Electrode structure, back contact solar cell and preparation method of back contact solar cell

Abstract

The invention relates to the technical field of solar energy, and discloses an electrode structure, a back contact solar cell and a preparation method thereof. The electrode structure is suitable for being arranged on a backlight surface of a back contact solar cell, and comprises a first area electrode with a first auxiliary grid structure and a second auxiliary grid structure which are symmetrically arranged along a first direction, and the first auxiliary grid structure comprises a first auxiliary grid with a first polarity and a second auxiliary grid with a second polarity which are annular and sleeved at an interval from inside to outside; and the second auxiliary grid structure comprises a third auxiliary grid with the first polarity and a fourth auxiliary grid with the second polarity, which are annular and are sleeved at intervals from inside to outside. According to the invention, the auxiliary grids are arranged to be annular structures, the annular auxiliary grids with different polarities form a structure shaped like a Chinese character'hui ', and when the annular auxiliary grids are provided with the main grids extending along the first direction or are directly provided with the welding strips to be led out, different main grids or welding strips with the same polarity have the same potential due to being connected with the communicated auxiliary grids at the same time; the power generation performance of the back contact solar cell is improved, and the back contact solar cell can adapt to a main-grid-free cell and is wide in application range.

Description

Technical Field

[0001] The present invention relates to the field of solar energy technology, and in particular to an electrode structure, a back-contact solar cell and a preparation method thereof. Background Art

[0002] Back Contact Solar Cell (BC cell) is a new type of solar cell technology that moves both the positive and negative metal contacts to the back of the cell. By integrating all the positive and negative electrodes on the back of the cell, it completely eliminates the grid line shading loss on the front of the traditional solar cell, significantly improves the cell's light absorption efficiency and appearance consistency, and has become an important technical direction in the photovoltaic field.

[0003] As the core process in the back contact solar cell manufacturing process, the rationality of the back electrode patterning scheme will significantly affect the carrier transmission and collection performance. The patterning scheme in conventional cells is usually a "branch-like" grid line structure, see Figure 1 As shown, this graphical solution is not only difficult to design, but also the grid line structures of the same polarity (both p-type or both n-type) are often independent of each other, which leads to a large potential difference between the grid line structures in different areas of the cell. It is easy for local areas on the surface of the back-contact solar cell to have inconsistent brightness, that is, it is easy to produce abnormal phenomena such as bright and dark patches, which in turn affects the power generation efficiency of the back-contact solar cell. Summary of the Invention

[0004] In view of this, the present invention provides an electrode structure, a back-contact solar cell and a preparation method thereof to solve the problem that the graphical scheme in the existing back-contact solar cell easily produces light and dark differences, affecting the performance of the back-contact solar cell.

[0005] In a first aspect, the present invention provides an electrode structure suitable for being arranged on the backlight surface of a back-contact solar cell, the electrode structure including a first regional electrode, the first regional electrode including a first sub-grid structure and a second sub-grid structure, the first sub-grid structure including a first sub-grid and a second sub-grid, the first sub-grid and the second sub-grid both being annular and spaced from the inside to the outside, the first sub-grid being of a first polarity, and the second sub-grid being of a second polarity opposite to the first polarity; the second sub-grid structure including a third sub-grid and a fourth sub-grid, the third sub-grid and the fourth sub-grid both being annular and spaced from the inside to the outside, the third sub-grid being of a second polarity, and the fourth sub-grid being of a first polarity.

[0006] Beneficial effect: The present invention sets the auxiliary grid as a closed ring structure, so that the annular auxiliary grids of different polarities are spaced apart from each other to form a "U"-shaped structure. When setting the lead-out electrode, such as setting the main grid or directly setting the welding strip for electrical lead-out in the main grid-free battery, the lead-out electrode can be directly connected to the first auxiliary grid structure and the second auxiliary grid structure of the "U"-shaped structure. Different main grids or different welding strips of the same polarity have equal electric potentials because they are connected to various interconnected auxiliary grids at the same time, thereby improving the power generation performance of the back-contact solar cell. In addition, such a design scheme can not only adapt to battery types with both main grids and auxiliary grids, but also adapt to batteries without main grids, and has broad application prospects.

[0007] In an optional embodiment, the first sub-gate structure also includes a fifth sub-gate, which is annular and is spaced apart on the outside of the second sub-gate, and the polarity of the fifth sub-gate is opposite to that of the second sub-gate; the second sub-gate structure also includes a sixth sub-gate, which is annular and is spaced apart on the outside of the fourth sub-gate, and the polarity of the sixth sub-gate is opposite to that of the fourth sub-gate.

[0008] Beneficial Effects: The number of sub-grids included in the first and second sub-grid structures of the present invention can be an odd number or an even number, and is not limited to two or three sub-grids. The number can be determined based on the size of the cell and the width and spacing of the sub-grids. Each sub-grid structure includes at least two annular sub-grids of different polarities, which are arranged alternately. The positions of the sub-grids of different polarities in the first and second sub-grid structures are complementary, so that in the overall structure of the first and second sub-grid structures, the total area of ​​the sub-grids of the first and second polarities is the same.

[0009] In an optional embodiment, the first sub-gate structure further includes a seventh sub-gate, which is strip-shaped and spaced apart on the inner side of the first sub-gate, and the polarity of the seventh sub-gate is opposite to that of the first sub-gate; the second sub-gate structure further includes an eighth sub-gate, which is strip-shaped and spaced apart on the inner side of the third sub-gate, and the polarity of the eighth sub-gate is opposite to that of the third sub-gate.

