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

Abstract

A conductive paste, a conductive electrode, a crystalline silicon solar cell, and a preparation method therefor. The conductive paste comprises: glass powder, accounting for 1 wt% to 4 wt% of the total weight of the conductive paste; a conductive metal, accounting for 84 wt% to 91 wt% of the total weight of the conductive paste; and an organic vehicle, accounting for 8 wt% to 12 wt% of the total weight of the conductive paste. On the basis of the mole percentage of the 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. A molar ratio of Bi2O3 to B2O3 satisfies: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

Description

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

[0001] Cross-reference to Related Applications

[0002] The present disclosure claims priority to Chinese Patent Application No. 202510278863.3, filed on March 10, 2025, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a conductive paste, a conductive electrode, a crystalline silicon solar cell and a preparation method thereof. BACKGROUND

[0004] In a crystalline silicon solar cell, PbO (lead oxide) is recognized as one of the important components of glass powder. The corrosiveness of PbO can provide a passivation layer structure for etching the surface of the crystalline silicon solar cell, thereby forming an ohmic electrical contact. However, lead and its compounds have high toxicity, which poses 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 the crystalline silicon solar cell. SUMMARY

[0005] Embodiments of the present disclosure provide a conductive paste, a conductive electrode, a crystalline silicon solar cell and a preparation method thereof to solve the problem of reduced photoelectric conversion efficiency caused by the use of lead-free glass powder in existing crystalline silicon solar cells.

[0006] A first aspect of embodiments of the present disclosure provides a conductive paste, comprising: glass powder, accounting for 1wt% to 4wt% of the total weight of the conductive paste; conductive metal, accounting for 84wt% to 91wt% of the total weight of the conductive paste; and organic carrier, accounting for 8wt% to 12wt% of the total weight of the conductive paste; the glass powder comprises, based on the mole percentage of the glass powder, 35mol% to 55mol% of B2O3, 15mol% to 30mol% of Bi2O3, 2mol% to 30mol% of SiO2, 5mol% to 25mol% of Al2O3 and 2mol% to 10mol% of Fe2O3; wherein the mole ratio range of Bi2O3 to B2O3 satisfies: 0.27≤Bi2O3 / B2O3≤0.86.

[0007] Optionally, the glass powder further comprises 0mol% to 10mol% of a glass modifier.

[0008] Optionally, the glass modifier is selected from at least one of Li2O, Na2O, Ag2O, BaO.

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

[0010] Optionally, silver comprises 84 wt% to 91 wt% of the total weight of the conductive paste.

[0011] Optionally, the silver salt includes at least one of AgCl, AgNO3, AgOOCCH3, AgOOCF3, and Ag3PO4.

[0012] Optional, silver powder D v 50 is 1μm~3μm, the D of silver powder v 50 represents the particle size corresponding to a cumulative volume percentage of 50% for the silver powder. Optionally, the conductive metal also includes aluminum, comprising 0–0.5 wt% of the total weight in the conductive paste; the aluminum is selected from aluminum powder, and the aluminum powder has a D... v 50 is 1μm~2μm, D v 50 represents the particle size corresponding to a cumulative volume percentage of 50 wt% for aluminum powder.

[0013] A second aspect of this disclosure provides a conductive electrode, comprising: a semiconductor substrate, including a substrate, a boron emitter disposed on the substrate, and a first passivation layer disposed on the side of the boron emitter facing away from the substrate; a first conductive structure disposed on the side of the first passivation layer facing away from the boron emitter, the first conductive structure penetrating the first passivation layer and electrically connected to the boron emitter; wherein the first conductive structure is formed from the aforementioned conductive paste, and the first conductive structure is electrically connected to the boron emitter through a conductive metal.

[0014] A third aspect of this disclosure provides a crystalline silicon solar cell, which includes the conductive electrodes as described above.

[0015] A fourth aspect of this disclosure provides a method for fabricating a crystalline silicon solar cell, the method comprising the following steps:

[0016] A semiconductor substrate is provided, comprising a substrate, a boron-diffractive emitter disposed on a first surface of the substrate, and a first passivation layer deposited on the side of the boron-diffractive emitter facing away from the substrate; the semiconductor substrate further comprises a tunneling layer disposed on a second surface of the substrate, a phosphorus-diffractive polysilicon layer disposed on the side of the tunneling layer facing away from the substrate, and a second passivation layer deposited on the side of the phosphorus-diffractive polysilicon layer facing away from the tunneling layer.

[0017] The conductive paste as described above is printed onto at least a portion of the surface of the first passivation layer;

[0018] A semiconductor substrate containing conductive paste is sintered, and glass powder in the conductive paste is etched and penetrates the first passivation layer during the sintering process. The semiconductor substrate is then subjected to laser-enhanced contact optimization. The first conductive structure is electrically connected to the boron diffuser through a conductive metal to obtain a crystalline silicon solar cell.

[0019] Optionally, the step of printing conductive paste on at least a portion of the surface of the first passivation layer includes: printing conductive paste in a patterned manner on at least a portion of the surface of the first passivation layer.

[0020] Optionally, the process of laser-enhanced contact optimization of 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.

[0021] Optionally, the process of laser-enhanced contact optimization of the semiconductor substrate satisfies at least one of the following conditions:

[0022] a) Reverse voltage is 5V to 20V;

[0023] b) The laser scanning time is 1ms to 100ms.

[0024] Beneficial Effects: This disclosure provides a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same. The conductive paste includes glass powder, a conductive metal, and an organic carrier. The glass powder includes B2O3, Bi2O3, SiO2, Al2O3, and Fe2O3. No lead is added to the glass powder, forming a lead-free Bi-B-Si-Al-Fe-O glass powder. Bi2O3 can form an etching effect on the first passivation layer on the boron diffuser electrode during the sintering process of the conductive paste. B2O3 and SiO2 are the main glass-forming agents used to adjust the glass transition temperature and high-temperature fluidity of the glass powder. Al2O3 and Fe2O3 serve as intermediates. The glass stability of the glass powder can be modified, and the ratio of Bi₂O₃ / B₂O₃ can be limited to 0.27≤Bi₂O₃ / B₂O₃≤0.86. By replacing traditional PbO with Bi₂O₃ in the glass powder, the glass transition temperature of the glass powder can be adjusted while maintaining the etching effect of the glass melt on the first passivation layer. This helps to improve the high-temperature fluidity of the glass powder, thereby promoting the formation of a more stable ohmic electrical contact between the conductive metal in the conductive paste and the boron diffuser. This improves the photoelectric conversion efficiency of the conductive electrode in the crystalline silicon solar cell without adding lead. Furthermore, the conductive electrode produced has low toxicity, which helps to reduce harm to the human body and the environment, and it is also easy to recycle.

