Method for manufacturing a heterojunction solar cell string and a corresponding heterojunction solar cell

Abstract

The present invention provides a heterojunction solar cell string and a manufacturing method of a corresponding heterojunction solar cell. The heterojunction solar cell involved includes a cell body, a first transparent conductive film layer disposed on the light-receiving surface side of the cell body, and a second transparent conductive film layer disposed on the backlight surface side of the cell body. The heterojunction solar cell further includes a composite sub-grid disposed on the surface of the first transparent conductive film layer and / or the second transparent conductive film layer and having an extending direction perpendicular to the first direction. The composite sub-grid includes a first grid line layer and a second grid line layer disposed on the surface of the first grid line layer facing away from the cell body. The second grid line layer is made of a different material from the first grid line layer and covers the two opposite side surfaces of the first grid line layer in the width direction. In the heterojunction solar cell involved in the present invention, a composite sub-grid different from the sub-grid structure printed by traditional low-temperature paste is provided, providing more choices for the manufacture of the collector of the heterojunction solar cell.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic manufacturing, and in particular to a heterojunction solar cell string and a manufacturing method of a corresponding heterojunction solar cell. Background Art

[0002] The heterojunction solar cell is a relatively efficient crystalline silicon solar cell at present. It combines the characteristics of crystalline silicon cells and silicon-based thin film cells, and has the advantages of a short manufacturing process, a low process temperature, a high conversion efficiency, and a large power generation. Since the temperature degradation coefficient of the heterojunction solar cell is small and it has double-sided power generation, under the same area condition, the annual power generation can be 15-30% higher than that of ordinary polycrystalline silicon cells, so it has great market potential.

[0003] Figure 1 The following shows a schematic structural diagram of a heterojunction solar cell involved in the prior art. From the light-receiving side towards the backlight side, it sequentially includes a first collector 51', a first transparent conductive film layer 41', a first doped amorphous layer 31', a first intrinsic amorphous layer 21', a silicon substrate 10', a second intrinsic amorphous layer 22', a second doped amorphous layer 32', a second transparent conductive film layer 42', and a second collector 52'. The first collector 51' and the second collector 52' involved usually both include a main grid and a sub-grid connected to each other.

[0004] In the prior art, limited by the low-temperature process, only low-temperature paste can be used when printing the first collector 51' and the second collector 52' using a screen plate. The manufacturing cost of the low-temperature paste is high, and its conductivity is worse than that of the high-temperature conductive paste, and the contact resistivity is high, which is not conducive to improving the fill factor FF of the heterojunction solar cell.

[0005] In view of this, it is necessary to provide an improved technical solution to solve the above problems. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To achieve the above invention purpose, the present invention provides a heterojunction solar cell string, and its specific design is as follows.

[0007] A heterojunction solar cell string includes a plurality of heterojunction solar cells connected in series along a first direction. The heterojunction solar cell includes a cell body, a first transparent conductive film layer disposed on the light-receiving surface side of the cell body, and a second transparent conductive film layer disposed on the backlight surface side of the cell body. The heterojunction solar cell further includes a composite sub-grid disposed on the surface of the first transparent conductive film layer and / or the second transparent conductive film layer, and the extending direction of the composite sub-grid is perpendicular to the first direction. The composite sub-grid includes a first grid line layer and a second grid line layer disposed on the surface of the first grid line layer facing away from the cell body. The second grid line layer is made of a material different from that of the first grid line layer and covers the two opposite side surfaces of the first grid line layer in the width direction.

[0008] Further, the composite sub-grid further includes a third grid line layer disposed on the surface of the first grid line layer facing the cell body and connected to the second grid line layer, and the third grid line layer is made of the same material as the second grid line layer.

[0009] Further, the first grid line layer is one of a nickel metal layer, a copper metal layer, and an aluminum metal layer, and the second grid line layer is a silver metal layer; or, the first grid line layer is a conductive carbon layer, and the second grid line layer is a nickel metal layer.

[0010] Further, when the first grid line layer is a nickel metal layer, a copper metal layer, or an aluminum metal layer, the mass ratio of silver in the composite sub-grid is 15%-25%; when the first grid line layer is a conductive carbon layer, the mass ratio of nickel in the composite sub-grid is 60%-75%.

[0011] Further, the width of the composite sub-grid is 40-65 μm, and the thickness is 12-21 μm.

[0012] Further, the heterojunction solar cell further includes a composite main grid disposed on the surface of the first transparent conductive film layer and / or the second transparent conductive film layer, and the extending direction of the composite main grid is the same as the first direction. The composite main grid includes a fourth grid line layer and a fifth grid line layer disposed on the surface of the fourth grid line layer facing away from the cell body. The fifth grid line layer is made of a material different from that of the fourth grid line layer and covers the two opposite side surfaces of the fourth grid line layer in the width direction.

[0013] Further, the composite main grid further includes a sixth grid line layer disposed on the surface of the fourth grid line layer facing the cell body and connected to the fifth grid line layer, and the sixth grid line layer is made of the same material as the fifth grid line layer.

[0014] Further, the fourth grid line layer is one of a nickel metal layer, a copper metal layer, an aluminum metal layer, and a glass powder layer, and the fifth grid line layer is a silver metal layer; or, the fourth grid line layer is a conductive carbon layer, and the fifth grid line layer is a nickel metal layer.

[0015] Further, when the fourth grid line layer is a nickel metal layer, a copper metal layer or an aluminum metal layer, the mass percentage of silver in the composite main grid is 15%-25%; when the fourth grid line layer is a glass powder layer, the mass percentage of silver in the composite main grid is 50%-75%; when the fourth grid line layer is a conductive carbon layer, the mass percentage of nickel in the composite main grid is 60%-75%.

[0016] Further, the width of the composite main grid is 0.1-0.2 mm, and the thickness is 17-33 μm.

