TOPcon battery front silver paste and preparation method thereof

Abstract

The invention relates to the technical field of front silver paste, in particular to TOPcon battery front silver paste and a preparation method thereof.The preparation method comprises the following steps that glass powder is ground, cleaned, dried and then put into oxygen plasma equipment, high-purity oxygen is introduced after vacuumizing, and modified glass powder is obtained; the first organic carrier and silver powder are mixed and then ground, and a first mixture is obtained; adding the modified glass powder and the additive, and uniformly stirring to obtain a second mixture; and adding a second organic carrier, grinding and uniformly mixing to obtain the front silver paste. By adopting the steps, through glass powder modification, silver powder compounding, organic carrier staged design and additive synergy, the prepared front silver paste has the advantages of being high in passive film penetrating capacity, compact in conductive network, high in printing precision and excellent in adhesive force.

Description

Technical Field

[0001] The present invention relates to the technical field of front silver paste, and in particular to a front silver paste for a TOPcon battery and a preparation method thereof. Background Art

[0002] As a high-efficiency N-type photovoltaic technology, the front silver paste of TOPCon (Tunnel Oxide Passivated Contact) cells needs to achieve breakthroughs in low-temperature sintering, high conductivity and interface ohmic contact. Traditional silver paste generally uses lead-containing glass powder, which has environmental pollution problems, and the sintering temperature is high (>800°C), which can easily cause damage to silicon wafers. Conventional glass powder has low surface activity and is difficult to evenly penetrate the passivation film during the sintering process, resulting in increased contact resistance between the electrode and the silicon wafer, affecting battery efficiency. The single particle size of silver powder can easily lead to high porosity and high contact resistance. The rheological properties of traditional organic carriers (such as thixotropy and viscosity) are difficult to meet the requirements of high-precision printing and electrode forming at the same time, and the interfacial bonding force with silver powder and glass powder is weak, affecting the stability and adhesion of the silver paste.

[0003] Therefore, there is an urgent need for a front silver paste preparation method that takes into account environmental protection, high conductivity and process adaptability. Summary of the Invention

[0004] The purpose of the present invention is to provide a TOPCon battery front silver paste and a preparation method thereof, which significantly improves the performance of the TOPCon battery front silver paste by using modified glass powder, silver powder grading design and step-by-step organic carrier addition.

[0005] To achieve the above object, the present invention provides a method for preparing a TOPcon battery front silver paste, comprising the following steps:

[0006] S1, grinding and cleaning the glass powder, drying it, placing it in an oxygen plasma device, evacuating it and introducing high-purity oxygen to obtain modified glass powder;

[0007] S2, mixing the first organic carrier and the silver powder and grinding them to obtain a first mixture;

[0008] S3, adding the modified glass powder and additives in S1 to the first mixture in S2, and stirring evenly to obtain a second mixture;

[0009] S4. Add the second organic vehicle to the second mixture in S3, grind and mix evenly to obtain the front silver paste.

[0010] Preferably, in S1, the glass powder includes one or more of Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2.

[0011] Preferably, in S1, the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen is 5-20 sccm, and the processing time is 5-30 min.

[0012] Preferably, in S2, the silver powder is a mixture of submicron spherical silver powder and micron-sized spherical silver powder in a mass ratio of 2-4:6-8.

[0013] Preferably, in S2, the mass ratio of ethyl cellulose to epoxy-polyurethane resin, organic solvent and thixotropic agent in the first organic vehicle is 1-20:60-80:1-5.

[0014] Preferably, in S3, the additive includes one or more of gallium salt, polyvinyl pyrrolidone, titanium nanoparticles and silica microspheres.

[0015] Preferably, in S4, the second organic vehicle comprises acrylic resin, organic solvent and thixotropic agent in a mass ratio of 1-20:60-80:1-5.

[0016] Preferably, the thixotropic agent includes one or more of polyamide wax, Span 80, hydrogenated castor oil, polyamide wax and cetyl alcohol.

[0017] Preferably, the mass ratio of the silver powder, the modified glass powder, and the total mass of the first organic vehicle and the second organic vehicle is 80-90:1-8:5-12.

