Photovoltaic cell, preparation method thereof and photovoltaic module

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a photovoltaic cell and a preparation method thereof, and a photovoltaic module, and the preparation method comprises the steps: providing a substrate comprising a first surface and a second surface; forming a hydrophobic layer covering the second surface; forming an aluminum oxide lamination layer on the first surface by adopting at least two atomic layer deposition process steps; the step of forming the aluminum oxide lamination comprises the following steps: placing a substrate covered with a hydrophobic layer in a reaction chamber, and introducing water vapor and trimethylaluminum into the reaction chamber in any circular deposition step, preset process parameters of any circulation deposition step in the (N + 1) th atomic layer deposition process are controlled to be lower than preset process parameters of any circulation deposition step in the Nth atomic layer deposition process, and the preset process parameters comprise at least one of water vapor flow, trimethylaluminum flow, water vapor introduction duration and trimethylaluminum introduction duration. The embodiment of the invention is at least beneficial to avoiding back surface winding plating and improving the film layer quality of the aluminum oxide laminated layer.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the photovoltaic field, and in particular to a photovoltaic cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] In photovoltaic cells, aluminum oxide film is a key film layer. Due to the large amount of fixed negative charge and low surface state density at the interface of aluminum oxide film, it plays a vital role in the passivation technology of photovoltaic cells. At present, there are many methods for preparing aluminum oxide film, including thermal oxidation, physical vapor deposition, chemical vapor deposition, etc.

[0003] However, the traditional preparation method has some problems, such as uneven film thickness and large surface roughness of aluminum oxide film, which will eventually affect the photoelectric conversion efficiency of photovoltaic cells. In addition, the process of preparing aluminum oxide film is prone to plating, resulting in the formation of aluminum oxide film at locations on the photovoltaic cell where it is not needed. If the extra aluminum oxide film is not removed, it will affect the normal operation of the photovoltaic cell. Summary of the invention

[0004] The embodiments of the present disclosure provide a photovoltaic cell and a method for preparing the same, as well as a photovoltaic module, which are at least beneficial in avoiding back-side plating and improving the film quality of the aluminum oxide laminate.

[0005] According to some embodiments of the present disclosure, on the one hand, an embodiment of the present disclosure provides a method for preparing a photovoltaic cell, comprising: providing a substrate, the substrate comprising a first surface and a second surface relative to each other; forming a hydrophobic layer covering the second surface; forming an aluminum oxide stack on the first surface using at least two atomic layer deposition process steps, and any one of the atomic layer deposition processes comprises multiple cyclic deposition steps; wherein the step of forming the aluminum oxide stack comprises: placing the substrate whose second surface is covered with the hydrophobic layer in a reaction chamber, and any one of the cyclic deposition steps comprises introducing water vapor and trimethylaluminum into the reaction chamber, and controlling the preset process parameters of any one of the cyclic deposition steps in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any one of the cyclic deposition steps in the Nth atomic layer deposition process, and the preset process parameters comprise at least one of a water vapor flow rate, a trimethylaluminum flow rate, a water vapor introduction time, and a trimethylaluminum introduction time, and N is a positive integer greater than or equal to 1.

[0006] In some embodiments, the hydrophobic layer covering the second surface is formed by a dip coating process, a roller coating process, a spray coating process or a spin coating process.

[0007] In some embodiments, the spraying process is used to form the hydrophobic layer covering the second surface; the steps of forming the hydrophobic layer using the spraying process include: providing a spray gun that can spray hydrophobic material, setting the pressure of the spray gun to 2.1 bar to 4.1 bar, controlling the straight-line distance between the spray gun and the second surface to 15 cm to 30 cm, and setting the spraying temperature of the spray gun to 327°C to 345°C to form the hydrophobic layer with a thickness of 30 μm to 60 μm.

[0008] In some embodiments, the material of the hydrophobic layer is polytetrafluoroethylene, and the decomposition temperature of the polytetrafluoroethylene is higher than any deposition temperature of the atomic layer deposition process.

[0009] In some embodiments, after providing the substrate and before forming the hydrophobic layer, the preparation method further includes: cleaning the first surface and / or the second surface of the substrate; and / or, between performing the Nth atomic layer deposition process and the (N+1)th atomic layer deposition process, the preparation method further includes: pre-treating the first surface, wherein the pre-treatment is used to saturate the surface dangling bonds of the aluminum oxide film that has been formed.

[0010] In some embodiments, the step of performing the cleaning treatment on the substrate includes: introducing a first cleaning gas into the reaction chamber, controlling the introduction time of the first cleaning gas to be a first time, and the flow rate of the first cleaning gas to be a first flow rate; the step of performing the pretreatment on the first surface includes: introducing a second cleaning gas into the reaction chamber, controlling the introduction time of the second cleaning gas to be a second time, and the flow rate of the second cleaning gas to be a second flow rate; wherein the first time is less than the second time, and the first flow rate is less than the second flow rate.

[0011] In some embodiments, the aluminum oxide stack is formed on the first surface using two atomic layer deposition process steps; the step of forming the aluminum oxide stack includes: controlling the preset process parameters of any of the cyclic deposition steps in the second atomic layer deposition process to be lower than the preset process parameters of any of the cyclic deposition steps in the first atomic layer deposition process, and the preset process parameters include water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time.

[0012] According to some embodiments of the present disclosure, on the other hand, the embodiments of the present disclosure further provide a photovoltaic cell, comprising: a substrate, the substrate comprising a first surface and a second surface relative to each other; an aluminum oxide stack, at least located on the first surface, the aluminum oxide stack comprising N layers of aluminum oxide films stacked in sequence, the aluminum content in the Nth aluminum oxide film being higher than the aluminum content in the (N+1)th aluminum oxide film, and the oxygen content in the Nth aluminum oxide film being lower than the oxygen content in the (N+1)th aluminum oxide film, and N is a positive integer greater than or equal to 1.

[0013] In some embodiments, the aluminum-silicon bond density in the Nth aluminum oxide film is higher than the aluminum-silicon bond density in the (N+1)th aluminum oxide film.

[0014] According to some embodiments of the present disclosure, another aspect of the embodiments of the present disclosure further provides a photovoltaic module, comprising: a cell string, formed by connecting a plurality of photovoltaic cells formed by the preparation method as described in any one of the above items, or formed by connecting a plurality of photovoltaic cells as described in any one of the above items; a packaging film, used to cover the surface of the cell string; and a cover plate, used to cover the surface of the packaging film facing away from the cell string.

