Silver nickel paste, preparation method thereof and N-type crystalline silicon solar cell

Abstract

The application discloses a silver-nickel paste, a preparation method thereof and an N-type crystalline silicon solar cell. The silver-nickel paste comprises an organic additive, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder and glass powder. The nickel-silver mixture comprises micron-sized spherical nickel powder and nanometer-sized spherical silver powder. The mass percentage of the organic additive in the silver-nickel paste is between 1.5% and 2.5%. The mass percentage of the micron-sized spherical silver powder in the silver-nickel paste is between 58% and 65%. The mass percentage of the micron-sized spherical nickel powder in the silver-nickel paste is between 8% and 15%. The mass percentage of the nanometer-sized spherical silver powder in the silver-nickel paste is between 1% and 3%. The mass percentage of the organic binder in the silver-nickel paste is between 12% and 29.5%. The mass percentage of the glass powder in the silver-nickel paste is between 2% and 2.5%. The cheap and high-quality silver-nickel paste solves the problem of high production cost caused by the high cost of the existing silver paste.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more particularly to a silver-nickel paste and its preparation method, and an N-type crystalline silicon solar cell. Background Technology

[0002] The continuous upgrading and iteration of photovoltaic cell structures has led to the accumulation of outdated production capacity, making cost reduction and efficiency improvement a key concern in the photovoltaic industry. Compared with P-type crystalline silicon cells, N-type crystalline silicon cells have a longer minority carrier lifetime, no light-induced degradation, better performance in low light conditions, and a smaller temperature coefficient, making them the hope for crystalline silicon solar cells to break through the theoretical maximum efficiency.

[0003] The back grid electrodes of existing N-type crystalline silicon solar cells primarily use silver paste. The wet weight of the silver paste for each cell is approximately 40 mg, while the unit price of silver paste is roughly 7200 yuan / kg. This translates to a cost of 0.288 yuan per cell for the back grid electrodes. Given that the current unit price of a finished solar cell is approximately 3.25 yuan / cell, the cost of the back grid electrodes constitutes a significant portion of the total cost of the finished cell, impacting manufacturers' profitability and economic efficiency. Therefore, there is an urgent need to find a cheaper and more conductive metal paste to replace pure silver paste and apply it to the fabrication of back grid electrodes for N-type crystalline silicon solar cells. Summary of the Invention

[0004] This invention provides a silver-nickel paste and its preparation method, as well as an N-type crystalline silicon solar cell. Compared with expensive pure silver paste, the inexpensive silver-nickel paste can maintain or even improve the photoelectric conversion efficiency of the finished cell, and also reduce the manufacturing cost of the finished cell.

[0005] In a first aspect, embodiments of the present invention provide a silver-nickel paste, comprising organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder, wherein the nickel-silver mixture comprises micron-sized spherical nickel powder and nano-sized spherical silver powder; wherein...

[0006] The organic additive in the silver-nickel paste is between 1.5% and 2.5% by mass.

[0007] The mass percentage of the micron-sized spherical silver powder in the silver-nickel paste is between 58% and 65%.

[0008] The mass percentage of the micron-sized spherical nickel powder in the silver-nickel paste is between 8% and 15%.

[0009] The mass percentage of the nano-sized spherical silver powder in the silver-nickel paste is between 1% and 3%.

[0010] The organic binder comprises between 12% and 29.5% by mass in the silver-nickel paste;

[0011] The glass powder constitutes a mass percentage of 2% to 2.5% in the silver-nickel paste.

[0012] Optionally, the particle size range of the micron-sized spherical silver powder is 4μm to 5μm.

[0013] Optionally, the organic additive includes at least one of fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, lauryl phosphate, silicone oil, diester and a mixture of lauryl phosphate.

[0014] Optionally, the organic adhesive comprises a polymer and an organic solvent; wherein,

[0015] The polymer is present in the organic adhesive at a mass percentage between 8% and 12%.

[0016] The organic solvent in the organic adhesive is between 88% and 92% by mass.

[0017] Optionally, the organic solvent includes at least five of the following: terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and 12-ol ester.

[0018] Optionally, the glass powder includes Bi2O3, Al2O3, SiO2, ZnO, Sb2O5, B2O3, and TeO3;

[0019] in,

[0020] The mass percentage of Bi2O3 in the glass powder is between 10% and 25%.

[0021] The mass percentage of AL2O3 in the glass powder is between 15% and 25%.

[0022] The mass percentage of SiO2 in the glass powder is between 12% and 20%.

[0023] The ZnO in the glass powder is between 20% and 25% by mass;

[0024] The mass percentage of Sb2O5 in the glass powder is between 15% and 20%.

[0025] The mass percentage of B2O3 in the glass powder is between 15% and 20%.

[0026] The mass percentage of TeO3 in the glass powder is between 8% and 10%.

[0027] Optionally, the particle size of the glass powder ranges from 2 μm to 2.5 μm.

[0028] Secondly, embodiments of the present invention also provide a method for preparing a silver-nickel paste, used to prepare the silver-nickel paste as described in any one of the first aspects, the method comprising:

[0029] Micron-sized spherical nickel powder and nano-sized spherical silver powder are mixed to prepare a nickel-silver mixture;

[0030] The organic binder and glass powder are mixed and dispersed to obtain a uniformly mixed first powder.

[0031] Micron-sized spherical silver powder and the nickel-silver mixture are added to the first powder, and the first powder, the micron-sized spherical silver powder and the nickel-silver mixture are dispersed and ground to obtain a uniformly mixed second powder;

[0032] An organic additive is added to the second powder, and the second powder and the organic additive are dispersed to obtain a uniformly mixed silver-nickel paste.

