Solar cell preparation method and solar cell

Abstract

The invention discloses a solar cell preparation method and a solar cell, and the method comprises the steps: completely laying a weld-aid auxiliary layer on the surface of a transparent conductive layer, laying a metal welding wire on the surface of the weld-aid auxiliary layer, and finally removing the weld-aid auxiliary layer which is not covered by the welding wire and a grid line, and does not need to carry out the positioning and alignment of the welding wire and the grid line. The steps of battery preparation are simplified, and the preparation efficiency of the battery is improved. Furthermore, a metal welding wire is used for completely or partially replacing a traditional metal slurry grid line, the metal welding wire can be used as the grid line and also can be used as a welding strip, the preparation cost of the grid line is reduced, the conductivity and the reliability of the grid line are better, the resistance loss can be effectively reduced, and the photoelectric conversion efficiency of the battery is improved. Besides, the welding-aid auxiliary layer is arranged between the transparent conductive layer and the grid line and the metal welding wire or between the transparent conductive layer and the metal welding wire, so that the contact between the welding wire and the grid line and the substrate is effectively improved, and the reliability and the stability of the cell are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell sheets, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0002] At present, the most common grid structure of solar cells is the main grid + sub-grid structure. The sub-grid is mainly responsible for conducting photogenerated carriers from the two poles of the cell to the main grid, and the main grid then conducts these currents to the welding strip. The main grid not only plays a conductive role, but also plays a role in carrying and connecting with the welding strip. The welding strip connects the cells to form a module. The grid material usually uses photovoltaic silver paste. In order to reduce the silver consumption, low-cost conductive materials such as silver-coated copper paste, copper paste, electroplated copper and copper wire technology are also being developed and batch verified. Among them, silver-coated copper paste can directly reduce the silver content to less than 50%, greatly saving material costs. However, copper paste is currently immature in terms of electrical performance, reliability, and printability.

[0003] In addition, the existing methods for making gate lines include screen printing, laser transfer and electroplating.

[0004] Among them, screen printing is dominant. However, the screen printing process requires high precision and is prone to printing defects. In addition, the conventional grid line design blocks a lot of light, thus limiting the photoelectric conversion efficiency of the battery.

[0005] In order to solve the above problems, the prior art has proposed a variety of new metallization methods, such as: (1) stack welding process: using thinner grid lines and welding strips for stack welding, and using the slurry underneath as a welding substrate to assist welding, but this method wastes printing and slurry costs, requires high positioning accuracy, and has high equipment costs; (2) using adhesive film and special welding layers of welding strips to directly weld with TCO, but the process is complicated, not conducive to testing, and it is difficult to directly weld the welding strip with TCO; (3) 0BB technology: removing the main grid and only using the auxiliary grid and welding strip, but requiring adhesive film or resin glue to fix the welding strip, there is a risk of cold welding. However, solar cells without main grids will have the risk of cold welding and insufficient welding strength, resulting in unstable connection between battery cells, thereby affecting the output power and service life of the component. Summary of the invention

[0006] The main purpose of the present invention is to reduce the preparation cost of the grid line part of the solar cell, improve the contact between the welding wire and the substrate, and enhance the reliability and stability of the battery.

[0007] The present invention discloses a method for preparing a solar cell, the method comprising the steps of:

[0008] Laying a flux auxiliary layer on the surface of the transparent conductive layer of the solar cell;

[0009] Laying metal welding wire on the surface of the flux auxiliary layer; or laying metal welding wire and metal slurry grid line on the surface of the flux auxiliary layer;

[0010] The part of the flux auxiliary layer whose surface is not covered by the metal welding wire is removed, or the part of the flux auxiliary layer whose surface is not covered by the metal welding wire and the metal paste grid line is removed.

[0011] Furthermore, the flux auxiliary layer is deposited on the surface of the transparent conductive layer by physical vapor deposition.

[0012] Furthermore, the metal welding wire is welded on the surface of the flux auxiliary layer by using a hot pressing welding method or / and a laser welding method.

[0013] Furthermore, a reverse etching process is used to remove part of the flux auxiliary layer.

[0014] The present invention also provides a solar cell, which is prepared by the above-mentioned solar cell preparation method, and the solar cell comprises:

[0015] A transparent conductive layer;

[0016] A flux auxiliary layer laid on the surface of the transparent conductive layer;

[0017] A metal welding wire laid on the surface of the flux auxiliary layer; or a metal welding wire and a metal slurry grid line laid on the surface of the flux auxiliary layer.

[0018] Furthermore, the thickness of the flux auxiliary layer is in the range of 50-500 nm.

