Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention belongs to the field of solar cells, and discloses a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises a silicon substrate, the silicon substrate is provided with a first surface and a second surface which are oppositely arranged, the second surface comprises a first area and a second area which are alternately arranged, the second surface is provided with a first doping layer, the doping type of the first doping layer is the same as that of the silicon substrate, and the orthographic projection of the first doping layer on the second surface is located in the first area; the oxide layer is positioned on one side, far away from the silicon substrate, of the first doping layer; the first passivation layer is arranged on the first area, the first passivation layer is located on the face, away from the silicon substrate, of the oxide layer, and the first passivation layer is in contact with the silicon substrate on the second area; and the first electrode is in electric contact with the first doped layer. Therefore, the second surface of the solar cell can be partitioned to achieve a good passivation effect.

Description

Technical Field

[0001] This application belongs to the field of solar cells, and particularly relates to a solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] Tunnel oxide passivated contact (TOPCon) solar cells have become the mainstream product for industrial solar cell manufacturers due to their excellent passivated contact structure, which can effectively reduce carrier recombination losses at the metal contacts on the cell surface.

[0003] The combination of a highly doped polycrystalline silicon layer (Poly silicon layer) and an extremely thin tunnel oxide (SiOx) layer gives TOPCon solar cells excellent surface and chemical passivation effects. However, the polycrystalline silicon layer formed on the tunnel oxide layer can introduce parasitic absorption, leading to a decrease in the short-circuit current of the solar cell. Furthermore, the quality of the tunnel oxide layer and the doped polycrystalline silicon layer can also affect the stability of the cell's passivation effect.

[0004] Therefore, current solar cells, their fabrication methods, and photovoltaic modules still need improvement. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a solar cell, a method for its fabrication, and a photovoltaic module.

[0006] In a first aspect, this application provides a solar cell, comprising:

[0007] A silicon substrate having a first surface and a second surface disposed opposite to each other, the second surface having a first doped layer having the same doping type as the silicon substrate, the second surface including alternating first regions and second regions, the orthographic projection of the first doped layer on the second surface being located in the first region;

[0008] An oxide layer is disposed on the side of the first doped layer away from the silicon substrate;

[0009] A first passivation layer is disposed on the side of the oxide layer away from the silicon substrate in the first region, and in the second region, the first passivation layer is in contact with the silicon substrate.

[0010] The first electrode is in electrical contact with the first doped layer.

[0011] According to the solar cell of this application, the second surface of the solar cell can be partitioned to achieve a good passivation effect.

[0012] According to one embodiment of this application, the silicon substrate protrudes in the first region in a direction away from the silicon substrate relative to the second region, and / or the silicon substrate is recessed in the second region in a direction closer to the silicon substrate relative to the first region.

[0013] According to one embodiment of this application, the height difference between the surface of the silicon substrate in the first region and the surface of the silicon substrate in the second region is 3 μm to 5 μm.

[0014] According to one embodiment of this application, the first passivation layer covers the sides of the oxide layer and the first doped layer.

[0015] According to one embodiment of this application, the first electrode penetrates the oxide layer and is in electrical contact with the first doped layer.

[0016] According to one embodiment of this application, the doping concentration of the first doped layer is greater than the doping concentration of the silicon substrate; and / or, the first doped layer has the same crystal structure as the silicon substrate.

[0017] According to an embodiment of this application, the first doped layer satisfies at least one of the following conditions:

[0018] The doping element of the first doped layer includes phosphorus.

[0019] The doping concentration of the first doped layer is 1×10 19 cm -3 ~1×10 22 cm -3 ;

[0020] The thickness of the first doped layer is 300 nm to 500 nm;

[0021] The sheet resistance of the first doped layer is 20Ω / sq to 70Ω / sq.

[0022] According to one embodiment of this application, at least one of the following conditions is met:

[0023] The oxide layer comprises silicon oxide;

[0024] The thickness of the oxide layer is 1 nm to 4 nm;

[0025] The first passivation layer comprises aluminum oxide;

[0026] The thickness of the first passivation layer is 2nm to 10nm.

[0027] According to one embodiment of this application, it also includes:

[0028] A first anti-reflection layer is located on the side of the first passivation layer away from the silicon substrate;

[0029] A second doped layer is located on the first surface of the silicon substrate, and the doping type of the second doped layer is opposite to that of the first doped layer.

[0030] A second passivation layer is located on the side of the second doped layer away from the silicon substrate;

[0031] A second antireflection layer is located on the side of the second passivation layer away from the silicon substrate;

[0032] The second electrode is located on the first surface of the silicon substrate and is in electrical contact with the second doped layer.

[0033] According to one embodiment of this application, at least one of the following conditions is met:

[0034] The first antireflective layer comprises one or more of silicon oxide, silicon nitride, and silicon oxynitride;

[0035] The thickness of the first antireflective layer is 10nm to 130nm;

[0036] The doping element of the second doped layer includes boron;

[0037] The doping concentration of the second doped layer is 1×10 18 cm -3 ~1×10 20 cm -3 ;

[0038] The sheet resistance of the second doped layer is 50Ω / sq to 400Ω / sq;

[0039] The second passivation layer comprises aluminum oxide;

[0040] The thickness of the second passivation layer is 2nm to 10nm;

[0041] The second antireflective layer comprises one or more of silicon oxide, silicon nitride, and silicon oxynitride;

[0042] The thickness of the second antireflective layer is 10nm to 130nm.

[0043] Secondly, this application provides a method for preparing a solar cell, the method comprising:

[0044] A silicon substrate is provided, the silicon substrate having a first surface and a second surface disposed opposite to each other, the second surface including alternating first regions and second regions;

[0045] The second surface of the silicon substrate is doped to form a full-layer first doped layer.

[0046] The first doped layer in the first region is subjected to laser oxidation to form an oxide layer;

[0047] Alkali etching is performed to remove the first doped layer on the second region;

[0048] A first passivation layer is formed on the second surface;

[0049] A first electrode is formed on the second surface.

