Solar cell, method of manufacturing the same, and photovoltaic module

Abstract

The application discloses a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises an N-type base, a P-type emitter layer, a first passivation layer, a barrier layer, a plurality of first electrodes, a tunneling medium layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes. A first surface of the N-type base comprises a metal region and a non-metal region. A first P-type emitter of the P-type emitter layer is located in the non-metal region, and a second P-type emitter of the P-type emitter layer is located in the metal region. A second doping concentration of the second P-type emitter is less than a first doping concentration of the first P-type emitter. The barrier layer is used for blocking diffusion of metal ions of the first electrode into the second P-type emitter, so that the content of the metal ions diffused into the second P-type emitter and the N-type base is reduced, the generation of metal particles is reduced, and the second P-type emitter and the N-type base are prevented from being damaged.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and more specifically, to a solar cell, a method for its fabrication, and a photovoltaic module. Background Technology

[0002] A solar cell is a device that converts light energy into electrical energy and is an important component of the renewable energy field. The diffusion process of metal ions in the solar cell electrodes plays a crucial role in the performance and efficiency of the solar cell. When the metal electrodes of the cell are sintered, the metal electrodes react with oxygen to generate metal ions, which then diffuse from the electrodes into other parts of the cell. However, excessive diffusion of metal ions can lead to their reaction with silicon ions in the cell to form elemental metals, which can damage other structures of the solar cell and thus affect the photoelectric conversion efficiency. Summary of the Invention

[0003] This application provides a solar cell, its fabrication method, and a photovoltaic module to solve the problem of reduced cell efficiency caused by excessive diffusion of electrode ions in the metal electrodes of solar cells in related technologies.

[0004] According to one aspect of this application, a solar cell is provided, comprising: an N-type substrate having opposing first and second surfaces, the first surface including a metal region and a non-metal region; a P-type emitter layer, a first passivation layer, a barrier layer, and a plurality of first electrodes located on the first surface, wherein the P-type emitter layer includes: a first P-type emitter and a second P-type emitter, the first P-type emitter being located in the non-metal region and having a first doping concentration, the second P-type emitter being located in the metal region and having a second doping concentration, the second doping concentration being less than the first doping concentration, the first passivation layer being located on a side of the P-type emitter layer opposite to the N-type substrate, and the first electrode being located on a side of the second P-type emitter opposite to the N-type substrate; the barrier layer being located between the first electrode and the second P-type emitter, the barrier layer being used to prevent metal ions from the first electrode from diffusing into the second P-type emitter; and a tunneling dielectric layer, a doped conductive layer, a second passivation layer, and a plurality of second electrodes located on the second surface.

[0005] Optionally, the first doping concentration is 1×10 20 cm -3 ~1×10 23 cm -3 The second doping concentration is 1×10 19 cm -3 ~1×10 22 cm -3 .

[0006] Optionally, the junction depth of the first P-type emitter is 0.5 μm to 2 μm, and the junction depth of the second P-type emitter is 0.2 μm to 1 μm.

[0007] Optionally, the sheet resistance of the second P-type emitter is 100Ω / square to 800Ω / square.

[0008] Optionally, the material of the barrier layer includes P-type amorphous silicon.

[0009] Optionally, the doping concentration of the barrier layer is less than or equal to the first doping concentration.

[0010] Optionally, the doping concentration of the barrier layer is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3 .

[0011] According to another aspect of this application, a method for fabricating a solar cell is provided, comprising: providing an N-type substrate having opposing first and second surfaces, the first surface including a metal region and a non-metal region; forming a P-type emitter layer, a first passivation layer, a barrier layer, and a plurality of first electrodes on the first surface, wherein: the P-type emitter layer includes: a first P-type emitter and a second P-type emitter, wherein the first P-type emitter is located in the non-metal region and has a first doping concentration, the second P-type emitter is located in the metal region and has a second doping concentration, the second doping concentration being less than the first doping concentration; the first electrode is located on the side of the second P-type emitter away from the N-type substrate; the first passivation layer is located on the side of the P-type emitter layer away from the N-type substrate; the barrier layer is located between the first electrode and the second P-type emitter, the barrier layer being used to prevent metal ions in the first electrode from diffusing into the N-type substrate; and forming a tunneling dielectric layer, a doped conductive layer, a second passivation layer, and a plurality of second electrodes on the second surface.

[0012] Optionally, the step of forming the P-type emitter layer and the barrier layer includes: forming a first P-type emitter on the first surface, the first P-type emitter having a first doping concentration; performing laser amorphization treatment on the first P-type emitter located in the metal region to obtain a second P-type emitter located in the metal region and the barrier layer, the barrier layer being located on the side of the second P-type emitter away from the N-type substrate, the second P-type emitter having a second doping concentration, the second doping concentration being less than the first doping concentration.

[0013] According to another aspect of this application, a photovoltaic module is provided, comprising a plurality of the aforementioned solar cells.

[0014] The solar cell of this application includes an N-type substrate, a P-type emitter layer, a first passivation layer, a barrier layer, multiple first electrodes, a tunneling dielectric layer, a doped conductive layer, a second passivation layer, and multiple second electrodes. The P-type emitter layer includes a first P-type emitter and a second P-type emitter. The barrier layer is located between the first electrodes and the second P-type emitter. When metal ions in the first electrodes diffuse towards the second P-type emitter, the barrier layer can block at least some of these metal ions, thereby reducing the number of metal ions diffusing into the second P-type emitter and the N-type substrate. This reduces the generation of metal particles and prevents damage to the second P-type emitter and the N-type substrate. This solves the problem in related technologies where excessive diffusion of electrode ions in the metal electrodes of solar cells leads to reduced cell efficiency. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0016] Figure 1 A cross-sectional structural schematic diagram of a solar cell provided in an embodiment according to this application is shown;

[0017] Figure 2 A schematic flowchart of a method for fabricating a solar cell according to an embodiment of this application is shown.

