CONDUCTIVE PASTE MIXTURE, SOLAR CELL MANUFACTURING METHODS, AND SOLAR CELLS

Abstract

The invention proposes a conductive paste mixture, a method for producing solar cells, and a solar cell. The conductive paste mixture consists of 0.5% by mass to 4% by mass glass powder, 80% by mass to 92% by mass conductive component, and 7% by mass to 16% by mass organic medium. The glass powder consists of oxides. Based on molar percentages of the oxides, the glass powder consists of 20% by molar to 50% by molar B2O3, and the glass powder also consists of 15% by molar to 50% by molar PbO, or 15% by molar to 50% by molar Bi2O3, or 15% by molar to 50% by molar a mixture of PbO and Bi2O3. The ratio of the total positive ion content of PbO and Bi2O3 to the positive ion content of B2O3 is between 0.30 and 1.25. After sintering, the conductive paste mixture can corrode the passivation layer on the surface of the battery and simultaneously achieve low charge carrier recombination efficiency.

Description

Conductive paste composition, preparation method of solar cell, and solar cell

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023, with application number 202311265866.0 and application name “Conductive paste composition, method for preparing solar cells and solar cells”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of photovoltaic devices, and specifically relates to a conductive paste composition, a method for preparing a solar cell, and a solar cell. Background Art

[0003] Metallization is one of the important steps in the production process of photovoltaic solar cells. It can effectively extract photogenerated carriers to achieve high photoelectric conversion efficiency. Among them, screen printing is the most preferred method for metallization. For N-type solar cells, such as n-TOPCon and other cells with tunneling oxide passivation contact structure, metallization paste containing silver powder and aluminum powder (silver aluminum paste or Ag-Al paste) is usually used under high temperature sintering to achieve the metallization effect on the p-side (or p-type doped layer) of the solar cell. The glass material in the silver aluminum paste is etched and opened during the sintering process, including SiN x 、SiNO x and AlO x The passivation film allows the metal in the paste to react with the p-type doped layer to form a silver-aluminum barb microstructure to achieve good ohmic contact. Technical issues

[0004] Silver-aluminum paste can form a low-resistivity ohmic contact with the p-type doped layer, but high carrier recombination, resulting in loss of open-circuit voltage and efficiency, is a significant factor affecting the photoelectric conversion efficiency of N-type solar cells. Furthermore, during high-temperature sintering, the glass frit in the silver-aluminum paste can etch or damage the passivation film, further increasing recombination losses. Technical Solutions

[0005] The present embodiment provides a conductive paste composition, which comprises, by weight percentage, 0.5 wt % to 4 wt % of glass frit, 80 wt % to 92 wt % of a conductive component, and 7 wt % to 16 wt % of an organic medium.

[0006] The glass frit includes oxides, and based on the molar percentage of the oxides, the glass frit includes 20 mol% to 50 mol% of B2O3; the glass frit further includes: 15 mol% to 50 mol% of PbO; or, 15 mol% to 50 mol% of Bi2O3; or, 15 mol% to 50 mol% of a mixture of PbO and Bi2O3;

[0007] The ratio of the sum of the cation contents of the PbO and Bi2O3 to the cation content of the B2O3 is 0.30-1.25.

[0008] In some embodiments, the glass frit further comprises a first additive, calculated by molar percentage of the oxide, wherein the content of the first additive is less than or equal to 18 mol %, and the first additive is selected from any one or more of Li2O, Al2O3, ZnO, SiO2, SeO2, and TeO2.

[0009] In some embodiments, the first additive satisfies at least one of the following conditions, based on the molar percentage of the oxide:

[0010] a) the first additive comprises Li2O, wherein the content of the Li2O is less than or equal to 15 mol%;

[0011] b) the first additive comprises Al2O3, wherein the content of Al2O3 is less than or equal to 10 mol%;

[0012] c) the first additive comprises ZnO, wherein the content of ZnO is less than or equal to 18 mol %;

[0013] d) the first additive comprises SiO2, and the content of the SiO2 is less than or equal to 15 mol%;

[0014] e) the first additive comprises SeO2, and the content of SeO2 is less than or equal to 15 mol%;

[0015] f) The first additive comprises TeO2, and the content of the TeO2 is less than or equal to 15 mol%.

[0016] In some embodiments, the glass frit further comprises, in terms of molar percentage of the oxides: 0-15 mol % of Li 2 O; 0-10 mol % of Al 2 O 3 ; 0-18 mol % of ZnO; and 0-15 mol % of SiO 2 .

[0017] In some embodiments, the glass frit further includes a second additive, calculated by mole percentage of the oxide, wherein the content of the second additive is less than or equal to 5 mol %, and the second additive is selected from any one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO, and BaO.

[0018] In some embodiments, the conductive paste composition further comprises less than or equal to 1 wt % of a filler, based on the mass percentage of the composition; the filler comprises at least one of aluminum powder, silicon powder, and aluminum-silicon alloy powder.

[0019] In some embodiments, the filler has a mass percentage in the conductive paste composition of greater than 0 and less than or equal to 1 wt %.

[0020] In some embodiments, the filler has a D v 50 is 1-4μm; among them, D v 50 is the particle size corresponding to when the cumulative volume percentage of the filler reaches 50%.

[0021] In some embodiments, the conductive component is selected from any one of silver, silver alloy, silver oxide and silver salt, or a mixture of several of them.

[0022] In some embodiments, a first conductive structure is formed in a solar cell, wherein the solar cell includes a substrate and a passivation layer located on at least one side of the substrate; when the solar cell is sintered, the conductive paste composition can penetrate the passivation layer to form the first conductive structure.

