Conductive paste and preparation method and application thereof

Abstract

The invention provides a conductive paste and a preparation method and application thereof, and the conductive paste comprises 84-91 wt% of a conductive phase, 0.8-5.2 wt% of a glass phase, 4-11 wt% of an organic carrier, 0.1-3 wt% of a dispersant, and the balance of a solvent. The conductive phase comprises 5-60 wt% of nickel alloy powder and 40-95 wt% of silver powder, the nickel alloy powder comprises at least one nickel alloy compound, the nickel alloy compound has a general formula of Ni-alpha-beta-gamma, alpha, beta and gamma are three non-nickel elements which are different from one another, and the sum of the alpha, the beta and the gamma is 100%. The elements alpha, beta and gamma are respectively selected from any one of transition metal, rare earth metal, alkaline earth metal and other non-nickel elements, the mass content of the nickel element is 10-99 wt%, and the sum of the mass content of the elements alpha, beta and gamma is 1-90 wt%. Nickel elements and non-nickel elements alpha, beta and gamma in a proper mass ratio are screened to form nickel alloy powder, so that the physical and chemical properties of the nickel alloy powder are improved, the ratio of the nickel alloy powder for replacing silver powder is increased, the electrical properties in the conductive slurry can be guaranteed, and the cost of the slurry is remarkably reduced.

Description

Technical Field

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

[0002] Metallic silver is widely used as a conductive material for photovoltaic electrodes due to its outstanding conductivity and antioxidant properties. However, as one of the precious metals, the high price of metallic silver is not conducive to the cost control of photovoltaic cells. In addition, silver ions are prone to ionization and directionally migration in adverse environments, forming conductive dendrites or bypassing to cause short circuits. In terms of technology, the high density of metallic silver will also increase the load on the subsequent printing equipment that loads the conductive paste, restricting the lightweight design of the printing equipment and the upper limit of high-speed printing.

[0003] One existing method for reducing the silver content in conductive pastes is to partially replace the silver with a base metal such as nickel. For example, patent publication number CN119993604A discloses a conductive paste, a crystalline silicon solar cell, and a method for preparing the same. The paste comprises the following solid components: 1.5 to 6 wt% glass frit, 9 to 15 wt% organic vehicle, 70 to 88 wt% first conductive metal, and 1 to 10 wt% second conductive metal. The first conductive metal is selected from at least one of silver powder, silver alloy powder, silver oxide, and a silver salt, and the second conductive metal is selected from nickel or a nickel alloy. CN119993604A reduces the amount of silver used by replacing silver powder with nickel powder having a specific specific surface area.

[0004] However, during the specific implementation process, the inventors found that the cost reduction effect achieved by replacing silver powder with 1wt% to 10wt% nickel metal powder is limited; and if the addition ratio of metallic nickel is further increased, the performance of the conductive paste cannot be guaranteed. On the one hand, nickel metal powder is easily oxidized into NiO during the high-temperature metallization sintering process, and NiO has electrical insulation properties, which will cause a surge in electrode resistivity; on the other hand, nickel metal powder is highly active and will chemically react with lead, bismuth, tellurium and other compound components in the glass powder at high temperatures, destroying the stability of the glass phase structure and weakening its ability to control the etching of the passivation layer, ultimately leading to an increase in contact resistance and a decay in open-circuit voltage. Summary of the Invention

[0005] In order to solve the above problems, while ensuring the performance of the conductive paste, the nickel addition ratio is increased. In the first aspect of the present application, a conductive paste is provided, comprising the following components in percentage by mass: 84-91 wt% of a conductive phase, 0.8-5.2 wt% of a glass phase, 4-11 wt% of an organic vehicle, and 0.1-3 wt% of a dispersant, with the remainder being a solvent; wherein the organic vehicle comprises a resin, an additive, and a carrier solvent, the conductive phase comprises 5-60 wt% of a nickel alloy powder and 40-95 wt% of a silver powder, the nickel alloy powder comprises at least one nickel alloy compound, and the nickel alloy compound It has the general formula: Ni-α-β-γ, wherein α, β, and γ are three different non-nickel elements, and the α, β, and γ elements are respectively selected from any one of titanium, vanadium, chromium, manganese, iron, cobalt, copper, zinc, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, aluminum, gallium, indium, tin, lead, antimony, bismuth, lithium, magnesium, calcium, strontium, yttrium, lanthanum, cerium, neodymium, samarium, silicon, germanium, arsenic, carbon, boron, nitrogen, and phosphorus. The mass content of the nickel element in the nickel alloy compound is 10-99wt%, and the sum of the mass contents of the α, β, and γ elements is 1-90wt%.

[0006] In some optional embodiments, the sum of the mass contents of the α, β and γ elements is x, and the oxidation rate v of the nickel alloy compound is oxid The relationship with x satisfies formula I: v oxid (x) = k1·exp(-k2·x)+v0, wherein k1 and k2 are constants, and v0 is the oxidation rate of the nickel element; the relationship between the resistivity ρ of the nickel alloy compound and x satisfies Formula II: ρ(x) = ρ Ni ·(1-x)+ρ A ·x+k3·x·(1-x)where ρ Ni Refers to the resistivity of nickel, ρ A refers to the average resistivity of the α, β and γ elements, k3·x·(1-x) is the additional resistance caused by the lattice distortion of the nickel alloy compound; there is a target range of ρ(x) value and v oxid The intersection of the ranges of x obtained by combining Formula I and Formula II is the range of the sum of the mass contents of the α, β and γ elements x.

[0007] In some optional embodiments, when the mass contents of the β element and the γ element are both 0, the nickel alloy compound is a binary alloy Ni-α, and the Ni-α is: Ni 70～90 Cr 10～30 , Ni 40～90 Cu 10～60 , Ni 20～90 Co 10～80 , Ni10～99 Mo 1～90 and Ni 15～95 W 5～85 Any one of .

[0008] In some optional embodiments, when the mass content of the γ element is 0, the nickel alloy compound is a ternary alloy Ni-α-β, and the α element and β element are two different non-nickel elements, respectively selected from any one of chromium, molybdenum, iron, copper and cobalt, wherein the mass content of the nickel element is 50-90wt%, the mass content of the α element is 1-45wt%, and the mass content of the β element is 1-30wt%.

[0009] In some optional embodiments, the ternary alloy Ni-α-β is: Ni 50～90 Cr 9～45 Mo 1～7 、Ni 50～ 90 Cr 5～40 Fe 5～15 、Ni 50～90 Cr 1～30 Cu 1～30 and Ni 50～90 Cu 7～45 Co 3～25 Any one of .

[0010] In some optional embodiments, the nickel alloy compound is a multinary alloy Ni-α-β-γ, and the α element, β element and γ element in the multinary alloy Ni-α-β-γ are three different non-nickel elements, respectively selected from any one of chromium, molybdenum, copper and yttrium, wherein the mass content of the nickel element is 50-90wt%, the mass content of the α element is 8.5-45wt%, the mass content of the β element is 1-7wt%, and the mass content of the γ element is 0.01-3wt%.

[0011] In some optional embodiments, the multi-component alloy Ni-α-β-γ is Ni 50～90 Cr 8.9～45 Mo 1～7 Y 0.01-0.1 or Ni 50～90 Cr 8.5～45 Mo 1～7 Cu 0.5-3 .

[0012] In some optional embodiments, the surface of the nickel alloy powder is coated with a silver shell layer which is formed by vapor-depositing silver atoms from silver trifluoroacetate after high-temperature decomposition on the surface of the nickel alloy powder. The silver shell layer accounts for 5-20 wt % of the sum of the mass of the silver shell layer and the nickel alloy powder, and the mass of the silver raw material contained in the silver shell layer is included in the silver powder.

