Photovoltaic cell and method for producing a photovoltaic cell, photovoltaic module

Abstract

The embodiment of the present disclosure relates to the field of photovoltaics, and provides a photovoltaic cell and a preparation method thereof, and a photovoltaic module. The preparation method comprises: providing a substrate comprising a first surface and a second surface; forming a hydrophobic layer covering the second surface; forming an aluminum oxide stack on the first surface by using at least two atomic layer deposition process steps; the step of forming the aluminum oxide stack comprises: placing the substrate covered with the hydrophobic layer in a reaction chamber, any one of the cyclic deposition steps comprises: introducing water vapor and trimethylaluminum into the reaction chamber, and controlling preset process parameters of any one of the cyclic deposition steps in the (N+1)th atomic layer deposition process to be lower than preset process parameters of any one of the cyclic deposition steps in the Nth atomic layer deposition process, the preset process parameters comprising at least one of a water vapor flow rate, a trimethylaluminum flow rate, a water vapor introduction duration and a trimethylaluminum introduction duration. The embodiment of the present disclosure is at least beneficial to avoid backside wrap plating and improve the film layer quality of the aluminum oxide stack.

Description

Technical Field

[0001] This disclosure relates to the photovoltaic field, and in particular to a photovoltaic cell, its preparation method, and a photovoltaic module. Background Technology

[0002] In photovoltaic cells, alumina thin films are a crucial thin film layer. Due to the large number of fixed negative charges and low surface state density at the alumina interface, they play a pivotal role in photovoltaic cell passivation technology. Currently, various methods can be used to prepare alumina thin films, including thermal oxidation, physical vapor deposition, and chemical vapor deposition.

[0003] However, traditional preparation methods have some problems, such as uneven film thickness and high surface roughness of the alumina film, which ultimately affect the photoelectric conversion efficiency of the photovoltaic cell. Furthermore, the alumina film preparation process is prone to plating wrapping, resulting in the formation of alumina film in areas of the photovoltaic cell where it is not intended. If this extra alumina film is not removed, it will subsequently affect the normal operation of the photovoltaic cell. Summary of the Invention

[0004] This disclosure provides a photovoltaic cell and its preparation method, as well as a photovoltaic module, which at least helps to avoid back-side coating and improve the film quality of the alumina stack.

[0005] According to some embodiments of this disclosure, one aspect of this disclosure provides a method for preparing a photovoltaic cell, comprising: providing a substrate, the substrate including opposing first and second surfaces; forming a hydrophobic layer covering the second surface; forming an alumina stack on the first surface using at least two atomic layer deposition (ALD) processes, each ALD process including multiple cyclic deposition steps; wherein the step of forming the alumina stack includes: placing the substrate with the hydrophobic layer covering the second surface in a reaction chamber, each cyclic deposition step including 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 ALD process to be lower than the preset process parameters of any cyclic deposition step in the Nth ALD process, the preset process parameters including at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time, where N is a positive integer greater than or equal to 1.

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

[0007] In some embodiments, the hydrophobic layer covering the second surface is formed using the spraying process; the step of forming the hydrophobic layer using the spraying process includes: providing a spray gun capable of spraying hydrophobic materials, 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, so as to form the hydrophobic layer with a thickness of 30 μm to 60 μm.

[0008] In some embodiments, the hydrophobic layer is made of polytetrafluoroethylene (PTFE), and the decomposition temperature of PTFE is higher than the deposition temperature of any of the atomic layer deposition processes.

[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 the Nth atomic layer deposition process and the (N+1)th atomic layer deposition process, the preparation method further includes: pretreating the first surface, the pretreating being used to saturate the surface dangling bonds of the already formed alumina film.

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

[0011] In some embodiments, the alumina stack is formed on the first surface using two atomic layer deposition process steps; the step of forming the alumina 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, wherein 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 this disclosure, another aspect of this disclosure also provides a photovoltaic cell, comprising: a substrate, the substrate including opposing first and second surfaces; an alumina stack, at least located on the first surface, the alumina stack comprising N sequentially stacked alumina films, wherein the aluminum content in the Nth alumina film is higher than the aluminum content in the (N+1)th alumina film, and the oxygen content in the Nth alumina film is lower than the oxygen content in the (N+1)th alumina film, where N is a positive integer greater than or equal to 1.

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

[0014] According to some embodiments of this disclosure, another aspect of this disclosure also provides a photovoltaic module, including: a battery string, which is formed by connecting multiple photovoltaic cells as prepared by any of the above methods, or is formed by connecting multiple photovoltaic cells as prepared by any of the above methods; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film away from the battery string.