[0017] Further, the battery cell body includes a silicon substrate, a first intrinsic amorphous layer and a first doped amorphous layer sequentially disposed on one side of the light-receiving surface of the silicon substrate, a second intrinsic amorphous layer and a second doped amorphous layer with a doping type opposite to that of the first doped amorphous layer sequentially disposed on one side of the backlight surface of the silicon substrate, and the first transparent conductive film and the second transparent conductive film are respectively disposed on the surfaces of the first doped amorphous layer and the second doped amorphous layer away from the silicon substrate.

[0018] The present invention also provides a manufacturing method of a heterojunction solar cell, which includes:

[0019] Providing a battery cell body;

[0020] Depositing a first transparent conductive film layer and a second transparent conductive film layer on the light-receiving surface and the backlight surface of the battery cell body respectively;

[0021] Printing a first paste and a second paste on at least one side of the battery cell body deposited with the first transparent conductive film layer and the second transparent conductive film layer in sequence to cure and form a composite sub-grid, the second paste is different from the first paste in material, and the printed second paste covers the first paste on the two opposite side surfaces in the width direction of the composite sub-grid.

[0022] Further, the manufacturing method further includes: before printing the first paste, printing a third paste at the position where the first paste is to be printed, the third paste is the same as the second paste in material, and the printed second paste and the third paste are connected.

[0023] Further, the first paste is one of a conductive nickel paste, a conductive copper paste and a conductive aluminum paste, and the second paste is a conductive nickel paste; or, the first paste is a conductive carbon paste, and the second paste is a conductive nickel paste.

[0024] Further, the manufacturing method further includes: printing a fourth paste and a fifth paste on at least one side of the cell body deposited with the first transparent conductive film layer and the second transparent conductive film layer in sequence to form a composite main grid with an extending direction perpendicular to the length direction of the composite sub-grid by curing. The fifth paste is different from the fourth paste in material, and the printed fifth paste covers the two opposite side surfaces of the fourth paste in the width direction of the composite main grid.

[0025] Further, the manufacturing method further includes: before printing the fourth paste, printing a sixth paste at the position where the fourth paste is to be printed. The sixth paste is the same as the fifth paste in material, and the printed fifth paste is connected to the sixth paste.

[0026] Further, the fourth paste is one of conductive nickel paste, conductive copper paste, conductive aluminum paste and glass powder, and the fifth paste is conductive nickel paste; or, the fourth paste is conductive carbon paste and the fifth paste is conductive nickel paste.

[0027] The beneficial effects of the present invention are as follows: In the heterojunction solar cell involved in the present invention, a composite sub-grid different from the sub-grid structure printed by traditional low-temperature paste is provided, providing more choices for the production of the collector of the heterojunction solar cell; by reasonably configuring the materials of the first grid line layer and the second grid line layer in the composite sub-grid of the heterojunction solar cell of the present invention, the production cost of the heterojunction solar cell can be effectively reduced, and the problem of high contact resistivity of the low-temperature paste in the prior art can be improved, reducing the loss of the fill factor FF. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts. The front and back referred to herein are only limited to the positional relationship in the drawings of the embodiments, that is, the front is equivalent to the upper surface of the drawing, and the back is equivalent to the lower surface in the drawing.

[0029] Figure 1 The figure shows a schematic structural diagram of a prior art heterojunction solar cell;

[0030] Figure 2 The figure shows a schematic structural diagram of the first embodiment of the heterojunction solar cell involved in the present invention;

[0031] Figure 3 The figure shows a schematic structural diagram of the second embodiment of the heterojunction solar cell involved in the present invention;

[0032] Figure 4 The following figure shows the schematic diagram of the third implementation structure of the heterojunction solar cell involved in the present invention;

[0033] Figure 5 The following figure shows the schematic diagram of the fourth implementation structure of the heterojunction solar cell involved in the present invention;

[0034] In the figure, 10 is a silicon substrate, 21 is a first intrinsic amorphous layer, 31 is a first doped amorphous layer, 41 is a first transparent conductive film layer, 51 is a front composite sub-grid, 511 is a first front grid line layer, 512 is a second front grid line layer, 513 is a third front grid line layer, 22 is a second intrinsic amorphous layer, 32 is a second doped amorphous layer, 42 is a second transparent conductive film layer, 52 is a back composite sub-grid, 521 is a first back grid line layer, 522 is a second back grid line layer, and 523 is a third back grid line layer. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] The present invention provides a heterojunction solar cell string, including a plurality of heterojunction solar cells connected in series along a first direction. Referring to Figures 2 - 5 the figure, the heterojunction solar cell includes a cell body, a first transparent conductive film layer 41 disposed on the light-receiving surface side of the cell body, and a second transparent conductive film layer 42 disposed on the backlight surface side of the cell body.

[0037] In this specific embodiment, the cell body includes a silicon substrate 10, a first intrinsic amorphous layer 21 and a first doped amorphous layer 31 sequentially disposed on the light-receiving surface side of the silicon substrate 10, and a second intrinsic amorphous layer 22 and a second doped amorphous layer 32 sequentially disposed on the backlight surface side of the silicon substrate 10. Correspondingly, in this embodiment, the first transparent conductive film 41 and the second transparent conductive film 42 are respectively disposed on the surfaces of the first doped amorphous layer 31 and the second doped amorphous layer 32 away from the silicon substrate 10.

[0038] The present invention provides a method for forming a cell body, which includes: providing a silicon substrate 10; forming a first intrinsic amorphous layer 21 and a second intrinsic amorphous layer 22 on the light-receiving surface and the backlight surface of the silicon substrate 10 respectively by PECVD process; forming a first doped amorphous layer 31 and a second doped amorphous layer 32 on the surface of the first intrinsic amorphous layer 21 and the surface of the second intrinsic amorphous layer 22 respectively by PECVD process.

[0039] In addition, the first transparent conductive film layer 41 and the second transparent conductive film layer 42 involved in the present invention can be formed on the surface of the first doped amorphous layer 31 and the surface of the second doped amorphous layer 32 respectively by PVD process. The first transparent conductive film layer 41 and the second transparent conductive film layer 42 can be ITO, IWO or ITO, etc.

[0040] Preferably, the silicon substrate 10 involved in the present invention is preferably a single crystal silicon substrate.

