Solar cell, preparation method thereof and photovoltaic equipment

Abstract

The invention provides a solar cell, a preparation method thereof and photovoltaic equipment. The method for preparing the solar cell comprises the following steps: forming a conductive seed layer on a light-facing surface and / or a backlight surface of a cell main body; forming a patterned photoresist on the surface, far away from the battery main body, of the conductive seed layer, wherein the photoresist exposes part of the surface of the conductive seed layer; arranging a conductive wire on the surface, far away from the battery main body, of the photoresist; forming a conductive connection layer in a gap between the conductive seed layer exposed by the photoresist and the conductive wire through electroplating; and removing the photoresist and the region of the conductive seed layer which is not covered by the conductive connection layer. A conductive connecting layer is formed between the conductive wire and the patterned conductive seed layer through electroplating, so that the conductive wire and the conductive connecting layer as well as the conductive connecting layer and the patterned conductive seed layer are electrically connected through contact, and a low-temperature electroplating process is adopted to replace a high-temperature welding process; and negative effects on the battery caused by high temperature in the welding process can be effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to solar cells, their fabrication methods, and photovoltaic devices. Background Technology

[0002] To reduce power generation losses in solar cells, a current collection path can be designed using tandem grid technology. Tandem grid cells innovatively combine the grid lines and solder strips into one. Specifically, a seed layer is first printed on the cell surface, and then fine conductive filaments are soldered to the seed layer. Connecting the fine conductive filaments of two cells allows current to be transferred between them. Therefore, the current transmission path of a tandem grid solar cell is as follows: current is transmitted through the semiconductor of the solar cell to the seed layer, then directly from the seed layer to the fine conductive filaments, and then along the fine conductive filaments. Tandem grid technology shortens the current transmission path, reduces current transmission losses, and improves the conversion efficiency of photovoltaic modules. However, tandem grid technology uses high-temperature welding to connect the fine conductive filaments to the seed layer. This high-temperature welding process can bring some negative effects to solar cells, such as residual thermal stress and the risk of solder joint breakage. Summary of the Invention

[0003] This invention aims to at least partially address one of the technical problems in related technologies. Therefore, one object of this invention is to provide a method for fabricating solar cells in which the connection between conductive wires and a conductive seed layer, achieved through a low-temperature electroplating process, helps to improve the performance of the solar cell.

[0004] In one aspect, the present invention provides a method for fabricating a solar cell. According to an embodiment of the present invention, the method for fabricating a solar cell includes: forming a conductive seed layer on the light-facing and / or back-facing side of a cell body; forming a patterned photoresist on the surface of the conductive seed layer away from the cell body, the photoresist exposing a portion of the surface of the conductive seed layer; disposing conductive wires on the surface of the photoresist away from the cell body; forming a conductive connection layer by electroplating in the gap between the conductive seed layer exposed by the photoresist and the conductive wires; and removing the photoresist and the areas of the conductive seed layer not covered by the conductive connection layer. Thus, in this method for fabricating a solar cell, the conductive wires and the patterned conductive seed layer form a conductive connection layer through electroplating, thereby enabling electrical connection between the conductive wires and the conductive connection layer, and between the conductive connection layer and the patterned conductive seed layer, through contact. Furthermore, the use of a low-temperature electroplating process instead of a high-temperature welding process effectively avoids the negative impact of high temperatures during welding on the cell.

[0005] According to an embodiment of the present invention, a conductive wire serves as a cathode, and a conductive connection layer is grown from the conductive wire to the conductive seed layer until the conductive connection layer is connected to the conductive seed layer.

[0006] According to an embodiment of the present invention, the conductive seed layer serves as the cathode, and a conductive connection layer is grown from the conductive seed layer to the conductive filament until the conductive connection layer is connected to the conductive filament.

[0007] According to an embodiment of the present invention, the thickness of the photoresist is the same as the thickness of the conductive interconnect layer.

[0008] According to an embodiment of the present invention, after the conductive wire is disposed on the surface of the photoresist away from the battery body, the conductive wire and the photoresist are fixed by adhesive.

[0009] According to an embodiment of the present invention, the thickness of the conductive connection layer is 5 to 15 micrometers.