[0010] Beneficial Effects: A strip-shaped sub-grid is disposed within the innermost annular sub-grid of each sub-grid structure. This strip-shaped sub-grid has an opposite polarity to the innermost annular sub-grid, further optimizing space utilization. The strip-shaped sub-grid also facilitates positioning and shaping of the annular sub-grid. Furthermore, the strip-shaped sub-grid arrangement results in an even number of sub-grids in each sub-grid structure. When the number of sub-grids in each sub-grid structure is even, the areas of the first polarity and second polarity sub-grids in a single sub-grid structure are similar, improving the current collection uniformity of each sub-grid structure and further optimizing the power generation performance of the back-contact solar cell.

[0011] In an optional embodiment, in a direction perpendicular to the first direction, in the first regional electrode, the area outside the end portions of the seventh sub-grid and the eighth sub-grid is the edge area, and the area inside the end portions is the middle area;

[0012] The auxiliary grid of the first polarity located in the middle area adopts the first slurry, and the auxiliary grid of the first polarity located in the edge area adopts the second slurry. The width of the auxiliary grid prepared by the first slurry is smaller than the width of the auxiliary grid prepared by the second slurry. The corrosiveness of the first slurry is smaller than the corrosiveness of the second slurry.

[0013] The second polarity sub-grid located in the middle area adopts the third slurry, and the second polarity sub-grid located in the edge area adopts the fourth slurry. The width of the sub-grid prepared with the third slurry is smaller than that prepared with the fourth slurry, and the corrosiveness of the third slurry is smaller than that of the fourth slurry.

[0014] Beneficial effect: Based on the set strip-shaped auxiliary grid, the area between the two ends is divided into the middle area, and the area to the left of the left end and to the right of the right end is divided into the edge area. In this way, the auxiliary grids in different areas can be prepared with different materials and widths in a targeted manner, so as to improve the sintering quality of the auxiliary grids in the edge areas and ensure the connection reliability of the auxiliary grids in different areas. In other words, the auxiliary grid is divided into the edge area and the middle area based on the strip-shaped auxiliary grid, and a slurry with a wider width and stronger corrosiveness is set in the edge area, and a slurry with a relatively smaller width and slightly less corrosiveness is set in the middle area. This ensures that the slurry in the edge area can quickly burn through the dielectric film even at a lower sintering temperature, forming an ohmic contact with the silicon sintering of the solar cell, ensuring the carrier transmission and collection performance, and avoiding the occurrence of poor contact at the edge position and blackening of electroluminescence (EL) detection during the subsequent printing and sintering of the slurry at different patterned positions.

[0015] In an optional embodiment, the first regional electrode further includes: a first main gate and a second main gate, the first main gate extending along the first direction to be arranged on the first sub-gate structure and the second sub-gate structure; the second main gate extending along the first direction to be arranged on the first sub-gate structure and the second sub-gate structure; the first main gate and the second main gate are alternately arranged along the second direction, and the second direction forms a preset angle with the first direction; among the first main gate and the second main gate, one of the two is of the first polarity, suitable for being electrically connected to the sub-gate of the first polarity in the first regional electrode; the other of the two is of the second polarity, suitable for being electrically connected to the sub-gate of the second polarity in the first regional electrode.

[0016] Beneficial effects: The first main grid and the second main grid both extend along the first direction and are alternately spaced along the second direction to connect the sub-grids with the same polarity in the sub-grid structure, and do not contact the sub-grids with different polarities, thereby respectively realizing the collection and derivation of different carriers. The potentials between multiple first main grids are equal, and the potentials between multiple second main grids are equal, ensuring that the brightness of the battery surface is consistent and improving battery performance.

[0017] In an optional embodiment, the first region structure further includes: a first insulating member and a second insulating member, wherein the first insulating member is arranged between the first main grid and the auxiliary grid with opposite polarity thereto, and the second insulating member is arranged between the second main grid and the auxiliary grid with opposite polarity thereto.

[0018] Beneficial effect: By arranging insulating material between the main grid and the auxiliary grid with different polarity to obtain the first insulating member and the second insulating member, it not only ensures the connection between different main grids and auxiliary grids with the same polarity, that is, realizes carrier collection and extraction, but also enhances the connection reliability of the main grid.

[0019] In an optional embodiment, it further includes a second regional electrode, which is symmetrically arranged with the first regional electrode along the second direction; the second regional electrode includes a third sub-gate structure and a fourth sub-gate structure, the third sub-gate structure is arranged beside the first sub-gate structure and has the same polarity as the second sub-gate structure, and the fourth sub-gate structure is arranged beside the second sub-gate structure and has the same polarity as the first sub-gate structure.

[0020] Beneficial Effects: While two symmetrical auxiliary grid structures along a first direction form a subunit, the present invention further provides another subunit in the second direction that is symmetrical to the subunit structure but has opposite polarity. These two subunits can be arranged in multiple configurations in the first or second direction as a whole unit, providing more options for battery electrode configuration and enhancing structural adaptability. The opposite polarity configuration ensures that within the whole unit, whether the two auxiliary grid structures in the first direction or the two auxiliary grid structures in the second direction, the subunits formed in pairs have the same area of ​​the same polarity, enabling uniform and efficient carrier collection at different locations.

[0021] In an optional embodiment, the second regional electrode further includes: a third main gate and a fourth main gate, the third main gate extending along the first direction to be arranged on the third sub-gate structure and the fourth sub-gate structure; the fourth main gate extending along the first direction to be arranged on the third sub-gate structure and the fourth sub-gate structure; the third main gate and the fourth main gate are alternately arranged along the second direction; among the third main gate and the fourth main gate, one of the two is the first polarity, suitable for electrically connecting to the sub-gate of the first polarity in the second regional electrode; the other of the two is the second polarity, suitable for electrically connecting to the sub-gate of the second polarity in the second regional electrode; the first main gate, the second main gate, the third main gate and the fourth main gate use a fifth slurry, and the fifth slurry is a non-corrosive slurry.

