Preparation method of solar cell and solar cell

Abstract

The invention relates to a preparation method of a solar cell and the solar cell. The preparation method of the solar cell comprises the following steps: providing a semiconductor substrate, wherein the semiconductor substrate comprises a first surface and a second surface which are oppositely arranged; performing first diffusion doping on the first surface by using a first doping element to form a first doping layer with a first doping concentration, and forming a winding and expanding layer with a second doping concentration on the second surface; second diffusion doping is conducted on the winding and expanding layer through a second doping element, the doping type of the second doping element is opposite to that of the first doping element, and the winding and expanding 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. According to the method, the problem that the flatness of the surface of the silicon wafer is poor due to etching of the winding and expanding layer can be solved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and particularly to a method for manufacturing a solar cell and a solar cell. Background Art

[0002] In the processing flow of solar cells, diffusion doping is commonly used to form layers such as polysilicon or doped polysilicon. During the diffusion doping process, there will be a very narrow gap on the surface where two silicon wafers are joined. During the process, a small amount of gas enters the gap, and diffusion doping occurs on the surface where the silicon wafers are joined, forming a diffusion bypass layer. The doping concentration of the diffusion bypass layer is lower than that of the normal diffusion surface. Moreover, since it is more difficult for gas to reach the middle region of the surface where the two silicon wafers are joined, the diffusion doping concentration of the diffusion bypass layer in the middle region of the joined surface is lower than that at the edge of the joined surface. For example, when a P-type doping layer or an N-type doping layer is prepared on the back surface of a silicon wafer by diffusion doping, a diffusion bypass layer will be formed on the front surface of the silicon wafer due to the diffusion of doping elements. The diffusion bypass layer can be regarded as a doping layer with the same doping elements as the P-type doping layer or the N-type doping layer but with a doping concentration lower than that of the P-type doping layer or the N-type doping layer. In the process flow after diffusion doping, it is necessary to remove the diffusion bypass layer. The traditional method for removing the diffusion bypass layer usually uses a mixed solution of an alkaline solution + an additive or an acidic mixed solution of hydrofluoric acid + nitric acid to etch the diffusion bypass layer. However, since the formation of the diffusion bypass layer on the silicon wafer surface is not uniform, it is easier to have the situation of incomplete removal or over-etching during the removal process of the diffusion bypass layer, thus resulting in poor flatness of the silicon wafer surface. Summary of the Invention

[0003] Based on this, it is necessary to provide a method for manufacturing a solar cell and a solar cell. The method for manufacturing the solar cell can improve the problem of poor flatness of the silicon wafer surface caused by etching the diffusion bypass layer.

[0004] In a first aspect, the present application provides a method for manufacturing a solar cell, including:

[0005] Providing a semiconductor substrate, the semiconductor substrate including a first surface and a second surface arranged oppositely;

[0006] Performing first diffusion doping on the first surface using a first doping element to form a first doping layer having a first doping concentration, and simultaneously forming a diffusion bypass layer having a second doping concentration on the second surface;

[0007] Performing second diffusion doping on the diffusion bypass layer using a second doping element, the doping type of the second doping element being opposite to that of the first doping element, to convert the diffusion bypass 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.

[0008] In some embodiments, during the second diffusion doping of the surround-extension 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.

[0009] In some embodiments, the first diffusion doping using a first doping element on the first surface includes:

[0010] Forming a first glass layer including the first doping element on the first surface by using a first doping source;

[0011] Diffusing the first doping element in the first glass layer into the semiconductor substrate to obtain the first doping layer.

[0012] In some embodiments, the first glass layer is a phosphosilicate glass layer or a borosilicate glass layer.

[0013] In some embodiments, before the second diffusion doping of the surround-extension layer using a second doping element, the following steps are further included:

[0014] Etching and removing the first glass layer.

[0015] In some embodiments, the second diffusion doping of the surround-extension layer using a second doping element includes:

[0016] Forming a second glass layer including the second doping element on the surround-extension layer by using a second doping source;

[0017] Diffusing the second doping element in the second glass layer into the surround-extension layer.

[0018] In some embodiments, the second glass layer is a phosphosilicate glass layer or a borosilicate glass layer.

