Preparation method of solar cell and solar cell

Abstract

The present invention relates to the field of solar cells, and provides a method for manufacturing a solar cell and a solar cell, comprising: providing a substrate, wherein the substrate includes a substrate and a doped layer located on one side of the substrate, and the substrate has a first region and a second region; performing ion implantation treatment on the first region to obtain a first oxidation region, wherein the ion source for the ion implantation treatment at least includes an oxygen source; performing a predetermined treatment on the first oxidation region to obtain a second oxidation region and a doped region, wherein the predetermined treatment at least includes a heat treatment, the depth of the second oxidation region is greater than the depth of the first oxidation region, and the doped region is located on the 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. The method for manufacturing 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 more particularly, to a method for manufacturing a solar cell and a solar cell. Background Art

[0002] During the manufacturing process of solar cells, in order to control costs, the usage amount of the electrode paste is reduced, resulting in an increase in the contact resistance between the paste and the surface of the cell wafer. Good ohmic contact is the key to ensuring that current can flow unobstructed between the cell wafer and the metal contact. The increase in contact resistance will reduce the fill factor of the cell wafer, thereby affecting the overall efficiency of the cell wafer.

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

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

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing a solar cell, including: providing a substrate, wherein the substrate includes a substrate and a doped layer located on one side of the substrate, and the substrate has a first region and a second region; performing ion implantation treatment on the first region to obtain a first oxidation region, wherein the ion source of the ion implantation treatment at least includes an oxygen source; performing a predetermined treatment on the first oxidation region to obtain a second oxidation region and a doped region, wherein the predetermined treatment at least includes a heat treatment, the depth of the second oxidation region is greater than the depth of the first oxidation region, and the doped region is located on the 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 opposite first and second surfaces. When the doped layer is located on the first surface, the depth of the second oxidation region is a first depth, and when the doped layer is located on the second surface, the depth of the second oxidation region is a second depth, and the first depth is greater than the second depth.

[0007] Further, the thickness of the doped layer is 0.3 - 0.5 μm.

[0008] Further, the depth of the first oxidation region is 20 nm - 0.6 μm.

[0009] Further, the depth of the second oxidation region is 40 nm - 0.7 μm.

[0010] Further, 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] Further, the second oxidation region is removed to form a groove, and an electrode is formed in the groove, including: removing the second oxidation region by selective wet etching to obtain the groove; filling the groove with a metal paste to obtain the electrode.

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

[0013] To achieve the above object, according to one aspect of the present invention, a solar cell is provided. The solar cell is prepared by using any one of the preparation methods of the solar cell. The solar cell includes: a substrate, the substrate includes a substrate and a doping layer, and the substrate has a groove provided on one side of the doping layer; a doping region located at the bottom of the groove; and an electrode at least partially disposed in the groove.

[0014] Further, the substrate has opposite first and second surfaces. When the doping layer is located on the first surface, the depth of the groove is a third depth, and when the doping layer is located on the second surface, the depth of the groove is a fourth depth, and 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, an oxygen source is implanted into the first region of the substrate by ion implantation technology to form a first oxidation region. Then, a predetermined treatment method including at least heat treatment is used to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the depth of the second oxidation region is relatively large, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first region, and further reducing the surface state density of the first region, which helps to increase the open-circuit voltage of the solar cell. Then, the second oxidation region is removed to form a groove, and an electrode is formed in the groove. One end of the electrode is in contact with the doping region, which can further form a good ohmic contact and reduce the contact resistance of the electrode, thereby increasing the fill factor. Combining the increase in the open-circuit voltage and the fill factor of the above solar cell can improve the efficiency of the solar cell, thus solving the technical problem of how to improve the efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic 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 drawings:

[0017] Figure 1The flowchart shows a method for fabricating a solar cell according to an embodiment of the present application;

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

[0019] Figure 3 It shows that on the basis of Figure 2 the schematic structural diagram of the formation of the first oxidation region is shown;

[0020] Figure 4 It shows another schematic structural diagram of the formation of the first oxidation region on the basis of Figure 2 ;

[0021] Figure 5 It shows that on the basis of Figure 3 the schematic structural diagram of the formation of the second oxidation region and the doping region is shown;

[0022] Figure 6 It shows that on the basis of Figure 5 the schematic structural diagram of forming an electrode by removing the second oxidation region is shown;

[0023] Figure 7 It shows another schematic structural diagram of the formation of the second oxidation region and the doping region on the basis of Figure 3 ;

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

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

[0026] Figure 10 The schematic structural diagram of a solar cell according to Embodiment 3 of the present application is shown.

