Silicon wafer for solar cell and its preparation method

Abstract

The present invention provides a silicon wafer for a solar cell and a preparation method thereof. One side of the solar cell wafer has a tower base structure, and the radial dimension of the tower base structure is 6 μm to 8 μm; and / or the height of the tower base structure is 0.6 μm to 0.9 μm. The preparation method of the silicon wafer for a solar cell of the present invention repairs the flocked surface after flocking by using an auxiliary solution including a potassium hydroxide solution, improves the flocking at the wire mark position, and improves the uniformity of the flocked surface after flocking, thereby improving the efficiency of the silicon wafer for a solar cell. Experiments show that the photoelectric conversion efficiency of the solar cell can be increased by more than 0.03%.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and more specifically, to a solar cell silicon wafer and a preparation method thereof. Background Art

[0002] To address issues such as global energy shortages and the increasing depletion of traditional energy sources (fossil fuels, coal, oil, etc.), it has become a global consensus to vigorously develop renewable energy. Solar energy, with its significant advantages of cleanliness, safety, and abundant resources, has become one of the fastest-growing renewable energy sources, and photovoltaic power generation is one of its most important utilization methods. After decades of development, photovoltaic power generation technology has also made great progress.

[0003] The PEPoly-TOPCon battery is a commonly used solar cell structure. Among them, the battery usually adopts a one-step texturing method. The one-step texturing method has the disadvantages that the texture at the edge or the wire mark position after texturing is less uniform than that at the center position, resulting in a low texture yield and poor edge contact after texturing, thereby affecting the overall efficiency of the solar cell. How to improve the texture yield through the texturing process to improve the overall efficiency of the solar cell has always been a research hotspot in this field.

[0004] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] Aiming at the problems in the prior art, the purpose of the present invention is to provide a solar cell silicon wafer and a preparation method thereof. Among them, after the traditional texturing process, the prepared texture surface is repaired by using an auxiliary solution including potassium hydroxide solution to improve the uniformity of the texture surface after texturing, thereby improving the efficiency of the solar cell silicon wafer.

[0006] The first aspect of the present invention provides a solar cell, one side of the solar cell has a tower base structure, and the radial dimension of the tower base structure is 6 μm to 8 μm; and / or

[0007] The height of the tower base structure is 0.6 μm to 0.9 μm.

[0008] The second aspect of the present invention provides a preparation method of a solar cell silicon wafer for preparing the solar cell silicon wafer, including the following steps:

[0009] S10: Provide a solar silicon wafer;

[0010] S20: Place the surface of the solar silicon wafer to be textured in a texturing solution for texturing; and

[0011] S30: Add an auxiliary solution to the texturing solution, and place the textured surface of the solar silicon wafer in the texturing solution added with the auxiliary solution for repair. The auxiliary solution includes a potassium hydroxide solution.

[0012] According to the second aspect of the present invention, the auxiliary solution in step S30 is a potassium hydroxide solution, and

[0013] In terms of mass percentage, the concentration of the potassium hydroxide solution is 0.5 - 2%.

[0014] According to the second aspect of the present invention, the texturing temperature in step S20 is 82 °C, and the temperature in step S30 is 60 °C.

[0015] According to the second aspect of the present invention, the texturing time in step S20 is 420 seconds, and the time in step S30 is 200 seconds.

[0016] According to the second aspect of the present invention, in terms of mass percentage, the auxiliary solution in step S30 further includes:

[0017] 0.25 - 0.35% 2-methyl-2,4-pentanediol;

[0018] 1.5 - 2.0% sodium carboxymethyl cellulose;

[0019] 0.18 - 0.22% 5-nitroguaiacol;

[0020] 0.15 - 0.20% 5-chloro-2-(2',4'-dichlorophenoxy)phenol;

[0021] 0.3 - 0.5% sodium hydroxide;

[0022] 0.15 - 0.25% sodium acetate;

[0023] 0.2 - 0.4% sodium chloride;

[0024] pigment and 96.0 - 97.0% water.

[0025] According to the second aspect of the present invention, the texturing temperature in step S20 is 82 °C, and the temperature in step S30 is 80 °C.

