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

Abstract

The invention 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, the first doped regions, the second doped regions and the isolation regions are arranged on the back surface of a silicon substrate, the first doped regions and the second doped regions are alternately arranged, the isolation regions are arranged between the first doped regions and the second doped regions, and the isolation regions are arranged between the first doped regions and the second doped regions. 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 invention, carrier transmission between the first doped region and the second doped region can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back contact cell, a back contact cell 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 the IBC cell are arranged in a cross-finger pattern on the backlight side of the cell. This design allows the front surface of the cell to be shielded by no metal grid lines, thereby maximizing the illuminated area and reducing optical losses, improving short-circuit current and overall photoelectric conversion efficiency. In order to prevent carriers from directly contacting the N-type doped region and the P-type doped region, resulting in the inability to effectively collect carriers, an isolation region needs to be set 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 invention

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

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

[0005] In order to solve the above problems, the present invention discloses a back contact battery, comprising a first doping region, a second doping region and an isolation region arranged on the back side of a silicon substrate, wherein the first doping region and the second doping region are arranged alternately, the isolation region is arranged between the first doping region and the second doping region, and the first doping region and the second doping region have opposite doping types;

[0006] The sidewall of the first doping region close to the isolation region is recessed toward 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.

[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 toward the first doped region to form first arc-shaped grooves, and the first arc-shaped grooves are sequentially connected to form a wavy structure.

[0008] As an improvement of the above technical solution, the sidewall of the second doping region close to the isolation region is recessed toward 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.

[0009] As an improvement of the above technical solution, the second recessed region includes periodically repeated second recessed units, the second recessed units are recessed toward the second doping region to form second arc-shaped grooves, 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] Two ends of the second arc-shaped groove are respectively a third endpoint and a fourth endpoint, and a distance between the third endpoint and the fourth endpoint is L2, where L1≥L2.

[0012] As an improvement of the above technical solution, the L1 is 75 μm to 500 μm, and the 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, the number of the second recessed units is N2, and N2 / N1=1.5-3.

[0014] As an improvement of the above technical solution, the first arc-shaped groove has a first vertex, which is the lowest point of the sidewall depression relative to the first doping region, the distance between the first endpoint and the first vertex is D1, the distance between the second endpoint 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 angle between the line connecting the first vertex and the second endpoint 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, which is the lowest point of the sidewall depression relative to the second doping region, the distance between the third endpoint and the second vertex is D3, and the distance between the fourth endpoint and the second vertex is D4, 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 angle between the line connecting the second vertex and the third endpoint and the horizontal plane where the second vertex is located is 5° to 30°.

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

[0021] Correspondingly, the present invention also discloses a solar cell assembly, comprising the above-mentioned back contact cell string.

[0022] The implementation of the present invention has the following beneficial effects:

[0023] 1. The present invention sets a recessed region on the side wall of the first doping region near the isolation region, and the recessed region includes a plurality of recessed units connected in sequence. The setting of the recessed region is beneficial to reducing the carrier recombination rate of the first doping region near the isolation region. In addition, the setting of the recessed region can also promote the transmission of carriers between the first doping region and the second doping region, thereby improving the working performance of the back contact battery.

[0024] 2. The present invention sets a recessed region on the side wall of the second doping region near the isolation region, and the recessed region includes a plurality of recessed units connected in sequence. The setting of the recessed region is beneficial to reducing the carrier recombination rate of the second doping region near the isolation region. In addition, the setting of the recessed region can also promote the transmission of carriers between the first doping region and the second doping region, thereby improving the working performance of the back contact battery.

