A low-temperature curing silver-coated copper slurry for heterojunction solar cells and a preparation method thereof

Abstract

The present invention belongs to the field of electrode slurry preparation, and provides a low-temperature curing silver-coated copper slurry for heterojunction solar cells and a preparation method thereof. The present invention adopts ethyl cellulose as a matrix material, and provides a stable matrix network for the slurry through its good adhesion and dispersibility. By adding chemically modified materials such as modified phenolic resin and organosilicon-modified epoxy acrylate to the slurry, a network structure with a high degree of crosslinking is formed, and the mechanical strength and adhesion of the slurry are further enhanced. The surface of inorganic fillers such as silver-coated copper powder and bismuth oxide is modified by silane coupling agents and titanate coupling agents, and the silicon-oxygen bonds formed on the surface of the filler enhance the interface bonding force between the filler and the organic matrix; by adding carboxylated polyamide wax and organic bentonite, the adsorption and electrostatic repulsion of filler particles are utilized to reduce the tendency of filler agglomeration, and the resulting conductive slurry has the characteristics of excellent conductivity and low-temperature rapid curing.

Description

Technical Field

[0001] The invention belongs to the field of electrode slurry preparation, and relates to a low-temperature solidified silver-coated copper slurry for a heterojunction solar cell and a preparation method thereof. Background Art

[0002] With the continuous increase in global energy demand, heterojunction solar cells have become one of the research hotspots of high-efficiency solar cells due to their excellent photoelectric conversion efficiency and good temperature stability. In heterojunction solar cells, the choice of electrode materials directly affects the electrical performance and stability of the battery. Silver-coated copper composite materials have good electrical conductivity. By coating with a silver layer, their conductivity, corrosion resistance and contact interface performance can be effectively improved, thereby further improving the overall efficiency of solar cells. However, there are some problems with the preparation process and curing process of the silver-coated copper material in the slurry. Traditional silver pastes often require higher curing temperatures (usually above 300°C), which affects the overall structure and efficiency of solar cells. Especially in the presence of some low-temperature sensitive materials (such as heterojunction layers), high-temperature curing may cause damage and performance degradation. The patent with the publication number CN113814396A discloses a method for preparing submicron silver-plated copper powder for low-temperature slurry of heterojunction solar cells, using a liquid phase reduction method to prepare metal copper powder with submicron particle size, and then adding silver nitrate and a reducing agent in the aforementioned liquid phase environment in sequence to allow the newly generated silver to be directly coated on the outer layer of the copper powder. The preparation method uses hydrazine hydrate, and the preparation process has a great safety hazard. Therefore, it is necessary to develop a low-temperature solidified silver-coated copper slurry that can achieve efficient electrode film formation under low temperature conditions and maintain its excellent electrical and mechanical properties. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a low-temperature curing silver-coated copper slurry for heterojunction solar cells and a preparation method thereof. In the slurry formula, polymers and crosslinking agents with a high degree of crosslinking, such as modified phenolic resin, silicone-modified epoxy acrylate, and epoxy linseed oil, are added. These materials form a crosslinked network structure through chemical reactions, which enhances the mechanical strength, adhesion and wear resistance of the slurry. The use of crosslinked polymers such as modified phenolic resin, silicone-modified epoxy acrylate, and modified polyethylene glycol monomethyl ether as organic carriers ensures good adhesion while allowing the slurry to be cured under low temperature conditions, thereby meeting the needs of actual production.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, the preparation method comprising:

[0006] Step S1, under a nitrogen atmosphere, dispersing ethyl cellulose in pentaerythritol, raising the temperature to a first temperature, adding maleic anhydride, raising the temperature to a second temperature, fully reacting, adjusting the temperature to a third temperature, sequentially adding 2-ethyl-4-methylimidazole, modified phenolic resin and diisopropylbenzene peroxide and stirring evenly, then sequentially adding organosilicon-modified epoxy acrylate, N-vinyl pyrrolidone, a silane coupling agent mixture, a titanate coupling agent, a modified polyethylene glycol monomethyl ether, a carboxylated polyamide wax, an organic bentonite, and a dispersant, stirring evenly to obtain an organic carrier;

[0007] Step S2, adding PVP and sodium citrate to the CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4-5, adding ascorbic acid solution, heating to a fourth temperature and stirring in a water bath, centrifuging and collecting copper nanoparticles and dispersing them in ethanol, adding CTAB solution for ultrasonication, dispersing the ultrasonicated copper nanoparticles in an AgNO3 solution, adjusting the temperature to a fifth temperature, adding ascorbic acid solution for sufficient reaction, filtering and washing, and then placing under vacuum drying at a fourth temperature to obtain a silver-coated copper powder;

[0008] Step S3, adding silver-coated copper powder, nano silver and bismuth oxide to an organic carrier in sequence, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0009] The preparation methods of modified phenolic resin, silicone-modified epoxy acrylate and modified polyethylene glycol monomethyl ether are as follows:

[0010] Step A1, heating the phenolic resin to a sixth temperature, adding bisphenol A, stirring evenly, adding sodium hydroxide solution to adjust to a target pH, adding formaldehyde solution to fully react, adding dimethylethanolamine, continuing the reaction, cooling to a seventh temperature, adding methyl isobutyl ketone, stirring evenly to obtain a modified phenolic resin;

[0011] Step A2, under a nitrogen atmosphere, heating the epoxy acrylate to a sixth temperature, adding hydroxyl-terminated silicone oil and stirring evenly, then adding hexamethyldisilazane, fully reacting, cooling to a seventh temperature, adding γ-methacryloxypropyltrimethoxysilane, fully reacting, then adding glycidyl methacrylate, continuing to react, adding benzoyl peroxide, adding methyl isobutyl ketone, stirring evenly to obtain silicone-modified epoxy acrylate;

[0012] Step A3, heating polyethylene glycol monomethyl ether to an eighth temperature, adding succinic anhydride, raising the temperature to a sixth temperature for sufficient reaction, cooling to a seventh temperature, sequentially adding N-hydroxymethyl acrylamide and triethylenetetramine to continue the reaction, adding epoxy linseed oil to continue the reaction, then adding glycidyl methacrylate to continue the reaction, adjusting the temperature to a ninth temperature, adding dimethylacetamide, and stirring evenly to obtain modified polyethylene glycol monomethyl ether.

[0013] The phenol molecular structure contains an aromatic ring and a hydroxyl group. The hydroxyl group increases the electron density of the ortho and para positions of the phenol ring, becoming a nucleophilic site. The formaldehyde molecule exhibits strong electrophilicity through its carbonyl group. Under alkaline conditions, the acidic hydrogen of the phenolic hydroxyl group is partially removed to produce phenol oxide anions, which further enhance the nucleophilicity of the aromatic ring. The carbonyl carbon in the formaldehyde molecule has a high electrophilicity and is susceptible to nucleophilic attack by the phenol molecule. In this system, the ortho or para carbon atom of the phenol attacks the carbonyl carbon of the formaldehyde molecule through the conjugation of the aromatic ring to produce hydroxymethylphenol. Bisphenol A is a compound with a bisphenol hydroxyl structure. Its molecular structure contains two phenol rings connected by a dimethyl bridge. The molecular characteristics of bisphenol A enable it to provide more reactive sites in the reaction and to adjust the mechanical properties of the material through its rigid skeleton. The two phenolic hydroxyl groups of bisphenol A are similar to ordinary phenols and also show high nucleophilicity under alkaline conditions. Each phenolic hydroxyl group can react with a formaldehyde molecule separately to generate a bisphenol A derivative with two hydroxymethyl substituents. The bisphenol A molecule introduces two hydroxymethyl groups, providing additional cross-linking reaction points. More importantly, the dimethyl bridge in the bisphenol A molecule has high spatial rigidity, which enables its derivatives to effectively improve the mechanical strength of the material during the cross-linking process while avoiding brittleness caused by overly tight cross-linking. After the reaction system is heated up, a dehydration condensation reaction occurs between the hydroxymethyl groups of the two hydroxymethylated phenol molecules to generate an ether bond. Because the ether bond has a large free rotation ability, the formation of the ether bond increases the flexibility of the cross-linked network. In addition, the ether bond gives the material a higher thermal stability, enabling it to maintain structural integrity under high temperature conditions. The hydroxymethyl group of the hydroxymethylated phenol can also directly react with the hydroxyl group of another phenol molecule to generate a methylene group. The formation of the methylene group increases the rigidity of the cross-linked network. The ether bond and the methylene group jointly construct the three-dimensional network structure of the phenolic resin. The ether bond gives the system a certain flexibility and thermal stability, while the methylene group provides rigidity and high cross-linking density. The synergistic effect of this structure enables the material to have both excellent mechanical properties and thermal stability.

