Solar topcon back fine grid high double-sided rate silver paste
By adding titanate additives and multi-sized silver powder to the silver paste formulation, the printing blockage and corrosion problems of fine grid silver paste on the back of N-type TopCon batteries were solved, achieving high bifaciality and high efficiency battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU RIYU PHOTOVOLTAIC NEW MATERIAL CO LTD
- Filing Date
- 2026-05-07
- Publication Date
- 2026-06-05
AI Technical Summary
When improving the bifaciality of N-type TopCon batteries, issues such as clogged grids and grid breakage due to narrow line width printing of fine grid silver paste on the back side, and low corrosion are difficult to balance with good electrode contact, resulting in the inability to simultaneously improve bifaciality and battery efficiency.
Titanate additives are added to the silver paste formulation, and a multi-sized silver powder and special glass powder system are combined to optimize the composition of the silver paste to improve printing performance and electrode contact.
It significantly improves the aspect ratio and light transmittance of the grid lines, reduces back-side shading loss, increases the bifaciality of the cell, and simultaneously forms a low-resistance, stable ohmic contact, thereby improving photoelectric conversion efficiency.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solar cell technology, and more specifically to a high bifaciality silver paste for a fine grid on the back side of a solar TopCon solar cell. Background Technology
[0002] In recent years, with the development and application of new technologies and processes in the photovoltaic industry, TopCon, BC and HJT cells have developed rapidly in the industry. Among them, the n-type tunneling oxide passivation cell (ToPCon) has become the main development direction of high-efficiency photovoltaic cells due to its superior efficiency and lower equipment modification costs.
[0003] In the development of N-type TopCon cells, bifaciality refers to the percentage of power generation efficiency on the back side of a photovoltaic module compared to that on the front side. The higher this value, the closer the module's ability to generate electricity using reflected and scattered light is to the front side. Therefore, improving bifaciality can achieve high-efficiency power generation gains through structural optimization without increasing the cost of silicon wafers and modules, which is crucial for reducing the levelized cost of electricity (LCOE) over the entire lifecycle.
[0004] The improvement in the bifaciality of N-type TopCon batteries is achieved through two main approaches: battery structure and conductive silver paste.
[0005] The main optimization methods for the battery structure are: 1. Using the Poly Finger process to thin the Poly layer in non-grid areas reduces the absorption of infrared light, decreases parasitic absorption in this area, and improves the light transmittance on the back side, thereby improving the bifaciality; 2. Using a stacked Poly process to reduce the thickness of the Poly layer increases light transmittance and improves the bifaciality. The screen angle design employs a "narrow grid, low density" approach to reduce the electrode's obstruction of light from the back side, thus improving the bifaciality.
[0006] The main optimization methods for conductive silver paste are: 1. Organic methods: reducing the line width and grid flatness of the printed paste. However, due to the cost reduction requirements of the client, whether it is a screen printing plate or a steel plate, the opening is relatively narrow, which places high demands on the paste. It needs to have strong ink penetration, leveling and adhesion. 2. Inorganic methods: mainly optimizing the glass type to reduce corrosion of the silicon wafer poly layer and reduce carrier recombination. This places high demands on the glass in the paste. Otherwise, not only will the contact be poor, but it will also affect the bifaciality of the cell.
[0007] Of the two technical routes mentioned above, conductive silver paste has become the preferred route for technology development due to its simple preparation and ease of adjustment. However, there are still shortcomings in the existing approach to improving the back-side fine grid paste of high bifaciality TopCon: 1. In order to improve the double-sided ratio, it is necessary to reduce the grid line width. Therefore, if the total amount or molecular weight of resin in the organic carrier of the conductive paste is large and the screen opening is narrow, the screen is easy to clog the mesh during screen printing, resulting in poor screen passage and thus leading to false printing and broken grids. 2. In order to improve the bifaciality, it is necessary to reduce the corrosion of silicon wafers by the paste. Therefore, the conductive paste contains fewer corrosive elements in the glass. If the glass type and combination do not match the customer's site, the contact after sintering will be insufficient, thus affecting the battery efficiency.
