Solar cell string, photovoltaic module and photovoltaic system

Abstract

The utility model is applicable to the technical field of solar cell production, and provides a solar cell string, a photovoltaic assembly and a photovoltaic system, the solar cell string comprises back contact cells and solder strips, one solder strip is welded on at least two adjacent backlight surfaces, each solder strip extends along a third direction, and the back contact cells are arranged on the back contact cells. An acute included angle is formed between the third direction and the first direction, a welding strip is cut off in the gap to form a cut-off part, the welding strip is cut off in the cut-off part to form two opposite free sections, and the length size of each free section is smaller than one half of the distance between any two adjacent welding strips. According to the utility model, the two free sections of the same cut-off part cannot be lapped together. Therefore, the possibility of short circuit of the back contact battery piece caused by connection of the two free sections in the same cut-off part is reduced, and the stability and the reliability of operation of the solar battery string are improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of solar cell production, and in particular relates to a solar cell string, a photovoltaic component and a photovoltaic system. Background Art

[0002] As the global climate worsens and the energy crisis intensifies, the demand for renewable clean energy is becoming more and more urgent. Solar energy, as a renewable clean energy source in nature, has received widespread attention and attention. In existing technologies, solar energy is mainly converted and utilized through photovoltaic modules, which can convert solar energy into electricity that can be used by people in daily life. Photovoltaic modules usually include a solar cell string composed of multiple solar cells, and a solar cell string is usually formed by multiple solar cells connected by welding ribbons. Since solar cells receive sunlight and convert solar energy into electricity, in existing solar cell strings, in order to reduce the area of ​​solar cells blocked by connection structures such as welding ribbons and metal grids, the electrodes of the solar cells are all set on the backlight side. This type of solar cell is called a back contact cell. This way, the front side of the solar cell that receives sunlight is not blocked by welding ribbons and metal grids, thereby increasing the area of ​​the solar cell that receives solar energy.

[0003] In a solar cell string composed of back-contact cells, every other solder ribbon is cut to leave a free section between adjacent back-contact cells, thereby enabling serial connection between multiple back-contact cells. However, the free section of the cut solder ribbon is typically of a certain length, and this free section can move between adjacent back-contact cells or between adjacent first and second doped layers on the same back-contact cell. Consequently, the free section may overlap the solder ribbon or adjacent doped layers on adjacent back-contact cells, causing a short circuit in the solar cell string and potentially damaging the string. Utility Model Content

[0004] The embodiment of the present utility model provides a battery string, which aims to reduce the possibility of line short circuit in the battery string and improve the operation stability and reliability of the battery string.

[0005] The embodiment of the present invention is implemented as follows: a solar cell string, comprising:

[0006] A back-contact cell, wherein a plurality of the back-contact cells are arranged at intervals in a first direction, each of the back-contact cells has a backlight surface, each of the backlight surfaces is provided with a plurality of first doped layers and a plurality of second doped layers, and in a second direction, the first doped layers and the second doped layers on one of the backlight surfaces are alternately arranged, and in the first direction, the first doped layers and the second doped layers are arranged opposite to each other, the polarities of the first doped layers and the second doped layers are opposite, and the first direction and the second direction intersect;

[0007] A plurality of solder strips are arranged at intervals in the second direction. In the first direction, one solder strip is soldered to at least two adjacent backlight surfaces to electrically connect the adjacent first doped layers and the second doped layers. Each solder strip extends along a third direction, and the third direction forms an acute angle with the first direction.

[0008] In the first direction, a gap is provided between two adjacent back-contact battery cells, and one of the welding strips is cut in the gap to form a truncation portion, and the welding strip is cut in the truncation portion to form two opposite free segments. In the second direction, the truncation portions are alternately arranged, and in the second direction, the length of each free segment is less than half of the distance between any two adjacent welding strips.

[0009] Furthermore, the angle α between the first direction and the third direction satisfies the following relationship: 0<tanα≤D / L;

[0010] Wherein, L is the total length of the farthest ends of the first and last battery cells in the battery string along the first direction, and D is the width of any doping layer of the battery cell along the second direction.