[0050] The method for preparing solar cells according to this application provides that the solar cells prepared by this method possess all the features and advantages of the solar cells described above, which will not be repeated here.

[0051] According to one embodiment of this application, a phosphorus-containing element is used as a diffusion source to dope the second surface of the silicon substrate to form a first doped layer with a thickness of 300 nm to 500 nm.

[0052] According to one embodiment of this application, the first doped layer on the first region is subjected to laser oxidation treatment, and the thickness of the oxide layer formed is 5nm to 15nm.

[0053] And / or, laser oxidation treatment is performed using ultraviolet picosecond laser or green picosecond laser, wherein the ultraviolet picosecond laser spot power is 3W to 20W, the spot diameter is 100μm to 150μm, the frequency is 500kHz to 600kHz, and the scan speed is 40000mm / s to 70000mm / s; the green picosecond laser spot power is 5W to 50W, the spot diameter is 100μm to 500μm, the frequency is 500kHz to 600kHz, and the scan speed is 40000mm / s to 70000mm / s.

[0054] According to one embodiment of this application, during alkaline etching, the oxide layer in the first region is thinned.

[0055] According to one embodiment of this application, it also includes:

[0056] Using BCl3 and / or BBr3 as a diffusion source, boron diffusion is performed on the first surface of the silicon substrate to form a second doped layer. The boron diffusion temperature is 900℃~1100℃. The doping type of the second doped layer is opposite to that of the first doped layer.

[0057] A second passivation layer is formed on the side of the second doped layer away from the silicon substrate;

[0058] A first antireflection layer is formed on the side of the first passivation layer away from the silicon substrate;

[0059] A second antireflection layer is formed on the side of the second passivation layer away from the silicon substrate;

[0060] A second electrode is formed.

[0061] Thirdly, this application provides a photovoltaic module, including the solar cell as described above.

[0062] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0063] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0064] Figure 1 This is a schematic diagram of the structure of a solar cell according to an embodiment of this application;

[0065] Figure 2 This is one of the partial flowcharts for the fabrication of solar cells according to embodiments of this application;

[0066] Figure 3 This is a second partial flowchart of the solar cell fabrication process according to an embodiment of this application;

[0067] Figure 4 This is the third part of the flowchart for fabricating solar cells according to the embodiments of this application;

[0068] Figure 5 This is the fourth part of the flowchart for preparing solar cells according to the embodiments of this application.

[0069] Figure label:

[0070] 1: Silicon substrate; 2: Second doped layer; 3: First doped layer; 4: Oxide layer; 5: First passivation layer; 6: First antireflection layer; 7: Second electrode; 8: First electrode; 9: Second passivation layer; 10: Second antireflection layer; 11: First region; 12: Second region; 13: Borosilicate glass layer; 14: Phosphosilicate glass layer. Detailed Implementation

[0071] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0072] In one aspect of this application, a solar cell is provided. In some embodiments of this application, reference is made to... Figure 1 The solar cell includes a silicon substrate 1, a first doped layer 3, an oxide layer 4, a first passivation layer 5, and a first electrode 8.

[0073] refer to Figure 1 The silicon substrate 1 has a first surface and a second surface disposed opposite to each other. The second surface has a first doped layer 3. The first doped layer 3 and the silicon substrate 1 have the same doping type. For example, the first doped layer 3 and the silicon substrate 1 are both N-type doped. The second surface includes an alternately arranged first region 11 and a second region 12. The orthographic projection of the first doped layer 3 on the second surface is located in the first region 11. The first surface corresponds to the light-receiving surface of the solar cell, and the second surface corresponds to the back-lighting surface of the solar cell. When the solar cell is in use, the first surface faces the light source, and the second surface faces away from the light source.

[0074] Electrodes are provided on the first region 11, and no electrodes are provided on the second region 12.

[0075] In some embodiments of this application, the first doped layer 3 has the same doping type as the silicon substrate 1, as shown in the reference. Figure 1 The first doped layer 3 is projected onto the second surface in the first region 11; the oxide layer 4 is located on the side of the first doped layer 3 away from the silicon substrate 1; in the first region 11, the first passivation layer 5 is located on the side of the oxide layer 4 away from the silicon substrate 1, and in the second region 12, the first passivation layer 5 is in contact with the silicon substrate 1; the first electrode 8 is in electrical contact with the first doped layer 3. Thus, the second surface of the solar cell can achieve a partitioned passivation effect.

[0076] In the first region, the oxide layer can combine with the dangling bonds on the surface of the first doped layer to achieve chemical passivation, and the positive charge in the oxide layer can also generate field-effect passivation. In the second region, the first passivation layer can play a passivation role and reduce the recombination rate.

[0077] In some embodiments of this application, the first electrode 8 penetrates the oxide layer 4 and is in electrical contact with the first doped layer 3.

[0078] In some embodiments of this application, reference is made to Figure 1 A first doped layer 3 is disposed on the second surface of the silicon substrate 1. The doping type of the first doped layer 3 is the same as that of the silicon substrate 1, and the doping concentration of the first doped layer 3 is greater than that of the silicon substrate 1. The oxide layer 4 includes silicon oxide, the first passivation layer 5 includes aluminum oxide, and the first electrode 8 penetrates the first passivation layer 5 and the oxide layer 4 to make electrical contact with the first doped layer 3. Thus, the second surface of the solar cell can be partitioned to achieve a good passivation effect.

[0079] The principle behind the solar cell proposed in this application, which achieves good passivation effect through partitioning on the second surface, is explained in detail below:

[0080] Taking the first doped layer and silicon substrate as N-type doping and the first passivation layer as aluminum oxide as an example, for the stacked structure of the second surface of the first region, the aluminum oxide in the first passivation layer has a high concentration of negative charge, which will adsorb minority carriers (holes) in the first doped layer to the surface of the first doped layer, increasing the surface recombination rate and hindering the improvement of the passivation effect.

