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

Abstract

The present disclosure relates to the field of photovoltaics, and provides a photovoltaic cell, a manufacturing method thereof, a laminated cell and a photovoltaic module. The manufacturing method comprises: providing a cell substrate having two opposite surface sides; forming a seed layer on at least one surface side; printing a first paste on the surface side with the seed layer, the first paste comprising first conductive particles and second conductive particles, the silver content of the first conductive particles being lower than that of the second conductive particles; and modifying the first paste to convert the first paste into a transport layer, the seed layer and the transport layer together forming a grid line. In the step of modifying the first paste, a part of the second conductive particles are connected to a part of the first conductive particles to form a conductive connection, and / or the first conductive particles comprise an inner core and an outer layer, and after a part of the second conductive particles are connected to a part of the outer layer as a whole, the inner core is also connected to form a conductive connection, which is at least beneficial to improve the collection efficiency of the grid line to the carriers.

Description

Cross-reference to related applications

[0001] This application is a divisional application of Chinese invention patent application filed on December 30, 2025, with application number 202512018753.6 and invention title "Photovoltaic Cell and Manufacturing Method Thereof, Tandem Cell and Photovoltaic Module". Technical Field

[0002] This disclosure relates to the photovoltaic field, and in particular to a photovoltaic cell and its manufacturing method, a tandem cell, and a photovoltaic module. Background Technology

[0003] With the gradual depletion of fossil fuels, photovoltaic (PV) cells are becoming increasingly widely used as a new energy alternative. A PV cell is a device that converts solar energy into electrical energy. PV cells utilize the photovoltaic principle to generate charge carriers, which are then extracted using grid lines, thus facilitating the efficient use of electrical energy. Current PV cells mainly include BC cells (BackContact), TOPCon (Tunnel Oxide Passivated Contact) cells, PERC cells (Passivated emitter and real cell), and HIT / HJT cells (Heterojunction Technology).

[0004] However, whether it is the high-temperature paste used in conventional TOPCon cells or the low-temperature paste used in conventional heterojunction cells, the paste has problems such as the formation of pores or oxidation during the formation of grid lines. In addition, the low-temperature paste also has the problem of weak burn-through performance, which will affect the grid lines' ability to collect charge carriers. Furthermore, the crosslinking agent in the paste itself will also affect the grid lines' ability to collect charge carriers.

[0005] Therefore, in order to improve the carrier collection capability of the final grid line, the composition of the slurry or the preparation process of the grid line needs further research. Summary of the Invention

[0006] This disclosure provides a photovoltaic cell and its manufacturing method, a tandem cell and a photovoltaic module, which at least help to improve the collection efficiency of charge carriers by the grid lines.

[0007] This disclosure provides a method for manufacturing a photovoltaic cell, comprising: providing a cell substrate having two surface sides opposite each other along a first direction; forming a seed layer on at least one of the surface sides; printing a first paste on the surface side on which the seed layer is formed, the first paste comprising at least a first conductive particle and a second conductive particle, both the first conductive particle and the second conductive particle containing silver, and the silver content of the first conductive particle being lower than the silver content of the second conductive particle; at least modifying the first paste to transform it into a transport layer, the seed layer and the transport layer together forming a grid line; in the step of performing the modification treatment, at least a portion of the second conductive particles are connected to a portion of the first conductive particles to form a conductive connection portion; and / or, the first conductive particle comprises an inner core and an outer layer located on the surface of the inner core, at least a portion of the second conductive particles are connected to the inner core after being integrally connected with a portion of the outer layer to form the conductive connection portion.

[0008] Optionally, in the step of printing the first paste, the first paste printed on the surface side is simultaneously heated to transform the first paste into an initial transport layer; or, after printing the first paste and before performing the modification treatment, the first paste is dried; the step of performing the modification treatment on at least the first paste includes: performing the modification treatment on the initial transport layer to transform the initial transport layer into the transport layer.

[0009] Optionally, the temperature provided to the first slurry by the heating treatment or the drying treatment is no greater than 300°C.

[0010] Optionally, the modification process includes: heating the first slurry with a heating device, irradiating the first slurry with a laser, or irradiating the first slurry with a xenon lamp.

[0011] Optionally, in the modification process, at least a portion of the second conductive particles are melted, recrystallized into a liquid phase, and then solidified into a silver layer, with a portion of the first conductive particles embedded within the silver layer to form the conductive connection portion; and / or, the first conductive particles include an inner core and an outer layer located on the surface of the inner core, and in the modification process, at least a portion of the second conductive particles and a portion of the outer layer are melted, recrystallized into a liquid phase, and then solidified into the silver layer, with a portion of the inner core embedded within the silver layer to form the conductive connection portion.

[0012] Optionally, in the first slurry printed, a portion of the area includes at least two mutually dispersed second conductive particles, and a first sintering neck is formed between adjacent at least two second conductive particles in the portion of the area; after the modification treatment, the at least two mutually dispersed second conductive particles in the portion of the area are connected into an integral structure, and the at least two second conductive particles with the first sintering neck are transformed into particles with a second sintering neck, wherein the ratio of the size of the second sintering neck to the size of the first sintering neck is greater than or equal to 130%.

[0013] Optionally, during the modification process, the ambient temperature of the battery substrate printed with the first paste is controlled to be less than 250°C.

[0014] This disclosure also provides a photovoltaic cell, comprising: a cell substrate having two surface sides opposite each other along a first direction; a seed layer located on at least one of the surface sides; a transport layer located on the surface side having the seed layer, the seed layer and the transport layer together forming a grid line; wherein the transport layer includes at least: a conductive connection portion, the conductive connection portion including a silver layer, the silver layer having a third conductive particle and / or a first conductive particle embedded therein; a body portion located between the conductive connection portion and the cell substrate and between the conductive connection portion and the seed layer, the body portion containing the first conductive particle and a second conductive particle; the first conductive particle including an inner core and an outer layer located on the surface of the inner core, the third conductive particle including only the inner core; and / or, both the first conductive particle and the second conductive particle contain silver, and the silver content of the first conductive particle is lower than the silver content of the second conductive particle.

[0015] Optionally, in the main body, at least two of the second conductive particles are connected in contact to form a whole to constitute a conductive part, and the conductive part is rod-shaped, branch-shaped, block-shaped or mesh-shaped.

[0016] Optionally, a portion of the conductive connection portions are in contact with the main body portion near the end of the battery substrate; and / or, a portion of the conductive connection portions are in contact with the battery substrate near the end of the battery substrate.

[0017] Optionally, at least two second conductive particles spaced apart from each other are present in at least a portion of the main body; and / or, a plurality of second conductive particles contained in at least a portion of the main body are in contact with each other.

[0018] Optionally, the resistivity of the transport layer is 2 μΩ·cm to 3 μΩ·cm.

[0019] Optionally, along the first direction, a portion of the thickness of the seed layer is embedded in the battery substrate.

[0020] Optionally, the transmission layer further includes: a small number of dispersed second conductive particles located on or partially embedded in the battery substrate, and located on the outer side of the conductive connection portion away from the main body portion.

[0021] Optionally, the surface side having the seed layer is taken as the target surface side, and the distance between the top surface of the seed layer away from the battery substrate and the target surface side along the first direction is 1 μm to 15 μm; and / or, the thickness of the transport layer along the first direction is 5 μm to 20 μm.

[0022] Optionally, the first conductive particle includes at least one of silver-coated copper particles, silver-coated nickel particles, or silver-nickel alloy particles, and the second conductive particle includes silver particles or silver alloy particles; and / or, the median diameter of the first conductive particle is greater than the median diameter of the second conductive particle.

[0023] This disclosure also provides a tandem solar cell, comprising: a base cell, which is a photovoltaic cell formed by the manufacturing method of a photovoltaic cell as described in any of the preceding claims, or a photovoltaic cell as described in any of the preceding claims; and a perovskite cell, which is located on one side of the base cell.

[0024] This disclosure also provides a photovoltaic module, comprising: a battery string, which is formed by connecting a plurality of photovoltaic cells manufactured by the method described in any one of the preceding claims, or by connecting a plurality of photovoltaic cells as described in any one of the preceding claims, or by connecting a plurality of stacked cells as described in the preceding claims; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film opposite to the battery string.

[0025] The technical solution provided in this disclosure has at least the following advantages: The fabrication process of the grid line is designed to include "forming a seed layer on the surface side" and "forming a transport layer on the surface side where the seed layer is formed." This design leverages the seed layer fabrication process to improve the contact performance between the seed layer and the battery substrate, laying the foundation for low contact resistance between the grid line and the battery substrate. Further modification treatment promotes the melting of various conductive particles in the first slurry, such as the first and / or second conductive particles melting and recrystallizing each other, increasing the contact area between multiple conductive particles. This forms a conductive connection with good conductivity, improving the conductivity of the transport layer. Moreover, the conductive connection helps protect other parts of the transport layer, reducing the risk of oxidation within the transport layer, thus further improving its conductivity. Therefore, the combined process of seed layer and transport layer fabrication improves the conductivity and contact performance with the battery substrate of the grid line from multiple aspects, thereby enhancing the grid line's carrier collection efficiency. Attached Figure Description

[0026] 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.

[0027] Figure 1 A process flow diagram of a method for manufacturing a photovoltaic cell according to an embodiment of this disclosure; Figure 2 This is a partial cross-sectional view of a photovoltaic cell manufacturing method according to an embodiment of the present disclosure after the grid lines have been formed. Figure 3 This is another partial cross-sectional view of the photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the grid lines have been formed; Figure 4 This is a partial cross-sectional schematic diagram of the first slurry after undergoing a first stage in a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure. Figure 5 A top-down scanning electron microscope image of the first slurry after it has undergone a first stage in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure; Figure 6 A comparative overhead scanning electron microscope image of the first slurry after undergoing a first stage and after undergoing two different second stages in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure; Figure 7A comparative overhead scanning electron microscope image of the first slurry after undergoing a first stage and a second stage in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure; Figure 8 This is a first partial cross-sectional schematic diagram of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the transport layer has been formed; Figure 9 This is a second partial cross-sectional schematic diagram of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the transport layer has been formed; Figure 10 This is a third partial cross-sectional view of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the transport layer has been formed; Figure 11 This is a partial cross-sectional schematic diagram of laser irradiation of a first slurry in a method for manufacturing a photovoltaic cell according to an embodiment of the present disclosure. Figure 12 This is a magnified overhead scanning electron microscope image of the transport layer in a photovoltaic cell provided in another embodiment of the present disclosure; Figure 13 This is another magnified overhead scanning electron microscope image of the transport layer in a photovoltaic cell provided in another embodiment of this disclosure; Figure 14 A partial cross-sectional schematic diagram of a stacked battery provided in yet another embodiment of this disclosure; Figure 15 A partial three-dimensional schematic diagram of a cell string in a photovoltaic module provided in another embodiment of the present disclosure; Figure 16 This is a partial cross-sectional schematic diagram of a photovoltaic module provided in another embodiment of the present disclosure.

