Laser cutting method for photovoltaic cell and photovoltaic cell

Abstract

The present invention relates to a laser cutting method for photovoltaic cells and photovoltaic cells. The method comprises: forming a first slit, a second slit, and a third slit in the photovoltaic cell by laser; the first slit and the third slit are respectively located at both ends of the second slit and connected to the second slit; the depth of the first slit is 60-70% of the thickness of the photovoltaic cell, the depth of the second slit is 20-30% of the thickness of the photovoltaic cell, and the depth of the third slit is 60-70% of the thickness of the photovoltaic cell. The laser cutting method for photovoltaic cells according to one embodiment of the present invention reduces the thermal damage to the cut surface of the cell caused by the laser during the cutting process, thereby enhancing the mechanical strength of most areas of the cut surface of the cell and reducing the vulnerability of the cut surface in subsequent production processes.

Description

Technical Field

[0001] The present invention relates to photovoltaic cells, and in particular to laser cutting of photovoltaic cells. Background Art

[0002] Currently, half-cell modules account for a significant share of the solar cell market. In the production of photovoltaic half-cell modules, the first step is laser cutting the entire cell. Existing technologies often use laser scribing machines to melt-cut the cell using conventional lasers. During the cutting process, the laser forms a single trajectory across the cell. Due to the nature of lasers, this trajectory is not easily altered. Therefore, laser scribing machines typically use an oscillating scanning mirror to alter the laser's trajectory. Since the laser's focal length is typically determined at the center of the cell, the kerf is created by thermally cutting the cell's silicon substrate, vaporizing / dusting the silicon wafer.

[0003] The cutting depth of the slit is usually 40% to 60% of the thickness of the cell. The uncut part is broken by a mechanical breaking arm to separate the whole cell into two half cells. However, during the laser thermal cutting process, the high energy will cause thermal burns on the cell slit. Therefore, after the cutting is completed, there will be a thermal damage layer formed by the high heat on the edge of the cell cut surface (such as Figure 1 As shown in the figure, the greater the thermal damage, the worse the mechanical properties of the battery cell, which makes the cut surface of the battery cell vulnerable to damage during the subsequent production process, resulting in an increase in the fragmentation rate and increased costs.

[0004] At the same time, the laser will make uneven cuts 100 on the cell cutting surface during oscillation scanning (such as Figure 2 As shown in the figure, the cutting depth in the center is deeper, while the cutting depth on both sides is shallower, which makes the edges of both sides prone to defects during the breaking process, such as multiple corners or missing corners.

[0005] In addition, non-destructive cutting is currently being introduced on the market, that is, no melting cutting cracks are formed on the cutting surface, but this method is expensive and has a high fragmentation rate after cutting, which will increase the production cost of photovoltaic cells. Summary of the Invention

[0006] To overcome at least one of the above-mentioned drawbacks of the prior art, in a first aspect, one embodiment of the present invention provides a laser cutting method for a photovoltaic cell, comprising: forming a first slit, a second slit, and a third slit in the photovoltaic cell using a laser; the first slit and the third slit are respectively located at opposite ends of the second slit and connected to the second slit;

[0007] The photovoltaic cell includes a first surface and a second surface. Along the thickness direction of the photovoltaic cell, the first surface and the second surface are respectively located at the two ends of the photovoltaic cell; the laser cuts the photovoltaic cell through the first surface, the depth of the first cut is 60% to 70% of the thickness of the photovoltaic cell, the depth of the second cut is 20% to 30% of the thickness of the photovoltaic cell, and the depth of the third cut is 60% to 70% of the thickness of the photovoltaic cell.

[0008] According to one embodiment of the present invention, the first slit is formed by a first laser, the second slit is formed by a second laser, and the third slit is formed by a third laser.

