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

Abstract

This application discloses a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a method for its preparation. The conductive paste comprises, by weight, the following components: conductive metal: 81-90 wt%; first glass powder: 0.5-2 wt%; second glass powder: 0.5-2 wt%; organic carrier: 9-15 wt%. The first glass powder comprises, by weight, the following components: first corrosive oxide: 10-22 mol%; first glass formation: 46-68 mol%; BaO: 6.5-28.5 mol%; modifier: 4-16 mol%. The first glass formation includes B₂O₃, and the modifier includes at least one of Fe₂O₃ and TiO₂. This conductive paste effectively reduces recombination losses of metallized carriers while ensuring good contact performance and a suitable sintering window, thus achieving a balance in open-circuit voltage, cell efficiency, and resistance to acetic acid degradation.

Description

Technical Field

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

[0002] A key factor driving the continuous improvement of photoelectric conversion efficiency in crystalline silicon solar cells is reducing recombination losses to increase open-circuit voltage. For example, for n-type solar cells, the use of a TOPCon structure on the back side significantly reduces surface and metallization recombination losses, thereby significantly improving open-circuit voltage and efficiency. Furthermore, the metallization paste is crucial to the reliability of cells and modules. A common evaluation method for cells is the acetic acid degradation test, which measures the performance degradation rate of cells after prolonged exposure to an acidic environment.

[0003] The dedicated conductive paste for TOPCon crystalline silicon solar cells mainly uses lead silicon boron oxide or bismuth silicon boron oxide glass frits. The low-corrosion design reduces the etching of the front antireflection layer. However, the weakening of the corrosivity of the glass frit leads to poor contact and narrowing of the sintering window, which in turn negatively affects the cell efficiency and production yield.

[0004] Therefore, the photovoltaic industry needs a conductive paste that can be used in n-TOPCon cells to achieve ideal open-circuit voltage and cell efficiency while ensuring excellent sintering window and resistance to acetic acid degradation. Summary of the Invention

[0005] This application provides a conductive paste, a conductive electrode, a crystalline silicon solar cell, and a fabrication method, aiming to solve the problem that existing conductive pastes cannot balance reducing recombination losses of metallization carriers and maintaining an excellent sintering window.

[0006] The first embodiment of this application provides a conductive paste, which, by mass, comprises the following components: Conductive metal: 81~90wt% First glass powder: 0.5~2wt%; Second glass powder: 0.5~2wt%; Organic carrier: 9~15wt% Based on the amount of the first glass powder, the first glass powder comprises the following components: First corrosive oxide: 10~22 mol% First glass-forming component: 46~68 mol% BaO: 6.5~28.5 mol% Modifier: 4~16 mol% Wherein, the first glass forming body comprises B2O3, and the modifier comprises at least one of Fe2O3 and TiO2; the second glass powder comprises a second corrosive oxide and a second glass forming body.

[0007] In some embodiments, the molar ratio of BaO to the modifier is 0.9 to 7:1.

[0008] In some embodiments, the first corrosive oxide includes at least one of PbO and Bi2O3.

[0009] In some embodiments, the first glass form further includes at least one of Al2O3 and SiO2.

[0010] In some embodiments, the molar percentage of B2O3 in the first glass forging is 42-87%.

[0011] In some embodiments, the second corrosive oxide includes at least one of PbO and Bi2O3.

[0012] In some embodiments, the second glass-forming body includes at least one of B2O3, Al2O3, and SiO2.

[0013] In some embodiments, the molar percentage of the second corrosive oxide in the second glass powder is 22-32%.

[0014] A second embodiment of this application provides a conductive electrode, comprising: A semiconductor substrate, the semiconductor substrate comprising a substrate, a boron-derived emitter and a first passivation layer stacked thereon, the boron-derived emitter 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.

[0015] In some embodiments, the substrate comprises an n-type doped semiconductor substrate.

