Conductive photovoltaic slurry for poly region and preparation method thereof

Abstract

The invention provides conductive photovoltaic slurry for a poly region and a preparation method thereof, and belongs to the field of solar cells. The conductive photovoltaic paste comprises the following chemical components: 40-70 parts of silver powder, 5-25 parts of silver coated copper, 1.5-5.5 parts of a glass material, 10-15 parts of an organic carrier, 1-3 parts of silica sol, 1-5 parts of polytetrafluoroethylene coated silver powder and 1-3 parts of epoxy resin coated silver coated copper. Through reasonable design of components of the conductive photovoltaic slurry, a good dispersion state among particles and a three-dimensional cross-linked structure of epoxy resin, the slurry can maintain high stability in a use process and is not easy to agglomerate and precipitate. And meanwhile, the bonding force between the slurry and the surface of the Poly region is jointly improved through the chemical bonding effect of the silica sol, the glass material and the surface of the Poly region and the three-dimensional cross-linked structure of the epoxy resin. Therefore, the stability of the conductive photovoltaic slurry for the poly region and the adhesive force of the conductive photovoltaic slurry on the surface of the poly region are improved at the same time.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and in particular to a conductive photovoltaic paste for the poly region and a preparation method thereof. Background Art

[0002] A conductive photovoltaic paste is a mixture composed of high-purity silver powder (or other conductive metal powders), glass oxides (or other inorganic binders), organic resins, and organic solvents. The high-purity silver powder or other conductive metal powders in the paste provide excellent electrical conductivity, enabling current to be effectively transmitted in the solar cell panel. Glass oxides or other inorganic binders can firmly bond the paste to the poly region, ensuring good contact between the paste and the cell panel. The paste forms a protective film on the surface of the cell panel, which can prevent the cell from being affected by the external environment, such as air, moisture, etc., thereby increasing the service life of the cell.

[0003] In the prior art, on the one hand, the stability of the conductive photovoltaic paste for the poly region is poor, and the silver powder is prone to precipitation. The layering phenomenon destroys the uniformity of the paste, making the composition of the paste coated on the surface of the poly region inconsistent. At the same time, agglomeration is likely to occur during the precipitation of the silver powder, forming larger silver powder particles. These agglomerated silver powder particles may not be fully dispersed during the sintering process, resulting in voids and defects in the sintered conductive film layer, thereby reducing the electrical conductivity. On the other hand, the adhesion of the paste on the surface of the Poly region is insufficient. During the operation of the cell, the paste may fall off from the Poly region or form voids. These fallen-off or voids will hinder the transmission of current, resulting in a decrease in the photoelectric conversion efficiency of the cell. At the same time, the contact resistance between the paste with poor adhesion and the Poly region may increase. The increase in contact resistance will cause the cell to generate more heat during operation, thereby reducing the efficiency and service life of the cell. Therefore, how to simultaneously improve the stability of the conductive photovoltaic paste for the poly region and the adhesion on the surface of the Poly region is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0004] This application provides a conductive photovoltaic paste for the poly region and a preparation method thereof to solve the following technical problems: how to simultaneously improve the stability of the conductive photovoltaic paste for the poly region and the adhesion on the surface of the Poly region.

[0005] In the first aspect, this application provides a conductive photovoltaic paste for the poly region. In parts by mass, the conductive photovoltaic paste includes the following chemical components: 40 - 70 parts of silver powder, 5 - 25 parts of silver-coated copper, 1.5 - 5.5 parts of glass material, 10 - 15 parts of organic carrier, 1 - 3 parts of silica sol, 1 - 5 parts of polytetrafluoroethylene-coated silver powder, and 1 - 3 parts of epoxy resin-coated silver-coated copper.

[0006] Optionally, the thickness of the polytetrafluoroethylene coating layer in the polytetrafluoroethylene-coated silver powder is 0.5 nm to 3 nm.

[0007] Optionally, the thickness of the epoxy resin coating layer in the epoxy resin-coated silver-coated copper is 0.5 to 2 nm.

[0008] Optionally, in terms of mole percentage, the glass material is composed of the following components: Bi2O3: 20 - 30 mol.%, B2O3: 40 - 50 mol.%, ZnO: 2 - 6 mol.%, SiO2: 2 - 6 mol.%, Al2O3: 1 - 5 mol.%, NaBr: 1 - 5 mol.%, SnO2: 1 - 5 mol.%, CdO: 1 - 5 mol.%, Ce2O3: 1 - 5 mol.%, Y2O3: 1 - 5 mol.%.

[0009] Optionally, the organic carrier is composed of epoxy resin, organic solvent and organic auxiliary agent, and the mass ratio of the epoxy resin, the organic solvent and the organic auxiliary agent is (25 - 35):(60 - 70):(3 - 8).

[0010] In a second aspect, the present application provides a method for preparing the conductive photovoltaic paste for the poly region according to any one of the embodiments in the first aspect, and the method includes:

[0011] Mix 40 - 70 parts of silver powder, silver-coated copper, glass material, organic carrier and silica sol to obtain a first blend;

[0012] Add polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the first blend to obtain a second blend;

[0013] Hydrothermally treat the second blend to obtain the conductive photovoltaic paste for the poly region.

[0014] Optionally, the temperature of the hydrothermal treatment is 80 - 120 °C, and the time of the hydrothermal treatment is 30 min - 90 min.

