Solar cell and method of manufacturing the same, stacked cell, and photovoltaic module

Abstract

The application relates to a solar cell and a preparation method thereof, a laminated cell and a photovoltaic module. The preparation method of the solar cell comprises the following steps: printing a conductive material on a cell substrate; sintering and solidifying the conductive material to form an electrode; the conductive material comprises silver powder, graphene-coated silver flakes, bismuth-based glass powder and vanadium-based glass powder, wherein the graphene-coated silver flakes comprise a core layer and a shell layer arranged on the outer surface of the core layer, the core layer comprises silver flakes, and the shell layer comprises graphene. The silver powder and the graphene-coated silver flakes are matched as a conductive phase, and the bismuth-based glass powder and the vanadium-based glass powder are matched as a bonding phase, so that the adhesion and ohmic contact performance of the conductive material and the cell substrate can be effectively improved, and then the photoelectric conversion efficiency and the stability of the solar cell can be effectively improved.

Description

Technical Field

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

[0002] With the increasing demand for clean energy, solar cells, as a key device for directly converting solar energy into electrical energy, have received widespread attention and research. Electrodes, as a core component of solar cells, directly affect their conductivity, photoelectric conversion efficiency, and long-term stability. Electrodes prepared using traditional methods are prone to problems such as insufficient conductivity and weak bonding with the cell substrate, affecting the photoelectric conversion efficiency and other performance characteristics of the solar cell.

[0003] Therefore, it is necessary to improve traditional technologies. Summary of the Invention

[0004] Based on this, this application provides a solar cell with high photoelectric conversion efficiency, its preparation method, a tandem cell, and a photovoltaic module.

[0005] The technical solution to the above-mentioned technical problems in this application is as follows.

[0006] The first aspect of this application provides a method for preparing a solar cell, comprising the following steps:

[0007] Print conductive material onto the battery body;

[0008] The conductive material is sintered and solidified to form an electrode; the conductive material includes silver powder, graphene-coated silver sheet, bismuth-based glass powder and vanadium-based glass powder, wherein the graphene-coated silver sheet includes a core layer and a shell layer disposed on the outer surface of the core layer, the core layer includes silver sheet and the shell layer includes graphene.

[0009] The method for fabricating a solar cell disclosed in this application includes printing a conductive material onto the cell body and sintering and curing it to form an electrode. The conductive material comprises silver powder and graphene-coated silver sheets as a conductive phase. The graphene in the graphene-coated silver sheets has a two-dimensional sheet structure, which enhances the aspect ratio. Simultaneously, the sheet-like silver and graphene sheets form surface-to-surface contact, effectively improving the connectivity of the conductive network and its mechanical interlocking ability with the rough surface of the black silicon substrate, thereby effectively improving the adhesion between the conductive material and the cell substrate. Bismuth-based glass powder and vanadium-based glass powder are combined as a binder phase and interact with the conductive phase, effectively reducing contact resistance and improving the ohmic contact performance between the conductive material and the cell substrate, thereby effectively improving the photoelectric conversion efficiency and stability of the solar cell.

[0010] The second aspect of this application provides a solar cell, which is prepared by the above-described method for preparing a solar cell. The solar cell includes a cell substrate and an electrode disposed on the cell substrate. The cell substrate includes a black silicon substrate, and the surface of the black silicon substrate has a textured structure. The textured structure includes a plurality of structural monomers, the height of which is 2.0 μm to 3.5 μm, the radial dimension is 90 nm to 400 nm, and the adjacent spacing is 200 nm to 610 nm.

[0011] A third aspect of this application provides a tandem solar cell, comprising a top cell and a bottom cell, wherein the bottom cell is the aforementioned solar cell and the top cell is a perovskite solar cell.

[0012] The fourth aspect of this application provides a photovoltaic module, the photovoltaic module comprising: a battery string, the battery string being formed by connecting multiple of the above-described solar cells or the above-described stacked cells. Detailed Implementation

[0013] The present application will be further described in detail below with reference to the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive.

[0014] It should also be understood that this application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various alterations or modifications without departing from the spirit of this application, and the resulting equivalent forms also fall within the protection scope of this application. For example, features described or illustrated as part of one embodiment can be combined in a suitable manner in another embodiment to produce new embodiments. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of this application; it should be understood that this application can be implemented without one or more of these details.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for descriptive purposes only and is not intended to be limiting of the application.

[0016] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0017] In this application, the terms "multiple", "various", "multiple times", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0018] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0019] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0020] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0021] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0022] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0023] 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 herein 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.

[0024] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0025] In this application, the terms "room temperature" or "normal temperature" generally refer to 4℃ to 35℃, for example, 20℃ ± 5℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10℃ to 30℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20℃ to 30℃.

[0026] In this application, if the unit of a data range is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0027] The mass or weight of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship of mass or weight between the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass or weight mentioned in the embodiments of this application can be units known in the chemical industry, such as μg, mg, g, and kg.

[0028] D50 particle size, also known as median particle size or median diameter, is obtained by laser diffraction and refers to the particle size value corresponding to 50% of the cumulative volume distribution in a sample.

[0029] Traditional silver paste is mainly composed of the following components:

[0030] Conductive phase: micron- and nano-sized silver powder (60 wt% to 92 wt% of the total mass of silver paste);

[0031] Binder phase: lead glass powder (1 wt%~5 wt% of the total mass of silver paste); used to etch the silicon nitride antireflective layer and form an ohmic contact with silicon;

[0032] Organic carrier: Composed of organic solvents, thixotropic agents, surfactants, etc. (accounting for 10 wt%~20 wt%), used to provide the rheological properties required for printing.

