Conductive paste and solar cell

Abstract

The present application provides a conductive paste and a solar cell. The conductive paste includes a conductive powder, a thermosetting component, a curing agent, a solvent, a silane coupling agent, and a conductive promoter including one or more of compounds having a structural formula satisfying formula (1), wherein R has an unsaturated bond, X1, X2, X3, X4 are each independently a monovalent cation, an atom, a polyether chain having 1-18 carbon atoms, a polyester chain having 1-18 carbon atoms, a polyurea chain having 1-18 carbon atoms, a polyamide chain having 1-18 carbon atoms, a polyacrylic acid chain having 1-18 carbon atoms, a polyurethane chain having 1-18 carbon atoms, an alkyl or fluorine-substituted alkyl having 1-18 carbon atoms, an alkenyl having 1-18 carbon atoms, or an alkylene glycol adduct of alkyl or alkenyl having 1-18 carbon atoms. Thus, by adding the conductive promoter, the grid line resistivity, bulk resistivity, and / or contact resistance of the conductive paste can be reduced.

Description

Technical Field

[0001] This invention relates to the field of conductive materials technology, specifically to conductive pastes and solar cells. Background Technology

[0002] Currently, the conductive pastes used in solar cell electrodes have high grid line resistivity, high volume resistivity, and high contact resistance. Furthermore, there is room for improvement in the cost reduction and efficiency enhancement of conductive pastes.

[0003] Therefore, current conductive pastes and solar cells still need improvement. Summary of the Invention

[0004] This application aims to at least partially alleviate or even resolve at least one of the aforementioned problems.

[0005] In one aspect of the invention, a conductive paste is provided. In some embodiments of the invention, the conductive paste comprises conductive powder, a thermosetting component, a curing agent, a solvent, a silane coupling agent, and a conductivity accelerator, wherein the conductivity accelerator comprises one or more compounds whose structural formula satisfies formula (1).

[0006]

[0007] In this system, R has an unsaturated bond, and X1, X2, X3, and X4 are each independently a monovalent cation, a polyether chain with 1 to 18 carbon atoms, a polyester chain with 1 to 18 carbon atoms, a polyurea chain with 1 to 18 carbon atoms, a polyamide chain with 1 to 18 carbon atoms, a polyacrylic acid chain with 1 to 18 carbon atoms, a polyurethane chain with 1 to 18 carbon atoms, an alkyl or fluorinated alkyl group with 1 to 18 carbon atoms, an alkenyl group with 1 to 18 carbon atoms, or an alkylene glycol adduct of an alkyl or alkenyl group with 1 to 18 carbon atoms. Therefore, by adding a conductivity promoter, the grid resistivity, bulk resistivity, and / or contact resistance of the conductive paste can be reduced.

[0008] In some embodiments of the present invention, R is anthraceneyl, naphthyl, pyridyl, or furanyl. This is beneficial for improving the conductivity of the conductive paste.

[0009] In some embodiments of the present invention, the conductivity promoter includes at least one of compounds with structural formulas (1-1), (1-2), and (1-3).

[0010]

[0011] In some embodiments of the present invention, the mass content of the conductivity promoter is 0.05% to 2% based on the total mass of the conductive paste.

[0012] In some embodiments of the present invention, the conductive powder satisfies at least one of the following conditions: the conductive powder includes at least one of silver powder and silver-coated powder; the silver-coated powder includes at least one of silver-coated copper powder, silver-coated copper alloy powder, silver-coated nickel powder, and silver-coated aluminum powder; the conductive powder includes at least one of spherical powder and flake powder; the conductive powder includes spherical powder and flake powder, and the mass ratio of spherical powder to flake powder is 2:3 to 7:3; the mass of the conductive powder is 70% to 99% of the sum of the mass of the conductive powder and the thermosetting component.

