Electrode structure of a back-contact cell, back-contact cell, back-contact cell module and back-contact cell system

Abstract

Back contact cell comprising an electrode structure and a back side, wherein the electrode structure is arranged on the back side of the back contact cell, wherein the back contact cell comprises a first polarity region, a second polarity region and a first edge, wherein the electrode structure comprises: a multitude of first fingers configured to collect the area of ​​first polarity; a multitude of second fingers configured to collect the area of ​​second polarity; a first busbar located on one side of the back contact cell near the first edge and connected to the first fingers; a multitude of initial pad points; and a plurality of first connecting electrodes, each connected to the first busbar and the first pad points, wherein a distance between each of the first pad points and the first edge is greater than a distance between the first busbar and the first edge.

Description

background

[0001] The disclosure belongs to the technical field of solar cells and in particular to an electrode structure of a back contact cell, a back contact cell, a back contact cell module and a back contact cell system.

[0002] A solar cell is a semiconductor device that can convert light energy into electrical energy. Relatively low production costs and relatively high energy conversion efficiency have always been the goals of the photovoltaic industry. In a conventional solar cell, an emitter contact electrode and a base contact electrode of the solar cell are located on two opposite sides of the solar cell. A front surface of the cell is a light-receiving surface. The coverage of a front metal emitter contact electrode inevitably leads to part of the incident sunlight being reflected and blocked by a metal electrode, resulting in some optical loss. The coverage area of ​​a front metal electrode of an ordinary crystalline silicon solar cell is about 7%. Therefore, the energy conversion efficiency of the cell can be directly improved by reducing the front surface coverage of the metal electrode.

[0003] Given the above situation, a back-contact solar cell is introduced. A back-contact solar cell is a cell in which both an emitter and a base contact electrode are arranged on the back (non-light-receiving surface) of the cell. A light-receiving surface of the cell is not shielded by a metal electrode, effectively increasing the short-circuit current of the cell. Furthermore, relatively wide metal fingers may be arranged on the back to reduce series resistance and thereby increase the fill factor. Furthermore, the cell with the unshielded front surface not only has high conversion efficiency but also is more aesthetically pleasing. Furthermore, a module with a full back-contact electrode is easy to assemble.

[0004] In the back-contact solar cell, the electrode pattern design is a core technology of the cell. Three electrode pattern designs of the existing back-contact solar cell are as follows. 1. With reference to Fig.1, electrodes with opposite polarities are printed with insulating paste 3 to be insulated. However, electrodes with the same polarity are exposed, and then pad dots 1 and a busbar 2 are printed to make the electrodes with the same polarity contact each other. However, the insulating paste 3 cannot withstand high temperatures, and the pad dots 1 and busbar 2 are formed by post-printing. Therefore, only low-temperature paste can be selected for the pad dots 1 and busbar 2, which increases the cost. The use of low-temperature paste has the problem of reliability. To form good insulation, the insulating paste 3 is about 30 µm high. To avoid separation, the heights of the pad dots 1 and busbar 2 must be greater than 30 µm. This can lead to high paste consumption, which further increases the cost.In addition, Insulating Paste 3 and some pastes have problems such as poor adhesion, which poses a major challenge for mass production. 2. With reference to Fig. 2, a finger 4 is separated at pad points 5 with opposite polarities and a busbar 6, while the pad points 5 are located at the edge and the busbar 6 is located at the farthest edge of a silicon wafer. The pad points 5 and the busbar 6 are located at the edge of the silicon wafer. During the module manufacturing process, a tape is also required to cover the edge of the silicon wafer. A large number of microcracks exist at the edges of the silicon wafer, causing stress concentration during the tape welding process, leading to cracking problems that reduce the yield and reliability of the module. 3. With reference to Fig.3, a finger 7 is separated by pad points 8 with opposite polarities and a bus bar 9. The outer pad points 8 and the bus bar 9 are at a certain distance from the farthest edge of the silicon wafer, and the outer pad points 8 and an outer periphery of the bus bar 9 are arranged to have the same polarity. Although the third design solves the problems existing in the first and second designs, photogenerated electron-hole pairs must be diffused into a region with an opposite polarity to form an effective collection. In the third design, the photogenerated electrons and holes on the outside must overcome a distance of mm or even cm to reach the region with the opposite polarity.Recombination loss of a diffusion process over a long distance leads to a drop in short-circuit current, an increase in series resistance and a loss in fill factor, resulting in very poor photoelectric conversion performance.

[0005] Therefore, it has always been one of the central research problems for professionals to design a back contact cell electrode structure, a back contact cell, a back contact cell module, and a back contact cell system to solve the above problems.

[0006] The disclosure provides an electrode structure of a back contact cell to solve technical problems of high cost, low reliability, and poor photoelectric conversion performance of the existing back contact solar cell.

[0007] An electrode structure of a back contact cell is provided; the back contact cell comprises a first polarity region, a second polarity region and a first edge, and the electrode structure comprises: a plurality of first fingers configured to collect the first polarity region; a plurality of second fingers configured to collect the second polarity region; a first bus bar disposed on one side of the back contact cell near the first edge and connected to the first fingers; a variety of first pad points; and a plurality of first connection electrodes each connected to the first bus bar and the first pad points, wherein a distance between each of the first pad points and the first edge is greater than a distance between the first busbar and the first edge.

