Metallized conductive paste, conductive electrode, and solar cell and method of manufacture

Abstract

The application discloses a metallized conductive paste, a conductive electrode, a solar cell and a preparation method, and belongs to the field of solar photovoltaic cells. The metallized conductive paste comprises a glass frit, which accounts for 1 wt% to 4 wt% of the mass percentage of the metallized conductive paste; the glass frit at least comprises 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3 based on the mole percentage of the glass frit; a conductive metal source, which accounts for 81 wt% to 91 wt% of the mass percentage of the metallized conductive paste; and an organic component, which accounts for 8 wt% to 15 wt% of the mass percentage of the metallized conductive paste. The application is helpful to improve the battery resistance to acetic acid, chemical durability and long-term reliability.

Description

Technical Field

[0001] This application belongs to the field of solar photovoltaic cell technology, specifically relating to metallized conductive paste, conductive electrodes, solar cells, and preparation methods. Background Technology

[0002] Solar photovoltaic (PV) cells need to be exposed to complex outdoor environments for extended periods, therefore PV modules require excellent long-term reliability and weather resistance. One mechanism leading to efficiency degradation in PV modules is the corrosion of the cell's metal electrodes by acetic acid. Acetic acid is a product formed from the decomposition of the ethylene vinyl acetate (EVA) film, the module's encapsulation material. Acetic acid corrodes the metal electrodes, increasing contact resistance and resulting in a significant loss of photoelectric conversion efficiency in the PV cells. Summary of the Invention

[0003] Purpose of the invention: This application provides a metallized conductive paste, a conductive electrode, a solar cell, and a preparation method, aiming to provide photovoltaic cells with higher acid degradation resistance while maintaining higher photoelectric conversion efficiency.

[0004] Technical solution: The metallized conductive paste described in the embodiments of this application includes:

[0005] The glass frit comprises 1 wt% to 4 wt% of the metallized conductive paste by mass percentage; based on the molar percentage of the glass frit, the glass frit comprises at least 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3.

[0006] A conductive metal source, comprising 81 wt% to 91 wt% of the metallized conductive paste by mass; and

[0007] Organic components, comprising 8 wt% to 15 wt% of the metallized conductive paste by mass.

[0008] In some embodiments, in the glass frit, the iron element in Fe2O3 is used to form Fe-O-Si bonds, Fe-OB bonds, and combinations of Fe-O-Si bonds and Fe-OB bonds with the boron element in B2O3 and the silicon element in SiO2, respectively.

[0009] In some embodiments, the glass material further comprises Bi2O3 with a content of less than or equal to 12 mol%, based on the molar percentage of the glass material.

[0010] In some embodiments, the glass frit comprises, based on the molar percentage of PbO, 25 mol% to 55 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3.

[0011] In some embodiments, based on the molar percentage of the glass charge, the glass charge consists of 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3, 0 mol% to 12 mol% of Bi2O3 and 1 mol% to 5 mol% of Al2O3.

[0012] In some embodiments, the metallized conductive paste further includes:

[0013] The additive comprises 0.05 wt% to 0.5 wt% of the metallized conductive paste by mass; wherein the additive is selected from at least one of elemental aluminum and aluminum alloy powder.

[0014] In some embodiments, the conductive metal source is selected from any one or a mixture of several of elemental silver, silver alloys, silver oxide, and silver salts.

[0015] In some embodiments, this application also provides a conductive electrode, comprising:

[0016] A semiconductor substrate, the semiconductor substrate comprising a substrate, a p-type doped layer and a passivation layer stacked thereon, the p-type doped layer being located between the substrate and the passivation layer;

[0017] A first conductive structure penetrates the passivation layer and forms an electrical connection with the p-type doped layer, the first conductive structure being formed by the metallized conductive paste.

[0018] In some embodiments, the substrate comprises an n-type doped semiconductor substrate.

[0019] In some embodiments, this application also provides a solar cell, the solar cell including the aforementioned conductive electrode.

[0020] In some embodiments, the solar cell is a solar cell containing a tunneling oxide passivation contact structure.

[0021] In some embodiments, the conversion efficiency of the solar cell is Eff1; the conductive electrode is treated in an environment with pH less than 7, and the conversion efficiency of the solar cell after treatment is Eff2; the solar cell further satisfies: -30% < (Eff2 - Eff1) / Eff1 < -5%.

[0022] In some embodiments, the processing steps specifically refer to: processing at a temperature of 80°C to 90°C for 5 to 10 hours.

[0023] In some embodiments, this application also provides a method for preparing a solar cell, comprising:

[0024] A semiconductor substrate is provided, the semiconductor substrate comprising a substrate, a p-type doped layer and a passivation layer stacked thereon, the p-type doped layer being located between the substrate and the passivation layer;

[0025] The metallized conductive paste is applied to at least a portion of the surface of the passivation layer;

[0026] A semiconductor substrate coated with the metallized conductive paste is sintered, so that the metallized conductive paste is etched and penetrates the passivation layer during the sintering process to form a first conductive structure that is electrically connected to the p-type doped layer.

[0027] After sintering, the semiconductor substrate is laser-scanned and a reverse voltage is applied to the semiconductor substrate to form an induced current in the first conductive structure, thereby obtaining the solar cell.

[0028] In some embodiments, the laser scanning time is from 1 ms to 100 ms, and the reverse voltage is from 5 V to 15 V.

