Battery sheet and preparation method thereof, laminated battery and photovoltaic module

Abstract

This application provides a solar cell and its fabrication method, a tandem solar cell, and a photovoltaic module. The fabrication method of the solar cell includes the following steps: providing a semiconductor substrate having opposing first and second surfaces; preparing a conductive paste; coating the conductive paste onto the first and / or second surfaces of the semiconductor substrate; and sintering to form electrodes. The conductive paste, by mass percentage, comprises: 60%–77% conductive powder, 1%–15% glass powder, 5%–15% organic carrier, and the balance being additives. The additives include molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds, wherein the particle size of the molybdenum-containing compounds is nanometer-scale. This application can effectively improve the electrode pull strength of the solar cell, increase the photoelectric conversion efficiency of the solar cell, and reduce the proportion of poor soldering when assembling the solar cell into a photovoltaic module.

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 solar cell and a photovoltaic module. Background Technology

[0002] Photovoltaic cells are a type of clean power generation system that uses sunlight to generate electricity. Photovoltaic power generation systems are expected to meet future electricity needs without harming the environment, and therefore public attention has been focused on photovoltaic power generation systems. The core component of a photovoltaic power generation system is the solar cell (also known as a 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 tensile strength of solar cells produced by current fabrication processes cannot meet the requirements. Summary of the Invention

[0004] This application provides a solar cell and its preparation method, a tandem solar cell and a photovoltaic module, which can effectively improve the electrode pull of the solar cell, improve the photoelectric conversion efficiency of the solar cell, and reduce the proportion of poor soldering when assembling solar cells into photovoltaic modules.

[0005] In a first aspect, this application provides a method for preparing a battery cell, comprising 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: 60% to 77% conductive powder, 1% to 15% glass powder, 5% to 15% organic carrier, and the balance being additives. The additives include molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds, wherein the particle size of the molybdenum-containing compounds is in the nanometer range.

[0006] Secondly, embodiments of this application provide a battery cell, which is formed using the battery cell manufacturing method described in the first aspect, and the battery 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 stacked battery, the stacked battery comprising: a perovskite top battery and a crystalline silicon bottom battery stacked sequentially, wherein the crystalline silicon bottom battery is a battery cell formed by the battery cell preparation method described in the first aspect or a battery 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 battery cells formed by the method of preparing battery cells described in the first aspect, or battery cells described in the second aspect, or stacked batteries 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: By adding additives including molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds to the conductive paste, the molybdenum-containing compounds with nano-sized particles can form an interfacial bond with the conductive powder, improving the cohesion and density of the conductive paste. The molybdenum-containing compounds can also bond tightly with the semiconductor substrate, enhancing the interfacial bonding between the conductive paste and the semiconductor substrate. Furthermore, the molybdenum-containing compounds can adjust the coefficient of thermal expansion of the conductive paste used to prepare the electrode by sintering, reducing the difference in coefficients of thermal expansion between the electrode and the semiconductor substrate, thus reducing thermal stress cracks during the cooling process of the conductive paste to form the electrode. This makes the electrode less prone to cracking and crack propagation, improving the tensile stability of the electrode. The iridium-containing compounds form a conductive mechanical pinning bond with the conductive powder, enhancing the cohesion of the conductive paste. Moreover, the iridium-containing compounds undergo metallurgical bonding with the semiconductor substrate during the sintering process of the conductive paste, improving the interfacial wetting ability between the conductive paste and the semiconductor substrate, achieving interatomic bonding between the conductive paste and the semiconductor substrate, thereby enhancing the interfacial bonding between the conductive paste and the semiconductor substrate. Titanium-containing compounds exhibit good stability, high hardness, and excellent conductivity, which can improve the dispersion stability, corrosion resistance, and conductivity of conductive pastes. Furthermore, this application incorporates molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds as additives into the conductive paste. The synergistic effect of these three compounds ensures stable distribution of the additives within the conductive paste, enhancing its anchoring effect. This, in turn, increases the tensile strength of the solar cells while maintaining their electrical performance, thereby improving the long-term reliability of the solar cells and the lifespan of the module. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a battery cell manufacturing process provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a battery cell provided in an embodiment of this application; Figure 3This is a schematic diagram of a stacked battery provided in an embodiment of this application; Figure 4 This is a schematic diagram 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, lead-containing substances, such as lead-containing glass powder, are added to the conductive paste to improve the adhesion between the cell electrodes and the silicon substrate. Lead is a toxic and hazardous substance, and its production and recycling processes can easily cause heavy metal pollution, failing to meet green and environmentally friendly production requirements and posing significant safety and environmental compliance risks. Furthermore, the use of lead can easily cause excessive corrosion of the battery PN junction, increasing contact resistance, intensifying carrier recombination, and severely reducing battery conversion efficiency. In addition, lead-containing conductive pastes result in poor electrode solderability, a high proportion of poor solder joints in cell string bonding, and low mass production yield, leading to easy heat generation and degradation of photovoltaic modules in later stages.

