Heterojunction solar cell and preparation method therefor

Abstract

The present application relates to a heterojunction solar cell and a preparation method therefor, and relates to the technical field of solar cell manufacturing. The preparation method for the heterojunction solar cell comprises: preparing a substrate layer; forming a patterned conductive seed layer on at least one side of the substrate layer, the patterned conductive seed layer covering part of the substrate layer; forming a filter layer on a side of the conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer; performing pattern processing on the filter layer to expose part of the patterned conductive seed layer; and forming a metal electrode on the exposed patterned conductive seed layer. By means of the preparation method for the heterojunction solar cell provided in the present application, the process of preparing a metal electrode can be significantly simplified, and a gate line of the prepared metal electrode can be made thinner while ensuring adhesion, thereby improving the filling factor and conversion efficiency of the heterojunction solar cell.

Description

Heterojunction solar cells and their fabrication methods

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410802518.0, filed on June 20, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of solar cell manufacturing technology, and more specifically, to a heterojunction solar cell and its preparation method. Background Technology

[0004] Heterojunction solar cells have become a hot topic in the development of silicon-based high-efficiency solar cells due to their excellent passivation effect, extremely high conversion efficiency, low temperature coefficient, and low-temperature manufacturing process.

[0005] Transparent conducting oxide films (TCOs) in heterojunction solar cells possess excellent conductivity, and when combined with metal electrodes, they can better conduct photocurrent. Typically, metal electrodes are formed using silver paste through screen printing. However, silver is a precious metal, and silver paste is expensive, leading to the development of alternatives such as electrochemically deposited copper electrodes. However, the conductivity of the transparent conducting oxide film makes electrochemical deposition of metal electrodes on it non-selective, and the adhesion between the directly electrochemically deposited metal electrode and the transparent conducting oxide film is poor. Therefore, current techniques generally involve first preparing a thin seed layer on the transparent conducting oxide film, and then fabricating the metal electrode using a masking process. After the metal electrode is formed, the opaque mask layer needs to be removed, and the seed layer etched back to expose the areas on the transparent conducting oxide film that are not covered by the metal electrode. Removing the mask layer and etching back the seed layer complicates the fabrication process of heterojunction solar cells, increases costs, and the etching back of the seed layer can damage the metal electrode, thus affecting the conductivity of the heterojunction solar cell.

[0006] Therefore, providing an electrochemical deposition method that is simple in process, low in cost, and can ensure the adhesion performance between the metal electrode and the transparent conductive film as well as the conductivity of the heterojunction solar cell is an urgent technical problem to be solved. Summary of the Invention

[0007] The purpose of this application is to address the shortcomings of the prior art by providing a heterojunction solar cell and its fabrication method, which simplifies the process, reduces costs, and ensures the adhesion performance between the metal electrode and the transparent conductive film, as well as the conductivity performance of the heterojunction solar cell.

[0008] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0009] A first aspect of this application provides a method for fabricating a heterojunction solar cell, comprising: fabricating a substrate layer; forming a patterned conductive seed layer on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer; forming a light-transmitting filter layer on the side of the patterned conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer; patterning the filter layer to expose a portion of the patterned conductive seed layer; and forming a metal electrode on the exposed patterned conductive seed layer.

[0010] Optionally, the filter layer is made of silicon oxide, fluoride, or silicon nitride.

[0011] Optionally, a filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer, including: using one or more processes selected from spin coating, physical vapor deposition, chemical vapor deposition, and atomic deposition to form the filter layer on the side of the patterned conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer.

[0012] Optionally, the filter layer is patterned to expose a portion of the patterned conductive seed layer, including: using one or more processes selected from inkjet printing etching solution, laser ablation, and plasma etching to pattern the filter layer, thereby removing a portion of the filter layer and exposing a portion of the patterned conductive seed layer.

[0013] Optionally, a patterned conductive seed layer is formed on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer, including: forming the patterned conductive seed layer on at least one side of the substrate layer using one or more processes selected from screen printing, inkjet printing, and slot spraying.

[0014] Optionally, forming a metal electrode on the exposed patterned conductive seed layer includes: forming a metal electrode on the exposed patterned conductive seed layer using an electrochemical deposition process.

[0015] Optionally, after forming a metal electrode on the exposed patterned conductive seed layer, the method further includes: coating the surface of the metal electrode with an oxidation-resistant conductive layer.

[0016] Optionally, the material of the patterned conductive seed layer is a metal, an alloy, or a conductive material that can be bonded to a metal electrode.

[0017] Optionally, the thickness of the patterned conductive seed layer is 50nm-500nm, the thickness of the filter layer is 100nm-500nm, and the thickness of the metal electrode is 5μm-15μm.

[0018] Optionally, the preparation of the substrate layer includes: providing a substrate; sequentially forming a first intrinsic layer, an N-type silicon layer, and a first transparent conductive thin film layer on one side of the substrate; and sequentially forming a second intrinsic layer, a P-type silicon layer, and a second transparent conductive thin film layer on the other side of the substrate.

