Preparation method of solar cell and solar cell

Abstract

The invention relates to the field of solar cells, and provides a preparation method of a solar cell and the solar cell, and the method comprises the steps: providing a substrate which comprises a substrate and a doping layer located at one side of the substrate, and is provided with a first region and a second region; ion implantation treatment is carried out on the first region to obtain a first oxidation region, and an ion source of the ion implantation treatment at least comprises an oxygen source; performing predetermined treatment on the first oxidation region to obtain a second oxidation region and a doped region, the predetermined treatment at least comprising heat treatment, the depth of the second oxidation region being greater than that of the first oxidation region, and the doped region being located at one side, close to the substrate, of the second oxidation region; and removing the second oxidation region to form a groove, and forming an electrode in the groove. The preparation method of the solar cell can improve the efficiency of the solar cell.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0002] In the process of preparing solar cells, in order to control costs, the amount of electrode slurry used is reduced, resulting in an increase in the contact resistance between the slurry and the surface of the cell. Good ohmic contact is the key to ensure that current can flow unimpeded between the cell and the metal contact. The increase in contact resistance will reduce the fill factor of the cell, thereby affecting the overall efficiency of the cell.

[0003] Therefore, there is an urgent need for a method for preparing a solar cell that can solve the problem of unsatisfactory efficiency of solar cells. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a solar cell and a solar cell, so as to solve the problem of how to improve the efficiency of the solar cell in the prior art.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a solar cell is provided, comprising: providing a substrate, wherein the substrate comprises a substrate and a doping layer located on one side of the substrate, and the substrate has a first region and a second region; performing ion implantation on the first region to obtain a first oxidation region, wherein an ion source of the ion implantation comprises at least an oxygen source; performing a predetermined treatment on the first oxidation region to obtain a second oxidation region and a doping region, wherein the predetermined treatment comprises at least a heat treatment, the depth of the second oxidation region is greater than the depth of the first oxidation region, and the doping region is located on a side of the second oxidation region close to the substrate; removing the second oxidation region to form a groove, and forming an electrode in the groove.

[0006] Further, the substrate has a first surface and a second surface relative to each other. When the doping layer is located on the first surface, the depth of the second oxide zone is a first depth. When the doping layer is located on the second surface, the depth of the second oxide zone is a second depth. The first depth is greater than the second depth.

[0007] Furthermore, the thickness of the doping layer is 0.3-0.5 μm.

[0008] Furthermore, the depth of the first oxidation zone is 20 nm to 0.6 μm.

[0009] Furthermore, the depth of the second oxidation zone is 40 nm to 0.7 μm.

[0010] Furthermore, the predetermined treatment is a secondary diffusion treatment, wherein the temperature is 800° C. to 1020° C. and the duration is 20 to 40 minutes.

[0011] Furthermore, removing the second oxide region to form a groove, and forming an electrode in the groove, comprises: removing the second oxide region by selective wet etching to obtain the groove; and filling the groove with metal slurry to obtain the electrode.

[0012] Furthermore, the oxygen source includes at least one of oxygen and ozone.

[0013] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a solar cell, wherein the solar cell is prepared by adopting any one of the methods for preparing a solar cell, and the solar cell comprises: a substrate, wherein the substrate comprises a backing and a doping layer, and the substrate has a groove arranged on one side of the doping layer; a doping region, which is located at the bottom of the groove; and an electrode, which is at least partially arranged in the groove.

[0014] Further, the substrate has a first surface and a second surface relative to each other. When the doping layer is located on the first surface, the depth of the groove is a third depth. When the doping layer is located on the second surface, the depth of the groove is a fourth depth. The third depth is greater than the fourth depth.

[0015] The beneficial effects of the present invention are as follows: applying the technical solution of the present invention, first, using ion implantation technology to implant an oxygen source into the first region of the substrate to form a first oxidation region, then using a predetermined treatment method including at least heat treatment to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the second oxidation region has a large depth, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first region, and then reducing the surface state density of the first region, which helps to improve the open circuit voltage of the solar cell; then remove the second oxidation region to form a groove, and form an electrode in the groove, one end of the electrode contacts the doping region, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. Combined with the above-mentioned increase in the open circuit voltage of the solar cell and the increase in the fill factor, the efficiency of the solar cell can be improved, thereby solving the technical problem of how to improve the efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0017] Figure 1A schematic diagram of a process of manufacturing a solar cell provided in accordance with an embodiment of the present application is shown;

