Photovoltaic cell, method of manufacturing the same, manufacturing apparatus, and photovoltaic module

Abstract

This application relates to the field of photovoltaic cells, providing a photovoltaic cell, its preparation method, manufacturing equipment, and photovoltaic module. The method includes: obtaining a cell sheet; cutting the cell sheet to form multiple segmented cells, each segmented cell including opposing predetermined surfaces and a cross-section connecting the predetermined surfaces; oxidizing the cross-section with ozone to form an oxide layer; and forming a passivation layer on the side of the oxide layer away from the cross-section, the passivation layer being made of aluminum oxide. This method can at least solve the problem of poor uniformity and density of the passivation layer formed on the cross-section of the segmented cell.

Description

Technical Field

[0001] This application relates to the field of photovoltaic cells, and in particular to a photovoltaic cell, its preparation method, manufacturing equipment, and photovoltaic module. Background Technology

[0002] Photovoltaic cells are the core components that convert solar energy into electrical energy. To reduce internal resistance losses and increase the output power of photovoltaic modules, the technology of cutting a single solar cell into multiple segments, connecting these segments in series, and then encapsulating them into a photovoltaic module is widely used. After the solar cell is cut, the segments have cross-sections formed by the cuts, and the recombination of charge carriers at these cross-sections affects the electrical performance of the photovoltaic cell. In related technologies, laser cutting is commonly used to cut the solar cell into segments, and a passivation layer is deposited on the cross-sections of the segments. Summary of the Invention

[0003] This application provides a photovoltaic cell, its preparation method, manufacturing equipment, and photovoltaic module, which at least helps to solve the problems of poor uniformity and density of the passivation layer formed on the cross-section of the cell and high carrier recombination rate at the cross-section.

[0004] This application provides a method for preparing a photovoltaic cell, comprising: obtaining a cell sheet; cutting the cell sheet to form multiple segmented cells, each segmented cell including opposing predetermined surfaces and a cross section connecting the predetermined surfaces; oxidizing the cross section with ozone to form an oxide layer on the cross section; and forming a passivation layer on the side of the oxide layer away from the cross section, wherein the material of the passivation layer includes aluminum oxide.

[0005] Optionally, the oxidation treatment includes: atomizing an ozone aqueous solution containing the ozone into droplets, and spraying the droplets onto the cross-section.

[0006] Optionally, the concentration of ozone in the ozone aqueous solution is 20 mg / L to 30 mg / L, and the temperature of the ozone aqueous solution is 20°C to 30°C.

[0007] Optionally, the method of atomizing the ozone aqueous solution to form the droplets includes at least one of ultrasonic atomization, jet atomization, or vibrating screen atomization; and / or, the average diameter of the droplets is 3 μm to 8 μm.

[0008] Optionally, the spraying pressure for spraying the droplets onto the cross-section is 0.1 MPa to 0.3 MPa, the spraying distance is 30 mm to 80 mm, and the spraying time is 60 s to 180 s.

[0009] Optionally, the oxidation treatment includes: introducing a process gas containing the ozone into the cross-section.

[0010] Optionally, the volume concentration of ozone in the process gas is 5% to 25%; and / or, the flow rate of the process gas is 3000 sccm to 4000 sccm, and the time for introducing the process gas is 1 s to 60 s; and / or, the temperature of the oxidation treatment is 150°C to 200°C.

[0011] Optionally, the oxidation treatment includes: introducing oxygen into the cross-section and irradiating the cross-section with ultraviolet light, wherein the oxygen generates ozone under the irradiation of the ultraviolet light.

[0012] Optionally, the wavelength of the ultraviolet light is 200nm to 400nm, the power density of the ultraviolet light is 50mW / cm², and the irradiation time of the ultraviolet light is 5min to 10min.

[0013] Optionally, the method for forming the passivation layer includes atomic layer deposition, wherein the deposition temperature of the atomic layer deposition is 180°C to 200°C.

[0014] Optionally, the thickness of the oxide layer is 1 nm to 10 nm.

[0015] This application also provides a photovoltaic cell, which is prepared using the photovoltaic cell preparation method described in any of the preceding claims. The photovoltaic cell includes: a segmented cell, each segmented cell having opposing predetermined surfaces and a cross-section connecting the predetermined surfaces; an oxide layer disposed on the cross-section; and a passivation layer disposed on the side of the oxide layer away from the cross-section. Thus, the cross-section of the photovoltaic cell has a continuously covered and dense passivation layer, thereby improving its photoelectric conversion efficiency.

[0016] This application also provides a photovoltaic cell manufacturing apparatus for implementing the photovoltaic cell preparation method as described in any of the above claims, or for manufacturing the aforementioned photovoltaic cells. The photovoltaic cell manufacturing apparatus includes: a slitting machine for cutting the cell sheets to form multiple slitting cells, each slitting cell including opposing predetermined surfaces and a cross-section connecting the predetermined surfaces; an oxidation machine for oxidizing the cross-section to form an oxide layer; and a coating machine for forming a passivation layer on the side of the oxide layer away from the cross-section. Thus, the cutting, oxidation, and coating processes are completed sequentially within the same manufacturing apparatus, reducing the number of times work-in-process is transferred between processes.

[0017] This application also provides a photovoltaic module, comprising: a battery string, the battery string comprising: a plurality of photovoltaic cells formed by a method for preparing photovoltaic cells as described in any of the preceding claims, or a plurality of the aforementioned photovoltaic cells, or photovoltaic cells manufactured by a manufacturing apparatus for a plurality of the aforementioned photovoltaic cells; an encapsulation layer for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulation layer away from the battery string. This improves the output power of the photovoltaic module.

[0018] The technical solution provided in this application has at least the following advantages: This application employs ozone to oxidize the cross-section of the segmented battery. Ozone, as a reactive oxygen species, reacts with silicon atoms at the cross-section to form an oxide layer. This transforms the cross-section from a chemically reactive exposed surface into a stable oxide layer surface with lower interfacial free energy, resulting in a continuous oxide layer covering the cross-section. The protruding areas, deep cracks, and areas damaged by cutting are all covered by the oxide layer formed by ozone oxidation, leading to a more uniform chemical activity on the cross-section surface. Based on this, the oxide layer serves as the growth substrate for the passivation layer. Its uniformly distributed active sites provide a uniform number and distribution of chemisorption sites for the precursor during alumina deposition, allowing alumina to grow in a layered manner from the initial deposition stage. This avoids pinholes and thickness fluctuations caused by island-like nucleation on cross-sections with varying chemical activity, thus improving the uniformity and density of the passivation layer. Simultaneously, the oxide layer and the alumina passivation layer constitute a composite passivation structure, which synergistically provides better chemical passivation and field-effect passivation effects. Ozone oxidation can be carried out at temperatures not exceeding 200°C. Combined with the low-temperature deposition of the alumina passivation layer, this keeps the passivation process at a relatively low temperature, reducing the impact on the already formed doped and metal contact structures. This reduces the carrier recombination rate at the cross-section of the slab-type solar cell, thereby improving the open-circuit voltage, fill factor, and 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 application or in 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 application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A step diagram illustrating a method for preparing a photovoltaic cell according to an embodiment of this application; Figure 2This is a schematic diagram of a photovoltaic cell fabrication method provided in an embodiment of this application, in which the cell is cut to form multiple cell segments. Figure 3 This is a schematic diagram of the structure of a photovoltaic cell after an oxide layer is formed on the cross section in a method for preparing a photovoltaic cell according to an embodiment of this application. Figure 4 This is a schematic diagram of the structure of a photovoltaic cell after the passivation layer is formed in a method for preparing a photovoltaic cell according to an embodiment of this application; Figure 5 This is a partial structural diagram of a cell string in a photovoltaic module provided in an embodiment of this application; Figure 6 This is a partial cross-sectional schematic diagram of a photovoltaic module provided in an embodiment of this application.

[0021] Explanation of reference numerals in the attached figures: 100. Cell; 110. Cell-cell structure; 111. Preset surface; 112. Cross section; 120. Oxide layer; 130. Passivation layer; 30. Photovoltaic cell; 31. Encapsulation layer; 32. Cover plate; 33. Solder strip. Detailed Implementation

[0022] As is known from the background art, solar cells are typically cut using laser cutting to form segmented solar cells, and a passivation layer is deposited on the cross-section of the segmented solar cells. However, the passivation layer formed in this way has varying thicknesses and low density at different points in the cross-section, while the carrier recombination rate at the cross-section remains relatively high.