[0013] In some optional embodiments, the particle size D50 of the silver powder is 1.3 μm, and the nickel alloy powder is spherical with an aspect ratio of less than 1.2, and the particle size D50 ranges from 1.0 to 10.0 μm.

[0014] In some optional embodiments, the glass phase includes 85 wt % and 15 wt % of a first glass powder and a second glass powder, respectively. The first glass powder includes the following components in the following mass percentages:

[0015] 20-50wt% Bi2O3, 20-35wt% PbO, 15-40wt% TeO2, 5-15wt% SiO2, 1-5wt% alkali metal oxide;

[0016] The second glass powder includes the following components in percentage by weight: 30-60 wt % of Bi2O3, 20-55 wt % of PbO, 2-10 wt % of SiO2, and 2-8 wt % of WO3.

[0017] In some optional embodiments, the resin is a mixture of ethyl cellulose, acrylic resin and epoxy resin in a mass ratio of 1:4:5, the auxiliary agent includes a thixotropic agent and a curing cross-linking agent, the carrier solvent includes a mixture of alcohol ester lauryl, butyl carbitol acetate and terpineol in a mass ratio of 1:6:3; the dispersant includes one or more of BYK-111, ED120, ED403 and ED420;

[0018] The remaining solvent is a mixture of alcohol ester dodecanol, butyl carbitol acetate, terpineol and diethyl adipate in a mass ratio of 1:6:2:1.

[0019] A second aspect of the present application provides a method for preparing the conductive paste described in any one of the above items, comprising the following steps:

[0020] S1: placing the carrier solvent in a heating container, slowly adding the auxiliary agent and the resin at 40-60° C., mechanically stirring for 0.5-1.0 h, heating to 75-85° C., and continuing mechanical stirring for 1.5-2 h to form the organic carrier;

[0021] S2: adding the nickel alloy powder and the dispersant to the organic vehicle and dispersing them uniformly to obtain a paste; and

[0022] S3: adding the glass phase, the silver powder and the remaining solvent to the paste, and stirring to uniformly disperse the materials to obtain the conductive paste.

[0023] In some optional embodiments, the nickel alloy powder is a silver-clad nickel alloy having a silver shell layer on its surface, and the preparation method of the silver-clad nickel alloy comprises the following steps:

[0024] S21: taking the nickel alloy powder raw material, sequentially cleaning the surface with ethanol and immersing it in hydrochloric acid for surface activation, rinsing it with deionized water until the surface of the nickel alloy powder is neutral, and then vacuum drying it at 60-80° C. for 2-4 hours;

[0025] S22: feeding the activated nickel alloy powder into a fluidized bed reactor, introducing Ar carrier gas, so that the activated nickel alloy powder is in a "fluidized state" under the action of the gas flow;

[0026] S23: starting the heating system to raise the temperature of the reaction zone to 250-350° C., preheating the nickel alloy powder and further removing moisture and gas adsorbed on the surface; and

[0027] S24: silver trifluoroacetate is placed in a vaporization chamber and heated to a vaporization temperature to form silver source vapor, and the silver source vapor is introduced into the reaction zone via Ar carrier gas. The silver source vapor is decomposed into silver atoms in the reaction zone and adsorbed onto the surface of the nickel alloy powder, and gradually grows epitaxially to form the continuous silver shell layer.

[0028] A third aspect of the present application provides an application of a conductive paste, wherein the conductive paste is any one of the conductive pastes described above or a conductive paste prepared according to any one of the preparation methods described above, and the conductive paste is applied to the back surface paste of a TOPCon battery.

[0029] This application has at least the following technical effects:

[0030] 1) The first aspect of the present application provides a conductive paste. By screening nickel elements and non-nickel elements α, β and γ in appropriate mass ratios, and utilizing the good compatibility of nickel elements with silver elements in the conductive paste, 10-99wt% of nickel elements in the nickel alloy can combine with silver powder to form a continuous conductive network, thereby reducing the interface resistance of the subsequently formed electrode and ensuring the electrical properties of the conductive paste; and the non-nickel elements α, β and γ in the nickel alloy at a ratio of 1-90wt% can play a corresponding role in at least one dimension of improving the oxidation resistance of nickel metal powder, improving the electronic conductivity of nickel metal powder, adjusting the thermal expansion coefficient of nickel metal powder to improve the slurry sintering density, enhancing the dispersibility of nickel metal powder in the slurry system, reducing the diffusion rate of nickel atoms to the silicon substrate, and reducing the interfacial chemical activity of the surface of nickel metal powder. The α, β and γ elements can also produce a synergistic effect, thereby improving the reliability and electrical properties of the subsequently formed electrode. When the addition ratio of nickel alloy powder in the conductive phase is increased to 60wt%, the conductive performance that is not inferior to that of pure silver conductive paste can still be achieved, significantly reducing the cost of the conductive paste and improving the economic effect.

[0031] 2) The second aspect of the present application provides a method for preparing a conductive paste, which is used to prepare the conductive paste described in any of the above items. The electrical performance of the prepared conductive paste is not inferior to that of pure silver conductive paste, and the paste cost is significantly reduced by replacing silver powder with a high proportion of nickel alloy powder.

[0032] 3) The third aspect of the present application provides an application of a conductive paste, wherein any of the conductive pastes described above is used as the back paste of a TOPCon cell, and high-temperature sintering is performed to form the back electrode contact structure of the TOPCon cell to ensure the electrical performance of the solar cell. DETAILED DESCRIPTION

[0033] Examples of this embodiment are described in detail below. The examples are only used to explain this embodiment and are not to be construed as limiting this embodiment.

[0034] In the description of the embodiments of the present application, it should be noted that all ranges disclosed in this application will be understood to encompass any and all subranges included therein. For example, the stated range "84-91 wt %" should be deemed to include any and all subranges that begin with a minimum of 84 wt % or greater and end with a maximum of 91 wt % or less, for example, 84-86 wt %, or 86-90 wt %, or 89-91 wt %. At the same time, all ranges disclosed in this application are also deemed to include the endpoints of the ranges, unless otherwise expressly stated. For example, the range "0.8-5.2 wt %" or "0.8 wt % to 5.2 wt %" or "between 0.8 wt % and 5.2 wt %" should generally be deemed to include the endpoints 0.8 wt % and 5.2 wt %.

[0035] In this document, unless otherwise specified, ratio refers to mass ratio and percentage refers to mass percentage.

[0036] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0037] The chemical formula of the nickel alloy compound mentioned in this application, such as Ni 70～90 Cr 10～30 , each subscript means the mass percentage of the corresponding element, that is, nickel alloy Ni 70～90 Cr 10～30 This means that the mass percentage of nickel element in the nickel alloy compound is 70-90wt%, and the mass percentage of chromium element in the nickel alloy compound is 10-30wt%.

[0038] The present application selects nickel elements and non-nickel elements α, β and γ in appropriate mass proportions, and utilizes the good compatibility of nickel elements with silver elements in conductive pastes. The nickel metal powder in the nickel alloy with a proportion of 10-99wt% can combine with the silver powder to form a continuous conductive network, thereby reducing the interface resistance of the subsequently formed electrode; and the non-nickel elements α, β and γ in the nickel alloy with a proportion of 1-90wt% can play a corresponding role in at least one dimension of improving the oxidation resistance of the nickel metal powder, improving the electronic conductivity of the nickel metal powder, enhancing and adjusting the high temperature resistance and corrosion resistance of the nickel metal powder, improving the thermal expansion coefficient of the slurry sintering density, enhancing the dispersibility of the nickel metal powder in the slurry system, reducing the diffusion rate of nickel atoms to the silicon substrate, reducing the interfacial chemical activity of the surface of the nickel metal powder, and improving the electronic conductivity of the nickel alloy. In the specific implementation process, the α, β and γ elements can also be present in the nickel alloy at the same time to produce a synergistic effect, thereby improving the reliability and electrical properties of the subsequently formed electrode.