[0013] In some embodiments of the present invention, the thermosetting component satisfies at least one of the following conditions: the thermosetting component includes at least one of epoxy resin and end-capped polyisocyanate prepolymer; the thermosetting component includes epoxy resin and end-capped polyisocyanate prepolymer, and the mass ratio of the epoxy resin to the end-capped polyisocyanate prepolymer is 1:9 to 9:1; based on the total mass of the conductive paste, the mass content of the thermosetting component is 1% to 20%.

[0014] In some embodiments of the present invention, the curing agent includes at least one of anhydride curing agents, imidazole curing agents, tertiary amine curing agents, Lewis acids containing boron fluoride, and Lewis salts containing boron fluoride; and / or, based on the total mass of the conductive paste, the mass content of the curing agent is 0.1% to 10%.

[0015] In some embodiments of the present invention, the solvent comprises at least one of saturated hydrocarbons, aromatic hydrocarbons, glycol ethers, alcohols, ketones, and esters; and / or, based on the total mass of the conductive paste, the mass content of the solvent is 2% to 20%; and / or, based on the total mass of the conductive paste, the mass content of the silane coupling agent is 0.1% to 1%.

[0016] In some embodiments of the present invention, the conductive paste further includes at least one of a leveling agent, an antioxidant, a defoamer, and a viscosity modifier.

[0017] In another aspect of the invention, a solar cell is proposed. In some embodiments of the invention, the solar cell includes electrodes formed by coating or printing the aforementioned conductive paste onto a substrate and then curing it. Thus, the solar cell possesses all the characteristics and advantages of the aforementioned conductive paste, which will not be repeated here. In general, the electrodes of this solar cell exhibit good conductivity and low grid resistivity, bulk resistivity, and / or contact resistance. Detailed Implementation

[0018] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0019] Given the high cost of metallization in heterojunction batteries, the demand for cost reduction in production is becoming increasingly strong. Thermosetting conductive paste compositions typically include conductive powder, thermosetting binder, curing agent, solvent, and other components. Conductive powder usually uses silver, which is expensive. To reduce costs, it is necessary to reduce the amount of silver paste consumed. There are two approaches to reducing the amount of silver paste consumed: (1) Reduce the absolute value of paste usage by improving the process to minimize the use or loss of silver paste in the metallization process, such as making the grid lines thinner and increasing the aspect ratio. The corresponding implementation paths include SMBB, screen printing optimization, steel plate printing, laser transfer, etc.; (2) Replace silver with non-precious metals to reduce, or even eliminate the need for silver paste in the future. The corresponding implementation path is to replace traditional silver paste with non-precious metals, including silver-coated copper and electroplated copper. Specifically, cheaper copper or copper alloy powder (copper-based powder) can be used as conductive powder, or silver-coated copper-based powder can be used as conductive powder after coating the surface of such copper-based powder. However, copper is prone to oxidation, which poses reliability issues.

[0020] The inventors discovered that the performance of conductive pastes can be improved by adding a conductivity promoter with a conjugated structure, resulting in lower grid resistivity, bulk resistivity, and / or contact resistance. Based on this, it is possible to add a certain amount of conductivity promoter to the conductive paste to reduce the amount of silver used, thereby reducing the cost of the paste.

[0021] In one aspect of the invention, a conductive paste is provided. In some embodiments of the invention, the conductive paste may include conductive powder, thermosetting components, a curing agent, a solvent, a silane coupling agent, and a conductivity accelerator, wherein the conductivity accelerator may include one or more compounds whose structural formula satisfies formula (1).

[0022]

[0023] In equation (1), R has an unsaturated bond, and X1, X2, X3, and X4 can each be a monovalent cation (e.g., NH4+). + ), atoms, polyether chains with 1 to 18 carbon atoms, polyester chains with 1 to 18 carbon atoms, polyurea chains with 1 to 18 carbon atoms, polyamide chains with 1 to 18 carbon atoms, polyacrylic acid chains with 1 to 18 carbon atoms, polyurethane chains with 1 to 18 carbon atoms, alkyl or fluorine-substituted alkyl groups with 1 to 18 carbon atoms, alkenyl groups with 1 to 18 carbon atoms, and alkylene glycol adducts of alkyl or alkenyl groups with 1 to 18 carbon atoms.

