Copper-based slurry, TOPCon battery and preparation method of TOPCon battery

Abstract

The invention relates to the technical field of solar cells, in particular to copper-based paste, a TOPCon cell and a preparation method of the TOPCon cell. The copper-based slurry includes: copper powder as main powder densified in a sintering process to form a conductive phase; the hydrogen storage material is used for releasing a hydrogen element in the sintering process and locally forming a reducing atmosphere so as to prevent the copper powder from being oxidized; the hydrogen storage material comprises a liquid hydrogen storage material; and the organic carrier provides fluidity and thixotropy for the slurry. Compared with solid hydrogenated metal particles, the liquid hydrogen storage material can be more uniformly dispersed in the copper-based slurry and can coat the copper powder, so that the hydrogen element released from the copper-based slurry is more uniform, and the oxidation of the copper powder can be comprehensively inhibited. Meanwhile, the dehydrogenation amount of the liquid hydrogen storage material is far higher than that of the solid hydrogenated metal particles, the release amount of hydrogen elements can be increased by multiple times under the same mass, and then more sufficient oxidation protection is provided for the copper powder.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a copper-based paste, a TOPCon (Tunnel Oxide Passivated Contact) cell, and a method for preparing the same. Background Technology

[0002] TOPCon is a selective contact structure formed by combining an ultrathin tunneling oxide layer with highly doped polycrystalline silicon. TOPCon cells based on this structure are high-efficiency passivated contact solar cells with an N-type silicon substrate. The cell structure, from top to bottom, consists of an antireflection layer (silicon nitride), a passivation layer (alumina), P+ type monocrystalline silicon, N-type monocrystalline silicon, a tunneling oxide layer (ultrathin silicon oxide), N+ type polycrystalline silicon, and a passivation layer (silicon nitride). The traditional method for fabricating TOPCon cells involves screen printing high-temperature silver paste onto the front and back of the cell, followed by sintering at 700℃-800℃. During this process, glass powder in the high-temperature silver paste penetrates the antireflection layer and passivation layer through chemical etching at high temperatures, achieving ohmic contact between the metal electrode and the silicon substrate, ultimately forming a reliable silver / silicon conductive path. However, this fabrication method has a silver consumption as high as 10 mg / W. With the continuous rise in silver prices, the fabrication cost of TOPCon cells has increased significantly, putting considerable pressure on the sustainable development of the industry. To address the cost issue of silver consumption, the industry has explored two alternative solutions: one is to use silver-clad copper materials instead of pure silver, and the other is to prepare copper grid lines through electroplating. However, the silver-clad copper solution has significant limitations. Its sintering temperature needs to be strictly controlled; if it is too high, the silver shell of the silver-clad copper particles will fall off, and the exposed copper will be oxidized, seriously affecting battery performance. Moreover, this solution cannot achieve complete silver removal. The electroplating copper grid line solution faces problems such as complex processes, high equipment investment, and environmental pollution caused by chemical reagents. If the silver paste is directly replaced with copper-based paste, copper is extremely prone to oxidation and failure under high temperature conditions, which will also seriously affect battery performance. Summary of the Invention

[0003] The objective of the first aspect of this application is to provide a copper-based paste to solve the problem of easy oxidation of existing copper-based pastes during sintering.

[0004] The second aspect of this application aims to provide a TOPCon battery in which the copper-based conductive grid lines are prepared using the aforementioned copper-based paste.

[0005] The purpose of the third aspect of this application is to provide a method for preparing the aforementioned TOPCon battery, which can solve the problems of complex manufacturing process, high cost, and environmental pollution associated with the preparation of copper grid lines in TOPCon batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a copper-based slurry, comprising: copper powder, which is densified as the main powder during sintering to form a conductive phase; Hydrogen storage material is used to release hydrogen during sintering and to create a reducing atmosphere within the grid lines to prevent oxidation of copper powder; the hydrogen storage material includes liquid hydrogen storage material. Organic carriers provide rheological and thixotropic properties to the slurry; By mass percentage, the copper powder content in the copper-based slurry is any value between 60% and 90%, the organic carrier content is any value between 5% and 30%, and the hydrogen storage material content is any value between 0.1% and 10%.

[0007] Furthermore, it also includes a catalytic metal for promoting the release of hydrogen from the hydrogen storage material; In the copper-based slurry, the content of the catalytic metal is 0.1%-3% by mass percentage.

