Solar cell and photovoltaic module

Abstract

The present application relates to the technical field of photovoltaics, and provides a solar cell and a photovoltaic module. The solar cell comprises: a silicon substrate; transport layers and passivation and anti-reflection layers, a passivation and anti-reflection layer having a plurality of openings; and collector grid lines, located at the positions of the openings and in contact with the transport layers, each collector grid line comprising: a first seed region and a second seed region, both of which are disposed on the side of a transport layer facing away from the silicon substrate, the second seed region at least partially wrapping the first seed region; and a slurry layer, located on the side of the second seed region facing away from the silicon substrate, the slurry layer comprising a base metal.

Description

Solar cells and photovoltaic modules

[0001] This application claims priority to Chinese Patent Application No. 202510080464.6, filed on January 17, 2025, entitled "Solar Cells and Photovoltaic Modules", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of photovoltaic technology, and in particular to a solar cell and a photovoltaic module. Background Technology

[0003] In solar cells, grid lines are primarily used for collecting and conducting current. Currently, most grid lines in solar cells are silver grid lines formed using silver paste.

[0004] As the photovoltaic industry market and production capacity continue to expand, the industry's demand for silver paste has also surged, causing the price of silver paste to rise accordingly, leading to a continuous increase in the cost of solar cells.

[0005] Application content

[0006] This application provides a solar cell and a photovoltaic module designed to address the high cost issue caused by the silver grid lines in existing solar cells.

[0007] A first aspect of this application provides a solar cell, comprising:

[0008] A silicon substrate having opposing sides in the thickness direction of the silicon substrate;

[0009] A transport layer and a passivation antireflection layer are stacked on at least one side of the silicon substrate;

[0010] The passivation antireflection layer has several openings;

[0011] A collector gate line passes through the opening and contacts the transport layer; the collector gate line includes a seed layer and a paste layer; the seed layer includes a first seed region and a second seed region, both of which are disposed on the side of the transport layer away from the silicon substrate, and the first seed region is closer to the silicon substrate; the second seed region at least partially encloses the first seed region; the paste layer is disposed on the side of the second seed region away from the silicon substrate, and the paste layer includes base metal.

[0012] In this application, the paste layer contains base metal, which can effectively reduce the cost of solar cells. By first setting a first seed region, which typically contains metal, and the material in the transport layer is mainly semiconductor, the properties of the metal in the first seed region are more similar to those of the metal in the second seed region. This makes it easier and faster for the second seed region to form on the first seed region than on the transport layer. The first seed region acts as a bridge, facilitating the faster setting of the second seed region on the transport layer, forming a dense second seed region, enhancing the bonding between the second seed region and the transport layer, and also helping to prevent the diffusion of metal from the paste layer. Furthermore, by at least partially enclosing the first seed region with the second seed region, the bonding area between the two is larger, which further facilitates the rapid formation of the second seed region, resulting in a denser second seed region. The dense second seed region can better prevent the diffusion of base metal from the paste layer to the silicon substrate, thereby improving the electrical performance of the collector grid. In summary, this application not only reduces the cost of solar cells, but also provides excellent performance of the collector grid, with good current collection and conduction effects.

[0013] In some embodiments, the first seed region is located at the opening position, and the first seed region includes one or more discontinuous portions.

[0014] In some embodiments, at least one cross section along or perpendicular to the extension direction of the collector gate line, the cross section being perpendicular to the thickness direction of the silicon substrate, wherein the first seed region has 80 to 500 discontinuous portions within the cross section; and / or, the thickness of the first seed region is less than or equal to the thickness of the second seed region.

[0015] In some embodiments, the thickness of the discontinuous portions is not entirely uniform;

[0016] In some embodiments, the thickness of the discontinuous portion is less than or equal to 200 nm.

[0017] In some embodiments, the first seed region includes at least one of zinc, platinum, gold, silver, chromium, rhodium, indium, palladium, and tin.

[0018] In some embodiments, at the edge of the opening, there is a gap between the transport layer and the passivation antireflection layer, and the first seed region and / or the second seed region exist in the gap.

[0019] In some embodiments, the length of the gap along the direction opposite to the opening is less than or equal to 5 μm.

[0020] In some embodiments, the second seed region at least partially covers the passivation antireflection layer along a direction opposite to the silicon substrate.

[0021] In some embodiments, the second seed region includes: metallic elements and / or non-metallic elements.

[0022] In some embodiments, the metallic element is selected from at least one of the following: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, niobium, ruthenium, indium, zinc, tantalum, and so on.

[0023] In some embodiments, the non-metallic element includes at least one of phosphorus and boron.

[0024] In some embodiments, the mass percentage of phosphorus in the second seed region is 2% to 8%.

[0025] In some embodiments, the transport layer has a protrusion on the side facing away from the silicon substrate.

[0026] In some embodiments, the transport layer at the opening has a plurality of first holes on the side facing away from the silicon substrate;

[0027] In some embodiments, a protrusion is formed at the edge of the first hole;

[0028] In some embodiments, an annular protrusion is formed at the edge of the first hole;

[0029] In some embodiments, the annular protrusion may be a closed ring or a non-closed ring;

[0030] The aforementioned ring shape includes not only a ring shape in a strict geometric sense, but also similar ring shapes, and can be arc segments with different curvatures.

[0031] In some embodiments, the first seed region is clustered at the protrusion of the transport layer.

[0032] In some embodiments, the first seed region is concentrated on the protrusion of the first hole.

[0033] In some embodiments, the transport layer at the opening has a plurality of first holes on the side facing away from the silicon substrate, and the distribution density of the first seed region on the inner wall and / or bottom of the first hole is less than the distribution density of the first seed region outside the first hole.

[0034] In some embodiments, the solar cell further includes: a busbar line located on the side of the collector grid line away from the silicon substrate and electrically connected to collector grid lines of the same polarity and electrically isolated from collector grid lines of different polarities.

[0035] In some embodiments, the seed layer further includes: a third seed region, wherein the second seed region encloses at least a portion of the third seed region and / or at least a portion of the first seed region; the surface of the transport layer away from the silicon substrate is a first surface, and the projections of the third seed region and the first seed region onto the first surface at least partially overlap or are located close to each other; and / or,

[0036] The materials of both the third seed region and the first seed region are different from the main elements of the second seed region and the main elements of the slurry layer.

[0037] First, this application sets a third seed region and a first seed region in the seed layer. The third seed region is easily uniformly and dispersedly distributed on the first surface. The projections of the third seed region and the first seed region on the first surface at least partially overlap or are close in position. Therefore, the third seed region can exist as an activation site for the first seed region, attracting the first seed region to preferentially nucleate and grow near the third seed region. Because the third seed region is more dispersedly distributed on the transport layer surface, the first seed region can also be uniformly and dispersedly distributed on the first surface of the transport layer away from the silicon substrate. On the other hand, the third seed region and the first seed region have better conductivity and can exist as activation sites for forming the second seed region of the seed layer. Therefore, at least one objective of this application is to make the growth rate of the seed layer at different positions on the transport layer surface tend to be consistent, and to obtain a second seed region of the seed layer with relatively uniform thickness. First, the electrochemical performance is relatively better, improving the current collection effect. At the same time, under the same current collection requirements, the material usage of the electrode structure or current collector grid can be appropriately reduced, thus reducing the battery cost. Second, in the electrode structure or current collector grid of this application, there is no precious metal or the proportion of precious metal in the slurry layer is very small, which can further reduce the battery cost. Third, the third seed region and the first seed region exist on the side of the seed layer closer to the transport layer, which is equivalent to adding an anti-diffusion barrier, enhancing the blocking effect of the seed layer on base metals, reducing the damage of the slurry layer to the transport layer and silicon substrate, reducing the recombination probability, and further improving the battery performance.

[0038] In some embodiments, the third seed region is distributed on the first surface in the form of scattered points and / or aggregates, and / or the first seed region is distributed on the first surface in the form of scattered points and / or aggregates.

[0039] In some embodiments, for the same opening:

[0040] The number of the third seed regions is greater than the number of the first seed regions; and / or,

[0041] The area ratio of the third seed region is greater than the area ratio of the first seed region; and / or,

[0042] The weight percentage of the third seed region is greater than the weight percentage of the first seed region; and / or,

[0043] The distribution trend of aggregates in the third seed region is the same as that of aggregates in the first seed region.

[0044] In some embodiments, for the same opening:

[0045] The aggregates in the third seed region and / or the aggregates in the first seed region are at least distributed in locations with higher surface roughness in the first surface; and / or,

[0046] In the thickness direction of the silicon substrate, the first surface has protrusions and depressions, and the agglomerates of the third seed region and / or the agglomerates of the first seed region are at least distributed at the protrusions of the first surface.

[0047] In some embodiments, the opening includes an edge region and a middle region located inside the edge region; for the same opening:

[0048] The size of at least a portion of the aggregates in the third seed region within the edge region is larger than the size of the aggregates in the third seed region within the middle region; and / or,

[0049] The size of at least a portion of the aggregates in the first seed region within the edge region is larger than the size of the aggregates in the first seed region within the middle region.

[0050] In some embodiments, the transport layer is divided into a first transport layer and a second transport layer with different polarities; the passivation and anti-reflection layer is divided into a first anti-reflection passivation layer and a second passivation and anti-reflection layer; the collector gate line is divided into a first collector gate line and a second collector gate line; the second transport layer has the same doping type as the silicon substrate, and the first transport layer has a different doping type than the silicon substrate.

[0051] In some embodiments, the opening includes an edge region and a middle region located inside the edge region;

[0052] The size of at least a portion of the aggregates in the third seed region within the edge region of the opening corresponding to the second transport layer is larger than the size of the aggregates in the third seed region within the edge region of the opening corresponding to the first transport layer; and / or,

[0053] The size of at least a portion of the aggregates in the first seed region within the edge region of the opening corresponding to the second transmission layer is larger than the size of the aggregates in the first seed region within the edge region of the opening corresponding to the first transmission layer.

[0054] In some embodiments, the opening includes an edge region and a middle region located inside the edge region;

[0055] The height of the seed layer in the edge region of the opening corresponding to the second transmission layer is greater than the height of the seed layer in the edge region of the opening corresponding to the first transmission layer.

[0056] In some embodiments, the opening includes an edge region and a middle region located inside the edge region; for the same opening, the height of the seed layer in the edge region is greater than the height of the seed layer in the middle region.

[0057] In some embodiments, for the same opening, the difference between the height of the seed layer in the edge region and the height of the seed layer in the middle region is less than or equal to 500 nm.

[0058] In some embodiments, the passivation antireflection layer has a gap near the opening, and the third seed region and / or the first seed region also exist in the gap.

[0059] In some embodiments, the materials of the third seed region and the first seed region are different;

[0060] The material of the third seed region is selected from at least one of platinum, gold, silver, cobalt, and indium.

[0061] A second aspect of this application provides a method for preparing a solar cell, comprising:

[0062] A silicon substrate is provided; the silicon substrate has opposing sides in the thickness direction of the silicon substrate;

[0063] A transport layer is formed on at least one side of the silicon substrate;

[0064] A passivation antireflection layer is prepared on the side of the transport layer away from the silicon substrate, and several openings are formed in the passivation antireflection layer;

[0065] The transport layer at the opening is processed, and a first seed region, a second seed region, and a slurry layer are formed on the side of the transport layer at the opening away from the silicon substrate; the second seed region encloses the first seed region, and the slurry layer comprises base metal.

[0066] A third aspect of this application provides a photovoltaic module, comprising: an electrical connector and any of the aforementioned solar cells;

[0067] The electrical connector is electrically connected to the collector grid lines in at least two of the solar cells.