[0023] The root cause of this problem lies in the fact that laser cutting creates a heat-affected zone with a depth of micrometers and a mechanically damaged zone formed by cleavage at the cross-section. The surface roughness of the cross-section is relatively large, and micrometer-sized cracks exist. After cutting, the cross-section is exposed to air, and some surfaces react with oxygen or moisture in the air to form a natural oxide layer. The growth process of this natural oxide layer is dominated by environmental conditions. Therefore, its thickness and coverage vary significantly between the raised areas, deep cracks, severely damaged areas, and relatively intact areas of the cross-section, exhibiting an island-like discontinuous distribution. During atomic layer deposition, precursors such as trimethylaluminum... The chemical adsorption of the passivation layer depends on the active sites such as hydroxyl groups on the surface. The chemical activity of the area covered by the natural oxide layer differs from that of the exposed surface. As a result, the distribution of the adsorption sites of the precursor is not uniform. Consequently, the nucleation density and growth rate of the passivation layer are inconsistent at different parts of the cross section. This leads to island-like nucleation, pinholes, and thickness fluctuations in the film, resulting in decreased density. In addition, the damaged area of ​​the cross section also contains residual cutting debris, organic matter, and other contaminants, as well as non-stoichiometric oxides formed under thermal stress. These residues affect the adhesion between the passivation layer and the cross section, as well as the stability of the passivation layer during service.

[0024] This application provides a method for fabricating a photovoltaic cell. After cutting the cell and before forming a passivation layer, ozone is used to oxidize the cross-section of the cell, forming an oxide layer on the cross-section. Then, a passivation layer, consisting of aluminum oxide, is formed on the side of the oxide layer away from the cross-section. Ozone, as an active oxygen species, undergoes an oxidation reaction at the cross-section to form an oxide layer, transforming it into a stable surface with low interfacial free energy. The protruding areas, deep cracks, and cutting damage areas of the cross-section can all be continuously covered by the oxide layer formed by ozone oxidation, resulting in uniform chemical activity on the cross-section surface. This oxide layer serves as the growth base for the passivation layer. The uniformly distributed active sites on its surface provide a uniform number and distribution of chemisorption sites for the precursor during aluminum oxide deposition, allowing aluminum oxide to grow in a layered manner from the initial deposition stage. This avoids pinholes and thickness fluctuations caused by island-like nucleation on the cross-section where chemical activity varies, thereby improving the uniformity and density of the passivation layer and reducing the carrier recombination rate at the cross-section of the cell.

[0025] 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. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

[0026] 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.

[0027] 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.

[0028] 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," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not 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. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of said other elements or features. Therefore, the term "below" may cover both above and below orientation depending on the context in which the term is used, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0029] 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.

[0030] In the description of the embodiments of this application, "electrically connected to one component" means that both components are made of conductive materials, and the two components are in direct contact and connected or connected via other conductive materials, so that current flows between the two components when the photovoltaic module is generating electricity. "Electrically contacting one component to another" means that the two components are not only in contact, but also that, since both components are made of conductive materials, current flows between the two components when the photovoltaic module is generating electricity.

[0031] In the description of embodiments of this application, the terms "about," "approximately," "roughly," or "about" for a numerical value referring to a specific parameter include the numerical value, and those skilled in the art will understand that the deviation from the numerical value is within the acceptable tolerance of the specific parameter. For example, "about" or "about" for a numerical value may include additional numerical values ​​that are in the range of 90.0% to 110.0% of the numerical value, such as in the range of 95.0% to 105.0%, 97.5% to 102.5%, 99.0% to 101.0%, 99.5% to 100.5%, or 99.9% to 100.1%.

[0032] In the accompanying drawings corresponding to the embodiments of this application, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. 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.

[0033] In the description of embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. 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 an intermediate component between the two components. Conversely, when describing a component on the surface of another component, or a component "directly" on another component, or a component surface on which another component is formed or disposed, it indicates that there is no intermediate component between the two components. For simplicity and clarity, various components may be drawn at any scale. In the drawings, some components may be omitted for simplicity.

[0034] 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 "the component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0035] The “components” mentioned above can refer to layers, membranes, regions, parts, plates, or structures, etc.

[0036] The embodiments of this application 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 application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0037] Figure 1 A step diagram illustrating a method for preparing a photovoltaic cell according to an embodiment of this application; Figure 2 This is a schematic diagram of a photovoltaic cell fabrication method provided in an embodiment of this application, in which the cell is cut to form multiple cell segments. Figure 3 This is a schematic diagram of the structure of a photovoltaic cell after an oxide layer is formed on the cross section in a method for preparing a photovoltaic cell according to an embodiment of this application. Figure 4 This is a schematic diagram of the structure of a photovoltaic cell after the passivation layer is formed in a method for preparing a photovoltaic cell according to an embodiment of this application.

[0038] refer to Figures 1 to 4 The methods for preparing photovoltaic cells include: S100, obtain the battery cell 100, cut the battery cell 100 to form multiple segmented batteries 110, each segmented battery 110 including opposing preset surfaces 111 and a cross section 112 connecting the preset surfaces 111; S200, ozone is used to oxidize the cross section 112 to form an oxide layer 120 on the cross section 112; S300, a passivation layer 130 is formed on the side of the oxide layer 120 away from the cross section 112, the material of the passivation layer 130 including aluminum oxide.

[0039] This embodiment of the application transforms the oxidation process of cross section 112 from being environmentally governed to being governed by process conditions. This results in cross section 112 having a continuously covered oxide layer 120 with a consistent stoichiometric ratio before the formation of passivation layer 130. Consequently, the nucleation basal plane of passivation layer 130 tends to be uniform across the entire cross section 112. Simultaneously, the oxide layer 120 and the passivation layer 130, which is made of alumina, constitute a composite passivation structure, combining the effects of chemical passivation and field-effect passivation. Therefore, the uniformity and density of passivation layer 130 are improved, the carrier recombination rate at cross section 112 is reduced, and the open-circuit voltage, fill factor, and photoelectric conversion efficiency of the photovoltaic cell are consequently increased.

[0040] The embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0041] Reference Figure 2As shown, in step S100, the battery cell 100 is a single, integral battery cell with photoelectric conversion functionality. The battery cell 100 is cut, that is, the integral battery cell 100 is divided into multiple smaller segmented cells 110 along a predetermined cutting path. Each segmented cell 110 includes opposing preset surfaces 111 and a cross-section 112 connecting the preset surfaces 111. The preset surfaces 111 refer to two surfaces of the segmented cell 110 that are positioned opposite each other along its thickness direction; one of the two preset surfaces 111 is the light-receiving surface of the segmented cell 110, and the other is the backlighting surface. The cross-section 112 refers to the surface on the segmented cell 110 that connects the two preset surfaces 111; this cross-section 112 is formed by the cutting process and did not exist in the battery cell 100 before the cutting process.

[0042] In some embodiments, the cutting process includes laser cutting and mechanical cutting. Laser cutting involves focusing a laser beam onto the cutting path of the solar cell 100, using localized thermal effects to melt, vaporize, or create thermal stress cracks in the cell material, then splitting the cell 100 into multiple individual solar cells 110. Laser cutting offers high processing precision and does not require contact with the solar cell 100. Mechanical cutting involves applying pressure to the solar cell 100 along the cutting path using a cutting tool, causing it to break and separate. This method has a simpler equipment structure and is suitable for applications where cutting precision requirements are relatively relaxed.

[0043] It should be noted that the cut section 112 is not an ideally flat surface: in the direction perpendicular to the preset surface 111, section 112 exhibits striped undulations caused by the cutting action; micron-sized cracks, cutting debris, and a recast layer formed under thermal stress are also distributed on section 112. Observation of the morphology of section 112 revealed that the characteristic scale of these undulations and cracks is on the order of microns, and their depth can reach several microns. The dangling bond density of these structural defects at section 112 is significantly higher than that at the preset surface 111, becoming recombination centers for charge carriers.

[0044] In some embodiments, before oxidizing the cross section 112, the cross section 112 is pre-cleaned to remove cutting debris and particles adhering to it. The pre-cleaning process can be achieved by rinsing with deionized water, ultrasonic cleaning, or airflow purging. After pre-cleaning, the obstruction effect of particles on the contact between the oxidant and the cross section surface is reduced, improving the continuity of the subsequently formed oxide layer 120 on the cross section 112. The pre-cleaning process described above is optional and its implementation is not limited to the specific method described.

