Solar cell, cell assembly and photovoltaic system

Abstract

The invention is applicable to the technical field of solar cells, and provides a solar cell, a cell module and a photovoltaic system. The solar cell includes: a silicon substrate including a first region and a second region; the P-type doped layer is arranged on the first region; the N-type doped layer is arranged on the second region; the first passivation layer is arranged on the P-type doped layer; the second passivation layer is arranged on the N-type doped layer; the first electrode comprises a first crystal structure and a second crystal structure, and the second crystal structure comprises a plurality of first trunks in contact with the P-type doped layer; the second electrode comprises a third crystal structure and a fourth crystal structure, the fourth crystal structure comprises a plurality of second trunks making contact with the N-type doping layer, the number of the first trunks is larger than that of the second trunks, and / or the length of the first trunks is larger than that of the second trunks. According to the solar cell, the contact performance of the first electrode and the P-type doping layer can be improved, and the cell efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell, a battery assembly and a photovoltaic system. Background Art

[0002] A solar cell is a semiconductor device that converts solar energy into electrical energy. When exposed to sunlight, a photocurrent is generated within the cell, which then outputs the electrical energy through electrodes. In recent years, advancements in solar cell production technology have led to continuous reductions in production costs and improvements in conversion efficiency. As a result, solar cell power generation is becoming increasingly widespread and has become a vital energy source for electricity supply.

[0003] In the existing technology, a screen printing process is typically used to form a P-type doped layer and a passivation layer disposed on the P-type doped layer in the P region of a solar cell, and an N-type doped layer and a passivation layer disposed on the N-type doped layer in the N region. Electrode paste is then screen-printed in the P and N regions and sintered, allowing the electrode paste to penetrate the passivation layers and form ohmic contacts with the corresponding doped layers, thereby forming positive and negative electrodes. However, the contact performance between the electrode in the P region and the P-type doped layer is typically worse than the contact performance between the electrode in the N region and the N-type doped layer, resulting in high contact resistance of the P region electrode, poor current collection capability of the P region electrode, and poor battery efficiency. Summary of the Invention

[0004] The present invention provides a solar cell, aiming to solve the problem in the prior art that the P-region electrode and the P-type doping layer have poor contact performance, resulting in large contact resistance of the P-region electrode, poor current collection capability of the P-region electrode, and poor cell efficiency.

[0005] The present invention is implemented by providing a solar cell comprising:

[0006] A silicon substrate, comprising a first region and a second region, wherein the first region and the second region are located on the same surface or on two opposite surfaces of the silicon substrate;

[0007] A P-type doped layer is disposed on the first region;

[0008] An N-type doped layer is disposed on the second region;

[0009] a first passivation layer disposed on the P-type doped layer;

[0010] a second passivation layer disposed on the N-type doped layer;

[0011] a first electrode, the first electrode passing through the first passivation layer and contacting the P-type doped layer, the first electrode including a first crystal structure and a second crystal structure formed on the first crystal structure, the second crystal structure including a plurality of first trunks connected to the first crystal structure, the first trunks contacting the P-type doped layer; and

[0012] a second electrode, the second electrode passing through the second passivation layer and contacting the N-type doped layer; the second electrode includes a third crystal structure and a fourth crystal structure formed on the third crystal structure, the fourth crystal structure includes a plurality of second trunks connected to the third crystal structure, the second trunks are in contact with the N-type doped layer, the number of the first trunks is greater than the number of the second trunks and / or the length of the first trunk is greater than the length of the second trunk; or, the second electrode includes a third crystal structure, and the second electrode is connected to the N-type doped layer only through the third crystal structure.

[0013] Preferably, the diameter of the first trunk is greater than the diameter of the second trunk.

[0014] Preferably, the second crystal structure further includes a plurality of first branches connected to the first trunk, wherein the first branches are in contact with the P-type doped layer;

[0015] The fourth crystal structure includes a plurality of second branches connected to the second trunk, wherein the second branches are in contact with the N-type doped layer;

[0016] The number of the first branches is greater than the number of the second branches and / or the length of the first branches is greater than the length of the second branches.

[0017] Preferably, the diameter of the first branch is greater than the diameter of the second branch.

[0018] Preferably, the first crystal structure includes a first extension portion extending into the P-type doped layer, a first eutectic layer is provided between the first extension portion and the P-type doped layer, and the second crystal structure is formed on the first extension portion, the second crystal structure passes through the first eutectic layer and contacts the P-type doped layer.

