Solar cell and method of manufacturing the same

Abstract

The application provides a solar cell and a preparation method thereof, and belongs to the technical field of semiconductors. The solar cell comprises: a semiconductor substrate having opposite first and second surfaces; a first passivation contact layer on the first surface of the semiconductor substrate; a first protective layer on the surface of the first passivation contact layer away from the semiconductor substrate, the first protective layer being provided with a slot penetrating in the thickness direction and a protective layer reserved part distributed in the slot; and a first electrode on the surface of the first protective layer away from the semiconductor substrate, at least part of the first electrode being located in the slot. The solar cell and the preparation method can improve the passivation effect and the electrode contact performance.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically, to a solar cell and a method for its fabrication. Background Technology

[0002] With the development of solar cell technology, solar cells have been classified into various types based on different cell structures. These different types of solar cells generally require metallization after passivation coating to fabricate electrodes on the passivation contact layer. The mainstream metallization methods include screen printing, electroplating, and vapor deposition.

[0003] However, these approaches have many challenges that are difficult to overcome. For example, the precision and quality of screen printing are difficult to guarantee, while the cost of using printing or photolithography to pattern electrodes during electroplating or vapor deposition is relatively high. Using laser film opening to pattern electroplating can easily damage the battery surface, and the electrodes have poor adhesion to the battery surface. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, this application provides a solar cell.

[0005] To achieve the above objectives, the technical solution of this application is as follows:

[0006] According to one aspect of this application, a solar cell is provided, comprising: a semiconductor substrate having opposing first and second surfaces; a first passivation contact layer located on the first surface of the semiconductor substrate; a first protective layer located on the surface of the first passivation contact layer away from the semiconductor substrate, the first protective layer having a through-groove in the thickness direction and protective layer pre-reserved portions distributed within the through-groove; and a first electrode located on the surface of the first protective layer away from the semiconductor substrate, at least a portion of the first electrode being located within the through-groove.

[0007] According to another embodiment of this application, a method for fabricating a solar cell is provided, comprising: sequentially forming a first passivation contact layer and a first protective layer on a first surface of a semiconductor substrate; irradiating a grooved region of the first protective layer with a laser, such that the first protective layer located in the laser irradiation region forms a groove and a protective layer reserved portion distributed in the groove; and depositing a first electrode in the groove of the first protective layer.

[0008] According to the embodiments of this application, the protective layer is irradiated with a laser, which can perform local grooving on the protective layer with high precision, so that there is a reserved part of the protective layer at the grooving position. On the one hand, it can ensure that the passivation contact layer under the protective layer is not damaged by the laser, so as to achieve a good passivation effect. On the other hand, using the reserved part of the protective layer as the electrode growth point can improve the adhesion of the electrode to the battery surface. Attached Figure Description

[0009] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0010] Figure 1 This is a partial structural schematic diagram of a solar cell according to an embodiment of this application;

[0011] Figure 2 This is a schematic diagram of the state of the reserved portion of the protective layer at the groove position of the first protective layer on the velvet area according to an embodiment of this application;

[0012] Figure 3A This is a scanning electron microscope (SEM) top view of the reserved portion of the protective layer at the first protective layer slot location in an embodiment of this application.

[0013] Figure 3B This is a SEM cross-sectional view of the reserved portion of the protective layer at the first protective layer slot location in an embodiment of this application;

[0014] Figure 3C This is a top SEM view of the reserved portion of the protective layer at the first protective layer slot location in the comparative embodiment of this application;

[0015] Figure 4 This is a schematic diagram of the state of the reserved portion of the protective layer at the first protective layer groove position on the polishing area, according to another embodiment of this application.

[0016] Figure 5A This is a SEM top view of the reserved portion of the protective layer at the first protective layer slot location according to another embodiment of this application;

[0017] Figure 5B This is a SEM top view of the first reserved portion at the first protective layer slot location according to another embodiment of this application;

[0018] Figure 6A This is a schematic diagram of the first electrode structure at the slotted position of the first protective layer in an embodiment of this application;

[0019] Figure 6B This is a schematic diagram of the first electrode structure at the slotted position of the first protective layer according to another embodiment of this application;

[0020] Figure 7This is a schematic diagram of the structure of a solar cell according to another embodiment of this application;

[0021] Figure 8A This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application;

[0022] Figure 8B This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application;

[0023] Figure 9 This is a SEM image of a solar cell in the first region according to another embodiment of this application;

[0024] Figure 10 This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application;

[0025] Figure 11 This is a schematic flowchart of a method for preparing a solar cell according to an embodiment of this application;

[0026] Figure 12 This is a schematic diagram of the fabrication process of the solar cell according to an embodiment of this application;

[0027] Figure 13 These are SEM images of electrodes deposited by electroplating at different electroplating times according to embodiments of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0029] In the following detailed description, numerous specific details are set forth for ease of explanation to provide a thorough understanding of the embodiments of this application. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0031] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0032] In this application, the relative position between two components (e.g., a membrane or region), as referred to by terms such as "above," "on," or "above," can mean that the two components are in direct contact or that they are not in direct contact. Similarly, the relative position between two components, as referred to by terms such as "below," "under," or "below," can mean that the two components are in direct contact or that they are not in direct contact. For example, when one component (e.g., a membrane or region) is referred to as "on another component," it can be directly on the other component, or there may be other components between them. On the other hand, when a component is referred to as "directly on another component," there are no components between them. Furthermore, when one component is referred to as "on another component," the two components have a vertical relationship in the planar view, and this component can be above or below the other component, thus this vertical relationship depends on the orientation of the device.