[0015] The technical solution provided by the embodiments of the present disclosure has at least the following advantages:

[0016] Firstly, before the subsequent formation of the aluminum oxide stack, a hydrophobic layer is formed on the second surface in advance. By utilizing the hydrophobicity of the hydrophobic layer, water vapor in the reaction precursor is prevented from approaching the second surface during the subsequent formation of the aluminum oxide stack. This is beneficial for preventing aluminum oxide from being formed on the second surface during the subsequent formation of the aluminum oxide stack on the first surface, that is, preventing the wrap-around plating phenomenon during the subsequent formation of the aluminum oxide stack on the first surface from the source.

[0017] Secondly, controlling the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process, on the one hand, is conducive to making the density of the portion of the aluminum oxide stack closer to the first surface higher and the uniformity higher, which is conducive to improving the passivation effect of the aluminum oxide stack on the first surface, reducing the recombination center on the first surface, and effectively reducing the recombination probability of carriers at the first surface; on the other hand, appropriately reducing the density of the portion of the aluminum oxide stack far away from the first surface is conducive to improving the contact performance between the aluminum oxide stack and other film layers subsequently formed on the side of the aluminum oxide stack away from the substrate, specifically, it is conducive to mutual penetration between the aluminum oxide stack and the other film layers, and improving the connection strength between the aluminum oxide stack and the other film layers; on the other hand, the aluminum content in the portion of the aluminum oxide stack close to the first surface is higher, containing more aluminum-silicon bonds, which is more conducive to improving the lattice fit between the aluminum oxide stack and the substrate; on the other hand, the oxygen content in the portion of the aluminum oxide stack far away from the first surface is higher, which is conducive to forming a rich charge field passivation effect on the substrate.

[0018] Therefore, the above aspects cooperate together to avoid the wrap-around plating phenomenon in the process of forming the aluminum oxide stack on the first surface, and improve the film quality of the aluminum oxide stack, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, and these exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise specified, the pictures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the traditional technology, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of a partial cross-sectional structure of a substrate provided in a preparation method provided in an embodiment of the present disclosure;

[0021] Figure 2 A schematic diagram of a partial cross-sectional structure of a hydrophobic layer formed on a substrate in a preparation method provided in an embodiment of the present disclosure;

[0022] Figure 3 A schematic diagram of a first partial cross-sectional structure of an aluminum oxide laminate formed on a substrate in a preparation method provided in an embodiment of the present disclosure;

[0023] Figure 4A schematic diagram of a second partial cross-sectional structure of an aluminum oxide laminate formed on a substrate in a preparation method provided in an embodiment of the present disclosure;

[0024] Figure 5 A schematic diagram of a partial cross-sectional structure of a photovoltaic cell in a preparation method provided in an embodiment of the present disclosure;

[0025] Figure 6 A schematic diagram of a partial three-dimensional structure of a photovoltaic assembly provided by another embodiment of the present disclosure;

[0026] Figure 7 for Figure 6 A schematic diagram of a cross-sectional structure along the cross-sectional direction MM1. DETAILED DESCRIPTION

[0027] As can be seen from the background technology, the film quality of aluminum oxide thin films needs to be improved, and the problem of winding plating in the preparation process of aluminum oxide thin films needs to be solved.

[0028] The present disclosure provides a photovoltaic cell and a preparation method thereof, and a photovoltaic module. In the preparation method, first, the hydrophobicity of the hydrophobic layer is utilized to prevent water vapor in the reaction precursor from approaching the second surface during the subsequent formation of the aluminum oxide stack, which is beneficial to avoid the wrap-around plating phenomenon from the source during the subsequent formation of the aluminum oxide stack on the first surface. Secondly, controlling the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process, on the one hand, is conducive to making the density of the part of the aluminum oxide stack closer to the first surface higher, which is conducive to improving the passivation effect of the aluminum oxide stack on the first surface; on the other hand, appropriately reducing the density of the part of the aluminum oxide stack far away from the first surface is conducive to improving the contact performance between other film layers subsequently formed on the side of the aluminum oxide stack away from the substrate and the aluminum oxide stack; on the other hand, making the aluminum content in the part of the aluminum oxide stack close to the first surface higher, containing more aluminum-silicon bonds, is more conducive to improving the lattice fit between the aluminum oxide stack and the substrate; on the other hand, making the oxygen content in the part of the aluminum oxide stack far away from the first surface higher, which is conducive to forming a rich charge field passivation effect on the substrate. Therefore, the above-mentioned aspects work together to avoid the circumferential plating phenomenon in the process of forming the aluminum oxide stack on the first surface, and improve the film quality of the aluminum oxide stack, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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).

[0033] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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 should not be understood as a limitation on the embodiments of the present application.

[0034] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0035] 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 the other component, or a third component can be present 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.

[0036] 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, a film, a region, or a 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, a film, a region, a plate, etc. is "directly located on" another component, or when a component such as a layer, a film, a region, a plate, etc. is located on the surface of another component, it means that no other components are located in between.

[0037] 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, "the components" are also intended to include plural forms unless the context clearly indicates otherwise. Among them, components include components such as layers, films, regions, or plates.

[0038] The following will describe the various embodiments of the present disclosure 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 disclosure, many technical details are provided in order to enable the reader to better understand the embodiments of the present disclosure. 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 disclosure can be implemented.

[0039] An embodiment of the present disclosure provides a method for preparing a photovoltaic cell. The method for preparing a photovoltaic cell provided by an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0040] refer to Figures 1 to 5 , the preparation method of the photovoltaic cell comprises the following steps:

[0041] S101: Reference Figure 1 , Figure 1A schematic diagram of a partial cross-sectional structure of a substrate provided in a preparation method provided in an embodiment of the present disclosure is provided. A substrate 100 is provided, and the substrate 100 includes a first surface 110 and a second surface 120 that are opposite to each other.

[0042] In some embodiments, the substrate 100 has a front side and a back side opposite to each other, wherein one of the first surface 110 and the second surface 120 is the front side and the other is the back side. For the convenience of subsequent description, the first surface 110 is the front side and the second surface 120 is the back side.

[0043] In some examples, the photovoltaic cell finally formed may be a single-sided cell, the front side of the substrate 100 may be a light-receiving surface for receiving incident light, and the back side may be a backlight surface. In other examples, the photovoltaic cell finally formed may be a double-sided cell, in which case both the front side and the back side of the substrate 100 may be light-receiving surfaces for receiving incident light. It is understood that the backlight surface referred to in one embodiment of the present disclosure is also capable of receiving incident light, but the degree of receiving the incident light is weaker than that of the light-receiving surface, and is therefore defined as a backlight surface.

