Master back contact cell, module and method of manufacturing the same

Abstract

The present application relates to a kind of main grid back contact cell, assembly and its preparation method, the grid line structure is equipped with on the back of the cell, the grid line structure includes the N-type grid line and P-type grid line parallel to each other arranged alternately;The N-type grid line includes the first solid section and the first point section arranged alternately along its extension direction, the first solid section is continuous conductive line, the first point section is composed of multiple discrete conductive points, and first solid section both ends are each equipped with first connecting pad;The P-type grid line includes the second solid section and the second point section arranged alternately along its extension direction, the second solid section is continuous conductive line, the second point section is composed of multiple discrete conductive points, and second solid section both ends are each equipped with second connecting pad;The N-type grid line and P-type grid line are parallel to each other and arranged alternately;Compared with the traditional full solid grid line, the amount of silver paste or silver aluminum paste can be reduced by 40%-50% by setting point section.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and in particular relates to gridless back contact cells, modules and their preparation methods. Background Technology

[0002] Back-contact solar cells, with their unobstructed front side, possess extremely high theoretical photoelectric conversion efficiency and represent a crucial technological development direction for the photovoltaic industry. In the back electrode design of back-contact cells, finger-shaped fine grids are typically fabricated to collect photogenerated carriers, which are then further extracted through bus electrodes.

[0003] However, traditional back-contact solar cells typically employ a fully continuous solid line design for the back grid, and a large area of ​​main grid needs to be printed to ensure current collection efficiency. This design consumes a large amount of precious metal paste, resulting in high material manufacturing costs for the cells and hindering large-scale industrialization. Secondly, the current travels a long path from the fine grid on the back to the main grid, which can easily lead to significant lateral series resistance losses, thus limiting further improvements in the overall output power of the module.

[0004] Therefore, this disclosure proposes a gridless back contact battery, a module, and a method for its fabrication. Summary of the Invention

[0005] The purpose of this invention is to provide a gridless back contact battery, module and its preparation method, which solves the problem of large paste consumption caused by the interlaced distribution of PN grid lines in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A back-contact battery, wherein a grid structure is provided on the back of the battery, the grid structure comprising alternating N-type grid lines and P-type grid lines that are parallel to each other;

[0008] The N-type gate line includes alternating first solid segments and first dotted segments along its extension direction. The first solid segment is a continuous conductive line, and the first dotted segment is composed of multiple discrete conductive points. Each end of the first solid segment is provided with a first connecting pad.

[0009] The P-type gate line includes alternating second solid segments and second dotted segments along its extension direction. The second solid segment is a continuous conductive line, and the second dotted segment is composed of multiple discrete conductive points. Each end of the second solid segment is provided with a second connecting pad.

[0010] The N-type grid lines and P-type grid lines are parallel to each other and arranged alternately.

[0011] This disclosure also proposes a gridless back contact battery assembly, which includes at least one back contact battery; a conductive adhesive layer is disposed on the surface of the first dotted segment, the second dotted segment, the first connecting pad, and the second connecting pad;

[0012] The battery has a conductive core plate on its back. The conductive core plate is electrically connected to the first dotted segment, the first connecting pad, the second dotted segment, and the second connecting pad through a conductive adhesive layer.

[0013] This disclosure also proposes a method for fabricating a gridless back-contact battery module, comprising the following steps:

[0014] S1. Insulation layer printing step: On the back of the back contact battery, an insulating adhesive is applied to the surface of the first solid segment and the second solid segment by a printing process. After curing, the insulating isolation layer is formed, and the insulating isolation layer exposes the first dotted segment, the second dotted segment, the first connecting pad and the second connecting pad.

[0015] S2. Coating of conductive adhesive layer: The conductive adhesive layer is precisely coated on the exposed surfaces of the first dotted segment, the second dotted segment, the first connecting pad, and the second connecting pad by dispensing or graphic printing process.

[0016] S3, Component stacking arrangement: First, lay the back contact batteries after the processing in step S2 flat, and then press the conductive core plate onto the back of each back contact battery to make the conductive core plate and the conductive adhesive layer in physical contact.

[0017] S4. Hot melt welding: The stacked structure is heated and welded to melt or solidify the conductive adhesive layer, forming an electrical connection between the conductive core board and the corresponding dotted segments and connecting pads.

