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

Abstract

The invention discloses a conductive paste, a conductive electrode, a crystalline silicon solar cell and a preparation method thereof, and belongs to the technical field of photovoltaic cells, the conductive paste comprises lead-free Bi-B-Si-Al-Fe-O glass powder, conductive metal and an organic carrier, lead is not added in the glass powder, Bi2O3 can form etching on a first passivation layer, and the conductive metal can form etching on a second passivation layer. B2O3 and SiO2 are used for adjusting the glass transition temperature and the high-temperature fluidity of the glass powder, Al2O3 and Fe2O3 can modify the glass stability of the glass powder, and Bi2O3 / B2O3 is limited to be larger than or equal to 0.27 and smaller than or equal to 0.86, so that the glass transition temperature of the glass powder is adjusted and the high-temperature fluidity of the glass powder is guaranteed while the etching effect of a glass melt on the first passivation layer is guaranteed, and the glass stability of the glass powder is improved. The stability of ohmic electric contact between the conductive metal in the conductive paste and the boron diffusion emitter is ensured, the photoelectric conversion efficiency of the conductive electrode is ensured under the condition that no lead element is added, and the harm to human bodies and the environment is reduced.

Description

Technical Field

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

[0002] In crystalline silicon solar cells, PbO (lead oxide) is recognized as one of the important components of glass powder. The corrosiveness of PbO can provide an etching of the passivation layer structure on the surface of crystalline silicon solar cells to form ohmic electrical contacts. However, lead and its compounds are highly toxic, posing a threat to human health and environmental safety. If lead-free glass powder is used, it will affect the etching effect on the passivation layer structure, thereby affecting the photoelectric conversion efficiency of crystalline silicon solar cells. Summary of the Invention

[0003] Embodiments of this application provide a conductive paste, conductive electrodes, crystalline silicon solar cells and their preparation methods to solve the problem of reduced photoelectric conversion efficiency caused by the use of lead-free glass powder in existing crystalline silicon solar cells.

[0004] In a first aspect of 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; conductive metal, accounting for 84 wt% to 91 wt% of the total weight of the conductive paste; and an organic carrier, accounting for 8 wt% to 12 wt% of the total weight of the conductive paste; based on the molar percentage of the glass powder, the glass powder includes 35 mol% to 55 mol% of B2O3, 15 mol% to 30 mol% of Bi2O3, 2 mol% to 30 mol% of SiO2, 5 mol% to 25 mol% of Al2O3, and 2 mol% to 10 mol% of Fe2O3; wherein, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0005] Optionally, the glass powder further includes 0 mol% to 10 mol% of glass modifiers.

[0006] Optionally, the glass modifiers are selected from at least one of Li2O, Na2O, Ag2O, and BaO.

[0007] Optionally, the conductive metal includes silver, and the silver is selected from at least one of silver powder, silver alloy powder, silver oxide, and silver salt.

[0008] Optionally, the conductive metal further includes aluminum, and the aluminum accounts for 0 to 0.5 wt% of the total weight of the conductive paste; the aluminum is selected from aluminum powder, and the D v 50 of the aluminum powder is 1 μm to 2 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the aluminum powder reaches 50 wt%.

[0009] In a second aspect of the embodiments of the present application, a conductive electrode is provided, comprising: a semiconductor substrate including a substrate, a boron-diffused emitter disposed on the substrate, and a first passivation layer disposed on a side of the boron-diffused emitter facing away from the substrate; a first conductive structure disposed 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, and the first conductive structure is electrically connected to the boron-diffused emitter through the conductive metal.

[0010] Optionally, the conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

[0011] In a third aspect of the embodiments of the present application, a crystalline silicon solar cell is provided, and the crystalline silicon solar cell includes the conductive electrode as described above.

[0012] In a fourth aspect of the embodiments of the present application, a method for manufacturing a crystalline silicon solar cell is provided, and the manufacturing method includes the following steps:

[0013] Provide a semiconductor substrate, the semiconductor substrate including a substrate, a boron-diffused emitter disposed on a first surface of the substrate, and a first passivation layer deposited on a side of the boron-diffused emitter facing away from the substrate; the semiconductor substrate further includes a tunneling layer disposed on a second surface of the substrate, a phosphorus-diffused polysilicon layer disposed on a side of the tunneling layer facing away from the substrate, and a second passivation layer deposited on a side of the phosphorus-diffused polysilicon layer facing away from the tunneling layer;

[0014] Print the conductive paste as described above on at least a part of the surface of the first passivation layer;

[0015] Sinter the semiconductor substrate containing the conductive paste so that the glass powder in the conductive paste is etched and penetrates through the first passivation layer during the sintering process, and 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 the conductive metal to obtain the crystalline silicon solar cell.

[0016] 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.

[0017] Optionally, the process of performing laser enhanced contact optimization on 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 in the first conductive structure.

[0018] Optionally, the process of optimizing the laser enhanced contact on the semiconductor substrate satisfies at least one of the following conditions:

[0019] a) The reverse voltage is 5V to 20V;

[0020] b) The time of laser scanning is 1ms to 100ms.

[0021] Beneficial effects: The embodiments of the present application provide a conductive paste, a conductive electrode, a crystalline silicon solar cell and a preparation method thereof. The conductive paste includes glass powder, conductive metal and organic carrier. The glass powder includes B2O3, Bi2O3, SiO2, Al2O3 and Fe2O3. No lead is added to the glass powder to form a lead-free Bi-B-Si-Al-Fe-O glass powder. Bi2O3 can form etching of the first passivation layer on the boron-diffused emitter during the sintering process of the conductive paste. B2O3 and SiO2 are the main glass formers to adjust the glass transition temperature and high-temperature fluidity of the glass powder. Al2O3 and Fe2O3 are used as intermediates to modify the glass stability of the glass powder, and 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86 is defined. Bi2O3 is used to replace traditional PbO in the glass powder. While ensuring the etching effect of the glass melt on the first passivation layer, the glass transition temperature of the glass powder is adjusted and the high-temperature fluidity of the glass powder is ensured. Furthermore, the stability of the ohmic contact between the conductive metal in the conductive paste and the boron-diffused emitter is ensured. Furthermore, without adding lead elements, the photoelectric conversion efficiency of the conductive electrode in the crystalline silicon solar cell is ensured, and the prepared conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment, and is also convenient for recycling.

