Solar cell and method of manufacturing the same, stacked cell, and photovoltaic module

Abstract

The application provides a solar cell and a preparation method thereof, a laminated cell and a photovoltaic module. The preparation method of the solar cell comprises the following steps: obtaining a semiconductor substrate, the semiconductor substrate having opposite first and second surfaces; obtaining a conductive paste, coating the conductive paste on the first and / or second surface of the semiconductor substrate, sintering, and forming an electrode; wherein, according to the mass percentage, the conductive paste comprises 50-85% of conductive powder, 1-8% of glass powder, and the balance of organic carrier; the conductive powder comprises first and second conductive powders, the first conductive powder comprises copper powder, and the second conductive powder comprises copper powder and a coating layer coated on the surface of the copper powder; the softening point of the glass powder is S1, the melting point of the coating material is S2, and the difference between S1 and S2 is greater than or equal to 60 DEG C. The application can improve the oxidation resistance and photoelectric conversion efficiency of the solar cell, and improve the long-term reliability of the solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell and its preparation method, a tandem cell and a photovoltaic module. Background Technology

[0002] A photovoltaic (PV) cell is a clean power generation system that uses sunlight to generate electricity. The core component of a PV cell power generation system is the solar cell, which can directly convert sunlight into electrical energy.

[0003] The fabrication process of solar cells requires the use of conductive paste to form electrodes, but the oxidation resistance of solar cells prepared by current processes cannot meet the requirements. Summary of the Invention

[0004] This application provides a solar cell and its preparation method, a tandem cell and a photovoltaic module, which can effectively improve the oxidation resistance and electrode quality of solar cells, improve the conversion efficiency of solar cells, and improve the long-term reliability of solar cells.

[0005] In a first aspect, this application provides a method for preparing a solar cell, comprising the following steps: A semiconductor substrate is obtained, the semiconductor substrate having opposing first and second surfaces; A conductive paste is obtained, 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: 50% to 85% conductive powder, 1% to 8% glass powder, and the remainder organic carrier. The conductive powder includes a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer covering the surface of the copper powder. The softening point of the glass powder is S1, the melting point of the coating layer is S2, and the difference between S1 and S2 is greater than or equal to 60°C.

[0006] Secondly, embodiments of this application provide a solar cell, which is formed using the solar cell fabrication method described in the first aspect, and the solar cell includes: 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.

[0007] Thirdly, embodiments of this application provide a tandem solar cell, the tandem solar cell comprising: a perovskite top cell and a crystalline silicon bottom cell stacked sequentially, wherein the crystalline silicon bottom cell is a solar cell formed by the method for preparing solar cells described in the first aspect or a solar cell described in the second aspect.

[0008] Fourthly, embodiments of this application provide a photovoltaic module, the photovoltaic module comprising: A battery string, wherein the battery string is formed by connecting multiple solar cells formed by the method of preparing solar cells described in the first aspect, or solar cells described in the second aspect, or stacked cells described in the third aspect; 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.

[0009] The beneficial effects of this application are as follows: This application uses a conductive paste to coat the first and / or second surfaces of a semiconductor substrate and then sinters to form electrodes. The conductive paste includes conductive powder, which comprises a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer on the surface of the copper powder. Because the conductive powder is formed by uniformly mixing the second and first conductive powders, the second conductive powder can be distributed in a dotted pattern on the surface of the first conductive powder, allowing the first conductive powder to be shielded by the second conductive powder, reducing the exposed area of ​​the first conductive powder, and thus helping to suppress oxidation in the early stages of sintering the conductive paste. The softening point of the glass powder is S1, and the melting point of the coating layer is S2. The difference between S1 and S2 is greater than or equal to 60℃, which helps to reduce the mutual influence between the coating material and the glass powder during sintering. On the one hand, it helps the copper powder to be protected evenly while the coating layer melts, and the softening of the glass powder allows for uniform spreading, so that the softened glass powder can be evenly distributed on the surface of the conductive powder, which is beneficial for suppressing the oxidation of copper powder in the later stages of conductive paste sintering. On the other hand, it avoids the drastic change in viscosity of the conductive paste caused by the simultaneous melting of the coating layer and softening of the glass powder, which is beneficial for improving the quality of the electrode formed by the conductive paste sintering. This application can protect the copper powder in the first and second conductive powders from oxidation by using different anti-oxidation mechanisms in the early and middle stages of conductive paste sintering, thereby improving the oxidation resistance and printing quality of the conductive paste. In addition, this application controls the mass content of conductive powder, glass powder, and organic carrier within the above-mentioned range to achieve synergistic optimization of the functions of each component, ensuring that the conductive paste has excellent printing performance, high conductivity of the electrode after curing, and stable mechanical properties. Attached Figure Description

[0010] Figure 1 A schematic diagram of the fabrication process of a solar cell provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a solar cell provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the stacked battery provided in the embodiments of this application; Figure 4 This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application.

[0011] In the attached image: 1000 - Photovoltaic modules; 100 - Solar cell; 10 - Semiconductor substrate; 20 - First passivation layer; 30 - Second passivation layer; 40 - First electrode; 50 - Second electrode; 200 - First cover plate; 300 - First encapsulating adhesive layer; 400 - Second encapsulating adhesive layer; 500 - Second cover plate; 2000-Stacked Battery; 2001-Perovskite Top Cell; 2002 - Crystalline silicon bottom cell. Detailed Implementation

[0012] In this embodiment of the application, unless otherwise stated, the character " / " indicates that the preceding and following objects are in an OR relationship. For example, A / B can represent A or B. "AND / OR" describes the relationship between the associated objects, indicating that three relationships can exist. For example, A AND / OR B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0013] It should be noted that the terms "first" and "second" used in the embodiments of this application are used only for distinguishing descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor should they be construed as indicating or implying order.