[0081] In this application, an oxide layer is provided between the first doped layer and the first passivation layer. On the one hand, the silicon oxide in the oxide layer can combine with the dangling bonds on the surface of the first doped layer to form Si-O bonds, thereby performing chemical passivation and improving the passivation effect. On the other hand, the fixed positive charge in the silicon oxide can generate a field-effect passivation effect, reduce the defect density on the surface of the first doped layer, isolate the passivation side effects of the first passivation layer on the first doped layer, and further improve the passivation effect of the first region of the second surface.

[0082] In the second region, the first passivation layer is in direct contact with the second surface of the silicon substrate. The high concentration of negative charge in the alumina will adsorb minority carriers (holes) in the silicon substrate to the surface. Since the electron concentration in the silicon substrate is low, the alumina will adsorb a large number of holes to the surface of the silicon substrate. The hole concentration on the surface of the silicon substrate is much higher than the electron concentration, which will form a p-type inversion layer. In the p-type inversion layer, electrons are minority carriers. The concentration of electrons can reduce the recombination rate, thereby playing a good passivation role. A positive charge electric field will be formed on the surface of the silicon substrate. The alumina can play a good passivation role for the film layer with positive charge as the charge carrier.

[0083] Similarly, when the doping type of the first doped layer and the silicon substrate is P-type, an oxide layer is set between the first doped layer and the first passivation layer in the first region of the second surface to form a stacked structure. In the second region, the first passivation layer is in direct contact with the silicon substrate, and the solar cell can also achieve a good passivation effect by partitioning the second surface.

[0084] In some specific embodiments of this application, the silicon substrate 1 can be an N-type silicon wafer or a P-type silicon wafer. When the silicon substrate 1 is an N-type silicon wafer, the resistivity can be 0.3 Ω·cm to 7 Ω·cm.

[0085] In some embodiments of this application, the silicon substrate 1 and the first doped layer 3 have the same doping type, preferably both being N-type doped.

[0086] In some embodiments of this application, the doping element of the silicon substrate 1 may include phosphorus.

[0087] In some embodiments of this application, the doping element of the first doped layer 3 may include phosphorus.

[0088] In some embodiments of this application, the doping concentration of the first doped layer 3 is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3 .

[0089] For example, the doping concentration of the first doped layer 3 can be 1×10⁻⁶. 19 cm -3 3×10 19 cm -3 5×10 19 cm -3 8×10 19 cm -3 , 1×10 20 cm -3 3×10 20 cm -3 5×10 20 cm -3 7×10 20 cm -3 , 1×10 21 cm -3 5×10 21 cm -3 Or 1×10 22 cm -3 .

[0090] In some specific embodiments of this application, the first doped layer 3 is a phosphorus-doped silicon layer, and the doping concentration of the first doped layer 3 is 1×10⁻⁶. 19 cm -3 ~1×10 22 cm -3 This improves the ohmic contact between the first doped layer 3 and the first electrode 8, reducing the series resistance.

[0091] In some embodiments of this application, the doping concentration of the first doped layer 3 is 5 × 10⁻⁶. 19 cm -3 ~5×10 20 cm -3 This can reduce surface recombination while improving the ohmic contact between the first doped layer 3 and the first electrode 8 and reducing the series resistance.

[0092] In some embodiments of this application, the thickness of the first doped layer 3 is no greater than 500 nm.

[0093] In some embodiments of this application, the thickness of the first doped layer 3 can be 300nm to 500nm. For example, the thickness of the first doped layer 3 can be 300nm, 350nm, 400nm, 450nm or 500nm.

[0094] It should be noted that the thickness of the first doped layer 3 refers to the distance between the surface of the first doped layer in contact with the oxide layer 4 and the surface of the first doped layer 3 in contact with the silicon substrate 1.

[0095] The thickness of the first doped layer 3 is within the above range, which can prevent the first electrode from penetrating the first doped layer, thereby preventing the first electrode from directly contacting the silicon substrate.

[0096] In some embodiments of this application, the sheet resistance of the first doped layer 3 is 20 Ω / sq to 70 Ω / sq. For example, the sheet resistance of the first doped layer 3 can be 20 Ω / sq, 30 Ω / sq, 40 Ω / sq, 50 Ω / sq, 60 Ω / sq, or 70 Ω / sq. Therefore, the first doped layer has good conductivity, which is beneficial for improving the contact effect of the second surface.

[0097] In some embodiments of this application, the thickness of oxide layer 4 is 1 nm to 4 nm. For example, the thickness of oxide layer 4 can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm or 4 nm.

[0098] If the oxide layer 4 is too thin, it will be difficult to achieve the desired passivation effect; if the oxide layer 4 is too thick, it will affect the ohmic contact between the first electrode 8 and the first doped layer 3.

[0099] In some embodiments of this application, the first passivation layer 5 may be an aluminum oxide layer.

[0100] The alumina layer in the second region can play a good passivation role. Specifically, the high concentration of negative charges in the alumina layer can adsorb minority carriers in the silicon substrate to the surface. The electron concentration in the silicon substrate is low, and the hole concentration adsorbed on the surface by the alumina is much higher than the electron concentration. This can form a P-type inversion layer near the surface of the silicon substrate. In the P-type inversion layer, electrons are minority carriers. The reduced concentration of electrons can reduce the recombination rate, thereby improving the passivation effect.

[0101] In some embodiments of this application, reference is made to Figure 1 The first passivation layer 5 covers the side surfaces of the oxide layer 4 and the first doped layer 3. Therefore, passivating the side surfaces with the first passivation layer improves the overall passivation effect.

[0102] In some embodiments of this application, the thickness of the first passivation layer 5 is 2nm to 10nm. For example, the thickness of the first passivation layer 5 can be 2nm, 3nm, 5nm, 6nm, 7nm, 9nm or 10nm.

[0103] A thinner first passivation layer can effectively reduce the recombination loss of electrons and holes in the second region, and has little impact on current transport, thus helping to further improve the performance of solar cells.

[0104] In some embodiments, the thickness of the first passivation layer 5 can be 2 nm to 7 nm.

