Low-cost back contact solar cell string
By integrating the fine grid lines of electrodes and the insulating layer onto a metal composite film in a back-contact heterojunction solar cell and employing hot-melt bonding technology, the problems of high production costs and complexity have been solved, achieving simplified fabrication and efficient production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-27
- Publication Date
- 2026-03-17
AI Technical Summary
Existing back-contact heterojunction solar cells have high production costs and complex manufacturing processes, requiring multiple insulating ink printing steps, which leads to a decrease in cell efficiency.
The electrode fine grid lines, insulating layer and main grid lines are integrated onto a metal composite film and bonded to the battery precursor by hot melting, which simplifies the preparation process, eliminates the need for string welding equipment, and adopts a transparent conductive film layer and electrode separator groove design to avoid short circuit problems.
This achievement enables efficient and stable fabrication of back-contact heterojunction battery strings, reducing production costs, improving production efficiency, and saving at least three printing processes.
Smart Images
Figure CN224007015U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of back-contact solar cells, and more particularly to a low-cost back-contact solar cell string. Background Technology
[0002] Currently, the general method for back-contact heterojunction solar cell strings and their fabrication is as follows: after the silicon wafer undergoes the back-contact heterojunction solar cell process, a cell precursor (PN junction fabrication) is formed to produce the grid lines. Then, silver paste grid lines, silver-copper paste grid lines, and copper alloy grid lines are attached to the cell precursor through printing, coating, electroplating, and other methods, thereby forming a series of cells with grid lines. In order to achieve higher output power, the cells need to be connected in series and parallel. The traditional method is to weld the grid lines on the cells to the solder ribbon to connect the cells together.
[0003] Metal electrodes in back-contact heterojunction solar cells are generally divided into silver paste grid line electrodes and copper alloy grid line electrodes. Using silver paste grid line electrodes, back-contact heterojunction cells consume a very large amount of silver paste due to their structure, resulting in high costs. Copper alloy grid line electrodes have a complex manufacturing process with many steps, leading to high equipment costs. Both technologies require string bonding of the cells, and string bonding equipment is the most expensive equipment in the module packaging environment. Furthermore, to avoid short circuits caused by the interlacing of the positive and negative electrode grids, back-contact heterojunction cells require the application of insulating ink at intervals at the intersections. To form a PN junction on the back side, an insulating channel needs to be created through etching or laser grooving. However, this insulating channel is highly susceptible to reaction with acidic substances generated by the encapsulation film, leading to a significant decrease in cell efficiency. Therefore, another layer of insulating protective ink needs to be printed. From a process perspective, to achieve insulation between electrodes and ensure the reliability of module packaging, 2-3 insulating ink printing processes are required.
[0004] Therefore, a back-contact solar cell string was designed to improve production efficiency and reduce production costs. Utility Model Content
[0005] To address the aforementioned problems, this invention provides a back-contact solar cell string that is easy to prepare, highly efficient, stable, and effectively reduces production costs.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a low-cost back-contact solar cell string, comprising several cell precursors and a metal composite film. The cell precursors are arranged alternately and in parallel pairs along the Y-axis, including first electrode regions and second electrode regions. A transparent conductive film layer is disposed on the outer surface of the first electrode regions and second electrode regions along the Z-axis. An electrode separating groove is formed on a portion of the transparent conductive film layer corresponding to the junction of the first electrode regions and the second electrode regions. The electrode separating groove divides the transparent conductive film layer into a first transparent conductive film layer and a second transparent conductive film layer. A first metal fine grid layer, a first insulating block film layer, a second metal fine grid layer, and a second insulating block film layer are disposed on the metal composite film. The system comprises an insulating block film layer, a metal main gate line layer, a carrier film layer, and a composite film layer. The metal main gate line layer is located above the carrier film layer and is arranged at intervals along the X-axis. The composite film layer fills the hollow areas of the metal main gate line layer to form an intermediate layer structure. The first metal fine gate line layer and the second metal fine gate line layer are located above the intermediate layer structure and are arranged in a one-to-one correspondence with the first electrode region and the second electrode region, and are perpendicular to the metal main gate line layer. The first metal fine gate line layer and the second metal fine gate line layer are designed in a discontinuous manner, and the first insulating block film layer and the second insulating block film layer are arranged on the discontinuous areas. The metal main gate line layer and the first metal fine gate line layer and the second metal fine gate line layer are ohmically connected to each other in the Z-axis direction.
