Back-contact solar cell, cell assembly and photovoltaic system

Abstract

The present disclosure is applicable to the technical field of solar cells. Provided are a back-contact solar cell, a cell assembly and a photovoltaic system. In the back-contact solar cell, the front surface of a silicon substrate is a first surface of a wafer, the surface of the wafer that faces away from the front surface is a second surface of the wafer, the wafer further comprises several side surfaces that connect the first surface and the second surface, the second surface has a first edge region and a first middle region, the first edge region is located at a junction of the second surface and the side surfaces, and the first middle region is located on the inner side of the first edge region. A passivation layer is stacked on the wafer, the passivation layer on the first edge region has a first thickness, the passivation layer on the first middle region has a second thickness, and the first thickness is greater than the second thickness. In this way, the passivation effect at an edge position of the second surface of the wafer can be improved, the edge recombination of the back-contact solar cell can be reduced, and the conversion efficiency can be improved.

Description

Back contact solar cells, battery modules and photovoltaic systems Technical Field

[0001] This disclosure relates to the field of solar cell technology, and more particularly to a back-contact solar cell, a cell module, and a photovoltaic system. Background Technology

[0002] Solar cell power generation is a sustainable and clean energy source that utilizes the photovoltaic effect of a semiconductor pn junction to convert sunlight into electrical energy. In solar cells, back-contact solar cells are those where both the p-region and n-region are located on the back (non-light-receiving surface) of the cell. The light-receiving surface of this cell has no metal electrodes obstructing it, thus effectively increasing the short-circuit current of the cell.

[0003] In related technologies, back-contact solar cells have P-type and N-type doped layers on a silicon substrate, and passivation layers are placed on both doped layers to passivate the cell. In current back-contact solar cells, edge recombination is significant, resulting in low conversion efficiency.

[0004] Public content

[0005] This disclosure provides a back-contact solar cell, a battery module, and a photovoltaic system.

[0006] This disclosure is implemented as follows: the back-contact solar cell of the embodiments of this disclosure includes:

[0007] A substrate, comprising a silicon substrate, a plurality of P-type doped layers and a plurality of N-type doped layers, wherein the silicon substrate has opposing front and back sides, and the plurality of P-type doped layers and N-type doped layers are alternately disposed on the back side of the silicon substrate, with a gap between adjacent P-type and N-type doped layers; the front side of the silicon substrate is a first surface of the substrate, and the surface of the substrate facing away from the front side is a second surface of the substrate; the substrate further includes a plurality of side surfaces connecting the first surface and the second surface, the second surface having a first edge region and a first middle region, the first edge region being located at the junction of the second surface and the side surfaces, and the first middle region being located inside the first edge region; and

[0008] A passivation layer is stacked on the substrate, the passivation layer covers the second surface, the passivation layer on the first edge region has a first thickness, the passivation layer on the first middle region has a second thickness, and the first thickness is greater than the second thickness.

[0009] In some embodiments, the ratio of the first thickness to the second thickness is greater than 1 and less than or equal to 3.

[0010] In some embodiments, in the first intermediate region, the thickness of the passivation layer on the N-type doped layer is greater than the thickness of the passivation layer on the P-type doped layer.

[0011] In some embodiments, the ratio of the thickness of the passivation layer on the N-type doped layer to the thickness of the passivation layer on the P-type doped layer is greater than 1 and less than or equal to 2.

[0012] In some embodiments, the passivation layer further covers at least a portion of the area of ​​at least a portion of the side surface, the passivation layer on the side surface having a third thickness greater than the second thickness and less than or equal to the first thickness.

[0013] In some embodiments, the first surface has a second edge region and a second middle region, the second edge region being located at the junction of the first surface and the side surface, and the second middle region being located inside the second edge region;

[0014] The passivation layer also covers the first surface, the passivation layer on the second edge region has a fourth thickness, the passivation layer on the second middle region has a fifth thickness, and the fourth thickness is greater than the fifth thickness.

[0015] In some embodiments, the ratio of the fourth thickness to the fifth thickness is greater than 1 and less than or equal to 3.

[0016] In some embodiments, the fourth thickness is less than the first thickness, and the fifth thickness is less than or equal to the second thickness.

[0017] In some embodiments, the passivation layer further covers at least a portion of the side surface, and the thickness of the passivation layer on the side surface is greater than or equal to the fourth thickness.

[0018] In some embodiments, the passivation layer includes a first film layer and a second film layer stacked sequentially, wherein the first film layer has the same thickness on the second surface, and the portion of the second film layer covering the first edge region has a greater thickness than the portion of the second film layer covering the first middle region.

