Back contact solar cells and photovoltaic modules

Abstract

The application discloses a back contact solar cell and a photovoltaic module, and belongs to the technical field of solar cells. The back contact solar cell comprises a substrate, first areas and second areas arranged alternately, a first dielectric layer arranged in the first areas and a second dielectric layer arranged in the second areas, a first conductive layer arranged on a side surface of the first dielectric layer away from the substrate, the first conductive layer having a different conductive type of doping elements from the substrate, a second conductive layer arranged on a side surface of the second dielectric layer away from the substrate, the second conductive layer having a same conductive type of doping elements as the substrate, a first passivation layer arranged on a side of the first conductive layer away from the substrate, a second passivation layer arranged on a side of the second conductive layer away from the substrate, and the thickness of the first passivation layer is smaller than the thickness of the second passivation layer. The back contact solar cell can reduce the probability of the back contact solar cell from having a film explosion phenomenon while achieving a good passivation effect.

Description

Technical Field

[0001] This application belongs to the field of solar cell technology, and particularly relates to a back-contact solar cell and photovoltaic module. Background Technology

[0002] Crystalline silicon solar cells are currently the mainstream technology in the field of solar cells. Their basic principle is to convert light energy into electrical energy through a PN junction. Among them, BC (Back Contact) solar cells are a new type of structure. BC solar cells achieve excellent passivation effects by introducing a tunneling oxide layer and a doped polycrystalline silicon layer on the back of the cell. Compared with traditional cells, the structure used in BC solar cells has higher conversion efficiency and lower recombination loss.

[0003] However, during the manufacturing process, BC solar cells are prone to stress concentration at the interface, which can cause the cell to burst, resulting in delamination or even cracking between the film layers, thus affecting the yield and efficiency of the cell. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a back-contact solar cell and photovoltaic module that reduces the probability of film bursting in back-contact solar cells, thereby improving the yield and efficiency of back-contact solar cells.

[0005] In a first aspect, this application provides a back-contact solar cell, comprising: A substrate, the back side of which has a plurality of alternating first and second regions; A first dielectric layer is disposed in the first region; A first conductive layer is disposed on the surface of the first dielectric layer away from the substrate, and the first conductive layer and the substrate are doped with dopants of different conductivity types. A second dielectric layer is disposed in the second region; A second conductive layer is disposed on the surface of the second dielectric layer away from the substrate, and the second conductive layer has doping elements of the same conductivity type as the substrate; A first passivation layer is disposed on the side of the first conductive layer away from the substrate. A second passivation layer is disposed on the side of the second conductive layer away from the substrate; The thickness of the first passivation layer is less than the thickness of the second passivation layer.

[0006] According to the back-contact solar cell provided in the embodiments of this application, the area where the first conductive layer is located is more prone to film bursting. By appropriately reducing the thickness of the first passivation layer deposited on the surface of the first conductive layer without affecting the thickness of the second passivation layer deposited on the surface of the second conductive layer, the back-contact solar cell can reduce the probability of film bursting while achieving a good passivation effect, thereby improving the yield and efficiency of the back-contact solar cell.

[0007] According to one embodiment of this application, the absolute value of the thickness difference between the first passivation layer and the second passivation layer is greater than or equal to 0.5 nm.

[0008] According to one embodiment of this application, the first passivation layer and / or the second passivation layer comprises aluminum oxide.

[0009] According to one embodiment of this application, the thickness of the first passivation layer is greater than or equal to 2 nm, and / or the thickness of the second passivation layer is greater than or equal to 3.5 nm.

[0010] According to one embodiment of this application, an isolation region is provided between the first region and the second region, and the first passivation layer and / or the second passivation layer covers the isolation region.

[0011] According to one embodiment of this application, the solar cell further includes: An anti-reflection layer that simultaneously covers both the first passivation layer and the second passivation layer.

[0012] According to one embodiment of this application, the antireflection layer is a single-layer film or a multilayer film comprising one or more of silicon nitride, silicon oxynitride, and silicon oxide.

