Battery sheet and method for manufacturing the same, photovoltaic module

Abstract

The application provides a battery piece, a preparation method of the battery piece, and a photovoltaic module. The preparation method of the battery piece comprises the following steps: providing a semiconductor substrate, the semiconductor substrate having opposite first and second surfaces; providing a conductive paste, coating the conductive paste on the first and / or second surface of the semiconductor substrate, and sintering to form an electrode; wherein the conductive paste comprises, in terms of mass percentage, 85-92% conductive powder, 2-4% glass powder, and the balance organic carrier; the conductive powder comprises metal powder and at least one layer of coating layer distributed on the surface of the metal powder, and the coating layer comprises an organic silicon material layer. The conductive paste is coated on the first and / or second surface of the semiconductor substrate, and sintering is performed to form an electrode. High printability and electrical performance can be maintained, the line width of the electrode is less than or equal to 25 μm, and the series resistance of the battery piece is controlled to be 1.0 mΩ·cm 2 The following.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to battery cells and their preparation methods, and photovoltaic modules. Background Technology

[0002] In the photovoltaic field, solar cells (also known as solar cells) are clean and efficient renewable energy conversion devices whose core function is to directly convert light energy into electrical energy. During this conversion process, the efficient collection and transport of photogenerated carriers is crucial, and this largely depends on the implementation of high-performance electrodes on the cell surface. These electrodes not only need to form good ohmic contact with the cell's semiconductor materials (such as crystalline silicon, thin-film silicon, or various compound semiconductors) to minimize contact resistance, but also need to possess high conductivity to reduce series resistance and power loss, thereby maintaining the cell's high photoelectric conversion efficiency.

[0003] How to provide a high-performance electrode for fabricating high-performance solar cells is an urgent problem to be solved in the field of solar cells. Summary of the Invention

[0004] This application provides a method for preparing solar cells and a photovoltaic module, which can effectively improve the dispersion stability, flowability and storage stability of conductive paste, improve electrode printing performance, and enhance the contact performance between electrodes and semiconductor substrates, thereby improving the electrical performance of solar cells.

[0005] In a first aspect, embodiments of this application provide a method for preparing a battery cell, comprising the following steps;

[0006] A semiconductor substrate is provided, the semiconductor substrate having opposing first and second surfaces;

[0007] A conductive paste is prepared, and the conductive paste is coated on the first and / or second surfaces of the semiconductor substrate and sintered to form an electrode.

[0008] The conductive paste, by weight percentage, comprises: 85% to 92% conductive powder, 2% to 4% glass powder, and the remainder being an organic carrier.

[0009] The conductive powder includes metal powder and at least one coating layer distributed on the surface of the metal powder, the coating layer including an organosilicon material layer.

[0010] Secondly, embodiments of this application provide a battery cell, which is formed using the battery cell manufacturing method of the first aspect, and the battery cell includes:

[0011] A semiconductor substrate, the semiconductor substrate including a first surface and a second surface disposed opposite to each other;

[0012] A first electrode forming an ohmic contact with a first surface of the semiconductor substrate; and / or

[0013] A second electrode that forms an ohmic contact with the second surface of the semiconductor substrate.

[0014] Thirdly, embodiments of this application provide a photovoltaic module, the photovoltaic module comprising:

[0015] A battery string, wherein the battery string is formed by connecting multiple battery cells formed by the method of preparing battery cells described in the first aspect or battery cells described in the second aspect;

[0016] An encapsulation layer that covers the surface of the battery string;

[0017] A cover plate for covering the surface of the encapsulation layer away from the battery string.

[0018] The technical solution of this application has at least the following beneficial effects:

[0019] This application employs a conductive paste coated on a first and / or second surface of a semiconductor substrate, followed by sintering to form an electrode. The conductive paste comprises conductive powder, which includes metal powder and at least one coating layer distributed on the surface of the metal powder. The coating layer includes an organosilicon material layer. By depositing the organosilicon material layer on the surface of the metal powder, the organosilicon material can cover the surface of the metal powder, reducing contact between metal powder particles, reducing agglomeration of the conductive powder, and improving the dispersibility of the conductive powder. This improves the dispersion uniformity, flowability, and stability of the conductive paste containing the conductive powder. Furthermore, the uniformly dispersed conductive powder can better contact the glass powder, organic carrier, and semiconductor substrate, improving the adhesion of the electrode prepared from the conductive paste. Moreover, the uniform coverage of the organosilicon material layer on the surface of the metal powder forms a more complete conductive network, improving the overall conductivity of the electrode prepared from the conductive paste. This application controls the mass content of the conductive powder, glass powder, and organic carrier within the aforementioned ranges to achieve synergistic optimization of the functions of each component, ensuring that the conductive paste possesses excellent printability, high conductivity of the cured electrode, and stable mechanical properties. Electrodes formed using the conductive paste of this application maintain high printability and electrical performance, with a linewidth of less than or equal to 25 μm and a series resistance of the solar cell controlled at 1.0 mΩ·cm. 2 the following. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the battery cell fabrication process provided in the embodiments of this application;

[0021] Figure 2 This is a schematic diagram of the structure of a conductive powder provided in an embodiment of this application;

[0022] Figure 3 This is another structural schematic diagram of the conductive powder provided in the embodiments of this application;

[0023] Figure 4 This is another structural schematic diagram of the conductive powder provided in the embodiments of this application;

[0024] Figure 5 This is a schematic diagram of the preparation process of the conductive paste provided in the embodiments of this application;

[0025] Figure 6 This is a schematic diagram of the structure of a battery cell provided in an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of a photovoltaic module provided in an embodiment of this application.

[0027] Figure label:

[0028] 1000 - Photovoltaic modules;

[0029] 100 - Solar cell; 10 - Semiconductor substrate; 20 - First passivation layer; 30 - Second passivation layer; 40 - First electrode; 50 - Second electrode;

[0030] 200 - First cover plate;

[0031] 300 - First encapsulating adhesive layer;

[0032] 400 - Second encapsulating adhesive layer;

[0033] 500 - Second cover plate;

[0034] 1-Conductive powder;

[0035] 11-Metallic powder;

[0036] 12-Organosilicon material layer;

[0037] 13-Carbon material layer. Detailed Implementation

[0038] The following examples illustrate this solution. These examples are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0039] This application provides a method for preparing a battery cell. Figure 1 This is a schematic diagram of the fabrication process for the solar cells in this application, as shown below. Figure 1 As shown, it includes the following steps;

[0040] A semiconductor substrate is provided, the semiconductor substrate having opposing first and second surfaces;

[0041] Prepare a conductive paste, coat the conductive paste on the first and / or second surfaces of a semiconductor substrate, and sinter to form an electrode;

[0042] The conductive paste, by weight percentage, comprises: 85% to 92% conductive powder, 2% to 4% glass powder, and the remainder organic carrier.

[0043] The conductive powder includes metal powder and at least one coating layer distributed on the surface of the metal powder, the coating layer including an organosilicon material layer.

