Conductive paste composition, method for manufacturing a solar cell, and solar cell

Abstract

Disclosed are a conductive paste composition, a method for manufacturing a solar cell, and a solar cell, comprising 0.5 wt% to 4 wt% glass frit, 80 wt% to 92 wt% conductive component, and 7 wt% to 16 wt% organic medium, wherein the glass frit contains oxides, and based on the molar percentage of oxides, the glass frit contains 20 mol% to 50 mol% B2O3, and further comprises 15 mol% to 50 mol% PbO, or 15 mol% to 50 mol% Bi2O3, or a mixture of 15 mol% to 50 mol% PbO and Bi2O3, wherein the ratio of the total cation content of PbO and Bi2O3 to the cation content of B2O3 is 0.30 to 1.25. The conductive paste composition of this application can etch the battery surface passivation layer after sintering, and at the same time achieve the effect of less carrier recombination.

Description

Technical Field

[0001] This application claims priority based on a Chinese patent application filed with the China National Intellectual Property Administration on September 27, 2023, with an application number of 202311265866.0 and an application title of "Conductive Paste Composition, Method for Manufacturing Solar Cell, and Solar Cell", and incorporates all the contents of the Chinese patent application herein by reference.

[0002] This application relates to the technical field of photovoltaic devices, specifically, to a conductive paste composition, a method for manufacturing 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, and can effectively extract photo-generated carriers to achieve high photoelectric conversion efficiency. Among them, currently, screen printing is the most preferred metallization method. In the case of N-type solar cells such as n-TOPCon and other cells with a tunnel oxide layer passivation contact structure, usually, a metallization paste (silver-aluminum paste or Ag-Al paste) containing silver powder and aluminum powder is used, and sintered at a high temperature to obtain a metallization effect on the p-side (or p-type doped layer) of the solar cell. The glass frit in the silver-aluminum paste etches and opens a passivation film containing SiNx, SiNOx, and AlOx during the sintering process, and the metal in the paste reacts with the p-type doped layer to form a fine structure of silver-aluminum barbs, realizing good ohmic contact.

Summary of the Invention

Problems to be Solved by the Invention

[0004] While silver-aluminum paste can form low-resistivity ohmic contact with the p-type doped layer, the loss of open-circuit voltage and efficiency of the cell due to high carrier recombination is a significant factor affecting the photoelectric conversion efficiency of N-type solar cells. Furthermore, etching or damage to the passivation film by glass frit in the silver-aluminum paste during high-temperature sintering further increases recombination losses. [Means for solving the problem]

[0005] The embodiments of the present application provide a conductive paste composition comprising, based on the mass percentage of the composition, 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. The glass frit contains an oxide, and based on the molar percentage of the oxide, the glass frit contains 20 mol% to 50 mol% of B2O3, and the glass frit further contains 15 mol% to 50 mol% of PbO, or 15 mol% to 50 mol% of Bi2O3, or a mixture of 15 mol% to 50 mol% of PbO and Bi2O3. Here, the ratio of the total cation content of PbO and Bi2O3 to the cation content of B2O3 is 0.30 to 1.25.

[0006] In some embodiments, the glass frit further comprises a first additive based on the molar percentage of the oxide, wherein the content of the first additive is 18 mol% or less, and the first additive is selected from one or more of Li2O, Al2O3, ZnO, SiO2, SeO2, and TeO2.

[0007] In some embodiments, based on the molar percentage of the oxide, the first additive satisfies at least one of the following conditions: a) The first additive contains Li2O, and the Li2O content is 15 mol% or less. b) The first additive contains Al2O3, and the Al2O3 content is 10 mol% or less. c) The first additive contains ZnO, and the ZnO content is 18 mol% or less. d) The first additive contains SiO2, and the SiO2 content is 15 mol% or less. e) The first additive contains SeO2, and the content of SeO2 is 15 mol% or less. f) The first additive contains TeO2, and the TeO2 content is 15 mol% or less.

[0008] In some embodiments, based on the molar percentage of the oxide, the glass frit further comprises 0-15 mol% Li2O, 0-10 mol% Al2O3, 0-18 mol% ZnO, and 0-15 mol% SiO2.

[0009] In some examples, based on the molar percentage of the oxide, the glass frit further contains a second additive, the content of which is 5 mol% or less, and the second additive is selected from one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO, and BaO.

[0010] In some embodiments, based on the mass percentage of the composition, the conductive paste composition further comprises 1 wt% or less of a filler, the filler comprising at least one of aluminum powder, silicon powder, and aluminum-silicon alloy powder.

[0011] In some examples, the mass percentage of the filler in the conductive paste composition is greater than 0 and 1 wt% or less.

[0012] In some embodiments, the Dv50 of the filler is 1 to 4 μm, where Dv50 is the particle size when the cumulative volume percentage of the filler reaches 50%.

[0013] In some embodiments, the conductive component is selected from one or a mixture of silver element, silver alloy, silver oxide, and silver salt.

[0014] In some embodiments, to form a first conductive structure in the solar cell, the solar cell includes a substrate and a passivation layer located on at least one side of the substrate, and when the solar cell is sintered, the conductive paste composition can penetrate the passivation layer to form the first conductive structure.

