Back contact type cell and preparation method thereof

Abstract

This invention provides a back-contact solar cell and its fabrication method. The back-contact solar cell includes a silicon substrate and further comprises: a first oxide layer, a first boron-doped layer, a second oxide layer, and a second boron-doped layer sequentially disposed in a first region of the silicon substrate away from the silicon substrate; and a first tunneling layer, a first phosphorus-doped layer, a second tunneling layer, and a second phosphorus-doped layer sequentially disposed in a second region of the silicon substrate away from the silicon substrate. The doping concentration of the first boron-doped layer is greater than that of the second boron-doped layer; the doping concentration of the first phosphorus-doped layer is less than that of the second phosphorus-doped layer; and the thickness of the first phosphorus-doped layer is less than that of the first boron-doped layer. The back-contact solar cell and its fabrication method provided by this invention can improve the field-effect passivation effect of the back-contact solar cell and reduce the performance differences between different polarity regions of the back-contact solar cell.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a back-contact solar cell and its preparation method. Background Technology

[0002] Under the current technological approach, improving the efficiency of back-contact batteries faces significant bottlenecks. Specifically, because boron doping concentration is usually much lower than phosphorus doping, the field-effect passivation effect is insufficient. At the same time, due to the small atomic radius of boron, it is more likely to damage the oxide layer and cause serious internal diffusion problems, resulting in a large difference between the performance of the emitter region and the back field region of the back-contact battery. Summary of the Invention

[0003] This invention provides a back-contact solar cell and its preparation method, aiming to improve the field-effect passivation effect of the back-contact solar cell and reduce the performance differences between different polarity regions of the back-contact solar cell.

[0004] The present invention provides a back-contact type solar cell, comprising a silicon substrate, wherein a first surface of the silicon substrate has an alternating first region and a second region; further comprising: a first oxide layer, a first boron doped layer, a second oxide layer, and a second boron doped layer sequentially disposed in the first region away from the silicon substrate, and a first tunneling layer, a first phosphorus doped layer, a second tunneling layer, and a second phosphorus doped layer sequentially disposed in the second region away from the silicon substrate.

[0005] The doping concentration of the first boron-doped layer is greater than that of the second boron-doped layer; the doping concentration of the first phosphorus-doped layer is less than that of the second phosphorus-doped layer.

[0006] The thickness of the first phosphorus-doped layer is less than the thickness of the first boron-doped layer.

[0007] Optionally, the silicon substrate has a boron-doped inner extension layer; the boron-doped inner extension layer is in contact with the first oxide layer, and the doping concentration of the boron-doped inner extension layer is in the range of 1×10⁻⁶. 18 cm -3 ~2×10 19 cm -3 The thickness of the boron-doped inner extension layer is 100nm~300nm.

[0008] Optionally, the doping concentration of the first boron doped layer is in the range of 4 × 10⁻⁶. 19 cm -3 ~2×10 20 cm -3 The doping concentration of the second boron doped layer ranges from 1×10⁻⁶. 19 cm -3 ~1×10 20 cm-3 .

[0009] Optionally, the thickness of the first boron-doped layer is 10 nm to 150 nm; the thickness of the second boron-doped layer is 30 nm to 300 nm.

[0010] The thickness of the first phosphorus-doped layer is 5 nm to 120 nm; the thickness of the second phosphorus-doped layer is 30 nm to 300 nm.

[0011] Optionally, the materials of both the first oxide layer and the second oxide layer include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

[0012] Optionally, the thickness of the first oxide layer is 1.5 nm to 4.0 nm, and the thickness of the second oxide layer is 0.8 nm to 1.5 nm.

[0013] Optionally, the thickness of the first tunneling layer is 0.8 nm to 4.0 nm, and the thickness of the second tunneling layer is 0.3 nm to 1.2 nm.

[0014] Optionally, the doping concentration of the first phosphorus doped layer is in the range of 1×10⁻⁶. 20 cm -3 ~5×10 20 cm -3 The doping concentration range of the second phosphorus doped layer is 1×10⁻⁶. 20 cm -3 ~1×10 21 cm -3 .

