Silicon-based heterojunction cell and preparation method therefor, and photovoltaic module

Abstract

The present application relates to the technical field of optoelectronic devices, and particularly relates to a silicon-based heterojunction cell and a preparation method therefor, and a photovoltaic module. The preparation method for a silicon-based heterojunction cell in the present application comprises the following steps: providing a cell substrate, wherein in the direction of thickness of the cell substrate, the cell substrate comprises a first surface and a second surface that are arranged opposite each other; respectively forming a first transparent conductive layer and a second transparent conductive layer on the first surface and the second surface of the cell substrate; printing a silver-coated copper paste on the surface of the side of the first transparent conductive layer that faces away from the cell substrate, so as to prepare a first electrode layer; and performing light-induced electroplating of copper on the surface of the side of the second transparent conductive layer that faces away from the cell substrate, so as to prepare a second electrode layer. By means of the preparation method for a silicon-based heterojunction cell provided in the present application, the content of silver in an electrode layer can be effectively reduced, and a copper electrode layer, which is tightly bonded to a transparent conductive layer, can be prepared by means of light-induced electroplating of copper without a copper seed layer; thus, the method has the advantage of being a simple process.

Description

Silicon-based heterojunction solar cells and their fabrication methods, photovoltaic modules Technical Field

[0001] This application relates to the field of optoelectronic device technology, specifically to crystalline silicon solar cells and their fabrication methods, and photovoltaic modules. Background Technology

[0002] Solar energy resources are abundant, renewable, and clean. Currently, solar energy is utilized in various ways, including light-to-thermal conversion, light-to-electricity conversion, and light-to-chemical energy conversion. Among these, solar cells are an important example of light-to-electricity conversion.

[0003] Solar cells are primarily silicon-based heterojunction solar cells. Silicon-based heterojunction cells are fabricated by sequentially depositing an amorphous silicon thin film, an N-type doped layer, and a transparent conductive layer on the front side of a crystalline silicon cell, and then sequentially depositing an amorphous silicon thin film, a P-type doped layer, and a transparent conductive layer on the back side. Metal grid lines are then printed to complete the cell fabrication. Currently, industrial production generally uses silver paste screen printing to prepare the metal grid lines. Although screen printing has advantages such as mature technology, simple steps, diverse patterns, and high production volume, silver, the main material used in screen printing, is expensive and accounts for a relatively high proportion of the cost of solar cells.

[0004] To reduce the use of silver grid electrodes, a common method is to electroplate copper onto the surface of a transparent conductive layer. However, the adhesion between the transparent conductive layer and copper is weak, so a seed copper layer needs to be prepared beforehand to ensure effective copper electroplating. After electroplating, the seed copper layer outside the grid area needs to be removed, requiring additional etching steps, which is a cumbersome process. Furthermore, current research has found that the preparation of the seed copper layer can lead to a decrease in the cell's transmittance, thus affecting the cell's photoelectric performance. Summary of the Invention

[0005] Based on this, this application provides a silicon-based heterojunction solar cell, its fabrication method, and a photovoltaic module. The fabrication method of the silicon-based heterojunction solar cell provided in this application can effectively reduce the silver content in the electrode layer, and can prepare a copper electrode layer tightly bonded to the transparent conductive layer without a seed copper layer by photo-induced copper electroplating, which has the advantage of simple process.

[0006] A first aspect of this application provides a method for fabricating a silicon-based heterojunction solar cell, comprising the following steps:

[0007] A battery substrate is provided; along the thickness direction of the battery substrate, the battery substrate includes a first surface and a second surface disposed opposite to each other;

[0008] A first transparent conductive layer and a second transparent conductive layer are formed on the first and second surfaces of the battery substrate, respectively.

[0009] A first electrode layer is prepared by printing silver-coated copper paste on the surface of the first transparent conductive layer that is away from the battery substrate.

[0010] A second electrode layer is prepared by photo-induced electroplating of copper on the side of the second transparent conductive layer opposite to the battery substrate.

[0011] In one embodiment, the step of preparing the second electrode layer by photo-induced copper plating on the side of the second transparent conductive layer opposite to the battery substrate includes:

[0012] A mask layer is prepared on the side surface of the second transparent conductive layer facing away from the battery substrate; wherein, the side surface of the second transparent conductive layer facing away from the battery substrate includes a preset electrode pattern area and a non-preset electrode pattern area, and the mask layer is located in the non-preset electrode pattern area;

[0013] The second transparent conductive layer containing the mask layer is chemically treated to form a metal-rich doped layer on the surface of the preset electrode pattern area of ​​the second transparent conductive layer.

[0014] The second electrode layer is prepared by photo-induced electroplating of copper on the surface of the metal-rich doped layer.

[0015] In one embodiment, in the step of chemically treating the second transparent conductive layer containing the mask layer, the processing solution used in the chemical treatment includes an etchant, an oxidant, a metal salt, and a buffer; the processing solution has one or more of the following characteristics:

[0016] (1) The molar concentration of the etchant in the treatment solution is 0.2 mol / L to 1.5 mol / L;

[0017] (2) The molar concentration of the oxidant in the treatment solution is 0.3 mol / L to 1.2 mol / L;

[0018] (3) The molar concentration of the metal salt in the treatment solution is 0.2 mol / L to 0.8 mol / L;

[0019] (4) The molar concentration of the buffer in the treatment solution is 0.01 mol / L to 0.2 mol / L;

[0020] (5) The etchant includes one or more of HF and HCl;

[0021] (6) The oxidant includes one or more of H2O2 and HNO3;

[0022] (7) The metal salt includes one or more of InCl3, SnCl4, KI, CuI, ZnSO4 and CuSO4;

[0023] (8) The buffer includes one or more of NaH2PO4, CH3COONa and sodium citrate;

[0024] (9) The temperature of the chemical treatment is 20℃~50℃.