[0028] Explanation of reference numerals in the attached figures: 100. Battery substrate; 110. Surface side; 110a. Target surface side; 120. Substrate; 130. Passivation and antireflection layer; 101. Initial transport layer; 111. Transport layer; 102. First conductive particle; 112. Inner core; 122. Outer layer; 103. Second conductive particle; 104. Conductive connection; 115. Seed layer; 106. Grid line; 107. Third conductive particle; 108. Main body; 118. Conductive part; 109. Stacked battery; 119. Bottom battery; 129. Perovskite battery; 40. Photovoltaic cell; 41. Encapsulation film; 42. Cover plate; 43. Conductive strip. Detailed Implementation

[0029] As can be seen from the background technology, the efficiency of grid lines in collecting charge carriers needs to be improved.

[0030] Analysis revealed that both the high-temperature paste used in conventional TOPCon batteries and the low-temperature paste used in HJT batteries have high silver content. Given the high price of silver, further reducing the silver content in the paste to lower costs would more easily lead to a narrowing of the final grid line width, causing problems such as grid breakage, incomplete printing, or increased line resistance, thus reducing the grid line's conductivity. Therefore, it is necessary to consider other approaches to reduce the fabrication cost of the grid lines.

[0031] If base metal pastes, such as copper paste or silver-coated copper paste, are used, the conductivity of the final grid line will decrease because copper is easily oxidized at high temperatures. To avoid oxidation of the paste during grid line formation, additional processes or equipment are needed to isolate oxygen or lower the temperature. Isolating oxygen with additional processes or equipment complicates the grid line fabrication process; lowering the temperature results in more conductive particles in the paste being dispersed, meaning adjacent conductive particles cannot effectively connect into a whole at low temperatures, resulting in point-to-point or line-to-line contact rather than face-to-face contact. This reduces the effective contact area between adjacent conductive particles, leading to poor conductivity of the final grid line. Therefore, it is necessary to balance simplifying the grid line fabrication process with reducing the conductivity of the grid line from other perspectives.

[0032] This disclosure provides a photovoltaic cell and its manufacturing method. The manufacturing method includes a grid wire preparation process comprising "forming a seed layer on the surface side" and "forming a transport layer on the surface side where the seed layer is formed." This process leverages the seed layer preparation technology to improve the contact performance between the seed layer and the cell substrate, laying the foundation for low contact resistance between the grid wire and the cell substrate. Further modification treatment promotes the melting of various conductive particles in the first slurry, such as the first conductive particles and / or the second conductive particles melting and recrystallizing each other, increasing the contact area between multiple conductive particles. This forms a conductive connection with good conductivity, improving the conductivity of the transport layer. Moreover, the conductive connection helps protect other parts of the transport layer, reducing the risk of oxidation within the transport layer, thereby further improving its conductivity. Thus, the combined seed layer preparation and transport layer preparation processes improve the conductivity of the grid wire and its contact performance with the cell substrate from multiple aspects, thereby increasing the grid wire's carrier collection efficiency.

[0033] In the description of the embodiments of this disclosure, 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 or secondary relationship of the indicated technical features. In the description of the embodiments of this disclosure, "a plurality of" means two or more, unless otherwise explicitly defined.

[0034] 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 disclosure. 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.

[0035] In the description of the embodiments of this disclosure, 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. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In the description of embodiments of this disclosure, 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).

[0037] In the description of the embodiments of this disclosure, 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 disclosure 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 disclosure.

[0038] In the description of the embodiments of this disclosure, 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. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0039] In the accompanying drawings corresponding to the embodiments of this disclosure, 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.

[0040] In the description of embodiments of this disclosure, when a component "includes" another component, other components are not excluded unless otherwise stated, and 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 another component may be present therein. Additionally, 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 therein.

[0041] 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.

[0042] 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.

[0043] This disclosure provides a method for manufacturing a photovoltaic cell according to an embodiment. The method for manufacturing a photovoltaic cell according to an embodiment of this disclosure will be described in detail below with reference to the accompanying drawings.

[0044] Refer to the image, in conjunction with the reference. Figures 1 to 5 , Figure 1 This is a process flow diagram of a method for manufacturing a photovoltaic cell according to an embodiment of the present disclosure. The method for manufacturing a photovoltaic cell includes at least the following steps: S1: Reference Figure 2 or Figure 3 , Figure 2 This is a partial cross-sectional view of a photovoltaic cell manufacturing method according to an embodiment of the present disclosure after the grid lines have been formed. Figure 3 This is another partial cross-sectional view of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the grid lines have been formed. A cell substrate 100 is provided, having two surface sides 110 opposite each other along a first direction X.

[0045] S2: Continue to refer to Figure 2 or Figure 3 A seed layer 115 is formed on at least one surface side 110.

[0046] S3: Refer to Figure 2 and Figures 4 to 5 or in conjunction with references Figures 3 to 5 A first paste (not shown in the figure) is printed on the surface side 110 where the seed layer 115 is formed. The first paste includes at least a first conductive particle 102 and a second conductive particle 103. Both the first conductive particle 102 and the second conductive particle 103 contain silver, and the silver content of the first conductive particle 102 is lower than the silver content of the second conductive particle 103.

[0047] It should be noted that since the first paste does not have a fixed form before printing, it will undergo at least a modification process after printing to become the transport layer 111. After the first paste undergoes subsequent modification processing, it can present a stable form on the battery substrate 100. Based on this, to illustrate the first conductive particles 102 and the second conductive particles 103 in the first paste, Figure 4 and Figure 5 The first slurry after the first stage is illustrated in different ways. Figure 4 This is a partial cross-sectional schematic diagram of the first slurry after undergoing a first stage in a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure. Figure 5 This is a partial overhead scanning electron microscope image of the first slurry after it has undergone a first stage in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure.

[0048] Furthermore, the first conductive particles 102 and the second conductive particles 103 in the first printing paste are... Figure 4 and Figure 5 The first conductive particles 102 and the second conductive particles 103 shown are similar, but the main difference is that: compared with the first slurry after the first stage, the distribution of the first conductive particles 102 and the second conductive particles 103 in the printed first slurry is more loose, and the connection strength of the two first conductive particles 102 connected in the printed first slurry may be lower than the connection strength of the two first conductive particles 102 connected in the first slurry after the first stage.

[0049] and, Figure 4 and Figure 5 Taking the modification process, including only the first stage, as an example, in practical applications, the modification process may not be divided into multiple stages. For instance, the energy density provided to the first paste by the modification process may remain constant throughout the entire process. Alternatively, the first paste after printing may undergo drying before undergoing modification. The modification process will be explained in detail later.

[0050] S4: Refer to Figure 2 and Figures 4 to 10 or in conjunction with references Figures 3 to 10 At least the first slurry is modified to transform it into a transport layer 111. The seed layer 115 and the transport layer 111 together form the gate line 106.

[0051] In the modification process, the morphological changes of the first conductive particle 102 and the second conductive particle 103 include at least the following two cases: In some cases, in conjunction with reference to... Figures 4 to 8 In the modification process, at least a portion of the second conductive particles 103 are connected to a portion of the first conductive particles 102 to form a conductive connection portion 104. And / or, in other cases, in conjunction with reference to... Figures 4 to 7 ,as well as Figure 9 or Figure 10 The first conductive particle 102 includes an inner core 112 and an outer layer 122 located on the surface of the inner core 112. At least a portion of the second conductive particles 103 are connected to a portion of the outer layer 122 as a whole and are also connected to the inner core 112 to form a conductive connection portion 104. It should be noted that the morphological changes of the first conductive particles 102 and the second conductive particles 103 during the modification process will be described in detail later.

[0052] It is worth noting that the process of preparing the grid line 106 is designed to include "forming a seed layer 115 on the surface side 110" and "forming a transport layer 111 on the surface side 110 where the seed layer 115 is formed". This is beneficial to improve the contact performance between the seed layer 115 and the battery substrate 100 by means of the preparation process of the seed layer 115, laying the foundation for low contact resistance between the grid line 106 and the battery substrate 100. Furthermore, the modification treatment promotes the melting and recrystallization of various conductive particles in the first slurry, such as the first conductive particles 102 and / or the second conductive particles 103, to increase the contact area between multiple conductive particles, thereby forming a conductive connection portion 104 with good conductivity to improve the conductivity of the transport layer 111. Moreover, the conductive connection portion 104 is beneficial to protect other parts in the transport layer 111, reduce the risk of oxidation inside the transport layer 111, and further improve the conductivity of the transport layer 111. Thus, with the combined fabrication processes of the seed layer 115 and the transport layer 111, the conductivity of the grid line 106 and its contact performance with the battery substrate 100 can be improved from multiple aspects, thereby enhancing the collection efficiency of the grid line 106 for charge carriers.

[0053] Furthermore, the first slurry is designed to include at least first conductive particles 102 and second conductive particles 103. Both the first conductive particles 102 and the second conductive particles 103 contain silver, and the silver content of the first conductive particles 102 is lower than that of the second conductive particles 103. Thus, by using modification treatment to improve the conductivity of the final transport layer 111, appropriately designing a certain number of first conductive particles 102 with lower silver content helps to appropriately reduce the preparation cost of the first slurry. Moreover, it is beneficial to balance the silver content of the first slurry by using two types of first conductive particles 102 and second conductive particles 103 with different silver contents, thereby avoiding a decrease in conductivity caused by excessively low silver content in the transport layer 111.

[0054] in, Figure 6 A comparative overhead scanning electron microscope image of the first slurry after undergoing a first stage and after undergoing two different second stages in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure; Figure 7 A comparative overhead scanning electron microscope image of the first slurry after undergoing a first stage and a second stage in a photovoltaic cell manufacturing method provided in an embodiment of this disclosure; Figure 8 This is a first partial cross-sectional schematic diagram of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the transport layer has been formed; Figure 9 This is a second partial cross-sectional schematic diagram of a photovoltaic cell manufacturing method provided in an embodiment of the present disclosure after the transport layer has been formed; Figure 10 This is a third partial cross-sectional view of a photovoltaic cell manufacturing method according to an embodiment of this disclosure after the transport layer has been formed. Further details will be provided in conjunction with specific embodiments. Figures 6 to 10 Please provide a detailed explanation.

[0055] In some cases, the first conductive particle 102 can be cut using focused ion beam (FIB) slicing technology. The cut surface of the first conductive particle 102 can then be observed using transmission electron microscopy (TEM) or scanning electron microscopy (SEM), revealing the inner core 112 and the outer layer 122 located on the surface of the inner core 112. FIB slicing technology enables precise processing and observation of materials at the nanoscale.

[0056] The following will describe in more detail a method for manufacturing a photovoltaic cell according to an embodiment of the present disclosure, with reference to the accompanying drawings.