[0019] Preferably, the third crystal structure includes a second extension portion extending into the N-type doped layer, a second eutectic layer is provided between the second extension portion and the N-type doped layer, and the fourth crystal structure is formed on the second extension portion, and the fourth crystal structure passes through the second eutectic layer and contacts the N-type doped layer.

[0020] Preferably, a depth of the first extension portion penetrating into the P-type doping layer is greater than a depth of the second extension portion penetrating into the N-type doping layer.

[0021] Preferably, the first electrode further includes a first glass layer, the first glass layer is located between the P-type doped layer and the first crystal structure, the first extension portion extends through the first glass layer into the P-type doped layer, and the first eutectic layer is provided between the first glass layer and the P-type doped layer.

[0022] Preferably, the second electrode further includes a second glass layer, the second glass layer is located between the N-type doped layer and the third crystal structure, the second extension portion extends through the second glass layer into the N-type doped layer, and the second eutectic layer is provided between the second glass layer and the N-type doped layer.

[0023] The present invention also provides a battery assembly, comprising the above-mentioned solar cell.

[0024] The present invention also provides a photovoltaic system comprising the above-mentioned battery assembly.

[0025] A solar cell provided by the present invention forms a second crystal structure on a first crystal structure of a first electrode, wherein the first electrode contacts and conducts electricity with a P-type doped layer using several first trunks of the second crystal structure; forms a fourth crystal structure on a third crystal structure of the second electrode, wherein the second electrode contacts and conducts electricity with several second trunks of the fourth crystal structure; and simultaneously controls the number of first trunks to be greater than the number of second trunks and / or the length of the first trunk to be greater than the length of the second trunk, so that the surface area of ​​the second crystal structure is greater than the surface area of ​​the fourth crystal structure, thereby making the contact area between the second crystal structure and the P-type doped layer greater than the contact area between the fourth crystal structure and the N-type doped layer, thereby increasing the contact area between the first electrode in the first region and the P-type doped layer, improving the contact performance between the first electrode in the first region and the P-type doped layer, thereby reducing the contact resistance of the first electrode, improving the current collection capability of the first electrode, and improving the efficiency of the solar cell; and further, since the surface area of ​​the fourth crystal structure is reduced, the process difficulty and cost can be reduced. Alternatively, the second electrode of the solar cell provided by the present invention is only connected to the N-type doped layer through the third crystal structure to achieve conductivity, while the first electrode is provided with a first crystal structure and a second crystal structure to be connected to the P-type doped layer for conductivity. Since the several first trunks of the second crystal structure of the first electrode can also increase the contact area between the first electrode and the P-type doped layer, while the second electrode does not form several trunk structures, the contact performance of the first electrode and the P-type doped layer is improved, the contact resistance of the first electrode is reduced, and the current collection capacity of the first electrode is improved, which is beneficial to improving the battery efficiency; since the second electrode does not have a fourth crystal structure, there is no need to form a fourth crystal structure on the third crystal structure. On the premise of improving the contact performance of the first electrode and the P-type doped layer, the process difficulty and cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a solar cell provided by an embodiment of the present invention;

[0027] Figure 2 A schematic structural diagram of another solar cell provided by an embodiment of the present invention;

[0028] Figure 3 for Figure 1 A magnified schematic diagram of part A in the middle;

[0029] Figure 4 for Figure 1 A magnified schematic diagram of part B in the middle;

[0030] Figure 5 A partial schematic diagram of another solar cell provided by an embodiment of the present invention.

[0031] Figure 6 Another partial schematic diagram of another solar cell provided by an embodiment of the present invention;

[0032] Figure 7 Another partial schematic diagram of another solar cell provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] In the description of the present invention, it should be understood that the terms "upper", "lower", "back", "front", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0036] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art will recognize the application of other processes and / or the use scenarios of other materials.

