Solar cell and preparation process thereof, laminated cell and photovoltaic module

Abstract

The invention relates to the field of photovoltaic technology, in particular to a solar cell and a preparation process thereof, a laminated cell and a photovoltaic module. The preparation process comprises the following steps: providing a silicon substrate, and preparing a passivation layer on the surface of the silicon substrate; printing a conductive material on the passivation layer; sintering and curing the conductive material to form an initial grid line; performing laser processing on the initial grid line; wherein the conductive material comprises metal powder, glass powder, an organic carrier, iridium oxide, lanthanum oxide and titanium dioxide; the metal powder comprises at least one of silver powder, nickel powder, copper powder, silver coated copper, silver coated nickel and aluminum powder. The iridium oxide, the lanthanum oxide and the titanium dioxide are simultaneously added into the conductive material adopted in the preparation process, so that the power attenuation of the module is reduced.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to solar cells and their fabrication processes, tandem cells and photovoltaic modules. Background Technology

[0002] Setting grid lines on the light-receiving and back-light-receiving surfaces of solar cells is a crucial step in solar cell fabrication, used to extract the electrical energy generated within the cell. Conductive materials are the primary material for these grid lines, typically printed onto the functional layer of the cell using screen printing technology, followed by sintering to form the grid lines used to collect and conduct current from the cell surface. However, grid lines made from traditional conductive materials are prone to interface corrosion, bonding degradation, and poor thermal cycling stability under high temperatures and thermal cycling, leading to significant power degradation in the module. Summary of the Invention

[0003] Therefore, it is necessary to provide a solar cell, its fabrication process, a tandem cell, and a photovoltaic module. The conductive material used in the fabrication process of the solar cell in this application possesses high interfacial bonding strength and thermal cycling stability to address the problem of module power degradation.

[0004] In a first aspect, this application provides a process for fabricating a solar cell, comprising the following steps: providing a silicon substrate; preparing a passivation layer on the surface of the silicon substrate; printing a conductive material on the passivation layer; sintering and solidifying the conductive material to form initial grid lines; and performing laser processing on the initial grid lines; wherein the conductive material includes metal powder, glass powder, organic carrier, iridium oxide, lanthanum oxide, and titanium dioxide; and the metal powder includes at least one of silver powder, nickel powder, copper powder, silver-coated copper, silver-coated nickel, and aluminum powder.

[0005] In some embodiments, the conductive material comprises the following components in weight percentages: 75% to 85% metal powder, 3% to 7% glass powder, 10.5% to 18.5% organic carrier, 0.15% to 0.25% iridium oxide, 0.05% to 0.15% lanthanum oxide, and 0.15% to 0.25% titanium dioxide.

[0006] In some embodiments, the glass powder comprises, by weight, 10-40 parts of SiO2, 5-30 parts of PbO, 10-40 parts of ZnO, 5-20 parts of BaO, 5-30 parts of Al2O3 and 5-20 parts of Bi2O3.

[0007] In some embodiments, the median particle size of iridium oxide, lanthanum oxide, and titanium dioxide is independently 30 nm to 80 nm.

[0008] In some embodiments, the mass ratio of iridium oxide, lanthanum oxide, and titanium dioxide is (1.95~2.05):1:(1.95~2.05).

[0009] In some embodiments, iridium oxide includes at least one of iridium dioxide and iridium trioxide.

[0010] In some embodiments, the titanium dioxide includes at least one of anatase titanium dioxide, rutile titanium dioxide, and brookite titanium dioxide.

[0011] In some embodiments, the median particle size of the metal powder is 0.5 μm to 2 μm.

[0012] In some embodiments, the particle size of the conductive material slurry is 3 μm to 5 μm.

[0013] In some embodiments, the laser processing includes scanning the initial gate lines with a laser and applying a bias voltage to the initial gate lines.

[0014] In some implementations, the laser power is 5W to 25W.

[0015] In some implementations, the bias voltage is 10V to 15V.

[0016] Secondly, this application provides a solar cell prepared using the solar cell preparation process described in any of the above-mentioned claims.

[0017] Thirdly, this application provides a tandem battery, including a top battery and a bottom battery, wherein the bottom battery includes the aforementioned solar cell.

[0018] Fourthly, this application provides a photovoltaic module, comprising: a cover plate; at least one battery string, the battery string including the aforementioned solar cells, or including the aforementioned tandem cells; and an encapsulation layer located between the cover plate and the battery string, the cover plate being connected to the battery string through the encapsulation layer.