[0008] Therefore, it is of great significance to provide a paste and its preparation method that has narrow linewidth, good corrosion resistance, reduced damage to silicon wafers, low carrier recombination, and is suitable for high double-sided printing of fine grids on the back side of solar TopCon.
[0009] In addition, some existing conductive silver paste products introduce titanate ester additives. For example, patent CN 114864178A discloses a UV-curable conductive silver paste and its preparation method, in which a titanate ester coupling agent with a specific structure is used as a conductive additive, which can reduce the amount of silver powder, improve the conductivity of the silver paste, and enhance the flexibility and bending resistance after curing. Patent CN116564579A discloses an HJT low-temperature conductive silver paste containing silver nanorods and its preparation method, which mentions that the coupling agent can be selected from neoalkoxytris(dioctylpyrophosphate) titanate, etc.
[0010] However, both of the aforementioned patents target low-temperature silver paste systems. Low-temperature silver pastes primarily rely on the adhesive force between additives and resins to achieve contact with the substrate. After curing, the organic solvents evaporate, and the resins and related additives form "molecular bridges" that connect the inorganic fillers through chemical reactions and remain permanently in the material. In contrast, this invention is applied to TopCon batteries and requires a high-temperature sintering process. During sintering, the organic solvents in the paste completely evaporate, and the organic components such as resins are also decomposed at high temperatures. Additives containing metal elements are decomposed at high temperatures, leaving only elemental metals (e.g., titanate additives leave only titanium elements). The final system consists only of inorganic materials such as silver powder and glass powder. The two have fundamental differences in their curing and film-forming mechanisms, therefore, the principles of the aforementioned patented technologies are significantly different from those of this invention. Summary of the Invention
[0011] Technical issues When improving the bifaciality of N-type TopCon batteries, issues such as clogged grids and grid breakage due to narrow line width printing of fine grid silver paste on the back side, and low corrosion are difficult to address while maintaining good electrode contact, resulting in the inability to simultaneously improve bifaciality and battery efficiency.
[0012] Technical solution To address the aforementioned technical problems, this invention provides a method for improving the bifaciality of TopCon batteries, wherein the method involves adding a titanate ester additive to the silver paste formulation.
[0013] Furthermore, the titanate additive includes one or more of isopropyl tris(stearoyloxy) titanate (KR-TTS), bis(dioctylpyrophosphoyloxy) ethylene titanate (KR-238S), tetraisopropyl di(dioctyl phosphite) titanate (KR-46B), and phosphite type (KR-46B).
[0014] The present invention also provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon, wherein the silver paste is composed of the following components by mass percentage: 1-5% micron-sized spherical silver powder, 80-88% submicron-sized spherical silver powder, 0.1-3% nano-sized silver powder, 1-3% glass powder, 0.5-2% organic dispersant, 1-2% thixotropic agent, 0.1-2% silicone oil, 0.5-2% organic solvent, 0.4-0.7% titanate additive, and 6-8% organic carrier.
[0015] Furthermore, the D50 particle size of the micron-sized spherical silver powder is 1.2-1.8 μm; the D50 particle size of the submicron-sized spherical silver powder is 0.8-1.3 μm; and the D50 particle size of the nano-sized silver powder is 0.5-1 μm. Grading silver powders of different particle sizes can increase the bulk density of the silver powder, thereby improving the conductivity of the paste and its contact performance with the silicon wafer.
[0016] Furthermore, the glass powder comprises the following components by mass percentage: Bi2O3 20-30wt%, Pb3O4 1-5wt%, Al2O3 10-15wt%, SiO2 20-25wt%, TeO2 1-5wt%, TiO2 10-15wt%, Li2O 10-15wt%, and B2O3 1-5wt%. This formulation of glass powder has good flowability and moderate reactivity with silicon wafers, enabling it to form good ohmic contact during sintering and improve the photoelectric conversion efficiency of the battery.
[0017] Furthermore, the organic dispersant is one or more of the following: polyphosphate ester BYK110, hexadecyl stearic acid, polycarboxylate solution of polyamine amide ANTI-TERRA-204, hydrophilic polyether polymer ED420 containing acid groups, hydrophilic polyether polymer ED120 containing acid and base groups, fatty diamine organic salt TDO, pectin, starch, and gum arabic. This type of dispersant can improve the flocculation of silver powder through steric hindrance or double-layer effect, enhance the uniformity of silver powder dispersion, reduce the viscosity of the silver paste and improve its fluidity, thereby reducing the electrode resistance of the battery.