[0025] 3. The first recessed area and / or the second recessed area of ​​the present invention are connected in sequence by periodically repeating arc-shaped grooves to form a wavy structure. The preparation process is simple and causes little damage to the side walls of the first recessed area and / or the second recessed area, which is beneficial to the conformal deposition of the subsequent back passivation layer, thereby improving the passivation performance of the back contact battery. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2 is a schematic structural diagram of the back side of a back contact battery provided by an embodiment of the present invention;

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

[0029] Figure 4 It is a 3D micrograph of the back side of a back contact battery provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0031] See also Figure 1 and Figure 2The present invention provides a back contact battery, comprising a first doping region 11, a second doping region 12 and an isolation region 13 arranged on the back of a silicon substrate 1, wherein the first doping region 11 and the second doping region 12 are arranged alternately, and the isolation region 13 is arranged between the first doping region 11 and the second doping region 12, and the doping type of the first doping region 11 is the same as or opposite to the doping type 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, and a PN junction is formed between the first doping region and the silicon substrate to effectively shunt 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 conducive to improving the photoelectric conversion efficiency of the back contact battery.

[0032] The sidewall 111 of the first doping region 11 close to the isolation region 13 is recessed toward 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 sidewall 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 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, thereby ensuring the electrical reliability of the back contact battery, and at the same time, it can ensure the range of the first doping region 11 and the second doping region 12, thereby improving the transmission of carriers from the second doping region 12 to the first doping region 11.

[0033] It should be noted that the first recessed unit 113 may have various shapes, such as a curve, an arc, a triangle, a square, etc., as long as it is recessed toward the first doping region.

[0034] In a preferred embodiment, the first recessed area includes a first recessed unit that is repeated periodically, and the first recessed unit is recessed toward the first doped area to form a first arc-shaped groove, and the first arc-shaped grooves are sequentially connected to form a wavy structure. The arc-shaped groove can be an arc, an elliptical arc, or any arc formed by deviation or bending from a straight line or a horizontal line. It should be noted that in the actual production process, since the crystal orientation and doping concentration of different regions of the silicon substrate are not completely consistent, it is difficult to achieve completely consistent periodic repetition even if the same preparation process and parameters are used for preparation, and it is also difficult for each first recessed unit to achieve completely consistent structural dimensions, but in general, the size deviation of the first recessed units of different periods can be controlled within 5%.

[0035] By connecting the periodically repeated first recessed units in sequence to form the first recessed area, the consistency of the process can be increased and the manufacturing process can be simplified. The formation of the periodically repeated arc-shaped groove is conducive to improving the processing efficiency during the preparation of the first recessed area, improving the diversion effect of the liquid required for subsequent cleaning, thereby improving the cleaning effect of the surface of the first recessed area. A good cleaning effect provides a better surface quality for the subsequent setting of the back passivation layer. The back passivation layer has a good passivation effect, which is conducive to the improvement of the open circuit voltage.

[0036] By providing a wavy groove, the surface area of ​​the side wall of the first doping 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 doping region, improving the passivation effect of the back passivation layer on the first doping region, and the wavy shape is also conducive to the conformal coverage of the subsequent back passivation layer on the side wall, improving the quality of the back passivation layer deposited on the side wall, ensuring the electrical reliability of the back contact battery while improving the transmission of carriers from the first doping region 11 to the second doping region 12. In addition, the wavy groove has lower requirements on the precision of the preparation process. Compared with the prior art, the wavy shape of this embodiment can be obtained by one laser, the preparation method is simple, and the continuity of laser etching can be improved.

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

[0038] By connecting the periodically repeated second recessed units in sequence to form the second recessed area, the consistency of the process can be increased and the manufacturing process can be simplified. The formation of the periodically repeated arc-shaped grooves is conducive to improving the processing efficiency during the preparation of the second recessed area, improving the diversion effect of the liquid required for subsequent cleaning, thereby improving the surface quality of the second recessed area, and the subsequent deposition of the back passivation layer has a good passivation effect, which is conducive to the improvement of the open circuit voltage.