[0016] The third embodiment of this application provides a crystalline silicon solar cell, which includes the conductive electrodes in any of the above embodiments; 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 boron-derived emitter, a first passivation layer, a tunneling layer, an n-type doped polysilicon layer, and a second passivation layer, wherein the boron-derived emitter is disposed on one side of the substrate, the first passivation layer is disposed on the side of the boron-derived emitter away from the substrate, the tunneling layer is disposed on the side of the substrate away from the boron-derived emitter, the n-type doped polysilicon layer is disposed on the side of the tunneling layer away from the substrate, and the second passivation layer is disposed on the side of the n-type doped polysilicon layer away from the tunneling layer; 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] This application provides a conductive paste, comprising the following components by weight: conductive metal: 81-90 wt%; first glass powder: 0.5-2 wt%; second glass powder: 0.5-2 wt%; organic carrier: 9-15 wt%. The first glass powder comprises the following components by weight: first corrosive oxide: 10-22 mol%; first glass formation: 46-68 mol%; BaO: 6.5-28.5 mol%; modifier: 4-16 mol%. The first glass formation comprises B2O3, and the modifier comprises at least one of Fe2O3 and TiO2. The second glass powder comprises a second corrosive oxide and a second glass formation. This application, by adding a Ba-MBO composite (M = Fe / Ti) glass powder formulation to the conductive paste, can effectively reduce recombination losses of metallized carriers, ensuring ideal open-circuit voltage and cell efficiency in crystalline silicon solar cells. Simultaneously, it ensures good contact performance and a good sintering window in the conductive paste, enabling the cell to exhibit ideal resistance to acetic acid degradation. Attached Figure Description

[0021] 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.

[0022] Figure 1 A cross-sectional view of the conductive electrode provided in an embodiment of this application; Figure 2 This is a cross-sectional view of a crystalline silicon solar cell provided in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures: 10-Semiconductor substrate, 101-Substrate, 102-Boron diffused emitter, 103-First passivation layer, 104-Tunneling layer, 105-n-type doped polysilicon layer, 106-Second passivation layer, 20-First conductive structure, 30-Second conductive structure. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] In the photovoltaic industry, for the front side (i.e., the light-receiving surface) of n-TOPCon cells, utilizing low-corrosion paste design combined with laser-assisted contact improvement technology can significantly reduce metallization carrier recombination losses, achieving substantial improvements in open-circuit voltage and cell efficiency—a feasible approach. However, the photovoltaic industry has a continuous need for efficiency improvements and cost reductions, and how to further enhance the open-circuit voltage based on existing conductive paste and cell technologies remains a major challenge. For glass powders such as lead-silicon-boron oxide or bismuth-silicon-boron oxide, maintaining an excellent sintering window while further reducing metallization carrier recombination losses presents a significant challenge.

[0027] The applicant discovered through research that using a Ba-MBO compounded glass powder formulation (M being Fe or Ti) in conductive paste can reduce the corrosivity of the glass powder while helping to stabilize the glass structure. This allows for an increase in open-circuit voltage without worsening acetic acid degradation, thus improving the overall performance of the battery.

[0028] The first embodiment of this application provides a conductive paste, which, based on the mass of the conductive paste, comprises the following components: Conductive metal: 81~90wt% First glass powder: 0.5~2wt%; Second glass powder: 0.5~2wt%; Organic carrier: 9~15wt% The following describes each component in the conductive paste.

[0029] glass powder In some embodiments, the first glass powder and the second glass powder refer to compositions containing one or more types of anions and cations, respectively. 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.

[0030] In some other embodiments, the first glass powder of this embodiment can be understood as a composition having a glass component. The mass percentage of the first glass powder in the conductive paste is 0.5wt% to 2wt%, and may also be 0.7wt% to 1.8wt%; may further be 0.9wt% to 1.6wt%; and may further be 1.1wt% to 1.4wt%.

[0031] Understandably, the ratio of the first glass powder and the second glass powder in the conductive paste needs to be adjusted to ensure that the sum of the weight percentages of all components in the conductive paste is 100%. The composition and ratio of the first glass powder and the second glass powder directly affect its melting properties, fluidity, and etching properties. Therefore, the composition of the glass powder needs to be well balanced to achieve excellent carrier recombination effect.

[0032] The first glass powder comprises the following components based on its molar amount: First corrosive oxide: 10~22 mol% First glass-forming component: 46~68 mol% BaO: 6.5~28.5 mol% Modifier: 4~16 mol% The first glass forming body includes B2O3, and the modifier includes at least one of Fe2O3 and TiO2; the second glass powder includes a second corrosive oxide and a second glass forming body.

[0033] 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.