[0019] The second aspect of this application provides a heterojunction solar cell prepared using the method described in the first aspect of this application.

[0020] A third aspect of this application provides a heterojunction solar cell, including a substrate layer, a patterned conductive seed layer on at least one side of the substrate layer, a patterned filter layer on the side of the patterned conductive seed layer away from the substrate layer, the patterned filter layer exposing at least a portion of the patterned conductive seed layer, and a metal electrode on the exposed patterned conductive seed layer.

[0021] Optionally, at least a portion of the patterned conductive seed layer is located between the patterned filter layer and the base layer.

[0022] The beneficial effects of this application include:

[0023] The heterojunction solar cell fabrication method provided in this application significantly simplifies the metal electrode fabrication process. The filter layer used serves two purposes: firstly, it filters light, providing insulation, reducing reflection, and increasing short-circuit current; secondly, it filters the shape of the metal electrode coating and isolates moisture. Furthermore, the filter layer is easy to fabricate, and a wide range of materials can be selected. Simultaneously, this heterojunction solar cell fabrication method avoids the mask removal and wet etching of the seed layer steps required in existing technologies, reducing process steps and costs. While ensuring adhesion, it allows for finer grid lines in the fabricated heterojunction solar cell, increasing light absorption and improving the fill factor and conversion efficiency. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 is a flowchart of one of the methods for fabricating a heterojunction solar cell provided in an embodiment of this application;

[0026] Figure 2 is one of the structural schematic diagrams of the semi-finished product of the heterojunction solar cell provided in the embodiments of this application;

[0027] Figure 3 is a second schematic diagram of the structure of the semi-finished product of the heterojunction solar cell provided in the embodiment of this application;

[0028] Figure 4 is a third schematic diagram of the structure of the semi-finished product of the heterojunction solar cell provided in the embodiments of this application;

[0029] Figure 5 is a fourth schematic diagram of the structure of the semi-finished product of the heterojunction solar cell provided in the embodiments of this application;

[0030] Figure 6 is a schematic diagram of the structure of a heterojunction solar cell provided in an embodiment of this application;

[0031] Figure 7 is a flowchart of the second method for fabricating a heterojunction solar cell provided in the embodiments of this application;

[0032] Figure 8 is a flowchart of the third method for fabricating a heterojunction solar cell provided in the embodiments of this application;

[0033] Figure 9 is a flowchart of the fourth step in the fabrication method of the heterojunction solar cell provided in the embodiments of this application.

[0034] Explanation of reference numerals in the attached figures: 110 - base layer; 111 - substrate; 112 - first intrinsic layer; 113 - N-type silicon layer; 114 - first transparent conductive thin film layer; 115 - second intrinsic layer; 116 - P-type silicon layer; 117 - second transparent conductive thin film layer; 121 - first conductive seed layer; 122 - second conductive seed layer; 131 - first filter layer; 1311 - first opening; 132 - second filter layer; 1321 - second opening; 141 - first metal electrode; 142 - second metal electrode; 151 - first oxidation-resistant conductive layer; 152 - second oxidation-resistant conductive layer. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] It should be understood that while the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0037] Similarly, it should be understood that when an element (such as a layer, region, or substrate) is referred to as "on top of another element" or "extending on top of another element," it may be directly on top of or extending directly on top of another element, or there may be intermediate elements. Conversely, when an element is referred to as "directly on top of another element" or "extending directly on top of another element," there are no intermediate elements. It should also be understood that when an element is referred to as "connected" or "coupled" to another element, it may be directly connected or coupled to another element, or there may be intermediate elements. Conversely, when an element is referred to as "directly connected" or "directly coupled" to another element, there are no intermediate elements.

[0038] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that the terms used herein should be interpreted as having the same meaning as they would in the context of this specification and the relevant field, and not in an idealized or overly formal sense, unless explicitly defined herein.

[0039] One aspect of this application, referring to FIG1, provides a method for fabricating a heterojunction solar cell, comprising:

[0040] S100: Preparation of the base layer.

[0041] Referring to Figure 2, the substrate 110 serves as the base layer for fabricating heterojunction solar cells, and is used to sequentially fabricate a conductive seed layer, a filter layer, and a metal electrode on its surface.

[0042] S200: A patterned conductive seed layer is formed on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer.

[0043] Referring to Figures 3 and 6, a patterned conductive seed layer is formed on at least one side of the substrate 110 to cover the area on the substrate 110 where the metal electrode needs to be disposed. It can be understood that forming a patterned conductive seed layer on at least one side of the substrate 110 includes three schemes: 1. Forming patterned conductive seed layers on opposite sides of the substrate 110 to fabricate the first metal electrode 141 and the second metal electrode 142; 2. Forming a patterned conductive seed layer on one side of the substrate 110 to fabricate the first metal electrode 141, while using conventional processes to fabricate the second metal electrode 142 on the other side; 3. Forming a patterned conductive seed layer on one side of the substrate 110 to fabricate the second metal electrode 142, while using conventional processes to fabricate the first metal electrode 141 on the other side. Schemes one to three simplify the fabrication process, reduce costs, and ensure adhesion between the metal electrode and the transparent conductive film compared to existing technologies. Among these, scheme one has the simplest process, the lowest cost, and produces a heterojunction solar cell with superior performance.

