Conductive capsule and preparation method thereof, conductive paste and preparation method thereof, and solar cell module

Abstract

The invention belongs to the field of photovoltaic modules, and particularly relates to a conductive capsule and a preparation method thereof, conductive paste and a preparation method thereof, and a solar cell module. The capsule wall of the conductive capsule is made of a matrix resin material, and the capsule core of the conductive capsule is made of a conductive filler; the conductive filler comprises a carbon material, a Ga-based liquid metal alloy and metal powder. Comprising the novel conductive filler has the characteristics of low cost, high conductivity (controllable conductivity), high stability, low-temperature curing and the like, has good wettability for battery pieces, and can remarkably reduce the production cost and the contact resistance between the battery pieces as a connecting material of a photovoltaic module. The conductive paste is low in cost, and the cost is about 1 / 2 of the price of the silver powder on the basis that the conductivity of the conductive paste reaches the conductivity of the silver powder, so that the cost of the conductive paste can be greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic modules, and particularly relates to conductive capsules and a preparation method thereof, conductive pastes and a preparation method thereof, and solar cell modules. Background Art

[0002] As an electronic functional material, conductive paste is widely used in main fields such as photovoltaic modules, lithium-ion batteries, capacitors, and the electronics industry. With the rapid development of the solar energy industry and the electronic information industry, the market's requirements for the specificity and functionality of printed conductive materials are becoming increasingly stringent. Conductive materials have gradually evolved from single materials such as metals and carbon to composite conductive pastes. Currently, the conductive silver pastes widely used at home and abroad for photovoltaic module connection and integrated circuit packaging are basically high-temperature sintered pastes with silver powder as the filler and glass powder as the binder. The high cost of silver powder makes the cost of conductive silver paste in photovoltaic modules as high as 8 - 10% and it is difficult to reduce the cost. At the same time, the current mainstream in the industry is still high-temperature sintered conductive paste. Although there are some domestic pastes on the domestic market, there is still a certain gap in product performance compared with imported products. Low-temperature curing silver paste has become an important development direction for conductive paste in the photovoltaic solar energy industry.

[0003] Silver powder has good electrical conductivity. Since its oxide also has certain electrical conductivity, silver powder or silver-plated materials are widely used as conductive fillers. In some fields where good electrical conductivity of conductive paste is required, silver powder conductive paste is generally used. However, silver powder conductive paste is prone to electromigration in a humid environment, reducing the reliability of photovoltaic modules. In addition, the cost of pure silver powder is relatively high and the sedimentation stability is poor. Copper powder has good electrical conductivity and its cost is much lower than that of silver powder. However, copper-based conductive paste is prone to oxidation, and its electrical conductivity decreases significantly after oxidation, and even a conductive path cannot be formed. Although copper-based conductive paste has made great progress after decades of development, instability is still a long-existing problem.

[0004] In recent years, some scholars have proposed a connection method using an organic substance as the matrix and a liquid metal (such as Ga) as the conductive medium. Its conductivity has been greatly improved compared with the conventional conductive paste system. And the overall elongation rate depends on the organic matrix, and different system elongation rates can be achieved by replacing the matrix material. However, due to the large surface tension of liquid metal, difficult dispersion, easy reaction with interface materials, and the characteristics that Ga is prone to oxidation, etc., this method exposes disadvantages such as low integration, low resolution, and poor stability. Summary of the Invention

[0005] In order to solve the problems of high cost and poor stability of existing conductive pastes, the purpose of the present invention is to provide a novel conductive paste for photovoltaic modules with high electrical conductivity and low curing temperature and a preparation method thereof.

[0006] In the first aspect of the present invention, a conductive capsule is provided. The capsule wall of the conductive capsule is a matrix resin material, and the core of the conductive capsule is a conductive filler; the conductive filler includes a carbon material, a Ga-based liquid metal alloy, and metal powder.

[0007] In one or more embodiments, the conductive capsule has one or more of the following characteristics:

[0008] The carbon material is selected from one or more of graphene, carbon nanotubes, graphene oxide, and activated carbon;

[0009] The mass fraction of the carbon material in the conductive filler is 1-5%;

[0010] The Ga-based liquid metal alloy is a mixture of gallium indium tin alloy and gallium oxide or a mixture of gallium indium alloy and gallium oxide;

[0011] The metal powder is selected from one or more of copper powder, tungsten powder, nickel powder, silver powder, and magnesium powder;

[0012] The mass ratio of the metal powder to the Ga-based liquid metal alloy is (1-20):100;

[0013] The matrix resin material includes a thermosetting resin and a curing agent;

[0014] In the conductive capsule, the mass fraction of the conductive filler is 50-90%, and the mass fraction of the matrix resin material is 10-50%;

[0015] In the matrix resin material, the mass ratio of the curing agent to the thermosetting resin is (10-30):100.

