Photovoltaic solder strip, solar cell string, welding method of solar cell string and photovoltaic module

Abstract

The invention provides a photovoltaic solder strip, a solar cell string, a welding method of the solar cell string and a photovoltaic module, the photovoltaic solder strip comprises a solder strip base body, the solder strip base body is provided with a welding area, the outer surface of the solder strip base body is coated with a passivation layer, and the passivation layer is arranged on the outer surface of the solder strip base body. A conductive tin layer is arranged on at least part of the surface of one side, far away from the photovoltaic welding strip, of the passivation layer corresponding to the welding area, the conductive tin layer comprises fluoride or phosphide, the conductive tin layer corrodes the passivation layer after being heated to form a connecting through hole, and the conductive tin layer permeates into the connecting through hole to be in butt joint with the welding strip base body. The invention has the advantages of low cost, strong conductivity, good light collection effect and long service life.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic equipment and relates to a photovoltaic welding strip, a solar cell string and its welding method, and a photovoltaic module. Background Technology

[0002] In the process of encapsulating photovoltaic cells into photovoltaic modules, multiple cells need to be connected in series with solder ribbons to form a cell string, and then the cell strings are combined through busbars to generate power for external output. Therefore, a good connection between the solder ribbons and the cell grid lines is crucial to the quality and use of photovoltaic modules.

[0003] Currently, copper-based solder strips are commonly used. The material itself is expensive, and the thick conductive layer surrounding the copper layer increases processing costs, further raising the overall cost of the solder strip. Additionally, the aluminum used in copper-clad aluminum solder strips is prone to oxidation in air, making it impossible to form an effective solder strip using ordinary welding processes. Furthermore, it is susceptible to corrosion from moisture and the adhesive film, leading to connection failure. Poor solder strip quality reduces the reliability of the connection between the solder strip and the metal grid lines, easily causing grid detachment or incomplete soldering. Insufficient contact area at the connection points also results in poor current collection efficiency of the cell string, severely impacting the performance of photovoltaic modules.

[0004] Therefore, providing a low-cost, corrosion-resistant, and highly stable solder strip is crucial for the development of photovoltaic modules. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a photovoltaic solder ribbon, a solar cell string, a welding method thereof, and a photovoltaic module, which effectively improves the conductivity of the solder ribbon, ensures a reliable connection between the solder ribbon and the metal grid lines, and extends the service life of the photovoltaic module.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a photovoltaic solder ribbon, the photovoltaic solder ribbon comprising a solder ribbon substrate having a welding area, the outer surface of the solder ribbon substrate being covered with a passivation layer, and at least a portion of the surface of the passivation layer corresponding to the welding area on the side away from the photovoltaic solder ribbon having a conductive tin layer, the conductive tin layer comprising a fluoride or a phosphide, wherein the conductive tin layer is heated to etch the passivation layer to form a connecting via and penetrates into the connecting via to connect with the solder ribbon substrate.

[0008] This invention utilizes a passivation layer to wrap the outer surface of the solder strip substrate, which can effectively isolate moisture and adhesive film, avoid corrosion of the substrate, and improve the reliability of the solder strip. At the same time, a conductive tin layer containing fluoride or phosphide is used to corrode the passivation layer area corresponding to the welding area to form an opening, which improves the conductivity of the solder strip, ensures its high mechanical strength, and achieves a good connection with the battery cell.

[0009] As a preferred embodiment of the present invention, the area of ​​the welding zone in the welding strip substrate is 3% to 90%, for example, it can be 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0010] As a preferred embodiment of the present invention, the width of the welding area is 0.2mm to 3.0mm, for example, it can be 0.2mm, 0.5mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm, 2.0mm, 2.3mm, 2.5mm, 2.8mm or 3.0mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] The length of the welding zone is 0.2mm to 6.0mm, for example, it can be 0.2mm, 0.5mm, 1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm or 6.0mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] As a preferred embodiment of the present invention, the mass percentage of fluoride or phosphide in the conductive tin layer is 0.1% to 20%, for example, it can be 0.1%, 1%, 2%, 3%, 5%, 6%, 10%, 12%, 15%, 18% or 20%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] As a preferred embodiment of the present invention, the fluoride includes HF and / or NH4F.

[0014] The phosphide includes at least one of H3PO4, (NH4)3PO4, NH4H2PO4 or (NH4)2HPO4.

[0015] As a preferred embodiment of the present invention, the mass percentage of tin in the conductive tin layer is 20% to 97%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 97%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] As a preferred embodiment of the present invention, the diameter of the connecting through hole is 0.1mm to 6.0mm, for example, 0.1mm, 1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm or 6.0mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] As a preferred embodiment of the present invention, the area of ​​the connecting through hole is 5% to 100% of the area of ​​the welding area, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0018] As a preferred embodiment of the present invention, the substrate of the welding strip is an aluminum substrate or an aluminum-titanium substrate.

