Photovoltaic ultrafine active welding wire, gateless line topcon cell sheet and assembly and preparation method

Abstract

The application provides a photovoltaic superfine active solder wire, a gridless TOPCon cell and an assembly and a preparation method, wherein the active solder of the photovoltaic superfine active solder wire comprises a first component and a matrix selected from specific substances; the first component can increase the wetting performance of the matrix solder, strengthen the beta-Sn phase / In phase / Zn phase grains in the solder matrix, improve the welding strength, reduce the risk of grid breakage of the assembly, and enhance the reliability of the assembly; the foregoing photovoltaic superfine active solder wire is used to replace the silver grid line in the prior art, the silver grid line does not need to be printed and sintered in the cell manufacturing process, the slurry and the printing and sintering process and equipment thereof are omitted, in addition, the transmission resistance and the contact resistance on the current output path of the cell after welding are small, and the electrical performance of the cell can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, in particular to a photovoltaic ultrafine active solder wire, a gridless TOPCon photovoltaic cell and module prepared by using the solder wire, and a preparation method of the gridless TOPCon photovoltaic cell and module. BACKGROUND

[0002] The tunnel oxide passivation contact (TOPCon) photovoltaic cell has become the most mainstream mass production photovoltaic cell technology at present, but the existing problem is that the existing TOPCon photovoltaic cell metallization scheme is silver grid line printing and sintering, the printed pattern is mostly dense sub-grid, multiple main grids and solder points matched on the main grid, and the grid line paste is mostly conductive silver paste, and the cost of silver paste accounts for about 35% of the non-silicon cost, which is the first non-silicon cost of photovoltaic cells. Therefore, reducing the metallization cost of the TOPCon photovoltaic cell is a key problem to be solved. SUMMARY

[0003] In view of the defects in the prior art, the purpose of the present application is to provide a photovoltaic ultrafine active solder wire, a gridless TOPCon photovoltaic cell and module prepared by using the solder wire, and a preparation method of the gridless TOPCon photovoltaic cell and module. The present application uses a specially prepared active solder to replace the silver grid line in the prior art. In the process of making the cell, there is no need to print and sinter the silver grid line, and the electrode paste is completely removed, thereby saving the paste and the printing and sintering process and equipment. In addition, the transmission resistance and contact resistance on the current output path of the cell after welding are small, which can improve the electrical performance of the cell.

[0004] To achieve the above-mentioned purpose of the application, the technical solution adopted by the present application is as follows:

[0005] According to a first aspect of the present application, a photovoltaic ultrafine active solder wire is provided, which comprises a solder wire core and a coating layer with a thickness of 1-100 um wrapped around the periphery of the solder wire core, the coating layer being an active solder, and the active solder comprising a base and a first component.

[0006] The base body is selected from any at least one of 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-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, In-Mg-Zn, wherein the X is Ce or La or Ce-La.

[0007] The first component is selected from any at least one of NiFe2O4, NiCo2O4, CoFe2O4, BaTiO3, SrTiO3, CaTiO3, MgTiO3, and POSS.

[0008] In the technical solution, the so-called "POSS" refers to polyhedral oligomeric silsesquioxanes. The photovoltaic ultrafine active welding wire provided by the technical solution adopts an active solder containing a specific base body and a first component. The addition of the first component can increase the wettability of the base body solder and strengthen the β-Sn phase / In phase / Zn phase grains in the solder base body, thereby improving the welding strength and reducing the risk of grid breakage of the prepared assembly, thereby making the prepared assembly have better reliability in snowy weather or when hot spot effect occurs.

[0009] It should be noted that the experimental data provided by the embodiments of the present application can confirm that the addition of the first component NiFe2O4, BaTiO3, and POSS can help improve the welding strength. Among other first components, SrTiO3, CaTiO3, and MgTiO3 are BaTiO3 homologous titanates, and NiCo2O4 and CoFe2O4 are NiFe2O4 homologous acid salts. Therefore, the mechanism of action of the base body in the solder is the same as that of BaTiO3 and NiFe2O4, and thus has the same effect of improving the welding strength.

[0010] Preferably, the base material accounts for 55wt% to 99.99wt% of the active solder content;

[0011] The base material 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, Sn-Mg-Pb;

[0012] When the base material contains Sn, the content of Sn in the base material accounts for 20wt% to 99.9wt% of the base material content, and the content of Ti or Zn or Mg accounts for 0.01wt% to 20wt% of the base material content.

[0013] More preferably in the present technical solution, the content of Sn in the base material accounts for 40wt% to 60wt% of the base material content, and the content of Ti or Zn or Mg accounts for 1wt% to 5wt% of the base material content.

[0014] Preferably, the first component is selected from any at least one of NiFe2O4, BaTiO3, POSS, and accounts for 0.01wt% to 5wt% of the active solder content.

[0015] More preferably in the present technical solution, the first component accounts for 1wt% to 3wt% of the active solder content.

[0016] 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, Hf, and the third component is selected from any at least one of Cu, Al, Ni, Cr, Mo, Ta;

[0017] 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.

[0018] More preferably in the present technical solution, the second component accounts for 1wt% to 5wt% of the active solder content, and the third component accounts for 1wt% to 5wt% of the active solder content. In the present technical solution, the addition of the second component can assist the diffusion of Ti, Zn, and Mg to the solder interface, and the addition of the third component can improve the thermal stability of the solder, thereby further improving the soldering strength.