[0022] Beneficial effect: The third main grid and the fourth main grid both extend along the first direction and are alternately spaced along the second direction to connect the sub-grids with the same polarity in the sub-grid structure, and do not contact the sub-grids with different polarities, thereby respectively realizing the collection and derivation of different carriers. The potentials between multiple third main grids are equal, and the potentials between multiple fourth main grids are equal, ensuring that the brightness of the battery surface is consistent and improving battery performance.

[0023] In an optional embodiment, the second regional electrode further includes: a third insulating member and a fourth insulating member, wherein the third insulating member is arranged between the third main grid and the auxiliary grid with opposite polarity, and the fourth insulating member is arranged between the fourth main grid and the auxiliary grid with opposite polarity.

[0024] Beneficial effect: In the second regional electrode, the third insulating member and the fourth insulating member are obtained by arranging insulating material between the main grid and the auxiliary grid with different polarity, which not only ensures the connection between different main grids and auxiliary grids with the same polarity, that is, realizes carrier collection and extraction, but also enhances the connection reliability of the main grid.

[0025] In a second aspect, the present invention further provides a back-contact solar cell comprising a cell substrate and the above-mentioned electrode structure, wherein the cell substrate has a light-receiving surface and a backlight surface that are arranged opposite to each other, and the electrode structure is arranged on the backlight surface.

[0026] Beneficial Effects: The back-contact solar cell of the present invention places both the positive and negative electrodes on the backlit surface, reducing sunlight obstruction by the front electrodes and improving sunlight utilization. More importantly, the secondary grid is configured as a ring structure, with two symmetrical secondary grid structures but opposite polarities arranged in the first direction. This ensures that when current is extracted and connected to the secondary grids, the potential of multiple main grids or welding strips of the same polarity is consistent, thus ensuring the power generation performance of the back-contact solar cell.

[0027] In a third aspect, the present invention further provides a method for preparing a back-contact solar cell, which is used to prepare the above-mentioned back-contact solar cell, comprising:

[0028] forming a cell substrate having a light-receiving surface and a backlight surface that are oppositely disposed;

[0029] An electrode structure is formed on the backlight surface.

[0030] Beneficial Effects: The present invention first prepares a cell substrate for a back-contact solar cell, then positions an electrode structure comprising positive and negative electrodes on the backlit surface, reducing the front electrode's shading of sunlight and improving sunlight utilization. When forming the electrode structure, the secondary grid is configured as a ring structure, and two secondary grid structures are arranged symmetrically but with opposite polarities in the first direction. This ensures that when current is extracted and connected to the secondary grids, the potentials of multiple main grids or welding strips of the same polarity are consistent, thus ensuring the power generation performance of the back-contact solar cell. This method is suitable for preparing both main grid-free and main grid-equipped cells, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 It is a structural diagram of a "branch-like" gate line structure in the related art;

[0033] Figure 2 is a schematic diagram of a first structural type of the auxiliary gate structure in the first regional electrode according to an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a second structural embodiment of the auxiliary gate structure in the first regional electrode of the embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of a first complete structure of a first regional electrode according to an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of a second complete structure of the first regional electrode according to an embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of a first structural type of the auxiliary gate structure in the first regional electrode and the second regional electrode according to an embodiment of the present invention;

[0038] Figure 7 1 is a schematic diagram of a first complete structure of the first regional electrode and the second regional electrode according to an embodiment of the present invention.

[0039] Description of reference numerals:

[0040] a. First polarity main grid; b. First polarity auxiliary grid; c. Second polarity main grid; d. Second polarity auxiliary grid;

[0041] A, marginal area; B, middle area;

[0042] 100, first regional electrode; 1, first sub-gate structure; 101, first sub-gate; 102, second sub-gate; 103, fifth sub-gate; 104, seventh sub-gate; 2, second sub-gate structure; 201, third sub-gate; 202, fourth sub-gate; 203, sixth sub-gate; 204, eighth sub-gate; 3, first main gate; 4, second main gate; 5, first insulating member; 6, second insulating member;

[0043] 200, second regional electrode; 7, third auxiliary gate structure; 8, fourth auxiliary gate structure; 9, third main gate; 10, fourth main gate; 11, third insulating member; 12, fourth insulating member. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit it. It should also be noted that, for ease of description, the drawings only illustrate some, but not all, structures relevant to the present invention. In the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion about the present invention. The accompanying drawings illustrate various schematic diagrams of structures according to embodiments of the present invention. These figures are not drawn to scale; certain details may be exaggerated or omitted for clarity. The shapes, relative sizes, and positional relationships of various regions and layers shown in the figures are merely illustrative and may vary in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions based on actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or an intervening layer / element may exist between them. In addition, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element would be "below" the other layer / element.

[0045] Example 1

[0046] refer to Figure 1 It can be seen that in the related art, the grid line structure of the back-contact solar cell is usually set to be "branch-like", including cross-arranged first polarity grid lines and second polarity grid lines, the first polarity grid lines include a first polarity main grid a and a first polarity sub-grid b arranged on both sides of the first polarity main grid a, the second polarity grid lines include a second polarity main grid c and a second polarity sub-grid d arranged on both sides of the second polarity main grid c, each first polarity grid line is relatively independent, and each second polarity grid line is also relatively independent. In this way, the relative independence between the grid line structures of the same polarity can easily form a large potential difference, thereby appearing different light and dark areas on the battery cell, affecting the power generation efficiency of the back-contact solar cell.