[0019] Furthermore, the flux auxiliary layer is a single metal layer or a metal composite layer.

[0020] Furthermore, the material of the soldering auxiliary layer includes at least one of copper, nickel, tin, indium, bismuth and lead.

[0021] Furthermore, the shape of the metal welding wire includes at least one of circular, rectangular and triangular.

[0022] Furthermore, the thickness of the metal welding wire is in the range of 40-200 μm.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] By laying a flux auxiliary layer on the surface of the transparent conductive layer, laying a metal welding wire on the surface of the flux auxiliary layer, and finally removing the flux auxiliary layer not covered by the welding wire and the gate line, there is no need to position the welding wire and the gate line, which simplifies the steps of battery preparation and improves the preparation efficiency. Furthermore, the metal welding wire is used to completely or partially replace the traditional metal slurry gate line. The metal welding wire can be used as a gate line or a welding strip, which reduces the preparation cost of the gate line, and has better conductivity and reliability, which can effectively reduce resistance loss and improve the photoelectric conversion efficiency of the battery. In addition, a flux auxiliary layer is set between the transparent conductive layer and the gate line and the metal welding wire, or between the transparent conductive layer and the metal welding wire, which effectively improves the contact between the welding wire and the gate line and the substrate, and enhances the reliability and stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a solar cell in Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the process of the solar cell manufacturing method in the second embodiment of the present invention;

[0027] Figure 3 is a schematic structural diagram of a solar cell in Embodiment 2 of the present invention;

[0028] Figure 4 is a schematic structural diagram of a solar cell in Embodiment 2 of the present invention;

[0029] Figure 5 It is a schematic diagram of the structure of a solar cell in the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] A method for preparing a solar cell and a solar cell of the present invention will be described below in conjunction with schematic diagrams, wherein preferred embodiments of the present invention are shown. It should be understood that those skilled in the art may modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0031] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0032] Embodiment 1

[0033] Please refer to Figure 1 This embodiment discloses a solar cell, which at least includes: a transparent conductive layer 1, a flux auxiliary layer 3 and a metal welding wire 4.

[0034] Specifically, the solar cell includes: a transparent conductive layer 1; a flux auxiliary layer 3 laid on the surface of the transparent conductive layer 1; a metal welding wire 4 laid on the surface of the flux auxiliary layer 3; or a metal welding wire 4 and a metal paste grid line (not shown) laid on the surface of the flux auxiliary layer 3.

[0035] In this embodiment, by laying a flux auxiliary layer 3 on the surface of the battery, the welding strength between the metal welding wire 4 and the metal paste grid line and the substrate is enhanced, making the welding more firm and reliable. At the same time, the metal welding wire 4 with lower price and better conductivity is used to completely or partially replace the main grid and sub-grid prepared by silver paste, effectively reducing resistance loss and further improving the photoelectric conversion efficiency of the battery.

[0036] Specifically, in this embodiment, the metal welding wire 4 can partially or completely replace the metal paste grid line as the secondary grid, and be welded to the main grid. This connection method reduces the manufacturing cost of the metal grid line and improves the preparation efficiency of the battery. In addition, the metal welding wire 4 can also partially or completely replace the metal paste grid line as the main grid, thereby realizing the OBB technology, that is, there is no need to use silver paste or other conductive materials to manufacture the main grid and the welding strip. The metal welding wire 4 directly assumes the function of the main grid and the welding strip. At this time, one end of the metal welding wire 4 can be directly welded to the main grid or bus bar of another battery, or welded to the junction box of the battery panel, thereby reducing the preparation cost of the metal grid line.

[0037] In this embodiment, the metal paste gate lines include metal paste gate lines such as silver paste gate lines, silver-clad copper paste gate lines and copper paste gate lines.

[0038] Furthermore, in this embodiment, the soldering auxiliary layer 3 is a nano-scale auxiliary layer with a thickness ranging from 50 to 500 nm, for example, 60 nm, 80 nm and 400 nm.

[0039] In this embodiment, the use of the nano-scale flux assisting layer 3 can save the preparation cost of the solar cell. In addition, the nano-scale flux assisting layer 3 can also provide more uniform metal coverage, which helps to form a tighter welding joint, thereby increasing the pull-off force of the welding and improving the mechanical strength of the battery.

[0040] Furthermore, in this embodiment, the flux auxiliary layer 3 is a single metal layer or a metal composite layer.