[0024] Compounds with the structural formula (1) possess a conjugated structure. In the hybrid orbital conductivity mechanism, electrons in organic molecules form covalent bonds through the overlap of hybrid orbitals. By introducing a conjugated structure, electrons within the conjugated system are delocalized across the entire molecular backbone. The amines associated with these delocalize to form ionic groups in the slurry, allowing electrons to transfer within the compound. These covalently bonded electrons can transfer within the molecule and carry current. During the slurry curing process, they participate in the agglomeration of conductive powders to form conductive clusters. These conductive clusters gradually grow and form a conductive network, promoting conductivity. Adding the aforementioned conductivity promoter to the conductive slurry can improve its conductivity, resulting in lower grid resistivity, bulk resistivity, and / or contact resistance.

[0025] In some embodiments of the present invention, R can be anthraceneyl, naphthyl, pyridyl, or furanyl. The presence of a conjugated structure in R can further promote conductivity, thereby further improving the performance of the conductive paste.

[0026] In some embodiments of the present invention, X1, X2, X3, and X4 may each be an alkyl or fluorine-substituted alkyl group having 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, or 18 carbon atoms.

[0027] In some embodiments of the present invention, the conductivity promoter may include at least one of compounds with structural formulas (1-1), (1-2), and (1-3).

[0028]

[0029] In some specific embodiments of the present invention, the conductivity promoter may be composed of a compound with the structural formula (1-1). In other specific embodiments of the present invention, the conductivity promoter may be composed of a compound with the structural formula (1-2). In still other specific embodiments of the present invention, the conductivity promoter may be composed of a compound with the structural formula (1-3). In still other specific embodiments of the present invention, the conductivity promoter may be composed of two or three of the compounds with the structural formulas (1-1), (1-2), and (1-3). The conjugated structure formed by the aromatic groups and ester groups in the compounds with the structural formulas (1-1), (1-2), and (1-3) can delocalize electrons in the conjugated system at the level of the entire molecular backbone. The amines attached to it form ionic groups in the slurry, and electrons can be transferred within the compound. Electrons in these covalent bonds can be transferred within the molecule and carry current, thereby improving the conductivity of the conductive slurry.

[0030] In some embodiments of the present invention, the mass content of the conductivity accelerator can be 0.05% to 2% based on the total mass of the conductive paste. For example, the mass content of the conductivity accelerator can be 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc. When the content of the conductivity accelerator is within the above range, it can effectively reduce the grid resistivity, bulk resistivity, and / or contact resistance of the paste.

[0031] In some embodiments of the present invention, the conductive powder may include at least one of silver powder and silver-coated powder, wherein the silver-coated powder may include at least one of silver-coated copper powder, silver-coated copper alloy powder, silver-coated nickel powder, silver-coated aluminum powder, etc. Both silver powder and silver-coated powder have good conductivity; using silver powder and / or silver-coated powder as the conductive powder is beneficial for improving the conductivity of the conductive paste. In some specific embodiments of the present invention, the conductive powder may be silver powder or silver-coated powder. In other specific embodiments of the present invention, the conductive powder may be a mixture of silver powder and silver-coated powder. It should be noted that silver-coated powder refers to powder in which silver is coated on the surface of conductive powder other than silver.

[0032] In this invention, there is no particular limitation on the specific shape of the conductive powder. The conductive powder can be spherical (granular) or flake-like (thin flakes or scales). It should be noted that, as flake powder, even if it is partially uneven and deformed, it can be powder that approximates a flat plate or a thin cuboid shape when viewed as a whole. As spherical powder, even if it is partially uneven and deformed, it can be powder that approximates a three-dimensional shape closer to a cube than a cuboid when viewed as a whole.

