Solar cell, manufacturing method thereof and photovoltaic module

Abstract

The embodiment of the invention provides a solar cell, a manufacturing method thereof and a photovoltaic module. The solar cell comprises a substrate, a chemical passivation layer, a first aluminum oxide layer, a barrier layer and a second aluminum oxide layer. The chemical passivation layer is located on the first side of the substrate and used for passivating the surface of the substrate; the first aluminum oxide layer is located on the surface, away from the substrate, of the chemical passivation layer and used for providing hydrogen atoms to the surface of the substrate; the barrier layer is located on the surface of the first alumina layer away from the chemical passivation layer; the second aluminum oxide layer is located on the surface, away from the first aluminum oxide layer, of the barrier layer and used for field passivation of the surface of the substrate; the first aluminum oxide layer contains negative charges and has a first charge density, the second aluminum oxide layer contains negative charges and has a second charge density, and the second charge density is larger than the first charge density. The surface passivation effect of the solar cell provided by the embodiment of the invention can be improved, so that the efficiency of the solar cell is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of photovoltaic technology, and in particular to a solar cell and a method for manufacturing the same, and a photovoltaic module. Background Art

[0002] Solar energy is an inexhaustible renewable energy source for mankind. Among the effective utilization of solar energy, solar photovoltaic utilization is one of the fastest-growing and most dynamic research fields in recent years.

[0003] Solar cells are devices that use solar energy to generate electricity. At present, the mainstream solar cells include passivated emitter and rear cell (PERC) solar cells, passivated emitter and rear locally-diffused (PERL) solar cells, silicon heterojunction (SHJ) solar cells, heterojunction back contact (HBC) solar cells, interdigital back contact (IBC) solar cells, tunnel oxide passivated contact (TOPCon) solar cells and polycrystalline silicon on oxide passivating contact (POLO) solar cells.

[0004] Surface passivation technology is one of the key processes for preparing solar cells. Surface passivation technology can effectively reduce the activity of the substrate surface, thereby reducing the recombination rate on the substrate surface. Surface passivation technology mainly reduces the recombination rate and increases the minority carrier lifetime in the following two ways: one is chemical passivation, which is to use the chemical bonds in the material to combine with the dangling bonds on the substrate surface to saturate various defect states on the substrate surface and reduce the concentration of interface defect states, thereby reducing the recombination centers on the substrate surface and reducing the recombination of photogenerated carriers on the substrate surface; the other is field passivation, which is to use the positive or negative charge inside the material to form an electric field on the substrate surface. This electric field can drive away the photogenerated carriers and keep the photogenerated carriers away from the substrate surface, thereby reducing the recombination of photogenerated carriers on the substrate surface.

[0005] However, the surface passivation effect of current solar cells still needs to be improved, and the open circuit voltage of solar cells needs to be increased accordingly. Summary of the invention

[0006] The embodiments of the present application provide a solar cell and a method for manufacturing the same, and a photovoltaic module, which are at least beneficial to improving the surface passivation effect of the solar cell, increasing the open circuit voltage of the solar cell, and thus improving the efficiency of the solar cell.

[0007] On the one hand, an embodiment of the present application provides a solar cell, comprising: a substrate, the substrate having a first side and a second side opposite to each other; a chemical passivation layer, the chemical passivation layer being located on the first side of the substrate, the chemical passivation layer being used to passivate the surface of the substrate; a first aluminum oxide layer, the first aluminum oxide layer being located on a surface of the chemical passivation layer away from the substrate, the first aluminum oxide layer being used to provide hydrogen atoms to the surface of the substrate; a barrier layer, the barrier layer being located on a surface of the first aluminum oxide layer away from the chemical passivation layer; a second aluminum oxide layer, the second aluminum oxide layer being located on a surface of the barrier layer away from the first aluminum oxide layer, the second aluminum oxide layer being used to field passivate the surface of the substrate; wherein the first aluminum oxide layer contains negative charges and has a first charge density, the second aluminum oxide layer contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

[0008] In some embodiments, the total thickness of the chemical passivation layer, the first aluminum oxide layer, and the barrier layer is 2 nm to 4.1 nm.

[0009] In some embodiments, the thickness of the chemical passivation layer is 0.4 nm to 0.8 nm; the thickness of the barrier layer is 0.8 nm to 1.7 nm; and the thickness of the first aluminum oxide layer is 0.8 nm to 1.6 nm.

[0010] In some embodiments, a hydrogen atom content in the first aluminum oxide layer is greater than a hydrogen atom content in the second aluminum oxide layer.

[0011] In some embodiments, the content of hydrogen atoms in the first aluminum oxide layer gradually increases in a direction from the second side to the first side.

[0012] In some embodiments, the first aluminum oxide layer includes a plurality of stacked aluminum oxide sub-layers, and in a direction from the second side to the first side, the hydrogen atom content in the adjacent aluminum oxide sub-layers increases layer by layer.

[0013] In some embodiments, the thickness of the second aluminum oxide layer is greater than the thickness of the first aluminum oxide layer.

[0014] In some embodiments, the thickness of the second aluminum oxide layer is 3.8 nm to 6 nm.

[0015] In some embodiments, the thickness of the barrier layer is greater than the thickness of the chemical passivation layer, and the density of the barrier layer is greater than the density of the chemical passivation layer.

[0016] In some embodiments, the material of the chemical passivation layer includes silicon oxide, silicon oxide containing hydroxide, or silicon oxide containing nitrogen; the material of the barrier layer includes silicon oxide or silicon oxide containing nitrogen.

[0017] On the other hand, an embodiment of the present application also provides a method for manufacturing a solar cell, including: providing a substrate, the substrate having a first side and a second side opposite to each other; forming a chemical passivation layer on the first side of the substrate, the chemical passivation layer being used to passivate the surface of the substrate; forming a first aluminum oxide layer on the chemical passivation layer, the first aluminum oxide layer being used to provide hydrogen atoms to the surface of the substrate; forming a blocking layer on the first aluminum oxide layer; forming a second aluminum oxide layer on the blocking layer, the second aluminum oxide layer being used to field passivate the surface of the substrate; wherein the first aluminum oxide layer contains negative charges and has a first charge density, the second aluminum oxide layer contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

[0018] In some embodiments, the process of forming the first aluminum oxide layer and the second aluminum oxide layer includes: forming the first aluminum oxide layer using a first atomic layer deposition process, the precursor provided in the first atomic layer deposition process includes a first hydrogen source gas, and the process temperature of the first atomic layer deposition process is a first temperature; forming the second aluminum oxide layer using a second atomic layer deposition process, the precursor provided in the second atomic layer deposition process includes a second hydrogen source gas, and the process temperature of the second atomic layer deposition process is a second temperature; wherein the gas flow rate of the first hydrogen source gas is greater than the gas flow rate of the second hydrogen source gas, and the first temperature is less than the second temperature.

[0019] In some embodiments, the first hydrogen source gas and the second hydrogen source gas satisfy: 120%×V2≤V1≤130%×V2, wherein V1 is the gas flow rate of the first hydrogen source gas, and V2 is the gas flow rate of the second hydrogen source gas.

[0020] In some embodiments, the first temperature is lower than or equal to 270°C; and the second temperature is 275°C to 300°C.

[0021] In some embodiments, the chemical passivation layer is formed by an oxidation process, and the barrier layer is formed by an atomic layer deposition process.

[0022] Another embodiment of the present application further provides a photovoltaic module, comprising: a module body, the module body comprising a battery string, a bus bar, a packaging film and a cover plate; the battery string is formed by connecting a plurality of solar cells provided by any of the above embodiments, or is formed by connecting a plurality of solar cells formed by the manufacturing method provided by any of the above embodiments; the packaging film is used to cover the surface of the battery string; the cover plate is used to cover the surface of the packaging film away from the battery string; and a frame is used to support the edge of the module body to support and fix the module body.