[0014] In the embodiments of this application, "at least one" means one or more, and "more than one" means two or more. Furthermore, "at least one of the following" or similar expressions refer to any combination of these items, which may include any combination of a single item or a plurality of items. For example, at least one of A, B, or C can represent: A, B, C, A and B, A and C, B and C, or A, B, and C. Each of A, B, and C can be an element itself or a set containing one or more elements.

[0015] In this application, terms such as "exemplary," "in some embodiments," and "in another embodiment" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the term "exemplary" is intended to present the concept in a concrete manner.

[0016] In the embodiments of this application, the term "equal to" can be used in conjunction with "greater than" to apply to technical solutions employing the condition of "greater than", and can also be used in conjunction with "less than" to apply to technical solutions employing the condition of "less than". It should be noted that when "equal to" is used with "greater than", it cannot be used with "less than"; and when "equal to" is used with "less than", it cannot be used with "greater than".

[0017] In related technologies, the front and back electrodes of crystalline silicon solar cells are prepared by sintering conductive paste. Common conductive pastes mainly use silver as the conductive phase. Although silver has excellent conductivity and solderability, silver is expensive, resulting in high manufacturing costs.

[0018] To reduce manufacturing costs, researchers have begun exploring the use of base metals (such as copper, aluminum, and nickel) to replace silver. Among these, copper has emerged as the most promising alternative due to its similar conductivity to silver and its lower price. However, copper paste faces numerous challenges in practical applications. Copper powder is highly susceptible to oxidation in air, especially in the high-temperature environment of sintering, forming non-conductive copper oxide, which leads to a sharp decline in the paste's conductivity and an increase in contact resistance.

[0019] Therefore, embodiments of this application provide a method for fabricating a solar cell. Figure 1 A schematic diagram of a solar cell fabrication process is shown, such as... Figure 1 As shown, the method for fabricating a solar cell includes the following steps: A semiconductor substrate is obtained, the semiconductor substrate having opposing first and second surfaces; A conductive paste is obtained, and the conductive paste is coated on the first and / or second surfaces of a semiconductor substrate and sintered to form an electrode. The conductive paste, by weight percentage, comprises: 50% to 85% conductive powder, 1% to 8% glass powder, and the remainder organic carrier. The conductive powder includes a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer on the surface of the copper powder. The softening point of the glass powder is S1, and the melting point of the coating material is S2. The difference between S1 and S2 is greater than or equal to 60℃.

[0020] 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 electrodes. The conductive paste comprises conductive powder, including a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer covering the surface of the copper powder. Since the conductive powder is formed by uniformly mixing the second and first conductive powders, the second conductive powder can be distributed in a dotted pattern on the surface of the first conductive powder. This allows the first conductive powder to be shielded by the second conductive powder, reducing its exposed area and thus helping to suppress oxidation in the early stages of sintering the conductive paste. The softening point of the glass powder is S1, and the melting point of the coating layer is S2. The difference between S1 and S2 is greater than or equal to 60℃, which helps to reduce the mutual influence between the coating material and the glass powder during sintering. On the one hand, it helps the copper powder to be protected evenly while the coating layer melts, and the softening of the glass powder allows for uniform spreading, so that the softened glass powder can be evenly distributed on the surface of the conductive powder, which is beneficial for suppressing the oxidation of copper powder in the later stages of conductive paste sintering. On the other hand, it avoids the drastic change in viscosity of the conductive paste caused by the simultaneous melting of the coating layer and softening of the glass powder, which is beneficial for improving the quality of the electrode formed by the conductive paste sintering. This application can protect the copper powder in the first and second conductive powders from oxidation by using different anti-oxidation mechanisms in the early and middle stages of conductive paste sintering, thereby improving the oxidation resistance and printing quality of the conductive paste. In addition, this application controls the mass content of conductive powder, glass powder, and organic carrier within the above-mentioned range to achieve synergistic optimization of the functions of each component, ensuring that the conductive paste has excellent printing performance, high conductivity of the electrode after curing, and stable mechanical properties.

[0021] The difference between the melting point of the coating layer and the softening point of the glass powder in this application is greater than or equal to 60°C. Specifically, it can be any value within the range of 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 300°C, or any two of the above values. The melting point of the coating layer and the softening point of the glass powder are separated in temperature range, and they do not interfere with each other. This allows the coating layer and the glass powder to synergistically improve the oxidation resistance and printing quality of the conductive paste.

[0022] When the softening point of the glass powder is lower than the melting point of the coating material (S2-S1 ≥ 60℃), as sintering progresses, the glass powder softens and coats the surface of the conductive powder, providing a physical barrier. The coating layer does not melt and mix with the glass powder, preventing the physical barrier from failing. When the softening point of the glass powder is higher than the melting point of the coating material (S1-S2 ≥ 60℃), as sintering progresses, the coating layer preferentially melts and diffuses into the copper powder, providing a physical barrier. The molten coating material can combine with copper to form an intermediate phase compound. As the sintering temperature increases, the glass powder softens, flows, and coats the surface of the conductive powder, providing a physical barrier.

[0023] If the difference between the melting point of the coating layer and the softening point of the glass powder is less than 60℃, the coating layer and the glass powder will soften simultaneously in the same or similar temperature environment. The contact reaction between the two will cause the fluidity of the conductive paste to run out of control, and the viscosity of the paste will change drastically and intensively, resulting in a significant deterioration of the antioxidant effect. In addition, the electrodes formed by sintering the conductive paste are prone to deformation, affecting the accuracy and edge clarity of the printed pattern.

