Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a solar cell, a preparation method thereof and a photovoltaic module, the solar cell comprises an N-type substrate, a P-type emitter layer, a first passivation layer, a barrier layer, a plurality of first electrodes, a tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes, and the first surface of the N-type substrate comprises a metal region and a non-metal region; a first P-type emitting electrode of the P-type emitting electrode layer is located in the non-metal region, a second P-type emitting electrode of the P-type emitting electrode layer is located in the metal region, the second doping concentration of the second P-type emitting electrode is smaller than the first doping concentration, and the barrier layer is used for blocking metal ions of the first electrode from diffusing into the second P-type emitting electrode. Therefore, the content of metal ions diffused to the second P-type emitter and the N-type substrate is reduced, the generation of metal particles is reduced, and the second P-type emitter and the N-type substrate are prevented from being damaged.

Description

Technical Field

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

[0002] Solar cells are devices that convert light energy into electrical energy and are an important part of the renewable energy sector. The diffusion process of metal ions in the solar cell electrodes plays a vital role in the performance and efficiency of solar cells. When the metal electrodes of the battery are sintered, the metal electrodes react with oxygen to generate metal ions, which diffuse from the electrodes to other structures of the battery. However, if there are too many diffused metal ions, the metal ions will react with the silicon ions in the battery to generate metal elements, which will damage other structures of the solar cell and affect the photoelectric conversion efficiency of the battery. Summary of the invention

[0003] The present application provides a solar cell, a preparation method thereof and a photovoltaic module to solve the problem in the related art that excessive diffusion of electrode ions in metal electrodes of solar cells leads to reduced cell efficiency.

[0004] According to one aspect of the present application, a solar cell is provided, comprising: an N-type substrate having a first surface and a second surface opposite to each other, 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 located on the first surface, wherein the P-type emitter layer comprises: a first P-type emitter and a second P-type emitter, the first P-type emitter being located in the non-metal region, the first P-type emitter having a first doping concentration, the second P-type emitter being located in 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 located on a side of the P-type emitter layer away from the N-type substrate, the first electrode being located on a side of the second P-type emitter away from 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 block metal ions of the first electrode from diffusing into the second P-type emitter; 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, a junction depth of the first P-type emitter is 0.5 μm to 2 μm, and a junction depth of the second P-type emitter is 0.2 μm to 1 μm.

[0007] Optionally, the square 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 blocking layer is less than or equal to the first doping concentration.

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

[0011] According to another aspect of the present application, a method for preparing a solar cell is provided, comprising: providing an N-type substrate, the N-type substrate having a first surface and a second surface opposite to each other, 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 and a second P-type emitter, wherein the first P-type emitter is located in the non-metal region, the first P-type emitter has a first doping concentration, the second P-type emitter is located in the metal region, the second P-type emitter has a second doping concentration, and the second doping concentration is less than the first doping concentration; the first electrode is located on a side of the second P-type emitter away from the N-type substrate; the first passivation layer is located on a 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, and the barrier layer is used to block metal ions in the first electrode from diffusing into the N-type substrate; and a tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes are formed 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 in the metal area to obtain the second P-type emitter and the barrier layer in the metal area, the barrier layer being located on a side of the second P-type emitter away from the N-type substrate, the second P-type emitter having a second doping concentration, and the second doping concentration being less than the first doping concentration.

[0013] According to another aspect of the present application, a photovoltaic assembly is provided, comprising a plurality of the above-mentioned solar cells.

[0014] The solar cell of the present application includes an N-type substrate, a P-type emitter layer, a first passivation layer, a barrier layer, a plurality of first electrodes, a tunnel dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes, wherein the P-type emitter layer includes a first P-type emitter and a second P-type emitter, and the barrier layer is located between the first electrode and the second P-type emitter. When the metal ions in the first electrode diffuse to the second P-type emitter, the barrier layer can block at least part of the above metal ions, thereby reducing the metal ions diffused into the second P-type emitter and the N-type substrate, reducing the generation of metal particles, and avoiding the second P-type emitter and the N-type substrate from being damaged. The problem of excessive diffusion of electrode ions in the metal electrodes of solar cells in the related art leading to reduced cell efficiency is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1 A schematic cross-sectional structure diagram of a solar cell provided in an embodiment of the present application is shown;

[0017] Figure 2 A schematic diagram of the process structure of a method for preparing a solar cell provided in an embodiment of the present application is shown;

[0018] Figure 3 The cross-sectional structure schematic diagram of the substrate after providing an N-type substrate and texturing the first surface of the N-type substrate in the method for preparing the solar cell of the present application is shown;

[0019] Figure 4 Shown in Figure 3 A schematic cross-sectional structure diagram of a substrate after a first P-type emitter is formed on a first surface of an N-type substrate formed in the process;

[0020] Figure 5 Shown in 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 substrate forms a second P-type emitter and a barrier layer;

[0021] Figure 6 Shown in Figure 5 A schematic diagram of the cross-sectional structure of the substrate after a first P-type emitter and a first passivation layer are formed on the barrier layer;

[0022] Figure 7 Shown in Figure 6A first electrode in a first passivation layer formed in the process, and a schematic cross-sectional structure diagram of a substrate after the first electrode penetrates through the first passivation layer.

