Main-grid-free back contact battery
By employing a staggered arrangement of contacts and welded components in a gridless back contact battery, the contact area is increased, the problem of welding stress concentration is solved, the battery's conductivity and reliability are improved, its service life is extended, and production costs are reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JIANGSU ZHONGSHENG MICRO TECHNOLOGY CO LTD
- Filing Date
- 2025-07-18
- Publication Date
- 2026-05-19
AI Technical Summary
In gridless back contact cells, the connection between the welding rod and the fine grid is prone to stress concentration, leading to microcracks and significant power transmission loss, which affects the reliability and service life of the module.
The design incorporates contact and welded components. By staggering the arrangement and increasing the width of the center, the contact area is increased, welding stress concentration is reduced, conductivity is improved, and power transmission loss is reduced.
It reduces power transmission loss, avoids power transmission interruptions, extends battery life, and reduces production costs.
Smart Images
Figure CN224265397U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of solar cells, and in particular to a gridless back contact solar cell. Background Technology
[0002] Solar cells are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect, and they are currently widely used. Crystalline silicon cells are the mainstream research direction for solar cells, with silicon wafers and silver paste accounting for a significant portion of their manufacturing cost. Gridless back-contact cells are cells with electrodes located on the back side and without large main grid lines. By reducing shading on the front side of the cell, photoelectric efficiency is improved. Furthermore, because gridless back-contact cells use solder rods on the back side instead of the main grid lines formed by silver paste printing on the front side for current conduction, the amount of silver paste used is significantly reduced, thereby lowering the cell's production cost.
[0003] Currently, in gridless back-contact cells, welding rods and corresponding grids are usually connected by spot welding or conductive adhesive to conduct current. However, spot welding on the back of the cell can easily cause stress concentration, resulting in microcracks and reducing module reliability. On the other hand, conductive adhesive has poor conductivity, which can lead to large power transmission losses or even interruptions, and can cause continuous damage to the module, affecting its service life. Utility Model Content
[0004] The purpose of this invention is to provide a gridless back contact battery with low current transmission loss.
[0005] To achieve the above objectives, this utility model provides the following technical solution:
[0006] A gridless back contact battery, comprising:
[0007] A silicon wafer substrate has a light-absorbing surface for absorbing light energy and a current-collecting surface opposite to the light-absorbing surface. The current-collecting surface of the silicon wafer substrate forms multiple mutually separated n-type doped regions and p-type doped regions.
[0008] Each of the first fine gates extends along a first direction and is connected to a contact or weldment in the middle. The contact and the weldment are both constructed as conductive structures. Each of the first fine gates is electrically connected to a different n-type doped region. Multiple first fine gates are arranged in a group along a second direction, and each group of first fine gates includes at least one weldment and at least one contact. Several groups of first fine gates are arranged along the first direction.
[0009] The second fine gates all extend along the first direction and are connected to the contact or the welding element in the middle. Each second fine gate is electrically connected to a different p-type doped region. Multiple second fine gates are arranged in a group along the second direction and are staggered with an adjacent group of first fine gates in the second direction. Each group of second fine gates includes at least one welding element and at least one contact element. Several groups of second fine gates are arranged along the first direction and are staggered with each group of first fine gates in the first direction.
[0010] The first solder strip extends along the second direction and is welded to the soldering point of any group of the first fine grids, and is electrically connected to the corresponding contact of the first fine grids through contact. Each of the first solder strips corresponds one-to-one with a group of the first fine grids.
[0011] The second welding strip extends along the second direction and is welded to the welding points of any group of second fine grids, and is electrically connected to the corresponding contact of the second fine grid through contact. Each second welding strip corresponds one-to-one with a group of second fine grids.
[0012] Optionally, the width of the middle portion of the contact and / or the welded part in the second direction is greater than the width of its two ends in the second direction.
[0013] Optionally, the contact and / or the weldment includes an intermediate section and a transition section. The intermediate section is rectangular, and its length in the first direction matches the corresponding first or second weld strip. The two transition sections are respectively connected to both sides of the intermediate section along the first direction. The end of the transition section away from the intermediate section is the connecting end of the contact and / or the weldment. The transition section is constructed such that its width in the second direction decreases in the direction away from the intermediate section. The width of the connecting end in the second direction matches the first or second fine grid to which it is connected. The ratio of the width of the intermediate section in the second direction to the width of the connecting end in the second direction is any value between 8 and 12.
