Manufacturing method for solar cell, and solar cell

Abstract

The present application relates to a manufacturing method for a solar cell, and a solar cell. The manufacturing method for a solar cell comprises: using a second doping element of a doping type opposite to that of a first doping element to carry out second diffusion doping on a wrap-around layer (230), so as to convert the wrap-around layer (230) into a second doped layer (320). Doping the wrap-around layer (230) with the element of a different type by means of the second diffusion doping cancels out the doping element formed in the wrap-around layer (230) during first diffusion doping. The method can ameliorate the problem of poor flatness of the surfaces of silicon wafers caused by etching wrap-around layers.

Description

Method for preparing solar cell, solar cell

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 15, 2023, with application number 2023115330592 and invention name “Method for preparing solar cells, solar cells”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of photovoltaic technology, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0003] In the processing flow of solar cells, diffusion doping is often used to form polysilicon or doped polysilicon film layers. During the diffusion doping process, there will be a very narrow gap between the two silicon wafers. During the process, a small amount of gas enters the gap and forms a diffusion doping layer on the surface where the silicon wafers are bonded. The doping concentration of the diffusion layer is lower than that of the normal diffusion surface. Because the gas in the middle of the bonding surface of the two silicon wafers is more difficult to reach, the diffusion doping concentration of the diffusion layer in the middle area of ​​the bonding surface is lower than that at the edge of the bonding surface. For example, when a P-type doped layer or an N-type doped layer is prepared on the back of the silicon wafer by diffusion doping, a diffusion layer will be formed on the front of the silicon wafer due to the diffusion of the doping elements. The diffusion layer can be considered as a doping layer with the same doping elements as the P-type doped layer or the N-type doped layer, but with a lower doping concentration than the P-type doped layer or the N-type doped layer. In the process flow after diffusion doping, the diffusion layer needs to be removed. Traditional methods for removing the wrap-around layer typically use a mixture of alkaline solution and additives or an acidic mixture of hydrofluoric acid and nitric acid to etch the wrap-around layer. However, since the wrap-around layer is not formed uniformly on the surface of the silicon wafer, the wrap-around layer is more likely to be removed incompletely or over-etched, resulting in poor surface flatness of the silicon wafer.

[0004] Summary of the Invention

[0005] Based on this, it is necessary to provide a method for preparing a solar cell and a solar cell, wherein the method for preparing a solar cell can improve the problem of poor flatness of the silicon wafer surface caused by etching the wrap-around layer.

[0006] In a first aspect, the present application provides a method for preparing a solar cell, comprising:

[0007] Providing a semiconductor substrate, the semiconductor substrate comprising a first surface and a second surface opposite to each other;

[0008] Performing a first diffusion doping on the first surface using a first doping element to form a first doping layer with a first doping concentration, and forming a wrap-around layer with a second doping concentration on the second surface;

[0009] The wrap-around layer is subjected to a second diffusion doping using a second doping element, wherein the second doping element has an opposite doping type to the first doping element, and the wrap-around layer is converted into a second doping layer; the doping concentration of the second doping element in the second doping layer is a third doping concentration, and the third doping concentration is higher than the second doping concentration.

[0010] In some embodiments, in the second diffusion doping of the wrap-around layer using a second doping element, the concentration of the second doping element diffused into the first doping layer is a fourth doping concentration, and the fourth doping concentration is less than the first doping concentration.

[0011] In some embodiments, performing a first diffusion doping on the first surface using a first doping element includes:

[0012] forming a first glass layer including a first doping element on the first surface using a first doping source;

[0013] The first doping element in the first glass layer is diffused into the semiconductor substrate to obtain the first doping layer.

[0014] In some embodiments, the first glass layer is a phosphosilicate glass layer or a borosilicate glass layer.

[0015] In some embodiments, before performing the second diffusion doping on the wrap-and-expand layer using the second doping element, the method further includes the following steps:

[0016] The first glass layer is removed by etching.

[0017] In some embodiments, performing a second diffusion doping on the wrap-around layer using a second doping element includes:

[0018] forming a second glass layer including a second doping element on the wrap-around layer using a second doping source;

[0019] The second doping element in the second glass layer is diffused into the diffusion layer.

[0020] In some embodiments, the second glass layer is a phosphosilicate glass layer or a borosilicate glass layer.

[0021] In some embodiments, after performing a second diffusion doping on the wrap-around layer using a second doping element, the method further includes the following steps:

[0022] The second glass layer is removed by etching.

