Back contact cell, back contact cell string and solar cell module

Abstract

The utility model discloses a back contact cell, a back contact cell string and a solar cell module, the back contact cell comprises first doped regions, second doped regions and isolation regions which are arranged on the back surface of a silicon substrate, and the first doped regions and the second doped regions are alternately arranged. The isolation region is arranged between the first doped region and the second doped region, and the doping types of the first doped region and the second doped region are opposite; the side wall, close to the isolation region, of the first doped region is recessed inwards to form a first recessed region, and the first recessed region comprises a plurality of first recessed units which are connected in sequence. According to the utility model, carrier transmission between the first doped region and the second doped region can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a back contact battery, a back contact battery string and a solar cell module. Background Art

[0002] Interdigitated Back Contact (IBC) is a high-efficiency solar cell technology. The positive and negative metal electrodes of an IBC cell are arranged in an interdigitated manner on the backlight side of the cell. This design enables the front surface of the cell to have no metal grid line obstruction, thereby maximizing the light-receiving area, reducing optical losses, increasing the short-circuit current, and improving the overall photoelectric conversion efficiency. To prevent carriers from directly contacting in the N-type doped region and the P-type doped region, resulting in ineffective carrier collection, an isolation region needs to be provided at the junction of the P-type doped region and the N-type doped region. The morphological characteristics of the isolation region will affect the performance of the IBC cell. Summary of the Utility Model

[0003] The technical problem to be solved by the utility model is to provide a back contact battery, which reduces the carrier recombination rate of the part of the first doped region and / or the second doped region close to the isolation region.

[0004] Another technical problem to be solved by the utility model is to provide a back contact battery string and a solar cell module with high photoelectric conversion efficiency.

[0005] To solve the above problems, the utility model discloses a back contact battery, which includes a first doped region, a second doped region and an isolation region provided on the back of a silicon substrate. The first doped region and the second doped region are arranged alternately, the isolation region is provided between the first doped region and the second doped region, and the doping types of the first doped region and the second doped region are opposite;

[0006] The side wall of the first doped region close to the isolation region is recessed towards the first doped region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence.

[0007] As an improvement of the above technical solution, the first recessed region includes periodically repeated first recessed units, the first recessed units are recessed towards the first doped region to form first arc-shaped grooves, and the first arc-shaped grooves are connected in sequence to form a wavy structure.

[0008] As an improvement of the above technical solution, the side wall of the second doped region close to the isolation region is recessed towards the second doped region to form a second recessed region, and the second recessed region includes a plurality of second recessed units connected in sequence.

[0009] As an improvement of the above technical solution, the second recessed area includes periodically repeated second recessed units, and each second recessed unit recesses towards the second doping area to form a second arc-shaped groove, and the second arc-shaped grooves are sequentially connected to form a wavy structure.

[0010] As an improvement of the above technical solution, the two ends of the first arc-shaped groove are respectively a first end point and a second end point, and the distance between the first end point and the second end point is L1.

[0011] The two ends of the second arc-shaped groove are respectively a third end point and a fourth end point, and the distance between the third end point and the fourth end point is L2, and L1≥L2.

[0012] As an improvement of the above technical solution, L1 is 75 μm to 500 μm, and L2 is 50 μm to 300 μm.

[0013] As an improvement of the above technical solution, the number of the first recessed units is N1, and the number of the second recessed units is N2, and N2 / N1 = 1.5 to 3.

[0014] As an improvement of the above technical solution, the first arc-shaped groove has a first vertex, the first vertex is the lowest point recessed relative to the side wall of the first doping area, the distance between the first end point and the first vertex is D1, and the distance between the second end point and the first vertex is D2, and D1<D2.

[0015] As an improvement of the above technical solution, the ratio of D1 to D2 satisfies the following formula: D1=(0.01 - 0.05)*D2.

[0016] As an improvement of the above technical solution, the included angle between the connection line of the first vertex and the second end point and the horizontal plane where the first vertex is located is 5° to 30°.

