Bifacial heterojunction solar cell, manufacturing method and module thereof

Abstract

The application relates to a bifacial heterojunction solar cell, which comprises a cell main body and a back composite grid metal electrode arranged on the back of the cell main body; the back composite grid metal electrode comprises a metal conductive layer arranged on the back of the cell main body and an anti-oxidation soldering layer arranged on the surface of the metal conductive layer; and the cell main body is a heterojunction solar cell with a transparent conductive film. The bifacial heterojunction solar cell provided by the application adopts a metal conductive layer as a grid metal electrode on the back, greatly reduces the amount of silver paste, and reduces the electrode cost; meanwhile, the anti-oxidation soldering layer and the solder strip form good physical connection and electrical contact, the solder strip is more firmly connected with the electrode, the product reliability is improved, and the product is more suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crystalline silicon solar cells, in particular to a bifacial heterojunction solar cell, a manufacturing method and a module thereof. BACKGROUND

[0002] Under the situation of increasingly tight energy demand, the solar cell industry is developing rapidly. The heterojunction solar technology has outstanding efficiency advantage, the production efficiency has reached 24%, and the laboratory efficiency has reached more than 26%, and the further efficiency improvement potential is huge, which has attracted much attention in recent years. However, the cost of heterojunction solar technology is relatively high, which is still the main obstacle to large-scale production at present. Compared with conventional crystalline silicon solar cells, the cost is relatively high in three aspects: equipment depreciation, silver paste consumption and silicon wafer cost.

[0003] In recent years, the heterojunction cell technology has been continuously matured, and its cost has been continuously reduced. In 2019, the comprehensive cost of heterojunction cell (MBB) is about 1.18 yuan / W, which is about 35% higher than the comprehensive cost of PERC cell (MBB) of 0.87 yuan / W. Among them, the non-silicon cost is about 0.86 yuan / W, which is slightly higher than that of PERC cell, and the low-temperature silver paste cost accounts for about 22% of the non-silicon cost, which still accounts for a large proportion.

[0004] Generally speaking, the front and back electrodes of the bifacial silicon-based heterojunction solar cell (HIT, HJT or HDT) adopt low-temperature silver paste, and the silver consumption of the silver paste is about twice that of the traditional crystalline silicon cell, while the current imported low-temperature silver paste price is about 1.5 times that of high-temperature silver paste. Therefore, reducing the amount of low-temperature silver paste is one of the main means to reduce the cost of heterojunction solar cells. SUMMARY

[0005] The purpose of the present application is to provide a bifacial heterojunction solar cell, which uses a metal conductive layer as a grid-shaped metal electrode on the back surface, greatly reduces the amount of silver paste used, and reduces the cost of the electrode; at the same time, a good physical connection and electrical contact are formed between the anti-oxidation welding layer and the solder strip, the connection between the solder strip and the electrode is more firm, the product reliability is improved, and it is more suitable for large-scale production.

[0006] The purpose of the present application is to provide a manufacturing method of a bifacial heterojunction solar cell, which can manufacture a back composite grid-shaped metal electrode composed of a metal conductive layer and an anti-oxidation welding layer to replace the back low-temperature silver paste electrode, and is suitable for large-scale production.

[0007] The purpose of the present application is to provide a bifacial heterojunction solar cell module, which can reduce the amount of silver paste on the back surface and significantly reduce the cost while maintaining the back surface power generation efficiency.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A bifacial heterojunction solar cell, comprising a cell body and a back composite grid metal electrode arranged on the back of the cell body; the back composite grid metal electrode comprises a metal conductive layer arranged on the back of the cell body and an oxidation-resistant soldering layer arranged on the surface of the metal conductive layer; the cell body is a heterojunction solar cell with a transparent conductive film formed.

