Silver carbon paste for heterojunction cells and use thereof

Abstract

This invention relates to the field of battery technology, specifically to a silver-carbon paste for heterojunction batteries and its application. This silver-carbon paste for heterojunction batteries comprises at least a silver-based conductive material and carbon nanotubes, wherein the carbon nanotubes have defects. By employing defective carbon nanotubes, this invention increases the adhesion sites of the silver-based conductive material on the carbon nanotubes, enhancing the adhesion between the silver-based conductive material and the carbon nanotubes. By increasing the filling of the silver-based conductive material within the carbon nanotubes, the conductivity is improved with the same amount of carbon nanotubes, thereby addressing the problem that the addition of carbon materials significantly increases the battery's contact resistance and series connection, leading to a significant decrease in battery efficiency.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a silver-carbon paste for heterojunction batteries and its application. Background Technology

[0002] Heterojunction (HJT) solar cells are a hybrid solar cell technology that uses amorphous silicon and crystalline silicon materials. Due to their high efficiency and low degradation, HJT cells are considered one of the future development directions of the photovoltaic industry. The silver content in the conductive silver paste used in heterojunction solar cells is generally above 85%. With the continuous rise in international silver prices, the price of silver paste has increased, raising the metallization cost of heterojunction cells. Current technologies typically reduce cell production costs by adding carbon materials such as carbon black and graphite; however, the addition of carbon materials significantly increases the cell's contact resistance and series resistance, thereby significantly reducing cell efficiency. Summary of the Invention

[0003] Based on this, the present invention provides a novel silver-carbon paste for heterojunctions. By employing defective carbon nanotubes, this silver-carbon paste exhibits better conductivity and lower resistance under the same carbon material addition amount, thereby effectively improving the problem that the addition of carbon materials significantly increases the contact resistance and series connection of the battery, thus significantly reducing the battery efficiency.

[0004] A first aspect of the present invention provides a silver-carbon paste for heterojunction batteries, comprising at least a silver-based conductive material and carbon nanotubes, wherein the carbon nanotubes have defects on their walls.

[0005] According to one embodiment of the present invention, the defect is a structural defect and / or a mechanical damage defect.

[0006] According to one embodiment of the present invention, the structural defect includes one or both of topological defects and vacancy defects; the mechanical damage defect includes one or both of lattice distortion and fracture.

[0007] According to one embodiment of the present invention, the defect is generated by physical treatment of carbon nanotubes.

[0008] According to one embodiment of the present invention, the physical treatment is grinding, the grinding frequency is 10-30Hz, and the grinding time is 5-30min.

[0009] According to one embodiment of the present invention, the carbon nanotube is a multi-walled carbon nanotube.

[0010] According to one embodiment of the present invention, the carbon nanotubes account for 5-10% of the total mass of the slurry, and the silver-based conductive material accounts for 60-80% of the total mass of the slurry.

[0011] According to one embodiment of the present invention, the silver-based conductive material is nano-silver powder.

[0012] According to one embodiment of the present invention, the nano silver powder includes spherical silver powder and flake silver powder, wherein the ratio of spherical silver powder to flake silver powder is (1:2) to (1:1).

[0013] According to one embodiment of the present invention, the silver-carbon paste further includes Mxene material, wherein the Mxene material accounts for 0.2-1% of the total mass of the paste.

[0014] According to one embodiment of the present invention, the silver-carbon paste further includes a binder, the binder accounting for 3-10% of the total mass of the paste.

[0015] According to one embodiment of the present invention, the silver-carbon paste further includes an additive, which accounts for 0.5-5% of the total mass of the paste.

[0016] According to one embodiment of the present invention, the silver-carbon paste further includes a solvent, the solvent accounting for 2-10% of the total mass of the paste.

[0017] According to one embodiment of the present invention, the binder is a resin; and / or the additive is one or more of a thixotropic agent, dispersant, plasticizer, curing agent, and defoamer; and / or the solvent is an organic solvent.