[0023] In some embodiments, the first doping element is phosphorus, and the first doping concentration is 1e 19 / cm 3 ~8e20 / cm 3 , the second doping concentration is 1e 18 / cm 3 ~8e 19 / cm 3 The second doping element is boron, and the third doping concentration is 2e 18 / cm 3 ~9e 19 / cm 3 , the fourth doping concentration is 2e 17 / cm 3 ~9e 18 / cm 3 .

[0024] In some embodiments, the first doping element is phosphorus, and the first doping concentration is 2e 20 / cm 3 ~6e 20 / cm 3 , the second doping concentration is 2e 19 / cm 3 ~6e 19 / cm 3 The second doping element is boron, and the third doping concentration is 3e 19 / cm 3 ~7e 19 / cm 3 , the fourth doping concentration is 3e 18 / cm 3 ~7e 18 / cm 3 .

[0025] In some embodiments, the first doping element is boron, and the first doping concentration is 1e 18 / cm 3 ~1e 19 / cm 3 , the second doping concentration is 1e 17 / cm 3 ~1e 18 / cm 3 The second doping element is phosphorus, and the third doping concentration is 2e 17 / cm 3 ~2e 18 / cm 3 , the fourth doping concentration is 2e 16 / cm 3 ~2e 17 / cm 3 .

[0026] In some embodiments, the first doping element is boron, and the first doping concentration is 6e 18 / cm 3 ~9e 18 / cm 3 , the second doping concentration is 6e 17 / cm 3 ~9e 17 / cm 3 The second doping element is phosphorus, and the third doping concentration is 7e 17 / cm 3 ~1e 18 / cm 3 , the fourth doping concentration is 7e 16 / cm 3 ~1e 17 / cm 3 .

[0027] In a second aspect, the present application provides a solar cell prepared by any of the above-mentioned methods for preparing a solar cell.

[0028] The preparation method of the above-mentioned solar cell includes performing a second diffusion doping on the expansion layer using a second doping element of the opposite doping type to the first doping element, thereby converting the expansion layer into a second doping layer. The doping concentration of the second doping element in the second doping layer is a third doping concentration, and the third doping concentration is higher than the second doping concentration. In the preparation method of the solar cell, the expansion layer is doped with different types of elements by the second diffusion doping to offset the doping elements in the expansion layer formed during the first diffusion doping, and the prepared semiconductor structure can be suitable for subsequent processing steps. This method can eliminate the influence of the expansion layer in the solar cell on the battery structure, and can replace the traditional method of using a mixture of alkaline solution + additives or an acidic mixture of hydrofluoric acid + nitric acid to etch and remove the expansion layer, and can improve the problem of poor flatness of the silicon wafer surface caused by etching the expansion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic flow chart of a method for preparing a solar cell according to an embodiment of the present application;

[0030] FIG2 is a schematic diagram showing the structure of preparing a first glass layer on the surface of a semiconductor substrate;

[0031] FIG3 is a schematic diagram of a structure for preparing a first doping layer and a wrap-around layer based on the structure shown in FIG2 ;

[0032] FIG4 is a schematic diagram of a structure for preparing a second glass layer based on the structure shown in FIG3 ;

[0033] FIG5 is a schematic diagram of a structure for preparing a second doping layer based on the structure shown in FIG4 ;

[0034] FIG6 is a schematic diagram of a structure in which the first glass layer and the second glass layer are removed from the structure shown in FIG5 .

[0035] Marking Description

[0036] 100, semiconductor substrate; 210, first glass layer; 220, first doped layer; 230, wrap-around layer; 310, second glass layer; 320, second doped layer. DETAILED DESCRIPTION

[0037] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0041] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," and the like should be interpreted broadly. For example, they may refer to fixed or removable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0042] 1 , an embodiment of the present application provides a method for preparing a solar cell, comprising:

[0043] S10: providing a semiconductor substrate 100, wherein the semiconductor substrate 100 comprises a first surface and a second surface opposite to each other.

[0044] S20 : ​​performing first diffusion doping on the first surface using a first doping element to form a first doping layer 220 having a first doping concentration, and forming a wrap-around layer 230 having a second doping concentration on the second surface.

[0045] S30: Performing a second diffusion doping on the wrap-around layer 230 using a second doping element, where the second doping element has a doping type opposite to that of the first doping element, thereby transforming the wrap-around layer 230 into a second doping layer 320. The doping concentration of the second doping element in the second doping layer 320 is a third doping concentration, which is higher than the second doping concentration.