[0019] This disclosure also provides a battery assembly including a plurality of back-contact solar cells as described in any of the preceding claims.

[0020] This disclosure also provides a photovoltaic system comprising the aforementioned battery module.

[0021] In the embodiments of the back-contact solar cell, cell module, and photovoltaic system disclosed herein, the front side of the silicon substrate is the first surface of the substrate, and the surface of the substrate opposite to the front side is the second surface of the substrate. The substrate also includes several side surfaces connecting the first and second surfaces. The second surface has a first edge region and a first intermediate region. The first edge region is located at the junction of the second surface and the side surfaces, and the first intermediate region is located inside the first edge region. A passivation layer is stacked on the substrate, covering the second surface. The passivation layer on the first edge region has a first thickness, and the passivation layer on the first intermediate region has a second thickness, with the first thickness being greater than the second thickness. Thus, the thickness of the passivation layer at the first edge region of the second surface of the substrate is greater than the thickness of the passivation layer at the first intermediate region, which can improve the passivation effect at the edge of the second surface of the substrate, reduce edge recombination of the back-contact solar cell, and thereby improve the conversion efficiency.

[0022] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the modules of the photovoltaic system provided in an embodiment of this disclosure;

[0024] Figure 2 is a schematic cross-sectional structure of a back-contact solar cell provided in an embodiment of this disclosure;

[0025] Figure 3 is a schematic cross-sectional view of another back-contact solar cell provided in an embodiment of this disclosure.

[0026] Figure 4 is another cross-sectional structural diagram of the back contact solar cell provided in the embodiment of this disclosure;

[0027] Figure 5 is a schematic cross-sectional view of the passivation layer provided in an embodiment of this disclosure.

[0028] Figure 6 is another cross-sectional structural schematic diagram of the passivation layer provided in an embodiment of this disclosure. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this disclosure and are not intended to limit this disclosure.

[0030] In the description of this disclosure, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", "side", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "several" means two or more, unless otherwise explicitly specified.

[0032] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0034] Please refer to Figure 1. The photovoltaic system 1000 in this embodiment may include the battery module 200 in this embodiment. The battery module 200 in this embodiment may include a plurality of back-contact solar cells 100 in this embodiment. The plurality of back-contact solar cells 100 may be connected together in series by soldering ribbon to form a plurality of battery strings. Each battery string may be connected in series, in parallel or in series-parallel manner to form the battery module 200.

[0035] Please refer to Figure 2. The back contact solar cell 100 in this embodiment may include a substrate 10 and a passivation layer 20.

[0036] The substrate 10 has a first surface 101 and a second surface 102. Specifically, as shown in FIG2, the substrate 10 may include a silicon substrate 11, a plurality of P-type doped layers 12 and a plurality of N-type doped layers 13. The silicon substrate 11 has a front side 111 and a back side 112. The plurality of P-type doped layers 12 and the plurality of N-type doped layers 13 are stacked on the back side 112 of the silicon substrate 11 and the plurality of P-type doped layers 12 and the plurality of N-type doped layers 13 are alternately arranged in sequence. There is a spacer region 110 between adjacent P-type doped layers 12 and N-type doped layers 13.

[0037] Among them, the front side 111 of the silicon substrate 11 is the first surface 101 of the substrate 10, and the surface of the substrate 10 away from the front side 111 is the second surface 102 of the substrate 10. That is, the second surface 102 includes the surface of the P-type doped layer 12 and the N-type doped layer 13 away from the back side 112 of the silicon substrate 11, the surface of the P-type doped layer 12 and the N-type doped layer 13 exposed at the spacer region 110, and the surface of the silicon substrate 11 exposed at the spacer region 110. It can be seen that the second surface 102 is not a flat surface.

[0038] The substrate 10 also includes several side surfaces 103 connecting the first surface 101 and the second surface 102. The second surface 102 has a first edge region 1021 and a first intermediate region 1022. The first edge region 1021 is located at the junction of the second surface 102 and the side surfaces 103, and the first intermediate region 1022 is located inside the first edge region 1021. That is, the first edge region 1021 is located at the edge of the second surface 102, and the first intermediate region 1022 is located in the middle of the second surface 102. The first edge region 1021 is located between the first intermediate region 1022 and the side surfaces 103. As shown in Figure 2, "first edge region 1021" refers to the edge region of the second surface 102 located at the junction of the second surface 102 and the side surfaces 103, and "first intermediate region 1022" refers to the region of the second surface 102 other than the first edge region 1021.