[0014] Optionally, the contact and / or the weld includes a reinforcement that extends along the second direction and is electrically connected to the first or second fine grid.
[0015] Optionally, multiple contacts connected to the same first or second solder strip are arranged in a group, and multiple welded parts are symmetrically arranged on both sides of the group of contacts along the second direction.
[0016] Optionally, the first solder strip and the second solder strip are staggered in the second direction.
[0017] Optionally, the first fine grid and / or the second fine grid includes a first segment and a second segment that both extend along the first direction and are separated from each other. The first segment and the second segment are arranged along the first direction and are electrically connected by the contact or the weldment. The first fine grid or the second fine grid and the contact or the weldment are respectively formed.
[0018] Optionally, the thickness of the first fine grid or the second fine grid is less than the thickness of the connected contact or the welded part.
[0019] Optionally, the first or second fine grid is integrally screen-printed with the contact or the weldment and has a uniform thickness.
[0020] Optionally, the silicon substrate includes a silicon wafer, an insulating tunneling layer is formed on one side surface of the silicon wafer, the n-type doped region and the p-type doped region are formed on the surface of the tunneling layer away from the silicon wafer, and a conductive layer is formed on the surface of the n-type doped region and the p-type doped region away from the tunneling layer, and the first fine gate or the second fine gate is formed on the surface of the conductive layer away from the tunneling layer.
[0021] The beneficial effects of this utility model are as follows: by setting contact elements, the number of welding points between the first solder strip and the first fine gate and the second solder strip and the first fine gate is reduced, thereby reducing the risk of stress concentration damage to the silicon wafer substrate caused by welding. The contact elements have good conductivity, which can reduce power transmission loss and avoid power transmission interruption, thereby improving energy efficiency and extending battery life.
[0022] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the structure of the gridless back contact battery shown in Embodiment 1 of this utility model;
[0024] Figure 2 This is a schematic cross-sectional view of the silicon wafer substrate and the first and second fine gates as shown in Embodiment 1 of this utility model.
[0025] Figure 3 for Figure 1 A magnified view of a section at point A in the middle;
[0026] Figure 4 This is an electroluminescence detection diagram of a gridless back contact battery as shown in Embodiment 1 of this utility model;
[0027] Figure 5 This is an electroluminescence detection diagram of a gridless back contact battery as shown in Comparative Example 1 of this utility model.
[0028] Legend: 1-Silicon substrate, 11-Silicon wafer, 12-Passivation layer, 13-Tunneling layer, 14-Doped layer, 15-Conductive layer, 2-First fine gate, 21-First segment, 22-Second segment, 23-Contact, 231-Middle segment, 232-Gradient segment, 233-Connection end, 24-Welding component, 241-Reinforcement part, 3-Second fine gate, 4-First solder strip, 5-Second solder strip. Detailed Implementation
[0029] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.
[0030] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0031] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0032] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.
[0033] The gridless back contact solar cell protected by this utility model application includes a silicon wafer substrate 1, a first fine grid 2, a second fine grid 3, a first solder strip 4, and a second solder strip 5. The silicon wafer substrate 1 has a light-absorbing surface for absorbing light energy and a current-collecting surface opposite to the light-absorbing surface. The current-collecting surface of the silicon wafer substrate 1 forms multiple mutually separated n-type doped regions and p-type doped regions. Each of the first fine grids 2 extends along a first direction and is connected to a contact 23 or a solder joint 24 in the middle. Both the contact 23 and the solder joint 24 are constructed as conductive structures. Each first fine grid 2 is electrically connected to a different n-type doped region. Multiple first fine grids 2 are arranged in a group along a second direction, and each group of first fine grids 2 includes at least one solder joint 24 and at least one contact 23. Several groups of first fine grids 2 are arranged along the first direction. The second fine gates 3 all extend along the first direction and are connected to a contact 23 or a weldment 24 in the middle. Each second fine gate 3 is electrically connected to a different p-type doped region. Multiple second fine gates 3 are arranged in a group along the second direction and are staggered and interspersed with an adjacent group of first fine gates 2 in the second direction. Each group of second fine gates 3 includes at least one weldment 24 and at least one contact 23. Several groups of second fine gates 3 are arranged along the first direction and are staggered with each group of first fine gates 2 in the first direction. The first solder strips 4 all extend along the second direction and are welded to the solder points of any group of first fine gates 2, and are electrically connected to the corresponding contact 23 of the first fine gate 2 through contact. The second solder strips 5 all extend along the second direction and are welded to the solder points of any group of second fine gates 3, and are electrically connected to the corresponding contact 23 of the second fine gate 3 through contact.