[0019] In some embodiments, after the second diffusion doping of the surround-extension layer using a second doping element, the following steps are further included:

[0020] Etching and removing the second glass layer.

[0021] 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 ~9e19 / cm 3 The fourth doping concentration is 2e 17 / cm 3 ~9e 18 / cm 3 .

[0022] 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 .

[0023] 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 .

[0024] 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 3The 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 .

[0025] In a second aspect, the present application provides a solar cell prepared by any of the above-mentioned methods for preparing a solar cell.

[0026] The preparation method of the above-mentioned solar cell includes performing a second diffusion doping on the winding expansion layer using a second doping element of the opposite doping type to the first doping element, and converting the winding 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 winding expansion layer is doped with different types of elements through the second diffusion doping to offset the doping elements in the winding 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 winding expansion layer on the battery structure in the solar cell, 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 winding expansion layer, and can improve the problem of poor flatness of the silicon wafer surface caused by etching the winding expansion layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a process for preparing a solar cell according to an embodiment of the present application;

[0028] Figure 2 A schematic diagram of a structure for preparing a first glass layer on the surface of a semiconductor substrate;

[0029] Figure 3 For Figure 2 A schematic diagram of a structure for preparing a first doping layer and a winding and expansion layer based on the structure shown;

[0030] Figure 4 For Figure 3 A schematic diagram of a structure for preparing a second glass layer based on the structure shown;

[0031] Figure 5 For Figure 4 A schematic diagram of a structure for preparing a second doping layer based on the structure shown;

[0032] Figure 6 For Figure 5Schematic diagram of the structure with the first glass layer and the second glass layer removed based on the shown structure.

[0033] Marking description

[0034] 100, semiconductor substrate; 210, first glass layer; 220, first doping layer; 230, diffusion layer; 310, second glass layer; 320, second doping layer. Detailed implementation manners

[0035] To make the above objects, features, and advantages of the present application more apparent and understandable, the following detailed description of the specific implementation manners of the present application will be given in conjunction with the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments 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 related listed items.

[0037] In the description of this application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying 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 construed as limiting this application.

[0038] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0039] In this application, unless otherwise clearly specified and defined, terms such as "install", "connect", "link", "fix", etc. shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0040] Referring to Figure 1 As shown, an embodiment of the present application provides a method for preparing a solar cell, including:

[0041] S10: Provide a semiconductor substrate 100, and the semiconductor substrate 100 includes a first surface and a second surface which are oppositely arranged.

[0042] S20: Perform first diffusion doping on the first surface using a first doping element to form a first doping layer 220 with a first doping concentration, and form a diffusion layer 230 with a second doping concentration on the second surface.

[0043] S30: Perform second diffusion doping on the diffusion layer 230 using a second doping element, the doping type of the second doping element is opposite to that of the first doping element, and convert the diffusion 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.

[0044] The above method for preparing a solar cell includes performing second diffusion doping on the diffusion layer 230 using a second doping element with a doping type opposite to that of the first doping element to convert the diffusion 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 this method for preparing a solar cell, different types of elements are doped into the diffusion layer 230 through second diffusion doping to offset the doping elements in the diffusion layer 230 formed during the first diffusion doping, and the prepared semiconductor structure can be suitable for subsequent processing steps. It can be understood that the doping concentration can be controlled by factors such as gas flow rate, temperature, and pressure. By this method, the influence of the diffusion layer 230 in the solar cell on the cell structure can be eliminated, and it can replace the traditional method of etching and removing the diffusion layer 230 using a mixed solution of an alkaline solution + additive or an acidic mixed solution of hydrofluoric acid + nitric acid, and can improve the problem of poor flatness of the silicon wafer surface caused by etching the diffusion layer 230.

[0045] It is understandable that the above method for preparing a solar cell is applicable to silicon-based solar cells with various different structures, and the specific structure of the solar cell is not limited in this application.

[0046] In some embodiments, during the second diffusion doping of the bypass diffusion layer 230 with a second doping element, the concentration of the second doping element diffused into the first doping layer 220 is the fourth doping concentration, and the fourth doping concentration is less than the first doping concentration. Controlling the fourth doping concentration to be less than the first doping concentration can ensure that the doping type of the first doping layer is not changed during the second diffusion doping.

