Photovoltaic active welding strip, main-grid-free photovoltaic module and preparation method of main-grid-free photovoltaic module

Abstract

The invention provides a photovoltaic active welding strip, a main-grid-free photovoltaic module and a preparation method thereof, active welding flux contained in the photovoltaic active welding strip comprises a specially selected matrix and a first component, the wetting effect of the matrix can be improved by adding the first component, the wetting performance of the welding flux is improved, the improvement of the welding strength is facilitated, and in addition, the main-grid-free photovoltaic module has the advantages that the main-grid-free photovoltaic module is not damaged. In the welding process, beta-Sn phase / In phase / Zn phase grains can be strengthened by adding the first component, Ti, Zn and Mg are promoted to be diffused to a welding interface, then the welding strength is greatly improved, the photovoltaic active welding strip can be directly welded to auxiliary grids on the surface of a battery piece and non-auxiliary grid positions between the auxiliary grids, an adhesive film or glue does not need to be used for auxiliary fixing in the welding process, scaling powder can not be used, and the welding efficiency is improved. The welding tension between the whole welding strip and a battery piece is large after welding, the grid breaking risk of the module can be reduced, and the reliability of the module is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a photovoltaic active welding strip, a non-auxiliary fixed direct welding main grid-free photovoltaic component prepared by using the photovoltaic active welding strip, and a method for preparing the component. Background Art

[0002] With the development of crystalline silicon cells, cost reduction and efficiency improvement are eternal topics. The grid lines of photovoltaic cells have gradually developed from busbars to busbarless technology. Busbarless technology does not print the busbar during the screen printing stage, which reduces the consumption of silver paste. At the same time, it uses welding strips to directly conduct current and reduce shading, which can improve efficiency compared to busbar components. There are two existing busbarless technology routes: welding first and welding later.

[0003] First welding means that the photovoltaic cell is first welded with a welding strip at the welding machine end, and then the route of the welding strip is fixed by glue dispensing. The problem is: on the one hand, since the main grid-free technology does not print the main grid at the battery end, and the secondary grid serves to collect current, its welding tension with the welding strip is poor; on the other hand, the secondary grid line is thin and the contact area with the welding strip is small, which is not conducive to welding. Although the above defects can be alleviated by improving the grid line pattern of the battery to alleviate the problem of poor welding force, this method always requires flux, and further glue application is required after welding to assist fixation, which not only requires a new glue application device at the welding machine end, but also increases the process steps and material costs.

[0004] Post-welding includes film wire pre-combination technology, film coating technology and adhesive technology. Post-welding refers to first assisting the fixation of low-temperature solder tape at the welding machine end, and then using the lamination temperature and pressure to weld the low-temperature solder tape to the battery cell during lamination. The problem is: post-welding technology requires the solder tape to be pre-fixed with adhesive film or glue before lamination, and requires pre-cross-linked modified adhesive film. Pre-cross-linked modified adhesive film is not only costly but also increases the overall weight of the component adhesive film package. In addition, there may be a risk of poor compatibility with the packaging adhesive film. This post-welding process can only be judged as bad through electroluminescence test (EL) after lamination, making rework difficult, and the welding effect of lamination welding cannot be directly judged. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a photovoltaic active welding strip, a direct-welded main-grid-free photovoltaic module prepared by using the photovoltaic active welding strip and a method for preparing the module. Through the special component design of the photovoltaic active welding strip, the photovoltaic active welding strip can be directly welded to the secondary grid on the surface of the battery cell and the non-secondary grid position between the secondary grids. The welding process does not require auxiliary fixation and does not require the use of flux. After welding, the entire welding strip and the battery cell have a large welding tension, which can reduce the risk of component grid breakage and enhance the reliability of the component.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a photovoltaic active solder strip, comprising a solder strip core and a coating layer wrapped around the outer periphery of the solder strip core, wherein the coating layer is an active solder, and the active solder comprises a matrix and a first component;