[0022] It can be understood that the conductive electrode, the crystalline silicon solar cell and the preparation method thereof 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

[0023] 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 following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic structural diagram of the conductive electrode provided by the embodiment of the present application;

[0025] Figure 2 It is a schematic structural diagram of the crystalline silicon solar cell provided by the embodiment of the present application.

[0026] Reference Signs:

[0027] 1. Crystalline silicon solar cell

[0028] 10. Semiconductor substrate, 110. Substrate, 111. First surface, 112. Second surface, 120. Boron-diffused emitter, 130. First passivation layer, 140. Tunneling layer, 150. Phosphorus-diffused polysilicon layer, 160. Second passivation layer

[0029] 20. First conductive structure

[0030] 30. Second conductive structure

[0031] X. Thickness direction Detailed implementation manners

[0032] 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 belong to the scope of protection of the present application

[0033] 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 therefore should not be construed as a limitation of the present application. In the description of the present application, the meaning of "a plurality" is two or more, and at least one means one, two or more, unless otherwise specifically limited

[0034] An important technological breakthrough of crystalline silicon solar cells is the use of the back passivated contact structure of TOPCon (Tunnel Oxide Passivated Contacts), which significantly improves the open circuit voltage (Voc) and cell efficiency of crystalline silicon solar cells. When preparing crystalline silicon solar cells, it is necessary to metallize the front (light-facing) side of the crystalline silicon solar cell. The metallization of the front conductive electrode (light-facing side) is usually performed by screen printing to print the conductive paste on the surface of the passivation layer in the desired pattern, and then sintering at high temperature to etch and penetrate the passivation layer of the conductive metal paste, and then form electrical contact with the emitter, thereby forming a conductive structure (or electrode) in the form of a conductive metal contact. The electrical contact quality of the conductive structure includes electrical contact resistance and carrier recombination caused by metallization, which directly affects the photoelectric conversion efficiency of the crystalline silicon solar cell. The conductive paste commonly used to form electrodes includes conductive metals (e.g., silver particles), glass materials, and organic carriers used as printing carriers.

[0035] In order to make the conductive paste form a good electrical contact with the emitter and balance the carrier recombination, the conductive paste needs to control the etching degree of the passivation layer at a reasonable level during high-temperature sintering. If the etching degree is insufficient, the passivation layer cannot be penetrated, so that the conductive paste cannot form an ohmic electrical contact with the emitter. If the etching degree is too large, the carrier recombination is greatly increased due to excessive etching, which will lead to a loss of the battery open circuit voltage Voc, and thus affect the photoelectric conversion efficiency.

[0036] As one of the important components of the conductive paste, the main function of the glass powder is to etch the passivation layer. Therefore, the composition of the glass powder will directly affect the photoelectric conversion efficiency of the metallized crystalline silicon solar cell.

[0037] Glass powder containing PbO is usually used in conductive pastes. In the field of metallized conductive pastes, PbO is recognized as one of the important components of glass powder, because glass powder containing PbO has an excellent glass forming window, good high-temperature fluidity and corrosiveness, and can provide a passivation layer structure for etching the surface of crystalline silicon solar cells, thereby enabling the conductive metal to form an ohmic electrical contact with the emitter. However, the toxicity of lead and lead compounds is well known, and its large-scale and widespread application in photovoltaics is a potential environmental problem.

[0038] Based on this, it is necessary to provide a conductive paste, a conductive electrode, a crystalline silicon solar cell and a preparation method thereof, which can ensure the stability of the ohmic electrical contact between the conductive metal in the conductive paste and the boron-diffused emitter of the conductive electrode, ensure the photoelectric conversion efficiency of the conductive electrode in the crystalline silicon solar cell without adding lead elements, and the prepared conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment, and is also convenient for recycling.

[0039] 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; conductive metal, accounting for 84 wt% to 91 wt% of the total weight of the conductive paste; and an organic carrier, accounting for 8 wt% to 12 wt% of the total weight of the conductive paste; based on the molar percentage of the glass powder, the glass powder includes 35 mol% to 55 mol% of B2O3, 15 mol% to 30 mol% of Bi2O3, 2 mol% to 30 mol% of SiO2, 5 mol% to 25 mol% of Al2O3 and 2 mol% to 10 mol% of Fe2O3; wherein, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0040] The glass powder and the conductive metal are solid components in the conductive paste; the organic carrier is a dispersed phase in the conductive paste and provides printing performance, including one or more components such as polymers, surfactants, thickeners, thixotropic agents, and adhesives that can endow functional properties. The sum of the weight percentages of each component in the conductive paste is 100%.

[0041] Each component in the conductive paste is described separately below.

[0042] glass powder

[0043] 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.

[0044] 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 values.

[0045] In some other embodiments, the mass percentage of the glass powder in the total weight of the conductive paste is 1.8 wt% to 2.2 wt%, and it can also be 1 wt% to 1.8 wt%; it can further be 2 wt% to 4 wt%; it can further be 2.2 wt% to 4 wt%.

[0046] 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%. The composition of the glass powder directly affects its fusibility, fluidity, and etchability. Therefore, the composition of the glass powder requires a good balance to achieve an excellent carrier recombination effect.

