Conductive paste and preparation method thereof, photovoltaic cell and preparation method thereof, and photovoltaic module

Abstract

The invention relates to conductive paste and a preparation method thereof, a photovoltaic cell and a preparation method thereof, and a photovoltaic module. The conductive paste comprises the following components in percentage by mass: 6%-10% of an organic carrier, 1%-5% of glass powder and 85%-90% of silver powder. The organic carrier comprises resin and organic solvents, and the organic solvents comprise at least three organic solvents with different boiling points; the glass powder comprises at least four kinds of glass powder with different softening temperatures. The conductive paste can improve the sintering compactness and reduce the contact resistance.

Description

Technical Field

[0001] The present application relates to the technical field of conductive pastes, and in particular to a conductive paste and a preparation method thereof, a photovoltaic cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Laser-assisted sintering (LECO), also known as laser-enhanced contact optimization (LECO), is a sintering technology used to improve the contact between metal electrodes and silicon wafers in solar cells. LAS utilizes high-intensity laser irradiation on the cell to excite charge carriers while simultaneously applying a deflection voltage. This generates a localized current, which then sinters at the corresponding locations, triggering interdiffusion between the silver paste and the silicon, significantly reducing the contact resistance between the metal and the semiconductor. During the LAS process, excessively high temperatures can negatively impact the cell's conversion efficiency, such as damage to the silicon wafer's crystal structure, failure of the passivation layer, or deterioration of the metal-silicon contact. Therefore, appropriately lowering the LAS temperature can help achieve higher conversion efficiencies in photovoltaic cells. However, LASing of conventional conductive pastes at reduced temperatures results in lower sintering density and higher contact resistance, which in turn affects the conversion efficiency of photovoltaic cells. Summary of the Invention

[0003] Based on this, it is necessary to provide a conductive paste and a preparation method thereof, a photovoltaic cell and a preparation method thereof, and a photovoltaic module. The conductive paste of the present application can improve the density of sintering and reduce contact resistance.

[0004] In a first aspect, the present application provides a conductive paste comprising the following components in percentage by mass: 6% to 10% of an organic vehicle, 1% to 5% of glass powder, and 85% to 90% of silver powder;

[0005] The organic vehicle includes a resin and an organic solvent, wherein the organic solvent includes at least three organic solvents with different boiling points; and the glass powder includes at least four glass powders with different softening temperatures.

[0006] In some embodiments, among the organic solvents having different boiling points, the difference in boiling points between every two organic solvents having similar boiling points is 20° C. to 50° C.

[0007] In some embodiments, the organic solvent includes at least three of an alcohol solvent, an amide solvent, and an ester solvent.

[0008] In some embodiments, the alcohol solvent includes at least one of terpineol, benzyl alcohol and n-butanol; the amide solvent includes at least one of dimethylacetamide and dimethylformamide; and / or the ester solvent includes at least one of methyl p-tert-butylbenzoate, diethylene glycol butyl ether acetate, butyl benzoate, hexadecene, benzyl benzoate, dibutyl phthalate and benzyl butyl phthalate.

[0009] In some embodiments, among the glass frits having different softening temperatures, the difference in softening temperature between any two glass frits having similar softening temperatures is 30° C. to 80° C.

[0010] In some embodiments, the glass powder includes at least four of a first lead-silicon-iron glass powder, a second lead-silicon-iron glass powder, a lead-bismuth glass powder, and a barium-lime glass powder; in the first lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4, and B2O3 is (60-80): (1-15): (1-15): (5-15): (0-25); in the second lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4, and B2O3 is (60-80): (1-15): (1-15): (5-15): (0-25); The mass ratio is (40-60): (5-15): (5-15): (5-15): (0-25); the mass ratio of PbO, Bi2O3, Al2O3, Fe3O4 and B2O3 in the lead-bismuth glass powder is (30-50): (20-40): (10-25): (5-15): (0-50); the mass ratio of BaCO3, CaCO3 and B2O3 in the barium-lime glass powder is (30-60): (5-35): (40-60).

[0011] In some embodiments, the glass powder has a D50 particle size of 1.1 μm to 1.4 μm.

[0012] In some embodiments, the silver powder includes nano silver powder and polycrystalline silver powder in a mass ratio of (2-10): (80-88); the D50 particle size of the nano silver powder is 50 nm-200 nm; and the D50 particle size of the polycrystalline silver powder is 0.8 μm-1.6 μm.

[0013] In some embodiments, in the polycrystalline silver powder, the mass proportion of the D50 particle size of 0.8 μm to 1 μm is 10% to 20%, the mass proportion of the D50 particle size greater than 1 μm and less than or equal to 1.2 μm is 20% to 40%, and the mass proportion of the D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm is 40% to 60%.

[0014] In some embodiments, the organic vehicle further comprises a thixotropic agent, silicone oil, and a dispersant.

[0015] In some embodiments, the mass ratio of the resin, the thixotropic agent, the organic solvent, the silicone oil, and the dispersant is (0.3~1.5):(0.1~0.3):(6~8):(0.2~0.6):(0.2~0.6).

[0016] In some embodiments, the resin includes at least one of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin, and polyester resin.

