A glass frit composition for improving the oxidation resistance of base metal paste and a base metal conductive paste

Abstract

The application discloses a glass powder composition for improving the oxidation resistance of base metal paste and a base metal conductive paste, and belongs to the technical field of photovoltaic cells. The glass powder composition comprises TeO2, PbO, Bi2O3, Li2O, WO3, ZnO, SiO2 and Na2O, and the surface of the glass powder composition is coated with lanthanum powder. The design of the glass powder composition and the content avoids the excessive consumption of active components of the glass in the sintering process, influences the electrical properties, guarantees the wettability of the glass powder to the silicon wafer, forms a good ohmic contact, and the lanthanum powder coated on the surface of the glass powder can reduce the base metal oxide to the base metal, reduces the oxidation of the base metal powder at the interface, thereby guaranteeing excellent linear resistance; in the sintering stage, part of the lanthanum element can enter the glass system, stabilizes the glass structure, thereby reducing the consumption of active components of the glass powder composition by the base metal, preserving the good activity of the glass powder, and improving the contact performance of the electrode.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a glass powder composition for improving the oxidation resistance of base metal pastes, a base metal conductive paste, its preparation method, and its application. Background Technology

[0002] Photovoltaic cells can convert light energy into electrical energy with high photoelectric conversion efficiency, and the conversion process produces no polluting byproducts, making it a core clean energy technology. In the fabrication of photovoltaic cells, conductive paste plays a crucial role, and glass powder composition, as a key component of the conductive paste, directly affects the quality of the conductive paste and the performance of the photovoltaic cell.

[0003] Traditional photovoltaic (PV) cells use silver paste as the conductive paste. Silver is a precious metal with highly volatile prices, and with the PV industry currently in a growth phase, the demand for silver is increasing year by year, leading to a corresponding rise in the cost of silver materials. Statistics show that silver paste now accounts for over 10% of the non-silicon cost of solar cells, becoming a major obstacle to cost reduction in PV cells. Replacing silver with base metals is a common approach to cost reduction; however, base metals have inherently high resistivity, which can affect the electrical performance of the cells. Furthermore, base metal conductive pastes face significant challenges during high-temperature sintering: firstly, base metals (such as copper and nickel) readily undergo redox reactions with active oxides (such as lead oxide and tellurium oxide) in the glass powder during the sintering heating stage. This not only leads to the formation of a high-resistivity oxide layer on the base metal surface, significantly increasing the line resistance of the electrode, but also consumes a large amount of the active components in the glass powder used for etching the silicon substrate and forming ohmic contacts, causing the glass structure to collapse and the adhesion between the electrode and the silicon wafer to drop sharply. Secondly, to ensure sufficient etching capability of the glass powder on the silicon wafer, existing technologies typically require maintaining a high glass transition temperature or adding specific sacrificial agents. However, these measures are often passive defenses: that is, only delaying the reaction before the glass powder melts, or introducing a conductive auxiliary phase into the glass system to compensate for the loss of conductivity. The above methods fail to fundamentally solve the problem of electron transfer in the initial stage of contact between glass powder and base metal powder at the microscopic interface. The loss of glass active components is still significant, resulting in high electrode contact resistance and large fluctuations in electrical performance during mass production.

[0004] Therefore, developing a glass powder material that can actively suppress interfacial redox reactions in the early stages of sintering while dynamically compensating for damage to the glass network structure has become crucial for improving the reliability and photoelectric conversion efficiency of base metal conductive pastes. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a glass powder composition and a base metal conductive paste that improve the oxidation resistance of base metal pastes. By selecting a glass powder mixture with a specific oxide combination and coating its surface with a layer of lanthanum powder, the sintering performance of the glass powder composition is improved, the consumption of active components of the glass powder composition by base metals is reduced, the good activity of the glass powder is preserved, and the contact performance of the conductive paste is improved, thereby improving the photoelectric conversion efficiency of photovoltaic cells.

[0006] To achieve the above objectives, the present invention first provides a glass powder composition comprising the following components in percentage content: 10-80wt% TeO2, 10-70wt% PbO, 0-20wt% Bi2O3, 0-20wt% Li2O, 0-20wt% WO3, 0-20wt% ZnO, 0-30wt% SiO2, and 0-10wt% Na2O, wherein the surface of the glass powder composition is coated with a layer of lanthanum powder.

[0007] In some embodiments of the present invention, the glass powder composition comprises the following components in percentage content: 35-70wt% TeO2, 20-40wt% PbO, 3-20wt% Bi2O3, 1-18wt% Li2O, 1-18wt% WO3, 1-18wt% ZnO, 2-28wt% SiO2, and 0-8wt% Na2O, wherein the surface of the glass powder composition is coated with a layer of lanthanum powder.

[0008] In some embodiments of the present invention, the coating amount of the lanthanum powder accounts for 1-15 wt% of the mass of the glass powder, preferably 1-10 wt%, more preferably 1-5 wt%, and the particle size D50 of the lanthanum powder is 0.2-2 μm.

[0009] In some embodiments of the present invention, the particle size D50 of the glass powder composition is in the range of 1.2-1.8 μm, and the maximum particle size Dmax is ≤8 μm.

[0010] In some embodiments of the present invention, the glass transition temperature Tg of the glass powder composition is 250-380°C, and the initial crystallization temperature Tc is 270-400°C.

