A copper-based metal electrode slurry for a silicon-based photovoltaic cell, a preparation process thereof, a copper-based metal electrode and a preparation method thereof, and a silicon-based photovoltaic cell

Abstract

The application provides a copper-based metal electrode paste for a silicon-based photovoltaic cell, a preparation process of the copper-based metal electrode paste, a copper-based metal electrode, a preparation method of the copper-based metal electrode and the silicon-based photovoltaic cell. Components of the copper-based metal electrode paste include spherical silver-coated copper powder, low-melting-point glass powder, metal powder and an organic carrier. The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder or nickel powder. The copper-based metal electrode paste provided by the application contains metal powder and low-melting-point glass powder, alloying of free copper is realized by using manganese powder, etching depth is regulated by using low-melting-point glass powder, copper diffusion is synergistically inhibited, formation of impurity recombination centers is effectively avoided, and therefore open-circuit voltage and conversion efficiency of the cell are significantly improved, thereby providing a solution for low-cost industrial application of copper electrode technology.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic cell technology, and relates to a copper-based metal electrode paste for silicon-based photovoltaic cells, and more particularly to a copper-based metal electrode paste for silicon-based photovoltaic cells and its preparation process, copper-based metal electrodes and their preparation methods, and silicon-based photovoltaic cells. Background Technology

[0002] Photovoltaic paste is a key functional material in solar cell manufacturing, primarily used to form the electrodes (grid lines) and back surface of the cell. Given the ongoing efforts in the photovoltaic industry to reduce costs and increase efficiency, achieving low-cost photovoltaic paste has become a key research focus. To this end, copper-based electrodes have been developed to replace silver electrodes, thereby reducing material costs. However, the application performance of copper-based electrodes has not met expectations. The main reason is that during the sintering process, copper ions diffuse into the silicon matrix, forming impurity recombination centers, leading to lower open-circuit voltage and insufficient efficiency. This problem has become a major bottleneck restricting the industrial application of copper electrode technology.

[0003] For example, CN115734467A discloses a copper electrode paste for COB-encapsulated glass substrates and its preparation method. The copper electrode paste formulation consists of the following components in weight percentages: 65%–75% copper powder, 15%–30% organic carrier, 5%–10% glass powder, and 0.2%–0.5% organic additives. The copper powder is a mixture of several copper powders with different particle sizes and morphologies, and the glass powder is a mixture of two glass powders with different sintering properties. However, when preparing electrodes using this disclosed copper electrode paste for COB-encapsulated glass substrates, sintering is required. Copper ions diffuse into the silicon substrate, forming carrier recombination centers, leading to a decrease in battery efficiency.

[0004] For example, CN103545016A discloses a conductive paste for the front electrode of a crystalline silicon solar cell and its preparation method. This conductive paste for the front electrode of a crystalline silicon solar cell is composed of an etchant, metal powder, an organic carrier, and glass powder; the etchant is one or more crystalline compounds with a melting point of 250℃~760℃; the glass powder has an amorphous structure. However, when preparing the front electrode of a crystalline silicon solar cell using this disclosed conductive paste, sintering is still required. Copper ions diffuse into the silicon substrate, forming carrier recombination centers, leading to a decrease in cell efficiency.

[0005] In summary, the copper-based metal electrode pastes for silicon-based photovoltaic cells disclosed in the prior art all have certain defects. During the preparation of the copper-based metal electrode, copper ions diffuse into the silicon substrate, forming impurity recombination centers, leading to low open-circuit voltage and insufficient efficiency. Therefore, developing a novel copper-based metal electrode paste for silicon-based photovoltaic cells, its preparation process, copper-based metal electrodes and their preparation methods, and silicon-based photovoltaic cells themselves are crucial. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a copper-based metal electrode paste for silicon-based photovoltaic cells, its preparation process, copper-based metal electrodes and their preparation methods, and silicon-based photovoltaic cells. The copper-based metal electrode paste provided by the present invention contains metal powder and low-melting-point glass powder. Manganese powder is used to alloy free copper, and low-melting-point glass powder is used to control the etching depth, synergistically suppressing copper diffusion and effectively avoiding the formation of impurity recombination centers. This significantly improves the open-circuit voltage and conversion efficiency of the cell, providing a solution for the low-cost industrial application of copper electrode technology.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a copper-based metal electrode paste for silicon-based photovoltaic cells, wherein the components of the copper-based metal electrode paste include spherical silver-coated copper powder, low-melting-point glass powder, metal powder and organic carrier;

[0009] The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder.

[0010] The copper-based metal electrode slurry provided by this invention contains metal powder. When copper-based metal electrodes are prepared by sintering the copper-based metal electrode slurry, the metal powder will form a copper-manganese alloy with the free copper in the spherical silver-coated copper powder, thereby achieving the alloying of free copper. This avoids the free copper from diffusing into the silicon matrix to form impurity recombination centers, and improves the open-circuit voltage and cell efficiency of the silicon-based photovoltaic cell containing the prepared copper-based metal electrode.

[0011] The copper-based metal electrode paste provided by this invention contains low-melting-point glass powder, which helps to ensure good etching depth, thereby lengthening the copper diffusion distance and avoiding over-etching that causes free copper to diffuse into the silicon substrate. This reduces the risk of free copper contacting the silicon substrate and forming impurity recombination centers, thereby further improving the open-circuit voltage and cell efficiency of silicon-based photovoltaic cells containing the prepared copper-based metal electrode.

[0012] In summary, the copper-based metal electrode paste provided by this invention contains metal powder and low-melting-point glass powder. Manganese powder is used to alloy free copper, and low-melting-point glass powder is used to control the etching depth, synergistically suppressing copper diffusion and effectively avoiding the formation of impurity recombination centers. This significantly improves the open-circuit voltage and conversion efficiency of the battery, providing a solution for the low-cost industrial application of copper electrode technology.

[0013] Preferably, the melting point of the low-melting-point glass powder is not higher than 400°C;

[0014] The low-melting-point glass powder includes Pb-Si-B-Bi-Sb system low-melting-point glass powder;

[0015] The D50 particle size of the Pb-Si-B-Bi-Sb series low melting point glass powder is 0.8μm~1μm.

[0016] Preferably, the copper-based metal electrode paste further includes additives;

[0017] The additives include dispersants and / or thixotropic agents;

[0018] In the copper-based metal electrode paste, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is (80~90):(3~5):(0.5~5):(8~10):(3~5).

[0019] In a second aspect, the present invention provides a preparation process for the copper-based metal electrode paste described in the first aspect, the preparation process comprising:

[0020] The copper-based metal electrode paste is obtained by mixing spherical silver-coated copper powder, low-melting-point glass powder, metal powder and organic carrier.

[0021] The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder.

[0022] Preferably, the method for preparing the low-melting-point glass powder includes:

[0023] PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then subjected to calcination, cooling crystallization, grinding and particle size classification to obtain low melting point glass powder.

[0024] By weight, the mixture contains 50 to 70 parts of PbO, 30 to 50 parts of SiO2, 5 to 10 parts of B2O3, 10 to 20 parts of Bi2O3, and 5 to 10 parts of Sb2O3.

[0025] The calcination includes sequential heating and holding. The heating rate is 30℃ / min to 50℃ / min, and the final temperature is the holding temperature. The holding temperature is 900℃ to 1000℃, and the holding time is 60min to 80min.