[0018] Figure 3 The diagram shows a cross-sectional structure of the substrate after texturing the first surface of the N-type substrate in the method for fabricating the solar cell of this application.

[0019] Figure 4 It shows in Figure 3 A schematic diagram of the cross-sectional structure of the substrate behind the first P-type emitter formed on the first surface of the N-type substrate formed in the middle;

[0020] Figure 5 It shows that according to Figure 4 A schematic diagram of the cross-sectional structure of the substrate after the metal region of the first P-type emitter formed in the middle forms the second P-type emitter and the barrier layer;

[0021] Figure 6 It shows that according to Figure 5 A schematic diagram of the cross-sectional structure of the substrate after the formation of the first P-type emitter and the first passivation layer on the barrier layer;

[0022] Figure 7 It shows in Figure 6A schematic diagram of the cross-sectional structure of the first electrode in the first passivation layer formed in the substrate, showing the first electrode penetrating the first passivation layer.

[0023] The above figures include the following reference numerals:

[0024] 10. N-type substrate; 11. Metal region; 12. Non-metal region; 20. P-type emitter layer; 21. First P-type emitter; 22. Second P-type emitter; 30. First passivation layer; 40. Barrier layer; 50. First electrode; 60. Tunneling dielectric layer; 70. Doped conductive layer; 80. Second passivation layer; 90. Second electrode. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] As described in the background section, currently, when sintering the metal electrodes of a battery, the metal electrodes react with oxygen to generate metal ions, which then diffuse from the electrodes into other parts of the battery structure. However, excessive diffusion of metal ions can cause them to react with silicon ions in the battery to generate elemental metals, which can damage other structures of the solar cell and thus affect the battery's photoelectric conversion efficiency.

[0029] To solve the aforementioned technical problems, according to one aspect of this application, such as Figure 1 As shown, a solar cell is provided, comprising:

[0030] The N-type substrate 10 has opposing first and second surfaces, wherein the first surface includes a metallic region and a non-metallic region.

[0031] The first surface includes a P-type emitter layer 20, a first passivation layer 30, a barrier layer 40, and a plurality of first electrodes 50. The P-type emitter layer 20 includes a first P-type emitter 21 and a second P-type emitter 22. The first P-type emitter 21 is located in the non-metallic region and has a first doping concentration. The second P-type emitter 22 is located in the metallic region and has a second doping concentration, which is less than the first doping concentration. The first passivation layer 30 is located on the side of the P-type emitter layer 20 away from the N-type substrate 10. The first electrodes 50 are located on the side of the second P-type emitter 22 away from the N-type substrate 10. The barrier layer 40 is located between the first electrode 50 and the second P-type emitter 22 and is used to prevent metal ions from the first electrode 50 from diffusing into the second P-type emitter 22.

[0032] The tunneling dielectric layer 60, the doped conductive layer 70, the second passivation layer 80, and the plurality of second electrodes 90 are located on the second surface.

[0033] The first surface of the N-type substrate can be the front side and the second surface can be the back side, or the first surface of the N-type substrate can be the back side and the second surface can be the front side, that is, the solar cell is a single-sided cell, where the front side can serve as the light-receiving surface to receive incident light, and the back side serves as the back-lighting surface. In some embodiments, the solar cell is a double-sided cell, that is, both the first and second surfaces of the N-type substrate can serve as light-receiving surfaces and can both be used to receive incident light.

[0034] The first surface and the second surface mentioned above can be flat surfaces or non-flat surfaces, that is, the first surface can be a flat surface or a non-flat surface, the second surface can be a flat surface or a non-flat surface, and the first surface and the second surface can be the same or different.

[0035] In some embodiments, both the first and second surfaces described above are non-flat surfaces. Non-flat surfaces can increase internal reflection of incident light, thereby further improving the light utilization efficiency of the solar cell. More specifically, the cross-section of the non-flat surface along a first predetermined direction is a line segment. This line segment can include at least one of straight segments and curved segments; that is, the line segment can be composed of straight segments, curved segments, or a combination of both. In the case where only straight segments are used, the line segment is composed of multiple sequentially connected straight segments. The first predetermined direction is the thickness direction of the N-type substrate. In one specific embodiment, such as... Figure 1 As shown, the cross-sections of the first and second surfaces along the first predetermined direction D1 are sawtooth-shaped, that is, they are composed of multiple straight line segments connected in sequence.

[0036] The aforementioned metallic region of the first surface refers to the area on the first surface used to form the first electrode, i.e., the projection of the first electrode on the first surface lies in this region, and the area of ​​the metallic region on the first surface is typically larger than the projected area of ​​the first electrode on the first surface. The non-metallic region of the first surface is the area on the first surface other than the metallic region. In some specific embodiments, the width of the metallic region of the first surface in the second predetermined direction D2 is 1.5 to 2 times the width of the first electrode in the second predetermined direction D2. This allows for a relatively large formable area for the first electrode during fabrication, making the requirements for the fabrication process more lenient. The second predetermined direction D2 is a direction perpendicular to the thickness of the N-type substrate, specifically as follows: Figure 1 As shown.