[0034] It is understood that the molar percentage of corrosive oxides in the first glass powder can be any value from 10 mol%, 12 mol%, 14 mol%, 16 mol%, 18 mol%, 20 mol%, or any value within a range of any two of these values. The molar percentage of the first glass forging in the first glass powder can be any value from 46 mol%, 48 mol%, 50 mol%, 52 mol%, 54 mol%, 56 mol%, 58 mol%, 60 mol%, 62 mol%, 64 mol%, 66 mol%, or 68 mol%, or any value within a range of any two of these values. The molar percentage of BaO in the first glass powder can be any value from 6.5 mol%, 10.5 mol%, 14.5 mol%, 18.5 mol%, 22.5 mol%, 26.5 mol%, or 28.5 mol%, or any value within a range of any two of these values. The molar percentage of the modifier in the first glass powder can be any value from 4mol%, 6mol%, 8mol%, 10mol%, 12mol%, 14mol%, 16mol%, or any value from a range of any two values.

[0035] The composition of the first glass powder has a significant impact on the process of forming a conductive structure in the conductive paste during high-temperature sintering. Specifically, the glass powder is adjusted in terms of glass transition temperature, glass melting temperature, coefficient of thermal expansion, high-temperature viscosity and fluidity, and corrosivity through the combination and formulation of corrosive oxides, the first glass forging body, BaO, and modifiers. This allows the glass powder to effectively etch the passivation layer during high-temperature rapid sintering, thereby forming a good conductive electrode structure.

[0036] The first corrosive oxide can be adjusted within a specified range to provide sufficient etching power, allowing the conductive paste to locally open the passivation layer during high-temperature sintering. This enables the metal in the conductive paste to form an electrical contact with the underlying boron-derived emitter 102 through a laser-enhanced contact optimization process. However, excessive corrosive oxide will etch too much of the passivation layer, affecting the passivation effect of the crystalline silicon solar cell and consequently its photoelectric conversion efficiency.

[0037] BaO can reduce the corrosivity of glass powder, achieve lower recombination loss of metallized carriers, and improve the open-circuit voltage of the battery. Meanwhile, Fe2O3 / TiO2, as a modifier, can form a network with Si, and the high-intermediate cations can encapsulate BaO. 2+ Increase Ba 2+ Stability within glass structures, avoiding Ba 2+Degradation or precipitation under acidic conditions leads to glassy phase dissolution and acetic acid degradation. On the other hand, BaO can introduce non-bridging oxygen by breaking Si-O-Si bonds. The introduced non-bridging oxygen can form a stable coordination structure with Fe-O-Si / Ti-O-Si bonds, which not only retains the network stability enhanced by Fe2O3 / TiO2 to resist acetic acid hydrolysis, but also allows BaO to degrade or precipitate, resulting in acetic acid degradation. 2+ The ionic bonding enhances the toughness of the glass phase, preventing film cracks in the sintered electrode that could lead to acetic acid penetration, thereby further improving the battery's resistance to acetic acid degradation.

[0038] Fe2O3 / TiO2 can reduce Ba... 2+ In addition to improving the battery's resistance to acetic acid degradation, the precipitation of silver can also serve as a crystal nucleus to refine silver particles, reduce the porosity of the silver layer, further reduce acetic acid permeation channels, and strengthen the glass structure.

[0039] The first glass forging is used to adjust the glass transition temperature (Tg) and high-temperature fluidity of the glass powder. Appropriate addition can stabilize the glass phase and adjust the melting point and fluidity of the glass powder. Specifically, B₂O₃ can lower the glass transition temperature (Tg) and increase the fluidity of the glass, thereby constructing an ideal glass structure while, in conjunction with BaO, further reducing the overall corrosivity of the glass powder and minimizing recombination losses of metal carriers.

[0040] In some embodiments, the molar ratio of BaO to the modifier is 0.9 to 7:1.

[0041] Understandably, the molar ratio of BaO to the modifier can be any value from 0.9:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, or any value within a range of any two values. On one hand, BaO and Fe2O3 / TiO2 need to achieve optimal interaction at a certain ratio to ensure low overall corrosivity of the glass powder while exhibiting ideal resistance to acetic acid degradation. On the other hand, excessive BaO may lead to an overly porous glass phase, weakening the densifying effect of Fe2O3 / TiO2, while excessive Fe2O3 / TiO2 may offset the reduction in glass powder viscosity caused by BaO. By controlling the molar ratio of BaO to the modifier to meet the above-mentioned range, the desired effect of the compound can be ensured.

[0042] In some embodiments, the molar percentage of B2O3 in the first glass forging is 42-87%.