[0019] Preferably, the base material of the welding wire core is selected from any at least one of copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium, and an alloy containing any of the foregoing; or

[0020] The base material of the welding wire core is selected from any at least two of copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and an alloy containing any of the foregoing, and the structure of the welding wire core is a core-shell cladding structure or a laminated structure composed of the selected materials.

[0021] In the technical solution, the core-shell cladding structure refers to a concentric structure formed by the base material of the welding wire core being wrapped layer by layer with one material as a core and other materials as shells. For example, when the base material of the welding wire core is selected from two materials, one material is a core and the other material is a shell to wrap the core material, thereby forming a core-shell cladding structure. When the base material of the welding wire core is selected from three materials, material 1 is a core, material 2 is a shell to wrap material 1, and material 3 is a further shell to wrap material 2, thereby forming a core-shell cladding structure. The laminated structure refers to a structure formed by the base material of the welding wire core being stacked layer by layer. For example, when the base material of the welding wire core is selected from two materials, one material forms a lower layer and the other material forms an upper layer stacked on the lower layer, thereby forming a laminated structure. When the base material of the welding wire core is selected from three materials, material 1 is a first layer, material 2 is a second layer stacked on material 1, and material 3 is a third layer stacked on material 2, thereby forming a laminated structure.

[0022] Preferably, the cross-sectional width of the photovoltaic ultrafine active welding wire is 10-120 μm, and the cross-sectional thickness is 10-120 μm; the thickness of the coating layer is 1-50 μm.

[0023] The cross-sectional shape of the welding wire is not limited in the technical solution, which can be any one or a combination of circular, elliptical, triangular, rectangular, trapezoidal and flat. As a further preferred mode, the cross-sectional width of the photovoltaic ultrafine active welding wire is 10-50 μm, the cross-sectional thickness is 10-50 μm, and the thickness of the coating layer is 5-20 μm. The photovoltaic ultrafine active welding wire of the technical solution has a small wire diameter, which can greatly reduce the grammage of the packaging film during packaging and achieve further cost reduction.

[0024] According to a second aspect of the present application, a preparation method of a gateless line TOPCon photovoltaic cell is provided, which adopts any of the following two modes:

[0025] The first mode is to sequentially perform texturing, doping, etching, oxide layer deposition, poly-Si deposition, welding and dielectric film deposition on the silicon wafer. The specific steps of welding are to directly weld a plurality of photovoltaic ultrafine active welding wires according to any one of the first aspect of the present application along the X direction and / or the Y direction on the P region and the N region doped layer.

[0026] The second method is to sequentially perform texturing, doping, etching, oxide layer deposition, poly-Si deposition, dielectric film deposition, dielectric film slotting, and welding on the silicon wafer, wherein the welding is performed by directly welding the photovoltaic ultrafine active welding wire according to any one of the first aspect of the present application along the X direction and / or the Y direction on the P region and the N region doping layer exposed at the slotting position.

[0027] In the above method, the extension directions parallel to the two intersecting edges of the silicon wafer are defined as the X direction and the Y direction, respectively.

[0028] In the present technical solution, first, regarding the definition of the X direction and the Y direction, the silicon wafer in the prior art is usually rectangular or square, so for the two edges intersecting at right angles, the X direction is the extension direction parallel to one of the right-angle edges of the silicon wafer, and the Y direction is the extension direction parallel to the other right-angle edge of the silicon wafer. In the embodiments shown in the following of the present application, based on the consistency of the foregoing and the following descriptions, when the silicon wafer is placed horizontally, the extension direction parallel to the horizontal right-angle edge thereof is defined as the X direction, and the extension direction parallel to the vertical right-angle edge thereof is defined as the Y direction. Second, in the present technical solution, the difference between the two preparation methods is that the method 1 directly performs welding of the photovoltaic ultrafine active welding wire after the deposition of the doped poly-Si, and then performs deposition of the dielectric film, while the method 2 first deposits the dielectric film and slots, and then performs welding of the photovoltaic ultrafine active welding wire. Regardless of which method is selected, the present technical solution uses the photovoltaic ultrafine active welding wire to replace the silver grid line in the prior art, so that the printing and sintering of the silver grid line are not required during the cell manufacturing process, the electrode paste is completely removed, the paste and the printing and sintering processes and equipment thereof are saved, in addition, the transmission resistance and the contact resistance on the current output path of the cell after welding are small, so that the electrical performance of the cell can be improved.

[0029] Preferably, the number of the photovoltaic ultrafine active welding wires welded on the P region or the N region is 20-300; the welding method is hot welding or ultrasonic welding or laser welding; when the photovoltaic ultrafine active welding wire is directly welded on the P region and the N region doping layer along the X direction and / or the Y direction, the welding temperature is above 400℃, and when the photovoltaic ultrafine active welding wire is directly welded on the P region and the N region doping layer exposed at the slotting position along the X direction and / or the Y direction, the welding temperature is 100-400℃.

