Back contact solar cell, cell module and photovoltaic system

Abstract

The utility model is applicable to 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, the back surface of the silicon substrate comprises an N-type region, a P-type region and an isolation region arranged between the N-type region and the P-type region, the N-type region, the P-type region and the isolation region are all polished surfaces, and the N-type region and the P-type region are polished surfaces. The N-type region, the P-type region and the isolation region all comprise a plurality of first tower footings. According to the back contact solar cell provided by the utility model, the N-type region, the P-type region and the isolation region are all arranged to be polished surfaces, so that the recombination loss of the back surface can be reduced, and the back reflection effect of incident light is improved, thereby improving the conversion efficiency of the cell; moreover, the N-type region, the P-type region and the isolation region are arranged to be of the same tower footing type, so that the thinning amount of the silicon substrate can be reduced, the dosage of chemicals can be reduced, and the silicon substrate with thinner thickness can be adopted to manufacture the battery, thereby reducing the production cost of the battery.

Description

Technical Field

[0001] This utility model relates to the field of solar cell technology, specifically to a back-contact solar cell, a battery module, and a photovoltaic system. Background Technology

[0002] Solar energy, due to its safety, low pollution, and renewability, has become an essential clean energy source for human development and has received much attention and promotion from various countries in recent years. However, the cost of photovoltaic power generation is a major factor restricting the wider application of photovoltaic products. Among them, back-contact solar cells, because both their positive and negative electrodes are designed on the back of the cell, completely avoid the shading of metal grid lines on the front surface compared to double-sided contact solar cells. This eliminates the optical losses caused by metal grid line shading and can significantly improve the cell conversion efficiency.

[0003] In existing technologies, the back side of a back-contact solar cell typically includes P-type and N-type regions arranged alternately, with an isolation region between adjacent P-type and N-type regions. This isolation region is usually configured with a pyramidal textured surface. This pyramidal textured surface increases the carrier transport path, leading to significant surface recombination losses and reducing the cell's power generation efficiency. Utility Model Content

[0004] This invention provides a back-contact solar cell, which aims to solve the problem of high back recombination loss and low power generation efficiency in existing back-contact solar cells.

[0005] This invention is implemented as follows: a back-contact solar cell is provided, comprising a silicon substrate. The back side of the silicon substrate includes an N-type region, a P-type region, and an isolation region disposed between the N-type region and the P-type region. The N-type region, the P-type region, and the isolation region are all polished surfaces. Each of the N-type region, the P-type region, and the isolation region includes a plurality of first bases.

[0006] Preferably, the surface of the first tower base in the isolation zone is provided with pits.

[0007] Preferably, the recess has an inverted pyramid structure.

[0008] Preferably, the longest diagonal length of the first tower base is 5 to 35 micrometers.

[0009] Preferably, the longest diagonal length of the first tower base is 20 to 30 micrometers.

[0010] Preferably, the longest diagonal length of the first tower base is 24 to 26 micrometers.

[0011] Preferably, the N-type region, the P-type region, and the isolation zone are arranged in a linear array of the first tower bases.

[0012] Preferably, the N-type region, the P-type region, and the isolation region are located on the same plane.

[0013] This invention also provides a battery assembly, including the aforementioned back-contact solar cell.

[0014] This utility model also provides a photovoltaic system, including the above-mentioned battery components.

[0015] This invention provides a back-contact solar cell where the N-type region, P-type region, and isolation region are all polished surfaces. This reduces the carrier transport path on the back side of the solar cell, decreases back-side recombination losses, and improves the power generation efficiency of the back-contact solar cell. Simultaneously, it increases the back reflection effect of incident light, reduces incident light transmission, and increases the short-circuit current of the cell, thereby improving the cell conversion efficiency. Furthermore, the N-type region, P-type region, and isolation region all include several first bases, meaning that the N-type region, P-type region, and isolation region are all of the same base type. This reduces the amount of silicon substrate thinning required, lowers the amount of chemicals used, and allows for the use of thinner silicon substrates to fabricate the cell, thus reducing the production cost of the cell. Attached Figure Description

[0016] Figure 1 A schematic diagram of the structure of a silicon substrate for a back-contact solar cell provided in an embodiment of this utility model;

[0017] Figure 2 Scanning electron microscope (SEM) images of the N-type region, P-type region, and isolation region of a silicon substrate for a back-contact solar cell provided in this embodiment of the present invention;

[0018] Figure 3 SEM image of the isolation region of a back-contact solar cell provided in an embodiment of this utility model. Detailed Implementation

[0019] 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.