[0015] Optionally, the method for preparing the polytetrafluoroethylene-coated silver powder includes:

[0016] Perform plasma treatment on silver powder to obtain pretreated silver powder;

[0017] Mix the pretreated silver powder with a pre-hydrolyzed solution of silane coupling agent to bond the silane coupling agent on the surface of the pretreated silver powder to obtain an intermediate;

[0018] Mix the intermediate with polytetrafluoroethylene to obtain the polytetrafluoroethylene-coated silver powder.

[0019] Optionally, the plasma treatment includes the following parameters: the power is 50 - 100 W, the treatment time is 10 - 20 min, and the oxygen flow rate is 30 - 80 mL / min.

[0020] Optionally, the preparation method of the epoxy resin-coated silver-coated copper includes:

[0021] Add the epoxy resin into deionized water and heat until the epoxy resin is completely dissolved to obtain a mixed solution;

[0022] Add the silver-coated copper into the mixed solution, and then perform ultrasonic-microwave combined treatment to obtain the epoxy resin-coated silver-coated copper; the parameters of the ultrasonic-microwave combined treatment include: the microwave power is 50 - 100 W, the ultrasonic power is 100 - 200 W, and the treatment time is 30 - 60 s.

[0023] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0024] The embodiments of the present application provide a conductive photovoltaic paste for the poly region. By reasonably designing the components of the conductive photovoltaic paste, silver, as a precious metal, has a relatively high price. While copper, as a base metal, has a price far lower than that of silver. Therefore, using silver-coated copper to replace part of the silver powder in the conductive photovoltaic paste can significantly reduce the material cost. And adding polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the conductive photovoltaic silver paste. On the one hand, the polytetrafluoroethylene (PTFE)-coated silver powder and the epoxy resin-coated silver-coated copper exist in a suspended form in the silver paste. Due to the chemical repulsion between the epoxy resin and polytetrafluoroethylene, these particles can maintain a good dispersed state during suspension. The suspended particles in the silver paste are not likely to agglomerate and precipitate. This helps to maintain the uniformity and stability of the silver paste, thereby improving its performance during use. On the other hand, the epoxy resin can form a three-dimensional cross-linked structure during the curing process, tightly wrapping the silver alloy conductive material therein. This structure not only improves the overall strength of the paste, but also makes the bond between the paste and the surface of the poly region more firm. At the same time, the silica sol can also chemically react with certain components in the glass material to form chemical bonding, further enhancing the bond strength between the paste and the surface of the poly region. Thus, improving the stability of the conductive photovoltaic paste for the poly region and its adhesion to the surface of the poly region simultaneously. Description of the Drawings

[0025] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present application, and are used together with the specification to explain the principles of the present application.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic flow chart of a preparation method of a conductive photovoltaic paste for the poly region provided by an embodiment of the present application. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0029] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0030] In a first aspect, the present application provides a conductive photovoltaic paste for the poly region. In terms of parts by mass, the conductive photovoltaic paste includes the following chemical components: 40 - 70 parts of silver powder, 5 - 25 parts of silver-coated copper, 1.5 - 5.5 parts of glass material, 10 - 15 parts of organic carrier, 1 - 3 parts of silica sol, 1 - 5 parts of polytetrafluoroethylene-coated silver powder, and 1 - 3 parts of epoxy resin-coated silver-coated copper.

[0031] As a precious metal, silver has a relatively high price. While copper, as a base metal, has a much lower price than silver. Therefore, using silver-coated copper to replace part of the silver powder in the conductive photovoltaic paste can significantly reduce the material cost. At the same time, copper itself has good electrical conductivity, and the electrical conductivity of the silver-coated copper powder after silver plating treatment is further improved, which can meet the requirements of photovoltaic cells for high electrical conductivity. In addition, pure copper powder is prone to oxidation, especially in humid and high-temperature environments. However, the silver-coated copper powder can form a protective silver layer on the surface of the copper powder through silver plating treatment, effectively preventing the oxidation of the copper powder, thereby improving the stability and service life of the paste.

[0032] The glass material can effectively improve the connection between silver particles, reduce the contact resistance, and thus improve the electrical conductivity efficiency of the paste. At the same time, the glass material can enhance the adhesion between the paste and the silicon wafer, ensure the tight combination of the electrode and the silicon wafer, and improve the stability of the electrode. In addition, the addition of the glass material can also enhance the durability of the electrode and extend the service life of the photovoltaic cell.

[0033] The polytetrafluoroethylene (PTFE)-coated silver powder plays the following roles in the slurry: Silver, as a conductive material, can provide excellent electrical conductivity to ensure the effective transmission of current in photovoltaic cells. At the same time, PTFE has good chemical resistance, which can protect the silver conductive material from the erosion of the external environment, thereby improving the stability and durability of the slurry. In addition, the abrasion resistance of PTFE helps to reduce the wear of the slurry during the coating process and maintain its good electrical conductivity.

[0034] The roles of epoxy resin-coated silver-coated copper in the slurry mainly include: The silver alloy, as a conductive material, also has excellent electrical conductivity. At the same time, epoxy resin, as a reinforcing material, can increase the strength and stability of the slurry, making it more durable. In addition, epoxy resin has strong adhesion, which can bond different types of materials together, thereby improving the overall performance of the slurry.