[0044] The patterned conductive seed layer can be formed in a single step, such as using screen printing or inkjet printing, by covering the area of ​​the substrate 110 where the metal electrode needs to be placed with the material for the conductive seed layer. Alternatively, it can be formed in multiple steps. For example, first, the material for the conductive seed layer is covered onto the substrate 110 to form a full-surface conductive seed layer. Methods for forming a full-surface conductive seed layer include physical vapor deposition, chemical vapor deposition, and electroplating. Then, the entire conductive seed layer is patterned (e.g., using etching or laser ablation) to remove excess portions, retaining only the conductive seed layer at the corresponding patterned locations. The material for the conductive seed layer can be a metal, alloy, or a conductive material that can bond with the metal electrode, such as silver or copper.

[0045] S300: A filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer, and the filter layer covers the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer.

[0046] S400: The filter layer is patterned to expose part of the patterned conductive seed layer.

[0047] Referring to Figures 4 and 5, a filter layer is formed on the patterned conductive seed layer. Then, a portion of the filter layer covering the patterned conductive seed layer is removed through patterning processing to expose the patterned conductive seed layer. Etching, laser ablation, or other processes can be used to partially remove the filter layer. It should be noted that the patterned filter layer only exposes the conductive seed layer and does not expose the substrate layer 110. The patterned conductive seed layer can be partially or completely exposed to the filter layer; preferably, the central region of the patterned conductive seed layer is exposed to the filter layer, while the regions on both sides remain covered by the filter layer. The filter layer should be light-transmitting so that light can reach the substrate layer. Generally, the transmittance of the filter layer to visible light is above 80% to allow the heterojunction solar cell to absorb more visible light. The material of the filter layer can be silicon oxide, fluoride, silicon nitride, etc. The filter layer serves three functions: first, it filters light by reducing reflection, allowing more light to be utilized, increasing short-circuit current, and thus improving power generation efficiency; second, it filters residual reaction liquid from subsequent electrochemical deposition, acting as a mask for the formation of metal electrodes to prevent electrochemical reactions at the covered locations from affecting the shape of the metal electrode coating; and third, it filters water vapor by effectively isolating it due to its impermeable properties.

[0048] S500: A metal electrode is formed on the exposed patterned conductive seed layer.

[0049] A heterojunction solar cell is obtained by forming a metal electrode on a patterned conductive seed layer exposed from the filter layer. The material of the metal electrode can be selected from one, two, or more good conductors such as silver and copper. When using two or more good conductors to prepare the metal electrode, a metal electrode structure in which one material encapsulates another can be formed, thereby reducing costs while ensuring conductivity. For example, the metal electrode may have a copper layer inside and a silver layer outside. Silver has good conductivity but is expensive, while copper, although less conductive than silver, is significantly cheaper. Therefore, the metal electrode structure with a silver layer encapsulating a copper layer can effectively reduce costs while ensuring conductivity. Specifically, the metal electrode can be prepared by electrochemical deposition.

[0050] It is understood that the patterned conductive seed layer includes a first conductive seed layer 121 and / or a second conductive seed layer 122, the filter layer includes a first filter layer 131 and / or a second filter layer 132, and the metal electrode includes a first metal electrode 141 and / or a second metal electrode 142; wherein, the first conductive seed layer 121, the first filter layer 131 and the first metal electrode 141 are located on one side of the substrate layer 110, and the second conductive seed layer 122, the second filter layer 132 and the second metal electrode 142 are located on the opposite side of the substrate layer 110.

[0051] Due to the poor adhesion between the metal electrode and the transparent conductive film layer (TCO layer) in heterojunction solar cells, a conductive seed layer is added between the metal electrode and the TCO layer. The conductive seed layer can be made of metal, alloy, or a conductive material that can bond with the metal electrode, thereby achieving high adhesion between the metal electrode and the TCO layer.

[0052] The filter layer is made of silicon oxide, fluoride, or silicon nitride. Silicon oxide, fluoride, or silicon nitride are common and easy to prepare. These materials can be physically or chemically treated to form a transparent film, thereby achieving triple filtration effects, including insulation and anti-reflection, filtration of residual reaction liquid, and water vapor isolation.

[0053] Optionally, in one possible implementation of this application, the thickness of the patterned conductive seed layer is 50nm-500nm, the thickness of the filter layer is 100nm-500nm, and the thickness of the metal electrode is 5μm-15μm. When the thicknesses of the conductive seed layer, filter layer, and metal electrode are within the aforementioned ranges, the resulting heterojunction solar cell exhibits superior performance. For example, in some specific implementations, the thickness of the patterned conductive seed layer can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, or 500nm, or any value within the aforementioned ranges, or any combination of both. In some specific implementations, the thickness of the filter layer can be 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 220nm, 250nm, 280nm, 300nm, 320nm, 350nm, 380nm, 400nm, 420nm, 450nm, 480nm, or 500nm, or any value within the aforementioned range, or any combination of both. To further improve the photoelectric conversion efficiency of the heterojunction solar cell, the thickness of the filter layer is preferably 100nm-200nm. In some specific implementations, the thickness of the metal electrode can be 5μm, 8μm, 10μm, 12μm, or 15μm, or any value within the aforementioned range, or any combination of both.