[0068] The aforementioned solar cells and their preparation methods, as well as photovoltaic modules, have the same or similar beneficial effects, and will not be repeated here to avoid repetition. Attached Figure Description

[0069] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0070] Figure 1 shows a side view of a solar cell structure according to an embodiment of this application;

[0071] Figure 2 shows a partial SEM side view of a solar cell according to an embodiment of this application;

[0072] Figures 3 to 5 show partially enlarged structural schematic diagrams of a solar cell according to an embodiment of this application;

[0073] Figure 6 shows a partial SEM top view of the transport layer in an embodiment of this application;

[0074] Figures 7 and 8 are schematic diagrams of several structures of solar cells according to embodiments of this application;

[0075] Figures 9, 10, 13 and 17 are several partial SEM images of solar cells according to embodiments of this application;

[0076] Figures 11 and 12 are schematic diagrams showing the distribution positions of several third seed regions and several first seed regions according to embodiments of this application;

[0077] Figures 14 to 16 are several partial EDS diagrams of solar cells according to embodiments of this application.

[0078] Explanation of the attached drawing numbers:

[0079] 1-Silicon substrate, 2-P-type transport layer, 21-Protrusion, 3-N-type transport layer, 4-Collector gate line, 5-Back passivation antireflection layer, 6-Front passivation antireflection layer, 7-Gap, 8-First hole, 41-First seed region, 42-Second seed region, 43-Paste layer, 44-Third seed region, 45-First seed layer, 46-First paste layer, 47-Second seed layer, 48-Second paste layer, 9-Second hole, 10-Tunneling oxide layer, 51-First part of back passivation antireflection layer, 52-Second part of back passivation antireflection layer. Specific Implementation

[0080] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0081] Those skilled in the art should understand that, in the disclosure of this application, the terms "first," "second," "third," "fourth," "fifth," etc., are only used to distinguish different structures and do not limit the number of specific structures, connection relationships, etc.; in addition, the orientation or positional relationship indicated by "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc., is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description, and is 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, the above terms should not be construed as limitations on this application.

[0082] This application provides a solar cell. Referring to Figures 1 to 16, the solar cell includes a silicon substrate 1, a transport layer, a passivation and antireflection layer, and current collector grid lines 4. Along the thickness direction Q of the silicon substrate 1, the silicon substrate 1 has opposite sides. During the operation of the solar cell, the side of the silicon substrate 1 that primarily receives light is its light-facing side. Along the thickness direction Q of the silicon substrate 1, the back-light side and the light-facing side are opposite each other. In Figures 1 and 2, the upper side of the silicon substrate 1 is its back-light side.

[0083] A transport layer and a passivation antireflection layer are stacked on at least one side of a silicon substrate 1. The transport layer is closer to the silicon substrate 1 than the passivation antireflection layer; that is, the passivation antireflection layer is located on the side of the transport layer opposite to the silicon substrate. The transport layer here may include a P-type transport layer 2 and an N-type transport layer 3. Referring to Figure 1, both the P-type transport layer 2 and the N-type transport layer 3 may be located on the back-light side of the silicon substrate 1. In this case, the passivation antireflection layer may include a back passivation antireflection layer 5 and a front passivation antireflection layer 6. Since the collector grid lines in the back-contact solar cell shown in Figure 1 are mainly located on the back-light side, an opening is formed in the back passivation antireflection layer 5. Alternatively, the P-type transport layer 2 may be located on one side of the silicon substrate 1, and the N-type transport layer 3 may be located on the other side of the silicon substrate 1. The specific material of the transport layer is not specifically limited. For example, the transport layer may include a doped polycrystalline silicon layer, the thickness of which may be from 50 nm to 250 nm.

[0084] The P-type transport layer may contain one or more elements from Group IIIA (e.g., boron). The N-type transport layer may contain one or more elements from Group VA (e.g., phosphorus). The materials for both the N-type and P-type transport layers can include any semiconductor material such as silicon, germanium-silicon, germanium, or gallium arsenide. In terms of material arrangement, the crystal phase of the transport layer can be amorphous, microcrystalline, nanocrystalline, single-crystal, or polycrystalline. The materials for both the N-type and P-type transport layers can include at least one of doped polycrystalline silicon, doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. Both the P-type and N-type transport layers can be obtained by in-situ doping on the surface of a semiconductor substrate or by deposition on the surface of a semiconductor substrate.

[0085] The passivation antireflection layer has several openings designed to expose a portion of the transport layer beneath it. A collector gate line, located on the side of the passivation antireflection layer facing away from the silicon substrate 1, collects charge carriers or current from the transport layer and discharges the current. A collector gate line 4 passes through the opening and contacts the transport layer; the collector gate line 4 can extend at least partially from the opening. The collector gate line 4 includes a seed layer and a paste layer. The seed layer includes a first seed region 41 and a second seed region 42, both located on the side of the transport layer facing away from the silicon substrate at the opening, with the first seed region 41 closer to the silicon substrate 1. Referring to Figures 3 and 4, the second seed region 42 at least partially encloses the first seed region 41. A paste layer 43 is located on the side of the second seed region 42 facing away from the silicon substrate. Referring to Figure 2, the collector gate line 4 here can be only an N-type collector gate line; or, the collector gate line 4 here can be only a P-type collector gate line; or, referring to Figure 1, the collector gate line 4 can be either an N-type collector gate line or a P-type collector gate line. It should be noted that the passivation antireflection layer mentioned in this application can provide good passivation and antireflection effects, and its specific material is not limited. For example, the passivation antireflection layer may include a stacked aluminum oxide layer and a silicon nitride layer, wherein the aluminum oxide layer is closer to the silicon substrate, the thickness of the aluminum oxide layer can be 4 nm to 10 nm, and the thickness of the silicon nitride layer can be 50 nm to 150 nm.

[0086] The mass of the paste layer in the collector grid typically accounts for a large portion of the grid's mass. In this application, the paste layer primarily uses base metals, which effectively reduces the cost of the solar cell compared to silver grids. By first setting a first seed region, which typically contains metal, while the transport layer is mainly composed of semiconductors, the properties of the metal in the first seed region are more similar to those in the second seed region. This makes it easier and faster for the second seed region to form on the first seed region than on the transport layer. The transition through the first seed region facilitates the faster establishment of the second seed region on the transport layer, forming a dense second seed region. Furthermore, by at least partially enclosing the first seed region with the second seed region, the bonding area between them is larger, further promoting the rapid formation of the second seed region and resulting in a denser second seed region. This denser second seed region better prevents the base metal in the paste layer from diffusing into the silicon substrate, improving the electrical performance of the collector grid. In summary, this application not only reduces the cost of the solar cell but also provides excellent collector grid performance, with good current collection and conduction effects.

[0087] It should be noted that the base metals referred to here mainly refer to those that do not contain silver or contain only a small amount of silver. For example, the paste layer here may include: a copper paste layer, an aluminum paste layer, or a paste layer with a precious metal content of less than 50% by mass, and the precious metal here may include silver. For example, the paste layer here may be a silver-coated copper paste layer, etc. The solar cells mentioned in this application can be various solar cells that require electrode structures. Both back-contact cells with electrode structures located on the same side of the cell and bifacial cells with electrode structures located on different sides of the cell are within the scope of protection of this application. It should be noted that, unless explicitly stated otherwise, the following descriptions in this application apply to at least one of the following four types of solar cells: the second collector grid line in a bifacial solar cell, the first collector grid line in a bifacial solar cell, the second collector grid line in a back-contact solar cell, and the first collector grid line in a back-contact solar cell.

[0088] In some embodiments, referring to FIG1, the first seed region 41 is located at the opening position, that is, the first seed region 41 is distributed at least within the opening. The first seed region 41 forms several discontinuous portions on the side of the transport layer away from the silicon substrate. That is to say, the transport layer away from the silicon substrate at an opening is not a continuous layer. The first seed region 41 is not set as a whole layer at the opening position. This can save the raw materials of the first seed region 41 and save the process cost. At the same time, the discontinuously distributed first seed region can also act as a bridge to guide the formation of the second seed layer and improve the bonding force between the second seed region and the transport layer. Combining the above advantages, the discontinuous setting of the first seed region can balance the cost, bonding force and other performance of the collector grid line 4 as a whole.

[0089] In Figures 1 to 3, M indicates the width direction of the opening, and Q indicates the thickness direction of the silicon substrate 1. Figure 3 is an enlarged view of the edge of the solar cell opening, and Figure 4 is an enlarged view of the area circled by the dashed line in Figure 3. SEM image refers to a scanning electron microscope image.

[0090] In some embodiments, at least one cross section along the extension direction of the collector grid line or perpendicular to the extension direction of the collector grid line, the cross section being perpendicular to the thickness direction of the silicon substrate, has 80 to 500 discontinuous portions in the first seed region 41 within the cross section. At the opening position, if the distribution density of the first seed region 41 is too high, it will cause waste of raw materials and increase the process cost. If the distribution density of the first seed region 41 is too low, it will result in insufficient traction transition effect of the first seed region, making it difficult to form the second seed region 42 and affecting the contact effect of the solar cell. In this application, the distribution density of the first seed region 41 is within the above range, which not only avoids waste of raw materials and reduces costs, but also provides a suitable traction transition effect of the first seed region 41, which is conducive to the formation of the second seed region 42, resulting in good contact effect of the solar cell. It should be noted that at least one cross-section is selected along the extension direction of the collector gate line or perpendicular to the extension direction of the collector gate line, and the cross-section is perpendicular to the thickness direction of the silicon substrate. Specifically, the cross-section refers to the area where the horizontal projected area of ​​the collector gate line and the opening position coincides. At least one cross-section is selected perpendicular to the thickness of the silicon substrate in the extension direction of the collector gate line or perpendicular to the extension direction of the collector gate line. Since the distribution of the first seed region is not completely uniform, at least one cross-section is selected to meet the aforementioned distribution density of the discontinuous part. The cross-section is selected in the middle part near the opening position, that is, the position where the opening width is larger, and the edge position of the opening needs to be avoided. For example, in a cross section perpendicular to the thickness direction of the silicon substrate, the first seed region 41 has 80, 90, 100, 120, 158, 159, 160, 180, 200, 220, 250, 280, 300, 320, 350, 400, 420, 450, 480, and 500 discontinuous portions.

[0091] It should be noted that, along a cross-section perpendicular to the thickness direction of the silicon substrate, the width of each discontinuous portion along the width direction M of the opening is greater than or equal to 10 nm. In the first seed region 41, portions with a dimension less than 10 nm along the width direction of the opening are not considered discontinuous portions. In Figure 1, for ease of illustration and display, the number of discontinuous portions in the first seed region 41 along a cross-section perpendicular to the thickness direction of the silicon substrate is an abbreviated schematic. In actual solar cells, the first seed region still has 80 to 500 discontinuous portions along a cross-section perpendicular to the thickness direction of the silicon substrate.

[0092] In some embodiments, the thickness of the first seed region 41 is less than or equal to the thickness of the second seed region 42. Specifically, if the thickness of the first seed region 41 is too large, it will result in a large amount of raw materials used and higher costs. If the thickness of the first seed region 41 is too small, it will result in insufficient traction and transition effect of the first seed region, making it difficult to form the second seed region 42 and affecting the contact effect of the solar cell. In this application, the thickness of the first seed region 41 is within the above range, which not only avoids waste of raw materials and lowers costs, but also provides a suitable transition effect of the first seed region 41, which is conducive to the formation of the second seed region 42 and results in good contact effect of the solar cell.

[0093] It should be noted that the thickness direction of the first seed region 41 and the thickness direction of the second seed region 42 are both parallel to the thickness direction Q of the silicon substrate.

[0094] It should be noted that Q in Figure 1 represents the thickness direction of the silicon substrate. In this application, the starting point of the first seed region 41 in the thickness direction of the silicon substrate is the surface of the transport layer away from the silicon substrate 1. The thickness of the first seed region 41 refers to the size of the first seed region 41 in the thickness direction of the silicon substrate 1, starting from the surface of the transport layer away from the silicon substrate 1. Similarly, the starting point of the second seed region 42 in the thickness direction of the silicon substrate 1 may be either the surface of the transport layer away from the silicon substrate 1 or the surface of the first seed region 41 away from the silicon substrate 1. The thickness of the second seed region 42 can refer to the size of the second seed region 42 in the thickness direction of the silicon substrate 1, starting from the surface of the transport layer away from the silicon substrate 1, or it can refer to the size of the second seed region 42 in the thickness direction of the silicon substrate 1, starting from the surface of the first seed region 41 away from the silicon substrate 1.