[0105] In some embodiments, the thickness of the first passivation layer 5 can be 3 nm to 6 nm.

[0106] In some embodiments of this application, the silicon substrate 1 protrudes in the first region 11 in a direction away from the silicon substrate 1 relative to the second region 12, and the silicon substrate 1 is recessed in the second region 12 in a direction closer to the silicon substrate 1 relative to the first region 11. That is, the silicon substrate 1 forms a boss in the first region 11 and a groove in the second region 12. The silicon substrate thickness in the first region 11 where the oxide layer 4 is located is greater than the silicon substrate thickness in the second region 12.

[0107] In some embodiments of this application, the height difference between the surface of the silicon substrate 1 in the first region 11 and the surface of the silicon substrate 1 in the second region 12 is 3 μm to 5 μm.

[0108] refer to Figure 1 The distance between the surface of silicon substrate 1 in the first region 11 and the first surface is a, the distance between the surface of silicon substrate 1 in the second region 12 and the first surface is b, a > b, and the height difference between the surface of silicon substrate 1 in the first region 11 and the surface of silicon substrate 1 in the second region 12 is ab = 3μm ~ 5μm.

[0109] For example, ab can be 3μm, 3.5μm, 4μm, 4.5μm or 5μm. The back side of the silicon substrate 1 is basically undamaged, which is beneficial to further improve the passivation effect.

[0110] In some embodiments of this application, the first electrode 8 may be a silver electrode.

[0111] In some embodiments, the first electrode 8 may include a main gate and a sub-gate.

[0112] In some embodiments of this application, reference is made to Figure 1 The solar cell may also include a first antireflection layer 6, which is located on the side of the first passivation layer 5 away from the silicon substrate 1. The first antireflection layer can reduce the reflectivity of incident light and improve the light utilization efficiency of the solar cell.

[0113] In some embodiments of this application, the first antireflective layer 6 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride.

[0114] In some embodiments, the first antireflective layer 6 may be a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer. In other embodiments, the first antireflective layer 6 may include a plurality of stacked film layers.

[0115] In some embodiments, the first antireflection layer 6 may include at least two of the following layers: a silicon nitride layer, a silicon oxide layer, and a silicon oxynitride layer.

[0116] In some embodiments of this application, the thickness of the first antireflection layer 6 is 10nm to 130nm. For example, the thickness of the first antireflection layer 6 can be 10nm, 30nm, 50nm, 60nm, 80nm, 100nm, 120nm or 130nm.

[0117] In some embodiments, the thickness of the first antireflective layer 6 can be 60 nm to 130 nm.

[0118] In some embodiments of this application, reference is made to Figure 1 The solar cell may include a second doped layer 2, which is located on the first surface of the silicon substrate 1. The doping type of the second doped layer 2 is opposite to that of the first doped layer 3, while the doping type of the first doped layer 3 is the same as that of the silicon substrate 1. Taking the first doped layer 3 as N-type, the second doped layer 2 as P-type, and the silicon substrate 1 as an N-type silicon wafer as an example, the second doped layer 2 acts as an emitter, forming a PN junction with the N-type silicon wafer. Under illumination, it can generate photocurrent, thereby realizing the photoelectric conversion function of the solar cell.

[0119] In some embodiments of this application, the doping element of the second doped layer 2 includes boron.

[0120] In some embodiments of this application, the doping concentration of the second doped layer 2 is 1×10⁻⁶. 18 cm -3 ~1×10 20 cm -3 For example, the doping concentration of the second doped layer 2 can be 1×10⁻⁶. 18 cm -3 5×10 18 cm -3 , 1×10 19 cm -3 5×10 19 cm -3 Or 1×10 20 cm -3 Therefore, the second doped layer has good conductivity, which is beneficial for current transmission.

[0121] In some specific embodiments, the boron doping concentration in the second doped layer 2 is 1×10⁻⁶. 18 cm -3 ~1×1020 cm -3 .

[0122] In some embodiments of this application, the sheet resistance of the second doped layer 2 is 50Ω / sq to 400Ω / sq. For example, the sheet resistance of the second doped layer 2 can be 50Ω / sq, 80Ω / sq, 100Ω / sq, 150Ω / sq, 200Ω / sq, 300Ω / sq or 400Ω / sq.

[0123] In some embodiments of this application, reference is made to Figure 1 The solar cell also includes a second passivation layer 9, which is located on the side of the second doped layer 2 away from the silicon substrate 1.

[0124] In some embodiments of this application, the second passivation layer 9 includes aluminum oxide, which can play a good role in the first surface passivation, thereby helping to further improve the performance of the solar cell.

[0125] In some embodiments of this application, the thickness of the second passivation layer 9 is 2nm to 10nm. For example, the thickness of the second passivation layer 9 can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm or 10nm.

[0126] In some embodiments, the thickness of the second passivation layer 9 can be 2 nm to 7 nm.

[0127] In other embodiments, the thickness of the second passivation layer 9 can be 3 nm to 6 nm.

[0128] In some embodiments of this application, reference is made to Figure 1 The solar cell may also include a second antireflection layer 10, which is located on the side of the second passivation layer 9 away from the silicon substrate 1.

[0129] In some embodiments of this application, the second antireflective layer 10 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride.

[0130] In some embodiments, the second antireflection layer 10 may be a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer.

[0131] In other embodiments, the second antireflection layer 10 may include a plurality of stacked film layers.

[0132] In some embodiments, the second antireflection layer 10 may include at least two of the following layers: a silicon nitride layer, a silicon oxide layer, and a silicon oxynitride layer.

[0133] In some embodiments of this application, the thickness of the second antireflection layer 10 is 10nm to 130nm. For example, the thickness of the second antireflection layer 10 can be 10nm, 30nm, 50nm, 60nm, 80nm, 100nm, 120nm or 130nm.

[0134] In some embodiments, the thickness of the second antireflection layer 10 can be 60 nm to 130 nm.

[0135] In some embodiments, reference Figure 1 The first surface of the silicon substrate 1 has a textured structure, and the second doped layer 2, the second passivation layer 9, and the second antireflection layer 10 above the silicon substrate 1 can also have textured structures.