[0013] According to one embodiment of this application, the solar cell further includes: An oxide layer is disposed between the first passivation layer and the antireflection layer, and / or the oxide layer is disposed between the second passivation layer and the antireflection layer.

[0014] According to one embodiment of this application, the oxide layer comprises silicon oxide.

[0015] According to one embodiment of this application, the thickness of the oxide layer is 0.5 nm to 3 nm.

[0016] According to one embodiment of this application, the material of the first dielectric layer includes one or more of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the material of the second dielectric layer includes one or more of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the first conductive layer is a doped polycrystalline silicon layer; and / or, the second conductive layer is a doped polycrystalline silicon layer.

[0017] According to one embodiment of this application, the thickness of the first dielectric layer is 0.5 nm to 3 nm; and / or, the thickness of the second dielectric layer is 0.5 nm to 3 nm; and / or, the thickness of the first conductive layer is 30 nm to 300 nm; and / or, the thickness of the second conductive layer is 30 nm to 300 nm.

[0018] Secondly, this application provides a photovoltaic module, which includes: The back-contact solar cell as described in the first aspect above.

[0019] According to the photovoltaic module provided in the embodiments of this application, the area where the first conductive layer is located in the back contact solar cell of the photovoltaic module is more prone to film bursting. By appropriately reducing the thickness of the first passivation layer deposited on the surface of the first conductive layer without affecting the thickness of the second passivation layer deposited on the surface of the second conductive layer, the probability of film bursting of the back contact solar cell can be reduced while achieving a good passivation effect, thereby improving the yield and efficiency of the back contact solar cell.

[0020] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is one of the structural schematic diagrams of a back-contact solar cell provided in the embodiments of this application; Figure 2 This is the second schematic diagram of the structure of the back-contact solar cell provided in the embodiments of this application; Figure 3 This is one of the fabrication flowcharts of a back-contact solar cell provided in the embodiments of this application; Figure 4 This is the second flowchart of the fabrication process of the back-contact solar cell provided in the embodiments of this application; Figure 5 This is the third flowchart of the fabrication process of the back-contact solar cell provided in the embodiments of this application; Figure 6 This is the fourth flowchart of the fabrication process of the back-contact solar cell provided in the embodiments of this application.

[0022] Figure label: Back contact solar cell 100, substrate 110, First dielectric layer 210, second dielectric layer 220 First conductive layer 310, second conductive layer 320 First passivation layer 410, second passivation layer 420 Antireflective layer 510, oxide layer 520. Detailed Implementation

[0023] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0024] BC structure solar cells are prone to stress concentration at the interface during manufacturing, which can cause the cell to burst, resulting in delamination or even cracking between the film layers, thus affecting the cell's yield and efficiency.

[0025] This application provides a back-contact solar cell that can reduce the probability of film bursting in back-contact solar cells while achieving good passivation effects, thereby improving the yield and efficiency of back-contact solar cells.

[0026] The back-contact solar cell provided in this application is described below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0027] like Figure 1 As shown, the back contact solar cell 100 includes a substrate 110, a first dielectric layer 210, a second dielectric layer 220, a first conductive layer 310, a second conductive layer 320, a first passivation layer 410, and a second passivation layer 420.

[0028] In the case of a solar cell with a back contact structure, the substrate 110 can be a silicon substrate 110 portion of the solar cell. The substrate 110 has two opposing sides, one of which has an alternately arranged first region and a second region.

[0029] Understandably, in solar cells with a back-contact structure, the conductive electrodes are also located on the side where the first and second regions are located, so that the other side is not blocked by the electrodes.

[0030] In practice, the side of the back-contact solar cell 100 that is not blocked by the electrodes is usually the main light-receiving side, that is, the front side of the back-contact solar cell 100, while the side containing the first and second regions is the back side.

[0031] In this embodiment, the first region and the second region are arranged alternately on the back side of the substrate 110 along a first direction, which can be a direction parallel to the plane of the substrate 110.