[0095] Regarding the two methods for measuring and verifying the thickness of the seed regions mentioned above, specifically, in the thickness direction of the silicon substrate 1, the starting point for setting the first seed region 41 is the surface of the transport layer away from the silicon substrate 1, which can be a flat surface and / or an uneven surface. In the thickness direction of the silicon substrate, the starting point for setting the second seed region 42 is the surface of the transport layer or the first seed region 41 away from the silicon substrate 1, which can be a flat surface and / or an uneven surface. The surface of the first seed region 41 away from the transport layer can be a flat surface and / or an uneven surface, and the surface of the second seed region 42 away from the transport layer can be a flat surface and / or an uneven surface.

[0096] For example, if all four surfaces are flat, and all four surfaces are perpendicular to the thickness direction Q of the silicon substrate, then any point on the surface of the transport layer away from the silicon substrate 1 and any point on the surface of the first seed region 41 away from the transport layer can be selected, and the distance between the two points in the thickness direction Q of the silicon substrate can be taken as the thickness of the first seed region 41. Alternatively, the average of several thicknesses can be selected as the thickness of the first seed region 41. The method for determining the thickness of the second seed region 42 is consistent with that of the first seed region 41.

[0097] For example, if all four surfaces include uneven surfaces, the uneven surfaces can have a peak structure (protrusion) and / or a valley structure (recess). In this case, the distance between the lowest / highest point of all protrusions on the surface of the transport layer away from the silicon substrate 1 and the lowest / highest point of all protrusions on the surface of the first seed region 41 away from the transport layer in the direction Q where the thickness of the silicon substrate is located can be selected as the thickness of the first seed region 41. Alternatively, the average of several thicknesses can be selected as the thickness of the first seed region 41. The method for determining the thickness of the second seed region 42 is consistent with that of the first seed region 41.

[0098] For example, if all four surfaces include uneven surfaces, the uneven surfaces can have protrusions and / or depressions. In this case, the distance between the lowest / highest point of all depressions on the surface of the transport layer away from the silicon substrate 1 and the lowest / highest point of all depressions on the surface of the first seed region 41 away from the transport layer in the direction Q where the thickness of the silicon substrate is located can be selected as the thickness of the first seed region 41. Alternatively, the average of several thicknesses can be selected as the thickness of the first seed region 41. The method for determining the thickness of the second seed region 42 is consistent with that of the first seed region 41.

[0099] This application may also select other vertices of the protrusions and depressions on the aforementioned surface to determine the thickness of the first seed region 41 and the second seed region 42, which will not be elaborated here. It should be noted that in this application, the methods for determining the several thicknesses to be compared are the same during the thickness comparison process. Other thickness determination methods in this application can all refer to the aforementioned examples, and will not be elaborated here.

[0100] It should be noted that, in this application, the thickness of the first seed region 41 is the thickness of the first seed region 41 projected within the aforementioned opening, and the thickness of the second seed region 42 is the thickness of the second seed region 42 projected within the aforementioned opening. Here, projection refers to projection onto a plane perpendicular to the thickness direction of the silicon substrate.

[0101] In some embodiments, the thickness of each discontinuous portion in the first seed region 41 is not entirely the same. This means that the first seed region 41 may contain discontinuous portions of the same thickness as well as discontinuous portions of different thicknesses. Specifically, the thickness of the discontinuous portions is not entirely the same, making them easy to fabricate and providing a good transition effect. And / or, the thickness of the discontinuous portions in the first seed region 41 is less than or equal to 200 nm. Within this thickness range, the first seed region can already provide a good transition effect, and the thickness of the discontinuous portions is not too large, thus avoiding waste of raw materials and resulting in lower costs. At the same time, discontinuous portions within this thickness range are easy to fabricate. The direction of the thickness of the discontinuous portion is parallel to the thickness direction Q of the silicon substrate. The thickness of the discontinuous portion can refer to the maximum dimension of the discontinuous portion on the side of the silicon substrate away from the silicon substrate in the thickness direction Q, or it can be determined in the same way as the thickness of the first seed region and the second seed region described above. No specific limitation is made in this regard.

[0102] For example, in the first seed region 41, the thickness of the discontinuous portion can be 200nm, 180nm, 150nm, 130nm, 160nm, 120nm, 110nm, 100nm, 90nm, 80nm, 70nm, 60nm, 50nm, 40nm, 30nm, 20nm, 10nm, 65nm, 75nm, 55nm, or 45nm.

[0103] In some embodiments, the first seed region 41 includes at least one of zinc (Zn), platinum (Pt), gold (Au), silver (Ag), chromium (Cr), rhodium (Rh), indium (In), palladium (Pd), and tin (Sn). These metal elements have low reduction barriers and readily aggregate in a point-like manner on the transport layer, which is beneficial for the formation of the second seed region 42. Furthermore, the elements also include some base metals, which can further reduce costs.

[0104] In some embodiments, referring to FIG3, a gap 7 is provided at the edge of the opening between the transport layer and the passivation antireflection layer. Referring to FIGS. 3 and 4, the first seed region 41 and / or the second seed region 42 extends into the gap 7. Here, only the first seed region may exist in the gap 7, or only the second seed region may exist in the gap 7, or both the first seed region 41 and the second seed region 42 may exist in the gap 7, as shown in FIGS. 3 and 4. Thus, the contact area between the first seed region 41 and / or the second seed region 42 and the transport layer is larger, and the contact effect is better.

[0105] Furthermore, hydrogen elements are typically formed during the formation of the passivation antireflection layer. For example, when the passivation antireflection layer material includes alumina, excess hydrogen is generated during the alumina deposition process due to the presence of water in the reaction. During the laser-induced delamination of the passivation antireflection layer, hydrogen can escape from the passivation antireflection layer under thermal effects, leading to film bursting and damaging both the passivation antireflection layer and the doped semiconductor layer, thus affecting the passivation effect. The gap 7 in this application is located near the edge of the passivation antireflection layer close to the opening, providing space for hydrogen to escape during the laser delamination process. This helps to mitigate or prevent film bursting, reducing damage caused by laser delamination and effectively ensuring the passivation effect of the solar cell. The gap 7 is mainly formed due to the thermal effects of laser delamination. Specifically, the gap may be formed when the passivation antireflection layer in the unopened area near the opening edge experiences slight warping, or when the transport layer develops micropores due to etching during the pre-treatment process for forming the collector grid 4.

[0106] In some embodiments, referring to FIG3, a second hole 9 is also provided in the gap 7 between the transport layer and the passivation antireflection layer at the edge of the opening. The second hole 9 here can also provide space for hydrogen to escape during the laser film opening process, thereby helping to alleviate or avoid film bursting, reduce the damage caused by laser film opening, and effectively ensure the passivation effect of the solar cell.

[0107] In some embodiments, on one side of an opening, along the width direction M of the opening and in a direction away from the opening, the extension length of the gap 7 is less than or equal to 5 μm. If the extension length of the gap 7 on one side of an opening is too long, the passivation and antireflection layer is prone to breakage and detachment, which is also detrimental to carrier transport and may lead to excessive laser damage. On one side of an opening, the extension length of the gap 7 along the width direction M of the opening is less than or equal to 5 μm, which not only does not have an adverse effect on carrier transport, but also results in less laser damage. Furthermore, the gap 7 of the above-mentioned size can provide sufficient space for hydrogen to escape from the passivation and antireflection layer, effectively preventing film bursting and improving the passivation effect. It should be noted that the extension length of the gap 7 on one side of an opening, along the width direction M of the opening and in a direction away from the opening, can refer to the length from the passivation and antireflection layer on one side of the opening to the farthest gap along the width direction M of the opening and in a direction away from the opening. For example, on one side of an opening, along the width direction M of the opening and in a direction away from the opening, the extension length of the gap 7 can be 5μm, 4.5μm, 4μm, 3.5μm, 3μm, 2.5μm, 2μm, 1.5μm, 1μm, or 0.5μm.

[0108] Furthermore, if the length of gap 7 is too small, hydrogen will escape during the laser film-opening process, and there will still be a risk of film bursting due to insufficient space for hydrogen escape. Therefore, in some examples, the length of gap 7 is greater than or equal to 0.01 μm, for example, it can be: 0.01 μm, 0.012 μm, 0.014 μm, 0.016 μm, 0.018 μm, 0.02 μm, 0.38 μm, 0.58 μm, 0.78 μm, 0.98 μm, 1.9 μm, 2.9 μm, 3.9 μm or 5.9 μm.

[0109] In some embodiments, the distribution density of the second seed region 42 in the gap 7 is less than the distribution density of the second seed region 42 at the opening. Specifically, the volume ratio of the second seed region 42 in the gap 7 is less than the volume ratio of the second seed region 42 at the opening, that is, the distribution density of the second seed region 42 in the gap 7 is less than the distribution density of the second seed region 42 at the opening. Specifically, current conduction enters the slurry layer from the second seed region 42 at the opening; a higher distribution density of the second seed region 42 at the opening provides more current transmission channels, which is more conducive to current conduction.

[0110] In some embodiments, the distribution density of the first seed region 41 in the gap 7 is greater than the distribution density of the second seed region 42 in the gap 7. Specifically, the proportion of the volume of the first seed region in the gap 7 is greater than the proportion of the volume of the second seed region in the gap 7. Therefore, the distribution density of the first seed region 41 in the gap 7 is greater than the distribution density of the second seed region 42 in the gap 7.

[0111] It should be noted that the distribution density of the first seed region 41 in the gap 7 can also be equal to the distribution density of the second seed region 42 in the gap 7; or, the distribution density of the first seed region 41 in the gap 7 can also be less than the distribution density of the second seed region 42 in the gap 7.

[0112] In some embodiments, referring to Figures 1 and 2, the second seed region 42 at least partially covers the passivation and antireflection layer. That is, the second seed region 42 includes a portion disposed corresponding to the opening and an extension portion extending from the opening to the side of the passivation and antireflection layer away from the silicon substrate, ensuring the adhesion of the second seed region 42 to the battery body and preventing the second seed region 42 from easily falling off. The fact that the second seed region 42 at least partially covers the passivation and antireflection layer also increases the area of ​​the upper surface of the second seed region 42, thereby increasing the contact area between the second seed region 42 and the passivation and antireflection layer, and improving the adhesion between the second seed region 42 and the passivation and antireflection layer. The adhesion between the anti-reflection layers is reduced, further decreasing the risk of the second seed region 42 detaching. The second seed region 42 at least partially covers the passivation anti-reflection layer, which can better block water, oxygen, and other elements from entering the battery at the opening, reducing the erosion or damage caused by other elements. In addition, the contact area between the extended portion and the slurry layer in the thickness direction of the battery can be appropriately increased, that is, the contact area between the side of the extended portion and the slurry layer is increased, further improving the contact area between the second seed region 42 and the slurry layer 43, reducing the contact resistance between the second seed region 42 and the slurry layer 43, and reducing current loss. At the same time, not only in the direction perpendicular to the thickness direction of the silicon substrate, the second seed region 42 at least partially covers the passivation anti-reflection layer, but also in the direction away from the silicon substrate 1, the second seed region 42 extends beyond the adjacent passivation anti-reflection layer. The first seed region can be thinner. The part of the collector grid line 4 other than the first seed region, namely the second seed region 42 and the slurry layer 43, has a larger thickness. Since the second seed region 42 and the slurry layer 43 have more options, base metals can be selected, which can further reduce costs.

[0113] It should be noted that either all of the second seed regions 42 may extend beyond the opening and cover the passivation and antireflection layer, or only some of the second seed regions 42 may extend beyond the opening and cover the passivation and antireflection layer; there is no specific limitation on this.