[0057] In some embodiments, reference Figure 3 In the step of forming the seed layer 115, a portion of the thickness of the seed layer 115 is embedded in the battery substrate 100 along the first direction X. Thus, the ultimately formed grid lines 106 can have good contact performance with the battery substrate 100.

[0058] In some cases, in addition to a substrate 120 including doped portions (not shown) for generating and collecting charge carriers, the interior of the battery substrate 100 generally also has a passivation and antireflection layer 130 formed on the doped portions. The passivation and antireflection layer 130 can both passivate and protect the doped portions and improve the absorption and utilization rate of incident light. Based on this, for the grid line 106 used to collect charge carriers, a portion of the grid line 106 needs to pass through the passivation and antireflection layer 130 to contact and connect with the doped portions.

[0059] The modification treatment is mainly used to increase the contact area between the first conductive particles 102 and / or the second conductive particles 103 in the first slurry. Generally, the temperature provided by the modification treatment to the first slurry is lower than that provided by the conventional sintering treatment. Therefore, the ability of the first slurry to pass through the passivation layer and / or antireflection layer needs to be further improved during the modification treatment step. To further ensure that the final grid line 106 can effectively collect carriers in the battery substrate 100, a seed layer 115 is formed on at least one surface side 110 before printing the first slurry. In this way, the partial thickness of the seed layer 115 can be embedded in the battery substrate 100, allowing the seed layer 115 to contact and connect with the doped portion to effectively collect carriers in the battery substrate 100. On this basis, the conductivity of the transport layer 111 is improved by using the manufacturing process of the transport layer 111. In this way, multiple factors can be combined to improve the carrier collection efficiency of the final grid line 106.

[0060] The morphological changes of the first conductive particle 102 and the second conductive particle 103 during the modification process are described in detail below.

[0061] In some embodiments, in conjunction with reference Figures 4 to 8 At least in the second stage II, at least a portion of the second conductive particles 103 connect to a portion of the first conductive particles 102 to form a conductive connection portion 104. In other words, the conductive connection portion 104 contains the first conductive particles 102. Furthermore, after the plurality of second conductive particles 103 melt and recrystallize into a liquid phase, they solidify into a whole, and their interior no longer has a very obvious dividing line, therefore... Figures 8 to 10 In the conductive connection portion 104, only the first conductive particle 102 is shown, and the second conductive particle 103 is not shown. In fact, multiple second conductive particles 103 and at least one first conductive particle 102 will melt and recrystallize into a whole to jointly constitute the conductive connection portion 104.

[0062] In other embodiments, in conjunction with reference to Figures 4 to 7 ,as well as Figure 9 or Figure 10 The first conductive particle 102 may include an inner core 112 and an outer layer 122 located on the surface of the inner core 112. At least a portion of the second conductive particles 103 are connected to a portion of the outer layer 122 as a whole and then connected to the inner core 112 to form a conductive connection portion 104. In other words, if the unmelted and recrystallized inner core 112 is used as an independent third conductive particle 107, then the conductive connection portion 104 may contain the third conductive particle 107 in addition to the first conductive particle 102.

[0063] In this process, not only do multiple second conductive particles 103 melt and recrystallize into a liquid phase, but a portion of the outer layer 122 also melts and recrystallizes into a liquid phase. Subsequently, the two solidify into a single entity, and the internal boundary no longer has a very clear dividing line. Figure 9 and Figure 10 In the conductive connection portion 104, only a portion of the outer layer 122 that has not been melted and recrystallized as first conductive particles 102 and a portion of the inner core 112 are shown. The outer layer 122 corresponding to the inner core 112 is not shown, nor are the second conductive particles 103 shown. In fact, multiple second conductive particles 103 and at least one first conductive particle 102 will melt and recrystallize into a whole to jointly constitute the conductive connection portion 104.

[0064] It should be noted that, in order to illustrate the positional relationship between the conductive connection portion 104 and the main body portion 108, Figure 10 The conductive connection portion 104 and the main body portion 108 are roughly divided in the transmission layer 111 by dashed lines.

[0065] In some cases, the first conductive particle 102 can be a silver particle, and the outer layer 122 can be a silver layer.

[0066] It should be noted that, depending on the selected process parameters for the modification treatment, the two embodiments described above correspond to different parameters. Figures 8 to 10 The three scenarios shown can exist in different modification processes, i.e., in different transport layers 111; or, based on the different effects of the modification processes on different regions of the first slurry, the two embodiments described above correspond to... Figures 8 to 10 At least two of the three scenarios shown can also exist simultaneously in the same modification process, that is, simultaneously in different regions of the same transport layer 111.

[0067] The following describes in detail the preparation process of transforming the first slurry into a transport layer through various embodiments.

[0068] In some embodiments, the first printing paste is pretreated before modification to achieve preliminary curing. The pretreatment includes at least the following two scenarios: In some cases, during the printing of the first slurry, the slurry printed on the surface side is simultaneously heated to transform it into an initial transport layer. In other words, the printing and heating of the first slurry can be performed concurrently. For example, 3D printing technology can be used to heat the first slurry while printing it, which helps to simplify the preparation process of the transport layer while ensuring good quality of the final transport layer. During the 3D printing process, the first slurry can be heated by methods such as heating the carrier plate, blowing hot air, or infrared irradiation.

[0069] In other cases, the first slurry is dried after printing and before modification. In other words, printing the first slurry, drying the first slurry, and then modifying the first slurry can be performed in separate steps. The first slurry can be printed using processes such as screen printing, nanoimprinting, or laser transfer.

[0070] Furthermore, in both of the above scenarios, the step of modifying the first slurry at least includes: modifying the initial transport layer to transform it into transport layer 111. It should be noted that since the first slurry has already been pre-treated to form an intermediate state, i.e., the initial transport layer, before the modification process, the main focus before subsequent modification is to promote the melting and recrystallization between the first conductive particles 102 and / or the second conductive particles 103. Therefore, the modification process can be designed to provide a stable energy density to the first slurry throughout the entire process, or it can be divided into multiple stages as described in subsequent embodiments.

[0071] In both of the above scenarios, the temperature provided to the first slurry by the heat treatment or drying process can be no greater than 300°C. For example, it can be 300°C, 290°C, 280°C, 270°C, 260°C, 250°C, 240°C, 230°C, 220°C, 210°C, or 200°C. This not only facilitates the initial solidification of the first slurry but also avoids the porosity problem caused by excessively rapid volatilization of organic components and reduces the thermal impact of the heat treatment or drying process on the battery substrate 100.

[0072] In other embodiments, in conjunction with reference to Figures 4 to 7 The modification process may include a first stage I and a second stage II. The energy density provided to the first slurry in the first stage I is lower than the energy density provided to the first slurry in the second stage II. The first slurry after undergoing the first stage I can be regarded as the initial transport layer 101. Subsequently, the initial transport layer 101 is transformed into the transport layer 111 after undergoing the second stage II.

[0073] Thus, a first stage I with lower energy density is used to treat organic residues or surface oxide layers in the first slurry to reduce impurities in the final transport layer 111, thereby improving the conductivity of the transport layer 111. Furthermore, the first slurry for printing typically contains a large amount of organic solvents. Directly modifying the first slurry with high energy density could easily lead to rapid evaporation of the organic solvents, forming voids within the final transport layer 111 or causing discontinuities. Therefore, using a first stage I with lower energy density to treat the first slurry helps reduce the risk of new defects forming within the first slurry while simultaneously curing it. Subsequently, a second stage II with higher energy density is used to treat the partially cured first slurry. This promotes the melting and recrystallization of various conductive particles in the first slurry, such as the first conductive particles 102 and / or the second conductive particles 103, increasing the contact area between multiple conductive particles. For example, this allows multiple conductive particles to connect into a single unit, thereby improving the conductivity of the final transport layer 111. In other words, the problems of residual impurities in the first slurry and the recrystallization of conductive particles can be addressed in two separate stages.

[0074] Furthermore, after printing the first slurry, there is no need to perform drying and sintering treatments on the transport layer 111 in sequence. The first slurry can be directly modified in two stages, which helps to simplify the preparation process of forming the transport layer 111.

[0075] It should be noted that, in order to demonstrate the different effects of Stage I and Stage II, as well as different Stage II methods, on the first slurry, Figure 6 The image shows, in sequence, the overhead scanning electron microscope (SEM) images of the first slurry after undergoing the first stage I, the first type of second stage IIa, and the first type of second stage IIb. Figure 6 The energy density provided to the first slurry by the first type of second stage IIa is lower than that provided to the first slurry by the second type of second stage IIb. To illustrate the different effects of the first stage I and the second stage II on the first slurry, Figure 7 The image shows, in sequence, the overhead scanning electron microscope (SEM) images of the first slurry after it has undergone the first stage I and the overhead SEM images of the first slurry after it has undergone the second stage II.

[0076] It is worth noting that, whether in Stage I or Stage II, the energy density provided by the modification treatment to the first slurry can refer to the amount of energy or heat provided by the modification treatment to a unit area of ​​the first slurry per unit time. Specifically, it can be expressed as the amount of heat provided by the modification treatment to a unit area of ​​the first slurry per unit time, or the amount of temperature increase that the modification treatment can achieve per unit area of ​​the first slurry per unit time.

[0077] Furthermore, the design that the energy density provided by the first stage I to the first slurry is lower than the energy density provided by the second stage II to the first slurry can mean that: the average energy density provided by the first stage I to the first slurry is lower than the average energy density provided by the second stage II to the first slurry, or the maximum energy density provided by the first stage I to the first slurry is lower than the minimum energy density provided by the second stage II to the first slurry.

[0078] In some cases, during the first stage I, the energy density supplied to the first slurry can gradually increase over time. This allows the organic components in the first slurry to gradually volatilize, providing the conductive particles near the volatilized organic components with time to fill the pores created by volatilization, thus preventing the formation of voids and improving the conductivity of the transport layer 111. In other cases, during the first stage I, the energy density supplied to the first slurry can remain a constant value over time.

[0079] In some cases, during the second stage II, the energy density supplied to the first slurry can gradually increase over time, which facilitates the full melting and recrystallization of the first conductive particles 102 and / or the second conductive particles 103. This allows multiple first conductive particles 102 and / or second conductive particles 103 to form a larger contact area, thereby improving the conductivity of the transport layer 111. In other cases, during the second stage II, the energy density supplied to the first slurry can first gradually increase and then gradually decrease over time, providing a cooling stage after the first conductive particles 102 and / or the second conductive particles 103 have fully melted and recrystallized. In still other cases, during the second stage II, the energy density supplied to the first slurry can remain a fixed value over time.

[0080] In some cases, the temperature provided to the first slurry in the first stage I may not exceed 300°C. For example, it can be 300°C, 290°C, 280°C, 270°C, 260°C, 250°C, 240°C, 230°C, 220°C, 210°C, or 200°C. This not only facilitates the initial curing of the first slurry but also avoids the porosity problem caused by the rapid volatilization of organic components and reduces the thermal impact of the first stage I on the battery substrate 100.