[0019] Compared to traditional technologies, this application offers at least the following advantages: In the solar cell fabrication process provided in this application, conductive materials, including iridium oxide, lanthanum oxide, and titanium dioxide, are printed on the passivation layer. Lanthanum oxide promotes the formation of a dense and robust chemical bond structure at the interface during glass powder sintering. Iridium oxide, with its excellent high-temperature oxidation resistance, forms an antioxidant barrier at the interface, effectively preventing the intrusion of corrosive media such as oxygen and water vapor, and inhibiting the oxidation and corrosion of the interface material during long-term thermal cycling. The synergistic effect of these two materials enhances the interfacial bonding strength and thermal cycling stability of the conductive material, reducing the risk of interfacial corrosion. Simultaneously, titanium dioxide exerts a dispersion strengthening effect in the sintered bulk phase, tightly bonding with the robust chemical bond interface constructed by lanthanum oxide, mutually supporting each other and effectively dissipating and resisting the shear stress generated during long-term thermal cycling, reducing the risk of grid line delamination or breakage. In summary, the combined effect of iridium oxide, lanthanum oxide, and titanium dioxide enhances the interfacial bonding strength and thermal cycling stability of the conductive material, reduces the risk of oxidation and corrosion of the interface material and grid line delamination or breakage during thermal cycling, thereby reducing module power decay. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the fabrication process of a solar cell provided in one embodiment of this application.

[0022] Figure 2 An electroluminescent image of a battery cell (TC400) made using the conductive material provided in Example 1 of this application.

[0023] Figure 3 An electroluminescent image of a solar cell (TC400) made using the conductive material provided in Comparative Example 1 of this application. Detailed Implementation

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0025] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0027] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include numerical interval types such as percentage intervals, ratio intervals, and proportion intervals.

[0028] In this application, where the method involves multiple steps, unless otherwise explicitly stated in this application, there is no strict order restriction on the execution of these steps; they can be executed in an order other than that described. Moreover, any step may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0029] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] In the accompanying drawings of this application, the thicknesses of layers, films, regions, substrates, etc., are exaggerated for clarity. Throughout the specification, the same reference numerals refer to the same elements. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on the other element or there may be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0032] In this application, room temperature refers to indoor temperature, normal temperature, or general temperature. Generally, room temperature can be any of the following temperature ranges: 23℃±2℃, 25℃±5℃, or 20℃±5℃.

[0033] Terminology: Median particle size (D50): This refers to the particle size that represents 50% of the total particle size distribution in a sample. It is also known as the median diameter or median particle size. For example, a median particle size of 30 nm means that particles smaller than 30 nm and particles larger than 30 nm each account for 50% of all particles. The median particle size can be determined by statistically analyzing particle size distribution from images taken using methods such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0034] Slurry fineness: This is a quantitative indicator of the degree of dispersion of solid particles in a slurry. Specifically, it represents the size of the largest detectable solid particle or hard agglomerate in the slurry under specified test conditions. Slurry fineness can be measured using a scraper fineness gauge.

[0035] like Figure 1 As shown, one embodiment of this application provides a process for fabricating a solar cell, including the following steps: S1, providing a silicon substrate and preparing a passivation layer on the surface of the silicon substrate; S2, printing a conductive material on the passivation layer; S3, sintering and solidifying the conductive material to form initial grid lines; S4, performing laser processing on the initial grid lines.

[0036] The conductive materials include metal powder, glass powder, organic carrier, iridium oxide, lanthanum oxide, and titanium dioxide; the metal powders include at least one of silver powder, nickel powder, copper powder, silver-coated copper, silver-coated nickel, and aluminum powder.

[0037] In the solar cell fabrication process provided in this application, conductive materials are printed on the passivation layer. These conductive materials include iridium oxide, lanthanum oxide, and titanium dioxide. Lanthanum oxide promotes the formation of a dense and robust chemical bond structure at the interface during glass powder sintering. Iridium oxide, with its excellent high-temperature oxidation resistance, forms an antioxidant barrier at the interface, effectively preventing the intrusion of corrosive media such as oxygen and water vapor, and inhibiting the oxidation and corrosion of the interface material during long-term thermal cycling. The synergistic effect of these two materials enhances the interfacial bonding strength and thermal cycling stability of the conductive material, reducing the risk of interfacial corrosion. Simultaneously, titanium dioxide exerts a dispersion strengthening effect in the sintered bulk phase, tightly bonding with the robust chemical bond interface constructed by lanthanum oxide, providing mutual support and effectively dissipating and resisting the shear stress generated during long-term thermal cycling, reducing the risk of grid line delamination or breakage. In summary, the combined effect of iridium oxide, lanthanum oxide, and titanium dioxide enhances the interfacial bonding strength and thermal cycling stability of the conductive material, reduces the risk of oxidation and corrosion of the interface material and grid line delamination or breakage during thermal cycling, thereby reducing module power decay.

