Main-grid-free back contact battery assembly and preparation method and application thereof

Abstract

The invention provides a main-grid-free back contact battery assembly and a preparation method and application thereof. The preparation method comprises the following steps: providing a plurality of main-grid-free back contact battery pieces, and carrying out whole string typesetting; providing a whole series of welding strips and a carrier film, wherein the carrier film comprises a wide film and a narrow film; laying a whole series of welding strips and all wide films on the surface of the main-grid-free back contact battery piece, and performing first hot pressing to complete film covering, so that the whole series of welding strips are fixed through the wide films; laying all narrow films on the area, which is not covered with the carrier film, of the surface of the battery string, and performing secondary hot pressing to complete film covering; and after the cell strings are typeset and laminated, the main-grid-free back contact cell assembly is obtained. High-precision placement of the solder strip can be achieved, short circuit caused by the fact that the solder strip is in lap joint with the anisotropic fine grid is avoided, use of solder paste and insulation paste is reduced, the assembly cost is reduced, and the assembly power and the double-sided rate can also be improved. And meanwhile, the step-by-step film coating process is adopted to realize full coverage of a cell piece carrier film, and the adhesive film is prevented from permeating below the welding strip to influence the reliability of the assembly.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a gridless back-contact solar cell module, its preparation method, and its application. Background Technology

[0002] Back-contact solar cells have both the PN junction and the metal contact area located on the back of the solar cell, while the front of the cell uses SiN. x / SiO x The double-layer anti-reflection passivation film, without the obstruction of metal electrodes, maximizes the utilization of incident light, reduces optical losses, brings more effective power generation area, and has a more aesthetically pleasing appearance, with huge market demand potential.

[0003] Back-contact cells, as a platform technology, can be combined with technologies such as HJT and TOPCon to form various technical routes such as HBC and TBC. Among them, the busbarless back-contact cell reduces the silver paste consumption of the cell by eliminating the main busbar design, while the sub-busbar current is directly led out from the solder strip, which shortens the current transmission path and further improves the module power.

[0004] Currently, gridless back-contact solar cells mainly employ three stringing methods: coating, dispensing, and welding + dispensing. The former requires printing insulating adhesive and solder paste onto the fine grid, demanding high printing accuracy and speed from the equipment. Missing printing of the insulating adhesive and solder paste can lead to module defects. Furthermore, during printing and manufacturing, some solder paste may be introduced, causing short circuits after the fine grid overlaps. The introduction of solder paste and insulating adhesive not only affects module yield but also increases manufacturing costs. The welding + dispensing process is a technological upgrade to the conventional stringing process for gridless back-contact solar cells. Through alloying and curing, it achieves strong tensile strength between the solder ribbon and the cell, resulting in high heat resistance. However, it places high demands on the precision and area of ​​the dispensing equipment. The rapid welding process can also easily damage the fine grid and cause cell warping, affecting process yield. Dispensing mainly uses adhesives such as UV glue and hot melt glue to fix the solder ribbon to the solar cell. The solder ribbon and solar cell are connected in a series through lamination. Because the solar cell is printed with insulating glue and solder paste, there is a height difference between the solder ribbon and the solar cell. During the lamination process, the adhesive film on the back can easily seep under the solder ribbon, causing the solder layer to fail to contact the solder ribbon, resulting in defects such as poor soldering after lamination.

[0005] Therefore, how to avoid the use of insulating adhesive and solder paste, reduce manufacturing costs, and improve the power, bifaciality, and reliability of components are urgent technical problems to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a gridless back-contact solar cell module, its fabrication method, and its applications. This invention utilizes gridless back-contact solar cells with grid line separation. Combined with a string of solder ribbons, this allows for high-precision placement of the ribbons, avoiding short circuits caused by overlapping irregular grid lines. It also eliminates the need for insulating adhesive and solder paste, reducing module cost and optical obstruction, while improving module power and bifaciality. Furthermore, the cell string employs a step-by-step lamination process to fix the solder ribbons and fully cover the cell string carrier film. This prevents the adhesive film from seeping under the solder ribbons during lamination, which could affect the metallurgical bond between the solder ribbons and the solar cells, thus improving module reliability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for fabricating a gridless back-contact battery module, the method comprising the following steps:

[0009] (a) Provide a plurality of gridless back contact solar cells and arrange them in a string; the surface of the gridless back contact solar cells has a plurality of positive fine grids and a plurality of negative fine grids, the plurality of positive fine grids and the plurality of negative fine grids are arranged alternately in a first direction; the positive fine grids have a plurality of spaced first partition regions in a second direction, and the negative fine grids have a plurality of spaced second partition regions in a second direction.