[0033] Optionally, micron-sized spherical nickel powder and nano-sized spherical silver powder are mixed to prepare a nickel-silver mixture, including:

[0034] The micron-sized spherical nickel powder and the nano-sized spherical silver powder are added together with alcohol in a ball mill for grinding.

[0035] The zirconia balls inside the ball mill after grinding were cleaned with pure water to obtain a turbid liquid;

[0036] The turbid liquid was evaporated and dried to obtain a solid.

[0037] The solid material is ground and sieved to obtain the nickel-silver mixture.

[0038] Thirdly, embodiments of the present invention also provide an N-type crystalline silicon solar cell, including a back grid line electrode, wherein the back grid line electrode is prepared using silver-nickel paste as described in any one of the first aspects.

[0039] This invention provides a silver-nickel paste and its preparation method, as well as an N-type crystalline silicon solar cell. The silver-nickel paste includes organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder. The nickel-silver mixture includes micron-sized spherical nickel powder and nano-sized spherical silver powder. The organic additives constitute 1.5% to 2.5% of the silver-nickel paste by mass; the micron-sized spherical silver powder constitutes 58% to 65% of the silver-nickel paste by mass; the micron-sized spherical nickel powder constitutes 8% to 15% of the silver-nickel paste by mass; the nano-sized spherical silver powder constitutes 1% to 3% of the silver-nickel paste by mass; the organic binder constitutes 12% to 29.5% of the silver-nickel paste by mass; and the glass powder constitutes 2% to 2.5% of the silver-nickel paste by mass. This embodiment provides a low-cost and high-quality silver-nickel paste. Applying this silver-nickel paste to the fabrication of the back grid electrode of an N-type crystalline silicon solar cell solves the problem of increased production costs due to the high cost of existing pure silver paste. Compared to expensive pure silver paste, using nickel powder to replace part of the silver powder effectively reduces the amount and cost of silver powder used. This low-cost silver-nickel paste can maintain or even improve the high photoelectric conversion efficiency of N-type crystalline silicon solar cells, achieving a long lifespan, maintaining stable short-circuit current and open-circuit voltage, thus maintaining a stable fill factor and stable photoelectric conversion efficiency. It also reduces the manufacturing cost of N-type crystalline silicon solar cells, achieving cost optimization and thus improving overall cost-effectiveness. This enhances the competitiveness of N-type crystalline silicon solar cells in the industry. Furthermore, the back side of an N-type crystalline silicon solar cell has lower requirements for parameters such as light utilization and shading area, providing a favorable opportunity for the application of silver-nickel paste in the fabrication of the back grid electrode. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic flowchart of a method for preparing silver-nickel paste according to an embodiment of the present invention;

[0042] Figure 2 This is a schematic flowchart of another method for preparing silver-nickel paste provided in an embodiment of the present invention. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0044] The terminology used in the embodiments of this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this invention. Furthermore, in the context, it should be understood that when referring to an element being formed "on" or "below" another element, it can be formed not only directly on or below the other element, but also indirectly on or below it through intermediate elements. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0046] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0047] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0048] First, it should be noted that this embodiment of the invention provides a silver-nickel paste for use as the back grid electrode of an N-type crystalline silicon solar cell. On the one hand, compared to expensive pure silver paste, the inexpensive silver-nickel paste can maintain or even improve the high photoelectric conversion efficiency of N-type crystalline silicon solar cells, solving the problem of increased production costs due to the high cost of existing pure silver paste. On the other hand, this embodiment illustrates that the silver-nickel paste can be applied to the fabrication process of the back grid electrode of an N-type crystalline silicon solar cell. It is understood that compared to the requirements for light utilization rate and light-transmitting area on the front side of an N-type crystalline silicon solar cell, the requirements for light utilization rate and light-transmitting area on the back side are lower, and the printing precision requirements for the back grid electrode are also lower. This provides a favorable opportunity for the application of silver-nickel paste in the fabrication of the back grid electrode of an N-type crystalline silicon solar cell.

[0049] The silver-nickel paste provided in this embodiment of the invention comprises organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder. The nickel-silver mixture includes micron-sized spherical nickel powder and nano-sized spherical silver powder. The organic additives constitute 1.5% to 2.5% of the silver-nickel paste by mass; the micron-sized spherical silver powder constitutes 58% to 65% of the silver-nickel paste by mass; the micron-sized spherical nickel powder constitutes 8% to 15% of the silver-nickel paste by mass; the nano-sized spherical silver powder constitutes 1% to 3% of the silver-nickel paste by mass; the organic binder constitutes 12% to 29.5% of the silver-nickel paste by mass; and the glass powder constitutes 2% to 2.5% of the silver-nickel paste by mass.

[0050] In this silver-nickel paste, micron-sized spherical silver powder forms the conductive matrix. The mass percentage of this powder can be adjusted according to conductivity requirements. The particle size of the micron-sized spherical silver powder directly affects the conductivity of the paste. Generally, smaller particles provide a larger surface area, resulting in more contact points, reduced resistance, and improved conductivity. For example, the particle size range of the micron-sized spherical silver powder can be 4μm to 5μm. Furthermore, higher purity of the micron-sized spherical silver powder leads to better conductivity in the prepared silver-nickel paste, which in turn improves the conductivity of the back grid electrode of the resulting N-type crystalline silicon solar cell. This effectively improves the power utilization rate and extends the lifespan of the N-type crystalline silicon solar cell. For example, the purity of the micron-sized spherical silver powder can be 99.9% or higher.