[0023] The above drawings 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 DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work 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 and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] As mentioned in the background technology, currently, when the metal electrode of the battery is sintered, the metal electrode will react with oxygen to generate metal ions, and the metal ions will diffuse from the electrode to other structures of the battery. However, if there are too many diffused metal ions, the metal ions will react with the silicon ions in the battery to generate metal elements, which will damage other structures of the solar cell and thus affect the photoelectric conversion efficiency of the battery.

[0029] In order to solve the above technical problems, according to one aspect of the present application, Figure 1 As shown, a solar cell is provided, comprising:

[0030] The N-type substrate 10 has a first surface and a second surface opposite to each other, wherein the first surface includes a metal region and a non-metal region;

[0031] A P-type emitter layer 20, a first passivation layer 30, a barrier layer 40 and a plurality of first electrodes 50 located on the first surface, wherein 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, the first P-type emitter 21 has a first doping concentration, the second P-type emitter 22 is located in the metal region, the second P-type emitter 22 has a second doping concentration, the second doping concentration is less than the first doping concentration, the first passivation layer 30 is located on a side of the P-type emitter layer 20 away from the N-type substrate 10, the first electrode 50 is located on a 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 the barrier layer 40 is used to block metal ions of the first electrode 50 from diffusing into the second P-type emitter 22;

[0032] A tunnel dielectric layer 60 , a doped conductive layer 70 , a second passivation layer 80 and a 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, the front side can be used as the light-receiving surface for receiving incident light, and the back side can be used as the backlight surface. In some embodiments, the solar cell is a bifacial cell, that is, the first surface and the second surface of the N-type substrate can both be used as light-receiving surfaces for receiving incident light.

[0034] The first surface and the second surface mentioned above can be flat surfaces or non-flat surfaces respectively, 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, the first surface and the second surface are both non-planar surfaces, and the non-planar surfaces can increase the internal reflection of the incident light, thereby further improving the utilization rate of the light by the solar cell. More specifically, the cross-section of the non-planar surface along the first predetermined direction is a line segment, and the line segment can include at least one of a straight line segment and a curved line segment, that is, the line segment can be composed of a straight line segment, or a curved line segment, or a curved line segment and a straight line segment. In the case where only straight line segments are composed, the line segment is composed of a plurality of straight line segments connected in sequence. The first predetermined direction is the thickness direction of the N-type substrate. In a specific embodiment, Figure 1 As shown, the cross-sections of the first surface and the second surface along the first predetermined direction D1 are sawtooth-shaped, that is, they are composed of a plurality of straight line segments connected in sequence.

[0036] The metal area of ​​the first surface mentioned above refers to the area of ​​the first surface used to form the first electrode, that is, the projection of the first electrode on the first surface is located in this area, and the area of ​​the metal area of ​​the first surface is generally larger than the projection area of ​​the first electrode on the first surface. The non-metal area of ​​the first surface is the area of ​​the first surface other than the metal area. In some specific embodiments, the width of the metal area 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. In this way, when the first electrode is manufactured, the formable area of ​​the electrode is relatively large, and the requirements for the manufacturing process are more relaxed. The second predetermined direction D2 is a direction perpendicular to the thickness of the N-type substrate, and can be specifically as follows Figure 1 shown.

[0037] It should be noted that the second surface of the present application actually also has a metal area and a non-metal area, and the metal area of ​​the second surface corresponds to the second electrode, that is, the relationship between the first electrode and the metal area of ​​the first surface in the above paragraph is also applicable to the second electrode and the metal area of ​​the second surface. In addition, the non-metal area of ​​the second surface also refers to the area of ​​the first surface excluding the metal area.

[0038] The material of the barrier layer is any material that can block the metal ions of the first electrode from diffusing into the second P-type emitter. A person skilled in the art can select a suitable material to form the barrier layer according to actual conditions. In addition, the barrier layer of the present application can have one layer or multiple layers. In the case of multiple layers, the materials of any two layers can be the same or different. A person skilled in the art can set a suitable number of layers and suitable materials according to actual conditions.