[0010] According to an embodiment of the present invention, the material of the conductive connection layer includes at least one of copper and silver.

[0011] According to an embodiment of the present invention, the material of the patterned conductive seed layer includes at least one of copper, nickel, silver and tin; and / or, the material of the conductive wire includes at least one of copper, nickel, silver and tin.

[0012] In another aspect, the present invention provides a solar cell prepared by the method described above. This solar cell exhibits good performance and excellent stability. Those skilled in the art will understand that this solar cell possesses all the features and advantages of the methods described above for preparing solar cells, which will not be elaborated upon further here.

[0013] In another aspect, the present invention provides a photovoltaic device. According to an embodiment of the invention, the photovoltaic device includes the solar cell described above, or includes a solar cell prepared by the methods described above. Therefore, the photovoltaic device has better cell efficiency and better circuit stability. Those skilled in the art will understand that the photovoltaic device possesses all the features and advantages of the solar cell described above, which will not be elaborated further here.

[0014] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1This is a flowchart of the fabrication of a solar cell in one embodiment of the present invention; Figure 2 This is a partial flowchart of the fabrication of a solar cell in another embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a solar cell in another embodiment of the present invention. Detailed Implementation

[0016] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0017] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0018] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0019] Current stacked grid technology typically uses high-temperature welding to attach conductive wires to the seed layer on the surface of solar cells. This high-temperature process results in significant thermal stress between the conductive wires, electrodes, and cells due to thermal deformation, posing a substantial risk of failure during subsequent use. Conductive wire detachment or breakage can lead to a significant drop in output power. Furthermore, the high-temperature process primarily relies on solder to form an alloy with the electrode metal for circuit connections. However, the tensile and yield strength of this alloy layer is far lower than that of the conductive wire itself, making the welded area relatively weak in resisting stress and prone to solder joint breakage, resulting in reduced cell power. Additionally, the solder alloy has poor conductivity, leading to significant current loss through the solder joint area.

[0020] In one aspect of the invention, a method for preparing the aforementioned solar cell is provided. According to an embodiment of the invention, referring to... Figure 1 Methods for preparing solar cells include: S100: A conductive seed layer 210 is formed on the light-facing surface 110 and / or the back-facing surface 120 of the battery body 100 (the example shown is that it is formed on the surface of the light-facing surface 110).

[0021] According to some embodiments of the present invention, the type of battery body is not limited, and those skilled in the art can make flexible selections according to actual needs. In some embodiments, the battery body can be a TOPCon (tunneling oxide passivated contact) battery, a BC (back contact) battery, an HJT (heterojunction) battery, or a crystalline silicon-perovskite tandem battery containing the above-mentioned crystalline silicon battery, etc.

[0022] According to some embodiments of the present invention, a conductive seed layer can be formed by deposition, such as by chemical vapor deposition, physical vapor deposition (PVD) or magnetron sputtering.

[0023] According to some embodiments of the present invention, a conductive seed layer covers the entire surface of the light-facing side 110 and / or the back-facing side 120 of the battery body 100.

[0024] According to some embodiments of the present invention, the conductive seed layer is made of at least one of copper, nickel, silver, and tin. Therefore, the above materials have good conductivity, enabling efficient current transmission and reducing energy loss. In some embodiments, the thickness of the conductive seed layer is less than 500 nm, which can reduce recombination loss and optical loss, while also lowering costs.

[0025] S200: A patterned photoresist 500 is formed on the surface of the conductive seed layer 210 away from the battery body 100, exposing a portion of the surface of the conductive seed layer 210. The portion of the conductive seed layer 210 exposed by the photoresist 500 is the location where the conductive interconnect layer needs to be formed in subsequent steps.

[0026] In some embodiments of the present invention, patterned photoresist can be prepared using either positive or negative photoresist. The following describes the preparation steps of patterned photoresist 50 using positive photoresist as an example. Figure 2 As shown: A whole photoresist layer 510 is formed by coating the conductive seed layer 210 on the surface away from the battery body 100; a predetermined area of ​​the whole photoresist layer 510 is exposed (i.e., the corresponding position of the part of the surface of the conductive seed layer 210 that needs to be exposed is exposed); the exposed area is developed using a developer to etch away the exposed photoresist, thereby obtaining a patterned photoresist 500.