[0038] In the conductive materials provided in this application embodiment, since iridium oxide already exists as an antioxidant barrier, effectively inhibiting the diffusion of oxygen to the interface during sintering, other low-cost, easily oxidizable metal powders can be flexibly selected besides silver powder. Specifically, these include: Copper powder: low cost and excellent conductivity; although easily oxidized, the iridium oxide barrier protects it from oxidation failure during sintering, significantly reducing the raw material cost of the conductive material. Silver-coated copper powder: with copper as its core, it combines the low cost and high conductivity of copper. The outer silver coating further enhances its antioxidant capacity. Combined with the dual protection of the iridium oxide barrier, it reduces costs while ensuring both conductivity and antioxidant performance. Nickel powder and aluminum powder: significantly lower in cost than silver powder, and some powders (such as aluminum powder) have lightweight advantages. Under the protection of iridium oxide, their oxidation defects can be effectively avoided, expanding the application scenarios of conductive materials and adapting to the differentiated needs of different fields regarding cost, weight, and conductivity.

[0039] In some embodiments, the conductive material comprises the following components in weight percentages: 75% to 85% metal powder, 3% to 7% glass powder, 10.5% to 18.5% organic carrier, 0.15% to 0.25% iridium oxide, 0.05% to 0.15% lanthanum oxide, and 0.15% to 0.25% titanium dioxide.

[0040] Optionally, the mass percentage of metal powder in the conductive material is 75%, 78%, 80%, 82%, or 85%, or the mass percentage of metal powder may be within the range of any two of the above mass percentages.

[0041] Within the range of the aforementioned mass percentage of metal powder, the conductive material can simultaneously possess good conductivity and flowability.

[0042] Optionally, the mass percentage of glass powder in the conductive material is 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%, or the mass percentage of glass powder may be within the range of any two of the above mass percentages.

[0043] Within the aforementioned mass percentage range of glass powder, the glass powder promotes the fusion of metal powder through a sintering mechanism, ensuring the adhesion between the grid lines and the substrate material.

[0044] Optionally, the mass percentage of the organic carrier in the conductive material is 10.5%, 12%, 13%, 14%, 15%, 16%, 17%, or 18.5%, or the mass percentage of the organic carrier may be within the range of any two of the above mass percentages.

[0045] Optionally, the mass percentage of iridium oxide in the conductive material is 0.15%, 0.18%, 0.2%, or 0.25%, or the mass percentage of iridium oxide can be within any two of the above-mentioned mass percentages. Within the above-mentioned mass percentage range of iridium oxide, while ensuring the performance of the metal powder in the conductive material, a continuous iridium-enriched layer is formed that can effectively block the diffusion of oxygen atoms at high temperatures; at the same time, excess iridium ions are prevented from segregating and precipitating at the grain boundaries in the form of elemental or oxide, reducing the risk of gate line breakage.

[0046] Optionally, the mass percentage of lanthanum oxide in the conductive material is 0.05%, 0.1%, 0.12%, or 0.15%, or the mass percentage of lanthanum oxide can be within any two of the above-mentioned mass percentages. When the lanthanum oxide content is too low, lanthanum ions cannot completely cover the interface defect sites, resulting in insufficient interfacial bonding strength; when the lanthanum oxide content is too high, excessive lanthanum ions cause excessive spreading of the glass powder during sintering, leading to gate line collapse or lateral overflow. Simultaneously, excess lanthanum ions enter the conductive phase lattice, inducing lattice distortion. Therefore, within the above-mentioned mass percentage range of lanthanum oxide, interfacial bonding strength and thermal cycling reliability are ensured; at the same time, excessive spreading of the glass phase is suppressed, ensuring the integrity of the gate line sintering morphology and reducing the degradation of conductivity caused by lanthanum ion-induced lattice distortion.

[0047] Optionally, the mass percentage of titanium dioxide in the conductive material is 0.15%, 0.18%, 0.2%, or 0.25%, or the mass percentage of titanium dioxide can be within any two of the above-mentioned mass percentages. Within the above-mentioned mass percentage range of titanium dioxide, while ensuring the continuous sintering network of the conductive phase, dispersed reinforcing particles are formed, which work synergistically with the lanthanum oxide-modified interfacial chemical bonding structure; at the same time, excessive titanium dioxide is avoided from causing particle agglomeration or the continuity of the insulating phase, thus suppressing the increase in grid resistance and the risk of interfacial delamination.