[0047] In some embodiments, based on the mole percentage of the glass powder, the glass powder includes 35 mol% to 55 mol% of B2O3, 15 mol% to 30 mol% of Bi2O3, 2 mol% to 30 mol% of SiO2, 5 mol% to 25 mol% of Al2O3, and 2 mol% to 10 mol% of Fe2O3.

[0048] Among them, the mole percentage of B2O3 in the glass powder can be any value among 35 mol%, 37 mol%, 39 mol%, 41 mol%, 43 mol%, 45 mol%, 47 mol%, 49 mol%, 51 mol%, 53 mol%, 55 mol% or any value within the range formed by any two of these values. The mole percentage of Bi2O3 can be any value among 15 mol%, 17 mol%, 19 mol%, 21 mol%, 23 mol%, 25 mol%, 27 mol%, 29 mol%, 30 mol% or any value within the range formed by any two of these values. The mole percentage of SiO2 can be any value among 2 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol% or any value within the range formed by any two of these values. The mole percentage of Al2O3 can be any value among 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol% or any value within the range formed by any two of these values. The mole percentage of Fe2O3 can be any value among 2 mol%, 4 mol%, 6 mol%, 8 mol%, 10 mol% or any value within the range formed by any two of these values.

[0049] In some embodiments, based on the mole percentage of the glass powder, the glass powder includes 35 mol% to 40 mol% of B2O3, 15 mol% to 22 mol% of Bi2O3, 2 mol% to 15 mol% of SiO2, 5 mol% to 15 mol% of Al2O3, and 2 mol% to 6 mol% of Fe2O3.

[0050] In some embodiments, based on the molar percentage of the glass powder, the glass powder comprises 40 mol% to 55 mol% of B2O3, 22 mol% to 30 mol% of Bi2O3, 15 mol% to 30 mol% of SiO2, 15 mol% to 25 mol% of Al2O3, and 6 mol% to 10 mol% of Fe2O3.

[0051] In some embodiments, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86. Specifically, the value of Bi2O3 / B2O3 can be any value among 0.27, 0.31, 0.35, 0.4, 0.45, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.86 or any value within the range formed by any two of these values.

[0052] In some embodiments, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.68.

[0053] In some embodiments, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.68 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0054] Although the glass powder containing PbO has a better etching effect on the passivation layer structure, the toxicity of lead and lead compounds makes the demand for lead-free conductive pastes urgent. Compared with the conductive paste containing PbO, the etching effect of the lead-free conductive paste on the passivation layer becomes weaker, and it will affect the photoelectric conversion efficiency of crystalline silicon solar cells. Especially for n-TOPCon crystalline silicon solar cells, since both the front conductive paste and the back conductive paste use lead-containing glass powder, the lead content in each conductive electrode is also significantly increased, affecting human health and the safety of the use environment.

[0055] The conductive paste provided by the embodiments of the present application comprises a glass powder, a conductive metal, and an organic carrier. The glass powder comprises B2O3, Bi2O3, SiO2, Al2O3, and Fe2O3. No lead is added to the glass powder to form a lead-free Bi-B-Si-Al-Fe-O glass powder. The glass powder comprises 35 mol% to 55 mol% of B2O3, 15 mol% to 30 mol% of Bi2O3, 2 mol% to 30 mol% of SiO2, 5 mol% to 25 mol% of Al2O3, and 2 mol% to 10 mol% of Fe2O3; and the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0056] Among them, Bi2O3 is a glass intermediate with corrosiveness, but the corrosiveness of Bi2O3 is weaker than that of PbO. Bi2O3 is used to adjust the etching ability of the glass melt formed during the high-temperature sintering of the glass powder on the first passivation layer. Similarly, too much Bi2O3 will etch too much of the first passivation layer, affecting the passivation and antireflection effects of the crystalline silicon solar cell, and further affecting the photoelectric conversion efficiency of the crystalline silicon solar cell. In addition, since the corrosiveness of PbO is stronger than that of Bi2O3, replacing PbO with Bi2O3 in the composition of the glass powder can ensure the etching effect on the first passivation layer while achieving the effect of low carrier recombination, thereby improving the open-circuit voltage and photoelectric conversion efficiency of the crystalline silicon solar cell. Moreover, the toxicity brought by lead and its compounds is removed, which is beneficial to human health and environmental safety and is conducive to the recycling of crystalline silicon solar cells.

[0057] B2O3 is the main glass former used to adjust the glass transition temperature and high-temperature fluidity of the glass powder. B2O3 can form a low-melting-point glass melt and provide good fluidity. SiO2 is a glass former used to adjust the glass transition temperature and high-temperature fluidity of the glass powder and to adjust the time required for the glass powder to form a glass melt during the high-temperature sintering process, so that Bi2O3 can etch the first passivation layer within the desired time, ensuring the etching effect on the first passivation layer, thereby locally opening the first passivation layer, and further ensuring the stability of the ohmic contact between the conductive metal in the conductive paste and the boron-diffused emitter. Without adding lead elements, the passivation effect of the crystalline silicon solar cell is ensured, and thus the photoelectric conversion efficiency of the crystalline silicon solar cell is ensured.

[0058] As intermediates, Al2O3 and Fe2O3 can modify the glass stability of the glass powder, adjust the glass transition temperature Tg and high-temperature fluidity of the glass powder, and adjust the time required for the glass powder to form a glass melt during the high-temperature sintering process.

