MWT solar cell, battery string, battery assembly and preparation method

Abstract

The present invention provides a MWT solar cell, a battery string, a battery assembly and a preparation method, wherein the MWT solar cell is provided with a front electrode on the light-receiving surface and a front electrode contact point and a back electrode contact point on the backlight surface, the front electrode contact point is connected to the front electrode through a through hole penetrating the MWT solar cell, the front electrode contact point and the back electrode contact point are arranged in N columns, N is a natural number greater than 3, wherein the first column and the Nth column are the front electrode contact points and the back electrode contact points, respectively, and each column from the second column to the N-1 column is alternately arranged by the front electrode contact points and the back electrode contact points. After the MWT solar cell according to the embodiment of the present invention is cut, the front electrode contact points and the back electrode contact points of two adjacent battery cells are in a straight line, and are directly connected by a narrow conductive material, which is easy to operate, saves costs, and reduces transmission losses on the welding strip.

Description

Technical Field

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

[0002] "Metal Wrap Through Cell", referred to as MWT cell, is a cell in which both the emitter contact electrode and the base contact electrode are located on the back of the cell. In the MWT cell structure, the emitter contact electrode located on the light-receiving side of the cell is guided from the silicon substrate to the back of the cell, and both the emitter contact electrode and the base contact electrode are located on the back of the cell, so that the current collected by the surface emitter flows out from the back of the cell. Compared with traditional solar cells, the conductive main grid line on the front of traditional solar cells is replaced by the emitter electrode located on the back of the MWT cell. Therefore, the shading area on the front of the MWT cell is reduced, and the area receiving light is increased, which effectively increases the short-circuit current of the cell, thereby improving the energy conversion efficiency of the cell.

[0003] Usually, in the packaging of MWT solar cell modules, adjacent MWT cells are interconnected in series, for example, using welding ribbons. However, the existing welding ribbon interconnection technology requires a large welding ribbon area and a large resistance, resulting in large transmission losses of module power on the welding ribbon; especially when using high-efficiency MWT cells with high voltage and high short-circuit current, most of the energy will be lost in the form of heat instead of being converted into electrical energy, and the high conversion efficiency obtained at the battery end cannot be fully reflected at the module end. In addition, there are also problems such as the relatively large number of welding ribbons, which has a certain negative impact on welding output. Summary of the invention

[0004] In view of this, the first object of the present invention is to provide a MWT solar cell sheet, which can be cut into MWT solar cell units for easy welding and interconnection, and the manufactured solar cell module has low transmission loss on the welding ribbon and high module efficiency.

[0005] The second object of the present invention is to provide a MWT solar cell string, wherein the solar cell module prepared by the MWT solar cell string has small transmission loss on the welding ribbon and high module efficiency.

[0006] A third object of the present invention is to provide a MWT solar cell module comprising the above-mentioned MWT solar cell string.

[0007] A fourth object of the present invention is to provide a method for preparing the above-mentioned MWT solar cell string.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] According to the MWT solar cell of the first aspect of the embodiment of the present invention, a front electrode is provided on the light-receiving surface, and an electrode contact point is provided on the backlight surface, the electrode contact point includes a front electrode contact point and a back electrode contact point, the front electrode contact point is connected to the front electrode via a through hole penetrating the MWT solar cell, the front electrode contact point and the back electrode contact point are arranged in N columns, N is a natural number greater than 3, wherein the 1st column and the Nth column are the front electrode contact points and the back electrode contact points, respectively, and each column from the 2nd column to the N-1th column is alternately arranged by the front electrode contact points and the back electrode contact points.

[0010] Furthermore, the number of the front electrode contact points and the back electrode contact points in each column is the same or differs by 1.

[0011] Furthermore, the spacing between each column is the same, or the area between two adjacent columns is the same.