[0010] (b) Provide a string of solder strips and a carrier film, the carrier film comprising a wide film and a narrow film.

[0011] After the battery string is arranged, the entire string of solder ribbons and all the wide films are laid on the surface, and the first hot pressing is performed so that the entire string of solder ribbons is fixed by the wide films.

[0012] The entire string of solder strips includes several positive electrode solder strips and several negative electrode solder strips. The positive electrode solder strips are laid along the first direction in the second partition area and are conductively connected to the positive electrode grid. The negative electrode solder strips are laid along the first direction in the first partition area and are conductively connected to the negative electrode grid. All the wide films are distributed at intervals along the first direction on each cell.

[0013] (c) Lay all the narrow films on the areas of the battery string surface that are not covered by the carrier film after step (b) and perform a second hot pressing to complete the coating;

[0014] (d) Lamination of the battery strings processed in step (c) yields the gridless back-contact battery assembly.

[0015] This invention employs gridless back-contact solar cells with grid line separation. Combined with a string of solder ribbons, it achieves high-precision placement of the ribbons, avoiding short circuits caused by overlapping irregular grid lines. It also eliminates the need for insulating adhesive and solder paste, reducing module cost and optical obstruction, while increasing module power and bifaciality. Furthermore, the phased lamination process secures the solder ribbons and fully covers the cell string carrier film, preventing adhesive film from seeping under the solder ribbons during lamination and affecting the metallurgical bond between the ribbons and cells, thus improving module reliability.

[0016] It should be noted that the coating described in step (c) can achieve full coverage of the carrier film of the battery string.

[0017] It should be noted that the first direction and the second direction are perpendicular to each other.

[0018] It should be noted that before laying all the narrow membranes, the welding strip clamps that fix the welding strips between the sheets need to be removed to make room for the laying of the narrow membranes.

[0019] Preferably, the material of the entire string of welding strips includes an alloy.

[0020] Preferably, the melting point of the alloy is 135-165℃, for example, it can be 135℃, 145℃, 155℃ or 165℃.

[0021] Preferably, the alloy comprises SnPbBi / or SnBiAg.

[0022] Preferably, the alloy contains rare earth elements. Examples include Ce, Nd, Y, or Sc.

[0023] In this invention, the purpose of adding rare earth elements is to improve the uniformity of the weld structure, reduce the enrichment of Bi elements, and increase the weld tensile strength.

[0024] Preferably, the rare earth element accounts for 0.2-1% of the mass fraction of the alloy, for example, it can be 0.2%, 0.4%, 0.6%, 0.8% or 1%, etc.

[0025] Preferably, the surface of the entire string of solder strips is coated with flux.

[0026] In this invention, the application of flux facilitates the metallurgical bonding between the solder ribbon and the battery cell, thereby improving the bonding strength between the solder ribbon and the battery cell.

[0027] Preferably, the thickness of the flux coating on the surface of the solder strip is 0.5-2μm, for example, it can be 0.5μm, 1μm, 1.5μm or 2μm.

[0028] Preferably, the flux includes an activator, a film-forming agent, a surfactant, and an antioxidant.

[0029] Preferably, the activator includes any one or a combination of at least two of sorbic acid, succinamide, or malic acid.

[0030] Preferably, the film-forming agent includes any one or a combination of at least two of rosin, phenolic resin, or vinyl chloride resin.

[0031] Preferably, the surfactant comprises any one or a combination of at least two of octylphenol polyoxyethylene ether, sodium dodecyl sulfate, or fatty hydrochloric acid.

[0032] Preferably, the antioxidant includes ascorbic acid and / or catechol.

[0033] Preferably, the mass ratio of the activator, film-forming agent, surfactant, and antioxidant is (10-20):(10-20):(2-3):1, wherein the activator is selected in the range of "10-20", for example, 10, 15, or 20, and the film-forming agent is selected in the range of "10-20", for example, 10, 15, or 20.

[0034] Preferably, the material of the carrier membrane includes any one of pre-crosslinked POE (polyolefin elastomer), EVA (ethylene-vinyl acetate copolymer), PVB (polyvinyl butyral), or TPO (thermoplastic polyolefin).

[0035] Preferably, the width of the wide membrane is 72-80mm, for example, 72mm, 74mm, 76mm, 78mm or 80mm, and the width of the narrow membrane is 13-21mm, for example, 13mm, 15mm, 17mm, 19mm or 21mm.

[0036] In this invention, a wide film of suitable width is more conducive to fixing the solder strip.

[0037] Preferably, the narrow membrane is an integral membrane or a separate membrane.