[0016] In the second aspect of the present invention, a method for preparing the conductive capsule described in the first aspect of the present invention is provided. The method includes the steps of:

[0017] (1) Reacting a mixture of the Ga-based liquid metal alloy and the metal powder by introducing a gas. The gas includes a carbon-containing gas and an optional protective gas, and the carbon material is generated by the reaction. After mixing evenly, a conductive filler is obtained;

[0018] (2) Mixing and coating the conductive filler with the matrix resin material to obtain the conductive capsule.

[0019] In some embodiments, step (1) has one or more of the following characteristics:

[0020] The protective gas is selected from one or more of nitrogen, helium, and argon;

[0021] The carbon-containing gas is selected from CO 2, one or more of ethylene, acetylene, and methane;

[0022] 2 - 30 mL of carbon-containing gas is introduced into each gram of the mixture of the Ga-based liquid metal alloy and the metal powder;

[0023] The reaction is carried out at 100 - 240 °C.

[0024] In some embodiments, step (2) has one or more of the following characteristics:

[0025] The matrix resin material is prepared by mixing a thermosetting resin and a curing agent;

[0026] Mixing and coating are carried out using a three-roll mill, a planetary ball mill, or a solder paste mixer;

[0027] The time for the mixing and coating is 20 - 120 min.

[0028] In a third aspect of the present invention, a conductive paste is provided. The conductive paste includes the conductive capsule described in the first aspect of the present invention and a dispersant. The dispersant includes an organic solvent and a polymer dispersant. Among them, the organic solvent is a poor solvent for the matrix resin material.

[0029] In some embodiments, the conductive paste has one or more of the following characteristics:

[0030] The organic solvent includes a first solvent, a second solvent, and a third solvent; the boiling point of the first solvent is 60 - 90 °C, the boiling point of the second solvent is 90 - 150 °C, and the boiling point of the third solvent is 150 - 190 °C;

[0031] The polymer dispersant is an acrylate polymer dispersant;

[0032] In the conductive paste, the content of the polymer dispersant is 0.1 - 3 wt%;

[0033] In the conductive paste, the mass ratio of the conductive capsule to the organic solvent is (1 - 9):1.

[0034] In a fourth aspect of the present invention, a method for preparing the conductive paste described in the third aspect of the present invention is provided. The method includes the steps of: mixing the conductive capsule with the organic solvent, and then adding a polymer dispersant and mixing to obtain the conductive paste.

[0035] In some embodiments, in the conductive paste, the mass ratio of the conductive capsule to the organic solvent is (1 - 9):1; and / or, in the conductive paste, the content of the polymer dispersant is 0.1 - 3 wt%.

[0036] In a fifth aspect of the present invention, a solar cell module is provided, wherein a back contact layer, a conductive path and / or a conductive film layer of the solar cell module are made of the conductive paste described in the third aspect of the present invention.

[0037] The present invention has the following beneficial effects:

[0038] The low-temperature conductive paste including the novel conductive filler of the present invention has the characteristics of low cost, high conductivity (controllable conductivity), high stability and low-temperature curability, has good wettability to the battery chip, and can significantly reduce the production cost and the contact resistance between battery chips as a connecting material of the photovoltaic module. The cost of this conductive paste is relatively low. On the basis that the conductive performance reaches that of silver powder, the cost is about 1 / 2 of the price of silver powder, so the cost of the conductive paste can be greatly reduced. At the same time, due to the low curing temperature of this conductive paste, the risk of hidden cracks and fragmentation of the battery chip caused by high temperature can be reduced; the cured conductive paste has good flexibility, can absorb the thermal stress between battery chips, and improves the reliability of the module. In addition, by using the conductive paste described in the present invention, the connection process of the existing photovoltaic module can be simplified, and the production efficiency and the yield of the photovoltaic module can be improved.

[0039] The volume resistivity of the conductive paste of the present invention after curing is between 2.3 - 8.2×10 -6 Ω·cm.

[0040] The welding tensile force of the conductive paste of the present invention after curing is between 1.9 - 2.8 N / mm.

[0041] The viscosity of the conductive paste of the present invention after curing is between 274 - 291 Pa·s. Description of the Drawings

[0042] Figure 1 It is an SEM picture of the graphene material obtained in Example 2.

[0043] Figure 2 It is the Raman test result of the graphene material obtained in Example 2. Detailed Embodiments

[0044] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0045] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0046] In this text, terms such as "comprising", "including", "containing" and similar terms cover the meanings of "consisting essentially of" and "consisting of". For example, when this text discloses that "A comprises B and C", "A consists essentially of B and C" and "A consists of B and C" should be considered to have been disclosed in this text.

[0047] In this text, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0048] In this text, unless otherwise specified, percentages refer to mass percentages and ratios refer to mass ratios.