[0039] Specifically, non-nickel elements that tend to form a stable oxide film on the particle surface of nickel metal powder to block the diffusion path of nickel atoms and reduce the contact between nickel and oxygen are screened out, such as chromium, zinc, tin, magnesium, calcium, aluminum, titanium, and zirconium; or non-nickel elements that increase the oxidation activation energy, slow down the rate at which nickel atoms diffuse to the surface and combine with oxygen, and inhibit the growth of a continuous nickel oxide layer are screened out, such as molybdenum, tungsten, tantalum, yttrium, cerium, platinum, palladium, and rhodium; or non-nickel elements that refine the grain structure of the oxide film, reduce the oxygen ion diffusion coefficient, and form a dense anti-oxidation protective layer are screened out, such as yttrium, lanthanum, cerium, neodymium, samarium, chromium, aluminum, and silicon; or non-nickel elements that refine the microscopic grain structure of the nickel alloy through heterogeneous nucleation, reduce grain boundary scattering, and improve the electron conduction efficiency are screened out, such as lithium, magnesium, calcium, strontium, lanthanum, neodymium, samarium, silicon, germanium, and arsenic; or non-nickel elements that reduce surface chemical activity and inhibit nickel Non-nickel elements that over-react with the glass phase and improve the contact performance of the slurry, such as titanium, zirconium, magnesium, calcium, silicon, germanium, yttrium, cerium, boron, and phosphorus; or non-nickel elements that have good compatibility with the silver interface, improve the wettability of nickel and silver, and enhance the dispersion performance of the slurry, such as indium, gallium, copper, magnesium, and boron; or non-nickel elements that adjust the microstructure of the nickel alloy to reduce the diffusion rate of nickel atoms to the silicon substrate, thereby reducing silicon wafer defects and minority carrier recombination losses, such as lead, antimony, titanium, zirconium, silicon, and germanium; or non-nickel elements that adjust the thermal expansion coefficient of the alloy to make it more compatible with the silver paste system and enhance sintering density, such as carbon, boron, nitrogen, and phosphorus; or non-nickel elements that optimize the electron cloud distribution and enhance electron conduction, such as copper, silver, platinum, and gold; or non-nickel elements that form stable intermetallic compounds with nickel and inhibit the diffusion of nickel atoms, such as silicon, germanium, and arsenic.

[0040] In general, the inventors of this application innovatively provide a conductive paste by screening nickel elements and non-nickel elements α, β and γ in an appropriate mass ratio, utilizing the good compatibility of nickel elements with silver elements in the conductive paste, as well as the antioxidant, strong conductivity and other properties of any one of the non-nickel elements α, β and γ. This not only retains the conductive activity of nickel metal powder and forms a conductive network, but also significantly enhances the antioxidant, electronic conduction efficiency and other properties of nickel alloy powder, inhibits the chemical reaction between nickel alloy powder and the glass phase, ensures the electrical properties of the conductive paste and the electrode sintering quality, improves the reliability of the battery, and thus promotes the electrical performance of the product.

[0041] Furthermore, the sum of the mass contents of the α, β and γ elements is x, and the oxidation rate v of the nickel alloy compound is oxid The relationship with x satisfies formula I: v oxid (x) = k1·exp(-k2·x)+v0, wherein k1 and k2 are constants, and v0 is the oxidation rate of the nickel element; the relationship between the resistivity ρ of the nickel alloy compound and x satisfies Formula II: ρ(x) = ρ Ni ·(1-x)+ρA ·x + k3·x·(1 - x), where ρ Ni refers to the resistivity of elemental nickel, ρ A refers to the average resistivity of the said α, β, and γ elements, and k3·x·(1 - x) is the additional resistance caused by the lattice distortion of the said nickel alloy compound; there is a target range of ρ(x) values and v oxid (x) values. By联立 the formula I and formula II, the intersection of the ranges of x obtained is the range of the sum x of the mass contents of the said α, β, and γ elements.

[0042] In the specific implementation process, one or more elements selected from chromium, zinc, tin, magnesium, calcium, aluminum, titanium, and zirconium can be combined with nickel to form a nickel alloy, and substituted into the above formula I and formula II to obtain the x value.

[0043] The design of non-nickel elements in nickel alloy powder needs to balance core properties such as oxidation resistance and conductivity. Taking the nickel-chromium binary alloy as an example, its mechanism of action can be analyzed in series through the correlation formula between key properties and chromium content. The following will be elaborated from low, medium, and high chromium content ranges, and the role will be explained in combination with the quantitative logic formula: The oxidation rate v oxid is negatively correlated with the Cr content and is dominated by the compactness of the surface Cr2O3 film. The formula is: v oxid = k1·exp(-k2·x) + v0, where k1 and k2 are constants, v0 is the oxidation rate (benchmark value) of elemental nickel, and x is the mass content of Cr. Based on the known resistivity values of Cr and Ni resistivity, the relationship between the resistivity of the nickel-chromium alloy and the Cr content is listed as: ρ = ρ Ni ·(1 - x) + ρ Cr ·x + k3·x·(1 - x), where k3·x·(1 - x) is the additional resistance (solid solution strengthening effect) caused by the Ni-Cr lattice distortion. At low Cr content (0 < x ≤ 10%): Cr is dispersed in the Ni lattice in a solid solution state, and discontinuous Cr2O3 crystal nuclei are formed on the surface. v oxid decreases but the amplitude is small (decrease < 50%), and ρ is close to that of pure Ni (increase < 10%), and the conductivity loss is small; at medium Cr content (10% < x < 30%): A continuous Cr2O3 film is formed on the surface, and v oxid drops below 10 -3 v0 (oxygen ion diffusion coefficient D O2- ≈ 10-15 cm 2 / s), basically completely blocking the continuous oxidation of Ni. ρ increases linearly with x (when x = 20%, ρ ≈ 1.5ρ Ni ), but still meets the conductive requirements of photovoltaic silver paste; at high Cr content (x ≥ 30%): v oxid ≈ 10 -4 It should be noted that the term "联立" in Chinese is not accurately translated here. It might be a specific technical term that needs more context to be precisely translated. The above translation is a rough approximation based on the overall context.v0, the oxidation resistance reaches its peak, but the excessive Cr2O3 film causes the interface contact resistance to increase, and ρ rises sharply (when x=30%, ρ≈3.5ρ Ni ). When the ρ(x) value and v are set oxid The range of (x) values ​​is substituted into the above formula to obtain two groups of x ranges. The intersection of the two groups of ranges can be used to obtain the chromium addition ratio range that balances oxidation resistance and conductivity. In practical applications, the values ​​of k1, k2, and k3 are: 2.1×10 -8 , 6.2×10 3 , 1.8×10 -6 Alternatively, the values ​​of k1, k2, and k3 are calculated through repeated experimental tests, and ultimately 10%-30% is determined to be the most suitable interval for the chromium addition ratio.

[0044] Furthermore, the optimal Cr content x can be obtained by formula III. opt :x opt =argmin(k4·ρ(x)+k5·v oxid (x)), where k4 and k5 are weight coefficients, which can be adjusted according to the process requirements of the battery for specific applications, such as TOPCon batteries.

