TBC solar cell slice and preparation method thereof, and cell module

Abstract

The TBC solar cell slice comprises a silicon substrate, and first areas and second areas are alternately arranged on the back face of the silicon substrate; the first region comprises a first tunneling oxide layer, a first conductive passivation layer, a first back passivation layer and a first metal electrode, and the first metal electrode is in ohmic contact with the first conductive passivation layer; the second region sequentially comprises a second tunneling oxide layer, a second conductive passivation layer, a second back passivation layer and a second metal electrode, and the second metal electrode is in ohmic contact with the second conductive passivation layer; the first conductive passivation layer and the second conductive passivation layer have opposite conductive media; the isolation region between the first region and the second region is recessed inwards; at least one end of the TBC solar cell slice along the first direction is an isolation area. According to the invention, the slicing position is in the isolation region, the damage to the first conductive passivation layer or the second conductive passivation layer caused by cutting the first region and the second region during slicing is avoided, the cutting damage is reduced, and the battery performance is improved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a TBC solar cell slice, a preparation method thereof, and a battery module. Background Art

[0002] A cell is the basic component unit of a solar cell, which can directly convert solar energy into electrical energy. With the development of large-size silicon wafer technology, the size of crystalline silicon cells is getting larger and larger, enabling a single module to obtain higher output power. However, since the current generated by a cell is related to the area of the cell, while large-size cells increase the power of the module, they also increase the module current, significantly increasing the series resistance loss (IR) generated during the current transmission process and reducing the packaging efficiency of the battery module. To reduce the series resistance loss, generally, the whole cell is cut into half slices and then made into a module through series-parallel connection or other methods.

[0003] Since laser cutting is through photothermal action, after the cell is irradiated by the visible red light of the aiming beam, the photon energy interacts with the crystal lattice, the vibration intensifies, the temperature rises, the material is damaged, and debris is generated on the surface. There will be a section of the silicon wafer near the laser action that melts and recasts to form a heat-affected zone, which will lead to a decrease in cell efficiency; and the performance consistency between the small cells after cutting is poor, easily causing a loss of the packaging power of the module; there is also a risk of hidden cracks in the small cells after cutting, increasing the probability of module repair and reducing production efficiency.

[0004] For TBC (Tunnel Oxide Passivated Contact) cells, when the middle cutting part is the P region or the N region, the laser beam cutting of the Poly layer will cause relatively serious mechanical damage and thermal influence on the cutting area, resulting in poor passivation performance at this part and affecting the performance of the cell. The patent with the publication number CN111599896A discloses a preparation method of a photovoltaic cell, by advancing the slicing process to between the printing process and the sintering process of the cell production preparation method, slicing the printed silicon wafer to form a silicon wafer slice, and then sintering the silicon wafer slice; however, this patent still has problems in improving the diffusion, cleaning, and passivation protection processes. Therefore, how to provide a TBC solar cell slice with excellent performance is a technical problem in this field. Summary of the Invention

[0005] In order to solve the problem of poor passivation performance after cell cutting in the prior art, the present invention provides a TBC solar cell slice, a preparation method thereof, and a battery module.

[0006] The present invention adopts the following technical solutions:

[0007] A TBC solar cell slice includes:

[0008] A silicon substrate having oppositely arranged front and back sides, a front passivation layer is provided on the front side of the silicon substrate, and a first region and a second region are alternately arranged on the back side of the silicon substrate;

[0009] The first region sequentially includes a first tunneling oxide layer, a first conductive passivation layer, a first back passivation layer, and a first metal electrode along the direction away from the silicon substrate, and the first metal electrode is in ohmic contact with the first conductive passivation layer;

[0010] The second region sequentially includes a second tunneling oxide layer, a second conductive passivation layer, a second back passivation layer, and a second metal electrode along the direction away from the silicon substrate, and the second metal electrode is in ohmic contact with the second conductive passivation layer;

[0011] The first conductive passivation layer and the second conductive passivation layer have opposite conductive media;

[0012] An isolation region located between the first region and the second region, the isolation region is recessed inward and is closer to the silicon substrate relative to the first region and the second region;

[0013] At least one end of the TBC solar cell slice along the first direction is an isolation region.

[0014] Further, both ends of the TBC solar cell slice along the first direction are isolation regions.

[0015] Further, the isolation region penetrates along the third direction of the silicon substrate.

[0016] Further, the first conductive passivation layer and / or the second conductive passivation layer is a doped polysilicon layer or a doped stacked polysilicon layer containing a silicon oxide layer; the stacked polysilicon layer containing a silicon oxide layer can be a polysilicon layer + silicon oxide layer + polysilicon layer structure.

[0017] The present invention also provides a method for preparing the above-mentioned TBC solar cell slice, including: slicing the TBC solar whole cell along the third direction in the isolation region.