[0017] In some embodiments, the thixotropic agent includes at least one of polyamide wax and stearamide.

[0018] In some embodiments, the dispersant includes at least one of polyethylene glycol and polyvinyl pyrrolidone.

[0019] In a second aspect, the present application provides a method for preparing a conductive paste, comprising the following steps:

[0020] The following components are mixed in mass percentage: 6% to 10% of an organic vehicle, 1% to 5% of glass powder, and 85% to 90% of silver powder; the organic vehicle comprises a resin and an organic solvent, the organic solvent comprises at least three organic solvents with different boiling points; the glass powder comprises at least four glass powders with different softening temperatures.

[0021] In a third aspect, the present application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0022] Provide battery pre-finished products;

[0023] Coating the conductive paste described in any one of the above or the conductive paste prepared by the above method of preparing the conductive paste on the surface of the battery pre-finished product;

[0024] The conductive paste is subjected to laser-assisted sintering to form a metal electrode.

[0025] In a fourth aspect, the present application provides a photovoltaic cell prepared by the above-mentioned method for preparing a photovoltaic cell.

[0026] In a fifth aspect, the present application provides a photovoltaic module, comprising:

[0027] cover;

[0028] At least one cell string, the cell string comprising a plurality of photovoltaic cells prepared by the above-mentioned method for preparing a photovoltaic cell; and

[0029] An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

[0030] The conductive paste comprises the following components in the following mass percentages: 6% to 10% of an organic vehicle, 1% to 5% of a glass powder, and 85% to 90% of a silver powder. The organic vehicle comprises a resin and an organic solvent, and the organic solvent comprises at least three organic solvents with different boiling points. The combination of three organic solvents with different boiling points can form a multi-gradient volatilization temperature, so that during the drying and sintering process of the organic vehicle in the conductive paste, the organic solvent gradually evaporates in a wider temperature range, reducing the problem of large porosity of the silver powder in the conductive paste caused by concentrated volatilization of the organic solvent, thereby improving the density of the paste sintering and reducing the bulk resistance. At the same time, the glass powder comprises at least four glass powders with different softening temperatures, that is, different glass powders can have a step-by-step softening temperature and fluidity. The step-by-step softening and flow of the glass powder during the sintering process forms a continuous process of wetting and dissolving the silver powder, thereby improving the wettability of the glass powder and the silver powder and the ability to melt silver, thereby improving the sintering density of the paste and reducing the bulk resistance and contact resistance. Furthermore, compared with the traditional laser-assisted sintering to prepare electrodes, the combination of the above-mentioned organic solvent and glass powder and the use of the conductive paste of the present application can achieve a higher sintering density and lower contact resistance while reducing the sintering temperature by 50°C to 100°C, thereby ensuring a higher conversion efficiency of the photovoltaic cell. DETAILED DESCRIPTION

[0031] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0034] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0035] One embodiment of the present application provides a conductive paste comprising the following components in the following weight percentages: 6% to 10% organic vehicle, 1% to 5% glass powder, and 85% to 90% silver powder. The organic vehicle comprises a resin and an organic solvent, wherein the organic solvent comprises at least three organic solvents with different boiling points; and the glass powder comprises at least four glass powders with different softening temperatures.

[0036] The conductive paste comprises the following components in the following mass percentages: 6% to 10% of an organic vehicle, 1% to 5% of a glass powder, and 85% to 90% of a silver powder. The organic vehicle comprises a resin and an organic solvent, and the organic solvent comprises at least three organic solvents with different boiling points. The combination of three organic solvents with different boiling points can form a multi-gradient volatilization temperature, so that during the drying and sintering process of the organic vehicle in the conductive paste, the organic solvent gradually evaporates in a wider temperature range, reducing the problem of large porosity of the silver powder in the conductive paste caused by concentrated volatilization of the organic solvent, thereby improving the density of the paste sintering and reducing the bulk resistance. At the same time, the glass powder comprises at least four glass powders with different softening temperatures, that is, different glass powders can have a step-by-step softening temperature and fluidity. The step-by-step softening and flow of the glass powder during the sintering process forms a continuous process of wetting and dissolving the silver powder, thereby improving the wettability of the glass powder and the silver powder and the ability to melt silver, thereby improving the sintering density of the paste and reducing the bulk resistance and contact resistance. Furthermore, compared with the traditional laser-assisted sintering to prepare electrodes, the combination of the above-mentioned organic solvent and glass powder and the use of the conductive paste of the present application can achieve a higher sintering density and lower contact resistance while reducing the sintering temperature by 50°C to 100°C, thereby ensuring a higher conversion efficiency of the photovoltaic cell.

[0037] Optionally, the mass percentage of the organic vehicle in the conductive paste is 6%, 7%, 8%, 9% or 10%, or the mass percentage of the organic vehicle may also be within the range between any two of the above mass percentages.

[0038] Optionally, the mass percentage of the glass powder in the conductive paste is 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, or the mass percentage of the glass powder may be within the range between any two of the above mass percentages.

[0039] Optionally, the mass percentage of silver powder in the conductive paste is 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5% or 90%, or the mass percentage of silver powder can also be within the range between any two of the above mass percentages.

