Electrode films for back contact photovoltaic cells

Abstract

The invention relates to the technical field of photovoltaics, and particularly discloses an electrode film for a back contact photovoltaic cell. The electrode film for the back contact photovoltaic cell comprises a carrier film, a copper conducting layer arranged on the surface of the carrier film and a protective layer fixedly arranged on the surface of the copper conducting layer, the copper conducting layer comprises a first main part, a plurality of first branch parts which are fixedly arranged on the first main part and extend out from the first main part, a second main part and a plurality of second branch parts which are fixedly arranged on the second main part and extend out from the second main part, and the plurality of first branch parts extend from the first main part to the second main part; the plurality of second branch parts extend from the second trunk part and from the gaps of the plurality of first branch parts to the first trunk part. Therefore, the electrode film can completely replace silver to serve as an electrode of a back contact photovoltaic cell, short circuit easily caused by multiple times of printing due to the fact that the distance between positive and negative fine grid lines is too small is avoided, and the yield of the back contact photovoltaic cell applying the electrode film is improved.

Description

Technical Field

[0001] The invention relates to the field of photovoltaics, in particular to an electrode film for a back-contact photovoltaic cell. Background Art

[0002] The power generation of photovoltaic modules is proportional to the light-receiving area of ​​the cell. The front of conventional crystalline silicon cells is blocked by the main grid and welding strip, which results in some areas being unable to receive sunlight. Reducing the front shading is an effective way to increase the power generation of photovoltaic modules. The positive and negative electrodes of back-contact photovoltaic cells (such as IBC cells and MWT cells) are both located on the back of the cell, which greatly reduces the blocking of sunlight by the front of the back-contact solar cell, thereby improving the conversion efficiency of solar cells. At the same time, in order to ensure the extraction of current, the number of fine grids is greatly increased, resulting in the same problem as traditional batteries - silver consumption.

[0003] The reason why silver consumption has become a common problem for photovoltaic modules is that the installed capacity of photovoltaic modules is increasing day by day, and will enter the terawatt (TW) era from the gigawatt (GW) era. It is estimated that once photovoltaic modules enter the terawatt (TW) era, the global industrial silver will not meet the needs of the photovoltaic industry. Therefore, in order to ensure the sustainable development of the photovoltaic industry, it is imperative to use metals with larger reserves instead of silver as the metal electrode of photovoltaic cells.

[0004] In order to reduce the amount of silver consumed and ensure the photoelectric conversion efficiency, different metal pastes are used for the positive and negative fine grid lines of back-contact photovoltaic cells. However, this leads to some problems different from those of traditional cells: (1) The spacing between the positive and negative fine grid lines is too small, and multiple printings can easily cause short circuits; (2) The sintering temperature is inconsistent, and multiple sinterings will cause multiple damages to the silicon substrate, reducing the yield. Due to different preparation processes, the positive and negative fine grid lines of some back-contact photovoltaic cells are not on the same horizontal plane, and the disadvantages of screen printing paste are particularly obvious.

[0005] In view of the above problems, the traditional photovoltaic cell electrode formation method can no longer meet the development of back-contact photovoltaic cells, and a new photovoltaic cell electrode formation method needs to be developed. Summary of the invention

[0006] The present invention provides an electrode film for a back-contact photovoltaic cell, which can completely replace silver as the electrode of the back-contact photovoltaic cell, avoid the short circuit easily caused by multiple printing due to the small spacing between positive and negative fine grid lines, and is beneficial to improving the yield of the back-contact photovoltaic cell using the electrode film.

[0007] The electrode film for the back contact photovoltaic cell adopts the following technical solution: including:

[0008] Carrier film;

[0009] A copper conductive layer disposed on the surface of the carrier film; and

[0010] A protective layer is fixedly arranged and coated on the surface of the copper conductive layer; wherein the copper conductive layer comprises:

[0011] A first main trunk, and a plurality of first branches fixed to the first main trunk and extending from the first main trunk;

[0012] A second main trunk, and a plurality of second branches fixed on the second main trunk and extending from the second main trunk, a plurality of first branches extending from the first main trunk to the second main trunk, and a plurality of second branches extending from the second main trunk and extending from the gaps between the plurality of first branches to the first main trunk.

[0013] Furthermore, it also includes an ink layer, which is arranged between the carrier film and the copper conductive layer.

[0014] Furthermore, the resistivity of the ink layer is greater than 1×10-3Ω·cm.

