Solar cell, preparation method thereof and printing screen

Abstract

The invention discloses a solar cell and a preparation method thereof and a printing screen printing plate, the solar cell comprises a silicon wafer and a grid line electrode arranged on the surface of the silicon wafer, the grid line electrode comprises a plurality of main grid lines and auxiliary grid lines, the main grid lines are distributed in parallel, and the auxiliary grid lines are distributed in parallel. A plurality of reinforcing lines connected with the auxiliary grid lines are distributed on each main grid line, the reinforcing lines perpendicularly intersect with the main grid lines, and alignment lines intersecting with the auxiliary grid lines are arranged at the two ends of the reinforcing lines. According to the invention, the reinforcing lines and the counterpoint lines are printed by adopting the main grid slurry and the main grid lines at the same time, so that the welding performance and reliability of the battery piece and the welding strip can be remarkably improved, and the consumption of the conductive slurry is reduced; through the arrangement of the alignment lines, the alignment problem of the auxiliary grid lines and the reinforcing lines can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a solar cell sheet, a preparation method thereof, and a printing screen. Background Art

[0002] With the rapid development of the photovoltaic industry, the performance and efficiency requirements of solar cells in both domestic and international markets are constantly increasing. As a result, industry manufacturers are focusing on the research and development of high-efficiency cells. The TOPCon (Tunnel Oxide Passivated Contact) cell is a new type of high-efficiency N-type cell. By sequentially depositing an ultra-thin tunnel oxide layer and a doped polysilicon layer on the back of the cell, it improves the cell's surface passivation, reduces the metal contact recombination current, and effectively increases the cell's open-circuit voltage and short-circuit current.

[0003] The metallization process of the TOPCon battery surface generally adopts screen printing technology. Screen printing is divided into four printing processes: back main grid, back sub-grid, front main grid and front sub-grid. At the same time, different conductive pastes (such as silver paste) are used in each printing process. The sub-grid paste mainly considers the contact performance with the silicon wafer, and the main grid paste needs to consider the welding performance with the soldering tape.

[0004] Existing MBB (Multi-Busbar) patterns typically use a PAD dot + thin connecting line design. This can easily lead to poor soldering and reliability issues at the junction of the solder ribbon and the secondary busbar after soldering. Therefore, a thickened design is typically applied at the junction of the secondary busbar and the main busbar, and this thickened structure is printed simultaneously with the secondary busbar. Due to the high solids content of the secondary busbar paste, the thickened structure consumes more silver paste. Furthermore, despite this thickened design, the secondary busbar paste has poor solderability, making the thickened structure more prone to soldering and reliability issues.

[0005] Therefore, in order to solve the above technical problems, it is necessary to provide a solar cell and a preparation method thereof, and a printing screen. Summary of the Invention

[0006] The object of the present invention is to provide a solar cell and a preparation method thereof, and a printing screen, which can improve the welding performance and reliability of the cell and reduce the consumption of conductive paste.

[0007] In order to achieve the above-mentioned purpose, the technical solution provided by one embodiment of the present invention is as follows:

[0008] A solar cell comprises a silicon wafer and a grid line electrode arranged on the surface of the silicon wafer, wherein the grid line electrode comprises a main grid line and a secondary grid line, wherein the main grid lines are multiple and arranged parallel to each other, and each main grid line is provided with a plurality of reinforcing lines connected to the secondary grid lines, wherein the reinforcing lines intersect the main grid lines at right angles, and alignment lines intersecting the secondary grid lines are provided at both ends of the reinforcing lines.

[0009] In one embodiment, at the intersection of the alignment line and the secondary gate line, the secondary gate line is stacked above the alignment line and is electrically connected to the secondary gate line.

[0010] In one embodiment, the reinforcement line intersects the alignment line perpendicularly, and the auxiliary gate line includes a first auxiliary gate line vertically distributed between two adjacent main gate lines, and two ends of the first auxiliary gate line respectively intersect the two alignment lines perpendicularly.

[0011] In one embodiment, the reinforcement line includes a main body and extensions located on both sides of the main body. The reinforcement part intersects the main grid line perpendicularly, and the two extensions are located on both sides of the main grid line respectively. The alignment line is provided on one end of the reinforcement part away from the main body.

[0012] In one embodiment, the width of the main body portion is greater than the width of the secondary gate line, and the width of the extension portion gradually decreases from the main body portion toward the outside.

[0013] In one embodiment, the interior of the reinforcement line is a hollow structure.