[0049] In this text, when describing embodiments or examples, it should be understood that it is not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0050] In this text, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0051] The present invention proposes a low-temperature conductive paste using a liquid metal composite material of an in-situ composite carbon material (carbon materials include graphene, carbon nanotubes, graphene oxide, activated carbon and other materials) as a conductive filler. A composite material is obtained by in-situ compounding a low-melting point metal alloy with a low melting point and high conductivity with a carbon element. The composite material is used as a conductive filler and compounded with organic matter to obtain a new low-temperature conductive paste. The low-temperature conductive paste of the present invention has the following advantages: (1) conductive pastes with different conductive properties can be obtained by controlling different process conditions, and the process formula window is wide, and different process conditions can be adjusted according to needs; (2) carbon materials such as graphene have good conductive properties, and the carbon materials are in-situ composited with metal alloys, which can avoid the defects of uneven powder dispersion and agglomeration; (3) the low melting point characteristic of the conductive paste can ensure that the formation of gaps between the metal particles is reduced during the curing process; (4) the conductive filler has been partially oxidized while ensuring its good conductivity, which can effectively prevent the conductive paste from being oxidized during use, resulting in a decrease in the conductive property of the conductive paste, thereby greatly increasing the stability of the conductive paste; (5) the curing temperature of the conductive paste is relatively low, which can avoid the embrittlement of the battery cell during the heating process and improve the product yield; (6) the conductive paste has a low cost. On the basis of achieving the conductive property of silver powder, the cost is about 1 / 2 of the price of silver powder, thereby greatly reducing the cost of the conductive paste.

[0052] Conductive filler

[0053] The conductive paste prepared by using the conductive filler of the present invention has lower volume resistivity, greater mechanical strength and greater viscosity after curing.Therefore, the present invention provides a conductive filler, which includes a carbon material, a Ga-based liquid metal alloy and a metal powder.

[0054] Herein, the carbon material is selected from one or more of graphene, carbon nanotubes, graphene oxide and activated carbon, preferably one or more of activated carbon, graphene and graphene oxide.

[0055] In some embodiments, the mass fraction of the carbon material in the conductive filler is 1-5%, such as 2%, 3%, 4% or a range between any two values.

[0056] In this text, the Ga-based liquid metal alloy can be a mixture of gallium-indium-tin alloy and gallium oxide or a mixture of gallium-indium alloy and gallium oxide. In the mixture of gallium-indium-tin alloy and gallium oxide, the mass ratio of gallium, indium, and tin is 1:(0.25 - 0.35):(0.1 - 0.2), such as 1:(0.26 - 0.32):(0.12 - 0.18), 1:(0.27 - 0.31):(0.1 - 0.2), 1:(0.26 - 0.30):(0.13 - 0.16), or 1:(0.28 - 0.31):(0.12 - 0.17). In the mixture of gallium-indium alloy and gallium oxide, the mass ratio of gallium and indium is 1:(0.25 - 0.35), such as 1:0.27, 1:0.29, 1:0.31, 1:0.33. In the mixture of gallium-indium-tin alloy and gallium oxide or the mixture of gallium-indium alloy and gallium oxide, based on the total mass of gallium element, the mass fraction of gallium element in gallium oxide is 3 - 10%. In some embodiments, the Ga-based liquid metal alloy is a mixture of gallium-indium-tin alloy and gallium oxide. The mixture of gallium-indium-tin alloy and gallium oxide contains 68 - 72 parts of gallium (Ga), 18 - 22 parts of indium (In), and 9 - 12 parts of tin (Sn). In some embodiments, the mixture of gallium-indium-tin alloy and gallium oxide contains 69 - 71 parts of gallium. In some embodiments, the mixture of gallium-indium-tin alloy and gallium oxide contains 19 - 21 parts of indium. In some embodiments, the mixture of gallium-indium-tin alloy and gallium oxide contains 10 - 11 parts of tin. In some embodiments, the mixture of Ga-based liquid metal alloy and gallium oxide can be prepared by melting. The melting temperature can be 80 - 100 °C, such as 85 °C, 90 °C, 95 °C, preferably 87 - 93 °C, 90 - 93 °C. The melting time can be 1 - 2 h, such as 1.5 h, 1.5 - 2 h.

[0057] In this text, the metal powder can be selected from one or more of copper powder, tungsten powder, nickel powder, silver powder, and magnesium powder. Preferably, the metal powder is selected from one or two of copper powder and nickel powder. The particle size of the metal powder can be 1 - 5 μm, such as 2 - 5 μm or 2 - 3 μm.

[0058] In some embodiments, the mass ratio of the metal powder to the Ga-based liquid metal alloy is (1 - 20):100, preferably (5 - 15):100 or (5 - 10):100.

[0059] The present invention also provides a method for preparing the conductive filler of the present invention. The method includes the following steps: introducing a gas into the mixture of the Ga-based liquid metal alloy and the metal powder for reaction. The gas includes a carbon-containing gas and an optional protective gas, and the carbon material is generated by the reaction, and then mixed evenly to obtain the conductive filler.

[0060] In the method for preparing the conductive filler, a carbon-containing gas is introduced into a mixture of a Ga-based liquid metal alloy and metal powder. By adjusting the reaction temperature and the flow rate of the carbon-containing gas, different types of carbon materials can be obtained. The carbon material is in-situ compounded with the Ga-based liquid metal alloy to obtain a conductive filler with excellent electrical conductivity.