[0047] In some embodiments, the third doping concentration is slightly higher than the second doping concentration. It is understandable that the third doping concentration being slightly higher than the second doping concentration means that during the second diffusion doping process, the doping type of the bypass diffusion layer 230 is just changed. In this case, the influence on the doping concentration of the first doping layer 220 during the second high-temperature doping process is relatively small.

[0048] Refer to Figures 2 - 3 as shown, wherein, Figure 2 is a schematic structural diagram of preparing the first glass layer 210 on the surface of the semiconductor substrate 100, Figure 3 is in Figure 2 is a schematic structural diagram of preparing the first doping layer 220 and the bypass diffusion layer 230 on the basis of the structure shown.

[0049] In some embodiments, the first diffusion doping with the first doping element on the first surface includes: using a first doping source to form a first glass layer 210 including the first doping element on the first surface. Making the first doping element in the first glass layer 210 diffuse into the semiconductor substrate 100 to obtain the first doping layer 220.

[0050] It is understandable that diffusion doping is a commonly used semiconductor doping process used to change the electron and hole concentrations in a semiconductor. When a semiconductor material from Group IV such as silicon is doped with a Group V atom such as phosphorus, the 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.

[0051] In some embodiments, making the first doping element in the first glass layer 210 diffuse into the semiconductor substrate 100 to obtain the first doping layer 220 includes: heating the semiconductor substrate 100 to make the first doping element in the first glass layer 210 diffuse into the semiconductor substrate 100 to obtain the first doping layer 220.

[0052] In some embodiments, the first doping source includes at least one of boron trichloride (BCl 3 ) and boron tribromide (BBr 3 ).

[0053] In some embodiments, the first doping source includes phosphorus oxychloride (POCl 3 ).

[0054] In some embodiments, the first glass layer 210 is a phosphosilicate glass (PSG) layer.

[0055] In some embodiments, the first glass layer 210 is a borosilicate glass (BSG) layer.

[0056] 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.

[0057] In some embodiments, before the second diffusion doping of the wrap-around diffusion layer 230 with a second doping element, the following steps are further included: etching away the first glass layer 210.

[0058] In some embodiments, the second doping source includes at least one of boron trichloride (BCl 3 ) and boron tribromide (BBr 3 ).

[0059] In some embodiments, the second doping source includes phosphorus oxychloride (POCl 3 ).

[0060] In some embodiments, etching away the first glass layer 210 includes: etching away the first glass layer 210 by wet etching.

[0061] In some embodiments, etching away the first glass layer 210 by wet etching includes: using hydrofluoric acid to etch away the first glass layer 210.

[0062] Referring to Figures 4 - 5 shown, wherein Figure 4 is a schematic structural diagram of preparing the second glass layer 310 based on the structure shown in Figure 3 shown, Figure 5 is a schematic structural diagram of preparing the second doping layer 320 based on the structure shown in Figure 4 shown.

[0063] In some embodiments, the second diffusion doping of the wrap-around diffusion layer 230 with a second doping element includes: forming a second glass layer 310 including the second doping element on the wrap-around diffusion layer 230 using the second doping source; diffusing the second doping element in the second glass layer 310 into the wrap-around diffusion layer 230.

[0064] 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 cause the second doping element in the second glass layer 310 to diffuse into the wrap-around diffusion layer 230.

[0065] In some embodiments, the second glass layer 310 is a phosphosilicate glass layer.

[0066] In some embodiments, the second glass layer 310 is a borosilicate glass layer.

[0067] In some embodiments, the temperature of the second diffusion doping is 900 °C to 1100 °C. Optionally, the temperature of the second 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.

[0068] In some embodiments, after performing second diffusion doping on the wrap-around diffusion layer 230 with the second doping element, the following steps are further included: etching away the second glass layer 310.

[0069] In some embodiments, etching away the second glass layer 310 includes: etching away the second glass layer 310 by wet etching.

[0070] In some embodiments, etching away the second glass layer 310 by wet etching includes: using hydrofluoric acid to remove the second glass layer 310.