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

[0016] In some embodiments, the present application further provides a method for manufacturing a solar cell, which includes the following steps: A substrate is provided, the substrate comprising a substrate, a p-type doped layer, and a passivation layer, the p-type doped layer being located between the substrate and the passivation layer. The conductive paste composition described above is applied to the passivation layer. A substrate covered with the conductive paste composition is sintered, and during the sintering process, the conductive paste composition etches the passivation layer to form a first conductive structure. The solar cell is obtained by performing laser-enhanced contact optimization on the substrate.

[0017] In some embodiments, covering the passivation layer with the conductive paste composition is, This includes applying the conductive paste composition to at least a portion of the surface of the passivation layer in a patterned form.

[0018] In some embodiments, the step of performing laser-enhanced contact optimization on the substrate is: The method further includes applying a reverse voltage to the substrate and simultaneously laser scanning the substrate to form an induced current within the first conductive structure.

[0019] In some embodiments, the manufacturing method satisfies at least one of the following conditions: g) The solar cell has a breakdown voltage, and the reverse voltage is lower than the breakdown voltage. h) The laser scanning time is from 1 ms to 100 ms, i) The induced current is from 100 A to 1000 A.

[0020] In some embodiments, the present application further provides a solar cell, and the solar cell includes a first conductive structure made of the above-described conductive paste composition.

[0021] In some embodiments, the present application further provides a solar cell, and the solar cell is manufactured using the above-described manufacturing method.

[0022] In some embodiments, the solar cell is a solar cell including a tunnel oxide layer passivation contact structure.

Advantages of the Invention

[0023] The conductive paste composition of the present application can be applied to the metallization of the p-side of a solar cell. After sintering, the passivation layer on the surface of the cell can be etched, and at the same time, the effect of low carrier recombination can be achieved. By limiting the cation ratio of Pb + Bi to B in the glass frit, the corrosion effect of the glass frit on the passivation layer can be further improved, and the excessive recombination loss caused by the etching of the passivation layer by the conductive paste composition can be reduced.

[0024] The manufacturing method of the solar cell provided by the present application achieves appropriate 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 with the laser enhanced contact optimization technology, so that a large number of carriers generated by laser scanning are induced to the first conductive structure through the applied reverse voltage 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, the open circuit voltage and conversion efficiency of the solar cell are greatly improved.

Brief Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings that are necessary for describing the embodiments are briefly introduced below. Clearly, the drawings in the following description represent only some embodiments of this application, and those skilled in the art can obtain other drawings based on these without any creative effort.

[0026] [Figure 1] This is a cross-sectional view of a solar cell provided in an embodiment of the present application. [Modes for carrying out the invention]

[0027] The technical solutions in the embodiments of this application are described below clearly and completely with reference to the accompanying drawings of the embodiments. Clearly, the embodiments described are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art without creative effort based on the embodiments of this application are included within the scope of protection of this application.

[0028] In the description of this application, the orientations and positional relationships indicated by terms such as "up," "down," "upper part," "lower part," "inside," and "outside" are based on the orientations and positional relationships shown in the drawings and are merely for the convenience and simplification of the description of this application, and are not intended to suggest or imply that the devices or elements referred to have a particular orientation, or must be constructed and operate in a particular orientation, and therefore should not be interpreted as limitations on this application. In the description of this application, "plural" means two or more unless otherwise specified, and "at least one" means one, two, or more than one.

[0029] Metallization is a crucial step in the production process of photovoltaic solar cells, enabling the effective extraction of photogenerated carriers and achieving high photoelectric conversion efficiency. Currently, screen printing is the most preferred metallization method. For N-type solar cells such as n-TOPCon and other cells with tunnel oxide layer passivation contact structures, a metallization paste (silver-aluminum paste or Ag-Al paste) containing silver and aluminum powder is typically used and sintered at high temperatures to achieve a metallization effect on the p-plane (or p-type doped layer) of the solar cell. During the sintering process, the glass frit in the silver-aluminum paste etches and opens the passivation film containing SiNx, SiNOx, and AlOx, allowing the metal in the paste to react with the p-type doped layer to form a microstructure of silver-aluminum barbs, resulting in good ohmic contact. While silver-aluminum paste can form low-resistivity ohmic contact with the p-type doped layer, the loss of open-circuit voltage and efficiency caused by high carrier recombination loss is a significant factor affecting the photoelectric conversion efficiency of N-type solar cells. Furthermore, surface passivation of the substrate significantly affects carrier recombination, and etching or damage to the passivation film by glass frit in the silver-aluminum paste during high-temperature sintering further increases recombination loss.

[0030] Based on this, there is a need to provide a conductive paste composition, a method for manufacturing a solar cell, and a conductive paste suitable for solar cells, particularly the p-plane, in order to achieve the effect of low carrier recombination and to achieve high open-circuit voltage and photoelectric conversion efficiency with this metallization method.

[0031] Some embodiments of the present application provide conductive paste compositions for forming low-carrier recombination and low-resistance electrical connections with the p-type doped layer of a solar cell.

[0032] The conductive paste compositions provided in some embodiments of the present application comprise, based on the mass percentage of the conductive paste composition, 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, wherein the glass frit comprises an oxide, and based on the molar percentage of the oxide, the glass frit comprises 20 mol% to 50 mol% of B2O3, and further comprises 15 mol% to 50 mol% of PbO, or 15 mol% to 50 mol% of Bi2O3, or a mixture of 15 mol% to 50 mol% of PbO and Bi2O3, where the ratio of the total cation content of PbO and Bi2O3 to the cation content of B2O3 is 0.30 to 1.25.