[0018] According to one embodiment of the present invention, the resin is one or more of epoxy resin, polyester resin, polyurethane resin, phenolic resin, and acrylic resin; and / or the thixotropic agent is one or more of hydrogenated castor oil, bentonite, or polyamide wax; and / or the dispersant is one or more of lauryl polyoxyethylene ether, sodium dodecylbenzene sulfonate, lauryl glucoside, and octadecylamine polyoxyethylene ether; and / or the plasticizer is one or more of tributyl citrate, phthalate, glyceryl stearate, and tributyl phosphate; and / or the curing agent is one or more of anhydride curing agents, isocyanate curing agents, and imidazole curing agents; and / or the defoamer is one or more of tributyl phosphate and lecithin; and / or the solvent is one or more of ethylene glycol ethyl ether acetate, terpineol, dibutyl phthalate, divalent ester, diethylene glycol butyl ether acetate, dimethyl adipate, and succinic acid.

[0019] According to one embodiment of the present invention, the anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride; and / or the isocyanate curing agent is one or more of polyisocyanate, triisocyanate, hexamethylene diisocyanate, or diphenylmethane isocyanate; and / or the imidazole curing agent is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, or 2-ethylimidazole.

[0020] A second aspect of the present invention provides a grid line prepared from the above-described silver-carbon paste for heterojunction solar cells.

[0021] A third aspect of the present invention provides a heterojunction battery having the above-described grid lines on its surface.

[0022] A fourth aspect of the present invention provides a power generation device including the heterojunction cell described above.

[0023] This invention utilizes defective carbon nanotubes, which provide more silver attachment sites, enhancing the adhesion between silver and carbon nanotubes. This effectively increases the filling of silver nanoparticles within the carbon nanotubes, resulting in lower resistance and better conductivity in the slurry with the same amount of carbon nanotubes added, thereby improving battery efficiency. Attached Figure Description

[0024] Figure 1 This is a structural diagram of a heterojunction battery provided by the present invention.

[0025] Figure labeling: 1 Single crystal silicon substrate, 2 Intrinsic hydrogenated amorphous silicon thin film, 31 n-type amorphous silicon thin film, 32 p-type amorphous silicon thin film, 4 ITO transparent conductive thin film, 5 Metal electrode. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] The present invention provides a silver-carbon paste for heterojunction batteries, comprising at least a silver-based conductive material and carbon nanotubes, wherein the carbon nanotubes have defects on their walls.

[0028] This invention employs defective carbon nanotubes, where defects provide more attachment sites for silver-based conductive materials, enhancing the adhesion between the silver-based conductive materials and the carbon nanotubes. By increasing the filling of silver-based conductive materials within the carbon nanotubes, the conductivity is improved with the same amount of carbon nanotubes. This addresses the problem that the addition of carbon materials significantly increases the contact resistance and series connection of the battery, leading to a significant reduction in battery efficiency.

[0029] Carbon nanotubes (CNTs) are one-dimensional nanomaterials with a unique structure, formed by rolling up one or more layers of graphene sheets to create a seamless, hollow tubular structure. CNTs are classified according to the number of wall layers into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). SWCNTs are formed by rolling up a single layer of graphene, while MWCNTs are formed by coaxially rolling up two or more layers of graphene. The type of carbon nanotube used in this invention is not limited; it can be single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture of both, with multi-walled carbon nanotubes being preferred.

[0030] It's easy to understand that the surface of carbon nanotubes is typically smooth, which is unfavorable for the adhesion of silver-based conductive materials. Defects on the surface of carbon nanotubes provide more adhesion sites for silver-based conductive materials, enhancing the adhesion between them. These defects can be generated during the carbon nanotube fabrication process or through post-processing such as physical treatments (e.g., grinding, ultrasonication, stretching, bombardment with high-energy particles), chemical treatments (oxidation, reduction, doping, etching), and plasma treatment. These defects can be one or more of the following: structural defects, chemical defects, mechanical damage defects, and topological defects.