[0018] Furthermore, the thixotropic agent is one or more of the following: Desparon 6500, Lambden ET2020, hydrogenated castor oil, fumed silica, bentonite, polyethylene wax, and THIXATROL MAX. This type of thixotropic agent can effectively improve the thixotropic properties of the paste, further optimizing the aspect ratio of the grid lines after printing.
[0019] Furthermore, the silicone oil is one or more of the following: dimethyl silicone oil Shin-Etsu KF-96-10, benzyl silicone oil Carfil® PT1, amino silicone oil MEM8031, hydroxyl silicone oil JP-H208, and alkyl-modified silicone oil KF-868. Silicone oil can improve the slip properties of the paste and enhance its printing leveling properties.
[0020] Furthermore, the organic carrier is composed of an organic solvent and an organic resin; based on the total mass of the organic carrier, the organic solvent accounts for 60-80 wt% and the organic resin accounts for 20-40 wt%.
[0021] Furthermore, the organic resin is one or a combination of several of the following: acrylic modified epoxy resin, rosin modified resin, cellulose acetate butyrate resin, and cellulose resin; the acrylic modified epoxy resin undergoes cross-linking and curing at the drying temperature, giving the slurry good adhesion to the silicon wafer; the rosin modified resin and the residual epoxy groups in the acrylic modified epoxy resin undergo ring-opening esterification under heating and curing conditions to form strong ester bonds, further improving adhesion.
[0022] Furthermore, the titanate additive includes one or more of isopropyl tris(stearoyloxy) titanate (KR-TTS), bis(dioctylpyrophosphoyloxy) ethylene titanate (KR-238S), tetraisopropyl di(dioctyl phosphite) titanate (KR-46B), and phosphite type (KR-46B).
[0023] Furthermore, the organic solvent is a mixture of at least two selected from diethylene glycol butyl ether acetate, hexadecyl alcohol ester, diethylene glycol butyl ether, dimethyl adipate, diethylene glycol ethyl ether acetate, dimethyl phthalate, and benzyl benzoate. The different solvents have different boiling points, resulting in a smoother boiling range after mixing, which helps ensure surface flatness during grid drying. Simultaneously, different solvents have different solubilities for the resin; mixing improves the resin's solubility in the solvent and also enhances the thixotropic properties of the slurry and the aspect ratio of the grid lines.
[0024] Specifically, the composition of the organic solvent, by mass parts, is as follows: 25-35 parts of diethylene glycol butyl ether acetate, 10-20 parts of dodecyl alcohol ester, 5-15 parts of dimethyl phthalate, 5-15 parts of dimethyl adipate, 1-5 parts of diethylene glycol butyl ether, and 1-5 parts of diethylene glycol ethyl ether acetate.
[0025] Specifically, the composition of the organic resin, by mass parts, is: 7-15 parts of acrylic acid modified bisphenol A epoxy resin, 7-15 parts of rosin modified resin, 2-5 parts of cellulose acetate butyrate, and 2-5 parts of ethyl cellulose.
[0026] Preferably, the ethyl cellulose is ethyl cellulose STD-4.
[0027] This invention also provides a method for preparing the high bifaciality silver paste for the back-side fine grid of a solar TopCon solar cell, comprising the following steps: (1) Preparation of organic carrier: Prepare organic solvent according to the above components, then add organic resin and stir at 500-1000 rpm for 0.5-2 hours at 50-80℃ to obtain organic carrier; (2) Preparation of premix: The organic carrier, organic dispersant, thixotropic agent, silicone oil, additives, and micron-sized spherical silver powder, submicron-sized spherical silver powder, nano-sized spherical silver powder, and glass powder are mixed and stirred. After stirring, the mixture is placed in a centrifuge and centrifuged at 1500~5000 rpm for 1~10 min. After mixing evenly, the premix is obtained. (3) Grinding and pulping: The premixed material is added to a three-roll mill for grinding. The grinding spacing is 10 μm-120 μm and the grinding speed is 100 r / min-200 r / min. When the fineness of the pulp is ≤3μm, the grinding is stopped and filtered to finally obtain the TopCon back grid silver paste.
