Back contact cell and cell string

Abstract

The present disclosure is applicable to the technical field of back contact cells. Provided are a back contact cell and a cell string. The cell comprises positive fine grids arranged in P regions and negative fine grids arranged N regions, wherein in the direction from the front surface to the back surface, the N regions are lower than the P regions, and the distance between the negative fine grids and the positive fine grids is less than the distance between the N regions and the P regions.

Description

Back contact cell and cell string

[0001] Cross-reference to related applications

[0002] The present disclosure claims priority from Chinese Patent Application No. 202411390784.3 entitled "Back Contact Solar Cell, Back Contact Cell String, Photovoltaic Module and Photovoltaic System" filed on September 30, 2024, which is incorporated by reference in its entirety into the present disclosure. TECHNICAL FIELD

[0003] The present disclosure belongs to the technical field of solar cells, and in particular relates to a back contact cell and a cell string. BACKGROUND

[0004] A back contact cell is a solar cell in which all electrodes of a cell sheet are designed on the back surface of the cell. Since the front surface of the back contact cell has no grid lines to block light, the cell has high photoelectric conversion efficiency.

[0005] At present, the back surface of the back contact cell has a plurality of P regions and a plurality of N regions, and the plurality of P regions and the plurality of N regions are alternately distributed in sequence. The grid lines of the existing back contact cell are prepared in a P-first-N-second manner, that is, silver paste is printed on the P regions to prepare positive electrodes, and then silver paste is printed on the N regions to prepare negative electrodes. Due to the production process, the P regions of the back contact cell are higher than the N regions, and the height difference between the positive electrodes printed on the P regions and the negative electrodes printed on the N regions is large, which increases the difficulty of subsequent electrode connection. SUMMARY

[0006] The embodiments of the present disclosure provide a back contact cell and a cell string, aiming to solve the problem that the height difference between the positive electrodes and the negative electrodes of the existing back contact cell is large, resulting in great difficulty in electrode connection.

[0007] The embodiments of the present disclosure are implemented in the following manner. A back contact cell comprises:

[0008] a silicon substrate having opposite front and back surfaces;

[0009] a plurality of P regions and a plurality of N regions disposed on the back surface, the plurality of P regions and the plurality of N regions being spaced apart in sequence along a first direction;

[0010] a positive fine grid disposed on the P regions; and

[0011] a negative fine grid disposed on the N regions.

[0012] In the direction from the front surface to the back surface, the N regions are lower than the P regions, and the height difference between the negative fine grid and the positive fine grid is smaller than the height difference between the N regions and the P regions.

[0013] In some embodiments, in the direction from the front surface to the back surface, the negative fine grid is flush with the P regions.

[0014] In some embodiments, the width of the positive fine grid and the negative fine grid is 10-50 μm.

[0015] In some embodiments, the back contact cell comprises a first main grid and a second main grid disposed on the back surface, the first main grid is connected with the positive fine grid, and the second main grid is connected with the negative fine grid.

[0016] In the second aspect, the disclosure further provides a back contact cell string comprising at least one back contact cell as described above.

[0017] In some embodiments, the adjacent two back contact cells are connected by an interconnection strip.

[0018] In some embodiments, the first main grid of each back contact cell is located in the same plane, and the second main grid of each back contact cell is located in the same plane.

[0019] In some embodiments, the spacing between adjacent back contact cells is 0.2-0.4 mm.

[0020] In the third aspect, the disclosure further provides a photovoltaic module comprising a back contact cell as described above.

[0021] In the fourth aspect, the disclosure further provides a photovoltaic system comprising a photovoltaic module as described above.

[0022] The back contact cell of the disclosure has the following beneficial effects. The back contact cell of the disclosure comprises a silicon substrate having opposite front and back surfaces, a plurality of P regions and a plurality of N regions disposed on the back surface, the plurality of P regions and the plurality of N regions are spaced apart along a first direction, a positive fine grid disposed on the P region, and a negative fine grid disposed on the N region, along the direction from the front surface to the back surface, the N region is lower than the P region, and the height difference between the negative fine grid and the positive fine grid is less than the height difference between the N region and the P region. Through the above arrangement, after printing the negative fine grid and the positive fine grid, the height difference between the negative fine grid and the positive fine grid is reduced, the difficulty of connecting the negative fine grid and the positive fine grid is reduced, and the production efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 is a structural schematic diagram of one embodiment of the back contact cell provided by the disclosure.