[0044] S102: Reference Figure 2 , Figure 2 A schematic diagram of a partial cross-sectional structure of a hydrophobic layer formed on a substrate in a preparation method provided in an embodiment of the present disclosure, forming a hydrophobic layer 101 covering the second surface 120.

[0045] It is worth noting that before the subsequent formation of the aluminum oxide stack, a hydrophobic layer 101 is formed on the second surface 120 of the substrate 100 in advance. By utilizing the hydrophobicity of the hydrophobic layer 101, in the subsequent process of forming the aluminum oxide stack, water vapor in the reaction precursor is prevented from approaching the second surface 120, so as to effectively inhibit the reaction between trimethylaluminum in the reaction precursor and water vapor on the second surface 120, which is beneficial to avoid from the source that aluminum oxide is also formed on the second surface 120 in the subsequent process of forming the aluminum oxide stack on the first surface 110, that is, to avoid from the source the phenomenon of wrap-around plating in the subsequent process of forming the aluminum oxide stack on the first surface 110. Further, when other film layers are subsequently formed on the second surface 120, the film color abnormality on the second surface 120 can be reduced due to the avoidance of the wrap-around plating phenomenon. When the grid lines are subsequently formed on the second surface 120, it is also beneficial to make the sintering contact of the grid lines more uniform, so as to improve the photoelectric conversion efficiency of the photovoltaic cell finally formed.

[0046] In other words, in the subsequent process of forming an aluminum oxide stack on the first surface 110, water and trimethylaluminum are reaction precursors, and the aluminum oxide stack is generated based on the reaction of water and trimethylaluminum at the first surface 110. In this process, the second surface 120 can be regarded as a non-deposition surface. Based on this, a hydrophobic layer 101 is formed on the second surface 120 of the substrate 100 in advance, so that the second surface 120, that is, the non-deposition surface has a hydrophobic property. In the process of passing trimethylaluminum, the second surface 120 lacks water reactants due to the presence of the hydrophobic layer 101, so that aluminum oxide will not be formed on the second surface 120, thereby effectively avoiding the plating-around phenomenon.

[0047] It should be noted that the process of forming the hydrophobic layer 101 in step S102 will be described in detail later.

[0048] S103: Reference Figure 3 or Figure 4 At least two atomic layer deposition process steps are used to form the aluminum oxide stack 102 on the first surface 110, and each of the atomic layer deposition processes includes multiple cyclic deposition steps.

[0049] Among them, the step of forming the aluminum oxide stack 102 includes: placing the substrate 100 whose second surface 120 is covered with a hydrophobic layer 101 in a reaction chamber (not shown in the figure), and any cyclic deposition step includes introducing water vapor and trimethylaluminum into the reaction chamber, and controlling the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process, and the preset process parameters include at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time, and N is a positive integer greater than or equal to 1.

[0050] It should be noted that Figure 3 A schematic diagram of a first partial cross-sectional structure of an aluminum oxide laminate formed on a substrate in a preparation method provided in an embodiment of the present disclosure; Figure 4 A schematic diagram of a second partial cross-sectional structure of an aluminum oxide laminate formed on a substrate in a preparation method provided in an embodiment of the present disclosure. In addition, Figure 3 In the example, the aluminum oxide stack 102 is formed on the first surface 110 by using two different atomic layer deposition process steps. Figure 4 In the example, only three different atomic layer deposition process steps are used to form the aluminum oxide stack 102 on the first surface 110. In actual applications, there is no limit to the number of different atomic layer deposition process steps used in the step of forming the aluminum oxide stack 102, for example, it can also be 4, 5 or 6 times.

[0051] It is worth noting that in the steps of the atomic layer deposition process, trimethylaluminum and water vapor are introduced alternately. In other words, the atomic layer deposition process usually involves a cycle of the following four steps, and one cycle is regarded as a cyclic deposition step. Any cyclic deposition step includes at least the following four steps:

[0052] Step 1: A first precursor, i.e., trimethylaluminum, is introduced into the reaction chamber. Trimethylaluminum is adsorbed on the OH group of the first surface 110 and reacts with the OH group. Step 2: A purge gas is introduced into the reaction chamber to remove the remaining Al(CH3)3 and CH4. Step 3: A second precursor, i.e., water vapor, is introduced into the reaction chamber. The water vapor oxidizes the first surface 110 at this time to finally form an aluminum oxide film and remove the surface ligands. Step 4: A purge gas is introduced into the reaction chamber to remove the remaining H2O and CH4.

[0053] Based on this, the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process are controlled to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process. The preset process parameters include at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time, which is beneficial to making the density of the aluminum oxide film 112 formed by the (N+1)th atomic layer deposition process lower than the density of the aluminum oxide film 112 formed by the Nth atomic layer deposition process.

[0054] In this way, on the one hand, it is beneficial to make the aluminum oxide film 112 closer to the first surface 110 in the aluminum oxide stack 102 have a higher density and higher uniformity, which is beneficial to improve the passivation effect of the aluminum oxide film 112 close to the first surface 110 on the first surface 110, that is, it is beneficial to fully reduce the defect state density on the first surface 110, reduce the recombination center on the first surface 110, and effectively reduce the recombination probability of carriers at the first surface 110; on the other hand, appropriately reducing the density of the aluminum oxide film 112 far from the first surface 110 in the aluminum oxide stack 102 is beneficial to improve the contact performance between other film layers subsequently formed on the side of the aluminum oxide stack 102 far from the substrate 100 and the aluminum oxide stack 102. Specifically, the aluminum oxide film 112 far from the first surface 110 in the aluminum oxide stack 102 On the other hand, if the density of the aluminum oxide film 112 is low, the aluminum oxide film 112 in the aluminum oxide stack 102 far away from the first surface 110 is relatively loose, which is conducive to the mutual penetration of the aluminum oxide film 112 in the aluminum oxide stack 102 far away from the first surface 110 and the other film layers, thereby improving the connection strength between the aluminum oxide stack 102 and the other film layers; on the other hand, the aluminum content in the aluminum oxide film 112 closer to the first surface 110 in the aluminum oxide stack 102 is higher, so as to contain more aluminum-silicon bonds, which is more conducive to the contact between the aluminum oxide stack 102 and the substrate 100, and improves the lattice adaptability between the aluminum oxide stack 102 and the substrate 100; on the other hand, the oxygen content in the aluminum oxide film 112 farther away from the first surface 110 in the aluminum oxide stack 102 is higher, which is conducive to forming a rich charge field passivation effect on the substrate 100. Therefore, the cooperation of multiple aspects is conducive to improving the film quality of the aluminum oxide stack 102, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell.