[0037] Please refer to Figure 1-Figure 4 , an embodiment of the present invention provides a solar cell, comprising:

[0038] A silicon substrate 1, comprising a first region 11 and a second region 12, wherein the first region 11 and the second region 12 are located on the same surface or on two opposite surfaces of the silicon substrate 1;

[0039] A P-type doped layer 2 is disposed on the first region 11;

[0040] An N-type doped layer 3 is disposed on the second region 12;

[0041] A first passivation layer 4 is provided on the P-type doped layer 2;

[0042] A second passivation layer 5 is provided on the N-type doped layer 3;

[0043] a first electrode 6, the first electrode 6 passing through the first passivation layer 4 and contacting the P-type doped layer 2, the first electrode 6 including a first crystal structure 61 and a second crystal structure 62 formed on the first crystal structure 61, the second crystal structure 62 including a plurality of first trunks 621 connected to the first crystal structure 61, the first trunks 621 contacting the P-type doped layer 2; and

[0044] The second electrode 7 passes through the second passivation layer 4 and contacts the N-type doped layer 3; the second electrode 7 includes a third crystal structure 71 and a fourth crystal structure 72 formed on the third crystal structure 71, the fourth crystal structure 72 includes a plurality of second trunks 721 connected to the third crystal structure 71, the second trunks 721 contact the N-type doped layer 3, the number of first trunks 621 is greater than the number of second trunks 721 and / or the length of the first trunk 621 is greater than the length of the second trunk 721.

[0045] In this embodiment of the present invention, the silicon substrate 1 includes a first surface 101 and a second surface 102, one of which is a light-receiving surface and the other is a backlighting surface. For a monofacial cell, the first surface 101 is the light-receiving surface and the second surface 102 is the backlighting surface. For a bifacial cell, both the first surface 101 and the second surface 102 can be light-receiving surfaces. The first region 11 is the P-type region of the solar cell, and the second region 12 is the N-type region of the solar cell.

[0046] like Figure 1 As shown, the solar cell is a back-contact solar cell, the first surface 101 is the light-receiving surface, the second surface 102 is the backlight surface, and the first region 11 and the second region 12 are both located on the same surface of the silicon substrate 1, that is, the first region 11 and the second region 12 are both located on the second surface 102. There are multiple first regions 11 and second regions 12, and the multiple first regions 11 and second regions 12 are alternately arranged in sequence. Figure 1 Only a first region 11 and a second region 12 are shown schematically.

[0047] like Figure 2 As shown, the solar cell is a double-sided contact solar cell, the first surface 101 is the light-receiving surface, the second surface 102 is the backlight surface, the first area 11 is located on the first surface 101 of the silicon substrate 1, and the second area 12 is located on the second surface 102 of the silicon substrate 1.

[0048] In the embodiment of the present invention, the second crystal structure 62 is formed on the first crystal structure 61 of the first electrode 6, and the first electrode 6 is connected to the P-type doped layer 2 through the first crystal structure 61 for electrical conduction, and the plurality of first trunks 621 of the second crystal structure 62 are used to contact and conduct the P-type doped layer 2; the fourth crystal structure 72 is formed on the third crystal structure 71 of the second electrode 7, and the second electrode 7 is connected to the N-type doped layer 3 through the third crystal structure 71 for electrical conduction, and the plurality of second trunks 721 of the fourth crystal structure 72 are used to contact and conduct the N-type doped layer 3, and the arrangement of the second crystal structure 62 is conducive to filling the internal gaps of the first crystal structure 61 and filling the gaps between the first crystal structure 61 and the P-type doped layer. 2, thereby reducing the connection resistance between the first crystal structure 61 and the P-type doped layer 2, improving the ability of the first crystal structure 61 to collect current, and avoiding the structural stability defects caused by the structural gap, which is beneficial to improving the conductive performance between the first electrode 6 and the P-type doped layer 2; the setting of the fourth crystal structure 72 is beneficial to filling the internal gap of the third crystal structure 71, and filling the gap between the third crystal structure 71 and the N-type doped layer 3, thereby reducing the connection resistance between the third crystal structure 71 and the N-type doped layer 3, improving the ability of the third crystal structure 71 to collect current, and avoiding the structural stability defects caused by the structural gap, which is beneficial to improving the conductive performance between the second electrode 7 and the N-type doped layer 3.

[0049] In the embodiment of the present invention, a plurality of first trunks 621 form a multi-branched structure on the first crystal structure 61, and a plurality of second trunks 721 form a multi-branched structure on the third crystal structure 71. In the embodiment of the present invention, by controlling the number of first trunks 621 to be greater than the number of second trunks 721 and / or the length of the first trunk 621 to be greater than the length of the second trunk 721, the surface area of ​​the second crystal structure 62 is greater than the surface area of ​​the fourth crystal structure 72, and the contact area between the second crystal structure 62 and the P-type doped layer 2 is greater than the contact area between the fourth crystal structure 72 and the N-type doped layer 3. This increases the contact area between the first electrode 6 and the P-type doped layer 2, thereby improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection capability of the first electrode 6, thereby improving battery efficiency. In an embodiment of the present invention, the P-type doped layer 2 can specifically be one or more of single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon doped with P-type doping elements; the N-type doped layer 3 can specifically be one or more of single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon doped with N-type doping elements.

