Photovoltaic front silver paste, preparation method thereof, front electrode and solar cell

Abstract

The invention discloses photovoltaic front silver paste and a preparation method thereof, a front electrode and a solar cell, and the photovoltaic front silver paste comprises the following components in percentage by weight: 85-90% of silver powder, 2.3-2.8% of glass powder and 6.5-10.0% of organic carrier, wherein the organic carrier comprises resin, a carbon nano tube and a solvent, the content of the resin in the silver paste is 0.6%-1.3%, the content of the carbon nano tube in the silver paste is 0.05%-0.3%, and the content of the solvent in the silver paste is 5.5%-6.5%. The printing performance of the silver paste and the photoelectric conversion efficiency of the solar cell are improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a photovoltaic front-side silver paste and its preparation method, a front-side electrode, and a solar cell. Background Technology

[0002] As the core device for converting light energy into electrical energy, the photoelectric conversion efficiency of solar cells directly determines the power generation capacity of photovoltaic systems, while cost affects the widespread adoption of their large-scale applications. In the manufacturing process of solar cells (especially crystalline silicon solar cells), the photovoltaic front-side silver paste is a key functional material for achieving efficient collection and extraction of photogenerated carriers. Its performance not only directly relates to the cell's conductivity but also has a decisive impact on the adaptability of printing processes, the stability of electrode structures, and long-term reliability. Therefore, it has become one of the core breakthrough directions for improving cell conversion efficiency and reducing manufacturing costs.

[0003] To improve the conversion efficiency and reduce the cost of solar cells, higher requirements are placed on the performance of photovoltaic front-side silver paste. As a crucial component of silver paste, the performance of the high-printability carrier directly affects the printing quality of the silver paste and the performance of the cell. A high-printability carrier can improve the rheological properties, thixotropic properties, and viscosity stability of the silver paste, allowing it to pass through the screen better during printing and forming grid lines with a good aspect ratio after sintering, thereby improving the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a photovoltaic front-side silver paste and its preparation method, front-side electrode, and solar cell, thereby improving the printing performance of the silver paste and the photoelectric conversion efficiency of the solar cell.

[0005] This invention provides a photovoltaic front-side silver paste, wherein, based on the total weight of the silver paste (100%), the weight percentage of each component is as follows: silver powder 85%-90%, glass powder 2.3%-2.8%, and organic carrier 6.5%-10.0%; wherein, the organic carrier includes resin, carbon nanotubes, and solvent, the content of the resin in the silver paste is 0.6%-1.3%, the content of the carbon nanotubes in the silver paste is 0.05%-0.3%, and the content of the solvent in the silver paste is 5.5%-6.5%.

[0006] In one embodiment, the resin includes an elastomer resin and a continuous resin, wherein the content of the elastomer resin in the silver paste is 0.5%-1.3%, and the content of the continuous resin in the silver paste is 0-0.2%.

[0007] In one embodiment, the organic carrier includes a first type of organic carrier and / or a second type of organic carrier; In the first type of organic carrier, the resin is an elastomeric resin, and the content of the elastomeric resin in the silver paste is 1.1%-1.3%; In the second type of organic carrier, the resin is an elastomer resin and a continuous resin, wherein the content of the elastomer resin in the silver paste is 0.5%-0.7%, and the content of the continuous resin in the silver paste is 0.1%-0.2%.

[0008] In one embodiment, the organic carrier includes a first type of organic carrier and a second type of organic carrier, wherein the mass ratio of the first type of organic carrier to the second type of organic carrier is 1:3-3:1.

[0009] In one embodiment, the elastomer resin comprises a styrene-ethylene-propylene-styrene block copolymer.

[0010] In one embodiment, the continuous resin includes one or more of ethyl cellulose, acrylic resin, hydroxypropyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, and methacrylic resin.

[0011] In one embodiment, the solvent includes one or more of the following: ethylene glycol dodecyl acetate, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, ethylene glycol hexadecyl acetate, diethylene glycol monobutyl ether, butyl carbitol acetate, dimethyl phthalate, propylene glycol phenyl ether acetate, tripropylene glycol monomethyl ether, dimethyl adipate, benzyl benzoate, butyl benzyl phthalate, and tripropylene glycol monobutyl ether.

