Back contact solar cell, cell module and photovoltaic system

Abstract

The utility model is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system, the back contact solar cell comprises a silicon substrate, and the backlight surface of the silicon substrate comprises a P region, an N region and an isolation region arranged between the P region and the N region; wherein at least part of the isolation area is set as a polished surface; or at least part of the isolation area is arranged to be a micro suede, and the length of the longest diagonal line of the tower footing of the micro suede is 2-5 microns. According to the back contact solar cell provided by the utility model, at least partial region of the isolation region between the P region and the N region is set to be the polished surface or at least partial region of the isolation region is set to be the micro-textured surface, so that the transmission path of current carriers can be reduced, the surface recombination loss is reduced, and the power generation efficiency of the back contact solar cell is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a back-contact solar cell, a battery assembly and a photovoltaic system. Background Art

[0002] Solar cells convert sunlight into electricity using the photovoltaic effect of semiconductors. They primarily include double-sided contact solar cells and back-contact solar cells. Back-contact solar cells, with their positive and negative electrodes located on the back of the cell, offer a significant improvement in conversion efficiency compared to double-sided contact solar cells, as the front surface of the cell is shielded by metal grid lines, eliminating the optical loss caused by such obstructions.

[0003] In the prior art, the backlight surface of a back-contact solar cell typically includes a P region and an N region spaced apart in sequence, with an isolation region disposed between adjacent P and N regions. The isolation region is typically configured as a pyramidal velvet structure, with the base diagonal length of the pyramidal velvet structure typically exceeding 15 microns. While this pyramidal velvet structure can increase the bifaciality of the solar cell, it also increases the carrier transport path, resulting in significant surface recombination losses and reduced solar cell power generation efficiency. Utility Model Content

[0004] The utility model provides a back-contact solar cell, aiming to solve the problem that the back-contact solar cell in the prior art has a pyramid velvet structure in the isolation area, which leads to large surface recombination loss and reduces the power generation efficiency of the cell.

[0005] The utility model is implemented by providing a back contact solar cell, comprising:

[0006] A silicon substrate, wherein a backlight surface of the silicon substrate includes a P region, an N region, and an isolation region provided between the P region and the N region;

[0007] Wherein, at least a part of the isolation area is set as a polished surface; or at least a part of the isolation area is set as a micro-suede surface, and the longest diagonal length of the tower base of the micro-suede surface is 2 to 5 microns.

[0008] Preferably, the entire area of ​​the isolation zone is a polished surface.

[0009] Preferably, the entire area of ​​the isolation zone is the micro-suede surface.

[0010] Preferably, the isolation area includes a first area and a second area, the first area is set as the polishing surface, and the second area is set as the micro-suede surface.

[0011] Preferably, the number of the first regions and the number of the second regions are both plural, and the first regions and the second regions are alternately arranged in the isolation area.

[0012] Preferably, the area of ​​the first region is larger than the area of ​​the second region.

[0013] Preferably, the ratio of the area of ​​the first region to the area of ​​the second region is 1-5.

[0014] Preferably, the isolation region is a trench.

[0015] Preferably, the P region is a micro-suede surface or a polished surface, and the N region is a polished surface.

[0016] Preferably, the P region is the micro-fleece surface, and the longest diagonal length of the tower base of the micro-fleece surface in the P region is greater than the longest diagonal length of the tower base of the micro-fleece surface in the isolation region.

[0017] The utility model also provides a battery assembly, comprising the above-mentioned back-contact solar cell.