[0033] Compared to screen printing, it is easier to deposit electrodes with better morphology and quality on the passivation contact layer through electroplating or vapor deposition. However, the protective layer needs to be patterned before the electrode is deposited. The commonly used printing or photolithography patterning method has the disadvantage of complex process, and the subsequently deposited electrode also has the problem of poor adhesion, which can easily lead to detachment and poor electrode contact, affecting the use of the battery.

[0034] In realizing the concept of this application, it was discovered that when using laser grooving followed by electroplating or vapor deposition of electrodes, the protective layer can be structured by reasonably controlling the laser energy. This allows for more precise local grooving of the protective layer, resulting in a reserved portion of the protective layer at the grooving location. This reserved portion can protect the passivation contact layer from laser damage, ensuring that the passivation contact layer maintains a good morphology and passivation effect. At the same time, it helps to increase the adhesion of the electrode and improve electrode contact.

[0035] Specifically, according to one embodiment of this application, a solar cell is provided. Figure 1 This is a partial structural diagram of the solar cell according to an embodiment of this application, as shown below. Figure 1 As shown, the solar cell includes a semiconductor substrate 1, a first passivation contact layer 2, a first protective layer 3, and a first electrode 4, wherein: the semiconductor substrate 1 has a first surface 1a and a second surface 1b opposite to each other; the first passivation contact layer 2 is located on the first surface 1a of the semiconductor substrate 1; the first protective layer 3 is located on the surface of the first passivation contact layer 2 away from the semiconductor substrate 1, and the first protective layer 3 is provided with a groove 31 extending through in the thickness direction, and protective layer pre-reserved portions (not shown in the figure) distributed in the groove 31; and the first electrode 4 is located on the surface of the first protective layer 3 away from the semiconductor substrate 1, at least a portion of the first electrode 4 is located in the groove 31. It should be noted that, unless otherwise specified, "thickness direction" generally refers to the direction of extension perpendicular to the surface of the semiconductor substrate.

[0036] According to embodiments of this application, the semiconductor substrate 1 can be an N-type or P-type crystalline silicon substrate, such as a semiconductor material selected from monocrystalline silicon, polycrystalline silicon, and microcrystalline silicon, preferably an N-type or P-type monocrystalline silicon substrate. The cell conversion efficiency based on a monocrystalline silicon substrate is higher than that of other types, such as polycrystalline silicon cells. An N-type crystalline silicon substrate is obtained by introducing donor impurities such as group VA elements like phosphorus (P), arsenic (As), or antimony (Sb) into these semiconductor materials, or a P-type crystalline silicon substrate is obtained by introducing acceptor impurities such as group IIIA elements like boron (B), aluminum (Al), or gallium (Ga).

[0037] According to embodiments of this application, the first surface 1a of the semiconductor substrate 1 can be either the front or back of the battery, without limitation. Generally, the front of the battery serves as the light-receiving surface and the back as the backlight surface, or it can be light-receiving on both sides, in which case both the front and back serve as light-receiving surfaces. The first surface 1a of the semiconductor substrate 1 can be a polished area with a pyramidal base structure or a textured area with a pyramidal structure, without particular limitation.

[0038] According to the embodiments of this application, the first passivation contact layer 2 of this application can adopt a variety of passivation contact structures, such as tunneling oxide passivation structures, heterojunction structures, etc. Therefore, the types of solar cells applicable to this application can be bifacial cells, such as bifacial heterojunction (Heterojunction with Intrinsic Thin-layer, abbreviated as HJT) cells, tunneling oxide passivated cell (Tunnel Oxide Passivated Cell, abbreviated as TOPCon) cells, etc., or back contact cells, such as back contact heterojunction (Heterojunction Back Contac, abbreviated as HBC) cells, hybrid HBC cells such as hybrid cells combining TBC (TopCon-BackContact) and HJT, etc., as long as the cell type that needs to improve the electrode contact performance should be applicable.

[0039] According to the embodiments of this application, the first protective layer 3 of this application can be a single layer or a stacked structure, and its material can be selected from at least one of alumina, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, etc., which can provide protection for the battery structure under the first protective layer 3, and can also play a passivation and anti-reflection effect.

[0040] According to embodiments of this application, the applicant discovered through experiments that when electroplating or vapor deposition is performed after laser grooving to fabricate electrodes, by reasonably controlling the laser energy, local grooving can be performed on the first protective layer. Furthermore, some protective layer residue, i.e., a protective layer pre-reserved portion, can remain at the grooving location of the first protective layer. This ensures that the first passivation contact layer under the first protective layer is not damaged by the laser, thus ensuring a good passivation effect. Simultaneously, using the protective layer pre-reserved portion as an electrode growth point improves the adhesion of the electrode to the battery surface, thereby enhancing electrode contact stability. After locally grooving the first protective layer by laser irradiation, an additional wet etching step can be added to clean the grooving location. Of course, under suitable laser energy conditions, this wet etching step can be omitted to achieve a good grooving morphology. For example, under picosecond laser conditions, the laser energy density can be adjusted to 2.6 J / cm². 2 .

[0041] To facilitate the explanation of the structure of the protective layer reserved area, Figure 2 This is a schematic diagram of the state of the reserved portion of the protective layer at the groove position of the first protective layer on the velvet area according to an embodiment of this application; as shown Figure 1 and 2As shown, taking the first surface 1a as an example with a textured area containing multiple pyramid structures, a protective layer reserved portion 32 is distributed in the groove 31. This distribution ensures that the first electrode 4 located in the groove 31 maintains good contact with the first passivation contact layer 2, and also ensures contact between the first electrode 4 and the protective layer reserved portion 32, thereby improving the adhesion of the first electrode.