[0033] The preparation method is not particularly limited regardless of whether the conductive powder is in the form of flakes or spheres; known methods can be used. For flake-shaped conductive powders, for example, spherical powder prepared using known methods can be used as the raw powder, and known mechanical processing can be applied to the raw powder to produce flake-shaped powder. The particle size, cohesiveness, and other physical properties of the raw powder can be appropriately selected according to the intended use of the conductive slurry. Furthermore, the preparation method is not particularly limited for spherical conductive powders; for example, spherical conductive powders can be powders prepared using wet reduction methods, or spherical powders prepared using other known methods such as electrolysis or spraying.

[0034] In some embodiments of the present invention, the conductive powder may be composed of spherical powder or flake powder. In other embodiments of the present invention, the conductive powder may be obtained by mixing spherical powder and flake powder.

[0035] In some embodiments of the present invention, the conductive powder may include spherical powder and flake powder, and the mass ratio of spherical powder to flake powder may be 2:3 to 7:3. For example, the mass ratio of spherical powder to flake powder may be 2:3, 1:1, 4:3, 5:3, 2:1, 7:3, etc. When the mass ratio of spherical powder to flake powder in the conductive powder is within the above range, it is beneficial to reduce or even eliminate the gap between the cured product (e.g., electrodes, wiring, etc.) and the substrate after the conductive paste has cured, ensuring close contact between the cured product and the substrate. When the mass ratio is within the above range, the conductive powder particles have good contact, which is beneficial to improving the conductivity of the conductive paste.

[0036] In some embodiments of the present invention, the mass of the conductive powder can be 70% to 99% of the sum of the mass of the conductive powder and the thermosetting component. For example, the mass of the conductive powder can be 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc. If the mass of the conductive powder is less than 70% of the sum of the mass of the conductive powder and the thermosetting component, the contact density between the conductive powder particles in the cured conductive slurry will be reduced. Poor contact between the conductive powder particles may lead to a decrease in conductivity and an increase in volume resistivity. If the mass of the conductive powder exceeds 99% of the sum of the mass of the conductive powder and the thermosetting component, the amount of thermosetting component will be less, which may result in insufficient uniform dispersion of the conductive powder.

[0037] In this invention, there are no particular limitations on the average particle size, specific surface area, tap density, etc. of the conductive powder; those skilled in the art can select and set these parameters according to actual conditions. In some embodiments of this invention, if the conductive powder is in flake form, its average particle size D50 can be in the range of 2–20 μm, and its BET specific surface area can be in the range of 0.1–2.0 μm. 2 Within the range of g / cm³, the tap density can be 3–10 g / cm³. 3 Within the range. In some other embodiments of the invention, if the conductive powder is spherical, its average particle size D50 can be in the range of 0.1 to 10 μm.

[0038] In some embodiments of the present invention, the thermosetting component may include at least one of epoxy resin and end-capped polyisocyanate prepolymer. The aforementioned thermosetting component has a certain degree of viscosity, which can promote close contact between conductive powders and improve the strength and viscosity of the cured conductive paste, thereby ensuring a firm bond between the cured film and the substrate.

[0039] In some embodiments of the present invention, the thermosetting component may include epoxy resin. In the present invention, the specific type of epoxy resin is not particularly limited, and it can be a multi-element epoxy resin having two or more oxygen rings (epoxy groups) in its molecule. For example, it can be a glycidyl ether type epoxy resin obtained by reacting epichlorohydrin with phenolic varnishes such as phenolic varnishes and cresol varnishes, polyphenols such as bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, and resorcinol, ethylene glycol, neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol, triethylene glycol, and polypropylene glycol; it can be a glycidyl amine type epoxy resin obtained by reacting epichlorohydrin with polyamine compounds such as ethylenediamine, triethylenetetramine, and aniline; it can be a glycidyl ester type epoxy resin obtained by reacting epichlorohydrin with polycarboxylic acid compounds such as adipic acid, phthalic acid, and isophthalic acid; it can be an alicyclic epoxy resin synthesized by the oxidation of olefins, etc. The epoxy resins mentioned above can be used alone or in combination.