[0032] For example, if the first direction is the vertical direction in the plane where the base 110 is located, then the first and second regions can be arranged alternately from top to bottom in the order of first region, second region, first region...

[0033] In practice, the substrate 110 can be N-type silicon.

[0034] In this embodiment, a first dielectric layer 210 is disposed in a first region, and a second dielectric layer 220 is disposed in a second region. The first dielectric layer 210 and the second dielectric layer 220 can passivate the substrate 110 in the first region and the second region, respectively, to improve the efficiency of the back contact solar cell 100.

[0035] In actual implementation, the first dielectric layer 210 and the second dielectric layer 220 can be the tunneling oxide layer 520.

[0036] In this embodiment, the first conductive layer 310 is disposed on the side surface of the first dielectric layer 210 away from the substrate 110, and the first conductive layer 310 and the substrate 110 have doped elements of different conductivity types. The second conductive layer 320 is disposed on the side surface of the second dielectric layer 220 away from the substrate 110, and the second conductive layer 320 and the substrate 110 have doped elements of the same conductivity type.

[0037] For example, if the substrate 110 is N-type silicon, that is, the substrate 110 is N-type doped, then the first conductive layer 310 is P-type doped, the first region is P-region, the second conductive layer 320 is N-type doped, and the second region is N-region.

[0038] In this embodiment, the first conductive layer 310 and the second conductive layer 320 can be doped polycrystalline silicon layers with opposite conductive polarities after undergoing different doping processes, that is, the first conductive layer 310 can be a P-poly layer and the second conductive layer 320 can be an N-poly layer.

[0039] In actual implementation, adjacent first conductive layer 310 and second conductive layer 320 are electrically insulated. For example, an isolation opening, i.e. a gap area, is provided between the first conductive layer 310 and the second conductive layer 320 to achieve electrical insulation between adjacent first conductive layer 310 and second conductive layer 320.

[0040] In this embodiment, the first passivation layer 410 is disposed on the surface of the first conductive layer 310 away from the substrate 110, and the second passivation layer 420 is disposed on the surface of the second conductive layer 320 away from the substrate 110.

[0041] It is understandable that in the back contact solar cell 100, the substrate 110, dielectric layer, conductive layer and passivation layer can be arranged in a stacked manner.

[0042] For example, if the back of the back-contact solar cell 100 is facing upwards, then the first dielectric layer 210 and the second dielectric layer 220 are located on the upper surface of the substrate 110. The first conductive layer 310 can be disposed on the upper surface of the first dielectric layer 210, the second conductive layer 320 can be disposed on the upper surface of the second dielectric layer 220, the first passivation layer 410 can be disposed on the surface of the first conductive layer 310 away from the substrate 110, that is, on the upper surface of the first conductive layer 310, and the second passivation layer 420 can be disposed on the surface of the second conductive layer 320 away from the substrate 110, that is, on the upper surface of the second conductive layer 320.

[0043] In practice, the first passivation layer 410 and the second passivation layer 420 can be aluminum oxide layers. The aluminum oxide layer can passivate the dangling bonds and defects in the first conductive layer 310, the second conductive layer 320 and the substrate 110, thereby improving the efficiency of the back contact solar cell 100.

[0044] It should be noted that in the manufacturing process of the back contact solar cell 100, the first conductive layer 310 and the second conductive layer 320 are prepared by stepwise deposition. After the first conductive layer 310 is prepared (e.g., Figure 3 As shown), excess first conductive layer 310 located in the second region and gap region will be selectively removed using laser and etching processes (e.g., Figure 4 As shown), then the second conductive layer 320 is deposited (as shown). Figure 5 As shown), and then selectively remove the excess second conductive layer 320 located in the gap area again using laser and etching processes (as shown). Figure 6 As shown in the figure, electrical insulation is achieved between the first conductive layer 310 and the second conductive layer 320.

