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

Abstract

This application discloses a conductive paste, a conductive electrode, a preparation method thereof, and a crystalline silicon solar cell. The conductive paste, by weight, comprises the following components: silver powder: 40-78 wt%; nickel powder: 10-40 wt%; glass powder: 2-6 wt%; organic carrier: 8-15 wt%. The glass powder, by molar amount, comprises the following components: PbO: 33-59 mol%; WO3: 2.5-12.5 mol%; B2O3: 1-27 mol%. This application, through optimization of the glass powder formulation, effectively reduces the oxidation of metallic nickel during high-temperature sintering, thereby ensuring that the silver-nickel conductive paste containing nickel powder achieves ideal conductivity. This makes it possible to produce silver-nickel conductive pastes with higher nickel content, effectively expanding the application scenarios of silver-nickel conductive pastes in the field of crystalline silicon solar cell fabrication.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic devices, specifically relating to a conductive paste, a conductive electrode and its preparation method, and a crystalline silicon solar cell. Background Technology

[0002] In the field of photovoltaic metallization pastes, silver powder is used as the main conductive phase in the metallization conductive paste for crystalline silicon solar cells. Silver is a stable precious metal that can be sintered into a dense, highly conductive electrode structure through a high-temperature sintering process. However, the cost of silver accounts for a large proportion of the manufacturing cost of crystalline silicon solar cells. Therefore, innovative solutions are needed to reduce the amount of silver used while maintaining good photoelectric conversion efficiency of solar cells.

[0003] Replacing a small portion of silver powder with nickel powder can reduce the silver content in the paste and lower the cost of conductive paste. However, since the sintering temperature of crystalline silicon solar cells is typically between 700 and 780°C, nickel powder will oxidize during the high-temperature rapid sintering process in an oxygen-containing atmosphere. The resulting nickel oxide is a non-conductive phase, which leads to a significant reduction in the conductivity of the resulting silver-nickel electrode, thereby causing a loss in the photoelectric conversion efficiency of the solar cell.

[0004] Therefore, how to improve the formulation of conductive paste, while increasing the nickel content in the conductive paste, and ensuring that the silver-nickel electrode formed subsequently by the conductive paste has good conductivity, is a technical problem that needs to be solved. Summary of the Invention

[0005] This application provides a conductive paste, a conductive electrode and a preparation method thereof, and a crystalline silicon solar cell, aiming to solve the problem that nickel powder in existing conductive pastes is prone to oxidation during sintering, resulting in unsatisfactory conductivity of the subsequently formed silver-nickel electrode.

[0006] The first embodiment of this application provides a conductive paste, which, by mass, comprises the following components: Silver powder: 40~78wt% Nickel powder: 10~40wt% Glass powder: 2~6wt% Organic carrier: 8~15wt% Based on the amount of the glass powder, the glass powder comprises the following components: PbO: 33~59 mol% WO3: 2.5~12.5 mol% B2O3: 1~27 mol%.

[0007] In some embodiments, the molar ratio of PbO to WO3 is 4.4 to 14:1.

[0008] In some embodiments, the D of the nickel powder 50 The particle size is 1~10μm.

[0009] In some embodiments, the D of the silver powder 50 The particle size is 0.5~3μm.

[0010] In some embodiments, the glass powder further includes TeO2, wherein the molar percentage of TeO2 in the glass powder is 0.01 to 13 mol.

[0011] In some embodiments, the glass powder further includes a modifier, wherein the modifier has a molar percentage of 19-37 mol in the glass powder.

[0012] In some embodiments, the modifier includes at least one selected from Na2O, Li2O, Bi2O3, SiO2, Al2O3, ZnO, CuO, TiO2, and Fe2O3.

[0013] A second embodiment of this application provides a conductive electrode, comprising: A semiconductor substrate, the semiconductor substrate comprising a substrate, an n-type doped polysilicon layer and a first passivation layer stacked thereon, the n-type doped polysilicon layer being located between the substrate and the first passivation layer; A first conductive structure, at least partially penetrating the first passivation layer, is formed from the conductive paste in any of the above embodiments.

[0014] In some embodiments, the substrate comprises an n-type doped semiconductor substrate.

[0015] In some embodiments, the semiconductor substrate further includes a tunneling layer; the tunneling layer is disposed between the substrate and the n-type doped polysilicon layer.

[0016] The third embodiment of this application provides a crystalline silicon solar cell, which includes the conductive electrodes in any of the above embodiments.

[0017] The fourth embodiment of this application provides a method for preparing a crystalline silicon solar cell, comprising the following steps: A semiconductor substrate is provided, the semiconductor substrate comprising a substrate, a tunneling layer, an n-type doped polysilicon layer, a first passivation layer, a boron-doped emitter, and a second passivation layer stacked thereon; wherein the tunneling layer is disposed on one side of the substrate, the n-type doped polysilicon layer is disposed on the side of the tunneling layer away from the substrate, the first passivation layer is disposed on the side of the n-type doped polysilicon layer away from the tunneling layer, the boron-doped emitter is disposed on the side of the substrate away from the tunneling layer, and the second passivation layer is disposed on the side of the boron-doped emitter away from the substrate; A conductive paste is printed on at least a portion of the surface of the first passivation layer, wherein the conductive paste is the conductive paste in any of the above embodiments; The semiconductor substrate and the conductive paste are sintered, such that the conductive paste is etched and at least partially penetrates the first passivation layer during the sintering process to form a first conductive structure; The semiconductor substrate is subjected to laser-enhanced contact optimization to obtain the crystalline silicon solar cell.