[0018] Beneficial effects:

[0019] In this disclosed scheme, approximately half of the length of the grid lines of both polarities is designed as dotted segments. Compared with traditional solid grid lines, this can reduce the amount of silver paste or silver-aluminum paste by 40% to 50%, while eliminating the independent main grid structure and further reducing the paste cost.

[0020] In this invention, the current flows directly from the solid line segment to the pad, and then enters the conductive core board via the solder paste above. This eliminates the need for long-distance transmission to the main busbar, shortens the transmission path, reduces contact resistance, and significantly improves the component fill factor (FF) and output power.

[0021] This disclosure covers the surface of continuous solid line segments with insulating adhesive, exposing only dotted segments and pads, and connecting the conductive core board with solder paste. The conductive core board only contacts dotted areas and pads of the same polarity and will not contact the gate lines of the other polarity at the same time, thus eliminating the risk of short circuit in principle.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the N-type grid structure disclosed in this paper;

[0025] Figure 2 This is a schematic diagram of the P-type grid structure disclosed in this paper;

[0026] Figure 3 This is a schematic diagram of the actual grid line structure of this disclosure;

[0027] Figure 4 This is a structural diagram of the insulating isolation layer disclosed herein;

[0028] Figure 5 This is a schematic diagram of the battery structure disclosed herein. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention discloses a gridless back contact battery, such as... Figure 5 As shown, its back side has alternating N-type grid lines 1 and P-type grid lines 2. The N-type grid lines 1 and P-type grid lines 2 are arranged in parallel and alternately. The center of the solid line segment of the N-type grid line 1 is opposite to the center of the dotted segment of the P-type grid line 2. The N-type grid lines 1 and P-type grid lines 2 form multiple sets of intersecting finger-like structures.

[0031] like Figure 1 As shown, the N-type gate lines 1 are all arranged on the back of the cell. The N-type gate lines 1 include alternating first solid segments 11 and first dot segments 12 along their extension direction. The first dot segments 12 are composed of multiple discrete conductive points, and the first solid segments 11 are continuous conductive lines. Each end of the first solid segments 11 is provided with a first connecting pad 13.

[0032] like Figure 2As shown, the P-type grid lines 2 are all arranged on the back of the cell. The P-type grid lines 2 include alternating second solid segments 21 and second dot segments 22 along their extension direction. The second dot segments 22 are composed of multiple discrete conductive points, and the second solid segments 21 are continuous conductive lines. Each end of the second solid segments 21 is provided with a second connecting pad 23.

[0033] The N-type grid lines and P-type grid lines are parallel to each other and alternately arranged;

[0034] The center of the solid segment of the N-type gate line is aligned vertically with the center of the dotted segment of the P-type gate line, and the center of the dotted segment of the N-type gate line is aligned with the center of the solid segment of the P-type gate line.

[0035] Furthermore, the dotted segments account for 30% to 49% of the total length of the grid line; the solid line segments account for 51% to 70% of the total length of the grid line.

[0036] Furthermore, the ratio of the spacing between adjacent conductive points in the dotted segment to the size of the conductive point itself is 2:1 to 10:1.

[0037] An insulating layer 3 is provided on the solid line segments of N-type grid line 1 and P-type grid line 2. The insulating layer 3 is an insulating adhesive layer formed by physical coating or printing, and its material is preferably any one of epoxy resin, polyimide or acrylic.

[0038] The insulating layer covers all solid line segments except for the connection pads at both ends, and has a thickness of 25μm after curing. The cell grid line thickness is about 10μm, and the insulating layer thickness is greater than the grid line thickness.

[0039] A conductive adhesive layer is provided above the dotted segments and the connecting pads. The conductive adhesive layer is in direct physical contact and electrically connected to the exposed surfaces of the first dotted segment 12, the second dotted segment 22, the first connecting pad 13, and the second connecting pad 23, respectively.

[0040] In this embodiment, the conductive adhesive layer is a cured lead-free solder paste layer with a thickness of 50µm.

[0041] The back of the battery cell is covered with rolled copper foil or copper-aluminum foil with a thickness of 50µm, which is used as the conductive core plate.

[0042] The conductive core plate, through the conductive adhesive layer, simultaneously forms a molten and solidified metal bonding electrical connection with the first dot segment 12 and the first connecting pad 13 of the N-type grid line 1 on the first battery, and the second dot segment 22 and the second connecting pad 23 of the P-type grid line 2 on the second battery.