[0033] Here, the glass frit and conductive components function as solid components in the conductive paste composition, and the organic medium functions as a dispersed phase in the conductive paste composition, imparting printability. The sum of the weight percentages of each component in the conductive paste composition is 100%. Cation content refers to the number or proportion of cations in a chemical substance, and in chemical formulas, cations are usually positively charged ions.

[0034] Each component will be explained individually below.

[0035] glass frit

[0036] In some embodiments, glass frit refers to a composition containing one or more anions and cations. Glass frit is fluid when heated and may be crystalline, partially or completely glassy, ​​or amorphous.

[0037] In some embodiments, the glass frit of these embodiments can be understood as a composition having a glass component, and the mass percentage of glass frit in the conductive paste composition is 0.5 wt% to 4 wt%. In some other embodiments, the mass percentage of glass frit in the conductive paste composition is 1.0 wt% to 3.8 wt%, may be 1.5 wt% to 3.5 wt%, may be 2.0 wt% to 3.0 wt%, and may be 2.2 wt% to 2.8 wt%. It can be understood that the proportion of glass frit in the conductive paste composition needs to be adjusted so that the sum of the weight percentages of each component in the conductive paste composition is 100%. Since the composition of the glass frit directly affects its mellutability, fluidity, and etching properties, a balance of the glass frit composition is necessary to achieve an excellent carrier recombination effect.

[0038] In some embodiments, the glass frit contains at least the following components, with PbO and / or Bi2O3 in molar percentages of 15 mol% to 50 mol% and B2O3 in molar percentages of oxide. In the following description, "mol%" for the content of each component of the glass frit means the molar percentage in terms of oxide unless otherwise specified. Note that 15 mol% to 50 mol% means that the range is ≥15 mol% and ≤50 mol%, and the same applies to other values.

[0039] In some embodiments, the glass frit is more preferably composed of 20 mol% to 40 mol% of PbO and / or Bi2O3 and 30 mol% to 40 mol% of B2O3, in terms of the molar percentage converted to oxides.

[0040] In some embodiments, PbO, Bi2O3, or a combination of both can form a low-melting-point glass phase and provide good fluidity, and both can corrode the passivation layer during the sintering process, because PbO and Bi2O3 are reactive with the passivation layer and work to improve the softening and fluidity of the glass.

[0041] In some embodiments, B2O3 functions as a glass-forming agent that can form low-melting-point glass and provide good fluidity. B2O3 forms a network structure, which helps stabilize the glass and improves the ability of the molten glass to bond to the substrate.

[0042] In several examples, the ratio of the total cation content of PbO and Bi2O3 to the cation content of B2O3 in the glass frit is between 0.30 and 1.25. For example, the ratio values ​​are within the range of any two of the following values: 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, 1.25. By limiting the cation ratio of Pb+Bi to B, the corrosive effect of glass frit can be improved because PbO is more corrosive than Bi2O3. Therefore, by replacing some of the PbO in the composition of glass frit with Bi2O3, the corrosive capacity can be adjusted. When the above-mentioned range of cation ratios is satisfied, the corrosive properties and reactivity of glass frit can be controlled by adjusting the cation ratio of Pb+Bi to B, satisfying the effect of low carrier recombination and improving the open-circuit voltage and photoelectric conversion efficiency.

[0043] In some embodiments, the glass frit further comprises a first additive in a molar percentage of 18 mol% or less converted to an oxide, the first additive being selected from one or more of Li2O, Al2O3, ZnO, SiO2, SeO2, and TeO2. More preferably, the glass frit further comprises a first additive in a molar percentage of 3 mol% to 15 mol% converted to an oxide, and even more preferably, a first additive in a molar percentage of 6 mol% to 10 mol% converted to an oxide.

[0044] In some embodiments, the first additive is used to modify the glass frit system and may further contain a glass forming agent or a glass modifier. In the glass frit manufacturing process, a glass forming agent is used to form the initial network structure of the glass, and when a glass modifier is incorporated into the glass network structure, the initial network structure formed by the glass forming agent is altered, thereby changing the original thermal properties and other properties of the glass. The content of each component in the first additive can be adjusted as appropriate according to the desired glass performance.

[0045] In some embodiments, TeO2 or SeO2 can be used as a glass-forming agent to enhance fluidity during glass molding. The SeO2 content in the glass frit is 15 mol% or less in terms of the molar percentage converted to oxide, and the TeO2 content in the glass frit is 15 mol% or less in terms of the molar percentage converted to oxide. It is even more preferable that the SeO2 content in the glass frit is 5 mol% or more and 10 mol% or less in terms of the molar percentage converted to oxide. It is even more preferable that the TeO2 or SeO2 content in the glass frit is 5 mol% or more and 7.5 mol% or less in terms of the molar percentage converted to oxide.