[0017] As an improvement of the above technical solution, the second arc-shaped groove has a second vertex, the second vertex is the lowest point recessed relative to the side wall of the second doping area, the distance between the third end point and the second vertex is D3, and the distance between the fourth end point and the second vertex is D4, and D3>D4.

[0018] As an improvement of the above technical solution, the ratio of D3 to D4 satisfies the following formula: D3=(3 - 13)*D4.

[0019] As an improvement of the above technical solution, the included angle between the connection line of the second vertex and the third end point and the horizontal plane where the second vertex is located is 5° to 30°.

[0020] Correspondingly, the present utility model also discloses a back contact battery string, including the above-mentioned back contact battery.

[0021] Correspondingly, the present utility model also discloses a solar cell module, including the above-mentioned back contact cell string.

[0022] Implementing the present utility model has the following beneficial effects:

[0023] 1. The present utility model provides a recessed area on the side wall of the first doping area close to the isolation area. The recessed area includes a number of recessed units connected in sequence. The setting of the recessed area is beneficial to reducing the carrier recombination rate of the first doping area close to the isolation area. In addition, the setting of the recessed area can also promote the transmission of carriers between the first doping area and the second doping area, thereby improving the working performance of the back contact cell.

[0024] 2. The present utility model provides a recessed area on the side wall of the second doping area close to the isolation area. The recessed area includes a number of recessed units connected in sequence. The setting of the recessed area is beneficial to reducing the carrier recombination rate of the second doping area close to the isolation area. In addition, the setting of the recessed area can also promote the transmission of carriers between the first doping area and the second doping area, thereby improving the working performance of the back contact cell.

[0025] 3. The first recessed area and / or the second recessed area of the present utility model are formed by connecting a number of periodically repeated arc-shaped grooves in sequence to form a wavy structure. The preparation process is simple, and the damage to the side walls of the first recessed area and / or the second recessed area is small, which is beneficial to the conformal deposition of the subsequent back passivation layer, thereby improving the passivation performance of the back contact cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of a back contact cell provided by an embodiment of the present utility model;

[0027] Figure 2 is a schematic structural diagram of the back of a back contact cell provided by an embodiment of the present utility model;

[0028] Figure 3 is a schematic diagram of the dimensions of a recessed structure provided by an embodiment of the present utility model;

[0029] Figure 4 is a 3D microscopic image of the back of a back contact cell provided by an embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] To make the objectives, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below.

[0031] See Figure 1 and Figure 2, the present utility model provides a back-contact battery, which includes a first doping region 11, a second doping region 12 and an isolation region 13 provided on the back surface of a silicon substrate 1. The first doping region 11 and the second doping region 12 are arranged alternately, and the isolation region 13 is provided between the first doping region 11 and the second doping region 12. The doping type of the first doping region 11 is the same as or opposite to that of the silicon substrate 1, and the doping types of the first doping region 11 and the second doping region 12 are opposite. For example, the silicon substrate is an N-type silicon substrate, the first doping region is a P-type doping region, and the second doping region is an N-type doping region. A PN junction is formed between the first doping region and the silicon substrate, effectively shunting carriers. The setting of the isolation region 13 can reduce the carrier recombination rate at the lateral junction of the first doping region and the second doping region, which is beneficial to improving the photoelectric conversion efficiency of the back-contact battery.

[0032] A side wall 111 of the first doping region 11 close to the isolation region 13 is recessed towards the first doping region 11 to form a first recessed region 112, and the first recessed region 112 includes a plurality of first recessed units 113 connected in sequence. Compared with setting the side wall 111 of the first doping region 11 close to the isolation region 13 as a flat surface, the formation of the first recessed region 112 can not only prevent leakage between the first doping region 11 and the second doping region 12 caused by the small distance between the first doping region 11 and the second doping region 12, ensuring the electrical reliability of the back-contact battery, but also ensure the ranges of the first doping region 11 and the second doping region 12, improving the carrier transmission from the second doping region 12 to the first doping region 11.