[0031] For example, defects on carbon nanotubes include structural defects and / or mechanical damage defects. Specifically, structural defects include one or both of topological defects and vacancy defects, and mechanical damage defects include one or both of lattice distortion and fracture.

[0032] Topological defects typically involve the presence of non-six-membered rings (such as pentagonal and heptagonal rings) in carbon nanotubes, leading to changes in the shape of the carbon nanotubes. Common topological defects include the Stone-Thrower-Wales (STW) defect, which is equivalent to a C-C bond on the wall of a graphite or perfect carbon nanotube being rotated 90 degrees, forming a pentagonal ring and a heptagonal structure connected together, also known as the "5-77-5 defect".

[0033] A vacancy defect is a defect in a carbon nanotube where one or more carbon atoms are missing from the crystal lattice, causing the surrounding carbon atoms to rearrange to fill the void.

[0034] Mechanical defects: such as bending, twisting, lattice distortion or fracture, which are usually caused by external forces or stress during the manufacturing process.

[0035] In some specific embodiments of the present invention, the defect is generated by physical treatment of carbon nanotubes. For example, this physical treatment is grinding. During grinding, the grinding frequency is controlled to be 10-30Hz, such as 10Hz, 15Hz, 20Hz, 25Hz, 30Hz, or any two of the above values; the grinding time is 5-30min, such as 5min, 10min, 15min, 20min, 25min, 30min, or any two of the above values. Under these conditions, the surface of the carbon nanotubes will develop the aforementioned structural and mechanical defects.

[0036] In this invention, the amount of carbon nanotubes generally accounts for 5-10% of the total mass of the slurry, such as 5%, 6%, 7%, 8%, 9%, 10%, and any range between the two mentioned above. The silver-based conductive material typically accounts for 60-80% of the total mass of the slurry, such as 60%, 65%, 70%, 75%, 80%, and any range between the two mentioned above.

[0037] The silver-based conductive material is primarily composed of nano-silver powder. In some specific embodiments of the present invention, the silver-based conductive material includes spherical silver powder and flake silver powder, with a ratio of (1:2) to (1:1). The spherical silver powders are in point-to-point contact with a relatively small contact area, while the flake silver powders contain a large number of surface-to-surface or surface-to-line contacts with a relatively large contact area. When the two are used in the above ratio, the spherical silver powder can fully fill the gaps between the flake silver powders, allowing previously non-contacting adjacent flake silver powders to come into contact with each other, increasing the conductive path and thus improving conductivity.

[0038] The work function of silver is around 4.26 eV, and that of carbon is around 4.4 eV. However, the work function of the TCO layer on the front side of a heterojunction cell is 3.6-5.0 eV, and that of the TCO layer on the back side is 5.0-6.2 eV. Therefore, silver-carbon paste generally has the problem of being compatible only with the front side of the heterojunction, but not with the TCO layer on the back side, which leads to increased cell resistance and decreased efficiency.

[0039] Further research by the inventors revealed that adding more Mxene material can effectively adjust the work function of the silver-carbon paste, reducing the work function mismatch with the TCO layer on the back side of the heterojunction.

[0040] Mxene materials are two-dimensional layered materials composed of transition metal carbides, nitrides, or carbonitrides. They possess advantages such as metal-like conductivity, excellent chemical stability, low cost, and ease of processing. Their work function is adjustable between 1.44 and 6.0 eV. Therefore, adding Mxene materials can adjust the work function of silver-carbon paste, making it compatible with both the front and back sides of heterojunction cells, thus reducing the cell's contact resistance and series resistance. The specific type of Mxene material used in this invention is not limited; for example, it can be Ti3C2T. x Cr2CT2, etc.

[0041] In this invention, the amount of Mxene material added is usually 0.2-1% of the total mass of the slurry, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. Controlling the amount added within this range can effectively regulate the work function of the slurry.

[0042] Understandably, in order to form a strong bond between the particles in the paste and to ensure the stability of the paste during the printing and curing process, a binder is usually added to the silver-carbon paste.