[0018] Further, the slicing adopts a laser thermal stress slicing technique, including:

[0019] (1) Determine a pre-slicing position along the third direction in the isolation region, and use laser A to slot both ends of the pre-slicing position;

[0020] (2) Use laser B to locally heat the middle region of the pre-slicing position, and then perform rapid cooling to cause the silicon wafer to crack and complete the slicing.

[0021] Further, in step (1), the slotting length is 1 - 2 mm, and the slotting depth is 25 - 35% of the thickness of the silicon wafer.

[0022] Further, the laser A and the laser B are infrared lasers; the parameters of the laser A are: wavelength 500 - 1500 nm, power 30 - 80 W; the parameters of the laser B are: wavelength 500 - 1500 nm, power 200 - 600 W, and the spot diameter is 1 - 3 mm.

[0023] Further, in step (2), the local heating temperature is 180 - 220 °C, and the length of the middle region along the third direction is 95 - 99% of the length of the silicon wafer.

[0024] The present invention also provides a battery assembly, which includes a plurality of series - connected or parallel - connected above - mentioned TBC solar cell slices or TBC solar cell slices prepared by the above - mentioned preparation method.

[0025] The TBC solar cell slice, its preparation method and the battery assembly of the present invention have the following beneficial effects:

[0026] For the TBC solar cell slice of the present invention, by defining at least one end of the TBC solar cell slice along the first direction as an isolation region after slicing, that is, the slicing position is in the isolation region, it avoids damaging the first conductive passivation layer or the second conductive passivation layer when cutting the first region and the second region during slicing, reduces the cutting damage, and improves the battery performance.

[0027] For the preparation method of the TBC solar cell slice of the present invention, by slicing in the isolation region, the isolation region does not contact the metal electrode, which avoids serious thermal influence and mechanical damage when the laser beam cuts the first region or the second region, ensures the passivation performance of the first region and the second region, and improves the performance of the battery slice.

[0028] The battery assembly of the present invention includes a plurality of series - connected or parallel - connected above - mentioned TBC solar cell slices. The performance consistency between the above - mentioned battery slices is good, reducing the loss of the power of the component packaging; at the same time, the risk of hidden cracks in the battery slices is reduced, the repair probability of the component is reduced, and the production efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1Schematic diagram of the sliced structure of the TBC solar cell of the present invention;

[0031] Figure 2 Another schematic diagram of the sliced structure of the TBC solar cell of the present invention;

[0032] Explanation of reference numerals: 1. Silicon substrate, 2. Front passivation layer, 3. First region, 31. First tunneling oxide layer, 32. First conductive passivation layer, 33. First back passivation layer, 34. First metal electrode, 4. Second region, 41. Second tunneling oxide layer, 42. Second conductive passivation layer, 43. Second back passivation layer, 44. Second metal electrode, 5. Isolation region. Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0034] Reference Figure 1 , in the present application, the first direction is the horizontal direction, the second direction is the vertical direction, and the third direction is perpendicular to the paper surface and perpendicular to both the first direction and the second direction.

[0035] Reference Figure 1 , the present invention provides a sliced TBC solar cell, including:

[0036] A silicon substrate 1 having opposite front and back surfaces, a front passivation layer 2 is provided on the front surface of the silicon substrate 1, and a first region 3 and a second region 4 are alternately provided on the back surface of the silicon substrate 1;

[0037] The first region 3 sequentially includes a first tunneling oxide layer 31, a first conductive passivation layer 32, a first back passivation layer 33, and a first metal electrode 34 along the direction away from the silicon substrate 1, and the first metal electrode 34 is in ohmic contact with the first conductive passivation layer 32;

[0038] The second region 4 sequentially includes a second tunneling oxide layer 41, a second conductive passivation layer 42, a second back passivation layer 43, and a second metal electrode 44 along the direction away from the silicon substrate 1, and the second metal electrode 44 is in ohmic contact with the second conductive passivation layer 42;

[0039] The first conductive passivation layer 32 and the second conductive passivation layer 42 have opposite conductive media;

[0040] An isolation region 5 (GAP region) located between the first region 3 and the second region 4, the isolation region 5 is recessed inward and is closer to the silicon substrate 1 relative to the first region 3 and the second region 4;

[0041] At least one end of the TBC solar cell slice along the first direction is the isolation region 5.

[0042] For the TBC solar cell slice of the present invention, by defining that at least one end of the TBC solar cell slice along the first direction is the isolation region after slicing the cell, that is, the slicing position is in the isolation region, it avoids damaging the first conductive passivation layer or the second conductive passivation layer when slicing, reduces the cutting damage, and improves the battery performance.

[0043] Specifically, in some embodiments of the present invention, the first conductive passivation layer 32 and / or the second conductive passivation layer 42 is a doped polysilicon layer or a stacked polysilicon layer doped with a silicon oxide layer; the stacked polysilicon layer containing a silicon oxide layer can be a polysilicon layer + silicon oxide layer + polysilicon layer structure.