[0018] The utility model also provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0019] The utility model provides a back-contact solar cell by setting at least a part of the isolation region between the P region and the N region as a polished surface or setting at least a part of the isolation region as a micro-velvet surface, wherein the longest diagonal length of the tower base of the micro-velvet surface is 2 to 5 microns. Compared with the pyramid velvet structure set in the isolation region of the traditional back-contact solar cell, the isolation region utilizes the polished surface or the micro-velvet structure, which can reduce the transmission path of the carriers, reduce the surface recombination loss, and improve the passivation performance, thereby improving the power generation efficiency of the back-contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic cross-sectional structure diagram of a back-contact solar cell provided by an embodiment of the present utility model;

[0021] Figure 2 A schematic cross-sectional structure diagram of a silicon substrate of a back-contact solar cell provided by an embodiment of the present utility model;

[0022] Figure 3 A schematic diagram of the backlight surface of a first silicon substrate of a back-contact solar cell provided by an embodiment of the present utility model;

[0023] Figure 4 A schematic diagram of the backlight surface of the second silicon substrate of the back-contact solar cell provided by an embodiment of the present invention;

[0024] Figure 5A schematic diagram of the backlight surface of the third silicon substrate of the back-contact solar cell provided by an embodiment of the present utility model;

[0025] Figure 6 This is an SEM image of the micro-texture surface of the back contact solar cell provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] An embodiment of the present invention provides a back-contact solar cell by setting at least a portion of the isolation region between the P region and the N region as a polished surface or setting at least a portion of the isolation region as a micro-velvet surface, wherein the longest diagonal length of the base of the micro-velvet surface is 2 to 5 microns. Compared with the pyramid velvet structure set in the isolation region of a traditional back-contact solar cell, the isolation region of the present invention utilizes a polished surface or a micro-velvet structure, which can reduce the carrier transmission path of the isolation region, reduce surface recombination loss, and improve the passivation performance, thereby improving the power generation efficiency of the back-contact solar cell.

[0028] Please refer to Figure 1-Figure 5 The present invention provides a back-contact solar cell, comprising:

[0029] A silicon substrate 1 includes a light-facing surface 11 and a backlight surface 12 disposed opposite to the light-facing surface 11 . The backlight surface 12 of the silicon substrate 1 includes a P region 121 , an N region 122 , and an isolation region 123 disposed between the P region 121 and the N region 122 .

[0030] At least a portion of the isolation area 123 is configured as a polished surface; or at least a portion of the isolation area 123 is configured as a micro-suede surface, and the longest diagonal length of the tower base of the micro-suede surface is 2 to 5 microns.

[0031] In an embodiment of the present invention, by setting at least a portion of the isolation region 123 as a polished surface or setting at least a portion of the isolation region 123 as a micro-velvet surface, the longest diagonal length of the base of the micro-velvet surface is 2 to 5 microns, and the surface of the isolation region 123 is set as a polished surface or a micro-velvet surface, the carrier transmission path can be reduced, the surface recombination loss can be reduced, the passivation performance can be improved, and the battery power generation efficiency can be improved.

[0032] In the embodiment of the present invention, the diagonal lengths of the tower bases of the micro-suede surface can be the same or different. The longest diagonal length of the tower bases of the micro-suede surface is 2 to 5 microns. This means that the longest diagonal length of the tower bases of the micro-suede surface is between 2 and 5 microns, making the surface of the isolation region 123 relatively flat, which helps reduce the carrier transmission path, reduces surface recombination losses, and improves the battery's power generation efficiency.

[0033] As a preferred embodiment of the present invention, the longest diagonal length of the micro-suede tower base is 2 to 3 microns, which can further reduce the carrier transmission path, reduce surface recombination losses, improve passivation performance, and improve battery power generation efficiency.

[0034] Please refer to Figure 3 As an embodiment of the present invention, the entire area of ​​the isolation region 123 is a polished surface.

[0035] In this embodiment, all areas within the isolation region 123 are polished. Compared to a pyramid velvet structure, the entire isolation region 123 is polished, significantly shortening the carrier transmission path, reducing surface recombination, and enhancing passivation, thereby improving battery power generation efficiency.