[0012] In one embodiment, the organic carrier further includes silicone oil, a thixotropic agent, and a dispersant. The thixotropic agent includes one or more of hydrogenated castor oil, polyamide wax, polyethylene wax, polyvinyl alcohol, polyacrylate, and polydiurea. The dispersant includes one or more of polydimethylsiloxane, oleic acid, stearic acid, silicone ether, polyvinylpyrrolidone, and silicates.

[0013] This invention also provides a method for preparing the above-mentioned photovoltaic front-side silver paste, comprising the following steps: Preparation of organic carrier: Weigh the raw materials for the organic carrier according to the set ratio, first mix carbon nanotubes and solvent to obtain a uniform carbon nanotube dispersion, and then mix the carbon nanotube dispersion and resin evenly to obtain the organic carrier. Preparation of silver paste: Add silver powder and glass powder to the prepared organic carrier according to the mass ratio, and mix and stir evenly to obtain the desired silver paste.

[0014] The present invention also provides a front electrode, which is obtained by sintering the photovoltaic front silver paste described above.

[0015] The present invention also provides a solar cell comprising a front electrode as described above.

[0016] The beneficial effects of this invention are as follows: Introducing carbon nanotubes (MWCNTs) into the front-side silver paste of photovoltaic cells can synergistically work with silver powder to increase the conductive pathway and improve the photoelectric conversion efficiency of photovoltaic cells; MWCNTs interact with resin and solvent to form a more stable structure, further enhancing the stability of the silver paste; MWCNTs have a large specific surface area, which can form strong chemical bonds and physical adsorption with silicon wafers, thereby improving the adhesion between the front-side silver paste and the silicon wafer, which helps to reduce the problem of gate detachment. Attached Figure Description

[0017] Figure 1 This is a TEM image of the MWCNTs of the present invention. Detailed Implementation

[0018] 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.

[0019] This invention provides a photovoltaic front-side silver paste. Based on the total weight of the silver paste (100%), the weight percentages of each component are: silver powder 85%-90%, glass powder 2.3%-2.8%, and organic carrier 6.5%-10.0%. The organic carrier includes resin, carbon nanotubes (CNTs), and solvent. The resin content in the silver paste is 0.6%-1.3%, the CNT content is 0.05%-0.3%, and the solvent content is 5.5%-6.5%. This invention introduces multi-wavelength carbon nanotubes (MWCNTs) into the photovoltaic front-side silver paste, which can synergistically work with silver powder to increase the conductive pathway and improve the photoelectric conversion efficiency of the photovoltaic cell. The interaction between MWCNTs and the resin and solvent forms a more stable structure, further enhancing the stability of the silver paste. MWCNTs have a large specific surface area, allowing them to form strong chemical bonds and physical adsorption with the silicon wafer, thereby improving the adhesion between the front-side silver paste and the silicon wafer, which helps reduce the problem of grid detachment. Thus, carbon nanotubes fully utilize their superior properties, solving problems such as printed grid breaks, dispersed grid breaks, and insufficient contact in photovoltaic front-side silver paste, significantly improving the printing performance of silver paste and the photoelectric conversion efficiency of solar cells. In this application, carbon nanotubes (MWCNTs, model TNSM7) were purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences, with a purity of 98%, a length of 0.5-2 μm, and a specific surface area of ​​80 m². 2 / g (TEM image of MWCNTs as shown) Figure 1 (As shown).

[0020] In the silver paste: silver powder can be 85%, 86%, 87%, 88%, 89%, or 90%; glass powder can be 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, or 2.8%; organic carrier can be 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, or 10.0%; furthermore, resin can be 0.6%, 0.8%, 1%, 1.2%, or 1.3%; carbon nanotubes can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%; and solvent can be 5.5%, 5.7%, 5.9%, 6.1%, 6.3%, or 6.5%. These are not listed individually here.

[0021] Furthermore, the silver powder is spherical, and the particle size D50 of the silver powder is 0.8-1.5μm.

