Photovoltaic cell, cell assembly and preparation process

Abstract

The application provides a photovoltaic cell, a cell assembly and a preparation process. The photovoltaic cell comprises a silicon substrate and a passivation layer on at least one surface of the silicon substrate. At least one side of the silicon substrate is printed with a grid line, a soldering point and an extension line. The grid line comprises a main grid and a sub-grid which are arranged in a cross manner, and the sub-grid is in contact with the silicon substrate. The extension line is connected with the main grid and the soldering point at two ends respectively, and the extension line is in contact with the silicon substrate. The height of the extension line gradually decreases from the soldering point to the main grid. The photovoltaic cell, the cell assembly and the preparation process provided by the application can reduce the unit consumption of the cell, ensure the reliability of the connection between the soldering point and the main grid, and ensure the effective current collection capacity even in the case that the part where the grid line is connected with the soldering point is corroded by the soldering alloy.

Description

[0001] This application is a divisional application of the original application with the application number 202110998160.X and the original filing date of August 27, 2021, and the entire contents of the original application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of photovoltaic cells, in particular to a photovoltaic cell, a cell module and a preparation process. BACKGROUND

[0003] With the reduction of the cost of photovoltaic cells, it is inevitable to reduce the metal consumption. For the multi-main grid technology, a larger number of main grids can be used, and the area of the welding points is reduced. Although this can reduce the consumption, the smaller welding points are difficult to ensure the reliability of the connection with the main grid, and also reduce the current collection capacity. SUMMARY

[0004] The purpose of the present application is to provide a photovoltaic cell, a cell module and a preparation process to solve the problem that the reduction of the welding point area cannot simultaneously reduce the consumption and ensure the reliability of the connection between the welding point and the main grid in the prior art.

[0005] The first aspect of the present application provides a photovoltaic cell, comprising a silicon substrate and a passivation layer on at least one surface of the silicon substrate.

[0006] At least one side of the silicon substrate is printed with a grid line, a welding point and an extension line, the grid line comprises a main grid and a sub-grid arranged in cross, and the sub-grid is in contact with the silicon substrate.

[0007] The extension line is connected to the main grid and the welding point at both ends, and the extension line is in contact with the silicon substrate.

[0008] The height of the extension line gradually decreases from the welding point to the direction of the main grid.

[0009] In a possible implementation, neither the main grid nor the welding point is in contact with the silicon substrate.

[0010] In a possible implementation, in the direction of the main grid extension line, the size of the extension line is less than or equal to 3 times the size of the welding point.

[0011] In a possible implementation, part of the extension line overlaps the main grid, and in the direction of the main grid extension line, the size of the overlapping region of the extension line and the main grid is less than 0.1 mm; and / or

[0012] The part of the extension line is coincident with the soldering point, and in the direction of the main grid extension line, the size of the area where the extension line is coincident with the soldering point is less than 0.1 mm.

[0013] In a possible implementation, the width of the extension line is 1-2 times the width of the main grid.

[0014] In a possible implementation, the shape of the extension line comprises one or more of a combination of a rectangle, a trapezoid and an ellipse.

[0015] The second aspect of the present application provides a photovoltaic module, wherein the photovoltaic module is sequentially glass, first adhesive film material, photovoltaic cell string, second adhesive film material and back sheet from the front to the back, wherein the photovoltaic cell string is composed of a plurality of photovoltaic cells, and the photovoltaic cell is the photovoltaic cell provided in the first aspect of the present application.

[0016] In a possible implementation, the photovoltaic cells are connected by solder wires, and the diameter of the solder wires is 0.2-0.3 mm.

[0017] The third aspect of the present application also provides a preparation process for preparing the photovoltaic cell provided in the first aspect of the present application, characterized in that the process comprises the following steps:

[0018] providing a photovoltaic substrate with at least one passivation layer;

[0019] printing a soldering point and a main grid on the photovoltaic substrate respectively by using non-burn-through paste;

[0020] printing an extension line and a sub-grid on the photovoltaic substrate respectively by using burn-through paste, so that the extension line is connected to the soldering point and the main grid respectively.

[0021] In a possible implementation, the burn-through paste used by the extension line and the sub-grid is different.

[0022] The technical solution provided in the present application can achieve the following beneficial effects:

[0023] The photovoltaic cell, the cell module and the preparation process provided in the present application can achieve the following beneficial effects:

[0024] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1A structure diagram of a photovoltaic cell provided by an embodiment of the present application is shown in FIG. 1.

[0026] Figure 2 For Figure 1 A local enlarged view at A is shown in FIG. 2.