[0018] Preferably, the organic solvent includes one or more of dodecyl alcohol, dimethyl adipate, terpineol, diethylene glycol butyl ether acetate, and dibutyl phthalate.

[0019] The positive silver paste is prepared by the above-mentioned method for preparing the positive silver paste of a TOPcon battery.

[0020] Therefore, the present invention adopts the above-mentioned TOPcon battery positive silver paste and preparation method thereof, and its beneficial effects are:

[0021] 1. The surface hydroxyl (-OH) and carboxyl (-COOH) contents of the modified glass powder after modification in the present invention are increased by 50%-80%, thereby enhancing compatibility with the first organic carrier and the second carrier, improving dispersion stability, and reacting Bi2O3 with SiO2 during sintering to form a low-melting-point Bi2SiO5 phase, thereby reducing contact resistance. Flux components such as Bi2O3 and P2O5 can further reduce the sintering temperature and reduce damage to the silicon wafer surface.

[0022] 2. The present invention uses compound silver powder, and submicron silver powder fills the gaps of micron silver powder to form a dense conductive path. The micron silver powder constructs a skeleton structure to reduce resistance loss, with a porosity of <5% and a lower square resistance value;

[0023] 3. The present invention uses ethyl cellulose and epoxy-polyurethane resin in the first organic carrier. The hydroxyl groups of ethyl cellulose and the polar groups of epoxy-polyurethane synergistically adsorb silver powder to form a double-layer structure to prevent agglomeration. The epoxy-polyurethane resin contains active groups (such as epoxy groups and amino groups) that form chemical bonds with the surface of the silver powder and the substrate to enhance adhesion and weather resistance. The second organic carrier supplements the rheological properties to ensure that the silver paste has low shear viscosity and high static viscosity during printing.

[0024] 4. Among the additives added in the present invention, gallium salt doping reduces the silver-silicon interface barrier, lowers the silver paste sintering temperature, and reduces the impact of silver ion diffusion on silicon wafers; titanium nanoparticles enhance the interface bonding between glass powder and silver powder, improving thermal cycling resistance. Gallium salt reduces the silver paste sintering temperature and reduces the impact of silver ion diffusion on silicon wafers; titanium nanoparticles enhance the interface bonding between glass powder and silver powder, improving thermal cycling resistance;

[0025] 5. The present invention prepares the front silver paste through glass powder modification, silver powder compounding, phased design of organic carrier and synergy of additives. The silver paste has the characteristics of strong ability to penetrate the passivation film, dense conductive network, high printing precision and excellent adhesion, which significantly improves the photoelectric conversion efficiency and long-term reliability of TOPcon batteries.

[0026] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the following embodiments. Unless otherwise defined, technical or scientific terms used herein shall have the same meanings as those commonly understood by persons of ordinary skill in the art to which the present invention pertains. The above-mentioned features or features described in the specific examples of the present invention may be combined in any manner. These specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0028] The present invention provides a method for preparing a TOPcon battery front silver paste, comprising the following steps:

[0029] S1, grinding and cleaning the glass powder, drying it, placing it in an oxygen plasma device, evacuating it and introducing high-purity oxygen to obtain modified glass powder;

[0030] S2, mixing the first organic carrier and the silver powder and grinding them to obtain a first mixture;

[0031] S3, adding the modified glass powder and additives in S1 to the first mixture in S2, and stirring evenly to obtain a second mixture;

[0032] S4. Add the second organic vehicle to the second mixture in S3, grind and mix evenly to obtain the front silver paste.

[0033] In some embodiments of the present invention, the glass frit in S1 includes one or more of Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO, and TeO2. In the composite glass frit, Bi2O3 is primarily composed (40-60%), supplemented by P2O5 and B2O3 (5-35%) to adjust the network structure, In2O3 and CuO (1-15%) to enhance conductivity, ZnO (1-18%) to balance process adaptability, and TeO2 (0.1-5%) to reduce light reflection.