[0015] The technical solutions provided in this disclosure have at least the following advantages:

[0016] First, a hydrophobic layer is formed on the second surface before the subsequent formation of the alumina stack. By utilizing the hydrophobicity of the hydrophobic layer, water vapor in the reaction precursors is prevented from approaching the second surface during the subsequent formation of the alumina stack on the first surface. This helps to prevent alumina from forming on the second surface during the subsequent formation of the alumina stack on the first surface, thus preventing the phenomenon of plating around the alumina 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 has several advantages. Firstly, it allows for higher density and uniformity in the portion of the alumina stack closer to the first surface, improving the passivation effect of the alumina stack on the first surface, reducing recombination centers on the first surface, and effectively lowering the recombination probability of charge carriers at the first surface. Secondly, appropriately reducing the density of the portion of the alumina stack farther from the first surface improves the contact performance between the alumina stack and other films formed on the side of the alumina stack away from the substrate. Specifically, it facilitates interpenetration between the alumina stack and these other films, increasing the connection strength between them. Thirdly, it results in a higher aluminum content in the portion of the alumina stack closer to the first surface, containing more aluminum-silicon bonds, which is more conducive to improving the lattice fit between the alumina stack and the substrate. Finally, it results in a higher oxygen content in the portion of the alumina stack farther from the first surface, which is beneficial for forming a charge-rich passivation effect on the substrate.

[0018] Therefore, the combined effect of the above factors helps to avoid the plating phenomenon during the formation of the alumina stack on the first surface and improve the film quality of the alumina stack, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this disclosure or the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A partial cross-sectional structural diagram of a substrate provided in a preparation method according to an embodiment of this disclosure;

[0021] Figure 2 This is a partial cross-sectional structural diagram of a hydrophobic layer formed on a substrate in a preparation method provided in an embodiment of the present disclosure.

[0022] Figure 3 This is a schematic diagram of a first partial cross-sectional structure of an alumina stack formed on a substrate in a preparation method provided in an embodiment of the present disclosure.

[0023] Figure 4This is a schematic diagram of a second partial cross-sectional structure in which an alumina stack is formed on a substrate in a preparation method provided in an embodiment of the present disclosure;

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

[0025] Figure 6 A partial three-dimensional structural schematic diagram of a photovoltaic module provided in yet another embodiment of this disclosure;

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

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

[0028] This disclosure provides a photovoltaic cell and its preparation method, as well as a photovoltaic module. In the preparation method, firstly, 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 alumina stack. This helps to avoid the phenomenon of plating around the surface during the subsequent formation of the alumina stack on the first surface from the source. Secondly, controlling the preset process parameters of any cycle deposition step in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any cycle deposition step in the Nth atomic layer deposition process has several advantages. Firstly, it allows for higher density in the portion of the alumina stack closer to the first surface, improving the passivation effect of the alumina stack on the first surface. Secondly, appropriately reducing the density in the portion of the alumina stack farther from the first surface improves the contact performance between the alumina stack and other films formed subsequently on the side of the alumina stack away from the substrate. Thirdly, it results in a higher aluminum content in the portion of the alumina stack closer to the first surface, containing more aluminum-silicon bonds, which further enhances the lattice fit between the alumina stack and the substrate. Finally, it results in a higher oxygen content in the portion of the alumina stack farther from the first surface, which facilitates the formation of a charge-rich passivation effect on the substrate. Therefore, the combined effect of these factors helps avoid plating around the alumina stack during its formation on the first surface and improves the film quality of the alumina stack, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell.

[0029] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0032] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0033] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0034] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0035] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" 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 portion of the edge of the entire surface.

[0036] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly" on the other component (i.e., located on the surface of the other component with no other components between them), or it can have another component present in between. Moreover, 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 indicates that no other components are located in between.

[0037] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0038] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the embodiments. However, the technical solutions claimed in the embodiments of this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0039] This disclosure provides a method for preparing a photovoltaic cell. The following will describe in detail the method for preparing a photovoltaic cell according to an embodiment of this disclosure with reference to the accompanying drawings.

[0040] refer to Figures 1 to 5 The preparation method of photovoltaic cells includes the following steps:

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

[0042] In some embodiments, the substrate 100 has a front and a back side, with one of the first surface 110 and the second surface 120 being the front side and the other being the back side. For ease of explanation, the first surface 110 will be used as the front side and the second surface 120 as the back side in the following examples.

[0043] In some examples, the final photovoltaic cell can be a single-sided cell, where the front side of the substrate 100 serves as the light-receiving surface to receive incident light, and the back side serves as the backlighting surface. In other examples, the final photovoltaic cell can be a bifacial cell, where both the front and back sides of the substrate 100 can serve as light-receiving surfaces to receive incident light. It is understood that the backlighting surface referred to in one embodiment of this disclosure can also receive incident light, but the degree of reception of incident light is weaker than that of the light-receiving surface, and therefore it is defined as a backlighting surface.