[0015] Furthermore, the melting point of the protective layer is ≥170°C.

[0016] Furthermore, the entire surface of the copper conductive layer is fixed and covered with a protective layer.

[0017] Furthermore, the protective layer is selected from nickel, zinc, tin or an alloy containing nickel, zinc and tin.

[0018] Furthermore, the copper conductive layer includes a first main trunk and a second main trunk, the first main trunk and the second main trunk are respectively located at edge areas on opposite sides of the carrier film, a plurality of first branches are fixedly arranged on and extend from the same side of the first main trunk, and a plurality of second branches are fixedly arranged on and extend from the same side of the second main trunk.

[0019] Furthermore, the copper conductive layer includes a plurality of first main trunks and a plurality of second main trunks, a plurality of first branches are fixedly provided on both sides of the plurality of first main trunks and extend therefrom, and a plurality of second branches are fixedly provided on both sides of the plurality of second main trunks and extend therefrom.

[0020] Furthermore, the copper conductive layer includes a first main stem and a second main stem, the first main stem and the second main stem are respectively located at edge regions on opposite sides of the carrier film, a plurality of first branches are fixedly arranged on the same side of the first main stem and extend therefrom, and a plurality of second branches are fixedly arranged on the same side of the second main stem and extend therefrom; and,

[0021] The copper conductive layer includes a plurality of first main trunks and a plurality of second main trunks, a plurality of first branches are fixedly arranged on both sides of the plurality of first main trunks and extend therefrom, a plurality of second branches are fixedly arranged on both sides of the plurality of second main trunks and extend therefrom, and the plurality of first main trunks and the plurality of second main trunks are alternately distributed in the middle area of ​​the carrier film.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The N region and P region of the back-contact photovoltaic cell are both on the back and the distance between them is very small. Conventional screen printing requires printing metal slurry in the N region and P region respectively to form positive and negative metal electrodes, which often causes slurry overflow, causing short circuit of the positive and negative metal electrodes. The electrode film for the back-contact photovoltaic cell provided by the present invention, wherein the copper conductive layer is designed according to the N region and P region of the back-contact photovoltaic cell, has a high degree of matching with the back-contact photovoltaic cell, and the copper conductive layer is formed on the carrier film rather than the battery surface, which can avoid the problem of short circuit of the positive and negative metal electrodes in advance, and is conducive to improving the yield of the back-contact photovoltaic cell using the electrode film. Using copper instead of silver as the metal electrode of the back-contact photovoltaic cell can also ensure the sustainable development of the photovoltaic industry.

[0024] 2. In the prior art, copper is electroplated on the surface of silicon-based cells, and copper paste is printed on the surface of silicon-based cells to form copper metal electrodes. However, it is found that copper is more active than silver, and copper ion migration may occur, thereby damaging the silicon substrate and reducing the photoelectric conversion efficiency. The electrode film for back-contact photovoltaic cells provided by the present invention, wherein the protective layer is fixedly arranged on the surface of the copper conductive layer to form a coating on the copper conductive layer, can effectively block the migration of copper ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of an embodiment of the present invention.

[0026] Figure 2 The present invention Figure 1 Schematic diagram of the cross-section of the copper conductive layer.

[0027] Figure 3 The present invention Figure 1 A partial cross-sectional schematic diagram of .

[0028] Figure 4 The present invention Figure 1 Another partial cross-sectional schematic diagram of .

[0029] Figure 5 The present invention Figure 1 Another partial cross-sectional schematic diagram of .

[0030] Figure 6 is a schematic diagram of an embodiment of the present invention.

[0031] Figure 7 is a schematic diagram of an embodiment of the present invention.

[0032] The corresponding relationship of the numbers in the accompanying drawings is as follows:

[0033] 10-carrier film; 21-first main body; 31-first branch;

[0034] 22 - second main body; 32 - second branching portion; 40 - protective layer; 50 - ink layer. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] At present, the photoelectric conversion efficiency of crystalline silicon cells is approaching or even reaching the theoretical limit, so a 0.1% increase in the photoelectric conversion efficiency of crystalline silicon cells is already a major breakthrough. In this context, the improvement of the photoelectric conversion efficiency of crystalline silicon cells by back contact technology has given back contact photovoltaic cells a large room for development, but the traditional crystalline silicon cell electrode preparation process affects the yield of back contact photovoltaic cells and also has the problem of silver consumption, which limits the development of back contact photovoltaic cells.