[0008] The matrix is ​​selected from Sn-Ti, Sn-Ti-In, Sn-Ti-Ag, Sn-Ti-Bi, Sn-Ti-Pb, Sn-Ti-Ag-In, Sn-Ti-Ag-Pb, Sn-Ti-Ag-Bi, Sn-Ti-Ag-Bi-Pb, Sn-Ti-Ga -X, Sn-Ti-Ag-Ga-X, Sn-Ti-Bi-Ga-X, Sn-Ti-Pb-Ga-X, Sn-Ti-Ag-Pb-Ga-X, Sn-Ti-Ag-Bi-Ga-X, Sn-Ti-Bi-Pb-Ga-X, Sn-Ti-Ag-Bi- Any at least one of Pb-Ga-X, Sn-Zn, Sn-Zn-Sb, Sn-Zn-Sb-Pb, Zn-Ag, Zn-Ag-Ti, Sn-Mg, Sn-Mg-In, Sn-Mg-Ag, Sn-Mg-Bi, Sn-Mg-Pb, Sn-Mg-Bi-In, Sn-Mg-Zn, Sn-Mg-Zn-In, Sn-Mg-Zn-Bi, Sn-Mg-Zn-Bi-Ag, Sn-Mg-Zn-Bi-In, In-Mg, In-Mg-Ag, and In-Mg-Zn, wherein X is Ce or La or Ce-La;

[0009] The first component is selected from any at least one of NiFe2O4, NiCo2O4, CoFe2O4, BaTiO3, SrTiO3, CaTiO3, MgTiO3, and POSS.

[0010] In the present technical solution, the so-called "POSS" refers to polyhedral oligomericsilsesquioxanes. The photovoltaic active solder strip provided by the present technical solution includes an active solder, which includes a specially selected matrix and a first component, wherein the addition of the first component can improve the wetting effect of the matrix and the wetting performance of the solder, and the improvement of the wetting performance is beneficial to the improvement of the welding strength. In addition, during the welding process, the first component can strengthen the β-Sn phase / In phase / Zn phase grains, promote the diffusion of Ti, Zn, and Mg to the welding interface, and thus greatly improve the welding strength. Moreover, in the case where the solder matrix contains Ga, the first component can also interact with Ga in the matrix to further enhance the wetting effect of Ga, thereby further increasing the wetting performance of the matrix solder.

[0011] It should be noted here that the experimental data provided in the embodiments of the present invention specification can confirm that the addition of the first components NiFe2O4, BaTiO3, and POSS can help improve the welding strength, and among the other first components, SrTiO3, CaTiO3, and MgTiO3 are titanates of the same family as BaTiO3, and NiCo2O4 and CoFe2O4 are acid salts of the same family as NiFe2O4. Therefore, the mechanism of action with the matrix in the solder is the same as that of BaTiO3 and NiFe2O4, and therefore has the same effect of improving the welding strength.

[0012] Preferably, the matrix accounts for 55wt% to 99.99wt% of the active solder content;

[0013] The matrix is ​​selected from any at least one of Sn-Ti-Ag-Bi-Ga-X, Sn-Ti-Bi-Ga-X, Sn-Ti-Ag-Ga-X, Sn-Zn-Sb-Pb, and Sn-Mg-Pb;

[0014] When the matrix contains Sn, the content of Sn in the matrix accounts for 20wt%~99.9wt% of the matrix content, and the content of Ti or Zn or Mg accounts for 0.01wt%~20wt% of the matrix content.

[0015] In the present technical solution, more preferably, the content of Sn in the matrix accounts for 40wt%~60wt% of the matrix content, and the content of Ti or Zn or Mg accounts for 1wt%~5wt% of the matrix content.

[0016] Preferably, the first component is selected from any at least one of NiFe2O4, BaTiO3, and POSS; the first component accounts for 0.01wt% to 5wt% of the active solder content.

[0017] In the present technical solution, more preferably, the first component accounts for 1wt%~3wt% of the active solder content.

[0018] Preferably, the active solder further comprises a second component and / or a third component, the second component is selected from any at least one of Zr, V, Nb, and Hf, and the third component is selected from any at least one of Cu, Al, Ni, Cr, Mo, and Ta;

[0019] The second component accounts for 0wt% to 20wt% of the active solder content, and the third component accounts for 0wt% to 20wt% of the active solder content.

[0020] In the present technical solution, more preferably, the second component accounts for 1wt%~5wt% of the active solder content, and the third component accounts for 1wt%~5wt% of the active solder content. In the present technical solution, the addition of the second component can assist Ti, Zn, and Mg in diffusing to the welding interface, and the addition of the third component can improve the thermal stability of the solder, thereby further improving the welding strength.