[0044] S102: Reference Figure 2 , Figure 2 This is a partial cross-sectional structural diagram 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 a hydrophobic layer 101 is formed on the second surface 120 of the substrate 100 before the subsequent formation of the alumina stack. The hydrophobicity of the hydrophobic layer 101 prevents water vapor in the reaction precursors from approaching the second surface 120 during the subsequent alumina stack formation process. This effectively inhibits the reaction between trimethylaluminum in the reaction precursors and water vapor on the second surface 120, thus preventing alumina from forming on the second surface 120 during the subsequent alumina stack formation on the first surface 110. In other words, it avoids the phenomenon of plating around the alumina stack formation on the first surface 110. Furthermore, when other films are subsequently formed on the second surface 120, the avoidance of plating around reduces film color anomalies on the second surface 120. It also helps to make the sintering contact of the grid lines more uniform during the subsequent formation of the grid lines, thereby improving the photoelectric conversion efficiency of the final photovoltaic cell.

[0046] In other words, during the subsequent formation of the alumina stack on the first surface 110, water and trimethylaluminum are the reaction precursors. The alumina stack is formed based on the reaction between 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, i.e., the non-deposition surface, has hydrophobic properties. During the introduction of trimethylaluminum, due to the presence of the hydrophobic layer 101, there is a lack of water reactants on the second surface 120, and therefore alumina will not form on the second surface 120, thereby effectively avoiding the phenomenon of plating around the surface.

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

[0048] S103: Reference Figure 3 or Figure 4 An alumina stack 102 is formed on the first surface 110 using at least two atomic layer deposition process steps, wherein each atomic layer deposition process includes multiple cyclic deposition steps.

[0049] The step of forming the alumina stack 102 includes: placing a substrate 100 with a hydrophobic layer 101 covering the second surface 120 in a reaction chamber (not shown in the figure); each 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. The preset process parameters include at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time, where N is a positive integer greater than or equal to 1.

[0050] It should be noted that, Figure 3 This is a schematic diagram of a first partial cross-sectional structure of an alumina stack formed on a substrate in a preparation method provided in an embodiment of the present disclosure. Figure 4 This is a schematic diagram of a second partial cross-sectional structure in which an alumina stack is formed on a substrate in a preparation method provided in an embodiment of this disclosure. Furthermore, Figure 3 The example used is the formation of an alumina stack 102 on the first surface 110 using two different atomic layer deposition processes. Figure 4 The example shown is the formation of an alumina stack 102 on the first surface 110 using three different atomic layer deposition process steps. In actual applications, there is no limit to the number of different atomic layer deposition process steps used in the formation of the alumina stack 102. For example, it can be 4, 5 or 6 times.

[0051] It is worth noting that in the atomic layer deposition (ALD) process, trimethylaluminum and water vapor are alternately introduced sequentially. In other words, the ALD process typically involves a cycle of the following four steps, with each cycle considered a cyclic deposition step. Any cyclic deposition step includes at least the following four steps:

[0052] Step 1: Introduce the first precursor, trimethylaluminum, into the reaction chamber. Trimethylaluminum adsorbs onto the OH groups on the first surface 110 and reacts with them. Step 2: Introduce a purge gas into the reaction chamber to remove remaining Al(CH3)3 and CH4. Step 3: Introduce the second precursor, water vapor, into the reaction chamber. The water vapor oxidizes the first surface 110 to ultimately form an alumina film and remove surface ligands. Step 4: Introduce a purge gas into the reaction chamber to remove remaining H2O and CH4.

[0053] Based on this, 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, the preset process parameters including at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time and trimethylaluminum introduction time, is beneficial to make the density of the alumina film 112 formed by the (N+1)th atomic layer deposition process lower than the density of the alumina film 112 formed by the Nth atomic layer deposition process.