[0045] Specifically, the conductive paste includes the following components in percentage by weight: 84-91 wt% of a conductive phase, 0.8-5.2 wt% of a glass phase; 4-11 wt% of an organic vehicle and 0.1-3 wt% of a dispersant, with the remainder being a solvent; wherein the organic vehicle includes a resin, an additive, and a carrier solvent, and the conductive phase includes 5-60 wt% of a nickel alloy powder and 40-95 wt% of a silver powder, wherein the nickel alloy powder includes at least one nickel alloy compound, and the nickel alloy compound has a general formula: Ni-α-β-γ, wherein α, β, γ are three different non-nickel elements, the α, β and γ elements are selected from titanium, vanadium, chromium, manganese, iron, cobalt, copper, zinc, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, aluminum, gallium, indium, tin, lead, antimony, bismuth, alkaline earth metals: lithium, magnesium, calcium, strontium, yttrium, lanthanum, cerium, neodymium, samarium, silicon, germanium, arsenic, carbon, boron, nitrogen and phosphorus, wherein the mass content of the nickel element in the nickel alloy compound is 10-99wt%, and the sum of the mass contents of the α, β and γ elements is 1-90wt%.

[0046] Furthermore, the mass content of the nickel element can be 70-90wt%, 40-90wt%, 20-90wt%, 10-90wt%, 15-95wt%, 15-80wt%, 15-99wt%, 60-90wt%, 50-70wt%, 40-85wt%, etc., and the sum of the mass content of the nickel element and the mass content of the α, β and γ elements should be equal to 100wt%.

[0047] In some embodiments, the nickel alloy corresponds to a binary alloy, the mass content of the nickel element is 10-99wt%, further can be 70-90wt%, 40-90wt%, 20-70wt%, 20-80wt%, 20-90wt%, 10-99wt%, 15-95wt%, etc., the mass content of the α element is 1-90wt%, further can be 10-50wt%, 10-30wt%, 10-80wt%, 30-85wt%, 5-85wt%, etc., the mass content of the β and γ elements is 0. The binary alloy Ni-α is: Ni 70～90 Cr 10～30 , Ni 40～90 Cu 10～60 , Ni 20～90 Co 10～80 , Ni 10～99 Mo 1～90 and Ni 15～95 W 5～85 Any one of the above, wherein the mass content of the α element needs to balance the oxidation resistance, interface chemical activity or electronic conductivity of the nickel alloy powder to obtain the best performance. 50～90 Cr 10～50 For example, when the chromium content is greater than 30wt%, the overall resistance of the nickel alloy system increases, and excessive Cr2O3 is prone to form a continuous insulating phase, further reducing the conductivity of the electrode formed subsequently; when the chromium content is less than 10wt%, the chromium content is too low, the stability of the Cr2O3 oxide layer and the protection of the nickel element will be insufficient, and ultimately the nickel-chromium alloy will have insufficient oxidation resistance; when the chromium content is 10-30wt%, the oxidation resistance and overall resistance of the nickel alloy system can be better balanced to obtain optimal performance. It is understandable that the nickel alloy powder can include the above-mentioned binary alloy Ni-α embodiment Ni 70～90 Cr 10～30 , Ni 40～90 Cu 10～60 , Ni 20～90 Co 10～80 , Ni 10～99 Mo 1～90 and Ni 15～95 W 5～85 One or more of .

[0048] It should be noted that when the nickel alloy is a nickel-chromium alloy, the chemical properties of chromium are more active than those of nickel. The chromium metal powder is oxidized first, and a chromium oxide protective film with good chemical stability is formed on the surface of the nickel metal powder, which prevents the uncontrollable oxidation of nickel during the sintering process and weakens the reaction activity of the nickel metal powder and the glass phase component. When the nickel alloy is a nickel-copper alloy, the electrical conductivity of copper is higher than that of nickel. After forming a nickel-copper alloy with nickel, the electronic conductivity of the nickel-copper alloy can be enhanced. When the nickel alloy is a nickel-cobalt alloy, the cobalt element changes the crystal structure of nickel through the solid solution strengthening mechanism to form a face-centered cubic Solid solution, the diffusion channel of nickel atoms is partially blocked by cobalt atoms, reducing the reaction rate of nickel and oxygen; when the nickel alloy is a nickel-molybdenum alloy, the molybdenum element can adjust the microstructure and electron cloud distribution of the nickel alloy, enhance the electronic conductivity of the conductive paste, and also improve the corrosion resistance of the nickel alloy, and enhance the stability and reliability of the subsequently formed electrode; when the nickel alloy is a nickel-tungsten alloy, the tungsten element has an extremely high melting point and strong chemical stability. After forming a solid solution with nickel, it will significantly increase the oxidation activation energy of the alloy, slow down the rate at which nickel atoms diffuse to the surface and combine with oxygen, and inhibit the growth of a continuous nickel oxide layer.

[0049] In the specific implementation process, the binary alloy can be selected from Ni 70 Cr 30 , Ni 80 Cr 20 , Ni 90 Cr 10 wait.

[0050] In some embodiments, the nickel alloy corresponds to a ternary alloy, and the α element and β element in the ternary alloy Ni-α-β are respectively selected from any one of chromium, molybdenum, iron, copper and cobalt. Specifically, the mass content of the nickel element is 50-90wt%, and can further be 50-90wt%, 60-70wt%, 70-90wt%, etc., the mass content of the α element is 1-45wt%, and can further be 1-30wt%, 5-40wt%, 7-45wt%, 10-45wt%, etc., the mass content of the β element is 1-30wt%, and can further be 1-7wt%, 5-15wt%, 1-30wt%, 3-25wt%, etc., and the mass content of the γ element is 0. The ternary alloy Ni-α-β is: Ni 50～90 Cr 9～45 Mo 1～7 、Ni 50～90 Cr 5～40 Fe 5～15 、Ni 50～90 Cr 1～ 30 Cu 1～30 and Ni 50～90 Cu7～45 Co 3～25 It is understood that the nickel alloy powder may include the above-mentioned ternary alloy Ni-α-β embodiment Ni 50～90 Cr 9～45 Mo 1～7 、Ni 50～90 Cr 5～40 Fe 5～15 、Ni 50～90 Cr 1～30 Cu 1～30 and Ni 50～ 90 Cu 7～45 Co 3～25 One or more of .

[0051] In the specific implementation process, the ternary alloy can be selected from: Ni 80 Cr 17.5 Mo 2.5 .

[0052] In some embodiments, the nickel alloy corresponds to a multi-element alloy, and the α element, β element and γ element in the multi-element alloy Ni-α-β-γ are respectively selected from any one of chromium, molybdenum, copper and yttrium. Specifically, the mass content of the nickel element is 50-90wt%, and can further be 70-90wt%, 50-85wt%, etc., the mass content of the α element is 8.5-45wt%, and can further be 25-45wt%, 8.5-30wt%, etc., the mass content of the β element is 1-7wt%, and the mass content of the γ element is 0.01-3wt%, and can further be 0.01-0.1wt%, 0.5-3wt%, etc. Specifically, the multi-element alloy can be: Ni 50～90 Cr 8.9～45 Mo 1～7 Y 0.01-0.1 and / or Ni 50～90 Cr 8.5～45 Mo 1～7 Cu 0.5-3 In the specific implementation process, the multi-element alloy can be selected from: Ni 80 Cr 17.45 Mo 2.5 Y 0.05 .

[0053] The addition of yttrium to the nickel alloy system can, on the one hand, refine the grains, inhibit the diffusion of nickel at high temperatures, and maintain the stability of the conductive network; on the other hand, it can optimize the interface contact between the nickel alloy and other components of the conductive paste and reduce the interface contact resistance.

