Photovoltaic cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a photovoltaic cell, a preparation method thereof and a photovoltaic module. The photovoltaic cell comprises a silicon substrate, a doped region and a first electrode, the silicon substrate is provided with a first surface and a second surface which are oppositely arranged; the first surface comprises a first area and a second area; the doped region is located in the first surface in the first region, and the doping concentration of the doped region is 1.2 * 10 < 20 > cm <-3 >-1.5 * 10 < 20 > cm <-3 >; the first electrode is electrically connected with the doped region; a groove is formed in the portion, located in the second area, of the first surface. In the photovoltaic cell provided by the invention, the doped silicon region has local uniform high doping concentration in the region in contact with the electrode, so that relatively high conversion efficiency of the photovoltaic cell can be realized.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic cell and its preparation method, and a photovoltaic module. Background Technology

[0002] Silicon-based photovoltaic cells are currently the most widely used type of photovoltaic cell. In silicon-based photovoltaic cells, P-type and N-type silicon are formed through doping, and a PN junction is formed at the interface between the two, generating a built-in electric field. Under the influence of this built-in electric field, photogenerated carriers move electrons towards the N-region and holes towards the P-region, thus achieving carrier separation. When an external circuit is closed, the separated electrons and holes flow in the circuit, forming a current, thereby converting solar energy into electrical energy. Summary of the Invention

[0003] Therefore, it is necessary to provide a photovoltaic cell, its fabrication method, and a photovoltaic module. In the photovoltaic cell of this application, the doped silicon region has a locally uniform high doping concentration in the area in contact with the electrode, thereby achieving a high conversion efficiency for the photovoltaic cell.

[0004] In a first aspect, this application provides a photovoltaic cell, including a silicon substrate, a doped region, and a first electrode; the silicon substrate has a first surface and a second surface disposed opposite to each other; the first surface includes a first region and a second region; the doped region is located within the first surface within the first region, and the doping concentration of the doped region is 1.2 × 10⁻⁶. 20 cm -3 ~1.5×10 20 cm -3 The first electrode and the doped region are electrically connected; a groove is provided on the portion of the first surface located in the second region.

[0005] In some embodiments, the depth of the groove along the thickness direction of the silicon substrate is 1.5µm to 3µm.

[0006] In some embodiments, the thickness of the doped region is 100 nm to 300 nm.

[0007] In some embodiments, the first surface has a velvety structure comprising a plurality of pyramidal structures; the radial width of the pyramidal structures gradually decreases along a direction gradually moving away from the second surface.

[0008] In some embodiments, the doping concentration of the portion located at the bottom of the pyramid structure in the doped region is less than or equal to the doping concentration of the portion located at the top of the pyramid structure; the difference between the doping concentration of the portion located at the bottom of the pyramid structure and the doping concentration of the portion located at the top of the pyramid structure in the doped region is less than or equal to 1 × 10⁻⁶.20 cm -3 .

[0009] In some embodiments, a tunneling oxide layer, a doped silicon layer, and a second electrode are sequentially stacked on the second surface, and the second electrode and the doped silicon layer are electrically connected; the doping type of the doped region is P-type doping; and the doping type of the doped silicon layer is N-type doping.

[0010] Secondly, this application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0011] A silicon substrate is provided; the silicon substrate has a first surface and a second surface disposed opposite to each other; the first surface includes a first region and a second region;

[0012] A cyclic process is performed on the first surface; the cyclic process includes the following steps: performing a first deposition on the first surface; performing a first push-bond process; performing a second deposition on the first surface; and performing a second push-bond process.

[0013] The first surface located in the second region is subjected to laser heat treatment;

[0014] The first surface is etched using a first alkaline solution to form a groove in the portion of the first surface located within the first region.

[0015] In some embodiments, the first push-junction process reduces the concentration of doped elements on the first surface by more than 30%.

[0016] In some embodiments, the first push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm to 150 nm.

[0017] In some embodiments, the second push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm to 100 nm.

[0018] In some implementations, the loop process is performed multiple times.

[0019] In some embodiments, the laser heat treatment allows the dopant element to penetrate to a depth of 1.4 µm or more into the silicon substrate.

[0020] In some embodiments, the laser heat treatment reduces the doping concentration at the first surface located in the second region to below 25% of the doping concentration after the first deposition.