[0037] It should be noted that the second surface of this application also has metallic and non-metallic regions. The metallic regions of the second surface correspond to the second electrode; that is, the relationship between the metallic regions of the first electrode and the first surface described above also applies to the metallic regions of the second electrode and the second surface. Furthermore, the non-metallic regions of the second surface refer to the areas of the first surface excluding the metallic regions.

[0038] The barrier layer can be made of any material capable of preventing metal ions from the first electrode from diffusing into the second P-type emitter. Those skilled in the art can select a suitable material to form the barrier layer based on the actual situation. Furthermore, the barrier layer of this application can be one layer or multiple layers. In the case of multiple layers, any two layers can be made of the same or different materials. Those skilled in the art can determine the appropriate number of layers and materials based on the actual situation.

[0039] The aforementioned solar cell incorporates a barrier layer. When metal ions in the first electrode diffuse towards the second P-type emitter, the barrier layer blocks at least a portion of these metal ions, thereby reducing the amount of metal ions diffusing into the second P-type emitter and the N-type substrate. This reduces the generation of elemental metals, preventing damage to the second P-type emitter and the N-type substrate by elemental metals. This solves the problem of reduced cell efficiency caused by excessive diffusion of electrode ions in the metal electrodes of solar cells in related technologies. Furthermore, in the P-type emitter layer of this solar cell, the second doping concentration of the second P-type emitter is lower than the first doping concentration of the first P-type emitter. This doping concentration design reduces carrier surface recombination caused by a higher doping concentration, ensuring a higher minority carrier lifetime and consequently higher open-circuit voltage and short-circuit current. On the other hand, this doping concentration design reduces the problem of higher contact resistance caused by a lower doping concentration, thus ensuring lower contact resistance and a lower turn-on voltage. Furthermore, the concentration difference between the first and second P-type emitters allows charge carriers to be transported to the N-type substrate more quickly, which also contributes to improved photoelectric conversion efficiency. Therefore, this concentration design results in a high photoelectric conversion efficiency for this solar cell.

[0040] In some embodiments, the N-type substrate material can be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon. The elemental semiconductor material can be monocrystalline, polycrystalline, amorphous, or microcrystalline (a state simultaneously possessing both monocrystalline and amorphous states is called microcrystalline). For example, silicon can be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0041] In some embodiments, the N-type substrate can also be a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanide, silicon carbide, gallium arsenide, indium gallium dihydrogen phosphate, perovskite, cadmium telluride, and copper indium selenide. The N-type substrate can also be a sapphire substrate, a silicon-on-insulator substrate, or a germanium-on-insulator substrate.

[0042] In some embodiments, the N-type substrate is doped with an N-type dopant element, which can be any one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which can be any one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or gallium (In). Optionally, the thickness of the N-type substrate can be 80 μm to 200 μm, such as 85 μm, 100 μm, 130 μm, 170 μm, 190 μm, etc.

[0043] The first passivation layer in the aforementioned solar cell can suppress carrier recombination at the interface, thus avoiding the problem of reduced photocurrent caused by carrier recombination and ensuring high photoelectric conversion efficiency of the cell. Optionally, the material of the first passivation layer can be a single-layer film or a composite film such as alumina, silicon nitride, silicon oxide, and silicon oxynitride. For example, if the first passivation layer is a single-layer film, it can be an alumina single-layer film, a silicon nitride single-layer film, a silicon oxide single-layer film, or a silicon oxynitride single-layer film; if the first passivation layer is a multilayer film, it can be a composite film of alumina and silicon oxide, or a composite film of alumina, silicon oxide, and silicon nitride. Of course, the material of the first passivation layer in this application is not limited to the above-mentioned materials, and those skilled in the art can select any suitable material to form the first passivation layer of this application according to the actual situation. Optionally, the thickness of the first passivation layer in this application can be 70nm~90nm, which can further ensure a reduction in the defect state density on the surface of the solar cell, reduce the probability of electron and hole recombination on the surface, and thus improve the photoelectric conversion efficiency.

[0044] The second passivation layer of this application can also suppress carrier recombination at the interface, thereby ensuring high photoelectric conversion efficiency of the battery. Similarly, the material of the second passivation layer can be a single layer or a composite layer such as aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride. The layer combination of the second passivation layer can be referred to the description of the layer combination of the first passivation layer, and will not be repeated here.

[0045] The aforementioned tunneling dielectric layer reduces the interface state density between the back side of the N-type substrate and the doped conductive layer, making the concentration of majority carriers much higher than that of minority carriers. This reduces the recombination probability of electrons and holes, increases the fill factor, short-circuit current, and open-circuit voltage of the solar cell, and improves the photoelectric conversion efficiency of the solar cell.

[0046] Optionally, the material of the tunneling dielectric layer may include at least one of silicon oxide, silicon oxynitride, titanium oxide, and silicon nitride. The thickness is generally small, around 1 nm, and the specific thickness can be set according to actual conditions, without limitation. For example, the tunneling dielectric layer can be an ultrathin silicon oxide layer, thereby giving the tunneling dielectric layer good passivation characteristics and allowing charge carriers to tunnel more easily. In some feasible embodiments, the tunneling dielectric layer can be formed on the second surface side of the N-type substrate using ozone oxidation, high-temperature thermal oxidation, nitric acid oxidation, chemical vapor deposition, or low-pressure chemical vapor deposition.