[0008] In one class of this embodiment, the second fingers comprise first bent fingers between the first bus bar and the first pad points, wherein the first bent fingers are each bent toward the first bus bar and the first pad points and are not in contact with either the first bus bar or the first pad points, or the first bent fingers are bent toward the first bus bar and are not in contact with the first bus bar, or the first bent fingers are bent toward the first pad points and are not in contact with the first pad points.

[0009] In one class of this embodiment, each of the first bent fingers passes through at least one of the first fingers.

[0010] In one class of this embodiment, a center line of each of the first connection electrodes and a center line of each of the first pad points do not lie on a same straight line.

[0011] In one class of this embodiment, the electrode structure further comprises third fingers, each connected to the first busbar and the first pad points. The third fingers are arranged adjacent to the first connection electrodes, and a width of each of the third fingers is smaller than a width of each of the first connection electrodes.

[0012] In one class of this embodiment, each of the second fingers is covered with a first insulating material in a portion of a center line of each of the first pad points.

[0013] In one class of this embodiment, the distance between the first busbar and the first edge is from 0.01 mm to 3 mm.

[0014] In one class of this embodiment, the distance between each of the first pad points and the first edge is between 1 mm and 20 mm.

[0015] In one class of this embodiment, the electrode structure further comprises: a second busbar disposed on one side of the back contact cell near a second edge and connected to the second busbar of the second fingers, the second edge being opposite the first edge; second pad points; and second connecting electrodes each connected to the second busbar and the second pad points, wherein a distance between each of the second pad points and the second edge is greater than a distance between the second busbar and the second edge.

[0016] In one class of this embodiment, the first fingers comprise second bent fingers between the second bus bar and the second pad points, wherein the second bent fingers are each bent towards the second bus bar and the second pad points and are not in contact with either the second bus bar or the second pad points, or the second bent fingers are bent towards the second bus bar and are not in contact with the second bus bar, or the second bent fingers are bent towards the second pad points and are not in contact with the second pad points.

[0017] In one class of this embodiment, each of the second bent fingers passes through at least one of the second fingers.

[0018] In one class of this embodiment, a center line of each of the second connection electrodes and a center line of each of the second pad points lie on a same straight line.

[0019] In one class of this embodiment, the electrode structure further comprises fourth fingers, each connected to the second busbar and the second pad points. The fourth fingers are arranged adjacent to the second connection electrodes, and a width of each of the fourth fingers is smaller than a width of each of the second connection electrodes.

[0020] In one class of this embodiment, each of the first fingers is covered with a second insulating material in a portion of a center line of each of the second pad points.

[0021] In one class of this embodiment, the distance between the second busbar and the second edge is between 0.01 mm and 3 mm.

[0022] In one class of this embodiment, the distance between each of the second pad points and the second edge is between 1 mm and 20 mm.

[0023] The disclosure further provides a back contact cell. The back contact cell includes the electrode structure described above, and the electrode structure is disposed on a back surface (a non-light-receiving surface) of the back contact cell.

[0024] The disclosure further provides a back contact cell module. The back contact cell module includes the back contact cell described above.

[0025] The disclosure further provides a back contact cell system. The back contact cell system includes the back contact cell module described above.

[0026] The advantageous effect of the disclosure is that the electrode structure includes the first fingers, the second fingers, the first bus bar, the first pad points, and the first connection electrodes, each connected to the first bus bar and the first pad points, to realize current collection. There is no need to print insulating paste over a large area of ​​the electrode structure. The first pad points and the first bus bar are not simultaneously arranged at the first edge of the back contact cell, and the photogenerated electrons and holes do not need to travel a long distance to reach the region with the opposite polarity. In this way, the electrode structure can improve reliability, reduce costs, increase product yield, and ensure excellent optoelectric conversion efficiency. Fig.1 is a schematic representation of a first prior art electrode pattern design. Fig. Figure 2 is a schematic representation of a second prior art electrode pattern design. Fig. Figure 3 is a schematic representation of a third prior art electrode pattern design. Fig. 4 is a schematic illustration of an electrode structure according to an embodiment of the disclosure. Fig. 5 is a schematic illustration of an electrode structure with curved fingers each extending to pad points and a bus bar, according to an embodiment of the disclosure. Fig. 6 is a schematic illustration of an electrode structure with bent fingers extending to the bus bar, according to one embodiment of the disclosure. Fig.7 is a schematic illustration of an electrode structure with curved fingers extending to pad points, according to an embodiment of the disclosure. Fig. 8 is a schematic illustration of the electrode structure with different finger designs at the edges of two ends of the back contact cell according to an embodiment of the disclosure. Fig. 9 is a schematic illustration of an electrode structure having third fingers and fourth fingers according to an embodiment of the disclosure. Fig. 10 is a schematic illustration of an electrode structure including a first insulating material and a second insulating material according to an embodiment of the disclosure. Fig. 11 is an edge model diagram of a second prior art electrode pattern design. Fig. 12 is an edge model diagram of a third prior art electrode pattern design. Fig. 13 is an edge model diagram based on the electrode structure of Fig. 4. Fig. 14 is an edge model diagram based on the electrode structure of Fig. 5 to Fig. 9.

[0027] To make the objectives, technical solutions, and advantages of the disclosure clearer and easier to understand, the disclosure will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments provided herein are for illustrative purposes and are not intended to limit the disclosure.