[0050] In the embodiment of the present invention, the film structure and film material of the first passivation layer 4 and the second passivation layer 5 can be the same or different. For example, the first passivation layer 4 and the second passivation layer 5 are at least one of an aluminum oxide film layer, a silicon oxide film layer, a silicon nitride film layer, a silicon carbide film layer, and a silicon oxynitride film layer, or a combination of multiple thereof, without limitation herein.

[0051] In an embodiment of the present invention, the first electrode 6 includes a first crystal structure 61 and a second crystal structure 62, with the second crystal structure 62 being a derivative of the first crystal structure 61. The second electrode 7 includes a third crystal structure 71 and a fourth crystal structure 72 formed on the third crystal structure 71, with the fourth crystal structure 72 being a derivative of the third crystal structure 71. The second crystal structure 62 is formed by grain regrowth and recrystallization based on the first crystal structure 61. The first crystal structure 61 can be directly or indirectly connected to the P-type doped layer 2 for electrical conductivity. The fourth crystal structure 72 is formed by grain regrowth and recrystallization based on the third crystal structure 71. The third crystal structure 71 can be directly or indirectly connected to the N-type doped layer 3 for electrical conductivity. Specifically, pulse voltages can be applied to the first crystal structure 61 and the third crystal structure 71, respectively, to form the second crystal structure 62 on the first crystal structure 61 and the fourth crystal structure 72 on the third crystal structure 71. The pulse voltages include at least one of a triangular wave pulse voltage, a rectangular wave pulse voltage, a sawtooth wave pulse voltage, and a trigonometric function pulse voltage. Of course, the formation method of the second crystal structure 62 and the fourth crystal structure 72 is not limited to the method of applying a pulse voltage, and other methods may also be used to form them.

[0052] In the embodiment of the present invention, Figure 3 and Figure 4 As shown, the shapes of the first trunk 621 and the second trunk 721 can be columnar, long curved, long straight or other irregular shapes. The specific shapes of the first trunk 621 and the second trunk 721 are not limited.

[0053] In the embodiment of the present invention, the number of first trunks 621 may be greater than the number of second trunks 721, or the length of the first trunk 621 may be greater than the length of the second trunk 721. Alternatively, the number of first trunks 621 may be greater than the number of second trunks 721, and the length of the first trunk 621 may be greater than the length of the second trunk 721. The fact that the number of first trunks 621 is greater than the number of second trunks 721 can be understood as meaning that the number of first trunks 621 is greater than the number of second trunks 721 per unit area. The unit area may be a local area of ​​the solar cell or the entire area of ​​the solar cell. In actual comparison, the same unit area may be taken from the first region 11 and the second region 12, and the number of first trunks 621 per unit area of ​​the first region 11 and the number of second trunks 721 per unit area of ​​the second region 12 may be compared. It can be found that the number of first trunks 621 per unit area of ​​the first region 11 is greater than the number of second trunks 721 per unit area of ​​the second region 12.

[0054] In this embodiment, since the number of the first trunks 621 is greater than the number of the second trunks 721, the surface area of ​​the second crystal structure 62 is greater than the surface area of ​​the fourth crystal structure 72, thereby increasing the contact area between the first electrode 6 and the P-type doped layer 2, improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection capacity of the first electrode 6, which is conducive to improving battery efficiency. Figure 3 Only the number of the first trunks 621 is shown as 4. Figure 4 Only two second trunks 721 are shown.

[0055] In the embodiment of the present invention, the length of the first trunk 621 is greater than the length of the second trunk 721. This can be understood as the average length of a set number of first trunks 621 within a unit area being greater than the average length of a set number of second trunks 721 within a unit area, or the length of any one of the first trunks 621 being greater than the length of any one of the second trunks 721. The unit area can be a local area on the surface of a solar cell or the entire area on the surface of a solar cell. The set number can be 2 to 10. For example, the average length of two first trunks 621 within a unit area is greater than the average length of two second trunks 721 within a unit area; for another example, the average length of three first trunks 621 within a unit area is greater than the average length of three second trunks 721 within a unit area.

