Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the technical field of solar cells, and provides a solar cell, a preparation method thereof and a photovoltaic module, and the method comprises the steps: providing a solar cell precursor which comprises a silicon substrate, a first passivation layer formed on the front surface of the silicon substrate, and a passivation contact layer, a carrier transmission layer and a second passivation layer which are sequentially formed on the back surface of the silicon substrate; the carrier transport layer comprises N-type doped regions and P-type doped regions which are arranged alternately; printing first silver paste on the second passivation layer corresponding to the N-type doped region, printing second silver paste on the second passivation layer corresponding to the P-type doped region, and then performing first drying treatment to form a silver paste layer; printing first silver-nickel paste on the silver paste layer corresponding to the N-type doped region, printing second silver-nickel paste on the silver paste layer corresponding to the P-type doped region, and then performing second drying treatment to form a silver-nickel paste layer; and the silver paste layer and the silver-nickel paste layer are sintered to obtain the solar cell, so that copper pollution is avoided, laser trepanning is not needed, the process is simple, and the cost is low.

Description

Technical Field

[0001] This application belongs to the field of solar cell technology, and in particular relates to a solar cell, its preparation method, and a photovoltaic module. Background Technology

[0002] Back-contact solar cells, by integrating all electrodes on the back of the cell to avoid the front grid lines blocking incident light, are one of the mainstream technologies for achieving high photoelectric conversion efficiency. However, the complex structure of the back electrode makes the fabrication process difficult, and the high cost of traditional pure silver electrodes has become a key bottleneck for industrialization.

[0003] To reduce electrode costs, the industry has proposed using a "base metal / silver composite electrode" solution. For example, the industry has tried a "silver seed layer + silver-coated copper paste" process, which first achieves ohmic contact with the silicon substrate by sintering a silver seed layer, and then uses a low-temperature cured silver-coated copper paste as the conductive substrate. However, this solution has significant drawbacks: copper ions can easily diffuse through the silver seed layer to the silicon substrate, causing contamination, leading to cell performance degradation, and seriously affecting the long-term reliability of the module. In addition, existing processes usually require laser drilling after depositing a back passivation layer to expose the silicon contact area. This step not only increases process complexity and equipment costs, but also introduces potential damage risks.

[0004] To address reliability issues, existing technologies propose a three-layer metal electrode stacked structure, where the second and third electrodes protect the first electrode layer containing base metal, thereby improving corrosion resistance and stability. However, the multi-layer structure increases fabrication difficulty and cost. Furthermore, while other improved designs such as bent gate lines or non-edge gate layouts can alleviate stress concentration, they do not fundamentally solve the problems of base metal oxidation or contamination.

[0005] Therefore, developing a novel electrode solution that can significantly reduce costs, avoid the risk of metal contamination, and has a simple preparation process is of great significance for promoting the large-scale application of back-contact solar cells. Summary of the Invention

[0006] The purpose of this application is to provide a solar cell, its preparation method, and a photovoltaic module, aiming to solve the problems of high cost, high reliability risk, and numerous process steps of existing back-contact solar cell electrodes.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a method for preparing a solar cell, comprising the following steps: A solar cell precursor is provided; the solar cell precursor includes a silicon substrate, a first passivation layer formed on the front side of the silicon substrate, and a passivation contact layer, a carrier transport layer, and a second passivation layer sequentially formed on the back side of the silicon substrate; the carrier transport layer includes alternating N-type doped regions and P-type doped regions, with a blank area separating adjacent N-type doped regions and P-type doped regions. A first silver paste is printed on the second passivation layer corresponding to the N-type doped region, and a second silver paste is printed on the second passivation layer corresponding to the P-type doped region. Then, a first drying process is performed to form a silver paste layer. A first silver-nickel paste is printed on the silver paste layer corresponding to the N-type doped region, and a second silver-nickel paste is printed on the silver paste layer corresponding to the P-type doped region. Then a second drying process is performed to form a silver-nickel paste layer stacked with the silver paste layer. The silver paste layer and the silver-nickel paste layer are sintered to obtain a solar cell.

[0008] Secondly, this application provides a solar cell, which is prepared by the method for preparing the solar cell provided in this application.

[0009] Thirdly, this application provides a photovoltaic module, including at least one solar cell prepared by the method for preparing the solar cell provided in this application.

[0010] Compared with the prior art, this application has the following beneficial effects: (1) This application adopts an integrated process of "printing silver paste first, then silver-nickel paste, and finally co-firing". The glass powder in the silver paste and silver-nickel paste plays a synergistic etching role, directly etching through the second passivation layer, so that the electrode and the N / P type doped region form an ohmic contact. In particular, the gradient design of the softening point of the first silver paste, the second silver paste, the first silver-nickel paste and the second silver-nickel paste allows the lower silver paste to etch the second passivation layer first, and the upper silver-nickel paste to gradually dissolve into the silver paste. This achieves a high-low viscosity combination, slows down the etching of the second passivation layer by the lower glass powder at high temperature, reduces metal-induced recombination, and improves the battery conversion efficiency. At the same time, the co-firing of the upper nickel-containing metal powder and the lower silver powder forms a dense and integrated composite electrode structure, which enables the upper silver-nickel to form a good ohmic contact with the N / P type doped region, reduces the contact resistance and improves the reliability of the battery.

[0011] (2) By etching through the second passivation layer, the step of laser drilling to construct ohmic contacts, which is required by traditional processes, is eliminated, thus reducing costs and simplifying the process.

[0012] (3) The silver-nickel system is used as the conductive body to replace the traditional pure silver electrode or silver-coated copper electrode, which greatly reduces the cost and avoids copper pollution, solves the inherent reliability problems of the silver-coated copper solution, and improves the battery durability and performance stability. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0014] Figure 1 This is a schematic diagram of each step in the method for preparing a solar cell provided in the embodiments of this application.