[0038] In this invention, when the narrow film is an integral film, the carrier film can be covered between several cells without main grid back contact; when the narrow film is a split film, there is no carrier film covering between several cells without main grid back contact, and a single cell without main grid back contact achieves full coverage of the carrier film.

[0039] It should be noted that when the carrier film and the front and back films of the glass are of the same type, the narrow film can be either an integral film or a separate film; when the carrier film and the front and back films of the glass are not of the same type, considering the differences in flowability of different types of films, and the potential for defects such as dense bubbles to be generated during component lamination, a separate film is selected.

[0040] It should be noted that when wide and narrow films are laid on the battery string, the films can be stacked to ensure full coverage of the battery cell carrier film.

[0041] Preferably, the split membrane is composed of two discontinuous half-membranes spliced ​​together; the width of the half-membrane is 6-10mm, for example, it can be 6mm, 7mm, 8mm, 9mm or 10mm, etc.

[0042] Preferably, the temperature of the first hot pressing is 115-130℃, for example, 115℃, 120℃, 125℃ or 130℃, and the time is 100-200s, for example, 100s, 120s, 140s, 160s, 180s or 200s.

[0043] Preferably, the temperature of the second hot pressing is 140-155℃, for example, 145℃, 150℃ or 155℃, and the time is 450-600s, for example, 450s, 500s, 550s, 560s, 570s, 580s, 590s or 600s.

[0044] In this invention, the second hot pressing at a suitable temperature enables the solder strip and the battery cell to achieve low-temperature interconnection, which is beneficial for the melting of the solder strip coating to achieve metallurgical bonding.

[0045] In a second aspect, the present invention provides a gridless back contact battery assembly, which is prepared by the preparation method described in the first aspect.

[0046] The gridless back contact battery assembly includes:

[0047] The battery string includes a plurality of gridless back-contact battery cells. The surface of each gridless back-contact battery cell has a plurality of positive electrode fine grids and a plurality of negative electrode fine grids. The plurality of positive electrode fine grids and the plurality of negative electrode fine grids are arranged alternately in a first direction. The positive electrode fine grids have a plurality of spaced first partition regions in a second direction, and the negative electrode fine grids have a plurality of spaced second partition regions in a second direction.

[0048] The entire string of solder strips includes several positive solder strips and several negative solder strips. The positive solder strips are laid along a first direction in the second partition area and are conductively connected to the positive grid. The negative solder strips are laid along the first direction in the first partition area and are conductively connected to the negative grid.

[0049] A carrier film is disposed on the entire string of solder strips and is fixedly connected to the battery string. The carrier film includes several wide films and several narrow films arranged at intervals. All the wide films are distributed at intervals in the middle area of ​​each battery cell along a first direction to fix the entire string of solder strips. All the narrow films are distributed in the interval area between adjacent wide films along the first direction.

[0050] Preferably, the welding strips in the entire string of welding strips are round wire welding strips.

[0051] Preferably, the diameter of the round wire welding strip is smaller than the width of the first partition area and the second partition area.

[0052] This invention uses the circular wire solder strips defined by the above conditions for high-precision placement, which can eliminate the need for insulating adhesive and solder paste for battery cells, thereby reducing the cost of component production.

[0053] Preferably, the width of the first partition area and the second partition area are each independently 2.5-3.5 times the diameter of the round wire welding strip, for example, 2.5 times, 3 times or 3.5 times, etc.

[0054] This invention limits this multiple to prevent problems such as insufficient machine precision and deviation onto non-standard grid lines when placing solder strips.

[0055] Preferably, the width of the first partition area and the second partition area are each independently 0.5-1mm, for example, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm.

[0056] Preferably, the number of solder ribbons on the gridless back contact cell is greater than or equal to 30, for example, 30, 40, 50 or 60 ribbons, etc.

[0057] Preferably, the positive electrode grid and the negative electrode grid are each made of silver or copper.

[0058] Preferably, the first discontinuity regions on adjacent positive electrode grids correspond to each other in the first direction, and the second discontinuity regions on adjacent negative electrode grids correspond to each other in the first direction.

[0059] Preferably, in the second direction, the first discontinuity zone and the second discontinuity zone are alternately spaced.

[0060] Preferably, a connecting line is provided near the edge of the non-main grid back contact cell of the positive electrode fine grid, and the connecting line is located in the first partition area for electrically connecting adjacent positive electrode fine grids.

[0061] Preferably, a connecting line is provided near the edge of the negative electrode grid that is in contact with the back of the non-main grid cell. The connecting line is located in the second partition area and is used to electrically connect the adjacent negative electrode grid.

[0062] In this invention, the purpose of designing the connecting wire is to avoid the inability to collect edge current of the fine grid and to prevent short circuits caused by excessively long solder strips overlapping the battery cells.