[0011] Furthermore, in the first direction, the length of the gap is set between 0.3 mm and 1.2 mm.

[0012] Furthermore, in the second direction, the distance between any two welding strips is set between 0.3 mm and 1.2 mm.

[0013] Furthermore, the solar cell string further includes metal grid lines provided on the backlight surface, a plurality of the metal grid lines are electrically connected to both the first doped layer and the second doped layer, and the welding ribbon covers or partially covers the metal grid lines.

[0014] Furthermore, in the second direction, the length of each free segment is less than half of the distance between any two adjacent metal grid lines.

[0015] Furthermore, in the second direction, the plurality of solder strips are arranged in parallel with each other, and the plurality of metal grid lines are arranged in parallel with each other.

[0016] Furthermore, an insulating layer is coated on the end of each free segment.

[0017] An embodiment of the present invention further provides a photovoltaic assembly, comprising the aforementioned solar cell string.

[0018] An embodiment of the present invention further provides a photovoltaic system, comprising the aforementioned photovoltaic assembly.

[0019] In the solar cell string of the present invention, the length of the soldering ribbon extends along the third direction and forms an acute angle with the first direction. This increases the electrical contact area between the soldering ribbon and the first and second doped layers, reduces the contact resistance between the soldering ribbon and the first and second doped layers, and reduces energy loss when current is directed to the soldering ribbon via the first or second doped layers, thereby improving the overall output power of the solar cell string. In the second direction, the length of each free segment is set to be less than half the distance between any two adjacent soldering ribbons, thereby reducing the length of each free segment. This prevents the free segment from overlapping or contacting adjacent soldering ribbons, reducing the possibility of the free segment and adjacent soldering ribbon causing a short circuit in the solar cell string, thereby improving the stability and reliability of the solar cell string operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a solar cell string provided by an embodiment of the present utility model;

[0021] Figure 2 This is a side view of a solar cell string provided by an embodiment of the present utility model;

[0022] Figure 3 This is a schematic structural diagram of a photovoltaic module provided by an embodiment of the present utility model;

[0023] Figure 4 It is a structural diagram of a photovoltaic system provided by an embodiment of the present utility model.

[0024] Explanation of the reference numerals: 100, solar cell string; 110, back contact cell; 111, backlight surface; 112, first doped layer; 113, second doped layer; 114, gap; 120, welding ribbon; 121, truncation portion; 122, free segment; 130, metal grid line; 140, insulating layer; 200, photovoltaic module; 300, photovoltaic system. DETAILED DESCRIPTION

[0025] 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. 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.

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated in the description of the direction and positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply 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.

[0027] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0028] 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 appreciate the application of other processes and / or the use of other materials.

[0029] In a solar cell string composed of back-contact cells, every other soldering ribbon is cut off so that there is a cut free section between adjacent back-contact cells, thereby enabling a series connection between multiple back-contact cells. However, the free section of the cut soldering ribbon generally has a certain length, and the free section may swing between adjacent back-contact cells, or move between adjacent first doping layers and second doping layers on the same back-contact cell. Therefore, the free section may overlap the soldering ribbon or adjacent doping layer on the adjacent back-contact cell, thereby causing a short circuit in the solar cell string and damaging the solar cell string. To this end, the present invention proposes a cell string that aims to reduce the possibility of a short circuit in the cell string and improve the operational stability and reliability of the cell string.

[0030] See also Figures 1 to 2The battery string proposed in an embodiment of the present invention includes a back-contact battery cell 110 and a welding ribbon 120. A plurality of back-contact battery cells 110 are arranged at intervals in the first direction. Each back-contact battery cell 110 has a backlight surface 111. Each backlight surface 111 is provided with a plurality of first doping layers 112 and a plurality of second doping layers 113. In the second direction, the first doping layers 112 and the second doping layers 113 on a backlight surface 111 are alternately arranged at intervals. In the first direction, the first doping layers 112 and the second doping layers 113 are arranged opposite to each other, the polarities of the first doping layers 112 and the second doping layers 113 are opposite, and the first direction and the second direction intersect.