[0023] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0024] In the technical solution of the solar cell provided by the embodiment of the present application, a chemical passivation layer is formed between the first side of the substrate and the first aluminum oxide layer, and the chemical passivation layer can be used to passivate the substrate surface, and the first aluminum oxide layer can also provide hydrogen atoms, which diffuse to the substrate surface after passing through the chemical passivation layer to achieve passivation of the substrate surface. In addition, the hydrogen atoms diffuse into the chemical passivation layer and can also repair the defects in the chemical passivation layer to further improve the passivation effect of the chemical passivation layer itself. Therefore, through the synergistic effect between the chemical passivation layer and the first aluminum oxide layer, the substrate surface can have an excellent chemical passivation effect. In addition, the barrier layer formed on the first aluminum oxide layer can block the hydrogen atoms in the first aluminum oxide layer from diffusing outward, so that the hydrogen atoms in the first aluminum oxide layer diffuse toward the substrate surface to the maximum extent to achieve passivation, which is conducive to strengthening the chemical passivation effect of the first aluminum oxide layer. A second aluminum oxide layer is formed on the barrier layer, and the second charge density of the negative charge in the second aluminum oxide layer is greater than the first charge density of the negative charge in the first aluminum oxide layer, so that the second aluminum oxide layer can perform field passivation on the substrate surface. Therefore, in the embodiment of the present application, the chemical passivation effect of the first aluminum oxide layer on the substrate surface can be enhanced without affecting the field passivation effect, thereby achieving the purpose of increasing the open circuit voltage of the solar cell and further improving the effect of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, which do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and the figures in the drawings do not constitute a scale limitation unless otherwise stated. In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of a cross-sectional structure of a solar cell;

[0027] Figure 2 A schematic diagram of a cross-sectional structure of a solar cell provided in an embodiment of the present application;

[0028] Figure 3 A schematic diagram of another cross-sectional structure of a solar cell provided in an embodiment of the present application;

[0029] Figure 4 A schematic flow chart of each step in the method for manufacturing a solar cell provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of a partial cross-sectional structure of a photovoltaic module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] As can be seen from the background technology, the performance of solar cells needs to be improved.

[0032] Figure 1 This is a schematic diagram of the cross-sectional structure of a solar cell. Figure 1 The solar cell includes a substrate 11 and an aluminum oxide layer 12 located on the substrate 11 .

[0033] The aluminum oxide layer 12 is a common passivation film layer used in solar cells. The aluminum oxide layer 12 contains negative charges, so that the aluminum oxide layer 12 can perform field passivation on the surface of the substrate 11; in addition, since a hydrogen source is provided during the deposition of the aluminum oxide layer 12, the aluminum oxide layer 12 contains hydrogen atoms, which can be combined with the dangling bonds on the surface of the substrate 11 after diffusing to the surface of the substrate 11 to chemically passivate the surface of the substrate 11. In other words, the aluminum oxide layer 12 can be used to achieve chemical passivation and field passivation on the surface of the substrate 11.

[0034] However, the passivation effect of the aluminum oxide layer 12 still has obvious limitations, resulting in the performance of solar cells still needing to be improved. For example, the open circuit voltage of solar cells still needs to be improved, so that the photoelectric conversion efficiency of solar cells also has room for improvement. Analysis found that the reasons for the insufficient passivation effect of the aluminum oxide layer 12 include: on the one hand, the chemical passivation ability of the H atoms in the aluminum oxide layer 12 on the surface of the substrate 11 is not enough to achieve the optimal passivation. On the other hand, there is a risk of H atoms in the aluminum oxide layer 12 diffusing outward, resulting in the loss of H atoms in the aluminum oxide layer 12, which reduces the content of H atoms that can diffuse inward to the surface of the substrate 11, and as the H atoms are lost, the chemical passivation ability of the aluminum oxide layer 12 on the surface of the substrate 11 will be affected accordingly. In particular, there is a high-temperature process in the manufacturing steps of solar cells, and the high-temperature process will especially aggravate the degree of outward diffusion of H atoms in the aluminum oxide layer 12.

[0035] At least to solve the above-mentioned technical problems, an embodiment of the present application provides a solar cell, on the substrate of which there is a stacked structure including a chemical passivation layer, a first aluminum oxide layer, a barrier layer and a second aluminum oxide layer, and the stacked structure can significantly improve the passivation effect of the substrate surface.

[0036] The following will be described in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the embodiments of the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the embodiments of the present application can be implemented.

[0037] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0038] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0040] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0041] In the description of the embodiments of the present application, technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0042] In the accompanying drawings corresponding to the embodiments of the present application, the thickness and area of ​​the layer are magnified for better understanding and ease of description. When describing a component (such as a layer, film, region or substrate) on another component or on the surface of another component, the component can be "directly" located on the surface of another component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a partial edge of the entire surface.

[0043] In the description of the embodiments of the present application, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it may be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may exist in between. In addition, when a component such as a layer, film, region, or plate is "directly located on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located in between.

[0044] The terms used in the description of the various embodiments described herein are only used to describe specific embodiments and are not intended to be limiting. As used in the description of the various embodiments described and in the appended claims, "component" is also intended to include the plural form unless the context clearly indicates otherwise. Among them, components include components such as layers, films, regions, or plates.

[0045] Figure 2 A schematic diagram of a cross-sectional structure of a solar cell provided in an embodiment of the present application.

[0046] refer to Figure 2 , the solar cell may include a substrate 100, the substrate 100 having a first side and a second side opposite to each other. The solar cell also includes a chemical passivation layer 101, a first aluminum oxide layer 102, a barrier layer 103 and a second aluminum oxide layer 104. The chemical passivation layer 101 is located on the first side of the substrate 100, and is used to passivate the surface of the substrate 100. The first aluminum oxide layer 102 is located on the surface of the chemical passivation layer 101 away from the substrate 100, and is used to provide hydrogen atoms to the surface of the substrate 100. The barrier layer 103 is located on the surface of the first aluminum oxide layer 102 away from the chemical passivation layer 101, and the second aluminum oxide layer 104 is located on the surface of the barrier layer 103 away from the first aluminum oxide layer 102, and the second aluminum oxide layer 104 is used to perform field passivation on the surface of the substrate 100. Among them, the first aluminum oxide layer 102 contains negative charges and has a first charge density, and the second aluminum oxide layer 104 contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

[0047] In the technical solution of the solar cell described above, a chemical passivation layer 101 is formed between the first side of the substrate 100 and the first aluminum oxide layer 102. The chemical passivation layer 101 can be used to passivate the surface of the substrate 100, and the first aluminum oxide layer 102 can also provide hydrogen atoms, which diffuse to the surface of the substrate 100 after passing through the chemical passivation layer 101, thereby passivating the surface of the substrate 100. Moreover, the diffusion of the hydrogen atoms into the chemical passivation layer 101 can also repair the defects in the chemical passivation layer 101, so as to further improve the passivation effect of the chemical passivation layer 101 itself. Therefore, through the synergistic effect between the chemical passivation layer 101 and the first aluminum oxide layer 102, the surface of the substrate 100 can have an excellent chemical passivation effect. In addition, the barrier layer 103 formed on the first aluminum oxide layer 102 can block the hydrogen atoms in the first aluminum oxide layer 102 from diffusing outward, so that the hydrogen atoms in the first aluminum oxide layer 102 can diffuse to the maximum extent toward the surface of the substrate 100 to achieve passivation, which is beneficial to enhance the chemical passivation effect of the first aluminum oxide layer 102. A second aluminum oxide layer 104 is formed on the barrier layer 103, and the second charge density of negative charges in the second aluminum oxide layer 104 is greater than the first charge density of negative charges in the first aluminum oxide layer 102, so that the second aluminum oxide layer 104 can perform field passivation on the surface of the substrate 100.

[0048] Therefore, in the embodiment of the present application, without affecting the field passivation effect, the chemical passivation effect of the first aluminum oxide layer 102 on the surface of the substrate 100 can also be improved, thereby achieving the purpose of increasing the open circuit voltage of the solar cell and further improving the effect of the solar cell.

[0049] The solar cell may be any one of a PERC solar cell, a PERL solar cell, a SHJ solar cell, a HBC solar cell, an IBC solar cell, a TOPCon solar cell or a POLO solar cell. The embodiment of the present application does not limit the type of solar cell.

[0050] The substrate 100 is used to receive incident light and generate photogenerated carriers. The material of the substrate 100 can be a single element semiconductor material or a compound semiconductor material. Among them, the single element semiconductor material can be silicon or germanium, and the single element semiconductor material can be a single crystal material, a polycrystalline material, an amorphous material or a microcrystalline material (a state having both single crystal and amorphous states is called a microcrystalline state). For example, silicon can be single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon. The compound semiconductor material can be silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride or copper indium selenide and other materials.

[0051] In addition, the substrate 100 may also be a sapphire substrate, a silicon on insulator substrate, or a germanium on insulator substrate.

[0052] In this embodiment, the material of the substrate 100 is single crystal silicon. It should be noted that the embodiment of the present application does not limit the material of the substrate.

[0053] The substrate 100 may be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type doping element, which may be any one of the V-group elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type doping element, which may be any one of the III-group elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0054] The solar cell can be a single-sided cell, then one of the first side or the second side can be used as the light-receiving side for receiving incident light, and correspondingly, the other of the first side or the second side can be used as the backlight side. The solar cell can be a double-sided cell, then both the first side and the second side can be used as the light-receiving side, and both can be used to receive incident light. It can be understood that the backlight side referred to in the embodiments of the present application can also receive incident light, but the degree of receiving the incident light is weaker than that of the light-receiving side, and therefore it is defined as the backlight side.