[0114] In some embodiments, the height d1 of the portion of the second seed region 42 extending beyond the adjacent passivation and antireflection layer is 200 nm to 1200 nm. Specifically, if d1 < 200 nm, the thickness of the extended portion is too small, which increases the contact resistance between the second seed region 42 and the slurry layer and may also adversely affect the arrangement of the slurry layer. If d1 > 1200 nm, the thickness of the extended portion is too large, which may adversely affect the arrangement of the second seed region and the slurry layer. For example, when the second seed region and the slurry layer are prepared in batches, a height d1 of the portion of the second seed region 42 extending beyond the adjacent passivation and antireflection layer that is less than 200 nm is detrimental to the arrangement of the slurry layer, and a height d1 of the portion of the second seed region 42 extending beyond the adjacent passivation and antireflection layer that is greater than 1200 nm is also detrimental to the arrangement of the slurry layer. On the one hand, a d1 range of 200nm to 1200nm is more suitable, as it provides good conductivity of the current collector grid and facilitates the setting of the slurry layer. On the other hand, this height range ensures sufficient adhesion between the second seed region 42 and the battery body, reducing the risk of detachment, while also ensuring a moderate contact area between the second seed region 42 and the slurry layer, and minimizing the contact resistance between them. The aforementioned thickness of the second seed region 42 can better prevent water, oxygen, and other elements from entering the battery body at the opening, reducing the erosion or damage caused by other elements to the battery body. In addition, the contact area between the second seed region 42 and the paste layer in the thickness direction of the silicon substrate can be appropriately increased, that is, the contact area between the side of the second seed region 42 and the paste layer can be increased, further improving the contact area between the second seed region 42 and the paste layer, reducing the contact resistance between the second seed region 42 and the paste layer, and reducing current loss; this height range can also increase the area of ​​the upper surface of the second seed region 42, thereby increasing the contact area between the second seed region 42 and the passivation antireflection layer, improving the adhesion between the second seed region 42 and the passivation antireflection layer, and further reducing the risk of the second seed region 42 falling off.

[0115] For example, the height d1 of the portion of the second seed region 42 that extends beyond the adjacent passivation and antireflection layer can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1100nm, 1150nm, or 1200nm.

[0116] It should be noted that the method for determining d1 here can refer to the method for determining the thickness of the first seed region and the second seed region mentioned above. To avoid repetition, it will not be repeated here.

[0117] In some embodiments, the second seed region 42 includes: a metallic element and / or a non-metallic element, wherein the metallic element is mainly used to provide current collection and conduction; in the process of forming the second seed region 42 by means of a redox reaction, the material containing the above-mentioned non-metallic element can play a reducing role, which can promote the substitution of silicon element for metal element, and facilitate the preparation of the second seed region 42.

[0118] In some embodiments, the metal element in the second seed region 42 may be selected from at least one of the following: titanium (Ti), tungsten (W), chromium (Cr), nickel (Ni), cobalt (Co), molybdenum (Mo), tin (Sn), lead (Pb), palladium (Pd), niobium (Nb), ruthenium (Ru), indium (In), zinc (Zn), tantalum (Ta), and vanadium (V). The selection of one or more of these elements is not specifically limited. In the second seed region 42, the aforementioned metal elements may exist in some compounds. For example, the second seed region 42 may contain titanium boride (TiB). x ), tantalum nitride (Ta), tungsten nitride (WN) x Titanium nitride (TiN) x Titanium-tungsten alloy (TiW) x ), titanium silicon compounds (TiSi) x Titanium silicon nitride (TiSiN), tantalum silicon nitride (TaSiN) x The second seed region is selected from at least one of nickel and vanadium (NiV). Specifically, the metal element selected for the second seed region is one of the aforementioned elements, as their electrical resistance and barrier properties against metal elements in the paste layer are well-suited for the second seed region. In particular, nickel and / or zinc are selected as materials for the second seed region because, firstly, both nickel and zinc have good contact performance; secondly, nickel and zinc do not penetrate into the silicon substrate, resulting in less recombination; and thirdly, nickel and zinc have a good barrier effect on metals in the paste layer on the side away from the silicon substrate, preventing metals in the paste layer from penetrating into the silicon substrate and reducing recombination. It should be noted that x in the above chemical formulas is a number greater than 0.

[0119] In some embodiments, the aforementioned non-metallic elements include at least one of phosphorus and boron. The material may contain phosphorus, boron, or both. During the formation of the second seed region 42 using a redox reaction, substances containing phosphorus and boron can provide good reduction, promoting the substitution of silicon for metal elements and facilitating the preparation of the second seed region 42. Furthermore, when the non-metallic element contains phosphorus, it constitutes N-type heavy doping in the second seed region 42, which is more conducive to the transport of carriers derived from the N-type transport layer, while reducing recombination and increasing the open-circuit voltage. Moreover, the phosphorus element is directly introduced during the formation of the collector grid line, eliminating the need for additional process steps and saving process steps. Similarly, when the non-metallic element contains boron, it constitutes P-type heavy doping in the second seed region 42, which is more conducive to the transport of carriers derived from the P-type transport layer, while reducing recombination. Furthermore, the boron element is directly introduced during the formation of the collector grid line, eliminating the need for additional process steps and saving process steps.

[0120] For example, boron, one of the aforementioned non-metallic elements, can be present in sodium borohydride and / or dimethylaminoborane. As another example, phosphorus, one of the aforementioned non-metallic elements, can be present in sodium hypophosphite. During the formation of the second seed region 42 via a redox reaction, the aforementioned materials can also act as a reducing agent, promoting the substitution of silicon with metallic elements and facilitating the preparation of the second seed region 42.

[0121] In some embodiments, when the second seed region 42 contains phosphorus, the mass percentage of phosphorus in the second seed region 42 is 2% to 8%. If the mass percentage of phosphorus is too high, it may lead to poor contact performance between the slurry layer 43 and the second seed region 42, affecting the battery's electrical performance. If the mass percentage of phosphorus is too low, the amount of reducing agent containing phosphorus participating in the reaction is too low, the entire redox reaction triggering conditions are harsh and the reaction is slow, affecting production efficiency. When the second seed region 42 contains phosphorus, the mass percentage or weight percentage of phosphorus in the second seed region 42 is 2% to 8%, which is the result of balancing contact performance and reaction rate.

[0122] It should be noted that one or more regions can be selected from the second seed region 42, and the size of the region is not limited. Here, the mass percentage of phosphorus in one region can be used as the mass percentage of phosphorus in the second seed region 42, or the average mass percentage of phosphorus in multiple regions can be used as the mass percentage of phosphorus in the second seed region 42.

[0123] For example, if the second seed region 42 contains phosphorus, the mass percentage of phosphorus in the second seed region 42 can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0124] Figure 5 is a schematic diagram of the protrusion of the transport layer. In some embodiments, referring to Figure 5, the transport layer has a protrusion 21 on the side facing away from the silicon substrate 1, and the first seed region 41 is gathered at the protrusion. Here, the protrusion 21 can be the edge of the base on the surface of the silicon substrate, causing the transport layer to have a protrusion on the side facing away from the silicon substrate 1. Alternatively, there may be a protrusion near the position corresponding to the edge of the base on the surface of the silicon substrate on the side of the transport layer facing away from the silicon substrate. Or, the protrusion may be a protrusion formed by forming an opening during processing. None of these are limited. The first seed region 41 is gathered at the protrusion, and thus the first seed region 41 is more likely to form a three-dimensional structure at the protrusion position, rather than a two-dimensional structure. Consequently, the combination of the first seed region 41 and the second seed region 42 is stronger, and the contact performance is better.

[0125] The shape of the protrusions is not specifically limited. Figure 5 is a cross-sectional view of the transport layer, which is formed by cutting the transport layer along the direction of its thickness relative to the silicon substrate. For example, referring to Figure 5, the protrusion 21 on the left is columnar, the protrusion in the middle of Figure 5 can be dot-shaped, and the protrusion on the right can be annular. As another example, in Figure 6, the protrusion below the first seed region 41 at the top is dot-shaped, the protrusion below the first seed region 41 in the middle of the vertical direction is prismatic, and the protrusion below the first seed region 41 at the bottom is annular. It should be noted that Figures 5 and 6 do not fully show the shapes of the protrusions; the shapes of the protrusions include, but are not limited to, the aforementioned columnar, dot-shaped, prismatic, and annular shapes. The annular protrusions here can be continuously distributed as closed annular shapes or intermittently distributed as non-closed annular shapes; neither is limited in this respect. The aforementioned ring shape includes not only a ring shape in a strict geometric sense, but also similar ring shapes, and can be arc segments with different curvatures.

[0126] In some embodiments, referring to Figures 5 and 6, the transport layer at the opening has a plurality of first holes 8 on the side facing away from the silicon substrate, and the edges of the first holes have non-closed protrusions with an approximately annular shape. First seed regions 41 converge at the edges of the first holes 8, and the first seed regions 41 serve as a transitional portion for the second seed regions 42, thus the second seed regions 42 preferentially form near the edges of the first holes 8. Specifically, the first holes 8 are formed because the laser energy is not uniform during the laser opening process, and the laser energy at the location of the first hole 8 is higher, causing the transport layer to burst open at this location, thus forming the first hole 8. Therefore, the transport layer at the edge of the first hole 8 melts and recrystallizes, exhibiting higher activity, making it easier to form the second seed region there. Furthermore, the convergence of the first seed regions 41 at the edges of the first holes 8 makes it easier for the first seed regions 41 to form a three-dimensional structure rather than a two-dimensional structure at the edges of the first holes 8, resulting in a stronger bond between the first seed regions 41 and the second seed regions 42 and better contact performance.

[0127] In some embodiments, referring to FIG6, the transport layer at the opening has a plurality of first holes 8 on the side facing away from the silicon substrate; as can be seen from FIG6, the protrusions of the first holes are sometimes closed rings and sometimes open rings. Referring to the first hole 8 marked on the far right of FIG6, the distribution density of the first seed region 41 on the inner wall and / or bottom of the first hole 8 is less than the distribution density of the first seed region 41 on the outside of the first hole 8. Specifically, during the formation of the first seed region 41, the transport layer at the opening needs to be immersed in the reaction liquid. The inner wall and / or bottom of the first hole 8 may be less susceptible to wetting by the reaction liquid than the outside of the first hole. Therefore, the distribution density of the first seed region 41 on the inner wall and / or bottom of the first hole 8 is less than that on the outside of the first hole 8. Consequently, the second seed region 42 will preferentially form outside the first hole 8. During the formation of the second seed region, the outside of the first hole 8 is also usually more likely to come into contact with the reaction raw materials, so it is easier to form the second seed region here, which is more compatible with the formation process of the second seed region. In addition, the first seed region 41 gathers outside the first hole 8, making it easier for the first seed region 41 to form a three-dimensional structure outside the first hole 8, rather than a uniformly distributed two-dimensional layer structure. As a result, the combination of the first seed region 41 and the second seed region 42 is stronger and the contact performance is better.

[0128] It should be noted that protrusions are more likely to form outside the first hole 8 and near its edge during the opening process. These protrusions can be distributed continuously or intermittently. As a result, the reacting raw materials are more likely to come into contact with these protrusions during the formation of both the first and second seed regions. Moreover, due to the catalytic effect of the first seed region, the second seed region will also be preferentially formed here, making it more compatible with the formation process of the second seed region. On the other hand, the first seed region is more likely to aggregate into a three-dimensional structure here rather than a two-dimensional structure. As a result, the combination of the first seed region 41 and the second seed region 42 is stronger and the contact performance is better.