[0043] Understandably, the molar percentage of B2O3 in the first glass forging can be any value from 42.0%, 49.5%, 57.0%, 64.5%, 72.0%, 79.5%, 87.0%, or any value within a range of any two values. B2O3 is a glass forging 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, with its structure composed of BO3 triangles linked by bridging oxygen, forms a stable glass network structure, which improves the structural stability and mechanical strength of the material.

[0044] In some embodiments, the first corrosive oxide includes at least one of PbO and Bi2O3.

[0045] Understandably, both Bi2O3 and PbO are corrosive and are used to etch the first passivation layer 103 to ensure good contact performance of the electrode and an ideal sintering window.

[0046] In some embodiments, the first glass form further includes at least one of Al2O3 and SiO2.

[0047] Understandably, SiO2 is also a glass forging agent used to adjust the glass transition temperature (Tg) and high-temperature fluidity of glass powder. Appropriate addition can stabilize the glass phase. SiO2 can also improve the weather resistance of glass. Silicon atoms form tetrahedral SiO4 with four oxygen atoms, which, by bridging oxygen ions to other tetrahedra, can enhance the stability of the glass powder and mitigate the corrosiveness of the glass melt to the first passivation layer 103. Al2O3 can adjust the glass transition temperature (Tg) and high-temperature fluidity of glass powder, and can also be used as a component to improve the weather resistance of glass powder.

[0048] In some embodiments, the second corrosive oxide includes at least one of PbO and Bi2O3.

[0049] In some embodiments, the second glass form includes at least one of B2O3, Al2O3, and SiO2.

[0050] In some embodiments, the second corrosive oxide has a molar percentage of 22-32% in the second glass powder.

[0051] It is understood that the molar percentage of the second corrosive oxide in the second glass powder can be any value from 22%, 24%, 26%, 28%, 30%, 32%, or any value within a range of any two values. When the molar percentage of the second corrosive oxide in the second glass powder meets the above-mentioned range, the second glass powder can meet the etching performance requirements of the passivation layer during sintering.

[0052] It is understood that the formulation of the second glass powder provided in this application is not limited to the specific composition and ratio listed in the above embodiments, and other glass powder formulations applicable to the art can also be used. As long as the second glass powder includes a second corrosive oxide and a second glass forging, and the formulation of the second glass powder can meet the etching performance requirements during the sintering process of the conductive paste, and form good compatibility with the first glass powder and the conductive metal, thereby reducing the recombination loss of metallized carriers and ensuring that the crystalline silicon solar cell has an ideal open-circuit voltage and cell efficiency, it can be used as the second glass powder of this invention in the conductive paste system.

[0053] Conductive metal In some embodiments, the conductive metal, serving as the 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, aluminum, nickel, and their alloys and mixtures. Preferably, the conductive component is substantially composed of silver, due to its excellent processability and high conductivity.

[0054] In some embodiments, the mass percentage of the conductive metal in the conductive paste is 81% to 90 wt%, and may be 81 wt% to 88 wt%; may be further 83 wt% to 86 wt%; and may be further 84 wt% to 85 wt%.

[0055] 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.

[0056] In some embodiments, the conductive metal includes at least one selected from silver powder, aluminum powder, and nickel powder; further, the conductive metal is preferably silver powder. The conductive metal may be a metal powder or 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. When the metal powder is silver powder, it should be understood to refer to elemental silver metal, silver alloy powder, silver oxide, silver salts, and mixtures thereof, and may further include silver oxide (Ag₂O or AgO) or silver salts such as AgCl, AgNO₃, AgOOCCH₃ (silver acetate), AgOOCF₃ (silver trifluoroacetate), Ag₃PO₄ (silver orthophosphate), or mixtures thereof. 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.

[0057] 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.

[0058] In some embodiments, the D of silver powder 50 The particle size is 1~3μm.

[0059] Understandably, the D of silver powder 50 The particle size can be any value from 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.

[0060] 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.

[0061] It is understood that the mass percentage content of the organic carrier can be any value from 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, or any value within a range of any two values.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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%.

[0067] 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, a boron-diffracting emitter 102 and a first passivation layer 103 stacked together, with the boron-diffracting emitter 102 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.

[0068] In some embodiments, substrate 101 includes an n-type doped semiconductor substrate 101.

