Conductive paste, conductive electrode, crystalline silicon solar cell and its preparation method

Abstract

This application discloses a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same, belonging to the field of crystalline silicon solar cell technology. The conductive paste, based on a total mass of 100 wt%, comprises the following components: nickel-based powder: 1 wt% to 20 wt%; silver powder: 60 wt% to 89 wt%; organic carrier: 9 wt% to 18 wt%; glass powder: 1 wt% to 5 wt%; wherein the nickel-based powder has a core-shell structure. The conductive paste of this application uses nickel-based powder, significantly reducing the amount of silver used while maintaining conductivity, thereby reducing the cost of the paste.

Description

Technical Field

[0001] This application relates to the field of crystalline silicon solar cell technology, specifically to a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same. Background Technology

[0002] High-temperature conductive paste is a key material for the photovoltaic industry to achieve metallization (i.e., electrode formation) of crystalline silicon solar cells. Its performance directly determines the photoelectric conversion efficiency and manufacturing cost of the cell.

[0003] Currently, the electrodes of commercially available high-efficiency crystalline silicon solar cells (such as PERC and TOPCon) are typically made using silver-based conductive pastes. Silver, due to its excellent conductivity, superior oxidation resistance, and good ohmic contact formation ability with silicon substrates, has become the irreplaceable preferred conductive phase material. However, silver is a precious metal, and its high and volatile price continues to drive up the manufacturing cost of solar cells, becoming a bottleneck restricting further cost reduction and efficiency improvement in the photovoltaic industry.

[0004] In the course of research and practice on related technologies, the inventors of this application discovered that the oxidation of nickel in untreated nickel powder under conventional air sintering processes affects the performance of solar cells. Summary of the Invention

[0005] This application provides a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same, aiming to improve the poor performance of the cell after the conductive paste is sintered in an air atmosphere.

[0006] This application provides a conductive paste, comprising, based on a total mass of 100wt%, the following components: nickel-based powder: 1wt% to 20wt%; silver powder: 60wt% to 89wt%; organic carrier: 9wt% to 18wt%; glass powder: 1wt% to 5wt%; wherein the nickel-based powder has a core-shell structure.

[0007] Optionally, in some embodiments of this application, the nickel-based powder includes: a core; an oxide layer, the oxide layer being disposed on at least a portion of the surface of the core; and a reducing agent layer, the reducing agent layer being disposed on at least a portion of the surface of the oxide layer.

[0008] Optionally, in some embodiments of this application, the core includes a metallic material selected from at least one of nickel and nickel alloys; the oxide layer includes a metal oxide, which includes at least one of the corresponding oxides of the metallic material; and the reducing agent layer includes a reducing material that reduces the metal oxide to a metallic element under heating conditions.

[0009] Optionally, in some embodiments of this application, the heating conditions include: the heating temperature T satisfies: 650℃≤T≤800℃.

[0010] Optionally, in some embodiments of this application, the reducing agent layer includes a first adhering substance; the first adhering substance covers at least a portion of the surface of the oxide layer; the first adhering substance includes a carbon material, which undergoes a carbothermic reduction reaction with the metal oxide under the heating conditions.

[0011] Optionally, in some embodiments of this application, the reducing agent layer includes a second adhesive that covers at least a portion of the first adhesive.

[0012] Optionally, in some embodiments of this application, the second attachment includes an attachment material having a standard reduction potential lower than that of the metal material.

[0013] Optionally, in some embodiments of this application, the core and the oxide layer constitute a composite, and the mass ratio of the first attachment to the composite ranges from 0.01 to 0.05.

[0014] Optionally, in some embodiments of this application, the mass ratio of the second attachment to the composite ranges from 0.01 to 0.05.

[0015] Optionally, in some embodiments of this application, the core and the oxide layer constitute a composite, the median particle size of the composite is a first median particle size, the median particle size of the particles of the first attachment is a second median particle size, and the median particle size of the particles of the second attachment is a third median particle size; wherein, the ratio of the second median particle size to the first median particle size ranges from 0.001 to 0.1.

[0016] Optionally, in some embodiments of this application, the ratio of the third median particle size to the first median particle size ranges from 0.001 to 0.1.

[0017] Optionally, in some embodiments of this application, the kernel is selected from one or more of spherical, near-spherical, and sheet-like shapes.

[0018] Optionally, in some embodiments of this application, the first median particle size ranges from 0.5 μm to 10 μm.

[0019] Optionally, in some embodiments of this application, the first attachment includes one or more of carbon black, graphite, graphene, fullerene, and carbon nanotubes.

[0020] Optionally, in some embodiments of this application, the second median particle size ranges from 1 nm to 100 nm.

[0021] Optionally, in some embodiments of this application, the second attachment includes one or more of boron, iron, zinc, gallium, indium, and their alloys.

[0022] Optionally, in some embodiments of this application, the third median particle size ranges from 5 nm to 200 nm.

[0023] Optionally, in some embodiments of this application, the conductive paste is applied to the front electrode, and the glass powder includes PbO, Bi2O3, and B2O3; or Based on the mass percentage of the glass powder, the glass powder satisfies at least one of the following conditions: a) The glass powder includes PbO, and the content of PbO ranges from 5 wt% to 35 wt%. b) The glass powder includes Bi2O3, and the content of Bi2O3 ranges from 5 wt% to 35 wt%. c) The glass powder includes B2O3, and the content of B2O3 ranges from 15wt% to 30wt%.