[0030] In the technical solution, the more preferable number of the photovoltaic ultrafine active welding wires welded in the P region or the N region is 30-150, when the second preparation method is used to prepare the cell piece and the laser welding is selected as the welding method, the laser grooving and the welding can be performed in the same laser equipment, thereby improving the process efficiency, the welding wires can be welded only in the X direction or the Y direction of the surface of the cell piece, or can be welded in the X direction and the Y direction in a mesh welding manner. In the technical solution, the "welding temperature is above 400 DEG C" includes the case that the welding temperature is 400 DEG C.

[0031] According to a third aspect of the present application, a gate-line-free TOPCon photovoltaic cell piece is provided, which is prepared by using the preparation method of the gate-line-free TOPCon photovoltaic cell piece according to any one of the second aspect of the present application.

[0032] Preferably, the TOPCon photovoltaic cell piece includes a photovoltaic cell with a front P region and a back N region, a front N region and a back P region, and a back contact (BC) photovoltaic cell with a back P region and a back N region.

[0033] According to a fourth aspect of the present application, a gate-line-free TOPCon photovoltaic module is provided, which is obtained by welding the gate-line-free TOPCon photovoltaic cell piece according to any one of the third aspect of the present application into a string and packaging the cell string.

[0034] According to a fifth aspect of the present application, a preparation method of a gate-line-free TOPCon photovoltaic module is provided, which includes the following steps:

[0035] The silicon wafer is sequentially subjected to texturing, doping, etching, deposition of an oxide layer, deposition of doped poly-Si, deposition of a dielectric film, and grooving of the dielectric film, to obtain a TOPCon photovoltaic cell piece body.

[0036] The TOPCon photovoltaic cell piece body is directly welded into a string by using the photovoltaic ultrafine active welding wire according to any one of the first aspect of the present application, and a gate-line-free TOPCon photovoltaic module is obtained by packaging the cell string.

[0037] The specific steps of the welding are as follows: defining the extension directions parallel to the two intersecting edges of the silicon wafer as the X direction and the Y direction, and directly welding the photovoltaic ultrafine active welding wire on the P region or the N region doping layer exposed at the grooving position along the X direction and / or the Y direction.

[0038] In the technical solution, firstly, regarding the definition of the X direction and the Y direction, the silicon wafer in the prior art is usually rectangular or square, so for the two edges intersecting at right angles, the X direction is the extension direction parallel to one of the right-angle edges of the silicon wafer, and the Y direction is the extension direction parallel to the other right-angle edge of the silicon wafer. Based on the consistency of the foregoing descriptions, in the embodiments shown in the following description of the present application, when the silicon wafer is placed horizontally, the extension direction parallel to the horizontal right-angle edge thereof is defined as the X direction, and the extension direction parallel to the vertical right-angle edge thereof is defined as the Y direction. Secondly, in the technical solution, the TOPCon photovoltaic cell body after the passivation film is slotted is directly welded into a string by using the photovoltaic ultra-fine active welding wire, and the photovoltaic module is prepared after the cell string is packaged. The photovoltaic ultra-fine active welding wire can be used without flux during welding, and a continuous and firm weld can be formed by welding, and the process of welding into a string is simple. After welding, the transmission resistance and contact resistance on the current output path of the cell are small, and the electrical performance of the cell can be improved.

[0039] According to a sixth aspect of the present application, a gate line-free TOPCon photovoltaic module is provided, which is prepared by the method for preparing a gate line-free TOPCon photovoltaic module according to the fifth aspect of the present application.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] 1. The gate line-free TOPCon photovoltaic cell and module provided by the present application replace the silver grid line in the prior art by adjusting the composition of the active solder in the photovoltaic ultra-fine active welding wire and directly welding it on the doped layer, completely remove the electrode paste, and eliminate the process and equipment for printing and sintering the paste. After the photovoltaic ultra-fine active welding wire is directly welded on the doped layer, the transmission resistance and contact resistance on the current output path of the cell are small, and the electrical performance of the cell and module can be improved.

[0042] 2. The photovoltaic ultra-fine active welding wire provided by the present application uses active solder, and the addition of the first component can increase the wetting performance of the solder matrix, strengthen the β-Sn phase / In phase / Zn phase grains in the solder matrix, improve the welding strength, reduce the risk of grid breakage of the module, and improve the reliability of the module in snowy weather or when hot spot effect occurs. BRIEF DESCRIPTION OF DRAWINGS

[0043] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0044] Figure 1 Structure diagram of the gate line-free TOPCon photovoltaic cell prepared for Example 1;

[0045] Figure 2Structure diagram of a gridless TOPCon photovoltaic cell prepared for Example 2;

[0046] Figure 3 Structure diagram of a gridless TOPCon photovoltaic cell prepared for Example 3;

[0047] Figure 4 Cross-sectional diagram of a gridless TOPCon photovoltaic cell prepared for Examples 1-3;

[0048] Figure 5 Structure diagram of a gridless TOPCon photovoltaic cell prepared for Example 4;

[0049] Figure 6 Structure diagram of a gridless TOPCon photovoltaic cell prepared for Example 5;

[0050] Figure 7 Structure diagram of a gridless TOPCon photovoltaic cell prepared for Example 6;

[0051] Figure 8 Cross-sectional diagram of a gridless TOPCon photovoltaic cell prepared for Examples 4-6;

[0052] Figure 9 Structure diagram of a TOPCon photovoltaic cell body used for a gridless TOPCon photovoltaic module prepared for Examples 7-9;

[0053] Figure 10 Structure diagram of a TOPCon photovoltaic cell body used for a gridless TOPCon photovoltaic module prepared for Example 10;

[0054] Figure 11 Structure diagram of a cell string required for a gridless TOPCon photovoltaic module prepared for Examples 7-9;

[0055] Figure 12 Structure diagram of a cell string required for a gridless TOPCon photovoltaic module prepared for Example 10.