[0029] Beneficial effects: Compared with the prior art, the metallized conductive paste of this application comprises: a glass frit, accounting for 1 wt% to 4 wt% of the metallized conductive paste by mass percentage; based on the molar percentage of the glass frit, the glass frit comprises at least 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3; a conductive metal source, accounting for 81 wt% to 91 wt% of the metallized conductive paste by mass percentage; and an organic component, accounting for 8 wt% to 15 wt% of the metallized conductive paste by mass percentage. In the metallization conductive paste of this application, Fe2O3 is added to the glass frit as an intermediate oxide to form a distorted ferrite tetrahedron and form a continuous and stable glass network structure with silicon-oxygen and boron-oxygen tetrahedra. This results in a more compact glass structure, which helps to improve the acetic acid resistance, chemical durability and long-term reliability of the subsequent solar cells.

[0030] It is understood that the conductive electrode, solar cell and its preparation method provided in the embodiments of this application may include all the technical features and beneficial effects of the above-mentioned metallized conductive paste, which will not be repeated here. Attached Figure Description

[0031] 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.

[0032] Figure 1 A cross-sectional view of the conductive electrode provided in an embodiment of this application;

[0033] Figure 2 EL images before and after acetic acid decay provided in the embodiments of this application;

[0034] Reference numerals: 10-semiconductor substrate, 20-first conductive structure, 30-second conductive structure, 101-substrate, 102-p-type doped layer, 103-passivation layer, 104-tunneling layer, 105-n + Polycrystalline silicon layer, 106-passivation film. Detailed Implementation

[0035] 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.

[0036] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In the description of this application, "a plurality of" means two or more, and "at least one" can mean one, two, or more, unless otherwise expressly specified.

[0037] The applicant found that photovoltaic (PV) modules need to be exposed to complex outdoor environments for extended periods, thus requiring excellent long-term reliability and weather resistance. One of the most common mechanisms of module efficiency degradation during outdoor operation and accelerated damp heat testing is the corrosion of the cell's metal electrodes by acetic acid. Acetic acid is a byproduct of the decomposition of ethylene vinyl acetate (EVA) films, a commonly used module encapsulation material. Acetic acid corrodes the PV cell and metal electrodes, increasing contact resistance and leading to a loss of photoelectric conversion efficiency. Among different solar cell technologies, including PERC (Passivated Emitter Rear Cell), TOPCon (Tunnel Oxide Passivated Contact), and HJT (Heterojunction with Intrinsic Thin-film), acetic acid degradation of the front metal electrode in TOPCon cells is particularly severe.

[0038] In the fabrication of TOPCon cells, during the screen printing metallization process, high-temperature rapid burning often leaves a residual glass layer at the interface between the sintered metal grid lines and the silicon wafer. This residual glass layer connects the metal and silicon, and its function and stability are crucial. However, acetic acid can degrade this interfacial glass layer, forming voids or gaps, leading to increased contact resistance and consequently efficiency loss. The components of this residual glass layer mainly originate from the glass powder used in the slurry composition; therefore, the composition of the glass powder in the slurry is critical to the acetic acid resistance of the metal electrodes. TOPCon cell P +The glass frit commonly used in metallization pastes is lead-silicon-boron oxide (Pb-B-Si-O). For lead-boron-silicon oxide, the stability of its glass network structure is the main factor affecting its acetic acid resistance. However, some optional external oxides, such as alkali metal oxides (Li2O, Na2O, K2O, etc.) and alkaline earth metal oxides (CaO, BaO, MgO, SrO, etc.), can break the borosilicate network connection, resulting in poorer acetic acid resistance.

[0039] Therefore, there is a need to provide a metallized conductive paste, a conductive electrode, a solar cell, and a preparation method, which improves the glass frit containing lead-silicon-boron oxide to achieve higher resistance to acetic acid degradation and maintain higher photoelectric conversion efficiency in solar cells.

[0040] Some embodiments of this application provide a metallized conductive paste comprising a glass frit, a conductive metal source, and an organic component; the glass frit accounts for 1 wt% to 4 wt% of the metallized conductive paste by mass percentage; based on the molar percentage of the glass frit, the glass frit comprises at least 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3, and 1 mol% to 5 mol% of Al2O3; the conductive metal source accounts for 81 wt% to 91 wt% of the metallized conductive paste by mass percentage; and the organic component accounts for 8 wt% to 15 wt% of the metallized conductive paste by mass percentage.

[0041] In this conductive paste, glass frit and conductive metal source serve as the solid components; organic components, including polymers, surfactants, thickeners, thixotropic agents, and binders, act as the dispersed phase and provide printing properties. The sum of the weight percentages of all components in the conductive paste is 100%.

[0042] Each component will be described separately below.

[0043] glass material

[0044] In some embodiments, glass frit refers to a composition containing one or more types of anions and cations. The glass frit is flowable upon heating and can be crystalline, partially or completely glassy, ​​or amorphous. In some embodiments, glass refers to a particulate solid form.

[0045] In some embodiments, the glass frit in this embodiment can be understood as a composition having glass components, and the mass percentage of the glass frit in the conductive paste composition is 1 wt% to 4 wt%; in other embodiments, the mass percentage of the glass frit in the conductive paste composition is 1.2 wt% to 3.8 wt%, or even 1.5 wt% to 3.5 wt%; or even further 2.0 wt% to 3.0 wt%; or even further 2.2 wt% to 2.8 wt%. It is understood that the adjustment of the proportion of glass frit in the conductive paste composition must ensure that the sum of the weight percentages of all components in the conductive paste composition is 100%. The composition of the glass frit directly affects its meltability, fluidity, and etchability; therefore, a good balance of the glass frit composition is needed to achieve excellent carrier recombination effects.