[0037] In order to reduce the silver consumption, avoid the short circuit caused by too small spacing between positive and negative fine grid lines and multiple printing, and improve the yield of back-contact photovoltaic cells, the present invention provides an electrode film for back-contact photovoltaic cells, and the technical solution is as follows:

[0038] See also Figures 1 to 7 , including a carrier film 10, a copper conductive layer arranged on the surface of the carrier film 10, and a protective layer 40 fixedly arranged and coated on the surface of the copper conductive layer, the copper conductive layer includes a first main body 21 and a plurality of first branch portions 31 fixedly arranged on the first main body 21 and extending from the first main body 21, a second main body 22 and a plurality of second branch portions 32 fixedly arranged on the second main body 22 and extending from the second main body 22, the plurality of first branch portions 31 extend from the first main body 21 to the second main body 22, the plurality of second branch portions 32 extend from the second main body 22, and extend from the gaps between the plurality of first branch portions 31 to the first main body 21.

[0039] The traditional metal electrode formation process is to print the metal paste on the surface of the photovoltaic cell by screen printing, and then sinter or solidify to form an electrical connection with the crystalline silicon cell. Silver has become the preferred metal electrode due to its high conductivity and good chemical stability, which helps to improve the photoelectric conversion efficiency. However, with the development of the photovoltaic industry, the consumption of silver has increased, and the stock of silver has become lower and lower, resulting in higher and higher costs for silver, which in turn limits the development of the photovoltaic industry. Copper is a metal with a relatively large stock, and its conductivity is close to that of silver, making it the preferred choice to replace silver in photovoltaic cells. However, copper is more active than silver and is easily oxidized, resulting in reduced conductivity. It is also prone to copper ion migration. Direct sintering or solidification on the surface of photovoltaic cells will gradually damage the photovoltaic cells and cause a decrease in photoelectric conversion efficiency. Therefore, copper has not yet successfully replaced silver and become the preferred metal electrode. By adopting the above technical solution, the copper conductive layer is arranged on the surface of the carrier film 10, and the protective layer 40 is fixed and coated on the surface of the copper conductive layer, which can prevent copper from directly contacting the photovoltaic cell, thereby preventing copper ions from damaging the photovoltaic cell, and further preventing the reduction of the photoelectric conversion efficiency; at the same time, the protective layer 40 can also prevent the oxidation of the copper conductive layer, prevent the conductivity of the copper conductive layer from being reduced, and ensure the extraction of current. Since the copper conductive layer is arranged on the surface of the carrier film 10 instead of on the surface of the back contact photovoltaic cell, the short circuit of the positive and negative fine grid lines of the back contact photovoltaic cell caused by multiple printing is avoided, and the hidden cracks of the silicon wafer caused by multiple sintering or curing are avoided, which helps to greatly improve the yield of the back contact photovoltaic cell surface using the above electrode film.

[0040] The N region and P region of the back contact photovoltaic cell are both on the back side, so the metal electrodes that are electrically connected to the N region and the P region on the back side of the back contact photovoltaic cell cannot contact each other to avoid short circuit of the cell. Therefore, the copper conductive layer includes a first trunk 21 and a plurality of first branches 31 fixedly arranged on the first trunk 21 and extending from the first trunk 21, a second trunk 22 and a plurality of second branches 32 fixedly arranged on the second trunk 22 and extending from the second trunk 22, a plurality of first branches 31 extending from the first trunk 21 to the second trunk 22, a plurality of second branches 32 extending from the second trunk 22 and from the gaps between the plurality of first branches 31 to the first trunk 21, a plurality of first branches 31 are used to form an electrical connection with the N region of the back contact photovoltaic cell, and a plurality of second branches 32 are used to form an electrical connection with the N region of the back contact photovoltaic cell, so that the plurality of first branches 31 and the plurality of second branches 32 are not in direct contact with each other, and thus a short circuit of the cell will not be caused. The first main body 21 is used to guide the electrons collected from the battery by the first branches 31, and the second main body 22 is used to guide the electrons collected from the battery by the second branches 32. This is equivalent to forming the fine grid and the main grid on the existing back-contact photovoltaic cell in one step, reducing the multiple screen printing processes for forming metal electrodes on the back-contact photovoltaic cell, and also avoiding the short circuit risks caused by multiple screen printing. Replacing the fine grid and the main grid on the existing back-contact photovoltaic cell with copper also reduces the silver consumption and ensures the sustainable development of the back-contact photovoltaic cell.