[0026] According to the second aspect of the present invention, the texturing time in step S20 is 360 seconds, and the time in step S30 is 120 seconds.

[0027] According to the second aspect of the present invention, the preparation method further includes the following steps:

[0028] S40: Polish the textured surface of the solar cell wafer to obtain a solar cell wafer with a surface having a tower base structure.

[0029] According to the second aspect of the present invention, the polishing liquid used in step S40 includes:

[0030] 1.5 - 2.5% sodium persulfate;

[0031] 2.5 - 4.0% sodium iodate;

[0032] 1.0 - 1.5% sodium gluconate;

[0033] 0.75 - 1.45% acidic solution;

[0034] 0.4 - 0.7% alkaline solution;

[0035] 88.0 - 90.0% water; and

[0036] an auxiliary agent, the auxiliary agent includes 0.5 - 1.0% potassium hydroxyethylidene diphosphonate and 1.0 - 1.5% diethylenetriamine pentaacetic acid;

[0037] the acidic solution includes 0.1 - 0.25% phosphoric acid, 0.45 - 0.65% sulfuric acid and 0.3 - 0.6% acetic acid, wherein the concentration of the phosphoric acid is greater than or equal to 85%, and the concentration of the sulfuric acid is greater than or equal to 98%; and

[0038] the alkaline solution includes 0.2 - 0.3% potassium hydroxide solution and 0.2 - 0.4% sodium hydroxide solution. For the silicon wafer of the solar cell and its preparation method of the present invention, in the preparation method, the fluff on the surface after texturing is repaired by texturing and using an auxiliary solution including potassium hydroxide solution, the fluff at the wire mark position is improved, and the uniformity of the surface after texturing is improved, thereby improving the efficiency of the silicon wafer of the solar cell. Experiments show that the photoelectric conversion efficiency of the solar cell can be increased by more than 0.03%; further, after the surface fluff is repaired, by polishing in a polishing liquid with an auxiliary agent of potassium hydroxyethylidene diphosphonate and diethylenetriamine pentaacetic acid, the corrosion rate of different crystal orientations of the solar cell wafer is changed, the pit depth of the tower base structure is deepened with basically no change in the tower base size, the back specific surface area is further improved, and the contact area when contacting with the paste is increased, improving the fill factor (FF) of the battery, and achieving the purpose of improving the photoelectric conversion efficiency of the solar cell. Description of the Drawings

[0039] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application. By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present invention will become more apparent. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0040] Figure 1 It is a flowchart of a method for preparing a silicon wafer of a solar cell according to an embodiment of the present invention. Detailed implementation manners

[0041] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0042] In the description of this specification, the representation of reference terms such as "an embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics represented in connection with the embodiment or example are included in at least one embodiment or example of this specification. Moreover, the specific features, structures, materials, or characteristics represented can be combined in any suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples represented in this specification and the features of different embodiments or examples.

[0043] It should be further understood that the terms "comprising" and "including" indicate the presence of the described features, steps, categories, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, categories, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or meaning any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A, B, and C". An exception to this definition will occur only when the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0044] Although not defined differently, including technical terms and scientific terms used herein, all terms have the same meaning as generally understood by those skilled in the technical field to which this specification pertains. Terms defined in commonly used dictionaries are additionally interpreted to have meanings consistent with the relevant technical literature and the content presented herein. As long as they are not defined, they shall not be over-interpreted as ideal or overly formulaic meanings.

[0045] In view of the existing technical problems, the present invention provides a solar cell silicon wafer and a preparation method thereof. One side of the solar cell silicon wafer has a tower base structure, and the radial dimension of the tower base structure is 6 μm to 8 μm; and / or the height of the tower base structure is 0.6 μm to 0.9 μm. In the preparation method of the solar cell silicon wafer of the present invention, during the preparation method, the surface to be textured is textured and the textured surface is repaired by using an auxiliary solution including a potassium hydroxide solution, which improves the emergence of texture at the position of wire marks and improves the uniformity of the textured surface after texturing, thereby improving the efficiency of the solar cell silicon wafer. Experiments show that the photoelectric conversion efficiency of the solar cell can be increased by more than 0.03%; further, after the surface texture repair, by polishing in a polishing solution having 1-hydroxyethylidene-1,1-diphosphonic acid potassium and diethylenetriaminepentaacetic acid auxiliary agents, the etching rates of different crystal orientations of the solar cell wafer are changed, and the pit depth of the tower base structure is deepened with the tower base size basically unchanged, further improving the back specific surface area and increasing the contact area when contacting with the paste, and improving the fill factor (FF) of the battery, so as to achieve the purpose of improving the photoelectric conversion efficiency of the solar cell.