[0033] Black silicon solar cells, with their unique light-trapping structure, can significantly reduce light reflection from the silicon wafer surface, thereby greatly improving the cell's absorption rate and conversion efficiency of incident light. They have become one of the important development directions for high-efficiency crystalline silicon solar cells. Traditional conductive silver paste for solar cells is mainly designed for conventional textured surfaces. When applied to black silicon surfaces, it easily leads to poor adhesion, increased contact resistance, and may even damage the fine anti-reflection texture, thus restricting the full performance of black silicon solar cells. Specifically:

[0034] Insufficient adhesion: The black silicon surface has a micro-nano composite sharp textured surface structure with a large specific surface area. After traditional silver paste sintering, the mechanical interlocking effect between the silver grains and the rough surface of the black silicon is weak, resulting in a significant decrease in the adhesion of the silver grid lines. They are prone to detachment during subsequent module lamination processes or under stress, causing module failure.

[0035] The sintering process window is narrow: to form a good ohmic contact, the glass frit needs to etch away the passivation layer on the back surface. Black silicon structures are relatively fragile and sensitive to corrosion. Glass frits such as lead glass powder can easily lead to over-corrosion, damaging the PN junction and causing leakage current (J). 0d Increase), parallel resistance (R) p The decrease in sintering temperature leads to a decrease in fill factor (FF) and conversion efficiency (η). Lowering the sintering temperature to prevent over-corrosion can easily result in under-corrosion, reducing contact resistance (R). c Increasing this will also affect FF and efficiency.

[0036] Cell warping and microcracks: The black silicon structure weakens the mechanical strength of silicon wafers. The thermal expansion coefficient (CTE) of traditional silver paste and silicon substrate do not match, generating large thermal stress during sintering and cooling, which can easily cause warping and microcracks in thin silicon wafers (such as those below 180μm), leading to an increased breakage rate.

[0037] Cost pressure: Silver is the main source of paste cost, and reducing silver content is a continuous pursuit of the industry.

[0038] One embodiment of this application provides a method for preparing a solar cell, comprising the following steps:

[0039] Printing conductive materials onto a battery substrate;

[0040] Conductive materials are sintered and solidified to form electrodes; the conductive materials include silver powder, graphene-coated silver sheets, bismuth-based glass powder and vanadium-based glass powder, wherein the graphene-coated silver sheets include a core layer and a shell layer disposed on the outer surface of the core layer, the core layer includes silver sheets and the shell layer includes graphene.

[0041] Graphene-encapsulated silver nanosheets (G-AgNS) are introduced as a functional conductive phase into the conductive material system. By replacing some of the silver powder with graphene-encapsulated silver nanosheets, the aspect ratio is enhanced by the two-dimensional sheet structure of graphene. The sheet-like silver forms a surface-to-surface contact with the graphene sheets, which can improve the connectivity of the conductive network. At the same time, the graphene nanosheets can also act as a conductive phase, interacting with the silver powder. This can improve the conductivity of the conductive material while reducing the silver content (reducing costs). In addition, the two-dimensional sheet structure of graphene enhances the aspect ratio, which can improve the mechanical interlocking ability of the conductive material with the surface of the battery substrate, significantly improving the adhesion.

[0042] The graphene shell in graphene-coated silver nanosheets plays an important role in the conductive network, which can maintain or even improve electrical performance while reducing the amount of silver powder used, effectively reducing costs; the use of lead-free glass system also makes it environmentally friendly.

[0043] In some embodiments, in the method for fabricating solar cells, the total mass of silver powder and graphene-coated silver sheets accounts for 60% to 85% of the total mass of the conductive material. It is understood that the percentage of the total mass of silver powder and graphene-coated silver sheets to the total mass of the conductive material includes, but is not limited to, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, and 85%. In some examples, it can be a range formed by any two of these values ​​as endpoints, and the same applies below. Optionally, the total mass of silver powder and graphene-coated silver sheets accounts for 70% to 80% of the total mass of the conductive material.

[0044] In some embodiments, the mass ratio of silver powder to graphene-coated silver sheet in the solar cell fabrication method is 1:0.2~0.5. It is understood that the mass ratio of silver powder to graphene-coated silver sheets includes, but is not limited to, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29, 1:0.3, 1:0.31, 1:0.32, 1:0.33, 1:0.34, 1:0.35, 1:0.36, 1:0.37, 1:0.38, 1:0.39, 1:0.4, 1:0.41, 1:0.42, 1:0.43, 1:0.44, 1:0.45, 1:0.46, 1:0.47, 1:0.48, 1:0.49, and 1:0.5. In some examples, any two of these point values ​​can be used as endpoints within a range, the same applies below. Optionally, the mass ratio of silver powder to graphene-coated silver sheet is 1:0.2~0.4. Optionally, the mass ratio of silver powder to graphene-coated silver sheet is 1:0.23~0.38. By controlling the mass ratio of silver powder to graphene-coated silver sheet, the connectivity of the conductive network and its mechanical interlocking ability with the substrate surface can be further improved while reducing the silver content and cost.

[0045] In some embodiments, in the method for fabricating solar cells, the total mass of bismuth-based glass powder and vanadium-based glass powder accounts for 1% to 5% of the total mass of the conductive material. It is understood that the percentage of the total mass of bismuth-based glass powder and vanadium-based glass powder to the total mass of the conductive material includes, but is not limited to, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, and 5%. In some examples, it can be any two of these values ​​forming a range, the same applies below. Optionally, the total mass of bismuth-based glass powder and vanadium-based glass powder accounts for 2% to 3% of the total mass of the conductive material.