[0046] In some embodiments, Li2O is used as a glass modifier. Adding an appropriate amount can improve the fluidity of the glass. However, because Li2O itself is corrosive, the amount added must be controlled within a certain range. The Li2O content in the glass frit is 15 mol% or less in terms of the molar percentage converted to oxide. More preferably, the Li2O content in the glass frit is 5 mol% to 10 mol% in terms of the molar percentage converted to oxide. Within this range, the fluidity and reactivity of the glass are improved, further enhancing the electrical properties of the solar cell.

[0047] In some embodiments, Al2O3 functions as a glass-forming agent that can stabilize the glass phase, increase the melting point of the glass, and decrease its fluidity, and can also be used as a component to improve the weather resistance of the glass. The Al2O3 content in the glass frit is 10 mol% or less in terms of the molar percentage converted to oxide. More preferably, the Al2O3 content in the glass frit is 3 mol% to 7 mol% in terms of the molar percentage converted to oxide. Within this range, the increase in the glass transition temperature is suppressed, and excellent fluidity can be exhibited during softening.

[0048] In some embodiments, ZnO is used as a glass modifier, and its electrical properties can be improved by appropriate addition. The ZnO content in the glass frit is 18 mol% or less in terms of the molar percentage converted to oxide. More preferably, the ZnO content in the glass frit is 6 mol% to 12 mol% in terms of the molar percentage converted to oxide. Within this range, on the one hand, the melting temperature of the glass frit can be lowered, the dissolution and melting performance of the glass frit can be promoted, and this is advantageous for glass manufacturing.

[0049] In some embodiments, SiO2 functions as a glass-forming agent, and appropriate addition can stabilize the glass phase, increase the melting point of the glass, and decrease its fluidity. SiO2 can also improve the weather resistance of the glass and adjust its ability to react with the substrate. The SiO2 content in the glass frit is 15 mol% or less in terms of the molar percentage converted to oxide. More preferably, the SiO2 content in the glass frit is 3 mol% to 10 mol% in terms of the molar percentage converted to oxide. By setting the content within this range, the glass transition temperature and the glass fluidity during firing can be adjusted, and the etching characteristics during glass firing can be controlled.

[0050] In some embodiments, the glass frit contains, in terms of molar percentage converted to oxide, 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.

[0051] In some embodiments, the glass frit contains, in terms of molar percentage converted to oxide, 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.

[0052] In some embodiments, the glass frit further contains a second additive in a molar percentage of 5 mol% or less, converted to an oxide, the second additive being selected from one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO, and BaO. It is understood that the second additive functions as a glass modifier and, in cooperation with the first additive in the glass frit manufacturing process, can further modify and adjust the melting point and fluidity of the glass frit.

[0053] conductive components

[0054] In some embodiments, the conductive component functions as a power source for the conductive paste composition, and in these embodiments, metal powders commonly used for electrodes formed on circuit boards such as semiconductor substrates can be used without particular limitation as the conductive component. Exemplary metals include, but are not limited to, silver, gold, copper, nickel, palladium, platinum, aluminum, and their alloys and mixtures. Alternatively, due to its excellent processability and high conductivity, the conductive component is basically composed of silver.

[0055] In some embodiments, the mass percentage of the conductive component in the conductive paste composition is 80 wt% to 92 wt%. In some other embodiments, the mass percentage of the conductive component in the conductive paste composition is 82 wt% to 90 wt%, may be 85 wt% to 88 wt%, and may even be 86 wt% to 87 wt%. It can be understood that the adjustment of the proportion of the conductive component in the conductive paste composition is necessary so that the sum of the weight percentages of each component in the conductive paste composition is 100%. The conductive component is used to conduct electricity after the solar cell has been formed.

[0056] In some embodiments, the conductive component may be a metal powder directly combined with the conductive paste composition of the present invention, or a mixture of two or more such metals or alloys directly combined, the metal being provided by a metal oxide or salt that decomposes to form a metal when exposed to the heat of firing. When the metal powder is silver powder, it should be understood that it refers to the element silver metal, silver alloy, silver oxide or silver salt, 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.

[0057] In some embodiments, the conductive component may be provided as finely dispersed particles in the form of powder, flakes, spheres, rods, granules, knots, layers, or coated shapes, other irregular shapes, or mixtures thereof.

[0058] In some examples, the median particle size of the conductive component is in the range of 0.5 to 3.5 μm. It is more preferable to use spherical silver powder having a median particle size of 1 to 3 μm, more preferably spherical silver powder having a median particle size of 1.5 to 2.5 μm, and even more preferably spherical silver powder having a median particle size of 2 μm. The main function of the silver powder is to form a high-density silver body after sintering and provide good conductivity, and spherical silver powder with a median particle size of 2 μm can also suppress aggregation and ensure uniform dispersion of the silver powder.

[0059] organic medium

[0060] In some embodiments, an organic medium functions as a liquid phase in a conductive paste composition, with respect to a solid component consisting of a conductive component and glass frit, and is used to disperse the solid component and form a paste of a predetermined viscosity. The viscosity and rheology of this paste not only enable the long-term stable dispersion of the conductive component and glass frit, but also allow the conductive paste composition to be dispersed on a printing screen, and a desired pattern to be applied to the passivation layer of a substrate by screen printing.