[0026] Preferably, additives are also mixed into the mixture;

[0027] The mixing process includes: first mixing spherical silver-coated copper powder, low-melting-point glass powder and metal powder to obtain a first mixture; then mixing the obtained first mixture with an organic carrier and additives to obtain a second mixture.

[0028] Thirdly, the present invention provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in the first aspect.

[0029] Fourthly, the present invention provides a method for preparing the copper-based metal electrode described in the third aspect, the method comprising:

[0030] The copper-based metal electrode paste described in the first aspect is coated onto the front fine grid of a silicon-based photovoltaic cell and then sintered to obtain a copper-based metal electrode.

[0031] Preferably, the sintering includes a first sintering, a second sintering, and a third sintering performed sequentially;

[0032] The first sintering temperature is 300℃-500℃, the second sintering temperature is 700℃~800℃, and the third sintering temperature is 200℃~300℃;

[0033] During the sintering process, the belt speed is 7m / min to 10m / min.

[0034] Fifthly, the present invention provides a silicon-based photovoltaic cell, the silicon-based photovoltaic cell comprising the copper-based metal electrode described in the third aspect.

[0035] 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.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The copper-based metal electrode slurry provided by the present invention contains metal powder. When the copper-based metal electrode is prepared by sintering the copper-based metal electrode slurry, the metal powder will form a copper-manganese alloy with the free copper in the spherical silver-coated copper powder, thereby achieving the alloying of free copper. This avoids the free copper from diffusing into the silicon matrix to form impurity recombination centers, and improves the open-circuit voltage and cell efficiency of the silicon-based photovoltaic cell containing the prepared copper-based metal electrode.

[0038] (2) The copper-based metal electrode paste provided by the present invention contains low melting point glass powder, which is beneficial to ensure good etching depth, thereby lengthening the distance of copper diffusion, avoiding over-etching that causes free copper to diffuse into the silicon substrate, reducing the risk of free copper contacting the silicon substrate and forming impurity recombination centers, thereby further improving the open circuit voltage and cell efficiency of silicon-based photovoltaic cells containing the prepared copper-based metal electrode.

[0039] (3) The copper-based metal electrode paste provided by the present invention contains metal powder and low melting point glass powder. Manganese powder is used to achieve the alloying of free copper, and low melting point glass powder is used to control the etching depth, which synergistically suppresses copper diffusion and effectively avoids the formation of impurity recombination centers, thereby significantly improving the open circuit voltage and conversion efficiency of the battery, and providing a solution for the low-cost industrial application of copper electrode technology. Attached Figure Description

[0040] Figure 1 This is a low-magnification SEM image of the spherical silver-coated copper powder used in Example 1.

[0041] Figure 2 This is a high-magnification SEM image of the spherical silver-coated copper powder used in Example 1.

[0042] Figure 3 This is the PL image corresponding to Example 1.

[0043] Figure 4 This is the PL image corresponding to Comparative Example 1.

[0044] Figure 5 This is the PL image corresponding to Example 4.

[0045] Figure 6 This is an SEM image of the copper-based metal electrode in Example 1.

[0046] Figure 7 This is an SEM image of the copper-based metal electrode in Example 4. Detailed Implementation

[0047] 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.

[0048] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0049] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] 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 places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0052] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0053] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These 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" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0054] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0055] In one embodiment, the present invention provides a copper-based metal electrode paste for silicon-based photovoltaic cells, wherein the components of the copper-based metal electrode paste include spherical silver-coated copper powder, low-melting-point glass powder, metal powder and organic carrier;

[0056] The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder.

[0057] In this invention, the metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder. Typical but non-limiting combinations include combinations of manganese powder and bismuth powder, combinations of bismuth powder and nickel powder, combinations of manganese powder and nickel powder, or combinations of manganese powder, bismuth powder, and nickel powder.

[0058] The copper-based metal electrode slurry provided by this invention contains metal powder. When copper-based metal electrodes are prepared by sintering the copper-based metal electrode slurry, the metal powder will form a copper-manganese alloy with the free copper in the spherical silver-coated copper powder, thereby achieving the alloying of free copper. This avoids the free copper from diffusing into the silicon matrix to form impurity recombination centers, and improves the open-circuit voltage and cell efficiency of the silicon-based photovoltaic cell containing the prepared copper-based metal electrode.

[0059] The copper-based metal electrode paste provided by this invention contains low-melting-point glass powder, which helps to ensure good etching depth, thereby lengthening the copper diffusion distance and avoiding over-etching that causes free copper to diffuse into the silicon substrate. This reduces the risk of free copper contacting the silicon substrate and forming impurity recombination centers, thereby further improving the open-circuit voltage and cell efficiency of silicon-based photovoltaic cells containing the prepared copper-based metal electrode.

[0060] In summary, the copper-based metal electrode paste provided by this invention contains metal powder and low-melting-point glass powder. Manganese powder is used to alloy free copper, and low-melting-point glass powder is used to control the etching depth, synergistically suppressing copper diffusion and effectively avoiding the formation of impurity recombination centers. This significantly improves the open-circuit voltage and conversion efficiency of the battery, providing a solution for the low-cost industrial application of copper electrode technology.

[0061] In some embodiments, the sphericity of the spherical silver-coated copper powder is not less than 0.8, for example, it can be 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96 or 0.98, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0062] In some embodiments, the D50 particle size of the spherical silver-coated copper powder is 1.0 μm to 3.0 μm, for example, it can be 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0063] In some embodiments, the melting point of the low-melting-point glass powder is not higher than 400°C;

[0064] The low-melting-point glass powder includes Pb-Si-B-Bi-Sb system low-melting-point glass powder;

[0065] The D50 particle size of the Pb-Si-B-Bi-Sb series low melting point glass powder is 0.8μm~1μm.

[0066] In this invention, the melting point of the low melting point glass powder is not higher than 400°C, for example, it can be 300°C, 320°C, 340°C, 360°C, 380°C or 400°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] In this invention, the D50 particle size of the Pb-Si-B-Bi-Sb low-melting-point glass powder is 0.8μm to 1μm, for example, it can be 0.80μm, 0.82μm, 0.84μm, 0.86μm, 0.88μm, 0.90μm, 0.92μm, 0.94μm, 0.96μm, 0.98μm or 1.00μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] In some embodiments, the metal powder is manganese powder.

[0069] In some embodiments, the D50 particle size of the metal powder is 1.0 μm to 3.0 μm, for example, it can be 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0070] In some embodiments, the organic carrier comprises a resin and a solvent.

[0071] In some embodiments, the resin comprises any one or a combination of at least two of ethyl cellulose, hydroxypropyl methylcellulose, or acrylic resin. Typical but non-limiting combinations include combinations of ethyl cellulose and hydroxypropyl methylcellulose, combinations of hydroxypropyl methylcellulose and acrylic resin, combinations of ethyl cellulose and acrylic resin, or combinations of ethyl cellulose, hydroxypropyl methylcellulose, and acrylic resin.

[0072] In some embodiments, the solvent includes any one or a combination of at least two of butyl carbitol, diethylene glycol butyl ether acetate, or dimethyl adipate. Typical but non-limiting combinations include a combination of butyl carbitol and diethylene glycol butyl ether acetate, a combination of diethylene glycol butyl ether acetate and dimethyl adipate, a combination of butyl carbitol and dimethyl adipate, or a combination of butyl carbitol, diethylene glycol butyl ether acetate, and dimethyl adipate.