[0009] According to one embodiment of the present invention, the first slit includes a first end portion and a second end portion disposed opposite to each other along its length direction, and the second laser is used to cut from the second end portion, and the second laser cuts the second end portion for straightening;

[0010] The second slit includes a third end and a fourth end arranged opposite to each other along its length direction, the third end is connected to the first slit, and is cut from the fourth end by the third laser, and the third laser cuts the fourth end for straightening.

[0011] According to one embodiment of the present invention, the length of the first slit is 3 to 5 mm, and the length of the third slit is 3 to 5 mm.

[0012] According to one embodiment of the present invention, the angle between the opening of the first slit located on the first surface and the opening of the second slit located on the first surface is 0 to 0.3°, and the angle between the opening of the third slit located on the first surface and the opening of the second slit located on the first surface is 0 to 0.3°.

[0013] According to an embodiment of the present invention, the opening of the first slit located on the first surface, the opening of the second slit located on the first surface, and the opening of the third slit located on the first surface are located on the same straight line.

[0014] In a second aspect, an embodiment of the present invention provides a photovoltaic cell produced by the above method.

[0015] In a third aspect, an embodiment of the present invention provides a photovoltaic cell, comprising a first surface and a second surface, wherein the first surface and the second surface are respectively located at two ends of the photovoltaic cell along the thickness direction of the photovoltaic cell; a first slit, a second slit, and a third slit are provided between the first surface and the second surface, formed by laser cutting from the first surface; the first slit and the third slit are respectively located at two ends of the second slit and connected to the second slit;

[0016] The depth of the first slit is 60-70% of the thickness of the photovoltaic cell, the depth of the second slit is 20-30% of the thickness of the photovoltaic cell, and the depth of the third slit is 60-70% of the thickness of the photovoltaic cell.

[0017] According to one embodiment of the present invention, the first slit includes a first bottom portion located between the first surface and the second surface, and an angle between an opening of the first slit located on the first surface and the first bottom portion is 0-1°;

[0018] The second slit includes a second bottom portion located between the first surface and the second surface, and an angle between an opening of the second slit located on the first surface and the second bottom portion is 0° to 1°;

[0019] The third slit includes a third bottom portion located between the first surface and the second surface. The angle between the opening of the third slit located on the first surface and the third bottom portion is 0-1°.

[0020] According to one embodiment of the present invention, the length of the opening of the first slit located on the first surface is the same as the length of the first bottom, the length of the opening of the second slit located on the first surface is the same as the length of the second bottom, and the length of the opening of the third slit located on the first surface is the same as the length of the third bottom.

[0021] According to one embodiment of the present invention, the angle between the opening of the first slit located on the first surface and the opening of the second slit located on the first surface is 0 to 0.3°, and the angle between the opening of the third slit located on the first surface and the opening of the second slit located on the first surface is 0 to 0.3°.

[0022] A laser cutting method for photovoltaic cells, according to one embodiment of the present invention, limits the depth of the first and third slits at the ends to 60-70% of the cell thickness (deep cutting) and the depth of the second slit in the middle to 20-30% of the cell thickness (shallow cutting). This reduces thermal damage to the cut surface of the cell caused by the laser during the cutting process, thereby enhancing the mechanical strength of the majority of the cut surface and reducing the vulnerability of the cut surface during subsequent production. Furthermore, limiting the depth of the first and third slits to 60-70% of the cell thickness reduces the difficulty of robotic cell breaking and reduces the frequency of excessive or insufficient corners.

[0023] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0025] Figure 1 This is a comparative example of the topography of the cut surface of a photovoltaic cell after laser cutting using the existing technology;

[0026] Figure 2 A schematic diagram of a vertical cross section of a conventional laser-cut photovoltaic cell along a cutting seam;

[0027] Figure 3 Schematic diagram of a vertical cross-section of a photovoltaic cell after laser cutting along a cutting seam according to one embodiment of the present invention;

[0028] Figure 4 A top view of a photovoltaic cell after laser cutting according to an embodiment of the present invention;

[0029] Figure 5 This is a photo of the cut surface of a photovoltaic cell after laser cutting according to one embodiment of the present invention;

[0030] Figure 6 This is a topographical image of a cutting surface of a first slit of a photovoltaic cell after laser cutting according to an embodiment of the present invention;

[0031] Figure 7 This is a topographical diagram of the cutting surface of the second slit of the photovoltaic cell after laser cutting according to an embodiment of the present invention.