[0021] Preferably, the base material of the welding ribbon core is selected from any at least one of the following materials: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and alloys containing any of the foregoing materials; or

[0022] The base material of the welding ribbon core is selected from any at least two of the following materials: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and alloys containing any of the foregoing materials, and the structure of the welding ribbon core is a core-shell coating structure or a stacked structure composed of the selected materials.

[0023] In the present technical solution, the so-called core-shell coating structure refers to the concentric structure morphology formed by the base material of the welding tape core, in which a certain substance is the core and other substances are successively wrapped as shells. For example, when the base material of the welding tape core is selected from two substances, one of the substances is the core and the other substance is the shell to wrap the core substance, that is, a core-shell coating structure is formed, and when the base material of the welding tape core is selected from three substances, substance 1 is the core, substance 2 is the shell to wrap substance 1, and substance 3 is further the shell to wrap substance 2, that is, a core-shell coating structure is formed. The so-called stacked structure refers to the structure morphology in which the base material of the welding tape core is stacked layer by layer. For example, when the base material of the welding tape core is selected from two substances, one of the substances forms the lower layer, and the other substance forms the upper layer superimposed on the lower layer substance, thereby forming a stacked structure, and when the base material of the welding tape core is selected from three substances, substance 1 is the first layer, substance 2 is the second layer superimposed on the first layer of substance 1, and substance 3 is the third layer superimposed on the second layer of substance 2, thereby forming a stacked structure.

[0024] Preferably, the cross-sectional width of the photovoltaic active welding strip is 50-500 μm, and the cross-sectional thickness is 50-500 μm; the thickness of the coating layer is 1-100 μm.

[0025] The cross-sectional shape of the active welding strip is not limited in the present technical solution, and it can be any one or more combinations of circular, elliptical, triangular, rectangular, trapezoidal, and flat. As a further preferred embodiment, the cross-sectional width of the photovoltaic active welding strip is 70~300μm, the cross-sectional thickness is 70~300μm, and the thickness of the coating layer is 5~50μm.

[0026] According to a second aspect of the present invention, there is provided a method for preparing a direct-welded busbar-free photovoltaic module without auxiliary fixation, comprising the following steps:

[0027] Obtaining a battery cell with a secondary grid on the surface;

[0028] Directly welding the photovoltaic active welding strip described in any one of the first aspects above to the secondary grid on the surface of the solar cell and the non-secondary grid position between the secondary grids to obtain a solar cell string;

[0029] The obtained battery strings are packaged to produce busbar-free photovoltaic modules.

[0030] The existing technology uses glue to assist in fixing, but the number and position of glue points are limited. The present invention uses active welding strips that can be welded not only at the auxiliary grid position, but also at non-auxiliary grid positions, thereby forming a continuous and firm welding of the entire line. After welding, the entire welding strip and the battery cell have a large welding tension, which improves the welding tension of the main grid-free assembly, so there is no need for auxiliary fixing. In addition, the front EL of the battery string layer prepared by this technical solution is clear, and the conventional multi-main grid assembly repair method can be used for rework, which can solve the problems existing in the rear welding route in the current main grid-free technology.

[0031] Preferably, the photovoltaic active welding strip is welded by thermal welding, ultrasonic welding or laser welding, and the welding temperature is 100°C to 400°C.

[0032] In the present technical solution, more preferably, the welding temperature is 100°C to 300°C.

[0033] According to a third aspect of the present invention, there is provided a busbar-less photovoltaic module, which is prepared by the method described in any one of the second aspects of the present invention.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The direct-welded main-grid-free photovoltaic module without auxiliary fixation provided by the present invention adopts active welding strips to directly weld into strings during welding. No flux is used during welding, and no glue or adhesive film is required for auxiliary fixation. Therefore, there is no need to add new processes and equipment for applying glue water and adhesive film.

[0036] 2. The prior art uses glue to assist fixation, but the number and position of glue points are limited. The present invention uses active welding strips to not only weld at the auxiliary grid position, but also at non-auxiliary grid positions, thereby forming a continuous and firm welding of the entire line. The present invention has a direct welding type main grid-free photovoltaic module without auxiliary fixation, and the composition and content of the active welding strip are flexibly matched. After welding, the entire welding strip has a large welding tension with the battery cell, the EL before the layer is clear, and the pre-layer repair is simple.