[0071] Refer to Figure 6 as shown Figure 6 For removing the first glass layer 210 and the second glass layer 310 on the basis of the structure shown Figure 5 is a schematic structural diagram. In some embodiments, after performing second diffusion doping on the wrap-around diffusion layer 230 with the second doping element, the following steps are further included: etching away the first glass layer 210 and the second glass layer 310.

[0072] In some embodiments, the first doping element includes boron, and the second doping element includes phosphorus.

[0073] In some embodiments, the first doping element includes phosphorus, and the second doping element includes boron.

[0074] In some embodiments, the first doping element is a phosphorus element, and the first doping concentration is 1e 19 / cm 3 ~8e 20 / cm 3 and the second doping concentration is 1e18 / 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 .

[0075] 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 also 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 / cm3 or 6e 19 / cm 3 。Or, the second doping concentration may also be within a range between any two of the above doping concentrations.

[0076] Optionally, the second doping element is boron, and the third doping concentration is 3e 19 / cm 3 ~7e 19 / cm 3 ,and the fourth doping concentration is 3e 18 / 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 。Or, the third doping concentration may also be within a 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 。Or, the fourth doping concentration may also be within a range between any two of the above doping concentrations.

[0077] In some embodiments, the first doping element is boron, and the first doping concentration is 1e18 / 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 .

[0078] 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 3Alternatively, the second doping concentration may also be within the range between any two of the above doping concentrations.

[0079] Optionally, the second doping element is phosphorus, the third doping concentration is 7e 17 / cm 3 ~1e 18 / cm 3 and 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 the range between any two of the above doping concentrations.

[0080] In some embodiments, before performing the first diffusion doping with the first doping element on the first surface, the following steps are further included: texturing the first surface and / or the second surface.

[0081] In some embodiments, after the first diffusion doping is performed on the first surface using the first doping element, before the second diffusion doping is performed on the wrap-around diffusion layer 230 using the second doping element, the following steps are further included: laser re-doping the first doping layer 220. It can be understood that laser re-doping means achieving doping with a doping concentration higher than the first doping concentration locally in the first doping layer 220 through laser irradiation.

[0082] In some embodiments, after removing the second glass layer 310 by wet etching, the following steps are further included: preparing a dielectric layer and / or a passivation layer on the first surface and the second surface respectively.

[0083] Another embodiment of the present application provides a solar cell, which is prepared by the preparation method of the solar cell according to any one of the above.

[0084] The following are specific embodiments

[0085] Embodiment 1

[0086] Preparation of an emitter-back passivated cell:

[0087] (1) Remove the cutting damage layer of the P-type silicon wafer, and use a mixed solution of deionized water, a texturing auxiliary agent, and sodium hydroxide to etch the silicon wafer and produce a uniform textured surface.

[0088] (2) Insert the cleaned and textured silicon wafer back-to-back into a quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use POCl 3 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, and the first doping concentration is 3e 20 / cm 3 , and a wrap-around diffusion layer 230 is formed on the back surface of the silicon wafer, and the second doping concentration is 3e 19 / cm 3 .

[0089] (3) Utilize the thermal effect of the laser to locally form heavy doping on the front surface of the silicon wafer.

[0090] (4) Insert the silicon wafer front-to-front into a quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BBr 3 or BCl 3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer, form a BSG layer, and transform the wrap-around diffusion layer 230 into a second doping layer 320. By controlling the gas flow rate, temperature, pressure, etc., control the doping concentration of boron elements so that the doping concentration of boron elements on the back surface of the silicon wafer is greater than the doping concentration of phosphorus elements on the back surface 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 make the doping concentration of boron element on the front side of the silicon wafer less 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 less than the first doping concentration, and the fourth doping concentration is 4e 18 / cm 3 .

[0091] (5) Use a hydrofluoric acid solution in a chain wet equipment or in a tank wet equipment to remove the PSG layer on the surface of the first doping layer 220 and the BSG layer on the surface of the second doping layer 320.

[0092] (6) Prepare a silicon oxide layer on the front side of the silicon wafer.