[0054] Thus, on the one hand, it is beneficial to have a higher density and higher uniformity of the alumina film 112 closer to the first surface 110 in the alumina stack 102, which is beneficial to improve the passivation effect of the alumina film 112 near the first surface 110, that is, to effectively reduce the defect state density on the first surface 110, reduce the recombination centers on the first surface 110, and effectively reduce the recombination probability of charge carriers at the first surface 110. On the other hand, appropriately reducing the density of the alumina film 112 far from the first surface 110 in the alumina stack 102 is beneficial to improve the contact performance between other films formed on the side of the alumina stack 102 away from the substrate 100 and the alumina stack 102. Specifically, the density of the alumina film 112 far from the first surface 110 in the alumina stack 102 is... The lower density of the alumina film 112 in the alumina stack 102, which is farther from the first surface 110, results in a more porous alumina film 112. This facilitates interpenetration between the alumina film 112 and the other film layers, improving the bonding strength between the alumina stack 102 and the other film layers. Furthermore, the higher aluminum content in the alumina film 112 closer to the first surface 110 allows for more aluminum-silicon bonds, which is more conducive to the contact between the alumina stack 102 and the substrate 100, improving the lattice fit between the alumina stack 102 and the substrate 100. Additionally, the higher oxygen content in the alumina film 112 farther from the first surface 110 is beneficial for creating a charge-rich passivation effect on the substrate 100. Therefore, the combined effect of these factors improves the film quality of the alumina 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 deposition cycle in the (N+1)th atomic layer deposition process to be lower than the preset process parameters of any deposition cycle in the Nth atomic layer deposition process includes at least the following situations:

[0056] In some cases, any one of the water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time is selected as the adjustment parameter. The adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process is controlled 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 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 following parameters are selected as adjustment parameters: water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time. The adjustment parameter of any cyclic deposition step in the (N+1)th atomic layer deposition process is lower than the corresponding adjustment parameter of any cyclic deposition step in the Nth atomic layer deposition process. The other two preset process parameters of any cyclic deposition step in the (N+1)th atomic layer deposition process are 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 the following can be selected as adjustment parameters: water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time. The adjustment parameter of any cycle deposition step in the (N+1)th atomic layer deposition process is lower than the corresponding adjustment parameter of any cycle deposition step in the Nth atomic layer deposition process. In addition, the remaining preset process parameter of any cycle deposition step in the (N+1)th atomic layer deposition process is the same as the corresponding preset process parameter of any cycle deposition step in the Nth atomic layer deposition process.

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

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

[0062] In some embodiments, in addition to the steps of introducing trimethylaluminum and water vapor (i.e., steps one and three in the aforementioned embodiments), any cyclic deposition step also includes introducing a purge gas after introducing trimethylaluminum (i.e., step two in the aforementioned embodiments), and introducing a purge gas after introducing water vapor (i.e., step four in the aforementioned embodiments). Therefore, steps two and four are both 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. This helps to ensure the removal of remaining reaction precursors, further avoids the generation and adhesion of intermediate by-products, and improves the uniformity of the alumina film formed in each cyclic deposition step.

[0063] In some cases, the purging gas introduced during the purging step can be an inert gas, such as nitrogen.

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

[0065] In some embodiments, reference Figure 2 In step S102, a hydrophobic layer 101 covering the second surface 120 can be formed by dip coating, roll coating, spray coating, or spin coating. This helps to ensure that the hydrophobic layer 101 uniformly covers the second surface 120, thereby improving the anti-coating effect on the second surface 120 during the subsequent formation of the alumina stack.

[0066] In some cases, step S102 will be described in detail using a spraying process to form a hydrophobic layer 101 covering the second surface 120 as an example. The step of forming the hydrophobic layer 101 using a spraying process may include: providing a spray gun (not shown in the figure) capable of spraying 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 cases, the pressure of the spray gun can 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 straight-line distance between the spray gun and the second surface 120 can be 16cm, 18cm, 20cm, 22cm, 4cm, 25cm, 27cm or 28cm.

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

[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 can be 32μm, 35μm, 38μm, 40μm, 42μm, 45μm, 48μm, 50μm, 52μm, 54μm, 55μm, 56μm, 58μm or 59μm.

[0071] In some cases, the preparation method may further include cleaning the second surface 120 of the substrate 100 and placing the second surface 120 upward when the substrate 100 is laid flat on the carrier plate, before spraying the hydrophobic material onto the second surface 120 using a spray gun.

[0072] In some cases, after spraying the hydrophobic material onto the second surface 120 with a spray gun, the preparation method may further include: heat-treating the hydrophobic material of a certain thickness sprayed onto the second surface 120, wherein the heat treatment temperature is controlled at 100℃~200℃ and the heat treatment duration is 3min~5min, so that the hydrophobic material is cured into a hydrophobic layer 101.

[0073] In some cases, the heat treatment temperature can be controlled at 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 heat treatment can 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 hydrophobic layer 101 may be made of a fluoropolymer.

[0076] In some cases, the hydrophobic layer 101 can be made of polytetrafluoroethylene (PTFE), and the decomposition temperature of PTFE is higher than the deposition temperature of any atomic layer deposition process. Thus, refer to... Figure 3 or Figure 4In step S103, during the formation of 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, the hydrophobic layer 101 has good stability in step S103, which can effectively avoid the plating phenomenon in step S103.