[0045] It is understandable that silicon is anisotropic to the acidic or alkaline solutions used in the etching process. The rate at which silicon is etched varies in different directions, resulting in a pyramid-like morphological structure on the etched surface of the substrate 110. In the manufacturing process of the back contact solar cell 100 described above, the substrate 110 region where the second conductive layer 320 is located undergoes one more etching process than the substrate 110 region where the first conductive layer 310 is located. This results in more and denser pyramid bases in the substrate 110 region where the second conductive layer 320 is located, which in turn makes the morphology of the second conductive layer 320 on top rougher. In other words, the flatness of the first conductive layer 310 is higher than that of the second conductive layer 320.

[0046] It should be noted that hydrogen gas is usually released during the preparation of the conductive layer and the passivation layer.

[0047] For example, the deposition of polycrystalline silicon layers often employs a silane decomposition process, which generates polycrystalline silicon and hydrogen gas after silane decomposition.

[0048] For example, the deposition of alumina layers often employs a process involving the reaction of trimethylaluminum and water, which can generate alumina and hydrogen gas.

[0049] Some of the hydrogen gas released during the fabrication of the conductive and passivation layers remains in the conductive and passivation layers as hydrogen ions. These hydrogen ions can combine with dangling bonds in the conductive and passivation layers, thereby improving the efficiency of the solar cell.

[0050] However, if hydrogen in the conductive or passivation layer leaks out during the deposition of subsequent films in the back contact solar cell 100, it will cause stress concentration between the films, leading to film bursting, which will affect the efficiency and yield of the back contact solar cell 100.

[0051] In this embodiment, the flatness of the first conductive layer 310 is higher than that of the second conductive layer 320, making it more prone to film bursting. By appropriately thinning the thickness of the first passivation layer 410, making the thickness of the first passivation layer 410 less than that of the second passivation layer 420, the occurrence of film bursting of the first conductive layer 310 can be reduced while maintaining a good passivation effect, thereby improving the efficiency and yield of the back contact solar cell 100.

[0052] In related technologies, passivation layers are commonly used in back-contact solar cells to passivate defects in the silicon substrate and various film layers, thereby improving the performance of the solar cell. However, passivation layers are prone to causing film bursting during the manufacturing process of subsequent film layers. Film bursting causes stress concentration at the cell interface, leading to delamination or even cracking between film layers, affecting cell yield and efficiency. Related technologies suppress film bursting by reducing the thickness of the passivation layer to lower the hydrogen content, but this method deteriorates the passivation of the solar cell, thus affecting cell efficiency. Related technologies also improve film bursting by increasing the processing temperature and processing time of subsequent film layers, but this method can cause severe cell warping, affecting the stability of the solar cell in use.

[0053] In this embodiment, the inventors discovered that the first conductive layer 310 has a higher flatness and is more prone to film bursting compared to the second conductive layer 320. The inventors optimized the passivation layer deposition process to a multi-stage deposition, achieving selective control of the passivation layer thickness in different regions. By appropriately thinning the thickness of the first passivation layer 410 deposited on the surface of the first conductive layer 310, the thickness of the first passivation layer 410 is less than the thickness of the second passivation layer 420 deposited on the surface of the second conductive layer 320. This is equivalent to reducing the hydrogen content in the region where the first conductive layer 310 is located, which can effectively reduce the probability of film bursting. Furthermore, the second conductive layer 320 is less prone to film bursting. The second passivation layer 420 deposited on the second conductive layer 320 can maintain its original thickness or even increase its thickness appropriately to provide a good passivation effect. By selectively controlling the thickness of the first passivation layer 410 and the second passivation layer 420, the probability of film bursting can be reduced while achieving a good passivation effect, thereby improving the yield and efficiency of the back contact solar cell 100.

[0054] According to the back contact solar cell 100 provided in the embodiments of this application, the area where the first conductive layer 310 is located is more prone to film bursting. By appropriately thinning the thickness of the first passivation layer 410 deposited on the surface of the first conductive layer 310 without affecting the thickness of the second passivation layer 420 deposited on the surface of the second conductive layer 320, the back contact solar cell 100 can reduce the probability of film bursting while achieving a good passivation effect, thereby improving the yield and efficiency of the back contact solar cell 100.