[0014] Epoxy acrylate is an organic molecule with epoxy groups and acrylate groups. The epoxy group has a three-membered ring structure, which is easy to open under the action of an initiator, and reacts with a nucleophilic reagent to open the ring structure, generating a reactive hydroxyl and ether bond and epoxy cross-linking network. In the structure of the acrylate group, the carbon-carbon double bond has a high reactivity and can participate in the polymerization reaction initiated by free radicals. The free radical initiator (peroxide) decomposes under the action of heat to generate active free radicals. These free radicals attack the double bonds of the acrylate group, open the double bonds and form active monomer free radicals. The active monomer free radicals further attack other acrylate double bonds, chain growth, and form long-chain polymers. The molecules of the acrylate group can not only form linear polymers, but also form a three-dimensional network structure through multi-point cross-linking (i.e., multiple double bonds are interconnected). The cross-linking monomer (multifunctional compound containing acrylate groups) participates in the reaction through its multiple double bonds during the free radical polymerization process, connecting different polymer chains to form cross-linking points. In the epoxy acrylate system, the ring-opening reaction of the epoxy group and the free radical polymerization of the acrylate group form a double cross-linked three-dimensional network. The ring-opening reaction of the epoxy group forms an epoxy cross-linked network, and due to the introduction of the ether bond, the material has higher chemical stability and heat resistance. The free radical polymerization of the acrylate group forms a fast cross-linked network, giving the material high strength. The double bond in the acrylate group is a highly reactive functional group that can undergo free radical polymerization under the action of a free radical initiator. The methacryloxy group in the γ-methacryloxypropyltrimethoxysilane molecule is also an unsaturated double bond that can participate in free radical polymerization with the acrylate group and become part of the main chain to increase the cross-linking density of the polymer network.

[0015] Polyethylene glycol monomethyl ether is a flexible molecule with a hydroxyl group at the end. The hydroxyl group in the molecule acts as a nucleophilic agent to attack the carbonyl group of succinic anhydride to generate a stable ester bond structure with high chemical tolerance. At the same time, the flexible ethoxy chain segment of polyethylene glycol monomethyl ether is introduced into the polymer network, giving the system a certain degree of softness, so that the cured material has better flexibility while having a high cross-linking density. The flexibility and low molecular weight of the polyethylene glycol monomethyl ether chain segment make the slurry show better fluidity before curing, which is conducive to coating or molding processing. N-hydroxymethyl acrylamide contains acryloyl and hydroxymethylamide groups. Acryloyl has a reactive carbon-carbon double bond and can form a polymer main chain through free radical polymerization. The hydroxymethylamide group provides additional reactivity and can be further cross-linked with other groups (such as carboxyl and hydroxyl) through condensation or addition reaction. The high reactivity of the acryloyl group enables N-hydroxymethyl acrylamide to cure quickly through free radical polymerization under low temperature conditions, improving the curing efficiency. The hydroxymethylamide group provides additional cross-linking points and enhances the integrity of the three-dimensional network structure. Epoxidized linseed oil is a multifunctional compound whose chemical properties are mainly reflected in the high reactivity of the epoxy group. The epoxy groups in epoxy linseed oil are easily attacked by nucleophilic reagents to undergo ring-opening reactions to generate hydroxyl groups and ether bonds. Since the epoxy linseed oil molecule has multiple epoxy groups, it can act as a cross-linking agent to form multiple connection points of the network structure during the curing process, significantly improving the cross-linking density during the curing process.

[0016] The chemical structure of ethyl cellulose is a cellulose derivative, in which part of the hydroxyl groups of the cellulose main chain are replaced by ethoxy groups. The polymer chain of ethyl cellulose can form a continuous network structure in the slurry, and interact with other components through intermolecular van der Waals forces and hydrogen bonds, thereby improving the overall bonding strength of the slurry. At the same time, ethyl cellulose has high solubility and rheological properties. Its molecular chain can coat the filler particles to prevent direct contact between particles and reduce the tendency of filler agglomeration. The flexible chain segments of the cellulose structure can be combined with the filler surface through physical adsorption or weak chemical bonds to further stabilize the dispersion state of the slurry. The silanol generated by the hydrolysis of the silane coupling agent is an active intermediate, which can undergo a condensation reaction with the hydroxyl groups on the filler surface to form a silicon oxygen bond and a titanium oxygen bond. Both are covalent bonds with high bonding strength. The silane coupling agent is firmly bonded to the filler surface, which greatly enhances the interfacial bonding force between the filler and the matrix. At the same time, the coupling agent forms an organic interface layer on the filler surface, which improves the surface wettability and dispersibility of the inorganic filler and reduces the tendency of particle aggregation. More uniform filler distribution and stronger interfacial bonding force help form the conductivity path of the conductive filler, thereby improving the conductive performance. The carboxylated polyamide wax molecules contain lipophilic segments (long-chain alkyl groups) that are compatible with the organic phase (ethyl cellulose) in the slurry, and the hydrophilic carboxyl groups can interact with the hydroxyl groups or oxides on the surface of the inorganic filler through hydrogen bonds or ionic bonds; in the slurry system, the organic bentonite flakes can expand through solvation and adsorb filler particles to form a physical isolation layer, and the surface of the organic bentonite flakes can combine with the filler or matrix molecules through electrostatic action or hydrogen bonds, thereby stabilizing the dispersion, improving the dispersion effect of the inorganic filler, avoiding uneven performance caused by excessive local filler concentration, and ensuring that the slurry forms a uniform material structure after curing.

[0017] As a preferred technical solution of the present invention, in step S1, the mass ratio of ethyl cellulose to pentaerythritol is (3-4):1, for example, it can be 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1 or 4:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In some optional instances, the first temperature is 130-140°C, for example, it can be 130.0°C, 131.0°C, 132.0°C, 133.0°C, 134.0°C, 135.0°C, 136.0°C, 137.0°C, 138.0°C, 139.0°C or 140.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In some optional examples, the mass of the maleic anhydride is 20-30% of the mass of the ethyl cellulose, for example, it can be 20.0%, 21.0%, 22.0%, 23.0%, 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 29.0% or 30.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some optional instances, the second temperature is 150-160°C, for example, it can be 150.0°C, 151.0°C, 152.0°C, 153.0°C, 154.0°C, 155.0°C, 156.0°C, 157.0°C, 158.0°C, 159.0°C or 160.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some optional examples, the reaction time at the second temperature is 3-4h, for example, 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some optional instances, the third temperature is 70-80°C, for example, it can be 70.0°C, 71.0°C, 72.0°C, 73.0°C, 74.0°C, 75.0°C, 76.0°C, 77.0°C, 78.0°C, 79.0% or 80.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In some optional examples, the mass of the 2-ethyl-4-methylimidazole is 15-20% of the mass of the ethyl cellulose, for example, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5% or 20.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In some optional examples, the mass of the modified phenolic resin is 10-15% of the mass of the ethyl cellulose, for example, it can be 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some optional examples, the mass of dicumyl peroxide is 5-8% of the mass of ethyl cellulose, for example, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional examples, the mass of the silicone-modified epoxy acrylate is 15-20% of the mass of the ethyl cellulose, for example, 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5% or 20.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional examples, the mass of N-vinyl pyrrolidone is 8-10% of the mass of ethyl cellulose, for example, 8.0%, 8.2%, 8.4%, 8.6%, 8.8%, 9.0%, 9.2%, 9.4%, 9.6%, 9.8% or 10.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] In some optional examples, the silane coupling agent mixture is KH550 and KH560 in a mass ratio of 1:1, and the mass of the silane coupling agent mixture is 10-15% of the mass of the ethyl cellulose, for example, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional examples, the titanate coupling agent is NDZ-201, and its mass is 3-5% of the mass of ethyl cellulose, for example, it can be 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In some optional examples, the mass of the modified polyethylene glycol monomethyl ether is 10-15% of the mass of ethyl cellulose, for example, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In some optional examples, the carboxylated polyamide wax is BYK-410, and its mass is 3-5% of the mass of ethyl cellulose, for example, it can be 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In some optional examples, the organic bentonite is Garamite-7305, and its mass is 3-5% of the mass of ethyl cellulose, for example, it can be 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional examples, the dispersant is BYK-2152, and its mass is 3-5% of the mass of ethyl cellulose, for example, it can be 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, 4.8% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] As a preferred technical solution of the present invention, in step S2, the concentration of the CuCl2 solution is 0.1M.