[0014] In one embodiment, the distance between two adjacent first secondary gate lines is less than or equal to the length of the reinforcement line, and the width of at least part of the reinforcement line is greater than the width of the secondary gate line.

[0015] In one embodiment, the gate line electrode further includes a plurality of frame lines extending outward from the end of the main gate line, and the auxiliary gate line further includes a second auxiliary gate line intersecting and connected with the frame line.

[0016] In one embodiment, the reinforcement lines are symmetrically distributed on both sides of the main grid line; and / or,

[0017] The alignment lines are symmetrically distributed on both sides of the reinforcement line; and / or,

[0018] The silicon wafer comprises a light-receiving surface and a backlight surface that are oppositely arranged, and the gate line electrode is located on the light-receiving surface and / or the backlight surface of the silicon wafer; and / or,

[0019] The solar cell is a TOPCon cell.

[0020] In one embodiment, the width of the main grid line is 15 μm to 100 μm, and the width of the secondary grid line is 10 μm to 20 μm; and / or,

[0021] The maximum width of the reinforcement line is 30 μm to 60 μm, and the length of the reinforcement line is 0.8 mm to 1.5 mm; and / or,

[0022] The width of the alignment line is 10 μm to 30 μm, and the length of the alignment line is 80 μm to 160 μm.

[0023] The technical solution provided by one embodiment of the present invention is as follows:

[0024] A method for preparing a solar cell, comprising the following steps:

[0025] First, busbar lines, reinforcement lines, and alignment lines are printed on the light-receiving surface and / or backlight surface of the silicon wafer using busbar slurry and dried, and then sub-grid lines are printed using sub-grid slurry and dried, wherein the solid content of the sub-grid slurry is greater than that of the busbar slurry;

[0026] The silicon wafer after printing the gate line electrode is sintered.

[0027] In one embodiment, the preparation method further comprises:

[0028] On the backlight surface of the silicon wafer, firstly, a first busbar paste is used to print busbar lines, reinforcement lines and alignment lines and then dried, and then a first sub-gate paste is used to print sub-gate lines and then dried, wherein the solid content of the first sub-gate paste is greater than the solid content of the first busbar paste;

[0029] On the light-receiving surface of the silicon wafer, the second main grid paste is first used to print the main grid lines, reinforcement lines and alignment lines and then dried, and then the second auxiliary grid paste is used to print the auxiliary grid lines and then dried. The solid content of the second auxiliary grid paste is greater than that of the second main grid paste.

[0030] In one embodiment, the drying temperature of the main gate lines, reinforcement lines and alignment lines on the backlight surface of the silicon wafer is 250° C. to 270° C., and the drying time is 5s to 60s;

[0031] The drying temperature of the secondary gate lines on the backlight surface of the silicon wafer is 320° C. to 400° C., and the drying time is 5s to 60s;

[0032] The drying temperature of the main grid lines, reinforcement lines and alignment lines on the light-receiving surface of the silicon wafer is 220° C. to 250° C., and the drying time is 5s to 60s;

[0033] The drying temperature of the secondary gate lines on the light-receiving surface of the silicon wafer is 240° C. to 310° C., and the drying time is 5 seconds to 60 seconds.

[0034] In one embodiment, in the step of sintering the silicon wafer after printing the gate line electrodes, the sintering temperature is 500° C. to 810° C., and the sintering time is 30 seconds to 120 seconds.

[0035] The technical solution provided by one embodiment of the present invention is as follows:

[0036] A printing screen comprises a first screen and a second screen, wherein the first screen is provided with a first printed pattern corresponding to main grid lines, reinforcement lines and alignment lines, and the second screen is provided with a second printed pattern corresponding to auxiliary grid lines.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention prints the reinforcement lines and alignment lines simultaneously with the main grid lines using main grid paste, which can significantly improve the welding performance and reliability of the battery cell and the welding strip, while reducing the consumption of conductive paste; by setting the alignment lines, the alignment problem of the secondary grid lines and the reinforcement lines can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0040] Figure 1 A schematic diagram of the structure of a solar cell in a pair of ratios of the present invention;

[0041] Figure 2 for Figure 1 Schematic diagram of the local enlarged structure at A in the middle;

[0042] Figure 3 Schematic diagram of the structure of the main grid line in a pair of ratios of the present invention;

[0043] Figure 4 for Figure 3 Schematic diagram of the local enlarged structure at B in the middle;

