Screen printing method of solar cell and preparation method of solar cell

Abstract

The invention discloses a screen printing method of a solar cell and a preparation method of the solar cell, and the method comprises the steps: carrying out the marking of a diffusion surface of an N-type silicon wafer after boron diffusion, and obtaining a silicon wafer with a first positioning mark; comparing and positioning the first positioning mark with a first positioning pattern on the first printing screen, and printing an electrode main grid pattern and a second positioning mark on the surface of the silicon wafer; and comparing and positioning the second positioning mark with a second positioning pattern on the second printing screen, and printing an electrode fine grid pattern and a third positioning mark on the surface of the silicon wafer printed with the main grid pattern. According to the invention, the main grid pattern is printed by comparing the positions of the first positioning mark and the first positioning pattern, and the fine grid pattern is printed by comparing the positions of the second positioning mark and the second positioning pattern, so that compared with a mode of directly grabbing the edge of the silicon wafer for positioning, a point-to-point positioning mode is adopted, the positioning precision is higher, and the offset rate of silk-screen printing is more favorably reduced.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a screen printing method for solar cells and a method for fabricating solar cells. Background Technology

[0002] In the fabrication of solar cells, main grid lines and fine grid lines need to be printed on silicon wafers using screen printing. During the printing process, the silicon wafer needs to be positioned. In existing technologies, a camera is usually used to capture the edge of the silicon wafer for positioning. However, the accuracy of this positioning method is often relatively low, which will cause the printed pattern to shift. This shift will affect the yield of the solar cells. On the other hand, when testing the electrical performance of the fabricated solar cells, it will cause the probes to be unable to accurately press on the electrode positions, thus affecting the testing efficiency and the reliability of the results.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a screen printing method for solar cells and a method for fabricating solar cells, thereby improving the positioning accuracy of silicon wafers during grid line printing and reducing the offset rate of grid line printing.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides a screen printing method for solar cells, comprising:

[0007] The diffusion surface of the N-type silicon wafer that has undergone boron diffusion treatment is marked to obtain a silicon wafer with the first positioning mark;

[0008] The first positioning mark and the first positioning pattern on the first printing screen are compared and positioned, and the electrode main gate pattern and the second positioning mark are printed on the silicon wafer surface with the first positioning mark according to the comparison and positioning result, so as to obtain a silicon wafer with the main gate pattern. The second positioning mark is printed from the first positioning pattern.

[0009] The second positioning mark is compared and positioned with the second positioning pattern on the second printing screen. Based on the comparison and positioning result, the electrode fine grid pattern and the third positioning mark are printed on the silicon wafer surface with the main grid pattern to obtain the silicon wafer with the electrode. The third positioning mark is printed from the second positioning pattern.

[0010] In an optional implementation, the second positioning identifier includes a first identifier adapted to the position of the first positioning identifier and a second identifier adapted to the position of the third positioning identifier.

[0011] In an optional embodiment, the first identifier is provided with a first mating area that can mate with the first positioning identifier, and the size and shape of the first mating area are adapted to the size and shape of the first positioning identifier.

[0012] In an optional embodiment, the second identifier is provided with a second mating area that can mate with the third positioning identifier, the size and shape of the second mating area being adapted to the size and shape of the third positioning identifier.

[0013] In an optional implementation, there are two or more first positioning identifiers, which are arranged in an array; each first positioning identifier is correspondingly provided with a second positioning identifier and a third positioning identifier.

[0014] In an optional embodiment, both the first positioning mark and the third positioning mark are circular, with the diameter of the first positioning mark being 0.35-0.45 mm and the diameter of the third positioning mark being 0.35-0.45 mm; both the first mark and the second mark are annular, with the radial width of the first mark being 0.05-0.15 mm and the radial width of the second mark being 0.05-0.15 mm.

[0015] In an optional embodiment, the diffusion surface is marked with a laser, wherein the laser power is 20-100W, the laser frequency is 400-500KHz, and the scanning speed is 10000-50000mm / s.