[0048] In some embodiments, the glass powder comprises, by weight, 10-40 parts of SiO2, 5-30 parts of PbO, 10-40 parts of ZnO, 5-20 parts of BaO, 5-30 parts of Al2O3 and 5-20 parts of Bi2O3.

[0049] In some embodiments, the metal powder is silver powder. Silver powder has high bulk conductivity, ensuring efficient energy transfer; it has good oxidation resistance, preventing the degradation of the conductive network during long-term use; it also has excellent sinterability, easily forming a robust neck and dense conductive network through surface diffusion at suitable temperatures, with a wide process window and good compatibility with glass powder.

[0050] In some embodiments, the median particle size of iridium oxide, lanthanum oxide, and titanium dioxide is independently 30 nm to 80 nm.

[0051] Optionally, the median particle size of iridium oxide, lanthanum oxide, and titanium dioxide can be independently 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, or 80 nm, or the median particle size of iridium oxide, lanthanum oxide, and titanium dioxide can be independently within the range between any two of the above median particle sizes.

[0052] Within the aforementioned median particle size range, iridium oxide, lanthanum oxide, and titanium dioxide are all ensured to possess high specific surface areas, providing sufficient active sites for interfacial reactions during subsequent sintering. Simultaneously, they are ensured to be well and stably dispersed in the conductive material, reducing solid particle agglomeration and sedimentation during printing. Furthermore, they are ensured to uniformly fill the gaps between metal particles and at the metal-semiconductor and metal-glass interfaces, enabling iridium oxide to efficiently catalyze interfacial reactions and form a continuous antioxidant barrier, ensuring lanthanum oxide to fully promote dense chemical bonding between the glass phase and the substrate, and ensuring titanium dioxide to fully exert its dispersion strengthening effect in the sintered bulk phase, tightly binding with the robust chemically bonded interface constructed by lanthanum oxide.

[0053] Optionally, the median particle size of iridium oxide is 40 nm to 70 nm. The median particle size of iridium oxide is 40 nm, 50 nm, 60 nm or 70 nm, or the median particle size of iridium oxide may be within the range of any two of the above median particle sizes.

[0054] Optionally, the median particle size of titanium dioxide is 30 nm to 70 nm. The median particle size of titanium dioxide is 30 nm, 40 nm, 50 nm, 60 nm or 70 nm, or the median particle size of titanium dioxide may be within the range of any two of the above median particle sizes.

[0055] In some embodiments, the mass ratio of iridium oxide, lanthanum oxide, and titanium dioxide is (1.95~2.05):1:(1.95~2.05).

[0056] Within the aforementioned mass ratio range of iridium oxide, lanthanum oxide, and titanium dioxide, it is possible to better ensure that the conductive material maintains high bonding strength, low oxidation corrosion, and excellent fatigue resistance during high-temperature sintering and long-term thermal cycling, thereby effectively reducing the power decay of photovoltaic modules.

[0057] Optionally, the mass ratio of iridium oxide, lanthanum oxide, and titanium dioxide is 2:1:2.

[0058] In some embodiments, iridium oxide includes at least one of iridium dioxide and iridium trioxide.

[0059] As an example, iridium oxide can be selected from either iridium dioxide or iridium trioxide, or from at least two of iridium dioxide and iridium trioxide, and may further be selected from iridium dioxide. Iridium dioxide possesses better thermodynamic stability, chemical inertness, and electrical conductivity, and can more reliably and persistently form a stable antioxidant barrier at the interface.

[0060] In some embodiments, the titanium dioxide includes at least one of anatase titanium dioxide, rutile titanium dioxide, and brookite titanium dioxide.

[0061] Optionally, the titanium dioxide is anatase titanium dioxide. Anatase titanium dioxide possesses high surface activity, excellent nano-dispersion, excellent sintering stability, and low cost, ensuring dispersion strengthening in the sintered bulk phase. In synergy with lanthanum oxide / iridium oxide, it constructs a robust, stable, and thermally stress-resistant conductive grid structure from the interface to the bulk phase, thereby reducing component power decay.

[0062] In some embodiments, the median particle size of the metal powder is 0.5 μm to 2 μm.