[0036] In this embodiment, an alkaline solution can be used to perform alkaline polishing on the entire area of ​​the isolation region 123. Specifically, sodium hydroxide (NaOH) or potassium hydroxide (KOH) is used for polishing. By performing alkaline polishing on the isolation region 123, the entire area of ​​the isolation region 123 has a smooth polished surface.

[0037] Please refer to Figure 4 As another embodiment of the present invention, the entire isolation region 123 is a micro-suede surface.

[0038] In this embodiment, the entire isolation region 123 is a micro-suede surface, with the longest diagonal length of the micro-suede tower base being 2 to 5 microns. In contrast, the diagonal length of the tower base of the pyramid suede structure in the isolation region 123 of a conventional back-contact solar cell is typically greater than 15 microns. Therefore, the micro-suede tower base is smaller than the pyramid suede structure, and the micro-suede structure has a more regular surface, which helps reduce surface recombination, enhance passivation, shorten carrier transmission paths, and improve cell power generation efficiency.

[0039] In this embodiment, the micro-suede surface can be made by commonly used alkali-based suede, specifically a micro-suede surface structure made from an alkali solution of a corresponding mass concentration. The micro-suede tower base refers to a microstructure provided on the silicon substrate of the solar cell, and the micro-suede tower base can specifically include at least one of a rhombus, a square, a trapezoid, a nearly rhombus, a nearly square, and a nearly trapezoid.

[0040] Please refer to Figure 5As another embodiment of the present invention, the isolation region 123 includes a first region 1231 and a second region 1232 , the first region 1231 is configured as a polished surface, and the second region 1232 is configured as a micro-suede surface.

[0041] In this embodiment, it can be understood that a local area of ​​the isolation region 123 is set as a polished surface, and a local area of ​​the isolation region 123 is set as a micro-suede surface, so that the surface of the isolation region 123 is a combination of a polished surface and a micro-suede surface.

[0042] In this embodiment, since local areas of the isolation region 123 are polished surfaces and local areas are micro-velvet surfaces, the advantages of the polished surface and the micro-velvet surface can be combined at the same time. Compared with the use of a fully polished surface in the entire isolation region 123, it is beneficial to improve the bifaciality of solar cells and improve the efficiency of sunlight utilization; and compared with the use of velvet or micro-velvet surfaces in the entire isolation region 123, it can reduce surface recombination, improve passivation performance, reduce carrier transmission distance, and improve battery efficiency, thereby balancing the bifaciality of solar cells and battery power generation efficiency.

[0043] As an embodiment of the present invention, the specific number of the first area 1231 and the second area 1232 is not limited, and the number of the first area 1231 and the second area 1232 can be one, two or more.

[0044] As an embodiment of the present invention, there are multiple first regions 1231 and multiple second regions 1232 , and the first regions 1231 and the second regions 1232 are alternately arranged in the isolation region 123 .

[0045] In this embodiment, the first regions 1231 and the second regions 1232 may be alternately arranged along the length direction of the isolation region 123 , and the first regions 1231 and the second regions 1232 may also be alternately arranged along the width direction of the isolation region 123 .

[0046] As an embodiment of the present invention, the area of ​​the first region 1231 is larger than the area of ​​the second region 1232 .

[0047] In this embodiment, the area of ​​the first region 1231 is larger than the area of ​​the second region 1232, that is, the area of ​​the polished surface of the isolation region 123 is larger than the area of ​​the micro-suede surface. On the premise of meeting a certain double-sidedness, the carrier transmission path of the isolation region 123 can be reduced, the surface recombination can be reduced, the passivation performance can be improved, and the battery efficiency can be improved.

[0048] As an embodiment of the present invention, the ratio of the area of ​​the first region 1231 to the area of ​​the second region 1232 is 1-5.

