Conductive paste for N-type TOPCon battery and preparation method of conductive paste

Abstract

The invention discloses conductive paste for an N-type TOPCon battery and a preparation method of the conductive paste, and the conductive paste comprises the following components in percentage by weight: 80-90 wt% of silver powder, 2-5 wt% of low-melting-point glass powder, 1-5 wt% of yttria-stabilized zirconia powder, 1-5 wt% of organic resin, 1-10 wt% of an organic solvent, 0.1-0.5 wt% of a thixotropic agent, 0.1-0.5 wt% of a dispersing agent and 0.1-0.5 wt% of silicone oil. According to the invention, the collaborative improvement of low contact resistance and high passivation quality is realized, and the reliability of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a conductive paste for N-type TOPCon cells and its preparation method. Background Technology

[0002] TOPCon (Tunnel Oxide Passivated Contact) cells are a type of high-efficiency crystalline silicon solar cell. Its core technology involves fabricating an ultrathin silicon dioxide (SiO2) tunneling oxide layer and a phosphorus-doped polycrystalline silicon (poly-Si) layer on the back surface of the cell, which together form a passivated contact structure. This effectively reduces surface recombination and metal-to-metal recombination, thereby improving cell efficiency. In recent years, TOPCon technology has become one of the mainstream high-efficiency photovoltaic technologies and has experienced rapid growth.

[0003] The existing TOPCon slurry has the following problems during the sintering process: during the sintering process of TOPCon slurry, silver ions diffuse into the SiO2 layer, causing damage to the passivation layer and resulting in low contact performance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a conductive paste for N-type TOPCon batteries and its preparation method, which aims to overcome the shortcomings of the above-mentioned background technology, achieve a synergistic improvement in low contact resistance and high passivation quality, and improve the reliability of the battery.

[0005] This invention provides a conductive paste for N-type TOPCon batteries, comprising the following components by weight percentage: 80-90 wt% silver powder, 2-5 wt% low melting point glass powder, 1-5 wt% yttrium-stabilized zirconium oxide powder, 1-5 wt% organic resin, 1-10 wt% organic solvent, 0.1-0.5 wt% thixotropic agent, 0.1-0.5 wt% dispersant, and 0.1-0.5 wt% silicone oil.

[0006] In one embodiment, the yttrium-stabilized zirconium oxide powder comprises yttrium oxide, wherein the doping content of yttrium oxide is 5-10 mol%, and the balance is zirconium oxide.

[0007] In one embodiment, the low melting point glass powder is bismuth-based glass powder, and the softening point of the bismuth-based glass powder is controlled at 400-600℃.

[0008] In one embodiment, the low-melting-point glass powder is a Bi2O3-TeO2 system, wherein the molar ratio of Bi2O3 to TeO2 in the low-melting-point glass powder is (3:7)-(7:3).

[0009] In one embodiment, the yttrium-stabilized zirconium oxide powder is in the form of nanoparticles with a particle size D50 of 10-30 nm; and / or, the silver powder is spherical with a particle size D50 of 1.0-2.5 μm and a specific surface area of ​​0.3-0.5 m². 2 / g, tap density is 5.5-6.0g / ml.

[0010] In one embodiment, the organic resin includes at least one of ethyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, acrylic resin, rosin resin, and epoxy resin.

[0011] In one embodiment, the organic solvent includes at least one selected from dibutyl phthalate, terpineol, butyl carbitol, butyl carbitol acetate, benzyl alcohol, diethylene glycol dibutyl ether, diethylene glycol butyl ether, dodecyl alcohol ester, and diethylene glycol butyl ether acetate.

[0012] In one embodiment, the thixotropic agent includes at least one of polyamide wax, polyethylene wax, hydrogenated castor oil, and fumed silica;

[0013] And / or, the dispersant includes at least one of fatty acid polyoxyethylene ether, shea butter-based propylene diamine oleate, lecithin, oleic acid, polyvinylpyrrolidone, and polyethylene glycol.