[0061] In some embodiments, the protective gas is a gas that does not participate in the reaction. In some embodiments, the protective gas is selected from one or more of nitrogen, helium, and argon.

[0062] In some embodiments, the carbon-containing gas is selected from 2 one or more of CO, ethylene, acetylene, and methane, preferably the carbon-containing gas is CO. 2

[0063] In this article, the carbon-containing gas is in far excess relative to the mixture of the Ga-based liquid metal alloy and the metal powder. In some embodiments, 2 - 30 mL of the carbon-containing gas is introduced per gram of the mixture of the Ga-based liquid metal alloy and the metal powder, such as 4 mL, 6 mL, 8 mL, 10 mL, 12 mL, 15 mL, 17 mL, 18 mL, 19 mL, 22 mL, 25 mL, 28 mL, preferably 5 - 20 mL, 8 - 19 mL.

[0064] The flow rates of both the carbon-containing gas and the protective gas can be selected according to specific experimental conditions. In some embodiments, the flow rate of the carbon-containing gas can be 30 - 90 mL / min, such as 35 mL / min, 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min, 60 mL / min, 65 mL / min, 70 mL / min, 75 mL / min, 80 mL / min, 85 mL / min, preferably 45 - 80 mL / min or 60 - 75 mL / min.

[0065] The gas ventilation time can be conventionally selected according to experimental parameters such as the total volume flow rate of the carbon-containing gas, the flow rate of the carbon-containing gas, and the flow rate of the protective gas. In some embodiments, the gas ventilation time can be 1.5 - 8 h, such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, preferably 2.5 - 5 h.

[0066] In some embodiments, the reaction can be carried out at 100 - 240 °C, such as 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, or within the range composed of any two values, preferably carried out at 120 - 220 °C.

[0067] In some embodiments, the method for preparing the conductive filler of the present invention can be carried out in a beaker, a conical flask or a bubble column reactor.

[0068] Conductive capsule

[0069] In this article, coating the surface of the conductive filler with a matrix resin material to form a conductive capsule can (1) provide a stable conductive path. For example, under bending destructive force, the liquid metal microcapsules (i.e., conductive capsules) at the bent part can be broken, and then fill a large number of gaps between the conductive powders formed by external force deformation, reducing the resistance change of the conductive circuit during bending; (2) ensure that the liquid metal microcapsules are evenly distributed in the conductive circuit and avoid or reduce the premature destruction of the liquid metal microcapsules during the printing and curing process. Therefore, the present invention provides a conductive capsule including the conductive filler of the present invention. The capsule wall of the conductive capsule of the present invention is a matrix resin material, and the capsule core of the conductive capsule is the conductive filler of the present invention.

[0070] In some embodiments, the matrix resin material includes a thermosetting resin and a curing agent. The thermosetting resin can be selected from one or more of unsaturated polyester resin, phenolic resin, melamine formaldehyde resin, furan resin, epoxy resin, polybutadiene resin, acrylic resin, and urea formaldehyde resin. The curing agent can be selected from one or more of acid anhydride curing agents, amino resins, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and diethylaminopropylamine. The epoxy resin can be selected from one or more of diglycidyl 4,5-epoxytetrahydrophthalate, diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate, 1,2-epoxy-4-vinylcyclohexane, vinylcyclohexene diepoxide, and bis-(2,3-epoxycyclopentyl)-ether. The acid anhydride curing agent can be selected from one or more of polyazelaic anhydride, tung oil anhydride, and glycerol trimellitate. The amino resin is selected from one or more of urea formaldehyde resin (UF), melamine formaldehyde resin (MF), and polyamide polyamine epichlorohydrin (PAE). In some embodiments, the thermosetting resin is an epoxy resin, such as diglycidyl 4,5-epoxytetrahydrophthalate. In some embodiments, the curing agent is an acid anhydride curing agent, such as polyazelaic anhydride.

[0071] In the conductive capsule of the present invention, the mass fraction of the conductive filler is 50-90%, and the mass fraction of the matrix resin material is 10-50%. In some embodiments, in the conductive capsule, the mass fraction of the conductive filler is 60-90%, preferably 70-90%, 80-90%, or 76-83%. In some embodiments, in the conductive capsule, the mass fraction of the matrix resin material is 10-40%, preferably 10-30%, 10-20%, or 17-24%.

[0072] In some embodiments, in the matrix resin material, the mass ratio of the curing agent to the thermosetting resin is (10-30):100, preferably (20-30):100 or (25-30):100.

[0073] The present invention also provides a method for preparing the conductive capsule of the present invention, which comprises mixing and coating a conductive filler with a matrix resin material to obtain the conductive capsule.

[0074] In the method for preparing the conductive capsule, the matrix resin material is prepared by mixing a thermosetting resin and a curing agent.

[0075] In some embodiments, the conductive capsules, the matrix resin material, the thermosetting resin, and the curing agent are as described in any embodiment herein.