[0046] In some embodiments, the mass ratio of bismuth-based glass powder to vanadium-based glass powder in the solar cell fabrication method is 1:0.4 to 1. It is understood that the mass ratio of bismuth-based glass powder to vanadium-based glass powder includes, but is not limited to, 1:0.4, 1:0.42, 1:0.45, 1:0.48, 1:0.5, 1:0.52, 1:0.55, 1:0.58, 1:0.6, 1:0.62, 1:0.65, 1:0.68, 1:0.7, 1:0.72, 1:0.75, 1:0.78, 1:0.8, 1:0.82, 1:0.85, 1:0.88, 1:0.9, 1:0.92, 1:0.95, 1:0.98, and 1:1. In some examples, any two of these point values ​​can be used as endpoints within a range, and the same applies below. Optionally, the mass ratio of bismuth-based glass powder to vanadium-based glass powder is 1:0.5~0.8. Optionally, the mass ratio of bismuth-based glass powder to vanadium-based glass powder is 1:0.6~0.7. By adjusting the mass ratio of bismuth-based glass powder to vanadium-based glass powder, the contact resistance is further reduced, the ohmic contact performance is improved, and over-corrosion is avoided, as well as the accumulation of thermal stress is reduced.

[0047] In some embodiments, the conductive material in the method for fabricating the solar cell further includes an organic carrier, the organic carrier accounting for 10% to 35% of the total mass of the conductive material. It is understood that the percentage of the organic carrier's mass to the total mass of the conductive material includes, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 27.5%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%. In some examples, it can be any two of these values ​​forming a range, the same applies below. Optionally, the conductive material further includes an organic carrier, the organic carrier accounting for 15% to 30% of the total mass of the conductive material.

[0048] In some embodiments, the bismuth-based glass powder used in the fabrication method of the solar cell includes a Bi2O3-B2O3-SiO2-ZnO glass powder. This bismuth-based glass powder has a low melting point (~450°C) and can melt and initiate the corrosion process at a lower peak temperature (<780°C), thus widening the process window and reducing thermal stress.

[0049] In some embodiments, the method for preparing the solar cell includes, by mass percentage, bismuth-based glass powder comprising: 60%~75% Bi₂O₃, 10%~20% B₂O₃, 5%~10% SiO₂, and 3%~8% ZnO. It is understood that the mass percentage of Bi₂O₃ in the bismuth-based glass powder includes, but is not limited to, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, and 75%; the mass percentage of B₂O₃ includes, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%; the mass percentage of SiO₂ includes, but is not limited to, 5%, 6%, 7%, 8%, 9%, and 10%; and the mass percentage of ZnO includes, but is not limited to, 3%, 4%, 5%, 6%, 7%, and 8%. In some examples, any two of these values ​​can be used as endpoints within a range, and the same applies below.

[0050] In some embodiments, the D50 particle size of the bismuth-based glass powder in the solar cell fabrication method is 1 μm to 2.5 μm. It is understood that the D50 particle size of the bismuth-based glass powder includes, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, and 2.5 μm. In some examples, it can be any two of these values ​​as endpoints, and the same applies below.

[0051] In some embodiments, the vanadium-based glass powder in the silver paste includes a V2O5-ZnO-B2O3-TeO2 series glass powder. This vanadium-based glass powder has moderate chemical activity and a milder corrosion rate. Its corrosivity can be controlled by the content of ZnO and B2O3 to achieve "precise and mild" corrosion of the black silicon structure and passivation layer, avoiding over-corrosion.

[0052] In some embodiments, the method for preparing the solar cell includes, by mass percentage, vanadium-based glass powder comprising 40%–60% V₂O₅, 20%–35% ZnO, 10%–20% B₂O₃, and 5%–10% TeO₂. Optionally, by mass percentage, the vanadium-based glass powder further includes 2%–5% Al₂O₃.

[0053] It is understood that in vanadium-based glass powder, the mass percentage of V2O5 includes, but is not limited to, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, and 60%; the mass percentage of ZnO includes, but is not limited to, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35%; the mass percentage of B2O3 includes, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%; and the mass percentage of TeO2 includes, but is not limited to, 5%, 6%, 7%, 8%, 9%, and 10%. Further, in vanadium-based glass powder, the mass percentage of Al2O3 includes, but is not limited to, 2%, 3%, 4%, and 5%. In some examples, any two of these point values ​​can be used as endpoints within a range, and the same applies below.

[0054] In some embodiments, the vanadium-based glass powder used in the solar cell fabrication method has a D50 particle size of 1.5 μm to 3.0 μm. It is understood that the D50 particle size of the bismuth-based glass powder includes, but is not limited to, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, and 3.0 μm. In some examples, it can be any two of these values ​​as endpoints, and the same applies below.

[0055] In some embodiments, the mass ratio of graphene to silver sheet in the solar cell fabrication method is 0.02 to 0.08:1. It is understood that the mass ratio of graphene to silver sheet includes, but is not limited to, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, and 0.08:1. In some examples, it can be any two of these values ​​forming a range, and the same applies below.

[0056] It is understandable that in graphene-coated silver sheets, the silver core layer provides the main electrical conduction path; the graphene shell effectively enhances mechanical strength and flexibility, acting as an "anchor" to hook onto the battery substrate (especially the nano-peaks of black silicon battery substrates), enhancing adhesion; its two-dimensional sheet structure forms a highly efficient conductive network in conductive materials; and some silver is replaced by graphene, achieving cost reduction.

[0057] In some embodiments, the diameter of the silver sheet in the solar cell fabrication method is 1 μm to 3 μm. It is understood that the diameter of the silver sheet includes, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, and 3.0 μm. In some examples, any two of these values ​​can be used as endpoints within a range, and the same applies below.

[0058] In some embodiments, the graphene sheet diameter in the solar cell fabrication method is 1 μm to 3 μm. It is understood that the graphene sheet diameter includes, but is not limited to, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, and 3.0 μm. In some examples, any two of these values ​​can be used as endpoints within a range, and the same applies below.