[0028] Finally, this invention provides a high bifaciality N-type TopCon battery, the preparation method of which is as follows: The front main grid silver paste, the front fine grid paste, the back main grid silver paste, and the back fine grid silver paste are printed on the silicon wafer respectively. The back fine grid silver paste is the high bifaciality silver paste for the back fine grid of the solar TopCon. Then, high-temperature sintering and LECO laser-assisted sintering are performed to obtain the high bifaciality TopCon cell.
[0029] Furthermore, the high-temperature sintering temperature is 700~800℃.
[0030] The role of the titanate ester additive in this invention is as follows: First, the titanate ester coupling agent possesses excellent thermal oxidation stability. Its long organic chains preferentially oxidize and decompose at high temperatures, or react with the glass phase to form transparent silicates, effectively reducing carbon residue and density defects inside the electrode after sintering. This ensures that the sintered silver grid lines not only have good conductivity but also higher light transmittance, reducing the proportion of back incident light "eaten up" by the metal electrode, laying the optical foundation for high bifaciality. Second, the titanate ester coupling agent forms a dense monomolecular protective layer on the surface of silver particles at high temperatures through Ti-O-Ag bonding. This film can inhibit surface migration and excessive fusion of silver particles at high temperatures, preventing grid line collapse and widening, thereby ensuring that the electrode maintains the designed narrow width and low coverage after sintering, minimizing metal shading, and allowing back light to effectively enter the substrate. Finally, on the one hand, the titanate additive molecular structure has good chemical compatibility with the Poly-Si (polycrystalline silicon) surface on the back of the TopCon, enabling it to wet and spread on the surface of the ultrathin Poly-Si layer. On the other hand, the titanate additive promotes the flowability of glass powder (Frit) between silver particles, forming a low-resistance ohmic contact. This combined effect of soft contact and hard connection allows for the achievement of narrow grid and low light shading while maintaining excellent contact resistance and fill factor (FF). This ensures that the charge carriers generated after light incident on the substrate can be efficiently collected, achieving a high bifaciality of the solar cell.
[0031] Beneficial effects This invention effectively solves the problems of screen clogging, false printing, and broken grids in narrow-linewidth printing by adding specific titanate additives to the silver paste for the fine grid on the back of a solar TopCon solar cell, combined with multi-level silver powder gradation and a special glass powder system. It also reduces corrosion and carrier recombination on the poly layer of the silicon wafer. It can significantly improve the aspect ratio and light transmittance of the grid lines, reduce back-side shading loss, greatly increase the bifaciality of the cell, and form a low-resistance, stable ohmic contact, thereby simultaneously improving the photoelectric conversion efficiency of the cell. The silver paste formulation of this invention is easy to adjust, compatible with existing sintering processes, has excellent overall performance, and is suitable for industrial applications. Detailed Implementation
[0032] The following detailed description, in conjunction with specific embodiments and comparative examples, illustrates a high bifaciality silver paste for the back-side fine grid of a solar TopCon solar cell and its preparation method. The present invention is not limited to the following embodiments.
[0033] Source of raw materials Acrylic modified epoxy resin EBECREL 3702 was purchased from Zhanxin New Materials Co., Ltd.; rosin modified resin SZ8205 was purchased from Yoshida Chemical Co., Ltd.; cellulose acetate butyrate CAB-551-0.01 was purchased from Eastman Group Corporation; isopropyl tris(dioctyl pyrophosphate) titanate additive KR-46B was purchased from Kenridge Petrochemicals, Inc.; and ethyl cellulose STD-4 was purchased from Dow Chemical Company, Inc.
[0034] Example 1 This embodiment provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon, the composition of which by weight percentage is as follows: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 1% organic solvent, and 6.4% organic carrier.
[0035] The micron-sized spherical silver powder has a D50 particle size of 1.2-1.8 μm; the submicron-sized spherical silver powder has a D50 particle size of 0.8-1.3 μm; and the nano-sized spherical silver powder has a D50 particle size of 0.5-1 μm. The glass powder comprises the following mass percentages: 27 wt% Bi₂O₃, 5 wt% Pb₃O₄, 12 wt% Al₂O₃, 23 wt% SiO₂, 4 wt% TeO₂, 13 wt% TiO₂, 13 wt% Li₂O, and 3 wt% B₂O₃.