[0024] Legend of reference signs: 100, silicon substrate; 200, N region; 300, P region; 400, negative fine grid; 500, positive fine grid. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the drawings and embodiments. Examples of the embodiments are shown in the drawings, in which the same or similar notations denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary only, and are merely used to explain the present disclosure, and should not be understood as limiting the present disclosure. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present disclosure, and should not be used to limit the present disclosure.

[0026] In the description of the present disclosure, it should be understood that the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are merely used to facilitate the description of the present disclosure and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present disclosure.

[0027] In addition, the terms "first", "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features. In the description of the present disclosure, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0028] In the description of the present disclosure, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances.

[0029] In the present disclosure, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include the direct contact of the first and second features, or can include the contact of the first and second features through another feature between them. Moreover, the "upper", "above" and "above" of the first feature to the second feature include the vertical direction of the first feature above and obliquely above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature to the second feature include the vertical direction of the first feature below and obliquely below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0030] The disclosure below provides many different embodiments or examples for implementing different structures of the disclosure. For the sake of simplicity, the description below foregoes much discussion of well-known semiconductor technology and manufacturing techniques. In the interest of clarity, not all features of an actual implementation can be described or shown. Moreover, the disclosure can refer to specific examples of components and arrangements of components, but it is understood that these are simply examples and not intended to be limiting. Furthermore, the disclosure can refer to a particular process, material, or apparatus, but it is understood that this is simply an example and not intended to be limiting. It is also understood that the disclosure can be used in various examples with different processes, materials, and apparatus.

[0031] The back contact cell of the disclosure includes a silicon substrate having opposite front and back surfaces, a plurality of P regions and a plurality of N regions disposed on the back surface, the plurality of P regions and the plurality of N regions being spaced apart along a first direction in sequence, a positive fine grid disposed on the P region, and a negative fine grid disposed on the N region, in the direction from the front surface to the back surface, the N region is lower than the P region, and the height difference between the negative fine grid and the positive fine grid is less than the height difference between the N region and the P region. Through the above arrangement, after printing to prepare the negative fine grid and the positive fine grid, the height difference between the negative fine grid and the positive fine grid is reduced, the difficulty of subsequent connection of the negative fine grid and the positive fine grid is reduced, and the production efficiency is improved.

[0032] Embodiment one

[0033] As shown in FIG. 1, some embodiments of the disclosure provide a back contact cell, comprising:

[0034] a silicon substrate 100 having opposite front and back surfaces;

[0035] a plurality of P regions 300 and a plurality of N regions 200 disposed on the back surface, the plurality of P regions 300 and the plurality of N regions 200 being spaced apart along a first direction in sequence;

[0036] a positive fine grid 500 disposed on the P region 300; and

[0037] a negative fine grid 400 disposed on the N region 200;

[0038] in the direction from the front surface to the back surface, the N region 200 is lower than the P region 300, and the height difference between the negative fine grid 400 and the positive fine grid 500 is less than the height difference between the N region 200 and the P region 300.

[0039] In implementation, the silicon substrate 100 can be an N-type silicon wafer or a P-type silicon wafer, wherein the N-type silicon wafer is obtained by adding 5-valence elements (such as phosphorus or arsenic) to the silicon raw material, which provides additional free electrons; the P-type silicon wafer is obtained by adding 3-valence elements (such as boron or gallium) to the silicon raw material, which controls the diffusion of electron holes, which is not described in detail.

[0040] The silicon substrate 100 has a front surface and a back surface, wherein the front surface of the silicon substrate 100 corresponds to the light-receiving surface of the solar cell, and the back surface of the silicon substrate 100 corresponds to the back surface of the solar cell.

[0041] In some embodiments, the silicon substrate 100 can be a single crystal silicon wafer, which is a single crystal formed by slowly cooling molten silicon raw material, and has a tightly ordered crystal structure, high conversion efficiency, stability and long life.

[0042] In some embodiments, the silicon substrate 100 can be a polycrystalline silicon wafer, which is a form of elemental silicon. When molten elemental silicon solidifies under supercooling conditions, silicon atoms arrange in a diamond lattice form to form many crystal nuclei. If these crystal nuclei grow into grains with different crystal orientations, these grains combine to form polycrystalline silicon.

[0043] In some embodiments, the surface of the silicon substrate 100 can be a polished surface or a textured surface, which is not limited.

[0044] A plurality of P regions 300 and a plurality of N regions 200 are arranged on the back surface of the silicon substrate 100, and the P regions 300 and the N regions 200 are arranged alternately along a first direction, that is, one N region 200 is arranged between two adjacent P regions 300, and one P region 300 is arranged between two adjacent N regions 200.