[0018] Therefore, existing lead-containing pastes cannot simultaneously meet the requirements of environmental protection, high conversion efficiency, and low solder joint failure, and there is an urgent need to optimize and develop lead-free high-performance conductive pastes.

[0019] Therefore, embodiments of this application provide a method for preparing a battery cell. Figure 1 A schematic diagram of a battery cell fabrication process is shown, such as... Figure 1 As shown, the method for preparing solar cells includes the following steps: A semiconductor substrate is provided, the semiconductor substrate having opposing first and second surfaces; 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; The composition, by mass percentage, consists of 60%–77% conductive powder, 1%–15% glass powder, 5%–15% organic carrier, and the remainder being additives. The additives include molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds, with the molybdenum-containing compounds having a particle size in the nanometer range.

[0020] In the above-described scheme, this application adds additives including molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds to the conductive paste. The molybdenum-containing compounds, with particle sizes in the nanometer range, can form an interfacial bond with the conductive powder, enhancing the cohesion and density of the conductive paste. The molybdenum-containing compounds can also bond tightly with the semiconductor substrate, improving the interfacial bonding between the conductive paste and the semiconductor substrate. Furthermore, the molybdenum-containing compounds can adjust the coefficient of thermal expansion of the conductive paste used to prepare the electrode by sintering, reducing the difference in the coefficient of thermal expansion between the electrode and the semiconductor substrate. This reduces thermal stress cracking during the cooling process of the conductive paste to prepare the electrode, making it less prone to cracking and crack propagation, thus improving the tensile stability of the electrode. The iridium-containing compounds form a conductive mechanical pinning bond with the conductive powder, enhancing the cohesion of the conductive paste. Moreover, the iridium-containing compounds undergo metallurgical bonding with the semiconductor substrate during the sintering process of the conductive paste, improving the interfacial wetting ability between the conductive paste and the semiconductor substrate, achieving interatomic bonding between the conductive paste and the semiconductor substrate, thereby enhancing the interfacial bonding between the conductive paste and the semiconductor substrate. Titanium-containing compounds exhibit good stability, high hardness, and excellent conductivity, which can improve the dispersion stability, corrosion resistance, and conductivity of conductive pastes. Furthermore, this application incorporates molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds as additives into the conductive paste. The synergistic effect of these three compounds ensures stable distribution of the additives within the conductive paste, enhancing its anchoring effect. This, in turn, increases the tensile strength of the solar cells while maintaining their electrical performance, thereby improving the long-term reliability of the solar cells and the lifespan of the module.

[0021] It should be noted that the tensile strength of the solar cell mainly refers to the force required to peel off the solder strips welded to the main busbar of the solar cell.

[0022] The preparation method of the battery cell of the present invention will be described in detail below.

[0023] S1 provides a semiconductor substrate having opposing first and second surfaces.

[0024] 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 (N), phosphorus (P), arsenic (As), antimony (Sb), or bismuth (Bi).