[0047] Based on this, reference Figures 2 to 7 This embodiment provides an electrode structure suitable for being arranged on the backlight surface of a back-contact solar cell, wherein the electrode structure includes a first regional electrode 100, which includes a first sub-grid structure 1 and a second sub-grid structure 2; the first sub-grid structure 1 includes a first sub-grid 101 and a second sub-grid 102, which are both annular and spaced from the inside to the outside, with the first sub-grid 101 having a first polarity and the second sub-grid 102 having a second polarity opposite to the first polarity; the second sub-grid structure 2 includes a third sub-grid 201 and a fourth sub-grid 202, which are both annular and spaced from the inside to the outside, with the third sub-grid 201 having a second polarity and the fourth sub-grid 202 having a first polarity.

[0048] Specifically, in this embodiment, the auxiliary grid is set as a rectangular closed ring structure, and of course closed ring structures of other shapes are not excluded. The first auxiliary grid structure 1 and the second auxiliary grid structure 2 are symmetrically arranged along the first direction. In this way, the annular auxiliary grids of different polarities are spaced apart from each other to form a "U"-shaped structure. When setting the lead-out electrode, such as setting the main grid or directly setting the welding strip for electrical extraction in the main grid-free battery, the lead-out electrode can be directly connected to the first auxiliary grid structure 1 and the second auxiliary grid structure 2 of the "U"-shaped structure. Different main grids or different welding strips of the same polarity have equal potentials due to the simultaneous connection of various interconnected auxiliary grids, thereby improving the power generation performance of the back-contact solar cell. In addition, such a design scheme can not only adapt to battery types with both main grids and auxiliary grids, but also adapt to main grid-free batteries, and has broad application prospects.

[0049] It is known that the first polarity can be n-type or p-type, and the second polarity can be p-type or n-type. In this embodiment, the first polarity is n-type and the second polarity is p-type as an example for description.

[0050] In one embodiment, the first sub-gate structure 1 further includes a fifth sub-gate 103, which is annular and spaced outside the second sub-gate 102, and the polarity of the fifth sub-gate 103 is opposite to that of the second sub-gate 102; the second sub-gate structure 2 further includes a sixth sub-gate 203, which is annular and spaced outside the fourth sub-gate 202, and the polarity of the sixth sub-gate 203 is opposite to that of the fourth sub-gate 202.

[0051] like Figure 3As shown, the number of sub-grids included in the first sub-grid structure 1 and the second sub-grid structure 2 of this embodiment can be an odd number or an even number, and is not limited to having two or three sub-grids in each of the above-mentioned sub-grid structures. It can be determined according to the size of the solar cell and the width and spacing of the sub-grids. It can be seen that each sub-grid structure includes at least two annular sub-grids of different polarities, and the sub-grids of different polarities are arranged alternately. The positions of the sub-grids of different polarities in the first sub-grid structure 1 and the second sub-grid structure 2 are complementary, that is, the position where the sub-grid of the first polarity is set in the first sub-grid structure 1 corresponds to the position where the sub-grid of the second polarity is set in the second sub-grid structure 2. In this way, in the overall structure of the first sub-grid structure 1 and the second sub-grid structure 2, the total area of ​​the sub-grid of the first polarity and the sub-grid of the second polarity are the same. In addition, when the number of sub-grids in each sub-grid structure is an even number, the area of ​​the sub-grid of the first polarity and the grid line of the second polarity in a single sub-grid structure is similar, which improves the current collection uniformity of each sub-grid structure and further optimizes the power generation performance of the back contact solar cell.

[0052] On the basis of the above scheme, the first sub-gate structure 1 further includes a seventh sub-gate 104, which is strip-shaped and spaced apart on the inner side of the first sub-gate 101, and has a polarity opposite to that of the first sub-gate 101; the second sub-gate structure 2 further includes an eighth sub-gate 204, which is strip-shaped and spaced apart on the inner side of the third sub-gate 201, and has a polarity opposite to that of the third sub-gate 201.

[0053] refer to Figure 2 and Figure 3 In this embodiment, a strip-shaped secondary grid is disposed within the innermost annular secondary grid of each secondary grid structure. This strip-shaped secondary grid has an opposite polarity to the innermost annular secondary grid, further optimizing space utilization. The provision of the strip-shaped secondary grid also facilitates positioning and forming the annular secondary grid. It is understood that multiple strip-shaped secondary grids may be provided, with multiple strip-shaped secondary grids of different polarities alternately arranged along the first direction. A strip-shaped secondary grid with the same polarity as the innermost annular secondary grid may communicate with the annular secondary grid.

[0054] Furthermore, if Figure 2 and Figure 3 As shown, in the direction perpendicular to the first direction, in the first regional electrode 100, the area outside the ends of the seventh sub-grid 104 and the eighth sub-grid 204 is the edge region A, and the area inside the ends is the middle region B. Taking the first direction as the longitudinal direction as an example, in the transverse direction, based on the provided strip-shaped sub-grid, the area between the two ends is divided into the middle region B, and the area to the left of the left end and to the right of the right end is divided into the edge region A. In this way, the sub-grids in different regions can be manufactured with different materials and widths in a targeted manner, thereby ensuring the reliability of the sub-grids in different regions.