[0045] In some embodiments, the time interval between the completion of the cutting process of the solar cell 100 and the start of the oxidation process of the cross-section 112 is controlled within a preset duration. During this time interval, the cross-section 112 is exposed to the ambient atmosphere, and its surface reacts with oxygen or moisture in the environment to form a natural oxide layer. The longer the time interval, the greater the amount of natural oxide layer growth. In a specific example, this time interval is controlled within 4 hours. Optionally, this time interval is controlled between 0.5 hours and 2 hours. Thus, the ozone oxidation reaction takes place on the silicon surface closer to its intrinsic state, there are fewer discontinuous coverage areas pre-formed on the cross-section 112 due to natural oxidation, and the continuity and stoichiometric consistency of the oxide layer 120 are correspondingly improved.

[0046] In some embodiments, between the completion of the cutting process and the commencement of the oxidation process, the segmented battery 110 is temporarily stored in an inert atmosphere or an environment with a low dew point temperature. The inert atmosphere can be a nitrogen atmosphere or an argon atmosphere, wherein the oxygen and moisture content is lower than the corresponding content in air. In a specific example, the dew point temperature of the temporary storage environment is controlled below -20°C. This method inhibits the growth of the natural oxide layer during temporary storage, thereby ensuring that the initial state of cross-section 112 is more uniform at the start of the oxidation process.

[0047] By controlling the exposure time and temporary atmosphere as described above, the growth of the natural oxide layer on section 112 is limited to a low level before the oxidation treatment. Then, ozone is used to oxidize section 112, covering it with an oxide layer 120 controlled by the process conditions. Compared to ozone oxidation after the natural oxide layer has fully grown, the combined approach of these two methods makes the formation of oxide layer 120 less affected by environmental conditions.

[0048] Reference Figure 3 As shown, in step S200, ozone is used to oxidize the cross-section 112. Ozone has a strong oxidizing ability. When ozone acts on the cross-section 112, an oxidation reaction occurs, and an oxide layer 120 is generated on the cross-section 112. Since this oxidation process is governed by process conditions such as the ozone supply, the reaction time, and the temperature, its extent can be controlled by adjusting the process conditions. Therefore, an oxide layer 120 with a consistent stoichiometric ratio can be generated in the protruding areas, deep cracks, and cutting damage areas of the cross-section 112.

[0049] In some embodiments, the material of oxide layer 120 includes silicon oxide. The function of oxide layer 120 is to saturate the silicon dangling bonds at cross section 112 with a stable oxide structure, and to provide a chemically uniform base surface for the deposition of passivation layer 130. Furthermore, an interface with a high degree of lattice matching is formed between oxide layer 120 and cross section 112, thereby effectively saturating the dangling bonds at cross section 112.

[0050] The segmented solar cell 110 includes a substrate and film layers disposed on the surface of the substrate, such as a doped layer, a passivation film, and an antireflection layer, along its thickness direction. The substrate is the main part of the segmented solar cell 110 that is responsible for the generation and transport of photogenerated carriers. Doped layers, passivation films, antireflection layers, and electrode structures may also be disposed on the surface of the substrate.

[0051] In some embodiments, the substrate material includes at least one of monocrystalline silicon, polycrystalline silicon, quasi-monocrystalline silicon, microcrystalline silicon, or amorphous silicon. All of these materials use a crystalline or amorphous network formed by silicon atoms bonded together by covalent bonds as their basic structure, wherein each silicon atom forms a covalent bond with its adjacent silicon atoms. This application does not limit the specific material of the substrate.

[0052] In some embodiments, the material of the doped layer includes at least one of doped polycrystalline silicon, doped microcrystalline silicon, or doped amorphous silicon. The doped layer is formed on the surface of a substrate by a deposition process and then doped, or is obtained by direct doping on the substrate; the doping type of the doped layer may differ from that of the substrate. The aforementioned materials also use a covalent network of silicon atoms as their basic structure.

[0053] The cutting process is performed along the thickness direction of the segmented cell 110, with the cutting path penetrating the substrate and the film layers disposed on the substrate surface. The cross-section 112 is formed by the fractures created along the cutting path by the substrate, doped layer, and other film layers. Since both the substrate and the doped layer are materials with silicon atoms forming a covalent bond network as their basic structure, the atoms exposed on the cross-section 112 are mainly silicon atoms. The cutting process breaks the covalent bonds between these silicon atoms and their adjacent silicon atoms, resulting in a large number of unpaired dangling bonds at the cross-section 112. The cross-section 112 becomes a silicon-rich and chemically active surface, providing reaction sites throughout the entire cross-section 112 for the subsequent ozone oxidation reaction.

[0054] When ozone acts on section 112, the active oxygen atoms decomposed from ozone combine with silicon atoms with dangling bonds at section 112, causing the silicon atoms to change from a state of direct bonding with adjacent silicon atoms to a Si-O-Si state bridged by oxygen atoms, thus generating an oxide layer 120 of silicon oxide on section 112.

[0055] Since the oxide layer 120 is formed by the oxidation of silicon atoms at the cross-section 112, rather than by the deposition of other elements introduced from the outside, the oxide layer 120 and the cross-section 112 are continuously transitioned by Si-O bonds, and there are no additional defects introduced due to the different material systems at the interface between the two. As a result, the bond between the oxide layer 120 and the cross-section 112 is relatively strong, and its interface is not prone to peeling or delamination in subsequent deposition and heat treatment processes.

[0056] Since both the substrate and the fracture surface of the doped layer are rich in silicon atoms that can participate in the oxidation reaction, the oxidation reaction can occur throughout the entire cross-section 112. The oxide layer 120 can continuously cover the cross-section 112, which is composed of fracture surfaces with different structures, and its coverage process is not interrupted by the replacement of the structure to which the fracture surface belongs.

[0057] In some embodiments, the thickness of the oxide layer 120 is 1 nm to 10 nm. Optionally, the thickness of the oxide layer 120 is 2 nm to 8 nm. Optionally, the thickness of the oxide layer 120 can be 1 nm, 2 nm, 4 nm, 6 nm, 8 nm, or 10 nm. If the thickness of the oxide layer 120 is too small, it is difficult for the oxide layer 120 to form a continuous coverage on the cross-section 112 where undulations and cracks coexist, and the partially exposed cross-sectional surface will still participate in the subsequent nucleation process; if the thickness of the oxide layer 120 is too large, the distance that charge carriers need to travel from the cross-section 112 to the passivation layer 130 increases, the effect of the electric field formed by the fixed charge in the passivation layer 130 on the charge carriers at the cross-section 112 weakens, and the efficiency of field-effect passivation decreases accordingly. In the embodiments of this application, the thickness of the oxide layer 120 is set to 1 nm to 10 nm to ensure the continuous coverage of the cross-section 112 by the oxide layer 120 and the effective field-effect passivation of the subsequent passivation layer 130.

[0058] It should be noted that the thickness of oxide layer 120 refers to the dimension of oxide layer 120 along the direction perpendicular to section 112, which can be measured by ellipsometer or by observing the cross-sectional morphology through transmission electron microscopy.

[0059] Ozone oxidation of section 112 can be achieved in various ways, such as dissolving ozone in a solution and applying it to section 112 in liquid phase, transporting ozone to section 112 in gas phase with a carrier gas, or generating ozone in situ from oxygen at section 112. The above methods are explained below.

[0060] In some embodiments, the oxidation treatment includes: atomizing an ozone aqueous solution containing the ozone into droplets, and spraying the droplets onto the cross-section 112. The ozone aqueous solution refers to a solution formed by dissolving ozone in a solvent, such as deionized water. After atomizing the ozone aqueous solution into droplets, it is sprayed onto the cross-section 112, where the droplets spread and undergo an oxidation reaction. On one hand, the ozone participating in the reaction contacts the cross-section 112 in liquid phase, and its molecular number per unit volume is higher than that in gas phase, thus increasing the oxidation reaction rate and shortening the time required to complete the oxidation treatment. On the other hand, after liquid phase oxidation treatment, the surface of the oxide layer 120 is rich in hydroxyl groups, and its hydroxyl density is higher than that formed by gas phase oxidation. Since hydroxyl groups are active sites for the chemisorption of precursors during atomic layer deposition, the increased hydroxyl density makes the adsorption sites of precursors on the surface of the oxide layer 120 more dense, and the nucleation density of the passivation layer 130 is correspondingly increased.