[0025] 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.

[0026] It should be noted that the "~" between two values ​​in this application represents the endpoint value including both values.

[0027] 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.

[0028] 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.

[0029] 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 surface of the semiconductor substrate by utilizing 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.

[0030] 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.

[0031] 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 semiconductor substrate surface using 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.

[0032] 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.

[0033] S2, Prepare conductive paste, apply conductive paste to the first and / or second surfaces of a semiconductor substrate, sinter to form an electrode.

[0034] S21, by mass percentage, 60%~77% conductive powder, 1%~15% glass powder, 5%~15% organic carrier, and the balance additives, including molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds, with the molybdenum-containing compounds having a particle size of nanometers, to obtain a premix.

[0035] In some embodiments, S21 may specifically be: adding 5% to 15% organic carrier and 1% to 15% glass powder to a planetary mixer for a first stirring process to fully disperse and uniformly obtain a mixed carrier; adding 60% to 77% conductive powder and the remainder of additives to the planetary mixer for a second stirring process to obtain a premix.

[0036] In some embodiments, the stirring speed for one stirring process is 300 rpm to 800 rpm, and the stirring time for one stirring process is 10 min to 30 min.

[0037] In some embodiments, the secondary stirring speed is 700 rpm to 1300 rpm, and the secondary stirring time is 10 min to 30 min.

[0038] 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.

[0039] In some embodiments, the mass percentage of the additive in the conductive paste is 0.4% to 0.8%, specifically 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, etc., and is not limited thereto. Controlling the mass percentage of the additive in the conductive paste within the above range can effectively improve the tensile strength of the solar cell without impairing the electrical and mechanical properties of the conductive paste.

[0040] It should be noted that this application includes additives containing molybdenum compounds, iridium compounds, and titanium compounds being added directly to the conductive paste, rather than to the glass powder.

[0041] In some embodiments, the mass percentage of molybdenum-containing compounds in the conductive paste is denoted as M1, and the sum of the mass percentages of iridium-containing compounds and titanium-containing compounds in the conductive paste is denoted as M2, where 3 ≤ 8 and M1 / M2 ≤ 8. Specifically, M1 / M2 can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 8, etc., and is not limited here. Controlling M1 / M2 within the above range can effectively improve the tensile strength of the solar cells while ensuring their electrical performance and reducing the proportion of poor soldering in photovoltaic modules.

[0042] In some embodiments, the molybdenum-containing compound includes molybdenum trioxide (MoO). Molybdenum trioxide has a surface rich in oxygen vacancies and hydroxyl groups, which can form Si-O-Mo bonds with silicon-based semiconductor substrates, significantly improving the interfacial adhesion between the conductive paste and the semiconductor substrate. Molybdenum trioxide can also combine with conductive powders in the conductive paste to form metal-oxygen bonds (Ag-O, Al-O, etc.), enhancing the adhesion of Molybdenum trioxide in the conductive paste and improving the cohesiveness of the conductive paste. Furthermore, after the conductive paste is prepared into solar cells, during the assembly of the solar cells into photovoltaic modules, the Molybdenum trioxide contained in the electrodes can also combine with the solder to form metal-oxygen bonds (Cu-O, Sn-O, and Pb-O, etc.), significantly enhancing the adhesion between the electrodes and the solder, thereby significantly improving the tensile strength of the solar cells.

[0043] In some embodiments, the particle size of molybdenum trioxide is 30nm~300nm, specifically 30nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm, 300nm, etc., and is not limited thereto. By controlling the particle size of molybdenum trioxide within the above range, molybdenum trioxide possesses high specific surface area and high activity, and good dispersibility. When added to conductive slurry, it can uniformly adhere to the surface of conductive powder. During sintering, the surface of molybdenum trioxide is more easily spread and forms a film at moderate temperatures, thereby significantly improving tensile strength through the pinning effect. Optionally, the particle size of molybdenum trioxide is 50nm~200nm, and more preferably 80nm~150nm.