[0061] In some embodiments, the organic medium may include polymers and organic solvents. Polymers may include cellulose, resins, esters, etc. Celluloses may include cellulose resins such as methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, benzylcellulose, propylcellulose, and nitrocellulose, or mixtures thereof. Resins may include wood rosin, phenolic resins, acrylic resins, or mixtures thereof. Esters may include polymethacrylates of lower alcohols, etc. Organic solvents may include terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol diacetate, α-terpenes, β-terpenes, dibutyl phthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol, etc.

[0062] In some embodiments, the viscosity and rheology of the organic medium make it suitable for printing methods including, but not limited to, screen printing. The organic medium may further contain nonionic surfactants, thixotropic agents, dispersants, rheological agents, and other auxiliary agents to accommodate various needs of the organic medium.

[0063] filler

[0064] In some examples, the mass percentage of filler in the conductive paste composition is greater than 0 and less than or equal to 1 wt%, where the filler is selected from at least one of aluminum powder, silicon powder, and aluminum-silicon alloy powder.

[0065] Unlike the aluminum powder added to commercially available silver-aluminum paste used in TOPCon batteries to improve contact effect in some embodiments, the aluminum powder added as a filler in this embodiment can further control the etching properties of the glass powder to achieve a higher open-circuit voltage. The reason for the above-mentioned improvement in open-circuit voltage is influenced by the amount of aluminum powder added. This is because a small amount of aluminum powder is added to the paste, and a small amount of aluminum oxide may be incorporated into the molten glass powder during the high-temperature sintering process. An increase in aluminum oxide in the molten glass frit reduces its fluidity and corrosiveness, thereby reducing damage to the passivation film and consequently reducing recombination, thus increasing the open-circuit voltage. However, if too much aluminum powder is added, it will be excessively incorporated into the molten glass frit during sintering, significantly reducing corrosiveness and negatively affecting the curve factor.

[0066] More preferably, the mass percentage of the filler in the conductive paste composition is greater than 0 and 0.75 wt% or less.

[0067] More preferably, the mass percentage of the filler in the conductive paste composition is in the range of 0.25 wt%, 0.50 wt%, 0.75 wt%, 1.0 wt%, or any two of these.

[0068] In some examples, the Dv50 of the filler is 1 to 4 μm, where Dv50 is the particle size when the cumulative volume percentage of the filler reaches 50%. More preferably, the Dv50 of the filler is 1 to 3 μm. More preferably, the Dv50 of the filler is 2 μm.

[0069] In some embodiments, the glass powder can be produced by methods conventionally used in the field of glass manufacturing. For example, oxides corresponding to the glass powder composition ratio described in the embodiments are blended and mixed, added to a crucible (such as a platinum crucible or a ceramic crucible), heated to a peak temperature (e.g., 800°C to 1400°C), and held for a certain period of time to melt the oxides together. The molten material can be rapidly cooled by any suitable means, including, but not limited to, passing it between counter-rotating stainless steel rollers to form a sheet 0.25 to 0.50 mm thick, pouring it onto a thick stainless steel plate, or pouring it into water. The resulting glass frit is then ground using common grinding techniques to form a powder with a particle size of 0.5 to 2 μm.

[0070] In some embodiments, the method for producing the conductive paste composition involves blending the paste components described in the examples, stirring and dispersing them, then dispersing and grinding them to a particle size of less than 10 μm using a three-roller system, and finally filtering. In some embodiments, the amounts of glass frit and aluminum powder added differ, but in these cases, the same amount of silver powder is used, and the amounts of other materials such as organic media remain unchanged. The ratios of glass frit, conductive components, organic media, and fillers need to be adjusted so that the sum of the mass percentages of each component in the conductive paste composition is 100%.

[0071] In some embodiments, the conductive paste composition of this embodiment is used to manufacture a first conductive structure 20 in a solar cell, where the solar cell comprises a substrate 101 having a main surface and at least one passivation layer 103 disposed on the main surface, where the conductive paste composition can penetrate at least one layer of the passivation layer 103 during sintering to form the first conductive structure 20.

[0072] It can be understood that the first conductive structure 20 can form an electrical connection with the p-type semiconductor in the substrate 101 with lower carrier recombination. The p-type semiconductor is preferably a p-type doped layer, and the substrate 101 may be an n-type doped semiconductor substrate. Furthermore, in TOPCon batteries, the p-type doped layer is also called a p-type emitter.

[0073] solar cells

[0074] As shown in Figure 1, several embodiments of the present invention provide solar cells, which are Tunnel Oxide Passivated Contacts, and utilize the conductive paste composition described above during manufacturing.

[0075] In some embodiments, solar cells containing a tunnel oxide layer passivated contact structure 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 surface passivation layer to improve the efficiency and performance of the cell. TOPCon solar cell structures exhibit low electron reflection and surface recombination, high photoelectric conversion efficiency, and fewer electronic defects.

[0076] In some embodiments, the 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 the side of the p-type doped layer 102 away from the substrate 101. As shown in Figure 1, the substrate 101 is located in the center of the TOPCon solar cell, and the substrate 101 may be an n-type doped semiconductor substrate, the p-type doped layer 102 is located on the front surface of the n-type doped semiconductor substrate, the passivation layer 103 is located on the surface of the p-type doped layer 102, and 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.

[0077] In some embodiments, referring to Figure 1, the substrate 10 further includes a first passivation film 104 located on the back side of an n-type doped semiconductor substrate, an n+ polysilicon layer 105 located on the surface of the first passivation film 104 away from the n-type doped semiconductor substrate, and a second passivation film 106 deposited on the surface of the n+ polysilicon layer 105 away from the first passivation film 104.