[0054] In the specific implementation process, the nickel alloy powder can be any one or more of the above nickel alloy compounds, and the nickel alloy compound can be one or more of binary alloy, ternary alloy and multi-element alloy. For example, the nickel alloy powder can be: two binary alloys Ni 70～90 Cr 10～30 , Ni 40～90 Cu 10～60 , compound two ternary alloy Ni 50～90 Cr 5～ 40 Fe 5～15 、Ni 50～90 Cu 7～45 Co 3～25 , and then mix a multi-element alloy Ni 50～90 Cr 8.9～45 Mo 1～7 Y 0.01-0.1 .

[0055] By rationally designing the composition and ratio of nickel and the non-nickel elements α, β, and γ in nickel alloy powder, a 10wt% nickel alloy addition ratio can be achieved while simultaneously promoting the product's electrical properties and reducing slurry costs to a certain extent. To further increase the nickel alloy addition ratio, while ensuring good conductivity, the continuity of the silver conductive network in the gate electrode is maintained to reduce the product's bulk resistivity and contact resistance. Furthermore, nickel alloy powders can agglomerate to varying degrees during the printing process. Small agglomerations result in a lack of silver connectivity between the nickel alloy powders, creating voids in the gate electrode and impairing electron conduction. Large agglomerations can virtually isolate the entire electrode, significantly hindering electron conduction. Furthermore, due to the difference in expansion coefficients between silver and nickel alloys, the interfacial bonding between silver powder and nickel alloy powder during sintering becomes another factor influencing electron conduction. Taking a 60wt% addition ratio as an example, achieving a high nickel alloy powder addition ratio requires ensuring the continuity of the conductive network while reducing the interfacial resistance between the silver and nickel alloys.

[0056] Based on this, in some embodiments of the present application, the surface of the nickel alloy powder is coated with a silver shell layer, and the silver shell layer is formed by vapor deposition of silver trifluoroacetate into silver atoms after high-temperature decomposition on the surface of the nickel alloy powder. A layer of silver shell layer is coated on the surface of the nickel alloy powder using vapor deposition, and the nickel alloy powders in the printed grid electrode are connected by silver, which can ensure the continuity of the silver conductive network. In addition, the silver shell layer coated by the vapor deposition method is formed by silver atoms adsorbed on the surface of the nickel alloy powder and gradually grown epitaxially. The interface between the silver atoms and the nickel alloy powder is densely bonded, and the interface resistance is low. Furthermore, by adjusting the coating amount of the silver shell layer, low volume resistivity and contact resistance values ​​of the product are achieved, which has a promoting effect on the electrical properties of the product, and ultimately achieves a nickel alloy addition ratio of up to 60wt%.

[0057] Furthermore, the silver shell layer accounts for 5-20 wt % of the sum of the mass of the silver shell layer and the nickel alloy powder, and the mass of the silver raw material contained in the silver shell layer is included in the silver powder. When the mass proportion of the silver shell layer is low, it is difficult for the conductive metal atoms in the nickel alloy powder to be completely interconnected by silver, the continuity of the conductive network is poor, and the conductivity of the subsequently formed electrode is poor; when the mass proportion of the silver shell layer is high, since the silver in the silver shell layer is coated on the surface of the nickel alloy core by vapor deposition, it is easy to form more lattice defects and nano-scale protrusions / wrinkles, the specific surface area is large, and the activity is higher than the remaining silver powder in the conductive paste. During the metallization sintering process, the sintering neck grows faster, the silver layer densifies prematurely, and hinders the flow of glass to the silicon substrate, thereby affecting the contact performance of the paste. The appropriate proportion of the silver shell layer can ensure the electrical properties of the conductive paste and is conducive to increasing the addition ratio of the nickel alloy. Specifically, the addition ratio of the nickel alloy can reach 60wt%, and the silver in the silver shell layer coating the nickel alloy powder has been included in the silver powder of the conductive phase, so there is no need to add additional silver powder, which greatly reduces the preparation cost of the conductive paste.

[0058] In a specific implementation process, the mass ratio of the silver shell layer can be achieved by controlling the feed ratio of the vapor deposition operation. The quantitative control method is relatively simple and does not require additional equipment for detection.

[0059] The preparation method of the silver shell layer comprises the following steps:

[0060] S21: taking the nickel alloy powder raw material, sequentially cleaning the surface with ethanol and immersing it in hydrochloric acid for surface activation, rinsing it with deionized water until the surface of the nickel alloy powder is neutral, and then vacuum drying it at 60-80° C. for 2-4 hours;

[0061] S22: feeding the activated nickel alloy powder into a fluidized bed reactor through a screw feeder, introducing Ar carrier gas, so that the activated nickel alloy powder is in a "fluidized state" under the action of the gas flow;

[0062] S23: starting the heating system to raise the temperature of the reaction zone to 250-350° C. to preheat the nickel alloy powder and further remove moisture and gas adsorbed on the surface;

[0063] S24: silver trifluoroacetate is placed in a vaporization chamber and heated to a vaporization temperature to form silver source vapor, and the silver source vapor is introduced into the reaction zone via Ar carrier gas. The silver source vapor is decomposed into silver atoms in the reaction zone and adsorbed onto the surface of the nickel alloy powder, and gradually grows epitaxially to form the continuous silver shell layer.

[0064] In some embodiments, the silver powder has a particle size D50 of 1.3 μm, and the nickel alloy powder is spherical with an aspect ratio of less than 1.2, and a particle size D50 ranging from 1.0 to 10.0 μm.

[0065] Since the particle size of nickel alloy powder is larger than that of silver powder, during the screen printing process of conductive paste, if the aspect ratio of nickel alloy powder is greater than 1.2, the sphericity is poor and the nickel alloy powder is easily stuck in the opening of the screen, resulting in broken screen. Controlling the aspect ratio of nickel alloy powder to less than 1.2 can effectively improve the broken screen phenomenon in printing.

[0066] In some embodiments, the glass phase includes 85 wt % and 15 wt % of a first glass powder and a second glass powder, respectively. The first glass powder includes the following components in the following mass percentages:

[0067] 20-50wt% Bi2O3, 20-35wt% PbO, 15-40wt% TeO2, 5-15wt% SiO2, 1-5wt% alkali metal oxide;

[0068] The second glass powder includes the following components in percentage by mass:

[0069] 30-60wt% Bi2O3, 20-55wt% PbO, 2-10wt% SiO2, 2-8wt% WO3.

[0070] In some embodiments, the resin is a mixture of ethyl cellulose, acrylic resin, and epoxy resin in a mass ratio of 1:4:5, the auxiliary agent includes a thixotropic agent and a curing cross-linking agent, and the carrier solvent includes a mixture of alcohol ester lauryl, butyl carbitol acetate, and terpineol in a mass ratio of 1:6:3;

[0071] The dispersant includes one or more of BYK-111, ED120, ED403 and ED420;

[0072] The remaining solvent is a mixture of alcohol ester dodecanol, butyl carbitol acetate, terpineol and diethyl adipate in a mass ratio of 1:6:2:1.

[0073] Among them, BYK is the prefix of products produced by BYK of Germany, BYK-111 refers to the dispersant product with serial number 111 produced by the company; ED is the ED series product produced by Kusunomoto Chemicals Co., Ltd., and ED120, ED403 and ED420 are the products with corresponding serial numbers in this series.

