Method for preparing electrode grid lines, and photovoltaic cell

Abstract

The present application relates to the field of photovoltaic technology, and relates to a method for preparing electrode grid lines, and a photovoltaic cell. The method comprises the following steps: S1, providing a substrate, and forming a polymer layer on the substrate; S2, using a first mold to form first grooves on the polymer layer by pressing; applying a first conductive paste on the polymer layer, so that the grooves are completely filled with the first conductive paste, and scraping off excess first conductive paste; S3, providing a base material, covering the base material with the polymer layer, and transfer-printing the polymer layer and the first conductive paste onto the base material at a certain temperature and pressure; S4, peeling off the substrate from the polymer layer, dissolving the polymer layer, and leaving the first conductive paste adhering to the base material; and S5, sintering the first conductive paste to form the electrode grid lines. In the present application, the blade coating, high-precision transfer printing, water dissolution, and high-temperature sintering technologies are used, the production process is efficient, and the accuracy of electrode patterns can be ensured.

Description

Preparation method of electrode grid line and photovoltaic cell TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, in particular to a preparation method of electrode grid line and photovoltaic cell. BACKGROUND

[0002] In the process of manufacturing photovoltaic cells, the printing technology of electrode grid line is a key production process. The existing electrode grid line printing technology includes screen printing, inkjet printing, offset printing and flexible printing, etc. Among them, the screen printing technology is widely used in photovoltaic cell production, which prints conductive paste (such as silver paste) onto silicon wafer through screen to form electrode pattern. Although the screen printing process is mature, the production cost is low and it is suitable for large-scale industrial production, but it is difficult to realize high-resolution fine pattern, which leads to electrode line width being too wide, reduces light absorption, increases the amount of silver paste, and has higher requirements for cleanliness. In addition, the production speed of screen printing is slow, which affects the production efficiency.

[0003] As a kind of non-contact printing technology, inkjet printing can accurately spray conductive ink onto the surface of the cell through the nozzle to form electrode pattern. This technology can realize higher resolution and finer electrode pattern, reduce the light-shielding area, improve the photoelectric conversion efficiency, and reduce the waste of conductive paste. However, the inkjet printing technology has higher requirements for equipment and process, especially the precision and durability of the nozzle, and the rheological properties of the ink, which need to be further optimized to meet the needs of large-scale production.

[0004] Offset printing technology transfers conductive paste to the surface of the cell through rubber blanket cylinder, which is suitable for high-precision and complex pattern printing. Flexible printing uses flexible printing plate for large-area continuous printing, which is suitable for the manufacturing of thin-film solar cells or flexible photovoltaic modules. Although offset printing and flexible printing have advantages in resolution and pattern complexity, their processes are more complex, and the cost of equipment and operation is higher. At present, they are mainly applied to specific types of photovoltaic cells and have not been widely used in mainstream silicon-based solar cells.

[0005] Therefore, it is an important problem to be solved to develop a photovoltaic cell electrode grid line printing technology with simple process, low cost and high resolution. SUMMARY

[0006] In order to develop a photovoltaic cell electrode grid line printing technology with simple process, low cost and high resolution, the present application provides a preparation method of electrode grid line and photovoltaic cell.

[0007] A preparation method of electrode grid line, comprising the following steps:

[0008] S1, providing a substrate, forming a polymer layer on the substrate;

[0009] S2, pressing a first groove corresponding to a required electrode pattern on the polymer layer by using a first mold; coating a first conductive paste on the polymer layer, so that the first conductive paste fills the groove, and scraping off the excess first conductive paste;

[0010] S3, providing a substrate, and covering the polymer layer on the substrate, and transferring the polymer layer and the first conductive paste to the substrate under a certain temperature and pressure;

[0011] S4, peeling off the substrate from the polymer layer, and dissolving the polymer layer, so that the first conductive paste is left adhered to the substrate;

[0012] S5, sintering the first conductive paste to form the electrode grid lines.

[0013] By adopting the technical scheme, the polymer layer is used to press the first groove on the polymer layer by using the first mold, and the first conductive paste is coated on the polymer layer, so that the first conductive paste fills the groove, and the excess first conductive paste is scraped off.

[0014] In a specific embodiment, the thickness of the polymer layer is 5-30 um, and the opening width of the electrode pattern is 3-10 um.

[0015] By adopting the technical scheme, the polymer layer is used to press the first groove on the polymer layer by using the first mold, and the first conductive paste is coated on the polymer layer, so that the first conductive paste fills the groove, and the excess first conductive paste is scraped off.

[0016] In a specific embodiment, the S2 to the S3 further comprises: S20, providing a second mold, pressing a second groove on the first conductive paste by using the second mold, and drying the first conductive paste; coating a second conductive paste on the first conductive paste, so that the second conductive paste fills the second groove, and scraping off the excess second conductive paste.

[0017] By adopting the technical scheme, the polymer layer is used to press the first groove on the polymer layer by using the first mold, and the first conductive paste is coated on the polymer layer, so that the first conductive paste fills the groove, and the excess first conductive paste is scraped off.

[0018] In a specific embodiment, the contact resistance of the second conductive paste is less than the contact resistance of the first conductive paste, and the conductivity of the second conductive paste is greater than the conductivity of the first conductive paste.

[0019] By adopting the technical scheme, the polymer layer is used to press the first groove on the polymer layer by using the first mold, and the first conductive paste is coated on the polymer layer, so that the first conductive paste fills the groove, and the excess first conductive paste is scraped off.

[0020] In a specific embodiment, in the S20, after pressing the second groove, the first conductive paste is dried at a temperature of 80-200 ℃.

[0021] In a specific embodiment, in the S3, the first conductive paste is adhered to the substrate, or the second conductive paste is adhered to the substrate, by applying a pressure of 5-20 MPa and a temperature of 80-180 ℃.

[0022] In a specific embodiment, in the S4, the polymer layer is dissolved by water at room temperature, and after the dissolution, the first conductive paste is left adhered to the substrate, or the first conductive paste and the second conductive paste are left adhered to the substrate.

[0023] In a specific embodiment, in the S5, the first conductive paste is sintered at a high temperature of 500-1000℃ to form the electrode grid lines, or the first conductive paste and the second conductive paste are sintered at a high temperature of 500-1000℃ to form the electrode grid lines.

[0024] In a specific embodiment, the width of the first groove is the same as the width of the second groove, and the height ratio of the first groove to the second groove is 2:1-5:1.

[0025] The first groove and the second groove are made by hot pressing, and the hot pressing temperature is 80-180℃.

[0026] The longitudinal cross-sectional shape of the first groove and the second groove is one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon.

[0027] By adopting the above technical solution,

[0028] In a specific embodiment, the material of the first mold and the second mold is one of single crystal silicon, polycrystalline silicon, copper, nickel, copper-nickel alloy, nickel-iron alloy, iron-aluminum alloy, and aluminum alloy.

[0029] In a specific embodiment, the glass transition temperature of the polymer layer is 70-120℃, and the material of the polymer layer is a water-soluble high polymer material.

[0030] The water-soluble high polymer material is one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, and polyvinyl alcohol-polyacrylonitrile.

[0031] By adopting the above technical solution, the

[0032] In a specific embodiment, the material of the substrate includes one of polyethylene terephthalate, polyimide, polyethylene terephthalate copolymer, polycarbonate, polypropylene, and polyurethane, and the thickness of the substrate is 25-200um.

[0033] In a specific embodiment, the substrate is one of a single crystal silicon substrate, a polycrystalline silicon substrate, a perovskite substrate, a glass substrate, and a plastic substrate.

[0034] A method for preparing an electrode grid line includes the following steps:

[0035] S1, providing a transfer film with composite conductive paste;

[0036] S2, providing a substrate, adhering the side of the transfer film with composite conductive paste to the substrate, and transferring the composite conductive paste to the substrate by pre-set process parameters of embossing; wherein the process parameters of embossing: pressure is 5-20 MPa, temperature is 80-180℃ and time is 1-10 min;

[0037] S3, removing part of the material of the transfer film to make the composite conductive paste remain on the substrate;

[0038] S4, sintering the composite conductive paste on the substrate to form the electrode grid line with a pre-set aspect ratio.

[0039] In a specific embodiment, the preparation method of the transfer film in S1 includes the following steps:

[0040] S11, providing a polymer layer, and using a first mold to press a first groove corresponding to the required electrode pattern on the polymer layer;

[0041] S12, coating a first conductive paste capable of filling the first groove on the embossed side of the polymer layer, and removing the excess first conductive paste on the surface of the polymer layer, so that the surface of the first groove and the first conductive paste are located on the same plane;

[0042] S13, using a second mold to emboss a second groove with a pre-set shape on the first conductive paste, and removing the excess first conductive paste after embossing;

[0043] S14, coating a second conductive paste in the second groove, and compounding the second conductive paste on the first conductive paste, and removing the excess second conductive paste on the surface of the polymer layer, to complete the preparation of the transfer film with composite conductive paste.

[0044] In a specific embodiment, S11 further includes: preparing a polymer layer with a thickness of 20-125 um by electrospinning or flat plate coating method;

[0045] Wherein, the width of the polymer layer is 200-800 um, the elongation at break is 20-60%, the tensile strength is 5-20 MPa, and the Shore A hardness is greater than 70HS.

[0046] In one specific embodiment, the polymer layer is made of a water-soluble polymer material, which is one of polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, polyvinyl alcohol-polyacrylonitrile, polyvinylpyrrolidone or polyethylene glycol.

[0047] In one specific embodiment, S11 specifically includes: placing the prepared polymer layer in the first mold through a precision hot press, and performing hot press molding at a temperature in the range of 80-180°C, so that the surface of the polymer layer forms micron-level or even nanometer-level first grooves corresponding to the electrode pattern;

[0048] In one specific embodiment, the first mold has a convex part, and the shape of the first grooves is one of isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid or rectangle.

[0049] In one specific embodiment, S12 specifically includes: uniformly applying the first conductive paste on the hot-pressed polymer layer by using a flat plate coating method, so that the first conductive paste completely fills the first grooves, and the excess first conductive paste is scraped off to ensure that the first conductive paste is completely filled and uniformly distributed without deformation.

[0050] In one specific embodiment, S13 specifically includes: using the second mold to press out the second grooves with a height of 2-5um and a width of 5um according to the preset requirements, and drying the first conductive paste at 80-200°C.

[0051] In one specific embodiment, S14 specifically includes: tightly contacting the coated second conductive paste with the formed first conductive paste to form a firm composite layer.

[0052] By heating or applying pressure, the conductive pastes are fused with each other, ensuring that the composite layer has no gap and forms a continuous conductive path.

[0053] In one specific embodiment, S14 further includes: after removing the excess paste, the conductive paste needs to be preliminarily dried at 80-200°C for 10-20 minutes, so that the solvent part in the paste is volatilized, and the first conductive paste and the second conductive paste can be completely attached.

[0054] In one specific embodiment, the first conductive paste is one of copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste and tantalum paste, and the second conductive paste is silver paste.

[0055] In one specific embodiment, the silver paste includes a binder, and the binder is one of phenolic resin and epoxy resin.

[0056] In a specific implementation, S2 specifically includes: heat pressing the first conductive paste and the second conductive paste onto the substrate by applying uniform pressure and heating to dry, while heating to dry the first conductive paste and the second conductive paste to tightly adhere to the surface of the substrate without deformation.

[0057] In a specific implementation, the substrate is one of a single-crystal silicon substrate, a polycrystalline silicon substrate, a perovskite substrate, a glass substrate, and a plastic substrate.

[0058] In a specific implementation, S3 specifically includes: placing the transferred substrate into water at 25-75°C for cleaning, so that the polymer layer dissolves and falls off, leaving the composite conductive paste pattern of the first conductive paste and the second conductive paste that have been successfully transferred, forming the base structure of the electrode grid lines.

[0059] In a specific implementation, S4 specifically includes: placing the substrate after transferring the first conductive paste and the second conductive paste into a high-temperature furnace for sintering treatment of the composite conductive paste; the sintering temperature is 500-1000°C, ensuring that the first conductive paste and the second conductive paste are completely sintered and form a tight connection with the substrate, generating the electrode grid lines with a preset aspect ratio.

[0060] A photovoltaic cell comprising the electrode grid lines prepared by the method described above.

[0061] In a specific implementation, the outer edge shape of the electrode grid lines is one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon; and the aspect ratio of the electrode grid lines is 2:1.

[0062] In summary, the present application includes at least one of the following beneficial technical effects: the recessed template and the triangular electrode pattern design produced by the hot pressing technology of the present application achieve high-resolution electrode patterns, making the electrode grid lines more fine and consistent, and significantly improving the photoelectric conversion efficiency; the application of the flat plate coating technology ensures that the conductive material uniformly fills the recesses and effectively scrapes off the excess material, thereby reducing material waste; in addition, during the transfer process, by applying pressure, the conductive material can be accurately transferred to the substrate, maintaining the accuracy of the electrode pattern, thereby improving the uniformity and stability of the electrode, ensuring excellent electrical performance; compared with traditional electrode preparation processes, the present method simplifies the production process, reduces multiple complex steps and equipment requirements, and through the combination of flat plate coating, high-precision transfer, water dissolution, and high-temperature sintering technologies, the production process becomes more efficient, capable of meeting the needs of large-scale production, and the high-temperature sintering step further ensures the stability and durability of the conductive material, improving the reliability and performance of the electrode. Attached Figure Description

[0063] Figure 1 is a schematic diagram of the process flow for the preparation method of the electrode grid line in Example 1.

[0064] Figure 2 is a schematic diagram illustrating the longitudinal cross-sectional shape of the electrode grid line in Embodiment 1.

[0065] Figure 3 is a schematic diagram of the process flow for the preparation method of the electrode grid line in Example 2.

[0066] Figure 4 is a schematic diagram illustrating the longitudinal cross-sectional shape of the electrode grid line in Embodiment 2.

[0067] Figure 5 is a schematic diagram of the process flow for the preparation method of the electrode grid line in Example 3.

[0068] Figure 6 is a schematic diagram illustrating the longitudinal cross-sectional shape of the electrode grid line in Embodiment 3.

[0069] Figure 7 is a schematic diagram of the process flow for the preparation method of the electrode grid line in Example 4.

[0070] Figure 8 is a schematic diagram illustrating the longitudinal cross-sectional shape of the electrode grid line in Embodiment 4.