[0129] In some embodiments, the solar cell further includes: a busbar, located on the side of the aforementioned collector grid 4 facing away from the silicon substrate, electrically connected to the collector grid 4 of the same polarity, and electrically isolated from the collector grid 4 of different polarities. This electrical isolation can be achieved through an insulating component or the like. In some embodiments, the busbar may include: a paste layer, which conducts the current on the collector grid 4. The paste layer of the busbar contains base metals, thereby reducing costs. The paste layer of the busbar can be formed in the same step as the paste layer of the collector grid, and both can be base metals, simplifying the process and saving costs; alternatively, the paste layer of the busbar and the paste layer of the collector grid can be formed in different steps, with their respective process parameters precisely controlled according to their required performance. In this case, the paste layer of the busbar can also be a paste layer containing base metals, which also reduces costs. It should be noted that the solar cell may also not include a busbar, or may have fewer busbars.

[0130] This application also provides another type of solar cell, comprising: a silicon substrate 1 having opposite sides in the thickness direction of the silicon substrate 1; a transport layer and a passivation antireflection layer, stacked on at least one side of the silicon substrate; the passivation antireflection layer having a plurality of openings; current collector grid lines located at the openings and in contact with the transport layer; the current collector grid lines containing metallic and / or non-metallic elements, wherein the metallic elements provide good conductivity and the non-metallic elements promote the formation of current collector grid lines on the transport layer at the openings. The non-metallic elements may include at least one of phosphorus and boron, and the functions of phosphorus and boron are similar to or the same as those described above; to avoid repetition, they will not be repeated here.

[0131] For example, in one embodiment, the collector grid line may include the aforementioned second seed region, which includes metallic elements and / or non-metallic elements. The metallic elements and non-metallic elements mentioned above can be referred to the relevant descriptions above and can achieve the same or similar beneficial effects. To avoid repetition, they will not be described again here.

[0132] For example, in another embodiment, the collector grid line may include the aforementioned second seed region, which includes metallic and / or non-metallic elements. The collector grid line may also include the aforementioned first seed region, and the second seed region at least partially encloses the first seed region. The first and second seed regions can be referred to the relevant descriptions above and can achieve the same or similar beneficial effects. To avoid repetition, they will not be described again here.

[0133] The silicon substrate, transport layer, passivation antireflection layer, opening, opening location, metal element, and non-metal element mentioned here can be referred to the relevant records above, and can achieve the same or similar beneficial effects. To avoid repetition, they will not be described again here.

[0134] The specific form of the collector grid line is not limited here. Apart from the collector grid line, other structures in this solar cell can refer to the other structures in the aforementioned solar cells.

[0135] For example, in this solar cell, a gap exists between the transport layer and the passivation antireflection layer at the edge of the opening, along the width direction of the opening, and a portion of the current collector grid lines exist within this gap. As another example, on one side of the opening, along the direction away from the opening, the extension length of the gap is less than or equal to 5 μm. As another example, the metal element in the current collector grid lines can be selected from at least one of: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, copper, niobium, ruthenium, indium, zinc, tantalum, and vanadium. As another example, this solar cell may further include: a busbar located on the side of the current collector grid lines away from the silicon substrate, electrically connected to current collector grid lines of the same polarity, and electrically isolated from current collector grid lines of different polarities. The specific details of each feature in this solar cell, and the function of each feature, are the same as or similar to the function of the corresponding features in the aforementioned solar cells, and can be referred to the corresponding features in the aforementioned solar cells; they will not be repeated here.

[0136] In some embodiments, the seed layer of this application may contain a third seed region in addition to the aforementioned first and second seed regions. It should be noted that the seed layer containing only the aforementioned first and second seed regions, or the seed layer containing the first, second, and third seed regions, are all within the scope of protection of this application. The following content mainly describes the differences from the foregoing when a third seed region is included; content identical to the foregoing will not be repeated to avoid repetition.

[0137] In this application, EDS refers to energy-dispersive spectroscopy. In the accompanying drawings of this application, structures without explicitly marked dimensions are schematic only and do not represent the actual relative sizes of the various structures.

[0138] The following explanations will use P-type transport layer 2 as the first transport layer and N-type transport layer 3 as the second transport layer as an example. In this application, Figures 9 and 13 to 15 all refer to the same opening in the second transport layer. Figure 9 is a SEM image of the second collector gate line in the edge region of the opening corresponding to the second transport layer; Figure 13 is a SEM image of the second collector gate line in the middle region of the opening corresponding to the second transport layer; Figure 14 is an EDS image of the third seed region in the edge region of the opening corresponding to the second transport layer; and Figure 15 is an EDS image of the first seed region in the edge region of the opening corresponding to the second transport layer. Figures 10 and 16 both refer to the same opening in the first transport layer. Figure 10 is a SEM image of the first collector gate line in the edge region of the opening corresponding to the first transport layer; and Figure 16 is an EDS image of the first collector gate line in the edge region of the opening corresponding to the first transport layer. Figures 14 to 16 correspond to the same magnification, and Figures 9, 10, and 13 correspond to the same magnification.

[0139] Referring to Figures 7 and 8, the transmission layer is divided into a second transmission layer and a first transmission layer with different polarities. One of them is an N-type transmission layer and the other is a P-type transmission layer. In this application, the second transmission layer can be described as an N-type transmission layer 3 and the first transmission layer is a P-type transmission layer 2. However, in this application, the second transmission layer being a P-type transmission layer and the first transmission layer being an N-type transmission layer are also within the scope of protection of this application.

[0140] In some embodiments, the second transport layer has the same doping type as the silicon substrate, while the first transport layer has a different polarity or doping type than the silicon substrate. For example, both the second transport layer and the silicon substrate are N-type doped, and the first transport layer is P-type doped.

[0141] The passivation antireflection layer is divided into a first passivation antireflection layer and a second passivation antireflection layer. For the bifacial solar cell shown in Figure 7, the first passivation antireflection layer can correspond to either the front passivation antireflection layer 6 or the back passivation antireflection layer 5, and the second passivation antireflection layer can correspond to the other of the front passivation antireflection layer and the back passivation antireflection layer. For example, in this application, for the bifacial solar cell shown in Figure 7, the example of the first passivation antireflection layer is the front passivation antireflection layer 6, and the example of the second passivation antireflection layer is the back passivation antireflection layer 5. For the back-contact solar cell shown in Figure 8, the first passivation antireflection layer can correspond to either the first portion 51 or the second portion 52 of the back passivation antireflection layer, and the second passivation antireflection layer can correspond to the other of the first portion 51 or the second portion 52 of the back passivation antireflection layer. For example, in this application, for the back-contact solar cell shown in FIG8, the first passivation antireflection layer is exemplified by the first portion 51 of the back passivation antireflection layer, and the second passivation antireflection layer is exemplified by the second portion 52 of the back passivation antireflection layer. The collector grid lines are divided into first collector grid lines and second collector grid lines. Along the thickness direction Q of the silicon substrate 1, the silicon substrate 1 includes opposing first and second sides, one of which is the light-facing side and the other is the second side. In this application, the first side is described as the back-light side. The case where the first side is the light-facing side is also within the scope of protection of this application. During normal operation of the solar cell, the side of the silicon substrate that mainly receives light is its light-facing side, and the back-light side is opposite to the light-facing side. For example, in FIG7, the lower side of the silicon substrate is its back-light side, and the upper side is its light-facing side.

[0142] Referring to Figure 7, a second transport layer and a second passivation antireflection layer are sequentially disposed on the first side of the silicon substrate 1, with the second transport layer closer to the silicon substrate 1. A second current collector grid line is located on the side of the second passivation antireflection layer opposite to the silicon substrate 1, used to collect and conduct current or charge carriers within the second transport layer. A first transport layer and a first passivation antireflection layer are sequentially disposed on the second side of the silicon substrate 1, with the first transport layer closer to the silicon substrate 1. A first current collector grid line is located on the side of the first passivation antireflection layer opposite to the silicon substrate 1, used to collect and conduct current or charge carriers within the first transport layer. This solar cell is a bifacial solar cell. For example, this bifacial solar cell can be a TOPcon (tunneling oxide passivated contact) cell, etc. This application does not limit the specific type of bifacial solar cell.

[0143] Referring to Figure 8, a second transport layer and a second passivation antireflection layer are sequentially disposed in a second region on a first side of the silicon substrate 1, with the second transport layer closer to the silicon substrate 1. A second current collector grid is located on the side of the second passivation antireflection layer away from the silicon substrate 1, used to collect and conduct current or charge carriers within the second transport layer. A first transport layer and a first passivation antireflection layer are sequentially disposed in a first region on a first side of the silicon substrate 1, with the first transport layer closer to the silicon substrate 1. A first current collector grid is located on the side of the first passivation antireflection layer away from the silicon substrate 1, used to collect and conduct current or charge carriers within the first transport layer. This solar cell is a back-contact solar cell with its electrode structure located on the back-light side of the silicon substrate. For example, this back-contact solar cell can be a TBC cell (a cell combining tunneling oxide passivation contact and interdigitated back contact), a back-contact hybrid cell, etc. This application does not limit the specific cell type. In a back-contact solar cell, the light-facing side of the silicon substrate 1 is not blocked by electrodes, resulting in better performance and potentially a more aesthetically pleasing appearance. The relative sizes of the first and second regions are not limited here.

[0144] The materials of the aforementioned first passivation antireflection layer and second passivation antireflection layer can be the same or different. In a back-contact solar cell, the first and second passivation antireflection layers can be an integral structure, or they can be formed in different processes, both of which are within the scope of protection of this application. When the transport layer is a doped polycrystalline silicon layer, the thickness of the transport layer can be 50 to 250 nm, etc.

[0145] Referring to Figures 10 to 17, the seed layer further includes a third seed region 44 (shown in Figures 14 and 16). The second seed region encloses at least a portion of the third seed region 44 and / or at least a portion of the first seed region 41; the surface of the transport layer away from the silicon substrate is a first surface, and the projections of the third seed region 44 and the first seed region 41 on this first surface at least partially overlap or are located close to each other. For example, in Figure 11, the first seed region 41 is attached to the third seed region 44, and the first seed region 41 encloses at least a portion of the third seed region 44. As another example, in Figure 12, the first seed region 41 and the third seed region 44 are distributed in approximately the same location, and the first seed region 41 intersperses and fills the gaps between adjacent third seed regions 44. It should be noted that the relative positions of the third seed region 44 and the first seed region 41 include, but are not limited to, the arrangements exemplified in Figures 11 and 12. The specific beneficial effects of the above solution are described in the invention description and will not be repeated here.

[0146] For example, as shown in Figures 11 and 12, and Figures 14 and 15, it can be seen that within the same opening, the distribution positions of the first seed region 41 and the third seed region 44 approximately overlap or are close to each other. Referring to Figure 11, the first seed region 41 may be attached to the third seed region 44, or, referring to Figure 12, the first seed region 41 may be interspersed and filled in the gaps between adjacent third seed regions 44. The third seed region 44 of this application provides arrangement points or activation points for the first seed region 41 on the transport layer, allowing the first seed region 41 to be more uniformly distributed within the opening of the first surface of the transport layer away from the silicon substrate.

[0147] It should be noted that one reason for setting a third seed region in this application is that the first seed region serves as the catalytic site for the second seed region of the seed layer. However, research has found that the reduction activity of the first seed region from an ionic state to a metal particle state is weak on the surface of the doped semiconductor layer or transport layer. This makes it difficult to form a sufficient number of catalytic sites on the first surface of the transport layer for the catalytic reduction of the second seed region of the subsequent seed layer. Ultimately, this not only leads to a longer reaction time and reduced battery production efficiency, but also results in a smaller and uneven distribution of the first seed region on the first surface, leading to weaker adhesion with the transport layer and poor contact performance. Therefore, in this application, by first setting a cheaper and more reactive third seed region, better-dispersed metal particle dots or aggregates are formed on the first surface of the transport layer. This encourages the first seed region to preferentially reduce and deposit at the location of the third seed region, allowing the subsequently formed first seed region to be more widely and evenly distributed on the first surface of the transport layer within the opening. This improves the adhesion between the third seed region, the second seed region of the seed layer, the slurry layer, and the transport layer, thereby improving contact performance and reaction speed.