[0018] In some embodiments, the step of printing conductive paste onto at least a portion of the surface of the first passivation layer further includes: The conductive paste is printed in a patterned form on at least a portion of the surface of the first passivation layer.

[0019] In some embodiments, the step of laser-enhanced contact optimization of the semiconductor substrate further includes: A reverse voltage is applied to the semiconductor substrate, and a laser scan is performed on the semiconductor substrate simultaneously to generate an induced current within the first conductive structure.

[0020] In some embodiments, the step of performing laser-enhanced contact optimization on the semiconductor substrate satisfies at least one of the following conditions: a) The reverse voltage is 5V~20V; b) The laser scanning time is 1ms to 100ms.

[0021] The fifth embodiment of this application provides a method for preparing a crystalline silicon solar cell, comprising the following steps: A semiconductor substrate is provided, the semiconductor substrate comprising a substrate, an n-type doped polysilicon layer, a first passivation layer, a p-type doped polysilicon layer, and a second passivation layer; wherein the n-type doped polysilicon layer and the p-type doped polysilicon layer are disposed side by side on the same side of the substrate, the first passivation layer is disposed on the side of the n-type doped polysilicon layer away from the substrate, and the second passivation layer is disposed on the side of the p-type doped polysilicon layer away from the substrate; A conductive paste is printed on at least a portion of the surface of the first passivation layer, wherein the conductive paste is the conductive paste in any of the above embodiments; The semiconductor substrate and the conductive paste are sintered, and the conductive paste is etched during the sintering process to at least partially penetrate the first passivation layer to form a first conductive structure; thus, the crystalline silicon solar cell is obtained. This application provides a conductive paste, comprising the following components by weight: silver powder: 40-78 wt%; nickel powder: 10-40 wt%; glass powder: 2-6 wt%; organic carrier: 8-15 wt%. The glass powder, by weight, comprises the following components: PbO: 33-59 mol%; WO3: 2.5-12.5 mol%; B2O3: 1-27 mol%. By optimizing the glass powder formulation, this application effectively reduces the oxidation of metallic nickel during high-temperature sintering, thereby ensuring that the silver-nickel conductive paste containing nickel powder achieves ideal conductivity. This makes it possible to produce silver-nickel conductive pastes with higher nickel content, effectively expanding the application scenarios of silver-nickel conductive pastes in the field of crystalline silicon solar cell fabrication. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A cross-sectional view of the conductive electrode provided in an embodiment of this application; Figure 2 A cross-sectional view of a conductive electrode provided in another embodiment of this application; Figure 3 The crystalline silicon solar cell provided in the embodiments of this application; Figure 4 A cross-sectional view of a crystalline silicon solar cell provided in another embodiment of this application.

[0024] Explanation of reference numerals in the attached figures: 10-Semiconductor substrate, 101-Substrate, 102-n-type doped polysilicon layer, 103-First passivation layer, 104-Tunneling layer, 105-Boron diffused emitter, 106-Second passivation layer, 107-p-type doped polysilicon layer, 108-Front-side textured structure, 20-First conductive structure, 30-Second conductive structure. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection, an indirect connection through an intermediate medium, or an indirect connection through a pipe or pipeline; they can refer to the internal communication of two components or the interaction between two components; they can refer to the connection between chemical substances through chemical bonds or an ohmic contact. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In the description of this application, "a plurality of" means two or more, unless otherwise expressly specified. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0027] Conductive paste is a crucial raw material for the fabrication of crystalline silicon solar cells. Replacing some silver powder with nickel powder in the conductive paste can effectively reduce the silver content and lower the cost. However, nickel powder is prone to oxidation at high temperatures. Furthermore, the glass powder used in the conductive paste for metallization of crystalline silicon solar cells significantly affects the oxidation of nickel powder. Since the glass powder (e.g., lead-tellurium oxide) in the conductive paste needs to penetrate the anti-reflection passivation layer on the cell surface to achieve electrical contact during high-temperature sintering, the glass powder used typically exhibits strong corrosive and oxidizing properties. Therefore, the high-temperature sintering of glass powder also increases the oxidation of nickel powder, reducing the conductivity of the resulting conductive electrode. This limits the usable nickel content in the silver-nickel paste to below 10%.

[0028] The applicant discovered through research that by optimizing the formulation of glass powder, it is possible to reduce the oxidation of metallic nickel by glass powder while maintaining the high-temperature corrosivity of glass powder, thereby overcoming the bottleneck that the nickel content in silver-nickel conductive paste cannot be too high.

[0029] The first embodiment of this application provides a conductive paste, which, based on the mass of the conductive paste, comprises the following components: Silver powder: 40~78wt% Nickel powder: 10~40wt% Glass powder: 2~6wt% Organic carrier: 8~15wt%.

[0030] The following describes each component in the conductive paste.

[0031] Conductive metal In some embodiments, the conductive metal serves as the power source for the conductive paste and can be any metal powder commonly used in electrodes formed on circuit substrates such as semiconductor substrates, without particular limitation. The conductive metal in this application includes silver powder and nickel powder, wherein the silver powder includes at least one of elemental silver and silver alloy powder, and the nickel powder includes at least one of elemental nickel, nickel alloy powder, and silver-coated nickel powder.