[0093] (7) Deposit an aluminum oxide film layer on the back side of the silicon wafer, and deposit a silicon nitride film layer on both the back side and the front side of the silicon wafer.

[0094] (8) Screen printing and sintering.

[0095] Example 2

[0096] Preparation of an emitter back surface passivated cell:

[0097] (1) Remove the cutting damage layer of the P-type silicon wafer, and use a mixed solution of deionized water, a texturing assistant, and sodium hydroxide to etch the silicon wafer and produce a uniform textured surface.

[0098] (2) Insert the cleaned and textured silicon wafers back to back into a quartz boat and send them into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use POCl 3 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, and the first doping concentration is 5e 20 / cm 3 , a wrap-around diffusion layer 230 is formed on the back surface of the silicon wafer, and the second doping concentration is 5e 19 / cm 3 .

[0099] (3) Utilize the thermal effect of the laser to locally form heavy doping on the front surface of the silicon wafer.

[0100] (4) Use hydrofluoric acid in a chain wet equipment or in a tank wet equipment to remove the PSG layer on the surface of the first doping layer 220.

[0101] (5) Insert the silicon wafers front to front into a quartz boat and send them into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BBr 3 or BCl 3High-temperature boron diffusion is carried out on the back surface of the silicon wafer using a doping source to form a BSG layer and convert the bypass diffusion layer 230 into a second doped layer 320. By controlling the gas flow rate, temperature, pressure, etc., the doping concentration of boron elements is controlled so that the doping concentration of boron elements on the back surface of the silicon wafer is greater than the doping concentration of phosphorus elements on the back surface 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 elements on the front surface of the silicon wafer is less than the doping concentration of phosphorus elements on the front surface of the silicon wafer in step (2), that is, the fourth doping concentration is less than the first doping concentration, and the fourth doping concentration is 6e 18 / cm 3 .

[0102] (6) Use a hydrofluoric acid solution in a chain wet equipment or a tank wet equipment to remove the BSG layer on the surface of the second doped layer 320.

[0103] (7) Prepare a silicon oxide layer on the front surface of the silicon wafer.

[0104] (8) Deposit an aluminum oxide film layer on the back surface of the silicon wafer, and deposit a silicon nitride film layer on the back surface and the front surface of the silicon wafer.

[0105] (9) Screen printing and sintering.

[0106] Example 3

[0107] Preparation of a tunneling oxide passivated contact cell:

[0108] (1) Remove the cutting damage layer of the N-type silicon wafer, and use a mixed solution of deionized water, a texturing assistant, and sodium hydroxide to etch the silicon wafer and produce a uniform textured surface.

[0109] (2) Insert the silicon wafer after cleaning and texturing back to back into a quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BCl 3 or BBr 3 as a doping source to perform high-temperature boron diffusion on the front surface of the silicon wafer. After the process is completed, a P-type doped layer and a BSG layer are formed on the front surface of the silicon wafer.

[0110] (3) Use a mixed solution of nitric acid and hydrofluoric acid to etch the four sides of the silicon wafer and polish the back surface. Drop water on the front surface of the silicon wafer through a water dripping device to retain the BSG layer and the P-type doped layer on the front surface of the silicon wafer.

[0111] (4) Put the silicon wafer with the polished back surface into an LPCVD device, and grow a tunneling oxide layer, and a polysilicon, amorphous silicon layer or a polysilicon amorphous silicon hybrid film layer on the back surface of the silicon wafer.

[0112] (5) Insert the silicon wafer face-to-face into the quartz boat and send it into a tube-type 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, with the first doping concentration being 4e 20 / cm 3 , and a wrap-around diffusion layer 230 is formed on the back of the silicon wafer, with the second doping concentration being 4e 19 / cm 3 .

[0113] (6) Insert the silicon wafer back-to-back into the quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BBr 3 or BCl 3 as the doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer, forming a BSG layer and converting the wrap-around diffusion layer 230 into a second doped layer 320. Control the doping concentration of boron element through gas flow rate, temperature, pressure, etc., so that the doping concentration of boron element on the front of the silicon wafer is greater than the doping concentration of phosphorus element 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 make the doping concentration of boron element on the back of the silicon wafer less than the doping concentration of phosphorus element 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 .