[0015] Optionally, the materials of both the first tunneling layer and the second tunneling layer include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

[0016] As another technical solution, the present invention also provides a method for preparing a back-contact type solar cell, which includes the following steps:

[0017] A silicon substrate is obtained, wherein a first surface of the silicon substrate includes alternating first and second regions;

[0018] A first oxide layer, a first boron-doped layer, a second oxide layer, and a second boron-doped layer are sequentially formed on the first surface of the silicon substrate; wherein the doping concentration of the first boron-doped layer is greater than the doping concentration of the second boron-doped layer.

[0019] A first mask pattern is formed on the surface of the second boron-doped layer and a first etching process is performed to remove the portions of the first oxide layer, the first boron-doped layer, the second oxide layer, and the second boron-doped layer located outside the first region;

[0020] A first tunneling layer, a first phosphorus-doped layer, a second tunneling layer, and a second phosphorus-doped layer are sequentially formed on the first surface; wherein the doping concentration of the first phosphorus-doped layer is less than the doping concentration of the second phosphorus-doped layer; and the thickness of the first phosphorus-doped layer is less than the thickness of the first boron-doped layer.

[0021] A second mask pattern is formed on the surface of the second phosphorus-doped layer and a second etching process is performed to remove the portions of the first tunneling layer, the first phosphorus-doped layer, the second tunneling layer, and the second phosphorus-doped layer located outside the second region.

[0022] The embodiments of the present invention have the following beneficial effects:

[0023] The back-contact solar cell provided in this embodiment of the invention includes a first oxide layer, a first boron doped layer, a second oxide layer, and a second boron doped layer sequentially disposed in a first region, and a first tunneling layer, a first phosphorus doped layer, a second tunneling layer, and a second phosphorus doped layer sequentially disposed in a second region away from the silicon substrate. The doping concentration of the first boron doped layer is greater than that of the second boron doped layer, and the doping concentration of the first phosphorus doped layer is lower than that of the second phosphorus doped layer. That is, the embodiment of the invention employs a double-layer doped design in both the first and second regions. This reduces the risk of diffused dopant atoms penetrating the first boron doped layer and the first oxide layer in the first region during subsequent heat treatment processes, and also improves the field-effect passivation effect in both regions, thereby maximizing the open-circuit voltage of the back-contact solar cell. Furthermore, this embodiment of the invention proposes that the thickness of the first phosphorus-doped layer is less than the thickness of the first boron-doped layer. By adjusting the thicknesses of the first phosphorus-doped layer and the first boron-doped layer, the heat resistance and total doping amount of both can be balanced. This avoids the first boron-doped layer from being burned through by the high-temperature electrode paste while preventing the first phosphorus-doped layer from becoming too thick, thus ensuring manufacturing costs and avoiding unnecessary resource waste. It also makes the field-effect passivation effects of the first boron-doped layer and the first phosphorus-doped layer nearly identical, thereby reducing the performance difference between the first and second regions of the solar cell. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. The above and other features and advantages will become more apparent to those skilled in the art from the detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0025] Figure 1 This is a simplified structural diagram of a back-contact type battery cell provided in an embodiment of the present invention;

[0026] Figure 2This is a flowchart illustrating a method for preparing a back-contact type battery cell according to an embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0028] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0029] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0031] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0032] This invention provides a back-contact type solar cell, which includes a silicon substrate, and the first surface of the silicon substrate has a first region and a second region arranged alternately.

[0033] Please refer to Figure 1The embodiment of the present invention provides a back-contact type solar cell that further includes: a first oxide layer 21, a first boron doped layer 22, a second oxide layer 23, and a second boron doped layer 24 sequentially disposed in a first region P away from the silicon substrate 1. That is, the first region P is a double-doped layer design, so that the first oxide layer 21 located between the silicon substrate 1 and the first boron doped layer 22 prevents boron atoms from diffusing from the first boron doped layer 22 to the silicon substrate 1, and at the same time, the second oxide layer 23 located between the first boron doped layer 22 and the second boron doped layer 24 organizes boron atoms from diffusing from the second boron doped layer 24 to the silicon substrate 1. Figure 1 As shown, the back-contact solar cell also includes: a first tunneling layer 31, a first phosphorus doped layer 32, a second tunneling layer 33, and a second phosphorus doped layer 34 sequentially disposed in the second region N away from the silicon substrate 1, that is, the second region N is also a double-doped layer design.