[0049] In this embodiment, the ratio of the area of ​​the first region 1231 to the area of ​​the second region 1232 is 1 to 5, that is, the ratio of the area of ​​the polished surface of the isolation region 123 to the area of ​​the micro-suede surface is 1 to 5. Specifically, when there is only one first region 1231 and one second region 1232, the ratio of the area of ​​each first region 1231 to the area of ​​each second region 1232 in the isolation region 123 is 1 to 5. When there are more than two first regions 1231 and second regions 1232, the ratio of the sum of the areas of the first regions 1231 to the sum of the areas of the second regions 1232 is 1 to 5.

[0050] In this embodiment, the ratio of the area of ​​the first region 1231 to the area of ​​the second region 1232 is set within a reasonable range of 1 to 5, which can not only achieve a good bifaciality of the back-contact solar cell, but also ensure that the isolation region 123 has a more suitable carrier transmission path length, reduce surface recombination, and can well balance the bifaciality of the back-contact solar cell and improve the battery power generation efficiency.

[0051] In this embodiment, the ratio of the area of ​​the first region 1231 to the area of ​​the second region 1232 can be set according to actual needs. For example, the ratio of the area of ​​the first region 1231 to the area of ​​the second region 1232 can be 1.01, or 1.1, or 1.3, or 1.5, or 1.9, or 2.0, or 2.3, or 2.8, or 3.0, or 3.2, or 3.5, or 3.8, or 4.0, or 4.6, or 4.9, or 5.0.

[0052] In the embodiment of the present invention, the tower bases of the micro-suede surface can be arranged regularly or irregularly. For example, the tower bases of the micro-suede surface can be arranged in a linear array.

[0053] As an embodiment of the present invention, the isolation region 123 is a trench.

[0054] In this embodiment, it can be understood that the isolation region 123 is configured as a groove that is recessed relative to the P region 121 and the N region 122, and the bottom surface of the groove is configured as a polished surface, a micro-suede surface, or a combination of a polished surface and a micro-suede surface. The side surfaces of the groove can also be configured as polished surfaces, a micro-suede surface, or a combination of a polished surface and a micro-suede surface. By utilizing the height difference formed by the groove structure with the P region 121 and the N region 122, good isolation of the P region 121 and the N region 122 can be achieved. Of course, in other embodiments, the isolation region 123 can also be a raised platform relative to the P region 121 and the N region 122, or the isolation region 123 can be configured flush with the P region 121 and the N region 122.

[0055] As an embodiment of the present invention, the P region 121 is a micro-suede surface or a polished surface, and the N region 122 is a polished surface.

[0056] In this embodiment, the P region 121 can have either a micro-textured surface or a polished surface. A micro-textured surface can increase the contact area between the doped layer in the P region 121 and the electrode, thereby enhancing the ohmic contact between the doped layer in the P region 121 and the electrode. A polished surface can reduce surface recombination and thus reduce recombination losses.

[0057] As an embodiment of the present invention, the P region 121 is a micro-suede surface, and the longest diagonal length of the tower base of the micro-suede surface of the P region 121 is greater than the longest diagonal length of the tower base of the micro-suede surface of the isolation region 123 .

[0058] In this embodiment, when the P region 121 is a micro-texture surface, the longest diagonal length of the tower base of the micro-texture surface of the P region 121 is greater than the longest diagonal length of the tower base of the micro-texture surface of the isolation region 123, which is beneficial to improving the ohmic contact effect between the doped layer of the P region 121 and the electrode.

[0059] As an embodiment of the present invention, the back contact solar cell further includes:

[0060] A first tunneling layer 2 provided in the P region 121;

[0061] A second tunneling layer 3 provided in the N region 122;

[0062] A P-type doped layer 4 provided on a side of the first tunneling layer 2 facing away from the silicon substrate 1;

[0063] An N-type doped layer 5 is provided on the side of the second tunneling layer 3 facing away from the silicon substrate 1 .

[0064] In the embodiment of the present invention, the silicon substrate 1 may be a P-type silicon substrate or an N-type silicon substrate.