[0010] A manufacturing method of a bifacial heterojunction solar cell,

[0011] A metal conductive layer and an oxidation-resistant soldering layer are sequentially formed on the back of the cell body;

[0012] An ink protection layer is coated on the surface of the oxidation-resistant soldering layer to form a pattern of the back grid metal electrode;

[0013] The oxidation-resistant soldering layer and the metal conductive layer outside the ink protection layer covering area are etched by using an etching solution;

[0014] The ink protection layer is removed.

[0015] A module with the bifacial heterojunction solar cell described above, comprising a back plate, a hot melt adhesive layer, a cell group, a hot melt adhesive layer and a module panel sequentially arranged from bottom to top and forming the module by lamination; the cell group comprises two or more heterojunction solar cells and a plurality of solder strips connected between the two heterojunction solar cells; the solder strip is connected between the front electrode of the heterojunction solar cell and the back electrode of the adjacent heterojunction solar cell.

[0016] Compared with the prior art, the advantages of the present application are:

[0017] (1) The metal conductive layer is used as the grid metal electrode on the back of the heterojunction solar cell, which can reduce the use of silver paste for the back electrode of the cell, and the consumption of silver paste for a single piece can be reduced by about 60%, significantly reducing the silver paste cost of the bifacial heterojunction solar cell.

[0018] (2) The oxidation-resistant soldering layer is used as the protection layer on the top of the back composite grid metal electrode, which can easily form good physical connection and electrical contact with the solder strip, and the connection between the solder strip and the electrode is more firm, improving the product reliability and being more suitable for mass production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structure schematic diagram of the bifacial heterojunction solar cell of the present application.

[0020] Figure 2 It is a back structure schematic diagram of the bifacial heterojunction solar cell of the present application.

[0021] Figure 3 It isFigure 2 A local enlarged schematic view of the back surface of the heterojunction solar cell.

[0022] Figure 4 A manufacturing step schematic view of the heterojunction solar cell for generating electricity on both surfaces.

[0023] Figure 5 A structure schematic view of the solder strip connecting the front surface electrode of the heterojunction solar cell and the back surface electrode of the adjacent heterojunction solar cell.

[0024] Figure 6 A structure schematic view of the heterojunction solar cell module for generating electricity on both surfaces.

[0025] Figure 7 A structure schematic view of the existing heterojunction solar cell with double surface silver paste electrodes.

[0026] Figure 8 A back surface electrode welding tensile force comparison schematic view of the embodiment of the present application and the prior art. DETAILED DESCRIPTION

[0027] A heterojunction solar cell for generating electricity on both surfaces, which comprises a cell main body and a back surface composite grid metal electrode arranged on the back surface of the cell main body; the back surface composite grid metal electrode comprises a metal conductive layer arranged on the back surface of the cell main body and an oxidation-resistant welding layer arranged on the surface of the metal conductive layer; the cell main body is a heterojunction solar cell with a transparent conductive film formed thereon; and the metal conductive layer and the oxidation-resistant welding layer are formed by vacuum coating deposition.

[0028] The metal conductive layer is at least one of Cu, Ag and Al; and the oxidation-resistant welding layer is at least one of Cu, Ag, Sn, Zn, Cr, Ti, Ni, Ni alloy, ITO and WTO.

[0029] The thickness of the metal conductive layer is 100-1000 nm, and the square resistance is less than 0.2 Ω / □.

[0030] The thickness of the oxidation-resistant welding layer is 5-100 nm.

[0031] The back surface composite grid metal electrode is in a multi-main grid pattern, the width of the main grid is 0.05-5 mm, and the number of the main grid is 8-18; the width of the fine grid is 0.05-0.5 mm, and the number of the fine grid is 150-300.

[0032] The cell main body is provided with a front surface grid metal electrode; and the front surface grid metal electrode is made of low-temperature silver paste.

[0033] The number of main grids of the front side grid-shaped metal electrode is consistent with the number of main grids of the back side composite grid-shaped metal electrode; the width of the main grid of the front side grid-shaped metal electrode is 0.05-0.3mm; the width of the fine grid of the front side grid-shaped metal electrode is 0.03-0.08mm, and the number of the fine grid is 50-100.