[0043] In some specific embodiments of the present invention, the adhesive is a resin, such as one or more of epoxy resin, polyester resin, polyurethane resin, phenolic resin, and acrylic resin.

[0044] In some specific embodiments of the present invention, the silver-carbon paste further includes additives to adjust the overall properties of the paste. The additives include one or more of thixotropic agents, dispersants, plasticizers, curing agents, and defoamers.

[0045] For example, the thixotropic agent is one or more of hydrogenated castor oil, bentonite, or polyamide wax; the dispersant is one or more of lauryl alcohol polyoxyethylene ether, sodium dodecylbenzene sulfonate, lauryl glucoside, or octadecylamine polyoxyethylene ether; the plasticizer is one or more of tributyl citrate, phthalate, glyceryl stearate, or tributyl phosphate; the curing agent is one or more of acid anhydride curing agents, isocyanate curing agents, or imidazole curing agents; and the defoamer is one or more of tributyl phosphate or lecithin.

[0046] Furthermore, the anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride; the isocyanate curing agent is one or more of polyisocyanate (such as diisocyanate), triisocyanate, hexamethylene diisocyanate, or diphenylmethane isocyanate; and the imidazole curing agent is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, or 2-ethylimidazole.

[0047] It is easy to understand that the silver-carbon paste also includes a solvent, which is generally an organic solvent. For example, the solvent is one or more of ethylene glycol ethyl ether acetate, terpineol, dibutyl phthalate, divalent ester, diethylene glycol butyl ether acetate, dimethyl adipate, and succinic acid.

[0048] In some specific embodiments of the present invention, the binder accounts for 3-10% of the total mass of the slurry, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values. The additive accounts for 0.5-5% of the total mass of the slurry, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any two of the above values. The solvent accounts for 2-10% of the total mass of the slurry, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values. In these cases, the bulk resistivity of the slurry can be reduced by approximately 0.5-1.5 μΩ·cm, and the battery efficiency can be increased by approximately 0.1-0.3%.

[0049] The preparation of the aforementioned silver-carbon paste can be achieved primarily through the mixing of the various raw materials. In actual preparation, to ensure sufficient dispersion of the raw materials, the binder and a portion of the solvent are typically mixed to prepare an organic carrier, which is then thoroughly mixed with the remaining raw materials. To ensure uniform mixing, grinding can be employed.

[0050] For example, the binder is mixed with all or part of the solvent at a mass ratio of 1:4-5:1, stirred at 30-50℃ for 15-30 minutes to ensure that the binder is fully dispersed, and then mixed with the remaining raw materials and ground evenly to obtain the silver carbon paste.

[0051] Furthermore, when Mxene material is present, the Mxene material is usually first mixed evenly with some dispersant and solvent to prepare a suspension, and then the organic carrier, suspension and other raw materials are blended together.

[0052] For example, Mxene material, solvent, and dispersant are ultrasonically treated at a mass ratio of 1:50:3 - 2:4:1 for 10-40 minutes to obtain a suspension in which Mxene material is fully dispersed. Then, it is mixed with an organic carrier and the remaining raw materials and ground evenly to obtain silver-carbon slurry.

[0053] The present invention also provides a grid line made of the above-mentioned silver-carbon paste for heterojunction solar cells.

[0054] The present invention also provides a photovoltaic cell having the above-described grid lines on its surface.

[0055] The present invention also provides a power generation device, including the aforementioned photovoltaic cell. This power generation device includes photovoltaic power generation equipment, portable photovoltaic power supply equipment, traffic lights, communication base stations, photovoltaic water pumps, etc.

[0056] The present invention will now be described in detail with reference to specific embodiments:

[0057] The raw materials used in the following embodiments were sourced as follows: silver powder: purchased from Jiangsu Boqian New Material Co., Ltd.; carbon nanotubes: purchased from Jiangsu Tiannai Technology Co., Ltd.; Mxene was Ti3C2T. x The following materials were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., item number: 103949; the epoxy resin was model E-51, purchased from Jiangsu Sanmu Group, SM618; terpineol, dibutyl phthalate, hydrogenated castor oil, sodium dodecylbenzene sulfonate, polyethylene glycol, tributyl citrate, 2-methylimidazole, and tributyl phosphate were purchased from Maclean.