[0044] Specifically, in some embodiments of the present invention, the first conductive passivation layer 32 is a P-type doped polysilicon layer, and the second conductive passivation layer 42 is an N-type doped polysilicon layer; the first metal electrode 34 is a metal positive electrode, and the second metal electrode 44 is a metal negative electrode; the P-type doped polysilicon layer forms an ohmic contact with the metal positive electrode, and the N-type doped polysilicon layer forms an ohmic contact with the metal negative electrode.

[0045] As another implementation manner of the present invention, the first conductive passivation layer 32 is an N-type doped polysilicon layer, and the second conductive passivation layer 42 is a P-type doped polysilicon layer; the first metal electrode 34 is a metal negative electrode, and the second metal electrode 44 is a metal positive electrode; the P-type doped polysilicon layer forms an ohmic contact with the metal positive electrode, and the N-type doped polysilicon layer forms an ohmic contact with the metal negative electrode.

[0046] Specifically, in some embodiments of the present invention, refer to Figure 2 , both ends of the TBC solar cell slice along the first direction are the isolation region 5. When slicing the whole battery, the slicing position can be the isolation regions at different positions arranged along the first direction, and it can be bisected, trisected, quadrisected, etc. The corresponding obtained battery slices can have one or two cutting surfaces, that is, only one end of the battery slice can be the isolation region, or both ends can be the isolation regions.

[0047] Specifically, in some embodiments of the present invention, the isolation region penetrates along the third direction of the silicon substrate. The whole cell is sliced along the third direction during the slicing process. In order to further reduce the cutting damage, the isolation region is made to penetrate in the third direction, that is, to ensure that the cutting surface is located in the isolation region, which can avoid affecting the passivation performance of the first region and the second region.

[0048] The present invention also provides a method for preparing the sliced TBC solar cell, including: slicing the whole TBC solar cell along the third direction in the isolation region.

[0049] By slicing in the isolation region, the isolation region does not come into contact with the metal electrode, avoiding serious thermal effects and mechanical damage caused when the laser beam cuts the first region or the second region, ensuring the passivation performance of the first region and the second region, having smaller cutting damage, and improving the performance of the cell.

[0050] Specifically, in some embodiments of the present invention, the slicing uses the laser thermal stress slicing technology, including:

[0051] (1) Determine the pre-slicing position along the third direction in the isolation region, and use laser A to groove both ends of the pre-slicing position;

[0052] (2) Use laser B to locally heat the middle region of the pre-slicing position, and then perform rapid cooling, causing the silicon wafer to crack and completing the slicing.

[0053] The present invention uses the laser thermal stress slicing technology to cut the isolation region. Compared with directly cutting in the first region or the second region, it can reduce the efficiency loss caused by the thermal affected zone to the cutting edge. At the same time, this method can effectively reduce the microcracks generated during the slicing process, and effectively inhibit the expansion of cracks during the slicing of the cell, thereby reducing the packaging loss from the cell to the module.

[0054] Specifically, in some embodiments of the present invention, first use a high-power laser A to groove, and then use laser B to locally heat the middle of the cell, while using the cooling device supporting the equipment to rapidly cool the heated part, forming an unbalanced temperature field in the middle processing region of the cell. This temperature field will form a temperature gradient on the cell surface, exciting the generation of thermal stress to slice the cell.

[0055] Specifically, in some embodiments of the present invention, in step (1), the slotting length is 1-2 mm, and the slotting depth is 25-35% of the thickness of the silicon wafer. More specifically, the slotting length is 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm or a range value composed of any two of them; the slotting depth is 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% of the thickness of the silicon wafer or a range value composed of any two of them; preferably, in step (1), the slotting length is 1.5 mm, and the slotting depth is 30% of the thickness of the silicon wafer.

[0056] Specifically, in some embodiments of the present invention, the parameters of the laser A are: wavelength 500-1500 nm, power 30-80 W; the parameters of the laser B are: wavelength 500-1500 nm, power 200-600 W, and the spot diameter is 1-3 mm. Preferably, the wavelengths of the laser A and the laser B are independently any one of 532 nm, 798 nm, and 1064 nm; more preferably, the wavelengths of the laser A and the laser B are 1064 nm. More specifically, the power of the laser A is 30 W, 35 W, 40 W, 45 W, 50 W, 55 W, 60 W, 65 W, 70 W, 75 W, 80 W or a range value composed of any two of them; the power of the laser B is 200 W, 250 W, 300 W, 350 W, 400 W, 450 W, 500 W, 550 W, 600 W or a range value composed of any two of them; the spot diameter is 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.4 mm, 2.5 mm, 2.7 mm, 2.8 mm, 3 mm or a range value composed of any two of them.

[0057] For the preparation method of the TBC solar cell slice of the present invention, the cutting surface is located in the isolation area. The thickness of the isolation area mainly includes the thickness of the silicon substrate and the thickness of the GAP area. The GAP area is thinner than the first area and the second area, so the thickness of the cutting surface is relatively thinner; correspondingly, during the laser slotting and thermal cracking of the cutting surface, a relatively small laser power can be used to achieve cutting, and the cutting surface is flat and smooth. Too high or too low power will cause the cutting surface to be rough and cause great damage to the passivation performance; specifically, too low power cannot cut the battery slice, and the cutting surface will be wavy, resulting in a rough cutting surface; too high power, with large energy, the laser spot will spread outwards, and the thermal influence area is large, resulting in a rough cutting surface.