[0015] The following are the labeling elements in the figure: 1—Silicon substrate, 2—First passivation layer, 3—Passivation contact layer, 4—Carrier transport layer, 41—N-type doped region, 42—P-type doped region, 5—Second passivation layer, 6—Silver paste layer, 61—First silver paste layer, 62—Second silver paste layer, 7—Silver-nickel paste layer, 71—First silver-nickel paste layer, 72—Second silver-nickel paste layer. Detailed Implementation

[0016] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] The first aspect of this application provides a method for preparing a solar cell, comprising the following steps: S1: Provides solar cell precursors; such as Figure 1 As shown in A, the solar cell precursor includes a silicon substrate 1, a first passivation layer 2 formed on the front side of the silicon substrate 1, and a passivation contact layer 3, a carrier transport layer 4, and a second passivation layer 5 formed sequentially on the back side of the silicon substrate 1; the carrier transport layer 4 includes alternating N-type doped regions 41 and P-type doped regions 42, with blank areas separating adjacent N-type doped regions 41 and P-type doped regions 42. S2: As Figure 1 As shown in B and C, a first silver paste is printed on the second passivation layer 5 corresponding to the N-type doped region 41, and a second silver paste is printed on the second passivation layer 5 corresponding to the P-type doped region 42. Then, a first drying process is performed to form a silver paste layer 6. S3: As Figure 1As shown in D and E, a first silver-nickel paste is printed on the silver paste layer corresponding to the N-type doped region 41, and a second silver-nickel paste is printed on the silver paste layer corresponding to the P-type doped region 42. Then, a second drying process is performed to form a silver-nickel paste layer 7 that is stacked with the silver paste layer 6. S4: The silver paste layer 6 and the silver-nickel paste layer 7 are sintered to obtain a solar cell.

[0018] The solar cell fabrication method provided in this application adopts an integrated process of "printing silver paste first, then silver-nickel paste, and finally co-firing". The glass powder in the silver and silver-nickel pastes acts as a synergistic etching agent, directly etching through the second passivation layer, enabling the electrode to form an ohmic contact with the N / P-type doped region. In particular, the gradient design of the softening points of the first silver paste, second silver paste, first silver-nickel paste, and second silver-nickel paste ensures that the lower silver paste etches the second passivation layer first, while the upper silver-nickel paste gradually dissolves into the silver paste. This achieves a high-low viscosity combination, slowing down the etching of the second passivation layer by the glass powder at high temperatures, reducing metal-induced recombination, and improving the cell conversion efficiency. Simultaneously, the co-firing of the upper nickel-containing metal powder with the lower silver powder forms a dense and integrated composite electrode structure, enabling good ohmic contact between the upper silver-nickel layer and the N / P-type doped region, reducing contact resistance and improving cell reliability. Therefore, this application uses a silver-nickel system as the conductive substrate, replacing traditional pure silver electrodes or silver-clad copper electrodes, significantly reducing costs and avoiding copper contamination, solving the inherent reliability issues of the silver-clad copper solution, and improving cell durability and performance stability. Furthermore, by etching through the second passivation layer, the step of laser drilling to construct ohmic contacts, which is required in traditional processes, is eliminated, thus reducing costs and simplifying the process.

[0019] Step S1: In this embodiment, the silicon substrate can be an N-type silicon wafer, which can be obtained commercially; the first passivation layer can be a silicon nitride layer with a thickness of 70-90 nm; the passivation contact layer can be a silicon oxide layer with a thickness of 1.0-2.0 nm; the P-type doped region is a boron-doped polycrystalline silicon layer with a thickness of 180-220 nm, and the N-type doped region is a p-doped polycrystalline silicon layer with a thickness of 130-170 nm; the second passivation layer consists of a stacked aluminum oxide layer and a silicon nitride layer, with the aluminum oxide layer having a thickness of 2.5-3.5 nm and the silicon nitride layer having a thickness of 70-90 nm, and the aluminum oxide layer being disposed between the carrier transport layer and the silicon nitride layer. The silicon nitride layer, silicon oxide layer, boron-doped polycrystalline silicon layer, p-doped polycrystalline silicon layer, aluminum oxide layer, etc., can be prepared by referring to the process methods and condition parameters described in the literature or books in this field. As mature technology in this field, to save space, the specific preparation methods and condition parameters of the solar cell precursor will not be described in detail here.

[0020] Step S2, in this embodiment, the first silver paste comprises silver powder, first glass powder, first additive, and organic carrier in a mass ratio of (80~90):(1~10):(0.05~1.0):(5~15), wherein the softening point of the first glass powder is 300~450℃. The silver powder has a particle size of 1.0~2.0μm and a tap density >4m³. 2 / g.

[0021] The first glass powder comprises PbO, TeO2, Bi2O3, SiO2, WO3, ZnO, alkali metal oxides, and a first modified oxide in a mass ratio of (10~50):(10~60):(5~30):(0.5~10):(0.5~20):(0.5~10):(1~10):(0~30); the alkali metal oxide is selected from at least one of Li2O, Na2O, and K2O, and the first modified oxide is selected from at least one of Fe2O3, Al2O3, Ga2O3, Ag2O, CuO, MoO3, V2O5, CeO2, Y2O5, MgO, Nb2O5, and La2O3. The specific composition and content design of the first glass powder control its softening point at 300~450℃, allowing it to melt and flow first during sintering, etching through the second passivation layer (alumina layer and silicon nitride layer). This opens a pathway for the silver seed layer to form an ohmic contact with the silicon material, eliminating the need for laser drilling. At the same time, it can also limit the etching rate of the N-type doped region (P-doped polycrystalline silicon layer), avoiding damage to the junction region due to excessive reaction, and achieving reliable interface contact.