[0032] The following are the descriptions of the reference numerals:

[0033] 10. First slit; 11. First bottom; 20. Second slit; 21. Second bottom; 30. Third slit; 31. Third bottom; 41. First surface; 42. Second surface; 51. First edge; 52. Second edge; 100. Slit; L, length of photovoltaic cell; H, thickness of photovoltaic cell. DETAILED DESCRIPTION

[0034] The following is a detailed description of the preferred embodiments of the present invention. The accompanying drawings constitute a part of the present invention and, together with the embodiments of the present invention, are used to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. A vertical cross section refers to a cross section along the thickness direction of a photovoltaic cell.

[0035] Reference Figure 3 、 4 As shown, an embodiment of the present invention provides a laser cutting method for a photovoltaic cell, comprising: forming a first slit 10, a second slit 20, and a third slit 30 in the photovoltaic cell by laser; along the length direction of the second slit 20, the first slit 10 and the third slit 30 are respectively located at both ends of the second slit 20 and connected to the second slit 20;

[0036] Among them, the photovoltaic cell includes a first surface 41 and a second surface 42 arranged opposite to each other along its thickness direction; the laser cuts the photovoltaic cell through the first surface 41, and the depth of the first slit 10 is 60% to 70% of the thickness of the photovoltaic cell, the depth of the second slit 20 is 20% to 30% of the thickness of the photovoltaic cell, and the depth of the third slit 30 is 60% to 70% of the thickness of the photovoltaic cell.

[0037] In one embodiment, the length direction of the second slit 20 is the same as the length L of the photovoltaic cell.

[0038] In one embodiment, the depths of the first, second, and third slits 10, 20, and 30 are oriented in the same direction as the thickness H of the photovoltaic cell. The depth of the first slit 10 may be 60% to 70% of the thickness of the photovoltaic cell, such as 61%, 62%, 63%, 65%, 66%, 68%, or 69%. The depth of the third slit 30 may be 60% to 70% of the thickness of the photovoltaic cell, such as 61%, 62%, 63%, 65%, 66%, 68%, or 69%. Furthermore, the depth of the first slit 10 may be the same as the depth of the third slit 30. The depth of the second slit 20 may be 20% to 30% of the thickness of the photovoltaic cell, such as 21%, 22%, 23%, 25%, 26%, 28%, or 29%.

[0039] In one embodiment, the length of the first slit 10 is 3 to 5 mm, for example, 4 mm; the length of the third slit 30 is 3 to 5 mm, for example, 4 mm. Furthermore, the sum of the lengths of the first slit 10, the second slit 20, and the third slit 30 is equal to the length L of the photovoltaic cell.

[0040] In one embodiment, the length L of the photovoltaic cell may be 150-200 mm, such as 158 mm, 168 mm, or 182 mm.

[0041] The laser cutting method of a photovoltaic cell according to an embodiment of the present invention further includes the step of breaking the cell along the first slit 10 , the second slit 20 , and the third slit 30 , to obtain two half-cells.

[0042] In one embodiment, the angle between the first slit 10 and the second slit 20 is 0 to 0.3°, for example, 0.1°, 0.2°, or 0.3°; further, the angle between the opening of the first slit 10 located on the first surface 41 and the opening of the second slit 20 located on the first surface 41 is 0 to 0.3°, for example, 0.1°, 0.2°, or 0.3°.