[0027] Figure 3 A state diagram of the connection of the soldering points, the extension lines and the main grids (I) is shown in FIG. 3.

[0028] Figure 4 A state diagram of the connection of the soldering points, the extension lines and the main grids (II) is shown in FIG. 4.

[0029] Figure 5 A state diagram of the connection of the soldering points, the extension lines and the main grids (III) is shown in FIG. 5.

[0030] Figure 6 A state diagram of the connection of the soldering points, the extension lines and the main grids (IV) is shown in FIG. 6.

[0031] Figure 7 A sectional structure diagram of a photovoltaic cell provided by an embodiment of the present application is shown in FIG. 7.

[0032] Figure 8 A structure diagram of a photovoltaic module provided by an embodiment of the present application is shown in FIG. 8.

[0033] Figure 9 A flow chart of a preparation process provided by an embodiment of the present application is shown in FIG. 9.

[0034] Reference signs:

[0035] 1-photovoltaic cell;

[0036] 11-main grid;

[0037] 12-sub grid;

[0038] 101-front grid line

[0039] 102-passivation layer

[0040] 103-emitter

[0041] 104-silicon substrate

[0042] 105-tunneling oxide layer

[0043] 106-doped doped layer

[0044] 107-back passivation layer

[0045] 108-back grid line

[0046] 2-soldering point;

[0047] 3-extension line;

[0048] a-coincidence area;

[0049] 4-glass;

[0050] 5-first encapsulant material;

[0051] 6-photovoltaic cell string;

[0052] 7-second encapsulant material;

[0053] 8-backsheet.

[0054] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate embodiments consistent with the application and serve to explain the principles of the application. DETAILED DESCRIPTION

[0055] In order to make the purposes, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and should not be used to limit the application.

[0056] In the description of the application, unless explicitly defined and limited, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "connection" can be fixed connection, can also be detachable connection, or integral connection, or electrical connection; can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0057] In the description of the specification, it should be understood that the "up", "down" and the like described in the embodiments of the application are described from the angle shown in the drawings, and should not be understood as limiting the embodiments of the application. In addition, in the context, it should also be understood that when referring to an element connected to another element "on" or "under", it can not only be directly connected to another element "on" or "under", but also indirectly connected to another element "on" or "under" through an intermediate element.

[0058] With the reduction of the cost of photovoltaic cells, there is still a large space for reducing the single consumption of metallization, and it is also an inevitable trend to reduce the cost of photovoltaic cells. The existing multi-main grid technology is relatively mature. For the multi-main grid technology, a larger number of main grids can be used, and the area of the solder joint can be reduced, thereby reducing the single consumption. However, although the reduction of the solder joint area can reduce the single consumption, the smaller solder joint is difficult to ensure the reliability of the connection with the main grid, and also reduces the current collection capacity, resulting in that the reduction of the single consumption and the reliability of the connection between the solder joint and the main grid and the current collection capacity cannot be considered at the same time.

[0059] Therefore, as shown in Figures 1 to 7 The embodiment of the present application provides a photovoltaic cell 1, which comprises a silicon substrate and a passivation layer located on at least one surface of the silicon substrate. The photovoltaic cell 1 can be a TOPcon cell, as shown in Figure 7 That is, from the front surface to the back surface of the cell, it comprises a front grid line 101, a front passivation layer 102, an emitter 103, an N-type silicon substrate 104, a tunneling oxide layer 105, a doped amorphous silicon doping layer 106, a back passivation layer 107 and a back grid line 108.

[0060] Specifically, at least one side of the silicon substrate of the photovoltaic cell 1 is printed with a grid line, a solder joint 2 and an extension line 3. When the photovoltaic cell 1 is a TOPcon cell, the front surface and the back surface of the silicon substrate are printed with the grid line, the solder joint 2 and the extension line 3. When the photovoltaic cell 1 is a PERC cell, the front surface of the PERC cell is printed with the grid line, the solder joint 2 and the extension line 3.

[0061] The grid line comprises a main grid 11 and a sub-grid 12 arranged in cross, and the sub-grid 12 is in contact with the silicon substrate. The extension line 3 is connected with the main grid and the solder joint 2 at both ends, and the extension line 3 is in contact with the silicon substrate.

[0062] The extension line 3 can realize the connection between the main grid 11 and the solder joint 2, and can directly contact the silicon substrate. Specifically, a screen printing process can be used to print a burn-through type paste, so that the paste penetrates the passivation layer and contacts the silicon substrate; or a laser punching method can be used, so that the passivation layer in the area where the extension line is located has an opening for accommodating the extension line before the paste is printed; or a laser transfer method is used to directly obtain the extension line in contact with the silicon substrate. Various methods can ensure the reliability of the connection between the solder joint 2 and the main grid 11, and ensure the current collection capacity of the solder joint 2.

