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

Abstract

The invention discloses conductive paste, a conductive electrode, a preparation method of the conductive electrode and a crystalline silicon solar cell, and belongs to the technical field of photovoltaic cells, the conductive paste comprises glass powder, silver, nickel and an organic carrier, the glass powder comprises B2O3, corrosive oxide and non-corrosive oxide, and the nickel is added to replace part of silver, so that the usage amount of silver in the conductive paste is reduced, and the cost is reduced. In addition, the molar ratio range of the corrosive oxide and the non-corrosive oxide in the glass powder is limited to be 0.7-2.6. The first passivation layer arranged on the boron diffusion emitter is opened during high-temperature sintering, and the oxidability and the flowability of the glass powder can be balanced to inhibit or delay the formation of an oxidized nickel shell on the surface of the nickel powder, so that a laser enhanced contact post-treatment process is matched; and the photoelectric conversion efficiency of the crystalline silicon solar cell is ensured.

Description

Technical Field

[0001] This application belongs to the technical field of solar photovoltaic cells, and particularly relates to conductive paste, conductive electrodes, their preparation methods, and crystalline silicon solar cells. Background Art

[0002] In crystalline silicon solar cells, silver powder is usually used as the conductive metal in the conductive paste. Silver is a precious metal and can be sintered into a highly conductive electrode structure with a dense structure after high-temperature sintering. However, the relatively high usage of silver will increase the manufacturing cost of crystalline silicon solar cells. Reducing the usage of silver will affect the photoelectric conversion efficiency of crystalline silicon solar cells. Summary of the Invention

[0003] Embodiments of this application provide a conductive paste, conductive electrodes, their preparation methods, and crystalline silicon solar cells to solve the problem that reducing the usage of silver in existing crystalline silicon solar cells affects the photoelectric conversion efficiency.

[0004] In a first aspect of the embodiments of this application, a conductive paste is provided, including: glass powder, accounting for 1 wt% to 4 wt% of the total weight of the conductive paste; silver, accounting for 57 wt% to 89 wt% of the total weight of the conductive paste; nickel, accounting for 1 wt% to 30 wt% of the total weight of the conductive paste; and an organic carrier, accounting for 9 wt% to 15 wt% of the total weight of the conductive paste; based on the molar percentage of the glass powder, the glass powder includes 24 mol% to 50 mol% of B 2 O 3 , 24 mol% to 44 mol% of corrosive oxides, and 13 mol% to 46 mol% of non-corrosive oxides; wherein, the molar ratio range of the corrosive oxides to the non-corrosive oxides satisfies: 0.7 to 2.6.

[0005] Optionally, the corrosive oxide is selected from at least one of PbO and Bi 2 O 3 in it.

[0006] Optionally, the non-corrosive oxide is selected from at least one of SiO 2 and Al 2 O 3 in it.

[0007] Optionally, the glass powder further includes 0 mol% to 10 mol% of functional oxides.

[0008] Optionally, the functional oxide is selected from at least one of Fe 2 O 3 , TiO 2 , ZnO, and BaO.

[0009] Optionally, the silver is selected from at least one of silver powder, silver alloy powder, silver oxide, and silver salt.

[0010] Optionally, the silver is selected from silver powder, and the D v 50 of the silver powder is 1 μm to 3 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the silver powder reaches 50 wt%.

[0011] Optionally, the nickel is selected from at least one of nickel powder and nickel alloy powder.

[0012] Optionally, the nickel is selected from nickel powder, and the D v 50 of the nickel powder is 1 μm to 5 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the nickel powder reaches 50 wt%.

[0013] In a second aspect of the embodiments of the present application, a conductive electrode is provided, including: a semiconductor substrate, including a substrate, a boron-diffused emitter provided on the substrate, and a first passivation layer provided on a side of the boron-diffused emitter facing away from the substrate; a first conductive structure, provided on a side of the first passivation layer facing away from the boron-diffused emitter, the first conductive structure penetrating through the first passivation layer and being electrically connected to the boron-diffused emitter; wherein, the first conductive structure is formed by the conductive paste as described above.

[0014] Optionally, the conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

[0015] In a third aspect of the embodiments of the present application, a method for preparing a conductive electrode is provided, and the preparation method includes the following steps:

[0016] Provide a semiconductor substrate, the semiconductor substrate including a substrate, a boron-diffused emitter provided on the substrate, and a first passivation layer deposited on a side of the boron-diffused emitter facing away from the substrate;

[0017] Print the conductive paste as described above on at least a part of the surface of the first passivation layer;

[0018] Sinter the semiconductor substrate containing the conductive paste, and etch and penetrate the first passivation layer by the glass powder in the conductive paste during sintering, and silver and nickel form a first conductive structure;

[0019] Perform a process of laser-enhanced contact optimization on the semiconductor substrate, and the first conductive structure forms an electrical connection with the boron-diffused emitter through silver and nickel to obtain the conductive electrode.

[0020] Optionally, the step of printing the conductive paste on at least a part of the surface of the first passivation layer includes: printing the conductive paste on at least a part of the surface of the first passivation layer in a patterned form.

[0021] The process of optimizing laser enhanced contact for the semiconductor substrate includes: applying a reverse voltage to the semiconductor substrate and simultaneously performing laser scanning on the semiconductor substrate to form an induced current within the first conductive structure.

[0022] Optionally, the process of optimizing laser enhanced contact for the semiconductor substrate satisfies at least one of the following conditions:

[0023] a) The reverse voltage is 5V to 20V;

[0024] b) The time of the laser scanning is 1ms to 100ms.

[0025] A fourth aspect of the embodiments of the present application provides a crystalline silicon solar cell, which includes the conductive electrode as described above, or the crystalline silicon solar cell includes the conductive electrode prepared by the preparation method of the conductive electrode as described above.

[0026] Beneficial effects: The embodiments of the present application provide a conductive paste, a conductive electrode, a preparation method thereof, and a crystalline silicon solar cell. The conductive paste includes glass powder, silver, nickel, and an organic carrier. The glass powder includes B 2 O 3 , a corrosive oxide, and a non-corrosive oxide. By adding nickel to replace part of the silver, the usage amount of silver in the conductive paste is reduced, and the manufacturing cost of the crystalline silicon solar cell is reduced. In addition, it is defined that the molar ratio range of the corrosive oxide to the non-corrosive oxide in the glass powder satisfies 0.7 to 2.6, so as to ensure that the glass powder has sufficient corrosiveness to open the first passivation layer provided on the boron-diffused emitter during high-temperature sintering to match the post-treatment of the laser improved contact process, and can balance the oxidizing property and fluidity of the glass powder to inhibit or delay the formation of the nickel oxide shell on the surface of the nickel powder, ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0027] It can be understood that the conductive electrode, the preparation method thereof, and the crystalline silicon solar cell provided by the embodiments of the present application may include all the technical features and beneficial effects of the above conductive paste, and will not be elaborated herein. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 This is a schematic structural diagram of the conductive electrode provided by the embodiment of the present application.

[0030] Reference numerals:

[0031] 1. Conductive electrode;

[0032] 10. Semiconductor substrate, 110. Substrate, 111. First surface, 112. Second surface, 120. Boron-diffused emitter, 130. First passivation layer, 140. Tunneling layer, 150. Polysilicon layer, 160. Second passivation layer;

[0033] 20. First conductive structure;

[0034] 30. Second conductive structure;

[0035] X. Thickness direction. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0037] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. In the description of the present application, "a plurality of" means two or more, and at least one means one, two or more, unless otherwise specifically defined.