[0025] In one embodiment, the preparation method has one or more of the following features:

[0026] (1) The thickness of the metal-rich doped layer is 50 nm to 100 nm;

[0027] (2) The material of the second transparent conductive layer includes one or more of FTO, ITO, AZO, ATO and IGO;

[0028] (3) The thickness of the second transparent conductive layer is 200nm~5μm.

[0029] In one embodiment, the step of photo-induced copper plating on the surface of the metal-rich doped layer includes:

[0030] Under illumination, the second transparent conductive layer containing the metal-rich doped layer is electroplated in a copper-ion-containing electroplating solution.

[0031] Optionally, the wavelength range of the illumination is 200nm to 800nm.

[0032] In one embodiment, the mask layer is prepared by nanoimprinting;

[0033] Optionally, the nanoimprinting includes one or more of thermal nanoimprinting and ultraviolet nanoimprinting.

[0034] In one embodiment, the step of preparing a mask layer on the surface of the second transparent conductive layer opposite to the battery substrate includes:

[0035] A thermoplastic film layer is formed on the surface of the second transparent conductive layer facing away from the battery substrate; wherein the thermoplastic film layer comprises a thermoplastic material; the thermoplastic film layer is subjected to a heat treatment; wherein the temperature of the heat treatment is greater than or equal to the glass transition temperature of the thermoplastic material; a non-preset electrode pattern area of ​​the second transparent conductive layer containing the thermoplastic film layer is hot-pressed, and then the thermoplastic film layer in the non-preset electrode pattern area is cured to prepare the mask layer;

[0036] Alternatively, a photocurable polymer material is coated on the surface of the second transparent conductive layer facing away from the battery substrate; the non-preset electrode pattern area of ​​the second transparent conductive layer coated with the photocurable polymer material is subjected to ultraviolet light irradiation treatment to cure the photocurable polymer material in the non-preset electrode pattern area, thereby preparing the mask layer.

[0037] In one embodiment, the preparation method has one or more of the following features:

[0038] (1) The thermoplastic material includes one or more of polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyetheretherketone and polyphenylene sulfide;

[0039] (2) The photocurable polymer material includes polyurethane acrylate.

[0040] In one embodiment, after the step of preparing the second electrode layer, the method further includes:

[0041] A tin protective layer is prepared by performing a tin-removing treatment on the surface of the second electrode layer.

[0042] In one embodiment, the silver-coated copper paste comprises silver with a mass fraction of ≤30%;

[0043] And / or, the material of the first transparent conductive layer includes one or more of FTO, ITO, AZO, ATO, and IGO;

[0044] And / or, the thickness of the first transparent conductive layer is 200 nm to 5 μm.

[0045] In one embodiment, the battery substrate includes an N-type doped layer, a silicon substrate, and a P-type doped layer stacked sequentially.

[0046] Wherein, the first surface is the surface of the P-type doped layer that is far from the N-type doped layer, and the second surface is the surface of the N-type doped layer that is far from the P-type doped layer.

[0047] In one embodiment, the battery substrate further includes a first amorphous silicon intrinsic layer, which is disposed between the silicon substrate and the P-type doped layer;

[0048] And / or, the battery substrate further includes a second amorphous silicon intrinsic layer, which is disposed between the silicon substrate and the N-type doped layer.

[0049] A second aspect of this application provides a silicon-based heterojunction solar cell, prepared by the fabrication method described in any embodiment of the first aspect of this application; the silicon-based heterojunction solar cell comprises:

[0050] A battery substrate; along the thickness direction of the battery substrate, the battery substrate includes a first surface and a second surface disposed opposite to each other;

[0051] A first transparent conductive layer; the first transparent conductive layer is disposed on the first surface of the battery substrate;

[0052] A second transparent conductive layer; the second transparent conductive layer is disposed on the second surface of the battery substrate;

[0053] A first electrode layer is disposed on the surface of the first transparent conductive layer that is away from the battery substrate;

[0054] The second electrode layer is disposed on the side surface of the second transparent conductive layer that is away from the battery substrate;

[0055] The first electrode layer is a silver-coated copper electrode layer; the second electrode layer is a copper electrode layer.

[0056] In one embodiment, the battery substrate includes an N-type doped layer, a second amorphous silicon intrinsic layer, a silicon substrate, a first amorphous silicon intrinsic layer, and a P-type doped layer stacked sequentially.

[0057] Wherein, the first surface is the surface of the P-type doped layer that is far from the N-type doped layer, and the second surface is the surface of the N-type doped layer that is far from the P-type doped layer.

[0058] A third aspect of this application provides a photovoltaic module, including a silicon-based heterojunction cell prepared by the preparation method described in any embodiment of the first aspect of this application.

[0059] The method for fabricating silicon-based heterojunction solar cells provided in this application has at least the following beneficial effects:

[0060] The preparation method provided in this application involves preparing the first electrode layer by printing silver-coated copper paste. This method combines the high conductivity of silver with the economic efficiency of copper, effectively ensuring the conductivity of the first electrode layer while reducing the use of precious silver and lowering the manufacturing cost of the battery. The second electrode layer is further prepared by photo-induced copper electroplating. This method helps ensure the interfacial bonding between the copper and the second transparent conductive layer, allowing for the preparation of a copper electrode tightly bonded to the transparent conductive layer without a seeded copper layer. Simultaneously, the copper electrode layer exhibits good conductivity and thermal conductivity, and is cost-effective. Furthermore, the preparation processes for the first and second electrode layers in this application are highly compatible with other preparation processes for silicon-based heterojunction batteries, enabling efficient preparation of the first and second electrode layers without affecting other battery structures and performance characteristics, which is beneficial for large-scale industrial production. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 is a process flow diagram of preparing an electrode layer by electroplating copper on the surface of a transparent conductive layer in the traditional technique.