[0114] (7) Use hydrofluoric acid solution in a chain wet equipment or a tank wet equipment to remove the PSG layer on the surface of the first doped layer 220 and the BSG layer on the surface of the second doped layer 320.

[0115] (8) Deposit an alumina film layer on the entire surface of the silicon wafer, and deposit a silicon nitride film layer on the back and front of the silicon wafer.

[0116] (9) Screen printing and sintering.

[0117] Example 4

[0118] Preparation of a tunneling oxide passivated contact cell:

[0119] (1) Remove the cutting damage layer of the N-type silicon wafer, and use a mixed solution of deionized water, texturing assistant, and sodium hydroxide to etch the silicon wafer and fabricate a uniform textured surface.

[0120] (2) Insert the cleaned and textured silicon wafer back-to-back into the quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BCl 3 or BBr 3 as the doping source to perform high-temperature boron diffusion on the front surface of the silicon wafer. After the process is completed, a P-type doped layer and a BSG layer are formed on the front of the silicon wafer.

[0121] (3) Use a mixed solution of nitric acid and hydrofluoric acid to etch the periphery of the silicon wafer and polish the back surface. Drop water on the front surface of the silicon wafer through a water-dropping device, and retain the BSG layer and P-type doping layer on the front surface of the silicon wafer.

[0122] (4) Place the silicon wafer with the polished back surface into an LPCVD device, and grow a tunneling oxide layer, as well as a polysilicon, amorphous silicon layer, or polysilicon amorphous silicon hybrid film layer on the back surface of the silicon wafer.

[0123] (5) Insert the silicon wafer with the front surface facing the front into a quartz boat and send it into a tube-type 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 doping layer as the first doping layer 220. The first doping concentration is 6e 20 / cm 3 , and a bypass diffusion layer 230 is formed on the back surface of the silicon wafer. The second doping concentration is 6e 19 / cm 3 .

[0124] (6) Use hydrofluoric acid in a chain wet equipment or a tank wet equipment to remove the PSG layer on the surface of the first doping layer 220.

[0125] (7) Insert the silicon wafer with the back surface facing the back into a quartz boat and send it into a tube-type low-pressure diffusion furnace. Under high-temperature conditions, use BBr 3 or BCl 3 as a doping source to perform high-temperature boron diffusion on the back surface of the silicon wafer, forming a BSG layer and converting the bypass diffusion layer 230 into a second doping layer 320. Control the doping concentration of boron elements through gas flow rate, temperature, pressure, etc., so that the doping concentration of boron elements on the front surface of the silicon wafer is greater than the doping concentration of phosphorus elements on the front surface of the silicon wafer in step (5), that is, the third doping concentration is greater than the second doping concentration. The third doping concentration is 7e 19 / cm 3 . And make the doping concentration of boron elements on the back surface of the silicon wafer less than the doping concentration of phosphorus elements on the back surface of the silicon wafer in step (5), that is, the fourth doping concentration is less than the first doping concentration. The fourth doping concentration is 7e 18 / cm 3 .

[0126] (8) Use a hydrofluoric acid solution in a chain wet equipment or a tank wet equipment to remove the BSG layer located on the surface of the second doping layer 320.

[0127] (9) Deposit an alumina film layer on the entire surface of the silicon wafer, and deposit a silicon nitride film layer on the back and front surfaces of the silicon wafer.

[0128] (10) Screen printing and sintering.

[0129] In Embodiments 1 to 4, the process of second diffusion doping is adopted to eliminate the influence of the diffusion bypass layer 230 on the battery structure. There is no need to use a mixed solution of an alkaline solution + an additive or an acidic mixed solution of hydrofluoric acid + nitric acid to etch the diffusion bypass layer 230, which can reduce the negative impact on the solar cell caused by etching the diffusion bypass layer 230. And this method is applicable to solar cells with different structures.

[0130] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0131] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the specification and the drawings can be used to explain the content of the claims.

Claims

1. A method for preparing a solar cell, characterized in that: include: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: 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, characterized in that: The solar cell is prepared by the method for preparing the solar cell according to any one of claims 1 to 12.

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