Silver paste, preparation method thereof and solar cell

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides silver paste, a preparation method thereof and a solar cell. The silver paste comprises silver powder, glass powder and an organic carrier, and the organic carrier comprises, by weight, 40-70 parts of a component A, 20-35 parts of a component B and 15-25 parts of a component C; the component A comprises 35-75 parts of a first solvent, 25-45 parts of thermosetting nitrogen-containing resin and 3-8 parts of an amide compound; the component B comprises 40-60 parts of a second solvent, 15-25 parts of thermoplastic aldehyde condensation resin and 20-45 parts of synthetic wax; and the component C comprises 45-70 parts of a third solvent, 5-15 parts of a polyoxyethylene ether compound and 15-25 parts of a silicone oil compound. According to the embodiment of the invention, the viscosity of the slurry is reduced and the thixotropic coefficient is increased through the synergistic effect and careful proportioning of the components A, B and C.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaics, in particular to a silver paste, a preparation method thereof and a solar cell. BACKGROUND

[0002] As an indispensable part of sustainable development, photovoltaic energy has attracted unprecedented attention in the global research and application in recent years. In this field, the core technology and material innovation of photovoltaic cells are particularly important, which is directly related to the conversion efficiency and controllability of the cost. Among them, silver paste, as a key material in the manufacturing process of photovoltaic cells, its performance directly affects the electrical performance and mechanical strength of the cell, and becomes the focus of continuous exploration and optimization in the industry.

[0003] Silver paste is mainly used to form electrode lines on the cell sheet, including the preparation of front-side metallization and back-side field contact area. In front-side metallization, silver paste needs to form a stable conductive path on a small line to connect the PN junction of the cell sheet with the external circuit, ensuring the effective flow of current; while in the back-side field contact area, silver paste not only needs to achieve good conductivity, but also needs to form effective contact with the cell sheet material to reduce the contact resistance and improve the overall performance of the cell.

[0004] Currently, with the wide application of TOPCon (tunnel oxide passivated contact) technology, the manufacturing of photovoltaic cells is constantly advancing towards higher efficiency and lower cost. However, the traditional silver paste has exposed a series of problems when facing the challenges of new technologies. First, the dispersibility of silver powder in the paste directly affects the printing quality and conductivity, especially when the cell sheet requires narrower and thinner electrode lines, the particle size and morphology of silver powder require more stringent requirements. Second, the viscosity and thixotropy of the paste are crucial to the grid breakage rate and plasticizing effect in the printing process, and too high or too low viscosity will lead to poor printing and affect the yield of the cell sheet. In addition, the precipitation of organic solvents not only affects the printing performance of silver paste, but also causes unnecessary energy consumption in the subsequent sintering process, reducing the utilization rate of silver paste. In order to solve the above problems, the industry tries to optimize the silver powder formula, improve the organic carrier components, etc. to improve the comprehensive performance of silver paste. For example, some enterprises try to use silver powder with special morphology to enhance its printability and conductivity; others focus on the organic part of the paste, trying to reduce the grid breakage rate and improve the plasticizing by adjusting the type of solvent, the content of resin and the proportion of thixotropic agent. However, these attempts are either limited by high cost or difficult to achieve good connection and sintering effect of silver powder under low viscosity conditions, especially in the application scenario of full opening steel plate printing technology, how to maintain high performance while ensuring low consumption has become a technical problem to be solved.

[0005] Therefore, how to improve the operation stability of the solar cell is an important technical problem to be solved in the field. SUMMARY

[0006] The application provides a silver paste, a preparation method thereof and a solar cell, and at least improves the operation stability of the solar cell.

[0007] According to some embodiments of the application, the first aspect of the embodiments of the application provides a silver paste, which comprises silver powder, glass powder and an organic carrier; the organic carrier comprises 40-70 parts of an A component, 20-35 parts of a B component and 15-25 parts of a C component according to weight; the A component comprises 35-75 parts of a first solvent, 25-45 parts of a thermosetting nitrogen-containing resin and 3-8 parts of an amide compound according to weight, wherein the first solvent is an amine solvent; the B component comprises 40-60 parts of a second solvent, 15-25 parts of a thermoplastic aldehyde condensation resin and 20-45 parts of a synthetic wax according to weight, wherein the second solvent is selected from one or more of an alcohol solvent, an ester solvent and a hydrocarbon solvent; and the C component comprises 45-70 parts of a third solvent, 5-15 parts of a polyoxyethylene ether compound and 15-25 parts of a silicone oil compound according to weight, wherein the third solvent is an organic solvent carrying an ether bond.

[0008] In some embodiments, the first solvent is selected from one or more of triethylamine, N-methyldiethylamine, monoethanolpropanolamine, triethanolpropanolamine, diethanolmonoiso-propanolamine and 2-methyl-6-ethyl aniline; and / or, the thermosetting nitrogen-containing resin is selected from one or more of etherified melamine formaldehyde resin, polyurethane resin and polyimide resin; and / or, the amide compound is selected from one or more of oleic acid amide, behenic acid amide, N'-methylene-bis-stearic acid amide and acetic acid amide.