[0008] Furthermore, the liquid hydrogen storage material is any one or more of methylcyclohexane, dibenzyltoluene, perhydrogenated ethylcarbazole, and cyclohexane.

[0009] Further, the copper powder includes a first copper powder and a second copper powder, wherein the average particle size of the first copper powder is any value between 1µm and 50µm, and the average particle size of the second copper powder is any value between 10nm and 500nm. The second copper powder fills the gaps between the first copper powder particles to improve the conductivity of the conductive phase; the mass of the second copper powder does not exceed 30% of the total amount of copper powder.

[0010] Furthermore, the organic carrier comprises a resin and an organic solvent; the resin is a conductive resin and / or a thermoplastic resin, and the organic solvent is a hydrocarbon with a boiling point not exceeding 300°C.

[0011] This application also provides a TOPCon battery, including: TOPCon battery cells and copper-based conductive grid lines; A metal conductive seed layer is deposited on the TOPCon solar cell, and the copper-based conductive grid lines are disposed on the TOPCon solar cell; the copper-based conductive grid lines are prepared by printing and sintering the aforementioned copper-based paste.

[0012] This application also provides a method for preparing the above-mentioned TOPCon battery, comprising the following steps: Step S1: Obtain TOPCon solar cells and deposit a metal conductive seed layer on the TOPCon solar cells; Step S2: Print the copper-based paste onto the metal conductive seed layer; Step S3: Perform segmented sintering on the TOPCon battery cell printed with the copper-based paste to form copper-based conductive grid lines on the TOPCon battery cell, thereby obtaining a TOPCon battery. The segmented sintering process includes a low-temperature annealing stage and a medium-temperature sintering stage, which are used to gradually solidify the copper-based slurry in stages to form copper-based conductive grid lines.

[0013] Furthermore, the temperature range of the low-temperature annealing stage is 100℃-200℃, which is used to remove the organic carrier and perform preliminary curing; The temperature range of the intermediate-temperature sintering stage is 300℃-500℃, which is used to release hydrogen from the hydrogen storage material and to densify the copper-based slurry to form copper-based conductive grid lines.

[0014] Furthermore, the deposition method of the metal conductive seed layer includes: using a laser process to open the antireflection layer and passivation layer on the TOPCon solar cell to form a laser opening on the TOPCon solar cell; and using a chemical plating or electroplating process to deposit a metal seed layer at the laser opening.

[0015] Furthermore, the material of the metal seed layer is a base metal.

[0016] The beneficial effects of this invention are as follows: The copper-based slurry provided in this application incorporates a liquid hydrogen storage material. Compared to solid hydride metal particles, the liquid hydrogen storage material can be more uniformly dispersed in the copper-based slurry and can coat the copper powder, resulting in a more uniform release of hydrogen from the copper-based slurry and thus comprehensively inhibiting copper powder oxidation. Simultaneously, the dehydrogenation capacity of the liquid hydrogen storage material is far higher than that of solid hydride metal particles, increasing the hydrogen release by several times for the same mass, thereby providing more adequate oxidation protection for the copper powder. The liquid hydrogen storage material can also promote densification between copper particles while inhibiting copper oxidation, further reducing its line resistance and improving its conductivity. Furthermore, the dehydrogenation products of the liquid hydrogen storage material are all gases with no residue, and therefore do not affect the resistance of the copper grid lines.

[0017] The copper-based slurry provided in this application significantly reduces the dehydrogenation temperature of the hydrogen storage material by introducing a catalytic metal, ensuring that it can effectively release hydrogen at a lower temperature, thereby significantly reducing the oxidation risk of copper powder during the heating process and suppressing the oxidation of copper powder as thoroughly as possible.