[0069] 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; In some embodiments, such as Figure 2As shown, the crystalline silicon solar cell structure is an n-TOPCon passivated contact cell, including a semiconductor substrate 10, 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 boron-derived emitter 102 and a first passivation layer 103 stacked on one side of the substrate 101; and a tunneling layer 104, an n-type doped polycrystalline silicon layer 105, and a second passivation layer 106 stacked on the other side of the substrate 101.

[0070] The tunneling layer 104 can be formed by a tunneling oxide passivation contact method, and the tunneling layer 104 can be an ultrathin silicon dioxide layer. The tunneling layer 104 is located on the back side of the substrate 101, and the substrate 101 can be an n-type doped semiconductor substrate 101; the n-type doped polysilicon layer 105 can be a phosphorus doped polysilicon layer, which is located on the surface of the tunneling layer 104 away from the substrate 101.

[0071] The first conductive structure 20 is prepared using the metallized conductive paste provided in the embodiments of this application. The conductive paste composition is applied to at least a portion of the surface of the first passivation layer 103 in a desired patterned form. During sintering, the conductive paste penetrates the first passivation layer 103 to obtain the first conductive structure 20 that forms a low-carrier recombination with the boron diffused emitter 102.

[0072] 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 PV6NL 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, glass powder in the silver paste etches and penetrates the second passivation layer 106, thereby forming an electrical contact with the n-type doped polycrystalline silicon layer 105 to form the second conductive structure 30 in the form of a conductive metal contact.

[0073] The fourth embodiment of this application provides a method for preparing a solar cell, comprising the following steps: Provide semiconductor substrate 10, such as Figure 2 As shown, the semiconductor substrate 10 includes a substrate 101, a boron-doped emitter 102, a first passivation layer 103, a tunneling layer 104, an n-type doped polysilicon layer 105, and a second passivation layer 106. The boron-doped emitter 102 is disposed on one side of the semiconductor substrate 10, the first passivation layer 103 is disposed on the side of the boron-doped emitter 102 away from the substrate 101, the tunneling layer 104 is disposed on the side of the substrate 101 away from the boron-doped emitter 102, the n-type doped polysilicon layer 105 is disposed on the side of the tunneling layer 104 away from the substrate 101, and the second passivation layer 106 is disposed on the side of the n-type doped polysilicon layer 105 away from the tunneling layer 104. 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; Sintering semiconductor substrate 10 and conductive paste, such that the conductive paste is etched and at least partially penetrates the first passivation layer 103 during the sintering process to form a first conductive structure 20; Metallized silver paste is printed onto at least a portion of the surface of the second passivation layer 106; The metallized silver paste is etched during the sintering process and at least partially penetrates the second passivation layer 106 to form the second conductive structure 30.

[0074] Laser-enhanced contact optimization was performed on the semiconductor substrate 10 to obtain a crystalline silicon solar cell.

[0075] It is understood that 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.

[0076] 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.

[0077] Specifically, the method for fabricating the solar cell provided in this application can be achieved through the following steps: 1) A semiconductor substrate 10 is provided, the structure of which is as follows: Figure 2 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, PVD2L slurry is used; b) Second stage: Backside fine grid, PV6NL slurry is used; c) Third stage: Front main grid, PVD2L slurry is used; d) Fourth layer: front fine grid, the paste is the metallized conductive paste provided in the embodiments of this application.

[0078] 3) Sintering semiconductor substrate 10, metallized conductive paste and metallized silver paste, so that the metallized conductive paste is etched and penetrates the passivation layer during the sintering process to form a first conductive structure 20 that is electrically connected to the boron diffuser 102, and the metallized silver paste is etched and penetrates the passivation layer during the sintering process to form a second conductive structure 30 that is electrically connected to the n-type doped polysilicon layer 105. The sintering equipment is a Maiwei 18 temperature zone sintering furnace.

[0079] The numbering of the steps above is not considered a restriction on the order of the steps.

[0080] In some embodiments, the laser-enhanced contact optimization method after sintering is a method of using lasers to improve the electrical contact of metallization paste during the solar cell manufacturing process. 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 solar cells. 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 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.

[0082] Understandably, using laser-enhanced contact optimization technology to treat conductive structures can reduce contact resistance, which is more conducive to increasing open-circuit voltage and improving efficiency.

[0083] In some embodiments, the reverse voltage is 5V~20V.

[0084] 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.

[0085] In some embodiments, the laser scanning time is 1ms to 100ms.

[0086] 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.