[0031] It is known that solar cells convert solar energy into electrical energy through a pn junction, and the pn junction is formed by a p-type doped layer and an n-type doped layer arranged on the solar cell. The back contact cell 110 mentioned above refers to a solar cell in which both the p-type doped layer and the n-type doped layer are arranged on the backlight surface 111 of the back contact cell 110. The backlight surface 111 here refers to the side of the back contact cell 110 that faces away from the sun and is not exposed to sunlight. In this way, by arranging the p-type doped layer and the n-type doped layer on the backlight surface 111 of the back contact cell 110, the area of ​​the back contact cell 110 blocked by the soldering ribbon 120 and other electrical connection structures is reduced, the area of ​​the back contact cell 110 exposed to sunlight is increased, and the photoelectric conversion efficiency of the back contact cell 110 is improved. In this article, the first doping layer 112 is configured as a p-type doping layer, and the second doping layer 113 is configured as an n-type doping layer. Since the main carriers in the p-type doping layer have positive charge characteristics and the main carriers in the n-type doping layer have negative charge characteristics, the polarities of the first doping layer 112 and the second doping layer 113 are opposite.

[0032] There are multiple soldering strips 120 arranged in the second direction. In the first direction, one soldering strip 120 is soldered to at least two adjacent backlight surfaces 111 to electrically connect the adjacent first doping layer 112 and the second doping layer 113. Each soldering strip 120 extends along the third direction, and the third direction forms an acute angle with the first direction.

[0033] Furthermore, a soldering ribbon 120 is connected to at least two adjacent backlight surfaces 111 in a first direction to connect the first doped layers 112 and second doped layers 113 disposed oppositely on two adjacent back-contact solar cells 110, thereby achieving a series connection of adjacent back-contact solar cells 110. It is understood that the number of back-contact solar cells 110 connected in series by the soldering ribbon 120 in the first direction is greater than two. The length of the soldering ribbon 120 extends along a third direction and forms an acute angle with the first direction to increase the electrical contact area between the soldering ribbon 120 and the first doped layers 112 and the second doped layers 113, thereby reducing the contact resistance between the soldering ribbon 120 and the first doped layers 112 and the second doped layers 113, and reducing energy loss when current is directed to the soldering ribbon 120 via the first doped layer 112 or the second doped layer 113, thereby increasing the overall output power of the solar cell string 100. Furthermore, the connection strength between the soldering ribbon 120 and the back contact cell 110 is increased, and the connection strength between the plurality of back contact cell sheets 110 is increased, thereby improving the overall structural stability of the solar cell string 100 .

[0034] In the first direction, a gap 114 is provided between two adjacent back-contact battery cells 110, and a welding strip 120 is cut in the gap 114 to form a truncation portion 121. The welding strip 120 is cut in the truncation portion 121 to form two opposite free segments 122. In the second direction, the truncation portions 121 are alternately arranged. In the second direction, the length of each free segment 122 is less than half of the distance between any two adjacent welding strips 120.

[0035] As can be seen, since multiple solder ribbons 120 connect multiple back-contact cells 110 to form a solar cell string 100, every other solder ribbon 120 must be cut, leaving a cut free segment 122 between adjacent back-contact cells 110. This allows for serial connection between the multiple back-contact cells 110. However, the free segments 122 of the cut solder ribbons 120 are typically of a certain length and are not constrained. These free segments 122 may sway between adjacent back-contact cells 110 or move between adjacent first doped layers 112 and second doped layers 113 on the same back-contact cell 110. Consequently, the free segments 122 may overlap the solder ribbons 120 or electrical connection structures on adjacent back-contact cells 110, causing a short circuit in the solar cell string 100 and potentially damaging the solar cell string 100.

[0036] Thus, in the second direction, the length of each free segment 122 is set to be less than half the distance between any two adjacent solder ribbons 120, thereby reducing the length of each free segment 122. This prevents the free segments 122 from overlapping or contacting adjacent solder ribbons 120, reducing the possibility of a short circuit in the solar cell string 100 caused by a free segment 122 and an adjacent solder ribbon 120, thereby improving the stability and reliability of the solar cell string 100. Because a cutout 121 includes two free segments 122 from the same solder ribbon 120, if only the length of the free segments 122 between two adjacent solder ribbons 120 is restricted, one free segment 122 may connect with another free segment 122 in the first direction, thereby causing a short circuit in the back contact cell 110. Therefore, the possibility of two free segments 122 in the same cutout 121 connecting and causing a short circuit in the back contact cell 110 is reduced, improving the stability and reliability of the solar cell string 100.