[0012] According to the second aspect of the present invention, the MWT solar cell string comprises a plurality of MWT solar cell units connected in series, the plurality of the MWT solar cell units are arranged in a row, the two side edges of each of the MWT solar cell units are respectively provided with a front electrode contact point and a back electrode contact point, the opposite side edges of two adjacent MWT solar cell units are respectively formed into matching concave and convex shapes, one side of the opposite side edges of two adjacent MWT solar cell units is formed with the front electrode contact point and the other side is formed with the back electrode contact point, and the front electrode contact point and the back electrode contact point are formed in a row.

[0013] Furthermore, the front electrode contact point and the back electrode contact point on opposite edges of two adjacent MWT solar cell units are connected by a conductive material.

[0014] Furthermore, the concave-convex shape is any one of a trapezoid, an arc, a square, and a triangle that alternates between positive and negative.

[0015] The MWT solar cell assembly according to the third aspect of the present invention comprises the MWT solar cell string described in any one of the above items.

[0016] Furthermore, it includes a first group of strings formed by connecting a plurality of said MWT solar cell strings in parallel, wherein the back electrode contact points of each said MWT solar cell string are connected by a conductive material to form a negative electrode and the front electrode contact points are connected by a conductive material to form a positive electrode.

[0017] Furthermore, the first strings are multiple and the first strings are multiple and connected in series or in parallel.

[0018] Furthermore, it comprises a second group of strings formed by connecting a plurality of the MWT solar cell strings in series, wherein the arrangement directions of the back electrode contact points and the front electrode contact points of two adjacent upper and lower MWT solar cell strings are opposite and they are connected by a conductive material.

[0019] Furthermore, the second group of strings comprises a plurality of the second groups of strings, and the plurality of the second groups of strings are connected in series or in parallel.

[0020] The method for preparing a MWT solar cell string according to the fourth embodiment of the present invention comprises the following steps:

[0021] Step S1, providing a MWT solar cell unit, wherein two side edges of each of the MWT solar cell units are respectively provided with a front electrode contact point and a back electrode contact point, and at least one side edge of the MWT solar cell unit is formed into a concave-convex shape;

[0022] Step S2, arranging the MWT solar cell units in a row, wherein the opposite edges of two adjacent MWT solar cell units are in matching concave-convex shapes, one of the opposite edges of the two adjacent MWT solar cell units is formed with the front electrode contact point and the other is formed with the back electrode contact point, and the front electrode contact point and the back electrode contact point are formed in a row;

[0023] Step S3, connecting the front electrode contact points and the back electrode contact points of two adjacent columns of the MWT solar cell units in series through welding strips, so that the MWT solar cell string forms a current path, and forms a positive electrode and a negative electrode at the head and tail ends of the MWT solar cell string, to obtain the MWT solar cell string.

[0024] Furthermore, before step S1, the method further includes the following steps:

[0025] Step S0, selecting any one of the above-mentioned MWT solar cell sheets, cutting the MWT solar cell sheets, and obtaining a plurality of the MWT solar cell units, wherein the edges of the MWT solar cell units obtained by cutting are concave-convex shapes.

[0026] The above technical solution of the present invention has at least one of the following beneficial effects:

[0027] (1) The front electrode contact points and the back electrode contact points of two adjacent battery cells are in a straight line and can be directly connected by a narrow conductive material, such as a narrow welding ribbon, which is easy to operate and can avoid the increase in cost caused by using a wide welding ribbon, thus saving costs;

[0028] (2) According to the MWT solar cell module of the embodiment of the present invention, by using a narrow solder strip, the transmission loss on the solder strip is small and the module output power is high;

[0029] (3) The gap between battery cells is relatively small, which makes full use of the effective space, increases the light receiving area of ​​the component, reduces power loss, increases component power, and reduces production costs and cost per kilowatt-hour;

[0030] (4) The MWT solar cell module according to the embodiment of the present invention does not require an expensive metal back plate, and can be directly interconnected by welding on the same surface through welding strips, thereby avoiding problems such as bending and insulation caused by the metal back plate, improving the reliability of the solar cell module, extending the service life of the cell module, and also greatly reducing the cost;