[0043] The component production process includes lamination, curing, trimming, framing and junction box installation, and final product testing.

[0044] In some disclosures, a gridless back contact battery includes a first battery and a second battery, wherein the N-type grid line 1 end of the first battery and the P-type grid line 2 end of the second battery are arranged opposite each other on a plane.

[0045] Compared to the traditional solid grid line structure with independent main grid, this design saves approximately 48% of silver paste for both the N-type and P-type grid lines, and eliminates the need for separate printing of the main grid.

[0046] In some disclosures, the length ratio of the spacing between adjacent conductive points to the diameter of the conductive point is preferably 5:1.

[0047] Furthermore, in some specific embodiments, the N-type gate line 1 has a total length of 180.69 mm, with alternating first solid segments 11 and first dotted segments 12 along its length. The first solid segment 11, including the pad, has a length of 11.93 mm, and each dotted segment has a length of 8.2 mm. Each dotted segment consists of 83 circular conductive dots with a diameter of 20 μm, with a spacing of 100 μm between adjacent conductive dots. The width of the solid segment is 18 μm. Each end of the N-type gate line has a 200 μm × 100 μm connection pad.

[0048] The P-type gate line 2 has a total length of 180.69 mm, with alternating solid line segments and dotted segments along its length. The solid line segment, including the pad, is 11.93 mm long, and each dotted segment is 8.2 mm long. Each dotted segment consists of 83 circular conductive dots with a diameter of 20 μm, spaced 100 μm apart. The solid line segment is 18 μm wide. Each end of the N-type gate line has a 200 μm × 100 μm connection pad.

[0049] Those skilled in the art should understand that, due to variations in cell size specifications, edge margin requirements, or layout arrays, when the aforementioned solid segments and dotted segments are alternately arranged at the end of the extension direction of the N-type grid line 1 or P-type grid line 2, the length of the last solid segment or dotted segment located at the outermost edge can be freely adjusted or finely tuned according to the actual remaining bus length, so that the sum of the lengths of all alternating segments achieves a precise closed loop and reasonable match with the total length of the grid line in spatial topology geometry. The above-mentioned baseline design parameters are only used to illustrate a typical multi-segment layout logic of the present invention and do not constitute a mechanical limitation on the absolute rigid addition of the lengths of each segment.

[0050] Furthermore, in order to be suitable for applications such as double-glass solar modules that have stringent requirements for high voltage resistance and leakage prevention.

[0051] The conductive core board is a conductive backplate with a composite laminate structure. The conductive backplate includes, from the inside out, an inner copper layer and an insulating PET layer compositely disposed on the outer surface of the inner copper layer.

[0052] Multiple patterned contact holes are formed on the insulating PET layer on the surface of the conductive backplate. In terms of spatial geometry, the multiple patterned contact holes are arranged and connected only to the positions directly above each of the first dot segments 12, the second dot segments 22 arranged in a finger-like pattern on the back of the battery cell, and the space above each connecting pad, thereby selectively exposing the local surface of the inner copper layer at these specific points.

[0053] A conductive adhesive layer fills the interior of each of the patterned contact holes in the insulating PET layer. The inner copper layer forms a stable mechanical hold and electrical connection with the corresponding dotted segments and connecting pads through the conductive adhesive layer in these contact holes.

[0054] In the static stacked and compressed state of the module, the first insulating adhesive layer coated above the solid segments of each grid line on the back of the cell is directly and rigidly pressed against the solid surface of the insulating PET layer on the conductive backplate, where no contact holes are opened. This forms double insulation.

[0055] This design effectively enhances the electrical insulation withstand voltage and anti-PID capability of the components under long-term high voltage and humid heat aging environments.

[0056] The above-mentioned process for fabricating a gridless back contact cell specifically includes the following steps:

[0057] S1. Insulating layer printing steps:

[0058] On the back side of the back contact cell, an insulating adhesive is applied to the upper surfaces of the first solid segment 11 and the second solid segment 21 using a screen printing process. The insulating adhesive is selected from any one or a combination of epoxy resin, polyimide, or acrylic adhesive. The insulating adhesive layer completely covers the entire solid segment area except for the end bonding pads.

[0059] After heat curing or UV curing, the thickness of the first insulating adhesive layer is 25 μm. In this embodiment, the physical thickness of the metal grid lines on the back of the battery cell is approximately 10 μm. Therefore, the thickness of the first insulating adhesive layer is significantly greater than the thickness of the grid lines themselves, forming an insulating step.