[0039] A passivation layer 20 is stacked on the substrate 10, and the passivation layer 20 covers the second surface 102. The passivation layer 20 on the first edge region 1021 has a first thickness D1, and the passivation layer 20 on the first middle region 1022 has a second thickness D2. The first thickness D1 is greater than the second thickness D2.

[0040] In the back-contact solar cell 100, cell module 200, and photovoltaic system 1000 of the embodiments of this disclosure, the front side 111 of the silicon substrate 11 is the first surface 101 of the substrate 10, and the surface of the substrate 10 opposite to the front side 111 is the second surface 102 of the substrate 10. The substrate 10 also includes a plurality of side surfaces 103 connecting the first surface 101 and the second surface 102. The second surface 102 has a first edge region 1021 and a first intermediate region 1022. The first edge region 1021 is located at the junction of the second surface 102 and the side surfaces 103, and the first intermediate region 1022 is located inside the first edge region 1021. A passivation layer 20 is stacked on the substrate 10, covering the second surface 102. The passivation layer 20 on the first edge region 1021 has a first thickness D1, and the passivation layer 20 on the first intermediate region 1022 has a second thickness D2. The first thickness D1 is greater than the second thickness D2. Thus, the thickness of the passivation layer 20 at the first edge region 1021 of the second surface 102 of the substrate 10 is greater than the thickness of the passivation layer 20 at the first middle region 1022. This can improve the passivation effect at the edge of the second surface 102 of the substrate 10, reduce edge recombination of the back contact solar cell 100, and thus improve the conversion efficiency.

[0041] Specifically, it is not difficult to understand that in the back contact solar cell 100, in the substrate 10, between the P-type doped layer 12 and the N-type doped layer 13 and the silicon substrate 11, a tunneling layer is typically also provided. Furthermore, it can be understood that the back contact solar cell 100 also includes a P-type electrode and an N-type electrode (not shown in the figure), with the P-type electrode penetrating the passivation layer 20 and contacting the P-type doped layer 12, and the N-type electrode penetrating the passivation layer 20 and contacting the N-type doped layer 13.

[0042] Furthermore, in this article, a membrane layer covering a surface or a membrane layer can mean that the membrane layer is directly stacked on the surface or a membrane layer, or that other membrane layers are disposed between the membrane layer and the surface or membrane layer. The term "covering" is merely used to define the specific placement range of the membrane layer.

[0043] In some embodiments, the ratio of the first thickness D1 to the second thickness D2 is greater than 1 and less than or equal to 3, that is, 1 < D1 / D2 ≤ 3.

[0044] By setting the ratio of the first thickness D1 and the second thickness D2 within this reasonable range, the passivation effect at the edge region of the second surface 102 can be improved while keeping the cost relatively low.

[0045] Specifically, in such embodiments, the ratio of the first thickness D1 to the second thickness D2 can be, for example, any value between 1.01, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.2, 2.4, 2.6, 2.8, 3, or greater than 1 and less than or equal to 3, without any specific limitation herein.

[0046] In some embodiments, in the first intermediate region 1022, the thickness of the passivation layer 20 on the N-type doped layer 13 is greater than the thickness of the passivation layer 20 on the P-type doped layer 12.

[0047] Thus, in the first intermediate region 1022, the passivation layer 20 on the N-type doped layer 13 has a larger thickness, which can improve the passivation effect of the region corresponding to the N-type doped layer 13, thereby achieving a better matching effect between the passivation effects of the regions corresponding to the P-type doped layer 12 and the N-type doped layer 13, and thus improving the performance of the back contact solar cell 100.

[0048] Furthermore, in such an embodiment, the ratio of the thickness of the passivation layer 20 on the N-type doped layer 13 to the thickness of the passivation layer 20 on the P-type doped layer 12 is greater than 1 and less than or equal to 2.

[0049] Thus, by setting the ratio between the thickness of the passivation layer 20 on the N-type doped layer 13 and the thickness of the passivation layer 20 on the P-type doped layer 12 within this reasonable range, the passivation effect of the corresponding regions of the P-type doped layer 12 and the N-type doped layer 13 can achieve the optimal matching effect while keeping the cost relatively low.

[0050] Specifically, in such embodiments, the thickness ratio of the two can be, for example, any value between 1.01, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, or greater than 1 and less than or equal to 2, without any specific limitation herein.

[0051] Referring to Figure 3, in some embodiments, the passivation layer 20 also covers at least a portion of the side surface 103, preferably completely covering at least a portion of the side surface 103. The passivation layer 20 on the side surface 103 has a third thickness D3, which is greater than the second thickness D2 and less than or equal to the first thickness D1.