[0024] Optionally, in some embodiments of this application, the conductive paste is applied to the back electrode, and the glass powder includes PbO, Bi2O3, TeO2, and Li2O; or Based on the mass percentage of the glass powder, the glass powder satisfies at least one of the following conditions: d) The glass powder includes PbO, and the content of PbO ranges from 20 wt% to 40 wt%. e) The glass powder includes Bi2O3, and the content of Bi2O3 ranges from 20wt% to 40wt%. f) The glass powder includes TeO2, and the content of TeO2 ranges from 20 wt% to 40 wt%. g) The glass powder includes Li2O, and the content of Li2O ranges from 1wt% to 5wt%.

[0025] Accordingly, this application also provides a conductive electrode, comprising: the conductive electrode being formed from the conductive paste as described above.

[0026] Accordingly, this application also provides a crystalline silicon solar cell, the crystalline silicon solar cell comprising: a crystalline silicon substrate; and the aforementioned conductive electrode disposed on at least one surface of the crystalline silicon substrate.

[0027] Optionally, in some embodiments of this application, the conductive electrode is at least one of a front fine gate, a back fine gate, a front main gate, or a back main gate.

[0028] In addition, this application also provides a method for preparing a crystalline silicon solar cell, comprising: providing a crystalline silicon substrate; printing the aforementioned conductive paste onto at least one surface of the crystalline silicon substrate to obtain a printed crystalline silicon substrate; and sintering the printed crystalline silicon substrate to form conductive electrodes.

[0029] Optionally, in some embodiments of this application, the sintering process is carried out in an air atmosphere at a sintering temperature of 650°C to 800°C.

[0030] The conductive paste of this application uses nickel-based powder, which significantly reduces the amount of silver used while maintaining conductivity, thereby reducing the cost of the paste. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of a nickel-based powder in one embodiment of this application, wherein the nickel-based powder includes a core, an oxide layer, and a reducing agent layer; Figure 2 This is a schematic diagram of the structure of a nickel-based powder in one embodiment of this application, wherein the reducing agent layer includes a first deposit; Figure 3 This is a schematic diagram of the structure of a nickel-based powder in one embodiment of this application, wherein the reducing agent layer includes a first attachment and a second attachment; Figure 4 This is a schematic diagram of the structure of a nickel-based powder in one embodiment of this application, wherein the second attachment includes second attachment particles; Figure 5 A cross-sectional view of a crystalline silicon solar cell provided in an embodiment of this application; Figure 6 This is a SEM image of nickel-based Ni-01 powder coated with carbon black and boron powder in one embodiment of this application; Figure 7 This is a SEM image of Ni-O4 nickel-based powder coated with carbon black in one embodiment of this application.

[0033] Explanation of reference numerals in the attached figures: 10. Nickel-based powder; 100. Composite; 110. Core; 120. Oxide layer; 130. Reducing agent layer; 131. First deposit; 132. Second deposit; 132a. Second deposit particles; 1. Crystalline silicon solar cell; 11. Crystalline silicon substrate; 12. First conductive structure; 13. Second conductive structure; 101. Substrate; 102. p-type doped layer; 103. First passivation insulating layer; 104. Tunneling layer; 105. n + Polycrystalline silicon layer; 106, second passivation insulating layer. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] This application provides a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same. These are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0036] This application provides a conductive paste, comprising, based on a total mass of 100wt%, the following components: nickel-based powder 10: 1wt% to 20wt%; silver powder: 60wt% to 89wt%; organic carrier: 9wt% to 18wt%; glass powder: 1wt% to 5wt%; wherein the nickel-based powder 10 has a core-shell structure.

[0037] In some embodiments, the glass powder, based on 100% by mass of the conductive paste, comprises a glass powder system with lead-boron oxide, bismuth-boron oxide, lead-bismuth-boron oxide, lead-tellurium oxide, bismuth-tellurium oxide, and lead-bismuth-tellurium oxide as its main structures. The glass powder's properties are further adjusted according to application requirements using oxides of different glass forming bodies, glass intermediates, and modifiers. It should be noted that the nickel-based powder described in this application differs from conventional nickel powder. Conventional nickel powder is easily oxidized during high-temperature sintering in air, leading to deterioration of its conductivity. To address this issue, this application provides a specially formulated nickel-based powder with a core-shell structure. By surface modification of the core, an oxide layer and a reducing agent layer are formed sequentially, thereby inhibiting oxidation during sintering and maintaining excellent conductivity. In this application, unless otherwise specified, "nickel-based powder" refers to the powder with the aforementioned core-shell structure.

[0038] The glass powder in the embodiments is only used as an example to demonstrate the implementation effect of the base metal solution of this application, and is not intended to limit this application.

[0039] The conductive paste of this application uses nickel-based powder 10, which can significantly reduce the amount of silver used while maintaining conductivity, thereby reducing the cost of the paste. The content of nickel-based powder 10 in the conductive paste ranges from 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 10wt%, 15wt%, to 20wt%, or any combination thereof. The content of silver powder in the conductive paste ranges from 60wt%, 65wt%, 68wt%, 70wt%, 75wt%, 78wt%, 80wt%, 83.5wt%, 85.5wt%, 87.5wt%, 88.5wt%, to 89wt%, or any combination thereof. The content of organic carrier in the conductive paste ranges from 9wt%, 9.5wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, to 18wt%, or any combination thereof. The glass powder content in the conductive paste can be any value or a range of two of the following: 1wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4wt%, 4.5wt%, and 5wt%.

[0040] In some embodiments, when the content of nickel-based powder 10 is increased in the conductive paste, the proportion of silver powder in the conductive paste is correspondingly reduced to maintain 100% of the total mass of the conductive paste.

[0041] In some embodiments, when the content of glass powder in the conductive paste is increased, the proportion of silver powder and nickel-based powder 10 in the conductive paste is reduced proportionally to maintain 100% of the total mass of the conductive paste.