[0016] In an optional implementation, a camera is used to capture a first positioning mark, and when the first mark coincides with a first mating area in the first positioning mark, an electrode main grid pattern is printed; a camera is used to capture a second mating area, and when a third positioning mark coincides with the second mating area, a fine grid pattern is printed.

[0017] In an optional embodiment, the fabrication of the silicon wafer with the first positioning mark further includes the following steps performed sequentially:

[0018] Remove the borosilicate glass from the back and edges of the marked silicon wafer and then polish it.

[0019] A tunnel oxide layer and a doped polysilicon layer are deposited on the back side;

[0020] Remove the phosphosilicate glass on the back;

[0021] Remove the doped polysilicon layer deposited on the front and edge sides;

[0022] Remove the front borosilicate glass;

[0023] Aluminum oxide is deposited on the front side;

[0024] Silicon nitride is deposited on both the front and back sides;

[0025] A pattern is printed on the back of the silicon wafer to obtain a silicon wafer with the first positioning mark.

[0026] Secondly, the present invention provides a method for preparing a solar cell, comprising:

[0027] The silicon wafer with printed electrodes is obtained by sintering, and the silicon wafer with printed electrodes is prepared by the screen printing method of the solar cell described in any one of the foregoing embodiments.

[0028] The present invention has the following beneficial effects:

[0029] In the screen printing method for solar cells provided by the embodiments of the present invention, the main grid pattern is printed by comparing the positions of the first positioning mark and the first positioning pattern, and the fine grid pattern is printed by comparing the positions of the second positioning mark and the second positioning pattern. Compared with directly grasping the edge of the silicon wafer for positioning, the point-to-point positioning method is adopted, which has higher positioning accuracy and is more conducive to reducing the offset rate of screen printing. Attached Figure Description

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of the structure of a silicon wafer with the first positioning mark;

[0032] Figure 2 An enlarged view of the first positioning marker;

[0033] Figure 3 This is a schematic diagram of the structure of the first printing screen;

[0034] Figure 4 This is an enlarged view of the first positioning graphic;

[0035] Figure 5 This is a schematic diagram of the structure of the second printing screen;

[0036] Figure 6 This is an enlarged view of the second positioning graphic;

[0037] Figure 7 This is a diagram showing the relative positions of the first, second, and third positioning marks when the printing is not offset.

[0038] Figure 8A diagram showing the possible relative positions of the first, second, and third positioning marks during printing offset;

[0039] Figure 9 A diagram showing the possible relative positions of the first, second, and third positioning marks during printing offset;

[0040] Figure 10 This is a flowchart of the fabrication method of the non-SE structure TOPCon battery in Example 1.

[0041] Illustration: 10-First positioning mark; 20-First positioning graphic; 21-First graphic; 22-Second graphic; 30-Second positioning mark; 41-First mark; 42-Second mark. Detailed Implementation

[0042] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0043] This invention provides a screen printing method for solar cells, comprising:

[0044] The diffusion surface of the N-type silicon wafer that has undergone boron diffusion treatment is marked to obtain a silicon wafer with a first positioning mark, such as... Figure 1 and Figure 2 As shown;

[0045] The first positioning mark 10 and the first positioning pattern 20 on the first printing screen are compared and positioned. Based on the comparison and positioning result, the electrode main gate pattern and the second positioning mark 30 are printed on the silicon wafer surface with the first positioning mark 10, resulting in a silicon wafer with the main gate pattern printed on it. The second positioning mark 30 is printed from the first positioning pattern 20. The position and shape of the first positioning pattern 20 on the first printing screen are as follows: Figure 3 and Figure 4 As shown;

[0046] The second positioning mark 30 is compared and positioned with the second positioning pattern on the second printing screen. Based on the comparison and positioning result, electrode fine grid patterns and the third positioning mark are printed on the silicon wafer surface with the main grid pattern, resulting in a silicon wafer with electrodes. The third positioning mark is printed from the second positioning pattern. The position and shape of the second positioning pattern on the second printing screen are as follows: Figure 5 and Figure 6 As shown.