[0063] Figure 2 is a schematic diagram of the structure of a battery substrate provided in an example of this application;

[0064] Figure 3 is a schematic diagram of the structure of a silicon-based heterojunction solar cell provided in an example of this application.

[0065] In the figure, battery substrate-1; silicon substrate-10; first amorphous silicon intrinsic layer-20; P-type doped layer-30; second amorphous silicon intrinsic layer-40; N-type doped layer-50; first surface-A; second surface-B; first transparent conductive layer-60; second transparent conductive layer-70; first electrode layer-80; second electrode layer-90. Detailed Implementation

[0066] The following detailed description, in conjunction with specific embodiments, provides a more complete and clear account of the silicon-based heterojunction solar cell, its fabrication method, and photovoltaic module of this application. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0067] Referring to Figure 1, in conventional techniques, the steps for preparing an electrode layer by electroplating copper on the surface of a transparent conductive layer generally include: taking a battery substrate, the surface of which includes two transparent conductive layers arranged opposite each other; (1) preparing a seed copper layer by physical vapor deposition (PVD) sputtering on the surface of the two transparent conductive layers; (2) then patterning to prepare a mask layer; (3) electroplating to prepare a copper electrode layer in the area without a mask layer; (4) removing the mask layer; (5) etching to remove the seed copper layer covering the mask layer; and (6) tinning on the surface of the copper electrode layer to prepare a protective layer for the copper electrode layer. The main disadvantages of the above conventional techniques include: (1) PVD sputtering will damage the transparent conductive layer, which will lead to a loss of battery efficiency; (2) the steps are complicated, such as the seed copper layer covering the mask layer, i.e., the excess seed copper layer outside the grid line area of ​​the copper electrode, which needs to be removed.

[0068] Based on this, the first aspect of this application provides a method for fabricating a silicon-based heterojunction solar cell, comprising the following steps:

[0069] S10: Provide a battery substrate; along the thickness direction of the battery substrate, the battery substrate includes a first surface and a second surface disposed opposite to each other.

[0070] S20: A first transparent conductive layer and a second transparent conductive layer are formed on the first and second surfaces of the battery substrate, respectively.

[0071] S30: Print silver-coated copper paste on the surface of the first transparent conductive layer away from the battery substrate to prepare the first electrode layer.

[0072] S40: Photo-induced copper plating is performed on the side of the second transparent conductive layer opposite to the battery substrate to prepare the second electrode layer.

[0073] The preparation method provided in this application involves preparing the first electrode layer by printing silver-coated copper paste. This method combines the high conductivity of silver with the economic efficiency of copper, effectively ensuring the conductivity of the first electrode layer while reducing the use of precious silver and lowering the manufacturing cost of the battery. The second electrode layer is further prepared by photo-induced copper electroplating. This method facilitates the interfacial bonding between the copper and the second transparent conductive layer, enabling the preparation of a copper electrode without a seeded copper layer. Simultaneously, the copper electrode layer exhibits good conductivity and thermal conductivity, and is cost-effective.

[0074] Furthermore, traditional electroplating methods require the use of electroplating clamps, meaning that during the electroplating process, the clamps on the electroplating fixture must be precisely aligned with specific positions on the area to be electroplated. This electroplating method is difficult to automate and hinders mass production; moreover, additional clamps need to be provided for alignment during patterning, making the operation cumbersome. This application uses photo-induced copper electroplating to prepare copper grid electrodes, which mainly relies on light energy to excite a chemical reaction: under light irradiation, photon energy is absorbed, causing electron transitions and generating electron-hole pairs, thereby creating a potential difference in the battery substrate. This potential difference can serve as a driving force to promote the electroplating reaction. Therefore, the preparation method provided in this application also has the advantage of not requiring clamp alignment, which also helps to shorten the preparation steps and reduce preparation costs.

[0075] Furthermore, the fabrication processes of the first and second electrode layers in this application are highly compatible with other fabrication processes of silicon-based heterojunction solar cells. They enable efficient fabrication of the first and second electrode layers without affecting other structures and performance of the cell, which is beneficial for large-scale industrial production.

[0076] In one example, before steps S30 and S40, the process includes annealing and photo-injection of the first and second transparent conductive layers, respectively. That is, before the fabrication of the first and second electrode layers, annealing and photo-injection steps are performed independently. This eliminates internal stress in the battery, activates material properties, and thus improves battery performance.

[0077] In one example, step S40: photo-induced copper plating on the side of the second transparent conductive layer opposite to the battery substrate to prepare the second electrode layer includes:

[0078] S410: A mask layer is prepared on the side surface of the second transparent conductive layer facing away from the battery substrate; wherein the side surface of the second transparent conductive layer facing away from the battery substrate includes a preset electrode pattern area and a non-preset electrode pattern area, and the mask layer is located in the non-preset electrode pattern area.

[0079] S420: The second transparent conductive layer containing the mask layer is chemically treated to form a metal-rich doped layer on the surface of the preset electrode pattern area of ​​the second transparent conductive layer.

[0080] S430: Photo-induced copper plating is performed on the surface of the metal-rich doped layer to prepare the second electrode layer.