[0042] Using nickel powder directly in photovoltaic conductive pastes faces a fundamental technical challenge: nickel is extremely prone to oxidation during high-temperature sintering in air, which severely damages the metallic contact between conductive particles, causing a sharp increase in electrode resistance and further deteriorating the contact performance between the paste and the silicon substrate, ultimately resulting in a significant decrease in the fill factor and photoelectric conversion efficiency of the cell.

[0043] To avoid the oxidation problem of nickel, the following two strategies are usually adopted, but both have obvious limitations: Sintering in an inert atmosphere such as nitrogen or argon can prevent oxidation, but it requires modification of existing production lines and the addition of a complex atmosphere control system, which greatly increases the complexity of the process and the cost of equipment, which runs counter to the photovoltaic industry's pursuit of low cost and large-scale production; Coating the surface of nickel powder with a layer of silver, copper or other anti-oxidation metals can alleviate oxidation to a certain extent, but the coating is often incomplete or fails at high temperatures, and it introduces additional precious metals or complex coating processes, resulting in limited cost reduction and insufficient performance stability.

[0044] like Figure 1 As shown, in some embodiments of this application, the nickel-based powder 10 includes: a core 110; an oxide layer 120, the oxide layer 120 covering at least a portion of the surface of the core 110; and a reducing agent layer 130, the reducing agent layer 130 covering at least a portion of the surface of the oxide layer 120.

[0045] Understandably, the structure of nickel-based powder 10 can inhibit nickel oxidation during high-temperature sintering and improve the oxidation resistance of the electrode.

[0046] In some embodiments of this application, the core 110 includes a metallic material selected from at least one of nickel and nickel alloys; the oxide layer 120 includes a metal oxide, which includes at least one of the corresponding oxides of the metallic material; and the reducing agent layer 130 includes a reducing material that reduces the metal oxide to a metallic element under heating conditions.

[0047] Understandably, by designing the reducing agent layer 130, in-situ reduction is achieved during the sintering process, effectively suppressing the oxidation of the core 110 and improving conductivity and structural stability.

[0048] In some embodiments of this application, the heating conditions include: the heating temperature T satisfies: 650℃≤T≤800℃.

[0049] It is understood that the conductive paste, within the scope of this application, reduces metal oxides in an air atmosphere at a heating temperature T, without requiring a specific inert atmosphere to prevent the core 110 from continuous oxidation at high temperatures and in an air atmosphere. The heating temperature T can be any value or a range of any two of the following: 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, and 800℃.

[0050] like Figure 2 As shown, in some embodiments of this application, the reducing agent layer 130 includes a first attachment 131; the first attachment 131 is applied to at least a portion of the surface of the oxide layer 120; the first attachment 131 includes a carbon material, which undergoes a carbothermic reduction reaction with the metal oxide under heated conditions.

[0051] Understandably, carbon material, as part of the reducing agent layer 130, can effectively remove the oxide layer 120 through carbothermic reduction reaction at high temperatures, thereby improving the continuity of the conductive path.

[0052] like Figure 3 As shown, in some embodiments of this application, the reducing agent layer 130 includes a second attachment 132, which covers at least a portion of the first attachment 131.

[0053] Understandably, the introduction of the second attachment 132 can further enhance the reducing power or provide a diffusion barrier, inhibit oxygen permeation at high temperatures, and improve antioxidant performance.

[0054] In some embodiments of this application, the second attachment 132 includes an attachment material having a standard reduction potential lower than that of a metallic material.

[0055] Understandably, the second attachment 132 is made of a material with a lower reduction potential, which can be preferentially oxidized during sintering, protecting the core metal 110 from oxidation and improving overall oxidation resistance.

[0056] In some embodiments of this application, the core 110 and the oxide layer 120 constitute a composite 100, and the mass ratio of the first attachment 131 to the composite 100 ranges from 0.01 to 0.05.

[0057] In some embodiments of this application, the mass ratio of the second attachment 132 to the composite 100 ranges from 0.01 to 0.05.

[0058] It is understandable that controlling the mass ratio of the first attachment 131 and the second attachment 132 to the composite 100 can optimize the reduction efficiency and structural integrity, avoiding excessive coating that affects conductivity or insufficient coating that leads to incomplete reduction. The mass ratio of the first attachment 131 to the composite 100 can range from any value of 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, to 0.05, or any combination thereof. The mass ratio of the second attachment 132 to the composite 100 can range from any value of 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, to 0.05, or any combination thereof.

[0059] like Figure 4 As shown, in some embodiments of this application, the core 110 and the oxide layer 120 constitute a composite 100, the median particle size of the composite 100 is a first median particle size, the median particle size of the first attachment 131 is a second median particle size, the second attachment 132 includes second attachment particles 132a, and the median particle size of the second attachment particles 132a is a third median particle size; wherein, the ratio of the second median particle size to the first median particle size ranges from 0.001 to 0.1.

[0060] In some embodiments of this application, the ratio of the third median particle size to the first median particle size ranges from 0.001 to 0.1.

[0061] Understandably, controlling the ratio of the second median particle size to the first median particle size, and the ratio of the third median particle size to the first median particle size, helps to achieve uniform coating, improve the coverage and reduction efficiency of the adhesion layer, and avoid agglomeration or detachment caused by particle size mismatch. The value range of the ratio of the second median particle size to the first median particle size includes any value or a range of any two of the following: 0.001, 0.002, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1. The ratio of the third median particle size to the first median particle size can be any value or a range of any two of the following: 0.001, 0.002, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1.

[0062] In some embodiments of this application, the kernel 110 is selected from one or more of the following: spherical, near-spherical, and sheet-like.

[0063] In some embodiments of this application, the first median particle size ranges from 0.5 μm to 10 μm.