[0071] Explanation of reference numerals in the attached drawings: 1. Substrate; 2. Polymer layer; 3. First mold; 4. First groove; 5. First conductive paste; 6. Second mold; 7. Second groove; 8. Second conductive paste; 9. Substrate; 10. Electrode grid line; 11. First conductive layer; 12. Second conductive layer; 13. Substrate layer. Detailed Implementation

[0072] The present application will be further described in detail below with reference to Figures 1-8.

[0073] Example 1

[0074] Referring to Figures 1 and 2, this application discloses a method for fabricating electrode grid lines, which includes the following steps:

[0075] S1, providing a substrate 1, and forming a polymer layer 2 on the substrate 1; in this process, the surface of the substrate 1 needs to be clean and flat to ensure the quality of the subsequent coating process, and surface treatment is performed on the substrate 1 to enhance the adhesion of the polymer layer 2; the thickness of the substrate 1 is 25-200um, and in this embodiment, the thickness of the substrate 1 is preferably 50um, and the material of the substrate 1 includes but is not limited to one of polyethylene terephthalate (PET), polyimide (PI), polyethylene terephthalate glycol (PETG), polycarbonate (PC), polypropylene (PP), and polyurethane (PU), and in this embodiment, the material of the substrate 1 is preferably polyimide, which has good heat resistance and can withstand high temperatures up to 400℃, and has high strength and toughness, providing good structural support and durability, and has good resistance to various chemicals and can remain stable in various environments;

[0076] Before coating, the substrate 1 needs to be pretreated as necessary, and the pretreatment method includes cleaning, drying and surface activation, which aims to remove contaminants on the surface of the substrate 1, increase the surface roughness and improve the adhesion of the polymer layer 2;

[0077] In this embodiment, a flat plate coating technique is used to form a polymer layer 2 on the substrate 1; specifically, a uniform polymer solution is coated on the substrate 1, and the uniformity and thickness of the coating are controlled, and after the coating is completed, the polymer layer 2 is dried or cured at an environmental condition of 50-100℃ to ensure that its physical and chemical properties meet the requirements, and in this embodiment, further drying treatment can be performed according to the properties of the polymer and the application requirements, including but not limited to heating in an oven to further harden the polymer layer 2 for long-term storage;

[0078] The thickness of the polymer layer 2 is 5-30um, and in this embodiment, the thickness of the polymer layer 2 is preferably 15±2um; the polymer layer 2 with this thickness can balance the strength, flexibility and conductivity, and is suitable for various application requirements, and the thin design of the polymer layer 2 helps to reduce material waste and makes it suitable for high-density integrated electronic devices or microstructures;

[0079] In the embodiment, the glass transition temperature of the polymer layer 2 is 70-120℃, the material of the polymer layer 2 includes but is not limited to water-soluble polymer material, and the water-soluble polymer material includes but is not limited to one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, and polyvinyl alcohol-polyacrylonitrile. In the embodiment, the water-soluble polymer material is preferably polyvinyl alcohol, which can be heated to 150℃, and will discolor and become brittle when heated above 180℃. The polyvinyl alcohol is insoluble in organic solvents such as gasoline, kerosene, vegetable oil, benzene, toluene, dichloroethane, carbon tetrachloride, acetone, ethyl acetate, methanol, and ethylene glycol. The polyvinyl alcohol is soluble in water, making the coating and film-forming process more convenient without the need for complex solvent treatment. The water-soluble property also makes it easy to clean after use, reducing the environmental burden.

[0080] In the embodiment, the water solubility of the polyvinyl alcohol can be adjusted by adjusting the alcoholysis degree or blending modification method, so that it can quickly dissolve at room temperature.

[0081] Specifically, increasing the alcoholysis degree of the polyvinyl alcohol (i.e., the degree of alcoholysis of the polyvinyl alcohol) can increase its dissolution speed in water, making it more easily penetrated and dissociated by water molecules, thereby speeding up the dissolution process. Blending the polyvinyl alcohol with other water-soluble polymers or additives can improve its water solubility. For example, blending with a hydrophilic polymer can enhance the solubility and dissolution rate of the polyvinyl alcohol. By optimizing the blending ratio and selecting appropriate modifiers, the solubility of the polyvinyl alcohol can be adjusted to meet the requirements of specific applications.

[0082] S2, using a hot pressing technology, a first mold 3 is used to hot press a first groove 4 corresponding to the required electrode pattern on the polymer layer 2 to obtain a template. In the embodiment, the material of the first mold 3 includes but is not limited to one of single crystal silicon, polycrystalline silicon, copper, nickel, copper-nickel alloy, nickel-iron alloy, iron-aluminum alloy, and aluminum alloy. The polymer layer 2 includes but is not limited to a first groove 4 corresponding to the electrode pattern formed by hot pressing with a hot press.

[0083] In the present embodiment, the opening width of the electrode pattern of the polymer layer 2 is 3-10 um, and the aspect ratio is 2:1, that is, the slot width of the first groove 4 is 3-10 um, and the aspect ratio is 2:1; in the precision process for preparing the solar electrode grid line 10, it is crucial to accurately control the thickness of the electrode grid line 10 and the width of the patterned opening, as these two parameters directly affect the filling effect of the subsequent conductive material, the dimensional accuracy of the electrode grid line 10, and the performance of the final battery; the thickness of the polymer layer 2 is in the range of 5-30 um, the width of the electrode patterned opening is in the range of 3-10 um, and the aspect ratio is 2:1; the above dimensions can balance the requirements of the filling efficiency of the subsequent conductive material and the dimensional accuracy of the electrode grid line 10, and the narrower opening width helps to reduce the parasitic resistance between the electrode grid lines 10, thereby improving the current collection efficiency of the battery; at the same time, within this width range, it can also ensure that the conductive material can be fully and uniformly filled into the opening, avoiding the generation of voids or defects; by accurately controlling the thickness of the polymer layer 2 and the width of the patterned opening, the dimensional accuracy of the electrode grid line 10 can be significantly improved, which helps to reduce the performance fluctuations and defective rates caused by dimensional deviations.

[0084] In the present embodiment, the hot pressing temperature of the polymer layer 2 is 80-180℃, and the hot pressing pressure is 5-20 MPa; preferably, the optimal hot pressing forming conditions are: hot pressing temperature of 120-180℃, hot pressing pressure of 10 MPa, and hot pressing time of 2 min, which can well hot press the groove;

[0085] Specifically, the dried polymer layer 2 is placed on the hot press, and according to the characteristics of the polymer layer 2 and the precision of the required electrode pattern, the temperature of the hot press is set to 120-180℃, the pressure is set to 10 MPa, and the time is set to 2 min; the temperature can soften the polymer layer 2, the pressure can ensure that the pattern of the mold on the hot press can be completely and accurately imprinted, and the time can ensure that the details of the pattern are accurately copied; after drying, the polymer layer 2 is placed on the hot plate of the hot press, and then the first mold 3 is aligned and pressed down; the hot plate is heated to the set temperature, and the first mold 3 is pressed into the polymer layer 2 under the pressure of the hot plate to form the first groove 4 corresponding to the required electrode pattern; after hot pressing, the mold and the polymer layer 2 need to be cooled to room temperature, and this cooling process allows the polymer layer 2 to maintain its shape in the mold, so that the shape and size of the first groove 4 are stable; after cooling is completed, the first mold 3 is carefully removed from the polymer layer 2, and the first groove 4 pattern is clearly visible and matches the required electrode pattern; careful inspection confirms whether the size and shape of the first groove 4 meet the requirements of the micron-level or even nanometer-level electrode pattern, and if necessary, it can be post-processed, for example, it can be washed to remove residues, or further refined to meet the requirements of subsequent processes.

[0086] In this process, the hot pressing temperature range is above the glass transition temperature of polyvinyl alcohol and below its melting point, avoiding discoloration and embrittlement of polymer layer 2 during hot pressing, ensuring material processability, stability and uniformity; under the above optimal hot pressing conditions, polymer layer 2 can better shape and form precise groove shapes, improving processing precision and product quality, and by controlling the hot pressing temperature within a safe range, reducing thermal stress caused by excessive temperature, thereby reducing thermal damage to the material;

[0087] The shape and size of the first groove 4 correspond to the electrode grid line 10, and in actual operation, the size and shape of the electrode grid line 10 required for transfer printing are controlled to reduce the ohmic loss of the electrode grid line 10; the longitudinal cross-sectional shape of the first groove 4 includes but is not limited to one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon, and in this embodiment, the longitudinal cross-sectional shape of the first groove 4 is preferably a triangle. The design of the longitudinal cross-section of the triangle helps to change the incident and refractive path of light, can better capture and guide light, can effectively reduce the reflection loss of light, so that more light is absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0088] S3, using a flat plate coating technique, applying first conductive paste 5 on polymer layer 2, so that first conductive paste 5 fills first groove 4, and the excess first conductive paste 5 is scraped off;

[0089] Specifically, on the polymer layer 2 with the first groove 4 formed, a flat plate coating technique is used to uniformly apply the first conductive paste 5. A suitable first conductive paste 5 is selected, and a flat plate coater or a doctor blade tool is used for coating. The first conductive paste 5 is uniformly applied on the polymer layer 2, ensuring that the material can fully fill all the gaps in the first groove 4 and cover the entire surface. After coating, a doctor blade or other tools are used to scrape off the excess first conductive paste 5 on the surface, ensuring that the first conductive paste 5 in the first groove 4 is flat and tightly combined with the polymer layer 2;

[0090] In this embodiment, the first conductive paste 5 includes but is not limited to silver paste. The composition of the silver paste includes an adhesive, which is a phenolic resin or an epoxy resin. The adhesive is used to enhance the bonding between the silver particles in the silver paste. In this embodiment, the shear strength of the adhesive is 10-30 MPa, with excellent adhesion and chemical resistance;

[0091] The design of the adhesive can effectively enhance the bonding force between the silver particles in the silver paste, thereby reducing the interruption of the conductive path in the silver paste and improving the electrical conductivity;

[0092] The polyvinyl alcohol polymer layer 2 is incompatible and non-reactive with the binder of the silver paste; the non-reactivity ensures that no chemical changes or degradation occur between the polyvinyl alcohol and the silver paste, maintaining the stability of the properties of both, ensuring that each material performs optimally in its intended application, avoiding mutual influence; and enabling the polymer layer 2 to be easily removed after processing by water solubility without affecting the properties of the silver paste;

[0093] S4, covering the substrate 1 with the first conductive paste 5, the polymer layer 2 on the base material 9, and the polymer layer 2 adhering to the base material 9 under a certain temperature and pressure, including but not limited to, bonding the polymer layer 2 and the first conductive paste 5 to the base material 9 by high temperature of 80-180°C and pressure of 5-20 MPa, in this embodiment, preferably, the optimal hot pressing transfer conditions are: hot pressing temperature of 120-180°C, hot pressing pressure of 10 MPa, and hot pressing time of 8 min, under which the first conductive paste 5 and the polymer layer 2 can be well adhered to the base material 9, the first conductive paste 5 is intact without deformation, and the polymer layer 2 can be well peeled off from the substrate 1;

[0094] Specifically, the surface of the base material 9 is cleaned to remove any contaminants or particles, ensuring that the surface of the base material 9 is clean and flat, the polymer layer 2 coated with the first conductive paste 5 is placed on the base material 9, ensuring that the pattern of the first conductive paste 5 is aligned with the position on the base material 9, an alignment tool or visual alignment system can be used to improve alignment accuracy, the base material 9 is gently placed to ensure that each part of the first conductive paste 5 is in close contact with the surface of the base material 9, 10 MPa pressure and 120-180°C hot pressing temperature are applied to press the first conductive paste 5 onto the base material 9, and the pressure needs to be evenly distributed to ensure that the first conductive paste 5 is completely adhered and forms a clear pattern, this step needs to ensure uniform pressure application to ensure accurate transfer of the first conductive paste 5, and after applying pressure, hot pressing between the base material 9 is maintained for 8 min to ensure that the first conductive paste 5 is in full contact and adhered to the base material 9;

[0095] In this embodiment, the binder in the silver paste can also enhance the bonding between the silver paste particles of the first conductive paste 5 and the base material 9, after hot pressing transfer, the first conductive paste 5 and the polymer layer 2 are tightly adhered to the base material 9, and the other side of the substrate 1 can be easily peeled off from the substrate 1, the binder in the silver paste can promote the adhesion between the silver paste particles and the base material 9, improve the bonding strength of the first conductive paste 5 and the base material 9, further optimize the conductive performance, and at the same time improve the overall durability and reliability.

[0096] S5, peeling the substrate 1 from the polymer layer 2 and dissolving the polymer layer 2, leaving the first conductive paste 5 adhered to the substrate 9; the substrate 9 includes but is not limited to one of a single crystal silicon substrate 9, a polycrystalline silicon substrate 9, a perovskite substrate 9, a glass substrate 9, a plastic substrate 9, and in the embodiment, preferably, the substrate 9 is a polycrystalline silicon substrate 9, which has good electronic conductivity and stability, and has good thermal stability and thermal conductivity, and is suitable for the manufacture of various electronic devices, and can be used in the photovoltaic cells of the application;

[0097] Specifically, after completing the transfer work, the substrate 1 is first peeled from the polymer layer 2, and then the polymer layer 2 is dissolved using normal temperature water, and in the embodiment, the temperature of the normal temperature water includes but is not limited to 20-25°C; after the substrate 1 is peeled, first, the polymer layer 2 coated with the first conductive paste 5 is immersed in a container containing normal temperature water, and the temperature of the water should be kept at room temperature 20-25°C, so as to avoid thermal damage to the first conductive paste 5 or the substrate 9, and during the immersion process, the polymer layer 2 will gradually dissolve in the water;

[0098] In order to ensure that the polymer layer 2 is completely dissolved, the water can be moderately stirred or the water temperature can be increased to promote the uniform progress of the dissolution process, and the time of this process depends on the thickness and material properties of the polymer layer 2, and during the process, the dissolution of the polymer layer 2 should be checked regularly to ensure that it is completely dissolved, and when the polymer layer 2 is completely dissolved, the pattern of the first conductive paste 5 on the surface of the polymer layer 2 will be completely retained on the substrate 9;

[0099] In order to further ensure the adhesion and stability of the first conductive paste 5, the surface of the substrate 9 can be rinsed with clean water to remove possible small fragments of the polymer layer 2, and finally, the transferred substrate 9 is dried or dried by other methods to prepare for the next step.