[0027] Among them, the above-mentioned drawings include the following reference numerals:

[0028] 100, substrate; 101, doping layer; 1011, doping layer on the first surface; 1012, doping layer on the second surface; 102, first oxidation region; 103, first region; 104, second region; 105, second oxidation region; 1051, second oxidation region on the first surface; 1052, second oxidation region on 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 implementation manners

[0029] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may 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 solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances for the embodiments of the present invention described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

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

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

[0034] Step S201, providing a substrate, wherein the substrate includes 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, obtaining a structure as Figure 2 shown;

[0035] Specifically, the substrate is used to receive incident light and generate photo-generated carriers. The above-mentioned substrate can be doped with N-type doping elements, such as at least one of Group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). In practical applications, the substrate can be textured on both sides to reduce the reflection of light on the substrate surface and increase the absorption of light. After the texturing is completed, a doped layer is formed on one surface of the substrate to form a PN junction. The above-mentioned doped layer can be doped with N-type doping elements or P-type doping elements, and the above-mentioned doped layer can be prepared by doping treatment. The above-mentioned doping treatment can adopt a single-sided doping process and be doped in a full-surface doping manner. Moreover, the substrate includes two opposite surfaces, and the doped layer can be located on any one of the surfaces.

[0036] It should be noted that in the subsequent preparation process, an electrode will be further provided on one side of the substrate. The projection of the electrode on the surface of the substrate is located within the above-mentioned first region. That is to say, the first region is the part of the substrate that contacts the above-mentioned electrode. The second region is the region outside the positive projection of the electrode on the first surface, or the second region can also be the region of the substrate except the above-mentioned first region.

[0037] Step S202: Perform ion implantation treatment on the above-mentioned first region 103 to obtain a first oxidation region 102. Among them, the ion source of the above-mentioned ion implantation treatment at least includes an oxygen source, and the structure shown in Figure 3 is obtained;

[0038] In practical applications, the ion implantation treatment on the above-mentioned first region can selectively implant an oxygen source into the first region by ion implantation. The specific steps are as follows: First, pre-treat the substrate prepared in the above-mentioned steps to remove defect regions or impurities; then use a patterned fixture to block the second region. These fixtures have specific patterns and can accurately align with the substrate to ensure that only the first region is exposed and the second region is blocked; place the substrate with the mask set in an ion implantation device and 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 uniformly and deeply implanted into the first region without affecting the characteristics of the second region. The above-mentioned oxygen source can be at least one of oxygen, ozone, water, hydrogen peroxide, and oxidants. In practical applications, the depth of the above-mentioned first oxidation region 102 can be greater than the depth of the doped layer 101, as shown in Figure 3 ; The depth of the above-mentioned first oxidation region 102 can also be equal to the depth of the doped layer 101, as shown in Figure 4 .

[0039] Step S203: Perform a predetermined treatment on the above-mentioned first oxidation region to obtain a second oxidation region 105 and a doping region 106. Among them, the above-mentioned predetermined treatment includes at least a heat treatment. The depth of the above-mentioned second oxidation region 105 is greater than the depth of the above-mentioned first oxidation region. The above-mentioned doping region 106 is located on the side of the above-mentioned second oxidation region 105 close to the above-mentioned substrate, obtaining a structure as shown in Figure 5 shown;

[0040] Specifically, the above-mentioned predetermined treatment is used to increase the depth of the first oxidation region. For example: annealing treatment and thermal oxidation treatment. The depth of the above-mentioned first oxidation region is the distance between the surface of the first oxidation region close to the substrate and the surface of the first oxidation region far from the substrate. The depth of the above-mentioned second oxidation region is the distance between the surface of the second oxidation region close to the substrate and the surface of the second oxidation region far from the substrate.