[0044] In some embodiments, molybdenum trioxide is at least one of nanorods, nanosheets, and nanoribbons. The molybdenum trioxide with these morphologies has a high specific surface area, providing more physical contact sites and thus significantly improving tensile strength. Specifically, molybdenum trioxide nanorods, nanosheets, and nanoribbons can form a layered structure during sintering. When the conductive paste is prepared as an electrode, slippage easily occurs between the layers of the aforementioned layered structure when the solar cell is bent or stretched, releasing residual stress and absorbing the bending or stretching effects on the solar cell, effectively preventing the propagation of cracks originating from the semiconductor substrate or electrode.

[0045] It should be noted that the particle size of molybdenum trioxide nanorods refers to the length of the nanorods, the particle size of molybdenum trioxide nanosheets refers to the lateral width of the nanosheets, and the particle size of molybdenum trioxide nanoribbons refers to the width of the nanoribbons.

[0046] It should be noted that this application does not apply to granular (spherical or near-spherical) molybdenum trioxide, which is prone to forming isolated agglomerated particles during high-temperature sintering. This agglomerates cannot effectively pin the grain boundaries of conductive powder to improve tensile strength. Furthermore, as an insulator, it will severely block the conductive path and become a stress concentration point, leading to a surge in resistivity and a decrease in adhesion.

[0047] In some embodiments, the mass percentage of molybdenum trioxide in the conductive slurry is 0.4% to 0.6%, specifically 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, etc., and is not limited thereto. Since molybdenum trioxide is non-conductive, controlling the mass percentage of molybdenum trioxide in the conductive slurry within the above range is beneficial for improving the tensile strength of the solar cell, while avoiding excessive molybdenum trioxide film covering the surface of the conductive powder, which would lead to a decrease in conductivity. This achieves a balance between the electrical performance and tensile strength of the solar cell.

[0048] In some embodiments, the iridium-containing compound includes iridium dioxide. On one hand, iridium dioxide is a metalloid; when added to the conductive paste, it can form a conductive mechanical pinning bond with the conductive powder, enhancing the cohesiveness of the conductive paste. When the solder ribbon is pulled up, the sintered electrode, due to its high strength, is less prone to cohesive failure, thereby increasing the tensile strength of the solar cell. On the other hand, iridium dioxide is stable and can prevent over-burning of the conductive powder during sintering. It also maintains the small particle size of the conductive powder through grain boundary pinning, improving the strength of the electrode sintered from the conductive paste and preventing crack propagation. Furthermore, as an active element, iridium dioxide can form IrSi, IrSi2, and other substances with the silicon semiconductor substrate during the sintering process of the conductive paste, promoting metallurgical bonding and further enhancing the adhesion between the electrode and the semiconductor substrate. Moreover, this metallurgical bonding improves corrosion resistance and reduces corrosion of the solar cell.

[0049] In some embodiments, the mass percentage of iridium dioxide in the conductive paste is 0.04% to 0.06%, specifically 0.04%, 0.45%, 0.05%, 0.055%, 0.06%, etc., and is not limited thereto. Controlling the mass percentage of iridium dioxide in the conductive paste within the above range is beneficial for improving the tensile strength of the solar cell, while avoiding the decrease in electrode conductivity caused by excessive iridium dioxide.

[0050] In some embodiments, the titanium-containing compound includes titanium nitride. Titanium nitride has good stability and high hardness. During the high-temperature sintering of conductive paste to form electrodes, titanium nitride can effectively prevent the slippage and growth of conductive powder at high temperatures, refine grains, and improve the cohesion of the conductive paste. Moreover, titanium nitride has metal-like high conductivity, which can effectively compensate for the decrease in conductivity caused by the addition of molybdenum trioxide.

[0051] In some embodiments, the additive may also include at least one of dispersants, thixotropic agents, sintering aids, adhesion promoters, and stabilizers to improve the performance of the conductive paste.

[0052] 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.