[0061] In some embodiments, the ozone concentration in the ozone aqueous solution is 20 mg / L to 30 mg / L. Optionally, the ozone concentration in the ozone aqueous solution is 22 mg / L to 28 mg / L. Optionally, the ozone concentration in the ozone aqueous solution can be 20 mg / L, 22 mg / L, 24 mg / L, 26 mg / L, 28 mg / L, or 30 mg / L. If the ozone concentration in the ozone aqueous solution is too low, the amount of oxidant carried by a unit volume of droplet is insufficient, and the area on cross section 112 far from the droplet landing point is difficult to be fully oxidized; if the concentration is too high, the dissolved state of ozone in the solution is not easily maintained stably, and the degree of oxidation reaction at different points on cross section 112 fluctuates.

[0062] In some embodiments, the temperature of the ozone aqueous solution is 20°C to 30°C. Optionally, the temperature of the ozone aqueous solution is 22°C to 28°C. Optionally, the temperature of the ozone aqueous solution can be 20°C, 24°C, 26°C, or 30°C. If the temperature of the ozone aqueous solution is too low, the activation degree of the oxidation reaction is insufficient, and the growth rate of the oxide layer 120 is low; if the temperature is too high, the solubility of ozone in water decreases and its own decomposition is accelerated, reducing the amount of ozone in the solution that can participate in the reaction.

[0063] In this embodiment, the concentration and temperature are set within this range to ensure that the droplets still have a sufficient amount of oxidant to complete oxidation when they reach section 112.

[0064] In some embodiments, the method of atomizing the ozone aqueous solution to form the droplets includes at least one of ultrasonic atomization, jet atomization, or vibrating sieve atomization.

[0065] Ultrasonic atomization refers to the use of an ultrasonic transducer to generate high-frequency vibrations in an ozone aqueous solution, causing the liquid at the surface to break into droplets due to the combined effects of cavitation and surface tension waves. The droplet size distribution is relatively concentrated, and the droplets sprayed onto section 112 tend to be uniform in size, thus improving the uniformity of the oxide layer 120 thickness on section 112.

[0066] Jet atomization refers to the process of spraying an ozone solution at high speed through tiny orifices in a nozzle under pressure. The liquid column breaks into droplets under shearing action with the gas. The high droplet generation rate improves the production efficiency of photovoltaic cells.

[0067] Vibrating screen atomization refers to the process of vibrating a screen plate with an array of micropores, causing ozone solution to be extruded through the micropores to form droplets. The droplet size is mainly determined by the pore size of the micropores, and the droplet size can be adjusted by changing the screen plate.

[0068] In some embodiments, the average diameter of the droplets is 3 μm to 8 μm. Optionally, the average diameter of the droplets is 4 μm to 7 μm. Optionally, the average diameter of the droplets can be 3 μm, 5 μm, 6 μm, or 8 μm. If the average diameter of the droplets is too large, the liquid film formed after the droplets spread on the cross-section 112 is thicker, the path for ozone inside the liquid film to diffuse to the cross-section 112 becomes longer, and the droplets are less likely to enter the micron-level cracks on the cross-section 112; if the average diameter of the droplets is too small, the amount of oxidant carried by the droplets is reduced, and they are more likely to escape with the airflow before reaching the cross-section 112. In this embodiment, the average diameter of the droplets is set to 3 μm to 8 μm, so that the size of the droplets matches the characteristic size of the cracks on the cross-section 112, ensuring that the oxidant can reach all areas of the cross-section 112.

[0069] In some embodiments, the average diameter of the droplets is on the same order of magnitude as the width of the cracks on section 112. Under this dimensional relationship, when the droplets contact the crack opening, the radius of curvature corresponding to their surface tension is comparable to the crack width. The droplets can be drawn into the crack interior by capillary action on the crack wall and spread along it. Compared to supplying the oxidant through immersion or continuous liquid flow, this method prevents the liquid phase from forming closed liquid bridges or trapped bubbles at the crack opening due to surface tension, thus allowing the surface deep within the crack to be covered by the oxidant as well. Consequently, the oxide layer 120 extends the coverage of section 112 into the crack interior, and the dangling bonds deep within the crack are also saturated.

[0070] In some embodiments, the spray pressure for spraying the droplets onto the cross-section 112 is 0.1 MPa to 0.3 MPa. Optionally, the spray pressure is 0.15 MPa to 0.25 MPa. Optionally, the spray pressure can be 0.1 MPa, 0.15 MPa, 0.2 MPa, or 0.3 MPa. If the spray pressure is too low, the flow rate of droplets reaching the cross-section 112 is insufficient, and the oxidation treatment time is prolonged; if the spray pressure is too high, the kinetic energy of the droplets impacting the cross-section 112 is large, which may cause new mechanical damage in areas where cracks have already formed.

[0071] In some embodiments, the spraying distance from which the droplets are sprayed onto the cross-section 112 is 30 mm to 80 mm. Optionally, the spraying distance from which the droplets are sprayed onto the cross-section 112 is 40 mm to 70 mm. Optionally, the spraying distance from which the droplets are sprayed onto the cross-section 112 can be 30 mm, 45 mm, 60 mm, or 80 mm. If the spraying distance is too small, the droplets will not be sufficiently dispersed after being sprayed before reaching the cross-section 112, and their distribution on the cross-section 112 will be concentrated in a local area; if the spraying distance is too large, the dispersion and coagulation of the droplets during flight will be intensified, and the particle size distribution of the droplets reaching the cross-section 112 will become wider.

[0072] In some embodiments, the spraying time for the droplets to be sprayed onto the cross-section 112 is 60 s to 180 s. Optionally, the spraying time for the droplets to be sprayed onto the cross-section 112 is 90 s to 150 s. Optionally, the spraying time for the droplets to be sprayed onto the cross-section 112 can be 60 s, 100 s, 140 s, or 180 s. If the spraying time is too short, the oxide layer 120 will not form a continuous coverage on the cross-section 112; if the spraying time is too long, the thickness of the oxide layer 120 will exceed the required range, and the processing cycle time will be extended.

[0073] In this embodiment, the above parameters are set within this range to ensure that the droplets are uniformly distributed on the cross section 112 and that the thickness of the oxide layer 120 is within the required range.

[0074] In some embodiments, the treatment of spraying droplets onto section 112 is carried out in a closed treatment chamber at a temperature of 25°C to 40°C. This keeps the temperature within the treatment chamber low and relatively stable, suppressing the decomposition rate of ozone within the chamber while avoiding changes in the oxidation rate caused by temperature fluctuations.

[0075] In some embodiments, after spraying droplets onto section 112 and before forming passivation layer 130, section 112 is purged and dried with nitrogen until no visible droplets remain on section 112. This avoids the vaporization of residual liquid during subsequent heating and the precipitation of solutes in the solution, keeping the surface of oxide layer 120 clean and facilitating a good bond between passivation layer 130 and oxide layer 120.

[0076] In some embodiments, the oxidation process includes: introducing a process gas containing ozone into the cross-section 112. The process gas refers to a gas that delivers ozone to the cross-section 112 in gaseous form; it can be ozone gas or a mixture of ozone and a carrier gas, where the carrier gas can be a gas that does not participate in the oxidation reaction, such as nitrogen. After the ozone-containing process gas is introduced into the cross-section 112, the ozone in the gaseous phase decomposes and undergoes an oxidation reaction at the cross-section 112.

[0077] On the one hand, the oxidation treatment using gaseous ozone eliminates the need for a liquid medium, allowing section 112 to proceed to subsequent processes without a drying step after oxidation. On the other hand, during the process of introducing ozone-containing process gas into section 112, the ozone reacts with residual organic pollutants on section 112, decomposing them into volatile products such as carbon dioxide and water, which are then discharged with the gas flow. Thus, the oxidation treatment cleans section 112 while generating oxide layer 120, thereby improving the adhesion between passivation layer 130 and oxide layer 120. Furthermore, the process of introducing ozone-containing process gas into section 112 and the process of forming passivation layer 130 are completed seamlessly within the same reaction chamber. Since both processes deliver reactants to section 112 in gaseous form and operate at similar temperatures, arranging them in the same reaction chamber allows the sectional battery 110 to proceed to the deposition process without being removed from the chamber after oxidation. Compared to arranging the two processes in different equipment, this method shortens the time interval between the formation of the oxide layer 120 and its coverage by the passivation layer 130. During this interval, the surface of the oxide layer 120 has less chance to adsorb moisture and particulate matter from the environment. At the same time, the number of times the work-in-process is transferred between processes and the floor space of the equipment are reduced.