[0064] Understandably, Core 110 possesses excellent conductivity and cost advantages, and the selection of its morphology and particle size is beneficial to the rheological properties of the slurry, making it suitable for printing. The first median particle size range includes any value or a range of any two of the following: 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm.

[0065] In some embodiments of this application, the first attachment 131 includes one or more of carbon black, graphite, graphene, fullerene, and carbon nanotubes.

[0066] In some embodiments of this application, the second median particle size ranges from 1 nm to 100 nm.

[0067] It is understood that the carbon material of this application has a high specific surface area and good reducing activity, which helps to initiate the reduction reaction at low temperatures. The range of the second median particle size includes any value or a range of any two of the following: 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm.

[0068] In some examples, the coating method for the first attachment 131 may employ wet coating, dry coating, melt coating, vapor deposition, plasma processing, or a combination of two or more of these techniques. Coating equipment includes fluidized bed coaters, spray bed coaters, bottom-spray fluidized beds, rotary drums, disc coaters, fluidized bed reactors with chemical vapor deposition, and plasma-enhanced chemical vapor deposition.

[0069] In some embodiments of this application, the second attachment includes one or more of boron, iron, zinc, gallium, indium, and their alloys.

[0070] In some embodiments of this application, the third median particle size ranges from 5 nm to 200 nm.

[0071] It is understood that the second adhering material is a material with a reduction potential lower than that of the nickel-based core, which can further reduce residual oxides in the high-temperature section. Its particle size is within the range of this application, which is beneficial to improving its distribution and coverage effect on the powder surface, thereby playing a role in reduction and diffusion barrier during high-temperature sintering. The third median particle size range includes any value or a range of any two of the following: 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 150nm, 160nm, 180nm, and 200nm.

[0072] In some examples, the coating method for the second attachment 132 may employ wet coating, dry coating, melt coating, vapor deposition, plasma processing, or a combination of two or more of these techniques. Coating equipment includes fluidized bed coaters, spray bed coaters, bottom-spray fluidized beds, rotary drums, disc coaters, fluidized bed reactors with chemical vapor deposition, and plasma-enhanced chemical vapor deposition.

[0073] In some embodiments of this application, the conductive paste is applied to the front electrode, and the glass powder includes PbO, Bi2O3, and B2O3; or Based on the mass percentage of glass powder, the glass powder meets at least one of the following conditions: a) The glass powder includes PbO, and the PbO content ranges from 5 wt% to 35 wt%. b) The glass powder includes Bi2O3, with the Bi2O3 content ranging from 5 wt% to 35 wt%. c) The glass powder includes B2O3, and the content of B2O3 ranges from 15wt% to 30wt%.

[0074] Understandably, when the conductive paste is applied to the front electrode, the glass powder system can moderately etch the front passivation layer during the sintering process, so that the conductive paste and the emitter can form an ohmic contact.

[0075] In some embodiments of this application, the conductive paste is applied to the back electrode, and the glass powder includes PbO, Bi2O3, TeO2, and Li2O; or Based on the mass percentage of glass powder, the glass powder meets at least one of the following conditions: d) The glass powder includes PbO, with the PbO content ranging from 20 wt% to 40 wt%. e) The glass powder includes Bi2O3, with the Bi2O3 content ranging from 20wt% to 40wt%. f) The glass powder includes TeO2, and the content of TeO2 ranges from 20wt% to 40wt%. g) The glass powder includes Li2O, and the content of Li2O ranges from 1wt% to 5wt%.

[0076] Understandably, the dense surface of the back electrode allows glass powder containing TeO2 and Li2O to have stronger etching capabilities, effectively penetrating the back passivation layer (such as SiN). x (or SiO2), to establish reliable electrical contact.

[0077] Accordingly, this application also provides a conductive electrode, comprising: the conductive electrode being formed from the conductive paste as described above.

[0078] Understandably, this electrode maintains high conductivity while possessing excellent oxidation resistance and cost advantages, making it suitable for high-efficiency crystalline silicon solar cells.

[0079] Correspondingly, such as Figure 5 As shown, this application also provides a crystalline silicon solar cell 1, which includes: a crystalline silicon substrate 11; and the aforementioned conductive electrodes are disposed on at least one surface of the crystalline silicon substrate 11.

[0080] Understandably, using this conductive electrode can improve the photoelectric conversion efficiency and long-term reliability of the battery, while reducing the amount of silver used, resulting in significant economic benefits.

[0081] In some embodiments, the solar cell is a solar cell with tunnel oxide passivated contacts, which utilizes the aforementioned conductive paste during fabrication.

[0082] In some embodiments, solar cells containing tunnel oxide passivated contact structures are called TOPCon solar cells (Tunnel Oxide Passivated Contact Solar Cells). These solar cells utilize the tunnel oxide layer as a charge transport channel and a surface passivation layer to improve cell efficiency and performance. TOPCon solar cell structures exhibit low electron reflection and surface recombination, while also possessing high photoelectric conversion efficiency and low electronic defects.

[0083] In some embodiments, in a crystalline silicon solar cell, the crystalline silicon substrate 11 further includes a tunneling layer 104 (such as a silicon dioxide layer), which is located on the back side of the substrate 101, the substrate 101 being an n-type doped semiconductor; + Polycrystalline silicon layer 105 (such as phosphorus-dilated polycrystalline silicon layer) is located on the surface of tunneling layer 104 away from substrate 101; second passivation insulating layer 106 is deposited on n + The polysilicon layer 105 is located away from the surface of the tunneling layer 104.

[0084] In some embodiments, the front side refers to the light-receiving surface of the solar cell, which is also the working surface. The back side is the back of the solar cell, which typically does not directly receive sunlight. The conductive paste of this application can be used to form a conductive structure on either the front or the back side. The front side can be... Figure 5 The upper surface of the middle.