[0033] It should be noted that the shape of the first recessed unit 113 can be various, such as curved, arc-shaped, triangular, square, etc., as long as it is recessed towards the first doping region.

[0034] In a preferred embodiment, the first recessed region includes periodically repeated first recessed units, and the first recessed units are recessed towards the first doping region to form first arc-shaped grooves, and the first arc-shaped grooves are connected in sequence to form a wavy structure. The arc-shaped groove can be a circular arc, an elliptical arc, or any arc formed by deviating or bending from a straight line or a horizontal line. It should be noted that in the actual production process, due to the incomplete consistency of the crystal orientation and doping concentration in different regions of the silicon substrate, it is difficult to achieve completely consistent periodic repetition even though the same preparation process and parameters are used for preparation, and it is also difficult to achieve completely consistent structural dimensions for each first recessed unit. Generally speaking, the size deviation of the first recessed units in different periods can be controlled within 5%.

[0035] The first recessed region is formed by sequentially connecting periodically repeated first recessed units, which can increase the process consistency and simplify the manufacturing process. Forming periodically repeated arc-shaped grooves is beneficial to improving the processing efficiency in the preparation process of the first recessed region, enhancing the diversion effect of the liquid medicine required for subsequent cleaning, thereby improving the cleaning effect on the surface of the first recessed region. A good cleaning effect provides better surface quality for the subsequent setting of the back passivation layer. With good passivation effect of the back passivation layer, it is beneficial to the improvement of the open circuit voltage.

[0036] By providing wavy grooves, the surface area of the sidewall of the first doped region 11 close to the isolation region 13 can be increased, thereby increasing the contact area between the subsequently deposited back passivation layer and the first doped region, improving the passivation effect of the back passivation layer on the first doped region. The wavy shape is also beneficial to the conformal coverage of the sidewall by the subsequent back passivation layer, improving the quality of the back passivation layer deposited on the sidewall, ensuring the electrical reliability of the back contact battery while improving the carrier transmission from the first doped region 11 to the second doped region 12. In addition, the wavy grooves have lower requirements for the precision of the preparation process. Compared with the prior art, the wavy shape in this embodiment can be obtained by one-time laser, the preparation method is simple, and the continuity of laser etching can be improved.

[0037] In addition to providing the first recessed region on one side of the first doped region, the sidewall 121 of the second doped region 12 close to the isolation region 13 is recessed towards the second doped region 12 to form a second recessed region 122. The second recessed region 122 includes a plurality of second recessed units 123 connected in sequence. In a preferred embodiment, the second recessed region includes periodically repeated second recessed units. The second recessed units are recessed towards the second doped region to form second arc-shaped grooves, and the second arc-shaped grooves are connected in sequence to form a wavy structure. The arc-shaped groove can be a circular arc, an elliptical arc, or any arc formed by deviation or bending from a straight line or horizontal. It should be noted that, similar to the first recessed region, it is also difficult to achieve completely consistent periodic repetition of the second recessed units in the second recessed region, and it is also difficult to achieve completely consistent structural dimensions for each second recessed unit. Generally speaking, the size deviation of the second recessed units in different periods can be controlled within 5%.

[0038] The second recessed region is formed by sequentially connecting periodically repeated second recessed units, which can increase the process consistency and simplify the manufacturing process. Forming periodically repeated arc-shaped grooves is beneficial to improving the processing efficiency in the preparation process of the second recessed region, enhancing the diversion effect of the liquid medicine required for subsequent cleaning, thereby improving the surface quality of the second recessed region. The passivation effect of the subsequently deposited back passivation layer is good, which is beneficial to the improvement of the open circuit voltage.