[0058] Specifically, in some embodiments of the present invention, the lasers for laser slotting and chipping are infrared lasers.

[0059] Specifically, in some embodiments of the present invention, in step (2), the local heating temperature is 180~220°C, and the length of the middle region along the third direction is 95~99% of the length of the silicon wafer. More specifically, in step (2), the local heating temperature is 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C or a range value composed of any two of them. During the laser slicing process, except for the two end grooving regions, the remaining middle region is heated; since the heat affected zone formed after heating may cause microcracks in the cell, which in turn leads to a decrease in the efficiency of the cell; by setting the slicing position in the GAP region, this problem can be effectively avoided.

[0060] Since the slicing position of the present invention is in the isolation region, it will not cause damage to the first region and the second region, and the generated cutting surface will not affect the passivation performance of the cell, that is, there is no need to passivate the cutting surface, which simplifies the process flow; at the same time, the slicing process of the present invention can be carried out arbitrarily after the isolation region is formed. Preferably, slicing is carried out after printing.

[0061] Specifically, in some embodiments of the present invention, the method for preparing a sliced TBC solar cell includes the following steps:

[0062] (1) Double-sided polishing the silicon wafer with an alkaline solution;

[0063] (2) Sequentially depositing a first tunneling oxide layer, a first conductive passivation layer, and a first mask layer on the back of the silicon wafer;

[0064] (3) Removing part of the first tunneling oxide layer, the first conductive passivation layer, and the first mask layer on the back of the silicon wafer in step (2) by first laser treatment and wet etching;

[0065] (4) Sequentially depositing a second tunneling oxide layer, a second conductive passivation layer, and a second mask layer on the back of the silicon wafer processed in step (3);

[0066] (5) Removing the second tunneling oxide layer, the second conductive passivation layer, and the second mask layer covering the first region and the isolation region on the back of the silicon wafer in step (4) by second laser treatment and wet etching;

[0067] (6) Cleaning the first region, the second region, and the isolation region with HF; using the texturing process to obtain a textured surface on the front of the silicon wafer;

[0068] (7) Depositing a front passivation layer on the front of the silicon wafer and a back passivation layer on the back; printing the first metal electrode and the second metal electrode respectively;

[0069] (8) Laser slicing along the third direction in the isolation region;

[0070] (9) Sinter each battery slice so that an ohmic contact is formed between the first metal electrode and the first conductive passivation layer, and an ohmic contact is formed between the second metal electrode and the second conductive passivation layer.

[0071] Specifically, in some embodiments of the present invention, the first region is a boron-doped region, the second region is a phosphorus-doped region, the first laser treatment uses a first laser, and the relevant parameters are: laser wavelength 300 - 1100 nm, frequency 500 - 1000 kHz, scanning speed 10 - 200 m / s, spot size > 200 μm; the second laser treatment uses a second laser, and the relevant parameters are: laser wavelength 330 - 420 nm, frequency 200 - 1000 kHz, scanning speed 10 - 100 m / s, spot size 20 - 40 μm. The second region and the GAP region are formed by the second laser treatment (the width of the cutting line is set to 650 μm ± 100 μm as the GAP region).

[0072] The present invention also provides a battery module, including a plurality of the above-mentioned TBC solar cell slices connected in series or in parallel, or TBC solar cell slices prepared by the above-mentioned preparation method.

[0073] The battery module is composed of a plurality of the above-mentioned battery slices connected in series or in parallel. The whole battery is cut into half slices, and the light-receiving area is reduced by half. The current is reduced by half in direct proportion to the light-receiving area, but the resistance loss is proportional to the square of the current. Therefore, the resistance loss of the half-cell is one-fourth of that of the whole cell, thereby achieving the purpose of improving the output power of the battery module.

[0074] Specifically, in some embodiments of the present invention, the preparation of the battery module includes:

[0075] (1) Arrange the sliced small battery slices in rows and columns so that the bottom surfaces of multiple small battery slices are coplanar; avoid power generation area loss caused by partial overlap of adjacent batteries;

[0076] (2) Weld the small battery slices into strings with tinned copper strips, arrange them in layers, gather the current through the busbars, conduct appearance and EL inspections. After there are no welding defects, laminate the battery slices, then perform edge trimming and cleaning, install the junction box, clean and cure, and finally perform IV and EL tests;

[0077] (3) Realize the series and parallel connection of multiple small battery slices through the main grid lines, and there is no need to deposit a transparent conductive film on the top surface, avoiding the influence of the light transmittance of the transparent conductive film on the CTM rate and improving the power generation efficiency of the photovoltaic module.