[0036] The organic dispersant accounts for 0.5% by weight in the slurry, specifically ED420.
[0037] The thixotropic agent accounts for 1% of the mass of the slurry, specifically the blueprint ET2020.
[0038] The silicone oil accounts for 0.6% of the mass of the slurry, specifically a dimethyl silicone oil with a viscosity of 50 mPa·s.
[0039] The organic solvent accounts for 1% of the mass of the slurry, specifically diethylene glycol butyl ether acetate.
[0040] The organic carrier accounts for 6.4% of the slurry by weight and mainly consists of resin and solvent. The organic carrier is prepared by mixing, heating, stirring, and cooking at 80°C for 1 hour. The resin accounts for 29% of the carrier by weight. The resin components in the organic carrier are: 12% acrylic-modified epoxy resin, 10% rosin-modified resin, 5% cellulose acetate butyrate, and 2% ethyl cellulose STD-4. The solvent accounts for 71% of the organic carrier by weight, specifically: 30% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 10% dimethyl phthalate, 10% dimethyl adipate, 3% diethylene glycol butyl ether, and 3% diethylene glycol ethyl ether acetate.
[0041] Table 1
[0042] Preparation method: Organic carrier, organic dispersant, thixotropic agent, silicone oil, organic solvent, and micron-sized spherical silver powder, submicron-sized spherical silver powder, nano-sized spherical silver powder, and glass powder were added to a mixing tank and mixed. After mixing, the mixture was placed in a centrifuge and centrifuged at 1500 rpm for 3 min to obtain a premix. Then, the premix was added to a three-roll mill for grinding. The grinding spacing was 10μm-120μm, and the grinding speed was 100 r / min-200 r / min. After multiple grindings, the fineness of the slurry was measured using a FOG scraper fineness meter. When the fineness of the slurry was ≤3 μm, grinding was stopped and the paste was filtered to obtain a high bifaciality silver paste for the back grid of solar TopCon.
[0043] Performance Testing: The conversion efficiency of the prepared back fine silver paste was tested. It was used as a second paste and screen-printed onto a silicon wafer along with the other three pastes. The first and third pastes used Nichisho Commercial main grid paste, and the fourth paste used Nichisho Commercial front fine grid paste. After printing, high-temperature sintering (700℃) was performed, followed by the LECO process to obtain TopCon solar cells. The photoelectric conversion efficiency of the front and back sides of the solar cells was tested using a Halm IV testing machine, and the bifaciality was calculated using the formula: Bifaciality = Front efficiency / Back efficiency * 100%.
[0044] Example 2 This embodiment provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon, the composition of which by weight percentage is as follows: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 0.6% organic solvent, 0.4% titanate additive, and 6.4% organic carrier.
[0045] The micron-sized spherical silver powder has a D50 particle size of 1.2-1.8 μm; the submicron-sized spherical silver powder has a D50 particle size of 0.8-1.3 μm; and the nano-sized spherical silver powder has a D50 particle size of 0.5-1 μm. The glass powder comprises the following mass percentages: 27 wt% Bi₂O₃, 5 wt% Pb₃O₄, 12 wt% Al₂O₃, 23 wt% SiO₂, 4 wt% TeO₂, 13 wt% TiO₂, 13 wt% Li₂O, and 3 wt% B₂O₃.
[0046] The organic dispersant accounts for 0.5% by weight in the slurry, specifically ED420.
[0047] The thixotropic agent accounts for 1% of the mass of the slurry, specifically the blueprint ET2020.
[0048] The silicone oil accounts for 0.6% of the mass of the slurry, specifically a dimethyl silicone oil with a viscosity of 50 mPa·s.
[0049] The organic solvent accounts for 0.6% of the mass of the slurry, specifically diethylene glycol butyl ether acetate.
[0050] The titanate additive accounts for 0.4% of the mass of the slurry, specifically the titanate type KR-46B.