[0037] 3. In the present invention, since the active solder strip can be directly welded to, for example, the transparent conductive oxide (TCO) layer on the surface of a silicon heterojunction (HJT) battery, the active solder strip can also collect current at a non-sub-grid position, while improving the contact with the non-sub-grid position, and also increasing the overall power of the HJT battery assembly.

[0038] 4. The photovoltaic solder strip provided by the present invention, wherein the addition of the first component in the active solder contained therein can increase the wetting performance of the base solder, and strengthen the β-Sn phase / In phase / Zn phase grains in the solder matrix, thereby improving the welding strength, reducing the risk of component breakage, and making the components more reliable when used in windy and snowy weather or when hot spot effects occur. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Further, the descriptions of "first", "second", etc. in the present application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0040] Example 1

[0041] (1) Preparation of photovoltaic active solder

[0042] Referring to Table 1, 50 g Sn, 5 g Ti, 2 g Ag, 42.8 g Bi, 0.1 g Ga, 0.1 g Ce, and 3 g NiFe2O4 were weighed, and all the above-weighed raw materials were placed in a crucible made of graphite. The solder was prepared in a vacuum high-frequency induction furnace. The temperature of the solder manufacturing was 1100°C. The solder was melted three times in the crucible, and the crucible was cooled in water to form a photovoltaic active solder ingot.

[0043] (2) Preparation of photovoltaic active ribbon

[0044] The prepared photovoltaic active solder ingot is used for the preparation of photovoltaic active welding strips. The photovoltaic active solder ingot is melted in a molten pool, and the molten pool temperature is maintained at 280°C. A copper wire with a circular cross-section and a diameter of 200 μm is pulled out of the molten pool after annealing and surface treatment. The thickness of the photovoltaic active solder on the surface of the copper wire is controlled by a wind knife to obtain a 15 μm thick coating layer. The coating layer is rolled up after cooling and vacuum-packaged to obtain a photovoltaic active welding strip.

[0045] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0046] The prepared photovoltaic active welding strip is used for the preparation of direct welding type main-grid-free photovoltaic modules without auxiliary fixation. HJT cells with sub-grids on the surface are used for heat welding (specifically infrared welding) on ​​a welding machine. The welding temperature is 180°C. The photovoltaic active welding strip is directly welded to the sub-grid on the surface of the cell and the non-sub-grid position between the sub-grids to obtain cell strings. The main-grid-free photovoltaic modules are obtained after arranging the cell strings, welding the bus bars, laying the film glass, laminating, framing, and installing the junction box.

[0047] Example 2

[0048] (1) Preparation of photovoltaic active solder

[0049] The photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed, and as shown in Table 1, the only difference was that 3g of NiFe2O4 in Example 1 was replaced by 3g of BaTiO3 in this example.

[0050] (2) Preparation of photovoltaic active ribbon

[0051] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0052] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0053] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0054] Example 3

[0055] (1) Preparation of photovoltaic active solder

[0056] The photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed, and as shown in Table 1, the only difference was that 3 g of NiFe2O4 in Example 1 was replaced by 3 g of POSS in this example.

[0057] (2) Preparation of photovoltaic active ribbon

[0058] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0059] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0060] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0061] Example 4

[0062] (1) Preparation of photovoltaic active solder

[0063] The photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed, and as shown in Table 1, the only difference was that 3g NiFe2O4 in Example 1 was replaced with 1g NiFe2O4, 1g BaTiO3, and 1g POSS in this example.

[0064] (2) Preparation of photovoltaic active ribbon

[0065] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0066] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0067] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0068] Example 5

[0069] (1) Preparation of photovoltaic active solder

[0070] The photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed. As shown in Table 1, the only difference was that 2 g of Zr was added to the formula of Example 1.

[0071] (2) Preparation of photovoltaic active ribbon

[0072] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0073] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0074] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0075] Example 6

[0076] (1) Preparation of photovoltaic active solder

[0077] The photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed. As shown in Table 1, the only difference was that 2 g of Ni was added to the formula of Example 1.