[0042] According to embodiments of this application, optionally, as Figure 2 As shown, the protective layer reserved portion 32 may include a plurality of first reserved portions 321. At least some of the first reserved portions 321 may have a porous structure, and / or the first reserved portions may have a sheet-like structure. This configuration can further increase the contact area between the first electrode 4 and the protective layer reserved portion 32, thereby improving the adhesion of the first electrode. At the same time, a portion of the first reserved portion 321 may form a gap space with the first passivation contact layer 2. That is, the edge portion of the first reserved portion 321 is raised in a direction away from the first passivation contact layer 2 to form the gap space. When the first electrode 4 is subsequently formed, its seed layer or first electrode layer can fill the gap space.

[0043] Alternatively, at least one pore 321a in the porous structure can be a through hole penetrating the first reserved portion 321, allowing the first electrode to pass through the through hole and contact the first passivation contact layer 2. This configuration improves the adhesion of the first electrode while simultaneously ensuring good electrical contact between the first electrode 4 and the first passivation contact layer 2.

[0044] According to an embodiment of this application, similarly, taking a first surface 1a having a textured area containing multiple pyramid structures as an example, along the direction away from the first surface 1a, the pyramid structure includes a base 12 and a top 11; the distribution density of the first reserved portion 321 located on the base 12 is greater than the distribution density of the first reserved portion 321 located on the top 11. Here, "distribution density" can be the number of first reserved portions 321 per unit cross-sectional area or per unit top-view area on the top 11 or base 12, or the area ratio of the first reserved portions 321 per unit cross-sectional area or per unit top-view area on the top 11 or base 12.

[0045] This configuration, by retaining more of the first reserved portion 321 on the bottom 12 of the tower, ensures that the first passivation contact layer on the bottom 12 maintains a good passivation effect and is less prone to damage. On the top 11 of the tower, the relatively fewer first reserved portions 321 facilitate edge contact and reduce contact resistance. This achieves a balance between good contact and passivation effect.

[0046] This application does not impose any limitations on the measurement of distribution density. Those skilled in the art can determine it using conventional methods. For example, the number of the first reserved portion can be measured using a scanning electron microscope (SEM). Since the first reserved portion differs significantly from other structures in the SEM test results of cross-sectional or top-view images, it can be directly found on the SEM test image. The cross-sectional image can be an SEM test image obtained after cutting the cell at a certain angle to the direction of the groove extension, such as 90°. Alternatively, the top-view image can be an SEM test image obtained after measuring the surface of the cell after partial grooving or after the first electrode has been peeled off. At least one area of ​​the same size is taken above the top or bottom of the tower, and the number of the first reserved portions observed in each area is counted and averaged to obtain the number of the first reserved portions.

[0047] For example, the area ratio of the first reserved portion can be obtained through SEM measurement. The first reserved portion can be found in the SEM test images of the cross-sectional view or top view. At least one area is selected above the top or bottom of the tower, and then the total area of ​​the first reserved portion observed in each area is calculated using image processing software. The area ratio of the total area of ​​the first reserved portion in the selected area is calculated and averaged, which is the area ratio of the first reserved portion.

[0048] According to embodiments of this application, optionally, as shown below... Figure 2 As shown, the protective layer reserved portion 32 may further include a plurality of second reserved portions 322, which are protruding particles extending from the surface of the first passivation contact layer 2 in a direction away from the first surface 101a. It is understood that these plurality of second reserved portions 322 are distinct from the first reserved portion 321 because they do not have obvious pores. Based on the arrangement of the second reserved portions 322, on the one hand, the first passivation contact layer can be protected from laser damage, and on the other hand, the adhesion of the first electrode can be improved to maintain good contact of the first electrode.

[0049] Further optionally, the particle size of the protruding particles is 50~300 nm, for example, it can be 50 nm, 100 nm, 130 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, etc. Protruding particles of suitable size are beneficial in increasing the adhesion of the first electrode without affecting the passivation effect of the first passivation contact layer 2.

[0050] According to an embodiment of this application, the second reserved portion 322 is a raised particle formed by the aggregation of the surface layer of the first passivation contact layer 2 and the first protective layer 3 during laser irradiation. In other words, the raised particle includes a mixture of the first protective layer material and the first passivation contact layer material. Since there is good contact between the first passivation contact layer 2 and the first protective layer 3, the formation of the second reserved portion 322 is jointly controlled by the first protective layer 3 and the first passivation contact layer 2, so that the second reserved portion 322 is randomly distributed on the surface of the first passivation contact layer 2.

[0051] For example, taking a first passivation contact layer 2 as a tunneling oxide passivation structure and a first protective layer as silicon nitride, the morphology of the reserved portion of the protective layer after local grooving of the first protective layer on the first passivation contact layer 2 is characterized. Specifically, as shown below... Figure 1 As shown, along the direction away from the first surface 101, the first passivation contact layer 2 includes a first tunneling layer 21 and a first semiconductor layer 22. The first tunneling layer 21 is silicon oxide (SiOx) in this example, but is not limited to it; it can also be aluminum oxide, titanium oxide, etc. The first semiconductor layer 22 is preferably a polycrystalline silicon layer in this example, but is not limited to it; it can also be a microcrystalline silicon layer, etc. The conductivity type of the first semiconductor layer 22 can be N-type or P-type. Specifically, an N-type first semiconductor layer 22 is formed by doping with at least one element from group VA, or a P-type first semiconductor layer 22 is formed by doping with at least one element from group IIIA. The first protective layer 3 located on the first passivation contact layer 2 is subjected to laser irradiation and wet etching, and a SEM top view is taken of the reserved portion of the protective layer located within the trench.

[0052] Figure 3A This is a scanning electron microscope (SEM) top view of the reserved portion of the protective layer at the first protective layer slot location in an embodiment of this application. Figure 3A As shown, after laser irradiation and wet etching of the first protective layer, the pyramid structure located within the groove retains its shape intact, and part of the protective layer remains. Specifically, multiple first reserved portions 321 and multiple second reserved portions 322 are distributed on the first semiconductor layer 22.