[0025] It is understood that the conductive electrode, crystalline silicon solar cell and its preparation method provided in the embodiments of this disclosure may include all the technical features and beneficial effects of the above-mentioned conductive paste, which will not be repeated here.

[0026] Brief description of the attached figures

[0027] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 is a schematic diagram of the structure of the conductive electrode provided in an embodiment of this disclosure;

[0029] Figure 2 is a schematic diagram of the structure of a crystalline silicon solar cell provided in an embodiment of this disclosure.

[0030] Reference numerals: 1. Crystalline silicon solar cell; 10. Semiconductor substrate; 110. Substrate; 111. First surface; 112. Second surface; 120. Boron-diffracted emitter; 130. First passivation layer; 140. Tunneling layer; 150. Phosphorus-diffracted polycrystalline silicon layer; 160. Second passivation layer; 20. First conductive structure; 30. Second conductive structure; X. Thickness direction. Detailed Implementation

[0031] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0032] In the description of this disclosure, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. In the description of this disclosure, "a plurality of" means two or more, and "at least one" can mean one, two, or more, unless otherwise expressly and specifically defined.

[0033] A significant technological breakthrough in crystalline silicon solar cells lies in the use of TOPCon (Tunnel Oxide Passivated Contacts) back-side passivation contact structures, which significantly improve the open-circuit voltage (Voc) and cell efficiency. The fabrication of crystalline silicon solar cells requires metallization of the front (light-facing) side. Metallization of the front conductive electrode (light-facing side) typically involves screen printing a conductive paste into a desired pattern onto the surface of the passivation layer. High-temperature sintering then etches the conductive metal paste through the passivation layer, forming an electrical contact with the emitter, thus creating a conductive structure (or electrode) in the form of conductive metal contacts. The quality of this electrical contact, including contact resistance and carrier recombination caused by metallization, directly affects the photoelectric conversion efficiency of the crystalline silicon solar cell. Conductive pastes commonly used to form the electrodes include conductive metals (e.g., silver particles), glass frits, and organic carriers used as printing substrates.

[0034] To ensure a good electrical contact between the conductive paste and the emitter, and to balance carrier recombination, the etching level of the passivation layer needs to be controlled at a reasonable level during high-temperature sintering. Insufficient etching will prevent penetration of the passivation layer, thus preventing the conductive paste from forming an ohmic electrical contact with the emitter. Excessive etching will lead to a significant increase in carrier recombination, resulting in a loss of the cell's open-circuit voltage (Voc) and consequently affecting the photoelectric conversion efficiency.

[0035] As an important component of conductive paste, glass powder's main function is to etch the passivation layer. Therefore, the composition of glass powder directly affects the photoelectric conversion efficiency of metallized crystalline silicon solar cells.

[0036] Lead-monoxide (PbO) glass powder is commonly used in conductive pastes. In the field of metallization conductive pastes, PbO is a crucial component of glass powder because it possesses excellent glass-forming windows, good high-temperature fluidity, and low corrosivity. It can provide a passivation layer structure for etching the surface of crystalline silicon solar cells, thereby enabling the conductive metal to form an ohmic contact with the emitter. However, the toxicity of lead and lead compounds is well-known, and their widespread application in photovoltaics poses a potential environmental problem.

[0037] Therefore, there is a need to provide a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for preparing the same, which promotes the formation of a more stable ohmic electrical contact between the conductive metal in the conductive paste and the boron-diffractive electrode of the conductive electrode. Without adding lead, the photoelectric conversion efficiency of the conductive electrode in the crystalline silicon solar cell is improved. Furthermore, the conductive electrode is low in toxicity, which helps to reduce harm to the human body and the environment, and it is also easy to recycle.

[0038] Some embodiments of this disclosure provide a conductive paste, comprising: glass powder, accounting for 1 wt% to 4 wt% of the total weight of the conductive paste; a 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; the glass powder, based on the molar percentage, comprises 35 mol% to 55 mol% boron trioxide (B2O3), 15 mol% to 30 mol% bismuth trioxide (Bi2O3), 2 mol% to 30 mol% silicon dioxide (SiO2), 5 mol% to 25 mol% aluminum trioxide (Al2O3), and 2 mol% to 10 mol% ferric oxide (Fe2O3); wherein the molar ratio of Bi2O3 to B2O3 satisfies the following range: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0039] Glass powder and conductive metals serve as the solid components in the conductive paste; the organic carrier serves as the dispersed phase and provides printability, including one or more components that impart functional properties, such as polymers, surfactants, thickeners, thixotropic agents, and binders. The sum of the weight percentages of all components in the conductive paste is 100%.

[0040] The following describes each component in the conductive paste.

[0041] glass powder

[0042] In some embodiments, glass powder refers to a composition containing one or more types of anions and cations. The glass powder has the ability to flow when heated, specifically during high-temperature sintering, and can be crystalline, partially or completely glassy, ​​or amorphous.

[0043] In some embodiments, the glass powder of this embodiment can be understood as a composition having glass components. 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%, and 4 wt%, or any value within a range of any two values.

[0044] In some other embodiments, the mass percentage of glass powder in the total weight of the conductive paste is 1.8 wt% to 2.2 wt%. Optionally, the mass percentage of glass powder in the total weight of the conductive paste may also be 1 wt% to 1.8 wt%. Optionally, the mass percentage of glass powder in the total weight of the conductive paste may also be 2 wt% to 4 wt%. Optionally, the mass percentage of glass powder in the total weight of the conductive paste may also be 2.2 wt% to 4 wt%.

[0045] The proportion of glass powder in conductive paste must be adjusted to ensure that the sum of the weight percentages of all components in the conductive paste is 100%. The composition of glass powder directly affects the meltability, fluidity, and etchability of the conductive paste. Therefore, a good balance of glass powder composition is needed to achieve excellent carrier recombination effect.

[0046] In some embodiments, based on the molar percentage of the 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.

[0047] The molar percentage of B2O3 in the glass powder can be any value from 35 mol%, 37 mol%, 39 mol%, 41 mol%, 43 mol%, 45 mol%, 47 mol%, 49 mol%, 51 mol%, 53 mol%, and 55 mol%, or any value within a range of any two values. The molar percentage of Bi2O3 can be any value from 15 mol%, 17 mol%, 19 mol%, 21 mol%, 23 mol%, 25 mol%, 27 mol%, 29 mol%, and 30 mol%, or any value within a range of any two values. The molar percentage of SiO2 can be any value from 2 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, and 30 mol%, or any value within a range of any two values. The molar percentage of Al2O3 can be any value from 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, or any value within a range of any two values. The molar percentage of Fe2O3 can be any value from 2 mol%, 4 mol%, 6 mol%, 8 mol%, 10 mol%, or any value within a range of any two values.

