Preparation method for electrode grid lines, and photovoltaic cell

Abstract

The present invention relates to the technical field of photovoltaic cells, and discloses a preparation method for electrode grid lines, and a photovoltaic cell. The preparation method for electrode grid lines comprises the following steps: S1, providing a polymer layer that serves as a transfer substrate; S2, coating the forming side of the polymer layer with a conductive paste that at least adequately fill up grooves thereon, and removing excess conductive paste from the surface of the polymer layer; S3, providing a substrate, attaching the side of the polymer layer having the conductive paste to the substrate, and transferring the conductive paste to the substrate by means of a transfer method having preset process parameters; S4, removing the polymer layer; and S5, sintering the conductive paste on the substrate to form high-resolution electrode grid lines with a preset aspect ratio. The present application improves the definition and resolution of electrode grid lines, realizes the preparation of finer patterns, and enables the fabrication of electrode grid lines having a width within 5 μm, which helps to improve the overall performance and photoelectric conversion efficiency of a photovoltaic cell; moreover, the process flow is simplified, and the production efficiency is improved.

Description

Electrode grid line preparation method and photovoltaic cell TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, and particularly relates to an electrode grid line preparation method and a photovoltaic cell. BACKGROUND

[0002] With the promotion of the national carbon peak and carbon neutralization target, the construction of a new power system with new energy as the main body is accelerating deployment, and the photovoltaic industry is significantly improving its position. Solar cells are the core components of photovoltaic systems, and industrial production of single-crystal silicon photovoltaic cells occupies an important position, accounting for more than 90% of the total solar cell production. The electrode grid line is a key component of the cell, which has a great influence on the performance of the solar cell. The material of the electrode grid line is mainly a material with good conductivity, and the conductive paste is one of the most widely used electrode grid line materials, which has excellent conductivity and chemical stability and is suitable for the preparation of photovoltaic cells. Optimizing the preparation process of the conductive paste grid line can effectively improve the photoelectric conversion efficiency of the solar cell.

[0003] The conductive paste grid line printing technology of the photovoltaic cell is one of the key production processes, which is mainly used to form electrodes on the silicon wafer to collect the current generated by the photovoltaic effect. Common electrode grid line printing technologies mainly include screen printing, inkjet printing, offset printing, and flexible printing. The screen printing technology is the most commonly used, which prints the conductive paste onto the surface of the photovoltaic cell through a screen to form an electrode pattern, thereby realizing the collection and conduction of electric energy.

[0004] Although the screen printing technology is commonly used, there are still some deficiencies compared with the transfer conductive paste technology. For example, the transfer conductive paste technology has higher resolution, more stable product quality, higher production efficiency, more extensive applicability, and stronger durability.

[0005] However, in the transfer technology, the transfer substrate film cannot meet the use requirements due to its flexibility, so that some substrate films are too soft, causing deformation after the conductive paste is filled in; some substrate films are too hard, causing them to be too brittle and unable to be used normally; and the subsequent substrate cannot be automatically separated from the base material, thereby affecting the grid line structure. In view of the above problems, no effective solution has been proposed. SUMMARY

[0006] The purpose of the present application is to provide an electrode grid line preparation method and a photovoltaic cell to at least solve one of the problems existing in the prior art.

[0007] Technical scheme: An electrode grid line preparation method comprises the following steps:

[0008] S1, providing a polymer layer as a transfer substrate;

[0009] S2, coating the concave groove of the polymer layer with conductive paste, and removing the excess conductive paste on the surface of the polymer layer, so that the concave groove and the surface of the conductive paste are in the same plane;

[0010] S3, providing a substrate, and bonding the polymer layer with the conductive paste to the substrate, and transferring the conductive paste to the substrate by a preset process parameter transfer method; wherein the process parameters of the transfer are: pressure 5-20 MPa, temperature 80-180℃ and time 1-10 min;

[0011] S4, removing the polymer layer so that the conductive paste remains on the substrate;

[0012] S5, sintering the conductive paste on the substrate to form an electrode grid line with a preset aspect ratio.

[0013] As a preferred, S1, providing a polymer layer as a transfer substrate, comprising the following steps:

[0014] S101, providing a mold with a preset shape complementary to the electrode pattern to be imprinted;

[0015] S102, preparing a polymer layer required according to a preset process parameter on the mold, and using it as a transfer substrate.

[0016] As a preferred, S102, preparing a polymer layer required according to a preset process parameter on the mold, and using it as a transfer substrate, comprising:

[0017] Preparation of a polymer layer with a thickness of 15-85μm with a concave groove on the mold, and after drying at 100-125℃, it is demolded from the mold side to obtain the required micron or nanometer electrode pattern polymer layer as a transfer substrate.

[0018] As a preferred, in S102, the thickness of the polymer layer is 15-50μm.

[0019] As a preferred, S1, providing a polymer layer as a transfer substrate, further comprising the following steps:

[0020] S111, providing a polymer layer;

[0021] S112, using a mold to hot-press the concave groove of the electrode pattern on the polymer layer.

[0022] As a preferred, in S1, the polymer layer is prepared by electrospinning or flat coating method.

[0023] As preferred, in S1, the polymer layer is prepared by electrospinning, including the following steps:

[0024] S11, dissolving the water-soluble polymer material in a predetermined solvent to prepare a uniform spinning solution;

[0025] S12, placing the spinning solution in a syringe and spinning through an electrospinning device;

[0026] S13, during the spinning process, the fibers form a film on a predetermined device, and the collected film is post-processed to obtain the desired polymer layer.

[0027] As preferred, S11, dissolving the water-soluble polymer material in a predetermined solvent to prepare a uniform spinning solution, including:

[0028] Dissolve PVP and tetrabutyl titanate in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 3-5% PVP and 18-22% tetrabutyl titanate.

[0029] As preferred, S11, dissolving the water-soluble polymer material in a predetermined solvent to prepare a uniform spinning solution, further including:

[0030] Slowly add PVP and diphenylalanine to a mixed solvent of methanol and N,N-methyl acetamide under stirring, continue stirring until completely dissolved, and obtain a transparent polymer solution.

[0031] As preferred, S12, placing the spinning solution in a syringe and spinning through an electrospinning device, including:

[0032] Place the prepared spinning solution in a syringe with a predetermined inner diameter and perform electrospinning at a predetermined working voltage intensity.

[0033] As preferred, S13, during the spinning process, the fibers form a film on a predetermined device, and the collected film is post-processed to obtain the desired polymer layer, including:

[0034] The polymer layer formed by spinning is uniformly deposited on the collection device, and corresponding pretreatment steps are performed according to the predetermined use of the fiber film.

[0035] As preferred, S111, providing a polymer layer, including:

[0036] Prepare a polymer layer with a thickness of 35-85 μm by electrospinning or flat plate coating.

[0037] As preferred, S112, using a mold to hot-press and form a groove of the electrode pattern on the polymer layer, including:

[0038] The prepared polymer layer is placed in a mold using a precision hot press and hot-pressed at 100-180℃ to form a micron- or even nano-scale electrode groove structure on the surface of the polymer layer.

[0039] Preferably, the mold is one of the following: monocrystalline silicon substrate, polycrystalline silicon substrate, copper substrate, nickel substrate, copper-nickel alloy substrate, nickel-iron alloy substrate, iron-aluminum alloy substrate, or aluminum alloy substrate.

[0040] Preferably, the shape of the protrusion of the mold is complementary to the shape of the groove;

[0041] The shape of the mold is one of the following: isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid, or rectangle.

[0042] Preferably, the aspect ratio of the mold shape is in the range of 1-3.

[0043] Preferably, the surface of the mold is coated with a self-assembled monolayer.

[0044] Preferably, the self-assembled monolayer is one of a silane compound, a siloxane compound, or a perfluorinated compound.

[0045] Preferably, step S2 involves applying a conductive paste that fills the grooves on the molding side of the polymer layer and removing excess conductive paste from the surface of the polymer layer so that the grooves and the surface of the conductive paste are on the same plane, including:

[0046] The conductive paste is evenly applied to the formed polymer layer using a flat plate coating method, so that the conductive paste completely fills the grooves. Excess conductive paste is scraped off to ensure that the conductive paste is completely and evenly distributed without deformation.