[0022] Furthermore, the resin includes elastomer resin and continuous resin. The content of elastomer resin in the silver paste is 0.5%-1.3%, which can be 0.5%, 0.7%, 0.9%, 1.1%, or 1.3%. The content of continuous resin in the silver paste is 0%-0.2%, which can be 0%, 0.05%, 0.1%, 0.15%, or 0.2%.

[0023] In one embodiment, the organic carrier includes a first type of organic carrier and / or a second type of organic carrier; In the first type of organic carrier, the resin is an elastomer resin, and the content of the elastomer resin in the silver paste is 1.1%-1.3%, which can be selected as 1.1%, 1.15%, 1.2%, 1.25%, or 1.3%. In the second type of organic carrier, the resin is an elastomer resin and a continuous resin. The content of the elastomer resin in the silver paste is 0.5%-0.7%, and can be selected from 0.5%, 0.55%, 0.6%, 0.65%, and 0.7%. The content of the continuous resin in the silver paste is 0.1%-0.2%, and can be selected from 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, and 0.2%.

[0024] In this embodiment, the organic carrier is selected from either the first type of organic carrier or the second type of organic carrier, or a mixture of the first type of organic carrier and the second type of organic carrier.

[0025] The first type of organic carrier has a high proportion of elastomer resin (1.1%-1.3%), which makes the molecular chain contain a large number of flexible segments, forming high elasticity and flexibility. This gives the organic carrier high elasticity and flexibility, and after the slurry is sintered, it can buffer the stress caused by the difference in thermal expansion coefficient between the silver electrode and the silicon wafer, reduce the risk of grid breakage, and improve printing stability.

[0026] The second type of organic carrier has a lower proportion of elastomeric resin (0.5%-0.7%), while increasing the proportion of continuous resin. The high proportion of continuous resin helps to assist silver powder particles in forming a more complete conductive path, which is beneficial to reducing grid line resistance. It can also thicken and stabilize the paste, ensuring that the paste has good viscosity stability and printability, preventing sedimentation, and assisting in adjusting the paste properties to improve printing stability. The prepared silver paste has more stable printing performance, higher line clarity, and is more suitable for manufacturing high-precision grid lines. The combination of the first type of organic carrier (highly elastic resin) and the second type of organic carrier (highly continuous resin) achieves complementary performance and synergistic effects, balancing the advantages and disadvantages of both materials. This ensures stability during slurry processing and imparts excellent mechanical properties to the sintered electrode, ultimately resulting in a leap in the overall performance of the material. The characteristics of the slurry can be precisely adjusted according to specific performance requirements (such as whether flexibility or printability is emphasized), enabling customized production.

[0027] In one embodiment, the organic carrier includes a first type of organic carrier and a second type of organic carrier, and the mass ratio of the first type of organic carrier to the second type of organic carrier is 1:3-3:1.

[0028] In one embodiment, the elastomer resin comprises a styrene-ethylene-propylene-styrene block copolymer.

[0029] In one embodiment, the continuous resin includes one or more of ethyl cellulose, acrylic resin, hydroxypropyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, and methacrylic resin.

[0030] In one embodiment, the solvent includes one or more of the following: ethylene glycol dodecyl acetate, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, ethylene glycol hexadecyl acetate, diethylene glycol monobutyl ether, butyl carbitol acetate, dimethyl phthalate, propylene glycol phenyl ether acetate, tripropylene glycol monomethyl ether, dimethyl adipate, benzyl benzoate, butyl benzyl phthalate, and tripropylene glycol monobutyl ether.

[0031] In one embodiment, the organic carrier further includes silicone oil, a thixotropic agent, and a dispersant. The thixotropic agent includes one or more of hydrogenated castor oil, polyamide wax, polyethylene wax, polyvinyl alcohol, polyacrylate, and polydiurea. The dispersant includes one or more of polydimethylsiloxane, oleic acid, stearic acid, silicone ether, polyvinylpyrrolidone, and silicates. The content of the thixotropic agent in the silver paste is 0%-0.6%, preferably 0.3%-0.6%; the content of the dispersant in the silver paste is 0%-0.8%, preferably 0.1%-0.3%; and the content of the silicone oil in the silver paste is 0%-0.8%, preferably 0.5%-0.8%.