[0038] An important technological breakthrough in crystalline silicon solar cells is the use of the back passivation contact structure of TOPCon (Tunnel Oxide Passivating Contacts), which significantly improves the open-circuit voltage (Voc) and cell efficiency of crystalline silicon solar cells. When preparing n-TOPCon crystalline silicon solar cells, the front (light-facing surface, p-side) and back (backlight-facing surface, n-side) of the crystalline silicon solar cells need to be metallized. The metallization of the conductive electrode on the front (light-facing surface) usually uses screen printing to print the conductive paste onto the surface of the passivation layer in a desired pattern, and then through high-temperature sintering, the conductive metal paste is etched and penetrates the passivation layer, and further forms an electrical contact with the boron-diffused emitter, thereby forming a conductive structure (or conductive electrode) in the form of a conductive metal contact. The electrical contact quality of this conductive structure includes the electrical contact resistance and the carrier recombination caused by metallization, which directly affects the photoelectric conversion efficiency of crystalline silicon solar cells. The conductive paste usually used to form the electrode includes a conductive metal (e.g., silver particles), a glass frit, and an organic carrier used as a printing carrier.

[0039] Silver is usually used as the conductive metal in the conductive paste. Silver is a stable noble metal and can be sintered into a highly conductive conductive electrode with a dense structure after the high-temperature sintering process. However, both the first conductive structure on the front (p-side) and the second conductive structure on the back (n-side) of the conductive electrode in the n-TOPCon crystalline silicon solar cell need to use a conductive paste containing silver. The consumption of silver paste accounts for a large proportion of the manufacturing cost of crystalline silicon solar cells, resulting in a relatively high manufacturing cost of crystalline silicon solar cells. Reducing the silver content will affect the photoelectric conversion efficiency of crystalline silicon solar cells.

[0040] Based on this, it is necessary to provide a conductive paste, a conductive electrode and its preparation method, and a crystalline silicon solar cell to reduce the amount of silver used in the conductive paste while ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell, thereby reducing the manufacturing cost of the crystalline silicon solar cell.

[0041] Some embodiments of the present application provide a conductive paste, including: glass powder, accounting for 1 wt% to 4 wt% of the total weight of the conductive paste; silver, accounting for 57 wt% to 89 wt% of the total weight of the conductive paste; nickel, accounting for 1 wt% to 30 wt% of the total weight of the conductive paste; and an organic carrier, accounting for 9 wt% to 15 wt% of the total weight of the conductive paste; based on the molar percentage of the glass powder, the glass powder includes 24 mol% to 50 mol% of B 2 O 3, 24 mol% to 44 mol% of corrosive oxides, and 13 mol% to 46 mol% of non-corrosive oxides; wherein, the molar ratio range of the corrosive oxides to the non-corrosive oxides satisfies: 0.7 to 2.6.

[0042] Glass powder, silver, and nickel are solid components in the conductive paste; the organic carrier is the dispersed phase in the conductive paste and provides printing properties, including one or more components such as polymers, surfactants, thickeners, thixotropic agents, and adhesives that can endow functional characteristics. The sum of the weight percentages of each component in the conductive paste is 100 wt%.

[0043] Each component in the conductive paste is described below.

[0044] glass powder

[0045] In some embodiments, the glass powder refers to a composition containing one or more types of anions and cations. When heated, specifically, when sintered at high temperature, the glass powder has the ability to flow, and the glass powder can be crystalline or partially or completely glassy or amorphous.

[0046] In some embodiments, the glass powder of this embodiment can be understood as a composition with a glass component. The mass percentage of the glass powder in the total weight of the conductive paste is 1 wt% to 4 wt%. Specifically, the mass percentage of the glass powder in the total weight of the conductive paste can be any value among 1 wt%, 2 wt%, 3 wt%, 4 wt% or any value in the range composed of any two of these values.

[0047] In some other embodiments, the mass percentage of the glass powder in the total solids of the conductive paste is 1.2 wt% to 3.8 wt%, and can also be 1.5 wt% to 3.5 wt%; it can further be 1.0 wt% to 2.0 wt%; it can further be 2 wt% to 4 wt%.

[0048] It can be understood that the adjustment of the proportion of the glass powder in the conductive paste needs to ensure that the sum of the weight percentages of each component in the conductive paste is 100 wt%. The components of the glass powder directly affect its fusibility, fluidity, and etching property. Therefore, the components of the glass powder need to be well balanced to achieve excellent electrical contact resistance and carrier recombination brought by metallization.

[0049] In some embodiments, the glass powder includes: 24 mol% to 50 mol% of B 2 O 3, 24 mol% to 44 mol% of corrosive oxides, and 13 mol% to 46 mol% of non-corrosive oxides. In the following description, unless otherwise specified, "mol%" of the content of each component of the frit represents the molar percentage in terms of oxide conversion.

[0050] Among them, in the glass powder, B 2 O 3 The molar percentage of can be any value among 24 mol%, 26 mol%, 28 mol%, 30 mol%, 32 mol%, 34 mol%, 36 mol%, 38 mol%, 40 mol%, 42 mol%, 44 mol%, 46 mol%, 48 mol%, 50 mol% or any value within the range value composed of any two of these values. The molar percentage of the corrosive oxide can be any value among 24 mol%, 26 mol%, 28 mol%, 30 mol%, 32 mol%, 34 mol%, 36 mol%, 38 mol%, 40 mol%, 42 mol%, 44 mol% or any value within the range value composed of any two of these values. The molar percentage of the non-corrosive oxide can be any value among 13 mol%, 16 mol%, 20 mol%, 22 mol%, 24 mol%, 26 mol%, 28 mol%, 30 mol%, 32 mol%, 34 mol%, 36 mol%, 38 mol%, 40 mol%, 42 mol%, 44 mol%, 46 mol% or any value within the range value composed of any two of these values.

[0051] In some embodiments, more preferably, in terms of the molar percentage in terms of oxide conversion, the glass powder includes: 24 mol% to 40 mol% of B 2 O 3 , 24 mol% to 35 mol% of corrosive oxides, and 13 mol% to 30 mol% of non-corrosive oxides.

[0052] In some embodiments, more preferably, in terms of the molar percentage in terms of oxide conversion, the glass powder includes: 40 mol% to 50 mol% of B 2 O 3 , 35 mol% to 44 mol% of corrosive oxides, and 30 mol% to 46 mol% of non-corrosive oxides.

[0053] In some embodiments, the molar ratio range of the corrosive oxide to the non-corrosive oxide satisfies: 0.7 to 2.6. Specifically, the molar ratio of the corrosive oxide to the non-corrosive oxide can be any value among 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6 or any value within the range formed by any two of these values.

[0054] In some embodiments, more preferably, the molar ratio range of the corrosive oxide to the non-corrosive oxide satisfies: 0.7 to 1.6.

[0055] In some embodiments, more preferably, the molar ratio range of the corrosive oxide to the non-corrosive oxide satisfies: 1.6 to 2.6.

[0056] The composition of the conductive paste has a significant impact on the structure of the conductive structure formed by high-temperature sintering, including the growth of conductive metal (such as silver) in the crystalline silicon layer. In particular, the glass powder used in the conductive paste plays a crucial role in the formation of the conductive structure of the conductive electrode. Specifically, during high-temperature sintering, the glass powder melts to form a glass melt, and the conductive metal dissolves into the glass melt. During the cooling stage of the sintering process, the dissolved conductive metal will precipitate to form conductive metal particles (such as silver particles) or conductive metal crystals (such as silver crystals) embedded in the silicon layer. In addition, silver, as an important conductive phase in the conductive paste, can be sintered into a dense and highly conductive conductive electrode after the high-temperature sintering process. However, the cost of using silver accounts for a large proportion of the manufacturing cost of crystalline silicon solar cells. Therefore, while reducing the amount of silver used, it is necessary to maintain the good photoelectric conversion efficiency of crystalline silicon solar cells. Using base metal powder to replace silver powder can reduce the silver content in the paste, thereby reducing the cost of the conductive paste. However, base metals are easily oxidized during the high-temperature rapid sintering process in an oxygen-containing (such as air) environment, so sintering needs to be carried out in an oxygen-free environment. However, for crystalline silicon solar cells, such as n-TOPCon crystalline silicon solar cells, the commonly used high-temperature sintering environment is oxygen-containing, and the temperature to which the conductive paste is subjected during the sintering process usually reaches 700°C to 780°C. In this oxygen-containing and high-temperature environment, base metal powders such as copper powder and nickel powder will oxidize, resulting in a significant reduction in the conductivity of the electrode, and thus a loss in the photoelectric conversion efficiency of the conductive electrode.