[0100] S6, sintering the first conductive paste 5 to form an electrode grid line 10 on the substrate 9, and in the embodiment, includes but is not limited to sintering the conductive material at a high temperature of 500-1000°C;

[0101] Specifically, the substrate 9 coated with the first conductive paste 5 is placed in a heating furnace or oven for high-temperature sintering at 500-1000°C. The temperature and time of the sintering process should be set according to the first conductive paste 5 to ensure that it can be fully sintered at high temperature without damaging the substrate 9. The sintering time should be set according to the characteristics of the first conductive paste 5 to ensure that the material has enough time to complete the chemical reaction or physical change at high temperature to achieve the best conductivity and adhesion. After sintering, the substrate 9 is allowed to cool naturally to room temperature to avoid thermal stress damage to the electrode grid lines 10. The sintered electrode grid lines 10 are inspected to ensure that the pattern is clear and well adhered, and there is no poor conductivity, defects or peeling phenomenon, ensuring that the quality of the electrode grid lines 10 meets the design requirements.

[0102] During this process, if necessary, cleaning is performed to remove any residues or contaminants from the sintering process, and electrical performance tests can also be performed to verify the conductivity of the electrode grid lines 10 and confirm their performance in actual applications.

[0103] The method process steps of the present application are simple, the material and equipment requirements are relatively low, and the overall production cost is reduced. The electrode pattern of the first groove 4 made by hot pressing technology realizes a high-resolution electrode pattern, making the electrode grid lines 10 more fine and consistent, and significantly improving the photoelectric conversion efficiency. The application of flat plate coating technology ensures that the first conductive paste 5 fills the first groove 4 uniformly and effectively scrapes off the excess material, thereby reducing material waste. In addition, during the transfer process, by applying pressure and temperature, the first conductive paste 5 can be accurately attached to the substrate 9, maintaining the accuracy of the electrode pattern, thereby improving the uniformity and stability of the electrode, ensuring excellent electrical performance. Compared with traditional electrode preparation processes, the present method simplifies the production process, reduces multiple complex steps and equipment requirements, and through the combination of flat plate coating technology, high-precision transfer, water dissolution and high-temperature sintering, the production process becomes more efficient, which can meet the needs of large-scale production. The high-temperature sintering step further ensures the stability and durability of the first conductive paste 5, improving the reliability and performance of the electrode.

[0104] The present application also provides a photovoltaic cell comprising the electrode grid lines 10 prepared by the preparation method as described above.

[0105] The longitudinal section of the electrode grid line 10 includes but is not limited to a triangle, a trapezoid or a half-ellipse, and can also be a rectangle, a diamond, a polygon, the shape of the longitudinal section of the electrode grid line 10 can refer to the shape shown in FIG. 2, which is only an example shape and can also be other shapes; the top angle of the triangle is 20°-60°, the height of the triangle is 10±2um, the width of the triangle is 5±1um, and the height-width ratio of the triangle is 2:1; the bottom angle of the trapezoid is 30°-70°, the height of the trapezoid is 10±2um, the width of the trapezoid is 5±1um, and the height-width ratio of the trapezoid is 2:1; the height of the half-ellipse is 10±2um, the height-width ratio of the half-ellipse is 2:1, and the width of the half-ellipse is 5±1um; the edges of the triangle, the trapezoid and the half-ellipse can better control the propagation direction of light, reduce reflection loss, increase light absorption, and help improve the path length of light in the battery, thereby increasing the light absorption efficiency;

[0106] In the present embodiment, the triangle is an isosceles triangle, the trapezoid is an isosceles trapezoid, and the ellipse is a symmetric half-ellipse; the design of the isosceles triangle, the isosceles trapezoid and the symmetric half-ellipse can not only reduce the use of conductive materials, but also reflect more light energy, can uniformly distribute light on the electrode surface, reduce the concentration effect of light, thereby improving the light capture efficiency, helping to achieve more uniform current distribution, reducing local resistance, improving the current output efficiency of the battery, and can provide better structural stability, helping to maintain the mechanical strength and long-term reliability of the electrode;

[0107] The photovoltaic cell prepared by the preparation method can significantly improve the photoelectric conversion efficiency of the photovoltaic cell, reduce the manufacturing cost, improve the production efficiency, and ensure the long-term stability and reliability of the battery, which helps to promote the application and development of photovoltaic cells.

[0108] Embodiment two

[0109] Referring to FIGS. 3 and 4, the difference between the present embodiment and embodiment one is that the method comprises the following steps:

[0110] S1, providing a polymer layer 2, in the present embodiment, the material of the polymer layer 2 includes but is not limited to one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, and polyvinyl alcohol-polyacrylonitrile; in the present embodiment, preferably, the polymer layer 2 is polyvinyl alcohol, which is soluble in water, making the coating and film forming process more convenient, without the need for complex solvent treatment, and the water-soluble property makes polyvinyl alcohol easy to clean after use, reducing the burden on the environment;

[0111] The thickness of the polymer layer 2 is 25-125 um, and in this embodiment, the thickness of the polymer layer 2 is preferably 30 um; the concentration of polyvinyl alcohol in the polymer layer 2 is 12-20 wt%, and in this embodiment, the concentration of the polymer layer 2 is preferably 15 wt%;

[0112] In this embodiment, the polymer layer 2 is prepared by, but not limited to, a flat plate coating technique; taking the most preferred polyvinyl alcohol as an example, the specific preparation method of the polymer layer 2 includes:

[0113] a. Prepare polyvinyl alcohol raw materials and solvents, which include but are not limited to deionized water or suitable organic solvents, and appropriate additives such as plasticizers, thickeners or other functional materials can also be selected according to actual needs;

[0114] b. Add the polyvinyl alcohol raw materials to the appropriate deionized water, heat and stir until completely dissolved, forming a uniform polyvinyl alcohol solution, adjust the concentration of the polyvinyl alcohol solution to ensure that the concentration of the polyvinyl alcohol is between 12-20 wt%;

[0115] c. Coat the polyvinyl alcohol solution on a smooth surface (such as glass or plastic film), control the thickness, and use a blade, brush or spray gun to control the coating speed and tool gap to achieve the desired film thickness of 30-125 um;

[0116] d. Dry at room temperature to remove part of the water, place the coated polyvinyl alcohol layer in an oven at 50-100°C environmental conditions to accelerate drying and curing, after drying, the polyvinyl alcohol layer can be naturally peeled off from the smooth surface to form an independent film, i.e. the polymer layer 2 is prepared.

[0117] The polyvinyl alcohol layer prepared by the above method has good tensile strength and flexibility in the thickness range of 30-125 um, and the solubility of the polyvinyl alcohol with a concentration of 12-20 wt% in water is good, making it easy to process and remove;

[0118] In this embodiment, the water solubility of polyvinyl alcohol can also be changed by adjusting the alcoholysis degree of polyvinyl alcohol or by blending modification method to make it dissolve quickly at room temperature; specifically, increasing the alcoholysis degree of polyvinyl alcohol (i.e. the degree of alcoholysis of polyvinyl alcohol) can increase its dissolution speed in water, resulting in easier penetration and dissociation of water molecules, thereby speeding up the dissolution process; blending polyvinyl alcohol with other polymers or additives that are soluble in water can improve its water solubility, for example, blending with hydrophilic polymers can enhance the solubility and dissolution rate of polyvinyl alcohol, and by optimizing the blending ratio and selecting appropriate modifiers, the solubility of polyvinyl alcohol can be adjusted to meet the specific application requirements.

[0119] S2, a first recess 4 corresponding to the required electrode pattern is hot-pressed on the polymer layer 2 by using the first mold 3 to obtain the polymer layer 2 with the electrode pattern, in the embodiment, the base material 9 of the first mold 3 includes but is not limited to one of a single crystal silicon base material 9, a polycrystalline silicon base material 9, a copper base material 9, a nickel base material 9, a copper-nickel alloy base material 9, a nickel-iron alloy base material 9, an iron-aluminum alloy base material 9, and an aluminum alloy base material 9, and the polymer layer 2 includes but is not limited to a first recess 4 formed by hot pressing of a hot press;

[0120] In the embodiment, the opening width of the electrode pattern of the polymer layer 2 is 3-10um, and the aspect ratio is 2:1, that is, the slot width of the first recess 4 is 3-10um, and the aspect ratio is 2:1; in the precision process of preparing the solar electrode grid line 10, it is crucial to accurately control the thickness of the electrode grid line 10 and the width of the patterned opening, which directly affects the filling effect of the subsequent first conductive paste 5, the size accuracy of the electrode grid line 10 and the performance of the final battery; the thickness of the polymer layer 2 is in the range of 30-125um, the width of the patterned opening of the electrode is in the range of 3-10um, and the aspect ratio is 2:1, the above size can meet the requirements of the filling efficiency of the subsequent first conductive paste 5 and the size accuracy of the electrode grid line 10, and the narrower opening width helps to reduce the parasitic resistance between the electrode grid lines 10 and improve the current collection efficiency of the battery, at the same time, the width range can also ensure that the first conductive paste 5 can be fully and uniformly filled into the opening, avoiding the generation of voids or defects, by accurately controlling the thickness of the polymer layer 2 and the width of the patterned opening, the size accuracy of the electrode grid line 10 can be significantly improved, which helps to reduce the performance fluctuation and the defective rate caused by the size deviation.

[0121] In the embodiment, the hot pressing temperature is 80-180℃, preferably, the best hot pressing forming condition is that the hot pressing temperature is 120-180℃, the hot pressing pressure is 10MPa, and the hot pressing time is 2min, which can well hot-press the first recess 4; in this process, the hot pressing temperature is above the glass transition temperature of polyvinyl alcohol and below the melting point, which avoids the discoloration and embrittlement of the polymer layer 2 during hot pressing, and ensures the processability, stability and uniformity of the material; under the above best hot pressing forming condition, the polymer layer 2 can be better shaped to form an accurate first recess 4 shape, improving the processing precision and product quality, by controlling the hot pressing temperature within a safe range, reducing the thermal stress caused by too high temperature, thereby reducing the thermal damage of the material;

[0122] Specifically, the dried polymer layer 2 is placed on a hot press, and the temperature of the hot press is set to 120-180°C, the pressure is set to 10 MPa, and the time is set to 2 min according to the characteristics of the polymer layer 2 and the accuracy of the required electrode pattern, the temperature can soften the polymer layer 2, the pressure can ensure that the pattern of the first mold 3 on the hot press can be completely high-precision embossed, and the time can ensure that the details of the pattern are accurately copied; the dried polymer layer 2 is placed on the hot plate of the hot press, and then the first mold 3 is aligned and pressed down, the hot plate is heated to the set temperature, and the first mold 3 is pressed into the polymer layer 2 under the pressure of the hot plate to form the first groove 4 corresponding to the required electrode pattern; after the hot pressing is completed, the first mold 3 and the polymer layer 2 need to be cooled to room temperature, and this cooling process allows the polymer layer 2 to maintain its shape in the first mold 3, so that the shape and size of the first groove 4 are stable; after cooling is completed, the first mold 3 is carefully removed from the polymer layer 2, the first groove 4 pattern is clearly visible, and matches the required electrode pattern; the polymer layer 2 after hot pressing is carefully checked to confirm whether the size and shape of the first groove 4 meet the requirements of the micron-level or even nanometer-level electrode pattern;

[0123] The shape and size of the first groove 4 correspond to the electrode grid line 10, and in actual operation, the size and shape of the required transferred electrode grid line 10 are controlled to reduce the ohmic loss of the electrode grid line 10; the longitudinal cross-sectional shape of the first groove 4 includes but is not limited to one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon, and in this embodiment, the longitudinal cross-sectional shape of the first groove 4 is preferably a triangle or a trapezoid. The longitudinal cross-sectional design of the triangle or the trapezoid is helpful to change the incident and refractive path of light, can better capture and guide light, can effectively reduce the reflection loss of light, so that more light is absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0124] A flat plate coating technique is used to apply the first conductive paste 5 on the polymer layer 2, so that the first conductive paste 5 fills the first groove 4, and the excess first conductive paste 5 is scraped off.

[0125] Specifically, the first conductive paste 5 is uniformly applied on the polymer layer 2 having the first groove 4 formed thereon by using a flat plate coating technique, a suitable first conductive paste 5 is selected, a flat plate coater or a doctor blade tool is used for coating, and the first conductive paste 5 is uniformly applied on the polymer layer 2 to ensure that the material can fully fill all gaps in the first groove 4 and cover the entire surface. After coating, a doctor blade or other tools are used to scrape off the excess first conductive paste 5 on the surface to ensure that the first conductive paste 5 in the first groove 4 is flat and tightly combined with the polymer layer 2;

[0126] The first conductive paste 5 includes, but is not limited to, silver paste, and the composition of the silver paste includes a binder, which is a phenolic resin or an epoxy resin, and the binder is used to enhance the binding between the silver particles in the silver paste. In this embodiment, the shear strength of the binder is 10-30 MPa, and the binder has excellent adhesion and chemical resistance.

[0127] The design of the binder effectively enhances the binding between the silver particles in the silver paste, thereby reducing the interruption of the conductive path in the silver paste and improving the electrical conductivity.

[0128] The polyvinyl alcohol polymer layer 2 is incompatible and non-reactive with the binder of the silver paste. The non-reactivity ensures that no chemical change or degradation occurs between the polyvinyl alcohol and the silver paste, maintaining the stability of their respective properties, ensuring that each material performs optimally in its intended application, and avoiding mutual influence. Furthermore, the polymer layer 2 can be easily removed by water solubility after processing without affecting the performance of the silver paste.

[0129] S3, the polymer layer 2 is covered on the substrate 9, and the polymer layer 2 is adhered to the substrate 9 under a certain temperature and pressure with the first conductive paste 5. In this process, the polymer layer 2 and the first conductive paste 5 are adhered to the substrate 9 by, but not limited to, high temperature of 80-180℃ and pressure of 5-20 MPa. In this embodiment, preferably, the optimal hot pressing transfer conditions are: hot pressing temperature of 120-180℃, hot pressing pressure of 10 MPa, and hot pressing time of 8 min. Under these conditions, the first conductive paste 5 and the polymer layer 2 can be well adhered to the substrate 9, and the first conductive paste 5 has complete form without deformation.