[0046] The above-mentioned method for preparing a solar cell includes performing a second diffusion doping on the winding expansion layer 230 using a second doping element of the opposite doping type to the first doping element, thereby converting the winding expansion layer 230 into a second doping layer 320. The doping concentration of the second doping element in the second doping layer 320 is a third doping concentration, and the third doping concentration is higher than the second doping concentration. In the method for preparing a solar cell, the winding expansion layer 230 is doped with different types of elements by the second diffusion doping to offset the doping elements in the winding expansion layer 230 formed during the first diffusion doping, and the prepared semiconductor structure is suitable for subsequent processing steps. It is understandable that the doping concentration can be controlled by gas flow, temperature, pressure, etc. This method can eliminate the influence of the winding expansion layer 230 on the cell structure in the solar cell, and can replace the traditional method of etching and removing the winding expansion layer 230 using a mixture of alkaline solution + additives or an acidic mixture of hydrofluoric acid + nitric acid, and can improve the problem of poor flatness of the silicon wafer surface caused by etching the winding expansion layer 230.

[0047] It is understandable that the above-mentioned method for preparing solar cells is applicable to silicon-based solar cells of various structures, and the specific structure of the solar cells is not limited in this application.

[0048] In some embodiments, during the second diffusion doping of the wrap-around layer 230 using the second doping element, the concentration of the second doping element diffused into the first doping layer 220 is a fourth doping concentration, which is less than the first doping concentration. Controlling the fourth doping concentration to be less than the first doping concentration ensures that the doping type of the first doping layer is not changed during the second diffusion doping.

[0049] In some embodiments, the third doping concentration is slightly higher than the second doping concentration. It is understood that the third doping concentration being slightly higher than the second doping concentration means that the doping type of the wrap-around layer 230 is just being transformed during the second diffusion doping process. In this case, the second high-temperature doping process has little effect on the doping concentration of the first doping layer 220.

[0050] 2 and 3 , FIG. 2 is a schematic structural diagram of preparing a first glass layer 210 on the surface of a semiconductor substrate 100 , and FIG. 3 is a schematic structural diagram of preparing a first doping layer 220 and a wrap-around expansion layer 230 based on the structure shown in FIG. 2 .

[0051] In some embodiments, performing first diffusion doping on the first surface using a first doping element includes forming a first glass layer 210 including the first doping element on the first surface using a first doping source, and diffusing the first doping element in the first glass layer 210 into the semiconductor substrate 100 to form a first doping layer 220.

[0052] It is understood that diffusion doping is a commonly used semiconductor doping process used to change the concentration of electrons and holes in a semiconductor. When a semiconductor material from Group IV, such as silicon, is doped with a Group V atom such as phosphorus, doping produces an N-type material. When a semiconductor material from Group IV, such as silicon, is doped with a Group III atom such as boron or gallium, a P-type material is produced.

[0053] In some embodiments, diffusing the first doping element in the first glass layer 210 into the semiconductor substrate 100 to obtain the first doping layer 220 includes heating the semiconductor substrate 100 to diffuse the first doping element in the first glass layer 210 into the semiconductor substrate 100 to obtain the first doping layer 220 .

[0054] In some embodiments, the first doping source includes at least one of boron trichloride (BCl 3 ) and boron tribromide (BBr 3 ).

[0055] In some embodiments, the first dopant source includes phosphorus oxychloride (POCl 3 ).

[0056] In some embodiments, the first glass layer 210 is a phosphosilicate glass (PSG) layer.

[0057] In some embodiments, the first glass layer 210 is a borosilicate glass (BSG) layer.

[0058] In some embodiments, the temperature of the first diffusion doping is 900° C. to 1100° C. Optionally, the temperature of the first diffusion doping is 900° C., 910° C., 920° C., 930° C., 940° C., 950° C., 960° C., 970° C., 980° C., 990° C., 1000° C., 1010° C., 1020° C., 1030° C., 1040° C., 1050° C., 1060° C., 1070° C., 1080° C., 1090° C., or 1100° C.

[0059] In some embodiments, before performing the second diffusion doping on the wrap-around layer 230 using the second doping element, the following step is further included: etching and removing the first glass layer 210 .

[0060] In some embodiments, the second doping source includes at least one of boron trichloride (BCl 3 ) and boron tribromide (BBr 3 ).

[0061] In some embodiments, the second dopant source includes phosphorus oxychloride (POCl 3 ).

[0062] In some embodiments, etching and removing the first glass layer 210 includes removing the first glass layer 210 by wet etching.

[0063] In some embodiments, removing the first glass layer 210 by wet etching includes removing the first glass layer 210 using hydrofluoric acid.

[0064] 4 and 5 , FIG. 4 is a schematic structural diagram of a second glass layer 310 prepared based on the structure shown in FIG. 3 , and FIG. 5 is a schematic structural diagram of a second doping layer 320 prepared based on the structure shown in FIG. 4 .