[0078] In some embodiments, the volume concentration of ozone in the process gas is 5% to 25%. Optionally, the volume concentration of ozone in the process gas is 10% to 20%. Optionally, the volume concentration of ozone in the process gas can be 5%, 10%, 15%, or 25%. If the volume concentration of ozone in the process gas is too low, the number of ozone molecules reaching cross-section 112 is insufficient, resulting in a low growth rate of the oxide layer 120; if the volume concentration is too high, the self-decomposition of ozone in the gas phase intensifies, the concentration difference at different locations within the chamber increases, and the uniformity of the oxide layer 120 thickness at various points along cross-section 112 decreases. This embodiment sets the volume concentration to 5% to 25%, ensuring that both the ozone concentration distribution and oxidation rate within the chamber are at appropriate levels.

[0079] In some embodiments, the flow rate of the process gas is 3000 sccm to 4000 sccm. Optionally, the flow rate of the process gas is 3200 sccm to 3800 sccm, which can be 3000 sccm, 3400 sccm, 3600 sccm, or 4000 sccm. If the flow rate of the process gas is too low, the gas renewal rate in the chamber is low, and the ozone consumed by the reaction is difficult to replenish in time; if the flow rate is too high, the flow field formed by the gas in the chamber will disturb the boundary layer near section 112, and the utilization rate of ozone will decrease.

[0080] In some embodiments, the process gas is introduced for a period of 1 to 60 seconds. Optionally, the process gas is introduced for a period of 5 to 30 seconds. Optionally, the process gas can be introduced for 1 second, 10 seconds, 20 seconds, or 60 seconds. If the process gas is introduced for too short a time, the oxide layer 120 will not form a continuous coverage on the cross-section 112; if the time is too long, the thickness of the oxide layer 120 will exceed the required range.

[0081] In this embodiment, the flow rate and time are set within this range so that the oxidation process can be completed within seconds and is compatible with the production line cycle time.

[0082] In some embodiments, the oxidation treatment temperature using gaseous ozone is 150°C to 200°C. Optionally, the oxidation treatment temperature using gaseous ozone is 160°C to 190°C. Optionally, the oxidation treatment temperature using gaseous ozone can be 150°C, 170°C, 180°C, or 200°C. If the oxidation treatment temperature is too low, the rate at which ozone decomposes into active oxygen atoms and the rate of the oxidation reaction are both low; if the temperature is too high, ozone decomposes in large quantities before reaching cross-section 112, and the heat load on the segmented battery 110 increases. In this embodiment, the oxidation treatment temperature is set to 150°C to 200°C, balancing the oxidation reaction rate and the thermal stability of the segmented battery 110.

[0083] In some embodiments, the oxidation process includes: introducing oxygen into the cross-section 112 and irradiating the cross-section 112 with ultraviolet light, wherein the oxygen generates ozone under the irradiation of the ultraviolet light. Oxygen molecules are excited and dissociate into oxygen atoms under the action of ultraviolet photons, and the oxygen atoms then combine with oxygen molecules to generate ozone. The generated ozone undergoes an oxidation reaction at the cross-section 112. Ozone is generated in situ near the cross-section 112 and immediately participates in the reaction, eliminating the need for external ozone generators and delivery pipelines, and avoiding ozone decomposition loss during transportation.

[0084] In some embodiments, during the irradiation of cross section 112, ultraviolet light alters the bonding state of silicon atoms on cross section 112 and promotes the formation of surface hydroxyl groups, resulting in more uniform chemical activity across cross section 112. Since surface hydroxyl groups are active sites for chemisorption of precursors during atomic layer deposition, the uniformity of hydroxyl group density directly affects the nucleation uniformity of the passivation layer 130. In addition to generating the oxide layer 120 and cleaning cross section 112, ultraviolet light irradiation also provides a surface with a uniform distribution of active sites for the uniform growth of the passivation layer 130.

[0085] In some embodiments, the wavelength of the ultraviolet light is from 200 nm to 400 nm. Optionally, the wavelength of the ultraviolet light is from 254 nm to 300 nm. Optionally, the wavelength of the ultraviolet light can be 200 nm, 254 nm, 280 nm, 350 nm, or 400 nm. It should be noted that the ultraviolet light emitted by the ultraviolet light source typically contains multiple wavelength components. The embodiments of this application set the wavelength of the ultraviolet light within the above range, which has a strong dissociation effect on oxygen molecules and is beneficial to increasing the ozone formation rate.

[0086] In some embodiments, the power density of the ultraviolet light is from 30 mW / cm² to 100 mW / cm². Optionally, the power density of the ultraviolet light is from 50 mW / cm² to 80 mW / cm². Optionally, the power density of the ultraviolet light can be 30 mW / cm², 40 mW / cm², 50 mW / cm², 60 mW / cm², 70 mW / cm², 80 mW / cm², 90 mW / cm², or 100 mW / cm². If the power density of the ultraviolet light is too low, the number of oxygen molecules excited per unit time is insufficient, and the ozone generation rate is low; if the power density is too high, the temperature near the cross-section 112 rises, and the film layer already formed on the preset surface 111 of the segmented battery 110 may be continuously irradiated by ultraviolet light.

[0087] In some embodiments, the irradiation time with ultraviolet light is 5 to 10 minutes. Optionally, the irradiation time with ultraviolet light is 6 to 9 minutes. Optionally, the irradiation time with ultraviolet light can be 5 minutes, 7 minutes, 8 minutes, or 10 minutes. If the irradiation time is too short, the oxide layer 120 will not form a continuous coverage on the cross-section 112; if the irradiation time is too long, the processing cycle is prolonged and the thickness of the oxide layer 120 exceeds the required range.

[0088] In this embodiment, the power density and irradiation time are set within this range to ensure continuous coverage of the oxide layer 120 on the cross section 112.

[0089] In some embodiments, the oxygen introduced into section 112 has a purity greater than or equal to 99.9%, the oxygen flow rate is 2000 sccm to 5000 sccm, the temperature of the cavity where ultraviolet light is irradiated is 120°C to 180°C, and the pressure of the cavity is maintained at 300 Pa to 800 Pa. Using high-purity oxygen can reduce the absorption of ultraviolet light by other gas components and their interference with the oxidation reaction; maintaining the cavity pressure at this level can match the number of oxygen molecules in the cavity with the penetration depth of ultraviolet light, providing a sufficient oxygen source for the oxidation reaction.

[0090] In some embodiments, during the irradiation of section 112 by ultraviolet light, the photon energy can break the C-C bonds and CH bonds in the organic pollutants on section 112, decomposing the organic pollutants into volatile small molecules such as carbon dioxide and water. The non-stoichiometric oxides formed by thermal stress during the cutting process, as well as environmental pollutants carried by residual moisture, are also removed under ultraviolet light irradiation. Thus, section 112 achieves a high degree of cleanliness during oxidation treatment, eliminating its adverse effects on the adhesion and stability of the passivation layer 130.

[0091] In some embodiments, the ultraviolet light irradiating the cross-section 112 includes multiple ultraviolet lights with different wavelengths. The ultraviolet light with shorter wavelengths has higher photon energy and primarily acts on the dissociation of oxygen molecules and the breaking of chemical bonds in organic pollutants; the ultraviolet light with longer wavelengths primarily acts on the activation of ozone and the formation of hydroxyl groups on the surface of the cross-section 112. By combining and setting the wavelengths and power as described above, the intensity of each effect of the oxidation film formation, cleaning the cross-section 112, and activating the cross-section 112 can be adjusted separately, so that the oxide layer 120 has a density similar to that of an oxide layer formed at a higher temperature at a lower processing temperature. The wavelengths, quantities, and combinations of the aforementioned multiple ultraviolet lights are not specifically limited here.

[0092] In some embodiments, the oxidation process includes a first stage and a second stage performed sequentially, and the oxide layer 120 includes a first oxide sublayer and a second oxide sublayer formed in the first stage and the second stage, respectively. In the first stage, a first oxide sublayer is formed on cross-section 112, and in the second stage, a second oxide sublayer is formed on the side of the first oxide sublayer facing away from cross-section 112. The first oxide sublayer and the second oxide sublayer together constitute the oxide layer 120, and the density of the second oxide sublayer is lower than that of the first oxide sublayer.