[0059] In addition, in the glass powder of the glass paste provided by the embodiments of the present application, the molar ratio range of Bi2O3 to B2O3 is limited to satisfy: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86. Using Bi2O3 to replace traditional PbO, the combination of B2O3 and SiO2 can adjust the glass transition temperature and high-temperature fluidity of the glass powder, form a low-melting-point glass melt and provide appropriate fluidity, so that Bi2O3 can etch the first passivation layer within the desired time, ensuring that the first passivation layer is locally opened during the high-temperature sintering process, thereby ensuring the passivation effect of the crystalline silicon solar cell. Without adding lead elements to the glass powder, the photoelectric conversion efficiency of the crystalline silicon solar cell is ensured, and the made conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment and is also convenient for recycling.

[0060] In some embodiments, the glass powder further comprises 0 mol% to 10 mol% of a glass modifier. Specifically, the molar percentage of the glass modifier 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 glass modifier can improve the softening temperature, fluidity, and corrosiveness of the glass melt formed during the sintering process of the glass powder.

[0061] In some embodiments, the glass modifier is selected from at least one of Li2O, Na2O, Ag2O, and BaO.

[0062] conductive metal

[0063] In some embodiments, the conductive metal serves as the current source of the conductive paste and can be used without particular limitation as the metal powder commonly used in electrodes formed on circuit boards such as semiconductor substrates. Exemplary conductive metals include, but are not limited to, silver, nickel, aluminum, and their alloys and mixtures. Alternatively, the conductive component consists essentially of silver, depending on its excellent processability and high conductivity.

[0064] In some embodiments, the conductive metal accounts for 84 wt% to 91 wt% of the total weight of the conductive paste. Specifically, the mass percentage of the conductive metal in the total weight of the conductive paste can be any value among 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt% or any value within the range formed by any two of these values.

[0065] In some other embodiments, the conductive metal accounts for 88.3 wt% to 88.7 wt% of the total weight of the conductive paste, and can also be 84 wt% to 88 wt%; it can further be 88 wt% to 91 wt%; it can further be 85 wt% to 89 wt%.

[0066] It can be understood that the adjustment of the proportion of the conductive metal in the conductive paste needs to ensure that the sum of the weight percentages of the components in the conductive paste is 100%. The conductive metal is used to play a conductive role after the crystalline silicon solar cell is formed.

[0067] In some embodiments, the conductive metal can be selected as metal powder, or can also be a mixture directly combining two or more such metals or alloys; the metal is provided by a metal oxide or salt, and the metal oxide or salt decomposes upon exposure to firing heat to form the metal.

[0068] In some embodiments, the conductive metal includes silver, and the silver is selected from at least one of silver powder, silver powder alloy, silver oxide, and silver salt. Specifically, it may further include silver oxide (Ag2O or AgO) or silver salts such as AgCl, AgNO3, AgOOCCH3 (silver acetate), AgOOCF3 (silver trifluoroacetate), Ag3PO4 (silver orthophosphate), or a mixture thereof. Any other form of conductive metal compatible with other components of the conductive paste can also be used in certain embodiments, and other metals used in the paste of the present application for functional conductive materials can be obtained similarly.

[0069] In some embodiments, silver accounts for 84 wt% to 91 wt% of the total weight of the conductive paste. In some other embodiments, silver accounts for 88.3 wt% to 88.7 wt% of the total weight of the conductive paste, and it can also be 84 wt% to 88 wt%; it can further be 88 wt% to 91 wt%; it can further be 85 wt% to 89 wt%.

[0070] In some embodiments, the conductive metal includes silver and aluminum, and aluminum accounts for 0 to 0.5 wt% of the total weight of the conductive paste. Among them, the aluminum is selected from aluminum powder. Aluminum can form aluminum oxide during the sintering process of the glass powder. The formed aluminum oxide can be partially dissolved into the glass melt formed during the sintering of the glass powder to adjust the fluidity of the glass melt and the corrosiveness of the glass melt to the first passivation layer, so as to etch the first passivation layer within the desired time, ensure that the first passivation layer is locally opened during the high-temperature sintering process, thereby ensuring the passivation effect of the crystalline silicon solar cell, and ensuring the photoelectric conversion efficiency of the crystalline silicon solar cell without adding lead elements to the glass powder.

[0071] In some other embodiments, aluminum accounts for 0.05 wt% to 0.3 wt% of the total weight of the conductive paste.

[0072] In some embodiments, the conductive metal can be provided in the form of finely dispersed particles with the following morphologies, such as powder form, flake form, spherical form, rod form, granular form, nodular form, layered or coated form, other irregular forms, or a mixture thereof.

[0073] 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%. In some embodiments, the silver powder has a median particle size D vThe silver powder 50 is spherical silver powder with a median particle size of 1 μm to 2.5 μm. In some embodiments, the silver powder is spherical silver powder with a median particle size of 1.5 μm to 2.5 μm. In some embodiments, the silver powder selected has a median particle size of 2 μm. The main function of the silver powder is to form high-density silver crystals after sintering to provide good electrical 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.

[0074] In some embodiments, the median particle size D of the aluminum powder v 50 is 1 μm to 2 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the aluminum powder reaches 50 wt%. In some embodiments, the aluminum powder is spherical aluminum powder with a median particle size D v 50 of 1 μm to 1.5 μm. In some embodiments, the aluminum powder is spherical aluminum powder with a median particle size of 1.5 μm to 2.0 μm. In some embodiments, the aluminum powder is spherical aluminum powder with a median particle size of 2 μm. The addition of the aluminum powder can form aluminum oxide during the sintering process of the glass powder. The formed aluminum oxide can be partially dissolved into the glass melt formed during the sintering of the glass powder as an additive to adjust the fluidity of the glass melt and the corrosiveness of the glass melt to the first passivation layer, so as to etch the first passivation layer within the desired time, ensure local opening of the first passivation layer during the high-temperature sintering process, and the relatively low addition amount of the aluminum powder can avoid the formation of silver-aluminum barbs during the sintering process, ensure the ohmic contact requirements between the conductive metal and the boron-diffused emitter, reduce the recombination loss after metallization, thereby ensuring the passivation effect of the crystalline silicon solar cell, and improving the open-circuit voltage (Voc) of the crystalline silicon solar cell and ensuring the photoelectric conversion efficiency (Eff) of the crystalline silicon solar cell without adding lead elements to the glass powder.

