Conductive paste for BC battery and preparation process of conductive paste

Abstract

The invention discloses conductive paste for a BC battery and a preparation process of the conductive paste. The conductive paste comprises the following components: 30-60 wt% of silver powder, 4-8 wt% of glass powder, 10-20 wt% of an additive, 5-10 wt% of an accelerant and the balance of a composite carrier, comprising the following steps: raw material preparation: weighing silver powder, glass powder, an additive, an accelerant and a composite carrier raw material, and mixing according to a preset proportion; mixing and grinding: grinding the mixed raw materials until a uniform and fine slurry state is achieved; the conductive paste has the beneficial effects that by optimizing the formula design, common good contact and compounding of the n region and the p region of the BC battery are realized, and the battery efficiency is improved; through compound optimization of an organic carrier and an inorganic system, the slurry consumption is reduced, and the battery cost is further reduced; the method is suitable for a laser secondary sintering process, and good co-firing of an N region and a P region in the laser process is ensured; the grid lines are full in morphology and narrow in line width, and the development direction of cell silk-screen printing towards high-mesh or net-knot-free matching fine gridding and high-speed printing is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive pastes, and in particular relates to a conductive paste for BC batteries and a preparation process thereof. Background Art

[0002] In 2023, N-type TOPCon cells based on N-type silicon wafer substrates and tunneling oxide passivation technology will enter large-scale production, with the efficiency of mass-produced cells reaching 25.5%, gradually becoming the mainstream solar cell technology; however, conductive silver paste is required to prepare electrodes on both sides of the TOPCon cell, which greatly increases the consumption of silver paste and increases cost pressure; at the same time, it is difficult to further improve the efficiency of TOPCon cells; and the back contact cell (BC cell) has no grid line blocking on the front, which is not only aesthetically pleasing, but also eliminates the optical loss caused by traditional grid line blocking, ensuring the maximum utilization of incident photons, and significantly improving the short-circuit current compared to conventional cells; at the same time, the BC cell structure has high compatibility and can be superimposed with passivation technologies such as TOPCon and HJT, such as TBC and HBC cells, to further improve the photoelectric conversion efficiency of the battery.

[0003] BC solar cells are a highly efficient, low-cost solar cell structure with enormous application potential. They can be used in photovoltaic power stations, rooftop photovoltaic power generation, electric vehicle charging stations, and other fields. With the continuous development of technology and the reduction of costs, BC solar cells are expected to become one of the mainstream solar cell technologies in the future. The photovoltaic industry is ushering in a major technological change, and the emergence of BC solar cells will have a profound impact on the global clean energy industry.

[0004] Publication number CN118571526A discloses a conductive paste for photovoltaic cells and a preparation method thereof. The patent discloses the following specific steps: weighing the following percentages of raw materials: 40-80wt% silver powder, 5-25wt% metal additives, 5-15wt% conductive promoter, 3-5wt% glass powder, and the remainder as a modified carrier, mixing and grinding the raw materials evenly to obtain a conductive paste for photovoltaic cells.

[0005] However, the process complexity and cost issues of BC batteries limit their widespread application; especially in the contact and recombination of n-region and p-region, due to the intrinsic differences between the two in passivation structure, doping, electrical state, etc., higher requirements are placed on the conductive paste. Summary of the Invention

[0006] The purpose of the present invention is to provide a conductive paste for BC batteries and its preparation process. By optimizing the formula design and combining it with the laser secondary sintering process, good contact and composite of the n-zone and p-zone are achieved; by optimizing the composite of organic carrier and inorganic system, the single-piece consumption of the paste for battery cell is reduced, further reducing the battery cost.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A conductive paste for BC batteries, comprising the following components: 30-60wt% silver powder, 4-8wt% glass powder, 10-20wt% additives, 5-10wt% promoter, and the remainder being a composite carrier.

[0008] As a preferred technical solution of the present invention, the silver powder adopts a multi-component micro-nano composite silver powder system, including micron, submicron and nano silver powders with different particle sizes, morphologies, particle size distributions, specific surface areas and surface-coated organic matter.