[0057] For TOPCon metallization, the front conductive silver paste needs to be properly sintered to form a continuous and dense structure to provide good conductivity. However, due to the high cost of silver, low-silver conductive pastes are a new research direction. To reduce the manufacturing cost of crystalline silicon solar cells, existing n-TOPCon crystalline silicon solar cells will add a small amount of aluminum powder to the front conductive paste. Usually, the aluminum powder accounts for 1wt% to 2wt% of the total solids in the conductive paste, making the conductive paste form a silver-aluminum paste, so that during the high-temperature sintering process, the conductive paste forms silver-aluminum barb contact sites on the p-side to meet the requirement of ohmic electrical contact with the boron-diffused emitter. However, the formation of silver-aluminum barbs will significantly increase the recombination loss after metallization, resulting in losses in the open-circuit voltage (Voc) and photoelectric conversion efficiency (Eff) of the conductive electrode.

[0058] The conductive paste provided by the embodiment of the present application includes glass powder, accounting for 1wt% to 4wt% of the total weight of the conductive paste; silver, accounting for 57wt% to 89wt% of the total weight of the conductive paste; nickel, accounting for 1wt% to 30wt% of the total weight of the conductive paste; and an organic carrier, accounting for 9wt% to 15wt% of the total weight of the conductive paste; based on the molar percentage of the glass powder, the glass powder includes 24mol% to 50mol% of B 2 O 3 , 24mol% to 44mol% of corrosive oxides, and 13mol% to 46mol% of non-corrosive oxides; wherein, the molar ratio range of the corrosive oxides to the non-corrosive oxides satisfies: 0.7 to 2.6.

[0059] Nickel is added to the conductive paste to replace part of the silver as the conductive metal, forming a silver-nickel conductive paste, thereby reducing the amount of silver used in the conductive paste and further reducing the manufacturing cost of crystalline silicon solar cells.

[0060] Among them, although replacing part of the silver powder with nickel powder can reduce the silver content in the conductive paste, after high-temperature sintering, a thin surface shell of nickel oxide (NiO) will form on the surface of the nickel powder in the paste. Since nickel oxide NiO is not conductive, the added nickel powder after sintering not only does not participate in the conductive function of the conductive electrode, but will instead reduce the conductivity of the conductive electrode. In addition, due to the blocking of the thin NiO shell on the surface, nickel powder cannot form sintering or alloying with nickel powder or silver powder. Therefore, after sintering, the nickel powder will remain in the electrode in a discrete particle form. In summary, adding nickel powder to the conductive paste will result in a less dense silver structure after sintering, making the conductivity of the conductive electrode worse. The worse conductivity of the conductive electrode will bring a higher series resistance, resulting in losses in the fill factor (FF) and photoelectric conversion efficiency (Eff).

[0061] By using the glass powder provided in the embodiments of the present application, through the design of the composition, the formation of the NiO shell can be effectively inhibited or delayed during the sintering process, thereby reducing its impact on the electrical performance of the battery, as follows:

[0062] B 2 O 3 is the main glass former, used to adjust the glass transition temperature and high-temperature fluidity of the glass powder. B 2 O 3 can form a low-melting glass melt and provide good fluidity, so that the corrosive oxide can etch the first passivation layer in a relatively short time. This can not only ensure the etching effect on the first passivation layer, achieve local opening of the first passivation layer, and thus ensure the stability of the ohmic contact between the conductive metal in the conductive paste and the boron-diffused emitter, but also ensure the passivation effect of the crystalline silicon solar cell and then the photoelectric conversion efficiency of the crystalline silicon solar cell in the case of a decrease in silver content caused by the addition of nickel.

[0063] The corrosive oxide can control its etching of the first passivation layer covering the surface of the boron-diffused emitter so that the conductive paste can locally open the first passivation layer during the high-temperature sintering process, ensuring that the conductive metal in the conductive paste can form an ohmic contact with the boron-diffused emitter and ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell. However, too much corrosive oxide will etch too much of the first passivation layer to increase the carrier recombination loss, thereby affecting the open-circuit voltage and photoelectric conversion efficiency of the crystalline silicon solar cell.

[0064] The non-corrosive oxide is used to adjust the glass transition temperature Tg and high-temperature fluidity of the glass powder. Appropriate addition can stabilize the glass phase, increase the melting point of the glass powder and reduce the fluidity. Thus, the oxidizing property and fluidity of the glass melt formed during the high-temperature sintering process of the glass powder are balanced to delay or even inhibit the oxidation of the nickel surface to form a NiO (nickel oxide) shell during the high-temperature sintering process, ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0065] In addition, in the glass powder of the conductive paste provided in the embodiments of the present application, the molar ratio range of the corrosive oxide to the non-corrosive oxide is limited to satisfy 0.7 to 2.6, that is, 0.7 ≤ corrosive oxide / non-corrosive oxide ≤ 2.6. Thus, while ensuring that the glass melt can locally open the first passivation layer to enable ohmic contact between silver and nickel and the boron-diffused emitter, the oxidizing property and fluidity of the glass melt during the high-temperature sintering process are controlled to delay or even inhibit the oxidation of the nickel surface to form a NiO (nickel oxide) shell during the high-temperature sintering process, ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0066] In some embodiments, the corrosive oxide is selected from PbO and Bi 2 O 3At least one of

[0067] Among them, PbO is a glass intermediate used to enhance the corrosiveness of the glass powder. The addition amount of PbO can regulate the etching of the first passivation layer coated on the surface of the boron-diffused emitter so that the conductive paste can locally open the first passivation layer during the high-temperature sintering process. PbO is also an intermediate glass former that can be incorporated into the glass network, and the residual PbO will exist outside the glass framework to act as a glass modifier. However, too much PbO will etch too much of the first passivation layer, affecting the passivation effect of the crystalline silicon solar cell and thus the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0068] Bi 2 O 3 is a glass intermediate. Bi 2 O 3 and PbO both have corrosiveness, but the corrosiveness of Bi 2 O 3 is weaker than that of PbO. Bi 2 O 3 is used in combination with PbO to adjust the etching ability of the glass powder on the first passivation layer. Similarly, too much Bi 2 O 3 will etch too much of the first passivation layer, affecting the passivation effect of the crystalline silicon solar cell and thus the photoelectric conversion efficiency of the crystalline silicon solar cell. In addition, since the corrosiveness of PbO is stronger than that of Bi 2 O 3 , replacing a part of PbO with Bi 2 O 3 in the composition of the glass powder can adjust the corrosion ability to meet the effect of low carrier recombination, thereby improving the open-circuit voltage and photoelectric conversion efficiency of the crystalline silicon solar cell.

[0069] In some embodiments, the non-corrosive oxide is selected from at least one of SiO 2 and Al 2 O 3 Among them, SiO

[0070] 2 is a glass former used to adjust the glass transition temperature Tg and high-temperature fluidity of the glass powder. Appropriate addition can stabilize the glass phase, increase the melting point of the glass powder, and reduce the fluidity. SiO 2 can also improve the weather resistance of the glass and adjust the reaction ability with the substrate. The silicon atom forms a tetrahedral shape of SiO4 with four oxygen atoms and is connected to other tetrahedrons through bridging oxygen ions, which can enhance the stability of the glass powder and reconcile the corrosiveness of the glass melt on the first passivation layer. The formed network structure can significantly increase metal cations (such as Ni 2+ , Ag​+ ) for enhancing the stability of the glass melt and reconciling the corrosiveness of the glass melt to the first passivation layer.

[0071] In some embodiments, the molar ratio range of the corrosive oxide to the non-corrosive oxide satisfies 0.7 to 2.6, that is, the sum of the molar percentages of PbO and Bi 2 O 3 in the glass powder and the sum of the molar percentages of SiO 2 and Al 2 O 3 in the glass powder, that is, 0.7 ≤ (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) ≤ 2.6.