[0063] In addition, it needs to be explained that for the battery with metal grid lines for conducting electricity, in order to reduce the cost, the thickness of the metal grid line is becoming lower and lower, and with the decrease of the thickness of the metal grid line, the part of the soldering wire and the grid line after soldering, especially the part of the soldering wire and the main grid, is in contact with silver tin or other alloy materials, which can cause the main grid to be eroded by the soldering alloy layer. The temperature at the soldering point is the highest during soldering, which causes the most soldering alloy near the soldering point, so that the thickness of the main grid at the connection position of the main grid and the soldering point is reduced, which is most likely to cause the main grid to be broken, affects the current collection, and causes EL to be poor. In addition, the existing main grid and soldering point are designed in one body, and the soldering point has a relatively long transverse length. The main grid and the soldering point are located above the passivation layer and do not contact the silicon substrate, but only contact the silicon substrate in a small area, which is easy to cause the main grid to be broken at the connection position of the main grid and the soldering point.

[0064] Therefore, the photovoltaic cell 1 provided by the embodiment of the present application can be connected with the grid line and the soldering point 2 through the extension line 3, so that the connection between the soldering point 2 and the grid line is enhanced through the extension line 3, and the extension line 3 directly contacts the silicon substrate. Even if the grid line is eroded by the soldering alloy and the thickness is reduced, the part of the extension line 3 contacting the silicon substrate will not be disconnected. That is, the extension line 3 can always maintain the connection with the grid line and the soldering point 2, so as to ensure the current collection ability.

[0065] Therefore, compared with the prior art, the photovoltaic cell 1 provided by the embodiment of the present application not only reduces the unit consumption of the cell, but also ensures the reliability of the connection between the soldering point 2 and the main grid 11, and can still ensure the effective current collection ability in the case that the part of the grid line and the soldering point 2 is eroded by the soldering alloy.

[0066] In the embodiment, the main grid 11 and the soldering point 2 do not contact the silicon substrate, and the soldering point 2 can be located away from the auxiliary grid 12, as shown in FIG. 1. Figure 2 It can be understood that the part of the main grid 11 which is easy to be eroded by the soldering alloy and easy to be broken is located at the connection position of the main grid 11 and the soldering point 2. In the embodiment, the soldering point 2 is connected with the main grid 11 through the extension line 3, and the extension line 3 can be printed on the silicon substrate through the screen printing process, so that the disconnection is not easy to occur, the connection between the grid line and the soldering point 2 is enhanced, and the problem of broken grid is avoided. In addition, the auxiliary grid 12 can also be located on both sides of the soldering point 2, as shown in FIG. 2. Figure 3

[0067] Specifically, in the direction of the extension line of the main grid 11, the size of the extension line 3 is less than or equal to 3 times the size of the soldering point 2. It needs to be explained that the soldering point and the soldering wire are welded through the pressing action of the probe row of the soldering machine. The area near the probe will form a soldering alloy. By making the size of the extension line 3 less than or equal to 3 times the size of the soldering point 2, the area of the soldering alloy near the probe can be avoided to be too large, so as to reduce the risk of the main grid being broken.​

[0068] As a specific implementation, as shown in Figure 5 and Figure 6 , the part of the extension line 3 coincides with the main grid 11, and in the direction of the extension line of the main grid 11, the size of the area a where the extension line 3 coincides with the main grid 11 is less than 0.1mm. It should be noted that if the size of the area a where the extension line 3 coincides with the main grid 11 is too large in the direction of the extension line of the main grid 11, the height of the area where the extension line 3 coincides with the main grid 11 will be large, which will affect the alignment of the relative position between the main grid 11 and the welding wire, and if the welding wire deviates to the side of the main grid 11, it is easy to cause the height of the auxiliary grid 12 near the deviated part of the main grid 11 to be reduced. As a specific implementation, the part of the extension line 3 coincides with the welding point 2, and in the direction of the extension line of the main grid 11, the size of the area where the extension line 3 coincides with the welding point 2 is less than 0.1mm. It should be noted that if the size of the area a where the extension line 3 coincides with the welding point 12 is too large in the direction of the extension line of the main grid 11, or the extension line 3 penetrates the welding point 2, it will cause the height of the area where the extension line 3 coincides with the welding point 2 to be large, which will affect the alignment of the relative position between the main grid 11 and the welding wire, and if the welding wire deviates to the side of the main grid 11, it is easy to cause the height of the auxiliary grid 12 near the deviated part of the main grid 11 to be reduced. As a specific implementation, the width of the extension line 3 is 1-2 times the width of the main grid 11. By making the extension line 3 have a larger width relative to the main grid 11, the current collection capability is enhanced, and at the same time the reliability of the connection between the extension line 3 and the main grid 11 and the welding point 2 is also improved.