[0055] In some embodiments, the absolute value of the thickness difference between the first passivation layer 410 and the second passivation layer 420 is greater than or equal to 0.5 nm.

[0056] In actual implementation, the thickness of the first passivation layer 410 and the second passivation layer 420 can be controlled by adjusting process parameters such as deposition time, deposition temperature and gas flow rate.

[0057] It is understandable that if the thickness of the first passivation layer 410 is too small compared to the second passivation layer 420, the area where the first conductive layer 310 is located is still prone to film bursting, affecting the yield and efficiency of the back contact solar cell 100.

[0058] In this embodiment, the absolute value of the thickness difference between the first passivation layer 410 and the second passivation layer 420 is greater than or equal to 0.5 nm, which can better suppress the film bursting phenomenon of the back contact solar cell 100 in subsequent processes.

[0059] In some embodiments, the first passivation layer 410 and / or the second passivation layer 420 comprise aluminum oxide.

[0060] In this embodiment, aluminum oxide layers are selected as the first passivation layer 410 and the second passivation layer 420, which can effectively passivate defects in the substrate 110, the first conductive layer 310 and the second conductive layer 320.

[0061] It is understandable that the oxygen in the alumina layer can combine with the dangling bonds of the polycrystalline silicon in the first conductive layer 310 and the second conductive layer 320 during the deposition process to form Si-O-Al bonds or Si-O-Si bonds, thereby passivating the dangling bonds and reducing carrier recombination. In addition, the alumina layer contains a large number of negative fixed charges, and the alumina layer can also improve the carrier migration efficiency through field effect passivation, thereby effectively improving the various photoelectric performance and efficiency of the back contact solar cell 100.

[0062] In practice, the precursor for the alumina layer can be trimethylaluminum, and the oxygen source can be water vapor. The alumina layer is deposited using the atomic layer deposition (ALD) process. The alumina layer prepared by the ALD process has a uniform thickness and a low defect density.

[0063] In some embodiments, the thickness of the first passivation layer 410 is greater than or equal to 2 nm, and / or the thickness of the second passivation layer 420 is greater than or equal to 3.5 nm.

[0064] Understandably, if the aluminum oxide layer is too thin, it will reduce the passivation effect and affect the efficiency of the back contact solar cell 100.

[0065] In this embodiment, the thickness of the first passivation layer 410 on the surface of the first conductive layer 310 is greater than or equal to 2 nm, and the thickness of the second passivation layer 420 is greater than or equal to 3.5 nm, which can provide good chemical passivation and field effect passivation effects. Furthermore, the thickness of the first passivation layer 410 is appropriately reduced compared to the second passivation layer 420, which can effectively reduce the occurrence of film bursting phenomenon in the back contact solar cell 100.

[0066] In some embodiments, the first passivation layer 410 and the second passivation layer 420 can be prepared by stepwise deposition.

[0067] In this embodiment, the second passivation layer 420 can be prepared by a double-sided ALD deposition process to simultaneously complete the passivation layer preparation of the entire front side and the area where the second conductive layer 320 is located on the back side of the substrate 110.

[0068] Then, the first passivation layer 410 is prepared by a single-sided ALD deposition process to complete the passivation layer preparation in the area where the first conductive layer 310 is located on the back side.

[0069] In practice, between the fabrication processes of the second passivation layer 420 and the first passivation layer 410, the second passivation layer 420 in the region where the first conductive layer 310 is located can be selectively removed by spin-coating photoresist and ultraviolet exposure technology.

[0070] Among them, spin-coating photoresist technology can uniformly coat liquid photoresist on the back side of the back contact solar cell 100 by high-speed rotation. The centrifugal force generated during rotation can cause the colloid to diffuse and form a uniform film, and the thickness is controlled by the rotation speed and the viscosity of the colloid.