[0148] The necessity of setting the first seed region in this application is that it is usually difficult to form the second seed region of the seed layer on the third seed region by means of redox reactions, which affects the quality of the second seed region of the seed layer and results in low production efficiency. In this application, by setting the first seed region as a catalyst for the second seed region, the difficulty of forming the seed layer by means of redox reactions is reduced, resulting in high production efficiency.

[0149] In summary, in this application, the third seed region and the first seed region cooperate with each other, so that the third seed region and the first seed region are widely and uniformly distributed on the transport layer within the opening, which improves the contact performance between the metal particles and the second seed region of the seed layer, increases the specific surface area of ​​the catalytic sites, and accelerates the formation rate of the second seed region of the seed layer; at the same time, the use of the cheaper third seed region can reduce the amount of the first seed region (catalyst), further reducing production costs.

[0150] It should be noted that in related technologies, the second seed region of the seed layer is typically formed using electrochemical deposition. However, the complex design and high cost of the equipment used in electrochemical deposition have hindered further cost reduction of solar cells. This application, by using a redox reaction to form the second seed region of the seed layer, further reduces the cost of solar cells.

[0151] In this application, the materials of both the third seed region and the first seed region are different from the main elements of the second seed region of the seed layer and the main elements of the slurry layer. The main elements of the second seed region of the seed layer refer to elements comprising 50% or more by weight or mass. The main elements of the slurry layer refer to elements comprising 50% or more by weight or mass. Because the materials of both the third seed region and the first seed region are different from the main elements of the second seed region of the seed layer and the main elements of the slurry layer, the materials of both the third seed region and the first seed region have different characteristics than the main elements of the second seed region of the seed layer and the main elements of the slurry layer, and can perform the functions required by the third seed region and the first seed region as described above.

[0152] In some embodiments, the Fermi level of the third seed region can be higher than that of the transport layer. This facilitates the simple and rapid formation of the aforementioned third seed region using redox reactions or other methods within the transport layer. This not only reduces damage to the transport layer and the silicon substrate but also lowers reaction costs, further reducing battery costs. The Fermi level of the transport layer mentioned in this application refers to the core parameter describing the electron filling state in the transport layer; it refers to the energy level position where electrons occupy a 50% probability under thermal equilibrium conditions. The doping type and concentration of the transport layer all affect its Fermi level. The Fermi level of the third seed region is the highest energy level occupied by electrons at absolute zero. This position directly reflects the conductivity of the third seed region. Specifically, generally, the higher the Fermi level of the third seed region, the better its conductivity. The size and material of the third seed region also affect its Fermi level. If the Fermi level of the third seed region is higher than that of the transport layer, the cations in the third seed region are more easily reduced to the third seed region by the transport layer.

[0153] It should be noted that whether the first seed region will also be directly attached to the transport layer inside the opening is not limited. For example, a small number of first seed regions can be directly attached to the transport layer inside the opening, and most of the first seed regions can be directly attached to the third seed region.

[0154] It should be noted that the second seed region of the seed layer (the second seed region of the second seed layer and the second seed region of the first seed layer) may contain noble metals. The seed layer may be directly electrically connected to the transport layer. The slurry layers (the first slurry layer 46 and the second slurry layer 48) cover at least a portion of the seed layer, and the slurry layers are electrically connected to the transport layer through the seed layer. The mass or weight percentage of base metals in the slurry layer is greater than or equal to 50%. The number of third seed regions and the number of first seed regions within an opening are not specifically limited. The seed layer and the slurry layer may also have portions located outside the opening.

[0155] The material of the second seed region of the second seed layer and the second seed region of the first seed layer can be the same or different; there is no specific limitation on this. The thickness of the seed layer or the second seed region of the seed layer can be 300-1200 nm.

[0156] In some embodiments, the third seed region is distributed in the form of scattered dots and / or agglomerates on the first surface of the transport layer away from the silicon substrate. The scattered dot distribution allows the third seed region to be distributed more uniformly and dispersedly on the first surface, thereby enabling the first seed region to also be distributed uniformly and dispersedly on the first surface. Ultimately, the third seed region and the first seed region can be uniformly and dispersedly distributed on the first surface of the transport layer away from the silicon substrate, thereby improving the dimensional uniformity of the second seed region of the seed layer at various locations. On the other hand, the third seed region here contains noble metal, and the scattered distribution at the opening also reduces costs. At the same time, agglomerates are beneficial for improving local contact effects. Therefore, the morphology of the third seed region in this application takes into account the dimensional uniformity of the second seed region of the seed layer at various locations, cost, and local improvement of contact effects.

[0157] For example, referring to Figures 14 and 16, the third seed region is distributed in the form of scattered clusters on the first surface of the transport layer away from the silicon substrate.

[0158] It should be noted that the scattered distribution of the third seed region mentioned in this application means that at least some of the third seed regions are discontinuously distributed within the opening, and there are gaps between at least some of the third seed regions.

[0159] In some embodiments, the first seed region is distributed in the form of scattered dots and / or agglomerates on the first surface of the transport layer away from the silicon substrate. The scattered dot distribution allows for a more uniform distribution of the first seed region on the first surface, enabling it to be evenly and dispersedly distributed across the first surface of the transport layer away from the silicon substrate, thereby improving the dimensional uniformity of the second seed region at various locations. Furthermore, the first seed region here contains noble metals, and this scattered distribution at the opening also reduces costs. Agglomerates are beneficial for improving local contact performance. Therefore, the morphology of the first seed region in this application balances the dimensional uniformity of the second seed region at various locations, cost, and improved local contact performance.

[0160] For example, the first seed region is mainly distributed in a scattered form on the first surface of the transport layer away from the silicon substrate. As another example, in Figure 15, the first seed region is distributed in a scattered, agglomerated form on the first surface of the transport layer away from the silicon substrate.

[0161] It should be noted that the first seed region mentioned in this application being distributed in a scattered manner means that within the opening, at least some of the first seed regions are discontinuously distributed, and at least some of the first seed regions have intervals between them.

[0162] In some embodiments, the weight percentage of the third seed region is greater than that of the first seed region within the same opening. Specifically, the third seed region mainly provides arrangement sites or activation sites for the first seed region on the transport layer. The number and distribution of these arrangement sites or activation sites significantly affect the arrangement sites and distribution of the first seed region. Therefore, in this application, the weight percentage of the third seed region within the same opening is relatively large, ensuring that the third seed region is sufficiently and uniformly distributed within the opening, thereby ensuring that sufficient active sites are provided to the first seed region, further improving the electrical performance of the battery. The weight percentage of the third seed region within the same opening can be obtained or determined by methods such as EDS. Within the same opening, a unit area or unit volume can be selected, and the weight percentage of the third seed region can be compared with that of the first seed region within that unit area or unit volume. The size of this unit area can be 0.1μm×0.1μm, 0.2μm×0.1μm, 0.2μm×0.2μm, 0.3μm×0.3μm, 0.3μm×0.5μm, etc.

[0163] In some embodiments, the area proportion of the third seed region in the same opening is greater than that of the first seed region. Similarly, in this application, the area proportion of the third seed region in the same opening is relatively large, ensuring that the third seed region is sufficiently and uniformly distributed in the opening, thereby ensuring that sufficient active sites are provided to the first seed region, further improving the electrical performance of the battery. The area proportion of the third seed region in the same opening can also be obtained or determined by methods such as EDS. A unit area can be selected in the same opening, and the area proportion of the third seed region can be compared with the area proportion of the first seed region within that unit area. An example of this unit area can be found in the aforementioned related descriptions.

[0164] In some embodiments, the distribution trend of aggregates in the third seed region within the same opening is the same as that of aggregates in the first seed region. Specifically, the distribution location of aggregates in the third seed region or its vicinity within the same opening is roughly the same as the distribution location of aggregates in the first seed region. This indicates that the third seed region acts as an activation site for the first seed region, attracting the first seed region to preferentially nucleate and grow near the third seed region. This, in turn, promotes the uniform and dispersed distribution of the third and first seed regions on the first surface of the transport layer away from the silicon substrate. Therefore, this application further makes the growth rate of the seed layer at different locations on the transport layer surface tend to be consistent, resulting in a second seed region with a relatively uniform thickness. The electrical performance of the seed layer is relatively better, improving the current collection effect. At the same time, under the same current collection requirements, the material usage of the electrode structure can be appropriately reduced, thereby reducing the battery cost.

[0165] For example, referring to Figures 14 and 15, the distribution location of aggregates in the third seed region or its vicinity within the same opening is roughly the same as the distribution location of aggregates in the first seed region.

[0166] In some embodiments, referring to FIG13, for the same opening, the agglomerates in the third seed region and / or the agglomerates in the first seed region are at least distributed at locations with higher roughness on the first surface of the transport layer away from the silicon substrate 1. That is, in the same opening, agglomerates are easily distributed at or near locations with higher roughness on the first surface, or agglomerates are easily distributed at or near locations with higher roughness on the first surface. Specifically, at or near locations with higher roughness on the first surface, the film quality of the second transport layer may be poor due to the higher roughness. By setting the third seed region and the aggregation of the first seed region at the rough location, the problem of uneven electrical performance caused by the poor film quality of the transport layer at the corresponding location in the rough region can be compensated, and the battery performance can be further improved.

[0167] For example, for the same opening: the roughness of the region shown by the dashed ellipse in Figure 13 is greater than that of the region shown by the dashed box in Figure 13 when the transport layer is away from the first surface of the silicon substrate 1; for the same opening, the agglomerates of the third seed region and the first seed region are more likely to be distributed in the region shown by the dashed ellipse in Figure 13.

[0168] It should be noted that at the same location, the size of the second seed region of the seed layer is strongly correlated with the aggregation of the aggregates in the third and first seed regions. This is because the aggregates in the third and first seed regions have better conductivity, so the formation rate of the second seed region of the seed layer at the location of the aggregates may be relatively faster. Moreover, the second seed region occupies most of the size of the seed layer. Therefore, in Figure 13, the thickness of the seed layer or the second seed region of the seed layer at the same location can be roughly equivalent to the aggregation or distribution of the aggregates in the third and first seed regions.

[0169] It should be noted that the roughness of the first surface can refer to the roughness of the first surface of the transport layer away from the silicon substrate, as determined by methods such as Ra and Rz, or the distance between the highest and lowest points along the thickness direction of the silicon substrate per unit area. The area of ​​this unit volume can be similar to that described above, and will not be repeated here to avoid repetition.

[0170] In some embodiments, referring to Figures 9, 10, and 13, such as the embodiment where the opening of the passivation antireflection layer is formed by laser, the first surface of the transport layer away from the silicon substrate 1 is affected by the instantaneous heat of the laser in the thickness direction Q of the silicon substrate, resulting in a melting and recondensation reaction process. This leads to protrusions and depressions on the first surface of the transport layer. The protrusions and depressions can be understood as the first surface being uneven, with undulations. In the thickness direction Q of the silicon substrate, the protrusions are further away from the silicon substrate, and the depressions are closer to the silicon substrate. For the same opening: the agglomerates of the third seed region and / or the agglomerates of the first seed region are at least distributed at the protrusions on the first surface. That is, in the same opening, the reactivity is higher at the protrusions on the first surface of the transport layer, and metal particle nuclei are preferentially generated at and near the protrusions, making it easier for metal particle agglomerates to accumulate at or near the protrusions on the first surface. Specifically, at or near the first surface protrusion, which is further away from the silicon substrate, the film quality of the transport layer may be poor during the formation of the transport layer. By setting a third seed region and having the first seed region cluster at the protrusion, the problem of uneven electrical performance caused by the poor film quality of the transport layer at the protrusion can be compensated, and the battery performance can be further improved.

[0171] For example, in the same opening: the transport layer is away from the first surface of the silicon substrate 1. The dashed ellipse in Figure 13 shows a protrusion location. The agglomerates of the third seed region and the first seed region are more likely to be distributed at the protrusion location shown by the dashed ellipse in Figure 13.