[0085] In some embodiments, the tunneling layers 104 and n are formed using a tunneling oxide passivation contact method. + Polycrystalline silicon layer 105.

[0086] In some embodiments, the first conductive structure 12 is formed using the conductive paste of this application. The conductive paste composition is applied to at least a portion of the surface of the first passivation insulating layer 103 in a desired patterned form, and during sintering, the conductive paste penetrates the first passivation insulating layer 103 to obtain the first conductive structure 12 which forms a low-carrier recombination electrical connection with the p-type doped layer 102.

[0087] In some embodiments, the second conductive structure 13 may utilize a commercially available conductive paste used in p-type or n-type crystalline silicon cells or the conductive paste of this application. The conductive paste composition is applied to at least a portion of the surface of the second passivation insulating layer 106 in a desired patterned form. During sintering, the conductive silver paste is etched and penetrates the second passivation insulating layer 106, thereby interacting with the n-type crystalline silicon cell. + The polysilicon layer 105 forms an electrical contact to facilitate the formation of a second conductive structure 13 in the form of a conductive metal contact.

[0088] In some embodiments of this application, the conductive electrode is at least one of a front fine gate, a back fine gate, a front main gate, or a back main gate.

[0089] Understandably, this electrode is suitable for various gate line structures and has good process adaptability and performance consistency.

[0090] In addition, this application also provides a method for preparing a crystalline silicon solar cell, comprising: providing a crystalline silicon substrate; printing the aforementioned conductive paste onto at least one surface of the crystalline silicon substrate to obtain a printed crystalline silicon substrate; and sintering the printed crystalline silicon substrate to form conductive electrodes.

[0091] Understandably, this method is simple, compatible with existing production lines, and can be sintered in an air atmosphere to achieve the preparation of high-performance electrodes.

[0092] In some embodiments of this application, the sintering process is carried out in an air atmosphere at a sintering temperature of 650°C to 800°C.

[0093] Understandably, sintering in an air atmosphere reduces process complexity and cost. The nickel-based powder 10 with the core-shell structure described in this application can still effectively suppress oxidation under these conditions, which is beneficial for improving electrode performance. The sintering temperature is any value or a range of any two of the following: 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, and 800℃.

[0094] The conductive paste, conductive electrode, crystalline silicon solar cell, and their fabrication method provided in this application are described below with reference to specific embodiments: Example 1 The nickel-based powder coating process is carried out under a nitrogen atmosphere, and the nickel-based powder is prepared according to the following steps: Step 1: The core uses spherical nickel powder A, and the first median particle size of the spherical nickel powder (Shanghai Pantian) is 4μm; Step 2: Carbon black nanopowder with a D50 of 20 nm (Shanghai Pantian) was coated onto the core surface using a dry coating method (Wuxi Taixian Powder VSH-0.3, 3500 rpm for 60 minutes), wherein the mass ratio of the first adhering material to the composite was 0.05. Step 3: Using boron nanopowder with a D50 of 50 nm (Shanghai Pantian), a dry coating method (Wuxi Taixian Powder VSH-0.3, 3500 rpm for 60 minutes) is used to coat at least part of the surface of the first attachment to form a second attachment, wherein the mass ratio of the second attachment to the composite is 0.01, and nickel-based powder Ni-01 is obtained. The conductive paste is prepared according to the following steps: Step 4: Mix the nickel-based powder Ni-01, silver powder, glass powder, and organic carrier from Step 3 at mass percentages of 3wt%, 85.5wt%, 2wt%, and 9.5wt%, respectively. Grind the mixture using a three-roll mill (330 rpm, 5 minutes) to form a conductive slurry. Disperse and grind the mixture using a three-roll mill to a fineness of less than 10 μm, and then further filter it. The proportions of glass powder, conductive metal, and organic carrier must be adjusted to ensure that the sum of the mass percentages of each component in the conductive slurry is 100wt%.

[0095] The silver powder used is spherical, with a median particle size of 1.5 μm; Based on 100wt% of the total organic carrier mass, the organic carrier includes: 15wt% ethyl cellulose, 18wt% polyvinyl butyral copolymer (PVB), 16wt% diethylene glycol butyl ether acetate, 5wt% silicone oil, 1.5wt% Duomeen TDO (nonionic surfactant, belonging to the amine oxide category), 1.5wt% Brij L4 (nonionic surfactant, belonging to the polyoxyethylene alcohol category), 6wt% Thixotrol plus (rheology modifier), 30wt% ethylenelated alcohol C12, and 7wt% diester.

[0096] Based on 100wt% of the total mass of the glass powder, the composition of the glass powder is as follows: Glass A (front): Lead-bismuth-silicon-boron oxide glass powder: 30wt%PbO, 21wt%Bi2O3, 25wt%B2O3, 4wt%Fe2O3, 2wt%SiO2, 18wt%Al2O3; D50 is 1.5μm; Glass B (reverse side): Lead-tellurium oxide glass powder: 36wt% PbO, 24.5wt% Bi2O3, 27.5wt% TeO2, 1wt% B2O3, 2.5wt% ZnO, 1.0wt% WO3, 2.5wt% Li2O, 2.0wt% Na2O, 2.0wt% SiO2, 1wt% Al2O3; D50 is 1.5μm.