[0055] In this embodiment, the solar cell is a single-sided cell and the first side is the backlight side as an example for description. It should be noted that the embodiment of the present application does not limit the first side, and in other embodiments, the first side may also be the light-receiving side.

[0056] At least one surface of the first side or the second side of the substrate 100 may also have a velvet structure, which is beneficial to enhancing the absorption utilization rate of the incident light by the substrate 100. Specifically, the velvet structure may be a pyramid structure, which, as a common velvet structure, not only reduces the reflectivity of the substrate 100 surface to the incident light, but also helps to form a light trap to enhance the absorption effect of the substrate 100 to the incident light, thereby improving the photoelectric conversion efficiency of the solar cell.

[0057] In some examples, the solar cell is a single-sided cell, and a velvet structure can be formed on the light-receiving side of the substrate 100, and the backlight side of the substrate 100 can be a polished surface, that is, the surface of the backlight side of the substrate 100 is flatter than the surface of the light-receiving side. It should be noted that for a single-sided cell, a velvet structure can also be provided on the surface of both the light-receiving side and the backlight side of the substrate 100. In other examples, the solar cell is a double-sided cell, and a velvet structure can be provided on the surface of both the first side and the second side of the substrate 100.

[0058] The chemical passivation layer 101 can passivate the dangling bonds on the surface of the substrate 100, which can be silicon dangling bonds. Specifically, part of the atoms in the precursor provided during the formation of the chemical passivation layer 101 are combined with unsaturated silicon atoms on the surface of the substrate 100 to reduce the density of the dangling bonds, thereby reducing the defect state density on the surface of the substrate 100, so that the substrate 100 has good interface properties, so that the recombination rate on the surface of the substrate 100 can be reduced, thereby playing a role in surface passivation.

[0059] In addition, the chemical passivation layer 101 can also play a role in stress buffering between the substrate 100 and the first aluminum oxide layer 102. Specifically, compared with the lattice difference between the substrate 100 and the first aluminum oxide layer 102, the lattice difference between the substrate 100 and the chemical passivation layer 101 is smaller, that is, the lattice matching between the substrate 100 and the chemical passivation layer 101 is better than the lattice matching between the substrate 100 and the first aluminum oxide layer 102. Therefore, the stress problem caused by the poor lattice matching can be avoided, and then the interface defects caused by the stress can be avoided, so that the substrate 100 and the chemical passivation layer 101 have good interface performance, which is more conducive to the passivation of the surface of the substrate 100.

[0060] In this embodiment, the material of the chemical passivation layer 101 is silicon oxide. Silicon oxide is composed of Si-O tetrahedrons, the center of the Si-O tetrahedron is a silicon atom, and the four vertices are oxygen atoms, and the four oxygen atoms at the vertices just satisfy the valence of the silicon atom. From the oxygen at the vertices to the silicon in the center, and then to the oxygen at another vertices, it is called an O-Si-O bond bridge. During the formation of the chemical passivation layer 101, the oxygen atoms will combine with the unsaturated silicon atoms (i.e., silicon dangling bonds) on the surface of the substrate 100 to form Si-O bonds, thereby reducing the number of unsaturated silicon atoms on the surface of the substrate 100 to achieve chemical passivation.

[0061] It is understandable that the embodiment of the present application does not limit the material of the chemical passivation layer 101. For example, in other embodiments, the material of the chemical passivation layer 101 may also be silicon hydroxide or silicon oxide containing nitrogen. In silicon hydroxide containing hydrogen, hydrogen elements exist in the form of hydrogen atoms, which may be unbonded dangling bonds, or they may combine with O atoms to form HO chemical bonds, or hydrogen atoms may combine with Si atoms to form Si-H bonds; in silicon oxide containing nitrogen, nitrogen elements exist in the form of nitrogen atoms, which may be unbonded dangling bonds, or they may combine with O atoms to form NO chemical bonds, or they may combine with Si atoms to form Si-N bonds.

[0062] The thickness of the chemical passivation layer 101 should not be too thin. If the thickness of the chemical passivation layer 101 is too thin, the passivation ability of the chemical passivation layer 101 for the dangling bonds on the surface of the substrate 100 is insufficient, and there are many lattice defects in the chemical passivation layer 101, which will also affect the passivation effect of the chemical passivation layer 101. The thickness of the chemical passivation layer 101 should not be too thick. If the thickness of the chemical passivation layer 101 is too thick, it will be difficult for the hydrogen atoms in the first aluminum oxide layer 102 to diffuse to the surface of the substrate 100, which will affect the passivation effect of the hydrogen atoms on the surface of the substrate 100, and will also affect the field passivation effect of the second aluminum oxide layer 104 on the surface of the substrate 100.

[0063] In addition, in this embodiment, the chemical passivation layer 101 can also be designed to allow majority carriers (majority carriers) to tunnel through while blocking minority carriers (minority carriers) from passing through, which is beneficial to improving the carrier collection efficiency. Therefore, the thickness of the chemical passivation layer 101 should not be too thick.

[0064] The solar cell also includes a plurality of electrodes (not shown) arranged at intervals, and the electrodes penetrate the second aluminum oxide layer 104, the barrier layer 103, the first aluminum oxide layer 102, and the chemical passivation layer 101, so as to achieve metallization contact between the electrodes and the substrate 100 to collect carriers. Generally, the electrodes are formed by a sintering process. If the thickness of the chemical passivation layer 101 is too thick, it may affect the contact performance between the electrodes formed by the sintering process and the substrate 100, and affect the overall performance of the electrodes. In addition, the chemical passivation layer 101 can also serve as a buffer between the substrate 100 and the electrode, which helps to reduce the damage of the electrode slurry to the substrate 100 during the sintering process.

[0065] It should be noted that, in other embodiments, the electrode may not penetrate the chemical passivation layer, and the electrode may contact the surface of the chemical passivation layer or extend into the interior of the chemical passivation layer.

[0066] Taking the above factors into consideration, in the present embodiment, the thickness of the chemical passivation layer 101 is 0.4 nm to 0.8 nm. For example, the thickness of the chemical passivation layer 101 may be 0.42 nm, 0.55 nm, 0.61 nm, 0.68 nm or 0.75 nm.

[0067] In a specific example, the thickness of the chemical passivation layer 101 can be 0.5nm to 0.7nm. Within this thickness range, the chemical passivation layer 101 ensures that the chemical passivation layer 101 itself has good chemical passivation on the surface of the substrate 100, and the chemical passivation layer 101 has a weak blocking ability for hydrogen atoms, ensuring the amount of hydrogen atoms diffused to the surface of the substrate 100 through the chemical passivation layer 101, ensuring the field passivation effect of the second aluminum oxide layer 104, and at the same time allowing majority carriers to tunnel through the chemical passivation layer 101 and blocking minority carriers, and ensuring the contact performance between the electrode and the substrate 100.

[0068] The first aluminum oxide layer 102 is used to provide hydrogen atoms to the surface of the substrate 100. The hydrogen atoms diffuse to the surface of the substrate 100 and can combine with the dangling bonds on the surface of the substrate 100, thereby reducing the interface state density on the surface of the substrate 100, so as to achieve the effect of reducing the recombination rate on the surface of the substrate 100, thereby achieving chemical passivation of the surface of the substrate 100. In addition, the hydrogen atoms can also diffuse into the interior of the substrate 100 to passivate the defects in the substrate 100, which is conducive to further improving the photoelectric conversion efficiency of the solar cell.

[0069] Specifically, on one hand, a hydrogen source gas is provided during the formation of the first aluminum oxide layer 102, and the hydrogen atoms in the hydrogen source gas can diffuse to the surface of the substrate 100 through the chemical passivation layer 101. On the other hand, after the first aluminum oxide layer 102 is formed, there are free hydrogen atoms in the first aluminum oxide layer 102, and the hydrogen atoms can also diffuse to the surface of the substrate 100 through the chemical passivation layer 101. The timing of the above two hydrogen atom diffusions is conducive to achieving chemical passivation of the surface of the substrate 100.

[0070] In addition, as can be seen from the above analysis, the thickness of the chemical passivation layer 101 is set relatively thin due to the fact that too thick thickness of the chemical passivation layer 101 will affect the field passivation effect of the second aluminum oxide layer 104. Due to the thin thickness of the chemical passivation layer 101, pinhole defects exist in the chemical passivation layer 101. The existence of the pinhole defects makes the chemical passivation ability of the chemical passivation layer 101 itself insufficient to play the best, and there are unbonded oxygen atoms (i.e., oxygen dangling bonds) or unbonded silicon atoms (i.e., silicon dangling bonds) at the pinhole defects. In particular, the pinhole defects adjacent to the surface of the substrate 100 will cause the interface state defect density between the substrate 100 and the chemical passivation layer 101 to become high.