[0019] The passivation layer is an aluminum oxide layer.

[0020] As a preferred embodiment of the present invention, the welding strip substrate is flat.

[0021] The thickness of the welding strip substrate is 0.1mm to 0.4mm, for example, it can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm or 0.4mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] The width of the welding strip substrate is 0.8mm to 3.0mm, for example, it can be 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm, 2.0mm, 2.3mm, 2.5mm, 2.8mm or 3.0mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] As a preferred embodiment of the present invention, the cross-section of the welding strip substrate is triangular, the height of the welding strip substrate is <0.4mm, and the width of the welding strip substrate is >1.5mm.

[0024] As a preferred embodiment of the present invention, the cross-section of the welding strip substrate is circular, and the diameter of the welding strip substrate is >0.5mm.

[0025] In a second aspect, the present invention provides a solar cell string comprising a plurality of cell cells connected in series and / or in parallel, wherein the cell cells are provided with metal grid lines, and the metal grid lines of two adjacent cell cells are connected by the photovoltaic ribbon described in the first aspect.

[0026] Thirdly, the present invention provides a welding method for a solar cell string as described in the second aspect. The welding method includes: stacking a plurality of individual cells in a predetermined order, such that the two ends of a photovoltaic solder strip correspond to the metal grid lines of two adjacent individual cells. The welding area is brought close to the metal grid lines, and the welding area of ​​the photovoltaic solder strip is locally heated by laser to etch a passivation layer through a conductive tin layer, forming a connecting via, and penetrating into the connecting via to butt-weld the solder strip substrate. After the conductive tin layer contacts the metal grid lines, welding is performed to achieve an electrical connection between the solder strip substrate and the metal grid lines.

[0027] As a preferred embodiment of the present invention, the temperature of the local laser heating is 300℃~1500℃, for example, it can be 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃ or 1500℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] As a preferred embodiment of the present invention, the local laser heating time is 1 ns to 1 s.

[0029] As a preferred embodiment of the present invention, the wavelength of the laser used for local laser heating is 600nm~1500nm, for example, it can be 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm or 1500nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] As a preferred embodiment of the present invention, the welding temperature is 120℃~250℃, for example, it can be 120℃, 140℃, 150℃, 180℃, 200℃, 210℃, 220℃, 230℃, 240℃ or 250℃, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] As a preferred embodiment of the present invention, the welding process takes 0.1s to 10s.

[0032] Fourthly, the present invention provides a photovoltaic module, the photovoltaic module comprising the solar cell string described in the second aspect, wherein at least one end of the solar cell string is provided with at least one busbar, the busbar being connected to a photovoltaic solder strip.

[0033] As a preferred embodiment of the present invention, the busbar is provided with an opening, the opening is filled with a solder paste layer, and the solder paste layer is connected to the photovoltaic solder strip.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention provides a photovoltaic solder ribbon, a solar cell string, a welding method thereof, and a photovoltaic module. A passivation layer is coated on the outer surface of the solder ribbon substrate to prevent corrosion by moisture or adhesive film. By etching open holes and filling them with a conductive tin layer, the contact area of ​​the welding surface is increased, the conductivity of the solder ribbon is improved, good connection and reliability of the solar cells are ensured, the light collection effect is improved, and the service life of the photovoltaic module is extended. Attached Figure Description

[0036] Figure 1 A flowchart of the welding method for solar cell strings provided by the present invention.

[0037] Figure 2 This is a schematic diagram of the structure of the photovoltaic welding strip provided in Embodiment 1 of the present invention.

[0038] Figure 3 This is a schematic diagram of the connection between the photovoltaic ribbon and the metal grid wire provided in Embodiment 8 of the present invention.

[0039] Figure 4 This is a schematic diagram of the connection between the photovoltaic ribbon and the metal grid wire provided in Embodiment 9 of the present invention.

[0040] Among them, 10-photovoltaic ribbon; 1-ribbon substrate; 2-passivation layer; 3-connection via; 4-conductive tin layer; 20-metal grid line; 30-cell cell. Detailed Implementation

[0041] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] In one specific embodiment, the present invention provides a photovoltaic solder ribbon, including a solder ribbon substrate having a welding area. The outer surface of the solder ribbon substrate is covered with a passivation layer. At least a portion of the surface of the passivation layer corresponding to the welding area on the side away from the photovoltaic solder ribbon is provided with a conductive tin layer. The conductive tin layer includes a fluoride or a phosphide. After being heated, the conductive tin layer corrodes the passivation layer to form a connecting via and penetrates into the connecting via to connect with the solder ribbon substrate.

[0044] The welding strip substrate includes an aluminum welding strip substrate or an aluminum-titanium alloy welding strip substrate, which has low material cost. By increasing the cross-sectional area of ​​the welding strip substrate, lower line resistance can be obtained, resulting in increased power efficiency for the photovoltaic module. The number and area of ​​the welding zones are adjusted according to the actual cell string structure and layout.