[0041] In a specific embodiment, the material of the soldering auxiliary layer 3 includes at least one of copper, nickel, tin, indium, bismuth and lead. For example, the material of the soldering auxiliary layer 3 is metallic copper, or the material of the soldering auxiliary layer 3 is a copper / tin composite layer, preferably a tin layer is laid on the surface of the TCO film layer, and a copper layer is laid on the surface of the tin layer. It is understandable that those skilled in the art can select a suitable metal material to prepare the soldering auxiliary layer 3 according to actual conditions.

[0042] In another specific embodiment, the thickness of the metal welding wire 4 is preferably 40-200 μm, for example, 40 μm, 60 μm and 100 μm.

[0043] In another specific example, the shape of the metal welding wire 4 includes at least one of a circle, a rectangle and a triangle. The circular welding wire is often used for laser welding and can provide good conductivity and welding strength. The rectangular welding wire is often used for hot pressing welding and can provide a larger welding area and welding strength.

[0044] Triangular welding wires are often used for welding of specific shapes. For example, the triangular welding surface can match the shape of the battery cell to provide better welding strength. Those skilled in the art can choose to prepare different shapes of metal welding wires 4 according to actual conditions.

[0045] Furthermore, the solar cell structure disclosed in this embodiment may be disposed on both surfaces of the substrate at the same time, or may be disposed on only one surface, which is not specifically limited herein.

[0046] Furthermore, the solar cell structure disclosed in this embodiment can be: HJT solar cell (heterojunction solar cell), TOPCON solar cell (tunnel oxide passivated contact solar cell) and BC solar cell (bonded solar cell), etc., without specific limitation here.

[0047] For example, a possible battery structure of a TOPCON battery is:

[0048] A p-type semiconductor layer, a passivation layer and an anti-reflection film layer are sequentially stacked on the front side of the substrate; a tunneling layer, an n-type polysilicon thin film layer and an anti-reflection film layer are sequentially stacked on the back side. The soldering auxiliary layer 3 is deposited on the TCO film layer on the front and back sides of the solar cell respectively, and the metal welding wire 4 is welded on the surface of the soldering auxiliary layer 3.

[0049] For another example, a possible battery structure of a HJT battery is:

[0050] The intrinsic a-Si:H film, the p-type doped a-Si:H film and the TCO film layer are sequentially stacked on the front side of the substrate; the intrinsic a-Si:H film, the n-type doped a-Si:H film and the TCO film layer are sequentially stacked on the back side. The soldering auxiliary layer 3 is deposited on the TCO film layer on the front and back sides of the solar cell respectively, and the metal welding wire 4 and the metal paste grid line are welded on the surface of the soldering auxiliary layer 3.

[0051] The following will take HJT (the size of the HTJ battery is 210mm*105mm) as an example, and the above is performed on the surface of the HJT battery.

[0052] In a specific embodiment, the above-mentioned grid line structure is laid on the back side (backlight side) of the HTJ battery, wherein the flux auxiliary layer 3 includes a Cu (metallic copper) layer with a thickness of 100nm and a Sn (metallic tin) layer with a thickness of 100nm, and 70 60um metal welding wires 4 are laid on the surface of the flux auxiliary layer 3 as auxiliary grids. There is no main grid on the back side of the battery, and the metal welding wires 4 assume the functions of the main grid and the welding strip.

[0053] In another specific embodiment, the grid line structure is laid on both the front and back sides of the HTJ battery. The soldering auxiliary layer 3 laid on both the front and back sides includes a Cu layer with a thickness of 100nm and a Sn layer with a thickness of 100nm. 70 40um metal paste grid lines and 18 60um triangular welding wires are laid on the surface of the soldering auxiliary layer 3 on the front side (facing the light) to form a secondary grid. 70 60um metal welding wires 4 are laid on the surface of the soldering auxiliary layer 3 on the back side. There is no main grid on both the front and back sides, and the metal welding wires 4 assume the functions of the main grid and the welding strip.

[0054] In another specific embodiment, the grid line structure is laid on both the front and back sides of the HTJ battery. The soldering auxiliary layer 3 includes Cu (PVD) with a thickness of 100nm and Sn with a thickness of 100nm. 70 60um triangular welding wires are laid on the front soldering auxiliary layer 3. The triangular welding wires are used to replace the auxiliary grid. There is no main grid on the front side of the HTJ battery. 70 60um welding wires are used as auxiliary grids on the back side of the HTJ battery. There is no main grid on the back side. The metal welding wire 4 takes on the functions of the main grid and welding strip.