[0039] The solar cell is formed with a barrier layer. When the metal ions in the first electrode diffuse to the second P-type emitter, the barrier layer can block at least part of the metal ions, thereby reducing the content of the metal ions diffused to the second P-type emitter and the N-type substrate, thereby reducing the generation of metal elements, avoiding the second P-type emitter and the N-type substrate from being destroyed by the metal elements, thereby solving the problem of excessive diffusion of electrode ions in the metal electrode of the solar cell in the related art, resulting in reduced battery efficiency. In the P-type emitter layer of the solar cell, the second doping concentration of the second P-type emitter is less than the first doping concentration of the first P-type emitter. Such a doping concentration design can reduce the recombination of the carrier surface caused by the high doping concentration, thereby ensuring a high life span of the minority carriers, thereby ensuring a high open circuit voltage and short circuit current of the battery; on the other hand, such a doping concentration design can reduce the problem of high contact resistance caused by low doping concentration, thereby ensuring a low contact resistance and a low opening voltage of the battery. On the other hand, due to the concentration difference between the first P-type emitter and the second P-type emitter, the carriers can be transferred to the N-type substrate faster, which is also conducive to improving the photoelectric conversion efficiency. Therefore, such a concentration design makes the photoelectric conversion efficiency of the solar cell higher.

[0040] In some embodiments, the material of the N-type substrate may be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon. The elemental semiconductor material may be single crystal, polycrystalline, amorphous, or microcrystalline (a state having both single crystal and amorphous states is referred to as microcrystalline), for example, silicon may be at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0041] In some embodiments, the material of the N-type substrate may also be a compound semiconductor material. Common compound semiconductor materials include but are not limited to silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride, copper indium selenide and the like. The N-type substrate may 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 doping element, and the N-type doping element may be any one of the V-group elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type element, and the P-type doping element may be any one of the III-group elements such as boron (B), aluminum (Al), gallium (Ga), or gallium (In). Optionally, the thickness of the N-type substrate may 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 above-mentioned solar cell can suppress the carrier recombination at the interface, so as to avoid the problem of reduced photocurrent due to carrier recombination, thereby ensuring the high photoelectric conversion efficiency of the battery. Optionally, the material of the above-mentioned first passivation layer can be a single-layer film or a composite film such as aluminum oxide, silicon nitride, silicon oxide and silicon oxynitride. For example, in the case where the first passivation layer is a single-layer film, the first passivation layer can be an aluminum oxide single-layer film, a silicon nitride single-layer film, a silicon oxide single-layer film, or a silicon oxynitride single-layer film; in the case where the first passivation layer is a multi-layer film, the first passivation layer can be a composite film of aluminum oxide and silicon oxide, or a composite film of aluminum oxide, silicon oxide and silicon nitride. Of course, the material of the first passivation layer of the present 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 the present application according to actual conditions. Optionally, the thickness of the first passivation layer of the present application can be 70nm to 90nm, which can further ensure that the defect state density on the surface of the battery cell is reduced, reducing the probability of electron and hole recombination on the surface, thereby improving the photoelectric conversion efficiency.

[0044] The second passivation layer of the present application can also suppress carrier recombination at the interface, thereby ensuring a 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 film layer combination of the second passivation layer can refer to the description of the film layer combination of the first passivation layer, and will not be repeated here.

[0045] The tunnel 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, thereby reducing the recombination probability of electrons and holes, increasing the fill factor, short-circuit current and open-circuit voltage of the solar cell, and improving the photoelectric conversion efficiency of the solar cell.

[0046] Optionally, the material of the above-mentioned tunnel dielectric layer may include at least one of silicon oxide, silicon oxynitride, titanium oxide and silicon nitride, and the thickness is generally small, about 1 nm. The specific thickness can be set according to the actual situation and is not limited here. Exemplarily, the tunnel dielectric layer can be an ultra-thin silicon oxide layer, so that the tunnel dielectric layer has good passivation characteristics and can make it easier for carriers to tunnel. In some feasible embodiments, the tunnel dielectric layer can be formed on the second surface side of the N-type substrate by ozone oxidation, high-temperature thermal oxidation, nitric acid oxidation, chemical vapor deposition, and low-pressure chemical vapor deposition.

[0047] In some embodiments, the doped conductive layer can be a doped polysilicon layer, or a silicon carbide layer, or a composite layer of a doped polysilicon layer and a silicon carbide layer, such as only silicon carbide or only polysilicon, or a doped material of silicon carbide and polysilicon; when the doped conductive layer is doped polysilicon (Doped poly-Si), it can be used as a field passivation layer to form a band bending on the surface of the silicon wafer, realize the selective transmission of carriers, and reduce the recombination loss. The thickness of the above-mentioned doped conductive layer can be 2nm to 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 actual conditions.