[0081] The modification process used in the two embodiments described above will be explained in detail below.

[0082] In both of the above embodiments, in conjunction with the reference Figures 4 to 7 The modification process may include heating the first slurry using a heating device.

[0083] It is worth noting that before the first slurry is modified, the arrangement of the first conductive particles 102 and the second conductive particles 103 within the first slurry is relatively loose. Based on this, a heating device can be used to directly provide a large amount of heat to the first slurry in a short time. This not only promotes the rapid melting and recrystallization of the first conductive particles 102 and the second conductive particles 103 in the first slurry, thereby increasing the contact area between the first conductive particles 102 and / or the second conductive particles 103, but also increases the heating rate to effectively reduce the risk of oxidation of some components in the first slurry, thus reducing the risk of the final transport layer 111 containing many oxide impurities. In this way, the conductivity of the final transport layer 111 can be improved in multiple ways.

[0084] In some cases, the modification process includes a first stage (I) and a second stage (II). In the first stage (I), the heating device provides a first temperature to the first slurry, and in the second stage (II), it provides a second temperature, with the first temperature controlled to be lower than the second temperature. A higher temperature provided to the first slurry is more conducive to heating it to a higher temperature in a shorter time. Therefore, designing the first temperature to be lower than the second temperature ensures that the energy density provided to the first slurry in the first stage (I) is lower than the energy density provided to the first slurry in the second stage (II).

[0085] In some cases, the step of heating the first paste using a heating device may include: placing the battery substrate 100 printed with the first paste on a carrier plate with a heating function, and transferring the heat from the carrier plate to the first paste by means of heat transfer; or, placing the battery substrate 100 printed with the first paste in a heating chamber, introducing hot air into the heating chamber, and transferring the heat to the first paste by means of the hot air blowing on the first paste.

[0086] In both of the above embodiments, in conjunction with the reference Figures 4 to 7 as well as Figure 11 , Figure 11 This is a partial cross-sectional view of a photovoltaic cell manufacturing method according to an embodiment of the present disclosure, in which a first slurry is irradiated with a laser. The step of modification treatment may include: irradiating the first slurry with a laser at least once.

[0087] It is worth noting that before the first slurry was modified, the arrangement of the first conductive particles 102 and the second conductive particles 103 within the first slurry was relatively loose. Based on this, a laser can be used to provide a large amount of heat to the first slurry in a short time. This not only promotes the rapid melting and recrystallization of the first conductive particles 102 and the second conductive particles 103, thereby increasing the contact area between the first conductive particles 102 and / or the second conductive particles 103, but also effectively reduces the risk of oxidation of some components in the first slurry due to the instantaneous heating characteristic of the laser, thus reducing the risk of the final transport layer 111 containing many oxide impurities. In this way, the conductivity of the final transport layer 111 can be improved in multiple ways.

[0088] In some cases, the modification process includes a first stage (I) and a second stage (II), where the laser power used in the first stage (I) is controlled to be lower than that used in the second stage (II). Higher laser power is more advantageous for heating the first slurry to a higher temperature in a shorter time. Therefore, controlling the laser power used in the first stage (I) to be lower than that used in the second stage (II) ensures that the energy density provided to the first slurry by the first stage (I) is lower than that provided by the second stage (II).

[0089] In some cases, the method of using a laser to irradiate at least the first paste may include: controlling the laser to irradiate only the area where the first paste is printed, thereby helping to reduce the influence of the laser on other areas of the battery substrate 100; or, controlling the laser to irradiate the entire surface side 110 where the first paste is printed.

[0090] In some cases, the wavelength of the laser used in the modification process can be 0.75μm~25μm, for example, it can be 0.75μm~1μm, 1μm~5μm, 5μm~10μm, 10μm~15μm, 15μm~20μm or 20μm~25μm, etc.

[0091] In some examples, at least in the second stage, infrared lasers can be used to irradiate the first slurry. Taking advantage of the short local heating time of infrared lasers, the first conductive particles 102 and the second conductive particles 103 in the first slurry can be rapidly melted and recrystallized, while reducing the risk of oxidation of some components in the first slurry. Furthermore, the silicon substrate in the battery substrate 100 has a low absorption rate of infrared lasers or is completely transparent, making it less likely for the infrared laser to damage the silicon substrate.

[0092] In both of the above embodiments, in conjunction with the reference Figures 4 to 7 The modification process may include: irradiating the first slurry with a xenon lamp.

[0093] It is worth noting that before the first slurry is modified, the arrangement of the first conductive particles 102 and the second conductive particles 103 in the first slurry is relatively loose. For example, some of the first conductive particles 102 and / or the second conductive particles 103 are spaced apart from each other. For the first conductive particles 102 and / or the second conductive particles 103 that are in contact with each other, the contact area is generally small, such as point-to-point contact connection, line-to-line contact area, small area face-to-face contact connection, etc.

[0094] Based on this, the xenon lamp emits a very continuous spectrum that is close to the solar spectrum, allowing it to provide a large radiant flux to the first slurry in a short time. This enables the first slurry to be heated to a high temperature quickly. On one hand, this promotes the rapid melting and recrystallization of the first conductive particles 102 and the second conductive particles 103 in the first slurry, thereby increasing the contact area between the first conductive particles 102 and / or the second conductive particles 103. For example, it can transform point-to-point or line-to-line contact areas into face-to-face contact areas, or increase the contact area of ​​small face-to-face contacts. On the other hand, the rapid heating by the xenon lamp can effectively reduce the risk of oxidation of some components in the first slurry, thus reducing the risk of the final transport layer 111 containing many oxide impurities. In this way, the conductivity of the final transport layer 111 can be improved in multiple ways.

[0095] In some cases, the modification process includes a first stage (I) and a second stage (II). The operating voltage of the xenon lamp in the first stage (I) can be controlled to be lower than that in the second stage (II). A higher operating voltage from the xenon lamp results in a greater radiant flux provided to the first slurry, which is more conducive to heating the first slurry to a higher temperature in a shorter time. Therefore, controlling the operating voltage of the xenon lamp in the first stage (I) to be lower than that in the second stage (II) ensures that the energy density provided to the first slurry in the first stage (I) is lower than that provided in the second stage (II).

[0096] In other cases, the modification treatment includes a first stage (I) and a second stage (II). The xenon lamp is a pulsed xenon lamp, and the pulse width of the xenon lamp in the first stage (I) can be controlled to be smaller than that in the second stage (II). A larger pulse width results in a longer single irradiation time, making it easier to provide a greater radiant flux to the first slurry per unit time, which is more conducive to heating the first slurry to a higher temperature in a shorter time. Therefore, controlling the pulse width of the xenon lamp in the first stage (I) to be smaller than that in the second stage (II) ensures that the energy density provided to the first slurry in the first stage (I) is lower than that provided in the second stage (II).

[0097] It should be noted that, in order to achieve a lower energy density provided to the first slurry in the first stage I than in the second stage II, while controlling the operating voltage of the xenon lamp in the first stage I to be lower than that in the second stage II, the pulse width of the xenon lamp in the first stage I can also be controlled to be smaller than that in the second stage II.

[0098] In some other embodiments, the modification process may include: irradiating the first slurry with a laser at least once, and simultaneously heating the first slurry during the laser irradiation step. In other words, the heating and laser irradiation can be performed simultaneously, which can simultaneously solve the problems of residual impurities in the first slurry and the melting and recrystallization of conductive particles, thus further simplifying the process steps for forming the transport layer and improving the manufacturing efficiency of the transport layer.

[0099] The following provides a detailed explanation of the specific design of laser irradiation when lasers are used in the modification process.

[0100] In some embodiments, reference Figure 11 The modification process may include: irradiating at least the first paste with a laser; designating the surface side 110 on which the first paste is printed as the target surface side 110a; when irradiating the first paste with a laser, the laser is positively defocused relative to the target surface side 110a and along the first direction X, and the distance between the focal plane formed by the laser and the target surface side 110a is the defocusing amount. z controls the defocus amount. z is greater than half the thickness d of transport layer 111.

[0101] It should be noted that, Figure 11 The focal plane formed by the laser is indicated by densely packed dashed lines; the focal plane formed by the laser refers to the cross-section with the smallest spot size and the highest energy density during laser irradiation.

[0102] Thus, the defocus amount is designed. The fact that z is greater than half the thickness d of the transmission layer 111 is beneficial for controlling the focal plane of the laser to be located within the transmission layer 111 and above the target surface side 110a. On the one hand, controlling the focal plane of the laser to be located within the transmission layer 111 allows for a more concentrated energy supply to the transmission layer 111, which helps the transmission layer 111 to obtain as much heat as possible through laser irradiation. This results in a tighter connection between the first conductive particles 102 and the second conductive particles 103 in the transmission layer 111, further improving the conductivity of the transmission layer 111. On the other hand, controlling the focal plane of the laser to be located above the target surface side 110a results in a larger spot size on the target surface side 110a, and a more dispersed energy supply to the target surface side 110a. This reduces the thermal impact of the laser on the target surface side 110a and the interior of the battery substrate 100, thereby reducing the risk of laser damage to the battery substrate 100.

[0103] In some cases, refer to Figures 4 to 7 as well as Figure 11 The modification process includes a first stage (I) and a second stage (II). In the first stage (I), the laser is primarily used for pretreatment of the first slurry and also serves as a transition, preventing the temperature of the first slurry from rising too rapidly, thereby reducing the risk of new defects appearing within the first slurry while it solidifies. In the second stage (II), the laser is mainly used to promote the melting and recrystallization of the first conductive particles 102 and / or the second conductive particles 103, increasing the contact area between the multiple conductive particles. Therefore, compared to the first stage (I), the second stage (II) requires a higher energy density from the laser to the first slurry, thus allowing for control of the defocusing amount, at least in the second stage (II). z is greater than half the thickness d of transport layer 111.

[0104] In some cases, the laser power used in the first stage I is inherently lower than that used in the second stage II, thus the risk of laser damage to the battery substrate 100 in the first stage I is inherently lower. Therefore, in the first stage I, the positional relationship between the focal plane formed by the laser and the battery substrate 100 does not need to be controlled. However, in other cases, to improve the energy density received by the transmission layer 111 in the first stage I, for example, to promote the melting and recrystallization of the first conductive particles 102 and / or the second conductive particles 103 as much as possible while avoiding excessively rapid evaporation of organic costs in the first stage I, a defocusing amount can also be designed. z is greater than half the thickness d of transport layer 111.