[0055] It should be noted that controlling the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process includes at least the following situations:

[0056] In some cases, any one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time is selected as an adjustment parameter to control the adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the adjustment parameter of any cyclic deposition step in the Nth atomic layer deposition process, and the other three preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process are respectively the same as the corresponding preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process.

[0057] In other cases, any two of the water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time are selected as adjustment parameters to control a certain adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the corresponding adjustment parameter of any cyclic deposition step in the Nth atomic layer deposition process, and the other two preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process are respectively the same as the corresponding preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process.

[0058] In some other cases, any three of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time are selected as adjustment parameters to control a certain adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the corresponding adjustment parameter of any cyclic deposition step in the Nth atomic layer deposition process, and the remaining preset process parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process is respectively the same as the corresponding preset process parameter of any cyclic deposition step in the Nth atomic layer deposition process.

[0059] In some further cases, the water vapor flow rate of any cyclic deposition step in the (N+1)th atomic layer deposition process is controlled to be lower than the water vapor flow rate of any cyclic deposition step in the Nth atomic layer deposition process, the trimethylaluminum flow rate of any cyclic deposition step in the (N+1)th atomic layer deposition process is lower than the trimethylaluminum flow rate of any cyclic deposition step in the Nth atomic layer deposition process, the water vapor introduction time of any cyclic deposition step in the (N+1)th atomic layer deposition process is lower than the water vapor introduction time of any cyclic deposition step in the Nth atomic layer deposition process, and the trimethylaluminum introduction time of any cyclic deposition step in the (N+1)th atomic layer deposition process is lower than the trimethylaluminum introduction time of any cyclic deposition step in the Nth atomic layer deposition process.

[0060] In some embodiments, any atomic layer deposition process includes multiple cyclic deposition steps, and in the same atomic layer deposition process, the water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time in the multiple cyclic deposition steps remain unchanged.

[0061] The embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings.

[0062] In some embodiments, any cyclic deposition step, in addition to the steps of introducing trimethylaluminum and introducing water vapor, i.e., step 1 and step 3 in the aforementioned embodiment, also includes introducing a purge gas after introducing trimethylaluminum, i.e., step 2 in the aforementioned embodiment, and introducing a purge gas after introducing water vapor, i.e., step 4 in the aforementioned embodiment. Based on this, both step 2 and step 4 are referred to as purge steps. In step S103, while controlling the adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the adjustment parameter of any cyclic deposition step in the Nth atomic layer deposition process, the purge time of the purge step included in any cyclic deposition step in the (N+1)th atomic layer deposition process can also be controlled to be lower than the purge time of the purge step included in any cyclic deposition step in the Nth atomic layer deposition process. In this way, it is beneficial to ensure the removal of the remaining reaction precursors, further avoid the generation and adhesion of intermediate by-products, and improve the uniformity of the aluminum oxide film formed in each cyclic deposition step.

[0063] In some examples, the purge gas introduced during the purge step may be an inert gas, such as nitrogen.

[0064] In some embodiments, the preparation method may further include: forming a functional layer on a side of the aluminum oxide stack 102 away from the substrate 100 , and the material of the functional layer may be silicon nitride, silicon oxynitride or silicon carbide.

[0065] In some embodiments, reference Figure 2 In step S102, a hydrophobic layer 101 covering the second surface 120 may be formed by a dip coating process, a roller coating process, a spray coating process or a spin coating process. In this way, the hydrophobic layer 101 is conducive to uniformly covering the second surface 120, so as to improve the anti-wrap plating effect on the second surface 120 in the subsequent process of forming the aluminum oxide stack.

[0066] In some cases, the step S102 is described in detail by taking the use of a spraying process to form a hydrophobic layer 101 covering the second surface 120. The step of using a spraying process to form the hydrophobic layer 101 may include: providing a spray gun (not shown in the figure) that can spray a hydrophobic material, setting the pressure of the spray gun to 2.1 bar to 4.1 bar, controlling the straight-line distance between the spray gun and the second surface 120 to be 15 cm to 30 cm, and setting the spraying temperature of the spray gun to 327° C. to 345° C., so as to form a hydrophobic layer 101 with a thickness of 30 μm to 60 μm.

[0067] In some examples, the pressure of the spray gun may be set to 2.5 bar, 2.8 bar, 3 bar, 3.2 bar, 3.5 bar, 3.7 bar or 4 bar.

[0068] In some examples, the linear distance between the spray gun and the second surface 120 may be 16 cm, 18 cm, 20 cm, 22 cm, 4 cm, 25 cm, 27 cm, or 28 cm.

[0069] In some examples, the spray temperature of the spray gun can be set to 330°C, 331°C, 332°C, 333°C, 334°C, 335°C, 336°C, 337°C, 338°C, 339°C, 340°C, 341°C, 342°C, 343°C or 344°C.

[0070] In some examples, the thickness of the hydrophobic layer 101 is the thickness in the direction from the first surface 110 to the second surface 120, and the thickness of the hydrophobic layer 101 may be 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 56 μm, 58 μm or 59 μm.

[0071] In some cases, before spraying the hydrophobic material on the second surface 120 with a spray gun, the preparation method may further include: cleaning the second surface 120 of the substrate 100, and placing the substrate 100 flat on a carrier with the second surface 120 facing upward.

[0072] In some cases, after spraying the hydrophobic material on the second surface 120 with a spray gun, the preparation method may also include: heat treating the hydrophobic material of a certain thickness sprayed on the second surface 120, the temperature of the heat treatment is controlled at 100°C to 200°C, and the duration of the heat treatment is 3min to 5min, so that the hydrophobic material is solidified into a hydrophobic layer 101.

[0073] In some examples, the temperature of the heat treatment may be controlled to be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or 190°C.

[0074] In some examples, the duration of the heat treatment may be 3.2 min, 3.5 min, 3.6 min, 3.8 min, 4 min, 4.2 min, 4.5 min, 4.6 min, or 4.8 min.

[0075] In some embodiments, the material of the hydrophobic layer 101 may be a fluorine-containing polymer.