[0035] The polytetrafluoroethylene (PTFE)-coated silver powder and epoxy resin-coated silver-coated copper exist in a suspended form in the silver paste. Due to the chemical repulsion between epoxy resin and polytetrafluoroethylene, these particles can maintain a good dispersion state in suspension. The suspended particles in the silver paste are not prone to agglomeration and precipitation. This helps to maintain the uniformity and stability of the silver paste, thereby improving its performance during use.

[0036] The organic carrier plays the following main roles in the slurry: The organic carrier, as a carrier for the conductive phase and the bonding phase, can control the fluidity of the slurry, making it easy to coat and process. At the same time, by adjusting the content of the organic carrier, the viscosity of the slurry can be adjusted to meet the requirements of different coating processes. In addition, the organic carrier helps to improve the dispersion of the conductive material in the slurry and ensure the uniform distribution of the slurry components.

[0037] The silica sol plays the following main roles in the slurry: The silica sol has good chemical stability and thermal stability, which can protect the slurry from the influence of the external environment, thereby improving its stability. At the same time, the silica sol can reduce the humidity of the solar cell panel and ensure its stability during the production process. In addition, the surface of the silica sol is a microporous structure, which can adsorb static substances such as foreign matters accumulated on the surface of the battery and impurities in the air, thereby preventing the generation of static electricity.

[0038] The conductive photovoltaic paste provided by the embodiments of the present application, during the process of being coated on the poly region, the glass material can soften and flow at high temperature, penetrate into the tiny pores of the Poly region, and form a mechanical locking effect. At the same time, some components in the glass material may chemically react with the substances on the surface of the Poly region to form chemical bonding, further enhancing the adhesion. The polytetrafluoroethylene coating layer has an extremely low friction coefficient and excellent lubricity, which can reduce the resistance of the paste during the coating process and make it easier to spread on the surface of the Poly region. At the same time, its corrosion resistance can protect the silver conductive material from the erosion of the external environment and maintain the stability and conductivity of the paste. Epoxy resin can form a three-dimensional cross-linked structure during the curing process, tightly wrapping the silver alloy conductive material therein. This structure not only improves the overall strength of the paste but also makes the bonding between the paste and the surface of the Poly region more firm. At the same time, the adhesiveness of epoxy resin can also promote the close combination of the paste and the surface of the Poly region. Silica sol has excellent adsorption ability and chemical stability, and can form a microporous structure on the surface of the Poly region. These microporous structures can adsorb other components in the paste, such as glass materials and conductive materials, etc., to form a tight adhesion layer. At the same time, silica sol can also chemically react with some components in the glass material to form chemical bonding, further enhancing the bonding strength between the paste and the surface of the Poly region.

[0039] In some embodiments, the polytetrafluoroethylene-coated silver powder comprises:

[0040] Silver powder;

[0041] A polytetrafluoroethylene coating layer, the polytetrafluoroethylene coating layer covers the surface of the silver powder, and the thickness of the polytetrafluoroethylene coating layer is 0.5 nm to 3 nm.

[0042] Polytetrafluoroethylene is a material with excellent corrosion resistance, high temperature resistance, and extremely low friction coefficient. This coating layer tightly covers the surface of the silver powder, playing a role of protection and enhancement. Its thickness is 0.5 nm to 3 nm, which not only ensures sufficient coating effect but also avoids the influence of too thick a coating layer on the conductivity.

[0043] In some embodiments, the epoxy resin-coated silver-coated copper comprises:

[0044] Silver-coated copper;

[0045] An epoxy resin coating layer, the epoxy resin coating layer covers the surface of the silver-coated copper, and the thickness of the epoxy resin coating layer is 0.5 to 2 nm.

[0046] Silver-coated copper is the core conductive material, composed of silver and copper. Silver, as the best conductive filler for high-performance conductive materials, has good electrical conductivity and ductility. The addition of copper, on the other hand, improves the hardness, melting point, and wear resistance of the material. Epoxy resin is a polymer film-forming substance with excellent adhesion, insulation, and chemical stability. Here, the epoxy resin acts as a coating layer, tightly coating the surface of the silver-coated copper to form a thin protective film. The thickness of the coating layer is 0.5 - 2 nm, which can provide sufficient protection without overly affecting the electrical conductivity of the material.

[0047] In some embodiments, in terms of mole percentage, the glass material consists of the following components: Bi2O3: 20 - 30 mol.%, B2O3: 40 - 50 mol.%, ZnO: 2 - 6 mol.%, SiO2: 2 - 6 mol.%, Al2O3: 1 - 5 mol.%, NaBr: 1 - 5 mol.%, SnO2: 1 - 5 mol.%, CdO: 1 - 5 mol.%, Ce2O3: 1 - 5 mol.%, Y2O3: 1 - 5 mol.%.

[0048] Bi2O3: Its main function is to lower the melting temperature of the glass and form structural units such as [BiO3] and [BiO6]. The changes in these unit structures will affect the network structure of the glass and thus its properties. At the same time, an appropriate amount of Bi2O3 helps to form a stable glass structure and provides a good carrier for the silver paste, but an excessive amount can lead to a loose glass structure and affect the electrical conductivity.

[0049] B2O3: It is one of the main glass-forming oxides, forming [BO3] and [BO4] structural units. It can improve the transparency and gloss of the glass, which is beneficial to the electrical conductivity of the silver paste. At the same time, it interacts with Bi2O3 to jointly affect the network structure and properties of the glass.