[0032] In some embodiments, the mass percentage of silver powder in the conductive paste is 40 wt% to 78 wt%, and may be 45 wt% to 75 wt%; may be further 50 wt% to 70 wt%; and may be further 55 wt% to 65 wt%.

[0033] In some embodiments, the mass percentage of nickel powder in the conductive paste is 10 wt% to 40 wt%, and may be 15 wt% to 35 wt%; may be further 20 wt% to 25 wt%; and may be further 23 wt% to 27 wt%.

[0034] Understandably, the ratio of silver powder and nickel powder 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 paste is used to conduct electricity after the formation of crystalline silicon solar cells. In this conductive paste, silver powder and nickel powder are used in combination, and the mass percentage of nickel powder is increased to 10~40wt%. This can significantly reduce the amount of silver used, thereby reducing costs while ensuring good conductivity and photoelectric conversion efficiency of crystalline silicon solar cells.

[0035] 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, for silver powder, it may be coated with a phosphorus-containing compound.

[0036] In some embodiments, the D of nickel powder 50 The particle size is 1~10μm, preferably 3~8μm, and more preferably 5~7μm.

[0037] Understandably, the D of nickel powder 50 The particle size can be any value from 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm, or any value within a range of any two values. Nickel powder particles can be spherical, puff-shaped, or similar to spherical shapes. The surface of the nickel powder can be smooth or rough. Spherical or near-spherical nickel powder helps achieve good dispersion and a good slurry state. 50 Particle size within the above range allows nickel powder to be in a better dispersed state in the conductive paste, which is beneficial for forming a more uniform conductive electrode during subsequent screen printing or other printing and coating methods applied to the surface of crystalline silicon solar cells.

[0038] In some embodiments, the D of silver powder 50 The particle size is 0.5~3μm.

[0039] Understandably, the D of silver powder 50 The particle size can be any value from 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, or any value within a range of any two values. The nickel powder particles can be spherical or near-spherical, or can be a mixture of one or more silver powders with different particle shapes. Spherical silver powder helps achieve good dispersion and a good slurry state. 50 Particle size within the above range allows silver powder to be better dispersed in the conductive paste, which is beneficial for forming a more uniform conductive electrode during subsequent screen printing or other printing and coating methods applied to the surface of crystalline silicon solar cells.

[0040] glass powder 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.

[0041] In some other embodiments, the glass powder of this embodiment can be understood as a composition having a glass component. The mass percentage of the glass powder in the conductive paste is 2 wt% to 6 wt%, and may also be 2.5 wt% to 5.5 wt%; may further be 3 wt% to 5 wt%; and may further be 3.5 wt% to 4.5 wt%.

[0042] Understandably, 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 the glass powder directly affects its meltability, flowability, and etchability; therefore, a good balance of glass powder composition is needed to achieve excellent carrier recombination. However, in conductive pastes containing silver and nickel powder, nickel powder becomes non-conductive after sintering due to surface oxidation. Therefore, a high proportion of nickel powder content will significantly reduce conductivity. Glass powder plays a crucial role in conductive pastes, including its influence on the densification of silver powder during sintering. The applicant's research has found that optimizing the glass powder formulation in conductive pastes containing silver and nickel powder can significantly reduce the impact of nickel powder on the conductivity of the electrode after sintering, thereby achieving a higher proportion of nickel content and reducing the manufacturing cost of crystalline silicon cells.

[0043] Based on the amount of substance, glass powder comprises the following components: PbO: 33~59 mol% WO3: 2.5~12.5 mol% B2O3: 1~27 mol%.

[0044] Unless otherwise specified, the “mol%” content of each component in the glass frit in the following description refers to the molar percentage converted from oxides.

[0045] It is understandable that the molar percentage of PbO in the glass powder can be any value or a range between any two of the following: 33 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 59 mol%. The molar percentage of WO3 in the glass powder can be any value or a range between any two of the following: 2.5 mol%, 4 mol%, 5.5 mol%, 7 mol%, 8.5 mol%, 10 mol%, 11.5 mol%, 12.5 mol%. The molar percentage of B2O3 in the glass powder can be any value or a range between any two of the following: 1 mol%, 4 mol%, 8 mol%, 12 mol%, 16 mol%, 20 mol%, 24 mol%, 27 mol%.

[0046] PbO, as a glass intermediate, not only enhances the corrosiveness of glass powder and etches the passivation layer on the surface of polycrystalline silicon, but also acts as an intermediate glass forming agent that can be incorporated into the glass network. Residual PbO exists outside the glass framework, acting as a glass modifier. WO3, due to the stability of the tungsten oxidation state in its crystal lattice, does not easily release oxygen atoms at high temperatures and can combine with free oxygen in the glass system, thus reducing the glass's ability to oxidize and corrode nickel powder. Simultaneously, WO3 can also regulate the electronic structure of the molten glass powder, reducing its overall oxidative activity and thus decreasing the probability of nickel powder oxidation. B2O3, a glass forming agent, is used to control the glass transition temperature (Tg) and high-temperature fluidity of glass. B2O3 can form low-melting-point glasses and provides good fluidity. Furthermore, B2O3, composed of BO3 triangles connected by bridging oxygen, forms a stable glass network structure, which improves the material's structural stability and mechanical strength. In addition, B2O3 can also help weaken the oxidation characteristics of glass powder, further inhibiting nickel powder oxidation. Therefore, the Pb-WBO glass frit system, composed of PbO, WO3 and B2O3, possesses both suitable high-temperature corrosion resistance and low oxidation characteristics. While ensuring the formation of electrical contact through the passivation layer, it reduces the oxidation of nickel powder, solving the problem of nickel powder oxidation and decreased electrode conductivity caused by the strong oxidation of glass frit. This enables the application of silver-nickel conductive pastes with high nickel content of 10~40wt%.