[0009] In some embodiments, the second solvent is selected from one or more of 12 alcohol ester, 16 alcohol ester, benzyl butyl phthalate, dimethyl adipate, butyl benzoate, diethylene glycol butyl ether acetate, ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tributyl citrate and D80 solvent oil; and / or, the thermoplastic aldehyde condensation resin is polyvinyl butyral resin and / or polyurethane-based acrylic formaldehyde resin; and / or, the synthetic wax is polyamide wax and / or maleic anhydride grafted polyethylene wax.

[0010] In some embodiments, the third solvent is selected from one or more of ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tripropylene glycol monobutyl ether, triethylene glycol ethyl ether and polyether polyol; and / or, the polyoxyethylene ether compound is selected from one or more of 18 amine polyoxyethylene ether, lauryl alcohol polyoxyethylene ether and tallow amine polyoxyethylene ether; and / or, the silicone oil compound is amino silicone oil and / or dimethyl silicone oil.

[0011] In some embodiments, the D50 of the silver powder is 0.9 μm to 3.0 μm, preferably 1.05 μm to 1.35 μm; and / or, the D50 of the glass powder is 1.0 μm to 3.0 μm, preferably 1.25 μm to 1.35 μm, and the glass powder comprises 55 to 70 parts of PbO, 8 to 15 parts of B2O3, 8 to 14 parts of Fe2O3, 4 to 8 parts of SiO2, 3 to 6 parts of BaO and 2 to 5 parts of Al2O3 by weight.

[0012] In some embodiments, the weight ratio of the silver powder, the glass powder and the organic carrier in the silver paste is (75 to 90):(1 to 10):(5 to 15), preferably (85 to 90):(2 to 5):(8 to 10).

[0013] In some embodiments, the fineness of the silver paste is 3 μm to 5 μm.

[0014] According to some embodiments of the present application, the second aspect of the embodiments of the present application provides a preparation method of a silver paste, the silver paste being the above-mentioned silver paste, the preparation method of the silver paste comprising: step S1, first mixing of a first solvent, a thermosetting nitrogen-containing resin and an amide compound to obtain an A component; second mixing of a second solvent, a thermoplastic aldehyde condensation resin and a synthetic wax to obtain a B component; third mixing of a third solvent, a polyoxyethylene ether compound and a silicone oil compound to obtain a C component; step S2, fourth mixing of the A component, the B component and the C component to obtain an organic carrier; and step S3, sequentially mixing and grinding of the organic carrier, silver powder and glass powder to obtain the silver paste.

[0015] In some embodiments, the first mixing, the third mixing and the fourth mixing are each independently carried out at 60 ± 5 °C; and / or, the second mixing is carried out at 90 ± 5 °C.

[0016] According to some embodiments of the present application, the third aspect of the embodiments of the present application provides a solar cell comprising an electrode grid line prepared from the above-mentioned silver paste.

[0017] The technical solutions provided by the embodiments of the present application have at least the following advantages: through the synergistic effect and careful proportioning of the A, B and C components, the viscosity of the paste is reduced and the thixotropic coefficient is improved, the stable flowability of the silver paste and excellent silver line shaping effect in full opening steel plate narrow line width printing are ensured, the broken grid is reduced, the printing yield and the finished product rate of the cell sheet are improved, and finally the cycle performance and contact resistance of the solar cell are significantly optimized. DETAILED DESCRIPTION

[0018] As can be known from the background art, the organic carrier of the photovoltaic silver paste in the prior art is difficult to meet the printing requirements while taking into account the characteristics of good plasticity and low solvent precipitation, so the corresponding silver paste cannot have high thixotropy coefficient, high miscibility and low viscosity, and the prepared solar cell has the problem of poor running stability. In order to solve the above problem, according to some embodiments of the present application, the first aspect of the embodiments of the present application provides a silver paste comprising silver powder, glass powder and organic carrier, wherein the organic carrier comprises 40-70 parts of A component, 20-35 parts of B component and 15-25 parts of C component by weight; the A component comprises 35-75 parts of a first solvent, 25-45 parts of a thermosetting nitrogen-containing resin and 3-8 parts of an amide compound by weight, wherein the first solvent is an amine solvent; the B component comprises 40-60 parts of a second solvent, 15-25 parts of a thermoplastic aldehyde condensation resin and 20-45 parts of a synthetic wax by weight, wherein the second solvent is selected from one or more of an alcohol solvent, an ester solvent and a hydrocarbon solvent; the C component comprises 45-70 parts of a third solvent, 5-15 parts of a polyoxyethylene ether compound and 15-25 parts of a silicone oil compound by weight, wherein the third solvent is an organic solvent carrying an ether bond.

[0019] The silver paste formula provided by the present application realizes the overall optimization of the performance of the silver paste through the synergistic effect of the A, B and C components, not only solves the common technical problems in full-opening steel plate printing, such as high broken grid rate, poor plasticity and solvent precipitation, but also effectively improves the electrical performance and mechanical strength of the solar cell, thereby providing strong technical support for the improvement of the efficiency and the reduction of the cost of the photovoltaic cell.