[0172] In some embodiments, referring to FIG14, the opening of the aforementioned passivation antireflection layer includes an edge region and a middle region located inside the edge region. It can be considered that for the same opening, the edge region is closer to the remaining passivation antireflection layer, while the middle region is farther away from the remaining passivation layer. For example, in the embodiment using a Gaussian laser spot to open the opening, the energy in the middle of the Gaussian spot is higher, the middle of the transport layer is heated more and the melting phenomenon is more severe, resulting in the surface roughness of the transport layer at the middle position of the opening being reduced due to melting and collapse. Conversely, the surface roughness of the transport layer near the edge of the opening is greater, which, from the perspective of cross-sectional morphology, means that the undulations are more obvious, the number of protrusions is greater, and the protrusions are higher. Therefore, the size of at least part of the aggregates in the third seed region of the edge region in the same opening is larger than the size of the aggregates in the third seed region of the middle region, that is to say, the aggregates in the third seed region are more likely to accumulate in the edge region of the opening. Specifically, due to the presence of the remaining passivation and antireflection layer, the contact area or contact reliability between the transport layer and the electrode structure or collector grid in the edge region of the opening is relatively weak. In this application, the agglomerates in the third seed region of the edge region of the opening are larger in size, thereby enhancing the electrical connection between the transport layer and the electrode structure or collector grid in the edge region of the opening, further improving the current collection and conduction effect of the solar cell, and improving the performance of the cell.

[0173] In this application, the size of the agglomerate may refer to at least one of the following: the length, width, and height of the agglomerate; the area of ​​the agglomerate projected onto the first surface; or the volume of the agglomerate.

[0174] It should be noted that the relative sizes of the central and edge regions are not limited for the same opening. When comparing the sizes of aggregates in the central and edge regions, the comparison can be limited to the same area or volume. This unit volume can be set with reference to the opening area and the opening depth. For example, the unit volume could be 1 / 20, 1 / 10, 1 / 9, or 1 / 8 of the opening area. For instance, when the opening area is on the order of square micrometers, the unit volume could be 1μm × 1μm × opening depth, 0.5μm × 0.1μm × opening depth, 0.5μm × 0.5μm × opening depth, 0.8μm × 1μm × opening depth, or 1μm × 1.2μm × opening depth. Here, the opening area refers to the area of ​​the projection of the opening onto the adjacent structure when illuminated by light parallel to the thickness direction Q of the silicon substrate. The unit area here can be 1μm×1μm, 0.5μm×0.1μm, 0.5μm×0.5μm, 0.8μm×1μm, 1μm×1.2μm, etc.

[0175] For the same opening, the difference between the size of a single aggregate in the edge region and the size of a single aggregate in the middle region is not limited. It should be noted that, in this application, when the sizes of aggregates at different locations in the edge region differ for the same opening, the size of the aggregates in the edge region can be the minimum size, maximum size, or arithmetic mean of two or more aggregates in the same opening and edge region. The method for determining the size of aggregates in the middle region of the same opening is the same as the method for determining the size of aggregates in the edge region of the same opening, and will not be repeated to avoid repetition.

[0176] In some embodiments, referring to FIG15, the opening of the aforementioned passivation antireflection layer includes an edge region and a middle region located inside the edge region. For the same opening, the size of at least a portion of the aggregates in the first seed region within the edge region is larger than the size of the aggregates in the first seed region within the middle region. This also enhances the electrical connection between the transport layer and the current collector grid lines in the edge region of the opening, further improving the current collection and conduction effect of the solar cell and enhancing the performance of the cell.

[0177] In some embodiments, referring to Figures 9, 13, and 17, for the same opening, the height H1 of the seed layer in the edge region is greater than the height H2 of the seed layer in the middle region. This enhances the electrical connection between the transport layer and the electrode structure or current collector grid in the edge region of the opening, further improving the current collection and conduction effect of the solar cell and thus improving the cell's performance. Figure 17 can be a top-view SEM image of the second seed layer within the opening.

[0178] It should be noted that, in this application, when the height of the seed layer varies at different locations within the same opening and edge region, the height of the seed layer within the same opening and edge region can be the minimum height, maximum height, or arithmetic mean of the heights of the seed layer at two or more locations within the same opening and edge region. The method for determining the height of the seed layer in the middle region of the same opening is the same as the method for determining the height of the seed layer in the edge region of the same opening, and will not be repeated here to avoid repetition.

[0179] In some embodiments, for the same opening, the difference between the height H1 of the seed layer in the edge region and the height H2 of the seed layer in the middle region is less than or equal to 500 nm. Specifically, if this difference is too large, that is, if the height difference between the seed layer in the edge region and the seed layer in the middle region is too large, it will affect the setting of structures such as slurry layers and interconnects thereon, and will be detrimental to obtaining a base metal layer with uniform performance thereon.

[0180] Furthermore, for the same opening, the difference between the height H1 of the seed layer in the edge region and the height H2 of the seed layer in the middle region is 30nm to 50nm. Specifically, if the difference is too small, the effect of electrical connection between the transport layer and the electrode structure or collector grid line in the edge region of the opening is not sufficiently enhanced. If the difference is too large, it will affect the setting of the paste layer and the like. Therefore, if the difference is within the above range, it will not only enhance the effect of electrical connection between the transport layer and the electrode structure or collector grid line in the edge region of the opening, but also will not affect the setting of the paste layer and the like.

[0181] For example, for the same opening, the difference between the height H1 of the seed layer in the edge region and the height H2 of the seed layer in the middle region can be 30nm, 40nm, 50nm, 60nm, 80nm, 100nm, 120nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, or 500nm.

[0182] In some embodiments, the third seed region and the first seed region are made of different materials and have different characteristics, which facilitates the third seed region and the first seed region to achieve the aforementioned corresponding functions.

[0183] In some embodiments, the material of the third seed region is selected from at least one of platinum, gold, silver, cobalt, and indium. On the one hand, the transport layer usually contains silicon, and the above materials can be quickly reduced by the silicon-containing transport layer, which can not only reduce damage to the transport layer and silicon substrate, but also reduce the reaction cost and further reduce the battery cost. On the other hand, the third seed region of the above materials can play a greater activating role on the first seed region.

[0184] In some embodiments, when the material of the first seed region is selected from the aforementioned materials, the first seed region of the aforementioned materials is more likely to be drawn to the third seed region for nucleation and growth in its vicinity, thereby enabling the third seed region and the first seed region to be more uniformly and dispersedly distributed on the first surface of the transport layer away from the silicon substrate.

[0185] In some embodiments, referring to FIG9, the passivation antireflection layer has a gap 7 near the opening (shown by the dashed elliptical box in FIG9), and a third seed region and / or a first seed region exist in the gap 7. Specifically, the gap 7 near the opening in the passivation antireflection layer, i.e., the edge of the opening, is filled with the third seed region and / or the first seed region. This enhances the electrical connection between the transport layer and the electrode structure or current collector grid in the edge region of the opening, further improving the current collection and conduction effect of the solar cell and improving the performance of the cell.

[0186] In some embodiments, for the aforementioned bifacial solar cells and back-contact solar cells, where a second seed layer 47 and a first seed layer 45 are simultaneously included in a single cell, referring to Figures 9 and 10, and Figures 14 and 16, the opening of the aforementioned passivation antireflection layer includes an edge region and a middle region located inside the edge region. It can be considered that for the same opening, the edge region is closer to the remaining passivation layer, while the middle region is farther from the remaining passivation layer. The edge region and middle region here can be referred to in the aforementioned descriptions; to avoid repetition, they will not be repeated. Based on the fact that the polarity or doping type of the second transport layer and the silicon substrate 1 are the same, the size of at least a portion of the agglomerates in the edge region of the third seed region in the opening corresponding to the second transport layer is larger than the size of the agglomerates in the edge region of the third seed region in the opening corresponding to the first transport layer. Specifically, the second transport layer and the silicon substrate have the same doping type, while the first transport layer and the silicon substrate have different doping types. More specifically, the second transport layer can correspond to an N-type transport layer, and the first transport layer can correspond to a P-type transport layer. N-type transport layers are easier to achieve higher doping concentrations, resulting in faster carrier generation and stronger conductivity. Therefore, in the opening corresponding to the second transport layer in this application, at least some of the agglomerates in the edge region are larger in size, facilitating the formation of a higher-quality second current collector line, allowing for faster current extraction and further improving battery performance. The distribution of the second metal particle agglomerates is similar and will not be elaborated further.

[0187] It should be noted that the size of the aggregates can be referred to the aforementioned relevant records, and will not be repeated here to avoid repetition.

[0188] In some embodiments, for the aforementioned bifacial solar cells and back-contact solar cells, when a second seed layer 47 and a first seed layer 45 are included in a single cell, based on the fact that the polarity or doping type of the second transport layer and the silicon substrate 1 are the same, referring to Figures 9 and 10, and Figures 14 to 16, the opening of the aforementioned passivation antireflection layer includes an edge region and a middle region located inside the edge region. The height H1 of the second seed layer 47 in the edge region corresponding to the opening of the second transport layer is greater than the height H3 of the first seed layer 45 in the edge region corresponding to the opening of the first transport layer. The above situation is because the charge carriers of the second transport layer are majority carriers and have stronger conductivity and transport capabilities. After the main elements of the slurry layer diffuse into the second transport layer, it is easy to cause more severe charge carrier annihilation. Therefore, it is necessary to set a higher or thicker seed layer in the edge region of the opening of the second transport layer to block the diffusion of base metals.

[0189] In some embodiments, where the electrode structure of the solar cell further includes a bus electrode, the base metal layer and the bus electrode can be fabricated simultaneously. The base metal layer can be fabricated using methods such as printing.

[0190] This application also provides a photovoltaic module comprising multiple series-connected and / or parallel-connected cell strings, each cell string including an electrical connector and any of the aforementioned solar cells. The electrical connector electrically connects at least two of the aforementioned solar cells. The electrical connector mentioned in this application may be a solder strip, a conductive electrical connector, etc.

[0191] For example, in a battery string, an electrical connector electrically connects the second collector grid line of one solar cell to the first collector grid line of the other solar cell in two adjacent solar cells.

[0192] This application also provides a method for preparing a solar cell, comprising the following steps.

[0193] Step 101: Provide a silicon substrate; the silicon substrate has opposite sides in the thickness direction.

[0194] Step 102: Prepare a transport layer on at least one side of the silicon substrate.

[0195] The transport layer can be formed using methods such as LPCVD (low-pressure chemical vapor deposition), and there are no restrictions on the specific formation method of the transport layer.

[0196] Step 103: Prepare a passivation antireflection layer on the side of the transport layer away from the silicon substrate and form several openings in the passivation antireflection layer.

[0197] The opening can be made using laser or wet etching, with no specific limitation. For example, picosecond laser engraving can be used to engrave the passivation antireflection layer according to the designed collector grid pattern to form the required micron-scale trench structure.

[0198] Step 104: Preprocess the transport layer at the opening, and set a seed layer and a slurry layer on the side of the transport layer at the opening away from the silicon substrate. The seed layer includes: a first seed region and a second seed region; the first seed region is closer to the silicon substrate; the second seed region at least partially encloses the first seed region, and the slurry layer includes base metal.

[0199] The pretreatment here is used to enhance the activity of the transport layer at the opening. The second seed region can be formed by redox reaction or electrochemical reaction, while the first seed region provides a transition during the formation of the second seed region. Compared with electrochemical reaction, the redox reaction method can further reduce costs in preparing the second seed region. The paste layer can be formed by screen printing followed by drying. The paste layer can be formed using low-temperature silver-coated copper paste, low-temperature copper paste, low-temperature nickel paste, etc. The use of low-temperature silver-free metallization technology for the paste layer avoids the price and supply disadvantages of silver paste products, saves the resource consumption caused by high-temperature technology, and avoids the thermal effects introduced by high-temperature technology, thus effectively reducing production costs.

[0200] More specifically, the steps of forming the first seed region and the third seed region may include: placing an activation liquid containing a first metal cation on the first surface of the exposed transport layer, wherein the first metal cation is reduced to the third seed region; depositing the first seed region on the first surface of the exposed transport layer, wherein the projections of the first seed region and the third seed region on the first surface at least partially overlap or are close in position; and forming the seed layer by a redox reaction on the exposed transport layer.