[0014] In one embodiment, the viscosity of the silicone oil is 5-5000 mPa·s, and the silicone oil includes at least one of polydimethylsiloxane, polymethylhydroxysiloxane, and polymethylethoxysiloxane.

[0015] The present invention also provides a method for preparing the conductive paste for N-type TOPCon batteries as described above, specifically including the following steps:

[0016] Add silver powder, low melting point glass powder, yttrium-stabilized zirconia nanoparticles, organic resin, organic solvent, thixotropic agent, dispersant and silicone oil to a stirring device and stir for 30-60 minutes;

[0017] The mixture obtained above is ground using a three-roll mill with a roller spacing of 10-120 μm and a grinding speed of 100-200 r / min to obtain a conductive slurry.

[0018] The beneficial effects of this invention are as follows: During the sintering process, the added YSZ powder preferentially migrates and accumulates at the silver polycrystalline silicon interface, forming the following dual functional layers: (1) an interface tunneling enhancement layer, where the wide bandgap characteristics (~5eV) of YSZ achieve excellent matching with the band structure of n+poly-Si, significantly enhancing the tunneling effect of charge carriers. This interface modification significantly reduces the contact resistivity between the metal and the semiconductor; (2) a passivation protection layer, where the accumulated YSZ forms a dense passivation protection layer at the interface, which effectively blocks silver ions (Ag) + During high-temperature sintering, diffusion into the ultrathin SiO2 tunneling layer is observed. Electroluminescence (EL) testing shows that the solar cells made using this slurry exhibit zero passivation layer damage, perfectly maintaining the passivation integrity of the TOPCon structure. The addition of YSZ powder achieves a synergistic improvement in low contact resistance and high passivation quality. Simultaneously, yttrium-stabilized zirconia nanoparticles form a three-dimensional network structure at the silver grain boundaries, which physically blocks Ag. + The migration path under electric field and humid heat environment effectively suppresses the increasing trend of battery resistance, thereby significantly reducing its resistance change rate and improving battery reliability (low degradation). Furthermore, by adding low-melting-point glass powder, the slurry can be sintered at a relatively low temperature. Within this temperature window, the low-melting-point glass powder melts before the silver powder during sintering, wetting the surface of the silver powder with the liquid phase, reducing the interfacial energy between particles, promoting the diffusion and necking of silver particles, and ultimately forming a dense conductive network, while not causing thermal damage to the passivation layer, thus improving the overall performance of the N-type TOPCon battery. Detailed Implementation

[0019] The term "range" disclosed herein takes the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this way are inclusive and composable; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0020] In this invention, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0021] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but it is preferred that they be performed sequentially.

[0022] This invention provides a conductive paste for N-type TOPCon batteries. By weight percentage, the conductive paste comprises the following components: 80-90 wt% silver powder, 2-5 wt% low-melting-point glass powder, 1-5 wt% yttrium-stabilized zirconia powder, 1-5 wt% organic resin, 1-10 wt% organic solvent, 0.1-0.5 wt% thixotropic agent, 0.1-0.5 wt% dispersant, and 0.1-0.5 wt% silicone oil. Specifically, the silver powder can be 80 wt%, 82 wt%, 84 wt%, 86 wt%, 88 wt%, or 90 wt%; the low-melting-point glass powder can be 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%; the yttrium-stabilized zirconia powder can be 1 wt%, 2 wt%, 3 wt%, 3.5 wt%, 4 wt%, or 5 wt%; and the organic resin can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%. Organic solvents can be 1 wt%, 3 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%; thixotropic agents can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%; dispersants can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%; and silicone oils can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%. These are not listed individually here.