[0007] Furthermore, the cell precursor is a silicon heterojunction cell with a PN junction already fabricated but without metal electrode grid lines, and the interlayer spacing of the cell precursor is 0.8-1.2 mm.
[0008] Furthermore, the first electrode region is an N-type doped layer formed by an intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer, with the intrinsic amorphous silicon layer having a thickness of 10 nm, the N-type doped amorphous silicon layer having a thickness of 120 nm, and an effective doping concentration of 8e20 / cm³; the second electrode region is a P-type doped layer formed by stacking an amorphous silicon passivation layer and a doped amorphous silicon layer, with the stacked amorphous silicon passivation layer having a thickness of 10 nm, the doped amorphous silicon layer having a thickness of 20 nm, and an effective doping concentration of 8e19 / cm³.
[0009] Furthermore, the first electrode region, the second electrode region, and the electrode partition groove are respectively arranged to extend along the X-axis direction, and the electrode polarities of the first electrode region and the second electrode region are opposite.
[0010] Furthermore, the electrode separation groove is formed by grooving a transparent conductive film layer with a wavelength of 532 nanometers using a green laser, and the width of the electrode separation groove is 60-120 μm.
[0011] Furthermore, the first and second transparent conductive film layers are tin-doped indium oxide with a thickness of 80-100 nm.
[0012] Furthermore, the metal main grid layer is composed of several flat copper wires, with a width of 0.8-2mm in the X-axis direction and a thickness of 0.2-0.3mm in the Z-axis direction.
[0013] Furthermore, the carrier film layer is a transparent PET film with a thickness of 0.2-0.5 mm.
[0014] Furthermore, the first and second metal fine grid lines have a width of 0.05-0.08 mm in the Y-axis direction and a thickness of 0.02-0.06 mm in the Z-axis direction. They are made of copper alloy and have an anti-oxidation low-temperature SnPb alloy layer on the surface.
[0015] Furthermore, the first insulating block film layer and the second insulating block film layer are transparent PET films with a thickness of 0.03-0.06mm, a length of 2-3mm in the X-axis direction, and a width of 0.5-0.8mm in the Y-axis direction.
[0016] A method for fabricating a low-cost back-contact solar cell string, the method comprising the following steps:
[0017] Provides precursors for solar cells;
[0018] A metal composite film adapted to the design of the corresponding battery cell precursor;
[0019] Based on the electrode arrangement of the battery string, several battery cell precursors are arranged on a metal composite film. The composite film layer is then thermally melted through methods such as rolling and lamination to complete the fabrication of a back-contact heterojunction solar cell string.
[0020] Furthermore, the metal main grid line layers at both ends of the metal composite film are extended along the Y-axis, and the composite film layer is peeled off, leaving only the metal main grid line layers.
[0021] Furthermore, the composite film layer of the metal composite film is a polypropylene film with a thickness of 0.2-0.4 mm, which fills and protects the electrode separator groove during the hot melting process and is firmly bonded to the surface of the battery cell precursor.
[0022] As can be seen from the above description of this utility model, compared with the prior art, this utility model has the following advantages:
[0023] This invention integrates the electrode fine grid lines, insulating layer, and main grid lines onto a metal composite film, simplifying the fabrication process. The back-contact heterojunction cell precursor and the metal composite film are directly bonded by thermal fusion, thereby outputting photogenerated carriers through the main grid lines on the metal composite film. The fabrication of the back-contact heterojunction cell string is highly efficient and stable, saving at least three printing processes and eliminating the need for existing, relatively expensive stringing equipment, thus significantly reducing production costs and improving production efficiency. Attached Figure Description
[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:
[0025] Figure 1 This is a schematic diagram of the structure of the back-contact heterojunction battery precursor in Example 1;
[0026] Figure 2 for Figure 1 A schematic diagram of the AA cross-section battery structure;
[0027] Figure 3 for Figure 1 A schematic diagram of the BB cross-section battery structure;
[0028] Figure 4 This is a schematic diagram of the structure of the back-contact heterojunction battery precursor after cutting and arranging in Example 1;
[0029] Figure 5 This is a schematic diagram of the structure of the metal composite film in Example 1;
[0030] Figure 6 for Figure 5 A schematic diagram of the CC cross-section battery structure;
[0031] Figure 7 for Figure 5 A schematic diagram of the DD cross-section battery structure;