[0043] In one embodiment, the angle between the third slit 30 and the second slit 20 is 0 to 0.3°, for example, 0.1°, 0.2°, or 0.3°; further, the angle between the opening of the third slit 30 located on the first surface 41 and the opening of the second slit 20 located on the first surface 41 is 0 to 0.3°, for example, 0.1°, 0.2°, or 0.3°.

[0044] In one embodiment, the angle between the first slit 10 and the second slit 20 is 0°, and the angle between the third slit 30 and the second slit 20 is 0°, that is, the first slit 10, the second slit 20, and the third slit 30 are located on the same straight line, so that the half-cell battery cell has a smoother cutting surface after being broken.

[0045] In one embodiment, the first slit 10 includes a first bottom 11 located between the first surface 41 and the second surface 42, and the distance between the first bottom 11 and the first surface 41 is the depth of the first slit 10; further, the angle between the first bottom 11 and the first surface 41 (or the angle between the opening of the first slit 10 located on the first surface 41 and the first bottom 11) is 0 to 1°, for example, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, or 1°; further, the angle between the first bottom 11 and the first surface 41 is 0°, in other words, the first bottom 11 is parallel to the first surface 41.

[0046] In one embodiment, the second slit 20 includes a second bottom 21 located between the first surface 41 and the second surface 42, and the distance between the second bottom 21 and the first surface 41 is the depth of the second slit 20; further, the angle between the second bottom 21 and the first surface 41 (or the angle between the opening of the second slit 20 located on the first surface 41 and the second bottom 21) is 0 to 1°, for example, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, or 1°; further, the angle between the second bottom 21 and the first surface 41 is 0°. In other words, the second bottom 21 is parallel to the first surface 41.

[0047] In one embodiment, the third slit 30 includes a third bottom 31 located between the first surface 41 and the second surface 42, and the distance between the third bottom 31 and the first surface 41 is the depth of the third slit 30; further, the angle between the third bottom 31 and the first surface 41 (or the angle between the opening of the third slit 30 located on the first surface 41 and the third bottom 31) is 0-1°, for example, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, or 1°; further, the angle between the third bottom 31 and the first surface 41 is 0°. In other words, the third bottom 31 is parallel to the first surface 41.

[0048] In one embodiment, disposing the first bottom 11 , the second bottom 21 , and the third bottom 31 parallel to the first surface 41 can further improve the uniformity of the cutting surface and reduce the occurrence of defects during the breaking process.

[0049] In one embodiment, the length of the opening of the first slit 10 on the first surface 41 is the same as the length of the first bottom 11, the length of the opening of the second slit 20 on the first surface 41 is the same as the length of the second bottom 21, and the length of the opening of the third slit 30 on the first surface 41 is the same as the length of the third bottom 31. Furthermore, the sum of the lengths of the first bottom 11, the second bottom 21, and the third bottom 31 is equal to the length of the photovoltaic cell.

[0050] In one embodiment, the first, second, and third laser beams are used to form the first, second, and third slits 10, 20, and 30, respectively. Using three laser beams to cut the cell makes the first, second, and third slits 10, 20, and 30 more regular, thereby reducing unevenness on the cut surface and minimizing defects during the cell breaking process.

[0051] In one embodiment, referring to Figure 4As shown, in the cutting area of ​​the first surface 41, a first slit 10 can be formed on the first surface 41 by a first laser; then, a second slit 20 can be formed on the first surface 41 by a second laser; finally, a third slit 30 can be formed on the first surface 41 by a third laser.

[0052] In one embodiment, during the cutting process, a first overlapping area and a second overlapping area for calibration are formed at the junction of the first slit 10 and the second slit 20 and at the junction of the second slit 20 and the third slit 30. The first overlapping area belongs to the area of ​​the first slit 10, and the second overlapping area belongs to the area of ​​the second slit 20. In order to make the first laser, the second laser, and the third laser be on the same straight line, and further make the first slit 10, the second slit 20 and the third slit 30 be on the same straight line, the second laser starts cutting from the first overlapping area, and the third laser starts cutting from the second overlapping area. That is, the first overlapping area is double-cut by the first laser and the second laser, and the second overlapping area is double-cut by the second laser and the third laser. The cross-section of the first overlapping area can be as follows Figure 5 As shown in the box, further, the lengths of the first overlapping area and the second overlapping area may be 3 to 5 mm.