[0072] In some embodiments, the glass powder further includes 0 mol% to 10 mol% of a functional oxide. Specifically, the molar percentage of the functional oxide in the glass powder can be any value among 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol% or any value within the range formed by any two of these values. The addition of the functional oxide can adjust the glass transition temperature Tg and the high-temperature fluidity of the glass powder, and can also be used as a component to improve the weather resistance of the glass powder.

[0073] In some embodiments, the functional oxide is selected from at least one of Fe 2 O 3 , TiO 2 , ZnO and BaO.

[0074] conductive metal

[0075] In some embodiments, the conductive metal, as the power source of the conductive paste, can be used without particular limitation as the metal powder commonly used in electrodes formed on circuit boards such as semiconductor substrates.

[0076] Therefore, in order to use nickel powder instead of silver powder to reduce the metallization cost of solar cells, it is necessary to select appropriate nickel powder to minimize its impact on the sintered structure of silver powder, so as to avoid a significant reduction in the conductivity of the sintered nickel / silver electrode. By screen-printing a conductive paste containing nickel powder, the nickel powder is dispersed throughout the conductive electrode. After high-temperature sintering, due to the NiO shell on the surface of the nickel powder, it cannot form an alloy with silver, and the remaining nickel powder can be conceived as "voids" in the silver electrode. Therefore, the nickel powder needs to minimize the void ratio of the sintered silver to ensure good conductivity. One relatively direct approach is to add only a very small amount of nickel powder, but this method can only very limitedly reduce the silver consumption and cost of metallization.

[0077] In the conductive paste provided by the embodiments of the present application, the conductive metal includes silver and nickel. Among them, silver accounts for 57% wt% to 89 wt% of the total weight in the conductive paste. Specifically, the mass percentage of silver in the total weight of the conductive paste can be any value among 57 wt%, 59 wt%, 61 wt%, 63 wt%, 65 wt%, 67 wt%, 69 wt%, 71 wt%, 73 wt%, 75 wt%, 77 wt%, 79 wt%, 81 wt%, 83 wt%, 85 wt%, 87 wt%, 89 wt% or any value within the range composed of any two of these values. Nickel accounts for 1 wt% to 30 wt% of the total weight in the conductive paste. Specifically, the mass percentage of nickel in the total weight of the conductive paste can be any value among 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 11 wt%, 13 wt%, 15 wt%, 17 wt%, 19 wt%, 21 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt% or any value within the range composed of any two of these values.

[0078] By designing 1 wt% to 30 wt% of nickel and 57 wt% to 89 wt% of silver in the conductive paste, combined with the composition of the glass powder as described above, it is possible to effectively delay or even inhibit the oxidation of the nickel surface to form a NiO (nickel oxide) shell during high-temperature sintering, and ensure the photoelectric conversion efficiency of crystalline silicon solar cells.

[0079] In some other embodiments, silver accounts for 79 wt% to 84 wt% of the total weight in the conductive paste, and can also be 84 wt% to 88 wt%; it can further be 57 wt% to 78 wt%; it can further be 78 wt% to 89 wt%.

[0080] In some other embodiments, nickel accounts for 10 wt% to 22 wt% of the total solids in the conductive paste, and can also be 5 wt% to 20 wt%; it can further be 1 wt% to 13 wt%; it can further be 13 wt% to 30 wt%.

[0081] It is understood that the adjustment of the ratio of silver and nickel in the conductive paste needs to ensure that the sum of the weight percentages of each component in the conductive paste is 100 wt%. Silver and nickel are used to play a conductive role after the formation of the crystalline silicon solar cell.

[0082] In some embodiments, silver is selected from at least one of silver powder, silver alloy powder, silver oxide, and silver salt. Specifically, silver can be a metal powder, or a mixture directly combining two or more kinds of silver or silver alloy; silver is provided by silver oxide or silver salt, and the silver oxide or silver salt decomposes upon exposure to firing heat to form silver. When the silver powder is silver powder, it should be understood to refer to elemental silver metal, silver alloy powder, silver oxide, silver salt, and their mixtures, and may further include those derived from silver oxide (Ag 2 O or AgO) or silver salts such as AgCl, AgNO 3 , AgOOCCH 3 (silver acetate), AgOOCF 3 (silver trifluoroacetate), Ag 3 PO 4 (silver orthophosphate), or their mixtures. Any other form of conductive metal compatible with other components of the conductive paste can also be used in some embodiments, and other metals used in the paste of the present application for functional conductive materials can be obtained similarly.

[0083] In some embodiments, silver can be provided as finely dispersed particles in the following forms, such as powder form, flake form, spherical form, rod form, granular form, nodular form, layered or coated form, other irregular forms, or their mixtures.

[0084] In some embodiments, the median particle size D v 50 of silver is 1 μm to 3 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the silver powder reaches 50 wt%. Further preferably, the silver used has a median particle size D v 50 of 1 μm to 2.5 μm spherical silver powder; even more preferably, the silver used is spherical silver powder with a median particle size of 1.5 μm to 2.5 μm; even more preferably, the spherical silver powder has a median particle size of 2 μm. The main function of the silver powder is to form a high-density silver body after sintering to provide good conductivity for ohmic contact with the crystalline silicon layer. The spherical silver powder with a median particle size of 2 μm can also inhibit agglomeration and ensure uniform dispersion of the silver powder.

[0085] In some embodiments, nickel is selected from at least one of nickel powder and nickel alloy powder.

[0086] In some embodiments, nickel may be provided as finely dispersed particles having the following forms, such as powder form, flake form, spherical form, rod form, granular form, nodular form, layered or coated form, other irregular forms, or mixtures thereof.

[0087] In some embodiments, nickel is selected from nickel powders, and the D v 50 of which is 1 μm to 5 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the nickel powder reaches 50 wt%. Further preferably, the nickel used is spherical nickel powder with a median particle size D v 50 of 1 μm to 2.5 μm; even more preferably, the nickel used is spherical nickel powder with a median particle size of 2.5 μm to 5 μm; even more preferably, the spherical nickel powder with a median particle size of 2.5 μm.

[0088] In some embodiments, when silver and nickel are in powder form, they can be in coated or uncoated forms; for example, they can be at least partially coated with a surfactant to facilitate processing. Suitable coating surfactants include, for example, stearic acid, palmitic acid, stearates, palmitates, and mixtures thereof. Other surfactants that can also be used include lauric acid, oleic acid, caprylic acid, myristic acid, linoleic acid, and mixtures thereof. Other surfactants that can also be used include polyethylene oxide, polyethylene glycol, benzotriazole, poly(ethylene glycol) acetic acid, and other similar organic molecules. Suitable counter-ions used in the coating surfactant include, but are not limited to, hydrogen, ammonium, sodium, potassium, and mixtures thereof. For example, silver can be coated with a phosphorus-containing compound.

[0089] organic carrier

[0090] In some embodiments, the organic carrier accounts for 9 wt% to 15 wt% of the total solids in the conductive paste. Specifically, the mass percentage of the organic carrier in the total solids of the conductive paste can be any value among 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt% or any value within the range composed of any two of these values.

[0091] In some embodiments, the organic carrier accounts for 11 wt% to 14 wt% of the total solids in the conductive paste. In some other embodiments, it can also be 9 wt% to 12 wt%. It can also further be 12 wt% to 15 wt%.

[0092] In some embodiments, relative to the solid matter composed of silver, nickel, and glass powder, the organic carrier serves as the liquid phase in the conductive paste to disperse the above-mentioned solid matter to form a paste with a certain viscosity. The viscosity and rheology of the paste can not only stably disperse the above-mentioned conductive metal and glass powder therein for a long time, but also enable the conductive paste to be dispersed on the printing screen, and apply the expected pattern on the surface of the first passivation layer of the semiconductor substrate in a screen printing manner.

[0093] In some embodiments, the organic carrier may include a polymer and an organic solvent. The polymer may include cellulose, resin, esters, etc. Cellulose includes cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, benzyl cellulose, propyl cellulose, nitrocellulose, or a mixture thereof. Resin includes wood rosin, phenolic resin, acrylic resin, or a mixture thereof. Esters include polymethacrylates of lower alcohols, etc. The organic solvent may include terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol diacetate, α-terpinene, β-terpinene, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol, etc.