[0037] Further, in some optional embodiments, the angle α between the first direction and the third direction satisfies the following relationship: 0<tanα≤D / L;

[0038] Wherein, L is the total length of the farthest ends of the first back contact cell 110 and the last back contact cell 110 in the solar cell string 100 along the first direction, and D is the width of any doped layer of the back contact cell 110 along the second direction.

[0039] In this way, the tilt angle of the solder ribbon 120 can be determined based on the length of the solar cell string 100. The angle can be adjusted for solar cell strings 100 of different lengths and types, so that a single solder ribbon 120 can completely cover the doped layers along the same straight line of multiple back-contact solar cells 110. This facilitates manufacturing processes. After the solder ribbon 120 connects multiple back-contact solar cells 110 in series, it can be selectively cut using a laser to form solar cell strings 100 in pairs.

[0040] Specifically, according to the length of the solar cell string 100 and the width of the doping layer, the inclination angle of the welding ribbon 120 is flexibly adjusted to adapt to the specific needs of different solar cell strings 100, ensuring that the welding ribbon 120 can completely cover the doping layer. Then, by accurately calculating the angle α, the welding ribbon 120 can extend in a straight line when covering the doping layer, thereby improving the efficiency and consistency of welding. One weld can completely cover the doping layers of multiple back contact cells 110 on the process production line, simplifying the welding process, reducing the welding steps, and improving production efficiency. After the welding ribbon 120 connects multiple back contact cells 110 in series, it is selectively sheared by laser to form a solar cell string 100 in groups of two. This method is efficient and accurate, and reduces the complexity of the production process.

[0041] For example, a solar cell string 100 may include nine back-contact cells 110 evenly distributed along a first direction, where L is the distance between the farthest ends of the nine back-contact cells 110. The tilt angle α is calculated based on this length and the width of the doped layer in the second direction, allowing the solder ribbon 120 to be tilted at the angle α.

[0042] In the embodiment of the present application, the angle range between the first direction and the third direction is not limited to meet different requirements. In this way, it can be adjusted according to the length of different solar cell strings 100 and the width of the doping layer in the second direction.

[0043] Furthermore, in the first direction, the length dimension of the gap 114 is set between 0.3 mm and 1.2 mm.

[0044] Thus, the length of gap 114 is set between 0.3 mm and 1.2 mm, keeping the length of gap 114 within a relatively suitable range. If the length of gap 114 is set to less than 0.3 mm, the gap 114 may be too small to easily cut the solder ribbon 120 within the gap 114, increasing the difficulty in processing the solder ribbon 120 and, consequently, the difficulty in manufacturing the solar cell string 100. If the length of gap 114 is set to greater than 1.2 mm, the gap 114 may be too large, reducing the effective power generation area of ​​the solar cell string 100 and, consequently, the overall output power of the solar cell string 100. The excessively large gap 114 may also increase the overall size of the solar cell string 100, or even the photovoltaic module 200.

[0045] Specifically, the length of the gap 114 can be, for example, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, etc.

[0046] Optionally, in one embodiment, in the second direction, the distance between any two welding strips 120 is set to be between 0.3 mm and 1.2 mm.

[0047] Specifically, the distance between the welding strips 120 may be, for example, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or other values.

[0048] Optionally, in one embodiment, the solar cell string 100 further includes a metal grid line 130 provided on the backlight surface 111 , and multiple metal grid lines 130 are electrically connected to the first doped layer 112 and the second doped layer 113 , and the welding ribbon 120 covers or partially covers the metal grid lines 130 .