[0034] By setting the contact element 23, the number of welding points between the first solder strip 4 and the first fine gate 2 and the second solder strip 5 and the first fine gate 2 is reduced, thereby reducing the risk of stress concentration damage to the silicon wafer substrate 1 caused by welding. The contact element 23 has good conductivity, which can reduce power transmission loss and avoid power transmission interruption, thereby improving energy efficiency and extending battery life.
[0035] In some embodiments, the width of the middle portion of the contact 23 and / or the weld 24 in the second direction is greater than the width of its two ends in the second direction. By increasing the width of the middle portion, the contact area between the first solder strip 4 and the second solder strip 5 and the contact 23 or the weld 24 is increased, thereby reducing current loss during transmission. Increasing only the width of the middle portion, without widening the two ends, helps to reduce silver paste loss, thereby reducing production costs.
[0036] In some embodiments, the contact 23 and / or the weld 24 includes a middle section 231 and a transition section 232. The middle section 231 is rectangular, and its length in the first direction matches the corresponding first weld strip 4 or second weld strip 5. The two transition sections 232 are respectively connected to both sides of the middle section 231 along the first direction. The end of the transition section 232 away from the middle section 231 is the connecting end 233 of the contact 23 and / or the weld 24. The transition section 232 is configured such that its width in the second direction decreases in the direction away from the middle section 231. The width of the connecting end 233 in the second direction matches the width of the first fine grid 2 or the second fine grid 3 to which it is connected. The ratio of the width of the middle section 231 in the second direction to the width of the connecting end 233 in the second direction is any value from 8 to 12, for example, any value from 8, 9, 10, 11 and 12.
[0037] In some embodiments, the contact 23 and / or the weld 24 include a reinforcing portion 241 that extends along a second direction and is electrically connected to the first fine grid 2 or the second fine grid 3. The reinforcing portion 241 further increases the contact area, which helps to reduce power loss and improve connection strength.
[0038] In some embodiments, multiple contacts 23 connected to the same first solder strip 4 or second solder strip 5 are arranged adjacently in a group, and multiple weld members 24 are symmetrically arranged on both sides of a group of contacts 23 along a second direction. Positioning the weld members 24 at both ends helps to achieve higher connection strength with fewer weld members 24, and helps to reduce damage to the battery assembly caused by welding stress.
[0039] In some embodiments, the first solder strip 4 and the second solder strip 5 are staggered in the second direction, which facilitates the electrical connection of multiple first solder strips 4 and multiple second solder strips 5 respectively, thereby reducing the risk of short circuit.
[0040] In some embodiments, the first fine grid 2 and / or the second fine grid 3 include a first segment 21 and a second segment 22 that both extend along a first direction and are separated from each other. The first segment 21 and the second segment 22 are arranged along the first direction and are electrically connected by a contact 23 or a weldment 24. The first fine grid 2 or the second fine grid 3 is respectively formed with the contact 23 or the weldment 24. Breaking the first fine grid 2 and / or the second fine grid 3 into two segments in the middle and separately forming the contact 23 and the weldment 24 helps to improve the uniformity of the thickness of the contact 23 and the weldment 24, reduces the thickness unevenness caused by overprinting, and helps to ensure that the contact 23 is in full contact with the first solder strip 4 or the second solder strip 5.
[0041] In some embodiments, the thickness of the first fine gate 2 or the second fine gate 3 is less than the thickness of the connected contact 23 or weld 24. Increasing the thickness of the contact 23 and weld 24 helps to reduce current transmission losses.
[0042] In some embodiments, the first fine grid 2 or the second fine grid 3 is integrally screen-printed with the contact 23 or the weld 24 and has a uniform thickness, which helps to simplify the operation and can prevent misalignment caused by printing errors from forming open circuits.