[0034] The doping concentration of the first boron doped layer 22 is greater than that of the second boron doped layer 24. By designing a higher doping concentration for the first boron doped layer 22, the field-effect passivation effect can be improved, thus preventing the field-effect passivation effect of the first region P from being lower than that of the second region N, thereby reducing the functional difference between the two electrodes of the back-contact solar cell. Furthermore, since the diffusion flux is proportional to the concentration gradient, designing a lower doping concentration for the second boron doped layer 24 can adjust the diffusion direction of boron atoms in the first boron doped layer 22. This induces boron atoms in the first boron doped layer 22 to diffuse towards the second oxide layer 23 and the second boron doped layer 24 when boron atoms diffuse from the high-concentration side to the low-concentration side at the film-layer interface under high-temperature conditions, such as during high-temperature annealing or other high-temperature processes. This reduces the diffusion of boron atoms from the first boron doped layer 22 to the first oxide layer 21 and the silicon substrate 1, effectively reducing the probability of boron atoms penetrating the first oxide layer 21. In this embodiment, the second oxide layer 23 has less resistance to the permeation of boron atoms than the first oxide layer 21, thereby promoting the diffusion of boron atoms doped in the first boron doped layer 22 into the second oxide layer 23 and inhibiting the diffusion of boron atoms into the first oxide layer 21, thereby further reducing the probability of boron atoms penetrating the first oxide layer 21.

[0035] In this embodiment, the doping concentration of the first phosphorus doped layer 32 is lower than that of the second phosphorus doped layer 34. Specifically, with the widespread application of thinner and lighter designs in solar cells, the passivation structure thickness in back-contact solar cells is becoming increasingly thinner. Consequently, the thickness of the single-layer phosphorus doped layer also needs to be as thin as possible. However, the thinner the phosphorus doped layer, the more difficult it is to balance the doping uniformity and performance of the phosphorus doped layer. Moreover, the degree of phosphorus diffusion in an excessively thin phosphorus doped layer is also difficult to control. In this embodiment, the first phosphorus doped layer 32 in the double-layer phosphorus doped layer is mainly used to form a passivation electric field to achieve field-effect passivation, while the second phosphorus doped layer 34 is mainly used to contact the electrode structure. This allows the first phosphorus doped layer 32 to be made as thin as possible and the doping concentration of the second phosphorus doped layer 34 to be higher. Furthermore, the second tunneling layer 33 can isolate the first phosphorus doped layer 32 and the second phosphorus doped layer 34, thereby avoiding mutual interference between the functions of the two phosphorus doped layers.

[0036] Furthermore, the thickness of the first phosphorus-doped layer 32 is less than the thickness of the first boron-doped layer 22. Specifically, the improvement in heat resistance of the doped layer by phosphorus atoms is greater than that by boron atoms. Therefore, designing the thickness of the first phosphorus-doped layer 32 to be less than that of the first boron-doped layer 22 can prevent the first boron-doped layer 22 from being burned through by the high-temperature electrode paste during subsequent electrode fabrication processes, while avoiding the first phosphorus-doped layer 32 from being too thick. Moreover, since the doping efficiency of phosphorus atoms in silicon-based materials is much higher than that of boron atoms in silicon-based materials, increasing the thickness of the first boron-doped layer 22 can increase the total amount of boron atoms in the first boron-doped layer 22, so that the total amount of boron atoms in the first boron-doped layer 22 is as consistent as possible with the total amount of phosphorus atoms in the first phosphorus-doped layer 32, thereby making the field-effect passivation effects produced by the first phosphorus-doped layer 32 and the first boron-doped layer 22 nearly identical.