[0078] Specifically, in some embodiments of the present invention, in order to further reduce the resistance of the battery assembly, when slicing the whole battery, an equal division method is adopted, that is, the obtained small battery slices have the same area, which can be bisected, trisected or quadrisected, etc.; this can effectively reduce the resistance loss of the battery slices, but as the number of cutting times increases, the fragmentation rate will also increase; comprehensively evaluate the balance point between the efficiency gain brought by the resistance loss and the cost increase brought by the increase in the fragmentation rate, and find the most suitable slicing form.

[0079] The following further describes the TBC solar cell slicing, its preparation method, and the battery assembly of the present invention with specific embodiments.

[0080] Embodiment 1

[0081] Refer to Figure 1 , a TBC solar cell slice, including:

[0082] A silicon substrate 1 with a front side and a back side arranged opposite to each other. A front passivation layer 2 is provided on the front side of the silicon substrate 1, and a first region 3 and a second region 4 are alternately arranged on the back side of the silicon substrate 1;

[0083] The first region 3 sequentially includes a first tunneling oxide layer 31, a P-type doped polysilicon layer, a first back passivation layer 33, and a metal positive electrode from the direction away from the silicon substrate 1, and the metal positive electrode is in ohmic contact with the P-type doped polysilicon layer;

[0084] The second region 4 sequentially includes a second tunneling oxide layer 41, an N-type doped polysilicon layer, a second back passivation layer 43, and a metal negative electrode from the direction away from the silicon substrate 1, and the metal negative electrode is in ohmic contact with the N-type doped polysilicon layer;

[0085] An isolation region 5 (GAP region) located between the first region 3 and the second region 4, the isolation region 5 is recessed inward and is closer to the silicon substrate 1 than the first region 3 and the second region 4;

[0086] One end of the TBC solar cell slice along the first direction is the isolation region 5.

[0087] The preparation method of the TBC solar cell slice in this embodiment includes the following steps:

[0088] (1) Double-sided polishing the silicon wafer with an alkaline solution;

[0089] (2) Sequentially deposit a first tunneling oxide layer, a P-type doped polysilicon layer, and a first mask layer on the back side of the silicon wafer;

[0090] (3) The first laser treatment and wet etching are used to remove the first tunneling oxide layer, the first conductive passivation layer, and the first mask layer on the back side of the silicon wafer in step (2); the first laser treatment uses a first laser, and the relevant parameters are: laser wavelength 1064 nm, frequency 700 kHz, scanning speed 100 m / s, spot size > 200 μm;

[0091] (4) A second tunneling oxide layer, a second conductive passivation layer, and a second mask layer are sequentially deposited on the back side of the silicon wafer processed in step (3);

[0092] (5) The second laser treatment and wet etching are used to remove the second tunneling oxide layer, the second conductive passivation layer, and the second mask layer covering the first region and the isolation region on the back side of the silicon wafer in step (4); the second laser treatment uses a second laser, and the relevant parameters are: laser wavelength 355 nm, frequency 500 kHz, scanning speed 50 m / s, spot size 30 μm;

[0093] (6) The first region, the second region, and the isolation region are cleaned with HF; using the texturing process, a textured surface is obtained on the front side of the silicon wafer;

[0094] (7) A front passivation layer is deposited on the front side of the silicon wafer, and a back passivation layer is deposited on the back side; the first metal electrode and the second metal electrode are printed respectively;

[0095] (8) Laser slicing: Laser slicing is performed along the center line position of the isolation region in the third direction: First, use laser A (wavelength 1064 nm, power 50 w) to cut a groove with a length of 1.5 mm and a depth of 30% of the silicon wafer thickness on both edges in the middle of the whole battery; then use laser B (wavelength 1064 nm, power 300 w, spot diameter 2 mm) to locally heat the middle of the battery cell, the heating temperature is 200 °C, and at the same time use the cooling device supporting the equipment to quickly cool the heated part, forming an unbalanced temperature field in the processing area in the middle of the battery cell. This temperature field will form a temperature gradient on the battery surface, and the generated thermal stress will cut the battery cell into half pieces;

[0096] (9) Sinter each battery slice so that the first metal electrode and the first conductive passivation layer form an ohmic contact, and the second metal electrode and the second conductive passivation layer form an ohmic contact.

[0097] The TBC solar cell slices in Example 1 are connected in series and encapsulated to make a 66-cell type battery module (that is, a battery module containing 66 battery slices).