[0009] As a preferred technical solution of the present invention, the additives include a conductive polymer, a surfactant, and an antioxidant.

[0010] As a preferred technical solution of the present invention, the conductive polymer includes poly(p-phenylene vinylene), polyaniline and polyacetylene, and the surfactant is prepared by mixing polyoxyethylene alkylphenol ether as the main component with polyoxyethylene fatty acid ester and alkyl glycoside.

[0011] As a preferred technical solution of the present invention, the antioxidant is based on sorbitol and is compounded with ascorbic acid and tocopherol.

[0012] As a preferred technical solution of the present invention, the accelerator is one of tert-butylbenzene peroxide and potassium cobaltate.

[0013] As a preferred technical solution of the present invention, the composite carrier is formed by mixing terpineol, butyl carbitol and resin.

[0014] The present invention also discloses a process for preparing a conductive paste for BC batteries, comprising the following steps:

[0015] Raw material preparation: weigh silver powder, glass powder, additives, accelerator and composite carrier raw materials and mix them according to the predetermined ratio;

[0016] Mixing and grinding: Grind the mixed raw materials until they reach a uniform and fine slurry state;

[0017] Composite optimization of organic carrier and inorganic system: By adjusting the molecular structure of the organic carrier, solvent type, and thixotropic additives, the viscosity, precipitation, ink permeability, printability, and mechanical properties of the slurry are optimized; by precisely controlling the formula and sintering activity of the glass powder, a good match between the slurry and the BC battery structure is achieved;

[0018] Slurry performance testing: Using battery and slurry fine detection technology, we conduct a comprehensive evaluation of the slurry's rheological properties, electrical properties, mechanical properties, grid line morphology, printing performance, and the photovoltaic conversion efficiency of the cell;

[0019] Slurry adjustment and optimization: Based on the performance test results, the slurry formula and preparation process are adjusted and optimized until the best performance is achieved.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The conductive paste achieves good contact and compounding between the n-region and p-region of the BC battery through optimized formula design, thus improving battery efficiency.

[0022] Through the composite optimization of organic carriers and inorganic systems, the slurry consumption is reduced, further reducing battery costs;

[0023] Applicable to laser secondary sintering process, ensuring good co-firing of N and P areas in the laser process;

[0024] The grid lines have full morphology and narrow line width, which is in line with the trend of screen printing of solar cells towards high mesh count or knot-free screen printing with fine grid and high-speed printing;

[0025] By precisely controlling the raw material ratio and preparation steps, the high performance of the conductive paste is achieved; the preparation process is simple and easy to operate, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart for preparing the conductive paste for BC batteries of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Example 1

[0029] See also Figure 1, which is the first embodiment of the present invention, provides a conductive paste for BC batteries, including the following components: 30wt% silver powder, 4wt% glass powder, 10wt% additive, 5wt% promoter, and the balance is a composite carrier; the silver powder adopts a multi-component micro-nano composite silver powder system, including micron, submicron, and nano silver powders with different particle sizes, morphologies, particle size distributions, and specific surface areas, and the surface is coated with organic matter to achieve tight overlap and good current conduction performance; the glass powder can achieve sufficient etching of the passivation layer while significantly reducing damage to the passivated polysilicon, ensuring low contact resistance and metal composite; the additive is used to improve the conductivity and stability of the paste; the promoter can effectively promote direct contact between the silver powder and the silicon substrate, reducing the contact resistivity; the composite carrier is based on a highly dispersed and highly adhesive composite organic carrier material to optimize the gate line morphology and reduce the paste consumption.

