High-conductivity photovoltaic cell metal slurry and preparation method and application thereof

Abstract

The invention relates to the field of branch cells, in particular to high-conductivity photovoltaic cell metal paste and a preparation method and application thereof, and the metal paste comprises the following raw materials in parts by weight: 10-90 parts of silver powder, 0.5-30 parts of indium powder, 1-60 parts of tin powder, 1-10 parts of lead-containing glass powder, 5-10 parts of an organic carrier, 0.1-1 part of an organic dispersing agent and 0.1-1 part of a slipping agent. The prepared finished product can be widely applied to electrode manufacturing of various photovoltaic cells such as silicon-based solar cells and thin-film solar cells, and has the advantages that the current transmission efficiency of the photovoltaic cells is remarkably improved, the production cost is reduced, and meanwhile, the long-term stability of the cells is kept or improved. In addition, the finished product also has good environmental adaptability, and is helpful for promoting sustainable development of the photovoltaic industry.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic cells, and in particular to a high-conductivity photovoltaic cell metal slurry and a preparation method and application thereof. Background Art

[0002] With the growing global demand for clean energy, photovoltaic solar cells, as an important component of renewable energy, have a direct impact on the popularity and application of solar power generation due to their performance and cost.

[0003] Traditional photovoltaic cell electrodes are often made using high-purity silver paste. While this paste offers excellent electrical conductivity, it is expensive and resource-limited. Therefore, the search for low-cost, high-performance alternative materials has become a research hotspot. Low-melting-point metals such as silver, indium, and tin are potential candidates due to their excellent electrical conductivity and relatively low cost. However, the use of a single metal often fails to simultaneously meet the requirements for conductivity, adhesion, and processability, necessitating the design and optimization of composite materials to address this issue. Summary of the Invention

[0004] To achieve the above objectives, the present invention aims to provide a highly conductive metal slurry for photovoltaic cells that can address the problems of the prior art. The slurry features low cost, high conductivity, and suitability for low-temperature manufacturing of photovoltaic cell electrodes. The slurry is intended to improve the current transmission efficiency of photovoltaic cells, reduce production costs, and promote the widespread application of photovoltaic technology. The present invention provides the following technical solutions:

[0005] A high-conductivity photovoltaic cell metal paste comprises the following raw materials in parts by weight: 10-90 parts of silver powder, 0.5-30 parts of indium powder, 1-60 parts of tin powder, 1-10 parts of lead-containing glass powder, 5-10 parts of organic carrier, 0.1-1 part of organic dispersant and 0.1-1 part of lubricant.

[0006] As a further embodiment of the present invention, the average particle size of the silver powder is 1-2.5 μm, and the tap density is 4.5-6.0 g / cm 3 , with a specific surface area of ​​0.5-1.5cm 2 / g, the average particle size of tin powder is 1-2.5μm, and the tap density is 2.0-4.0g / cm 3 , with a specific surface area of ​​0.2-1.0cm 2 / g.

[0007] As a further solution of the present invention: the average particle size of the indium powder is 1-2.5 μm, and the tap density is 2.0-4.0 g / cm 3 , with a specific surface area of ​​0.2-1.0cm 2 / g.

[0008] As a further solution of the present invention: the lead-containing glass powder includes the following raw materials in parts by weight: 30-80 parts of Pb oxide and / or Pb salt, 0.5-20 parts of B2O3, 0.2-10 parts of SiO2, 0.1-5 parts of Al2O3, 1-15 parts of ZnO and 0-20 parts of modified oxides, the modified oxides including one or more combinations of Li2O, Na2O, K2O, Sb2O3, V2O5, TeO2, Ga2O3, In2O3, Bi2O3, GeO2, MgO, BaO, CaO, Ni2O3, Ag2O, La2O3 and Tl2O3, the modified oxides act in the glass system to change the properties of the glass powder.