[0044] In the above-described scheme, this application employs a conductive paste coated on the first and / or second surfaces of a semiconductor substrate, followed by sintering to form an electrode. The conductive paste comprises conductive powder, which includes metal powder and at least one coating layer distributed on the surface of the metal powder. The coating layer includes an organosilicon material layer. By depositing the organosilicon material layer on the surface of the metal powder, the organosilicon material can cover the surface of the metal powder, reducing contact between metal powder particles, reducing agglomeration of the conductive powder, and improving the dispersibility of the conductive powder. This improves the dispersion uniformity, flowability, and stability of the conductive paste containing the conductive powder. Furthermore, the uniformly dispersed conductive powder can better contact the glass powder, organic carrier, and semiconductor substrate, improving the adhesion of the electrode prepared from the conductive paste. Moreover, the uniform coverage of the organosilicon material layer on the surface of the metal powder forms a more complete conductive network, improving the overall conductivity of the electrode prepared from the conductive paste. This application controls the mass content of the conductive powder, glass powder, and organic carrier within the aforementioned ranges to achieve synergistic optimization of the functions of each component, ensuring that the conductive paste possesses excellent printability, high conductivity of the cured electrode, and stable mechanical properties. Electrodes formed using the conductive paste of this application maintain high printability and electrical performance, with a linewidth of less than or equal to 25 μm and a series resistance of the solar cell controlled at 1.0 mΩ·cm. 2 the following.

[0045] The preparation method of the battery cell of the present invention will be described in detail below.

[0046] S1 provides a semiconductor substrate having opposing first and second surfaces.

[0047] In some embodiments, the semiconductor substrate is an N-type crystalline silicon substrate (or silicon wafer), but it can also be a P-type crystalline silicon substrate (silicon wafer). The crystalline silicon substrate may be, for example, a polycrystalline silicon substrate, a monocrystalline silicon substrate, a microcrystalline silicon substrate, or a silicon carbide substrate. This application does not limit the specific type of semiconductor substrate. Optionally, the semiconductor substrate may be an N-type crystalline silicon substrate.

[0048] In some embodiments, the thickness of the semiconductor substrate is 60μm to 240μm, specifically 60μm, 80μm, 90μm, 100μm, 120μm, 150μm, 200μm or 240μm, etc., and is not limited here.

[0049] In some embodiments, the first surface of the semiconductor substrate corresponds to the front side of the solar cell, which is the sun-facing surface (i.e., the light-receiving surface). In other embodiments, the first surface of the semiconductor substrate corresponds to the back side of the solar cell, which is the surface facing away from the sun (i.e., the back-shielded surface). The following description uses the example of the first surface corresponding to the front side of the solar cell.

[0050] The process after S1 and before S2 includes: forming a first passivation layer on a first surface of the semiconductor substrate and forming a second passivation layer on a second surface of the semiconductor substrate.

[0051] In some embodiments, the first passivation layer may be, but is not limited to, a single-layer oxide layer or a multi-layer structure such as silicon oxide, silicon nitride, silicon oxynitride, or aluminum oxide. Of course, other types of passivation layers can also be used, and the present invention does not limit the specific material of the first passivation layer. The first passivation layer can reduce the minority carrier concentration on the substrate surface through the passivation effect, suppress carrier recombination on the surface of the solar cell, thereby reducing the surface recombination rate. It can also reduce series resistance and improve electron transport capability.

[0052] In some implementations, plasma-enhanced chemical vapor deposition can be used to deposit the first passivation layer. Of course, other methods can also be used, such as organic chemical vapor deposition.

[0053] In some embodiments, the second passivation layer includes, but is not limited to, single-layer or multi-layer oxide structures such as silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide. Of course, other types of passivation layers can also be used, and the specific material of the second passivation layer is not limited in this invention. The second passivation layer can reduce the minority carrier concentration on the substrate surface through the passivation effect, suppress carrier recombination on the surface of the solar cell, thereby reducing the surface recombination rate. It can also reduce series resistance and improve electron transport capability. It should be noted that the second passivation layer can also reduce incident light reflection; in some instances, it can be called an anti-reflection layer. For example, a chain magnetron sputtering process can be used to form the second passivation layer.

[0054] In some implementations, plasma-enhanced chemical vapor deposition can be used to deposit the second passivation layer. Of course, other methods can also be used, such as organic chemical vapor deposition.

[0055] S2, Prepare conductive paste, apply conductive paste to the first and / or second surfaces of a semiconductor substrate, sinter to form an electrode.

[0056] S21, Prepare conductive paste.

[0057] (Preparation of conductive powder)

[0058] S100. The silane coupling agent, solvent and acid solution are mixed and hydrolyzed to obtain a premixed solution.

[0059] In some embodiments, the silane coupling agent is an aminosilane coupling agent or an epoxysilane coupling agent. Optionally, the silane coupling agent includes at least one selected from silane coupling agent KH-550, silane coupling agent KH-540, silane coupling agent A-1100, and silane coupling agent A-1110. The epoxysilane coupling agent includes at least one selected from silane coupling agent KH-560, silane coupling agent A-187, silane coupling agent Z-6040, and silane coupling agent KBM-403.

[0060] In some embodiments, the solvent includes at least one of an alcohol solvent and deionized water, wherein the alcohol solvent includes, but is not limited to, deionized ethanol. Optionally, the solvent includes deionized ethanol and deionized water in a volume ratio of 95:5.

[0061] In some embodiments, the acid solution includes at least one of acetic acid and citric acid.

[0062] In some embodiments, the pH of the acid solution is 4 to 5. This application controls the pH of the acid solution within the above range to promote the hydrolysis of the silane coupling agent while preventing the silane coupling agent from self-polymerizing to form a gel.

[0063] In some implementations, the hydrolysis reaction takes 20 to 60 minutes.

[0064] S200: Provide metal powder, mix the metal powder with a premixed liquid, and perform solid-liquid separation and drying on the mixture to obtain a first precursor.

[0065] S201, Provide metal powder.

[0066] In some embodiments, the metal powder includes at least one of silver powder, copper powder, gold powder, nickel powder, and aluminum powder.

[0067] In some embodiments, the metal powder includes at least one of spherical powder and flake powder.

[0068] In some embodiments, the median particle size of the metal powder is 0.5 μm to 1.2 μm.

[0069] In some embodiments, the process of providing the metal powder further includes: pre-treating the metal powder to remove oxides, such as silver oxide, from the surface of the metal powder to improve the adhesion of subsequent metal powders.

[0070] Specifically, this includes the following steps: mixing metal powder and acid solution, ultrasonic treatment, washing with deionized water until neutral, and drying.

[0071] In some embodiments, the acid solution includes at least one of nitric acid and sulfuric acid at a concentration of 3% to 8%.

[0072] In some implementations, the ultrasonic treatment time is 5 to 10 minutes.

[0073] In some embodiments, the drying temperature is 70°C to 100°C, and the drying time is 1 hour to 3 hours.

[0074] S202. The metal powder and the premixed liquid are mixed, and the mixture is subjected to solid-liquid separation and drying to obtain the first precursor.

[0075] Metal powder and premixed liquid are mixed, and the hydrolysis products of silane coupling agent undergo condensation reaction and are coated on the surface of metal powder. After solid-liquid separation and drying, conductive powder is obtained. The conductive powder includes metal powder and an organosilicon material layer distributed on the surface of metal powder.