[0044] Figure 5 Schematic diagram of the structure of the auxiliary grid line and the reinforcement line in a pair of ratios of the present invention;

[0045] Figure 6 for Figure 5 Schematic diagram of the local enlarged structure at C in the middle;

[0046] Figure 7 This is a schematic diagram of the structure of the reinforcement wire in a pair of proportions of the present invention;

[0047] Figure 8 Schematic diagram of the structure of the solar cell in Example 1 of the present invention;

[0048] Figure 9 for Figure 8 Schematic diagram of the local enlarged structure at D in the middle;

[0049] Figure 10 for Figure 8 Schematic diagram of the local enlarged structure at E in the middle;

[0050] Figure 11 A schematic structural diagram of the main grid lines, reinforcement lines, and alignment lines in Example 1 of the present invention;

[0051] Figure 12 for Figure 11 Schematic diagram of the local enlarged structure at F in the middle;

[0052] Figure 13 for Figure 11 Schematic diagram of the local enlarged structure at G in the middle;

[0053] Figure 14 A schematic structural diagram of the auxiliary gate line in embodiment 1 of the present invention;

[0054] Figure 15 for Figure 14 Schematic diagram of the local enlarged structure at H in the middle;

[0055] Figure 16 A partial cross-sectional view of the first secondary gate line, the alignment line, and the reinforcement line in Example 1 of the present invention;

[0056] Figure 17 Schematic diagram of the structure of the reinforcement line and the alignment line in Example 1 of the present invention;

[0057] Figure 18 Schematic diagram of the structure of the reinforcement line and the alignment line in Example 2 of the present invention;

[0058] Figure 19 Schematic diagram of the structure of the reinforcement line and the alignment line in Example 3 of the present invention;

[0059] Figure 20 Schematic diagram of the structure of the reinforcement line and the alignment line in Example 4 of the present invention. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0061] And, it should be understood that although the terms first, second etc. can be used to describe various elements or structures in this article, these described objects should not be restricted by these terms.These terms are only used to distinguish these description objects from each other.For example, the first secondary grid line can be called the second secondary grid line, and similarly the second secondary grid line also can be called the first secondary grid line, and this does not deviate from protection scope of the present invention.

[0062] The present invention discloses a solar cell, comprising a silicon wafer and a grid line electrode arranged on the surface of the silicon wafer, wherein the grid line electrode comprises a main grid line and a secondary grid line, wherein the main grid lines are multiple and are distributed parallel to each other, and each main grid line is provided with a plurality of reinforcing lines connected to the secondary grid lines, wherein the reinforcing lines intersect the main grid lines at right angles, and alignment lines intersecting the secondary grid lines are provided at both ends of the reinforcing lines.

[0063] The present invention also discloses a method for preparing a solar cell, comprising the following steps:

[0064] First, busbar lines, reinforcement lines, and alignment lines are printed on the light-receiving surface and / or backlight surface of the silicon wafer using busbar slurry and dried, and then sub-grid lines are printed using sub-grid slurry and dried, wherein the solid content of the sub-grid slurry is greater than that of the busbar slurry;

[0065] The silicon wafer after printing the gate line electrode is sintered.

[0066] The present invention also discloses a printing screen, including a first screen and a second screen, wherein the first screen is provided with a first printed pattern corresponding to the main grid lines, reinforcement lines and alignment lines, and the second screen is provided with a second printed pattern corresponding to the auxiliary grid lines.

[0067] The present invention can significantly improve the welding performance and reliability of the battery cell, solve the alignment problem in the printing process, and reduce the consumption of the conductive paste.

[0068] The present invention is further described below with reference to specific examples.

[0069] Comparative Example:

[0070] Ginseng Figure 1 The figure shows a schematic planar structure of a solar cell used in this comparative example. The solar cell comprises a silicon wafer and a gate electrode 100' located on the wafer's surface. Taking a TOPCon 210 cell as an example, the full-cell solar cell measures 210mm by 210mm and consists of two identical halves, with a dicing path 101' reserved between them.

[0071] Ginseng Figure 1 and combined Figures 2 to 6As shown, the gate line electrode 100' includes a main gate line 11', a reinforcement line 13' and an auxiliary gate line 12'. The main gate lines 11' are multiple and distributed in parallel along a first direction, and the auxiliary gate lines 12' are multiple and distributed in parallel along a second direction. The first direction (vertical) and the second direction (horizontal) are perpendicular to each other.