[0045] The P regions 300 and the N regions 200 have opposite polarities, wherein the P regions 300 are positive electrode regions, and the N regions 200 are negative electrode regions. The positive electrode fine grid 500 is arranged on the P region 300, and the negative electrode fine grid 400 is arranged on the N region 200.

[0046] In some possible embodiments, the back surface of the solar cell further comprises a passivation layer, that is, the P regions 300 and the N regions 200 are provided with the passivation layer away from the side surface of the silicon substrate 100, the positive electrode fine grid 500 is arranged on the passivation layer of the P region 300, and the negative electrode fine grid 400 is arranged on the passivation layer of the N region 200.

[0047] The positive electrode fine grid 500 and the negative electrode fine grid 400 are made by printing silver paste and high-temperature sintering. In some embodiments, the silver paste includes but is not limited to silver powder, glass body and organic carrier. The silver powder is a conductive phase, mainly for conduction, and the quality of the silver powder directly affects the bulk resistance, contact resistance and other properties of the electrode material. The glass body is a bonding phase, which serves as a conductive film layer medium and connects the conductive phase and the silicon substrate. If the proportion of the glass body itself and the content of the whole in the silver paste are too high, the conductivity of the silver paste will be poor, and if they are too low, the silver paste cannot penetrate into the passivation layer and the silicon substrate to form a conductive contact. The organic carrier is composed of organic matter and part of liquid, which mainly serves as a carrier for the conductive phase and the bonding phase, and controls the fluidity of the paste.

[0048] Due to the silicon wafer preparation process, the P region 300 is higher than the N region 200, that is, the P region 300 and the N region 200 are distributed in a high-low manner on the back of the silicon substrate 100. In the process of preparing the metal electrode, the metal electrode of the N region 200 can be prepared first, and then the metal electrode of the P region 300 is prepared, that is, the negative fine grid 400 is prepared first, and the negative fine grid 400 is flush or substantially flush with the P region 300, and then the positive fine grid 500 is prepared. Compared with the traditional metal electrode preparation process in which the metal electrode of the P region 300 is prepared first, the height difference between the metal electrode of the P region 300 and the N region 200 is increased, which leads to a large difficulty in metal electrode preparation. The present disclosure reduces the difficulty in metal electrode preparation and improves the production efficiency by preparing the negative fine grid 400 first, reducing the height difference between the negative fine grid 400 and the P region 300, and then preparing the positive fine grid 500. In addition, by designing the height of the negative fine grid 400 to be greater than the height of the positive fine grid 500, the height difference between the negative fine grid 400 and the positive fine grid 500 is reduced, so that the positive fine grid 500 and the negative fine grid 400 are flush or substantially flush, which makes it easier to connect the positive fine grid 500 and the negative fine grid 400 in the subsequent process, simplifies the production and preparation process of the solar cell, and improves the production efficiency.

[0049] As a possible implementation, the height difference between the negative fine grid 400 and the P region 300 is less than a certain value in the direction from the front surface to the back surface, for example, the height difference between the negative fine grid 400 and the P region 300 is 0.1 mm, 0.2 mm, 0.5 mm, or less than 1 mm, which can be considered as that the negative fine grid 400 is flush with the P region 300.

[0050] In implementation, the height of the metal electrode refers to the vertical distance between the end point of the metal electrode and the corresponding region in the direction from the front surface to the back surface of the silicon substrate 100, for example, the vertical distance between the end of the positive fine grid 500 away from the silicon substrate 100 and the P region 300 is the height of the positive fine grid 500, and the end of the positive fine grid 500 away from the silicon substrate 100 has the surface of the positive fine grid 500 facing away from the silicon substrate 100. Similarly, the vertical distance between the end of the negative fine grid 400 away from the silicon substrate 100 and the N region 200 is the height of the negative fine grid 400.

[0051] As a possible implementation, the width of the positive fine grid 500 and the negative fine grid 400 is 10 μm to 50 μm, for example, the width of the positive fine grid 500 and the negative fine grid 400 can be any value in the range of 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, or 20 μm to 50 μm, without limitation.