[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 GF-A1 to GF-A14 were prepared as first glass powders, with each number representing one portion of the first glass powder. The component content of each portion of the first glass powder is shown in Table 1. The sum of all components in each portion of the first glass powder is 100 mol%. Among them, the ratio of BaO-Fe2O3 / TiO2-B2O3 was adjusted in GF-A1 to GF-A13, while the first glass powder in GF-A14 did not contain Fe2O3 / TiO2.

[0088] Table 1

[0089] A glass powder designated GF-B1 was prepared as the second glass powder, and its component content is shown in Table 2. As can be seen from Table 2, GF-B1 does not contain BaO.

[0090] Table 2

[0091] The first glass powder, numbered GF-A1 to GF-A14, and the second glass powder, numbered GF-B1, were compounded to prepare a conductive paste, which was then further used to fabricate an n-TOPCon crystalline silicon solar cell. The fabrication steps are as follows: 1) A semiconductor substrate 10 is provided, the structure of which is as follows: Figure 2 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, PVD2L slurry is used; b) Second stage: Backside fine grid, PV6NL slurry is used; c) Third stage: Front main grid, PVD2L slurry is used; d) Fourth layer: front fine grid, the paste is the metallized conductive paste provided in the embodiments of this application.

[0092] 3) Sintering the semiconductor substrate 10, the metallized conductive paste, and the 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 102, 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 105. The sintering equipment is a Maiwei 18-zone sintering furnace, and the sintering furnace is set as follows: 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.

[0093] 4) Laser-enhanced contact optimization is performed on the sintered solar cells (DR Laser DR-M4XS-LIF-1000, laser bias: 45%, laser power: 20%).

[0094] Examples 1-13 and Comparative Examples 1-3 were prepared using the above method. The photoelectric conversion efficiency of the crystalline silicon solar cells of Examples 1-13 and Comparative Examples 1-3 was tested using a commercially available HALM IV curve testing system. The test items included efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), current (Isc), and line resistance (Rgrid).

[0095] Acetic acid degradation experiments were further conducted on the crystalline silicon solar cells of Examples 1-13 and Comparative Examples 1-3, including the following steps: Add 120 grams of potassium chloride and 500 grams of purified water to a 50-liter sealed container and mix them together. Then add 25 grams of acetic acid to make a test solution. Prepare a basket suitable for the size of the silicon wafers, ensuring all wafers are aligned front and back with the main grid lines perpendicular to the bottom. The spacing between the wafers should be approximately 5mm. Place the basket with the wafers in the center of a sealed container, with the liquid level approximately 5cm below the wafers. Seal the container and gently transfer it to an oven. Use a constant current source to power the fan inside the sealed container and place it in the oven at 85°C for 6 hours. Then remove the wafers and test their performance data after the acetic acid test, calculating the degradation rate.

[0096] The composition of the conductive paste and the test results of the crystalline silicon solar cells in Examples 1-13 and Comparative Examples 1-3 are shown in Table 3.

[0097] Table 3

[0098] As can be seen from Examples 1 to 13, the composite use of Ba-MBO glass described in this invention demonstrates that this solution improves open-circuit voltage and battery efficiency without negatively impacting acetic acid degradation.

[0099] As can be seen from Comparative Example 1, the combination of barium glass GF-A14 and GF-B1 without Fe2O3 / TiO2 has the effect of improving the open circuit voltage, but it also worsens the acetic acid decay.

[0100] As can be seen from Comparative Example 2, the open-circuit voltage is low when glass powder GF-B1 is used alone.

[0101] Glass powders numbered GF-B2 to GF-B3 were prepared as second glass powders, and their component contents are shown in Table 4. Among them, GF-B2 is a lead-silicon-boron system glass powder, and GF-B3 is a bismuth-silicon-boron system glass powder.

[0102] Table 4

[0103] The first glass powder, numbered GF-A13, and the second glass powder, numbered GF-B1 to GF-B3, were compounded to prepare a conductive paste, which was then further processed into an n-TOPCon crystalline silicon solar cell, resulting in Examples 14 to 20 and Comparative Example 4. Electrical performance tests and acetic acid degradation experiments were conducted using the same methods as above.

[0104] The composition of the conductive paste and the test results of the crystalline silicon solar cells in Examples 14-20 and Comparative Example 4 are shown in Table 5.