[0046] In some embodiments, the glass frit comprises at least 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3, and 1 mol% to 5 mol% of Al2O3. In the following description, unless otherwise specified, the "mol%" content of each component in the glass frit indicates a molar percentage converted from oxides.

[0047] In some embodiments, more preferably, the glass frit comprises, in molar percentages converted from oxides: 25 mol% to 50 mol% of PbO, 30 mol% to 40 mol% of B2O3, 10 mol% to 30 mol% of SiO2, 3 mol% to 10 mol% of Fe2O3 and 3 mol% to 4.5 mol% of Al2O3.

[0048] In some embodiments, more preferably, the glass frit comprises, in molar percentages converted from oxides: 30 mol% to 45 mol% of PbO, 35 mol% to 40 mol% of B2O3, 15 mol% to 25 mol% of SiO2, 3 mol% to 8 mol% of Fe2O3 and 3.5 mol% to 4 mol% of Al2O3.

[0049] It should be noted that in the metallized conductive paste of this application, by adding Fe2O3 to the glass frit as an intermediate oxide, a distorted ferrite tetrahedron is formed, which together with silicon-oxygen and boron-oxygen tetrahedra form a continuous and stable glass network structure. Due to the small radius of Fe ions, the Fe-O bond is stronger, thus forming a more compact glass structure. The more stable Fe-OB and Fe-O-Si bonds, compared with BOB and Si-O-Si bonds, help improve the chemical durability of the material, thereby forming a more compact glass structure and helping to improve the acetic acid resistance and long-term reliability of the paste.

[0050] In some embodiments, in the glass frit, iron in Fe2O3 forms Fe-O-Si bonds, Fe-OB bonds, and combinations of Fe-O-Si and Fe-OB bonds with boron in B2O3 and silicon in SiO2, respectively. It is understood that, compared to BOB or Si-O-Si bonds, the incorporation of Fe2O3 can form more stable Fe-O-Si and Fe-OB bonds. Through the formation of Fe-O-Si and Fe-OB bonds, iron in Fe2O3 interconnects with boron and silicon to form a stable glass network structure, which improves the structural stability and mechanical strength of the material. Secondly, the formation of Fe-O-Si and Fe-OB bonds improves the chemical stability of the material, enabling it to better resist corrosion from environmental media such as acids, which helps improve the material's durability and long service life. Simultaneously, the introduction of iron can modulate the band structure of the material, improving photoelectric conversion performance. The localized charge generated through the combination of Fe-O-Si and Fe-OB bonds can optimize the band structure and charge transport characteristics of optoelectronic devices, thereby improving photoelectric conversion efficiency.

[0051] In some embodiments, the glass frit of this application is formed by adding Fe2O3 to a lead-iron-boron-silicon oxide base material to form a lead-iron-boron-silicon oxide glass frit.

[0052] In some embodiments, the PbO contained in the glass frit of this application is the main component controlling the corrosion of the glass, which enables the etching of the passivation layer. PbO is also an intermediate glass forming agent that can be incorporated into the glass network, and the residual PbO will exist outside the glass skeleton as a glass modifier.

[0053] In some embodiments, the B2O3 contained in the glass frit of this application is the main glass forming agent, used to control the glass transition temperature (Tg) and high-temperature fluidity of the glass. B2O3 can form low-melting-point glass and provide good fluidity. B2O3 can also form a network structure, which helps stabilize the glass and improves the bonding ability between the molten glass and the substrate.

[0054] In some embodiments, the SiO2 contained in the glass frit of this application serves as a glass forming agent, used to adjust the glass transition temperature (Tg) and high-temperature fluidity of the glass. Appropriate addition can stabilize the glass phase, increase the glass melting point, and reduce fluidity. SiO2 can also improve the weather resistance of the glass and regulate its reactivity with the substrate.

[0055] In some embodiments, the Fe2O3 contained in the glass frit of this application serves as an intermediate oxide, which can significantly enhance the glass's resistance to acetic acid while achieving excellent electrical properties.

[0056] In some embodiments, based on the molar percentage of the glass frit, the glass frit further includes Bi₂O₃ at a content of less than or equal to 12 mol%. Bi₂O₃ can be used to partially replace PbO to adjust the corrosivity of the glass frit. When the glass frit contains both PbO and Bi₂O₃, both can corrode the passivation layer during sintering because PbO and Bi₂O₃ are reactive with the passivation layer and have the function of improving the softening and fluidity of the glass. Furthermore, since PbO is more corrosive than Bi₂O₃, replacing a portion of PbO with Bi₂O₃ in the composition of the glass frit can adjust the corrosion resistance to achieve the effect of low carrier recombination and improve the open-circuit voltage and photoelectric conversion efficiency of the battery.

[0057] In some embodiments, Bi₂O₃ can further form an interface similar to a "barrier layer" with Fe₂O₃, which can block the entry of oxygen, acidic gases, or moisture, reduce the oxidation rate on the glass powder surface, and thus improve the stability of the material. After Bi₂O₃ and Fe₂O₃ combine, the local environment inside the crystal can be altered by regulating the lattice structure and atomic arrangement, thereby adjusting the stability of the material. This combination can optimize the grain boundary structure, reduce grain boundary energy and grain boundary sensitivity, and improve the stability of the material.

[0058] In some embodiments, the glass frit may further optionally include Bi2O3 with a content of greater than or equal to 2 mol% and less than or equal to 8 mol%.