[0056] In this embodiment, since the length of the first trunk 621 is greater than the length of the second trunk 721, the surface area of ​​the first trunk 621 is greater than the surface area of ​​the second trunk 721, and the surface area of ​​the second crystal structure 62 is greater than the surface area of ​​the fourth crystal structure 72. This can increase the contact area between the first electrode 6 and the P-type doped layer 2, improve the contact performance between the first electrode 6 and the P-type doped layer 2 in the first region 11, reduce the electrode contact resistance of the first region 11, and improve the electrode current collection capacity of the first region 11, which is beneficial to improving battery efficiency.

[0057] As an embodiment of the present invention, the diameter of the first trunk 621 is greater than the diameter of the second trunk 721 .

[0058] The cross-sections of the first trunk 621 and the second trunk 721 are roughly circular. The diameter of the first trunk 621 is greater than the diameter of the second trunk 721. It can be understood that the average diameter of a set number of first trunks 621 in a unit area is greater than the average diameter of a set number of second trunks 721 in a unit area, or the diameter of any one of the first trunks 621 is greater than the diameter of any one of the second trunks 721. The unit area can be a local area on the surface of the solar cell or the entire area on the surface of the solar cell. The set number can be 2 to 10. For example, the average diameter of the two first trunks 621 in the unit area is greater than the average diameter of the two second trunks 721 in the unit area; for another example, the average diameter of the three first trunks 621 in the unit area is greater than the average diameter of the three second trunks 721 in the unit area.

[0059] In this embodiment, since the diameter of the first trunk 621 is greater than the diameter of the second trunk 721, the surface area of ​​the second crystal structure 62 can also be increased, thereby increasing the contact area between the first electrode 6 and the P-type doped layer 2, improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection ability of the first electrode 6, which is beneficial to improving battery efficiency.

[0060] Please refer to Figure 5 and Figure 6 As an embodiment of the present invention, the second crystal structure 62 further includes a plurality of first branches 622 connected to the first trunk 621, and the first branches 622 are in contact with the P-type doped layer 2; the fourth crystal structure 72 includes a plurality of second branches 722 connected to the second trunk 721, and the second branches 722 are in contact with the N-type doped layer 3, and the number of the first branches 622 is greater than the number of the second branches 722 and / or the length of the first branches 622 is greater than the length of the second branches 722.

[0061] In this embodiment, each first trunk 621 is connected to a plurality of first branches 622, and each second trunk 721 is connected to a plurality of second branches 722. The specific shapes of the first branches 622 and the second branches 722 are not limited. For example, the shapes of the first branches 622 and the second branches 722 can be cylindrical, elongated curved, elongated straight, or other irregular shapes. Preferably, the second crystal structure 62 and the fourth crystal structure 72 are both multi-branched dendritic structures, which can further increase the contact area between the second crystal structure 62 and the fourth crystal structure 72 and the P-type doped layer 2 and the N-type doped layer 3, respectively.

[0062] In this embodiment, the number of first branches 622 may be greater than the number of second branches 722, or the length of the first branch 622 may be greater than the length of the second branch 722. Alternatively, the number of first branches 622 may be greater than the number of second branches 722, and the length of the first branch 622 may be greater than the length of the second branch 722. The number of first branches 622 being greater than the number of second branches 722 can be understood as meaning that, per unit area, the number of first branches 622 is greater than the number of second branches 722. The unit area may be a local area on the solar cell surface or the entire area on the solar cell surface. In actual comparison, the same unit area may be taken from the first region 11 and the second region 12, and the number of first branches 622 per unit area of ​​the first region 11 and the number of second branches 722 per unit area of ​​the second region 12 may be observed. It can be observed that the number of first branches 622 per unit area of ​​the first region 11 is greater than the number of second branches 722 per unit area of ​​the second region 12.

[0063] In this embodiment, since the number of first branches 622 is greater than the number of second branches 722, the surface area of ​​the second crystal structure 62 can be further increased, thereby further increasing the contact area between the first electrode 6 and the P-type doped layer 2, improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection capacity of the first electrode 6, which is conducive to improving battery efficiency. Figure 5 Only the number of the first branches 622 is shown as 8. Figure 6 Only six second branches 722 are shown.