[0022] The first additive is a mixed oxide powder with a particle size of 10-100 nm, which is obtained by ball milling a mixture of Al2O3 powder, SiO2 powder, and ZrO2 powder. During sintering, this mixed oxide powder is enriched at the Ag / N-type doped region interface, limiting excessive penetration of silver atoms into the N-type doped region, reducing carrier recombination centers introduced by metal impurities, and simultaneously optimizing the interface structure and reducing the carrier recombination rate at the silver-silicon interface.

[0023] The organic carrier comprises a resin, a solvent, and organic additives in a mass ratio of (0.5~10):(2~30):(0.1~5); wherein the resin includes at least one of ethyl cellulose, acrylic resin, cellulose acetate butyrate, and polyvinyl butyral; the solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, terpineol, benzyl benzoate, and diethylene glycol dibutyl ether; and the organic additives include at least one of sodium dodecyl sulfate dispersant, silicone oil, and acrylate leveling agent. The composition and content of the organic carrier in this embodiment ensure that the silver paste possesses excellent rheological properties, printability, and film-forming properties, forming a dense preform after drying, thus guaranteeing the formation of a high-quality electrode through subsequent high-temperature sintering.

[0024] In an embodiment, the method for preparing the first silver paste includes: adding resin to a solvent, heating to 50~100℃, and stirring at a stirring speed of 500~3000rpm for 0.5~24h to obtain a dispersion; adding silver powder, first glass powder, first additive and organic additive to the dispersion and stirring evenly, and then grinding to obtain the first silver paste with a fineness of <10μm.

[0025] In this embodiment, the second silver paste comprises silver powder, second glass powder, second additive, and an organic carrier in a mass ratio of (80~90):(1~10):(0.05~1.5):(5~15), wherein the softening point of the second glass powder is 350~500℃. The silver powder has a particle size of 1.0~2.0 μm and a tap density >4 m³ / s. 2 / g.

[0026] The second glass powder comprises Bi₂O₃, B₂O₃, SiO₂, ZnO, Al₂O₃, and a second modified oxide in a mass ratio of (10~80):(5~30):(1~20):(2~20):(0.5~6):(0.5~10). The second modified oxide is selected from at least one of CaO, BaO, Li₂O, Na₂O, K₂O, TiO₂, V₂O₅, ZrO, Nb₂O₅, Y₂O₅, GeO₂, Ga₂O₃, Sb₂O₃, and CeO₂. The specific composition and content of the second glass powder are designed to control its softening point at 350~500℃, thereby melting and eroding through the second passivation layer (silicon nitride layer) first during sintering. This opens a pathway for the formation of ohmic contact between the silver seed layer and the silicon material, eliminating the need for laser drilling. At the same time, it improves the wettability of silver on the surface of the P-type doped region, providing a stable reaction environment for interface nucleation and silver growth.

[0027] The second additive is selected from silver salt powder with a particle size of less than 100 nm. The silver salt powder includes Ag2SO4 powder, Ag2CO4 powder, and AgNO3 powder in a mass ratio of (20~50):(0~30):(50~80). Further, the silver salt powder includes Ag2SO4 powder, Ag2CO4 powder, and AgNO3 powder in a mass ratio of (20~50):(2~20):(50~78). The introduction of these silver salt powders allows for decomposition during the early stages of sintering, generating nano-silver nuclei in situ at the interface between the Ag and P-type doped regions. These highly active nuclei serve as additional nucleation and growth sites, effectively increasing the density of interfacial contact points, reducing the Schottky barrier, and decreasing contact resistance. Simultaneously, the in-situ generated nano-silver also helps optimize the interfacial band structure, alleviating the carrier transport barrier caused by the work function difference between the metal and semiconductor (Ag / P-type doped regions), fundamentally promoting the formation of ohmic contacts.

[0028] The organic carrier comprises a resin, solvent, and organic additives in a mass ratio of (0.5~10):(2~30):(0.1~5); the resin includes at least one of ethyl cellulose, acrylic resin, cellulose acetate butyrate, and polyvinyl butyral; the solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, terpineol, benzyl benzoate, and diethylene glycol dibutyl ether; and the organic additives include at least one of sodium dodecyl sulfate dispersant, silicone oil, and acrylate leveling agent. The design of the organic carrier composition and content in this embodiment ensures that the silver paste possesses excellent rheological properties, printability, and film-forming properties, forming a dense preform after drying, thus guaranteeing the formation of a high-quality electrode through subsequent high-temperature sintering.

[0029] In an embodiment, the method for preparing the second silver paste includes: adding resin to a solvent, heating to 50~100℃, and stirring at a stirring speed of 500~3000rpm for 0.5~24h to obtain a dispersion; adding silver powder, second glass powder, second additive and organic additive to the dispersion and stirring evenly, and then grinding to obtain a second silver paste with a fineness of <10μm.

[0030] In an embodiment, such as Figure 1 As shown in Figures B and C, printing the first silver paste on the second passivation layer 5 corresponding to the N-type doped region 41 and printing the second silver paste on the second passivation layer 5 corresponding to the P-type doped region 42 means that: on the second passivation layer 5, the first silver paste is printed at the position corresponding to the N-type doped region 41 to form a first silver paste layer 61, and the second silver paste is printed at the position corresponding to the P-type doped region 42 to form a second silver paste layer 62. A first drying process is then performed to obtain a silver paste layer 6 composed of the first silver paste layer 61 and the second silver paste layer 62. The thickness of both the first silver paste layer 61 and the second silver paste layer 62 is 0.1~2 μm, that is, the thickness of the silver paste layer 6 is 0.1~2 μm.

[0031] In the embodiment, the temperature of the first drying process is 100~250°C and the time is 0.1~5 min.

[0032] Step S3, in this embodiment, the first silver-nickel paste comprises silver powder, nickel-containing metal powder, third glass powder, third additive, and organic carrier in a mass ratio of (5~50):(50~85):(1~10):(0.05~5.0):(5~15). The softening point of the third glass powder is 350~550℃. The silver powder has a particle size of 1.0~2.0μm and a tap density >4m³. 2 / g. The particle size of the nickel-containing metal powder is 1.0~5.0μm, and the tap density is >2m³. 2 / g; Nickel-containing metal powder includes silver-coated nickel powder or nickel powder, with a silver content of 5~50wt% in silver-coated nickel powder.