[0011] The present invention also provides a method for preparing the above-mentioned glass powder composition, comprising the following steps: S1: After thoroughly mixing the analytical grade raw materials and reagents of each component in the glass powder composition according to the proportion, place them in a crucible, heat them to 1000-1300℃ with a silicon molybdenum rod, keep them at that temperature for 20-50 minutes, and then cold roll or water quench them to obtain glass sheets. S2: Place the glass sheet obtained in step S1 and 20mm diameter zirconium beads in a nylon ball milling jar at a mass ratio of 1:6, and ball mill them at 450r / min for 40-90min using a planetary ball mill. Then pass the mixture through a 100-mesh sieve to obtain coarse glass powder. S3: Add the coarse glass powder obtained in step S2, 2mm diameter zirconium beads, and alcohol to a nylon ball mill jar in a mass ratio of 1:6:3. Use a planetary ball mill at 350r / min for 30-120min. Measure the particle size every 30min. When the glass powder particle size D50 is found to be in the range of 1.2-1.8μm, transfer the glass powder to a vacuum drying oven, dry it, and pass it through a 200-mesh sieve to obtain a glass powder mixture. S4: Mix commercially available lanthanum powder (D50 range 0.2-2μm) and the glass powder mixture prepared by the above process at a weight ratio of (0.2-3):20, and simultaneously add an organic mixture of dispersant and alcohol (ratio 0.02-5:100). Add the above mixture of glass powder and lanthanum powder, 2mm diameter zirconium beads and organic mixture at a mass ratio of 1:6:3 into a nylon ball mill jar, and ball mill using a planetary ball mill at a speed of 350r / min for 30-60min. Transfer the glass powder mixture to a vacuum drying oven, dry it, and pass it through a 200-mesh sieve to obtain the glass powder composition.

[0012] The present invention also provides a base metal conductive paste, the base metal conductive paste comprising the following components by weight percentage: 88-92 wt% conductive metal, 2-6 wt% glass powder composition and 6-10 wt% organic carrier, wherein the glass powder composition is the glass powder composition as described in any of the preceding claims or the glass powder composition prepared by the aforementioned preparation method.

[0013] In some embodiments of the present invention, the conductive metal is base metal powder or a mixture of base metal powder and silver powder, wherein the base metal powder includes one or more of nickel powder, copper powder, aluminum powder, tin powder and zinc powder, and the combination includes physical mixing and / or alloying.

[0014] In some embodiments of the present invention, the base metal powder is added in a mixture of base metal powder and silver powder at a ratio of 1 to 70%, preferably 5 to 50%.

[0015] In some embodiments of the present invention, the organic carrier comprises: Organic solvents include one or more of acetone, terpineol, hexylcarbitol, butylcarbitol acetate, dimethyl adipate diol ether, and butylcarbitol; Binders include one or more of the following: ethyl cellulose, phenolic resin, polyvinyl butyral, polyethylene resin, polyacrylic acid, polyurethane resin, and rosin derivatives; Thixotropic agents: including one or more of castor oil derivatives, polyamides, polyamide derivatives, and fatty acid derivatives; and Surfactants include one or more of the following: polyethylene oxide, dodecylaminopropionic acid, benzotriazole, polyethylene glycol, silicone oil, lauric acid, oleic acid, capric acid, myristic acid, stearate, and palmitic acid.

[0016] In some embodiments of the present invention, the thixotropic index of the conductive paste is TI=η5R / η50R, where 4.4≤TI≤6.5.

[0017] The present invention also provides a method for preparing the above-mentioned base metal conductive paste, wherein the conductive metal, the glass powder composition and the organic carrier are weighed, stirred and centrifuged, and then repeatedly rolled and ground by a ceramic three-roll mill to obtain the base metal conductive paste after being mixed evenly.

[0018] The present invention also provides an application of the base metal conductive paste as described in any of the foregoing claims or the base metal conductive paste prepared by the foregoing preparation method, wherein the base metal conductive paste is applied to a solar cell, the solar cell including PERC cell, TOPCon cell and BC cell.

[0019] Beneficial effects: 1) This invention, through the design of reasonable glass powder composition and content, makes the transition temperature (Tg) of the glass powder composition relatively higher. The glass powder composition can maintain a longer glassy state in the initial heating stage of the sintering process, inhibiting atomic diffusion, thus delaying the start time of the reaction between the base metal material and the glass material, reducing the initial rate of the reaction between the base metal material and the glass material, thereby avoiding the premature consumption of glass active components, ensuring the etching effect of glass powder on silicon wafers, and forming good ohmic contact. This invention sets the Bi2O3 content to less than 20%, which increases the content of active ingredients in the glass powder composition. This avoids excessive consumption of glass active ingredients during sintering, which would affect electrical performance and ensure the wettability of the glass powder to the silicon wafer, forming good ohmic contact. In addition, coating the glass powder surface with a layer of lanthanum powder has two advantages. First, lanthanum has a relatively low reduction potential, which can reduce base metal oxides to base metals, reducing the oxidation of base metal powder at the interface and thus ensuring excellent line resistance. Second, during the sintering stage, some lanthanum can enter the glass system, stabilizing the glass structure and reducing the consumption of base metals on the active ingredients of the glass powder composition, preserving the good activity of the glass powder and improving the contact performance of the electrode.

[0020] 2) The glass powder composition prepared by the method of the present invention is compatible with the base metal conductive system. Lanthanum can inhibit the oxidation of base metals and stabilize the glass structure. The glass powder has good etching activity and improves the electrical performance of the electrode structure formed by the base metal conductive paste.

[0021] 3) The base metal conductive paste formed by combining the glass powder composition of the present invention with a base metal-dominated conductive metal system can reduce the activity consumption of glass powder in the early stage of sintering. Lanthanum can not only inhibit the oxidation of base metals, but also stabilize the glass structure, and prepare an electrode structure with performance comparable to traditional silver paste, significantly reducing the manufacturing cost of conductive paste and improving the economic benefits of the industry.

[0022] 4) The method for preparing base metal conductive paste of the present invention can achieve a breakthrough in the technical path of reducing the cost of conductive paste and improve the economic benefits of the industry.