[0041] In the specific implementation process, the light-receiving surface of the silicon substrate 10 involved in this embodiment is the surface where the heterojunction solar cell directly receives sunlight, and the backlight surface is the surface where the heterojunction solar cell does not directly receive sunlight, that is, the surface opposite to the light-receiving surface. The first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 are both intrinsic amorphous silicon. The doping types of the first doped amorphous layer 31 and the second doped amorphous layer 32 are opposite, one of which is N-type doping, that is, phosphorus doping; the other is P-type doping, that is, boron doping.

[0042] In the present invention, although the silicon substrate 10 can specifically be a P-type silicon substrate or an N-type single crystal silicon substrate; but as a preferred implementation manner of the present invention, the silicon substrate 10 is an N-type silicon substrate. Generally, the thickness of the silicon substrate 10 is 90 - 16 μm, and the side length is 156 - 210 mm. Further preferably, the first doped amorphous layer 31 is an N-type doped amorphous layer, and the second doped amorphous layer 32 is a P-type doped amorphous layer.

[0043] In the present invention, the heterojunction solar cell further includes a composite sub-grid disposed on the surface of the first transparent conductive film layer 41 and / or the second transparent conductive film layer 42 and extending in a direction perpendicular to the first direction. The composite sub-grid includes a first grid line layer and a second grid line layer disposed on the surface of the first grid line layer facing away from the battery chip body. The second grid line layer is made of a different material from the first grid line layer and covers the two opposite side surfaces of the first grid line layer in the width direction.

[0044] Reference Figure 2 As shown, in this specific embodiment, composite sub-grids are disposed on the surfaces of both the first transparent conductive film layer 41 and the second transparent conductive film layer 42. Specifically, the composite sub-grid includes a front composite sub-grid 51 disposed on the surface of the first transparent conductive film layer 41 and a back composite sub-grid 52 disposed on the surface of the second transparent conductive film layer 42.

[0045] As shown in the figure, the front composite auxiliary grid 51 includes a front first grid line layer 511 and a front second grid line layer 512 disposed on the surface of the front first grid line layer 511 facing away from the battery cell body. The front second grid line layer 512 is made of a different material from the front first grid line layer 511, and the front second grid line layer 512 covers the opposite two side surfaces of the front first grid line layer 511 in the width direction. In this embodiment, the front second grid line layer 512 completely covers the opposite two side surfaces of the front first grid line layer 511 in the width direction, and thus forms a direct connection with the first transparent conductive film layer 41.

[0046] Correspondingly, in Figure 2 the embodiment shown, the back composite auxiliary grid 52 includes a back first grid line layer 521 and a back second grid line layer 522 disposed on one surface of the back first grid line layer 521 facing away from the battery cell body. The back second grid line layer 522 is made of a different material from the back first grid line layer 521, and the back second grid line layer 522 covers the opposite two side surfaces of the back first grid line layer 521 in the width direction. In this embodiment, the back second grid line layer 522 completely covers the opposite two side surfaces of the back first grid line layer 521 in the width direction, and thus forms a direct connection with the second transparent conductive film layer 42.

[0047] It can be understood that in some other embodiments of the present invention, only one of the surfaces of the first transparent conductive film layer 41 and the second transparent conductive film layer 42 may be provided with the composite auxiliary grid having the above-mentioned structure, and the other is provided with an auxiliary grid structure the same as that of the traditional technology, such as a silver auxiliary grid.

[0048] In the heterojunction solar cell involved in the present invention, a composite auxiliary grid different from the auxiliary grid structure printed by traditional low-temperature paste is provided, which provides more choices for the production of the collector of the heterojunction solar cell; by reasonably configuring the materials of the first grid line layer and the second grid line layer in the composite auxiliary grid of the heterojunction solar cell of the present invention, the production cost of the heterojunction solar cell can be effectively reduced, and the problem of high contact resistivity of the low-temperature paste in the prior art can be improved, and the loss of the fill factor FF is reduced.

[0049] In still some other embodiments of the present invention, the composite auxiliary grid may further include a third grid line layer disposed on the surface of the first grid line layer facing the battery cell body and connected to the second grid line layer, and the third grid line layer is made of the same material as the second grid line layer.

[0050] In an embodiment of the present invention, referring to Figure 3 shown, the structure of the back composite auxiliary grid 52 is the same as that of the back composite auxiliary grid 52 in the Figure 2 embodiment shown. The difference is that Figure 3In the illustrated embodiment, the front composite sub-grid 51 further includes a front third grid layer 513 disposed on the surface of the front first grid layer 511 facing the battery cell body and connected to the front second grid layer 512. Among them, the front third grid layer 513 is made of the same material as the front second grid layer 512.

[0051] In another embodiment of the present invention, referring to Figure 4 as shown, the structure of the front composite sub-grid 51 is the same as that of the front composite sub-grid 51 in the embodiment shown in Figure 2 The difference is that Figure 4 in the illustrated embodiment, the back composite sub-grid 52 includes a back third grid layer 523 disposed on the surface of the back first grid layer 521 facing the battery cell body and connected to the back second grid layer 522. Among them, the back third grid layer 523 is made of the same material as the back second grid layer 522.

[0052] Furthermore, referring to Figure 5 as shown, in this embodiment, the front composite sub-grid 51 includes a front third grid layer 513 disposed on the surface of the front first grid layer 511 facing the battery cell body and connected to the front second grid layer 512; the back composite sub-grid 52 includes a back third grid layer 523 disposed on the surface of the back first grid layer 521 facing the battery cell body and connected to the back second grid layer 522.

[0053] In the present invention, the first grid layer is one of a nickel metal layer, a copper metal layer, and an aluminum metal layer, and the second grid layer is a silver metal layer; or, the first grid layer is a conductive carbon layer and the second grid layer is a nickel metal layer. The first grid layer involved in the present invention includes the front first grid layer 511 and the back first grid layer 521, and the second grid layer involved in the present invention includes the front second grid layer 512 and the back second grid layer 522.