[0040] In some embodiments of the present invention, the thermosetting component may include a capped polyisocyanate prepolymer. The capped polyisocyanate prepolymer may be a compound containing terminal isocyanate groups, synthesized by reacting polyisocyanate with a polyol using a known method. The polyol is not particularly limited and may be a polyether polyol, a polyester polyol, a polycarbonate polyol, a polyalkylene polyol, etc.

[0041] The isocyanate compounds required for preparing end-capped polyisocyanate prepolymers can be the following: aromatic isocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, dimethylbiphenyl diisocyanate, phenylenediamine diisocyanate, and naphthalene diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate, isoflurone diisocyanate, hydrogenated phenylenediamine diisocyanate, dicyclohexylmethane diisocyanate, octamethylene diisocyanate, and trimethylhexamethylene diisocyanate. One or a combination of the above polyisocyanate compounds can be used. These polyisocyanate compounds can also be of the isocyanurate type, adduct type, or biuret type.

[0042] End-capped polyisocyanate prepolymers are compounds obtained by end-capping the aforementioned polyisocyanate compounds. In this invention, there are no particular restrictions on the end-capping agents for the polyisocyanate compounds, and imidazoles, phenols, oximes, etc., can be used for end-capping treatment.

[0043] In some embodiments of the present invention, the mass content of the thermosetting component can be 1% to 20% based on the total mass of the conductive paste. For example, the mass content of the thermosetting component can be 1%, 3%, 5%, 8%, 10%, 15%, 20%, etc. A content of the thermosetting component within the above range is beneficial for the uniform dispersion of the conductive powder and sufficient contact between the conductive powder particles, thereby helping to reduce the resistance of the cured film and promoting a strong bond between the cured film and the substrate. If the content of the thermosetting component is too low, the conductive powder may not be able to be uniformly dispersed, and the adhesion of the cured film may be poor. If the content of the thermosetting component is too high, the contact density between the conductive powder particles in the cured film will decrease, potentially causing an increase in volume resistivity.

[0044] In some embodiments of the present invention, the thermosetting component may include epoxy resin and end-capped polyisocyanate prepolymer, wherein the mass ratio of epoxy resin to end-capped polyisocyanate prepolymer may be 1:9 to 9:1, for example, the mass ratio of epoxy resin to end-capped polyisocyanate prepolymer may be 1:9, 1:4, 2:3, 1:1, 3:2, 4:1, 9:1, etc. Therefore, the thermosetting component has good viscosity, which is beneficial to improving the strength and adhesion of the film layer after the conductive paste is cured. The thermosetting component in the above proportion is beneficial to improving the contact effect between conductive powders, thereby improving the conductivity of the cured film layer.

[0045] In some embodiments of the present invention, the thermosetting component may contain resins or compounds other than epoxy resins and / or end-capped polyisocyanate prepolymers. For example, the thermosetting component may contain, but is not limited to, resin components such as phenolic resins, polyester resins, polyurethane resins, acrylic resins, melamine resins, polyimide resins, or silicone resins.