[0039] In a preferred embodiment, Figure 2 and Figure 3 As shown, the two ends of the first arc-shaped groove are respectively the first endpoint 113a and the second endpoint 113b, the distance between the first endpoint 113a and the second endpoint 113b is L1, the two ends of the second arc-shaped groove are respectively the third endpoint 123a and the fourth endpoint 123b, the distance between the third endpoint 123a and the fourth endpoint 123b is L2, L1≥L2. Correspondingly, the number of the first recessed units is N1, the number of the second recessed units is N2, N2 / N1=1.5~3, preferably, N2 / N1=2~2.5. The present invention sets different recessed areas for different doping areas, the width of the first arc-shaped groove is greater than the width of the second arc-shaped groove, and the number of the first recessed units is less than the number of the second recessed units, which is conducive to reducing the carrier recombination rate of the first doping area close to the isolation area 13.

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

[0041] More preferably, the width of the first arc-shaped groove (i.e., the distance between the first endpoint 113a and the second endpoint 113b) L1 is 50μm to 500μm, and is exemplarily 80μm, 100μm, 150μm, 300μm, 400μm or 450μm, but not limited thereto. Preferably, the width L1 of the first arc-shaped groove is 75μm to 300μm. If the width L1 of the first arc-shaped groove is too small, the damage to the sidewall of the first doping region by the laser will increase, affecting the overall efficiency of the back contact battery. The width of the second arc-shaped groove (i.e., the distance between the third endpoint 123a and the fourth endpoint 123b) L2 is 30μm to 400μm, and is exemplarily 35μm, 50μm, 100μm, 200μm, 300μm or 350μm, but not limited thereto. Preferably, the width L2 of the second arc-shaped groove is 50μm to 300μm. If the width L2 of the second arc-shaped groove is too large, the carrier transmission effect will be affected.

[0042] It can be understood that by limiting the specific shape of the first arc-shaped groove, the performance of the back contact battery can be further improved, and the leakage risk on the backlight side of the back contact battery can be reduced, while ensuring that the first doping region and the second doping region of the back contact battery have excellent carrier collection and transmission 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 of the sidewall depression relative to 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, and D1<D2. During the preparation process, by adjusting the inclination angle of the laser beam projected to the spot where the first depression area needs to be formed, the depth of the arc-shaped groove can be controlled under the premise of ensuring the width L1 of the first arc-shaped groove, so as to avoid the excessive depth of the arc-shaped groove from adversely affecting the quality of the first doping region.

[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 5μm-30μm, preferably, D1 is 8μm-15μm. 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°-30°, preferably, θ1 is 8°-15°. The angle θ1 is conducive to the bottom of the first arc-shaped groove being an obtuse angle or a right angle, and is more conducive to the back passivation layer conformally covering the side wall of the isolation groove, reducing the difficulty of forming the back passivation layer.

[0044] It can be understood that by limiting 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 of the sidewall depression relative to 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, and D3>D4. Preferably, the ratio of D3 to D4 satisfies the following formula, D3=(3~13)*D4, and the distance D4 between the fourth endpoint 123b and the second vertex 123c is 3μm~30μm. If D4<3μm, the current transmission is affected and the composite loss increases; if D4>30μm, it is easy to cause a short circuit. Preferably, D4 is 5μm~8μm. An angle θ2 between a line connecting the second vertex 123c and the third end point 123a and a horizontal plane where the second vertex 123c is located is 5° to 30°. Preferably, θ2 is 15° to 30°.

[0045] Figure 4This is a 3D micrograph of the back side of the back-contact battery provided by an embodiment of the present invention. At a magnification of 20× to 100×, it can be clearly observed that a wavy first recessed area 112 formed by sequentially connecting first recessed units and a wavy second recessed area 122 formed by sequentially connecting second recessed units.

[0046] In addition, the back contact battery of the present invention further comprises 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 of the silicon substrate, and the back passivation film layer is stacked on the back of the silicon substrate. The front passivation film layer and the back passivation film layer can be one or more of an aluminum oxide layer, a silicon carbide layer, a silicon nitride layer, and a silicon oxynitride layer. The provision 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 the back passivation film layer and contacts the first doped region, and the second electrode penetrates the back passivation film layer and contacts the second doped region. The materials of the first electrode and the second electrode can be one or more of silver, aluminum, copper, and nickel.