[0020] The use of amine solvents (first solvents) in the A component improves the miscibility of the slurry, reduces the viscosity of the slurry, making the slurry more smooth in the printing process, and reducing the phenomenon of broken grid. At the same time, the dispersibility of amine solvents enhances the uniform distribution of silver powder, improves the plastic quality of silver wire after printing, and is beneficial to the effective sintering and low resistance of silver powder. The stable resin network formed during the curing process of thermosetting nitrogen-containing resin enhances the connection between silver powders, further reduces the contact resistance, improves the open-circuit voltage and short-circuit current of the battery, and thus improves the efficiency. The presence of amide compounds increases the thixotropy coefficient of the slurry, which can ensure excellent plasticity of silver powder after printing even under low viscosity conditions, avoid deformation of silver wire, and ensure the electrical performance and mechanical strength of the battery sheet. In the B component, the mixture of alcohol, ester and hydrocarbon solvents (second solvents) adjusts the viscosity and fluidity of the slurry, ensures the stable delivery of the slurry during printing, and reduces printing defects. Thermoplastic aldehyde condensation resin provides good formability during printing and mechanical strength after curing, while synthetic wax prevents silver wire deformation after sintering, enhancing the mechanical stability and electrical performance of silver wire. In the C component, the organic solvent (third solvent) carrying ether bond and polyoxyethylene ether compound synergistically improve the thixotropy and printing precision of the slurry, ensure uniform wetting and leveling during printing, and reduce printing defects. The addition of silicone oil compound further optimizes the rheological properties of the slurry, enhances the dispersibility of silver powder, reduces the agglomeration of silver powder during printing, improves the surface quality of silver wire after sintering, and reduces the contact resistance.

[0021] In particular, the weight fraction of the A component is 40-70 parts, which enables the slurry to have sufficient fluidity for high-quality printing, while ensuring the formation of a resin network to support the plasticity and sintering of silver powder. The weight fraction of the B component is 20-35 parts, in which the thermoplastic resin and synthetic wax synergistically provide the necessary support for silver wire formation, while not excessively increasing the viscosity of the slurry, which is beneficial for continuous printing. The weight fraction of the C component is 15-25 parts, within this range, the third solvent and surfactant have a significant effect, ensuring the stability of the slurry during printing and the good plasticity of silver wire, reducing the risk of solvent precipitation, and improving the printing efficiency.

[0022] More importantly, the three components, A, B, and C, work synergistically to form a unified whole, enhancing the performance of the silver paste. Specifically, the high solubility of the amine solvent in component A with the resin, combined with the solvents in components B and C, enhances the miscibility of the paste. This significantly reduces the amount of organic solvent precipitated during sintering, decreasing energy consumption and improving the utilization rate of the silver paste. Furthermore, the synergistic effect of the thermosetting resin and amide compounds, along with the assistance of synthetic wax and silicone oil after sintering, ensures effective contact between the silver powder and silicon material, significantly reducing contact resistance and improving current conduction efficiency. Simultaneously, the optimized silver paste performance improves the cycle performance of the battery and extends the lifespan of the photovoltaic cell.

[0023] Preferably, the organic carrier comprises 40-45 parts of component A, 25-30 parts of component B, and 15-20 parts of component C; and by weight, component A comprises 70-75 parts of a first solvent, 25-30 parts of a thermosetting nitrogen-containing resin, and 5-8 parts of an amide compound; by weight, component B comprises 55-60 parts of a second solvent, 20-25 parts of a thermoplastic aldehyde condensation resin, and 20-25 parts of a synthetic wax; and by weight, component C comprises 65-70 parts of a third solvent, 5-8 parts of a polyoxyethylene ether compound, and 20-25 parts of a silicone oil compound. The more precise proportions of components A, B, and C in the above-mentioned organic carrier significantly reduce the viscosity of the paste and increase the thixotropic coefficient, improving the stable flowability and excellent silver line shaping effect of the silver paste in narrow-linewidth printing on a fully open steel plate, reducing grid breakage, and improving printing yield and the yield of finished solar cells.

[0024] In some embodiments, the first solvent is selected from one or more of triethylamine, N-methyldiethylamine, monoethylpropanolamine, triethylpropanolamine, diethanolmonoisopropanolamine, and 2-methyl-6-ethylaniline; and / or, the thermosetting nitrogen-containing resin is selected from one or more of etherified melamine-formaldehyde resin, polyurethane resin, and polyimide resin; and / or, the amide compound is selected from one or more of oleamide, betaine, N'-methylenebis-stearamide, and acetate. In component A above, compared to other amine solvents, triethylamine, N-methyldiethylamine, etc., have stronger dissolving power and lower surface tension, which can more effectively reduce the viscosity of the silver paste, while promoting the suspension and dispersion of silver powder, thus promoting uniform deposition of silver powder during the printing process to form continuous and stable conductive lines. Monoethylpropanolamine, triethylpropanolamine, and other amine solvents, in addition to providing good solubility, also have a certain degree of hydrophilicity, which helps the paste wet the silicon wafer surface, improving printing quality and the adhesion of the solar cell. Complex molecular structures such as diethanolamine and 2-methyl-6-ethylaniline provide a more balanced miscibility and thixotropy, enabling the silver paste to maintain good flowability during printing while rapidly recovering viscosity after printing, preventing sagging and improving the clarity and shaping of the silver wires. For the aforementioned thermosetting nitrogen-containing resins, the preferred etherified melamine-formaldehyde resin exhibits good heat resistance and chemical stability, forming a more stable resin skeleton during sintering, supporting the connections between silver powders, improving the mechanical strength of the silver wires, reducing the risk of short circuits, and simultaneously enhancing conductivity and the open-circuit voltage of the battery. Polyurethane resin provides additional shaping support for the silver paste during curing, further reducing distortion of the silver wires during drying or sintering, and improving the continuity and stability of the sintered silver wires. Polyimide resin significantly improves the thermal stability of the silver paste, reduces the decomposition of organic matter under high-temperature sintering conditions, reduces residues after silver wire sintering, and maintains good contact resistance. Aliphatic amides such as oleamide and betaine amide can act as leveling agents and antistatic agents, improving the rheological properties of silver paste, reducing silver wire breakage during printing, and simultaneously improving the contact quality between the cured silver wires and the silicon wafer, thus reducing contact resistance. Amide derivatives such as N'-methylene-bis-stearamide and acetate amide can further enhance the dispersion of silver powder in organic carriers, reduce silver powder agglomeration, and thus significantly improve the overall photoelectric conversion efficiency and reliability of the final solar cell.