[0076] In some embodiments, the mass ratio of silane coupling agent to metal powder is (0.15~0.2):1, specifically 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.2:1, or any two of the above values. Controlling the mass ratio of silane coupling agent to metal powder within the above range allows for the formation of an organosilicon material coating layer of suitable thickness on the surface of the metal powder, with the thickness of the organosilicon material layer being 2nm~5nm.

[0077] In some embodiments, mixing is carried out under stirring conditions to promote uniform distribution of the metal powder and the premixed liquid.

[0078] In some embodiments, the mixing temperature is 50°C to 80°C, specifically 50°C, 60°C, 70°C, 80°C or any two of the above values.

[0079] In some implementations, the mixing time is 1 hour to 3 hours, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or any two of the above values.

[0080] The process includes steps S200, S300, and S400, as well as mixing the first precursor, carbon source solution, catalyst and reducing agent, separating the mixture into solid and liquid components, and drying the mixture.

[0081] In the above steps, the carbon source solution is dehydrated and carbonized into amorphous carbon distributed on the surface of the organosilicon material layer under the action of catalyst and reducing agent.

[0082] In some embodiments, the carbon source solution includes at least one of an aqueous glucose solution, an aqueous fructose solution, an aqueous sucrose solution, and an aqueous maltose solution.

[0083] In some embodiments, the concentration of the carbon source solution is 0.1 mol / L to 1 mol / L, specifically 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, or any two of the above values.

[0084] In some embodiments, the catalyst includes an amino compound. In some embodiments, the catalyst is an organosilicon material layer on the surface of the metal powder. The silane coupling agent of this application is an aminosilane coupling agent, which forms an organosilicon material through hydrolysis and condensation. The surface of the organosilicon material has amino groups, which can be used as a reducing agent for the carbon source solution. That is, the organosilicon material layer of this application can not only improve the dispersibility of the metal powder, but also promote the formation of carbon materials with improved conductivity.

[0085] In some embodiments, the reducing agent includes at least one of deionized hydrazine hydrate and ascorbic acid.

[0086] In some embodiments, the concentration of the reducing agent is 0.01 mol / L to 0.2 mol / L, specifically 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, or any two of the above values.

[0087] In some embodiments, the solid-liquid ratio of the first precursor to the carbon source solution is 1g:(5~15)ml, specifically 1g:5ml, 1g:8ml, 1g:10ml, 1g:12ml, 1g:15ml, or any two of the above values. By controlling the solid-liquid ratio of the first precursor to the carbon source solution within the above range, a carbon material layer of suitable thickness can be formed, thereby improving the conductivity of the conductive powder.

[0088] In some embodiments, the mixing temperature is 50°C to 100°C, specifically 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or any two of the above values.

[0089] In some implementations, the mixing time is 1 hour to 3 hours, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or any two of the above values.

[0090] S300. The first precursor is heat-treated to obtain conductive powder.

[0091] In some embodiments, the heat treatment is carried out in an inert gas atmosphere, such as nitrogen or argon. In some embodiments, the inert gas flow rate is 3 L / min to 8 L / min.

[0092] In some embodiments, the heat treatment temperature is 150°C to 250°C, specifically 150°C, 180°C, 200°C, 220°C, 240°C, 250°C, or any two of the above values.

[0093] In some implementations, the heat treatment time is 0.5h to 2h, specifically 0.5h, 1h, 1.5h, 2h or any two of the above values.

[0094] Controlling the temperature and time of heat treatment within the above range can enhance the cross-linking of organosilicon materials and promote the formation of amorphous carbon containing sp. 2 Hybridized amorphous carbon.

[0095] In some embodiments, the heat treatment is followed by a step of ball milling the heat-treated product to further improve dispersibility.

[0096] In some embodiments, ball milling is carried out in a planetary ball mill, the grinding balls are ZrO2, the ball-to-material ratio is 5:1, the ball milling is carried out in an argon gas atmosphere, the stirring speed of the ball mill is 200 rpm to 500 rpm, and the ball milling time is 10 min to 40 min.

[0097] Figure 2 A schematic diagram of a conductive powder structure is shown, such as... Figure 2 The conductive powder 1 includes a metal powder 11 and an organosilicon material layer 12, with the organosilicon material layer 12 distributed on the surface of the metal powder 11 to form a coating layer.

[0098] In some embodiments, the silicone material layer 12 is covalently bonded to the metal powder 11.

[0099] The silicone material layer 12 is covalently bonded to the metal powder 11, which enhances the interfacial bonding between the silicone material layer 12 and the metal powder 11, forming a tightly connected core-shell structure conductive powder. The core is the metal powder 11, and the outer shell is the silicone material layer 12. The silicone material layer 12 effectively encapsulates the metal powder 11, reducing its agglomeration and improving its dispersibility. It also enhances the oxidation resistance of the metal powder 11 and improves the long-term stability of the conductive paste. Compared to conductive powders formed by physically mixing metal powder and silicon material, the core-shell structure conductive powder of this application directly isolates the metal powder from each other, significantly optimizing the dispersibility of the metal powder. At the same time, the silicone material is less likely to be dispersed freely in the conductive paste, avoiding the problem of hydrolysis of free silicone material leading to the inability to store the conductive paste.

[0100] It should be noted that, in order to prove that the organosilicon material layer 12 and the metal powder 11 are connected by covalent bonds, the conductive powder, the metal powder alone, and the organosilicon material alone can be subjected to Fourier transform infrared spectroscopy analysis to observe the difference in their infrared spectra, thereby confirming that the organosilicon material has been grafted onto the surface of the metal powder through chemical bonding.

[0101] In some embodiments, the silicone material layer 12 is connected to the metal powder 11 via Si-OM bonds, where M is a metal element in the metal powder 11.

[0102] In some embodiments, the material of the organosilicon material layer 12 includes a siloxane polymer. In some embodiments, the siloxane polymer may be an aminosiloxane polymer, an epoxysiloxane polymer, etc. The siloxane polymer of this application is a three-dimensional network polymer formed by deionized hydrolysis and condensation of a silane coupling agent. In the core-shell structure conductive powder of this application, Si-OM bonds are formed between the siloxane and the metal powder, which improves the bonding between the metal powder and the siloxane polymer. At the same time, the amino and other functional groups in the siloxane polymer are located on the surface of the organosilicon material layer, which can interact with the glass powder and the components in the organic carrier, forming a stable steric hindrance or electrostatic shield on the surface of the metal powder, thereby achieving ultra-uniform and stable dispersion.

[0103] In some embodiments, the thickness of the silicone material layer 12 is 2nm to 5nm, specifically 2nm, 3nm, 4nm, 5nm, or any two of the above values. The thickness of the silicone material layer 12 in this application is moderate, which can prevent the dispersion of silver powder without significantly affecting the viscosity of the conductive paste.

[0104] In some embodiments, the conductive powder 1 further includes a carbon material layer 13 distributed on the surface of the organosilicon material layer 12. Figure 3 Another structural schematic diagram of conductive powder is shown, such as... Figure 3As shown, the conductive powder 1 includes metal powder 11 and two coating layers on the surface of the metal powder 11, one of which is an organosilicon material layer 12 and the other is a carbon material layer 13, and the organosilicon material layer 12 is distributed between the metal powder 11 and the carbon material layer 13.