[0041] In some embodiments, the carrier film 10 is selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCT (polyethylene terephthalate 1,4-cyclohexanedimethanol), PC (polycarbonate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol), PMMA (polymethyl methacrylate), COC (cycloolefin copolymer), PVA (polyvinyl alcohol), EVA (ethylene-vinyl acetate polymer), POE (ethylene-alpha olefin polymer), EMA (ethylene-methyl acrylate copolymer), EAA (ethylene-acrylic acid copolymer), EMMA (ethylene-methyl methacrylate copolymer), epoxy resin, silicone resin, PMA (acrylate), PU (polyurethane), VAE (vinyl acetate-ethylene copolymer emulsion), PVB (polyvinyl butyral) or a composite material thereof. Composite materials refer to multi-layer composite structures, such as PET and POE laminated composites to form a PET / POE double-layer composite sheet.

[0042] In certain embodiments, see Figure 1 and Figure 4The melting point of the protective layer 40 is ≥ 170°C. The function of the protective layer 40 is to prevent oxidation of the copper conductive layer and to prevent the migration of copper ions. To ensure that the protective layer 40 is effective for a long time, the copper conductive layer is not exposed. Considering that the lamination temperature of photovoltaic modules is generally around 150°C and that there may be temperature anomalies during the lamination process, the melting point of the protective layer 40 needs to be above 170°C to ensure that the protective layer 40 is effective for a long time and will not melt and deform to expose the copper conductive layer.

[0043] In certain embodiments, see Figure 3 Considering the existence of the carrier film 10, one side of the copper conductive layer has been protected, and the protective layer 40 is fixed and coated on all surfaces of the copper conductive layer except the surface facing the carrier film, thereby preventing the copper conductive layer from being oxidized and blocking the migration of copper ions. Preferably, see Figure 4 The protective layer 40 is fixedly arranged and coated on all surfaces of the copper conductive layer, that is, the surface of the copper conductive layer facing the carrier film is also fixedly arranged and coated with the protective layer 40, thereby comprehensively enhancing the protection of the copper conductive layer by the protective layer 40 and comprehensively eliminating the possibility of oxidation of the copper conductive layer and migration of copper ions.

[0044] In some embodiments, the protective layer 40 is preferably nickel, zinc, tin or an alloy containing nickel, zinc or tin. Nickel, zinc, tin or an alloy containing nickel, zinc or tin has a melting point above 170°C, has a high electrical conductivity and excellent chemical stability, can be fixed and coated on the surface of the copper conductive layer, and will not fall off easily. With a high electrical conductivity, it will not hinder the conduction of current; with excellent chemical stability, it can ensure its permanent protection of the copper conductive layer and permanent barrier to copper ions; it will not fall off easily, and can prevent delamination or peeling to lose its protection of the copper conductive layer and barrier to copper ions.

[0045] See also Figure 1 , Figure 2 and Figure 5 The electrode film for back contact photovoltaic cells provided by the present invention further includes an ink layer 50, which is disposed between the carrier film 10 and the copper conductive layer. The ink layer 50 is the basis for the copper conductive layer to be formed on the surface of the carrier film 10, and the ink layer 50 also serves to bond the copper conductive layer to the carrier film 10. In some embodiments, the copper conductive layer is formed on the surface of the carrier film 10 by electroplating. Preferably, the resistivity of the ink layer 50 is greater than 1×10 -3 Ω·cm.

[0046] In certain embodiments, see Figure 1The copper conductive layer includes a first main trunk 21 and a second main trunk 22. The first main trunk 21 and the second main trunk 22 are respectively located at the edge areas on opposite sides of the carrier film 10. A plurality of first branch portions 31 are fixedly arranged on the same side of the first main trunk 21 and extend therefrom. A plurality of second branch portions 32 are fixedly arranged on the same side of the second main trunk 22 and extend therefrom. A plurality of first branch portions 31 extend from the first main trunk 21 to the second main trunk 22. A plurality of second branch portions 32 extend from the second main trunk 22 and from the gaps between the plurality of first branch portions 31 to the first main trunk 21.

[0047] In certain embodiments, see Figure 6 The copper conductive layer includes a plurality of first main trunks 21 and a plurality of second main trunks 22. A plurality of first branch portions 31 are fixedly provided on both sides of the plurality of first main trunks 21 and extend therefrom. A plurality of second branch portions 32 are fixedly provided on both sides of the plurality of second main trunks 22 and extend therefrom. A plurality of first branch portions 31 extend from the first main trunks 21 to the second main trunks 22. A plurality of second branch portions 32 extend from the second main trunks 22 and from the gaps between the plurality of first branch portions 31 to the first main trunks 21.