[0077] In some examples, polytetrafluoroethylene (PTFE) is an organic compound with a decomposition temperature 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 alumina stack 102, the preparation method may further include: forming a functional layer (not shown in the figure) on the second surface 120 using a coating process, or forming a functional layer on the side of the alumina stack 102 away from the substrate 100. Based on this, in conjunction with reference to the reference... Figure 3 and Figure 5 , Figure 5 This is a partial cross-sectional structural diagram 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 cases, the temperature of the coating process can be controlled between 450°C and 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 alumina stack 102 is formed, the hydrophobic layer 101 may not be removed in subsequent gas processing steps. The material of the hydrophobic layer 101 may be a fluoropolymer. Fluoropolymers themselves have 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 only 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 from the surface of the substrate 100, so as to avoid the impurities affecting the uniformity of the hydrophobic layer 101 formed in step S102 and to avoid the impurities affecting the uniformity of the alumina stack 102 formed in step S103, which is beneficial to improving the film quality of the hydrophobic layer 101 and the alumina stack 102.

[0082] It should be noted that, depending on the actual needs, it is possible to choose to clean only the first surface 110, only the second surface 120, or both the first surface 110 and the second surface 120.

[0083] In some cases, the cleaning process may include: introducing water vapor into the reaction chamber and purging the first surface 110 and / or the second surface 120 with 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 steam 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 steam introduction time in any cyclic cleaning step may be 4 s to 5 s.

[0085] In some examples, any cyclic cleaning step includes a purging step after the introduction of water vapor for a certain period of time, in which purging 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 purging time of the purging step, that is, the duration of the purging gas introduction, can be 10s to 14s, for example, 11s, 12s or 14s.

[0087] In some examples, the cleaning process may include 2 to 6 cycles of cleaning steps; for example, the number of cycles of cleaning steps may be 3, 4, or 5.

[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, the pre-treating being used to saturate the surface dangling bonds of the already formed alumina film.

[0089] It is worth noting that after the Nth atomic layer deposition process, the alumina film formed on the first surface 110 is rich in aluminum, resulting in a large number of aluminum dangling bonds on the surface of the alumina film. The reactive gas introduced during the pretreatment can saturate these aluminum dangling bonds, thus facilitating the deposition and adsorption of reaction precursors on the already formed alumina film surface during the (N+1)th atomic layer deposition process. Furthermore, the reactive gas introduced during the pretreatment can also purge the surface of the substrate 100 with the formed alumina film, further removing the adhesion of intermediate by-products and reducing the number of recombination centers caused by impurities in the final alumina stack 102, thereby further improving the film quality of the final alumina stack 102.

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

[0091] In some examples, the 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 6 s to 8 s, for example, 7 s.

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

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

[0094] In some examples, preprocessing may include 2 to 6 cycles of preprocessing steps; for example, the number of cycles of preprocessing steps may be 3, 4, or 5.

[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 duration of the introduction of the first cleaning gas to a first duration, and controlling the flow rate of the first cleaning gas to a first flow rate; (Refer to...) Figure 3 or Figure 4The step of pretreating the first surface 110 may include: introducing a second cleaning gas into the reaction chamber, controlling the duration of the introduction of the second cleaning gas to be a second duration, and controlling the flow rate of the second cleaning gas to be a second flow rate; wherein the first duration is less than the second duration, and the first flow rate is less than the second flow rate.

[0096] Therefore, compared to the cleaning process, the pretreatment step between the Nth and (N+1)th atomic layer deposition processes involves a longer flow rate and duration of the second cleaning gas. This benefits both the pretreatment process by increasing the purging force on the surface of the substrate 100 with the formed alumina film, effectively preventing the adhesion of intermediate byproducts, and ensuring good saturation of the aluminum dangling bonds on the surface of the formed alumina film. These two aspects work together to improve the contact performance between the alumina films formed in the Nth and (N+1)th atomic layer deposition processes, and effectively reduce composite centers caused by impurities in the final alumina stack 102, thereby significantly improving the film quality of the final alumina stack 102.

[0097] In some cases, both the first and second cleaning gases can be water vapor.

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

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

[0100] In some embodiments, reference Figure 3 An alumina stack 102 can be formed on the first surface 110 using two atomic layer deposition processes. The steps for forming the alumina stack 102 may include controlling the preset process parameters of any cycle deposition step in the second atomic layer deposition process to be lower than the preset process parameters of any cycle deposition step in the first atomic layer deposition process. The preset process parameters include water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time.

[0101] Thus, in the second atomic layer deposition process and the first atomic layer deposition process, the four preset process parameters in the cyclic deposition step are different: water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time. This is to ultimately achieve a higher density of alumina film 112 formed by the first atomic layer deposition process than that formed by the second atomic layer deposition process.