[0025] In some embodiments, the second solvent is selected from one or more of 12-ol esters, 16-ol esters, benzyl butyl phthalate, dimethyl adipate, butyl benzoate, diethylene glycol butyl ether acetate, ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tributyl citrate, and D80 solvent oil; and / or, the thermoplastic aldehyde condensation resin is polyvinyl butyral resin and / or polyurethane-based formaldehyde acrylate resin; and / or, the synthetic wax is polyamide wax and / or maleic anhydride-grafted polyethylene wax. In the above-mentioned component B, the preferred second solvent can more effectively adjust the viscosity of the silver paste, making it easy to flow and less prone to over-penetration during printing, thereby further improving the clarity and thickness consistency of the silver lines. Polyvinyl butyral resin and polyurethane-based formaldehyde acrylate resin, these two preferred thermoplastic aldehyde condensation resins, have better low-temperature fluidity and higher curing temperatures, which can more effectively maintain the stability and viscosity of the paste before sintering, while rapidly curing into a film during high-temperature sintering, further enhancing the adhesion between the silver lines and the silicon wafer surface. Synthetic waxes such as polyamide wax and maleic anhydride-grafted polyethylene wax can be combined with thermoplastic aldehyde condensation resins to further improve the printability of silver paste and the shaping of silver wires, and ultimately optimize the operational stability of the resulting solar cells.

[0026] In some embodiments, the third solvent is selected from one or more of ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tripropylene glycol monobutyl ether, triethylene glycol ethyl ether, and polyether polyols; and / or, the polyoxyethylene ether compound is selected from one or more of 18-amine polyoxyethylene ether, lauryl polyoxyethylene ether, and tallow amine polyoxyethylene ether; and / or, the silicone oil compound is amino silicone oil and / or dimethyl silicone oil. In the above-mentioned component C, the preferred ether solvents can significantly reduce the surface tension of the silver paste, improve wettability, and make the silver paste flow and spread more easily during printing, forming more uniform and continuous silver lines. The preferred polyoxyethylene ether compounds can further optimize the rheology and printability of the silver paste by reducing the interfacial tension between the silver powder and the organic carrier, improving the dispersion of the silver powder, reducing the deformation and breakage of the silver lines after printing, while enhancing the sintering performance of the silver paste and reducing contact resistance. In addition, amino silicone oil and dimethyl silicone oil can be used as additives to more effectively inhibit the premature precipitation of organic solvents. At the same time, they form a thin protective film during the curing or sintering process, further reducing contact resistance and improving the performance of the resulting solar cells.

[0027] Furthermore, in component A, the first solvent includes triethylpropanolamine and 2-methyl-6-ethylaniline, with a weight ratio of triethylpropanolamine to 2-methyl-6-ethylaniline of (1.5~1.6):1. At this ratio, triethylpropanolamine, with its amine structure, effectively improves the overall solubility and miscibility of the paste, while 2-methyl-6-ethylaniline, through its amine properties, enhances the dispersibility of silver powder and the rheological properties of the paste. The combined use of these two components according to the aforementioned ratio not only improves the solubility and miscibility of the paste and optimizes the thixotropic coefficient, but also further reduces solvent precipitation, enabling continuous and stable printing of silver paste under low viscosity conditions, reducing the grid breakage rate of silver lines, and improving the overall performance and production efficiency of the solar cells.

[0028] Furthermore, for component B, the preferred second solvent includes 12-ol ester, dimethyl adipate, and D80 solvent oil, with a weight ratio of 12-ol ester, dimethyl adipate, and D80 solvent oil of 5:(2~3):(2~3). The addition of dimethyl adipate and D80 solvent oil facilitates the formation of more ideal silver powder molding during the drying and sintering processes after printing. In particular, the ester structure of dimethyl adipate helps promote the close packing of silver powder, while D80 solvent oil, as a light oil, effectively regulates the fluidity of the paste, ensuring uniform distribution of silver powder during printing. Simultaneously, its low-temperature volatility during sintering helps eliminate excess solvent, optimizes the sintering environment of the silver powder, and reduces contact resistance. Using 12-ol ester, dimethyl adipate, and D80 solvent oil in the above-mentioned proportions as the second solvent more effectively balances the viscosity and printability of the resulting silver paste, optimizes the molding and sintering processes, and further improves the performance of the final solar cell.