[0094] In some embodiments, the consistency and rheology of the organic carrier make it suitable for printing methods, including but not limited to screen printing. The organic medium may also include other additives such as non-ionic surfactants, thixotropic agents, dispersants, rheological agents, etc. to adapt to organic media with different requirements.

[0095] In some embodiments, the glass powder can be prepared by using methods commonly used in the glass manufacturing field. For example, according to the oxides corresponding to the composition ratio of the glass powder described in the embodiments, ingredients are prepared, mixed, added to a crucible (such as a platinum or ceramic crucible), heated to a peak temperature (for example, 800 °C to 1400 °C), and held for a period of time to melt the oxides together. The molten material can then be quenched in any suitable manner, including but not limited to passing it between reversely rotating stainless steel rollers to form flakes with a thickness of 0.25 mm to 0.50 mm, pouring it onto a thick stainless steel plate, or pouring it into water. Then, the obtained frit is ground by common grinding techniques to form a powder with a particle size of 0.5 μm to 2 μm. Common grinding techniques include, for example, jet milling, ball milling, sand milling, or planetary milling.

[0096] In some embodiments, the preparation method of the conductive paste may include: preparing ingredients according to the components of the conductive paste described in the embodiments, stirring and dispersing, then dispersing and grinding with a three-roll mill to a fineness of less than 10 μm, and then further filtering. Adjusting the ratio of the glass powder, silver, nickel, and organic carrier needs to ensure that the sum of the mass percentages of each component in the conductive paste is 100 wt%.

[0097] In some embodiments of the present application, a conductive electrode 1 is further provided. Refer to Figure 1 , the conductive electrode 1 includes: a semiconductor substrate 10, a first conductive structure 20, and a second conductive structure 30. The semiconductor substrate 10 has a thickness direction X.

[0098] The semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 disposed on the substrate 110, and a first passivation layer 130 disposed on a side of the boron-diffused emitter 120 facing away from the substrate 110. Specifically, the substrate 110 includes a first surface 111 and a second surface 112 oppositely disposed along the thickness direction X. A tunneling layer 140 is disposed on the second surface 112 of the substrate 110. A polysilicon layer 150 is disposed on a side of the tunneling layer 140 facing away from the substrate 110 along the thickness direction X. A second passivation layer 160 is disposed on a side of the polysilicon layer 150 facing away from the substrate 110 along the thickness direction X. The first conductive structure 20 is disposed on a side of the first passivation layer 130 facing away from the boron-diffused emitter 120. The first conductive structure 20 penetrates through the first passivation layer 130 and is electrically connected to the boron-diffused emitter 120. Among them, the first conductive structure 20 is formed by the conductive paste provided by the embodiments of the present application. At least part of the conductive metals (silver and nickel) in the conductive paste penetrate through the first passivation layer 130 and are in electrical contact with a surface of the boron-diffused emitter 120 facing the first passivation layer 130. The first conductive structure 20 is electrically connected to the boron-diffused emitter 120 through the conductive metals (silver and nickel). The first conductive structure 20 is formed by high-temperature sintering of the conductive paste provided by the embodiments of the present application.

[0099] Since the first conductive structure 20 in the conductive electrode 1 is formed by high-temperature sintering of the conductive paste provided by the embodiments of the present application, the glass powder in the conductive paste melts to form a glass melt during high-temperature sintering. The corrosive oxides in the glass melt form etching of the first passivation layer 130. By adjusting the glass transition temperature and high-temperature fluidity of the glass powder through non-corrosive oxides, a low-melting-point glass melt is formed and good fluidity is provided, thereby enabling the corrosive oxides to form etching of the first passivation layer 130, ensuring that the first passivation layer 130 is locally opened during high-temperature sintering, thus ensuring the passivation and antireflection effects of the crystalline silicon solar cell, and moreover, it can delay or even inhibit the oxidation of the nickel surface during high-temperature sintering to form a NiO (nickel oxide) shell, ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0100] In some embodiments, refer to Figure 1 , the conductive electrode 1 further includes a second conductive structure 30, and the semiconductor substrate 10 further includes a tunneling layer 140, a polysilicon layer 150, and a second passivation layer 160.

[0101] The tunneling layer 140 is disposed on the second surface 112 of the substrate 110. The polysilicon layer 150 is disposed on the surface of the tunneling layer 140 facing away from the substrate 110. The second passivation layer 160 is disposed on the surface of the polysilicon layer 150 facing away from the substrate 110 along the thickness direction X. The second conductive structure 30 penetrates through the second passivation layer 160 and is electrically connected to the polysilicon layer 150. Among them, the second conductive structure 30 is formed by high-temperature sintering of commercially available conductive paste.

[0102] In some embodiments, the conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

[0103] In some embodiments, the substrate 110 may be an n-type doped semiconductor substrate, the tunneling layer 140 is an ultra-thin silicon dioxide layer, and the polysilicon layer 150 is an n + polysilicon layer (such as a phosphorus-doped polysilicon layer), the boron-diffused emitter 120 is a p-type doped layer. In an n-TOPCon crystalline silicon solar cell, the p-type doped layer is also called a p-type emitter. The first passivation layer 130 and the second passivation layer 160 respectively include Al 2 O 3 、SiN x O y 、SiN x at least one of them. The first passivation layer 130 and the second passivation layer 160 can also be respectively called an insulating layer or an antireflection layer. The first passivation layer 130 and the second passivation layer 160 respectively play the roles of passivation and antireflection to improve the photoelectric conversion efficiency of the crystalline silicon solar cell. The first passivation layer 130 and the second passivation layer 160 can be deposited by chemical vapor deposition, sputtering or other methods.

[0104] Among them, the substrate 110 is an n-type crystalline silicon bottom sheet, also called an n-type lightly doped substrate, which is an n-TOPCon crystalline silicon solar cell blue film formed by lightly doping and diffusing a phosphorus source on a crystalline silicon wafer. The first surface 111 of the substrate 110 faces the front surface (p surface) of the crystalline silicon solar cell, and the second surface 112 faces the back surface (n surface) of the crystalline silicon solar cell. The front surface refers to the light-receiving surface of the crystalline silicon solar cell and is also the working surface of the crystalline silicon solar cell. The back surface is the back surface of the crystalline silicon solar cell and usually does not directly receive light.

[0105] The boron-diffused emitter 120 is formed by doping a trivalent element in an n-type crystalline silicon bottom sheet using a diffusion method. The trivalent element is boron. The acceptor impurity source for providing boron element can include boron trioxide, boron nitride, trimethyl borate, tripropyl borate, boron tribromide or diborane, etc.

[0106] In some embodiments, nickel is selected from at least one of nickel powder and nickel alloy powder; through the silver-nickel conductive paste and the electrode preparation method of the present application, nickel may be able to directly contact with silicon in the boron-diffused emitter 120 to form a nickel-silicon alloy or nickel silicide.

[0107] The conductive paste provided by the embodiments of the present application can control the oxidizing property and fluidity of the glass melt during the high-temperature sintering process through the composition design of the glass powder, so as to delay or even inhibit the formation of a NiO (nickel oxide) shell on the surface of nickel during the high-temperature sintering process. Furthermore, the nickel in the conductive paste may be alloyed with silicon in the boron-diffused emitter 120 to form a nickel-silicon alloy or nickel silicide, ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell.

[0108] In some embodiments of the present application, a method for preparing a conductive electrode is provided. The preparation method includes the following steps:

[0109] S1. Provide a semiconductor substrate 10, where the semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 disposed on the substrate 110, and a first passivation layer 130 deposited on a side of the boron-diffused emitter 120 facing away from the substrate 110.