[0041] Step S204: Remove the above-mentioned second oxidation region to form a groove, and form an electrode 107 in the above-mentioned groove, obtaining a structure as shown in Figure 6 shown.

[0042] In practical applications, the above-mentioned second oxide layer can be removed by chemical cleaning. Since only the oxide reacts during the chemical cleaning process, the above-mentioned doping region is retained. After forming the groove, the doping 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 above-mentioned electrode is in contact with the doping region to achieve better ohmic contact.

[0043] For the preparation method of the solar cell of the present application, first, an oxygen source is implanted into the first region of the substrate by ion implantation technology to form a first oxidation region. Then, a predetermined treatment method including at least a heat treatment is adopted to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the depth of the second oxidation region is relatively large, it has a good ability to absorb impurities, thereby reducing the doping concentration of the first region and further reducing the surface state density of the first region, which can improve the open-circuit voltage of the solar cell; then the second oxidation region is removed to form a groove, and an electrode is formed in the groove. One end of the electrode is in contact with the doping region, which can further form a good ohmic contact and reduce the contact resistance of the electrode, thereby increasing the fill factor. Combining the above improvement of the open-circuit voltage and the increase of the fill factor of the solar cell, 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, as shown in Figure 7As shown, the above-mentioned substrate 100 has opposite first and second surfaces. When the doping layer 101 is located on the first surface (i.e., the doping layer 1011 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 on the second surface), the depth of the second oxidation region 1052 on the second surface is the second depth L2, and 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. There is also a tunneling dielectric layer 108 between the doping layer 1012 on the second surface and the substrate 100. In practical applications, the above-mentioned first surface and second surface are respectively the light-facing surface and the backlight-facing surface of the solar cell. In order to reduce the light absorption on the light-facing surface, no polysilicon layer is provided on the light-facing surface, while a polysilicon layer is provided on the backlight-facing surface. Therefore, when the first surface is the light-facing surface and the second surface is the backlight-facing surface, when the doping layer 101 is located on the first surface, since no polysilicon layer is provided on the first surface and a polysilicon layer is provided on the second surface, the depth of the second oxidation region 1051 on the first surface is greater than the depth of the second oxidation region 1052 on the second surface, which can further reduce the light absorption on the light-facing surface of the solar cell, thereby further improving the efficiency of the solar cell.

[0045] Specifically, the above-mentioned first surface and second surface can be respectively the light-facing surface or the backlight-facing surface. For example: the first surface is the light-facing surface and the second surface is the backlight-facing surface. It should be noted that since the groove is formed by removing the second oxidation region, the depth of the groove can be approximately equal to the depth of the second oxidation region.

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

[0047] Specifically, the thickness of the above-mentioned doping layer can be 0.3 μm, 0.4 μm, and 0.5 μm. And the above-mentioned doping layer can be prepared by a phosphorus diffusion process or a boron diffusion process. The doping concentration of the above-mentioned doping layer can be 3E19 - 1E20 cm -3 。

[0048] In some other embodiments, the depth of the above-mentioned 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, thus saturating these dangling bonds. Therefore, the above setting can further reduce the surface state density of the first region, thereby further increasing the open-circuit voltage of the solar cell.

[0049] In practical applications, the depth of the above-mentioned first oxidation region can be greater than the thickness of the doping layer or equal to the thickness of the doping layer. When the above-mentioned first oxidation region is located on different surfaces of the substrate, the depth of the first oxidation region may be different. The substrate has opposite first and second surfaces. When the first oxidation region is located on the first surface, the depth of the above-mentioned 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 above-mentioned first oxidation region is 20 nm to 100 nm. The above-mentioned first oxidation region can 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 above-mentioned 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, thus saturating these dangling bonds. Therefore, the above setting can further reduce the surface state density of the first region, thereby further increasing the open-circuit voltage of the solar cell.

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

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

[0053] In practical applications, taking boron diffusion treatment as an example, the first boron diffusion treatment and the second 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 first boron diffusion treatment, through the combination of the first boron diffusion and laser doping technology, a selective emitter structure can be formed on the substrate, while reducing the contact resistance, increasing the fill factor, reducing carrier recombination, and improving the cell efficiency. The second boron diffusion treatment can reduce the high-temperature process brought by laser doping in the first boron diffusion treatment, which is beneficial to reducing the damage to the textured surface.