[0093] The oxide layer 120 plays different roles on its two sides along its thickness direction: the side facing section 112 is in direct contact with silicon atoms, and the silicon-oxygen network arrangement on this side determines the interface state density at section 112; the side away from section 112 is in contact with the precursor of passivation layer 130, and the hydroxyl density on this side determines the number of nucleation sites in passivation layer 130. These two roles impose different requirements on the properties of oxide layer 120: a tightly packed silicon-oxygen network in oxide layer 120 results in a lower interface state density, but the oxidation reaction in this state is constrained by the diffusion process, leading to slow thickness growth, and requires maintenance at higher temperatures for a longer time; a faster oxidation reaction allows oxide layer 120 to thicken more easily, but its network arrangement is looser, resulting in a higher interface state density at the point of direct contact with section 112.

[0094] Furthermore, cross section 112 is composed of fractures in the substrate, doped layer, and other films. The doping type and concentration differ in each fracture region, resulting in different oxidation rates. If the oxidation process continues to advance from the surface of cross section 112 under a single condition, the oxide layer 120 thickness in fracture regions with higher doping concentrations is greater than that in fracture regions with lower doping concentrations. Consequently, the distance that charge carriers need to travel from cross section 112 to passivation layer 130 varies across cross section 112, leading to differences in the intensity of field-effect passivation across cross section 112.

[0095] In some embodiments, a higher oxidation temperature and a lower ozone supply concentration are used in the first stage, and the reaction time is shorter than that of the second stage. In a specific example, the first stage involves introducing an ozone-containing process gas into section 112 at an oxidation temperature of 180°C to 200°C, an ozone volume concentration of 5% to 10% in the process gas, and a gas introduction time of 1 s to 10 s. The higher temperature allows the newly generated silicon-oxygen network sufficient migration capacity to complete reconstruction, while the lower ozone supply concentration controls the rate of reaction, resulting in similar reactivity of active oxygen atoms throughout section 112.

[0096] On the one hand, the silicon-oxygen network of the first oxide sublayer is densely arranged, forming an interface with a high degree of lattice matching between it and section 112, and the dangling bonds at section 112 are fully saturated. The first oxide sublayer directly undertakes the chemical passivation effect on section 112, and the interface state density between it and section 112 is at a low level, and the carrier recombination channels caused by unsaturated coordination at the interface are correspondingly reduced.

[0097] On the other hand, the first oxide sublayer is relatively thin, and its formation process is in the initial stage of oxidation. In this stage, active oxygen atoms directly bond with silicon atoms on the surface of section 112, and the degree of oxidation is determined by the number of silicon atoms available for reaction on this surface. The influence of the doping state on the oxidation rate is mainly reflected in the subsequent process where active oxygen atoms need to diffuse into the already formed oxide. Therefore, the thickness difference of the first oxide sublayer at various locations on section 112 is smaller than the thickness difference formed by continued oxidation under the same conditions, allowing the first oxide sublayer to form a uniform thickness coverage across the entire section 112, including the inner wall of the crack. In the second stage, active oxygen atoms need to diffuse through the first oxide sublayer downwards to bond with silicon atoms. The rate of oxidation is determined by the diffusion properties of the first oxide sublayer, and the influence of the doping state of each fracture region below it on this rate is weakened accordingly. Since the thickness and structure of the first oxide sublayer are consistent at various locations on section 112, the oxidation rate of each fracture region tends to be similar in the second stage. In addition to its chemical passivation function, the first oxide sublayer also serves as an interface layer that shields the doping differences between the substrate and the doped layer. The uniformity of the thickness of the oxide layer 120 on the cross section 112 mainly depends on the consistency of the first oxide sublayer itself, and is less affected by the doping state of each fracture region.

[0098] In some embodiments, in the second stage, the oxidation temperature is lowered and the ozone supply flux is increased, allowing the oxide layer 120 to thicken to the desired thickness in a shorter time. In a specific example, the second stage involves atomizing an ozone-containing aqueous solution into droplets and spraying it onto section 112. The ozone concentration in the aqueous solution is 20 mg / L to 30 mg / L, and the temperature of the aqueous solution is 20°C to 30°C. The number of ozone molecules per unit volume in the liquid phase is higher than in the gas phase, resulting in a higher rate of oxidation reaction. The lower temperature also leads to a lower degree of reconstruction of the newly formed silicon-oxygen network compared to the first stage, resulting in a relatively loose arrangement of the second oxide sublayer. Compared to thickening the oxide layer 120 to the desired thickness under the conditions of the first stage, this method eliminates the need for network reconstruction time during the oxide layer 120 thickening process, correspondingly shortening the time required to complete the oxidation process and reducing the residence time of the sectional cell 110 at higher temperatures.

[0099] The second oxide sublayer has a lower density, with more unsaturated sites and surface hydroxyl groups in its network compared to the portion formed under the conditions of the first stage. Since hydroxyl groups are active sites for chemisorption of precursors during atomic layer deposition, the second oxide sublayer provides a denser number of nucleation sites for the deposition of the passivation layer 130, thus increasing the nucleation density of the passivation layer 130. Therefore, the side of the oxide layer 120 facing section 112 serves to reduce the interface state density and shield doping differences, while the side facing away from section 112 serves to provide nucleation sites for the passivation layer 130. These two functions are controlled by the conditions of their respective stages.

[0100] In some embodiments, the thickness of the first oxide sublayer is less than the thickness of the second oxide sublayer. In some embodiments, the thickness of the first oxide sublayer is 0.5 nm to 2 nm, the thickness of the second oxide sublayer is 3 nm to 8 nm, and the sum of their thicknesses is in the range of 1 nm to 10 nm. The first oxide sublayer serves to establish an interface with a low interface state density, and the required thickness is limited to continuously covering the cross section 112 and saturating its dangling bonds.

[0101] In some embodiments, the second oxide sublayer formed in the second stage has a loosely arranged network and exhibits a certain degree of deformability under external force. Located between the first oxide sublayer and the passivation layer 130, the second oxide sublayer can buffer the stress accumulated in the first oxide sublayer during its growth and the volume increase generated by oxidation products within the crack. Consequently, the degree to which stress within the oxide layer 120 is transmitted to the inner wall of the crack is reduced, which helps prevent the crack from propagating along its depth under stress.

[0102] In some embodiments, the cell 110 is transferred from the processing chamber of the first stage to the processing chamber of the second stage between the first and second stages; in another implementation, the first and second stages are carried out continuously in the same processing chamber, and the switching between the two stages is achieved by adjusting the temperature of the chamber and the ozone supply method. The above two implementations can be selected according to the equipment configuration of the production line, and this application does not limit them.

[0103] It should be noted that the density of each part of the oxide layer 120 is characterized by its corrosion rate in a diluted hydrofluoric acid solution. The parts with a denser silicon-oxygen network have a lower corrosion rate. The thickness of the first oxide sublayer and the second oxide sublayer can be measured by observing the cross-sectional morphology of the oxide layer 120 using a transmission electron microscope.

[0104] Reference Figure 4As shown, in step S300, a passivation layer 130 is formed on the side of the oxide layer 120 away from the cross-section 112. The material of the passivation layer 130 includes aluminum oxide. The aluminum oxide layer contains a high density of negative fixed charges, and the electric field it forms near the cross-section 112 repels minority carriers, causing them to move away from the recombination center at the cross-section 112, thereby suppressing carrier recombination at the cross-section 112 through field-effect passivation.

[0105] In some embodiments, the method for forming the passivation layer 130 includes atomic layer deposition (ALD). ALD involves alternately introducing precursors into a reaction chamber to deposit them layer-by-layer on the surface of the oxide layer 120 via a self-limiting surface reaction. For example, trimethylaluminum and water or ozone are alternately introduced into the reaction chamber as precursors to form an alumina layer. The thickness of the passivation layer 130 can be precisely controlled by the number of deposition cycles, and the passivation layer 130 can maintain uniform coverage on surfaces with undulating topography, such as cross-section 112.

[0106] In some embodiments, the deposition temperature of atomic layer deposition (ALD) is 180°C to 200°C. Optionally, the deposition temperature of ALD is 185°C to 195°C. Optionally, the deposition temperature of ALD can be 180°C, 185°C, 190°C, or 200°C. If the deposition temperature is too low, the chemical adsorption and ligand removal of the precursor on the oxide layer 120 surface are insufficient, resulting in more residual organic groups in the formed alumina layer and a decrease in the film density. If the deposition temperature is too high, the precursor undergoes gas-phase decomposition before reaching the oxide layer 120 surface, resulting in particulate deposits in the film layer and an increase in the thermal load on the sectional battery 110. In this embodiment, the deposition temperature is set to 180°C to 200°C, balancing the density of the alumina layer with the thermal stability of the sectional battery 110.