[0071] In this embodiment, the first aluminum oxide layer 102 is also used to provide hydrogen atoms to the chemical passivation layer 101 to repair the pinhole defects in the chemical passivation layer 101, thereby ensuring that the chemical passivation layer 101 has a good passivation effect. Specifically, for the pinhole defects adjacent to the surface of the substrate 100, the chemical passivation ability of the chemical passivation layer 101 at this location is insufficient, and the hydrogen atoms diffused to this location can improve the degree of chemical passivation at this location. The hydrogen atoms can modify the silicon dangling bonds at this location so that the silicon dangling bonds and hydrogen atoms are combined to form Si-H bonds, and can modify the oxygen dangling bonds at this location so that the oxygen dangling bonds and hydrogen atoms are combined to form HO bonds, so as to further reduce the interface state defects on the surface of the substrate 100. In addition, for the defects inside the chemical passivation layer 101, the hydrogen atoms can also combine with the unbonded oxygen atoms or unbonded silicon atoms at the defect to repair the defects inside the chemical passivation layer 101, thereby further improving the quality of the chemical passivation layer 101.

[0072] To sum up, in this embodiment, the chemical passivation layer 101 and the first aluminum oxide layer 102 work synergistically to strengthen the chemical passivation effect of the hydrogen atoms in the first aluminum oxide layer 102 on the surface of the substrate 100, and strengthen the chemical passivation effect of the chemical passivation layer 101 on the surface of the substrate 100, so that the surface of the substrate 100 is better passivated.

[0073] The first aluminum oxide layer 102 mainly plays a role of chemical passivation, and the field passivation ability of the first aluminum oxide layer 102 is relatively weak. Therefore, the first aluminum oxide layer 102 has a relatively high hydrogen content, and the hydrogen atom content in the first aluminum oxide layer 102 is greater than the hydrogen atom content in the second aluminum oxide layer 104. In this way, the first aluminum oxide layer 102 can provide more hydrogen atoms to passivate the surface of the substrate 100, so that the chemical passivation effect of the synergistic effect of the first aluminum oxide layer 102 and the chemical passivation layer 101 is optimized.

[0074] It should be noted that in the embodiments of the present application, the hydrogen atom content refers to the content of hydrogen atoms per unit volume.

[0075] The thickness of the first aluminum oxide layer 102 should not be too thin or too thick. If the thickness of the first aluminum oxide layer 102 is too thin, the content of hydrogen atoms in the first aluminum oxide layer 102 is relatively small, and the chemical passivation ability provided by the hydrogen atoms is limited. If the thickness of the first aluminum oxide layer 102 is too thick, the field passivation effect of the second aluminum oxide layer 104 may be affected.

[0076] Therefore, in this embodiment, the thickness of the first aluminum oxide layer 102 is 0.8 nm to 1.6 nm, for example, 0.9 nm, 1.1 nm, 1.3 nm, 1.45 nm or 1.55 nm.

[0077] In some examples, the thickness of the first aluminum oxide layer 102 is 1 nm to 1.5 nm. Within this thickness range, the first aluminum oxide layer 102 can provide sufficient hydrogen atoms and ensure that the first aluminum oxide layer 102 has a relatively small or negligible effect on the field passivation effect of the second aluminum oxide layer 104.

[0078] In some examples, the hydrogen atom content in the first aluminum oxide layer 102 may gradually increase in a direction from the second side to the first side, that is, the closer to the surface of the first side of the substrate 100, the smaller the hydrogen atom content in the first aluminum oxide layer 102, and the closer to the barrier layer 103, the larger the hydrogen atom content in the first aluminum oxide layer 102. In this way, the hydrogen atom content in the first aluminum oxide layer 102 presents a gradient change, and the hydrogen atoms have a tendency to diffuse from the high-concentration area to the low-concentration area. The hydrogen atoms inside the first aluminum oxide layer 102 have a tendency to diffuse toward the surface of the substrate 100, which is beneficial to further reduce the degree of outward diffusion of hydrogen atoms; and the hydrogen atom content in the first aluminum oxide layer 102 adjacent to the chemical passivation layer 101 is relatively small, and the hydrogen atom content in the first aluminum oxide layer 102 away from the chemical passivation layer 101 is relatively high. In this way, it can be ensured that there are sufficient hydrogen atoms to diffuse toward the surface of the substrate 100, and a large number of hydrogen atoms can be avoided from escaping from the first aluminum oxide layer 102 at the same time, thereby avoiding the problem of bulging of the chemical passivation layer 101 that may be caused by a large number of hydrogen atoms entering the chemical passivation layer 101 at the same time.

[0079] That is to say, the closer to the surface of the substrate 100, the smaller the hydrogen atom content in the first aluminum oxide layer 102 is, which is beneficial to further improve the passivation effect on the surface of the substrate 100 and avoid damage to the chemical passivation layer 101. At the same time, it is also beneficial to further reduce the degree of outward diffusion of hydrogen atoms, so that the thickness of the barrier layer 103 can be made thinner. In this way, the field passivation effect of the second aluminum oxide layer 104 can be further optimized.

[0080] In some other examples, the hydrogen atom content in the first aluminum oxide layer 102 in the direction from the second side to the first side may also be the same or substantially the same.

[0081] The first aluminum oxide layer 102 may be a single-layer structure. In some examples, the hydrogen atom content in the first aluminum oxide layer 102 is the same or substantially the same in the direction from the second side to the first side. In other examples, the hydrogen atom content in the first aluminum oxide layer 102 may also gradually increase in the direction from the second side to the first side.

[0082] Figure 3 This is another cross-sectional diagram of a solar cell. Figure 3 , the first aluminum oxide layer 102 may also include a plurality of stacked aluminum oxide sub-layers 112, and in the direction from the second side to the first side, the hydrogen atom content in the aluminum oxide sub-layers 112 of adjacent layers increases layer by layer. In other words, the hydrogen atom content in the aluminum oxide sub-layer 112 adjacent to the barrier layer 103 is the largest, and the hydrogen atom content in the aluminum oxide sub-layer 112 adjacent to the surface of the substrate 100 is the smallest.

[0083] The first aluminum oxide layer 102 may include 2 to 4 aluminum oxide sublayers 112, so that when the total thickness of the first aluminum oxide layer 102 is relatively thin, the lattice defects of the single aluminum oxide sublayer 112 can be ensured to be small, and the requirement of gradient distribution of hydrogen atom content in the first aluminum oxide layer 102 can also be met. In some examples, the thickness of each aluminum oxide sublayer 112 can be the same.

[0084] In some specific examples, the first aluminum oxide layer 102 may include two aluminum oxide sub-layers 112, and the thickness of the aluminum oxide sub-layer 112 adjacent to the barrier layer 103 is greater than the thickness of the aluminum oxide sub-layer 112 adjacent to the chemical passivation layer 101. Since the hydrogen atom content of the adjacent barrier layer 103 is greater than the hydrogen atom content of the adjacent chemical passivation layer 101, and the thicknesses of the two satisfy the aforementioned relationship, under the barrier of the barrier layer 103 and the driving force of the difference in hydrogen atom concentration between the two aluminum oxide sub-layers 112, it is more conducive to improving the ability of hydrogen atoms in the two aluminum oxide sub-layers 112 to diffuse to the surface of the substrate 100, thereby further improving the chemical passivation effect on the surface of the substrate 100.

[0085] It should be noted that the direction from the second side to the first side refers to the stacking direction along the chemical passivation layer 101 , the first aluminum oxide layer 102 , the barrier layer 103 and the second aluminum oxide layer 104 .

[0086] The barrier layer 103 is used to block the hydrogen atoms in the first aluminum oxide layer 102 from diffusing outward, ensuring that the hydrogen atoms in the first aluminum oxide layer 102 can passivate the surface of the substrate 100 to the maximum extent. Specifically, the barrier layer 103 can prevent the hydrogen atoms from passing through, so that the first aluminum oxide layer 102 can have a sufficient content of hydrogen atoms diffusing toward the substrate 100, thereby ensuring that the hydrogen atoms have a good passivation effect on the surface of the substrate 100 for a long period of time. In addition, the barrier layer 103 is also conducive to improving the diffusion capacity of the hydrogen atoms in the first aluminum oxide layer 102 to diffuse toward the surface of the substrate 100.

[0087] In this embodiment, the thickness of the barrier layer 103 is greater than the thickness of the chemical passivation layer 101, and the density of the barrier layer 103 is greater than the density of the chemical passivation layer 101. In this way, the barrier layer 103 can improve its ability to block hydrogen atoms.