[0078] (2) Preparation of photovoltaic active ribbon

[0079] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0080] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0081] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0082] Example 7

[0083] (1) Preparation of photovoltaic active solder

[0084] Photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed, as shown in Table 1, to 12.6 g Sn, 10 g Ti, 2 g Ag, 35 g Bi, 0.2 g Ga, 0.2 g Ce, 20 g Zr, 20 g Ni, 1 g NiFe2O4, 1 g BaTiO3, and 1 g POSS.

[0085] (2) Preparation of photovoltaic active ribbon

[0086] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0087] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0088] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0089] Example 8

[0090] (1) Preparation of photovoltaic active solder

[0091] Photovoltaic active solder was prepared by the same method as in Example 1, except that the solder formula was changed, as shown in Table 1, to 79.4 g Sn, 0.1 g Ti, 2 g Ag, 18.4 g Bi, 0.05 g Ga, 0.05 g Ce, 1 g NiFe2O4, 1 g BaTiO3, and 1 g POSS.

[0092] (2) Preparation of photovoltaic active ribbon

[0093] The photovoltaic active welding strip was prepared by the same method as in Example 1.

[0094] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0095] The same method as in Example 1 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0096] Comparative Example 1

[0097] (1) Preparation of photovoltaic solder

[0098] The photovoltaic solder was prepared by the same method as in Example 1, except that the solder formula was changed to 60 g Sn and 40 g Pb.

[0099] (2) Preparation of photovoltaic ribbon

[0100] The photovoltaic welding strip is prepared by the same method as in Example 1.

[0101] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0102] The photovoltaic module was prepared by the same method as in Example 1, but it was found that it could not be welded into strings, so a busbar-free photovoltaic module could not be obtained.

[0103] Table 1 shows the formula of the solder in the above Examples 1 to 8 and Comparative Example 1 and the applicable battery types, wherein the unit of the content of each substance is gram (g).

[0104] Table 1

[0105]

[0106] Example 9

[0107] (1) Preparation of photovoltaic active solder

[0108] Referring to Table 2, 60 g Sn, 8 g Zn, 2 g Sb, 40 g Pb, and 4.5 g NiFe2O4 were weighed, and all the above-weighed raw materials were placed in a crucible made of graphite. The solder was prepared in a vacuum high-frequency induction furnace. The temperature of the solder manufacturing was 1100°C. The solder was melted three times in the crucible, and the crucible was cooled in water to form a photovoltaic active solder ingot.

[0109] (2) Preparation of photovoltaic active ribbon

[0110] The prepared photovoltaic active solder ingot is used for the preparation of photovoltaic active welding strips. The photovoltaic active solder ingot is melted in a molten pool, and the molten pool temperature is maintained at 280°C. A copper wire with a circular cross-section and a diameter of 200 μm is pulled out of the molten pool after annealing and surface treatment. The thickness of the photovoltaic active solder on the surface of the copper wire is controlled by a wind knife to obtain a 15 μm thick coating layer. The coating layer is rolled up after cooling and vacuum-packaged to obtain a photovoltaic active welding strip.

[0111] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0112] The prepared photovoltaic active welding ribbon is used for the preparation of direct welding type busbar-free photovoltaic modules without auxiliary fixation. A tunneling oxide passivation contact (TOPCon) cell with a sub-grid on the surface is used. Thermal welding (specifically infrared welding) is performed on a welding machine at a welding temperature of 250°C. The photovoltaic active welding ribbon is directly welded to the sub-grid on the surface of the cell and the non-sub-grid position between the sub-grids to obtain a cell string. The busbar-free photovoltaic module is obtained after arranging the cell string, welding the busbars, laying the film glass, laminating, framing, and installing the junction box.

[0113] Example 10

[0114] (1) Preparation of photovoltaic active solder

[0115] The photovoltaic active solder was prepared by the same method as in Example 9, except that the solder formula was changed, and as shown in Table 2, the only difference was that 4.5 g NiFe2O4 in Example 9 was replaced by 1.5 g NiFe2O4, 1.5 g BaTiO3, and 1.5 g POSS in this example.

[0116] (2) Preparation of photovoltaic active ribbon

[0117] The photovoltaic active welding strip was prepared by the same method as in Example 9.