[0105] Table 5

[0106] Examples 14-16 are examples of different glass powder blends, and Comparative Example 3 is a comparative example without Ba-MBO glass powder. The performance test results of the prepared n-TOPCON batteries clearly show that: The glass powder used in the Ba-MBO compound and Comparative Example 3 both achieved significant improvements in opening pressure and efficiency, demonstrating the effects described in this invention. Furthermore, it can be seen that the improvement in opening pressure becomes more pronounced with increasing Ba-MBO dosage.

[0107] The acetic acid decay rate test also showed that the glass powder compounded with Ba-MBO exhibited a lower decay rate.

[0108] 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. A conductive paste, characterized in that, The conductive paste comprises the following components by mass: Conductive metal: 81~90wt% First glass powder: 0.5~2wt%; Second glass powder: 0.5~2wt%; Organic carrier: 9~15wt% Based on the amount of the first glass powder, the first glass powder comprises the following components: First corrosive oxide: 10~22 mol% First glass-forming component: 46~68 mol% BaO: 6.5~28.5 mol% Modifier: 4~16 mol% Wherein, the first glass forming body comprises B2O3, and the modifier comprises at least one of Fe2O3 and TiO2; the second glass powder comprises a second corrosive oxide and a second glass forming body.

2. The conductive paste according to claim 1, characterized in that, The molar ratio of BaO to the modifier is 0.9 to 7:

1.

3. The conductive paste according to claim 1, characterized in that, The first corrosive oxide includes at least one of PbO and Bi2O3.

4. The conductive paste according to claim 1, characterized in that, The first glass-forming body further includes at least one of Al2O3 and SiO2.

5. The conductive paste according to claim 4, characterized in that, The molar percentage of B2O3 in the first glass forging is 42-87%.

6. The conductive paste according to claim 1, characterized in that, The second corrosive oxide includes at least one of PbO and Bi2O3; and / or, The second glass-forming body includes at least one of B2O3, Al2O3, and SiO2.

7. The conductive paste according to claim 1, characterized in that, The second corrosive oxide has a molar percentage of 22-32% in the second glass powder.

8. A conductive electrode, characterized in that, include: A semiconductor substrate (10) includes a substrate (101), a boron-diffracting emitter (102), and a first passivation layer (103) stacked together, wherein the boron-diffracting emitter (102) is located between the substrate (101) and the first passivation layer (103); A first conductive structure (20) is formed of at least a portion of the first conductive structure (20) penetrating the first passivation layer (103), and the first conductive structure (20) is formed of the conductive paste according to any one of claims 1-7.

9. The conductive electrode according to claim 8, characterized in that, The substrate (101) includes an n-type doped semiconductor substrate.

10. A crystalline silicon solar cell, characterized in that, The crystalline silicon solar cell includes a conductive electrode as described in any one of claims 8 to 9.

11. A method for fabricating a crystalline silicon solar cell, characterized in that, Includes the following steps: A semiconductor substrate (10) is provided, the semiconductor substrate (10) including a substrate (101), a boron-doped emitter (102), a first passivation layer (103), a tunneling layer (104), an n-type doped polysilicon layer (105), and a second passivation layer (106), wherein the boron-doped emitter (102) is disposed on one side of the substrate (101), the first passivation layer (103) is disposed on the side of the boron-doped emitter (102) away from the substrate (101), the tunneling layer (104) is disposed on the side of the substrate (101) away from the boron-doped emitter (102), the n-type doped polysilicon layer (105) is disposed on the side of the tunneling layer (104) away from the substrate (101), and the second passivation layer (106) is disposed on the side of the n-type doped polysilicon layer (105) away from the tunneling layer (104); 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 according to any one of claims 1 to 6; The semiconductor substrate (10) and the conductive paste are sintered, such that the conductive paste is etched and at least partially penetrates the first passivation layer (103) during the sintering process to form a first conductive structure (20). Laser-enhanced contact optimization is performed on the semiconductor substrate (10) to obtain the crystalline silicon solar cell.

12. The method for preparing a crystalline silicon solar cell according to claim 11, characterized in that, 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 form on at least a portion of the surface of the first passivation layer (103).

13. The method for preparing a crystalline silicon solar cell according to claim 11, characterized in that, The step of performing laser-enhanced contact optimization on the semiconductor substrate (10) further 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).

14. The method for preparing a crystalline silicon solar cell according to claim 13, characterized in that, 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 laser scanning time is 1ms to 100ms.

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