[0037] This invention provides a double-layer doped layer and a double-layer oxide tunneling layer in both the first region P and the second region N. This reduces the risk of the oxide tunneling layer in both regions P and N being penetrated by doped atoms, and simultaneously improves the field-effect passivation effect in both regions P and N. Furthermore, it makes the field-effect passivation effect in both regions P and N nearly identical, thereby maximizing the open-circuit voltage and operating efficiency of the back-contact solar cell.

[0038] In some specific embodiments, the silicon substrate 1 can be an N-type monocrystalline silicon wafer. The thickness of the N-type monocrystalline silicon wafer can be 50 μm to 200 μm, and the resistivity of the N-type monocrystalline silicon wafer can be 0.1 Ω·cm to 50 Ω·cm.

[0039] In some specific embodiments, the first boron doped layer 22 and the second boron doped layer 24 can both be doped polycrystalline silicon layers; the first phosphorus doped layer 32 and the second phosphorus doped layer 34 can both be doped polycrystalline silicon layers.

[0040] In some specific embodiments, if the materials of the first oxide layer 21 and the second oxide layer 23 are the same, the thickness of the second oxide layer 23 is less than the thickness of the first oxide layer 21, so that the second oxide layer 23 is more easily penetrated by boron atoms than the first oxide layer 21, thereby promoting the diffusion of boron atoms doped in the first boron doped layer 22 to the second oxide layer 23, and thus achieving protection of the first oxide layer 21.

[0041] In some embodiments, the silicon substrate 1 has a boron-doped inner extension layer 11, which is in contact with the first oxide layer 21. Specifically, the boron-doped inner extension layer 11 located in the first region P is a lightly boron-doped region on the surface of the silicon substrate 1. The doping concentration of the boron-doped inner extension layer 11 ranges from 1 × 10⁻⁶. 18 cm -3 ~2×10 19 cm -3 Within this range, the doping concentration of the boron-doped inner extension layer 11 is sufficient to ensure a sufficiently strong passivation electric field is formed between it and the first boron-doped layer 22, thus ensuring the passivation effect of the field effect. The boron-doped inner extension layer 11 will also not experience excessive Auger recombination due to excessive doping concentration, thereby reducing recombination losses and improving the open-circuit voltage of the back-contact solar cell. Furthermore, the thickness of the boron-doped inner extension layer 11 is 100nm~300nm. Specifically, in the fabrication process, boron atoms can be implanted into the surface layer of the silicon substrate 1 using doping processes such as plasma implantation or laser doping to form the boron-doped inner extension layer 11. Within this thickness range, the boron doping depth will not be too shallow, leading to difficulty in controlling doping uniformity, nor will the boron doping depth be too deep, resulting in overdoping and damage to the non-inner extension region of the silicon substrate 1.

[0042] In some embodiments, the materials of the first oxide layer 21 and the second oxide layer 23 both include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

[0043] In some embodiments, the thickness of the first oxide layer 21 is 1.5 nm to 4.0 nm. Within this thickness range, the first oxide layer 21 is not easily penetrated and is not too thick, thus benefiting the thinner design of the back-contact type solar cell while ensuring the function of the first oxide layer 21. The thickness of the second oxide layer 23 is 0.8 nm to 1.5 nm. Within this thickness range, the second oxide layer 23 can effectively isolate the first boron doped layer 22 and the second boron doped layer 24, and helps guide boron atoms in the first boron doped layer 22 to diffuse into the second boron doped layer 24, thereby effectively preventing the first oxide layer 21 from being penetrated and failing.

[0044] In some embodiments, the doping concentration of the first boron-doped layer 22 is in the range of 4 × 10⁻⁶. 19 cm -3 ~2×10 20 cm -3 The doping concentration range of the second boron doped layer 24 is 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

[0045] It is easy to understand that the thinner the first boron doped layer 22 and the higher the doping concentration, the better the field effect passivation effect.