[0051] The silver-nickel paste in this embodiment can be understood as being prepared by replacing part of the silver powder in pure silver paste with nickel powder. This further reduces the paste cost while maintaining high photoelectric conversion efficiency. Extensive experimental verification has shown that when the mass percentage of micron-sized spherical nickel powder in the silver-nickel paste is between 8% and 15%, the resulting solar cell exhibits the highest photoelectric conversion efficiency. The nickel-silver mixture includes micron-sized spherical nickel powder and nano-sized spherical silver powder. In this embodiment, the nickel-silver mixture can be understood as a mixture of large nickel powder particles with small silver powder particles attached to their surfaces. Exemplarily, the nickel-silver mixture in this embodiment can be prepared by ball milling the micron-sized spherical nickel powder and the nano-sized spherical silver powder. The particle size of nano-sized spherical silver powder differs from that of micron-sized spherical silver powder and micron-sized spherical nickel powder. The nano-sized spherical silver powder is chosen because its small particle size allows it to easily adhere to the surface of the micron-sized spherical nickel powder during mixing. This results in a larger contact area between the nano-sized and micron-sized spherical nickel powders, improving both the conductivity and adhesion of the micron-sized nickel powder. For example, the particle size range of the micron-sized spherical nickel powder can be 1 μm to 3 μm, and consequently, the particle size range of the nickel-silver mixture can also be 1 μm to 3 μm. It is understood that the higher the purity of the micron-sized spherical nickel powder, the better the conductivity of the prepared silver-nickel paste, and consequently, the better the conductivity of the back grid electrode of the prepared N-type crystalline silicon solar cell. This effectively improves the power utilization rate of the N-type crystalline silicon solar cell and extends its lifespan. For example, the purity of the micron-sized spherical nickel powder can be 99.9% or higher. Furthermore, the higher the purity of the nano-sized spherical silver powder, the better the conductivity of the prepared silver-nickel paste, and consequently, the better the conductivity of the back grid electrode of the prepared N-type crystalline silicon solar cell. This can effectively improve the power utilization rate of the N-type crystalline silicon solar cell and extend its lifespan. For example, the purity of the nano-sized spherical silver powder can be 99.9% or higher.

[0052] Glass powder is an inorganic binder that enables the bonding of the nickel-silver mixture with micron-sized spherical silver powder. The mass percentage of glass powder in the silver-nickel paste can be adjusted based on the total amount of the nickel-silver mixture and the micron-sized spherical silver powder. The particle size of the glass powder directly affects the flowability of the silver-nickel paste. Generally, smaller glass powder particles are more easily dispersed in the silver-nickel paste, thereby improving its flowability and coatability. For example, the particle size range of the glass powder can be 2 μm to 2.5 μm.

[0053] The organic binder is mainly used for dispersing and printing the nickel-silver mixture, and for bonding the components before the glass powder is activated. Subsequently, the mass percentage of the organic binder in the silver-nickel paste can be adjusted according to the total amount of the nickel-silver mixture and the micron-sized spherical silver powder.

[0054] Organic additives possess excellent weather resistance, corrosion resistance, and high activity, serving as dispersants and diluents. They improve and regulate the performance of the formed silver-nickel paste, maintaining good printing shape. After the silver-nickel paste is printed in the area corresponding to the back grid electrodes of an N-type crystalline silicon solar cell, it contributes to the overall performance improvement of the N-type crystalline silicon solar cell. Furthermore, the stability of the silver-nickel paste is a crucial indicator of its performance, encompassing two aspects: the oxidation resistance of the paste and the dispersibility of the silver powder (or nickel powder). The organic additives may also contain antioxidants to prevent oxidation of the silver-nickel paste and dispersants to prevent the agglomeration of the silver powder (or nickel powder). In organic carriers, antioxidants primarily address the issue of the silver powder's susceptibility to oxidation, while dispersants are needed to disperse the silver powder (or nickel powder) to prevent agglomeration. The types of organic additives can be selected appropriately as needed. Optionally, organic additives include at least one of fatty alcohol ether phosphates, aluminate coupling agents, silane coupling agents, zirconium aluminate coupling agents, lauryl phosphates, silicone oils, diesters, and mixtures of lauryl phosphates.

[0055] Specifically, each raw material component plays a specific role in the silver-nickel paste. The raw material components are formulated according to their respective mass percentages in the silver-nickel paste, allowing for adjustments based on the solid content of each component during formulation. For example, in one specific embodiment, the organic additive accounts for 1.5% of the silver-nickel paste by mass, the micron-sized spherical silver powder accounts for 62% by mass, the nickel-silver mixture accounts for 13.5% by mass (of which the micron-sized spherical nickel powder accounts for 12% by mass and the nano-sized spherical silver powder accounts for 1.5% by mass), the organic binder accounts for 21% by mass, and the glass powder accounts for 2% by mass.

[0056] The technical solution in this embodiment of the invention provides a low-cost and high-quality silver-nickel paste. Applying this silver-nickel paste to the fabrication process of the back grid electrode of an N-type crystalline silicon solar cell solves the problem of increased production costs due to the high cost of existing pure silver paste. Compared to expensive pure silver paste, using nickel powder to replace part of the silver powder in pure silver paste effectively reduces the amount and cost of silver powder used. This low-cost silver-nickel paste can maintain or even improve the high photoelectric conversion efficiency of N-type crystalline silicon solar cells, achieving a long lifespan, maintaining stable short-circuit current and open-circuit voltage, thus maintaining a stable fill factor and stable photoelectric conversion efficiency. It can also reduce the manufacturing cost of N-type crystalline silicon solar cells, achieving cost optimization and thus improving overall cost-effectiveness. This enhances the competitiveness of N-type crystalline silicon solar cells in the industry. Furthermore, the back side of an N-type crystalline silicon solar cell has lower requirements for parameters such as light utilization and shading area, providing a favorable opportunity for the application of silver-nickel paste in the fabrication of the back grid electrode.