[0063] Optionally, the median particle size of the metal powder is 0.5 μm, 1 μm, 1.5 μm, or 2 μm, or it can be within any two of the above median particle sizes. If the median particle size of the metal powder is too large, it will cause printing difficulties and result in a loss of photoelectric conversion efficiency; if the median particle size is too small, its viscosity will be too low, making it difficult to accumulate and resulting in excessive flowability, leading to an excessively wide grid line width after printing, thus causing a loss of photoelectric conversion efficiency. At the same time, small-particle-size metal powders are more expensive, increasing costs. Therefore, by controlling the median particle size of the metal powder to 0.5 μm to 2 μm, the loss of photoelectric conversion efficiency and cost can be reduced.

[0064] In some embodiments, the organic carrier includes a resin, a solvent, a thixotropic agent, and a dispersant.

[0065] In some embodiments, the organic carrier comprises 2% to 4% resin, 2% to 4% solvent, 2.5% to 4.5% thixotropic agent, and 4% to 6% dispersant, based on the total mass of the conductive material.

[0066] Optionally, the mass percentage of resin in the conductive material is 2%, 3%, or 4%, or the mass percentage of resin may be within the range of any two of the above mass percentages.

[0067] Optionally, the mass percentage of the solvent in the conductive material is 2%, 3%, or 4%, or the mass percentage of the solvent may be within the range of any two of the above mass percentages.

[0068] Within the aforementioned solvent mass percentage range, ensure that the conductive material has good ink permeability, while also ensuring good adhesion between the conductive material and the substrate.

[0069] Optionally, the mass percentage of the thixotropic agent in the conductive material is 2.5%, 3%, or 4.5%, or the mass percentage of the thixotropic agent may be within the range of any two of the above mass percentages.

[0070] Optionally, the mass percentage of the dispersant in the conductive material is 4%, 5%, or 6%, or the mass percentage of the dispersant may be within the range of any two of the above mass percentages.

[0071] In some embodiments, the resin includes at least one selected from ethyl cellulose, hydroxypropyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin, styrene resin, and polyester resin.

[0072] Optionally, the styrene resin includes one or more of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS), and is further optionally styrene-ethylene-propylene-styrene block copolymer (SEPS).

[0073] In some embodiments, the solvent includes at least one of alcohol ester dodecyl, alcohol ester hexadecyl, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.

[0074] In some embodiments, the thixotropic agent includes at least one of hydrogenated castor oil, hydrogenated castor oil derivatives, and polyamide wax.

[0075] In some embodiments, the dispersant includes at least one of polyethylene glycol, polyvinylpyrrolidone, polyhydroxystearic acid, and sodium polycarboxylate.

[0076] In some embodiments, the particle size of the conductive material slurry is 3 μm to 5 μm.

[0077] Optionally, the fineness of the conductive material slurry is 3μm, 3.5μm, 4μm, 4.5μm or 5μm, or the fineness of the conductive material slurry can be within the range of any two of the above slurry finenesses.

[0078] In some embodiments, the laser processing includes scanning the initial gate lines with a laser and applying a bias voltage to the initial gate lines.

[0079] In some embodiments, the power of the laser that generates the laser is 5W to 25W during laser processing.

[0080] Optionally, the power of the laser is 5W, 10W, 15W, 20W or 25W, or the power of the laser may be within any two of the above power ranges.

[0081] In some embodiments, during laser processing, a bias voltage of 10V to 15V is applied to the initial gate line.

[0082] Optionally, the bias voltage is 10V, 11V, 12V, 13V, 14V or 15V, or the bias voltage may be within the range of any two of the above bias voltages.

[0083] By incorporating iridium oxide, lanthanum oxide, and titanium dioxide into the conductive material, iridium oxide effectively suppresses oxygen diffusion and stabilizes the interface structure, lanthanum oxide passivates interface defects, and titanium dioxide improves interface contact characteristics. The synergistic effect of these three compounds modifies the metal-silicon interface into a high-quality interface with low defects. Based on this interface optimization, the laser power is set to 5W~25W to heat and activate the interface between the conductive material and the silicon substrate through laser irradiation. Simultaneously, a bias voltage of 10V~15V is applied, utilizing Joule heating generated by the local current to achieve in-situ sintering. This power range allows for efficient interface activation while mitigating thermal damage to the passivation layer; the voltage range stabilizes the driving current and generates moderate Joule heating, promoting interdiffusion of interfacial elements between the metal powder and the silicon substrate, significantly reducing the contact resistance between the grid lines and the silicon substrate, thereby improving the photoelectric conversion efficiency of the solar cell.

[0084] Another embodiment of this application provides a method for preparing a conductive material, comprising the following steps: mixing raw materials comprising the following components in the indicated mass percentages: 75%~85% metal powder, 3%~7% glass powder, 10.5%~18.5% organic carrier, 0.15%~0.25% iridium oxide, 0.05%~0.15% lanthanum oxide, and 0.15%~0.25% titanium dioxide.