[0201] Specifically, an activation solution containing a first metal cation can be applied to the exposed first surface of the transport layer using methods such as coating. The formation of the third seed region mainly consists of two stages: a nucleation stage and a growth stage. In the nucleation stage, because the Fermi level of the third seed region is higher than that of the transport layer, the first metal cation in the activation solution provides holes. The silicon or other materials in the transport layer in contact with these third seed regions are randomly oxidized, while the first metal cations in the activation solution gain electrons from the silicon or other materials in the transport layer in contact with them, thus being reduced to the third seed region and nucleating on the surface of the transport layer. In the nucleation stage, the size of the third seed region is very small, but its adhesion is relatively uniform. In the growth stage, some third seed regions already exist on the first surface of the transport layer within the opening. Because these third seed regions have good conductivity, more negative ions in the transport layer rapidly accumulate on the surface of the third seed regions, further causing the first metal cations in the activation solution to rapidly accumulate on the surface of the third seed regions, thus gradually growing.

[0202] The formation of the first seed region also belongs to the pre-deposition process. In this application, the third seed region and the first seed region reduce the chemical reaction potential energy of the second seed region of the seed layer, promote the formation of the second seed region of the seed layer, and, under the promoting effect of the third seed region and the first seed region, the thickness of the second seed region of the seed layer is relatively more uniform and the electrical performance is relatively better.

[0203] This application also provides a photovoltaic module, including: an electrical connector and any of the aforementioned solar cells. The electrical connector serves as a conductive interconnect; for example, it can be a solder strip or a conductive backsheet, etc., and there is no specific limitation on the electrical connector. The electrical connector is electrically connected to the collector grid lines of at least two of the aforementioned solar cells. This connection can be direct or indirect, and there is no limitation on either method. The electrical connector can electrically connect the positive collector grid line of one of two adjacent aforementioned solar cells to the negative collector grid line of the other solar cell, achieving conductive interconnection.

[0204] The photovoltaic module may also include encapsulating films located on both sides of the solar cells, and no specific limitations are made on other structures in the photovoltaic module.

[0205] It should be noted that in this application, the photovoltaic module, solar cell and the method for preparing the solar cell are related to each other and can achieve the same or similar beneficial effects. To avoid repetition, they will not be described in detail here.

[0206] The present application will be further explained below with reference to specific embodiments.

[0207] Example

[0208] The first step is to provide a silicon substrate, which includes a backlighting surface and a light-facing surface opposite each other in its thickness direction Q. The backlighting surface includes a first conductive region and a second conductive region, and an isolation region may exist between the first conductive region and the second conductive region to avoid short circuits.

[0209] The second step is to prepare the transport layer. Specifically, a P-type transport layer 2 is prepared on the side of the first conductive region away from the silicon substrate on the back surface of the silicon substrate, and an N-type transport layer 3 is prepared on the side of the second conductive region away from the silicon substrate. The N-type transport layer 3 includes N-type doped polycrystalline silicon.

[0210] The third step is to prepare a back passivation antireflection layer on the side of the N-type transport layer 3 and the P-type transport layer 2 that is away from the silicon substrate.

[0211] The fourth step involves using picosecond laser engraving technology to engrave the passivation and antireflection layer according to the designed collector grid pattern, forming the required micron-level trench structure, which is the opening.

[0212] The fifth step is to preprocess the transport layer at the opening, and set a first seed region, a second seed region, and a paste layer on the side of the transport layer at the opening away from the silicon substrate, and simultaneously set a bus gate line, with the second seed region wrapping the first seed region.

[0213] The first seed region 41 has a discontinuously distributed transport layer on the side away from the silicon substrate at an opening. The opening is approximately 80 μm wide, and along the width direction M of the opening, in a cross-section perpendicular to the thickness direction of the silicon substrate, the first seed region 41 has 159 discontinuous portions. The thickness of each discontinuous portion in the first seed region is less than or equal to 200 nm, and the average thickness of the discontinuous portion on the side of the transport layer away from the silicon substrate at the opening is approximately 40 nm. The second seed region 42 is prepared using a redox method, and the paste layer 43 and busbars are prepared by screen printing and drying at a temperature of 200 °C. The paste layer 43, the second seed region 42, and the busbars all contain base metals. The non-metallic element in the second seed region 42 includes phosphorus, which accounts for 5% of the mass of the second seed region 42. On one side of the opening, along the width direction M of the opening, there is a gap 7 between the transport layer and the passivation anti-reflection layer, and both the first and second seed regions extend into the gap 7. On one side of the opening, along the width direction M of the opening and in a direction away from the opening, the extension length of the gap is approximately 3 μm. Along the direction away from the silicon substrate: the second seed region at least partially covers the passivation antireflection layer, and the second seed region 42 extends beyond the adjacent passivation antireflection layer; the height d1 of the portion of the second seed region 42 extending beyond the adjacent passivation antireflection layer is approximately 500 nm. The structure of the solar cell formed in the embodiment is generally shown with reference to FIG1.

[0214] The solar cell formed in the embodiment achieves good contact performance between the metal and the silicon substrate under low-temperature conditions (below 300°C, such as around 200°C), without the need for high-temperature furnace sintering, and introduces very little heat-affected zone into the solar cell. The solar cell formed in the embodiment was measured under national standard conditions, and the contact resistance of the first conductive region was less than or equal to 0.8 mΩ × cm. 2 The contact resistance of the second conductive region is less than or equal to 0.1 mΩ × cm. 2 This is superior to solar cells using related technologies.

[0215] It should be noted that the various embodiments provided in this application may exist independently or in combination without contradiction, and all are within the protection scope of this application.

[0216] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0217] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims. All of these forms are within the protection scope of this application.

Claims

1. A solar cell, wherein, include: A silicon substrate having opposing sides in the thickness direction of the silicon substrate; A transport layer and a passivation antireflection layer are stacked on at least one side of the silicon substrate; The passivation antireflection layer has several openings; The collector grid line contacts the transmission layer through the opening; The collector grid line includes a seed layer and a paste layer. The seed layer includes a first seed region and a second seed region, both of which are disposed on the side of the transport layer away from the silicon substrate, with the first seed region being closer to the silicon substrate. The second seed region at least partially encloses the first seed region. The paste layer is disposed on the side of the second seed region away from the silicon substrate, and the paste layer includes base metal.

2. The solar cell according to claim 1, wherein, The first seed region is located at the opening position, and the first seed region includes one or more discontinuous portions.

3. The solar cell according to claim 2, wherein, At least one cross section along or perpendicular to the extension direction of the collector gate line, the cross section being perpendicular to the thickness direction of the silicon substrate, wherein the first seed region has 80 to 500 discontinuous portions within the cross section; And / or, the thickness of the first seed region is less than or equal to the thickness of the second seed region.

4. The solar cell according to claim 2 or 3, wherein, The thickness of the discontinuous portions is not entirely the same; and / or, the thickness of the discontinuous portions is less than or equal to 200 nm.

5. The solar cell according to claim 1, wherein, The first seed region includes at least one of zinc, platinum, gold, silver, chromium, rhodium, indium, palladium, and tin.

6. The solar cell according to claim 1, wherein, At the edge of the opening, there is a gap between the transport layer and the passivation antireflection layer, and the first seed region and / or the second seed region exist in the gap.

7. The solar cell according to claim 6, wherein, Along the direction opposite to the opening, the extension length of the gap is less than or equal to 5 μm.

8. The solar cell according to claim 1, wherein, Along a direction away from the silicon substrate, the second seed region at least partially covers the passivation antireflection layer.

9. The solar cell according to claim 1, wherein, The second seed region includes: metallic elements and / or non-metallic elements.

10. The solar cell according to claim 9, wherein, The metallic element is selected from at least one of the following: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, niobium, ruthenium, indium, zinc, tantalum, and vanadium.

11. The solar cell according to claim 9, wherein, The non-metallic element includes at least one of phosphorus and boron.

12. The solar cell according to claim 11, wherein, The phosphorus content in the second seed region is 2% to 8% by mass.

13. The solar cell according to claim 1, wherein, The transport layer has a protrusion on the side opposite to the silicon substrate, and the first seed region is gathered on the protrusion.

14. The solar cell according to any one of claims 1 to 13, wherein, The seed layer further includes: a third seed region, wherein the second seed region encloses at least a portion of the third seed region; the surface of the transport layer away from the silicon substrate is a first surface, and the projections of the third seed region and the first seed region onto the first surface at least partially overlap or are located close to each other; and / or, The materials of both the third seed region and the first seed region are different from the main elements of the second seed region and the main elements of the slurry layer.

15. The solar cell according to claim 14, characterized in that, The third seed region is distributed on the first surface in the form of scattered points and / or aggregates, and / or the first seed region is distributed on the first surface in the form of scattered points and / or aggregates.

16. The solar cell according to claim 15, characterized in that, For the same opening: The number of the third seed regions is greater than the number of the first seed regions; and / or, The area ratio of the third seed region is greater than the area ratio of the first seed region; and / or, The weight percentage of the third seed region is greater than the weight percentage of the first seed region; and / or, The distribution trend of aggregates in the third seed region is the same as that of aggregates in the first seed region.

17. The solar cell according to claim 15, characterized in that, For the same opening: The aggregates in the third seed region and / or the aggregates in the first seed region are at least distributed in locations with higher surface roughness in the first surface; and / or, In the thickness direction of the silicon substrate, the first surface has protrusions and depressions, and the agglomerates of the third seed region and / or the agglomerates of the first seed region are at least distributed at the protrusions of the first surface.

18. The solar cell according to claim 15, characterized in that, The opening includes an edge region and a middle region located inside the edge region; for the same opening: The size of at least a portion of the aggregates in the third seed region within the edge region is larger than the size of the aggregates in the third seed region within the middle region; and / or, The size of at least a portion of the aggregates in the first seed region within the edge region is larger than the size of the aggregates in the first seed region within the middle region.

19. The solar cell according to claim 15, characterized in that, The transport layer is divided into a first transport layer and a second transport layer with different polarities; the passivation and anti-reflection layer is divided into a first passivation and anti-reflection layer and a second passivation and anti-reflection layer; the collector gate line is divided into a first collector gate line and a second collector gate line; the second transport layer has the same doping type as the silicon substrate, while the first transport layer has a different doping type than the silicon substrate.

20. The solar cell according to claim 19, characterized in that, The opening includes an edge region and a middle region located inside the edge region; The size of at least a portion of the aggregates in the third seed region within the edge region of the opening corresponding to the second transport layer is larger than the size of the aggregates in the third seed region within the edge region of the opening corresponding to the first transport layer; and / or, The size of at least a portion of the aggregates in the first seed region within the edge region of the opening corresponding to the second transmission layer is larger than the size of the aggregates in the first seed region within the edge region of the opening corresponding to the first transmission layer.

21. The solar cell according to claim 14, characterized in that, The opening includes an edge region and a middle region located inside the edge region; for the same opening, the height of the seed layer in the edge region is greater than the height of the seed layer in the middle region.

22. The solar cell according to claim 19, characterized in that, The opening includes an edge region and a middle region located inside the edge region; The height of the seed layer in the edge region of the opening corresponding to the second transmission layer is greater than the height of the seed layer in the edge region of the opening corresponding to the first transmission layer.

23. The solar cell according to claim 14, characterized in that, There is a gap between the transport layer and the passivation antireflection layer, and the third seed region and / or the first seed region also exist in the gap.

24. The solar cell according to any one of claims 14 to 23, characterized in that, The third seed region is made of a different material than the first seed region; The material of the third seed region is selected from at least one of platinum, gold, silver, cobalt, and indium.

25. A photovoltaic module, wherein, include: Electrical connectors and solar cells according to any one of claims 1 to 24; The electrical connector is electrically connected to the collector grid lines in at least two of the solar cells.

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