[0023] 5) The base metal conductive paste of the present invention can be applied to solar cells, including PERC cells, TOPCon cells and BC cells. The electrode contact structure is formed by high-temperature sintering, which has excellent conductivity and ohmic contact performance, thus ensuring the electrical performance of crystalline silicon cells. Detailed Implementation

[0024] The embodiments of this implementation are described in detail below. These embodiments are only used to explain this implementation and should not be construed as limiting this implementation.

[0025] In the description of the embodiments of this invention, it should be noted that all ranges disclosed in this invention are to be understood to encompass any and all subranges included therein. For example, the stated range "1.2-1.8 μm" should be considered to include any and all subranges that begin with a minimum value of 1.2 μm or greater and end with a maximum value of 1.8 μm or less, such as 1.2-1.4 μm, or 1.3-1.5 μm, or 1.6-1.8 μm. Furthermore, all ranges disclosed in this invention are also considered to include the endpoints of the ranges, unless otherwise explicitly stated. For example, the ranges "10~80 wt%" or "10 wt% to 80 wt%" or "between 10 wt% and 80 wt%" should generally be considered to include the endpoints 10 wt% and 80 wt%.

[0026] Unless otherwise specified, in this article, ratio refers to mass ratio and percentage refers to mass percentage.

[0027] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0028] In the field of photovoltaic cells, replacing silver with base metals has significant economic benefits. However, the glass powder system in traditional silver paste is poorly compatible with base metals such as nickel and iron, and is prone to redox reactions in the early stages of sintering. This consumes the etching activity of the glass powder, affects ohmic contact performance, and the conductivity of the oxidized base metal itself drops sharply, damaging the electrode conductivity. Based on this, the present invention has designed a novel glass powder composition adapted to base metal conductive systems. On the one hand, it can preserve the etching activity of the glass powder and improve contact performance; on the other hand, it can improve the conductivity of the base metal conductive system.

[0029] Based on this, the first aspect of the present invention provides a glass powder composition comprising the following components in percentage content: 10-80wt% TeO2, 10-70wt% PbO, 0-20wt% Bi2O3, 0-20wt% Li2O, 0-20wt% WO3, 0-20wt% ZnO, 0-30wt% SiO2, and 0-10wt% Na2O, wherein the surface of the glass powder composition is coated with a layer of lanthanum powder.

[0030] By designing the composition and content of glass powder appropriately, the transition temperature (Tg) of the glass powder composition can be relatively increased. This allows the glass powder composition to maintain a longer glassy state during the initial heating stage of the sintering process, inhibiting atomic diffusion, delaying the onset time of the reaction between the base metal and the glass material, and reducing the initial rate of the reaction between the base metal and the glass material. This avoids the premature consumption of the glass active components, ensures the etching effect of the glass powder on the silicon wafer, and forms a good ohmic contact.

[0031] Further, the glass powder composition comprises the following components in percentage content: 35-70wt% TeO2, 20-40wt% PbO, 3-20wt% Bi2O3, 1-18wt% Li2O, 1-18wt% WO3, 1-18wt% ZnO, 2-28wt% SiO2, and 0-8wt% Na2O, and the surface of the glass powder composition is coated with a layer of lanthanum powder.

[0032] Among them, TeO2 and PbO are the main active components of the glass powder composition. The TeO2 content must be greater than or equal to 35%, and the Bi2O3 content must be less than 20%. They are the main raw materials for subsequent silicon wafer etching. A layer of lanthanum powder is coated on the surface of the glass powder. On the one hand, lanthanum has a relatively low reduction potential, which can reduce base metal oxides to base metals, reduce the oxidation of base metal powder at the interface, and thus ensure excellent line resistance. On the other hand, during the sintering stage, some lanthanum can enter the glass system, stabilize the glass structure, thereby reducing the consumption of base metals on the active components of the glass powder composition, preserving the good activity of the glass powder, and improving the contact performance of the electrode.

[0033] Furthermore, the addition of Bi2O3, Li2O, WO3, ZnO, SiO2, and Na2O can play a role in at least one dimension of increasing the glass transition temperature and enhancing the etching activity of the glass powder.

[0034] Specifically, components such as Bi2O3, Li2O, and Na2O can further enhance the etching activity of the glass powder composition; components such as WO3 and SiO2 can further increase the transition temperature of the glass powder composition. Furthermore, there are synergistic effects among the components; for example, a high content of SiO2 is beneficial for WO3 to play its role in increasing the transition temperature of the glass powder system.

[0035] For example, the glass powder composition comprises: 43wt% TeO2, 32wt% PbO, 4wt% Bi2O3, 7wt% Li2O, 3wt% WO3, 3wt% ZnO, 7wt% SiO2, 1wt% Na2O, and 1wt% lanthanum powder; or 40wt% TeO2, 34wt% PbO, 8wt% Bi2O3, 6wt% Li2O, 2wt% WO3, 2wt% ZnO, 7wt% SiO2, 1wt% Na2O, and 1.5wt% lanthanum powder; or 37wt% TeO2, 35wt% PbO, 12wt% Bi2O3, 9wt% Li2O, 2wt% WO3, 2wt% ZnO, 2wt% SiO2, 1wt% Na2O, and 5wt% lanthanum powder.

[0036] In some implementations, the coating amount of lanthanum powder accounts for 1-15 wt% of the glass powder mass, preferably 1-10 wt%, and more preferably 1-5 wt%. The coating amount of lanthanum powder has a significant impact on the performance of the glass powder and the slurry. If the coating amount of lanthanum powder is less than 1 wt%, the reduction effect of lanthanum powder on the base metal interface is negligible, and it cannot effectively prevent the loss of glass active components. If the coating amount is higher than 15 wt%, excessive lanthanum powder will hinder the softening and flow of the glass powder and induce glass phase separation. Only when the coating amount is controlled at 1-15 wt% can the base metal oxides be efficiently reduced in the early stage of sintering, while allowing lanthanum ions to enter the glass network, thus preserving the glass activity and enhancing the long-term reliability of the electrode.