[0031] (5) The preparation method of the MWT solar cell string and the battery module according to the embodiment of the present invention is simple, high-quality and reliable, does not require much improvement to the existing module production line, is low-cost, has a simple and easy-to-operate process, and can be directly applied to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of a MWT solar cell according to Example 1 of the present invention;

[0033] Figure 2 Schematic diagram of cutting of a MWT solar cell according to Example 1 of the present invention, wherein: (a) shows its back side; (b) shows its front side;

[0034] Figure 3 Based on Figure 1 The schematic diagram of the structure of a MWT solar cell string formed by connecting MWT solar cells in series after being cut is shown;

[0035] Figure 4 Based on Figure 3 A schematic diagram of the structure of a first group of strings formed by connecting MWT solar cells in parallel;

[0036] Figure 5 Based on Figure 4 The schematic diagram of the arrangement of the MWT solar cell module formed by the first group of strings shown;

[0037] Figure 6 Based on Figure 3 A schematic diagram of the structure of a second group of strings formed by connecting MWT solar cell strings in series;

[0038] Figure 7 Based on Figure 6 A circuit diagram of a MWT solar cell assembly formed by a second group of strings is shown;

[0039] Figure 8 Schematic diagram of cutting of a MWT solar cell according to Example 3 of the present invention, wherein: (a) shows its back side; (b) shows its front side;

[0040] Fig. 9 Based on Figure 8 The schematic diagram of the structure of a MWT solar cell string formed by connecting MWT solar cells in series after being cut is shown;

[0041] Fig.10 Based on Fig. 9 A schematic diagram of the structure of a first group of strings formed by connecting MWT solar cells in parallel;

[0042] Fig.11 Based on Fig.10 The schematic diagram of the arrangement of the MWT solar cell module formed by the first group of strings shown;

[0043] Fig.12 Based on Fig. 9 A schematic diagram of the structure of a second group of strings formed by connecting MWT solar cell strings in series;

[0044] Fig.13 Based on Fig.12 A circuit diagram of a MWT solar cell assembly formed by a second group of strings is shown;

[0045] Fig.14 Schematic diagram of cutting of a MWT solar cell according to Example 5 of the present invention, wherein: (a) shows its back side; (b) shows its front side;

[0046] Fig.15 Schematic diagram of cutting of the MWT solar cell sheet according to Example 6 of the present invention, wherein: (a) shows its back side; (b) shows its front side. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the embodiment of the present invention more clear, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the present invention.

[0048] Example 1

[0049] The following description is made by taking a p-type local back field MWT solar cell as an example, but the present invention is not limited thereto, and is also applicable to an n-type local back field MWT solar cell. In addition, for ease of description, first, taking a MWT solar cell having 6 columns of front electrode contact points and 6 columns of back electrode contact points formed on the back as an example, its structure and preparation method are described with reference to the accompanying drawings. It should be noted that the MWT solar cell of the present invention is not limited to this case, for example, 3 columns of front electrode contact points and 3 columns of back electrode contact points may be formed respectively.

[0050] like Figure 1 As shown, the MWT solar cell in this embodiment has a light-receiving surface that includes, from the inside to the outside, a p-type silicon substrate 1, an emitter 2, a passivation dielectric layer 3, a passivation anti-reflection layer 4, a front electrode 5 and a through hole 6; and a backlight surface that includes, from the inside to the outside, a passivation dielectric layer 7, a passivation protective layer 8, a front electrode contact point 9, a back electrode contact point 10 and a back aluminum layer 11, and has a local back field 12 under the passivation dielectric layer.

[0051] A front electrode 5 is provided on the passivation anti-reflection film layer 4 on the front side of the MWT solar cell, a back aluminum layer 11 and a front electrode contact point 9 serving as a front electrode contact point are distributed on the back passivation protection layer 8, and a back electrode contact point 10 serving as a back electrode contact point is distributed on the back aluminum layer 11, and the front electrode contact point 9 is connected to the front electrode 5 via a through hole 6 that penetrates the MWT solar cell.