[0034] In some embodiments of the present invention, Bi2O3 reacts with SiO2 to form a low-melting-point Bi2SiO5, forming a Bi-Si-O intermediate phase, which reduces contact resistance. The PO bond in P2O5 breaks and releases active oxygen, forming a PO tetrahedral structure, which enhances the stability of the glass network. The BO bond in B2O3 forms a covalent network with the Si-O bond, which enhances interfacial bonding and reduces hygroscopicity, thereby reducing the decrease in slurry stability caused by moisture absorption of the glass powder. In2O3 forms an In-Ag-O composite phase with Ag, which enhances the continuity of the conductive network. 3+ Doping improves glass conductivity and reduces resistivity. ZnO and Bi2O3 form a ZnBi2O4 spinel structure, inhibiting glass crystallization, balancing sintering speed and densification, and reducing pinhole defects. 2+ During sintering, it is reduced to Cu, promoting the removal of oxides on the surface of silver particles. It then reacts with AgNO3 to form an Ag-Cu alloy, optimizing interfacial conductivity. The Cu-O bond chemically anchors the silicon surface. TeO2 and Ag form a highly transparent glass phase, reducing light scattering.

[0035] In some embodiments of the present invention, the glass powder is modified by plasma treatment, and the modified glass powder obtained has hydroxyl groups. The hydroxyl groups form hydrogen bonds with the silicon hydroxyl groups, which can reduce the agglomeration between the glass powder particles, help to form a more uniform microstructure after the silver paste is cured, reduce the scattering and obstruction of electrons during transmission, and make the conductive film formed by the silver paste have better conductivity. In addition, the hydroxyl groups obtained after the glass powder is modified form hydrogen bonds with the silicon hydroxyl groups, which can enhance the adhesion between the silver paste and the silicon-based substrate, and help to improve the electrical performance stability of the silver paste during long-term use.

[0036] In some embodiments of the present invention, the glass powder is modified by plasma treatment, and the modified glass powder has carboxyl groups, which are ionized into carboxyl groups (COO-) in the solvent, giving the modified glass powder a negative charge on the surface. The electrostatic repulsion between the particles prevents agglomeration. The carboxyl groups can also react with the silver ions (Ag +) form chelates, and the chelation effect regulates the migration rate of metal ions, optimizes the interface reaction between the glass phase and silver particles during sintering, reduces contact resistance, and improves the quality of ohmic contact. At the same time, the active substances (water vapor, active oxygen) produced by the decomposition of hydroxyl groups work synergistically with the metal ions chelated by the carboxyl groups to promote the fluidity of the glass phase at low temperatures and reduce sintering energy consumption.

[0037] In some embodiments of the present invention, in S1, grinding reduces the glass powder particle size to the submicron level, increases the specific surface area, and enhances the active sites for subsequent reactions; cleaning removes impurities (such as organic pollutants and metal ions) adsorbed on the surface to avoid introducing additional defects.

[0038] In some embodiments of the present invention, in S1, the vacuum degree is 10- 3 -10- 2 Pa, with a high-purity oxygen flow rate of 5-20 sccm and a treatment time of 5-30 minutes. High-energy oxygen plasma is used to bombard the glass powder surface, inducing physical etching and breaking chemical bonds. This generates active sites that combine with oxygen to form polar groups (carboxyl and hydroxyl groups), enhancing the wettability of the glass powder in organic solvents, reducing agglomeration, and improving dispersion stability. The modified glass powder reacts more easily with silver particles and the silicon substrate during sintering, forming a low-resistance ohmic contact.

[0039] In some embodiments of the present invention, in S2, the silver powder agglomerates are destroyed by shear force during grinding to form a uniform suspension system, and the solvent (such as terpineol) in the organic carrier is adsorbed on the surface of the silver powder to form steric hindrance and inhibit re-agglomeration.