[0059] In some embodiments, the number of graphene layers in the solar cell fabrication method is 1 to 3. It is understood that the number of graphene layers includes, but is not limited to, 1, 2, and 3 layers.

[0060] In some embodiments, the silver powder used in the solar cell fabrication method is spherical silver powder.

[0061] In some embodiments, the silver powder has a D50 particle size of 0.5 μm to 4 μm in the method for preparing the solar cell. It can be understood that the D50 particle size of the silver powder includes but is not limited to 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm. In some examples, the range can be defined by any two of these point values ​​as endpoints, and the same applies below.

[0062] Controlling the particle size of bismuth-based glass powder, vanadium-based glass powder, and silver powder, as well as the particle size of silver flakes and graphene in graphene-coated silver flakes, can further improve the conductivity and adhesion of silver paste.

[0063] In some embodiments, the organic support in the method for preparing the solar cell includes at least one of terpineol and butyl carbitol acetate. Optionally, the organic support also includes at least one of ethyl cellulose and hydrogenated castor oil.

[0064] Using ethyl cellulose and hydrogenated castor oil as thixotropic agents, combined with high-boiling-point solvents such as terpineol and butyl carbitol acetate, the thixotropic properties of conductive materials are effectively improved: the viscosity is high when stationary, preventing seepage; the viscosity drops rapidly during printing and shearing, making it easy to fill the micropores on the surface of the battery substrate; the viscosity recovers after printing, maintaining the grid line shape and avoiding printing defects and residual bubbles during the sintering process.

[0065] Among them, black silicon has a high specific surface area and a deep porous structure; conductive materials using ethyl cellulose and hydrogenated castor oil as thixotropic agents, combined with high-boiling-point solvents such as terpineol and butyl carbitol acetate, are particularly suitable for black silicon battery substrates, which can effectively improve the adhesion and ohmic contact performance between conductive materials and the surface of black silicon battery substrates.

[0066] In some embodiments, the sintering temperature in the solar cell fabrication method is 730℃~820℃, and the time is 1 s~10 s. It is understood that the sintering temperature includes, but is not limited to, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, and 820℃, and the time includes, but is not limited to, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, and 10s. In some examples, any two of these point values ​​can be used as endpoints within a range, and the same applies below.

[0067] In some embodiments, the cell substrate in the method for fabricating the solar cell includes a silicon substrate. Optionally, the silicon substrate may be doped with either P-type or N-type doping.

[0068] In some embodiments, the silicon substrate in the method for fabricating the solar cell is a black silicon substrate.

[0069] In some embodiments, the fabrication steps of the black silicon substrate in the solar cell fabrication method include: performing reactive ion etching (RIE) or metal-assisted chemical etching (MACE) on the surface of the silicon wafer.

[0070] Optionally, reactive ion etching includes the following steps: placing a silicon wafer in a reactive ion etching apparatus, introducing a mixed gas of SF6 and O2, and performing reactive ion etching on the silicon wafer surface under the action of plasma. Optionally, the flow rate of SF6 is 50 sccm~200 sccm, the flow rate of O2 is 10 sccm~50 sccm, the etching power is 500W~1500W, and the etching time is 1 min~10 min. It can be understood that performing reactive ion etching on the silicon wafer surface in this way can form a micro-nano composite textured structure on the silicon wafer surface.

[0071] Optionally, metal-assisted chemical etching includes the following steps: after depositing a catalyst on the silicon wafer surface, metal-assisted chemical etching is performed in an etching solution; the catalyst includes at least one of silver nanoparticles and gold nanoparticles, and the etching solution is a mixed solution including HF and H2O2. It is understood that performing metal-assisted chemical etching on the silicon wafer surface in this way can form nanopores or nanowire structures on the silicon wafer surface.

[0072] The conductive materials, including silver powder, graphene-coated silver flakes, bismuth-based glass powder, and vanadium-based glass powder, are printed onto a black silicon substrate. The graphene shell of the graphene-coated silver flakes has a two-dimensional sheet structure, which can act like a "fishhook" or "anchor" to create a strong mechanical interlocking effect with the sharp, high aspect ratio nanotextured structure on the surface of the black silicon battery substrate, effectively improving adhesion. The high strength and high flexibility of graphene itself also ensure the integrity of the structure. Bismuth-based glass powder (Bi-glass) and vanadium-based glass powder (V-glass) are used as a binder phase. The bismuth-based glass powder melts at a relatively low peak temperature to initiate the ohmic contact formation process. Vanadium-based glass powder has higher chemical stability and moderate reactivity, which can effectively inhibit the excessive corrosion of bismuth-based glass powder. It acts as a "buffer" to effectively control the corrosion depth, thereby effectively protecting the PN junction and avoiding leakage and reduction in parallel resistance caused by over-corrosion. By utilizing the low-temperature sintering characteristics of bismuth-based glass powder (the peak temperature can be reduced by 20℃~30℃), the accumulation of thermal stress is reduced from the source. At the same time, the introduction of graphene replaces some of the more rigid silver, which can absorb and release some stress, reduce the stiffness of the overall conductive material layer, effectively improve the toughness of the electrode, reduce cell warpage and microcracks, make the silicon wafer less prone to tearing, and improve the long-term reliability of the module.

[0073] It is understood that, in some of these embodiments, the methods for preparing solar cells can be used to prepare PERC (passivated emitter back contact) cells, TOPCon (tunneling oxide passivated contact) cells, HJT (heterojunction) cells, and BC (back contact) cells, etc.; furthermore, all of the above-mentioned cells can be further prepared as bifacial light-receiving structure cells.

[0074] In some embodiments, the method for fabricating a solar cell further includes, before printing the conductive material, preparing a passivation layer on the surface of a silicon substrate. It is understood that the conductive material is printed on the side of the passivation layer away from the silicon substrate.