[0098] Example 2

[0099] Refer to Figure 1-2 , a TBC solar cell slice, comprising:

[0100] A silicon substrate 1 with a relatively arranged front and back, a front passivation layer 2 is arranged on the front of the silicon substrate 1, and a first region 3 and a second region 4 are alternately arranged on the back of the silicon substrate 1;

[0101] The first region 3 sequentially includes a first tunneling oxide layer 31, a P-type doped polysilicon layer, a first back passivation layer 33, and a metal positive electrode along the direction away from the silicon substrate 1, and the metal positive electrode is in ohmic contact with the P-type doped polysilicon layer;

[0102] The second region 4 sequentially includes a second tunneling oxide layer 41, an N-type doped polysilicon layer, a second back passivation layer 43, and a metal negative electrode along the direction away from the silicon substrate 1, and the metal negative electrode is in ohmic contact with the N-type doped polysilicon layer;

[0103] An isolation region 5 (GAP region) located between the first region 3 and the second region 4, the isolation region 5 is recessed inward and is closer to the silicon substrate 1 relative to the first region 3 and the second region 4;

[0104] One end or both ends of the TBC solar cell slice along the first direction are the isolation region 5.

[0105] The preparation method of the TBC solar cell slice of this embodiment includes the following steps:

[0106] (1) Double-sided polishing treatment of the silicon wafer with an alkaline solution;

[0107] (2) Sequentially deposit a first tunneling oxide layer, a P-type doped polysilicon layer, and a first mask layer on the back of the silicon wafer;

[0108] (3) The first laser treatment and wet etching are used to remove the first tunneling oxide layer, the first conductive passivation layer, and the first mask layer on the back of the silicon wafer in step (2); the first laser treatment uses a first laser, and the relevant parameters are: laser wavelength 1064nm, frequency 700kHz, scanning speed 100m / s, spot size >200μm;

[0109] (4) Sequentially deposit a second tunneling oxide layer, a second conductive passivation layer, and a second mask layer on the back of the silicon wafer processed in step (3);

[0110] (5) The second laser treatment and wet etching are used to remove the second tunneling oxide layer, the second conductive passivation layer, and the second mask layer covering the first region and the isolation region on the back of the silicon wafer in step (4); the second laser treatment uses a second laser, and the relevant parameters are: laser wavelength 355nm, frequency 500kHz, scanning speed 50m / s, spot size 30μm;

[0111] (6) Clean the first region, the second region, and the isolation region with HF; use the texturing process to obtain a textured surface on the front side of the silicon wafer;

[0112] (7) Deposit a front passivation layer on the front side of the silicon wafer and a back passivation layer on the back side; print the first metal electrode and the second metal electrode respectively;

[0113] (8) Laser slicing: Perform laser slicing along the third direction at the center line positions of the two isolation regions respectively: First, use laser A (wavelength 1064 nm, power 50 w) to cut a groove with a length of 1.5 mm and a depth of 30% of the silicon wafer thickness at both edges on both sides of the middle of the whole cell; Then, use laser B (wavelength 1064 nm, power 300 w, spot diameter 2 mm) to locally heat the middle of the cell, with the heating temperature being 200 °C. At the same time, use the cooling device supporting the equipment to quickly cool the heated part, forming an unbalanced temperature field in the processing area in the middle of the cell. This temperature field will form a temperature gradient on the cell surface, and the generated thermal stress will cut the cell into three slices;

[0114] (9) Sinter each cell slice so that the first metal electrode forms an ohmic contact with the first conductive passivation layer, and the second metal electrode forms an ohmic contact with the second conductive passivation layer.

[0115] Connect the TBC solar cell slices in Example 2 in series for packaging to make a 66-cell version battery module (i.e., containing 66 cell slices).

[0116] Example 3

[0117] Refer to Figure 1-2 , a TBC solar cell slice, comprising:

[0118] A silicon substrate 1 with a front side and a back side arranged oppositely. A front passivation layer 2 is provided on the front side of the silicon substrate 1, and a first region 3 and a second region 4 are alternately arranged on the back side of the silicon substrate 1;

[0119] The first region 3 sequentially includes a first tunneling oxide layer 31, a P-type doped polysilicon layer, a first back passivation layer 33, and a metal positive electrode from the direction away from the silicon substrate 1. The metal positive electrode is in ohmic contact with the P-type doped polysilicon layer;

[0120] The second region 4 sequentially includes a second tunneling oxide layer 41, an N-type doped polysilicon layer, a second back passivation layer 43, and a metal negative electrode from the direction away from the silicon substrate 1. The metal negative electrode is in ohmic contact with the N-type doped polysilicon layer;

[0121] An isolation region 5 (GAP region) located between the first region 3 and the second region 4, the isolation region 5 being recessed inward and closer to the silicon substrate 1 relative to the first region 3 and the second region 4;

[0122] One end or both ends of the TBC solar cell slice along the first direction are the isolation region 5.

