies; S3, using hot-press welding, each conductive assembly obtained in step S2 is arranged in parallel on the upper surface of the second transition layer prefabricated layer (8) prepared in step S1 at intervals of 0.5-2mm to obtain an electrode preform (7), wherein the lower surface of the first conductive body (5) in the conductive assembly is in contact with the upper surface of the second transition layer prefabricated layer (8). S4, chemically etch the electrode preform (7) to remove the area in the second transition layer preform (8) that is not covered by the conductive assembly.

5. The method for preparing the electrode structure for the TCO surface of a heterojunction solar cell according to claim 4, characterized in that: In step S3, the temperature of the hot-press welding is 20-250℃ and the pressure is 0.01-3MPa.

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