Silver-coated copper paste and back contact solar cell

Abstract

The application provides a silver-coated copper paste and a back contact solar cell, the silver-coated copper paste comprising silver-coated copper particles, silver particles, an organic solvent and an additive; the silver-coated copper particles comprising a copper core and a silver shell layer coated on the surface of the copper core; the particle size of the silver particles and the particle size of the copper core satisfying: 30>R 铜核 / r 银颗粒 >1, R 铜核 being the particle size of the copper core, r 银颗粒 being the particle size of the silver particles. The application introduces silver-coated copper particles and silver particles, and strictly controls the particle size ratio of the copper core and the silver particles to satisfy 30>R 铜核 / r 银颗粒 >1, which not only significantly reduces the amount of noble metal and the cost of the paste, but also enables the silver-coated copper particles and the silver particles to form good gradation and packing density within the range of the particle size ratio, so that the paste greatly improves the economy and process adaptability on the premise of maintaining the conductive performance and contact resistance comparable to pure silver paste.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a silver-coated copper paste and a back-contact solar cell. Background Technology

[0002] Back-contact (BC) solar cells have become an important research direction in crystalline silicon solar cells due to their advantages such as no grid lines obstructing the front side, high short-circuit current, and excellent conversion efficiency. Currently, the electrode fabrication of BC solar cells mainly adopts screen printing technology, and the conductive paste used is mostly silver paste. Silver paste uses high-purity silver powder as the conductive phase and has advantages such as good conductivity, low contact resistance, and strong adhesion to the silicon substrate, which can meet the stringent requirements of BC solar cells for electrode fineness, high aspect ratio, and electrical performance.

[0003] However, silver, as a precious metal, has a high market price, resulting in silver paste accounting for a significant proportion of the total manufacturing cost of BC solar cells. With the photovoltaic industry's pursuit of cost reduction and efficiency improvement, and the continuous expansion of BC solar cell production capacity, relying solely on silver paste is no longer sufficient to meet the demands of large-scale, low-cost production. This severely restricts the further promotion and application of BC solar cell technology.

[0004] Therefore, how to effectively reduce the cost of electrode paste is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a silver-coated copper paste and a back-contact solar cell. This invention introduces a composite of silver-coated copper particles and silver particles, and strictly controls the particle size ratio of the copper core to the silver particles to satisfy 30 > R. 铜核 / r 银颗粒 A particle size ratio greater than 1 not only significantly reduces the amount of precious metals used and the cost of the paste, but also allows the silver-coated copper particles and silver particles to form a good gradation and packing density within this particle size ratio range. This enables the paste to maintain conductivity and contact resistance comparable to pure silver paste while greatly improving its economy and process adaptability.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a silver-coated copper paste, the silver-coated copper paste comprising silver-coated copper particles, silver particles, an organic solvent, and additives.

[0007] The silver-coated copper particles include a copper core and a silver shell layer covering the surface of the copper core.

[0008] The particle size of the silver particles and the particle size of the copper core satisfy the following condition: 30 > R 铜核 / r 银颗粒 >1, where R 铜核r is the particle size of the copper core. 银颗粒 The particle size of the silver particles is denoted as .

[0009] This invention introduces a compound of silver-coated copper particles and silver particles, and strictly controls the particle size ratio of the copper core to the silver particles to satisfy 30 > R. 铜核 / r 银颗粒 A particle size ratio greater than 1 not only significantly reduces the amount of precious metals used and the cost of the paste, but also allows the silver-coated copper particles and silver particles to form a good gradation and packing density within this particle size ratio range. This enables the paste to maintain conductivity and contact resistance comparable to pure silver paste while greatly improving its economy and process adaptability.