[0136] In some embodiments of this application, reference is made to Figure 1 The solar cell also includes a second electrode 7, which is located on the first surface of the silicon substrate 1 and is in electrical contact with the P-type first doped layer 2.

[0137] In some embodiments of this application, reference is made to Figure 1 The second electrode 7 penetrates the second antireflection layer 10 and the second passivation layer 9 to contact the second doped layer 2. (Reference) Figure 1 The second electrode 7 does not penetrate the second doped layer 2.

[0138] In some embodiments, the second electrode 7 may be a silver electrode.

[0139] In some embodiments, the second electrode 7 may include a main gate and a sub-gate.

[0140] In another aspect of this application, a method for preparing the aforementioned solar cell is proposed.

[0141] In some embodiments of this application, reference is made to Figures 2 to 5 The method for preparing the aforementioned solar cell may include the following steps:

[0142] S100: Provides silicon substrate 1.

[0143] refer to Figure 2 The silicon substrate 1 has a first surface and a second surface disposed opposite to each other, the second surface including alternating first regions 11 and second regions 12. In subsequent fabrication processes, electrodes are formed on the first region 11, but no electrodes are formed on the second region 12.

[0144] The silicon substrate 1 can be an N-type silicon wafer with a resistivity of 0.3 Ω·cm to 7 Ω·cm.

[0145] In some embodiments of this application, the silicon substrate may be a monocrystalline silicon wafer or a polycrystalline silicon wafer.

[0146] Before phosphorus diffusion, the silicon substrate 1 can be texturized on both sides, as shown in the reference. Figure 2 Alkali solution can be used for texturing to form a pyramidal textured surface on the first and second surfaces of the silicon substrate 1.

[0147] In some embodiments of this application, reference is made to Figure 2 A second doped layer 2 and a borosilicate glass layer (BSG) 13 can be formed on the first surface of the silicon substrate 1 by tubular diffusion. The doping type of the second doped layer 2 is opposite to that of the first doped layer 3.

[0148] In some embodiments of this application, BCl3 and / or BBr3 can be used as diffusion sources to perform boron diffusion on the first surface of the silicon substrate 1 to form a second doped layer 2, and the boron diffusion temperature is 900℃~1100℃.

[0149] In some embodiments, BCl3 or BBr3 can be used as a diffusion source for boron diffusion, allowing boron to enter the silicon matrix and form a boron-doped silicon layer of a certain depth.

[0150] In some embodiments, the boron diffusion temperature can be 900°C, 950°C, 1000°C, 1050°C, or 1100°C. At these temperatures, boron can be doped into the silicon substrate to form a second doped layer 2. During the boron diffusion process, a borosilicate glass (BSG) layer 13 is formed on the surface of the second doped layer 2.

[0151] In some embodiments, the sheet resistance of the second doped layer 2 can be 50 Ω / sq to 400 Ω / sq, and the doping concentration of the second doped layer 2 can be 1 × 10⁻⁶. 18 cm -3 ~1×10 20 cm -3 .

[0152] In some embodiments, the thickness of the borosilicate glass layer 13 can be 30 nm to 150 nm.

[0153] It should be noted that during the boron diffusion process, boron also diffuses into the second surface and surrounding areas of the silicon substrate, forming a borosilicate glass layer on the surface. Figure 2 Not shown in the diagram. Before phosphorus diffusion, the silicon wafer can first pass through a single-sided HF chain apparatus to remove the borosilicate glass layer on the second surface and around the silicon substrate. Then, it passes through a tank apparatus for alkaline polishing of the second surface to remove the edge junctions and the second surface diffusion, retaining the BSG and boron junction (second doped layer) on the first surface, as shown in the diagram. Figure 2 As shown. Alkali polishing of the second surface can remove the pyramidal texture of the second surface, allowing it to maintain a planar structure, as shown. Figure 2 As shown.

[0154] S200: Phosphorus diffusion is performed on the second surface of silicon substrate 1 to form a full-layer first doped layer 3.

[0155] refer to Figure 3 After alkaline polishing of the second surface, phosphorus diffusion is performed on the second surface of the silicon substrate 1 to form a full-layer first doped layer 3.

[0156] In some embodiments of this application, phosphorus diffusion can be performed by using POCl3 as a diffusion source through tubular diffusion to form a first doped layer with a thickness of 300 nm to 500 nm.

[0157] In some embodiments of this application, reference is made to Figure 3 During the phosphorus diffusion process, a phosphorus silicate glass (PSG) layer will form on the outermost layer.14

[0158] In some embodiments, the thickness of the phosphosilicate glass layer 14 can be 2 nm to 50 nm.

[0159] In some embodiments of this application, reference is made to Figure 3 After phosphorus diffusion, the phosphorus-silicon glass layer 14 on the second surface can be removed using a single-sided HF chain device.

[0160] S300: Laser oxidation is performed on the first doped layer 3 on the first region 11 to form an oxide layer 4.

[0161] In some embodiments of this application, reference is made to Figure 3 The first doped layer 3 on the first region 11 is subjected to laser oxidation treatment, and the thickness of the oxide layer 4 formed can be 5nm to 15nm. For example, the thickness of the oxide layer formed by laser oxidation treatment can be 5nm, 7nm, 10nm, 12nm or 15nm. The oxide layer of the above thickness can play a certain protective role in the subsequent alkaline etching process.

[0162] In some embodiments of this application, the first doped layer 3 on the first region 11 can be laser oxidized in an air atmosphere, so that the first doped layer 3 on the first region 11 is partially oxidized and converted into silicon oxide to form an oxide layer 4.

[0163] In some embodiments of this application, ultraviolet picosecond lasers or green picosecond lasers can be used to perform laser oxidation treatment on the first doped layer in the first region.

[0164] In some embodiments, an ultraviolet picosecond laser can be used to perform laser oxidation treatment on the first doped layer in the first region. The ultraviolet picosecond laser spot power can be 3W to 20W, the spot diameter can be 100μm to 150μm, the frequency can be 500kHz to 600kHz, and the scan speed can be 40000mm / s to 70000mm / s.