[0018] Figure 2 A schematic structural diagram of a substrate provided according to an embodiment of the present application is shown;

[0019] Figure 3 Shown in Figure 2 A schematic diagram of a structure in which a first oxidation zone is formed on the basis of

[0020] Figure 4 Shows another Figure 2 A schematic diagram of a structure in which a first oxidation zone is formed on the basis of

[0021] Figure 5 Shown in Figure 3 A schematic diagram of a structure in which a second oxide region and a doping region are formed on the basis of

[0022] Figure 6 Shown in Figure 5 A schematic diagram of a structure in which the second oxide region is removed to form an electrode;

[0023] Figure 7 Shows another Figure 3 A schematic diagram of a structure in which a second oxide region and a doping region are formed on the basis of

[0024] Figure 8 A schematic structural diagram of a solar cell according to Embodiment 1 of the present application is shown;

[0025] Fig. 9 A schematic structural diagram of a solar cell according to Embodiment 2 of the present application is shown;

[0026] Fig.10 A schematic structural diagram of a solar cell according to Example 3 of the present application is shown.

[0027] The above drawings include the following reference numerals:

[0028] 100, substrate; 101, doping layer; 1011, doping layer of the first surface; 1012, doping layer of the second surface; 102, first oxide region; 103, first region; 104, second region; 105, second oxide region; 1051, second oxide region of the first surface; 1052, second oxide region of the second surface; 106, doping region; 107, electrode; 108, tunneling dielectric layer; 109, doped conductive layer; 110, front electrode; 111, back electrode; L1, first depth; L2, second depth. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes 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.

[0032] As described in the background technology, in the prior art, due to the reduction in the amount of slurry used, the contact resistance between the cell and the metal electrode increases, thereby affecting the cell efficiency. In order to solve the above technical problems, the present application proposes a method for preparing a solar cell and a solar cell.

[0033] Figure 1 FIG. 1 is a flow chart of a method for manufacturing a solar cell according to an embodiment of the present application. Figure 1 As shown, including:

[0034] Step S201, providing a substrate, wherein the substrate comprises a substrate 100 and a doping layer 101 located on one side of the substrate 100, and the substrate has a first region and a second region, and the substrate is obtained as follows Figure 2 The structure shown;

[0035] Specifically, the substrate is used to receive incident light and generate photogenerated carriers. The substrate may be doped with N-type doping elements, for example, at least one of the Group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb) or arsenic (As). In practical applications, the substrate may be textured on both sides to reduce the reflection of light on the substrate surface and increase the absorption of light. After the texture is completed, a doping layer is formed on one side of the substrate to form a PN junction. The doping layer may be doped with N-type doping elements or P-type doping elements, and the doping layer may be prepared by a doping treatment, and the doping treatment may be performed by a single-sided doping process, and the doping may be performed by a whole-surface doping method. In addition, the substrate includes two opposite surfaces, and the doping layer may be located on the surface of either side.

[0036] It should be noted that in the subsequent preparation process, an electrode will continue to be arranged on one side of the substrate, and the projection of the electrode on the surface of the substrate is located in the first region, that is, the first region is the portion of the substrate that is in contact with the electrode. The second region is the region other than the positive projection of the electrode on the first surface, or the second region may also be the region of the substrate other than the first region.

[0037] Step S202, performing ion implantation on the first region 103 to obtain the first oxidized region 102, wherein the ion source of the ion implantation at least includes an oxygen source, and obtaining Figure 3 The structure shown;

[0038] In practical applications, the ion implantation treatment for the first region can be performed by selectively implanting an oxygen source into the first region by means of ion implantation. The specific steps are as follows: First, the substrate prepared in the above steps is pretreated to remove defective areas or impurities; then a graphic fixture is used to block the second region. These fixtures have specific patterns and can be accurately aligned with the substrate to ensure that only the first region is exposed and the second region is blocked; the masked substrate is placed in an ion implantation device to implant the exposed first region. During the implantation process, the implantation energy, implantation dose and implantation angle can be controlled to ensure that the oxygen source can be evenly and deeply implanted into the first region without affecting the characteristics of the second region. The oxygen source can be at least one of oxygen, ozone, water, hydrogen peroxide and an oxidant. In practical applications, the depth of the first oxidation region 102 can be greater than the depth of the doping layer 101, such as Figure 3 The depth of the first oxide region 102 may also be equal to the depth of the doping layer 101, as shown in FIG. Figure 4 shown.