[0037] In some embodiments, the particle size D50 of the glass powder composition ranges from 1.2 to 1.8 μm, and the maximum particle size Dmax ≤ 8 μm. The particle size D50 range and the maximum particle size Dmax of the glass powder composition can affect the fineness of the subsequently formed conductive paste, and the limitation of the glass powder particle size is used to improve the filling and printability of the conductive paste.

[0038] In some embodiments, the glass transition temperature (Tg) of the glass powder composition is 250-380°C, and the initial crystallization temperature (Tc) is 270-400°C. A high standard glass transition temperature (Tg) allows the glass powder composition to maintain a longer glassy state during the initial heating stage of the sintering process, inhibiting atomic diffusion, delaying the onset time of the reaction between the base metal and the glass material, and reducing the initial reaction rate between the base metal and the glass material. This prevents premature consumption of the glass active components, ensuring the etching effect of the glass powder on the silicon wafer and facilitating the formation of good ohmic contacts. The initial crystallization temperature (Tc) characterizes the thermal stability of the glass powder system during the high-temperature drying stage of sintering, which is beneficial for controllable etching of the silicon wafer and balancing etching activity and reliability.

[0039] A second aspect of the present invention provides a method for preparing a glass powder composition as described in any of the preceding claims, comprising the following steps: S1: After thoroughly mixing the analytical grade raw materials and reagents of each component in the glass powder composition according to the proportion, place them in a crucible, heat them to 1000-1300℃ with a silicon molybdenum rod, keep them at that temperature for 20-50 minutes, and then cold roll or water quench them to obtain glass sheets. S2: Place the glass sheet and 20mm diameter zirconium beads in a nylon ball milling jar at a mass ratio of 1:6, and ball mill them at 450r / min for 40-90min using a planetary ball mill. Then, pass the mixture through a 100-mesh sieve to obtain coarse glass powder. S3: Add the glass coarse powder, 2mm diameter zirconium beads, and alcohol to a nylon ball mill jar in a mass ratio of 1:6:3. Use a planetary ball mill at 350r / min for 30-120min, measuring the particle size every 30min. When the glass powder particle size D50 is found to be in the range of 1.2-1.8μm, transfer the glass powder to a vacuum drying oven, dry it, and pass it through a 200-mesh sieve to obtain the glass powder composition.

[0040] S4: Mix commercially available lanthanum powder (D50 range 0.2-2μm) and the glass powder prepared by the above process at a weight ratio of (0.2-3):20, and simultaneously add an organic mixture of dispersant and alcohol (ratio 0.02-5:100). Add the above glass powder mixture, 2mm diameter zirconium beads and organic mixture to a nylon ball mill jar at a mass ratio of 1:6:3. Use a planetary ball mill at 350r / min for 30-60min. Transfer the glass powder mixture to a vacuum drying oven, dry it and pass it through a 200-mesh sieve to obtain the glass powder composition.

[0041] The preparation process is simple and efficient. The resulting glass powder composition is compatible with base metal conductive systems. By coating the glass powder with a layer of lanthanum powder, on the one hand, the low reduction potential of lanthanum can reduce base metal oxides to base metals, reducing the oxidation of base metal powder at the interface and thus ensuring excellent line resistance. On the other hand, during the sintering stage, some lanthanum can enter the glass system, stabilizing the glass structure and reducing the consumption of active components of the glass powder composition by base metals, preserving the good activity of the glass powder, improving the contact performance of the electrode, and enhancing the etching activity of the glass powder, thereby improving the electrical performance of the electrode structure formed by the base metal conductive paste.

[0042] A third aspect of this invention provides a base metal conductive paste, comprising the following percentage components: 88-92 wt% conductive metal, 2-6 wt% glass powder composition, and 6-10 wt% organic carrier. Using any one of the aforementioned glass powder compositions, combined with a base metal-dominated conductive metal system, the resulting base metal conductive paste reduces the activity consumption of glass powder in the early stages of sintering. Lanthanum can both inhibit base metal oxidation and stabilize the glass structure, producing an electrode structure with performance comparable to traditional silver paste. This significantly reduces the manufacturing cost of the conductive paste and improves industrial economic benefits.

[0043] In some embodiments, the conductive metal is a base metal powder or a mixture of base metal powder and silver powder, wherein the base metal powder includes one or more of nickel powder, copper powder, aluminum powder, tin powder and zinc powder, and the combination includes physical mixing and / or alloying.

[0044] Preferably, the conductive metal is a mixture of silver powder and base metal powder, an alloy powder of silver and base metal, or a mixture of mixed powder and alloy powder. The mixture of silver powder and base metal powder can also be a silver shell coating the base metal with silver powder as the outer shell.

[0045] In some implementations, the organic carrier includes: Organic solvents include one or more of acetone, terpineol, hexylcarbitol, butylcarbitol acetate, dimethyl adipate diol ether, and butylcarbitol; Binders include one or more of the following: ethyl cellulose, phenolic resin, polyvinyl butyral, polyethylene resin, polyacrylic acid, polyurethane resin, and rosin derivatives; Thixotropic agents: including one or more of castor oil derivatives, polyamides, polyamide derivatives, and fatty acid derivatives; and Surfactants include one or more of polyethylene oxide, dodecylaminopropionic acid, benzotriazole, polyethylene glycol, silicone oil, lauric acid, oleic acid, capric acid, myristic acid, stearate and palmitic acid esters.

[0046] Furthermore, the thixotropic index TI of the conductive paste is η5R / η50R, where 4.4 ≤ TI ≤ 6.5. The highly thixotropic conductive paste exhibits high static stability and low coating resistance, ensuring its printability.

[0047] The fourth aspect of this invention provides a method for preparing a base metal conductive paste, which is used to prepare the aforementioned base metal conductive paste, thereby achieving a breakthrough in the cost reduction technology path of conductive paste and improving industrial economic benefits.