[0105] This application incorporates a carbon material layer 13 on the surface of the silicone material layer 12. Carbon material possesses excellent conductivity, which improves the conductivity of the conductive powder, reduces its contact resistance, and increases its overall conductivity. After the conductive paste is prepared as an electrode, the carbon material layer 13 enhances the electron tunneling effect and reduces the electrode contact resistance. The silicone material layer 12 and the carbon material layer 13 coating the surface of the metal powder 11 cooperate with each other, simultaneously improving the dispersion uniformity and conductivity of the conductive powder. Furthermore, the silicone material layer 12 enhances the bonding between the metal powder 11 and the carbon layer 13.

[0106] In some embodiments, the carbon material layer 13 is made of conductive carbon material, which includes at least one of amorphous carbon and graphite-like carbon.

[0107] It should be noted that the amorphous carbon in this application is sp... 2 Hybridized carbon, an amorphous form of carbon, can provide delocalized π electrons to form a conductive network, thereby maintaining the overall conductivity of the conductive paste even with low metal powder 11 content. Graphite-like carbon includes at least one of artificial graphite, graphitized carbon, and carbon nanotubes, and the aforementioned graphite-like carbons possess abundant sp... 2 Hybrid layered structures can enhance efficient electron conduction networks.

[0108] In some embodiments, the thickness of the carbon material layer 13 is 5 nm to 20 nm, specifically 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm, or any two of the above values. The thickness of the carbon material layer 13 in this application is moderate, enabling the formation of a complete conductive network layer on the surface of the organosilicon material layer 12, effectively improving conductivity. If the thickness of the carbon material layer 13 is greater than 20 nm, the excessively thick carbon material layer 13 will have more internal defects, leading to a deterioration of the interface with the conductive paste and resulting in increased contact resistance.

[0109] In some embodiments, the metal powder 11 includes at least one of silver powder, copper powder, gold powder, nickel powder, and aluminum powder.

[0110] In some embodiments, the metal powder 11 includes at least one of spherical powder and flake powder. Figure 1 This is a schematic diagram of the structure of a spherical conductive powder. Figure 4 This is a schematic diagram of the structure of a conductive powder in flake form, such as... Figure 4As shown, the silicone material layer 12 is distributed on each surface of the flake metal powder 11. When the metal powder 11 includes flake powder, the cost of flake powder is lower. By sequentially setting the silicone material layer 12 and the carbon material layer 13 on the surface of the flake metal powder 11, the dispersion uniformity and conductivity of the conductive powder can be improved at the same time, and the cost can be reduced, resulting in a conductive paste with excellent comprehensive performance.

[0111] Optionally, the metallic silver is silver powder. The conductive paste of this application has good dispersibility and conductivity. The metallic silver powder can be domestic silver powder, which can be spherical powder or flake powder.

[0112] In some embodiments, the median particle size of the metal powder 11 is 0.5 μm to 1.2 μm, specifically it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm or any two of the above values.

[0113] It should be noted that when metal powder 11 is spherical, the median particle size refers to the volumetric particle size distribution D. 50 Volumetric particle size distribution D 50 The particle size of the additive particles represents the volume percentage content reaching 50% on the cumulative curve, that is, D. 50 This refers to the particle size at which the cumulative quantity (or mass) of the additive particles reaches 50% of the total quantity (or mass) after sorting them by particle size. When metal powder 11 is flake-shaped powder, the median particle size refers to the statistical median of the "equivalent circle diameter" or "major diameter" within the plane of the flake-shaped powder. The thickness of the flake-shaped powder is 0.05μm~0.5μm.

[0114] In some embodiments, the agglomeration index of the conductive powder 1 is less than or equal to 0.15, specifically it can be 0.15, 0.13, 0.1, 0.08, 0.5 or any two of the above values.

[0115] The conductive powder 1 of this application has a low agglomeration index, indicating that it has excellent dispersion stability. The low agglomeration index of the conductive powder 1 allows for rapid and uniform dispersion in an organic carrier without the need for prolonged high-speed stirring. This results in a conductive slurry with good storage stability, a uniform and dense printed film, and an increase in electrode conductivity of 2 to 5 times after sintering.

[0116] It should be noted that the agglomeration index of the conductive powder 1 in this application was determined by laser particle size distribution method.

[0117] (Preparation of conductive paste).

[0118] In some embodiments, the method further includes a step of preparing glass powder, specifically including: mixing 40%~70% Bi2O3, 10%~30% B2O3, 5%~20% ZnO and 0.3%~0.8% Y2O3 uniformly by mass percentage, and then subjecting the mixture to melting, quenching and pulverizing to obtain glass powder.

[0119] The glass powder of this application belongs to the Bi-B-Zn system, which can achieve low melting characteristics, controllable reactivity, and interfacial compatibility. Moreover, the Bi2O3 in the glass powder can significantly reduce the softening point and viscosity of the glass powder. During the sintering of the conductive paste, the glass powder has good fluidity and can be evenly spread on the surface of the silicon wafer, promoting the corrosion reaction. At the same time, Y2O3 is also added to the glass powder of this application, which can slow down the corrosion of the silicon wafer to a certain extent, thereby balancing the over-corrosion of the silicon wafer caused by the addition of Bi2O3 and reducing metal recombination.

[0120] In some embodiments, the mass percentage of Y2O3 in the glass powder is 0.3% to 0.8%, specifically 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any two of the above values. If the mass percentage of Y2O3 in the glass powder is too high, the glass powder has poor corrosion ability on the silicon wafer, making it impossible to form a good ohmic contact between the electrode formed by the conductive paste and the silicon wafer, resulting in excessively high contact resistance. If the mass percentage of Y2O3 in the glass powder is too low, the electrode formed by the conductive paste will over-corrode the silicon wafer, leading to intensified metal recombination.

[0121] In some embodiments, the melting process includes placing the material obtained in S401 in a platinum crucible, heating it to 1000°C to 1500°C at a rate of 5°C / min to 10°C / min in an air atmosphere, and holding it at that temperature for 1 hour to 5 hours, stirring once every 30 minutes during the process.

[0122] In some embodiments, the quenching process includes rapidly pouring the melt obtained from the melting process between two high-speed rotating stainless steel rollers to quench it into a glass sheet with a thickness of about 0.1 mm to 0.3 mm.

[0123] In some embodiments, the pulverization process includes coarsely crushing the glass sheets, wet ball milling them in a zirconia ball mill for 12 hours, followed by spray drying and granulation, and finally obtaining glass powder through air classification.

[0124] In some embodiments, the method further includes a step of preparing an organic carrier, specifically including: dispersing the resin in a solvent and stirring at 70°C to 100°C for 0.2 to 2 hours to obtain the organic carrier.

[0125] In some embodiments, the organic carrier includes a resin and a solvent, and the organosilicon material layer 12 in the conductive powder 1 can enhance the compatibility between the conductive powder and the resin in the organic carrier, further improving the flowability and viscosity of the conductive slurry.

[0126] In some embodiments, the resin includes at least one of ethyl cellulose, cellulose acetate butyrate, and hydrogenated rosin.