[0035] In some optional examples, the mass of the PVP is 1-2% of the mass of the CuCl2 solution, for example, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In some optional examples, the mass of the sodium citrate is 0.5-1% of the mass of the CuCl2 solution, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional examples, the concentration of the ascorbic acid solution is 0.2M, and the mass is 50-60% of the mass of the CuCl2 solution, for example, it can be 50.0%, 51.0%, 52.0%, 53.0%, 54.0%, 55.0%, 56.0%, 57.0%, 58.0%, 59.0% or 60.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In some optional instances, the fourth temperature is 60-70°C, for example, it can be 60.0°C, 61.0°C, 62.0°C, 63.0°C, 64.0°C, 65.0°C, 66.0°C, 67.0°C, 68.0°C, 69.0°C or 70.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional examples, the water bath stirring time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional examples, the concentration of the CTAB solution is 0.5 g / L, and the mass is 30-40% of the mass of the CuCl2 solution, for example, it can be 30.0%, 31.0%, 32.0%, 33.0%, 34.0%, 35.0%, 36.0%, 37.0%, 38.0%, 39.0% or 40.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some optional instances, the concentration of the AgNO3 solution is 0.05M, and its mass is 110-120% of the mass of the CuCl2 solution, for example, it can be 110.0%, 111.0%, 112.0%, 113.0%, 114.0%, 115.0%, 116.0%, 117.0%, 118.0%, 119.0% or 120.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In some optional examples, the mass of the ascorbic acid solution added at the fifth temperature is 50-60% of the mass of the CuCl2 solution, for example, 50.0%, 51.0%, 52.0%, 53.0%, 54.0%, 55.0%, 56.0%, 57.0%, 58.0%, 59.0% or 60.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional examples, the reaction time at the fifth temperature is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional examples, the vacuum drying time is 12-14 hours, for example, it can be 12.0 hours, 12.2 hours, 12.4 hours, 12.6 hours, 12.8 hours, 13.0 hours, 13.2 hours, 13.4 hours, 13.6 hours, 13.8 hours or 14.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] As a preferred technical solution of the present invention, in step S3, the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8;

[0046] In some optional examples, the mass of the nanosilver is 1-2% of the mass of the silver-coated copper powder, for example, it can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some optional examples, the mass of the bismuth oxide is 1-2% of the mass of the silver-coated copper powder, for example, it can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] As a preferred technical solution of the present invention, in step A1, the sixth temperature is 110-120°C, for example, it can be 110.0°C, 111.0°C, 112.0°C, 113.0°C, 114.0°C, 115.0°C, 116.0°C, 117.0°C, 118.0°C, 119.0°C or 120.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In some optional examples, the mass of bisphenol A is 30-40% of the mass of the phenolic resin, for example, it can be 30.0%, 31.0%, 32.0%, 33.0%, 34.0%, 35.0%, 36.0%, 37.0%, 38.0%, 39.0% or 40.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In some optional instances, the mass fraction of the sodium hydroxide solution is 10-15wt.%, for example, it can be 10.0wt.%, 10.5wt.%, 11.0wt.%, 11.5wt.%, 12.0wt.%, 12.5wt.%, 13.0wt.%, 13.5wt.%, 14.0wt.%, 14.5wt.% or 15.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In some optional examples, the target pH is 8-9, for example, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] In some optional instances, the mass fraction of the formaldehyde solution is 20-25wt.%, for example, it can be 20.0wt.%, 20.5wt.%, 21.0wt.%, 21.5wt.%, 22.0wt.%, 22.5wt.%, 23.0wt.%, 23.5wt.%, 24.0wt.%, 24.5wt.% or 25.0wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some optional examples, the mass of the formaldehyde solution is 40-50% of the mass of the phenolic resin, for example, it can be 40.0%, 41.0%, 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0% or 50.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In some optional examples, the reaction time after adding the formaldehyde solution is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] In some optional examples, the mass of the dimethylethanolamine is 3-5% of the mass of the phenolic resin, for example, it can be 3.0%, 3.5%, 4.0%, 4.5% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In some optional examples, the reaction time after adding dimethylethanolamine is 30-60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min, 57 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In some optional instances, the seventh temperature is 90-100°C, for example, it can be 90.0°C, 91.0°C, 92.0°C, 93.0°C, 94.0°C, 95.0°C, 96.0°C, 97.0°C, 98.0°C, 99.0°C or 100.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] In some optional examples, the mass of the methyl isobutyl ketone is 40-50% of the mass of the phenolic resin, for example, it can be 40.0%, 41.0%, 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0% or 50.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] As a preferred technical solution of the present invention, in step A2, the mass of the terminal hydroxyl silicone oil is 40-50% of the mass of the epoxy acrylate, for example, it can be 40.0%, 41.0%, 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0% or 50.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] In some optional examples, the mass of the hexamethyldisilazane is 5-7% of the mass of the epoxy acrylate, for example, it can be 5.0%, 5.2%, 5.4%, 5.6%, 5.8%, 6.0%, 6.2%, 6.4%, 6.6%, 6.8% or 7.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In some optional examples, the reaction time after adding hexamethyldisilazane is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] In some optional examples, the mass of the γ-methacryloxypropyltrimethoxysilane is 8-10% of the mass of the epoxy acrylate, for example, it can be 8.0%, 8.2%, 8.4%, 8.6%, 8.8%, 9.0%, 9.2%, 9.4%, 9.6%, 9.8% or 10.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In some optional examples, the reaction time after adding γ-methacryloxypropyltrimethoxysilane is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] In some optional examples, the mass of the glycidyl methacrylate is 10-15% of the mass of the epoxy acrylate, for example, it can be 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] In some optional examples, the reaction time after adding glycidyl methacrylate is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] In some optional examples, the mass of the benzoyl peroxide is 2-3% of the mass of the epoxy acrylate, for example, it can be 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] In some optional examples, the mass of the methyl isobutyl ketone is 40-50% of the mass of the epoxy acrylate, for example, it can be 40.0%, 41.0%, 42.0%, 43.0%, 44.0%, 45.0%, 46.0%, 47.0%, 48.0%, 49.0% or 50.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] As a preferred technical solution of the present invention, in step A3, the eighth temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0069] In some optional examples, the mass of succinic anhydride is 20-30% of the mass of polyethylene glycol monomethyl ether, for example, it can be 20.0%, 21.0%, 22.0%, 23.0%, 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 29.0% or 30.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] In some optional examples, the reaction time after adding succinic anhydride is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In some optional examples, the mass of the N-hydroxymethyl acrylamide is 15-20% of the mass of the polyethylene glycol monomethyl ether, for example, it can be 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5% or 20.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] In some optional examples, the mass of the triethylenetetramine is 2-5% of the mass of the polyethylene glycol monomethyl ether, for example, it can be 2.0%, 2.3%, 2.6%, 2.9%, 3.2%, 3.5%, 3.8%, 4.1%, 4.4%, 4.7% or 5.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0073] In some optional examples, the reaction time after adding triethylenetetramine is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0074] In some optional examples, the mass of the epoxidized linseed oil is 5-10% of the mass of polyethylene glycol monomethyl ether, for example, it can be 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5% or 10.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0075] In some optional examples, the mass of the glycidyl methacrylate is 10-15% of the mass of polyethylene glycol monomethyl ether, for example, it can be 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0076] In some optional examples, the reaction time after adding glycidyl methacrylate is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0077] In some optional instances, the ninth temperature is 70-80°C, for example, it can be 70.0°C, 71.0°C, 72.0°C, 73.0°C, 74.0°C, 75.0°C, 76.0°C, 77.0°C, 78.0°C, 79.0°C or 80.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0078] In some optional examples, the mass of the dimethylacetamide is 20-30% of the mass of polyethylene glycol monomethyl ether, for example, it can be 20.0%, 21.0%, 22.0%, 23.0%, 24.0%, 25.0%, 26.0%, 27.0%, 28.0%, 29.0% or 30.0%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] In a second aspect, the present invention provides a low-temperature curing silver-coated copper slurry for heterojunction solar cells obtained by the preparation method described in the first aspect.