[0123] The preparation method of the TBC solar cell slice of this embodiment includes the following steps:

[0124] (1) Double-sided polishing treatment of the silicon wafer using an alkaline solution;

[0125] (2) Sequentially depositing a first tunneling oxide layer, a P-type doped polysilicon layer, and a first mask layer on the back of the silicon wafer;

[0126] (3) The first laser treatment and wet etching are used to remove the first tunneling oxide layer, the first conductive passivation layer, and the first mask layer on the back of the silicon wafer in step (2); the first laser treatment uses a first laser, and the relevant parameters are: laser wavelength 1064 nm, frequency 700 kHz, scanning speed 100 m / s, spot size > 200 μm;

[0127] (4) Sequentially depositing a second tunneling oxide layer, a second conductive passivation layer, and a second mask layer on the back of the silicon wafer processed in step (3);

[0128] (5) The second laser treatment and wet etching are used to remove the second tunneling oxide layer, the second conductive passivation layer, and the second mask layer covering the first region and the isolation region on the back of the silicon wafer in step (4); the second laser treatment uses a second laser, and the relevant parameters are: laser wavelength 355 nm, frequency 500 kHz, scanning speed 50 m / s, spot size 30 μm;

[0129] (6) Cleaning the first region, the second region, and the isolation region with HF; using a texturing process to obtain a textured surface on the front of the silicon wafer;

[0130] (7) Depositing a front passivation layer on the front of the silicon wafer and a back passivation layer on the back; printing a first metal electrode and a second metal electrode respectively;

[0131] (8) Laser slicing: Laser slicing is performed along the third direction at the center line positions of the three isolation regions respectively: First, use laser A (wavelength 1064 nm, power 50 w) to cut a groove with a length of 1.5 mm and a depth of 30% of the silicon wafer thickness at both edges in the middle of the whole battery; Then use laser B (wavelength 1064 nm, power 300 w, spot diameter 2 mm) to locally heat the middle of the battery cell, with the heating temperature being 200 °C. At the same time, use the cooling device supporting the equipment to quickly cool the heated part, forming an unbalanced temperature field in the processing area in the middle of the battery cell. This temperature field will form a temperature gradient on the battery surface, and the generated thermal stress will cut the battery cell into four pieces;

[0132] (9) Sinter each battery slice so that the first metal electrode and the first conductive passivation layer form an ohmic contact, and the second metal electrode and the second conductive passivation layer form an ohmic contact.

[0133] The TBC solar cell slices in Example 2 are connected in series and encapsulated to make a 66-cell version battery module (that is, it contains 66 battery slices).

[0134] Example 4

[0135] The TBC solar cell slices in this example are basically the same as those in Example 1, with the only difference being the laser slicing process in step (8) of the preparation method.

[0136] Specifically, in step (8) of this example, laser slicing is performed along the third direction at the center line position of the isolation region: First, use laser A (wavelength 1064 nm, power 30 w) to cut a groove with a length of 1 mm and a depth of 25% of the silicon wafer thickness at both edges in the middle of the whole battery; Then use laser B (wavelength 1064 nm, power 200 w, spot diameter 2 mm) to locally heat the middle of the battery cell, with the heating temperature being 180 °C. At the same time, use the cooling device supporting the equipment to quickly cool the heated part.

[0137] Example 5

[0138] The TBC solar cell slices in this example are basically the same as those in Example 1, with the only difference being the laser slicing process in step (8) of the preparation method.

[0139] Specifically, in step (8) of this embodiment, laser slicing is performed along the third direction at the center line position of the isolation region: First, use laser A (wavelength 1064 nm, power 80 w) to cut a slot with a length of 2 mm and a depth of 35% of the silicon wafer thickness at both edges in the middle of the whole battery; then use laser B (wavelength 1064 nm, power 600 w, spot diameter 2 mm) to locally heat the middle of the battery cell, with the heating temperature being 220 °C, and at the same time use the cooling device supporting the equipment to quickly cool the heated part.

[0140] Example 6

[0141] In this embodiment, the slicing of the TBC solar cell is basically the same as that in Example 1, and the only difference lies in the laser slicing process in step (8) of the preparation method.

[0142] Specifically, in step (8) of this embodiment, laser slicing is performed along the third direction at the center line position of the isolation region: First, use laser A (wavelength 1064 nm, power 50 w) to cut a slot with a length of 1.5 mm and a depth of 30% of the silicon wafer thickness at both edges in the middle of the whole battery; then use laser B (wavelength 1064 nm, power 180 w, spot diameter 2 mm) to locally heat the middle of the battery cell, with the heating temperature being 200 °C, and at the same time use the cooling device supporting the equipment to quickly cool the heated part.

[0143] Example 7

[0144] In this embodiment, the slicing of the TBC solar cell is basically the same as that in Example 1, and the only difference lies in the laser slicing process in step (8) of the preparation method.

[0145] Specifically, in step (8) of this embodiment, laser slicing is performed along the third direction at the center line position of the isolation region: First, use laser A (wavelength 1064 nm, power 50 w) to cut a slot with a length of 1.5 mm and a depth of 30% of the silicon wafer thickness at both edges in the middle of the whole battery; then use laser B (wavelength 1064 nm, power 620 w, spot diameter 2 mm) to locally heat the middle of the battery cell, with the heating temperature being 200 °C, and at the same time use the cooling device supporting the equipment to quickly cool the heated part.

[0146] Comparative Example 1

[0147] This comparative example includes most of the content of Example 1, and the only difference is that: laser slicing is performed along the third direction in the first region.