[0045] In some embodiments, the solder ribbon substrate is flat, which can reduce the thickness of the encapsulating film. The thickness of the solder ribbon substrate is 0.1mm to 0.4mm, and the width of the solder ribbon substrate is 0.8mm to 3.0mm.

[0046] Furthermore, the cross-section of the solder ribbon substrate can be triangular, which improves the light collection performance by reflecting the light irradiated on the photovoltaic solder ribbon into the cell. The height of the solder ribbon substrate is <0.4mm and the width is >1.5mm.

[0047] Furthermore, the cross-section of the welding strip substrate can also be circular, which improves the surface light collection effect by reducing the effective light-blocking area. The diameter of the welding strip substrate is >0.5mm, preferably >0.8mm.

[0048] The passivation layer, with a thickness of 5-200 nm, encapsulates the solder ribbon substrate and effectively isolates it from moisture and adhesive film, thus protecting the solder ribbon substrate. Specifically, the passivation layer is an aluminum oxide layer.

[0049] The conductive tin layer is conductive and contains 20wt% to 97wt% tin. It also contains 0.1% to 20% fluoride or phosphide by weight. Specifically, the fluoride can be HF and / or NH4F, and the phosphide can be at least one of H3PO4, (NH4)3PO4, NH4H2PO4, or (NH4)2HPO4, making the conductive tin layer corrosive to etch the passivation layer and form a through-hole penetrating the passivation layer. As the through-hole forms, the conductive tin layer gradually penetrates into it and contacts the solder strip substrate, achieving electrical connection between the solder strip substrate and the outside environment. Specifically, the diameter of the through-hole is 0.1mm to 6.0mm, and the area of ​​the through-hole is 5% to 100% of the area of ​​the soldering area. Furthermore, the shape of the through-hole includes circular, square, or other irregular shapes.

[0050] In another specific embodiment, the present invention provides a solar cell string comprising a plurality of cell cells connected in series and / or in parallel, wherein the cell cells are provided with metal grid lines, and the metal grid lines of two adjacent cell cells are connected by a photovoltaic ribbon as described in a specific embodiment.

[0051] The battery cells include, but are not limited to, PERC cells, TOPcon cells, and BC cells. Each battery cell generally has a front and a back side, with the front side being the light-receiving surface and the back side being the back side. The location of the metal grid lines varies depending on the type of battery cell, typically on the front and / or the back.

[0052] For PERC cells, a metal grid is provided on the front side, and a localized aluminum back field is provided on the back side. In a PERC cell string, the metal grid on the front side of the preceding cell is connected to the localized aluminum back field of the following cell via photovoltaic ribbons. For TOPcon cells, metal grids of opposite polarity are provided on the front and back sides. In a TOPcon cell string, the metal grid on the front side of the preceding cell is connected to the metal grid on the back side of the following cell via photovoltaic ribbons. For BC cells, at least one passivation layer is provided on the front side, and metal grids of opposite polarity are provided on the back side. Different types of metal grids can be alternately arranged. In a BC cell string, the metal grid on the back side of the preceding cell is connected to the metal grid on the back side of the following cell via photovoltaic ribbons.

[0053] The metal grid lines typically include main grid lines and fine grid lines. The fine grid lines collect the photocurrent generated by the solar cell, while the main grid lines collect all the current collected by the fine grid lines and deliver it to the photovoltaic ribbon before it is discharged to the outside of the cell. There are fewer main grid lines and more fine grid lines, and the width of the main grid lines is usually greater than the width of the fine grid lines.

[0054] In another specific embodiment, the present invention provides a method for welding solar cell strings as described in another specific embodiment, such as... Figure 1 As shown, the welding method includes:

[0055] S1: Stack several battery cells in a preset order so that the two ends of the photovoltaic ribbon correspond to the metal grid lines of two adjacent battery cells.

[0056] The solar cell strings of this invention require multiple photovoltaic solder ribbons on both the back and / or front sides. After the individual cells are stacked, the welding area of ​​each photovoltaic solder ribbon covers the corresponding metal grid lines of two adjacent cells for precise welding. The stacking order of the cells in this invention can be full-cell series, half-cell series, or multiple-cell series-parallel connections, or staggered stacking. This invention does not impose specific limitations on this; those skilled in the art can stack the cells according to actual series-parallel connection requirements.

[0057] S2: Local laser heating of the welding area of ​​the photovoltaic welding strip.

[0058] This invention involves laser heating of the conductive tin layer corresponding to the welding area, causing the conductive tin layer to erode the passivation layer and form a connecting via that breaks through the passivation layer. Conductive tin fills the connecting via and contacts the welding area of ​​the solder ribbon substrate, while the exposed portion contacts the metal grid lines, thus achieving an electrical connection between the photovoltaic solder ribbon and the metal grid lines. Simultaneously, localized laser welding provides a localized high temperature, causing mutual diffusion between the solder ribbon substrate and the conductive tin layer, increasing the welding tensile strength.