[0055] Specifically, in this embodiment, the first slurry is used for the auxiliary grid of the first polarity located in the central region B, and the second slurry is used for the auxiliary grid of the first polarity located in the edge region A. The width of the auxiliary grid prepared with the first slurry is smaller than the width of the auxiliary grid prepared with the second slurry, and the first slurry is less corrosive than the second slurry. The third slurry is used for the auxiliary grid of the second polarity located in the central region B, and the fourth slurry is used for the auxiliary grid of the second polarity located in the edge region A. The width of the auxiliary grid prepared with the third slurry is smaller than the width of the auxiliary grid prepared with the fourth slurry, and the third slurry is less corrosive than the fourth slurry.

[0056] When preparing the sub-gate structure, it is necessary to place the battery in a sintering furnace for sintering after printing the slurry. When a dielectric layer such as aluminum oxide or silicon nitride is coated on the silicon wafer to form a battery cell, the coating process often causes wrap-around plating in the edge area A of the silicon wafer, making the dielectric layer in the edge area A thicker, which is prone to not being burned through during the slurry sintering process. Moreover, the heating lamps in the sintering furnace, such as infrared heating lamps, are often located in the middle position. During the sintering process, the distance between the edge area A of the silicon wafer and the heating lamps is farther than the distance between the middle area B of the silicon wafer and the heating lamps. As a result, during the heating process of the heating lamps, the sintering temperature of the edge area A of the battery cell is relatively low, which further increases the risk of poor slurry sintering.

[0057] Based on this, in this embodiment, the edge area A and the middle area B of the sub-gate are divided based on the strip-shaped sub-gate. A slurry with a larger width and stronger corrosiveness is set in the edge area A, and a slurry with a relatively smaller width and slightly weaker corrosiveness is set in the middle area B to ensure that the slurry in the edge area A can quickly burn through the dielectric film even at a lower sintering temperature, and form ohmic contact with the silicon of the battery cell to ensure carrier transmission and collection performance, and avoid poor contact at the edge position and blackening of electroluminescence (EL) detection during the subsequent printing and sintering process of the slurry at different patterned positions.

[0058] Specifically, the steps of preparing the auxiliary gate structure include:

[0059] S1. First, a less corrosive first paste is printed on the n-type region of the central region B of the cell substrate to form the n-type sub-gate in the central region B. The sub-gate prepared with the first paste has a line width range of 10-15 μm. The first paste comprises silver powder, glass powder, and a solvent. The glass powder contains low-softening-point oxides such as lead oxide (PbO), bismuth trioxide (Bi2O3), and tellurium dioxide (TeO2), with the lead oxide content being less than 60% by weight. The glass powder is larger than 2 μm in size. The solvent can be selected from terpineol, methyl formate, or other solvents. During the high-temperature sintering process, the glass powder melts and burns through the aluminum oxide and silicon nitride dielectric films on the cell substrate surface. Simultaneously, the silver particles in the first paste melt at high temperature and recrystallize during the cooling process to form an ohmic contact layer of silver-silicon alloy with silicon.

[0060] S2, printing a second paste with stronger corrosiveness than the first paste on the n-type region of the edge region A of the cell substrate to form an n-type sub-gate in the edge region A. The sub-gate prepared with the second paste has a line width ranging from 10 to 20 μm, slightly wider than the sub-gate prepared with the first paste. The second slurry includes: phosphorus-doped silver powder, glass powder and solvent, wherein the phosphorus content of the phosphorus-doped silver powder is in the range of 0.1-1.0wt%, and phosphorus (+5 valence) can be further doped into the silicon substrate to form a high-concentration electron-doped surface, which is beneficial to improving contact performance; the glass powder contains low-softening-point oxides such as lead oxide (PbO), bismuth trioxide (Bi2O3) and tellurium dioxide (TeO2), wherein the mass ratio of lead oxide is greater than or equal to 60wt%, and the size of the glass powder is less than or equal to 2μm. In addition, a small amount of fluoride, such as calcium fluoride (CaF) and / or lithium fluoride (LiF), is introduced into the glass portion of the second slurry to accelerate the dissolution of silicon oxide, the main component of the glass powder, through fluoride ions; the solvent can also be selected from terpineol, methyl formate, etc.

[0061] S3. A less corrosive third paste is printed on the p-type region of the central region B of the cell substrate to form the p-type sub-gate in the central region B. Because the contact characteristics of the p-region surface differ from those of the n-region, the corresponding corrosive paste properties of the sub-gate on the p-region surface are also different. The line width of the sub-gate prepared with the third paste ranges from 10 to 20 μm. The third paste also includes silver powder, glass powder, and solvent, but the glass powder contains materials such as boron oxide (B2O3), sodium oxide (Na2O), and silicon dioxide (SiO2). The mass ratio of boron oxide is less than 30% by weight, and the size of the glass powder is greater than 2 μm. The solvent for the third paste can be selected from diethylene glycol butyl ether, polyacrylate, etc.

[0062] S4, printing a fourth paste with stronger corrosiveness than the third paste on the p-type region of the edge region A of the cell substrate to form a p-type sub-gate in the edge region A. The line width of the sub-gate prepared by the fourth paste is greater than the line width of the sub-gate prepared by the third paste, and ranges from 20 to 40 μm. The fourth slurry includes: aluminum-doped silver powder, glass powder and solvent, wherein the mass ratio of aluminum in the aluminum-doped silver powder is in the range of 1 to 5wt%, and aluminum is preferentially oxidized to form aluminum oxide (Al2O3) during sintering, and the local release of heat promotes the etching of the borosilicate glass layer by the glass powder. At the same time, aluminum is +3 valence and can be further doped into the silicon substrate to form a high-concentration hole-doped surface, which is beneficial to improve the contact performance; the glass powder contains materials such as boron oxide (B2O3), sodium oxide (Na2O) and silicon dioxide (SiO2), wherein the mass ratio of boron oxide is greater than or equal to 30wt%, and increasing the content of boron oxide helps to reduce the viscosity of the glass and enhance the etching activity. The higher the activity, the stronger the sintering performance. A small amount of lithium metaborate (LiBO2) is also added to the glass powder, and the mass ratio of lithium metaborate is in the range of 1 to 3wt%. + The strong migration ability enhances the reaction activity of the glass powder and the oxide layer; the solvent of the fourth slurry can be selected from diethylene glycol butyl ether, polyacrylate, etc.