[0029] In component C, the preferred third solvent includes ethylene glycol phenyl ether acetate and 2-phenoxyethanol, with a weight ratio of ethylene glycol phenyl ether acetate to 2-phenoxyethanol of (4~5):9; and / or, the preferred silicone oil compound is a mixed silicone oil formed by amino silicone oil and dimethyl silicone oil, with a weight ratio of dimethyl silicone oil to amino silicone oil of (1.2~1.5):1. In the above scheme, the ratio of ethylene glycol phenyl ether acetate to 2-phenoxyethanol further optimizes the leveling and thixotropy of the slurry, improving the surface quality of the silver wires; while the mixed use of dimethyl silicone oil and amino silicone oil more significantly achieves a dual improvement in the thixotropy of the slurry and the dispersibility of silver powder, reducing the contact resistance of the silver wires, and ultimately further improving the efficiency of the finally prepared solar cell.

[0030] In several particularly preferred embodiments, the organic carrier comprises, by weight, 44-45 parts of component A, 25-26 parts of component B, and 15-17 parts of component C; and component A comprises 40-42 parts of triethylpropanolamine, 24-25 parts of 2-methyl-6-ethylaniline, 28-30 parts of polyurethane resin, and 4-5 parts of N'-methylene-bis-stearamide, and component B comprises 25-26 parts of... The formula comprises 12 parts of alcohol ester, 14-15 parts of dimethyl adipate, 14-15 parts of D80 solvent oil, 24-25 parts of polyvinyl butyral resin, and 20-22 parts of maleic anhydride-grafted polyethylene wax. Component C includes 20-22 parts of ethylene glycol phenyl ether acetate, 42-45 parts of 2-phenoxyethanol, 8-10 parts of tallow amine polyoxyethylene ether, 14-15 parts of dimethyl silicone oil, and 10-12 parts of amino silicone oil. Through extensive experimentation, the inventors have optimized the above-mentioned more precise organic carrier formulation. In this formulation, the raw materials in components A, B, and C can better synergize, thereby significantly improving the thixotropic coefficient and miscibility of the resulting silver paste, while reducing its viscosity. This facilitates better sintering and shaping during the fabrication of electrode grid lines and reduces resistance, resulting in a solar cell with better overall performance.

[0031] In some embodiments, the D50 of the silver powder is 0.9 μm to 3.0 μm, preferably 1.05 μm to 1.35 μm; and / or, the D50 of the glass powder is 1.0 μm to 3.0 μm, preferably 1.25 μm to 1.35 μm, and by weight, the glass powder comprises 55 to 70 parts of PbO, 8 to 15 parts of B2O3, 8 to 14 parts of Fe2O3, 4 to 8 parts of SiO2, 3 to 6 parts of BaO, and 2 to 5 parts of Al2O3. In the above embodiments, by optimizing the particle size range of the silver powder and the glass powder, and by optimizing the type and formulation of the glass powder, it is possible to better match the above-mentioned organic carrier, so that the resulting silver paste can form more stable contact points during sintering, further reducing contact resistance and improving battery efficiency.

[0032] In order to further optimize the fineness and rheological properties of the obtained silver paste, thereby improving the printability, stability and quality of the obtained silver paste under low consumption conditions, in some embodiments, the weight ratio of silver powder, glass powder and organic carrier in the silver paste is preferably (75~90):(1~10):(5~15), more preferably (85~90):(2~5):(8~10).

[0033] In some embodiments, the FOG (Field of Gain) of the silver paste is 3 μm to 5 μm. Under this fineness condition, the organic carrier in the silver paste can more significantly exert its plasticity and low precipitation effect, thereby more effectively reducing printing discontinuities and grid breakage problems. It also helps to further improve the flatness and smoothness of the silver lines, reduce surface defects, and improve the photoelectric conversion efficiency and appearance quality of the resulting solar cells.

[0034] According to some embodiments of this application, a second aspect of this application provides a method for preparing silver paste, wherein the silver paste is the aforementioned silver paste. The method for preparing silver paste includes: step S1, a first solvent, a thermosetting nitrogen-containing resin, and an amide compound are mixed in a first mixing to obtain component A; a second solvent, a thermoplastic aldehyde condensation resin, and a synthetic wax are mixed in a second mixing to obtain component B; a third solvent, a polyoxyethylene ether compound, and a silicone oil compound are mixed in a third mixing to obtain component C; step S2, component A, component B, and component C are mixed in a fourth mixing to obtain an organic carrier; step S3, the organic carrier, silver powder, and glass powder are sequentially mixed and ground to obtain silver paste.

[0035] In response to the aforementioned silver paste, this application provides a corresponding preparation method. In step S1, components A, B, and C are prepared separately and independently. In step S2, components A (high solubility and dispersibility), B (good flowability and adhesion), and C (optimized thixotropy and surface activity) are mixed to form an organic carrier with excellent printability, high plasticity, low viscosity, and low solvent precipitation. Subsequently, in step S3, silver powder and glass powder are added, and the dispersion of silver powder is further optimized through grinding to reduce the presence of large particles and further improve the stability and reliability of the silver paste.

[0036] In some embodiments, the first and third mixing are each carried out independently at 60±5°C. That is, for components A and C, mixing is performed under this condition to facilitate good dissolution of other components by the first or third solvent, while reducing the damage of certain sensitive components to high temperatures. Preferably, the second mixing is carried out at 90±5°C to promote more efficient dissolution of thermoplastic resins and synthetic waxes, thereby optimizing the thixotropic and malleable properties of the resulting component B and the final silver paste. Finally, preferably, the fourth mixing is carried out at 60±5°C to more effectively disperse and mix components A, B, and C, ultimately improving the continuity and uniformity of the silver paste during the printing process, and resulting in battery components with low contact resistance and high cycle performance after sintering.