[0075] In some embodiments, the method for preparing the conductive material in the fabrication method of the solar cell includes the following steps:

[0076] A graphene-coated silver sheet was prepared by growing a graphene layer on the surface of a silver sheet using chemical vapor deposition.

[0077] Graphene-coated silver sheets are mixed and ground with silver powder, bismuth-based glass powder, and vanadium-based glass powder.

[0078] In some embodiments, the mixing step in the method for preparing conductive materials further includes adding an organic carrier.

[0079] In some embodiments, the chemical vapor deposition (CVD) temperature is 940°C to 960°C, and the deposition time is 10 min to 30 min. It is understood that the CVD temperature includes, but is not limited to, 40°C, 941°C, 942°C, 943°C, 944°C, 945°C, 946°C, 947°C, 948°C, 949°C, 950°C, 951°C, 952°C, 953°C, 954°C, 955°C, 956°C, 957°C, 958°C, 959°C, and 960°C; and the deposition time includes, but is not limited to, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, and 30 min. In some examples, the range can be defined by any two of these point values ​​as endpoints, and the same applies below.

[0080] A graphene layer was grown on the surface of a silver sheet using chemical vapor deposition. Through its unique two-dimensional sheet structure, a qualitative change was achieved from "point bonding" to "surface anchoring", thereby synergistically solving multiple technical contradictions such as high adhesion, high conductivity, low stress and low cost.

[0081] In some embodiments, the method for fabricating a solar cell includes the following steps:

[0082] S1. Texturing process: The silicon wafer is cleaned and texturized to obtain a texturized black silicon wafer.

[0083] S2. Diffusion doping: The texturized black silicon wafer is subjected to diffusion treatment to form a PN junction.

[0084] Optionally, for P-type silicon wafers, phosphorus oxychloride (POCl3) source is used for phosphorus diffusion to form N-type emitters; optionally, the diffusion temperature is 800℃~900℃ and the diffusion time is 20min~60min; optionally, the sheet resistance of the N-type emitter is 80Ω / □~150Ω / □.

[0085] Optionally, for N-type silicon wafers, boron tribromide (BBr3) source is used for boron diffusion to form a P-type emitter. Optionally, the diffusion temperature is 900℃~1000℃, and the diffusion time is 30min~90min; optionally, the sheet resistance of the P-type emitter is 60Ω / □~120Ω / □.

[0086] S3. Glass Removal and Edge Isolation: Remove the phosphosilicate glass layer (PSG) or borosilicate glass layer (BSG) and perform edge isolation.

[0087] Optionally, the glass layer can be removed by cleaning with hydrofluoric acid solution, and edge isolation can be achieved by laser edge etching or plasma etching.

[0088] S4. Back passivation layer deposition: A passivation layer is deposited on the back of the texturized black silicon wafer to form a back passivation structure.

[0089] Optionally, for PERC cells, the passivation layer is a stacked structure of an aluminum oxide layer and a silicon nitride layer. Optionally, this includes: depositing an aluminum oxide layer with a thickness of 5 nm to 20 nm using atomic layer deposition (ALD); and then depositing a silicon nitride layer with a thickness of 50 nm to 120 nm using plasma-enhanced chemical vapor deposition (PECVD). Optionally, the total thickness of the passivation layer is 50 nm to 150 nm.

[0090] Optionally, for TOPCon cells, the passivation layer is a stacked structure of a tunneling oxide layer and a doped polycrystalline silicon layer. Optionally, this includes: growing an ultrathin silicon oxide layer with a thickness of 1.0 nm to 2.0 nm on the back side of a silicon wafer using thermal oxidation or nitric acid oxidation; then depositing an amorphous silicon layer with a thickness of 80 nm to 200 nm using low-pressure chemical vapor deposition (LPCVD) or PECVD; subsequently performing high-temperature annealing to convert the amorphous silicon into polycrystalline silicon, and then doping it with phosphorus or boron. Optionally, a silicon nitride antireflection layer with a thickness of 50 nm to 100 nm is also deposited on the surface of the doped polycrystalline silicon layer.

[0091] Optionally, for HJT cells, the passivation layer is a stacked structure of an intrinsic amorphous silicon layer and a doped amorphous silicon layer. Optionally, it includes: depositing an intrinsic amorphous silicon layer with a thickness of 5nm~15nm on the back side of a silicon wafer using a PECVD process; then depositing a doped amorphous silicon layer (N-type or P-type) with a thickness of 5nm~20nm; and depositing a transparent conductive oxide (TCO) layer, such as indium tin oxide (ITO) or indium tungsten oxide (IWO), with a thickness of 70nm~120nm as the outermost layer.

[0092] S5. Front Anti-reflection Layer Deposition: An anti-reflection layer is deposited on the front side of the black silicon wafer.

[0093] Optionally, a silicon nitride layer with a thickness of 70 nm to 90 nm and a refractive index of 1.9 to 2.1 is deposited using a PECVD process. Optionally, the antireflective layer is a stacked structure of silicon oxide and silicon nitride.

[0094] Optionally, for PERC cells, including S6, the grooving process involves laser grooving of the back passivation layer to form local contact windows. Optionally, nanosecond or picosecond lasers are used for grooving, with a grooving linewidth of 30μm~50μm and a grooving spacing of 0.8mm~1.2mm. The grooving depth penetrates the passivation layer but does not damage the black silicon wafer. It is understood that the grooving process is suitable for PERC cells; TOPCon cells, HJT cells, and BC cells do not require grooving.

[0095] S7. Back electrode printing: The above-mentioned conductive material is printed on the surface of the passivation layer or on the back of the black silicon wafer after slotting.