[0030] In this embodiment, preferably, the additives include conductive polymers, surfactants, and antioxidants; the conductive polymer is a mixture of various organic conductive polymers including poly(p-styrene), specifically including poly(p-styrene), polyaniline, and polyacetylene; poly(p-styrene) has good intrinsic conductivity, and its conjugated structure is conducive to the transmission of electrons; polyaniline can exhibit high conductivity in an acidic environment and has good environmental stability, and can maintain stable conductive properties in the slurry; polyacetylene has a unique linear conjugated structure, high electron mobility, and can quickly conduct current. These three organic conductive polymers work synergistically through different molecular structures and conductive mechanisms to improve the overall conductive properties of the slurry; surface active The surfactant is a mixture of polyoxyethylene alkylphenol ether as the main component, and other surfactants with different hydrophilic and hydrophobic properties and interfacial activity such as fatty acid polyoxyethylene esters and alkyl glucosides. Fatty acid polyoxyethylene esters have good emulsifying ability and can better mix the oily components and aqueous components in the slurry; alkyl glucoside has the advantages of low toxicity, environmental protection, and good foam stability, which can enhance the dispersion effect of various components in the slurry and improve the surface properties of the slurry; the antioxidant is based on sorbitol, and is compounded with ascorbic acid and tocopherol. The antioxidant mechanisms of different antioxidants are complementary to each other, which improves the antioxidant stability of the slurry during storage and use, and effectively prevents the components in the slurry from being oxidized and affecting the performance.

[0031] In this embodiment, preferably, the accelerator is tert-butylbenzene peroxide.

[0032] In this embodiment, preferably, the composite carrier is formed by mixing terpineol, butyl carbitol and resin.

[0033] A process for preparing a conductive paste for BC batteries comprises the following steps:

[0034] Raw material preparation: weigh silver powder, glass powder, additives, accelerator and composite carrier raw materials and mix them according to the predetermined ratio;

[0035] Mixing and grinding: Grind the mixed raw materials until they reach a uniform and fine slurry state;

[0036] Composite optimization of organic carrier and inorganic system: By adjusting the molecular structure of the organic carrier, solvent type, and thixotropic additives, the viscosity, precipitation, ink permeability, printability, and mechanical properties of the slurry are optimized; by precisely controlling the formula and sintering activity of the glass powder, a good match between the slurry and the BC battery structure is achieved;

[0037] Slurry performance testing: Using battery and slurry fine detection technology, we conduct a comprehensive evaluation of the slurry's rheological properties, electrical properties, mechanical properties, grid line morphology, printing performance, and the photovoltaic conversion efficiency of the cell;

[0038] Slurry adjustment and optimization: Based on the performance test results, the slurry formula and preparation process are adjusted and optimized until the best performance is achieved.

[0039] Example 2

[0040] See also Figure 1 , which is the second embodiment of the present invention, provides a conductive paste for BC batteries, including the following components: 45wt% silver powder, 6wt% glass powder, 15wt% additives, 8wt% promoter, and the balance being a composite carrier; the silver powder adopts a multi-component micro-nano composite silver powder system, including micron, submicron, and nano silver powders with different particle sizes, morphologies, particle size distributions, and specific surface areas, and the surface is coated with organic matter to achieve tight overlap and good current conduction performance; the glass powder can significantly reduce the damage to the passivated polysilicon while achieving sufficient etching of the passivation layer, ensuring low contact resistance and metal composite; the additive is used to improve the conductivity and stability of the paste; the promoter can effectively promote direct contact between the silver powder and the silicon substrate, reducing the contact resistivity; the composite carrier is based on a highly dispersed and highly adhesive composite organic carrier material to optimize the gate line morphology and reduce the paste consumption.

[0041] In this embodiment, preferably, the additives include conductive polymers, surfactants, and antioxidants; the conductive polymer is a mixture of various organic conductive polymers including poly(p-styrene), specifically including poly(p-styrene), polyaniline, and polyacetylene; poly(p-styrene) has good intrinsic conductivity, and its conjugated structure is conducive to the transmission of electrons; polyaniline can exhibit high conductivity in an acidic environment and has good environmental stability, and can maintain stable conductive properties in the slurry; polyacetylene has a unique linear conjugated structure, high electron mobility, and can quickly conduct current. These three organic conductive polymers work synergistically through different molecular structures and conductive mechanisms to improve the overall conductive properties of the slurry; surface active The surfactant is a mixture of polyoxyethylene alkylphenol ether as the main component, and other surfactants with different hydrophilic and hydrophobic properties and interfacial activity such as fatty acid polyoxyethylene esters and alkyl glucosides. Fatty acid polyoxyethylene esters have good emulsifying ability and can better mix the oily components and aqueous components in the slurry; alkyl glucoside has the advantages of low toxicity, environmental protection, and good foam stability, which can enhance the dispersion effect of various components in the slurry and improve the surface properties of the slurry; the antioxidant is based on sorbitol, and is compounded with ascorbic acid and tocopherol. The antioxidant mechanisms of different antioxidants are complementary to each other, which improves the antioxidant stability of the slurry during storage and use, and effectively prevents the components in the slurry from being oxidized and affecting the performance.