[0048] In some embodiments, the tunneling dielectric layer and the doped conductive layer constitute a passivation contact structure. The doped conductive layer can form an energy band bending on the surface of the N-type substrate. The tunneling dielectric layer causes an asymmetric shift in the energy band on the surface of the N-type substrate, so that the potential barrier to the majority carriers (also called majority carriers) among the carriers is lower than the potential barrier to the minority carriers (also called minority carriers) among the carriers. Therefore, the majority carriers can more easily perform quantum tunneling through the tunneling dielectric layer, while the minority carriers find it difficult to pass through the tunneling dielectric layer, so as to realize the selective transmission of carriers.

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

[0050] In some embodiments, the material of the barrier layer can be any one or more of aluminum oxide, silicon nitride, polycrystalline silicon and amorphous silicon, which can block the metal ions of the first electrode from diffusing into the second P-type emitter. In some more specific embodiments, the thickness of the barrier layer is 0.3 μm to 1 μm. This can not only ensure a good blocking effect, but also ensure a high electron collection efficiency, further ensuring a high efficiency of the solar cell. Those skilled in the art can select the appropriate material and thickness of the barrier layer according to actual conditions, and this application does not limit it.

[0051] In some optional embodiments, the first doping concentration of the first P-type emitter is 1×10 20 cm -3 ~1×10 23 cm -3 , the second doping concentration of the second P-type emitter is 1×10 19 cm -3 ~1×10 22 cm -3Such a doping concentration range can further reduce the contact resistance, reduce the recombination of carriers, and further ensure that the photoelectric conversion efficiency of the solar cell is high.

[0052] In some embodiments, the material of the first P-type emitter or the second P-type emitter can be single crystal silicon or polycrystalline silicon. In other embodiments, the junction depth of the first P-type emitter is 0.5μm to 2μm, which has a good passivation effect on the one hand, and ensures that the square resistance of the first P-type emitter is small on the other hand, further ensuring that the photoelectric conversion rate of the solar cell is high, and the junction depth can also ensure that the first P-type emitter has a good passivation effect, which is conducive to reducing the recombination of carriers and improving the open circuit voltage and short circuit current of the solar cell; the junction depth of the second P-type emitter is 0.2μm to 1μm, which can prevent the metal ions of the first electrode from penetrating the second P-type emitter during the sintering process, 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, so that a more uniform and dense passivation film can be formed on the contact surface between the second P-type emitter and the N-type substrate, thereby improving the passivation effect of the metal area and reducing the composite defects of the battery.

[0054] In some embodiments, the doping concentration of the second P-type emitter is lower than the doping concentration 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] In order to further ensure that the contact resistance of the second P-type emitter is small and further reduce the recombination of carriers, the square resistance of the second P-type emitter is 100Ω / square to 800Ω / square.

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

[0057] In the above optional implementation, when the material of the barrier layer is amorphous silicon, for example, the slurry 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- ions, the reaction principle is as follows:

[0059]

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

[0061]

[0062] Since the electron mobility of amorphous silicon is 2 to 3 orders of magnitude lower than that of crystalline silicon (electron mobility: amorphous silicon is 0.5 to 1 cm 2 / v·s, crystalline silicon is 1000~1500cm 2 / v·s), the migration of electrons in amorphous silicon is limited, and amorphous silicon can provide Ag + The electrons in the ion reaction are less and the reaction speed is slower. Therefore, compared with the first electrode directly contacting the crystalline silicon emitter, the barrier layer made of amorphous silicon is located between the first electrode and the second P-type emitter, which will reduce the electrons in the ion reaction and the reaction speed. + The ability of ions to provide electrons can reduce Ag + The ions obtain Ag particles generated by electrons, thereby reducing the damage to the second P-type emitter, reducing composite defects and improving 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 one-time laser amorphization process for the first P-type emitter, and there is no need to adopt an additional preparation process to form the barrier layer (for example, there is no need to form a barrier layer on the emitter in the metal area by deposition or other processes after the emitters in the metal area and the non-metal area are prepared), which makes the preparation process of the battery simpler and suitable for large-scale mass production.

[0064] In some embodiments, during the laser amorphization process of the first P-type emitter, the laser will melt the surface of the N-type substrate, and the doping ions in the first P-type emitter will penetrate into the N-type substrate, so that the doping concentration of the generated second P-type emitter and the barrier layer will be lower than the doping concentration of the first P-type emitter. Since the barrier layer is located on the side of the second P-type emitter away from the N-type substrate, during the process of the doping ions penetrating into the N-type substrate, the doping ions in the second P-type emitter will first enter the N-type substrate, and the doping ions in the barrier layer will penetrate into the second P-type emitter and then penetrate into the N-type substrate through the second P-type emitter. In the case where the laser process is performed on the first P-type emitter for a short time, the doping concentration of the doping ions in the second P-type emitter will be almost the same as that of the barrier layer. In the case where the laser process is performed on the first P-type emitter for a long time, most of the doping ions in the barrier layer will enter the first P-type emitter to supplement the doping ions of the first P-type emitter. Therefore, after the laser amorphization process is completed, the doping concentration of the doping ions in the second P-type emitter will be greater than or equal to that of the barrier layer. Optionally, the doping concentration of the barrier layer is 1×10 19 cm -3 ~1×10 22 cm -3 The doping concentration can not only ensure that the barrier layer has a good barrier effect, but also ensure that the sheet resistance of the barrier layer is small.