[0049] Accordingly, the present invention also provides a method for preparing the above-mentioned back contact battery, comprising:

[0050] S1, providing a silicon substrate;

[0051] S2. Forming alternately arranged first doping regions and second doping regions on the back side of the silicon substrate, etching the area between the first doping regions and the second doping regions to form an isolation region; the sidewall of the first doping region close to the isolation region is recessed toward the first doping region to form a first recessed region.

[0052] In one implementation, a sidewall of the second doping region close to the isolation region is recessed toward the second doping region to form a second recessed region.

[0053] Compared with the prior art in which the sidewalls of the first recessed region and / or the second recessed region of the present invention are set as a straight structure after the isolation region is formed, the process difficulty can be reduced.

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

[0055] Example 1

[0056] This embodiment provides a back contact battery, including a P-type doping region, an N-type doping region and an isolation region arranged on the back of an N-type silicon substrate, wherein the P-type doping region and the N-type doping region are alternately arranged, and the isolation region is arranged between the P-type doping region and the N-type doping region. The side wall of the N-type doping region near the isolation region is recessed toward the N-type doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence, and the first recessed units are recessed toward the first doping region to form a first arc-shaped groove, and the first recessed units are periodically arranged and sequentially connected to form a wavy structure. The distance between the first end point and the second end point of the first arc-shaped groove is 200μm, the distance between the first end point and the first vertex is 150μm, and the distance between the second end point and the first vertex is 150μm.

[0057] Example 2

[0058] The present embodiment provides a back contact battery, comprising a P-type doping region, an N-type doping region and an isolation region arranged on the back of an N-type silicon substrate, wherein the P-type doping region and the N-type doping region are alternately arranged, and the isolation region is arranged between the P-type doping region and the N-type doping region. The side wall of the N-type doping region near the isolation region is recessed toward the N-type doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence, and the first recessed units are recessed toward the first doping region to form a first arc-shaped groove, and the first recessed units are periodically arranged 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.

[0059] Example 3

[0060] This embodiment provides a back contact battery, including a P-type doping region, an N-type doping region and an isolation region arranged on the back of an N-type silicon substrate, wherein the P-type doping region and the N-type doping region are alternately arranged, and the isolation region is arranged between the P-type doping region and the N-type doping region. The side wall of the N-type doping region near the isolation region is recessed toward the N-type doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence, and the first recessed units are recessed toward the first doping region to form a first arc-shaped groove, and the first recessed units are periodically arranged and sequentially connected to form a wavy structure. The distance between the first end point and the second end point of the first arc-shaped groove is 200μm, the distance between the first end point and the first vertex is 150μm, and the distance between the second end point and the first vertex is 150μm.

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

[0062] Example 4

[0063] The present embodiment provides a back contact battery, comprising a P-type doping region, an N-type doping region and an isolation region arranged on the back of an N-type silicon substrate, wherein the P-type doping region and the N-type doping region are alternately arranged, and the isolation region is arranged between the P-type doping region and the N-type doping region. The side wall of the N-type doping region near the isolation region is recessed toward the N-type doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence, and the first recessed units are recessed toward the first doping region to form a first arc-shaped groove, and the first recessed units are periodically arranged 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 doping region near the isolation region is recessed toward the P-type doping region to form a second recessed region, the second recessed region includes a plurality of second recessed units connected in sequence, the second recessed units are recessed toward the second doping region to form a second arc-shaped groove, and the second recessed units are periodically arranged and sequentially connected to form a wavy structure. The distance between the third endpoint and the fourth endpoint of the second arc-shaped groove is 100 μm, the distance between the third endpoint and the second vertex is 60 μm, and the distance between the fourth endpoint and the second vertex is 60 μm.