[0028] The disclosure provides an electrode structure of a back contact cell. The electrode structure includes first fingers, second fingers, a first bus bar, first pad points, and first connection electrodes, each connected to the first bus bar and the first pad points. The first fingers collect currents in a region of first polarity, and the currents flow through the first pad points and the first connection electrodes to the first bus bar, thereby realizing the collection of the currents. There is no need to print insulating paste over a large area of ​​the electrode structure. The first pad points and the first bus bar are not simultaneously arranged at the first edge of the back contact cell, and the photogenerated electrons and holes do not have to travel a long distance to reach the region of opposite polarity.In this way, the electrode structure can improve reliability, reduce costs, increase product yield, and ensure excellent optoelectric conversion efficiency. Embodiment 1

[0029] With reference to Fig. Figure 4 illustrates an electrode structure of a back contact cell in Embodiment 1. The electrode structure includes: first fingers 10 configured to collect a first polarity region; second fingers 20 configured to collect a second polarity region; a first busbar 51 arranged on one side of the back contact cell near a first edge and connected to the first fingers 10; first pad points 31; and first connecting electrodes 41, each connected to the first busbar 51 and the first pad points 31.

[0030] A distance between each of the first pad points 31 and the first edge is greater than a distance between the first busbar 51 and the first edge.

[0031] In one embodiment of the disclosure, the first finger 10 is configured to collect currents from the first polarity region, and the second finger 20 is configured to collect currents from the second polarity region. When the polarities of the first finger 10 and the second finger 20 are opposite, the polarities of the first polarity region and the second polarity region are also opposite. For example, if the first finger 10 is a positive electrode finger and is configured to collect positive electrode currents in a positive electrode region, the second finger 20 is a negative electrode finger and is configured to collect negative electrode currents in a negative electrode region.Alternatively, if the first finger 10 is the negative electrode finger and is configured to collect negative electrode currents in the negative electrode region, then the second finger 20 is the positive electrode finger and is configured to collect positive electrode currents in the positive electrode region. The positive electrode finger is arranged in a p-type doped region of the back contact cell, and the negative electrode finger is arranged in an n-type doped region of the back contact cell.

[0032] With reference to the Fig. 4 to Fig.10, for ease of identification, the polarities of the first fingers 10 are the same in a blackened portion, the polarities of the second fingers 20 are the same in an unprinted portion, and the polarities of the first fingers 10 and the second fingers 20 are opposite. On the other hand, the first pad points 31, the first connecting electrodes 41, and the first bus bar 51 in the blackened portion have the same polarity as the first fingers 10.

[0033] The first fingers 10 and the second fingers 20 are arranged alternately, and the first fingers 10 and the second fingers 20 are all parallel to an edge line of the back contact cell. For example, the first fingers 10 and the second fingers 20 are shown in FIG. Fig.4 alternately distributed in the vertical direction, and the first fingers 10 and the second fingers 20 are parallel to both an upper edge line and a lower edge line of the back contact cell. The back contact cell has a substantially rectangular shape. The back contact cell having the substantially rectangular shape may, for example, have a square shape or other rectangular shape, and may have standard corners, truncated corners, or rounded corners. The back contact cell is designed according to actual production requirements, which are not specifically limited here. The numbers of the first fingers 10 and the second fingers 20 of the back contact cell are determined according to the actual size of the back contact cell and the widths of the first fingers 10 and the second fingers 20 and the distance between them, which are not specifically limited here.

[0034] Furthermore, the first finger 10 or the second finger 20 is an aluminum finger, a silver finger, a copper finger, or a silver-coated copper finger. It can be understood that in this embodiment of the disclosure, the same metal type or different metal types of fingers can be selected as the first finger 10 and the second finger 20 of the back contact cell. For example, the aluminum finger is selected as the first finger 10 and the second finger 20, or the aluminum finger is selected as the first finger 10 and the silver finger as the second finger 20. If the first finger 10 or the second finger 20 is the aluminum finger or the silver finger, the first finger or the second finger is screen-printed onto the doped region of the back contact cell.If the first finger 10 or the second finger 20 is the copper finger, the first finger or the second finger is plated onto the doped region of the back contact cell by electroplating, evaporation or similar processes.

[0035] The distance between each of the first pad points 31 and the first edge is greater than the distance between the first busbar 51 and the first edge. For example, with reference to Fig. 4 the distance between a leftmost side of the first pad points 31 and an edge of a leftmost side of the back contact cell is greater than the distance between a leftmost side of the first busbar 51 and the edge of the leftmost side of the back contact cell.

[0036] In this embodiment, the distance between the first busbar 51 and the first edge ranges from 0.01 mm to 3 mm, which here is the distance between an edge of the first busbar 51 near the first edge and the first edge. For example, the distance between the first busbar 51 and the first edge is 0.05 mm, 1 mm, 2 mm, 3 mm, or other parameter values ​​from 0.01 mm to 3 mm. The distance between each of the first pad points 31 and the first edge ranges from 1 mm to 20 mm, which here is the distance between an edge of the first pad point 31 near the first edge and the first edge. For example, the distance between the first pad point 31 and the first edge is 1 mm, 5 mm, 10 mm, 20 mm, or other parameter values ​​from 1 mm to 20 mm, but the distance between the first pad point 31 and the first edge is greater than the distance between the first busbar 51 and the first edge.