[0054] It can be understood that when the front composite sub-grid 51 and the back composite sub-grid 52 also have a front third grid layer 513 and a back third grid layer 523 respectively, the constituent material of the front third grid layer 513 is the same as that of the corresponding front second grid layer 512, and the constituent material of the back third grid layer 523 is the same as that of the corresponding back second grid layer 522.

[0055] Based on the above design method, the present invention can effectively reduce the manufacturing cost of the composite sub-grid on the premise of ensuring that the composite sub-grid has a relatively low resistance.

[0056] Preferably, in the specific implementation process of the present invention, when the front first gate line layer 511 and the back first gate line layer 521 are one of a nickel metal layer, a copper metal layer, and an aluminum metal layer, the mass ratio of silver in the corresponding front composite sub-gate 51 and back composite sub-gate 52 is 15%-25%. When the front first gate line layer 511 and the back first gate line layer 521 are conductive carbon layers, the mass ratio of nickel in the corresponding front composite sub-gate 51 and back composite sub-gate 52 is 60%-75%.

[0057] In the present invention, the width of the composite sub-gate is 40-65 μm, and the thickness is 12-21 μm.

[0058] Preferably, the width and thickness of the front composite sub-gate 51 involved in the present invention are respectively smaller than those of the back composite sub-gate 52. In the specific implementation process, the width of the front composite sub-gate 51 involved in the present invention is 40-60 μm, and the thickness is 12-18 μm; the width of the back composite sub-gate 52 is 50-65 μm, and the thickness is 14-21 μm.

[0059] Based on the above settings, the shielding effect of each front composite sub-gate 51 on solar light is smaller than that of each back composite sub-gate 52, which can effectively improve the light-receiving intensity on the front side of the heterojunction solar cell and increase the photocurrent.

[0060] It can be understood that the sub-gates involved in the present invention can be composite sub-gates or sub-gates in a traditional form, such as silver sub-gates. As a preference, the distance between two adjacent sub-gates on the light-receiving side of the battery cell body is greater than the distance between two adjacent sub-gates on the light-shielding side of the battery cell body, that is, the number of sub-gates on the light-receiving side is less than that on the light-shielding side, and the shielding area of the sub-gates on the light-receiving side is less than that of the sub-gates on the light-shielding side. In this way, in a specific application scenario, a larger distance between two adjacent sub-gates on the light-receiving side can increase the effective light-receiving area on the light-receiving side, and a smaller distance between two adjacent sub-gates on the light-shielding side can reduce the series resistance of the heterojunction solar cell. The two combined can effectively optimize the photoelectric conversion efficiency of the heterojunction solar cell.

[0061] During specific implementation, the distance between two adjacent sub-gates on the light-receiving side of the battery cell body is 1.5-2.0 mm; the distance between two adjacent sub-gates on the light-shielding side of the battery cell body is 1.0-1.9 mm.

[0062] It can be understood that in some other embodiments of the present invention, the widths of the sub-gates on the light-receiving side and the light-shielding side are the same, and there are only differences in the sub-gate spacing, which will not be further elaborated here.

[0063] For a better understanding of the design structure of the composite sub-grid in the present invention, the present invention also provides a specific formation method therefor. Among them, for the front composite sub-grid 51, when it only includes the front first grid line layer 511 and the front second grid line layer 512, its manufacturing method includes successively printing a first paste and a second paste on the surface of the first transparent conductive film 41, and then curing so that the first paste and the second paste respectively form the front first grid line layer 511 and the front second grid line layer 512.

[0064] It is relatively easy to understand that when the front first grid line layer 511 is a nickel metal layer, a copper metal layer, an aluminum metal layer or a conductive carbon layer, the corresponding first pastes are respectively conductive nickel paste, conductive copper paste, conductive aluminum paste and conductive carbon paste; when the front second grid line layer 512 is a silver metal layer or a nickel metal layer, the corresponding second pastes are respectively conductive silver paste and conductive nickel paste.

[0065] Further, when the front composite sub-grid 51 further includes a front third grid line layer 513, during the manufacturing process of the front composite sub-grid 51, before printing the first paste, it further includes printing a third paste on the surface of the first transparent conductive film 41, and the composition of the involved third paste is the same as that of the second paste.

[0066] The manufacturing method of the back composite sub-grid 52 involved in the present invention can refer to the manufacturing method of the front composite sub-grid 51, and will not be elaborated herein specifically.

[0067] In the present invention, the heterojunction solar cell further includes a composite main grid (not shown in the figure) disposed on the surface of the first transparent conductive film layer 41 and / or the second transparent conductive film layer 42 and extending in the same direction as the first direction. The composite main grid includes a fourth grid line layer and a fifth grid line layer disposed on the surface of the fourth grid line layer facing away from the battery cell body. The fifth grid line layer is made of a different material from the fourth grid line layer and covers the two opposite side surfaces of the fourth grid line layer in the width direction.

[0068] In some embodiments of the present invention, composite main grids are disposed on the surfaces of both the first transparent conductive film layer 41 and the second transparent conductive film layer 42. Specifically, the composite main grid includes a front composite main grid disposed on the surface of the first transparent conductive film layer 41 and a back composite main grid disposed on the surface of the second transparent conductive film layer 42.

[0069] In other embodiments of the present invention, only one of the surfaces of the first transparent conductive film layer 41 and the second transparent conductive film layer 42 may be provided with a composite main grid having the above-mentioned structure, and the other is provided with a main grid structure the same as that of the traditional technology, such as a silver main grid.

[0070] In the heterojunction solar cell involved in the present invention, a composite main grid different from the main grid structure printed by traditional low-temperature conductive silver paste is provided, providing more choices for the production of the collector of the heterojunction solar cell; by reasonably configuring the materials of the fourth grid line layer and the fifth grid line layer in the composite main grid of the heterojunction solar cell of the present invention, the production cost of the heterojunction solar cell can also be effectively reduced, and the problem of high contact resistivity of low-temperature paste in the prior art can be improved, reducing the loss of the fill factor FF.