[0057] Optionally, the organic adhesive includes a polymer and an organic solvent; wherein the polymer accounts for 8% to 12% of the organic adhesive by mass, and the organic solvent accounts for 88% to 92% of the organic adhesive by mass.

[0058] Specifically, polymers primarily achieve a strong bond between two or more objects through the interaction between their molecular chains and the surfaces of the adhered objects, thereby improving the adhesion and bonding effect of organic adhesives. Organic solvents can adjust the viscosity of organic adhesives to achieve optimal performance and also enable rapid curing, improving production efficiency. For example, an organic adhesive may comprise 12% by weight of a polymer and 88% by weight of an organic solvent. For example, the polymer may comprise ethyl cellulose N50. For example, the polymer may be a polymer with a low viscoelastic modulus after sintering. For example, the organic solvent may comprise at least five of the following: terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and twelfth alcohol ester. For example, in one specific embodiment, the organic solvent may be composed of five components: terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, and Span 85. The terpineol component comprises 10% by mass, the butylcarbiol component comprises 20% by mass, the butylcarbiol acetate component comprises 15% by mass, the tributyl citrate component comprises 15% by mass, and the Span 85 component comprises 40% by mass. Each component in the organic solvent exhibits good solubility and stability. Formulating it in this organic solvent ratio effectively improves the stability of the silver-nickel paste, enabling the prepared silver-nickel paste to be used durablely.

[0059] Optionally, the glass powder includes Bi₂O₃ (bismuth trioxide), Al₂O₃ (aluminum trioxide), SiO₂ (silicon dioxide), ZnO (zinc oxide), Sb₂O₅ (antimony pentoxide), B₂O₃ (boron trioxide), and TeO₃ (tellurium trioxide); wherein the mass percentage of Bi₂O₃ in the glass powder is between 10% and 25%; the mass percentage of Al₂O₃ in the glass powder is between 15% and 25%; the mass percentage of SiO₂ in the glass powder is between 12% and 20%; the mass percentage of ZnO in the glass powder is between 20% and 25%; the mass percentage of Sb₂O₅ in the glass powder is between 15% and 20%; the mass percentage of B₂O₃ in the glass powder is between 15% and 20%; and the mass percentage of TeO₃ in the glass powder is between 8% and 10%.

[0060] Specifically, the glass powder can be obtained by mixing Bi2O3, Al2O3, SiO2, ZnO, Sb2O5, B2O3, and TeO3 in a certain proportion, melting them at high temperature, and then sintering and pulverizing them. For example, in one specific embodiment, the mass percentage of Bi2O3 in the glass powder is 13%, Al2O3 is 15%, SiO2 is 12%, ZnO is 20%, Sb2O5 is 15%, B2O3 is 15%, and TeO3 is 10%.

[0061] It should also be noted that the glass powder in this embodiment does not contain lead, which can effectively increase the corrosion resistance of the silver-nickel paste to protective films such as silicon nitride. Furthermore, after the silver-nickel paste is prepared and applied to the printing of the back grid electrodes of the N-type crystalline silicon solar cell, it undergoes high-temperature sintering, light injection, and laser-induced treatment in sequence. This reduces metal recombination, improves the photoelectric conversion efficiency of the cell, reduces the manufacturing cost of the N-type crystalline silicon solar cell, and enhances the economic benefits for the manufacturer. It also compensates to some extent for the problem of accelerated aging caused by the lack of lead in the glass powder. In other words, the absence of lead in the glass powder, combined with the subsequent laser-induced steps, can maintain or even extend the lifespan of the prepared N-type crystalline silicon solar cell to a certain extent.

[0062] Based on the same inventive concept, this invention also provides a method for preparing silver-nickel paste. Figure 1 This is a schematic flowchart of a method for preparing a silver-nickel paste according to an embodiment of the present invention. This method is used to prepare the silver-nickel paste as provided in any one of the embodiments of the present invention. Figure 1 As shown, the preparation method includes:

[0063] S110. Micron-sized spherical nickel powder and nano-sized spherical silver powder are mixed to prepare a nickel-silver mixture.

[0064] Specifically, the silver-nickel paste in this embodiment can be understood as being prepared by replacing part of the silver powder in pure silver paste with nickel powder. The nickel-silver mixture includes micron-sized spherical nickel powder and nano-sized spherical silver powder. In this embodiment, the nickel-silver mixture can be understood as a mixture of large nickel powder particles with small silver powder particles attached to their surfaces. For example, the nickel-silver mixture in this embodiment can be prepared by ball milling the micron-sized spherical nickel powder and the nano-sized spherical silver powder. To improve the adhesion between the nickel powder and silver powder during sintering, the nickel powder and silver powder are ball-milled (using zirconia material), causing small silver powder particles to attach to the surface of the large nickel powder particles, thus fusing the surfaces of the large nickel powder particles with the small silver powder particles. In this way, the resistivity of the nickel-silver grid lines is reduced during subsequent sintering. Without affecting the photoelectric conversion efficiency of the solar cell, the paste cost is reduced, the fill factor is increased, and the economic benefits for the solar cell company are improved.