[0047] In some embodiments, the doped conductive layer can be a doped polysilicon layer, a silicon carbide layer, or a composite layer of doped polysilicon and silicon carbide layers. For example, it can be only silicon carbide or only polysilicon, or a doped material of silicon carbide and polysilicon. When the doped conductive layer is doped polysilicon, it can serve as a field passivation layer, forming band bends on the silicon wafer surface to achieve selective carrier transport and reduce recombination losses. The thickness of the doped conductive layer can be 2nm~100nm, such as 5nm, 20nm, 50nm, 80nm, 95nm, etc. The specific thickness and material are not limited in this application and can be selected according to the actual situation.

[0048] In some embodiments, the tunneling dielectric layer and the doped conductive layer constitute a passivated contact structure. The doped conductive layer can form a band bend on the surface of the N-type substrate, and the tunneling dielectric layer causes an asymmetric shift in the energy band on the surface of the N-type substrate. This results in a lower potential barrier for majority carriers than for minority carriers. Therefore, majority carriers can more easily tunnel through the tunneling dielectric layer, while minority carriers have difficulty passing through it, thus achieving selective transport of carriers.

[0049] The materials of the first electrode and the second electrode described above can be independently selected from copper, silver, nickel, or aluminum; the thickness of the first electrode can be 2 μm to 20 μm. This application does not limit the materials and thicknesses of the first and second electrodes, and those skilled in the art can select appropriate materials and thicknesses to form the first and second electrodes according to actual conditions.

[0050] In some embodiments, the barrier layer can be made of any one or more of alumina, silicon nitride, polycrystalline silicon, and amorphous silicon. These materials can prevent metal ions from the first electrode from diffusing to the second P-type emitter. In more specific embodiments, the thickness of the barrier layer is 0.3 μm to 1 μm. This not only ensures a good barrier effect but also guarantees high electron collection efficiency, further ensuring high efficiency of the solar cell. Those skilled in the art can select appropriate materials and thicknesses for the barrier layer according to actual conditions; this application does not impose any limitations.

[0051] In some alternative embodiments, the first doping concentration of the first P-type emitter is 1 × 10⁻⁶. 20 cm -3 ~1×10 23 cm -3 The second doping concentration of the second P-type emitter is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3This range of doping concentrations can further reduce contact resistance, decrease carrier recombination, and further ensure high photoelectric conversion efficiency of the solar cell.

[0052] In some embodiments, the material of the first P-type emitter or the second P-type emitter can be monocrystalline silicon or polycrystalline silicon. In other embodiments, the junction depth of the first P-type emitter is 0.5 μm to 2 μm. This junction depth provides good passivation and ensures a low sheet resistance of the first P-type emitter, further guaranteeing a high photoelectric conversion efficiency of the solar cell. This junction depth also ensures good passivation of the first P-type emitter, which helps reduce carrier recombination and improve the open-circuit voltage and short-circuit current of the solar cell. The junction depth of the second P-type emitter is 0.2 μm to 1 μm. This junction depth prevents metal ions from penetrating the second P-type emitter during the sintering process of the first electrode, thereby ensuring the reliability of the solar cell.

[0053] Furthermore, the lower doping concentration of the second P-type emitter can reduce impurities introduced by doping, thus forming a more uniform and dense passivation film on the contact surface between the second P-type emitter and the N-type substrate, thereby improving the passivation effect of the metal region and reducing recombination defects in the battery.

[0054] In some embodiments, the doping concentration of the second P-type emitter is lower than that of the first P-type emitter, and the concentration difference between the second P-type emitter and the first P-type emitter can also form a high-low junction, further improving the open-circuit voltage of the battery.

[0055] To further ensure a low contact resistance of the second P-type emitter and further reduce carrier recombination, the sheet resistance of the second P-type emitter is 100Ω / square to 800Ω / square.

[0056] In order to better block metal ions from the first electrode, in some specific embodiments, the material of the barrier layer includes P-type amorphous silicon.

[0057] In the above optional embodiments, when the material of the barrier layer is amorphous silicon, for example, when the paste material of the first electrode is Ag, the following chemical reaction will occur when the first metal is sintered in an oxygen-containing gas environment:

[0058] 1) Ag reacts with O2 to form Ag in the glass frit of the slurry. + Ions and O 2- The reaction principle is as follows:

[0059] ;

[0060] 2) Ag in glass feed+ The ions react with Si in the second P-type emitter or N-type substrate, wherein Si transforms into Ag. + Ions donate electrons to form Ag particles and Si particles in the glass frit of the slurry. 4+ The reaction principle is as follows:

[0061] ;

[0062] Because the electron mobility of amorphous silicon is 2-3 orders of magnitude lower than that of crystalline silicon (electron mobility: 0.5-1 cm² / v·s for amorphous silicon, 1000-1500 cm² / v·s for crystalline silicon), electron migration in amorphous silicon is limited, and amorphous silicon can provide Ag with electrons. + Since ionic reactions involve fewer electrons and have a slower reaction rate, the amorphous silicon barrier layer, located between the first electrode and the second P-type emitter, reduces the electron flow rate to Ag compared to the first electrode being in direct contact with the crystalline silicon emitter. + The ability of ions to donate electrons can reduce Ag. + The Ag particles generated by ions gaining electrons reduce damage to the second P-type emitter, reduce recombination defects, and improve battery efficiency.

[0063] When the material of the barrier layer is the same as that of the P-type emitter layer, that is, when both are P-type amorphous silicon, the barrier layer can be prepared by a single laser amorphization process on the first P-type emitter. No additional preparation process is required to form the barrier layer (e.g., no deposition or other process is required on the emitter in the metal region after the emitter in the metal region and the emitter in the non-metal region are prepared). This makes the preparation process of the battery simpler and suitable for mass production.