[0033] The third glass powder comprises PbO, TeO2, Bi2O3, SiO2, WO3, ZnO, alkali metal oxides, and a third modified oxide in a mass ratio of (5~40):(5~50):(5~25):(5~35):(5~25):(1~15):(0.5~8):(1~25); the alkali metal oxide is selected from at least one of Li2O, Na2O, and K2O, and the third modified oxide is selected from at least one of Fe2O3, Al2O3, Ga2O3, Ag2O, CuO, MoO3, V2O5, CeO2, Y2O5, MgO, Nb2O5, and La2O3. The specific composition and content design of the third glass powder control its softening point between 350 and 550°C. During sintering, its melting occurs later than that of the first glass powder in the silver seed layer, which has a lower softening point. This stepwise melting and flow allows the third glass powder melt to gradually melt into the silver paste and regulate the interfacial reaction between the silver seed layer and the silver-nickel alloy layer, preventing excessive nickel diffusion and thus stabilizing the silver-coated nickel electrode structure.

[0034] The third additive is selected from silver oxide powder and acetylene black powder with a particle size of 50~200nm, and the mass ratio of silver oxide powder to acetylene black powder is (50~80):(0~50); further, the mass ratio of silver oxide powder to acetylene black powder is (50~80):(10~30). These third additives induce the formation of a continuous metal bridging structure between silver-coated nickel particles during sintering, reduce discontinuous interfaces in the conductive path, and improve the integrity and stability of the conductive network in the electrode.

[0035] The organic carrier comprises a resin, solvent, and organic additives in a mass ratio of (0.5~10):(2~30):(0.1~5); the resin includes at least one of ethyl cellulose, acrylic resin, cellulose acetate butyrate, and polyvinyl butyral; the solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, terpineol, benzyl benzoate, and diethylene glycol dibutyl ether; and the organic additives include at least one of sodium dodecyl sulfate dispersant, silicone oil, and acrylate leveling agent. The design of the organic carrier composition and content in this embodiment ensures that the silver paste possesses excellent rheological properties, printability, and film-forming properties, forming a dense preform after drying, thus guaranteeing the formation of a high-quality electrode through subsequent high-temperature sintering.

[0036] In an embodiment, the method for preparing the first silver-nickel paste includes: adding resin to a solvent, heating to 50~100℃, and stirring at a stirring speed of 500~3000rpm for 0.5~24h to obtain a dispersion; adding silver powder, third glass powder, third additive and organic additive to the dispersion and stirring evenly, and then grinding to obtain the first silver-nickel paste with a fineness of <10μm.

[0037] In this embodiment, the second silver-nickel paste comprises silver powder, nickel-containing metal powder, a fourth glass powder, a fourth additive, and an organic carrier in a mass ratio of (5~50):(50~85):(1~10):(0.05~5.0):(5~15). The softening point of the fourth glass powder is 380~600℃. The silver powder has a particle size of 1.0~2.0 μm and a tap density >4 m³ / s. 2 / g. The particle size of the nickel-containing metal powder is 1.0~5.0μm, and the tap density is >2m³. 2 / g; Nickel-containing metal powder includes silver-coated nickel powder or nickel powder, with a silver content of 5~50wt% in silver-coated nickel powder.

[0038] The fourth glass powder comprises PbO, B2O3, SiO2, ZnO, Al2O3 and a fourth modified oxide in a mass ratio of (5~70):(10~35):(5~25):(3~25):(1~8):(0.5~12), wherein the fourth modified oxide is selected from at least one of Bi2O3, CaO, BaO, Li2O, Na2O, K2O, TiO2, V2O5, ZrO, Nb2O5, Y2O5, GeO2, Ga2O3, Sb2O3 and CeO2. The specific composition and content design of the fourth glass powder control its softening point between 350 and 550°C. During sintering, its melting occurs later than that of the second glass powder in the silver seed layer, which has a lower softening point. This stepwise melting and flow allows the fourth glass powder melt to gradually melt into the silver paste and regulates the interfacial reaction between the silver seed layer and the silver-nickel alloy layer, preventing excessive nickel diffusion and thus stabilizing the silver-coated nickel electrode structure.

[0039] The fourth additive is selected from silver oxide powder and acetylene black powder with a particle size of 50~200nm, and the mass ratio of silver oxide powder to acetylene black powder is (50~80):(20~50). These fourth additives induce the formation of a continuous metal bridging structure between silver-coated nickel particles during sintering, reduce discontinuous interfaces in the conductive path, and improve the integrity and stability of the conductive network in the electrode.

[0040] The organic carrier includes a resin, solvent, and organic additives in a mass ratio of (0.5~10):(2~30):(0.1~5); the resin includes at least one of ethyl cellulose, acrylic resin, cellulose acetate butyrate, and polyvinyl butyral; the solvent includes at least one of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, terpineol, benzyl benzoate, and diethylene glycol dibutyl ether; and the organic additives include at least one of sodium dodecyl sulfate dispersant, silicone oil, and acrylate leveling agent.

[0041] In an embodiment, the method for preparing the second silver-nickel paste includes: adding resin to a solvent, heating to 50~100℃, and stirring at a stirring speed of 500~3000rpm for 0.5~24h to obtain a dispersion; adding silver powder, fourth glass powder, fourth additive and organic additive to the dispersion and stirring evenly, and then grinding to obtain a second silver-nickel paste with a fineness of <10μm.