[0009] As a further embodiment of the present invention, the organic carrier includes a resin, a thixotropic agent, and a solvent, wherein the resin includes at least one of ethyl cellulose, polyvinyl butyral, acrylic resin, phenoxy resin, and rosin resin, and the solvent includes at least one of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dimethyl phthalate, terpineol, dimethyl adipate, diethylene glycol dibutyl ether, benzyl benzoate, alcohol ester dodecahydrate, and alcohol ester hexadecahydrate; the thixotropic agent includes at least one of polyamide wax and polyurea thixotropic agents, and the organic carrier is prepared by stirring the resin, thixotropic agent, and solvent using a high-speed disperser until the molecular chains of the resin and the thixotropic agent are substantially completely stretched and dissolved in the solvent, thereby obtaining a uniform organic carrier.

[0010] As a further embodiment of the present invention, the organic dispersant includes one or both of a fatty acid dispersant and an organic amine dispersant; the lubricant is a mixture of silicone oil and modified siloxane. Modified siloxane is a base siloxane (such as polydimethylsiloxane, PDMS) that has been structurally or functionally modified by chemical or physical methods to impart specific properties (such as hydrophilicity, reactivity, and temperature resistance). Chemical modification involves introducing functional groups into the siloxane backbone or side chains through chemical reactions, thereby altering its molecular structure. Physical modification improves performance through physical mixing or filling without changing the chemical structure of the siloxane.

[0011] A method for preparing a high-conductivity photovoltaic cell metal slurry comprises the following steps:

[0012] (1) Prepare the raw materials according to weight ratio;

[0013] (2) mixing silver powder, indium powder and tin powder, and compounding them by mechanical ball milling or chemical synthesis to obtain composite powder;

[0014] (3) Add the composite powder to the organic carrier, then add the remaining raw materials thereto, stir and mix thoroughly until uniform, and then the finished product can be obtained.

[0015] As a further solution of the present invention, the viscosity, rheological properties, etc. of the finished product can be adjusted as needed, the finished product can be filtered to remove impurities, and then sealed and packaged.

[0016] The application of the above-mentioned high-conductivity photovoltaic cell metal paste in the preparation of TOPCon / HJT / BC crystalline silicon solar cells.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The finished product produced by this invention can be widely used in the manufacture of electrodes for various photovoltaic cells, including silicon-based solar cells and thin-film solar cells. Its advantages include significantly improving the current transmission efficiency of photovoltaic cells, reducing production costs, and maintaining or improving the long-term stability of the cells. Furthermore, the finished product exhibits good environmental adaptability, contributing to the sustainable development of the photovoltaic industry. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] The present invention selects silver (Ag), indium (In) and tin (Sn) as the main raw materials. All three are low-melting-point metals with good electrical conductivity and certain ductility. The high electrical conductivity and chemical stability of silver ensure the main properties of the slurry, while the addition of indium and tin helps to adjust the melting point, reduce costs and may bring other beneficial physical and chemical effects. By accurately adjusting the ratio of silver, indium and tin, combined with appropriate amounts of organic carriers, organic dispersants and other auxiliary materials, a metal slurry formula with excellent comprehensive performance is designed. By optimizing the ratio, it is aimed to achieve high conductivity, good adhesion and suitable processing viscosity. Advanced nanotechnology or physical mixing methods are used to achieve uniform compounding of silver and indium. By controlling parameters such as temperature and time during the compounding process, the interaction between silver, indium and tin is promoted to form a stable intermetallic compound or solid solution, further improving the electrical conductivity and stability of the slurry. During the slurry preparation process, special conductive additives are introduced or surface treatment technologies such as silver plating and coating are used to enhance the surface activity and contact area of ​​the silver particles, thereby improving the electrical conductivity of the slurry. At the same time, by optimizing the dispersibility and rheological properties of the slurry, its uniform coating and good curing on the photovoltaic cell electrodes are ensured.