[0065] S120. The organic binder and glass powder are mixed and dispersed to obtain a uniformly mixed first powder.

[0066] Specifically, after the organic binder and glass powder are mixed, a disperser can be used to mix and stir them, which can provide a better dispersion effect, avoid the aggregation or sedimentation of the mixed powder, and make the powder mixture more uniform.

[0067] S130. Add micron-sized spherical silver powder and nickel-silver mixture to the first powder, and disperse and grind the first powder, micron-sized spherical silver powder and nickel-silver mixture to obtain a uniformly mixed second powder.

[0068] Specifically, a mixture of micron-sized spherical silver powder and nickel-silver is added to the first powder. A disperser is used to mix and stir the first powder, the micron-sized spherical silver powder and the nickel-silver mixture, and then a grinding device is used to reduce the surface roughness of the mixed powder to obtain a finer secondary powder.

[0069] It should also be noted that S110 is the step of preparing the nickel-silver mixture, S120 is the step of preparing the first powder, and S130 is the step of mixing the nickel-silver mixture with the first powder. This embodiment only illustrates the order of preparation of S110 and S120 and does not limit it. For example, S110 can be performed first and then S120, or S120 can be performed first and then S110, or S110 and S120 can be performed simultaneously.

[0070] S140. Add organic additives to the second powder and disperse the second powder and organic additives to obtain a uniformly mixed silver-nickel paste.

[0071] Specifically, an organic additive is added to the second powder, and the second powder and the organic additive are further dispersed and mixed at high speed using a disperser to obtain the silver-nickel paste of this application.

[0072] The technical solution in this embodiment of the invention firstly involves mixing micron-sized spherical nickel powder and nano-sized spherical silver powder to prepare a nickel-silver mixture. Then, an organic binder and glass powder are mixed and dispersed to obtain a uniformly mixed first powder. Next, the micron-sized spherical silver powder and the nickel-silver mixture are added to the first powder, and the first powder, the micron-sized spherical silver powder and the nickel-silver mixture are dispersed and ground to obtain a uniformly mixed second powder. Finally, an organic additive is added to the second powder, and the second powder and the organic additive are dispersed to obtain a uniformly mixed silver-nickel paste. The above method solves the problem of increased production costs caused by the high cost of existing pure silver paste. Compared with expensive pure silver paste, using nickel powder to replace part of the silver powder in pure silver paste effectively reduces the amount of silver powder used and the cost. The inexpensive silver-nickel paste can maintain or even improve the high photoelectric conversion efficiency of N-type crystalline silicon solar cells, achieve a long service life of N-type crystalline silicon solar cells, maintain stable short-circuit current and open-circuit voltage, thereby maintaining the stability of the fill factor and achieving stable photoelectric conversion efficiency of N-type crystalline silicon solar cells. It can also reduce the manufacturing cost of N-type crystalline silicon solar cells, achieving cost optimization of N-type crystalline silicon solar cells, thus achieving the effect of cost reduction and efficiency improvement, improving the overall cost performance of the finally prepared N-type crystalline silicon solar cells, enhancing the competitiveness of N-type crystalline silicon solar cells in the industry. In addition, the back side of N-type crystalline silicon solar cells has lower requirements for parameters such as light utilization and shading area, which also provides a favorable opportunity for the application of silver-nickel paste in the preparation of back grid electrodes of N-type crystalline silicon solar cells.

[0073] Figure 2 This is a schematic flowchart of another method for preparing silver-nickel paste provided in this embodiment of the invention. This embodiment is an optimization based on the above embodiment. Optionally, micron-sized spherical nickel powder and nano-sized spherical silver powder are mixed to prepare a nickel-silver mixture, including:

[0074] Micron-sized spherical nickel powder and nano-sized spherical silver powder are added together with alcohol in a ball mill for grinding.

[0075] The zirconia balls inside the ball mill after grinding were cleaned with pure water, resulting in a turbid liquid.

[0076] The turbid liquid was evaporated and dried to obtain a solid.

[0077] The solid material was ground and sieved to obtain a nickel-silver mixture.

[0078] For details not covered in this embodiment, please refer to the above embodiments. Figure 2 As shown, the preparation method includes:

[0079] S210. Micron-sized spherical nickel powder and nano-sized spherical silver powder are added together with alcohol to a ball mill for grinding.

[0080] Specifically, the nickel-silver mixture includes micron-sized spherical nickel powder and nano-sized spherical silver powder. The mass percentage of micron-sized spherical nickel powder in the nickel-silver paste is between 8% and 15%, while the mass percentage of nano-sized spherical silver powder is between 1% and 3%. In other words, the mass percentage of micron-sized spherical nickel powder in the nickel-silver mixture is approximately between 80% and 95%, and the mass percentage of nano-sized spherical silver powder is approximately between 5% and 20%.

[0081] For example, first weigh 5 parts (or 10 parts) of nano-sized spherical silver powder, add it to 95 parts (or 90 parts) of micron-sized spherical nickel powder for mixing, and then add the mixture to a ball mill, adding alcohol. The grinding balls in the ball mill are zirconia balls. A volume ratio of 10 mm zirconia balls, 5 mm zirconia balls, and 2.5 mm zirconia balls is used. The ratio of the nickel-silver mixture to the zirconia balls is 2.5 parts:2.5 parts, and the alcohol is 5 parts, or the alcohol is ground into the nickel-silver mixture and zirconia balls up to 3 cm above the surface. Then start the ball mill for grinding. When the grinding speed is 600-800 rpm, the grinding time is 12-16 hours; when the speed is 800-1000 rpm, the grinding time is 10-12 hours.