[0040] In some embodiments of the present invention, in S2, the silver powder is a mixture of submicron spherical silver powder and micron-sized spherical silver powder in a mass ratio of 2-4:6-8. Micron-sized silver powder acts as a skeleton to provide structural support, and submicron-sized silver powder (0.1-1 μm) fills the gaps between micron-sized silver powder (1-5 μm) to form a tightly packed structure, reducing porosity (can be reduced to <8%), reducing resistance and improving conductivity. Micron-sized silver powder dominates the fluidity of the slurry, and submicron-sized silver powder preferentially melts at low temperatures, reducing sedimentation and promoting fusion between micron-sized particles. The viscosity after compounding in proportion is more suitable for screen printing (shear thinning characteristics), and the line width accuracy is improved (error <3 μm). If the submicron spherical silver powder exceeds 40%, the resistance will increase due to agglomeration, and if it is less than 20%, the gaps cannot be effectively filled.

[0041] In some embodiments of the present invention, in S2, the mass ratio of ethyl cellulose to epoxy-polyurethane resin, organic solvent, and thixotropic agent in the first organic vehicle is 1-20:60-80:1-5. The hydroxyl groups of ethyl cellulose and the polar groups of epoxy-polyurethane synergistically adsorb silver powder to form a double electric layer structure and prevent agglomeration. At low temperatures, ethyl cellulose dominates the viscosity, while at high temperatures (under printing shear force), the epoxy-polyurethane cross-linked network maintains the structure. During sintering, the epoxy-polyurethane resin decomposes to generate active groups (epoxy ring opening), which promotes the formation of an Ag-Si alloy layer at the silver-silicon interface and reduces the contact resistance.

[0042] In some embodiments of the present invention, in S3, the modified glass powder is used as a sintering aid to promote the silver-silicon interface reaction, and the additive optimizes the slurry performance.

[0043] In some embodiments of the present invention, the additives in S3 include one or more of gallium salts, polyvinyl pyrrolidone, titanium nanoparticles, and silica microspheres. Polyvinyl pyrrolidone ensures particle dispersion, gallium salts promote low-temperature sintering, and SiO2 optimizes rheology, collectively achieving a highly dense, low-resistance electrode. The silica microspheres buffer thermal stress, while the titanium nanoparticles enhance strength, significantly improving electrode reliability. Among the titanium nanoparticles, TiN enhances conductivity, while TiO2 suppresses light reflection, synergistically boosting battery efficiency.

[0044] In some embodiments of the present invention, in S4, the second organic vehicle comprises an acrylic resin, an organic solvent, and a thixotropic agent in a mass ratio of 1-20:60-80:1-5. The linear structure of the acrylic resin shrinks rapidly during drying, promoting close packing of silver particles, reducing sheet resistance, and precisely controlling printability and electrode morphology.

[0045] In some embodiments of the present invention, the thixotropic agent includes one or more of polyamide wax, Span 80, hydrogenated castor oil, a silicone leveling agent, polyamide wax, and hexadecanol. The silicone leveling agent reduces surface energy, thereby eliminating the Maragni effect during printing. Hydrogenated castor oil forms a hydrogen bonding network, increasing viscosity in static conditions (to prevent sedimentation) and reducing viscosity in dynamic conditions.

[0046] In some embodiments of the present invention, the mass ratio of silver powder, modified glass powder to the total mass of the first organic vehicle and the second organic vehicle is 80-90:1-8:5-12. The pre-mixing of S2 and the final adjustment of S4 are phased to optimize the viscosity of the silver paste to adapt to the high shear rate (10 3 -10 4 s - 1) With low shear standing requirements.

[0047] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0048] Example 1

[0049] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0050] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0051] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 3:7) are mixed and then ground. The mass ratio of ethyl cellulose and epoxy-polyurethane resin (mass ratio of 3:16), organic solvent (terpineol and diethylene glycol butyl ether acetate are mixed in a volume ratio of 1:1) and thixotropic agent silica in the first organic carrier is 20:77:3 to obtain a first mixture.

[0052] S3. Add the modified glass powder and additives (gallium salt, polyvinyl pyrrolidone and silica microspheres mixed in a mass ratio of 1:1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0053] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent diethylene glycol butyl ether acetate and thixotropic agent hydrogenated castor oil in a mass ratio of 20:80:5, and grind and mix evenly to obtain a front silver paste.