[0165] In some specific embodiments, the ultraviolet picosecond laser spot power can be 3W, 5W, 8W, 10W, 12W, 15W, 17W or 20W, the spot diameter can be 100μm, 110μm, 120μm, 140μm or 150μm, the frequency can be 500kHz, 510kHz, 530kHz, 550kHz, 580kHz or 600kHz, and the scan speed can be 40000mm / s, 50000mm / s, 60000mm / s or 70000mm / s.

[0166] In some embodiments, a green picosecond laser can be used to perform laser oxidation treatment on the first doped layer in the first region, wherein the green picosecond laser spot power is 5W to 50W, the spot diameter is 100μm to 500μm, the frequency is 500kHz to 600kHz, and the scan speed is 40000mm / s to 70000mm / s.

[0167] In some specific embodiments, the green picosecond laser spot power can be 5W, 10W, 20W, 30W or 50W, the spot diameter can be 100μm, 200μm, 300μm, 400μm or 500μm, the frequency can be 500kHz, 530kHz, 550kHz, 570kHz or 600kHz, and the scan speed can be 40000mm / s, 50000mm / s, 60000mm / s or 70000mm / s.

[0168] Laser oxidation of the first doped layer in the first region using ultraviolet picosecond laser or green picosecond laser can partially oxidize the first doped layer to form silicon oxide. The silicon oxide can combine with the dangling bonds on the surface of the first doped layer to form silicon-oxygen bonds, thus performing chemical passivation. The fixed positive charge of silicon oxide can also generate field effect passivation, reducing the defect density on the surface of the first doped layer.

[0169] S400: Perform alkaline etching to remove the first doped layer 3 on the second region 12 and thin the oxide layer 4 on the first region 11.

[0170] In some embodiments of this application, reference is made to Figure 4Alkali etching can be performed using a tank-type equipment to remove the first doped layer 3 on the second region 12 and thin the oxide layer 4 on the first region 11. During the etching process, the first surface and edge plating will also be removed.

[0171] In some embodiments of this application, during alkaline etching, the oxide layer 4 on the first region 11 can play a certain protective role. The first doped layer 3 on the first region 11 is retained, and the oxide layer 4 will participate in the reaction and be partially etched, retaining an oxide layer 4 with a thickness of 1nm to 4nm. The retained oxide layer can improve the passivation effect of the first region.

[0172] In some embodiments of this application, reference is made to Figure 4 During alkaline etching, a portion of the silicon substrate 1 on the second region 12 can be etched away, creating a height difference between the silicon substrate 1 on the second region 12 and the first region 11. This allows for the complete removal of the first doped layer on the second region, thereby improving the passivation effect of the second region.

[0173] In some embodiments of this application, reference is made to Figure 4 During alkaline etching, a portion of the oxide layer 4 on the first region 11 is etched away, leaving an oxide layer 4 with a thickness of 1nm to 4nm. During laser processing, thermal damage occurs, removing the damaged oxide layer to a certain depth, which helps improve the passivation effect.

[0174] In some embodiments of this application, the alkaline etching time can be 300s to 500s, the temperature can be 50℃ to 90℃, and the volume concentration of alkali (sodium hydroxide and / or potassium hydroxide) in the etching solution used for alkaline etching can be 0.5% to 2%, and the volume concentration of additives can be 0.5% to 1%.

[0175] In some embodiments, reference Figure 4 After alkaline etching, the borosilicate glass layer 13 on the first surface of the silicon substrate 1 can be removed using an HF solution.

[0176] S500: A first passivation layer 5 is formed on the second surface.

[0177] In some embodiments, the first passivation layer 5 may include aluminum oxide.

[0178] In some specific embodiments, the first passivation layer 5 can be an aluminum oxide layer.

[0179] In the first region 11, an oxide layer 4 is disposed between the first doped layer 3 and the first passivation layer 5. The oxide layer 4 can isolate the passivation side effect of the first passivation layer 5 on the first doped layer 3.

[0180] In some embodiments, reference Figure 4The method for preparing solar cells also includes forming a second passivation layer 9 on the side of the second doped layer 2 away from the silicon substrate 1.

[0181] In some embodiments, an aluminum oxide passivation layer can be deposited on the first surface and the second surface using ALD (atomic layer deposition) single insertion. The thickness of the first passivation layer and the thickness of the second passivation layer can each be independently 2 nm to 10 nm.

[0182] In some embodiments of this application, reference is made to Figure 4 The method for preparing a solar cell further includes: forming a first antireflection layer 6 on the side of the first passivation layer 5 away from the silicon substrate 1; and forming a second antireflection layer 10 on the side of the second passivation layer 9 away from the silicon substrate 1.

[0183] In some specific embodiments, antireflection layers can be deposited on the first and second surfaces using PECVD (plasma-enhanced chemical vapor deposition), and the antireflection layers can be one or more stacked films of silicon nitride, silicon oxynitride, and silicon oxide.

[0184] S600: A first electrode 8 is formed on the second surface.

[0185] In some embodiments of this application, forming the first electrode 8 includes the following steps: printing electrode paste; and performing laser-assisted sintering. Laser-assisted sintering can improve the contact effect of the second surface, thereby further enhancing the performance of the solar cell.

[0186] In some embodiments, silver electrode paste, including a second surface main grid and a second surface sub-grid, can be printed on the second surface by screen printing, and then the paste can be sintered using laser-assisted sintering technology to optimize the contact effect of the second surface.

[0187] In some embodiments of this application, reference is made to Figure 5 The method for preparing solar cells also includes: forming a second electrode 7.

[0188] In some embodiments, forming the second electrode 7 may include the following steps: printing electrode paste; performing laser-assisted sintering.

[0189] In some embodiments, silver electrode paste, including a first surface main grid and a first surface sub-grid, can be printed on the first surface by screen printing, and then the paste can be sintered using laser-assisted sintering technology.