[0058] Example 1

[0059] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 1 below:

[0060] Table 1

[0061]

[0062] This silver-carbon paste was prepared by the following method:

[0063] (1) Preparation of defective MWCNTs: MWCNTs were placed in a planetary ball mill and ground at a frequency of 15 Hz for 15 min to obtain defective MWCNTs.

[0064] (2) Mix the binder and organic solvent, and heat and stir for 5 min using a high-speed mixer and a constant temperature water bath to obtain a well mixed organic carrier. The binder is epoxy resin E-51, and the solvent is terpineol and dibutyl phthalate in a mass ratio of 1:1. The amount of solvent used here is 1 wt% of the slurry.

[0065] (3) Mix the MXene material, organic solvent and dispersant, and sonicate for 40 min to form an MXene suspension. MXene is a purchased material with hydroxyl and terminal oxygen groups on its surface. The solvent is terpineol and dibutyl phthalate in a mass ratio of 1:1, and the amount of solvent used here is 1 wt% of the slurry. The dispersant is sodium dodecylbenzenesulfonate, and the amount used is 0.5 wt% of the slurry.

[0066] (4) Mix and stir the MXene suspension, organic carrier, defective MWCNTs, nano silver powder, solvent and additives, use a vacuum degassing machine to mix and degas, and then use a three-roll mill to grind the silver-carbon slurry to obtain a fineness of less than 10 μm. The solvent here is terpineol, with an addition mass fraction of 8wt%, and the additives are thixotropic agents, dispersants, plasticizers, curing agents and defoamers.

[0067] The conductive silver-carbon electrode was prepared by screen printing the silver-carbon paste onto a silicon substrate and curing it at 180°C for 30 min in an air atmosphere.

[0068] Example 2

[0069] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 2 below:

[0070] Table 2

[0071]

[0072] The preparation method of this silver-carbon paste is as described in Example 1.

[0073] Example 3

[0074] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 3 below:

[0075] Table 3

[0076]

[0077] The preparation method of this silver-carbon paste is as described in Example 1.

[0078] Example 4

[0079] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 4 below:

[0080] Table 4

[0081]

[0082] The preparation method of this silver-carbon paste is as described in Example 1.

[0083] Example 5

[0084] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 5 below:

[0085] Table 5

[0086]

[0087] The preparation method of this silver-carbon paste is as described in Example 1.

[0088] Example 6

[0089] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 6 below:

[0090] Table 6

[0091]

[0092] The preparation method of this silver-carbon paste is as described in Example 1.

[0093] Example 7

[0094] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 7 below:

[0095] Table 7

[0096]

[0097] The preparation method of this silver-carbon paste is as described in Example 1.

[0098] Example 8

[0099] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 8 below:

[0100] Table 8

[0101]

[0102] The preparation method of this silver-carbon paste is as described in Example 1.

[0103] Example 9

[0104] This embodiment provides a silver-carbon paste, the components and contents of which are shown in Table 9 below:

[0105] Table 9

[0106]

[0107] The preparation method of this silver-carbon paste is as described in Example 1.

[0108] Comparative Example 1

[0109] Comparative Example 1 provides a silver-carbon paste, which differs from Example 1 in that it directly uses multi-walled carbon nanotubes. This silver-carbon paste is prepared by the following method:

[0110] (1) Mix the binder and organic solvent, and heat and stir for 5 min using a high-speed mixer and a constant temperature water bath to obtain a well mixed organic carrier. The binder is epoxy resin E-51, and the solvent is terpineol and dibutyl phthalate in a mass ratio of 1:1. The amount of solvent used is 1 wt% of the slurry.

[0111] (2) Mix MXene material, organic solvent and dispersant, and sonicate for 40 min to form MXene suspension. MXene is a purchased material with hydroxyl and terminal oxygen groups on its surface. The solvent is terpineol and dibutyl phthalate in a mass ratio of 1:1, and the amount of solvent used is 1 wt% of the slurry. The dispersant is sodium dodecylbenzenesulfonate, and the amount used is 0.5 wt% of the slurry.