[0064] In this embodiment, the length of the first branch 622 is greater than the length of the second branch 722. This can be understood as the average length of a set number of first branches 622 per unit area being greater than the average length of a set number of second branches 722 per unit area, or the length of any one first branch 622 being greater than the length of any one second branch 722. The unit area can be a local area on the back side of the solar cell or the entire area on the back side of the solar cell. The set number can be 2 to 10. For example, the average length of two first branches 622 per unit area is greater than the average length of two second branches 722 per unit area; for another example, the average length of three first branches 622 per unit area is greater than the average length of three second branches 722 per unit area.

[0065] In this embodiment, since the length of the first branch 622 is greater than the length of the second branch 722, the surface area of ​​the second crystal structure 62 can be further increased, thereby increasing the contact area between the first electrode 6 and the P-type doped layer 2, improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection ability of the first electrode 6, which is beneficial to improving battery efficiency.

[0066] As an embodiment of the present invention, the diameter of the first branch 622 is greater than the diameter of the second branch 722 .

[0067] The cross-sections of the first branch 721 and the second branch 722 are roughly circular. The diameter of the first branch 721 is greater than the diameter of the second branch 722. It can be understood that the average diameter of a set number of first branches 721 within a unit area is greater than the average diameter of a set number of second branches 722 within a unit area, or the diameter of any one of the first branches 721 is greater than the diameter of any one of the second branches 722. The unit area can be a local area on the surface of the solar cell or the entire area on the surface of the solar cell. The set number can be 2 to 10. For example, the average diameter of the two first branches 721 within the unit area is greater than the average diameter of the two second branches 722 within the unit area; for another example, the average diameter of the three first branches 721 within the unit area is greater than the average diameter of the three second branches 722 within the unit area.

[0068] In this embodiment, since the diameter of the first branch 721 is larger than the diameter of the second branch 722, the surface area of ​​the second crystal structure 62 can also be increased, thereby increasing the contact area between the first electrode 6 and the P-type doped layer 2, improving the contact performance between the first electrode 6 and the P-type doped layer 2, reducing the contact resistance of the first electrode 6, and improving the current collection ability of the first electrode 6, which is beneficial to improving battery efficiency.

[0069] As an embodiment of the present invention, the first crystal structure 61 includes a first extension portion 611 extending into the P-type doped layer 2, a first eutectic layer 9 is provided between the first extension portion 611 and the P-type doped layer 2, and a second crystal structure 62 is formed on the first extension portion 611, the second crystal structure 62 passes through the first eutectic layer 9 and contacts the P-type doped layer 2.

[0070] In this embodiment, a first eutectic layer 9 is disposed between the first extension 611 and the P-type doped layer 2. The first eutectic layer 9 comprises the material of the first electrode 6 and the material of the P-type doped layer 2. The first extension 611 of the first crystal structure 61 contacts the P-type doped layer 2 through the first eutectic layer 9, thereby enabling both the first crystal structure 61 and the second crystal structure 62 to be electrically connected to the P-type doped layer 2. Furthermore, the first trunk 621 of the second crystal structure 62 penetrates the first eutectic layer 9 and contacts the P-type doped layer 2, thereby enabling direct electrical contact between the second crystal structure 62 and the P-type doped layer 2.

[0071] As an embodiment of the present invention, the third crystal structure 71 includes a second extension portion 711 extending into the N-type doped layer 3, a second eutectic layer 10 is provided between the second extension portion 711 and the N-type doped layer 3, and a fourth crystal structure 72 is formed on the second extension portion 711. The fourth crystal structure 72 passes through the second eutectic layer 10 and contacts the N-type doped layer 3.

[0072] In this embodiment, a second eutectic layer 10 is provided between the second extension portion 711 and the N-type doped layer 3. The second eutectic layer 10 includes the material of the second electrode 7 and the material of the N-type doped layer 3. The second extension portion 711 of the third crystal structure 71 contacts the N-type doped layer 3 through the second eutectic layer 10, thereby achieving a conductive connection between the third crystal structure 71 and the N-type doped layer 3. At the same time, the second trunk 721 of the fourth crystal structure 72 passes through the second eutectic layer 10 and contacts the N-type doped layer 3, thereby achieving direct conductive contact between the fourth crystal structure 72 and the N-type doped layer 3.

[0073] As an embodiment of the present invention, a depth H1 of the first extension portion 611 penetrating into the P-type doping layer 2 is greater than a depth H2 of the second extension portion 711 penetrating into the N-type doping layer 3 .