[0071] Ultraviolet (UV) exposure technology uses UV light to irradiate specific areas of photoresist through a mask, causing the photoresist in that area to change from insoluble to soluble. After being dissolved in the solution, the specific area is exposed, while the other unexposed areas still have the photoresist mask.

[0072] In this embodiment, after spin-coating photoresist on the back side of the back contact solar cell 100, the second passivation layer 420 in the area where the first conductive layer 310 is located is exposed by ultraviolet exposure. The second passivation layer 420 in the area where the second conductive layer 310 is located is covered by a photoresist mask. After etching, the second passivation layer 420 in the area where the first conductive layer 310 is located can be selectively removed.

[0073] In practice, after the first passivation layer 410 is deposited on the entire back side using single-sided ALD deposition, the first passivation layer 410 in the area where the second conductive layer 320 is located can be selectively removed by spin-coating photoresist and ultraviolet exposure techniques to obtain the desired result. Figure 1 and Figure 2 As shown, the area where the second conductive layer 320 is located is provided with a second passivation layer 420, and the area where the first conductive layer 310 is located is provided with a first passivation layer 410.

[0074] In some embodiments, an isolation region is provided between the first region and the second region, and the first passivation layer 410 and / or the second passivation layer 420 cover the isolation region.

[0075] In this embodiment, the isolation region can achieve electrical isolation between the first conductive layer 310 and the second conductive layer 320, also known as the gap region.

[0076] It is understandable that when selectively removing the first passivation layer 410 and the second passivation layer 420 by spin-coating photoresist and ultraviolet exposure, such as Figure 1 and Figure 2 As shown, the first passivation layer 410 or the second passivation layer 420 in the isolation area can be retained, or both the first passivation layer 410 and the second passivation layer 420 can be retained simultaneously, so that the first passivation layer 410 and / or the second passivation layer 420 cover the isolation area, thereby providing a better back-side passivation effect.

[0077] In some embodiments, a first passivation layer 410 can be prepared first by a single-sided ALD deposition process to complete the passivation layer preparation in the area where the first conductive layer 310 is located on the back side, and then a second passivation layer 420 can be prepared by a double-sided ALD deposition process to simultaneously complete the passivation layer preparation in the entire front side of the substrate 110 and the area where the second conductive layer 320 is located on the back side.

[0078] In some embodiments, such as Figure 1 As shown, the back contact solar cell 100 also includes an antireflection layer 510, which simultaneously covers the first passivation layer 410 and the second passivation layer 420.

[0079] In this embodiment, the antireflection layer 510 can be deposited on the surface of the first passivation layer 410 and the second passivation layer 420 in a full-surface deposition manner to achieve full back-side passivation of the back contact solar cell 100.

[0080] In some embodiments, the antireflection layer 510 is a single-layer film or a multilayer film comprising one or more of silicon nitride, silicon oxynitride, and silicon oxide.

[0081] In this embodiment, the silicon nitride layer can be prepared by a plasma-enhanced chemical vapor deposition (PECVD) process.

[0082] Understandably, if the silicon nitride layer is too thick, it will lead to increased light absorption loss, reducing the short-circuit current and overall photoelectric conversion efficiency of the back contact solar cell 100. If the thickness is too small, it will not provide sufficient surface passivation effect, and the anti-reflection performance will also be weakened.

[0083] In this embodiment, the antireflection layer 510 has a thickness of 70-80 nm, which can simultaneously possess good optical performance and passivation effect.

[0084] In this embodiment, the antireflection layer 510 may also be a silicon oxynitride layer, or a combination of silicon nitride layers and silicon oxynitride layers in different numbers and orders.

[0085] In this embodiment, the silicon nitride layer and the silicon oxynitride layer can passivate defects on the back side of the back contact solar cell 100 and can also serve as optical layers on the back side, providing anti-reflection or anti-reflection effects. In addition, the silicon nitride layer and the silicon oxynitride layer are more stable and can play a protective role for the internal film layers, thereby improving the stability of the back contact solar cell 100 in use.