[0076] In some cases, the material of the hydrophobic layer 101 may be polytetrafluoroethylene, and the decomposition temperature of polytetrafluoroethylene is higher than the deposition temperature of any atomic layer deposition process. Figure 3 or Figure 4In step S103: during the process of forming the aluminum oxide stack 102 on the first surface 110, the hydrophobic layer 101 will not decompose due to the deposition temperature of any atomic layer deposition process. In other words, in step S103, the hydrophobic layer 101 has good stability and can effectively avoid the wrap-around plating phenomenon in step S103.

[0077] In some examples, polytetrafluoroethylene is an organic substance, and the decomposition temperature of polytetrafluoroethylene is greater than 350°C. The deposition temperature of any atomic layer deposition process in step S103 is 275°C to 300°C. For example, the deposition temperature can be 276°C, 279°C, 280°C, 282°C, 285°C, 288°C, 290°C, 293°C, 295°C, 296°C or 298°C.

[0078] In some embodiments, after forming the aluminum oxide laminate 102, the preparation method may further include: forming a functional layer (not shown in the figure) on the second surface 120 by using a coating process, or forming a functional layer on a side of the aluminum oxide laminate 102 away from the substrate 100. Based on this, combined with reference Figure 3 and Figure 5 , Figure 5 A schematic diagram of a partial cross-sectional structure of a photovoltaic cell in a preparation method provided in an embodiment of the present disclosure. During the coating process, the hydrophobic layer 101 can be decomposed and discharged during the purging step.

[0079] In some examples, the temperature of the coating process can be controlled at 450°C to 600°C, for example, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C or 590°C.

[0080] In other embodiments, after the aluminum oxide stack 102 is formed, the hydrophobic layer 101 may not be removed in the subsequent gas process steps. The material of the hydrophobic layer 101 may be a fluoropolymer. The fluoropolymer itself has very high chemical resistance, barrier properties, high temperature resistance and good electrical properties. Based on its good electrical properties and the fact that it contains organic elements, the hydrophobic layer 101 will not affect other processes.

[0081] In some embodiments, in conjunction with reference Figures 1 to 5After providing the substrate 100 and before forming the hydrophobic layer 101, the preparation method may further include: cleaning the first surface 110 and / or the second surface 120 of the substrate 100 to remove impurities on the surface of the substrate 100 to prevent the impurities from affecting the uniformity of the hydrophobic layer 101 formed in step S102, and to prevent the impurities from affecting the uniformity of the aluminum oxide stack 102 formed in step S103, which is beneficial to improving the film quality of the hydrophobic layer 101 and the aluminum oxide stack 102.

[0082] It should be noted that, according to actual needs, only the first surface 110 , only the second surface 120 , or both the first surface 110 and the second surface 120 may be cleaned.

[0083] In some cases, the cleaning step may include: introducing water vapor into the reaction chamber, and sweeping the first surface 110 and / or the second surface 120 with the water vapor to clean the surface of the substrate 100 .

[0084] In some examples, the cleaning process may include multiple cyclic cleaning steps, and the water vapor flow rate introduced in any cyclic cleaning step may be 15 sccm to 25 sccm, for example, 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm; the time for introducing water vapor in any cyclic cleaning step may be 4s to 5s.

[0085] In some examples, in any cyclic cleaning step, after water vapor is introduced for a certain period of time, a purge step is further included, that is, a purge gas is introduced into the reaction chamber to remove impurities and excess water vapor cleaned out in the cyclic cleaning step.

[0086] In one example, in any cyclic cleaning step, the purge time of the purge step, that is, the duration of the introduction of the purge gas, may be 10 s to 14 s, for example, 11 s, 12 s or 14 s.

[0087] In some examples, the cleaning process may include 2 to 6 cyclic cleaning steps. For example, the cleaning process may include 3, 4, or 5 cyclic cleaning steps.

[0088] In some embodiments, reference Figure 1 Between the Nth atomic layer deposition process and the (N+1)th atomic layer deposition process, the preparation method may further include: pre-treating the first surface 110, wherein the pre-treatment is used to saturate the surface dangling bonds of the aluminum oxide film that has been formed.

[0089] It is worth noting that after the Nth atomic layer deposition process, the aluminum oxide film formed on the first surface 110 is rich in aluminum elements, so that the surface of the aluminum oxide film has more aluminum dangling bonds. With the help of the reaction gas introduced in the pretreatment, the aluminum dangling bonds on the surface of the aluminum oxide film can be saturated, which is conducive to the deposition and adsorption of the reaction precursor on the surface of the formed aluminum oxide film in the (N+1)th atomic layer deposition process. In addition, the reaction gas introduced in the pretreatment can also purge the surface of the substrate 100 on which the aluminum oxide film has been formed, so as to further remove the attachment of intermediate byproducts and reduce the recombination centers caused by impurities in the finally formed aluminum oxide stack 102, so as to further improve the film quality of the finally formed aluminum oxide stack 102.

[0090] In some examples, the reaction gas introduced during the pretreatment may be water vapor. The water vapor introduced into the reaction chamber may generate more oxygen bonds to saturate the aluminum dangling bonds on the surface of the formed aluminum oxide film.

[0091] In some examples, pretreatment may include multiple cyclic pretreatment steps, and the water vapor flow rate introduced in any cyclic pretreatment step may be 18 sccm to 25 sccm, for example, 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm; the water vapor introduction time in any cyclic pretreatment step may be 6s to 8s, for example, 7s.

[0092] In some examples, in any cyclic pretreatment step, after water vapor is introduced for a certain period of time, a purge step is further included, that is, a purge gas is introduced into the reaction chamber to remove the intermediate byproducts and excess water vapor purged in the cyclic pretreatment step.

[0093] In one example, in any cyclic pretreatment step, the purge time of the purge step, that is, the duration of the introduction of the purge gas, may be 12s to 16s, for example, 13s, 14s or 15s.

[0094] In some examples, the pretreatment may include 2 to 6 cycles of pretreatment steps. For example, the pretreatment may include 3, 4, or 5 cycles of pretreatment steps.

[0095] In some embodiments, reference Figure 1 The step of cleaning the substrate 100 may include: introducing a first cleaning gas into the reaction chamber, controlling the introduction time of the first cleaning gas to be a first time length, and the flow rate of the first cleaning gas to be a first flow rate; referring to Figure 3 or Figure 4The step of pre-treating the first surface 110 may include: introducing a second cleaning gas into the reaction chamber, controlling the introduction time of the second cleaning gas to be a second time, and the flow rate of the second cleaning gas to be a second flow rate; wherein the first time is less than the second time, and the first flow rate is less than the second flow rate.