[0054] Referring to Figures 2 and 7, optionally, in one feasible embodiment of the method for fabricating a heterojunction solar cell according to this application, the preparation of the substrate layer includes:

[0055] S110: Provides a substrate;

[0056] S120: A first intrinsic layer, an N-type silicon layer, and a first transparent conductive thin film layer are sequentially formed on one side of the substrate;

[0057] S130: A second intrinsic layer, a P-type silicon layer, and a second transparent conductive thin film layer are sequentially formed on the other side of the substrate.

[0058] The substrate 111 can be a silicon wafer. The first intrinsic layer 112 and the second intrinsic layer 115 can be amorphous silicon layers, single-sided microcrystalline silicon layers, or double-sided microcrystalline silicon layers, etc. The N-type silicon layer 113 can be an N-type amorphous silicon layer or an N-type microcrystalline silicon layer, etc., and the P-type silicon layer 116 can be a P-type amorphous silicon layer or a P-type microcrystalline silicon layer, etc. The first intrinsic layer 112, the N-type silicon layer 113, the first transparent conductive thin film layer 114, the second intrinsic layer 115, the P-type silicon layer 116, and the second transparent conductive thin film layer 117 can be sequentially stacked on two opposite surfaces of the substrate 111 by physical vapor deposition, chemical vapor deposition, magnetron sputtering, etc. For example, the first intrinsic layer 112, the N-type silicon layer 113, the second intrinsic layer 115, and the P-type silicon layer 116 are formed by plasma chemical vapor deposition (PECVD), and the first transparent conductive thin film layer 114 and the second transparent conductive thin film layer 117 are formed by magnetron sputtering. Plasma-chemical vapor deposition (PCVDC) has a low deposition temperature, which has less impact on the structure and physical properties of the existing substrate, and the resulting film has good uniformity, dense structure, and strong adhesion. The first transparent conductive film layer 114 and the second transparent conductive film layer 117 prepared by magnetron sputtering are more conducive to reducing the transport barrier between the transparent conductive film layer interface and the amorphous silicon layer, thereby reducing the interfacial series resistance of the battery.

[0059] Referring to Figures 1 and 8, optionally, in one possible implementation of this application, a patterned conductive seed layer is formed on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer, including: S210: forming a patterned conductive seed layer on at least one side of the substrate layer using one or more processes selected from screen printing, inkjet printing, and slot spraying.

[0060] The method for preparing the substrate layer in step S100 of Figure 8 can be referred to the aforementioned steps S110 to S130.

[0061] Screen printing refers to using a screen as a printing plate and creating a patterned conductive seed layer on the surface of a substrate layer 110 through a photosensitive plate-making method. Inkjet printing refers to directly spraying a metallized slurry or nanoparticle solution containing conductive seed layer material onto the surface of the substrate layer 110 to form a patterned conductive seed layer. The composition of the metallized slurry or nanoparticle solution containing conductive seed layer material is existing technology; for example, the metallized slurry may include metal resin acid, acid resin, and terpineol, where the metal resin acid contains metal ions used to form the conductive seed layer, such as silver ions, copper ions, or gold ions. Slit spraying refers to extruding a coating liquid containing conductive seed layer material through the slits of a coating mold under certain pressure and flow rate, thereby transferring it onto the substrate layer 110 to form a patterned conductive seed layer. The composition of the coating liquid containing conductive seed layer material is existing technology; for example, the coating liquid containing conductive seed layer material is a solution formed by melting the conductive seed layer material at high temperature. Slit spraying offers fast coating speed, high precision, and uniform wet thickness. The conductive seed layer can be prepared using any one of the three processes described above, or by combining two or three of them. The above printing process can directly form a patterned conductive seed layer without a mask, avoiding the mask removal step and wet etching back step required in existing technologies, effectively simplifying the process and reducing production costs.

[0062] In one achievable embodiment of this application, the metallization slurry used for forming the conductive seed layer in inkjet printing comprises 0-20 wt% metal resin acid, 10-20 wt% acid resin, and 5-10 wt% terpineol, with the remainder being solvents (such as glycol ethers and alcohols) and additives (such as dispersants and surfactants) to ensure that the metallization slurry meets the requirements of inkjet printing. For example, in some achievable embodiments, the viscosity of the metallization slurry is <20 mPa·s, and the surface tension is approximately 28-35 mN / m. Optionally, in one achievable embodiment of this application, a filter layer is formed on the side of the conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer, comprising:

[0063] S310: A filter layer is formed on the side of the conductive seed layer away from the substrate layer using one or more processes such as spin coating, physical vapor deposition, chemical vapor deposition, and atomic deposition. The filter layer covers the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer.