[0072] In addition, the reinforcement lines 13 ′ are distributed on the secondary grid lines 12 ′ along the second direction, and the reinforcement lines are distributed in an array. Each main grid line 11 ′ is connected to a plurality of reinforcement lines 13 ′ in the first direction.

[0073] The maximum width of the reinforcing wire 13' is 30 μm to 60 μm, and the length is 0.8 mm to 1.5 mm, while the width of the auxiliary grid line 12' is 10 μm to 20 μm. The provision of the reinforcing wire can avoid the problem of poor contact between the welding strip and the auxiliary grid line.

[0074] Ginseng Figure 7 As shown, the width of the reinforcement line 13' in this comparative example gradually decreases from the middle position to the brightness. The middle position is the widest, which is 40 μm, and the width at both ends is the smallest, which is 20 μm. The length of the reinforcement line is 1 mm.

[0075] In addition, in this comparative example, the number of main grid lines (BB number) is 16 to 20, and the number of secondary grid lines is 150 to 250. For example, taking 18BB as an example, each grid line electrode includes 18 parallel main grid lines, the width of the main grid line is 15 μm to 100 μm, preferably 60 μm, and each half-cell solar cell includes 115 secondary grid lines, the width of the secondary grid lines is 10 μm to 20 μm, preferably 20 μm.

[0076] The preparation method of the solar cell in this comparative example comprises the following steps:

[0077] S1. First, on the backlight side (or back side) of the silicon wafer, use the first main grid paste to print the main grid lines and dry them, and then use the first sub-grid paste to print the sub-grid lines and reinforcement lines and dry them.

[0078] The main grid lines on the back are printed using a printing screen, which has a printed pattern corresponding to the main grid lines on the back. The secondary grid lines and reinforcement lines on the back are printed using another printing screen, which has a printed pattern corresponding to the secondary grid lines and reinforcement lines on the back.

[0079] After the back main grid line is printed, it is dried in a chain dryer at a drying temperature of 250℃~270℃ and a drying time of 5s~60s; after the back auxiliary grid line and reinforcement line are printed, they are dried in a chain dryer at a drying temperature of 320℃~400℃ and a drying time of 5s~60s.

[0080] S2. First, the second main grid paste is used to print the main grid lines on the light-receiving surface (or front surface) of the silicon wafer and the main grid lines are dried. Then, the second sub-grid paste is used to print the sub-grid lines and the reinforcing lines and the sub-grid lines are dried.

[0081] The main grid lines on the front are printed using a printing screen, on which a printed pattern corresponding to the main grid lines on the front is provided. The secondary grid lines and reinforcement lines on the front are printed using another printing screen, on which a printed pattern corresponding to the secondary grid lines and reinforcement lines on the front is provided.

[0082] After the main grid lines on the front are printed, they are dried in a chain dryer at a temperature of 220°C to 250°C and a drying time of 5s to 60s. After the secondary grid lines and reinforcement lines on the back are printed, they are dried in the pre-sintering area of ​​a sintering furnace at a drying temperature of 240°C to 310°C and a drying time of 5s to 60s.

[0083] S3. Finally, the silicon wafer after printing the gate line electrode is sintered.

[0084] After the front and back gate electrodes are printed, they are sintered in the sintering zone of a sintering furnace at a temperature of 500°C to 810°C for 30 to 120 seconds. This sintering process dries the slurry on the silicon wafer, burns off any organic matter in the slurry, and forms a good ohmic contact between the slurry and the silicon wafer.

[0085] The main grid paste and the secondary grid paste are both composed of silver powder, glass powder, and organic matter. The silver powder and glass powder content represents the solid content of the paste. For example, in this embodiment, the first main grid paste and the second main grid paste on the back side are made of the same paste, with a solid content of approximately 86%. The first secondary grid paste on the back side has a solid content of approximately 90%, and the second secondary grid paste on the front side has a solid content of approximately 92%.

[0086] In this comparative example, the main grid lines are printed first on the front and back sides of the silicon wafer, and then the secondary grid lines and reinforcement lines are printed. The length of the reinforcement line is the distance between the two secondary grid lines. The reinforcement line intersects the main grid lines vertically, and at the intersection of the reinforcement line and the main grid line, the reinforcement line is stacked above the main grid line and is electrically conductive to each other.

[0087] Example 1:

[0088] Ginseng Figure 8 Figure 1 shows a schematic planar structure of a solar cell in this embodiment. The solar cell comprises a silicon wafer and a gate electrode 100' located on the surface of the wafer. Taking a TOPCon 210 cell as an example, the dimensions of a full-cell solar cell are 210mm x 210mm. The full-cell solar cell consists of two identical half-cells with a dicing street 101 reserved in between.