[0065] As one embodiment of the present invention, the first tunneling layer 2 and the second tunneling layer 3 are one or a combination of at least two of silicon oxide, silicon oxynitride, and silicon nitride. The first tunneling layer 2 and the second tunneling layer 3 provide tunneling and passivation functions on the surface of the silicon substrate 1, thereby improving the efficiency of the solar cell. The thickness of the first tunneling layer 2 and the second tunneling layer 3 can be set according to actual conditions. For example, the thickness of the first tunneling layer 2 and the second tunneling layer 3 can be 0.5 to 5 nanometers.

[0066] As an embodiment of the present invention, the P-type doping layer 4 and the N-type doping layer 5 are one or a combination of at least two of doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, and doped amorphous silicon.

[0067] The materials of the P-type doped layer 4 and the N-type doped layer 5 can be set according to actual needs. The P-type doped layer 4 and the N-type doped layer 5 can be one of doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, or doped amorphous silicon. The P-type doped layer 4 and the N-type doped layer 5 can also be a combination of at least two of doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, or doped amorphous silicon. Preferably, the P-type doped layer 4 and the N-type doped layer 5 are both doped polycrystalline silicon.

[0068] In this embodiment, the P-type doping layer 4 is doped with a P-type dopant, and the N-type doping layer 5 is doped with an N-type dopant. The P-type dopant is a Group IIIA element dopant, and the N-type dopant is a Group VA element dopant. For example, the P-type dopant may be a boron dopant, and the N-type dopant may be a phosphorus dopant.

[0069] As an embodiment of the present invention, the back contact solar cell further includes:

[0070] The back passivation film layer 6 is provided on the side of the P-type doped layer 4 and the N-type doped layer 5 facing away from the silicon substrate 1 .

[0071] In this embodiment, the back passivation film layer 6 is used to passivate and protect the back surfaces of the P-type doped layer 4 and the N-type doped layer 5, thereby further improving the battery efficiency. The back passivation film layer 6 covers both the P-type doped layer 4, the N-type doped layer 5, and the isolation region 123.

[0072] In this embodiment, the back passivation film layer 6 may be one of silicon nitride, silicon oxynitride, and silicon oxide, or a combination of at least two of them. For example, the back passivation film layer 6 may be sequentially stacked on aluminum oxide and silicon nitride on the doped layer, thereby achieving a good back passivation effect on the doped layer and providing good protection for the doped layer.

[0073] As an embodiment of the present invention, the solar cell further includes:

[0074] A first electrode 7 provided in the P region 121 , the first electrode being in contact with the P-type doped layer 4 in the P region 121 ;

[0075] The second electrode 8 is provided in the N region 122 , and the second electrode is in contact with the N-type doped layer 5 in the N region 122 .

[0076] In this embodiment, the first electrode 7 contacts the P-type doped layer 4 in the P region 121 to form an ohmic contact, and the second electrode 8 contacts the N-type doped layer 5 in the N region 122 to achieve current extraction from the solar cell. Specifically, the first electrode 7 passes through the back passivation film layer 6 at the location of the P region 121 to contact the P-type doped layer 4, and the second electrode 8 passes through the back passivation film layer 6 at the location of the N region 122 to contact the N-type doped layer 5.

[0077] An embodiment of the present invention provides a back-contact solar cell by setting at least a portion of the isolation region 123 between the P region 121 and the N region 122 as a polished surface or setting at least a portion of the isolation region 123 as a micro-velvet surface, wherein the longest diagonal length of the tower base of the micro-velvet surface is 2 to 5 microns. Compared with the pyramid velvet structure set in the isolation region 123 of the traditional back-contact solar cell, the isolation region 123 utilizes the polished surface or the micro-velvet structure to reduce the transmission path of the carriers, reduce the surface recombination loss, improve the passivation performance, and improve the power generation efficiency of the back-contact solar cell.

[0078] The present invention also provides a battery assembly comprising the back-contact solar cell of the aforementioned embodiment. It should be noted that the battery assembly and the back-contact solar cell have the same or similar beneficial effects, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they will not be described here.