[0047] In some embodiments, the molar ratio of PbO to WO3 is 4.4 to 14:1.

[0048] It is understandable that the molar ratio of PbO to WO3 can be any value within the range of 4.4:1, 7:1, 9:1, 11:1, 13:1, or 14:1, or any two values ​​in between. Excessive PbO content may over-etch the passivation layer, leading to excessive recombination loss and reduced cell efficiency; conversely, insufficient PbO content may result in incomplete etching of the passivation layer, failing to form the required ohmic contact, leading to excessively high series resistance, which in turn affects the fill factor and causes efficiency loss. Excessive WO3 content will cause the glass powder to melt at an excessively high temperature, making it difficult to flow during sintering; while insufficient WO3 content will fail to inhibit nickel oxidation. Therefore, when the molar ratio of PbO to WO3 meets the above-mentioned range, the glass powder has a suitable liquidus temperature, ensuring a balance between corrosivity, low oxidation, and flowability.

[0049] In some embodiments, the glass powder may further include TeO2, wherein the molar percentage of TeO2 in the glass powder is 0.1 to 13 mol.

[0050] Understandably, the molar percentage of TeO2 in glass powder can be any value from 0.01 mol%, 0.5 mol%, 2 mol%, 4 mol%, 6 mol%, 8 mol%, 10 mol%, 12 mol%, or 13 mol%, or any value within a range of any two. TeO2 can increase the fluidity of glass, and adding a small amount can adjust the high-temperature fluidity and corrosivity of the glass powder. However, on the other hand, TeO2 has strong oxidizing properties; a high TeO2 content will exacerbate the oxidation of nickel powder, affecting the conductivity of the silver-nickel electrode after high-temperature sintering. Therefore, the molar percentage of TeO2 in glass powder needs to be limited to below 13 mol% to ensure that while increasing the fluidity and corrosivity of the glass powder, the negative impact on the conductivity of the silver-nickel electrode is reduced.

[0051] In other embodiments, the glass powder does not contain TeO2 to avoid oxidation of the nickel powder.

[0052] In some embodiments, the glass powder further includes a modifier, wherein the modifier has a molar percentage of 19 to 37 mol in the glass powder.

[0053] It is understandable that the molar percentage of the modifier in the glass powder can be any value from 19mol%, 22mol%, 25mol%, 28mol%, 31mol%, 34mol%, or 37mol%, or any value within a range of two of these. Furthermore, the modifier is an oxide. By adding a modifier that meets the above-mentioned value range to the glass powder, the properties of the glass powder, including the coefficient of thermal expansion, glass transition point, glass flowability, and corrosivity, can be further adjusted.

[0054] In some embodiments, the modifier includes at least one selected from Na2O, Li2O, Bi2O3, SiO2, Al2O3, ZnO, CuO, TiO2, and Fe2O3.

[0055] It is understandable that by adding the aforementioned modifiers to the glass powder, the network structure of the glass layer can be modified to adjust the physical, chemical, and thermal properties of the resulting glass, such as high-temperature fluidity, softening temperature, and melting temperature. For example, Al2O3 and ZnO can adjust the glass transition temperature (Tg) and high-temperature fluidity of the glass powder, and can also be used as components to improve the weather resistance of the glass powder; TiO2 can improve the glass material's resistance to acid and alkali corrosion, and increase the hardness and strength of the glass layer; Na2O and Li2O can lower the glass softening temperature; Bi2O3 can improve the stability of the glass; SiO2 can adjust the corrosivity of the glass powder, ultimately matching the sintering requirements of different batteries (such as TOPCon, TBC, etc.), without further aggravating the oxidation of nickel powder.

[0056] organic carrier Organic carriers serve as the dispersed phase in conductive pastes and provide printability. They include one or more components that can impart functional properties, such as polymers, surfactants, thickeners, thixotropic agents, and binders.

[0057] It is understood that the mass percentage content of the organic carrier can be any value from 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, or any value within a range of any two values.

[0058] In some embodiments, an organic carrier is used as the liquid phase in the conductive paste to disperse the solids, relative to the solids composed of silver powder and glass powder, to form a paste with a certain viscosity. The viscosity and rheological properties of this paste enable the silver powder and glass powder to be dispersed stably in 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 passivation layer surface of the semiconductor substrate 10 by screen printing.

[0059] 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.

[0060] 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.

[0061] 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 within 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.

[0062] 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 dispersing and 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 should be adjusted to ensure that the sum of the mass percentages of each component in the conductive paste is 100%.

[0063] conductive electrodes The second embodiment of this application provides a conductive electrode, such as... Figure 1 As shown, it includes: The semiconductor substrate 10 includes a substrate 101, an n-type doped polysilicon layer 102 and a first passivation layer 103 stacked together, wherein the n-type doped polysilicon layer 102 is located between the substrate 101 and the first passivation layer 103. The first conductive structure 20, at least a portion of which penetrates the first passivation layer 103, is formed from the conductive paste in any of the above embodiments.