[0051] The organic carrier accounts for 6.4% of the slurry by weight and mainly consists of resin and solvent. The organic carrier is prepared by mixing, heating, stirring, and cooking at 80°C for 1 hour. The resin accounts for 29% of the carrier by weight. The resin components in the organic carrier are: 12% acrylic-modified epoxy resin, 10% rosin-modified resin, 5% cellulose acetate butyrate, and 2% ethyl cellulose STD-4. The solvent accounts for 71% of the organic carrier by weight, specifically: 30% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 10% dimethyl phthalate, 10% dimethyl adipate, 3% diethylene glycol butyl ether, and 3% diethylene glycol ethyl ether acetate.
[0052] The preparation method and performance testing are the same as in Example 1.
[0053] Example 3 This embodiment provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon, the composition of which by weight percentage is as follows: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 0.3% organic solvent, 0.7% titanate additive, and 6.4% organic carrier.
[0054] The micron-sized spherical silver powder has a D50 particle size of 1.2-1.8 μm; the submicron-sized spherical silver powder has a D50 particle size of 0.8-1.3 μm; and the nano-sized spherical silver powder has a D50 particle size of 0.5-1 μm. The glass powder comprises the following mass percentages: 27 wt% Bi₂O₃, 5 wt% Pb₃O₄, 12 wt% Al₂O₃, 23 wt% SiO₂, 4 wt% TeO₂, 13 wt% TiO₂, 13 wt% Li₂O, and 3 wt% B₂O₃.
[0055] The organic dispersant accounts for 0.5% by weight in the slurry, specifically ED420.
[0056] The thixotropic agent accounts for 1% of the mass of the slurry, specifically the blueprint ET2020.
[0057] The silicone oil accounts for 0.6% of the mass of the slurry, specifically a dimethyl silicone oil with a viscosity of 50 mPa·s.
[0058] The organic solvent accounts for 0.3% of the mass of the slurry, specifically diethylene glycol butyl ether acetate.
[0059] The titanate additive accounts for 0.7% of the mass of the slurry, specifically the titanate type KR-46B.
[0060] The organic carrier accounts for 6.4% of the slurry by weight and mainly consists of resin and solvent. The organic carrier is prepared by mixing, heating, stirring, and cooking at 80°C for 1 hour. The resin accounts for 29% of the carrier by weight. The resin components in the organic carrier are: 12% acrylic-modified epoxy resin, 10% rosin-modified resin, 5% cellulose acetate butyrate, and 2% ethyl cellulose STD-4. The solvent accounts for 71% of the organic carrier by weight, specifically: 30% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 10% dimethyl phthalate, 10% dimethyl adipate, 3% diethylene glycol butyl ether, and 3% diethylene glycol ethyl ether acetate.
[0061] The preparation method and performance testing are the same as in Example 1.
[0062] Example 4 This embodiment provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon solar panel, the composition of which by weight percentage is as follows: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 1% titanate additive, and 6.4% organic carrier.
[0063] The micron-sized spherical silver powder has a D50 particle size of 1.2-1.8 μm; the submicron-sized spherical silver powder has a D50 particle size of 0.8-1.3 μm; and the nano-sized spherical silver powder has a D50 particle size of 0.5-1 μm. The glass powder comprises the following mass percentages: 27 wt% Bi₂O₃, 5 wt% Pb₃O₄, 12 wt% Al₂O₃, 23 wt% SiO₂, 4 wt% TeO₂, 13 wt% TiO₂, 13 wt% Li₂O, and 3 wt% B₂O₃.
[0064] The organic dispersant accounts for 0.5% by weight in the slurry, specifically ED420.
[0065] The thixotropic agent accounts for 1% of the mass of the slurry, specifically the blueprint ET2020.
[0066] The silicone oil accounts for 0.6% of the mass of the slurry, specifically a dimethyl silicone oil with a viscosity of 50 mPa·s.
[0067] The titanate additive accounts for 1% of the mass of the slurry, specifically the titanate type KR-46B.