[0056] Shown in the figure are:

[0057] 1 - Gridless TOPCon photovoltaic cell;

[0058] 2 - Photovoltaic ultrafine active solder wire;

[0059] 3 - Grooving position;

[0060] 4 - Dielectric film;

[0061] 5 - TOPCon photovoltaic cell body. DETAILED DESCRIPTION

[0062] So that the purposes, technical solutions and advantages of the embodiments of the present application are more apparent, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0063] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0064] It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, all directional indications (such as up, down, left, right, front, back, bottom, etc.) in the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly. Further, the description involving "first", "second", etc. in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features.

[0065] Embodiment 1

[0066] The present embodiment provides a gridless TOPCon photovoltaic cell, as shown in Figure 1 and Figure 4 The surface of the cell 1 is provided with 100 parallel photovoltaic ultrafine active welding wires 2 in the X direction, which serve as metal electrodes of the cell and cancel the grid lines in the prior art.

[0067] The preparation method of the gridless TOPCon photovoltaic cell 1 includes the following steps: the silicon wafer is sequentially subjected to texturing, doping, etching, oxide layer deposition, doped poly-Si deposition, welding, and dielectric film 4 deposition. After the doped poly-Si deposition, the photovoltaic ultrafine active welding wire 2 is directly welded on the doped layer, and the welding temperature is 400°C. The slurry in the prior art is omitted, and the step does not use the existing screen printing technology, and the printing and sintering processes and equipment are also omitted.

[0068] The preparation method of the photovoltaic ultrafine active welding wire used in the embodiment comprises the following steps: the specially prepared photovoltaic active solder is used for the preparation of the photovoltaic ultrafine active welding wire, specifically, the specially prepared photovoltaic active solder ingot is melted in a molten pool, the temperature of the molten pool is kept at 450 DEG C, the copper wire with a circular cross section and a diameter of 25 μm is pulled out from 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, a 5 μm thick coating layer is obtained, and the photovoltaic ultrafine active welding wire is obtained after cooling and winding, vacuum packaging.

[0069] The preparation method of the specially prepared photovoltaic active solder in the embodiment comprises the following steps: referring to Table 1, 50 g of Ag, 10 g of Ti, 15 g of Zn, 20 g of V, 20 g of Al, 1 g of NiFe2O4, 1 g of BaTiO3 and 1 g of POSS are weighed, and the weighed raw materials are all put into a graphite crucible, and the solder is prepared in a vacuum high-frequency induction furnace, the temperature of the solder manufacturing is 1100 DEG C, the crucible is melted three times in the crucible, and the crucible is cooled in water to form a photovoltaic active solder ingot.

[0070] Embodiment 2

[0071] The embodiment provides a gate line-free TOPCon photovoltaic cell piece, which is prepared by the same method as in Embodiment 1, and the difference lies in that:

[0072] As shown in Figure 2 In the embodiment, the photovoltaic ultrafine active welding wire 2 is arranged on the surface of the cell piece 1 in the Y direction.

[0073] Embodiment 3

[0074] The embodiment provides a gate line-free TOPCon photovoltaic cell piece, which is prepared by the same method as in Embodiment 1, and the difference lies in that:

[0075] As shown in Figure 3 In the embodiment, the photovoltaic ultrafine active welding wire 2 is arranged on the surface of the cell piece 1 in the Y direction.

[0076] Comparative Example 1

[0077] The same method as in Embodiment 1 is used, and the difference is that the photovoltaic ultrafine active welding wire prepared by using the specially prepared photovoltaic active solder described in Embodiment 1 is not used, but a common ultrafine welding wire is used, and the common ultrafine welding wire is prepared by using a common solder on the market, as shown in Table 1, and the common solder formula is 60 g of Sn and 40 g of Pb. It is found that the ultrafine welding wire cannot be welded with the cell piece body during the preparation process, so the gate line-free TOPCon photovoltaic cell piece cannot be obtained.

[0078] Embodiment 4

[0079] The embodiment provides a gridless TOPCon photovoltaic cell, as shown in the drawings. Figure 5 And Figure 8 As shown in the drawings, the surface of the cell 1 is provided with 100 parallel photovoltaic ultrafine active welding wires 2 in the X direction, which are used as metal electrodes of the cell and cancel the grid lines in the prior art.

[0080] The preparation method of the gridless TOPCon photovoltaic cell 1 comprises the following steps: sequentially performing texturing, doping, etching, oxide layer deposition, poly-Si deposition, dielectric film 4 deposition, dielectric film 4 slotting, and welding on a silicon wafer. After the dielectric film 4 is slotted, the doped layer is exposed at the slotting position 3, and the photovoltaic ultrafine active welding wire 2 is directly welded on the doped layer, thereby eliminating the slurry in the prior art, and the step does not use the existing screen printing technology, and the printing and sintering process and equipment are also eliminated.