[0048] In some embodiments, based on the molar percentage of the glass powder, the glass powder comprises 35 mol% to 40 mol% B₂O₃, 15 mol% to 22 mol% Bi₂O₃, 2 mol% to 15 mol% SiO₂, 5 mol% to 15 mol% Al₂O₃, and 2 mol% to 8 mol% Fe₂O₃. By limiting B₂O₃, Bi₂O₃, Al₂O₃, and Fe₂O₃ to a relatively low molar percentage range, the corrosiveness and reactivity of the glass melt formed during high-temperature sintering to the first passivation layer are more moderate and controllable, reducing the risk of over-etching; and, since SiO₂ is in a lower range, it is beneficial to form a low-melting-point glass melt with suitable fluidity more stably during sintering.

[0049] In some embodiments, based on the molar percentage of the glass powder, the glass powder comprises 40 mol% to 55 mol% B₂O₃, 22 mol% to 30 mol% Bi₂O₃, 15 mol% to 30 mol% SiO₂, 15 mol% to 25 mol% Al₂O₃, and 6 mol% to 10 mol% Fe₂O₃. By limiting B₂O₃ and Bi₂O₃ to a relatively high molar percentage range, a glass melt with a low melting point and good high-temperature fluidity is formed, thereby enhancing the etching ability of the glass melt on the first passivation layer, thus rapidly and fully opening the first passivation layer locally during sintering. At the same time, limiting SiO₂, Al₂O₃, and Fe₂O₃ to a relatively high molar percentage range allows the glass melt to maintain strong etching ability while still possessing controllable formation timing and stability.

[0050] In some embodiments, the molar ratio of Bi2O3 to B2O3 satisfies the following range: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86. Specifically, the value of Bi2O3 / B2O3 can be any value from 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 a range of any two values.

[0051] In some embodiments, the molar ratio of Bi2O3 to B2O3 is within the range of 0.27 ≤ Bi2O3 / B2O3 ≤ 0.68. By limiting the ratio of Bi2O3 to B2O3 to a relatively low range, the etching intensity of the glass melt on the first passivation layer is made more gentle and easier to control.

[0052] In some embodiments, the molar ratio of Bi2O3 to B2O3 is within the range of 0.68 ≤ Bi2O3 / B2O3 ≤ 0.86. By limiting the ratio of Bi2O3 to B2O3 to a relatively high range, the etching ability of the glass melt on the first passivation layer is enhanced, and the first passivation layer is more fully and locally opened during sintering, thereby improving the sufficiency and uniformity of through-hole formation.

[0053] Although PbO-containing glass powder has a good 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 PbO-containing conductive pastes, lead-free conductive pastes have a weaker etching effect on the passivation layer and can affect the photoelectric conversion efficiency of crystalline silicon solar cells. Especially for n-TOPCon crystalline silicon solar cells, since both the front and back conductive pastes use lead-containing glass powder, the lead content in each conductive electrode is significantly increased, affecting human health and environmental safety.

[0054] The conductive paste provided in this embodiment 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 lead-free Bi-B-Si-Al-Fe-O glass powder. The glass powder includes 35 mol% to 55 mol% B2O3, 15 mol% to 30 mol% Bi2O3, 2 mol% to 30 mol% SiO2, 5 mol% to 25 mol% Al2O3, and 2 mol% to 10 mol% Fe2O3. The molar ratio of Bi2O3 to B2O3 satisfies the following range: 0.27 ≤ Bi2O3 / B2O3 ≤ 0.86.

[0055] Bi₂O₃ is a glass intermediate with corrosive properties, but its corrosivity 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 glass powder on the first passivation layer. Similarly, excessive Bi₂O₃ will etch too much of the first passivation layer, affecting the passivation and anti-reflection effects of crystalline silicon solar cells, thus impacting their photoelectric conversion efficiency. Furthermore, since PbO is more corrosive than Bi₂O₃, replacing PbO with Bi₂O₃ in the glass powder composition achieves the desired etching effect on the first passivation layer while also satisfying the low carrier recombination effect, thereby improving the open-circuit voltage and photoelectric conversion efficiency of crystalline silicon solar cells. Moreover, it eliminates the toxicity of lead and its compounds, benefiting human health and environmental safety, and facilitating the recycling of crystalline silicon solar cells.

[0056] B2O3 is the main glass forging agent 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 also a glass forging agent used to adjust the glass transition temperature and high-temperature fluidity of the glass powder and adjust the time required for the glass powder to form a glass melt during high-temperature sintering. This allows Bi2O3 to etch the first passivation layer within the desired time, achieving the etching effect of the first passivation layer. This partially opens the first passivation layer, thereby ensuring the stability of the ohmic electrical contact between the conductive metal in the conductive paste and the boron diffuser emitter. Without adding lead, this improves the passivation effect of crystalline silicon solar cells, thereby enhancing the photoelectric conversion efficiency of crystalline silicon solar cells.

[0057] Al2O3 and Fe2O3, as intermediates, can modify the glass stability of glass powder, adjust the glass transition temperature (Tg) and high-temperature fluidity of glass powder, and adjust the time required for glass powder to form glass melt during high-temperature sintering.

[0058] Furthermore, in the glass powder of the glass slurry provided in this embodiment, the molar ratio of Bi2O3 to B2O3 is limited to the range of 0.27≤Bi2O3 / B2O3≤0.86. By 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, forming a low-melting-point glass melt and providing suitable fluidity. This allows Bi2O3 to etch the first passivation layer within the desired time, thereby partially opening the first passivation layer during high-temperature sintering. Without adding lead to the glass powder, the photoelectric conversion efficiency of the crystalline silicon solar cell is improved. Moreover, the conductive electrode made has low toxicity, which helps to reduce harm to the human body and the environment, and is also easy to recycle.

[0059] In some embodiments, the glass powder further includes 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 from 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, and 10 mol%, or any value within a range of any two values. The glass modifier can improve the softening temperature, fluidity, and corrosivity of the glass melt formed during sintering.

[0060] In some embodiments, the glass modification is selected from at least one of Li2O, Na2O, Ag2O, and BaO.

[0061] In some embodiments, the glass modifier comprises Li₂O and Na₂O. Li₂O and Na₂O, as alkali metal oxides, synergistically lower the softening temperature of the glass melt and improve its high-temperature fluidity, making it easier for the glass powder to form a glass melt with suitable fluidity during sintering. In some embodiments, the glass modifier comprises Li₂O and Ag₂O. Li₂O is used to improve the softening temperature and fluidity of the glass melt, while Ag₂O can participate in regulating the reactivity of the glass melt during sintering, resulting in more uniform etching of the first passivation layer by the glass melt.