[0052] Thus, the side surface 103 of the substrate 10 is also covered with a passivation layer 20, and the passivation layer 20 on the side surface 103 is greater than the second thickness D2 and less than the first thickness D1. This allows for efficient passivation of the side surface 103 of the substrate 10, further reducing edge recombination and thus further improving conversion efficiency.

[0053] Specifically, in such embodiments, the passivation layer 20 preferably completely covers all sides 103 of the substrate 10 to achieve the optimal passivation effect. Of course, it is understood that in some embodiments, the passivation layer 20 may only cover part of the sides 103. For example, in one possible embodiment, in a half-cell battery, after cutting, the side 103 formed by cutting the half-cell battery does not have the passivation layer 20, while the other sides 103 have the passivation layer 20.

[0054] Referring to Figure 4, in some embodiments, the first surface 101 has a second edge region 1011 and a second intermediate region 1012. The second edge region 1011 is located at the junction of the first surface 101 and the side surface 103, and the second intermediate region 1012 is located inside the second edge region 1011. That is, the second edge region 1011 is located at the edge of the first surface 101, and the second intermediate region 1012 is located in the middle of the first surface 101. The second edge region 1011 is located between the second intermediate region 1012 and the side surface 103. In other words, as shown in Figure 4, "second edge region 1011" refers to the edge region of the first surface 101 located at the junction of the first surface 101 and the side surface 103, and "second intermediate region 1012" refers to the region of the first surface 101 other than the second edge region 1011.

[0055] In such an embodiment, the passivation layer 20 also covers the first surface 101, that is, the passivation layer 20 covers the first surface 101, the second surface 102, and at least a portion of the side surface 103. The passivation layer 20 on the second edge region 1011 has a fourth thickness D4, and the passivation layer 20 on the second intermediate region 1012 has a fifth thickness D5, wherein the fourth thickness D4 is greater than the fifth thickness D5.

[0056] Thus, the thickness of the passivation layer 20 at the second edge region 1011 of the first surface 101 of the substrate 10 is greater than the thickness of the passivation layer 20 at the second middle region 1012. This can improve the passivation effect at the edge of the first surface 101 of the substrate 10, further reduce edge recombination of the back contact solar cell 100, and thus further improve the conversion efficiency.

[0057] In some embodiments, the ratio of the fourth thickness D4 to the fifth thickness D5 is greater than 1 and less than or equal to 3, that is, 1 < D4 / D5 ≤ 3.

[0058] Thus, by setting the ratio of the fourth thickness D4 to the fifth thickness D5 within this reasonable range, the passivation effect at the edge region of the first surface 101 can be improved while keeping the cost relatively low.

[0059] Specifically, in such embodiments, the ratio of the fourth thickness D4 to the fifth thickness D5 can be, for example, any value between 1.01, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.2, 2.4, 2.6, 2.8, 3, or greater than 1 and less than or equal to 3, without any specific limitation herein.

[0060] In some embodiments, the fourth thickness D4 is less than the first thickness D1, and the fifth thickness D5 is less than or equal to the second thickness D2.

[0061] In this way, by reasonably configuring the thickness of the passivation layer 20 in each region of the first surface 101 and the second surface 102, a better matching effect of passivation effect can be achieved in each region, while also keeping the cost relatively low.

[0062] Furthermore, in such an embodiment, the passivation layer 20 also covers at least a portion of the side surface 103, and the thickness of the passivation layer 20 on the side surface 103 is greater than or equal to a fourth thickness D4, that is, the third thickness D3 mentioned above is greater than or equal to the fourth thickness D4. In this way, the passivation effect of the side surface 103 can be improved to reduce edge commingling while achieving a better matching state of passivation effect in each region.

[0063] In this document, a thickness greater than or equal to another thickness can mean that the thickness of the passivation layer 20 in one region is greater than the thickness of the passivation layer 20 in another region at any location, or it can mean that the thickness of the passivation layer 20 in one region is greater than the thickness of the passivation layer 20 in another region, while the thickness of the passivation layer 20 in other parts of the region is the same as the thickness of the passivation layer 20 in another region. If the same description appears in the following text, please refer to this document for understanding.

[0064] Referring to Figure 5, in some embodiments, the passivation layer 20 may include a first film layer 21 and a second film layer 22 stacked sequentially. The first film layer 21 has the same thickness on the second surface 102, and the thickness of the portion of the second film layer 22 covering the first edge region 1021 is greater than the thickness of the portion of the second film layer 22 covering the first middle region 1022.

[0065] In this way, the passivation layer 20 can achieve different thicknesses in different regions by adjusting the thickness of the second film layer 22.