[0023] In this embodiment, the slurry uses silver powder as the main conductive phase, low-melting-point glass powder as the binder phase, and yttrium-stabilized zirconium oxide (YSZ) powder as a functional additive. The remaining components (organic resin, solvent, thixotropic agent, dispersant, silicone oil) together constitute an organic carrier to impart suitable rheological and printability to the slurry. During the sintering process, (1) the interface tunneling reinforcement layer is formed. The wide bandgap characteristics (~5eV) of YSZ achieve excellent matching with the band structure of n+poly-Si, significantly enhancing the tunneling effect of charge carriers. This interface modification significantly reduces the contact resistivity between the metal and the semiconductor; (2) the passivation protection layer is formed. The enriched YSZ forms a dense passivation protection layer at the interface. This protection layer can effectively block silver ions (Ag) + During high-temperature sintering, diffusion into the ultrathin SiO2 tunneling layer is observed. Electroluminescence (EL) testing shows that the solar cells made using this slurry exhibit zero passivation layer damage, perfectly maintaining the passivation integrity of the TOPCon structure. The addition of YSZ powder achieves a synergistic improvement in low contact resistance and high passivation quality. Simultaneously, yttrium-stabilized zirconia nanoparticles form a three-dimensional network structure at the silver grain boundaries, which physically blocks Ag. +The migration path under electric field and humid heat environment effectively suppresses the increasing trend of battery resistance, thereby significantly reducing its resistance change rate and improving battery reliability (low degradation). Furthermore, the use of low-melting-point glass powder allows the slurry to be sintered at a relatively low temperature (400-600℃ below). Within this temperature window, the low-melting-point glass powder melts before the silver powder during sintering, wetting the surface of the silver powder with the liquid phase, reducing the interfacial energy between particles, promoting the diffusion and necking of silver particles, and ultimately forming a dense conductive network, while not causing thermal damage to the passivation layer, thus improving the overall performance of the N-type TOPCon battery.

[0024] Furthermore, the yttrium-stabilized zirconia powder includes yttrium oxide, with a doping content of 5-10 mol%, and the remainder being zirconia. When the yttrium oxide doping content is 5-10 mol%, this doping range ensures that YSZ maintains a stable cubic phase crystal structure after sintering and within the battery operating temperature range. This stable cubic phase crystal structure mainly has the following effects:

[0025] (1) Effects on the rheology and printability of the paste: It helps to prepare a paste with stable viscosity and good thixotropy, and it is easy to obtain clear, flat and neat grid lines through screen printing; the aspect ratio is easy to be increased, reducing light loss.

[0026] (2) The effects on sintering behavior and electrode formation are specifically manifested in:

[0027] Good matching of coefficient of thermal expansion (CTE): The coefficient of thermal expansion of cubic phase YSZ is more compatible with that of silicon, resulting in less thermal stress during sintering and cooling, which helps to reduce damage to silicon wafers (such as microcracks) and warping of solar cells.

[0028] Stable "pinning" effect: YSZ nanoparticles effectively suppress excessive growth and migration of silver particles during sintering. This results in a finer and more uniform porous silver electrode structure. This structure provides more and more uniform reaction channels, allowing the glass powder melt to corrode SiN more uniformly. x The layer forms a uniform contact point, reducing the contact resistance (Rc).

[0029] Maintaining high conductivity of the grid lines: The fine silver network ensures that the resistivity of the grid lines themselves is low.

[0030] Controllable reaction: The entire burn-through process is more stable and controllable, avoiding over-burning or under-burning, and the process window is wider.

[0031] Cubic YSZ exhibits excellent oxygen ion conductivity and chemical stability, effectively blocking silver ion migration and suppressing Ag diffusion into the SiO2 / poly-Si layer. This is crucial for improving the open-circuit voltage (Voc) and fill factor (FF) of the battery. Preferably, the yttrium oxide doping content is 5-8 mol%.