[0063] It should be noted that the material of the connecting wire only needs to be conductive.

[0064] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] This invention employs gridless back-contact solar cells with grid line separation. Combined with a string of solder ribbons, it achieves high-precision placement of the ribbons, avoiding short circuits caused by overlapping irregular grid lines. It also eliminates the need for insulating adhesive and solder paste, reducing module cost and optical obstruction, while increasing module power and bifaciality. Furthermore, the phased lamination process secures the solder ribbons and fully covers the cell string carrier film, preventing adhesive film from seeping under the solder ribbons during lamination and affecting the metallurgical bond between the ribbons and cells, thus improving module reliability. Attached Figure Description

[0067] Figure 1 This is a partial structural diagram of the gridless back contact solar cell provided in Embodiment 1 of the present invention.

[0068] Figure 2 This is a schematic diagram of the carrier membrane provided in Example 1 of the present invention.

[0069] Figure 3 This is a schematic diagram of the cut wide film provided in Embodiment 1 of the present invention.

[0070] Figure 4 This is a schematic diagram of the cut narrow membrane provided in Embodiment 1 of the present invention.

[0071] Figure 5 This is a schematic diagram of the battery string after laying the entire string of solder strips and all the wide films, as provided in Embodiment 1 of the present invention.

[0072] Figure 6 This is a schematic diagram of a battery string after the surface carrier film is fully covered, as provided in Embodiment 1 of the present invention.

[0073] Figure 7 This is a schematic diagram of the carrier membrane provided in Example 2 of the present invention.

[0074] Figure 8 This is a schematic diagram of the cut wide film provided in Embodiment 2 of the present invention.

[0075] Figure 9 This is a schematic diagram of the cut narrow membrane provided in Embodiment 2 of the present invention.

[0076] Figure 10This is a schematic diagram of the battery string after laying the entire string of solder ribbons and all the wide films, as provided in Embodiment 2 of the present invention.

[0077] Figure 11 This is a schematic diagram of a battery string after the surface carrier film is fully covered, as provided in Embodiment 2 of the present invention.

[0078] Wherein, 1-positive electrode fine grid; 1'-negative electrode fine grid; 2-first partition region; 2'-second partition region; 3-connecting line. Detailed Implementation

[0079] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0080] Example 1

[0081] This embodiment provides a method for fabricating a gridless back-contact battery module, the method comprising the following steps:

[0082] (a) Provide several grid-less back-contact solar cells and arrange them in a string; a partial structural diagram of the grid-less back-contact solar cells is shown below. Figure 1 As shown in the figure, the surface of the gridless back-contact battery cell has a plurality of positive electrode fine grids 1 and a plurality of negative electrode fine grids 1', which are arranged alternately in a first direction. The positive electrode fine grids 1 have a plurality of spaced first interruption regions 2 in a second direction, and the negative electrode fine grids 1' have a plurality of spaced second interruption regions 2' in the second direction. The first interruption regions 2 on adjacent positive electrode fine grids 1 correspond to each other in the first direction, and the second interruption regions 2' on adjacent negative electrode fine grids 1' correspond to each other in the first direction. In the first direction, they correspond to each other; in the second direction, the first interruption region 2 and the second interruption region 2' are alternately arranged; a connecting line 3 (made of silver paste) is provided on the positive electrode fine grid 1 near the edge of the gridless back contact cell, the connecting line 3 is located in the first interruption region 2, and is used to electrically connect the adjacent positive electrode fine grid 1; a connecting line 3 (made of silver paste) is provided on the negative electrode fine grid 1' near the edge of the gridless back contact cell, the connecting line 3 is located in the second interruption region 2', and is used to electrically connect the adjacent negative electrode fine grid 1'. The width of both the first interruption region 2 and the second interruption region 2' is 0.8 mm; the positive electrode fine grid 1 and the negative electrode fine grid 1' are made of silver paste.

[0083] Provide a complete string of solder ribbons and a carrier film, and cut the carrier film into wide films and narrow films, such as... Figures 2-4As shown. The material of the entire string of solder ribbons is an alloy comprising SnPbBi and rare earth element Sc, with the rare earth element accounting for 0.5% of the alloy's mass fraction. The number of solder ribbons on the gridless back contact cell is 32. The surface of the solder ribbons in the entire string is coated with a flux with a thickness of 2μm, the flux comprising sorbic acid, rosin, octylphenol polyoxyethylene ether, and ascorbic acid in a mass ratio of 20:20:2:1. The material of the carrier membrane is pre-crosslinked POE. The solder ribbons in the entire string are round wire solder ribbons, the diameter of which is smaller than the width of the first and second partition regions, the width of which is three times the diameter of the round wire solder ribbon. The width of the wide membrane is 80mm, and the width of the narrow membrane is 13mm; the narrow membrane is an integral membrane.