[0074] A second aspect of the present application provides a method for preparing a conductive paste, wherein the method is used to prepare any of the conductive pastes described above, comprising the following steps:

[0075] S1: placing the carrier solvent in a heating container, slowly adding the auxiliary agent and the resin at 40-60° C., mechanically stirring for 0.5-1.0 h, heating to 75-85° C., and continuing mechanical stirring for 1.5-2 h to form the organic carrier;

[0076] S2: adding the nickel alloy powder and the dispersant to the organic vehicle and dispersing them uniformly to obtain a paste; and

[0077] S3: adding the glass phase, the silver powder and the remaining solvent to the paste, and stirring to uniformly disperse the materials to obtain the conductive paste.

[0078] In some embodiments, the nickel alloy powder is a silver-coated nickel alloy powder having a silver shell layer on its surface, and the preparation method of the silver-coated nickel alloy powder comprises the following steps:

[0079] S21: adding the nickel alloy powder to an ethanol solution, ultrasonically cleaning for 30-60 minutes to remove residual oil and organic reagents on the surface, rinsing with deionized water for 3-5 times, adding 5%-10% by mass dilute hydrochloric acid and soaking for 10-20 minutes to remove the surface oxide layer, and finally rinsing with deionized water until neutral (pH = 6.5-7.5), and vacuum drying at 60-80 ° C for 2-4 hours to obtain activated nickel alloy powder;

[0080] S22: feeding the activated nickel alloy powder into a fluidized bed reactor through a screw feeder, introducing 5-10 L / min of Ar carrier gas, so that the nickel alloy powder is in a "fluidized state" under the action of the gas flow; and

[0081] S23: starting the heating system to raise the temperature of the reaction zone to 250-350° C., preheating the nickel alloy powder and further removing moisture and gas adsorbed on the surface;

[0082] S24: Silver trifluoroacetate is heated to a vaporization temperature of 140-160° C. in a vaporization chamber to form silver source vapor, which is introduced into a reaction zone via an Ar carrier gas at a flow rate of 2-5 L / min. The silver source is decomposed into silver atoms in the reaction zone. The silver atoms are adsorbed and diffused on the surface of the nickel alloy powder, gradually growing epitaxially to form a continuous silver shell.

[0083] A third aspect of the present application provides an application of a conductive paste, wherein the conductive paste is the conductive paste according to any one of the above items, and the conductive paste is applied to the back surface paste of a TOPCon battery.

[0084] The present application is further explained below with reference to examples.

[0085] The reagents and raw materials used in the examples and comparative examples of the present application are all commercially available.

[0086] Example 1

[0087] Example 1 provides a method for preparing a conductive paste, comprising the following steps:

[0088] S1: Weigh 320g of the carrier solvent and place it in a heating container. Slowly add 6g of the auxiliary agent and 74g of the resin at 50°C, mechanically stir for 0.5h, raise the temperature to 80°C, and continue mechanically stirring for 1.5-2h to allow the auxiliary agent, the resin, and the solvent to be dissolved and mixed uniformly to form the organic vehicle. The organic vehicle is then placed at room temperature for more than 12h for standby use.

[0089] S2: Weigh 36 g of nickel alloy powder and 0.8 g of dispersant, add them to 17.6 g of the organic vehicle, and disperse them evenly to obtain a paste; and

[0090] S3: Weigh 12 g of glass phase, 324 g of silver powder and 9.6 g of the remaining solvent and add them to the paste, and continue stirring and dispersing to obtain the conductive paste.

[0091] The components of the conductive paste in Example 1 are: 90wt% conductive phase, 3wt% glass phase, 4.4wt% organic vehicle, 0.2wt% dispersant and 2.4wt% balance solvent; the conductive phase contains 90wt% silver powder and 10wt% nickel-chromium alloy powder.

[0092] Furthermore, the particle size D50 of the silver powder is 1.3 μm, the particle size D50 of the nickel-chromium alloy powder is in the range of 1.0-10.0 μm, the aspect ratio is less than 1.2, and the specific composition is Ni 70 Cr 30 , that is, the nickel content is 70wt% and the chromium content is 30wt%;

[0093] The glass phase includes 85 wt% of the first glass powder and 15 wt% of the second glass powder, based on the total mass of the glass phase:

[0094] The first glass powder includes 20-50 wt% of Bi2O3, 20-35 wt% of PbO, 15-40 wt% of TeO2, 5-15 wt% of SiO2, and 1-5 wt% of alkali metal oxide.

[0095] The second glass powder includes 30-60 wt% of Bi2O3, 20-55 wt% of PbO, 2-10 wt% of SiO2, and 2-8 wt% of WO3.

[0096] The organic carrier includes:

[0097] Additives, including thixotropic agents and curing crosslinking agents;

[0098] A resin comprising a mixture of ethyl cellulose, acrylic resin, and epoxy resin in a mass ratio of 1:4:5;

[0099] a carrier solvent comprising a mixture of alcohol ester lauryl, butyl carbitol acetate and terpineol in a mass ratio of 1:6:3;

[0100] The dispersant includes one or more of BYK-111, ED120, ED403 and ED420;

[0101] The remaining solvent is a mixture of alcohol ester lauryl, butyl carbitol acetate, terpineol and diethyl adipate in a mass ratio of 1:6:2:1.

[0102] Example 2

[0103] Example 2 provides a conductive paste, which differs from Example 1 only in that the nickel-chromium alloy powder is composed of Ni 80 Cr 20 , that is, the proportion of nickel is 80wt% and the proportion of chromium is 20wt%.

[0104] Example 3

[0105] Example 3 provides a conductive paste, which differs from Example 1 only in that the nickel-chromium alloy powder is composed of Ni 90 Cr 10 , that is, the proportion of nickel is 90wt% and the proportion of chromium is 10wt%.

[0106] Example 4

[0107] Example 4 provides a conductive paste, which is different from Example 1 only in that the nickel alloy powder is nickel-chromium-molybdenum alloy powder, and the nickel-chromium-molybdenum alloy powder is composed of Ni 80 Cr 17.5 Mo 2.5 , that is, the proportion of nickel is 80wt%, the proportion of chromium is 17.5wt%, and the proportion of molybdenum is 2.5wt%.

[0108] Example 5

[0109] Example 5 provides a conductive paste, which is different from Example 1 only in that the nickel alloy powder is nickel-chromium-molybdenum-yttrium alloy powder, and the nickel-chromium-molybdenum-yttrium alloy powder is composed of Ni 80 Cr 17.45 Mo 2.5 Y 0.05 , that is, the proportion of nickel is 80wt%, the proportion of chromium is 17.45wt%, the proportion of molybdenum is 2.5wt%, and the proportion of yttrium is 0.05wt%.

[0110] Example 6

[0111] Example 6 provides a conductive paste, which differs from Example 1 only in that the nickel alloy powder is silver-coated nickel-chromium-molybdenum-yttrium alloy powder, and the mass percentage of the silver-coated nickel-chromium-molybdenum-yttrium alloy powder in the conductive phase is 65wt%, wherein the proportion of nickel-chromium-molybdenum-yttrium alloy powder is 60wt%, and the proportion of the silver shell layer is 5wt%.

[0112] Example 7

[0113] Example 7 provides a conductive paste, which differs from Example 6 only in that the mass percentage of the silver-coated nickel-chromium-molybdenum-yttrium alloy powder in the conductive phase is 70wt%, wherein the proportion of the nickel-chromium-molybdenum-yttrium alloy powder is 60wt% and the proportion of the silver shell layer is 10wt%.