[0048] In certain embodiments, see Figure 7 The copper conductive layer includes a first main body 21 and a second main body 22, the first main body 21 and the second main body 22 are respectively located at the edge areas on opposite sides of the carrier film 10, a plurality of first branches 31 are fixedly arranged on the same side of the first main body 21 and extend therefrom, and a plurality of second branches 32 are fixedly arranged on the same side of the second main body 22 and extend therefrom; and

[0049] The copper conductive layer includes a plurality of first main trunks 21 and a plurality of second main trunks 22. A plurality of first branch portions 31 are fixedly provided on both sides of the plurality of first main trunks 21 and extend therefrom. A plurality of second branch portions 32 are fixedly provided on both sides of the plurality of second main trunks 22 and extend therefrom. The plurality of first main trunks 21 and the plurality of second main trunks 22 are alternately distributed in the middle area of ​​the carrier film 10. The plurality of first branch portions 31 extend from the first main trunks 21 to the second main trunks 22. The plurality of second branch portions 32 extend from the second main trunks 22 and from the gaps between the plurality of first branch portions 31 to the first main trunks 21.

[0050] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the description should be regarded as illustrative rather than restrictive.

Claims

1. An electrode film for a back contact photovoltaic cell, Features: include: Carrier film; A copper conductive layer disposed on the surface of the carrier film; as well as, A protective layer is fixedly arranged and coated on the surface of the copper conductive layer; wherein the copper conductive layer comprises: A first main trunk, and a plurality of first branches fixed to the first main trunk and extending from the first main trunk; A second main trunk, and a plurality of second branches fixed on the second main trunk and extending from the second main trunk, a plurality of the first branches extending from the first main trunk to the second main trunk, a plurality of the second branches extending from the second main trunk, and extending from the gaps between the plurality of the first branches to the first main trunk.

2. The electrode film for a back contact photovoltaic cell according to claim 1, Features: The invention also comprises an ink layer, wherein the ink layer is arranged between the carrier film and the copper conductive layer.

3. The electrode film for a back contact photovoltaic cell according to claim 2, Features: The resistivity of the ink layer is >1×10 -3 Ω·cm.

4. The electrode film for a back contact photovoltaic cell according to claim 1, Features: The melting point of the protective layer is ≥170°C.

5. The electrode film for a back contact photovoltaic cell according to claim 4, Features: The surface of the copper conductive layer is completely fixed and covered with the protective layer.

6. The electrode film for a back contact photovoltaic cell according to claim 5, Features: The protective layer is selected from nickel, zinc, tin or an alloy containing nickel, zinc and tin.

7. The electrode film for a back contact photovoltaic cell according to any one of claims 1 to 6, Features: The copper conductive layer includes a first main trunk and a second main trunk, wherein the first main trunk and the second main trunk are respectively located at edge areas on opposite sides of the carrier film, a plurality of first branches are fixedly arranged on and extend from the same side of the first main trunk, and a plurality of second branches are fixedly arranged on and extend from the same side of the second main trunk.

8. The electrode film for a back contact photovoltaic cell according to any one of claims 1 to 6, Features: The copper conductive layer includes a plurality of first main trunks and a plurality of second main trunks, a plurality of first branch portions are fixedly disposed on both sides of the plurality of first main trunks and extend therefrom, and a plurality of second branch portions are fixedly disposed on both sides of the plurality of second main trunks and extend therefrom.

9. The electrode film for a back contact photovoltaic cell according to any one of claims 1 to 6, Features: The copper conductive layer includes a first main body and a second main body, the first main body and the second main body are respectively located at edge areas on opposite sides of the carrier film, a plurality of first branches are fixedly arranged on the same side of the first main body and extend therefrom, and a plurality of second branches are fixedly arranged on the same side of the second main body and extend therefrom; and The copper conductive layer includes a plurality of first main trunks and a plurality of second main trunks, a plurality of first branch portions are fixedly arranged on both sides of the plurality of first main trunks and extend therefrom, a plurality of second branch portions are fixedly arranged on both sides of the plurality of second main trunks and extend therefrom, and the plurality of first main trunks and the plurality of second main trunks are alternately distributed in the middle area of ​​the carrier film.

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