[0118] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0119] The same method as in Example 9 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0120] Embodiment 11

[0121] (1) Preparation of photovoltaic active solder

[0122] The photovoltaic active solder was prepared in the same manner as in Example 9, except that the solder formula was changed, and as shown in Table 2, the formula was changed to 60 g Sn, 40 g Pb, 10 g Mg and 4.5 g BaTiO3.

[0123] (2) Preparation of photovoltaic active ribbon

[0124] The photovoltaic active welding strip was prepared by the same method as in Example 9.

[0125] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0126] The same method as in Example 9 was used to prepare a direct-welded busbar-free photovoltaic module without auxiliary fixation.

[0127] Comparative Example 2

[0128] (1) Preparation of photovoltaic solder

[0129] The photovoltaic solder was prepared by the same method as in Example 9, except that the solder formula was changed, and as shown in Table 2, the formula was changed to 60 g Sn, 40 g Pb.

[0130] (2) Preparation of photovoltaic ribbon

[0131] The photovoltaic welding strip is prepared by the same method as in Example 9.

[0132] (3) Preparation of direct welding busbar-free photovoltaic modules without auxiliary fixation

[0133] The photovoltaic modules were prepared in the same manner as in Example 9, but it was found that they could not be welded into strings, and thus a busbar-free photovoltaic module could not be obtained.

[0134] Comparative Example 3

[0135] (1) Preparation of photovoltaic solder

[0136] The photovoltaic solder was prepared by the same method as in Example 9, except that the solder formula was changed, and as shown in Table 2, the formula was changed to 60 g Sn, 40 g Pb.

[0137] (2) Preparation of photovoltaic ribbon

[0138] The photovoltaic welding strip is prepared by the same method as in Example 9.

[0139] (3) Using the existing technology to prepare busbar-free photovoltaic modules by first welding

[0140] Photovoltaic welding ribbons are used for the first welding route to prepare busbar-free photovoltaic modules. TOPCon cells with auxiliary grids on the surface are used for thermal welding (specifically infrared welding) on ​​a welding machine. The welding temperature is 250°C. After welding, glue is applied to the head, middle and tail of each welding ribbon of each cell to assist in fixing the welding ribbon to obtain cell strings. After arranging the cell strings, welding the bus bars, laying the film glass, laminating, framing and installing the junction box, busbar-free photovoltaic modules are obtained.

[0141] Comparative Example 4

[0142] The busbar-free TOPCon module is a commercially available module that is prepared using the coating technology in the post-welding route of the existing busbar-free technology. Since the post-welding route does not involve welding at the welding machine end, the peeling force test at the welding machine end is not involved, and the commercially available TOPCon coated busbar-free module is directly selected for subsequent testing.

[0143] Table 2 shows the formula of the solder in the above Examples 9 to 11 and Comparative Examples 2 to 3 and the applicable battery types, wherein the unit of the content of each substance is gram (g).

[0144] Table 2

[0145]

[0146] Performance Testing

[0147] (1) Peel force test

[0148] A multi-grid photovoltaic special peeling force tester is used to test the peeling force of the battery cells after welding by a welding machine. The welding ribbon is clamped with a spring-type fixing device to achieve fixation. The battery cells are fixed by four rubber strips with magnets at both ends. The test data is automatically integrated by a special computer app program, and the average value is recorded.

[0149] (2) Thermal Cycle (TC) Test

[0150] The prepared busbar-free photovoltaic module was placed in a hot and cold cycle environment box for testing. The temperature was uniformly reduced from 25°C to -40°C within 1 hour, kept warm for 15 minutes, then uniformly increased from -40°C to 85°C within 3 hours, kept warm for 15 minutes, and then uniformly reduced from 85°C to 25°C within 2 hours. The test was repeated 200 times in total. Power tests were performed before and after the test, and the recorded data was displayed as the percentage of the relative change after the test compared with that before the test.

[0151] Test Results

[0152] The peel force test results of each group and the percentage of power change (ΔPmax (%)) and the percentage of series resistance change (ΔRs (%)) after the TC test compared to before the test are listed in Table 3, where a negative ΔPmax (%) value represents power attenuation after the TC test, and a positive ΔRs (%) value represents an increase in series resistance after the TC test.