[0114] Example 8

[0115] Example 8 provides a conductive paste, which differs from Example 6 only in that the mass percentage of the silver-coated nickel-chromium-molybdenum-yttrium alloy powder in the conductive phase is 80wt%, of which the proportion of the nickel-chromium-molybdenum-yttrium alloy powder is 60wt% and the proportion of the silver shell layer is 20wt%.

[0116] Comparative Example 1

[0117] Comparative Example 1 provides a conductive paste, which differs from Example 1 only in that the conductive phase includes 90 wt % silver powder and 10 wt % nickel powder.

[0118] Comparative Example 2

[0119] Comparative Example 2 provides a conductive paste, which differs from Example 1 only in that the conductive phase includes 40 wt % silver powder and 60 wt % nickel powder.

[0120] Comparative Example 3

[0121] Comparative Example 3 provides a conductive paste, which differs from Example 1 only in that the conductive phase is 100 wt % silver powder.

[0122] Silicon crystalline solar cells were prepared using the conductive pastes provided in Examples 1-8 and Comparative Examples 1-3.

[0123] Using screen printing technology, the conductive pastes provided in Examples 1-8 and Comparative Examples 1-3 were respectively printed on silicon wafer substrates to form cell sheets. The cell sheets were dried in a belt drying furnace, and then sintered in a belt firing furnace at 760-820°C. After sintering, they were cooled to form silicon crystalline solar cells.

[0124] After screen printing and sintering, the cross-sections of the metal gate lines of Examples 1-8 were close to Gaussian distribution, with line width controlled at approximately 29 μm and line height at approximately 5 μm.

[0125] The conversion efficiency, open circuit voltage, short circuit current, and fill factor electrical properties of the silicon crystalline solar cells obtained in Examples 1-8 and Comparative Examples 1-3 were tested using an IV tester. The IV data were based on Comparative Example 3 (pure silver paste), and then characterized by the difference values ​​of the various indicators of each embodiment compared with the comparative example 3, where ΔEff refers to the conversion efficiency difference, ΔUoc refers to the open circuit voltage difference, ΔIsc refers to the short circuit current difference, and ΔFF refers to the fill factor difference. The body resistivity and contact resistance were tested using a TLM contact resistance meter, where ρ refers to the body resistivity and Rc refers to the contact resistance value. The actual test results of the electrical properties of the conversion efficiency, open circuit voltage, short circuit current, fill factor, body resistivity, and contact resistance of the silicon crystalline solar cell obtained in Comparative Example 3 are shown in Table 1 below:

[0126] Table 1 - Electrical performance test results of Comparative Example 3

[0127] Eff(%) Uoc(mV) Isc(mA) FF(%) Volume resistivity ρ(%) Rc(ohm) Comparative Example 3 26.211 0.7307 14.765 86.05 100 0.72

[0128] The electrical performance test results of Examples 1-8 and Comparative Examples 1-3 are shown in Table 2 below:

[0129] Table 2 - Electrical performance test results of Examples 1-8 and Comparative Examples 1-3

[0130] ΔEff (%) ΔUoc(mV) ΔIsc(mA) ΔFF(%) Volume resistivity ρ(%) Rc(ohm) Example 1 0.06 0.1 1.2 0.15 117 0.51 Example 2 0.12 0.4 5.8 0.30 110 0.56 Example 3 0.05 0.6 2.4 0.09 112 0.62 Example 4 0.14 0.4 6.2 0.35 107 0.58 Example 5 0.18 0.5 7.5 0.43 106 0.44 Example 6 0.02 0.4 3.2 0.05 147 0.57 Example 7 0.07 0.6 8.2 0.18 126 0.62 Example 8 0.04 0.8 4.8 0.10 119 0.82 Comparative Example 1 -0.01 0.4 4.2 -0.05 135 0.87 Comparative Example 2 -0.12 0.4 -0.9 -0.31 238 1.25 Comparative Example 3 / / / / 100 0.72

[0131] From Table 2 we can see that:

[0132] It can be seen from the experimental data of Examples 1-3 and Comparative Examples 1-2 that the electrical performance of Comparative Example 1 is relatively poor compared with that of the Example. This is because the nickel powder has a high degree of oxidation during the high-temperature sintering process, and the bulk resistivity of the electrode increases significantly. At the same time, the nickel powder also reacts chemically with the glass phase components, resulting in a high contact resistance. The electrical performance of Comparative Example 2 is the worst. This is because when the nickel powder addition ratio is increased to 60wt%, a part of the nickel powder will also agglomerate into large agglomerates, which is equivalent to forming large areas of poor conductive properties in the silver powder network. The continuity of the silver conductive network is destroyed, and therefore the bulk resistivity ρ increases significantly. In Examples 1-3, nickel-chromium alloy powder is used. Due to the addition of chromium, the oxidation resistance and chemical stability of the nickel-chromium alloy powder are significantly improved. Among them, the electrical properties of Example 2 are better. This is because the chromium content in Example 1 is 30wt%, which is too high, increasing the overall resistance of the nickel alloy system, and excessive Cr2O3 easily forms a continuous insulating phase, further reducing the conductivity of the subsequently formed electrode; while the chromium addition ratio of 10wt% in Example 3 is too low, the stability of the Cr2O3 oxide layer and the protection of the nickel element will be insufficient, and ultimately the oxidation resistance of the nickel-chromium alloy is insufficient.

[0133] In Example 4, Eff is improved compared to pure silver paste, and the bulk resistivity ρ is further reduced compared to the nickel-chromium alloy powder in Examples 1-3. This is because the addition of Mo to the nickel alloy compound can adjust the microstructure and electron cloud distribution of the nickel alloy compound, which is more conducive to electron conduction.

[0134] In Example 5, Eff is improved compared with pure silver paste, and the contact resistance Rc is further reduced compared with Example 4. This is because the addition of Y in the nickel alloy compound can, on the one hand, refine the grains and inhibit the diffusion of Ni at high temperatures; on the other hand, it can optimize the interface contact between the nickel alloy powder and the silver powder in the conductive paste, thereby reducing the interface contact resistance Rc of the subsequently formed electrode.

[0135] It can be seen from the experimental data of Examples 6-8 that a silver shell layer is coated on the surface of the nickel-chromium-molybdenum-yttrium alloy powder. When the silver shell coating ratio is increased from 5wt% (Example 6) to 10wt% (Example 7), the volume resistivity ρ is effectively reduced and the Eff is increased accordingly; when the silver shell coating ratio is further increased to 20wt% (Example 8), the volume resistivity ρ is further reduced, but the Eff is attenuated. This is because when the silver shell coating ratio is 20wt%, the silver-coated nickel alloy powder accounts for 80wt% of the entire conductive phase, and the silver particles in the silver shell are more active. In the actual metallization sintering process, the sintering neck grows faster, and the silver powder quickly forms a continuous silver layer conductive network. However, premature densification of the silver layer will hinder the flow of the glass phase to the silicon substrate, resulting in an increase in contact resistance and deterioration of the electrical properties of the conductive slurry.

[0136] In summary, by rationally designing the composition and proportion of nickel alloy powder, the oxidation resistance of nickel alloy can be improved, its conductivity can be balanced, and the chemical reaction between nickel alloy powder and glass phase components can be inhibited, thereby improving the electrical properties of the conductive paste. While making its electrical performance not inferior to that of pure silver conductive paste, the paste cost can be significantly reduced, thereby improving economic benefits.