[0084] (b) Using solder strip clamps, the entire string of solder strips and all the wide films are laid on the surface of the battery string after it has been arranged, and a first hot pressing is performed to fix the entire string of solder strips through the wide films, such as... Figure 5 As shown.

[0085] The entire string of solder strips includes several positive electrode solder strips and several negative electrode solder strips. The positive electrode solder strips are laid along the first direction in the second partition area and are conductively connected to the positive electrode grid. The negative electrode solder strips are laid along the first direction in the first partition area and are conductively connected to the negative electrode grid. All the wide films are distributed at intervals on each cell along the first direction. The temperature of the first hot pressing is 120°C and the time is 120 seconds.

[0086] (c) Remove the solder ribbon clips, and then lay all the narrow films on the areas of the battery string surface that are not covered by the carrier film after the treatment in step (b), such as... Figure 6 As shown, a second hot pressing is performed to complete the film coating, and then the obtained battery strings are arranged and laminated to obtain the gridless back contact battery assembly.

[0087] The second hot pressing was performed at a temperature of 150°C for 575 seconds.

[0088] Example 2

[0089] This embodiment provides a method for fabricating a gridless back-contact battery module, the method comprising the following steps:

[0090] (a) A plurality of gridless back-contact solar cells are provided and arranged in a string; the surface of the gridless back-contact solar cells has a plurality of positive electrode fine grids and a plurality of negative electrode fine grids, the plurality of positive electrode fine grids and the plurality of negative electrode fine grids are arranged alternately in a first direction; the positive electrode fine grids have a plurality of spaced first partition regions in a second direction, and the negative electrode fine grids have a plurality of spaced second partition regions in a second direction; the first partition regions on adjacent positive electrode fine grids correspond to each other in the first direction, and the second partition regions on adjacent negative electrode fine grids correspond to each other in the first direction; in the second direction, the first partition regions and the second partition regions are arranged alternately in a second direction; a connecting line (made of silver paste) is provided on the positive electrode fine grids near the edge of the gridless back-contact solar cells, the connecting line is located in the first partition region, and is used to electrically connect adjacent positive electrode fine grids; a connecting line (made of silver paste) is provided on the negative electrode fine grids near the edge of the gridless back-contact solar cells, the connecting line is located in the second partition region, and is used to electrically connect adjacent negative electrode fine grids. The width of both the first and second partition regions is 0.5 mm; the positive and negative electrode grids are made of silver paste.

[0091] Provide a complete string of solder ribbons and a carrier film, and cut the carrier film into wide films and narrow films, such as... Figures 7-9 As shown. The material of the entire string of solder ribbons is an alloy comprising SnBiAg and the rare earth element Ce, with the rare earth element accounting for 0.3% of the alloy's mass fraction. The number of solder ribbons on the gridless back contact cell is 35. The surface of the solder ribbons in the entire string is coated with a flux of 1 μm thickness, comprising succinamide, phenolic resin, sodium dodecyl sulfate, and catechol in a mass ratio of 10:10:2:1. The material of the carrier membrane is pre-crosslinked EVA. The solder ribbons in the entire string are round wire solder ribbons, the diameter of which is smaller than the width of the first and second partition regions, the width of which is three times the diameter of the round wire solder ribbon. The width of the wide membrane is 72 mm, and the width of the narrow membrane is 20 mm. The narrow membrane is a split membrane, composed of two discontinuous half-membranes spliced ​​together, each half-membrane being 10 mm wide.

[0092] (b) Using solder strip clamps, the entire string of solder strips and all the wide films are laid on the surface of the battery string after it has been arranged, and a first hot pressing is performed to fix the entire string of solder strips through the wide films, such as... Figure 10 As shown.

[0093] The entire string of solder strips includes several positive electrode solder strips and several negative electrode solder strips. The positive electrode solder strips are laid along the first direction in the second partition area and are conductively connected to the positive electrode grid. The negative electrode solder strips are laid along the first direction in the first partition area and are conductively connected to the negative electrode grid. All the wide films are distributed at intervals on each cell along the first direction. The temperature of the first hot pressing is 115°C and the time is 150 seconds.

[0094] (c) Remove the solder ribbon clips, and then lay all the narrow films on the areas of the battery string surface that are not covered by the carrier film after the treatment in step (b), such as... Figure 11 As shown, a second hot-pressing process is performed to complete the film coating. Subsequently, the obtained battery strings are arranged and laminated to obtain the gridless back contact battery assembly.