[0089] Ginseng Figure 8Combined with Figures 9 to 15 As shown, the gate electrode 100 includes a main gate line 11, a secondary gate line 12, a reinforcement line 13, and an alignment line 14. Specifically, the main gate lines 11 are multiple and distributed in parallel along a first direction, and the secondary gate lines 12 are multiple and distributed in parallel along a second direction. The first direction (vertical) and the second direction (lateral) are perpendicular to each other.

[0090] In this embodiment, the number of main grid lines (BB number) is 16 to 20, and the number of secondary grid lines is 150 to 250. For example, taking 18BB as an example, each grid electrode includes 18 parallel main grid lines, the width of the main grid lines is 15 μm to 100 μm, preferably 60 μm, and each half solar cell includes 115 secondary grid lines, the width of the secondary grid lines is 10 μm to 20 μm, preferably 20 μm.

[0091] Ginseng Figure 8 、 Figure 11 Combined with Figure 10 、 Figure 13 As shown, in this embodiment, a plurality of pads 15 are evenly distributed on the busbar line 11 , and the end of the busbar line 11 is connected to one of the pads 15 . The pad at the end 15 has a plurality of border lines 16 extending outward.

[0092] Ginseng Figure 8 、 Figure 11 Combined with Figure 14 、 Figure 15 As shown, the secondary grid lines 12 include a first secondary grid line 121 vertically distributed between two adjacent main grid lines 11 , and a second secondary grid line 122 cross-connected with the frame line 16 in a direction perpendicular to the main grid lines.

[0093] Specifically, the first secondary grid lines 121 and the second secondary grid lines 122 are both arranged in a transverse direction, with the spacing between two adjacent first secondary grid lines 121 being greater than or equal to 0.8 mm. The second secondary grid lines 122 can be arranged in a single line or in a plurality of spaced-apart lines in the transverse direction. The arrangement of the frame lines 16 and the second secondary grid lines 122 is similar to that of conventional solar cells and will not be further described here.

[0094] Ginseng Figure 8 、 Figure 11 Combined with Figure 9 、 Figure 12 、 Figure 17 As shown, the reinforcing lines 13 intersect perpendicularly with the main grid lines 11, and the reinforcing lines 11 are arranged in an array. Each main grid line 11 is evenly distributed with multiple reinforcing lines 13 connected to the first secondary grid lines 121. At both ends of the reinforcing lines 13 are provided with alignment lines 14 arranged perpendicularly to the reinforcing lines, and the two ends of the first secondary grid lines 121 are respectively connected to two alignment lines 14.

[0095] Specifically, the reinforcement line 13 in this embodiment includes a main portion 131 and extension portions 132 located on either side of the main portion. The reinforcement portion 131 is perpendicularly and symmetrically distributed on the busbar 11, and the two extension portions 132 are located on either side of the busbar. The alignment line 14 is provided on the reinforcement portion 13 at one end away from the main portion 131. Preferably, the width of the reinforcement line is 30μm to 60μm, the length of the reinforcement line is 0.8mm to 1.5mm, the width of the alignment line is 10μm to 30μm, and the length of the alignment line is 80μm to 160μm.

[0096] Preferably, the width of the main portion 131 is greater than the width of the first secondary gate line, and the width of the extending portion 132 gradually decreases from the main portion 131 outward.

[0097] In this embodiment, the reinforcement line is approximately 1.1 mm long. The main body 131 is rectangular and 60 μm wide. The extension 132 is an isosceles trapezoid, with its width gradually decreasing from 60 μm to 20 μm from the main body outward. The alignment lines 14 are rectangular and symmetrically distributed on both sides of the reinforcement line 13. The alignment lines are 20 μm wide and 120 μm long.

[0098] Preparation method of solar cell in this comparative example:

[0099] S1. First, on the backlight side (or back side) of the silicon wafer, use the first main grid paste to print the main grid lines, reinforcement lines and alignment lines and dry them, and then use the first sub-grid paste to print the sub-grid lines and dry them.

[0100] The main grid lines, reinforcement lines and alignment lines on the back are printed using a printing screen, and the printing screen is provided with printed patterns corresponding to the main grid lines, reinforcement lines and alignment lines on the back. The secondary grid lines on the back are printed using another printing screen, and the printing screen is provided with printed patterns corresponding to the secondary grid lines on the back.