[0032] Furthermore, the low-melting-point glass powder is bismuth-based, with its softening point controlled between 400-600℃. Yttrium-stabilized zirconia nanoparticles are combined with the low-melting-point glass powder. During sintering at 600℃, the yttrium-stabilized zirconia nanoparticles react with the glass phase to form a bismuth yttrium oxide (BiYO3) transition layer, improving adhesion. This solves the problem of existing TOPCon slurries having excessively high sintering temperatures (around 700℃-780℃), leading to easy detachment of the back-side slurry and insufficient adhesion.

[0033] Furthermore, the low-melting-point glass powder is a Bi₂O₃-TeO₂ system, in which the molar ratio of Bi₂O₃ to TeO₂ is (3:7)-(7:3). The particle size D50 of the glass powder is 1-3 μm, and the softening point of the Bi₂O₃-TeO₂ system glass powder is 450℃. During the sintering heating process, the TeO₂-based glass powder softens into a molten state. 4+ The ions have a high field strength, which allows them to react with SiN. x The Si-N bonds in the SiN undergo a chemical reaction, resulting in the localized and controllable dissolution of SiN. x The layer opens a channel for the silver particles in the slurry to contact the silicon surface.

[0034] Furthermore, the yttrium-stabilized zirconium oxide powder is in the form of nanoparticles with a particle size D50 of 10-30 nm; and / or, the silver powder is spherical with a particle size D50 of 1.0-2.5 μm and a specific surface area of ​​0.3-0.5 m². 2 / g, tap density is 5.5-6.0g / ml. Among them, YSZ nanoparticles have regular morphology (mostly spherical or near-spherical) and relatively good dispersibility; silver powder is high-tap monodisperse spherical silver powder.

[0035] Furthermore, the organic resin includes at least one of ethyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, acrylic resin, rosin resin, and epoxy resin. Preferably, the organic resin includes at least two of the above, taking into account both the storage stability and printing rheology of the paste.

[0036] Furthermore, the organic solvent includes at least one of dibutyl phthalate, terpineol, butyl carbitol, butyl carbitol acetate, benzyl alcohol, diethylene glycol dibutyl ether, diethylene glycol butyl ether, dodecyl alcohol ester, and diethylene glycol butyl ether acetate. Preferably, the organic solvent includes at least three of the above, and using them in combination helps with the wettability of the powder; printing with a single solvent is not good.

[0037] Furthermore, the thixotropic agent includes at least one of polyamide wax, polyethylene wax, hydrogenated castor oil, and fumed silica; the thixotropic agent can impart excellent thixotropic properties to the paste, that is, high viscosity when at rest to prevent solid phase sedimentation, rapid viscosity reduction when subjected to shear force (such as the action of a printing doctor blade) to facilitate printing, and rapid viscosity recovery after the shear force is eliminated, thereby ensuring clear printing grid lines, no smudging, and good aspect ratio.

[0038] And / or, the dispersant includes at least one of fatty acid polyoxyethylene ether, tallow-based propylene diamine oleate, lecithin, oleic acid, polyvinylpyrrolidone, and polyethylene glycol; the dispersant can be adsorbed on the surface of silver powder, glass powder, and YSZ nanoparticles, and through steric hindrance or electrostatic repulsion, effectively prevent solid particles from agglomerating and settling in the organic carrier, thereby improving the storage stability and consistency of the slurry.

[0039] Furthermore, the viscosity of the silicone oil is 5-5000 mPa·s, and the silicone oil includes at least one of polydimethylsiloxane, polymethylhydroxysiloxane, and polymethylethoxysilicone. Appropriate amounts of silicone oil with suitable viscosity act as efficient defoamers and leveling agents, eliminating air bubbles introduced during paste preparation and printing, improving the wettability of the paste on the silicon wafer surface, and ensuring printing quality.

[0040] The following description provides further details using specific embodiments and comparative examples.