[0024] Optionally, the difference between the melting point of the coating layer and the softening point of the glass powder is 60℃~300℃.

[0025] The preparation method of the solar cell of the present invention will be described in detail below.

[0026] S1, Obtain a semiconductor substrate having a first surface and a second surface opposite to each other.

[0027] 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 is an N-type crystalline silicon substrate, and the doping element of the N-type crystalline silicon substrate is at least one of nitrogen, phosphorus, arsenic, antimony, or bismuth.

[0028] 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.

[0029] It should be noted that the "~" between two values ​​in this application represents the endpoint value that includes both values.

[0030] In some embodiments, the first surface of the semiconductor substrate corresponds to the front side of the solar cell, which is the surface facing the sun (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.

[0031] 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.

[0032] 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 may 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 the series resistance and improve electron transport capability.

[0033] 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.

[0034] 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 solar cell surface, 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.

[0035] 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.

[0036] S2, Obtain conductive paste, apply conductive paste to the first and / or second surfaces of the semiconductor substrate, sinter, and form electrodes.

[0037] S21, by mass percentage, 50%~85% conductive powder, 1%~8% glass powder and the balance organic carrier are mixed to obtain a premix.

[0038] In some embodiments, S21 may specifically be: adding conductive powder and glass powder sequentially to a planetary mixer for a first stirring process to ensure that they are fully dispersed and uniform; then adding an organic carrier to the planetary mixer for a second stirring process to obtain a premix.

[0039] Of course, the mixing order of the materials in the above premix can also be used, as long as the materials are mixed evenly. This application does not impose any restrictions on this.

[0040] In some embodiments, the mass percentage of conductive powder in the conductive slurry is 50% to 85%, specifically it can be 50%, 55%, 60%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 82%, 85%, or any value within the range of any two of the above values.

[0041] In some embodiments, the conductive powder includes a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer on the surface of the copper powder, i.e., coated copper powder. In this application, the conductive powder is a combination of copper powder and coated copper powder. Copper powder has excellent conductivity and can build a continuous conductive path inside the slurry, effectively reducing the overall resistivity of the electrode. The coated copper powder relies on the surface coating layer to block the copper powder from contact with air and high-temperature sintering atmosphere, alleviating the problem of high-temperature oxidation of the powder. At the same time, the coating layer can improve the interfacial compatibility between the powder and the glass phase and organic carrier, and improve the adhesion strength between the electrode and the semiconductor substrate after the conductive slurry is sintered.

[0042] In some embodiments, the coating material includes at least one of silver, tin, aluminum oxide, and silicon dioxide. These materials can form a high-strength, dense coating on the surface of copper powder, effectively isolating the copper powder from oxygen and moisture corrosion. Furthermore, silver, tin, and aluminum oxide have good electrical conductivity; their coating on the surface of the copper powder ensures the conductivity of the conductive paste and the ohmic contact between the electrode prepared from the conductive paste and the semiconductor substrate.

[0043] In some embodiments, 900℃≤S2≤2100℃, within the above range, the material of the coating layer includes any one of silver, aluminum oxide and silicon dioxide, and S2 can specifically be any value within the range of 900℃, 950℃, 1000℃, 1050℃, 1080℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, 1900℃, 2000℃, 2100℃ or any two of the above values.

[0044] In some embodiments, 200℃≤S2≤250℃, within the above range, the coating material includes tin, which has a melting point of 231.9℃, but rapidly oxidizes to SnO2 after melting, with a melting point of 1630℃, and can also cover the surface of copper powder as a protective layer. S1 can specifically be 200℃, 205℃, 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, or any value within the range of any two of the above values.

[0045] It should be noted that the melting point of the coating material in this application was obtained by observation during high-temperature furnace sintering. Specifically, under a nitrogen atmosphere, a certain amount of coating material was placed in a high-temperature furnace for heat treatment. By observing the adhesion and wetting of the particles, the temperature at which the particles begin to wet and clump together is the melting point.

[0046] In some embodiments, the thickness of the coating layer is 10 nm to 100 nm. Specifically, the thickness of the coating layer can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value within the range of any two of the above values.

[0047] Controlling the coating thickness within the aforementioned range helps to achieve a balance between cost control, improved conductivity, and ensuring coating effectiveness. If the coating thickness is less than 10 nm, it is impossible to guarantee complete coverage of the copper powder surface. If the coating thickness is greater than 100 nm, it will lead to increased costs, deteriorated mechanical and processing properties, and potential electrical hazards.

[0048] In some embodiments, the coating layer has a mass percentage content of 3% to 30% in the second conductive powder, specifically 3%, 5%, 8%, 10%, 15%, 20%, 25%, 28%, 30%, or any value within the range of any two of the above values.

[0049] In some embodiments, the mass percentage of the second conductive powder in the conductive powder is 1% to 10%, specifically it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of the above values. This application controls the mass percentage of the second conductive powder in the conductive powder to be 1% to 10%, that is, the mass percentage of the first conductive powder in the conductive powder is 90% to 99%. The conductive powder of this application is mainly composed of the first conductive powder, which has excellent conductivity and sintering activity, and can form a continuous and dense metallic conductive network, reducing resistance. By controlling the ratio of the first and second conductive powders in the conductive powder, this application enables the conductive powder to achieve both high conductivity and oxidation resistance.

[0050] In some embodiments, the copper powder includes at least one of spherical powder, near-spherical powder, and flake powder.