[0078] In some embodiments, referring to Figure 1, the TOPCon solar cell further includes a second conductive structure 30, the second conductive structure 30 penetrating at least a portion of the second passivation film 106 and forming an electrical connection with the n+ polysilicon layer 105.

[0079] In some embodiments, the front refers to the illuminated surface of the solar cell, which is also the working surface of the solar cell. The back is the back side of the solar cell, which is usually not directly exposed to light.

[0080] In some embodiments, the first passivation film 104 and the n+ polysilicon layer 105 are formed by a tunnel oxide layer passivation contact method.

[0081] 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 the desired pattern shape, and during the sintering process, the conductive paste composition penetrates into 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.

[0082] In some embodiments, the second conductive structure 30 can be a commercially available metallized silver paste used in P-type or N-type crystalline silicon batteries, 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 the required pattern shape, and during the sintering process, the silver paste containing Pb-Te-O glass powder etches and penetrates the second passivation film 106 to form electrical contact with the n+ polysilicon layer 105, facilitating the formation of the second conductive structure 30 in the form of a conductive metal contact.

[0083] The embodiments of this application provide a method for manufacturing a solar cell, which includes the following: 1) A substrate 10 is provided, which 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 the 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 surface of the substrate 101 to form a p-type doped layer 102 on the front surface of the n-type doped semiconductor substrate, and the passivation layer 103 is formed on the surface of the p-type doped layer 102 using a deposition method. 2) The conductive paste composition provided in this embodiment is applied onto the passivation layer 103, specifically, the conductive paste composition is applied in a patterned form to at least a portion of the surface of the passivation layer 103, the patterning method may be screen printing, and it is understood that the conductive paste composition according to this embodiment is used as a p-plane fine grid of a solar cell including a tunnel oxide layer passivation contact structure, with four screen printing machines corresponding to the rear main grid, rear fine grid, front main grid, and front fine grid, and the conductive paste composition of this embodiment is used for the p-plane fine grid, usually the fourth front fine grid. 3) The substrate 10 and the conductive paste composition are sintered, and during the sintering process, the conductive paste composition etches the passivation layer 103 to form the first conductive structure 20. The production of the second conductive structure 30 is the same as the production of the first conductive structure 20. 4) Laser-enhanced contact optimization is performed on the substrate 10 to manufacture a solar cell.

[0084] The step numbers above do not restrict the order of the steps.

[0085] In some embodiments, in step 4), laser-enhanced contact improvement optimization is a method of improving the electrical contact of a metallized paste using a laser during the solar cell manufacturing process. The basic principle of laser-enhanced contact improvement technology is to use a large number of carriers generated by the laser, guide these carriers to the formed metallized contacts using a bias voltage, and use the thermal energy generated by the current to improve the contact effect and uniformity, thereby improving the uniformity of electrical contact and reducing contact defects, thereby improving the efficiency and reliability of solar cells. In this technology, better contact uniformity and improvement effect can be achieved by controlling the amount of carriers injected with parameters such as laser power and time.

[0086] In some embodiments, the step of performing laser-enhanced contact optimization on a substrate 10 further includes applying a reverse voltage to the substrate 10 while laser scanning the substrate 10 to form an induced current in the first conductive structure 20. Processing the conductive structure using laser-enhanced contact optimization techniques can reduce contact resistance, thereby increasing the open-circuit voltage and improving efficiency.

[0087] In some embodiments, the reverse voltage is lower than the breakdown voltage of the solar cell. This avoids damage due to failure, extends the lifespan of the solar cell, improves battery safety, and protects battery performance.

[0088] In some embodiments, the laser scanning time is between 1 ms and 100 ms. For example, it may be any of the following values: 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, 100 ms, or a range between two of these values.

[0089] In some embodiments, the induced current is between 100A and 1000A. For example, it may be one of the values ​​of 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 of these values.

[0090] The technical solution of the present application is further described below with reference to specific embodiments.

[0091] The content of each component in the glass frits of Examples 1-13 and Comparative Examples 1-4 is shown in Table 1. The total content of each component in the glass frits of the Examples and Comparative Examples is 100%. Here, each value in Table 1 is a mole percentage (mol%). The glass frits of Comparative Examples 1-2 have a (Pb+Bi) / B cation ratio that is not within the range of 0.30-1.25, and the content of the first additive TeO2 added in Comparative Examples 3-4 is too high. [Table 1]

[0092] The glass frits of Examples 1-13 and Comparative Examples 1-4 in Table 1 were combined into a conductive paste composition, and solar cells were manufactured to obtain the corresponding Examples 14-26 and Comparative Examples 5-8. Performance tests were conducted on the cells of Examples 14-26 and Comparative Examples 5-8, and the quality test data are shown in Table 2.