[0053] from Figure 3A It can be seen that a portion of the first reserved portion 321 has a porous structure, and through holes penetrating the first reserved portion 321 exist in the multiple pores 321a of the porous structure, allowing the first electrode to pass through the through holes and contact the first semiconductor layer 22 of the first passivation contact layer 2. It can also be observed that the first reserved portion 321 has a sheet-like structure, forming a space between it and the first semiconductor layer 22. Furthermore, it can be seen from... Figure 3A It was observed that the first reserved portion 321 is mainly distributed at the bottom of the tower, that is, the distribution density of the first reserved portion 321 at the bottom of the tower is greater than that at the top of the tower.

[0054] Figure 3B This is a SEM cross-sectional view of the protective layer reserved portion at the first protective layer slot location in an embodiment of this application, showing the cross-sectional morphology after the first electrode 4 is formed at the slot. For example... Figure 3B As shown, the distribution morphology of multiple first reserved portions 321 can be clearly observed, and a gap space is formed between some of the first reserved portions 321 and the first semiconductor layer 22, and the first electrode 4 fills the gap space.

[0055] And again Figure 3A As shown, these second reserved portions 322 are randomly distributed mainly on the first semiconductor layer 22 at the bottom and top of the tower. Light-colored protruding particles, which are the second reserved portions, can be easily observed through SEM images. The particle size of the second reserved portions 322 is between 50 and 100 nm. Detection using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) revealed that these protruding particles contain components of both the first protective layer and the polycrystalline silicon layer, and are particles formed by the agglomeration of the protective layer and the polycrystalline silicon layer after laser irradiation.

[0056] Furthermore, by adjusting the laser conditions, the laser energy density can be adjusted to a higher level (e.g., greater than 4 J / cm²). 2 ), and observe the morphology at the slotted location. Figure 3C This is a SEM top view of the reserved portion of the protective layer at the first protective layer slot location in the comparative embodiment of this application, as shown. Figure 3C As shown, even when no granular second reserved portion is observed, or even when only a small portion of the protective layer is distributed, the pyramid structure is still disrupted. The first semiconductor layer 22 forms a microstructure with an uneven surface, which impairs the field passivation effect of the first semiconductor layer 22, leading to a decrease in battery efficiency. This comparative embodiment is a suboptimal solution, as it somewhat damages the passivation of the first passivation contact layer 2. Furthermore, increasing the laser energy density will cause the protective layer reserved portion to almost disappear, resulting in excessive damage to the passivation of the entire grooved area 31, and a significant decrease in the overall battery efficiency.

[0057] For ease of explanation and illustration, in this example, the first reserved portion 321 and the second reserved portion 322 coexist and are distributed within the groove 31. However, it can be understood that if the purpose is to improve the adhesion of the first electrode to the surface, either one can exist and be distributed within the groove 31. This can be achieved by adjusting the appropriate laser energy and wet etching conditions.

[0058] According to embodiments of this application, in other implementations, at least a portion of the first surface 1a may also be a polished region with a tower-based structure, in which case protective layer reserved portions 32 are similarly distributed within the groove 31. Unlike the aforementioned partial grooving of the protective layer on the textured surface region, the protective layer reserved portions 32 are randomly distributed within the groove 31. Since the polished region has a lower roughness than the textured surface region, its poor electrode adhesion is more pronounced. The provision of the protective layer reserved portions 32 not only protects the first passivation contact layer but also enhances electrode adhesion and improves electrode contact in the polished region.

[0059] Figure 4 This is a schematic diagram of the state of the reserved portion of the protective layer at the groove position of the first protective layer on the polished area, according to another embodiment of this application; as shown. Figure 4 As shown, protective layer reserved portions 32 are distributed in the groove 31 located on the polishing area. The protective layer reserved portions 32 may include a plurality of first reserved portions 321 and / or a plurality of second reserved portions 322.

[0060] The first reserved portion 321 has a sheet-like structure, and optionally, at least a portion of the first reserved portion 321 has a porous structure. This further increases the contact area between the first electrode 4 and the protective layer reserved portion 32. Further optionally, at least one pore 321a in the porous structure can be a through-hole penetrating the first residual portion 321, allowing the first electrode 4 to pass through the through-hole and contact the first passivation contact layer 2. The second residual portion 322 is also a protruding particle protruding from the surface of the first passivation contact layer 2 in a direction away from the first surface 101a.

[0061] Alternatively, in the direction away from the first surface 101a, the thickness of the first reserved portion 321 located in the polished area can be less than the thickness of the portion of the first protective layer 3 excluding the groove 31. Similarly, the height of the second reserved portion 322 located in the polished area can also be less than the thickness of the portion of the first protective layer 3 excluding the groove 31. Appropriately sized first and second reserved portions 321 and 322 help maintain a good passivation effect while reducing contact resistance.

[0062] For example, taking the first passivation contact layer 2 as a tunneling oxide passivation structure and the first protective layer as silicon nitride, the morphology of the reserved portion of the protective layer after local trenching of the first protective layer 3 located in the polished area is characterized. Specifically, in this example, the first passivation contact layer includes a first tunneling layer 21 and a first semiconductor layer 22, wherein the first semiconductor layer is preferably a polysilicon layer. The first protective layer 3 is irradiated with a laser, and a SEM top view is acquired of the reserved portion of the protective layer located in the trench.