[0040] In some embodiments, the organic solvent comprises three to six organic solvents having different boiling points. Alternatively, the organic solvent comprises three, four, five or six organic solvents having different boiling points.

[0041] In some embodiments, the mass percentages of the organic solvents having different boiling points are the same.

[0042] In some embodiments, the glass powder includes four to eight glass powders having different softening temperatures. Optionally, the glass powder includes four, five, six, seven or eight glass powders having different softening temperatures.

[0043] In some embodiments, the glass powders having different softening temperatures have the same mass percentage.

[0044] In some embodiments, among the organic solvents having different boiling points, the difference in boiling points between every two organic solvents having similar boiling points is 20° C. to 50° C.

[0045] Within the range of the difference in boiling point between the two organic solvents with similar boiling points, the combination of organic solvents can form a more uniform gradient of volatilization temperature, so that during the drying and sintering process of the organic carrier in the conductive paste, the organic solvent gradually evaporates within a wider temperature range, reducing the problem of large porosity of the silver powder in the conductive paste caused by concentrated volatilization of the organic solvent, improving the density of the slurry sintering, and reducing the bulk resistance. Optionally, among the organic solvents with different boiling points, the difference in boiling point between each two organic solvents with similar boiling points is 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C, or the difference in boiling point between each two organic solvents with similar boiling points can also be within the range between any two of the above differences.

[0046] In some embodiments, the organic solvent includes at least three of an alcohol solvent, an amide solvent, and an ester solvent.

[0047] In some embodiments, the alcohol solvent includes at least one of terpineol, benzyl alcohol and n-butanol; the amide solvent includes at least one of dimethylacetamide and dimethylformamide; and / or the ester solvent includes at least one of methyl p-tert-butylbenzoate, diethylene glycol butyl ether acetate, butyl benzoate, hexadecene, benzyl benzoate, dibutyl phthalate and benzyl butyl phthalate.

[0048] In some embodiments, among the glass frits having different softening temperatures, the difference in softening temperature between any two glass frits having similar softening temperatures is 30° C. to 80° C.

[0049] Within the range of the softening temperature difference between two glass frits with similar softening temperatures, a relatively uniform step-wise increase in softening temperature can be formed between different glass frits. The step-wise softening flow of the glass frits during sintering forms a continuous process of wetting and dissolving the silver powder, improving the wettability of the glass frits with the silver powder and the silver dissolving ability, thereby enhancing the sintering density of the slurry and reducing the bulk resistance and contact resistance. Optionally, among the glass frits with different softening temperatures, the softening temperature difference between two glass frits with similar softening temperatures is 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. Alternatively, the softening temperature difference between two glass frits with similar softening temperatures can also be within the range between any two of the above-mentioned differences.

[0050] In some embodiments, the glass powder includes at least four of a first lead-silicon-iron glass powder, a second lead-silicon-iron glass powder, a lead-bismuth glass powder, and a barium-lime glass powder; in the first lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4, and B2O3 is (60-80): (1-15): (1-15): (5-15): (0-25); in the second lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4, and B2O3 is (60-80): (1-15): (1-15): (5-15): (0-25); The mass ratio of PbO, Bi2O3, Al2O3, Fe3O4 and B2O3 in lead-bismuth glass powder is (40~60): (5~15): (5~15): (5~15): (0~25); the mass ratio of BaCO3, CaCO3 and B2O3 in barium-lime glass powder is (30~60): (5~35): (40~60).

[0051] It should be noted that the following mass fractions of various components in different glass powders are only used to describe the mass ratios of the various components in the glass powder.

[0052] In some embodiments, the mass fraction of PbO in the first lead-ferrosilicon glass powder is 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 80 by mass ratio, or the mass fraction of PbO in the first lead-ferrosilicon glass powder can also be within the range between any two of the above mass fractions.

[0053] In some embodiments, the mass fraction of SiO2 in the first lead-silicon-iron glass powder is 1, 3, 5, 7, 9, 11, 13 or 15, or the mass fraction of SiO2 in the first lead-silicon-iron glass powder is within the range between any two of the above mass fractions.

[0054] In some embodiments, the mass fraction of Al2O3 in the first lead-silicon-iron glass powder is 1, 3, 5, 7, 9, 11, 13 or 15, or the mass fraction of Al2O3 in the first lead-silicon-iron glass powder is also within the range between any two of the above mass fractions.

[0055] In some embodiments, the mass fraction of Fe3O4 in the first lead-silicon-iron glass powder is 5, 7, 9, 11, 13 or 15, or the mass fraction of Fe3O4 in the first lead-silicon-iron glass powder is also within the range between any two of the above mass fractions.

[0056] In some embodiments, the mass fraction of B2O3 in the first lead-ferrosilicon glass powder is 0, 2, 5, 8, 10, 12, 15, 18, 20, 22 or 25, or the mass fraction of B2O3 in the first lead-ferrosilicon glass powder is within the range between any two of the above mass fractions.

[0057] In some embodiments, the mass fraction of PbO in the second lead-ferrosilicon glass powder is 40, 42, 44, 46, 48, 50, 52, 54, 56, 58 or 60, or the mass fraction of PbO in the second lead-ferrosilicon glass powder is within the range between any two of the above mass fractions.