[0059] Specifically, the localized laser heating uses a laser wavelength of 600nm~1500nm, a temperature of 300℃~1500℃, and a duration of 1ns~1s. This invention, by adjusting the process parameters of localized laser heating, ensures that the conductive tin layer can smoothly penetrate the passivation layer and reach the welding area of ​​the solder ribbon substrate, while simultaneously avoiding damage to the battery caused by overall high temperature.

[0060] S3: Bring the soldering area close to the metal grid line, and perform soldering after the conductive tin layer comes into contact with the metal grid line.

[0061] In the welding process, the photovoltaic welding strip is straightened and the welding area is aligned with the corresponding metal grid line. The welding temperature is controlled at 120℃~250℃ and the time is 0.1s~10s to ensure that the welding area is solid.

[0062] In another specific embodiment, the present invention provides a photovoltaic module, which includes a solar cell string as described in another specific embodiment. At least one end of the solar cell string is provided with at least one busbar, which is connected to a photovoltaic solder strip and is used to collect the current of a plurality of individual cells and output the current to an external junction box.

[0063] For PERC cells, busbars are located on both the front and back sides, connecting to the photovoltaic ribbons at both ends of the cell to collect current. Similarly, for TOPcon cells, busbars are located on both the front and back sides to connect to the photovoltaic ribbons at both ends of the cell for current collection. For BC cells, busbars are only located on the back side, connecting to the corresponding photovoltaic ribbons to collect current.

[0064] In some embodiments, the busbar has an opening filled with a solder paste layer that connects to the photovoltaic solder strip.

[0065] Specifically, the busbar uses an aluminum substrate, and the outer surface of the aluminum substrate is zinc-plated to form a zinc layer. Tin is then plated on the outer surface of the zinc layer to form a solder paste layer. The opening penetrates the zinc layer, allowing the solder paste to fill the opening and form mutual expansion after contacting the aluminum substrate, thus creating a bridge that enables the busbar to be electrically connected to the outside.

[0066] Example 1

[0067] This embodiment provides a photovoltaic solder ribbon, including a solder ribbon substrate 1 with multiple soldering zones, wherein the solder ribbon substrate 1 is made of an aluminum substrate. Figure 2 As shown, the solder strip substrate 1 is flat and 0.2 mm thick. The cross-section of the solder strip substrate 1 is triangular, with a height of 0.2 mm and a maximum side length of 2 mm. The outer surface of the solder strip substrate 1 is covered with an aluminum oxide passivation layer 2, which protects the internal soldering substrate 1. The area of ​​the soldering zone in the solder strip substrate 1 accounts for 60% of the total area, with a width of 1 mm and a length of 3 mm. A conductive tin layer 4 is provided on the surface of the passivation layer 2 corresponding to the soldering zone, on the side furthest from the photovoltaic solder strip. The conductive tin layer 4 includes HF, which accounts for 10% of the total mass, and tin accounts for 90% of the total mass. The conductive tin layer 4 can etch the passivation layer 2 to form a circular, 5 mm diameter connecting via 3, and penetrate into the connecting via 3 to butt-weld the solder strip substrate 1.

[0068] Example 2

[0069] This embodiment provides a photovoltaic solder ribbon, including a solder ribbon substrate 1 with multiple soldering zones, the substrate 1 being made of aluminum-titanium alloy. The solder ribbon substrate 1 is flat, 0.2 mm thick, and has a circular cross-section with a diameter of 1 mm. The outer surface of the solder ribbon substrate 1 is covered with an aluminum oxide passivation layer 2, which protects the internal soldering substrate 1. The area of ​​the soldering zones in the solder ribbon substrate accounts for 90%, with a width of 3 mm and a length of 5 mm. A conductive tin layer 4 is provided on the surface of the passivation layer 2 corresponding to the soldering zones on the side away from the photovoltaic solder ribbon. The conductive tin layer 4 includes NH4F, with a fluoride mass percentage of 5% and a tin mass percentage of 95%. The conductive tin layer 4 can etch the passivation layer 2 to form a circular connection via 3 with a diameter of 4 mm, and penetrate into the connection via 3 to butt-weld the solder ribbon substrate 1.

[0070] Example 3

[0071] This embodiment provides a photovoltaic solder ribbon, including a solder ribbon substrate with multiple soldering zones, the substrate being made of aluminum. The solder ribbon substrate is flat, 0.1 mm thick, with a angular cross-section, a height of 0.1 mm, and a maximum side length of 2.5 mm. The outer surface of the solder ribbon substrate is covered with an aluminum oxide passivation layer, which protects the internal soldering substrate. The area of ​​the soldering zones in the solder ribbon substrate accounts for 5%, with a width of 0.2 mm and a length of 0.5 mm. A conductive tin layer is provided on the surface of the passivation layer corresponding to the soldering zones on the side away from the photovoltaic solder ribbon. The conductive tin layer includes HF, with a fluoride mass percentage of 20%, and a tin mass percentage of 80%. The conductive tin layer can etch the passivation layer to form a circular connection via with a diameter of 6 mm, and penetrate into the connection via to butt-weld the solder ribbon substrate.