[0046] In some embodiments of the present invention, the curing agent may include at least one of acid anhydride curing agents, imidazole curing agents, tertiary amine curing agents, Lewis acids containing boron fluoride, and Lewis salts containing boron fluoride. In some embodiments of the present invention, the curing agent may include one or more of the following materials: phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, succinic anhydride, etc.; imidazole curing agents such as imidazole, 2-methylimidazolium, 2-ethyl-4-methylimidazolium, 2-undecylimidazolium, 2-heptadecanylimidazolium, 1-benzyl-2-methylimidazolium, 2-phenyl-4-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-aminoethyl-2-methylimidazolium, 1-methylimidazolium, 2-ethylimidazolium, etc.; dimethyl octylamine. Tertiary amine curing agents include dimethyldecylamine, dimethyllaurylamine, dimethyltetradecylamine, dimethylhexadecylamine, dimethyloctadecylamine, dimethyldocodialkylamine, dilauryl monoethylamine, methyldidecylamine, methyldioleylamine, triallylamine, triisopropanolamine, triethylamine, 3-(dibutylamino)propylamine, tri-n-octylamine, 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine, methyldiethanolamine, and diazabicycloundecene; Lewis acids containing boron fluoride or their salts, such as boron trifluoride ethyl ether, boron trifluoride phenol, boron trifluoride piperidine, boron trifluoride acetate, boron trifluoride monomethylamine, boron trifluoride monoethylamine, boron trifluoride triethanolamine, and boron trifluoride monoethanolamine. These curing agents can cure thermosetting components, thereby improving the performance of conductive pastes. Of course, those skilled in the art can also select other types of curing agents according to the actual situation, as long as they can cure thermosetting components.

[0047] In embodiments of the present invention, the mass content of the curing agent can be 0.1% to 10% based on the total mass of the conductive paste. For example, the mass content of the curing agent can be 0.1%, 0.5%, 0.8%, 1%, 5%, 10%, etc. This allows the thermosetting components to be fully cured, which is beneficial to improving the conductivity of the cured film.

[0048] In some embodiments of the present invention, the solvent may include at least one of saturated hydrocarbons, aromatic hydrocarbons, glycol ethers, alcohols, ketones, and esters. Specifically, the solvent may include one or more of the following materials: saturated hydrocarbons such as hexane; aromatic hydrocarbons such as toluene; glycol ethers (solubilizers) such as ethyl cellosolve, butyl cellosolve, and butyl cellosolve acetate; glycol ethers such as diethylene glycol diethyl ether and butyl carbitol (diethylene glycol monobutyl ether); acetates of glycol ethers such as diethylene glycol butyl ether acetate and carbitol butyl ether acetate; alcohols such as diacetone alcohol, terpineol, and benzyl alcohol; ketones such as cyclohexanone and methyl ethyl ketone; and esters such as DBE (divalent ester), 2,2,4-trimethyl-1,3-pentanediol monoisobutyl ester, and 2,2,4-trimethyl-1,3-pentanediol diisobutyl ester.

[0049] In some embodiments of the present invention, the mass content of the solvent can be 2% to 20% based on the total mass of the conductive paste. For example, the mass content of the solvent can be 2%, 5%, 10%, 15%, 20%, etc. This is beneficial for obtaining a conductive paste with suitable viscosity, which has good molding ability and good shear flowability.

[0050] In some embodiments of the present invention, the mass content of the silane coupling agent can be 0.1%-1% based on the total mass of the conductive slurry. For example, the mass content of the silane coupling agent can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, etc. Thus, the silane coupling agent can connect the conductive powder particles, promote the contact between the conductive powder particles, and thereby help to further improve the conductivity of the conductive slurry and the uniformity of the distribution of the conductive powder particles.

[0051] In some embodiments of the present invention, the conductive paste may further include at least one of additives such as leveling agents, antioxidants, defoamers, and viscosity modifiers to further improve the leveling properties, antioxidant properties, viscosity, etc. of the conductive paste. The specific types and amounts of additives such as leveling agents, antioxidants, defoamers, and viscosity modifiers are not particularly limited in the present invention, and those skilled in the art can select and set them according to actual needs.

[0052] In summary, this invention, by adding a specially structured amine compound as a conductivity promoter to the conductive paste, can at least partially reduce the grid line resistivity, bulk resistivity, and / or contact resistance of the cured film. Based on this, the amount of silver powder used can be relatively reduced, while simultaneously giving the cured conductive paste excellent conductivity. This reduces costs while lowering the grid line resistance, bulk resistance, and / or contact resistance of the cured conductive paste, thereby improving the electrical performance of heterojunction solar cells.