[0080] Compared with the prior art, the present invention has the following beneficial effects: (1) bisphenol A reacts with formaldehyde molecules under alkaline conditions to introduce hydroxymethyl groups, and the hydroxymethyl groups of the hydroxymethylated phenol molecules undergo a dehydration condensation reaction to generate ether bonds, which increases the flexibility of the cross-linked network. The hydroxymethylated phenol can also generate methylene groups, which increases the rigidity of the cross-linked network. The ether bonds and methylene groups together construct a three-dimensional network structure of the phenolic resin. The ether bonds give the system certain flexibility and thermal stability, while the methylene groups provide rigidity and high cross-linking density. The synergistic effect of this structure enables the material to have both excellent mechanical properties and thermal stability; (2) the acryloyl group has reactive carbon-carbon The double bond can form a polymer main chain through free radical polymerization. The hydroxymethylamide group provides additional reactivity and can be further cross-linked through condensation or addition reaction. The high reactivity of the acryloyl group enables the slurry to cure quickly under low temperature conditions, thereby improving the curing efficiency. (3) The polymer chain of ethyl cellulose can form a continuous network structure in the slurry and interact with other components through intermolecular van der Waals forces and hydrogen bonds, thereby improving the overall bonding strength of the slurry. At the same time, ethyl cellulose has high solubility and rheological properties. Its molecular chain can coat the filler particles to prevent direct contact between particles and reduce the tendency of filler agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 This is a TEM image of the silver-coated copper powder prepared in Example 1 of the present invention;

[0082] Figure 2 This is the HRTEM image of the silver-coated copper powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0083] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0084] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products without further purification.

[0085] Example 1

[0086] This embodiment provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, and the preparation method specifically comprises the following steps:

[0087] Step A1, heating the phenolic resin to 114° C., adding bisphenol A in an amount of 32% by weight of the phenolic resin, stirring evenly, adding 12wt.% sodium hydroxide solution to adjust the pH to 8.2, adding 22wt.% formaldehyde solution in an amount of 45% by weight of the phenolic resin to fully react for 2.5 hours, adding dimethylethanolamine in an amount of 4% by weight of the phenolic resin, continuing the reaction for 45 minutes, cooling to 92° C., adding methyl isobutyl ketone in an amount of 45% by weight of the phenolic resin, stirring evenly to obtain a modified phenolic resin;

[0088] Step A2, under a nitrogen atmosphere, the epoxy acrylate is heated to 114°C, 40% of KF-6001 by weight of the epoxy acrylate is added and stirred evenly, and then 5.3% of hexamethyldisilazane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 2.0 hours, and the temperature is lowered to 90°C, 8.9% of γ-methacryloxypropyltrimethoxysilane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 1.0 hours, and then 13% of glycidyl methacrylate by weight of the epoxy acrylate is added, and the reaction is continued for 1.0 hours, and 2.8% of benzoyl peroxide by weight of the epoxy acrylate is added, and 47% of methyl isobutyl ketone by weight of the epoxy acrylate is added, and the reaction is uniformly carried out to obtain silicone-modified epoxy acrylate;

[0089] Step A3, heating polyethylene glycol monomethyl ether to 80°C, adding succinic anhydride in an amount of 20% by weight of polyethylene glycol monomethyl ether, raising the temperature to 110°C and fully reacting for 2h, cooling to 90°C, sequentially adding N-hydroxymethyl acrylamide in an amount of 15% by weight of polyethylene glycol monomethyl ether and triethylenetetramine in an amount of 2% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1h, adding epoxy linseed oil in an amount of 5% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1h, then adding glycidyl methacrylate in an amount of 10% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1h, adjusting the temperature to 70°C, adding dimethylacetamide in an amount of 20% by weight of polyethylene glycol monomethyl ether, and stirring evenly to obtain modified polyethylene glycol monomethyl ether;

[0090] Step S1, under nitrogen atmosphere, ethyl cellulose is dispersed in pentaerythritol, the mass ratio of ethyl cellulose to pentaerythritol is 3.6:1, the temperature is raised to 130°C, maleic anhydride is added at 20% by mass of ethyl cellulose, the temperature is raised to 150°C, the reaction is fully carried out for 3 hours, the temperature is adjusted to 70°C, 2-ethyl-4-methylimidazole at 15% by mass of ethyl cellulose, 10% of modified phenolic resin and 5% of diisopropylbenzene peroxide are added in sequence, and stirred evenly, and then in sequence Add 15% of ethyl cellulose mass of organosilicon-modified epoxy acrylate, 8% of N-vinyl pyrrolidone, 10% of silane coupling agent mixture, 3% of titanate coupling agent NDZ-201, 11.3% of modified polyethylene glycol monomethyl ether, 3.9% of carboxylated polyamide wax BYK-410, 3.5% of organic bentonite Garamite-7305 and 4.5% of dispersant BYK-2152, and stir evenly to obtain an organic carrier;

[0091] Step S2, adding 1.8% PVP by mass of the CuCl2 solution and 0.84% ​​sodium citrate by mass of the CuCl2 solution to a 0.1M CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4.3, adding 0.2M ascorbic acid solution by mass of 58% by mass of the CuCl2 solution, heating to 60°C and stirring in a water bath for 1.6 hours, collecting copper nanoparticles by centrifugation and dispersing them in ethanol, adding 0.5g / L CTAB solution by mass of 33% by mass of the CuCl2 solution and ultrasonicating, dispersing the ultrasonicated copper nanoparticles in 0.05MAgNO3 solution by mass of 113% by mass of the CuCl2 solution, adjusting the temperature to 44°C, adding 56% ascorbic acid solution by mass of the CuCl2 solution and fully reacting for 2.6 hours, filtering and washing, and then placing at 66°C for vacuum drying for 13.2 hours to obtain a silver-coated copper powder;

[0092] Step S3, adding silver-coated copper powder, nanosilver and bismuth oxide to an organic carrier in sequence, wherein the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8, the mass of the nanosilver is 1.6% of the mass of the silver-coated copper powder, and the mass of the bismuth oxide is 1.3% of the mass of the silver-coated copper powder, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0093] Figure 1 TEM image of the silver-coated copper powder prepared in this example; Figure 2 This is the HRTEM image of the silver-coated copper powder prepared in this example, in which the contact interface between silver and copper can be clearly seen.