[0021] In some embodiments, the first etching process thins the silicon substrate located in the second region by 1.5µm to 3µm.

[0022] Thirdly, this application provides a photovoltaic module, comprising:

[0023] Cover plate;

[0024] At least one battery string, the battery string comprising the photovoltaic cell described in any one of the above-mentioned methods, or the photovoltaic cell prepared by the method described in any one of the above-mentioned methods;

[0025] And an encapsulation layer, which is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

[0026] In the aforementioned photovoltaic cells, the doped silicon region has a locally uniform high doping concentration in the area in contact with the electrode, thereby enabling the photovoltaic cells to achieve high conversion efficiency.

[0027] Furthermore, in the aforementioned photovoltaic cell fabrication method, a cyclic processing is performed on the first surface of the silicon substrate. This cyclic processing involves first depositing dopant elements to the first surface until the doping concentration approaches saturation, followed by a push-junction process. Then, a second deposition process is performed to bring the doping concentration of the dopant elements on the first surface to near saturation, followed by a second push-junction process. This allows the formation of a highly uniform, near-saturated doped silicon region on the first surface. Further, laser thermal treatment is then applied to the first surface located in the second region. This allows the dopant elements in the second region to continue diffusing into the silicon substrate, thereby reducing the doping concentration on the first surface in the second region. The first region that has not undergone laser thermal treatment remains in a near-saturated doped state. The first surface is then etched using a first alkaline solution. The first alkaline solution etches the doped silicon in the second region, where the doping concentration is lower, at a faster rate. However, the doped silicon in the near-saturated doping state in the first region has more lattice defects, resulting in a slower etching rate. Furthermore, the increased number of lattice defects leads to a non-hydrophobic surface. Organic active molecules in the first alkaline solution adsorb onto the surface of the first region, blocking the alkali from etching the doped silicon, thus enabling localized etching to form grooves in the second region, thereby obtaining a patterned doped silicon region. The un-etched doped silicon in the first surface, serving as the doped region, has a high doping concentration and is used for contact with the electrode. This higher doping concentration facilitates carrier transport. The region on the first surface where grooves are formed is etched due to its lower doping concentration, and as a non-metallic region, it reduces carrier recombination. Therefore, the photovoltaic cell fabrication method of this application can produce a doped silicon region with a locally uniform high doping concentration in the region in contact with the electrode, thereby achieving a high conversion efficiency for the photovoltaic cell. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a photovoltaic cell provided in one embodiment of this application;

[0029] Figure 2 A schematic diagram of the structure of a photovoltaic cell provided in yet another embodiment of this application;

[0030] Figure 3 This is a graph showing the relationship between doping concentration and doping depth in Example 1 of this application;

[0031] Figure 4 This is a diagram showing the test results of the groove depth in Embodiment 1 of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 10-Silicon substrate; 11-First surface; 12-Second surface; 13-First region; 14-Second region; 15-Groove; 20-Doped region; 30-First electrode; 40-Tunneling oxide layer; 50-Doped silicon layer; 60-Second electrode. Detailed Implementation

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0039] Reference Figure 1 As shown, one embodiment of this application provides a photovoltaic cell, including a silicon substrate 10, a doped region 20, and a first electrode 30; the silicon substrate 10 has a first surface 11 and a second surface 12 disposed opposite to each other; the first surface 11 includes a first region 13 and a second region 14; the doped region 20 is located on the first surface 11 within the first region 13, and the doping concentration of the doped region 20 is 1.2 × 10⁻⁶. 20 cm -3 ~1.5×10 20 cm -3 The first electrode 30 and the doped region 20 are electrically connected; the portion of the first surface 11 located within the second region 14 is provided with a groove 15.

[0040] It is understandable that the core of silicon-based photovoltaic cells is the separation of photogenerated carriers through PN junctions, and the non-electrode region is the main generation area of ​​photogenerated carriers. If unnecessary doped silicon regions exist in the non-electrode regions, a large number of recombination centers will be introduced, leading to the loss of photogenerated carriers. In the above photovoltaic cell, the first region 13 serves as the electrode region, the width of the first region 13 is greater than or equal to the width of the first electrode 30, and a doped region 20 with a high doping concentration is provided and electrically connected to the first electrode 30. The second region 14 serves as the non-electrode region and has a groove 15. The photovoltaic cell of this application has a locally uniform high doping concentration in the region in contact with the electrode, thereby achieving a high conversion efficiency of the photovoltaic cell.