[0021] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0022] Example Group A

[0023] Preparation of lead-containing glass powder: The ingredients are prepared according to the formula of lead-containing glass powder raw materials by weight in Table 1; the oxide mixture is smelted in a high-temperature melting furnace at 1000°C for 60 minutes. After it is fully melted, the glass liquid is rapidly cooled using a stainless steel roller to obtain glass slag; the glass slag is quickly crushed using a jet mill to make the average particle size of the glass powder 1.5-2.0 μm, and glass powder 1# and glass powder 2# are obtained respectively.

[0024] Table 1 Lead-containing glass powder raw material weight formula

[0025]

[0026] The specific steps for preparing high-conductivity photovoltaic cell metal paste are as follows:

[0027] (1) Preparation of organic vehicle A: According to the proportions in Table 2, weigh the solvent, resin, and thixotropic agent, and stir them using a high-speed disperser at a stirring speed of 2000 r / min and a heating temperature of 65°C until the molecular chains of the resin and thixotropic agent are substantially completely stretched and dissolved in the solvent, thereby obtaining a uniform organic vehicle A.

[0028] (2) Mixing and preparing ingredients: According to the proportions in Table 3, weigh silver powder, indium powder, tin powder, lead-containing glass powder, organic carrier, organic dispersant and lubricant, and mix and stir to obtain a semi-finished product slurry;

[0029] (3) Rolling: The semi-finished slurry is ground using a three-roll grinder and the fineness is evaluated using a scraper fineness meter. The slurry grinding fineness is below 10 μm, and the silver indium tin composite photovoltaic cell metal slurry for high-reliability TOPCon crystalline silicon solar cells is obtained.

[0030] Table 2 Organic carrier components

[0031]

[0032] Table 3 High conductivity photovoltaic cell metal paste components (parts by weight)

[0033]

[0034] The silver powder has an average particle size of 1-2.5 μm, a tap density of 4.5-6.0 g / cm³, and a specific surface area of ​​0.5-1.5 cm² / g. The tin powder has an average particle size of 1-2.5 μm, a tap density of 2.0-4.0 g / cm³, and a specific surface area of ​​0.2-1.0 cm² / g. The indium powder has an average particle size of 1-2.5 μm, a tap density of 2.0-4.0 g / cm³, and a specific surface area of ​​0.2-1.0 cm² / g. Organic Carrier A was used as the organic carrier.

[0035] The finished products of Examples 1-5 and Comparative Example 1 were obtained according to the formulations in Tables 1, 2, and 3 and the preparation methods described above. The lubricant used in Examples 1-5 and Comparative Example 1 was Wacker silicone oil AK350, and the commercially available organic dispersant was BYK 110. The organic additive was a silicone defoamer, BYK 1796. The preparation methods for Examples 1-5 and Comparative Example 1 were identical, with the difference being that Comparative Example 1 used pure silver powder, a standard photovoltaic conductive silver paste.

[0036] The finished products of Examples 1-5 and the finished product of Comparative Example 1 were applied to TOPCon crystalline silicon solar cells. The specific cell preparation method includes:

[0037] N-type crystalline silicon wafers are pre-cleaned, textured, and post-cleaned. A front p+ layer is then formed via high-temperature diffusion or plasma doping. A tunnel oxide layer is then formed on the back surface via oxidation, and a back polysilicon film is deposited using LPCVD or PECVD equipment. Using PECVD or ALD processes, a 3-5nm / 80-90nm thick layer of Al2O3 / SiNx is deposited on the front of the wafer, and an 80-90nm layer of SiNx is deposited on the back surface, forming front and back passivation dielectric films. The finished products of Examples 1-5 and Comparative Example 1 are screen-printed onto the front of a TOPCon semi-finished blue film. Similarly, the finished products of Examples 1-5 and Comparative Example 1 are printed onto the back of a TOPCon semi-finished blue film. After drying and sintering, the finished products of Examples 1-5 and Comparative Example 1 undergo organic volatilization or combustion cracking, softening and leveling the glass powder, and wetting silver powder, indium powder, tin powder, or other inorganic powders. The lead-containing glass powder in the finished products of Examples 1-5 and Comparative Example 1 melts the front surface dielectric film and a small amount of the p+ layer substrate at high temperatures. Simultaneously, a small amount of silver powder oxidizes and dissolves into the glass layer. Upon cooling, the silver colloid in the glass recrystallizes, forming nanosilver colloids. This promotes good ohmic contact between the silver electrode or alloy electrode and the substrate, and between the ultra-thin glass film and the substrate. The same reaction occurs on the back side of the semi-finished blue film, dissolving the backside dielectric film, such as silicon nitride, to form a good ohmic contact with the backside polysilicon film, n-poly. After the above process, a complete TOPCon crystalline silicon solar cell is formed.

[0038] The conversion efficiency of the solar cells was evaluated using a current-voltage electrical tester (IV tester) commonly used for solar cells. The test results are shown in Table 4.

[0039] Table 4 Electrical performance of TOPCon crystalline silicon solar cells

[0040]

[0041] The sintering peak temperature in Table 4 is 720°C. In the electrical properties, Voc is the open circuit voltage, Isc is the short circuit current, FF is the fill factor, Rs is the series resistance, Rsh is the parallel resistance, Eta is the conversion efficiency, and Irev2 is the saturation leakage current.

[0042] As can be seen from Table 4, in Example 1, when 5% indium powder is added, the series resistance Rs is slightly higher, the fill factor is slightly lower, and the efficiency is only 0.04% lower; in Example 2, when 5% tin powder is added, the series resistance Rs decreases, and the conversion efficiency is 0.03% higher. Because the price of tin powder is much lower than that of silver powder, tin powder is directly used to replace silver powder, and the conversion efficiency is improved at the same time, and the overall cost reduction and efficiency improvement are obvious; in Example 3, 5% indium powder and 5% tin powder are added at the same time to replace silver powder, the overall series resistance is slightly lower, the conversion efficiency is 0.06% higher, and the overall cost reduction and efficiency improvement are obvious. However, Examples 4 and 5 show that when too much indium powder and tin powder are added to replace silver powder, the overall series resistance will increase significantly, the body resistance will increase, and the conversion efficiency will decrease significantly. Therefore, in actual product development, it is necessary to add an appropriate amount of indium powder and tin powder to replace silver powder to balance the cost reduction and conversion efficiency loss.

[0043] The bulk resistivity of the sintered electrode was evaluated using a constant current source, and the contact resistivity between the electrode and the silicon substrate after sintering with different slurries was evaluated using the TLM test method. The test results are shown in Table 5.

[0044] Table 5 Test results of resistivity of different silver / alloy electrodes and contact resistivity with substrate

[0045] Test results Volume resistivity (Ω·cm) <![CDATA[Contact resistivity (mΩ·cm 2 )]]> Comparative Example 1 <![CDATA[3.2×10 -6 ]]> 1.23 Example 1 <![CDATA[3.9×10 -6 ]]> 1.31 Example 2 <![CDATA[3.3×10 -6 ]]> 1.12 Example 3 <![CDATA[3.2×10 -6 ]]> 1.02 Example 4 <![CDATA[4.5×10 -6 ]]> 1.35 Example 5 <![CDATA[4.9×10 -6 ]]> 1.42

[0046] Combined with the data in Table 5, it can be seen from Example 1 that adding conductive indium powder will cause a slight increase in volume resistivity and a slight increase in contact resistivity, so the conversion efficiency decreases slightly; from Example 2, it can be seen that adding conductive tin powder, the volume resistivity remains basically unchanged, but the contact resistivity decreases, which should be due to the partial oxidation of tin powder during high-temperature sintering, providing more tin oxide to the glass layer, improving the contact performance; Example 3 shows that when 5% indium powder and tin powder are added at the same time, the volume resistivity is basically maintained, but the contact resistivity decreases more significantly, which contributes more to the conversion efficiency; the results of Examples 4 and 5 show that excessive indium powder and tin powder replace silver powder, resulting in a significant increase in the overall volume resistivity and contact resistivity, and a significant decrease in conversion efficiency.