[0032] In one embodiment, the glass powder is a PbO-B2O3-SiO2-Bi2O3-Al2O3-FeO-TiO2-ZnO system, with the following content by mass percentage: PbO content 33%-35%, B2O3 content 10%-11%, SiO2 content 3%-5%, Bi2O3 content 30%-32%, Al2O3 content 10%-13%, FeO content 4%-6%, TiO2 content 2%-3%, and ZnO content 2%; the particle size D50 is 0.8μm-1.3μm.

[0033] This invention also provides a method for preparing the above-mentioned photovoltaic front-side silver paste, comprising the following steps: Preparation of organic carrier: Weigh the raw materials for the organic carrier according to the set ratio, first mix carbon nanotubes and solvent to obtain a uniform carbon nanotube dispersion, and then mix the carbon nanotube dispersion and resin evenly to obtain the organic carrier. Preparation of silver paste: Add silver powder and glass powder to the prepared organic carrier according to the mass ratio, and mix and stir evenly to obtain the desired silver paste.

[0034] When carbon nanotubes and solvents are mixed to form a carbon nanotube dispersion, MWCNTs can be ultrasonically dispersed in diethylene glycol butyl ether acetate (under ultrasonic conditions of 40 kHz frequency and 80 W power for 30 min) to obtain a uniform MWCNTs dispersion. The dispersion is then mixed uniformly with other solvents, silver powder and glass powder to obtain the desired silver paste.

[0035] The present invention also provides a front electrode, which is obtained by sintering the photovoltaic front silver paste described above.

[0036] The present invention also provides a solar cell comprising a front electrode as described above.

[0037] The beneficial effects of this invention are: (1) This invention introduces one-dimensional MWCNTs materials into a solvent. By mixing and combining them with different resins, MWCNTs can work synergistically with thixotropic agents and resins to adjust the rheological properties of the carrier, giving it more suitable viscosity and thixotropy. During the screen printing process, these optimized rheological properties can ensure that the carrier is transferred quickly and smoothly from the screen to the silicon wafer surface, effectively solving the problem of difficult screen removal, while reducing the occurrence of printing defects such as incomplete printing and broken grids.

[0038] (2) MWCNTs possess excellent electrical properties. Introducing them into an organic carrier can significantly improve the conductivity of the carrier, thereby reducing the grid resistance formed by printing silver paste on the front side of the photovoltaic cell. Furthermore, the network structure formed by MWCNTs within the carrier enhances the bonding force between the carrier and the silver powder particles, allowing the silver paste to better maintain the grid shape during printing, reducing deformation and collapse, and improving printing accuracy. This helps improve the carrier transport efficiency of the solar cell and enhances its photoelectric conversion efficiency.

[0039] (3) Dispersants can effectively disperse silver powder and prevent particle agglomeration. Their introduction can also adjust the viscosity of silver paste, making the silver paste have more suitable fluidity during the printing process. It is neither too viscous to pass through the printing screen, nor too thin to cause the grid lines to be too low. This helps to improve the overall fluidity consistency of the paste, which is beneficial to forming a tighter conductive network and comprehensively improving the electrical properties of the silver paste.

[0040] (4) The combination of the first type of organic carrier (high elastomer resin) and the second type of organic carrier (high continuity resin) can balance the advantages and disadvantages of the two materials through complementary performance and synergistic effect, and finally achieve a leap in the comprehensive performance of the materials.

[0041] The preparation method of photovoltaic front-side silver paste includes the following steps: (1) Weighing various raw materials: Weigh the raw materials, glass powder and silver powder used for the organic carrier according to the set ratio; (2) Preparation of organic carriers; The first type of organic carrier includes: 1.1%-1.3% styrene-ethylene-propylene-styrene block copolymer (Kerteng G1701), 2.5%-3.0% diethylene glycol butyl ether acetate, 0.05%-0.3% MWCNTs, 1.0%-1.2% benzyl benzoate, 0.4%-0.6% dodecyl alcohol ester, 0.2%-0.4% diethylene glycol dibutyl ether, 0.4%-0.6% butyl benzyl phthalate, 0.2%-0.4% tripropylene glycol monobutyl ether, 0.3%-0.5% polyamide wax, 0.5%-0.8% silicone oil (100cst silicone oil, 50cst silicone oil), and 0.1%-0.2% silicone ether; Preparation of the first type of organic carrier: First, MWCNTs were ultrasonically dispersed in diethylene glycol butyl ether acetate (under ultrasonic conditions of 40 kHz frequency and 80 W power for 30 min) to obtain a uniform MWCNTs dispersion; then, the dispersion was mixed with the other substances mentioned above and stirred evenly to obtain the first type of organic carrier.