[0072] Example 4

[0073] This embodiment provides a photovoltaic solder ribbon, which differs from Embodiment 1 in that the fluoride content in the conductive tin layer is 25%, while the remaining structural and dimensional parameters are the same as in Embodiment 1.

[0074] Example 5

[0075] This embodiment provides a photovoltaic welding strip, which differs from Embodiment 1 in that the area of ​​the connecting through hole is 1% of the area of ​​the welding zone, while the remaining structural and dimensional parameters are the same as those in Embodiment 1.

[0076] Example 6

[0077] This embodiment provides a photovoltaic welding ribbon, which differs from Embodiment 1 in that the area of ​​the welding zone in the welding ribbon substrate accounts for 1%, while the remaining structural and dimensional parameters are the same as in Embodiment 1.

[0078] Example 7

[0079] This embodiment provides a photovoltaic solder ribbon, which differs from Embodiment 1 in that the conductive tin layer contains H3PO4, which accounts for 10% of the mass, while the remaining structural and dimensional parameters are the same as those in Embodiment 1.

[0080] Comparative Example 1

[0081] This comparative example provides a photovoltaic solder ribbon, which differs from Example 1 in that the conductive tin layer is made of conventional tin material and does not contain fluorides, while the remaining structure and dimensional parameters are the same as in Example 1.

[0082] Comparative Example 2

[0083] This comparative example provides a photovoltaic solder ribbon, including a solder ribbon substrate with multiple soldering zones. The solder ribbon substrate is made of copper-clad aluminum, and a conventional conductive tin layer is provided on the outer surface of the soldering zones. Its shape and size parameters are the same as those in Example 1.

[0084] Example 8

[0085] This embodiment provides a solar cell string and its welding method. The solar cell includes multiple cell units 30 connected in series. Each cell unit 30 has two metal grid lines 20 disposed on its back and front sides, respectively. Figure 3 As shown, the front metal grid line 20 of one battery cell 30 and the back metal grid line 20 of another battery cell 30 are connected by a photovoltaic welding ribbon 10 provided in Embodiment 1.

[0086] The welding method for solar cell strings in this embodiment includes the following steps:

[0087] Multiple battery cells 30 are stacked in a preset order, such that the two ends of each photovoltaic ribbon 10 cover the metal grid lines 20 of two adjacent battery cells 30 respectively.

[0088] The welding area is brought close to the metal grid line 20, and the welding area of ​​the photovoltaic solder ribbon 10 is locally heated by laser. The wavelength of the laser used is 800nm, the temperature is 800℃, and the time is 0.5s. This causes the conductive tin layer 4 to etch the passivation layer 2 to form a connecting via 3, and penetrates into the connecting via 3 to butt weld the solder ribbon substrate 1.

[0089] After the conductive tin layer 4 comes into contact with the metal gate line 20, a soldering process is performed at a temperature of 150°C for 1 second to achieve electrical connection between the solder strip substrate 1 and the metal gate line 20.

[0090] Example 9

[0091] This embodiment provides a solar cell string and its welding method, which differs from Embodiment 8 in that: the solar cell includes multiple battery cells 30 connected in series, the front side of each battery cell 30 is provided with an aluminum oxide layer, and the back side is provided with multiple metal grid lines 20, such as... Figure 4As shown, the back metal grid line 20 of one battery cell 30 is connected to the back metal grid line 20 of another battery cell 30 by a photovoltaic solder ribbon 10 provided in Embodiment 1.

[0092] The preparation method in this embodiment is the same as that in Example 8.

[0093] Example 10

[0094] This embodiment provides a solar cell string and its welding method. The solar cell includes multiple cells connected in series. Two metal grids are respectively provided on the back and front of the cell. The metal grid on the front of one cell is connected to the metal grid on the back of another cell by a photovoltaic welding ribbon provided in Embodiment 2.

[0095] The welding method for solar cell strings in this embodiment includes the following steps:

[0096] Multiple battery cells are stacked in a preset order, so that the two ends of each photovoltaic ribbon cover the metal grid lines of the two adjacent battery cells respectively.

[0097] The welding area is brought close to the metal grid line, and the welding area of ​​the photovoltaic solder ribbon is locally heated by laser. The laser wavelength is 600nm, the temperature is 300℃, and the time is 1s. This causes the conductive tin layer to etch the passivation layer to form a connection via and penetrate into the connection via to butt weld the solder ribbon substrate.