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

[0103] In some examples, the water vapor flow rate in any cyclic deposition step of the first atomic layer deposition process can 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 flow rate in any cyclic deposition step of the second atomic layer deposition process can 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.

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

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

[0106] In some examples, both the first and second atomic layer deposition processes may include 8 to 20 cyclic deposition steps. For example, the number of cyclic deposition steps included in the first or 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 water vapor (i.e., steps one and three in the aforementioned embodiments), also includes introducing purge gas after introducing trimethylaluminum (i.e., step two in the aforementioned embodiments), and introducing purge gas after introducing water vapor (i.e., step four in the aforementioned embodiments). Therefore, steps two and four are both referred to as purge steps. Accordingly, the purge time in the first atomic layer deposition process can be 12s to 16s, for example, 13s, 14s, or 15s; the purge time 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 alumina 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 alumina stack 102, and forming a new alumina stack on the second surface 120.

[0109] In summary, firstly, before forming the alumina stack 102, a hydrophobic layer 101 is formed on the second surface 120 in advance. 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 alumina stack 102. This helps to prevent alumina from forming on the second surface 120 during the subsequent formation of the alumina stack 102 on the first surface 110, thus preventing the phenomenon of plating around the alumina stack 102 during the subsequent formation of the alumina stack 102 on the first surface 110. 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 has several advantages. On the one hand, it helps to increase the density and uniformity of the portion of the alumina stack 102 closer to the first surface, thereby improving the passivation effect of the alumina stack 102 on the first surface 110, reducing recombination centers on the first surface 110, and effectively reducing the recombination probability of charge carriers at the first surface 110. On the other hand, appropriately reducing the density of the portion of the alumina stack 102 away from the first surface 110 helps to improve the contact performance between the alumina stack 102 and other films formed on the side of the alumina stack 102 away from the substrate 100. Specifically, it helps to make the alumina stack 102 and the other films interpenetrate, thereby increasing the connection strength between the alumina stack 102 and the other films. Therefore, the combined effect of the above aspects helps to avoid the plating phenomenon during the formation of the aluminum oxide stack 102 on the first surface 110, and improves the film quality of the aluminum oxide stack 102, thereby further improving the photoelectric conversion efficiency of the photovoltaic cell.

[0110] Another embodiment of this disclosure provides a photovoltaic cell, formed by the preparation method provided in the foregoing embodiments. The photovoltaic cell provided in another embodiment of this disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that parts that are the same as or corresponding to those in the foregoing embodiments 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 including a first surface 110 and a second surface 120 opposite to each other; an alumina stack 102, at least located on the first surface 110, the alumina stack 102 including N layers of alumina films 112 stacked sequentially, the aluminum content in the Nth alumina film 112 being higher than the aluminum content in the (N+1)th alumina film 112, and the oxygen content in the Nth alumina film 112 being lower than the oxygen content in the (N+1)th alumina film 112, where N is a positive integer greater than or equal to 1.

[0112] It should be noted that, Figure 3 The example only uses the alumina stack 102, which includes two sequentially stacked alumina films 112. Figure 4 The example only shows that the alumina stack 102 includes three layers of alumina film 112 stacked sequentially. In actual applications, there is no limitation on the number of layers of alumina film 112 stacked in the alumina stack 102. For example, it can also be 4, 5 or 6 layers.

[0113] In some embodiments, the material of substrate 100 can be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. The elemental semiconductor material can be monocrystalline, polycrystalline, amorphous, or microcrystalline (a state simultaneously possessing monocrystalline and amorphous states is called microcrystalline). For example, silicon can be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the material of substrate 100 can also be a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanide, silicon carbide, gallium arsenide, indium gallium dichromate, perovskite, cadmium telluride, or copper indium selenide. The following description uses a crystalline silicon substrate as an example to illustrate photovoltaic cells.

[0114] It is worth noting that the aluminum content in the alumina film 112 closer to the first surface 110 in the alumina stack 102 is higher, which means it contains more aluminum-silicon bonds, which is more conducive to the contact between the alumina stack 102 and the substrate 100 and improves the lattice fit between the alumina stack 102 and the substrate 100. In addition, the oxygen content in the alumina film 112 farther away from the first surface 110 in the alumina stack 102 is higher, which is beneficial to forming a charge-rich 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 alumina film 112 is higher than that in the (N+1)th alumina film 112. This further ensures good lattice fit between the alumina stack 102 and the substrate 100.