[0051] In some embodiments, the median particle size D of the copper powder 50The median particle size is 0.5μm to 5μm, specifically 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, or any value within the range of any two of the above values. Controlling the median particle size of the copper powder within this range is beneficial for the close packing of conductive powder to form a continuous conductive network, while simultaneously improving the dispersibility of the conductive powder in the conductive slurry, reducing the porosity of the conductive slurry, and enhancing the density and interfacial adhesion of the conductive sintered electrode. Optionally, the median particle size D of the copper powder... 50 The range is 0.5μm to 3μm.

[0052] It should be noted that the cumulative particle size distribution of the volume reference determined by the laser diffraction method, D 50 This represents the particle size at which the cumulative particle size distribution percentage reaches 50%, also known as the median particle size. When the copper powder is spherical or flake-shaped, no instrument replacement is required during testing. Simply increase the ultrasonic dispersion time and adjust the dispersant dosage appropriately to break up any agglomerated particles. The instrument then calculates D based on the equivalent spherical diameter. 50 data.

[0053] In some embodiments, the glass powder includes at least one of the Bi2O3-B2O3-ZnO system and the Bi2O3-ZnO-P2O5 system.

[0054] In some embodiments, the mass percentage of glass powder in the conductive paste is 1% to 8%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any value within the range of any two of the above values.

[0055] In some embodiments, the glass powder comprises, by mass percentage, 40% to 70% Bi2O3, 10% to 30% B2O3, 5% to 20% ZnO, 0.5% to 5% MoO3, and 0.1% to 3% P2O5.

[0056] By adding specific amounts of MoO3 and P2O5 to the glass powder, the softening point of the glass powder is lowered. During the sintering of the conductive paste to form the electrode, the glass powder softens and coats the surface of the conductive powder when the copper powder undergoes significant oxidation, providing a physical barrier and inhibiting the oxidation of the conductive powder. Furthermore, the glass powder with the specific composition described above can gently etch the silicon nitride antireflective film, forming a good ohmic contact with the semiconductor substrate without excessively eroding the PN junction. It also effectively anchors the semiconductor substrate, resulting in a good ohmic contact, low contact resistance, and high adhesion between the conductive paste and the semiconductor substrate. In addition, the glass powder described above does not contain lead, ensuring green and environmentally friendly production requirements while maintaining the conversion efficiency of the solar cell.

[0057] In some embodiments, the mass percentage of MoO3 in the glass powder is 0.5% to 5%, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values. If the mass percentage of MoO3 in the glass powder is too low, its ability to lower the softening point of the glass powder is insufficient; if the mass percentage of MoO3 in the glass powder is too high, it can easily lead to problems such as overheating, overflow, and crystallization during the printing and sintering of conductive paste, causing the softening point of the glass powder to stop decreasing.

[0058] In some embodiments, the mass percentage of P2O5 in the glass powder is 0.1% to 3%, specifically 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or any value within the range of any two of the above values. If the mass percentage of P2O5 in the glass powder is too low, its ability to lower the softening point of the glass powder is insufficient; if the mass percentage of P2O5 in the glass powder is too high, it will lead to a decrease in the water resistance and thermal stability of the glass powder.

[0059] In some embodiments, the softening point of the glass powder is 400℃~600℃, specifically it can be 400℃, 430℃, 450℃, 480℃, 500℃, 520℃, 550℃, 570℃, 600℃ or any value within the range of any two of the above values.

[0060] This application uses copper powder as the main conductive phase. The oxidation degree of copper powder varies at different temperatures. Below 600°C, the oxidation of copper powder is not severe, while at 600°C or higher, the oxidation reaction intensifies. The conductive slurry of this application exhibits different anti-oxidation mechanisms at different sintering stages. In the initial sintering stage, below 600°C, by controlling the proportion of the second conductive powder, the second conductive powder forms a discrete point distribution in the conductive slurry. The second conductive powder acts as a solid barrier, reducing the oxidation of the first conductive powder. Moreover, when the second conductive powder is tin-coated copper powder, the tin begins to melt at 231.9°C. The tin on the surface immediately oxidizes to form a dense tin dioxide protective layer, while the tin inside contacts the copper to form an intermediate phase compound, effectively blocking oxygen diffusion to the copper powder, thus still achieving anti-oxidation function. In the middle stage of sintering, above 600°C, glass powder softens and flows, coating the surface of the conductive powder to form a physical barrier.

[0061] It should be noted that the softening point of the glass powder in this application was determined according to the ASTM C338-24 standard test method. Specifically, the glass to be tested was made into uniform glass fibers with a diameter of 0.55 mm to 0.75 mm and a length of approximately 235 mm. The fibers were heated in a furnace at a rate of 5℃ / min ± 1℃ / min. The temperature at which the fibers elongated at a rate of 1 mm / min under their own gravity was recorded was the softening point of the glass powder.

[0062] In some embodiments, the organic carrier has a mass percentage of 5% to 10% in the conductive paste, specifically 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of the above values.

[0063] In some embodiments, the organic carrier includes a resin and a solvent.

[0064] In some embodiments, the resin is dispersed in a solvent and stirred at 70°C to 100°C for 0.2 to 2 hours to obtain an organic carrier.

[0065] In some embodiments, the resin includes at least one of ethyl cellulose, cellulose acetate butyrate, and hydrogenated rosin.

[0066] 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 value within the range of any two of the above values.

[0067] 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.

[0068] 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 value within the range of any two of the above values.

[0069] In some embodiments, the conductive paste further includes additives, the additives being present in the conductive paste at a mass percentage of 0.5% to 3%, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or any value within the range of any two of the above values.

[0070] In some embodiments, the additive may also include at least one of dispersants, thixotropic agents, sintering aids, adhesion promoters, antioxidants, and stabilizers to improve the performance of the conductive paste.