[0037] In this embodiment of the disclosure, the first pad point 31 is located away from the first bus bar 51, and the connection between the first pad point 31 and the first bus bar 51 is realized by the first connection electrode 41. However, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell. During current collection, the first finger 10 collects the currents of the first polarity region, then transfers the collected currents to the first pad point 31, and then transfers the collected currents from the first pad point 31 to the first bus bar 51 via the first connection electrode 41 to complete the current collection.Compared with the first electrode pattern design in the prior art, there is no need to print the insulating paste over a large area of ​​the electrode structure of the present disclosure, and high-temperature paste can be selected for the first pad point 31 and the first bus bar 51, thereby reducing costs and ensuring reliability. Furthermore, the heights of the first pad point 31 and the first bus bar 51 do not need to be too high, thus reducing paste consumption. Furthermore, since there is no need to print the insulating paste over a large area, the problem of poor adhesion of some pastes does not occur, thereby reducing the difficulty of mass production.Compared with the second electrode pattern design in the prior art, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell to avoid stress concentration in the welding process, thereby improving the yield of the module and enhancing the reliability of the module. Compared with the third electrode pattern design in the prior art, the photogenerated electrons and holes do not need to travel a long distance to reach the opposite polarity region to collect the currents, thus fully ensuring a relatively high photoelectric conversion efficiency. Embodiment 2

[0038] Based on Embodiment 1, the second finger 20 of Embodiment 2 includes first bent fingers between the first bus bar 51 and the first pad points 31, the first bent fingers are respectively bent toward the first bus bar 51 and the first pad points 31 and are in contact with neither the first bus bar 51 nor the first pad points 31, or the first bent fingers are bent toward the first bus bar 51 and are not in contact with the first bus bar 51, or the first bent fingers are bent toward the first pad points 31 and are not in contact with the first pad points 31.

[0039] With reference to Fig.5, the first bent fingers are defined as first bent sub-fingers 21. The first fingers 10 include first pad point connection fingers 11 connected to the first pad points 31 and first bus bar connection fingers 12 connected to the first bus bar 51. The first pad point connection fingers 11 are arranged adjacent to the first bus bar connection fingers 12, and a gap is formed between them. The first bent sub-fingers 21 extend through the gap, are each bent toward the first bus bar 51 and the first pad points 31, and are in contact with neither the first bus bar 51 nor the first pad points 31. In other implementations, the first pad point connection fingers 11 and / or the first bus bar connection fingers 12 may be omitted.However, by arranging the first pad point connecting fingers 11 and / or the first bus bar connecting fingers 12, the fingers can be arranged more uniformly, so that the current collection is implemented in a small area.

[0040] With reference to Fig.6, the first bent fingers are defined as second bent sub-fingers 24. The first fingers 10 include second busbar connecting fingers 14 connected to the first busbar 51, and a gap is formed between the second busbar connecting fingers 14 and the first pad points 31. The second bent sub-fingers 24 extend through the gap, are bent toward the first busbar 51, and are not in contact with the first busbar 51. In other implementations, the pad point connecting finger may be added to achieve a more uniform arrangement of the fingers and implement current collection in a small area.

[0041] With reference to Fig.7, the first bent fingers are defined as third bent sub-fingers 27. The first fingers 10 include the second pad point connecting fingers 16, which are connected to the first pad points 31. A gap is formed between the second pad point connecting fingers 16 and the first bus bar 51, and the third bent sub-fingers 27 extend through the gap, are bent toward the first pad points 31, and are not in contact with the first pad points 31. In other implementations, the bus bar connecting finger can be added so that a more uniform arrangement of the fingers is achieved and current collection is implemented in a small area.

[0042] In this embodiment of the disclosure, a length of the first bent finger is determined according to the size of an available area. The first bent fingers form a divergent extension to fully utilize the area in which the currents can be collected, thereby further improving the current collection capability.

[0043] Furthermore, based on the above implementations, each of the first bent fingers passes through at least one of the first fingers 10. A plurality of first fingers 10 may be arranged in the area between or near the first pad points 31 and the first bus bar 51, and a plurality of gaps are formed by arranging the first fingers 10. In this way, the first bent fingers may pass through the gaps sequentially and then form a divergent extension after passing through each of the gaps, further enhancing the current collection capability. Embodiment 3

[0044] With reference to the Fig. 5 to Fig. 7, based on Embodiment 2, a center line of each of the first connection electrodes 41 and a center line of each of the first pad points 31 in Embodiment 3 are not on the same straight line.

[0045] In this embodiment of the disclosure, the centerline of the first pad point 31 is located on an adjustment line of the second fingers 20, and the polarities of the first pad points 31 and the second fingers 20 are opposite. For example, the first pad point 31 has a positive polarity and the second finger 20 has a negative polarity. Thus, the centerline of the first connection electrode 41 is offset from the centerline of the first pad point 31. That is, the centerline of the first connection electrode 41 is offset from the adjustment line of the second finger 20, so that the centerline of the first connection electrode 41 can be located on the adjustment line of the first finger 10.The polarities of the first connecting electrode 41 and the first finger 10 are the same, thereby achieving a more uniform distribution of fingers with opposite polarities in the area adjacent to the first pad point 31 and further improving the current collection capability. Embodiment 4

[0046] With reference to Fig. 9, based on Embodiment 2, the electrode structure of Embodiment 4 further includes a third finger 18 connected to the first bus bar 51 and the first pad point 31, respectively. The third finger 18 is disposed adjacent to the first connection electrode 41, and the width of the third finger 18 is smaller than the width of the first connection electrode 41.