[0130] Specifically, the surface of the substrate 9 is cleaned to remove any contaminants or particles, ensuring that the surface of the substrate 9 is clean and flat. The polymer layer 2 coated with the first conductive paste 5 is placed on the substrate 9, ensuring that each part of the first conductive paste 5 on the polymer layer 2 is in close contact with the surface of the substrate 9. A pressure of 10 MPa and a hot pressing temperature of 120-180℃ are applied to press the polymer layer 2 onto the substrate 9. The pressure needs to be evenly distributed to ensure that the first conductive paste 5 is completely adhered and forms a clear pattern. This step needs to ensure uniform pressure application to ensure accurate transfer of the first conductive paste 5. After applying the pressure, the hot pressing between the polymer layer 2 and the substrate 9 is maintained for 8 min to ensure that the first conductive paste 5 is in full contact and adhered to the substrate 9.

[0131] In the present embodiment, the adhesive can also enhance the adhesion between the silver paste particles and the substrate 9. After the hot-press transfer printing, the first conductive paste 5 silver paste and the polymer layer 2 are tightly adhered to the substrate 9. At this time, the adhesive in the silver paste can promote the adhesion between the silver paste particles and the substrate 9, improve the bonding strength of the first conductive paste 5 and the substrate 9, further optimize the conductive performance, and improve the overall durability and reliability.

[0132] S4, dissolving the polymer layer 2, after the polymer layer 2 is dissolved, the first conductive paste 5 is left adhered to the substrate 9; the substrate 9 includes but is not limited to one of a single crystal silicon substrate 9, a polycrystalline silicon substrate 9, a perovskite substrate 9, a glass substrate 9, and a plastic substrate 9. In the present embodiment, the substrate 9 is preferably a polycrystalline silicon substrate 9, which has good electronic conductivity and stability, and has good thermal stability and thermal conductivity, and is suitable for the manufacture of various electronic devices, and can be used in photovoltaic cells applied in the present application;

[0133] Specifically, after the transfer printing is completed, the polymer layer 2 is dissolved using normal temperature water. In the present embodiment, the temperature of the normal temperature water includes but is not limited to 20-25°C. First, the polymer layer 2 coated with the first conductive paste 5 is immersed in a container containing normal temperature water, and the temperature of the water should be kept at room temperature 20-25°C to avoid thermal damage to the first conductive paste 5 or the substrate 9. During the immersion process, the polymer layer 2 will gradually dissolve in the water;

[0134] In order to ensure that the polymer layer 2 is completely dissolved, the water can be moderately stirred or the water temperature can be increased to promote the uniform progress of the dissolution process. The time of this process depends on the thickness and material properties of the polymer layer 2. During the process, the dissolution of the polymer layer 2 should be checked regularly to ensure that it is completely dissolved. After the polymer layer 2 is completely dissolved, the pattern of the first conductive paste 5 will be completely retained on the substrate 9;

[0135] In order to further ensure the adhesion and stability of the first conductive paste 5, the surface of the substrate 9 can be rinsed with clean water to remove possible small fragments of the polymer layer 2. Finally, the transferred substrate 9 is dried or dried using other methods to prepare for the next step.

[0136] S5, sintering the first conductive paste 5 to form the electrode grid line 10 on the substrate 9. In the present embodiment, it includes but is not limited to sintering the conductive material at a high temperature of 500-1000°C.

[0137] Specifically, the substrate 9 coated with the first conductive paste 5 is placed in a heating furnace or oven for high-temperature sintering at 500-1000℃. The temperature and time of the sintering process should be set according to the first conductive paste 5 to ensure that it can be fully sintered at high temperature without damaging the substrate 9. The sintering time should be set according to the characteristics of the first conductive paste 5 to ensure that the material has enough time to complete the chemical reaction or physical change at high temperature to achieve the best conductivity and adhesion. After sintering, the substrate 9 is allowed to cool naturally to room temperature to avoid thermal stress damage to the electrode grid lines 10. The sintered electrode grid lines 10 are inspected to ensure that the pattern is clear and well adhered, and there is no poor conductivity, defects or peeling phenomenon, ensuring that the quality of the electrode grid lines 10 meets the design requirements.

[0138] The present application also provides a photovoltaic cell comprising the electrode grid lines 10 prepared by the above-mentioned method;

[0139] The longitudinal section of the electrode grid lines 10 includes but is not limited to a triangle, trapezoid or semi-ellipse, and can also be a rectangle, diamond, polygon, etc. The shape of the longitudinal section of the electrode grid lines 10 can refer to Figure 4, which is only an example and can also be other shapes. The top angle of the triangle is 20°-60°, the height of the triangle is 10±2um, and the width is 5±1um, with a height-to-width ratio of 2:1. The bottom angle of the trapezoid is 30°-70°, the height of the trapezoid is 10±2um, and the width is 5±1um, with a height-to-width ratio of 2:1. The height of the semi-ellipse is 10±2um, the height-to-width ratio of the semi-ellipse is 2:1, and the width is 5±1um. The edges of the triangle, trapezoid and semi-ellipse can better control the propagation direction of light, reduce reflection loss, increase light absorption, and help improve the path length of light inside the cell, thereby increasing the light absorption efficiency.

[0140] In this embodiment, the triangle is an isosceles triangle, the trapezoid is an isosceles trapezoid, and the ellipse is a symmetric semi-ellipse. The design of the isosceles triangle, isosceles trapezoid and symmetric semi-ellipse can reduce the use of conductive materials, reflect more light energy, evenly distribute light on the electrode surface, reduce the concentration effect of light, improve the light capture efficiency, help achieve more uniform current distribution, reduce local resistance, improve the current output efficiency of the cell, and provide better structural stability, helping to maintain the mechanical strength and long-term reliability of the electrode.

[0141] The photovoltaic cell with the electrode grid lines 10 prepared by this method can significantly improve the photoelectric conversion efficiency of the photovoltaic cell, reduce the manufacturing cost, improve the production efficiency, and ensure the long-term stability and reliability of the cell, which helps to promote the application and development of photovoltaic cells.

[0142] Embodiment three

[0143] Referring to FIG. 5 and FIG. 6, the difference between this embodiment and embodiment one is that between S2 and S3, there are also S20, providing a second mold 6, using the second mold 6 to press a second groove 7 on the first conductive paste 5, and drying the first conductive paste 5; applying a second conductive paste 8 on the first conductive paste 5, so that the second conductive paste 8 fills the second groove 7, and scraping off the excess second conductive paste 8.

[0144] The preparation method of the electrode grid line 10 of this embodiment includes the following steps:

[0145] S1, providing a substrate 1, forming a polymer layer 2 on the substrate 1; in this process, it is necessary to ensure that the surface of the substrate 1 is clean and flat to ensure the quality of the subsequent coating process, and surface treatment is performed on the substrate 1 to enhance the adhesion of the polymer layer 2; the thickness of the substrate 1 is 100-200um, and in this embodiment, the thickness of the substrate 1 is preferably 150um, the material of the substrate 1 includes but is not limited to one of polyethylene terephthalate (PET), polyimide (PI), polyethylene terephthalate copolymer (PETG), polycarbonate (PC), polypropylene (PP), and polyurethane (PU), and in this embodiment, the material of the substrate 1 is preferably polyimide, which has good heat resistance and can withstand high temperatures up to 400℃, and has high strength and toughness, providing good structural support and durability, and has good resistance to a variety of chemicals and can remain stable in a variety of environments;

[0146] Before coating, the substrate 1 is subjected to necessary pretreatment, and the pretreatment method includes cleaning, drying and surface activation, which aims to remove contaminants on the surface of the substrate 1, increase the surface roughness and improve the adhesion of the polymer layer 2; the specific pretreatment method includes but is not limited to: first, use deionized water, acetone and isopropyl alcohol to clean in turn to remove possible impurities and grease, then place the substrate 1 in an ultrasonic cleaner, the ultrasonic frequency is 40kHz, and the cleaning time is 15 minutes to ensure that the surface is free of any small particles, after cleaning, place the substrate 1 in a hot air circulation device, keep the temperature at 60℃, and dry for 30 minutes to ensure complete drying;

[0147] A polymer layer 2 is prepared on the cleaned and treated substrate 1. In this embodiment, a flat plate coating technique is used to form a polymer layer 2 on the substrate 1. Specifically, a uniform polymer solution is coated on the substrate 1, the uniformity and thickness of the coating are controlled, and a reasonable doctor blade angle (generally 30°-45°) is set to ensure uniform and smooth coating. After coating, the substrate 1 is placed in a well-ventilated dry environment, or the solvent is accelerated to evaporate by heating, including but not limited to drying in a hot air oven, setting the temperature at 90-110°C, and drying the polymer solution for 20-30 minutes to promote polymer crosslinking and form a polymer layer 2 of 10-12um thickness.

[0148] The thickness of the polymer layer 2 includes but is not limited to 5-30um. In this embodiment, the thickness of the polymer layer 2 is preferably 15um. The polymer layer 2 of this thickness can balance strength, flexibility and conductivity, suitable for various application requirements, and the thin design of the polymer layer 2 helps to reduce material waste and makes it suitable for high-density integrated electronic devices or microstructures.

[0149] In this embodiment, the glass transition temperature of the polymer layer 2 is 70-100°C. The material of the polymer layer 2 includes but is not limited to water-soluble polymer material, which includes but is not limited to polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), modified polyvinyl alcohol (MPVA), sodium polyacrylate (PAAS), polyvinyl alcohol-polyacrylic acid (PVA-PAA), and one of polyvinyl alcohol-polyacrylonitrile (PVA-PAN). In this embodiment, the water-soluble polymer material is preferably polyvinyl alcohol, which can be heated to 150°C and will not discolor and become brittle until heated to above 180°C, providing a wider processing temperature range. Polyvinyl alcohol is insoluble in gasoline, kerosene, vegetable oil, benzene, toluene, dichloroethane, carbon tetrachloride, acetone, ethyl acetate, methanol, ethylene glycol and other organic solvents. Polyvinyl alcohol is easily soluble in water, making the coating and film forming process more convenient without the need for complex solvent treatment. The water-soluble property makes polyvinyl alcohol easy to clean after use, has excellent biocompatibility, is friendly to the human body and the environment, and reduces the burden on the environment.

[0150] Polyvinyl alcohol is a polymer with a large number of strong hydrophilic -OH, has good hydrophilic characteristics, its water solubility is largely determined by the degree of polymerization, especially alcoholysis degree, due to the presence of a large number of hydroxyl groups lead to the existence of strong hydrogen bonds within and between polyvinyl alcohol molecules, hindered the solubility of polyvinyl alcohol in water, therefore, the higher the alcoholysis degree, the poorer the water solubility of polyvinyl alcohol; in addition, the residual acetic acid on the partially alcoholized polyvinyl alcohol molecular chain should be hydrophobic, but its presence can also weaken the hydrogen bonds within and between adjacent molecules, so the presence of appropriate acetate can improve the water solubility of polyvinyl alcohol, with the increase of acetate, the dissolution endotherm increases, the critical temperature of phase separation decreases, the solubility at high temperature gradually decreases, so the water solubility of polyvinyl alcohol is complex;

[0151] In the present embodiment, the water solubility of polyvinyl alcohol can be changed by adjusting the alcoholysis degree of polyvinyl alcohol or by blending modification method, so that it can be quickly dissolved at room temperature; specifically, including:

[0152] a, the alcoholysis degree of polyvinyl alcohol (i.e. the alcoholysis degree of polyvinyl alcohol) is appropriately adjusted, specifically, sodium hydroxide aqueous solution is added to the methanol solution of polyvinyl acetate (containing 1%-2% water) to generate polyvinyl alcohol (referring to reaction formula (1.1)); in the alcoholysis process, there is water in the system, the molar ratio of alkali is large, the reaction formula (1.1) speed is accelerated, at the same time, under the action of water, the degree of dissociation of alkali is large, the catalytic effect is enhanced, the ester exchange reaction formula (1.2) speed is also accelerated, the whole reaction speed is very fast, only about 1 min can be completed, the characteristics of this method of wet alcoholysis (high alkali alcoholysis) is fast reaction speed, small equipment volume, high production capacity, and the alcoholysis process is continuous.

[0153] Specifically, the polyvinyl acetate methanol solution is heated by a preheater, then rapidly and uniformly mixed with the alcoholysis catalyst sodium methoxide solution in a static mixer, the mixing time is 0.1-0.3 min, then enters the double screw extrusion alcoholysis machine, and is alcoholized at 45-75℃ for 0.5-4 min, the alcoholysis product is washed by a solvent containing acid, then dried to obtain white granular partially alcoholized polyvinyl alcohol product;

[0154] In the present embodiment, the alcoholysis degree can be adjusted according to actual needs, such as using polyvinyl alcohol with an alcoholysis degree of 80% for low temperature water solution at 40℃, and using 88% for high temperature water solution.

[0155] b. The water solubility of polyvinyl alcohol can be improved by blending it with other water-soluble polymers or additives. Specifically, hydrophilic polymers or additives with good compatibility with polyvinyl alcohol, such as polyacrylic acid, polyglycolic acid, etc., are selected. Different blending ratios can be designed according to application requirements. Common blending ratios can be between 10% and 50%. Different ratios have a direct impact on water solubility and physical properties. The selected ratio of polyvinyl alcohol and blending materials is melted at high temperature, and then cooled to form a blend. Thus, the solubility and dissolution rate of polyvinyl alcohol can be enhanced. By optimizing the blending ratio and selecting appropriate modifiers, the solubility of polyvinyl alcohol can be adjusted to meet specific application requirements.

[0156] After alcoholysis or blending treatment, the water solubility of polyvinyl alcohol can be tested. Specifically, the sample is placed in water, and the dissolution time is observed and recorded. The mechanical strength, ductility, and tensile strength of polyvinyl alcohol can also be tested to evaluate the impact of blending modification on material properties.

[0157] S2, a first mold 3 is provided, and a first groove 4 corresponding to the required electrode pattern is pressed on the polymer layer 2 using the hot pressing technology of the first mold 3. In this embodiment, the material of the first mold 3 is one of single crystal silicon, polycrystalline silicon, copper, nickel, copper-nickel alloy, nickel-iron alloy, iron-aluminum alloy, and aluminum alloy. In this embodiment, the groove depth of the first groove 4 is 15±2um, and the aspect ratio of the first groove 4 is 2:1.