[0062] In some embodiments, the glass modifier comprises Na₂O and BaO. Na₂O is used to lower the softening temperature of the glass melt and improve its fluidity, while BaO, as an alkaline earth metal oxide, can improve the stability of the glass network and regulate the high-temperature viscosity, thereby improving the glass melt formation efficiency while suppressing the risk of over-etching caused by excessive fluidity.

[0063] In some embodiments, the glass modifier includes Li₂O, Na₂O, and BaO. By enhancing the softening temperature and fluidity of the alkali metal oxides, and combining this with the constraining effect of BaO on the stability and viscosity of the glass, the formation timing and rheological properties of the glass melt are more easily brought into the process controllable window.

[0064] Conductive metal

[0065] In some embodiments, the conductive metal, acting as a power source for the conductive paste, can be any metal powder commonly used in electrodes formed on circuit substrates such as semiconductor substrates, without particular limitation. Exemplary conductive metals include, but are not limited to, silver, nickel, aluminum, and their alloys and mixtures. Alternatively, the conductive component may be substantially composed of silver, due to its excellent processability and high conductivity.

[0066] 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 from 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, or any value within a range of any two values.

[0067] In some other embodiments, the conductive metal accounts for 88.3 wt% to 88.7 wt% of the total weight of the conductive paste. Optionally, the conductive metal may also account for 84 wt% to 88 wt% of the total weight of the conductive paste. Optionally, the conductive metal may also account for 88 wt% to 91 wt% of the total weight of the conductive paste. Optionally, the conductive metal may also account for 85 wt% to 89 wt% of the total weight of the conductive paste.

[0068] Understandably, the proportion of conductive metal in the conductive paste must be adjusted to ensure that the sum of the weight percentages of all components in the conductive paste is 100%. The conductive metal is used to conduct electricity after the formation of crystalline silicon solar cells.

[0069] In some embodiments, the conductive metal may be selected from metal powder or as a mixture of two or more such metals or alloys directly bonded together; the metal is provided by a metal oxide or salt that decomposes upon exposure to firing heat to form the metal.

[0070] In some embodiments, the conductive metal includes silver, which is selected from at least one of silver powder, silver powder alloy, silver oxide, and silver salts. Silver oxide may include at least one of Ag₂O and AgO, and silver salts may include at least one of AgCl (silver chloride), AgNO₃ (silver nitrate), AgOOCCH₃ (silver acetate), AgOOCF₃ (silver trifluoroacetate), and Ag₃PO₄ (silver orthophosphate).

[0071] In some embodiments, the conductive metal includes silver, which is selected from a combination of silver powder and silver salt, wherein the silver salt is selected as AgNO3. AgNO3 thermally decomposes during sintering and generates metallic silver in situ, thereby providing a more readily reactant silver source and promoting the filling and connection of the silver phase within the through-hole.

[0072] In some embodiments, the conductive metal includes silver, selected from at least one of silver oxide and silver salts. Any other form of conductive metal compatible with other components of the conductive paste may also be used in some embodiments, and other metals used in this paste for functional conductive materials can be similarly obtained.

[0073] In some embodiments, the conductive metal includes silver, which is selected from a combination of silver oxide and silver salt, wherein the silver oxide is selected as Ag₂O and the silver salt is selected as AgNO₃. Ag₂O and AgNO₃ can decompose, reduce and generate metallic silver in situ under the action of sintering heat, thereby providing a continuous silver source replenishment at different temperature ranges, promoting silver phase densification and silver phase filling of through-hole regions.

[0074] In some embodiments, silver comprises 84 wt% to 91 wt% of the total weight of the conductive paste. In other embodiments, silver comprises 88.3 wt% to 88.7 wt% of the total weight of the conductive paste; silver may also comprise 84 wt% to 88 wt% of the total weight of the conductive paste; silver may also comprise 88 wt% to 91 wt% of the total weight of the conductive paste; silver may also comprise 85 wt% to 89 wt% of the total weight of the conductive paste.

[0075] In some embodiments, the conductive metal includes silver and aluminum, with aluminum accounting for 0 to 0.5 wt% of the total weight of the conductive paste. The aluminum is selected from aluminum powder, which can form alumina during the sintering of the glass powder. The formed alumina can partially dissolve into the glass melt formed during the sintering process, thereby adjusting the fluidity of the glass melt and its corrosiveness to the first passivation layer. This allows for etching of the first passivation layer within a desired time, enabling localized opening of the first passivation layer during high-temperature sintering, thus improving the passivation effect of the crystalline silicon solar cell and enhancing the photoelectric conversion efficiency of the crystalline silicon solar cell without adding lead to the glass powder.

[0076] In some other embodiments, aluminum accounts for 0.05 wt% to 0.3 wt% of the total weight of the conductive paste. Specifically, it is any value within the range of any two of the following: 0.05 wt%, 0.08 wt%, 0.11 wt%, 0.14 wt%, 0.17 wt%, 0.20 wt%, 0.23 wt%, 0.26 wt%, 0.29 wt%, and 0.30 wt% of the total weight of the conductive paste.

[0077] In some embodiments, the conductive metal may be provided as finely dispersed particles having the following forms: powder, flake, sphere, rod, granular, nodular, layered or coated, other irregular forms, or mixtures thereof.

[0078] In some embodiments, the median particle size D of the silver powder v 50 is 1μm to 3μm, D v 50 represents the particle size corresponding to a cumulative volume percentage of 50% for silver powder.

[0079] In some embodiments, the silver powder uses a median particle size D v 50 consists of spherical silver powder ranging from 1μm to 2.5μm. By limiting the silver powder particle size to a relatively small range, the silver powder is more easily and uniformly dispersed in the organic carrier, forming a denser and more continuous conductive framework after screen printing.

[0080] In some embodiments, the silver powder used is spherical silver powder with a median particle size of 1.5 μm to 2.5 μm. By limiting the silver powder particle size to a relatively large range, the risk of agglomeration and paste rheological fluctuations caused by excessively fine particles is reduced while maintaining good dispersion and printability.

[0081] In some embodiments, spherical silver powder with a median particle size of 2 μm is selected. The main function of the silver powder is to form high-density silver crystals after sintering to provide good conductivity for ohmic electrical contact with the crystalline silicon layer. The spherical silver powder with a median particle size of 2 μm can also inhibit agglomeration and promote uniform dispersion of the silver powder.

[0082] In some embodiments, the median particle size D of the aluminum powder v 50 is 1μm~2μm, D v 50 represents the particle size corresponding to a cumulative volume percentage of 50 wt% for aluminum powder.