[0063] Figure 5AThis is a SEM top view of the reserved portion of the protective layer at the first protective layer slot location according to another embodiment of this application; Figure 5B This is a SEM top view of the first reserved portion at the first protective layer slot location, according to another embodiment of this application. (See attached image.) Figure 5A and Figure 5B As shown, the protective layer reserved portions 32 are relatively randomly distributed on the first semiconductor layer 22 within the slot 31. It can be observed that the protective layer reserved portions 32 include a first reserved portion 321 with a sheet-like structure and a second reserved portion 322 with dot-like protruding particles. The first reserved portion 321 with its sheet-like structure also contains pores 321a, thus forming a porous structure.

[0064] According to an embodiment of this application, for example... Figure 1 As shown, the first electrode 4 located on the first protective layer 3 can be prepared by electroplating or vapor deposition. The first electrode 4 can be a single-layer structure formed by one or more metals such as gold, silver, copper, nickel, tin, and chromium, but is not limited to this.

[0065] To further improve the contact performance between the first electrode 4 and the first passivation contact layer 2 within the groove 31, the structure of the first electrode 4 can be optimized to form a stacked structure. Specifically, Figure 6A This is a schematic diagram of the electrode structure at the groove location of the protective layer in an embodiment of this application. Figure 6A As shown, in an optional embodiment, along the direction away from the first surface 101, the first electrode 4 includes a first electrode layer 41 and a second electrode layer 42, with the protective layer pre-reserved portion 32 encased within the first electrode layer 41. Through this stacked arrangement, the first electrode layer 41 serves as a seed layer, suitable for direct contact with the first passivation contact layer 2 to provide a link, while also acting as a barrier layer to prevent material from the second electrode layer 42 from reaching the first passivation contact layer 2. Furthermore, the first electrode layer 41 is easy to deposit and prepare, readily encasing the protective layer pre-reserved portion 32. The second electrode layer 42, as the conductive body, balances cost and conductivity, and can be fabricated using base metals such as copper through low-cost methods such as printing.

[0066] Exemplarily, optionally, the first electrode layer 41 can be made of materials such as nickel and / or silver, which have a low diffusion rate and are not easily doped into the substrate, and can form chemical bonds with silicon, thereby reducing contact resistance. The second electrode layer 42 can be made of materials such as copper, tin, and / or chromium, which have good conductivity and low cost.

[0067] According to an embodiment of this application, the thickness of the first electrode 41 is greater than the thickness of the first protective layer 3. By covering the first protective layer 3, a suitable resistance can be obtained while improving mechanical stability, thus balancing current collection and stability.

[0068] According to embodiments of this application, the thickness of the first electrode layer 41 can be 0.1 μm to 5 μm, for example, it can be 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. The thickness of the second electrode layer 42 can be 1 μm to 100 μm, for example, it can be 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0069] By setting the layers of the first electrode within the aforementioned thickness range, it is beneficial for the first electrode layer to effectively cover the reserved portion of the protective layer. Since the first electrode layer readily bonds well to the first passivation contact layer and the reserved portion of the protective layer, the overall bonding strength of the first electrode on the battery surface is ensured. As the conductive core, optimizing the thickness of the second electrode layer facilitates the control of resistance and mechanical stability, achieving a balance between current collection and stability.

[0070] Figure 6B This is a schematic diagram of the electrode structure at the groove location of the protective layer in an embodiment of this application. Figure 6B As shown, in another optional embodiment, along the direction away from the first surface 101, the first electrode 4 may include a third electrode layer 43 in addition to the first electrode layer 41 and the second electrode layer 42. Especially when the second electrode layer 42 is an electroplated layer obtained by electroplating, it is preferable to have a third electrode layer 43. The third electrode layer can serve as an electrode protective layer, protecting the second electrode layer 42. Exemplarily, the third electrode layer 43 can be made of materials such as nickel and / or silver, which have good oxidation resistance.

[0071] According to embodiments of this application, optionally, the thickness of the third electrode layer 43 can be 0.005 μm to 5 μm, for example, 0.005 μm, 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. Optimizing the thickness of the third electrode layer 43 is beneficial for balancing cost and protection of the second electrode layer.

[0072] According to embodiments of this application, further optionally, such as Figure 1 , Figure 6A or Figure 6B As shown, on a cross-section perpendicular to the extension direction of the first electrode 4, the width of the first electrode 4 is greater than the width of the slot 31. This arrangement helps to reduce resistance and achieve good contact between the first electrode and the first passivation contact layer 2.

[0073] According to embodiments of this application, similarly, taking the first passivation contact layer 2 as a tunneling oxidation passivation structure as an example, the first passivation contact layer 2 can be as follows: Figure 1 As shown, the entire surface of the first surface 1a is covered, thereby creating a localized groove in the first protective layer 3 located on the first passivation contact layer 2. This achieves a good passivation effect. In other embodiments, the first passivation contact layer 2 can be disposed in a portion of the first surface 1a, thereby reducing the optical parasitic absorption of the first semiconductor layer 22 while ensuring the passivation effect, thus achieving a balance between passivation and carrier transport effects.

[0074] Specifically, Figure 7 This is a schematic diagram of the structure of a solar cell according to another embodiment of this application, as shown below. Figure 7 As shown, the first passivation contact layer 2 is located on the first region A of the first surface 1a; and, along a direction away from the first surface 1a, the first passivation contact layer 2 includes a first tunneling layer 21 and a first semiconductor layer 22, the first semiconductor layer 22 being preferably a polysilicon layer, and the extension direction of the groove 31 on the first passivation contact layer 2 is the same as the extension direction of the first region A. Thus, the first passivation contact layer 2 forms a poly-finger structure.

[0075] According to an embodiment of this application, in an optional implementation, in order to better balance the passivation effect and the carrier transport effect, and to be compatible with the electrode structure of the current collector electrode that can improve the light-shielding effect, the first passivation contact layer 2 and the slot 31 can be patterned to form a parallel and spaced strip pattern.