[0042] The second type of organic carrier includes: 0.5%-0.7% styrene-ethylene-propylene-styrene block copolymer (Kreteng G1701), 0.04%-0.08% polyvinyl butyral (Kuraray B30H), 0.04%-0.08% ethyl cellulose (Dow Std-10), and 0.02%-0.04% methacrylic acid resin (NeoCryl). B725), 2.8%-3.2% diethylene glycol butyl ether acetate, 0.05%-0.3% MWCNTs, 1.0%-1.2% propylene glycol phenyl ether acetate, 0.5%-0.7% hexadecyl alcohol ester, 0.4%-0.6% diethylene glycol dibutyl ether, 0.6%-0.8% dimethyl phthalate, 0.1%-0.3% tripropylene glycol monobutyl ether, 0.3%-0.6% polyamide wax, 0.5%-0.8% silicone oil (50cst), and 0.1%-0.3% silicone ether; Preparation of the second type of organic carrier: First, MWCNTs were ultrasonically dispersed in diethylene glycol butyl ether acetate (under ultrasonic conditions of 40 kHz frequency and 80 W power for 30 min) to obtain a uniform MWCNTs dispersion; then, the dispersion was mixed with the other substances mentioned above and stirred evenly to obtain the second type of organic carrier.

[0043] (2) Mixing: Add silver powder (85%-90%) and glass powder (2.3%-2.8%) to the first type of organic carrier and / or the second type of organic carrier prepared above in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain the photovoltaic front silver paste.

[0044] The following examples and comparative examples provide further illustration.

[0045] Example 1 (1) A first type of organic carrier was prepared according to the above preparation method, which includes: 1.2% styrene-ethylene-propylene-styrene block copolymer (Kerteng G1701), 2.65% diethylene glycol butyl ether acetate, 0.05% MWCNTs, 1.2% benzyl benzoate, 0.6% dodecyl alcohol ester, 0.3% diethylene glycol dibutyl ether, 0.6% butyl benzyl phthalate, 0.4% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (0.4% 100cst silicone oil, 0.3% 50cst silicone oil), and 0.2% silicone ether; (2) Mixing: Silver powder (89.0%) and glass powder (2.6%) were added to the first type of organic carrier and stirred at room temperature. After the silver powder and glass powder were completely impregnated, the mixture was dispersed using a three-roll mill (6 times). Each dispersion required rolling the slurry at least twice to obtain photovoltaic front-side silver paste containing MWCNTs. The glass powder, based on 100% of the total weight, had the following content: PbO 34%, B2O3 10%, SiO2 4%, Bi2O3 30%, Al2O3 11%, FeO 6%, TiO2 3%, and ZnO 2%.