[0047] Preferably, S3, providing a substrate, and bonding the side of the polymer layer having the conductive paste to the substrate, including:

[0048] At a preset temperature, the conductive paste is tightly bonded to the substrate surface by applying uniform pressure while the conductive paste is dried; and within the temperature and pressure range, the macroscopic morphology of the conductive paste transferred to the substrate remains unchanged.

[0049] The substrate is one of the following: crystalline silicon wafer, glass, perovskite, metal, or polymer substrate.

[0050] Preferably, step S4, removing the polymer layer to leave the conductive paste on the substrate, includes:

[0051] The transferred silicon wafer is placed in an aqueous solution at 25-75℃ to dissolve and remove the polymer layer, leaving behind the successfully transferred conductive paste pattern, which forms the basic structure of the electrode grid lines.

[0052] As preferred, S5, sintering the conductive paste on the substrate to form the electrode grid lines with the preset aspect ratio, comprises:

[0053] After transferring the conductive paste, the silicon wafer is placed in a high-temperature furnace for sintering treatment of the conductive paste; the sintering temperature is 500-800℃, ensuring that the conductive paste is completely sintered and forms a tight connection with the silicon wafer, generating electrode grid lines with a preset aspect ratio.

[0054] As preferred, the conductive paste is one of silver paste, aluminum paste, copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste or tantalum paste.

[0055] As preferred, the glass transition temperature of the polymer layer is 60-120℃, and the material of the polymer layer is a water-soluble high molecular material.

[0056] As preferred, the water-soluble high molecular material is one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid or polyvinyl alcohol-polyacrylonitrile.

[0057] Among them, the average polymerization degree of the polyvinyl alcohol is 1700, and the alcoholysis degree is 88-92%; the polyvinyl alcohol is ordinary polyvinyl alcohol and modified polyvinyl alcohol; the modified polyvinyl alcohol is carboxyl modified polyvinyl alcohol, and the carboxyl modification degree is 2-8%.

[0058] As preferred, S102 further comprises: a bonding layer is arranged on the side of the polymer layer away from the mold, and a substrate is arranged on the side of the bonding layer away from the polymer layer.

[0059] As preferred, the substrate is one of polyimide, polyethylene terephthalate, polyamide or polycarbonate.

[0060] As preferred, S3 further comprises: when transferring under the preset process parameters, the bonding layer and the substrate are separated from the polymer layer.

[0061] In order to achieve the above-mentioned purpose, according to another aspect of the present application, a photovoltaic cell is also provided.

[0062] The photovoltaic cell according to the present application comprises the electrode grid lines prepared.

[0063] Beneficial effects: in the embodiment of the present application, the electrode grid line is prepared by the transfer printing method, S1, a polymer layer is provided as a transfer printing substrate; S2, the conductive paste capable of filling the groove is coated on the shaped side of the polymer layer, and the excess conductive paste on the surface of the polymer layer is removed, so that the groove and the surface of the conductive paste are located on the same plane; S3, a substrate is provided, the side of the polymer layer with the conductive paste is attached to the substrate, and the conductive paste is transferred to the substrate by the transfer printing method with preset process parameters; wherein the process parameters of the transfer printing: the pressure is 5-20MPa, the temperature is 80-180℃ and the time is 1-10min; S4, the polymer layer is removed, so that the conductive paste remains on the substrate; S5, the conductive paste is sintered on the substrate to form an electrode grid line with a preset aspect ratio, an electrode grid line with a preset aspect ratio is formed, the purpose of preparing the electrode grid line is achieved, thereby realizing the technical effects of saving process time, simplifying process flow, the substrate film having good flexibility and being easy to separate, and further solving the problems that in the transfer printing technology, the substrate film cannot meet the use demand due to the flexibility, some substrate films are too soft, leading to the deformation after the silver paste is filled in, some substrate films are too hard, leading to the brittleness and unable to be normally used, and the subsequent substrate cannot be automatically separated from the substrate, thereby affecting the grid line structure. BRIEF DESCRIPTION OF DRAWINGS

[0064] Fig. 1 is a structural flowchart of the electrode grid line preparation method of the present application;

[0065] Fig. 2 is a structural flowchart of another electrode grid line preparation method of the present application;

[0066] Fig. 3 is a structural flowchart of another electrode grid line preparation method of the present application;

[0067] Fig. 4 is a structural flowchart of another electrode grid line preparation method of the present application;

[0068] Fig. 5 is a flowchart of the electrode grid line preparation method of the present application;

[0069] Fig. 6 is a flowchart of another electrode grid line preparation method of the present application;

[0070] Fig. 7 is a flowchart of another electrode grid line preparation method of the present application;

[0071] Fig. 8 is a flowchart of the polymer layer preparation method of the present application; and

[0072] Fig. 9 is a mold structure diagram in the electrode grid line preparation method of the present application.

[0073] The reference signs are: 1, mold; 2, polymer layer; 3, groove; 4, conductive paste; 5, substrate; 6, electrode grid line; 7, adhesive layer; 8, base. DETAILED DESCRIPTION

[0074] In order to make the person skilled in the art better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0075] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0076] In addition, the terms "mount", "set", "provided with", "connected", "connected", "sleeved" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally configured; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For the person skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0077] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0078] As shown in FIGS. 1-9, the present application relates to an electrode grid line preparation method and a photovoltaic cell. As shown in FIGS. 1 and 5, the electrode grid line preparation method comprises the following steps:

[0079] S1, providing a polymer layer 2 as a transfer substrate;

[0080] It can ensure good transfer effect, thereby providing guarantee for normal implementation of subsequent processes.

[0081] As shown in Fig. 2-3 and 6, according to the embodiment of the present application, preferably, S1, providing a polymer layer 2 as a transfer substrate, comprising the following steps:

[0082] S101, providing a mold 1 with a shape complementary to the electrode pattern to be formed;

[0083] The effect of obtaining the required polymer layer can be achieved, thereby providing a guarantee for the subsequent process.

[0084] It should be noted that PVP is polyvinylpyrrolidone, which is a non-ionic high molecular compound, has good water solubility, biocompatibility and film forming property.

[0085] The present application is based on the deep understanding of photovoltaic conductive paste and the water solubility of polyvinylpyrrolidone (PVP) material, it is found that PVP has no reactivity and weak adhesion with conductive paste binder and solvent, and can be used as an ideal carrier for transferring conductive paste.

[0086] As a synthetic water-soluble polymer compound, PVP has the general properties of water-soluble polymer compounds, such as colloidal protection, film forming property, adhesion, hygroscopicity, solubilization or condensation, but its most characteristic is its excellent solubility and physiological compatibility. In synthetic polymers, it is not common to have both water solubility and solubility in most organic solvents, very low toxicity and good physiological compatibility, especially in the fields closely related to health such as medicine, food and cosmetics, with the price of its raw material butyrolactone decreasing, PVP shows good prospects for development.

[0087] The PVP with large molecular weight has no obvious adhesion and reactivity with the conductive paste, which meets the function of PVP as a carrier of conductive paste. When the conductive paste is coated on the PVP, the residual conductive paste on the surface can be scraped clean, which ensures that the properties of the conductive paste in the groove remain unchanged.

[0088] The glass transition temperature of PVP is 80-120℃, and the processing conditions are easy to meet when transferring to a silicon wafer under a certain temperature (80-160℃) and pressure (5-20MPa).

[0089] According to the embodiment of the present application, preferably, in S1, the mold is one of single crystal silicon substrate, polycrystalline silicon substrate, copper substrate, nickel substrate, copper-nickel alloy substrate, nickel-iron alloy substrate, iron-aluminum alloy substrate or aluminum alloy substrate.

[0090] The effect of multiple materials for selection can be achieved, thereby achieving the effect of flexible use, and further achieving the effect of easy realization.

[0091] It should be noted that the single crystal silicon substrate has excellent thermal stability and is commonly used in the manufacture of high-efficiency photovoltaic cells.