[0065] In some embodiments, the sum of the thickness of the above-mentioned barrier layer and the junction depth of the above-mentioned second P-type emitter is the same as the junction depth of the above-mentioned first P-type emitter. During the preparation process, the first P-type emitter in the metal area is subjected to a laser amorphization process. During the process of laser irradiation on the first P-type emitter, the portion of the first P-type emitter close to the upper surface is melted by the laser. After the laser is removed, the above-mentioned molten area will cool down rapidly to form amorphous silicon with a disordered and directionless molecular structure arrangement. In combination with the process described above, the laser will cause the doped ions to diffuse into the N-type substrate. The above-mentioned barrier layer and the above-mentioned second P-type emitter can be simultaneously formed through a single laser amorphization process, thereby simplifying the preparation process of the battery.

[0066] According to another aspect of the present application, a method for preparing a solar cell is provided, such as Figure 2 As shown, including:

[0067] Step S101: Figure 3 As shown, an N-type substrate 10 is provided, wherein the N-type substrate 10 has a first surface and a second surface opposite to each other, wherein the first surface includes a metal region 11 and a non-metal region 12;

[0068] Step S102: 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, wherein: the P-type emitter layer 20 includes: a first P-type emitter 21 and a second P-type emitter 22, wherein the first P-type emitter 21 is located in the non-metallic region, the first P-type emitter 21 has a first doping concentration, the second P-type emitter 22 is located in the metal region, the second P-type emitter 22 has a second doping concentration, and the second doping concentration is less than the first doping concentration; the first electrode 50 is located on the side of the second P-type emitter 22 away from the N-type substrate 10; 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 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 block the metal ions in the first electrode 50 from diffusing into the N-type substrate 10.

[0069] Step S103: Figure 1 As shown, a tunnel 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 preparation method has a barrier layer. When the metal ions in the first electrode diffuse to the second P-type emitter, the barrier layer can block at least part of the metal ions, thereby reducing the content of the metal ions diffused into the second P-type emitter and the N-type substrate, thereby reducing the generation of metal elements, and avoiding the second P-type emitter and the N-type substrate from being destroyed by metal elements. Thus, the problem of excessive diffusion of electrode ions in the metal electrode of the solar cell in the related art leading to reduced battery efficiency is solved. In the P-type emitter layer of the solar cell, the second doping concentration of the second P-type emitter is less than the first doping concentration of the first P-type emitter. Such a doping concentration design can reduce the recombination of the carrier surface caused by the high doping concentration, thereby ensuring a high life of the minority carriers, and thus ensuring a high open circuit voltage and short circuit current of the battery; on the other hand, such a doping concentration design can reduce the problem of high contact resistance caused by low doping concentration, thereby ensuring that the contact resistance of the battery is small and the opening voltage is small. On the other hand, due to the concentration difference between the first P-type emitter and the second P-type emitter, the carriers can be transferred to the N-type substrate faster, which is also conducive to improving the photoelectric conversion efficiency. Therefore, such a concentration design makes the photoelectric conversion efficiency of the solar cell higher.

[0071] The first surface of the above-mentioned 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, the front side can be used as the light-receiving surface for receiving incident light, and the back side is used as the backlight surface. In some embodiments, the solar cell is a double-sided cell, that is, the first surface and the second surface of the N-type substrate can both be used as light-receiving surfaces, and can both be used to receive incident light. The thickness of the N-type substrate can be 80μm to 200μm, such as 85μm, 100μm, 130μm, 170μm, 190μm, etc. The first surface of the N-type substrate can be textured to increase the roughness of the first surface, so that other structures can be better prepared on the N-type substrate later.

[0072] The first surface and the second surface mentioned above can be flat surfaces or non-flat surfaces respectively, 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, the first surface and the second surface are both non-planar surfaces, and the non-planar surfaces can increase the internal reflection of the incident light, thereby further improving the utilization rate of the light by the solar cell. More specifically, the cross-section of the non-planar surface along the first predetermined direction is a line segment, and the line segment can include at least one of a straight line segment and a curved line segment, that is, the line segment can be composed of a straight line segment, or a curved line segment, or a curved line segment and a straight line segment. In the case where only straight line segments are composed, the line segment is composed of a plurality of straight line segments connected in sequence. The first predetermined direction is the thickness direction of the N-type substrate. In a specific embodiment, Figure 1 As shown, the cross-sections of the first surface and the second surface along the first predetermined direction D1 are sawtooth-shaped, that is, they are composed of a plurality of straight line segments connected in sequence.