[0052] like Figure 2 As shown, the front electrode contact points 9 on the backlight surface are distributed in 6 arrays, and the back electrode contact points 10 are also distributed in 6 arrays. The front electrode contact points 9 and the back electrode contact points 10 on the backlight surface are distributed in 7 columns as a whole, wherein the electrode contact points in each of the 2nd to 6th columns are alternately arranged by the front electrode contact points and the back electrode contact points. Preferably, the number of the front electrode contact points and the back electrode contact points in each column is the same or differs by 1( Figure 2 The difference shown is 1).

[0053] Furthermore, if Figure 2 As shown, the spacing between each column is the same, so that MWT solar cell units 100 with the same area can be formed after cutting.

[0054] Therefore, if Figure 2 and Figure 3 As shown, the MWT solar cell is Figure 2The laser cutting line shown can be cut into 6 MWT solar cell units 100, and the cut edges of each solar cell unit 100 present alternating positive and negative arc shapes, and the area of ​​each MWT solar cell unit 100 is the same. Among them, the back side of each MWT solar cell unit 100 after cutting has a column of front electrode contact points 9 and a column of back electrode contact points 10, which are respectively located on the two side edges of the back side of the MWT solar cell unit 100.

[0055] The MWT solar cell sheet according to the above-mentioned embodiment 1 of the present invention can be prepared by the following manufacturing method:

[0056] A. Texturing: placing the p-type silicon substrate 1 in a texturing tank, texturing with sodium hydroxide to form a velvet structure, and then cleaning the surface;

[0057] B. Preparation of emitter 2: Phosphorus diffusion is performed through a furnace tube at 790°C-850°C to form a positive surface n+ emitter 2 on the front (light-receiving) surface of the silicon substrate, and its sheet resistance is 40-300 ohm / sq;

[0058] C. Opening holes: The diffused wafer is laser-opened with 16 through holes 6 arranged in an array in the p-type silicon substrate 1, and the laser-opened silicon substrate is placed in a wet etching machine to remove the back junction and phosphorus silicon glass;

[0059] D. Preparation of the front passivation dielectric layer 3: First, the surface of the silicon substrate after the opening is cleaned, and then a layer of silicon oxide passivation dielectric layer 3 is formed on the front surface through an oxidation process;

[0060] E. Preparing a back passivation dielectric layer 7: Thereafter, an aluminum oxide (AlOx) layer and a titanium nitride (TiOx) layer with a thickness of 15 nm are deposited on the back to form a back passivation dielectric layer 7;

[0061] F. Preparing a front passivation anti-reflection layer 4 and a back passivation protective layer 8: Next, 70 nm and 120 nm silicon nitride (SiNx) films are prepared on the front and back sides respectively to form a front passivation anti-reflection layer 4 and a back passivation protective layer 8;

[0062] G. Laser grooving: Use laser to make grooves on the surface of the back passivation protective film, with a groove width of 20um and a line spacing of 500um;

[0063] H. Printing and sintering: This step mainly includes the following steps:

[0064] a) Filling: first use the filling slurry to fill the through hole 6 formed in the above step C;

[0065] b) Contact point printing: Printing on the back surface to form front electrode contact points 9 and back electrode contact points 10 at the same time, wherein the front electrode contact points 9 are distributed in a 6-array, and the back electrode contact points 10 are also distributed in a 6-array. The front electrode contact points 9 and the back electrode contact points 10 on the backlight surface are distributed in 7 columns as a whole, wherein the electrode contact points in each column from the 2nd to the 6th column are alternately arranged by the front electrode contact points and the back electrode contact points;

[0066] c) Printing a local back field 12: Printing a back aluminum line on the back grooved area to form a local back field 12 after sintering as described below;

[0067] d) Printing the front electrode 5: Then, the front electrode is printed on the front emitter layer;

[0068] e) Sintering: Finally, sintering is performed to form a back local back field 12 and a back aluminum layer 11, and to make the front electrode contact point 9 and the back electrode contact point 10 form contact characteristics respectively, wherein the back aluminum wire and the silicon substrate in the opening area react to form an aluminum-silicon alloy and a back local back field 12, and a back aluminum layer 11 is formed in the ungrooved area, thereby obtaining the above-mentioned MWT solar cell.