[0047] In this embodiment of the disclosure, the first connection electrode 41 is not in contact with a substrate of the back contact cell under normal circumstances. At this point, the photogenerated electrons and holes cannot be effectively collected in the area where the first connection electrode 41 is located. Therefore, the third finger 18 is arranged in the region adjacent to the first connection electrode 41, and the third finger 18 can be in contact with the substrate, further improving the current collection capability. Embodiment 5

[0048] With reference to Fig. 10, based on Embodiment 1, the second finger 20 of Embodiment 5 is covered with a first insulating material 62 in a portion located on a center line of the first pad point 31.

[0049] The first insulating material 62 may be coated with the insulating paste, with only the second finger 20 in the portion located on the center line of the first pad point 31 being coated with the insulating paste, thereby not increasing the product cost. Of course, the first insulating material 62 may also be used in other configurations as long as the insulation purpose can be achieved.

[0050] During band welding, the insulating effect of the first insulating material 62 prevents the second finger 20 from contacting the band in the portion located on the center line of the first contact point 31, effectively preventing the occurrence of short circuits. Furthermore, the first insulating material 62 is formed after the first pad point 31 and the first busbar 51 are formed and does not affect the selection of the electrode materials for the first pad point 31 and the first busbar 51. Embodiment 6

[0051] As in Fig. 4, based on Embodiment 1, the electrode structure of Embodiment 6 further comprises: a second bus bar 52 disposed on one side of the back contact cell near a second edge and connected to the second finger 20, the second edge being opposite the first edge; second pad points 32; and a second connection electrode 42 connected to the second bus bar 52 and the second pad points 32, respectively.

[0052] A distance between each of the second pad points 32 and the second edge is greater than a distance between the second busbar 52 and the second edge.

[0053] With reference to Fig. 4, the first edge is the leftmost side of the back contact cell, and the second edge is the rightmost side of the back contact cell. A plurality of pad points are also arranged between the first pad point 31 and the second pad point 32. The pad points can be arranged on the same straight line as the busbar with the same polarity.

[0054] The distance between each of the second pad points 32 and the second edge is greater than the distance between the second bus bar 52 and the second edge. For example, with reference to Fig. 4, the distance between a leftmost side of the second pad points 32 and an edge of the leftmost side of the back contact cell is greater than the distance between a leftmost side of the second bus bar 52 and an edge of the leftmost side of the back contact cell.

[0055] In this embodiment, the distance between the second busbar 52 and the second edge ranges from 0.01 mm to 3 mm, which here is the distance between an edge of the second busbar 52 near the second edge and the second edge. The distance between the second busbar 52 and the second edge is, for example, 0.05 mm, 1 mm, 2 mm, 3 mm, or other parameter values ​​from 0.01 mm to 3 mm. The distance between each of the second pad points 32 and the second edge ranges from 1 mm to 20 mm, which here is the distance between an edge of the second pad point 32 near the second edge and the second edge. For example, the distance between each of the second pad points 32 and the second edge is 1 mm, 5 mm, 10 mm, 20 mm, or other parameter values ​​from 1 mm to 20 mm, but the distance between each of the second pad points 32 and the second edge is greater than the distance between the second busbar 52 and the second edge.

[0056] In this embodiment of the disclosure, the second pad point 32 is located away from the second bus bar 52, and the connection between the second pad point 32 and the second bus bar 52 is realized by the second connection electrode 42. However, the second bus bar 52 is located at the second edge of the back contact cell, and the second pad point 32 is located away from the second edge of the back contact cell. During current collection, the second finger 20 collects the currents of the second polarity region, then transfers the collected currents to the second pad point 32, and then transfers the collected currents from the second pad point 32 to the second bus bar 52 via the second connection electrode 42 to complete the current collection. Pad points, bus bars, and connection electrodes, which are respectively connected to the pad points and the bus bars, are arranged at the edges of two ends of the back contact cell.Compared with the first prior art electrode pattern design, there is no need to print the insulating paste over a large area, and high-temperature paste can be selected for the pad points and busbars, reducing costs and ensuring reliability. Furthermore, the heights of the pad points and busbars do not need to be too high, thus reducing paste consumption. Furthermore, since there is no need to print the insulating paste over a large area, the problem of poor adhesion with some pastes is eliminated, thus reducing the difficulty of mass production.Compared with the second prior art electrode pattern design, the busbars are located at the edge of the back contact cell, and the pad points are spaced away from the edge of the back contact cell to avoid stress concentration during the welding process, thereby improving the module yield and enhancing module reliability. Compared with the third prior art electrode pattern design, the photogenerated electrons and holes do not need to travel a long distance to reach the opposite polarity region to collect the currents, fully ensuring a relatively high photoelectric conversion efficiency. Embodiment 7

[0057] Based on Embodiment 6, the first finger 10 of Embodiment 7 includes second bent fingers between the second bus bar 52 and the second pad points 32, the second bent fingers are respectively bent toward the second bus bar 52 and the second pad points 32 and are not in contact with the second bus bar 52 and the second pad points 32, or the second bent fingers are bent toward the second bus bar 52 and are not in contact with the second bus bar 52, or the second bent fingers are bent toward the second pad points 32 and are not in contact with the second pad points 32.