[0082] S220. The zirconia balls inside the ball mill after grinding are cleaned with pure water to obtain a turbid liquid.

[0083] Here, zirconia balls refer to grinding balls inside the ball mill made of zirconia. Specifically, after grinding, cleaning is performed to obtain a turbid liquid. For example, after grinding, the zirconia balls and their inner walls inside the ball mill can be cleaned to obtain a turbid liquid, which actually contains a suspension of a silver-nickel mixture.

[0084] S230. The turbid liquid is evaporated and dried to obtain a solid.

[0085] Specifically, the turbid liquid can be evaporated and dried in an oven at a temperature range of 50℃ to 55℃ for 12 hours until the liquid evaporates and a solid is obtained.

[0086] S240. Grind and sieve the solid material to obtain a nickel-silver mixture.

[0087] Specifically, the solid material is ground and sieved through a 400-mesh screen to obtain a powder that is a large nickel powder with small silver particles attached, which is the nickel-silver mixture.

[0088] S250. The organic binder and glass powder are mixed and dispersed to obtain a uniformly mixed first powder.

[0089] S260. Add a mixture of micron-sized spherical silver powder and nickel-silver to the first powder, and disperse and grind the first powder, the micron-sized spherical silver powder and nickel-silver mixture to obtain a uniformly mixed second powder.

[0090] S270. Add organic additives to the second powder and disperse the second powder and organic additives to obtain a uniformly mixed silver-nickel paste.

[0091] Based on the same inventive concept, this invention also provides an N-type crystalline silicon solar cell. This N-type crystalline silicon solar cell includes a back grid electrode, which is fabricated using a silver-nickel paste as provided in any of the embodiments of this invention. Therefore, this N-type crystalline silicon solar cell possesses the beneficial effects corresponding to the silver-nickel paste, which will not be elaborated further here.

[0092] Example 1

[0093] In this embodiment, the silver-nickel paste comprises organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder. The nickel-silver mixture comprises micron-sized spherical nickel powder and nano-sized spherical silver powder. The components and their weight percentages are as follows: organic additives 1.5%, micron-sized spherical silver powder 62%, micron-sized spherical nickel powder 12%, nano-sized spherical silver powder 1.5%, organic binder 21%, and glass powder 2%. The organic binder comprises a polymer and an organic solvent, with the following components and their weight percentages: polymer 12% and organic solvent 88%. The glass powder comprises Bi₂O₃, Al₂O₃, SiO₂, ZnO, Sb₂O₅, B₂O₃, and TeO₃, with the following components and their weight percentages: Bi₂O₃ 12%, Al₂O₃ 15%, SiO₂ 15%, ZnO 20%, Sb₂O₅ 15%, B₂O₃ 15%, and TeO₃ 8%. Furthermore, this embodiment does not impose specific requirements or limitations on the types and compositions of organic additives and organic solvents, and these can be selected and set according to actual conditions.

[0094] Preparation of the nickel-silver mixture: Five parts of nano-sized spherical silver powder, 95 parts of micron-sized spherical nickel powder, and alcohol were added to a ball mill for grinding. First, 5 parts of nano-sized spherical silver powder were weighed and mixed with 95 parts of micron-sized spherical nickel powder. This mixture was then added to the ball mill, followed by the addition of alcohol. The grinding balls in the ball mill were zirconia balls. A volume ratio of 10 mm, 5 mm, and 2.5 mm zirconia balls was used. The ratio of the nickel-silver mixture to the zirconia balls was 2.5 parts:2.5 parts, and the alcohol was 5 parts. Alternatively, the alcohol was ground into the silver-nickel mixture and zirconia balls up to 3 cm above the surface. The ball mill was then started for grinding at 600-800 rpm for 12-16 hours.

[0095] After grinding, a turbid liquid is obtained by cleaning. Specifically, after grinding, the zirconia balls inside the ball mill, i.e., their inner walls, are cleaned to obtain a turbid liquid; this turbid liquid actually contains a suspension of a nickel-silver mixture.

[0096] The turbid liquid was evaporated and dried to obtain a solid. Specifically, the turbid liquid was evaporated and dried in an oven at 55°C for 12 hours until the liquid evaporated, thus obtaining a solid.

[0097] The solid material is ground and sieved. Specifically, the solid material is ground and sieved through a 400-mesh sieve, and the resulting powder is the silver-nickel mixture.

[0098] After preparing the silver-nickel paste, it can be screen-printed onto an N-type crystalline silicon solar cell (e.g., a monocrystalline N-TOPCon silicon wafer) with dimensions of 182.2 mm × 183.75 mm using a 520-mesh screen to form the back grid electrode (i.e., the silver fine grid). The cell is then sintered in a sintering furnace; exemplarily, the peak sintering temperature can be 758 °C. After sintering, light injection treatment is required; exemplarily, the light injection treatment temperature can be 532 °C, and the light intensity can be 8000 W / m². 2After light injection, laser-induced enhancement processing is required. For example, the reverse voltage for laser-induced enhancement can be 15V, and the laser power can be 12W. Laser-induced enhancement involves scanning the area corresponding to the back grid electrodes of the N-type crystalline silicon solar cell and performing a laser-induced process after light injection. This induces silver-silicon interdiffusion, significantly reducing contact resistance, increasing the fill factor, and effectively improving the cell efficiency. The N-type crystalline silicon solar cell prepared in this embodiment, after relevant electrical experiments, shows an open-circuit voltage of 0.7418V, a short-circuit current of 13.951A, a fill factor of 85.65%, and a photoelectric conversion efficiency of 26.481%. It is also evident that the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in this embodiment is 0.03% higher than that of the control group, and the cost reduction per cell for this N-type crystalline silicon solar cell is approximately 0.05 yuan.