[0023] In some embodiments, the substrate comprises an n-type doped semiconductor substrate.

[0024] In some embodiments, the present application further provides a method for preparing a solar cell, comprising the following steps:

[0025] Providing a substrate, the substrate comprising a substrate, a p-type doped layer, and a passivation layer, wherein the p-type doped layer is located between the substrate and the passivation layer;

[0026] Covering the conductive paste composition on the passivation layer;

[0027] sintering the substrate coated with the conductive paste composition, so that the conductive paste composition etches the passivation layer during the sintering process to form a first conductive structure;

[0028] Laser enhanced contact optimization is performed on the substrate to obtain the solar cell.

[0029] In some embodiments, coating the conductive paste composition on the passivation layer comprises:

[0030] The conductive paste composition is applied to at least a portion of the surface of the passivation layer in a patterned form.

[0031] In some embodiments, the step of performing laser enhanced contact optimization on the substrate further comprises:

[0032] A reverse voltage is applied to the substrate, and a laser is scanned on the substrate simultaneously to form an induced current in the first conductive structure.

[0033] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0034] g) the solar cell has a breakdown voltage, and the reverse voltage is less than the breakdown voltage;

[0035] h) the laser scanning time is 1ms to 100ms;

[0036] i) The induced current is 100A to 1000A.

[0037] In some embodiments, the present application further provides a solar cell comprising a first conductive structure made of the conductive paste composition.

[0038] In some embodiments, the present application also provides a solar cell, which is manufactured using the above-mentioned manufacturing method.

[0039] In some embodiments, the solar cell is a solar cell having a tunnel oxide layer passivation contact structure. Beneficial effects

[0040] The conductive paste composition of the present application can be applied to the metallization of the p-side of solar cells. After sintering, it can etch the passivation layer on the surface of the cell and simultaneously achieve the effect of low carrier recombination. By limiting the cation ratio of Pb+Bi relative to B in the glass material, the corrosion effect of the glass material on the passivation layer is further improved, and the excessive recombination loss caused by the conductive paste composition when etching the passivation layer can be reduced.

[0041] The preparation method of the solar cell provided in the present application achieves moderate corrosion of the passivation layer after sintering the conductive paste composition used, reduces the high recombination of carriers formed under excessive corrosion, and further combines the laser enhanced contact optimization technology. By applying a reverse voltage, a large number of carriers generated by laser scanning are guided into the first conductive structure to form an induced current, and the energy generated by the current is used to improve the contact effect and uniformity of the first conductive structure, thereby achieving a significant improvement in the open circuit voltage and conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] FIG1 is a cross-sectional view of a solar cell provided in an embodiment of the present application;

[0044] Reference numerals: 10 - substrate, 20 - first conductive structure, 30 - second conductive structure, 101 - substrate, 102 - p-type doped layer, 103 - passivation layer, 104 - first passivation film, 105 - n + Polysilicon layer 106 - second passivation film.

[0045] Implementation Methods of the Application

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0047] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting this application. In the description of this application, "plurality" means two or more, and "at least one" means one, two, or more than two, unless otherwise expressly and specifically defined.

[0048] Metallization is one of the important steps in the production process of photovoltaic solar cells. It can effectively extract photogenerated carriers to achieve high photoelectric conversion efficiency. Among them, screen printing is the most preferred method for metallization. For N-type solar cells, such as n-TOPCon and other cells with tunneling oxide passivation contact structure, metallization paste containing silver powder and aluminum powder (silver aluminum paste or Ag-Al paste) is usually used under high temperature sintering to achieve the metallization effect on the p-side (or p-type doped layer) of the solar cell. The glass material in the silver aluminum paste is etched and opened during the sintering process, including SiN x 、SiNO x and AlO xThe passivation film allows the metal in the paste to react with the p-type doped layer, forming a silver-aluminum barb microstructure to achieve good ohmic contact. Although the silver-aluminum paste can form a low-resistivity ohmic contact with the p-type doped layer, high carrier recombination losses, resulting in a loss of open-circuit voltage and efficiency, are significant factors affecting the photoelectric conversion efficiency of N-type solar cells. In addition, because the surface passivation of the substrate significantly affects carrier recombination, etching or damage of the passivation film by the glass frit in the silver-aluminum paste during high-temperature sintering further increases recombination losses.

[0049] Based on this, it is necessary to provide a conductive paste composition, a method for preparing a solar cell, and a solar cell, especially a conductive paste suitable for the p-side, to achieve the effect of low carrier recombination and enable the metallization method to achieve higher open circuit voltage and photoelectric conversion efficiency.

[0050] Some embodiments of the present application provide a conductive paste composition for forming an electrical connection with a p-type doped layer of a solar cell with low carrier recombination and low resistance.

[0051] Some embodiments of the present application provide a conductive paste composition, which includes, by mass percentage, 0.5 wt%-4 wt% of glass frit, 80 wt%-92 wt% of a conductive component, and 7 wt%-16 wt% of an organic medium; the glass frit includes an oxide, and by molar percentage of the oxide, the glass frit includes 20 mol%-50 mol% of B2O3; the glass frit also includes: 15 mol%-50 mol% of PbO; or, 15 mol%-50 mol% of Bi2O3; or, a mixture of 15 mol%-50 mol% of PbO and Bi2O3; wherein the ratio of the sum of the cation content of PbO and Bi2O3 to the cation content of B2O3 is 0.30-1.25.

[0052] The glass frit and conductive component serve as the solid components of the conductive paste composition, while the organic medium serves as the dispersed phase and provides printing performance. The sum of the weight percentages of each component in the conductive paste composition is 100%. Cationic content refers to the amount or proportion of cations in a chemical substance. In a chemical formula, cations are generally positively charged ions.