[0058] With reference to Fig.5, the second bent fingers are defined as fourth bent sub-fingers 13. The second fingers 20 include third pad point connection fingers 22 connected to the second pad points 32 and third bus bar connection fingers 23 connected to the second bus bar 52. The third pad point connection fingers 22 are arranged adjacent to the third bus bar connection fingers 23, and a gap is formed between them. The fourth bent sub-fingers 13 extend through the gap, are each bent toward the second bus bar 52 and the second pad points 32, and are in contact with neither the second bus bar 52 nor the second pad points 32. In other implementations, the third pad point connection finger 22 and / or the third bus bar connection finger 23 may be omitted.However, by arranging the third pad point connecting finger 22 and / or the third bus bar connecting finger 23, the fingers can be arranged more uniformly, so that the current collection is implemented in a small area.

[0059] With reference to Fig.6, the second bent fingers are defined as fifth bent sub-fingers 15. The second fingers 20 include fourth pad point connection fingers 25 connected to the second pad points 32 and fourth bus bar connection fingers 26 connected to the second bus bar 52. The fourth pad point connection fingers 25 are arranged adjacent to the fourth bus bar connection fingers 26, and a gap is formed between them. The fifth bent sub-fingers 15 extend through the gap, are each bent toward the second bus bar 52, and are not in contact with the second bus bar 52. In other implementations, the fourth pad point connection fingers 25 and / or the fourth bus bar connection fingers 26 may be omitted.However, by arranging the fourth pad point connecting fingers 25 and / or the fourth bus bar connecting fingers 26, the fingers can be arranged more uniformly, so that the current collection is implemented in a small area.

[0060] With reference to Fig.7, the second bent fingers are defined as sixth bent sub-fingers 17. The second fingers 20 include the fifth pad point connecting fingers 28, which are connected to the second pad points 32. A gap is formed between the fifth pad point connecting fingers 28 and the second bus bar 52, and the sixth bent sub-fingers 17 extend through the gap, are bent toward the second pad point 32, and are not in contact with the second pad points 32. In other implementations, the bus bar connecting finger can be added so that a more uniform arrangement of the fingers is achieved and current collection is implemented in a small area.

[0061] In this embodiment of the disclosure, a length of the second bent finger is determined according to the size of an available area. The second bent fingers form a divergent extension to fully utilize the area in which the currents can be collected, thereby further improving the current collection capability.

[0062] Furthermore, based on the above implementations, each of the second bent fingers passes through at least one of the second fingers 20. A plurality of second fingers 20 may be disposed in the area between or near the second pad point 32 and the second bus bar 52, and a plurality of gaps are formed by arranging the second fingers 20. In this way, the second bent fingers may pass sequentially through the gaps and then form a divergent extension after passing through each of the gaps, further enhancing the current collection capability.

[0063] In combination with Embodiment 2, the arrangement of the first bent finger and the second bent finger at the edges of two ends of the back contact cell can be arranged in different ways, and the arrangement manner of the first bent finger and the second bent finger can be selected according to an actual situation. For example, with reference to Fig. 8, the first edge of the back contact cell is not provided with the first bent finger, and the second edge of the back contact cell is provided with the second bent finger. The second bent fingers are each bent toward the second busbar 52 and the second pad point 32. Embodiment 8

[0064] With reference to the Fig. 5 to Fig.7, based on Embodiment 7, a center line of the second connection electrode 42 and a center line of the second pad point 32 in Embodiment 8 are on the same straight line.

[0065] In this embodiment of the disclosure, the center line of the second pad point 32 is located on a setting line of the second finger 20, and the second pad point 32 has the same polarity as the second finger 20. For example, the second pad point 32 has a negative polarity and the second finger 20 has a negative polarity. Thus, the center line of the second connection electrode 42 and the center line of the second pad point 32 are arranged on the same straight line, so that the center line of the second connection electrode 42 is arranged on the setting line of the second finger 20. The second connection electrode 42 has the same polarity as the second finger 20, thereby achieving a more uniform distribution of fingers with opposite polarities in the area adjacent to the second pad point 32 and further improving the current collection capacity. Embodiment 9

[0066] Based on Embodiment 7, the electrode structure of Embodiment 9 further includes a fourth finger 29 connected to the second bus bar 52 and the second pad point 32, respectively. The fourth finger 29 is disposed adjacent to the second connection electrode 42, and a width of the fourth finger 29 is smaller than the width of the second connection electrode 42.

[0067] In this embodiment of the disclosure, the second connection electrode 42 is not in contact with a substrate of the back contact cell under normal circumstances. At this point, the photogenerated electrons and holes cannot be effectively collected in the region where the second connection electrode 42 is located. Therefore, the fourth finger 29 is arranged in the region adjacent to the second connection electrode 42, and the fourth finger 29 can be in contact with the substrate, further improving the current collection capability. Embodiment 10

[0068] Based on Embodiment 6, the first finger 10 of Embodiment 10 is covered with a second insulating material 61 in a partial area on a center line of the second pad point 32.

[0069] The second insulating material 61 can be coated with the insulating paste, with only the first finger 10 in the partial area on the center line of the second pad point 32 being covered with the insulating paste, thereby not increasing the product cost. Of course, the second insulating material 61 can also be used in other configurations as long as the insulation purpose can be achieved.