[0047] In the screen printing method for solar cells provided by the embodiments of the present invention, the main grid pattern is printed by comparing the positions of the first positioning mark 10 and the first positioning pattern 20, and the fine grid pattern is printed by comparing the positions of the second positioning mark 30 and the second positioning pattern. Compared with directly grasping the edge of the silicon wafer for positioning, the point-to-point positioning method is adopted, which has higher positioning accuracy and is more conducive to reducing the offset rate of screen printing.

[0048] Meanwhile, the silicon wafer obtained by the method of the present invention contains a first positioning mark 10, a second positioning mark 30 and a third positioning mark. By the relative positions of the three positioning marks, it is possible to determine whether the printing of the main grid and the fine grid pattern has shifted and the degree of shift, which facilitates subsequent screening, grading and other work of the solar cells.

[0049] In an optional embodiment, the second positioning identifier 30 includes a first identifier 41 adapted to the position of the first positioning identifier 10 and a second identifier 42 adapted to the position of the third positioning identifier.

[0050] Since screen printing requires printing the main grid pattern first and then the fine grid pattern, which necessitates two positioning steps, this embodiment of the invention uses laser doping to form a first positioning mark 10 on the silicon wafer. This first mark 10 is used to coordinate with the first mark 41 for positioning. A third positioning mark is used to position the wafer with the second mark 42. The first mark 41 is printed from the first pattern 21, and the second mark 42 is printed from the second pattern 22. Compared to using laser doping to form two positioning marks on the silicon wafer, which are then used to coordinate with the second and third positioning marks respectively, this method reduces damage to the silicon wafer caused by the marking process and is more effective in minimizing the relative positional shift between the main grid pattern and the fine grid pattern on the silicon wafer.

[0051] In an optional embodiment, the first identifier 41 is provided with a first mating area that can mate with the first positioning identifier 10, and the size and shape of the first mating area are adapted to the size and shape of the first positioning identifier 10.

[0052] In an optional embodiment, the second identifier 42 is provided with a second mating area that can mate with the third positioning identifier, the size and shape of the second mating area being adapted to the size and shape of the third positioning identifier.

[0053] The size and shape of the first mating area and the first mark 41 or the second mating area and the second mark 42 are compatible. When the first mating area or the second mating area is completely covered, it indicates that no offset has occurred. Figure 7 As shown; if any area within the first or second mating zone is not covered, it indicates that a shift of varying degrees has occurred, such as... Figure 8 and 9 As shown, the degree of offset can be determined based on the size of the uncovered area.

[0054] In an optional embodiment, there are two or more first positioning identifiers 10, and the two or more first positioning identifiers 10 are arranged in an array; each first positioning identifier 10 is correspondingly provided with a second positioning identifier 30 and a third positioning identifier.

[0055] In some embodiments, four of the first positioning marker 10, the second positioning marker 30, and the third positioning marker are provided, respectively located near the four corners of the silicon wafer, such as... Figure 1 , 3 As shown in Figure 5, the angle and distance between the line connecting the two first positioning marks 10 and the line connecting the two corresponding first marks 41, or the angle and distance between the line connecting the two second marks 42 and the line connecting the two corresponding third positioning marks, can be measured to determine the offset of the main grid and the offset of the fine grid.

[0056] In an optional embodiment, both the first positioning mark 10 and the third positioning mark are circular, with the diameter of the first positioning mark 10 being 0.35-0.45 mm and the diameter of the third positioning mark being 0.35-0.45 mm; both the first mark 41 and the second mark 42 are annular, with the radial width of the first mark 41 being 0.05-0.15 mm and the radial width of the second mark 42 being 0.05-0.15 mm.