[0034] The surface of the oxidation-resistant soldering layer is provided with a soldering reinforcing layer; the soldering reinforcing layer completely covers the main grid of the back side composite grid-shaped metal electrode, or the soldering reinforcing layer partially covers the main grid of the back side composite grid-shaped metal electrode.

[0035] The soldering reinforcing layer is tin paste or low-temperature silver paste; the tin paste is Sn or a mixed paste of Sn and at least one of Bi, Ag, In and Pb.

[0036] A manufacturing method of the aforementioned bifacial heterojunction solar cell,

[0037] A metal conductive layer and an oxidation-resistant soldering layer are sequentially formed on the back side of the cell body;

[0038] An ink protective layer is coated on the surface of the oxidation-resistant soldering layer to form a pattern of the back side grid-shaped metal electrode;

[0039] The oxidation-resistant soldering layer and the metal conductive layer outside the area covered by the ink protective layer are corroded by etching liquid;

[0040] The ink protective layer is removed.

[0041] The manufacturing method of the bifacial heterojunction solar cell further comprises manufacturing a soldering reinforcing layer on the surface of the oxidation-resistant soldering layer.

[0042] The soldering reinforcing layer is manufactured by screen printing, pad printing, inkjet printing or dispensing.

[0043] The metal conductive layer and the oxidation-resistant soldering layer are manufactured by sputtering, thermal evaporation or reactive plasma plating.

[0044] The thickness of the ink protective layer is 2-20um, and the ink protective layer is baked at a temperature of 100-200℃ or cured by UV; the ink protective layer is resistant to acid or weak alkali liquid with a PH less than 10 after being cured.

[0045] A module with the aforementioned bifacial heterojunction solar cell, which comprises a back plate, a hot melt adhesive layer, a cell group, a hot melt adhesive layer and a module panel sequentially arranged from bottom to top and forming the module by lamination; the cell group comprises two or more heterojunction solar cells and a plurality of solder strips connected between the two heterojunction solar cells; the solder strip is connected between the front side electrode of the heterojunction solar cell and the back side electrode of the adjacent heterojunction solar cell.

[0046] The solder strip is a round tin-plated copper strip with a diameter of 100-400 um and a surface tin alloy material coating thickness of 20-100 um.

[0047] The application will be described in detail below with reference to the accompanying drawings and examples:

[0048] As Figures 1 to 3 An embodiment of a bifacial heterojunction solar cell provided by the application is shown in the figure.

[0049] A bifacial heterojunction solar cell, the cell body comprising a cell substrate 1 with a passivation layer and a PN junction, and transparent conductive layers 2 and 3 arranged on the front and back of the cell substrate. The heterojunction solar cell comprises a front grid metal electrode 8 arranged on the surface of the front transparent conductive layer 2, a back composite grid metal electrode 6 comprising a metal conductive layer 4 and an oxidation-resistant solder layer 5 arranged on the surface of the back transparent conductive layer 3, and a solder enhancement layer 9 arranged on the surface of the main grid 6-1 of the back composite grid metal electrode 6. The solder enhancement layer 9 only covers part of the main grid 6-1 of the back composite grid metal electrode 6.

[0050] The passivation layer of the heterojunction solar cell substrate is composed of at least one material selected from intrinsic amorphous silicon, silicon oxide, silicon oxynitride, silicon oxycarbide, N-type doped amorphous silicon, and N-type doped polycrystalline silicon.

[0051] The PN junction of the heterojunction solar cell substrate is composed of at least one material selected from intrinsic amorphous silicon, silicon oxide, silicon oxynitride, silicon oxycarbide, P-type doped amorphous silicon, and P-type doped polycrystalline silicon.

[0052] The transparent conductive layers 2 and 3 are at least one selected from indium oxide doped with tungsten (IWO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), and gallium-doped zinc oxide (GZO), and the thickness of the transparent conductive layer is 50-150 nm.