[0037] According to some embodiments of this application, a third aspect of this application provides a solar cell including electrode grid lines, which are prepared from the aforementioned silver paste. The resulting silver paste, relying on a high-performance organic carrier, possesses a high thixotropic coefficient, high miscibility, and low viscosity. The high thixotropic coefficient ensures the stability of the silver paste and the clarity of the grid lines during the printing process, reducing grid breakage and improving the yield of the solar cell. High miscibility allows for more uniform dispersion of silver powder in the organic carrier, promoting effective contact between the silver powder and silicon material, reducing contact resistance, and improving current conduction efficiency. Low viscosity not only reduces silver paste consumption but also increases printing speed and efficiency, which is particularly important for large-scale production. Furthermore, these characteristics work together to ensure the cycle performance and stability of the solar cell under long-term operation, reducing the failure rate and extending its service life.

[0038] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0041] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0042] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are used only to facilitate the description of the embodiments of this application and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0043] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0044] In the embodiments of this application, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0045] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0046] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0047] The embodiments of this application will now be described in detail. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0048] Example 1

[0049] Preparation of a silver paste:

[0050] (1) Weigh and prepare components A, B and C.

[0051] (1-1) Preparation of component A: Based on the weight of the obtained component A as 100%, 40% of triethylpropanolamine and 25% of 2-methyl-6-ethylaniline were weighed as the first solvent; 30% of polyurethane resin was used as the thermosetting nitrogen-containing resin; and 5% of N'-methylene-bis-stearamide was used as the amide compound. After mixing at 60°C, the mixture was first stirred and dispersed at a speed of 500 rpm / min for 5 min, and then stirred and dispersed at a speed of 1200 rpm / min for 15 min to obtain component A.

[0052] (1-2) Preparation of component B: Based on the weight of the obtained component B as 100%, weigh 25% of 12 alcohol ester, 15% of dimethyl adipate, and 15% of D80 solvent oil as the second solvent; weigh 25% of polyvinyl butyral resin as the thermoplastic aldehyde condensation resin and 20% of maleic anhydride grafted polyethylene wax as the synthetic wax. After mixing at 90°C, first stir and disperse at a speed of 500 rpm / min for 5 min, and then stir and disperse at a speed of 1200 rpm / min for 15 min to obtain component B.

[0053] (1-3) Preparation of component C: Based on the weight of the obtained component C as 100%, weigh 22% ethylene glycol phenyl ether acetate and 45% 2-phenoxyethanol as the third solvent; 8% tallow amine polyoxyethylene ether as a polyoxyethylene ether compound; 15% dimethyl silicone oil and 10% amino silicone oil as silicone oil compounds. After mixing at 60°C, first stir and disperse at a speed of 500 rpm / min for 5 min, then stir and disperse at a speed of 1200 rpm / min for 15 min to obtain component C.

[0054] (2) Based on the total weight of the final silver paste as 100%, weigh 4.4% of component A, 2.6% of component B and 1.7% of component C and mix them at 60°C to obtain an organic carrier.

[0055] (3) Based on the total weight of the final silver paste as 100%, weigh 88.8% of the silver powder (D50 is 1.05μm~1.35μm) and mix it with the obtained organic carrier. Stir and disperse it on a dispersion device at a speed of 500 rpm / min for 5 min. Then weigh 2.5% of the glass powder (D50 is 1.25μm~1.35μm; by weight percentage, it includes 55% PbO, 15% B2O3, 14% Fe2O3, 8% SiO2, 6% BaO and 2% Al2O3) and add it to it. Stir it evenly with an ink knife. Stir and disperse it on a dispersion device at a speed of 500 rpm / min for 2 min, and then stir and disperse it at a speed of 1200 rpm / min for 2 min. After that, transfer the paste to a three-roll mill. After the three-roll mill is completed, a silver paste with a fineness FOG of 4μm is obtained.

[0056] Example 2

[0057] Preparation of a silver paste:

[0058] The only difference between this embodiment and Example 1 is that the amount of triethylpropanolamine added to the first solvent of component A is changed to 32.5%, and the amount of 2-methyl-6-ethylaniline added is also changed to 32.5%, that is, the weight ratio of triethylpropanolamine to 2-methyl-6-ethylaniline is changed to 1:1.

[0059] Example 3

[0060] Preparation of a silver paste:

[0061] The only difference between this embodiment and Example 1 is that the amount of 12-ol ester added to the second solvent of component B is changed to 27.5%, the amount of dimethyl adipate added is changed to 5.5%, and the amount of D80 solvent oil added is changed to 22%, that is, the weight ratio of 12-ol ester, dimethyl adipate and D80 solvent oil is changed to 5:1:4.

[0062] Example 4

[0063] Preparation of a silver paste:

[0064] The only difference between this embodiment and Example 1 is that the amount of ethylene glycol phenyl ether acetate added to the third solvent of component C is changed to 16.75% and the amount of 2-phenoxyethanol added is changed to 50.25%, that is, the weight ratio of ethylene glycol phenyl ether acetate and 2-phenoxyethanol is changed to 1:3.

[0065] Example 5

[0066] Preparation of a silver paste:

[0067] The only difference between this embodiment and Example 1 is that 2-methyl-6-ethylaniline was not added to component A.