[0065] In some embodiments, performing second diffusion doping on the expansion layer 230 using the second doping element includes: forming a second glass layer 310 including the second doping element on the expansion layer 230 using the second doping source; and diffusing the second doping element in the second glass layer 310 into the expansion layer 230 .

[0066] In some embodiments, diffusing the second doping element in the second glass layer 310 into the wrap-around diffusion layer 230 includes heating the semiconductor substrate 100 to diffuse the second doping element in the second glass layer 310 into the wrap-around diffusion layer 230 .

[0067] In some embodiments, the second glass layer 310 is a phosphosilicate glass layer.

[0068] In some embodiments, the second glass layer 310 is a borosilicate glass layer.

[0069] In some embodiments, the second diffusion doping temperature is 900° C. to 1100° C. Optionally, the second diffusion doping temperature is 900° C., 910° C., 920° C., 930° C., 940° C., 950° C., 960° C., 970° C., 980° C., 990° C., 1000° C., 1010° C., 1020° C., 1030° C., 1040° C., 1050° C., 1060° C., 1070° C., 1080° C., 1090° C., or 1100° C.

[0070] In some embodiments, after performing the second diffusion doping on the wrap-around layer 230 using the second doping element, the method further includes the following steps: etching and removing the second glass layer 310 .

[0071] In some embodiments, etching and removing the second glass layer 310 includes: removing the second glass layer 310 by wet etching.

[0072] In some embodiments, removing the second glass layer 310 by wet etching includes removing the second glass layer 310 using hydrofluoric acid.

[0073] 6 is a schematic diagram illustrating the structure of FIG5 without the first glass layer 210 and the second glass layer 310. In some embodiments, after the second diffusion doping of the wrap-around layer 230 with the second doping element, the following further steps are included: etching to remove the first glass layer 210 and the second glass layer 310.

[0074] In some embodiments, the first doping element includes boron, and the second doping element includes phosphorus.

[0075] In some embodiments, the first doping element includes phosphorus and the second doping element includes boron.

[0076] In some embodiments, the first doping element is phosphorus, and the first doping concentration is 1e 19 / cm 3 ~8e 20 / cm 3 , the second doping concentration is 1e 18 / cm 3 ~8e 19 / cm 3 The second doping element is boron, and the third doping concentration is 2e 18 / cm 3 ~9e 19 / cm 3 , the fourth doping concentration is 2e 17 / cm 3 ~9e 18 / cm 3 .

[0077] Optionally, the first doping element is phosphorus, and the first doping concentration is 2e 20 / cm 3 ~6e 20 / cm 3 , the second doping concentration is 2e 19 / cm 3 ~6e 19 / cm 3 . Further optionally, the first doping concentration is 2e 20 / cm 3 , 2.5e 20 / cm 3 、3e 20 / cm 3 , 3.5e 20 / cm 3 、4e 20 / cm 3 , 4.5e 20 / cm 3 、5e 20 / cm 3 , 5.5e 20 / cm 3 or 6e 20 / cm 3 Alternatively, the first doping concentration may be within the range between any two of the above doping concentrations. Further, optionally, the second doping concentration is 2e 19 / cm 3 , 2.5e 19 / cm 3 、3e 19 / cm 3 , 3.5e 19 / cm 3 、4e 19 / cm 3 , 4.5e 19 / cm 3 、5e 19 / cm 3 , 5.5e 19 / cm 3 or 6e 19 / cm 3 Alternatively, the second doping concentration may also be within a range between any two of the above doping concentrations.

[0078] Optionally, the second doping element is boron, and the third doping concentration is 3e 19 / cm 3 ~7e 19 / cm 3 , the fourth doping concentration is 3e18 / cm 3 ~7e 18 / cm 3 . Further optionally, the third doping concentration is 3e 19 / cm 3 , 3.5e 19 / cm 3 、4e 19 / cm 3 , 4.5e 19 / cm 3 、5e 19 / cm 3 , 5.5e 19 / cm 3 、6e 19 / cm 3 , 6.5e 19 / cm 3 or 7e 19 / cm 3 Alternatively, the third doping concentration may also be within the range between any two of the above doping concentrations. Further optionally, the fourth doping concentration is 3e 18 / cm 3 , 3.5e 18 / cm 3 、4e 18 / cm 3 , 4.5e 18 / cm 3 、5e 18 / cm 3 , 5.5e 18 / cm 3 、6e 18 / cm 3 , 6.5e 18 / cm 3 or 7e 18 / cm 3 Alternatively, the fourth doping concentration may also be within a range between any two of the above doping concentrations.