[0098] After the conductive tin layer comes into contact with the metal gate wire, it is soldered at a temperature of 250°C for 0.5 seconds to achieve electrical connection between the solder strip substrate and the metal gate wire.

[0099] Example 11

[0100] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 10 is that the solar cell includes multiple cells connected in series. The front side of the cell is provided with an aluminum oxide layer, and the back side is provided with multiple metal grid lines. The back metal grid lines of one cell are connected to the back metal grid lines of another cell through a photovoltaic welding ribbon provided in Embodiment 2.

[0101] The preparation method in this embodiment is the same as that in Example 10.

[0102] Example 12

[0103] This embodiment provides a solar cell string and its welding method. The solar cell includes multiple cells connected in series. Two metal grids are respectively provided on the back and front of the cell. The metal grid on the front of one cell is connected to the metal grid on the back of another cell by a photovoltaic welding ribbon provided in Embodiment 3.

[0104] The welding method for solar cell strings in this embodiment includes the following steps:

[0105] Multiple battery cells are stacked in a preset order, so that the two ends of each photovoltaic ribbon cover the metal grid lines of the two adjacent battery cells respectively.

[0106] The welding area is brought close to the metal grid line, and the welding area of ​​the photovoltaic solder ribbon is locally heated by laser. The laser wavelength is 1500nm, the temperature is 1200℃, and the time is 1s. This causes the conductive tin layer to etch the passivation layer to form a connection via and penetrate into the connection via to butt weld the solder ribbon substrate.

[0107] After the conductive tin layer comes into contact with the metal gate wire, it is soldered at a temperature of 120°C for 1 second to achieve electrical connection between the solder strip substrate and the metal gate wire.

[0108] Example 13

[0109] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 12 is that the solar cell includes multiple cells connected in series. The front side of the cell is provided with an aluminum oxide layer, and the back side is provided with multiple metal grid lines. The back metal grid lines of one cell are connected to the back metal grid lines of another cell through a photovoltaic welding ribbon provided in Embodiment 3.

[0110] The preparation method in this embodiment is the same as that in Example 12.

[0111] Example 14

[0112] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the back metal grid lines of one cell are connected to the back metal grid lines of another cell through a photovoltaic welding ribbon provided in Embodiment 7.

[0113] The preparation method in this embodiment is the same as that in Example 8.

[0114] Example 15

[0115] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 14 is that the solar cell includes multiple cells connected in series. The front side of the cell is provided with an aluminum oxide layer, and the back side is provided with multiple metal grid lines. The back metal grid lines of one cell are connected to the back metal grid lines of another cell through a photovoltaic welding ribbon provided in Embodiment 7.

[0116] The preparation method in this embodiment is the same as that in Example 14.

[0117] The photovoltaic solder ribbons used in embodiments 8-15 of the present invention have low material costs and can effectively prevent corrosion from moisture and adhesive film. At the same time, the use of an etchable passivation layer conductive tin layer allows the solder ribbon substrate and the tin layer to form mutual expansion, which improves the welding strength and welding success rate. In addition, the conductivity of the photovoltaic solder ribbon is enhanced, ensuring good electrical connection.

[0118] Example 16

[0119] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the metal grid lines of two individual cells are connected by the photovoltaic welding ribbon provided in Embodiment 4. The rest of the structure and welding method are the same as in Embodiment 8.

[0120] In this embodiment, the conductive tin layer of the photovoltaic solder ribbon has too much fluoride, which can easily cause excessive corrosion of the passivation layer and damage to the solder ribbon substrate.

[0121] Example 17

[0122] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 9 is that the metal grid lines of two individual cells are connected by the photovoltaic welding ribbon provided in Embodiment 4. The rest of the structure and welding method are the same as in Embodiment 9.

[0123] In this embodiment, the conductive tin layer of the photovoltaic solder ribbon has too much fluoride, which can easily cause excessive corrosion of the passivation layer and damage to the solder ribbon substrate.

[0124] Example 18

[0125] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the metal grid lines of two individual cells are connected by the photovoltaic welding ribbon provided in Embodiment 5. The rest of the structure and welding method are the same as in Embodiment 8.

[0126] In this embodiment, the area of ​​the connecting via formed in the photovoltaic solder ribbon is too small, and the amount of conductive tin filled is too small. This makes it impossible to effectively form mutual expansion with the solder ribbon substrate, which reduces conductivity and affects the electrical connection between the photovoltaic solder ribbon and the metal grid line.

[0127] Example 19

[0128] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the metal grid lines of two individual cells are connected by the photovoltaic welding ribbon provided in Embodiment 6. The rest of the structure and welding method are the same as in Embodiment 8.

[0129] In this embodiment, the area of ​​the welding zone formed in the photovoltaic welding ribbon is too small, resulting in unstable welding and easy detachment.

[0130] Example 20

[0131] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the laser wavelength used for laser heating during the welding process is 500nm, while the rest of the structure and welding method are the same as in Embodiment 8.