[0032] Figure 8 This is a schematic diagram of a back-contact solar cell string structure according to Example 1;
[0033] Figure 9 for Figure 8 A schematic diagram of the EE cross-section battery structure;
[0034] Figure 10 for Figure 8 A schematic diagram of the FF cross-section battery structure;
[0035] Figure 11 A schematic diagram of the structure of the metal composite film in Example 2;
[0036] Figure 12 for Figure 11 A schematic diagram of the GG cross-section battery structure. Detailed Implementation
[0037] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0038] Example 1
[0039] refer to Figure 1 , Figure 2 , Figure 3 As shown, a cell precursor X for a back-contact cell string is a silicon-based heterojunction solar cell with a thickness of 120 μm. A first electrode region 100 and a second electrode region 200 are disposed on the back side of the cell precursor, and the first electrode region 100 and the second electrode region 200 are arranged alternately and in parallel pairs. The first electrode region 100 is a semiconductor layer, formed by an intrinsic amorphous silicon layer (10 nm thick) and an N-type doped amorphous silicon layer (120 nm thick, effective doping concentration 8e20 / cm³). The second electrode region 200 is a semiconductor layer, formed by stacking an amorphous silicon passivation layer (10 nm thick) and a doped amorphous silicon layer (20 nm thick, effective doping concentration 8e19 / cm³). A first transparent conductive film layer 100-1 is disposed in the Z-axis direction of the first electrode region 100; a second transparent conductive film layer 200-1 is disposed in the second electrode region 200. The first transparent conductive film layer 100-1 and the second transparent conductive film layer 200-1 are tin-doped indium oxide with a thickness of 90 nm.
[0040] An electrode separating groove 300 is provided at the boundary between the first electrode region 100 and the second electrode region 200, between the first transparent conductive film layer 100-1 and the second transparent conductive film layer 200-1. The electrode polarities of the first electrode region 100 and the second electrode region 200 are opposite, with the first electrode region 100 forming a positive electrode 100-4 and the second electrode region 200 forming a negative electrode 200-4. The electrode separating groove 300 is formed by grooving the transparent conductive film layer with a wavelength of 532 nm using a green laser, forming the first transparent conductive film layer 100-1 and the second transparent conductive film layer 200-1, thus separating the first electrode region 100 and the second electrode region 200 to form two different electrodes. The width of the electrode separating groove 300 is 80 μm.
[0041] refer to Figure 4 As shown, Figure 1The precursor of the battery cell is located in the central region of the Y-axis and is cut along the X-axis direction to obtain... Figure 4 The cell precursors X1 and X2 shown are given, and several cell precursors X1 and X2 are as follows: Figure 4 As shown, the cells are arranged in an orderly manner along the Y-axis, and the spacing between the cells is set to 1.0 mm.
[0042] refer to Figure 5 As shown, the metal composite film M is provided with a first metal fine grid line layer 1, a first insulating block film layer 2, a second metal fine grid line layer 3, a second insulating block film layer 4, a metal main grid line layer 5, a carrier film layer 6, and a composite film layer 7. The carrier film layer 6 is a 0.2mm thick transparent PET film. The metal main grid line layer 5 is located above the carrier film layer 6 and is arranged at intervals along the X-axis direction. The metal main grid line layer 5 is composed of several flat copper wires, with a width of 1mm in the X-axis direction and a thickness of 0.25mm in the Z-axis direction. (Reference) Figure 6 As shown, the composite film layer 7 fills the hollowed-out area of the metal main grid layer 5 to form the intermediate layer structure 8. The composite film layer 7 is a 0.25mm thick polypropylene film. The first metal fine grid layer 1 and the second metal fine grid layer 3 are disposed above the intermediate layer structure 8, and as shown... Figure 8 As shown, the first metal fine gate line layer 1, the second metal fine gate line layer 3, and the first electrode region 100 and the second electrode region 200 are arranged in a one-to-one correspondence, and are perpendicular to the metal main gate line layer 5. (Refer to...) Figure 5 , Figure 6 As shown, the first metal fine gate layer 1 and the second metal fine gate layer 3 are designed in an intermittent manner. The metal main gate layer 5 is ohmically connected to the first metal fine gate layer 1 and the second metal fine gate layer 3 in the Z-axis direction. The width of the first metal fine gate layer 1 and the second metal fine gate layer 3 in the Y-axis direction is 0.06 mm, and the thickness in the Z-axis direction is 0.05 mm. The material is copper alloy, and the surface is plated with an anti-oxidation low-temperature SnPb alloy layer.