[0064] Spin coating refers to rotating the substrate layer 110 along an axis perpendicular to its surface while simultaneously coating the substrate layer 110 with liquid filter material, thus forming a filter layer. This filter layer covers both a patterned conductive seed layer and the unpatterned substrate layer. Physical vapor deposition (PVD) forms the filter layer by vaporizing the filter material into gaseous atoms or molecules, or partially ionizing them, under vacuum conditions using physical methods, and then depositing the filter layer onto the surface of the substrate layer 110 using a low-pressure gas (or plasma) process. Chemical vapor deposition (CVD) forms the filter layer by chemically reacting one or more gaseous compounds or elements containing filter layer elements on the surface of the substrate layer 110. Atomic deposition (ADC) forms the filter layer by depositing the filter material layer by layer as a single-atom film onto the surface of the substrate layer 110 to ultimately form the filter layer. The filter layer can be prepared using any one of the above four processes alone, or by a combination of two, three, or four of the above processes.

[0065] In one possible implementation of this application, the filter layer is patterned to expose a portion of the patterned conductive seed layer, including:

[0066] S410: The filter layer is patterned using one or more of the following processes: inkjet printing etching solution, laser ablation, and plasma etching, in order to remove part of the filter layer and expose part of the patterned conductive seed layer.

[0067] When inkjet printing etchant is used to pattern the filter layer, the etchant partially removes the filter layer by eroding it, exposing the patterned conductive seed layer covered by the filter layer. The etchant should contain components that can chemically react with and remove the filter layer. For example, if the filter layer is made of silicon nitride, the etchant may include an aqueous phosphoric acid solution and silicon additives. When laser ablation is used to pattern the filter layer, a laser beam is focused on the surface of the filter layer to bombard it and partially remove it. When plasma etching is used to pattern the filter layer, an electric field accelerates the plasma, causing it to release sufficient energy to partially remove the filter layer. The patterning of the filter layer can be done using any one of the three processes mentioned above, or a combination of two or three of them.

[0068] Optionally, in one possible implementation of this application, forming a metal electrode on the exposed patterned conductive seed layer includes:

[0069] S510: A metal electrode is formed on the exposed patterned conductive seed layer using an electrochemical deposition process.

[0070] Specifically, the preparation of metal electrodes using electrochemical deposition involves passing an electric current into an electrolyte solution of the metal electrode material under the influence of an external electric field. This causes positive and negative ions in the solution to migrate and undergo redox reactions on a conductive seed layer, thereby forming a metal electrode on the patterned conductive seed layer. Electrochemical deposition can produce nanomaterials of various grain sizes and is simple to operate, low in cost, and highly efficient.

[0071] Referring to Figure 9, optionally, in one possible implementation of this application, after forming a metal electrode on the exposed patterned conductive seed layer based on the flowchart shown in Figure 1, the method further includes:

[0072] S600: An oxidation-resistant conductive layer is wrapped around the surface of the metal electrode.

[0073] If the metal electrode is made of an easily oxidizable material, an oxidation-resistant conductive layer needs to be prepared on the surface of the metal electrode to prevent oxidation without affecting conductivity. It can be understood that the oxidation-resistant conductive layer does not need to cover the area of ​​the metal electrode covered by the filter layer. The material of the oxidation-resistant conductive layer can be a metal that is not easily oxidized, such as tin or nickel. The oxidation-resistant conductive layer can be formed by electroless tin plating or electroless nickel plating. Taking electroless tin plating on the surface of a copper metal electrode as an example, a copper electrode without a metal oxide layer is placed in a tin plating bath containing molten tin. The copper electrode undergoes a displacement reaction with the molten tin, thereby achieving electroless tin plating on the surface of the copper electrode. The main components of the molten tin include stannous sulfate, sulfuric acid, polyethylene glycol, and deionized water.

[0074] As can be understood, as shown in Figure 6, the oxidation-resistant conductive layer includes a first oxidation-resistant conductive layer 151 and a second oxidation-resistant conductive layer 152. The first oxidation-resistant conductive layer 151 wraps around the first metal electrode 141, and the second oxidation-resistant conductive layer 152 wraps around the second metal electrode 142.

[0075] Another aspect of this application provides a heterojunction solar cell prepared using the preparation method of this application, the structure of which is shown in Figures 2, 5 and 6.

[0076] In another aspect of this application, referring to Figures 2, 5 and 6, a heterojunction solar cell is provided, including a substrate layer 110. A conductive seed layer is provided on at least one side of the substrate layer 110, and a patterned filter layer is provided on the side of the conductive seed layer away from the substrate layer 110. The conductive seed layer exposes at least a portion of the conductive seed layer in the patterned filter layer, and a metal electrode is provided on the exposed conductive seed layer.

[0077] This heterojunction solar cell can be prepared using any of the above methods, which are simple, low-cost, and have high conversion efficiency.