[0064] In some embodiments, substrate 101 includes an n-type doped semiconductor substrate 101.

[0065] In other embodiments, such as Figure 2 As shown, the semiconductor substrate 10 further includes a tunneling layer 104; the tunneling layer 104 is disposed between the substrate 101 and the n-type doped polysilicon layer 102.

[0066] Solar cells The third embodiment of this application provides a crystalline silicon solar cell, which includes the conductive electrodes in any of the above embodiments.

[0067] In some embodiments, the crystalline silicon solar cell structure is an n-TOPCon cell, such as... Figure 3As shown, the semiconductor substrate 10 includes a first conductive structure 20 and a second conductive structure 30, which are respectively disposed on opposite sides of the semiconductor substrate 10. The semiconductor substrate 10 includes: a substrate 101; a tunneling layer 104, an n-type doped polysilicon layer 102, and a first passivation layer 103 stacked on one side of the substrate 101; and a boron diffused emitter 105 and a second passivation layer 106 stacked on the other side of the substrate 101.

[0068] Specifically, the tunneling layer 104 is disposed on one side of the substrate 101, the n-type doped polysilicon layer 102 is disposed on the side of the tunneling layer 104 away from the substrate 101, the first passivation layer 103 is disposed on the side of the n-type doped polysilicon layer 102 away from the tunneling layer 104, the boron diffused emitter 105 is disposed on the side of the substrate 101 away from the tunneling layer 104, and the second passivation layer 106 is disposed on the side of the boron diffused emitter 105 away from the substrate 101.

[0069] The substrate 101 can be an n-type doped semiconductor substrate 101. The tunneling layer 104, the n-type doped polysilicon layer 102, and the first passivation layer 103 are located on the back side of the substrate 101; the tunneling layer 104 can be formed by the tunneling oxide passivation contact method, and the tunneling layer 104 can be an ultrathin silicon dioxide layer; the n-type doped polysilicon layer 102 can be a phosphorus doped polysilicon layer.

[0070] Based on the above embodiments, the first conductive structure 20 is prepared using the metallized conductive paste provided in the embodiments of this application. The conductive paste is applied to at least a portion of the surface of the first passivation layer 103 in a desired patterned form. During the sintering process, the glass powder in the conductive paste etches and penetrates the first passivation layer 103, thereby forming an electrical contact with the n-type doped polysilicon layer 102, so as to form the first conductive structure 20 in the form of conductive metal contacts.

[0071] The second conductive structure 30 can be prepared using commercially available metallization silver pastes used in p-type or n-type crystalline silicon solar cells, such as Solamet PV3NL silver paste. The silver paste is applied to at least a portion of the surface of the second passivation layer 106 in a desired patterned form. During sintering, the silver paste penetrates the second passivation layer 106 to obtain the second conductive structure 30, which forms a low-carrier recombination with the boron diffused emitter 105.

[0072] It is understandable that the first conductive structure 20 is the back electrode of the n-TOPCon crystalline silicon solar cell, and the second conductive structure 30 is the front electrode of the n-TOPCon crystalline silicon solar cell. Since the back electrode has no light-shielding limitations and does not require a fine grid design, the higher nickel content in the conductive paste can not only significantly reduce the cost of the conductive paste, but the metallic nickel can also improve the hardness and wear resistance of the formed silver-nickel electrode.

[0073] In other embodiments, the crystalline silicon solar cell structure is a TBC cell, such as... Figure 4 As shown, the semiconductor substrate 10 includes a first conductive structure 20 and a second conductive structure 30, with the first conductive structure 20 and the second conductive structure 30 disposed on the same side of the semiconductor substrate 10. The semiconductor substrate 10 includes a substrate 101, an n-type doped polysilicon layer 102, a first passivation layer 103, a p-type doped polysilicon layer 107, and a second passivation layer 106. The n-type doped polysilicon layer 102 and the p-type doped polysilicon layer 107 are disposed side-by-side and spaced apart on the same side of the substrate 101. The first passivation layer 103 is disposed on the side of the n-type doped polysilicon layer 102 away from the substrate 101, and the second passivation layer 106 is disposed on the side of the p-type doped polysilicon layer 107 away from the substrate 101.

[0074] Furthermore, a front textured structure 108 is provided on the side of the substrate 101 away from the n-type doped polysilicon layer 102 and the p-type doped polysilicon layer 107. A third passivation layer (not shown in the figure) may also be provided on the side of the front textured structure 108 away from the substrate 101.

[0075] Based on the above embodiments, the first conductive structure 20 is prepared using the metallized conductive paste provided in the embodiments of this application. The conductive paste is applied to at least a portion of the surface of the first passivation layer 103 in a desired patterned form. During the sintering process, the glass powder in the conductive paste etches and penetrates the first passivation layer 103, thereby forming an electrical contact with the n-type doped polysilicon layer 102, so as to form the first conductive structure 20 in the form of conductive metal contacts.

[0076] The second conductive structure 30 can be prepared using commercially available metallization silver pastes used in p-type or n-type crystalline silicon solar cells, such as Solamet PV9P1 silver paste. The silver paste is applied to at least a portion of the surface of the second passivation layer 106 in a desired patterned form. During sintering, the silver paste penetrates the second passivation layer 106 to obtain the second conductive structure 30 that forms an electrical contact with the p-type doped polycrystalline silicon layer 107.