[0046] Example 2 (1) A first type of organic carrier was prepared according to the above preparation method, which includes: 1.2% styrene-ethylene-propylene-styrene block copolymer (Kerteng G1701), 2.6% diethylene glycol butyl ether acetate, 0.1% MWCNTs, 1.2% benzyl benzoate, 0.6% dodecyl alcohol ester, 0.3% diethylene glycol dibutyl ether, 0.6% butyl benzyl phthalate, 0.4% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (0.4% 100cst silicone oil, 0.3% 50cst silicone oil), and 0.2% silicone ether; (2) Mixing: Add silver powder (89.0%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the first type of organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0047] Example 3 (1) A first type of organic carrier was prepared according to the above preparation method, which includes: 1.2% styrene-ethylene-propylene-styrene block copolymer (Kerteng G1701), 2.5% diethylene glycol butyl ether acetate, 0.2% MWCNTs, 1.2% benzyl benzoate, 0.6% dodecyl alcohol ester, 0.3% diethylene glycol dibutyl ether, 0.6% butyl benzyl phthalate, 0.4% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (0.4% 100cst silicone oil, 0.3% 50cst silicone oil), and 0.2% silicone ether; (2) Mixing: Add silver powder (89.0%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the first type of organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0048] Example 4 (1) A second type of organic carrier was prepared according to the above preparation method, which includes: 0.65% styrene-ethylene-propylene-styrene block copolymer (Kertene G1701), 0.08% polyvinyl butyral (Kuraray B30H), 0.08% ethyl cellulose (Dow Std-10), 0.04% methacrylic acid resin (NeoCryl B725), 2.95% diethylene glycol butyl ether acetate, 0.05% MWCNTs, 1.1% propylene glycol phenyl ether acetate, 0.6% hexadecyl alcohol ester, 0.5% diethylene glycol dibutyl ether, 0.75% dimethyl phthalate, 0.2% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (50cst), and 0.2% silicone ether; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the second type of organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0049] Example 5 (1) A second type of organic carrier was prepared according to the above preparation method, which includes: 0.65% styrene-ethylene-propylene-styrene block copolymer (Kertene G1701), 0.08% polyvinyl butyral (Kuraray B30H), 0.08% ethyl cellulose (Dow Std-10), 0.04% methacrylic acid resin (NeoCryl B725), 2.9% diethylene glycol butyl ether acetate, 0.1% MWCNTs, 1.1% propylene glycol phenyl ether acetate, 0.6% hexadecyl alcohol ester, 0.5% diethylene glycol dibutyl ether, 0.75% dimethyl phthalate, 0.2% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (50cst), and 0.2% silicone ether; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the second type of organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0050] Example 6 (1) A second type of organic carrier was prepared according to the above preparation method, which includes: 0.65% styrene-ethylene-propylene-styrene block copolymer (Kertene G1701), 0.08% polyvinyl butyral (Kuraray B30H), 0.08% ethyl cellulose (Dow Std-10), 0.04% methacrylic acid resin (NeoCryl B725), 2.8% diethylene glycol butyl ether acetate, 0.2% MWCNTs, 1.1% propylene glycol phenyl ether acetate, 0.6% hexadecyl alcohol ester, 0.5% diethylene glycol dibutyl ether, 0.75% dimethyl phthalate, 0.2% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (50cst), and 0.2% silicone ether; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the second type of organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0051] Example 7 (1) The first type of organic carrier in Example 2 and the second type of organic carrier in Example 4 were mixed in a ratio of 1:3 to obtain a mixed carrier; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the above mixed carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0052] Example 8 (1) The first type of organic carrier in Example 2 and the second type of organic carrier in Example 4 were mixed in a 1:1 ratio to obtain a mixed carrier; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the above mixed carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0053] Example 9 (1) The first type of organic carrier in Example 2 and the second type of organic carrier in Example 4 were mixed in a ratio of 3:1 to obtain a mixed carrier; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the above mixed carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste containing MWCNTs.

[0054] Comparative Example 1 (1) An organic carrier was prepared according to the above preparation method, which includes: 1.2% styrene-ethylene-propylene-styrene block copolymer (Kerteng G1701), 2.7% diethylene glycol butyl ether acetate, 1.2% benzyl benzoate, 0.6% dodecyl alcohol ester, 0.3% diethylene glycol dibutyl ether, 0.6% butyl benzyl phthalate, 0.4% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (0.4% 100cst silicone oil, 0.3% 50cst silicone oil), and 0.2% silicone ether; (2) Mixing: Add silver powder (89.0%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the above organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste.

[0055] Comparative Example 2 (1) An organic carrier was prepared according to the above preparation method, which includes: 0.65% styrene-ethylene-propylene-styrene block copolymer (Kreteng G1701), 0.08% polyvinyl butyral (Kuraray B30H), 0.08% ethyl cellulose (Dow Std-10), 0.04% methacrylic acid resin (NeoCryl B725), 3% diethylene glycol butyl ether acetate, 1.1% propylene glycol phenyl ether acetate, 0.6% hexadecyl alcohol ester, 0.5% diethylene glycol dibutyl ether, 0.75% dimethyl phthalate, 0.2% tripropylene glycol monobutyl ether, 0.5% polyamide wax, 0.7% silicone oil (50cst), and 0.2% silicone ether; (2) Mixing: Add silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) to the above organic carrier in proportion, stir at room temperature, and disperse using a three-roll mill (6 times) after the silver powder and glass powder are completely impregnated. Each dispersion requires rolling the slurry at least twice to obtain photovoltaic front silver paste.