[0041] It should be noted that the doping concentration in this application refers to the effective doping concentration obtained by ECV measurement.

[0042] Optionally, the doping concentration of doped region 20 is 1.2 × 10⁻⁶. 20 cm -3 1.22×10 20 cm -3 1.24×10 20 cm -3 1.26×10 20 cm -3 1.28×10 20 cm -3 1.3×10 20 cm -3 1.32×10 20 cm -3 1.34×10 20 cm -3 1.36×10 20 cm -3 1.38×10 20 cm -3 1.4×10 20 cm -3 1.42×10 20 cm -3 1.44×10 20 cm -3 1.46×10 20 cm -3 1.48×10 20 cm -3 Or 1.5×10 20 cm -3 Alternatively, the doping concentration of the doped region 20 can also be within the range between any two of the above doping concentrations.

[0043] In some embodiments, the depth of the groove 15 along the thickness direction of the silicon substrate 10 is 1.5µm to 3µm.

[0044] It should be noted that within the depth range of the aforementioned groove 15, the light-trapping effect of the first surface 11 is enhanced. Simultaneously, it avoids light shading caused by excessive depth of the groove 15, i.e., excessive height of the doped region 20 and the first electrode 30, thus ensuring high conversion efficiency of the photovoltaic cell. For example, referring to… Figure 1 As shown, Figure 1In this context, 'a' represents the depth of the groove 15. Optionally, along the thickness direction of the silicon substrate 10, the depth of the groove 15 is 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2µm, 2.1µm, 2.2µm, 2.3µm, 2.4µm, 2.5µm, 2.6µm, 2.7µm, 2.8µm, 2.9µm, or 3µm. Alternatively, along the thickness direction of the silicon substrate 10, the depth of the groove 15 can also be within any two of the aforementioned depths.

[0045] In some embodiments, the thickness of the doped region 20 is 100 nm to 300 nm.

[0046] Optionally, the thickness of the doped region 20 is 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm or 300nm, or the thickness of the doped region 20 may be within any two of the above thicknesses.

[0047] In some embodiments, the first surface 11 has a velvety structure, which includes a plurality of pyramidal structures; the radial width of the pyramidal structures gradually decreases along a direction that moves away from the second surface 12.

[0048] In some embodiments, the doping concentration of the portion at the bottom of the pyramid structure in the doped region 20 is less than or equal to the doping concentration of the portion at the top of the pyramid structure; the difference between the doping concentration of the portion at the bottom of the pyramid structure and the doping concentration of the portion at the top of the pyramid structure in the doped region 20 is less than or equal to 1 × 10⁻⁶. 20 cm -3 .

[0049] It is understandable that the photovoltaic cell structure of this application can also be implemented on a textured surface. In traditional photovoltaic cells, because it is difficult for the doping source to penetrate to the base of the pyramid, a doped silicon region is usually formed where the doping concentration at the base of the pyramid is much lower than that at the top of the pyramid structure, resulting in poor doping uniformity in the doped silicon region. In this application, in the doped region 20, the difference between the doping concentration at the base of the pyramid structure and the doping concentration at the top of the pyramid structure is less than or equal to 1 × 10⁻⁶. 20 cm -3 That is, the doped region 20 of this application has a high doping concentration with high uniformity, which facilitates the achievement of high conversion efficiency of photovoltaic cells. Optionally, in the doped region 20, the difference between the doping concentration of the portion located at the bottom of the pyramid structure and the doping concentration of the portion located at the top of the pyramid structure is 0 and 1×10⁻⁶, respectively. 16 cm -3 1×10 17 cm -30.5×10 18 cm -3 1×10 18 cm -3 0.2×10 19 cm -3 0.5×10 19 cm -3 1×10 19 cm -3 0.2×10 20 cm -3 0.5×10 20 cm -3 Or 1×10 20 cm -3 Alternatively, in the doped region 20, the difference between the doping concentration of the portion at the bottom of the pyramid structure and the doping concentration of the portion at the top of the pyramid structure can also be within the range of any two of the above differences.