[0060] S2, Conductive adhesive layer coating step:

[0061] A conductive adhesive layer is precisely coated on the surfaces of the first dotted segment 12, the second dotted segment 22, and the exposed pads at both ends using surface dispensing or patterned printing processes. In this embodiment, the conductive adhesive layer specifically uses lead-free solder paste, and its printing coating thickness is 50 μm.

[0062] S3, Component stacking arrangement steps:

[0063] At least two back-contact solar cells, processed in steps S1 and S2, are laid flat on a stacking platform with the back of the cells facing upwards. The positions of the solar cells are adjusted so that the N-type grid line 1 end of the first solar cell is horizontally opposite the P-type grid line 2 end of the adjacent second solar cell. A 50μm thick rolled copper foil or copper-aluminum composite foil is used as the entire conductive core board. This conductive core board is pressed onto the N-type dotted segment and corresponding first connecting pad 13 of the first solar cell, and the P-type dotted segment and corresponding second connecting pad 23 of the second solar cell, ensuring that they are in physical contact with the lead-free solder paste layer.

[0064] S4. Hot melt welding and three-dimensional conductive construction steps:

[0065] The stacked structure is then placed in an infrared heating furnace for welding and heating. The heating temperature is controlled to fully melt the lead-free solder paste, which is then cooled and solidified to form a stable metal bond and micro-ohm level electrical connection between the conductive core board and the corresponding dot segments and connecting pads.

[0066] During the infrared heating welding process, the first insulating adhesive layer maintains a stable solid morphology without melting or flowing, thereby continuously and absolutely isolating the first solid segment 11, the second solid segment 21, and the conductive core plate, eliminating the risk of short circuits between opposite polarity grid lines from a topological perspective.

[0067] S5. Post-packaging steps:

[0068] The interconnected battery strings are then subjected to a series of standard processes, including subsequent lamination, overall lamination, heat curing, edge trimming, outer frame assembly, junction box installation, and finished product electrical performance testing, to finally complete the manufacturing of the conductive core board interconnection assembly.

[0069] By using the above technical solution, compared with the traditional component structure with solid grid lines and independent main grids, the present invention locally patterns the finger grid lines into discrete dot segments, which saves about 48% of the amount of silver paste or silver-aluminum paste used for both N-type grid lines 1 and P-type grid lines 2. Furthermore, since it is no longer necessary to print the main grid separately, the cost of precious metal materials for solar cells is greatly reduced.

[0070] By eliminating the independent main grid, the current no longer needs to flow a long distance laterally to the main grid. Instead, it enters the highly conductive core plate directly longitudinally through the nearest point segment, significantly shortening the electrical conduction path.

[0071] The 60 half-cell modules prepared using the structure of this embodiment, according to actual measurements, show that the overall output power of the finished modules is increased by approximately 5.2W compared to the traditional continuous grid line module structure.

[0072] Furthermore, this embodiment provides a back-contact battery interconnection module with higher insulation reliability, suitable for applications such as double-glass solar modules that have stringent requirements for high voltage resistance and leakage prevention. The difference between this embodiment and Embodiment 1 lies in the internal structure of the conductive core plate and the contact method of the interconnection interface, as detailed below:

[0073] In this embodiment, the conductive core board is not made of bare metal foil, but rather a conductive backplate with a composite laminate structure. The conductive backplate includes an inner copper layer and an insulating PET layer compositely disposed on the outer surface of the copper layer. Before the component stacking assembly, the insulating PET layer on the conductive backplate is precisely patterned and exposed only at the spatial positions of each dot segment and each connecting pad on the back of the battery using laser scribing or mechanical punching processes, thereby selectively exposing the internal copper layer. Anisotropic conductive adhesive is applied to the localized locations where the copper layer is exposed through the openings to achieve mechanical fixation and electrical connection between the copper layer inside the conductive backplate and the corresponding dot segments and connecting pads.

[0074] In the stacked and compressed state, the first insulating adhesive layer coated above each solid segment of the grid lines on the back of the battery directly presses against the surface of the unopened insulating PET layer on the conductive backplate. Because the first insulating adhesive layer and the insulating PET layer are spatially superimposed, a physical double insulating barrier consisting of the "first insulating adhesive layer + insulating PET layer" is constructed between each solid segment and the internal copper layer of the conductive backplate.