[0042] In this embodiment, preferably, the accelerator is potassium percobaltate.

[0043] In this embodiment, preferably, the composite carrier is formed by mixing terpineol, butyl carbitol and resin.

[0044] A process for preparing a conductive paste for BC batteries comprises the following steps:

[0045] Raw material preparation: weigh silver powder, glass powder, additives, accelerator and composite carrier raw materials and mix them according to the predetermined ratio;

[0046] Mixing and grinding: Grind the mixed raw materials until they reach a uniform and fine slurry state;

[0047] Composite optimization of organic carrier and inorganic system: By adjusting the molecular structure of the organic carrier, solvent type, and thixotropic additives, the viscosity, precipitation, ink permeability, printability, and mechanical properties of the slurry are optimized; by precisely controlling the formula and sintering activity of the glass powder, a good match between the slurry and the BC battery structure is achieved;

[0048] Slurry performance testing: Using battery and slurry fine detection technology, we conduct a comprehensive evaluation of the slurry's rheological properties, electrical properties, mechanical properties, grid line morphology, printing performance, and the photovoltaic conversion efficiency of the cell;

[0049] Slurry adjustment and optimization: Based on the performance test results, the slurry formula and preparation process are adjusted and optimized until the best performance is achieved.

[0050] Example 3

[0051] See also Figure 1 , which is the third embodiment of the present invention, provides a conductive paste for BC batteries, including the following components: 60wt% silver powder, 8wt% glass powder, 20wt% additives, 10wt% promoter, and the balance being a composite carrier; the silver powder adopts a multi-component micro-nano composite silver powder system, including micron, submicron, and nano silver powders with different particle sizes, morphologies, particle size distributions, and specific surface areas, and the surface is coated with organic matter to achieve tight overlap and good current conduction performance; the glass powder can significantly reduce the damage to the passivated polysilicon while achieving sufficient etching of the passivation layer, ensuring low contact resistance and metal composite; the additive is used to improve the conductivity and stability of the paste; the promoter can effectively promote direct contact between the silver powder and the silicon substrate, reducing the contact resistivity; the composite carrier is based on a highly dispersed and highly adhesive composite organic carrier material to optimize the gate line morphology and reduce the paste consumption.

[0052] In this embodiment, preferably, the additives include conductive polymers, surfactants, and antioxidants; the conductive polymer is a mixture of various organic conductive polymers including poly(p-styrene), specifically including poly(p-styrene), polyaniline, and polyacetylene; poly(p-styrene) has good intrinsic conductivity, and its conjugated structure is conducive to the transmission of electrons; polyaniline can exhibit high conductivity in an acidic environment and has good environmental stability, and can maintain stable conductive properties in the slurry; polyacetylene has a unique linear conjugated structure, high electron mobility, and can quickly conduct current. These three organic conductive polymers work synergistically through different molecular structures and conductive mechanisms to improve the overall conductive properties of the slurry; surface active The surfactant is a mixture of polyoxyethylene alkylphenol ether as the main component, and other surfactants with different hydrophilic and hydrophobic properties and interfacial activity such as fatty acid polyoxyethylene esters and alkyl glucosides. Fatty acid polyoxyethylene esters have good emulsifying ability and can better mix the oily components and aqueous components in the slurry; alkyl glucoside has the advantages of low toxicity, environmental protection, and good foam stability, which can enhance the dispersion effect of various components in the slurry and improve the surface properties of the slurry; the antioxidant is based on sorbitol, and is compounded with ascorbic acid and tocopherol. The antioxidant mechanisms of different antioxidants are complementary to each other, which improves the antioxidant stability of the slurry during storage and use, and effectively prevents the components in the slurry from being oxidized and affecting the performance.