[0046] In some specific embodiments, the ratio of the doping concentration of the first boron doped layer 22 to the doping concentration of the second boron doped layer 24 can be in the range of 1 to 10. Within this range, it can be ensured that the doping concentration of the first boron doped layer 22 is greater than that of the second boron doped layer 24, without causing the doping concentration of the first boron doped layer 22 to be too high, which would significantly increase the manufacturing difficulty.

[0047] In some embodiments, the thickness of the first boron-doped layer 22 is 10 nm to 150 nm; the thickness of the second boron-doped layer 24 is 50 nm to 300 nm. Specifically, the thickness of the first boron-doped layer 22 is smaller than that of the second boron-doped layer 24, so that the boron atoms in the first boron-doped layer 22 are distributed as close to the interface as possible. This is equivalent to increasing the effective doping concentration at the interface of the first boron-doped layer 22, thereby generating a stronger electric field and improving the field-effect passivation effect. Furthermore, the aforementioned thickness range of the first boron-doped layer 22 can effectively prevent the first boron-doped layer 22 from being burned through by the high-temperature electrode paste during subsequent sintering processes, and prevent the first boron-doped layer 22 from being too thick, which would lead to excessively high manufacturing costs. It also contributes to the thinner design of back-contact solar cells.

[0048] The thickness of the first phosphorus doped layer 32 is 5 nm to 120 nm; the thickness of the second phosphorus doped layer 34 is 30 nm to 300 nm, so that the thickness of the first phosphorus doped layer 32 is less than the thickness of the second phosphorus doped layer 34, thereby maximizing the uniformity of phosphorus atom distribution in the interface region of the first phosphorus doped layer 32 when the doping concentration of the first phosphorus doped layer 32 is low, and thus ensuring the field effect passivation effect.

[0049] Moreover, the thickness range of the first boron doped layer 22 proposed in this embodiment is generally higher than the thickness range of the first phosphorus doped layer 32, so that the heat resistance and total doping amount of the first boron doped layer 22 are close to and consistent with the heat resistance and total doping amount of the first phosphorus doped layer 32, thereby making the performance of the first region P and the second region N of the solar cell as close as possible.

[0050] In some embodiments, the doping concentration of the first phosphorus doped layer 32 ranges from 1 × 10⁻⁶. 20 cm -3 ~5×10 20 cm -3 Within this doping concentration range, the doping concentration will not be too high to ensure good doping uniformity of phosphorus atoms, nor will it be too low to prevent the first phosphorus doped layer 32 from failing to meet passivation requirements. The doping concentration range of the second phosphorus doped layer 34 is 1×10⁻⁶. 20 cm -3 ~1×10 21 cm -3 Within this doping concentration range, the surface doping concentration of the second phosphorus doped layer 34 can be sufficiently high, thereby enabling the formation of a good ohmic contact with the electrode structure. Furthermore, within this doping concentration range, the functional difference between the first region P and the second region N of the back-contact solar cell is low, thereby increasing the open-circuit voltage of the back-contact solar cell.

[0051] In some embodiments, the materials of the first tunneling layer 31 and the second tunneling layer 33 both include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

[0052] In some embodiments, if the first tunneling layer 31 and the second tunneling layer 33 are made of the same material, the thickness of the second tunneling layer 33 is less than the thickness of the first tunneling layer 31. This is to reduce the probability of phosphorus atom diffusion by utilizing the first tunneling layer 31, and to further block the diffusion of phosphorus atoms by utilizing the second tunneling layer 33. Moreover, designing the thickness of the second tunneling layer 33 to be less than the thickness of the first tunneling layer 31 can effectively reduce the resistance of the second tunneling layer 33, thereby reducing Auger recombination and thus reducing recombination loss.

[0053] Furthermore, in some embodiments, the thickness of the first tunneling layer 31 is 0.8 nm to 4.0 nm. Within this thickness range, the first tunneling layer 31 is not easily penetrated and can be made as thin as possible, thereby benefiting the lightweight design of the back contact type solar cell while ensuring the function of the first tunneling layer 31. The thickness of the second tunneling layer 33 is 0.3 nm to 1.2 nm.