[0076] Specifically, Figure 8A This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application, as shown below. Figure 8A As shown, the first region A includes a plurality of first strip regions A1 extending along the second direction S2 and spaced apart along the first direction S1, wherein the first direction S1 and the second direction S2 intersect.

[0077] The width W1 of the first passivation contact layer 2 located on the first strip region A1 in the first direction S1 is 5~100μm (for example, it can be 5μm, 20μm, 50μm, 80μm, 100μm, etc.), and the width W2 of the groove 31 located on the first strip region A1 in the first direction S1 is 5~80μm (for example, it can be 5μm, 20μm, 30μm, 50μm, 60μm, 80μm, etc.).

[0078] Furthermore, the first electrode 4 located on the first strip region A1 can be a current collector electrode 4a. In this case, since no current collector electrode intersects with the current collector electrode 4a, the interconnection of the battery cells is achieved through other current collector structures such as solder ribbons, which saves the amount of electrode material.

[0079] In another alternative embodiment, the first electrode 4 may include a current collector electrode as well as a current collector electrode, so that the first passivation contact layer 2 and the slot 31 may be patterned to form a "cross" pattern in order to adapt to the configuration of the current collector electrode.

[0080] Specifically, Figure 8B This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application, as shown below. Figure 8B As shown, the first region A further includes a second strip region A2 extending along the first direction S1. The width W3 of the first passivation contact layer 2 on the second strip region A2 in the second direction S2 is 5~300μm (for example, it can be 5μm, 20μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 230μm, 250μm, 280μm, 300μm, etc.). The width W4 of the slot 31 on the second strip region A2 in the second direction S2 is 5~250μm (for example, it can be 5μm, 20μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 230μm, 250μm, etc.).

[0081] Furthermore, the first electrode located on the first strip region A1 can be a current collector electrode 4a, and the first electrode 4 located on the second strip region A2 can be a current collector electrode 4b. The widths of the current collector electrode 4b and the current collector electrode 4a can be the same or different.

[0082] For example, Figure 9 Here is a SEM image of a solar cell in the first region according to another embodiment of this application, as shown below. Figure 9 As shown, the central "cross-shaped" area represents the Poly-Finger structure formed by the first passivation contact layer 2. The light-colored "cross-shaped" structure within the central "cross-shaped" area is the first electrode, with the horizontal direction representing the current collector electrode 4a and the vertical direction representing the current bus electrode 4b. The slot 31 located in the first region is not depicted in this SEM image.

[0083] It should be noted that, although Figure 8A , 8B and Figure 9The slot 31 shown is continuous. In some other embodiments, the slot 31 may be discontinuous. For example, multiple opening regions may be provided at intervals along the extension direction of the first strip region A1 to form a discontinuous slot 31.

[0084] To facilitate understanding of the specific structure of the discontinuous slot 31, exemplarily, Figure 10 This is a schematic diagram of a partial grooving structure of a solar cell in the first region according to another embodiment of this application, as shown below. Figure 10 As shown, the slot 31 includes a plurality of openings spaced apart along the extension direction S2 of the first strip region A1. The shape of these openings is schematically circular, but not limited to this; for example, they can also be polygonal or other shapes. Furthermore, alternatively, the non-continuous slot 31 can be located on the textured area or polished area of ​​the semiconductor substrate 1, without any particular limitation.

[0085] By setting a discontinuous slot 31, on the one hand, the protective layer reserved portion 32 in the slot 31 can be used to improve the adhesion of the first electrode 4. On the other hand, the part of the first protective layer 3 other than the slot 31 is not irradiated by laser, so the passivation effect of the first contact passivation layer will not be damaged. This is beneficial to balance current collection and passivation effect.

[0086] According to the embodiments of this application, the above is an example of a solar cell with a tunneling oxide passivation structure, but it is not limited to this. For example, Figure 1 As shown, the tunneling oxidation passivation structure of the first passivation contact layer 2 can also be replaced with other passivation contact structures, thereby covering the entire first surface 1a, or a portion of the first surface 1a.

[0087] For example, the first passivation contact layer 2 can adopt a heterojunction structure. In this case, the first tunneling layer 21 and the first semiconductor layer 22 can be entirely replaced with the second semiconductor layer along the direction away from the first surface. Further optionally, the second semiconductor layer can include an intrinsic semiconductor layer and a doped semiconductor layer. The intrinsic semiconductor layer can be, for example, an intrinsic amorphous silicon layer, and the doped semiconductor layer can be, for example, a doped amorphous silicon layer or a doped microcrystalline silicon layer.

[0088] According to an embodiment of this application, for example... Figure 7 As shown, the solar cell further includes a second passivation contact layer 5, a second protective layer 7, and a second electrode 8. The second passivation contact layer 5 is located on the second surface 1b of the semiconductor substrate 1, and has a different conductivity type than the first passivation contact layer 2. The second protective layer 7 is located on the surface of the second passivation contact layer 5 away from the semiconductor substrate 1. The second electrode 8 is located on the surface of the second protective layer 7 away from the semiconductor substrate 1, and the second electrode 8 contacts the second passivation contact layer 5 through the second protective layer 7.

[0089] According to embodiments of this application, the second surface 1b of the semiconductor substrate can also have a polished area with a pyramidal base structure or a textured area with a pyramidal structure, without any particular limitation.

[0090] Alternatively, the second passivation contact layer 5 can also adopt various passivation contact structures, such as tunneling oxide passivation structures, heterojunction structures, etc. For example, taking a tunneling oxide passivation structure as an example, along the direction away from the second surface 1b, the second passivation contact layer 5 may include a second tunneling layer 51 and a third semiconductor layer 52. The arrangement of the second tunneling layer 51 is similar to that of the first tunneling layer 21, and the arrangement of the third semiconductor layer 52 is similar to that of the first semiconductor layer 22; these will not be described in detail here.