[0053] The metal conductive layer 4 is at least one selected from Cu, Ag, and Al, with a thickness of 100-1000 nm and a square resistance of less than 0.2 Ω / □.

[0054] The oxidation-resistant solder layer 5 is at least one selected from Cu, Ag, Sn, Zn, Cr, Ti, Ni, Ni alloy, ITO, and WTO, and the oxidation-resistant solder layer 5 can be soldered with the solder strip to form good physical connection and electrical contact. The thickness of the oxidation-resistant solder layer 5 is 5-100 nm.

[0055] The back composite grid metal electrode 6 is a multi-main grid pattern, the main grid width is 0.05-5mm, the main grid quantity is 8-18; the fine grid width is 0.05-0.5mm, the fine grid quantity is 150-300.

[0056] The welding enhancement layer 9 is one of tin paste and low-temperature silver paste, the tin paste is Sn or a mixed paste of Sn and at least one of Bi, Ag, In and Pb.

[0057] The front grid metal electrode 8 is made of low-temperature silver paste, the main grid quantity is consistent with that of the back composite grid metal electrode 6, and the main grid width is 0.05-0.3mm; the fine grid width of the front grid metal electrode 8 is 0.03-0.08mm, and the fine grid quantity is 50-100.

[0058] As shown in Figure 4 It is an embodiment schematic diagram of a manufacturing method of a double-sided power generation heterojunction solar cell provided by the application.

[0059] A manufacturing method of a double-sided power generation heterojunction solar cell, a heterojunction solar cell piece substrate 1 which has been made with a passivation layer and a PN junction is selected, a transparent conductive layer 2 is plated on the front of the cell piece substrate 1, a transparent conductive layer 3, a metal conductive layer 4 and an oxidation-resistant welding layer 5 are sequentially deposited on the back of the cell piece substrate 1, an ink protection layer 7 is covered on the surface of the oxidation-resistant welding layer 5, a pattern of a back composite grid metal electrode 6 is formed, an etching liquid is used to sequentially corrode the oxidation-resistant welding layer 5 and the metal conductive layer 4 outside the ink protection layer 7 covering area and remove the ink protection layer 7, a front grid metal electrode 8 is made on the surface of the front transparent conductive layer 2, and a welding enhancement layer 9 is made on the surface of the main grid 6-1 of the back composite grid metal electrode 6.

[0060] The transparent conductive layers 2 and 3, the metal conductive layer 4 and the oxidation-resistant welding layer 5 are made by sputtering plating, thermal evaporation plating or reactive plasma plating.

[0061] The ink protection layer 7, the metal electrode 8 and the welding enhancement layer 9 are made by screen printing, pad printing, inkjet printing or dispensing.

[0062] The thickness of the ink protection layer 7 is 2-20um, and the ink protection layer 7 can be baked at a temperature of 100-200℃ or UV cured; after the ink protection layer 7 is cured, it can resist acid or weak alkali solution with a PH less than 10.

[0063] The etching liquid can be an acidic etching solution or a weak alkaline etching solution.

[0064] The method for removing the ink protection layer 7 is to soak or spray at least one of a NAOH solution, a KOH solution, an alkaline organic solution and a surfactant to remove the ink protection layer 7.

[0065] As Figure 5 and Figure 6 An embodiment of a bifacial heterojunction solar cell module provided by the present application is shown in the schematic diagram.

[0066] A bifacial heterojunction solar cell module is formed by connecting the back composite grid metal electrode 6 of the heterojunction solar cell with the front grid metal electrode 8 of the adjacent heterojunction solar cell using the solder strip 10 to form a cell group, and then laminating the module back plate 11, the hot melt adhesive layer 12, the cell group, the hot melt adhesive layer 13, and the module panel 14 in order from bottom to top to form the module.

[0067] The solar cell is a full cell or a segmented half cell for making a module.

[0068] The solder strip 10 is a round tin-plated copper strip with a diameter of 100-400 um and a surface tin alloy material coating thickness of 20-100 um.