[0058] In some embodiments, the mass fraction of SiO2 in the second lead-silicon-iron glass powder is 5, 7, 9, 11, 13 or 15 by mass ratio, or the mass fraction of SiO2 in the second lead-silicon-iron glass powder by mass ratio can also be within the range between any two of the above mass fractions.

[0059] In some embodiments, the mass fraction of Al2O3 in the second lead-silicon-iron glass powder is 5, 7, 9, 11, 13 or 15, or the mass fraction of Al2O3 in the second lead-silicon-iron glass powder is also within the range between any two of the above mass fractions.

[0060] In some embodiments, the mass fraction of Fe3O4 in the second lead-silicon-iron glass powder is 5, 7, 9, 11, 13 or 15, or the mass fraction of Fe3O4 in the second lead-silicon-iron glass powder is also within the range between any two of the above mass fractions.

[0061] In some embodiments, the mass fraction of B2O3 in the second lead-ferrosilicon glass powder is 0, 2, 5, 8, 10, 12, 15, 18, 20, 22 or 25, or the mass fraction of B2O3 in the second lead-ferrosilicon glass powder is within the range between any two of the above mass fractions.

[0062] In some embodiments, the mass fraction of PbO in the lead-bismuth glass powder is 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50, or the mass fraction of PbO in the lead-bismuth glass powder is within the range between any two of the above mass fractions.

[0063] In some embodiments, the mass fraction of Bi2O3 in the lead-bismuth glass powder is 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 or 40, or the mass fraction of Bi2O3 in the lead-bismuth glass powder is also within the range between any two of the above mass fractions.

[0064] In some embodiments, the mass fraction of Al2O3 in the lead-bismuth glass powder is 10, 12, 15, 18, 20, 22 or 25, or the mass fraction of Al2O3 in the lead-bismuth glass powder can also be within the range between any two of the above mass fractions.

[0065] In some embodiments, the mass fraction of Fe3O4 in the lead-bismuth glass powder is 5, 7, 9, 11, 13 or 15, or the mass fraction of Fe3O4 in the lead-bismuth glass powder can also be within the range between any two of the above mass fractions.

[0066] In some embodiments, the mass fraction of B2O3 in the lead-bismuth glass powder is 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50, or the mass fraction of B2O3 in the lead-bismuth glass powder is within the range between any two of the above mass fractions.

[0067] In some embodiments, the mass fraction of BaCO3 in the barium-lime glass powder is 30, 35, 40, 45, 50, 55 or 60, or the mass fraction of BaCO3 in the barium-lime glass powder can also be within the range between any two of the above mass fractions.

[0068] In some embodiments, the mass fraction of CaCO3 in the barium-lime glass powder is 5, 10, 15, 20, 25, 30 or 35, or the mass fraction of CaCO3 in the barium-lime glass powder is within the range between any two of the above mass fractions.

[0069] In some embodiments, the mass fraction of B2O3 in the barium-lime glass powder is 40, 42, 44, 46, 48, 50, 52, 54, 56, 58 or 60, or the mass fraction of B2O3 in the barium-lime glass powder is within the range between any two of the above mass fractions.

[0070] In some embodiments, the glass powder includes at least one of a first lead-ferrosilicon glass powder, a second lead-ferrosilicon glass powder, a lead-bismuth glass powder, and a barium-lime glass powder.

[0071] In some embodiments, the glass powder has a D50 particle size of 1.1 μm to 1.4 μm.

[0072] Within the aforementioned D50 particle size range, the glass powder exhibits excellent wettability with silver powder and excellent silver dissolution, which can improve the slurry's sintering density. Alternatively, the glass powder's D50 particle size is 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, or 1.4 μm. Alternatively, the glass powder's D50 particle size can be within a range between any two of the aforementioned D50 particle sizes.

[0073] In some embodiments, the silver powder includes nano silver powder and polycrystalline silver powder in a mass ratio of (2-10): (80-88); the D50 particle size of the nano silver powder is 50 nm-200 nm; and the D50 particle size of the polycrystalline silver powder is 0.8 μm-1.6 μm.

[0074] It is understood that polycrystalline silver powder is a powdered material composed of numerous tiny silver grains, exhibiting polycrystalline characteristics in its microstructure. The basic building blocks of polycrystalline silver powder are silver atoms, which crystallize into micron-sized individual grains. These grains randomly stack or combine to form a powdery substance. While the atoms within each grain of polycrystalline silver powder are orderly arranged (having a face-centered cubic structure), the crystallographic orientations of the grains vary, and grain boundaries exist between them. Among the silver powders with the aforementioned mass ratio, nanosilver powder is more active and easier to sinter. This silver powder can fill pores and enhance sintering density during the printing flow and sintering shrinkage of the conductive paste. The addition of polycrystalline silver powder, which also exhibits high activity, allows for a higher silver powder packing density, improved paste sintering density, lowered bulk resistance, and increased contact area between the silver powder and the silicon wafer, reducing surface porosity on the wafer.

[0075] Optionally, according to the mass ratio of nano silver powder to polycrystalline silver powder, the mass fraction of nano silver powder is 2, 3, 4, 5, 6, 7, 8, 9 or 10, or the mass fraction of nano silver powder can also be within the range between any two of the above mass fractions.