[0086] It is understood that the specific structure and parameters of the antireflection layer 510 can be set according to actual needs, and this embodiment does not limit them here.

[0087] In some embodiments, such as Figure 2 As shown, the back contact solar cell 100 also includes an oxide layer 520, which is disposed between the first passivation layer 410 and the antireflection layer 510, and / or, the oxide layer 520 is disposed between the second passivation layer 420 and the antireflection layer 510.

[0088] In this embodiment, the oxide layer 520 can alleviate the interfacial stress between the first passivation layer 410 and the antireflection layer 510, and between the second passivation layer 420 and the antireflection layer 510, and further release hydrogen in the conductive layer and the passivation layer, thereby improving the bursting film.

[0089] In actual implementation, the oxide layer 520 can be deposited on the surface of the first passivation layer 410 and the second passivation layer 420 in a whole-surface deposition manner. That is, a connected whole oxide layer 520 is provided between the first passivation layer 410 and the anti-reflection layer 510, between the second passivation layer 420 and the anti-reflection layer 510, and between the gap area and the anti-reflection layer 510, which can better alleviate interface stress and the phenomenon of film bursting.

[0090] In some embodiments, the oxide layer 520 comprises silicon oxide.

[0091] In practice, the silicon oxide layer can be prepared using the PECVD process.

[0092] In this embodiment, a silicon oxide layer is selected as the oxide layer 520. The preparation process of the oxide layer 520 can be integrated into the preparation process of the antireflection layer 510. That is, an oxide layer 520 is prepared first, and then the antireflection layer 510 is deposited on the surface of the oxide layer 520, thereby simplifying the preparation process and improving the production efficiency of the back contact solar cell 100.

[0093] In some embodiments, the thickness of the oxide layer 520 is 0.5-3 nm.

[0094] It is understandable that the conductivity of the silicon oxide layer is relatively weak. If the thickness of the silicon oxide layer is too large, it will affect the carrier collection efficiency on the back side of the back contact solar cell 100. If the thickness of the silicon oxide layer is too small, it will not be able to relieve stress and prevent the film from bursting.

[0095] In this embodiment, the thickness of the silicon oxide layer is 0.5-3nm, which allows charge carriers to tunnel through the silicon oxide layer and effectively alleviates the interface stress between the first passivation layer 410 and the anti-reflection layer 510 and between the second passivation layer 420 and the anti-reflection layer 510.

[0096] In some embodiments, the material of the first dielectric layer 210 includes one or more of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the material of the second dielectric layer 220 includes one or more of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the first conductive layer 310 is a doped polycrystalline silicon layer; and / or, the second conductive layer 320 is a doped polycrystalline silicon layer.

[0097] In this embodiment, the first dielectric layer 210 and the second dielectric layer 220 may include one or more of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride. The first conductive layer 310 and the second conductive layer 320 may be polycrystalline silicon layers with different doping polarities, thereby enabling the first dielectric layer 210 and the first conductive layer 310 to achieve a good passivation effect on the substrate 110 in the first region, and the second dielectric layer 220 and the second conductive layer 320 to achieve a good passivation effect on the substrate 110 in the second region.

[0098] In some embodiments, the thickness of the first dielectric layer 210 is 0.5 nm to 3 nm; and / or, the thickness of the second dielectric layer 220 is 0.5 nm to 3 nm; and / or, the thickness of the first conductive layer 310 is 30 nm to 300 nm; and / or, the thickness of the second conductive layer 320 is 30 nm to 300 nm.

[0099] It is understandable that the thicknesses of the first dielectric layer 210, the second dielectric layer 220, the first conductive layer 310, and the second conductive layer 320 are within a suitable range.

[0100] In this embodiment, the thickness of the first dielectric layer 210 is 0.5nm~3nm, the thickness of the second dielectric layer 220 is 0.5nm~3nm, the thickness of the first conductive layer 310 is 30nm~300nm, and the thickness of the second conductive layer 320 is 30nm~300nm, which can improve the passivation effect on the substrate 110, thereby improving the efficiency of the back contact solar cell 100.