[0091] Alternatively, the second passivation contact layer 5 may cover the entire surface of the second surface 1b, or be located in a portion of the second surface 1b, for example, forming a Poly-Finger structure. It is foreseeable that the second protective layer 7 located on the second passivation contact layer 5 may have localized grooves similar to those in the first protective layer 3, thereby obtaining a protective layer pre-reserved portion in the second protective layer 7 with a structure similar to that on the first surface 101, which will not be elaborated further here.

[0092] Furthermore, the solar cells provided according to the embodiments of this application are not limited to [specific types]. Figure 7 The bifacial battery shown can also be a back-contact battery. Unlike the solar cell described above, the first passivation contact layer 2 and the second passivation contact layer 5 are located on the same surface of the solar cell, namely the first surface 1a. In this case, the first surface 1a includes an alternately spaced first region A and a second region B. The first passivation contact layer 2 can be located in the first region A of the first surface 1a, and the second passivation contact layer 5 can be located in the second region B of the first surface 1a. At this time, the first protective layer 3 located on the first region A and the second protective layer 7 located on the second region B can be locally grooved, thereby obtaining protective layer reserved portions with similar structures in the first protective layer 3 and the second protective layer 7, which will not be described in detail here.

[0093] According to another embodiment of this application, a method for fabricating a solar cell is provided. Figure 11 This is a schematic flowchart illustrating the method for fabricating a solar cell according to an embodiment of this application. Figure 12 This is a schematic diagram of the fabrication process of the solar cell according to an embodiment of this application, as shown below. Figure 11 and Figure 12 As shown, the preparation method of this application embodiment includes operations S1~S3:

[0094] In operation S1, a first passivation contact layer 2 and a first protective layer 3 are sequentially formed on the first surface 1a of the semiconductor substrate 1.

[0095] In operation S2, the slotted area of ​​the first protective layer 3 is irradiated with a laser, so that the first protective layer 3 located in the laser irradiation area forms a slot 31 and a protective layer reserved portion 32 distributed in the slot 31.

[0096] In operation S3, the first electrode 4 is deposited in the slot 31 of the first protective layer 3.

[0097] According to the embodiments of this application, the first protective layer is partially grooved by laser irradiation, and a protective layer reserved portion 32 is distributed in the formed groove 31. On the one hand, there is no need to use complex processes such as printing or photolithography when patterning the first protective layer, which has the advantage of simple patterning; on the other hand, compared with traditional laser film opening conditions, it is not easy to damage the battery surface, thereby maintaining a good passivation effect; furthermore, the protective layer reserved portion 32 can be distributed in the groove 31, which is beneficial to improving the adhesion of the electrode to the battery surface.

[0098] According to an embodiment of this application, in operation S1, the first passivation contact layer 2 can be prepared using a common deposition method. Taking the first passivation contact layer 2 as a tunneling oxide passivation structure as an example, the first passivation contact layer 2 can be prepared using plasma chemical vapor deposition (PECVD). Specifically, a first tunneling layer 21 and a doped polysilicon layer serving as the first semiconductor layer 22 can be sequentially formed on the first surface 1a of the semiconductor substrate 1, such as... Figure 12 As shown in Figure (a). The deposition conditions of the tunneling layer and the doped polysilicon layer can be selected according to actual needs, which is not the focus of this application and will not be elaborated here.

[0099] Further optionally, the thickness of the tunneling layer can be 2~10nm, for example, 2nm, 3nm, 5nm, 8nm, 10nm, etc., and the thickness of the doped polycrystalline silicon layer can be 80~250nm, such as 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, etc.

[0100] According to the embodiments of this application, the first protective layer 3 can be prepared using common deposition methods, such as PECVD or physical vapor deposition (PVD).

[0101] According to an embodiment of this application, in operation S2, the conditions for laser irradiation are not specifically limited and can be flexibly adjusted according to actual needs. Specifically, the laser energy density can be adjusted within a relatively wide wavelength range. For example, for the same film layer, lasers with different wavelengths, energy densities, and overlap rates can be used. Multiple matching laser parameters can be obtained through gradient experiments, as long as the protective layer pre-reserved portion can be formed. For example, the laser energy density can be 2.5~3.1 J / cm². 2 For example, it can be 2.5 J / cm 2 2.6 J / cm 2 2.7 J / cm 2 2.8 J / cm 2 2.9 J / cm 2 3.0 J / cm 2 3.1 J / cm 2 wait.

[0102] According to an embodiment of this application, optionally, in operation S2, after laser irradiation of the first protective layer 3, wet etching can be added to clean the trenched area. There are no special restrictions on the method of wet etching of the first protective layer 3; for example, acid etching can be used. Acid etching can be performed by immersing the layer in an HF solution of appropriate concentration (e.g., 0.5%, 1%, 2%) for a certain time (e.g., 10s, 20s, 30s, 1min, etc.). Based on the difference in porosity between the first protective layer 3 in the laser irradiation area and the first protective layer 3 in other areas, it is easier to achieve local trenching by combining wet etching, and to distribute the protective layer pre-reserved portion within the trench, such as... Figure 12 As shown in Figure (b). Of course, it is not limited to this; pure water cleaning can also be used instead of wet etching to clean the grooved area.

[0103] According to an embodiment of this application, in order to balance good electrical contact of the electrodes and cost, in an optional implementation, operation S3 may specifically include: depositing a first electrode layer 41 of the first electrode 4 on the first passivation contact layer 2 within the groove 31, until the first electrode layer 41 covers the protective layer reserved portion 32; sequentially depositing a second electrode layer 42 and a third electrode layer 43 of the first electrode 4 on the first electrode layer 41 to obtain the first electrode 4, as shown below. Figure 12 As shown in Figure (c).