[0076] Optionally, according to the mass ratio of nano silver powder to polycrystalline silver powder, the mass fraction of polycrystalline silver powder is 80, 81, 82, 83, 84, 85, 86, 87 or 88, or the mass fraction of polycrystalline silver powder can also be within the range between any two of the above mass fractions.

[0077] Optionally, the D50 particle size of the nano-silver powder is 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm or 200 nm, or the D50 particle size of the nano-silver powder may also be within the range between any two of the above D50 particle sizes.

[0078] Optionally, the D50 particle size of the polycrystalline silver powder is 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm or 1.6 μm, or the D50 particle size of the polycrystalline silver powder may also be within the range between any two of the above D50 particle sizes.

[0079] In some embodiments, in the polycrystalline silver powder, the mass proportion of the D50 particle size of 0.8 μm to 1 μm is 10% to 20%, the mass proportion of the D50 particle size greater than 1 μm and less than or equal to 1.2 μm is 20% to 40%, and the mass proportion of the D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm is 40% to 60%.

[0080] In polycrystalline silver powder with the aforementioned particle size distribution, the combination of silver powders of different particle sizes, combined with nano-silver powder, can achieve a higher packing density of the silver powder. Furthermore, the particle size distribution of the silver powder in this application, combined with the selection of organic solvents and glass powder, can achieve good wettability between the glass powder and the silver powder during sintering, and better pore filling by the nano-silver powder, thereby improving the sintering density of the slurry and reducing both bulk and contact resistance.

[0081] Optionally, in the polycrystalline silver powder, the mass proportion of the particles with a D50 particle size of 0.8 μm to 1 μm is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, or, in the polycrystalline silver powder, the mass proportion of the particles with a D50 particle size of 0.8 μm to 1 μm may also be within the range between any two of the above mass percentages.

[0082] Optionally, in the polycrystalline silver powder, the mass proportion of the D50 particle size greater than 1 μm and less than or equal to 1.2 μm is 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38% or 40%, or, in the polycrystalline silver powder, the mass proportion of the D50 particle size greater than 1 μm and less than or equal to 1.2 μm may also be within the range between any two of the above mass percentages.

[0083] Optionally, in the polycrystalline silver powder, the mass proportion of the D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm is 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58% or 60%, or the mass proportion of the D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm may also be within the range between any two of the above mass percentages.

[0084] In some embodiments, the organic vehicle further comprises a thixotropic agent, silicone oil, and a dispersant.

[0085] In some embodiments, the mass ratio of resin, thixotropic agent, organic solvent, silicone oil, and dispersant is (0.3-1.5):(0.1-0.3):(6-8):(0.2-0.6):(0.2-0.6).

[0086] Optionally, based on the mass ratio of resin, thixotropic agent, organic solvent, silicone oil and dispersant, the mass fraction of resin is 0.3, 0.5, 0.7, 0.9, 1.1, 1.3 or 1.5, or the mass fraction of resin can also be within the range between any two of the above mass fractions.

[0087] Optionally, based on the mass ratio of resin, thixotropic agent, organic solvent, silicone oil and dispersant, the mass fraction of the thixotropic agent is 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28 or 0.3, or the mass fraction of the thixotropic agent can also be within the range between any two of the above mass fractions.

[0088] Optionally, based on the mass ratio of resin, thixotropic agent, organic solvent, silicone oil and dispersant, the mass fraction of organic solvent is 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8 or 8, or the mass fraction of organic solvent can also be within the range between any two of the above mass fractions.

[0089] Optionally, based on the mass ratio of resin, thixotropic agent, organic solvent, silicone oil and dispersant, the mass fraction of silicone oil is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 or 0.6, or the mass fraction of silicone oil can also be within the range between any two of the above mass fractions.

[0090] Optionally, based on the mass ratio of resin, thixotropic agent, organic solvent, silicone oil and dispersant, the mass fraction of the dispersant is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 or 0.6, or the mass fraction of the dispersant can also be within the range between any two of the above mass fractions.

[0091] In some embodiments, the resin includes at least one of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin, and polyester resin.

[0092] In some embodiments, the thixotropic agent includes at least one of polyamide wax and stearamide.

[0093] In some embodiments, the dispersant includes at least one of polyethylene glycol and polyvinyl pyrrolidone.

[0094] Another embodiment of the present application provides a method for preparing a conductive paste, comprising the following steps:

[0095] The components including the following mass percentages are mixed: 6% to 10% of an organic vehicle, 1% to 5% of glass powder, and 85% to 90% of silver powder; the organic vehicle includes a resin and an organic solvent, the organic solvent includes at least three organic solvents with different boiling points; the glass powder includes at least four glass powders with different softening temperatures.

[0096] Another embodiment of the present application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0097] Provide battery pre-finished products;

[0098] Coating any of the above conductive pastes or the conductive paste prepared by the above conductive paste preparation method on the surface of the battery pre-finished product;

[0099] The conductive paste is subjected to laser-assisted sintering to form metal electrodes.

[0100] In some embodiments, the maximum temperature of the laser-assisted sintering process is 600° C. to 700° C.