[0093] In the conductive paste compositions of Examples 14-26 and Comparative Examples 5-8, the mass percentage of glass frit was 1.5 wt%, and spherical silver powder with a median particle size of 2 μm was used as the conductive component. The mass percentage of glass frit in the conductive component was 89.5 wt%, and the mass percentage of the organic medium was 9 wt%, where the organic medium consisted of 1.5 wt% ethyl cellulose, 1.5 wt% polyvinyl butyraldehyde copolymer (PVB), 1.6 wt% diethylene glycol butyl ether acetate, 0.3 wt% silicone oil, 0.15 wt% Duomeen TDO (nonionic surfactant, amine oxide category), 0.15 wt% Brij L4 (nonionic surfactant, polyoxyethylene alcohol category), 0.4 wt% Thixotrol plus (rheological agent), and 2.8 wt% ethoxylated alcohol 12. The compound contains C12 and 0.6 wt% of a dibasic acid ester. The specific method for producing the conductive paste composition is to blend the above components, stir and disperse them, then disperse and grind them to 10 μm or less using a three-roller system, and finally filter them to obtain the result.

[0094] The manufacturing process involves first producing the blue diaphragm of the TOPCon battery, passing it through four screen printing machines corresponding to the rear main grid, rear fine grid, front main grid, and front fine grid, applying a conductive paste composition to the front fine grid on the p-side, sintering the substrate and the conductive paste composition, and during the sintering process the conductive paste composition etches the passivation layer to form a conductive structure on the p-side of the substrate, and then performing laser-enhanced contact optimization on the conductive structure to manufacture the solar cell.

[0095] Here, the detection data in Table 2 was measured using the following method. a) Suns-Voc test: Test Suns-Voc after sintering using a Sinton WCT120 tester. Use the tested Voc to characterize and compare the carrier recombination performance of various conductive pastes after sintering. b) IV test: The photoelectric conversion efficiency of the battery is tested using a commercially available IV tester. Test items include efficiency (Eff), open-circuit voltage (Voc), curve factor (FF), and current (Isc). Experimental data are presented in the form of differential values ​​ΔEff, ΔVoc, ΔFF, and ΔIsc to illustrate the electrical performance of the examples and comparative examples. [Table 2]

[0096] As can be seen from Table 2, the batteries of Examples 14 to 26 achieved an efficiency performance of ±0.1%, and compared with Comparative Examples 5 to 8, the conductive paste compositions of the present invention, combined with laser-enhanced contact improvement, achieved a significant improvement in open-circuit voltage and conversion efficiency, indicating that the conductive paste compositions provided in this invention can significantly improve the p-plane metallization recombination effect of TOPCon structure batteries. Here, the effects of Comparative Examples 5 and 6 were inferior to those of the examples. This is because in Comparative Example 5, the (Pb+Bi) / B cation ratio of the glass powder was too high, resulting in excessive corrosiveness of the glass powder and leading to a loss of open-circuit voltage. In Comparative Example 6, the (Pb+Bi) / B cation ratio was too low, resulting in insufficient corrosiveness of the glass powder, preventing the formation of good ohmic contact and significantly reducing the FF. Furthermore, in Comparative Examples 7 and 8, the amount of TeO2 added to the glass frit was too high, resulting in excessive glass fluidity, causing excessive damage to the passivation film during sintering and a decrease in the open-circuit voltage.

[0097] Examples 27-30 and Comparative Example 9 are provided, where the process for manufacturing the solar cells of Examples 27-30 is the same as in Example 14, except that the conductive paste compositions of Examples 27-30 further contain a filler, the filler being aluminum powder with a median particle size of 2 μm. Here, since aluminum powder is added to the components, it is necessary to adjust the content of silver powder in the conductive components so that the total mass content is 100%. Comparative Example 9 is the same as in Example 27, except that the amount of aluminum powder added exceeds 1 wt%. For specific dosages and test data, please refer to Table 3. [Table 3]

[0098] As can be seen from Table 3, adding a small amount of aluminum powder further reduces recombination and improves the open-circuit voltage. This is because a small amount of aluminum oxide formed by the small amount of aluminum powder during the high-temperature sintering process may dissolve into the glass frit. The increase in aluminum oxide in the molten glass frit reduces its fluidity and corrosiveness, thereby reducing damage to the passivation layer. However, adding large amounts of aluminum powder is not suitable because it significantly reduces the curve factor and decreases efficiency. In Table 3, when using the glass frit of Example 1, Comparative Example 9 has more than 1 wt% aluminum powder, which increases the FF loss and is insufficient to compensate for the increase in open-circuit voltage. Since the amount of aluminum that can be incorporated into different glass frits after melting varies somewhat, adding aluminum powder in amounts of 0-1 wt% can further reduce recombination and improve the open-circuit voltage.

[0099] Examples 31 and Comparative Examples 10-11 are provided, where the solar cell manufacturing process in Example 31 is the same as in Example 14, except that the glass frit content in Example 31 is 3 wt%; in Comparative Example 10, the glass frit content exceeds the specified range at 4.5 wt%; and Comparative Example 11 uses a commercially available silver-aluminum paste (containing 3-7 wt% glass frit, 1-2 wt% aluminum powder, and about 10% organic carriers, with the remainder being silver powder). See Table 4 for specific dosages and test data. [Table 4]

[0100] As can be seen from Table 4, compared to commercially available high-efficiency silver-aluminum pastes, the conductive paste composition used in this embodiment can significantly reduce recombination after sintering, as shown in the Suns-Voc in Table 4. The effect is that a significant open-circuit voltage and an efficiency improvement of more than 0.3% can be achieved after the laser-enhanced contact improvement process following sintering. As can be seen from the data of Comparative Example 10, increasing the amount of glass powder to 4.5 wt% increases damage to the passivation layer and leads to a loss of Suns-Voc, so the glass frit content should be in the range of 0.5 wt% to 4 wt%.