[0096] Optionally, screen printing is used with a screen mesh count of 250-300 mesh and a printing wet weight of 0.10g / piece to 0.20g / piece. Optionally, for TOPCon batteries, a high mesh count screen of 450-550 mesh can be used to achieve fine grid line printing of 15μm-25μm.

[0097] S8. Drying treatment: Dry the printed battery cells.

[0098] Optionally, the drying temperature is 120℃~180℃, and the drying time is 1min~5min. The drying process causes the solvent in the organic carrier to evaporate, forming an electrode precursor with a certain strength.

[0099] S9. Front Electrode Printing and Drying: The front electrode paste is printed on the front side of the solar cell and then dried. Optionally, the front electrode paste is silver paste or silver-aluminum paste. Optionally, the front electrode and the back electrode are printed in a step-by-step manner, with the back electrode printed and dried first, followed by the front electrode printed and dried.

[0100] S10, Co-sintering: The dried battery cells are co-sintered at high temperature to solidify the conductive material and form electrodes.

[0101] Optionally, a chain sintering furnace is used for sintering. The sintering furnace has multiple temperature zones, with a peak temperature zone of 730℃~820℃. The residence time of the solar cell in the peak temperature zone is 1s~10s. Optionally, the belt speed of the sintering furnace is 200ipm~350ipm.

[0102] During the sintering process, the organic carrier in the conductive material completely volatilizes and decomposes, the glass powder softens and melts, corrodes the passivation layer and migrates to the surface of the silicon substrate, the silver powder forms an ohmic contact with the silicon, and the graphene-coated silver sheet forms a mechanical intercalation with the surface of the silicon substrate, ultimately forming an electrode with low resistance and high adhesion.

[0103] S11. Testing and sorting: Perform electrical performance testing (IV testing) and appearance inspection on the sintered solar cells, and sort them according to the test results.

[0104] It is understood that one embodiment of this application provides a silver paste, which, by mass percentage, comprises: 60% to 85% conductive phase, 1% to 5% binder phase, and 10% to 35% organic carrier;

[0105] The conductive phase, by mass percentage, comprises 65% to 85% silver powder and 15% to 35% graphene-coated silver flakes.

[0106] By mass percentage, the binder phase comprises 50%–70% bismuth-based glass powder and 30%–50% vanadium-based glass powder.

[0107] The silver paste provided in this application is a carbon-containing back-side silver paste that is particularly suitable for black silicon solar cells. When used on black silicon solar cells, it can effectively improve the adhesion and ohmic contact performance between the paste and the black silicon solar cells, and it also has good corrosion resistance.

[0108] It is understood that in some embodiments, the silver paste consists of 60% to 85% conductive phase, 1% to 5% binder phase, and 10% to 35% organic carrier by weight percentage.

[0109] One embodiment of this application provides a solar cell, which is prepared using the solar cell preparation method described above.

[0110] The solar cells prepared by the above-mentioned method have high photoelectric conversion efficiency and good long-term reliability.

[0111] In some embodiments, the surface of the black silicon substrate in the solar cell has a textured structure, which comprises multiple structural units. Optionally, the height of the structural unit is 2.0 μm to 3.5 μm, the radial dimension of the structural unit is 90 nm to 400 nm, and the spacing between adjacent structural units is 200 nm to 610 nm. Optionally, the tip diameter of the structural unit is less than 50 nm. Optionally, the average reflectivity of the black silicon substrate in the wavelength range of 400 nm to 1000 nm is less than 5%; further, the average reflectivity is 1% to 3%. It is understood that the height of the structural monomers includes, but is not limited to, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, and 3.5μm; the radial dimensions of the structural monomers include, but are not limited to, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, and 260nm. nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm; the spacing between adjacent structural units includes, but is not limited to, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, 400nm, 420nm, 440nm, 460nm, 480nm, 500nm, 520nm, 540nm, 560nm, 580nm, 600nm, 610nm.

[0112] In some embodiments, the solar cell further includes a passivation layer disposed on at least one side of a silicon substrate. Optionally, an electrode is electrically connected to the silicon substrate through the passivation layer.

[0113] One embodiment of this application provides a tandem solar cell, including the solar cell described above. Optionally, the tandem solar cell includes a top cell and a bottom cell, wherein the bottom cell is the solar cell described above, and the top cell is a perovskite solar cell.

[0114] It is understood that stacked batteries include, but are not limited to, two-terminal stacked batteries, three-terminal stacked batteries, and four-terminal stacked batteries.

[0115] One embodiment of this application provides a photovoltaic module, including the above-described solar cell or the above-described tandem cell.

[0116] It is understandable that photovoltaic modules include the aforementioned solar cells, and can give photovoltaic modules the same advantages as the aforementioned solar cells, such as higher photoelectric conversion efficiency and better long-term reliability.

[0117] In some embodiments, the photovoltaic module includes:

[0118] A battery string is formed by connecting multiple of the aforementioned solar cells or stacked cells.

[0119] In some embodiments, the photovoltaic module further includes:

[0120] Encapsulating film, used to cover the surface of the battery string; and

[0121] A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

[0122] It can be understood that solar cells or tandem cells are electrically connected in the form of a single sheet or multiple segments to form multiple cell strings, and multiple cell strings are electrically connected in series and / or parallel. Furthermore, solar cells or tandem cells can be single-sheet cells or sliced ​​cells; sliced ​​cells refer to cells formed from a single, complete cell through a cutting process.

[0123] In some embodiments, multiple battery strings can be electrically connected via conductive strips.

[0124] In some embodiments, the encapsulating film includes a first encapsulating layer and a second encapsulating layer, the first encapsulating layer covering one of the front and back sides of the battery, and the second encapsulating layer covering the other of the front and back sides of the battery; further, the first encapsulating layer and the second encapsulating layer may each independently include at least one of organic encapsulating films such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene coelastomer (POE) film, and polyethylene terephthalate (PET) film.