[0079] In some embodiments, the first doping element is boron, and the first doping concentration is 1e 18 / cm 3 ~1e 19 / cm 3 , the second doping concentration is 1e 17 / cm 3 ~1e 18 / cm 3 The second doping element is phosphorus, and the third doping concentration is 2e 17 / cm 3 ~2e 18 / cm3 , the fourth doping concentration is 2e 16 / cm 3 ~2e 17 / cm 3 .

[0080] Optionally, the first doping element is boron, and the first doping concentration is 6e 18 / cm 3 ~9e 18 / cm 3 , the second doping concentration is 6e 17 / cm 3 ~9e 17 / cm 3 . Further optionally, the first doping concentration is 6e 18 / cm 3 , 6.5e 18 / cm 3 、7e 18 / cm 3 , 7.5e 18 / cm 3 、8e 18 / cm 3 , 8.5e 18 / cm 3 or 9e 18 / cm 3 Alternatively, the first doping concentration may also be within the range between any two of the above doping concentrations. Further optionally, the second doping concentration is 6e 17 / cm 3 , 6.5e 17 / cm 3 、7e 17 / cm 3 , 7.5e 17 / cm 3 、8e 17 / cm 3 , 8.5e 17 / cm 3 or 9e 17 / cm 3 Alternatively, the second doping concentration may also be within a range between any two of the above doping concentrations.

[0081] Optionally, the second doping element is phosphorus, and the third doping concentration is 7e 17 / cm 3 ~1e 18 / cm 3 , the fourth doping concentration is 7e 16 / cm 3 ~1e 17 / cm 3. Further optionally, the third doping concentration is 7e 17 / cm 3 , 7.5e 17 / cm 3 、8e 17 / cm 3 , 8.5e 17 / cm 3 、9e 17 / cm 3 , 9.5e 17 / cm 3 or 1e 18 / cm 3 Alternatively, the third doping concentration may also be within the range between any two of the above doping concentrations. Further optionally, the fourth doping concentration is 7e 16 / cm 3 , 7.5e 16 / cm 3 、8e 16 / cm 3 , 8.5e 16 / cm 3 、9e 16 / cm 3 , 9.5e 16 / cm 3 or 1e 17 / cm 3 Alternatively, the fourth doping concentration may also be within a range between any two of the above doping concentrations.

[0082] In some embodiments, before performing the first diffusion doping on the first surface using the first doping element, the method further includes the following step: texturing the first surface and / or the second surface.

[0083] In some embodiments, after performing a first diffusion doping on the first surface using a first doping element, and before performing a second diffusion doping on the wrap-around layer 230 using a second doping element, the following step is further included: performing laser heavy doping on the first doping layer 220. It is understood that laser heavy doping is to achieve a doping concentration higher than the first doping concentration in a part of the first doping layer 220 by laser irradiation.

[0084] In some embodiments, after removing the second glass layer 310 by wet etching, the method further includes the following steps: forming a dielectric layer and / or a passivation layer on the first surface and the second surface respectively.

[0085] Yet another embodiment of the present application provides a solar cell, which is prepared by any of the above-mentioned methods for preparing a solar cell.

[0086] The following are specific embodiments

[0087] Example 1

[0088] Preparation of emitter back passivation battery:

[0089] (1) Remove the P-type silicon wafer cutting damage layer, use a mixed solution of deionized water, texturing auxiliary agent and sodium hydroxide to corrode the silicon wafer and make a uniform texturing surface.

[0090] (2) The back of the cleaned and textured silicon wafer is inserted into a quartz boat and sent into a tubular low-pressure diffusion furnace. Under high temperature conditions, POCl3 is used as a doping source to perform high-temperature phosphorus diffusion on the front surface of the silicon wafer. After the process is completed, an n-type first doping layer 220 and a PSG layer are formed on the front surface of the silicon wafer. The first doping concentration is 3e 20 / cm 3 , a wrap-around layer 230 is formed on the back of the silicon wafer, and the second doping concentration is 3e 19 / cm 3 .

[0091] (3) Using the thermal effect of laser, heavy doping is formed locally on the front side of the silicon wafer.

[0092] (4) Insert the front side of the silicon wafer into a quartz boat and place it into a tubular low-pressure diffusion furnace. Under high temperature conditions, use BBr3 or BCl3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer to form a BSG layer and transform the wrap-around layer 230 into a second doping layer 320. The boron doping concentration is controlled by gas flow, temperature, pressure, etc., so that the boron doping concentration on the back side of the silicon wafer is greater than the phosphorus doping concentration on the back side of the silicon wafer in step (2), that is, the third doping concentration is greater than the second doping concentration, and the third doping concentration is 4e 19 / cm 3 , and the doping concentration of boron element on the front side of the silicon wafer is lower than the doping concentration of phosphorus element on the front side of the silicon wafer in step (2), that is, the fourth doping concentration is lower than the first doping concentration, and the fourth doping concentration is 4e 18 / cm 3 .