[0068] The organic carrier accounts for 6.4% of the slurry by weight and mainly consists of resin and solvent. The organic carrier is prepared by mixing, heating, stirring, and cooking at 80°C for 1 hour. The resin accounts for 29% of the carrier by weight. The resin components in the organic carrier are: 12% acrylic-modified epoxy resin, 10% rosin-modified resin, 5% cellulose acetate butyrate, and 2% ethyl cellulose STD-4. The solvent accounts for 71% of the organic carrier by weight, specifically: 30% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 10% dimethyl phthalate, 10% dimethyl adipate, 3% diethylene glycol butyl ether, and 3% diethylene glycol ethyl ether acetate.
[0069] The preparation method and performance testing are the same as in Example 1.
[0070] Example 5 This embodiment provides a high bifaciality silver paste for the back-side fine grid of a solar TopCon, the composition of which by weight percentage is as follows: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 0.6% organic solvent, 0.4% titanate additive, and 6.4% organic carrier.
[0071] The micron-sized spherical silver powder has a D50 particle size of 1.2-1.8 μm; the submicron-sized spherical silver powder has a D50 particle size of 0.8-1.3 μm; and the nano-sized spherical silver powder has a D50 particle size of 0.5-1 μm. The glass powder comprises the following mass percentages: 27 wt% Bi₂O₃, 5 wt% Pb₃O₄, 12 wt% Al₂O₃, 23 wt% SiO₂, 4 wt% TeO₂, 13 wt% TiO₂, 13 wt% Li₂O, and 3 wt% B₂O₃.
[0072] The organic dispersant accounts for 0.5% by weight in the slurry, specifically ED420.
[0073] The thixotropic agent accounts for 1% of the mass of the slurry, specifically the blueprint ET2020.
[0074] The silicone oil accounts for 0.4% of the mass of the slurry, specifically a dimethyl silicone oil with a viscosity of 50 mPa·s.
[0075] The organic solvent accounts for 0.6% of the mass of the slurry, specifically diethylene glycol butyl ether acetic acid.
[0076] The titanate additive accounts for 0.4% of the mass of the slurry, specifically the titanate type KR-46B.
[0077] The organic carrier accounts for 6.4% of the slurry by weight and mainly consists of resin and solvent. The organic carrier is prepared by mixing, heating, stirring, and cooking at 80°C for 1 hour. The resin accounts for 29% of the carrier by weight. The resin components in the organic carrier are: 12% acrylic-modified epoxy resin, 10% rosin-modified resin, 5% cellulose acetate butyrate, and 2% ethyl cellulose STD-100. The solvent accounts for 71% of the organic carrier by weight, specifically: 30% diethylene glycol butyl ether acetate, 15% dodecyl alcohol ester, 10% dimethyl phthalate, 10% dimethyl adipate, 3% diethylene glycol butyl ether, and 3% diethylene glycol ethyl ether acetate.
[0078] The preparation method and performance testing are the same as in Example 1.
[0079] Comparative Example 1 The commonly available TopCon back-side fine-grid conductive silver paste, model TPRY02, has the following components by weight percentage: 3% micron-sized spherical silver powder, 84.7% submicron-sized spherical silver powder, 0.5% nano-sized silver powder, 2.5% glass powder, 0.5% organic dispersant, 1.0% thixotropic agent, 0.4% silicone oil, 0.6% organic solvent, and 6.8% organic carrier. This paste system does not contain titanate additives.
[0080] The performance test was the same as in Example 1.
[0081] Test Results The comparison of paste viscosity, aspect ratio, and printing status is shown in Table 2 below: Table 2
[0082] Battery performance comparison is shown in Table 3 below: Table 3
[0083] The data in the table above shows that Example 2 improved by 0.2% compared to Comparative Example 1, which is a significant improvement. Example 3 has a viscosity comparable to Comparative Example 1, exhibits good printing performance under narrow linewidths, has a certain advantage in aspect ratio, and demonstrates better double-sided performance. While Examples 4 and 5 have better aspect ratios, their printing performance under narrow linewidths is poor, prone to incomplete printing and broken lines. This is mainly due to excessive addition of titanate, leading to a decrease in the paste's screen transfer properties. Example 5 also shows improvement due to the use of STD resin. 100 Replace STD 4. This further increases the viscosity of the slurry, making it less able to pass through the screen, exacerbating the problem of false printing and broken grids, and ultimately causing a decrease in the double-sided ratio.