[0125] In some embodiments, the cover plate can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function.

[0126] The present application will be described in further detail below with reference to specific embodiments, but the embodiments of the present application are not limited thereto.

[0127] The raw materials used in the following examples or comparative examples are as follows:

[0128] Preparation steps of graphene-coated silver sheet (G-AgNS): Two graphene layers were deposited on the surface of a silver sheet by chemical vapor deposition (temperature 950℃, time 20min) to prepare graphene-coated silver sheet; the mass ratio of graphene to silver sheet in the graphene-coated silver sheet was 0.05:1, and the diameter of the silver sheet and graphene sheet was 2.0 μm ± 0.5 μm.

[0129] By mass percentage, the bismuth-based glass powder consists of: Bi₂O₃ 70%, B₂O₃ 15%, SiO₂ 8%, ZnO 5%, and Al₂O₃ 2%; the D50 particle size is 1.5 μm.

[0130] By mass percentage, the vanadium-based glass powder consists of: 50% V2O5, 30% ZnO, 15% B2O3, and 5% TeO2; the D50 particle size is 2 μm.

[0131] Example 1

[0132] S1. Texturing process: The silicon wafer is cleaned and texturized to obtain a texturized black silicon wafer.

[0133] A P-type silicon wafer is placed in a reactive ion etching apparatus, and a mixture of SF6 and O2 gas is introduced to perform anisotropic etching on the surface of the silicon wafer under the action of plasma.

[0134] S2. Diffusion doping: Phosphorus diffusion treatment is performed on the texturized black silicon wafer to form a PN junction.

[0135] S3. Remove the borosilicate glass layer and perform edge isolation.

[0136] S4. Backside passivation layer deposition: A passivation layer is deposited on the backside of the texturized black silicon wafer. The passivation layer is a stacked structure of aluminum oxide layer and silicon nitride layer.

[0137] S5. Front Anti-reflection Layer Deposition: An anti-reflection layer (silicon nitride layer) is deposited on the front side of the black silicon wafer.

[0138] S6. Grooving treatment: Laser grooving is performed on the back passivation layer to form local contact windows.

[0139] S7. Back Electrode Printing: Mix 65g of spherical silver powder, 15g of graphene-coated silver sheet, 1.8g of bismuth-based glass powder and 1.2g of vanadium-based glass powder evenly, add 17g of organic carrier (ethyl cellulose to terpineol in a mass ratio of 1:6), mix in a planetary mixer, grind with a three-roll mill, and degas under vacuum to obtain a slurry; wherein the mass ratio of silver powder to graphene-coated silver sheet is approximately 1:0.23, and the mass ratio of bismuth-based glass powder to vanadium-based glass powder is approximately 1:0.67; print the slurry onto the back of the grooved black silicon wafer using a screen printing machine (280 mesh screen), and dry it through a drying channel (150℃, 2min).

[0140] S8. Front electrode printing and drying: Print the front electrode silver paste on the front of the cell and then dry it.

[0141] S9. Co-sintering: The dried battery cells are sintered in an eight-zone sintering furnace (peak temperature ~780℃, belt speed ~270ipm) to solidify and form electrodes.

[0142] Example 2

[0143] The difference from Example 1 is that in the slurry of S7, 50g of spherical silver powder, 20g of graphene-coated silver sheet, 1.5g of bismuth-based glass powder and 1g of vanadium-based glass powder are mixed evenly, and 27.5g of organic carrier is added; wherein, the mass ratio of silver powder to graphene-coated silver sheet is 1:0.4, and the mass ratio of bismuth-based glass powder to vanadium-based glass powder is approximately 1:0.67.

[0144] Example 3

[0145] The difference from Example 1 is that in the slurry of S7, 65g of spherical silver powder, 15g of graphene-coated silver sheet, 2g of bismuth-based glass powder and 1g of vanadium-based glass powder are mixed evenly, and 17g of organic carrier is added; wherein, the mass ratio of silver powder to graphene-coated silver sheet is about 1:0.27, and the mass ratio of bismuth-based glass powder to vanadium-based glass powder is 1:0.5.

[0146] Example 4

[0147] The difference from Example 1 is that in the slurry of S7, 58g of spherical silver powder, 22g of graphene-coated silver sheet, 1.8g of bismuth-based glass powder and 1.2g of vanadium-based glass powder are mixed evenly, and 17g of organic carrier is added; wherein, the mass ratio of silver powder to graphene-coated silver sheet is about 1:0.38, and the mass ratio of bismuth-based glass powder to vanadium-based glass powder is about 1:0.67.

[0148] Comparative Example 1

[0149] The difference from Example 1 is that in S7, 80g of spherical silver powder and 3g of lead-containing glass powder (PbO-B2O3-SiO2 system) are mixed evenly, and 17g of organic carrier is added.

[0150] Comparative Example 2

[0151] The difference from Example 1 is that in the slurry of S7, bismuth-based glass powder is omitted, and 65g of spherical silver powder, 15g of graphene-coated silver sheet and 3g of vanadium-based glass powder are mixed evenly and 17g of organic carrier is added.

[0152] Comparative Example 3

[0153] The difference from Example 1 is that in the slurry of S7, the graphene-coated silver sheet is omitted, and 80g of spherical silver powder, 1.8g of bismuth-based glass powder and 1.2g of vanadium-based glass powder are mixed evenly and 17g of organic carrier is added.

[0154] Comparative Example 4

[0155] The difference from Example 1 is that the graphene-coated silver sheet in the slurry of S7 is replaced with graphene-coated silver powder.