[0057] If the location marker is too large, it will affect the battery efficiency; if it is too small, it will increase the difficulty for the camera to capture it. Therefore, the size of the location marker needs to be chosen appropriately.

[0058] In an optional embodiment, the diffusion surface is marked with a laser, wherein the laser power is 20-100W, the laser frequency is 400-500KHz, and the scanning speed is 10000-50000mm / s.

[0059] In this invention, after marking and before printing the main grid, other operations need to be performed on the silicon wafer. Therefore, during the marking process, a sufficiently high laser power, frequency and scanning speed are required to ensure that the first positioning mark 10 is clear enough to be captured by the camera when printing the main grid.

[0060] In an optional implementation, a camera is used to capture the first positioning mark 10, and when the first mark 41 coincides with the first mating area in the first positioning mark 10, the electrode main grid pattern is printed; a camera is used to capture the second mating area, and when the third positioning mark coincides with the second mating area, the fine grid pattern is printed.

[0061] Instead of having the camera capture the second mating area, the instruction to print the fine grid is to have the third positioning pattern overlap with the second mating area. This is more conducive to reducing the offset between the main grid and the fine grid, and can avoid the problem that the area where the first positioning mark 10 is designed to mate with the third positioning mark is blocked due to the offset of the main grid, which would lead to the problem that the positioning mark is difficult or impossible to capture when printing the fine grid pattern.

[0062] In an optional embodiment, the fabrication of the silicon wafer having the first positioning mark 10 further includes the following steps performed sequentially:

[0063] Remove the borosilicate glass from the back and edges of the marked silicon wafer and then polish it.

[0064] A tunnel oxide layer and a doped polysilicon layer are deposited on the back side;

[0065] Remove the phosphosilicate glass on the back;

[0066] Remove the doped polysilicon layer deposited on the front and edge sides;

[0067] Remove the front borosilicate glass;

[0068] Aluminum oxide is deposited on the front side;

[0069] Silicon nitride is deposited on both the front and back sides;

[0070] A pattern is printed on the back of the silicon wafer to obtain a silicon wafer with a first positioning mark 10.

[0071] In this embodiment of the invention, the silicon wafer is first marked, and then the borosilicate glass layer is removed and other operations are performed to treat the surface of the silicon wafer. This can avoid the marking process from damaging the subsequent deposition layers and thus affecting the performance of the battery.

[0072] This invention also provides a method for preparing a solar cell, comprising:

[0073] The silicon wafer with printed electrodes is obtained by sintering, and the silicon wafer with printed electrodes is prepared by the screen printing method of the solar cell described in any one of the foregoing embodiments.

[0074] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0075] Example 1

[0076] This embodiment provides a method for fabricating a non-SE structure TOPCon battery, such as... Figure 1-10 As shown, it includes the following steps:

[0077] Step 1. Provide an N-type silicon substrate and perform a texturing process on the surface of the silicon substrate;

[0078] Step 2. Boron diffusion is performed on the silicon wafer surface to form a PN junction;

[0079] Step 3. Use a laser to mark the diffusion surface to form four first positioning marks 10; the laser power is 30W, the laser frequency is 400KHz, the scanning speed is 20000mm / s, and the diameter of the first positioning mark 10 is 0.4mm.

[0080] Step 4. Remove the borosilicate glass from the back and edges of the silicon wafer and polish it;

[0081] Step 5. Deposit a tunnel oxide layer and a doped polysilicon layer on the back side;

[0082] Step 6. Remove the phosphosilicate glass on the back, then remove the doped polysilicon layer on the front and edge, and finally remove the borosilicate glass on the front.

[0083] Step 7. Deposit aluminum oxide on the front side, and then deposit silicon nitride sequentially on the front and back sides;

[0084] Step 8. Print the pattern on the back of the silicon wafer;

[0085] Step 9. Use a camera to capture the first positioning mark 10. When the first mark 41 coincides with the first mating area in the first positioning mark 10, print the electrode main grid pattern; use a camera to capture the second mating area. When the third positioning mark coincides with the second mating area, print the fine grid pattern; the second positioning mark 30 has an inner diameter of 0.4 mm and an outer diameter of 0.5 mm; the third positioning mark has a diameter of 0.4 mm.