[0010] In this invention, 30 > R 铜核 / r 银颗粒 >1, for example, it can be 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 or 29, etc. With a suitable particle size ratio, on the one hand, copper can replace part of the silver with the maximum content, significantly reducing the amount of precious metal silver used, thereby greatly reducing the cost of the slurry. On the other hand, the relatively small silver particles can effectively fill the gaps between the relatively large silver-coated copper particles, increasing the packing density of solid particles. This results in a more continuous and dense conductive network after the sintering process in the battery manufacturing process, while reducing porosity defects and improving the conductivity and adhesion of the electrode.

[0011] Preferably, 20 ≥ R 铜核 / r 银颗粒 ≥5, for example, it can be 5, 10, 15, or 20, etc. The present invention preferably uses 20≥R. 铜核 / r 银颗粒 ≥5 is because within this preferred range, it ensures that small silver particles fully fill the gaps between large silver-coated copper particles, while avoiding agglomeration caused by excessively fine silver particles and an increase in the amount of organic carrier. This further optimizes the rheological properties of the slurry, maximizes the substitution ratio of silver-coated copper particles for pure silver, significantly reduces the cost of electrode slurry, and achieves the best balance between cost and performance.

[0012] Preferably, the copper core has a particle size of 0.5-10 μm, such as 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 105 μm.

[0013] Preferably, the thickness of the shell layer is in the range of 0.1-1 μm, for example, it can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm or 1 μm.

[0014] Preferably, the silver particles have a particle size of 0.2-3 μm, for example, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0015] Preferably, 60% > S 铜总 / S 银总 >5%, of which S 铜总 and S 银总 These are the percentages of the copper phase and silver phase in any unit area of ​​the sintered layer formed after the silver-coated copper paste is sintered, respectively. For example, these percentages can be 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 58%.

[0016] In this invention, by limiting 60% > S 铜总 / S 银总 A ratio of >5% can effectively control the amount of silver used while ensuring the conductivity of the slurry. This ratio can ensure that the copper core is fully coated to form a good conductive path, and also achieve the purpose of replacing part of the silver with copper, thus achieving a reasonable balance between conductivity, reliability and material cost.

[0017] Preferably, 40% ≥ S 铜总 / S 银总 ≥10%, for example, it can be 10%, 20%, 30% or 40%, etc.

[0018] The present invention preferably has 40% ≥ S 铜总 / S 银总 ≥10% is because within this preferred range, the area ratio of copper to silver is more balanced: on the one hand, the appropriate proportion of silver phase indicates that the paste will not have an adverse effect on the resistivity and contact resistance of the electrode body; on the other hand, the appropriate proportion of copper phase indicates that the paste maximizes cost advantage and is the best range that balances performance, cost and reliability.

[0019] Preferably, in the silver-coated copper paste, the mass ratio of copper to silver is (60-80):(10-30), wherein the mass of copper is selected from the range of "60-80", for example, 60, 70 or 80, and the mass of silver is selected from the range of "10-30", for example, 10, 20 or 30.

[0020] The copper-coated silver paste provided by this invention utilizes a suitable mass ratio of copper to silver to facilitate good gradation and packing density between the copper and silver particles. This significantly improves the economic efficiency and process adaptability of the paste while maintaining conductivity and contact resistance comparable to pure silver paste. If the mass ratio of copper to silver is too small, i.e., the silver content is too high, the cost is high, and excessive silver is prone to electrochemical migration during high-temperature sintering, reducing the long-term reliability of the electrodes. If the mass ratio of copper to silver is too large, i.e., the copper content is too high, the conductivity of the paste is poor, and the excessive large-diameter copper-coated silver particles can clog the screen, affecting printing efficiency, easily producing defects such as broken grid nodes, and resulting in numerous grid line voids, severely impacting grid line conductivity.

[0021] Preferably, the additives include any one or a combination of at least two of the following: plasticizers, dispersants, or resins.

[0022] For example, the plasticizer may be dibutyl phthalate, dioctyl phthalate, dioctyl adipate, polyethylene glycol, or ethyl cellulose. The dispersant may be oleic acid, fatty acids with a carbon chain of C15-C25, fatty acid esters with a carbon chain of C15-C25, organosilanes, organotitanium compounds, sodium polyacrylate, polyacrylamide, styrene-maleic anhydride copolymer, sodium phosphate, sodium silicate, sodium carbonate, sodium metasilicate, sodium citrate, or sodium humate. The resin may be polyurethane, epoxy resin, acrylic resin, or polyester resin.