[0053] Each component is described below.

[0054] glass frit

[0055] In some embodiments, glass frit refers to a composition containing one or more types of anions and cations. Glass frit has the ability to flow when heated, and the glass frit can be crystalline or partially or completely glassy or amorphous.

[0056] In some embodiments, the glass frit of this embodiment can be understood as a composition having a glass component, and the glass frit comprises 0.5 wt% to 4 wt% of the conductive paste composition. In other embodiments, the glass frit comprises 1.0 wt% to 3.8 wt% of the conductive paste composition, or 1.5 wt% to 3.5 wt% of the conductive paste composition, or 2.0 wt% to 3.0 wt% of the conductive paste composition, or 2.2 wt% to 2.8 wt% of the conductive paste composition. It should be understood that the proportion of the glass frit in the conductive paste composition should be adjusted to ensure that the sum of the weight percentages of the components in the conductive paste composition is 100%. The composition of the glass frit directly affects its solubility, flowability, and etching properties. Therefore, a well-balanced composition of the glass frit is required to achieve excellent carrier recombination.

[0057] In some embodiments, the glass frit contains at least the following components: 15 mol% to 50 mol% PbO and / or Bi2O3, and 20 mol% to 50 mol% B2O3, calculated as oxides. In the following description, unless otherwise specified, "mol%" for each component in the glass frit refers to the molar percentage of the oxides. Furthermore, "15 mol% to 50 mol%" may represent a range of 15 mol% to 50 mol%, and the same applies to other components.

[0058] In some embodiments, further preferably, the glass frit includes, in terms of molar percentage converted into oxides: 20 mol % or more and 40 mol % or less of PbO and / or Bi 2 O 3 , and 30 mol % or more and 40 mol % or less of B 2 O 3 .

[0059] In some embodiments, PbO, Bi2O3 or a combination of the two can form a low-melting-point glass phase and provide good fluidity, and both can corrode the passivation layer during the sintering process. This is because PbO and Bi2O3 are reactive with the passivation layer and have the function of improving the softening fluidity of the glass.

[0060] In some embodiments, B2O3, as a glass former, can form low-melting-point glass and provide good fluidity. B2O3 can form a network structure, which helps stabilize the glass and improves the bonding ability of the glass to the substrate after melting.

[0061] In some embodiments, the ratio of the sum of the cation content of PbO and Bi2O3 to the cation content of B2O3 in the glass frit is 0.30 to 1.25. For example, the ratio can be any one of 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.21, 1.22, 1.23, 1.24, and 1.25, or a range between any two of these values. By limiting the cation ratio of Pb+Bi relative to B, the corrosion effect of the glass frit can be improved. This is because PbO is more corrosive than Bi2O3. Therefore, replacing part of PbO with Bi2O3 in the composition of the glass frit can adjust the corrosion ability. Therefore, when the above cation ratio range is met, the corrosion properties and reactivity of the glass frit can be controlled by adjusting the cation ratio of Pb+Bi relative to B to achieve the effect of low carrier recombination, and the open circuit voltage and photoelectric conversion efficiency can be improved.

[0062] In some embodiments, the glass frit further comprises, on a molar basis, 18 mol% or less of a first additive selected from any one or more of Li2O, Al2O3, ZnO, SiO2, SeO2, and TeO2. Furthermore, preferably, on a molar basis, the glass frit further comprises 3 mol% or more and 15 mol% or less of the first additive. Even more preferably, on a molar basis, the glass frit further comprises 6 mol% or more and 10 mol% or less of the first additive.

[0063] In some embodiments, the first additive is used to modify the glass frit system and may further include a glass former or glass modifier. During the glass frit preparation process, the glass former forms the initial network structure of the glass. When the glass modifier is incorporated into the glass network, it changes the initial network structure formed by the glass former, thereby changing the original thermal properties of the glass. The content of each component in the first additive can be adjusted accordingly depending on the desired glass properties.

[0064] In some embodiments, TeO2 or SeO2, as glass formers, can increase the fluidity of the glass during molding. The SeO2 content in the glass frit is 15 mol% or less, calculated as a molar percentage of oxides. Furthermore, preferably, the SeO2 content in the glass frit is 5 mol% or more and 10 mol% or less, calculated as a molar percentage of oxides. Furthermore, preferably, the TeO2 or SeO2 content in the glass frit is 5 mol% or more and 7.5 mol% or less, calculated as a molar percentage of oxides.

[0065] In some embodiments, Li2O acts as a glass modifier. The addition of an appropriate amount can increase the fluidity of the glass. However, Li2O itself has a corrosive effect, so its addition level must be controlled within a certain range. The Li2O content in the glass frit is preferably 15 mol% or less, calculated as a molar percentage of oxides. Furthermore, the Li2O content in the glass frit is preferably 5 mol% or more and 10 mol% or less, calculated as a molar percentage of oxides. Within this range, the fluidity and reactivity of the glass can be enhanced, further improving the electrical properties of the solar cell.

[0066] In some embodiments, Al2O3 acts as a glass former, stabilizing the glass phase, raising the glass melting point, and reducing fluidity. It can also improve the weatherability of the glass. The Al2O3 content in the glass frit is 10 mol% or less, calculated as an oxide. More preferably, the Al2O3 content in the glass frit is 3 mol% to 7 mol%, calculated as an oxide. Within this range, the glass transition temperature rise is suppressed, and excellent fluidity is exhibited during softening.