[0078] For example, referring to Figures 2, 5, and 6, a heterojunction solar cell includes: a substrate layer 110, a first conductive seed layer 121, a first filter layer 131, and a first metal electrode 141 sequentially disposed on one side of the substrate layer 110, and a second conductive seed layer 122, a second filter layer 132, and a second metal electrode 142 sequentially disposed on the other side of the substrate layer 110; the first conductive seed layer 121 and the second conductive seed layer 122 respectively partially cover both sides of the substrate layer 110, and the first filter layer 131 covers the first conductive seed layer 122. 21. A first opening 1311 is provided on the first filter layer 131, exposing the first conductive seed layer 121. The first metal electrode 141 is connected to the first conductive seed layer 121 exposed through the first opening 1311. A second filter layer 132 covers the second conductive seed layer 122. A second opening 1321 is provided on the second filter layer 132, exposing the second conductive seed layer 122. The second metal electrode 142 is connected to the second conductive seed layer 122 exposed through the second opening 1321.

[0079] The first conductive seed layer 121 and the second conductive seed layer 122, the first filter layer 131 and the second filter layer 132, the first metal electrode 141 and the second metal electrode 142 are symmetrically disposed on opposite sides of the substrate layer 110. The first filter layer 131 and the second filter layer 132 are respectively provided with a first opening 1311 and a second opening 1321 to expose the lower first conductive seed layer 121 and the second conductive seed layer 122. Then, the first metal electrode 141 is formed on the first conductive seed layer 121 exposed from the first opening 1311, and the second metal electrode 142 is formed on the second conductive seed layer 122 exposed from the second opening 1321.

[0080] Optionally, in one possible implementation of this application, the substrate layer 110 includes a substrate 111, a first intrinsic layer 112, an N-type silicon layer 113 and a first transparent conductive thin film layer 114 sequentially disposed on one side of the substrate 111, and a second intrinsic layer 115, a P-type silicon layer 116 and a second transparent conductive thin film layer 117 sequentially disposed on the other side of the substrate 111.

[0081] The first conductive seed layer 121 and the first filter layer 131 are sequentially stacked on the surface of the first transparent conductive film layer 114, and the second conductive seed layer 122 and the second filter layer 132 are sequentially stacked on the surface of the second transparent conductive film layer 117.

[0082] In one possible implementation of this application, at least a partially patterned conductive seed layer is located between the patterned filter layer and the substrate layer. Referring to FIG6, at least a portion of the first conductive seed layer 121 is located between the first filter layer 131 and the substrate layer, and at least a portion of the second conductive seed layer 122 is located between the second filter layer 132 and the substrate layer. That is, the patterned conductive seed layer is not completely exposed from the patterned filter layer, and the conductive seed layer disposed under the patterned filter layer can play a role in lateral carrier transport. The above-described method for fabricating heterojunction solar cells can significantly reduce the complexity of the metal electrode fabrication process. The filter layer used is easy to fabricate and has a wide range of material selection. On the one hand, it can filter light, playing a role in insulation and anti-reflection, and increasing short-circuit current. On the other hand, it can also be regarded as filtering the shape of the metal electrode coating, and at the same time, it can also play a role in isolating moisture. This method for fabricating heterojunction solar cells avoids the mask removal step and wet etching seed layer step in the prior art. Under the premise of ensuring adhesion, the grid lines can be made finer, increasing the light absorption of heterojunction solar cells, improving the conversion efficiency of heterojunction solar cells, reducing process steps, and reducing costs.

[0083] Example 1

[0084] This embodiment illustrates the method for preparing the heterojunction solar cell of this application, including the following steps:

[0085] S1. Fabrication of the substrate layer: A substrate is provided. A first intrinsic layer and an N-type silicon layer are sequentially formed on one side of the substrate using plasma chemical vapor deposition. A second intrinsic layer and a P-type silicon layer are sequentially formed on the other side of the substrate. A first transparent conductive thin film layer is formed on the surface of the N-type silicon layer using magnetron sputtering, and a second transparent conductive thin film layer is formed on the surface of the P-type silicon layer. Both the first and second intrinsic layers are intrinsic amorphous silicon. The thickness of the first intrinsic layer is 10 nm, the thickness of the second intrinsic layer is 10 nm, the thickness of the N-type silicon layer is 20 nm, and the thickness of the P-type silicon layer is 25 nm.

[0086] S2. A patterned conductive seed layer is formed on at least one side of the substrate layer using inkjet printing. The patterned conductive seed layer covers a portion of the substrate layer. The slurry of the patterned conductive seed layer includes 15 wt% silver resin acid, 15 wt% acrylic resin and 8 wt% terpineol (the remainder being solvents and additives). The thickness of the patterned conductive seed layer is 200 nm.

[0087] S3. A light-transmitting filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer by spin coating. The filter layer covers the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer. The material of the filter layer is silicon dioxide and the thickness is 150nm.

[0088] S4. The filter layer is patterned by laser ablation to expose part of the patterned conductive seed layer; the width of the exposed patterned conductive seed layer is 15μm.

[0089] S5. A metal electrode is formed on the exposed patterned conductive seed layer by screen printing; the metal electrode is made of silver and has a thickness of 15μm.