[0076] In some embodiments, the thermosetting resin and the curing agent are weighed according to the ratio, and the mixture is stirred and mixed to obtain a matrix resin material. The thermosetting resin and the curing agent are stirred and mixed to form a uniform system. The stirring method can be high-speed disperser stirring, centrifugal stirring or magnetic stirring, preferably magnetic stirring.

[0077] In some embodiments, a three-roll mill, a planetary ball mill, or a solder paste mixer is used for mixing and coating, and preferably a solder paste mixer is used for mixing and coating.

[0078] In some embodiments, the mixing and coating time is 20-120 min, preferably 40-60 min.

[0079] Conductive paste

[0080] The present invention provides a conductive slurry including the conductive capsule of the present invention. A composite material obtained by in-situ compounding a low-melting-point metal alloy with high conductivity and a carbon element is used as a conductive filler, and then the conductive filler is composite-coated with a resin to obtain a conductive capsule, and then the conductive capsule is dissolved in a dispersant to obtain a new low-temperature conductive slurry.

[0081] The present invention provides a conductive paste, which comprises conductive capsules and a dispersant, wherein the dispersant comprises an organic solvent and a polymer dispersant, wherein the organic solvent is a poor solvent for a resin material of a capsule wall matrix of the conductive capsule.

[0082] In some embodiments, the organic solvent includes a first solvent, a second solvent and a third solvent; the boiling point of the first solvent is 60-90°C, the boiling point of the second solvent is 90-150°C, and the boiling point of the third solvent is 150-190°C. In some embodiments, the first solvent can be selected from CH 3 COO(CH 2 O) 2 CH 3, isobutyl formate, methyl ethyl ketone, acetone, diethyl ether, methanol, tetrahydrofuran, ethyl acetate, and ethanol, or one or more of them. In some embodiments, the second solvent may be selected from CH 3 COO(CH 2 O) 3 CH 3 、CH 3 COO(CH 2 O) 4 CH 3 , propyl propionate, isobutyl methyl ketone, cyclohexanone, heptane, butanol, acetic acid, xylene, and butyl acetate, or one or more of them. In some embodiments, the third solvent may be selected from CH 3 COO(CH 2 O) 5 CH 3 、CH 3 COO(CH 2 O) 6 CH 3 , isopentyl butyrate, 4-heptanone, ethylene glycol, N-methylpyrrolidone, phenol, o-cresol, and p-cresol, or one or more of them. In some embodiments, the first solvent is selected from CH 3 COO(CH 2 O) 2 CH 3 , acetone, ethanol, and tetrahydrofuran, or one or more of them. In some embodiments, the second solvent is selected from propyl propionate and butyl acetate, or one or more of them. In some embodiments, the third solvent is selected from 4-heptanone, N-methylpyrrolidone, and ethylene glycol, or one or more of them. It should be noted that the first solvent can be a single-component first solvent or a mixture of multiple first solvents. When the first solvent is a mixture of multiple first solvents, as long as the boiling points of the respective first solvents are within the boiling point range of the first solvent. Similarly, the second solvent and the third solvent can also be single-component solvents or mixtures of multiple solvents.

[0083] In some embodiments, the organic solvent comprises 30-60 wt% of the first solvent, 30-50 wt% of the second solvent, and 10-20 wt% of the third solvent. In some embodiments, the organic solvent comprises 36-50 wt% of the first solvent. In some embodiments, the organic solvent comprises 32-48 wt% of the second solvent. In some embodiments, the organic solvent comprises 15-18 wt% of the third solvent.

[0084] In some embodiments, the polymeric dispersant is an acrylate-based polymeric dispersant; preferably, the polymeric dispersant may be selected from methacrylic acid, polyoxyethylene-polyoxypropylene ether methacrylate, allyl alcohol polyoxyethylene-polyoxypropylene ether, and acrylamide, or one or more of them.

[0085] In some embodiments, in the conductive paste, the content of the polymer dispersant is 0.1-3 wt%, preferably 0.1-1 wt%, 0.1-0.5 wt% or 0.3-0.5 wt%.

[0086] In some embodiments, in the conductive paste, the mass ratio of the conductive capsule to the organic solvent is (1-9):1, preferably (1-5):1, (1-3):1, (1-2):1 or (1.5-2):1.

[0087] The present invention provides a method for preparing the conductive paste of the present invention. The method includes the steps of mixing the conductive capsule with the organic solvent, and then adding the polymer dispersant, and mixing to obtain the conductive paste.

[0088] In the method for preparing the conductive paste, the organic solvent and the polymer dispersant are as described in any embodiment herein.

[0089] In some embodiments, in the method for preparing the conductive paste, in the conductive paste, the mass ratio of the conductive capsule to the organic solvent is (1-9):1, preferably (1-5):1, (1-3):1, (1-2):1 or (1.5-2):1.

[0090] In some embodiments, in the method for preparing the conductive paste, in the conductive paste, the content of the polymer dispersant is 0.1-3 wt%, preferably 0.1-1 wt%, 0.1-0.5 wt% or 0.3-0.5 wt%.