[0018] The TOPCon cell fabrication method provided in this application first uses laser technology to form laser openings and deposit a metal seed layer on the surface of the TOPCon cell, constructing a physical barrier to prevent copper diffusion into the silicon substrate and avoid cell performance degradation. Then, copper-based paste is used instead of silver paste for printing and sintering to obtain copper-based conductive grid lines with conductivity and stability comparable to silver grid lines. This fabrication method has low production costs and, compared to copper electroplating, does not generate electroplating wastewater, reducing environmental pollution. It provides a sustainable development path for the TOPCon cell industry and is expected to promote the widespread adoption of high-efficiency solar cells.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the reaction principle during the sintering of the copper-based slurry as shown in this invention. Figure 2 This is a thermogravimetric analysis diagram of the copper-based slurry during sintering as shown in Example 1 of the present invention; Figure 3 This is a schematic diagram of the microstructure of the copper-based conductive grid line shown in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the microstructure of the copper-based conductive grid line shown in Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of the TOPCon battery structure shown in Embodiment 3 of the present invention; Figure 6 This is a schematic diagram of the TOPCon battery structure shown in Comparative Example 1 of the present invention; Figure label: 1. Copper powder particles; 2. Liquid mixture; 3. Retained oxygen; 4. Atmospheric oxygen; 5. Surface oxide; 6. Sintering neck; 7. Nickel seed layer; 8. Copper-based grid lines; 9. Silver grid lines; 10. TOPCon solar cell; 11. Silicon nitride; 12. Alumina; 13. P+ type monocrystalline silicon; 14. N type monocrystalline silicon; 15. Ultrathin silicon oxide; 16. N+ type polycrystalline silicon. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not 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 invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] This application provides a copper-based slurry comprising copper powder, a hydrogen storage material, and an organic carrier. The copper powder, as the main powder, gradually densifies during sintering to form a conductive phase. The hydrogen storage material releases hydrogen during sintering, creating a reducing atmosphere within the grid lines and reacting with oxygen on the surface of the copper powder, thereby effectively preventing oxidation of the copper powder.

[0025] Hydrogen storage materials can be solid hydride metal particles or liquid hydrogen storage materials. Liquid hydrogen storage materials can be liquid hydrocarbons, such as methylcyclohexane, dibenzyltoluene, perhydrogenated ethylcarbazole, cyclohexane, or one or more of these. When using liquid hydrogen storage materials, such as... Figure 1As shown, the liquid hydrogen storage material in the copper-based slurry is mixed with an organic solvent to form a liquid mixture 2, which penetrates between the copper powder particles 1 and adheres to the surface of the copper powder particles 1. During sintering, it releases hydrogen to expel residual oxygen 3 in the copper-based slurry and reacts with surface oxides 5 on the surface of the copper powder particles 1. It also prevents the oxidation of the copper powder by atmospheric oxygen 4 in the sintering atmosphere, thereby inhibiting the oxidation of the copper powder. After sintering, the liquid hydrogen storage material is completely converted into gas and discharged, leaving no residue between the copper powder particles, thus allowing for the formation of more pronounced sintering necks 6 between the copper powder particles 1. The hydride metal particles can be selected from one or more of the following metal particles: MgH2, CrH2, ZnH2, BaH2, CaH2, CuH, NiH, LiH, NaH, KH, etc., and the particle size of the hydride metal particles does not exceed the particle size of the copper powder. To ensure the conductivity of copper-based conductive grids or effectively suppress copper powder oxidation, CuH particles with the same metal element as the main powder are preferred, or MgH2 powder with strong hydrogen storage capacity is preferred. However, if other hydride metal particles besides cuprous hydride particles are used as hydrogen storage materials, there may be a problem of balancing the effect of suppressing copper powder oxidation with its resistivity. That is, when the amount of hydride metal particles added is large, the reducing atmosphere generated by its dehydrogenation reaction can more effectively suppress copper powder oxidation, but the excess metal particles will form more conductive inclusions, resulting in a significant increase in the resistivity of the copper-based conductive grid. Conversely, if the amount of hydride metal added is reduced to lower the resistivity, the effect of suppressing copper powder oxidation will be weakened, especially in the early stage of high-temperature sintering, which can easily lead to local oxidation, thereby damaging the grid conductivity and the long-term reliability of the battery. In addition, a composite system of solid cuprous hydride particles and liquid hydrogen storage material can be used as the hydrogen storage material. This composite system not only releases active hydrogen during sintering to remove oxygen and prevent copper powder oxidation, but the copper particles formed by the decomposition of cuprous hydride particles during sintering can also serve as additional conductive connection points, further improving its conductivity. The organic carrier includes resin and organic solvent, mainly providing flowability and thixotropy to the slurry. The resin is preferably a conductive resin and / or a thermoplastic resin, and the organic solvent is a low-boiling-point hydrocarbon, i.e., a hydrocarbon with a boiling point not exceeding 300℃, such as diethylene glycol monobutyl ether, diethylene glycol butyl ether acetate, dimethyl diacid, tributyl citrate, etc. In this copper-based slurry, the content of copper powder is 60%-90% by mass percentage, the content of organic carrier is 5%-30%, and the content of hydrogen storage material is 0.1%-10%, to achieve the optimal overall performance of the slurry.