[0066] Specifically, in the embodiments of this disclosure, the first film layer 21 may be an aluminum oxide film layer, and the second film layer 22 may be a silicon nitride film layer. The first film layer 21 may be prepared by atomic deposition, and the second film layer 22 may be prepared by PECVD deposition. Furthermore, it is understood that, in this document, all regions of the passivation layer 20 with different thicknesses can achieve different thicknesses by controlling the thickness of the second film layer 22.

[0067] Of course, referring to Figure 6, it can be understood that in some embodiments, the passivation layer 20 may also include a third film layer 23. The third film layer 23 may be stacked between the first film layer 21 and the substrate 10, and the second film layer 22 may be stacked on the first film layer 21. For example, in some embodiments, the third film layer 23 may be a silicon oxide film layer. The third film layer 23 may also be prepared by PECVD deposition process. In such cases, the thickness difference of the passivation layer 20 in different regions can be achieved by controlling the thickness difference of the second film layer 22 and / or the third film layer 23.

[0068] As shown in Figure 4, in this disclosure, the structure shown in Figure 4 is preferably adopted, wherein the passivation layer 20 covers the first surface 101, the side surface 103 and the second surface 102, wherein the first thickness D1 is greater than the second thickness D2, the third thickness D3 is greater than the second thickness D2 and less than or equal to the first thickness D1, and the fourth thickness D4 is greater than the fifth thickness D5 and less than the third thickness D3.

[0069] In the description of this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above 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 one or more embodiments or examples.

[0070] Furthermore, the above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A back contact solar cell, comprising: a substrate, the substrate comprising a silicon base having opposite front and back surfaces, a plurality of P-type doped layers and a plurality of N-type doped layers, the plurality of P-type doped layers and N-type doped layers being arranged alternately on the back surface of the silicon base in sequence, and having a spacing between adjacent P-type doped layers and N-type doped layers; the front surface of the silicon base being a first surface of the substrate, a surface of the substrate facing away from the front surface being a second surface of the substrate, the substrate further comprising a plurality of side surfaces connecting the first surface and the second surface, the second surface having a first edge region and a first middle region, the first edge region being located at the junction of the second surface and the side surfaces, and the first middle region being located inside the first edge region; and a passivation layer stacked on the substrate, the passivation layer covering the second surface, the passivation layer on the first edge region having a first thickness, and the passivation layer on the first middle region having a second thickness, the first thickness being greater than the second thickness.

2. The back contact solar cell of claim 1, wherein, The ratio of the first thickness to the second thickness is greater than 1 and less than or equal to 3.

3. The back contact solar cell of claim 1, wherein, In the first middle region, the thickness of the passivation layer on the N-type doped layer is greater than the thickness of the passivation layer on the P-type doped layer.

4. The back contact solar cell of claim 3, wherein, The ratio of the thickness of the passivation layer on the N-type doped layer to the thickness of the passivation layer on the P-type doped layer is greater than 1 and less than or equal to 2.

5. The back contact solar cell of claim 1, wherein, The passivation layer also covers at least part of the area of at least part of the side surfaces, the passivation layer on the side surfaces having a third thickness, the third thickness being greater than the second thickness and less than or equal to the first thickness.

6. The back contact solar cell of claim 1, wherein, The first surface has a second edge region and a second middle region, the second edge region being located at the junction of the first surface and the side surfaces, and the second middle region being located inside the second edge region; The passivation layer also covers the first surface, the thickness of the passivation layer on the second edge region having a fourth thickness, and the thickness of the passivation layer on the second middle region having a fifth thickness, the fourth thickness being greater than the fifth thickness.

7. The back contact solar cell of claim 6, wherein, The ratio of the fourth thickness to the fifth thickness is greater than 1 and less than or equal to 3.

8. The back contact solar cell of claim 6, wherein, The fourth thickness is less than the first thickness, and the fifth thickness is less than or equal to the second thickness.

9. The back contact solar cell of claim 6, wherein, The passivation layer also covers at least part of the side surfaces, the thickness of the passivation layer on the side surfaces being greater than or equal to the fourth thickness.

10. The back contact solar cell of any of claims 1-9, wherein, The passivation layer comprises a first film layer and a second film layer stacked in sequence, the thickness of the first film layer on the second surface being the same, and the thickness of the second film layer covering part of the first edge region being greater than the thickness of the second film layer covering part of the first middle region. 11.A battery assembly comprising a plurality of back contact solar cell according to any one of claims 1-10. 12.A photovoltaic system comprising the battery assembly according to claim 11.

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