[0091] Solar cell module

[0092] The present invention provides a solar cell module. In some embodiments, the back contact layer, the conductive path and / or the conductive film layer of the solar cell module are made of the conductive paste of the present invention. The back contact layer, the conductive path and the conductive film layer are as described in any embodiment herein.

[0093] Application

[0094] The present invention provides the application of the conductive paste of the present invention in the preparation of a solar cell module.

[0095] The curing temperature of the conductive paste of the present invention is 80-180 °C, such as 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 150 °C, 170 °C, 180 °C, or within the range composed of any two values, preferably 90-150 °C. In some embodiments, the curing time of the conductive paste of the present invention is 20-90 min, preferably 30-60 min.

[0096] In some embodiments, the application is the use of the conductive paste of the present invention in preparing the back contact layer of a solar cell module. On the back of the solar cell module, a layer of conductive paste can be coated as the back contact layer, and this layer of conductive paste helps the current to flow from the back of the cell to the back electrode, thereby improving the conductivity efficiency of the cell.

[0097] In some embodiments, the application is the use of the conductive paste of the present invention in preparing the conductive path inside a solar cell module. In a polycrystalline silicon cell, the conductive paste is used to connect the metal grids between the cell wafers to form the guiding and distribution of current.

[0098] In some embodiments, the application is the use of the conductive paste of the present invention in preparing the conductive film layer of a solar cell module. The conductive paste can be directly coated on the cell surface as the conductive film layer to form a conductive layer for current collection and transmission.

[0099] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0100] In this article, the types of carbon materials are confirmed by scanning electron microscopy (SEM) and Raman spectroscopy testing methods.

[0101] In this article, the content of carbon materials in the conductive filler is determined by ESD energy spectrum testing.

[0102] In this article, the determination method of the content of gallium element in gallium oxide (calculated based on the total mass of gallium in the Ga-based liquid metal alloy) is as follows: Use an oxygen analyzer to test the oxygen content in the metal alloy to determine the gallium oxide content, and then determine the content of gallium element in gallium oxide.

[0103] Example 1

[0104] (1) Heat 69 parts of Ga, 20 parts of In, and 11 parts of Sn to 90 °C for melting to obtain the above-mentioned Ga-based liquid metal alloy; the melting time is 1.5 h, and after melting, cool to room temperature for standby;

[0105] (2) According to the mass ratio of the Ga-based liquid metal alloy to silver powder of 100:5, add silver powder particles to the Ga-based liquid metal alloy obtained in step (1), and mix and stir evenly to obtain a liquid metal alloy containing silver powder;

[0106] (3) Transfer 1050 g of the liquid metal alloy containing silver powder obtained in step (2) to a beaker, and introduce CO 2 , set CO 2The flow rate is 60 mL / min, the reaction temperature is adjusted to 120 °C, and the gas passing time is 2.5 h to obtain a liquid metal composite material of an in-situ composite carbon material;

[0107] (4) After the reaction is completed, transfer the liquid metal composite material of the in-situ composite carbon material prepared in step (3) into a stirring tank for stirring and mixing, and use the uniformly stirred liquid metal composite material of the in-situ composite carbon material as a conductive filler for standby; Through testing, it is confirmed that the carbon material obtained under the reaction conditions of step (3) is activated carbon, and the carbon material content is 3 wt%, based on the total mass of the prepared conductive filler; The content of gallium element in gallium oxide is measured to be 4.2% (based on the total mass of gallium in the Ga-based liquid metal alloy);

[0108] (5) Weigh diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate and polyazelaic anhydride according to the mass ratio of 100:30, and stir with a magnetic stirrer for 30 min to obtain a matrix resin material;

[0109] (6) Mix the conductive filler obtained in step (4) and the matrix resin material obtained in step (5) according to the mass ratio of 100:25, and stir with a solder paste mixer for 40 min to obtain a conductive capsule;

[0110] (7) Prepare an organic solvent: Prepare an organic solvent according to the mass ratio of 45% CH 3 COO(CH 2 O) 2 CH 3 , 40% propyl propionate, and 15% ethylene glycol;

[0111] (8) Add the conductive capsule prepared in step (6) to the organic solvent prepared in step (7), and add the polymer dispersant methacrylic acid, where the mixing mass ratio is: 60% conductive capsule: 39.6% organic solvent: 0.4% polymer dispersant, and mix evenly to obtain a low-temperature conductive paste.