[0026] In one embodiment, to further optimize the performance of the hydrogen storage material and ensure its effective release of hydrogen at lower temperatures, a catalytic metal can be introduced into the copper-based slurry. The catalytic metal can be any one or more metals such as platinum, nickel, copper, cobalt, and iron. This measure significantly reduces the dehydrogenation temperature of the hydrogen storage material, promotes hydrogen release under milder conditions, and effectively lowers the temperature required for subsequent sintering processes. This significantly reduces the oxidation risk of copper powder during the heating process, suppresses copper powder oxidation as thoroughly as possible, and improves production efficiency and energy utilization. The catalytic metal content in the copper-based slurry is 0.1%-3% by mass. This proportion ensures significant catalytic effects while avoiding potential side effects such as increased resistivity due to the introduction of inclusion phases caused by excessive addition.

[0027] In one embodiment, the copper powder includes at least a first copper powder with an average particle size of 1µm-50µm. Since the closer the contact between copper powder particles, the better the conductivity of the copper-based conductive grid formed by sintering the copper-based slurry, provided the copper powder is unoxidized, the copper powder can also include a second copper powder with an average particle size of 10nm-500nm to achieve a dense conductive network structure in the sintered copper-based conductive grid. The particle size of the second copper powder is significantly smaller than that of the first copper powder, allowing it to fill the gaps between the first copper powder particles, thereby significantly improving the conductivity of the conductive phase. The mass of the second copper powder does not exceed 30% of the total copper powder to balance the rheology of the slurry and the conductivity after sintering. In some embodiments, cuprous hydride particles with a particle size significantly smaller than the first copper powder can also be selected as the second copper powder and added to the copper-based slurry to fill the gaps between the first copper powder particles while releasing hydrogen during sintering to inhibit the oxidation of the copper powder.

[0028] This application also provides a TOPCon battery, which includes a TOPCon cell and copper-based conductive grid lines disposed on the TOPCon cell. The copper-based conductive grid lines are prepared by printing and sintering the aforementioned copper-based paste.

[0029] Because copper has high diffusivity, high temperatures during the fabrication and use of TOPCon cells can cause copper to diffuse into silicon, leading to decreased battery performance and shortened lifespan, posing a reliability risk. To suppress copper diffusion into silicon, a metal conductive seed layer can be deposited on the TOPCon cell before printing copper-based conductive grid lines.

[0030] This application also provides a method for preparing the above-mentioned TOPCon battery, which includes the following steps: Step S1: Obtain a TOPCon solar cell and deposit a relatively inexpensive conductive metal seed layer on the TOPCon solar cell. The material of the metal seed layer may be one of nickel, titanium, aluminum, or chromium. In this application, a nickel seed layer is preferred. The deposition method of the conductive metal seed layer includes: using a laser process to open the antireflection layer and passivation layer on the TOPCon solar cell, forming laser openings on the TOPCon solar cell. During this process, the size, depth, and distribution of the openings need to be precisely controlled to minimize the impact on the photoelectric performance of the solar cell; and depositing the metal seed layer at the laser openings using a chemical plating or electroplating process.

[0031] Step S2: First, the copper-based paste is printed onto the deposited metal conductive seed layer. Then, the printed TOPCon solar cell is placed in a sintering equipment for segmented sintering to form copper-based conductive grid lines on the TOPCon solar cell, ultimately obtaining the TOPCon solar cell. The segmented sintering process includes a low-temperature annealing stage and a medium-temperature sintering stage, allowing the copper-based paste to gradually solidify in stages to form the copper-based conductive grid lines. The low-temperature annealing stage is controlled within the range of 100℃-200℃. For example, low-temperature annealing is performed under constant temperature conditions such as 100℃, 120℃, 150℃, and 175℃ to volatilize and remove the organic carrier and perform preliminary solidification, thereby removing air bubbles and stress between copper powder particles. The processing temperature during the medium-temperature sintering stage is controlled within the range of 300℃-500℃. For example, medium-temperature sintering is carried out under constant temperature conditions such as 350℃, 425℃, 450℃, and 500℃. This is used to dehydrogenate the hydrogen storage material and release hydrogen elements to inhibit the oxidation of copper powder, to completely volatilize and remove the organic carrier, and to promote the formation of a strong metallurgical bond and densification between copper powder particles to form copper-based conductive grid lines.