[0049] In this manner, multiple metal grid lines 130 are electrically connected to both the first doped layer 112 and the second doped layer 113, and the soldering ribbon 120 is soldered to the metal grid lines 130. The metal grid lines 130 are primarily used to collect current generated by carriers in the first doped layer 112 and the second doped layer 113. The soldering ribbon 120 is soldered to the metal grid lines 130 to conduct the current on the metal grid lines 130 to an external circuit. Therefore, multiple soldering points are formed between the metal grid lines 130 and the soldering ribbon 120. The provision of multiple metal grid lines 130 prevents the soldering ribbon 120 from shifting or falling off, thereby enhancing the connection stability of the soldering ribbon 120 to the back contact cell 110 and thereby improving the overall structural strength of the solar cell string 100.

[0050] Furthermore, in the second direction, the length of each free segment 122 is less than half of the distance between any two adjacent metal gate lines 130 .

[0051] As such, since the metal grid lines 130 are metal elements with good electrical conductivity, if the free segments 122 overlap the metal grid lines 130, it will also cause a short circuit in the solar cell string 100, thereby damaging the solar cell string 100. Therefore, the length of the free segments 122 is set to be less than half the distance between any two adjacent metal grid lines 130 to reduce the possibility of the free segments 122 overlapping adjacent metal grid lines 130, thereby improving the operational stability and reliability of the solar cell string 100.

[0052] As can be seen, the metal grid line 130 is a metal element with a certain width. Specifically, in some embodiments, if the width of the metal grid line 130 is greater than or equal to the width of the welding strip 120, the distance between two adjacent metal grid lines 130 in the second direction is less than or equal to the distance between two adjacent welding strips 120. Therefore, it is only necessary to set the length of the free segment 122 to be less than or equal to the distance between two adjacent metal grid lines 130 to prevent the free segment 122 from overlapping the adjacent metal grid lines 130. If the width of the metal grid line 130 is less than the width of the welding strip 120, the distance between two adjacent metal grid lines 130 in the second direction is greater than the distance between two adjacent welding strips 120. Therefore, it is necessary to set the length of the free segment 122 to be less than the distance between two adjacent welding strips 120 to prevent the free segment 122 from overlapping the adjacent metal grid lines 130.

[0053] Furthermore, in the second direction, the plurality of solder strips 120 are arranged in parallel with each other, and the plurality of metal grid lines 130 are arranged in parallel with each other.

[0054] Thus, arranging multiple solder ribbons 120 in parallel in the second direction helps evenly distribute the current generated by the back-contact cell 110, reducing the concentration of current in a single area that can lead to overheating of the back-contact cell 110, or uneven stress that can cause fracture, thereby improving the service life and operational stability of the solar cell string 100. Furthermore, arranging multiple solder ribbons 120 in parallel can reduce the possibility of end-to-end contact between the solder ribbons 120 and improve the overall appearance of the solar cell string 100. Arranging multiple metal grid lines 130 in parallel in the second direction provides a larger contact area between the metal grid lines 130 and the solder ribbons 120, improving the electrical conductivity between the solder ribbons 120 and the metal grid lines 130, and improving the overall appearance of the solar cell string 100.

[0055] Optionally, in one embodiment, an insulating layer 140 is coated on the end of each free segment 122 .

[0056] In this way, an insulating layer 140 is coated on the end of each free segment 122 to insulate the end of the free segment 122, reduce the possibility of leakage of the free segment 122 or electrical connection with other components, and further reduce the possibility of short circuit in the solar cell string 100 line.

[0057] See also Figure 3 The present invention also provides a photovoltaic module 200 comprising the aforementioned solar cell string 100. The details of the solar cell string 100 are described in detail in the aforementioned embodiments. Since the photovoltaic module 200 utilizes all of the technical solutions of all of the aforementioned embodiments, it at least possesses all of the beneficial effects brought about by the technical solutions of the aforementioned embodiments, and therefore, no further details will be given here.

[0058] Of course, in this embodiment, a complete photovoltaic module 200 generally includes the aforementioned solar cell string 100 composed of back-contact cells 110, as well as a junction box for collecting the current generated by the back-contact cells 110 to direct the current to an external circuit. In addition, there are components such as a frame and a backsheet provided on the back-contact cells 110 to provide mechanical support for the back-contact cells 110, thereby enhancing the overall structural stability of the photovoltaic module 200, as well as connectors for connecting to equipment such as a photovoltaic inverter or combiner box. Of course, an identification label is generally affixed to the outside of the photovoltaic module 200 to display the technical parameters of the photovoltaic module 200, such as rated power, open-circuit voltage, short-circuit current, and warning light information.