[0081] This application chemically treats the second transparent conductive layer to create a metal-rich doped region on the surface of the pre-defined electrode pattern area. This region provides a good substrate for copper electroplating, effectively increasing the adhesion between the copper plating layer and the transparent conductive layer, thus preventing detachment. Furthermore, directly electroplating copper on the metal-rich doped region simplifies the process, reduces the need for additional steps in preparing and removing the seed copper layer, thereby improving production efficiency and reducing production costs.

[0082] In one example, in step S420, the chemical treatment of the second transparent conductive layer containing the mask layer, the treatment solution used in the chemical treatment includes an etchant, an oxidant, a metal salt, and a buffer.

[0083] In one example, the molar concentration of the etchant in the treatment solution is 0.2 mol / L to 1.5 mol / L. For example, the molar concentration of the etchant includes, but is not limited to, 0.3 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, or any two of the above values ​​as endpoints.

[0084] In one example, the molar concentration of the oxidant in the treatment solution is 0.3 mol / L to 1.2 mol / L. For example, the molar concentration of the oxidant includes, but is not limited to, 0.4 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, or any two of the above values ​​as endpoints.

[0085] In one example, the molar concentration of the metal salt in the treatment solution is 0.2 mol / L to 0.8 mol / L. For example, the molar concentration of the metal salt includes, but is not limited to, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, or any two of the above values ​​as endpoints.

[0086] In one example, the molar concentration of the buffer in the treatment solution is 0.01 mol / L to 0.2 mol / L. For example, the molar concentration of the buffer includes, but is not limited to, 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, or any two of the above values ​​as endpoints.

[0087] In one example, the etchant includes one or more of HF and HCl.

[0088] In one example, the oxidant includes one or more of H2O2 and HNO3.

[0089] In one example, the metal salt includes one or more of InCl3, SnCl4, KI, CuI, ZnSO4, and CuSO4.

[0090] In one example, the buffer includes one or more of NaH2PO4, CH3COONa, and sodium citrate.

[0091] In one example, the temperature of the chemical treatment is 20°C to 50°C. For example, the temperature of the chemical treatment includes, but is not limited to, 20°C, 22°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 48°C, 50°C, or any two of the above point values ​​as endpoints.

[0092] The material of the transparent conductive layer is generally a metal oxide. In this application, the surface of the second transparent conductive layer is chemically treated. At this time, the metal on the surface of the second transparent conductive layer without the mask layer, that is, the area of ​​the preset electrode pattern, is reduced. Therefore, a metal-rich doped layer is formed on the surface of the preset electrode pattern area. This metal-rich doped layer can serve as a seed layer for copper electroplating deposition, making it easier for the copper electroplating layer to grow.

[0093] For example, the material of the second transparent conductive layer includes one or more of FTO, ITO, AZO, ATO, and IGO. The aforementioned material of the second transparent conductive layer has high transmittance and, after chemical treatment, can effectively form a metal-rich doped layer.

[0094] In one example, the thickness of the metal-rich doped layer is 50 nm to 100 nm. Understandably, in this application, the metal-rich doped layer is formed on the surface of a predetermined electrode pattern region. At this time, the metal concentration of the metal-rich doped layer is higher than the metal concentration in the non-predetermined electrode pattern region of the surface area of ​​the second transparent conductive layer. Furthermore, the thickness of the chemically treated metal-rich doped layer is selected from the above range, which provides sufficient charge carriers to ensure its adhesion to the electroplated copper layer while maintaining the transparency of the second transparent conductive layer, preventing reduced transparency from affecting battery performance. For example, the thickness of the metal-rich doped layer includes, but is not limited to, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, or any two of the above values ​​as endpoints.

[0095] Understandably, the thickness of the metal-rich doped layer is less than the thickness of the second transparent conductive layer. In one example, the thickness of the second transparent conductive layer is 200 nm to 5 μm. The thickness of the second transparent conductive layer is selected within the above range to ensure good conductivity while providing a suitable substrate for chemical processing to form the metal-rich doped layer. For example, the thickness of the second transparent conductive layer includes, but is not limited to, 200 nm, 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, or any two of the above values ​​as endpoints.

[0096] In one example, step S430, the step of photo-induced copper plating on the surface of the metal-rich doped layer, includes:

[0097] Under illumination, the second transparent conductive layer containing the metal-rich doped layer is electroplated in a copper-ion-containing electroplating solution.

[0098] Electroplating under illumination enables high-precision copper deposition, allowing for precise control of the copper layer's thickness and shape, making it suitable for manufacturing micro-scale grid electrodes. This application reveals that under screen printing conditions, it is difficult to achieve grid linewidths within 20 μm. However, through the photo-induced electroplating process of this application, the grid linewidth can be reduced to within 10 μm, which has a significant effect on improving the battery's light-shielding performance. Simultaneously, compared to screen printing, this electroplating process effectively reduces contact resistance.

[0099] In one example, the wavelength range of the illumination is 200nm to 800nm. For example, the wavelength range of the illumination includes, but is not limited to, 200nm, 280nm, 300nm, 350nm, 400nm, 450nm, 480nm, 500nm, 600nm, 700nm, 800nm, or any two of the above values ​​as endpoints.

[0100] For example, copper ion plating solutions may include copper sulfate.

[0101] For example, the temperature of the copper ion electroplating solution is 40–65°C. For example, the temperature of the copper ion electroplating solution includes, but is not limited to, 40°C, 44°C, 48°C, 50°C, 55°C, 58°C, 60°C, 62°C, 65°C, or any two of the above values ​​as endpoints.

[0102] Cu in copper ion electroplating solution 2+ The mass concentration is 100 g / L to 150 g / L. For example, the Cu in the copper ion electroplating solution... 2+ The mass concentration includes, but is not limited to, 100 g / L, 110 g / L, 115 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, or any two of the above point values ​​as endpoints within the range.