[0020] This utility model embodiment provides a back-contact solar cell where the N-type region, P-type region, and isolation region are all polished surfaces. This reduces the carrier transport path on the back side of the back-contact solar cell, reduces back-side recombination losses, and improves the power generation efficiency of the back-contact solar cell. Furthermore, since the N-type region, P-type region, and isolation region are all polished surfaces, the back reflection effect of incident light is increased, the transmission of incident light is reduced, and the short-circuit current of the cell is increased, thereby improving the cell conversion efficiency. Moreover, the N-type region, P-type region, and isolation region all include several first bases, that is, the N-type region, P-type region, and isolation region are set with the same base type, which can reduce the amount of silicon substrate thinning, reduce the amount of chemicals used, and allow the use of thinner silicon substrates to manufacture the cell, thereby reducing the production cost of the cell.

[0021] Please refer to Figures 1-2 This utility model provides a back-contact solar cell, including a silicon substrate 1. The back side of the silicon substrate 1 includes an N-type region 11, a P-type region 12, and an isolation region 13 disposed between the N-type region 11 and the P-type region 12. The N-type region 11, the P-type region 12, and the isolation region 13 are all polished surfaces. The N-type region 11, the P-type region 12, and the isolation region 13 each include a plurality of first bases 101.

[0022] This embodiment of the invention provides a back-contact solar cell. By setting the N-type region 11, P-type region 12, and isolation region 13 as polished surfaces, on the one hand, the carrier transport path on the back side of the back-contact solar cell can be reduced, the back recombination loss can be reduced, and the power generation efficiency of the back-contact solar cell can be improved. Moreover, since the N-type region 11, P-type region 12, and isolation region 13 are all polished surfaces, the back reflection effect of incident light can be increased, the transmission of incident light can be reduced, and the short-circuit current of the cell can be increased, thereby improving the cell conversion efficiency. On the other hand, the N-type region 11, P-type region 12, and isolation region 13 all include a plurality of first bases 101, that is, the N-type region 11, P-type region 12, and isolation region 13 are of the same base type and have the same polishing morphology. This can reduce the amount of thinning required for the silicon substrate 1, reduce the amount of chemicals used, and allow for the use of thinner silicon wafers to manufacture the cell, thereby reducing the production cost of the cell.

[0023] The first tower base 101 refers to a microstructure disposed on the silicon substrate 1 of the solar cell. The first tower base 101 typically appears in the form of a tower or cone, with a planar top surface and a polygonal outer contour, specifically including at least one of rhombus, square, trapezoidal, approximate rhombus, approximate square, and approximate trapezoidal shapes. The number of first tower bases 101 disposed in the N-type region 11, P-type region 12, and isolation region 13 is unlimited. The first tower bases 101 in the N-type region 11, P-type region 12, and isolation region 13 can be disposed side-by-side. Alternatively, some of the first tower bases 101 can be stacked, i.e., some first tower bases 101 are disposed on top of other first tower bases 101. This increases the complexity of the tower bases, further increasing the optical path of diffusely reflected light from the back side. The longer the travel path of photons in the silicon substrate 1, the greater the probability of absorption, thereby improving the photoelectric response of the solar cell.

[0024] The first tower base 101 is formed on the N-type region 11, P-type region 12 and isolation region 13 of the silicon substrate 1 by a certain process method; for example, the first tower base 101 can be formed on the N-type region 11, P-type region 12 and isolation region 13 by alkaline polishing.

[0025] As one embodiment of this utility model, the longest diagonal length of the first tower base 101 is 5 to 35 micrometers.

[0026] In this embodiment, the top surface of the first tower base 101 is typically polygonal. The longer the diagonal of the first tower base 101, the larger the area of ​​the top surface of the tower base. The longest diagonal of the first tower base 101 is the longest diagonal length among all first tower bases 101, that is, the longest diagonal length of the first tower base 101 with the largest top surface area.

[0027] When measuring the longest diagonal length of the tower base, the surface calibration of the membrane layer can be directly measured using testing instruments such as optical microscopes, atomic force microscopes, scanning electron microscopes, and transmission electron microscopes.