[0063] S5, placing the cell after printing the paste into a sintering furnace, and sintering at a temperature of 700-800°C to form the final ohmic contact.

[0064] refer to Figure 4 and Figure 5 On the basis of the above scheme, in a solar cell that is not a busbar-less cell, the above-mentioned first regional electrode 100 further includes: a first busbar 3 and a second busbar 4, the first busbar 3 extending along the first direction to be arranged on the first sub-grid structure 1 and the second sub-grid structure 2; the second busbar 4 extending along the first direction to be arranged on the first sub-grid structure 1 and the second sub-grid structure 2; the first busbar 3 and the second busbar 4 are alternately arranged along the second direction, and the second direction forms a preset angle with the first direction; among the first busbar 3 and the second busbar 4, one of the two is of the first polarity and is suitable for being electrically connected to the sub-grid of the first polarity in the first regional electrode 100; the other of the two is of the second polarity and is suitable for being electrically connected to the sub-grid of the second polarity in the first regional electrode 100.

[0065] Specifically, in this embodiment, the first direction is the longitudinal direction, and the second direction is the transverse direction. Of course, it is not ruled out that the second direction may be slightly offset. In this embodiment, each sub-grid structure includes three sub-grids for schematic illustration. The first main grid 3 and the second main grid 4 both extend along the first direction and are alternately spaced along the second direction to connect the sub-grids of the same polarity in the sub-grid structure and not contact the sub-grids of different polarities, thereby respectively realizing the collection and extraction of different carriers. The potentials of the multiple first main grids 3 are equal, and the potentials of the multiple second main grids 4 are equal, ensuring uniform brightness on the surface of the cell and improving cell performance.

[0066] In one embodiment, reference Figure 4 and Figure 5 The above-mentioned first region structure also includes: a first insulating member 5 and a second insulating member 6, the first insulating member 5 is arranged between the first main grid 3 and the auxiliary grid with opposite polarity, and the second insulating member 6 is arranged between the second main grid 4 and the auxiliary grid with opposite polarity.

[0067] By providing an insulating material between the main grid and the auxiliary grid with different polarity to form the first insulating member 5 and the second insulating member 6, the connection between the different main grids and the auxiliary grids with the same polarity is ensured, that is, carrier collection and extraction is achieved, and the connection reliability of the main grid is enhanced. The above-mentioned insulating material can be selected from materials such as insulating glue.

[0068] In one embodiment, see Figure 6 The electrode structure also includes a second regional electrode 200, which is symmetrically arranged with the first regional electrode 100 along the second direction; the second regional electrode 200 includes a third sub-gate structure 7 and a fourth sub-gate structure 8, the third sub-gate structure 7 is arranged beside the first sub-gate structure 1 and has the same polarity as the second sub-gate structure 2, and the fourth sub-gate structure 8 is arranged beside the second sub-gate structure 2 and has the same polarity as the first sub-gate structure 1.

[0069] The symmetrical setting of this embodiment only includes symmetry in shape and size, and does not include symmetry in polarity. Specifically, under the premise that two auxiliary grid structures symmetrical along the first direction form a sub-unit, this embodiment can also set another sub-unit symmetrical to the sub-unit structure but with opposite polarity in the second direction. These two sub-units can be arranged in multiple ways in the first direction or the second direction as an integral unit, providing more options for the arrangement of battery electrodes and enhancing structural adaptability. It should be understood that when multiple arrangements are made along the first direction, the multiple main grids extending along the first direction can all be set as continuous long strip structures. The setting with opposite polarity makes it possible that in the integral unit, whether it is the two auxiliary grid structures in the first direction or the two auxiliary grid structures in the second direction, the sub-units formed in pairs have the same area of ​​the same polarity, and the carrier collection at different positions can be uniform and efficient.

[0070] Similarly, reference Figure 7 The above-mentioned second regional electrode 200 also includes a third main grid 9 and a fourth main grid 10. The third main grid 9 extends along the first direction to be set on the third sub-grid structure 7 and the fourth sub-grid structure 8; the fourth main grid 10 extends along the first direction to be set on the third sub-grid structure 7 and the fourth sub-grid structure 8; the third main grid 9 and the fourth main grid 10 are alternately arranged along the second direction; among the third main grid 9 and the fourth main grid 10, one of the two is of the first polarity and is suitable for electrically connecting to the sub-grid of the first polarity in the second regional electrode 200; the other of the two is of the second polarity and is suitable for electrically connecting to the sub-grid of the second polarity in the second regional electrode 200; the first main grid 3, the second main grid 4, the third main grid 9 and the fourth main grid 10 use the fifth slurry, which is a non-corrosive slurry.

[0071] Specifically, the third main grid 9 and the fourth main grid 10 both extend along the first direction and are alternately spaced along the second direction to connect the sub-grids with the same polarity in the sub-grid structure and do not contact the sub-grids with different polarities, thereby respectively realizing the collection and extraction of different carriers. The potentials between multiple third main grids 9 are equal, and the potentials between multiple fourth main grids 10 are equal, ensuring that the brightness of the battery cell surface is consistent and improving battery performance.