[0039] In a preferred embodiment, as Figure 2 andFigure 3 As shown, the two ends of the first arc-shaped groove are the first end point 113a and the second end point 113b respectively. The distance between the first end point 113a and the second end point 113b is L1. The two ends of the second arc-shaped groove are the third end point 123a and the fourth end point 123b respectively. The distance between the third end point 123a and the fourth end point 123b is L2, and L1≥L2. Correspondingly, the number of the first recessed units is N1, and the number of the second recessed units is N2. N2 / N1 = 1.5 to 3. Preferably, N2 / N1 = 2 to 2.5. The utility model sets different recessed areas for different doping regions. The width of the first arc-shaped groove is greater than that of the second arc-shaped groove, and the number of the first recessed units is less than that of the second recessed units, which is beneficial to reducing the carrier recombination rate of the part of the first doping region close to the isolation region 13.

[0040] In a preferred embodiment, the first doping region is an N-type doping region, and the second doping region is a P-type doping region. The width of the first arc-shaped groove on the side of the N-type doping region is greater than the width of the second arc-shaped groove on the side of the P-type doping region (or in other words, the number of the first arc-shaped grooves is less than the number of the second arc-shaped grooves), which is beneficial to the transfer of carriers from the N region to the P region and reduces the recombination loss and resistance loss during the transfer process.

[0041] More preferably, the width (i.e., the distance between the first end point 113a and the second end point 113b) L1 of the first arc-shaped groove is 50 μm to 500 μm, such as 80 μm, 100 μm, 150 μm, 300 μm, 400 μm or 450 μm by way of example, but not limited thereto. Preferably, the width L1 of the first arc-shaped groove is 75 μm to 300 μm. If the width L1 of the first arc-shaped groove is too small, it will increase the damage of the laser to the side wall of the first doping region and affect the overall efficiency of the back contact battery. The width (i.e., the distance between the third end point 123a and the fourth end point 123b) L2 of the second arc-shaped groove is 30 μm to 400 μm, such as 35 μm, 50 μm, 100 μm, 200 μm, 300 μm or 350 μm by way of example, but not limited thereto. Preferably, the width L2 of the second arc-shaped groove is 50 μm to 300 μm. If the width L2 of the second arc-shaped groove is too large, it will affect the transfer effect of the carriers.

[0042] It can be understood that by defining the specific shape of the first arc-shaped groove, the performance of the back-contact battery can be further improved. While reducing the leakage risk on the backlight side of the back-contact battery, it ensures that the first doping region and the second doping region of the back-contact battery have excellent carrier collection and transport capabilities, and the obtained back-contact battery has high electrical reliability. The first arc-shaped groove has a first vertex 113c, and the first vertex 113c is the lowest point sunken relative to the side wall of the first doping region. The distance between the first endpoint 113a and the first vertex 113c is D1, and the distance between the second endpoint 113b and the first vertex 113c is D2, where D1 < D2. During the preparation process, by adjusting the tilt angle of the laser beam spot projected onto the position where the first depression region needs to be formed, it is possible to control the depth of the arc-shaped groove while ensuring the width L1 of the first arc-shaped groove, and avoid adverse effects on the quality of the first doping region caused by excessive depth of the arc-shaped groove.

[0043] In a preferred embodiment, the ratio of D1 to D2 satisfies the following formula: D1 = (0.01 - 0.05) * D2. The distance D1 between the first endpoint 113a and the first vertex 113c is 5 μm to 30 μm, and preferably, D1 is 8 μm to 15 μm. The angle θ1 between the line connecting the first vertex 113c and the second endpoint 113b and the horizontal plane where the first vertex 113c is located is 5° to 30°, and preferably, θ1 is 8° to 15°. The angle θ1 is beneficial for the bottom of the first arc-shaped groove to be an obtuse angle or a right angle, which is more conducive to the conformal coverage of the side walls of the isolation groove by the back surface passivation layer and reduces the difficulty of forming the back surface passivation layer.