[0190] In some embodiments of this application, a laser with a wavelength of 1064nm or a green light with a wavelength of 532nm can be used to perform laser-assisted sintering of the slurry.

[0191] In some embodiments, the laser width can be 100 μm.

[0192] In other embodiments, the laser width can be 1mm to 2mm.

[0193] After the first and second electrodes are formed, the solar cells can be tested, sorted, and selected.

[0194] The method proposed in this application for fabricating solar cells involves directly diffusing phosphorus onto a silicon substrate to form the first doped layer, which avoids parasitic absorption caused by growing a separate polycrystalline silicon layer and optimizes the passivation effect of the second surface. Laser oxidation is used to partially oxidize the first doped layer to form an oxide layer, which significantly improves the passivation effect of the electrode region on the second surface. The non-electrode region of the second surface is directly passivated using a film containing aluminum oxide. Aluminum oxide adsorbs minority carriers (holes) from the silicon substrate to the surface. The hole concentration adsorbed on the surface by aluminum oxide is much higher than the electron concentration on the silicon substrate surface, which can form a p-type inversion layer. Since electrons are minority carriers, the reduced concentration lowers the recombination rate, resulting in better passivation. Furthermore, during the electrode fabrication process on the second surface, laser-assisted sintering of the electrode paste can improve the contact effect of the second surface.

[0195] In another aspect of this application, a photovoltaic module is proposed.

[0196] In some embodiments of this application, the photovoltaic module may include the solar cell described above. Thus, the photovoltaic module possesses all the features and advantages of the solar cell described above.

[0197] In some embodiments of this application, a photovoltaic module may include multiple solar cells as described above, and the multiple solar cells may be connected in series or in parallel to form a photovoltaic module.

[0198] The present application will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the present application in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0199] Example 1

[0200] 1. Double-sided texturing: N-type silicon wafer with a resistivity of 1Ω·cm; using alkaline texturing to form a pyramid texture on the first and second surfaces of the silicon wafer, with a pyramid size of 1μm.

[0201] 2. Preparation of P+ emitter (second doped layer): Boron diffusion was performed using BCl3 as the diffusion source via tubular diffusion at a controlled temperature of 950℃. The sheet resistance of the second doped layer was 300 Ω / sq, the BSG thickness was 100 nm, and the doping concentration was 5 × 10⁻⁶. 19 cm -3 .

[0202] 3. HF chain + tank alkaline polishing: The silicon wafer first passes through a single-sided HF chain machine to remove the BSG on the second surface and around the perimeter. Then, it passes through a tank machine to perform alkaline polishing on the second surface to remove the edge junctions and the expansion of the second surface, while retaining the BSG and boron junctions on the first surface.

[0203] 4. Preparation of the second surface N+ layer (first doped layer): Phosphorus diffusion is carried out by tubular diffusion using POCl3 as the diffusion source, with a doping depth of 300 nm. The sheet resistance of the first doped layer is 50 Ω / sq. A PSG mask with a thickness of 20 nm is formed on the outermost layer.

[0204] 5. HF chain type: The PSG mask is removed from the entire surface of the second surface.

[0205] 6. Laser oxidation: In the second surface metal region (first region), the first doped layer is oxidized using a laser to prepare a silicon oxide layer with a thickness of 10nm. The silicon oxide plays a certain protective role in the subsequent alkaline etching process. The conditions for laser oxidation are as follows: the ultraviolet picosecond laser spot power is 10W, the spot diameter is 100μm, the frequency is 500kHz, and the scan speed is 50000mm / s.

[0206] 7. Tank-type alkaline etching + HF chain: Alkaline etching removes the first doped layer on the first surface, edge-coated and the non-metallic region (second region) of the second surface. The silicon oxide thickness retained on the first doped layer of the metallic region (first region) is 2nm, which improves the passivation effect of the first region.

[0207] 8. Preparation of passivation layer on the positive second surface: Using ALD single insertion, an aluminum oxide passivation layer with a thickness of 3nm is deposited on the positive second surface.

[0208] 9. Preparation of antireflection layer on the positive second surface: Antireflection layers are deposited on the positive second surface using PECVD. The material of the antireflection layer is silicon oxynitride, and the thickness is 80 nm.

[0209] 10. Screen-printed metal electrodes: Metal electrode paste is printed on the positive second surface by screen printing, including the main and secondary gates on the positive second surface.

[0210] 11. Laser-assisted sintering technology: Laser-assisted sintering technology is used to optimize the sintering of the slurry on the second surface of the battery. The laser wavelength is 1064nm and the laser width is 100μm.

[0211] 12. Testing and sorting: The solar cells are tested, sorted, and selected.

[0212] Comparative Example 1

[0213] Unlike Example 1, Comparative Example 1 did not perform laser oxidation treatment on the first doped layer of the metal region; that is, no silicon oxide (oxide layer) was prepared in Comparative Example 1, and the aluminum oxide passivation layer of the metal region (first region) was in direct contact with the first doped layer. The other steps and parameters in Comparative Example 1 were consistent with those in Example 1.

[0214] The performance of the solar cells prepared in the test examples and comparative examples was tested. The composite current density of the sample in Example 1 was 5 fA / cm². 2 ~6fA / cm 2 Within the range, the composite current density of the sample in Comparative Example 1 is 15 fA / cm². 2 ~20fA / cm 2 Within this range, it can be seen that the solar cell proposed in this application has an excellent second surface passivation effect.

[0215] In summary, the method proposed in this application for fabricating solar cells has the following advantages: In this application, the second surface does not require the growth of an N-poly layer (N-type doped polycrystalline silicon layer) on silicon oxide, eliminating the need for high-temperature equipment used in polycrystalline silicon fabrication. This removes parasitic absorption on the second surface caused by polycrystalline silicon layer growth, improving the efficiency of the solar cell. Passivation optimization is performed on the second surface of the solar cell by partitioning it into sections: the metal region is passivated using an oxide layer containing silicon oxide, and the non-metal region is passivated using a passivation layer containing aluminum oxide, resulting in a better passivation effect on the second surface. The method of preparing the oxide layer (silicon oxide layer) using laser oxidation of the first doped layer has a simple process flow and high film quality, which is beneficial for improving yield and reducing production costs. After printing the electrode paste on the second surface, the paste is sintered using a laser-assisted sintering method, which optimizes the contact effect of the second surface.