[0085] A second aspect of this application provides a solar cell prepared using the solar cell fabrication process described in any of the above claims.

[0086] Understandably, solar cells can be either TOPCon cells or HJT cells, or a combination of both. TOPCon is an abbreviation for Tunnel Oxide Passivating Contact, and a TOPCon cell refers to a cell with a tunnel oxide passivating contact. HJT is an abbreviation for Heterojunction with Intrinsic Thin-layer, and an HJT cell refers to an intrinsic thin-film heterojunction cell.

[0087] A third aspect of this application provides a stacked battery, comprising a top battery, an adhesive layer, and a bottom battery stacked sequentially, wherein the bottom battery comprises the aforementioned solar cell.

[0088] For example, in some embodiments, the top cell can be a perovskite solar cell, which includes: a first transport layer, a perovskite substrate, a second transport layer, a transparent conductive layer, and an antireflection layer stacked together. The first transport layer is directly opposite the bottom cell. The first transport layer can be either an electron transport layer or a hole transport layer, and the second transport layer can be either an electron transport layer or a hole transport layer.

[0089] It should be noted that the tandem cell of this application is based on the same concept as the solar cell of any of the above claims, and the tandem cell has the same or similar effects as the solar cell of any of the above claims, which will not be repeated here.

[0090] A fourth aspect of this application provides a photovoltaic module, including a cover plate, at least one cell string, and an encapsulation layer. The cell string includes the aforementioned solar cells, or includes the aforementioned tandem cells. The encapsulation layer is located between the cover plate and the cell string, and the cover plate is connected to the cell string through the encapsulation layer.

[0091] The following description is further illustrated with specific embodiments and comparative examples. Unless otherwise specified, the raw materials involved in the following specific embodiments and comparative examples are all commercially available. Unless otherwise specified, the instruments used are all commercially available. Unless otherwise specified, the processes involved are conventionally selected by those skilled in the art.

[0092] Example 1

[0093] The components and mass percentages of the conductive material in Example 1 are as follows: 80% silver powder, 5% glass powder, 14.5% organic carrier, 0.2% iridium dioxide, 0.1% lanthanum oxide (anatase type), and 0.2% titanium dioxide. The glass powder comprises 30 parts SiO2, 20 parts PbO, 15 parts ZnO, 15 parts BaO, 10 parts Al2O3, and 10 parts Bi2O3. The organic carrier consists of 3% resin, 3% solvent, 3.5% thixotropic agent, and 5% dispersant by mass percentage. The resin is a styrene-ethylene-propylene-styrene block copolymer, the solvent is hexadecyl alcohol ester, the thixotropic agent is polyamide wax, and the dispersant is polyethylene glycol.

[0094] The preparation method of the conductive material is as follows: Iridium dioxide (median particle size of 55nm), lanthanum oxide (median particle size of 55nm), and titanium dioxide (median particle size of 50nm) are mixed and dried to prepare a composite additive; the composite additive is mixed with silver powder and glass powder under nitrogen atmosphere using a shear mill; an organic carrier is added to the mixed raw materials, and the mixture is ground using a three-roll mill until a conductive material with a slurry fineness of 3μm~5μm is obtained. The fineness of the slurry is tested using a scraper fineness meter.

[0095] Example 2

[0096] This embodiment is basically the same as Embodiment 1, except that, by mass percentage, the conductive material is: 80% silver powder, 5% glass powder, 14.5% organic carrier, 0.15% iridium dioxide, 0.1% lanthanum oxide, and 0.25% titanium dioxide.

[0097] Example 3

[0098] This embodiment is basically the same as Embodiment 1, except that, by mass percentage, the conductive material is: 80% silver powder, 5% glass powder, 14.5% organic carrier, 0.25% iridium dioxide, 0.1% lanthanum oxide, and 0.15% titanium dioxide.

[0099] Example 4

[0100] This embodiment is basically the same as Embodiment 1, except that, by mass percentage, the conductive material is: 80% silver powder, 5% glass powder, 14.5% organic carrier, 0.2% iridium dioxide, 0.05% lanthanum oxide, and 0.25% titanium dioxide.

[0101] Example 5

[0102] This embodiment is basically the same as Embodiment 1, except that, by mass percentage, the conductive material is: 80% silver powder, 5% glass powder, 14.5% organic carrier, 0.2% iridium dioxide, 0.15% lanthanum oxide, and 0.15% titanium dioxide.

[0103] Example 6

[0104] This embodiment is basically the same as Embodiment 1, except that the median particle size of iridium oxide, lanthanum oxide and titanium dioxide is 20 nm.