[0059] In some embodiments, based on the molar percentage of the glass frit, the glass frit consists of 25 mol% to 55 mol% PbO, 25 mol% to 45 mol% B₂O₃, 5 mol% to 32 mol% SiO₂, 1.8 mol% to 15 mol% Fe₂O₃, and 1 mol% to 5 mol% Al₂O₃. Therefore, the glass frit contains only PbO, B₂O₃, SiO₂, Fe₂O₃, and Al₂O₃, with a total molar percentage of 100%. In this case, Fe₂O₃ can simultaneously form more stable bonds with both B₂O₃ and SiO₂, preventing corrosion from external factors and improving the chemical durability of the glass powder.

[0060] In some embodiments, Al2O3, as an intermediate glass oxide, can also be incorporated in appropriate amounts to adjust the glass transition temperature (Tg) and high-temperature fluidity of the glass, and can also be used as a component to improve the weather resistance of the glass.

[0061] In some embodiments, Al2O3 itself possesses good chemical stability, and when combined with Fe2O3, it can form a barrier layer to block the penetration of external chemical substances and slow down or prevent the chemical reaction of the glass powder. Furthermore, the combination of Al2O3 and Fe2O3 can introduce a physical mechanism-based structural strengthening effect, making the structure of the glass powder more stable.

[0062] In some embodiments, based on the molar percentage of the glass frit, the glass frit consists of 25 mol% to 55 mol% PbO, 25 mol% to 45 mol% B₂O₃, 5 mol% to 32 mol% SiO₂, 1.8 mol% to 15 mol% Fe₂O₃, 0 mol% to 12 mol% Bi₂O₃, and 1 mol% to 5 mol% Al₂O₃. Therefore, the glass frit contains only PbO, B₂O₃, SiO₂, Fe₂O₃, Bi₂O₃, and Al₂O₃, and the total molar percentage is 100%.

[0063] Conductive metal source

[0064] In some embodiments, the conductive metal source, 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 metals include, but are not limited to, silver, gold, copper, nickel, palladium, platinum, aluminum, and their alloys and mixtures. Alternatively, the conductive component may be substantially composed of silver, due to its excellent processability and high conductivity.

[0065] In some embodiments, the conductive metal source accounts for 81 wt% to 91 wt% of the metallized conductive paste by mass; in other embodiments, the conductive metal source accounts for 82 wt% to 90 wt% of the metallized conductive paste by mass, and may further be 83 wt% to 89 wt%; and may even be 84 wt% to 88 wt%. It is understood that the proportion of the conductive metal source 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 source is used to provide conductivity after the solar cell is formed.

[0066] In some embodiments, the conductive metal source may be 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 alloys, silver oxides or silver salts, and mixtures thereof, and may further include sources derived from 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 metallized conductive paste may also be used in some embodiments, and other metals used in this paste for functional conductive materials can be similarly obtained.

[0067] In some embodiments, the conductive metal source may be provided as finely dispersed particles having the following forms: powder, flake, sphere, rod, granular, nodular, layered or coated, other irregular forms, or mixtures thereof.

[0068] In some embodiments, the median particle size of the conductive metal source is in the range of 0.5-3.5 μm. The median particle size, D50, refers to the 50% volume distribution size. More preferably, the conductive metal source uses spherical silver powder with a median particle size of 1-3 μm; even more preferably, it uses spherical silver powder with a median particle size of 1.5-2.5 μm; and even more preferably, it uses spherical silver powder with a median particle size of 2 μm. The main function of the silver powder is to form a high-density silver body after sintering to improve conductivity. The spherical silver powder with a median particle size of 2 μm also inhibits agglomeration and ensures uniform dispersion.

[0069] In some embodiments, when the conductive metal source 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 source is silver, it may be coated with a phosphorus-containing compound.

[0070] organic components

[0071] In some embodiments, the organic component accounts for 8 wt% to 15 wt% of the metallized conductive paste by mass. In some other embodiments, it may be 9 wt% to 14 wt%. It may also be 10 wt% to 13 wt%.

[0072] In some embodiments, relative to the solid material composed of a conductive metal source and glass frit, an organic component is used as the liquid phase in the conductive paste to disperse the solid material, thereby forming a paste with a certain viscosity. The viscosity and rheological properties of this paste enable the conductive metal source and glass frit to be dispersed stably therein over a long period of time, and also enable the conductive paste composition to be dispersed on a printing screen, and the desired pattern to be applied to the passivation layer surface of the substrate by screen printing.

[0073] In some embodiments, the organic component 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 of lower alcohols, etc. Organic solvents may include terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol diacetate, α-hydroxymethyl ether acetate, etc. Terpenes, β Terpenes, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexanediol, etc.

[0074] In some embodiments, the consistency and rheological properties of the organic components make them suitable for printing methods, including but not limited to screen printing. Organic media may also include other additives such as nonionic surfactants, thixotropic agents, dispersants, and rheology modifiers to suit different organic media requirements.

[0075] additive

[0076] In some embodiments, the metallized conductive paste further includes additives, comprising 0.05 wt% to 0.5 wt% of the metallized conductive paste by mass; wherein the additives are selected from at least one of elemental aluminum and aluminum alloy powder. During the firing process, Al or Al alloy powder helps to regulate the corrosivity of the molten glass. During firing, Al is oxidized to Al2O3 and incorporated into the molten glass, thereby further regulating the fluidity and corrosivity of the glass melt.