[0101] After the back main grid lines, reinforcement lines and alignment lines are printed, they are dried in a chain dryer at a drying temperature of 250℃~270℃ and a drying time of 5s~60s; after the back secondary grid lines are printed, they are dried in a chain dryer at a drying temperature of 320℃~400℃ and a drying time of 5s~60s.

[0102] S2. First, on the light-receiving surface (or front surface) of the silicon wafer, the main grid lines, the reinforcement lines and the alignment lines are printed using the second main grid paste and dried, and then the secondary grid lines are printed using the second secondary grid paste and dried.

[0103] The main grid lines, reinforcement lines and alignment lines on the front are printed using a printing screen, and the printing screen is provided with printed graphics corresponding to the main grid lines, reinforcement lines and alignment lines on the front. The secondary grid lines on the front are printed using another printing screen, and the printing screen is provided with printed graphics corresponding to the secondary grid lines on the front.

[0104] After the main grid lines, reinforcement lines and alignment lines on the front are printed, they are dried in a chain dryer at a drying temperature of 220℃~250℃ and a drying time of 5s~60s; after the secondary grid lines on the back are printed, they are dried in the pre-sintering area of ​​a sintering furnace at a drying temperature of 240℃~310℃ and a drying time of 5s~60s.

[0105] S3. Finally, the silicon wafer after printing the gate line electrode is sintered.

[0106] After the front and back gate electrodes are printed, they are sintered in the sintering zone of a sintering furnace at a temperature of 500°C to 810°C for 30 to 120 seconds. This sintering process dries the slurry on the silicon wafer, burns off any organic matter in the slurry, and forms a good ohmic contact between the slurry and the silicon wafer.

[0107] The main grid paste and the secondary grid paste are both composed of silver powder, glass powder, and organic matter. The silver powder and glass powder content represents the solid content of the paste. For example, in this embodiment, the first main grid paste and the second main grid paste on the back side are made of the same paste, with a solid content of approximately 86%. The first secondary grid paste on the back side has a solid content of approximately 90%, and the second secondary grid paste on the front side has a solid content of approximately 92%.

[0108] Ginseng Figure 16 As shown, in this embodiment, the busbars 11, reinforcement lines 13, and alignment lines 14 are printed first on both the front and back sides of the silicon wafer, followed by the secondary grid lines 12. Therefore, the busbars 11, reinforcement lines 13, and alignment lines 14 have the same thickness. After the secondary grid lines 12 are printed, at the intersection of the alignment lines 14 and the first secondary grid lines 121, the first secondary grid lines 121 are stacked above the alignment lines 14 and are electrically conductive to each other.

[0109] Furthermore, when the printing screen is accurately registered, the first secondary grid line 121 can continue to be stacked on part of the reinforcement line 13. When the printing screen is not accurately registered, the first secondary grid line 121 and the reinforcement line 13 will have a certain offset and cannot be stacked on the reinforcement line 13, but the first secondary grid line 121 will be stacked on the alignment line 14, and the electrical conduction between the secondary grid line and the reinforcement line is achieved through the alignment line 14.

[0110] In this embodiment, the provision of the reinforcement wire can improve the current transmission effect between the welding ribbon and the grid electrode on the solar cell, improve the current collection capability of the secondary grid line, and thus improve the battery efficiency.

[0111] In the comparative example, the reinforcement line is printed together with the secondary grid line, so there is no problem of alignment between the reinforcement line and the secondary grid line. In this embodiment, the reinforcement line is printed together with the main grid line. The width of the reinforcement line is 30μm~60μm, and the width of the secondary grid line is 10μm~20μm. The difficulty of printing screen registration is very large. In the actual printing process, the secondary grid line and the reinforcement line are easily offset, resulting in the inability to connect the secondary grid line and the reinforcement line.

[0112] Therefore, in this embodiment, alignment lines are added on both sides of the reinforcement line, which can significantly improve the alignment problem between the auxiliary gate line and the reinforcement line. Even if the auxiliary gate line and the reinforcement line are offset, electrical conduction between the auxiliary gate line and the reinforcement line can be achieved through the alignment lines.

[0113] Furthermore, printing the reinforcement and alignment lines together with the busbars, using the same paste as the main-grid paste, significantly improves the soldering performance and reliability between the cell and the solder ribbon. This reduces the risk of EL blackening at the junction of the solder ribbon and the busbars after soldering or thermal cycling. Furthermore, the lower solids content and viscosity of the busbar paste significantly reduces overall conductive paste consumption.