[0105] Furthermore, for photovoltaic cells with grid lines on both sides, such as TOPCon cells, the target surface side 110a can be one of the two opposing surface sides 110 of the cell substrate 100. In other words, the first paste is used in the manufacturing process of the transport layer 111 on only one surface side 110. Alternatively, the target surface side 110a can be either of the two opposing surface sides 110 of the cell substrate 100. In other words, the first paste can be used to prepare the transport layer 111 in the process of forming grid lines on both surface sides 110. For photovoltaic cells with grid lines on one side, such as BC cells, the target surface side 110a can be one of the two opposing surface sides 110 of the cell substrate 100. Generally, the surface side 110 where the grid lines are formed is referred to as the back side.

[0106] In some embodiments, reference Figure 11 The surface side 110 printed with the first paste is designated as the target surface side 110a. Along the first direction X, the distance between the top surface of the seed layer 115 away from the battery substrate 100 and the target surface side 110a is 1μm to 15μm. For example, it can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm. In other words, the thickness of the portion of the seed layer 115 protruding from the battery substrate 100 is 1μm to 15μm.

[0107] The distance between the top surface of the seed layer 115 away from the battery substrate 100 and the target surface side 110a is designed to be 1μm~15μm. On the one hand, this helps to avoid the seed layer 115 protruding too much relative to the battery substrate 100, reducing the impact of the portion of the seed layer 115 protruding from the battery substrate 100 on the morphology of the subsequently formed transport layer 111, thereby improving the quality of the finally formed transport layer 111 and grid lines 106. On the other hand, designing the seed layer 115 to protrude appropriately from the battery substrate 100 is beneficial to use the seed layer 115 as a positioning reference when printing the first paste in the subsequent process, thereby improving the positioning accuracy between the seed layer 115 and the transport layer 111 in the grid lines 106 and reducing the risk of printing offset of the first paste.

[0108] In some embodiments, reference Figure 11 Along the first direction X, the thickness d of the transmission layer 111 can be 5μm to 20μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, etc.

[0109] The thickness d of the transport layer 111 can be 5μm to 20μm. On the one hand, this helps to ensure that the transport layer 111 has a sufficiently large thickness to wrap the seed layer 115, thus ensuring a sufficiently large contact area between the transport layer 111 and the seed layer 115. On the other hand, it helps to control the material cost of the transport layer 111 while ensuring that the transport layer 111 has a large cross-sectional area.

[0110] The positional relationship between the transmission layer 111 and the seed layer 115 in the gate line 106 is described in detail below.

[0111] In some embodiments, reference Figure 2 or Figure 3 A gate line 106 includes at least a transport layer 111 and at least one sub-layer 115, and the gate line 106 is a main gate or a fine gate. The seed layer 115 is mainly used to be embedded in the battery substrate 100 to collect carriers, while the transport layer 111 does not need to be embedded in the battery substrate 100 and can be located on the surface of the seed layer 115 to collect the carriers in the seed layer 115.

[0112] In some examples, in conjunction with references Figure 2 and Figure 11 The gate line 106 may also include a transmission layer 111 and a sub-layer 115. In the same gate line 106, both the seed layer 115 and the transmission layer 111 can be long strip-shaped structures extending along the second direction Y.

[0113] In other examples, in conjunction with references Figure 3 and Figure 11 The gate line 106 may include a transmission layer 111 and at least two seed layers 115 spaced apart along the second direction Y. Within the same gate line 106, the transmission layer 111 may be a long, linear structure extending along the second direction Y. The cross-sectional shape of the seed layer 115 in a section perpendicular to the second direction Y may be approximately circular, elliptical, square, or trapezoidal. The pattern formed by multiple seed layers 115 in a gate line 106 may be a series of discontinuous short lines, a dot matrix, or a grid. It should be noted that... Figure 3 The example given is that the cross-sectional shape of the seed layer 115 in the section perpendicular to the second direction Y can be approximated as an ellipse.

[0114] It should be noted that in a photovoltaic cell, at least the fine grid needs to penetrate the passivation layer to contact and connect with the doped portion. The fine grid is mainly used to collect the charge carriers generated in the cell substrate 100. Furthermore, the photovoltaic cell may also include a main grid. The fine grid and the main grid extend in different directions. One main grid is used to collect the charge carriers collected by multiple fine grids. Therefore, provided that it is electrically connected to the fine grid, the main grid can penetrate the passivation layer to contact and connect with the doped portion, or it can be located only on the surface of the cell substrate. Based on this, the grid line 106, including the seed layer 115 and the transport layer 111, can be either a fine grid in the photovoltaic cell or a main grid in the photovoltaic cell.

[0115] In some embodiments, reference Figure 11 Along the third direction Z, the width of the transport layer 111 can be greater than the width of the seed layer 115. Thus, the transport layer 111 can wrap around the portion of the seed layer 115 that protrudes from the battery substrate 100, increasing the contact area between the transport layer 111 and the seed layer 115, thereby improving the conductivity of the gate line 106. In this case, the transport layer 111 has a groove in its cross-sectional shape perpendicular to the second direction Y for accommodating a portion of the seed layer 115. The thickness d of the transport layer 111 refers to the distance along the first direction X between the bottom surface of the transport layer 111 that contacts the surface side 110 and the top surface of the transport layer 111 that is away from the battery substrate 100.

[0116] It should be noted that the first direction X is the thickness direction of the battery substrate 100, and the first direction X, the second direction Y, and the third direction Z intersect each other pairwise. In one example, the first direction X, the second direction Y, and the third direction Z can be orthogonal to each other. In practical applications, the included angle formed by any two of the first direction, the second direction, and the third direction can be either acute or obtuse.

[0117] The intersection of the first direction X and the second direction Y includes the following scenarios: the first direction X and the second direction Y are orthogonal; the included angle is obtuse; or the included angle is acute. In some examples, the included angle of the first direction X and the second direction Y can be between 10° and 90°, for example, 10°, 20°, 45°, 55°, 70°, 82°, or 90°. In some specific examples, the included angle of the first direction X and the second direction Y can also be between 45° and 90°. It should be noted that the intersection of the second direction Y and a third direction Z, and the intersection of the first direction X and a third direction Z, are similar to the cases of the intersection of the first direction X and the second direction Y described above, and will not be elaborated further here.

[0118] The manufacturing method for forming the seed layer 115 is described in detail below.

[0119] In some embodiments, reference Figure 2or Figure 3 The step of forming the seed layer 115 includes: printing a second slurry (not shown) on at least one surface side 110; and simultaneously heating the second slurry printed on the surface side 110 to transform it into the seed layer 115. In other words, the printing and heating of the second slurry can be performed simultaneously. For example, 3D printing technology can be used to print the second slurry while simultaneously heating it, which helps to simplify the preparation process of the seed layer 115 while ensuring good quality of the final seed layer 115. During the 3D printing process, the second slurry can be heated by means of carrier plate heating, hot air blowing, or infrared irradiation.

[0120] In other embodiments, after printing the second paste, the second paste is sequentially dried; then, it is sintered to transform the second paste into a seed layer. In other words, printing the second paste, drying the second paste, and sintering the second paste can also be performed in separate steps, wherein the second paste can be printed using processes such as screen printing, nanoimprinting, or laser transfer.

[0121] In some embodiments, the second paste may include at least one of silver paste, silver-nickel paste, silver-tin paste, or silver-aluminum paste. The silver paste, silver-nickel paste, silver-tin paste, or silver-aluminum paste are all suitable for sintering and facilitate the formation of good contact between the second paste and the doped portions in the battery substrate 100 during the sintering process.

[0122] In some cases, the inorganic components in the second slurry may include metal particles and glass powder, while the organic components may include organic solvents and dispersants. The metal particles may be at least one of silver particles, silver-nickel particles, silver-tin particles, or silver-aluminum particles.

[0123] In some cases, the temperature provided to the second slurry during the drying process can be between 200℃ and 300℃, for example, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, or 300℃. This drying process allows some of the organic components in the second slurry to evaporate, resulting in a semi-solidified state.

[0124] In some cases, during the sintering process of the second slurry, the temperature provided to the second slurry can be 700℃~800℃, for example, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, or 800℃. Thus, during the sintering process, the inorganic components in the second slurry, such as glass powder, etch the film layer (passivation layer) on the surface of the battery substrate 100 to form channels. Some metal particles dissolve and precipitate in the glass powder, forming small-sized metal particles that form metal-semiconductor contacts with components in the battery substrate 100, such as silicon, or form alloys with components in the battery substrate 100, such as silicon. Other metal particles melt and recrystallize, ultimately forming a dense and highly conductive seed layer 115.

[0125] The following provides a detailed description of the specific components and processes involved in the first slurry.

[0126] In some embodiments, reference Figure 4 and Figure 5 The first conductive particle 102 may include at least one of silver-coated copper particles, silver-coated nickel particles, or silver-nickel alloy particles, and the second conductive particle 103 includes silver particles or silver alloy particles.

[0127] Thus, by using the first conductive particles 102, a small amount of lower-cost conductive materials such as copper or nickel can be introduced into the first slurry, so as to reduce the manufacturing cost of the transport layer 111 as much as possible while improving the conductivity of the formed transport layer 111 through modification treatment.

[0128] In some cases, the melting point of the second conductive particle 103 is greater than that of the first conductive particle 102. In the modification process, the first conductive particle 102 melts first, so that a larger contact area is ultimately formed by the adhesion of the first conductive particle 102 to other conductive particles. Moreover, compared with the sintering process, the first slurry can promote the tight connection between the first conductive particle 102 and / or the second conductive particle 103 at a lower temperature, thereby reducing the thermal stress caused by the modification process to the battery substrate 100.

[0129] In some cases, a small amount of more inert conductive particles, such as gold or palladium particles, can be added to the first slurry to help suppress the electrochemical migration and sulfidation corrosion of silver in humid environments, thereby improving the service life of the transport layer 111.

[0130] In some cases, the inorganic components in the first slurry may include first conductive particles 102 and second conductive particles 103, etc., and the organic components in the first slurry may include organic solvents, adhesives and curing agents, etc.

[0131] In some embodiments, the median diameter of the first conductive particle 102 may be greater than the median diameter of the second conductive particle 103.

[0132] It is worth noting that the median diameter can characterize the size of the conductive particles. In the modification process, in addition to promoting the melting and recrystallization of the first conductive particle 102 and / or the second conductive particle 103, the smaller second conductive particles 103 can also fill the gaps between adjacent larger first conductive particles 102, thereby forming a denser and more continuous conductive path inside the first slurry, which helps to reduce the resistance of the finally formed transport layer 111. In addition, conductive particles with larger median diameters have a larger specific surface area and are easier to melt in the modification process. Therefore, designing a difference between the median diameters of the first conductive particles 102 and the second conductive particles 103 is beneficial to allow the larger first conductive particles 102 to melt first in the modification process, followed by a portion of the second conductive particles 103 gradually melting. This allows the first-melted conductive particles to adhere to other conductive particles, ultimately forming a larger contact area, thereby improving the conductivity of the finally formed transport layer 111.