[0137] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and intent of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A conductive paste, characterized in that: The conductive paste comprises the following components in percentage by weight: 84-91 wt% of a conductive phase, 0.8-5.2 wt% of a glass phase, 4-11 wt% of an organic vehicle, and 0.1-3 wt% of a dispersant, with the remainder being a solvent; wherein the organic vehicle comprises a resin, an additive, and a carrier solvent, and the conductive phase comprises 5-60 wt% of a nickel alloy powder and 40-95 wt% of a silver powder, wherein the nickel alloy powder comprises at least one nickel alloy compound, and the nickel alloy compound has a general formula: Ni-α-β-γ, wherein α, β, γ is three different non-nickel elements, and the α, β and γ elements are respectively selected from any one of titanium, vanadium, chromium, manganese, iron, cobalt, copper, zinc, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, aluminum, gallium, indium, tin, lead, antimony, bismuth, lithium, magnesium, calcium, strontium, yttrium, lanthanum, cerium, neodymium, samarium, silicon, germanium, arsenic, carbon, boron, nitrogen and phosphorus, wherein the mass content of the nickel element in the nickel alloy compound is 10-99wt%, and the sum of the mass contents of the α, β and γ elements is 1-90wt%.

2. The conductive paste according to claim 1, characterized in that The sum of the mass contents of the α, β and γ elements is x, and the oxidation rate of the nickel alloy compound is v oxid The relationship with x satisfies formula I: v oxid (x) = k1·exp(-k2·x)+v0, wherein k1 and k2 are constants, and v0 is the oxidation rate of the nickel element; the relationship between the resistivity ρ of the nickel alloy compound and x satisfies Formula II: ρ(x) = ρ Ni ·(1-x)+ρ A ·x+k3·x·(1-x)where ρ Ni Refers to the resistivity of nickel, ρ A refers to the average resistivity of the α, β and γ elements, k3·x·(1-x) is the additional resistance caused by the lattice distortion of the nickel alloy compound; there is a target range of ρ(x) value and v oxid The intersection of the ranges of x obtained by combining Formula I and Formula II is the range of the sum of the mass contents of the α, β and γ elements x.

3. The conductive paste according to claim 1, characterized in that When the mass contents of the β element and the γ element are both 0, the nickel alloy compound is a binary alloy Ni-α, and the Ni-α is: Ni 70～90 Cr 10～30 , Ni 40～90 Cu 10～60 , Ni 20～90 Co 10～80 , Ni 10～99 Mo 1～90 and Ni 15～95 W 5～85 Any one of .

4. The conductive paste according to claim 1, characterized in that When the mass content of the γ element is 0, the nickel alloy compound is a ternary alloy Ni-α-β, the α element and the β element are two different non-nickel elements, respectively selected from any one of chromium, molybdenum, iron, copper and cobalt, wherein the mass content of the nickel element is 50-90wt%, the mass content of the α element is 1-45wt%, and the mass content of the β element is 1-30wt%.

5. The conductive paste according to claim 4, characterized in that: The ternary alloy Ni-α-β is: Ni 50～90 Cr 9～ 45 Mo 1～7 、Ni 50～90 Cr 5～40 Fe 5～15 、Ni 50～90 Cr 1～30 Cu 1～30 and Ni 50～90 Cu 7～45 Co 3～25 Any one of .

6. The conductive paste according to claim 1, characterized in that The nickel alloy compound is a multi-component alloy Ni-α-β-γ, wherein the α element, β element and γ element in the multi-component alloy Ni-α-β-γ are three different non-nickel elements, respectively selected from any one of chromium, molybdenum, copper and yttrium, wherein the mass content of the nickel element is 50-90wt%, the mass content of the α element is 8.5-45wt%, the mass content of the β element is 1-7wt%, and the mass content of the γ element is 0.01-3wt%.

7. The conductive paste according to claim 6, characterized in that The multi-element alloy Ni-α-β-γ is Ni 50～ 90 Cr 8.9～45 Mo 1～7 Y 0.01-0.1 or Ni 50～90 Cr 8.5～45 Mo 1～7 Cu 0.5-3 .

8. The conductive paste according to claim 1, characterized in that The surface of the nickel alloy powder is coated with a silver shell layer which is formed by vapor-depositing silver atoms after high-temperature decomposition of silver trifluoroacetate on the surface of the nickel alloy powder. The silver shell layer accounts for 5-20wt% of the sum of the mass of the silver shell layer and the nickel alloy powder, and the mass of the silver raw material contained in the silver shell layer is included in the silver powder.

9. The conductive paste according to claim 1, characterized in that: The particle size D50 of the silver powder is 1.3 μm, and the nickel alloy powder is spherical with an aspect ratio of less than 1.2, and the particle size D50 ranges from 1.0 to 10.0 μm.

10. The conductive paste according to claim 1, characterized in that: The glass phase includes a first glass powder and a second glass powder in amounts of 85 wt % and 15 wt % respectively, wherein the first glass powder includes the following components in percentages by mass: 20-50wt% Bi2O3, 20-35wt% PbO, 15-40wt% TeO2, 5-15wt% SiO2, 1-5wt% alkali metal oxide; The second glass powder includes the following components in percentage by mass: 30-60wt% Bi2O3, 20-55wt% PbO, 2-10wt% SiO2, 2-8wt% WO3.

11. The conductive paste according to claim 1, characterized in that: The resin is a mixture of ethyl cellulose, acrylic resin and epoxy resin in a mass ratio of 1:4:5, the auxiliary agent includes a thixotropic agent and a curing cross-linking agent, and the carrier solvent includes a mixture of alcohol ester lauryl, butyl carbitol acetate and terpineol in a mass ratio of 1:6:3; The dispersant includes one or more of BYK-111, ED120, ED403 and ED420; The remaining solvent is a mixture of alcohol ester dodecanol, butyl carbitol acetate, terpineol and diethyl adipate in a mass ratio of 1:6:2:

1.

12. A method for preparing the conductive paste according to any one of claims 1 to 11, characterized in that: The following steps are involved: S1: placing the carrier solvent in a heating container, slowly adding the auxiliary agent and the resin at 40-60° C., mechanically stirring for 0.5-1.0 h, heating to 75-85° C., and continuing mechanical stirring for 1.5-2 h to form the organic carrier; S2: adding the nickel alloy powder and the dispersant to the organic vehicle and dispersing them uniformly to obtain a paste; and S3: adding the glass phase, the silver powder and the remaining solvent to the paste, and stirring to uniformly disperse the materials to obtain the conductive paste.

13. The preparation method according to claim 12, characterized in that The nickel alloy powder is a silver-clad nickel alloy having a silver shell layer on its surface. The preparation method of the silver-clad nickel alloy comprises the following steps: S21: taking the nickel alloy powder raw material, sequentially cleaning the surface with ethanol and immersing it in hydrochloric acid for surface activation, rinsing it with deionized water until the surface of the nickel alloy powder is neutral, and then vacuum drying it at 60-80° C. for 2-4 hours; S22: feeding the activated nickel alloy powder into a fluidized bed reactor, introducing Ar carrier gas, so that the activated nickel alloy powder is in a "fluidized state" under the action of the gas flow; S23: starting the heating system to raise the temperature of the reaction zone to 250-350° C., preheating the nickel alloy powder and further removing moisture and gas adsorbed on the surface; and S24: silver trifluoroacetate is placed in a vaporization chamber and heated to a vaporization temperature to form silver source vapor, and the silver source vapor is introduced into the reaction zone via Ar carrier gas. The silver source vapor is decomposed into silver atoms in the reaction zone and adsorbed onto the surface of the nickel alloy powder, and gradually grows epitaxially to form the continuous silver shell layer.

14. An application of a conductive paste, characterized in that: The conductive paste is the conductive paste according to any one of claims 1 to 11 or the conductive paste prepared according to the preparation method of claim 12 or 13, and the conductive paste is applied to the back surface paste of the TOPCon battery.