[0093] (5) Using a hydrofluoric acid solution in a chain wet process equipment or a tank wet process equipment, remove the PSG layer located on the surface of the first doping layer 220 and the BSG layer located on the surface of the second doping layer 320 .

[0094] (6) Prepare a silicon oxide layer on the front side of the silicon wafer.

[0095] (7) An aluminum oxide film layer is deposited on the back of the silicon wafer, and a silicon nitride film layer is deposited on the back and front of the silicon wafer.

[0096] (8) Screen printing and sintering.

[0097] Example 2

[0098] Preparation of emitter back passivation battery:

[0099] (1) Remove the P-type silicon wafer cutting damage layer, use a mixed solution of deionized water, texturing auxiliary agent and sodium hydroxide to corrode the silicon wafer and make a uniform texturing surface.

[0100] (2) The back of the cleaned and textured silicon wafer is inserted into a quartz boat and sent into a tubular low-pressure diffusion furnace. Under high temperature conditions, POCl3 is used as a doping source to perform high-temperature phosphorus diffusion on the front surface of the silicon wafer. After the process is completed, an n-type first doping layer 220 and a PSG layer are formed on the front surface of the silicon wafer. The first doping concentration is 5e 20 / cm 3 , a wrap-around layer 230 is formed on the back of the silicon wafer, and the second doping concentration is 5e 19 / cm 3 .

[0101] (3) Using the thermal effect of laser, heavy doping is formed locally on the front side of the silicon wafer.

[0102] (4) Using hydrofluoric acid in a chain wet process equipment or a tank wet process equipment, remove the PSG layer on the surface of the first doping layer 220 .

[0103] (5) Insert the front side of the silicon wafer into a quartz boat and place it into a tubular low-pressure diffusion furnace. Under high temperature conditions, use BBr3 or BCl3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer to form a BSG layer and transform the wrap-around layer 230 into a second doping layer 320. The boron doping concentration is controlled by gas flow, temperature, pressure, etc., so that the boron doping concentration on the back of the silicon wafer is greater than the phosphorus doping concentration on the back of the silicon wafer in step (2), that is, the third doping concentration is greater than the second doping concentration, and the third doping concentration is 6e 19 / cm 3 , and the doping concentration of boron element on the front side of the silicon wafer is lower than the doping concentration of phosphorus element on the front side of the silicon wafer in step (2), that is, the fourth doping concentration is lower than the first doping concentration, and the fourth doping concentration is 6e 18 / cm 3 .

[0104] (6) Using a hydrofluoric acid solution in a chain wet process equipment or a tank wet process equipment, remove the BSG layer located on the surface of the second doping layer 320 .

[0105] (7) Prepare a silicon oxide layer on the front side of the silicon wafer.

[0106] (8) An aluminum oxide film layer is deposited on the back of the silicon wafer, and a silicon nitride film layer is deposited on the back and front of the silicon wafer.

[0107] (9) Screen printing and sintering.

[0108] Example 3

[0109] Preparation of tunneling oxide passivation contact cell:

[0110] (1) Remove the cutting damage layer of the N-type silicon wafer, use a mixed solution of deionized water, a texturing auxiliary agent and sodium hydroxide to corrode the silicon wafer and make a uniform texturing surface.

[0111] (2) The back of the cleaned and textured silicon wafer is inserted into a quartz boat and sent into a tubular low-pressure diffusion furnace. Under high temperature conditions, high-temperature boron diffusion is performed on the front surface of the silicon wafer using BCl3 or BBr3 as a doping source. After the process is completed, a P-type doping layer and a BSG layer are formed on the front surface of the silicon wafer.

[0112] (3) Using a mixed solution of nitric acid and hydrofluoric acid, the four sides of the silicon wafer are etched and the back is polished. Water is dripped on the front of the silicon wafer through a dripping device to retain the BSG layer and P-type doping layer on the front of the silicon wafer.

[0113] (4) The back-polished silicon wafer is placed in an LPCVD device to grow a tunneling oxide layer, as well as a polycrystalline silicon, an amorphous silicon layer, or a polycrystalline silicon and amorphous silicon mixed film layer on the back of the silicon wafer.