[0132] Example 21

[0133] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the laser heating temperature is 200°C during the welding process, while the rest of the structure and welding method are the same as in Embodiment 8.

[0134] Example 22

[0135] This embodiment provides a solar cell string and its welding method. The difference from Embodiment 8 is that the laser heating temperature is 1800℃ during the welding process, while the rest of the structure and welding method are the same as in Embodiment 8.

[0136] In Example 21, the laser heating temperature was too low, preventing the fluoride in the conductive tin layer from fully penetrating the passivation layer, thus worsening the contact between the fluoride and the solder ribbon substrate and reducing conductivity. In Example 22, the laser heating temperature was too high, leading to increased energy consumption and potential damage to individual battery cells in the high-temperature environment.

[0137] Comparative Example 3

[0138] This comparative example provides a solar cell string and its welding method, which differs from Example 8 in that the metal grid lines of two individual cells are connected by the photovoltaic ribbon provided in Comparative Example 1. Furthermore, no laser heating step is performed during the fabrication process.

[0139] Comparative Example 4

[0140] This comparative example provides a solar cell string and its welding method, which differs from Example 9 in that the metal grid lines of two individual cells are connected by the photovoltaic ribbon provided in Comparative Example 1. Furthermore, no laser heating step is performed during the fabrication process.

[0141] In Comparative Examples 3 and 4, the photovoltaic solder ribbon used is isolated from the conductive tin layer by a passivation layer, which prevents effective contact and significantly reduces conductivity.

[0142] Comparative Example 5

[0143] This comparative example provides a solar cell string and its welding method, which differs from Example 8 in that the metal grid lines of two individual cells are connected by the photovoltaic ribbon provided in Comparative Example 2. Furthermore, no laser heating step is performed during the fabrication process.

[0144] Comparative Example 6

[0145] This comparative example provides a solar cell string and its welding method, which differs from Example 9 in that the metal grid lines of two individual cells are connected by the photovoltaic ribbon provided in Comparative Example 2. Furthermore, no laser heating step is performed during the fabrication process.

[0146] Comparative Examples 5 and 6 used copper-clad aluminum as the base material for their photovoltaic solder ribbons. Although this ensured the conductivity of the solder ribbons, the high price of copper increased the material cost. In addition, the addition of an extra copper cladding process during the preparation of the photovoltaic solder ribbons not only increased the difficulty of preparation but also further increased the preparation cost.

[0147] Application Example 1

[0148] This application example provides a photovoltaic module, including the solar cell string provided in Example 8. Two busbars are respectively disposed on the front and back of the solar cell string. The busbars are made of an aluminum substrate, and the outer surface of the aluminum substrate is zinc-plated to form a zinc layer. The busbars have openings that penetrate the zinc layer, and the openings are filled with solder paste to ensure contact between the solder paste layer and the aluminum substrate. Photovoltaic solder strips are soldered to the solder paste layer of the busbars to collect the current from the solar cell string and output the current to an external junction box.

[0149] Application Example 2

[0150] This application example provides a photovoltaic module, including the solar cell string provided in Example 9. Two busbars are disposed on the back of the solar cell string. The busbars are made of an aluminum substrate, and the outer surface of the aluminum substrate is zinc-plated to form a zinc layer. The busbars have openings that penetrate the zinc layer, and the openings are filled with solder paste to ensure contact between the solder paste layer and the aluminum substrate. Photovoltaic solder strips are soldered to the solder paste layer of the busbars to collect the current from the solar cell string and output the current to an external junction box.

[0151] Application Example 3

[0152] This application example provides a photovoltaic module, including the solar cell string provided in Example 10, with two busbars at each end of the solar cell string. The busbars are made of an aluminum substrate, and the outer surface of the aluminum substrate is zinc-plated to form a zinc layer. The busbars have openings that penetrate the zinc layer, and the openings are filled with solder paste to ensure contact between the solder paste and the aluminum substrate. Photovoltaic solder strips are soldered to the solder paste layer of the busbars to collect the current from the solar cell string and output the current to an external junction box.

[0153] Application Example 4

[0154] This application example provides a photovoltaic module, including the solar cell string provided in Example 11, with two busbars at each end of the solar cell string. The busbars are made of an aluminum substrate, and the outer surface of the aluminum substrate is zinc-plated to form a zinc layer. The busbars have openings that penetrate the zinc layer, and the openings are filled with solder paste to ensure contact between the solder paste and the aluminum substrate. Photovoltaic solder strips are soldered to the solder paste layer of the busbars to collect the current from the solar cell string and output the current to an external junction box.

[0155] Application Example 5

[0156] This application example provides a photovoltaic module that differs from Application Example 1 in that it uses the solar cell string provided in Example 14, while the rest of the structure is the same as in Example 1.