[0054] The mass ratio of the silver powder, the modified glass powder and the total mass of the first organic carrier and the second organic carrier is 90:5:10, and the mass ratio of the first organic carrier to the second organic carrier is 7:3.

[0055] Example 2

[0056] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0057] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0058] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 4:6) are mixed and ground, and the mass ratio of ethyl cellulose to epoxy-polyurethane resin, organic solvent and thixotropic agent polyamide wax in the first organic carrier is 18:70:2 to obtain a first mixture.

[0059] S3. Add the modified glass powder and additives (gallium salt, polyvinyl pyrrolidone and TiN titanium nanoparticles, TiO2 titanium nanoparticles in a mass ratio of 1:1:1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0060] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent and thixotropic agent (polyamide wax and hexadecanol in a volume ratio of 1:1) in a mass ratio of 15:80:3, and grind and mix evenly to obtain a front silver paste.

[0061] The mass ratio of the silver powder, the modified glass powder and the total mass of the first organic carrier and the second organic carrier is 85:6:8, and the mass ratio of the first organic carrier to the second organic carrier is 6:4.

[0062] Example 3

[0063] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0064] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0065] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 4:6) are mixed and ground, and the mass ratio of ethyl cellulose to epoxy-polyurethane resin, organic solvent and thixotropic agent hydrogenated castor oil in the first organic carrier is 18:70:2 to obtain a first mixture.

[0066] S3. Add the modified glass powder and additives (gallium salt and polyvinyl pyrrolidone in a mass ratio of 1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0067] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent terpineol and thixotropic agent (polyamide wax and hexadecanol in a volume ratio of 1:1) in a mass ratio of 18:750:2, and grind and mix evenly to obtain a front silver paste.

[0068] The mass ratio of the silver powder, the modified glass powder and the total mass of the first organic carrier and the second organic carrier is 90:5:10, and the mass ratio of the first organic carrier to the second organic carrier is 7:3.

[0069] Example 4

[0070] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0071] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0072] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 3:7) are mixed and ground. The mass ratio of ethyl cellulose to epoxy-polyurethane resin (mass ratio of 4:16), organic solvent (terpineol and diethylene glycol butyl ether acetate in a volume ratio of 1:1) and thixotropic agent silica in the first organic carrier is 20:80:3 to obtain a first mixture.

[0073] S3. Add the modified glass powder and additives (polyvinyl pyrrolidone and silica microspheres in a mass ratio of 1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0074] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent diethylene glycol butyl ether acetate and thixotropic agent hydrogenated castor oil in a mass ratio of 20:80:5, and grind and mix evenly to obtain a front silver paste.

[0075] The mass ratio of the silver powder, the modified glass powder and the total mass of the first organic carrier and the second organic carrier is 90:5:10, and the mass ratio of the first organic carrier to the second organic carrier is 7:3.

[0076] Example 5

[0077] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0078] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0079] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 3:7) are mixed and ground. The mass ratio of ethyl cellulose to epoxy-polyurethane resin (mass ratio of 3:16), organic solvent (terpineol and diethylene glycol butyl ether acetate in a volume ratio of 1:1) and thixotropic agent silica in the first organic carrier is 20:77:3 to obtain a first mixture.

[0080] S3. Add the modified glass powder and additives (gallium salt, polyvinyl pyrrolidone and silica microspheres in a mass ratio of 1:1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0081] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent diethylene glycol butyl ether acetate and thixotropic agent hydrogenated castor oil in a mass ratio of 20:75:5, and grind and mix evenly to obtain a front silver paste.

[0082] The mass ratio of the silver powder, the modified glass powder and the total mass of the first organic carrier and the second organic carrier is 90:5:10, and the mass ratio of the first organic carrier to the second organic carrier is 6:4.

[0083] Comparative Example 1

[0084] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0085] S1. Grind glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), clean it, and dry it to obtain glass powder.