[0050] In some embodiments, a tunneling oxide layer 40, a doped silicon layer 50, and a second electrode 60 are sequentially stacked on the second surface 12, and the second electrode 60 and the doped silicon layer 50 are electrically connected; the doping type of the doped region 20 is P-type doping; and the doping type of the doped silicon layer 50 is N-type doping.

[0051] Reference Figure 2 As shown, in some embodiments, the second surface 12 includes a third region and a fourth region, the tunneling oxide layer 40, the doped silicon layer 50 and the second electrode 60 are disposed in the third region, and the tunneling oxide layer 40, the doped silicon layer 50 and the second electrode 60 are not disposed in the fourth region.

[0052] It is understood that the back surface of the photovoltaic cell of this application can be fabricated with a tunneling oxide layer 40 and a doped silicon layer 50 over the entire surface, or it can be fabricated with a patterned tunneling oxide layer 40 and a doped silicon layer 50. The third region may correspond completely or partially to the first region. The patterned tunneling oxide layer 40 and the doped silicon layer 50 can be fabricated by any feasible fabrication method in the art, and this application does not limit the fabrication method. For example, the patterned tunneling oxide layer 40 and the doped silicon layer 50 can be obtained by fabricating the tunneling oxide layer 40 and the doped silicon layer 50 over the entire surface and then by laser etching.

[0053] In some embodiments, the width of the doped silicon layer 50 is greater than or equal to the width of the second electrode 60.

[0054] In some embodiments, the doping concentration of the doped silicon layer 50 is 1 × 10⁻⁶. 19 cm -3 ~5×10 20 cm -3.

[0055] Optionally, the doping concentration of the silicon layer 50 is 1×10⁻⁶. 19 cm -3 2×10 19 cm -3 5×10 19 cm -3 8×10 19 cm -3 1×10 20 cm -3 2×10 20 cm -3 3×10 20 cm -3 4×10 20 cm -3 Or 5×10 20 cm -3 Alternatively, the doping concentration of the silicon layer 50 can also be within the range between any two of the above doping concentrations.

[0056] Another embodiment of this application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0057] A silicon substrate 10 is provided; the silicon substrate 10 has a first surface 11 and a second surface 12 disposed opposite to each other; the first surface 11 includes a first region 13 and a second region 14;

[0058] A cyclic process is performed on the first surface 11; the cyclic process includes the following steps: performing a first deposition on the first surface 11; performing a first push-bond process; performing a second deposition on the first surface 11; and performing a second push-bond process.

[0059] The first surface 11 located in the second region 14 is subjected to laser heat treatment;

[0060] The first surface 11 is etched using a first alkaline solution, forming a groove 15 in the portion of the first surface 11 located within the second region 14.

[0061] In the aforementioned photovoltaic cell fabrication method, a cyclic processing is performed on the first surface 11 of the silicon substrate 10. This cyclic processing involves first depositing dopant elements to the first surface 11 until the doping concentration approaches saturation, followed by a push-junction process. Then, a second deposition process is performed to bring the doping concentration of the dopant elements on the first surface 11 to near saturation, followed by a second push-junction process. This allows the formation of a highly uniform, near-saturated doped silicon region on the first surface 11. Furthermore, laser thermal treatment is applied to the first surface 11 located within the second region 14. This allows the dopant elements within the second region 14 to continue diffusing into the silicon substrate 10, thereby reducing the doping concentration of the first surface 11 within the second region 14. The first region 13, which has not undergone laser thermal treatment, remains in a near-saturated doped state. The first alkaline solution is then used to perform a first etching treatment on the entire first surface 11. The first alkaline solution has a faster etching rate for the doped silicon in the second region 14, where the doping concentration is relatively low. However, the doped silicon in the near-saturated doping state in the first region 13 has more lattice defects, resulting in a slower etching rate. Furthermore, the increased number of lattice defects leads to a non-hydrophobic surface. Organic active molecules in the first alkaline solution adsorb onto the surface of the first region 13, blocking the alkali from etching the doped silicon, thus enabling localized etching to form grooves 15 in the second region 14, thereby obtaining a patterned doped silicon region. The un-etched doped silicon on the first surface 11 serves as the doped region 20, with a higher doping concentration, for contact with the electrode. This higher doping concentration facilitates carrier transport. The region on the first surface 11 where the grooves 15 are formed is etched due to its lower doping concentration, and as a non-metallic region, it reduces carrier recombination. Therefore, the photovoltaic cell fabrication method of this application can produce a doped silicon region with a locally uniform high doping concentration in the region in contact with the electrode, thereby achieving a high conversion efficiency for the photovoltaic cell.