[0075] In some embodiments, when the conductive metal is in powder form, it can be in a coated or uncoated form; for example, it 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, capric 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, when the conductive metal is silver, it can be coated with a phosphorus-containing compound.

[0076] organic carrier

[0077] In some embodiments, the organic carrier accounts for 8 wt% to 12 wt% of the total weight in the conductive paste. Specifically, the mass percentage of the organic carrier in the total weight of the conductive paste can be any value among 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt% or any value within the range composed of any two of these values.

[0078] In some embodiments, with respect to the solids composed of conductive metal and glass powder, the organic carrier serves as the liquid phase in the conductive paste to disperse the above-mentioned solids, so as to form a paste with a certain viscosity. The viscosity and rheology of this paste can not only enable the above-mentioned conductive metal and glass powder to be stably dispersed therein for a long time, but also enable the conductive paste to be dispersed on the printing screen, and cover the surface of the first passivation layer of the semiconductor substrate with the desired pattern in a screen printing manner.

[0079] 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 mixtures thereof. Resins include wood rosin, phenolic resins, acrylic resins, or mixtures thereof. Esters include polymethacrylates of lower alcohols, etc. Organic solvents 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.

[0080] 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, rheology modifiers, etc., to adapt to the organic medium with different requirements.

[0081] In some embodiments, the glass powder can be prepared by using methods commonly used in the glass manufacturing field. For example, according to the oxide composition ratio of the glass powder described in the embodiment, ingredients are proportioned, mixed, added to a crucible (such as a platinum or ceramic crucible), heated to the peak temperature (for example, 800 °C to 1400 °C) and maintained 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 a sheet 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.

[0082] In some embodiments, the method for preparing the conductive paste may include: proportioning and stirring and dispersing according to the components of the conductive paste described in the embodiments, then dispersing and grinding with a three-roll mill to a fineness of less than 10 μm, and then further filtering. The adjustment of the ratio of the glass powder, the conductive metal, and the organic carrier needs to ensure that the sum of the mass percentages of each component in the conductive paste is 100%.

[0083] Some embodiments of the present application also provide a conductive electrode. Referring to Figure 1 , the conductive electrode includes a semiconductor substrate 10 and a first conductive structure 20.

[0084] The semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 disposed on the first surface 111 of the substrate 110, and a first passivation layer 130 disposed on the side of the boron-diffused emitter 120 facing away from the substrate 110. Specifically, the substrate 110 has a thickness direction X. The substrate 110 includes a first surface 111 and a second surface 112 oppositely disposed along the thickness direction X. The boron-diffused emitter 120 is disposed on the first surface 111, and the first passivation layer 130 is disposed on the side of the boron-diffused emitter 120 facing away from the substrate 110 along the thickness direction X.

[0085] The first conductive structure 20 is disposed on the 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 metal in the conductive paste penetrates through the first passivation layer 130 and makes ohmic electrical contact with the boron-diffused emitter 120. The first conductive structure 20 is electrically connected to the boron-diffused emitter 120 through the conductive metal.

[0086] In some embodiments, the conductive electrode provided by the embodiments of the present application is an n-TOPCon crystalline silicon solar cell electrode.

[0087] Some embodiments of the present application also provide a crystalline silicon solar cell 1 including the conductive electrode described in the embodiments of the present application. Referring to Figure 2 , the crystalline silicon solar cell 1 includes: a semiconductor substrate 10, a first conductive structure 20, and a second conductive structure 30.

[0088] The semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 disposed on the first surface 111 of the substrate 110, and a first passivation layer 130 disposed on the side of the boron-diffused emitter 120 facing away from the substrate 110. The semiconductor substrate 10 further includes a tunneling layer 140 disposed on the second surface 112 of the substrate 110, a phosphorus-diffused polysilicon layer 150 disposed on the side of the tunneling layer 140 facing away from the substrate 110, and a second passivation layer 160 deposited on the side of the phosphorus-diffused polysilicon layer 150 facing away from the tunneling layer 140.

[0089] The first conductive structure 20 is disposed on a side of the first passivation layer 130 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.

[0090] The second conductive structure 30 is disposed on a side of the second passivation layer 160 away from the phosphorus-diffused polysilicon layer 150. The second conductive structure 30 penetrates through the second passivation layer 160 and is electrically connected to the phosphorus-diffused polysilicon layer 150.

[0091] Wherein, 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 metal in the conductive paste penetrates through the first passivation layer 130 and makes ohmic electrical contact with the boron-diffused emitter 120. The first conductive structure 20 is electrically connected to the boron-diffused emitter 120 through the conductive metal. The second conductive structure 30 is formed by high-temperature sintering of a commercially available conductive paste.

[0092] 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, the phosphorus-diffused 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 a 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 at least one of Al2O3, SiN x O y 、SiN x . The first passivation layer 130 and the second passivation layer 160 can also be respectively called insulating layers. The first passivation layer 130 and the second passivation layer 160 respectively play a passivation effect 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.

[0093] Wherein, the substrate 110 is an n-type crystalline silicon wafer, 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.

[0094] The boron-diffused emitter 120 is formed by doping a trivalent element in an n-type crystalline silicon substrate by a diffusion method. The trivalent element is boron. The acceptor impurity source for providing boron element may include boron trioxide, boron nitride, trimethyl borate, tripropyl borate, boron tribromide, boron trichloride or diborane, etc.