[0096] Thus, compared with the cleaning process, in the pretreatment step performed between the Nth atomic layer deposition process and the (N+1)th atomic layer deposition process, the flow rate of the second cleaning gas is introduced for a longer time. On the one hand, it is beneficial to improve the sweeping force of the pretreatment on the surface of the substrate 100 on which the aluminum oxide film has been formed, so as to effectively avoid the attachment of intermediate byproducts. On the other hand, it is beneficial to ensure a good saturation effect of the aluminum dangling bonds on the surface of the formed aluminum oxide film. In this way, the two aspects work together to improve the contact performance between the aluminum oxide film formed by the Nth atomic layer deposition process and the aluminum oxide film formed by the (N+1)th atomic layer deposition process, and effectively reduce the recombination centers caused by impurities in the finally formed aluminum oxide stack 102, so as to effectively improve the film quality of the finally formed aluminum oxide stack 102.

[0097] In some examples, both the first cleaning gas and the second cleaning gas may be water vapor.

[0098] In some examples, the first duration may be 4s to 5s, and the third duration may be 6s to 8s.

[0099] In some examples, the first flow rate may be 15 sccm to 25 sccm, and the second flow rate may be 18 sccm to 25 sccm.

[0100] In some embodiments, reference Figure 3 , an aluminum oxide stack 102 can be formed on the first surface 110 by using two atomic layer deposition process steps; the steps of forming the aluminum oxide stack 102 may include: controlling the preset process parameters of any cyclic deposition step in the second atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the first atomic layer deposition process, the preset process parameters including water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time.

[0101] In this way, in the second atomic layer deposition process and the first atomic layer deposition process, the four preset process parameters, namely the water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time in the cyclic deposition step, are different, so as to ultimately achieve that the density of the aluminum oxide film 112 formed by the first atomic layer deposition process is greater than the density of the aluminum oxide film 112 formed by the second atomic layer deposition process.

[0102] In some examples, the trimethylaluminum flow rate of any cyclic deposition step in the first atomic layer deposition process can be 18 sccm to 25 sccm, for example, it can be 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm; the trimethylaluminum flow rate of any cyclic deposition step in the second atomic layer deposition process can be 15 sccm to 25 sccm, for example, it can be 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm.

[0103] In some examples, the water vapor flow rate of any cyclic deposition step in the first atomic layer deposition process can be 18 sccm to 25 sccm, for example, it can be 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm; the water vapor flow rate of any cyclic deposition step in the second atomic layer deposition process can be 15 sccm to 25 sccm, for example, it can be 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm, 23 sccm or 24 sccm.

[0104] In some examples, the time length of the introduction of trimethylaluminum in any cyclic deposition step in the first atomic layer deposition process can be 7s to 10s, for example, 8s or 9s; the time length of the introduction of trimethylaluminum in any cyclic deposition step in the second atomic layer deposition process can be 6s to 8s, for example, 7s.

[0105] In some examples, the time length for introducing water vapor in any cyclic deposition step in the first atomic layer deposition process can be 7s to 10s, for example, 8s or 9s; the time length for introducing water vapor in any cyclic deposition step in the second atomic layer deposition process can be 6s to 8s, for example, 7s.

[0106] In some examples, the first atomic layer deposition process and the second atomic layer deposition process may both include 8 to 20 cyclic deposition steps. For example, the number of cyclic deposition steps included in the first atomic layer deposition process or the second atomic layer deposition process may be 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19.

[0107] In some cases, any cyclic deposition step, in addition to the steps of introducing trimethylaluminum and introducing water vapor, i.e., step one and step three in the aforementioned embodiment, also includes introducing a purge gas after introducing trimethylaluminum, i.e., step two in the aforementioned embodiment, and introducing a purge gas after introducing water vapor, i.e., step four in the aforementioned embodiment. Based on this, both step two and step four are referred to as purge steps. Based on this, the purge time of the purge step in the first atomic layer deposition process can be 12s to 16s, for example, 13s, 14s or 15s; the purge time of the purge step in the second atomic layer deposition process can be 10s to 14s, for example, 11s, 12s or 14s.

[0108] In some embodiments, after forming the aluminum oxide stack 102 on the first surface 110 , the preparation method may further include: decomposing the hydrophobic layer 101 formed on the second surface 120 , forming a new hydrophobic layer on the aluminum oxide stack 102 , and forming a new aluminum oxide stack on the second surface 120 .

[0109] To summarize, first, before forming the aluminum oxide stack 102, a hydrophobic layer 101 is formed on the second surface 120 in advance. By utilizing the hydrophobicity of the hydrophobic layer 101, water vapor in the reaction precursor is prevented from approaching the second surface 120 during the subsequent formation of the aluminum oxide stack 102. This is beneficial for preventing aluminum oxide from being formed on the second surface 120 during the subsequent formation of the aluminum oxide stack 102 on the first surface 110, i.e., preventing the wrap-around plating phenomenon during the subsequent formation of the aluminum oxide stack 102 on the first surface 110 from the source. Secondly, controlling the preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cyclic deposition step in the Nth atomic layer deposition process is beneficial, on the one hand, to making the portion of the aluminum oxide stack 102 closer to the first surface have higher density and higher uniformity, which is beneficial to improving the passivation effect of the aluminum oxide stack 102 on the first surface 110, reducing the recombination centers on the first surface 110, and effectively reducing the recombination probability of carriers at the first surface 110; on the other hand, appropriately reducing the density of the portion of the aluminum oxide stack 102 far from the first surface 110 is beneficial to improving the contact performance between the aluminum oxide stack 102 and other film layers subsequently formed on the side of the aluminum oxide stack 102 far from the substrate 100, specifically, it is beneficial to make the aluminum oxide stack 102 and the other film layers penetrate each other, thereby improving the connection strength between the aluminum oxide stack 102 and the other film layers. Therefore, the above aspects cooperate together to avoid the wrap-around phenomenon in the process of forming the aluminum oxide stack 102 on the first surface 110 and improve the film quality of the aluminum oxide stack 102, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell.

[0110] Another embodiment of the present disclosure also provides a photovoltaic cell, which is formed by the preparation method provided in the above embodiment. The photovoltaic cell provided in another embodiment of the present disclosure 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 embodiment will not be repeated here.

[0111] refer to Figure 3 , Figure 4 or Figure 5 The photovoltaic cell includes: a substrate 100, the substrate 100 includes a first surface 110 and a second surface 120 relative to each other; an aluminum oxide stack 102, at least located on the first surface 110, the aluminum oxide stack 102 includes N layers of aluminum oxide films 112 stacked in sequence, the aluminum content in the N-th aluminum oxide film 112 is higher than the aluminum content in the (N+1)-th aluminum oxide film 112, and the oxygen content in the N-th aluminum oxide film 112 is lower than the oxygen content in the (N+1)-th aluminum oxide film 112, and N is a positive integer greater than or equal to 1.