[0114] (5) Insert the front side of the silicon wafer into a quartz boat and send it into a tubular low-pressure diffusion furnace. Perform high-temperature phosphorus diffusion on the back polysilicon layer to form a PSG layer as the first glass layer 210 and an N-type doped layer as the first doped layer 220. The first doping concentration is 4e 20 / cm 3 , a wrap-around layer 230 is formed on the back of the silicon wafer, and the second doping concentration is 4e 19 / cm 3 .

[0115] (6) Insert the back of the silicon wafer into a quartz boat and place it into a tubular low-pressure diffusion furnace. Under high temperature conditions, use BBr3 or BCl3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer to form a BSG layer and transform the wrap-around layer 230 into a second doping layer 320. The boron doping concentration is controlled by gas flow, temperature, pressure, etc., so that the boron doping concentration on the front of the silicon wafer is greater than the phosphorus doping concentration on the front of the silicon wafer in step (5), that is, the third doping concentration is greater than the second doping concentration, and the third doping concentration is 5e 19 / cm 3 And the doping concentration of boron on the back of the silicon wafer is less than the doping concentration of phosphorus on the back of the silicon wafer in step (5), that is, the fourth doping concentration is less than the first doping concentration, and the fourth doping concentration is 5e 18 / cm 3 .

[0116] (7) Using a hydrofluoric acid solution in a chain wet process equipment or a tank wet process equipment, remove the PSG layer located on the surface of the first doping layer 220 and the BSG layer located on the surface of the second doping layer 320 .

[0117] (8) An aluminum oxide film layer is deposited on the entire surface of the silicon wafer, and a silicon nitride film layer is deposited on the back and front of the silicon wafer.

[0118] (9) Screen printing and sintering.

[0119] Example 4

[0120] Preparation of tunneling oxide passivation contact cell:

[0121] (1) Remove the cutting damage layer of the N-type silicon wafer, use a mixed solution of deionized water, a texturing auxiliary agent and sodium hydroxide to corrode the silicon wafer and make a uniform texturing surface.

[0122] (2) The back of the cleaned and textured silicon wafer is inserted into a quartz boat and sent into a tubular low-pressure diffusion furnace. Under high temperature conditions, high-temperature boron diffusion is performed on the front surface of the silicon wafer using BCl3 or BBr3 as a doping source. After the process is completed, a P-type doping layer and a BSG layer are formed on the front surface of the silicon wafer.

[0123] (3) Using a mixed solution of nitric acid and hydrofluoric acid, the four sides of the silicon wafer are etched and the back is polished. Water is dripped on the front of the silicon wafer through a dripping device to retain the BSG layer and P-type doping layer on the front of the silicon wafer.

[0124] (4) The back-polished silicon wafer is placed in an LPCVD device to grow a tunneling oxide layer, as well as a polycrystalline silicon, an amorphous silicon layer, or a polycrystalline silicon and amorphous silicon mixed film layer on the back of the silicon wafer.

[0125] (5) Insert the front side of the silicon wafer into a quartz boat and send it into a tubular low-pressure diffusion furnace. Perform high-temperature phosphorus diffusion on the back polysilicon layer to form a PSG layer as the first glass layer 210 and an N-type doped layer as the first doped layer 220. The first doping concentration is 6e 20 / cm 3 , a wrap-around layer 230 is formed on the back of the silicon wafer, and the second doping concentration is 6e 19 / cm 3 .

[0126] (6) Using hydrofluoric acid in a chain wet process equipment or a tank wet process equipment, remove the PSG layer on the surface of the first doping layer 220 .

[0127] (7) Insert the back of the silicon wafer into a quartz boat and place it into a tubular low-pressure diffusion furnace. Under high temperature conditions, use BBr3 or BCl3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer to form a BSG layer and transform the wrap-around layer 230 into a second doping layer 320. The boron doping concentration is controlled by gas flow, temperature, pressure, etc., so that the boron doping concentration on the front of the silicon wafer is greater than the phosphorus doping concentration on the front of the silicon wafer in step (5), that is, the third doping concentration is greater than the second doping concentration, and the third doping concentration is 7e 19 / cm 3 And the doping concentration of boron on the back of the silicon wafer is less than the doping concentration of phosphorus on the back of the silicon wafer in step (5), that is, the fourth doping concentration is less than the first doping concentration, and the fourth doping concentration is 7e 18 / cm 3 .

[0128] (8) Using a hydrofluoric acid solution in a chain wet process equipment or a tank wet process equipment, remove the BSG layer located on the surface of the second doping layer 320 .

[0129] (9) An aluminum oxide film layer is deposited on the entire surface of the silicon wafer, and a silicon nitride film layer is deposited on the back and front of the silicon wafer.

[0130] (10) Screen printing and sintering.