[0092] Polysilicon substrate: relatively low cost, high mechanical strength and stability, widely used in photovoltaic field;

[0093] Copper substrate: good electrical conductivity and thermal conductivity, suitable for applications requiring fast conduction;

[0094] Nickel substrate: excellent corrosion resistance and mechanical strength, suitable for long-term use of electrode manufacturing;

[0095] Copper-nickel alloy substrate: combines the electrical conductivity of copper and the corrosion resistance of nickel, suitable for high-demand electrical equipment;

[0096] Nickel-iron alloy substrate: magnetic and corrosion resistant, commonly used in the manufacture of electromagnetic devices;

[0097] Iron-aluminum alloy substrate: light weight, high temperature and corrosion resistant, suitable for aerospace and high temperature environment electrode applications;

[0098] Aluminum alloy substrate: light weight, good thermal conductivity, widely used in photovoltaic cell frame and electrical conductor.

[0099] S102, the mold 1 is prepared according to the preset process parameters to obtain the required polymer layer 2, and the mold 1 is used as a transfer substrate;

[0100] By directly preparing a polymer layer 2 with micron or even nanoscale grooves on the mold, and using the polymer layer 2 as a transfer substrate, the production process can be simplified, the production cost can be reduced, and the production efficiency can be improved.

[0101] According to the embodiment of the application, preferably, S102, the mold 1 is prepared according to the preset process parameters to obtain the required polymer layer 2, and the mold 1 is used as a transfer substrate, comprising:

[0102] A polymer layer 2 with a thickness of 15-85 μm and grooves 3 is prepared on the mold 1, and after drying at 100-180℃, it is demolded from the mold 1 side to obtain the required micron or nanoscale electrode pattern polymer layer 2 as a transfer substrate.

[0103] According to the embodiment of the application, preferably, in S102, the thickness of the polymer layer 2 is 15-50 μm. Preferably, the thickness of the polymer layer is 20-30 μm.

[0104] From the above description, it can be seen that the application achieves the following technical effects:

[0105] In the embodiment of the present application, the polymer layer is prepared directly on the mold and the electrode grid line is prepared by transfer printing. The steps are as follows: S101, providing a mold which is complementary to the shape of the electrode pattern to be formed by pressing; S102, preparing a polymer layer on the mold according to predetermined process parameters, and using the polymer layer as a transfer printing substrate; S2, coating the conductive paste on the forming side of the polymer layer which can fill the grooves, and removing the excess conductive paste on the surface of the polymer layer so that the surface of the grooves and the conductive paste are located on the same plane; S3, providing a substrate, and bonding the polymer layer with the conductive paste to the substrate, and transferring the conductive paste to the substrate by transfer printing with predetermined process parameters; the process parameters of transfer printing are: pressure of 5-20 MPa, temperature of 80-180℃ and time of 1-10 min; S4, removing the polymer layer so that the conductive paste remains on the substrate; S5, sintering the conductive paste on the substrate to form an electrode grid line with a predetermined aspect ratio, thereby achieving the purpose of obtaining a required polymer layer and preparing an electrode grid line, and realizing the technical effects of saving process time, simplifying process flow, improving the service life of the mold, and the substrate film having good flexibility and being easy to separate, thereby solving the technical problems that in the transfer printing technology, the substrate film cannot meet the use requirements due to its flexibility, some substrate films are too soft to deform after the subsequent conductive paste is filled, and some substrate films are too hard and brittle to be used normally, the subsequent substrate cannot be automatically separated from the substrate, thereby affecting the grid line structure, and the mold is damaged due to repeated high pressure pressing and film tearing in the process of combining high-precision hot stamping and transfer printing to make a high-resolution electrode grid line, thereby shortening the service life of the mold.

[0106] As shown in FIGS. 4 and 7, according to the embodiment of the present application, preferably, S1, providing a polymer layer as a transfer printing substrate, further comprises the following steps:

[0107] S111, providing a polymer layer;

[0108] According to the embodiment of the present application, preferably, S111, providing a polymer layer, comprises:

[0109] The polymer layer with a thickness of 15-85 μm is prepared by electrospinning or flat plate coating.

[0110] Specifically, electrospinning is a technology for stretching polymer solution into nanometer or micrometer fibers by electrostatic force, which is used for preparing a high polymer film; the polymer layer prepared by the above method can meet the good performance requirements.

[0111] Of course, as a person skilled in the art, when flat plate coating is used, the process is well known.

[0112] The electrode pattern can be obtained by hot-pressing, so that the effects of improving precision and facilitating implementation can be achieved.

[0113] According to the embodiment of the present application, preferably, S112, hot-pressing and forming the electrode pattern groove on the polymer layer using the mold comprises:

[0114] The prepared polymer layer is placed in the mold by a precision hot-pressing machine, and hot-pressing and forming is performed at 100-180 DEG C, so that the surface of the polymer layer forms a micron-level or even nanometer-level electrode groove structure.

[0115] By using the hot-pressing machine, the precision of the PVP transfer coating after hot-pressing can be ensured, the size and shape of the grid line can be reasonably designed, and the ohmic loss can be reduced.

[0116] According to the embodiment of the present application, preferably, in S1, the polymer layer 2 is prepared by using an electrospinning method or a flat coating method.

[0117] Specifically, electrospinning is a technology for stretching a polymer solution into nanometer or micrometer fibers by electrostatic force, and is used for preparing a high polymer material film.

[0118] By using the electrospinning method or the flat coating method, a polymer layer with a thickness of 15-85 mu m can be prepared, and good performance requirements can be ensured, so that good matching effects can be achieved.

[0119] Of course, as a person skilled in the art, when the flat coating method is used for preparation, the process thereof should be well known.

[0120] From the above description, it can be seen that the present application achieves the following technical effects:

[0121] In the embodiment of the present application, the hot press forming method is adopted, S111, a polymer layer is provided; S112, a mold is used to hot press imprint the recesses of the electrode pattern on the polymer layer; S2, the conductive paste capable of filling the recesses is coated on the formed side of the polymer layer, and the excess conductive paste on the surface of the polymer layer is removed, so that the recesses and the surface of the conductive paste are located on the same plane; S3, a substrate is provided, the polymer layer with the conductive paste is attached to the substrate, and the conductive paste is transferred to the substrate by the transfer method with the preset process parameters; wherein the process parameters of the transfer: the pressure is 5-20 MPa, the temperature is 80-180℃, and the time is 1-10 min; S4, the polymer layer is removed, so that the conductive paste remains on the substrate; S5, the conductive paste is sintered on the substrate to form the electrode grid lines with a preset aspect ratio, which achieves the purpose of improving the adhesion of the transferred silver paste, thereby realizing the effects of ensuring the firm attachment of the silver paste to the silicon wafer, improving the precision and stability of the electrode pattern, and reducing the production cost and the production efficiency, thereby solving the technical problems that the precision of the screen printing process is limited by the screen aperture and the printing pressure, it is difficult to realize very small patterns and high-resolution printing, and the general silver paste line width is at least several tens of microns; at the same time, a certain amount of waste is generated during the screen printing process, resulting in waste of materials; moreover, the service life of the screen is limited, and the overall cost is high; and the screen printing is a relatively slow production process, which cannot meet the needs of large-scale production, affecting the production efficiency.

[0122] As shown in FIG. 9, according to the embodiment of the present application, preferably, the convex part of the mold 1 is complementary in shape to the recess 3;

[0123] The shape of the convex part of the mold 1 is one of an isosceles triangle, an isosceles trapezoid, an ellipse, a hexagon, a right trapezoid, or a rectangle. The shape and size of the convex part correspond to the electrode grid lines, and in actual operation, the size and shape of the electrode grid lines required for transfer are controlled to reduce the ohmic loss of the electrode grid lines; 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 the 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 refraction 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] By designing the convex part of the mold and the recess to be complementary in shape, precise docking and press imprinting effects during mold forming can be ensured, thereby realizing high-precision transfer effects and improving the quality of the electrode grid lines of the final product.

[0125] Specifically, the shape of the mold can be selected from the following geometric structures:

[0126] Isosceles triangle: suitable for scenarios requiring concentrated force transmission, capable of forming sharp and clear transfer effects at the edges of the electrode grid lines.

[0127] Isosceles trapezoid: with a larger base width and a narrower top structure, suitable for applications requiring gradually widening electrode grid lines, ensuring uniform filling during the transfer process.