[0055] Embodiment 2

[0056] Please refer to Figure 2 The present invention discloses a method for preparing a solar cell, and the method comprises the steps of:

[0057] S1. Laying a flux auxiliary layer 3 on the surface of the transparent conductive layer 1 of the solar cell;

[0058] S2. Laying a metal welding wire 4 on the surface of the flux auxiliary layer 3; or, laying a metal welding wire 4 and a metal slurry grid line on the surface of the flux auxiliary layer 3;

[0059] S3. Remove the portion of the soldering auxiliary layer 3 whose surface is not covered by the metal soldering wire 4 or remove the portion of the soldering auxiliary layer 3 whose surface is not covered by the metal soldering wire 4 and the metal paste grid line.

[0060] In this embodiment, by laying the flux auxiliary layer 3 on the surface of the battery, using the metal welding wire 4 to directly replace or partially replace the traditional grid line, and finally removing the flux auxiliary layer 3 other than the welding wire and the grid line, the amount of silver paste is reduced, the material cost, and the preparation time and preparation cost of the printing and sintering processes are reduced. In addition, the steps disclosed in this embodiment are to first lay the flux auxiliary layer 3, and then remove the flux auxiliary layer 3 other than the welding wire and the grid line after the metal welding wire 4 and the grid line are welded. There is no need for grid line patterning and positioning, which simplifies the steps of battery preparation and improves preparation efficiency.

[0061] For details, please refer to Figure 3 Before step S1, a semi-finished solar cell 2 is first required. The solar cell selection includes but is not limited to HJT cells, TOPCON cells and BC cells. The semi-finished solar cell 2 refers to a solar cell on which the remaining thin film layers have been stacked in sequence on the substrate, for example: a solar cell on which a passivation layer, a doping layer and a TCO layer are sequentially deposited on the surface of the substrate.

[0062] Preferably, the substrate of the solar cell preferably has a smooth surface, which is conducive to welding and further improves the firmness of the substrate and the welding wire. If the substrate surface is pyramid-shaped. It can be improved by roughening the surface of the metal welding wire 4 and adjusting the thickness of the outer low-temperature welding layer. For example: using sandpaper or shot peening to treat the copper welding wire, a tiny concave-convex structure is formed on the surface of the substrate to increase the surface roughness. Or a layer of tin solder is coated on the surface of the copper welding wire to reduce the welding temperature, so that the solder is easier to melt and fill the gap between the welding wire and the battery surface, thereby improving the welding efficiency and quality.

[0063] In step S2, please refer to Figure 4 The material of the soldering auxiliary layer 3 (e.g., copper metal) can be deposited on the surface of the solar cell substrate (e.g., TCO layer) by PVD (physical vapor deposition) technology to form a thin film. At this time, the soldering auxiliary layer 3 completely covers the surface of the transparent conductive layer 1, and has the same area as the transparent conductive layer 1.

[0064] A possible operation process is: put the cleaned solar cell (including the TCO layer) into the vacuum chamber of the PVD equipment. Heat the metal copper material to the evaporation temperature to evaporate it into gas. The evaporated metal copper gas molecules condense on the surface of the substrate to form a thin film. In this process, adjust the PVD process parameters, such as deposition rate and deposition time, to control the thickness of the flux auxiliary layer 3 to be in the range of 50-500nm.

[0065] For further information, please refer to Figure 5 In step S3, the metal welding wire 4 is welded on the surface of the flux auxiliary layer 3 by hot pressing welding or / and laser welding, or the metal welding wire 4 and the metal paste grid line are welded. If the metal welding wire 4 and the metal paste grid line need to be welded, the welding sequence is not specifically limited here. The metal welding wire 4 can be welded first, and then the metal paste grid line; or the metal paste grid line can be welded first, and then the metal welding wire 4. The welding temperature and welding time can be selected according to the actual welding wire material and the material of the flux auxiliary layer 3, and are not specifically limited here.

[0066] In a specific embodiment, the grid line structure is laid on the back side (backlight side) of the HTJ battery, and the wire is placed on the front side of the battery cell, and it is ensured to be aligned with the flux auxiliary layer 3. The metal welding wire 4 is welded to the flux auxiliary layer 3 pre-coated on the surface of the battery cell by hot pressing welding to form a secondary grid. Then, the other end of the metal welding wire 4 is welded to the battery cell to connect the battery cells into a component, wherein the welding temperature of the metal welding wire 4 is 300°C and the welding time is 2s.