[0050] ZnO: It has a relatively small impact on the glass structure but can enhance the transparency and chemical stability of the glass. In the silver paste, ZnO can act as a flux, helping the sintering of silver particles and the formation of a conductive network.

[0051] SiO2: It is an important component for glass formation, which can increase the hardness and chemical stability of the glass. In the silver paste, an appropriate amount of SiO2 helps to form a dense conductive network and improve the electrical conductivity.

[0052] Al2O3: It can improve the chemical stability and mechanical strength of the glass. In the silver paste, Al2O3 can act as a strengthening agent, helping to form a stable conductive network.

[0053] NaBr: As a halide additive, it can lower the melting point of the glass while increasing the transparency and gloss of the glass. In the silver paste, NaBr can contribute to the sintering of silver particles and the optimization of the conductive network.

[0054] SnO2: It is a conductive oxide that can form a good interfacial bond with silver particles, improving the conductivity of the silver paste. In the glass, SnO2 can also increase the refractive index and gloss of the glass.

[0055] CdO: It is a conductive oxide that can increase the refractive index and fusibility of the glass. In the silver paste, CdO can play a similar role in enhancing conductivity.

[0056] Ce2O3, Y2O3: These oxides act as network modifiers in the glass, which can change the network structure and properties of the glass. They can also act as stabilizers to improve the chemical and thermal stability of the glass. Meanwhile, in the silver paste, these oxides can indirectly affect the conductivity of the silver paste by influencing the structure and properties of the glass.

[0057] In some embodiments, the organic carrier is composed of epoxy resin, organic solvent and organic additives, and the mass ratio of the epoxy resin, the organic solvent and the organic additives is (25 - 35):(60 - 70):(3 - 8).

[0058] The epoxy resin and organic additives in the organic carrier, through their adhesiveness and dispersibility, help to stably suspend the components in the slurry in the system. The organic solvent, by adjusting the viscosity of the slurry, enables the components to be more evenly distributed in the slurry.

[0059] There is good chemical compatibility between the epoxy resin and the epoxy resin-coated silver-coated copper. The interaction between them will not cause changes in chemical properties or adverse reactions. At the same time, the molecular chains of the epoxy resin can physically entangle with the epoxy resin coating on the surface of the epoxy resin-coated silver-coated copper, forming a tight bond. This physical entanglement helps to stably disperse the silver alloy conductive material in the slurry, preventing its agglomeration and sedimentation. In addition, as part of the organic carrier, the epoxy resin can fill the voids between the silver alloy conductive material particles, forming a continuous film. This film not only enhances the overall stability of the slurry but also reduces the friction and collision between particles, thus avoiding sedimentation.

[0060] Figure 1 It is a schematic flow chart of a preparation method of a conductive photovoltaic paste for the poly region provided by the embodiments of the present application.

[0061] As Figure 1As shown, the present application provides a preparation method of a conductive photovoltaic paste for the poly region according to any one of the embodiments in the first aspect, and the method includes:

[0062] S1. Mix silver powder, silver-coated copper, glass material, organic carrier and silica sol to obtain a first blend;

[0063] S2. Add polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the first blend to obtain a second blend;

[0064] S3. Hydrothermally treat the second blend to obtain the conductive photovoltaic paste for the poly region.

[0065] In some embodiments, the temperature of the hydrothermal treatment is 80 - 120 °C, and the time of the hydrothermal treatment is 30 min - 90 min.

[0066] During the hydrothermal treatment, components such as the glass material, organic carrier, silica sol, polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper in the paste will fuse with each other under high temperature and high pressure conditions to form a more compact and uniform structure. This fusion helps to improve the overall performance and stability of the paste.

[0067] Meanwhile, the hydrothermal treatment can enhance the dispersibility of each component in the paste, making them more evenly distributed in the paste. This helps to reduce the occurrence of agglomeration and precipitation phenomena, and improve the uniformity and consistency of the paste. Through the hydrothermal treatment, stronger chemical bonds and physical entanglements will be formed between the components in the paste, thus improving the stability of the paste. This stability helps the paste to maintain its excellent performance during subsequent processing and application. The hydrothermal treatment can also optimize the performance of the paste. For example, it can improve the conductivity, adhesion and chemical stability of the paste, etc. The optimization of these performances helps the paste to play a better role in specific application fields such as the poly region.

[0068] In addition, during the preparation process of the paste, certain stress and defects may be generated between the components. Through the hydrothermal treatment, these stress and defects can be eliminated, making the structure of the paste more complete and stable. The hydrothermal treatment can provide a high temperature and high pressure environment to accelerate the chemical reactions between the components in the paste. This helps to shorten the preparation time and improve the production efficiency.

[0069] In some embodiments, the preparation method of the polytetrafluoroethylene-coated silver powder includes:

[0070] S11. Plasma-treat the silver powder to obtain pretreated silver powder;

[0071] In some embodiments, the plasma treatment includes the following parameters: the power is 50-100 W, the treatment time is 10-20 min, and the oxygen flow rate is 30-80 mL / min.

[0072] Through plasma treatment, the chemical properties of the silver powder surface can be changed, increasing its active sites and providing favorable conditions for subsequent bonding with the silane coupling agent.