[0095] The second hot pressing was performed at a temperature of 145℃ for 600 seconds.

[0096] Example 3

[0097] This embodiment provides a method for fabricating a gridless back-contact battery module, the method comprising the following steps:

[0098] (a) A plurality of gridless back-contact solar cells are provided and arranged in a string; the surface of the gridless back-contact solar cells has a plurality of positive electrode fine grids and a plurality of negative electrode fine grids, the plurality of positive electrode fine grids and the plurality of negative electrode fine grids are arranged alternately in a first direction; the positive electrode fine grids have a plurality of spaced first partition regions in a second direction, and the negative electrode fine grids have a plurality of spaced second partition regions in a second direction; the first partition regions on adjacent positive electrode fine grids correspond to each other in the first direction, and the second partition regions on adjacent negative electrode fine grids correspond to each other in the first direction; in the second direction, the first partition regions and the second partition regions are arranged alternately in a second direction; a connecting line (made of copper) is provided on the positive electrode fine grids near the edge of the gridless back-contact solar cells, the connecting line is located in the first partition region, and is used to electrically connect adjacent positive electrode fine grids; a connecting line (made of copper) is provided on the negative electrode fine grids near the edge of the gridless back-contact solar cells, the connecting line is located in the second partition region, and is used to electrically connect adjacent negative electrode fine grids. The width of both the first and second partition areas is 0.5-1mm; both the positive and negative fine grids are copper-plated grid lines.

[0099] A complete string of solder ribbons and a carrier film are provided, and the carrier film is cut into wide films and narrow films. The material of the complete string of solder ribbons is an alloy comprising SnPbBi and rare earth elements (Nd and Y), with the rare earth elements accounting for 0.4% of the alloy by mass. The number of solder ribbons on the gridless back contact cell is 40. The surface of the solder ribbons in the complete string is coated with a flux with a thickness of 2 μm, the flux comprising malic acid, vinyl chloride resin, octylphenol polyoxyethylene ether, and ascorbic acid in a mass ratio of 10:10:2:1. The material of the carrier film is pre-crosslinked PVB. The solder ribbons in the complete string are round wire solder ribbons, the diameter of which is smaller than the width of the first and second partition regions, the width of which is three times the diameter of the round wire solder ribbon. The width of the wide film is 72 mm, and the width of the narrow film is 21 mm; the narrow film is an integral film.

[0100] (b) The entire string of welding strips and all the wide films are laid on the surface of the battery string after the entire string is arranged by means of welding strip clamps, and the first hot pressing is performed so that the entire string of welding strips is fixed by the wide films.

[0101] The entire string of solder strips includes several positive electrode solder strips and several negative electrode solder strips. The positive electrode solder strips are laid along the first direction in the second partition area and are conductively connected to the positive electrode grid. The negative electrode solder strips are laid along the first direction in the first partition area and are conductively connected to the negative electrode grid. All the wide films are distributed at intervals on each cell along the first direction. The temperature of the first hot pressing is 130°C and the time is 130 seconds.

[0102] (c) Remove the solder strip clips, and then lay all the narrow films on the areas of the battery string surface that are not covered by the carrier film after step (b) and perform a second hot pressing to complete the film coating. Then, lay out and laminate the obtained battery strings to obtain the gridless back contact battery assembly.

[0103] The second hot pressing was performed at a temperature of 155℃ for 550 seconds.

[0104] Example 4

[0105] The difference between this embodiment and Embodiment 1 is that the material of the entire string of welding strips is an alloy, and the alloy does not contain rare earth elements.

[0106] The remaining preparation methods and parameters are consistent with those in Example 1.

[0107] Example 5

[0108] The difference between this embodiment and Embodiment 1 is that the rare earth element accounts for 2% of the mass fraction of the alloy.

[0109] The remaining preparation methods and parameters are consistent with those in Example 1.

[0110] Example 6

[0111] The difference between this embodiment and Embodiment 1 is that the surface of the solder strips in the entire string of solder strips is not coated with flux.

[0112] The remaining preparation methods and parameters are consistent with those in Example 1.

[0113] Example 7

[0114] The difference between this embodiment and Embodiment 1 is that the flux does not contain surfactants.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Example 8

[0117] The difference between this embodiment and Embodiment 1 is that the temperature of the first hot pressing in step (b) is 90°C.

[0118] The remaining preparation methods and parameters are consistent with those in Example 1.

[0119] Example 9

[0120] The difference between this embodiment and Embodiment 1 is that the temperature of the first hot pressing in step (b) is 150°C.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Example 10

[0123] The difference between this embodiment and Embodiment 1 is that no connecting wires are provided in the back contact cell without a main grid.