[0156] Comparative Example 5

[0157] The difference from Example 1 is that in S7, the spherical silver powder is omitted, and 80g of graphene-coated silver sheet, 1.8g of bismuth-based glass powder and 1.2g of vanadium-based glass powder are mixed evenly and 17g of organic carrier is added.

[0158] The following performance tests were performed on the sintered solar cells:

[0159] Electrical performance: Open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF), conversion efficiency (Eta), and series resistance (Rs) were measured using a standard IV tester (Berger Lichttechnik).

[0160] Adhesion: The adhesion of the main grid lines was tested using a tensile tester (Dage Series 4000) with a 90° peel test (unit: N / mm).

[0161] EL testing: Electroluminescence (EL) imaging is used to detect whether the solar cells have microcracks, broken grids caused by excessive corrosion, or leakage points.

[0162] Appearance: Observe the electrode morphology and uniformity.

[0163] The test results are shown in Table 1.

[0164] Table 1

[0165]

[0166] As can be seen from Table 1, compared with Comparative Example 1, the silver content of the paste used to prepare the electrode in the Examples is reduced, the fill factor and conversion efficiency are higher, and the series resistance is lower; indicating that the paste provided by the Examples has advantages in forming excellent ohmic contacts and reducing leakage current.

[0167] The adhesion of Comparative Example 1 was only 1.8 N / mm, which could not meet the requirements for component manufacturing; the adhesion of the slurry prepared in the Example exceeded 3.5 N / mm, which met or even far exceeded the industry standard (usually required >2.0 N / mm); indicating that the slurry prepared in the Example had good mechanical bonding ability with the rough surface of the black silicon substrate.

[0168] EL imaging results showed that the edge of the solar cell in Comparative Example 1 had dark areas (leakage points) caused by excessive corrosion, while the solar cell in the embodiment had uniform and bright EL images without defects; indicating that the slurry prepared in the embodiment achieved precise and gentle corrosion of the black silicon structure and passivation layer, effectively protecting the PN junction.

[0169] 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.

[0170] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. 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 scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a solar cell, characterized in that, Includes the following steps: A conductive material is printed on a battery substrate; the battery substrate includes a black silicon substrate. The conductive material is sintered and solidified to form an electrode; the conductive material includes silver powder, graphene-coated silver sheet, bismuth-based glass powder and vanadium-based glass powder, wherein the graphene-coated silver sheet includes a core layer and a shell layer disposed on the outer surface of the core layer, the core layer includes silver sheet, and the shell layer includes graphene; the mass ratio of silver powder to graphene-coated silver sheet is 1:0.2~0.

5.

2. The method for preparing a solar cell as described in claim 1, characterized in that, The total mass of the silver powder and the graphene-coated silver sheet accounts for 60% to 85% of the total mass of the conductive material.

3. The method for preparing a solar cell as described in claim 2, characterized in that, The mass ratio of the silver powder to the graphene-coated silver sheet is 1:0.2~0.

4.

4. The method for preparing a solar cell as described in claim 1, characterized in that, The total mass of the bismuth-based glass powder and the vanadium-based glass powder accounts for 1% to 5% of the total mass of the conductive material.

5. The method for preparing a solar cell as described in claim 4, characterized in that, The mass ratio of the bismuth-based glass powder to the vanadium-based glass powder is 1:0.4~1.

6. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The conductive material satisfies at least one of the following conditions: (1) By mass percentage, the bismuth-based glass powder comprises: 60%~75% Bi2O3, 10%~20% B2O3, 5%~10% SiO2 and 3%~8% ZnO; (2) By mass percentage, the vanadium-based glass powder comprises 40%~60% V2O5, 20%~35% ZnO, 10%~20% B2O3 and 5%~10% TeO2.

7. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The conductive material satisfies at least one of the following conditions: (1) The D50 particle size of the bismuth-based glass powder is 1 μm to 2.5 μm; (2) The D50 particle size of the vanadium-based glass powder is 1.5 μm to 3.0 μm; (3) The D50 particle size of the silver powder is 0.5 μm to 4 μm.

8. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The mass ratio of graphene to silver sheet is 0.02~0.08:

1.

9. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The silver sheet has a diameter of 1 μm to 3 μm, the graphene sheet has a diameter of 1 μm to 3 μm, and the graphene has 1 to 3 layers.

10. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The sintering temperature is 730℃~820℃, and the time is 1 s~10 s.

11. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The preparation of the black silicon substrate includes the following steps: Reactive ion etching or metal-assisted chemical etching is performed on the silicon wafer surface.

12. The method for preparing a solar cell as described in claim 11, characterized in that, The reactive ion etching includes the following steps: A mixture of SF6 and O2 gas is introduced, and reactive ion etching is performed on the surface of the silicon wafer under the action of plasma; wherein the flow rate of SF6 is 50sccm~200sccm, the flow rate of O2 is 10sccm~50sccm, the etching power is 500W~1500W, and the etching time is 1min~10min. And / or, the metal-assisted chemical etching includes the following steps: After depositing a catalyst on the silicon wafer surface, metal-assisted chemical etching is performed in an etching solution; the catalyst includes at least one of silver nanoparticles and gold nanoparticles, and the etching solution is a mixed solution including HF and H2O2.

13. A solar cell, characterized in that, The solar cell is prepared by the method of any one of claims 1 to 12; the solar cell includes a cell substrate and an electrode disposed on the cell substrate, the cell substrate includes a black silicon substrate, the surface of the black silicon substrate has a textured structure, the textured structure includes a plurality of structural units, the height of the structural units is 2.0 μm to 3.5 μm, the radial dimension is 90 nm to 400 nm, and the adjacent spacing is 200 nm to 610 nm.

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

15. A photovoltaic module, characterized in that, The photovoltaic module includes: a battery string, which is formed by connecting multiple solar cells as described in claim 13 or tandem cells as described in claim 14.

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