[0105] Example 7

[0106] This embodiment is basically the same as Embodiment 1, except that the median particle size of iridium oxide, lanthanum oxide and titanium dioxide is 100 nm.

[0107] Example 8

[0108] This embodiment is basically the same as Embodiment 1, except that the organic carrier is composed of 4% resin, 2% solvent, 2.5% thixotropic agent and 6% dispersant by mass percentage.

[0109] Example 9

[0110] This embodiment is basically the same as Embodiment 1, except that the organic carrier is composed of 2% resin, 4% solvent, 4.5% thixotropic agent and 4% dispersant by mass percentage.

[0111] Comparative Example 1

[0112] The comparative example is basically the same as Example 1, except that the conductive material in this comparative example does not contain iridium dioxide, lanthanum oxide and titanium dioxide, and the mass percentage of silver powder is 80.5%.

[0113] Comparative Example 2

[0114] The comparative example is basically the same as Example 1, except that no iridium dioxide is added to the conductive material of the comparative example, and the mass percentage of silver powder is 80.2%.

[0115] Comparative Example 3

[0116] This comparative example is basically the same as Example 1, except that no lanthanum oxide was added to the conductive material in this comparative example, and the mass percentage of silver powder was 80.1%.

[0117] Comparative Example 4

[0118] The comparative example is basically the same as Example 1, except that no titanium dioxide is added to the conductive material of the comparative example, and the mass percentage of silver powder is 80.2%.

[0119] Comparative Example 5

[0120] The comparative example is basically the same as Example 1, except that, by mass percentage, the conductive material is: 81.5% silver powder, 5% glass powder, 14.5% organic carrier, 0.05% iridium dioxide, 0.1% lanthanum oxide and 0.2% titanium dioxide.

[0121] Comparative Example 6

[0122] The comparative example is basically the same as Example 1, except that, by mass percentage, the conductive material is: 79.9% silver powder, 5% glass powder, 14.5% organic carrier, 0.3% iridium dioxide, 0.1% lanthanum oxide, and 0.2% titanium dioxide.

[0123] The composition of the conductive materials in the above embodiments and comparative examples is shown in Table 1 below.

[0124] Test case

[0125] A silicon substrate is provided, and a passivation layer is prepared on the surface of the silicon substrate. The conductive material prepared in the above embodiments and comparative examples is printed on the passivation layer. The silicon substrate with the conductive material is transferred to a drying device to dry and shape the conductive material. The dried and shaped conductive material is sintered and solidified to form initial grid lines on the light-receiving surface of the silicon substrate. The initial grid lines are laser-processed to form grid lines, and then assembled to obtain solar cells and photovoltaic modules.

[0126] The solar cells in the various embodiments and comparative examples are identical in structure and fabrication parameters, except for the conductive materials used.

[0127] TC400 power degradation test: Referring to IEC61215-2 (MQT11 test item), the photovoltaic module was tested for 400 cycles in a high and low temperature cycling environment aging chamber under conditions of -40℃ to 85℃. The output power of the photovoltaic module before and after aging was compared to obtain the test data. The test results are shown in Table 2 below.

[0128] TC400 Cell Failure Rate Test: An electroluminescence (EL) detector was used. EL images of the solar cells were captured while the cells were powered on. The number of cells with noticeable bright line breaks or darkening (i.e., false printing) was counted using image analysis software or manual interpretation. The cell failure rate was calculated as (number of cells with cell failures or severe false printing / total number of cells) × 100%. Test results are shown in Table 2 below.

[0129] See Figure 2 , Figure 2 The image shows the electroluminescence of a battery cell (TC400) made using the conductive material provided in Example 1, without any darkening.

[0130] See Figure 3 , Figure 3 The electroluminescent image of the solar cell (TC400) made using the conductive material provided in Comparative Example 1 shows a darkening phenomenon.

[0131] Table 1

[0132]

[0133] Table 2

[0134]

[0135] Comparing the test results of Examples 1-9 and Comparative Examples 1-4, it can be seen that compared with solar cells prepared by conductive materials without the addition of iridium oxide, lanthanum oxide, and titanium dioxide, or by conductive materials with only one or two of the three, the examples of this application simultaneously add the above three substances. Lanthanum oxide promotes the formation of a dense and strong chemical bond structure at the interface during sintering; iridium oxide forms an antioxidant barrier at the interface, inhibiting the oxidation and corrosion of the interface material during long-term thermal cycling; and titanium dioxide produces a dispersion strengthening effect in the sintered bulk phase, tightly combining with the strong chemical bond interface constructed by lanthanum oxide, mutually supporting each other, effectively dissipating and resisting the shear stress generated during long-term thermal cycling, reducing the risk of grid line delamination or breakage. The three substances work together to improve the interfacial bonding force and thermal cycling stability of the conductive material, reduce the risk of oxidation and corrosion of the interface material and grid line delamination or breakage during thermal cycling, and thus reduce the power decay of the module.