[0075] This configuration not only fully inherits the silver paste saving and power improvement effects of Embodiment 1, but also significantly enhances the overall insulation voltage resistance and anti-PID capability of the component.

[0076] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A back-contact battery, characterized in that, The back of the battery is provided with a grid structure, which includes alternating N-type grid lines and P-type grid lines that are parallel to each other. The N-type gate line includes alternating first solid segments and first dotted segments along its extension direction. The first solid segment is a continuous conductive line, and the first dotted segment is composed of multiple discrete conductive points. Each end of the first solid segment is provided with a first connecting pad. The P-type gate line includes alternating second solid segments and second dotted segments along its extension direction. The second solid segment is a continuous conductive line, and the second dotted segment is composed of multiple discrete conductive points. Each end of the second solid segment is provided with a second connecting pad. The N-type grid lines and P-type grid lines are parallel to each other and arranged alternately.

2. A back contact battery according to claim 1, characterized in that, In the first dotted segment and the second dotted segment, the ratio of the distance between two adjacent discrete conductive points to the diameter of the discrete conductive point is 2:1 to 10:

1.

3. A back contact battery according to claim 1, characterized in that, Dotted segments account for 30% to 49% of the total length of the grid line; solid segments account for 51% to 70% of the total length of the grid line.

4. A back contact battery according to claim 1, characterized in that, The surfaces of both the first solid segment and the second solid segment are covered with an insulating layer.

5. A back contact battery according to claim 4, characterized in that, The thickness of the insulating isolation layer is greater than the thickness of the gate line.

6. A gridless back-contact battery assembly, comprising at least one back-contact battery as described in claim 1, Its characteristics are: A conductive adhesive layer is provided on the surfaces of the first dotted segment, the second dotted segment, the first connecting pad, and the second connecting pad; The battery has a conductive core plate on its back side. The conductive core plate is electrically connected to the first dotted segment, the first connecting pad, the second dotted segment, and the second connecting pad through a conductive adhesive layer.

7. A gridless back-contact battery assembly according to claim 6, characterized in that, The conductive core board is a copper foil, a copper-aluminum composite foil, or a conductive backplate with a copper layer on the inner layer.

8. A gridless back-contact battery assembly according to claim 6, characterized in that, The conductive core board is a conductive back plate with a composite laminate structure. The conductive back plate includes, from the inside out, an inner copper layer and an insulating PET layer disposed on the outer surface of the inner copper layer. Multiple patterned contact holes are formed on the insulating PET layer. Each of the patterned contact holes is respectively set and connected to the first point segment, the second point segment, the first connecting pad, and the second connecting pad in spatial geometry. The conductive adhesive layer fills the interior of each of the patterned contact holes, so that the inner copper layer is electrically connected to the corresponding first dot segment, second dot segment, first square connection solder, and second connection pad. The insulating isolation layer above the first solid segment and the second solid segment is pressed against the solid surface of the insulating PET layer on the conductive back plate without contact holes.

9. A method for fabricating a gridless back-contact battery module as described in claim 6, characterized in that, Includes the following steps: S1. Insulation layer printing step: On the back of the back contact battery, an insulating adhesive is applied to the surface of the first solid segment and the second solid segment by a printing process. After curing, the insulating isolation layer is formed, and the insulating isolation layer exposes the first dotted segment, the second dotted segment, the first connecting pad and the second connecting pad. S2. Coating of conductive adhesive layer: The conductive adhesive layer is precisely coated on the exposed surfaces of the first dotted segment, the second dotted segment, the first connecting pad, and the second connecting pad by dispensing or graphic printing process. S3, Component stacking arrangement: First, lay the back contact batteries after the processing in step S2 flat, and then press the conductive core plate onto the back of each back contact battery to make the conductive core plate and the conductive adhesive layer in physical contact. S4. Hot melt welding: The stacked structure is heated and welded to melt or solidify the conductive adhesive layer, forming an electrical connection between the conductive core board and the corresponding dotted segments and connecting pads.

10. The method for preparing a gridless back-contact battery module according to claim 9, characterized in that, The component includes two or more batteries, and when the components are stacked, the N-type grid line ends of the batteries are aligned with the P-type grid line ends of the adjacent batteries in the horizontal direction.

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