[0042] In an embodiment, such as Figure 1 As shown in Figures D and E, printing a first silver-nickel paste on the silver paste layer 6 corresponding to the N-type doped region 41, and printing a second silver-nickel paste on the silver paste layer 6 corresponding to the P-type doped region, followed by a second drying process, forms a silver-nickel paste layer 7 stacked on the silver paste layer 6. This means that on the silver paste layer 6, the first silver-nickel paste is printed on the surface of the first silver paste layer 61 to form a first silver-nickel paste layer 71, and the second silver-nickel paste is printed on the surface of the second silver paste layer 62 to form a second silver-nickel paste layer 72. A second drying process is then performed, so that the first silver-nickel paste layer 71 and the second silver-nickel paste layer 72 together constitute the silver-nickel paste layer 7 stacked on the silver paste layer 6. The thickness of both the first silver-nickel paste layer 71 and the second silver-nickel paste layer 72 is 5~30 μm, that is, the thickness of the silver-nickel paste layer 7 is 5~30 μm.

[0043] In this embodiment, the temperature of the second drying process is 100~250°C and the time is 0.1~5 min.

[0044] Step S4: In this embodiment, the sintering temperature is 700~800℃ and the time is 10~60 s.

[0045] A second aspect of this application provides a solar cell, which is prepared by the method for preparing a solar cell provided in this application.

[0046] The solar cells provided in this application embodiment are prepared by the method provided in this application embodiment, and therefore have advantages such as low cost, high long-term reliability, no risk of copper contamination, and high conversion efficiency.

[0047] A third aspect of this application provides a photovoltaic module, including at least one solar cell prepared by the method for preparing a solar cell provided in this application.

[0048] The photovoltaic module provided in this application embodiment has advantages such as high module power, stable output and low product cost because it contains a solar cell prepared by the solar cell preparation method provided in this application embodiment.

[0049] The following description is based on specific embodiments.

[0050] Example 1 This embodiment provides a method for preparing a solar cell, including the following steps: (1) Using existing technologies to prepare solar cell precursors (such as...) Figure 1 As shown in Figure A), it includes an N-type silicon wafer, a silicon nitride layer (80 nm thick) formed on the front side of the N-type silicon wafer, and a silicon oxide layer (1.5 nm thick), a carrier transport layer, an aluminum oxide layer (3 nm thick), and a silicon nitride layer (80 nm thick, without laser-drilled holes) formed sequentially on the back side of the N-type silicon wafer. The carrier transport layer consists of alternating N-type doped regions and P-type doped regions, with blank areas separating adjacent N-type doped regions and P-type doped regions. The P-type doped regions are polycrystalline silicon layers doped with B (200 nm thick), and the N-type doped regions are polycrystalline silicon layers doped with P (150 nm thick).

[0051] (2) Preparation of the first silver paste: Weigh appropriate amounts of PbO powder, TeO2 powder, Bi2O3 powder, SiO2 powder, WO3 powder, ZnO powder, Li2O powder, Na2O powder, MgO powder, and Nb2O5 powder in a mass ratio of 30:35:10:5:6:4:1:3:2:4, mix them, and place them in an alumina crucible. Then place the crucible in a melting furnace and hold it at 1200℃ for 60 minutes to form a glass melt. Pour the glass melt into deionized water for quenching, and then dry and pulverize it to obtain the first glass powder with a softening point of 350℃. Weigh out an appropriate amount of silver powder with a mass ratio of 85:5:0.5:9.5 (D50=1.5μm, tap density=4.5m). 2 / g), first glass powder, first additive and organic carrier; wherein, the first additive is a mixed oxide powder of Al2O3, SiO2 and ZrO2 (D50=60nm); the organic carrier is composed of ethyl cellulose, terpineol and acrylic leveling agent in a mass ratio of 5:15:3; Ethyl cellulose was added to terpineol, heated to 90°C, and stirred at 1000 rpm for 4 hours to obtain a dispersion. Silver powder, first glass powder, mixed oxide powder and acrylic leveling agent were added to the dispersion and stirred evenly. Then, the mixture was ground to obtain a first silver paste with a fineness of <10 μm.

[0052] (3) Preparation of the second silver paste: Weigh appropriate amounts of Bi₂O₃ powder, B₂O₃ powder, SiO₂ powder, ZnO powder, Al₂O₃ powder, Na₂O powder, and Y₂O₅ powder in a mass ratio of 55:15:10:10:4:3:3, mix them, and place them in an alumina crucible. Then, place the crucible in a melting furnace and hold it at 1200℃ for 60 minutes to form a glass melt. Pour the glass melt into deionized water for quenching, and then dry and pulverize it to obtain a second glass powder with a softening point of 400℃. Weigh out an appropriate amount of silver powder with a mass ratio of 85:5:1:9 (D50=1.5μm, tap density=4.5m). 2 / g), second glass powder, second additive, and organic carrier; wherein, the second additive is silver halide powder with a particle size of less than 100nm, and the silver halide powder is composed of Ag2SO4 powder, Ag2CO4 powder, and AgNO3 powder in a mass ratio of 35:5:60; the organic carrier is composed of ethyl cellulose, terpineol, and acrylic leveling agent in a mass ratio of 5:15:3; Ethyl cellulose was added to terpineol, heated to 90°C, and stirred at 1000 rpm for 4 hours to obtain a dispersion. Silver powder, second glass powder, silver salt powder, and acrylic leveling agent were added to the dispersion and stirred evenly. Then, the mixture was ground to obtain a second silver paste with a fineness of <10 μm.