[0052] The back contact cell of the present disclosure comprises a silicon substrate 100 having opposite front and back surfaces, a plurality of P regions 300 and a plurality of N regions 200 disposed on the back surface, the plurality of P regions 300 and the plurality of N regions 200 being spaced apart along a first direction in sequence, a positive electrode fine grid 500 disposed on the P region 300, and a negative electrode fine grid 400 disposed on the N region 200, along the direction from the front surface to the back surface, the N region 200 is lower than the P region 300, and the distance between the negative electrode fine grid 400 and the positive electrode fine grid 500 is less than the distance between the N region 200 and the P region 300. Through the above arrangement, after the negative electrode fine grid 400 and the positive electrode fine grid 500 are printed, the height difference between the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, the difficulty of subsequent connection of the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, and the production efficiency is improved.

[0053] In some optional embodiments, the back contact cell comprises a first main grid (not shown in the figure) and a second main grid (not shown in the figure) disposed on the back surface, the first main grid is connected with the positive electrode fine grid 500, and the second main grid is connected with the negative electrode fine grid 400.

[0054] In implementation, the fine grid is used to guide the current, and the main grid is used to collect the current guided by the fine grid, in other words, the positive electrode fine grid is used to collect and guide the current of the P region, the first main grid is used to collect the current guided by the positive electrode fine grid 500, similarly, the negative electrode fine grid 400 is used to collect and guide the current of the N region, and the second main grid is used to collect the current guided by the negative electrode fine grid 400. Among them, the current conducting capacity of the main grid is related to the number of fine grids contained therein, in general, the more the number of fine grids, the more the guided current, and the more the current conducted by the main grid.

[0055] In some embodiments, the main grid and the fine grid are both prepared by silver paste preparation process. In the silver paste preparation process, the amount of silver paste used is related to the number of main grids and fine grids, the more the number of main grids and fine grids, the more the amount of silver paste used, and the less the number of main grids and fine grids, the less the amount of silver paste used. Therefore, in order to reduce the amount of silver paste used, the number and cross-sectional size of the fine grid can be adjusted while increasing the number of main grids, so as to match the silver consumption of the main grid and the fine grid, and reduce the production cost while improving the current conducting capacity.

[0056] Embodiment two

[0057] In some optional embodiments, the present disclosure provides a back contact cell string comprising at least one back contact cell as described above.

[0058] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the above-described back contact cell string can refer to the corresponding structure and implementation principle in the aforementioned embodiment one and embodiment two, which will not be repeated here.

[0059] The back contact cell of the present disclosure comprises a silicon substrate 100 having opposite front and back surfaces, a plurality of P regions 300 and a plurality of N regions 200 arranged on the back surface, the plurality of P regions 300 and the plurality of N regions 200 being spaced apart along a first direction, a positive electrode fine grid 500 arranged on the P region 300, and a negative electrode fine grid 400 arranged on the N region 200, along the direction from the front surface to the back surface, the N region 200 is lower than the P region 300, and the distance between the negative electrode fine grid 400 and the positive electrode fine grid 500 is less than the distance between the N region 200 and the P region 300. Through the above arrangement, after the negative electrode fine grid 400 and the positive electrode fine grid 500 are printed, the height difference between the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, the difficulty of connecting the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, and the production efficiency is improved.

[0060] In some optional embodiments, two adjacent back contact cells are connected by interconnection strips (not shown in the figure).

[0061] In implementation, the back contact cell is provided with a plurality of positive electrode fine grids 500 and a plurality of negative electrode fine grids 400, and the positive electrode fine grid 500 and the negative electrode fine grid 400 of two adjacent back contact cells can be connected by interconnection strips to realize the series or parallel connection of two back contact cells. For example, the positive electrode fine grid 500 of the previous back contact cell is connected to the positive electrode fine grid 500 of the subsequent back contact cell by an interconnection strip, and at the same time, the negative electrode fine grid 400 of the previous back contact cell is connected to the negative electrode fine grid 400 of the subsequent back contact cell by another interconnection strip, to realize the parallel electrical connection of two back contact cells. Or the positive electrode fine grid 500 of the previous back contact cell is connected to the negative electrode fine grid 400 of the subsequent back contact cell by an interconnection strip, to realize the series electrical connection of two back contact cells.

[0062] As a possible implementation, when the back contact cell is also provided with a main grid, the first main grid of the previous back contact cell is connected to the first main grid of the subsequent back contact cell by an interconnection strip, and at the same time, the second main grid of the previous back contact cell is connected to the second main grid of the subsequent back contact cell by another interconnection strip, to realize the parallel electrical connection of two back contact cells. Or the first main grid of the previous back contact cell is connected to the second main grid of the subsequent back contact cell by an interconnection strip, to realize the series electrical connection of two back contact cells.

[0063] In some optional embodiments, the first main grid of each back contact cell is located in the same plane, and the second main grid of each back contact cell is located in the same plane, so that the bending of the interconnection strip can be avoided when the interconnection strip is used for connection.