[0081] The preparation method of the photovoltaic ultrafine active welding wire used in the embodiment comprises the following steps: a specially prepared photovoltaic active solder is used for the preparation of the photovoltaic ultrafine active welding wire. Specifically, the specially prepared photovoltaic active solder ingot is melted in a molten pool, the temperature of the molten pool is kept at 280℃, a copper wire with a circular cross section and a diameter of 25μm is drawn from 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, a 5μm thick coating layer is obtained, and the photovoltaic ultrafine active welding wire is obtained after cooling and winding, vacuum packaging.

[0082] The preparation method of the specially prepared photovoltaic active solder in the embodiment comprises the following steps: referring to Table 1, 60g of Sn, 4.8g of Ti, 40g of Bi, 0.1g of Ga, 0.1g of Ce, and 3g of BaTiO3 are weighed, and the weighed raw materials are all put into a graphite crucible, and the solder is prepared in a vacuum high-frequency induction furnace, the temperature of the solder manufacturing is 1100℃, the crucible is cooled in water to form a photovoltaic active solder ingot.

[0083] Embodiment 5

[0084] The embodiment provides a gridless TOPCon photovoltaic cell, which is prepared by the same method as in Embodiment 4, and the difference is that:

[0085] (1) As shown in the drawings, in the embodiment, the photovoltaic ultrafine active welding wire 2 is arranged on the surface of the cell 1 in the Y direction. Figure 6

[0086] (2) As shown in Table 1, the specially prepared photovoltaic active solder used in the embodiment has the following formula: 60g of Sn, 5g of Mg, 40g of Pb, and 3g of NiFe2O4.

[0087] Embodiment 6​

[0088] The embodiment provides a gridless TOPCon photovoltaic cell piece, which is prepared by using the same method as in the embodiment 4, and the difference is that:

[0089] (1) As shown in the formula (1), in the embodiment, the photovoltaic superfine active solder wire 2 is arranged in 80 pieces along the X direction and 24 pieces along the Y direction on the surface of the cell piece 1. Figure 7

[0090] (2) As shown in the table 1, the formula of the special photovoltaic active solder used in the embodiment is 60g Sn, 40g Pb, 4g Zn, 1g Sb and 3g POSS.

[0091] Comparative example 2

[0092] The same method as in the embodiment 4 is used, and the difference is that the photovoltaic superfine active solder wire prepared by using the special photovoltaic active solder in the embodiment 4 is not used, but a common superfine solder wire is used. The common superfine solder wire is prepared by using a common solder on the market, and the formula of the common solder is 60g Sn and 40g Pb, as shown in the table 1. It is found that the superfine solder wire cannot be welded with the cell piece body in the preparation process, so the gridless TOPCon photovoltaic cell piece cannot be obtained.

[0093] The table 1 shows the formula of the solder used in the above embodiments 1-6 and comparative examples 1-2 and the welding direction of the solder wire on the surface of the cell piece, wherein the unit of the content of each substance is gram (g).

[0094] Table 1

[0095]

[0096] Embodiment 7

[0097] The embodiment provides a gridless TOPCon photovoltaic module, as shown in the formula (2) and the formula (3). Figure 9 and Figure 11 ​As shown, the TOPCon photovoltaic cell 1 used in the photovoltaic module has no grid lines on the surface, the TOPCon photovoltaic cell body 5 is slotted after the dielectric film is coated, and then used for module preparation. The metallization process of the cell and the module stringing process are carried out at the same time. The prepared photovoltaic module has no grid lines on the surface and is directly interconnected by the photovoltaic ultrafine active solder wire 2. The preparation method of the gridless TOPCon photovoltaic module includes the following steps: 150 photovoltaic ultrafine active solder wires 2 are drawn out from the welding machine equipment and directly welded with the exposed doped layer at the slotted position 3 of the surface dielectric film of the TOPCon photovoltaic cell body 5. The cell body 5 is welded into a string along the Y direction. The welding form adopts hot welding (specifically infrared welding), and the welding temperature is 250°C. After the stringing, the cell string is laid out, the bus bar is welded, the adhesive film glass is laid, the lamination is carried out, the frame is installed, and the junction box is installed to prepare the gridless TOPCon photovoltaic module.

[0098] The preparation method of the photovoltaic ultrafine active solder wire used in the embodiment includes the following steps: a specially prepared photovoltaic active solder is used for the preparation of the photovoltaic ultrafine active solder wire. Specifically, the specially prepared photovoltaic active solder ingot is melted in a molten pool, the temperature of the molten pool is kept at 280°C, a copper wire with a circular cross-section and a diameter of 25μm is drawn out from 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 air knife, a coating layer with a thickness of 5μm is obtained, and the photovoltaic ultrafine active solder wire is obtained after cooling and winding, vacuum packaging.

[0099] The preparation method of the specially prepared photovoltaic active solder used in the embodiment includes the following steps: referring to Table 2, 60g of Sn, 4.8g of Ti, 40g of Bi, 0.1g of Ga, 0.1g of Ce, 1g of NiFe2O4, 1g of BaTiO3, and 1g of POSS are weighed. Put all the weighed raw materials into a graphite crucible and prepare in a vacuum high-frequency induction furnace. The temperature for solder manufacturing is 1100°C. The crucible is cooled in water to form a photovoltaic active solder ingot after melting three times in the crucible.