[0032] Compared with the traditional method of electroplating and depositing copper grid lines on TOPCon solar cells with metal seed layers, the preparation method provided in this application is simple to operate and does not require expensive equipment. The equipment investment cost and preparation cost are significantly lower. More importantly, this preparation method does not generate electroplating waste liquid that would pollute the environment, effectively reducing environmental pollution and providing a sustainable development path for the TOPCon solar cell industry.

[0033] Example 1 Preparation of copper-based slurry: 80g of copper powder with an average particle size of 3µm, 5g of methylcyclohexane, 7.5g of bisphenol A epoxy resin, and 7.5g of diethylene glycol monobutyl ether were added to a homogenizer and stirred at 1500 rad / s for 90s to obtain a copper-based slurry mixture. The copper-based slurry mixture was then transferred to a three-roll mill for homogenization to obtain a copper-based slurry. A suitable amount of the copper-based slurry was taken as a sample, and the changes in mass and mass change rate with temperature were analyzed using thermogravimetric analysis (TG) and derivative thermogravimetric analysis (DTG). The thermogravimetric curves (TG curve and DTG curve) were recorded and plotted. The relevant results are as follows: Figure 2 As shown in the curves, within the temperature range of 0℃-500℃, the mass of the copper-based slurry initially decreases gradually with increasing temperature, corresponding to the vaporization and decomposition of the organic solvent and resin. When the temperature reaches approximately 350℃, its mass reaches its lowest point, then slowly increases, corresponding to partial oxidation of the copper powder particles. When the temperature reaches approximately 400℃, its mass decreases again, corresponding to the reduction reaction caused by the dehydrogenation of methylcyclohexane. Therefore, it can be concluded that the copper-based slurry undergoes a series of complex chemical changes during sintering, including decomposition, oxidation, and reduction. In the middle stage of heating, oxidation occurs in the copper-based slurry, causing the copper powder particles to be oxidized to a certain extent, but subsequently, the copper powder is reduced by the dehydrogenation of methylcyclohexane.

[0034] Step S1: Obtain TOPCon solar cells, use laser technology to open the antireflection layer and passivation layer on the TOPCon solar cells, and form laser openings on the TOPCon solar cells; then, use chemical plating technology to deposit a nickel metal seed layer at the laser openings.

[0035] Step S2: First, the copper-based paste is printed on the metal conductive seed layer. Then, the printed TOPCon cell is placed in a sintering equipment for segmented sintering. The segmented sintering process includes: first, low-temperature annealing at 180°C for 5 minutes to remove the organic carrier in the copper-based paste; then, the temperature is raised to 400°C and held for 5 minutes to perform medium-temperature sintering to bond and solidify the copper-based paste, forming copper-based conductive grid lines on the TOPCon cell, and finally obtaining the TOPCon cell.

[0036] Example 2 Preparation of copper-based slurry: 75g of copper powder with an average particle size of 3µm, 10g of cuprous hydrogen hydride powder with an average particle size of 500nm, 7.5g of bisphenol A epoxy resin and 7.5g of diethylene glycol monobutyl ether were weighed and added to a homogenizer. After stirring at a speed of 1500rad / s for 90s, a copper-based slurry mixture was obtained. The copper-based slurry mixture was transferred to a three-roll mill for uniform mixing to obtain copper-based slurry.

[0037] Step S1: Obtain TOPCon solar cells, use laser technology to open the antireflection layer and passivation layer on the TOPCon solar cells, and form laser openings on the TOPCon solar cells; then, use chemical plating technology to deposit a nickel metal seed layer at the laser openings.

[0038] Step S2: First, the copper-based paste is printed onto the metal conductive seed layer. Then, the printed TOPCon solar cell is placed in a sintering equipment for segmented sintering. The segmented sintering process includes: first, low-temperature annealing at 180°C for 5 minutes to remove the organic carrier in the copper-based paste; then, the temperature is raised to 400°C and held for 5 minutes to perform medium-temperature sintering to bond and solidify the copper-based paste, forming copper-based conductive grid lines on the TOPCon solar cell. Figure 3 The diagram shown is a microstructure of the copper-based conductive grid, which ultimately yields the TOPCon battery.

[0039] Example 3 Preparation of copper-based slurry: 70g of first copper powder with an average particle size of 3µm, 10g of second copper powder with an average particle size of 500nm, 5g of methylcyclohexane, 7.5g of bisphenol A epoxy resin and 7.5g of diethylene glycol monobutyl ether were weighed and added to a homogenizer. After stirring at a speed of 1500rad / s for 90s, a copper-based slurry mixture was obtained. The copper-based slurry mixture was transferred to a three-roll mill for uniform mixing to obtain copper-based slurry.