[0073] S12. Mix the pretreated silver powder with the pre-hydrolyzed solution of the silane coupling agent to bond the silane coupling agent to the surface of the pretreated silver powder, obtaining an intermediate.

[0074] The silane coupling agent needs to be pre-hydrolyzed before adding the silver powder. The purpose of this step is to make the hydrolysis groups (such as alkoxy groups) in the silane coupling agent molecules undergo hydrolysis reactions to generate silanol groups, providing active sites for subsequent bonding with the silver powder surface.

[0075] The surface of the silver powder treated by plasma has abundant active sites and can form chemical bonds with the silanol groups in the silane coupling agent. This bonding not only enhances the binding force between the silver powder and the silane coupling agent but also provides a firm substrate for subsequent coating with PTFE.

[0076] S13. Mix the intermediate with polytetrafluoroethylene to obtain the polytetrafluoroethylene-coated silver powder.

[0077] During the mixing process, PTFE molecules will penetrate into the voids and defects on the silver powder surface and interact with the silane coupling agent to form strong chemical bonds. In this way, a uniform PTFE coating layer is formed.

[0078] In some embodiments, the preparation method of the epoxy resin-coated silver-coated copper includes:

[0079] S21. Add epoxy resin to deionized water and heat until the epoxy resin is completely dissolved to obtain a mixed solution.

[0080] S22. Add silver-coated copper to the mixed solution and then perform ultrasonic-microwave combined treatment to obtain the epoxy resin-coated silver-coated copper. The parameters of the ultrasonic-microwave combined treatment include: the microwave power is 50-100 W, the ultrasonic power is 100-200 W, and the treatment time is 30-60 s.

[0081] The cavitation effect of ultrasonic waves can generate instant high temperature, high pressure, and high-speed jets, transferring energy to molecules, activating epoxy resin molecules, and uniformly dispersing them in the mixed solution.

[0082] The heating effect of microwaves can cause the molecules in the mixture to polarize, orient, friction, and collide, thereby generating a thermal effect. This thermal effect helps the epoxy resin molecules to better penetrate into the voids and defects on the surface of silver-coated copper, forming strong chemical bonds.

[0083] Through the combined treatment of ultrasonic and microwave, the epoxy resin can be more evenly coated on the surface of silver-coated copper, forming a dense coating layer.

[0084] In summary, the conductive photovoltaic paste for the poly region provided by this application and its preparation method have the following advantages:

[0085] (1) Excellent electrical conductivity: The combination of polytetrafluoroethylene (PTFE)-coated silver powder and epoxy resin-coated silver-coated copper ensures that the paste has excellent electrical conductivity. At the same time, silver and silver alloys as the core conductive materials provide good electrical conductivity, while the coating layers of PTFE and epoxy resin enhance the stability and durability of the material.

[0086] (2) Good adhesion and stability: The addition of glass materials effectively improves the connection between silver particles, reduces the contact resistance, and enhances the adhesion between the paste and the silicon wafer. Epoxy resin as a reinforcing material further improves the strength and stability of the paste. The addition of silica sol enhances the chemical stability and thermal stability of the paste, preventing the generation of static electricity.

[0087] (3) High efficiency in dispersion and uniformity: During the preparation process, through steps such as hydrothermal treatment, the components in the paste are more closely and evenly integrated, reducing the phenomena of agglomeration and precipitation. The chemical repulsion between polytetrafluoroethylene and epoxy resin maintains a good dispersion state of the particles in suspension.

[0088] (4) Optimized processing performance: The organic carrier, as the carrier of the conductive phase and the bonding phase, can control the fluidity of the paste, making it easy to coat and process. By adjusting the content and composition of the organic carrier, the requirements of different coating processes can be met.

[0089] (5) Innovative preparation process: The preparation methods of polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper are unique. Through steps such as plasma treatment, silane coupling agent bonding, and combined ultrasonic-microwave treatment, the uniform coating and tight combination of the materials are achieved. At the same time, the hydrothermal treatment process further enhances the overall performance and stability of the paste, optimizing its key properties such as electrical conductivity, adhesion, and chemical stability.

[0090] (6) Wide application prospects: This conductive photovoltaic paste is particularly suitable for specific application fields such as the poly region, and can meet the requirements of the photovoltaic industry for high performance, high stability, and high durability. At the same time, its excellent performance and innovative preparation process provide new possibilities and directions for the development of photovoltaic cells.

[0091] The following further elaborates on this application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0092] Example 1

[0093] This example provides a conductive photovoltaic paste for the poly region. Calculated by mass fraction, the conductive photovoltaic paste is composed of the following chemical components: 55 parts of silver powder, 20 parts of silver-coated copper, 3 parts of glass material, 12 parts of organic carrier, 3 parts of silica sol, 4 parts of polytetrafluoroethylene-coated silver powder, and 3 parts of epoxy resin-coated silver-coated copper. Among them,

[0094] The polytetrafluoroethylene-coated silver powder includes:

[0095] Silver powder (model: ECKART silver powder STANDARTAT46149);

[0096] A polytetrafluoroethylene coating layer, the polytetrafluoroethylene coating layer covers the surface of the silver powder, and the thickness of the polytetrafluoroethylene (model: F4BM217) coating layer is 2 nm.

[0097] The epoxy resin-coated silver-coated copper includes:

[0098] Silver-coated copper (model: AgCu50);

[0099] An epoxy resin coating layer, the epoxy resin coating layer covers the surface of the silver powder, and the thickness of the epoxy resin (bisphenol A epoxy resin) coating layer is 1 nm.