[0112] (3) The MXene suspension, organic carrier, defective MWCNTs, nano-silver powder, solvent, and additives were mixed and stirred. The mixture was then degassed using a vacuum degassing machine, followed by grinding using a three-roll mill to obtain a silver-carbon slurry with a fineness of less than 10 μm. The solvent was terpineol, with an addition mass fraction of 8 wt%. The additives were thixotropic agents, dispersants, plasticizers, curing agents, and defoamers. The thixotropic agent was hydrogenated castor oil, with an addition mass fraction of 1 wt%; the dispersant was sodium dodecylbenzenesulfonate, with an addition mass fraction of 1 wt%; the plasticizer was tributyl citrate, with an addition mass fraction of 1 wt%; the curing agent was 2-methyl-imidazole, with an addition mass fraction of 1 wt%; and the defoamer was tributyl phosphate, with an addition mass fraction of 1 wt%.

[0113] The conductive silver-carbon electrode was prepared by screen printing the silver-carbon paste onto a silicon substrate and curing it at 180°C for 30 min in an air atmosphere.

[0114] Comparative Example 2

[0115] Comparative Example 1 provides a silver-carbon paste, which differs from Example 4 in that it directly uses multi-walled carbon nanotubes.

[0116] The pastes prepared in the above embodiments and comparative examples were screen printed on a silicon substrate. After curing at 180°C for 30 min, their resistivity and work function were measured respectively. Heterojunction cells were further prepared according to the following method and their series resistance was measured. The results are shown in Tables 10 and 11 below.

[0117] Step 1: Clean and cut the silicon wafer to obtain a single-crystal silicon substrate 1;

[0118] Step 2: Fabricate intrinsic hydrogenated amorphous silicon thin films 2 on the front and back surfaces of the single-crystal silicon substrate 1, respectively.

[0119] Step 3: Fabricate an n-type amorphous silicon thin film 31 and a p-type amorphous silicon thin film 32 on the intrinsic hydrogenated amorphous silicon thin film 2, respectively.

[0120] Step 4: Fabricate ITO transparent conductive films 4 on n-type amorphous silicon film 31 and p-type amorphous silicon film 32 respectively;

[0121] Step 5: Screen print the paste from the above embodiments and comparative examples onto the ITO transparent conductive film 4, cure at 180°C for 30 minutes, and then fabricate the metal electrode 5, thus obtaining the desired result. Figure 1 The heterojunction cell shown.

[0122] Table 10

[0123]

[0124] Table 11

[0125]

[0126] As can be seen from Examples 1 and 2, and Examples 4 and 2, under the same conditions, the resistivity of the slurry prepared using defective multi-walled carbon nanotubes is significantly lower than that of the slurry prepared using normal multi-walled carbon nanotubes, and the battery efficiency is significantly higher than that of the slurry prepared using normal multi-walled carbon nanotubes. Specifically, in Example 1, the resistivity of the slurry prepared using defective multi-walled carbon nanotubes was reduced by approximately 1.2 μΩ compared to the slurry prepared using normal multi-walled carbon nanotubes in Comparative Example 1, and the battery efficiency was increased by approximately 0.2-0.3%. In Example 4, the resistivity of the slurry prepared using defective multi-walled carbon nanotubes was reduced by approximately 0.3 μΩ compared to the slurry prepared using normal multi-walled carbon nanotubes in Comparative Example 2, and the battery efficiency was increased by approximately 0.1%.

[0127] A comparison of Examples 1-3 and Example 4 shows that, under the premise that the content of conductive phase and the amount of other raw materials are the same, the resistivity of the slurry prepared in Examples 1-3 containing Mxene and the series resistance of the heterojunction cell are both lower than those in Example 4 without Mxene. This is because the addition of Mxene makes the work function of the slurry match the work function of the front and back sides of the heterojunction cell, thereby reducing the contact resistance and series resistance of the cell.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silver-carbon paste for heterojunction batteries, characterized in that, It includes at least a silver-based conductive material and carbon nanotubes, wherein the carbon nanotubes have defects on their walls.