[0039] Step S203, performing a predetermined treatment on the first oxidation region to obtain a second oxidation region 105 and a doping region 106, wherein the predetermined treatment at least includes a heat treatment, the depth of the second oxidation region 105 is greater than the depth of the first oxidation region, and the doping region 106 is located on a side of the second oxidation region 105 close to the substrate, and the following is obtained: Figure 5 The structure shown;

[0040] Specifically, the predetermined treatment is used to increase the depth of the first oxidation zone, such as annealing and thermal oxidation. The depth of the first oxidation zone is the distance between the surface of the first oxidation zone close to the substrate and the surface of the first oxidation zone away from the substrate, and the depth of the second oxidation zone is the distance between the surface of the second oxidation zone close to the substrate and the surface of the second oxidation zone away from the substrate.

[0041] Step S204, removing the second oxidation region to form a groove, and forming an electrode 107 in the groove to obtain Figure 6 The structure shown.

[0042] In practical applications, the second oxide layer can be removed by chemical cleaning. Since the chemical cleaning process only reacts with the oxide, the doped region is retained. After the groove is formed, the doped region is located at the bottom of the groove. The electrode can be formed by one of screen printing, laser sintering, electroplating, magnetron sputtering and laser sputtering, and one end of the electrode contacts the doped region to achieve better ohmic contact.

[0043] The preparation method of the solar cell of the present application firstly uses ion implantation technology to implant an oxygen source into the first region of the substrate to form a first oxidation region, and then uses a predetermined treatment method including at least heat treatment to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the second oxidation region has a large depth, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first region, and then reducing the surface state density of the first region, which can improve the open circuit voltage of the solar cell; then remove the second oxidation region to form a groove, and form an electrode in the groove, one end of the electrode contacts the doping region, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. Combined with the improvement of the open circuit voltage of the solar cell and the increase of the fill factor, the efficiency of the solar cell can be improved, thereby solving the technical problem of how to improve the efficiency of the solar cell.

[0044] In some embodiments, Figure 7As shown, the substrate 100 has a first surface and a second surface relative to each other. When the doping layer 101 is located on the first surface (i.e., the doping layer 1011 located on the first surface), the depth of the second oxidation region 1051 on the first surface is the first depth L1. When the doping layer 101 is located on the second surface (i.e., the doping layer 1012 located on the second surface), the depth of the second oxidation region 1052 on the second surface is the second depth L2. The first depth L1 is greater than the second depth L2. It should be noted that the second oxidation region 1051 on the first surface and the second oxidation region 1052 on the second surface are both the second oxidation region 105. A tunneling dielectric layer 108 is also included between the doping layer 1012 on the second surface and the substrate 100. In practical applications, the first surface and the second surface are the light-facing surface and the backlight surface of the solar cell, respectively. In order to reduce the light absorption of the light-facing surface, no polysilicon layer is provided on the light-facing surface, while a polysilicon layer is provided on the backlight surface. Therefore, when the first surface is the light-facing surface and the second surface is the backlight surface, and when the above-mentioned doping layer 101 is located on the above-mentioned first surface, since the first surface is not provided with a polysilicon layer and the second surface is provided with a polysilicon layer, the depth of the second oxidation zone 1051 on the first surface is greater than the depth of the second oxidation zone 1052 on the second surface, which can further reduce the light absorption of the light-facing surface of the solar cell, thereby further improving the efficiency of the solar cell.

[0045] Specifically, the first surface and the second surface can be light-facing surfaces or backlight surfaces, for example, the first surface is light-facing surfaces and the second surface is backlight surfaces. It should be noted that since the groove is formed by removing the second oxide region, the depth of the groove can be approximately equal to the depth of the second oxide region.

[0046] In the specific implementation process, the thickness of the above-mentioned doping layer is 0.3~0.5μm. In practical applications, therefore, the thickness of the above-mentioned doping layer is set within the above-mentioned range, which can not only ensure the reduction of the depletion region, thereby reducing the reverse breakdown voltage, but also ensure the reduction of carrier scattering and recombination to increase the forward conduction voltage, thereby further comprehensively improving the performance of the solar cell.