[0157] Comparative Application Example 1

[0158] This comparative application example provides a photovoltaic module that differs from Application Example 1 in that the busbar uses a copper-clad aluminum substrate and has no openings on its surface; the rest of the structure is the same as in Application Example 1.

[0159] Comparative Application Example 2

[0160] This comparative application example provides a photovoltaic module that differs from Application Example 2 in that the busbar uses a copper-clad aluminum substrate and has no openings on its surface; the rest of the structure is the same as in Application Example 1.

[0161] Compared to the solar photovoltaic module in Application Example 1, the busbars used in Application Examples 1 and 2 have higher material costs and lower conductivity, resulting in poor overall electrical connection performance.

[0162] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A photovoltaic welding strip, characterized in that, The photovoltaic ribbon includes a ribbon substrate with a welding area. The outer surface of the ribbon substrate is covered with a passivation layer. At least a portion of the surface of the passivation layer corresponding to the welding area on the side away from the photovoltaic ribbon is provided with a conductive tin layer. The conductive tin layer includes fluoride or phosphide. After being heated, the conductive tin layer corrodes the passivation layer to form a connecting via and penetrates into the connecting via to connect with the ribbon substrate.

2. The photovoltaic welding strip according to claim 1, characterized in that, In the weld strip substrate, the area of ​​the welded zone accounts for 3% to 90%.

3. The photovoltaic welding strip according to claim 1 or 2, characterized in that, The width of the welding area is 0.2mm to 3.0mm, and the length of the welding area is 0.2mm to 6.0mm.

4. The photovoltaic welding strip according to claim 1, characterized in that, The mass percentage of fluoride or phosphide in the conductive tin layer is 0.1% to 20%.

5. The photovoltaic welding strip according to claim 1 or 4, characterized in that, The fluorides include HF and / or NH4F; The phosphide includes at least one of H3PO4, (NH4)3PO4, NH4H2PO4 or (NH4)2HPO4.

6. The photovoltaic welding strip according to claim 1, characterized in that, The tin content in the conductive tin layer is 20% to 97% by mass.

7. The photovoltaic welding strip according to claim 1, characterized in that, The area of ​​the connecting through hole is 5% to 100% of the area of ​​the welding area.

8. The photovoltaic welding strip according to claim 1 or 7, characterized in that, The diameter of the connecting through hole is 0.1mm to 6.0mm.

9. The photovoltaic welding strip according to claim 1, characterized in that, The substrate of the welding strip is an aluminum substrate or an aluminum-titanium substrate; The passivation layer includes an aluminum oxide layer.

10. The photovoltaic welding strip according to claim 1, characterized in that, The welding strip substrate is flat; The thickness of the welding strip substrate is 0.1mm to 0.4mm, and the width of the welding strip substrate is 0.8mm to 3.0mm.

11. The photovoltaic welding strip according to claim 1, characterized in that, The cross-section of the welding strip substrate is triangular, the height of the welding strip substrate is <0.4mm, and the width of the welding strip substrate is >1.5mm.

12. The photovoltaic welding strip according to claim 1, characterized in that, The cross-section of the welding strip substrate is circular, and the diameter of the welding strip substrate is >0.5mm.

13. A solar cell string, comprising a plurality of individual cells connected in series and / or in parallel, characterized in that, The battery cell is provided with metal grid lines, and the metal grid lines of two adjacent battery cells are connected by the photovoltaic welding strip as described in any one of claims 1-12.

14. A welding method for a solar cell string according to claim 13, characterized in that, The welding method includes: Several individual cells are stacked in a preset order, so that the two ends of the photovoltaic ribbon correspond to the metal grid lines of two adjacent individual cells respectively. The welding area is brought close to the metal grid line, and the welding area of ​​the photovoltaic solder ribbon is locally laser heated to etch the passivation layer of the conductive tin layer to form a connection through hole, and penetrate into the connection through hole to butt weld the solder ribbon substrate. After the conductive tin layer comes into contact with the metal gate line, a soldering process is performed to achieve electrical connection between the solder strip substrate and the metal gate line.

15. The welding method according to claim 14, characterized in that, The temperature of the local laser heating is 300℃~1500℃.

16. The welding method according to claim 14 or 15, characterized in that, The local laser heating time is 1 ns to 1 s.

17. The welding method according to claim 14, characterized in that, The wavelength of the laser used for the local laser heating is 600nm~1500nm.

18. The welding method according to claim 14, characterized in that, The welding temperature is 120℃~250℃.

19. The welding method according to claim 14, characterized in that, The welding process takes 0.1s to 10s.

20. A photovoltaic module, characterized in that, The photovoltaic module includes the solar cell string of claim 13, wherein at least one end of the solar cell string is provided with at least one busbar, and the busbar is connected to the photovoltaic ribbon.

21. The photovoltaic module according to claim 20, characterized in that, The busbar has an opening, the opening is filled with a solder paste layer, and the solder paste layer is connected to the photovoltaic solder strip.

Images