[0071] In some embodiments, the dispersant includes, but is not limited to, stearic acid, oleic acid, palmitic acid, triethanolamine, ethanolamine, etc. The dispersant can improve the agglomeration and sedimentation of conductive powder and glass powder, and improve the dispersion uniformity of conductive powder and glass powder in organic carrier.

[0072] In some embodiments, the thixotropic agent includes, but is not limited to, hydrogenated castor oil, fumed silica, organobentonite, polyamide wax, ethyl cellulose, etc. The thixotropic agent can adjust the viscosity and thixotropy of the conductive paste and improve the storage and settling stability of the conductive paste.

[0073] In some embodiments, sintering aids include, but are not limited to, molybdenum oxide, tungsten oxide, zinc oxide, bismuth oxide, etc. These sintering aids can reduce the sintering temperature of the conductive paste and decrease the interfacial contact resistance.

[0074] In some embodiments, adhesion promoters include, but are not limited to, silane coupling agents, titanate coupling agents, and nano-silica. These adhesion promoters can enhance the interfacial bonding between the electrode and the semiconductor substrate.

[0075] In some embodiments, the antioxidant includes, but is not limited to, at least one of hydroquinone, propyl gallate, and sodium borohydride. The aforementioned adhesion promoters can enhance the antioxidant properties of the conductive paste.

[0076] In some embodiments, stabilizers include, but are not limited to, benzotriazole, lecithin, organophosphorus compounds, etc. These stabilizers can prevent the oxidation of conductive powder, inhibit the performance degradation of conductive slurry, and improve storage and damp heat aging stability.

[0077] S22, the premixed material is rolled to obtain the precursor.

[0078] The rolling process specifically includes: transferring the premixed material to a three-roll mill for grinding. The gaps between the rollers are set sequentially to 50μm, 25μm, and 15μm, and each is repeatedly ground 5 times until the fineness is less than 10μm when checked with a fineness plate.

[0079] S23. The precursor is subjected to vacuum degassing treatment to obtain conductive slurry.

[0080] The vacuum degassing process specifically includes: 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 then allowing it to stand and mature at 10°C to 40°C for 12 to 36 hours to obtain the conductive slurry.

[0081] S24. A conductive paste is applied to the first and / or second surfaces of a semiconductor substrate and sintered to form an electrode.

[0082] In some embodiments, 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.

[0083] 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.

[0084] In some embodiments, coating includes, but is not limited to, at least one of screen printing, plate printing, inkjet printing, and blade coating.

[0085] In some embodiments, the drying and sintering steps are both carried out in a tunnel furnace, the temperature of which is distributed in a gradient, and the time spent in the tunnel furnace is 1 min to 3 min.

[0086] The sintering of this application is carried out in an air atmosphere, which eliminates the need for an inert gas atmosphere and can suppress the oxidation of the conductive paste.

[0087] In some embodiments, the sintering process includes: heating from room temperature to 600°C to 800°C at a heating rate of 100°C / s to 300°C / s, holding at that temperature for 5s to 10s, and then cooling back to room temperature at a cooling rate of 50°C / s to 150°C / s.

[0088] It should be noted that room temperature refers to 23±2℃.

[0089] In some embodiments, the peak sintering temperature is 600℃~800℃, specifically 600℃, 630℃, 650℃, 680℃, 700℃, 720℃, 750℃, 780℃, 800℃, or any value within the range of any two of the above values. Controlling the peak sintering temperature and holding time within the above range ensures that the glass powder can fully melt, which is beneficial for the bonding of the conductive powder and the semiconductor substrate to form a dense structure, while also ensuring the conductivity of the sintered electrode.

[0090] In some embodiments, the holding time is 5s to 10s, specifically 5s, 6s, 7s, 8s, 9s, 10s, or any value within the range of any two of the above values. Controlling the holding time within the above range improves the densification of the conductive slurry while reducing the oxidation of the conductive powder.

[0091] In some embodiments, the heating rate from room temperature to 600°C to 800°C is 3°C / min to 10°C / min, specifically 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any value within the range of any two of the above values. Controlling the heating rate from room temperature to 600°C to 800°C within the above range is beneficial for improving the densification of the conductive paste during sintering into electrodes, while reducing abnormal grain growth and the generation of microcracks.

[0092] This application embodiment also provides a solar cell, the solar cell comprising: Semiconductor substrate, the semiconductor substrate includes a first surface and a second surface disposed opposite to each other; The first electrode forms an ohmic contact with the first surface of the semiconductor substrate; and / or A second electrode that forms an ohmic contact with the second surface of a semiconductor substrate; At least one of the first electrode and the second electrode is formed using the aforementioned conductive paste.

[0093] The conductive paste of this application can improve the antioxidant properties and printing quality of the conductive paste. The first electrode and / or the second electrode formed by the conductive paste of this application can maintain high stability and improve the interface stability of the first electrode and / or the second electrode, which is beneficial to improving the photoelectric conversion efficiency of the solar cell.

[0094] The solar cell of this application can be one or any combination of PERC (Passivated Emitter Rear Ce1l), IBC (Interdigitated Back Contact), TOPCon (Tunnel Oxide Passivated Contact), and HIT / HTT (Heterojunction Technology) cells. It is understood that all of the above-mentioned solar cells can be fabricated using the methods described in this application.

[0095] It should be noted that, based on the above-mentioned different types of solar 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.

[0096] Specifically, Figure 2 A schematic diagram of a solar cell structure is shown, such as... Figure 2As shown, the solar 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.

[0097] It should be noted that in some embodiments, the solar cell 100 contains only the second electrode 50.