[0158] In this embodiment, the opening width of the electrode pattern of the polymer layer 2 is 3-10um, and the aspect ratio is 2:1, i.e., the slot width of the first groove 4 is 3-10um, and the aspect ratio is 2:1. Using the design of the polymer layer 2 with a thickness in the range of 5-30um, the width of the electrode patterned opening in the range of 3-10um, and the aspect ratio of 2:1, the above dimensions can meet the requirements of the filling efficiency of the conductive paste and the size accuracy of the electrode grid line 10. A narrower opening width helps to reduce the parasitic resistance between the electrode grid lines 10 and improve the current collection efficiency of the battery. At the same time, within this width range, the conductive paste can also be fully and uniformly filled into the opening to avoid voids or defects. By precisely controlling the thickness of the polymer layer 2 and the width of the patterned opening, the size accuracy of the electrode grid line 10 can be significantly improved, which helps to reduce the performance fluctuations and defective rates caused by size deviations.

[0159] In the present embodiment, the first groove 4 corresponding to the electrode pattern is formed by hot pressing the polymer layer 2 in a hot press. In the present embodiment, the hot pressing temperature of the polymer layer 2 is 80-180°C, preferably, the optimal hot pressing forming condition is that the hot pressing temperature is 120-180°C, the hot pressing pressure is 10 MPa, and the hot pressing time is 2 min, under which the first groove 4 can be well hot pressed out.

[0160] Specifically, the dried polymer layer 2 is placed on the hot press, and the temperature, pressure and time of the hot press are set according to the characteristics of the polymer layer 2 and the accuracy of the required electrode pattern, i.e. the temperature is 120-180°C, the pressure is 10 MPa, and the time is 2 min, the temperature can soften the polymer layer 2, the pressure can ensure that the pattern of the first mold 3 on the hot press can be completely and high-precision imprinted, and the time can ensure that the details of the pattern are accurately copied; the dried polymer layer 2 is placed on the hot plate of the hot press, and then the first mold 3 is aligned and pressed down, the hot plate is heated to a temperature of 120-180°C, and the first mold 3 is pressed into the polymer layer 2 under the pressure of 10 MPa of the hot plate to press out the first groove 4 corresponding to the required electrode pattern, which is 10 um deep and 5 um wide, and the hot pressing is performed for 2 min to ensure that the polymer layer 2 is fully formed under high temperature and high pressure; after the hot pressing is completed, the first mold 3 and the polymer layer 2 need to be cooled to room temperature, and this cooling process allows the polymer layer 2 to maintain its shape in the first mold 3, so that the shape and size of the first groove 4 are stabilized; after the cooling is completed, the first mold 3 is carefully removed from the polymer layer 2, the first groove 4 pattern is clearly visible, and matches the required electrode pattern; careful inspection confirms whether the size and shape of the first groove 4 meet the requirements of the micron-level or even nanometer-level electrode pattern.

[0161] In this process, the hot pressing temperature is above the glass transition temperature of polyvinyl alcohol and below the melting point of polyvinyl alcohol, which avoids discoloration and embrittlement of the polymer layer 2 during hot pressing, and ensures the processability, stability and uniformity of the material; under the above optimal hot pressing forming condition, the polymer layer 2 can be better shaped to form an accurate first groove 4 shape, which improves the processing precision and product quality, and by controlling the hot pressing temperature within a safe range, thermal stress caused by excessively high temperature is reduced, thereby reducing thermal damage to the material.

[0162] The shape and size of the first groove 4 correspond to the electrode grid line 10. In actual operation, the size and shape of the electrode grid line 10 required for transfer are controlled to reduce the ohmic loss of the electrode grid line 10. The longitudinal cross-sectional shape of the first groove 4 includes but is not limited to one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon. In this embodiment, the longitudinal cross-sectional shape of the first groove 4 is preferably a triangle or a trapezoid or a semi-elliptical shape. The above longitudinal cross-sectional design helps to change the incident and refractive path of light, can better capture and guide light, can effectively reduce the reflection loss of light, so that more light is absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0163] A flat plate coating technique is used to coat the first conductive paste 5 on the polymer layer 2, so that the first conductive paste 5 fills the first groove 4, and the excess first conductive paste 5 is scraped off.

[0164] Specifically, the first conductive paste 5 is uniformly coated on the polymer layer 2 having the first groove 4 formed thereon by using a flat plate coating technique. A suitable first conductive paste 5 is selected, and a flat plate coater or a doctor blade tool is used for coating. The first conductive paste 5 is uniformly coated on the polymer layer 2. The first conductive paste 5 is moved along the surface of the polymer layer 2 at a smooth speed with appropriate pressure to ensure that the first conductive paste 5 is extruded into the first groove 4. It is ensured that the material can fully fill all the gaps in the first groove 4 and cover the entire surface. After coating, the excess first conductive paste 5 on the surface is scraped off using a doctor blade or other tools to ensure that the first conductive paste 5 in the first groove 4 is flat and tightly combined with the polymer layer 2.

[0165] In this embodiment, the first conductive paste 5 includes but is not limited to one of aluminum paste, copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste, and tantalum paste. Preferably, the first conductive paste 5 is aluminum paste. Aluminum has good conductivity, which can meet the conductivity requirements of many electronic devices and circuits. Compared with other metal pastes, the cost of aluminum paste is lower, and the manufacture and use of aluminum paste are more economically feasible, especially in large-scale applications. Aluminum paste can be widely used in conductive coatings, flexible electronic components, solar cells, PCBs (printed circuit boards), and other fields.

[0166] S20, a second mold 6 is provided. A second groove 7 is pressed out on the first conductive paste 5 by using the second mold 6 through a hot pressing technique, and the first conductive paste 5 is dried. In this embodiment, the material of the second mold 6 is one of single crystal silicon, polycrystalline silicon, copper, nickel, copper-nickel alloy, nickel-iron alloy, iron-aluminum alloy, and aluminum alloy.

[0167] In the embodiment, the second groove 7 is formed by hot pressing the first conductive paste 5 through a hot press. In the embodiment, the hot pressing temperature of the first conductive paste 5 is 80-180°C. Preferably, the optimal hot pressing forming condition is that the hot pressing temperature is 120-180°C, the hot pressing pressure is 10 MPa, and the hot pressing time is 2 min. Under the condition, the second groove 7 can be well hot pressed. In the embodiment, the groove depth of the second groove 7 is 2-5 um, the width of the second groove 7 is the same as the width of the first groove 4, and the height ratio of the first groove 4 to the second groove 7 is 2:1-5:1. Preferably, the height ratio of the first groove 4 to the second groove 7 is 3:1. The same width design ensures good butt joint between the two conductive layers, which helps to improve the conductivity and stability of the electrode.

[0168] Specifically, the temperature of the hot press is set to 120-180°C, the pressure is set to 10 MPa, and the time is set to 2 min. The temperature can soften the first conductive paste 5, the pressure can ensure that the pattern of the second mold 6 on the hot press can be completely imprinted with high precision, and the time can ensure that the details of the pattern are accurately copied. After the polymer layer 2 and the first conductive paste 5 are dried, they are placed on the heating plate of the hot press, and then the second mold 6 is aligned and pressed down. The heating plate is heated to a temperature of 120-180°C, and the second mold 6 is pressed into the first conductive paste 5 under the pressure of 10 MPa on the heating plate to press out a second groove 7 pattern with a depth of 2-5 um and a width of 5 um. The hot pressing time is 2 min, and the first conductive paste 5 overflowing on the surface of the polymer layer 2 is scraped off. After the hot pressing is completed, the first conductive paste 5 is dried at a temperature of 80-200°C, preferably at a temperature of 120-180°C. This process allows the first conductive paste 5 to maintain its shape in the second mold 6, so that the shape and size of the second groove 7 are stabilized. After the drying is completed, the second mold 6 is removed, and the second groove 7 pattern is clearly visible. Careful inspection confirms whether the size and shape of the second groove 7 meet the requirements of the micron-level or even nanometer-level electrode pattern.

[0169] Under the optimal hot pressing forming condition, the first conductive paste 5 can be better shaped to form an accurate second groove 7 shape, improving the processing precision and product quality. By controlling the hot pressing temperature within a safe range, thermal stress caused by excessively high temperature is reduced, thereby reducing thermal damage to the material.

[0170] A flat plate coating technique is used to apply the second conductive paste 8 on the first conductive paste 5, so that the second conductive paste 8 fills the second groove 7, and the excess second conductive paste 8 is scraped off.

[0171] Specifically, on the first conductive paste 5 where the second groove 7 has been formed, a second conductive paste 8 is uniformly applied using a flat plate coating technique. The second conductive paste 8 is selected and applied using a flat plate coater or a doctor blade tool to ensure that the material fills all the gaps in the second groove 7 and covers the entire surface. After application, the excess second conductive paste 8 on the surface is scraped off using a doctor blade or other tools to ensure that the second conductive paste 8 in the second groove 7 is flat and tightly bonded to the first conductive paste 5.

[0172] In this embodiment, the contact resistance of the second conductive paste 8 is less than that of the first conductive paste 5, and the electrical conductivity of the second conductive paste 8 is greater than that of the first conductive paste 5. As the material that will subsequently come into direct contact with the substrate 9, the low contact resistance and high electrical conductivity of the second conductive paste 8 can improve the connection performance between the substrate 9 and the electrode, ensuring smooth flow of current through each contact point. Good electrical properties help improve the overall reliability of the device and avoid performance degradation or failure due to poor contact.

[0173] In this embodiment, the second conductive paste 8 preferably includes but is not limited to silver paste. By limiting the use of silver paste to the area in contact with the substrate 9, the amount of silver paste used can be significantly reduced while still ensuring the overall circuit's conductivity efficiency. In contrast, the first conductive paste 5 can use materials with better electrical conductivity to compensate for some of the performance. The combination of silver paste for the second conductive paste 8 and other lower-cost first conductive paste 5 aluminum paste in this application not only reduces production costs but also brings technical advantages in improving product performance, ensuring conductivity efficiency, and improving mechanical strength.

[0174] The composition of the silver paste includes a binder. The binder in the silver paste has no reactivity. The binder is a phenolic resin or an epoxy resin. The binder is used to enhance the bonding between the silver particles in the silver paste. In this embodiment, the shear strength of the binder is 10-30 MPa, with excellent adhesion and chemical resistance. The design of the binder effectively enhances the bonding force between the silver particles in the silver paste, thereby reducing the interruption of the conductive path in the silver paste and improving the electrical conductivity.

[0175] The polymer layer 2 of polyvinyl alcohol is incompatible and non-reactive with the binder of the silver paste. The non-reactivity ensures that there is no chemical change or degradation between polyvinyl alcohol and silver paste, maintaining the stability of their respective properties. This ensures that each material performs optimally in its intended application, avoids mutual influence, and allows the polymer layer 2 to be easily removed after processing without affecting the performance of the silver paste.

[0176] S3, providing a substrate 9, covering the polymer layer 2 on the substrate 9, transferring the polymer layer 2, the first conductive paste 5 and the second conductive paste 8 to the substrate 9 under a certain temperature and pressure, and drying and setting the second conductive paste 8 at the same time to enhance the adhesion to the surface of the substrate 9; in this process, the polymer layer 2, the first conductive paste 5 and the second conductive paste 8 are adhered to the substrate 9 by high temperature and high pressure, but are not limited to 80-180°C high temperature and 5-20MPa pressure; in this embodiment, preferably, the optimal hot-pressing transfer conditions are: hot-pressing temperature of 120-180°C, hot-pressing pressure of 10MPa, and hot-pressing time of 8min, under which the polymer layer 2, the first conductive paste 5 and the second conductive paste 8 can be well adhered to the substrate 9; in this process, the second conductive paste 8 is dried and set at the same time to enhance the adhesion to the surface of the substrate 9; the first conductive paste 5 and the second conductive paste 8 are in a complete form without deformation, and the polymer layer 2 and the substrate 1 can be well peeled off;

[0177] Specifically, the surface of the substrate 9 is cleaned to remove any contaminants or particles, ensuring that the surface of the substrate 9 is clean and flat, the polymer layer 2 coated with the first conductive paste 5 and the second conductive paste 8 is covered on the substrate 9, accurately aligned with the substrate 9, ensuring that the first conductive paste 5 and the second conductive paste 8 are aligned with the position on the substrate 9, an alignment tool or a visual alignment system can be used to improve the alignment accuracy, gently placed on the substrate 9, ensuring that each part of the second conductive paste 8 is in close contact with the surface of the substrate 9, applying a pressure of 10MPa and a hot-pressing temperature of 120-180°C, pressing the polymer layer 2, the first conductive paste 5 and the second conductive paste 8 onto the substrate 9, and the pressure needs to be evenly distributed to ensure that the first conductive paste 5 and the second conductive paste 8 are completely attached and form a clear pattern, this step needs to ensure uniform pressure to ensure accurate transfer of the first conductive paste 5 and the second conductive paste 8, after applying the pressure, maintaining the hot-pressing between the substrate 9 for 8min to ensure that the first conductive paste 5 and the second conductive paste 8 are in full contact and adhered to the substrate 9;

[0178] In this embodiment, the adhesive can also enhance the bonding between the silver particles of the second conductive paste 8 and the substrate 9, after hot-pressing transfer, the first conductive paste 5, the second conductive paste 8 and the polymer layer 2 are tightly adhered to the substrate 9, and the other side can be easily peeled off from the substrate 1, the adhesive in the silver paste can promote the adhesion between the silver particles and the substrate 9, improve the bonding strength between the second conductive paste 8 and the substrate 9, further optimize the conductive performance, and improve the overall durability and reliability.

[0179] S4, the substrate 1 is peeled off from the polymer layer 2, and the polymer layer 2 is dissolved, leaving the first conductive paste 5 and the second conductive paste 8 adhered to the substrate 9; the substrate 9 includes but is not limited to one of a single crystal silicon substrate 9, a polycrystalline silicon substrate 9, a perovskite substrate 9, a glass substrate 9, and a plastic substrate 9, and in this embodiment, the substrate 9 is preferably a polycrystalline silicon substrate 9, which has good electronic conductivity and stability, and has good thermal stability and thermal conductivity, and is suitable for the manufacture of various electronic devices, and can be used in the photovoltaic cells of the present application;

[0180] Specifically, after the transfer work is completed, the substrate 1 is first peeled off from the polymer layer 2, and then the polymer layer 2 is dissolved using normal temperature water, and in this embodiment, the temperature of the normal temperature water includes but is not limited to 20-25°C; after the substrate 1 is peeled off, first, the polymer layer 2 is immersed in a container containing normal temperature water, and the temperature of the water should be kept at room temperature of 20-25°C, so as to avoid thermal damage to the first conductive paste 5, the second conductive paste 8 or the substrate 9, and during the immersion process, the polymer layer 2 will gradually dissolve in the water;

[0181] In order to ensure that the polymer layer 2 is completely dissolved, the water can be moderately stirred or the water temperature can be increased to promote the uniform progress of the dissolution process, and the time of this process depends on the thickness and material properties of the polymer layer 2, and during the process, the dissolution of the polymer layer 2 should be checked regularly to ensure that it is completely dissolved, and when the polymer layer 2 is completely dissolved, the first conductive paste 5 and the second conductive paste 8 patterns on the surface of the polymer layer 2 will be completely retained on the substrate 9;

[0182] In order to further ensure the adhesion and stability of the first conductive paste 5 and the second conductive paste 8, the surface of the substrate 9 can be rinsed with clean water to remove possible small fragments of the polymer layer 2, and finally, the transferred substrate 9 is dried or dried by other methods to prepare for the next step.