[0083] In some embodiments, the aluminum powder uses a median particle size D v 50 consists of spherical aluminum powder ranging from 1μm to 1.5μm. By limiting the particle size of the aluminum powder to a relatively small range, it is easier to disperse the aluminum powder evenly in the slurry.

[0084] In some embodiments, the aluminum powder used is spherical aluminum powder with a median particle size of 1.5 μm to 2.0 μm. By limiting the particle size of the aluminum powder to a relatively large range, the risk of agglomeration and excessively rapid reaction caused by excessively fine particles is reduced while maintaining good dispersibility.

[0085] In some embodiments, the aluminum powder used is spherical aluminum powder with a median particle size of 2 μm. The addition of aluminum powder can form alumina during the sintering process of the glass powder. The formed alumina can be partially dissolved into the glass melt formed during the sintering process as an additive to adjust the fluidity of the glass melt and its corrosiveness to the first passivation layer. This allows the first passivation layer to be etched within a desired time, thereby locally opening the first passivation layer during high-temperature sintering. Moreover, the low amount of aluminum powder added can avoid the formation of silver-aluminum barbs during sintering, satisfying the ohmic electrical contact requirements between the conductive metal and the boron diffuser emitter while reducing recombination losses after metallization. This improves the passivation effect of the crystalline silicon solar cell and increases the open-circuit voltage (Voc) and photoelectric conversion efficiency (Eff) of the crystalline silicon solar cell without adding lead to the glass powder.

[0086] In some embodiments, when the conductive metal is in powder form, it may be in a coated or uncoated form; for example, it may 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 may also be used include lauric acid, oleic acid, capric acid, myristic acid, linoleic acid, and mixtures thereof. Other surfactants that may also be used include polyethylene oxide, polyethylene glycol, benzotriazole, poly(ethylene glycol)acetic acid, and other similar organic molecules. Suitable counterions used in coating surfactants include, but are not limited to, hydrogen, ammonium, sodium, potassium, and mixtures thereof. For example, when the conductive metal is silver, it may be coated with a phosphorus-containing compound.

[0087] organic carrier

[0088] In some embodiments, the organic carrier accounts for 8 wt% to 12 wt% of the total weight of 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%, and 12 wt%, or any value within a range of any two values.

[0089] In some embodiments, an organic carrier serves as the liquid phase in the conductive paste, relative to the solid material composed of conductive metal and glass powder, to disperse the solid material and form a paste with a certain viscosity. The viscosity and rheological properties of this paste enable the conductive metal and glass powder to be dispersed stably within it over a long period of time, and also enable the conductive paste to be dispersed on a printing screen, and the desired pattern to be applied to the surface of the first passivation layer of the semiconductor substrate by screen printing.

[0090] In some embodiments, the organic carrier may include a polymer and an organic solvent. The polymer may include cellulose, resins, esters, etc. Cellulose includes cellulose resins such as methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, benzylcellulose, propylcellulose, and nitrocellulose, or mixtures thereof. Resins include rosin, phenolic resins, acrylic resins, or mixtures thereof. Esters include polymethyl methacrylates, etc., of lower alcohols. Organic solvents may include terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol diacetate, α-terpenes, β-terpenes, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexanediol, etc.

[0091] In some embodiments, the consistency and rheological properties 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 nonionic surfactants, thixotropic agents, dispersants, and rheology modifiers to suit different organic medium requirements.

[0092] In some embodiments, the glass powder can be prepared using methods conventionally used in the glass manufacturing industry. For example, oxides corresponding to the glass powder composition ratios described in the embodiments are batched, mixed, added to a crucible (e.g., a platinum or ceramic crucible), heated to a peak temperature (e.g., 800°C to 1400°C), and held for a period of time to allow the oxides to melt together. The molten material can then be quenched by any suitable means, including but not limited to passing it between counter-rotating stainless steel rollers to form flakes 0.25 mm to 0.50 mm thick, by pouring it onto a thick stainless steel plate, or by pouring it into water. The resulting glass powder is then ground using common grinding techniques to form powder with a particle size of 0.5 μm to 2 μm. Common grinding techniques include air jet milling, ball milling, sand milling, or planetary milling.

[0093] In some embodiments, the preparation method of the conductive paste may include: mixing and dispersing the components of the conductive paste as described in the embodiments, then grinding it to a fineness of less than 10 μm using a three-roll mill, and then further filtering. The ratio of glass powder, conductive metal, and organic carrier must be adjusted to ensure that the sum of the mass percentages of each component in the conductive paste is 100%.

[0094] Some embodiments of this disclosure also provide a conductive electrode. Referring to FIG1, the conductive electrode includes a semiconductor substrate 10 and a first conductive structure 20.

[0095] The semiconductor substrate 10 includes a substrate 110, a boron-derived emitter 120 disposed on a first surface 111 of the substrate 110, and a first passivation layer 130 disposed on the side of the boron-derived emitter 120 facing away from the substrate 110. Specifically, the substrate 110 has a thickness direction X, and the substrate 110 includes a first surface 111 and a second surface 112 disposed opposite to each other along the thickness direction X. The boron-derived emitter 120 is disposed on the first surface 111, and the first passivation layer 130 is disposed on the side of the boron-derived emitter 120 facing away from the substrate 110 along the thickness direction X.

[0096] The first conductive structure 20 is disposed on the side of the first passivation layer 130 opposite to the boron-emitting electrode 120. The first conductive structure 20 penetrates the first passivation layer 130 and is electrically connected to the boron-emitting electrode 120. The first conductive structure 20 is formed from the conductive paste provided in this embodiment of the present disclosure. At least a portion of the conductive metal in the conductive paste penetrates the first passivation layer 130 and makes ohmic electrical contact with the boron-emitting electrode 120. The first conductive structure 20 is electrically connected to the boron-emitting electrode 120 through the conductive metal.

[0097] In some embodiments, the conductive electrode provided in this disclosure is an n-TOPCon crystalline silicon solar cell electrode.

[0098] Some embodiments of this disclosure also provide a crystalline silicon solar cell 1 containing the conductive electrodes provided in the embodiments of this disclosure. Referring to FIG2, the crystalline silicon solar cell 1 includes: a semiconductor substrate 10, a first conductive structure 20, and a second conductive structure 30.

[0099] The semiconductor substrate 10 includes a substrate 110, a boron-diffracted emitter 120 disposed on a first surface 111 of the substrate 110, and a first passivation layer 130 disposed on the side of the boron-diffracted emitter 120 facing away from the substrate 110. The semiconductor substrate 10 also includes a tunneling layer 140 disposed on a second surface 112 of the substrate 110, a phosphorus-diffracted 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-diffracted polysilicon layer 150 facing away from the tunneling layer 140.