[0069] Next, the above MWT solar cell sheet, such as Figure 2 As shown, according to Figure 2 By cutting along the laser cutting line shown, six MWT solar cell units 100 can be formed, wherein the two side edges of each of the MWT solar cell units 100 are respectively provided with a front electrode contact point 9 and a back electrode contact point 10, and the edges after cutting are in an alternating positive and negative arc shape.

[0070] It should be noted that the concave-convex shape formed after cutting is not limited to this. By designing different laser cutting lines, the concave-convex shape can also be, for example, a trapezoidal shape with alternating positive and negative directions (such as Fig.15 As shown), square (including rectangular, square), triangle, etc., detailed description is omitted here.

[0071] Afterwards, if Figure 3 As shown, the cut 6 MWT solar cell units 100 are laid flat on a plane, so that the multiple MWT solar cell units 100 are arranged in a row, so that one side of the opposite edges of two adjacent MWT solar cell units 100 forms a front electrode contact point 9 and the other side forms a back electrode contact point 10, and the front electrode contact point 9 and the back electrode contact point 10 form a row. Here, it should be noted that the so-called forming a row means roughly forming a row, and a certain degree of deviation can be allowed according to the specific width of the conductive material 13 (such as the welding strip) described later, the process accuracy requirements, etc.

[0072] Next, the six MWT solar cell units are connected in series through a conductive material 13 (e.g., five solder strips, or printed conductive adhesive) to obtain Figure 3 A MWT solar cell string 200 is shown.

[0073] By further connecting a plurality of MWT solar cell strings 200, MWT solar cell strings can be formed. Figure 4 As shown, a plurality of MWT solar cell strings 200 are connected in parallel to form a first group of strings 301. Specifically, a plurality of MWT solar cell strings 200 are arranged in the same arrangement direction (the so-called same arrangement direction means that the front electrode contact points 9 and the back electrode contact points 10 at both sides of the back edge of each MWT solar cell string 200 are respectively located on the same side to form a row), and then the electrode contact points of the same polarity are connected through the conductive material 13, that is, the back electrode contact points 10 of each MWT solar cell string 200 are connected through the conductive material 13 to form a negative electrode, and the front electrode contact points 9 are connected through the conductive material 13 to form a positive electrode.

[0074] Then, if Figure 5 As shown, 10 (there is no special regulation on the number of the first group of strings, which can be set as needed) first group of strings 301 are arranged vertically in a row, connected in series with each other, and then connected to a junction box, packaged, and other processes to form an MWT solar cell module.

[0075] Example 2

[0076] In addition, if Figure 6 As shown, the multiple MWT solar cell strings 200 formed in the above-mentioned embodiment 1 can also be connected in series to form a second group of strings 302. Specifically, the multiple MWT solar cell strings 200 are arranged vertically in a manner in which two adjacent arrangement directions are opposite (the so-called arrangement directions are opposite, that is, in two adjacent MWT solar cell strings 200, the front electrode contact point 9 on the back of one is located in a row with the back electrode contact point 10 of the other, and at the same time, the back electrode contact point 10 of the one is located in a row with the front electrode contact point 9 of the other). Thereafter, the upper and lower MWT solar cell strings 200 are connected in series through the conductive material 13, and the back electrode contact point 10 of the MWT solar cell string 200 located first in the vertical direction is led out through the conductive material 13 to form a negative electrode, and the front electrode contact point 9 of the MWT solar cell string 200 located at the lowest position in the vertical direction is connected through the conductive material 13 to form a positive electrode.

[0077] Then, if Figure 7As shown, the six second strings 302 are arranged in a row horizontally, the negative electrodes are connected to each other, and the positive electrodes are connected to each other, so as to connect the six second strings 302 in parallel, and then connected to a junction box, packaged, etc. to form an MWT solar cell module.