[0053] 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 slurry and improve the storage and settling stability of the conductive slurry.

[0054] 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.

[0055] 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.

[0056] 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 degradation of slurry performance, and improve storage and damp heat aging stability.

[0057] In some embodiments, the mass percentage of conductive powder in the conductive slurry is 60% to 77%, specifically 60%, 63%, 65%, 68%, 70%, 73%, 75%, 77%, or any value within the range of any two of the above values.

[0058] In some embodiments, the conductive powder includes at least one of silver powder, copper powder, gold powder, nickel powder, and aluminum powder.

[0059] In some embodiments, the conductive powder includes at least one of spherical powder and flake powder.

[0060] In some embodiments, the mass percentage of glass powder in the conductive paste is 1% to 15%, specifically 1%, 3%, 5%, 8%, 10%, 12%, 15%, or any value within the range of any two of the above values.

[0061] In some embodiments, the glass powder includes at least one of the Bi2O3-B2O3-ZnO system and the Bi2O3-ZnO-P2O5 system. The glass powder of this application does not contain lead, ensuring green and environmentally friendly production requirements while also guaranteeing the battery conversion efficiency of the solar cells.

[0062] In some embodiments, the organic carrier accounts for 5% to 15% of the mass percentage in the conductive paste, specifically 5%, 8%, 10%, 12%, 13%, 14%, 15%, 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 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 two of the above values.

[0069] S22, the premixed material is rolled to obtain the precursor.

[0070] Specifically, this involves 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 ground repeatedly 5 times until the fineness is less than 10μm when checked with a fineness stencil.

[0071] S23. The precursor is subjected to vacuum degassing treatment to obtain conductive slurry.

[0072] 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.

[0073] S24. A conductive paste is applied to the first and / or second surfaces of a semiconductor substrate and sintered to form an electrode.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] In some embodiments, coating includes, but is not limited to, at least one of screen printing, plate printing, inkjet printing, and blade coating.

[0078] In some embodiments, the sintering step after printing the conductive paste is carried out in a tunnel furnace with a gradient temperature distribution and a time of 1 min to 3 min in the tunnel furnace.

[0079] The sintering in this application is carried out in an oxygen-containing atmosphere, which may be, for example, an oxygen atmosphere, an air atmosphere, or a nitrogen-oxygen mixed gas atmosphere with controllable oxygen content, wherein the volume percentage of oxygen in the nitrogen-oxygen mixed gas atmosphere is greater than 50%. Sintering in an oxygen-containing atmosphere can suppress the volatilization of molybdenum-containing compounds.

[0080] In some embodiments, the sintering process includes: 1) Preheat the conductive paste by raising the temperature from room temperature to 200℃~300℃ and holding it for 5s~10s to dry it.

[0081] 2) Increase the temperature from 200℃~300℃ to 400℃~500℃, hold for 10s~30s, then increase the temperature to 650℃~750℃, hold for 10s~40s, and then decrease the temperature to room temperature.

[0082] It should be noted that room temperature refers to 23±2℃.

[0083] In some embodiments, a heat preservation step is set before the sintering temperature reaches the peak temperature, with the temperature being 400℃~500℃. Specifically, it can be 400℃, 420℃, 450℃, 480℃, 500℃, etc., and is not limited here. Controlling the temperature within the above range is beneficial for the full flow of molybdenum trioxide, uniformly coating the conductive powder, and at the same time, it allows the conductive powder to undergo preliminary solid-state diffusion, which is beneficial for improving the density of the conductive slurry prepared into an electrode.

[0084] In some embodiments, the peak sintering temperature is 650℃~750℃, specifically 650℃, 680℃, 700℃, 720℃, 750℃, etc., and is not limited thereto. Controlling the peak sintering temperature within the above range avoids excessively high temperatures that could cause molybdenum trioxide to vaporize and form pores, thus disrupting the continuity of the electrode.

[0085] This application embodiment also provides a battery cell, the battery 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.