[0098] Based on the same inventive concept, this application also provides a stacked battery. Figure 3 This is a schematic diagram of the structure of a stacked battery, as shown below. Figure 3 As shown, the stacked cell 2000 includes a perovskite top cell 2001 and a crystalline silicon bottom cell 2002 stacked sequentially along a preset direction; wherein, the crystalline silicon bottom cell 2002 includes the solar cell 100 provided in the above embodiments of the present invention. It should be noted that the stacked cell 2000 provided by the present invention has the technical effects of the solar cell 100 in the present invention, and the repeated parts will not be described again.

[0099] Based on the same inventive concept, this application also provides a photovoltaic module, which includes: A battery string, which is composed of multiple solar cells connected together as described above; Encapsulation layer, which covers the surface of the battery string; Cover plate, used to cover the surface of the encapsulation layer away from the battery string.

[0100] Specifically, Figure 4 A schematic diagram of a photovoltaic module is shown below. Please refer to [link / reference]. Figure 4 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.

[0101] In some embodiments, the solar cell string includes a plurality of solar cells 100 as described above connected by conductive strips. The connection between the solar cells 100 can be partially stacked or spliced.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] Example 1 (1) An organic carrier is prepared by mixing 85% terpineol, 10% ethyl cellulose, 3% hydrogenated castor oil and 2% polyvinylpyrrolidone by mass percentage.

[0108] (2) Take 70 parts by weight of spherical copper powder (D 50 =1.5μm), 2.1 parts by weight of silver-coated copper powder (silver coating thickness is 30nm, silver coating content in silver-coated copper powder is 10% by weight, silver melting point is 961.8℃), and 5 parts by weight of glass powder (by mass percentage, Bi2O3: 60%, B2O3: 20%, ZnO: 15%, MoO3: 3%, P2O3: 1.5μm), Bi2O3: 60%, B2O3: 20%, ZnO: 15%, MoO3: 3%, P2O3: 1.5μm), Bi2O3: 1.5μm), B2O3: 2.1 parts by weight of copper-coated silver powder (silver coating thickness is 30nm, silver coating content in copper-coated silver powder is 10% by mass, silver melting point is 961.8℃), Bi2O3: 1.5μm), B2O3: 2.1 parts by weight of copper-coated silver powder (silver coating thickness is 30nm, silver coating content in copper-coated silver powder is 10% by mass, silver melting point is 961.8℃), Bi2O3: 1.5μm), B2O3: 2.1 parts by weight of copper-coated silver powder (silver coating thickness is 30nm, silver coating content in copper-coated silver powder is 10% by mass, silver melting point is 961.8℃), Bi2O3: 1.5μm), B2O3: 2.1 parts by mass of copper-coated silver powder (silver coating thickness is 1 ... 5: 2% (softening point 520℃), 0.5 parts by weight of γ-aminopropyltriethoxysilane and 0.5 parts by weight of bismuth nitrate were mixed in a V-type mixer for 30 min.

[0109] (3) Pour the material obtained in step (2) and 21.9 parts by weight of the organic carrier described in step (1) into a planetary mixer, stir at 500 r / min for 15 min, and then stir at 1500 r / min for 45 min to obtain a premix.

[0110] (4) Transfer the premixed material to a three-roll mill for grinding. The gap between the rollers is set to 50μm, 25μm and 15μm respectively. Grind each roller repeatedly for 5 times until the fineness is less than 8μm when checked by scraping with a fineness plate. Place the ground material in a vacuum degassing machine at a vacuum degree of -0.095MPa for 20 minutes, then restore normal pressure, and then let the slurry stand at 30℃ for 24 hours to obtain conductive slurry.

[0111] (5) The conductive paste is screen-printed onto the upper surface of the silicon wafer, which is then placed in a tunnel furnace. In an air atmosphere, the temperature is first increased from room temperature to 650°C at a heating rate of 8°C / min, held for 5s, and then cooled to room temperature at a cooling rate of 5°C / min 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. In an air atmosphere, the temperature is first increased from room temperature to 650°C at a heating rate of 8°C / min, held for 5s, and then cooled to room temperature at a cooling rate of 5°C / min to obtain the second electrode, thus obtaining the solar cell.

[0112] Example 2 Unlike Example 1, the conductive paste, by mass percentage, comprises: 75 parts by mass of spherical copper powder, 1.5 parts by mass of silver-coated copper powder, 4 parts by mass of glass powder, 18.5 parts by mass of organic carrier, 0.5 parts by mass of γ-aminopropyltriethoxysilane, and 0.5 parts by mass of bismuth nitrate.

[0113] Example 3 Unlike Example 1, the conductive paste, by mass percentage, comprises: 65 parts by mass of spherical copper powder, 3 parts by mass of silver-coated copper powder, 6 parts by mass of glass powder, 24 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane, and 1 part by mass of bismuth nitrate.

[0114] Example 4 Unlike Example 1, the conductive paste, by mass percentage, comprises: 50 parts by mass of spherical copper powder, 5 parts by mass of silver-coated copper powder, 8 parts by mass of glass powder, 35 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane, and 1 part by mass of bismuth nitrate.

[0115] Example 5 Unlike Example 1, the conductive paste, by mass percentage, comprises: 80 parts by mass of spherical copper powder, 8 parts by mass of silver-coated copper powder, 5 parts by mass of glass powder, 5 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane, and 1 part by mass of bismuth nitrate.

[0116] Example 6 Unlike Example 1, (2) uses silver-coated copper powder (the thickness of the silver coating layer is 10 nm, and the mass percentage of the silver coating layer in the silver-coated copper powder is 3%).