[0053] (4) Preparation of the first silver-nickel paste: Weigh appropriate amounts of PbO powder, TeO2 powder, Bi2O3 powder, SiO2 powder, WO3 powder, ZnO powder, Na2O powder, and MoO3 powder in a mass ratio of 25:25:10:10:10:5:5:10, mix them, and place them in an alumina crucible. Then place the crucible in a melting furnace and hold it at 1200℃ for 60 minutes to form a glass melt. Pour the glass melt into deionized water for quenching, and then dry and pulverize it to obtain a third glass powder with a softening point of 450℃. Weigh out an appropriate amount of silver powder with a mass ratio of 15:65:7:3:10 (D50=1.5μm, tap density=4.5m). 2 / g), silver-coated nickel powder (D50=3μm, tap density=2.5m) 2 / g, silver content 20wt%), third glass powder, third auxiliary agent and organic carrier; wherein, the third auxiliary agent is composed of silver oxide powder and acetylene black powder with a particle size of 100~150nm and a mass ratio of 70:30; the organic carrier is composed of ethyl cellulose, terpineol and acrylic leveling agent with a mass ratio of 5:15:3. Ethyl cellulose was added to terpineol, heated to 90°C, and stirred at 1000 rpm for 4 hours to obtain a dispersion. Silver powder, silver-coated nickel powder, third glass powder, silver oxide powder, acetylene black powder, and acrylic leveling agent were added to the dispersion and stirred evenly. Then, the mixture was ground to obtain a first silver-nickel paste with a fineness of <10 μm.

[0054] (5) Preparation of the second silver-nickel paste: Weigh appropriate amounts of PbO powder, B2O3 powder, SiO2 powder, ZnO powder, Al2O3 powder, and K2O powder in a mass ratio of 50:20:10:10:4:6, mix them, and place them in an alumina crucible. Then place the crucible in a melting furnace and hold it at 1200℃ for 60 minutes to form a glass melt. Pour the glass melt into deionized water for quenching, and then dry and pulverize it to obtain a fourth glass powder with a softening point of 500℃. Weigh out an appropriate amount of silver powder with a mass ratio of 15:65:7:3:10 (D50=1.5μm, tap density=4.5m). 2 / g), silver-coated nickel powder (D50=3μm, tap density=2.5m) 2 / g (silver content 20wt%), fourth glass powder, fourth auxiliary agent, and organic carrier. The fourth auxiliary agent consists of silver oxide powder and acetylene black powder with a particle size of 100-150nm and a mass ratio of 70:30; the organic carrier consists of ethyl cellulose, terpineol, and acrylic leveling agent in a mass ratio of 5:15:3. Ethyl cellulose was added to terpineol, heated to 90°C, and stirred at 1000 rpm for 4 hours to obtain a dispersion. Silver powder, silver-coated nickel powder, fourth glass powder, silver oxide powder, acetylene black powder, and acrylic leveling agent were added to the dispersion and stirred evenly. Then, the mixture was ground to obtain a second silver-nickel paste with a fineness of <10 μm.

[0055] (6) Preparation of silver paste layer: On the second silicon nitride layer, a first silver paste is printed at the position corresponding to the N-type doped region to form a first silver paste layer, and a second silver paste is printed at the position corresponding to the P-type doped region to form a second silver paste layer. Then, the layers are baked in an oven at 200°C for 2 minutes to form a silver paste layer consisting of a first silver paste layer (thickness of 1.5 μm) and a second silver paste layer (thickness of 1.5 μm).

[0056] (7) Preparation of silver-nickel paste layer: A first silver-nickel paste is printed on the surface of the first silver paste layer to form a first silver-nickel paste layer, and a second silver-nickel paste is printed on the surface of the second silver paste layer to form a second silver-nickel paste layer. Then, the layers are baked in an oven at 180°C for 2 minutes, so that the first silver-nickel paste layer (thickness of 20 μm) and the second silver-nickel paste layer (thickness of 20 μm) together constitute a silver-nickel paste layer stacked on the silver paste layer.

[0057] (8) Sintering: The silicon wafer is transferred to a sintering furnace and heated to 800°C, where it is held for 20 seconds. During this process, the glass powder in the two slurry layers softens sequentially and works together to etch through the second silicon nitride layer and the alumina layer. At the same time, silver and silver-coated nickel particles are sintered, ultimately forming a composite electrode. After cooling, a solar cell is obtained.

[0058] Example 2 This embodiment provides a method for preparing a solar cell, which differs from Embodiment 1 in that the paste does not contain the corresponding additives: Step (2) Preparation of the first silver paste: Without adding the first additive, weigh an appropriate amount of silver powder with a mass ratio of 85:5:10 (D50=1.5μm, tap density=4.5m). 2 / g), first glass powder and organic carrier; Step (3) Preparation of the second silver paste: Without adding a second additive, weigh an appropriate amount of silver powder with a mass ratio of 85:5:10 (D50=1.5μm, tap density=4.5m). 2 / g), second glass powder and organic carrier; Step (4) Preparation of the first silver-nickel paste: Without adding a third additive, weigh an appropriate amount of silver powder (D50=1.5μm, tap density=4.5m) in a mass ratio of 15∶65∶7∶13. 2 / g), silver-coated nickel powder (D50=3μm, tap density=2.5m) 2 / g, silver content of 20wt%), third glass powder and organic carrier; Step (5) Preparation of the second silver-nickel paste: Without adding the fourth additive, weigh an appropriate amount of silver powder (D50=1.5μm, tap density=4.5m) in a mass ratio of 15∶65∶7∶13. 2 / g), silver-coated nickel powder (D50=3μm, tap density=2.5m) 2 / g, silver content 20wt%), fourth glass powder and organic carrier.

[0059] Example 3 This embodiment provides a method for preparing a solar cell, which differs from Embodiment 1 in the adjustment of the glass powder: In step (4), the first silver-nickel paste is replaced with the "third glass powder"; In step (5), the second silver-nickel paste replaces the "fourth glass powder" with the "second glass powder".

[0060] Comparative Example 1 This comparative example provides a method for preparing a solar cell, comprising the following steps: (1) A solar cell precursor is prepared using existing technology, which includes an N-type silicon wafer, a silicon nitride layer (thickness of 80 nm) formed on the front side of the N-type silicon wafer, and a silicon oxide layer (thickness of 1.5 nm), a carrier transport layer, an aluminum oxide layer (thickness of 3 nm), and a silicon nitride layer (thickness of 80 nm, without laser aperture) formed sequentially on the back side of the N-type silicon wafer. The carrier transport layer is composed of alternating N-type doped regions and P-type doped regions, with a blank area separating adjacent N-type doped regions and P-type doped regions. The P-type doped region is a polycrystalline silicon layer doped with B (thickness of 200 nm), and the N-type doped region is a polycrystalline silicon layer doped with P (thickness of 150 nm).