[0073] In some embodiments, by weight, the organic carrier contains no more than 5 parts of ethyl cellulose, no more than 3 parts of hydroxypropyl methyl cellulose, no more than 5 parts of acrylic resin, 30 to 50 parts of butyl carbitol, 30 to 50 parts of diethylene glycol butyl ether acetate, and 10 to 30 parts of dimethyl adipate.

[0074] In this invention, the weight of ethyl cellulose in the organic carrier is no more than 5 parts, for example, it can be 0 parts, 1 part, 2 parts, 3 parts, 4 parts or 5 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] In this invention, the amount of hydroxypropyl methylcellulose in the organic carrier is no more than 3 parts by weight, for example, it can be 0 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] In this invention, the acrylic resin in the organic carrier is not more than 5 parts by weight, for example, it can be 0 parts, 1 part, 2 parts, 3 parts, 4 parts or 5 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0077] In this invention, the organic carrier contains 30 to 50 parts by weight, for example, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 parts by weight, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] In this invention, the amount of diethylene glycol butyl ether acetate in the organic carrier is 30 to 50 parts by weight, for example, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] In this invention, the amount of dimethyl adipate in the organic carrier is 10 to 30 parts by weight, for example, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 or 30 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0080] In some embodiments, the copper-based metal electrode paste further includes additives;

[0081] The additives include dispersants and / or thixotropic agents;

[0082] In the copper-based metal electrode paste, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is (80~90):(3~5):(0.5~5):(8~10):(3~5).

[0083] In this invention, the mass ratio of spherical silver-coated copper powder to low-melting-point glass powder in the copper-based metal electrode slurry is (80~90):(3~5), for example, it can be 80:3, 82:3.5, 84:4, 86:4.5, 88:5 or 90:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In this invention, the mass ratio of spherical silver-coated copper powder to metal powder in the copper-based metal electrode slurry is (80~90):(0.5~5), for example, it can be 80:0.5, 82:1.5, 84:2.5, 86:3.5, 88:4.5 or 90:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0085] In this invention, the mass ratio of spherical silver-coated copper powder to organic carrier in the copper-based metal electrode slurry is (80~90):(8~10), for example, it can be 80:8, 82:8.5, 84:9, 86:9.5, 88:10 or 90:10, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0086] In this invention, the mass ratio of spherical silver-coated copper powder to additives in the copper-based metal electrode slurry is (80~90):(3~5), for example, it can be 80:3, 82:3.5, 84:4, 86:4.5, 88:5 or 90:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0087] In some embodiments, the mass ratio of dispersant to thixotropic agent in the additive is 1:(2~5), for example, it can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0088] In some embodiments, the dispersant comprises an organic salt of fatty diamine (TDO).

[0089] In some embodiments, the thixotropic agent comprises polyamide wax and / or fumed silica.

[0090] In one embodiment, the present invention provides a preparation process for the above-mentioned copper-based metal electrode paste, the preparation process comprising:

[0091] The copper-based metal electrode paste is obtained by mixing spherical silver-coated copper powder, low-melting-point glass powder, metal powder and organic carrier.

[0092] The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder.

[0093] In this invention, the metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder. Typical but non-limiting combinations include combinations of manganese powder and bismuth powder, combinations of bismuth powder and nickel powder, combinations of manganese powder and nickel powder, or combinations of manganese powder, bismuth powder, and nickel powder.

[0094] In some embodiments, the method for preparing the low-melting-point glass powder includes:

[0095] PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then subjected to calcination, cooling crystallization, grinding and particle size classification to obtain low melting point glass powder.

[0096] By weight, the mixture contains 50 to 70 parts of PbO, 30 to 50 parts of SiO2, 5 to 10 parts of B2O3, 10 to 20 parts of Bi2O3, and 5 to 10 parts of Sb2O3.

[0097] The calcination includes sequential heating and holding. The heating rate is 30℃ / min to 50℃ / min, and the final temperature is the holding temperature. The holding temperature is 900℃ to 1000℃, and the holding time is 60min to 80min.

[0098] In this invention, the weight of PbO in the mixture is 50 to 70 parts, for example, it can be 50, 52, 54, 56, 58, 60, 62, 64, 66, 68 or 70 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0099] In this invention, the weight of SiO2 in the mixture is 30 to 50 parts, for example, it can be 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0100] In this invention, the weight of B2O3 in the mixture is 5 to 10 parts, for example, it can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or 10 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0101] In this invention, the weight of Bi2O3 in the mixture is 10 to 20 parts, for example, it can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0102] In this invention, the weight of Sb2O3 in the mixture is 5 to 10 parts, for example, it can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts or 10 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0103] In this invention, the heating rate during calcination is 30℃ / min to 50℃ / min, for example, it can be 30℃ / min, 32℃ / min, 34℃ / min, 36℃ / min, 38℃ / min, 40℃ / min, 42℃ / min, 44℃ / min, 46℃ / min, 48℃ / min or 50℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0104] In this invention, the holding temperature during calcination is 900℃~1000℃, for example, it can be 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃ or 1000℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0105] In this invention, the holding time during calcination is 60 min to 80 min, for example, it can be 60 min, 62 min, 64 min, 66 min, 68 min, 70 min, 72 min, 74 min, 76 min, 78 min or 80 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0106] In some embodiments, the calcination is carried out in a muffle furnace, and the mixture is placed in a ceramic crucible, the capacity of which may be, for example, 100 mL to 200 mL.

[0107] In this invention, the capacity of the ceramic crucible can be, for example, 100mL to 200mL, such as 100mL, 110mL, 120mL, 130mL, 140mL, 150mL, 160mL, 170mL, 180mL, 190mL or 200mL, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0108] In some embodiments, the cooling crystallization includes: placing the molten glass mixture in a steel drum filled with ice water for water quenching, thereby rapidly cooling and crystallizing the glass mixture.

[0109] In some embodiments, the grinding includes: using an air jet mill to grind the solid obtained after cooling and crystallization, thereby avoiding the heat generated during the grinding process from causing the glass powder to deteriorate due to heat or introducing impurities.

[0110] In some embodiments, the particle size classification includes: using an air classifier to perform precise particle size classification to obtain finished low-melting-point glass powder.

[0111] In some embodiments, the method for preparing the organic carrier includes:

[0112] In an electric mixer, the components in the organic carrier are stirred and mixed for 6 to 8 hours at a speed of 500 to 1000 r / min at a temperature of 70 to 90°C to obtain a homogeneous, transparent and highly viscous liquid. After cooling, the organic carrier is obtained.

[0113] In this invention, stirring and mixing are carried out at 70℃~90℃, for example, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃ or 90℃, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0114] In this invention, the stirring and mixing is carried out at a speed of 500 r / min to 1000 r / min, for example, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 850 r / min, 900 r / min, 950 r / min or 1000 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0115] In this invention, the stirring and mixing is carried out for 6 to 8 hours, for example, 6.0h, 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, 7.8h or 8.0h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0116] In some embodiments, additives are also incorporated into the mixture;

[0117] The mixing process includes: first mixing spherical silver-coated copper powder, low-melting-point glass powder and metal powder to obtain a first mixture; then mixing the obtained first mixture with an organic carrier and additives to obtain a second mixture.