[0094] Example 2

[0095] This embodiment provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, and the preparation method specifically comprises the following steps:

[0096] Step A1, heating the phenolic resin to 112° C., adding bisphenol A in an amount of 35% by weight of the phenolic resin, stirring evenly, adding 11wt.% sodium hydroxide solution to adjust the pH to 8.5, adding 21wt.% formaldehyde solution in an amount of 42% by weight of the phenolic resin to fully react for 2.2h, adding dimethylethanolamine in an amount of 3.5% by weight of the phenolic resin, continuing the reaction for 40min, cooling to 95° C., adding methyl isobutyl ketone in an amount of 42% by weight of the phenolic resin, stirring evenly to obtain a modified phenolic resin;

[0097] Step A2, under a nitrogen atmosphere, the epoxy acrylate is heated to 112°C, 42% of KF-6001 by weight of the epoxy acrylate is added and stirred evenly, and then 5.9% of hexamethyldisilazane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 2.5 hours, and the temperature is lowered to 92°C, 8.4% of γ-methacryloxypropyltrimethoxysilane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 1.5 hours, and then 14% of glycidyl methacrylate by weight of the epoxy acrylate is added, and the reaction is continued for 1.8 hours, 2.4% of benzoyl peroxide by weight of the epoxy acrylate is added, and 42% of methyl isobutyl ketone by weight of the epoxy acrylate is added, and the mixture is stirred evenly to obtain silicone-modified epoxy acrylate;

[0098] Step A3, heating polyethylene glycol monomethyl ether to 85°C, adding succinic anhydride in an amount of 25% by weight of polyethylene glycol monomethyl ether, raising the temperature to 115°C and fully reacting for 2.5h, cooling to 95°C, sequentially adding N-hydroxymethyl acrylamide in an amount of 18% by weight of polyethylene glycol monomethyl ether and triethylenetetramine in an amount of 3% by weight of polyethylene glycol monomethyl ether, and continuing to react for 1.5h, adding epoxy linseed oil in an amount of 7% by weight of polyethylene glycol monomethyl ether, and continuing to react for 1.5h, then adding glycidyl methacrylate in an amount of 12% by weight of polyethylene glycol monomethyl ether, and continuing to react for 1.5h, adjusting the temperature to 75°C, adding dimethylacetamide in an amount of 25% by weight of polyethylene glycol monomethyl ether, and stirring evenly to obtain modified polyethylene glycol monomethyl ether;

[0099] Step S1, under nitrogen atmosphere, ethyl cellulose is dispersed in pentaerythritol, the mass ratio of ethyl cellulose to pentaerythritol is 3.2:1, the temperature is raised to 135°C, maleic anhydride of 25% by mass of ethyl cellulose is added, the temperature is raised to 155°C, the reaction is fully carried out for 3.5h, the temperature is adjusted to 75°C, 2-ethyl-4-methylimidazole of 18% by mass of ethyl cellulose, 12% of modified phenolic resin and 6% of diisopropylbenzene peroxide are added in sequence, and stirred evenly, and then the mixture is stirred at room temperature. Add 17% of ethyl cellulose mass of organosilicon-modified epoxy acrylate, 9% of N-vinyl pyrrolidone, 12% of silane coupling agent mixture, 4% of titanate coupling agent NDZ-201, 12.9% of modified polyethylene glycol monomethyl ether, 4.0% of carboxylated polyamide wax BYK-410, 3.9% of organic bentonite Garamite-7305 and 4.0% of dispersant BYK-2152, stir well to obtain an organic carrier;

[0100] Step S2, adding 1.3% PVP by mass of the CuCl2 solution and 1.0% sodium citrate by mass of the CuCl2 solution to a 0.1M CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 5.0, adding a 0.2M ascorbic acid solution by mass of 50% by mass of the CuCl2 solution, heating to 70°C and stirring in a water bath for 1.0h, collecting copper nanoparticles by centrifugation and dispersing them in ethanol, adding a 0.5g / L CTAB solution by mass of 38% by mass of the CuCl2 solution and ultrasonicating, dispersing the ultrasonicated copper nanoparticles in a 0.05M AgNO3 solution by mass of 110% by mass of the CuCl2 solution, adjusting the temperature to 49°C, adding an ascorbic acid solution by mass of 50% by mass of the CuCl2 solution and fully reacting for 2.0h, filtering and washing, and then placing at 63°C for vacuum drying for 12.7h to obtain a silver-coated copper powder;

[0101] Step S3, adding silver-coated copper powder, nanosilver and bismuth oxide to an organic carrier in sequence, wherein the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8, the mass of the nanosilver is 1.2% of the mass of the silver-coated copper powder, and the mass of the bismuth oxide is 2.0% of the mass of the silver-coated copper powder, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0102] Example 3

[0103] This embodiment provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, and the preparation method specifically comprises the following steps:

[0104] Step A1, heating the phenolic resin to 117° C., adding bisphenol A in an amount of 38% by weight of the phenolic resin, stirring evenly, adding 13wt.% sodium hydroxide solution to adjust the pH to 8.7, adding 24wt.% formaldehyde solution in an amount of 48% by weight of the phenolic resin to fully react for 2.8h, adding dimethylethanolamine in an amount of 4.5% by weight of the phenolic resin, continuing the reaction for 50min, cooling to 93° C., adding methyl isobutyl ketone in an amount of 47% by weight of the phenolic resin, stirring evenly to obtain a modified phenolic resin;

[0105] Step A2, under a nitrogen atmosphere, the epoxy acrylate is heated to 117°C, 45% of KF-6001 by weight of the epoxy acrylate is added and stirred evenly, and then 6.6% of hexamethyldisilazane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 3.0 hours, and the temperature is lowered to 95°C, 9.1% of γ-methacryloxypropyltrimethoxysilane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 2.0 hours, and then 12% of glycidyl methacrylate by weight of the epoxy acrylate is added, and the reaction is continued for 1.5 hours, 2.6% of benzoyl peroxide by weight of the epoxy acrylate is added, and 49% of methyl isobutyl ketone by weight of the epoxy acrylate is added, and the mixture is stirred evenly to obtain silicone-modified epoxy acrylate;

[0106] Step A3, heating polyethylene glycol monomethyl ether to 90°C, adding succinic anhydride in an amount of 30% by weight of polyethylene glycol monomethyl ether, raising the temperature to 120°C and fully reacting for 3h, cooling to 100°C, sequentially adding N-hydroxymethyl acrylamide in an amount of 20% by weight of polyethylene glycol monomethyl ether and triethylenetetramine in an amount of 4% by weight of polyethylene glycol monomethyl ether, and continuing to react for 2h, adding epoxy linseed oil in an amount of 10% by weight of polyethylene glycol monomethyl ether, and continuing to react for 2h, then adding glycidyl methacrylate in an amount of 15% by weight of polyethylene glycol monomethyl ether, and continuing to react for 2h, adjusting the temperature to 80°C, adding dimethylacetamide in an amount of 30% by weight of polyethylene glycol monomethyl ether, and stirring evenly to obtain modified polyethylene glycol monomethyl ether;

[0107] Step S1, under nitrogen atmosphere, ethyl cellulose is dispersed in pentaerythritol, the mass ratio of ethyl cellulose to pentaerythritol is 3.8:1, the temperature is raised to 140°C, 30% of maleic anhydride by mass of ethyl cellulose is added, the temperature is raised to 160°C, the reaction is fully carried out for 4 hours, the temperature is adjusted to 80°C, 20% of 2-ethyl-4-methylimidazole by mass of ethyl cellulose, 15% of modified phenolic resin and 7% of diisopropylbenzene peroxide are added in sequence, and stirred evenly, and then added in sequence Add 20% of ethyl cellulose by mass of organosilicon-modified epoxy acrylate, 10% of N-vinyl pyrrolidone, 15% of silane coupling agent mixture, 5% of titanate coupling agent NDZ-201, 14.6% of modified polyethylene glycol monomethyl ether, 5.0% of carboxylated polyamide wax BYK-410, 4.7% of organic bentonite Garamite-7305 and 3.2% of dispersant BYK-2152, and stir evenly to obtain an organic carrier;