[0064] In some embodiments, during the laser amorphization process on the first P-type emitter, the laser melts the surface of the N-type substrate, allowing dopant ions from the first P-type emitter to penetrate into the N-type substrate. Consequently, the doping concentration of the resulting second P-type emitter and the barrier layer is lower than that of the first P-type emitter. Since the barrier layer is located on the side of the second P-type emitter furthest from the N-type substrate, during the penetration of dopant ions into the N-type substrate, the dopant ions from the second P-type emitter first enter the N-type substrate, and then the dopant ions from the barrier layer penetrate into the second P-type emitter and then into the N-type substrate. If the laser processing time for the first P-type emitter is short, the doping concentration of the second P-type emitter will be almost identical to that of the barrier layer. If the laser processing time for the first P-type emitter is long, most of the dopant ions from the barrier layer will enter the first P-type emitter to replenish its dopant concentration. Therefore, after the laser amorphization process is complete, the doping concentration of the second P-type emitter will be greater than or equal to that of the barrier layer. Optionally, the doping concentration of the aforementioned barrier layer is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3 This doping concentration not only ensures that the barrier layer has a good barrier effect, but also ensures that the sheet resistance of the barrier layer is low.

[0065] In some embodiments, the sum of the thickness of the barrier layer and the junction depth of the second P-type emitter is the same as the junction depth of the first P-type emitter. During the fabrication process, the first P-type emitter in the metal region is subjected to a laser amorphization process. During the laser irradiation of the first P-type emitter, the portion of the first P-type emitter near the upper surface is melted by the laser. After the laser is removed, the melted area is rapidly cooled, forming amorphous silicon with a disordered and non-directional molecular structure arrangement. Combined with the laser process described above that causes doped ions to diffuse into the N-type substrate, the barrier layer and the second P-type emitter can be formed simultaneously through a single laser amorphization process, simplifying the battery fabrication process.

[0066] According to another aspect of this application, a method for preparing a solar cell is provided, such as... Figure 2 As shown, it includes:

[0067] Step S101: As Figure 3 As shown, an N-type substrate 10 is provided, the N-type substrate 10 having opposing first and second surfaces, the first surface including a metal region 11 and a non-metal region 12;

[0068] Step S102: As Figures 4 to 7As shown, a P-type emitter layer 20, a first passivation layer 30, a barrier layer 40, and a plurality of first electrodes 50 are formed on the first surface. The P-type emitter layer 20 includes a first P-type emitter 21 and a second P-type emitter 22. The first P-type emitter 21 is located in the non-metallic region and has a first doping concentration. The second P-type emitter 22 is located in the metallic region and has a second doping concentration, which is less than the first doping concentration. The first electrodes 50 are located on the side of the second P-type emitter 22 facing away from the N-type substrate 10. The first passivation layer 30 is located on the side of the P-type emitter layer 20 facing away from the N-type substrate 10. The barrier layer 40 is located between the first electrode 50 and the second P-type emitter 22, and the barrier layer 40 is used to prevent metal ions in the first electrode 50 from diffusing into the N-type substrate 10.

[0069] Step S103: As Figure 1 As shown, a tunneling dielectric layer 60, a doped conductive layer 70, a second passivation layer 80, and a plurality of second electrodes 90 are formed on the second surface.

[0070] The solar cell prepared by the above method has a barrier layer. When metal ions in the first electrode diffuse to the second P-type emitter, the barrier layer can block at least some of the metal ions, thereby reducing the content of metal ions diffused into the second P-type emitter and the N-type substrate. This reduces the generation of elemental metals and prevents the second P-type emitter and the N-type substrate from being damaged by elemental metals. This solves the problem of reduced cell efficiency caused by excessive diffusion of electrode ions in the metal electrodes of solar cells in related technologies. Furthermore, in the P-type emitter layer of this solar cell, the second doping concentration of the second P-type emitter is lower than the first doping concentration of the first P-type emitter. This doping concentration design can reduce recombination on the carrier surface caused by a high doping concentration, thereby ensuring a high minority carrier lifetime and thus a high open-circuit voltage and short-circuit current. On the other hand, this doping concentration design can reduce the problem of high contact resistance caused by a low doping concentration, thereby ensuring a low contact resistance and a low turn-on voltage of the cell. Furthermore, the concentration difference between the first and second P-type emitters allows charge carriers to be transported to the N-type substrate more quickly, which also contributes to improved photoelectric conversion efficiency. Therefore, this concentration design results in a high photoelectric conversion efficiency for this solar cell.

[0071] The first surface of the aforementioned N-type substrate can be a front surface and the second surface a back surface, or the first surface of the N-type substrate can be a back surface and the second surface a front surface, i.e., the solar cell is a single-sided cell, where the front surface serves as the light-receiving surface to receive incident light, and the back surface serves as the back-lighting surface. In some embodiments, the solar cell is a double-sided cell, i.e., both the first and second surfaces of the N-type substrate can serve as light-receiving surfaces and can be used to receive incident light. The thickness of the N-type substrate can be 80μm~200μm, such as 85μm, 100μm, 130μm, 170μm, 190μm, etc. The first surface of the N-type substrate can be texturized to increase its roughness compared to the first surface, so that other structures can be better fabricated on the N-type substrate subsequently.

[0072] The first surface and the second surface mentioned above can be flat surfaces or non-flat surfaces, that is, the first surface can be a flat surface or a non-flat surface, the second surface can be a flat surface or a non-flat surface, and the first surface and the second surface can be the same or different.