[0077] The fourth embodiment of this application provides a method for fabricating a crystalline silicon solar cell. The fabrication of an n-TOPCon crystalline silicon solar cell includes the following steps: A semiconductor substrate 10 is provided, comprising a substrate 101, a tunneling layer 104, an n-type doped polysilicon layer 102, a first passivation layer 103, a boron-doped emitter 105, and a second passivation layer 106 stacked together. The tunneling layer 104 is disposed on one side of the substrate 101, the n-type doped polysilicon layer 102 is disposed on the side of the tunneling layer 104 away from the substrate 101, the first passivation layer 103 is disposed on the side of the n-type doped polysilicon layer 102 away from the tunneling layer 104, the boron-doped emitter 105 is disposed on the side of the substrate 101 away from the tunneling layer 104, and the second passivation layer 106 is disposed on the side of the boron-doped emitter 105 away from the substrate 101. A conductive paste is printed on at least a portion of the surface of the first passivation layer 103, wherein the conductive paste is the conductive paste in any of the above embodiments; Metallized silver paste is printed on at least a portion of the surface of the second passivation layer 106. The metallized silver paste may be the same as the conductive paste provided in this application or may be a commercially available metallized silver paste that is different from the conductive paste provided in this application. The semiconductor substrate 10 is sintered, and the conductive paste is etched during the sintering process to at least partially penetrate the first passivation layer 103 to form a first conductive structure 20; the metallized silver paste is etched during the sintering process to at least partially penetrate the second passivation layer 106 to form a second conductive structure 30. Laser-enhanced contact optimization was performed on the semiconductor substrate 10 to obtain a crystalline silicon solar cell.

[0078] In some embodiments, the step of printing conductive paste onto at least a portion of the surface of the first passivation layer 103 further includes: The conductive paste is printed in a patterned manner onto at least a portion of the surface of the first passivation layer 103. Specifically, the patterning method can be screen printing.

[0079] In some embodiments, the step of laser-enhanced contact optimization of the semiconductor substrate 10 further includes: A reverse voltage is applied to the semiconductor substrate 10, and a laser scan is performed on the semiconductor substrate 10 simultaneously to form an induced current within the first conductive structure 20.

[0080] Understandably, laser-enhanced contact optimization after sintering is a method used in solar cell manufacturing to improve the electrical contact of the metallization paste using lasers. 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 efficiency and reliability of the solar cell. In this technology, the injection amount of charge carriers can be controlled by parameters such as laser power and time to achieve better contact uniformity and improvement effect.

[0081] In some embodiments, the reverse voltage is 5V~20V.

[0082] It is understandable that the value of the reverse voltage (unit: V) is any value from 5, 8, 10, 12, 14, 16, 18, 20 or any value from any two of these ranges.

[0083] In some embodiments, the laser scanning time is 1ms to 100ms.

[0084] It is understandable that the laser scanning time (in milliseconds) can be any value from the range of 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100, or any two of these values. When the reverse voltage and laser scanning time meet the above range, the contact resistance can be effectively reduced, while avoiding damage to the conductive structure caused by excessively high reverse voltage and excessively long laser scanning time.

[0085] In other embodiments, this application also provides a method for preparing a TBC crystalline silicon solar cell, comprising the following steps: A semiconductor substrate 10 is provided, which includes a substrate 101, an n-type doped polysilicon layer 102, a first passivation layer 103, a p-type doped polysilicon layer 107, and a second passivation layer 106. The n-type doped polysilicon layer 102 and the p-type doped polysilicon layer 107 are disposed side by side on the same side of the substrate 101, the first passivation layer 103 is disposed on the side of the n-type doped polysilicon layer 102 away from the substrate 101, and the second passivation layer 106 is disposed on the side of the p-type doped polysilicon layer 107 away from the substrate 101. A conductive paste is printed on at least a portion of the surface of the first passivation layer 103, wherein the conductive paste is the conductive paste in any of the above embodiments; Metallized silver paste is printed on at least a portion of the surface of the second passivation layer 106. The metallized silver paste may have the same composition as the conductive paste provided in this application, or it may be a commercially available metallized silver paste that is different from the conductive paste provided in this application.

[0086] The semiconductor substrate 10 is sintered, and the conductive paste is etched during the sintering process to at least partially penetrate the first passivation layer 103 to form a first conductive structure 20; the metallized silver paste is etched during the sintering process to at least partially penetrate the second passivation layer 106 to form a second conductive structure 30.

[0087] The conductive paste, conductive electrode, crystalline silicon solar cell, and fabrication method provided in this application are described below with reference to specific embodiments: Glass powders numbered GF1 to 10 were prepared, each number representing one unit of glass powder. The component content of each unit of glass powder is shown in Table 1. The sum of all components in each unit of glass powder is 100 mol%. Among them, GF1 to 8 and GF9 to 10 were used to adjust the Pb-WB ratio and the amount of TeO2 added, respectively, to regulate the conductivity of the conductive paste. Among them, the glass powders in GF6 to 8 did not contain TeO2, while the TeO2 content in the glass powders in GF9 to 10 all exceeded 13 mol%.