[0183] S5, sintering the first conductive paste 5 and the second conductive paste 8 to form the electrode grid lines 10; in this embodiment, the first conductive paste 5 and the second conductive paste 8 are sintered at a high temperature of 500-1000°C, including but not limited to;

[0184] Specifically, the substrate 9 coated with the first conductive paste 5 and the second conductive paste 8 is placed in a heating furnace for high-temperature sintering at 500-1000℃. The temperature and time of the sintering process should be set according to the first conductive paste 5 and the second conductive paste 8 to ensure that they can be fully sintered at high temperature without damaging the substrate 9. The sintering time should be set according to the characteristics of the first conductive paste 5 and the second conductive paste 8 to ensure that the materials have enough time to complete the chemical reaction or physical change at high temperature to achieve the best conductive performance and adhesion. After sintering, the substrate 9 is naturally cooled to room temperature to avoid damage to the electrode grid line 10 caused by thermal stress. The sintered electrode grid line 10 is checked to ensure that the pattern is clear and well adhered, and whether there is poor conductivity, defects or shedding phenomenon, to ensure that the quality of the electrode grid line 10 meets the design requirements.

[0185] During this process, if necessary, cleaning is performed to remove any residues or contaminants during the sintering process, and electrical performance testing can also be performed to verify whether the conductivity of the electrode grid line 10 meets the specifications and to confirm its performance in actual application.

[0186] The method of the present application uses a two-layer conductive paste structure, which helps to improve the conductivity, stability and performance of the electrode, so that the electrode exhibits better electrical characteristics in actual application, while effectively reducing production costs. By using a mold to press grooves on the polymer layer 2, the pressure and temperature during the transfer process ensure that the first conductive paste 5 and the second conductive paste 8 are accurately transferred and adhered to the substrate 9, maintaining the accuracy of the electrode pattern, achieving high-resolution and high-precision electrode pattern manufacturing, ensuring the accuracy and repeatability of the electrode structure, and meeting the strict requirements of optoelectronic devices for electrode shape and size.

[0187] This process integrates multiple steps together, using flat plate coating technology, transfer, water dissolution, drying, high-temperature sintering and other technologies to achieve accurate application and solidification of the first conductive paste 5 and the second conductive paste 8 on the polymer layer 2 carrier, ensuring the accuracy and stability of the electrode pattern, reducing the complex process in traditional manufacturing methods, improving production efficiency, and reducing manufacturing costs. By combining heat and pressure, good contact and bonding between different materials are ensured, which helps to improve the adhesion of the conductive paste on the substrate 9, ensuring that the electrode does not easily fall off during long-term use, enhancing the overall performance of the electrode and prolonging the service life of the device. The use of the polymer layer 2 can be removed by dissolution in subsequent steps, which helps to reduce waste generated in traditional processes and reduce environmental pollution. Compared with the traditional screen printing method, the present application can improve the production rate to a certain extent, meet the demand for large-scale production, and thus improve the market competitiveness.

[0188] The present application provides a photovoltaic cell comprising an electrode grid line 10 prepared by the method described above.

[0189] The electrode grid line 10 comprises a first conductive layer 11 formed by the first conductive paste 5 and a second conductive layer 12 formed by the second conductive paste 8, the first conductive layer 11 and the second conductive layer 12 share the same bottom surface, and the height ratio of the first conductive layer 11 and the second conductive layer 12 is 2:1-5:1; the design of sharing the same bottom surface helps to enhance the bonding force between the layers, reduce the poor current conduction caused by the interface problem between the materials, and improve the mechanical strength and long-term stability of the battery;

[0190] Since the second conductive layer 12 is a conductive layer in direct contact with the substrate 9, the material of the second conductive layer 12 is silver paste, and the material of the first conductive layer 11 is aluminum paste, which provides a cost-effective conductive solution as the first conductive layer 11, while the silver paste as the second conductive layer 12 promotes higher conductivity, as the conductivity of silver is superior to that of aluminum, by adjusting the height ratio of the two layers (2:1-5:1), the current flow path can be optimized, the current transmission efficiency is improved, and the overall conductivity of the electrode is improved;

[0191] Compared with the use of a single high-cost conductive material (such as silver paste), the use of this layered design can reduce the amount of silver paste used without sacrificing electrode performance, thereby effectively reducing production costs. The electrode grid line 10 design not only improves the performance of the photovoltaic cell, but also provides a guarantee for cost-effectiveness and long-term stability.

[0192] In this embodiment, the height of the electrode grid line 10 includes but is not limited to 10±2um, and the height-width ratio of the electrode grid line 10 is 2:1; the outer edge shape of the electrode grid line 10 includes but is not limited to one of a triangle, a trapezoid, a rectangle, a diamond, a semicircle, and a polygon; the outer edge shape of the electrode grid line 10 is a plurality of geometric shapes, which can effectively balance light capture and current export, and different shape designs can affect the effective contact area of the entire electrode, thereby affecting the conductivity effect;

[0193] The outer edge shape of the first conductive layer 11 is an isosceles triangle, an isosceles trapezoid, or a symmetric semicircle, the top angle of the isosceles triangle is 20°-60°, the bottom angle of the isosceles trapezoid is 30°-70°, and the height-width ratio of the first conductive layer 11 is 2:1; the outer edge shape of the second conductive layer 12 is an isosceles triangle, the top angle of the isosceles triangle is 120°-160°, and the height-width ratio of the second conductive layer 12 is 1:2;

[0194] The first conductive layer 11 and the second conductive layer 12 adopt a symmetrical pattern design, which can optimize the current flow path and reduce the resistance of the current in the conductive layer, thereby improving the conductivity; under the premise that the height ratio of the first conductive layer 11 to the second conductive layer 12 is 2:1-5:1, the height-width ratio of the first conductive layer 11 is 2:1, which can provide better bearing capacity and current conduction capacity, and is suitable for efficient current conduction; the height-width ratio of the second conductive layer 12 is 1:2, which can effectively increase the contact area of the electrode while ensuring uniform stress distribution of the conductive layer, thereby further improving the conductivity; and the first conductive layer 11 and the second conductive layer 12 utilize the above-mentioned angle design, which helps to reduce the return loss of the current, thereby enhancing the effective conduction of the current.

[0195] The photovoltaic cell of the electrode grid line 10 obtained by using the preparation method has obvious advantages in conductivity, production efficiency, environmental protection and structural stability, etc., can effectively reduce the manufacturing cost of the photovoltaic cell, improve the production efficiency, and is expected to be widely used in the photovoltaic cell industry; the combination structure of the first conductive paste 5 and the second conductive paste 8 ensures good conductivity of the electrode grid line 10, the second conductive paste 8 provides low contact resistance on the contact surface of the cell, thereby improving the current collection efficiency, and the parasitic resistance between the electrode grid lines 10 is effectively reduced by the precisely designed electrode pattern and opening width, thereby further improving the energy conversion efficiency of the photovoltaic cell; the technical scheme of using aluminum and silver paste to prepare the electrode grid line 10 has high innovation and practicability, and is expected to promote the development of the printing technology of the electrode grid line 10 of the photovoltaic cell, and bring new development opportunities for the photovoltaic industry.

[0196] Moreover, the method integrates multiple steps by means of mold pressing and transfer printing, can realize high-resolution electrode pattern manufacturing, good electrode adhesion and environmental resistance make the battery more stable in long-term use, prolong the service life, and can ensure the accuracy and repeatability of the electrode structure, meet the strict requirements of photovoltaic devices on electrode shape and size; by controlling the structure of the electrode grid line 10, the light absorption efficiency can be improved, and more photons can be effectively converted into electrical energy.

[0197] Embodiment four

[0198] Referring to FIGS. 7 and 8, the difference between the present embodiment and embodiment one is that the preparation method of the electrode grid line includes the following steps:

[0199] S1, providing a transfer film with a composite conductive paste;

[0200] In the present embodiment, the preparation method of the transfer film with a composite conductive paste includes the following steps:

[0201] S11, providing a polymer layer 2, using a first mold 3 to press a first groove 4 corresponding to the required electrode pattern on the polymer layer 2; the required electrode pattern can be obtained by embossing, thereby achieving the effects of improving precision and facilitating implementation, wherein the embossing can be hot embossing; in this embodiment, the polymer layer 2 includes but is not limited to a PVA film;

[0202] Preferably, S11 specifically includes: placing the prepared PVA film in the first mold 3 by a precision hot press, and performing hot embossing in a temperature range of 80-180 DEG C, so that the surface of the PVA film forms a micron-level or even nanometer-level first groove 4 structure corresponding to the electrode pattern;

[0203] Specifically, the above process steps include but are not limited to:

[0204] 1. Mould preparation: clean the preset mould thoroughly to ensure that the surface is free of stains and particles, so as to ensure the embossing quality;

[0205] 2. Polymer layer 2 preparation: prepare the polymer layer 2 to ensure that the surface is flat and clean; for example, the polymer layer 2 is a PVA film;

[0206] 3. Heating and embossing: align the first mold 3 with the polymer layer 2, and perform embossing at a set temperature; the pressure and time are controlled by the above parameters, so as to ensure that the pattern of the first mold 3 is completely pressed into the polymer layer 2;

[0207] Of course, the parameter control can be set according to the actual use requirement, which is not limited in the present application.

[0208] 4. Cooling and demolding: after embossing, cool the first mold 3 and the polymer layer 2 to ensure that the material is shaped, and then carefully demold to obtain the polymer layer 2 with electrode pattern grooves.

[0209] By using a hot embossing machine, the precision of the PVA transfer coating after hot embossing can be ensured, the size and shape of the grid line can be reasonably designed, and the ohmic loss can be reduced.

[0210] According to the embodiment of the present application, preferably, the first mold 3 is one of a single crystal silicon substrate 9, a polycrystalline silicon substrate 9, a copper substrate 9, a nickel substrate 9, a copper-nickel alloy substrate 9, a nickel-iron alloy substrate 9, an iron-aluminum alloy substrate 9 or an aluminum alloy substrate 9.

[0211] The effect of multiple materials for selection can be achieved, thereby achieving the effect of flexible use, and further achieving the effect of easy implementation.

[0212] It is known that single crystal silicon substrate: has excellent electrical conductivity and thermal stability, commonly used in the manufacture of high-efficiency photovoltaic cells; Polysilicon substrate: relatively low cost, and has high mechanical strength and stability, widely used in photovoltaic field; Copper substrate: has good electrical conductivity and thermal conductivity, suitable for applications that require fast conduction; Nickel substrate: has excellent corrosion resistance and mechanical strength, suitable for long-term use of electrode manufacturing; Copper-nickel alloy substrate: combines the electrical conductivity of copper and the corrosion resistance of nickel, suitable for high-demand electrical equipment; Nickel-iron alloy substrate: has magnetic properties and corrosion resistance, commonly used in the manufacture of electromagnetic devices; Iron-aluminum alloy substrate: light weight, high temperature and corrosion resistant, suitable for aerospace and high temperature environment electrode applications; Aluminum alloy substrate: light weight, good thermal conductivity, widely used in photovoltaic cell frames and electrical conductors.

[0213] According to the embodiment of the application, preferably, the convex part of the first mold 3 and the shape of the first groove 4 are complementary;

[0214] The shape of the first mold 3 is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right trapezoid or a rectangle. It can be understood that the shape and size of the convex part correspond to the electrode grid line 10, and in actual operation, the size and shape of the electrode grid line 10 required for transfer printing are controlled to reduce the ohmic loss of the electrode grid line 10; The longitudinal cross-sectional shape of the convex part includes but is not limited to one of a triangle, a trapezoid, a rectangle, a diamond, a semicircle, and a polygon; In this embodiment, preferably, the longitudinal cross-sectional shape of the convex part is a triangle or a trapezoid. The longitudinal cross-sectional design of the triangle or the trapezoid helps to change the incident and refractive path of light, can better capture and guide light, can effectively reduce the reflection loss of light, so that more light is absorbed by the semiconductor material and converted into electrical energy, thereby improving the photoelectric conversion efficiency.

[0215] By designing the shape of the convex part of the first mold 3 and the first groove 4 as a complementary structure, precise docking and impression molding effect during mold forming can be ensured, thereby realizing high-precision transfer printing effect and improving the quality of the electrode grid line 10 of the final product.

[0216] Specifically, the shape of the first mold 3 can be selected from a group including but not limited to the following geometric structures: isosceles triangle: suitable for scenarios requiring concentrated force transmission, capable of forming sharp and clear transfer effects on the edges of the photovoltaic electrode grid lines 10. Isosceles trapezoid: with a larger base width and a narrower top structure, suitable for applications requiring gradually widening electrode grid lines 10, ensuring uniform filling during the transfer process. Ellipse: capable of providing smooth edge transition effects, suitable for electrode designs requiring more uniform current distribution, reducing resistance and local stress concentration. Hexagon: stable structure, with good density distribution effect, suitable for electrode grid line 10 designs requiring improved transfer precision and stability. Right trapezoid: suitable for photovoltaic electrode designs requiring uniform grid line width and neat edges, ensuring the accuracy of current distribution. Rectangle: a classic and common design, suitable for the transfer of standardized photovoltaic electrode grid lines 10, providing maximum contact area to improve current conduction efficiency.

[0217] According to the embodiment of the present application, preferably, the aspect ratio of the shape of the first mold 3 is in the range of 1-3.

[0218] By setting the aspect ratio of the mold shape in the range of 1-3, the relationship between the height and width of the convex part of the mold can be effectively adjusted, thereby optimizing the transfer effect of the electrode grid lines 10.

[0219] By setting the aspect ratio of the mold shape in the range of 1-3, the relationship between the height and width of the convex part of the mold can be effectively adjusted, thereby optimizing the transfer effect of the electrode grid lines 10.