[0071] In some other embodiments of the present invention, the composite main grid may further include a sixth grid line layer disposed on the surface of the fourth grid line layer facing the battery cell body and connected to the fifth grid line layer, and the sixth grid line layer has the same material as the fifth grid line layer.

[0072] In the present invention, the setting structures of the fourth grid line layer, the fifth grid line layer, and the sixth grid line layer involved in the composite main grid can respectively refer to the setting structures of the first grid line layer, the second grid line layer, and the third grid line layer in the above-described composite sub-grid, and specific schematic diagrams will not be made separately.

[0073] In the present invention, the fourth grid line layer is one of a nickel metal layer, a copper metal layer, an aluminum metal layer, and a glass powder layer, and the fifth grid line layer is a silver metal layer; or, the fourth grid line layer is a conductive carbon layer, and the fifth grid line layer is a nickel metal layer. The fourth grid line layer involved in the present invention includes a front fourth grid line layer and a back fourth grid line layer, and the fifth grid line layer involved in the present invention includes a front fifth grid line layer and a back fifth grid line layer.

[0074] It can be understood that when the composite main grid further has a sixth grid line layer, the constituent material of the sixth grid line layer is the same as that of the corresponding fifth grid line layer.

[0075] Based on the above design method, the present invention can effectively reduce the production cost of the composite main grid on the premise of ensuring that the composite main grid has a relatively low resistance.

[0076] Preferably, in the specific implementation process of the present invention, when the fourth grid line layer is a nickel metal layer, a copper metal layer, or an aluminum metal layer, the mass ratio of silver in the corresponding composite main grid is 15%-25%. When the fourth grid line layer is a glass powder layer, the mass ratio of silver in the corresponding composite main grid is 50%-75%. When the front fourth grid line layer is a conductive carbon layer, the mass ratio of nickel in the corresponding composite main grid is 60%-75%.

[0077] In the specific implementation process, the width of the composite main grid involved in the present invention is 0.1-0.2 mm, and the thickness is 17-33 μm.

[0078] Among them, for a better understanding of the design structure of the composite main grid in the present invention, the present invention also provides a specific formation method thereof. For the front composite main grid, when it only includes the front fourth grid line layer and the front fifth grid line layer, its manufacturing method includes sequentially printing the fourth paste and the fifth paste on the surface of the first transparent conductive film 41, and then curing so that the fourth paste and the fifth paste respectively form the front fourth grid line layer and the front fifth grid line layer.

[0079] It is relatively easy to understand that when the front fourth grid line layer is a nickel metal layer, a copper metal layer, an aluminum metal layer, a glass powder layer or a conductive carbon layer, the corresponding fourth pastes are respectively conductive nickel paste, conductive copper paste, conductive aluminum paste, glass powder paste and conductive carbon paste; when the front fifth grid line layer is a silver metal layer or a nickel metal layer, the corresponding fifth pastes are respectively conductive silver paste and conductive nickel paste.

[0080] Further, when the front composite main grid further includes a front sixth grid line layer, during the manufacturing process of the front composite main grid, before printing the fourth paste, it further includes printing a sixth paste on the surface of the first transparent conductive film 41, and the composition of the sixth paste involved is the same as that of the fifth paste.

[0081] The manufacturing method of the back composite main grid involved in the present invention can refer to the manufacturing method of the front composite main grid, and will not be elaborated here specifically.

[0082] In a more specific implementation process of the present invention, when one side of the battery cell body simultaneously has the composite sub-grid and the composite main grid involved in the present invention, in some embodiments, the first grid line layer, the second grid line layer, and the third grid line layer constituting the composite sub-grid can be simultaneously printed and formed with the fourth grid line layer, the fifth grid line layer, and the sixth grid line layer constituting the composite main grid; in other embodiments, the composite sub-grid and the composite main grid can also be printed and formed separately.

[0083] It can be understood that the main grid involved in the present invention can be a composite main grid or a main grid in a traditional form, such as a silver main grid. Among them, the main grid and the sub-grid located on the surface of the first transparent conductive film layer 41 together constitute the first collector, and the main grid and the sub-grid located on the surface of the second transparent conductive film layer 42 together constitute the second collector.

[0084] Corresponding to the above-described heterojunction solar cell, the manufacturing method of the heterojunction solar cell involved in the present invention includes:

[0085] Providing a battery cell body;

[0086] Depositing a first transparent conductive film layer 41 and a second transparent conductive film layer 42 on the light-receiving surface and the backlight surface of the battery cell body respectively;

[0087] On at least one side of the battery cell body deposited with the first transparent conductive film layer 41 and the second transparent conductive film layer 42, the first paste and the second paste are sequentially printed and cured to form a composite sub-grid 51. The second paste is different from the first paste in material, and the printed second paste covers the two opposite side surfaces of the first paste in the width direction of the composite sub-grid.

[0088] Further, the manufacturing method further includes: before printing the first paste, a third paste is printed at the position where the first paste is to be printed. The third paste is the same as the second paste in material, and the printed second paste is connected to the third paste.

[0089] Further, the first paste is one of a conductive nickel paste, a conductive copper paste, and a conductive aluminum paste, and the second paste is a conductive nickel paste; or, the first paste is a conductive carbon paste and the second paste is a conductive nickel paste.

[0090] In some other embodiments of the present invention, the manufacturing method further includes: on at least one side of the battery cell body deposited with the first transparent conductive film layer 41 and the second transparent conductive film layer 42, a fourth paste and a fifth paste are sequentially printed to cure and form a composite main grid whose extending direction is perpendicular to the length direction of the composite sub-grid. The fifth paste is different from the fourth paste in material, and the printed fifth paste covers the two opposite side surfaces of the fourth paste in the width direction of the composite main grid.

[0091] Further, the manufacturing method further includes: before printing the fourth paste, a sixth paste is printed at the position where the fourth paste is to be printed. The sixth paste is the same as the fifth paste in material, and the printed fifth paste is connected to the sixth paste.

[0092] Further, the fourth paste is one of a conductive nickel paste, a conductive copper paste, a conductive aluminum paste, and glass powder, and the fifth paste is a conductive nickel paste; or, the fourth paste is a conductive carbon paste and the fifth paste is a conductive nickel paste.