[0067] In another specific embodiment, a grid line structure including a metal paste grid line and a metal welding wire 4 is laid simultaneously on the front and back sides of the HTJ battery. Specifically, the metal paste grid line is printed on the front side of the battery cell, and it is ensured that it is aligned with the soldering auxiliary layer 3. The metal paste grid line and the soldering auxiliary layer 3 are heated and pressurized using hot pressing welding equipment to melt the silver paste and form a firm welding connection with the soldering auxiliary layer 3. Then, a triangular welding wire is placed on the front side of the battery cell, and it is ensured that it is aligned with the soldering auxiliary layer 3. The triangular welding wire and the soldering auxiliary layer 3 are heated and pressurized using hot pressing welding to melt the welding wire and form a firm welding connection with the soldering auxiliary layer 3. Finally, a laser welding device is used to focus the laser beam on the contact portion of the metal paste grid line and the triangular welding wire, so that the metal paste grid line and the triangular welding wire form a firm connection, and the same operation can be used on the reverse side. Among them, the welding temperature of the metal welding wire 4 and the metal paste grid line is 300°C, and the welding time is 2s.

[0068] In step S4, after welding the metal welding wire 4 on the TCO film layer, or welding the metal welding wire 4 and the metal paste grid line, a reverse etching process is used to remove the portion of the soldering auxiliary layer that does not cover the metal welding wire 4 and the metal paste grid line, or the portion of the soldering auxiliary layer that does not cover the metal welding wire 4, so that the laying area of ​​the metal welding wire 4 and the metal paste grid line is equal to the laying area of ​​the soldering auxiliary layer 3, or the laying area of ​​the metal welding wire 4 is equal to the laying area of ​​the soldering auxiliary layer 3.

[0069] In a specific embodiment, a chemical etchant is used to dissolve the soldering auxiliary layer 3 not covered by the metal solder wire 4 or the metal solder wire 4 and the metal paste grid line. Commonly used chemical etchants include a mixed solution of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2).

[0070] A possible solar cell preparation process is as follows:

[0071] S11. Prepare a solar cell, wherein the solar cell is a semi-finished product on which a TCO film layer has been deposited.

[0072] S12. Using PVD technology, a flux auxiliary layer 3 with a thickness ranging from 50 to 500 nm is deposited on the surface of the TCO film layer, such as metal copper.

[0073] S13. Place a metal welding wire 4 (e.g., a copper welding wire) on the back of the battery cell, ensure that it is aligned with the flux assisting layer 3, use hot pressing welding or laser welding to weld the metal welding wire 4 to the flux assisting layer 3, and weld the other end of the metal welding wire 4 to the battery cell, thereby connecting the battery cells into a component.

[0074] S14. Use a chemical etchant to dissolve the flux auxiliary layer 3 that is not covered by the metal welding wire 4.

[0075] S15. Encapsulate the battery cells to form a module.

[0076] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a solar cell, characterized in that: The method comprises the steps of: Laying a flux auxiliary layer on the surface of the transparent conductive layer of the solar cell; Laying metal welding wire on the surface of the flux auxiliary layer; or laying metal welding wire and metal slurry grid line on the surface of the flux auxiliary layer; The part of the flux auxiliary layer whose surface is not covered by the metal welding wire is removed, or the part of the flux auxiliary layer whose surface is not covered by the metal welding wire and the metal paste grid line is removed.

2. The method for preparing a solar cell according to claim 1, wherein: The flux auxiliary layer is deposited on the surface of the transparent conductive layer by using a physical vapor deposition method.

3. The method for preparing a solar cell according to claim 1, wherein: The metal welding wire is welded on the surface of the flux auxiliary layer by using a hot pressing welding method or / and a laser welding method.

4. The method for preparing a solar cell according to claim 1, wherein: The part of the soldering auxiliary layer is removed by using a reverse etching process.

5. A solar cell, prepared by the solar cell preparation method according to any one of claims 1 to 4, characterized in that: The solar cell comprises: A transparent conductive layer; A flux auxiliary layer laid on the surface of the transparent conductive layer; A metal welding wire laid on the surface of the flux auxiliary layer; or a metal welding wire and a metal slurry grid line laid on the surface of the flux auxiliary layer.

6. The solar cell according to claim 5, characterized in that The thickness of the flux auxiliary layer is in the range of 50-500 nm.

7. The solar cell according to claim 5, characterized in that The soldering auxiliary layer is a single metal layer or a metal composite layer.

8. The solar cell according to claim 5, characterized in that The material of the soldering auxiliary layer includes at least one of copper, nickel, tin, indium, bismuth and lead.

9. The solar cell according to claim 5, characterized in that: The shape of the metal welding wire includes at least one of a circle, a rectangle and a triangle.

10. The solar cell according to claim 5, wherein: The thickness of the metal welding wire is in the range of 40-200 μm.

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