[0086] Step 10. The battery cells are formed by high-temperature sintering.

[0087] Example 2

[0088] This embodiment provides a method for preparing a non-SE structure TOPCon battery. The only difference from Embodiment 1 is that the first positioning mark 10 has a diameter of 0.35 mm, the second positioning mark 30 has an inner diameter of 0.35 mm and an outer diameter of 0.5 mm, and the third positioning mark has a diameter of 0.35 mm.

[0089] Example 3

[0090] This embodiment provides a method for preparing a non-SE structure TOPCon battery. The only difference from Embodiment 1 is that the first positioning mark 10 has a diameter of 0.45 mm, the second positioning mark 30 has an inner diameter of 0.45 mm and an outer diameter of 0.5 mm, and the third positioning mark has a diameter of 0.45 mm.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a non-SE structure TOPCon battery. The only difference from Example 1 is that the size of each positioning mark is too large. The first positioning mark 10 has a diameter of 0.6 mm, the second positioning mark 30 has an inner diameter of 0.6 mm and an outer diameter of 0.8 mm, and the third positioning mark has a diameter of 0.6 mm.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing a non-SE structure TOPCon battery. The only difference from Example 1 is that the size of each positioning mark is too small. The first positioning mark 10 has a diameter of 0.2 mm, the second positioning mark 30 has an inner diameter of 0.2 mm and an outer diameter of 0.25 mm, and the third positioning mark has a diameter of 0.2 mm.

[0095] Comparative Example 3

[0096] This comparative example provides a method for preparing a non-SE structure TOPCon battery. The only difference from Example 1 is that the arrangement of the positioning marks is different. There are four positioning points, four positioning points, and four positioning points, which are arranged in a trapezoidal shape.

[0097] Comparative Example 4

[0098] This comparative example provides a method for preparing a non-SE structure TOPCon battery. The only difference from Example 1 is that step 3 is moved after step 8 and before step 9.

[0099] Comparative Example 5

[0100] This comparative example provides a method for preparing a non-SE structure TOPCon battery. The only difference from Example 1 is that the first positioning mark 10 formed in step 3, the marking process, includes two positioning points with a diameter of 0.4 mm; in step 9, the first positioning pattern 20 on the first printing screen is a positioning ring, and the second positioning pattern on the second printing screen is a positioning ring. The two positioning rings are respectively matched with the two positioning points. That is, the camera is used to capture the first positioning point in the first positioning mark 10, and when the first positioning point matches the first positioning pattern 20, the electrode main grid pattern is printed; the camera is used to capture the second positioning point in the first positioning mark 10, and when the second positioning point matches the second positioning pattern, the fine grid pattern is printed.

[0101] Comparative Example 6

[0102] This comparative example provides a method for preparing a non-SE structure TOPCon cell. The only difference from Example 1 is that step (3) is omitted. In step 9, no positioning patterns are set on the first and second printing screens. A camera is used to capture the edge of the silicon wafer to position the silicon wafer. When the silicon wafer reaches the designated position, the main grid pattern and the fine grid pattern are printed in sequence.