[0118] In some implementations, the first mixing is carried out using a V-type mixer, wherein the cylinder speed of the V-type mixer in the first mixing is 10 rpm to 20 rpm and the power is 1 kW to 3 kW.

[0119] In this invention, the cylinder rotation speed of the V-type mixer in the first mixing process is 10 rpm to 20 rpm, for example, it can be 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm or 20 rpm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0120] In this invention, the power of the V-type mixer in the first mixing process is 1kW to 3kW, for example, it can be 1.0kW, 1.2kW, 1.4kW, 1.6kW, 1.8kW, 2.0kW, 2.2kW, 2.4kW, 2.6kW, 2.8kW or 3.0kW, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0121] In some embodiments, the second mixing includes: first centrifugally dispersing the first mixture with an organic carrier and additives in a centrifugal disperser, then grinding and dispersing it in a three-roll mill, and finally performing a second centrifugal disperser.

[0122] In some embodiments, in the first centrifugal dispersion, the speed of the centrifuge is 3000 rpm to 5000 rpm, and the number of centrifugations is not less than 2.

[0123] In this invention, during the first centrifugal dispersion, the rotation speed of the centrifugal disperser is 3000 rpm to 5000 rpm, for example, it can be 3000 rpm, 3250 rpm, 3500 rpm, 3750 rpm, 4000 rpm, 4250 rpm, 4500 rpm, 4750 rpm or 5000 rpm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0124] In this invention, the number of centrifugations in the first centrifugal dispersion is not less than 2 times, for example, it can be 2, 3, 4, 5, 6, 7, 8, 9 or 10 times, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0125] In some embodiments, in the grinding and dispersion process, the rotational speed ratio of the front roller, middle roller and rear roller of the three-roll mill is (2~4):(4~6):(8~12), and the rotational speed of the middle roller is 300rpm~500rpm.

[0126] In this invention, during the grinding and dispersion process, the rotational speed ratio of the front roller, middle roller, and rear roller of the three-roll mill is (2~4):(4~6):(8~12), for example, it can be 2:4:8, 2.5:4.5:9, 3:5:10, 3.5:5.5:11 or 4:6:12, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0127] In this invention, during the grinding and dispersing process, the rotational speed of the middle roller is 300 rpm to 500 rpm, for example, it can be 300 rpm, 325 rpm, 350 rpm, 375 rpm, 400 rpm, 425 rpm, 450 rpm, 475 rpm or 500 rpm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0128] In some embodiments, in the second centrifugal dispersion, the centrifuge speed is 3000 rpm to 5000 rpm, and the number of centrifugations is 3 to 5.

[0129] In this invention, during the second centrifugal dispersion, the rotation speed of the centrifugal disperser is 3000 rpm to 5000 rpm, for example, it can be 3000 rpm, 3250 rpm, 3500 rpm, 3750 rpm, 4000 rpm, 4250 rpm, 4500 rpm, 4750 rpm or 5000 rpm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0130] In this invention, the second centrifugal dispersion involves centrifugation 3 to 5 times, for example, 3, 4 or 5 times.

[0131] In one embodiment, the present invention provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described above.

[0132] In one embodiment, the present invention provides a method for preparing the copper-based metal electrode described in the third aspect, the method comprising:

[0133] The copper-based metal electrode paste is coated onto the front fine grid of a silicon-based photovoltaic cell and then sintered to obtain a copper-based metal electrode.

[0134] In some implementations, the coating method includes screen printing.

[0135] In some embodiments, the sintering is used to perform electrode etching to achieve ohmic contact between the copper-based metal electrode and the front grid of the silicon-based photovoltaic cell.

[0136] In some embodiments, the sintering includes a first sintering, a second sintering, and a third sintering performed sequentially;

[0137] The first sintering temperature is 300℃-500℃, the second sintering temperature is 700℃~800℃, and the third sintering temperature is 200℃~300℃;

[0138] During the sintering process, the belt speed is 7m / min to 10m / min.

[0139] In the method for preparing the copper-based metal electrode provided by this invention, a belt speed of 7 m / min to 10 m / min is used during sintering, combined with a first sintering at a temperature of 300℃ to 500℃, a second sintering at a temperature of 700℃ to 800℃, and a third sintering at a temperature of 200℃ to 300℃. Under the set matching relationship between belt speed and temperature range, the alloying of metal powder and free copper is further ensured, thereby reducing the risk of forming impurity recombination centers. At the same time, under the set matching relationship between belt speed and temperature range, the softening temperature of low melting point glass powder can also be further matched, allowing the glass powder to rapidly transform and crystallize in the cooling zone, avoiding over-etching. This further avoids the risk of free copper diffusing into the silicon substrate due to over-etching, thereby forming impurity recombination centers.

[0140] In this invention, the temperature of the first sintering is 300℃-500℃, for example, it can be 300℃, 325℃, 350℃, 375℃, 400℃, 425℃, 450℃, 475℃ or 500℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0141] In this invention, the second sintering temperature is 700℃~800℃, for example, it can be 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0142] In this invention, the temperature of the third sintering is 200℃~300℃, for example, it can be 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃ or 300℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0143] In this invention, during the sintering process, the belt speed is 7 m / min to 10 m / min, for example, it can be 7.0 m / min, 7.2 m / min, 7.4 m / min, 7.6 m / min, 7.8 m / min, 8.0 m / min, 8.2 m / min, 8.4 m / min, 8.6 m / min, 8.8 m / min, 9.0 m / min, 9.2 m / min, 9.4 m / min, 9.6 m / min, 9.8 m / min or 10.0 m / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0144] In some embodiments, the sintering is carried out in a sintering furnace, with the first sintering taking place in a preheating zone, the second sintering in a sintering zone, and the third sintering in a cooling zone.

[0145] In one embodiment, the present invention provides a silicon-based photovoltaic cell, the silicon-based photovoltaic cell comprising the aforementioned copper-based metal electrode.

[0146] Example 1

[0147] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. The components of the copper-based metal electrode paste include spherical silver-coated copper powder (SEM image shown). Figure 1 and Figure 2 As shown, the composition includes: sphericity 0.86, D50 particle size 2.8 μm; low melting point glass powder (Pb-Si-B-Bi-Sb series low melting point glass powder, melting point 320°C, D50 particle size 0.8 μm); metal powder (manganese powder, D50 particle size 2.0 μm); organic carrier and additives (including dispersant and thixotropic agent in a mass ratio of 1:2, the dispersant being an aliphatic diamine organic salt, and the thixotropic agent including polyamide wax and fumed silica in a mass ratio of 1:1).

[0148] By weight, the organic carrier comprises 4 parts by weight of ethyl cellulose, 3 parts by weight of hydroxypropyl methyl cellulose, 1 part by weight of acrylic resin, 40 parts by weight of butyl carbitol, 40 parts by weight of diethylene glycol butyl ether acetate, and 20 parts by weight of dimethyl adipate.

[0149] In the copper-based metal electrode slurry, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is 84:3:2:8:3.