[0127] In some embodiments, the resin content in the organic carrier is 5% to 10% by mass, specifically 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values.

[0128] In some embodiments, the solvent includes an organic solvent with a boiling point of 200°C to 300°C, and the organic solvent includes at least one of alcohol ester-12, diethylene glycol butyl ether acetate, divalent ester and tributyl citrate.

[0129] In some embodiments, the solvent content in the organic carrier is 90% to 95% by mass, specifically 90%, 91%, 92%, 93%, 94%, 95%, or any two of the above values.

[0130] S400: According to the mass percentage, 85%~92% of conductive powder, 2%~4% of glass powder and the balance of organic carrier are mixed to obtain a premixed slurry.

[0131] S401. In a planetary mixer, add 8%~12% organic carrier and 2%~4% glass powder in sequence and stir once to fully disperse and evenly disperse them to obtain a mixed carrier.

[0132] In some implementations, the stirring speed is 300 rpm to 800 rpm and the stirring time is 10 min to 30 min.

[0133] In some embodiments, the hybrid carrier of this application further includes additives, including but not limited to surfactants, leveling agents, thixotropic agents, defoamers, sintering regulators, etc.

[0134] In some embodiments, the additive content in the conductive paste is 0.1% to 0.5% by mass.

[0135] S402. Add 85%~92% conductive powder to the planetary mixer and perform secondary dispersion to obtain premixed slurry.

[0136] In some embodiments, the secondary stirring speed is 700 rpm to 1300 rpm, and the secondary stirring time is 10 min to 30 min.

[0137] S500: The premixed slurry is rolled to obtain the precursor.

[0138] Specifically, this involves transferring the premixed slurry to a three-roll mill for grinding. The gaps between the rollers are set sequentially to 50μm, 25μm, and 15μm, and each is ground repeatedly 5 times until the fineness is less than 10μm when checked with a fineness stencil.

[0139] S600: The precursor is subjected to vacuum degassing treatment to obtain conductive slurry.

[0140] Specifically, the process involves placing the precursor in a vacuum degassing machine at a vacuum level below 0 MPa for 10 to 30 minutes, then restoring it to normal pressure, and finally allowing the slurry to stand and mature at 10°C to 40°C for 12 to 36 hours to obtain the conductive slurry.

[0141] S22, a conductive paste is coated and sintered on the first and / or second surfaces of a semiconductor substrate to form an electrode.

[0142] In some implementations, a conductive paste is coated only on the second surface of the semiconductor substrate, and electrodes are formed by sintering, resulting in a back-contact solar cell.

[0143] In some embodiments, conductive paste is coated on the first and second surfaces of a semiconductor substrate, and then sintered to form a first electrode on the first surface of the semiconductor substrate and a second electrode on the second surface of the semiconductor substrate, resulting in a bifacial solar cell.

[0144] The following example illustrates the preparation of a battery cell by coating conductive paste on the first and second surfaces of a semiconductor substrate, including the following steps: first, a conductive paste is coated on the first surface of the semiconductor substrate, dried, and then a conductive paste is coated on the second surface of the semiconductor substrate, dried, and sintered.

[0145] In some embodiments, coating includes, but is not limited to, at least one of screen printing, plate printing, inkjet printing, and blade coating.

[0146] In some embodiments, the drying and sintering steps after printing the front silver electrode paste are both carried out in a tunnel furnace. The temperature in the tunnel furnace is gradient-distributed, the time spent in the tunnel furnace is 1 min to 3 min, the peak sintering temperature is 700℃ to 970℃, and the sintering time at the peak temperature is 0.5 s to 2 s. Optionally, the sintering process also includes a preheating process in the tunnel furnace, with a preheating temperature of 200℃ to 300℃ and a preheating time of 30 s to 60 s.

[0147] This application embodiment also provides a battery cell, the battery cell comprising:

[0148] Semiconductor substrate, the semiconductor substrate includes a first surface and a second surface disposed opposite to each other;

[0149] The first electrode forms an ohmic contact with the first surface of the semiconductor substrate; and / or

[0150] A second electrode that forms an ohmic contact with the second surface of a semiconductor substrate;

[0151] At least one of the first electrode and the second electrode is formed using the aforementioned conductive paste.

[0152] The conductive paste of this application can simultaneously improve dispersibility and conductivity. The first and / or second electrodes formed using the conductive paste of this application can maintain high printability and electrical performance. The linewidth of the first and / or second electrodes is less than or equal to 25 μm, and the series resistance of the solar cell is controlled at 1.0 mΩ·cm. 2 the following.

[0153] The solar cells of this application can be one or any combination of PERC (Passivated Emitter Rear Ce1l), IBC (Interdigitated Back Contact), TOPCon (Tumnel Oxide Passivated Contact), and HIT / HTT (Heterojunction Technology) cells. It is understood that all of the above-mentioned solar cells can be prepared using the methods described in this application.

[0154] It should be noted that, based on the above-mentioned different types of battery cells, the first and second surfaces of the semiconductor substrate can also be provided with different film layer structures as needed, and this application does not impose any restrictions here.

[0155] Specifically, Figure 5 A schematic diagram of a battery cell structure is shown, such as... Figure 5 As shown, the battery cell 100 includes a first electrode 40, a first passivation layer 20, a semiconductor substrate 10, a second passivation layer 30, and a second electrode 50.

[0156] It should be noted that in some embodiments, the battery cell 100 only contains the second electrode 50.

[0157] This application embodiment also provides a photovoltaic module, the photovoltaic module comprising:

[0158] A battery string is composed of multiple of the aforementioned battery cells connected together.

[0159] Encapsulation layer, which covers the surface of the battery string;

[0160] Cover plate, used to cover the surface of the encapsulation layer away from the battery string.

[0161] Specifically, Figure 6 A schematic diagram of a photovoltaic module is shown below. Please refer to [link / reference]. Figure 6 The photovoltaic module 1000 includes a first cover plate 200, a first encapsulating layer 300, a solar cell string, a second encapsulating layer 400, and a second cover plate 500.

[0162] In some embodiments, the solar cell string includes a plurality of cells 100 as described above connected by conductive strips, and the connection between the cells 100 can be partially stacked or spliced.

[0163] In some embodiments, the first cover plate 200 and the second cover plate 500 can be transparent or opaque covers, such as glass covers or plastic covers.

[0164] The first encapsulating adhesive layer 300 is in contact with and bonded to the first cover plate 200 and the battery string on both sides, respectively. The second encapsulating adhesive layer 400 is in contact with and bonded to the second cover plate 500 and the battery string on both sides, respectively. The first encapsulating adhesive layer 300 and the second encapsulating adhesive layer 400 can be ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene coelastomer (POE) film, or polyethylene terephthalate (PET) film, respectively.

[0165] The photovoltaic module 1000 can also be fully encapsulated on the sides, that is, the sides of the photovoltaic module 1000 are completely covered and encapsulated with encapsulating tape to prevent lamination shift during the lamination process.