[0108] Step S2, adding 1.0% PVP by mass of the CuCl2 solution and 0.77% sodium citrate by mass of the CuCl2 solution to a 0.1M CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4.6, adding 0.2M ascorbic acid solution by mass of 53% by mass of the CuCl2 solution, heating to 67°C and stirring in a water bath for 1.4 hours, collecting copper nanoparticles by centrifugation and dispersing them in ethanol, adding 0.5g / L CTAB solution by mass of 40% by mass of the CuCl2 solution and ultrasonicating, dispersing the ultrasonicated copper nanoparticles in 0.05MAgNO3 solution by mass of 118% by mass of the CuCl2 solution, adjusting the temperature to 50°C, adding 53% ascorbic acid solution by mass of the CuCl2 solution and fully reacting for 2.4 hours, filtering and washing, and then placing at 60°C for vacuum drying for 12.4 hours to obtain a silver-coated copper powder;

[0109] Step S3, adding silver-coated copper powder, nanosilver and bismuth oxide to an organic carrier in sequence, wherein the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8, the mass of the nanosilver is 2.0% of the mass of the silver-coated copper powder, and the mass of the bismuth oxide is 1.5% of the mass of the silver-coated copper powder, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0110] Example 4

[0111] This embodiment provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, and the preparation method specifically comprises the following steps:

[0112] Step A1, heating the phenolic resin to 116° C., adding bisphenol A in an amount of 30% by weight of the phenolic resin, stirring evenly, adding 14wt.% sodium hydroxide solution to adjust the pH to 8.4, adding 23wt.% formaldehyde solution in an amount of 40% by weight of the phenolic resin to fully react for 3 hours, adding 3% by weight of dimethylethanolamine to react for 35 minutes, cooling to 98° C., adding 40% by weight of methyl isobutyl ketone to react evenly to obtain a modified phenolic resin;

[0113] Step A2, under a nitrogen atmosphere, the epoxy acrylate is heated to 116°C, 48% of KF-6001 by weight of the epoxy acrylate is added and stirred evenly, and then 6.2% of hexamethyldisilazane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 2.2 hours, and the temperature is lowered to 97°C, 9.6% of γ-methacryloxypropyltrimethoxysilane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 1.8 hours, and then 11% of glycidyl methacrylate by weight of the epoxy acrylate is added, and the reaction is continued for 1.3 hours, 2.1% of benzoyl peroxide by weight of the epoxy acrylate is added, and 43% of methyl isobutyl ketone by weight of the epoxy acrylate is added, and the mixture is stirred evenly to obtain silicone-modified epoxy acrylate;

[0114] Step A3, heating polyethylene glycol monomethyl ether to 88°C, adding succinic anhydride in an amount of 22% by weight of polyethylene glycol monomethyl ether, raising the temperature to 112°C and fully reacting for 2.2h, cooling to 92°C, sequentially adding N-hydroxymethyl acrylamide in an amount of 16% by weight of polyethylene glycol monomethyl ether and triethylenetetramine in an amount of 3.5% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.2h, adding epoxy linseed oil in an amount of 6% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.3h, then adding glycidyl methacrylate in an amount of 11% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.4h, adjusting the temperature to 72°C, adding dimethylacetamide in an amount of 22% by weight of polyethylene glycol monomethyl ether, and stirring evenly to obtain modified polyethylene glycol monomethyl ether;

[0115] Step S1, under nitrogen atmosphere, ethyl cellulose is dispersed in pentaerythritol, the mass ratio of ethyl cellulose to pentaerythritol is 3.4:1, the temperature is raised to 132°C, maleic anhydride (22% by mass of ethyl cellulose) is added, the temperature is raised to 152°C, the reaction is fully carried out for 3.2h, the temperature is adjusted to 72°C, 2-ethyl-4-methylimidazole (16% by mass of ethyl cellulose), 11% of modified phenolic resin and 5.5% of diisopropylbenzene peroxide are added in sequence, stirred evenly, and then Add 16% of ethyl cellulose by mass of organosilicon-modified epoxy acrylate, 8.5% of N-vinyl pyrrolidone, 11% of a silane coupling agent mixture, 3.5% of a titanate coupling agent NDZ-201, 13.7% of modified polyethylene glycol monomethyl ether, 3.0% of a carboxylated polyamide wax BYK-410, 4.1% of an organic bentonite Garamite-7305 and 4.8% of a dispersant BYK-2152, and stir evenly to obtain an organic carrier;

[0116] Step S2, adding 1.6% PVP by mass of the CuCl2 solution and 0.63% sodium citrate by mass of the CuCl2 solution to a 0.1M CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4.1, adding 0.2M ascorbic acid solution by mass of 54% by mass of the CuCl2 solution, heating to 62°C and stirring in a water bath for 2.0h, collecting copper nanoparticles by centrifugation and dispersing them in ethanol, adding 0.5g / L CTAB solution by mass of 36% by mass of the CuCl2 solution and ultrasonicating, dispersing the ultrasonicated copper nanoparticles in 0.05MAgNO3 solution by mass of 115% by mass of the CuCl2 solution, adjusting the temperature to 42°C, adding 51% ascorbic acid solution by mass of the CuCl2 solution and fully reacting for 2.8h, filtering and washing, and then placing under vacuum at 70°C for 14.0h to obtain a silver-coated copper powder;

[0117] Step S3, adding silver-coated copper powder, nanosilver and bismuth oxide to an organic carrier in sequence, wherein the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8, the mass of the nanosilver is 1.0% of the mass of the silver-coated copper powder, and the mass of the bismuth oxide is 1.7% of the mass of the silver-coated copper powder, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0118] Example 5

[0119] This embodiment provides a method for preparing a low-temperature curing silver-coated copper slurry for a heterojunction solar cell, and the preparation method specifically comprises the following steps:

[0120] Step A1, heating the phenolic resin to 113° C., adding bisphenol A in an amount of 37% by weight of the phenolic resin, stirring evenly, adding 10wt.% sodium hydroxide solution to adjust the pH to 8.3, adding 20wt.% formaldehyde solution in an amount of 46% by weight of the phenolic resin to fully react for 2.7 hours, adding dimethylethanolamine in an amount of 4.2% by weight of the phenolic resin, continuing the reaction for 55 minutes, cooling to 97° C., adding methyl isobutyl ketone in an amount of 43% by weight of the phenolic resin, stirring evenly to obtain a modified phenolic resin;

[0121] Step A2, under a nitrogen atmosphere, the epoxy acrylate is heated to 113°C, 50% of KF-6001 by weight of the epoxy acrylate is added and stirred evenly, and then 7.0% of hexamethyldisilazane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 2.8 hours, and the temperature is lowered to 99°C, 10.0% of γ-methacryloxypropyltrimethoxysilane by weight of the epoxy acrylate is added, and the reaction is fully carried out for 1.2 hours, and then 10% of glycidyl methacrylate by weight of the epoxy acrylate is added, and the reaction is continued for 2.0 hours, 3.0% of benzoyl peroxide by weight of the epoxy acrylate is added, and 50% of methyl isobutyl ketone by weight of the epoxy acrylate is added, and the reaction is uniformly carried out to obtain silicone-modified epoxy acrylate;