[0216] In the description of this application, the terms "first surface", "second surface", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and do not require this application to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0217] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0218] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A solar cell, characterized in that, include: A silicon substrate having a first surface and a second surface disposed opposite to each other, the second surface having a first doped layer having the same doping type as the silicon substrate, the second surface including alternating first regions and second regions, the orthographic projection of the first doped layer on the second surface being located in the first region; An oxide layer is disposed on the side of the first doped layer away from the silicon substrate; A first passivation layer is disposed on the side of the oxide layer away from the silicon substrate in the first region, and in the second region, the first passivation layer is in contact with the silicon substrate. The first electrode is in electrical contact with the first doped layer.

2. The solar cell according to claim 1, characterized in that, The silicon substrate protrudes in the first region in a direction away from the silicon substrate relative to the second region, and / or the silicon substrate is recessed in the second region in a direction closer to the silicon substrate relative to the first region.

3. The solar cell according to claim 2, characterized in that, The height difference between the surface of the silicon substrate in the first region and the surface of the silicon substrate in the second region is 3 μm to 5 μm.

4. The solar cell according to claim 1, characterized in that, The first passivation layer covers the sides of the oxide layer and the first doped layer.

5. The solar cell according to claim 1, characterized in that, The first electrode penetrates the oxide layer and is in electrical contact with the first doped layer.

6. The solar cell according to claim 1, characterized in that, The doping concentration of the first doped layer is greater than that of the silicon substrate; and / or, the first doped layer has the same crystal structure as the silicon substrate.

7. The solar cell according to claim 1, characterized in that, The first doped layer satisfies at least one of the following conditions: The doping element of the first doped layer includes phosphorus. The doping concentration of the first doped layer is 1×10 19 cm -3 ~1×10 22 cm -3 ; The thickness of the first doped layer is 300 nm to 500 nm; The sheet resistance of the first doped layer is 20Ω / sq to 70Ω / sq.

8. The solar cell according to claim 1, characterized in that, At least one of the following conditions must be met: The oxide layer comprises silicon oxide; The thickness of the oxide layer is 1 nm to 4 nm; The first passivation layer comprises aluminum oxide; The thickness of the first passivation layer is 2nm to 10nm.

9. The solar cell according to any one of claims 1-8, characterized in that, Also includes: A first anti-reflection layer is located on the side of the first passivation layer away from the silicon substrate; A second doped layer is located on the first surface of the silicon substrate, and the doping type of the second doped layer is opposite to that of the first doped layer. A second passivation layer is located on the side of the second doped layer away from the silicon substrate; The second antireflection layer is located on the side of the second passivation layer away from the silicon substrate; The second electrode is located on the first surface of the silicon substrate and is in electrical contact with the second doped layer.

10. The solar cell according to claim 9, characterized in that, At least one of the following conditions must be met: The first antireflective layer comprises one or more of silicon oxide, silicon nitride, and silicon oxynitride; The thickness of the first antireflective layer is 10 nm to 130 nm; The doping element of the second doped layer includes boron; The doping concentration of the second doped layer is 1×10 18 cm -3 ~1×10 20 cm -3 ; The sheet resistance of the second doped layer is 50Ω / sq to 400Ω / sq; The second passivation layer comprises aluminum oxide; The thickness of the second passivation layer is 2nm to 10nm; The second antireflective layer comprises one or more of silicon oxide, silicon nitride, and silicon oxynitride; The thickness of the second antireflective layer is 10nm to 130nm.

11. A method for preparing a solar cell, characterized in that, include: A silicon substrate is provided, the silicon substrate having a first surface and a second surface disposed opposite to each other, the second surface including alternating first regions and second regions; The second surface of the silicon substrate is doped to form a full-layer first doped layer. The first doped layer in the first region is subjected to laser oxidation to form an oxide layer; Alkali etching is performed to remove the first doped layer on the second region; A first passivation layer is formed on the second surface; A first electrode is formed on the second surface.

12. The method for preparing a solar cell according to claim 11, characterized in that, The second surface of the silicon substrate is doped using phosphorus-containing elements as a diffusion source to form a first doped layer with a thickness of 300 nm to 500 nm.

13. The method for preparing a solar cell according to claim 11, characterized in that, The first doped layer in the first region is subjected to laser oxidation treatment, and the thickness of the oxide layer formed is 5nm to 15nm. And / or, laser oxidation treatment is performed using ultraviolet picosecond laser or green picosecond laser, wherein the ultraviolet picosecond laser spot power is 3W to 20W, the spot diameter is 100μm to 150μm, the frequency is 500kHz to 600kHz, and the scan speed is 40000mm / s to 70000mm / s; the green picosecond laser spot power is 5W to 50W, the spot diameter is 100μm to 500μm, the frequency is 500kHz to 600kHz, and the scan speed is 40000mm / s to 70000mm / s.

14. The method for preparing a solar cell according to claim 11, characterized in that, During alkaline etching, the oxide layer in the first region is thinned.

15. The method for preparing a solar cell according to any one of claims 11-14, characterized in that, Also includes: Using BCl3 and / or BBr3 as a diffusion source, boron diffusion is performed on the first surface of the silicon substrate to form a second doped layer. The boron diffusion temperature is 900℃~1100℃. The doping type of the second doped layer is opposite to that of the first doped layer. A second passivation layer is formed on the side of the second doped layer away from the silicon substrate; A first antireflection layer is formed on the side of the first passivation layer away from the silicon substrate; A second antireflection layer is formed on the side of the second passivation layer away from the silicon substrate; A second electrode is formed.

16. A photovoltaic module, characterized in that, Includes the solar cell according to any one of claims 1-10.

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