[0100] The first conductive structure 20 is disposed on the 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.

[0101] The second conductive structure 30 is disposed on the side of the second passivation layer 160 away from the phosphorus-expanded polysilicon layer 150. The second conductive structure 30 penetrates the second passivation layer 160 and is electrically connected to the phosphorus-expanded polysilicon layer 150.

[0102] The first conductive structure 20 is formed from the conductive paste provided in this embodiment. At least a portion of the conductive metal in the conductive paste penetrates 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 from a commercially available conductive paste by high-temperature sintering.

[0103] In some embodiments, the substrate 110 may be an n-type doped semiconductor substrate, the tunneling layer 140 may be an ultrathin silicon dioxide layer, and the phosphorus-doped polysilicon layer 150 may be an n-type doped semiconductor substrate. + The polycrystalline silicon layer (such as a phosphorus-doped polycrystalline silicon layer), the boron-diffused emitter 120 is a p-type doped layer. In TOPCon crystalline silicon solar cells, 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 Al2O3 and SiN. x O y (Silicon oxynitride), SiN x At least one of silicon nitride, the first passivation layer 130 and the second passivation layer 160 can also be referred to as insulating layers, and the first passivation layer 130 and the second passivation layer 160 respectively serve to passivate, thereby improving the photoelectric conversion efficiency of crystalline silicon solar cells. The first passivation layer 130 and the second passivation layer 160 can be deposited by vapor deposition, sputtering or other methods.

[0104] The substrate 110 is an n-type crystalline silicon substrate, also known as an n-type lightly doped substrate. It is an n-TOPCon crystalline silicon solar cell blue film formed by light doping diffusion of a phosphorus source onto the crystalline silicon wafer. The first surface 111 of the substrate 110 faces the front side (p-side) of the crystalline silicon solar cell, and the second surface 112 faces the back side (n-side) of the crystalline silicon solar cell. The front side refers to the light-receiving surface of the crystalline silicon solar cell, which is also the working surface. The back side is the back side of the crystalline silicon solar cell and is usually not directly exposed to sunlight.

[0105] The boron-diffracted emitter 120 is formed by diffusion doping a trivalent element, boron, into an n-type silicon substrate. Acceptor impurity sources for providing boron can include boron trioxide, boron nitride, trimethyl borate, tripropyl borate, boron tribromide, boron trichloride, or diborane, etc.

[0106] In some embodiments of this disclosure, a method for fabricating a crystalline silicon solar cell is provided, the method comprising the following steps:

[0107] S1. A semiconductor substrate 10 is provided. The semiconductor substrate 10 includes a substrate 110, a boron-diffracted emitter 120 disposed on a first surface 111 of the substrate 110, and a first passivation layer 130 deposited on the side of the boron-diffracted emitter 120 facing away from the substrate 110. The semiconductor substrate 10 also includes a tunneling layer 140 disposed on a second surface 112 of the substrate 110, a phosphorus-diffracted 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-diffracted polysilicon layer 150 facing away from the tunneling layer 140.

[0108] Specifically, a boron-doped emitter 120 is formed by doping boron on the first surface 111 of a diffusion substrate 110, and a first passivation layer 130 is deposited on the surface of the boron-doped emitter 120 using a deposition method. A second passivation layer 160 is deposited on the surface of a phosphorus-doped polysilicon layer 150 using a deposition method.

[0109] S2. The conductive paste provided in this embodiment is patterned and printed on at least a portion of the surface of the first passivation layer 130. A commercially available conductive paste is patterned and printed on at least a portion of the surface of the second passivation layer 160. The semiconductor substrate 10 containing the conductive paste is sintered, and the conductive paste provided in this embodiment is etched and penetrates the first passivation layer 130 during the sintering process to form a first conductive structure 20. The commercially available conductive paste is etched and penetrates the second passivation layer 160 during the sintering process to form a second conductive structure 30.

[0110] During the high-temperature sintering process, the glass powder in the conductive paste melts to form a glass melt. The glass melt dissolves a small amount of the conductive metal in the conductive paste. The 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, thereby allowing Bi2O3 to etch the first passivation layer 130 within a desired time, penetrating the first passivation layer 130 in a localized area, forming a through-hole (not shown in the figure) extending along the thickness direction X through the first passivation layer 130. In addition, a small portion of the silver in the conductive metal is dissolved by the glass melt, while the remaining silver powder densifies during the sintering process. When the conductive metal includes aluminum, aluminum can form alumina during the sintering of glass powder. The formed alumina can partially dissolve into the glass melt formed during the sintering process of glass powder, thereby adjusting the fluidity of the glass melt and its corrosiveness to the first passivation layer 130. This allows the first passivation layer 130 to be etched within a desired time, thereby partially opening the first passivation layer 130 during high-temperature sintering. This improves the passivation effect of the crystalline silicon solar cell. Without adding lead to the glass powder, the photoelectric conversion efficiency of the crystalline silicon solar cell is improved. Furthermore, the conductive electrode produced has low toxicity, which helps to reduce harm to the human body and the environment, and it is also easy to recycle.

[0111] The patterning method can be screen printing. The conductive paste involved in this embodiment is used as a fine grid on the front (p-side) of a crystalline silicon solar cell 1. Specifically, it is screen printed on the back main grid, back fine grid, front main grid, and front fine grid respectively. The conductive paste in this embodiment is used on the front fine grid, typically the fourth layer. After each layer is printed, it is dried before the next layer is printed. The front and back main grids use commercially available Solamet PVD2L conductive paste, and the back fine grid uses commercially available Solamet PV6NL conductive paste.

[0112] 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 some 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 towards the boron emitter 120 to form the first conductive structure 20.

[0113] In step S2, the high-temperature sintering uses a commercially available sintering furnace, such as the Maiwei sintering furnace with 18 zones. The high-temperature sintering environment is usually oxygen-containing, and the temperature of the conductive slurry during sintering typically reaches 700℃ to 780℃.

[0114] S3. A process of laser-enhanced contact optimization of semiconductor substrate 10, wherein the first conductive structure 20 is electrically connected to the boron diffused emitter 120 through conductive metal, and the second conductive structure 30 is electrically connected to the phosphorus diffused polycrystalline silicon layer 150 through conductive metal in commercially available conductive paste, thereby obtaining crystalline silicon solar cell 1.