[0112] Example 2

[0113] (1) Heat 71 parts of Ga, 20 parts of In, and 9 parts of Sn to 90 °C for melting to obtain the Ga-based liquid metal alloy; The melting time is 1.5 h, and after melting is completed, cool to room temperature for standby;

[0114] (2) Add nickel powder particles to the Ga-based liquid metal alloy obtained in step (1) according to the mass ratio of Ga-based liquid metal alloy to nickel powder of 100:10, and mix and stir evenly to obtain a liquid metal alloy containing nickel powder;

[0115] (3) Transfer 1010 g of the liquid metal alloy containing nickel powder obtained in step (2) to a conical flask, and introduce CO 2, set the CO 2 The flow rate was adjusted from 75 mL / min to a reaction temperature of 160 °C, and the aeration time was 4 h to obtain a liquid metal composite of the in-situ composite carbon material;

[0116] (4) After the reaction is completed, transfer the liquid metal composite of the in-situ composite carbon material prepared in step (3) to a stirring tank for stirring and mixing, and use the uniformly stirred liquid metal composite of the in-situ composite carbon material as a conductive filler for standby. It is confirmed by testing that the carbon material obtained under the reaction conditions of step (3) is a graphene material, and the carbon material content is 4.5 wt%, based on the total mass of the prepared conductive filler; The characterization of the graphene material is as Figure 1-2 shown, where Figure 1 (a) and Figure 1 (b) are electron micrographs observed at different positions of the material; the content of gallium element in gallium oxide is 5.5% (based on the total mass of gallium in the Ga-based liquid metal alloy);

[0117] (5) Weigh diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate and polyazelaic anhydride according to a mass ratio of 100:28, and stir with a magnetic stirrer for 30 min to obtain a matrix resin material;

[0118] (6) Mix the conductive filler obtained in step (4) with the matrix resin material obtained in step (5) according to a mass ratio of 100:15, and stir with a solder paste mixer for 40 min to obtain a conductive capsule;

[0119] (7) Prepare an organic solvent: Prepare an organic solvent according to a mass ratio of 23% acetone, 27% ethanol, 32% butyl acetate, and 18% N-methylpyrrolidone;

[0120] (8) Add the conductive capsule prepared in step (6) to the organic solvent prepared in step (7), and add a polymer dispersant polyoxyethylene polyoxypropylene methacrylate ester, where the added mixing mass ratio is: 65% conductive capsule: 34.5% organic solvent: 0.5% polymer dispersant, and mix evenly to obtain a low-temperature conductive paste.

[0121] Example 3

[0122] (1) Heat 68 parts of Ga, 21 parts of In, and 11 parts of Sn to 90 °C for melting to obtain the Ga-based liquid metal alloy; the melting time is 1.5 h, and after melting, cool to room temperature for standby;

[0123] (2) Add copper powder particles to the Ga-based liquid metal alloy obtained in step (1) according to a mass ratio of Ga-based liquid metal alloy to copper powder of 100:5, and mix and stir evenly to obtain a liquid metal alloy containing copper powder;

[0124] (3) Transfer the 1050 g of liquid metal alloy containing copper powder obtained in step (2) to a bubble column reactor, and introduce CO 2 , set the flow rate of CO 2 to 65 mL / min, adjust the reaction temperature to 220 °C, and the aeration time to 5 h to obtain a liquid metal composite material of in-situ composite carbon material;

[0125] (4) After the reaction is completed, transfer the liquid metal composite material of in-situ composite carbon material prepared in step (3) to a stirring tank for stirring and mixing, and use the uniformly stirred liquid metal composite material of in-situ composite carbon material as a conductive filler for standby. It is confirmed by testing that the carbon material obtained under the reaction conditions of step (3) is graphene oxide material, and the carbon material content is 5.5 wt%, based on the total mass of the prepared conductive filler; the content of gallium element in gallium oxide is measured to be 7.5% (based on the total mass of gallium in the Ga-based liquid metal alloy);

[0126] (5) Weigh diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate and polyazelaic anhydride according to the mass ratio of 100:25, and stir with a magnetic stirrer for 30 min to obtain a matrix resin material;

[0127] (6) Mix the conductive filler obtained in step (4) and the matrix resin material obtained in step (5) according to the mass ratio of 100:20, and stir with a solder paste mixer for 40 min to obtain a conductive capsule;

[0128] (7) Prepare an organic solvent: Prepare an organic solvent according to the mass ratio of 36% tetrahydrofuran, 22% propyl propionate, 26% butyl acetate, and 16% 4-heptanone;

[0129] (8) Add the conductive capsule prepared in step (6) to the organic solvent prepared in step (7), and add the polymer dispersant acrylamide, where the mixing mass ratio is: 63% conductive capsule: 36.7% organic solvent: 0.3% polymer dispersant, and mix evenly to obtain a low-temperature conductive paste.

[0130] Comparative Example 1

[0131] (1) Heat 69 parts of Ga, 20 parts of In, and 11 parts of Sn to 90 °C for melting to obtain the above-mentioned Ga-based liquid metal alloy; the melting time is 1.5 h, and after melting, it is cooled to room temperature for standby;

[0132] (2) Based on the mass of the Ga-based liquid metal alloy, add silver powder particles with a mass fraction of 5% to the Ga-based liquid metal alloy obtained in step (1), and mix and stir evenly to obtain a liquid metal alloy containing silver powder; the content of gallium element in gallium oxide is measured to be 1% (based on the total mass of gallium in the Ga-based liquid metal alloy);

[0133] (3) Weigh diglycidyl 4,5-epoxytetrahydrophthalate and polyazelaic anhydride according to the mass ratio of 100:30, and stir them with a magnetic stirrer for 30 min to obtain the matrix resin material;