[0046] The following further gives examples to illustrate the structure of the solar cell silicon wafer of the present invention and each step of its preparation method. It should be understood that the examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention.

[0047] Figure 1 is a flowchart of the preparation method of the solar cell silicon wafer of an embodiment of the present invention; specifically, the preparation method of the solar cell silicon wafer includes the following steps:

[0048] S10: Provide a solar silicon wafer. The solar silicon wafer can be divided into a single crystal silicon wafer and a polycrystalline silicon wafer. The solar silicon wafer can be an N-type silicon wafer or an IP-type silicon wafer.

[0049] S20: Place the surface of the solar silicon wafer to be textured in a texturing solution for texturing; there are some differences in the texturing solutions and process conditions for single crystal silicon wafers and polycrystalline silicon wafers.

[0050] S30: Add an auxiliary solution to the texturing solution, and place the textured surface of the solar silicon wafer in the texturing solution added with the auxiliary solution for repair. The auxiliary solution includes a potassium hydroxide solution. In the preparation method of the present invention, after directly adding the auxiliary solution to the texturing solution, the repair in step S30 is carried out, which simplifies the preparation process.

[0051] Example 1

[0052] In terms of mass percentage, the auxiliary solution in step S30 is a potassium hydroxide solution. In terms of mass percentage, the concentration of the potassium hydroxide solution is 0.5 - 2%. In this example, the texturing temperature in step S20 is 82 °C, and the texturing time is 420 seconds. The temperature in step S30 is 60 °C, and the time is 200 seconds.

[0053] In this example, the texturing time in step S20 is equivalent to that of the traditional texturing process. After step S20 in the texturing tank, step S30 is added. Add a KOH solution to the texturing solution in the tank and adjust the temperature to 60 °C. Step S30 modifies the position of the line marks and the edges of the textured surface, increasing the number of emerging hairs.

[0054] Example 2

[0055] Different from Example 1, in terms of mass percentage, the auxiliary solution in step S30 includes, in addition to the potassium hydroxide solution: 0.25 - 0.35% 2-methyl-2,4-pentanediol; 1.5 - 2.0% sodium carboxymethylcellulose; 0.18 - 0.22% 5-nitroguaiacol; 0.15 - 0.20% 5-chloro-2-(2',4'-dichlorophenoxy)phenol; 0.3 - 0.5% sodium hydroxide; 0.15 - 0.25% sodium acetate; 0.2 - 0.4% sodium chloride; pigment, and 96.0 - 97.0% water. The concentration of the potassium hydroxide solution is 0.5 - 2%.

[0056] Table 1 is the component table of the auxiliary solution of the solar silicon wafer in Example 2.

[0057] Component Number Component Name Mass Percentage / % 1 Potassium Hydroxide ～0.5～2％ 2 2-Methyl-2,4-pentanediol ～0.25-0.35 3 Sodium Carboxymethyl Cellulose ～1.5-2.0 4 5-Nitroguaiacol ～0.18-0.22 5 5-Chloro-2-(2',4'-dichlorophenoxy)phenol ～0.15-0.20 6 Sodium Hydroxide ～0.3-0.5 7 Sodium Acetate ～0.15-0.25 8 Sodium Chloride ～0.2-0.4 9 Pigment Appropriate Amount 10 Water ～96.0-97.0

[0058] The texturing temperature in step S20 is 82 °C, and the texturing time is 360 seconds. The temperature in step S30 is 80 °C, and the time is 120 seconds. In this example, after texturing in step S20, step S30 is added. Add a KOH solution or the solvent components in Table 1 to the texturing solution in the texturing tank and adjust the temperature to 80 °C. The process time is 120 s. Step S30 enables the entire textured surface to grow in the improvement tank for several times.