[0133] It should be noted that median diameter is a method of representing particle size in mixed particle size distribution. It represents the particle diameter at which the cumulative particle size distribution reaches 50%, sometimes referred to as the 50% diameter. Median diameter includes both count median diameter and mass median diameter. Both the median diameter of the first conductive particle 102 and the median diameter of the second conductive particle 103 can be either count median diameter or mass median diameter. Count median diameter refers to the particle diameter at which, when particles are sorted by size, the number of particles larger than or smaller than the median diameter each accounts for 50% of the total number of particles. Mass median diameter refers to the particle diameter at which, when particles are sorted by size, the mass of particles larger than or smaller than the median diameter each accounts for 50% of the total mass of particles.

[0134] In some cases, the median diameter of the first conductive particle 102 can be greater than 1 μm, for example, it can be 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm or 1.6 μm, etc.; the median diameter of the second conductive particle 103 can be less than 500 nm, for example, it can be 495 nm, 490 nm, 485 nm, 480 nm, 475 nm, 470 nm, 465 nm, 460 nm, 455 nm, 450 nm, 445 nm, 440 nm, 435 nm, 430 nm, 425 nm, 420 nm, 415 nm, 410 nm, 405 nm or 400 nm, etc.

[0135] In some cases, the first conductive particle 102 includes an inner core 112 and an outer layer 122 located on the surface of the inner core 112. Along the diameter direction of the first conductive particle 102, the thickness of the outer layer 122 can be 10 nm to 2 μm, for example, 10 nm to 100 nm, 100 nm to 200 nm, 200 nm to 300 nm, 300 nm to 400 nm, 400 nm to 500 nm, 500 nm to 600 nm, or 600 nm. m~700nm, 700nm~800nm, 800nm~900nm, 900nm~1μm, 1μm~1.1μm, 1.1μm~1.2μm, 1.2μm~1.3μm, 1.3 μm~1.4μm, 1.4μm~1.5μm, 1.5μm~1.6μm, 1.6μm~1.7μm, 1.7μm~1.8μm, 1.8μm~1.9μm or 1.9μm~2μm, etc.

[0136] In some examples, when the first conductive particle 102 includes at least one of silver-coated copper particles or silver-coated nickel particles, the outer layer 122 can be a silver layer, and the inner core 112 can include at least one of copper particles or nickel particles; in other examples, when the first conductive particle 102 includes silver-nickel alloy particles, the materials of both the outer layer 122 and the inner core 112 can be silver-nickel alloy, the difference being that the outer layer 122 will melt during the modification process, but the inner core 112 will not completely melt during the modification process, at least some areas of the inner core 112 will not melt.

[0137] The following details the changes in the properties of the first slurry before and after the modification treatment.

[0138] In some embodiments, in conjunction with reference Figures 5 to 7 or in conjunction with references Figure 4 ,as well as Figures 8 to 10 The porosity of the first slurry before modification is a first porosity, and the porosity of the transport layer 111 formed after modification is a second porosity; wherein the second porosity is less than the first porosity.

[0139] It is worth noting that the lower the porosity, the tighter the connection between the first conductive particles 102 and / or the second conductive particles 103 in the transport layer 111, or in other words, the larger the contact area of ​​the first conductive particles 102 and / or the second conductive particles 103, which is more conducive to reducing the resistance of the transport layer 111.

[0140] During the modification process, whether in the first or second stage, the conductive particles may melt and recrystallize under the influence of temperature. This causes the originally dispersed conductive particles to aggregate into a single entity. From a macroscopic perspective, at least a portion of the width of the first slurry begins to shrink inward, thus forming a unified conductive structure. The gaps between the conductive particles that were originally present are filled during the modification process. The aforementioned conductive particles are the first conductive particle 102 and / or the second conductive particle 103.

[0141] In some cases, the modification treatment includes a first stage and a second stage. The energy density provided to the first slurry in the first stage is lower than that provided to the first slurry in the second stage. The first stage is mainly used to promote the volatilization of organic components and the pre-curing of the first slurry, while the second stage is mainly used to promote the melting and recrystallization of the first conductive particles 102 and / or the second conductive particles 103. Therefore, compared to the first porosity, the reduction in porosity of the first slurry after the first stage is not significant or even non-existent, but the second porosity of the first slurry after the second stage will be significantly lower than the first porosity.

[0142] In some embodiments, in conjunction with reference Figures 5 to 7 or in conjunction with references Figure 4 ,as well as Figures 8 to 10 In the first slurry printed, a portion of the area includes at least two mutually dispersed second conductive particles 103, and a first sintering neck is formed between adjacent at least two second conductive particles 103 in the portion of the area; after modification treatment, the at least two mutually dispersed second conductive particles 103 in the portion of the area are connected into an integral structure, and the at least two second conductive particles 103 with the first sintering neck are transformed into having a second sintering neck, wherein the ratio of the size of the second sintering neck to the size of the first sintering neck is greater than or equal to 130%.

[0143] A sintered neck refers to a neck-like connection formed between two second conductive particles 103 through atomic migration during the modification process. Furthermore, as the modification process progresses, atomic diffusion at the interface between the two second conductive particles 103 causes the neck region to gradually increase, thereby transforming at least two second conductive particles 103 with a first sintered neck into those with a second sintered neck. In other words, two second conductive particles 103 that originally had sintered necks will form larger sintered necks after modification. Moreover, after modification, at least two previously dispersed second conductive particles 103 in a portion of the first slurry connect into a single structure; that is, two second conductive particles 103 that originally did not have sintered necks will form sintered necks after modification.

[0144] In either case, the modification treatment is beneficial to give the first slurry more and larger sintering necks after the modification treatment, thereby giving the final transport layer 111 a denser and more continuous conductive path, so as to reduce the resistance of the final transport layer 111.

[0145] It should be noted that, at least after the modification treatment, a sintering neck may also be formed between the first conductive particle 102 and the second conductive particle 103, and a sintering neck may also be formed between adjacent second conductive particles.

[0146] Furthermore, the energy density provided to the first slurry in the first stage is lower than that provided to the first slurry in the second stage. The first stage is mainly used to promote the volatilization of organic components and the pre-curing of the first slurry, while the second stage is mainly used to promote the melting and recrystallization of the first conductive particles 102 and / or the second conductive particles 103. Therefore, the increase in size of the first sintering neck in the first stage is not significant or even non-existent, but in the second stage, the first sintering neck will significantly increase to become the second sintering neck.

[0147] In some embodiments, in conjunction with reference Figures 5 to 7 or in conjunction with references Figure 4 ,as well as Figures 8 to 10 The resistivity of the first printing paste is a first resistivity, and the resistivity of the transport layer 111 formed after modification is a second resistivity. The ratio of the second resistivity to the first resistivity is 0.4 to 0.75, for example, it can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or 0.75, etc.

[0148] In some cases, the first resistivity can be 4μΩ·cm to 5μΩ·cm, for example, it can be 4μΩ·cm, 4.1μΩ·cm, 4.2μΩ·cm, 4.3μΩ·cm, 4.4μΩ·cm, 4.5μΩ·cm, 4.6μΩ·cm, 4.7μΩ·cm, 4.8μΩ·cm, 4.9μΩ·cm or 5μΩ·cm, etc.; the second resistivity can be 2μΩ·cm to 3μΩ·cm, for example, it can be 2μΩ·cm, 2.1μΩ·cm, 2.2μΩ·cm, 2.3μΩ·cm, 2.4μΩ·cm, 2.5μΩ·cm, 2.6μΩ·cm, 2.7μΩ·cm, 2.8μΩ·cm, 2.9μΩ·cm or 3μΩ·cm, etc.

[0149] In some embodiments, in conjunction with reference Figures 5 to 7 or in conjunction with references Figure 4 ,as well as Figures 8 to 10During the modification process, the ambient temperature of the battery substrate 100, on which the first paste is printed, is controlled to be below 250°C. For example, it can be 245°C, 240°C, 235°C, 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, or 200°C. Controlling the ambient temperature of the battery substrate 100 below 250°C also helps reduce the risk of oxidation of some components within the transport layer 111 during its formation.

[0150] In some embodiments, in conjunction with reference Figures 2 to 10 The silver content of the first conductive particle 102 can be less than 50%, for example, it can be 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31% or 30%, etc.; the silver content of the second conductive particle 103 can be greater than 50%, for example, it can be 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68% or 69%, etc.

[0151] In summary, designing the process for preparing the grid line 106 to include "forming a seed layer 115 on the surface side 110" and "forming a transport layer 111 on the surface side 110 where the seed layer 115 is formed" is beneficial for improving the contact performance between the seed layer 115 and the battery substrate 100 by utilizing the preparation process of the seed layer 115, laying the foundation for low contact resistance between the grid line 106 and the battery substrate 100. Furthermore, the modification treatment promotes the melting of various conductive particles in the first slurry, such as the first conductive particles 102 and / or the second conductive particles 103 melting and recrystallizing with each other, thereby increasing the contact area between multiple conductive particles and forming a conductive connection portion 104 with good conductivity to improve the conductivity of the transport layer 111. Moreover, the conductive connection portion 104 is beneficial for protecting other parts of the transport layer 111, reducing the risk of oxidation inside the transport layer 111, and further improving the conductivity of the transport layer 111. Thus, with the combined fabrication processes of the seed layer 115 and the transport layer 111, the conductivity of the grid line 106 and its contact performance with the battery substrate 100 can be improved from multiple aspects, thereby enhancing the collection efficiency of the grid line 106 for charge carriers.

[0152] Another embodiment of this disclosure provides a photovoltaic cell formed by the manufacturing method of the photovoltaic cell 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.

[0153] Reference Figure 2 , Figure 3 as well as Figures 8 to 11 The photovoltaic cell includes: a cell substrate 100 having two surface sides 110 opposite each other along a first direction X; a seed layer 115 located on at least one surface side 110; and a transport layer 111 located on the surface side 110 having the seed layer 115, wherein the seed layer 115 and the transport layer 111 together form a grid line 106; wherein the transport layer 111 includes at least: a conductive connection portion 104, the conductive connection portion 104 containing a third conductive particle 107 and / or a first conductive particle 102; and a main body portion 108 located on the conductive connection portion 104. Between part 104 and battery substrate 100, and between conductive connection part 104 and seed layer 115, the main body part 108 contains first conductive particles 102 and second conductive particles 103; the first conductive particle 102 includes an inner core 112 and an outer layer 122 located on the surface of the inner core 112, and the third conductive particle 107 includes only the inner core 112; and / or, both the first conductive particle 102 and the second conductive particle 103 contain silver, and the silver content of the first conductive particle 102 is lower than the silver content of the second conductive particle 103.

[0154] Among them, in conjunction with reference Figures 8 to 11 The conductive connection portion 104 containing a third conductive particle 107 and / or a first conductive particle 102 means that the conductive connection portion 104 includes a silver layer (not shown in the figure), on which the third conductive particle 107 and / or the first conductive particle 102 are embedded.