[0070] During band welding, the insulating effect of the second insulating material 61 prevents the first finger 10 from coming into contact with the band in the portion on the center line of the second pad point 32, effectively preventing the occurrence of short circuits. Additionally, the second insulating material 61 is formed after the second pad point 32 and the second busbar 52 are formed and does not affect the selection of the electrode materials for the second pad point 32 and the second busbar.

[0071] Based on Embodiment 1 to Embodiment 10 described above, the modeling calculation is performed here.

[0072] Fig. 11 shows an edge model diagram based on the electrode structure of Fig. 2. Fig. 12 shows an edge model diagram based on the electrode structure of Fig. 3. Fig.Figure 13 shows an edge model diagram based on the electrode structure of Fig. 4. Fig. 14 shows an edge model diagram based on the electrode structure of Fig. 5 to Fig. 9.

[0073] The following table can be created: Scheme V DC (mV) I SC (mA / cm 2 ) FF (%) Conversion efficiency (%) Efficiency loss value (%) assuming that an edge region represents 10% of the total area Scheme of Fig. 2 744,1 42,28 83,24 26,18 - Scheme of Fig. 3 743,8 30,56 80,48 18,30 0,789 Scheme of Fig. 4 744,2 40,82 82,26 24,99 0,120 Schemes of Fig. 5 to Fig. 9 744,5 42,19 83,26 26,15 0,003

[0074] Cell conversion efficiency is an important performance evaluation index for the back-contact cell. Higher cell conversion efficiency leads to better performance, and every 0.1% increase is a breakthrough for the industry. It can be seen that the scheme of Fig. 3 is adopted, the problem of module yield and reliability is solved, but the power is greatly reduced by 0.789%. If the scheme of Fig. 4 of the disclosure, the efficiency loss is reduced to 0.12% in a case where the module yield and reliability are resolved. If the optimization scheme of the Fig. 5 to Fig.9 of the disclosure, the efficiency loss can be reduced to 0.003%. Currently, the repeatability of the back-contact cell conversion efficiency test is approximately ± 0.05%, and the efficiency loss is too small to be monitored and can be ignored. Embodiment 11

[0075] Embodiment 11 provides a back contact cell. The back contact cell includes the electrode structure described in Embodiment 1 to Embodiment 10, and the electrode structure is disposed on a backlight surface of the back contact cell.

[0076] In the electrode structure provided in this embodiment of the disclosure, the first pad point 31 is located away from the first bus bar 51, and the connection between the first pad point 31 and the first bus bar 51 is realized by the first connection electrode 41. However, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell. During current collection, the first finger 10 collects the currents of the first polarity region, then transfers the collected currents to the first pad point 31, and then transfers the collected currents from the first pad point 31 to the first bus bar 51 via the first connection electrode 41 to complete the current collection.Compared with the first electrode pattern design in the prior art, there is no need to print the insulating paste over a large area of ​​the electrode structure of the present disclosure, and a high-temperature paste can be selected for the first pad dot 31 and the first bus bar 51, thereby reducing costs and ensuring reliability. Furthermore, the heights of the first pad dot 31 and the first bus bar 51 do not need to be too high, thus reducing paste consumption. Furthermore, since there is no need to print the insulating paste over a large area, the problem of poor adhesion with some pastes does not occur, thereby reducing the difficulty of mass production.Compared with the second prior art electrode pattern design, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell to avoid stress concentration in the welding process, thereby improving the module yield and reliability. Compared with the third prior art electrode pattern design, the photogenerated electrons and holes do not need to travel a long distance to reach the opposite polarity region to collect the currents, thus fully ensuring a relatively high photoelectric conversion efficiency. Embodiment 12

[0077] Embodiment 12 provides a back contact cell module. The back contact cell module includes the back contact cell described in Embodiment 12.

[0078] In the electrode structure provided in this embodiment of the disclosure, the first pad point 31 is located away from the first bus bar 51, and the connection between the first pad point 31 and the first bus bar 51 is realized by the first connection electrode 41. However, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell. During current collection, the first finger 10 collects the currents of the first polarity region, then transfers the collected currents to the first pad point 31, and then transfers the collected currents from the first pad point 31 to the first bus bar 51 via the first connection electrode 41 to complete the current collection.Compared with the first electrode pattern design in the prior art, there is no need to print the insulating paste over a large area of ​​the electrode structure of the present disclosure, and a high-temperature paste can be selected for the first pad dot 31 and the first bus bar 51, thereby reducing costs and ensuring reliability. Furthermore, the heights of the first pad dot 31 and the first bus bar 51 do not need to be too high, thus reducing paste consumption. Furthermore, since there is no need to print the insulating paste over a large area, the problem of poor adhesion with some pastes does not occur, thereby reducing the difficulty of mass production.Compared with the second electrode pattern design in the prior art, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell to avoid stress concentration in the welding process, thereby improving the yield of the module and enhancing the reliability of the module. Compared with the third electrode pattern design in the prior art, the photogenerated electrons and holes do not need to travel a long distance to reach the opposite polarity region to collect the currents, thus fully ensuring a relatively high photoelectric conversion efficiency. Embodiment 13

[0079] Embodiment 13 provides a back contact cell system. The back contact cell system includes the back contact cell module described in Embodiment 12.