[0062] In some embodiments, a first deposition is performed on the first surface 11 such that the doping concentration of the dopant element at the first surface 11 is close to saturation.

[0063] In some embodiments, a second deposition is performed on the first surface 11 such that the doping concentration of the doped element at the first surface 11 is close to saturation.

[0064] In some embodiments, the first push-junction process reduces the concentration of doped elements on the first surface 11 by more than 30%.

[0065] The first push-junction process reduces the concentration of doped elements on the first surface 11 by more than 30%, which facilitates the formation of a high-doped silicon region with high uniformity and near-saturation doping concentration on the first surface 11 through cyclic processing.

[0066] In some embodiments, the first push-junction process reduces the concentration of doped elements on the first surface 11 to 2 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 .

[0067] Optionally, the first push-junction treatment reduces the concentration of doped elements on the first surface 11 to 2 × 10⁻⁶. 19 cm -3 3×10 19 cm -3 4×10 19 cm -3 5×10 19 cm -3 6×10 19 cm -3 7×10 19 cm -3 8×10 19 cm -3 9×10 19 cm -3 Or 1×10 20 cm -3 Alternatively, the first push-junction process reduces the concentration of doped elements on the first surface 11 to within the range between any two of the aforementioned doping concentrations.

[0068] In some embodiments, the first push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm to 150 nm.

[0069] Optionally, the first push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, or 150 nm. Alternatively, the first push-junction process can also allow the dopant element to penetrate the substrate to a depth between any two of the above depths.

[0070] In some embodiments, the second push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm to 100 nm.

[0071] Optionally, the second push-junction process allows the dopant element to penetrate the substrate to a depth of 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or 100 nm. Alternatively, the second push-junction process can also allow the dopant element to penetrate the substrate to a depth between any two of the above depths.

[0072] Within the range of the depths into which the dopant element penetrates the substrate by the first push-junction treatment and the second push-junction treatment, it is convenient to prepare a doped region 20 with a suitable doping concentration and doping depth, thereby enabling the photovoltaic cell to achieve a high conversion efficiency.

[0073] In some implementations, the process is repeated multiple times.

[0074] In some embodiments, laser heat treatment allows the dopant element to penetrate to a depth of more than 1.4 µm into the silicon substrate 10.

[0075] Laser thermal treatment allows the dopant element to penetrate the silicon substrate 10 to a depth of 1.4 µm or more, facilitating the fabrication of a groove 15 with a depth of 1.5 µm to 3 µm via subsequent alkaline etching. Optionally, the laser thermal treatment allows the dopant element to penetrate the silicon substrate 10 to a depth of 1.4 µm to 2.8 µm. More preferably, the laser thermal treatment allows the dopant element to penetrate the silicon substrate 10 to a depth of 1.4 µm, 1.6 µm, 1.8 µm, 2 µm, 2.2 µm, 2.4 µm, 2.6 µm, or 2.8 µm. Alternatively, the laser thermal treatment can also allow the dopant element to penetrate the silicon substrate 10 to a depth within any two of the aforementioned depths.

[0076] In some embodiments, laser heat treatment reduces the doping concentration at the first surface 11 within the second region 14 to below 25% of the doping concentration after the first deposition.

[0077] Laser thermal treatment reduces the doping concentration at the first surface 11 within the second region 14 to below 25% of the doping concentration after the first deposition. This facilitates the fabrication of a groove 15 with a depth of 1.5µm to 3µm via subsequent alkaline etching, increases the etching rate of the second region 14, reduces etching time, and minimizes damage to the first region 13. Optionally, laser thermal treatment reduces the doping concentration at the first surface 11 within the second region 14 to below 20% of the doping concentration after the first deposition; alternatively, laser thermal treatment reduces the doping concentration at the first surface 11 within the second region 14 to below 15% of the doping concentration after the first deposition; or alternatively, laser thermal treatment reduces the doping concentration at the first surface 11 within the second region 14 to below 10% of the doping concentration after the first deposition.

[0078] In some embodiments, the first etching process thins the silicon substrate 10 located in the second region 14 by 1.5µm to 3µm.