[0136] Comparing the test results of Example 1 and Comparative Examples 5-6, it can be seen that both excessively low and excessively high iridium oxide content are detrimental to the performance of conductive materials. The possible mechanisms are as follows: When the iridium oxide content is too low, a continuous and dense antioxidant barrier cannot be formed at the interface. In the TC400 (-40℃~85℃) thermal cycling test, corrosion will start from the weak points of the antioxidant barrier and spread, accelerating interface aging, leading to increased contact resistance, decreased adhesion, and ultimately, accelerated power decay of the component. When the iridium oxide content is too high, excessive iridium oxide particles are more likely to agglomerate in the slurry and during sintering, forming large particles or clusters. This easily reduces the dispersibility of iridium oxide particles, making the antioxidant barrier uneven and even forming stress concentration points in local areas. Simultaneously, excessive, especially agglomerated, iridium oxide particles can block the chemical bonding between silver, glass, and the substrate promoted by lanthanum oxide, reducing interfacial adhesion.

[0137] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0138] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A process for fabricating a solar cell, characterized in that, Includes the following steps: A silicon substrate is provided, and a passivation layer is formed on the surface of the silicon substrate; A conductive material is printed on the passivation layer; The conductive material is sintered and solidified to form the initial gate lines; The initial grid lines are subjected to laser processing; The conductive material includes metal powder, glass powder, organic carrier, iridium oxide, lanthanum oxide, and titanium dioxide; The metal powder includes at least one of silver powder, nickel powder, copper powder, silver-coated copper, silver-coated nickel, and aluminum powder.

2. The fabrication process of the solar cell according to claim 1, characterized in that, The conductive material comprises the following components in the indicated mass percentages: 75%–85% metal powder, 3%–7% glass powder, 10.5%–18.5% organic carrier, 0.15%–0.25% iridium oxide, 0.05%–0.15% lanthanum oxide, and 0.15%–0.25% titanium dioxide.

3. The fabrication process of the solar cell according to claim 1, characterized in that, The glass powder comprises, by weight, 10-40 parts of SiO2, 5-30 parts of PbO, 10-40 parts of ZnO, 5-20 parts of BaO, 5-30 parts of Al2O3 and 5-20 parts of Bi2O3.

4. The fabrication process of the solar cell according to any one of claims 1-3, characterized in that, The median particle size of the iridium oxide, the lanthanum oxide, and the titanium dioxide is independently 30 nm to 80 nm.

5. The fabrication process of the solar cell according to any one of claims 1-3, characterized in that, The mass ratio of the iridium oxide, the lanthanum oxide, and the titanium dioxide is (1.95~2.05):1:(1.95~2.05).

6. The fabrication process of the solar cell according to any one of claims 1-3, characterized in that, The iridium oxide includes at least one of iridium dioxide and iridium trioxide.

7. The fabrication process of the solar cell according to any one of claims 1-3, characterized in that, The titanium dioxide includes at least one of anatase titanium dioxide, rutile titanium dioxide, and brookite titanium dioxide.

8. The fabrication process of the solar cell according to any one of claims 1 to 3, characterized in that, The median particle size of the metal powder is 0.5 μm to 2 μm.

9. The fabrication process of the solar cell according to any one of claims 1 to 3, characterized in that, The fineness of the conductive material slurry is 3μm~5μm.

10. The fabrication process of a solar cell according to any one of claims 1 to 3, characterized in that, The laser processing includes: scanning the initial gate line with a laser and applying a bias voltage to the initial gate line.

11. The fabrication process of the solar cell according to claim 10, characterized in that, The power of the laser is 5W~25W.

12. The fabrication process of the solar cell according to claim 10, characterized in that, The bias voltage is 10V~15V.

13. A solar cell, characterized in that, It is prepared using the solar cell fabrication process described in any one of claims 1 to 12.

14. A stacked battery, comprising a top battery and a bottom battery, characterized in that, The bottom battery includes the solar cell of claim 13.

15. A photovoltaic module, characterized in that, include: Cover plate; At least one battery string, the battery string comprising the solar cell of claim 13, or comprising the tandem battery of claim 14; as well as An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

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