[0103] The offset and electrical performance of the solar cells obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0104] Table 1

[0105] Total number of solar cells, per cell Offset quantity, slice Offset percentage, % Short-circuit current, A efficiency,% Example 1 25381 5 0.02 18.504 26.50 Example 2 24713 10 0.04 18.504 26.50 Example 3 25937 13 0.05 18.504 26.50 Comparative Example 1 24892 7 0.03 18.486 26.47 Comparative Example 2 25849 73 0.28 18.516 26.52 Comparative Example 3 24839 159 0.64 18.492 26.48 Comparative Example 4 26329 8 0.04 18.481 26.46 Comparative Example 5 24932 20 0.08 18.485 26.47 Comparative Example 6 25642 131 0.51 18.520 26.53

[0106] In Table 1, offset refers to: the distance between the center point of the printed pattern and the center point of the silicon wafer > 0.3 mm or the angular deviation between the printed pattern and the silicon wafer > 0.3°; current, efficiency, etc. are the average values ​​of all tested cells.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A screen printing method for solar cells, characterized in that, include: The diffusion surface of the N-type silicon wafer that has undergone boron diffusion treatment is marked to obtain a silicon wafer with the first positioning mark; The first positioning mark and the first positioning pattern on the first printing screen are compared and positioned, and the electrode main gate pattern and the second positioning mark are printed on the silicon wafer surface with the first positioning mark according to the comparison and positioning result, so as to obtain a silicon wafer with the main gate pattern. The second positioning mark is printed from the first positioning pattern. The second positioning mark is compared and positioned with the second positioning pattern on the second printing screen. Based on the comparison and positioning result, the electrode fine grid pattern and the third positioning mark are printed on the silicon wafer surface with the main grid pattern to obtain the silicon wafer with the electrode. The third positioning mark is printed from the second positioning pattern.

2. The screen printing method for solar cells according to claim 1, characterized in that, The second positioning identifier includes a first identifier that is adapted to the position of the first positioning identifier and a second identifier that is adapted to the position of the third positioning identifier.

3. The screen printing method for solar cells according to claim 2, characterized in that, The first identifier has a first mating area that can mate with the first positioning identifier, and the size and shape of the first mating area are adapted to the size and shape of the first positioning identifier.

4. The screen printing method for solar cells according to claim 3, characterized in that, The second identifier has a second mating area that can mate with the third positioning identifier, and the size and shape of the second mating area are adapted to the size and shape of the third positioning identifier.

5. The screen printing method for solar cells according to claim 2, characterized in that, Both the first and third positioning marks are circular, with the first positioning mark having a diameter of 0.35-0.45 mm and the third positioning mark having a diameter of 0.35-0.45 mm; both the first and second marks are annular, with the first mark having a radial width of 0.05-0.15 mm and the second mark having a radial width of 0.05-0.15 mm.

6. The screen printing method for solar cells according to claim 4, characterized in that, There are two or more first positioning identifiers, and the two or more first positioning identifiers are arranged in an array; each first positioning identifier is correspondingly provided with a second positioning identifier and a third positioning identifier.

7. The screen printing method for solar cells according to claim 1, characterized in that, The diffusion surface is marked using a laser, wherein the laser power is 20-100W, the laser frequency is 400-500KHz, and the scanning speed is 10000-50000mm / s.

8. The screen printing method for solar cells according to claim 4, characterized in that, A camera is used to capture the first positioning mark. When the first mark coincides with the first mating area in the first positioning mark, the main grid pattern of the electrode is printed. A camera is used to capture the second mating area. When the third positioning mark coincides with the second mating area, the fine grid pattern is printed.

9. The screen printing method for solar cells according to claim 1, characterized in that, The preparation of the silicon wafer with the first positioning mark also includes the following steps performed sequentially: Remove the borosilicate glass from the back and edges of the marked silicon wafer and then polish it. A tunnel oxide layer and a doped polysilicon layer are deposited on the back side; Remove the phosphosilicate glass on the back; Remove the doped polysilicon layer deposited on the front and edge sides; Remove the front borosilicate glass; Aluminum oxide is deposited on the front side; Silicon nitride is deposited on both the front and back sides; A pattern is printed on the back of the silicon wafer to obtain a silicon wafer with the first positioning mark.

10. A method for preparing a solar cell, characterized in that, include: The silicon wafer with printed electrodes is obtained by sintering, and the silicon wafer with printed electrodes is prepared by the screen printing method of the solar cell according to any one of claims 1-9.

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