[0078] Of course, other forms of strings can be formed as needed, which will not be listed here.

[0079] Furthermore, in the above-mentioned MWT solar cell assembly, the specific number of the first string group 301 and the second string group 302, and the number of the MWT solar cell strings 200 contained in the first string group 301 and the second string group 302 are not limited to the above-mentioned specific embodiments, and can be appropriately set as needed.

[0080] Example 3

[0081] In this embodiment, the structure of the MWT solar cell is different from that of the embodiment 1 in that the number of columns of electrode contact points is different.

[0082] In addition, the arrangement of battery components is also different.

[0083] like Figure 8 As shown, in this embodiment, the front electrode contact points 9 on the backlight surface of the MWT solar cell are distributed in 3 arrays, and the back electrode contact points 10 are also distributed in 3 arrays. The front electrode contact points 9 and the back electrode contact points 10 on the backlight surface are distributed in 4 columns as a whole, wherein the electrode contact points of each of the second column and the third column are alternately arranged by the front electrode contact points 9 and the back electrode contact points 10.

[0084] like Figure 8 As shown, the MWT solar cell sheet can be cut into three MWT solar cell units, wherein the back of each cell unit 100' has a column of front electrode contact points 9 and a column of back electrode contact points 10, which are respectively located at the two side edges of the back of the MWT solar cell unit 100'.

[0085] Thereafter, in the same manner as in Example 1, Fig. 9 As shown, a MWT solar cell string 200 ′ is formed.

[0086] Next, if Fig.10 As shown, the MWT solar cell strings 200' are connected in parallel to form a first string 301'. Next, 20 Fig.10 The first group of strings 301' shown in FIG. 1 is connected in series to obtain Fig.11 The MWT solar cell assembly shown. In order to facilitate access to the junction box, preferably, as Fig.11 As shown, the positive electrode and the negative electrode are respectively led out from the lateral middle of the MWT solar cell assembly.

[0087] Example 4

[0088] In addition, if Fig.12 As shown, the plurality of MWT solar cell strings 200 ′ formed in the above-mentioned embodiment 3 may also be connected in series to form a second group of strings 302 ′.

[0089] Next, if Fig.13 As shown, the second group of strings 302' are connected in parallel to obtain a MWT solar cell assembly.

[0090] Example 5

[0091] In this embodiment, the structure of the battery assembly and the assembly preparation method are different from those in Embodiment 3 in that: Fig.14 As shown, the MWT solar cell unit formed by cutting the MWT solar cell sheet has an edge after cutting that presents alternating positive and negative arc shapes with straight lines superimposed at the beginning and the end.

[0092] Example 6

[0093] In this embodiment, the structure of the battery assembly and the assembly preparation method are different from those in Embodiment 3 in that: Fig.15 As shown, the MWT solar cell unit formed by cutting the MWT solar cell sheet has its edges after cutting showing alternating positive and negative trapezoids.

[0094] The MWT solar cell module prepared according to the above embodiment has the following advantages:

[0095] (1) The front electrode contact points and the back electrode contact points of two adjacent battery cells are in a straight line and can be directly connected by a narrow conductive material, such as a narrow welding ribbon, which is easy to operate and can avoid the increase in cost caused by using a wide welding ribbon, thus saving costs;

[0096] (2) According to the MWT solar cell module of the embodiment of the present invention, by using a narrow solder strip, the transmission loss on the solder strip is small and the module output power is high;

[0097] (3) The gap between battery cells is relatively small, which makes full use of the effective space and increases the light-receiving area of ​​the module, thereby reducing power loss, increasing module power, and reducing production costs and cost per kilowatt-hour;

[0098] (4) The MWT solar cell module according to the embodiment of the present invention does not require an expensive metal back plate, and can be directly interconnected by welding on the same surface through welding strips, thereby avoiding problems such as bending and insulation caused by the metal back plate, improving the reliability of the solar cell module, extending the service life of the cell module, and also greatly reducing the cost;

[0099] (5) The preparation method of the MWT solar cell string and the battery module according to the embodiment of the present invention is simple, high-quality and reliable, does not require much improvement to the existing module production line, is low-cost, has a simple and easy-to-operate process, and can be directly applied to large-scale production.