[0099] Example 2

[0100] In this embodiment, the silver-nickel paste comprises organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder. The nickel-silver mixture comprises micron-sized spherical nickel powder and nano-sized spherical silver powder, wherein the components and their weight percentages are as follows: organic additives 2.5%, micron-sized spherical silver powder 65%, micron-sized spherical nickel powder 15%, nano-sized spherical silver powder 2%, organic binder 13.3%, and glass powder 2.2%. The organic binder comprises a polymer and an organic solvent, wherein the components and their weight percentages are as follows: polymer 8%, organic solvent 92%. The glass powder comprises Bi₂O₃, Al₂O₃, SiO₂, ZnO, Sb₂O₅, B₂O₃, and TeO₃, wherein the components and their weight percentages are as follows: Bi₂O₃ 10%, Al₂O₃ 15%, SiO₂ 12%, ZnO 20%, Sb₂O₅ 15%, B₂O₃ 18%, and TeO₃ 10%. Furthermore, this embodiment does not impose specific requirements or limitations on the types and compositions of organic additives and organic solvents, and these can be selected and set according to actual conditions.

[0101] Preparation of the nickel-silver mixture: 10 parts of nano-sized spherical silver powder, 90 parts of micron-sized spherical nickel powder, and alcohol are added to a ball mill for grinding. First, weigh 10 parts of nano-sized spherical silver powder and mix it with 90 parts of micron-sized spherical nickel powder. Then, add the mixture to the ball mill and add alcohol. The grinding balls in the ball mill are zirconia balls. A volume ratio of 10 mm, 5 mm, and 2.5 mm zirconia balls is used. The ratio of the nickel-silver mixture to the zirconia balls is 2.5 parts:2.5 parts, and the alcohol is 5 parts. Alternatively, the alcohol can be ground to a depth of 3 cm above the silver-nickel mixture and zirconia balls. Then, start the ball mill for grinding at 800-1000 rpm for 10-12 hours.

[0102] After grinding, a turbid liquid is obtained by cleaning. Specifically, after grinding, the zirconia balls inside the ball mill, i.e., their inner walls, are cleaned to obtain a turbid liquid; this turbid liquid actually contains a suspension of a nickel-silver mixture.

[0103] The turbid liquid was evaporated and dried to obtain a solid. Specifically, the turbid liquid was evaporated and dried in an oven at 55°C for 12 hours until the liquid evaporated, thus obtaining a solid.

[0104] The solid material is ground and sieved. Specifically, the solid material is ground and sieved through a 400-mesh sieve, and the resulting powder is the silver-nickel mixture.

[0105] After preparing the silver-nickel paste, it can be screen-printed onto an N-type crystalline silicon solar cell (e.g., a monocrystalline N-TOPCon silicon wafer) with dimensions of 182.2 mm × 183.75 mm using a 520-mesh screen to form the back grid electrode (i.e., the silver fine grid). The cell is then sintered in a sintering furnace; exemplarily, the peak sintering temperature can be 762 °C. After sintering, light injection treatment is required; exemplarily, the light injection treatment temperature can be 535 °C, and the light intensity can be 7600 W / m². 2After light injection, laser-induced enhancement processing is required. For example, the reverse voltage for laser-induced enhancement can be 15V, and the laser power can be 12W. Laser-induced enhancement involves scanning the area corresponding to the back grid electrodes of the N-type crystalline silicon solar cell and performing a laser-induced process after light injection. This induces silver-silicon interdiffusion, significantly reducing contact resistance, increasing the fill factor, and effectively improving the cell efficiency. The N-type crystalline silicon solar cell prepared in this embodiment, after relevant electrical experiments, shows an open-circuit voltage of 0.7422V, a short-circuit current of 13.962A, a fill factor of 85.68%, and a photoelectric conversion efficiency of 26.525%. It is also evident that the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in this embodiment is 0.07% higher than that of the control group, and the cost reduction per cell for this N-type crystalline silicon solar cell is approximately 0.02 yuan.

[0106] control group

[0107] In this embodiment, existing silver paste is used to fabricate the back grid electrode of an N-type crystalline silicon solar cell. The silver paste comprises organic additives, silver powder, organic binder, and glass powder, with the following composition and weight percentages: organic additives 1.5%, silver powder 76%, organic binder 20%, and glass powder 2.5%. The organic binder comprises a polymer and an organic solvent, with the following composition and weight percentages: polymer 9%, organic solvent 91%. The glass powder comprises Bi₂O₃, Al₂O₃, SiO₂, ZnO, Sb₂O₅, B₂O₃, and TeO₃, with the following composition and weight percentages: Bi₂O₃ 12%, Al₂O₃ 15%, SiO₂ 15%, ZnO 18%, Sb₂O₅ 12%, B₂O₃ 12%, and TeO₃ 16%. Furthermore, the types and compositions of the organic additives and organic solvents are not specifically required or limited in this embodiment and can be selected and set according to actual conditions.