[0220] Specifically, when the aspect ratio is 1, the height of the mold is equal to the width, which is suitable for electrode structures that require flat grid lines with uniform thickness and width. It can ensure that the electrode has good conductivity, and the silver paste can be evenly distributed during the transfer process.

[0221] In this embodiment, preferably, when the aspect ratio is close to 2, an appropriate thickness and width are provided, so that the grid line has a certain height, which can improve the mechanical strength of the electrode, and also does not become too wide to maintain the fine structure. It is suitable for conventional photovoltaic electrode manufacturing, balancing resistance, strength and process difficulty.

[0222] When the aspect ratio is 3, the height of the grid line is significantly greater than the width, which is suitable for more fine and narrow electrode designs, which can effectively reduce resistance and improve current density, but requires higher mold precision during manufacturing to ensure sufficient filling of silver paste in the narrow groove.

[0223] Therefore, the flexible setting of the aspect ratio range allows the geometry of the electrode grid lines 10 to be adjusted according to different photovoltaic cell design requirements to achieve the best balance of conductivity, mechanical strength and production process.

[0224] S12, coating the first conductive paste 5 capable of filling the first groove 4 on the embossed side of the polymer layer 2, and removing the excess first conductive paste 5 on the surface of the polymer layer 2, so that the surface of the first groove 4 and the first conductive paste 5 are located in the same plane;

[0225] The first conductive paste 5 can be uniformly coated and distributed in the first groove 4 of the polymer layer 2, thereby providing a basis and guarantee for subsequent embossing.

[0226] According to the embodiment of the present application, preferably, S12 specifically comprises: uniformly applying the first conductive paste 5 on the polymer layer 2 which has been hot-pressed into a shape by using a flat plate coating method, so that the first conductive paste 5 completely fills the first groove 4, and the excess first conductive paste 5 is scraped off to ensure that the first conductive paste 5 is completely and uniformly distributed without deformation. The polymer layer 2 is a PVA film.

[0227] Specifically, the above process steps include but are not limited to:

[0228] I. Prepare the coating environment

[0229] 1.1 Fix the polymer layer 2 which has been hot-pressed into a shape on the workbench of the flat plate coating machine to ensure its stability and avoid movement or deformation during the coating process;

[0230] 1.2 Prepare the first conductive paste 5 to ensure that it is uniformly stirred without particle deposition and has moderate viscosity; the ideal viscosity range of the conductive paste is usually 1000-5000 cP, which is determined according to the coating requirements.

[0231] II. Coating process

[0232] 2.1 Uniform coating: uniformly apply the first conductive paste 5 on the surface of the polymer layer 2 by using the flat plate coating machine, and control the coating thickness appropriately to ensure that the groove can be completely filled;

[0233] 2.2 Pressure control: the pressure applied during coating should be moderate to ensure that the paste can enter the first groove 4 uniformly without causing deformation of the substrate 9; the pressure range can be controlled between 0.1 MPa and 0.5 MPa, and the specific value is adjusted according to the flexibility of the substrate 9 and the groove shape.

[0234] III. Scraping excess paste

[0235] 3.1 Scraper operation: use a scraper to gently scrape off the excess first conductive paste 5 on the surface of the substrate 9 to ensure that the first conductive paste 5 only fills the first groove 4 area and the surface is flat without deformation or accumulation; the scraper should be used with moderate pressure to prevent the paste in the groove from being scraped off; the angle of the scraper is recommended to be controlled between 45° and 60°, and the scraper should be operated at a stable speed to avoid damaging the surface of the substrate 9;

[0236] 3.2 Scraper material: The scraper is recommended to be made of a material with moderate hardness, such as polytetrafluoroethylene (PTFE), polyurethane (PU), or flexible metal, to avoid scratching the substrate 9 during operation.

[0237] Four, paste filling inspection

[0238] 4.1 Visual inspection: Check whether the groove is completely filled with conductive paste by optical microscopy or other visual inspection methods; ensure that there are no bubbles or voids in the groove, and that the surface paste is evenly distributed;

[0239] 4.2 Thickness control: Detect whether the thickness of the paste after coating meets the predetermined standard. The thickness of the paste in the groove can be measured by a thickness gauge or a surface profiler to ensure the uniformity of the conductive layer.

[0240] It should be noted that one of the main components of photovoltaic silver paste is the binder (phenolic resin, epoxy resin, etc.), which serves to form a stable bond between the silver paste particles and the silicon wafer.

[0241] S13, using the second mold 6 to press the first conductive paste 5 in the first groove 4 into a second groove 7 with a predetermined shape, and removing the excess first conductive paste 5 after pressing;

[0242] According to the embodiment of the present application, preferably, S13 specifically includes: using the second mold 6 to press out a second groove 7 with a height of 2-5um and a width of 5um according to the predetermined requirements, removing the excess first conductive paste 5 after pressing, and drying the first conductive paste 5 at 80-200℃.

[0243] Specifically, the above process steps include but are not limited to:

[0244] Second mold 6 pressing groove: The height of the pressing groove of the second mold 6 is 2-5um, and the width is 5um. The bottom of the mold should have high-precision micro-nano structures, and the material should be hard alloy or hardened steel to ensure durability and accuracy; the surface of the mold should be treated with an anti-sticking coating, such as a fluorinated coating, to prevent the conductive paste from adhering to the surface of the mold.

[0245] Apply pressure: The pressure of the pressing should be kept stable to ensure that the paste is completely pressed into the pressing groove. Generally, the pressure is recommended to be controlled at 0.1MPa-0.5MPa; too high pressure will cause too much paste overflow, and too low pressure will not be able to completely compact the paste.

[0246] Pressing time: The time should be determined according to the fluidity of the first conductive paste 5 and the pressing pressure; the pressing time is 30 seconds-2 minutes, too short time may cause incomplete pressing, and too long time may cause deformation of the substrate 9.

[0247] The temperature of the second mold 6 can be controlled in the range of 100-200℃; proper heating of the second mold 6 can improve the flowability of the first conductive paste 5, helping it to better fill the embossed groove of the second mold 6.

[0248] Gap reservation: during the embossing process, the second groove 7 is formed by the design of the second mold 6 or by controlling the pressure. The height of the second groove 7 can be in the range of 0.5-1um, in order to facilitate subsequent process operations.

[0249] Drying of the first conductive paste 5

[0250] Drying temperature: the drying temperature should be selected between 80-200℃; the specific temperature selection depends on the composition of the conductive paste, especially the volatility of the solvent in the silver paste or copper paste.

[0251] It should be noted that the silver paste is usually dried at 80-200℃, and sintered at 500-1000℃.

[0252] Drying time: within this temperature range, the drying time is controlled in the range of 0.5min-20min, and the specific time is adjusted according to the thickness of the paste and the performance of the drying equipment; the time can be shortened at higher temperature, and the drying time needs to be extended at lower temperature.

[0253] Drying environment: a hot air circulation oven is used to ensure that the substrate 9 and the conductive paste are dried at a uniform temperature; of course, according to actual needs, the paste can be dried in an inert gas (such as nitrogen) environment to avoid oxidation or contamination.

[0254] S14, coating the second conductive paste 8 in the second groove 7, and combining the second conductive paste 8 on the first conductive paste 5, and removing the excess second conductive paste 8 on the surface of the polymer layer 2;

[0255] In this embodiment, preferably, S14 specifically includes:

[0256] The coated second conductive paste 8 is in close contact with the formed first conductive paste 5 to form a firm composite layer;

[0257] By heating or applying pressure, the conductive pastes are fused with each other to ensure that the composite layer has no gap and forms a continuous conductive path; the heating temperature is 80-200℃, and the duration is 5-10min;

[0258] In this embodiment, preferably, S14 further includes:

[0259] After removing the excess paste, the conductive paste needs to be preliminarily dried at 80-200℃ for 10-20min to volatilize part of the solvent in the paste, and the first conductive paste 7 and the second conductive paste 8 can be completely attached.

[0260] Specifically, the second conductive paste 8 can be selected from silver paste or other conductive materials, which should have excellent conductivity and good adhesion; the viscosity of the paste should be moderate to ensure uniform distribution and filling of the grooves during coating.

[0261] Flat plate coating method: the second conductive paste 8 is uniformly poured on the polymer layer 2, and then a scraper or roller is used to press on the surface, the coating thickness is controlled at the groove depth to ensure that the paste fills the preset shape.

[0262] Pressure compounding: after coating, a certain pressure can be applied to make the second conductive paste 8 tightly combined with the first conductive paste 5. The pressure value can be controlled within the range of 0.1 MPa-0.3 MPa to avoid excessive compaction.

[0263] Drying: the first conductive paste 7 and the second conductive paste 8 need to be dried, usually the drying temperature is controlled at 80-200℃, the time is 10-20 minutes, to ensure that the solvent part of the paste volatilizes, and the first conductive paste 7 and the second conductive paste 8 can be completely attached.

[0264] Bonding force enhancement: to increase the bonding force between the two layers of conductive paste, a small amount of adhesive or interface treatment agent can be added to the paste to improve the adhesion effect of the two.

[0265] After coating and compounding are completed, a precision scraper or coating removal device is used to remove the excess second conductive paste 8 on the surface of the polymer layer 2. When scraping, the scraper should be kept parallel to the surface to avoid damaging the formed groove structure.

[0266] The material of the scraper should be selected from materials with moderate hardness and wear resistance, such as stainless steel or hard rubber, to avoid damaging the conductive paste. The pressure of the scraper should be kept uniform, generally controlled within the range of 0.05 MPa-0.1 MPa, to ensure that the paste is only retained in the grooves and the surface is smooth and flat.

[0267] Further, in the embodiment, the first conductive paste 5 is one of copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste, and tantalum paste, and the second conductive paste 8 is silver paste.

[0268] The composition of the silver paste includes a binder, and the binder is phenolic resin or epoxy resin.

[0269] Further, the polymer layer 2 is made of water-soluble polymer material, and the water-soluble polymer material is one of polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, polyvinyl alcohol-polyacrylonitrile, polyvinylpyrrolidone, or polyethylene glycol.

[0270] It is to be understood that the polymer layer 2 in the present application is polyvinyl alcohol (PVA film).

[0271] Further, the longitudinal section shape of the groove of the electrode pattern is one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, or a polygon.

[0272] According to the embodiment of the present application, preferably, before S11, a polymer layer 2 with a preset thickness and a stamping forming groove with an electrode pattern is provided, further comprising:

[0273] The PVA film with a thickness of 25-125 um is prepared by electrospinning or flat plate coating.

[0274] Specifically, electrospinning is a technology for preparing a high polymer material film by stretching a polymer solution into nanometer or micrometer fibers through electrostatic force.

[0275] By using electrospinning or flat plate coating, a PVA film with a thickness of 25-125 um can be prepared, which can ensure good performance requirements and achieve good matching effect.

[0276] According to the embodiment of the present application, preferably, the width of the PVA film is 200-800 um, the elongation at break is 20-60%, the tensile strength is 5-20 MPa, and the Shore A hardness is greater than 70 HS.

[0277] According to the embodiment of the present application, preferably, the PVA content of the PVA film is greater than or equal to 90%, the average alcoholysis degree of PVA is 86-90%, and the plasticizer content is 1-3%.

[0278] By using the PVA film with the above parameters, the problem that the PVA film on the market cannot meet the silver / copper paste transfer function due to high softness, complex plasticizer composition, and high specific gravity (10-20%) of the plasticizer can be solved.

[0279] According to the transfer test of three PVA films prepared in the laboratory and purchased on the market, the PVA film for silver / copper paste transfer needs to have the following physical and chemical properties:

[0280] From the above table, it can be seen that:

[0281] Unlike coating a PVA coating on a high-temperature-resistant film, directly using a PVA film as a carrier can reduce the step of tearing the film after transfer, reduce the silicon chip fragmentation caused by tearing the film, and reduce a process, but correspondingly, the hardness requirement of the PVA film is higher, and in addition, since the thickness is larger than that of the PVA film coated on the high-temperature-resistant film, the PVA film in this scheme needs to be dissolved for a longer time, about 2-5 minutes, at a higher water temperature.

[0282] Of course, as a person skilled in the art, when prepared by the plate coating method, the process should be well known.

[0283] The present application controls the size and shape of the PVA film transfer printed composite conductive grid line by the parameters (heating temperature, pressure, time, etc.) of the precision hot press and different molds, and reduces the ohmic loss of the electrode grid line 10. The PVA film is a biodegradable environmentally friendly material, which has low harm to the environment. The water-soluble PVA film at room temperature can greatly reduce the demolding cost. The method is simple, the materials and equipment involved are economical and environmentally friendly, and the process cost is low. It is a new technology that can change the current photovoltaic cell silver electrode grid line 10 printing pattern. The contact part of the conductive paste and the silicon wafer determines its contact resistance, so the use of better silver paste for the contact surface can ensure the conductive efficiency. The upper conductive part can be replaced by copper paste / copper paste to reduce the cost. At present, only this nano-imprinting and transfer process can achieve this. Moreover, similar to this, it can also be made into a trapezoidal shape, a rectangular shape, etc. as shown in FIG. 8. It needs to be known that the light gray is the copper paste / carbon paste, and the dark gray is the silver paste.

[0284] S2, a substrate 9 is provided, and the transfer film prepared in S1 is attached to the substrate 9 with the side of the composite conductive paste, and the first conductive paste 5 and the second conductive paste 8 are transferred to the substrate 9 by pre-set process parameters of the imprinting method; wherein the process parameters of the imprinting: the pressure is 5-20 MPa, the temperature is 80-180℃ and the time is 1-10 min;

[0285] According to the embodiment of the present application, preferably, S2 specifically includes:

[0286] The first conductive paste 5 and the second conductive paste 8 are hot-pressed and transferred to the substrate 9 by applying uniform pressure and heating and drying, and at the same time, the first conductive paste 5 and the second conductive paste 8 are heated and dried to tightly attach to the surface of the substrate 9 without deformation; wherein the substrate 9 is one of a single crystal silicon substrate 9, a polycrystalline silicon substrate 9, a perovskite substrate 9, a glass substrate 9, and a plastic substrate 9.