[0067] In some embodiments, ZnO, as a glass modifier, can be added to improve electrical properties. The ZnO content in the glass frit is preferably 18 mol% or less, calculated as an oxide. Furthermore, the ZnO content in the glass frit is preferably 6 mol% or more and 12 mol% or less, calculated as an oxide. Within this range, the melting temperature of the glass frit can be lowered, improving its melting and fusion properties, thereby facilitating glass production.

[0068] In some embodiments, SiO2 acts as a glass former, and 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 adjust its reactivity with the substrate. The SiO2 content in the glass frit is 15 mol% or less, calculated as a molar percentage of oxides. Further preferably, the SiO2 content in the glass frit is 3 mol% or more and 10 mol% or less, calculated as a molar percentage of oxides. Within the above range, the glass transition temperature and the fluidity of the glass during sintering can be adjusted, and the etching properties of the glass during sintering can be controlled.

[0069] In some embodiments, the glass frit includes, in terms of molar percentage of oxides: 15 mol% to 50 mol% of PbO and / or Bi2O3; 20 mol% to 50 mol% of B2O3; 0 to 15 mol% of Li2O; 0 to 10 mol% of Al2O3; 0 to 18 mol% of ZnO; and 0 to 15 mol% of SiO2.

[0070] In some embodiments, the glass frit includes, in terms of molar percentage of oxides: 15 mol% to 50 mol% of PbO and / or Bi2O3; 20 mol% to 50 mol% of B2O3; 0 to 15 mol% of Li2O; 0 to 10 mol% of Al2O3; 0 to 18 mol% of ZnO; 0 to 15 mol% of SiO2; and 0 to 15 mol% of SeO2 or TeO2.

[0071] In some embodiments, the glass frit further includes, in terms of oxide molar percentage, up to 5 mol% of a second additive, the second additive being selected from any one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO, and BaO. It will be appreciated that the second additive, acting as a glass modifier, can be combined with the first additive during the preparation of the glass frit to further modify and adjust the melting point and fluidity of the glass frit.

[0072] Conductive component

[0073] In some embodiments, the conductive component serves as a source of electrical conductivity for the conductive paste composition. The conductive component in this embodiment 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 alloys and mixtures thereof. Alternatively, the conductive component can consist essentially of silver due to its excellent workability and high electrical conductivity.

[0074] In some embodiments, the conductive component comprises 80 wt% to 92 wt% of the conductive paste composition. In other embodiments, the conductive component comprises 82 wt% to 90 wt%, 85 wt% to 88 wt%, or even 86 wt% to 87 wt%. It should be understood that the proportion of the conductive component in the conductive paste composition must be adjusted to ensure that the sum of the weight percentages of the components in the conductive paste composition is 100%. The conductive component is used to provide electrical conductivity after forming a solar cell.

[0075] In some embodiments, the conductive component may be a metal powder directly incorporated into the conductive paste composition of the present application; or a mixture of two or more such metals or alloys may be directly incorporated; the metal is provided by a metal oxide or salt that decomposes to form the metal when exposed to the heat of firing. 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 silver oxide (Ag2O or AgO) or silver salts such as AgCl, AgNO3, AgOOCCH3 (silver acetate), AgOOCF3 (silver trifluoroacetate), Ag3PO4 (silver orthophosphate), or mixtures thereof.

[0076] In some embodiments, the conductive component may be provided as finely dispersed particles having a morphology such as powder form, flake form, spherical form, rod form, granular form, nodular form, layered or coated form, other irregular forms, or mixtures thereof.

[0077] In some embodiments, the median particle size of the conductive component is in the range of 0.5-3.5 μm. A further preferred conductive component utilizes spherical silver powder with a median particle size of 1-3 μm; an even more preferred conductive component utilizes spherical silver powder with a median particle size of 1.5-2.5 μm; and an even more preferred spherical silver powder with a median particle size of 2 μm. The primary function of silver powder is to form a high-density silver body after sintering, thereby enhancing good conductivity. Spherical silver powder with a median particle size of 2 μm also inhibits agglomeration and ensures uniform dispersion of the silver powder.

[0078] organic medium

[0079] In some embodiments, an organic medium, as the liquid phase in the conductive paste composition, is used to disperse the solids comprised of the conductive component and glass frit, thereby forming a paste having a certain viscosity. The viscosity and rheological properties of the paste ensure both long-term stability in the dispersion of the conductive component and glass frit, and the ability to disperse the conductive paste composition on a printing screen and apply a desired pattern to the passivation layer of the substrate via screen printing.

[0080] In some embodiments, the organic medium may include a polymer and an organic solvent. The polymer may include cellulose, resin, ester, etc. Cellulose includes cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, benzyl cellulose, propyl cellulose, nitrocellulose, or mixtures thereof. Resins include wood rosin, phenolic resins, acrylic resins, or mixtures thereof. Esters include polymethacrylates of lower alcohols, etc. The organic solvent may include terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol diacetate, α-terpene, β-terpene, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol, etc.

[0081] In some embodiments, the organic medium has a consistency and rheological properties that make it suitable for printing methods, including but not limited to screen printing. The organic medium may also include other additives such as non-ionic surfactants, thixotropic agents, dispersants, and rheological agents to adapt the organic medium to different needs.

[0082] filler

[0083] In some embodiments, the mass percentage of the filler in the conductive paste composition is greater than 0 and less than or equal to 1 wt %; wherein the filler is selected from at least one of aluminum powder, silicon powder, and aluminum-silicon alloy powder.