[0153] Comparing Examples 1 to 8 with Comparative Example 1, it can be seen from the above experimental process that the photovoltaic active welding strips prepared by Examples 1 to 8 can prepare a direct welding type busbar-free photovoltaic module without auxiliary fixation, while the photovoltaic welding strips used in the prior art module prepared by Comparative Example 1 cannot directly weld the busbar-free cells into strings to make modules. Further, from the test results of Examples 1 to 8, it can be seen that the cells welded by the photovoltaic active welding strips prepared by Examples 1 to 8 have high peeling force and high welding strength, and thus more effectively resist fatigue damage of the cells and welding strips when the modules are prepared for TC testing, so the power attenuation after TC testing is low and the increase in string resistance is not obvious.

[0154] Compared with comparative example 1, in embodiments 1 to 8, the Ti element in the solder included in the photovoltaic active solder strip can diffuse to the welding interface to realize the welding of the photovoltaic active solder strip and the battery sheet, and the addition of NiFe2O4, BaTiO3, and POSS in the solder can improve the wetting effect of the solder matrix, and when the solder matrix includes Ga, it can act with the Ga in the matrix, further improve the wetting effect of Ga, and the matrix solder wettability is greatly increased under the dual effect, and the increase in wettability is quite beneficial to the improvement of welding strength. In addition, in the welding process, the NiFe2O4, BaTiO3, and POSS in the solder can act with the Sn, Ti, and Ag in the solder matrix, strengthen the β-Sn phase grains, hinder the formation of SnTi and SnAg alloys, promote Ti to diffuse to the welding interface, and then the welding strength is greatly improved.

[0155] In addition, compared with Comparative Example 1 and Example 1, the addition of Zr in Example 5 can assist the diffusion of Ti, and the addition of Ni in Example 6 can improve the thermal stability of the solder. Therefore, based on Example 1, the welding strength of Examples 5 and 6 is slightly improved.

[0156] Moreover, for Examples 7 to 8, after changing some of the proportions, the peeling force and the power attenuation and the increase in series resistance after TC testing are consistent with those of Examples 1 to 6.

[0157] Comparing Examples 9 to 11 with Comparative Example 2, it can be seen from the above experimental process that the photovoltaic active welding strips prepared by Examples 9 to 11 can prepare direct welding type busbar-free photovoltaic modules without auxiliary fixation, while the photovoltaic welding strips used in the prior art modules prepared by Comparative Example 2 cannot directly weld busbar-free cells into strings to make modules. Further, from the test results of Examples 9 to 11, it can be seen that the cells welded by the photovoltaic active welding strips prepared by Examples 9 to 11 have high peeling force, low power attenuation after TC test, and no obvious increase in string resistance.

[0158] Compared with Comparative Example 2, in Examples 9 to 11, the Zn and Mg elements in the solder contained in the photovoltaic active solder strip can diffuse to the welding interface to realize the welding of the active solder strip and the battery cell, and the addition of NiFe2O4, BaTiO3, and POSS in the solder can improve the wetting effect of the solder matrix, and the increase in wetting performance is beneficial to the improvement of welding strength; in addition, during the welding process, NiFe2O4, BaTiO3, and POSS in the solder can react with Sn, Zn, and Mg in the solder matrix to strengthen β-Sn phase grains, hinder the formation of SnZn and SnMg alloys, and promote the diffusion of Zn and Mg to the welding interface, thereby greatly improving the welding strength.

[0159] Compared with Comparative Example 3, the peeling force of Examples 9 to 11 is higher, because the active welding strips prepared in Examples 9 to 11 can be welded not only at the auxiliary grid position, but also at the non-auxiliary grid position, thereby forming a continuous and firm welding of the entire line. In addition, compared with Comparative Examples 3 to 4, the power attenuation after TC testing of Examples 9 to 11 is lower, and the increase in series resistance is smaller, which indicates that the busbar-free photovoltaic module prepared by the present invention has better reliability than the busbar-free module in the prior art.