[0128] Ellipse: capable of providing smooth edge transition effects, suitable for electrode designs that require more uniform current distribution, reducing resistance and local stress concentration.

[0129] Hexagon: stable structure with good density distribution effect, suitable for electrode grid line designs that require improved transfer precision and stability.

[0130] Right trapezoid: suitable for photovoltaic electrode designs that require uniform grid line width and neat edges, ensuring the accuracy of current distribution.

[0131] Rectangle: a classic and common design, suitable for the transfer of standardized electrode grid lines, providing maximum contact area to improve current conduction efficiency.

[0132] According to the embodiment of the present application, preferably, the aspect ratio of the mold shape ranges from 1 to 3.

[0133] By setting the aspect ratio of the mold shape to be in the range of 1 to 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.

[0134] Specifically, when the aspect ratio is 1, the height of the mold is equal to the width, 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 conductive paste 4 can be uniformly distributed during the transfer process.

[0135] 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 does not become too wide to maintain a fine structure. Suitable for conventional photovoltaic electrode manufacturing, balancing resistance, strength and process difficulty.

[0136] When the aspect ratio is 3, the height of the grid line is significantly greater than the width, suitable for more fine and narrow electrode designs that require, which can effectively reduce resistance and improve current density, but require higher mold precision during manufacturing to ensure sufficient filling of the conductive paste 4 in the narrow slot.

[0137] Therefore, the flexible setting of the aspect ratio range allows adjusting the geometry of the electrode grid lines according to different photovoltaic cell design requirements to achieve the best balance of electrical conductivity, mechanical strength and production process.

[0138] According to the embodiment of the present application, preferably, the surface of the mold is coated with a self-assembled monolayer.

[0139] Coating the mold surface with a self-assembled monolayer (SAM) can further improve the pattern fidelity and easy peelability of the polymer layer, while effectively prolonging the service life of the mold.

[0140] Of course, the main purpose of coating the mold surface with a self-assembled monolayer (SAM) is to improve the properties of the mold surface, including but not limited to the following points:

[0141] Reducing adhesion: the SAM layer can reduce the adhesion of the mold surface, making it easier for plastics or other materials to separate from the mold surface during injection molding or calendering, thereby improving production efficiency.

[0142] Controlling surface energy: the SAM layer can adjust the hydrophilic or hydrophobic properties of the mold surface, making it have better anti-adhesion performance, and also affecting the wettability of the material, which is beneficial to the flow and molding of the material during the production process. In our patent, the hydrophobicity of the mold is improved.

[0143] Improving corrosion resistance: the SAM layer can improve the corrosion resistance of the mold surface, prolonging the service life of the mold.

[0144] According to the embodiment of the present application, preferably, the self-assembled monolayer is one of a silane compound, a siloxane compound or a perfluorinated compound.

[0145] Specifically, the silane compound can be octadecyltrichlorosilane (OTS).

[0146] The siloxane compound can be octamethylcyclotetrasiloxane (OMCTS) and octamethyl-disiloxane (OMDS), etc., which can form a silicone protective layer on the surface of crystalline silicon and have a certain hydrophobicity.

[0147] The perfluorinated compound can be perfluorooctylthiol (PFOT) and perfluorooctyltrichlorosilane (PFOTS), 1H, 1H, 2H, 2H-perfluorodecyl-trichlorosilane, etc.

[0148] The above material can form a SAM layer on the surface of the mold by a soaking method, an evaporation method or a chemical modification method, etc. In general, coating the SAM layer can improve the performance of the mold surface, improve the production efficiency, prolong the service life of the mold, and ensure the precision and quality of the embossing.

[0149] S2, coating the conductive paste 4 capable of filling the groove 3 on the polymer layer 2 on the forming side, and removing the excess conductive paste 4 on the surface of the polymer layer 2, so that the surface of the groove 3 and the conductive paste 4 are located on the same plane;

[0150] The conductive paste 4 can be uniformly distributed on the polymer layer.

[0151] According to the embodiment of the present application, preferably, S2, the conductive paste 4 capable of filling the groove 3 on the polymer layer 2 is coated on the forming side, and the excess conductive paste 4 on the surface of the polymer layer 2 is removed, so that the surface of the groove 3 and the conductive paste 4 are located on the same plane, comprising:

[0152] The conductive paste is uniformly applied on the polymer layer which has been high-precision embossed and formed by using the flat plate coating method, which can ensure that the conductive paste is tightly filled in the groove of the polymer layer, and at the same time, the excess conductive paste on the surface is scraped off, so as to ensure that the conductive paste is completely and uniformly distributed without deformation.

[0153] It should be known that one of the main components of the photovoltaic conductive paste is the adhesive (phenolic resin, epoxy resin, etc.), which forms a stable combination between the particles of the conductive paste and the particles, and between the particles and the silicon wafer.

[0154] S3, a substrate 5 is provided, and the side of the polymer layer 2 with the conductive paste 4 is attached to the substrate 5, and the conductive paste 4 is transferred to the substrate 5 by a transfer method with preset process parameters; wherein the process parameters of the transfer are: the pressure is 5-20 MPa, the temperature is 80-180℃, and the time is 1-10 min;

[0155] According to the embodiment of the present application, more preferably, S3, the side of the polymer layer 2 with the conductive paste 4 is attached to the substrate 5, comprising:

[0156] The conductive paste 4 is dried by applying uniform pressure to tightly adhere the conductive paste 4 to the surface of the substrate 5 at a preset temperature, and the macroscopic morphology of the conductive paste 4 transferred to the substrate 5 does not change within the temperature and pressure range; wherein the substrate 5 is one of a crystalline silicon wafer, glass, metal or polymer substrate.

[0157] By applying uniform pressure to the side of the polymer layer which is not coated with the conductive paste and heating and drying, the conductive paste can be transferred to the silicon wafer due to the adhesion of the conductive paste to the silicon wafer, and the conductive paste can be tightly adhered to the silicon wafer, thereby ensuring good transfer effect and further ensuring the stability of the structure of the conductive paste.

[0158] S4, removing the polymer layer 2 so that the conductive paste is retained on the substrate 5;

[0159] According to the embodiment of the present application, preferably, S4, removing the polymer layer 2 so that the conductive paste 4 is retained on the substrate 5, comprises:

[0160] The silicon wafer after transfer is placed in an aqueous solution at 25-75°C to dissolve and fall off the polymer layer, leaving the conductive paste pattern which has been successfully transferred, forming the basic structure of the electrode grid line 6.

[0161] The polymer layer can be dissolved and fallen off, so that the conductive paste pattern is completely retained on the silicon wafer, thereby achieving good dissolution and separation effect.

[0162] It should be understood that the operation mode is as follows: the back of the silicon wafer is sucked by an electric suction cup, and the silicon wafer is suspended and longitudinally or transversely immersed in water, and the polymer layer is dissolved and fallen off by agitating the aqueous solution or shaking the silicon wafer.

[0163] The polymer layer dissolution method includes but is not limited to low-frequency ultrasonic oscillation dissolution, magnetic stirring dissolution, mechanical oscillation dissolution and static dissolution.

[0164] Of course, by changing the molecular weight of PVP, blending modification and other methods, the water solubility of PVP can be changed so that it can be quickly dissolved in water.

[0165] S5, sintering the conductive paste 4 on the substrate 5 to form the electrode grid line 6 with a preset aspect ratio.

[0166] According to the embodiment of the present application, preferably, S5, sintering the conductive paste 4 on the substrate 5 to form the electrode grid line 6 with a preset aspect ratio, comprises:

[0167] The silicon wafer after transfer of the conductive paste 4 is placed in a high-temperature furnace for sintering treatment of the conductive paste 4; the sintering temperature is 500-800°C, which ensures that the conductive paste is completely sintered and tightly connected with the silicon wafer, generating a high-precision electrode grid line 6 with a preset aspect ratio.

[0168] After the conductive paste is sintered at high temperature, the conductive paste electrode grid line 6 with the required depth and width can be formed. Preferably, the size of the conductive paste electrode grid line is 10 μm deep and 5 μm wide.