[0114] Taking the TOPCon 210 battery in the comparative example and Example 1 as an example, the consumption of the conductive paste is as follows:

[0115]

[0116] It can be seen that the silver paste consumption of the battery cell in the comparative example is 141 mg / pcs, while the silver paste consumption in Example 1 is 134 mg / pcs. Each battery cell can save 7 mg of silver paste consumption, which is reduced by about 5% compared with the comparative example.

[0117] It is worth noting that in this embodiment, the grid line electrodes on the front and back sides of the solar cell adopt similar structures. In other embodiments, the above-mentioned reinforcement lines and alignment lines can be set only on the front side or only on the back side, and the other side can use the existing grid line electrodes.

[0118] Example 2:

[0119] The structure and preparation method of the solar cell in this embodiment are substantially the same as those in the first embodiment, except that the structure of the reinforcing wire 13 is different, and the alignment wire 14 is the same as that in the first embodiment.

[0120] Ginseng Figure 18 As shown, the reinforcing wire 13 in this embodiment has a hollow structure inside, which can further reduce the consumption of the conductive paste.

[0121] Example 3:

[0122] The structure and preparation method of the solar cell in this embodiment are substantially the same as those in the first embodiment, except that the structure of the reinforcing wire 13 is different, and the alignment wire 14 is the same as that in the first embodiment.

[0123] Ginseng Figure 19 As shown, the reinforcing wire 13 in this embodiment is a longitudinally long rectangle with a width of 30 μm to 60 μm and a length of 0.8 mm to 1.5 mm.

[0124] Example 4:

[0125] The structure and preparation method of the solar cell in this embodiment are substantially the same as those in the first embodiment, except that the structure of the reinforcing wire 13 is different, and the alignment wire 14 is the same as that in the first embodiment.

[0126] Ginseng Figure 20 As shown, the reinforcement wire 13 in this embodiment also includes a main body 131 and extensions 132 located on both sides of the main body. The main body 131 is rectangular, and the extensions 132 are right-angled trapezoids. The width of the extensions 132 gradually decreases from the main body 131 outward. Specifically, one side of the extension is flush with one side of the main body, and the other side is connected to the other side of the main body at an obtuse angle.

[0127] It should be understood that the above embodiments 1-4 illustrate the reinforcement lines with different structures. In other embodiments, the structure of the reinforcement lines is not limited to the above embodiments. Any scheme in which alignment lines are added on both sides of the reinforcement lines and the reinforcement lines and the auxiliary gate lines are aligned by the alignment lines falls within the scope of protection of the present invention.

[0128] In addition, the alignment lines 14 in the above embodiments 1-4 are described as being in the form of a longitudinal rectangle. In other embodiments, other shapes may be used, such as a gradient structure with a width gradually decreasing from the middle to both ends, etc., which will not be described one by one here.

[0129] Example 5:

[0130] This embodiment discloses a printing screen, including a first screen and a second screen. The first screen is provided with a first printed pattern (eg, Figure 11 ), a second printed pattern corresponding to the secondary grid line 12 in Example 1 is provided on the second screen (eg Figure 14 ).

[0131] In the manufacturing process of solar cells, the grid line electrodes on the front and back are usually different, so different first and second screens need to be used for printing the grid line electrodes on the back and back.

[0132] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0133] The present invention prints the reinforcement lines and alignment lines simultaneously with the main grid lines using main grid paste, which can significantly improve the welding performance and reliability of the battery cell and the welding strip, while reducing the consumption of conductive paste; by setting the alignment lines, the alignment problem of the secondary grid lines and the reinforcement lines can be significantly improved.

[0134] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0135] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A solar cell, characterized in that: The solar cell includes a silicon wafer and a grid line electrode arranged on the surface of the silicon wafer. The grid line electrode includes a main grid line and a secondary grid line. There are multiple main grid lines and they are distributed parallel to each other. Each main grid line is distributed with a number of reinforcement lines connected to the secondary grid lines. The reinforcement lines intersect the main grid lines perpendicularly, and alignment lines intersecting with the secondary grid lines are provided at both ends of the reinforcement lines.

2. The solar cell according to claim 1, wherein: At the intersection of the alignment line and the auxiliary gate line, the auxiliary gate line is stacked on the alignment line and is electrically connected to the auxiliary gate line.