[0093] Preferably, both the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 involved in the present invention include at least two layers of stacked intrinsic amorphous silicon films. In the specific implementation process, by controlling the characteristics of each layer of intrinsic amorphous silicon film, the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 with better comprehensive performance can be formed.

[0094] Specifically, in the first intrinsic amorphous layer 21 of the present invention, the hydrogen content of the intrinsic amorphous silicon film close to the single-crystalline silicon substrate 10 is higher than that of the intrinsic amorphous silicon film far from the single-crystalline silicon substrate, and in the second intrinsic amorphous layer 22, the hydrogen content of the intrinsic amorphous silicon film close to the single-crystalline silicon substrate 10 is higher than that of the intrinsic amorphous silicon film far from the single-crystalline silicon substrate.

[0095] It is relatively easy to understand that among the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22, the intrinsic amorphous silicon film closer to the single-crystalline silicon substrate 10 has a more obvious passivation effect. A higher hydrogen content in the intrinsic amorphous silicon film close to the single-crystalline silicon substrate 10 can enable the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 to have an optimal passivation effect on the single-crystalline silicon substrate 10.

[0096] As a preferred embodiment, when the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 each include three layers of stacked intrinsic amorphous silicon films, in the direction away from the single-crystalline silicon substrate 10, the hydrogen content ranges of the three layers of intrinsic amorphous silicon films in the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 are successively 20%-40%, 10%-25%, and 8%-20%.

[0097] Preferably, the first doped amorphous layer 31 involved in the present invention includes a first doped amorphous silicon film on the surface of the first intrinsic amorphous layer 21 and a doped amorphous silicon oxide film on the surface of the first doped amorphous silicon film.

[0098] Doped amorphous silicon oxide has more excellent light transmittance than doped amorphous silicon. In the prior art, the first doped amorphous layer usually has a single-layer doped amorphous silicon film structure; in this embodiment, the first doped amorphous layer 31 adopts a double-layer film design. Among them, the first doped amorphous silicon film can ensure good contact between the first doped amorphous layer 31 and the first intrinsic amorphous layer 21, and the doped amorphous silicon oxide film is equivalent to replacing part of the doped amorphous silicon in the prior art with doped amorphous silicon oxide with high light transmittance. In this way, the overall light transmittance of the first doped amorphous layer 31 can be improved, the loss of sunlight when passing through the first intrinsic amorphous layer and the first doped amorphous layer can be reduced, and thus the short-circuit current of the heterojunction solar cell can be increased, which is beneficial to the optimization of the photoelectric conversion efficiency.

[0099] That is, based on the cooperation of the first doped amorphous silicon film and the doped amorphous silicon oxide film, the heterojunction solar cell provided by the present invention has relatively excellent optical and electrical properties.

[0100] In the specific implementation process, the thickness of the first doped amorphous silicon film is less than or equal to the thickness of the doped amorphous silicon oxide film; preferably, the thickness of the first doped amorphous silicon film is usually less than the thickness of the doped amorphous silicon oxide film. In this way, while ensuring good contact between the first doped amorphous layer 31 and the first intrinsic amorphous layer 21, the first doped amorphous layer 31 can have good light transmittance to a great extent.

[0101] In some other embodiments of the present invention, the first doped amorphous layer 31 further includes a second doped amorphous silicon film located on the surface of the doped amorphous silicon oxide film. Doped amorphous silicon generally has relatively excellent conductivity. The arrangement of the second doped amorphous silicon film can enable better contact between the first doped amorphous layer 31 and the first transparent conductive film layer 41, thereby further reducing the contact resistance and enabling the battery to have a higher fill factor. Specifically, during implementation, the doping concentration of the second doped amorphous silicon film can be higher than that of the first doped amorphous silicon film.

[0102] In this embodiment, the thickness of the second doped amorphous silicon film is less than or equal to the thickness of the doped amorphous silicon oxide film; preferably, the thickness of the second doped amorphous silicon film is also generally less than the thickness of the doped amorphous silicon oxide film, thereby enabling the first doped amorphous layer 31 to have better light transmittance.

[0103] Furthermore, in some other embodiments of the present invention, the second doped amorphous layer 32 includes a third doped amorphous silicon film located on the surface of the second intrinsic amorphous layer 22 and a fourth doped amorphous silicon film located on the surface of the third doped amorphous silicon film and having a doping concentration greater than that of the third doped amorphous silicon film.

[0104] Preferably, the carrier concentration of the fourth doped amorphous silicon film is 5E19 - 5E21 / cm 3 . Correspondingly, the carrier concentration of the third doped amorphous silicon film is set to 5E18 - 5E19 / cm 3

[0105] In this embodiment, due to the relatively low doping concentration, the third doped amorphous silicon film can reduce the influence on the second intrinsic amorphous layer 22, reduce the lattice distortion of the second intrinsic amorphous layer 22, and effectively ensure the passivation effect on the back surface of the heterojunction solar cell; due to the relatively high doping concentration, the fourth doped amorphous silicon film can improve the contact between the second doped amorphous layer 32 and the second transparent conductive film, reduce the contact resistance between the two, and improve the battery fill factor.

[0106] In the present invention, the thickness of the third doped amorphous silicon film is less than or equal to that of the fourth doped amorphous silicon film; preferably, the thickness of the third doped amorphous silicon film is generally less than that of the fourth doped amorphous silicon film.

[0107] Preferably, in the present invention, the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is less than the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32.

[0108] For a heterojunction solar cell, the light absorption effect on the light-receiving surface has a much greater impact on the photoelectric conversion efficiency of the cell than that on the backlight surface. Since the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is less than the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32, it can effectively reduce the loss of sunlight on the light-receiving surface when passing through the first intrinsic amorphous layer 21 and the first doped amorphous layer 31, improve the short-circuit current of the heterojunction solar cell, and enable the heterojunction solar cell to have better photoelectric conversion efficiency.