[0088] Table 1

[0089] Glass powders numbered GF1~10 were prepared into conductive pastes, and then further processed into silver-nickel electrodes. The bulk resistivity of the silver-nickel electrodes was tested using the following method: The aforementioned glass powder was prepared into a high-glass-concentration conductive paste, and line patterns were created using screen printing (graphics: 700µm wide × 17.5cm), followed by high-temperature sintering. After sintering, the actual line width (W) and line height (H) were measured using a profilometer, and the line resistance (R) was tested using a Keithley multimeter. The volume resistivity was then calculated using ρ = R × Area / Length.

[0090] The composition and test results of the prepared conductive paste are shown in Table 2.

[0091] Table 2

[0092] As shown in Table 2, the silver and nickel powder contents are the same in Examples 1-8 and Comparative Examples 1-2. The difference lies in that the TeO2 content in the glass powder used in Examples 1-8 does not exceed 13 mol%, while the glass powder used in Comparative Examples 1 and 2 contains 30 mol% and 19 mol% TeO2, respectively. Examples 1-5 show that, with the same proportion of nickel powder added, the bulk resistivity decreases as the TeO2 content in the glass powder decreases. Examples 6-8 show that when the glass powder contains no TeO2, the bulk resistivity slightly increases again, indicating that when the glass powder contains a small amount of TeO2 within the range provided in this application, it can provide the most ideal improvement to the electrical properties of the conductive paste. Comparative Examples 1-2 show that when the TeO2 content in the glass powder is too high, it will have a significant negative impact on the bulk resistivity of the silver-nickel electrode.

[0093] Glass powders numbered GF11 to GF17 were prepared, with each number representing one unit of glass powder. The component content of each unit of glass powder is shown in Table 3. The sum of all components in each unit of glass powder is 100 mol%. Among them, GF11 to GF17 respectively adjusted the Pb-WB ratio and the amount of modifier added to regulate the glass powder's properties such as glass transition temperature, melting temperature, high-temperature fluidity, viscosity, and corrosivity.

[0094] Table 3

[0095] Glass powders numbered GF1~9 and GF10~17 were prepared into conductive pastes and further fabricated into n-TOPCon crystalline silicon solar cells. The fabrication steps are as follows: 1) A semiconductor substrate 10 is provided, the structure of which is as follows: Figure 3 As shown; 2) The main gate and fine gate pastes are sequentially printed on the back and front sides of the semiconductor substrate 10, corresponding to one to four printing presses. After each printing, the substrate is dried before printing the next printing. The printing sequence is as follows: a) First stage: Back main grid, using commercially available Solamet PVD2L slurry; b) Second stage: Backside fine grid, the paste used is the conductive paste provided in the embodiments of this application; c) Third stage: Front main grid, using commercially available Solamet PVD2L paste; d) Fourth stage: front fine grid, using commercially available Solamet PV3NL slurry.

[0096] 3) Sintering the semiconductor substrate 10, metallized conductive paste, and metallized silver paste, wherein the metallized conductive paste is etched and penetrates the passivation layer during sintering to form a first conductive structure 20 electrically connected to the boron diffuser 105, and the metallized silver paste is etched and penetrates the passivation layer during sintering to form a second conductive structure 30 electrically connected to the n-type doped polysilicon layer 102. The sintering equipment and sintering conditions are a Maiwei sintering furnace, a furnace temperature zone of 18, and the sintering furnace settings are: a) Upper temperature zone 7~18 settings: 390℃, 420℃, 440℃, 500℃, 600℃, 700℃, 730℃, 750℃, 760℃, 780℃, 830℃, 680℃; b) Lower temperature zone 7~18 settings: 400℃, 440℃, 460℃, 530℃, 620℃, 700℃, 730℃, 760℃, 790℃, 880℃, 890℃, 650℃; c) Belt speed: 16 inch / min.

[0097] 4) Laser-enhanced contact optimization was performed on the sintered solar cells (DR Laser DR-M4XS-LIF-1000, laser bias: 45%, laser power: 20%).

[0098] Examples 9-22 and Comparative Examples 3-4 were prepared using the above method. The photoelectric conversion efficiency of the crystalline silicon solar cells in Examples 9-22 and Comparative Examples 3-4 was tested using a commercially available HALM IV curve testing system. Test parameters included efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), current (Isc), and line resistance (Rgrid). The composition of the conductive paste in Examples 9-22 and Comparative Examples 3-4 and the test results are shown in Table 4.

[0099] Table 4

[0100] As can be seen from Tables 3 and 4, the glass powder obtained by the scheme provided in this application can maintain good battery efficiency in conjunction with the high content of nickel powder in the conductive paste. A comparison of Examples 9-18 and Comparative Example 3 shows that controlling the TeO2 content in the glass powder to below 13 mol% can achieve the advantage of line resistance Rgrid, thereby improving the fill factor FF and battery efficiency Eff. Example 18 shows that although reducing PbO reduces the corrosivity of the glass material, by adding other modifiers for synergistic effects and controlling the PbO content in the glass powder to be greater than 33 mol%, a good corrosion effect of the conductive paste on the passivation layer can still be ensured, thus ensuring the final battery efficiency. Example 22 shows that when the nickel content in the conductive paste reaches 40 wt%, it will have a certain impact on battery efficiency. However, considering the cost reduction that can be achieved with a nickel content of 40 wt%, the reduction in battery efficiency can be balanced, allowing the battery to still have relatively ideal overall performance. Comparative Example 4 shows that when the glass material does not contain B2O3, the line resistance Rgrid will increase, affecting battery efficiency and resulting in poor overall battery performance.