[0068] Example 6

[0069] Preparation of a silver paste:

[0070] The only difference between this embodiment and Example 1 is that dimethyl adipate was not added to component B.

[0071] Example 7

[0072] Preparation of a silver paste:

[0073] The only difference between this embodiment and Example 1 is that ethylene glycol phenyl ether acetate was not added to component C.

[0074] Example 8

[0075] Preparation of a silver paste:

[0076] The only difference between this embodiment and Embodiment 1 is that the D50 of the silver powder used is changed to 0.9 μm, and the D50 of the glass powder used is changed to 3.0 μm.

[0077] Example 9

[0078] Preparation of a silver paste:

[0079] The only difference between this embodiment and Embodiment 1 is that the percentage content of each component in the silver paste is changed to: 7.0% of component A, 3.5% of component B, 2.5% of component C, 77.0% of silver powder, and 10.0% of glass powder.

[0080] Example 10

[0081] Preparation of a silver paste:

[0082] The only difference between this embodiment and Embodiment 1 is that the temperature conditions during the silver paste preparation process are uniformly set to 40°C.

[0083] Comparative Example 1

[0084] Preparation of a silver paste:

[0085] The only difference between this comparative example and Example 1 is that component A was not added.

[0086] Comparative Example 2

[0087] Preparation of a silver paste:

[0088] The only difference between this comparative example and Example 1 is that component B was not added.

[0089] Comparative Example 3

[0090] Preparation of a silver paste:

[0091] The only difference between this comparative example and Example 1 is that component C was not added.

[0092] Comparative Example 4

[0093] Preparation of a silver paste:

[0094] The only difference between this comparative example and Example 1 is that, based on the total weight of the final silver paste being 100%, the amount of component A added is changed to 3.0%, the amount of component B added is changed to 1.8%, and the amount of component C added is changed to 3.9% (that is, by weight, the organic carrier of the silver paste includes 30 parts of component A, 18 parts of component B, and 39 parts of component C).

[0095] Comparative Example 5

[0096] Preparation of a silver paste:

[0097] The only difference between this comparative example and Example 1 is that, based on the total weight of the final silver paste being 100%, the amount of component A added is changed to 7.2%, the amount of component B added is changed to 0.5%, and the amount of component C added is changed to 1.0% (that is, by weight, the organic carrier of the silver paste includes 72 parts of component A, 5 parts of component B, and 10 parts of component C).

[0098] Test methods

[0099] Silver paste viscosity: The viscosity was obtained by using a rotational viscometer with a No. 14 rotor at 1 revolution, 15 revolutions, and 50 revolutions.

[0100] Solar cell sample preparation and performance testing: The silver paste obtained from the above embodiments and comparative examples was screen-printed onto silicon wafers to form wet grid lines. These were then dried and sintered to form electrode grid lines. The resulting solar cell samples were then assembled, and their photoelectric efficiency was tested. The results were compared with the final test results from the production stage. Simultaneously, during the above process, the electrode grid lines formed after drying were tested and observed. Higher and narrower grid lines indicate higher efficiency and longer operational lifespan of the final solar cell.

[0101] The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104] As can be seen from the above description, compared with the comparative examples, the above embodiments of the present invention achieve the preparation of a high-performance organic carrier, and the resulting silver paste relies on the high-performance organic carrier to have a high thixotropic coefficient, high miscibility and low viscosity. Finally, a solar cell with high cycle performance and stability is prepared.

[0105] In the table above, Isc is the short-circuit current, which is the maximum current output when the positive and negative terminals of the battery are short-circuited under standard illumination; a larger value indicates better light absorption performance of the battery. Uoc is the open-circuit voltage; a larger value means a stronger ability of the battery to generate voltage. Rs is the series resistance, which is the equivalent resistance inside the battery; a larger value means greater current loss during current flow inside the battery. FF is the fill factor; a larger value indicates a more "square" IV curve, indicating that the battery performance is closer to the theoretical limit. Additionally, wet weight represents the slurry state during electrode preparation. It is the weight of the wet slurry per unit area measured after printing and before sintering. By controlling this value window, the efficiency and cost of the resulting battery can be more effectively balanced.

[0106] In the above embodiments, specifically:

[0107] Comparing Examples 2 and 5 with Example 1, it can be seen that by optimizing the composition of the first solvent of component A and further optimizing the weight ratio of triethylpropanolamine to 2-methyl-6-ethylaniline, the solubility and miscibility of the paste can be improved, the thixotropic coefficient can be optimized, and the silver paste can be printed more continuously and stably under low viscosity conditions, reducing its grid breakage rate and ultimately significantly improving the overall performance of the battery cell.

[0108] Comparing Examples 3 and 6 with Example 1, it can be seen that by optimizing the composition of the second solvent of component B and further optimizing the weight ratio of 12 alcohol ester, dimethyl adipate and D80 solvent oil, the viscosity and printability of the obtained silver paste can be more effectively balanced, its molding and sintering process can be optimized, thereby further improving the performance of the final obtained solar cell.

[0109] Comparing Examples 4 and 7 with Example 1, it can be seen that by optimizing the composition of the third solvent in component C and further optimizing the weight ratio of ethylene glycol phenyl ether acetate and 2-phenoxyethanol, the thixotropic properties of the slurry and the dispersibility of silver powder can be better improved, the contact resistance of the silver wire can be reduced, and the efficiency of the final prepared solar cell can be further improved.