[0056] Comparative Example 3 Commercially available photovoltaic front-side organic carriers were used as comparative samples, which did not contain MWCNTs. Silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) were added to the organic carrier in proportion and stirred at room temperature. After the silver powder and glass powder were completely impregnated, the mixture was dispersed using a three-roll mill (6 times). Each dispersion required rolling the slurry at least twice to obtain photovoltaic front-side silver paste.

[0057] Comparative Example 4 A commercially available photovoltaic front-side organic carrier was used as a comparison sample. MWCNTs were added to the commercially available photovoltaic front-side organic carrier to make the organic carrier contain MWCNTs (0.05% in the silver paste). Silver powder (89%) and glass powder (2.6%, prepared according to the ratio of Example 1) were added to the organic carrier in proportion and stirred at room temperature. After the silver powder and glass powder were completely impregnated, the mixture was dispersed using a three-roll mill (6 times). Each dispersion required rolling the slurry at least twice to obtain the photovoltaic front-side silver paste.

[0058] The content data of silver powder, glass powder, organic carrier and MWCNTs in the examples and comparative examples are shown in Table 1 below.

[0059] Table 1. Content of each component in the examples and comparative examples.

[0060] Silver paste was printed on N-type solar cells and sintered at 730-760℃ (preferably 745℃). The photovoltaic silver paste prepared in the embodiments and comparative examples of the present invention was tested for IV electrical performance using a Halm tester. The performance test results are shown in Table 2 below.

[0061] Table 2 Performance Test Table

[0062] As can be seen from the table above: In the first type of organic carrier, Example 2 (0.1% MWCNTs) showed superior electrical performance compared to Comparative Example 1 and Comparative Example 3. The fill factor (FF) was 0.1% higher than that of Comparative Example 1, and the height-to-width ratio of the gate line was also higher. This indicates that the introduction of MWCNTs promoted a better synergistic effect between the organic carrier, glass powder, and silver powder. While the glass powder melted and flowed onto the silicon wafer during sintering, the silver powder particles sintered and necked at high temperature, forming a continuous silver conductive network. At the same time, this silver conductive network increased the amount of glass flowing onto the silicon wafer surface, which further improved the photoelectric conversion efficiency.

[0063] In the second type of organic carrier, due to its higher proportion of continuous resin, the elastomer content is less than that of the first type of carrier. One-dimensional MWCNTs also form a network structure in the carrier. Therefore, the lower MWCNTs (0.05%) content (Example 4) will bring excellent electrical properties and linearity, further enhance the bonding force between the carrier and the silver powder particles, and enable the silver paste to better maintain the grid line shape during the printing process, reduce deformation and collapse, and improve printability.

[0064] Furthermore, when the first type of organic carrier (high elastomer resin) and the second type of organic carrier (high continuity resin) are used together, Example 9 exhibits excellent electrical properties and a high aspect ratio. At the same time, the high proportion of elastomer is also beneficial to the height of the grid lines, which further generates high current. In addition, the high proportion of elastomer can alleviate the "fatigue cracking" of the resin under long-term shearing action, which is conducive to the formation of long-term stable printability.

[0065] In summary, the analysis shows that: (1) By optimizing the organic carrier (such as the ratio of elastomer / continuous resin) and introducing carbon nanotubes, the FF can be improved and thus the EFF can be slightly improved (the EFF of Example 9 is 0.023% higher than that of Comparative Example 4). Although the absolute value is small, it is significant in the efficiency competition in the photovoltaic industry where every millimeter counts. (2) The embodiments provide more flexible control over grid line size (H, W, H / W), enabling both high H / W (54.7% in Embodiment 5) to adapt to high-efficiency batteries and efficiency (46.8% in Embodiment 7) at low H / W. This indicates that the formulation optimization enhances the "process tolerance" of the silver paste, making it adaptable to different printing equipment and screen precision, and reducing production line debugging costs.