[0100] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate quantity restrictions, but indicate the existence of at least one. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0101] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A MWT solar cell, characterized in that: The MWT solar cell is provided with a front electrode (5) on the light-receiving surface and an electrode contact point on the backlight surface, the electrode contact point comprising a front electrode contact point (9) and a back electrode contact point (10), the front electrode contact point (9) being connected to the front electrode (5) via a through hole penetrating the MWT solar cell, the front electrode contact point (9) and the back electrode contact point (10) being arranged in N columns, N being a natural number greater than 3, wherein the first column and the Nth column are the front electrode contact points (9) and the back electrode contact points (10) respectively, and each column from the second column to the N-1 column is alternately arranged by the front electrode contact points (9) and the back electrode contact points (10).

2. The MWT solar cell according to claim 1, characterized in that: The number of the front electrode contact points (9) and the back electrode contact points (10) in each column is the same or differs by 1.

3. The MWT solar cell according to claim 1, characterized in that: The spacing between each column is the same, or the area between two adjacent columns is the same.

4. A MWT solar cell string (200, 200'), characterized in that: The invention comprises a plurality of MWT solar cell units (100, 100') connected in series, wherein the plurality of MWT solar cell units (100) are arranged in a row, and the two side edges of each MWT solar cell unit (100) are respectively provided with a front electrode contact point (9) and a back electrode contact point (10), and the opposite sides of two adjacent MWT solar cell units (100) are respectively formed into matching concave-convex shapes, and the opposite sides of two adjacent MWT solar cell units (100) are formed with the front electrode contact point on one side and with the back electrode contact point on the other side, and the front electrode contact point and the back electrode contact point are formed in a row.

5. The MWT solar cell string according to claim 4, characterized in that: The front electrode contact point (9) and the back electrode contact point (10) on opposite edges of two adjacent MWT solar cell units (100) are connected via a conductive material (13).

6. The MWT solar cell string according to claim 4, characterized in that: The concave-convex shape is any one of a trapezoid, an arc, a square, and a triangle that alternates between positive and negative.

7. A MWT solar cell module, characterized in that: The invention comprises a plurality of MWT solar cell strings (200, 200'), wherein the MWT solar cell string is the MWT solar cell string according to any one of claims 4 to 6.

8. The MWT solar cell assembly according to claim 7, characterized in that: It comprises a first group of strings (301, 301') formed by connecting a plurality of MWT solar cell strings in parallel, wherein the back electrode contact points of each MWT solar cell string are connected by a conductive material to form a negative electrode, and the front electrode contact points are connected by a conductive material to form a positive electrode.

9. The MWT solar cell assembly according to claim 8, characterized in that: It comprises a plurality of the first groups of strings, and the plurality of the first groups of strings are connected in series or in parallel.

10. A method for preparing a MWT solar cell string, characterized in that: The steps include: Step S1, providing a MWT solar cell unit (100), wherein two side edges of each of the MWT solar cell units are respectively provided with a front electrode contact point (9) and a back electrode contact point (10), and at least one side edge of the MWT solar cell unit is formed into a concave-convex shape; Step S2, arranging the MWT solar cell units (100) in a row, wherein the opposite edges of two adjacent MWT solar cell units (100) are in matching concave-convex shapes, one of the opposite edges of the two adjacent MWT solar cell units (100) is formed with the front electrode contact point (9) and the other is formed with the back electrode contact point (10), and the front electrode contact point and the back electrode contact point are formed in a row; Step S3, connecting the front electrode contact points (9) and the back electrode contact points (10) of two adjacent columns of the MWT solar cell units (100) in series through a conductive material (13), so that the MWT solar cell string forms a current path, and a positive electrode and a negative electrode are formed at the head and tail ends of the MWT solar cell string, thereby obtaining the MWT solar cell string.

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