[0054] Furthermore, it should be noted that since the diffusion rate of phosphorus atoms in silicon oxide is much lower than that of boron atoms in silicon oxide, the risk of the first tunneling layer 31 in the second region N being penetrated is lower. Therefore, the thickness of the first tunneling layer 31 and the second tunneling layer 33 can be made thinner compared to the first oxide layer 21 and the second oxide layer 23.

[0055] In some embodiments, the surface of the silicon substrate 1 further has a GAP region located between any adjacent second region N and first region P. The GAP region is used to completely separate the corresponding first region P and second region N, so that adjacent first regions P and second regions N do not contact each other, thereby achieving isolation between the first region P and the second region N. Furthermore, the width of the GAP region is greater than 0 and less than or equal to 1000 μm.

[0056] In some embodiments, the back-contact solar cell further comprises a plurality of positive electrode structures 41 and a plurality of negative electrode structures 42, wherein the positive electrode structures 41 are disposed in a first region P to collect photogenerated carriers; and the negative electrode structures 42 are disposed in a second region N to collect photogenerated electrons. The positive electrode structures 41 are in ohmic contact with the second boron-doped layer 24; and the negative electrode structures 42 are in ohmic contact with the second phosphorus-doped layer 34.

[0057] In some specific embodiments, the materials of the plurality of positive electrode structures 41 and the plurality of negative electrode structures 42 all include at least one of silver, nickel, and copper.

[0058] In some embodiments, the positive electrode structure 41 includes multiple gate line structures disposed in multiple first regions P, and the width of the region in contact with the surface of the second boron doped layer 24 is 50 μm to 1000 μm, that is, the width of the fine gate contact region of any first region P is 50 μm to 1000 μm.

[0059] The negative electrode structure 42 includes multiple gate line structures disposed in multiple second regions N, and the width of the region in contact with the surface of the second phosphorus doped layer 34 is 50 μm to 1000 μm, that is, the width of the fine gate contact region of any second region N is 50 μm to 1000 μm.

[0060] In some embodiments, the first region P and the second region N are arranged alternately along a first direction, and the ratio of the width of the first region P in the first direction to the width of the second region N in the first direction is 1:5 to 5:1. Preferably, this ratio can be 1:1 or close to 1:1, so that the functional difference between the first region P and the second region N of the back contact type battery cell is as small as possible.

[0061] In some embodiments, the ratio of the width of the GAP region in the first direction to the width of the first region P or the second region N in the first direction is 1:5 to 5:1. Specifically, under the condition that the battery series resistance and short-circuit current are suitable, the larger this ratio is, the larger the output current is.

[0062] In some embodiments, a passivation antireflection film 5 is coated on the side surface of the silicon substrate 1 away from all the first regions P, second regions N and GAP regions to reduce the reflectivity of light on the surface of the back-contact solar cell, thereby reducing light loss and improving the conversion efficiency of the back-contact solar cell.

[0063] Furthermore, in some embodiments, the passivation antireflection film 5 comprises one or more layers selected from silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride. Moreover, the total thickness of the passivation antireflection film 5 is 20 nm to 200 nm.

[0064] In some specific embodiments, such as Figure 1 As shown, the positive electrode structure 41 penetrates the passivation antireflection film 5 and is in contact with the surface of the second boron doped layer 24.

[0065] In some specific embodiments, such as Figure 1 As shown, the negative electrode structure 42 penetrates the passivation antireflection film 5 and is in contact with the surface of the second phosphorus doped layer 34.

[0066] As another technical solution, embodiments of the present invention also provide a method for preparing a back-contact type battery cell, such as... Figure 2 As shown, the preparation method specifically includes the following steps:

[0067] S1: Obtain silicon substrate 1, the first surface of silicon substrate 1 includes a first region P and a second region N arranged alternately;

[0068] Specifically, the first surface is a polished surface or a velvety surface;

[0069] S2: A first oxide layer 21, a first boron doped layer 22, a second oxide layer 23, and a second boron doped layer 24 are sequentially formed on the first surface of the silicon substrate 1; wherein the doping concentration of the first boron doped layer 22 is greater than the doping concentration of the second boron doped layer 24.