[0095] In some embodiments of the present application, a method for preparing a crystalline silicon solar cell is provided. The preparation method includes the following steps:

[0096] S1. Provide a semiconductor substrate 10, where the semiconductor substrate 10 includes a substrate 110, a boron-diffused emitter 120 disposed 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. The semiconductor substrate 10 further includes a tunneling layer 140 disposed on the second surface 112 of the substrate 110, a phosphorus-diffused polysilicon layer 150 disposed on the side of the tunneling layer 140 facing away from the substrate 110, and a second passivation layer 160 deposited on the side of the phosphorus-diffused polysilicon layer 150 facing away from the tunneling layer 140.

[0097] Among them, the first surface 111 of the substrate 110 is doped with boron element by diffusion method to form the boron-diffused emitter 120, and the first passivation layer 130 is deposited on the surface of the boron-diffused emitter 120 by deposition method. The second passivation layer 160 is deposited on the surface of the phosphorus-diffused polysilicon layer 150 by deposition method.

[0098] S2. Print the conductive paste provided in the embodiments of the present application on at least a part of the surface of the first passivation layer 130 in a patterned manner, print the commercially available conductive paste on at least a part of the surface of the second passivation layer 160 in a patterned manner, sinter the semiconductor substrate 10 containing the conductive paste, and etch and penetrate the first passivation layer 130 by the conductive paste provided in the embodiments of the present application during the sintering process to form a first conductive structure 20, and etch and penetrate the second passivation layer 160 by the commercially available conductive paste during the sintering process to form a second conductive structure 30.

[0099] During the high-temperature sintering process, the glass powder in the conductive paste melts to form a glass melt. The glass melt slightly dissolves the conductive metal in the conductive paste. Bi2O3 in the glass powder corrodes and etches the first passivation layer 130. The combination of B2O3 and SiO2 can adjust the glass transition temperature and high-temperature fluidity of the glass powder, so that Bi2O3 can etch the first passivation layer 130 within a desired time to penetrate the first passivation layer 130 in a local area 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. In addition, a small part of the silver in the conductive metal will be dissolved by the glass melt, and the remaining silver powder will be densified during the sintering process. When the conductive metal includes aluminum, aluminum can form aluminum oxide during the sintering process of the glass powder. The formed aluminum oxide can be partially dissolved into the glass melt formed during the sintering process of the glass powder to adjust the fluidity of the glass melt and the corrosiveness of the glass melt to the first passivation layer 130, so as to etch the first passivation layer 130 within a desired time, ensure that the first passivation layer 130 is locally opened during the high-temperature sintering process, thus ensuring the passivation effect of the crystalline silicon solar cell. Without adding lead elements to the glass powder, the photoelectric conversion efficiency of the crystalline silicon solar cell is ensured, and the formed conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment and is also convenient for recycling.

[0100] Among them, the patterning method can be screen printing. It can be understood that the conductive paste involved in the embodiments of the present application is used as a fine grid for the front (p surface) in the crystalline silicon solar cell 1. 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 the embodiments of the present application 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.

[0101] 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. Specifically, the precipitated conductive metal can extend from the through hole formed by etching on the first passivation layer 130 and grow in the direction close to the boron diffusion emitter 120 to form the first conductive structure 20.

[0102] Among them, the high-temperature sintering in step S2 uses a commercially available sintering furnace, such as the Meyer sintering furnace with 18-zone furnace temperature. Usually, the high-temperature sintering environment used is oxygen-containing, and the temperature to which the conductive paste is subjected during the sintering process usually reaches 700°C to 780°C.

[0103] S3. Process for optimizing laser enhanced contact of semiconductor substrate 10. The first conductive structure 20 forms an electrical connection with the boron-diffused emitter 120 through a conductive metal, and the second conductive structure 30 forms an electrical connection with the phosphorus-diffused polysilicon layer 150 through the conductive metal in a commercially available conductive paste, obtaining a crystalline silicon solar cell 1.

[0104] 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 laser enhanced contact optimization technology is to utilize a large number of carriers generated by the laser, 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 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, using the ohmic contact points of silver-silicon alloy generated by high current, the preparation method of the conductive electrode provided by the embodiments of the present application can effectively achieve the metallization effect of the front electrode in the n-TOPCon cell, enabling the conductive metal in the first conductive structure 20 to form an ohmic electrical contact with the boron-diffused emitter 120.

[0105] In some embodiments, the process of optimizing laser enhanced contact of the semiconductor substrate 10 in step S3 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.

[0106] 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 5V, 6V, 8V, 10V, 12V, 14V, 16V, 18V, 20V or any value within the range value composed of any two of these values.

[0107] In some embodiments, the time of laser scanning is 1ms to 100ms. Specifically, the time of laser scanning on 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. Using the laser enhanced contact optimization technology to process the first conductive structure 20 can reduce the contact resistance, which is more conducive to the increase of open circuit voltage and the improvement of photoelectric conversion efficiency.

[0108] The technical solutions of the present application will be further described below in conjunction with specific embodiments.

[0109] As shown in Table 1, the compositions of the glass powder in Examples 1 to 20 are provided in the embodiments of the present application. A glass modifier Li2O is further added to the glass powder provided in Example 13, a glass modifier Na2O is further added to the glass powder provided in Example 14, a glass modifier Ag2O is further added to the glass powder provided in Example 15, and a glass modifier BaO is further added to the glass powder provided in Example 16. The glass powder composition of Comparative Example 1 contains PbO.

[0110] Table 1

[0111]

[0112]

[0113] As shown in Table 2, Examples 21 to 46 in Table 2 are the compositions of the conductive paste provided in the embodiments of the present application. Among them, the conductive pastes provided in Examples 21 to 46 respectively use the glass powders provided in Examples 1 to 20, and the conductive paste provided in Comparative Example 2 uses the PbO-containing glass powder provided in Comparative Example 1.