[0073] In some embodiments, both the first and second surfaces described above are non-flat surfaces. Non-flat surfaces can increase internal reflection of incident light, thereby further improving the light utilization efficiency of the solar cell. More specifically, the cross-section of the non-flat surface along a first predetermined direction is a line segment. This line segment can include at least one of straight segments and curved segments; that is, the line segment can be composed of straight segments, curved segments, or a combination of both. In the case where only straight segments are used, the line segment is composed of multiple sequentially connected straight segments. The first predetermined direction is the thickness direction of the N-type substrate. In one specific embodiment, such as... Figure 1 As shown, the cross-sections of the first and second surfaces along the first predetermined direction D1 are sawtooth-shaped, that is, they are composed of multiple straight line segments connected in sequence.

[0074] The aforementioned metallic region of the first surface refers to the area on the first surface used to form the first electrode, i.e., the projection of the first electrode on the first surface lies in this region, and the area of ​​the metallic region on the first surface is typically larger than the projected area of ​​the first electrode on the first surface. The non-metallic region of the first surface is the area on the first surface other than the metallic region. In some specific embodiments, the width of the metallic region of the first surface in the second predetermined direction is 1.5 to 2 times the width of the first electrode in the second predetermined direction. This allows for a relatively large formable area for the first electrode during fabrication, making the requirements for the fabrication process more lenient. The second predetermined direction D2 is a direction perpendicular to the thickness of the N-type substrate, specifically as follows: Figure 1 As shown.

[0075] It should be noted that the second surface of this application also has metallic and non-metallic regions. The metallic regions of the second surface correspond to the second electrode; that is, the relationship between the metallic regions of the first electrode and the first surface described above also applies to the metallic regions of the second electrode and the second surface. Furthermore, the non-metallic regions of the second surface refer to the areas of the first surface excluding the metallic regions.

[0076] The barrier layer can be made of any material capable of preventing metal ions from the first electrode from diffusing into the second P-type emitter. Those skilled in the art can select a suitable material to form the barrier layer based on the actual situation. Furthermore, the barrier layer of this application can be one layer or multiple layers. In the case of multiple layers, any two layers can be made of the same or different materials. Those skilled in the art can determine the appropriate number of layers and materials based on the actual situation.

[0077] In some alternative implementations, such as Figure 4 and Figure 5 As shown, the steps of forming the P-type emitter layer 20 and the barrier layer 40 include: forming a first P-type emitter 21 on the first surface, the first P-type emitter 21 having a first doping concentration; performing laser amorphization treatment on the first P-type emitter 21 located in the metal region to obtain the second P-type emitter 22 located in the metal region and the barrier layer 40, the barrier layer 40 being located on the side of the second P-type emitter 22 away from the N-type substrate 10, the second P-type emitter 22 having a second doping concentration, the second doping concentration being less than the first doping concentration.

[0078] Optionally, the material of the barrier layer can be the same as that of the P-type emitter layer. The barrier layer can be prepared by a single laser amorphization process on the first P-type emitter, without the need for additional preparation processes to form the barrier layer (e.g., without the need to deposit or use other processes to form a barrier layer on the emitter in the metal region after preparing the emitter in the metal region and the emitter in the non-metal region). This makes the preparation process of the battery simpler and suitable for mass production.

[0079] In the above optional implementations, such as Figure 4 As shown, a first P-type emitter 21 is formed on the first surface of the texturized N-type substrate 10 using a physical deposition process or a chemical deposition process.

[0080] like Figure 5As shown, the first P-type emitter 21 located in the metal region is irradiated with a laser using a laser amorphization process. During the laser amorphization process, the portion of the first P-type emitter 21 near its upper surface is melted by the laser. After the laser is removed, the molten region cools rapidly, forming amorphous silicon with a disordered and non-directional molecular structure, thus forming a barrier layer 40. The barrier layer 40, made of amorphous silicon, reduces the ability of metal ions to provide electrons to the first electrode 50, thereby reducing the metal particles generated by the metal ions gaining electrons and reducing the damage caused by the metal particles to the second P-type emitter 22 and the N-type substrate 10. Furthermore, the laser melts the surface of the N-type substrate 10, and the doped ions in the first P-type emitter 21 penetrate into the N-type substrate 10, thus forming a second P-type emitter 22 with a lower doping concentration than the first P-type emitter 21.

[0081] Optionally, the doping concentration of the second P-type emitter is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3 Setting the doping concentration of the second P-type emitter within the aforementioned range avoids both excessively high doping concentration leading to increased carrier recombination and excessively low doping concentration leading to increased contact resistance between the first electrode and the N-type substrate. Therefore, the concentration setting of the second P-type emitter can reduce surface recombination, improve minority carrier lifetime, and keep the contact resistance between the first electrode and the N-type substrate at a low level, thereby increasing the open-circuit voltage and improving battery efficiency.

[0082] Optionally, the junction depth of the first P-type emitter is 0.5 μm to 2 μm, and the doping concentration is 1 × 10⁻⁶. 20 cm -3 ~1×10 23 cm -3 The doping concentration of the first P-type emitter is lower than that of the non-metallic emitter in the prior art, which can reduce surface recombination, increase open-circuit voltage, and improve the photoelectric conversion efficiency of the battery.

[0083] As described above, the doping concentrations of the first and second P-type emitters can maintain a low contact resistance between the first electrode and the N-type substrate while reducing surface recombination, improving minority carrier lifetime, and increasing battery efficiency. Furthermore, the lower doping concentration of the second P-type emitter results in fewer doped impurities, allowing the second P-type emitter to form a more uniform and dense passivation film on the surface of the N-type substrate, thus enhancing the passivation capability of the battery surface.