[0080] In the electrode structure provided in this embodiment of the disclosure, the first pad point 31 is located away from the first bus bar 51, and the connection between the first pad point 31 and the first bus bar 51 is realized by the first connection electrode 41. However, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell. During current collection, the first finger 10 collects the currents of the first polarity region, then transfers the collected currents to the first pad point 31, and then transfers the collected currents from the first pad point 31 to the first bus bar 51 via the first connection electrode 41 to complete the current collection.Compared with the first electrode pattern design in the prior art, there is no need to print the insulating paste over a large area of ​​the electrode structure of the present disclosure, and a high-temperature paste can be selected for the first pad dot 31 and the first bus bar 51, thereby reducing costs and ensuring reliability. Furthermore, the heights of the first pad dot 31 and the first bus bar 51 do not need to be too high, thus reducing paste consumption. Furthermore, since there is no need to print the insulating paste over a large area, the problem of poor adhesion with some pastes does not occur, thereby reducing the difficulty of mass production.Compared with the second electrode pattern design in the prior art, the first bus bar 51 is located at the first edge of the back contact cell, and the first pad point 31 is located away from the first edge of the back contact cell to avoid stress concentration in the welding process, thereby improving the module yield and enhancing the module reliability. Compared with the third electrode pattern design in the prior art, the photogenerated electrons and holes do not need to travel a long distance to reach the opposite polarity region to collect the currents, thus fully ensuring a relatively high photoelectric conversion efficiency.

[0081] The above descriptions are merely exemplary embodiments of the disclosure and are not intended to limit the disclosure. Any modification, equivalent substitution, or improvement made without departing from the spirit and principle of the disclosure should be considered within the scope of the disclosure.

Claims

[1] A back contact cell comprising an electrode structure and a back side, wherein the electrode structure is arranged on the back side of the back contact cell, wherein the back contact cell comprises a region of first polarity, a region of second polarity and a first edge, wherein the electrode structure comprises: a plurality of first fingers configured to collect the first polarity region; a plurality of second fingers configured to collect the second polarity region; a first bus bar disposed on one side of the back contact cell near the first edge and connected to the first fingers; a variety of first pad points; and a plurality of first connection electrodes each connected to the first bus bar and the first pad points, wherein a distance between each of the first pad points and the first edge is greater than a distance between the first busbar and the first edge. [2] The back contact cell of claim 1, wherein the second fingers comprise first bent fingers between the first bus bar and the first pad points, the first bent fingers being bent toward the first bus bar and the first pad points, respectively, and not in contact with either the first bus bar or the first pad points, or the first bent fingers being bent toward the first bus bar and not in contact with the first bus bar, or the first bent fingers being bent toward the first pad points and not in contact with the first pad points. [3] The back contact cell of claim 2, wherein each of the first bent fingers passes through at least one of the first fingers. [4] The back contact cell according to claim 2, wherein a center line of each of the first connection electrodes and a center line of each of the first pad points do not lie on a same straight line. [5] The back contact cell of claim 2, further comprising third fingers respectively connected to the first bus bar and the first pad points, wherein the third fingers are disposed adjacent to the first connection electrodes, and a width of each of the third fingers is smaller than a width of each of the first connection electrodes. [6] The back contact cell of claim 1, wherein each of the second fingers is covered with a first insulating material in a portion of a center line of each of the first pad points. [7] The back contact cell of claim 1, wherein the distance between the first bus bar and the first edge is between 0.01 mm and 3 mm. [8] The back contact cell of claim 7, wherein the distance between each of the first pad points and the first edge is between 1 mm and 20 mm. [9] Back contact cell according to one of claims 1-8, further comprising: a second busbar disposed on one side of the back contact cell near a second edge of the back contact cell and connected to the second busbar of the second fingers, the second edge being opposite the first edge; second pad points; and second connecting electrodes each connected to the second busbar and the second pad points, wherein the distance between each of the second pad points and the second edge is greater than the distance between the second busbar and the second edge. [10] The back contact cell of claim 9, wherein the first fingers comprise second bent fingers between the second bus bar and the second pad points, the second bent fingers being bent toward the second bus bar and the second pad points, respectively, and not in contact with either the second bus bar or the second pad points, or the second bent fingers being bent toward the second bus bar and not in contact with the second bus bar, or the second bent fingers being bent toward the second pad points and not in contact with the second pad points. [11] The back contact cell of claim 10, wherein each of the second bent fingers passes through at least one of the second fingers. [12] The back contact cell according to claim 10, wherein a center line of each of the second connection electrodes and a center line of each of the second pad points lie on a same straight line. [13] The back contact cell of claim 10, further comprising fourth fingers connected to the second bus bar and the second pad points, respectively, wherein the fourth fingers are disposed adjacent to the second connection electrodes, and a width of each of the fourth fingers is smaller than a width of each of the second connection electrodes. [14] The back contact cell of claim 9, wherein each of the first fingers is covered with a second insulating material in a portion of a center line of each of the second pad points. [15] The back contact cell of claim 9, wherein the distance between the second bus bar and the second edge is between 0.01 mm and 3 mm. [16] The back contact cell of claim 15, wherein the distance between each of the second pad points and the second edge is between 1 mm and 20 mm. [17] A back contact cell module comprising the back contact cell according to any one of claims 1 to 16. [18] A back contact cell system comprising the back contact cell module according to claim 17.

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