[0086] The solar cell of this application has excellent tensile strength while ensuring the electrical performance of the solar cell, thereby improving the long-term reliability of the solar cell and the service life of the module.

[0087] The solar cells 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 prepared using the methods described in this application.

[0088] 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.

[0089] Specifically, Figure 2 A schematic diagram of a battery cell structure is shown, such as... Figure 2 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.

[0090] It should be noted that in some embodiments, the battery cell 100 only contains the second electrode 50.

[0091] 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 tandem battery, as shown below. Figure 3 As shown, the stacked solar cell 2000 includes a perovskite top solar cell 2001 and a crystalline silicon bottom solar cell 2002 stacked sequentially along a preset direction; wherein, the crystalline silicon bottom solar cell 2002 includes the solar cell 100 provided in the above embodiments of the present invention. It should be noted that the stacked solar 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.

[0092] Based on the same inventive concept, this application also provides a photovoltaic module, which includes: A battery string is composed of multiple of the aforementioned battery cells connected together. 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] Example 1 (1) In a planetary mixer, add 10 parts by mass of organic carrier (model OS-200), 15 parts by mass of Bi2O3-B2O3-ZnO system glass powder (model BYB0725), 2 parts by mass of hydrogenated castor oil and 2.4 parts by mass of stearic acid in sequence and stir for 20 minutes at a stirring speed of 500 rpm to fully disperse and obtain a mixed carrier.

[0101] (2) Place 70 parts by weight of spherical silver powder in an oven at 105℃ and dry for 2 hours to remove surface adsorbed moisture. Add 0.5 parts by weight of molybdenum trioxide (molybdenum trioxide nanorods with an average length of 150nm), 0.05 parts by weight of iridium dioxide and 0.05 parts by weight of titanium nitride to a planetary mixer and stir at a stirring speed of 1000rpm for 20 minutes to obtain a premix.

[0102] (3) Transfer the premixed material to a three-roll mill for grinding. The gap between the rollers is set to 50μm, 25μm and 15μm respectively, and each is ground repeatedly for 5 times until the fineness is less than 10μm 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 20min, then restore the pressure to normal, and then let the slurry stand at 30℃ for 24h to obtain conductive slurry.

[0103] (4) 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 10 seconds, then raised to 450°C for 20 seconds, and then raised to 700°C for 25 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 10 seconds, then raised to 450°C for 20 seconds, and then raised to 700°C for 25 seconds to obtain the second electrode, which is the solar cell.

[0104] Example 2 Unlike Example 1, the conductive paste, by mass percentage, comprises: 0.4 parts by mass of molybdenum trioxide, 0.04 parts by mass of iridium dioxide, 0.04 parts by mass of titanium nitride, 10 parts by mass of organic carrier, 15 parts by mass of high-lead glass powder, 2 parts by mass of hydrogenated castor oil, 2.52 parts by mass of stearic acid, and 70 parts by mass of spherical silver powder.

[0105] Example 3 Unlike Example 1, the conductive paste, by mass percentage, comprises: 0.6 parts by mass of molybdenum trioxide, 0.06 parts by mass of iridium dioxide, 0.06 parts by mass of titanium nitride, 10 parts by mass of organic carrier, 15 parts by mass of high-lead glass powder, 2 parts by mass of hydrogenated castor oil, 2.28 parts by mass of stearic acid, and 70 parts by mass of spherical silver powder.

[0106] Example 4 Unlike Example 1, the conductive paste, by mass percentage, comprises: 0.4 parts by mass of molybdenum trioxide, 0.065 parts by mass of iridium dioxide, 0.065 parts by mass of titanium nitride, 10 parts by mass of organic carrier, 15 parts by mass of high-lead glass powder, 2 parts by mass of hydrogenated castor oil, 2.47 parts by mass of stearic acid, and 70 parts by mass of spherical silver powder.