[0047] Specifically, the thickness of the doped layer can be 0.3 μm, 0.4 μm and 0.5 μm. Moreover, the doped layer can be prepared by a phosphorus diffusion process or a boron diffusion process. The doping concentration of the doped layer can be 3E19~1E20cm -3 .

[0048] In some other embodiments, the depth of the first oxidation region is 20 nm to 0.6 μm. Since the oxygen atoms in the first oxidation region can combine with some of the dangling bonds in the first region, thereby saturating these dangling bonds, the above arrangement can further reduce the surface state density of the first region, thereby further improving the open circuit voltage of the solar cell.

[0049] In practical applications, the depth of the first oxidation region may be greater than the thickness of the doping layer, or may be equal to the thickness of the doping layer. When the first oxidation region is located on different surfaces of the substrate, the depth of the first oxidation region may be different. The substrate has a first surface and a second surface relative to each other. When the first oxidation region is located on the first surface, the depth of the first oxidation region is 0.1 to 0.6 μm; when the first oxidation region is located on the second surface, the depth of the first oxidation region is 20 nm to 100 nm. The first oxidation region may be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm and 0.6 μm.

[0050] In some specific embodiments, the depth of the second oxidation region is 40 nm to 0.7 μm. Since the oxygen atoms in the second oxidation region can combine with some of the dangling bonds in the first region, thereby saturating these dangling bonds, the above arrangement can further reduce the surface state density of the first region, thereby further improving the open circuit voltage of the solar cell.

[0051] Specifically, when the second oxidation region is located on different surfaces of the substrate, the depth of the second oxidation region may be different. The substrate has a first surface and a second surface relative to each other. When the second oxidation region is located on the first surface, the depth of the second oxidation region is 0.2~0.7μm; when the second oxidation region is located on the second surface, the depth of the second oxidation region is 40nm~120nm. The second oxidation region can be 40nm, 60nm, 80nm, 100nm, 120nm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm and 0.7μm. However, the depth of the second oxidation region is greater than the depth of the first oxidation region, that is, when the thickness of the first oxidation region is 1μm, the depth of the second oxidation region is 1.5μm.

[0052] The predetermined treatment is a secondary diffusion treatment, wherein the temperature is 800°C to 1020°C and the duration is 20 to 40 minutes. The secondary diffusion treatment may be a secondary boron diffusion treatment or a secondary phosphorus diffusion treatment. The predetermined treatment may share the heating stage of the secondary diffusion treatment, and increase the depth of the first oxidation zone to form the second oxidation zone without adding additional steps. Therefore, the above setting may further save the process flow of the solar cell.

[0053] In practical applications, taking boron diffusion treatment as an example, primary boron diffusion treatment and secondary boron diffusion treatment are two different processes for boron doping, which can be used to form a selective emitter structure to improve the efficiency of solar cells. In the primary boron diffusion treatment, a selective emitter structure can be formed on the substrate through primary boron diffusion combined with laser doping technology, while reducing contact resistance, increasing fill factor, reducing carrier recombination, and improving battery efficiency. The secondary boron diffusion treatment can reduce the high temperature process caused by laser doping in the primary boron diffusion treatment, which is beneficial to reduce damage to the suede surface.

[0054] In some embodiments, the above step S204 can be implemented by the following steps: step S2041, using selective wet etching to remove the above second oxide region to obtain the above groove; step S2042, filling the above groove with metal slurry to obtain the above electrode. Selective wet etching is used to selectively remove only the second oxide region without damaging other structures, and the second oxide region can be removed more uniformly. Therefore, selective wet etching can further improve the uniformity and accuracy of removing the second oxide region. In addition, filling with metal slurry can form a good conductive path, reduce contact points, and further improve the electrical performance of solar cells.

[0055] Specifically, the specific steps of removing the second oxide region by selective wet etching are as follows: according to the thickness of the second oxide region, select a suitable etching solution. For example, use a diluted hydrofluoric acid solution or a buffered oxide etching solution. Control the removal time and temperature to achieve the desired removal thickness. Afterwards, remove the residual etching solution and then dry. The above-mentioned metal slurry can be silver slurry, copper slurry or its alloy slurry.

[0056] The oxygen source includes at least one of oxygen and ozone. Using oxygen or ozone as the oxygen source for ion implantation can further improve the implantation efficiency of ion implantation and the implantation quality of the first oxidation region.