[0053] In this embodiment, preferably, the accelerator is tert-butylbenzene peroxide.

[0054] In this embodiment, preferably, the composite carrier is formed by mixing terpineol, butyl carbitol and resin.

[0055] A process for preparing a conductive paste for BC batteries comprises the following steps:

[0056] Raw material preparation: weigh silver powder, glass powder, additives, accelerator and composite carrier raw materials and mix them according to the predetermined ratio;

[0057] Mixing and grinding: Grind the mixed raw materials until they reach a uniform and fine slurry state;

[0058] Composite optimization of organic carrier and inorganic system: By adjusting the molecular structure of the organic carrier, solvent type, and thixotropic additives, the viscosity, precipitation, ink permeability, printability, and mechanical properties of the slurry are optimized; by precisely controlling the formula and sintering activity of the glass powder, a good match between the slurry and the BC battery structure is achieved;

[0059] Slurry performance testing: Using battery and slurry fine detection technology, we conduct a comprehensive evaluation of the slurry's rheological properties, electrical properties, mechanical properties, grid line morphology, printing performance, and the photovoltaic conversion efficiency of the cell;

[0060] Slurry adjustment and optimization: Based on the performance test results, the slurry formula and preparation process are adjusted and optimized until the best performance is achieved.

[0061] Experimental verification:

[0062]

[0063]

[0064] Although the embodiments of the present invention have been shown and described, as detailed above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A conductive paste for BC batteries, characterized by: The invention comprises the following components: 30-60 wt% of silver powder, 4-8 wt% of glass powder, 10-20 wt% of additive, 5-10 wt% of accelerator, and the balance being a composite carrier.

2. The conductive paste for BC batteries according to claim 1, characterized in that: The silver powder adopts a multi-element micro-nano composite silver powder system, including micron, submicron and nano silver powders with different particle sizes, morphologies, particle size distributions and specific surface areas, and the surfaces are coated with organic matter.

3. The conductive paste for BC batteries according to claim 1, characterized in that: The additives include conductive polymers, surfactants, and antioxidants.

4. The conductive paste for BC batteries according to claim 3, characterized in that: The conductive polymer includes poly(p-phenylene vinylene), polyaniline and polyacetylene, and the surfactant is prepared by mixing polyoxyethylene alkylphenol ether as a main component with polyoxyethylene fatty acid ester and alkyl glycoside.

5. The conductive paste for BC batteries according to claim 3, characterized in that: The antioxidant is based on sorbitol and is compounded with ascorbic acid and tocopherol.

6. The conductive paste for BC batteries according to claim 1, characterized in that: The accelerator is one of tert-butylbenzene peroxide and potassium cobaltate.

7. The conductive paste for BC batteries according to claim 1, characterized in that: The composite carrier is prepared by mixing terpineol, butyl carbitol and resin.

8. The process for preparing a conductive paste for BC batteries according to any one of claims 1 to 7, characterized in that: The steps include: Raw material preparation: weigh silver powder, glass powder, additives, accelerator and composite carrier raw materials and mix them according to the predetermined ratio; Mixing and grinding: Grind the mixed raw materials until they reach a uniform and fine slurry state; Composite optimization of organic carrier and inorganic system: By adjusting the molecular structure of the organic carrier, solvent type, and thixotropic additives, the viscosity, precipitation, ink permeability, printability, and mechanical properties of the slurry are optimized; by precisely controlling the formula and sintering activity of the glass powder, a good match between the slurry and the BC battery structure is achieved; Slurry performance testing: Using battery and slurry fine detection technology, we conduct a comprehensive evaluation of the slurry's rheological properties, electrical properties, mechanical properties, grid line morphology, printing performance, and the photovoltaic conversion efficiency of the cell; Slurry adjustment and optimization: Based on the performance test results, the slurry formula and preparation process are adjusted and optimized until the best performance is achieved.

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