[0044] It can be understood that by defining the specific shape of the second arc-shaped groove, the performance of the back-contact battery can be further improved. The second arc-shaped groove has a second vertex 123c, and the second vertex 123c is the lowest point sunken relative to the side wall of the second doping region. The distance between the third endpoint 123a and the second vertex 123c is D3, and the distance between the fourth endpoint 123b and the second vertex 123c is D4, where D3 > D4. Preferably, the ratio of D3 to D4 satisfies the following formula: D3 = (3 - 13) * D4. The distance D4 between the fourth endpoint 123b and the second vertex 123c is 3 μm to 30 μm. If D4 < 3 μm, it affects current transmission and the recombination loss increases; if D4 > 30 μm, it is easy to cause a short circuit. Preferably, D4 is 5 μm to 8 μm. The angle θ2 between the line connecting the second vertex 123c and the third endpoint 123a and the horizontal plane where the second vertex 123c is located is 5° to 30°, and preferably, θ2 is 15° to 30°.

[0045] Figure 4It is a 3D microscopic image of the back surface of the back-contact battery provided by the embodiment of the present invention. Under the magnification of 20× to 100×, the wavy first recessed area 112 formed by sequentially connecting the first recessed units and the wavy second recessed area 122 formed by sequentially connecting the second recessed units can be clearly observed.

[0046] In addition, the back-contact battery of the present invention further includes a front passivation film layer, a back passivation film layer, a first electrode, and a second electrode;

[0047] The front passivation film layer is stacked on the front surface of the silicon substrate, and the back passivation film layer is stacked on the back surface of the silicon substrate. The front passivation film layer and the back passivation film layer can be one or more of an alumina layer, a silicon carbide layer, a silicon nitride layer, and a silicon oxynitride layer. The setting of the first recessed area and / or the second recessed area can increase the contact area with the back passivation film layer subsequently deposited on its surface, and the contact area between the side wall of the isolation area and the back passivation film layer is larger, thereby improving the passivation effect of the back passivation film layer on the isolation area, reducing the carrier recombination rate on the surface of the isolation area, and thus improving the photoelectric conversion efficiency of the back-contact battery.

[0048] The first electrode penetrates through the back passivation film layer and contacts the first doped area, and the second electrode penetrates through the back passivation film layer and contacts the second doped area. The materials of the first electrode and the second electrode can be one or more of silver, aluminum, copper, and nickel.

[0049] Correspondingly, the present invention also provides a preparation method for the above-mentioned back-contact battery, including:

[0050] S1. Provide a silicon substrate;

[0051] S2. Form an alternately arranged first doped area and a second doped area on the back surface of the silicon substrate, etch the area between the first doped area and the second doped area to form an isolation area; the side wall of the first doped area close to the isolation area is recessed towards the first doped area to form a first recessed area.

[0052] In one embodiment, the side wall of the second doped area close to the isolation area is recessed towards the second doped area to form a second recessed area.

[0053] After the first recessed area and / or the second recessed area of the present invention are formed, compared with the prior art in which the side wall is set as a straight structure, the process difficulty can be reduced.

[0054] The present invention will be further described below with specific embodiments:

[0055] Embodiment 1

[0056] This embodiment provides a back-contact battery, which includes a P-type doped region, an N-type doped region, and an isolation region provided on the back surface of an N-type silicon substrate. The P-type doped region and the N-type doped region are alternately arranged, and the isolation region is provided between the P-type doped region and the N-type doped region. The side wall of the N-type doped region close to the isolation region is recessed toward the N-type doped region to form a first recessed region. The first recessed region includes a plurality of first recessed units connected in sequence. The first recessed unit is recessed toward the first doped region to form a first arc-shaped groove. The first recessed units are periodically arranged in a repeating manner and connected in sequence to form a wavy structure. The distance between the first endpoint and the second endpoint of the first arc-shaped groove is 200 μm, the distance between the first endpoint and the first vertex is 150 μm, and the distance between the second endpoint and the first vertex is 150 μm.

[0057] Example 2

[0058] This embodiment provides a back-contact battery, which includes a P-type doped region, an N-type doped region, and an isolation region provided on the back surface of an N-type silicon substrate. The P-type doped region and the N-type doped region are alternately arranged, and the isolation region is provided between the P-type doped region and the N-type doped region. The side wall of the N-type doped region close to the isolation region is recessed toward the N-type doped region to form a first recessed region. The first recessed region includes a plurality of first recessed units connected in sequence. The first recessed unit is recessed toward the first doped region to form a first arc-shaped groove. The first recessed units are periodically arranged in a repeating manner and connected in sequence to form a wavy structure. The distance between the first endpoint and the second endpoint of the first arc-shaped groove is 200 μm, the distance between the first endpoint and the first vertex is 10 μm, and the distance between the second endpoint and the first vertex is 205 μm.