[0074] The metal area of ​​the first surface mentioned above refers to the area of ​​the first surface used to form the first electrode, that is, the projection of the first electrode on the first surface is located in this area, and the area of ​​the metal area of ​​the first surface is generally larger than the projection area of ​​the first electrode on the first surface. The non-metal area of ​​the first surface is the area of ​​the first surface other than the metal area. In some specific embodiments, the width of the metal area 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. In this way, when the first electrode is manufactured, the formable area of ​​the electrode is relatively large, and the requirements for the manufacturing process are more relaxed. The second predetermined direction D2 is a direction perpendicular to the thickness of the N-type substrate, and can be specifically as follows Figure 1 shown.

[0075] It should be noted that the second surface of the present application actually also has a metal area and a non-metal area, and the metal area of ​​the second surface corresponds to the second electrode, that is, the relationship between the first electrode and the metal area of ​​the first surface in the above paragraph is also applicable to the second electrode and the metal area of ​​the second surface. In addition, the non-metal area of ​​the second surface also refers to the area of ​​the first surface excluding the metal area.

[0076] The material of the barrier layer is any material that can block the metal ions of the first electrode from diffusing into the second P-type emitter. A person skilled in the art can select a suitable material to form the barrier layer according to actual conditions. In addition, the barrier layer of the present application can have one layer or multiple layers. In the case of multiple layers, the materials of any two layers can be the same or different. A person skilled in the art can set a suitable number of layers and suitable materials according to actual conditions.

[0077] In some optional embodiments, such as Figure 4 and Figure 5 As shown, the steps of forming the above-mentioned P-type emitter layer 20 and the above-mentioned barrier layer 40 include: forming a first P-type emitter 21 on the above-mentioned first surface, and the above-mentioned first P-type emitter 21 has a first doping concentration; performing laser amorphization treatment on the above-mentioned first P-type emitter 21 located in the above-mentioned metal area to obtain the above-mentioned second P-type emitter 22 and the above-mentioned barrier layer 40 located in the above-mentioned metal area, and the above-mentioned barrier layer 40 is located on the side of the above-mentioned second P-type emitter 22 away from the above-mentioned N-type substrate 10, and the above-mentioned second P-type emitter 22 has a second doping concentration, and the above-mentioned second doping concentration is 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 an additional preparation process to form the barrier layer (for example, there is no need to form a barrier layer on the emitter in the metal area by deposition or other processes after the emitter in the metal area and the non-metal area are prepared), thereby making the preparation process of the battery simpler and suitable for large-scale mass production.

[0079] In the above optional implementation, if Figure 4 As shown, a first P-type emitter 21 is formed on the first surface of the N-type substrate 10 after texturing by using a physical deposition process or a chemical deposition process.

[0080] like Figure 5As shown, the laser amorphization process is used to irradiate the first P-type emitter 21 located in the metal region with laser. During the laser amorphization process of the first P-type emitter 21, the portion of the first P-type emitter 21 close to the upper surface is melted by the laser. After the laser is removed, the melted area is rapidly cooled to form amorphous silicon with disordered and non-directional molecular structure arrangement, forming a barrier layer 40. The barrier layer 40 made of amorphous silicon will reduce the ability to provide electrons to the metal ions of the first electrode 50, and can reduce the metal particles generated by the metal ions obtaining electrons, thereby reducing the damage of the metal particles to the second P-type emitter 22 and the N-type substrate 10. The laser will melt the surface of the N-type substrate 10, and the doped ions in the first P-type emitter 21 will penetrate into the N-type substrate 10, thereby forming a second P-type emitter 22 with a doping concentration lower than that of the first P-type emitter 21.

[0081] Optionally, the doping concentration of the second P-type emitter is 1×10 19 cm -3 ~1×10 22 cm -3 Setting the doping concentration of the second P-type emitter to the above range will neither increase the carrier recombination due to excessively high doping concentration, nor increase the contact resistance between the first electrode and the N-type substrate due to excessively low doping concentration. Therefore, the concentration setting of the second P-type emitter can reduce surface recombination and increase the minority carrier lifetime, and can also keep the contact resistance between the first electrode and the N-type substrate at a lower state, thereby increasing the open circuit voltage and thus improving the 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 20 cm -3 ~1×10 23 cm -3 The doping concentration of the first P-type emitter is lower than the doping concentration of the non-metallic region emitter in the prior art, which can reduce surface recombination, increase the open circuit voltage, and improve the photoelectric conversion efficiency of the battery.