[0047] The above performance tests and actual application in photovoltaic cell electrode production have verified its performance under actual working conditions. The above comparison shows that compared with traditional silver paste, the paste of the present invention should show higher conductivity, better processability and lower cost.

[0048] The above performance tests and actual application in photovoltaic cell electrode production have verified its performance under actual working conditions. The above comparison shows that compared with traditional silver paste, the paste of the present invention should show higher conductivity, better processability and lower cost.

[0049] It should be noted that, in the present invention, unless otherwise expressly specified or limited, the terms "fixed" and "disposed" should be understood in a broad sense. For example, they can refer to welded connections, bolted connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise expressly specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0050] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A high-conductivity photovoltaic cell metal paste, characterized in that: The invention comprises the following raw materials in parts by weight: 10-90 parts of silver powder, 0.5-30 parts of indium powder, 1-60 parts of tin powder, 1-10 parts of lead-containing glass powder, 5-10 parts of organic carrier, 0.1-1 part of organic dispersant and 0.1-1 part of lubricant.

2. The high-conductivity photovoltaic cell metal paste according to claim 1, characterized in that: The lead-containing glass powder includes the following raw materials in parts by weight: 30-80 parts of Pb oxide and / or Pb salt, 0.5-20 parts of B2O3, 0.2-10 parts of SiO2, 0.1-5 parts of Al2O3, 1-15 parts of ZnO and 0-20 parts of modified oxide, and the modified oxide includes a combination of one or more of Li2O, Na2O, K2O, Sb2O3, V2O5, TeO2, Ga2O3, In2O3, Bi2O3, GeO2, MgO, BaO, CaO, Ni2O3, Ag2O, La2O3 and Tl2O3.

3. The high-conductivity photovoltaic cell metal paste according to claim 1 or 2, characterized in that: The organic carrier includes a resin, a thixotropic agent and a solvent, the resin includes at least one of ethyl cellulose, polyvinyl butyral, acrylic resin, phenoxy resin and rosin resin, the solvent includes at least one of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dimethyl phthalate, terpineol, dimethyl adipate, diethylene glycol dibutyl ether, benzyl benzoate, alcohol ester dodecahydrate and alcohol ester hexadecene; the thixotropic agent includes at least one of polyamide wax and polyurea thixotropic agent.

4. The high-conductivity photovoltaic cell metal paste according to claim 1, characterized in that: The organic dispersant includes one or both of a fatty acid dispersant and an organic amine dispersant.

5. The high-conductivity photovoltaic cell metal paste according to claim 1 or 4, characterized in that: The lubricant is a mixture of silicone oil and modified silicone.

6. The high-conductivity photovoltaic cell metal paste according to claim 1, characterized in that: The silver powder has an average particle size of 1-2.5 μm and a tap density of 4.5-6.0 g / cm 3 , with a specific surface area of ​​0.5-1.5cm 2 / g.

7. A method for preparing a high-conductivity photovoltaic cell metal paste, characterized in that: The following steps are involved: (1) Prepare the raw materials according to weight ratio; (2) mixing silver powder, indium powder and tin powder, and compounding them by mechanical ball milling or chemical synthesis to obtain composite powder; (3) Add the composite powder to the organic carrier, then add the remaining raw materials thereto, stir and mix thoroughly until uniform, and then the finished product can be obtained.

8. Use of the high-conductivity photovoltaic cell metal paste as described in 1-6 in the preparation of TOPCon / HJT / BC crystalline silicon solar cells.

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