[0059] After texturing in step S20, the surface texture is repaired with an auxiliary solution containing a KOH solution (step S30). In the KOH solution, the surface texture at the edge / scratch position undergoes secondary growth, increasing the surface texture height at this position, enhancing the overall specific surface area, and improving the front contact. Further testing of multiple batches of solar cell wafers obtained by the preparation method of the present invention shows that, compared with existing solar cell wafers in the same process path, the Isc increases by 10 - 13 mA, the fill factor increases by 0.08% - 0.11%, and the overall efficiency of the solar cell increases by 0.03% compared with the control group. The additional repair step S30 of the method of this application is completed by directly adding an auxiliary solution to the solution in step S20 without removing the solar cell wafers in step S20, which simplifies the process while improving the performance of the solar cell wafers.

[0060] To further improve the performance of the solar cell wafers, in some other embodiments, after step S30, the preparation method further includes a polishing process, specifically including:

[0061] S40: Polish the textured surface of the solar cell to obtain a solar cell with a surface having a tower base structure. The polishing solution used in step S40 includes: 1.5 - 2.5% sodium persulfate; 2.5 - 4.0% sodium iodate; 1.0 - 1.5% sodium gluconate; 0.75 - 1.45% acidic solution; 0.4 - 0.7% alkaline solution; 88.0 - 90.0% water; wherein, an auxiliary agent, the auxiliary agent includes 0.5 - 1.0% potassium hydroxyethylidene diphosphonate and 1.0 - 1.5% diethylenetriamine pentaacetic acid. The acidic solution can be a mixed solution of phosphoric acid, sulfuric acid, and acetic acid. For example, the acidic solution includes 0.1 - 0.25% phosphoric acid, 0.45 - 0.65% sulfuric acid, and 0.3 - 0.6% acetic acid, wherein the concentration of the phosphoric acid is greater than or equal to 85%, and the concentration of the sulfuric acid is greater than or equal to 98%. The alkaline solution is a mixed solution of potassium hydroxide solution and sodium hydroxide solution. For example, the alkaline solution includes 0.2 - 0.3% potassium hydroxide solution and 0.2 - 0.4% sodium hydroxide solution. Table 2 shows the component table of the polishing solution for a solar cell in an embodiment.

[0062] After obtaining the solar cell wafers in Example 2 and polishing them with the components of the polishing solution in Table 2, one side of the solar cell wafer has a tower base structure, and the radial dimension of the tower base structure is 6 μm to 8 μm; and / or the height of the tower base structure is 0.6 μm to 0.9 μm. The radial dimension of the tower base structure here refers to the distance between the two farthest points on the cross-section of the tower base structure. In the present invention, the ratio between potassium hydroxyethylidene diphosphonate and diethylenetriaminepentaacetic acid in the polishing solution can be adjusted, and the ratio of potassium hydroxyethylidene diphosphonate / diethylenetriaminepentaacetic acid is less than 0.3. At this time, the difference in corrosion rate between the (0,0,1) and (1,0,0) crystal orientations of the solar cell wafer in the polishing rate becomes larger. Without significant change in the tower base size, the examples show that the pit depth (depth of the pit) of the tower base structure changes from 500 nm (without the additive) to about 900 nm (with the additive), and the back specific surface area is also improved, increasing from 1.26% to 1.35% in the experimental group. The contact area between the solar cell wafer with a larger specific surface area and the paste further increases, improving the fill factor of the battery. Correspondingly, the photoelectric conversion efficiency of the battery is improved.