[0107] In some embodiments, the method for forming the passivation layer 130 further includes plasma-enhanced chemical vapor deposition or chemical vapor deposition. These methods can also form the passivation layer 130 on the side of the oxide layer 120 away from the cross-section 112, with a relatively high film formation rate, suitable for applications where film thickness accuracy requirements are relatively relaxed. The above film formation methods can be implemented individually, and this application does not limit the specific method for forming the passivation layer 130.

[0108] In some embodiments, after the passivation layer 130 is formed, the segmented battery 110 is annealed at a temperature below 200°C. The annealing process further reconstructs the interface structure between the oxide layer 120 and the passivation layer 130, reducing the defect density at the interface; simultaneously, hydrogen in the passivation layer 130 diffuses into the cross section 112 under thermal action and saturates the dangling bonds deep within the cross section 112.

[0109] The oxide layer 120 and the passivation layer 130 constitute a composite passivation structure. On one hand, there are fewer interface defect states between the oxide layer 120 and the cross-section 112, resulting in a decrease in the interface state density at the cross-section 112, which is chemical passivation. On the other hand, oxygen atoms on the surface of the oxide layer 120 combine with aluminum atoms in the precursor during the initial deposition stage, forming a Si-O-Al structure at the interface between the oxide layer 120 and the alumina layer. This interface structure enables the composite passivation structure to achieve field-effect passivation. The combined effect of these two aspects further reduces the carrier recombination rate at the cross-section 112.

[0110] It should be noted that the role of oxide layer 120 in the above-mentioned composite passivation structure is different from that of silicon oxide used alone as a passivation layer. When silicon oxide is used alone as a passivation layer, its thickness is relatively large in order to obtain sufficient chemical passivation and a certain field-effect passivation, and its contribution to field-effect passivation is relatively limited.

[0111] It should be noted that the processing temperatures for the three methods of oxidizing section 112 with ozone are all below 200℃. Specifically, the gas-phase method is performed at 150℃ to 200℃, the liquid-phase method at room temperature to 40℃, and the chamber temperature for in-situ ultraviolet ozone generation is 120℃ to 180℃. These temperatures, combined with the atomic layer deposition (ALD) temperature of 180℃ to 200℃ and the annealing temperature not exceeding 200℃, ensure that the temperature throughout the entire process chain from oxidation to the formation of the passivation layer 130 does not exceed 200℃. This avoids the redistribution of dopants at high temperatures, the performance degradation of the metal contact structure, and the warping of the sectional cell 110 due to temperature gradients, thereby improving the yield of the sectional cell 110.

[0112] In some embodiments, the photovoltaic cells include at least one of the following: TOPCon cells (Tunnel Oxide Passivated Contact cells), HJT cells (Heterojunction with Intrinsic Thin-layer cells), PERC cells (Passivated Emitter and Rear Cell cells), BC cells (Back Contact cells), PSC cells (Perovskite Solar Cell cells), or tandem cells.

[0113] To better illustrate the beneficial effects of the embodiments of this application, corresponding embodiments and comparative examples are provided below. Embodiment 1 is a photovoltaic cell manufactured using the photovoltaic cell preparation method provided in this application, specifically a photovoltaic cell that forms a passivation layer after ozone oxidation treatment of the cross-section. Comparative Example 1 is a photovoltaic cell where the cross-section is not oxidized, but a passivation layer is directly formed on the cross-section. The photovoltaic cells prepared in the following embodiments and comparative examples were tested for their electrical performance using a digital source meter under AM1.5G simulated sunlight and 25 degrees Celsius conditions. The condition parameters not shown in the table are the same for both embodiments and comparative examples; please refer to the table below for details: Table 1

[0114] As can be seen from Example 1 and Comparative Example 1 in Table 1, after adopting the photovoltaic cell fabrication method provided in this application, the open-circuit voltage increased from 0.7335V to 0.7377V, the fill factor increased from 89.09% to 89.33%, the photoelectric conversion efficiency increased from 26.83% to 26.98%, and the module power increased from 632.3W to 635.6W. The increase in open-circuit voltage and fill factor indicates a decrease in the carrier recombination rate at cross-section 112, which is consistent with the morphological observation results of the passivation layer 130 obtaining continuous and uniform coverage on cross-section 112. It can be seen that pre-treating the cross-section before forming the passivation layer and forming a continuous oxide layer on the cross-section surface with ozone can improve the chemical passivation and field-effect passivation effect of the composite passivation structure composed of oxide layer and passivation layer. In addition, it can also improve the uniformity and density of passivation layer 130, reduce the carrier recombination rate at cross-section 112, and thus improve the open-circuit voltage, fill factor, and photoelectric conversion efficiency of photovoltaic cell.

[0115] Accordingly, another embodiment of this application also provides a photovoltaic cell. The photovoltaic cell provided in another embodiment of this application will be described in detail below with reference to the accompanying drawings. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding descriptions of the foregoing embodiments; detailed descriptions will not be repeated below.

[0116] Reference Figure 4 As shown, the photovoltaic cell includes: a cell 110, an oxide layer 120, and a passivation layer 130.

[0117] The segmented battery 110 includes opposing preset surfaces 111 and a cross section 112 connecting the preset surfaces 111. The segmented battery 110 is a part obtained by cutting a whole battery cell. One of its two preset surfaces 111 is the light-receiving surface and the other is the backlight surface. The cross section 112 is formed by the cutting process and has striped undulations and micron-sized cracks distributed on it.

[0118] An oxide layer 120 is disposed on section 112. The oxide layer 120 continuously covers section 112. The material of the oxide layer 120 includes silicon oxide, and the dangling bonds at section 112 are saturated by the Si-O-Si structure in the oxide layer 120, so that the chemical activity at all locations of section 112 tends to be uniform.

[0119] In some embodiments, the thickness of the oxide layer 120 is 1 nm to 10 nm.

[0120] A passivation layer 130 is disposed on the side of the oxide layer 120 away from the cross-section 112. The material of the passivation layer 130 includes aluminum oxide, which is grown in a layered manner on the surface of the oxide layer 120. As a result, the passivation layer 130 has a uniform and dense thickness on the cross-section 112, and the negative fixed charge inside it forms an electric field that repels minority carriers near the cross-section 112.

[0121] The photovoltaic cell provided in this application embodiment has an oxide layer 120 continuously covering the cross-section 112 and a passivation layer 130 made of aluminum oxide, which are sequentially disposed at the cross-section 112. The oxide layer 120 reduces the interface state density at the cross-section 112, and the structure formed at the interface between the oxide layer 120 and the passivation layer 130 gives the composite passivation structure a high density of negative fixed charge. As a result, the carrier recombination rate at the cross-section 112 is at a low level, and the open-circuit voltage, fill factor, and photoelectric conversion efficiency of the photovoltaic cell are correspondingly improved.

[0122] Accordingly, another embodiment of this application also provides a photovoltaic cell manufacturing apparatus. The photovoltaic cell manufacturing apparatus provided in another embodiment of this application will be described in detail below with reference to the accompanying drawings. For parts that are the same as or corresponding to those in the foregoing embodiments, please refer to the corresponding descriptions in the foregoing embodiments; detailed descriptions will not be repeated below.

[0123] The manufacturing equipment is used to implement the photovoltaic cell preparation method provided in any of the above embodiments, or to manufacture the photovoltaic cell provided in any of the above embodiments. The manufacturing equipment includes: a slitting machine, an oxidation machine, and a coating machine.

[0124] A slitting machine is used to cut solar cells into multiple slitting cells. Each slitting cell includes opposing pre-defined surfaces and a cross-section connecting the pre-defined surfaces. The slitting machine includes a platform for carrying the solar cells and an actuator for applying the cutting action. This actuator can be a laser, a cutting tool, a stamping die, or a diamond wire.