[0043] refer to Figure 5 , Figure 6 , Figure 7 As shown, the first insulating block film layer 2 is disposed above the intermediate layer structure 8 and is placed in the spacer area of the first metal fine grid line layer 1; the second insulating block film layer 4 is disposed above the intermediate layer structure 8 and is placed in the spacer area of the second metal fine grid line layer 3; the first insulating block film layer 2 and the second insulating block film layer 4 are transparent PET films with a thickness of 0.05mm, a length of 3mm in the X-axis direction, and a width of 0.5mm in the Y-axis direction.
[0044] Along the Y-axis, the metal main grid line layers at both ends of the metal composite film M are extended by 10mm. The composite film layer 7 in the extended area is peeled off and removed, leaving only the metal main grid line layer 5. This area will be used for series and parallel connection between the back contact battery strings when the components are subsequently packaged.
[0045] Will Figure 4 The battery cell precursors X1 and X2 shown are placed in Figure 5 On the metal composite film M shown, the composite film layer 7 on the metal composite film M is thermally bonded to the first transparent conductive film layer 100-1, the second transparent conductive film layer 200-1, and the electrode separator groove 300 of the battery cell precursors X1 and X2 by roll forming, thereby obtaining... Figure 8 , Figure 9 , Figure 10 The back-contact solar cell string shown;
[0046] refer to Figure 8 , Figure 9 , Figure 10 As shown, in order to better conduct and output the photogenerated carriers generated on the solar cell precursors X1 and X2 after illumination from the first electrode region 100 and the second electrode region 200, the first electrode region 100 corresponds to the positive electrode, and the photogenerated carriers are transmitted through the first metal fine grid layer 1 to the metal main grid layer 5 for current output. The second electrode region 200 corresponds to the negative electrode, and the photogenerated carriers are transmitted through the second metal fine grid layer 3 to the metal main grid layer 5 for current output. In order to avoid short circuits caused by contact between the metal main grid layer 5 and the first transparent conductive film layer 100-1 and the second transparent conductive film layer 200-1 on the first electrode region 100 and the second electrode region 200, a first insulating block film layer 2 and a second insulating block film layer 4 are provided.
[0047] A battery string of 12 cells is prepared in the above manner, and the 12 battery strings are arranged in series and parallel through busbars. 200g / ㎡ and 300g / ㎡ of EVA film are applied to the front and back of the battery string, respectively, and then laminated with high-transparency coated tempered glass with a front and back panel thickness of 2mm to form a photovoltaic module.
[0048] Example 2
[0049] The procedure was carried out in accordance with Example 1, except that, in Example 1, the procedure was carried out in accordance with Example 2. Figure 11 , Figure 12As shown, the first metal fine grid layer 1 and the second metal fine grid layer 3 are linearly designed. A portion of the first metal fine grid layer 1 and the second metal fine grid layer 3 are placed on top of the first insulating block film layer 2 and the second insulating block film layer 4. This portion is isolated from the metal main grid layer 5 by the first insulating block film layer 2 and the second insulating block film layer 4. The remaining portion of the metal main grid layer 5 is ohmically connected to the first metal fine grid layer 1 and the second metal fine grid layer 3 in the Z-axis direction. The carrier film layer 6 is a 0.3mm thick transparent PET film to ensure that when the composite film layer 7 on the metal composite film M is hot-melted and bonded during roll forming, the carrier film layer 6 provides a certain buffering effect, ensuring that the first metal fine grid layer 1 and the second metal fine grid layer 3 form good ohmic contact with the first transparent conductive film layer 100-1 and the second transparent conductive film layer 200-1 of the battery cell precursors X1 and X2.
[0050] Compared with Example 1, although Example 2 can increase the collection capacity of photogenerated carriers, the bifaciality of the component will be lower than that of Example 1 because the back-side shading area is increased.
[0051] Example 3
[0052] The process is carried out in accordance with Example 1, except that the carrier film layer 6 is replaced by a photovoltaic fluorine-containing backsheet. At the same time, the arrangement and preparation of multiple cell strings are completed. EVA film and photovoltaic front panel are applied to the front of the cell, and then encapsulated into a single glass module. This scheme is suitable for preparing single glass modules with lower production costs.