[0041] The present invention also provides a method for preparing the conductive paste for N-type TOPCon batteries as described above, specifically including the following steps:

[0042] Add silver powder, low melting point glass powder, yttrium-stabilized zirconia nanoparticles, organic resin, organic solvent, thixotropic agent, dispersant and silicone oil to a stirring device and stir for 30-60 minutes;

[0043] The mixture obtained above was ground using a three-roll mill with a roller spacing of 10-120 μm and a grinding speed of 100-200 r / min to obtain a conductive slurry with a fineness of less than 5 μm as measured by an FOG scraper fineness gauge.

[0044] Example 1

[0045] The conductive paste is made from the following raw materials in parts by weight:

[0046] Yttrium-stabilized zirconia nanoparticles (D50 10-30 nm, yttrium oxide doping 5 mol%): 1% Silver powder (D50 1.0-2.5 μm): 85%

[0047] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0048] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0049] Thixotropic agent: 0.2% polyamide wax

[0050] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0051] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0052] Solvents: diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 6.3%, dodecyl alcohol ester 1.5%

[0053] The preparation method of conductive paste is as follows:

[0054] Silver powder, glass powder, yttrium-stabilized zirconia nanoparticles, organic resin, organic solvent, dispersant, thixotropic agent and silicone oil are added to the reaction apparatus and mixed.

[0055] Stir the mixture to ensure that all materials are evenly wetted. Stirring time is 30-60 minutes.

[0056] The material was ground using a three-roll mill with a grinding gap of 10μm-120μm and a grinding speed of 100-200r / min, resulting in a slurry with a fineness of less than 5μm as measured by an FOG scraper fineness gauge.

[0057] Example 2

[0058] The conductive paste is made from the following raw materials in parts by weight:

[0059] Yttrium-stabilized zirconia nanoparticles (D50 10-30 nm, yttrium oxide doping 5 mol%): 3% Silver powder (D50 1.0-2.5 μm): 85%

[0060] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0061] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0062] Thixotropic agent: 0.2% polyamide wax

[0063] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0064] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0065] Solvents: Diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 4.3%, dodecyl alcohol ester 1.5%

[0066] The slurry of Example 2 was prepared using the preparation method described in Example 1.

[0067] Example 3

[0068] The conductive paste is made from the following raw materials in parts by weight:

[0069] Yttrium-stabilized zirconia nanoparticles (D50 10-30 nm, yttrium doping 5 mol%): 3.5%

[0070] Silver powder (D50 1.0-2.5μm): 85%

[0071] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0072] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0073] Thixotropic agent: 0.2% polyamide wax

[0074] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0075] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0076] Solvents: diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 3.8%, dodecyl alcohol ester 1.5%

[0077] The slurry of Example 3 was prepared using the preparation method described in Example 1.

[0078] Example 4

[0079] The conductive paste is made from the following raw materials in parts by weight:

[0080] Yttrium-stabilized zirconia nanoparticles (D50 10-30 nm, yttrium doping 5 mol%): 4%

[0081] Silver powder (D50 1.0-2.5μm): 85%

[0082] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0083] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0084] Thixotropic agent: 0.2% polyamide wax

[0085] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0086] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0087] Solvents: diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 3.3%, dodecyl alcohol ester 1.5%

[0088] The slurry of Example 4 was prepared using the preparation method described in Example 1.

[0089] Example 5

[0090] The conductive paste is made from the following raw materials in parts by weight:

[0091] Yttrium-stabilized zirconia nanoparticles (D50 10-30 nm, yttrium doping 5 mol%): 5%

[0092] Silver powder (D50 1.0-2.5μm): 85%

[0093] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0094] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0095] Thixotropic agent: 0.2% polyamide wax

[0096] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0097] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0098] Solvents: diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 2.3%, dodecyl alcohol ester 1.5%

[0099] The slurry of Example 5 was prepared using the preparation method described in Example 1.