[0112] It should be noted that Figure 3 In the example, the aluminum oxide stack 102 includes two layers of aluminum oxide films 112 stacked in sequence. Figure 4 In the figure, the aluminum oxide stack 102 includes three layers of aluminum oxide films 112 stacked in sequence as an example. In practical applications, there is no limitation on the number of layers of the aluminum oxide films 112 stacked in the aluminum oxide stack 102, for example, it can also be 4, 5 or 6 layers.

[0113] In some embodiments, the material of the substrate 100 may be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. Among them, the elemental semiconductor material may be single crystal, polycrystalline, amorphous or microcrystalline (a state having both single crystal and amorphous states is called microcrystalline), for example, silicon may be at least one of single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon. In other embodiments, the material of the substrate 100 may also be a compound semiconductor material. Common compound semiconductor materials include but are not limited to materials such as silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride or copper indium selenide. The following uses the substrate 100 as a crystalline silicon substrate as an example to illustrate the photovoltaic cell.

[0114] It is worth noting that the closer the aluminum content in the aluminum oxide film 112 is to the first surface 110 in the aluminum oxide stack 102, the more aluminum-silicon bonds it contains, which is more conducive to the contact between the aluminum oxide stack 102 and the substrate 100, and improves the lattice fit between the aluminum oxide stack 102 and the substrate 100; in addition, the farther the aluminum oxide film 112 is from the first surface 110 in the aluminum oxide stack 102, the higher the oxygen content is, which is conducive to forming a rich charge field passivation effect on the substrate 100.

[0115] In some embodiments, reference Figure 3, Figure 4 or Figure 5 , the aluminum-silicon bond density in the Nth aluminum oxide film 112 is higher than the aluminum-silicon bond density in the (N+1)th aluminum oxide film 112. In this way, the aluminum oxide stack 102 and the substrate 100 are further guaranteed to have good lattice matching.

[0116] In some embodiments, the density of the Nth layer of aluminum oxide film 112 is higher than the density of the (N+1)th layer of aluminum oxide film 112. On the one hand, it is beneficial to make the aluminum oxide film 112 closer to the first surface 110 in the aluminum oxide stack 102 have a higher density, so as to improve the passivation effect of the aluminum oxide film 112 close to the first surface 110 on the first surface 110, that is, it is beneficial to fully reduce the defect state density on the first surface 110, reduce the recombination center on the first surface 110, and effectively reduce the recombination probability of carriers at the first surface 110; on the other hand, appropriately reducing the density of the aluminum oxide film 112 far away from the first surface 110 in the aluminum oxide stack 102 is beneficial to make the aluminum oxide film 112 far away from the first surface 110 in the aluminum oxide stack 102 penetrate each other with the other film layers, thereby improving the connection strength between the aluminum oxide stack 102 and the other film layers.

[0117] In some embodiments, reference Figure 3 or Figure 4 The photovoltaic cell may further include: a hydrophobic layer 101 located on the second surface 120 .

[0118] In some other embodiments, the photovoltaic cell may further include: a second aluminum oxide stack (not shown in the figure) located on the second surface.

[0119] Another embodiment of the present disclosure further provides a photovoltaic assembly, which includes a plurality of photovoltaic cells formed by the preparation method provided in the above embodiment, or a plurality of photovoltaic cells provided in the above embodiment, and the photovoltaic assembly is used to convert received light energy into electrical energy. It should be noted that the parts that are the same or corresponding to the above embodiment can refer to the corresponding description of the above embodiment, and will not be repeated below.

[0120] Combined with reference Figure 6 and Figure 7 The photovoltaic module includes: a battery string, which is formed by connecting multiple photovoltaic cells 40 formed by the preparation method provided in the above embodiment, or by connecting multiple photovoltaic cells 40 provided in the above embodiment; a packaging film 41, which is used to cover the surface of the battery string; a cover plate 42, which is used to cover the surface of the packaging film 41 away from the battery string. The photovoltaic cells 40 are electrically connected in the form of a whole piece or multiple pieces to form multiple battery strings, and the multiple battery strings are electrically connected in series and / or parallel.

[0121] in, Figure 6A schematic diagram of a partial three-dimensional structure of a photovoltaic assembly provided by another embodiment of the present disclosure; Figure 7 for Figure 6 A schematic diagram of a cross-sectional structure along the cross-sectional direction MM1.

[0122] In some embodiments, the photovoltaic cell 40 includes, but is not limited to, one or any combination of PERC cells (Passivated Emitter Rear Cell), IBC cells (Interdigitated Back Contact), TOPCon cells (Tunnel Oxide Passivated Contact), HIT / HJT cells (Heterojunction Technology heterojunction cells), solar thin-film cells, and stacked cells. Among them, solar thin-film cells include, but are not limited to, perovskite solar thin-film cells, copper indium selenide solar thin-film cells, gallium arsenide solar thin-film cells, and cadmium sulfide solar thin-film cells. Stacked cells include, but are not limited to, perovskite cells superimposed on crystalline silicon cells, perovskite cells superimposed on perovskite cells, and perovskite cells superimposed on thin-film cells.

[0123] In some embodiments, the photovoltaic cell 40 may be a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell or a multi-compound solar cell, and the multi-compound solar cell may be a cadmium sulfide solar cell, a gallium arsenide solar cell, a copper indium selenide solar cell or a perovskite solar cell. In addition, the photovoltaic cell 40 may be a whole cell or a sliced ​​cell, and a sliced ​​cell refers to a cell formed by a complete whole cell through a cutting process.

[0124] In some embodiments, reference Figure 6 , multiple battery strings can be electrically connected through the conductive tape 402. Figure 6 Only one positional relationship between photovoltaic cells is illustrated, that is, the arrangement direction of the electrodes with the same polarity of the cells is the same, or the electrodes with positive polarity of each cell are arranged toward the same side, so that the conductive tape connects different sides of two adjacent cells. In some embodiments, the cells can also be arranged in the order of electrodes with different polarities facing the same side, that is, the electrodes of multiple adjacent cells are arranged in the order of the first polarity, the second polarity, and the first polarity, and the conductive tape connects two adjacent cells on the same side.

[0125] In some embodiments, no intervals are set between the battery cells, that is, the battery cells overlap each other.