[0122] Step A3, heating polyethylene glycol monomethyl ether to 82°C, adding succinic anhydride in an amount of 28% by weight of polyethylene glycol monomethyl ether, raising the temperature to 118°C and fully reacting for 2.8h, cooling to 98°C, sequentially adding N-hydroxymethyl acrylamide in an amount of 19% by weight of polyethylene glycol monomethyl ether and triethylenetetramine in an amount of 5% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.8h, adding epoxy linseed oil in an amount of 8% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.7h, then adding glycidyl methacrylate in an amount of 14% by weight of polyethylene glycol monomethyl ether, and continuing the reaction for 1.6h, adjusting the temperature to 78°C, adding dimethylacetamide in an amount of 27% by weight of polyethylene glycol monomethyl ether, and stirring evenly to obtain modified polyethylene glycol monomethyl ether;

[0123] Step S1, under nitrogen atmosphere, ethyl cellulose is dispersed in pentaerythritol, the mass ratio of ethyl cellulose to pentaerythritol is 4:1, the temperature is raised to 138°C, maleic anhydride (28% by mass of ethyl cellulose) is added, the temperature is raised to 158°C, the reaction is fully carried out for 3.8h, the temperature is adjusted to 78°C, 2-ethyl-4-methylimidazole (19% by mass of ethyl cellulose), 14% of modified phenolic resin and 6.5% of diisopropylbenzene peroxide are added in sequence, and stirred evenly, and then added in sequence Add 19% of ethyl cellulose by weight of organosilicon-modified epoxy acrylate, 9.5% of N-vinyl pyrrolidone, 14% of a silane coupling agent mixture, 4.5% of a titanate coupling agent NDZ-201, 15.0% of a modified polyethylene glycol monomethyl ether, 4.6% of a carboxylated polyamide wax BYK-410, 5.0% of an organic bentonite Garamite-7305 and 3.6% of a dispersant BYK-2152, and stir evenly to obtain an organic carrier;

[0124] Step S2, adding 2.0% PVP by mass of the CuCl2 solution and 0.52% sodium citrate by mass of the CuCl2 solution to a 0.1M CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4.4, adding 0.2M ascorbic acid solution by mass of 60% of the CuCl2 solution, heating to 68°C and stirring in a water bath for 1.7h, collecting copper nanoparticles by centrifugation and dispersing them in ethanol, adding 0.5g / L CTAB solution by mass of 0% of the CuCl2 solution and ultrasonicating, dispersing the ultrasonicated copper nanoparticles in 0.05MAgNO3 solution by mass of 120% of the CuCl2 solution, adjusting the temperature to 40°C, adding 60% ascorbic acid solution by mass of the CuCl2 solution and fully reacting for 3.0h, filtering and washing, and then placing at 64°C for vacuum drying for 13.8h to obtain a silver-coated copper powder;

[0125] Step S3, adding silver-coated copper powder, nanosilver and bismuth oxide to an organic carrier in sequence, wherein the mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8, the mass of the nanosilver is 1.4% of the mass of the silver-coated copper powder, and the mass of the bismuth oxide is 1.0% of the mass of the silver-coated copper powder, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

[0126] Comparative Example 1

[0127] This comparative example provides a method for preparing a low-temperature cured silver-coated copper slurry for heterojunction solar cells. The difference from Example 1 is that the mass of N-hydroxymethyl acrylamide in step A3 is 25% of the mass of polyethylene glycol monomethyl ether, which is 10% higher than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0128] Comparative Example 2

[0129] This comparative example provides a method for preparing a low-temperature cured silver-coated copper slurry for heterojunction solar cells. The difference from Example 1 is that the mass of N-hydroxymethyl acrylamide in step A3 is 5% of the mass of polyethylene glycol monomethyl ether, which is 10% less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0130] Comparative Example 3

[0131] This comparative example provides a method for preparing a low-temperature cured silver-coated copper slurry for heterojunction solar cells. The difference from Example 1 is that the mass fraction of maleic anhydride in step S1 is adjusted to 35%, which is an increase of 15% compared with Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0132] Comparative Example 4

[0133] This comparative example provides a method for preparing a low-temperature cured silver-coated copper slurry for heterojunction solar cells. The difference from Example 1 is that the mass fraction of maleic anhydride in step S1 is adjusted to 5%, which is 15% less than that in Example 1, and the other process parameters and operating conditions are exactly the same as those in Example 1.

[0134] The adhesion test standard of the slurry in the present invention is GB / T 17473.4-2008; the square resistance test standard is GB / T17473.3-2008; the heat aging test standard is: the prepared slurry is placed at 70±2°C for 240 hours, and its square resistance change is tested. The test results are shown in Table 1.

[0135] Table 1 Test results of low temperature curing silver-coated copper paste for heterojunction solar cells prepared in Examples 1-5 and Comparative Examples 1-4

[0136]

[0137] It can be seen from the data in the table that, compared with Example 1, the adhesion, square resistance and heat aging test of Comparative Example 1 are all worse than those of Example 1; the adhesion, square resistance and heat aging test of Comparative Example 2 are all worse than those of Example 1. This is because, in Comparative Example 1, N-hydroxymethyl acrylamide is excessive, the cross-linking density is too high, the matrix material loses sufficient toughness after curing, and the volatile by-products released during the curing process may produce micropores or cracks, destroying the close contact between the conductive fillers, resulting in discontinuous conductive paths and increased square resistance. Materials with high cross-linking density are more likely to cause microcracks due to stress concentration under long-term heat aging conditions, and the square resistance fluctuates greatly. Therefore, the adhesion, square resistance and heat aging test of Comparative Example 1 are all worse than those of Example 1. In Comparative Example 2, N-hydroxymethyl acrylamide is insufficient, the cross-linking reaction points are reduced, and a complete three-dimensional network structure cannot be formed. The mechanical strength and bonding force of the matrix material are reduced. Due to the insufficient mechanical stability of the matrix, the conductive network is easily displaced or broken under external force or environmental stress, resulting in an increase in the square resistance value. Due to the low mechanical strength of the matrix material, material flow or surface shrinkage is likely to occur during the thermal aging process, destroying the continuity of the conductive network, resulting in a large fluctuation in the square resistance value. Therefore, the adhesion, square resistance and heat aging resistance tests of Comparative Example 2 are all worse than those of Example 1.

[0138] It can be seen from the data in the table that, compared with Example 1, the adhesion, square resistance and heat aging test of Comparative Example 3 are all worse than those of Example 1; the adhesion, square resistance and heat aging test of Comparative Example 4 are all worse than those of Example 1. In Comparative Example 3, the anhydride group in maleic anhydride reacts with the hydroxyl group of ethyl cellulose for esterification, and its double bond can participate in chain growth or react with other groups to form a cured network with high cross-linking density. Too much maleic anhydride will reduce the flexibility of the matrix material, and the generated network structure is too rigid. It is difficult for the conductive filler to form a dense conductive path in the matrix, and microcracks are prone to occur during the thermal aging process, destroying the continuity of the conductive network. Therefore, the adhesion, square resistance and heat aging test of Comparative Example 3 are all worse than those of Example 1. In Comparative Example 4, maleic anhydride is insufficient, resulting in low mechanical strength of the base material. After curing, the material is easily broken or peeled off under external force. The insufficient mechanical strength makes the conductive path easy to break under external force or environmental stress, and the square resistance value fluctuates greatly during use. Therefore, the adhesion, square resistance value and heat aging resistance test of Comparative Example 4 are worse than those of Example 1.