[0117] Example 7 Unlike Example 1, (2) uses silver-coated copper powder (the thickness of the silver coating layer is 100 nm, and the mass percentage of the silver coating layer in the silver-coated copper powder is 29%).

[0118] Example 8 Unlike Example 1, in (2), the silver-coated copper powder is replaced with silicon dioxide-coated copper powder (the thickness of the silicon dioxide coating layer is 50 nm, the mass percentage of the silicon dioxide coating layer in the silicon dioxide-coated copper powder is 18%, and the melting point of silicon dioxide is 1713 °C).

[0119] Example 9 Unlike Example 1, in (2), the silver-coated copper powder is replaced with tin-coated copper powder (the thickness of the tin coating is 30 nm, the mass percentage of the tin coating in the tin-coated copper powder is 9.5%, and the melting point of tin is 231.9 °C).

[0120] Example 10 Unlike Example 1, in (2) the glass powder, by mass percentage, is Bi2O3: 62%, B2O3: 21%, ZnO: 16.4%, MoO3: 0.5%, and P2O3: 0.5%. 5: 0.1%, softening point 400℃.

[0121] Example 11 Unlike Example 1, in (2) the glass powder, by mass percentage, is Bi2O3: 42%, B2O3: 30%, ZnO: 20%, MoO3: 5%, and P2O3: 5%. 5: 3%, softening point 600℃.

[0122] Comparative Example 1 Unlike Example 1, the conductive paste, by weight percentage, comprises: 80 parts by weight of spherical silver powder, 3 parts by weight of glass powder (by weight percentage: Bi₂O₃: 60%, B₂O₃: 20%, ZnO: 15%, MoO₃: 3%, P₂O₃: 3%), and 10 parts by weight of glass powder. 5: 2% (softening point 520℃), 15 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane and 1 part by mass of bismuth nitrate.

[0123] Comparative Example 2 Unlike Example 1, the conductive paste, by weight percentage, comprises: 80 parts by weight of spherical copper powder, 3 parts by weight of glass powder (by weight percentage: Bi₂O₃: 60%, B₂O₃: 20%, ZnO: 15%, MoO₃: 3%, P₂O₃: 3%), and Bi₂O₃: 60%, B₂O₃: 20%, ZnO: 15%, MoO₃: 3%, P₂O₃: 3%). 5: 2% (softening point 520℃), 15 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane and 1 part by mass of bismuth nitrate.

[0124] Comparative Example 3 Unlike Example 1, the conductive paste, by weight percentage, comprises: 80 parts by weight of spherical silver-coated copper powder (silver coating thickness of 30 nm, silver coating content in the silver-coated copper powder is 10%), and 3 parts by weight of glass powder (by weight percentage, Bi2O3: 60%, B2O3: 20%, ZnO: 15%, MoO3: 3%, P2O3: 3%). 5: 2% (softening point 520℃), 15 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane and 1 part by mass of bismuth nitrate.

[0125] Comparative Example 4 Unlike Example 1, the conductive paste, by mass percentage, comprises: 80 parts by mass of spherical copper powder, 3 parts by mass of glass powder (by mass percentage, Bi2O3: 65%, B2O3: 20%, ZnO: 15%, softening point 620°C), 15 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane, and 1 part by mass of bismuth nitrate.

[0126] Comparative Example 5 Unlike Example 1, silver-coated copper powder was replaced with magnesium-coated copper powder (magnesium coating thickness was 30 nm, magnesium coating content in the magnesium-coated copper powder was 2.5% by mass, and magnesium melting point was 648.8°C). The conductive paste, by mass percentage, comprised: 70 parts by mass of spherical copper powder (D... 50 =1.5μm), 2.1 parts by mass of magnesium-coated copper powder, 3 parts by mass of glass powder (by mass percentage, Bi2O3: 65%, B2O3: 20%, ZnO: 15%, softening point 620℃), 15 parts by mass of organic carrier, 1 part by mass of γ-aminopropyltriethoxysilane and 1 part by mass of bismuth nitrate.

[0127] Performance testing: The solar cells prepared in each embodiment and comparative example were tested for electrical performance parameters and adhesion. The test results are shown in Table 1.

[0128] Adhesion testing was conducted according to ASTM D903-20 "Test Standard for Peel Strength of Adhesive Tapes" and IEC 61215-2:2021 "Design Qualification and Type Approval of Ground-Mounted Photovoltaic Modules". Specifically, a 156 mm diameter sample was taken. A 156mm polycrystalline silicon solar cell was used. Electrode paste for testing was printed using screen printing (1.5mm line width, 15±2μm thickness). Sintering was performed according to the process conditions described in Example 1. After cooling to room temperature, conductive silver paste (0.1mm thickness) was uniformly coated onto the electrode surface. A 10mm wide copper foil was then attached as a tensile test lead, and the mixture was cured for 12 hours (25℃ / 50% RH). A tensile testing machine was used to perform a 90° peel at a speed of 50mm / min. The maximum peel force was recorded. The adhesion strength was calculated using the formula: maximum peel force (N) / electrode width (mm). The average value of at least three test points was taken. The testing environment was 25℃ / 50% RH, and the electrode width was measured using an optical microscope.

[0129] Table 1. Test results of solar cells prepared in each embodiment and comparative example

[0130] The solar cells prepared by the conductive paste provided by the present invention have a conversion efficiency very close to that of the silver paste of Comparative Example 1, and excellent adhesion, which fully meets the requirements of industrial applications. At the same time, the cost is significantly reduced.

[0131] In Examples 1 to 5, by adjusting the proportions of copper powder, silver-coated copper powder, and glass powder in the conductive paste, the electrical and interfacial properties of the conductive paste as an electrode can be adjusted, and all are within a relatively optimal range.