[0027] S300: Conductive wires 400 are disposed on the surface of photoresist 500 away from the battery body 100.

[0028] According to some embodiments of the present invention, there are no limitations on the placement of the conductive wire, and those skilled in the art can flexibly design the position of the conductive wire according to actual needs.

[0029] According to some embodiments of the present invention, the conductive wire is made of at least one of copper, nickel, silver, and tin. Conductive wires made of the above materials have good conductivity, which can improve current transmission efficiency and reduce energy loss; moreover, they have good corrosion resistance and good mechanical properties such as tensile strength and bending resistance.

[0030] According to some embodiments of the present invention, after conductive wires are formed on the surface of the photoresist away from the battery body, adhesive is used to fix the conductive wires and the photoresist, such as glue, tape or other adhesives. In this way, the movement of the conductive wires can be effectively avoided in the subsequent process of forming the conductive connection layer, thereby affecting the formation of the conductive connection layer and improving the yield of forming the conductive connection layer.

[0031] S400: A conductive interconnect layer 300 is formed by electroplating in the gap between the conductive seed layer 210 exposed by the photoresist 500 and the conductive wire 400.

[0032] In the above steps, the use of electroplating, a low-temperature process, to form a conductive connection layer can avoid the thermal stress caused by high-temperature processes (such as high-temperature welding), thereby helping to improve the quality and output power of solar cells. The conductive connection layer formed by electroplating has better strength and good and stable contact with conductive wires and patterned conductive seed layers, which can effectively reduce functional losses.

[0033] According to some embodiments of the present invention, a specific method for electroplating to form a conductive connection layer can be implemented by one of the following methods: In some embodiments, a conductive wire 400 is energized, serving as a cathode, and a conductive connection layer is grown on its surface by electroplating. The conductive connection layer grows from the conductive wire 400 towards the conductive seed layer 210 in the gap between the photoresist-exposed conductive seed layer 210 and the conductive wire 400. When the conductive connection layer grows to the point of just contacting the conductive seed layer 210, the conductive seed layer 210 is electrically connected to the cathode. Further electroplating allows the reduced metal to fill the micro-gap between the conductive connection layer and the conductive seed layer 210, thereby forming a strong mechanical connection and a stable electrical connection between the conductive connection layer and the conductive seed layer 210.

[0034] In other embodiments, the conductive seed layer 210 is energized, serving as the cathode. A conductive connection layer is grown on the exposed surface of the seed layer near the conductive wire using electroplating. When the conductive connection layer grows to the point where it just contacts the conductive wire 400, the conductive wire 400 also connects to the cathode. Further electroplating allows the metal reduced from the electroplating to fill the micro-gap between the conductive connection layer and the conductive wire 400, thereby forming a strong mechanical connection and a stable electrical connection between the conductive connection layer and the conductive wire 400.

[0035] In the aforementioned example, the conductive wire 400 or the conductive seed layer 210 can be connected to the cathode, while the material of the conductive connection layer serves as the anode. Specifically, when the conductive connection layer is copper, pure copper is used as the anode, and a salt solution containing copper ions is used as the electrolyte. When the conductive connection layer is silver, pure silver is used as the anode, and a salt solution containing silver ions is used as the electrolyte.

[0036] Preferably, the conductive bonding layer is copper, pure copper is the anode, and a salt solution containing copper ions is the electrolyte.

[0037] In the above embodiments, the copper salt can be copper sulfate, copper nitrate, copper chloride, or other copper salts. During electroplating, the concentration of the copper salt can be 0.5-5 mol / L, and the current density can be 0.5-5.0 A / dm².

[0038] According to some embodiments of the present invention, the conductive connection layer is made of at least one of copper and silver. Therefore, the conductive connection layer made of the above-mentioned materials exhibits superior conductivity, is widely available, and is easier to manufacture. In some embodiments, the conductive connection layer is made of copper, which results in lower cost and better conductivity.