[0114] Among them, the conductive metal in the conductive pastes provided in Examples 21 to 43 and Comparative Example 2 is silver powder. In addition to silver powder, the conductive metal in the conductive pastes provided in Examples 44 to 46 also contains a small amount of aluminum powder as an additive.

[0115] Table 2

[0116]

[0117]

[0118] Table 3

[0119]

[0120] Among them, as shown in Table 1, in the glass powder provided in the embodiments of the present application, the molar ratio range of Bi2O3 to B2O3 is limited to satisfy: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86. Bi2O3 is used to replace traditional PbO. The combination of B2O3 and SiO2 can adjust the glass transition temperature and high-temperature fluidity of the glass powder, form a low-melting-point glass melt and provide appropriate fluidity, so that Bi2O3 can etch the first passivation layer within a desired time, ensure that the first passivation layer is locally opened during the high-temperature sintering process, thereby ensuring the passivation effect of the crystalline silicon solar cell. Without adding lead elements to the glass powder, the photoelectric conversion efficiency of the crystalline silicon solar cell is ensured, and the manufactured conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment, and is also convenient for recycling.

[0121] Among them, the preparation method of the crystalline silicon solar cell using the conductive pastes provided in Examples 21 to 46 and Comparative Example 2 shown in Table 2 is as follows:

[0122] S1. Provide a crystalline silicon blue film (i.e., semiconductor substrate 10) of the conductive electrode in the n-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 phosphorus-diffused 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.

[0123] S2. Screen-print the conductive pastes provided in Examples 21 to 46 and Comparative Example 2 on at least a part of the surface of the first passivation layer 130 in a patterned manner, screen-print a commercially available conductive paste on at least a part of the surface of the second passivation layer 160 in a patterned manner, 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 pastes provided in Examples 21 to 46 and Comparative Example 2 during the sintering process to form a first conductive structure 20, and etch and penetrate the second passivation layer 160 with the glass powder in the commercially available conductive paste during the sintering process to form a second conductive structure 30.

[0124] Among them, the conductive pastes provided in Examples 21 to 46 and Comparative Example 2 are respectively used as the front (p-side) fine grids of the crystalline silicon solar cell. Specifically, the metallization process of the crystalline silicon solar cell requires 4 screen-printings by a screen printer, and these 4 screen-printings respectively correspond to the formation of the back main grid, the back fine grid, the front main grid, and the front fine grid. The conductive pastes provided in Examples 21 to 46 and Comparative Example 2 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 the back main grid respectively use commercially available Solamet PVD2L conductive paste, and the back fine grid uses commercially available Solamet PV6NL conductive paste.

[0125] The first passivation layer 130 and the second passivation layer 160 generally include SiN x 、SiN x O y 、at least one of Al2O3.

[0126] S3. Process for optimizing laser enhanced contact of semiconductor substrate 10. The first conductive structure 20 forms an electrical connection with the boron-diffused emitter 120 through the conductive metal in the conductive pastes provided by Examples 21 - 46 and Comparative Example 2. The second conductive structure 30 forms an electrical connection with the phosphorus-diffused polysilicon layer 150 through the conductive metal in the commercially available conductive paste, obtaining the crystalline silicon solar cell 1.

[0127] As shown in Table 3, Examples 47 - 72 are the IV test results of the crystalline silicon solar cells 1 prepared by using the conductive pastes provided by Examples 21 - 46 respectively, and Comparative Example 3 is the IV test result of the crystalline silicon solar cell prepared by using the conductive paste provided by Comparative Example 2.

[0128] Among them, the method for obtaining the IV test results is as follows:

[0129] Use a commercially available IV tester, that is, a Current-Voltage tester, to perform IV tests on the crystalline silicon solar cells 1 prepared in Examples 47 - 72 and Comparative Example 3 respectively. The IV test items include: photoelectric conversion efficiency (Eff), open circuit voltage (Voc), fill factor (FF), and short circuit current (Isc).

[0130] Based on the IV test results of the crystalline silicon solar cell prepared in Comparative Example 3, 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 prepared in Comparative Example 3, perform a difference operation on the measured IV test results of the crystalline silicon solar cells 1 prepared in Examples 47 - 72 and the IV test results of the crystalline silicon solar cell prepared in Comparative Example 3 respectively.

[0131] Specifically, perform a difference operation on the photoelectric conversion efficiency (Eff) value, short circuit current (Isc) value, open circuit voltage (Voc) value, and fill factor (FF) obtained from the IV test of the crystalline silicon solar cells 1 prepared in Examples 47 - 72 and the photoelectric conversion efficiency (Eff) value, short circuit current (Isc) value, open circuit voltage (Voc) value, and fill factor (FF) obtained from the IV test of the crystalline silicon solar cell prepared in Comparative Example 3 respectively, that is, obtain the ΔEff value, ΔIsc value, ΔVoc value, and ΔFF value of the IV test of the crystalline silicon solar cells 1 prepared in Examples 47 - 72, and the obtained results are shown in Table 3.

[0132] Among them, as shown in Table 3, the crystalline silicon solar cells 1 prepared in Examples 70 to 72 respectively contain the conductive pastes provided in Examples 44 to 46, and the conductive pastes provided in Examples 44 to 46 are respectively added with 0.05 wt% of aluminum powder, 0.15 wt% of aluminum powder, and 0.30 wt% of aluminum powder. The addition of aluminum powder can form aluminum oxide during the sintering process of the glass powder. The formed aluminum oxide can be partially dissolved into the glass melt formed by the glass powder during the sintering process as an additive to adjust the fluidity of the glass melt and the corrosivity of the glass melt to the first passivation layer, so as to etch the first passivation layer within the desired time. Moreover, the low addition amount of aluminum powder can avoid the formation of silver-aluminum barbs during the sintering process, ensure the self-checking ohmic electrical contact requirements of the conductive metal and the boron-diffused emitter, and reduce the recombination loss after metallization, thereby ensuring the passivation effect of the crystalline silicon solar cell. Compared with Comparative Example 2, in the case of not adding lead element to the glass powder, the open circuit voltage (ΔVoc) and the photoelectric conversion efficiency (ΔEff) of the crystalline silicon solar cell 1 are improved.