[0101] Compared to traditional conductive pastes that require laser-assisted sintering at 700°C to 800°C, the conductive paste of the present application can be sintered at a lower temperature of 600°C to 700°C, reducing the risk of damage to photovoltaic cells caused by high temperatures during high-temperature assisted sintering, and can also achieve higher sintering density and lower contact resistance. Optionally, the maximum temperature of the laser-assisted sintering process is 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C or 700°C, or the maximum temperature of the laser-assisted sintering process can also be within the range between any two of the above temperatures.

[0102] Another embodiment of the present application provides a photovoltaic cell, which is prepared by the above-mentioned method for preparing a photovoltaic cell.

[0103] Another embodiment of the present application provides a photovoltaic module, comprising:

[0104] cover;

[0105] At least one battery string, the battery string comprising a plurality of photovoltaic cells prepared by the above-mentioned method for preparing a photovoltaic cell; and

[0106] The encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

[0107] The following are specific examples.

[0108] Example 1

[0109] The conductive paste in Example 1 consists of 7% by mass of an organic vehicle, 3% of glass powder, and 90% of silver powder. The organic vehicle comprises a resin, a thixotropic agent, an organic solvent, silicone oil, and a dispersant in a mass ratio of 1:0.2:7:0.4:0.4. The resin is a mixed resin of ethyl cellulose, acrylic resin, and polyvinyl butyral resin; the thixotropic agent is polyamide wax; the organic solvent comprises terpineol, dimethylacetamide, and methyl p-tert-butylbenzoate in a mass ratio of 2:1:4; and the dispersant is polyethylene glycol. The glass powders are 70PbO-5SiO2-5Al2O3-10Fe3O4-10B2O3 glass powder, 60PbO-5SiO2-10Al2O3-10Fe3O4-15B2O3 glass powder, 45PbO-25Bi2O3-10Al2O3-10Fe3O4-10B2O3 glass powder, and 40BaCO3-10CaCO3-50B2O3 glass powder in a mass ratio of 1:1:0.5:0.5, with softening temperatures of 350°C, 380°C, 420°C, and 500°C, respectively. The silver powder is nanosilver powder and polycrystalline silver powder in a mass ratio of 3:87. The D50 particle size of the nano silver powder is 50 nm. Among the polycrystalline silver powder, the mass ratio of polycrystalline silver powder with a D50 particle size of 0.8 μm to 1 μm, polycrystalline silver powder with a D50 particle size greater than 1 μm and less than or equal to 1.2 μm, and polycrystalline silver powder with a D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm is 10:27:50.

[0110] Example 2

[0111] The components of the conductive paste in Example 2 differ from those in Example 1 only in that the organic solvent is benzyl alcohol, dimethylformamide, and butyl 4-diglycol acetate in a mass ratio of 2:1:4.

[0112] Example 3

[0113] The components of the conductive paste in Example 3 differ from those in Example 1 only in that the glass powder is 75PbO-5SiO2-5Al2O3-10Fe3O4-5B2O3 glass powder, 50PbO-5SiO2-5Al2O3-10Fe3O4-30B2O3 glass powder, 40PbO-30Bi2O3-10Al2O3-10Fe3O4-10B2O3 glass powder and 40BaCO3-10CaCO3-50B2O3 glass powder with a mass percentage of 1.2:0.5:0.5:0.8, and their softening temperatures are 340°C, 370°C, 410°C and 480°C, respectively.

[0114] Example 4

[0115] The components of the conductive paste in Example 4 differed only from those in Example 1 in that the silver powder consisted of nanosilver powder and polycrystalline silver powder in a mass ratio of 5:85%. The nanosilver powder had a D50 particle size of 100 nm. Within the polycrystalline silver powder, the mass ratios of polycrystalline silver powder with a D50 particle size of 0.8 μm to 1 μm, polycrystalline silver powder with a D50 particle size greater than 1 μm and less than or equal to 1.2 μm, and polycrystalline silver powder with a D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm were 15:45:25.

[0116] Example 5

[0117] The components of the conductive paste in Example 5 are different from those in Example 1 only in that the components of the conductive paste in Example 5 are 10% by mass of an organic vehicle, 5% by mass of glass powder, and 85% by mass of silver powder.

[0118] Example 6

[0119] The components of the conductive paste in Example 6 are different from those in Example 1 only in that the components of the conductive paste in Example 6 are 6% by mass of an organic vehicle, 4% by mass of glass powder, and 90% by mass of silver powder.

[0120] Example 7

[0121] The components of the conductive paste in Example 7 are different from those in Example 1 only in that the components of the conductive paste in Example 7 are 10 parts by mass of an organic vehicle, 1 part by mass of glass powder, and 89 parts by mass of silver powder.

[0122] Example 8

[0123] The components of the conductive paste in Example 8 differ from those in Example 1 only in that the D50 particle size of the nano silver powder is 200 nm; and the silver powder is a mixture of nano silver powder and polycrystalline silver powder in a mass ratio of 10:80.

[0124] Example 9

[0125] The components of the conductive paste in Example 9 differ from those in Example 1 only in that, in the polycrystalline silver powder, the mass ratio of polycrystalline silver powder with a D50 particle size of 0.8 μm to 1 μm, polycrystalline silver powder with a D50 particle size greater than 1 μm and less than or equal to 1.2 μm, and polycrystalline silver powder with a D50 particle size greater than 1.2 μm and less than or equal to 1.6 μm is 20:40:40.