[0069] In the embodiment, the shape of the extension line 3 is trapezoidal, H-shaped, inverted H-shaped, rectangular or elliptical. Since the width of the welding point 2 is greater than the width of the main grid 11, the end of the extension line 3 with a larger width is connected to the welding point 2, which can enhance the strength of the connection with the welding point 2. Of course, the extension line 3 can also have other shapes. In the embodiment, the trapezoidal shape is preferred, as shown in Figure 4 , the end of the trapezoidal extension line 3 with a larger width is connected to the welding point 2, and the end with a smaller width is connected to the main grid 11.

[0070] As a specific implementation, the height of the extension line 3 gradually decreases from the welding point 2 to the direction of the main grid 11. By making the height of the extension line 3 gradually decrease from the welding point 2 to the direction of the main grid 11, the reliability of the connection between the extension line 3 and the welding point 2 is improved, and the current collection capability is also improved, that is, the closer the extension line 3 is to the position with a larger height of the welding point 2, the stronger the current collection capability, and at the same time the occurrence of broken grid can be avoided.

[0071] Specifically, the height of the two ends of the extension line 3 can be greater than the height of the middle region, so that the reliability of the connection between the extension line 3 and the welding point 2 and the main grid 11 can be improved at the same time.

[0072] It should be noted that the photovoltaic cell 1 can be an N-type or P-type photovoltaic cell 1, and the silicon substrate can be an N-type or P-type silicon substrate. In this embodiment, the photovoltaic cell 1 is preferably an N-type photovoltaic cell 1, and the N-type silicon substrate is an N-type silicon substrate.

[0073] As a specific implementation, the height of the main grid is less than or equal to 8um, so as to reduce the unit consumption.

[0074] As a specific implementation, when the photovoltaic cell 1 is an N-type photovoltaic cell, the width of the grid line on the front surface of the N-type photovoltaic cell is less than 30um, and the width of the grid line on the back surface of the N-type photovoltaic cell is less than 37um. Since the back surface of the N-type photovoltaic cell is relatively smooth, the width of the grid line on the back surface of the N-type photovoltaic cell is greater than that on the front surface, which can make the connection of the grid line on the back surface of the N-type photovoltaic cell more reliable.

[0075] As a specific implementation, for the N-type photovoltaic cell, the height of the solder joint 2 is greater than or equal to 5um and less than or equal to 7um. Within this height range, the current collection capability can be ensured, and the unit consumption can be reduced.

[0076] As a specific implementation, for the N-type photovoltaic cell, the thickness of the solder joint 2 is less than the thickness of the grid line.

[0077] As a specific implementation, the position projection of at least part of the solder joint on the front surface of the N-type photovoltaic cell does not coincide with the position projection of at least part of the solder joint on the back surface of the N-type photovoltaic cell. Thus, the effect of evenly distributing the lamination load can be achieved, and the process breakage can be reduced.

[0078] As a specific implementation, the solder joint 2 includes a hollow area, and in a direction parallel to the N-type photovoltaic cell, the area of the hollow area is not more than 30% of the total area of the solder joint 2. Thus, the current collection capability can be ensured, and the unit consumption can be reduced.

[0079] As a specific implementation, in order to achieve low unit consumption, in a direction parallel to the N-type photovoltaic cell, the area of the non-hollow area of the solder joint 2 is less than or equal to 0.3mm 2 .

[0080] As a specific implementation, the length of the solder joint 2 in the direction perpendicular to the main grid 11 is greater than the length of the solder joint 2 in the direction parallel to the main grid 11.

[0081] As a specific implementation, the number of main grids 11 is greater than or equal to 9 and less than or equal to 18. Thus, the photovoltaic cell 1 can have a strong current collection capability.