[0097] The conductive electrode is prepared according to the following steps: Step 5: Print the conductive paste onto a commercially available blue film for crystalline silicon solar cells according to the designed pattern, including: an n-type doped semiconductor substrate, with the front side sequentially comprising a p-type doped layer (boron diffused emitter) and a first passivation insulating layer; and the back side sequentially comprising a tunneling layer (SiO2), n... + Polycrystalline silicon layer (phosphide-expanded polycrystalline silicon layer), second passivation insulating layer; conductive electrodes are printed on the corresponding positions of the blue film in the following order using screen printing: Rear main grid: Commercial silver paste (Solamet® PVD2L) is used. Backside fine grid: using commercial silver paste (Solamet® PV6NL); Front main grid: using commercial silver paste (Solamet® PVD2L); Front-side fine grid: using the conductive paste obtained in step 4; Step 6: Place the substrate in a sintering furnace and sinter it in an air atmosphere to obtain conductive electrodes. The temperature (unit: °C) of the sintering furnace (Maiwei) is set as follows: Upper temperature zone 7~18: 390, 420, 440, 500, 600, 700, 730, 750, 760, 780, 830, 680; Lower temperature zone 7~18: 400, 440, 460, 530, 620, 700, 730, 760, 790, 880, 890, 650; Belt speed: 16 m / min. Step 7: Using the DR Laser DR-M4XS-LIF-1000 equipment, laser-assisted sintering optimization treatment is performed on the sintered solar cells, with a laser bias of 45% and a laser power of 20%.

[0098] Example 2 The difference between this embodiment and embodiment 1 is that the mass ratio of the first attachment to the composite in step 2 is 0.01, and the second attachment is not coated in step 3 to obtain nickel-based powder Ni-O2; the conductive paste in step 4 includes 5 wt% Ni-O2, 83.5 wt% silver powder, 2.0 wt% glass A and 9.5 wt% organic carrier.

[0099] Example 3 The difference between this embodiment and embodiment 1 is that the mass ratio of the first attachment to the composite in step 2 is 0.025, and the second attachment is not coated in step 3 to obtain nickel-based powder Ni-O3; the conductive paste in step 4 includes 3 wt% Ni-O3, 85.5 wt% silver powder, 2.0 wt% glass A and 9.5 wt% organic carrier.

[0100] Example 4 The difference between this embodiment and embodiment 1 is that the mass ratio of the first attachment to the composite in step 2 is 0.05, and the second attachment is not coated in step 3 to obtain nickel-based powder Ni-04; the conductive paste in step 4 includes 3 wt% Ni-04, 85.5 wt% silver powder, 2.0 wt% glass A and 9.5 wt% organic carrier.

[0101] Example 5 The difference between this embodiment and embodiment 1 is that in step 2, the mass ratio of the first attachment to the composite is 0.05, and in step 3, the mass ratio of the second attachment to the composite is 0.03, thus obtaining nickel-based powder Ni-05; in step 4, the conductive paste includes 1 wt% Ni-05, 87.5 wt% silver powder, 2.0 wt% glass A, and 9.5 wt% organic carrier.

[0102] Example 6 The difference between this embodiment and Embodiment 1 is that, in step 1, the core uses hydrangea-shaped nickel powder B with a first median particle size of 3.5 μm; in step 2, the mass ratio of the first attachment to the composite is 0.025, and in step 3, no second attachment is applied, resulting in nickel-based powder Ni-06; in step 4, the conductive paste includes 3 wt% Ni-06, 85.5 wt% silver powder, 2.0 wt% glass A, and 9.5 wt% organic carrier.

[0103] Example 7 The difference between this embodiment and Embodiment 1 is that, in step 1, the core uses hydrangea-shaped nickel powder B with a first median particle size of 3.5 μm; in step 2, the mass ratio of the first attachment to the composite is 0.025; in step 3, the mass ratio of the second attachment to the composite is 0.025, thus obtaining nickel-based powder Ni-07; in step 4, the conductive paste includes 3 wt% Ni-07, 85.5 wt% silver powder, 2.0 wt% glass A, and 9.5 wt% organic carrier.

[0104] Example 8 The difference between this embodiment and embodiment 2 is that the conductive paste in step 4 includes 10wt% Ni-O2, 78.5wt% silver powder, 2.0wt% glass A and 9.5wt% organic carrier.

[0105] Example 9 The difference between this embodiment and embodiment 1 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 10wt% Ni-01, 78wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0106] Example 10 The difference between this embodiment and embodiment 2 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 10wt% Ni-O2, 78wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0107] Example 11 The difference between this embodiment and embodiment 3 is that in step 4, the conductive paste is used for back-side fine grid printing and glass B is used; the conductive paste includes 10wt% Ni-O3, 78wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0108] Example 12 The difference between this embodiment and embodiment 5 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 5wt% Ni-05, 83wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0109] Example 13 The difference between this embodiment and embodiment 5 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 10wt% Ni-05, 78wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0110] Example 14 The difference between this embodiment and embodiment 6 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 10wt% Ni-O6, 78wt% silver powder, 2.5wt% glass B and 9.5wt% organic carrier.

[0111] Example 15 The difference between this embodiment and embodiment 6 is that the conductive paste in step 4 is used for back-side fine grid printing and glass B is used; the conductive paste includes 20wt% Ni-O6, 67.5wt% silver powder, 3.0wt% glass B and 9.5wt% organic carrier.

[0112] Comparative Example 1 The difference between this comparative example and Example 1 is that the conductive paste in step 4 does not contain nickel-based powder, the silver powder content is 88.5 wt%, the glass A content is 2.0 wt%, and the organic carrier content is 9.5 wt%.

[0113] Comparative Example 2 The difference between this comparative example and Example 9 is that the conductive paste in step 4 does not contain nickel-based powder, the silver powder content is 88 wt%, the glass B content is 2.5 wt%, and the organic carrier content is 9.5 wt%.

[0114] Comparative Example 3 The difference between this comparative example and Example 9 is that step 1 uses uncoated hydrangea-shaped nickel powder B, that is, the nickel powder has no first or second adhering substances, the content of nickel-based powder is 20wt%, the content of silver powder is 67.5wt%, the content of glass B is 3.0wt%, and the content of organic carrier is 9.5wt%.