[0028] In this embodiment, the longest diagonal length of the first tower base 101 is set to 5-35 micrometers. This not only reduces back recombination loss and improves passivation performance, but also significantly increases the back reflection effect of incident light, reduces the transmission of incident light, and increases the short-circuit current of the battery, thereby improving the battery conversion efficiency. Moreover, it ensures that the tower base structures of the N-type region 11, P-type region 12, and isolation region 13 can work together in a coordinated manner and give full play to their respective advantages. This can better balance the back recombination loss of the battery and the back reflection effect of incident light, thereby improving the overall conversion efficiency of the battery.

[0029] For example, the longest diagonal length of the first tower base 101 can be any value among 5 micrometers, 6 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 15 micrometers, 17 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 24 micrometers, 25 micrometers, 28 micrometers, 30 micrometers, 32 micrometers, 34 micrometers, and 35 micrometers.

[0030] As one embodiment of this utility model, the longest diagonal length of the first tower base 101 is 20-30 micrometers.

[0031] In this embodiment, the longest diagonal length of the first tower base 101 is 20-30 micrometers, which can further reduce surface recombination loss, reduce the transmission of incident light, increase the short-circuit current of the battery, and thus improve the battery conversion efficiency. Moreover, it can further ensure that the tower base structures of the N-type region 11, P-type region 12 and isolation region 13 work together in a coordinated manner, further balance the recombination loss on the back of the battery and the back reflection effect of incident light, and improve the overall conversion efficiency of the battery.

[0032] As one embodiment of this utility model, the longest diagonal length of the first tower base 101 is 24-26 micrometers.

[0033] In this embodiment, the longest diagonal length of the first tower base 101 is 24-26 micrometers, which can further reduce surface recombination losses, reduce the transmission of incident light, increase the short-circuit current of the battery, and thus improve the battery conversion efficiency. Furthermore, it can further ensure the coordinated operation of the tower base structures of the N-type region 11, P-type region 12, and isolation region 13, further balancing the recombination losses on the back of the battery and the back reflection effect of incident light, thereby improving the overall conversion efficiency of the battery. Preferably, the longest diagonal length of the first tower base 101 can be 25 micrometers.

[0034] As an embodiment of the present invention, a plurality of first tower bases 101 within the N-type region 11, the P-type region 12 and the isolation region 13 are arranged in a linear array.

[0035] In this embodiment, the plurality of first tower bases 101 within the N-type region 11, the P-type region 12, and the isolation region 13 are arranged in a regular linear array, that is, they are arranged along a certain direction at a certain spacing and according to a certain pattern, forming a neat linear structure. The linear array arrangement of the first tower bases 101 can be determined according to design requirements, and parameters such as the array spacing, arrangement direction, and density can be determined to achieve optimal performance. Of course, the plurality of first tower bases 101 within the N-type region 11, the P-type region 12, and the isolation region 13 can also be arranged irregularly.

[0036] Please refer to Figure 3 As an embodiment of the present invention, a pit 104 is provided on the surface of the first tower base 101 of the isolation zone 13.

[0037] In this embodiment, the specific shape and number of the recesses 104 on the first tower base 101 are not limited. They can be inverted pyramid structures, circular countersunk holes, triangular countersunk holes, trapezoidal countersunk holes, quadrilateral countersunk holes, polygonal countersunk holes, or other irregular countersunk holes. By providing recesses 104 on the surface of the first tower base 101, the presence of the recesses 104 can increase the adhesion of the back film layer (such as alumina or silicon nitride film) of the isolation region 13 to the silicon substrate 1, avoiding the occurrence of bubble bursting during subsequent sintering processes, thereby improving the production yield of back contact solar cells.

[0038] As a preferred embodiment of this utility model, the pit 104 has an inverted pyramid structure, which can further improve the adhesion of the back film layer of the isolation region 13 to the silicon substrate 1, further prevent the occurrence of bubble bursting during subsequent sintering processes, thereby improving the production yield of solar cells.

[0039] In one embodiment of this utility model, the N-type region 11, the P-type region 12, and the isolation region 13 are located on the same plane.

[0040] In this embodiment, the N-type region 11, the P-type region 12 and the isolation region 13 are located on the same plane. In this way, the N-type region 11, the P-type region 12 and the isolation region 13 do not need to have a height difference, which is convenient for processing and also facilitates the deposition of the N-type doped layer 2 of the N-type region 11 and the P-type doped layer 3 of the P-type region 12.