[0103] For example, the cathode current density in photo-induced electroplating is 3 A / dm³. 2 ~8A / dm 2 For example, the cathode current density in photo-induced electroplating includes, but is not limited to, 3 A / dm². 2 3.5A / dm 2 3.8A / dm 2 4A / dm 2 4.5A / dm 2 4.8A / dm 2 5A / dm 2 5.2A / dm 2 5.5A / dm 2 6A / dm 2 7A / dm 2 8A / dm2 , or the range formed by any two of the above point values ​​as endpoint values.

[0104] In one example, the step of preparing the second electrode layer by photo-induced copper electroplating follows the step of preparing the first electrode layer by printing silver-coated copper paste. Since the first electrode layer already has grid lines printed on it, the battery substrate and other components exhibit good conductivity. When copper is electroplated onto the surface of the second transparent conductive layer, Cu deposition can occur relatively easily. 2+ +2e — =The reaction of Cu can reduce the difficulty of electroplating.

[0105] In one example, the mask layer is prepared by nanoimprinting.

[0106] In one example, the nanoimprint includes one or more of thermal nanoimprinting and ultraviolet nanoimprinting.

[0107] In one example, the step of fabricating a mask layer on the surface of the second transparent conductive layer facing away from the battery substrate includes:

[0108] a1. A thermoplastic film layer is formed on the surface of the second transparent conductive layer facing away from the battery substrate; wherein the thermoplastic film layer comprises a thermoplastic material.

[0109] a2. The thermoplastic film layer is subjected to heat treatment; wherein the temperature of the heat treatment is ≥ the glass transition temperature of the thermoplastic material.

[0110] a3. Perform hot embossing on the non-preset electrode pattern area of ​​the second transparent conductive layer containing the thermoplastic film layer, and then cure the thermoplastic film layer in the non-preset electrode pattern area to prepare the mask layer.

[0111] Understandably, this example provides the steps of thermal nanoimprinting. After heating the thermoplastic film layer, its fluidity increases. Then, thermal imprinting is performed on areas without a pre-defined electrode pattern. At this point, the thermoplastic film layer can be used for high-precision molding of these areas and will make close contact with them, achieving good bonding with the second transparent conductive layer. Furthermore, nanoimprinting facilitates the fabrication of triangular grid lines, which positively impacts reducing light-blocking area, improving light capture efficiency, and enhancing current transmission performance.

[0112] In one example, the thermoplastic material includes one or more of polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyetheretherketone, and polyphenylene sulfide. These thermoplastic materials are less expensive than inks or photoresists, effectively reducing the production cost of nanoimprinting and improving economic efficiency.

[0113] In another example, the step of fabricating a mask layer on the surface of the second transparent conductive layer facing away from the battery substrate includes:

[0114] b1. Coat the surface of the second transparent conductive layer on the side opposite to the battery substrate with a photocurable polymer material;

[0115] b2. The non-preset electrode pattern area coated with the second transparent conductive layer of the photocurable polymer material is subjected to ultraviolet light irradiation treatment to cure the photocurable polymer material in the non-preset electrode pattern area, thereby preparing the mask layer.

[0116] Understandably, this example provides the steps for ultraviolet (UV) nanoimprinting. Under UV irradiation, photocurable polymer materials can cure rapidly, thereby improving the efficiency of mask layer fabrication and making it suitable for large-scale production. UV nanoimprinting also has the advantages of high pattern precision, enabling accurate curing of areas with non-preset electrode patterns. Therefore, UV nanoimprinting can fabricate mask layers with high-precision patterns, which is beneficial for fabricating triangular grid lines, reducing the shading area, improving light capture efficiency, and enhancing current transport performance.

[0117] In one example, the photocurable polymer material includes polyurethane acrylate.

[0118] In one example, after the step of preparing the second electrode layer, the following is also included:

[0119] S50: Remove the mask layer from the non-preset electrode pattern area.

[0120] In one example, after the step of preparing the second electrode layer, the following is also included:

[0121] S60: Perform tin melting treatment on the surface of the second electrode layer to prepare a tin protective layer.

[0122] Understandably, the order of steps S50 and S60 is not limited. Preferably, step S50 is performed before step S60. Removing the mask layer at this time can prevent it from interfering with the operation in subsequent tinning processes.

[0123] Tinning is performed on the surface of the second electrode layer. At this time, a tin protective layer is generated on the surface of the copper electrode layer. This protective layer can isolate the air, prevent further oxidation of copper, and extend the battery's service life.

[0124] In one example, in step S30, the silver-coated copper paste contains a silver mass fraction of ≤30%. For example, the silver mass fraction includes, but is not limited to, 10%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any two of the above values ​​as endpoints.

[0125] In this application, the silver content in the silver-clad copper is relatively low, which effectively reduces the use of precious metals and helps save costs. Furthermore, copper has similar conductivity to silver, allowing both to effectively transfer charge in electrode applications and reduce energy loss.

[0126] In one example, the material of the first transparent conductive layer includes one or more of FTO, ITO, AZO, ATO, and IGO.

[0127] In one example, the thickness of the first transparent conductive layer is 200 nm to 5 μm.

[0128] Refer to Figure 2. In one example, the battery substrate includes an N-type doped layer 50, a silicon substrate 10, and a P-type doped layer 30 stacked sequentially.

[0129] Wherein, the first surface A is the surface of the P-type doped layer 30 that is away from the N-type doped layer 50, and the second surface B is the surface of the N-type doped layer 50 that is away from the P-type doped layer 30.