[0100] Example 8

[0101] The embodiment provides a gridless TOPCon photovoltaic module, which is prepared by the same method as in Example 7, except that in the preparation of the photovoltaic active solder, referring to Table 2, the solder formula is: 60g of Sn, 40g of Pb, 5g of Mg, 1g of NiFe2O4, 1g of BaTiO3, and 1g of POSS.

[0102] Example 9

[0103] The embodiment provides a gate line-free TOPCon photovoltaic module, which is prepared by the same method as in the embodiment 7, and the difference lies in that the photovoltaic active solder is prepared by referring to Table 2, and the solder formula is: 60g Sn, 4g Zn, 1g Sb, 40g Pb, 1g NiFe2O4, 1g BaTiO3, and 1g POSS.

[0104] Embodiment 10

[0105] The embodiment provides a gate line-free TOPCon photovoltaic module, which is prepared by the same method as in the embodiment 7, and the difference lies in that the photovoltaic active solder is prepared by referring to Table 2, and the solder formula is: 60g Sn, 4g Zn, 1g Sb, 40g Pb, 1g NiFe2O4, 1g BaTiO3, and 1g POSS.

[0106] (1) As shown in FIGS. 1 and 2, in the embodiment, the leading direction of the photovoltaic ultrafine active solder wire 2 in the welding machine device is 80 in the X direction and 24 in the Y direction. Figure 10 Figure 12 (2) As shown in Table 2, in the embodiment, the formula of the photovoltaic active solder is: 60g Sn, 4.8g Ti, 40g Bi, 0.1g Ga, 0.1g Ce, 5g V, 5g Cr, 1g NiFe2O4, 1g BaTiO3, and 1g POSS.

[0107] Comparative Example 3

[0108] The same method as in the embodiment 7 is used, and the difference is that the photovoltaic ultrafine active solder wire prepared by using the special photovoltaic active solder described in the embodiment 7 is not used, but a common ultrafine solder wire is used. The common ultrafine solder wire is prepared by using a common solder on the market, and the formula of the common solder is shown in Table 2, which is: 60g Sn and 40g Pb. It is found that the ultrafine solder wire cannot be welded with the cell body during the preparation process, so the gate line-free TOPCon photovoltaic module cannot be obtained.

[0109] Comparative Example 4

[0110] The comparative example provides a conventional TOPCon photovoltaic module, and the photovoltaic cell used in the photovoltaic module is a conventional TOPCon photovoltaic cell with gate lines sintered on the surface. The conventional TOPCon photovoltaic cell is welded into a string by using a conventional solder wire, and after the cell string is laid out, the busbar is welded, the adhesive film glass is laid, the lamination is performed, the frame is mounted, and the junction box is installed, the conventional TOPCon photovoltaic module is prepared, and the version of the conventional TOPCon photovoltaic module is the same as that of the embodiment 10.

[0111] The comparative example provides a conventional TOPCon photovoltaic module, and the photovoltaic cell used in the photovoltaic module is a conventional TOPCon photovoltaic cell with gate lines sintered on the surface. The conventional TOPCon photovoltaic cell is welded into a string by using a conventional solder wire, and after the cell string is laid out, the busbar is welded, the adhesive film glass is laid, the lamination is performed, the frame is mounted, and the junction box is installed, the conventional TOPCon photovoltaic module is prepared, and the version of the conventional TOPCon photovoltaic module is the same as that of the embodiment 10.

[0112] ​The preparation method of the conventional solder wire used in the present comparative example is the same as that described in Example 7, except that the specially prepared photovoltaic active solder described in Example 7 is not used to prepare the photovoltaic ultrafine active solder wire, but a conventional solder wire is used, the copper wire diameter of which is 250 μm, and the coating thickness is 15 μm. The conventional solder wire is prepared using a commonly used solder on the market, as shown in Table 2. The commonly used solder formula is: 60 g Sn, 40 g Pb.

[0113] Table 2 shows the formula of the solder in Examples 7-10 and Comparative Examples 3-4 above and the welding direction of the solder wire on the surface of the cell sheet, wherein the unit of the content of each substance is gram (g).

[0114] Table 2

[0115]

[0116] Performance test

[0117] (1) Peel strength test

[0118] A multi-gate photovoltaic special peel strength tester is used to test the peel strength of the cell sheet after welding by the welding machine. The solder wire is clamped by a spring type fixing device to realize fixation, and the cell sheet is fixed by four rubber strips with magnets at both ends. The test data is automatically integrated by a computer special app program, and the average value is recorded.

[0119] (2) Thermal cycle (TC) test

[0120] The prepared gridless line TOPCon photovoltaic module is placed in a cold and hot cycle environment box for testing. The temperature is uniformly reduced from 25℃ to -40℃ in 1h, kept for 15min, then uniformly increased from -40℃ to 85℃ in 3h, kept for 15min, then uniformly decreased from 85℃ to 25℃ in 2h, and the test is repeated for 200 cycles. The power test is carried out before and after the test, and the data is recorded as the relative change percentage of the test after the test compared with the test before the test.

[0121] (3) Module power test

[0122] The gridless line TOPCon photovoltaic module prepared in Example 10 and the conventional TOPCon photovoltaic module prepared in Comparative Example 4 are subjected to power test, and the IV curve power detector is used for testing. The data recorded is the difference ΔPmax (W) of the maximum power of Example 10 compared with Comparative Example 4.