[0041] As one embodiment of this utility model, it also includes:

[0042] An N-type doped layer 2 is provided in the N-type region 11;

[0043] A P-type doped layer 3 is provided in the P-type region 12.

[0044] In this embodiment, the thickness of the N-type doped layer 2 and the thickness of the P-type doped layer 3 can be the same or different. Preferably, the thickness of the N-type doped layer 2 and the thickness of the P-type doped layer 3 are different. Since the N-type region 11, the P-type region 12 and the isolation region 13 are located on the same plane, setting the thickness of the N-type doped layer 2 and the thickness of the P-type doped layer 3 to be different, so that the isolation region 13 has a different height difference with the N-type doped layer 2 and the P-type doped layer 3, can reduce the leakage risk between the N-type region 11 and the P-type region 12.

[0045] In one embodiment of this utility model, the thickness of the N-type doped layer 2 is 100-300 nm, and the thickness of the P-type doped layer 3 is 100-300 nm.

[0046] In this embodiment, the thicknesses of the N-type doped layer 2 and the P-type doped layer 3 are 100–300 nm, which can be set according to actual conditions. For example, the thickness of the N-type doped layer 2 can be 200 nm, and the thickness of the P-type doped layer 3 can be 150 nm.

[0047] This utility model embodiment also provides a battery assembly, which includes the back-contact solar cell of the above embodiment. It should be noted that the battery assembly has the same or similar beneficial effects as the back-contact solar cell, and the related parts between the two can be referred to each other. To avoid repetition, they will not be described again here.

[0048] In this embodiment, multiple back-contact solar cells in the battery module can be connected in series to form a battery string, thereby achieving series current output. For example, the battery cells can be connected in series by setting solder strips (busbars, interconnecting strips), conductive backplates, etc.

[0049] It is understood that in such embodiments, the battery assembly may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film may be filled between the front and back of the back-contact solar cell, the photovoltaic glass, adjacent cells, etc. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the encapsulating film may be an EVA film or a POE film, and the specific choice can be made according to the actual situation, without limitation.

[0050] Photovoltaic glass can be applied to the encapsulating film on the front side of the back-contact solar cell. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 92%, protecting the solar cell while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the back-contact solar cell together, providing sealing, insulation, and waterproofing.

[0051] The backsheet can be attached to the adhesive film on the back of the back-contact solar cell. The backsheet protects and supports the back-contact solar cell, providing reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, aluminum alloy TPT composite film, etc., and the specific choice depends on the specific circumstances and is not limited here. The backsheet, back-contact solar cell, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire solar cell module, providing stable support and installation. For example, the solar cell module can be installed at the desired location using the metal frame.

[0052] This utility model embodiment also provides a photovoltaic system, which includes the battery module of the above embodiment. It should be noted that this photovoltaic system has the same or similar beneficial effects as the back-contact solar cell described above, and the related parts between the two can be referred to each other. To avoid repetition, they will not be described again here.

[0053] In this embodiment, the photovoltaic system can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants. It can also be applied to equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may 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 combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0054] The above are merely preferred embodiments of the present utility model and are 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 back-contact solar cell, characterized in that, The device includes a silicon substrate, the back side of which includes an N-type region, a P-type region, and an isolation region disposed between the N-type region and the P-type region. The N-type region, the P-type region, and the isolation region are all polished surfaces, and each of the N-type region, the P-type region, and the isolation region includes a plurality of first bases.

2. The back-contact solar cell according to claim 1, characterized in that, The surface of the first tower base in the isolation zone is provided with pits.

3. The back-contact solar cell according to claim 2, characterized in that, The depression has an inverted pyramid structure.

4. The back-contact solar cell according to claim 1, characterized in that, The longest diagonal length of the first tower base is 5 to 35 micrometers.

5. The back-contact solar cell according to claim 1, characterized in that, The longest diagonal length of the first tower base is 20 to 30 micrometers.

6. The back-contact solar cell according to claim 1, characterized in that, The longest diagonal length of the first tower base is 24–26 micrometers.

7. The back-contact solar cell according to claim 1, characterized in that, The N-type region, the P-type region, and the isolation zone are arranged in a linear array of several first tower bases.

8. The back-contact solar cell according to claim 1, characterized in that, The N-type region, the P-type region, and the isolation zone are located on the same plane.

9. A battery assembly, characterized in that, Including the back-contact solar cell as described in any one of claims 1 to 8.

10. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 9.

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