[0059] See also Figure 4The present invention also provides a photovoltaic system 300 including the aforementioned photovoltaic module 200. The specific details of the photovoltaic module 200 are described in the aforementioned embodiments. Since the photovoltaic system 300 utilizes all the technical solutions of all the aforementioned embodiments, it at least has all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, and therefore will not be described in detail here.

[0060] In this embodiment, the photovoltaic assembly 200 and the photovoltaic system 300 can be used in photovoltaic power stations, such as rooftop power stations, water surface power stations, etc. They can also be used in devices that use solar energy to generate electricity, such as solar power banks, solar cars, solar mobile phones, etc. Of course, the application scenarios of the photovoltaic system 300 are not limited to this. The photovoltaic system 300 can be used in all fields that require the use of solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system 300 may include a junction box and a photovoltaic inverter. For example, a plurality of back-contact cells 110 can form a plurality of photovoltaic arrays, and the photovoltaic arrays are connected to a junction box. The junction box can converge the current generated by the photovoltaic arrays, and the converged current flows through the photovoltaic inverter to be converted into the current required for people's daily production and life.

[0061] It is understandable that those skilled in the art can, under the guidance of the above embodiments, combine various implementation methods in the above embodiments to obtain technical solutions of multiple implementation methods.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements 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 string, characterized in that: include: A back-contact cell, wherein a plurality of the back-contact cells are arranged at intervals in a first direction, each of the back-contact cells has a backlight surface, each of the backlight surfaces is provided with a plurality of first doped layers and a plurality of second doped layers, and in a second direction, the first doped layers and the second doped layers on one of the backlight surfaces are alternately arranged, and in the first direction, the first doped layers and the second doped layers are arranged opposite to each other, the polarities of the first doped layers and the second doped layers are opposite, and the first direction and the second direction intersect; A plurality of solder strips are arranged at intervals in the second direction. In the first direction, one solder strip is soldered to at least two adjacent backlight surfaces to electrically connect the adjacent first doped layers and the second doped layers. Each solder strip extends along a third direction, and the third direction forms an acute angle with the first direction. In the first direction, a gap is provided between two adjacent back-contact battery cells, and one of the welding strips is cut in the gap to form a truncation portion, and the welding strip is cut in the truncation portion to form two opposite free segments. In the second direction, the truncation portions are alternately arranged, and in the second direction, the length of each free segment is less than half of the distance between any two adjacent welding strips.

2. The solar cell string according to claim 1, wherein: The angle α between the first direction and the third direction satisfies the following relationship: 0<tanα≤D / L; Wherein, L is the total length of the farthest ends of the first and last battery cells in the battery string along the first direction, and D is the width of any doping layer of the battery cell along the second direction.

3. The solar cell string according to claim 1, wherein: In the first direction, the length dimension of the gap is set between 0.3 mm and 1.2 mm.

4. The solar cell string according to claim 1, wherein: In the second direction, the distance between any two welding strips is set between 0.3 mm and 1.2 mm.

5. The solar cell string according to claim 1, wherein: The solar cell string further includes metal grid lines arranged on the backlight surface. A plurality of the metal grid lines are electrically connected to both the first doped layer and the second doped layer. The welding strip covers or partially covers the metal grid lines.

6. The solar cell string according to claim 5, wherein: In the second direction, the length of each free segment is less than half of the distance between any two adjacent metal grid lines.

7. The solar cell string according to claim 5, wherein: In the second direction, the plurality of solder strips are arranged in parallel with each other, and the plurality of metal grid lines are arranged in parallel with each other.

8. The solar cell string according to claim 1, wherein: An insulating layer is coated on the end of each free segment.

9. A photovoltaic module, characterized in that: The invention comprises the solar cell string according to any one of claims 1 to 8.

10. A photovoltaic system, characterized in that: Comprising the photovoltaic module as claimed in claim 9.

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