[0040] Copper-based conductive grid lines were fabricated on the TOPCon cell 10 using the same fabrication method as in Example 2, such as... Figure 4 The diagram shows the microstructure of the copper-based conductive grid lines. The TOPCon cell 10, from top to bottom, comprises silicon nitride 11, aluminum oxide 12, P+ type monocrystalline silicon 13, N-type monocrystalline silicon 14, ultrathin silicon oxide 15, N+ type polycrystalline silicon 16, and silicon nitride 11. A nickel seed layer 7 is first deposited on the TOPCon cell 10, followed by the deposition of copper-based grid lines to finally obtain the TOPCon cell; as shown... Figure 5 The diagram shown is a schematic representation of the TOPCon battery.

[0041] Example 4 Preparation of copper-based slurry: 70g of first copper powder with an average particle size of 3µm, 10g of second copper powder with an average particle size of 500nm, 5g of methylcyclohexane, 0.5g of nickel, 7.5g of bisphenol A epoxy resin, and 7.5g of diethylene glycol monobutyl ether were added to a homogenizer and stirred at 1500 rad / s for 90s to obtain a copper-based slurry mixture. The copper-based slurry mixture was then transferred to a three-roll mill for uniform mixing to obtain a copper-based slurry. Nickel was used as a catalyst to further reduce the dehydrogenation temperature of the liquid hydrogen storage material, enabling it to release hydrogen at a lower temperature.

[0042] Step S1: Obtain TOPCon solar cells, use laser technology to open the antireflection layer and passivation layer on the TOPCon solar cells, and form laser openings on the TOPCon solar cells; then, use chemical plating technology to deposit a nickel metal seed layer at the laser openings.

[0043] Step S2: First, the copper-based paste is printed on the metal conductive seed layer. Then, the printed TOPCon cell is placed in a sintering equipment for segmented sintering. The segmented sintering process includes: first, low-temperature annealing at 150°C for 5 minutes to remove the organic carrier in the copper-based paste; then, the temperature is raised to 330°C and held for 5 minutes to perform medium-temperature sintering to bond and solidify the copper-based paste, forming copper-based conductive grid lines on the TOPCon cell, and finally obtaining the TOPCon cell.

[0044] Example 5 Preparation of copper-based slurry: 65g of first copper powder with an average particle size of 3µm, 15g of second copper powder with an average particle size of 350nm, 5g of dibenzyltoluene, 7.5g of bisphenol A epoxy resin and 7.5g of diethylene glycol monobutyl ether were weighed and added to a homogenizer. After stirring at a speed of 1500rad / s for 90s, a copper-based slurry mixture was obtained. The copper-based slurry mixture was transferred to a three-roll mill for uniform mixing to obtain copper-based slurry.

[0045] Step S1: Obtain TOPCon solar cells, use laser technology to open the antireflection layer and passivation layer on the TOPCon solar cells, and form laser openings on the TOPCon solar cells; then, use chemical plating technology to deposit a nickel metal seed layer at the laser openings.

[0046] Step S2: First, the copper-based paste is printed on the metal conductive seed layer. Then, the printed TOPCon cell is placed in a sintering equipment for segmented sintering. The segmented sintering process includes: first, low-temperature annealing at 180°C for 5 minutes to remove the organic carrier in the copper-based paste; then, the temperature is raised to 350°C and held for 5 minutes to perform medium-temperature sintering to bond and solidify the copper-based paste, forming copper-based conductive grid lines on the TOPCon cell, and finally obtaining the TOPCon cell.

[0047] Comparative Example 1 Silver grid lines 9 are formed on the TOPCon solar cell 10 by high-temperature silver paste sintering, ultimately resulting in the commercially available TOPCon solar cell, such as... Figure 6 The diagram shown is a structural schematic of the commonly used TOPCon battery on the market.

[0048] Comparative Example 2 Preparation of copper-based slurry: 70g of first copper powder with an average particle size of 3µm, 10g of second copper powder with an average particle size of 500nm, 7.5g of bisphenol A epoxy resin and 7.5g of diethylene glycol monobutyl ether were weighed and added to a homogenizer. After stirring at a speed of 1500rad / s for 90s, a copper-based slurry mixture was obtained. The copper-based slurry mixture was transferred to a three-roll mill and mixed evenly to obtain a copper-based slurry.