[0059] Example 3

[0060] This embodiment provides a back-contact battery, which includes a P-type doped region, an N-type doped region, and an isolation region provided on the back surface of an N-type silicon substrate. The P-type doped region and the N-type doped region are alternately arranged, and the isolation region is provided between the P-type doped region and the N-type doped region. The side wall of the N-type doped region close to the isolation region is recessed toward the N-type doped region to form a first recessed region. The first recessed region includes a plurality of first recessed units connected in sequence. The first recessed unit is recessed toward the first doped region to form a first arc-shaped groove. The first recessed units are periodically arranged in a repeating manner and connected in sequence to form a wavy structure. The distance between the first endpoint and the second endpoint of the first arc-shaped groove is 200 μm, the distance between the first endpoint and the first vertex is 150 μm, and the distance between the second endpoint and the first vertex is 150 μm.

[0061] The side wall of the P-type doped region close to the isolation region is recessed towards the P-type doped region to form a second recessed region. The second recessed region includes a plurality of second recessed units connected in sequence. The second recessed unit is recessed towards the second doped region to form a second arc-shaped groove. The second recessed units are arranged periodically and connected in sequence to form a wavy structure. The distance between the third end point and the fourth end point of the second arc-shaped groove is 100 μm, the distance between the third end point and the second vertex is 60 μm, and the distance between the fourth end point and the second vertex is 60 μm.

[0062] Example 4

[0063] This embodiment provides a back-contact battery, which includes a P-type doped region, an N-type doped region and an isolation region arranged on the back surface of an N-type silicon substrate. The P-type doped region and the N-type doped region are arranged alternately, and the isolation region is arranged between the P-type doped region and the N-type doped region. The side wall of the N-type doped region close to the isolation region is recessed towards the N-type doped region to form a first recessed region. The first recessed region includes a plurality of first recessed units connected in sequence. The first recessed unit is recessed towards the first doped region to form a first arc-shaped groove. The first recessed units are arranged periodically and connected in sequence to form a wavy structure. The distance between the first end point and the second end point of the first arc-shaped groove is 200 μm, the distance between the first end point and the first vertex is 10 μm, and the distance between the second end point and the first vertex is 205 μm.

[0064] The side wall of the P-type doped region close to the isolation region is recessed towards the P-type doped region to form a second recessed region. The second recessed region includes a plurality of second recessed units connected in sequence. The second recessed unit is recessed towards the second doped region to form a second arc-shaped groove. The second recessed units are arranged periodically and connected in sequence to form a wavy structure. The distance between the third end point and the fourth end point of the second arc-shaped groove is 100 μm, the distance between the third end point and the second vertex is 60 μm, and the distance between the fourth end point and the second vertex is 60 μm.

[0065] Example 5

[0066] This embodiment provides a back-contact battery, which includes a P-type doped region, an N-type doped region and an isolation region arranged on the back surface of an N-type silicon substrate. The P-type doped region and the N-type doped region are arranged alternately, and the isolation region is arranged between the P-type doped region and the N-type doped region. The side wall of the N-type doped region close to the isolation region is recessed towards the N-type doped region to form a first recessed region. The first recessed region includes a plurality of first recessed units connected in sequence. The first recessed unit is recessed towards the first doped region to form a first arc-shaped groove. The first recessed units are arranged periodically and connected in sequence to form a wavy structure. The distance between the first end point and the second end point of the first arc-shaped groove is 200 μm, the distance between the first end point and the first vertex is 10 μm, and the distance between the second end point and the first vertex is 205 μm.