[0048] Specifically, the conductive metal, the glass powder composition, and the organic carrier are weighed, stirred and centrifuged, and then repeatedly rolled and ground by a ceramic three-roll mill to obtain the base metal conductive slurry after being mixed evenly.

[0049] The fifth aspect of the application provides an application of a base metal conductive paste, wherein the base metal conductive paste prepared by any of the above-mentioned methods or the base metal conductive paste prepared by the aforementioned methods is applied to a solar cell, wherein the solar cell includes PERC cell, TOPCon cell and BC cell, and the electrode contact structure is formed by high-temperature sintering, which has excellent conductivity and ohmic contact performance, thus ensuring the electrical performance of the crystalline silicon cell.

[0050] The present invention will be further explained and illustrated below with reference to embodiments.

[0051] Unless otherwise specified, all reagents and materials used in the following examples and comparative examples are commercially available. All reagents and raw materials used in the examples and comparative examples of this invention are commercially available.

[0052] Example 1 A glass powder composition comprising the following components in percentage: 43wt%TeO2, 33wt%PbO, 4wt%Bi2O3, 7wt%Li2O, 3wt%WO3, 3wt%ZnO, 6wt%SiO2, and 1wt%Na2O, wherein the surface of the glass powder composition is coated with a layer of lanthanum powder, wherein the coating amount of lanthanum powder accounts for 1% of the mass of the glass powder.

[0053] A method for preparing a glass powder composition includes the following steps: S1: After thoroughly mixing the analytical grade raw materials and reagents of each component in the above glass powder composition according to the proportion, place them in a crucible, heat them to 1000°C with a silicon molybdenum rod, keep them at that temperature for 30 minutes, and then take them out and pour them into a cold rolling mill for rolling or water quenching to form glass sheets. S2: Place the glass plate obtained in step S1 and 20mm diameter zirconium beads in a 500mL nylon ball milling jar at a mass ratio of 1:6, and ball mill them at 450r / min for 60min using a planetary ball mill. Then pass the mixture through a 100-mesh sieve to obtain coarse glass powder. S3: Add the coarse glass powder obtained in step S2, 2mm diameter zirconium beads, and alcohol to a nylon ball mill jar in a mass ratio of 1:6:3. Use a planetary ball mill at 350r / min for 75min, measuring the particle size every 30min. When the glass powder particle size D50 is found to be in the range of 1.2-1.8μm, transfer the glass powder to a vacuum drying oven and bake for 3h. Then, sieve it through a 200-mesh sieve to obtain the glass powder composition.

[0054] S4: Mix lanthanum powder (D50 range of 0.2-2μm) purchased from the market with the glass powder prepared in step S3 at a weight ratio of 1:100. At the same time, add an organic mixture of dispersant (TDO) and alcohol (weight ratio of 0.02:100). Add the above glass powder mixture, 2mm diameter zirconium beads and organic mixture to a nylon ball mill jar at a mass ratio of 1:6:3. Use a planetary ball mill to ball mill at 350r / min for 45min. Transfer the glass powder mixture to a vacuum drying oven, dry it and pass it through a 200-mesh sieve. The resulting glass powder composition is denoted as CN-1.

[0055] A conductive paste, by mass percentage, comprises 88.5% silver-nickel mixed powder, 2.5% of the aforementioned glass powder composition, and 9% organic carrier. The silver-nickel mixed powder is composed of silver powder and nickel powder mixed in a mass ratio of 9.5:0.5, with the silver powder having a D50 of 1.5 μm and the nickel powder having a D50 of 1.8 μm. The organic carrier consists of 40 wt% dimethyl adipate glycol ether, 40 wt% butylcarbidol acetate, 15 wt% a mixture of ethyl cellulose and butylcarbidol acetate, 2 wt% sodium oleate, 1 wt% polyether-modified siloxane, and 2% hydrogenated castor oil.

[0056] A method for preparing a conductive paste includes the following steps: mixing glass powder composition CN-1 with silver-nickel mixed powder and organic carrier in a mass ratio of 2.5:88.5:9, stirring and centrifuging, and then repeatedly rolling and grinding the mixture using a ceramic three-roll mill to obtain the base metal conductive paste, which is designated as MT-1.

[0057] Example 2 The difference between Example 2 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-2.

[0058] The difference between the preparation method of the glass powder composition and Example 1 is that the glass powder composition formulation CN-2 in Table 1 is used, and in S2, a planetary ball mill is used to ball mill at 450 r / min for 50 min, and in S3, a planetary ball mill is used to ball mill at 350 r / min for 65 min. In step S4, the mass ratio of lanthanum powder to glass powder is 3:100.

[0059] A conductive paste differs from Example 1 in that the glass powder composition is different, and the mass ratio of silver powder to nickel powder in the silver-nickel mixed powder is 8.5:1.5. The base metal conductive paste prepared is designated as MT-2.

[0060] Example 3 The difference between Example 3 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-3.

[0061] The difference between the preparation method of the glass powder composition and Example 1 is that the glass powder composition formulation CN-3 in Table 1 is used, and in S1, a silicon molybdenum rod is used to heat to 1050°C, in S3, a planetary ball mill is used to ball mill at 350 r / min for 70 min, and in step S4, the mass ratio of lanthanum powder to glass powder is 4:100.

[0062] A conductive paste differs from Example 1 in that the glass powder composition is different. The mass ratio of silver powder to nickel powder in the silver-nickel mixed powder is 7.5:2.5. The organic carrier consists of 45 wt% dimethyl adipate, 35 wt% butylcarbidol acetate, 15 wt% a mixture of ethyl cellulose and butylcarbidol acetate, 2 wt% sodium oleate, 1.5 wt% polyether-modified siloxane and 1.5% hydrogenated castor oil. The resulting base metal conductive paste is designated MT-3.