[0086] S2. The first organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 3:7) are mixed and ground. The mass ratio of ethyl cellulose to epoxy-polyurethane resin (mass ratio of 3:16), organic solvent (terpineol and diethylene glycol butyl ether acetate in a volume ratio of 1:1) and thixotropic agent silica in the first organic carrier is 20:77:3 to obtain a first mixture.

[0087] S3. Add the glass powder and additives (gallium salt, polyvinyl pyrrolidone and silica microspheres in a mass ratio of 1:1:1) in S1 to the first mixture in S2, and stir evenly to obtain a second mixture.

[0088] S4. Add a second organic carrier to the second mixture in S3, wherein the second organic carrier includes acrylic resin, organic solvent diethylene glycol butyl ether acetate and thixotropic agent hydrogenated castor oil in a mass ratio of 20:80:5, and grind and mix evenly to obtain a front silver paste.

[0089] The mass ratio of the silver powder, the glass powder to the total mass of the first organic carrier and the second organic carrier is 90:5:10, and the mass ratio of the first organic carrier to the second organic carrier is 7:3.

[0090] Comparative Example 2

[0091] A method for preparing a TOPcon battery front silver paste comprises the following steps:

[0092] S1. Grind and clean glass powder (Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2 mixed in a mass ratio of 55:17:12:5:5:3:2), dry it, put it into an oxygen plasma device, evacuate it and introduce high-purity oxygen, and the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen was 15 sccm, and the treatment time was 30 min to obtain modified glass powder.

[0093] S2. The organic carrier and silver powder (submicron spherical silver powder and micron-sized spherical silver powder are mixed in a mass ratio of 3:7) are mixed and ground. The mass ratio of ethyl cellulose to epoxy-polyurethane resin (mass ratio of 3:16), organic solvent (terpineol and diethylene glycol butyl ether acetate in a volume ratio of 1:1) and thixotropic agent silica in the organic carrier is 20:77:3 to obtain a first mixture.

[0094] S3. Add the modified glass powder and additives (gallium salt, polyvinyl pyrrolidone and silica microspheres in a mass ratio of 1:1:1) in S1 to the first mixture in S2, stir evenly to obtain a second mixture, grind and mix evenly to obtain a front silver paste.

[0095] The mass ratio of silver powder, modified glass powder and organic carrier is 90:5:10.

[0096] Test Example 1

[0097] a. Silver powder performance

[0098] The tap density, specific surface area and loss on ignition rate data of the silver powder in Example 1 and Example 2 are shown in Table 1.

[0099] Table 1, Silver Powder Performance Data Table in Example 1 and Example 2

[0100] <![CDATA[Tap density g / cm 3 > <![CDATA[Specific surface area m 2 / g]]> Loss on ignition (%) Example 1 6.6 1.7 0.47 Example 2 7.1 2.2 0.52

[0101] As can be seen from Table 1, the tap density of the silver powder in Example 1 (submicron spherical silver powder and micron-sized spherical silver powder mixed in a mass ratio of 3:7) is greater than that of the silver powder in Example 2 (submicron spherical silver powder and micron-sized spherical silver powder mixed in a mass ratio of 4:6). It can be seen that the silver powder in Example 1 forms a denser pile, and the silver layer structure after sintering the silver paste is also denser. The silver powder in Example 1 has a smaller specific surface area than the silver powder in Example 2, and the wetted surface area of ​​the silver powder in Example 1 is smaller than that of the silver powder in Example 2. The loss on ignition rate of the silver powder in Example 2 is higher than that of the silver powder in Example 1. Excessive loss on ignition rate can lead to a decrease in the effective silver content of the electrode.

[0102] b. Biohmic contact resistivity test

[0103] The ohmic contact resistivity of the silver paste after sintering in Examples 1-5 and Comparative Examples 1-2 was measured using a rectangular transmission line method (TLM). Silver paste was printed according to the designed test pattern and sintered to obtain test samples of the ohmic contact resistivity. The results are shown in Table 2.