[0115] Laser-enhanced contact optimization is a method that uses lasers to improve the electrical contact of slurry during the manufacturing process of crystalline silicon solar cells. The basic principle of laser-enhanced contact optimization technology is to utilize the large number of charge carriers generated by the laser, guide these charge carriers through the formed metallized contact points using a bias voltage, and use the heat energy generated by the current to improve the contact effect and uniformity. This 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, utilizing the ohmic contact points of the silver-silicon alloy generated by the high current, the conductive electrode preparation method provided in this embodiment, through screen printing metallization and laser-enhanced contact optimization processes, 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 diffuser 120.

[0116] In some embodiments, the laser-enhanced contact optimization process for 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 within 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 5V, 6V, 8V, 10V, 12V, 14V, 16V, 18V, and 20V, or any value within a range of any two values.

[0118] In some embodiments, the laser scanning time is from 1 ms to 100 ms. Specifically, the laser scanning time of the semiconductor substrate 10 can be any value from 1 ms, 5 ms, 10 ms, 20 ms, 30 ms, 40 ms, 50 ms, 60 ms, 70 ms, 80 ms, 90 ms, and 100 ms, or any value within a range of any two values. Using laser-enhanced contact optimization technology to process the first conductive structure 20 can reduce contact resistance, which is more conducive to increasing the open-circuit voltage and improving the photoelectric conversion efficiency.

[0119] The technical solutions of this disclosure will be further described below with reference to specific embodiments.

[0120] As shown in Table 1, Examples 1-20 represent the composition of the glass powder in the conductive pastes provided in this disclosure. The glass powder in Example 13 further contains lithium oxide (Li₂O), the glass powder in Example 14 further contains sodium oxide (Na₂O), the glass powder in Example 15 further contains Ag₂O, and the glass powder in Example 16 further contains barium oxide (BaO). Comparative Example 1 contains PbO in its glass powder composition.

[0121] Table 1

[0122] As shown in Table 2, Examples 21 to 46 in Table 2 are the composition of the conductive pastes provided in the embodiments of this application. The conductive pastes provided in Examples 21 to 46 respectively use the glass powders provided in Examples 1 to 20, and the conductive pastes provided in Comparative Example 2 use the PbO-containing glass powders provided in Comparative Example 1.

[0123] In Examples 21-43 and Comparative Example 2, the conductive metal in the conductive pastes is silver powder. In Examples 44-46, the conductive metal contains silver powder and a small amount of aluminum powder as an additive.

[0124] Table 2

[0125] Table 3

[0126] As shown in Table 1, in the glass powder provided in this embodiment, the molar ratio of Bi2O3 to B2O3 is limited to the range of 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, forming a low-melting-point glass melt and providing suitable fluidity. This allows Bi2O3 to etch the first passivation layer within the desired time, thereby partially opening the first passivation layer during high-temperature sintering, thus improving the passivation effect of crystalline silicon solar cells. Without adding lead to the glass powder, the photoelectric conversion efficiency of crystalline silicon solar cells is improved. Furthermore, the conductive electrode made has low toxicity, which helps to reduce harm to the human body and the environment, and is also easy to recycle.

[0127] The specific methods for preparing crystalline silicon solar cells using the conductive pastes provided in Examples 21-46 and Comparative Example 2, as shown in Table 2, are as follows:

[0128] S1. A crystalline silicon blue film (i.e., semiconductor substrate 10) is provided as a conductive electrode in an n-TOPCon crystalline silicon solar cell. The semiconductor substrate 10 includes a substrate 110, a boron-diffracted emitter 120 disposed on a first surface 111 of the substrate 110, and a first passivation layer 130 deposited on the side of the boron-diffracted emitter 120 facing away from the substrate 110. A tunneling layer 140 and a phosphorus-diffracted polycrystalline silicon layer 150 are formed on the second surface 112 of the substrate 110 using a tunneling oxide passivation contact method. A second passivation layer 160 is deposited on the surface of the polycrystalline silicon layer 150 using a deposition method.

[0129] S2. The conductive pastes provided in Examples 21-46 and Comparative Example 2 are screen-printed in a patterned manner on at least a portion of the surface of the first passivation layer 130. A commercially available conductive paste is screen-printed in a patterned manner on at least a portion of the surface of the second passivation layer 160. The semiconductor substrate 10 containing the conductive paste is sintered, and the glass powder in the conductive pastes provided in Examples 21-46 and Comparative Example 2 is etched and penetrates the first passivation layer 130 during the sintering process to form a first conductive structure 20. The glass powder in the commercially available conductive paste is etched and penetrates the second passivation layer 160 during the sintering process to form a second conductive structure 30.

[0130] The conductive pastes provided in Examples 21-46 and Comparative Example 2 were used as the fine grids on the front (p-side) of crystalline silicon solar cells. Specifically, the metallization process of crystalline silicon solar cells requires four screen printing passes, which correspond to forming the back main grid, the back fine grid, the front main grid, and the front fine grid, respectively. The conductive pastes provided in Examples 21-46 and Comparative Example 2 were used for the front fine grid, typically the fourth pass. After each pass was printed, the surface was dried before the next pass was printed. The front and back main grids used commercially available Solamet PVD2L conductive paste, while the back fine grid used commercially available Solamet PV6NL conductive paste.

[0131] The first passivation layer 130 and the second passivation layer 160 typically include SiN. x SiN x O y At least one of Al2O3.

[0132] S3. In the process of laser-enhanced contact optimization of semiconductor substrate 10, the first conductive structure 20 is electrically connected to the boron diffused emitter 120 through the conductive metal in the conductive paste provided in Examples 21-46 and Comparative Example 2, and the second conductive structure 30 is electrically connected to the phosphorus diffused polycrystalline silicon layer 150 through the conductive metal in the commercially available conductive paste, thereby obtaining crystalline silicon solar cell 1.

[0133] As shown in Table 3, Examples 47 to 72 are the IV test results of crystalline silicon solar cells 1 prepared using the conductive pastes provided in Examples 21 to 46, respectively, and Comparative Example 3 is the IV test result of crystalline silicon solar cells prepared using the conductive pastes provided in Comparative Example 2.

[0134] The IV test results are obtained as follows:

[0135] Using a commercially available IV tester, i.e., a current-voltage tester, the crystalline silicon solar cells 1 prepared in Examples 47-72 and Comparative Example 3 were subjected to IV tests. The IV test items included: photoelectric conversion efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), and short-circuit current (Isc).

[0136] Using the IV test results of the crystalline silicon solar cell prepared in Comparative Example 3 as a benchmark, that is, using 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 as a benchmark, the IV test results of the crystalline silicon solar cell 1 prepared in Examples 47 to 72 were compared with the IV test results of the crystalline silicon solar cell prepared in Comparative Example 3.