[0110] Comparing Examples 8 and 9 with Example 1, it can be seen that by optimizing the particle size range of silver powder and glass powder, and optimizing the type and formulation of glass powder, it is possible to better match with the organic carrier in the formulation, so that the resulting silver paste can form more stable contact points during printing and sintering, further reducing contact resistance and improving battery efficiency.

[0111] Comparing Example 10 with Example 1, it can be seen that by optimizing the temperature conditions of the first mixing, second mixing, third mixing and fourth mixing in the silver paste preparation process, the continuity and uniformity of the silver paste during the printing process can be significantly improved, and the battery module obtained after sintering can have better performance.

[0112] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A silver paste, comprising silver powder, glass powder, and an organic carrier, characterized in that, The organic carrier comprises, by weight, 40-70 parts of component A, 20-35 parts of component B, and 15-25 parts of component C; By weight, component A comprises 35 to 75 parts of a first solvent, 25 to 45 parts of a thermosetting nitrogen-containing resin, and 3 to 8 parts of an amide compound, wherein the first solvent is an amine solvent; By weight, component B comprises 40-60 parts of a second solvent, 15-25 parts of a thermoplastic aldehyde condensation resin, and 20-45 parts of a synthetic wax, wherein the second solvent is selected from one or more of alcohol solvents, ester solvents, and hydrocarbon solvents; By weight, component C comprises 45 to 70 parts of a third solvent, 5 to 15 parts of a polyoxyethylene ether compound, and 15 to 25 parts of a silicone oil compound, wherein the third solvent is an organic solvent carrying ether bonds.

2. The silver paste according to claim 1, characterized in that, In component A, The first solvent is selected from one or more of triethylamine, N-methyldiethylamine, monoethylpropanolamine, triethylpropanolamine, diethanolmonoisopropanolamine, and 2-methyl-6-ethylaniline; and / or, The thermosetting nitrogen-containing resin is selected from one or more of etherified melamine-formaldehyde resin, polyurethane resin, and polyimide resin; and / or, The amide compound is selected from one or more of oleamide, behenamide, N'-methylene-bis-stearamide, and acetate.

3. The silver paste according to claim 1, characterized in that, In component B, The second solvent is selected from one or more of 12-ol esters, 16-ol esters, benzyl butyl phthalate, dimethyl adipate, butyl benzoate, diethylene glycol butyl ether acetate, ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tributyl citrate, and D80 solvent oil; and / or, The thermoplastic aldehyde condensation resin is polyvinyl butyral resin and / or polyurethane-based acrylic formaldehyde resin; and / or, The synthetic wax is a polyamide wax and / or maleic anhydride-grafted polyethylene wax.

4. The silver paste according to any one of claims 1 to 3, characterized in that, In the C component, The third solvent is selected from one or more of ethylene glycol phenyl ether acetate, 2-phenoxyethanol, tripropylene glycol monobutyl ether, triethylene glycol ethyl ether, and polyether polyols; and / or, The polyoxyethylene ether compound is selected from one or more of 18-amine polyoxyethylene ether, lauryl alcohol polyoxyethylene ether, and tallow amine polyoxyethylene ether; and / or The silicone oil compounds are amino silicone oil and / or dimethyl silicone oil.

5. The silver paste according to any one of claims 1 to 3, characterized in that, The silver powder has a D50 of 0.9 μm to 3.0 μm, preferably 1.05 μm to 1.35 μm; and / or, The glass powder has a D50 of 1.0 μm to 3.0 μm, preferably 1.25 μm to 1.35 μm, and by weight, the glass powder comprises 55 to 70 parts of PbO, 8 to 15 parts of B2O3, 8 to 14 parts of Fe2O3, 4 to 8 parts of SiO2, 3 to 6 parts of BaO, and 2 to 5 parts of Al2O3.

6. The silver paste according to any one of claims 1 to 3, characterized in that, In the silver paste, the weight ratio of the silver powder, the glass powder, and the organic carrier is (75-90):(1-10):(5-15), preferably (85-90):(2-5): (8～10)。 7. The silver paste according to any one of claims 1 to 3, characterized in that, The fineness (FOG) of the silver paste is 3.5 μm to 5 μm.

8. A method for preparing silver paste, characterized in that, The silver paste is the silver paste according to any one of claims 1 to 7, and the preparation method of the silver paste includes: Step S1: The first solvent, the thermosetting nitrogen-containing resin, and the amide compound are mixed in a first process to obtain component A; the second solvent, the thermoplastic aldehyde condensation resin, and the synthetic wax are mixed in a second process to obtain component B; the third solvent, the polyoxyethylene ether compound, and the silicone oil compound are mixed in a third process to obtain component C. In step S2, component A, component B, and component C are mixed for the fourth time to obtain the organic carrier; In step S3, the organic carrier, the silver powder, and the glass powder are mixed and ground sequentially to obtain the silver paste.

9. The method for preparing silver paste according to claim 8, characterized in that, The first mixing, the third mixing, and the fourth mixing are each carried out independently at 60±5°C; And / or, the second mixing is carried out at 90±5°C.

10. A solar cell, comprising electrode grid lines, characterized in that, The electrode grid lines are prepared from the silver paste according to any one of claims 1 to 7.

Images