[0077] Further optionally, the additive accounts for 0.1 wt% to 0.3 wt% of the metallized conductive paste by mass.

[0078] In some embodiments, the glass powder can be prepared using methods conventionally used in the glass manufacturing industry. For example, oxides corresponding to the glass powder composition ratios described in the embodiments are batched, mixed, added to a crucible (e.g., a platinum or ceramic crucible), heated to a peak temperature (e.g., 800°C to 1400°C), and held for a period of time to allow the oxides to melt together. The molten material can then be quenched by any suitable means, including but not limited to passing it between counter-rotating stainless steel rollers to form flakes 0.25 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.

[0079] In some embodiments, the preparation method of the conductive paste may include: mixing and dispersing the paste components as described in the embodiments, then grinding them to a fineness of less than 10 μm using a three-roll mill, and then further filtering. The amounts of glass frit and aluminum powder added may differ in some embodiments; in these cases, silver powder is used as an equal substitute, while the amounts of other components, such as organic components, remain unchanged. The proportions of the glass frit, conductive metal source, organic components, and additives must be adjusted to ensure that the sum of the mass percentages of each component in the conductive paste is 100%.

[0080] conductive electrodes

[0081] In some embodiments, see Figure 1 This embodiment also provides a conductive electrode, which includes a semiconductor substrate 10 and a first conductive structure 20. The semiconductor substrate 10 includes a substrate 101, a p-type doped layer 102 and a passivation layer 103 stacked together, with the p-type doped layer 102 located between the substrate 101 and the passivation layer 103. The first conductive structure 20 penetrates the passivation layer 103 and forms an electrical connection with the p-type doped layer 102. The first conductive structure 20 is formed by sintering the metallized conductive paste of this embodiment.

[0082] Understandably, the first conductive structure 20 can form an electrical connection with the p-type semiconductor that has low carrier recombination. The p-type semiconductor can be a p-type doped layer 102, and the substrate 101 can be an n-type doped semiconductor substrate 101. Furthermore, in a TOPCon cell, the p-type doped layer 102 is also referred to as a p-type emitter.

[0083] Solar cells

[0084] like Figure 1 As shown, some embodiments of this application provide a solar cell, which is a solar cell with a tunnel oxide passivated contact structure, and which utilizes the aforementioned metallized conductive paste during its fabrication.

[0085] In some embodiments, solar cells containing tunnel oxide passivated contact structures are called TOPCon solar cells (Tunnel Oxide Passivated Contact Solar Cells). These solar cells utilize the tunnel oxide layer as a charge transport channel and a surface passivation layer to improve cell efficiency and performance. TOPCon solar cell structures exhibit low electron reflection and surface recombination, while also possessing high photoelectric conversion efficiency and low electronic defects.

[0086] In some embodiments, in the TOPCon solar cell, the semiconductor substrate 10 further includes a tunneling layer 104 (such as an ultrathin silicon dioxide layer) located on the back side of the n-type doped semiconductor substrate 101; n + Polycrystalline silicon layer 105 (such as phosphorus-doped polycrystalline silicon layer) is located on the surface of tunneling layer 104 away from n-type doped semiconductor substrate 101; passivation film 106 is deposited on n-type doped semiconductor substrate 101. + The polysilicon layer is located away from the surface of the tunneling layer 104; and the second conductive structure 30 penetrates at least a portion of the passivation film 106 and is connected to n + The polycrystalline silicon layer forms an electrical connection.

[0087] In some embodiments, the front side refers to the light-receiving surface of the solar cell, which is also the working surface. The back side is the back of the solar cell, which typically does not directly receive sunlight. The metallized conductive paste of this application can be used to form a conductive structure on the front side. The front side can be... Figure 1 The upper surface of the middle.

[0088] In some embodiments, the tunneling layer 104 and n are formed using a tunneling oxide passivation contact method. + Polycrystalline silicon layer 105.

[0089] In some embodiments, the first conductive structure 20 is formed using the metallized conductive paste of this embodiment. The conductive paste composition is applied to at least a portion of the surface of the passivation layer 103 in a desired patterned form, and during sintering, the conductive paste penetrates the passivation layer 103 to obtain the first conductive structure 20 which forms a low-carrier recombination electrical connection with the p-type doped layer 102.

[0090] In some embodiments, the second conductive structure 30 may utilize commercially available silver metallization pastes used in p-type or n-type crystalline silicon cells, such as those containing Pb. Te Silver paste containing O-glass powder. The conductive paste composition is applied in a desired patterned form to at least a portion of the surface of the passivation film, and during sintering, the Pb-containing... Te The silver paste of O glass powder is etched and penetrates the passivation film 106, thereby interacting with n + The polysilicon layer 105 forms an electrical contact to facilitate the formation of a second conductive structure 30 in the form of a conductive metal contact.

[0091] In some embodiments, the conversion efficiency of the solar cell is Eff1; after treating the conductive electrode in an environment with a pH less than 7, the conversion efficiency of the solar cell is Eff2; the solar cell further satisfies: -30% < (Eff2 - Eff1) / Eff1 < -5%. Here, (Eff2 - Eff1) / Eff1 characterizes the degree of degradation in the conversion efficiency of the solar cell before and after treatment in an acidic environment, i.e., the degradation rate. It is understood that when the range of -30% < (Eff2 - Eff1) / Eff1 < -5% is met, it indicates that in this embodiment, adding Fe2O3 to the glass frit can significantly enhance the glass's resistance to acetic acid and maintain the excellent electrical performance of the solar cell.