[0108] After preparing the silver paste, it can be screen-printed onto an N-type crystalline silicon solar cell (e.g., a monocrystalline N-TOPCon silicon wafer) with dimensions of 182.2 mm × 183.75 mm using a 520-mesh screen to form the back grid electrode (i.e., the silver fine grid). The cell is then sintered in a sintering furnace; for example, the peak sintering temperature can be 752 °C. After sintering, light injection treatment is required, followed by laser-induced efficiency enhancement treatment. The N-type crystalline silicon solar cell prepared in this control group, after relevant electrical experiments, showed an open-circuit voltage of 0.7403 V, a short-circuit current of 13.989 A, a fill factor of 85.486%, and a photoelectric conversion efficiency of 26.451%.

[0109] It should be noted that, compared with the control group, the silver-nickel paste prepared in Examples 1 and 2, when applied to N-type crystalline silicon solar cells, showed a certain degree of improvement in photoelectric conversion efficiency compared to the control group. It is reasonable to believe that with continuous process improvement and adjustments to the mass percentage and combination of components in the silver-nickel paste, even greater breakthroughs are possible. Similarly, Examples 1 and 2 also showed slightly higher performance than the control group in electrical experimental parameters such as open-circuit voltage, short-circuit current, and fill factor. Moreover, compared to the rarer and more expensive pure silver paste, the nickel powder used in the silver-nickel paste is inexpensive and produced in high quantities, thus significantly reducing costs. Furthermore, the silver-nickel paste also exhibited superior performance compared to pure silver paste in aging tests. In the fabrication process of the back grid line electrode of N-type crystalline silicon solar cells, the requirements for light utilization, light transmission area, light shading area, and grid line fabrication precision are relatively low. The silver-nickel paste in this embodiment can replace the existing pure silver paste, effectively reducing the production cost of N-type crystalline silicon solar cells.

[0110] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A silver-nickel paste, characterized in that, It includes organic additives, micron-sized spherical silver powder, a nickel-silver mixture, an organic binder, and glass powder, wherein the nickel-silver mixture comprises micron-sized spherical nickel powder and nano-sized spherical silver powder; wherein, The organic additive in the silver-nickel paste is between 1.5% and 2.5% by mass. The mass percentage of the micron-sized spherical silver powder in the silver-nickel paste is between 58% and 65%. The mass percentage of the micron-sized spherical nickel powder in the silver-nickel paste is between 8% and 15%. The mass percentage of the nano-sized spherical silver powder in the silver-nickel paste is between 1% and 3%. The organic binder comprises between 12% and 29.5% by mass in the silver-nickel paste; The glass powder constitutes a mass percentage of 2% to 2.5% in the silver-nickel paste.

2. The silver-nickel paste according to claim 1, characterized in that, The particle size range of the micron-sized spherical silver powder is 4μm to 5μm.

3. The silver-nickel paste according to claim 1, characterized in that, The organic additives include at least one of fatty alcohol ether phosphates, aluminate coupling agents, silane coupling agents, zirconium aluminate coupling agents, lauryl phosphates, silicone oils, dicarboxylic acid esters, and mixtures of lauryl phosphates.

4. The silver-nickel paste according to claim 1, characterized in that, The organic adhesive comprises a polymer and an organic solvent; wherein... The polymer is present in the organic adhesive at a mass percentage between 8% and 12%. The organic solvent in the organic adhesive is between 88% and 92% by mass.

5. The silver-nickel paste according to claim 4, characterized in that, The organic solvent includes at least five of the following: terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and ester 12.

6. The silver-nickel paste according to claim 1, characterized in that, The glass powder comprises Bi₂O₃, Al₂O₃, SiO₂, ZnO, Sb₂O₅, B₂O₃, and TeO₃; wherein, The mass percentage of Bi2O3 in the glass powder is between 10% and 25%. The mass percentage of AL2O3 in the glass powder is between 15% and 25%. The mass percentage of SiO2 in the glass powder is between 12% and 20%. The ZnO in the glass powder is between 20% and 25% by mass; The mass percentage of Sb2O5 in the glass powder is between 15% and 20%. The mass percentage of B2O3 in the glass powder is between 15% and 20%. The mass percentage of TeO3 in the glass powder is between 8% and 10%.

7. The silver-nickel paste according to claim 1, characterized in that, The glass powder has a particle size range of 2μm to 2.5μm.

8. A method for preparing a silver-nickel paste, characterized in that, The method for preparing the silver-nickel paste as described in any one of claims 1-7 comprises: Micron-sized spherical nickel powder and nano-sized spherical silver powder are mixed to prepare a nickel-silver mixture; The organic binder and glass powder are mixed and dispersed to obtain a uniformly mixed first powder. Micron-sized spherical silver powder and the nickel-silver mixture are added to the first powder, and the first powder, the micron-sized spherical silver powder and the nickel-silver mixture are dispersed and ground to obtain a uniformly mixed second powder; An organic additive is added to the second powder, and the second powder and the organic additive are dispersed to obtain a uniformly mixed silver-nickel paste.

9. The method for preparing silver-nickel paste according to claim 8, characterized in that, A nickel-silver mixture is prepared by mixing micron-sized spherical nickel powder and nano-sized spherical silver powder, including: The micron-sized spherical nickel powder and the nano-sized spherical silver powder are added together with alcohol in a ball mill for grinding. The zirconia balls inside the ball mill after grinding were cleaned with pure water to obtain a turbid liquid; The turbid liquid was evaporated and dried to obtain a solid. The solid material is ground and sieved to obtain the nickel-silver mixture.

10. An N-type crystalline silicon solar cell, characterized in that, It includes a back grid line electrode, which is prepared using a silver-nickel paste as described in any one of claims 1-7.

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