[0115] Nickel-based powders Ni-02 to Ni-07 were prepared according to steps 1 to 3 in Example 1, with reference to Table 1.

[0116] Table 1 shows the compositional differences of nickel-based powders from Ni-01 to Ni-07.

[0117] Table 1

[0118] Among them, the median particle size of hydrangea-shaped nickel powder B is 3.5μm (Changsha Liyou).

[0119] Following steps 4 to 7 in Example 1, and referring to Table 2, the battery cells of Examples 2 to 7 and Comparative Example 1 were prepared, and corresponding performance tests were performed.

[0120] Table 2 shows the performance tests of the solar cells in Examples 1 to 8 and Comparative Example 1.

[0121] Table 2

[0122] Referring to Table 3, the conductive paste was prepared according to step 4 of Example 1. The obtained conductive paste was then used in step 5 of Example 1 to screen print conductive electrodes onto the corresponding positions of the blue film in the following order: Rear main grid: Commercial silver paste (Solamet® PVD2L) is used. Backside fine grid: using conductive pastes from Examples 9 to 15 and Comparative Examples 2 and 3; Front main grid: using commercial silver paste (Solamet® PVD2L); Front-side fine grid: using commercial silver paste (Solamet® PV6NL).

[0123] The obtained battery cells were tested.

[0124] Table 3 shows the performance tests of the battery cells in Examples 9 to 15 and Comparative Example 2.

[0125] Table 3

[0126] Battery performance evaluation methods The photoelectric conversion performance of sintered crystalline silicon solar cells was characterized using the HALM solar cell IV curve testing system. The test conditions were standard test conditions (STC), specifically: a light source irradiance of 1000 W / m², a test temperature of 25℃±1℃, and spectral matching conforming to IEC 60904-3 standard. The equipment was calibrated using standard solar cells before testing to ensure the accuracy and repeatability of the test results.

[0127] The measured electrical performance parameters are defined as follows: Isc (A): Short-circuit current, which refers to the current value of the battery when the output voltage is zero. The unit is ampere (A), which reflects the battery's photogenerated carrier collection capability. Voc (V): Open circuit voltage, which refers to the voltage value of the battery when the output current is zero. The unit is volt (V), which reflects the built-in electric field strength and recombination suppression capability of the battery. FF (%): Fill factor, which is the percentage ratio of the battery's maximum output power to the product of short-circuit current and open-circuit voltage. It is dimensionless and reflects the battery's contact characteristics and series / parallel resistance status. Eff (%): Photoelectric conversion efficiency, which is the percentage ratio of the battery's maximum output power to the incident light power. It is dimensionless and is a core indicator for comprehensively evaluating battery performance.

[0128] Each experimental condition requires testing no fewer than 10 battery cells, and the average value is taken as the final test result to ensure the statistical significance of the data.

[0129] Figure 6 This is a SEM image of the nickel-based powder 10Ni-01 from this application; Figure 7 This is a SEM image of the nickel-based powder 10Ni-04 from this application.

[0130] According to Examples 1 to 8 and Comparative Example 1 of this application, this application verifies the improving effect of the reducing agent layer 130 on electrode performance by applying a core-shell structured nickel-based powder 10 to a conductive paste for a front-side fine grid. Specifically, the nickel-based powder 10 in Examples 1 and 5 includes a first attachment 131 coated on the surface of the oxide layer 120 and a second attachment 132 coated on the surface of the first attachment 131, the standard reduction potential of the second attachment 132 being lower than that of the core metal material 110; the nickel-based powder 10 in Examples 2 to 4 and 6 includes the first attachment 131 but does not include the second attachment 132; the nickel-based powder 10 in Example 7 adopts a hydrangea-shaped core 110 and includes both the first attachment 131 and the second attachment 132; the conductive paste of Comparative Example 1 does not contain the nickel-based powder 10. Experimental results show that, compared with embodiments without the second attachment 132, the conductive electrodes of embodiments including the second attachment 132 exhibit better contact performance and conversion efficiency; embodiments including the first attachment 131 all possess electrode performance comparable to Comparative Example 1, and significantly reduce the amount of silver powder used; embodiments employing the hydrangea-shaped core 110 also achieve stable electrode performance. This demonstrates that the nickel-based powder 10 of this application, by providing a reducing agent layer 130 on the surface of the oxide layer 120, can suppress the oxidation of the core 110 under air atmosphere sintering conditions, maintain the continuity of the conductive path, and thus ensure the overall performance of the conductive electrodes while reducing the silver content.

[0131] According to Examples 9 to 15 and Comparative Example 2 of this application, the nickel-based powder 10 with a core-shell structure was further applied to a conductive paste for a back-side fine grid, and the applicability of the nickel-based powder 10 under different doping amounts and different coating structures was investigated. Examples 9 to 15 respectively used nickel-based powder 10 including a first adhering substance 131 or further including a second adhering substance 132, and the proportion of nickel-based powder 10 in the conductive paste was in the range of 5 wt% to 20 wt%; the conductive paste of Comparative Example 2 did not contain nickel-based powder 10. Experimental results show that Examples 9 and 12, which include the double-layer coated nickel-based powder 10, still achieve electrode performance comparable to Comparative Example 2 even with a high nickel-based powder 10 content. Examples 10, 11, and 14, where the nickel-based powder 10 only includes the first adhering substance 131, also exhibit stable contact performance and conversion efficiency. The conversion efficiency of Example 15 is comparable to Comparative Example 2. Compared to Comparative Example 3, which uses uncoated hydrangea-shaped nickel powder B, Example 15 shows a significantly improved conversion efficiency, indicating that using the nickel-based powder 10 of this application helps reduce the amount of silver powder used and lower costs. This demonstrates that the nickel-based powder 10 of this application has good process adaptability and oxidation resistance under different electrode positions and different doping conditions, and can effectively replace part of the silver powder in air atmosphere sintering, achieving low-cost preparation of conductive electrodes for crystalline silicon solar cells.