[0092] In some embodiments, the conversion efficiency Eff1 or Eff2 of the solar cell can be obtained according to the description in GB / T18911-2002. Standard test conditions: AM1.5, 1000W / m 2 25℃.

[0093] In some embodiments, the step of treating in an acidic environment specifically refers to: positioning the solar cell towards an acidic source, where the acidic source volatilizes an acidic medium that comes into contact with a first conductive structure on the surface of the solar cell; the specific treatment temperature is in the range of 80°C to 90°C, and the treatment time is 5 h to 10 h. The acidic source can be acetic acid, etc.

[0094] This application provides a method for preparing a solar cell, comprising:

[0095] 1) A semiconductor substrate 10 is provided, the semiconductor substrate 10 including a substrate 101, a p-type doped layer 102 and a passivation layer 103 stacked thereon, the p-type doped layer 102 being located between the substrate 101 and the passivation layer 103; wherein, a trivalent element (such as boron or gallium) is doped on the front side of the substrate 101, thereby forming a p-type doped layer 102 on the front side of the n-type doped semiconductor substrate 101; the passivation layer 103 is deposited on the surface of the p-type doped layer 102 by a deposition method;

[0096] 2) The metallization conductive paste provided in this embodiment is applied to the passivation layer 103; specifically, the metallization conductive paste is applied to at least a portion of the surface of the passivation layer 103 in a patterned form; the patterning method can be screen printing; it is understood that the conductive paste composition involved in this embodiment is used as a fine grid on the front side (P side) of a solar cell with a tunneling oxide passivation contact structure, and is printed by four screen printing machines corresponding to the back main grid, the back fine grid, the front main grid, and the front fine grid respectively; the conductive paste in this embodiment is used on the front fine grid, usually the fourth front fine grid, and each layer of printing is dried before the next layer of paste is printed;

[0097] 3) Sintering the semiconductor substrate 10 and the metallized conductive paste assembly, so that the metallized conductive paste is etched and penetrates the passivation layer 103 during the sintering process to form a first conductive structure 20 that is electrically connected to the p-type doped layer 102; in addition, the preparation of the second conductive structure 30 is the same as the preparation of the first conductive structure 20.

[0098] 4) After sintering, the semiconductor substrate 10 is laser scanned and a reverse voltage is applied to the semiconductor substrate 10 to form an induced current in the first conductive structure 20, thereby obtaining a solar cell.

[0099] The numbering of the steps above is not considered a restriction on the order of the steps.

[0100] In some embodiments, step 4) is a laser-enhanced contact improvement and optimization method. This method uses lasers to improve the electrical contact of the metallization paste during solar cell manufacturing. The basic principle of laser-enhanced contact improvement 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 the 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.

[0101] In some embodiments, the laser scanning time is from 1 ms to 100 ms, and the reverse voltage is from 5 V to 15 V. Using laser-enhanced contact optimization technology to treat the conductive structure can reduce contact resistance, which is more conducive to increasing open-circuit voltage and improving efficiency.

[0102] The technical solution of this application will be further described below with reference to specific embodiments.

[0103] The component contents of the glass frits in Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1. The sum of the components in the glass frits of the examples and comparative examples is 100 mol%. Specifically, the lead-iron-boron-silicon oxide in Examples 1 to 10 covers different mol% contents of Fe2O3; Examples 7 and 8 correspond to different SiO2 contents to adjust the high-temperature physical properties of the glass powder; Example 9 uses Bi2O3 to replace a portion of PbO to control the corrosivity of the glass frit; Example 10 uses Al2O3 to adjust the high-temperature physical properties of the glass powder. Comparative Example 1 is Fe2O3-free; Comparative Example 2 is ZnO-containing glass powder, and ZnO also has the properties of an intermediate oxide; Comparative Example 3 contains Fe2O3 but at a content of 1 mol%, which does not meet the scope defined in this application.

[0104] Table 1

[0105]

[0106] The stability of glass powder was tested for Examples 1 to 6 and Comparative Examples 1 to 3 in Table 1. The specific test procedure was as follows: 2.5 grams of glass material corresponding to the examples and comparative examples were taken and soaked in 0.1 wt% acetic acid (49.95 grams of pure water and 0.05 grams of acetic acid) for 12 hours. Then, the supernatant water was separated by centrifugation, and the content of metals Pb, B, Fe and Zn in the supernatant water was detected by ICP. The experimental results are shown in Table 2 below, where ND indicates not detected.

[0107] Table 2

[0108]

[0109] Table 2 shows that adding Fe2O3 as an intermediate oxide to the glass frit significantly reduces the levels of B and Pb after decomposition, resulting in a more stable glass frit. Furthermore, the amount of Pb and B precipitated further decreases with increasing Fe2O3 content, indicating better stability. Comparative Example 1, which contains no Fe2O3, exhibits the highest levels of Pb and B precipitation, indicating poor glass frit stability. Comparative Example 2, containing 5 mol% ZnO, slightly improves the stability of the glass frit. Comparative Example 3, containing 1 mol% Fe2O3, also shows some improvement, but due to insufficient Fe2O3 content, a significant amount of Pb and B still precipitates.