[0104] Table 2. Data of silver paste specific ohmic contact resistivity in Examples 1-5 and Comparative Examples 1-2

[0105]

[0106] As can be seen from Table 2, the specific ohmic contact resistivity in Examples 1-5 is significantly lower than that in Comparative Examples 1 and 2, while the specific ohmic contact resistivity in Comparative Example 2 is lower than that in Comparative Example 1. This shows that oxygen plasma treatment enhances interfacial reaction activity. The surface hydroxyl and carboxyl groups after oxygen plasma treatment promote silver-silicon interfacial reaction, forming a Bi2SiO5 intermediate layer and lowering the potential barrier. The contact resistance of conventional lead-containing glass powder is approximately 2.0-3.0 mΩ·cm. 2 , the present invention reduces 25%-40%.

[0107] c. Solar cell IV performance test

[0108] The IV performance test was performed on the solar cells printed with silver paste on the front side in Examples 1-5 and Comparative Examples 1-2. The results are shown in Table 3.

[0109] Table 3. Solar cell IV performance test data

[0110] Conversion efficiency η Open circuit voltage Voc Short-circuit current Jsc Fill factor FF Example 1 25.3 732 40.2 83.3 Example 2 25.1 729 40.5 83.6 Example 3 24.8 730 41.3 83.5 Example 4 26.4 736 42.7 84.2 Example 5 26.2 731 42.1 84.1 Comparative Example 1 19.2 692 38.8 79.2 Comparative Example 2 20.9 703 39.2 81.3

[0111] As can be seen from Table 3, the solar cells prepared with the silver paste in Examples 1-5 have a low specific ohmic contact resistivity on the front side of the silver paste, which improves the conversion efficiency, and the first organic carrier and the second organic carrier cooperate with each other to improve the fill factor.

[0112] Therefore, the present invention adopts the above-mentioned TOPcon battery front silver paste and its preparation method. Through glass powder modification, silver powder compounding, organic carrier staged design and additive synergy, the prepared front silver paste has the characteristics of strong ability to penetrate the passivation film, dense conductive network, high printing precision, excellent adhesion, etc., which significantly improves the photoelectric conversion efficiency and long-term reliability of the TOPcon battery.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a TOPcon battery front silver paste, characterized in that: The following steps are involved: S1, grinding and cleaning the glass powder, drying it, placing it in an oxygen plasma device, evacuating it and introducing high-purity oxygen to obtain modified glass powder; S2, mixing the first organic carrier and the silver powder and grinding them to obtain a first mixture; S3, adding the modified glass powder and additives in S1 to the first mixture in S2, and stirring evenly to obtain a second mixture; S4. Add the second organic vehicle to the second mixture in S3, grind and mix evenly to obtain the front silver paste.

2. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S1, the glass powder includes one or more of Bi2O3, P2O5, B2O3, In2O3, ZnO, CuO and TeO2.

3. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S1, the vacuum degree is 10- 3 -10- 2 Pa, the introduction rate of high-purity oxygen is 5-20 sccm, and the processing time is 5-30 min.

4. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S2, the silver powder is a mixture of submicron spherical silver powder and micron-sized spherical silver powder in a mass ratio of 2-4:6-8.

5. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S2, the mass ratio of ethyl cellulose to epoxy-polyurethane resin, organic solvent and thixotropic agent in the first organic vehicle is 1-20:60-80:1-5.

6. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S3, the additive includes one or more of gallium salt, polyvinyl pyrrolidone, titanium nanoparticles and silica microspheres.

7. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: In S4, the second organic vehicle includes an acrylic resin, an organic solvent, and a thixotropic agent in a mass ratio of 1-20:60-80:1-5.

8. The method for preparing a TOPcon battery front silver paste according to claim 7, characterized in that: The thixotropic agent includes one or more of polyamide wax, Span 80, hydrogenated castor oil, polyamide wax and cetyl alcohol.

9. The method for preparing a TOPcon battery front silver paste according to claim 1, characterized in that: The mass ratio of the silver powder, the modified glass powder, and the total mass of the first organic carrier and the second organic carrier is 80-90:1-8:5-12.

10. A front silver paste prepared according to the method for preparing a front silver paste for a TOPcon battery according to any one of claims 1 to 9.

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