[0054] In some embodiments, the above step S204 can be implemented through 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 paste to obtain the above electrode. Using selective wet etching can selectively remove only the second oxide region without damaging other structures, and can more evenly remove the second oxide region. Therefore, using selective wet etching can further improve the uniformity and accuracy of removing the second oxide region. In addition, filling with metal paste can form a good conductive path, reduce the contact point resistance, and further improve the electrical performance of the solar cell.

[0055] Specifically, the specific steps of using selective wet etching to remove the second oxide region are as follows: Select a suitable etching solution according to the thickness of the second oxide region. For example, use a diluted hydrofluoric acid solution or a buffered oxide etchant. Control the removal time and temperature to achieve the required removal thickness. Then, remove the residual etching solution and then dry. The above metal paste can be silver paste, copper paste or their alloy paste.

[0056] The above 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 oxide region.

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

[0058] Next, the preparation method of the solar cell of the present application will be specifically described in combination with specific embodiments 1 to 8.

[0059] Embodiment 1

[0060] Example 1 provides a method for manufacturing a solar cell. The solar cell manufactured by using the method for manufacturing a solar cell of Example 1 is as shown in Figure 8 and the method includes the following steps:

[0061] Step S301: Provide an N-type substrate 100 and perform double-sided texturing treatment on the substrate 100. The above substrate 100 includes opposite first and second surfaces, wherein the first surface is the front surface and the second surface is the back surface;

[0062] Step S302: Perform a first boron diffusion treatment on the first surface of the textured substrate 100 to form a boron-doped layer 101 on the first surface, obtaining a substrate. The thickness of the boron-doped layer 101 is 0.4 μm, and the first surface of the substrate has a first region 103 and a second region 104;

[0063] Step S303: Perform ion implantation treatment on the above first region 103 to obtain a first oxidation region. The ion source for the above ion implantation treatment is oxygen, and the depth of the first oxidation region is 0.1 μm;

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

[0065] Step S305: Use wet etching to remove the above second oxidation region to form a groove, and use screen printing to fill the groove with metal paste to form a front electrode 110;

[0066] Step S306: Form a tunneling 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 manufacturing 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 manufacturing 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 using the method for preparing a solar cell of Example 4 is as Figure 9 shown. This method includes the following steps:

[0073] Step S401: Provide an N-type substrate 100, and perform double-sided texturing treatment on the substrate 100. The above substrate 100 includes opposite first and second surfaces, where the first surface is the front surface and the second surface is the back surface;

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

[0075] Step S403: Perform ion implantation treatment on the above first region 103 to obtain a first oxidation region. The ion source of the above ion implantation treatment is oxygen, and the depth of the first oxidation region is 20 nm;

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

[0077] Step S405: Use wet etching to remove the above second oxidation region to form a groove, and use screen printing to fill the groove with metal paste to form a back electrode 111;

[0078] Step S406: Form a tunneling 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 region is 100 nm, and the depth of the second oxidation region is 120 nm.

[0081] Example 6

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

[0083] Example 7

[0084] Example 7 provides a method for preparing a solar cell. The solar cell prepared by using the method for preparing a solar cell of Example 7 is as Figure 10 shown, and the method includes the following steps:

[0085] Step S501: Provide an N-type substrate 100 and perform double-sided texturing treatment on the substrate 100. The above substrate 100 includes opposite first and second surfaces, where the first surface is the front surface and the second surface is the back surface;

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

[0087] Step S503: Perform ion implantation treatment on the above first region 103 of the first surface to obtain a first oxidation region. The ion source of the above ion implantation treatment is oxygen, and the depth of the first oxidation region is 0.35 μm;

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

[0089] Step S505: Use wet etching to remove the above second oxidation region to form a groove, and fill the groove with metal paste by screen printing to form a front electrode 110;

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

[0091] Step S507: Perform ion implantation treatment on the above first region 103 of the second surface to obtain a first oxidation region. The ion source of the above ion implantation treatment is oxygen, and the depth of the first oxidation region is 40 nm;