[0110] The glass frits of Examples 1 to 10 in Table 1 and the glass frits of Comparative Examples 1 to 3 were used to prepare metallized conductive pastes and fabricated into solar cells. Examples 11 to 25 and Comparative Examples 4 to 6 were obtained accordingly. In the following examples, the composition of the conductive paste can be adjusted accordingly to obtain suitable performance to meet the requirements; for example, the amount of glass frit can be easily adjusted according to the end-use requirements. The specific contents are shown in Table 3. The conductive metal source is spherical silver powder with an average particle size of 0.5 to 3 μm. The organic components specifically include: 1.5 wt% ethyl cellulose, 1.5 wt% polyvinyl butyral copolymer (PVB), 1.6 wt% diethylene glycol butyl ether acetate, 0.3 wt% silicone oil, 0.15 wt% Duomeen TDO (a nonionic surfactant belonging to the amine oxide category), 0.15 wt% Brij L4 (a nonionic surfactant belonging to the polyoxyethylene alcohol category), 0.4 wt% Thixotrol plus (rheology modifier), 2.8 wt% ethylene-substituted alcohol C12, and 0.6 wt% diester. The remainder is solvent. The specific preparation process of the conductive paste composition is as follows: the above components are mixed, stirred, dispersed, and then milled using a three-roll mill to a fineness of less than 10 μm, followed by further filtration.

[0111] Table 3

[0112]

[0113] In Table 3, the glass frits of Examples 21 to 25 were obtained by compounding Example 3 and Comparative Example 1. Therefore, the composition of the glass frits corresponding to Examples 21 to 25 is shown in Table 4.

[0114] Table 4

[0115]

[0116] The fabrication of the solar cell is as follows: First, a blue film for a TOPCon cell is prepared, which is then screen-printed in four stages corresponding to the back main grid, back fine grid, front main grid, and front fine grid, respectively. A conductive paste composition is applied to the front fine grid on the P-side. The blue film and the conductive paste are sintered, and the conductive paste composition is etched with a passivation layer during the sintering process to form a conductive structure on the P-side of the blue film. The conductive structure is then laser-enhanced to optimize the contact, thereby obtaining the solar cell.

[0117] The blue film is a commercially available semi-finished TOPCon solar cell. The blue film has an n-type substrate silicon wafer with a TOPCon cell structure, specifically a tunnel oxide passivated back side with an n-doped polycrystalline silicon layer, which is then passivated by a dielectric layer. The front side is based on a boron-diffused emitter, which is also passivated by a dielectric layer. The dielectric insulating layer typically includes SiN. x SiN x O y Al2O3 or combinations thereof.

[0118] The metallization process uses a four-stage screen printing machine for screen printing. High-temperature sintering uses a commercially available Maiwei sintering furnace with 18 temperature zones; laser contact enhancement technology is a post-processing technique that enhances the contact of the sintered solar cells.

[0119] Based on the components in Table 3, additives ranging from 0.05 wt% to 0.5 wt% can be added to the prepared metallized conductive paste, ensuring that the total mass of each component is 100%. The process for preparing the battery is the same as described above.

[0120] Solar cell performance evaluation

[0121] The photoelectric conversion efficiency of the solar cells was tested using a commercially available IV meter. The test items included efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), and current (Isc).

[0122] Electroluminescence imaging (EL imaging): High contact resistance can cause dark areas or foggy black spots to appear in EL imaging.

[0123] Acetic acid decay test

[0124] Acetic acid degradation testing is a method for evaluating the stability of metallized solar cells under moisture and acid conditions. Specific acetic acid degradation methods include:

[0125] (1) Prepare the solution: Add 120g of potassium chloride and 500g of purified water to a 50L sealed box and mix them together, then add 25g of acetic acid;

[0126] (2) Prepare a basket suitable for the size of the silicon wafers. All the wafers should be aligned with the front and back sides and the main grid lines should be perpendicular to the bottom. The spacing between the wafers should be about 5mm. Place the basket with the wafers in the middle of the sealed box, with the liquid level about 5cm away from the wafers. Seal the box and then gently transfer it into an oven. Use a constant current source to supply the fan inside the sealed box and place it in the oven at 85°C for 6 hours. Then take out the wafers, test the performance data of the wafers after the acetic acid test, and calculate the degradation rate (Eff2-Eff1) / Eff1.

[0127] See Tables 5 and 6 for the specific evaluation results.

[0128] Table 5

[0129]

[0130] Referring to Table 5, ΔEff, ΔVoc, and ΔFF in Table 5 refer to the differences obtained after comparing the data of Comparative Example 4 with the efficiency (Eff), open-circuit voltage (Voc), and fill factor (FF) of the corresponding embodiments. Examples 11 to 20 have a higher efficiency advantage compared to Comparative Examples 4 to 6, demonstrating that glass frits with different Fe2O3 mol% contents can maintain high cell efficiency, due to the increase in open-circuit voltage (Voc). As shown in Examples 21 to 25, Fe2O3-containing glass frits can be used alone or mixed with other glasses. The metallized conductive paste used in the embodiments of this application can help maintain high conversion efficiency in solar cells.