[0169] According to the embodiment of the present application, preferably, the conductive paste 4 is one of silver paste, aluminum paste, copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste or tantalum paste. It can be understood that the above-mentioned materials all have good conductivity, and the effect of multiple material selection can be achieved, thereby the effect of flexible use is achieved, and the effect of improving market competitiveness is achieved. In the present application, more preferably, the conductive paste 4 is silver paste.

[0170] According to the embodiment of the present application, preferably, the glass transition temperature of the polymer layer 2 is 60-120℃, and the material of the polymer layer is water-soluble high molecular material.

[0171] According to the embodiment of the present application, preferably, the water-soluble high molecular material is one of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylic acid sodium (PAAS), polyvinyl alcohol-polyacrylic acid (PVA-PAA) or polyvinyl alcohol-polyacrylonitrile (PVA-PAN).

[0172] Among them, the average polymerization degree of the polyvinyl alcohol is 1700, and the alcoholysis degree is 88-92%; the polyvinyl alcohol is ordinary polyvinyl alcohol and modified polyvinyl alcohol; the modified polyvinyl alcohol is carboxyl modified polyvinyl alcohol, and the carboxyl modification degree is 2-8%. It should be known that the above-mentioned materials all have good solubility and biocompatibility, which can meet the use requirements of the present application. In the present application, more preferably, the water-soluble high molecular material is polyvinylpyrrolidone (PVP); PVP has good solubility in water, and PVP with different polymerization degrees can also be dissolved in various organic solvents such as ethanol and acetone; PVP can form a uniform and transparent film, and has good flexibility and adhesion; PVP is non-toxic and non-irritating, and has good biocompatibility; PVP has certain thermal stability in the processing process, and is suitable for various thermal processing processes.

[0173] As shown in FIG. 3, according to the embodiment of the present application, in S102, a bonding layer 7 is further arranged on the side of the polymer layer 2 away from the mold 1, and a substrate 8 is arranged on the side of the bonding layer 7 away from the polymer layer 2. It can be understood that by adopting the composite structure of the bonding layer 7 and the substrate 8, the stability, adhesion and other physical properties of the composite material can be improved, and the effects of facilitating separation of the polymer layer from the mold and protection of the polymer layer can be achieved. Preferably, the bonding layer 7 is a heat-sensitive debonding glue; the effect of good heat separation can be achieved, thereby the effect of facilitating separation from the polymer layer is achieved.

[0174] According to the embodiment of the present application, preferably, the substrate 8 is one of polyimide, polyethylene terephthalate, polyamide or polycarbonate. It can be understood that the substrate layer provides mechanical support for the entire structure and enables it to withstand stress and deformation during processing, and the substrate layer can impart specific rigidity, strength and durability to the material; at the same time, by selecting various substrate materials, the effect of flexible selection and easy use can be achieved, thereby improving the practicality.

[0175] According to the embodiment of the present application, preferably, S3 further comprises: when the transfer is performed under the preset process parameters, the adhesive layer 7 and the substrate 8 are separated from the polymer layer 2. It can be understood that when the transfer hot pressing process is in progress, due to the high temperature environment, the thermosensitive debonding glue loses its adhesion, so when the transfer is completed, the thermosensitive debonding glue will automatically fall off from the polymer layer with the substrate, thereby achieving a good automatic separation effect, and further ensuring the smooth progress of the process. The thermosensitive release adhesive will release when heated, that is, the adhesion between the glue and the substrate will be significantly reduced, so that it can be easily separated.

[0176] The present application can obtain a micron-level polymer layer with a groove structure through the structural design of the mold, thereby controlling the size and shape of the electrode grid lines and reducing the ohmic loss of the electrode grid lines; the conductive efficiency of the three-prism-shaped conductive paste grid lines is better than that of the cuboid-shaped conductive paste grid lines, and more light incident on the triangular side can be refracted into the battery panel and fully utilized; PVP is a biodegradable and environmentally friendly material with low environmental hazards, and the water-soluble PVP polymer layer at room temperature can greatly reduce the demolding cost; the method has a simple process, the materials and equipment involved are economical and environmentally friendly, and the process cost is low.

[0177] The present application can precisely control the size and shape of the transferred electrode grid lines and reduce the ohmic loss of the electrode grid lines through electrospinning or coating and transfer processes. The conductive efficiency of the three-prism-shaped conductive paste grid lines is better than that of the cuboid-shaped conductive paste grid lines, and more light incident on the triangular side can be refracted into the battery panel and fully utilized. PVP is a biodegradable and environmentally friendly material with low environmental hazards. The water-soluble PVP coating at room temperature can greatly reduce the demolding cost. The method has a simple process, the materials and equipment involved are economical and environmentally friendly, and the process cost is low.

[0178] The present application also has the following beneficial effects:

[0179] 1. Improve the adhesion of the conductive paste: by using polyvinylpyrrolidone (PVP) as an ideal carrier, the present application realizes stronger adhesion between the conductive paste and the substrate; the water-solubility and biocompatibility of the PVP coating enable the conductive paste to fill the grooves more tightly during the transfer process, thereby ensuring the firm fit of the conductive paste and the substrate.

[0180] Specifically, the appropriate carrier material: PVP as a water-soluble, biocompatible and film-forming polymer compound has good adhesion and can be used as an ideal carrier for the transfer of conductive paste, ensuring the firm fit of the conductive paste and the substrate.

[0181] 2. Improve the precision and stability of the electrode pattern: by electrospinning to prepare PVP film with micron or even nanoscale electrode pattern; the present application realizes high precision and stability of the electrode pattern, which helps to improve the performance and efficiency of photovoltaic cells.

[0182] 3. Simplify the production process: using flat plate coating method to spread the conductive paste on the PVP film, and transferring it on the substrate, the present application simplifies the production process, reduces the production cost and time, and improves the production efficiency.

[0183] Specifically, using flat plate coating method to spread the conductive paste, transferring it on the silicon wafer, and water cleaning the PVP film at appropriate temperature to make it dissolve and fall off, finally forming micron-scale electrode grid lines with 10 μm depth and 5 μm width, realizing the successful transfer and sintering of the conductive paste.

[0184] From the above description, it can be seen that the present application realizes the following technical effects:

[0185] In the embodiments of the present application, the electrode grid line is prepared by the transfer printing method. S1, a polymer layer is provided as a transfer printing substrate; S2, the conductive paste is coated on the shaped side of the polymer layer to fill the grooves, and the excess conductive paste on the surface of the polymer layer is removed, so that the grooves and the surface of the conductive paste are located in the same plane; S3, a substrate is provided, and the polymer layer with the conductive paste is attached to the substrate, and the conductive paste is transferred to the substrate by the transfer printing method with preset process parameters; the process parameters of the transfer printing are: pressure 5-20 MPa, temperature 80-180℃ and time 1-10 min; S4, the polymer layer is removed, so that the conductive paste remains on the substrate; S5, the conductive paste is sintered on the substrate to form an electrode grid line with a preset aspect ratio, which achieves the purpose of preparing the electrode grid line, thereby realizing the technical effects of saving process time, simplifying process flow, good flexibility of the substrate film and easy separation, and further solving the problems that in the transfer printing technology, the flexible substrate film cannot meet the use requirements due to flexibility, resulting in some substrate films being too soft, causing deformation after the subsequent conductive paste is filled; some substrate films are too hard, causing them to be too brittle and unable to be used normally; and the subsequent substrate cannot be automatically separated from the substrate, thereby affecting the grid line structure.

[0186] The transfer printing conductive paste technology has the following advantages compared to screen printing:

[0187] 1. Higher resolution: The transfer printing conductive paste technology can usually achieve higher resolution, because it can accurately transfer the conductive paste on smaller sizes, thereby realizing more fine patterns and lines.

[0188] 2. More stable product quality: Since the transfer printing conductive paste technology can be carried out in a controlled environment, it can obtain more stable and consistent product quality, avoiding problems such as uneven ink flow that may occur in screen printing.

[0189] 3. Higher production efficiency: The transfer printing conductive paste technology usually enables automated production, improving production efficiency, reducing manual operation, saving time and cost.

[0190] 4. Wider applicability: The transfer printing conductive paste technology can be applied to various substrates and materials, including flexible substrates and non-flat surfaces, with wider applicability.