[0023] For example, the organic solvent may be diethylene glycol butyl ether, diethylene glycol butyl ether acetate, decyl alcohol ester, hexadecyl alcohol ester, dimethyl adipate, dimethyl glutarate, tributyl citrate, acetylated tributyl citrate, triethylene glycol butyl ether, tripropylene glycol monomethyl ether, tripropylene glycol butyl ether, diethylene glycol monoethyl ether acetate, dibutyl phthalate, dioctyl phthalate, or terpineol, etc.

[0024] Preferably, the solid content of the silver-coated copper paste is 65-90%, for example, it can be 65%, 70%, 75%, 80%, 85% or 90%, etc.

[0025] In a second aspect, the present invention provides a method for preparing the silver-coated copper paste as described in the first aspect, the method comprising the following steps: The silver-coated copper powder, silver powder, additives and organic solvent are mixed to obtain the silver-coated copper paste.

[0026] Preferably, the preparation method includes the following steps: The silver-coated copper powder, silver powder, additives and organic solvents are premixed to obtain a premix.

[0027] The premixed material is ground at a speed of 200-800 rpm (e.g., 200 rpm, 400 rpm, 600 rpm, or 800 rpm) for 10-60 min (e.g., 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min) until the particle fineness meets the preset requirements to obtain the silver-coated copper paste.

[0028] Thirdly, the present invention provides a back-contact solar cell, wherein the raw materials for preparing the back-contact solar cell include the silver-coated copper paste as described in the first aspect.

[0029] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0030] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces a compound of silver-coated copper particles and silver particles, and strictly controls the particle size ratio of the copper core to the silver particles to satisfy 30 > R. 铜核 / r 银颗粒 A particle size ratio greater than 1 not only significantly reduces the amount of precious metals used and the cost of the paste, but also allows the silver-coated copper particles and silver particles to form a good gradation and packing density within this particle size ratio range. This enables the paste to maintain conductivity and contact resistance comparable to pure silver paste while greatly improving its economy and process adaptability. Attached Figure Description

[0031] Figure 1 This is a surface SEM image of the sintered layer formed after sintering of the silver-coated copper paste provided in Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0033] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0034] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0035] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0036] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0037] Example 1 This embodiment provides a silver-coated copper paste, which includes silver-coated copper particles, silver particles, organic solvents, and additives.

[0038] The silver-coated copper particles comprise a copper core and a silver shell covering the surface of the copper core; the particle size of the silver particles and the particle size of the copper core satisfy the following condition: 30 > R. 铜核 / r 银颗粒 >1, where R 铜核 r is the particle size of the copper core. 银颗粒 The particle size of the silver particles is 0.5-10 μm; the particle size of the copper core is 0.1-1 μm; the thickness of the silver shell is 0.2-3 μm.

[0039] Among them, 60% > S 铜总 / S 银总 >5%, of which S 铜总 and S 银总 These are the percentage of the area occupied by the copper phase and the silver phase in any unit area of ​​the sintered layer formed after the silver-coated copper paste is sintered, respectively.

[0040] In the silver-coated copper paste, the mass ratio of copper to silver is 70:20; the mass content of additives in the silver-coated copper paste is 8%, and the additives include a dispersant and a resin in a mass ratio of 1:3, wherein the dispersant is polyacrylamide and the resin is epoxy resin; the organic solvent is diethylene glycol butyl ether; and the solid content of the silver-coated copper paste is 80%.

[0041] This embodiment also provides a method for preparing the above-mentioned silver-coated copper paste, the preparation method comprising the following steps: (1) Add silver-coated copper powder, silver powder and additives to diethylene glycol butyl ether and premix to obtain a premix.