[0155] It should be noted that, Figure 8 Taking the conductive connection portion 104 containing the first conductive particle 102 as an example. Figure 9 and Figure 10 The conductive connection portion 104 is illustrated by an example containing a third conductive particle 107 and a first conductive particle 102. In practical applications, due to changes in the process parameters of the modification treatment, the interior of the conductive connection portion may contain only the third conductive particle; that is, after the first slurry undergoes modification treatment, the outer layer of the first conductive particle is melted. Furthermore, the case where the first conductive particle 102 includes an inner core 112 and an outer layer 122, and the third conductive particle 107 includes only the inner core 112, can coexist in the same gate line 106 as the case where both the first conductive particle 102 and the second conductive particle 103 contain silver, or they can coexist in different gate lines 106 or in different regions of the same gate line 106.

[0156] The grid line 106 is designed with a composite structure including a seed layer 115 and a transport layer 111. On the one hand, the seed layer 115 helps to improve the contact performance between the grid line 106 and the battery substrate 100. On the other hand, compared with the current grid lines formed by low-temperature slurry without sintering, which have a relatively loose distribution of internal conductive particles, the conductive connection portion 104 in the transport layer 111 is a whole. It not only retains the third conductive particles 107 and / or the first conductive particles 102 inside, but also avoids the third conductive particles 107 and / or the first conductive particles 102 from being exposed to the air. The particle 102 is an independent conductive structure, which facilitates the improvement of the conductivity of the transport layer 111 by means of the conductive connection portion 104. Furthermore, the design of the main body 108, located between the conductive connection portion 104 and the battery substrate 100, and between the conductive connection portion 104 and the seed layer 115, also facilitates the protection of the main body 108 and the seed layer 115 by the conductive connection portion 104, preventing the oxidation of some components in the main body 108 and the seed layer 115, thereby ensuring that the main body 108 and the seed layer 115 also have good conductivity. Thus, it is beneficial to improve the conductivity of the grid line 106 and its contact performance with the battery substrate 100 from multiple aspects, thereby improving the carrier collection efficiency of the grid line 106.

[0157] Furthermore, designing the silver content of the first conductive particle 102 to be lower than that of the second conductive particle 103 helps to appropriately reduce the fabrication cost of the transport layer 111, and balances the silver content of the transport layer 111 by using the two conductive particles 102 and 103 with different silver contents, so as to avoid the situation where the conductivity of the transport layer 111 is reduced due to the silver content being too low.

[0158] The following provides a detailed description of a photovoltaic cell provided in another embodiment of this disclosure.

[0159] In some embodiments, in conjunction with reference Figure 2 , Figure 3 and Figure 11 Along the first direction X, a portion of the thickness of the seed layer 115 is embedded in the battery substrate 100. In this way, the grid lines 106 can have good contact performance with the battery substrate 100.

[0160] In some embodiments, reference Figure 2 or Figure 3 A gate line 106 includes at least a transmission layer 111 and at least one sublayer 115, and the gate line 106 is a main gate or a fine gate.

[0161] In some examples, in conjunction with references Figure 2 and Figure 11 The gate line 106 may also include a transmission layer 111 and a sub-layer 115. In the same gate line 106, both the seed layer 115 and the transmission layer 111 can be long strip-shaped structures extending along the second direction Y.

[0162] In other examples, in conjunction with references Figure 3 and Figure 11 The gate line 106 may include a transmission layer 111 and at least two seed layers 115 spaced apart along the second direction Y. In the same gate line 106, the transmission layer 111 may be a long strip-shaped structure extending along the second direction Y. The cross-sectional shape of the seed layer 115 in the section perpendicular to the second direction Y may be approximately circular, elliptical, square or trapezoidal, etc. The pattern formed by multiple seed layers 115 in a gate line 106 may be multiple discontinuous short lines, dot matrix or grid, etc.

[0163] In some embodiments, reference Figures 8 to 10 The first conductive particle 102 may include at least one of silver-coated copper particles, silver-coated nickel particles, or silver-nickel alloy particles, and the second conductive particle 103 may include silver particles or silver alloy particles.

[0164] In some examples, when the first conductive particle 102 comprises at least one of silver-coated copper particles or silver-coated nickel particles, the outer layer 122 can be a silver layer, and the inner core 112 can comprise at least one of copper particles or nickel particles. In other examples, when the first conductive particle 102 comprises silver-nickel alloy particles, both the outer layer 122 and the inner core 112 can be made of silver-nickel alloy, the difference being that the outer layer 122 melts during the modification process, but the inner core 112 does not melt during the modification process. Based on this, the third conductive particle 107 can comprise at least one of copper particles, nickel particles, or silver-nickel alloy particles.

[0165] In some embodiments, reference Figures 8 to 10 The conductive connection portion 104 does not contain organic components, while the main body portion 108 contains non-volatile organic components. These organic components are the organic components in the slurry used to prepare the transport layer 111, i.e., the organic components in the first slurry. Figures 8 to 10 The organic components in the main body 108 are not shown, but the presence of organic components in the main body 108 is implied by leaving blank space.

[0166] In some embodiments, in conjunction with reference Figure 6 , Figures 8 to 10 , Figure 12 and Figure 13 In the main body 108, at least two second conductive particles 103 are connected in contact to form a whole to constitute a conductive part 118. The conductive part 118 can be rod-shaped, branch-shaped, block-shaped or mesh-shaped.

[0167] in, Figure 12 This is a magnified overhead scanning electron microscope image of the transport layer in a photovoltaic cell provided in another embodiment of the present disclosure; Figure 13Another magnified overhead scanning electron microscope image of the transport layer in a photovoltaic cell provided in another embodiment of this disclosure.

[0168] It is worth noting that, compared to the first slurry used to prepare the transport layer 111, which contains first conductive particles 102 and second conductive particles 103 and has a morphology similar to spherical particles, making it easier to print, the morphology of the conductive parts 118 in the formed transport layer 111 changes, becoming rod-shaped, branch-shaped, block-shaped, or mesh-shaped, making it easier to form surface contact. Moreover, adjacent conductive parts 118 are more likely to form an overlapping relationship, thereby effectively improving the conductivity of the main body 108.

[0169] It should be noted that the rod-shaped, branch-shaped, block-shaped, or mesh-shaped conductive parts 118 can also be regarded as particulate matter in the main body 108, but the shape of the particulate matter is not conventionally spherical. The rod-shaped, branch-shaped, block-shaped, or mesh-shaped conductive parts 118 can be understood as a larger conductive structure formed by the aggregation of multiple spherical particulate conductive particles and the formation of sintered necks between them.

[0170] The conductive connection part 104 will be described in detail below.

[0171] In some embodiments, reference Figure 8 A number of conductive connections 104 are in contact with the main body 108 near the end of the battery substrate 100. In other words, the main body 108 is spaced between a number of conductive connections 104 and the battery substrate 100. The conductive connections 104 can be regarded as the top shell of the transmission layer 111 away from the battery substrate 100. Along the second direction Y, the conductive connections 104 can cover a plurality of first conductive particles 102 and second conductive particles 103 in the main body 108, but the conductive connections 104 do not completely cover the main body 108. This is at least beneficial for protecting a part of the main body 108 to prevent some components in the main body 108 from being oxidized.

[0172] In some embodiments, reference Figure 9 or Figure 10 A number of conductive connection portions 104 are in contact with the battery substrate 100 near their ends. In other words, the conductive connection portions 104 can be regarded as the outer shell covering the main body portion 108 in the transmission layer 111, which helps to protect the main body portion 108 and prevent some components in the main body portion 108 from being oxidized.

[0173] In some cases, refer to Figure 7 and Figure 9 or in conjunction with references Figure 7 and Figure 10The transport layer 111 may further include a small number of dispersed second conductive particles 103, located on or partially embedded in the battery substrate 100, and located on the outer side of the conductive connection portion 104 away from the main body portion 108.

[0174] It should be noted that in the above embodiments, along the cross-section perpendicular to the second direction Y, the conductive shape of the conductive connection portion 104 is similar to a fan-shaped ring. Figures 8 to 10 The difference in arc length and / or radius exists within the central sector ring. In other words, Figures 6 to 8 The contact area between the conductive connecting part 104 and the main body part 108 is different.

[0175] Furthermore, based on the different process parameters in the fabrication process of the transport layer 111, or the different influences of the fabrication process on different regions of the transport layer 111, the conductive connection portion 104 shown in the above two embodiments can exist in different transport layers 111, or can exist simultaneously in different regions of a transport layer 111.

[0176] The main body 108 will be described in detail below.

[0177] In some embodiments, reference Figure 8 or Figure 9 The main body 108 has at least two second conductive particles 103 spaced apart from each other in at least a portion of its area. It is worth noting that the spaced-apart second conductive particles 103 can all be in contact with the same first conductive particle 102, or they can be in contact with different first conductive particles 102. This facilitates the electrical connection of multiple first conductive particles 102 and conductive connection portions 104 using multiple second conductive particles 103, thereby forming more conductive pathways and improving the conductivity of the transport layer 111.

[0178] In some embodiments, in conjunction with reference Figure 2 and Figure 10 In this configuration, at least a portion of the main body 108 contains multiple second conductive particles 103 that are in contact with each other. This helps to maximize the conductivity of the main body 108. It should be noted that, in order to demonstrate… Figure 10 The degree of melting and recrystallization of the second conductive particles in the first slurry under the shown condition. Figure 10 The second conductive particle was not shown.

[0179] It should be noted that, based on the different process parameters in the fabrication process of the transport layer 111, or the different influences of the fabrication process on different regions of the transport layer 111, the main body 108 shown in the above two embodiments can exist in different transport layers 111, or can exist simultaneously in different regions of a transport layer 111.

[0180] In some embodiments, reference Figures 8 to 10 The resistivity of the transport layer 111 can be 2μΩ·cm to 3μΩ·cm, for example, it can be 2μΩ·cm, 2.1μΩ·cm, 2.2μΩ·cm, 2.3μΩ·cm, 2.4μΩ·cm, 2.5μΩ·cm, 2.6μΩ·cm, 2.7μΩ·cm, 2.8μΩ·cm, 2.9μΩ·cm or 3μΩ·cm, etc.

[0181] Another embodiment of this disclosure provides a tandem battery, which includes a photovoltaic cell formed by the manufacturing method of the photovoltaic cell provided in the foregoing embodiments, or the photovoltaic cell provided in the foregoing embodiments. The tandem battery 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.

[0182] refer to Figure 14 , Figure 14 This is a partial cross-sectional schematic diagram of a tandem solar cell (TSC) 109 provided in another embodiment of the present disclosure. The tandem solar cell (TSC) 109 includes: a bottom cell 119, which is a photovoltaic cell formed by the manufacturing method of the photovoltaic cell provided in the foregoing embodiment, or a photovoltaic cell provided in the foregoing embodiment; and a perovskite cell 129, which is located on one side of the bottom cell 119.