[0069] The solder strip 10 is connected to the back composite grid metal electrode 6 of the heterojunction solar cell and the front grid metal electrode 8 of the adjacent heterojunction solar cell by soldering through a stringer, and the main grid of the front grid metal electrode 8 of the adjacent heterojunction solar cell and the main grid of the back composite grid metal electrode 6 are connected.

[0070] The solder strip 10 is connected to the back composite grid metal electrode 6 by forming a physical connection and electrical contact between the surface tin of the solder strip 10 and the oxidation-resistant soldering layer 5 of the main grid of the back composite grid metal electrode 6. When the soldering enhancement layer 9 is provided, the surface tin coating of the solder strip 10 forms a physical connection and electrical contact with the oxidation-resistant soldering layer 5 and the soldering enhancement layer 9 of the main grid of the back composite grid metal electrode 6. When the soldering enhancement layer 9 is made of tin paste, the soldering enhancement layer 9 will be integrated with the tin on the solder strip.

[0071] The hot melt adhesive layers 12 and 13 are one of EVA, POE, and Surly adhesive film, and the module panel is glass.

[0072] The module back plate is glass or a photovoltaic back plate.

[0073] The lamination temperature is 140-180℃, and the lamination time is 10-35 minutes.

[0074] As Figure 7As shown, the existing heterojunction solar cell with double-sided silver paste electrode comprises a heterojunction solar cell piece substrate d01 on which a passivation layer and a PN junction have been made, a transparent conductive layer d02 arranged on the front surface of the piece substrate, a transparent conductive layer d03 arranged on the back surface of the piece substrate, a grid-shaped metal electrode d05 arranged on the surface of the front transparent conductive layer d02, and a back silver paste electrode d04 arranged on the surface of the back transparent conductive layer d03. The comparative example of the present application is made of N-type monocrystalline silicon as the substrate. The difference between the comparative example and the embodiment of the present application is only in the manufacture of the back grid-shaped metal electrode.

[0075] In the embodiment one, the back metal electrode is made according to the present application, the metal conductive layer and the oxidation-resistant soldering layer are used as the back metal electrode, and the soldering ribbon is directly soldered with the oxidation-resistant soldering layer.

[0076] In the embodiment two, the back metal electrode is made according to the present application, the metal conductive layer and the oxidation-resistant soldering layer are used as the back metal electrode, and the silver-containing solder paste is used as the soldering enhancement layer material and partially covers the main grid of the back composite grid-shaped metal electrode.

[0077] The measurement results of the silver paste weight of the comparative example and the embodiment are as follows:

[0078]

[0079] In the manufacture of the soldering enhancement layer, the material completely or partially covering the main grid with silver component is used. In the embodiment two, the weight of the solder paste used for the main grid of the back composite grid-shaped metal electrode is 10.5 mg, which is actually the weight of the solder paste used for the soldering enhancement layer made of silver-containing solder paste and partially covering the main grid of the back composite grid-shaped metal electrode.

[0080] Meanwhile, the comparison of the soldering pull force of the back electrode of the embodiment and the comparative example is shown in the following table. Figure 8 .

[0081] In the comparative example, the back metal electrode is only made of low-temperature silver paste, the average value of the pull force of each solder joint on the back surface is about 2.3 N, the pull force of some solder ribbons is less than 1 N, and the distribution of the pull force of each solder joint is relatively discrete.

[0082] In the embodiment one, the average value of the soldering pull force of each solder joint on the back surface is about 3.2 N, the pull force of more than 90% of the solder joints is greater than 1 N, the pull force of a small amount of solder joints is less than 1 N, and the distribution of the pull force of the solder joints is improved compared with the comparative example.

[0083] In the embodiment two, the average value of the pull force of each solder joint on the back surface is about 3.5 N, the pull force of all the solder joints is greater than 1 N, and the distribution of the pull force of the solder joints is relatively concentrated. This is conducive to improving the reliability of the soldering of the module.