[0100] Comparative Example 1

[0101] The conductive paste is made from the following raw materials in parts by weight:

[0102] Silver powder (D50 1.0-2.5μm): 85%

[0103] Low melting point glass powder (Bi2O3-TeO2 system, molar ratio of Bi2O3 to TeO2 is 4:6, D50 is 1-3μm): 2.5%

[0104] Organic resins: 1% ethyl cellulose (Dow STD-7), 0.5% polyvinyl butyral resin (Kuraray B30H)

[0105] Thixotropic agent: 0.2% polyamide wax

[0106] Dispersant: 0.3% fatty acid polyoxyethylene ether

[0107] Silicone oil: Polydimethylsiloxane (viscosity 100 mPa·s) 0.5%

[0108] Solvents: Diethylene glycol butyl ether 1.2%, diethylene glycol butyl ether acetate 7.3%, dodecyl alcohol ester 1.5%

[0109] The slurry of Comparative Example 1 was prepared using the preparation method described in Example 1.

[0110] Table 1 shows the quantitative relationships of each component in Examples 1-5 and Comparative Example 1.

[0111] Table 1. Quantitative relationships of components in the examples and comparative examples.

[0112]

[0113] Using the conductive pastes of Examples 1-5 and Comparative Example 1 as samples, each sample was printed on the same substrate for relevant property tests. The test process is as follows:

[0114] 1. Contact resistance: After printing specific patterns of conductive paste onto N-type TOPcon solar cells, the cells are dried and sintered; solar cells of a specified size with printed patterns are cut out using a laser slicing machine; and contact resistance is measured using a contact resistance device.

[0115] 2. Welding Tensile Strength: For the welding tensile strength test, N-type TOPcon solar cells printed with conductive paste were screen-printed, then dried, sintered, and cooled to obtain conductive silver grids. Copper-based tin-bismuth-lead solder ribbons were then welded onto the conductive silver grids (to conduct current) at a welding temperature of 300℃ to form the test sample. The test sample was then pulled off at a uniform speed of 180° using a universal testing machine, and the average tensile strength was measured.

[0116] 3. Viscosity test: Take a sample of 15-20g of slurry and use a Brookfield DV2 viscometer and a rotor SC-14 to measure the average viscosity of the slurry under the conditions of 25℃ / speed and 10rpm / 60 seconds.

[0117] 4. Printability Test: The conductive pastes from the above embodiments and comparative examples were printed onto the back of the silicon wafer using screen printing technology. The screen specifications used for printability testing were a knotless, multi-aperture screen with 500 mesh / 9μm wire diameter / total thickness of 18-18.5μm / apertures of 15μm, 13μm, 11μm, and 9μm respectively. The solar cells were dried in an infrared drying oven, and then the printability of the paste was observed with the naked eye and an optical microscope to determine whether there were any broken grids or incomplete prints.

[0118] 5. Damp heat aging test: Damp heat test chamber, capable of controlling temperature and humidity. Set temperature 85℃, humidity 85%, and measure the resistivity change rate after 1000 hours.

[0119] The results of contact resistance, welding tensile strength, viscosity test, printability and damp heat aging test are summarized in Table 2.

[0120] Table 2 Performance test data for the embodiments and comparative examples

[0121]

[0122] As can be seen from Table 2, Comparative Example 1 and Examples 1-5:

[0123] (1) When yttrium-stabilized zirconia nanoparticles are added to the slurry, the contact resistance decreases (3 mΩ·cm in Comparative Example 1). 2 Example 2 is 1.5 mΩ·cm 2 The welding tensile strength increased (1.8 N / mm in Comparative Example 1, 3.1 N / mm in Example 2), printing performance remained normal, and the rate of change in resistance under damp heat aging decreased (12.5% ​​increase in Comparative Example 1, 0.9% increase in Example 2). This indicates that the addition of yttrium-stabilized zirconia nanoparticles to the slurry allows the nanoparticles to preferentially migrate to the silver-polycrystalline silicon interface during sintering, forming a functional layer and reducing contact resistance. When yttrium-stabilized zirconia nanoparticles are combined with low-melting-point glass powder (Bi2O3-TeO2, softening point 450℃) and sintered at 600℃, the nanoparticles react with the glass phase to form a bismuth yttrium oxide (BiYO3) transition layer, improving adhesion. Furthermore, the yttrium-stabilized zirconia nanoparticles form a three-dimensional network structure at the silver grain boundaries, and after aging at 85℃ / 85%RH for 1000 hours, the rate of change in resistance is <1.5%.