[0053] In one embodiment, photovoltaic cells can be cut using an existing laser scribing machine, such as a standard offline laser scribing machine. The machine parameters can be adjusted to create kerf depths of varying depths. Unlike non-destructive laser scribing and welding machines, standard offline laser scribing machines can be retrofitted online without incurring additional costs.

[0054] In one embodiment, the laser scribing machine used for cutting photovoltaic cells may be an offline scribing machine with adjustable laser trajectory.

[0055] In one embodiment of the present invention, a laser cutting method for photovoltaic cells is used to cut (or scribing) the cell using three-segment lasers. High laser parameters are used for re-scribing on both side edges to form a first slit and a third slit with a depth of 60 to 70%. Low laser parameters are used for shallow scribing in the middle area to form a second slit with a depth of 20 to 30%.

[0056] The inventors' experiments revealed that the deeper and longer the laser slits are, the greater the probability of uneven cutting depth. One embodiment of the present invention improves the uniformity of the second slits by dividing the laser cutting into three stages and reducing the depth of the longer second slit. Because the relatively long second slits suffer less laser damage, the mechanical properties of most areas of the cell are preserved, making it less susceptible to breakage during subsequent production. Furthermore, deep cuts are made on both edges, making it less susceptible to breakage during mechanical separation.

[0057] One embodiment of the present invention provides a photovoltaic cell, which is manufactured by the above method.

[0058] One embodiment of the present invention provides a photovoltaic cell, comprising a first surface 41 and a second surface 42. The first surface 41 and the second surface 42 are respectively located at two ends of the photovoltaic cell along the thickness direction of the photovoltaic cell. A first slit 10, a second slit 20, and a third slit 30 formed by laser cutting are provided between the first surface 41 and the second surface 42. Along the length direction of the second slit 20, the first slit 10 and the third slit 30 are respectively located at two ends of the second slit 20. The angle between the first slit 10 and the second slit 20 is 0 to 0.3°, and the angle between the third slit 30 and the second slit 20 is 0 to 0.3°.

[0059] The depth of the first slit 10 is 60-70% of the thickness of the photovoltaic cell, the depth of the second slit 20 is 20-30% of the thickness of the photovoltaic cell, and the depth of the third slit 30 is 60-70% of the thickness of the photovoltaic cell.

[0060] The above-mentioned definitions apply to the first slit 10 , the second slit 20 , the third slit 30 , the first surface 41 , etc. in the photovoltaic cell of one embodiment of the present invention.

[0061] The following further describes the laser cutting method of photovoltaic cells according to one embodiment of the present invention in conjunction with the accompanying drawings and specific examples. Figure 1 、 6 The morphology images of 7 were obtained by electron microscopy with a magnification of about 400 times.

[0062] Example

[0063] S1: Provide a photovoltaic cell with a length of 168 mm and a thickness of 140-180 μm. Along the length L of the photovoltaic cell, the photovoltaic cell includes a first side 51 and a second side 52 on both sides;

[0064] S2: Using a first laser, cutting is performed from the first edge 51 of the first surface 41 toward the second edge 52 to form a first slit 10. The first slit 10 has a length of 3 to 5 mm and a depth of 60 to 70% of the thickness of the photovoltaic cell. The first slit 10 includes a first end and a second end oppositely disposed along its length. The first end is flush with the first edge 51, and the second end is located within the first surface 41.

[0065] S3: A second laser is used to cut from the second end of the first slit 10. The second laser also cuts the second end of the first slit 10 (also the first overlapping region) for straightening. The second laser cutting forms a second slit 20 connected to the first slit 10 on the first surface 41. The second slit 20 has a length of 158 to 162 mm and a depth of 20 to 30%. The second slit 20 includes a third end and a fourth end oppositely disposed along its length. The third end is connected to the first slit 10, and the fourth end is located within the first surface 41.