[0100] Calculated by mole percentage, the glass material is composed of the following components: Bi2O3: 25 mol.%, B2O3: 45 mol.%, ZnO: 5 mol.%, SiO2: 3 mol.%, Al2O3: 2 mol.%, NaBr: 2 mol.%, SnO2: 3 mol.%, CdO: 2 mol.%, Ce2O3: 3 mol.%, Y2O3: 5 mol.%.

[0101] The organic carrier is composed of epoxy resin, organic solvent and organic additives. The mass ratio of the epoxy resin (bisphenol A epoxy resin), the organic solvent and the organic additives is 30:65:5. The organic solvent is diethylene glycol butyl ether acetate, the organic additive is a dispersant, and the dispersant is polyvinylpyrrolidone (model PVPK17).

[0102] Based on the above conductive photovoltaic paste for the poly region, the present application also provides a preparation method for the conductive photovoltaic paste for the poly region, and the method includes:

[0103] S11. Mix silver powder, silver-coated copper, glass material, organic carrier and silica sol to obtain a first blend;

[0104] S21. Add silver powder coated with polytetrafluoroethylene and silver-coated copper coated with epoxy resin to the first blend to obtain a second blend;

[0105] S31. Hydrothermally treat the second blend to obtain the conductive photovoltaic paste for the poly region.

[0106] Among them, the temperature of the hydrothermal treatment is 100 °C, and the time of the hydrothermal treatment is 60 min.

[0107] The preparation method of the silver powder coated with polytetrafluoroethylene includes:

[0108] S111. Plasma-treat silver powder to obtain pretreated silver powder; the plasma treatment includes the following parameters: power is 80 W, treatment time is 15 min, and oxygen flow rate is 50 mL / min.

[0109] S112. Mix the pretreated silver powder with a pre-hydrolyzed solution of silane coupling agent to bond the silane coupling agent on the surface of the pretreated silver powder to obtain an intermediate;

[0110] S113. Mix the intermediate with polytetrafluoroethylene to obtain the silver powder coated with polytetrafluoroethylene.

[0111] The preparation method of the silver-coated copper coated with epoxy resin includes:

[0112] S211. Add epoxy resin to deionized water and heat until the epoxy resin is completely dissolved to obtain a mixed solution;

[0113] S212. Add silver-coated copper to the mixed solution, and then perform ultrasonic-microwave combined treatment to obtain the silver-coated copper coated with epoxy resin; the parameters of the ultrasonic-microwave combined treatment include: microwave power is 70 W, ultrasonic power is 150 W, and treatment time is 45 s.

[0114] Example 2

[0115] This example provides a conductive photovoltaic paste for the poly region. By mass, the conductive photovoltaic paste is composed of the following components: 70 parts of silver powder, 5 parts of silver-coated copper, 5.5 parts of glass material, 14.5 parts of organic carrier, 3 parts of silica sol, 1 part of polytetrafluoroethylene-coated silver powder, and 1 part of epoxy resin-coated silver-coated copper. Among them,

[0116] The polytetrafluoroethylene-coated silver powder includes:

[0117] Silver powder (model: ECKART silver powder STANDARTAT46149);

[0118] A polytetrafluoroethylene coating layer, which is coated on the surface of the silver powder, and the thickness of the polytetrafluoroethylene (model: F4BM217) coating layer is 3 nm.

[0119] The epoxy resin-coated silver-coated copper includes:

[0120] Silver-coated copper (model: AgCu50);

[0121] An epoxy resin coating layer, which is coated on the surface of the silver powder, and the thickness of the epoxy resin (bisphenol A epoxy resin) coating layer is 0.5 nm.

[0122] By mole percentage, the glass material is composed of the following components: Bi2O3: 30 mol.%, B2O3: 40 mol.%, ZnO: 6 mol.%, SiO2: 4 mol.%, Al2O3: 6 mol.%, NaBr: 2 mol.%, SnO2: 2 mol.%, CdO: 5 mol.%, Ce2O3: 3 mol.%, Y2O3: 2 mol.%.

[0123] The organic carrier is composed of epoxy resin, organic solvent and organic auxiliary. The mass ratio of the epoxy resin (bisphenol A epoxy resin), the organic solvent and the organic auxiliary is 25:70:8. The organic solvent is diethylene glycol butyl ether acetate, and the organic auxiliary is a dispersant, and the dispersant is polyvinylpyrrolidone (model: PVPK17).

[0124] Based on the above conductive photovoltaic paste for the poly region, this application also provides a preparation method of the conductive photovoltaic paste for the poly region. The method includes:

[0125] S11. Mix the silver powder, silver-coated copper, glass material, organic carrier and silica sol to obtain a first blend;

[0126] S21. Add polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the first blend to obtain a second blend;

[0127] S31. Hydrothermally treat the second blend to obtain the conductive photovoltaic paste for the poly region.

[0128] Among them, the temperature of the hydrothermal treatment is 120 °C, and the time of the hydrothermal treatment is 30 min.

[0129] The preparation method of the polytetrafluoroethylene-coated silver powder includes:

[0130] S111. Plasma-treat the silver powder to obtain pretreated silver powder; the parameters of the plasma treatment are as follows: power is 100 W, treatment time is 10 min, and oxygen flow rate is 80 mL / min.