[0092] Step S508: Perform secondary phosphorus diffusion treatment on the above-mentioned first oxidation region to obtain a second oxidation region and a phosphorus-doped region 106. Among them, the depth of the above-mentioned second oxidation region is greater than that of the first oxidation region, and the phosphorus-doped region 106 is located on the side of the second oxidation region close to the substrate. The depth of the second oxidation region is 60 nm, the temperature of the secondary phosphorus diffusion treatment is 820 °C, and the duration is 500 s;

[0093] Step S509: Remove the above-mentioned second oxidation region by wet etching to form a groove, and fill 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, which includes the following steps:

[0096] Step S601: Provide an N-type substrate and perform double-sided texturing treatment on the substrate. The above-mentioned substrate includes opposite first and second surfaces, where the first surface is the front surface and the second surface is the back surface;

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

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

[0099] Step S604: Form a tunneling dielectric layer and doped polysilicon on the second surface to form a passivated contact structure;

[0100] 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 region is 120 nm, and the depth of the second oxidation region is 140 nm.

[0105] Test the performance of the solar cells prepared by the methods in the above Examples 1-8 and Comparative Examples, and the test results are shown in Table 1:

[0106] Table 1

[0107]

[0108] The photoelectric conversion efficiencies of Examples 1 to 7 are all greater than those of Comparative Examples 1 to 3, and the fill factors of Examples 1 to 7 are all greater than those of Comparative Examples 1 to 3, indicating that the solar cells prepared by the preparation method of the solar cell of the present application can reduce the carrier recombination loss and improve the photoelectric conversion efficiency. Moreover, the open circuit voltages in Examples 1 to 7 are higher than those in Comparative Examples 1 to 3, which indicates that the solar cells prepared by the preparation method of the solar cell of the present application can increase the open circuit voltage. In addition, the photoelectric conversion efficiencies of Examples 1 to 7 are significantly greater than those of Comparative Example 1, and the fill factors of Examples 1 to 7 are significantly greater than those of Comparative Example 1, indicating that compared with the conventional solar cell preparation method in the prior art, the solar cells prepared by the preparation method of the solar cell of the present application can reduce the carrier recombination loss and improve the photoelectric conversion efficiency. Moreover, compared with Comparative Example 2, the photoelectric conversion efficiencies and fill factors of Examples 1 to 3 are greater, indicating that by adopting the depth ranges of the first oxidation region and the second oxidation region of the present application, the photoelectric conversion efficiency and the fill factor can be made greater. In addition, if a greater depth (such as 0.7 μm) is adopted for the first oxidation region and a greater depth (such as 0.8 μm) is adopted for the second oxidation region to prepare the solar cell, its photoelectric conversion efficiency and fill factor will not be significantly better than those of Examples 1 to 3. Therefore, the value ranges of the depths of the first oxidation region and the second oxidation region set in the present application are relatively reasonable and can ensure relatively large photoelectric conversion efficiency and fill factor. In addition, compared with Comparative Example 3, the photoelectric conversion efficiencies and fill factors of Examples 4 to 6 are greater, indicating that on the other surface of the solar cell, by adopting the depth ranges of the first oxidation region and the second oxidation region of the present application, the electrical conversion efficiency and the fill factor can also be made greater. If a greater depth (such as 120 nm) is adopted for the first oxidation region and a greater depth (such as 140 nm) is adopted for the second oxidation region to prepare the solar cell, its photoelectric conversion efficiency and fill factor will not be significantly better than those of Examples 4 to 6, and the energy consumption and man-hour consumption caused are much higher than those of Examples 4 to 6. Therefore, the value ranges of the depths of the first oxidation region and the second oxidation region set in the present application are relatively reasonable, which can not only ensure relatively large photoelectric conversion efficiency and fill factor, but also 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 preparation method of the solar cell of the present application on the light-facing surface is better than that on the backlight surface. In addition, the photoelectric conversion efficiency and fill factor of Example 7 are significantly greater than those of Examples 3 and 6, indicating that adopting the preparation method of the solar cell of the present application on both surfaces of the solar cell can further improve the photoelectric conversion efficiency and fill factor of the solar cell.