[0109] In some more specific embodiments of the present invention, the sum of the thicknesses of the first intrinsic amorphous layer 21 and the first doped amorphous layer 31 is 6 - 21 nm, and the sum of the thicknesses of the second intrinsic amorphous layer 22 and the second doped amorphous layer 32 is 7 - 30 nm.

[0110] As a further preference, the thickness of the first intrinsic amorphous layer 21 is less than or equal to the thickness of the second intrinsic amorphous layer 22, and the thickness of the first doped amorphous layer 31 is less than or equal to the thickness of the second doped amorphous layer 32.

[0111] Specifically, the thickness of the first doped amorphous layer 31 is 3 - 15 nm, and the thickness of the second doped amorphous layer 32 is 3 - 20 nm. Correspondingly, in Figure 1 the illustrated embodiment, the thickness of the first intrinsic amorphous layer 21 is 3 - 6 nm, and the thickness of the second intrinsic amorphous layer 22 is 4 - 10 nm.

[0112] Further preferably, the thickness of the first doped amorphous layer 31 is 4 - 5 nm, and the thickness of the second doped amorphous layer 32 is 4 - 5 nm. Correspondingly, in Figure 1 the illustrated embodiment, the thickness of the first intrinsic amorphous layer 21 is 4 - 5 nm, and the thickness of the second intrinsic amorphous layer 22 is 5 - 6 nm.

[0113] Furthermore, in the present invention, the thickness of the first transparent conductive film layer 41 is less than or equal to the thickness of the second transparent conductive film layer 42. For a heterojunction solar cell, since the thickness of the first transparent conductive film layer 41 is relatively small, it can effectively reduce the loss of sunlight on the light-receiving surface when passing through the first transparent conductive film layer 41, and thus enable the heterojunction solar cell to have better photoelectric conversion efficiency.

[0114] Generally, the thickness range of the first transparent conductive film layer 41 and the second transparent conductive film layer 42 is 65 - 75 nm.

[0115] In the present invention, when the silicon substrate 10 is an N-type silicon substrate, the first doped amorphous layer 31 is an N-type doped amorphous layer, and the second doped amorphous layer 32 is a P-type doped amorphous layer. The first transparent conductive film layer 41 involved in the present invention includes a first TCO film attached to the surface of the first doped amorphous layer 31 and a second TCO film (not shown in the figure) attached to the surface of the first TCO film. Among them, the mass ratio of the doped oxide in the first TCO film 411 is greater than the mass ratio of the doped oxide in the second TCO film 412.

[0116] In the heterojunction solar cell structure provided by the present invention, based on its specific design structure, the first TCO film can ensure good contact between the first transparent conductive film layer 41 and the first doped amorphous layer 31 due to high doping, thereby reducing the contact resistance and improving the fill factor of the heterojunction solar cell; while the second TCO film can increase the light transmittance of the first transparent conductive film layer 41 as a whole due to low doping, and can improve the short-circuit current of the heterojunction solar cell.

[0117] Preferably, in the specific implementation process of the present invention, the mass ratio of the doped oxide in the first TCO film is 5%-20%, and the mass ratio of the doped oxide in the second TCO film is 0.5%-5%.

[0118] Furthermore, the second transparent conductive film layer 42 in the present invention includes a third TCO film attached to the surface of the second doped amorphous layer 32 and a fourth TCO film attached to the surface of the third TCO film. Among them, the mass ratio of the doped oxide in the third TCO film is less than the mass ratio of the doped oxide in the fourth TCO film.

[0119] Since the third TCO film is in direct contact with the second doped amorphous layer 32, when the third TCO film has a low doping concentration, the Schottky contact barrier between the two is reduced, and thus the best contact between the two can be achieved, improving the fill factor of the heterojunction solar cell. In addition, the fourth TCO film has good conductivity due to its high doping concentration and has good electrical contact with the second collector, which can also improve the fill factor of the heterojunction solar cell. It can be known that since the second transparent conductive film layer 42 is located on the backlight side of the heterojunction solar cell, in specific applications, the proportion of sunlight passing through the second transparent conductive film layer 42 and irradiating into the heterojunction solar cell is very low, and its light transmittance has little impact on the overall performance of the heterojunction solar cell.

[0120] In the specific implementation process, the mass ratio of the doped oxide in the third TCO film is 0.5%-5%, and the mass ratio of the doped oxide in the fourth TCO film is 5%-20%.

[0121] As a more specific embodiment, when the silicon substrate 10 is an N-type silicon substrate, the first doped amorphous layer 31 is an N-type doped amorphous layer, and the second doped amorphous layer 32 is a P-type doped amorphous layer. Each constituent layer of the first transparent conductive film layer and the second transparent conductive film layer is made of an ITO film (formed by doping indium oxide with SnO2).

[0122] Among them, on the light-receiving surface side of the cell body, the first transparent conductive film layer 41 includes two TCO layers. The first TCO film has a composition of ITO(90:10) and a film thickness of 5 - 10 nm, and the second TCO film has a composition of ITO(97:3) and a film thickness of 55 - 70 nm; on the backlight surface side of the cell body, the second transparent conductive film layer 42 also includes two TCO layers. The third TCO film has a composition of ITO(97:3) and a film thickness of 5 - 10 nm, and the fourth TCO film has a composition of ITO(90:10) and a film thickness of 55 - 70 nm.

[0123] It should be understood that the above-mentioned ITO(97:3) refers to the mass ratio of indium oxide to SnO2 in the ITO film being 97:3. Correspondingly, that is, the mass fraction of the doped oxide (SnO2) is 3%; ITO(90:10) refers to the mass ratio of indium oxide to SnO2 in the ITO film being 90:10. Correspondingly, that is, the mass fraction of the doped oxide (SnO2) is 10%.

[0124] In other embodiments of the present invention, the first transparent conductive film layer 41 and the second transparent conductive film layer 42 may also include only one TCO film. The TCO film involved may be ITO(97:3) or ITO(90:10).