[0139] The above description is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells, characterized in that: The preparation method is: Step S1, under a nitrogen atmosphere, dispersing ethyl cellulose in pentaerythritol, raising the temperature to a first temperature, adding maleic anhydride, raising the temperature to a second temperature, fully reacting, adjusting the temperature to a third temperature, sequentially adding 2-ethyl-4-methylimidazole, modified phenolic resin and diisopropylbenzene peroxide and stirring evenly, then sequentially adding organosilicon-modified epoxy acrylate, N-vinyl pyrrolidone, a silane coupling agent mixture, a titanate coupling agent, a modified polyethylene glycol monomethyl ether, a carboxylated polyamide wax, an organic bentonite, and a dispersant, stirring evenly to obtain an organic carrier; Step S2, adding PVP and sodium citrate to the CuCl2 solution in sequence, stirring and dissolving, adjusting the pH to 4-5, adding ascorbic acid solution, heating to a fourth temperature and stirring in a water bath, centrifuging and collecting copper nanoparticles and dispersing them in ethanol, adding CTAB solution for ultrasonication, dispersing the ultrasonicated copper nanoparticles in an AgNO3 solution, adjusting the temperature to a fifth temperature, adding ascorbic acid solution for sufficient reaction, filtering and washing, and then placing under vacuum drying at a fourth temperature to obtain a silver-coated copper powder; Step S3, adding silver-coated copper powder, nano silver and bismuth oxide to an organic carrier in sequence, and stirring evenly to obtain a low-temperature curing silver-coated copper slurry for heterojunction solar cells.

2. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 1, characterized in that: The preparation method of the modified phenolic resin, silicone-modified epoxy acrylate and modified polyethylene glycol monomethyl ether is as follows: Step A1, heating the phenolic resin to a sixth temperature, adding bisphenol A, stirring evenly, adding sodium hydroxide solution to adjust to a target pH, adding formaldehyde solution to fully react, adding dimethylethanolamine, continuing the reaction, cooling to a seventh temperature, adding methyl isobutyl ketone, stirring evenly to obtain a modified phenolic resin; Step A2, under a nitrogen atmosphere, heating the epoxy acrylate to a sixth temperature, adding hydroxyl-terminated silicone oil and stirring evenly, then adding hexamethyldisilazane, fully reacting, cooling to a seventh temperature, adding γ-methacryloxypropyltrimethoxysilane, fully reacting, then adding glycidyl methacrylate, continuing to react, adding benzoyl peroxide, adding methyl isobutyl ketone, stirring evenly to obtain silicone-modified epoxy acrylate; Step A3, heating polyethylene glycol monomethyl ether to an eighth temperature, adding succinic anhydride, raising the temperature to a sixth temperature for sufficient reaction, cooling to a seventh temperature, sequentially adding N-hydroxymethyl acrylamide and triethylenetetramine to continue the reaction, adding epoxy linseed oil to continue the reaction, then adding glycidyl methacrylate to continue the reaction, adjusting the temperature to a ninth temperature, adding dimethylacetamide, and stirring evenly to obtain modified polyethylene glycol monomethyl ether.

3. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 1, characterized in that: In step S1, The mass ratio of ethyl cellulose to pentaerythritol is (3-4): 1; The first temperature is 130-140°C; The mass of the maleic anhydride is 20-30% of the mass of the ethyl cellulose; The second temperature is 150-160°C; The reaction time of the second temperature is 3-4h; The third temperature is 70-80°C; The mass of the 2-ethyl-4-methylimidazole is 15-20% of the mass of the ethyl cellulose; The mass of the modified phenolic resin is 10-15% of the mass of ethyl cellulose; The mass of the dicumyl peroxide is 5-8% of the mass of the ethyl cellulose; The mass of the organosilicon-modified epoxy acrylate is 15-20% of the mass of the ethyl cellulose; The mass of the N-vinyl pyrrolidone is 8-10% of the mass of the ethyl cellulose; The silane coupling agent mixture is KH550 and KH560, the mass ratio is 1:1, and the mass of the silane coupling agent mixture is 10-15% of the mass of ethyl cellulose; The titanate coupling agent is NDZ-201, and its mass is 3-5% of the mass of ethyl cellulose; The mass of the modified polyethylene glycol monomethyl ether is 10-15% of the mass of ethyl cellulose; The carboxylated polyamide wax is BYK-410, and its mass is 3-5% of the mass of ethyl cellulose; The organic bentonite is Garamite-7305, and its mass is 3-5% of the mass of ethyl cellulose; The dispersant is BYK-2152, and its mass is 3-5% of the mass of ethyl cellulose.

4. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 1, characterized in that: In step S2, The concentration of the CuCl2 solution is 0.1M; The mass of the PVP is 1-2% of the mass of the CuCl2 solution; The mass of the sodium citrate is 0.5-1% of the mass of the CuCl2 solution; The concentration of the ascorbic acid solution is 0.2M, and the mass is 50-60% of the mass of the CuCl2 solution; The fourth temperature is 60-70°C; The stirring time in the water bath is 1-2h.

5. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 1, characterized in that: In step S2, The concentration of the CTAB solution is 0.5 g / L, and the mass is 30-40% of the mass of the CuCl2 solution; The concentration of the AgNO3 solution is 0.05M, and the mass is 110-120% of the mass of the CuCl2 solution; The fifth temperature is 40-50°C; The mass of the ascorbic acid solution added at the fifth temperature is 50-60% of the mass of the CuCl2 solution; The reaction time of the fifth temperature is 2-3h; The vacuum drying time is 12-14 hours.

6. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 1, characterized in that: In step S3, The mass ratio of the silver-coated copper powder to the organic carrier is 1:0.8; The mass of the nano silver is 1-2% of the mass of the silver-coated copper powder; The mass of the bismuth oxide is 1-2% of the mass of the silver-coated copper powder.

7. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 2, characterized in that: In step A1, The sixth temperature is 110-120° C. The mass of the bisphenol A is 30-40% of the mass of the phenolic resin; The mass fraction of the sodium hydroxide solution is 10-15wt.%; The target pH is 8-9; The mass fraction of the formaldehyde solution is 20-25wt.%; The mass of the formaldehyde solution is 40-50% of the mass of the phenolic resin; The reaction time after adding the formaldehyde solution is 2-3h; The mass of the dimethylethanolamine is 3-5% of the mass of the phenolic resin; The reaction time after adding dimethylethanolamine is 30-60min; The seventh temperature is 90-100° C. The mass of the methyl isobutyl ketone is 40-50% of the mass of the phenolic resin.

8. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 2, characterized in that: In step A2, The terminal hydroxyl silicone oil is KF-6001, and its mass is 40-50% of the mass of epoxy acrylate; The mass of the hexamethyldisilazane is 5-7% of the mass of the epoxy acrylate; The reaction time after adding hexamethyldisilazane is 2-3h; The mass of the γ-methacryloxypropyltrimethoxysilane is 8-10% of the mass of the epoxy acrylate; The reaction time after adding γ-methacryloxypropyltrimethoxysilane is 1-2h; The mass of the glycidyl methacrylate is 10-15% of the mass of the epoxy acrylate; The reaction time after adding glycidyl methacrylate is 1-2h; The mass of the benzoyl peroxide is 2-3% of the mass of the epoxy acrylate; The mass of the methyl isobutyl ketone is 40-50% of the mass of the epoxy acrylate.

9. The method for preparing a low-temperature curing silver-coated copper slurry for heterojunction solar cells according to claim 2, characterized in that: In step A3, The eighth temperature is 80-90° C. The mass of the succinic anhydride is 20-30% of the mass of polyethylene glycol monomethyl ether; The reaction time after adding succinic anhydride is 2-3h; The mass of the N-hydroxymethyl acrylamide is 15-20% of the mass of polyethylene glycol monomethyl ether; The mass of the triethylenetetramine is 2-5% of the mass of polyethylene glycol monomethyl ether; The reaction time after adding triethylenetetramine is 1-2h; The mass of the epoxidized linseed oil is 5-10% of the mass of polyethylene glycol monomethyl ether; The mass of the glycidyl methacrylate is 10-15% of the mass of polyethylene glycol monomethyl ether; The reaction time after adding glycidyl methacrylate is 1-2h; The ninth temperature is 70-80°C; The mass of the dimethylacetamide is 20-30% of the mass of polyethylene glycol monomethyl ether.

10. A low-temperature curing silver-coated copper slurry for heterojunction solar cells obtained according to the preparation method according to any one of claims 1 to 9.

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