[0133] In addition, the crystalline silicon solar cells 1 prepared in Examples 47 to 69 respectively contain the conductive pastes provided in Examples 21 to 43, and the conductive pastes provided in Examples 21 to 43 respectively adopt the lead-free Bi-B-Si-Al-Fe-O glass powder provided in Examples 1 to 20. In the glass powder provided in Examples 1 to 20, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86. Using Bi2O3 to replace traditional PbO, the combination of B2O3 and SiO2 can adjust the glass transition temperature and high-temperature fluidity of the glass powder, form a low-melting-point glass melt and provide appropriate fluidity, so that Bi2O3 can etch the first passivation layer 130 within the desired time, ensure that the first passivation layer 130 is locally opened during the high-temperature sintering process, and thus ensure the passivation effect of the crystalline silicon solar cell. Compared with Comparative Example 2, in the case of not adding lead element to the glass powder in Examples 21 to 43, the photoelectric conversion efficiency (ΔEff) of the crystalline silicon solar cell 1 is ensured, and the formed conductive electrode has low toxicity, which is beneficial to reducing the harm to the human body and the environment, and is also convenient for recycling.

[0134] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0135] The above has introduced in detail the conductive paste, conductive electrode, crystalline silicon solar cell and its preparation method provided by the embodiments of the present application, 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 cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A conductive paste, characterized in that, Comprising: Glass powder, accounting for 1 wt% to 4 wt% of the total weight in the conductive paste; Conductive metal, accounting for 84 wt% to 91 wt% of the total weight in the conductive paste; and, Organic carrier, accounting for 8 wt% to 12 wt% of the total weight in the conductive paste; Based on the molar percentage of the glass powder, the glass powder includes 35 mol% to 55 mol% of B2O3, 15 mol% to 30 mol% of Bi2O3, 2 mol% to 30 mol% of SiO2, 5 mol% to 25 mol% of Al2O3, and 2 mol% to 10 mol% of Fe2O3; Wherein, the molar ratio range of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.

86.

2. The conductive paste according to claim 1, wherein The glass powder further includes 0 mol% to 10 mol% of glass modifiers.

3. The conductive paste according to claim 2, wherein The glass modifiers are selected from at least one of Li2O, Na2O, Ag2O, and BaO.

4. The conductive paste according to claim 1, wherein The conductive metal includes silver, and the silver is selected from at least one of silver powder, silver alloy powder, silver oxide, and silver salt.

5. The conductive paste according to claim 4, wherein, The conductive metal further includes aluminum, and the aluminum accounts for 0 to 0.5 wt% of the total weight in the conductive paste; The aluminum is selected from aluminum powder, and the D v 50 of the aluminum powder is 1 μm to 2 μm, and D v 50 is the particle size corresponding to when the cumulative volume percentage of the aluminum powder reaches 50 wt%.

6. A conductive electrode, characterized in that, Comprising: A semiconductor substrate (10), including 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), disposed on a side of the first passivation layer (130) facing away from the boron-diffused emitter (120), and the first conductive structure (20) penetrates through 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 5, and the first conductive structure (20) is electrically connected to the boron-diffused emitter (120) through the conductive metal.

7. The conductive electrode according to claim 6, wherein The conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

8. A crystalline silicon solar cell, characterized in that, The crystalline silicon solar cell includes the conductive electrode according to claim 6 or 7.

9. A method for preparing a crystalline silicon solar cell, characterized in that, The preparation method includes the following steps: Providing a semiconductor substrate (10), the semiconductor substrate (10) including a substrate (110), a boron-diffused emitter (120) disposed on a first surface (111) of 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); the semiconductor substrate (10) further includes a tunneling layer (140) disposed on a second surface (112) of the substrate (110), a phosphorus-diffused polysilicon layer (150) disposed on a side of the tunneling layer (140) facing away from the substrate (110), and a second passivation layer (160) deposited on a side of the phosphorus-diffused polysilicon layer (150) facing away from the tunneling layer (140); Printing the conductive paste according to any one of claims 1 to 5 on at least a part of the surface of the first passivation layer (130); Sintering the semiconductor substrate (10) containing the conductive paste causes the glass powder in the conductive paste to etch and penetrate through the first passivation layer (130) during the sintering process, and a process of optimizing laser enhanced contact for the semiconductor substrate (10) is carried out. The first conductive structure (20) forms an electrical connection with the boron-diffused emitter (120) through the conductive metal, and the crystalline silicon solar cell is obtained.

10. The preparation method of the crystalline silicon solar cell according to claim 9, characterized in that, The step of printing the conductive paste on at least a part of the surface of the first passivation layer (130) includes: Printing the conductive paste on at least a part of the surface of the first passivation layer (130) in a patterned form.

11. The method for preparing a crystalline silicon solar cell according to claim 9, wherein The process of optimizing laser enhanced contact 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 within the first conductive structure (20).

12. The manufacturing method of the crystalline silicon solar cell according to claim 11, characterized in that, The process of optimizing laser enhanced contact for the semiconductor substrate (10) satisfies at least one of the following conditions: a) The reverse voltage is 5V to 20V; b) The time of the laser scanning is 1ms to 100ms.

Images