[0126] Comparative Example 1

[0127] The components of the conductive paste in Comparative Example 1 differ from those in Example 1 only in that the organic solvent is only diethylene glycol butyl ether acetate.

[0128] Comparative Example 2

[0129] The components of the conductive paste in Comparative Example 2 differ from those in Example 1 only in that the organic solvent is diethylene glycol butyl ether acetate and alcohol ester dodecanol in a mass ratio of 6:1.

[0130] Comparative Example 3

[0131] The components of the conductive paste in Comparative Example 3 differ from those in Example 1 only in that the glass powder is 75PbO-5SiO2-5Al2O3-10Fe3O4-5B2O3 glass powder, and its softening temperature is 340°C.

[0132] Comparative Example 4

[0133] The components of the conductive paste in Comparative Example 4 differ from those in Example 1 only in that the glass powder is 75PbO-5SiO2-5Al2O3-10Fe3O4-5B2O3 glass powder, 50PbO-5SiO2-5Al2O3-10Fe3O4-30B2O3 glass powder, and 40PbO-30Bi2O3-10Al2O3-10Fe3O4-10B2O3 glass powder in a mass percentage of 1.2:0.5:0.5, and their softening temperatures are 340°C, 370°C, and 410°C, respectively.

[0134] Comparative Example 5

[0135] The components of the conductive paste in Comparative Example 5 are different from those in Example 1 only in that the components of the conductive paste in Comparative Example 5 are 9% by mass of an organic vehicle, 6% by mass of glass powder, and 85% by mass of silver powder.

[0136] Comparative Example 6

[0137] The components of the conductive paste in Comparative Example 6 differ from those in Example 1 only in that the components of the conductive paste in Comparative Example 6 are 10% by mass of an organic vehicle, 0.8% by mass of glass powder, and 89.2% by mass of silver powder.

[0138] Comparative Example 7

[0139] The components of the conductive paste in Comparative Example 7 are different from those in Example 1 only in that the components of the conductive paste in Comparative Example 7 are 13% by mass of an organic vehicle, 3% by mass of glass powder, and 84% by mass of silver powder.

[0140] Comparative Example 8

[0141] The components of the conductive paste in Comparative Example 8 are different from those in Example 1 only in that the components of the conductive paste in Comparative Example 8 are 3% by mass of an organic vehicle, 3% by mass of glass powder, and 94% by mass of silver powder.

[0142] In Comparative Example 8, the amount of the organic carrier was too little, so that the organic carrier could not fully cover the glass powder and the silver powder, and the viscosity of the mixture was too high to form a printable slurry.

[0143] Using the conductive pastes in Examples 1 to 9 and Comparative Examples 1 to 8 above, an 8-micron line width screen was used to screen print the conductive paste onto the cell with the back main grid and front main grid printed on it to form a front main grid. The cells were sintered in a sintering and annealing furnace and laser-assisted sintering was performed for preparation, wherein the maximum sintering temperature of the sintering furnace was 700°C. The photovoltaic cells in each embodiment and comparative example had the same structure and preparation parameters except for the different conductive pastes used. The above photovoltaic cells were tested, and the test results are shown in Table 1 below:

[0144] Table 1

[0145]

[0146] It can be seen from the test results of Comparative Examples 1 to 9 and Comparative Examples 1 and 3 that, compared with the photovoltaic cells prepared by using only one organic solvent or one glass powder conductive paste, in each embodiment of the present application, a multi-gradient volatilization temperature can be formed by combining at least three organic solvents with different boiling points, and at least four glass powders with different softening temperatures can be used to make the glass powders have a step-by-step increase in softening temperature and fluidity, thereby improving the density of the slurry sintering, reducing the body resistance and contact resistance, and improving the conversion efficiency of the photovoltaic cell.

[0147] By comparing the test results of Examples 1 to 9 and Comparative Example 2, it can be seen that when two organic solvents with different boiling points are used, the effect of improving the conversion efficiency of the photovoltaic cell is not obvious. This is because when the conductive paste includes at least three organic solvents with different boiling points, the effect of forming a multi-gradient volatilization temperature is better, so that the organic solvent in the organic carrier in the conductive paste can be gradually volatilized in a wider temperature range during the drying and sintering process, reducing the problem of large porosity of the silver powder in the conductive paste caused by concentrated volatilization of the organic solvent, and can improve the density of the paste sintering.

[0148] Comparing the test results of Examples 1 to 9 and Comparative Example 4, it can be seen that the use of three organic solvents with different softening temperatures does not significantly improve the conversion efficiency of the photovoltaic cell. This is because the conductive paste includes at least four glass powders with different softening temperatures, which can have a good step-by-step softening temperature and fluidity. The step-by-step softening and flow of the glass powder during the sintering process forms a continuous process of wetting and dissolving the silver powder, improving the wettability of the glass powder and silver powder and the silver-melting ability, thereby improving the sintering density of the paste and reducing the bulk resistance and contact resistance.