[0053] In another aspect of the invention, a solar cell is proposed. In some embodiments of the invention, the solar cell includes electrodes formed by coating or printing the aforementioned conductive paste onto a substrate and then curing it. Thus, the solar cell possesses all the features and advantages of the aforementioned conductive paste, which will not be repeated here. In general, the electrodes of this solar cell have good conductivity and low contact resistance between the electrodes and the substrate.

[0054] In addition, there are no particular limitations on the method of coating or printing conductive paste on the substrate to form electrode patterns. One or more of the following methods can be used: screen printing, gravure printing, offset printing, inkjet printing, dispenser method, and immersion method.

[0055] The present application will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the present application in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0056] Example 1

[0057] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³). 3 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 3.9 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, 0.5 parts by weight of silane coupling agent and 0.5 parts by weight of conductive accelerator with structural formula (1-1) are premixed using a planetary agitator degassing machine and rolled to a fineness of less than 5 μm using a three-roll mill to obtain conductive slurry.

[0058] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0059] Example 2

[0060] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³).3 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 3.9 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, 0.5 parts by weight of silane coupling agent and 0.5 parts by weight of conductive promoter with structural formula (1-2) are premixed using a planetary agitator degassing machine and rolled to a fineness of less than 5 μm using a three-roll mill to obtain conductive slurry.

[0061] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0062] Example 3

[0063] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³). 3 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 3.9 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, 0.5 parts by weight of silane coupling agent and 0.5 parts by weight of conductive accelerator with structural formula (1-3) are premixed using a planetary agitator degassing machine and rolled to a fineness of less than 5 μm using a three-roll mill to obtain conductive slurry.

[0064] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0065] Example 4

[0066] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³). 3 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 4.35 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, 0.5 parts by weight of silane coupling agent and 0.05 parts by weight of conductive accelerator with structural formula (1-3) are premixed using a planetary agitator degassing machine and rolled to a fineness of less than 5 μm using a three-roll mill to obtain conductive slurry.

[0067] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0068] Example 5

[0069] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³). 3 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 3.4 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, 0.5 parts by weight of silane coupling agent and 1 part by weight of conductive accelerator with structural formula (1-3) are premixed using a planetary agitator degassing machine and rolled to a fineness of less than 5 μm using a three-roll mill to obtain conductive slurry.

[0070] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0071] Comparative Example 1

[0072] (1) 54.0 parts by weight of spherical silver powder (average particle size 0.3 μm, tap density 4.2 g / cm³) 3 The above), 38.0 parts by weight of flake silver powder (average particle size 2.9μm, tap density 5-6g / cm³). 3 The conductive slurry is prepared by premixing 2.5 parts by weight of thermosetting component bisphenol epoxy resin, 4.4 parts by weight of solvent diethylene glycol butyl ether acetate, 0.6 parts by weight of curing agent boron trifluoride monoethanolamine, and 0.5 parts by weight of silane coupling agent using a planetary agitator degasser and then rolling it to a fineness of less than 5 μm using a three-roll mill.

[0073] (2) Using a screen printing machine, conductive paste is printed on a TCO / Si substrate according to the design pattern of the heterojunction solar cell unit under a squeegee pressure of 0.18MPa. The paste is dried at 150℃ and cured at 200℃ to form a heterojunction solar cell unit.

[0074] The resistivity, bulk resistance, and contact resistance of the prepared grid wire (the grid wire electrode obtained after the conductive paste has been cured) were measured, and the test results are recorded in Table 1 below.

[0075] Table 1 Performance test results of each embodiment and comparative example

[0076]

[0077] As shown in Table 1, adding a certain amount of conductivity accelerator can reduce the resistivity, bulk resistivity, and / or contact resistance of the grid lines. Therefore, adding a certain amount of conductivity accelerator to the paste can reduce the grid line resistance, bulk resistance, and / or contact resistance of the grid lines, achieving cost reduction, efficiency improvement, and a reduction in silver content.