[0110] Among them, a tunneling layer 140 and a polysilicon layer 150 are formed on the second surface 112 of the substrate 110 by the tunneling oxidation layer passivation contact method, and a second passivation layer 160 is deposited on the surface of the polysilicon layer 150 by a deposition method. Specifically, a commercially available conductive paste is printed on at least a part of the surface of the second passivation layer 160, and the semiconductor substrate 10 containing the commercially available conductive paste is sintered, and the glass powder in the commercially available conductive paste is etched and penetrates through the second passivation layer 160 during the sintering process. The patterning method can be screen printing.

[0111] S2. Print the conductive paste provided by the embodiments of the present application on at least a part of the surface of the first passivation layer 130, sinter the semiconductor substrate 10 containing the conductive paste, and the glass powder in the conductive paste is etched and penetrates through the first passivation layer 130 during the sintering process, and silver and nickel form a first conductive structure 20.

[0112] Among them, the conductive paste is applied to at least a part of the surface of the first passivation layer 130 along the thickness direction X away from the boron-diffused emitter 120 in a desired patterned form. During the high-temperature sintering process, the glass powder in the conductive paste melts to form a glass melt, and the glass melt dissolves the metal in the conductive paste. Specifically, a small part of nickel may be dissolved by the glass melt, and most of the nickel will not be melted by the glass melt. Mainly, a small part of silver will be dissolved by the glass melt, and the remaining silver powder will be densified during the sintering process. The corrosive oxides in the glass powder form corrosion and etching of the first passivation layer 130 to open and penetrate the first passivation layer 130 in a local range, and form a through hole (not shown in the figure) that penetrates the first passivation layer 130 along the thickness direction X on the first passivation layer 130. The patterning method can be screen printing. It can be understood that the conductive paste involved in this embodiment is used as a fine grid for the front (p-side) of the conductive electrode 1 in a crystalline silicon solar cell. Specifically, it corresponds to the back main grid, back fine grid, front main grid, and front fine grid through a screen printing machine respectively. The conductive paste of this embodiment is used for the front fine grid, usually the fourth front fine grid. After each printing, it will be dried and then the next paste will be printed. The front main grid and the back main grid use commercially available Solamet PVD2L conductive paste, and the back fine grid uses commercially available Solamet PV6NL conductive paste.

[0113] Among them, the sintering process includes a heating process and a cooling process. During the heating process, the glass powder melts to form a glass melt and dissolves part of the conductive metal. During the cooling process, the molten conductive metal precipitates to form the first conductive structure 20.

[0114] S3. A process of optimizing laser-enhanced contact on the semiconductor substrate 10. The first conductive structure 20 forms an electrical connection with the boron-diffused emitter 120 through silver and nickel to obtain the conductive electrode 1.

[0115] Among them, laser-enhanced contact optimization is a method of using laser to improve the electrical contact of the paste during the manufacturing process of crystalline silicon solar cells. The basic principle of the laser-enhanced contact optimization technology is to utilize a large number of carriers generated by the laser, and use a bias voltage to guide these carriers through the formed metallization contact points, and use the heat energy generated by the current to improve the contact effect and uniformity, which can improve the uniformity of the electrical contact, reduce contact defects, and thus improve the photoelectric conversion efficiency and reliability of crystalline silicon solar cells. Through the laser-enhanced contact optimization process, the ohmic contact points of silver-silicon alloy are generated by high current. The preparation method of the conductive electrode provided by the embodiment of the present application can effectively achieve the metallization effect of the conductive electrode 1 in the n-TOPCon crystalline silicon solar cell through screen printing metallization and laser-enhanced contact optimization process, so that the silver and nickel in the first conductive structure 20 may form a direct contact with the silicon in the boron-diffused emitter 120, for example, by forming contact points of nickel-silicon alloy or nickel silicide to provide an ohmic contact with low recombination loss, thereby ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell while reducing the silver usage.

[0116] Among them, the high-temperature sintering in step S2 uses a commercially available Meyer sintering furnace with 18-zone furnace temperature. The commonly used high-temperature sintering environment is oxygen-containing, and the temperature received by the conductive paste during the sintering process usually reaches 700°C to 780°C. In some embodiments, the laser-enhanced contact optimization process for the semiconductor substrate 10 includes: applying a reverse voltage to the semiconductor substrate 10 and simultaneously performing laser scanning on the semiconductor substrate 10 to form an induced current in the first conductive structure 20.

[0117] In some embodiments, the reverse voltage is 5V to 20V. Specifically, the reverse voltage applied to the semiconductor substrate 10 can be any value among 6V, 7V, 9V, 9V, 10V, 11V, 12V, 13V, 14V, 15V, 16V, 17V, 18V, 19V, 20V or any value within the range value composed of any two of these values.

[0118] In some embodiments, the laser scanning time is 1ms to 100ms. Specifically, the laser scanning time for the semiconductor substrate 10 can be any value among 1ms, 5ms, 10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 70ms, 80ms, 90ms, 100ms or any value within the range value composed of any two of these values. Processing the first conductive structure 20 using the laser-enhanced contact optimization technology can reduce the contact resistance, which is more conducive to the increase of the open-circuit voltage and the improvement of the efficiency.

[0119] Some embodiments of the present application further provide a crystalline silicon solar cell, which includes the conductive electrode 1 as described above, or the crystalline silicon solar cell includes the conductive electrode 1 prepared by the preparation method of the conductive electrode as described above.

[0120] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0121] As shown in Table 1, Examples 1 to 16 are the component compositions of the glass powder in the conductive paste provided by the embodiments of the present application. In the glass powder provided by Comparative Example 1, the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 +Al 2 O 3 ) exceeds the upper limit value of 0.7 to 2.6 defined by the embodiments of the present application. In the glass powder provided by Comparative Example 4, the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 +Al 2 O 3 ) is lower than the lower limit value of 0.7 to 2.6 defined by the embodiments of the present application. In the glass powders provided by Comparative Examples 2 and 3, TeO 2 , TeO 2 that do not exist in the glass powder provided by the embodiments of the present application are respectively added. TeO 2 , TeO 2 can significantly increase the fluidity of the glass, which will accelerate the oxidation of Ni to form a NiO shell and thus lead to a loss of battery efficiency.

[0122] Table 1

[0123]

[0124] As shown in Table 2, Examples 17 to 47 in Table 2 are the component compositions of the conductive paste provided by the embodiments of the present application. Among them, the conductive pastes provided in Examples 17 to 32 respectively use the glass powders provided in Examples 1 to 16. The conductive pastes provided in Examples 33 to 47 all use the glass powder provided in Example 1, but the percentage of the glass powder in the total weight of the conductive paste is different. The conductive paste provided by Comparative Example 5 is an existing conductive paste without adding nickel powder. The conductive pastes provided by Comparative Examples 6 to 10 respectively use the glass powders provided by Comparative Examples 1 to 4.

[0125] Table 2

[0126]

[0127]

[0128] Among them, as shown in Table 1, the glass powder needs to etch the first passivation layer 130 sufficiently so that the conductive metal in the conductive paste forms an ohmic electrical contact with the boron-diffused emitter 120. The corrosiveness or etching ability of the glass powder depends on the content of corrosive oxides (PbO and Bi 2 O 3 ) and non-corrosive oxides (SiO 2 and Al 2 O 3 ) in the glass powder, as well as the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ). The higher the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) is, the stronger the corrosiveness of the glass powder. The addition amount of the glass powder in the conductive paste shown in Table 2 needs to be low to avoid over-etching of the first passivation layer 130. Conversely, the lower the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) is, the weaker the corrosiveness and fluidity of the glass powder. The addition amount of the glass powder in the conductive paste shown in Table 2 needs to be increased correspondingly to meet the etching requirement for the first passivation layer 130. As shown in Table 2, Examples 17 to 47 are designed for the corrosiveness of the glass powder corresponding to different conductive paste components, and then the addition amount of the glass powder in the conductive paste is adjusted correspondingly.

[0129] In addition, referring to Examples 33 to 47, the addition amount of nickel in the conductive paste provided in Examples 33 to 47 is increased from 1.0 wt% to 30.0 wt%, which in turn causes the addition amount of silver in the conductive paste to decrease from 88.3 wt% to 57.0 wt%. That is, the amount of silver used in the conductive paste is significantly reduced. Therefore, the addition amount of the glass powder in the conductive paste is increased from 1.2 wt% to 4.0 wt% to compensate for the etching ability required for the first passivation layer 130 by the conductive paste.