[0130] In one example, the battery substrate further includes a first amorphous silicon intrinsic layer 20 disposed between the silicon substrate 10 and the P-type doped layer 30.

[0131] In one example, the battery substrate further includes a second amorphous silicon intrinsic layer 40 disposed between the silicon substrate 10 and the N-type doped layer 50.

[0132] In one example, the battery substrate includes an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20, and a P-type doped layer 30 stacked sequentially.

[0133] Referring to Figure 3. A second aspect of this application provides a silicon-based heterojunction solar cell, prepared by the fabrication method described in any example of the first aspect of this application.

[0134] The silicon-based heterojunction solar cell includes:

[0135] Battery substrate 1; along the thickness direction of the battery substrate 1, the battery substrate 1 includes a first surface and a second surface disposed opposite to each other;

[0136] A first transparent conductive layer 60 is disposed on the first surface of the battery substrate 1.

[0137] Second transparent conductive layer 70; the second transparent conductive layer 70 is disposed on the second surface of the battery substrate 1;

[0138] The first electrode layer 80 is disposed on the side surface of the first transparent conductive layer 60 that is away from the battery substrate 1.

[0139] The second electrode layer 90 is disposed on the side surface of the second transparent conductive layer 70 that is away from the battery substrate 1.

[0140] The first electrode layer 80 is a silver-coated copper electrode layer; the second electrode layer 90 is a copper electrode layer.

[0141] In one example, the battery substrate 1 includes an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20, and a P-type doped layer 30, which are stacked sequentially. The first surface is the surface of the P-type doped layer away from the N-type doped layer, and the second surface is the surface of the N-type doped layer away from the P-type doped layer.

[0142] For example, the silicon-based heterojunction solar cell provided in this application includes a second electrode layer 90, a second transparent conductive layer 70, an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20, a P-type doped layer 30, a first transparent conductive layer 60, and a first electrode layer 80, which are stacked sequentially.

[0143] In one example, a tin protective layer is also provided on the side surface of the second electrode layer 90 facing away from the second transparent conductive layer 70.

[0144] A third aspect of this application provides a photovoltaic module, including a silicon-based heterojunction cell prepared by the preparation method described in any example of the first aspect of this application.

[0145] In one example, the photovoltaic module includes: a frame and a laminate disposed within the frame, with silicone filling the space between the laminate and the frame, and the laminate including a cover plate, a silicon-based heterojunction cell and a photovoltaic module backsheet stacked sequentially.

[0146] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0147] Example 1

[0148] Example 1 provides a silicon-based heterojunction solar cell and its preparation method.

[0149] Structure of silicon-based heterojunction solar cell: Refer to Figure 3. The silicon-based heterojunction solar cell includes a tin protective layer (not shown in the figure), a second electrode layer 90, a second transparent conductive layer 70, an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20, a P-type doped layer 30, a first transparent conductive layer 60, and a first electrode layer 80, which are stacked sequentially.

[0150] Methods for fabricating silicon-based heterojunction solar cells:

[0151] (1) Provide a battery substrate; the battery substrate 1 includes an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20 and a P-type doped layer 30 stacked sequentially.

[0152] (2) Preparation of the first transparent conductive layer and the second transparent conductive layer: A first transparent conductive layer 60 (ITO, with a thickness of about 300 nm) and a second transparent conductive layer 70 (ITO, with a thickness of about 300 nm) are prepared on the surface of the P-type doped layer 30 and the N-type doped layer 50, respectively.

[0153] (3) Printing silver-coated copper paste to prepare the first electrode layer: Silver-coated copper paste is screen-printed on the surface of the first transparent conductive layer 60 away from the P-type doped layer 30, and then dried to prepare the first electrode layer; in this step, the mass fraction of silver in the silver-coated copper included in the silver-coated copper paste is 28%.

[0154] (4) Nanoimprinting to prepare a mask layer: A thermoplastic thin film layer is formed on the surface of the second transparent conductive layer 70 away from the N-type doped layer 50; wherein, the thermoplastic thin film layer includes a thermoplastic material (polymethyl methacrylate); the thermoplastic thin film layer is heated to above the glass transition temperature of the thermoplastic material; hot imprinting is performed on the non-preset electrode pattern area of ​​the second transparent conductive layer containing the thermoplastic thin film layer, and the thermoplastic thin film layer in the non-preset electrode pattern area is cured to form a mask layer in the non-preset electrode pattern area.

[0155] (5) Chemical treatment of the second transparent conductive layer 70 containing the mask layer: The second transparent conductive layer 70 containing the mask layer is chemically treated at 30°C using a treatment solution, wherein the treatment solution includes HF with a molar concentration of 0.5 mol / L, HNO3 with a molar concentration of 1 mol / L, KI with a molar concentration of 0.5 mol / L, and CH3COONa with a molar concentration of 0.01 mol / L. At this time, a metal-rich doped layer (with a thickness of approximately 50 nm) is formed on the surface of the preset electrode pattern area of ​​the second transparent conductive layer 70.

[0156] (6) Photo-induced copper plating to prepare the second electrode layer 90: Under illumination (wavelength of 300 nm), the second transparent conductive layer containing a metal-rich doped layer is placed in a copper ion plating solution (temperature of the copper ion plating solution 50 °C, Cu in the copper ion plating solution). 2+ The mass concentration was 120 g / L, and the cathode current density for photo-induced electroplating was 5 A / dm³. 2 Electroplating is performed; a second electrode layer 90 is formed on the metal-rich doped layer.

[0157] (7) Remove the mask layer.

[0158] (8) Tinning: Tinning treatment is performed on the surface of the second electrode layer 90 to prepare a tin protective layer. At this time, silicon-based heterojunction cell A is prepared.