Claims

1. A bifacial heterojunction solar cell for generating electricity, characterized by: It includes a battery body and a back composite grid metal electrode arranged on the back of the battery body; the back composite grid metal electrode includes a metal conductive layer arranged on the back of the battery body and an oxidation-resistant soldering layer arranged on the surface of the metal conductive layer; the battery body is a heterojunction solar cell with a transparent conductive film formed; the surface of the oxidation-resistant soldering layer is provided with a soldering enhancement layer; the soldering enhancement layer partially covers the main grid of the back composite grid metal electrode; the back composite grid metal electrode is a multi-main-grid pattern, the main grid width is 0.05-5mm, the number of main grids is 8-18, the fine grid width is 0.05-0.5mm, and the number of fine grids is 150-300; the front surface of the battery body is provided with a front grid metal electrode, the number of main grids of the front grid metal electrode is consistent with that of the back composite grid metal electrode; the main grid width of the front grid metal electrode is 0.05-0.3mm; the fine grid width of the front grid metal electrode is 0.03-0.08mm, and the number of fine grids is 50-100; the front grid metal electrode is made of low-temperature silver paste; the metal conductive layer is at least one of Cu and Al; the metal conductive layer and the oxidation-resistant soldering layer are made by sputtering, thermal evaporation or reactive plasma plating.

2. The bifacial power generating heterojunction solar cell according to claim 1, characterized in that: The oxidation-resistant soldering layer is at least one of Cu, Ag, Sn, Zn, Cr, Ti, Ni, Ni alloy, ITO and WTO.

3. The bifacial power generating heterojunction solar cell according to claim 2, characterized in that: The thickness of the metal conductive layer is 100-1000nm, and the square resistance is less than 0.2Ω / □; the thickness of the oxidation-resistant soldering layer is 5-100nm.

4. The bifacial power generating heterojunction solar cell according to claim 1, wherein: The soldering enhancement layer is tin paste or low-temperature silver paste; the tin paste is Sn or a mixed paste of Sn and at least one of Bi, Ag, In and Pb.

5. A manufacturing method of the bifacial power generation heterojunction solar cell according to any one of claims 1-4, characterized in that: a metal conductive layer and an oxidation-resistant soldering layer are sequentially formed on the back of the battery body, and the metal conductive layer and the oxidation-resistant soldering layer are made by sputtering, thermal evaporation or reactive plasma plating; an ink protection layer is coated on the surface of the oxidation-resistant soldering layer to form a pattern of the back grid metal electrode; the oxidation-resistant soldering layer and the metal conductive layer outside the ink protection layer are etched by an etching liquid; a soldering enhancement layer is made on the surface of the oxidation-resistant soldering layer; the ink protection layer is removed.

6. The method of manufacturing a bifacial power-generating heterojunction solar cell according to claim 5, wherein: The soldering enhancement layer is made by screen printing, pad printing, inkjet printing or dispensing.

7. The method of producing a bifacial heterojunction solar cell of any of claims 5-6, wherein: The thickness of the ink protection layer is 2-20um, and the ink protection layer is baked at a temperature of 100-200℃ or cured by UV; the ink protection layer is resistant to acid or weak alkali liquid with a PH less than 10 after curing.

8. A module with the bifacial power generating heterojunction solar cell according to any one of claims 1 to 4, characterized in that: It includes a back plate, a hot melt adhesive layer, a battery pack, a hot melt adhesive layer and a module panel sequentially arranged from bottom to top and formed into a module by lamination; the battery pack includes two or more heterojunction solar cells and a plurality of solder strips connected between the two heterojunction solar cells; the solder strip is connected between the front electrode of the heterojunction solar cell and the back electrode of the adjacent heterojunction solar cell.

9. The bifacial power generating heterojunction solar cell module according to claim 8, characterized in that: The welding strip is a round tin-plated copper strip with a diameter of 100-400 um and a surface tin alloy material coating thickness of 20-100 um.

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