[0057] In practical applications, the oxygen concentration in the mixed gas of oxygen and ozone is higher, which can provide more oxygen atoms for ion implantation, thereby improving the efficiency of oxygen ion generation. In addition, ozone molecules are more active than oxygen molecules and are more likely to decompose to produce oxygen atoms. These highly active oxygen atoms are more likely to be ionized to form oxygen ions, thereby improving the efficiency of oxygen ion implantation.

[0058] The method for preparing the solar cell of the present application will be described in detail below in conjunction with specific embodiments 1 to 8.

[0059] Example 1

[0060] Example 1 provides a method for preparing a solar cell. The solar cell prepared by the method for preparing a solar cell of Example 1 is as follows: Figure 8 As shown, the method comprises the following steps:

[0061] Step S301: providing an N-type substrate 100, and performing a double-sided texturing process on the substrate 100, wherein the substrate 100 comprises a first surface and a second surface opposite to each other, wherein the first surface is a front surface, and the second surface is a back surface;

[0062] Step S302: performing a boron diffusion treatment on the first surface of the textured substrate 100 to form a boron doped layer 101 on the first surface to obtain a base, wherein the thickness of the boron doped layer 101 is 0.4 μm, and the first surface of the base has a first region 103 and a second region 104;

[0063] Step S303: performing ion implantation on the first region 103 to obtain a first oxidized region, wherein the ion source of the ion implantation is oxygen and the depth of the first oxidized region is 0.1 μm;

[0064] Step S304: performing a secondary boron diffusion treatment on the first oxide region to obtain a second oxide region and a boron-doped region 106, wherein the depth of the second oxide region is greater than the depth of the first oxide region, the boron-doped region 106 is located on a side of the second oxide region close to the substrate, the depth of the second oxide region is 0.2 μm, the temperature of the secondary boron diffusion treatment is 800° C., and the duration is 20 min;

[0065] Step S305: removing the second oxide region by wet etching to form a groove, and filling the groove with metal paste by screen printing to form a front electrode 110;

[0066] Step S306 : forming a tunnel dielectric layer 108 , a doped conductive layer 109 and a back electrode 111 on the second surface, and one end of the back electrode 111 is in contact with the doped conductive layer 109 .

[0067] Example 2

[0068] Example 2 provides a method for preparing a solar cell. The only difference between this method and Example 1 is that the depth of the first oxidation region 102 is 0.6 μm, and the depth of the second oxidation region 105 is 0.7 μm.

[0069] Example 3

[0070] Example 3 provides a method for preparing a solar cell. The only difference between this method and Example 1 is that the depth of the first oxidation region 102 is 0.35 μm, and the depth of the second oxidation region 105 is 0.45 μm.

[0071] Example 4

[0072] Example 4 provides a method for preparing a solar cell. The solar cell prepared by the method for preparing a solar cell of Example 4 is as follows: Fig. 9 As shown, the method comprises the following steps:

[0073] Step S401: providing an N-type substrate 100, and performing a double-sided texturing process on the substrate 100, wherein the substrate 100 comprises a first surface and a second surface opposite to each other, wherein the first surface is a front surface, and the second surface is a back surface;

[0074] Step S402: performing a phosphorus diffusion treatment on the second surface of the textured substrate 100, forming a phosphorus doped layer 101 on the second surface, and obtaining a substrate, wherein the thickness of the phosphorus doped layer 101 is 0.15 μm, and the second surface of the substrate has a first region 103 and a second region 104, and the temperature of the phosphorus diffusion is 820° C., and the duration is 500 s;

[0075] Step S403: performing ion implantation on the first region 103 to obtain a first oxidized region, wherein the ion source of the ion implantation is oxygen and the depth of the first oxidized region is 20 nm;

[0076] Step S404: performing secondary phosphorus diffusion treatment on the first oxide region to obtain a second oxide region and a phosphorus-doped region 106, wherein the depth of the second oxide region is greater than the depth of the first oxide region, the phosphorus-doped region 106 is located on a side of the second oxide region close to the substrate, the depth of the second oxide region is 40 nm, the temperature of the secondary phosphorus diffusion treatment is 820° C., and the duration is 500 s;

[0077] Step S405: removing the second oxide region by wet etching to form a groove, and filling the groove with metal paste by screen printing to form a back electrode 111;

[0078] Step S406 : forming a tunnel dielectric layer 108 , a doped conductive layer 109 and a front electrode 110 on the first surface, and one end of the front electrode 110 is in contact with the doped conductive layer 109 .