[0125] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A heterojunction solar cell string, comprising a plurality of heterojunction solar cells connected in series along a first direction, wherein each heterojunction solar cell comprises a cell body, a first transparent conductive film layer disposed on the light-receiving surface side of the cell body, and a second transparent conductive film layer disposed on the backlight surface side of the cell body, characterized in that, The heterojunction solar cell further includes a composite sub-grid disposed on the surface of the first transparent conductive film layer and / or the second transparent conductive film layer, and the extending direction of the composite sub-grid is perpendicular to the first direction. The composite sub-grid includes a first grid line layer and a second grid line layer disposed on the surface of the first grid line layer facing away from the battery cell body. The second grid line layer is made of a different material from the first grid line layer and covers the two opposite side surfaces of the first grid line layer in the width direction, and the second grid line layer is in direct contact with the first transparent conductive film layer or the second transparent conductive film layer on the side where the composite sub-grid is located; the first grid line layer is one of a nickel metal layer, a copper metal layer, and an aluminum metal layer, the second grid line layer is a silver metal layer, and the mass ratio of silver in the composite sub-grid is 15%-25%; or, the first grid line layer is a conductive carbon layer, the second grid line layer is a nickel metal layer, and the mass ratio of nickel in the composite sub-grid is 60%-75%; the battery cell body includes a silicon substrate, a first intrinsic amorphous layer and a first doped amorphous layer sequentially disposed on one side of the light-receiving surface of the silicon substrate, a second intrinsic amorphous layer and a second doped amorphous layer with a doping type opposite to that of the first doped amorphous layer sequentially disposed on one side of the backlight surface of the silicon substrate, and the first transparent conductive film and the second transparent conductive film are respectively disposed on the surfaces of the first doped amorphous layer and the second doped amorphous layer away from the silicon substrate.

2. The heterojunction solar cell string according to claim 1, characterized in that, The composite sub-grid further includes a third grid line layer disposed on the surface of the first grid line layer facing the battery cell body and connected to the second grid line layer, and the third grid line layer is made of the same material as the second grid line layer.

3. The heterojunction solar cell string according to claim 1 or 2, characterized in that, The width of the composite sub-grid is 40-65μm, and the thickness is 12-21μm.

4. The heterojunction solar cell string according to claim 1, characterized in that, The heterojunction solar cell further includes a composite main grid disposed on the surface of the first transparent conductive film layer and / or the second transparent conductive film layer, and the extending direction of the composite main grid is the same as the first direction. The composite main grid includes a fourth grid line layer and a fifth grid line layer disposed on the surface of the fourth grid line layer facing away from the battery cell body. The fifth grid line layer is made of a different material from the fourth grid line layer and covers the two opposite side surfaces of the fourth grid line layer in the width direction.

5. The heterojunction solar cell string according to claim 4, characterized in that, The composite main grid further includes a sixth grid line layer disposed on the surface of the fourth grid line layer facing the battery cell body and connected to the fifth grid line layer, and the sixth grid line layer is made of the same material as the fifth grid line layer.

6. The heterojunction solar cell string according to claim 4 or 5, characterized in that, The fourth grid line layer is one of a nickel metal layer, a copper metal layer, an aluminum metal layer, and a glass powder layer, and the fifth grid line layer is a silver metal layer; or, the fourth grid line layer is a conductive carbon layer, and the fifth grid line layer is a nickel metal layer.

7. The heterojunction solar cell string according to claim 6, characterized in that, When the fourth grid line layer is a nickel metal layer, a copper metal layer, or an aluminum metal layer, the mass ratio of silver in the composite main grid is 15%-25%; when the fourth grid line layer is a glass powder layer, the mass ratio of silver in the composite main grid is 50%-75%; when the fourth grid line layer is a conductive carbon layer, the mass ratio of nickel in the composite main grid is 60%-75%.

8. The heterojunction solar cell string according to claim 4 or 5, characterized in that, The width of the composite main grid is 0.1-0.2mm, and the thickness is 17-33μm.

9. A method for manufacturing a heterojunction solar cell, characterized in that, Including: Provide a battery cell body; Deposit a first transparent conductive film layer and a second transparent conductive film layer on the light-receiving surface and the backlight surface of the battery cell body respectively; Print a first paste and a second paste in sequence on at least one side of the battery cell body deposited with the first transparent conductive film layer and the second transparent conductive film layer to cure and form a composite sub-grid. The second paste is different in material from the first paste, and the printed second paste covers the first paste on the two opposite side surfaces in the width direction of the composite sub-grid. The first paste is one of a conductive nickel paste, a conductive copper paste, and a conductive aluminum paste, and the second paste is a conductive silver paste. The mass ratio of silver in the formed composite sub-grid is 15%-25%; or, the first paste is a conductive carbon paste, and the second paste is a conductive nickel paste. The mass ratio of nickel in the formed composite sub-grid is 60%-75%.

10. The method for manufacturing a heterojunction solar cell according to claim 9, characterized in that, The manufacturing method further includes: before printing the first paste, print a third paste at the position where the first paste is to be printed. The third paste is the same in material as the second paste, and the printed second paste is connected to the third paste.

11. The method for manufacturing a heterojunction solar cell according to claim 9, characterized in that, The manufacturing method further includes: print a fourth paste and a fifth paste in sequence on at least one side of the battery cell body deposited with the first transparent conductive film layer and the second transparent conductive film layer to cure and form a composite main grid whose extension direction is perpendicular to the length direction of the composite sub-grid. The fifth paste is different in material from the fourth paste, and the printed fifth paste covers the fourth paste on the two opposite side surfaces in the width direction of the composite main grid.

12. The method for manufacturing a heterojunction solar cell according to claim 11, characterized in that, The manufacturing method further includes: before printing the fourth paste, print a sixth paste at the position where the fourth paste is to be printed. The sixth paste is the same in material as the fifth paste, and the printed fifth paste is connected to the sixth paste.

13. The method for manufacturing a heterojunction solar cell according to claim 11 or 12, characterized in that, The fourth paste is one of a conductive nickel paste, a conductive copper paste, a conductive aluminum paste, and glass powder, and the fifth paste is a conductive nickel paste; or, the fourth paste is a conductive carbon paste, and the fifth paste is a conductive nickel paste.

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