[0183] In some embodiments, the perovskite solar cell 129 may include: a first transport layer, a perovskite substrate, a second transport layer, a transparent conductive layer, and an antireflection layer stacked together. The first transport layer is directly opposite the base cell 119.

[0184] In some examples, the first transport layer can be either an electron transport layer or a hole transport layer, and the second transport layer can be either an electron transport layer or a hole transport layer.

[0185] In some embodiments, the bandgap width of the perovskite cell 129 is wider than that of the bottom cell 119. Therefore, stacking the perovskite cell 129 on top of the bottom cell 119 can give the stacked cell 109 a wider spectral response range, thereby maximizing the utilization of solar energy and improving the efficiency of the stacked cell 109.

[0186] In some embodiments, the stacked cell 109 may further include an intermediate connection layer (not shown in the figure), which connects the bottom cell 119 and the perovskite cell 129.

[0187] In some cases, the intermediate connecting layer is typically a tunnel junction or a very thin metal or transparent electrode composite layer. Optionally, the intermediate connecting layer can be a transparent conductive oxide, which has good photoelectric properties, high photon transmittance, and high conductivity, thereby enabling the perovskite solar cell 129 and the bottom cell 119 to maintain good ohmic contact.

[0188] In other cases, the grid lines in the photovoltaic cell 119, which serves as the bottom cell, can also be used as an intermediate connecting layer to achieve electrical connection with the perovskite cell 129.

[0189] Another embodiment of this disclosure provides a photovoltaic module, which is formed by connecting multiple photovoltaic cells manufactured by the methods described in the foregoing embodiments, or by connecting multiple photovoltaic cells provided in the foregoing embodiments, or by connecting multiple tandem cells provided in the foregoing embodiments. The photovoltaic module provided in another embodiment of this disclosure will be described 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.

[0190] Reference Figure 15 , Figure 16 as well as Figures 1 to 14 The photovoltaic module includes: a battery string, which is formed by connecting multiple photovoltaic cells 40 formed by the manufacturing method of photovoltaic cells provided in the foregoing embodiments, or by connecting multiple photovoltaic cells 40 as provided in the foregoing embodiments, or by connecting multiple stacked cells 109 as provided in the foregoing embodiments; an encapsulating film 41 for covering the surface of the battery string; and a cover plate 42 for covering the surface of the encapsulating film 41 away from the battery string.

[0191] in, Figure 15 A partial three-dimensional schematic diagram of a cell string in a photovoltaic module provided in another embodiment of the present disclosure; Figure 16 This is a partial cross-sectional schematic diagram of a photovoltaic module provided in another embodiment of the present disclosure.

[0192] In some embodiments, the photovoltaic cell 40 includes, but is not limited to, one or any combination of PERC cells, BC cells, TOPCon cells, HIT / HJT cells, 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.

[0193] In some embodiments, the photovoltaic cell 40 can be a monocrystalline silicon photovoltaic cell, a polycrystalline silicon photovoltaic cell, an amorphous silicon photovoltaic cell, or a multi-component compound photovoltaic cell. Specifically, the multi-component compound photovoltaic cell can be a cadmium sulfide photovoltaic cell, a gallium arsenide photovoltaic cell, a copper indium selenide photovoltaic cell, or a perovskite photovoltaic cell.

[0194] In some embodiments, the photovoltaic cells 40 are electrically connected in the form of a single cell or multiple segments to form multiple cell strings, and the multiple cell strings are electrically connected in series and / or parallel. The photovoltaic cells 40 can be a single cell or a sliced ​​cell, where a sliced ​​cell refers to a cell formed by cutting a complete single cell.

[0195] In some embodiments, in conjunction with reference Figure 15 and Figure 16 Multiple photovoltaic cells 40 can be electrically connected to each other via conductive strips 43. Figure 15 and Figure 16 This illustration only depicts one possible positional relationship between photovoltaic cells 40, where each photovoltaic cell 40 has grid lines on both sides, and the grid lines of the same polarity are arranged in the same direction, or in other words, the grid lines of the positive polarity of each photovoltaic cell 40 are arranged facing the same side. Thus, the conductive strip 43 connects different sides of two adjacent photovoltaic cells 40. In other embodiments, the photovoltaic cells can also be arranged with grid lines of different polarities facing the same side, i.e., the grid lines of multiple adjacent photovoltaic cells are arranged in the order of first polarity, second polarity, and first polarity again, in which case the conductive strip connects the same side of two adjacent photovoltaic cells.

[0196] In some embodiments, there may be no gap between adjacent photovoltaic cells, that is, adjacent photovoltaic cells may overlap each other.

[0197] 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 + EVA film; and PVP film refers to a co-extruded film formed by stacking POE film + EVA film + 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.

[0198] 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.

[0199] 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.

[0200] In some embodiments, the photovoltaic cell 40 may be a cell with a main grid or a cell without a main grid.

[0201] 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 manufacturing a photovoltaic cell, characterized in that, include: A battery substrate is provided, having two surface sides opposite each other along a first direction; A seed layer is formed on at least one of the surface sides; A first paste is printed on the surface side on which the seed layer is formed. The first paste includes at least a first conductive particle and a second conductive particle. Both the first conductive particle and the second conductive particle contain silver, and the silver content of the first conductive particle is lower than the silver content of the second conductive particle. The first slurry is modified to transform it into a transport layer, wherein the seed layer and the transport layer together form a gate line; in the step of performing the modification treatment, at least a portion of the second conductive particles are connected to a portion of the first conductive particles to form a conductive connection; and / or, the first conductive particles include an inner core and an outer layer located on the surface of the inner core, wherein at least a portion of the second conductive particles are connected to the outer layer as a whole and then connected to the inner core to form the conductive connection.

2. The method for manufacturing a photovoltaic cell according to claim 1, characterized in that, In the step of printing the first paste, the first paste printed on the surface side is simultaneously heated to transform the first paste into an initial transport layer. Alternatively, after printing the first paste and before performing the modification treatment, the first paste may be dried. The step of modifying the first slurry at least includes: modifying the initial transport layer to transform the initial transport layer into the transport layer.

3. The method for manufacturing a photovoltaic cell according to claim 2, characterized in that, The temperature provided to the first slurry by the heat treatment or the drying treatment shall not exceed 300°C.

4. The method for manufacturing a photovoltaic cell according to any one of claims 1 to 3, characterized in that, The modification process includes: heating the first slurry with a heating device, irradiating the first slurry with a laser, or irradiating the first slurry with a xenon lamp.

5. The method for manufacturing a photovoltaic cell according to claim 1, characterized in that, In the modification process, at least a portion of the second conductive particles are melted, recrystallized into a liquid phase, and then solidified into a silver layer. A portion of the first conductive particles are embedded in the silver layer to form the conductive connection. And / or, the first conductive particle includes an inner core and an outer layer located on the surface of the inner core. In the step of performing the modification treatment, at least a portion of the second conductive particles and a portion of the outer layer are melted and recrystallized together into a liquid phase and then solidified into the silver layer. A portion of the inner core is embedded inside the silver layer to form the conductive connection portion.

6. The method for manufacturing a photovoltaic cell according to claim 1, characterized in that, In the first slurry printed, a portion of the area includes at least two second conductive particles that are dispersed from each other, and a first sintering neck is formed between at least two adjacent second conductive particles in the portion of the area. After the modification treatment, at least two second conductive particles that are dispersed in a certain region are connected into a single structure, and at least two second conductive particles with the first sintered neck are transformed into particles with a second sintered neck, wherein the ratio of the size of the second sintered neck to the size of the first sintered neck is greater than or equal to 130%.

7. The method for manufacturing a photovoltaic cell according to claim 1, characterized in that, During the modification process, the ambient temperature of the battery substrate printed with the first paste is controlled to be less than 250°C.

8. A photovoltaic cell, characterized in that, include: The battery substrate has two surface sides opposite each other along a first direction; Seed layer located on at least one of the surface sides; A transport layer located on the surface side having the seed layer, the seed layer and the transport layer together forming a gate line; The transmission layer includes at least: a conductive connection portion comprising a silver layer, wherein a third conductive particle and / or a first conductive particle are embedded within the silver layer; a main body portion located between the conductive connection portion and the battery substrate and between the conductive connection portion and the seed layer, the main body portion containing the first conductive particle and a second conductive particle; the first conductive particle comprising an inner core and an outer layer located on the surface of the inner core, the third conductive particle comprising only the inner core; and / or, both the first conductive particle and the second conductive particle contain silver, and the silver content of the first conductive particle is lower than the silver content of the second conductive particle.

9. The photovoltaic cell according to claim 8, characterized in that, In the main body, at least two of the second conductive particles are connected in contact to form a whole to constitute a conductive part, and the conductive part is rod-shaped, branch-shaped, block-shaped or mesh-shaped.

10. The photovoltaic cell according to claim 8, characterized in that, A portion of the conductive connection portions are in contact with the main body portion near the end of the battery substrate; and / or, a portion of the conductive connection portions are in contact with the battery substrate near the end of the battery substrate.

11. The photovoltaic cell according to claim 8, characterized in that, The main body has at least two second conductive particles spaced apart from each other in at least a portion of its area; and / or, a plurality of second conductive particles contained in at least a portion of the main body are in contact with each other.

12. The photovoltaic cell according to claim 8, characterized in that, The resistivity of the transport layer is 2 μΩ·cm to 3 μΩ·cm.

13. The photovoltaic cell according to claim 8, characterized in that, Along the first direction, a portion of the thickness of the seed layer is embedded in the battery substrate.

14. The photovoltaic cell according to claim 8, characterized in that, The transmission layer further includes a small number of dispersed second conductive particles, located on or partially embedded in the battery substrate, and located on the outer side of the conductive connection portion away from the main body portion.

15. The photovoltaic cell according to claim 8, characterized in that, Taking the surface side with the seed layer as the target surface side, along the first direction, the distance between the top surface of the seed layer away from the battery substrate and the target surface side is 1μm~15μm; And / or, along the first direction, the thickness of the transmission layer is 5μm~20μm.

16. The photovoltaic cell according to claim 8, characterized in that, The first conductive particle includes at least one of silver-coated copper particles, silver-coated nickel particles, or silver-nickel alloy particles; the second conductive particle includes silver particles or silver alloy particles; and / or, the median diameter of the first conductive particle is greater than the median diameter of the second conductive particle.

17. A stacked battery, characterized in that, include: The bottom cell is a photovoltaic cell formed by the manufacturing method of a photovoltaic cell as described in any one of claims 1 to 7, or a photovoltaic cell as described in any one of claims 8 to 16; A perovskite solar cell, wherein the perovskite solar cell is located on one side of the bottom solar cell.

18. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple photovoltaic cells formed by the manufacturing method of photovoltaic cells as described in any one of claims 1 to 7, or by connecting multiple photovoltaic cells as described in any one of claims 8 to 16, or by connecting multiple stacked cells as described in claim 17; 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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