[0079] Example 5

[0080] Example 5 provides a method for preparing a solar cell. The only difference between this method and Example 4 is that the depth of the first oxidation zone is 100 nm, and the depth of the second oxidation zone is 120 nm.

[0081] Example 6

[0082] Example 6 provides a method for preparing a solar cell. The only difference between this method and Example 4 is that the depth of the first oxidation zone is 40 nm, and the depth of the second oxidation zone is 60 nm.

[0083] Example 7

[0084] Example 7 provides a method for preparing a solar cell. The solar cell prepared by the method for preparing a solar cell of Example 7 is as follows: Fig.10 As shown, the method comprises the following steps:

[0085] Step S501: providing an N-type substrate 100, and performing a double-sided texturing process on the substrate 100, wherein the substrate 100 comprises a first surface and a second surface opposite to each other, wherein the first surface is a front surface, and the second surface is a back surface;

[0086] Step S502: performing a boron diffusion treatment on the first surface of the textured substrate 100, forming a boron doped layer 101 on the first surface, and obtaining a substrate, wherein the thickness of the boron doped layer 101 is 0.4 μm, and the first surface and the second surface of the substrate respectively have a first region 103 and a second region 104, and the temperature of the first boron diffusion is 800° C., and the duration is 20 min;

[0087] Step S503: performing ion implantation on the first region 103 of the first surface to obtain a first oxidized region, wherein an ion source of the ion implantation is oxygen and the depth of the first oxidized region is 0.35 μm;

[0088] Step S504: performing a secondary boron diffusion treatment on the first oxide region to obtain a second oxide region and a boron-doped region 106, wherein the depth of the second oxide region is greater than the depth of the first oxide region, the boron-doped region 106 is located on a side of the second oxide region close to the substrate, the depth of the second oxide region is 0.45 μm, the temperature of the secondary boron diffusion treatment is 800° C., and the duration is 30 min;

[0089] Step S505: removing the second oxide region by wet etching to form a groove, and filling the groove with metal paste by screen printing to form a front electrode 110;

[0090] Step S506: forming a tunnel dielectric layer 108 and a doped conductive layer 109 on the second surface;

[0091] Step S507: performing ion implantation on the first region 103 of the second surface to obtain a first oxidized region, wherein the ion source of the ion implantation is oxygen and the depth of the first oxidized region is 40 nm;

[0092] Step S508: performing secondary phosphorus diffusion treatment on the first oxide region to obtain a second oxide region and a phosphorus-doped region 106, wherein the depth of the second oxide region is greater than the depth of the first oxide region, the phosphorus-doped region 106 is located on a side of the second oxide region close to the substrate, the depth of the second oxide region is 60 nm, the temperature of the secondary phosphorus diffusion treatment is 820° C., and the duration is 500 s;

[0093] Step S509 : removing the second oxide region by wet etching to form a groove, and filling the groove with metal paste by screen printing to form a back electrode 111 .

[0094] Comparative Example 1

[0095] This embodiment provides a method for preparing a solar cell, the method comprising the following steps:

[0096] Step S601: providing an N-type substrate and performing a double-sided texturing process on the substrate, wherein the substrate comprises a first surface and a second surface opposite to each other, wherein the first surface is a front surface and the second surface is a back surface;

[0097] Step S602: performing a boron diffusion process on the first surface of the textured substrate to obtain a boron doped layer;

[0098] Step S603: removing the BSG and back junction formed during the diffusion process by wet etching;

[0099] Step S604: forming a tunnel dielectric layer and doped polysilicon on the second surface to form a passivation contact structure;

[0100] S60 Step S605: Form electrodes on the first surface and the second surface respectively.

[0101] Comparative Example 2

[0102] Comparative Example 2 provides a method for preparing a solar cell. The only difference between this method and Example 1 is that the depth of the first oxidation region 102 is 0.7 μm, and the depth of the second oxidation region 105 is 0.8 μm.

[0103] Comparative Example 3

[0104] Comparative Example 3 provides a method for preparing a solar cell. The only difference between this method and Example 4 is that the depth of the first oxidation zone is 120 nm, and the depth of the second oxidation zone is 140 nm.