[0053] This invention integrates the electrode fine grid lines, insulating layer, and main grid lines onto a metal composite film, simplifying the fabrication process. The back-contact heterojunction cell precursor and the metal composite film are directly bonded by thermal fusion, thereby outputting photogenerated carriers through the main grid lines on the metal composite film. The fabrication of the back-contact heterojunction cell string is highly efficient and stable, saving at least three printing processes and eliminating the need for existing, relatively expensive stringing equipment, thus significantly reducing production costs and improving production efficiency.
[0054] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A low cost back contact solar cell string characterized in that: The battery piece precursor and the metal composite film are included, the battery piece precursor is arranged alternately along the Y-axis direction and parallel to the first electrode area and the second electrode area, the Z-axis direction outer surface of the first electrode area and the second electrode area is provided with a transparent conductive film layer, the electrode separation groove is set on the corresponding part of the transparent conductive film layer at the junction of the first electrode area and the second electrode area, the electrode separation groove divides the transparent conductive film layer into the first transparent conductive film layer and the second transparent conductive film layer, the metal composite film is provided with the first metal fine grid line layer, the first insulating block film layer, the second metal fine grid line layer, the second insulating block film layer, the metal main grid line layer, the bearing film layer and the composite film layer, the metal main grid line layer is located above the bearing film layer and is arranged at intervals along the X-axis direction, the composite film layer fills the hollow area of the metal main grid line layer to form an intermediate layer structure, the first metal fine grid line layer and the second metal fine grid line layer are located above the intermediate layer structure and are arranged in one-to-one correspondence with the first electrode area and the second electrode area and are perpendicular to the metal main grid line layer, the first metal fine grid line layer and the second metal fine grid line layer are designed in an intermittent manner, the first insulating block film layer and the second insulating block film layer are arranged on the intermittent area, and the metal main grid line layer is ohmically connected with the first metal fine grid line layer and the second metal fine grid line layer in the Z-axis direction.
2. The low cost back contact solar cell string of claim 1, wherein: The battery piece precursor is a silicon heterojunction battery piece whose PN junction has been prepared but whose metal electrode grid line has not been made, and the piece spacing of the battery piece precursor is 0.8-1.2 mm.
3. The low cost back contact solar cell string of claim 1, wherein: The first electrode area is an N-type doped layer prepared by an intrinsic amorphous silicon layer and an N-type doped amorphous silicon layer, the thickness of the intrinsic amorphous silicon layer is 10 nm, the thickness of the N-type doped amorphous silicon layer is 120 nm, and the effective doping concentration is 8e20 / cm³; the second electrode area is a P-type doped layer prepared by stacking an amorphous silicon passivation layer and a doped amorphous silicon layer, the thickness of the amorphous silicon passivation layer is 10 nm, the thickness of the doped amorphous silicon layer is 20 nm, and the effective doping concentration is 8e19 / cm³.
4. The low cost back contact solar cell string of claim 1, wherein: The first electrode area, the second electrode area and the electrode separation groove are respectively arranged along the X-axis direction, and the electrode polarity of the first electrode area and the second electrode area is opposite.
5. The low cost back contact solar cell string of claim 1, wherein: The width of the electrode separation groove is 60-120 μm.
6. The low cost back contact solar cell string of claim 1, wherein: The first transparent conductive film layer and the second transparent conductive film layer are tin-doped indium oxide, and the thickness is 80-100 nm.
7. The low cost back contact solar cell string of claim 1, wherein: The metal main grid line layer is composed of a plurality of flat copper wires, the width of the copper wire in the X-axis direction is 0.8-2 mm, and the thickness in the Z-axis direction is 0.2-0.3 mm.
8. The low cost back contact solar cell string of claim 1, wherein: The bearing film layer is a transparent PET film with a thickness of 0.2-0.5 mm.
9. The low cost back contact solar cell string of claim 1, wherein: The width of the first metal fine grid line layer and the second metal fine grid line layer in the Y-axis direction is 0.05-0.08 mm, the thickness in the Z-axis direction is 0.02-0.06 mm, the material is copper alloy, and the surface is plated with an oxidation-resistant low-temperature SnPb alloy layer.
10. The low cost back contact solar cell string of claim 1, wherein: The first insulating block film layer and the second insulating block film layer are transparent PET films with a thickness of 0.03-0.06 mm, a length of 2-3 mm in the X-axis direction, and a width of 0.5-0.8 mm in the Y-axis direction.