[0191] 5. Stronger durability: The transfer printing conductive paste technology usually achieves better adhesion and durability, making the printed patterns more durable and stable, and less susceptible to external environmental influences.

[0192] As shown in FIG. 8, the present application also relates to a polymer layer preparation method, comprising the following steps:

[0193] S11, dissolving the water-soluble polymer material in a preset solvent to prepare a uniform spinning solution;

[0194] The solution preparation can be realized to obtain the uniform spinning solution.

[0195] According to the embodiment of the present application, preferably, S11, dissolving PVP in a preset solvent to prepare a uniform spinning solution, such as:

[0196] The PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 3-5% PVP and 18-22% tetrabutyl titanate, respectively.

[0197] According to the embodiment of the present application, more preferably, the PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 4% PVP and 20% tetrabutyl titanate.

[0198] According to the embodiment of the present application, preferably, S11, dissolving the water-soluble polymer material in a preset solvent to prepare a uniform spinning solution, further comprising:

[0199] The PVP and diphenylalanine are slowly added to a mixed solvent of methanol and N, N-methyl acetamide under stirring, and the stirring is continued until complete dissolution to obtain a transparent polymer solution.

[0200] Specifically, in order to obtain a suitable polymer layer, it is necessary to first prepare a uniform spinning solution, and the key of the process is to select appropriate solvents and precursor substances to ensure that the spinning solution has appropriate viscosity and uniformity, thereby facilitating the formation of stable fibers by electrospinning.

[0201] Of course, the present application provides a variety of solution preparation schemes, which can be selected according to actual needs to achieve the effect of flexible use.

[0202] S12, placing the spinning solution in a syringe and spinning through an electrospinning device;

[0203] According to the embodiment of the present application, preferably, S12, placing the spinning solution in a syringe and spinning through an electrospinning device, comprising:

[0204] The spinning solution prepared by configuration is placed in a syringe with a preset inner diameter, and electrospinning is performed at a preset working voltage intensity.

[0205] During the spinning process, the temperature and humidity are controlled to prevent fiber breakage or excessive stretching, and to ensure the stability, thickness uniformity and morphology consistency of the fibers.

[0206] Of course, the specific parameter settings can be set according to the actual use requirements, and in this application, no limitation is made.

[0207] S13, in the spinning process, the fiber will form a film on the preset device, and the collected film is post-processed to obtain the required polymer layer. The preset device includes but is not limited to a mold or a collection device.

[0208] According to the embodiment of the application, preferably, S13, in the spinning process, the fiber will form a film on the preset device, and the collected film is post-processed to obtain the required polymer layer, comprising:

[0209] The polymer layer formed by spinning is uniformly deposited on the collection device, and according to the preset purpose of the fiber film, the corresponding pretreatment step is performed.

[0210] Specifically, in the spinning process, the fiber will form a film on the collection device, and the fiber film is collected to obtain the PVP fiber film to be post-processed;

[0211] The silicon oil is added to the PVP fiber film to be post-processed for synchronous modification;

[0212] The PVP fiber film after synchronous modification is placed in a programmed temperature device, and the target temperature is reached according to the predetermined temperature curve and maintained for a predetermined time, and finally the required PVP fiber film is obtained.

[0213] Of course, the polymer layer formed by spinning needs to be uniformly deposited on the collection device or the mold; the subsequent processing steps may be different according to the final use of the polymer layer.

[0214] Through the above steps, a suitable polymer layer can be prepared, and the molecular structure of the polymer layer is:

[0215] As a person skilled in the art, this molecular structure should be known.

[0216] The polymer layer prepared by the polymer layer preparation method of the application has a certain flexibility and will not be too brittle; at the same time, the substrate film will not be too soft, which can avoid deformation after the conductive paste is filled in; and it can also be dissolved in water and automatically separated from the silicon wafer, leaving the conductive paste unaffected.

[0217] The glass transition temperature of the polymer layer is 60-120℃, so the properties of PVP guarantee that it will not rebound after hot pressing and the shape will not change.

[0218] From the above description, it can be seen that the application achieves the following technical effects:

[0219] In the embodiment of the present application, the polymer layer is prepared by electrospinning. In S11, a water-soluble polymer material is dissolved in a predetermined solvent to prepare a uniform spinning solution. In S12, the spinning solution is placed in a syringe and spun by an electrospinning device. In S13, during the spinning process, the fibers form a film on the predetermined device. The collected film is post-processed to obtain the desired polymer layer, thereby achieving the technical effect of a substrate film with good flexibility and easy separation. This solves the problem that in the transfer printing technology, the substrate film cannot meet the use requirements due to its flexibility, resulting in some substrate films being too soft, causing deformation after the subsequent conductive paste is filled in; some substrate films are too hard, causing them to be too brittle and unable to be used normally; and the subsequent substrate cannot be automatically separated from the base material, thereby affecting the grid line structure.

[0220] Direct electrospinning of the polymer layer on the mold can reproduce the depth of the groove, achieve very high precision, and avoid repeated stamping of the mold, prolonging its service life.

[0221] The method of preparing a polymer layer on a mold is further illustrated by the following embodiments:

[0222] Embodiment 1

[0223] I. Solution preparation: PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 4% PVP and 20% tetrabutyl titanate;

[0224] II. Provide a mold and electrospin on the mold: use a working voltage of 1.8 kV / cm, the inner diameter of the syringe is 0.43 mm, the flow rate of the spinning solution is 0.5 mL / h, the temperature is controlled at 25°C, the humidity is controlled at 45%, and the spinning directly forms a polymer layer with an electrode pattern on the mold with a thickness of 50 μm;

[0225] III. Conductive paste coating and transfer printing: use a flat coating method to uniformly coat the conductive paste on the surface of the PVP film, and after scraping off the excess conductive paste, transfer it to the surface of a silicon wafer;

[0226] IV. PVP removal: wash in water at 60°C for 3 minutes to completely dissolve and remove the polymer layer;

[0227] V. Conductive paste sintering: place the transferred silicon wafer in a sintering furnace at 700°C for half a minute to form a conductive paste electrode grid line.

[0228] At this time, the test results of the electrode grid line transfer printing method are as follows: the depth of the conductive paste electrode grid line is 10 μm, the width is 5 μm, the conductive paste is tightly combined with the silicon wafer, the conductivity is excellent, and it is suitable for application in high-efficiency photovoltaic cells.

[0229] Example 2

[0230] Example 2 differs from Example 1 in that, one, solution preparation: PVP and diphenylalanine are dissolved in a mixed solvent of methanol and N,N-dimethylacetamide at a mass fraction of 4% and 10% respectively to form a uniform polymer solution;

[0231] two, providing a mold and electrospinning on the mold: the same electrospinning conditions are adopted to form a polymer layer with a thickness of 65 μm;

[0232] three, conductive paste coating and transfer: the conductive paste is coated and transferred in the same way;

[0233] four, PVP removal: PVP is removed by dissolving in water at 70°C for 7 minutes;

[0234] five, conductive paste sintering: sintering at 800°C for half a minute.

[0235] At this time, the test results of the electrode grid line transfer method are that the depth of the conductive paste electrode grid line is 9 μm, the width is 6 μm, and the conductive paste transfer quality is good.

[0236] Example 3

[0237] Example 3 differs from Example 1 in that, one, solution preparation: the same PVP and tetrabutyl titanate solution as in Example 1 is used;

[0238] two, providing a mold and electrospinning on the mold: the flow rate of the spinning solution is increased to 1 mL / h to form a polymer layer with a thickness of 85 μm;

[0239] three, conductive paste coating and transfer: the conductive paste is coated and transferred in the same way;

[0240] four, PVP removal: PVP is removed by dissolving in water at 55°C for 8 minutes;

[0241] five, conductive paste sintering: sintering at 700°C for 1 minute.

[0242] At this time, the test results of the electrode grid line transfer method are that the depth of the conductive paste electrode grid line is 12 μm, the width is 7 μm, and the conductivity is comparable to the previous examples, but due to the thicker polymer layer, the conductive paste transfer is uneven in some areas, resulting in a slight decrease in conductivity.