[0066] (3) Data verification shows that “0.05%-0.3% MWCNTs + elastomer / continuous resin compound” can simultaneously optimize printability (H / W, grid breakage rate) and electrical properties (EFF, FF), balancing photoelectric conversion efficiency and printing stability.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content without departing from the scope of the technical solution of the present invention, which are equivalent embodiments with equivalent changes. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A photovoltaic front-side silver paste, characterized in that, Based on the total weight of the silver paste (100%), the weight percentage of each component is as follows: silver powder 85%-90%, glass powder 2.3%-2.8%, and organic carrier 6.5%-10.0%. The organic carrier includes resin, carbon nanotubes, and solvent. The resin content in the silver paste is 0.6%-1.3%, the carbon nanotube content is 0.05%-0.3%, and the solvent content is 5.5%-6.5%.

2. The photovoltaic front-side silver paste as described in claim 1, characterized in that, The resin includes an elastomer resin and a continuous resin, wherein the content of the elastomer resin in the silver paste is 0.5%-1.3%, and the content of the continuous resin in the silver paste is 0-0.2%.

3. The photovoltaic front-side silver paste as described in claim 2, characterized in that, The organic carrier includes a first type of organic carrier and / or a second type of organic carrier; In the first type of organic carrier, the resin is an elastomeric resin, and the content of the elastomeric resin in the silver paste is 1.1%-1.3%; In the second type of organic carrier, the resin is an elastomer resin and a continuous resin, wherein the content of the elastomer resin in the silver paste is 0.5%-0.7%, and the content of the continuous resin in the silver paste is 0.1%-0.2%.

4. The photovoltaic front-side silver paste as described in claim 3, characterized in that, The organic carrier includes a first type of organic carrier and a second type of organic carrier, and the mass ratio of the first type of organic carrier to the second type of organic carrier is 1:3-3:

1.

5. The photovoltaic front-side silver paste as described in claim 2, characterized in that, The elastomer resin includes a styrene-ethylene-propylene-styrene block copolymer.

6. The photovoltaic front-side silver paste as described in claim 2, characterized in that, The continuous resin includes one or more of ethyl cellulose, acrylic resin, hydroxypropyl cellulose, cellulose acetate butyrate, polyvinyl butyral resin, and methacrylic resin.

7. The photovoltaic front-side silver paste as described in claim 1, characterized in that, The solvent includes one or more of the following: alcohol ester dodecyl, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, alcohol ester hexadecyl, diethylene glycol monobutyl ether, butyl carbitol acetate, dimethyl phthalate, propylene glycol phenyl ether acetate, tripropylene glycol monomethyl ether, dimethyl adipate, benzyl benzoate, butyl benzyl phthalate, and tripropylene glycol monobutyl ether.

8. The photovoltaic front-side silver paste as described in claim 1, characterized in that, The organic carrier further includes silicone oil, a thixotropic agent, and a dispersant. The thixotropic agent includes one or more of hydrogenated castor oil, polyamide wax, polyethylene wax, polyvinyl alcohol, polyacrylate, and polydiurea. The dispersant includes one or more of polydimethylsiloxane, oleic acid, stearic acid, silicone ether, polyvinylpyrrolidone, and silicates.

9. A method for preparing photovoltaic front-side silver paste according to any one of claims 1-8, characterized in that, The process includes the following steps: Preparation of organic carrier: Weigh the raw materials for the organic carrier according to the set ratio, first mix carbon nanotubes and solvent to obtain a uniform carbon nanotube dispersion, and then mix the carbon nanotube dispersion and resin evenly to obtain the organic carrier. Preparation of silver paste: Add silver powder and glass powder to the prepared organic carrier according to the mass ratio, and mix and stir evenly to obtain the desired silver paste.

10. A front electrode, characterized in that, The front electrode is obtained by sintering the photovoltaic front silver paste according to any one of claims 1-8.

11. A solar cell, characterized in that, It includes the front electrode as described in claim 10.

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