[0084] In some embodiments, unlike the aluminum powder added to the commercially available silver-aluminum paste for TOPCon cells to improve contact, the aluminum powder added as a filler in this embodiment can further control the etching properties of the glass frit to achieve a higher open-circuit voltage. It is understandable that the reason for achieving the above-mentioned increase in open-circuit voltage is affected by the amount of aluminum powder added. This is because when a small amount of aluminum powder is added to the paste, the melted glass frit can further incorporate a small amount of aluminum oxide during the high-temperature sintering process. The increase in aluminum oxide in the melted glass frit reduces its fluidity and corrosiveness, thereby causing less damage to the passivation film. The effect is that lower recombination leads to an increase in open-circuit voltage. However, excessive aluminum powder addition will cause the melted glass frit to incorporate too much aluminum powder during sintering, significantly reducing its corrosiveness and having a negative impact on the fill factor.

[0085] More preferably, the mass percentage of the filler in the conductive paste composition is greater than 0 and less than or equal to 0.75 wt %.

[0086] More preferably, the mass percentage of the filler in the conductive paste composition is any one of 0.25 wt%, 0.50 wt%, 0.75 wt%, 1.0 wt%, or a range between any two of them.

[0087] In some embodiments, the filler D v 50 is 1-4μm; among them, D v50 is the particle size corresponding to when the cumulative volume percentage of the filler reaches 50%. v 50 is 1-3 μm. More preferably, the filler D v 50 is 2μm.

[0088] In some embodiments, the preparation method of glass powder can be produced by methods conventionally used in the field of glass manufacturing. For example, the oxides corresponding to the composition ratio of the glass powder described in the embodiment are batched, mixed, added to a crucible (e.g., platinum or ceramic crucible), heated to a peak temperature (e.g., 800°C to 1400°C) and maintained for a period of time so that the oxides inside melt together. The molten material can then be quenched in any suitable manner, including but not limited to passing it between counter-rotating stainless steel rollers to form a sheet 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 material is then subjected to conventional grinding techniques to form a powder with a particle size of 0.5-2 μm.

[0089] In some embodiments, the preparation method of the conductive paste composition may include preparing the paste components described in the embodiments, stirring and dispersing the mixture, and then grinding the mixture using a three-roll mill to a fineness of less than 10 μm, followed by filtration. The amounts of glass frit and aluminum powder added may vary in some embodiments. In these cases, silver powder is substituted in equal amounts, while the amounts of other components, such as the organic medium, remain unchanged. The proportions of the glass frit, conductive component, organic medium, and filler must be adjusted to ensure that the total mass percentage of each component in the conductive paste composition is 100%.

[0090] In some embodiments, the conductive paste composition of this embodiment is used to form a first conductive structure 20 in a solar cell, wherein the solar cell includes a substrate 101, the substrate 101 having a main surface and at least one passivation layer 103 provided on the main surface, wherein the conductive paste composition can penetrate at least one passivation layer 103 during sintering to form the first conductive structure 20.

[0091] It is understood that the first conductive structure 20 can form an electrical connection with the p-type semiconductor in the substrate 101, resulting in low carrier recombination. The p-type semiconductor can preferably be a p-type doped layer, and the substrate 101 can be an n-type doped semiconductor substrate. In addition, in a TOPCon cell, the p-type doped layer is also referred to as a p-type emitter.

[0092] solar cells

[0093] As shown in FIG1 , some embodiments of the present application provide a solar cell having a tunnel oxide passivated contact structure (Tunnel Oxide Passivated Contacts), which is prepared using the above-mentioned conductive paste composition.

[0094] In some embodiments, a solar cell with a tunnel oxide passivated contact structure is referred to as a TOPCon solar cell (Tunnel Oxide Passivated Contact Solar Cell). This type of solar cell utilizes a tunnel oxide layer as a charge transfer channel and surface passivation layer to improve cell efficiency and performance. The TOPCon solar cell structure offers reduced electron reflection and surface recombination, high photoelectric conversion efficiency, and low electron defectivity.

[0095] In some embodiments, a TOPCon solar cell includes a substrate 10 and a first conductive structure 20, wherein the substrate 10 includes a substrate 101, a p-type doped layer 102 formed on one side of the substrate 101, and a passivation layer 103 formed on a side of the p-type doped layer 102 away from the substrate 101; taking Figure 1 as an example, the substrate 101 is located in the middle of the TOPCon solar cell, and the substrate 101 can be an n-type doped semiconductor substrate; the p-type doped layer 102 is located on the front side of the n-type doped semiconductor substrate, and the passivation layer 103 is located on the surface of the p-type doped layer 102; the conductive structure 20 penetrates at least a portion of the passivation layer 103 and forms an electrical connection with the p-type doped layer 102.

[0096] In some embodiments, referring to FIG. 1 , the substrate 10 further includes: a first passivation film 104 located on the back side of the n-type doped semiconductor substrate; + The polysilicon layer 105 is located on the surface of the first passivation film 104 away from the n-type doped semiconductor substrate; the second passivation film 106 is deposited on the n-type doped semiconductor substrate. + The polysilicon layer 105 is spaced apart from the surface of the first passivation film 104 .

[0097] In some embodiments, referring to FIG. 1 , the TOPCon solar cell further includes a second conductive structure 30 that penetrates at least a portion of the second passivation film 106 and is in contact with the n + The polysilicon layer 105 forms an electrical connection.

[0098] In some embodiments, the front side refers to the light-exposed side of the solar cell, which is also the working side of the solar cell. The back side refers to the back side of the solar cell, which generally does not directly receive light.

[0099] In some embodiments, the first passivation film 104 and the n-type passivation film 106 are formed by a tunnel oxide passivation contact method. +Polysilicon layer 105 .