[0065] Example 5

[0066] The present embodiment provides a back contact battery, comprising a P-type doping region, an N-type doping region and an isolation region arranged on the back of an N-type silicon substrate, wherein the P-type doping region and the N-type doping region are alternately arranged, and the isolation region is arranged between the P-type doping region and the N-type doping region. The side wall of the N-type doping region near the isolation region is recessed toward the N-type doping region to form a first recessed region, and the first recessed region includes a plurality of first recessed units connected in sequence, and the first recessed units are recessed toward the first doping region to form a first arc-shaped groove, and the first recessed units are periodically arranged 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 doping region near the isolation region is recessed toward the P-type doping region to form a second recessed region, the second recessed region includes a plurality of second recessed units connected in sequence, the second recessed units are recessed toward the second doping region to form a second arc-shaped groove, and the second recessed units are periodically arranged and sequentially connected to form a wavy structure. The distance between the third endpoint and the fourth endpoint of the second arc-shaped groove is 100 μm, the distance between the third endpoint and the second vertex is 8 μm, and the distance between the fourth endpoint and the second vertex is 98 μm.

[0068] The back contact cells prepared in Examples 1 to 5 were subjected to printed electrodes, sintered and alloyed, and then annealed to obtain finished solar cells. The photoelectric conversion efficiency of the finished solar cells was measured, and the results are shown in the following table.

[0069] Photoelectric 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 is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A back contact battery, characterized in that: The method comprises a first doping region, a second doping region and an isolation region arranged on the back side of a silicon substrate, wherein the first doping region and the second doping region are arranged alternately, the isolation region is arranged between the first doping region and the second doping region, and the first doping region and the second doping region have opposite doping types; The sidewall of the first doping region close to the isolation region is recessed toward 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 cell according to claim 1, characterized in that The first recessed region includes periodically repeated first recessed units, the first recessed units are recessed toward the first doped region to form first arc-shaped grooves, and the first arc-shaped grooves are sequentially connected to form a wavy structure.

3. The back contact cell according to claim 2, characterized in that The sidewall of the second doping region close to the isolation region is recessed toward 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 cell according to claim 3, characterized in that The second recessed region includes periodically repeated second recessed units, the second recessed units are recessed toward the second doping region to form second arc-shaped grooves, and the second arc-shaped grooves are sequentially connected to form a wavy structure.

5. The back contact cell according to claim 4, characterized in that 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. Two ends of the second arc-shaped groove are respectively a third endpoint and a fourth endpoint, and a distance between the third endpoint and the fourth endpoint is L2, where L1≥L2.

6. The back contact cell according to claim 5, characterized in that The L1 is 75 μm to 500 μm, and the L2 is 50 μm to 300 μm.

7. The back contact cell 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=1.5-3.

8. The back contact cell according to claim 5, characterized in that The first arc-shaped groove has a first vertex, which is the lowest point of the sidewall depression relative to the first doping region. The distance between the first endpoint and the first vertex is D1, and the distance between the second endpoint and the first vertex is D2, where D1<D2.

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

10. The back contact cell according to claim 8, characterized in that The angle between the line connecting the first vertex and the second endpoint and the horizontal plane where the first vertex is located is 5° to 30°.

11. The back contact cell according to claim 5, characterized in that The second arc-shaped groove has a second vertex, which is the lowest point of the sidewall depression relative to the second doping region. The distance between the third endpoint and the second vertex is D3, and the distance between the fourth endpoint and the second vertex is D4, where D3>D4.

12. The back contact cell according to claim 11, characterized in that The ratio of D3 to D4 satisfies the following formula: D3=(3-13)*D4.

13. The back contact cell according to claim 11, characterized in that An angle between a line connecting the second vertex and the third endpoint and a horizontal plane where the second vertex is located is 5° to 30°.

14. A back contact battery string, characterized in that: Comprising a back contact battery as claimed in any one of claims 1 to 13.

15. A solar cell module, characterized in that: Comprising a back-contact cell string as claimed in claim 14.

Images