[0130] As shown in Table 3, the IV test results of crystalline silicon solar cells including the conductive electrodes 1 prepared by using the conductive pastes provided in Examples 17 to 47 are shown in Examples 48 to 78 in Table 3. Among them, Examples 48 to 63 show the IV test result examples of crystalline silicon solar cells including the conductive electrodes 1 prepared by using the conductive pastes provided in Examples 17 to 32 when the nickel content in the conductive paste is the same (both 3 wt%). Examples 64 to 78 show the IV test result examples of crystalline silicon solar cells including the conductive electrodes 1 prepared by using the conductive pastes provided in Examples 33 to 47 when the nickel content in the conductive paste increases (from 1.0 wt% to 30.0 wt%). Comparative Example 10 shows the IV test result example of a crystalline silicon solar cell including the conductive electrode prepared by using the conductive paste provided in Comparative Example 5. The conductive paste provided in Comparative Example 5 does not contain nickel. Comparative Examples 11 to 14 show the IV test result examples of crystalline silicon solar cells including the conductive electrodes 1 prepared by using the conductive pastes provided in Comparative Examples 6 to 9. The conductive pastes provided in Comparative Examples 6 to 9 respectively use the glass powder provided in Examples 1 to 4, and nickel is added to the conductive pastes provided in Comparative Examples 6 to 9.

[0131] Among them, the method for preparing the conductive electrode by using the conductive pastes provided in Examples 17 to 47 and Comparative Examples 5 to 9 is as follows:

[0132] S1. Provide a crystalline silicon blue film (i.e., semiconductor substrate 10) of the conductive electrode in a TOPCon crystalline silicon solar cell. The semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 provided on the first surface 111 of the substrate 110, and a first passivation layer 130 deposited on the side of the boron-diffused emitter 120 facing away from the substrate 110. A tunneling layer 140 and a polysilicon layer 150 are formed on the second surface 112 of the substrate 110 by the tunneling oxidation layer passivation contact method, and a second passivation layer 160 is deposited on the surface of the polysilicon layer 150 by the deposition method;

[0133] S2. Print the conductive pastes provided in Examples 17 to 47 and Comparative Examples 5 to 9 respectively on at least a part of the surface of the first passivation layer 130, sinter the semiconductor substrate 10 containing the conductive paste, and etch and penetrate the first passivation layer 130 with the glass powder in the conductive paste during sintering. Among them, the conductive paste is applied to at least a part of the surface of the first passivation layer 130 along the thickness direction X away from the boron-diffused emitter 120 in the form of screen printing. During the high-temperature sintering process, the glass powder in the conductive paste melts to form a glass melt, the glass melt dissolves the metal in the conductive paste, and the corrosive oxides in the glass powder form corrosion and etching of the first passivation layer 130 to open and penetrate the first passivation layer 130 in a local range, and form a through hole penetrating the first passivation layer 130 along the thickness direction X on the first passivation layer 130, and silver and nickel form the first conductive structure 20.

[0134] Among them, the conductive pastes provided in Examples 17 to 47 and Comparative Examples 5 to 9 are respectively applied as the front (p-side) fine grids of the conductive electrodes 1 in crystalline silicon solar cells. Specifically, the metallization process of crystalline silicon solar cells requires 4 screen printings by a screen printing machine, and these 4 screen printings respectively correspond to the formation of the back main grid, back fine grid, front main grid and front fine grid. The conductive pastes provided in Examples 17 to 47 and Comparative Examples 5 to 9 are used for the front fine grid, usually the fourth front fine grid. After each printing, drying is carried out and then the next paste is printed. The front main grid and back main grid respectively use commercially available Solamet PVD2L conductive paste, and the back fine grid uses commercially available Solamet PV6NL conductive paste.

[0135] The first passivation layer 130 and the second passivation layer 160 generally include SiN x 、SiN x O y 、Al 2 O 3 at least one of them.

[0136] S3. Perform the process of laser-enhanced contact optimization on the semiconductor substrate 10. The first conductive structure 20 forms an electrical connection with the boron-diffused emitter 120 through silver and nickel to obtain the conductive electrode 1.

[0137] Examples 48 to 78 are the IV test results of crystalline silicon solar cells containing the conductive electrodes 1 prepared by using the conductive pastes provided in Examples 17 to 47 respectively, and Comparative Examples 10 to 14 are the IV test results of crystalline silicon solar cells containing the conductive electrodes prepared by using the conductive pastes provided in Comparative Examples 5 to 9 respectively. Among them, the method for obtaining the IV test results is as follows:

[0138] Using a commercially available IV tester, i.e., a Current-Voltage tester, IV tests were conducted on crystalline silicon solar cells containing the conductive electrodes prepared in Comparative Examples 10 to 14, and IV tests were separately conducted on crystalline silicon solar cells containing the conductive electrode 1 prepared in Examples 50 to 82 using a commercially available IV tester. The IV test items include: photoelectric conversion efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), and short-circuit current (Isc).

[0139] Based on the IV test results of the crystalline silicon solar cell containing the conductive electrode prepared in Comparative Example 10, that is, based on the photoelectric conversion efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), and short-circuit current (Isc) of the crystalline silicon solar cell containing the conductive electrode prepared in Comparative Example 10, the IV test results of the crystalline silicon solar cells containing the conductive electrode 1 prepared in Examples 48 to 78, and the IV test results of the crystalline silicon solar cells containing the conductive electrodes prepared in Comparative Examples 11 to 14 were respectively subjected to a difference operation with the IV test results of the crystalline silicon solar cell containing the conductive electrode prepared in Comparative Example 10.

[0140] Specifically, the photoelectric conversion efficiency (Eff) values, short-circuit current (Isc) values, open-circuit voltage (Voc) values, and fill factor (FF) obtained from the IV tests of the crystalline silicon solar cells containing the conductive electrode 1 prepared in Examples 48 to 78, and the photoelectric conversion efficiency (Eff) values, short-circuit current (Isc) values, open-circuit voltage (Voc) values, and fill factor (FF) obtained from the IV tests of the crystalline silicon solar cells containing the conductive electrodes prepared in Comparative Examples 11 to 14 were respectively subjected to a difference operation with the photoelectric conversion efficiency (Eff) values, short-circuit current (Isc) values, open-circuit voltage (Voc) values, and fill factor (FF) obtained from the IV tests of the crystalline silicon solar cell containing the conductive electrode 1 prepared in Comparative Example 10, that is, the ΔEff values, ΔIsc values, ΔVoc values, and ΔFF values of the IV tests of the crystalline silicon solar cells containing the conductive electrode 1 prepared in Examples 48 to 78, and the ΔEff values, Δisc values, ΔVoc values, and ΔFF values of the IV tests of the crystalline silicon solar cells containing the conductive electrodes prepared in Comparative Examples 11 to 14 were obtained, and the obtained results are shown in Table 3.

[0141] Table 3

[0142]

[0143]

[0144] As shown in Table 3, the crystalline silicon solar cell provided in Example 48 contains the conductive paste provided in Example 17, and the conductive paste provided in Example 17 contains 1.6 wt% of glass powder provided in Example 1. Compared with the crystalline silicon solar cell provided in Comparative Example 10, the difference in the crystalline silicon solar cell provided in Example 48 is that the glass powder of the conductive paste used to prepare the conductive electrode 1 contains 3 wt% of nickel, thereby achieving the gain of the open-circuit voltage Voc and the fill factor FF of the crystalline silicon solar cell provided in Example 48. The effect after adding nickel to the paste is significantly better than that of the all-silver paste. The applicant believes that this is because a low-recombination Ohmic contact structure, such as nickel-silver alloy or nickel silicide, is formed after the laser-enhanced contact optimization technology.