[0126] 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 or back sides of the photovoltaic cell 40, and the second encapsulation layer covers the other of the front or back sides of the photovoltaic cell 40. Specifically, at least one of the first encapsulation layer or the second encapsulation layer can be an organic encapsulation film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene co-elastic (POE) film or polyethylene terephthalate (PET) film, or at least one of the first encapsulation layer or the second encapsulation layer can also be an EP film, EPE film or PVP film. Among them, EP film refers to a co-extruded film composed of stacked EVA film and POE film, EPE film refers to a co-extruded film formed by stacked EVA film + POE film + EVA film, and PVP film refers to a co-extruded film formed by stacked POE film + EVA film + POE film. The co-extruded film can be prepared by sequentially extruding one or more raw materials onto another already manufactured film during the film processing, or by bonding different types of already manufactured films together.

[0127] In some cases, there is a boundary 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 41.

[0128] 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 or a velvet surface including a plurality of convex structures, 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.

[0129] In some embodiments, the photovoltaic cell 40 may be a busbar cell or a busbar-less cell.

[0130] In some cases, when the photovoltaic cell 40 is a main grid cell, the surface of the photovoltaic cell 40 has a plurality of main grids arranged at intervals along the first direction X and a plurality of sub-grids arranged at intervals along the second direction Y, and the main grid includes a main grid connection line and a pad located on the main grid connection line. In the process of constructing a battery string using the photovoltaic cell 40, the conductive tape 402 is electrically connected to at least one main grid on each of the two adjacent photovoltaic cells 40. The conductive tape 402 can be electrically connected to the main grid by welding, or the conductive tape 402 can be fixed on the main grid by glue points in advance, and the conductive tape 402 can be electrically connected to the main grid by using the fusion of the glue points and the deformation of the conductive tape 402 during the lamination process.

[0131] In other cases, when the photovoltaic cell 40 is a main grid-free cell, the surface of the photovoltaic cell 40 has a plurality of sub-grids arranged at intervals along the second direction Y. In the process of constructing a cell string using the photovoltaic cell 40, the conductive tape 402 is electrically connected to the plurality of sub-grids on each of the two adjacent photovoltaic cells 40. The conductive tape 402 can be fixed at a specific position above the photovoltaic cell 40 by glue dots, and then the electrical connection between the conductive tape 402 and the sub-grids is achieved by utilizing the fusion of the glue dots and the deformation of the conductive tape 402 during the lamination process.

[0132] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present disclosure, 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 disclosure. 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 disclosure, so the protection scope of the embodiments of the present disclosure shall be based on the scope defined in the claims.

Claims

1. A method for preparing a photovoltaic cell, characterized in that: include: providing a substrate comprising opposing first and second surfaces; forming a hydrophobic layer covering the second surface; Forming an aluminum oxide stack on the first surface using at least two atomic layer deposition process steps, each of which includes multiple cyclic deposition steps; Among them, the step of forming the aluminum oxide stack includes: placing the substrate whose second surface is covered with the hydrophobic layer in a reaction chamber, any of the cyclic deposition steps includes introducing water vapor and trimethylaluminum into the reaction chamber, and controlling the preset process parameters of any of the cyclic deposition steps in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any of the cyclic deposition steps in the Nth atomic layer deposition process, the preset process parameters include at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time, and N is a positive integer greater than or equal to 1.

2. The preparation method according to claim 1, characterized in that: The hydrophobic layer covering the second surface is formed by a dip coating process, a roller coating process, a spray coating process or a spin coating process.

3. The preparation method according to claim 2, characterized in that: The hydrophobic layer covering the second surface is formed by the spraying process; the steps of forming the hydrophobic layer by the spraying process include: Provide a spray gun that can spray hydrophobic material, set the pressure of the spray gun to 2.1 bar to 4.1 bar, control the straight-line distance between the spray gun and the second surface to 15 cm to 30 cm, and set the spraying temperature of the spray gun to 327° C. to 345° C. to form the hydrophobic layer with a thickness of 30 μm to 60 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The material of the hydrophobic layer is polytetrafluoroethylene, and the decomposition temperature of the polytetrafluoroethylene is higher than any deposition temperature of the atomic layer deposition process.

5. The preparation method according to claim 1, characterized in that: After providing the substrate and before forming the hydrophobic layer, the preparation method further comprises: cleaning the first surface and / or the second surface of the substrate; and / or, Between performing the Nth atomic layer deposition process and the (N+1)th atomic layer deposition process, the preparation method further includes: pre-treating the first surface, wherein the pre-treatment is used to saturate the surface dangling bonds of the aluminum oxide film that has been formed.

6. The preparation method according to claim 5, characterized in that: The step of performing the cleaning treatment on the substrate includes: introducing a first cleaning gas into the reaction chamber, controlling the introduction time of the first cleaning gas to be a first time length, and the flow rate of the first cleaning gas to be a first flow rate; The step of pre-treating the first surface includes: introducing a second cleaning gas into the reaction chamber, controlling the introduction time of the second cleaning gas to be a second time, and controlling the flow rate of the second cleaning gas to be a second flow rate; The first duration is smaller than the second duration, and the first flow rate is smaller than the second flow rate.

7. The preparation method according to claim 1, characterized in that: forming the aluminum oxide stack on the first surface using the atomic layer deposition process steps twice; The steps of forming the aluminum oxide stack include: The preset process parameters for controlling any of the cyclic deposition steps in the second atomic layer deposition process are lower than the preset process parameters for controlling any of the cyclic deposition steps in the first atomic layer deposition process, and the preset process parameters include water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time.

8. A photovoltaic cell, characterized in that: include: a substrate comprising opposing first and second surfaces; An aluminum oxide stack is at least located on the first surface, and the aluminum oxide stack includes N layers of aluminum oxide films stacked in sequence, the aluminum content in the Nth aluminum oxide film is higher than the aluminum content in the (N+1)th aluminum oxide film, and the oxygen content in the Nth aluminum oxide film is lower than the oxygen content in the (N+1)th aluminum oxide film, and N is a positive integer greater than or equal to 1.

9. The photovoltaic cell according to claim 8, characterized in that: The aluminum-silicon bond density in the N-th aluminum oxide film is higher than the aluminum-silicon bond density in the (N+1)-th aluminum oxide film.

10. A photovoltaic module, characterized in that: include: A battery string, formed by connecting a plurality of photovoltaic cells formed by the preparation method according to any one of claims 1 to 7, or formed by connecting a plurality of photovoltaic cells according to claim 8 or 9; A packaging film, 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.

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