[0088] From the above analysis, it can be seen that the barrier layer 103 needs to have sufficient blocking ability for hydrogen atoms, and the barrier layer 103 itself will not introduce new defects, and the barrier layer 103 cannot affect the distribution of negative charges in the second aluminum oxide layer 104, so as to ensure that the second aluminum oxide layer 104 has a good field passivation effect on the substrate 100. Based on this, in this embodiment, the material of the barrier layer 103 can be the same as the material of the chemical passivation layer 101, and the thickness of the barrier layer 103 is greater than the thickness of the chemical passivation layer 101, and the density of the barrier layer 103 is greater than the density of the chemical passivation layer 101. In this way, it can be ensured that the process of forming the barrier layer 103 will not introduce new defects, and because the thickness of the barrier layer 103 is relatively thick and the density is relatively large, it can provide a sufficient blocking effect for hydrogen atoms.

[0089] In this embodiment, the material of the barrier layer 103 is silicon oxide. In other embodiments, the material of the barrier layer may also be silicon oxide containing nitrogen.

[0090] It is understood that in other embodiments, the material of the barrier layer may be different from the material of the chemical passivation layer. For example, the material of the chemical passivation layer is silicon oxide, and the material of the barrier layer is silicon oxide containing nitrogen.

[0091] The thickness of the barrier layer 103 should not be too thin or too thick. If the thickness of the barrier layer 103 is too thin, the barrier layer 103's barrier capability for hydrogen atoms needs to be strengthened; if the thickness of the barrier layer 103 is too thick, the field passivation effect of the second aluminum oxide layer 104 may be affected, and the sintering process when forming the electrode may be affected, so that the overall performance of the electrode needs to be strengthened.

[0092] Therefore, in this embodiment, the thickness of the barrier layer 103 is 0.8 nm to 1.7 nm, for example, 0.9 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.55 nm or 1.65 nm.

[0093] In some examples, the thickness of the barrier layer 103 may be 1 nm to 1.5 nm. Within this thickness range, the barrier layer 103 is conducive to ensuring that the barrier layer 103 has sufficient hydrogen atom diffusion blocking capability while making the barrier layer 103 have negligible or no effect on the field passivation effect of the second aluminum oxide layer 104.

[0094] The second aluminum oxide layer 104 is used to perform field passivation on the surface of the substrate 100. Specifically, the second charge density of the second aluminum oxide layer 104 is greater than the first charge density of the first aluminum oxide layer 102, and the hydrogen atoms that passivate the surface of the substrate 100 mainly come from the first aluminum oxide layer 102, so the hydrogen content in the second aluminum oxide layer 104 is less than the hydrogen content in the first aluminum oxide layer 102.

[0095] The negative charges in the second aluminum oxide layer 104 form a built-in electric field on the surface of the substrate 100. The built-in electric field puts the surface of the substrate 100 in an inversion state, thereby reducing the probability of carriers meeting and recombining on the surface of the substrate 100, thereby reducing the recombination rate on the surface of the substrate 100, and achieving field passivation on the surface of the substrate 100.

[0096] The thickness of the second aluminum oxide layer 104 is greater than that of the first aluminum oxide layer 102 , so that the second aluminum oxide layer 104 contains a large amount of negative charges.

[0097] Since there are chemical passivation layer 101, first aluminum oxide layer 102 and barrier layer 103 between substrate 100 and second aluminum oxide layer 104, in order to enable the second aluminum oxide layer 104 to exert the best field passivation effect, the total thickness of chemical passivation layer 101, first aluminum oxide layer 102 and barrier layer 103 is less than or equal to 4.1nm. This is because if the total thickness of chemical passivation layer 101, first aluminum oxide layer 102 and barrier layer 103 is too thick, the distance between the second aluminum oxide layer 104 and the surface of substrate 100 is relatively large, and the negative charge in the second aluminum oxide layer 104 makes the built-in electric field formed at the surface of substrate 100 relatively weak, which will affect the field passivation effect exerted by the second aluminum oxide layer 104.

[0098] In addition, as can be seen from the above analysis, the chemical passivation layer 101, the first aluminum oxide layer 102 and the barrier layer 103 each need to play their respective roles. To ensure that each layer plays a strong role, the total thickness of the chemical passivation layer 101, the first aluminum oxide layer 102 and the barrier layer 103 should not be too thin.

[0099] To this end, in this embodiment, the total thickness of the chemical passivation layer 101, the first aluminum oxide layer 102 and the barrier layer 103 is 2nm to 4.1nm. For example, the total thickness of the chemical passivation layer 101, the first aluminum oxide layer 102 and the barrier layer 103 can be 2.5nm, 3nm, 3.2nm, 3.5nm, 3.7nm or 3.9nm.

[0100] In some examples, the total thickness of the chemical passivation layer 101, the first aluminum oxide layer 102, and the barrier layer 103 is 3 nm to 4 nm. Within this thickness range, the chemical passivation layer 101 and the first aluminum oxide layer 102 work together to achieve the best chemical passivation effect, and the barrier layer 103 has a strong barrier capability against the outward diffusion of hydrogen atoms, while the second aluminum oxide layer 104 can also achieve the best field passivation effect.

[0101] The thickness of the second aluminum oxide layer 104 should not be too thin or too thick. If the thickness of the second aluminum oxide layer 104 is too thin, the field passivation capability provided by the second aluminum oxide layer 104 needs to be strengthened; if the thickness of the second aluminum oxide layer 104 is too thick, it will affect the sintering process when forming the electrode, so that the overall performance of the electrode needs to be strengthened.

[0102] In this embodiment, the thickness of the second aluminum oxide layer 104 is 3.8 nm to 6 nm. For example, the thickness of the second aluminum oxide layer 104 may be 4.2 nm, 4.4 nm, 4.5 nm, 4.7 nm, 4.9 nm, 5.5 nm, 5.7 nm or 5.85 nm.

[0103] In some examples, the thickness of the second aluminum oxide layer 104 may be 4 nm to 5 nm. The second aluminum oxide layer 104 within this thickness range can ensure that the second aluminum oxide layer 104 has sufficient field passivation effect and avoid the problem that the electrode performance needs to be enhanced due to the second aluminum oxide layer 104 being too thick.

[0104] In this embodiment, the total thickness of the chemical passivation layer 101, the first aluminum oxide layer 102, the barrier layer 103 and the second aluminum oxide layer 104 can be 6nm to 10nm, for example, 7nm, 7.4nm, 7.9nm, 8.2nm, 8.5nm, 8.8nm, 9.2nm, 9.5nm or 9.8nm. Within this thickness range, each layer can play a corresponding role, making the overall thickness of the solar cell relatively thin, which is conducive to reducing the overall weight of the solar cell.

[0105] In some examples, the total thickness of the chemical passivation layer 101 , the first aluminum oxide layer 102 , the barrier layer 103 , and the second aluminum oxide layer 104 may be 6.5 nm to 9 nm.

[0106] In a specific example, the thickness of the chemical passivation layer 101 may be 0.5 nm to 0.7 nm, the thickness of the first aluminum oxide layer 102 may be 1 nm to 1.5 nm, the thickness of the barrier layer 103 may be 1 nm to 1.5 nm, and the thickness of the second aluminum oxide layer 104 may be 4 nm to 5 nm.

[0107] It is understandable that as time goes by, the amount of hydrogen atoms in the first aluminum oxide layer 102 diffusing toward the surface of the substrate 100 increases, the hydrogen atom content in the first aluminum oxide layer 102 will decrease relatively, and the hydrogen atom content in the second aluminum oxide layer 104 may be equal to or slightly greater than the hydrogen atom content in the first aluminum oxide layer 102.

[0108] It should also be noted that the stacked passivation film layer composed of the chemical passivation layer 101, the first aluminum oxide layer 102, the barrier layer 103 and the second aluminum oxide layer 104 in the above embodiment can also be simultaneously arranged on the first side and the second side of the substrate 100, that is, the stacked passivation film layer can be simultaneously applied to the light-receiving side and the backlight side of the substrate 100.

[0109] The solar cell also has an emitter (not shown) and a surface field (not shown). The emitter can be arranged on the first side or the second side of the substrate 100, the surface field can be arranged on the first side or the second side of the substrate 100, and a PN junction is formed between the emitter and the substrate 100, that is, the doping type of the emitter is different from the doping type of the substrate 100, the doping type of the emitter is one of N-type doping or P-type doping, the doping type of the substrate 100 is the other of N-type doping or P-type doping, and the doping type of the surface field and the doping type of the substrate 100 are both N-type doping or P-type doping, and the doping concentration of the surface field is greater than the doping concentration of the substrate 100.

[0110] It should be noted that, depending on the type of solar cell, the positions of the emitter and the surface field in the substrate 100 are also different. The specific positions of the emitter and the surface field are not limited in the embodiments of the present application.