[0083] As can be seen from the above description, the doping concentration of the first P-type emitter and the doping concentration of the second P-type emitter can be set to reduce surface recombination, increase minority carrier lifetime, and improve battery efficiency while maintaining low contact resistance between the first electrode and the N-type substrate. The low doping concentration of the second P-type emitter will also result in less doping impurities, so that the second P-type emitter can form a more uniform and dense passivation film on the surface of the N-type substrate, thereby enhancing the passivation ability of the battery surface.

[0084] Specifically, Figure 6As shown, a first passivation layer 30 is formed on the P-type emitter layer 20 by a deposition process. Optionally, the thickness of the first passivation layer 30 may be 70 nm to 90 nm. The material of the first passivation layer 30 may be a single layer or a composite layer such as aluminum oxide, silicon nitride, silicon oxide, and silicon oxynitride. Figure 7 As shown, the metal area of ​​the first passivation layer 30 is opened, and the first electrode 50 is formed by a printing process. Optionally, the first electrode 50 can be made of copper, silver, nickel or aluminum; the thickness of the first electrode can be 2μm to 20μm. Figure 6 and Figure 7 The structures not mentioned in the above text can be referred to Figure 5 Related description in .

[0085] like Figure 1 As shown, a tunnel 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 by a deposition process. Optionally, the material of the tunnel dielectric layer 60 may be silicon oxide, silicon oxynitride, titanium oxide and silicon nitride, etc., and the thickness may be 0.5nm to 2nm; optionally, the material of the doped conductive layer 70 may be at least one of silicon carbide and polycrystalline silicon, and the thickness may be 2nm to 100nm; optionally, the material of the second passivation layer 80 may be a single film layer or a composite film layer such as aluminum oxide, silicon nitride, silicon oxide and silicon oxynitride, and the thickness may be 60nm to 100nm. Figure 1 As shown, a hole is opened in the metal area of ​​the second passivation layer 80, and a second electrode 90 is prepared by a printing process or a magnetron sputtering process. The second electrode 90 is in contact with the doped conductive layer 70 through the above-mentioned 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 the present application, a photovoltaic module is provided, comprising a plurality of the above-mentioned solar cells.

[0087] The technical solution of the present application can be used in full back electrode contact cells with busbar-free technology (0BB, Zero Busbar) or multi-busbar technology (MBB, MULTI-BUSBAR), full back electrode contact cells (IBC, Interdigitated Back Contact), full back contact cell solar cells (ABC, All Back Contact), composite passivated back contact cells (HPBC, Hybrid Passivated Back Contact), emitter back passivated cells (PERC, Passivated Emitter and Rear Cell), tunneling oxide passivated contact cells (TOPcon, Tunnel Oxide Passivated Contact), TOPcon-IBC cells, crystalline silicon heterojunction solar cells (HJT, Heterojunction with Intrinsic Thin-layer), perovskite stacked cells, flexible cells and other photovoltaic cells.

[0088] The method for preparing the solar cell of the present application will be described in detail below with reference to specific embodiments and comparative examples.

[0089] Example 1

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

[0091] Providing an N-type substrate, and performing texturing on a first surface of the N-type substrate, wherein the first surface includes a metal region and a non-metal region, and the material of the N-type substrate is silicon-based and has a thickness of 100 μm;

[0092] A second P-type emitter is formed on the first surface, and the doping concentration of the second P-type emitter is 1×10 19 cm -3 , the junction depth is 0.5μm;

[0093] The second P-type emitter located in the metal region is subjected to laser amorphization treatment, so that the second P-type emitter in the metal region forms a first P-type emitter and a barrier layer, the first P-type emitter is located between the barrier layer and the N-type substrate, and the doping concentration of the first P-type emitter is 1×10 20 cm -3 , the junction depth is 1μm, the material of the barrier layer is P-type amorphous silicon, and the thickness is 0.5μm;

[0094] Depositing a first passivation layer on the barrier layer and the second P-type emitter, and performing an opening process on the portion of the first passivation layer in the metal region, wherein the material of the first passivation layer is silicon oxide and has a thickness of 70 nm;

[0095] Printing a first electrode on the first passivation layer, the first electrode is in contact with the isolation layer through the opening, the first electrode has a thickness of 70 nm and is made of Ag;

[0096] A tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes are formed on the second surface of the N-type substrate along the direction from the first passivation layer to the N-type substrate, wherein the material of the tunneling dielectric layer is silicon oxide with a thickness of 1 nm, the material of the doped conductive layer is silicon carbide with a thickness of 50 nm, and the material of the second electrode is Ag with a thickness of 5 μm.

[0097] Example 2

[0098] The present application provides a method for preparing a solar cell. The only difference between this method and Example 1 is that the doping concentration of the first P-type emitter is 1×10 22 cm -3 , the doping concentration of the second P-type emitter is 1×10 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 23 cm -3 , the doping concentration of the second P-type emitter is 1×10 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 20 cm -3 , the doping concentration of the first P-type emitter is 1×10 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 20 cm -3 , the doping concentration of the first P-type emitter is 1×10 19 cm -3 .