[0078] In the description of this specification, the references to terms such as "embodiment," "some embodiments," "other embodiments," "some specific embodiments," and "other specific embodiments" refer to specific features, structures, materials, or characteristics described in connection with that embodiment, which are included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A conductive paste, characterized in that, It includes conductive powder, thermosetting components, curing agent, solvent, silane coupling agent, and conductivity promoter, wherein the conductivity promoter includes one or more compounds whose structural formula satisfies formula (1). Wherein, R has an unsaturated bond, and X1, X2, X3, and X4 are each independently a monovalent cation, an atom, a polyether chain with 1 to 18 carbon atoms, a polyester chain with 1 to 18 carbon atoms, a polyurea chain with 1 to 18 carbon atoms, a polyamide chain with 1 to 18 carbon atoms, a polyacrylic acid chain with 1 to 18 carbon atoms, a polyurethane chain with 1 to 18 carbon atoms, an alkyl or fluorinated alkyl group with 1 to 18 carbon atoms, an alkenyl group with 1 to 18 carbon atoms, or an alkylene glycol adduct of an alkyl or alkenyl group with 1 to 18 carbon atoms.

2. The conductive paste according to claim 1, characterized in that, R can be anthracene, naphthyl, pyridyl, or furanyl.

3. The conductive paste according to claim 1, characterized in that, The conductivity promoter includes at least one of compounds with structural formulas (1-1), (1-2), and (1-3).

4. The conductive paste according to any one of claims 1 to 3, characterized in that, Based on the total mass of the conductive paste, the mass content of the conductivity accelerator is 0.05% to 2%.

5. The conductive paste according to any one of claims 1 to 3, characterized in that, The conductive powder satisfies at least one of the following conditions: The conductive powder includes at least one of silver powder and silver-coated powder, and the silver-coated powder includes at least one of silver-coated copper powder, silver-coated copper alloy powder, silver-coated nickel powder, and silver-coated aluminum powder. The conductive powder includes at least one of spherical powder and flake powder; The conductive powder includes spherical powder and flake powder, and the mass ratio of spherical powder to flake powder is 2:3 to 7:

3. The mass of the conductive powder is 70% to 99% of the sum of the mass of the conductive powder and the thermosetting component.

6. The conductive paste according to any one of claims 1 to 3, characterized in that, The thermosetting component satisfies at least one of the following conditions: The thermosetting component includes at least one of epoxy resin and end-capped polyisocyanate prepolymer; The thermosetting component includes epoxy resin and capped polyisocyanate prepolymer, wherein the mass ratio of epoxy resin to capped polyisocyanate prepolymer is 1:9 to 9:

1. Based on the total mass of the conductive paste, the mass content of the thermosetting component is 1% to 20%.

7. The conductive paste according to any one of claims 1 to 3, characterized in that, The curing agent includes at least one of acid anhydride curing agents, imidazole curing agents, tertiary amine curing agents, Lewis acids containing boron fluoride, and Lewis salts containing boron fluoride. And / or, based on the total mass of the conductive paste, the mass content of the curing agent is 0.1% to 10%.

8. The conductive paste according to any one of claims 1 to 3, characterized in that, The solvent includes at least one of saturated hydrocarbons, aromatic hydrocarbons, glycol ethers, alcohols, ketones, and esters; And / or, based on the total mass of the conductive paste, the mass content of the solvent is 2% to 20%; And / or, based on the total mass of the conductive paste, the mass content of the silane coupling agent is 0.1%-1%.

9. The conductive paste according to any one of claims 1 to 3, characterized in that, The conductive paste further includes at least one of a leveling agent, an antioxidant, a defoamer, and a viscosity modifier.

10. A solar cell, characterized in that, Includes electrodes, which are formed by coating or printing the conductive paste according to any one of claims 1 to 9 onto a substrate and then curing it.

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