[0123] Test results

[0124] The peeling force test results of each group and the percentage of power change after TC test compared to before test (APmax (%)), the percentage of string resistance change (ARs (%)) are listed in Tables 3-4, wherein the negative value of APmax (%) represents the power attenuation after TC test, and the positive value of ARs (%) represents the increase of string resistance after TC test. The component power test results are listed in Table 5, wherein the positive value of APmax (W) represents the increase of component power of Example 10 compared to Comparative Example 4.

[0125] Comparing Examples 1-3 and Comparative Example 1, through the foregoing experimental process, it can be known that the photovoltaic ultra-fine active welding wire prepared by using the special active solder described in Examples 1-3 can directly weld and prepare a gridless TOPCon photovoltaic cell piece and ensure the welding strength, and the ultra-fine welding wire prepared by using the solder in the prior art described in Comparative Example 1 cannot make a gridless TOPCon photovoltaic cell piece.

[0126] Further, compared with Comparative Example 1, the special active solder used in the preparation of the photovoltaic ultra-fine active welding wire in Examples 1-3, the Zn and Ti elements in the solder can diffuse to the welding interface to realize the welding of the photovoltaic ultra-fine active welding wire and the cell piece, the addition of NiFe2O4, BaTiO3 and POSS in the solder can improve the wetting effect of the solder matrix, and the increase of the wetting performance is beneficial to the improvement of the welding strength; in addition, in the welding process, NiFe2O4, BaTiO3 and POSS can act with Zn, Ag and Ti in the solder matrix, strengthen the Zn phase grains, hinder the formation of AgZn and ZnTi alloys, and promote the diffusion of Zn and Ti to the welding interface.

[0127] In addition, in Examples 1-3, the addition of V can assist the diffusion of Zn and Ti, and the addition of Al improves the thermal stability of the solder, so that the solder can meet the welding at 400°C.

[0128] Comparing Examples 4-6 and Comparative Example 2, through the foregoing experimental process, it can be known that the photovoltaic ultra-fine active welding wire prepared by using the special active solder described in Examples 4-6 can directly weld and prepare a gridless TOPCon photovoltaic cell piece and ensure the welding strength, and the ultra-fine welding wire prepared by using the solder in the prior art described in Comparative Example 2 cannot make a gridless TOPCon photovoltaic cell piece.

[0129] Further, compared with Comparative Example 2, the special active solder used in the preparation of the photovoltaic ultrafine active welding wire in Examples 4-6 can diffuse Zn, Mg and Ti elements in the solder to the welding interface to realize the welding of the photovoltaic ultrafine active welding wire and the cell piece. The addition of NiFe2O4, BaTiO3 and POSS in the solder can improve the wetting effect of the solder matrix. The increase in the wetting performance is beneficial to the improvement of the welding strength. In addition, in the welding process, NiFe2O4, BaTiO3 and POSS can react with Sn, Zn, Mg and Ti in the solder matrix to strengthen the β-Sn phase grains, hinder the formation of SnZn, SnMg and SnTi alloys, and promote the diffusion of Zn, Mg and Ti to the welding interface.

[0130] By the foregoing experimental process, it can be known that, compared with Comparative Example 3, the photovoltaic ultrafine active welding wire prepared by using the special active solder described in Examples 7-10 can be directly welded into a string to make a module using the body of a no-grid-line TOPCon photovoltaic cell piece, and the welding strength is ensured. Therefore, when the module prepared is subjected to TC test, the fatigue damage of the cell piece and the welding wire is more effectively resisted, and thus the power attenuation and the string resistance increase are smaller in the TC test, and the reliability of the module in subsequent use can be ensured. However, the ultrafine welding wire prepared by using the solder in the prior art described in Comparative Example 3 cannot be directly welded into a string to make a module using the body of a no-grid-line TOPCon photovoltaic cell piece.

[0131] Compared with Comparative Example 3, the special active solder used in the preparation of the photovoltaic ultrafine active welding wire in Examples 7-10 can diffuse Zn, Mg and Ti elements in the solder to the welding interface to realize the welding of the photovoltaic ultrafine active welding wire and the cell piece. The addition of NiFe2O4, BaTiO3 and POSS in the solder can improve the wetting effect of the solder matrix. The increase in the wetting performance is beneficial to the improvement of the welding strength. In addition, in the welding process, NiFe2O4, BaTiO3 and POSS can react with Sn, Zn, Mg and Ti in the solder matrix to strengthen the β-Sn phase grains, hinder the formation of SnZn, SnMg and SnTi alloys, and promote the diffusion of Zn, Mg and Ti to the welding interface. Compared with Example 7, in Example 10, the addition of V can assist the diffusion of Zn, and the addition of Cr can improve the thermal stability of the solder, and thus the peeling force of Example 10 is slightly improved, and the TC power attenuation is slightly smaller.

[0132] Compared with Comparative Example 4, the power of the gridless TOPCon photovoltaic module prepared in Example 10 is higher than that of the conventional TOPCon photovoltaic module, because the photovoltaic ultrafine active welding wire used in the photovoltaic module prepared in Example 10 is directly welded on the doped layer, the transmission resistance and contact resistance on the current conduction path of the cell piece are small, and therefore the power of the module can be improved compared with the conventional TOPCon photovoltaic module.