[0101] The conductive paste, conductive electrode, crystalline silicon solar cell, and preparation method provided in the embodiments of this application have been described in detail above. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. 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 application.

Claims

1. An electrically conductive paste, characterized by, The conductive paste comprises the following components by mass of the conductive paste: Silver powder: 40-78 wt%; Nickel powder: 10-40 wt%; Glass powder: 2-6 wt%; Organic vehicle: 8-15 wt%; The glass powder comprises the following components by amount of substance of the glass powder: PbO: 33-59 mol%; WO3: 2.5-12.5 mol%; B2O3: 1-27 mol%.

2. The electroconductive paste according to claim 1, characterized by The molar ratio of the PbO and the WO3 is 4.4-14:

1.

3. The electrically conductive paste of claim 1, wherein The nickel powder has a D 50 a particle size of 1 to 10 μm; and / or, The silver powder has a D 50 The particle size is 0.5-3 μm.

4. The conductive paste of claim 1, wherein The glass powder further comprises TeO2, the mole percentage of the TeO2 in the glass powder is 0.01-13 mol%.

5. The electrically conductive paste of claim 1, wherein The glass powder further comprises a modifier, the mole percentage of the modifier in the glass powder is 19-37 mol%.

6. The electroconductive paste according to claim 5, wherein The modifier comprises at least one of Na2O, Li2O, Bi2O3, SiO2, Al2O3, ZnO, CuO, TiO2 and Fe2O3.

7. An electrically conductive electrode, characterized by The semiconductor substrate (10) comprises a substrate (101), an n-doped polysilicon layer (102) and a first passivation layer (103) which are arranged in a stack, the n-doped polysilicon layer (102) being between the substrate (101) and the first passivation layer (103); The first conductive structure (20) penetrates at least part of the first passivation layer (103), the first conductive structure (20) being formed by the conductive paste according to any one of claims 1-6. The substrate (101) comprises an n-doped semiconductor substrate.

8. The conductive electrode according to claim 7, wherein The semiconductor substrate (10) further comprises a tunneling layer (104); the tunneling layer (104) is arranged between the substrate (101) and the n-doped polysilicon layer (102).

9. The conductive electrode of claim 7, wherein, The crystalline silicon solar cell comprises the conductive electrode according to any one of claims 7-9.

10. A crystalline silicon solar cell, characterized by, The method comprises the following steps:

11. A method of fabricating a crystalline silicon solar cell, characterized by, providing a semiconductor substrate (10) comprising a substrate (101), a tunneling layer (104), an n-doped polysilicon layer (102), a first passivation layer (103), a boron-diffused emitter (105) and a second passivation layer (106); wherein the tunneling layer (104) is arranged on one side of the substrate (101), the n-doped polysilicon layer (102) is arranged on a side of the tunneling layer (104) away from the substrate (101), the first passivation layer (103) is arranged on a side of the n-doped polysilicon layer (102) away from the tunneling layer (104); the boron-diffused emitter (105) is arranged on a side of the substrate (101) away from the tunneling layer (104), and the second passivation layer (106) is arranged on a side of the boron-diffused emitter (105) away from the substrate (101); printing a conductive paste on at least part of the surface of the first passivation layer (103), the conductive paste being the conductive paste according to any one of claims 1-6; ​ sintering the semiconductor substrate (10) and the conductive paste, so that the conductive paste etches and at least partially penetrates the first passivation layer (103) during the sintering process to form a first conductive structure (20); performing laser enhanced contact optimization on the semiconductor substrate (10) to obtain the crystalline silicon solar cell.

12. The method of claim 11, wherein the method further comprises: The step of printing the conductive paste on at least part of the surface of the first passivation layer (103) further comprises: The step of printing the conductive paste on at least part of the surface of the first passivation layer (103) further comprises:

13. The method of claim 11, wherein the method further comprises: The step of performing laser enhanced contact optimization on the semiconductor substrate (10) further comprises: applying a reverse voltage to the semiconductor substrate (10) and simultaneously performing laser scanning on the semiconductor substrate (10) to form induced current in the first conductive structure (20).

14. The method of producing a crystalline silicon solar cell according to claim 13, wherein The step of performing laser enhanced contact optimization on the semiconductor substrate (10) satisfies at least one of the following conditions: a) the reverse voltage is 5V-20V; b) the time of the laser scanning is 1ms-100ms.

15. A method of fabricating a crystalline silicon solar cell, characterized by, The method comprises the following steps: providing a semiconductor substrate (10), the semiconductor substrate (10) comprising a substrate (101), an n-type doped polysilicon layer (102), a first passivation layer (103), a p-type doped polysilicon layer (107) and a second passivation layer (106); wherein the n-type doped polysilicon layer (102) and the p-type doped polysilicon layer (107) are arranged side by side on the same side of the substrate (101), the first passivation layer (103) is arranged on the side of the n-type doped polysilicon layer (102) away from the substrate (101), and the second passivation layer (106) is arranged on the side of the p-type doped polysilicon layer (107) away from the substrate (101); printing a conductive paste on at least part of the surface of the first passivation layer (103), the conductive paste being the conductive paste according to any one of claims 1-6; sintering the semiconductor substrate (10) and the conductive paste, so that the conductive paste etches and at least partially penetrates the first passivation layer (103) during the sintering process to form a first conductive structure (20), to obtain the crystalline silicon solar cell.

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