[0132] The conductive paste, conductive electrode, crystalline silicon solar cell, and their preparation method provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A conductive paste, characterized in that, The conductive paste comprises the following components based on a total mass of 100 wt%: Nickel-based powder (10): 1wt% to 20wt%; Silver powder: 60wt% to 89wt%; Organic carrier: 9wt% to 18wt%; Glass powder: 1wt% to 5wt%; The nickel-based powder (10) has a core-shell structure.

2. The conductive paste according to claim 1, characterized in that, The nickel-based powder (10) comprises: Kernel (110); An oxide layer (120) is disposed on at least a portion of the surface of the core (110); A reducing agent layer (130) is disposed on at least a portion of the surface of the oxide layer (120).

3. The conductive paste according to claim 2, characterized in that, The core (110) includes a metallic material, wherein the metallic material is selected from at least one of nickel and nickel alloys; The oxide layer (120) comprises a metal oxide, which includes at least one of the corresponding oxides of the metal material; The reducing agent layer (130) includes a reducing material that reduces the metal oxide to a metallic element under heating conditions.

4. The conductive paste according to claim 3, characterized in that, The heating conditions include: The heating temperature T satisfies: 650℃≤T≤800℃.

5. The conductive paste according to claim 4, characterized in that, The reducing agent layer (130) includes a first attachment (131); The first attachment (131) covers at least a portion of the surface of the oxide layer (120); The first attachment (131) comprises a carbon material, which undergoes a carbothermic reduction reaction with the metal oxide under the heating conditions.

6. The conductive paste according to claim 5, characterized in that, The reducing agent layer (130) includes a second attachment (132) which covers at least a portion of the first attachment (131).

7. The conductive paste according to claim 6, characterized in that, The second attachment (132) includes an attachment material having a standard reduction potential lower than that of the metal material.

8. The conductive paste according to claim 6 or 7, characterized in that, The core (110) and the oxide layer (120) constitute a composite (100), and the mass ratio of the first attachment (131) to the composite (100) ranges from 0.01 to 0.

05. And / or, the mass ratio of the second attachment (132) to the composite (100) is in the range of 0.01 to 0.

05.

9. The conductive paste according to claim 6 or 7, characterized in that, The core (110) and the oxide layer (120) constitute a composite (100), the median particle size of the composite (100) is a first median particle size, the median particle size of the particles of the first attachment (131) is a second median particle size, and the median particle size of the particles of the second attachment (132) is a third median particle size. The ratio of the second median particle size to the first median particle size ranges from 0.001 to 0.

1. And / or, the ratio of the third median particle size to the first median particle size ranges from 0.001 to 0.

1.

10. The conductive paste according to claim 9, characterized in that, The kernel (110) is selected from one or more of the following: spherical, near-spherical, and sheet-like. And / or, the first median particle size ranges from 0.5 μm to 10 μm.

11. The conductive paste according to claim 9, characterized in that, The first attached material (131) includes one or more of carbon black, graphite, graphene, fullerene, and carbon nanotubes; And / or, the second median particle size ranges from 1 nm to 100 nm.

12. The conductive paste according to claim 9, characterized in that, The second adhering material (132) includes one or more of boron, iron, zinc, gallium, indium and their alloys; And / or, the third median particle size ranges from 5 nm to 200 nm.

13. The conductive paste according to claim 1, characterized in that, The conductive paste is applied to the front electrode; the glass powder includes PbO, Bi2O3, and B2O3; or Based on the mass percentage of the glass powder, the glass powder satisfies at least one of the following conditions: a) The glass powder includes PbO, and the content of PbO ranges from 5 wt% to 35 wt%. b) The glass powder includes Bi2O3, and the content of Bi2O3 ranges from 5 wt% to 35 wt%. c) The glass powder includes B2O3, and the content of B2O3 ranges from 15wt% to 30wt%.

14. The conductive paste according to claim 1, characterized in that, The conductive paste is applied to the back electrode, and the glass powder includes PbO, Bi2O3, TeO2, and Li2O; or Based on the mass percentage of the glass powder, the glass powder satisfies at least one of the following conditions: d) The glass powder includes PbO, and the content of PbO ranges from 20 wt% to 40 wt%. e) The glass powder includes Bi2O3, and the content of Bi2O3 ranges from 20wt% to 40wt%. f) The glass powder includes TeO2, and the content of TeO2 ranges from 20 wt% to 40 wt%. g) The glass powder includes Li2O, and the content of Li2O ranges from 1wt% to 5wt%.

15. A conductive electrode, characterized in that, The conductive electrode is formed from the conductive paste as described in any one of claims 1 to 14.

16. A crystalline silicon solar cell (1), characterized in that, The crystalline silicon solar cell (1) includes: Crystalline silicon substrate (11); The conductive electrode as claimed in claim 15 is disposed on at least one surface of the crystalline silicon substrate (11).

17. The crystalline silicon solar cell according to claim 16, characterized in that, The conductive electrode is at least one of the following: front fine grid, back fine grid, front main grid, or back main grid.

18. A method for preparing a crystalline silicon solar cell, characterized in that, Includes the following steps: Provide crystalline silicon substrates; The conductive paste as described in any one of claims 1 to 14 is printed onto at least one surface of the crystalline silicon substrate to obtain a printed crystalline silicon substrate; The printed silicon substrate is sintered to form conductive electrodes.

19. The preparation method according to claim 18, characterized in that, The sintering process is carried out in an air atmosphere at a temperature of 650°C to 800°C.

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