[0063] Example 4 The difference between Example 4 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-4.

[0064] The difference between the preparation method of the glass powder composition and Example 1 is that the glass powder composition formulation CN-4 in Table 1 is used, and a planetary ball mill is used in S2 to ball mill at 450 r / min for 50 min, and a planetary ball mill is used in S3 to ball mill at 350 r / min for 60 min. In step S4, the mass ratio of lanthanum powder to glass powder is 6:100.

[0065] A conductive paste differs from Example 1 in that the glass powder composition is different. The silver-nickel mixed powder has a silver powder to nickel powder mass ratio of 6.5:3.5. The organic carrier consists of 40 wt% dimethyl adipate, 40 wt% butylcarbidol acetate, 15 wt% a mixture of ethyl cellulose and butylcarbidol acetate, 2 wt% sodium oleate, 1.5 wt% polyether-modified siloxane and 1.5% hydrogenated castor oil. The resulting base metal conductive paste is designated MT-4.

[0066] Example 5 The difference between Example 5 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-5.

[0067] A conductive paste differs from Example 1 in that the glass powder composition is different, the mass ratio of lanthanum powder to glass powder is 8:100, and the silver-nickel mixed powder is replaced with silver-copper mixed powder, wherein the mass ratio of silver powder to copper powder in the silver-copper mixed powder is 9:1, the D50 of the silver powder is 1.5μm, and the D50 of the copper powder is 1.8μm. The resulting base metal conductive paste is designated as MT-5.

[0068] Example 6 The difference between Example 6 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-6.

[0069] A conductive paste differs from Example 1 in that the glass powder composition is different, the mass ratio of lanthanum powder to glass powder is 10:100, and the silver-nickel mixed powder is replaced with a silver-copper mixed powder, wherein the mass ratio of silver powder to copper powder in the silver-copper mixed powder is 8:2, the D50 of the silver powder is 1.5μm, and the D50 of the copper powder is 1.8μm. The resulting base metal conductive paste is designated as MT-6.

[0070] Example 7 The difference between Example 7 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-7.

[0071] A conductive paste differs from Example 1 in that the glass powder composition is different, the mass ratio of lanthanum powder to glass powder is 12:100, and the silver-nickel mixed powder is replaced with silver-aluminum mixed powder. In the silver-aluminum mixed powder, the mass ratio of silver powder to aluminum powder is 7:3, the D50 of the silver powder is 1.5μm, and the D50 of the aluminum powder is 1.8μm. The resulting base metal conductive paste is designated as MT-7.

[0072] Example 8 The difference between Example 8 and Example 1 is that the components of the glass powder composition are different, as shown in Table 1. The glass powder composition is designated as CN-8.

[0073] A conductive paste differs from Example 1 in that the glass powder composition is different, the mass ratio of lanthanum powder to glass powder is 14:100, and the silver-nickel mixed powder is replaced with a silver-zinc mixed powder. In the silver-zinc mixed powder, the mass ratio of silver powder to zinc powder is 6:4, the D50 of the silver powder is 1.5μm, and the D50 of the zinc powder is 1.8μm. The resulting base metal conductive paste is designated as MT-8.

[0074] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the glass powder composition has different components and is not coated with lanthanum powder. The components are shown in Table 1. The glass powder composition is designated as CN-9.

[0075] A base metal conductive paste, designated MT-9, was prepared using glass powder composition CN-9 according to the formulation and preparation method of the conductive paste in Example 1.

[0076] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the glass powder composition has different components and is not coated with lanthanum powder. The components are shown in Table 1. The glass powder composition is designated as CN-10.

[0077] A base metal conductive paste, designated MT-10, was prepared using the glass powder composition CN-10 according to the formulation and preparation method of the conductive paste in Example 1.

[0078] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the glass powder composition has different components and is not coated with lanthanum powder. The components are shown in Table 1. The glass powder composition is designated as CN-11.

[0079] A base metal conductive paste, designated MT-11, was prepared using the glass powder composition CN-11 according to the formulation and preparation method of the conductive paste in Example 1.

[0080] The difference between Comparative Example 4 and Example 1 is that the glass powder composition has different components and is not coated with lanthanum powder. The components are shown in Table 1. The glass powder composition is designated as CN-12.

[0081] A base metal conductive paste, designated MT-12, was prepared using the glass powder composition CN-12 according to the formulation and preparation method of the conductive paste in Example 1.

[0082] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the coating amount of lanthanum powder in the glass powder composition is 0.5%, and the glass powder composition is designated as CN-13.

[0083] A base metal conductive paste, designated MT-13, was prepared using the glass powder composition CN-13 according to the formulation and preparation method of the conductive paste in Example 1.

[0084] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the lanthanum powder coating content in the glass powder composition is 20%, and the glass powder composition is designated as CN-14.

[0085] A base metal conductive paste, designated MT-14, was prepared using the glass powder composition CN-14 according to the formulation and preparation method of the conductive paste in Example 1.

[0086] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that the preparation method of the glass powder composition is different. An equal amount of lanthanum powder is directly added to the glass powder for dispersion. The glass powder composition is designated as CN-15.

[0087] A base metal conductive paste, designated MT-15, was prepared using the glass powder composition CN-15 according to the formulation and preparation method of the conductive paste in Example 1.

[0088] Comparative Example 8 The difference between Comparative Example 8 and Comparative Example 7 is that the glass powder composition is different. An equal amount of lanthanum powder is replaced with an equal mass of lanthanum oxide, which is directly added to the glass powder for dispersion. The glass powder composition is denoted as CN-16.

[0089] A base metal conductive paste, designated MT-16, was prepared using the glass powder composition CN-16 according to the formulation and preparation method of the conductive paste in Example 1.