[0131] S112. Mix the pretreated silver powder with the pre-hydrolyzed solution of the silane coupling agent to bond the silane coupling agent on the surface of the pretreated silver powder to obtain an intermediate;

[0132] S113. Mix the intermediate with polytetrafluoroethylene to obtain the polytetrafluoroethylene-coated silver powder.

[0133] The preparation method of the epoxy resin-coated silver-coated copper includes:

[0134] S211. Add epoxy resin to deionized water and heat until the epoxy resin is completely dissolved to obtain a mixed solution;

[0135] S212. Add silver-coated copper to the mixed solution, and then perform ultrasonic-microwave combined treatment to obtain the epoxy resin-coated silver-coated copper; the parameters of the ultrasonic-microwave combined treatment are as follows: microwave power is 100 W, ultrasonic power is 200 W, and treatment time is 30 s.

[0136] Example 3

[0137] This example provides a conductive photovoltaic paste for the poly region. By mass, the conductive photovoltaic paste is composed of the following components: 50 parts of silver powder, 25 parts of silver-coated copper, 2 parts of glass material, 15 parts of organic carrier, 3 parts of silica sol, 2 parts of polytetrafluoroethylene-coated silver powder, and 3 parts of epoxy resin-coated silver-coated copper. Among them,

[0138] The polytetrafluoroethylene-coated silver powder includes:

[0139] Silver powder (model: ECKART silver powder STANDARTAT46149);

[0140] A polytetrafluoroethylene coating layer, the polytetrafluoroethylene coating layer is coated on the surface of the silver powder, and the thickness of the polytetrafluoroethylene (model F4BM217) coating layer is 0.5 nm.

[0141] The epoxy resin-coated silver-coated copper includes:

[0142] Silver-coated copper (model AgCu50);

[0143] An epoxy resin coating layer, the epoxy resin coating layer is coated on the surface of the silver powder, and the thickness of the epoxy resin (bisphenol A epoxy resin) coating layer is 2 nm.

[0144] In terms of molar percentage, the glass material is composed of the following components: Bi2O3: 20 mol.%, B2O3: 50 mol.%, ZnO: 6 mol.%, SiO2: 4 mol.%, Al2O3: 5 mol.%, NaBr: 5 mol.%, SnO2: 3 mol.%, CdO: 2 mol.%, Ce2O3: 3 mol.%, Y2O3: 2 mol.%.

[0145] The organic carrier is composed of epoxy resin, organic solvent and organic auxiliary. The mass ratio of the epoxy resin (bisphenol A epoxy resin), the organic solvent and the organic auxiliary is 35:70:3. The organic solvent is diethylene glycol butyl ether acetate, and the organic auxiliary is a dispersant. The dispersant is polyvinylpyrrolidone (model PVPK17).

[0146] Based on the above conductive photovoltaic paste for the poly region, the present application also provides a preparation method for the conductive photovoltaic paste for the poly region. The method includes:

[0147] S11. Mix silver powder, silver-coated copper, glass material, organic carrier and silica sol to obtain a first blend;

[0148] S21. Add polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the first blend to obtain a second blend;

[0149] S31. Hydrothermally treat the second blend to obtain the conductive photovoltaic paste for the poly region.

[0150] Among them, the temperature of the hydrothermal treatment is 80 °C, and the time of the hydrothermal treatment is 90 min.

[0151] The preparation method of the polytetrafluoroethylene-coated silver powder includes:

[0152] S111. Perform plasma treatment on silver powder to obtain pretreated silver powder. The plasma treatment includes the following parameters: power is 50 W, treatment time is 20 min, and oxygen flow rate is 30 mL / min.

[0153] S112. Mix the pretreated silver powder with a pre-hydrolyzed solution of silane coupling agent to bond the silane coupling agent on the surface of the pretreated silver powder, obtaining an intermediate.

[0154] S113. Mix the intermediate with polytetrafluoroethylene to obtain the polytetrafluoroethylene-coated silver powder.

[0155] The preparation method of the epoxy resin-coated silver-coated copper includes:

[0156] S211. Add epoxy resin to deionized water and heat until the epoxy resin is completely dissolved to obtain a mixed solution.

[0157] S212. Add silver-coated copper to the mixed solution and then perform combined ultrasonic-microwave treatment to obtain the epoxy resin-coated silver-coated copper. The parameters of the combined ultrasonic-microwave treatment include: microwave power is 50 W, ultrasonic power is 100 W, and treatment time is 60 s.

[0158] Comparative Example 1

[0159] This comparative example is modified as follows based on Example 1:

[0160] Do not add silica sol to the conductive photovoltaic paste.

[0161] Comparative Example 2

[0162] This comparative example is modified as follows based on Example 1:

[0163] Replace the polytetrafluoroethylene-coated silver powder in the conductive photovoltaic paste with silver powder, and replace the epoxy resin-coated silver-coated copper with silver-coated copper.

[0164] Comparative Example 3

[0165] This comparative example is modified as follows based on Example 1:

[0166] Replace the polytetrafluoroethylene-coated silver powder in the conductive photovoltaic paste with silver powder.

[0167] Comparative Example 4

[0168] This comparative example is modified as follows based on Example 1:

[0169] Replace the epoxy resin-coated silver-coated copper in the conductive photovoltaic paste with silver-coated copper.