[0072] In this embodiment, after printing the auxiliary grid paste, the insulating member is first set, and then the main grid is printed, and finally the sintering process is performed. Since the main grid serves to connect the auxiliary grid and the current collector, a non-corrosive paste is selected. The resistivity of the non-corrosive paste layer in contact with silicon is generally greater than or equal to 10mΩ.cm. 2 The non-corrosive paste contains aluminum-free or low-aluminum-doped silver powder, a resin binder, and a solvent. The aluminum content of the low-aluminum-doped silver powder should be less than or equal to 0.5wt%. The resin binder can be a dispersible latex powder or a modified resin. The solvent can be disodium EDTA, stearic acid, or other solvents. Furthermore, during this busbar printing process, a PAD can be printed on the busbar simultaneously to facilitate connection to the solder ribbon.

[0073] On the basis of the above scheme, Figure 7 As shown, the second regional electrode 200 further includes a third insulating member 11 and a fourth insulating member 12. The third insulating member 11 is arranged between the third main grid 9 and the auxiliary grid with opposite polarity thereto, and the fourth insulating member 12 is arranged between the fourth main grid 10 and the auxiliary grid with opposite polarity thereto.

[0074] Similarly, in the second regional electrode 200, by providing an insulating material between the main grid and the auxiliary grid with different polarity, the third insulating member 11 and the fourth insulating member 12 are formed. This not only ensures the connection between the different main grids and the auxiliary grids with the same polarity, thus achieving carrier collection and extraction, but also enhances the connection reliability of the main grid. The above-mentioned insulating material can be selected from materials such as insulating glue.

[0075] Example 2

[0076] refer to Figures 2 to 7 This embodiment provides a back-contact solar cell, including a cell substrate and the electrode structure of the above-mentioned embodiment 1. The cell substrate has a light-receiving surface and a backlight surface that are relatively arranged, and the electrode structure is arranged on the backlight surface.

[0077] Specifically, the back-contact solar cell arranges both the positive and negative electrodes on the backlight surface, reducing the shading of sunlight by the front electrode and improving the utilization rate of sunlight. In this embodiment, the auxiliary grid is arranged as a ring structure, and two auxiliary grid structures with symmetrical structures but opposite polarities are arranged in the first direction to ensure that when the current is extracted and connected to the auxiliary grid, the potential of multiple main grids or welding strips of the same polarity is consistent, thereby ensuring the power generation performance of the back-contact solar cell. The back-contact solar cell of this embodiment can be a main grid-free cell or a main grid cell, and has a wide range of applications.

[0078] In other embodiments, the number of sub-grids in each sub-grid structure of a back-contact solar cell can be flexibly adjusted to enhance compatibility with the cell substrate. Furthermore, this embodiment further improves the ohmic contact in edge region A by applying sub-grid pastes of different corrosive properties in the central region B and the edge region A, ultimately further ensuring the performance of the back-contact solar cell.

[0079] Example 3

[0080] This embodiment provides a method for preparing a back-contact solar cell, which is used to prepare the back-contact solar cell in Example 2, comprising the following steps:

[0081] Step S101 : forming a cell substrate, wherein the cell substrate has a light-receiving surface and a backlight surface that are oppositely disposed.

[0082] Exemplarily, the cell substrate may include an anti-reflection layer, a front passivation layer, a substrate, a back diffusion region (including relatively isolated p-type and n-type regions) and a back passivation layer, which are arranged in sequence from the light-receiving side to the backlight side. Taking the substrate as an n-type substrate as an example, the back diffusion region includes a p+ region and an n+ region, and the p+ region and the n-type substrate form a pn junction.

[0083] Step S102: forming an electrode structure on the backlight surface.

[0084] Exemplarily, the sub-grid of the electrode structure needs to pass through the above-mentioned back passivation layer and be connected to the back diffusion region, and the sub-grids of different polarities are connected to the p-type region or the n-type region. In a battery without a main grid, forming the electrode structure includes printing the sub-grid paste on the backlight surface and then sintering it; in a battery with a main grid, the sub-grid paste is first printed on the backlight surface, and then an insulating part is formed at a specific position according to the design requirements, and then the main grid and PAD are printed, and finally sintering is performed. The details of the sub-grid printing, main grid printing, insulating parts and sintering treatment are not repeated here, and please refer to the relevant content in Example 1.

[0085] This embodiment first prepares a cell substrate for a back-contact solar cell. Then, an electrode structure, including positive and negative electrodes, is positioned on the backlight surface according to design requirements. This reduces the front electrode's shading of sunlight and improves sunlight utilization. When forming the electrode structure, a secondary grid is configured as a ring structure, and two secondary grid structures, symmetrical in structure but with opposite polarity, are positioned in the first direction. This ensures that the potentials of multiple main grids or solder strips of the same polarity are consistent when current is extracted and connected to the secondary grids, thus ensuring the power generation performance of the back-contact solar cell. This method is suitable for the preparation of both main grid-free and main grid-equipped cells and has a wide range of applications.

[0086] The further functional description of each of the above structures is the same as that of the above corresponding embodiments and will not be repeated here.

[0087] While the above description does not provide detailed technical details regarding patterning and etching of each layer, those skilled in the art will appreciate that various technical means can be employed to form layers, regions, and the like in desired shapes. Furthermore, those skilled in the art may devise methods that differ from those described above to form the same structure. Furthermore, while each embodiment has been described separately, this does not mean that the measures in each embodiment cannot be advantageously combined.