[0131] In Examples 1-4, a second diffusion doping process is employed to eliminate the effects of the wrap-around layer 230 on the solar cell structure. This eliminates the need to etch the wrap-around layer 230 using a mixture of an alkaline solution and an additive, or an acidic mixture of hydrofluoric acid and nitric acid. This reduces the negative effects of etching the wrap-around layer 230 on the solar cell. Furthermore, this method is applicable to solar cells of varying structures.

[0132] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. A method for preparing a solar cell, comprising: A semiconductor substrate (100) is provided, wherein the semiconductor substrate (100) comprises a first surface and a second surface which are arranged opposite to each other; Performing first diffusion doping on the first surface using a first doping element to form a first doping layer (220) having a first doping concentration, and forming a wrap-around layer (230) having a second doping concentration on the second surface; The winding expansion layer (230) is subjected to a second diffusion doping using a second doping element, wherein the second doping element and the first doping element have opposite doping types, so that the winding expansion layer (230) is transformed into a second doping layer (320); the doping concentration of the second doping element in the second doping layer (320) is a third doping concentration, and the third doping concentration is higher than the second doping concentration.

2. The method for preparing a solar cell according to claim 1, wherein: In the second diffusion doping of the expansion layer (230) using a second doping element, the concentration of the second doping element diffused into the first doping layer (220) is a fourth doping concentration, and the fourth doping concentration is less than the first doping concentration.

3. The method for preparing a solar cell according to claim 1, wherein: Performing a first diffusion doping on the first surface using a first doping element includes: Using a first doping source to form a first glass layer (210) including a first doping element on the first surface; The first doping element in the first glass layer (210) is diffused into the semiconductor substrate (100) to obtain the first doping layer (220).

4. The method for preparing a solar cell according to claim 3, wherein: The first glass layer (210) is a phosphosilicate glass layer or a borosilicate glass layer.

5. The method for preparing a solar cell according to claim 3, wherein: Before the second diffusion doping of the winding and expansion layer (230) using the second doping element, the following steps are also included: The first glass layer (210) is removed by etching.

6. The method for preparing a solar cell according to claim 1, wherein: Performing a second diffusion doping on the winding and expansion layer (230) using a second doping element comprises: Using a second doping source to form a second glass layer (310) including a second doping element on the winding and expansion layer (230); The second doping element in the second glass layer (310) is diffused into the wrapping and diffusion layer (230).

7. The method for preparing a solar cell according to claim 6, wherein: The second glass layer (310) is a phosphosilicate glass layer or a borosilicate glass layer.

8. The method for preparing a solar cell according to claim 7, wherein: After the second diffusion doping of the winding and expansion layer (230) using the second doping element, the following steps are also included: The second glass layer is removed by etching (310).

9. The method for preparing a solar cell according to any one of claims 1 to 8, wherein: The first doping element is phosphorus, and the first doping concentration is 1e 19 / cm 3 ~8e 20 / cm 3 , the second doping concentration is 1e 18 / cm 3 ~8e 19 / cm 3 The second doping element is boron, and the third doping concentration is 2e 18 / cm 3 ~9e 19 / cm 3 , the fourth doping concentration is 2e 17 / cm 3 ~9e 18 / cm 3 .

10. The method for preparing a solar cell according to claim 9, wherein: The first doping element is phosphorus, and the first doping concentration is 2e 20 / cm 3 ~6e 20 / cm 3 , the second doping concentration is 2e 19 / cm 3 ~6e 19 / cm 3 The second doping element is boron, and the third doping concentration is 3e 19 / cm 3 ~7e 19 / cm 3 , the fourth doping concentration is 3e 18 / cm 3 ~7e 18 / cm 3 .

11. The method for preparing a solar cell according to any one of claims 1 to 8, wherein: The first doping element is boron, and the first doping concentration is 1e 18 / cm 3 ~1e 19 / cm 3 , the second doping concentration is 1e 17 / cm 3 ~1e 18 / cm 3 The second doping element is phosphorus, and the third doping concentration is 2e 17 / cm 3 ~2e 18 / cm 3 , the fourth doping concentration is 2e 16 / cm 3 ~2e 17 / cm 3 .

12. The method for preparing a solar cell according to claim 11, wherein: The first doping element is boron, and the first doping concentration is 6e 18 / cm 3 ~9e 18 / cm 3 , the second doping concentration is 6e 17 / cm 3 ~9e 17 / cm 3 The second doping element is phosphorus, and the third doping concentration is 7e 17 / cm 3 ~1e 18 / cm 3 , the fourth doping concentration is 7e 16 / cm 3 ~1e 17 / cm 3 .

13. A solar cell prepared by the method for preparing a solar cell according to any one of claims 1 to 12.

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