[0111] The solar cell may further include a plurality of electrodes, which penetrate the second aluminum oxide layer 104, the barrier layer 103, the first aluminum oxide layer 102 and the chemical passivation layer 101 to achieve electrical contact with the emitter or the surface field.

[0112] Table 1 is a comparison table of the efficiencies of solar cells provided in the embodiments of the present application (ie, the experimental group) and solar cells in the related art (ie, the control group).

[0113] Table 1

[0114] Group Eta(%) Voc(unit:V) Isc (unit: mA) FF(%) Control group 26.39 0.732 18.51 85.78 Experimental Group 26.44 0.733 18.51 85.85

[0115] Among them, Eta refers to conversion efficiency; Voc refers to open circuit voltage. A high open circuit voltage means that under the same light intensity, its output voltage will also increase accordingly; Isc refers to short circuit current, which is the maximum current generated by the solar cell; FF refers to fill factor. The higher the fill factor, the more fully the solar cell can utilize light energy and the higher the output power. The formation process and thickness of the aluminum oxide layer in the control group are the same as the formation process and thickness of the second aluminum oxide layer in the experimental group.

[0116] It can be seen from Table 1 that, compared with the control group, the open circuit voltage Voc of the solar cell in the embodiment of the present application is increased by 1 mV, the conversion efficiency Eta is increased by 0.05%, and the fill factor FF is increased by 0.07%, which indicates that the efficiency of the solar cell provided in the embodiment of the present application is effectively improved.

[0117] In the technical solution of the above-mentioned solar cell, the chemical passivation layer 101 can provide chemical passivation to the surface of the substrate 100, and can also serve as a buffer layer between the substrate 100 and the first aluminum oxide layer 102, which helps to improve the interface performance between the layers; the first aluminum oxide layer 102 contains a large number of hydrogen atoms, and the hydrogen atoms diffuse to the surface of the substrate 100 through the chemical passivation layer 101 to achieve chemical passivation of the surface of the substrate 100. In addition, the hydrogen atoms can also synergize with the chemical passivation layer 101 to enhance the passivation effect of hydrogen atoms on the surface of the substrate 100, and increase the passivation effect of the chemical passivation layer 101 on the surface of the substrate 100, so that the surface of the substrate 100 has a high degree of chemical passivation.

[0118] The first aluminum oxide layer 102 may contain more hydrogen atoms, and the barrier layer 103 may block the outward expansion of hydrogen atoms, thereby ensuring that the hydrogen atoms chemically passivate the surface of the substrate 100 to the maximum extent, thereby further optimizing the chemical passivation effect of the surface of the substrate 100 .

[0119] The second aluminum oxide layer 104 can provide field passivation to the surface of the substrate 100 to further optimize the passivation effect of the surface of the substrate 100 .

[0120] In summary, the solar cell provided in the embodiment of the present application can greatly improve the problem of insufficient passivation effect on the surface of the substrate 100 and the diffusion of hydrogen atoms, thereby achieving a better passivation effect, effectively improving the open circuit voltage of the solar cell, and further improving the efficiency of the solar cell.

[0121] The present application also provides a method for manufacturing a solar cell, which can be used to form the solar cell provided in the above embodiment. The method for manufacturing a solar cell will be described in detail below. It should be noted that the relevant description of the solar cell in the above embodiment is also applicable to the method for manufacturing a solar cell. In order to avoid redundancy, for the technical content that is the same or corresponding to the above embodiment, please refer to the detailed description of the above embodiment, and no further description will be given below.

[0122] Figure 4 This is a schematic diagram corresponding to the method for manufacturing a solar cell provided in an embodiment of the present application. Figures 2 to 4 The manufacturing method provided in the embodiments of the present application is described in detail.

[0123] Combined with reference Figures 2 to 4The method for manufacturing a solar cell provided in the embodiment of the present application comprises the following steps:

[0124] Step S1: providing a substrate 100, wherein the substrate 100 has a first side and a second side opposite to each other.

[0125] In this embodiment, the first side is the backlight side, and the second side is the light receiving side. The manufacturing method may further include: performing a texturing treatment on the surface of the substrate 100 facing the second side to form a suede structure.

[0126] The manufacturing method further includes: forming an emitter and a surface field. Taking the solar cell as a PERC cell as an example, an emitter is formed on or inside the surface of the substrate 100 facing the second side, and a surface field is formed on or inside the surface of the substrate 100 facing the first side.

[0127] Step S2 : forming a chemical passivation layer 101 on the first side of the substrate 100 . The chemical passivation layer 101 is used to passivate the surface of the substrate 100 .

[0128] In this embodiment, an oxidation process is used to form the chemical passivation layer 101. Specifically, the surface of the substrate 100 is oxidized to form the chemical passivation layer 101. The oxidation process is conducive to better repairing defects on the surface of the substrate 100, such as a high degree of saturation of dangling bonds on the surface of the substrate 100.

[0129] Specifically, a dry oxygen oxidation process may be used to form the chemical passivation layer 101. Specifically, the dry oxygen oxidation process includes: providing oxygen, oxidizing the surface of the substrate 100 in the range of 200° C. to 300° C. to form the chemical passivation layer 101. Within this process range, the generated thinner chemical passivation layer 101 has relatively few defects, and the thickness uniformity of the chemical passivation layer 101 is good, so that the formed chemical passivation layer 101 has high quality performance, which is conducive to further improving the passivation effect of the chemical passivation layer 101 on the surface of the substrate 100.

[0130] In some other examples, a wet oxygen oxidation process may also be used to form the chemical passivation layer. Specifically, the wet oxygen oxidation process includes: providing oxygen and deionized water, and oxidizing the surface of the substrate 100 at a temperature ranging from 200° C. to 300° C. to form the chemical passivation layer.

[0131] Before forming the chemical passivation layer 101 , the process may further include: cleaning the surface of the substrate 100 .

[0132] In other embodiments, the chemical passivation layer may be formed by plasma enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD).

[0133] Step S3 , forming a first aluminum oxide layer 102 on the chemical passivation layer 101 , wherein the first aluminum oxide layer 102 is used to provide hydrogen atoms to the surface of the substrate 100 .

[0134] In this embodiment, the first aluminum oxide layer 102 is formed by a first atomic layer deposition process, and the precursor provided by the first atomic layer deposition process includes a first hydrogen source gas, and the process temperature of the first atomic layer deposition process is a first temperature.

[0135] The atomic layer deposition process is a process in which different gas-phase precursor reactants are alternately introduced into a reaction chamber, chemically adsorbed and reacted on a substrate 100 to form a thin film, and the deposition process is controlled at the atomic level in a self-limiting surface reactant manner.

[0136] The first hydrogen source gas may be water vapor, and the precursor provided by the first atomic layer deposition process further includes an aluminum-containing precursor, wherein the aluminum-containing precursor may be trimethylaluminum (TMA).

[0137] During the process of forming the first aluminum oxide layer 102 by the first atomic layer deposition process, trimethyl aluminum first adsorbs and reacts with the OH groups on the surface of the substrate 100 until saturation, generating new surface functional groups. After extracting the remaining trimethyl aluminum, the first hydrogen source gas enters the reaction chamber and reacts with the new surface functional groups to saturation, generating new OH groups on the surface; the remaining first hydrogen source gas is extracted and exhausted, and this series of reactions constitutes a cycle. By controlling the number of cycles, the desired thickness of the first aluminum oxide layer 102 can be obtained. The first atomic layer deposition process can accurately control the thickness and quality of the first aluminum oxide layer 102, so that the formed first aluminum oxide layer 102 has a large area thickness uniformity.

[0138] If the first temperature is too high, the content of hydrogen atoms in the first aluminum oxide layer 102 will decrease as the first temperature increases. To ensure that there are sufficient hydrogen atoms in the first aluminum oxide layer 102, the first temperature should not be too high.

[0139] To this end, in this embodiment, the first temperature is lower than or equal to 270°C.

[0140] The first temperature should not be too low. If the first temperature is too low, although the hydrogen atom content in the first aluminum oxide layer 102 is high, undesirable byproducts will be produced in the first aluminum oxide layer 102, and the byproducts will affect the quality of the first aluminum oxide layer 102 itself. Therefore, in this embodiment, the first temperature is 240°C to 270°C, for example, 245°C, 250°C, 258°C, 261°C or 267°C. Within this temperature range, it can ensure that the hydrogen atom content in the first aluminum oxide layer 102 is sufficient, and it can avoid the generation of undesirable byproducts, and it can also avoid the film bubbling problem caused by excessive hydrogen atoms. Among them, the film bubbling problem includes: the first aluminum oxide layer 102 itself is damaged or even bubbling due to excessive hydrogen atoms; excessive hydrogen atoms diffuse into the chemical passivation layer 101, causing the chemical passivation layer 101 to be damaged or even bubbling; excessive hydrogen atoms diffuse into the barrier layer 103, causing the barrier layer 103 to be damaged or even bubbling.