[0125] An oxidation unit is used to oxidize the cross-section to form an oxide layer. The oxidation unit is located downstream of the slab-forming unit and includes a processing chamber for accommodating the slab-forming cells and a supply unit for supplying ozone to the cross-section. When oxidation is performed in a liquid phase, the supply unit includes a container holding an ozone aqueous solution, an atomizing component for atomizing the ozone aqueous solution into droplets, and a spraying component for spraying the droplets onto the cross-section. When oxidation is performed in a gas phase, the supply unit includes an inlet component for introducing ozone-containing process gas into the processing chamber. When oxidation is performed in an in-situ generation manner, the supply unit includes an inlet component for introducing oxygen into the processing chamber and an ultraviolet light source for irradiating the cross-section.

[0126] A coating machine is used to form a passivation layer on the side of the oxide layer away from the cross-section. The coating machine is located downstream of the oxide machine and includes a reaction chamber for accommodating the cell segments and a conveying component for alternately introducing precursors.

[0127] In some embodiments, the processing chamber of the oxidation unit and the reaction chamber of the coating unit are the same chamber. In this case, the process of introducing ozone-containing process gas into the cross-section and the process of forming the passivation layer are completed in this chamber. As a result, the cells do not need to be transferred out of the chamber between the two processes, the chance of the oxide layer surface adsorbing moisture and particulate matter from the environment during the process interval is reduced, and the footprint of the manufacturing equipment is correspondingly reduced.

[0128] The photovoltaic cell manufacturing equipment provided in this application embodiment divides the three processes of cutting, oxidation, and passivation layer formation into three separate processes: a slitting machine, an oxidation machine, and a coating machine, which are sequentially connected along the process flow. Therefore, the entire process of forming the cell cross-section and having it covered by the passivation layer is completed within the same manufacturing equipment. This reduces the number of times the work-in-process is transferred between processes, thereby decreasing the chance of contamination and damage to the cross-section during transfer.

[0129] Accordingly, in another aspect, this application also provides a photovoltaic module, which includes the photovoltaic cell 30 described in any of the above embodiments, or the photovoltaic cell 30 prepared by the preparation method of the photovoltaic cell 30 in any of the above embodiments, or the photovoltaic cell manufactured by the manufacturing equipment of the photovoltaic cell described in the above embodiments. It should be noted that the parts that are the same as or corresponding to the foregoing embodiments can be referred to the corresponding descriptions of the foregoing embodiments, and will not be repeated below.

[0130] Figure 5 This is a partial structural diagram of a cell string in a photovoltaic module provided in an embodiment of this application. Figure 6 This is a partial cross-sectional schematic diagram of a photovoltaic module provided in an embodiment of this application.

[0131] Reference Figure 5 and Figure 6As shown, the photovoltaic module includes: a cell string, which is formed by connecting multiple photovoltaic cells 30 of any of the above embodiments, or by connecting photovoltaic cells 30 prepared by the method of preparing photovoltaic cells 30 of any of the above embodiments, or by connecting multiple photovoltaic cells 30 manufactured by the manufacturing equipment of photovoltaic cells as described in the above embodiments. The photovoltaic module also includes an encapsulation layer 31 and a cover plate 32; the encapsulation layer 31 is used to cover the surface of the cell string; the cover plate 32 is used to cover the surface of the encapsulation layer 31 facing away from the cell string.

[0132] Multiple photovoltaic cells 30 can be electrically connected through solder strips 33.

[0133] In some embodiments, the encapsulation layer 31 includes a first encapsulation sublayer and a second encapsulation sublayer. The first encapsulation sublayer covers one of the front and back sides of the photovoltaic cell 30, and the second encapsulation sublayer covers the other of the front and back sides of the photovoltaic cell 30. Specifically, at least one of the first and second encapsulation sublayers can be an organic encapsulation layer 31 such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene coelastomer (POE) film, or polyethylene terephthalate (PET) film. Alternatively, at least one of the first and second encapsulation sublayers 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 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.

[0134] In some cases, the first encapsulation sublayer and the second encapsulation sublayer still have a boundary line before lamination. After lamination, the photovoltaic module will no longer have the concept of the first encapsulation sublayer and the second encapsulation sublayer. That is, the first encapsulation sublayer and the second encapsulation sublayer have formed an integral encapsulation layer 31.

[0135] In some embodiments, the cover plate 32 can be a glass cover plate 32, a plastic cover plate 32, or other cover plate 32 with light-transmitting function. Specifically, the surface of the cover plate 32 facing the encapsulation layer 31 can be an uneven surface or a textured structure containing multiple raised areas, thereby increasing the utilization rate of incident light. The cover plate 32 may include a first cover plate 32 and a second cover plate 32, with the first cover plate 32 opposite to the first encapsulation sublayer and the second cover plate 32 opposite to the second encapsulation sublayer.

[0136] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for preparing a photovoltaic cell, characterized in that, include: A battery cell is obtained and then cut into multiple battery cells. Each battery cell includes opposing preset surfaces and a cross section connecting the preset surfaces. The cross section is oxidized with ozone to form an oxide layer on the cross section; A passivation layer is formed on the side of the oxide layer away from the cross section, and the material of the passivation layer includes aluminum oxide.

2. The method for preparing a photovoltaic cell according to claim 1, characterized in that, The oxidation treatment includes: atomizing an ozone aqueous solution containing the ozone into droplets, and spraying the droplets onto the cross-section.

3. The method for preparing a photovoltaic cell according to claim 2, characterized in that, The concentration of ozone in the ozone aqueous solution is 20 mg / L to 30 mg / L, and the temperature of the ozone aqueous solution is 20°C to 30°C.

4. The method for preparing a photovoltaic cell according to claim 2, characterized in that, The method of atomizing the ozone aqueous solution to form the droplets includes at least one of ultrasonic atomization, jet atomization, or vibrating screen atomization; And / or, the average diameter of the droplets is 3 μm to 8 μm.

5. The method for preparing a photovoltaic cell according to claim 2, characterized in that, The spraying pressure for spraying the droplets onto the cross-section is 0.1 MPa to 0.3 MPa, the spraying distance is 30 mm to 80 mm, and the spraying time is 60 s to 180 s.

6. The method for preparing a photovoltaic cell according to claim 1, characterized in that, The oxidation process includes: introducing a process gas containing ozone into the cross-section.

7. The method for preparing a photovoltaic cell according to claim 6, characterized in that, The volume concentration of ozone in the process gas is 5% to 25%; And / or, the flow rate of the process gas is 3000 sccm to 4000 sccm, and the time for introducing the process gas is 1 s to 60 s; And / or, the oxidation treatment is performed at a temperature of 150°C to 200°C.

8. The method for preparing a photovoltaic cell according to claim 1, characterized in that, The oxidation treatment includes: introducing oxygen into the cross section and irradiating the cross section with ultraviolet light, wherein the oxygen produces ozone under the irradiation of the ultraviolet light.

9. The method for preparing a photovoltaic cell according to claim 8, characterized in that, The wavelength of the ultraviolet light is 200nm to 400nm, the power density of the ultraviolet light is 50mW / cm², and the irradiation time of the ultraviolet light is 5min to 10min.

10. The method for preparing a photovoltaic cell according to claim 1, characterized in that, The method for forming the passivation layer includes atomic layer deposition, wherein the deposition temperature of the atomic layer deposition is 180°C to 200°C.

11. The method for preparing a photovoltaic cell according to claim 1, characterized in that, The thickness of the oxide layer is 1 nm to 10 nm.

12. A photovoltaic cell, characterized in that, The photovoltaic cell is prepared using the photovoltaic cell preparation method as described in any one of claims 1 to 11, and the photovoltaic cell comprises: The segmented battery includes opposing preset surfaces and a cross section connecting the preset surfaces; An oxide layer is disposed in the cross section; A passivation layer is disposed on the side of the oxide layer away from the cross section.

13. A photovoltaic cell manufacturing apparatus, characterized in that, The equipment for manufacturing a photovoltaic cell according to any one of claims 1 to 11, or for manufacturing a photovoltaic cell according to claim 12, comprises: A slitting machine is used to cut battery cells into multiple slitting cells. Each slitting cell includes opposing preset surfaces and a cross section connecting the preset surfaces. An oxidation machine, used to oxidize the cross section to form an oxide layer; A coating machine for forming a passivation layer on the side of the oxide layer away from the cross section.

14. A photovoltaic module, characterized in that, include: A battery string, comprising: a plurality of photovoltaic cells formed by the method of preparing photovoltaic cells as described in any one of claims 1 to 11, or a plurality of photovoltaic cells as described in claim 12, or photovoltaic cells manufactured by the equipment of manufacturing photovoltaic cells as described in claim 13; Encapsulation layer, the encapsulation layer being used to cover the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

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