[0090] Table 1 Formulations of the glass powder compositions in Examples 1-8 and Comparative Examples 1-8

[0091] The particle size and physical properties of the glass powder compositions prepared in Examples 1-8 and Comparative Examples 1-8 were tested, and the experimental results are shown in Table 2. Particle size was measured using a laser particle size analyzer. D50 represents the particle size parameter of the glass powder composition, specifically the particle size value corresponding to a cumulative particle size distribution of 50%, indicating that particles larger than and smaller than this value each account for 50%. Dmax represents the maximum particle size of the glass powder composition. The glass transition temperature Tg and initial crystallization temperature Tc were obtained using differential scanning calorimetry, where Tg represents the glass transition temperature of the glass powder composition, and Tc represents the initial crystallization temperature of the glass powder composition.

[0092] Table 2. Particle size and physical property data of the glass powder compositions prepared in Examples 1-8 and Comparative Examples 1-8

[0093] As shown in Table 2, the glass powder compositions of Comparative Examples 1-4 were not coated with lanthanum powder and had different contents of TeO2 and Bi2O3. The temperature characteristics of the resulting glass powder compositions differed by tens of degrees from those of the examples. During the sintering process, the glass powder compositions of Comparative Examples 1-4 prematurely transformed from a glassy state to a highly elastic state, and the active components reacted with base metal powders such as nickel powder prematurely, ultimately resulting in poor etching effect and deteriorated contact performance.

[0094] The properties of the base metal conductive pastes in Examples 1-8 and Comparative Examples 1-8 are shown in Table 3. The viscosity of the pastes was tested using a viscometer. η5R represents the viscosity of the conductive paste at 5 rpm, η10R represents the viscosity at 10 rpm, η30R represents the viscosity at 30 rpm, and η50R represents the viscosity at 50 rpm. TI represents the thixotropic index, calculated as: TI = η5R / η50R.

[0095] Table 3 Viscosity test data of the conductive pastes prepared in Examples 1-8 and Comparative Examples 1-8

[0096] The performance tests of the electrode structures made from base metal conductive pastes in Examples 1-8 and Comparative Examples 1-8 are shown in Table 4. During the electrode structure performance tests, the base metal conductive paste was printed onto the solar cell using a cell screen printing machine, sintered in a chain furnace at a maximum temperature of 790°C, and cell defects were repaired using a light injection device. The contact resistivity ρ of the manufactured cell was measured using a TLM device. c Its photoelectric conversion efficiency Eta was tested under IV testing machine.

[0097] Table 4 Performance test results of electrode structures made from the conductive pastes prepared in Examples 1-8 and Comparative Examples 1-8

[0098] Table 3 shows that the thixotropic index of each embodiment is comparable to that of the comparative examples, their printing performance is similar, and the resulting electrode structures are highly consistent, allowing for a horizontal comparison of electrical performance. Table 4 shows that the dispersion r values ​​of each embodiment and the comparative examples are comparable, indicating high data reliability, allowing for a horizontal comparison of specific contact resistivity ρc. Combining Tables 2-4, the contact resistance of Examples 1-8 remains between 0.16-0.21Ω, which is more than half lower than the average value of Comparative Examples 1-8. The specific contact resistivity ρc of Examples 1-8 remains between 0.25-0.46 (mΩ·cm). 2 The efficiency of the lanthanum powder coating decreased by more than half compared to the average of Comparative Examples 1-8. Due to the coating of lanthanum powder, the reduction potential of the glass powder can be reduced, the redox reaction between the glass powder and the base metal can be suppressed, and the contact performance of the final electrode contact structure can be improved. In addition, as can be seen from Table 4, the coating of lanthanum powder also benefits from its good conductivity. The photoelectric conversion efficiency of the battery cell can be maintained above 27.3% by increasing the base metal powder from 5 wt% in Example 1 to 40 wt% in Example 8, which is more than 0.3% higher than the comparative examples. Moreover, the glass powder composition of the present invention is universally compatible with base metals such as nickel, copper, aluminum and zinc, and the photoelectric conversion efficiency of the resulting slurry can be maintained at a high level.

[0099] Comparative Examples 5 and 6 showed that the amount of lanthanum powder added was reduced and increased, respectively. The results showed that too much or too little lanthanum powder would affect the performance of the slurry, significantly increasing the contact resistance and contact resistivity, thus leading to a significant decrease in battery efficiency. The main reason is that when the coating amount is low, such as less than 1%, the lanthanum powder cannot play a reducing role, while too much lanthanum powder coating will affect the original glass powder's wetting of the metal powder and its corrosion of the silicon wafer, thereby affecting the contact resistance and thus the battery efficiency.

[0100] Comparative Example 7 did not coat the lanthanum powder; instead, it directly mixed the lanthanum powder with the glass powder. The results showed a significant increase in contact resistance and resistivity in the resulting slurry, leading to a significant decrease in battery efficiency. This may be because the lanthanum powder failed to effectively protect the glass powder, and the reduction effect was uneven. Comparative Example 8, which replaced the lanthanum powder in Comparative Example 7 with lanthanum oxide, also produced a slurry with high contact resistance. This is likely because the lanthanum oxide failed to properly reduce the base metal powder.