[0043] In some embodiments, the silicon substrate 1 includes a silicon wafer 11, an insulating tunneling layer 13 is formed on one side surface of the silicon wafer 11, an n-type doped region and a p-type doped region are formed on the surface of the tunneling layer 13 away from the silicon wafer 11, and a conductive layer 15 is formed on the surface of the n-type doped region and the p-type doped region away from the tunneling layer 13, and a first fine gate 2 or a second fine gate 3 is formed on the surface of the conductive layer 15 away from the tunneling layer 13.
[0044] After absorbing photons, silicon wafer 11 generates photogenerated carriers. These carriers tunnel through tunneling layer 13, where electrons are attracted to the n-type doped region and transported through conductive layer 15 to the first fine gate 2, then output to the external circuit via the first solder ribbon 4. Holes migrate to the p-type doped region, transport through conductive layer 15 to the second fine gate 3, and then output to the external circuit via the second solder ribbon 5, thus enabling the internal circuitry of the battery to conduct.
[0045] Please refer to the following examples for details.
[0046] Example 1:
[0047] Please see Figure 1 The gridless back contact cell shown in a preferred embodiment of this application includes a silicon wafer substrate 1, a first fine grid 2, a second fine grid 3, a first solder strip 4, and a second solder strip 5.
[0048] Please see Figure 2The silicon substrate 1 includes a silicon wafer 11, a passivation layer 12, a tunneling layer 13, a doped layer 14, and a conductive layer 15. The passivation layer 12 and the tunneling layer 13 are formed on opposite sides of the silicon wafer 11, respectively. The insulating and chemically stable passivation layer 12 protects the silicon wafer 11 and reduces surface recombination of photogenerated carriers, improving light absorption efficiency. The insulating and chemically stable tunneling layer 13 protects the silicon wafer 11 and provides a tunneling path. The tunneling layer 13 can be made of, for example, amorphous silicon or silicon dioxide and has a small thickness. In this embodiment, the tunneling layer 13 is made of amorphous silicon and has a thickness of only 5 nm. Multiple elongated n-type and p-type doped regions are formed on the surface of the tunneling layer 13 away from the silicon substrate 1 and are separated from each other. In other embodiments, each n-type and p-type doped region can form an insulating structure for further isolation. The conductive layer 15 is formed on the surface of each n-type and p-type doped region away from the tunneling layer 13. The surface of the conductive layer 15 away from the tunneling layer 13 is used to form a first fine gate 2 or a second fine gate 3, and each first fine gate 2 corresponds one-to-one with each n-type doped region, and each second fine gate 3 corresponds one-to-one with each p-type doped region. The surface of the silicon substrate 1 that connects the first fine gate 2 and the second fine gate 3 is the collector surface, and the surface of the silicon substrate 1 away from the first fine gate 2 and the second fine gate 3 is the light-absorbing surface.
[0049] Please see Figure 1 and Figure 3The first fine grid 2 and the second fine grid 3 have the same structure, both extending along the first direction, and both are broken in the middle to form a first segment 21 and a second segment 22 that are separate from each other. The first segments 21 and 22 of each first fine grid 2 and second fine grid 3 are connected by contact members 23 or welded members 24. The first fine grid 2 and the second fine grid 3 are arranged in an array along the first direction and a second direction perpendicular to the first direction. Multiple first fine grids 2 or second fine grids 3 arranged along the first direction form a row, and multiple first fine grids 2 or second fine grids 3 arranged along the second direction form a column. Multiple rows of first fine grids 2 and second fine grids 3 are interlaced and staggered along the second direction, and multiple columns of first fine grids 2 and second fine grids 3 are staggered along the first direction. Multiple contact members 23 that are sequentially adjacent along the second direction form a group, and two adjacent welded members 24 are symmetrically arranged on both sides of each group of contact members 23 along the second direction. Multiple rectangular strip-shaped first weld strips 4 and second weld strips 5 extend along the second direction and have the same structure. The first solder strip 4 is spot-welded to a row of first fine gates 2 via soldering parts 24, and is in close contact with each corresponding contact 23 to achieve electrical connection. The second solder strip 5 is spot-welded to a row of second fine gates 3 via soldering parts 24, and is in close contact with each corresponding contact 23 to achieve electrical connection. The first solder strip 4 passes through a row of first fine gates 2, with one end basically flush with the outermost soldering part 24, and the other end extending to the outside of the silicon substrate 1. The second solder strip 5 passes through a row of second fine gates 3, with one end basically flush with the outermost soldering part 24, and the other end extending to the outside of the silicon substrate 1. Multiple first solder strips 4 correspond one-to-one with multiple rows of first fine gates 2, and multiple second solder strips 5 correspond one-to-one with multiple rows of second fine gates 3. The first solder strips 4 and the second solder strips 5 are arranged flush with each other, and the first solder strips 4 and the second solder strips 5 extend to opposite sides of the silicon substrate 1, facilitating separate electrical connection to form positive and negative electrodes.