[0160] Table 3

[0161]

[0162] The above describes the specific embodiments of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A photovoltaic active welding strip, characterized in that: It comprises a soldering ribbon core and a coating layer wrapped around the outer periphery of the soldering ribbon core, wherein the coating layer is an active solder, and the active solder comprises a matrix and a first component; The matrix is ​​selected from Sn-Ti, Sn-Ti-In, Sn-Ti-Ag, Sn-Ti-Bi, Sn-Ti-Pb, Sn-Ti-Ag-In, Sn-Ti-Ag-Pb, Sn-Ti-Ag-Bi, Sn-Ti-Ag-Bi-Pb, Sn-Ti-Ga -X, Sn-Ti-Ag-Ga-X, Sn-Ti-Bi-Ga-X, Sn-Ti-Pb-Ga-X, Sn-Ti-Ag-Pb-Ga-X, Sn-Ti-Ag-Bi-Ga-X, Sn-Ti-Bi-Pb-Ga-X, Sn-Ti-Ag-Bi- Any at least one of Pb-Ga-X, Sn-Zn, Sn-Zn-Sb, Sn-Zn-Sb-Pb, Zn-Ag, Zn-Ag-Ti, Sn-Mg, Sn-Mg-In, Sn-Mg-Ag, Sn-Mg-Bi, Sn-Mg-Pb, Sn-Mg-Bi-In, Sn-Mg-Zn, Sn-Mg-Zn-In, Sn-Mg-Zn-Bi, Sn-Mg-Zn-Bi-Ag, Sn-Mg-Zn-Bi-In, In-Mg, In-Mg-Ag, and In-Mg-Zn, wherein X is Ce or La or Ce-La; The first component is selected from any at least one of NiFe2O4, NiCo2O4, CoFe2O4, BaTiO3, SrTiO3, CaTiO3, MgTiO3, and POSS.

2. The photovoltaic active welding strip according to claim 1, characterized in that: The matrix accounts for 55wt% to 99.99wt% of the active solder content; The matrix is ​​selected from any at least one of Sn-Ti-Ag-Bi-Ga-X, Sn-Ti-Bi-Ga-X, Sn-Ti-Ag-Ga-X, Sn-Zn-Sb-Pb, and Sn-Mg-Pb; When the matrix contains Sn, the content of Sn in the matrix accounts for 20wt%~99.9wt% of the matrix content, and the content of Ti or Zn or Mg accounts for 0.01wt%~20wt% of the matrix content.

3. The photovoltaic active welding strip according to claim 1, characterized in that: The first component is selected from any at least one of NiFe2O4, BaTiO3, and POSS; the first component accounts for 0.01wt% to 5wt% of the active solder content.

4. The photovoltaic active welding strip according to claim 1, characterized in that: The active solder further comprises a second component and / or a third component, wherein the second component is selected from at least one of Zr, V, Nb, and Hf, and the third component is selected from at least one of Cu, Al, Ni, Cr, Mo, and Ta; The second component accounts for 0wt% to 20wt% of the active solder content, and the third component accounts for 0wt% to 20wt% of the active solder content.

5. The photovoltaic active welding strip according to claim 1, characterized in that: The base material of the welding ribbon core is selected from any at least one of the following materials: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and alloys containing any of the foregoing materials; or The base material of the welding ribbon core is selected from any at least two of the following materials: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and alloys containing any of the foregoing materials, and the structure of the welding ribbon core is a core-shell coating structure or a stacked structure composed of the selected materials.

6. The photovoltaic active welding strip according to claim 1, characterized in that: The cross-sectional width of the photovoltaic active welding strip is 50-500 μm, and the cross-sectional thickness is 50-500 μm; the thickness of the coating layer is 1-100 μm.

7. A method for preparing a direct-welded busbar-free photovoltaic module without auxiliary fixation, characterized in that: The steps include: Obtaining a battery cell with a secondary grid on the surface; Directly welding the photovoltaic active welding strip according to any one of claims 1 to 6 to the auxiliary grid on the surface of the solar cell and the non-auxiliary grid position between the auxiliary grids to obtain a solar cell string; The obtained battery strings are packaged to produce busbar-free photovoltaic modules.

8. The method for preparing a direct-welded busbar-free photovoltaic module without auxiliary fixation according to claim 7, characterized in that: The photovoltaic active welding strip is welded by thermal welding, ultrasonic welding or laser welding, and the welding temperature is 100°C to 400°C.

9. A busbar-free photovoltaic module, characterized in that: The method according to any one of claims 7 to 8 is used for preparation.

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