[0039] According to some embodiments of the present invention, the thickness of the conductive interconnect layer is 5 to 15 micrometers, such as 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, 15 micrometers, etc. Conductive interconnect layers of the above thicknesses are easy to fabricate and have good contact with the conductive wires and patterned conductive seed layers, enabling efficient current transmission; moreover, thinner conductive interconnect layers can reduce light loss.

[0040] According to some embodiments of the present invention, the thickness of the photoresist 500 is consistent with the thickness of the conductive interconnect layer 300 to be formed. This improves the fabrication precision and yield of the conductive interconnect layer. If the photoresist is too thin, the metal material formed by electroplating during the formation of the conductive interconnect layer will escape from the trenches of the photoresist (i.e., the trenches formed by exposure), easily leading to defects in the conductive interconnect layer, such as at the junction of conductive interconnect layers in adjacent trenches, resulting in circuit defects. If the photoresist is too thick, it may lead to poor contact between the seed layer and the conductive wire, or due to excessive photoresist thickness, incomplete curing or the formation of bubbles may occur during the photoresist curing process.

[0041] S500: Remove the photoresist 500 and the area of ​​the conductive seed layer 210 not covered by the conductive interconnect layer 300 to form a patterned conductive seed layer 200. See the schematic diagram for the structural representation. Figure 3 As shown. Thus, in the solar cell of the present invention, the grid stacking technology is used. The current is transmitted through the semiconductor of the solar cell to the patterned conductive seed layer 200, and then from the patterned conductive seed layer 200 through the conductive connection layer 300 to the conductive wire 400, and then along the conductive wire 400.

[0042] According to some embodiments of the present invention, with reference to Figure 3In the solar cell prepared by the above method, the orthographic projection of the conductive connection layer 300 on the cell body 100 lies within the orthographic projection of the patterned conductive seed layer 200 on the cell body 100. Specifically, the orthographic projections of the conductive connection layer 300 and the patterned conductive seed layer 200 on the cell body 100 may overlap, meaning the patterns of the conductive connection layer and the patterned conductive seed layer are identical. Alternatively, the orthographic projection of the conductive connection layer 300 on the cell body 100 may lie within the orthographic projection of the patterned conductive seed layer 200 on the cell body 100, and the area of ​​the orthographic projection of the conductive connection layer 300 on the cell body 100 may be smaller than the area of ​​the orthographic projection of the patterned conductive seed layer 200 on the cell body 100. Therefore, the conductive connection layer 300 and the patterned conductive seed layer 200 have a better contact area, which can improve the contact effect between the layer structures, increase current transmission efficiency, reduce energy loss, and reduce the risk of circuit malfunctions. The aforementioned “overlap” includes the case where the orthographic projections of the conductive connection layer 300 and the patterned conductive seed layer 200 completely overlap, as well as the case where complete overlap is impossible due to unavoidable operational errors in the process, but overall the orthographic projections of the two basically overlap.

[0043] According to some embodiments of the present invention, the photoresist 500 is first removed, and then the seed layer region to be removed is removed to obtain a patterned conductive seed layer 200.

[0044] According to some embodiments of the present invention, photoresist can be removed by cleaning with an alkaline solution.

[0045] According to some embodiments of the present invention, the areas of the conductive seed layer 210 not covered by the conductive connection layer 300 can be removed by an acid solution such as dilute sulfuric acid and / or dilute nitric acid.

[0046] As those skilled in the art will understand, during the process of removing the area of ​​the conductive seed layer 210 not covered by the conductive connection layer 300 using an acid solution, although the acid solution also corrodes the sides of the conductive connection layer to some extent, since the width of the conductive connection layer is much larger than the thickness of the seed layer, the corrosion will not have a significant impact on the conductive connection layer, that is, it will not affect the normal operation and use of the conductive connection layer.