[0084] Specifically, such as Figure 6As shown, a first passivation layer 30 is formed on the P-type emitter layer 20 using a deposition process. Optionally, the thickness of the first passivation layer 30 can be 70 nm to 90 nm. The material of the first passivation layer 30 can be a single layer or a composite layer such as alumina, silicon nitride, silicon oxide, or silicon oxynitride. Figure 7 As shown, an opening is made in the metal region of the first passivation layer 30, and a first electrode 50 is formed by printing or other processes. Optionally, the material of the first electrode 50 can be copper, silver, nickel or aluminum; the thickness of the first electrode can be 2μm to 20μm. Figure 6 and Figure 7 For structures not mentioned in the above text, please refer to Figure 5 The relevant description in the document.

[0085] like Figure 1 As shown, a tunneling dielectric layer 60, a doped conductive layer 70, and a second passivation layer 80 are sequentially formed on the second surface of the N-type substrate 10 using a deposition process. Optionally, the material of the tunneling dielectric layer 60 can be silicon oxide, silicon oxynitride, titanium oxide, and silicon nitride, etc., and the thickness can be 0.5 nm to 2 nm; optionally, the material of the doped conductive layer 70 can be at least one of silicon carbide and polycrystalline silicon, and the thickness can be 2 nm to 100 nm; optionally, the material of the second passivation layer 80 can be a single layer or composite layer such as aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride, and the thickness can be 60 nm to 100 nm. Figure 1 As shown, an opening is made in the metal region of the second passivation layer 80, and a second electrode 90 is prepared by printing or magnetron sputtering. The second electrode 90 contacts the doped conductive layer 70 through the opening. Optionally, the material of the first electrode 50 can be copper, silver, nickel or aluminum; the thickness of the first electrode can be 2μm to 20μm.

[0086] According to another aspect of this application, a photovoltaic module is provided, comprising a plurality of the aforementioned solar cells.

[0087] The technical solutions of this application can be used in photovoltaic cells such as gridless (OBB, Zero Busbar) or multi-busbar (MBB, MULTI-BUSBAR) all-back contact cells, interdigitated back contact cells (IBC, Interdigitated Back Contact), all-back contact solar cells (ABC, All Back Contact), hybrid passivated back contact cells (HPBC, Hybrid Passivated Back Contact), emitter and rear passivated cells (PERC, Passivated Emitter and Rear Cell), tunneling oxide passivated contact cells (TOPcon, Tnuuel Oxide Passivated Contact), TOPcon-IBC (Interdigitated Back Contact, IBC) cells, crystalline silicon heterojunction solar cells (HJT, Heterojunction with Intrinsic Thin-layer), perovskite tandem cells, and flexible cells.

[0088] The preparation method of the solar cell described above in this application will be specifically described below with reference to specific embodiments and comparative examples.

[0089] Example 1

[0090] This application provides a method for preparing a solar cell, comprising:

[0091] An N-type substrate is provided, and a first surface of the N-type substrate is texturized. The first surface includes a metal region and a non-metal region. The N-type substrate is made of silicon and has a thickness of 100 μm.

[0092] A first P-type emitter is formed on the first surface, and the doping concentration of the first P-type emitter is 1×10⁻⁶. 20 cm -3 The junction depth is 1 μm;

[0093] The first P-type emitter located in the metal region is subjected to laser amorphization treatment to form a second P-type emitter and a barrier layer in the metal region. The second P-type emitter is located between the barrier layer and the N-type substrate, and the doping concentration of the second P-type emitter is 1×10⁻⁶. 19 cm -3 The junction depth is 0.5 μm, and the barrier layer is made of P-type amorphous silicon with a thickness of 0.5 μm.

[0094] A first passivation layer is deposited on the barrier layer and the second P-type emitter, and the portion of the first passivation layer located in the metal region is made into an opening. The material of the first passivation layer is silicon oxide and the thickness is 70 nm.

[0095] A first electrode is printed on the first passivation layer. The first electrode contacts the isolation layer through an opening. The thickness of the first electrode is 70 nm, and the material is Ag.

[0096] On the second surface of the N-type substrate, along the direction from the first passivation layer to the N-type substrate, a tunneling dielectric layer, a doped conductive layer, a second passivation layer, and a plurality of second electrodes are formed. The tunneling dielectric layer is made of silicon oxide and has a thickness of 1 nm. The doped conductive layer is made of silicon carbide and has a thickness of 50 nm. The second electrodes are made of Ag and have a thickness of 5 μm.

[0097] Example 2

[0098] This application provides a method for fabricating a solar cell, the only difference between this method and Example 1 being that the doping concentration of the first P-type emitter is 1×10⁻⁶. 22 cm -3 The doping concentration of the second P-type emitter is 1×10⁻⁶. 21 cm -3 .

[0099] Example 3

[0100] The only difference from Example 1 is that the doping concentration of the first P-type emitter is 1×10⁻⁶. 23 cm -3 The doping concentration of the second P-type emitter is 1×10⁻⁶. 22 cm -3 .

[0101] Comparative Example 1

[0102] The difference from Example 1 is that no barrier layer is formed.

[0103] Comparative Example 2

[0104] The difference from Example 1 is that the doping concentration of the second P-type emitter is higher than that of the first P-type emitter; the doping concentration of the second P-type emitter is 1 × 10⁻⁶. 20 cm -3 The doping concentration of the first P-type emitter is 1×10⁻⁶. 19 cm -3 .