[0049] Copper-based conductive grid lines were fabricated on the TOPCon cell using the same preparation method as in Example 1, and the TOPCon cell was finally obtained.

[0050] The resistivity of the copper-based conductive grid lines prepared in Examples 1-5 and the copper-based conductive grid line prepared in Comparative Example 2 were measured using a four-probe method. The four probes were arranged in a straight line with equal spacing. A suitable constant current I was applied to the two outer probes, and the voltage V was detected by the two inner probes. The resistivity was determined using the formula ρ = (V / I). S / L, used to calculate resistivity, where S is the cross-sectional area of ​​the grid line and L is the length of the grid line being measured. Test results are shown in Table 1.

[0051] Table 1. Comparison of line resistance of copper-based conductive grid lines in the embodiments and comparative examples of the present invention.

[0052]

[0053] As shown in Table 1, the line resistance of the copper-based conductive grids prepared in Examples 1-5 is significantly lower than that of the copper-based conductive grids prepared in Comparative Example 2. This comparison strongly demonstrates that introducing hydrogen storage materials into the copper-based slurry can effectively inhibit the oxidation process of copper powder, thereby significantly improving the conductivity of the sintered copper-based conductive grids. The line resistance of the copper-based conductive grids prepared in Examples 3-5 is significantly lower than that of the copper-based conductive grids prepared in Examples 1 and 2, further demonstrating that using liquid hydrogen storage materials to formulate the copper-based slurry can better inhibit the oxidation of copper powder during sintering, thus obtaining superior conductivity. Figure 3 , Figure 4As shown, comparing the microscopic images of the copper-based conductive grids prepared in Examples 2 and 3, it can be seen that the surface of the copper particles in Example 3 is smoother, and the oxide layer on its surface is significantly less than that on the surface of the copper particles in Example 2. This microstructural feature provides strong evidence for the aforementioned conclusion that "using liquid hydrogen storage materials to prepare copper-based slurries can better suppress the oxidation of copper powder." Furthermore, the copper-based conductive grids obtained in Example 3 have more pronounced sintering necks between particles. This structural feature also facilitates smooth electron transport, resulting in superior conductivity. Moreover, from the perspective of the dispersion and mechanism of action of hydrogen storage materials, unlike the way hydride metal particles are dispersed in copper powder, liquid hydrogen storage materials are dispersed in the slurry in liquid form and can uniformly coat the surface of copper powder. During sintering, the liquid hydrogen storage material releases hydrogen more uniformly, suppressing copper powder oxidation in all directions without dead angles. Furthermore, analyzing the dehydrogenation rate, the dehydrogenation rate of liquid hydrogen storage materials is significantly higher than that of cuprous hydride. For example, cuprous hydride has a dehydrogenation rate of approximately 1.56 wt%, while methylcyclohexane has approximately 6.16 wt%. This means that when adding the same mass of methylcyclohexane and cuprous hydride particles, methylcyclohexane produces 4 to 5 times more hydrogen than cuprous hydride. This large release of hydrogen effectively prevents copper powder oxidation, providing a solid guarantee for the excellent conductivity of copper-based conductive grid wires.

[0054] Comparing Example 3 and Example 4, it is evident that the simultaneous introduction of a catalytic metal into the slurry significantly reduces the dehydrogenation temperature of the liquid hydrogen storage material, enabling it to release hydrogen at lower temperatures. This means the liquid hydrogen storage material can begin releasing hydrogen at lower sintering temperatures, effectively suppressing the oxidation of copper powder during sintering, especially at higher temperatures, thereby significantly improving its conductivity. Since the catalytic metal possesses a certain degree of conductivity, a small amount of it can be uniformly distributed as an inclusion phase within the copper-based conductive grid without affecting the resistivity of the grid.

[0055] The electrical performance of the TOPCon battery obtained in Example 3 and the TOPCon battery cell in Comparative Example 1 were tested. The current-voltage (IV) curves were measured under AM1.5G spectrum according to the IEC60904-1 standard. The test results are shown in Table 2.

[0056] Table 2. Comparison of electrical parameters between the TOPCon battery obtained in Example 3 and the conventional battery in Comparative Example 1.