[0063] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those skilled in the art, it is obvious that this application is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of this application, this application can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of this application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed by this application. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A solar cell silicon wafer, characterized in that: One side of the solar cell has a tower base structure, and the radial dimension of the tower base structure is 6 μm to 8 μm; and / or The height of the tower base structure is 0.6 μm to 0.9 μm; The solar cell silicon wafer is obtained by a preparation method, and the preparation method comprises the following steps: S10: Provide solar silicon wafers; S20: placing the surface of the solar silicon wafer to be textured in a texturing liquid for texturing; and S30: adding an auxiliary solution to the texturing liquid, placing the texturing surface of the solar silicon wafer after texturing in the texturing liquid to which the auxiliary solution is added for repair, wherein the auxiliary solution includes a potassium hydroxide solution; In terms of mass percentage, the concentration of the potassium hydroxide solution is 0.5-2%; The auxiliary solution of step S30 further includes: 0.25-0.35% 2-methyl-2,4-pentanediol; 1.5-2.0% sodium carboxymethyl cellulose; 0.18-0.22% 5-nitroguaiacol; 0.15-0.20% 5-chloro-2-(2',4'-dichlorophenoxy)phenol; 0.3-0.5% sodium hydroxide; 0.15-0.25% sodium acetate; 0.2-0.4% sodium chloride; Pigment and 96.0-97.0% water; The texturing temperature in step S20 is 82° C., and the temperature in step S30 is 80° C.; The texturing time in step S20 is 360 seconds, and the time in step S30 is 120 seconds; The preparation method further comprises the following steps: S40: polishing the surface of the solar cell after texturing to obtain a solar cell with a tower base structure surface; The polishing liquid used in step S40 includes: 1.5-2.5% sodium persulfate; 2.5-4.0% sodium iodate; 1.0-1.5% sodium gluconate; 0.75-1.45% acidic solution; 0.4-0.7% alkaline solution; 88.0-90.0% water; and An auxiliary agent, wherein the auxiliary agent includes 0.5-1.0% potassium hydroxyethylidene diphosphate and 1.0-1.5% diethylenetriaminepentaacetic acid; The acidic solution comprises 0.1-0.25% phosphoric acid, 0.45-0.65% sulfuric acid and 0.3-0.6% acetic acid, wherein the concentration of the phosphoric acid is greater than or equal to 85%, and the concentration of the sulfuric acid is greater than or equal to 98%; and The alkaline solution includes 0.2-0.3% potassium hydroxide solution and 0.2-0.4% sodium hydroxide solution.

2. A method for preparing a solar cell silicon wafer, used for preparing the solar cell silicon wafer according to claim 1, characterized in that: The steps include: S10: Provide solar silicon wafers; S20: placing the surface of the solar silicon wafer to be textured in a texturing liquid for texturing; and S30: adding an auxiliary solution to the texturing liquid, placing the texturing surface of the solar silicon wafer after texturing in the texturing liquid to which the auxiliary solution is added for repair, wherein the auxiliary solution includes a potassium hydroxide solution; In terms of mass percentage, the concentration of the potassium hydroxide solution is 0.5-2%; The auxiliary solution of step S30 further includes: 0.25-0.35% 2-methyl-2,4-pentanediol; 1.5-2.0% sodium carboxymethyl cellulose; 0.18-0.22% 5-nitroguaiacol; 0.15-0.20% 5-chloro-2-(2',4'-dichlorophenoxy)phenol; 0.3-0.5% sodium hydroxide; 0.15-0.25% sodium acetate; 0.2-0.4% sodium chloride; Pigment and 96.0-97.0% water; The texturing temperature in step S20 is 82° C., and the temperature in step S30 is 80° C.; The texturing time in step S20 is 360 seconds, and the time in step S30 is 120 seconds; The preparation method further comprises the following steps: S40: polishing the surface of the solar cell after texturing to obtain a solar cell with a tower base structure surface; The polishing liquid used in step S40 includes: 1.5-2.5% sodium persulfate; 2.5-4.0% sodium iodate; 1.0-1.5% sodium gluconate; 0.75-1.45% acidic solution; 0.4-0.7% alkaline solution; 88.0-90.0% water; and An auxiliary agent, wherein the auxiliary agent includes 0.5-1.0% potassium hydroxyethylidene diphosphate and 1.0-1.5% diethylenetriaminepentaacetic acid; The acidic solution comprises 0.1-0.25% phosphoric acid, 0.45-0.65% sulfuric acid and 0.3-0.6% acetic acid, wherein the concentration of the phosphoric acid is greater than or equal to 85%, and the concentration of the sulfuric acid is greater than or equal to 98%; and The alkaline solution includes 0.2-0.3% potassium hydroxide solution and 0.2-0.4% sodium hydroxide solution.

Images