2. The silver-carbon paste for heterojunction batteries according to claim 1, characterized in that, The defects are structural defects and / or mechanical damage defects.

3. The silver-carbon paste for heterojunction batteries according to claim 2, characterized in that, The structural defects include one or both of topological defects and vacancy defects; and / or The mechanical damage defects include one or both of lattice distortion and fracture.

4. The silver-carbon paste for heterojunction batteries according to any one of claims 1-3, characterized in that, The defects were generated by physical treatment of carbon nanotubes.

5. The silver-carbon paste for heterojunction batteries according to claim 4, characterized in that, The physical treatment is grinding, with a grinding frequency of 10-30Hz and a grinding time of 5-30min.

6. The silver-carbon paste for heterojunction batteries according to any one of claims 1-5, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes.

7. The silver-carbon paste for heterojunction batteries according to any one of claims 1-6, characterized in that, The carbon nanotubes account for 5-10% of the total mass of the slurry, and the silver-based conductive material accounts for 60-80% of the total mass of the slurry.

8. The silver-carbon paste for heterojunction batteries according to any one of claims 1-7, characterized in that, The silver-based conductive material is nano-silver powder.

9. The silver-carbon paste for heterojunction batteries according to claim 8, characterized in that, The nano silver powder includes spherical silver powder and flake silver powder, and the ratio of spherical silver powder to flake silver powder is (1:2) to (1:1).

10. The silver-carbon paste for heterojunction batteries according to any one of claims 1-9, characterized in that, It also includes Mxene material, which accounts for 0.2-1% of the total mass of the slurry.

11. The silver-carbon paste for heterojunction solar cells according to any one of claims 1-10, characterized in that, It also includes a binder, which comprises 3-10% of the total mass of the slurry; and / or Additives, wherein the additives constitute 0.5-5% of the total mass of the slurry; and / or Solvent, wherein the solvent accounts for 2-10% of the total mass of the slurry.

12. The silver-carbon paste for heterojunction batteries according to claim 11, characterized in that, The adhesive is a resin; and / or The additive is one or more of the following: thixotropic agent, dispersant, plasticizer, curing agent, and defoamer; and / or The solvent is an organic solvent.

13. The silver-carbon paste for heterojunction batteries according to claim 12, characterized in that, The resin is one or more selected from epoxy resin, polyester resin, polyurethane resin, phenolic resin, and acrylic resin; and / or The thixotropic agent is one or more of hydrogenated castor oil, bentonite, or polyamide wax; and / or The dispersant is one or more of lauryl alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, lauryl glucoside, and octadecylamine polyoxyethylene ether; and / or The plasticizer is one or more of tributyl citrate, phthalate, glyceryl stearate, and tributyl phosphate; and / or The curing agent is one or more of acid anhydride curing agents, isocyanate curing agents, and imidazole curing agents; and / or The defoamer is one or more of tributyl phosphate and lecithin; and / or The solvent is one or more of ethylene glycol ethyl ether acetate, terpineol, dibutyl phthalate, divalent ester, diethylene glycol butyl ether acetate, dimethyl adipate, and succinic acid.

14. The silver-carbon paste for heterojunction batteries according to claim 13, characterized in that, The anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride; and / or The isocyanate curing agent is one or more of polyisocyanates, triisocyanates, hexamethylene diisocyanates, or diphenylmethane isocyanates; and / or The imidazole curing agent is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, or 2-ethylimidazole.

15. A grid line, characterized in that, The grid lines are made of silver-carbon paste for heterojunction solar cells as described in any one of claims 1-14.

16. A heterojunction battery, characterized in that, The surface of the heterojunction cell has the grid lines as described in claim 15.

17. A power generation device, characterized in that, Including the heterojunction battery as described in claim 16.

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