3. The solar cell according to claim 1, wherein: The reinforcement line intersects the alignment line perpendicularly. The auxiliary gate line includes a first auxiliary gate line vertically distributed between two adjacent main gate lines. Two ends of the first auxiliary gate line respectively intersect the two alignment lines perpendicularly.

4. The solar cell according to claim 1, wherein: The reinforcement line includes a main body and extensions on both sides of the main body. The reinforcement part intersects the main grid line perpendicularly. The two extensions are respectively located on both sides of the main grid line. The alignment line is provided on one end of the reinforcement part away from the main body.

5. The solar cell according to claim 4, characterized in that: The width of the main body is greater than that of the secondary gate line, and the width of the extension gradually decreases from the main body toward the outside.

6. The solar cell according to claim 1 or 4, characterized in that: The interior of the reinforcement line is a hollow structure.

7. The solar cell according to claim 3, wherein: The distance between two adjacent first secondary gate lines is less than or equal to the length of the reinforcement line, and the width of at least part of the reinforcement line is greater than the width of the secondary gate line.

8. The solar cell according to claim 3, wherein: The gate line electrode further includes a plurality of frame lines extending outward from the end of the main gate line, and the auxiliary gate line further includes a second auxiliary gate line intersecting and connected with the frame line.

9. The solar cell according to claim 1, wherein: The reinforcement lines are symmetrically distributed on both sides of the main grid line; and / or, The alignment lines are symmetrically distributed on both sides of the reinforcement line; and / or, The silicon wafer comprises a light-receiving surface and a backlight surface that are oppositely arranged, and the gate line electrode is located on the light-receiving surface and / or the backlight surface of the silicon wafer; and / or, The solar cell is a TOPCon cell.

10. The solar cell according to claim 1, wherein: The width of the main grid line is 15 μm to 100 μm, and the width of the secondary grid line is 10 μm to 20 μm; and / or, The maximum width of the reinforcement line is 30 μm to 60 μm, and the length of the reinforcement line is 0.8 mm to 1.5 mm; and / or, The width of the alignment line is 10 μm to 30 μm, and the length of the alignment line is 80 μm to 160 μm.

11. A method for preparing a solar cell, characterized in that: The preparation method comprises the following steps: On the light-receiving surface and / or the backlight surface of the silicon wafer, the busbar lines, reinforcement lines and alignment lines according to any one of claims 1 to 10 are first printed with a busbar slurry and dried, and then the busbar lines according to any one of claims 1 to 10 are printed with a sub-grid slurry and dried, wherein the solid content of the sub-grid slurry is greater than the solid content of the busbar slurry; The silicon wafer after printing the gate line electrode is sintered.

12. The preparation method according to claim 11, characterized in that The preparation method further comprises: On the backlight surface of the silicon wafer, firstly, a first busbar paste is used to print busbar lines, reinforcement lines and alignment lines and then dried, and then a first sub-gate paste is used to print sub-gate lines and then dried, wherein the solid content of the first sub-gate paste is greater than the solid content of the first busbar paste; On the light-receiving surface of the silicon wafer, the second main grid paste is first used to print the main grid lines, reinforcement lines and alignment lines and then dried, and then the second auxiliary grid paste is used to print the auxiliary grid lines and then dried. The solid content of the second auxiliary grid paste is greater than that of the second main grid paste.

13. The preparation method according to claim 12, characterized in that The drying temperature of the main grid lines, reinforcement lines and alignment lines on the backlight surface of the silicon wafer is 250° C. to 270° C., and the drying time is 5s to 60s; The drying temperature of the secondary gate lines on the backlight surface of the silicon wafer is 320° C. to 400° C., and the drying time is 5s to 60s; The drying temperature of the main grid lines, reinforcement lines and alignment lines on the light-receiving surface of the silicon wafer is 220° C. to 250° C., and the drying time is 5s to 60s; The drying temperature of the secondary gate lines on the light-receiving surface of the silicon wafer is 240° C. to 310° C., and the drying time is 5 seconds to 60 seconds.

14. The preparation method according to claim 11, characterized in that In the step of sintering the silicon wafer after printing the gate line electrode, the sintering temperature is 500° C. to 810° C., and the sintering time is 30 seconds to 120 seconds.

15. A printing screen, characterized in that: The printing screen includes a first screen and a second screen, the first screen is provided with a first printed pattern corresponding to the main grid lines, reinforcement lines and alignment lines in any one of claims 1 to 10, and the second screen is provided with a second printed pattern corresponding to the secondary grid lines in any one of claims 1 to 10.

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