[0101] Furthermore, two sets of comparative data were conducted using commercially available high-efficiency silver-aluminum paste. The manufacturing process for the two sets was the same as in Example 14, but the difference was in the manufacturing process; please refer to Table 5 for the test results. [Table 5]

[0102] As can be seen from Table 5, commercially available high-efficiency silver-aluminum pastes do not show any further efficiency improvement when combined with laser-enhanced contact improvement technology after sintering. This indicates that laser-enhanced contact improvement technology requires the improved conductive paste composition of the present invention to achieve higher battery conversion efficiency.

[0103] In the embodiments described above, each embodiment is explained with its own emphasis; however, for aspects not explained in detail in one embodiment, please refer to the relevant descriptions in other embodiments.

[0104] The conductive paste composition, the method for manufacturing a solar cell, and the solar cell provided in the embodiments of this application are described in detail above, and specific examples have been used to illustrate the principles and embodiments of this application. The above description of embodiments is for the sole purpose of understanding the technical solutions and core ideas of this application, and those skilled in the art should understand that they may modify the technical solutions described in the above embodiments or make equivalent substitutions for some technical features, and that such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of each embodiment of this application. [Explanation of Symbols]

[0105] 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.

Claims

1. A conductive paste composition, Based on the mass percentage of the conductive paste composition, the conductive paste composition comprises 0.5 wt% to 4 wt% glass frit, 80 wt% to 92 wt% conductive component, and 7 wt% to 16 wt% organic medium. The glass frit contains an oxide, and based on the molar percentage of the oxide, the glass frit contains 20 mol% to 50 mol% of B2O3, and the glass frit further contains 15 mol% to 50 mol% of PbO, or 15 mol% to 50 mol% of Bi2O3, or a mixture of 15 mol% to 50 mol% of PbO and Bi2O3. Here, the ratio of the total cation content of PbO and Bi2O3 to the cation content of B2O3 is 0.30 to 1.

25. Conductive paste composition.

2. Based on the molar percentage of the oxide, the glass frit further comprises a first additive, the content of which is 18 mol% or less, and the first additive is selected from one or more of Li2O, Al2O3, ZnO, SiO2, SeO2, and TeO2. The conductive paste composition according to claim 1.

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

4. Based on the molar percentage of the oxides, the glass frit further comprises 0 to 15 mol% Li₂O, 0 to 10 mol% Al₂O₃, 0 to 18 mol% ZnO, and 0 to 15 mol% SiO₂. The conductive paste composition according to claim 1.

5. Based on the molar percentage of the oxide, the glass frit further comprises a second additive, the content of which is 5 mol% or less, and the second additive is selected from one or more of AgO2, Ag2O, AgO, Na2O, K2O, MgO, CaO, and BaO. The conductive paste composition according to claim 1.

6. Based on the mass percentage of the composition, the conductive paste composition further comprises 1 wt% or less of a filler, the filler comprising at least one of aluminum powder, silicon powder, and aluminum-silicon alloy powder. The conductive paste composition according to claim 1.

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

8. The Dv50 of the filler is 1 to 4 μm, where Dv50 is the particle size when the cumulative volume percentage of the filler reaches 50%. The conductive paste composition according to claim 6.

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

10. To form a first conductive structure (20) in a solar cell, the solar cell includes a substrate (101) and a passivation layer (103) located on at least one side of the substrate (101). When the solar cell is sintered, the conductive paste composition penetrates the passivation layer (103) to form the first conductive structure (20). The conductive paste composition according to claim 1.

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

12. A method for manufacturing a solar cell, comprising the following steps: A base material (10) is provided, the base material (10) comprising a substrate (101), a p-type doped layer (102), and a passivation layer (103), wherein the p-type doped layer (102) is located between the substrate (101) and the passivation layer (103), The conductive paste composition according to any one of claims 1 to 11 is applied to the passivation layer (103), The substrate (10) covered with the conductive paste composition is sintered, and during the sintering process, the conductive paste composition etches the passivation layer (103) to form a first conductive structure (20). The solar cell is obtained by performing laser-enhanced contact optimization on the substrate (10). A method for manufacturing solar cells.

13. Covering the passivation layer (103) with the conductive paste composition is, This includes applying the conductive paste composition to at least a portion of the surface of the passivation layer (103) in a patterned form. A method for manufacturing a solar cell according to claim 12.

14. The step of performing laser-enhanced contact optimization on the substrate (10) is: The process includes applying a reverse voltage to the substrate (10) and simultaneously laser scanning the substrate (10) to form an induced current within the first conductive structure (20). A method for manufacturing a solar cell according to claim 12.

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

16. It is a solar cell, The solar cell includes a first conductive structure (20) made of the conductive paste composition described in any one of claims 1 to 11. Solar cell.

17. It is a solar cell, The solar cell is manufactured using the manufacturing method described in any one of claims 12 to 15. Solar cell.

18. The solar cell is a solar cell that includes a tunnel oxide layer passivation contact structure. A solar cell according to any one of claims 16 to 17.

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