[0150] The preparation process of the copper-based metal electrode paste is as follows:

[0151] (1) Preparation of low melting point glass powder: PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then heated to 900℃ in a muffle furnace at a rate of 30℃ / min and held for 60min to obtain a molten glass mixture; the molten glass mixture is placed in a steel drum filled with ice water for water quenching to rapidly cool and crystallize; the solid obtained after cooling and crystallization is then ground using an air jet mill to avoid heat generation during grinding, which could cause the glass powder to deteriorate or introduce impurities; the particle size is then precisely classified using an air classifier to obtain low melting point glass powder.

[0152] By weight, the mixture contains 50 parts of PbO, 30 parts of SiO2, 5 parts of B2O3, 10 parts of Bi2O3, and 5 parts of Sb2O3.

[0153] (2) Preparation of organic carrier: In an electric mixer, at 75°C and a speed of 600 r / min, the components in the organic carrier are stirred and mixed for 6 hours to obtain a uniform, transparent and highly viscous liquid. After cooling, the organic carrier is obtained.

[0154] (3) The spherical silver-coated copper powder, the low melting point glass powder obtained in step (1) and the metal powder are mixed in a V-type mixer. The cylinder speed of the V-type mixer is controlled at 15 rpm and the power is 1.5 kW to obtain the first mixture.

[0155] The first mixture obtained is then centrifuged five times in a centrifugal disperser with the organic carrier and additives obtained in step (2) at a speed of 4000 rpm. Then, it is ground and dispersed in a three-roll mill. During the grinding and dispersion, the speed ratio of the front roller, middle roller and rear roller of the three-roll mill is controlled to be 3:5:10, and the speed of the middle roller is 500 rpm. Then, it is centrifuged and dispersed three times in a centrifugal disperser at a speed of 4000 rpm to obtain copper-based metal electrode slurry.

[0156] This embodiment also provides a copper-based metal electrode, which is prepared from the above-mentioned copper-based metal electrode paste;

[0157] The method for preparing the copper-based metal electrode is as follows:

[0158] The copper-based metal electrode paste described in this embodiment is screen-printed onto the front fine grid of a silicon-based photovoltaic cell, and then etched in a sintering furnace to achieve ohmic contact between the copper-based metal electrode and the front fine grid of the silicon-based photovoltaic cell, thus obtaining the copper-based metal electrode.

[0159] In the sintering process, the belt speed is controlled at 8 m / min. After the first sintering is carried out in the preheating zone at a temperature of 350°C, the second sintering is carried out in the sintering zone at a temperature of 750°C, and the third sintering is carried out in the cooling zone at a temperature of 200°C.

[0160] Example 2

[0161] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. The components of the copper-based metal electrode paste include spherical silver-coated copper powder (sphericity 0.84, D50 particle size 2.0 μm), low-melting-point glass powder (Pb-Si-B-Bi-Sb series low-melting-point glass powder, melting point 330°C, D50 particle size 1 μm), metal powder (manganese powder, D50 particle size 3.0 μm), organic carrier and additives (including a dispersant (aliphatic diamine organic salt) in a mass ratio of 1:3.5 and a thixotropic agent (polyamide wax and fumed silica in a mass ratio of 1:1)).

[0162] By weight, the organic carrier comprises 4 parts by weight of ethyl cellulose, 2 parts by weight of hydroxypropyl methyl cellulose, 4 parts by weight of acrylic resin, 30 parts by weight of butyl carbitol, 30 parts by weight of diethylene glycol butyl ether acetate, and 30 parts by weight of dimethyl adipate.

[0163] In the copper-based metal electrode paste, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is 80:3:2:10:5.

[0164] The preparation process of the copper-based metal electrode paste is as follows:

[0165] (1) Preparation of low melting point glass powder: PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then heated to 1000℃ in a muffle furnace at a rate of 50℃ / min and held for 60min to obtain a molten glass mixture; the molten glass mixture is placed in a steel drum filled with ice water for water quenching to rapidly cool and crystallize; the solid obtained after cooling and crystallization is then ground using an air jet mill to avoid heat generation during grinding, which could cause the glass powder to deteriorate or introduce impurities; the particle size is then precisely classified using an air classifier to obtain low melting point glass powder.

[0166] By weight, the mixture contains 70 parts of PbO, 30 parts of SiO2, 10 parts of B2O3, 20 parts of Bi2O3, and 10 parts of Sb2O3.

[0167] (2) Preparation of organic carrier: In an electric mixer, at 90°C and a speed of 500 r / min, the components in the organic carrier are stirred and mixed for 8 hours to obtain a uniform, transparent and highly viscous liquid. After cooling, the organic carrier is obtained.

[0168] (3) The spherical silver-coated copper powder, the low melting point glass powder obtained in step (1) and the metal powder are mixed in a V-type mixer. The cylinder speed of the V-type mixer is controlled at 20 rpm and the power is 1 kW to obtain the first mixture.

[0169] The first mixture obtained is then centrifuged three times in a centrifuge at a speed of 5000 rpm, along with the organic carrier and additives obtained in step (2). Then, it is ground and dispersed in a three-roll mill. During the grinding and dispersion, the speed ratio of the front roller, middle roller and rear roller of the three-roll mill is controlled to be 4:4:8, and the speed of the middle roller is 500 rpm. Then, it is centrifuged three times in a centrifuge at a speed of 3000 rpm to obtain a copper-based metal electrode slurry.

[0170] This embodiment also provides a copper-based metal electrode, which is prepared from the above-mentioned copper-based metal electrode paste;

[0171] The method for preparing the copper-based metal electrode is as follows:

[0172] The copper-based metal electrode paste described in this embodiment is screen-printed onto the front fine grid of a silicon-based photovoltaic cell, and then etched in a sintering furnace to achieve ohmic contact between the copper-based metal electrode and the front fine grid of the silicon-based photovoltaic cell, thus obtaining the copper-based metal electrode.

[0173] In the sintering process, the belt speed is controlled at 10 m / min. After the first sintering is carried out in the preheating zone at a temperature of 300°C, the second sintering is carried out in the sintering zone at a temperature of 800°C, and the third sintering is carried out in the cooling zone at a temperature of 200°C.

[0174] Example 3

[0175] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. The components of the copper-based metal electrode paste include spherical silver-coated copper powder (sphericity 0.92, D50 particle size 1.0 μm), low-melting-point glass powder (Pb-Si-B-Bi-Sb series low-melting-point glass powder, melting point 340°C, D50 particle size 0.9 μm), metal powder (manganese powder, D50 particle size 1.0 μm), organic carrier and additives (including a dispersant (aliphatic diamine organic salt) in a mass ratio of 1:5 and a thixotropic agent (polyamide wax and fumed silica in a mass ratio of 1:1)).

[0176] By weight, the organic carrier comprises 5 parts ethyl cellulose, 3 parts hydroxypropyl methyl cellulose, 5 parts acrylic resin, 50 parts butyl carbitol, 50 parts diethylene glycol butyl ether acetate, and 10 parts dimethyl adipate.

[0177] In the copper-based metal electrode slurry, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is 90:3:0.5:8:3.

[0178] The preparation process of the copper-based metal electrode paste is as follows:

[0179] (1) Preparation of low melting point glass powder: PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then heated to 950℃ in a muffle furnace at a rate of 40℃ / min and held for 80min to obtain a molten glass mixture; the molten glass mixture is placed in a steel drum filled with ice water for water quenching to rapidly cool and crystallize; the solid obtained after cooling and crystallization is then ground using an air jet mill to avoid heat generation during grinding, which could cause the glass powder to deteriorate or introduce impurities; the particle size is then precisely classified using an air classifier to obtain low melting point glass powder.