[0116] In some embodiments, the density of the Nth alumina film 112 is higher than that of the (N+1)th alumina film 112. On the one hand, this is beneficial to make the density of the alumina film 112 closer to the first surface 110 in the alumina stack 102 higher, thereby improving the passivation effect of the alumina film 112 close to the first surface 110 on the first surface 110. That is, it is beneficial to sufficiently reduce the defect state density on the first surface 110, reduce the recombination centers on the first surface 110, and effectively reduce the recombination probability of charge carriers at the first surface 110. On the other hand, appropriately reducing the density of the alumina film 112 far from the first surface 110 in the alumina stack 102 is beneficial to make the alumina film 112 far from the first surface 110 in the alumina stack 102 interpenetrate with the other film layers, thereby improving the connection strength between the alumina stack 102 and the other film layers.

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

[0118] In other embodiments, the photovoltaic cell may further include a second alumina stack (not shown) located on the second surface.

[0119] Another embodiment of this disclosure provides a photovoltaic module, which includes multiple photovoltaic cells formed by the preparation method provided in the foregoing embodiments, or multiple photovoltaic cells provided in the foregoing embodiments. The photovoltaic module is used to convert received light energy into electrical energy. It should be noted that the parts that are the same as or corresponding to those in the foregoing embodiments can be referred to the corresponding descriptions in the foregoing embodiments, and will not be repeated below.

[0120] Reference Figure 6 and Figure 7 The photovoltaic module includes: a cell string, which is formed by connecting multiple photovoltaic cells 40 as prepared by the method provided in the foregoing embodiments, or by connecting multiple photovoltaic cells 40 as provided in the foregoing embodiments; an encapsulating film 41 for covering the surface of the cell string; and a cover plate 42 for covering the surface of the encapsulating film 41 facing away from the cell string. The photovoltaic cells 40 are electrically connected in a whole or in multiple segments to form multiple cell strings, and the multiple cell strings are electrically connected in series and / or parallel.

[0121] in, Figure 6A partial three-dimensional structural schematic diagram of a photovoltaic module provided in yet another embodiment of this 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 RearCell), IBC cells (Interdigitated Back Contact), TOPCon cells (Tunnel Oxide Passivated Contact), HIT / HJT cells (Heterojunction Technology), thin-film solar cells, and tandem cells. Thin-film solar cells include, but are not limited to, perovskite thin-film solar cells, copper indium selenide (CIGS) thin-film solar cells, gallium arsenide (GaAs) thin-film solar cells, and cadmium sulfide (CdS) thin-film solar cells. Tandem cells include, but are not limited to, perovskite cells stacked with crystalline silicon cells, perovskite cells stacked with perovskite cells, and perovskite cells stacked with thin-film cells.

[0123] In some embodiments, the photovoltaic cell 40 can be a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, or a multi-component compound solar cell. Specifically, the multi-component compound solar cell can be a cadmium sulfide solar cell, a gallium arsenide solar cell, a copper indium selenide solar cell, or a perovskite solar cell. Furthermore, the photovoltaic cell 40 can be a single cell or a sliced ​​cell; a sliced ​​cell refers to a cell formed by cutting a single, complete cell.

[0124] In some embodiments, reference Figure 6 Multiple battery strings can be electrically connected through conductive strip 402. Figure 6 This illustration only depicts one type of positional relationship between photovoltaic cells, where the electrodes of the same polarity are arranged in the same direction, or where the positive electrode of each cell faces the same side, thus the conductive strip connects different sides of two adjacent cells. In some embodiments, the cells can also be arranged with electrodes of different polarities facing the same side, i.e., the electrodes of multiple adjacent cells are arranged in the order of first polarity, second polarity, and first polarity, respectively, then the conductive strip connects two adjacent cells on the same side.

[0125] In some embodiments, there is no spacing between the solar cells, meaning that the solar cells overlap each other.

[0126] In some embodiments, the encapsulating film 41 includes a first encapsulating layer and a second encapsulating layer. The first encapsulating layer covers one of the front or back sides of the photovoltaic cell 40, and the second encapsulating layer covers the other of the front or back sides of the photovoltaic cell 40. Specifically, at least one of the first or second encapsulating layer can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene elastomer (POE) film, or polyethylene terephthalate (PET) film. Alternatively, at least one of the first or second encapsulating layer can also be an EP film, an EPE film, or a PVP film. Here, 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 sequentially stacking EVA film, POE film, and EVA film; and PVP film refers to a co-extruded film formed by stacking POE film, EVA film, and POE film. Co-extruded films can be prepared by sequentially extruding one or more raw materials onto another pre-made film during the film processing, or by bonding different types of pre-made films together.

[0127] In some cases, the first encapsulation layer and the second encapsulation layer still have a boundary line before lamination. After lamination, the photovoltaic module will no longer have the concept of a first encapsulation layer and a 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 can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function. Specifically, the surface of the cover plate 42 facing the encapsulating film 41 can be an uneven surface or a textured surface containing multiple raised structures, thereby increasing the utilization rate of incident light. The cover plate 42 includes a first cover plate and a second cover plate, the first cover plate being opposite to the first encapsulation layer, and the second cover plate being opposite to the second encapsulation layer.