[0074] In this embodiment, the depth H1 of the first extension portion 611 entering the P-type doped layer 2 is greater than the depth H2 of the second extension portion 711 entering the N-type doped layer 3, which is beneficial to improving the conductivity of the first extension portion 611 of the first crystal structure 61 and the P-type doped layer 2, and can further improve the battery efficiency.

[0075] As an embodiment of the present invention, the first electrode 6 also includes a first glass layer 63, the first glass layer 63 is located between the P-type doped layer 2 and the first crystal structure 61, the first extension portion 611 extends through the first glass layer 63 into the P-type doped layer 2, and a first eutectic layer 9 is arranged between the first glass layer 63 and the P-type doped layer 2.

[0076] In this embodiment, only the first extension portion 611 of the first crystal structure 61 extends through the first glass material layer 63 into the P-type doped layer 2, and the rest of the first crystal structure 61 does not extend into the P-type doped layer 2. The first glass material layer 63 is beneficial for reducing the ablation depth of the first crystal structure 61, which is beneficial for reducing internal defects caused by ablation, reducing carrier recombination caused by internal defects, achieving a balance between contact area and recombination loss, and improving the photoelectric conversion efficiency of the battery.

[0077] As an embodiment of the present invention, the second electrode 7 further includes a second glass layer 73, the second glass layer 73 is located between the N-type doped layer 3 and the third crystal structure 71, the second extension portion 711 extends through the second glass layer 73 into the N-type doped layer 3, and a second eutectic layer 10 is provided between the second glass layer 73 and the N-type doped layer 3.

[0078] The first glass frit layer 63 and the second glass frit layer 73 are made of glass material, which may include at least one of metallic glass particles, tellurium-containing glass particles, lead-containing glass particles, or lead-free glass particles.

[0079] Please refer to Figure 7 As another embodiment of the present invention, the second electrode 7 only includes the third crystal structure 71 , and the second electrode 7 is connected to the N-type doped layer 3 through the third crystal structure 71 .

[0080] In this embodiment, Figure 3 or Figure 5As shown, the first electrode 6 includes a first crystal structure 61 and a second crystal structure 62 formed on the first crystal structure 61, the second crystal structure 62 is in contact with the P-type doped layer 22, and the second crystal structure 62 includes a plurality of first trunks 621 connected to the first crystal structure 61, and the first trunk 621 is in contact with the P-type doped layer 2; the second electrode 7 only includes the third crystal structure 71, that is, the second electrode 7 does not have the fourth crystal structure 72, and the second electrode 7 is only connected to the N-type doped layer 3 through the third crystal structure 71 to achieve conductivity, and the first electrode 6 simultaneously utilizes the first crystal structure 6 to conduct electricity with the P-type doped layer 2, and utilizes the plurality of first trunks 621 of the second crystal structure 62 to contact and conduct electricity with the P-type doped layer 2, which can also increase the contact area between the first electrode 6 and the P-type doped layer 2, improve the contact performance of the first electrode 6 and the P-type doped layer 2, reduce the contact resistance of the first electrode 6, and improve the current collection capacity of the first electrode 6, which is beneficial to improving the battery efficiency. Since the second electrode 7 does not have the fourth crystal structure 72, there is no need to form the fourth crystal structure 72 on the third crystal structure 71, which can reduce the process difficulty and cost. The third crystal structure 71 can directly contact and connect with the N-type doped layer 3. A second eutectic layer 10 can also be provided between the third crystal structures 71. The third crystal structure 71 is indirectly connected to the N-type doped layer 3 through the second eutectic layer 10 for electrical conduction.

[0081] The present invention also provides a battery assembly including the solar cell of the above embodiment. It should be noted that the battery assembly and the solar cell have the same or similar beneficial effects, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they will not be described here.

[0082] In this embodiment, multiple solar cells in the battery assembly can be connected in series in sequence to form a battery string, thereby realizing the series bus output of the current. For example, the series connection of the battery cells can be realized by setting welding strips (bus bars, interconnecting bars), conductive backplanes, etc.

[0083] It is understood that in such an embodiment, the battery assembly may further include a metal frame, a backplane, photovoltaic glass, and an adhesive film. The adhesive film may be filled between the front and back surfaces of the solar cell, the photovoltaic glass, and adjacent cells. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the adhesive film may be EVA film or POE film. The specific choice can be made according to actual conditions and is not limited here.