[0110] In still another typical embodiment of the present application, a solar cell is provided, as Figure 6 shown. The solar cell includes:

[0111] A substrate, the substrate includes a substrate 100 and a doping layer 101. The substrate has a groove provided on one side of the doping layer 101. The substrate has opposite first and second surfaces. The first surface has a first region 103 and a second region 104;

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

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

[0114] In some embodiments, the substrate has opposite first and second surfaces. 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. 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 on the light-facing surface, a 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, when the doping layer is located on the first surface, since no polysilicon layer is provided on the first surface and a 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 setting can further reduce the light absorption on 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. Preparation method of the solar cell of the present application. First, an oxygen source is implanted into the first region of the substrate by using ion implantation technology to form a first oxidation region. Then, a predetermined treatment method including at least heat treatment is adopted to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the depth of the second oxidation region is relatively large, it has good ability to absorb impurities, thereby reducing the doping concentration of the first region, and further reducing the surface state density of the first region, which helps to improve the open circuit voltage of the solar cell. Then, the second oxidation region is removed to form a groove, and an electrode is formed in the groove. One end of the electrode is in contact with the doping region, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. By combining the improvement of the open circuit voltage of the solar cell and the increase of the fill factor as described above, 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 using the preparation method of the above-mentioned solar cell. First, an oxygen source is implanted into the first region of the substrate by using ion implantation technology to form a first oxidation region. Then, a predetermined treatment method including at least heat treatment is adopted to further increase the depth of the first oxidation region to form a second oxidation region and a doping region. Since the depth of the second oxidation region is relatively large, it has good ability to absorb impurities, thereby reducing the doping concentration of the first region, and further reducing the surface state density of the first region, which helps to improve the open circuit voltage of the solar cell. Then, the second oxidation region is removed to form a groove, and an electrode is formed in the groove. One end of the electrode is in contact with the doping region, which can further form a good ohmic contact, reduce the contact resistance of the electrode, and thus increase the fill factor. By combining the improvement of the open circuit voltage of the solar cell and the increase of the fill factor as described above, 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, Comprising: Providing a substrate, wherein the substrate includes a substrate body and a doped layer on one side of the substrate body, and the substrate has a first region and a second region; Performing ion implantation treatment on the first region to obtain a first oxidation region, wherein the ion source for the ion implantation treatment at least includes an oxygen source; Performing a predetermined treatment on the first oxidation region to obtain a second oxidation region and a doped region, wherein the predetermined treatment at least includes a heat treatment, the depth of the second oxidation region is greater than the depth of the first oxidation region, and the doped region is located on the 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.

2. The manufacturing method of the solar cell according to claim 1, characterized in that, The substrate body has opposite first and second surfaces. When the doped layer is located on the first surface, the depth of the second oxidation region is a first depth; when the doped layer is located on the second surface, the depth of the second oxidation region is a second depth, and the first depth is greater than the second depth.

3. The method for preparing a solar cell according to claim 1, wherein, The thickness of the doped 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 region is 20 nm - 0.6 μm.

5. The manufacturing method of the solar cell according to claim 1, wherein The depth of the second oxidation region is 40 nm - 0.7 μm.

6. The manufacturing method of the solar cell according to claim 1, characterized in that, The predetermined treatment is a secondary diffusion treatment, wherein the temperature is 800°C - 1020°C and the duration is 20 - 40 min.

7. The manufacturing method of the solar cell according to claim 1, characterized in that, Removing the second oxidation region to form a groove, and forming an electrode in the groove, including: Removing the second oxidation region by selective wet etching to obtain the groove; Filling a metal paste in the groove to obtain the electrode.

8. The manufacturing method of 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 using the preparation method of the solar cell according to any one of claims 1 to 8, and the solar cell includes: A substrate, the substrate includes a substrate body and a doped layer, and the substrate has a groove provided on one side of the doped layer; A doped region, located at the bottom of the groove; An electrode, at least partially disposed in the groove.

10. The solar cell according to claim 9, characterized in that, The substrate body has opposite first and second surfaces. 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, and the third depth is greater than the fourth depth.

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