[0133] Table 3

[0134]

[0135] Table 4

[0136]

[0137] Table 5

[0138]

[0139] The above describes specific embodiments of the present application, and through the above description, relevant personnel can certainly make various changes and modifications within the scope of not deviating from the technical idea of the present application.

Claims

1. A photovoltaic active welding wire, characterized in that, It includes a welding wire core and a coating layer with a thickness of 1~100um wrapped around the welding wire core, wherein the coating layer is an active solder and the active solder includes 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- 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, In-Mg-Zn, wherein X is Ce or La or Ce-La; The first component is selected from any one of NiFe2O4, NiCo2O4, CoFe2O4, BaTiO3, SrTiO3, CaTiO3, MgTiO3, and POSS; The matrix accounts for 55wt% to 99.99wt% of the active solder content, and the first component accounts for 0.01wt% to 5wt% of the active solder content.

2. The photovoltaic active welding wire according to claim 1, characterized in that, 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 Sn content in the matrix accounts for 20wt% to 99.9wt% of the matrix content, and the Ti, Zn, or Mg content accounts for 0.01wt% to 20wt% of the matrix content.

3. The photovoltaic active welding wire according to claim 1, characterized in that, The first component is selected from any one of NiFe2O4, BaTiO3, and POSS.

4. The photovoltaic active welding wire according to claim 1, characterized in that, The active solder further includes 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 0 wt% to 20 wt% of the active solder content, and the third component accounts for 0 wt% to 20 wt% of the active solder content.

5. The photovoltaic active welding wire according to claim 1, wherein the base material of the welding wire core is selected from at least one of the following substances: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium, and alloys containing any of the foregoing substances; or The base material of the welding wire core is selected from any two of the following substances: copper, aluminum, zinc, nickel, tungsten, titanium, chromium, cobalt, magnesium and alloys containing any of the aforementioned substances, and the structure of the welding wire core is a core-shell cladding structure or a laminated structure composed of the selected substances.

6. The photovoltaic active welding wire according to claim 2, characterized in that, The cross-sectional width of the photovoltaic active welding wire is 10~120μm, and the cross-sectional thickness is 10~120μm; the thickness of the coating layer is 1~50μm.

7. A method for fabricating a gridless TOPCon photovoltaic cell, characterized in that, Use either of the following two methods: The first method involves sequentially texturing, doping, etching, oxide layer deposition, poly-Si doping deposition, welding, and dielectric film deposition on a silicon wafer; the specific welding steps are as follows: the photovoltaic active welding wire described in any one of claims 1 to 6 is directly welded to the P-region and N-region doped layers along the X-direction and / or Y-direction. The second method involves sequentially texturing, doping, etching, oxide layer deposition, doped poly-Si deposition, dielectric film deposition, dielectric film grooving, and welding of the silicon wafer. The specific welding steps are as follows: the photovoltaic active welding wire described in any one of claims 1 to 6 is directly welded along the X direction and / or Y direction to the P-region and N-region doped layer exposed at the grooving position. In the above method, the extension directions parallel to the two intersecting edges of the silicon wafer are defined as the X direction and the Y direction, respectively.

8. The method for preparing a gridless TOPCon photovoltaic cell according to claim 7, characterized in that, The number of photovoltaic active welding wires welded in the P-region or N-region is 20 to 300; the welding method is thermal welding, ultrasonic welding, or laser welding; when the photovoltaic active welding wire is directly welded to the doped layer of the P-region or N-region along the X-direction and / or Y-direction, the welding temperature is above 400℃; when the photovoltaic active welding wire is directly welded to the doped layer of the P-region or N-region exposed at the slotted position along the X-direction and / or Y-direction, the welding temperature is 100℃ to 400℃.

9. A gridless TOPCon photovoltaic cell, characterized in that, The TOPCon photovoltaic cell without grid lines is prepared using the preparation method described in any one of claims 7 to 8.

10. The gridless TOPCon photovoltaic cell according to claim 9, characterized in that, The TOPCon photovoltaic cells include photovoltaic cells with a front P-area and a back N-area, photovoltaic cells with a front N-area and a back P-area, and back contact (BC) photovoltaic cells with a back P-area and a back N-area.

11. A gridless TOPCon photovoltaic module, characterized in that, It is obtained by welding the gridless TOPCon photovoltaic cells as described in claim 9 or 10 into strings and then encapsulating the strings.

12. A method for fabricating a gridless TOPCon photovoltaic module, characterized in that, Includes the following steps: The silicon wafer is sequentially texturized, doped, etched, deposited oxide layer, deposited doped poly-Si, deposited dielectric film, and grooved dielectric film to obtain the TOPCon photovoltaic cell body. The TOPCon photovoltaic cell body is directly welded into a string using the photovoltaic active welding wire described in any one of claims 1 to 6, and the cell string is then encapsulated to obtain a gridless TOPCon photovoltaic module. The specific steps of the welding are as follows: define the extension directions parallel to the two intersecting edges of the silicon wafer as the X direction and the Y direction, respectively, and directly weld the photovoltaic active welding wire along the X direction and / or the Y direction onto the exposed P-region and N-region doped layers at the slotted position.

13. A gridless TOPCon photovoltaic module, characterized in that, The TOPCon photovoltaic module without grid lines is prepared using the preparation method described in claim 12.

Images