[0088] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An electrode structure suitable for being arranged on the backlight surface of a back contact solar cell, characterized in that: comprising a first regional electrode, wherein the first regional electrode comprises: A first auxiliary grid structure includes a first auxiliary grid and a second auxiliary grid, wherein the first auxiliary grid and the second auxiliary grid are both ring-shaped and spaced from the inside to the outside, the first auxiliary grid is a first polarity, and the second auxiliary grid is a second polarity opposite to the first polarity; The second sub-grid structure is symmetrically arranged with the first sub-grid structure along the first direction; the second sub-grid structure includes a third sub-grid and a fourth sub-grid, the third sub-grid and the fourth sub-grid are both annular and spaced from the inside to the outside, the third sub-grid is the second polarity, and the fourth sub-grid is the first polarity.

2. The electrode structure according to claim 1, characterized in that The first auxiliary grid structure further includes a fifth auxiliary grid, which is annular and spaced outside the second auxiliary grid. The fifth auxiliary grid has a polarity opposite to that of the second auxiliary grid. The second sub-grid structure further includes a sixth sub-grid, which is ring-shaped and sleeved outside the fourth sub-grid at intervals. The polarity of the sixth sub-grid is opposite to that of the fourth sub-grid.

3. The electrode structure according to claim 2, characterized in that The first auxiliary grid structure further includes a seventh auxiliary grid, the seventh auxiliary grid is in a strip shape and is spaced apart and arranged inside the first auxiliary grid, and the polarity of the seventh auxiliary grid is opposite to that of the first auxiliary grid; The second sub-grid structure further includes an eighth sub-grid, which is in a strip shape and is spaced apart and arranged inside the third sub-grid. The eighth sub-grid has a polarity opposite to that of the third sub-grid.

4. The electrode structure according to claim 3, characterized in that In a direction perpendicular to the first direction, in the first regional electrode, the areas outside the ends of the seventh sub-grid and the eighth sub-grid are edge areas, and the areas inside the ends are middle areas; The auxiliary grid of the first polarity located in the middle area adopts a first slurry, and the auxiliary grid of the first polarity located in the edge area adopts a second slurry, the width of the auxiliary grid prepared by the first slurry is smaller than the width of the auxiliary grid prepared by the second slurry, and the corrosiveness of the first slurry is smaller than the corrosiveness of the second slurry; The second polarity sub-grid located in the middle area adopts the third slurry, and the second polarity sub-grid located in the edge area adopts the fourth slurry. The width of the sub-grid prepared by the third slurry is smaller than the width of the sub-grid prepared by the fourth slurry, and the corrosiveness of the third slurry is smaller than the corrosiveness of the fourth slurry.

5. The electrode structure according to any one of claims 1 to 4, characterized in that: The first regional electrode further includes: a first main gate extending along the first direction to be disposed on the first auxiliary gate structure and the second auxiliary gate structure; a second main gate extending along the first direction to be disposed on the first auxiliary gate structure and the second auxiliary gate structure; the first main gate and the second main gate are alternately arranged along a second direction, and the second direction forms a preset angle with the first direction; Among the first main gate and the second main gate, one of them is of first polarity and is suitable for electrically connecting to the first polarity sub-gate in the first regional electrode; the other of them is of second polarity and is suitable for electrically connecting to the second polarity sub-gate in the first regional electrode.

6. The electrode structure according to claim 5, characterized in that The first regional structure further includes: a first insulating member, disposed between the first main grid and a secondary grid having a polarity opposite thereto; The second insulating member is arranged between the second main grid and the auxiliary grid having the opposite polarity thereto.

7. The electrode structure according to claim 6, characterized in that The invention also includes a second regional electrode, which is symmetrically arranged with the first regional electrode along the second direction; the second regional electrode includes: a third auxiliary gate structure, disposed beside the first auxiliary gate structure and having the same polarity as the second auxiliary gate structure; The fourth auxiliary gate structure is disposed beside the second auxiliary gate structure and has the same polarity as the first auxiliary gate structure.

8. The electrode structure according to claim 7, characterized in that The second regional electrode further comprises: a third main gate extending along the first direction to be disposed on the third auxiliary gate structure and the fourth auxiliary gate structure; a fourth main grid extending along the first direction to be disposed on the third auxiliary grid structure and the fourth auxiliary grid structure; the third main grid and the fourth main grid are alternately disposed along the second direction; Among the third main gate and the fourth main gate, one of them is of the first polarity, suitable for electrically connecting to the sub-gate of the first polarity in the second regional electrode; the other of them is of the second polarity, suitable for electrically connecting to the sub-gate of the second polarity in the second regional electrode; the first main gate, the second main gate, the third main gate and the fourth main gate use the fifth slurry, and the fifth slurry is a non-corrosive slurry.

9. The electrode structure according to claim 8, characterized in that The second regional electrode further comprises: a third insulating member, disposed between the third main grid and the auxiliary grid having a polarity opposite thereto; The fourth insulating member is provided between the fourth main grid and the auxiliary grid having the opposite polarity thereto.

10. A back contact solar cell, characterized in that: include: A cell substrate, the cell substrate having a light-receiving surface and a backlight surface that are oppositely disposed; And the electrode structure according to any one of claims 1 to 9, wherein the electrode structure is arranged on the backlight surface.

11. A method for preparing a back-contact solar cell, for preparing the back-contact solar cell according to claim 10, characterized in that: include: forming a cell substrate, wherein the cell substrate has a light-receiving surface and a backlight surface that are oppositely disposed; An electrode structure is formed on the backlight surface.

Images