[0104] In another alternative embodiment, in order to further reduce the cost of electrode manufacturing, operation S3 specifically includes: depositing a first electrode layer 41 on the first passivation contact layer 2 in the groove 31 until the first electrode layer 41 covers the reserved portion of the protective layer; printing a second electrode layer 42 on the first electrode layer 41 to obtain the first electrode 4.

[0105] At this time, the printing method of the second electrode layer 42 in the first electrode 4 includes, but is not limited to, screen printing, inkjet printing, etc. The printed electrode paste may contain antioxidants, or additional antioxidants may be applied to passivate the surface of the second electrode layer 42. Thus, there is no need to set the third electrode layer 43, thereby simplifying the electrode manufacturing process and reducing the electrode manufacturing cost.

[0106] Alternatively, the deposition method of the first electrode 4 may include, but is not limited to, electroplating, vapor deposition, etc. Taking the deposition of nickel as the first electrode layer by electroplating as an example, Figure 13 These are SEM images of electrodes deposited by electroplating at different electroplating times according to embodiments of this application, such as... Figure 13 As shown, during the first 5-10 seconds of electroplating, the electroplated nickel particles are generated in the areas not covered by the first protective layer 3 (including the pores of the protective layer reserved portion 32). During the subsequent 10-30 seconds, they are plated onto the protective layer reserved portion 32 and its sides, until the last 60 seconds when the protective layer reserved portion 32 is completely covered and the pores inside the protective layer reserved portion 32 are filled, thus forming the first electrode layer nickel.

[0107] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A solar cell, comprising: A semiconductor substrate having opposing first and second surfaces; A first passivation contact layer is located on the first surface of the semiconductor substrate; A first protective layer is located on the surface of the first passivation contact layer away from the semiconductor substrate. The first protective layer is provided with a slot that extends through the thickness direction and a protective layer reserved portion distributed in the slot. as well as A first electrode is located on the surface of the first protective layer away from the semiconductor substrate, at least a portion of the first electrode is located within the slot, and on a cross-section perpendicular to the extension direction of the first electrode, the width of the first electrode is greater than the width of the slot.

2. The solar cell according to claim 1, wherein, The protective layer reserved portion includes a plurality of first reserved portions, at least a portion of which has a porous structure, and / or the first reserved portion has a sheet-like structure.

3. The solar cell according to claim 2, wherein, The porous structure includes at least one pore that is a through hole penetrating the first reserved portion; The first electrode passes through the through hole and contacts the first passivation contact layer.

4. The solar cell according to claim 2 or 3, wherein, The first surface has a velvety area containing multiple pyramid structures, and along a direction away from the first surface, the pyramid structure includes a base and a top. The distribution density of the first reserved section located at the bottom of the tower is greater than the distribution density of the first reserved section located at the top of the tower.

5. The solar cell according to claim 1, wherein, The protective layer reserved portion includes a plurality of second reserved portions, wherein the second reserved portions are protruding particles that protrude from the surface of the first passivation contact layer in a direction away from the first surface.

6. The solar cell according to claim 5, wherein, The protruding particles have a particle size of 50~300nm, and / or the protruding particles comprise a mixture of a first protective layer material and a first passivation contact layer material.

7. The solar cell according to claim 5 or 6, wherein, The second reserved portion is randomly distributed on the surface of the first passivated contact layer.

8. The solar cell according to claim 1, wherein, Along a direction away from the first surface, the first electrode sequentially includes a first electrode layer and a second electrode layer, and the reserved portion of the protective layer is wrapped within the first electrode layer.

9. The solar cell according to claim 8, wherein, The thickness of the first electrode is greater than the thickness of the first protective layer.

10. The solar cell according to claim 8 or 9, wherein, The thickness of the first electrode layer is 0.1 μm to 5 μm, and the thickness of the second electrode layer is 1 μm to 100 μm.

11. The solar cell according to claim 1, wherein, The first passivated contact layer is located on a first region of the first surface; Furthermore, along the direction away from the first surface, the first passivation contact layer includes a first tunneling layer and a polysilicon layer; The groove located on the first passivation contact layer extends in the same direction as the first region.

12. The solar cell according to claim 11, wherein, The first region includes a plurality of first strip regions that extend along a second direction and are spaced apart along a first direction, wherein the first direction intersects the second direction; The width of the first passivation contact layer located on the first strip region in the first direction is 5~100μm, and the width of the groove located on the first strip region in the first direction is 5~80μm.

13. A method for preparing a solar cell, comprising: A first passivation contact layer and a first protective layer are sequentially formed on the first surface of a semiconductor substrate; The grooved area of ​​the first protective layer is irradiated with a laser, so that the first protective layer located in the laser irradiation area forms a groove and a reserved portion of the protective layer distributed in the groove. A first electrode is formed within a groove in the first protective layer, and on a cross-section perpendicular to the extension direction of the first electrode, the width of the first electrode is greater than the width of the groove.

14. The preparation method according to claim 13, wherein, The deposition of the first electrode within the groove of the first protective layer includes: A first electrode layer is deposited on the first passivation contact layer within the groove, until the first electrode layer covers the reserved portion of the protective layer. A second electrode layer is printed on the first electrode layer to obtain the first electrode.

15. The preparation method according to claim 13, wherein, The deposition of the first electrode within the groove of the first protective layer includes: A first electrode layer is deposited on the first passivation contact layer within the groove, until the first electrode layer covers the reserved portion of the protective layer. A second electrode layer and a third electrode layer are sequentially deposited on the first electrode layer to obtain the first electrode.

Images