[0159] Example 2

[0160] Example 2 is basically the same as Example 1, the main difference being that step (4) of nanoimprinting to prepare the mask layer is different. Step (4) is as follows:

[0161] (4) Nanoimprinting to prepare a mask layer: Photocuring polymer material (polyurethane acrylate) on the side of the second transparent conductive layer 70 away from the N-type doped layer 50; UV irradiation treatment on the non-preset electrode pattern area of ​​the second transparent conductive layer coated with photocuring polymer material to cure the photocuring polymer material in the non-preset electrode pattern area to prepare a mask layer.

[0162] Example 2 shows the preparation of silicon-based heterojunction solar cell B.

[0163] Comparative Example 1

[0164] Comparative Example 1 uses a traditional seed copper electroplating process to prepare silicon-based heterojunction solar cells.

[0165] The structure of the silicon-based heterojunction solar cell is the same as in Example 1.

[0166] Methods for fabricating silicon-based heterojunction solar cells:

[0167] (1) Provide a battery substrate; the battery substrate 1 includes a second electrode layer 90, a second transparent conductive layer 70, an N-type doped layer 50, a second amorphous silicon intrinsic layer 40, a silicon substrate 10, a first amorphous silicon intrinsic layer 20, a P-type doped layer 30, a first transparent conductive layer 60 and a first electrode layer 80, which are stacked sequentially.

[0168] (2) Preparation of the first transparent conductive layer and the second transparent conductive layer: The first transparent conductive layer 60 (ITO) and the second transparent conductive layer 70 (ITO) are prepared on the surface of the P-type doped layer 30 and the N-type doped layer 50, respectively.

[0169] (3) PVD sputtering to prepare seed copper layers: Seed copper layers are prepared by PVD sputtering on the surface of the first transparent conductive layer 60 away from the P-type doped layer 30 and the surface of the second transparent conductive layer 70 away from the N-type doped layer 50, respectively.

[0170] (4) Double-sided patterning: After printing photoresist on the surfaces of two seed copper layers, drying, exposure and development, a mask layer is formed in the non-preset electrode area of ​​the seed copper layer.

[0171] (5) Double-sided electroplating: Electroplating is performed on the surfaces of two seed copper layers containing a mask layer by pinch alignment, and a first electrode layer 80 and a second electrode layer 90 are formed in the preset electrode areas of the two seed copper layers respectively.

[0172] (6) Remove the mask layer.

[0173] (7) Tinning: Tinning treatment is performed on the surfaces of the first electrode layer 80 and the second electrode layer 90 to prepare a tin protective layer. At this time, a silicon-based heterojunction cell C is prepared.

[0174] The silicon-based heterojunction cells prepared in the examples and comparative examples were assembled into photovoltaic modules. The photovoltaic module specifically includes: a frame and a laminate disposed within the frame, with silicone filling the space between the laminate and the frame. The laminate includes a cover plate, a silicon-based heterojunction cell, and a photovoltaic module backsheet stacked sequentially. At 25°C, 1000 W / m 2 The power output of the modules was tested using a Pasan test bench. The corresponding test results are shown in Table 1. The production efficiency of the embodiment was calculated as: (Number of silicon-based heterojunction cells prepared by the embodiment per unit time - Number of silicon-based heterojunction cells prepared by Comparative Example 1 per unit time) / Number of silicon-based heterojunction cells prepared by Comparative Example 1 per unit time × 100%. For example, the production efficiency of Example 1 was calculated as: (Number of silicon-based heterojunction cells prepared by Example 1 per unit time - Number of silicon-based heterojunction cells prepared by Comparative Example 1 per unit time) / Number of silicon-based heterojunction cells prepared by Comparative Example 1 per unit time × 100%.

[0175] Table 1

[0176]

[0177] 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.

[0178] 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 fabricating a silicon-based heterojunction solar cell, characterized in that, Includes the following steps: A battery substrate is provided; wherein, along the thickness direction of the battery substrate, the battery substrate includes a first surface and a second surface disposed opposite to each other; A first transparent conductive layer and a second transparent conductive layer are formed on the first and second surfaces of the battery substrate, respectively. A first electrode layer is prepared by printing silver-coated copper paste on the surface of the first transparent conductive layer that is away from the battery substrate. A second electrode layer is prepared by photo-induced electroplating of copper on the side of the second transparent conductive layer opposite to the battery substrate.

2. The method for preparing a silicon-based heterojunction solar cell according to claim 1, characterized in that, The step of preparing the second electrode layer by photo-induced copper plating on the side of the second transparent conductive layer opposite to the battery substrate includes: A mask layer is prepared on the side surface of the second transparent conductive layer facing away from the battery substrate; wherein, the side surface of the second transparent conductive layer facing away from the battery substrate includes a preset electrode pattern area and a non-preset electrode pattern area, and the mask layer is located in the non-preset electrode pattern area; The second transparent conductive layer containing the mask layer is chemically treated to form a metal-rich doped layer on the surface of the preset electrode pattern area of ​​the second transparent conductive layer. The second electrode layer is prepared by photo-induced electroplating of copper on the surface of the metal-rich doped layer.