[0050] In this embodiment, both the contact element 23 and the welded element 24 include an intermediate section 231 and a transition section 232. The intermediate section 231 is constructed as a rectangle extending along a first direction. The transition section 232 connects the two ends of the intermediate section 231 along the first direction and is constructed as an isosceles trapezoid. Its width in the second direction decreases in the direction away from the intermediate section 231. The end of the transition section 232 away from the intermediate section 231 is a connecting end 233, which is connected to the first segment 21 and the second segment 22 of the first fine grid 2 or the second fine grid 3, respectively. In this embodiment, the width of the middle section 231 of the contact member 23 and the welded member 24 is approximately ten times the width of the corresponding connecting end 233. The length of the middle section 231 of the contact member 23 is greater than the length of the middle section 231 of the welded member 24. The length of the middle section 231 of the welded member 24 is equal to the width of the first weld strip 4 in the first direction. The width of the connecting end 233 of the contact member 23 is greater than the width of the connecting end 233 of the welded member 24. The width of the connecting end 233 of the welded member 24 is slightly greater than the width of the first fine grid 2 in the second direction.
[0051] In this embodiment, the contact member 23 further includes a reinforcing portion 241 extending along the second direction. The two reinforcing portions 241 are respectively connected to the middle portion of the intermediate section 231 on both sides along the second direction, thereby increasing the contact area between the contact member 23 and the first solder strip 4 or the second solder strip 5.
[0052] In this embodiment, both the first fine grid 2 and the second fine grid 3 are made of silver paste and are simultaneously formed by copper screen printing. The contact 23 and the weldment 24 are also made of silver paste and are simultaneously formed by copper screen printing, and their thickness is greater than that of the first fine grid 2 and the second fine grid 3. The first solder strip 4 and the second solder strip 5 are both made of copper and are spot welded to the weldment 24 by silver paste.
[0053] Electroluminescence detection was performed on the gridless back-contact battery in this embodiment, and the detection results are shown in [the table below]. Figure 4 As can be seen from the image, there are no obvious black spots.
[0054] Example 2:
[0055] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the first fine grid 2, the second fine grid 3, the contact 23, and the welding part 24 are integrally formed by screen printing with silver paste, and the thickness is uniform overall.
[0056] Example 3:
[0057] The only difference between this embodiment and Embodiment 1 is that the welded part 24 in this embodiment also includes a reinforcing part 241, which improves the welding tensile strength.
[0058] Example 4:
[0059] The only difference between this embodiment and Embodiment 1 is that in this embodiment, the contact member 23 does not include the reinforcing part 241.
[0060] Comparative Example 1:
[0061] The only difference between this comparative example and Example 1 is that the contact element 23 is not provided in this comparative example; each of the first fine grids 2 and the second fine grids 3 is welded to the first solder strip 4 or the second solder strip 5 via a welding element 24. Electroluminescence detection was performed on the gridless back contact battery in this comparative example, and the detection results are shown below. Figure 5 As can be seen in the image, there are several areas that appear blackened.
[0062] Comparative Example 2:
[0063] The only difference between this comparative example and Example 1 is that the weldment 24 and the contact 23 in this comparative example are constructed as conventional rectangular pads, and the amount of silver paste applied to the weldment 24 and the contact 23 in this comparative example is increased by about 33% compared to Example 1.
[0064] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0065] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.