[0141] The gas flow rate of the first hydrogen source gas is relatively large so that the hydrogen atom content in the formed first aluminum oxide layer 102 is relatively large. The gas flow rate of the first hydrogen source gas should not be too large. If the gas flow rate of the first hydrogen source gas is too large, it may cause an increase in byproducts generated during the formation of the first aluminum oxide layer 102 and an excessive amount of hydrogen atoms in the first aluminum oxide layer 102.

[0142] In this embodiment, the gas flow rate of the first hydrogen source gas can be 20 sccm to 25 sccm, where sccm refers to Standard Cubic Centimeter per Minute, for example, 21 sccm, 22 sccm, 23 sccm or 24 sccm. When the first hydrogen source gas is within this range, the hydrogen atom content in the formed first aluminum oxide layer 102 is moderate, which can ensure that the hydrogen atoms have a sufficient passivation effect on the substrate 100 and avoid the problem of film damage caused by excessive hydrogen atoms.

[0143] It should be noted that the relatively large gas flow rate of the first hydrogen source gas means that the gas flow rate of the first hydrogen source gas is larger than the gas flow rate of the second hydrogen source gas when the second aluminum oxide layer is subsequently formed. The relationship between the gas flow rate of the first hydrogen source gas and the gas flow rate of the second hydrogen source gas will be described in detail later.

[0144] In some examples, the hydrogen atom content in the first aluminum oxide layer 102 is the same or substantially the same in the direction from the second side to the first side, and accordingly, during the formation of the first aluminum oxide layer 102, the flow rate of the first hydrogen source gas provided remains unchanged.

[0145] In other examples, as the first atomic layer deposition process proceeds, the hydrogen atom content in the first aluminum oxide layer 102 gradually increases, and accordingly, the content of the first hydrogen source gas provided gradually increases during the formation of the first aluminum oxide layer 102. In the direction from the second side to the first side, the hydrogen atom content in the first aluminum oxide layer 102 may gradually increase, that is, the closer to the surface of the first side of the substrate 100, the smaller the hydrogen atom content in the first aluminum oxide layer 102, and the closer to the barrier layer 103, the larger the hydrogen atom content in the first aluminum oxide layer 102.

[0146] Specifically, the first atomic layer deposition process includes a plurality of cycles, and the gradual increase in the content of the first hydrogen source gas provided may be any of the following situations: the flow rate of the first hydrogen source gas provided in the adjacent cycles performed in sequence increases in sequence, so that the hydrogen atom content in the first aluminum oxide layer 102 may also gradually increase in the direction from the second side to the first side; or, at least two cycles performed in sequence constitute a cycle unit, the flow rate of the first hydrogen source gas provided in the same cycle unit is the same, and the flow rate of the first hydrogen source gas provided in the adjacent cycle units performed in sequence increases in sequence. For the scheme in which the flow rate of the first hydrogen source gas provided in the adjacent cycle units increases in sequence, the formed first aluminum oxide layer 102 may also include multiple layers of aluminum oxide sublayers stacked, and in the direction from the second side to the first side, the hydrogen atom content in the aluminum oxide sublayers of the adjacent layers increases layer by layer.

[0147] It should be noted that, in other embodiments, the first aluminum oxide layer may also be formed by a plasma chemical vapor deposition process.

[0148] Step S4 , forming a barrier layer 103 on the first aluminum oxide layer 102 .

[0149] In this embodiment, an atomic layer deposition process is used to form the barrier layer 103. The barrier layer 103 formed by the atomic layer deposition process has a uniform thickness and high density, which is conducive to improving the barrier layer 103's ability to block hydrogen atoms and reducing the effect of the barrier layer 103 on the field passivation of the second aluminum oxide layer formed subsequently.

[0150] In order to improve production efficiency, the barrier layer 103 and the first aluminum oxide layer 102 can be formed in the same ALD chamber. Specifically, after forming the first aluminum oxide layer 102, the ALD chamber is evacuated to prepare for forming the barrier layer 103. Then, silicon source gas and oxygen source gas are alternately provided to the ALD chamber to form the barrier layer 103.

[0151] In this embodiment, the material of the barrier layer 103 is silicon oxide, the silicon source gas may be hexamethylsilane, and the oxygen source gas may be water vapor.

[0152] The process temperature of forming the barrier layer 103 by the atomic layer deposition process may be 250° C. to 300° C., for example, 265° C., 270° C., 280° C., 291° C. or 296° C. Within this process temperature range, it is beneficial to further improve the thickness uniformity and density of the formed barrier layer 103, thereby further improving the barrier layer 103's barrier capability against hydrogen atom diffusion.

[0153] It should be noted that, in other embodiments, the barrier layer may also be formed by a chemical vapor deposition process.

[0154] Step S5, forming a second aluminum oxide layer 104 on the blocking layer 103, the second aluminum oxide layer 104 is used to field passivate the surface of the substrate 100, and the first aluminum oxide layer 102 contains negative charges and has a first charge density, and the second aluminum oxide layer 104 contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

[0155] In this embodiment, a second atomic layer deposition process is used to form the second aluminum oxide layer 104. The precursor provided in the second atomic layer deposition process includes a second hydrogen source gas, and the process temperature of the second atomic layer deposition process is a second temperature. The gas flow rate of the first hydrogen source gas is greater than the gas flow rate of the second hydrogen source gas, and the first temperature is less than the second temperature. In this way, it is conducive to forming a first aluminum oxide layer 102 that can fully exert the chemical passivation effect, and forming a second aluminum oxide layer 104 that can fully exert the field passivation effect.

[0156] The second hydrogen source gas may be water vapor, and the precursor provided by the second atomic layer deposition process further includes an aluminum-containing precursor, wherein the aluminum-containing precursor may be trimethylaluminum.

[0157] In this embodiment, the first hydrogen source gas and the second hydrogen source gas may also satisfy: 120%×V 2 ≤V 1 ≤130%×V 2 , where V 1 is the gas flow rate of the first hydrogen source gas, V 2 The difference between the gas flow rate of the first hydrogen source gas and the gas flow rate of the second hydrogen source gas is moderate, which can ensure that there are sufficient hydrogen atoms in the first aluminum oxide layer 102, further improve the quality of the formed first aluminum oxide layer 102, and avoid damage to other film layers.

[0158] In some examples, the gas flow rate of the first hydrogen source gas may be 21%, 25%, 27%, 28% or 29% higher than the gas flow rate of the second hydrogen source gas. In a specific example, the gas flow rate of the second hydrogen source gas may be 18 sccm to 20 sccm.

[0159] The second temperature may be 275° C. to 300° C., such as 280° C., 285° C., 290° C. or 285° C. The second temperature within this range is beneficial to improving the quality of the formed second aluminum oxide layer 104 , thereby further optimizing the field passivation effect of the second aluminum oxide layer 104 .

[0160] In order to further improve production efficiency, the second aluminum oxide layer 104, the barrier layer 103, and the first aluminum oxide layer 102 can be formed in the same ALD chamber. Specifically, after forming the barrier layer 103, the ALD chamber is evacuated to prepare for forming the second aluminum oxide layer 104. Then, an aluminum-containing precursor and a second hydrogen source gas are alternately provided to the ALD chamber to form the second aluminum oxide layer 104.

[0161] It should be noted that, in other embodiments, the second aluminum oxide layer may also be formed by a chemical vapor deposition process.

[0162] It should be noted that, for the relevant descriptions on the thickness of each layer, etc., please refer to the corresponding description in the aforementioned embodiment of the solar cell, which will not be repeated here.

[0163] Subsequent process steps also include: forming a plurality of electrodes electrically connected to the substrate 100. Specifically, the electrodes may be formed by a sintering process, during which the slurry penetrates the second aluminum oxide layer 104, the barrier layer 103, the first aluminum oxide layer 102 and the chemical passivation layer 101 to form electrodes by sintering.

[0164] In the technical solution of the above-mentioned method for manufacturing solar cells, an oxidation process is used to form a chemical passivation layer 101 on the surface of a substrate 100, and an atomic layer deposition process is used to sequentially form a first aluminum oxide layer 102, a barrier layer 103 and a second aluminum oxide layer 104, which is not only beneficial to improving the production efficiency of solar cells, but also can improve the surface passivation effect of the substrate 100 of the formed solar cell, thereby improving the efficiency of the solar cell.