[0070] Specifically, in step S2, the first oxide layer 21 and the second oxide layer 23 can be formed by a deposition process; the first boron doped layer 22 and the second boron doped layer 24 can be formed by a deposition process and a doping process.

[0071] S3: A first mask pattern is formed on the surface of the second boron doped layer 24 and a first etching process is performed to remove the portions of the first oxide layer 21, the first boron doped layer 22, the second oxide layer 23, and the second boron doped layer 24 located outside the first region P;

[0072] S4: A first tunneling layer 31, a first phosphorus doped layer 32, a second tunneling layer 33, and a second phosphorus doped layer 34 are sequentially formed on the first surface of the silicon substrate 1; wherein, the doping concentration of the first phosphorus doped layer 32 is less than the doping concentration of the second phosphorus doped layer 34; and the thickness of the first phosphorus doped layer 32 is less than the thickness of the first boron doped layer 22.

[0073] Specifically, in step S4, the first tunneling layer 31 and the second tunneling layer 33 can be formed by a deposition process; the first phosphorus doped layer 32 and the second phosphorus doped layer 34 can be formed by a deposition process and a doping process.

[0074] S5: A second mask pattern is formed on the surface of the second phosphorus doped layer 34 and a second etching process is performed to remove the portions of the first tunneling layer 31, the first phosphorus doped layer 32, the second tunneling layer 33, and the second phosphorus doped layer 34 located outside the second region N, thereby forming the first region P, the second region N, and the GAP region located between the first region P and the second region N.

[0075] In some embodiments, in step S1 above, the silicon substrate 1 obtained is a polished N-type single-crystal silicon wafer.

[0076] In some embodiments, after obtaining the silicon substrate 1 in step S1 above, the following steps may also be included:

[0077] S11: Perform a boron doping process on the first region P of the first surface of the silicon substrate 1 to form a boron-doped inner extension layer 11 in the silicon substrate 1.

[0078] In some embodiments, the step of forming a mask pattern on the surface of the second boron-doped layer 24 in step S3 specifically includes:

[0079] A borosilicate glass (BSG) layer or a silicon nitride layer is formed on the surface of the second boron-doped layer 24 using a chemical vapor deposition process to serve as the first mask pattern.

[0080] In some embodiments, after completing the first etching process described above, step S3 further includes:

[0081] The surface of the silicon substrate 1 with the second boron doped layer 24 is cleaned and polished to process the surface of the silicon substrate 1 in the non-emitter region into a polished surface;

[0082] Alternatively, the surface of the silicon substrate 1 having the second boron doped layer 24 can be texturized to process the surface of the silicon substrate 1 in the non-emitter region into a textured surface.

[0083] In some embodiments, the preparation method further includes the following step in step S5 above:

[0084] A phosphorus-silicon glass (PSG) layer or a silicon nitride layer is formed on the surface of the second phosphorus-doped layer 34 using a chemical vapor deposition process to serve as a second mask pattern.

[0085] In some embodiments, after step S5 above, the preparation method further includes the following step:

[0086] S6: Deposit a passivation antireflection film 5 on the second boron doped layer 24, the second phosphorus doped layer 34 and the GAP region, and form a passivation antireflection film 5 on the second layer surface of the silicon substrate 1.

[0087] S7: Fabricate positive electrode structure 41 and negative electrode structure 42 on the first region P and the second region N respectively;

[0088] Specifically, the positive electrode structure 41 and the negative electrode structure 42 can be fabricated using vacuum evaporation, electroplating, or magnetron sputtering.

[0089] It is understood that the various preparation method embodiments mentioned above in this invention can be combined with each other to form combined embodiments without violating the underlying principles and logic. Due to space limitations, these will not be elaborated upon further in this invention. Those skilled in the art will understand that the specific execution order of each step in the above preparation method of the specific embodiments should be determined based on its function and possible internal logic.