[0180] By weight, the mixture contains 60 parts of PbO, 40 parts of SiO2, 8 parts of B2O3, 15 parts of Bi2O3, and 8 parts of Sb2O3.

[0181] (2) Preparation of organic carrier: In an electric mixer, at 80°C and a speed of 1000 r / min, the components in the organic carrier are stirred and mixed for 7 hours to obtain a uniform, transparent and highly viscous liquid. After cooling, the organic carrier is obtained.

[0182] (3) The spherical silver-coated copper powder, the low melting point glass powder obtained in step (1) and the metal powder are mixed in a V-type mixer. The cylinder speed of the V-type mixer is controlled at 10 rpm and the power is 3 kW to obtain the first mixture.

[0183] The first mixture obtained is then centrifuged four times in a centrifugal disperser with the organic carrier and additives obtained in step (2) at a speed of 3000 rpm. Then, it is ground and dispersed in a three-roll mill. During the grinding and dispersion, the speed ratio of the front roller, middle roller and rear roller of the three-roll mill is controlled to be 2:6:12, and the speed of the middle roller is 300 rpm. Then, it is centrifuged and dispersed five times in a centrifugal disperser at a speed of 5000 rpm to obtain copper-based metal electrode slurry.

[0184] This embodiment also provides a copper-based metal electrode, which is prepared from the above-mentioned copper-based metal electrode paste;

[0185] The method for preparing the copper-based metal electrode is as follows:

[0186] The copper-based metal electrode paste described in this embodiment is screen-printed onto the front fine grid of a silicon-based photovoltaic cell, and then etched in a sintering furnace to achieve ohmic contact between the copper-based metal electrode and the front fine grid of the silicon-based photovoltaic cell, thus obtaining the copper-based metal electrode.

[0187] In the sintering process, the belt speed is controlled at 7 m / min. After the first sintering is carried out in the preheating zone at a temperature of 500°C, the second sintering is carried out in the sintering zone at a temperature of 700°C, and the third sintering is carried out in the cooling zone at a temperature of 300°C.

[0188] Example 4

[0189] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with commercially available glass powder (melting point 450°C).

[0190] That is, step (1) in the preparation process of the copper-based metal electrode paste is omitted, and the low melting point glass powder used in step (3) is replaced with commercially available glass powder (melting point of 450°C). The rest is the same as in Example 1.

[0191] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0192] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0193] Example 5

[0194] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with (Si-B-Bi-Sb series low-melting-point glass powder, melting point of 380°C, D50 particle size of 0.8μm).

[0195] In other words, step (1) of the preparation process of the copper-based metal electrode paste is omitted. Except for the PbO mixed in the mixture, the rest is the same as in Example 1.

[0196] Example 6

[0197] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with (Pb-B-Bi-Sb series low-melting-point glass powder, melting point 390°C, D50 particle size 0.8μm).

[0198] In other words, except for the SiO2 mixed in the mixture, the step (1) of the preparation process of the copper-based metal electrode paste is omitted and is the same as in Example 1.

[0199] Example 7

[0200] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with (Pb-Si-Bi-Sb series low-melting-point glass powder with a melting point of 410°C and a D50 particle size of 0.8μm).

[0201] In other words, except for the B2O3 mixed in the mixture, the preparation process of the copper-based metal electrode paste is omitted in step (1). In Example 1, the preparation process is the same.

[0202] Example 8

[0203] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with (Pb-Si-B-Sb series low-melting-point glass powder, melting point 390°C, D50 particle size 0.8μm).

[0204] In other words, except for Bi2O3 mixed in the mixture, the preparation process of the copper-based metal electrode slurry in step (1) is omitted, and everything else is the same as in Example 1.

[0205] Example 9

[0206] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder is replaced with (Pb-Si-B-Bi series low-melting-point glass powder, melting point of 400°C, D50 particle size of 0.8μm).

[0207] In other words, except for the Sb2O3 mixed in the mixture, the preparation process of the copper-based metal electrode paste is omitted in step (1), and everything else is the same as in Example 1.

[0208] Example 10

[0209] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except for the D50 particle size of the low-melting-point glass powder being 0.5 μm, the rest is the same as in Example 1.

[0210] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0211] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0212] Example 11

[0213] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except for the D50 particle size of the low-melting-point glass powder being 1.5 μm, the rest is the same as in Example 1.

[0214] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0215] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0216] Example 12

[0217] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except that the mass ratio of spherical silver-coated copper powder to low-melting-point glass powder in the copper-based metal electrode paste is 86:1, all other aspects are the same as in Example 1.

[0218] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0219] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0220] Example 13

[0221] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except that the mass ratio of spherical silver-coated copper powder to low-melting-point glass powder in the copper-based metal electrode paste is 86:10, the rest is the same as in Embodiment 1.

[0222] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0223] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0224] Example 14

[0225] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except that the mass ratio of spherical silver-coated copper powder to manganese powder in the copper-based metal electrode paste is 86:4, all other aspects are the same as in Embodiment 1.

[0226] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0227] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0228] Example 15

[0229] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells. Except that the mass ratio of spherical silver-coated copper powder to manganese powder in the copper-based metal electrode paste is 86:15, all other aspects are the same as in Embodiment 1.

[0230] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0231] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0232] Example 16

[0233] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, which is the same as that in Embodiment 1.

[0234] This embodiment also provides a copper-based metal electrode, except that the belt speed is controlled at 4 m / min during sintering in the preparation method of the copper-based metal electrode, the rest is the same as in Embodiment 1.

[0235] Example 17

[0236] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, which is the same as that in Embodiment 1.

[0237] This embodiment also provides a copper-based metal electrode, except that the belt speed is controlled at 15m / min during sintering in the preparation method of the copper-based metal electrode, the rest is the same as in Embodiment 1.

[0238] Example 18

[0239] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, which is the same as that in Embodiment 1.

[0240] This embodiment also provides a copper-based metal electrode, except that in the preparation method of the copper-based metal electrode, the second sintering is carried out at a temperature of 550°C in the sintering zone, and the rest is the same as in Embodiment 1.

[0241] Example 19

[0242] This embodiment provides a copper-based metal electrode paste for silicon-based photovoltaic cells, which is the same as that in Embodiment 1.

[0243] This embodiment also provides a copper-based metal electrode, except that in the preparation method of the copper-based metal electrode, the second sintering is carried out at a temperature of 950°C in the sintering zone, and the rest is the same as in Embodiment 1.

[0244] Comparative Example 1

[0245] This comparative example provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the metal powder (manganese powder, D50 particle size of 1.0μm~3.0μm) in the copper-based metal electrode paste is omitted.

[0246] In step (3) of the preparation process of copper-based metal electrode paste, except for the manganese powder mixed in during the first mixing, everything else is the same as in Example 1.

[0247] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0248] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0249] Comparative Example 2

[0250] This comparative example provides a copper-based metal electrode paste for silicon-based photovoltaic cells, except that the low-melting-point glass powder (Pb-Si-B-Bi-Sb series low-melting-point glass powder) in the composition of the copper-based metal electrode paste is omitted.

[0251] In step (3) of the preparation process of copper-based metal electrode paste, except for the low-melting-point glass powder mixed in during the first mixing, everything else is the same as in Example 1.