[0079] Optionally, the first etching process thins the silicon substrate 10 located in the second region 14 by 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2µm, 2.1µm, 2.2µm, 2.3µm, 2.4µm, 2.5µm, 2.6µm, 2.7µm, 2.8µm, 2.9µm, or 3µm. Alternatively, the thickness of the silicon substrate 10 located in the second region 14 thinned by the first etching process may also be within the range of any two of the above thicknesses.

[0080] Another embodiment of this application provides a photovoltaic module, including:

[0081] Cover plate;

[0082] At least one battery string, the battery string comprising a photovoltaic cell of any one of the above, or a photovoltaic cell prepared by any one of the above methods;

[0083] And the encapsulation layer, which is located between the cover plate and the battery string, with the cover plate connected to the battery string through the encapsulation layer.

[0084] The following are specific examples:

[0085] Example 1

[0086] Methods for preparing photovoltaic cells:

[0087] (1) Provide an N-type silicon wafer and texture the front side of the N-type silicon wafer to form a pyramid-shaped textured surface;

[0088] (2) The first deposition was performed on the front side of the silicon wafer at a deposition temperature of 830℃, a boron chloride flow rate of 300 sccm, an oxygen flow rate of 500 sccm, a nitrogen flow rate of 1000 sccm, a pressure of 200 mbar, and a deposition time of 15 min, until the surface boron element reached near saturation and the surface boron element concentration reached 1.5 × 10⁻⁶. 20 ;

[0089] (3) The first junction pushing treatment was performed under a nitrogen atmosphere (20L), a pressure of 800mbar, a junction activation temperature of 870℃, a junction pushing time of 15min, and a junction activation depth of 130nm. After the first junction pushing treatment, the surface boron doping concentration was 7.4×10⁻⁶. 19 ;

[0090] (4) A second deposition was performed on the front side of the silicon wafer at a deposition temperature of 870℃, a boron chloride flow rate of 300 sccm, an oxygen flow rate of 500 sccm, a nitrogen flow rate of 1000 sccm, a pressure of 200 mbar, and a deposition time of 10 min, until the surface boron element reached near saturation again and the surface boron element concentration reached 1.5 × 10⁻⁶. 20 ;

[0091] (5) Perform the second junction push treatment under a nitrogen atmosphere (20L), pressure of 800mbar, junction activation temperature of 890℃, junction push time of 5min, junction activation depth of 230nm, and near-surface boron doping concentration of 1.2×10 after the second junction push treatment. 20 To achieve a near-saturated doped surface state;

[0092] (6) Local laser thermal treatment was performed on the doped layer using a laser wavelength of 1064 nm. The boron source in the laser treatment area was pushed into the deeper silicon mass, and the surface boron doping concentration was reduced to 3 × 10⁻⁶. 19 The doping depth reaches 1.4µm;

[0093] (7) The front side of the silicon wafer is etched with alkaline solution to remove the doped silicon after laser heat treatment and form a patterned doped region 20.

[0094] (8) A first passivation antireflection layer is prepared on the front side of the silicon wafer, and a first electrode 30 is prepared on the first passivation antireflection layer, wherein the first electrode 30 and the doped region 20 are in electrical contact;

[0095] (9) Prepare the back structure of the photovoltaic cell to obtain the photovoltaic cell.

[0096] Reference Figure 3 As shown, Figure 3 The graph showing the relationship between doping concentration and doping depth in Example 1 shows that the doping depth in step 6 can reach 1.4 µm. (Refer to...) Figure 4 As shown, Figure 4 The image shows the test results of the groove 15 depth in Example 1. It can be seen that the depth of the groove 15 formed by removing the doped silicon after laser heat treatment is about 3µm.

[0097] Comparative Example 1

[0098] The preparation method of the photovoltaic cell in Comparative Example 1 is basically the same as that in Example 1, except that steps (2) to (7) are not performed. The preparation steps of its doped region 20 are as follows:

[0099] (2) Deposition was performed on the front side of the silicon wafer at a deposition temperature of 830℃, a boron chloride flow rate of 300 sccm, an oxygen flow rate of 500 sccm, a nitrogen flow rate of 1000 sccm, a pressure of 200 mbar, and a deposition time of 25 min, resulting in a surface boron concentration of 1.5 × 10⁻⁶. 20 ;

[0100] (3) Perform bonding treatment under a nitrogen atmosphere (20L), a pressure of 800mbar, a bonding activation temperature of 910℃, a bonding time of 15min, a bonding activation depth of 230nm, and a surface boron doping concentration of 1×10⁻⁶ after bonding treatment. 19 ; Prepare doped region 20.