[0166] The photovoltaic module 1000 also includes an edge sealing component, which is fixedly encapsulated on a portion of the edge of the photovoltaic module 1000. This edge sealing component can be fixedly encapsulated on the edge of the photovoltaic module 1000 near a corner. The edge sealing component can be a high-temperature resistant tape. This high-temperature resistant tape has excellent high-temperature resistance properties and will not decompose or detach during lamination, ensuring reliable encapsulation of the photovoltaic module 1000. The two ends of the high-temperature resistant tape are respectively fixed to the second cover plate 500 and the first cover plate 200. The two ends of the high-temperature resistant tape can be bonded to the second cover plate 500 and the first cover plate 200 respectively, while the middle portion can limit the side of the photovoltaic module 1000, preventing lamination displacement of the photovoltaic module 1000 during the lamination process.

[0167] The following are specific embodiments illustrating this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0168] Example 1

[0169] (1) D 50 Flake silver powder with a diameter of 0.5μm to 1.2μm and a thickness of 0.1μm was ultrasonically treated in 5% nitric acid for 10 minutes, then washed with deionized water until neutral, and then placed in a vacuum drying oven and dried at 80℃ for 2 hours.

[0170] (2) Mix 2g of KH-550 (γ-aminopropyltriethoxysilane), acetic acid, anhydrous ethanol and deionized water in 50ml of a mixed solvent and carry out hydrolysis reaction for 30min. The volume ratio of anhydrous ethanol to deionized water is 95:5. The pH of the hydrolysis reaction is 4.5. After the hydrolysis reaction is completed, add 100g of silver powder obtained in step (1) and stir at 60℃ for 2h to allow the KH-550 hydrolysis product to undergo condensation reaction on the surface of the silver powder. After the reaction is completed, centrifuge and wash with ethanol. Finally, dry at 60℃ to obtain modified metal powder.

[0171] (3) The modified metal powder was dispersed in a glucose solution (concentration of 0.5 mol / L) with a solid-liquid ratio of 1 g: 10 ml. Hydrazine hydrate (concentration of 0.1 mol / L) was added and reacted at 80 °C for 1.5 h. The resulting product was centrifuged, washed with water, dried at 60 °C for 4 h, and finally placed in a sintering furnace under nitrogen protection for heat treatment at 180 °C for 1 h.

[0172] (4) Place the material obtained in (3) into a ball mill, the grinding ball is ZrO2, the ball-to-material ratio is 5:1, the ball milling is carried out in argon gas, the stirring speed of the ball mill is 300 rpm, the ball milling time is 25 min, and conductive powder is obtained.

[0173] (5) Mix 50% Bi2O3, 24% B2O3, 25.5% ZnO and 0.5% Y2O3 by mass percentage. Then place the mixture in a platinum crucible and heat it to 1250℃ at 8℃ / min in air atmosphere and hold it at that temperature for 2 hours, stirring once every 30 minutes. Then quickly pour the melt obtained from the melting treatment between two high-speed rotating stainless steel rollers and quench it into glass sheets with a thickness of about 0.1mm to 0.3mm. The glass sheets are first coarsely crushed, then wet ball milled in a zirconia ball mill for 12 hours, then spray dried and granulated, and finally obtained as glass powder by air classification.

[0174] (6) According to the mass fraction, add 10 parts of organic carrier and 3 parts of glass powder to the planetary mixer in sequence, and stir at 500 rpm for 10 min to make it fully dispersed and uniform, so as to obtain a mixed carrier; then add 87 parts of the conductive powder obtained in (4) to the planetary mixer, and stir at 800 rpm for 30 min to obtain a dispersion; transfer the dispersion to a three-roll mill for grinding. The gap between the rollers is set to 50 μm, 25 μm and 15 μm in sequence, and each is ground repeatedly for 5 times until the fineness is less than 10 μm when checked by scraping with a fineness plate; place the ground material under a vacuum of -0.095 MPa in a vacuum degasser for 20 min, then restore normal pressure, and then let the slurry stand at 30℃ for 24 h to mature, so as to obtain a conductive slurry.

[0175] (7) The conductive paste is screen-printed onto the upper surface of the silicon wafer, which is then placed in a tunnel furnace. The temperature is first set at 300°C for 50 seconds, and then gradually increased to 900°C for 2 seconds to obtain the first electrode. The conductive paste is then screen-printed onto the lower surface of the silicon wafer, which is then placed in a tunnel furnace. The temperature is first set at 300°C for 50 seconds, and then gradually increased to 900°C for 2 seconds to obtain the second electrode, thus obtaining the solar cell.

[0176] The conductive paste in Example 1 comprises conductive powder, glass powder, and an organic carrier. The conductive powder includes flake silver powder and an organosilicon material layer and a carbon material layer distributed on the surface of the flake silver powder. The organosilicon material layer is an aminosiloxane polymer formed by the hydrolysis and condensation of silane coupling agent KH-550. The carbon material layer is a polymer with sp... 2 The hybrid carbon is amorphous carbon with an organosilicon material layer thickness of 5 nm and a carbon material layer thickness of 15 nm.

[0177] The conductive powder of Example 1 was measured by Fourier transform infrared spectroscopy. In the obtained infrared spectrum, at 1050 cm⁻¹... -1 The presence of a strong absorption band nearby indicates the presence of a silicon-oxygen bond network in the conductive powder, and moreover, at 950 cm⁻¹... -1 The absence of obvious sharp characteristic peaks indicates that there are almost no Si-OH bonds in the conductive powder, suggesting that the silanol groups of the silane have fully reacted. Finally, at 3360 cm⁻¹... -1 Nearby and 3290cm -1 Two characteristic peaks are present nearby, namely the NH stretching vibration peak, indicating that the position of the NH stretching vibration peak has changed, that is, the chemical environment of the amino group has changed due to its combination with the surface of the silver powder. Through the above analysis, it can be seen that the conductive powder of Example 1 contains Si-O-Ag bonds.

[0178] Example 2

[0179] Unlike Example 1, in (2), the amount of KH-550 (γ-aminopropyltriethoxysilane) added is 1.75g.

[0180] In Example 2, the thickness of the organosilicon material layer is 3.5 nm, and the thickness of the carbon material layer is 15 nm.

[0181] Example 3

[0182] Unlike Example 1, in (2), the amount of KH-550 (γ-aminopropyltriethoxysilane) added is 1.5g.

[0183] In Example 3, the thickness of the organosilicon material layer is 2.3 nm, and the thickness of the carbon material layer is 15 nm.

[0184] Example 4

[0185] Unlike Example 1, in (2), the amount of KH-550 (γ-aminopropyltriethoxysilane) added is 4g.

[0186] In Example 4, the thickness of the silicone material layer is 9 nm, and the thickness of the carbon material layer is 15 nm.

[0187] Example 5

[0188] Unlike Example 1, in (3), the solid-liquid ratio is 1g:5ml.

[0189] In Example 5, the thickness of the organosilicon material layer is 5 nm, and the thickness of the carbon material layer is 8 nm.

[0190] Example 6

[0191] Unlike Example 1, in (3), the solid-liquid ratio is 1g:15ml.

[0192] In Example 5, the thickness of the organosilicon material layer is 5 nm, and the thickness of the carbon material layer is 20 nm.

[0193] Example 7

[0194] Unlike Example 1, in (3), the solid-liquid ratio is 1g:20ml.