[0057]

[0058] As shown in Table 2, the TOPCon battery prepared using the method provided in this application exhibits electrical performance comparable to, or even slightly superior to, commonly used TOPCon batteries on the market. Specifically, the TOPCon battery prepared in Example 3 shows improvements in key indicators such as energy conversion efficiency (Eta), open-circuit voltage (Voc), and fill factor (FF), while the series resistance (Rs) is reduced, and the short-circuit current (Isc) remains at a level similar to that of the commonly used TOPCon battery in Comparative Example 1. These data clearly demonstrate that the TOPCon battery prepared using the method provided in this application can replace traditional TOPCon batteries using silver conductive grids. More importantly, the TOPCon battery preparation scheme provided in this application achieves silver-free production, significantly reducing the dependence of TOPCon batteries on silver materials, thereby greatly reducing preparation costs and effectively addressing the challenge of soaring TOPCon battery manufacturing costs due to the continuous rise in silver prices, providing the industry with a more economical and efficient solution.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A copper-based paste, characterized in that, Copper-based slurry includes: copper powder, which is densified during sintering to form a conductive phase; Hydrogen storage material is used to release hydrogen during sintering and to create a reducing atmosphere locally to prevent the oxidation of copper powder; the hydrogen storage material includes liquid hydrogen storage material. Organic carriers provide fluidity and thixotropy to the slurry; By mass percentage, the copper powder content in the copper-based slurry is any value between 60% and 90%, the organic carrier content is any value between 5% and 30%, and the hydrogen storage material content is any value between 0.1% and 10%.

2. The copper-based paste as described in claim 1, characterized in that, It also includes a catalytic metal for promoting the release of hydrogen from the hydrogen storage material, wherein the catalytic metal is any one or more of platinum, nickel, copper, cobalt, and iron; In the copper-based slurry, the content of the catalytic metal is 0.1%-3% by mass percentage.

3. The copper-based paste as described in claim 1 or 2, characterized in that, The liquid hydrogen storage material is any one or more of methylcyclohexane, dibenzyltoluene, perhydrogenated ethylcarbazole, and cyclohexane.

4. The copper-based paste as described in claim 3, characterized in that, The copper powder includes a first copper powder and a second copper powder. The average particle size of the first copper powder is any value between 1µm and 50µm, and the average particle size of the second copper powder is any value between 10nm and 500nm. The second copper powder fills the gaps between the first copper powder particles to improve the conductivity of the conductive phase. The mass of the second copper powder does not exceed 30% of the total amount of copper powder.

5. The copper-based paste as described in claim 3, characterized in that, The organic carrier includes a resin and an organic solvent; the resin is a conductive resin and / or a thermoplastic resin, and the organic solvent is a hydrocarbon with a boiling point not exceeding 300°C.

6. A TOPCon battery, characterized in that, include: TOPCon solar cells and copper-based conductive grid lines; A metal conductive seed layer is deposited on the TOPCon solar cell, and the copper-based conductive grid lines are disposed on the TOPCon solar cell; the copper-based conductive grid lines are prepared by printing and sintering the copper-based paste according to any one of claims 1-5.

7. The method for preparing the TOPCon battery according to claim 6, characterized in that, Includes the following steps: Step S1: Obtain TOPCon solar cells and deposit a metal conductive seed layer on the TOPCon solar cells; Step S2: Print the copper-based paste onto the metal conductive seed layer; Step S3: Perform segmented sintering on the TOPCon battery cell printed with the copper-based paste to form copper-based conductive grid lines on the TOPCon battery cell, thereby obtaining a TOPCon battery. The segmented sintering process includes a low-temperature annealing stage and a medium-temperature sintering stage, which are used to gradually solidify the copper-based slurry in stages to form copper-based conductive grid lines.

8. The method for preparing a TOPCon battery as described in claim 7, characterized in that, The temperature range of the low-temperature annealing stage is 100℃-200℃, which is used to remove the organic carrier and perform preliminary curing. The temperature range of the intermediate-temperature sintering stage is 300℃-500℃, which is used to dehydrogenate the hydrogen storage material to release hydrogen and to densify the copper-based slurry to form copper-based conductive grid lines.

9. The method for preparing a TOPCon battery as described in claim 7, characterized in that, The deposition method of the metal conductive seed layer includes: using a laser process to open the antireflection layer and passivation layer on the TOPCon solar cell to form a laser opening on the TOPCon solar cell; and using a chemical plating or electroplating process to deposit a metal seed layer at the laser opening.

10. The method for preparing a TOPCon battery as described in claim 9, characterized in that, The material of the metal seed layer is a base metal.

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