[0082] As Figure 8As shown, the embodiment of the present application also provides a photovoltaic module, which is glass 4, first adhesive film material 5, photovoltaic cell string 6, second adhesive film material 7, back plate 8 from front to back, wherein the photovoltaic cell string is composed of a plurality of photovoltaic cells, and the photovoltaic cell is the photovoltaic cell piece 1 provided by any embodiment of the present application. Wherein the photovoltaic module is an N-type photovoltaic module

[0083] Wherein the photovoltaic cell pieces 1 are connected by welding wires, and the diameter of the welding wires is 0.2-0.3mm. Since the N-type photovoltaic cell piece 1 provided by the embodiment of the present application can further reduce the size of the welding point 2, the width of the welding wire connected with the welding point 2 can be further reduced, and a larger number of main grids 11 can be arranged, and the current collection capacity can be improved.

[0084] As shown, Figure 9 The embodiment of the present application also provides a preparation process for preparing the photovoltaic cell piece provided by any embodiment of the present application, which comprises the following steps:

[0085] Step S1, providing a photovoltaic substrate with at least one passivation layer.

[0086] Step S2, printing the welding point and the main grid on the photovoltaic substrate respectively by using non-burn-through paste.

[0087] Wherein the non-burn-through paste can be silver paste, silver-aluminum paste, etc. The paste used by the welding point and the main grid can be the same or different. In the specific printing operation, the welding point can be printed first, and then the main grid can be printed, or the welding point and the main grid can be printed at one time.

[0088] Step S3, printing the extension line and the auxiliary grid on the photovoltaic substrate respectively by using burn-through paste, and the extension line is connected with the welding point and the main grid respectively.

[0089] Wherein the burn-through paste can be a composite paste formed by silver powder, aluminum powder, glass powder and organic matter. The paste of the extension line and the auxiliary grid can be the same or different. In the specific printing operation, the extension line can be printed first, and then the auxiliary grid can be printed, or the extension line and the auxiliary grid can be printed at one time.

[0090] By using the burn-through paste for the extension line, the extension line can be directly contacted with the silicon substrate, which can effectively avoid the grid line from being broken due to the corrosion of the welding alloy, and can improve the current collection capacity.

[0091] Specifically, the burn-through paste comprises solid content of 88%-92%, organic matter content of 2-6%, and glass powder content of 2-6%; the solid content comprises silver powder content of 90-92%, aluminum powder content of 2-6%, and trace metal or rare earth element content of 2-6%.

[0092] The above descriptions are only the preferred embodiments of the present application, and are not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A photovoltaic cell, characterized by, The silicon substrate and a passivation layer on at least one surface of the silicon substrate; At least one surface of the silicon substrate is printed with a gate line, a solder point and an extension line, the gate line comprises a main gate and a sub gate arranged in cross, the sub gate is in contact with the silicon substrate; The extension line is connected with the main gate and the solder point at both ends respectively, and the extension line is in contact with the silicon substrate; The height of the extension line gradually decreases from the solder point to the main gate; The main gate and the solder point are not in contact with the silicon substrate.

2. The photovoltaic cell of claim 1, wherein, In the direction of the extension line of the main gate, the size of the extension line is less than or equal to 3 times the size of the solder point.

3. The photovoltaic cell of claim 1, wherein, Part of the extension line overlaps with the main gate, and in the direction of the extension line of the main gate, the size of the overlapping area of the extension line and the main gate is less than 0.1 mm; and / or Part of the extension line overlaps with the solder point, and in the direction of the extension line of the main gate, the size of the overlapping area of the extension line and the solder point is less than 0.1 mm.

4. The photovoltaic cell of claim 1, wherein, The width of the extension line is 1-2 times the width of the main gate.

5. The photovoltaic cell of claim 1, wherein, The shape of the extension line comprises one or more combinations of a rectangle, a trapezoid and an oval.

6. A photovoltaic module, characterized by, The photovoltaic module comprises, from front to back, a glass, a first adhesive film material, a photovoltaic cell string, a second adhesive film material and a back plate, wherein the photovoltaic cell string is composed of a plurality of photovoltaic cells, and the photovoltaic cell is the photovoltaic cell piece of any one of claims 1-5.

7. The photovoltaic module of claim 6, wherein, The photovoltaic cells are connected by a solder wire with a diameter of 0.2-0.3 mm.

8. A production process for producing the photovoltaic cell according to any one of claims 1 to 7, characterized by, The method comprises the following steps: Providing a photovoltaic substrate with at least one surface having a passivation layer; Printing a solder point and a main gate on the photovoltaic substrate using non-burn-through paste respectively; Printing an extension line and a sub gate on the photovoltaic substrate using burn-through paste respectively, so that the extension line is connected with the solder point and the main gate respectively.

9. The manufacturing process of claim 8, wherein, The burn-through paste used by the extension line and the sub gate is different.

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