[0252] This embodiment also provides a copper-based metal electrode, which is prepared from the copper-based metal electrode slurry described in this embodiment;

[0253] Except for replacing the copper-based metal electrode slurry used in the preparation method of the copper-based metal electrode with the copper-based metal electrode slurry in this embodiment, everything else is the same as in Example 1.

[0254] After preparing a copper-based metal electrode on the front fine grid of a silicon-based photovoltaic cell using the preparation method provided in the comparative examples above, the surface grid lines were removed using HF. Then, the material inside the silicon substrate was ground into powder and subjected to XRF elemental analysis. The proportions of each element in the powder are shown in Table 1.

[0255] Table 1

[0256]

[0257] From Table 1, we can see that

[0258] XRF test results show that the proportion of copper in the silicon substrate in the comparative example is 1.2%, while the proportion of copper in Example 1 is only 0.01%, indicating that the copper-based electrode material in Example 1 basically did not diffuse copper into the silicon substrate.

[0259] After fabricating a copper-based metal electrode on the front fine grid of a silicon-based photovoltaic cell using the preparation method provided in the comparative examples above, the proportion of defect recombination centers of copper diffusion was monitored using a photodetector (PL). The grayscale values ​​obtained from the PL test results are shown in Table 2; where the PL image corresponding to Example 1 is shown below. Figure 3 As shown, the PL image corresponding to Comparative Example 1 is as follows: Figure 4 As shown, the PL image corresponding to Example 4 is as follows: Figure 5 As shown.

[0260] Table 2

[0261]

[0262] From Table 2, we can see that

[0263] The brightness value of Example 1 is higher than that of Comparative Example 1 and Example 4, indicating that the addition of manganese powder and low melting point glass powder, combined with a matching sintering process, resulted in no copper diffusion in the copper-based electrode. The radiation recombination efficiency at this location is high, the non-equilibrium minority carrier concentration is large, and the copper diffusion ratio is greatly reduced compared to Comparative Example 1 and Example 4.

[0264] Minority carrier lifetime statistics were performed on the copper-based metal electrodes provided in the above embodiments and comparative examples, and the minority carrier lifetimes are shown in Table 3.

[0265] Table 3

[0266]

[0267] From Table 3, we can see that...

[0268] The minority carrier lifetime of Example 1 is higher than that of Comparative Example 1 and Example 4. This is mainly because the copper in Example 1 did not form an impurity recombination center, while the copper in Comparative Examples 1 and 2 diffused to the silicon substrate and formed an impurity recombination center, which greatly reduced the minority carrier lifetime.

[0269] The etching depth of the copper-based metal electrodes provided in the above embodiments and comparative examples was measured using a scanning electron microscope. The SEM image of the copper-based metal electrode in Example 1 is shown below. Figure 6 As shown, the SEM image of the copper-based metal electrode in Example 4 is as follows. Figure 7 As shown.

[0270] Depend on Figure 6 and Figure 7 It can be seen that the copper-based metal electrode provided in Example 1 has a lower etching depth than the copper-based metal electrode provided in Example 4. This is because Example 1 uses low-melting-point glass powder to ensure a good etching depth, avoiding the diffusion of free copper to the silicon substrate caused by over-etching, thereby lengthening the distance of copper diffusion and preventing free copper from making diffusion contact with the silicon substrate.

[0271] After preparing a copper-based metal electrode on the front fine grid of a silicon-based photovoltaic cell using the preparation method provided in the comparative examples above, the electrochemical performance of the silicon-based photovoltaic cell was tested. The test method was as follows: under standard test conditions (AM1.5G spectrum, 1000W / m² irradiance, 25℃ cell temperature), the current-voltage characteristic curve of the cell was measured using a solar simulator and IV test system. The open-circuit voltage (Vsc), short-circuit current (Isc), fill power (FF), and conversion efficiency (Ncell) of the silicon-based photovoltaic cell are shown in Table 4.

[0272] Table 4

[0273]

[0274] From Table 4, we can obtain:

[0275] (1) After the copper-based metal electrode is prepared on the front fine grid of the silicon-based photovoltaic cell by the preparation method provided in Examples 1 to 3 of the present invention, the silicon-based photovoltaic cell has excellent electrochemical performance, exhibiting high open-circuit voltage, high short-circuit current, high fill factor and high conversion efficiency.

[0276] (2) By comparing Example 1 and Example 4, it can be seen that compared with commercially available glass powder, the Pb-Si-B-Bi-Sb low melting point glass powder provided by the present invention is beneficial to improving the electrochemical performance of silicon-based photovoltaic cells. This is because during the sintering process, the low melting point glass powder has a lower melting point than conventional high melting point glass powder, and can be softened and flowed first at a suitable temperature, thereby selectively corroding the silicon nitride antireflection film on the surface of the silicon wafer. This corrosion effect allows the molten silver paste to directly contact the silicon body below to form "silver crystal silicon", thereby constructing an efficient ohmic contact channel (the key starting step for current to be conducted from the silicon wafer to the metal electrode).

[0277] (3) By comparing Examples 1 with Examples 5-9, it can be seen that in this invention, when the low-melting-point glass powder is a Pb-Si-B-Bi-Sb system low-melting-point glass powder, compared with the low-melting-point glass powders of Si-B-Bi-Sb system, Pb-B-Bi-Sb system, Pb-Si-Bi-Sb system, Pb-Si-B-Sb system, or Pb-Si-B-Bi system, the silicon-based photovoltaic cell exhibits better electrochemical performance. This is because in the Pb-Si-B-Bi-Sb system low-melting-point glass powder, Pb, Si, B, Bi, and Sb are present in a more uniform manner. Five metal elements form a stable glass structure through synergistic coordination. The structural stability of this Pb-Si-B-Bi-Sb low-melting-point glass powder is significantly better than that of formulation systems lacking other single elements. The highly stable glass structure significantly improves the adhesion performance of silver powder particles, thereby optimizing the performance of copper-based metal electrodes and silicon-based photovoltaic cells.

[0278] (4) By comparing Example 1 with Examples 10 and 11, it can be seen that in this invention, the D50 particle size of low melting point glass powder affects the electrochemical performance of copper-based metal electrodes and silicon-based photovoltaic cells. When the D50 particle size of low melting point glass powder is 0.8μm~1μm, silicon-based photovoltaic cells exhibit better electrochemical performance. This is because low melting point glass powder particles that are too large or too small are not compatible with silver powder particles. Glass powder particles that are too small do not have a good bonding effect on silver powder particles and are difficult to form a high-quality ohmic contact. Glass powder particles that are too large will cause the resistance between particles to increase and the electrical performance to decrease.

[0279] (5) By comparing Example 1 with Examples 12 and 13, it can be seen that in the present invention, the mass ratio of spherical silver-coated copper powder to low-melting-point glass powder in the copper-based metal electrode slurry affects the electrochemical performance of the copper-based metal electrode and the silicon-based photovoltaic cell. When the mass ratio of spherical silver-coated copper powder to low-melting-point glass powder is (80~90):(3~5), the silicon-based photovoltaic cell exhibits better electrochemical performance. This is because under this ratio, the spherical silver-coated copper powder and the low-melting-point glass powder can form the optimal particle size distribution relationship, which can ensure the close packing of the spherical silver-coated copper powder and allow the low-melting-point glass powder to fully fill the gaps of the spherical silver-coated copper powder, thereby improving the density and conductivity continuity of the copper-based metal electrode, and finally optimizing the performance of the copper-based metal electrode and the silicon-based photovoltaic cell.