[0107] The performance of the solar cells prepared by the methods for preparing solar cells in the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 3 was tested, and the test results are as follows:

[0108] Table 1

[0109]

[0110]

[0111] It can be seen from the above experimental data that the turn-on voltage, short-circuit current density, fill factor and photoelectric conversion efficiency in Examples 1 to 3 are higher than those in Comparative Examples 1 to 3, indicating that the solar cell in the present application having a barrier layer and a second P-type emitter in the metal region whose doping concentration is lower than that of the first P-type emitter in the metal region can effectively reduce the excessive diffusion of electrode ions of the metal electrode, and reduce the contact resistance and surface recombination between the first electrode and the N-type substrate, thereby improving the battery efficiency.

[0112] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0113] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0114] The solar cell proposed in the present application is formed with a blocking layer. When the metal ions in the first electrode diffuse to the second P-type emitter, the blocking layer can block at least part of the above metal ions, thereby reducing the content of the metal ions diffused into the second P-type emitter and the N-type substrate, thereby reducing the generation of metal elements, avoiding the second P-type emitter and the N-type substrate from being destroyed by the metal element, thereby solving the problem of excessive diffusion of electrode ions in the metal electrode of the solar cell in the related art leading to reduced battery efficiency. And in the P-type emitter layer of the solar cell, the above second doping concentration of the above second P-type emitter is less than the above first doping concentration of the above first P-type emitter. Such a doping concentration design can reduce the recombination of the carrier surface caused by the high doping concentration, thereby ensuring a high life of the minority carriers, thereby ensuring a high open circuit voltage and short circuit current of the battery; on the other hand, such a doping concentration design can reduce the problem of high contact resistance caused by low doping concentration, thereby ensuring a low contact resistance and a low opening voltage of the battery. On the other hand, due to the concentration difference between the first P-type emitter and the second P-type emitter, the carriers can be transferred to the N-type substrate faster, which is also conducive to improving the photoelectric conversion efficiency. Therefore, such a concentration design makes the photoelectric conversion efficiency of the solar cell higher.

[0115] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A solar cell, characterized in that: include: An N-type substrate having a first surface and a second surface opposite to each other, wherein the first surface includes 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 comprises: a first P-type emitter and a second P-type emitter, the first P-type emitter is located in the non-metallic region, the first P-type emitter has a first doping concentration, the second P-type emitter is located in the metal region, the second P-type emitter has a second doping concentration, the second doping concentration is less than the first doping concentration, the first passivation layer is located on a side of the P-type emitter layer away from the N-type substrate, the first electrode is located on a side of the second P-type emitter away from the N-type substrate, the barrier layer is located between the first electrode and the second P-type emitter, and the barrier layer is used to block metal ions of the first electrode from diffusing into the second P-type emitter; A tunneling dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes are located on the second surface.

2. The solar cell according to claim 1, characterized in that 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 .

3. The solar cell according to claim 1, characterized in that 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.

4. The solar cell according to claim 1, characterized in that The square resistance of the second P-type emitter is 100Ω / square to 800Ω / square.

5. The solar cell according to claim 1, characterized in that: The material of the barrier layer includes P-type amorphous silicon.

6. The solar cell according to claim 1, characterized in that The doping concentration of the blocking layer is less than or equal to the first doping concentration.

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

8. A method for preparing a solar cell according to any one of claims 1 to 7, characterized in that: include: Providing an N-type substrate, the N-type substrate having a first surface and a second surface opposite to each other, 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 are formed 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-metallic region and has a first doping concentration, and the second P-type emitter is located in the metal region and has a second doping concentration, which is less than the first doping concentration; The first electrode is located on a side of the second P-type emitter away from the N-type substrate; The first passivation layer is located on a side of the P-type emitter layer away from the N-type substrate; The blocking layer is located between the first electrode and the second P-type emitter, and the blocking layer is used to block the metal ions in the first electrode from diffusing into the N-type substrate; A tunnel dielectric layer, a doped conductive layer, a second passivation layer and a plurality of second electrodes are formed on the second surface.

9. The preparation method according to claim 8, characterized in that: The steps of forming the P-type emitter layer and the barrier layer include: 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 in the metal region is subjected to laser amorphization treatment to obtain the second P-type emitter and the barrier layer in the metal region, wherein the barrier layer is located on the side of the second P-type emitter away from the N-type substrate, and the second P-type emitter has a second doping concentration, which is less than the first doping concentration.

10. A photovoltaic module, characterized in that: Comprising at least one solar cell according to any one of claims 1 to 7.

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