[0090] S6. A layer of oxidation-resistant conductive layer is wrapped around the surface of the metal electrode. The material of the oxidation-resistant conductive layer is tin, and the thickness is 1μm.

[0091] Comparative Example 1

[0092] This comparative example demonstrates a method for preparing heterojunction solar cells using existing masking techniques, comprising the following steps:

[0093] 1) Substrate preparation: The surface of the substrate is subjected to strict cleaning treatment to ensure that the surface of the substrate is clean and free of impurities; the cleaning treatment methods include rinsing with deionized water, ultrasonic cleaning, nitrogen drying, etc.; the preparation method of the substrate and the obtained substrate are the same as step S1 in Example 1;

[0094] 2) PVD full-surface seed layer deposition: A conductive seed layer is continuously and uniformly deposited on the entire surface of a clean substrate using DC magnetron sputtering; the material of the conductive seed layer is silver, and the thickness of the conductive seed layer is 200nm.

[0095] 3) Mask layer coating: Liquid positive photoresist is uniformly spin-coated on the surface of the conductive seed layer away from the substrate layer to form a mask layer for subsequent photolithography processes. The thickness of the photoresist is 5-15μm by controlling the spin-coating parameters (such as rotation speed and time).

[0096] 4) Pre-baking: The substrate layer coated with photoresist is placed on a hot plate for soft baking (pre-baking) to evaporate some of the solvent in the photoresist; the temperature of the pre-baking process is 90-120℃ and the time is 60-120s.

[0097] 5) Exposure: The pre-baked substrate is placed in a stepper projection lithography machine, an optical mask with the target gate pattern is placed on the photoresist surface, and the photoresist is exposed to form a negative image of the required gate lines (using positive photoresist).

[0098] 6) Development: Immerse the exposed substrate layer in an alkaline developer to remove the photoresist in the exposed area, expose the metal area corresponding to the final gate line pattern on the conductive seed layer, and rinse with deionized water; the alkaline developer is a tetramethylammonium hydroxide (TMAH) solution of about 0.4wt%, and the development time is 30-90s.

[0099] 7) Post-bake: Perform a post-bake (hard bake) process on the developed substrate to completely remove the residual solvent in the photoresist; the post-bake temperature is 110-150℃ and the time is 2-10min;

[0100] 8) Electroplated gate lines and tin plating: The substrate layer with the photoresist mask pattern is placed in an electroplating bath. Copper metal gate lines are grown on the exposed conductive seed layer through an electroplating process. Tin (Sn) is electroplated on the copper layer to form an anti-oxidation and solderable "tin plating" protective layer. The thickness of the metal gate lines is 15μm and the width is 30μm. The thickness of the anti-oxidation tin layer is 1μm.

[0101] 9) Mask removal: After cleaning and drying the substrate layer with the electroplated metal gate lines, immerse it in a high-concentration NaOH solution to completely remove the photoresist;

[0102] 10) Conductive seed layer etch-back: The substrate layer with the photoresist removed is immersed in the etch-back solution to etch back the conductive seed layer, and then rinsed clean to obtain the solar cell; wherein, the etch-back solution is a mixture of sulfuric acid and hydrogen peroxide, and the mass fraction of H2SO4 is 1%; the etch-back time is 1 min.

[0103] IV measurements were performed on the heterojunction solar cells prepared by the method described in Example 1 and the heterojunction solar cells prepared by the masking process in Comparative Example 1 (the prior art).

[0104] Specifically, the heterojunction solar cells prepared in the above embodiments and comparative examples were tested using a single-flash simulator according to the method disclosed in IEC 904-1. The test conditions were standard test conditions (STC): light intensity of 1000 W / m². 2 The spectrum was AM1.5; the temperature was 25℃. The experimental results are shown in Table 1 below:

[0105] Table 1

[0106] Among them, control group 1 and control group 2 are heterojunction solar cells prepared from the same batch of cells in comparison example 1, and experimental group 1 and experimental group 2 are heterojunction solar cells prepared from the same batch of cells in example 1. Uoc is the open circuit voltage, Isc is the short circuit current, FF is the fill factor, and Eta is the conversion efficiency.

[0107] As shown in the table above, whether comparing experimental group 1 with control group 1, experimental group 2 with control group 2, or the average value of experimental groups 1-2 with the average value of control groups 1-2, compared with the heterojunction solar cells prepared using the existing masking process in the comparative example, the heterojunction solar cells prepared in the examples show an increase in open-circuit voltage of approximately 0.08%, short-circuit current of approximately 0.4%, fill factor of approximately 2.7%, and overall conversion efficiency of 2.8%. The data indicate that the overall performance of the solar cells provided in this application is improved, with particularly significant increases in fill factor FF and conversion efficiency Eta. Therefore, the heterojunction solar cells prepared using the method provided in this application exhibit better output performance and higher conversion efficiency.

[0108] Example 2

[0109] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the silicon dioxide filter layer prepared in step S3 is 100 nm.