[0101] The photovoltaic cells prepared in Example 1 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1 below:

[0102] Table 1

[0103]

[0104] As can be seen from the test results in Table 1, the solar cell prepared in Example 1 has a higher conversion efficiency than the solar cell in Comparative Example 1. The photovoltaic cell preparation method of this application can prepare a silicon-doped region with a locally uniform high doping concentration in the region in contact with the electrode, thereby achieving a higher conversion efficiency for the photovoltaic cell.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A photovoltaic cell, characterized in that, The device includes a silicon substrate, a doped region, and a first electrode; the silicon substrate has a first surface and a second surface disposed opposite to each other; the first surface includes a first region and a second region; the doped region is located within the first surface within the first region, and the doping concentration of the doped region is 1.2 × 10⁻⁶. 20 cm -3 ~1.5×10 20 cm -3 The first electrode and the doped region are electrically connected; a groove is provided on the portion of the first surface located in the second region.

2. The photovoltaic cell according to claim 1, characterized in that, Along the thickness direction of the silicon substrate, the depth of the groove is 1.5µm to 3µm.

3. The photovoltaic cell according to claim 1, characterized in that, The thickness of the doped region is 100nm~300nm.

4. The photovoltaic cell according to claim 1, characterized in that, The first surface has a velvety structure, which includes multiple pyramidal structures; the radial width of the pyramidal structures gradually decreases along a direction that gradually moves away from the second surface.

5. The photovoltaic cell according to claim 4, characterized in that, In the doped region, the doping concentration of the portion located at the bottom of the pyramid structure is less than or equal to the doping concentration of the portion located at the top of the pyramid structure; the difference between the doping concentration of the portion located at the bottom of the pyramid structure and the doping concentration of the portion located at the top of the pyramid structure is less than or equal to 1 × 10⁻⁶. 20 cm -3 .

6. The photovoltaic cell according to any one of claims 1 to 5, characterized in that, A tunneling oxide layer, a doped silicon layer, and a second electrode are sequentially stacked on the second surface, and the second electrode and the doped silicon layer are electrically connected; the doping type of the doped region is P-type doping; and the doping type of the doped silicon layer is N-type doping.

7. A method for preparing a photovoltaic cell, characterized in that, Includes the following steps: A silicon substrate is provided; the silicon substrate has a first surface and a second surface disposed opposite to each other; the first surface includes a first region and a second region; A cyclic process is performed on the first surface; the cyclic process includes the following steps: performing a first deposition on the first surface; performing a first push-bond process; performing a second deposition on the first surface; and performing a second push-bond process. The first surface located in the second region is subjected to laser heat treatment; The first surface is etched using a first alkaline solution to form a groove in the portion of the first surface located in the second region.

8. The method for preparing a photovoltaic cell according to claim 7, characterized in that, The first push-junction treatment reduces the concentration of doped elements on the first surface by more than 30%; and / or, The first push-junction process allows the doped element to penetrate the substrate to a depth of 50 nm to 150 nm; and / or, The second push-junction process allows the doped element to penetrate the substrate to a depth of 50 nm to 100 nm.

9. The method for preparing a photovoltaic cell according to claim 7, characterized in that, The loop process is performed multiple times.

10. The method for preparing a photovoltaic cell according to claim 7, characterized in that, The laser heat treatment allows the doped elements to penetrate the silicon substrate to a depth of 1.4 µm or more; and / or, The laser heat treatment reduces the doping concentration at the first surface located in the second region to below 25% of the doping concentration after the first deposition.

11. The method for preparing a photovoltaic cell according to any one of claims 7 to 10, characterized in that, The first etching process thins the silicon substrate located in the second region by 1.5µm to 3µm.

12. A photovoltaic module, characterized in that, include: Cover plate; At least one battery string, the battery string comprising a photovoltaic cell according to any one of claims 1 to 6, or a photovoltaic cell prepared by the method of preparing a photovoltaic cell according to any one of claims 7 to 11; And an encapsulation layer, which is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

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