[0280] (6) By comparing Example 1 with Examples 14 and 15, it can be seen that in the present invention, the mass ratio of spherical silver-coated copper powder to manganese powder in the copper-based metal electrode slurry affects the electrochemical performance of the copper-based metal electrode and the silicon-based photovoltaic cell. When the mass ratio of spherical silver-coated copper powder to metal powder is (80~90):(0.5~5), the silicon-based photovoltaic cell exhibits better electrochemical performance. This is because when manganese powder is used for alloying free copper, there is an optimal range for the mass ratio of free copper to manganese powder. Too little manganese powder leads to too much free copper, and free copper becomes a recombination center. Too much manganese powder will lead to a decrease in the proportion of silver powder at the silicon-based sintering interface. Since the conductivity of manganese is much lower than that of silver, it will affect the electrical transport performance of charge carriers at the silicon-based interface.

[0281] (7) By comparing Example 1 with Examples 16-19, it can be seen that in the preparation method of copper-based metal electrode provided by the present invention, a belt speed of 7m / min to 10m / min is used during sintering, and a first sintering at a temperature of 300℃-500℃, a second sintering at a temperature of 700℃ to 800℃, and a third sintering at a temperature of 200℃ to 300℃ are combined. Under the matching relationship between the set belt speed and the temperature zone, the metal powder and free copper are further guaranteed to form an alloy, thereby reducing the risk of forming impurity recombination centers. At the same time, under the matching relationship between the set belt speed and the temperature zone, the softening temperature of the low melting point glass powder can be further matched, and the glass powder can be rapidly transformed and crystallized in the cooling zone to avoid over-etching. This further avoids the risk of free copper diffusing to the silicon substrate due to over-etching, thereby forming impurity recombination centers. This improves the electrochemical performance of silicon-based photovoltaic cells.

[0282] (8) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the copper-based metal electrode slurry provided by the present invention contains metal powder. When the copper-based metal electrode is prepared by sintering the copper-based metal electrode slurry, the metal powder will form a copper-manganese alloy with the free copper in the spherical silver-coated copper powder, thereby achieving the alloying of free copper. This avoids the free copper from diffusing into the silicon matrix to form impurity recombination centers, and improves the open-circuit voltage and cell efficiency of the silicon-based photovoltaic cell containing the prepared copper-based metal electrode.

[0283] The copper-based metal electrode paste provided by this invention contains low-melting-point glass powder, which helps to ensure good etching depth, thereby lengthening the copper diffusion distance and avoiding over-etching that causes free copper to diffuse into the silicon substrate. This reduces the risk of free copper contacting the silicon substrate and forming impurity recombination centers, thereby further improving the open-circuit voltage and cell efficiency of silicon-based photovoltaic cells containing the prepared copper-based metal electrode.

[0284] In summary, the copper-based metal electrode paste provided by this invention contains metal powder and low-melting-point glass powder. Manganese powder is used to alloy free copper, and low-melting-point glass powder is used to control the etching depth, synergistically suppressing copper diffusion and effectively avoiding the formation of impurity recombination centers. This significantly improves the open-circuit voltage and conversion efficiency of the battery, providing a solution for the low-cost industrial application of copper electrode technology.

[0285] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A copper-based metal electrode paste for silicon-based photovoltaic cells, characterized in that, The components of the copper-based metal electrode paste include spherical silver-coated copper powder, low-melting-point glass powder, metal powder, additives, and organic carrier. The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder; In the copper-based metal electrode paste, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is (80~90):(3~5):(0.5~5):(8~10):(3~5); The sphericity of the spherical silver-coated copper powder is not less than 0.8; the D50 particle size of the spherical silver-coated copper powder is 1.0μm~3.0μm; The low-melting-point glass powder includes Pb-Si-B-Bi-Sb series low-melting-point glass powder; the D50 particle size of the Pb-Si-B-Bi-Sb series low-melting-point glass powder is 0.8μm~1μm.

2. The copper-based metal electrode paste according to claim 1, characterized in that, The melting point of the low-melting-point glass powder is not higher than 400℃.

3. The copper-based metal electrode paste according to claim 1 or 2, characterized in that, The additives include dispersants and / or thixotropic agents.

4. A process for preparing the copper-based metal electrode paste according to any one of claims 1 to 3, characterized in that, The preparation process includes: The copper-based metal electrode slurry is obtained by mixing spherical silver-coated copper powder, low-melting-point glass powder, metal powder, additives and organic carrier; The metal powder includes any one or a combination of at least two of manganese powder, bismuth powder, or nickel powder; In the copper-based metal electrode paste, the mass ratio of spherical silver-coated copper powder, low-melting-point glass powder, metal powder, organic carrier and additives is (80~90):(3~5):(0.5~5):(8~10):(3~5); The sphericity of the spherical silver-coated copper powder is not less than 0.8; the D50 particle size of the spherical silver-coated copper powder is 1.0μm~3.0μm; The low-melting-point glass powder includes Pb-Si-B-Bi-Sb series low-melting-point glass powder; the D50 particle size of the Pb-Si-B-Bi-Sb series low-melting-point glass powder is 0.8μm~1μm.

5. The preparation process according to claim 4, characterized in that, The method for preparing the low-melting-point glass powder includes: PbO, SiO2, B2O3, Bi2O3 and Sb2O3 are mixed to obtain a mixture; the mixture is then subjected to calcination, cooling crystallization, grinding and particle size classification to obtain low melting point glass powder. By weight, the mixture contains 50 to 70 parts of PbO, 30 to 50 parts of SiO2, 5 to 10 parts of B2O3, 10 to 20 parts of Bi2O3, and 5 to 10 parts of Sb2O3. The calcination includes sequential heating and holding. The heating rate is 30℃ / min to 50℃ / min, and the final temperature is the holding temperature. The holding temperature is 900℃ to 1000℃, and the holding time is 60min to 80min.

6. The preparation process according to claim 4 or 5, characterized in that, The mixing process includes: first mixing spherical silver-coated copper powder, low-melting-point glass powder and metal powder to obtain a first mixture; then mixing the obtained first mixture with an organic carrier and additives to obtain a second mixture.

7. A copper-based metal electrode, characterized in that, The copper-based metal electrode is prepared from the copper-based metal electrode slurry according to any one of claims 1 to 3.

8. A method for preparing the copper-based metal electrode according to claim 7, characterized in that, The preparation method includes: The copper-based metal electrode paste according to any one of claims 1 to 3 is coated onto the front fine grid of a silicon-based photovoltaic cell and then sintered to obtain a copper-based metal electrode.

9. The preparation method according to claim 8, characterized in that, The sintering includes a first sintering, a second sintering and a third sintering performed sequentially; The first sintering temperature is 300℃-500℃, the second sintering temperature is 700℃~800℃, and the third sintering temperature is 200℃~300℃; During the sintering process, the belt speed is 7m / min to 10m / min.

10. A silicon-based photovoltaic cell, characterized in that, The silicon-based photovoltaic cell includes the copper-based metal electrode as described in claim 7.

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