[0107] Example 5 Unlike Example 1, the conductive paste, by mass percentage, comprises: 0.6 parts by mass of molybdenum trioxide, 0.037 parts by mass of iridium dioxide, 0.038 parts by mass of titanium nitride, 10 parts by mass of organic carrier, 15 parts by mass of high-lead glass powder, 2 parts by mass of hydrogenated castor oil, 2.325 parts by mass of stearic acid, and 70 parts by mass of spherical silver powder.

[0108] Example 6 Unlike Example 1, the conductive paste, by mass percentage, comprises: 1 part by mass of molybdenum trioxide, 0.05 parts by mass of iridium dioxide, 0.05 parts by mass of titanium nitride, 10 parts by mass of organic carrier, 15 parts by mass of high-lead glass powder, 2 parts by mass of hydrogenated castor oil, 1.9 parts by mass of stearic acid, and 70 parts by mass of spherical silver powder.

[0109] Example 7 Unlike Example 1, the molybdenum trioxide is in particulate form with an average particle size of 1 μm.

[0110] Comparative Example 1 Unlike Example 1, molybdenum trioxide was not added.

[0111] Comparative Example 2 Unlike Example 1, iridium dioxide was not added.

[0112] Comparative Example 3 Unlike Example 1, titanium nitride was not added.

[0113] Tensile test: The solar cells prepared in each embodiment and comparative example were tested according to the T / CSTM 00461-2022 standard. The solder strip used was a fixed-specification tin-coated copper solder strip with a thickness of 0.22~0.28mm and a width of 1.0~1.4mm. It used an oxygen-free copper substrate with a lead-free tin-silver-copper alloy plating. The test environment was controlled at a temperature of 23±2℃ and a relative humidity of 45%~75%. An electronic tensile testing machine and a special fixture for solar cells were used to fix the solar cells with solder strips stably on the fixture, leaving a free end of not less than 30mm and clamping it in the tensile testing machine fixture. A 180° peeling method was used, and the tensile speed was set to 10mm / min. The strip was stretched at a uniform speed until it separated from the main grid of the solar cell or the strip broke. The maximum tensile force value at each test point was recorded, and the average value of the multi-point test was used as the basis for evaluating the tensile performance.

[0114] Cold solder joint ratio test: The solar cells prepared in each embodiment and comparative example were assembled into photovoltaic modules of the same specifications. The procedure was performed in accordance with T / CPIA0009-2019 "Method for Electroluminescence Imaging Test of Defects in Crystalline Silicon Photovoltaic Modules". Photovoltaic modules prepared by welding tin-coated copper solder strips of the same specifications as those described above were used as test samples. The modules were placed in an EL testing device in a dark room, a forward bias voltage was applied and the overall electroluminescence image of the module was acquired. The cold solder joints were determined based on the brightness of the connection position between the solder strip and the main grid of the solar cell in the image: obvious dark lines, broken lines or gray-scale abnormal areas in the corresponding area of ​​the main grid were identified as cold solder joints. The total number of all solder joints in the module and the number of cold solder joints were counted. The overall cold solder joint ratio of the module was calculated by dividing the number of cold solder joints by the total number of solder joints.

[0115] For the above tensile test and cold solder joint ratio test, 50 cells were tested for each example or comparative example, and the average value was calculated. The test results are shown in Table 1.

[0116] Table 1. Test results of the battery cells prepared in each embodiment and comparative example

[0117] As shown in Table 1, compared with Comparative Examples 1 to 3, Examples 1 to 7 of this application, by adding additives including molybdenum-containing compounds, iridium-containing compounds and titanium-containing compounds to the conductive paste, and with molybdenum trioxide having a particle size of nanometers, can effectively improve the tensile strength of the solar cells and reduce the proportion of poor soldering in photovoltaic modules.

[0118] According to the test data of Example 6, the amount of molybdenum trioxide added in Example 6 was excessive, and the amount of molybdenum trioxide, iridium dioxide and titanium nitride added did not meet the requirement that M1 / M2 is 3~8, which led to a significant reduction in the tensile strength of the prepared solar cell.