[0134] (4) Mix the conductive filler obtained in step (2) with the matrix resin material obtained in step (3) according to the mass ratio of 100:25, and stir with a solder paste mixer for 40 min to obtain conductive capsules;

[0135] (5) Prepare an organic solvent: Prepare the organic solvent according to the mass ratio of 45% CH 3 COO(CH 2 O) 2 CH 3 , 40% propyl propionate, and 15% ethylene glycol;

[0136] (6) Add the conductive capsules prepared in step (4) to the organic solvent prepared in step (5), and add the polymer dispersant methacrylic acid. The mixing mass ratio is: 60% conductive capsules: 39.6% organic solvent: 0.4% polymer dispersant, and mix evenly to obtain a low-temperature conductive paste.

[0137] Test Example

[0138] The method for curing the conductive paste is to cure it by heating in an oven. The curing temperature and time are shown in the following table.

[0139] Use a four-probe surface resistance tester to measure the volume resistivity.

[0140] The test method for the welding tensile force is as follows: Use a universal testing machine according to the tensile test method for metallic materials in GB / T228-2002.

[0141] The test method for the viscosity is as follows: Use a rotational viscometer to test according to the test standard in ISO3219. The test performance parameters of the conductive pastes prepared in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0142] Table 1: Test performance parameters of the conductive paste

[0143]

Claims

1. A conductive capsule, characterized in that: The capsule wall of the conductive capsule is a matrix resin material, and the capsule core of the conductive capsule is a conductive filler; the conductive filler includes a carbon material, a Ga-based liquid metal alloy and a metal powder.

2. The conductive capsule according to claim 1, characterized in that: The conductive capsule has one or more of the following features: The carbon material is selected from one or more of graphene, carbon nanotubes, graphene oxide and activated carbon; The mass fraction of the carbon material in the conductive filler is 1-5%; The Ga-based liquid metal alloy is a mixture of a gallium-indium-tin alloy and gallium oxide or a mixture of a gallium-indium alloy and gallium oxide; The metal powder is selected from one or more of copper powder, tungsten powder, nickel powder, silver powder and magnesium powder; The mass ratio of the metal powder to the Ga-based liquid metal alloy is (1-20):100; The matrix resin material includes a thermosetting resin and a curing agent; In the conductive capsule, the mass fraction of the conductive filler is 50-90%, and the mass fraction of the matrix resin material is 10-50%; In the matrix resin material, the mass ratio of the curing agent to the thermosetting resin is (10-30):

100.

3. A method for preparing the conductive capsule according to claim 1 or 2, characterized in that: The method comprises the steps of: (1) introducing a gas into a mixture of the Ga-based liquid metal alloy and the metal powder for reaction, wherein the gas includes a carbon-containing gas and an optional protective gas, reacting to generate the carbon material, and mixing the mixture uniformly to obtain a conductive filler; (2) The conductive filler is mixed with the matrix resin material and coated to obtain the conductive capsule.

4. The method according to claim 3, characterized in that Step (1) has one or more of the following characteristics: The protective gas is selected from one or more of nitrogen, helium and argon; The carbon-containing gas is selected from one or more of CO2, ethylene, acetylene and methane; 2-30 mL of carbon-containing gas is introduced into the mixture of the Ga-based liquid metal alloy and the metal powder per gram; The reaction is carried out at 100-240°C.

5. The method according to claim 3, characterized in that Step (2) has one or more of the following characteristics: The matrix resin material is prepared by mixing a thermosetting resin and a curing agent; Use a three-roll mill, planetary ball mill or solder paste mixer for mixing and coating; The mixing and coating time is 20-120 minutes.

6. A conductive paste, characterized in that: The conductive paste comprises the conductive capsule according to claim 1 or 2 and a dispersant, wherein the dispersant comprises an organic solvent and a polymer dispersant, wherein the organic solvent is a poor solvent for the base resin material.

7. The conductive paste according to claim 6, characterized in that: The conductive paste has one or more of the following characteristics: The organic solvent includes a first solvent, a second solvent and a third solvent; the boiling point of the first solvent is 60-90°C, the boiling point of the second solvent is 90-150°C, and the boiling point of the third solvent is 150-190°C; The polymer dispersant is an acrylic polymer dispersant; In the conductive paste, the content of the polymer dispersant is 0.1-3wt%; In the conductive slurry, the mass ratio of the conductive capsule to the organic solvent is (1-9):

1.

8. A method for preparing the conductive paste according to claim 6 or 7, characterized in that: The method comprises the steps of: mixing the conductive capsules with the organic solvent, adding a polymer dispersant, and mixing to obtain a conductive slurry.

9. The method according to claim 8, characterized in that In the conductive paste, the mass ratio of the conductive capsule to the organic solvent is (1-9):1; and / or, in the conductive paste, the content of the polymer dispersant is 0.1-3wt%.

10. A solar cell module, characterized in that: The back contact layer, the conductive path and / or the conductive film layer of the solar cell module are made of the conductive paste according to claim 6 or 7.

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