[0061] (2) A laser with a power of 50W and a frequency of 100Hz is used to open holes in the alumina layer and silicon nitride layer on the carrier transport layer to form a single slot with a width of 40μm, a depth of 100nm, and a spacing of 1.0mm.

[0062] (3) Preparation of the first silver paste: Weigh appropriate amounts of PbO powder, TeO2 powder, Bi2O3 powder, SiO2 powder, WO3 powder, ZnO powder, Li2O powder, Na2O powder, MgO powder, and Nb2O5 powder in a mass ratio of 30:35:10:5:6:4:1:3:2:4, mix them, and place them in an alumina crucible. Then place the crucible in a melting furnace and hold it at 1200℃ for 60 minutes to form a glass melt. Pour the glass melt into deionized water for quenching, and then dry and pulverize it to obtain the first glass powder with a softening point of 350℃. Weigh out an appropriate amount of silver powder with a mass ratio of 85:5:0.5:9.5 (D50=1.5μm, tap density=4.5m). 2 / g), first glass powder, first additive and organic carrier; wherein, the first additive is a mixed oxide powder of Al2O3, SiO2 and ZrO2 (D50=60nm); the organic carrier is composed of ethyl cellulose, terpineol and acrylic leveling agent in a mass ratio of 5:15:3; Ethyl cellulose was added to terpineol, heated to 90°C, and stirred at 1000 rpm for 4 hours to obtain a dispersion. Silver powder, first glass powder, mixed oxide powder and acrylic leveling agent were added to the dispersion and stirred evenly. Then, the mixture was ground to obtain a first silver paste with a fineness of <10 μm.

[0063] (4) Print the first silver paste in the laser-drilled area and then bake it in the oven at 200°C for 2 minutes to form a silver seed layer with a thickness of 1.5 μm.

[0064] (5) Continue printing the first silver paste on the seed layer, and then bake in the oven at 180°C for 2 min to form a silver metal layer with a thickness of 20 μm.

[0065] (8) The silicon wafer with the first silver paste printed is transferred to the sintering furnace, heated to 800°C, held for 20 seconds to form electrodes, and then cooled to obtain a solar cell.

[0066] Relevant performance test analysis: The solar cells prepared in Examples 1-3 and Comparative Example 1 were subjected to relevant performance tests, and the test results are shown in the table below: Table 1 As shown in Table 1, the solar cell prepared in Example 1 has the highest open-circuit voltage, fill factor, and short-circuit current density, with a final conversion efficiency of 24.83%. This is mainly due to the design of its slurry composition and the optimization of the electrode structure: the first additive (nano-Al2O3-SiO2-ZrO2 mixed oxide powder) optimizes the metal (Ag)-semiconductor (Si) interface structure and reduces carrier recombination; the second additive (silver salt powder) alleviates the carrier transport barrier caused by the work function mismatch between the metal (Ag) and the semiconductor (Si), while the in-situ generated nano-silver nuclei help to form a denser electrode to reduce contact resistance; the third and fourth additives (nano-silver oxide powder and acetylene black powder) induce the formation of a continuous metal bridging structure between silver-coated nickel particles, improving the conductivity of the electrode; the first Through a gradient design of softening points, the glass powder, second glass powder, third glass powder, and fourth glass powder enable the lower silver paste to etch the alumina layer and silicon nitride layer first, while the upper silver-nickel paste gradually dissolves into the silver paste. This slows down the etching rate of the alumina layer and silicon nitride layer by the glass powder at high temperatures, improves the contact between the metal (Ag) and the semiconductor (Si), reduces the series resistance, and reduces metal-induced recombination. Therefore, under the synergistic effect of the first additive, second additive, third additive, fourth additive, first glass powder, second glass powder, third glass powder, and fourth glass powder, the open-circuit voltage, fill factor, short-circuit current density, and battery conversion efficiency of the battery are significantly improved.

[0067] In Example 2, the performance indicators decreased significantly after the removal of the additives, indicating that the additives are crucial for optimizing the interface structure, mitigating the difference in work function between the metal (Ag) and semiconductor (Si) layers, reducing recombination losses, and improving electrode conductivity.

[0068] In Example 3, after adjusting the glass powder (without gradient design of the glass powder softening point), all performance indicators decreased, indicating that the design of the glass powder softening point plays a key role in the contact between the metal (Ag) and the semiconductor (Si), reducing series resistance, and reducing metal-induced recombination.

[0069] Comparative Example 1 uses laser-based aperture opening, with a conversion efficiency of 19.7%. The main reason for this is likely that the laser causes damage to the silicon wafer, increasing surface recombination centers and leading to a significant reduction in short-circuit current and fill factor. In contrast, Example 1 uses glass powder in the slurry to etch apertures and form electrodes in a single step, reducing damage to the silicon wafer.

[0070] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a solar cell, characterized in that, Includes the following steps: A solar cell precursor is provided; the solar cell precursor includes a silicon substrate, a first passivation layer formed on the front side of the silicon substrate, and a passivation contact layer, a carrier transport layer, and a second passivation layer sequentially formed on the back side of the silicon substrate; the carrier transport layer includes alternating N-type doped regions and P-type doped regions, with a blank area separating adjacent N-type doped regions and P-type doped regions. A first silver paste is printed on the second passivation layer corresponding to the N-type doped region, and a second silver paste is printed on the second passivation layer corresponding to the P-type doped region. Then, a first drying process is performed to form a silver paste layer. A first silver-nickel paste is printed on the silver paste layer corresponding to the N-type doped region, and a second silver-nickel paste is printed on the silver paste layer corresponding to the P-type doped region. Then a second drying process is performed to form a silver-nickel paste layer stacked with the silver paste layer. The silver paste layer and the silver-nickel paste layer are sintered to obtain a solar cell.

2. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The thickness of the silver paste layer is 0.1~2μm; The thickness of the silver-nickel paste layer is 5~30μm; The temperature for the first drying treatment and the second drying treatment is 100~250℃, and the time is 0.1~5min; The sintering process is carried out at a temperature of 700-800℃ for 10-60 seconds.

3. The preparation method according to claim 1, characterized in that, At least one of the following conditions must be met: The first passivation layer is a silicon nitride layer; The passivation contact layer is a silicon oxide layer; The P-type doped region is a polycrystalline silicon layer doped with B, and the N-type doped region is a polycrystalline silicon layer doped with P; The second passivation layer consists of a stacked aluminum oxide layer and a silicon nitride layer.

4. The preparation method according to claim 3, characterized in that, At least one of the following conditions must be met: The thickness of the silicon nitride layer is 70~90nm; The thickness of the silicon oxide layer is 1.0~2.0 nm; The thickness of the B-doped polycrystalline silicon layer is 180~220 nm; The thickness of the P-doped polycrystalline silicon layer is 130~170 nm; The thickness of the alumina layer is 2.5~3.5 nm.

5. The preparation method according to any one of claims 1 to 4, characterized in that, At least one of the following conditions must be met: The first silver paste comprises silver powder, first glass powder, first additive and organic carrier in a mass ratio of (80~90):(1~10):(0.05~1.0):(5~15), and the softening point of the first glass powder is 300~450℃. The second silver paste comprises silver powder, second glass powder, second additive and organic carrier in a mass ratio of (80~90):(1~10):(0.05~1.5):(5~15), and the softening point of the second glass powder is 350~500℃; The first silver-nickel paste comprises silver powder, nickel-containing metal powder, third glass powder, third additive, and organic carrier in a mass ratio of (5~50):(50~85):(1~10):(0.05~5.0):(5~15), wherein the softening point of the third glass powder is 350~550℃. The second silver-nickel paste comprises silver powder, nickel-containing metal powder, fourth glass powder, fourth additive, and organic carrier in a mass ratio of (5~50):(50~85):(1~10):(0.05~5.0):(5~15), wherein the softening point of the fourth glass powder is 380~600℃.

6. The preparation method according to claim 5, characterized in that, At least one of the following conditions must be met: The first additive is selected from mixed oxide powder with a particle size of 10~100nm, which is obtained by ball milling Al2O3 powder, SiO2 powder and ZrO2 powder; The second additive is selected from silver salt powder with a particle size of less than 100 nm. The silver salt powder includes Ag2SO4 powder, Ag2CO4 powder and AgNO3 powder in a mass ratio of (20~50):(0~30):(50~80). The third and fourth additives are both selected from silver oxide powder and acetylene black powder with a particle size of 50~200nm, and the mass ratio of silver oxide powder to acetylene black powder is (50~80):(20~50).

7. The preparation method according to claim 5, characterized in that, At least one of the following conditions must be met: The first glass powder comprises PbO, TeO2, Bi2O3, SiO2, WO3, ZnO, alkali metal oxides, and a first modified oxide in a mass ratio of (10~50):(10~60):(5~30):(0.5~10):(0.5~20):(0.5~10):(1~10):(0~30); the alkali metal oxide is selected from at least one of Li2O, Na2O, and K2O, and the first modified oxide is selected from at least one of Fe2O3, Al2O3, Ga2O3, Ag2O, CuO, MoO3, V2O5, CeO2, Y2O5, MgO, Nb2O5, and La2O3; The second glass powder comprises Bi2O3, B2O3, SiO2, ZnO, Al2O3 and a second modified oxide in a mass ratio of (10~80):(5~30):(1~20):(2~20):(0.5~6):(0.5~10), wherein the second modified oxide is selected from at least one of CaO, BaO, Li2O, Na2O, K2O, TiO2, V2O5, ZrO, Nb2O5, Y2O5, GeO2, Ga2O3, Sb2O3 and CeO2; The third glass powder comprises PbO, TeO2, Bi2O3, SiO2, WO3, ZnO, alkali metal oxides, and a third modified oxide in a mass ratio of (5~40):(5~50):(5~25):(5~35):(5~25):(1~15):(0.5~8):(1~25); the alkali metal oxide is selected from at least one of Li2O, Na2O, and K2O, and the third modified oxide is selected from at least one of Fe2O3, Al2O3, Ga2O3, Ag2O, CuO, MoO3, V2O5, CeO2, Y2O5, MgO, Nb2O5, and La2O3; The fourth glass powder comprises PbO, B2O3, SiO2, ZnO, Al2O3 and a fourth modified oxide in a mass ratio of (5~70):(10~35):(5~25):(3~25):(1~8):(0.5~12), wherein the fourth modified oxide is selected from at least one of Bi2O3, CaO, BaO, Li2O, Na2O, K2O, TiO2, V2O5, ZrO, Nb2O5, Y2O5, GeO2, Ga2O3, Sb2O3 and CeO2.

8. The preparation method according to claim 5, characterized in that, At least one of the following conditions must be met: The silver powder has a particle size of 1.0~2.0μm and a tap density >4m³. 2 / g; The nickel-containing metal powder has a particle size of 1.0~5.0μm and a tap density >2m³. 2 / g; The nickel-containing metal powder includes silver-coated nickel powder or nickel powder, wherein the silver content in the silver-coated nickel powder is 5-50 wt%; The organic carrier comprises resin, solvent, and organic additives in a mass ratio of (0.5~10):(2~30):(0.1~5).

9. A solar cell, characterized in that, The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 8.

10. A photovoltaic module, characterized in that, The solar cell includes at least one solar cell prepared by the method for preparing a solar cell as described in any one of claims 1 to 8.

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