[0119] According to the test data of Example 7, the molybdenum trioxide added to the conductive paste is spherical and has a large particle size. The tensile strength of the prepared battery cell is significantly lower than that of Examples 1 to 5 of this application. The main reason is that molybdenum trioxide itself is a low conductivity semiconductor. The particulate form will hinder the formation of a continuous conductive network during the sintering process of the conductive paste, reduce the density and mechanical strength of the electrode body prepared by sintering, and cause the main grid tensile strength to be unable to increase or even decrease.

[0120] According to the test data of Comparative Example 1, the tensile strength of the prepared solar cell was significantly reduced to only 1.5N because no molybdenum trioxide was added to the conductive paste.

[0121] According to the test data of Comparative Example 2, the tensile strength of the prepared battery cell was significantly reduced to only 1.7N because iridium dioxide was not added to its conductive paste.

[0122] According to the test data of Comparative Example 3, the conductive paste without titanium nitride resulted in a higher tensile strength in the prepared solar cell compared to Comparative Examples 1 and 2, but still lower than that of Examples 1 to 5. Furthermore, the poor conductivity of the conductive paste without titanium nitride led to low electrode density, poor continuity of conductive powder particles, and high porosity in the sintered electrode. These defects cause the electrode to appear as dark areas / broken lines in EL imaging, and the interface between the solder ribbon and the main grid is difficult to distinguish in the image, directly resulting in an increased statistical value of the proportion of poorly soldered electrodes.

[0123] 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 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: 60% to 77% conductive powder, 1% to 15% glass powder, 5% to 15% organic carrier, and the balance being additives. The additives include molybdenum-containing compounds, iridium-containing compounds, and titanium-containing compounds, wherein the particle size of the molybdenum-containing compounds is in the nanometer range.

2. The method for preparing a battery cell according to claim 1, characterized in that, The particle size of the molybdenum-containing compound is 30 nm to 300 nm.

3. The method for preparing a battery cell according to claim 1, characterized in that, The mass percentage of the molybdenum-containing compound in the conductive paste is denoted as M1, and the sum of the mass percentages of the iridium-containing compound and the titanium-containing compound in the conductive paste is denoted as M2, where 3 ≤ M1 / M2 ≤ 8.

4. The method for preparing a battery cell according to claim 1, characterized in that, The additive is present in the conductive paste at a mass percentage of 0.4% to 0.8%.

5. The method for preparing a battery cell according to claim 1, characterized in that, The molybdenum-containing compound includes molybdenum trioxide, and the molybdenum trioxide in the conductive paste has a mass percentage of 0.4% to 0.6%.

6. The method for preparing a battery cell according to claim 5, characterized in that, The molybdenum trioxide is at least one of nanorods, nanosheets, and nanoribbons.

7. The method for preparing a battery cell according to claim 1, characterized in that, The iridium-containing compound includes iridium dioxide, and the iridium dioxide in the conductive paste has a mass percentage of 0.04% to 0.06%.

8. The method for preparing a battery cell according to claim 1, characterized in that, The titanium-containing compound includes titanium nitride, and the mass percentage of titanium nitride in the conductive paste is 0.04% to 0.06%.

9. The method for preparing a battery cell according to any one of claims 1 to 8, characterized in that, The sintering is carried out in an oxygen-containing atmosphere and includes the following steps: first, heating the temperature from room temperature to 200℃~300℃ and holding it for 5s~10s, then heating the temperature to 400℃~500℃ and holding it for 10s~30s, then heating the temperature to 650℃~750℃ and holding it for 10s~40s, and then cooling the temperature back to room temperature.

10. 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 9, 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.

11. A stacked battery, characterized in that, The stacked 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 the solar cell according to any one of claims 1 to 9 or a solar cell according to claim 10.

12. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string, wherein the battery string is formed by connecting multiple battery cells prepared by the method of preparing battery cells according to any one of claims 1 to 9, or battery cells according to claim 10, or stacked batteries according to claim 11; 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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