[0148] Comparative Example 2

[0149] This comparative example includes most of the content of Example 1, with the only difference being that laser slicing is performed in the second region along the third direction.

[0150] The battery modules obtained from the examples and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0151] Table 1

[0152] Group Voc (V) Isc (A) Vpm (V) Ipm (A) Rs (Ω) Rsh (Ω) Pmax (W) FF (%) Example 1 49.49 16.06 42.98 15.18 0.239 178.53 652.54 82.6 Example 2 49.20 16.09 43.00 15.19 0.240 175.30 653.29 82.5 Example 3 49.16 16.17 42.95 15.23 0.238 171.37 654.03 82.3 Example 4 49.08 16.23 42.35 15.33 0.240 208.53 649.19 81.5 Example 5 49.07 16.24 42.34 15.32 0.241 166.70 648.59 81.4 Example 6 49.08 16.20 42.40 15.29 0.238 195.08 648.42 81.5 Example 7 49.07 16.21 42.37 15.29 0.238 178.10 647.97 81.5 Comparative Example 1 49.08 16.20 42.38 15.23 0.241 132.20 645.34 81.2 Comparative Example 2 49.08 16.24 42.34 15.27 0.241 135.74 646.61 81.1

[0153] As can be seen from the test results of Example 1 and Comparative Examples 1-2 in Table 1, by setting the slicing position in the isolation region, the present invention avoids serious thermal effects and mechanical damage caused by the laser beam cutting the first region or the second region, ensures the passivation performance of the first region and the second region, and the performance of the obtained battery module is better. As can be seen from the test results of Examples 1-7, when slicing is performed in the isolation region and the power of the laser during the slicing process is further limited, the roughness of the cutting surface can be further controlled, and the passivation performance of the battery can be optimized. And regardless of whether the silicon wafer is bisected, trisected or quartered, as long as the cutting surface is located in the isolation region, regardless of the number of equal parts, a battery module with better performance can be obtained.

[0154] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A TBC solar cell slice, characterized in that, include: A silicon substrate having a front side and a back side arranged opposite to each other, wherein the front side of the silicon substrate is provided with a front side passivation layer, and the back side of the silicon substrate is alternately provided with a first region and a second region; The first region includes, in sequence along a direction away from the silicon substrate, a first tunneling oxide layer, a first conductive passivation layer, a first back passivation layer, and a first metal electrode, wherein the first metal electrode is in ohmic contact with the first conductive passivation layer; The second region includes, in sequence along a direction away from the silicon substrate, a second tunneling oxide layer, a second conductive passivation layer, a second back passivation layer, and a second metal electrode, wherein the second metal electrode is in ohmic contact with the second conductive passivation layer; The first conductive passivation layer and the second conductive passivation layer have opposite conductive media; An isolation region located between the first region and the second region, the isolation region being recessed inwardly and closer to the silicon substrate than the first region and the second region; At least one end of the TBC solar cell slice along the first direction is an isolation region.

2. The TBC solar cell slice according to claim 1, characterized in that, Both ends of the TBC solar cell slice along the first direction are isolation areas.

3. The TBC solar cell slice according to claim 1, wherein, The isolation regions are interconnected along a third direction of the silicon substrate.

4. The TBC solar cell slice according to claim 1, characterized in that, The first conductive passivation layer and / or the second conductive passivation layer is a doped polysilicon layer or a doped stacked polysilicon layer containing a silicon oxide layer.

5. The preparation method of the TBC solar cell slice according to any one of claims 1-4, characterized in that, include: The whole TBC solar cell is sliced in the isolation area along the third direction.

6. The preparation method of the TBC solar cell slice according to claim 5, wherein, The slicing adopts laser thermal stress slicing technology, including: (1) Determine the pre-slicing position along the third direction in the isolation area, and use laser A to groove both ends of the pre-slicing position; (2) Use laser B to locally heat the middle area of the pre-slicing position, and then quickly cool it to crack the silicon wafer and complete the slicing.

7. The preparation method of the TBC solar cell slice according to claim 6, characterized in that, In step (1), the length of the groove is 1-2 mm, and the depth of the groove is 25-35% of the thickness of the silicon wafer.

8. The preparation method of the TBC solar cell slice according to claim 6, characterized in that, The laser A and laser B are infrared lasers; the parameters of the laser A are: wavelength 500~1500nm, power 30~80W; the parameters of the laser B are: wavelength 500~1500nm, power 200~600W, spot diameter 1~3mm.

9. The preparation method of the TBC solar cell slice according to claim 6, characterized in that, In step (2), the local heating temperature is 180-220° C., and the length of the middle region along the third direction is 95-99% of the length of the silicon wafer.

10. A battery assembly, characterized in that, The invention comprises a plurality of TBC solar cell slices according to any one of claims 1 to 4 connected in series or in parallel, or a TBC solar cell slice prepared by the preparation method according to any one of claims 5 to 9.

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