[0287] The first conductive paste 5 and the second conductive paste 8 are hot-pressed and transferred to the substrate 9 by applying uniform pressure and heating and drying, and at the same time, the first conductive paste 5 and the second conductive paste 8 are heated and dried to tightly attach to the surface of the substrate 9 without deformation;

[0288] By applying uniform pressure and heating and drying to the side of the PVA film without silver paste, the photovoltaic paste can be transferred to the silicon wafer due to the adhesion of the photovoltaic paste to the silicon wafer, and the first conductive paste 5 and the second conductive paste 8 can tightly attach to the silicon wafer, thereby ensuring good transfer effect and further ensuring the stability of the paste structure.

[0289] S3, removing the transfer film so that the first conductive paste 5 and the second conductive paste 8 remain on the substrate 9;

[0290] According to the embodiment of the present application, preferably, S3 specifically comprises:

[0291] The substrate 9 after transfer is placed in water at 25-75°C for cleaning, so that the PVA film is dissolved and falls off, leaving the composite conductive paste pattern that has been successfully transferred, forming the basic structure of the electrode grid line 10.

[0292] The substrate 9 can be dissolved and fall off, so that the composite conductive paste pattern is completely retained on the substrate 9, thereby achieving good dissolution and separation effect. The substrate 9 is a PVA film.

[0293] It should be noted that by changing the alcoholysis degree of PVA, blending modification and other methods, the water solubility of PVA can be changed, so that it can be quickly dissolved at room temperature, and PVA is insoluble in organic solvents such as gasoline, kerosene, vegetable oil, benzene, toluene, dichloroethane, carbon tetrachloride, acetone, ethyl acetate, methanol, ethylene glycol. PVA is incompatible and non-reactive with the binder in the silver paste.

[0294] S4, sintering the first conductive paste 5 and the second conductive paste 8 on the substrate 9 to form the electrode grid line 10 of the composite conductive paste with a preset aspect ratio.

[0295] According to the embodiment of the present application, preferably, S4 specifically comprises:

[0296] The silicon wafer after transferring the first conductive paste 5 and the second conductive paste 8 is placed in a high-temperature furnace for sintering treatment of the composite conductive paste; the sintering temperature is 500-1000°C, ensuring that the silver paste is completely sintered and forms a tight connection with the substrate 9, generating the electrode grid line 10 of the high-precision electrode grid line 10 with a preset aspect ratio.

[0297] After high-temperature sintering, the first conductive paste 5 and the second conductive paste 8 can form silver paste electrode grid lines 10 with the required depth and width. Preferably, the size of the silver paste electrode grid line 10 is 10um deep and 5um wide.

[0298] The preparation process of the high-resolution composite silver / copper paste transfer film based on the PVA carrier has the following beneficial effects:

[0299] 1. High resolution: this method can realize micron-level or even nanometer-level electrode patterns, which has higher resolution than traditional screen printing technology, and helps to improve the performance and efficiency of photovoltaic cells.

[0300] 2. Simple process: using PVA carrier as the transfer carrier, the preparation process is relatively simple and convenient to operate, which is suitable for large-scale production.

[0301] 3. Low cost: PVA material cost is low, and the method can reduce waste generation and reduce material waste, thereby reducing production cost. At the same time, compared with using silver paste as the whole conductive path, the addition of copper paste can greatly reduce the cost while ensuring the conductivity efficiency.

[0302] 4. High adhesion: PVA has no reactivity and weak adhesion with silver paste adhesive and solvent, which can effectively serve as an ideal carrier for transferring silver paste and facilitate the close adhesion of silver paste to the silicon wafer.

[0303] 5. High efficiency production: Compared with screen printing technology, the method has higher production efficiency and can meet the demand of large-scale production, thereby improving production efficiency.

[0304] 6. Environmentally sustainable: PVA carrier is dissolved after washing with warm water, which is environmentally sustainable and beneficial to reduce the impact on the environment

[0305] 7. By mixing copper paste and silver paste, the purpose of reducing production cost while ensuring conductivity efficiency is achieved.

[0306] 8. Using PVA as a transfer carrier, the effective transfer of copper paste and silver paste is achieved, ensuring the close adhesion of copper / silver paste to the silicon wafer.

[0307] 9. Using a precision hot press and mold, high-resolution electrode pattern preparation is achieved, which helps to improve the performance and efficiency of photovoltaic cells

[0308] 10. PVA has no reactivity and weak adhesion with copper paste and silver paste adhesive and solvent, which can serve as an ideal transfer carrier and facilitate the close adhesion of copper / silver paste to the silicon wafer.

[0309] 11. Through the process steps of hot pressing and drying, the accurate coating and sintering of copper / silver paste on the PVA carrier are achieved, ensuring the accuracy and stability of the electrode pattern.

[0310] The application also relates to a photovoltaic cell comprising the electrode grid line 10 prepared by the preparation method described above.

[0311] Further comprising: a substrate layer 13;

[0312] A second conductive layer 12 is arranged on the substrate layer 13 along the length direction of the substrate layer 13;

[0313] A first conductive layer 11 is connected with the second conductive layer 12 along the thickness direction perpendicular to the substrate layer 13;

[0314] The longitudinal section shape of the first conductive layer 11 is one of isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid or rectangle; and the longitudinal section shape of the second conductive layer 12 is isosceles trapezoid.

[0315] Further, a passivation coating is arranged between the first conductive layer 11 and the second conductive layer 12. It can be understood that a layer of passivation material, such as aluminum oxide film or transparent organic coating, is coated between the copper layer and the silver layer or above the silver layer to prevent moisture or corrosive substances in the environment from entering the interface between the two.

[0316] The photovoltaic cell provided in the embodiment and applying the electrode grid line 10 has the same basic principle and technical effects as the above-mentioned embodiments. For the parts not mentioned in the embodiment, please refer to the corresponding contents of the above-mentioned embodiments.

[0317] The above are preferred embodiments of the present application, which do not limit the protection scope of the present application, so: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method of making an electrode grid, characterized by: The method comprises the following steps: S1, providing a substrate, and forming a polymer layer on the substrate; S2, using a first mold to press a first groove corresponding to a required electrode pattern on the polymer layer, applying a first conductive paste on the polymer layer to fill the groove, and scraping off the excess first conductive paste; S3, providing a substrate, and covering the polymer layer on the substrate, and transferring the polymer layer and the first conductive paste to the substrate under a certain temperature and pressure; S4, peeling off the substrate from the polymer layer, and dissolving the polymer layer, so that the first conductive paste is left adhered to the substrate; S5, sintering the first conductive paste to form the electrode grid lines.

2. The method of claim 1, wherein: The thickness of the polymer layer is 5-30 um, and the opening width of the electrode pattern is 3-10 um.

3. The method of claim 1, wherein: Between the S2 and the S3, the method further comprises the following steps: S20, providing a second mold, using the second mold to press a second groove on the first conductive paste, and drying the first conductive paste; applying a second conductive paste on the first conductive paste to fill the second groove, and scraping off the excess second conductive paste.

4. The method of claim 3, wherein: The contact resistance of the second conductive paste is less than that of the first conductive paste, and the conductivity of the second conductive paste is greater than that of the first conductive paste.

5. The method of claim 3, wherein: In the S20, after pressing the second groove, the first conductive paste is dried at a temperature of 80-200 ℃.

6. The method of claim 1 or 3, wherein: In the S3, the first conductive paste is adhered to the substrate, or the second conductive paste is adhered to the substrate, by applying a pressure of 5-20 MPa and a temperature of 80-180 ℃.

7. The method of claim 1 or 3, wherein: In the S4, the polymer layer is dissolved by using normal temperature water, and after the dissolution, the first conductive paste is left adhered to the substrate, or the first conductive paste and the second conductive paste are left adhered to the substrate.

8. The method of claim 1 or 3, wherein: In the S5, the first conductive paste is sintered at a high temperature of 500-1000 ℃ to form the electrode grid lines, or the first conductive paste and the second conductive paste are sintered at a high temperature of 500-1000 ℃ to form the electrode grid lines.

9. The method of claim 1 or 3, wherein: The width of the first groove is the same as that of the second groove, and the height ratio of the first groove to the second groove is 2:1-5:

1. The first groove and the second groove are made by hot pressing, and the hot pressing temperature is 80-180 ℃. The longitudinal cross-sectional shape of the first groove and the second groove is one of a triangle, a trapezoid, a rectangle, a rhombus, a semicircle, and a polygon.

10. The method of claim 1 or 3, wherein: The material of the first mold and the second mold is one of single crystal silicon, polycrystalline silicon, copper, nickel, copper-nickel alloy, nickel-iron alloy, iron-aluminum alloy, and aluminum alloy.

11. The method of claim 1, wherein: The glass transition temperature of the polymer layer is 70-120 ℃, and the material of the polymer layer is a water-soluble polymer material. The water-soluble polymer material is one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, and polyvinyl alcohol-polyacrylonitrile.

12. The method of claim 1, wherein: The material of the substrate comprises one of polyethylene terephthalate, polyimide, polyethylene terephthalate copolymer, polycarbonate, polypropylene, polyurethane, and the thickness of the substrate is 25-200 um.

13. The method of claim 1, wherein: The substrate is one of monocrystalline silicon substrate, polycrystalline silicon substrate, perovskite substrate, glass substrate, plastic substrate.

14. A method of making an electrode grid, characterized by: The method comprises the following steps: S1, providing a transfer film with composite conductive paste; S2, providing a substrate, adhering one side of the transfer film with composite conductive paste to the substrate, and transferring the composite conductive paste to the substrate by pre-set process parameters of embossing, wherein the process parameters of embossing are: pressure 5-20 MPa, temperature 80-180℃ and time 1-10 min; S3, removing part of the material of the transfer film to make the composite conductive paste remain on the substrate; S4, sintering the composite conductive paste on the substrate to form the electrode grid line with a preset aspect ratio.

15. The method of claim 14, wherein the electrode grid line is prepared by a method comprising: The preparation method of the transfer film with composite conductive paste in S1 comprises the following steps: S11, providing a polymer layer, and using a first mold to press a first groove corresponding to the required electrode pattern on the polymer layer; S12, coating the first conductive paste capable of filling the first groove on the embossed side of the polymer layer, and removing the excess first conductive paste on the surface of the polymer layer, so that the surface of the first groove and the first conductive paste are located on the same plane; S13, using a second mold to emboss a second groove with a preset shape on the first conductive paste, and removing the excess first conductive paste after embossing; S14, coating the second conductive paste in the second groove, and compounding the second conductive paste on the first conductive paste, and removing the excess second conductive paste on the surface of the polymer layer to complete the preparation of the transfer film with composite conductive paste.

16. The method of claim 15, wherein: The preparation method of the transfer film with composite conductive paste in S1 comprises the following steps: The polymer layer has a thickness of 20-125 um, a width of 200-800 um, an elongation at break of 20-60%, a tensile strength of 5-20 MPa, and a Shore A hardness of more than 70HS.

17. The method of claim 16, wherein: The polymer layer adopts a water-soluble polymer material, and the water-soluble polymer material is one of polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid, polyvinyl alcohol-polyacrylonitrile, polyvinylpyrrolidone or polyethylene glycol.

18. The method of claim 15, wherein: The polymer layer is placed in the first mold by a precision hot press, and hot embossing is performed in a temperature range of 80-180℃, so that the surface of the polymer layer forms micron-level or even nanometer-level first grooves corresponding to the electrode pattern; The convex part of the first mold is complementary to the shape of the first groove, and the shape of the first groove is one of isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid or rectangle.

19. The method of claim 15, wherein: The S12 specifically includes: using a flat plate coating method to uniformly apply the first conductive paste on the polymer layer which has been hot-pressed into a shape, so that the first conductive paste completely fills the first groove, and the excess first conductive paste is scraped off to ensure that the first conductive paste is completely filled and uniformly distributed without deformation.

20. The method of claim 15, wherein: The S13 specifically includes: using the second mold to press the second groove with a height of 2-5um and a width of 5um according to the preset requirements, and drying the first conductive paste at 80-200℃.

21. The method of claim 15, wherein: The S14 specifically includes: tightly contacting the coated second conductive paste with the formed first conductive paste to form a firm composite layer. By heating or applying pressure, the conductive pastes are fused with each other to ensure that the composite layer has no gap and forms a continuous conductive path.

22. The method of claim 21, wherein: The S14 also includes: after removing the excess paste, the conductive paste needs to be preliminarily dried, dried at 80-200℃ for 10-20 minutes, so that the solvent part in the paste is volatilized, and the first conductive paste and the second conductive paste can be completely attached.

23. The method of claim 15, wherein: The first conductive paste is one of copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste, and tantalum paste, and the second conductive paste is silver paste. The composition of the silver paste includes a binder, and the binder is phenolic resin or epoxy resin.

24. The method of claim 14, wherein: The S2 specifically includes: hot-pressing and transferring the first conductive paste and the second conductive paste to the substrate by applying uniform pressure and heating and drying, and simultaneously heating and drying the first conductive paste and the second conductive paste to tightly attach them to the surface of the substrate without deformation. The substrate is one of a single crystal silicon substrate, a polycrystalline silicon substrate, a perovskite substrate, a glass substrate, and a plastic substrate.

25. The method of claim 14, wherein: The S2 specifically includes: hot-pressing and transferring the third conductive paste and the fourth conductive paste to the substrate by applying uniform pressure and heating and drying, and simultaneously heating and drying the third conductive paste and the fourth conductive paste to tightly attach them to the surface of the substrate without deformation. The substrate is one of a single crystal silicon substrate, a polycrystalline silicon substrate, a perovskite substrate, a glass substrate, and a plastic substrate.

26. The method of claim 14, wherein: The S3 specifically includes: placing the transferred substrate into water at 25-75℃ for cleaning, so that the polymer layer is dissolved and falls off, leaving the composite conductive paste pattern of the first conductive paste and the second conductive paste which have been successfully transferred, and forming the basic structure of the electrode grid line.

27. The method of claim 14, wherein: The S4 specifically includes: placing the substrate after transferring the first conductive paste and the second conductive paste into a high-temperature furnace for sintering treatment of the composite conductive paste; the sintering temperature is 500-1000℃, ensuring that the first conductive paste and the second conductive paste are completely sintered and tightly connected with the substrate, generating the electrode grid line with a preset aspect ratio.

27. A photovoltaic cell comprising the electrode grid line prepared by the preparation method of any one of claims 1-13, or comprising the electrode grid line prepared by the preparation method of any one of claims 14-26.

28. The photovoltaic cell of claim 27, wherein: The outer edge shape of the electrode grid line is one of a triangle, a trapezoid, a rectangle, a diamond, a semicircle and a polygon; and the height-width ratio of the electrode grid line is 2:1.

Images