[0195] In Example 5, the thickness of the silicone material layer is 5 nm, and the thickness of the carbon material layer is 24 nm.

[0196] Example 8

[0197] Unlike Example 1, step (3) is not performed.

[0198] In Example 5, the thickness of the organosilicon material layer is 5 nm.

[0199] Example 9

[0200] Unlike Example 1, (1): flake silver powder is replaced with spherical silver powder.

[0201] Example 10

[0202] Unlike Example 1, Y2O3 is not added in (5).

[0203] Comparative Example 1

[0204] The difference from Example 1 is that steps (2) and (3) are not performed.

[0205] Comparative Example 2

[0206] The difference from Example 1 is that step (2) is: KH-5502g and 100g of silver powder obtained in step (1) are mixed evenly under stirring conditions.

[0207] Performance testing:

[0208] (1) Aggregation index determination:

[0209] The agglomeration index of conductive powder is determined by laser particle size analysis. Specifically, a laser particle size analyzer is used to first perform dry measurement at a low dispersion pressure (e.g., 0.2 MPa) to obtain the median particle size D1. Then, the sample is placed in a medium with added dispersant (usually deionized water, ethanol, or deionized water), and after ultrasonic treatment, wet measurement is performed to obtain the median particle size D2. The agglomeration index is calculated as D1 / D2.

[0210] (2) Measurement of volume resistivity:

[0211] The conductive pastes prepared in the various embodiments and comparative examples were screen-printed onto an inert substrate (such as an alumina ceramic sheet) to create straight strip patterns of known length (L) and uniform width (W). These strips were then processed according to the specified sintering / curing process to obtain strip electrodes. The resistance (R) at both ends of the strip electrodes was precisely measured using a four-probe tester. The average thickness (H) and width (W) of the sintered electrode strips were precisely measured using a profilometer or scanning electron microscope. The volume resistivity was calculated using the formula: Volume Resistivity = R (W) H) / L, convert the result to μΩ·cm.

[0212] (3) Determination of antioxidant temperature:

[0213] The conductive pastes prepared in the various embodiments and comparative examples were screen-printed onto an inert substrate (such as an alumina ceramic sheet) to create straight strip patterns of known length (L) and uniform width (W). These strips were then processed according to the specified sintering / curing process to obtain strip electrodes. The strip electrodes were placed in a programmable tube furnace and heated to 220°C at a constant rate (e.g., 5°C / min) in air or a specific atmosphere. The discoloration of the strip electrode surface was observed in real time, and the temperature at which the discoloration occurred was recorded.

[0214] (4) Slurry viscosity stability:

[0215] The freshly prepared conductive pastes from each embodiment and comparative example were placed on a rheometer measurement platform and subjected to a set temperature (e.g., 25°C) and a fixed shear rate (e.g., 10 s). -1 Under the same conditions, the initial viscosity h0 was measured. The conductive paste was then sealed and placed in a constant temperature and humidity environment (25℃, 50%RH) for standing. Samples were taken at regular intervals (e.g., day 1, day 3, day 7, day 14, and day 30), and the viscosity h0 was measured again under the same test conditions as the initial viscosity. t , where h t Let represent the viscosity on day t. According to the formula: Viscosity growth rate = (h... t -h0)h0 100%.

[0216] (5) Measurement of printed electrode linewidth:

[0217] Using a laser-cut screen with a specific aperture width (e.g., 20 μm), a set of parallel patterns are printed on a silicon wafer using conductive pastes prepared according to the various examples and comparative examples. The wafer is then processed according to the sintering / curing process specified by the paste to obtain strip grid lines. The top width of the strip grid lines is measured at multiple different locations (typically 5 or more measurement locations) using a scanning electron microscope and is denoted as the electrode linewidth.

[0218] The conductive pastes prepared in Examples 1-10 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1.

[0219] Table 1. Performance tests of examples and comparative examples

[0220]

[0221] This application employs a conductive paste coated on a first and / or second surface of a semiconductor substrate, followed by sintering to form an electrode. The conductive paste comprises conductive powder, which includes metal powder and at least one coating layer distributed on the surface of the metal powder. The coating layer includes an organosilicon material layer. By depositing the organosilicon material layer on the surface of the metal powder, the organosilicon material can cover the surface of the metal powder, reducing contact between metal powder particles, reducing agglomeration of the conductive powder, and improving the dispersibility of the conductive powder. This improves the dispersion uniformity, flowability, and stability of the conductive paste containing the conductive powder. Furthermore, the uniformly dispersed conductive powder can better contact the glass powder, organic carrier, and semiconductor substrate, improving the adhesion of the electrode prepared from the conductive paste. Moreover, the uniform coverage of the organosilicon material layer on the surface of the metal powder forms a more complete conductive network, improving the overall conductivity of the electrode prepared from the conductive paste. This application controls the mass content of the conductive powder, glass powder, and organic carrier within the aforementioned ranges to achieve synergistic optimization of the functions of each component, ensuring that the conductive paste possesses excellent printability, high conductivity of the cured electrode, and stable mechanical properties. Electrodes formed using the conductive paste of this application maintain high printability and electrical performance, with a linewidth of less than or equal to 25 μm and a series resistance of the solar cell controlled at 1.0 mΩ·cm. 2 the following.

[0222] According to the test data of Examples 1 to 4, by adjusting the amount of silane coupling agent added, the thickness of the organosilicon material layer can be actively and controllably designed, the agglomeration index of the conductive powder can be adjusted, thereby improving the dispersibility of metal powder in the conductive paste, making the metal powder less prone to agglomeration, improving the dispersion uniformity, fluidity and stability of the conductive paste, thereby improving the viscosity stability of the paste, and enhancing the long-term service life, oxidation resistance and printing ability of the electrode.

[0223] According to the test data of Examples 1, 5 to 8, the thickness of the carbon material layer can be adjusted by adjusting the solid-liquid ratio of the modified metal powder and the carbon source solution. A suitable thickness of the carbon material layer can simultaneously improve the conductivity and dispersibility of the conductive powder.

[0224] In Example 7, the excessive addition of carbon source solution resulted in an excessively thick carbon material layer on the surface of the metal powder. On the one hand, this led to an insufficient proportion of metal powder in the conductive powder, and on the other hand, the metal powder and carbon material were prone to interfacial delamination, resulting in increased contact resistance. Furthermore, it resulted in too many internal defects in the carbon material, leading to an increase in the intrinsic resistivity of the carbon material layer.

[0225] In Example 8, no carbon source solution was added, meaning the conductive powder consisted of metal powder and an organosilicon material layer distributed on the surface of the metal powder, and the volume resistivity of the prepared electrode increased sharply.

[0226] According to the test data of Examples 1 and 9, the morphology of metal powder has little effect on the dispersibility and conductivity of conductive paste. Spherical metal powder performs slightly better than flake metal powder. However, the finished product of flake metal powder is significantly lower than that of spherical metal powder. Therefore, inexpensive flake metal powder can be used to prepare conductive paste, which can ensure the high performance of conductive paste while reducing the preparation cost.