[0149] Comparing the test results of Examples 1-9 and Comparative Examples 5-8, it can be seen that excessive or insufficient glass powder content, or excessive or insufficient organic vehicle content, can reduce the synergistic effect of the organic solvent and glass powder, leading to decreased photovoltaic cell performance. In Comparative Example 8, due to the insufficient amount of organic vehicle, the organic vehicle was unable to fully coat the glass powder and silver powder, resulting in a mixture with too high a viscosity, making it impossible to form a printable slurry.

[0150] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0151] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims, and the specification may be used to interpret the content of the claims.

Claims

1. A conductive paste, characterized in that: The invention comprises the following components in the following mass percentages: 6% to 10% of an organic vehicle, 1% to 5% of glass powder, and 85% to 90% of silver powder; The organic vehicle includes a resin and an organic solvent, wherein the organic solvent includes at least three organic solvents with different boiling points; and the glass powder includes at least four glass powders with different softening temperatures.

2. The conductive paste according to claim 1, characterized in that Among the organic solvents having different boiling points, the difference in boiling points between any two organic solvents having similar boiling points is 20° C. to 50° C.

3. The conductive paste according to claim 1, characterized in that The organic solvent includes at least three of an alcohol solvent, an amide solvent and an ester solvent.

4. The conductive paste according to claim 3, characterized in that The alcohol solvent includes at least one of terpineol, benzyl alcohol and n-butanol; the amide solvent includes at least one of dimethylacetamide and dimethylformamide; and / or the ester solvent includes at least one of methyl p-tert-butylbenzoate, diethylene glycol butyl ether acetate, butyl benzoate, hexadecene, benzyl benzoate, dibutyl phthalate and benzyl butyl phthalate.

5. The conductive paste according to claim 1, characterized in that Among the glass powders having different softening temperatures, the difference in softening temperature between any two glass powders having similar softening temperatures is 30° C. to 80° C.

6. The conductive paste according to claim 1, characterized in that The glass powder includes at least four of a first lead-silicon-iron glass powder, a second lead-silicon-iron glass powder, a lead-bismuth glass powder and a barium-lime glass powder; in the first lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4 and B2O3 is (60-80): (1-15): (1-15): (5-15): (0-25); in the second lead-silicon-iron glass powder, the mass ratio of PbO, SiO2, Al2O3, Fe3O4 and B2O3 is ( The mass ratio of PbO, Bi2O3, Al2O3, Fe3O4 and B2O3 in the lead-bismuth glass powder is (30-50): (20-40): (10-25): (5-15): (0-50); the mass ratio of BaCO3, CaCO3 and B2O3 in the barium-lime glass powder is (30-60): (5-35): (40-60).

7. The conductive paste according to claim 1, characterized in that: The D50 particle size of the glass powder is 1.1 μm to 1.4 μm.

8. The conductive paste according to any one of claims 1 to 7, characterized in that The silver powder includes nano silver powder and polycrystalline silver powder in a mass ratio of (2-10): (80-88); the D50 particle size of the nano silver powder is 50 nm-200 nm; the D50 particle size of the polycrystalline silver powder is 0.8 μm-1.6 μm.

9. The conductive paste according to claim 8, characterized in that: In the polycrystalline silver powder, the mass proportion of the D50 particle size of 0.8μm~1μm is 10%~20%, the mass proportion of the D50 particle size greater than 1μm and less than or equal to 1.2μm is 20%~40%, and the mass proportion of the D50 particle size greater than 1.2μm and less than or equal to 1.6μm is 40%~60%.

10. The conductive paste according to any one of claims 1 to 7 and 9, characterized in that: The organic vehicle further comprises a thixotropic agent, silicone oil and a dispersant.

11. The conductive paste according to claim 10, characterized in that: The mass ratio of the resin, the thixotropic agent, the organic solvent, the silicone oil, and the dispersant is (0.3-1.5): (0.1-0.3): (6-8): (0.2-0.6): (0.2-0.6); and / or, The resin includes at least one of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin; and / or, The thixotropic agent includes at least one of polyamide wax and stearic acid amide; and / or, The dispersant includes at least one of polyethylene glycol and polyvinyl pyrrolidone.

12. A method for preparing a conductive paste, characterized in that: The steps include: The following components are mixed in mass percentage: 6% to 10% of an organic vehicle, 1% to 5% of glass powder, and 85% to 90% of silver powder; the organic vehicle comprises a resin and an organic solvent, the organic solvent comprises at least three organic solvents with different boiling points; the glass powder comprises at least four glass powders with different softening temperatures.

13. A method for preparing a photovoltaic cell, characterized in that: The steps include: Provide battery pre-finished products; Coating the conductive paste according to any one of claims 1 to 11 or the conductive paste prepared by the method for preparing the conductive paste according to claim 12 on the surface of the battery pre-product; The conductive paste is subjected to laser-assisted sintering to form a metal electrode.

14. A photovoltaic cell, characterized in that: The photovoltaic cell is prepared by the method for preparing the photovoltaic cell according to claim 13.

15. A photovoltaic module, characterized in that: include: cover; at least one battery string, the battery string comprising a plurality of photovoltaic cells prepared by the method for preparing a photovoltaic cell according to claim 14; as well as An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

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