[0131] Table 6

[0132]

[0133] Referring to Table 6, compared to the data from Comparative Examples 4 to 6, the solar cells provided in Examples 11 to 26 of this application exhibit a degradation rate greater than -30% and less than -5%, indicating a lower degree of degradation. Examples 11 to 15, corresponding to the addition of 3 mol% to 15 mol% Fe2O3, all showed significant improvements in acetic acid resistance. Examples 21 to 25 demonstrate that adding Fe2O3 at a certain mixing ratio can also achieve significant degradation improvement. Comparative Example 4, lacking Fe2O3, had a degradation rate of -37%. Comparative Example 5 used ZnO, which can serve as an intermediate oxide, but the degradation rate remained high at 39%, indicating that Fe2O3 can improve the chemical stability of the glass structure, while ZnO cannot. Comparative Example 6, containing 1 mol% Fe2O3, showed some improvement in acetic acid resistance, but the overall degradation rate of -30% was still too high and did not meet the requirements of practical applications. In summary, the addition of Fe2O3 in this application, as an intermediate oxide, forms a distorted ferrite tetrahedron and, together with silicon-oxygen and boron-oxygen tetrahedra, constitutes a continuous and stable glass network structure. Due to the small radius of Fe ions, the Fe-O bond is stronger, resulting in a more compact glass structure. This helps to improve the chemical durability of the material, thereby enabling the glass material to form a more compact glass structure and improving the acetic acid resistance and long-term reliability of solar cells.

[0134] See further Figure 2The images show the EL images before and after acetic acid degradation. In Comparative Examples 4 and 5, the contact resistance was significantly affected by acetic acid, with the higher contact resistance resulting in noticeable fogging in the EL images, consistent with the significant decrease in FF after IV acetic acid degradation.

[0135] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0136] The metallized conductive paste, conductive electrode, solar cell, and preparation method provided in the embodiments of this application have been described in detail above. Specific examples have been used 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 metallized conductive paste, characterized in that, The metallized conductive paste is used in solar photovoltaic modules, the solar photovoltaic modules comprising an ethylene-vinyl acetate film, the metallized conductive paste being suitable for laser-enhanced contact optimization technology, and the metallized conductive paste comprising: The glass frit comprises 1 wt% to 4 wt% of the metallized conductive paste by mass percentage; based on the molar percentage of the glass frit, the glass frit comprises at least 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3; A conductive metal source, comprising 81 wt% to 91 wt% of the metallized conductive paste by mass; the conductive metal source is selected from at least one of silver, gold, copper, nickel, palladium, and platinum; and Organic components, comprising 8 wt% to 15 wt% of the metallized conductive paste by mass.

2. The metallized conductive paste according to claim 1, characterized in that, In the glass frit, the iron element in Fe2O3 is used to form Fe-O-Si bonds, Fe-OB bonds, and combinations of Fe-O-Si bonds and Fe-OB bonds with the boron element in B2O3 and the silicon element in SiO2, respectively.

3. The metallized conductive paste according to claim 1, characterized in that, Based on the molar percentage of the glass material, the glass material also includes Bi2O3 with a content of less than or equal to 12 mol%.

4. The metallized conductive paste according to claim 1, characterized in that, Based on the molar percentage of the glass charge, the glass charge consists of 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3 and 1 mol% to 5 mol% of Al2O3.

5. The metallized conductive paste according to claim 3, characterized in that, Based on the molar percentage of the glass charge, the glass charge consists of 25 mol% to 55 mol% of PbO, 25 mol% to 45 mol% of B2O3, 5 mol% to 32 mol% of SiO2, 1.8 mol% to 15 mol% of Fe2O3, 0 mol% to 12 mol% of Bi2O3 and 1 mol% to 5 mol% of Al2O3.

6. The metallized conductive paste according to claim 1, characterized in that, The metallized conductive paste further includes: The additive comprises 0.05 wt% to 0.5 wt% of the metallized conductive paste by mass; wherein the additive is selected from at least one of elemental aluminum and aluminum alloy powder.

7. The metallized conductive paste according to claim 1, characterized in that, The conductive metal source is selected from any one or a mixture of several of elemental silver, silver alloys, silver oxide, and silver salts.

8. A conductive electrode, characterized in that, include: A semiconductor substrate, the semiconductor substrate comprising a substrate, a p-type doped layer and a passivation layer stacked thereon, the p-type doped layer being located between the substrate and the passivation layer; A first conductive structure penetrates the passivation layer and forms an electrical connection with the p-type doped layer, wherein the first conductive structure is formed by the metallization conductive paste according to any one of claims 1-7.

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

10. A solar cell, characterized in that, The solar cell includes the conductive electrode as described in claim 8 or 9.

11. The solar cell according to claim 10, characterized in that, The solar cell is a solar cell containing a tunnel oxide passivation contact structure.

12. The solar cell according to claim 10, characterized in that, The conversion efficiency of the solar cell is Eff1; the conversion efficiency of the solar cell is Eff2 after the conductive electrode is placed in an environment with pH less than 7; the solar cell further satisfies: -30% < (Eff2 - Eff1) / Eff1 < -5%.

13. The solar cell according to claim 12, characterized in that, The specific steps of the treatment are: treating at a temperature of 80°C to 90°C for 5 to 10 hours.

14. A method for preparing a solar cell, characterized in that, include: A semiconductor substrate is provided, the semiconductor substrate comprising a substrate, a p-type doped layer and a passivation layer stacked thereon, the p-type doped layer being located between the substrate and the passivation layer; The metallized conductive paste as described in any one of claims 1-7 is applied to at least a portion of the surface of the passivation layer; A semiconductor substrate coated with the metallized conductive paste is sintered, so that the metallized conductive paste is etched and penetrates the passivation layer during the sintering process to form a first conductive structure that is electrically connected to the p-type doped layer. After sintering, the semiconductor substrate is laser-scanned and a reverse voltage is applied to the semiconductor substrate to form an induced current in the first conductive structure, thereby obtaining the solar cell.

15. The method for preparing a solar cell according to claim 14, characterized in that, The laser scanning time is from 1ms to 100ms, and the reverse voltage is from 5V to 15V.

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