[0124] The remaining preparation methods and parameters are consistent with those in Example 1.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 1 is that the carrier film is not cut, but the entire string of solder ribbons and the carrier film are laid directly on the surface of the battery string after the entire string is arranged.

[0127] The remaining preparation methods and parameters are consistent with those in Example 1.

[0128] Comparative Example 2

[0129] The difference between this comparative example and Example 1 is that the carrier film is not cut. Instead, the entire string of solder ribbons is first laid on the surface of the battery string after the entire string is arranged, and then the carrier film is laid.

[0130] The remaining preparation methods and parameters are consistent with those in Example 1.

[0131] Performance testing

[0132] The gridless back contact battery modules provided in the above embodiments and comparative examples were subjected to EL (electroluminescence) testing and TC (temperature cycling) reliability testing.

[0133] The test results are shown in Table 1.

[0134] Table 1

[0135] EL TC400 attenuation Example 1 No abnormalities ≤2％ Example 2 No abnormalities ≤2％ Example 3 No abnormalities ≤2％ Example 4 No abnormalities ＞5％ Example 5 No abnormalities ＞5％ Example 6 No abnormalities ＞5％ Example 7 No abnormalities ＞6％ Example 8 cold solder joint ＞5％ Example 9 No abnormalities ≤2％ Example 10 Cold solder joint / short circuit ≤2％ Comparative Example 1 normal ＞5％ Comparative Example 2 Cold solder joint / short circuit ≤2％

[0136] analyze:

[0137] As shown in the table above, this invention employs gridless back-contact solar cells with grid line separation. Combined with a full string of solder ribbons, this allows for high-precision placement of the ribbons, avoiding short circuits caused by overlapping of irregularly shaped grids. It also eliminates the need for insulating adhesive and solder paste, reducing module cost and optical obstruction, while increasing module power and bifaciality. Furthermore, the phased lamination process for fixing the solder ribbons and fully covering the cell string carrier film prevents adhesive film from seeping under the solder ribbons during lamination, which could affect the metallurgical bond between the ribbons and the cells, thus improving module reliability. Moreover, the gridless back-contact solar module provided by this invention exhibits excellent reliability.

[0138] As can be seen from Examples 1 and 4-5, if the alloy does not contain rare earth elements, the component will have a large degradation after the TC test; if the mass fraction of rare earth elements in the alloy is too large, the cost of the solder strip will be high.

[0139] As can be seen from Examples 1 and 6, if the surface of the solder strips in the entire string of solder strips is not coated with flux, the component will have a large degradation after the TC test.

[0140] As can be seen from Examples 1 and 7, if the flux does not contain surfactant components, it will affect the metallurgical bonding between the solder ribbon and the battery cell, resulting in a larger degradation of the module after TC testing.

[0141] As can be seen from Examples 1 and 8-9, if the temperature of the first hot pressing in step (b) is too low, the coating time will be too long and the welding strip cannot be fixed; if the temperature of the first hot pressing in step (b) is too high, the adhesion between the carrier film and the battery cell will be too high, and the battery string cannot be repaired.

[0142] As can be seen from Examples 1 and 10, if no connecting wire is provided in the back contact cell without a main grid, the current of the edge grid cannot be collected and the excessively long solder strip overlaps the cell, causing a short circuit, reducing the module power and affecting the module reliability.

[0143] As can be seen from Example 1 and Comparative Example 1, if the entire string of solder ribbons and carrier film are laid on the surface of the battery string after the entire string is arranged, it is impossible to achieve full coverage of the battery cell carrier film below the solder ribbons.

[0144] As can be seen from Example 1 and Comparative Example 2, if the entire string of solder ribbons is laid on the surface of the battery string after the entire string is arranged, and then the carrier film is laid, the solder ribbons of the battery string are prone to misalignment, and the module will have multiple poor solder joints or short circuits, affecting the module power and reliability.

[0145] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for fabricating a gridless back-contact battery module, characterized in that, The preparation method includes the following steps: (a) Provide a plurality of gridless back contact solar cells and arrange them in a string; the surface of the gridless back contact solar cells has a plurality of positive fine grids and a plurality of negative fine grids, the plurality of positive fine grids and the plurality of negative fine grids are arranged alternately in a first direction; the positive fine grids have a plurality of spaced first partition regions in a second direction, and the negative fine grids have a plurality of spaced second partition regions in a second direction. (b) Providing a complete string of solder ribbons and a carrier film, the carrier film comprising a wide film and a narrow film; After the entire string is arranged, the entire string of welding ribbons and all the wide films are laid on the surface of the gridless back contact cells, and the first hot pressing is performed to complete the film coating, so that the entire string of welding ribbons is fixed by the wide films. The entire string of solder strips includes several positive electrode solder strips and several negative electrode solder strips. The positive electrode solder strips are laid along the first direction in the second partition area and are conductively connected to the positive electrode grid. The negative electrode solder strips are laid along the first direction in the first partition area and are conductively connected to the negative electrode grid. All the wide films are distributed at intervals along the first direction on each cell. (c) Lay all the narrow films on the areas of the battery string surface that are not covered by the carrier film after step (b) and perform a second hot pressing and heating to complete the coating; (d) After laminating the battery strings processed in step (c), the gridless back contact battery assembly is obtained.