[0042] (2) Grind the premixed material at a speed of 500 rpm for 30 min until the particle fineness reaches the preset requirement to obtain the silver-coated copper paste.

[0043] Figure 1 The SEM image of the surface of the sintered layer formed after sintering of the silver-coated copper paste provided in Example 1 is shown.

[0044] Example 2 This embodiment provides a silver-coated copper paste, which includes silver-coated copper particles, silver particles, organic solvents, and additives.

[0045] The silver-coated copper particles comprise a copper core and a silver shell covering the surface of the copper core; the particle size of the silver particles and the particle size of the copper core satisfy the following condition: 20 ≥ R 铜核 / r 银颗粒 ≥5, where R 铜核 r is the particle size of the copper core. 银颗粒The particle size of the silver particles is 0.5-10 μm; the particle size of the copper core is 0.1-1 μm; the thickness of the silver shell is 0.2-3 μm.

[0046] Among them, 40%≥S 铜总 / S 银总 ≥10%, of which S 铜总 and S 银总 These are the percentage of the area occupied by the copper phase and the silver phase in any unit area of ​​the sintered layer formed after the silver-coated copper paste is sintered, respectively.

[0047] In the silver-coated copper paste, the mass ratio of copper to silver is 60:30; the mass content of additives in the silver-coated copper paste is 8%, and the additives include a dispersant and a resin in a mass ratio of 1:3, wherein the dispersant is polyacrylamide and the resin is epoxy resin; the organic solvent is diethylene glycol butyl ether; and the solid content of the silver-coated copper paste is 80%.

[0048] This embodiment also provides a method for preparing the above-mentioned silver-coated copper paste, the preparation method comprising the following steps: (1) Add silver-coated copper powder, silver powder and additives to diethylene glycol butyl ether and premix to obtain a premix.

[0049] (2) Grind the premixed material at a speed of 500 rpm for 30 min until the particle fineness reaches the preset requirement to obtain the silver-coated copper paste.

[0050] Example 3 This embodiment provides a silver-coated copper paste, which includes silver-coated copper particles, silver particles, organic solvents, and additives.

[0051] The silver-coated copper particles comprise a copper core and a silver shell covering the surface of the copper core; the particle size of the silver particles and the particle size of the copper core satisfy the following condition: 20 ≥ R 铜核 / r 银颗粒 ≥5, where R 铜核 r is the particle size of the copper core. 银颗粒 The particle size of the silver particles is 0.5-10 μm; the particle size of the copper core is 0.1-1 μm; the thickness of the silver shell is 0.2-3 μm.

[0052] Among them, 40%≥S 铜总 / S 银总 ≥10%, of which S 铜总 and S 银总These are the percentage of the area occupied by the copper phase and the silver phase in any unit area of ​​the sintered layer formed after the silver-coated copper paste is sintered, respectively.

[0053] In the silver-coated copper paste, the mass ratio of copper to silver is 80:10; the mass content of additives in the silver-coated copper paste is 8%, and the additives include a dispersant and a resin in a mass ratio of 1:3, wherein the dispersant is polyacrylamide and the resin is epoxy resin; the organic solvent is diethylene glycol butyl ether; and the solid content of the silver-coated copper paste is 80%.

[0054] This embodiment also provides a method for preparing the above-mentioned silver-coated copper paste, the preparation method comprising the following steps: (1) Add silver-coated copper powder, silver powder and additives to diethylene glycol butyl ether and premix to obtain a premix.

[0055] (2) Grind the premixed material at a speed of 500 rpm for 30 min until the particle fineness reaches the preset requirement to obtain the silver-coated copper paste.

[0056] Example 4 The only difference between this embodiment and Embodiment 1 is that the amount of silver powder added is adjusted so that the mass ratio of copper to silver in the silver-coated copper paste is 90:10, meaning that the silver-coated copper paste does not satisfy 60% > S. 铜总 / S 银总 >5%.