[0105] The performance of the solar cells prepared by the methods in the above Examples 1 to 8 and the comparative example was tested, and the test results are shown in Table 1:

[0106] Table 1

[0107]

[0108] The photoelectric conversion efficiency of Examples 1 to 7 is greater than that of Comparative Examples 1 to 3, and the filling factors of Examples 1 to 7 are greater than those of Comparative Examples 1 to 3, indicating that the solar cell prepared by the method for preparing a solar cell of the present application can reduce carrier recombination losses and improve photoelectric conversion efficiency. Moreover, the open circuit voltage in Examples 1 to 7 is higher than the open circuit voltage in Comparative Examples 1 to 3, indicating that the solar cell prepared by the method for preparing a solar cell of the present application can improve the open circuit voltage. In addition, the photoelectric conversion efficiency of Examples 1 to 7 is significantly greater than that of Comparative Example 1, and the filling factors of Examples 1 to 7 are significantly greater than that of Comparative Example 1, indicating that compared with the conventional solar cell preparation method in the prior art, the solar cell prepared by the method for preparing a solar cell of the present application can reduce carrier recombination losses and improve photoelectric conversion efficiency. Moreover, compared with Comparative Example 2, the photoelectric conversion efficiency of Examples 1 to 3 is greater and the filling factor is greater, indicating that the depth range of the first oxidation zone and the depth range of the second oxidation zone of the present application can make the photoelectric conversion efficiency and filling factor greater. In addition, if the first oxidation zone adopts a greater depth (such as 0.7 μm) and the second oxidation zone adopts a greater depth (such as 0.8 μm) to prepare a solar cell, its photoelectric conversion efficiency and filling factor will not be significantly better than Examples 1 to 3. Therefore, the value range of the depth of the first oxidation zone and the depth of the second oxidation zone set in the present application is more reasonable, which can ensure that the photoelectric conversion efficiency and filling factor are larger. In addition, compared with Comparative Example 3, the photoelectric conversion efficiency of Examples 4 to 6 is greater and the filling factor is greater, indicating that on the other surface of the solar cell, the depth range of the first oxidation zone and the depth range of the second oxidation zone of the present application can also make the electrical conversion efficiency and filling factor greater. If the first oxidation zone adopts a greater depth (such as 120 nm) and the second oxidation zone adopts a greater depth (such as 140 nm) to prepare a solar cell, its photoelectric conversion efficiency and filling factor will not be significantly better than Examples 4 to 6, and the energy consumption and man-hour consumption caused are much higher than Examples 4 to 6. Therefore, the value range of the depth of the first oxidation zone and the depth of the second oxidation zone set in the present application is more reasonable, which can ensure that the photoelectric conversion efficiency and filling factor are larger and avoid the waste of energy and man-hours.

[0109] On the other hand, the photoelectric conversion efficiency of Example 3 is significantly greater than that of Example 6, and the fill factor of Example 3 is significantly greater than that of Example 6, indicating that the effect of the solar cell preparation method of the present application on the light-facing side is better than that on the backlight side. In addition, the photoelectric conversion efficiency and fill factor of Example 7 are significantly greater than those of Examples 3 and 6, indicating that the photoelectric conversion efficiency and fill factor of the solar cell can be further improved by using the solar cell preparation method of the present application on both surfaces of the solar cell.

[0110] In another typical embodiment of the present application, a solar cell is provided, such as Figure 6 As shown, the solar cell comprises:

[0111] A substrate, wherein the substrate comprises a substrate 100 and a doping layer 101, the substrate has a groove arranged on one side of the doping layer 101, the substrate has a first surface and a second surface opposite to each other, and the first surface has a first region 103 and a second region 104;

[0112] A doped region 106, located at the bottom of the groove;

[0113] The electrode 107 is at least partially disposed in the groove, and the electrode 107 is located in the first area 103 .

[0114] In some embodiments, the substrate has a first surface and a second surface relative to each other. When the doped layer is located on the first surface, the depth of the groove is a third depth. When the doped layer is located on the second surface, the depth of the groove is a fourth depth. The third depth is greater than the fourth depth. In practical applications, the first surface and the second surface are respectively the light-facing surface and the backlight surface of the solar cell. In order to reduce the light absorption of the light-facing surface, a polysilicon layer is provided on the light-facing surface, and a polysilicon layer is provided on the backlight surface. Therefore, when the first surface is the light-facing surface and the second surface is the backlight surface, and when the doped layer is located on the first surface, since the polysilicon layer is not provided on the first surface and the polysilicon layer is provided on the second surface, the depth of the groove on the first surface is greater than the depth of the groove on the second surface, that is, the third depth is greater than the fourth depth. Therefore, the above-mentioned setting can further reduce the light absorption of the light-facing surface of the solar cell, thereby further improving the efficiency of the solar cell.