[0227] According to the test data of Examples 1 and 10, Y2O3 was not added to the glass powder in Example 10, and the resistivity of the electrode was significantly deteriorated. The main reason is that the lack of Y2O3 in the glass powder makes it easy for the conductive paste to over-corrode the silicon wafer during the printing process of the conductive paste on the silicon wafer. This leads to an increase in the saturation current density of the paste-semiconductor contact area, which deteriorates the contact quality, resulting in increased contact resistance and decreased overall volume resistivity.

[0228] According to the test data of Example 1 and Comparative Example 1, the metal powder in Comparative Example 1 was not modified with silane coupling agent or coated with carbon material. The metal powder has a large specific surface area and high surface energy, which makes the metal powder, especially silver powder, easy to agglomerate in the conductive paste. The agglomeration index of the conductive powder is greater than 0.15, which leads to uneven dispersion of the prepared conductive paste, and problems such as screen clogging and grid breakage during printing. After being prepared as electrodes, the semiconductor substrate and electrode grain boundary resistance and contact resistance increase sharply.

[0229] According to the test data of Example 1 and Comparative Example 2, in Comparative Example 2, the metal powder and organosilicon material are physically mixed, and the organosilicon material can only partially adhere to the surface of the metal powder, which has limited effect on improving the dispersion of the metal powder. Moreover, the free organosilicon material in the conductive paste may hinder its electronic conduction, and the overall resistivity of the conductive paste as an electrode increases. In addition, the free organosilicon material is easily hydrolyzed when the conductive paste is stored, which greatly reduces the storage time of the paste.

[0230] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A method for preparing a battery cell, characterized in that, Includes the following steps; A semiconductor substrate is provided, the semiconductor substrate having opposing first and second surfaces; A conductive paste is prepared, and the conductive paste is coated on the first and / or second surfaces of the semiconductor substrate and sintered to form an electrode. The conductive paste, by weight percentage, comprises: 85% to 92% conductive powder, 2% to 4% glass powder, and the remainder being an organic carrier. The conductive powder includes metal powder and at least one coating layer distributed on the surface of the metal powder, wherein the coating layer includes an organosilicon material layer and a carbon material layer distributed on the surface of the organosilicon material layer. The method for preparing the conductive paste includes: A premixed solution is obtained by mixing a silane coupling agent, a solvent, and an acid solution and then hydrolyzing the mixture. Metal powder is provided, the metal powder is mixed with the premixed liquid, and the mixture is subjected to solid-liquid separation and drying to obtain a first precursor. The first precursor, carbon source solution, catalyst and reducing agent are mixed, and the mixture is subjected to solid-liquid separation and drying. The dried material is then subjected to heat treatment to obtain conductive powder.

2. The method for preparing a battery cell according to claim 1, characterized in that, The organosilicon material layer is covalently connected to the metal powder.

3. The method for preparing the battery cell according to claim 2, characterized in that, The organosilicon material layer is connected to the metal powder via Si-OM bonds, where M is a metal element in the metal powder.

4. The method for preparing a battery cell according to claim 1, characterized in that, The material of the organosilicon material layer includes siloxane polymers.

5. The method for preparing a battery cell according to claim 1, characterized in that, The thickness of the organosilicon material layer is 2nm~5nm.

6. The method for preparing a battery cell according to claim 1, characterized in that, The carbon material layer is made of conductive carbon material, which includes at least one of amorphous carbon and graphite-like carbon.

7. The method for preparing a battery cell according to claim 6, characterized in that, The thickness of the carbon material layer is 5nm~20nm.

8. The method for preparing a battery cell according to claim 1, characterized in that, The metal powder includes at least one of silver powder, copper powder, gold powder, nickel powder, and aluminum powder; and / or The metal powder includes at least one of spherical powder and flake powder; and / or The median particle size of the metal powder is 0.5 μm to 1.2 μm.

9. The method for preparing a battery cell according to claim 1, characterized in that, The agglomeration index of the conductive powder is less than or equal to 0.

15.

10. The method for preparing a battery cell according to claim 1, characterized in that, The glass powder comprises, by mass percentage, 40% to 70% Bi₂O₃, 10% to 30% B₂O₃, 5% to 20% ZnO, and 0.3% to 0.8% Y₂O₃.

11. The method for preparing a battery cell according to any one of claims 1 to 10, characterized in that, The preparation of the conductive paste further includes the following steps: According to the mass percentage, 85% to 92% of the conductive powder, 2% to 4% of the glass powder, and the balance of the organic carrier are mixed to obtain a premixed slurry; The premixed slurry is subjected to roll forming to obtain a second precursor; The second precursor is subjected to vacuum degassing to obtain a conductive slurry.

12. The method for preparing a battery cell according to claim 11, characterized in that, The metal powder includes at least one of silver powder, copper powder, gold powder, nickel powder, and aluminum powder; The metal powder includes at least one of spherical powder and flake powder; The median particle size of the metal powder is 0.5 μm to 1.2 μm; The silane coupling agent is an aminosilane coupling agent; The silane coupling agent includes at least one of silane coupling agent KH-550, silane coupling agent KH-540, silane coupling agent A-1100, and silane coupling agent A-1110; The solvent includes at least one of alcohol solvents and deionized water; The pH of the acid solution is 4-5; The acid solution includes at least one of acetic acid and citric acid; The mass of the silane coupling agent is 1.5% to 2.0% of the mass of the metal powder; The mixing temperature is 50℃~80℃; The mixing time is 1 hour to 3 hours; The heat treatment is carried out in an inert gas atmosphere; The heat treatment temperature is 150℃~250℃; The heat treatment time is 0.5h to 2h; The heat treatment is followed by a step of ball milling the product of the heat treatment.

13. The method for preparing a battery cell according to claim 11, characterized in that, Before mixing the metal powder and the premixed solution, the process further includes: mixing the metal powder and the acid solution, ultrasonic treatment, washing with deionized water until neutral, and drying. The acid solution includes at least one of nitric acid and sulfuric acid with a concentration of 3% to 8%.

14. The method for preparing a battery cell according to claim 1, characterized in that, The carbon source solution includes at least one of glucose aqueous solution, fructose aqueous solution, sucrose aqueous solution and maltose aqueous solution; The concentration of the carbon source solution is 0.1 mol / L to 1 mol / L; The catalyst includes an amino compound; The reducing agent includes at least one of deionized hydrazine hydrate and ascorbic acid; The concentration of the reducing agent is 0.01 mol / L to 0.2 mol / L; The solid-liquid ratio of the first precursor to the carbon source solution is 1 g: (5~15) ml; The mixing temperature is 50℃~100℃; The mixing time is 1 hour to 3 hours.

15. A battery cell, characterized in that, The battery cell is formed using the method for preparing a battery cell according to any one of claims 1 to 14, and the battery cell comprises: A semiconductor substrate, the semiconductor substrate including a first surface and a second surface disposed opposite to each other; A first electrode forming an ohmic contact with a first surface of the semiconductor substrate; and / or A second electrode that forms an ohmic contact with the second surface of the semiconductor substrate.

16. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string, wherein the battery string is formed by connecting multiple battery cells formed by the method of preparing battery cells according to any one of claims 1 to 14 or battery cells according to claim 15; An encapsulation layer that covers the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

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