[0110] Example 3

[0111] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the silicon dioxide filter layer prepared in step S3 is 200 nm.

[0112] Example 4

[0113] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the silicon dioxide filter layer prepared in step S3 is 220 nm.

[0114] Example 5

[0115] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the silicon dioxide filter layer prepared in step S3 is 300 nm.

[0116] Example 6

[0117] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the silicon dioxide filter layer prepared in step S3 is 500 nm.

[0118] Example 7

[0119] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the conductive seed layer prepared in step S2 is 50 nm.

[0120] Example 8

[0121] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the conductive seed layer prepared in step S2 is 500 nm.

[0122] Example 9

[0123] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the thickness of the metal electrode prepared in step S5 is 5 μm.

[0124] Example 10

[0125] The method for preparing heterojunction solar cells in this embodiment is the same as in Embodiment 1, except that the material of the filter layer prepared in step S3 is silicon nitride.

[0126] The photoelectric conversion efficiency of the heterojunction solar cells prepared in Examples 2 to 10 was tested, and the results are shown in Table 2.

[0127] Table 2

[0128] As shown in Table 2, compared with the heterojunction solar cells prepared by existing masking processes in Comparative Example 1, the overall conversion efficiency of the heterojunction solar cells prepared by the method provided in this application is improved when the thickness of the filter layer is 100nm-500nm. In particular, when the thickness of the filter layer is in the range of 100nm-200nm, the overall conversion efficiency of the heterojunction solar cells is significantly improved.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for fabricating a heterojunction solar cell, characterized in that, include: Preparation of the substrate layer; A patterned conductive seed layer is formed on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer; A light-transmitting filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer; The filter layer is patterned to expose a portion of the patterned conductive seed layer. Metal electrodes are formed on the exposed patterned conductive seed layer.

2. The method for fabricating a heterojunction solar cell as described in claim 1, characterized in that, The filter layer is made of silicon oxide, fluoride, or silicon nitride.

3. The method for preparing a heterojunction solar cell as described in claim 1 or 2, characterized in that, A filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer, the filter layer covering the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer, including: The filter layer is formed on the side of the patterned conductive seed layer away from the substrate layer using one or more processes such as spin coating, physical vapor deposition, chemical vapor deposition, and atomic deposition. The filter layer covers the patterned conductive seed layer and the substrate layer exposed by the patterned conductive seed layer.

4. The method for preparing a heterojunction solar cell according to any one of claims 1-3, characterized in that, The step of patterning the filter layer to expose a portion of the patterned conductive seed layer includes: The filter layer is patterned using one or more of the following processes: inkjet printing etching solution, laser ablation, and plasma etching, in order to remove part of the filter layer and expose part of the patterned conductive seed layer.

5. The method for preparing a heterojunction solar cell according to any one of claims 1-4, characterized in that, A patterned conductive seed layer is formed on at least one side of the substrate layer, the patterned conductive seed layer covering a portion of the substrate layer, including: The patterned conductive seed layer is formed on at least one side of the substrate layer using one or more processes, such as screen printing, inkjet printing, or slot spraying.

6. The method for fabricating a heterojunction solar cell according to any one of claims 1-5, characterized in that, Forming metal electrodes on the exposed patterned conductive seed layer includes: A metal electrode is formed on the exposed patterned conductive seed layer using an electrochemical deposition process.

7. The method for preparing a heterojunction solar cell according to any one of claims 1-6, characterized in that, After forming the metal electrode on the exposed patterned conductive seed layer, the process further includes: An oxidation-resistant conductive layer is wrapped around the surface of the metal electrode.

8. The method for preparing a heterojunction solar cell according to any one of claims 1-7, characterized in that, The material of the patterned conductive seed layer is a metal, alloy, or conductive material that can be bonded to the metal electrode.

9. The method for preparing a heterojunction solar cell according to any one of claims 1-8, characterized in that, The thickness of the patterned conductive seed layer is 50nm-500nm, the thickness of the filter layer is 100nm-500nm, and the thickness of the metal electrode is 5μm-15μm.

10. The method for preparing a heterojunction solar cell according to any one of claims 1-9, characterized in that, The preparation of the substrate layer includes: Provide substrate; A first intrinsic layer, an N-type silicon layer, and a first transparent conductive thin film layer are sequentially formed on one side of the substrate; A second intrinsic layer, a P-type silicon layer, and a second transparent conductive thin film layer are sequentially formed on the other side of the substrate.

11. A heterojunction solar cell prepared by any one of the preparation methods described in claims 1-10.

12. A heterojunction solar cell, comprising a substrate layer, characterized in that, At least one side of the substrate layer is provided with a patterned conductive seed layer, and a patterned filter layer is provided on the side of the patterned conductive seed layer away from the substrate layer. The patterned filter layer exposes at least a portion of the patterned conductive seed layer, and a metal electrode is provided on the exposed patterned conductive seed layer.

13. The heterojunction solar cell according to claim 12, characterized in that, At least a portion of the patterned conductive seed layer is located between the patterned filter layer and the base layer.

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