[0115] Specifically, the first depth may be equal to the third depth, and the second depth may be equal to the fourth depth. From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0116] 1. The preparation method of the solar cell of the present application, first, uses ion implantation technology to implant an oxygen source into the first region of the substrate to form a first oxidation region, then uses a predetermined treatment method including at least heat treatment to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the second oxidation region has a large depth, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first region, and then reducing the surface state density of the first region, which helps to improve the open circuit voltage of the solar cell; then remove the second oxidation region to form a groove, and form an electrode in the groove, one end of the electrode contacts the doping region, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. Combined with the above-mentioned increase in the open circuit voltage of the solar cell and the increase in the fill factor, the efficiency of the solar cell can be improved, thereby solving the technical problem of how to improve the efficiency of the solar cell.

[0117] 2. The solar cell of the present application is prepared by the above-mentioned preparation method of the solar cell. First, an oxygen source is injected into the first area of ​​the substrate by ion implantation technology to form a first oxidation area. Then, a predetermined treatment method including at least heat treatment is adopted to further increase the depth of the first oxidation area to form a second oxidation area and a doping area. Since the second oxidation area has a large depth, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first area, and then reducing the surface state density of the first area, which helps to improve the open circuit voltage of the solar cell; then the second oxidation area is removed to form a groove, and an electrode is formed in the groove. One end of the electrode contacts the doping area, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. Combined with the improvement of the open circuit voltage of the above-mentioned solar cell and the increase of the fill factor, the efficiency of the solar cell can be improved, thereby solving the technical problem of how to improve the efficiency of the solar cell.

Claims

1. A method for preparing a solar cell, characterized in that: include: Providing a substrate, wherein the substrate comprises a substrate and a doping layer located on one side of the substrate, and the substrate has a first region and a second region; Performing ion implantation on the first region to obtain a first oxidized region, wherein an ion source of the ion implantation includes at least an oxygen source; Performing a predetermined treatment on the first oxidation region to obtain a second oxidation region and a doping region, wherein the predetermined treatment includes at least a heat treatment, the depth of the second oxidation region is greater than the depth of the first oxidation region, and the doping region is located on a side of the second oxidation region close to the substrate; The second oxide region is removed to form a groove, and an electrode is formed in the groove.

2. The method for preparing a solar cell according to claim 1, characterized in that: The substrate has a first surface and a second surface relative to each other. When the doping layer is located on the first surface, the depth of the second oxide region is a first depth. When the doping layer is located on the second surface, the depth of the second oxide region is a second depth. The first depth is greater than the second depth.

3. The method for preparing a solar cell according to claim 1, characterized in that: The thickness of the doping layer is 0.3-0.5 μm.

4. The method for preparing a solar cell according to claim 1, characterized in that: The depth of the first oxidation zone is 20 nm to 0.6 μm.

5. The method for preparing a solar cell according to claim 1, characterized in that: The depth of the second oxidation zone is 40 nm to 0.7 μm.

6. The method for preparing a solar cell according to claim 1, characterized in that: The predetermined treatment is a secondary diffusion treatment, wherein the temperature is 800° C. to 1020° C. and the duration is 20 to 40 minutes.

7. The method for preparing a solar cell according to claim 1, characterized in that: Removing the second oxide region to form a groove, and forming an electrode in the groove, comprising: removing the second oxide region by selective wet etching to obtain the groove; The groove is filled with metal slurry to obtain the electrode.

8. The method for preparing a solar cell according to claim 1, characterized in that: The oxygen source includes at least one of oxygen and ozone.

9. A solar cell, characterized in that: The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 8, and the solar cell comprises: A substrate, comprising a substrate and a doping layer, wherein the substrate has a groove arranged on one side of the doping layer; a doped region located at the bottom of the groove; The electrode is at least partially disposed in the groove.

10. The solar cell according to claim 9, characterized in that: The substrate has a first surface and a second surface relative to each other. When the doping layer is located on the first surface, the depth of the groove is a third depth. When the doping layer is located on the second surface, the depth of the groove is a fourth depth. The third depth is greater than the fourth depth.

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