[0100] In some embodiments, the first conductive structure 20 is formed using the conductive paste composition 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 manner. During the sintering process, the conductive paste composition penetrates the passivation layer 103 to form the first conductive structure 20 that is electrically connected to the p-type doped layer 102 to achieve low carrier recombination.

[0101] In some embodiments, the second conductive structure 30 can utilize a metallization silver paste used in P-type or N-type crystalline silicon cells on the market, such as a silver paste containing Pb-Te-O glass powder. The conductive paste composition is applied to at least a portion of the surface of the second passivation film 106 in a desired patterned form. During the sintering process, the silver paste containing Pb-Te-O glass powder etches and penetrates the second passivation film 106, thereby contacting the n-type crystalline silicon cell. + The polysilicon layer 105 forms an electrical contact to facilitate forming the second conductive structure 30 in the form of a conductive metal contact.

[0102] The present invention provides a method for preparing a solar cell, comprising:

[0103] 1) Providing a substrate 10, the substrate 10 comprising a substrate 101, a p-type doped layer 102 formed on one side of the substrate 101, and a passivation layer 103 formed on a side of the p-type doped layer 102 away from the substrate 101; wherein a trivalent element (such as boron or gallium) is doped on the front side of the substrate 101 to form the p-type doped layer 102 on the front side of the n-type doped semiconductor substrate; and depositing the passivation layer 103 on the surface of the p-type doped layer 102 by a deposition method;

[0104] 2) applying the conductive paste composition provided in this embodiment to the passivation layer 103; specifically, applying the conductive paste composition to at least a portion of the surface of the passivation layer 103 in a patterned manner; the patterning method can be screen printing; it can be understood that the conductive paste composition involved in this embodiment is used as a fine grid for the P side of a solar cell containing a tunneling oxide layer passivation contact structure, and passes through four screen printing machines corresponding to the back main grid, back fine grid, front main grid, and front fine grid respectively; the conductive paste composition of this embodiment is used for the fine grid on the P side, usually the fourth front fine grid;

[0105] 3) sintering the substrate 10 and the conductive paste composition, so that the conductive paste composition etches the passivation layer 103 during the sintering process to form the first conductive structure 20; in addition, the preparation of the second conductive structure 30 is the same as the preparation of the first conductive structure 20;

[0106] 4) Performing laser enhanced contact optimization on the substrate 10 to prepare a solar cell.

[0107] The sequence numbers of the above steps are not to be construed as limiting the order of the steps.

[0108] In some embodiments, in step 4), laser-enhanced contact improvement optimization is a method of using lasers to improve the electrical contact of metallization pastes during the solar cell manufacturing process. The basic principle of laser-enhanced contact improvement technology is to utilize the large number of carriers generated by the laser, guide these carriers through the formed metallization contact points using bias voltage, and use the heat energy generated by the current to improve the contact effect and uniformity. This can improve the uniformity of electrical contact, reduce contact defects, and thus improve the efficiency and reliability of the solar cell. In this technology, the amount of carrier injection can be controlled by parameters such as laser power and time to achieve better contact uniformity and improvement effect.

[0109] In some embodiments, the step of performing laser-enhanced contact optimization on the substrate 10 further includes applying a reverse voltage to the substrate 10 while simultaneously scanning the substrate 10 with a laser to generate an induced current within the first conductive structure 20. Using laser-enhanced contact optimization technology to process the conductive structure can reduce contact resistance, further facilitating an increase in open-circuit voltage and improved efficiency.

[0110] In some embodiments, the reverse voltage is less than the breakdown voltage of the solar cell, thereby avoiding breakdown damage, extending the life of the solar cell, improving battery safety, and protecting battery performance.

[0111] In some embodiments, the laser scanning time is 1 ms to 100 ms, for example, any value among 1 ms, 2 ms, 3 ms, 5 ms, 10 ms, 20 ms, 30 ms, 40 ms, 50 ms, 60 ms, 70 ms, 80 ms, 90 ms, and 100 ms, or a range between any two values.

[0112] In some embodiments, the induced current is 100A to 1000A. For example, the induced current can be any value among 100A, 150A, 200A, 250A, 300A, 350A, 400A, 450A, 500A, 550A, 600A, 650A, 700A, 750A, 800A, 850A, 900A, 950A, and 1000A, or a range between any two values.

[0113] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0114] The component contents of the glass frits of Examples 1 to 13 and Comparative Examples 1 to 4 are shown in Table 1. The sum of the components in the glass frits of Examples and Comparative Examples is 100%. The values ​​in Table 1 are in mole percentage (mol%). In the glass frits of Comparative Examples 1-2, the (Pb+Bi) / B cation ratio was not within the range of 0.30-1.25, and the content of the first additive TeO2 added in Comparative Examples 3-4 was too high.

[0115] Table 1

[0116] The glass frits of Examples 1 to 13 and Comparative Examples 1 to 4 in Table 1 were mixed into conductive paste compositions and fabricated into solar cells, yielding corresponding Examples 14 to 26 and Comparative Examples 5 to 8. The performance of the cells of Examples 14 to 26 and Comparative Examples 5 to 8 was tested, and the quality test data is shown in Table 2.

[0117] In the conductive paste compositions of Examples 14 to 26 and Comparative Examples 5 to 8, the mass percentage of glass frit is 1.5 wt %; the conductive component uses spherical silver powder with a median particle size of 2 μm, and the mass percentage of the conductive component glass frit is 89.5 wt %; the mass percentage of the organic medium is 9 wt %, wherein the organic medium specifically comprises: 1.5 wt % of ethyl cellulose, 1.5 wt % of polyvinyl butyral copolymer (PVB), 1.6 wt % of diethylene glycol butyl ether acetate, 0.3 wt % of silicone oil, 0.15 wt % of Duomeen TDO (a nonionic surfactant belonging to the amine oxide category), 0.15 wt % of Brij L4 (a nonionic surfactant belonging to the polyoxyethylene alcohol category), 0.4 wt % of Thixotrol plus (rheological agent), 2.8 wt % of ethoxylated alcohol C12, and 0.6 wt % of dibasic acid ester. The specific preparation process of the conductive paste composition is: the above components are mixed, stirred and dispersed, and then grinded with a three-roll mill to a fineness of less than 10 μm, and then filtered to obtain the conductive paste composition.