[0084] Photovoltaic glass can cover the adhesive film on the front of the solar cell. The photovoltaic glass can be ultra-clear glass, which has high light transmittance and transparency, as well as excellent physical, mechanical, and optical properties. For example, ultra-clear glass can have a light transmittance of over 92%, protecting the solar cell while minimizing its efficiency. The adhesive film also bonds the photovoltaic glass and solar cell together, providing sealing, insulation, and waterproofing.

[0085] The backsheet can be attached to the film on the back of the solar cell. The backsheet provides protection and support for the solar cell, offering reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, organic glass, and aluminum alloy TPT composite film. The specific backsheet material can be configured based on specific circumstances and is not limited here. The backsheet, solar cell, film, and photovoltaic glass assembly can be mounted on a metal frame. The metal frame serves as the primary external support structure for the entire battery assembly and provides stable support and installation for the battery assembly. For example, the metal frame allows the battery assembly to be installed in the desired location.

[0086] The present invention also provides a photovoltaic system including the battery assembly of the above embodiment. It should be noted that the photovoltaic system and the above solar cell have the same or similar beneficial effects, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they are not described here.

[0087] In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple battery modules. For example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

[0088] Throughout this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" indicate that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon substrate, comprising a first region and a second region, wherein the first region and the second region are located on the same surface or on two opposite surfaces of the silicon substrate; A P-type doped layer is disposed on the first region; An N-type doped layer is disposed on the second region; a first passivation layer disposed on the P-type doped layer; a second passivation layer disposed on the N-type doped layer; a first electrode, the first electrode passing through the first passivation layer and contacting the P-type doped layer, the first electrode including a first crystal structure and a second crystal structure formed on the first crystal structure, the second crystal structure including a plurality of first trunks connected to the first crystal structure, the first trunks contacting the P-type doped layer; and a second electrode, the second electrode passing through the second passivation layer and contacting the N-type doped layer; the second electrode includes a third crystal structure and a fourth crystal structure formed on the third crystal structure, the fourth crystal structure includes a plurality of second trunks connected to the third crystal structure, the second trunks are in contact with the N-type doped layer, the number of the first trunks is greater than the number of the second trunks and / or the length of the first trunk is greater than the length of the second trunk; or, the second electrode includes a third crystal structure, and the second electrode is connected to the N-type doped layer only through the third crystal structure.

2. The solar cell according to claim 1, wherein The diameter of the first trunk is greater than the diameter of the second trunk.

3. The solar cell according to claim 1, wherein The second crystal structure further includes a plurality of first branches connected to the first trunk, wherein the first branches are in contact with the P-type doped layer; The fourth crystal structure includes a plurality of second branches connected to the second trunk, wherein the second branches are in contact with the N-type doped layer; The number of the first branches is greater than the number of the second branches and / or the length of the first branches is greater than the length of the second branches.

4. The solar cell according to claim 3, characterized in that A diameter of the first branch is greater than a diameter of the second branch.

5. The solar cell according to claim 1, wherein The first crystal structure includes a first extension portion extending into the P-type doped layer, a first eutectic layer is provided between the first extension portion and the P-type doped layer, and the second crystal structure is formed on the first extension portion, the second crystal structure passes through the first eutectic layer and contacts the P-type doped layer.

6. The solar cell according to claim 5, characterized in that The third crystal structure includes a second extension portion extending into the N-type doped layer, a second eutectic layer is provided between the second extension portion and the N-type doped layer, and the fourth crystal structure is formed on the second extension portion, the fourth crystal structure passes through the second eutectic layer and contacts the N-type doped layer.

7. The solar cell according to claim 6, characterized in that A depth of the first extension portion penetrating into the P-type doping layer is greater than a depth of the second extension portion penetrating into the N-type doping layer.

8. The solar cell according to claim 5, characterized in that The first electrode also includes a first glass layer, the first glass layer is located between the P-type doped layer and the first crystal structure, the first extension portion extends through the first glass layer into the P-type doped layer, and the first eutectic layer is provided between the first glass layer and the P-type doped layer.

9. The solar cell according to claim 6, characterized in that The second electrode further includes a second glass layer, the second glass layer is located between the N-type doped layer and the third crystal structure, the second extension portion extends through the second glass layer into the N-type doped layer, and the second eutectic layer is provided between the second glass layer and the N-type doped layer.

10. A battery assembly, characterized in that: The solar cell comprises the solar cell according to any one of claims 1 to 9.

11. A photovoltaic system, characterized in that: Comprising the battery assembly as claimed in claim 10.

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