[0137] Specifically, the photoelectric conversion efficiency (Eff), short-circuit current (Isc), open-circuit voltage (Voc), and fill factor (FF) obtained from the IV test of the crystalline silicon solar cells 1 prepared in Examples 47-72 were compared with the photoelectric conversion efficiency (Eff), short-circuit current (Isc), open-circuit voltage (Voc), and fill factor (FF) obtained from the IV test of the crystalline silicon solar cells prepared in Comparative Example 3. The difference was calculated to obtain the ΔEff, ΔIsc, ΔVoc, and ΔFF values ​​of the crystalline silicon solar cells 1 prepared in Examples 47-72. The results are shown in Table 3.

[0138] As shown in Table 3, the crystalline silicon solar cells 1 prepared in Examples 70-72 respectively contain the conductive pastes provided in Examples 44-46. The conductive pastes provided in Examples 44-46 respectively contain 0.05 wt% aluminum powder, 0.15 wt% aluminum powder, and 0.30 wt% aluminum powder. The addition of aluminum powder can form alumina during the glass powder sintering process. The formed alumina can be partially dissolved into the glass melt formed during the glass powder sintering process as an additive, thereby adjusting the fluidity of the glass melt and its corrosiveness to the first passivation layer. This allows for etching of the first passivation layer within the desired time. Furthermore, the low amount of aluminum powder added avoids the formation of silver-aluminum barbs during sintering, meeting the ohmic contact requirements between the conductive metal and the boron diffused emitter while reducing recombination losses after metallization, thus improving the passivation effect of the crystalline silicon solar cell. Compared to Comparative Example 2, without adding lead to the glass powder, the open-circuit voltage (ΔVoc) and photoelectric conversion efficiency (ΔEff) of the crystalline silicon solar cell 1 are improved.

[0139] 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. The conductive pastes provided in Examples 21 to 43 respectively use lead-free Bi-B-Si-Al-Fe-O glass powders provided in Examples 1 to 20. In the glass powders provided in Examples 1 to 20, the molar ratio of Bi2O3 to B2O3 is satisfied in the range of 0.27≤Bi2O3 / B2O3≤0.86. Bi2O3 is used to replace the 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 suitable fluidity, so that Bi2O3 can etch the first passivation layer 130 within the desired time, so as to partially open the first passivation layer 130 during the high-temperature sintering process, thereby improving the passivation effect of the crystalline silicon solar cell. Compared to Comparative Example 2, Examples 21-43 improved the photoelectric conversion efficiency (ΔEff) of the crystalline silicon solar cell 1 without adding lead to the glass powder, and the conductive electrode made therefrom has low toxicity, which helps to reduce harm to the human body and the environment, and is also easy to recycle.

[0140] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not described in detail in a particular embodiment can be found in the relevant descriptions of other embodiments. The embodiments can be combined with each other, but will not be described in detail here.

[0141] The conductive paste, conductive electrode, crystalline silicon solar cell, and their preparation method provided in the embodiments of this disclosure have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this disclosure. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A conductive paste, comprising: Glass powder, accounting for 1 wt% to 4 wt% of the total weight of the conductive paste; A conductive metal, comprising 84 wt% to 91 wt% of the total weight of the conductive paste; and, An organic carrier, comprising 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 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. The molar ratio of Bi2O3 to B2O3 is within the range of 0.27 ≤ Bi2O3 / B2O3 ≤ 0.

86.

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

3. The conductive paste according to claim 2, wherein, The glass modification is 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, which 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 silver comprises 84 wt% to 91 wt% of the total weight of the conductive paste.

6. The conductive paste according to claim 4, wherein, The silver salt includes at least one of AgCl, AgNO3, AgOOCCH3, AgOOCF3, and Ag3PO4.

7. The conductive paste according to claim 4, wherein, The silver powder D v 50 is 1μm to 3μm, D v 50 is the particle size corresponding to the cumulative volume percentage of the silver powder reaching 50%.

8. The conductive paste according to claim 4, wherein, The conductive metal also includes aluminum, which accounts for 0 to 0.5 wt% of the total weight of the conductive paste; Aluminum is selected from aluminum powder, wherein the aluminum powder has a D v 50 is 1μm~2μm, D v 50 is the particle size corresponding to the cumulative volume percentage of the aluminum powder reaching 50%.

9. A conductive electrode, comprising: The semiconductor substrate (10) includes a substrate (110), a boron-derived emitter (120) disposed on the substrate (110), and a first passivation layer (130) disposed on the side of the boron-derived emitter (120) facing away from the substrate (110); A first conductive structure (20) is disposed on the 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). The first conductive structure (20) is formed of a conductive paste as described in any one of claims 1 to 8, and the first conductive structure (20) is electrically connected to the boron diffuser (120) through the conductive metal.

10. The conductive electrode according to claim 9, wherein, The conductive electrode is an n-TOPCon crystalline silicon solar cell electrode.

11. A crystalline silicon solar cell, comprising the conductive electrode as described in claim 9 or 10.

12. A method for fabricating a crystalline silicon solar cell, comprising the following steps: A semiconductor substrate (10) is provided, the semiconductor substrate (10) including a substrate (110), a boron-diffracted emitter (120) disposed on a first side (111) of the substrate (110) and a first passivation layer (130) deposited on the side of the boron-diffracted emitter (120) facing away from the substrate (110); the semiconductor substrate (10) further includes a tunneling layer (140) disposed on a second side (112) of the substrate (110), a phosphorus-diffracted 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-diffracted polysilicon layer (150) facing away from the tunneling layer (140); The conductive paste as described in any one of claims 1 to 8 is printed on at least a portion of the surface of the first passivation layer (130); The semiconductor substrate (10) containing the conductive paste is sintered, and the glass powder in the conductive paste is etched and penetrates the first passivation layer (130) during the sintering process. The semiconductor substrate (10) is then subjected to a laser-enhanced contact optimization process. The first conductive structure (20) is electrically connected to the boron diffuser (120) through the conductive metal to obtain the crystalline silicon solar cell.

13. The method for preparing a crystalline silicon solar cell according to claim 12, wherein, The step of printing the conductive paste onto at least a portion of the surface of the first passivation layer (130) includes: The conductive paste is printed in a patterned form on at least a portion of the surface of the first passivation layer (130).

14. The method for preparing a crystalline silicon solar cell according to claim 12, wherein, The process of laser-enhanced contact optimization of the semiconductor substrate (10) includes: A reverse voltage is applied to the semiconductor substrate (10), and the semiconductor substrate (10) is simultaneously laser-scanned to form an induced current within the first conductive structure (20).

15. The method for preparing a crystalline silicon solar cell according to claim 14, wherein, The process of laser-enhanced contact optimization of 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 1ms to 100ms.

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