[0132] In Examples 1 and 6-7, by adjusting the thickness of the coating layer on the surface of the copper powder, the electrical and interfacial properties of the conductive paste prepared as an electrode can be adjusted, and all are within a relatively optimal range.

[0133] In Examples 1, 8 and 9, different coated metal powders were selected. The difference between the softening point of the coating material on the surface of the metal powder and that of the glass powder was greater than 60°C. The conductive paste was prepared as an electrode with good electrical and interfacial properties.

[0134] In Comparative Example 2, only spherical copper powder was used as the conductive phase. The copper powder lacked antioxidant protection during the initial sintering stage, leading to a sharp increase in the contact resistance of the solar cell, reaching 5.3 mΩ·cm. 2 The fill factor decreased, and the conversion efficiency was significantly lower than that of the solar cell prepared in Example 1 of this application.

[0135] In Comparative Example 3, only silver-coated copper powder was used as the conductive phase. This single conductive phase resulted in low packing density of the conductive powder, a sparse conductive network formed by the conductive paste, and a high sheet resistance. Consequently, the contact resistance of the solar cell increased to 3.5 mΩ·cm. 2 Furthermore, the high silver content in the conductive paste increases costs.

[0136] In Comparative Example 4, only copper powder was used as the conductive phase, and the softening point of the glass powder was too high. During the sintering process, when the temperature reached approximately 300℃, the copper powder had already begun to oxidize, while the glass powder had not yet melted. Therefore, a protective layer could not be formed before the critical temperature for copper oxidation, and the adhesion of the electrodes decreased significantly. Consequently, the contact resistance of the solar cell increased, reaching 3.1 mΩ·cm. 2 The fill factor decreased, and the conversion efficiency was significantly lower than that of the solar cell prepared in Example 1 of this application.

[0137] In Comparative Example 5, when magnesium-coated copper powder was added to the conductive phase, it was severely oxidized above 300°C during the sintering heating stage, forming a porous MgO layer that could not protect the internal copper powder. Moreover, the melting point of magnesium and the softening point of glass powder are both less than 60°C. The reaction between magnesium and glass powder caused the slurry to lose control of its fluidity, resulting in a linewidth deformation rate of more than 30% for the screen-printed electrodes.

[0138] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for preparing a solar cell, characterized in that, Includes the following steps: A semiconductor substrate is obtained, the semiconductor substrate having opposing first and second surfaces; A conductive paste is obtained, 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: 50% to 85% conductive powder, 1% to 8% glass powder, and the remainder being an organic carrier. The conductive powder includes a first conductive powder and a second conductive powder. The first conductive powder includes copper powder, and the second conductive powder includes copper powder and a coating layer covering the surface of the copper powder. The softening point of the glass powder is S1, the melting point of the coating layer is S2, and the difference between S1 and S2 is greater than or equal to 60°C.

2. The method for preparing a solar cell according to claim 1, characterized in that, S1 is 400℃~600℃.

3. The method for preparing a solar cell according to claim 1 or 2, characterized in that, The glass powder comprises, by mass percentage, 40% to 70% Bi₂O₃, 10% to 30% B₂O₃, 5% to 20% ZnO, 0.5% to 5% MoO₃, and 0.1% to 3% P₂O₅.

4. The method for preparing a solar cell according to claim 1, characterized in that, 200℃≤S2≤250℃, or 900℃≤S2≤2100℃.

5. The method for preparing a solar cell according to claim 1 or 4, characterized in that, The coating material includes at least one of silver, tin, aluminum oxide, and silicon dioxide.

6. The method for preparing a solar cell according to claim 1, characterized in that, The thickness of the coating layer is 10nm~100nm.

7. The method for preparing a solar cell according to claim 1, characterized in that, The coating layer has a mass percentage content of 3% to 30% in the second conductive powder.

8. The method for preparing a solar cell according to claim 1, characterized in that, The second conductive powder has a mass percentage content of 1% to 10% in the conductive powder.

9. The method for preparing a solar cell according to claim 1, characterized in that, The copper powder includes at least one of spherical powder, near-spherical powder, and flake powder; The median particle size D of the copper powder 50 The range is 0.5μm to 5μm.

10. The method for preparing a solar cell according to claim 1 or 2, characterized in that, The median particle size D of the glass powder 50 The range is 0.5μm to 3μm.

11. The method for preparing a solar cell according to claim 1, characterized in that, The sintering is carried out in an air atmosphere, the peak temperature of the sintering is 600℃~800℃, and the holding time of the sintering is 5s~10s.

12. The method for preparing a solar cell according to claim 11, characterized in that, The sintering heating rate is 3℃ / min to 10℃ / min.

13. A solar cell, characterized in that, The solar cell is formed using the method for preparing a solar cell according to any one of claims 1 to 12, and the solar cell comprises: A semiconductor substrate, the semiconductor substrate including a first surface and a second surface disposed opposite to each other; The first electrode electrically connected to the first surface of the semiconductor substrate; and / or A second electrode electrically connected to the second surface of the semiconductor substrate.

14. A stacked battery, characterized in that, The tandem solar cell includes a perovskite top cell and a crystalline silicon bottom cell stacked sequentially, wherein the crystalline silicon bottom cell is a solar cell formed by the method of preparing a solar cell according to any one of claims 1 to 12 or a solar cell according to claim 13.

15. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string, wherein the battery string is formed by connecting multiple solar cells formed by the method of preparing solar cells according to any one of claims 1 to 12, or the solar cells according to claim 13, or the stacked cells according to claim 14; 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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