[0047] According to an embodiment of the present invention, in this method for preparing a solar cell, a conductive connection layer is formed between the conductive wire and the patterned conductive seed layer by electroplating, thereby enabling electrical connection between the conductive wire and the conductive connection layer, and between the conductive connection layer and the patterned conductive seed layer, through contact. Moreover, the use of a low-temperature electroplating process instead of a high-temperature welding process can avoid the negative impact of high temperatures during welding on the cell. For example, using a low-temperature electroplating process to form the conductive connection layer can avoid the thermal stress caused by high-temperature processes (such as high-temperature welding), thereby helping to improve the quality and output power of the solar cell. The conductive connection layer formed by electroplating has better strength and good contact with the conductive wire and the patterned conductive seed layer, which can effectively reduce functional losses.

[0048] In another aspect, the present invention provides a solar cell prepared by the method described above. This solar cell exhibits good performance and excellent stability. Those skilled in the art will understand that this solar cell possesses all the features and advantages of the methods described above for preparing solar cells, which will not be elaborated upon further here.

[0049] In the solar cell of this invention, grid stacking technology is used. The current is transmitted through the semiconductor of the solar cell to the patterned conductive seed layer 200, and then from the patterned conductive seed layer 200 through the conductive connection layer 300 to the conductive wire 400, and then along the conductive wire 400.

[0050] According to some embodiments of the present invention, with reference to Figure 3 The conductive connection layer 300 is located between the conductive wire 400 and the patterned conductive seed layer 200. Its orthographic projection on the battery body 100 lies within the orthographic projection of the patterned conductive seed layer 200 on the battery body 100. Specifically, the orthographic projection of the conductive connection layer 300 on the battery body 100 may overlap with the orthographic projection of the patterned conductive seed layer 200 on the battery body 100, meaning that the patterns of the conductive connection layer and the patterned conductive seed layer are consistent. Alternatively, the orthographic projection of the conductive connection layer 300 on the battery body 100 may lie within the orthographic projection of the patterned conductive seed layer 200 on the battery body 100, and the area of ​​the orthographic projection of the conductive connection layer 300 on the battery body 100 may be smaller than the area of ​​the orthographic projection of the patterned conductive seed layer 200 on the battery body 100.

[0051] In another aspect, the present invention provides a photovoltaic device. According to an embodiment of the invention, the photovoltaic device includes the solar cell described above, or includes a solar cell prepared by the methods described above. Therefore, the photovoltaic device has better cell efficiency and better circuit stability. Those skilled in the art will understand that the photovoltaic device possesses all the features and advantages of the solar cell described above, which will not be elaborated further here.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a solar cell, characterized in that, include: A conductive seed layer is formed on the light-facing and / or back-facing surfaces of the battery body; A patterned photoresist is formed on the surface of the conductive seed layer away from the battery body, the photoresist exposing a portion of the surface of the conductive seed layer; Conductive wires are disposed on the surface of the photoresist away from the battery body; A conductive connection layer is formed by electroplating in the gap between the conductive seed layer exposed by the photoresist and the conductive wire. Remove the photoresist and the areas of the conductive seed layer not covered by the conductive interconnect layer.

2. The method according to claim 1, characterized in that, The conductive filament serves as the cathode, and the conductive connection layer grows from the conductive filament into the conductive seed layer until the conductive connection layer connects with the conductive seed layer.

3. The method according to claim 1, characterized in that, The conductive seed layer serves as the cathode, and the conductive connection layer grows from the conductive seed layer toward the conductive filament until the conductive connection layer is connected to the conductive filament.

4. The method according to any one of claims 1 to 3, characterized in that, The thickness of the photoresist is the same as the thickness of the conductive interconnect layer.

5. The method according to any one of claims 1 to 3, characterized in that, After the conductive wire is placed on the surface of the photoresist away from the battery body, the conductive wire and the photoresist are fixed together with adhesive.

6. The method according to any one of claims 1 to 3, characterized in that, The thickness of the conductive connection layer is 5 to 15 micrometers.

7. The method according to any one of claims 1 to 3, characterized in that, The material of the conductive connection layer includes at least one of copper and silver.

8. The method according to any one of claims 1 to 3, characterized in that, The material of the conductive seed layer includes at least one of copper, nickel, silver and tin; And / or, the material of the conductive wire includes at least one of copper, nickel, silver and tin.

9. A solar cell, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. A photovoltaic device, characterized in that, Includes the solar cell as described in claim 9.

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