[0067] The side wall of the P-type doped region close to the isolation region is recessed toward the P-type doped region to form a second recessed region. The second recessed region includes a plurality of sequentially connected second recessed units. The second recessed unit is recessed toward the second doped region to form a second arc-shaped groove. The second recessed units are periodically arranged in a repeating manner and are sequentially connected to form a wavy structure. The distance between the third end point and the fourth end point of the second arc-shaped groove is 100 μm, the distance between the third end point and the second vertex is 8 μm, and the distance between the fourth end point and the second vertex is 98 μm.

[0068] The printed electrodes of the back contact batteries prepared in Examples 1 to 5 were subjected to annealing treatment after sintering alloying to obtain finished solar cell wafers, and the photoelectric conversion efficiencies of the finished solar cell wafers were measured. The results are shown in the following table.

[0069] Photovoltaic conversion efficiency Example 1 26.64％ Example 2 26.68％ Example 3 26.69％ Example 4 26.72％ Example 5 26.78％

[0070] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A back-contact battery, characterized in that, It includes a first doping region, a second doping region, and an isolation region provided on the back surface of a silicon substrate. The first doping region and the second doping region are arranged alternately, the isolation region is provided between the first doping region and the second doping region, and the doping types of the first doping region and the second doping region are opposite; The side wall of the first doping region close to the isolation region is recessed towards the first doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence.

2. The back-contact battery according to claim 1, wherein The first recessed region includes periodically repeated first recessed units, the first recessed units are recessed towards the first doping region to form first arc-shaped grooves, and the first arc-shaped grooves are connected in sequence to form a wavy structure.

3. The back-contact battery according to claim 2, characterized in that, The side wall of the second doping region close to the isolation region is recessed towards the second doping region to form a second recessed region, and the second recessed region includes a plurality of second recessed units connected in sequence.

4. The back-contact battery according to claim 3, wherein, The second recessed region includes periodically repeated second recessed units, the second recessed units are recessed towards the second doping region to form second arc-shaped grooves, and the second arc-shaped grooves are connected in sequence to form a wavy structure.

5. The back-contact battery according to claim 4, characterized in that, The two ends of the first arc-shaped groove are a first end point and a second end point respectively, and the distance between the first end point and the second end point is L1. The two ends of the second arc-shaped groove are a third end point and a fourth end point respectively, and the distance between the third end point and the fourth end point is L2, and L1≥L2.

6. The back-contact battery according to claim 5, wherein The L1 is 75μm to 500μm, and the L2 is 50μm to 300μm.

7. The back-contact battery according to claim 3, characterized in that, The number of the first recessed units is N1, the number of the second recessed units is N2, and N2 / N1 = 1.5 to 3.

8. The back-contact battery according to claim 5, characterized in that, The first arc-shaped groove has a first vertex, the first vertex is the lowest point recessed relative to the side wall of the first doping region, the distance between the first end point and the first vertex is D1, the distance between the second end point and the first vertex is D2, and D1<D2.

9. The back contact battery according to claim 8, characterized in that, The ratio of D1 to D2 satisfies the following formula, D1=(0.01 to 0.05)*D2.

10. The back-contact battery according to claim 8, wherein, The included angle between the connection line of the first vertex and the second end point and the horizontal plane where the first vertex is located is 5° to 30°.

11. The back-contact battery according to claim 5, characterized in that, The second arc-shaped groove has a second vertex, the second vertex is the lowest point recessed relative to the side wall of the second doping region, the distance between the third end point and the second vertex is D3, the distance between the fourth end point and the second vertex is D4, and D3>D4.

12. The back-contact battery according to claim 11, wherein, The ratio of D3 to D4 satisfies the following formula, D3=(3 to 13)*D4.

13. The back contact battery according to claim 11, characterized in that, The included angle between the connection line of the second vertex and the third end point and the horizontal plane where the second vertex is located is 5° to 30°.

14. A back-contact battery string, characterized in that, It includes a back-contact battery according to any one of claims 1 to 13.

15. A solar cell module, characterized in that, It includes a back-contact battery string according to claim 14.

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