[0105] Comparative Example 3

[0106] The difference from Example 1 is that no barrier layer is formed and the doping concentration of the second P-type emitter is higher than that of the first P-type emitter; the doping concentration of the second P-type emitter is 1 × 10⁻⁶. 20 cm -3 The doping concentration of the first P-type emitter is 1×10⁻⁶. 19 cm -3 .

[0107] The performance of the solar cells prepared using the methods described in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are as follows:

[0108] Table 1

[0109]

[0110] The experimental data above show that the turn-on voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency in Examples 1 to 3 are all higher than those in Comparative Examples 1 to 3. This indicates that the solar cell with a barrier layer and a lower doping concentration of the second P-type emitter in the metal region than the first P-type emitter in the metal region can effectively reduce excessive diffusion of electrode ions in the metal electrode, and reduce the contact resistance and surface recombination between the first electrode and the N-type substrate, thereby improving the cell efficiency.

[0111] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0112] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0113] The solar cell proposed in this application has a barrier layer formed. When metal ions in the first electrode diffuse towards the second P-type emitter, the barrier layer can block at least a portion of the metal ions, thereby reducing the content of metal ions diffused into the second P-type emitter and the N-type substrate. This reduces the generation of elemental metals and prevents the second P-type emitter and the N-type substrate from being damaged by elemental metals, thus solving the problem of reduced cell efficiency caused by excessive diffusion of electrode ions in the metal electrodes of solar cells in related technologies. Furthermore, in the P-type emitter layer of this solar cell, the second doping concentration of the second P-type emitter is lower than the first doping concentration of the first P-type emitter. This doping concentration design can reduce carrier recombination at the surface due to a higher doping concentration, thereby ensuring a higher minority carrier lifetime and thus ensuring a higher open-circuit voltage and short-circuit current of the cell. On the other hand, this doping concentration design can reduce the problem of higher contact resistance due to a lower doping concentration, thereby ensuring a lower contact resistance and a lower turn-on voltage of the cell. Furthermore, the concentration difference between the first and second P-type emitters allows charge carriers to be transported to the N-type substrate more quickly, which also contributes to improved photoelectric conversion efficiency. Therefore, this concentration design results in a high photoelectric conversion efficiency for this solar cell.

[0114] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A solar cell, characterized by, The application provides a semiconductor device, comprising: an N-type substrate having opposite first and second surfaces, the first surface comprising a metal region and a non-metal region; a P-type emitter layer, a first passivation layer, a barrier layer and a plurality of first electrodes on the first surface, wherein the P-type emitter layer comprises a first P-type emitter on the non-metal region, the first P-type emitter having a first doping concentration, and a second P-type emitter on the metal region, the second P-type emitter having a second doping concentration, the second doping concentration being less than the first doping concentration, the first passivation layer being on a side of the P-type emitter layer facing away from the N-type substrate, the first electrodes being on a side of the second P-type emitter facing away from the N-type substrate, the barrier layer being between the first electrodes and the second P-type emitter, the barrier layer being configured to block diffusion of metal ions from the first electrodes into the second P-type emitter, the barrier layer having a doping concentration less than or equal to the first doping concentration; a tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes on the second surface.

2. The solar cell according to claim 1, characterized in that, a first doping concentration of 1 x 1016cm-3 20 cm -3 ~1x 1017cm-3 23 cm -3 , and a second doping concentration of 1 x 1016cm-3 19 cm -3 ~1x 1017cm-3 22 cm -3 .

3. The solar cell according to claim 1, characterized in that, The first P-type emitter has a junction depth of 0.5-2 μm, and the second P-type emitter has a junction depth of 0.2-1 μm.

4. The solar cell of claim 1, wherein The second P-type emitter has a sheet resistance of 100-800 Ω / square.

5. The solar cell of claim 1, wherein The barrier layer comprises P-type amorphous silicon.

6. The solar cell according to claim 5, characterized in that, The doping concentration of the barrier layer is 1 x 10 19 cm -3 ~1 x 10 22 cm -3 .

7. A method of producing a solar cell according to any one of claims 1 to 6, characterized by, The application provides a method for manufacturing a semiconductor device, comprising: providing an N-type substrate having opposite first and second surfaces, the first surface comprising a metal region and a non-metal region; forming a P-type emitter layer, a first passivation layer, a barrier layer and a plurality of first electrodes on the first surface, wherein: the P-type emitter layer comprises a first P-type emitter on the non-metal region, the first P-type emitter having a first doping concentration, and a second P-type emitter on the metal region, the second P-type emitter having a second doping concentration, the second doping concentration being less than the first doping concentration; the first electrodes are on a side of the second P-type emitter facing away from the N-type substrate; the first passivation layer is on a side of the P-type emitter layer facing away from the N-type substrate; the barrier layer is between the first electrodes and the second P-type emitter, the barrier layer being configured to block diffusion of metal ions from the first electrodes into the N-type substrate; forming a tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes on the second surface.

8. The production method according to claim 7, characterized by, The steps of forming the P-type emitter layer and the barrier layer comprise: forming a first P-type emitter on the first surface, the first P-type emitter having a first doping concentration; The first P-type emitter located in the metal region is subjected to laser amorphization treatment to obtain the second P-type emitter and the barrier layer located in the metal region. The barrier layer is located on the side of the second P-type emitter away from the N-type substrate. The second P-type emitter has a second doping concentration, which is less than the first doping concentration.

9. A photovoltaic module, characterized by, It includes at least one solar cell according to any one of claims 1 to 6.

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