[0090] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A back-contact type solar cell, comprising a silicon substrate, wherein a first surface of the silicon substrate has alternating first and second regions; characterized in that, Also includes: A first oxide layer, a first boron doped layer, a second oxide layer, and a second boron doped layer are sequentially disposed in the first region away from the silicon substrate, and a first tunneling layer, a first phosphorus doped layer, a second tunneling layer, and a second phosphorus doped layer are sequentially disposed in the second region away from the silicon substrate. The doping concentration of the first boron-doped layer is greater than that of the second boron-doped layer; the doping concentration of the first phosphorus-doped layer is less than that of the second phosphorus-doped layer. The thickness of the first phosphorus-doped layer is less than the thickness of the first boron-doped layer.

2. The back-contact type battery cell according to claim 1, characterized in that, The silicon substrate has a boron-doped inner extension layer; the boron-doped inner extension layer is in contact with the first oxide layer, and the doping concentration of the boron-doped inner extension layer is in the range of 1×10⁻⁶. 18 cm -3 ~2×10 19 cm -3 The thickness of the boron-doped inner extension layer is 100nm~300nm.

3. The back-contact type battery cell according to claim 1, characterized in that, The doping concentration of the first boron-doped layer is in the range of 4 × 10⁻⁶. 19 cm -3 ~2×10 20 cm -3 The doping concentration of the second boron doped layer ranges from 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

4. The back-contact type battery cell according to claim 1, characterized in that, The thickness of the first boron-doped layer is 10 nm to 150 nm; the thickness of the second boron-doped layer is 30 nm to 300 nm. The thickness of the first phosphorus-doped layer is 5 nm to 120 nm; the thickness of the second phosphorus-doped layer is 30 nm to 300 nm.

5. The back-contact type battery cell according to claim 1, characterized in that, The materials of both the first oxide layer and the second oxide layer include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

6. The back-contact type battery cell according to claim 1, characterized in that, The thickness of the first oxide layer is 1.5 nm to 4.0 nm, and the thickness of the second oxide layer is 0.8 nm to 1.5 nm.

7. The back-contact type battery cell according to claim 1, characterized in that, The thickness of the first tunneling layer is 0.8 nm to 4.0 nm, and the thickness of the second tunneling layer is 0.3 nm to 1.2 nm.

8. The back-contact type battery cell according to claim 1, characterized in that, The doping concentration range of the first phosphorus doped layer is 1×10⁻⁶. 20 cm -3 ~5×10 20 cm -3 The doping concentration range of the second phosphorus doped layer is 1×10⁻⁶. 20 cm -3 ~1×10 21 cm -3 .

9. The back-contact type battery cell according to claim 1, characterized in that, The materials of both the first tunneling layer and the second tunneling layer include at least one of silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride.

10. A method for preparing a back-contact type solar cell, characterized in that, Includes the following steps: A silicon substrate is obtained, wherein a first surface of the silicon substrate includes alternating first and second regions; A first oxide layer, a first boron-doped layer, a second oxide layer, and a second boron-doped layer are sequentially formed on the first surface of the silicon substrate; wherein the doping concentration of the first boron-doped layer is greater than the doping concentration of the second boron-doped layer. A first mask pattern is formed on the surface of the second boron-doped layer and a first etching process is performed to remove the portions of the first oxide layer, the first boron-doped layer, the second oxide layer, and the second boron-doped layer located outside the first region; A first tunneling layer, a first phosphorus-doped layer, a second tunneling layer, and a second phosphorus-doped layer are sequentially formed on the first surface; wherein the doping concentration of the first phosphorus-doped layer is less than the doping concentration of the second phosphorus-doped layer; and the thickness of the first phosphorus-doped layer is less than the thickness of the first boron-doped layer. A second mask pattern is formed on the surface of the second phosphorus-doped layer and a second etching process is performed to remove the portions of the first tunneling layer, the first phosphorus-doped layer, the second tunneling layer, and the second phosphorus-doped layer located outside the second region.

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