[0084] In summary, the high bifaciality silver paste for TopCon back-side fine gate prepared in Example 3 has excellent comprehensive performance in terms of conductivity, printability and bifaciality conversion efficiency, and can meet the current market mainstream TopCon back-side fine gate's high bifaciality requirements.
[0085] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.
Claims
1. A high bifaciality silver paste for the back-side grid of a solar TopCon solar panel, characterized in that, The silver paste is composed of the following components by mass percentage: 1-5% micron-sized spherical silver powder, 80-88% submicron-sized spherical silver powder, 0.1-3% nano-sized silver powder, 1-3% glass powder, 0.5-2% organic dispersant, 1-2% thixotropic agent, 0.1-2% silicone oil, 0.5-2% organic solvent, 0.4-0.7% titanate additive, and 6-8% organic carrier; The titanate additive is one or more of isopropyl tris(stearoyloxy) titanate, bis(dioctylpyrophosphoyloxy) ethylene titanate, tetraisopropyl di(dioctyl phosphite) titanate, and phosphite type.
2. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The D50 particle size of the micron-sized spherical silver powder is 1.2-1.8 μm; the D50 particle size of the submicron-sized spherical silver powder is 0.8-1.3 μm; and the D50 particle size of the nano-sized silver powder is 0.5-1 μm.
3. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The glass powder comprises the following components by mass percentage: Bi2O3 20-30wt%, Pb3O4 1-5wt%, Al2O3 10-15wt%, SiO2 20-25wt%, TeO2 1-5wt%, TiO2 10-15wt%, Li2O 10-15wt%, and B2O3 1-5wt%.
4. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The organic dispersant includes one or more of the following: polyphosphate ester, hexadecyl stearic acid, polycarboxylate solution of polyamine amide, hydrophilic polyether polymer containing acid groups, hydrophilic polyether polymer containing acid and base groups, fatty diamine organic salts, pectin, starch, and gum arabic.
5. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The thixotropic agent is one or more of the following: DISPARON 6500, LAND ET2020, hydrogenated castor oil, fumed silica, bentonite, polyethylene wax, and THIXATROL MAX.
6. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The silicone oil is one or more of the following: dimethyl silicone oil Shin-Etsu KF-96-10, benzyl silicone oil Carfil® PT1, amino silicone oil MEM8031, hydroxyl silicone oil JP-H208, and alkyl-modified silicone oil KF-868.
7. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 1, characterized in that, The organic carrier is composed of an organic solvent and an organic resin; based on the total mass of the organic carrier, the organic solvent accounts for 60-80 wt% and the organic resin accounts for 20-40 wt%. The organic resin is one or a combination of several of the following: acrylic modified epoxy resin, rosin modified resin, cellulose acetate butyrate resin, and cellulose resin; the organic solvent is a mixture of at least two of the following: diethylene glycol butyl ether acetate, hexadecyl alcohol ester, diethylene glycol butyl ether, dimethyl adipate, diethylene glycol ethyl ether acetate, dimethyl phthalate, and benzyl benzoate.
8. The high bifaciality silver paste for the back-side fine grid of a solar TopCon as described in claim 7, characterized in that, The composition of the organic solvent, by mass parts, is: 25-35 parts diethylene glycol butyl ether acetate, 10-20 parts dodecyl alcohol ester, 5-15 parts dimethyl phthalate, 5-15 parts dimethyl adipate, 1-5 parts diethylene glycol butyl ether, and 1-5 parts diethylene glycol ethyl ether acetate; the composition of the organic resin, by mass parts, is: 7-15 parts acrylic acid modified bisphenol A epoxy resin, 7-15 parts rosin modified resin, 2-5 parts cellulose acetate butyrate, and 2-5 parts ethyl cellulose.
9. A high bifaciality N-type TopCon battery, characterized in that, The method for preparing the N-type TopCon battery is as follows: Front main grid silver paste, front fine grid paste, back main grid silver paste and back fine grid silver paste are printed on the silicon wafer respectively, wherein the back fine grid silver paste is the high bifaciality silver paste for back fine grid of solar TopCon according to any one of claims 1 to 8, and then high temperature sintering and LECO laser-assisted sintering are performed to obtain a high bifaciality TopCon cell; the high temperature sintering temperature is 700~800℃.