3. The method for preparing a silicon-based heterojunction solar cell according to claim 2, characterized in that, In the step of chemically treating the second transparent conductive layer containing the mask layer, the processing solution used in the chemical treatment includes an etchant, an oxidant, a metal salt, and a buffer; the processing solution has one or more of the following characteristics: (1) The molar concentration of the etchant in the treatment solution is 0.2 mol / L to 1.5 mol / L; (2) The molar concentration of the oxidant in the treatment solution is 0.3 mol / L to 1.2 mol / L; (3) The molar concentration of the metal salt in the treatment solution is 0.2 mol / L to 0.8 mol / L; (4) The molar concentration of the buffer in the treatment solution is 0.01 mol / L to 0.2 mol / L; (5) The etchant includes one or more of HF and HCl; (6) The oxidant includes one or more of H2O2 and HNO3; (7) The metal salt includes one or more of InCl3, SnCl4, KI, CuI, ZnSO4 and CuSO4; (8) The buffer includes one or more of NaH2PO4, CH3COONa and sodium citrate; (9) The temperature of the chemical treatment is 20℃~50℃.

4. The method for preparing a silicon-based heterojunction solar cell according to claim 2, characterized in that, The preparation method has one or more of the following characteristics: (1) The thickness of the metal-rich doped layer is 50 nm to 100 nm; (2) The material of the second transparent conductive layer includes one or more of FTO, ITO, AZO, ATO and IGO; (3) The thickness of the second transparent conductive layer is 200nm~5μm.

5. The method for preparing a silicon-based heterojunction solar cell according to claim 2, characterized in that, The step of photo-induced copper plating on the surface of the metal-rich doped layer includes: Under illumination, the second transparent conductive layer containing the metal-rich doped layer is electroplated in a copper-ion-containing electroplating solution. Optionally, the wavelength range of the illumination is 200nm to 800nm.

6. The method for preparing a silicon-based heterojunction solar cell according to claim 2, characterized in that, The mask layer is prepared by nanoimprinting. Optionally, the nanoimprinting includes one or more of thermal nanoimprinting and ultraviolet nanoimprinting.

7. The method for preparing a silicon-based heterojunction solar cell according to claim 6, characterized in that, The step of preparing a mask layer on the surface of the second transparent conductive layer opposite to the battery substrate includes: A thermoplastic film layer is formed on the surface of the second transparent conductive layer facing away from the battery substrate; wherein the thermoplastic film layer comprises a thermoplastic material; the thermoplastic film layer is subjected to a heat treatment; wherein the temperature of the heat treatment is greater than or equal to the glass transition temperature of the thermoplastic material; a non-preset electrode pattern area of ​​the second transparent conductive layer containing the thermoplastic film layer is hot-pressed, and then the thermoplastic film layer in the non-preset electrode pattern area is cured to prepare the mask layer; Alternatively, a photocurable polymer material is coated on the surface of the second transparent conductive layer facing away from the battery substrate; the non-preset electrode pattern area of ​​the second transparent conductive layer coated with the photocurable polymer material is subjected to ultraviolet light irradiation treatment to cure the photocurable polymer material in the non-preset electrode pattern area, thereby preparing the mask layer.

8. The method for preparing a silicon-based heterojunction solar cell according to claim 7, characterized in that, The preparation method has one or more of the following characteristics: (1) The thermoplastic material includes one or more of polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyetheretherketone and polyphenylene sulfide; (2) The photocurable polymer material includes polyurethane acrylate.

9. The method for preparing a silicon-based heterojunction solar cell according to any one of claims 1 to 8, characterized in that, After the step of preparing the second electrode layer, the method further includes: A tin protective layer is prepared by performing a tin-removing treatment on the surface of the second electrode layer.

10. The method for preparing a silicon-based heterojunction solar cell according to any one of claims 1 to 8, characterized in that, The silver-coated copper paste contains silver with a mass fraction of ≤30%; And / or, the material of the first transparent conductive layer includes one or more of FTO, ITO, AZO, ATO and IGO; and / or, the thickness of the first transparent conductive layer is 200nm to 5μm.

11. The method for preparing a silicon-based heterojunction solar cell according to any one of claims 1 to 8, characterized in that, The battery substrate includes an N-type doped layer, a silicon substrate, and a P-type doped layer stacked sequentially. Wherein, the first surface is the surface of the P-type doped layer that is far from the N-type doped layer, and the second surface is the surface of the N-type doped layer that is far from the P-type doped layer.

12. The method for preparing a silicon-based heterojunction solar cell according to claim 11, characterized in that, The battery substrate further includes a first amorphous silicon intrinsic layer, which is disposed between the silicon substrate and the P-type doped layer; And / or, the battery substrate further includes a second amorphous silicon intrinsic layer, which is disposed between the silicon substrate and the N-type doped layer.

13. A silicon-based heterojunction solar cell, characterized in that, The silicon-based heterojunction solar cell is prepared by the preparation method according to any one of claims 1 to 12; the silicon-based heterojunction solar cell comprises: A battery substrate; along the thickness direction of the battery substrate, the battery substrate includes a first surface and a second surface disposed opposite to each other; A first transparent conductive layer; the first transparent conductive layer is disposed on the first surface of the battery substrate; A second transparent conductive layer; the second transparent conductive layer is disposed on the second surface of the battery substrate; A first electrode layer is disposed on the surface of the first transparent conductive layer that is away from the battery substrate; The second electrode layer is disposed on the side surface of the second transparent conductive layer that is away from the battery substrate; The first electrode layer is a silver-coated copper electrode layer; the second electrode layer is a copper electrode layer.

14. The silicon-based heterojunction solar cell according to claim 13, characterized in that, The battery substrate includes an N-type doped layer, a second amorphous silicon intrinsic layer, a silicon substrate, a first amorphous silicon intrinsic layer, and a P-type doped layer stacked sequentially. Wherein, the first surface is the surface of the P-type doped layer that is far from the N-type doped layer, and the second surface is the surface of the N-type doped layer that is far from the P-type doped layer.

15. A photovoltaic module, characterized in that, Including silicon-based heterojunction solar cells prepared by the preparation method according to any one of claims 1 to 12.

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