2. The preparation method according to claim 1, characterized in that, The material of the entire string of welding strips includes alloys; Preferably, the melting point of the alloy is 135-165℃; Preferably, the alloy comprises SnPbBi / or SnBiAg; Preferably, the alloy contains rare earth elements; Preferably, the rare earth element accounts for 0.2-1% of the mass fraction of the alloy.

3. The preparation method according to claim 1 or 2, characterized in that, The surface of the entire string of welding strips is coated with flux; Preferably, the thickness of the flux coating on the surface of the solder strip is 0.5-2 μm; Preferably, the flux includes an activator, a film-forming agent, a surfactant, and an antioxidant; Preferably, the mass ratio of the activator, film-forming agent, surfactant and antioxidant is (10-20):(10-20):(2-3):

1.

4. The preparation method according to any one of claims 1-3, characterized in that, The material of the carrier membrane includes any one of pre-crosslinked POE, EVA, PVB or TPO; Preferably, the width of the wide membrane is 72-80 mm, and the width of the narrow membrane is 13-21 mm; Preferably, the narrow membrane is an integral membrane or a separate membrane; Preferably, the split membrane is composed of two discontinuous half-membranes spliced ​​together; the width of the half-membrane is 6-10 mm.

5. The preparation method according to any one of claims 1-4, characterized in that, The temperature of the first hot pressing is 110-130℃, and the time is 100-200s; Preferably, the temperature of the second hot pressing is 140-155℃ and the time is 450-600s.

6. A gridless back-contact battery assembly, characterized in that, The gridless back contact battery assembly is prepared using the preparation method described in any one of claims 1-5; The gridless back contact battery assembly includes: A battery string, comprising a plurality of gridless back-contact battery cells, the surface of which has a plurality of positive electrode fine grids and a plurality of negative electrode fine grids, the plurality of positive electrode fine grids and the plurality of negative electrode fine grids being arranged alternately in a first direction; the positive electrode fine grids having a plurality of spaced first partition regions in a second direction, and the negative electrode fine grids having a plurality of spaced second partition regions in a second direction. The entire string of solder strips includes several positive solder strips and several negative solder strips. The positive solder strips are laid along a first direction in the second partition area and are conductively connected to the positive grid. The negative solder strips are laid along the first direction in the first partition area and are conductively connected to the negative grid. A carrier film is disposed on the entire string of solder strips and is fixedly connected to the battery string. The carrier film includes several wide films and several narrow films arranged at intervals. All the wide films are distributed at intervals on each battery cell along a first direction to fix the entire string of solder strips. All the narrow films are distributed along the first direction in the interval area between adjacent wide films.

7. The gridless back-contact battery assembly according to claim 6, characterized in that, The welding strips in the entire string of welding strips are round wire welding strips; Preferably, the diameter of the round wire welding strip is smaller than the width of the first partition area and the second partition area; Preferably, the width of the first partition area and the second partition area are each independently 2.5-3.5 times the diameter of the round wire welding strip; Preferably, the width of the first partition area and the second partition area are each independently 0.5-1mm; Preferably, the number of solder ribbons on the gridless back contact cell is greater than or equal to 30.

8. The gridless back-contact battery assembly according to claim 6 or 7, characterized in that, The positive and negative electrode grids are each made of either silver or copper. Preferably, the first discontinuity regions on adjacent positive electrode grids correspond to each other in the first direction, and the second discontinuity regions on adjacent negative electrode grids correspond to each other in the first direction; Preferably, in the second direction, the first discontinuity zone and the second discontinuity zone are alternately spaced.

9. The gridless back-contact battery assembly according to any one of claims 6-8, characterized in that, A connecting line is provided near the edge of the non-main grid back contact battery cell. The connecting line is located in the first partition area and is used to electrically connect adjacent positive grids. Preferably, a connecting line is provided near the edge of the negative electrode grid that is in contact with the back of the non-main grid cell. The connecting line is located in the second partition area and is used to electrically connect the adjacent negative electrode grid.

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