[0079] In this embodiment, multiple back-contact solar cells in the battery assembly can be connected in series in sequence to form a battery string, thereby realizing the series bus output of the current. For example, the series connection of the battery cells can be realized by setting welding strips (bus bars, interconnecting bars), conductive back plates, etc.

[0080] It is understood that in such an embodiment, the battery assembly may further include a metal frame, a backsheet, photovoltaic glass, and an adhesive film. The adhesive film may be filled between the front and back surfaces of the back-contact solar cell, the photovoltaic glass, adjacent cells, etc., and may be a transparent colloid with good light transmittance and aging resistance. For example, the adhesive film may be EVA film or POE film. The specific choice can be made according to actual conditions and is not limited here.

[0081] Photovoltaic glass can cover the adhesive film on the front side of the back-contact solar cell. The photovoltaic glass can be ultra-clear glass, which has high light transmittance, high transparency, and excellent physical, mechanical, and optical properties. For example, ultra-clear glass can have a light transmittance of over 92%, protecting the back-contact solar cell while minimizing the impact on its efficiency. The adhesive film also bonds the photovoltaic glass to the back-contact solar cell, providing sealing, insulation, and waterproofing.

[0082] A backsheet can be attached to the film on the back of the back-contact solar cell. The backsheet provides protection and support for the back-contact solar cell, offering reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, organic glass, and aluminum alloy TPT composite film. The specific backsheet material can be configured based on specific circumstances and is not limited here. The backsheet, back-contact solar cell, film, and photovoltaic glass assembly can be mounted on a metal frame. The metal frame serves as the primary external support structure for the entire solar cell assembly and provides stable support and mounting for the assembly. For example, the metal frame allows the solar cell assembly to be mounted in the desired location.

[0083] The present invention also provides a photovoltaic system comprising the battery assembly of the above embodiment. It should be noted that the photovoltaic system has the same or similar beneficial effects as the above-mentioned back-contact solar cell, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they will not be described here.

[0084] In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple solar cell modules. For example, multiple solar cell modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein a backlight surface of the silicon substrate includes a P region, an N region, and an isolation region provided between the P region and the N region; Wherein, at least a part of the isolation area is set as a polished surface; or at least a part of the isolation area is set as a micro-suede surface, and the longest diagonal length of the tower base of the micro-suede surface is 2 to 5 microns.

2. The back contact solar cell according to claim 1, wherein: The entire isolation region is a polished surface.

3. The back contact solar cell according to claim 1, wherein: The entire area of ​​the isolation zone is the micro-suede surface.

4. The back contact solar cell according to claim 1, wherein: The isolation region includes a first area and a second area, the first area is configured as the polishing surface, and the second area is configured as the micro-suede surface.

5. The back contact solar cell according to claim 4, characterized in that There are a plurality of the first regions and a plurality of the second regions, and the first regions and the second regions are alternately arranged in the isolation area.

6. The back contact solar cell according to claim 4, characterized in that The area of ​​the first region is greater than that of the second region.

7. The back contact solar cell according to claim 6, characterized in that The ratio of the area of ​​the first region to the area of ​​the second region is 1-5.

8. The back contact solar cell according to claim 1, wherein: The isolation region is a trench.

9. The back contact solar cell according to claim 1, wherein: The P region is a micro-suede surface or a polished surface, and the N region is a polished surface.

10. The back contact solar cell according to claim 1, wherein: The P region is the micro-fleece surface, and the longest diagonal length of the tower base of the micro-fleece surface of the P region is greater than the longest diagonal length of the tower base of the micro-fleece surface of the isolation region.

11. A battery assembly, characterized in that: The invention comprises a back contact solar cell according to any one of claims 1 to 10.

12. A photovoltaic system, characterized in that: Comprising the battery assembly as claimed in claim 11.

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