[0170] Comparative Example 5

[0171] This comparative example is modified as follows based on Example 1:

[0172] In step S31, hydrothermal treatment is not performed.

[0173] Comparative Example 6

[0174] This comparative example is modified as follows based on Example 1:

[0175] In step S111, plasma treatment is not performed.

[0176] The present invention tests the performance of the conductive photovoltaic pastes prepared in Examples 1 to 3 and Comparative Examples 1 to 6. The specific test method is as follows, and the test results are shown in Table 1.

[0177] Viscosity: Using the DV2T mode of a Mars40 dynamic shear rheometer, with the temperature controlled at 25°C, the viscosity of the paste is tested;

[0178] Resistivity after curing: Printing a fixed pattern on the test piece, measuring the resistance value after curing (0.6×60 mm), and calculating the resistivity according to the formula R = ρ·L / S;

[0179] Welding tensile strength: Using a 0.35 mm tinned solder tape to weld the front and back electrodes of the battery at 360°C, and performing a tensile test with a tensile testing machine.

[0180] Table 1 Performance of the conductive photovoltaic paste

[0181]

[0182] As can be seen from Table 1, the viscosity of the main grid electrode silver paste in Examples 1 to 3 is 175 to 185 Pa·s, the conductivity is 7.5 to 8.5×10 -6 Ω·cm, and the welding tensile strength is 2.5 to 3.0 N / mm.

[0183] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0184] In addition, in the description of the specification of this application, terms such as "including" and "comprising" mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, both A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural.

[0185] The above are only specific implementation manners of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A conductive photovoltaic paste for the poly region, characterized in that, The conductive photovoltaic paste includes the following chemical components by mass parts: 40 - 70 parts of silver powder, 5 - 25 parts of silver-coated copper, 1.5 - 5.5 parts of glass material, 10 - 15 parts of organic carrier, 1 - 3 parts of silica sol, 1 - 5 parts of polytetrafluoroethylene-coated silver powder, and 1 - 3 parts of epoxy resin-coated silver-coated copper.

2. The conductive photovoltaic paste for the poly region according to claim 1, wherein The thickness of the polytetrafluoroethylene coating layer in the polytetrafluoroethylene-coated silver powder is 0.5 nm - 3 nm.

3. The conductive photovoltaic paste for the poly region according to claim 1, characterized in that The thickness of the epoxy resin coating layer in the epoxy resin-coated silver-coated copper is 0.5 - 2 nm.

4. The conductive photovoltaic paste for the poly region according to claim 1, wherein By mole percentage, the glass material consists of the following components: Bi2O3: 20 - 30 mol.%, B2O3: 40 - 50 mol.%, ZnO: 2 - 6 mol.%, SiO2: 2 - 6 mol.%, Al2O3: 1 - 5 mol.%, NaBr: 1 - 5 mol.%, SnO2: 1 - 5 mol.%, CdO: 1 - 5 mol.%, Ce2O3: 1 - 5 mol.%, Y2O3: 1 - 5 mol.%.

5. The conductive photovoltaic paste for the poly region according to claim 1, wherein The organic carrier consists of epoxy resin, organic solvent and organic auxiliary agent, and the mass ratio of the epoxy resin, the organic solvent and the organic auxiliary agent is (25 - 35):(60 - 70):(3 - 8).

6. The preparation method of the conductive photovoltaic paste for the poly region according to any one of claims 1 to 5, characterized in that, The method includes: Mixing silver powder, silver-coated copper glass material, organic carrier and silica sol to obtain a first blend; Adding polytetrafluoroethylene-coated silver powder and epoxy resin-coated silver-coated copper to the first blend to obtain a second blend; Performing hydrothermal treatment on the second blend to obtain the conductive photovoltaic paste for the poly region.

7. The preparation method of the conductive photovoltaic paste for the poly region according to claim 6, characterized in that The temperature of the hydrothermal treatment is 80 - 120 °C, and the time of the hydrothermal treatment is 30 min - 90 min.

8. The preparation method of the conductive photovoltaic paste for the poly region according to claim 6, wherein, The preparation method of the polytetrafluoroethylene-coated silver powder includes: Performing plasma treatment on silver powder to obtain pretreated silver powder; Mixing the pretreated silver powder with a pre-hydrolyzed solution of silane coupling agent to bond the silane coupling agent on the surface of the pretreated silver powder to obtain an intermediate; Mixing the intermediate with polytetrafluoroethylene to obtain the polytetrafluoroethylene-coated silver powder.

9. The preparation method of the conductive photovoltaic paste for the poly region according to claim 8, characterized in that, The plasma treatment includes the following parameters: power is 50 - 100 W, treatment time is 10 - 20 min, and oxygen flow rate is 30 - 80 mL / min.

10. The preparation method of the conductive photovoltaic paste for the poly region according to claim 6, wherein, The preparation method of the epoxy resin-coated silver-coated copper includes: Adding epoxy resin to deionized water and heating until the epoxy resin is completely dissolved to obtain a mixed solution; Adding silver-coated copper to the mixed solution, and then performing ultrasonic-microwave combined treatment to obtain the epoxy resin-coated silver-coated copper; the parameters of the ultrasonic-microwave combined treatment include: microwave power is 50 - 100 W, ultrasonic power is 100 - 200 W, and treatment time is 30 - 60 s.

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