[0165] The embodiment of the present application also provides a photovoltaic assembly, which includes a battery string, which is formed by connecting a plurality of solar cells provided in any of the above embodiments, or by connecting a plurality of solar cells formed by the manufacturing method provided in the above embodiments, and the photovoltaic assembly is used to convert received light energy into electrical energy. The photovoltaic assembly provided in the embodiment of the present application will be described in detail below in conjunction with the accompanying drawings. It should be noted that the parts that are the same or corresponding to the above embodiments can refer to the corresponding description of the above embodiments, and will not be repeated below.

[0166] Figure 5 A schematic diagram of a partial cross-sectional structure of a photovoltaic module provided in an embodiment of the present application.

[0167] refer to Figure 5, the photovoltaic module includes a module body and a frame (not shown). The module body includes a battery string, a bus bar, a packaging film 41 and a cover plate 42. The battery string is formed by connecting a plurality of solar cells 40 provided in any of the aforementioned embodiments, or by connecting a plurality of solar cells 40 formed by the manufacturing method provided in the aforementioned embodiments. The bus bar is used to electrically connect the battery string; the packaging film 41 is used to cover the surface of the battery string; the cover plate 42 is used to cover the surface of the packaging film 41 away from the battery string. The frame is used to carry the edge of the module body to support and fix the module body.

[0168] In some examples, in the same battery string, adjacent solar cells 40 may be spaced apart from each other. In other examples, in the same battery string, adjacent solar cells 40 may not be spaced apart from each other, that is, adjacent solar cells 40 may overlap each other.

[0169] In some embodiments, the encapsulation film 41 includes a first encapsulation layer and a second encapsulation layer, the first encapsulation layer covers one of the front side or the back side of the solar cell 40, and the second encapsulation layer covers the other of the front side or the back side of the solar cell 40. Specifically, at least one of the first encapsulation layer or the second encapsulation layer can be an organic encapsulation film such as a polyvinyl butyral (PVB) film, an ethylene-vinyl acetate copolymer (EVA) film, a polyethylene octene co-elastomer (POE) film, or a polyethylene terephthalate (PET) film.

[0170] In some cases, there is a boundary line between the first encapsulation layer and the second encapsulation layer before lamination. After the lamination process, the photovoltaic module is formed and there is no longer the concept of the first encapsulation layer and the second encapsulation layer, that is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation film.

[0171] In some embodiments, the cover plate 42 may be a glass cover plate, a plastic cover plate or the like with a light-transmitting function. Specifically, the surface of the cover plate 42 facing the encapsulation film 41 may be a concave-convex surface, thereby increasing the utilization rate of the incident light. The cover plate 42 includes a first cover plate and a second cover plate, the first cover plate is opposite to the first encapsulation layer, and the second cover plate is opposite to the second encapsulation layer.

[0172] The photovoltaic module may further include a welding ribbon 402 , and the welding ribbon 402 is used to electrically connect adjacent solar cells 40 .

[0173] The frame is one of the important components of the photovoltaic module, which can enhance the strength of the photovoltaic module to facilitate transportation, installation and protection of the photovoltaic module. The frame can be an aluminum alloy frame, a steel frame or a composite material frame, etc., and the embodiments of the present application do not limit the frame type. In some examples, the frame has a receiving cavity, and the edge portion of the component body is located in the receiving cavity. From the above embodiments, the photovoltaic module provided by the embodiments of the present application has the advantage of high conversion efficiency.

[0174] It can be understood by those skilled in the art that the above-mentioned embodiments are specific embodiments of the present application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the embodiments of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of the present application, so the protection scope of the embodiments of the present application shall be based on the scope defined in the claims.

Claims

1. A solar cell, characterized in that: include: a substrate having opposing first and second sides; A chemical passivation layer, the chemical passivation layer is located on the first side of the substrate, and the chemical passivation layer is used to passivate the surface of the substrate; a first aluminum oxide layer, wherein the first aluminum oxide layer is located on a surface of the chemical passivation layer away from the substrate, The first aluminum oxide layer is used to provide hydrogen atoms to the surface of the substrate; A barrier layer, the barrier layer is located on a surface of the first aluminum oxide layer away from the chemical passivation layer; a second aluminum oxide layer, the second aluminum oxide layer being located on a surface of the barrier layer away from the first aluminum oxide layer, and the second aluminum oxide layer being used for field passivation of the substrate surface; The first aluminum oxide layer contains negative charges and has a first charge density, and the second aluminum oxide layer contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

2. The solar cell according to claim 1, characterized in that The total thickness of the chemical passivation layer, the first aluminum oxide layer and the barrier layer is 2 nm to 4.1 nm.

3. The solar cell according to claim 1 or 2, characterized in that: The thickness of the chemical passivation layer is 0.4 nm to 0.8 nm; the thickness of the barrier layer is 0.8 nm to 1.7 nm; and the thickness of the first aluminum oxide layer is 0.8 nm to 1.6 nm.

4. The solar cell according to claim 1, characterized in that The hydrogen atom content in the first aluminum oxide layer is greater than the hydrogen atom content in the second aluminum oxide layer.

5. The solar cell according to claim 1 or 4, characterized in that: In a direction from the second side to the first side, the content of hydrogen atoms in the first aluminum oxide layer gradually increases.

6. The solar cell according to claim 5, characterized in that The first aluminum oxide layer includes a plurality of aluminum oxide sub-layers stacked together, and in a direction from the second side to the first side, the hydrogen atom contents in the aluminum oxide sub-layers of adjacent layers increase layer by layer.

7. The solar cell according to claim 1, characterized in that The thickness of the second aluminum oxide layer is greater than the thickness of the first aluminum oxide layer.

8. The solar cell according to claim 7, characterized in that: The thickness of the second aluminum oxide layer is 3.8 nm to 6 nm.

9. The solar cell according to claim 1, characterized in that: The thickness of the barrier layer is greater than the thickness of the chemical passivation layer, and the density of the barrier layer is greater than the density of the chemical passivation layer.

10. The solar cell according to claim 1 or 9, characterized in that: The material of the chemical passivation layer includes silicon oxide, silicon oxide containing hydroxide or silicon oxide containing nitrogen; the material of the barrier layer includes silicon oxide or silicon oxide containing nitrogen.

11. A method for manufacturing a solar cell, characterized in that: include: providing a substrate having opposing first and second sides; forming a chemical passivation layer on the first side of the substrate, the chemical passivation layer being used to passivate the surface of the substrate; forming a first aluminum oxide layer on the chemical passivation layer, wherein the first aluminum oxide layer is used to provide hydrogen atoms to the surface of the substrate; forming a barrier layer on the first aluminum oxide layer; forming a second aluminum oxide layer on the barrier layer, wherein the second aluminum oxide layer is used for field passivation of the substrate surface; The first aluminum oxide layer contains negative charges and has a first charge density, and the second aluminum oxide layer contains negative charges and has a second charge density, and the second charge density is greater than the first charge density.

12. The method for manufacturing a solar cell according to claim 11, characterized in that: The process of forming the first aluminum oxide layer and the second aluminum oxide layer includes: The first aluminum oxide layer is formed by a first atomic layer deposition process, wherein a precursor provided in the first atomic layer deposition process includes a first hydrogen source gas, and a process temperature of the first atomic layer deposition process is a first temperature; The second aluminum oxide layer is formed by a second atomic layer deposition process, wherein the precursor provided in the second atomic layer deposition process includes a second hydrogen source gas, and the process temperature of the second atomic layer deposition process is a second temperature; Wherein, the gas flow rate of the first hydrogen source gas is greater than the gas flow rate of the second hydrogen source gas, and the first temperature is lower than the second temperature.

13. The method for manufacturing a solar cell according to claim 12, characterized in that: The first hydrogen source gas and the second hydrogen source gas satisfy: 120%×V2≤V1≤130%×V2, wherein V1 is the gas flow rate of the first hydrogen source gas, and V2 is the gas flow rate of the second hydrogen source gas.

14. The method for manufacturing a solar cell according to claim 12, characterized in that: The first temperature is lower than or equal to 270°C; the second temperature is 275°C to 300°C.

15. The method for manufacturing a solar cell according to claim 11, characterized in that: The chemical passivation layer is formed by an oxidation process, and the barrier layer is formed by an atomic layer deposition process.

16. A photovoltaic module, characterized in that: include: The component body includes: a battery string, a bus bar, a packaging film and a cover plate; The battery string is formed by connecting a plurality of solar cells according to any one of claims 1 to 10, or by connecting a plurality of solar cells formed by the manufacturing method according to any one of claims 11 to 15; The bus bar is used to electrically connect the battery strings; The packaging film is used to cover the surface of the battery string; The cover plate is used to cover the surface of the packaging film away from the battery string; A frame is used to carry the edge of the component body to support and fix the component body.

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