[0124] (2) When yttrium-stabilized zirconia nanoparticles are added at 3 wt%, the performance in all aspects is optimal; when the addition amount is 1 wt%, the amount is too small and does not show the optimal effect; when the addition amount is 3.5 wt%, 4 wt%, and 5 wt%, the addition amount is too large, which leads to an increase in the viscosity of the paste, affects the printing performance, and causes false printing and broken grids. As a preferred option, the content of yttrium-stabilized zirconia nanoparticles is 1-3 wt%.

[0125] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A conductive paste for N-type TOPCon batteries, characterized in that, The conductive paste comprises the following components by weight percentage: 80-90 wt% silver powder, 2-5 wt% low melting point glass powder, 1-5 wt% yttrium-stabilized zirconia powder, 1-5 wt% organic resin, 1-10 wt% organic solvent, 0.1-0.5 wt% thixotropic agent, 0.1-0.5 wt% dispersant, and 0.1-0.5 wt% silicone oil.

2. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The yttrium-stabilized zirconia powder comprises yttrium oxide, wherein the yttrium oxide doping content is 5-10 mol%, and the balance is zirconia.

3. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The low-melting-point glass powder is bismuth-based glass powder, and the softening point of the bismuth-based glass powder is controlled at 400-600℃.

4. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The low-melting-point glass powder is a Bi2O3-TeO2 system, and the molar ratio of Bi2O3 to TeO2 in the low-melting-point glass powder is (3:7)-(7:3).

5. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The yttrium-stabilized zirconium oxide powder is in the form of nanoparticles with a particle size D50 of 10-30 nm; And / or, the silver powder is spherical with a particle size D50 of 1.0-2.5 μm and a specific surface area of ​​0.3-0.5 m². 2 / g, tap density is 5.5-6.0g / ml.

6. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The organic resin includes at least one of ethyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, acrylic resin, rosin resin, and epoxy resin.

7. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The organic solvent includes at least one of dibutyl phthalate, terpineol, butyl carbitol, butyl carbitol acetate, benzyl alcohol, diethylene glycol dibutyl ether, diethylene glycol butyl ether, dodecyl alcohol ester, and diethylene glycol butyl ether acetate.

8. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The thixotropic agent includes at least one of polyamide wax, polyethylene wax, hydrogenated castor oil, and fumed silica; And / or, the dispersant includes at least one of fatty acid polyoxyethylene ether, shea butter-based propylene diamine oleate, lecithin, oleic acid, polyvinylpyrrolidone, and polyethylene glycol.

9. The conductive paste for N-type TOPCon batteries as described in claim 1, characterized in that, The viscosity of the silicone oil is 5-5000 mPa·s, and the silicone oil includes at least one of polydimethylsiloxane, polymethylhydroxysiloxane, and polymethylethoxysiloxane.

10. A method for preparing a conductive paste for an N-type TOPCon battery as described in any one of claims 1-9, characterized in that, Specifically, the following steps are included: Add silver powder, low melting point glass powder, yttrium-stabilized zirconia nanoparticles, organic resin, organic solvent, thixotropic agent, dispersant and silicone oil to a stirring device and stir for 30-60 minutes; The mixture obtained above is ground using a three-roll mill with a roller spacing of 10-120 μm and a grinding speed of 100-200 r / min to obtain a conductive slurry.

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