[0101] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A lanthanum powder coated glass powder composition characterized in that, The glass powder composition, calculated by weight percentage, comprises the following components: 10-80 wt% TeO2, 10-70 wt% PbO, 0-20 wt% Bi2O3, 0-20 wt% Li2O, 0-20 wt% WO3, 0-20 wt% ZnO, 0-30 wt% SiO2, and 0-10 wt% Na2O. The surface of the glass powder composition is coated with a layer of lanthanum powder. The preparation method of the lanthanum powder-coated glass powder composition includes the following steps: S1: After thoroughly mixing all components in the glass powder composition, place it in a crucible, heat it to 1000-1300℃ with a silicon molybdenum rod, hold it at that temperature for 20-50 minutes, and then cold roll or water quench it to obtain a glass sheet; S2: Place the glass sheet obtained in step S1 and 20mm diameter zirconium beads in a nylon ball milling jar at a mass ratio of 1:6, and ball mill them at 450r / min for 40-90min using a planetary ball mill. Then pass the mixture through a 100-mesh sieve to obtain coarse glass powder. S3: Add the coarse glass powder obtained in step S2, 2mm diameter zirconium beads, and alcohol to a nylon ball mill jar in a mass ratio of 1:6:

3. Use a planetary ball mill at 350r / min for 30-120min. Measure the particle size every 30min. When the glass powder particle size D50 is found to be in the range of 1.2-1.8μm, transfer the glass powder to a vacuum drying oven, dry it, and pass it through a 200-mesh sieve to obtain a glass powder mixture. S4: Mix the lanthanum powder and the glass powder mixture obtained in step S3 at a weight ratio of (0.2-3):20, and simultaneously add the organic mixture of dispersant and alcohol. Add the mixture of glass powder and lanthanum powder, 2mm diameter zirconium beads and organic mixture at a mass ratio of 1:6:3 into a nylon ball mill jar, and ball mill using a planetary ball mill at a speed of 350r / min for 30-60min. Transfer to a vacuum drying oven, dry and pass through a 200-mesh sieve to obtain the lanthanum powder-coated glass powder composition.

2. The lanthanide powder-coated glass powder composition of claim 1, wherein, The glass powder composition comprises the following components by weight percentage: 35-70wt%TeO2, 20-40wt%PbO, 3-20wt%Bi2O3, 1-18wt%Li2O, 1-18wt%WO3, 1-18wt%ZnO, 2-28wt%SiO2, and 0-8wt%Na2O. The surface of the glass powder composition is coated with a layer of lanthanum powder.

3. The lanthanum powder-coated glass powder composition according to claim 1 or 2, characterized in that, The lanthanum powder coating amount accounts for 1-15 wt% of the glass powder mass, and the particle size D50 of the lanthanum powder is 0.2-2 μm.

4. The lanthanum powder-coated glass powder composition according to claim 1, characterized in that, The particle size D50 of the lanthanum powder-coated glass powder composition ranges from 1.2 to 1.8 μm, and the maximum particle size Dmax is ≤ 8 μm.

5. The lanthanum powder-coated glass powder composition according to claim 1, characterized in that, The glass transition temperature (Tg) of the lanthanum powder-coated glass powder composition is 250-380℃, and the initial crystallization temperature (Tc) is 270-400℃.

6. A method for preparing a lanthanum powder-coated glass powder composition according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: After thoroughly mixing all components in the glass powder composition, place it in a crucible, heat it to 1000-1300℃ with a silicon molybdenum rod, hold it at that temperature for 20-50 minutes, and then cold roll or water quench it to obtain a glass sheet; S2: Place the glass sheet obtained in step S1 and 20mm diameter zirconium beads in a nylon ball milling jar at a mass ratio of 1:6, and ball mill them at 450r / min for 40-90min using a planetary ball mill. Then pass the mixture through a 100-mesh sieve to obtain coarse glass powder. S3: Add the coarse glass powder obtained in step S2, 2mm diameter zirconium beads, and alcohol to a nylon ball mill jar in a mass ratio of 1:6:

3. Use a planetary ball mill at 350r / min for 30-120min. Measure the particle size every 30min. When the glass powder particle size D50 is found to be in the range of 1.2-1.8μm, transfer the glass powder to a vacuum drying oven, dry it, and pass it through a 200-mesh sieve to obtain a glass powder mixture. S4: Mix the lanthanum powder and the glass powder mixture obtained in step S3 at a weight ratio of (0.2-3):20, and simultaneously add the organic mixture of dispersant and alcohol. Add the mixture of glass powder and lanthanum powder, 2mm diameter zirconium beads and organic mixture at a mass ratio of 1:6:3 into a nylon ball mill jar, and ball mill using a planetary ball mill at a speed of 350r / min for 30-60min. Transfer to a vacuum drying oven, dry and pass through a 200-mesh sieve to obtain the lanthanum powder-coated glass powder composition.

7. A base metal conductive paste, characterized in that, The base metal conductive paste comprises the following components by weight percentage: 88-92 wt% conductive metal, 2-6 wt% lanthanum powder-coated glass powder composition as described in any one of claims 1 to 5, and 6-10 wt% organic carrier. The conductive metal is base metal powder or a mixture of base metal powder and silver powder. The base metal powder includes one or more of nickel powder, copper powder, aluminum powder, tin powder, and zinc powder, and the combination includes physical mixing and / or alloying.

8. The base metal conductive paste according to claim 7, characterized in that, In the mixture of base metal powder and silver powder, the addition ratio of base metal powder is 1-70%. The organic carrier includes organic solvent, binder, thixotropic agent and surfactant. The organic solvent includes one or more of acetone, terpineol, hexylcarbitol, butylcarbitol acetate, dimethyl adipate glycol ether and butylcarbitol. The binder includes one or more of ethyl cellulose, phenolic resin, polyvinyl butyral, polyethylene resin, polyacrylic acid, polyurethane resin and rosin derivative. The thixotropic agent includes one or more of castor oil derivative, polyamide, polyamide derivative and fatty acid derivative. The surfactant includes one or more of polyethylene oxide, dodecylaminopropionic acid, benzotriazole, polyethylene glycol, silicone oil, lauric acid, oleic acid, decanoic acid, myristic acid, stearate and palmitate.

9. The base metal conductive paste according to claim 7 or 8, characterized in that, The thixotropic index of the base metal conductive paste is TI = η5R / η50R, where 4.4 ≤ TI ≤ 6.

5.

10. The application of the base metal conductive paste according to any one of claims 7 to 9 in the field of solar cells, wherein the solar cells include PERC cells, TOPCon cells, or BC cells.

Images