[0145] Similarly, for the crystalline silicon solar cells provided in Examples 49 to 78, the conductive pastes used to prepare the conductive electrode 1 respectively adopt glass powders with different contents, and different contents of nickel are respectively used in the conductive pastes. Compared with the all-silver paste used for the conductive paste to prepare the conductive electrode 1 in the crystalline silicon solar cell provided in Comparative Example 10, there is a gain in the open-circuit voltage Voc or the photoelectric conversion efficiency Eff.

[0146] In addition, the molar ratio of the corrosive oxide to the non-corrosive oxide in the glass powder provided in Examples 1 to 16 ((PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) ranges from 0.7 to 2.6, so as to ensure that the glass powder has sufficient corrosiveness to open the first passivation layer provided on the boron-diffused emitter at high-temperature sintering, and can balance the oxidizing property and fluidity of the glass powder to inhibit or delay the formation of the nickel oxide shell on the surface of the nickel powder, and further match the laser-enhanced contact post-treatment process to ensure the photoelectric conversion efficiency of the crystalline silicon solar cells provided in Examples 48 to 78.

[0147] The crystalline silicon solar cell provided in Comparative Example 11 contains the conductive paste provided in Comparative Example 6, and the conductive paste provided in Comparative Example 6 contains the glass powder provided in Comparative Example 1. The ratio of (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) in the glass powder provided in Comparative Example 1 exceeds the upper limit value of 0.7 to 2.6 defined in the examples of the present application. The corrosiveness of the glass powder is too strong, and the damage to the first passivation layer 130 is too high, resulting in the loss of the open-circuit voltage Voc and the photoelectric conversion efficiency Eff.

[0148] The crystalline silicon solar cells provided in Comparative Examples 12 and 13 respectively contain the conductive pastes provided in Comparative Examples 7 and 8, and the conductive pastes provided in Comparative Examples 7 and 8 respectively contain the glass powders provided in Comparative Examples 2 and 3. TeO is added to the glass powders provided in Comparative Examples 2 and 3 respectively. 2 , TeO 2 can enhance the fluidity and wettability of the glass melt formed during the sintering process of the glass powder, accelerate the formation of the NiO shell, significantly affect the contact performance, and cause a loss in the fill factor FF of the crystalline silicon solar cells provided in Comparative Examples 12 and 13. The content of TeO in the glass powder provided in Comparative Example 3 2 is higher than that in Comparative Example 2, so its influence on the fill factor FF of the crystalline silicon solar cell provided in Comparative Example 13 is more serious.

[0149] The crystalline silicon solar cell provided in Comparative Example 14 contains the conductive paste provided in Comparative Example 9, and the conductive paste provided in Comparative Example 9 contains the glass powder provided in Comparative Example 4. In the glass powder provided in Comparative Example 4, the ratio of (PbO + Bi 2 O 3 ) / (SiO 2 + Al 2 O 3 ) is lower than the lower limit value of 0.7 - 2.6 defined in the embodiments of the present application. That is, the addition amount of non-corrosive oxides (SiO 2 and Al 2 O 3 ) in the glass powder provided in Comparative Example 4 is too high, resulting in too weak corrosion of the glass powder, and further causing a significant loss in the fill factor FF of the crystalline silicon solar cell provided in Comparative Example 14.

[0150] In the above embodiments, the descriptions of each embodiment have their own focuses. For parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0151] The conductive paste, conductive electrode and their preparation methods, and crystalline silicon solar cells provided in the embodiments of the present application have been introduced in detail above, and specific examples have been used to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of the present application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A conductive paste, characterized in that: include: Glass powder, accounting for 1wt% to 4wt% of the total weight of the conductive paste; Silver, accounting for 57wt% to 89wt% of the total weight of the conductive paste; Nickel, accounting for 1wt% to 30wt% of the total weight of the conductive paste; and The rest is an organic carrier, accounting for 9wt% to 15wt% of the total weight of the conductive paste; Based on the mole percentage of the glass powder, the glass powder includes 24 mol% to 50 mol% of B2O3, 24 mol% to 44 mol% of corrosive oxides, and 13 mol% to 46 mol% of non-corrosive oxides; The molar ratio of the corrosive oxide to the non-corrosive oxide is in the range of 0.7 to 2.

6.

2. The conductive paste according to claim 1, characterized in that: The corrosive oxide is selected from at least one of PbO and Bi2O3.

3. The conductive paste according to claim 1, characterized in that: The non-corrosive oxide is selected from at least one of SiO2 and Al2O3.

4. The conductive paste according to claim 1, characterized in that: The glass frit further includes 0 mol % to 10 mol % of a functional oxide.

5. The conductive paste according to claim 4, characterized in that: The functional oxide is selected from at least one of Fe2O3, TiO2, ZnO and BaO.

6. The conductive paste according to claim 1, characterized in that: Silver is selected from at least one of silver powder, silver alloy powder, silver oxide and silver salt.

7. The conductive paste according to claim 1, characterized in that: Silver is selected from silver powder, wherein D v 50 is 1μm~3μm, D v 50 is the particle size corresponding to when the cumulative volume percentage of the silver powder reaches 50wt%.

8. The conductive paste according to claim 1, characterized in that: Nickel is selected from at least one of nickel powder and nickel alloy powder.

9. The conductive paste according to claim 1, characterized in that: Nickel is selected from nickel powder, wherein D v 50 is 1μm~5μm, D v 50 is the particle size corresponding to when the cumulative volume percentage of the nickel powder reaches 50wt%.

10. A conductive electrode, characterized in that: include: A semiconductor substrate (10) comprises a substrate (110), a boron diffused emitter (120) disposed on the substrate (110), and a first passivation layer (130) disposed on a side of the boron diffused emitter (120) facing away from the substrate (110); A first conductive structure (20) is arranged on a side of the first passivation layer (130) away from the boron diffused emitter (120), the first conductive structure (20) penetrates the first passivation layer (130) and is electrically connected to the boron diffused emitter (120); Wherein, the first conductive structure (20) is formed by the conductive paste according to any one of claims 1 to 9.

11. The conductive electrode according to claim 10, characterized in that The conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

12. A method for preparing a conductive electrode, characterized in that: The preparation method comprises the following steps: A semiconductor substrate (10) is provided, wherein the semiconductor substrate (10) comprises a substrate (110), a boron diffused emitter (120) disposed on the substrate (110), and a first passivation layer (130) deposited on a side of the boron diffused emitter (120) facing away from the substrate (110); Printing the conductive paste according to any one of claims 1 to 9 on at least a portion of the surface of the first passivation layer (130); Sintering the semiconductor substrate (10) containing the conductive paste, and allowing the glass powder in the conductive paste to etch and penetrate the first passivation layer (130) during the sintering process, so that silver and nickel form a first conductive structure (20); The semiconductor substrate (10) is subjected to a laser enhanced contact optimization process, wherein the first conductive structure (20) is electrically connected to the boron diffused emitter (120) via silver and nickel to obtain the conductive electrode.

13. The method for preparing a conductive electrode according to claim 12, characterized in that: The step of printing the conductive paste on at least a portion of the surface of the first passivation layer (130) comprises: The conductive paste is printed on at least a portion of the surface of the first passivation layer (130) in a patterned manner.

14. The method for preparing a conductive electrode according to claim 12, characterized in that: The process of performing laser enhanced contact optimization on the semiconductor substrate (10) comprises: A reverse voltage is applied to the semiconductor substrate (10), and a laser is simultaneously scanned on the semiconductor substrate (10) to form an induced current in the first conductive structure (20).

15. The method for preparing a conductive electrode according to claim 14, characterized in that: The process of performing laser enhanced contact optimization on the semiconductor substrate (10) satisfies at least one of the following conditions: a) the reverse voltage is 5V to 20V; b) The laser scanning time is 1 ms to 100 ms.

16. A crystalline silicon solar cell, characterized in that: The crystalline silicon solar cell comprises the conductive electrode according to any one of claims 10 to 11, or the crystalline silicon solar cell comprises the conductive electrode prepared by the method for preparing a conductive electrode according to any one of claims 12 to 15.

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