[0057] Comparative Example 1 The only difference between this comparative example and Example 1 is that the size of the silver powder in step (1) is adjusted so that R in the silver-coated copper paste... 铜核 / r 银颗粒 >30.

[0058] Performance testing The resistivity of the silver-coated copper paste provided in the above embodiments and comparative examples was tested using the four-probe method. The specific method is as follows: the silver-coated copper paste is coated on the substrate and sintered to form a sintered layer. The resistivity of the sintered layer is measured using a four-probe resistivity tester.

[0059] The test results are shown in Table 1.

[0060] Table 1 analyze: As shown in Table 1, this invention introduces silver-coated copper particles and silver particles in combination, and strictly controls the particle size ratio of the copper core to the silver particles to satisfy 30 > R. 铜核 / r 银颗粒 >1, 60% >S 铜总 / S银总 With a concentration greater than 5%, not only is the amount of precious metals used and the cost of the paste significantly reduced, but the silver-coated copper particles and silver particles can also form a good gradation and packing density, which greatly improves the economy and process adaptability of the paste while maintaining conductivity and contact resistance comparable to pure silver paste.

[0061] A comparison of Examples 1 and 4 shows that when the mass ratio of copper to silver in the copper-plated paste is 90:10, even if the copper-plated paste does not meet the requirement of 60% > S... 铜总 / S 银总 When the content is greater than 5%, the excessive copper content makes the conductivity of the paste poor, and the excessive large-diameter silver-coated copper particles formed can easily clog the screen, affecting printing efficiency, causing poor appearance such as broken grid nodes, and resulting in more grid line voids, which seriously affects the conductivity of the grid lines.

[0062] As can be seen from the comparison between Example 1 and Comparison 1, when R in the silver-coated copper paste 铜核 / r 银颗粒 When the temperature is greater than 30, the copper nuclei with excessively large particle size will result in the formation of excessively large silver-coated copper particles. Since it is difficult for large-sized particles to form a tight packing, the porosity inside the sintered conductive film layer increases and the conductive pathway is reduced, which seriously affects the conductivity.

[0063] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A silver-coated copper paste, characterized in that, The silver-coated copper paste includes silver-coated copper particles, silver particles, organic solvents, and additives; The silver-coated copper particles include a copper core and a silver shell layer covering the surface of the copper core. The particle size of the silver particles and the particle size of the copper core satisfy the following condition: 30 > R 铜核 / r 银颗粒 >1, where R 铜核 r is the particle size of the copper core. 银颗粒 The particle size of the silver particles is denoted as .

2. The silver-coated copper paste according to claim 1, characterized in that, 20≥R 铜核 / r 银颗粒 ≥5。 3. The silver-coated copper paste according to claim 1 or 2, characterized in that, The copper core has a particle size of 0.5-10 μm.

4. The silver-coated copper paste according to any one of claims 1-3, characterized in that, The thickness of the silver shell layer ranges from 0.1 to 1 μm.

5. The silver-coated copper paste according to any one of claims 1-4, characterized in that, The silver particles have a particle size of 0.2-3 μm.

6. The silver-coated copper paste according to any one of claims 1-5, characterized in that, 60% > S 铜总 / S 银总 >5%, of which S 铜总 and S 银总 These are the percentage of the area occupied by the copper phase and the silver phase in any unit area of ​​the sintered layer formed after the silver-coated copper paste is sintered, respectively.

7. The silver-coated copper paste according to claim 6, characterized in that, 40%≥S 铜总 / S 银总 ≥10%。 8. The silver-coated copper paste according to any one of claims 1-7, characterized in that, In the silver-coated copper paste, the mass ratio of copper to silver is (60-80):(10-30).

9. The silver-coated copper paste according to claim 1, characterized in that, The additives include any one or a combination of at least two of plasticizers, dispersants, or resins; And / or, the solid content of the silver-coated copper paste is 65-90%.

10. A back-contact solar cell, characterized in that, The raw materials for preparing the back-contact solar cell include the silver-coated copper paste as described in any one of claims 1-9.

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