[0129] In some embodiments, the photovoltaic cell 40 may be a cell with a main grid or a cell without a main grid.

[0130] In some cases, when the photovoltaic cell 40 is a busbar cell, the surface of the photovoltaic cell 40 has multiple main grids spaced apart along a first direction X and multiple sub-grids spaced apart along a second direction Y. The main grid includes main grid connection lines and pads located on the main grid connection lines. During the process of constructing a cell string using the photovoltaic cells 40, the conductive strip 402 is electrically connected to at least one main grid on each of two adjacent photovoltaic cells 40. The conductive strip 402 can be electrically connected to the main grid by soldering to the pads, or it can be pre-fixed to the main grid with adhesive dots, and the electrical connection with the main grid is achieved by the fusion of the adhesive dots and the deformation of the conductive strip 402 during the lamination process.

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

[0132] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the embodiments of this disclosure. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the embodiments of this disclosure; therefore, the scope of protection of the embodiments of this disclosure should be determined by the scope defined in the claims.

Claims

1. A method for preparing a photovoltaic cell, characterized in that, include: A substrate is provided, the substrate including opposing first and second surfaces; A hydrophobic layer is formed covering the second surface; An alumina stack is formed on the first surface using at least two atomic layer deposition (ALD) processes, wherein each ALD process includes multiple cyclic deposition steps. The step of forming the alumina stack includes: placing the substrate with the hydrophobic layer covering the second surface in a reaction chamber; each of the cyclic deposition steps 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. The preset process parameters include at least one of water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time, where N is a positive integer greater than or equal to 1; the first surface corresponds to the deposition surface of the alumina stack, the second surface corresponds to the non-deposition surface of the alumina stack, and the hydrophobic layer makes the non-deposition surface hydrophobic.

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

3. The preparation method according to claim 2, characterized in that, The hydrophobic layer covering the second surface is formed using the spraying process described above; the step of forming the hydrophobic layer using the spraying process includes: A spray gun capable of spraying hydrophobic materials is provided, wherein the pressure of the spray gun is set to 2.1 bar to 4.1 bar, the straight-line distance between the spray gun and the second surface is controlled to be 15 cm to 30 cm, and the spraying temperature of the spray gun is set to 327°C to 345°C, so as to form a 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 hydrophobic layer is made of polytetrafluoroethylene (PTFE), and the decomposition temperature of PTFE is higher than the deposition temperature of any of the atomic layer deposition processes described.

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 includes: cleaning the first surface and / or the second surface of the substrate; and / or, Between the Nth and (N+1)th atomic layer deposition processes, the preparation method further includes: pre-treating the first surface, the pre-treating being used to saturate the surface dangling bonds of the already formed alumina film.

6. The preparation method according to claim 5, characterized in that, The step of cleaning the substrate includes: introducing a first cleaning gas into the reaction chamber, controlling the duration of the first cleaning gas introduction to a first duration, and controlling the flow rate of the first cleaning gas to a first flow rate; The pretreatment step of the first surface includes: introducing a second cleaning gas into the reaction chamber, controlling the introduction time of the second cleaning gas to a second duration, and controlling the flow rate of the second cleaning gas to a second flow rate; Wherein, the first duration is less than the second duration, and the first traffic volume is less than the second traffic volume.

7. The preparation method according to claim 1, characterized in that, The alumina stack is formed on the first surface using two atomic layer deposition processes. The steps for forming the alumina stack include: The preset process parameters of any of the cyclic deposition steps in the second atomic layer deposition process are controlled to be lower than the preset process parameters of any of the cyclic deposition steps in the first atomic layer deposition process. The preset process parameters include water vapor flow rate, trimethylaluminum flow rate, water vapor introduction time, and trimethylaluminum introduction time.

8. A photovoltaic cell, formed by the method for preparing a photovoltaic cell as described in any one of claims 1 to 7, characterized in that, include: A substrate, the substrate comprising opposing first and second surfaces; An alumina stack, at least located on the first surface, the alumina stack comprising N layers of alumina films stacked sequentially, wherein the aluminum content in the Nth alumina film is higher than the aluminum content in the (N+1)th alumina film, and the oxygen content in the Nth alumina film is lower than the oxygen content in the (N+1)th alumina film, where 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 Nth layer of the alumina film is higher than that in the (N+1)th layer of the alumina film.

10. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple photovoltaic cells formed by the preparation method as described in any one of claims 1 to 7, or by connecting multiple photovoltaic cells as described in claim 8 or 9; An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

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