[0243] Example 4

[0244] Example 4 differs from Example 1 in that a traditional PVP coating process is used.

[0245] I. PVP coating: using traditional coating method, PVP solution is directly coated on the mold, with a thickness of 25 μm.

[0246] At this time, the test results of the electrode grid line transfer method are as follows: the depth of the conductive paste electrode grid line is 12 μm, the width is 6 μm, and the conductivity is equivalent to the previous examples.

[0247] Example 5

[0248] Example 5 is different from example 1 in that PEG is used as a substrate material.

[0249] At this time, the test results of the electrode grid line transfer method are as follows: the depth of the conductive paste electrode grid line is 11 μm, the width is 6 μm, and the conductivity is equivalent to the previous examples.

[0250] Example 6

[0251] Example 6 is different from example 4 in that PVA is used as a substrate material, and a flat plate coating method is used to coat it on the mold.

[0252] At this time, the test results of the electrode grid line transfer method are as follows: the depth of the conductive paste electrode grid line is 11 μm, the width is 6 μm, and the conductivity is equivalent to the previous examples.

[0253] From the above test results, it can be seen that:

[0254] Examples 1-6 can all achieve high-precision conductive paste electrode grid lines, with good conductivity and low contact resistance, especially example 1, which shows the best performance, the scheme improves the photoelectric conversion efficiency and reduces the industrialization cost.

[0255] The application further illustrates by another following example that the method of preparing a polymer layer by mold hot pressing:

[0256] Example 7

[0257] I. Solution preparation: PVP and tetrabutyl titanate are dissolved in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 4% PVP and 20% tetrabutyl titanate;

[0258] II. Electrospinning: using a working voltage of 1.8 kV / cm, the inner diameter of the syringe is 0.43 mm, the flow rate of the spinning solution is 0.5 mL / h, the temperature is controlled at 25℃, and the humidity is controlled at 45%, the spinning forms a PVP film with a thickness of 50 μm;

[0259] III. High-precision imprinting: at 135℃, the fiber film surface is formed with micron or nanometer scale groove pattern by using a precision hot press machine through the mold with a pressure of 20 MPa;

[0260] Four, silver paste coating and transfer: using flat plate coating method, the silver paste is evenly coated on the surface of PVP film, and the excess silver paste is scraped off, and then transferred to the surface of silicon wafer;

[0261] Five, PVP removal: cleaning in water at 50°C for 5 minutes, so that the PVP film is completely dissolved and falls off;

[0262] Six, silver paste sintering: the transferred silicon wafer is sintered at 700°C for 1 minute to form a silver paste electrode grid line.

[0263] At this time, the test results of the electrode grid line transfer method are that the depth of the silver paste electrode grid line is 10 μm, the width is 7 μm, the silver paste is combined with the silicon wafer tightly, the conductivity is excellent, and it is suitable for application of high-efficiency photovoltaic cells.

[0264] Example 8

[0265] The difference between Example 8 and Example 7 is that, one, solution preparation: the same PVP and tetrabutyl titanate solution as in Example 1 is used;

[0266] Two, electrospinning: by increasing the spinning solution flow rate to 1 mL / h, a PVP film with a thickness of 85 μm is formed;

[0267] Three, high-precision imprinting and hot pressing: hot pressing is performed at 125°C and 25 MPa to form micron-level grooves;

[0268] Four, silver paste coating and transfer: silver paste is coated and transferred by the same method;

[0269] Five, PVP removal: cleaning in water at 55°C for 8 minutes to dissolve and remove PVP;

[0270] Six, silver paste sintering: sintering at 700°C for 1 minute.

[0271] At this time, the test results of the electrode grid line transfer method are that the depth of the silver paste electrode grid line is 9 μm, the width is 7 μm, and the conductivity is comparable to the previous examples, but due to the thicker PVP film, the film thickness after spinning is not uniform, resulting in incomplete silver paste transfer in some areas and slight decrease in conductivity.

[0272] Example 9

[0273] The difference between Example 9 and Example 7 is that, one, PVA solution preparation: 8 g of PVA powder is weighed and dissolved in 92 mL of distilled water to form an 8% PVA solution; stirring at 80°C for 1 hour until the PVA is completely dissolved to form a uniform solution;

[0274] II. Electrospinning equipment settings: inject the PVA solution into a 0.43 mm inner diameter syringe; set the high-voltage power supply to 15 kV, and keep the distance between the collection plate and the syringe needle at 12 cm;

[0275] III. Spinning process: under the action of the electric field, the PVA solution is sprayed through the syringe needle to form nanofibers, which are deposited on the rotating collection plate; spinning continues for 30 minutes until a uniform fiber network film is formed on the collection plate;

[0276] IV. Drying and post-processing: after spinning is completed, the film is dried in a drying oven at 40°C for 12 hours to remove moisture and stabilize the film.

[0277] At this time, the test results of the electrode grid line transfer method are: the PVA film prepared by electrospinning has a nanoscale fiber structure, with a fiber diameter of 150-300 nm, and the film has a porous structure; the film has a high porosity, which is suitable for gas filtration and biomedical materials; the tensile strength of the fiber film is 20 MPa, and the elongation at break is 50%.

[0278] At this time, the test results of the electrode grid line transfer method are: the depth of the conductive paste electrode grid line is 8 μm, the width is 8 μm, the conductive paste is tightly combined with the silicon wafer, the conductivity is excellent, and it is suitable for application in high-efficiency photovoltaic cells.

[0279] Example 10

[0280] Example 10 differs from Example 7 in that a traditional PVP coating process is used

[0281] I. PVP coating: using a traditional coating method, PVP solution is directly coated on the silicon wafer with a thickness of 40 μm;

[0282] II. Hot pressing: at 100°C, apply a pressure of 10 MPa to hot press the electrode groove;

[0283] III. Silver paste coating and transfer: silver paste is coated and transferred in the same way;

[0284] IV. PVP removal: wash in water at 30°C for 6 minutes;

[0285] V. Silver paste sintering: sinter at 700°C for 1 minute.

[0286] At this time, the test results of the electrode grid line transfer method are: the depth of the silver paste electrode grid line is 6 μm, and the width is 10 μm. Due to the good uniformity of the PVP coating and the good filling effect of the silver paste, the electrode line width is uniform, the conductivity is good, and it meets the high-precision requirements of photovoltaic cells.

[0287] Comparative Example 1

[0288] The difference between the comparative example 1 and the example 7 is that, one, solution preparation: PVP and diphenylalanine are dissolved in the mixed solvent of methanol and N, N-methylacetamide with the mass fraction of 4% and 10% respectively to form a uniform polymer solution;

[0289] Two, electrospinning: the same electrospinning condition is adopted to spin to form a PVP film with a thickness of 65 μm;

[0290] Three, high-precision imprinting and hot-pressing: hot-pressing is performed at 70 ℃ under the pressure of 15 MPa to form a micron-scale groove;

[0291] Four, silver paste coating and transfer: the silver paste is coated and transferred in the same way;

[0292] Five, PVP removal: PVP is removed by dissolving in water at 60 ℃ for 7 minutes;

[0293] Six, silver paste sintering: sintering is performed at 800 ℃ for half a minute.

[0294] At this time, the test result of the electrode grid line transfer method is that the depth of the silver paste electrode grid line is 2 μm, the width is 6 μm, and the silver paste transfer quality is poor.

[0295] From the above test results, it can be seen that:

[0296] 1. It can be seen from the examples 7-10 that the above examples can all prepare high-precision silver paste electrode grid lines, and have good conductivity, flexibility, water solubility and bonding strength, especially the example 7 shows the best performance.

[0297] 2. It can be seen from the example 7 and the comparative example 1 that if the hot-pressing temperature is too low, the PVP film cannot be completely compacted, so that the silver paste electrode groove is not clear, and the conductivity is affected.

[0298] The application also relates to a photovoltaic cell comprising the electrode grid line prepared as above. The photovoltaic electrode grid line prepared in the example can be applied to a photovoltaic cell, and has the same basic principle and technical effects as the above examples. The part not mentioned in the example is referred to the corresponding content of the above examples.