[0118] The preparation process is as follows: first prepare the blue film of the TOPCon battery, and pass it through four screen printing machines corresponding to the back main grid, back fine grid, front main grid, and front fine grid respectively; apply the conductive paste composition to the front fine grid of the P side; sinter the substrate and the conductive paste composition, so that the conductive paste composition etches the passivation layer during the sintering process to obtain a conductive structure on the p side of the substrate; perform laser enhanced contact optimization on the conductive structure to prepare a solar cell.

[0119] Among them, the test data in Table 2 were measured by the following method:

[0120] a) Suns-Voc test: Using a Sinton WCT120 tester, Suns-Voc is measured after sintering. The measured Voc is used to characterize and compare the carrier recombination performance of different conductive pastes after sintering.

[0121] b) IV Testing: A commercially available IV tester was used to test the photovoltaic conversion efficiency of the cells. Test parameters included efficiency (Eff), open-circuit voltage (Voc), fill factor (FF), and current (Isc). The experimental data is presented as the difference values ​​(ΔEff, ΔVoc, ΔFF, and ΔIsc) to illustrate the electrical performance of the Examples and Comparative Examples.

[0122] Table 2

[0123] As can be seen from Table 2, the batteries of Examples 14 to 26 achieve an efficiency performance of ±0.1%. Compared with Comparative Examples 5-8, the conductive paste compositions of the embodiments of the present application combined with laser enhanced contact improvement can achieve a significant improvement in open circuit voltage and conversion efficiency, indicating that the conductive paste compositions provided by the present application can significantly improve the effect of the p-side metallization composite of the TOPCon structure battery. Among them, the effects of Comparative Examples 5 and 6 are worse than those of the embodiments. This is because the (Pb+Bi) / B cation ratio in the glass powder corresponding to Comparative Example 5 is too high, resulting in too strong corrosiveness of the glass powder and a loss of opening voltage; the (Pb+Bi) / B cation ratio in Comparative Example 6 is too low, and the corrosiveness of the glass powder is too weak to form a good ohmic contact, resulting in a significant reduction in FF. In addition, in Comparative Examples 7 and 8, the glass is too fluid due to the high amount of TeO2 added to the glass frit, which causes excessive damage to the passivation film during sintering, resulting in a loss of opening voltage.

[0124] Examples 27 to 30 and Comparative Example 9 are provided. The solar cell preparation process in Examples 27 to 30 is the same as that in Example 14, except that the conductive paste compositions of Examples 27 to 30 also contain a filler, aluminum powder with a median particle size of 2 μm. Due to the addition of aluminum powder, the content of the conductive component, silver powder, needs to be adjusted to ensure a total weight content of 100%. Comparative Example 9 is similar to Example 27, except that the amount of aluminum powder added exceeds 1 wt%. Specific amounts and test data are shown in Table 3.

[0125] Table 3

[0126] As shown in Table 3, adding a small amount of aluminum powder can further reduce recombination and improve open-circuit voltage. This is because the aluminum oxide formed during the high-temperature sintering process can be melted into the glass frit. The increased aluminum oxide in the melted glass frit reduces its fluidity and corrosiveness, thereby causing less damage to the passivation layer. However, adding large amounts of aluminum powder is not suitable as it significantly reduces the fill factor and, consequently, efficiency. In Table 3, when used with the glass frit of Example 1, since the aluminum powder content of Comparative Example 9 exceeds 1wt%, the loss in FF increases, which is insufficient to compensate for the increase in open-circuit voltage. Since different glass frits can incorporate varying amounts of aluminum after melting, adding aluminum powder in an amount of 0-1wt% can further reduce recombination and improve the open-circuit voltage.

[0127] Example 31 and Comparative Examples 10 to 11 are provided. The process for preparing a solar cell in Example 31 is the same as that in Example 14, except that the glass frit content in Example 31 is 3 wt %; the glass frit content in Comparative Example 10 exceeds the specified range, being 4.5 wt %. Comparative Example 11 uses a commercially available silver-aluminum paste (containing 3-7 wt % glass frit, 1-2 wt % aluminum powder, and approximately 10 wt % organic vehicle, with the remainder being silver powder). Specific amounts used and test data are shown in Table 4.

[0128] Table 4

[0129] As shown in Table 4, compared to commercially available high-efficiency silver-aluminum pastes, the conductive paste composition used in this example significantly reduces composites after sintering, as shown in the Suns-Voc ratio in Table 4. This results in a significant increase in open-circuit voltage and efficiency of over 0.3% after laser-enhanced contact treatment after sintering. The data from Comparative Example 10 shows that increasing the glass frit content to 4.5wt% increases damage to the passivation layer, leading to a loss in Suns-Voc. Therefore, the glass frit content should be within the range of 0.5wt% to 4wt%.

[0130] Furthermore, two sets of data comparison were conducted using commercially available high-efficiency silver-aluminum paste. The preparation of the two sets was the same as in Example 14, but the difference was that the process was different. The test results are shown in Table 5.