[0064] In some optional embodiments, the spacing between adjacent back contact cells is 0.2-0.4 mm, for example, the spacing between adjacent back contact cells is 0.2 mm, 0.25 mm, 0.3 mm, or any value in the range of 0.2-0.4 mm, as long as the gap between adjacent back contact cells meets the minimum electrical distance, which is not limited.

[0065] Embodiment Three

[0066] In some optional embodiments, the present disclosure provides a photovoltaic module comprising the back contact cell as described above.

[0067] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the photovoltaic module described above can refer to the corresponding structure and implementation principle in the foregoing embodiment one and embodiment two, which will not be repeated here.

[0068] The back contact cell of the present disclosure comprises a silicon substrate 100 having opposite front and back surfaces, a plurality of P regions 300 and a plurality of N regions 200 disposed on the back surface, the plurality of P regions 300 and the plurality of N regions 200 being spaced apart along a first direction, a positive fine grid 500 disposed on the P region 300, and a negative fine grid 400 disposed on the N region 200, along the direction from the front surface to the back surface, the N region 200 is lower than the P region 300, and the distance between the negative fine grid 400 and the positive fine grid 500 is less than the distance between the N region 200 and the P region 300. Through the above arrangement, after printing the negative fine grid 400 and the positive fine grid 500, the height difference between the negative fine grid 400 and the positive fine grid 500 is reduced, which reduces the difficulty of subsequent connection of the negative fine grid 400 and the positive fine grid 500, and improves the production efficiency.

[0069] Embodiment Four

[0070] In some optional embodiments, the present disclosure provides a photovoltaic system comprising the photovoltaic module as described above.

[0071] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the photovoltaic system described above can refer to the corresponding structure and implementation principle in the foregoing embodiment one, embodiment two and embodiment three, which will not be repeated here.

[0072] The back contact cell of the present disclosure comprises a silicon substrate 100 having opposite front and back surfaces, a plurality of P regions 300 and a plurality of N regions 200 arranged on the back surface, the plurality of P regions 300 and the plurality of N regions 200 being spaced apart along a first direction in sequence, a positive electrode fine grid 500 arranged on the P region 300, and a negative electrode fine grid 400 arranged on the N region 200, along the direction from the front surface to the back surface, the N region 200 is lower than the P region 300, and the distance between the negative electrode fine grid 400 and the positive electrode fine grid 500 is less than the distance between the N region 200 and the P region 300. Through the above arrangement, after the negative electrode fine grid 400 and the positive electrode fine grid 500 are prepared by printing, the height difference between the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, the difficulty of subsequently connecting the negative electrode fine grid 400 and the positive electrode fine grid 500 is reduced, and the production efficiency is improved.

[0073] The above only is the preferred embodiment of the present disclosure, and does not limit the present disclosure, any modification, equivalent replacement and improvement within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A back contact cell, comprising: a silicon substrate having opposite front and back surfaces; a plurality of P regions and a plurality of N regions disposed on the back surface, the plurality of P regions and the plurality of N regions being spaced apart sequentially along a first direction; positive fine grids disposed on the P regions; and negative fine grids disposed on the N regions; in a direction from the front surface to the back surface, the N regions are lower than the P regions, and a height difference between the negative fine grids and the positive fine grids is smaller than a height difference between the N regions and the P regions.

2. The back contact cell of claim 1, wherein, in the direction from the front surface to the back surface, the negative fine grids are flush with the P regions.

3. The back contact cell of claim 1, wherein, a width of each of the positive fine grids and the negative fine grids is 10 μm to 50 μm.

4. The back contact cell of claim 1, wherein, the back contact cell includes first and second main grids disposed on the back surface, the first main grids are connected with the positive fine grids, and the second main grids are connected with the negative fine grids.

5. A back contact cell string, wherein, at least one back contact cell as claimed in any one of claims 1 to 4.

6. The back contact cell string of claim 5, wherein, two adjacent back contact cells are connected by an interconnection strip.

7. The back contact cell string of claim 6, wherein, the first main grids of each of the back contact cells are located in a same plane, and the second main grids of each of the back contact cells are located in a same plane.

8. The back contact cell string of claim 6, wherein, a distance between adjacent back contact cells is 0.2 mm to 0.4 mm. 9.A photovoltaic module, comprising the back contact cell as claimed in any one of claims 1 to 4. 10.A photovoltaic system, comprising the photovoltaic module as claimed in claim 9.

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