[0299] The preferred embodiments of the application are described in detail above with reference to the drawings, but the application is not limited to the specific details in the above embodiments. Within the technical concept of the application, various equivalent transformations can be made to the technical solutions of the application, and these equivalent transformations all belong to the protection scope of the application.

Claims

1. A method of producing electrode grid lines, characterized by The method comprises the following steps: S1, providing a polymer layer as a transfer substrate; S2, coating the conductive paste on the forming side of the polymer layer at least to fill the grooves thereon, and removing the excess conductive paste on the surface of the polymer layer, so that the grooves and the surface of the conductive paste are located on the same plane; S3, providing a substrate, and bonding the polymer layer with the conductive paste to the substrate, and transferring the conductive paste to the substrate by a preset process parameter transfer method; wherein the process parameters of the transfer are: pressure 5-20 MPa, temperature 80-180℃ and time 1-10 min; S4, removing the polymer layer so that the conductive paste remains on the substrate; S5, sintering the conductive paste on the substrate to form an electrode grid line with a preset aspect ratio.

2. The electrode grid preparation method according to claim 1, wherein S1, providing a polymer layer as a transfer substrate, comprising the following steps: S101, providing a mold with a shape complementary to the electrode pattern to be imprinted; S102, preparing a polymer layer required according to preset process parameters on the mold, and taking it as a transfer substrate.

3. The electrode grid preparation method according to claim 2, wherein S102, preparing a polymer layer required according to preset process parameters on the mold, and taking it as a transfer substrate, comprising: Preparation of a polymer layer with grooves on the mold, the thickness of which is 15-85μm, and after drying at 100-125℃, it is demolded from the mold side to obtain the required micron or nanometer electrode pattern polymer layer as a transfer substrate.

4. The electrode grid preparation method according to claim 2, wherein In S102, the thickness of the polymer layer is 15-50μm.

5. The method of claim 1, wherein S1, providing a polymer layer as a transfer substrate, further comprising the following steps: S111, providing a polymer layer; S112, using a mold to hot-emboss the grooves of the electrode pattern on the polymer layer.

6. The method of claim 1, wherein In S1, the polymer layer is prepared by electrospinning or flat coating method.

7. The method of claim 1, wherein In S1, the polymer layer is prepared by electrospinning, comprising the following steps: S11, dissolving water-soluble polymer materials in a predetermined solvent to prepare a uniform spinning solution; S12, placing the spinning solution in a syringe and spinning by electrospinning equipment; S13, during the spinning process, the fibers form a film on the preset equipment, and the collected film is post-processed to obtain the required polymer layer.

8. The electrode grid preparation method according to claim 7, wherein S11, dissolving water-soluble polymer materials in a predetermined solvent to prepare a uniform spinning solution, comprising: Dissolve PVP and tetrabutyl titanate in a mixed solvent of ethanol and acetic acid to prepare a precursor solution with a mass fraction of 3-5% PVP and 18-22% tetrabutyl titanate.

9. The electrode grid preparation method according to claim 7, wherein S11, dissolving water-soluble polymer materials in a predetermined solvent to prepare a uniform spinning solution, further comprising: Slowly add PVP and diphenylalanine to the mixed solvent of methanol and N,N-methyl acetamide under stirring, continue to stir until completely dissolved, and obtain a transparent polymer solution.

10. The method of claim 1, wherein S12, placing the spinning solution in a syringe and spinning by electrospinning equipment, comprising: Place the prepared spinning solution in a syringe with a predetermined inner diameter, and perform electrospinning with a preset working voltage intensity.

11. The method of claim 1, wherein S13, in the spinning process, the fiber will form a film on the preset device, and the collected film is post-processed to obtain the required polymer layer, including: The polymer layer formed by spinning is uniformly deposited on the collecting device, and corresponding pretreatment steps are performed according to the preset use of the fiber film.

12. The method of claim 5, wherein the electrode grid is prepared by a method comprising: S111, providing a polymer layer, including: Preparation of a polymer layer with a thickness of 35-85 μm by electrospinning or flat plate coating method.

13. The method of claim 5, wherein the electrode grid is prepared by a method comprising: S112, using a mold to hot emboss the groove of the electrode pattern on the polymer layer, including: Put the prepared polymer layer into the mold through the precision hot press, and perform hot embossing at 100-180 ℃, so that the surface of the polymer layer forms micron or even nanometer electrode groove structure.

14. The electrode grid production method according to claim 2 or 5, wherein The mold is one of single crystal silicon substrate, polycrystalline silicon substrate, copper substrate, nickel substrate, copper-nickel alloy substrate, nickel-iron alloy substrate, iron-aluminum alloy substrate or aluminum alloy substrate.

15. The method of claim 2 or 5, wherein The convex part of the mold is complementary to the shape of the groove. The shape of the mold is one of isosceles triangle, isosceles trapezoid, ellipse, hexagon, right trapezoid or rectangle.

16. The electrode grid production method according to claim 2 or 5, wherein The aspect ratio of the shape of the mold ranges from 1 to 3.

17. The electrode grid production method according to claim 2 or 5, wherein The surface of the mold is coated with a self-assembled monolayer.

18. The method of claim 17, wherein, The self-assembled monolayer is one of silane compounds, siloxane compounds or perfluorinated compounds.

19. The method of claim 1, wherein S2, coating the conductive paste capable of filling the groove on the formed side of the polymer layer, and removing the excess conductive paste on the surface of the polymer layer, so that the groove and the surface of the conductive paste are located on the same plane, including: Uniformly spread the conductive paste on the formed polymer layer by flat plate coating method, so that the conductive paste completely fills the groove, and the excess conductive paste is scraped off to ensure that the conductive paste is completely filled and uniformly distributed without deformation.

20. The method of claim 1, wherein S3, providing a substrate, and adhering the side of the polymer layer with the conductive paste to the substrate, including: At a preset temperature, the conductive paste is tightly adhered to the surface of the substrate by applying uniform pressure, and the conductive paste is dried at the same time; and the macroscopic morphology of the conductive paste transferred to the substrate does not change within the temperature and pressure range. The substrate is one of crystalline silicon wafer, glass, perovskite, metal or polymer substrate.

21. The method of claim 1, wherein S4, removing the polymer layer to leave the conductive paste on the substrate, including: Place the transferred silicon wafer in a water solution at 25-75 ℃ to dissolve and fall off the polymer layer, leaving the conductive paste pattern that has been successfully transferred, forming the basic structure of the photovoltaic electrode grid line.

22. The method of claim 1, wherein S5, sintering the conductive paste on the substrate to form an electrode grid line with a preset aspect ratio, including: Put the silicon wafer after transferring the conductive paste into a high temperature furnace to sinter the conductive paste; the sintering temperature is 500-800 ℃, which ensures that the conductive paste is completely sintered and tightly connected with the silicon wafer, generating an electrode grid line with a preset aspect ratio.

23. The method of claim 1, wherein The conductive paste is one of silver paste, aluminum paste, copper paste, chromium paste, tin paste, indium paste, nickel paste, titanium paste or tantalum paste.

24. The method of claim 1, wherein The glass transition temperature of the polymer layer is 60-120 ℃, and the material of the polymer layer is water-soluble polymer material.

25. The method of claim 24, wherein The water-soluble polymer material is one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, sodium polyacrylate, polyvinyl alcohol-polyacrylic acid or polyvinyl alcohol-polyacrylonitrile. The polyvinyl alcohol has an average polymerization degree of 1700 and an alcoholysis degree of 88-92%, and the polyvinyl alcohol is ordinary polyvinyl alcohol and modified polyvinyl alcohol; the modified polyvinyl alcohol is carboxyl modified polyvinyl alcohol with a carboxyl modification degree of 2-8%.

26. The method of claim 2, wherein In S102, the polymer layer is provided with a bonding layer on the side away from the mold, and the bonding layer is provided with a substrate on the side away from the polymer layer.

27. The method of claim 26, wherein The substrate is one of polyimide, polyethylene terephthalate, polyamide or polycarbonate.

28. The method of claim 26, wherein: In S3, when the transfer is performed under the preset process parameters, the bonding layer and the substrate are separated from the polymer layer.

29. A photovoltaic cell characterized by, The electrode grid line is prepared by the preparation method in any one of claims 1 to 28.

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