[0131] Table 5

[0132] As can be seen from Table 5, the commercially available high-efficiency silver-aluminum paste does not achieve further efficiency improvement after sintering when combined with the laser-enhanced contact improvement technology. This shows that the laser-enhanced contact improvement technology requires the improved conductive paste composition of this application to achieve higher battery conversion efficiency.

[0133] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0134] The above is a detailed introduction to the conductive paste composition, solar cell preparation method and solar cell provided in the embodiments of the present application, and specific examples are used to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and core idea of ​​the present application; ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solution of the embodiments of the present application.

Claims

1. A conductive paste composition, wherein: According to the mass percentage of the conductive paste composition, the conductive paste composition includes 0.5wt%-4wt% of glass frit, 80wt%-92wt% of conductive component, and 7wt%-16wt% of organic medium; The glass frit includes an oxide, and according to the molar percentage of the oxide, the glass frit includes 20mol%-50mol% of B2O3; the glass frit also includes: 15mol%-50mol% of PbO; or, 15mol%-50mol% of Bi2O3; or, 15mol%-50mol% of a mixture of PbO and Bi2O3; Wherein, the ratio of the sum of the cation contents of the PbO and the Bi2O3 to the cation content of the B2O3 is 0.30-1.

25.

2. The conductive paste composition according to claim 1, wherein Calculated by molar percentage of the oxide, the glass material further comprises a first additive, the content of the first additive is less than or equal to 18 mol %, and the first additive is selected from any one or more of Li2O, Al2O3, ZnO, SiO2, SeO2 and TeO2.

3. The conductive paste composition according to claim 2, wherein: In terms of molar percentage of the oxide, the first additive satisfies at least one of the following conditions: a) the first additive comprises Li2O, and the content of Li2O is less than or equal to 15 mol%; b) the first additive comprises Al2O3, and the content of Al2O3 is less than or equal to 10 mol%; c) the first additive comprises ZnO, and the content of ZnO is less than or equal to 18 mol %; d) the first additive comprises SiO2, and the content of SiO2 is less than or equal to 15 mol%; e) the first additive comprises SeO2, and the content of SeO2 is less than or equal to 15 mol%; f) The first additive comprises TeO2, and the content of TeO2 is less than or equal to 15 mol%.

4. The conductive paste composition according to claim 1, wherein Calculated by molar percentage of the oxides, the glass material further comprises: 0 to 15 mol % of Li2O; 0 to 10 mol % of Al2O3; 0 to 18 mol % of ZnO; and 0 to 15 mol % of SiO2.

5. The conductive paste composition according to claim 1, wherein Calculated by molar percentage of the oxide, the glass material further comprises a second additive, the content of the second additive is less than or equal to 5 mol%, and the second additive is selected from any one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO and BaO.

6. The conductive paste composition according to claim 1, wherein The conductive paste composition further comprises less than or equal to 1 wt % of filler in terms of mass percentage of the composition; the filler comprises at least one of aluminum powder, silicon powder and aluminum-silicon alloy powder.

7. The conductive paste composition according to claim 6, wherein: The mass percentage of the filler in the conductive paste composition is greater than 0 and less than or equal to 1 wt %.

8. The conductive paste composition according to claim 6, wherein: The D of the filler v 50 is 1-4μm, D v 50 is the particle size corresponding to when the cumulative volume percentage of the filler reaches 50%.

9. The conductive paste composition according to claim 1, wherein: The conductive component is selected from any one or a mixture of silver, silver alloy, silver oxide and silver salt.

10. The conductive paste composition according to claim 1, wherein: Used to form a first conductive structure (20) in a solar cell, the solar cell comprising a substrate (101) and a passivation layer (103) located at least on one side of the substrate (101); when sintering the solar cell, the conductive paste composition can penetrate the passivation layer (103) to form the first conductive structure (20).

11. The conductive paste composition according to claim 10, wherein: The substrate (101) comprises an n-type doped semiconductor substrate.

12. A method for preparing a solar cell, wherein: The following steps are involved: Providing a substrate (10), the substrate (10) comprising a substrate (101), a p-type doping layer (102), and a passivation layer (103), wherein the p-type doping layer (102) is located between the substrate (101) and the passivation layer (103); Applying the conductive paste composition according to any one of claims 1 to 11 on the passivation layer (103); Sintering the substrate (10) coated with the conductive paste composition, so that the conductive paste composition etches the passivation layer (103) during the sintering process to form a first conductive structure (20); Laser enhanced contact optimization is performed on the substrate (10) to obtain the solar cell.

13. The method for preparing a solar cell according to claim 12, wherein: The conductive paste composition is coated on the passivation layer (103), comprising: The conductive paste composition is applied to at least a portion of the surface of the passivation layer (103) in a patterned form.

14. The method for preparing a solar cell according to claim 12, wherein: The step of performing laser enhanced contact optimization on the substrate (10) comprises: A reverse voltage is applied to the substrate (10), and laser scanning is performed on the substrate (10) at the same time, so as to form an induced current in the first conductive structure (20).

15. The method for preparing a solar cell according to claim 14, wherein: The preparation method satisfies at least one of the following conditions: g) the solar cell has a breakdown voltage, and the reverse voltage is less than the breakdown voltage; h) The laser scanning time is 1ms to 100ms; i) The induced current is 100A to 1000A.

16. A solar cell, wherein: The solar cell comprises a first conductive structure (20) made of the conductive paste composition according to any one of claims 1 to 11.

17. A solar cell, wherein: The solar cell is manufactured by the manufacturing method according to any one of claims 12 to 15.

18. The solar cell according to any one of claims 16 to 17, wherein: The solar cell is a solar cell having a tunneling oxide layer passivation contact structure.

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