Claims
1. A back contact cell with no busbars, characterized in that, include: A silicon substrate (1) has a light-absorbing surface for absorbing light energy and a current-collecting surface opposite to the light-absorbing surface. The current-collecting surface of the silicon substrate (1) forms a plurality of mutually separated n-type doped regions and p-type doped regions. Each of the first fine gates (2) extends along the first direction and is connected to a contact (23) or a weld (24) in the middle. The contact (23) and the weld (24) are both constructed as conductive structures. Each of the first fine gates (2) is electrically connected to different n-type doped regions. Multiple first fine gates (2) are arranged in a group along the second direction. Each group of first fine gates (2) includes at least one weld (24) and at least one contact (23). Several groups of first fine gates (2) are arranged along the first direction. The second fine gate (3) extends along the first direction and is connected in the middle by the contact (23) or the welding element (24). Each second fine gate (3) is electrically connected to a different p-type doped region. Multiple second fine gates (3) are arranged in a group along the second direction and are staggered with an adjacent group of first fine gates (2) in the second direction. Each group of second fine gates (3) includes at least one welding element (24) and at least one contact element (23). Several groups of second fine gates (3) are arranged along the first direction and are staggered with each group of first fine gates (2) in the first direction. The first welding strip (4) extends along the second direction and is welded to the welding point of any group of first fine grids (2), and is electrically connected to the contact (23) of the corresponding first fine grid (2) through contact. Each first welding strip (4) corresponds to a group of first fine grids (2). The second welding strip (5) extends along the second direction and is welded to the welding point of any group of second fine grids (3), and is electrically connected to the contact (23) of the corresponding second fine grid (3) through contact. Each second welding strip (5) corresponds to a group of second fine grids (3).
2. The gridless back contact cell of claim 1, wherein, The width of the middle portion of the contact (23) and / or the weld (24) in the second direction is greater than the width of its two ends in the second direction.
3. The gridless back contact cell of claim 2, wherein, The contact (23) and / or the weld (24) include a middle section (231) and a transition section (232). The middle section (231) is rectangular, and its length in the first direction matches the corresponding first weld strip (4) or second weld strip (5). The two transition sections (232) are respectively connected to the two sides of the middle section (231) along the first direction. The end of the transition section (232) away from the middle section (231) is the connecting end (233) of the contact (23) and / or the weld (24). The transition section (232) is constructed such that its width in the second direction decreases in the direction away from the middle section (231). The width of the connecting end (233) in the second direction matches the first fine grid (2) or the second fine grid (3) to which it is connected. The ratio of the width of the middle section (231) in the second direction to the width of the connecting end (233) in the second direction is any value between 8 and 12.
4. The gridless back contact cell of claim 1, wherein, The contact (23) and / or the weld (24) include a reinforcement (241) that extends along the second direction and is electrically connected to the first fine gate (2) or the second fine gate (3).
5. The gridless back contact cell of claim 1, wherein, Multiple contact elements (23) connected to the same first solder strip (4) or second solder strip (5) are arranged in a group adjacent to each other, and multiple weld elements (24) are symmetrically arranged on both sides of the group of contact elements (23) along the second direction.
6. The eni -grid back contact ceU of claim 1, wherein, The first solder strip (4) and the second solder strip (5) are staggered in the second direction.
7. The gridless back contact cell of claim 1 wherein, The first fine grid (2) and / or the second fine grid (3) include a first segment (21) and a second segment (22) that both extend along the first direction and are separated from each other. The first segment (21) and the second segment (22) are arranged along the first direction and are electrically connected by the contact (23) or the weld (24). The first fine grid (2) or the second fine grid (3) and the contact (23) or the weld (24) are respectively formed.
8. The eni -main grid back contact cell of claim 7, wherein, The thickness of the first fine grid (2) or the second fine grid (3) is less than the thickness of the connected contact (23) or the weld (24).
9. The gridless back contact cell of claim 1 wherein, The first fine grid (2) or the second fine grid (3) is integrally screen-printed with the contact (23) or the welded part (24) and has a uniform thickness.
10. The eni -main grid back contact cell of claim 1, wherein, The silicon substrate (1) includes a silicon wafer (11), an insulating tunneling layer (13) is formed on one side surface of the silicon wafer (11), the n-type doped region and the p-type doped region are formed on the surface of the tunneling layer (13) away from the silicon wafer (11), and a conductive layer (15) is formed on the surface of the n-type doped region and the p-type doped region away from the tunneling layer (13), and the first fine gate (2) or the second fine gate (3) is formed on the surface of the conductive layer (15) away from the tunneling layer (13).