[0066] S4: Using a third laser to cut from the fourth end of the second slit 20, and the third laser to cut the fourth end of the second slit 20 (also the second overlapping area) for straightening. The third laser cutting forms a third slit 30 connected to the second slit 20 on the first surface 41. The third slit 30 has a length of 3 to 5 mm and a depth of 60 to 70% of the thickness of the photovoltaic cell. The third slit 30 includes a fifth end and a sixth end oppositely disposed along its length. The fifth end is connected to the second slit 20, and the sixth end is flush with the second edge 52.

[0067] S5: Break the cut battery cell into two half-cells.

[0068] Comparative Example

[0069] S1: Provide a photovoltaic cell identical to that in the embodiment. Along the length L of the photovoltaic cell, the photovoltaic cell includes a first side portion 51 and a second side portion 52 on both sides.

[0070] S2: A laser is used to directly cut through the first surface 41 from the first edge 51 to the second edge 52 to form Figure 2 The cutting depth of the slit 100 shown is 40-60% of the thickness of the cell;

[0071] S3: Break the cut battery cell into two half-cells.

[0072] Figure 1 This is a morphology diagram of the cut surface (or cross section) of the cell after laser cutting in the comparative example; Figure 6 This is a topography image of the first slit 10 area on the cut surface of the cell after laser cutting in the embodiment. Figure 7 2 is a morphology diagram of the second slit 20. Compared with the cut surface of the comparative example, the cut surface of the embodiment of the present invention, especially the cut surface of the second slit 20 with a larger area, has less damage and better uniformity.

[0073] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for laser cutting a photovoltaic cell, comprising: Forming a first slit, a second slit, and a third slit in the photovoltaic cell by laser; the first slit and the third slit are respectively located at two ends of the second slit and connected to the second slit; The photovoltaic cell comprises a first surface and a second surface, and along the thickness direction of the photovoltaic cell, the first surface and the second surface are respectively located at two ends of the photovoltaic cell; the laser cuts the photovoltaic cell through the first surface, the depth of the first cut is 60% to 70% of the thickness of the photovoltaic cell, the depth of the second cut is 23% to 30% of the thickness of the photovoltaic cell, and the depth of the third cut is 60% to 70% of the thickness of the photovoltaic cell; The first laser is used to form a first slit on the first surface; the second laser is used to form a second slit on the first surface; and finally, the third laser is used to form a third slit on the first surface. A first overlapping area and a second overlapping area for calibration are formed at the junction of the first slit and the second slit, and at the junction of the second slit and the third slit; wherein the first overlapping area belongs to the area of ​​the first slit, and the second overlapping area belongs to the area of ​​the second slit; the second laser starts cutting from the first overlapping area, and the third laser starts cutting from the second overlapping area.

2. The method according to claim 1, wherein The first slit includes a first end and a second end oppositely disposed along its length, and the second laser is used to cut from the second end, and the second laser cuts the second end for straightening; The second slit includes a third end and a fourth end arranged opposite to each other along its length direction, the third end is connected to the first slit, and is cut from the fourth end by the third laser, and the third laser cuts the fourth end for straightening.

3. The method according to claim 1, wherein The length of the first slit is 3 to 5 mm, and the length of the third slit is 3 to 5 mm.

4. The method according to claim 1, wherein The angle between the opening of the first slit located on the first surface and the opening of the second slit located on the first surface is 0-0.3°, and the angle between the opening of the third slit located on the first surface and the opening of the second slit located on the first surface is 0-0.3°.

5. The method according to claim 1, wherein The opening of the first slit located on the first surface, the opening of the second slit located on the first surface, and the opening of the third slit located on the first surface are located on the same straight line.

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