[0101] The complete fabrication process of the back-contact solar cell 100 is described below through some specific examples.

[0102] Example 1: Using an N-type silicon wafer with dimensions of 182mm*182mm-mm*mm as the substrate 110, after polishing, a first dielectric layer 210 and a first conductive layer 310 (P-poly) are deposited on the entire back side. Then, a laser is used to remove the mask on the P-poly of the N region (i.e., the area where the second conductive layer 320 is to be deposited) and the Gap region. Subsequently, the first dielectric layer 210 and P-poly of the N region are selectively removed by etching.

[0103] Then, a second dielectric layer 220 and a second conductive layer 320 (N-poly) are deposited on the back side. Similarly, the N-poly of the P region (i.e. the area where the first conductive layer 310 is deposited) and the Gap region are selectively removed using laser and etching methods, thereby obtaining staggered P / N regions and Gap regions that achieve electrical isolation between the P / N regions. The width of the P region is ≥80μm, the width of the N region is ≥120μm, and the width of the Gap region is ≥10μm.

[0104] After texturing the front side of the substrate 110, a second passivation layer 420 (AlO) is deposited on both sides of the substrate 110 using a single-insertion ALD deposition process. x The process temperature is 200℃~290℃. The pretreatment ventilation time of H2O on the 110 substrate surface is 3~10s. In each cycle, the ventilation time of trimethylaluminum (TMA) is 5~10s, the TMA purging time is 10~20s, the H2O ventilation time is 5~10s, and the H2O purging time is 10~20s. After 20~30 cycles, a full-surface AlO2 substrate with a thickness ≥3.5nm on both sides is obtained. x .

[0105] Selective removal of AlO2 over the P-region was achieved using spin-coating photoresist and ultraviolet exposure techniques. x A first passivation layer 410 (AlO) was deposited on the back side of substrate 110 by ALD deposition. x The thickness of the first passivation layer 410 is ≥2nm, and the first passivation layer 410 above the N region is selectively removed by spin-coating photoresist and ultraviolet exposure technology, thereby obtaining AlO with different thicknesses on the back N region and P region. x AlO in the Gap region x The thickness is the sum of the thicknesses of the two depositions.

[0106] Annealing and preparation of front-side SiN using PECVD x Annealing was performed at 500℃~550℃ for 10min~30min to further release H, resulting in the deposition of SiN with a thickness of 70 nm~90 nm. x .

[0107] The antireflection layer 510 (SiN) on the back side was prepared by PECVD. x The antireflective layer 510 has a thickness of 70-80 nm. Finally, conductive electrodes are printed onto the corresponding positions on the back side to complete the process. Figure 1 Fabrication of the back-contact solar cell 100 shown.

[0108] Example 2: Using an N-type silicon wafer with dimensions of 182mm*182mm-mm*mm as the substrate 110, after polishing, a first dielectric layer 210 and a first conductive layer 310 (P-poly) are deposited on the entire back side. Then, a laser is used to remove the mask on the P-poly of the N region (i.e., the area where the second conductive layer 320 is to be deposited) and the Gap region. Subsequently, the first dielectric layer 210 and P-poly of the N region are selectively removed by etching.

[0109] Then, a second dielectric layer 220 and a second conductive layer 320 (N-poly) are deposited on the back side. Similarly, the N-poly of the P region (i.e. the area where the first conductive layer 310 is deposited) and the Gap region are selectively removed using laser and etching methods, thereby obtaining staggered P / N regions and Gap regions that achieve electrical isolation between the P / N regions. The width of the P region is ≥80μm, the width of the N region is ≥120μm, and the width of the Gap region is ≥10μm.

[0110] After texturing the front side of the substrate 110, a second passivation layer 420 (AlO) is deposited on both sides of the substrate 110 using a single-insertion ALD deposition process. x The process temperature is 200℃~290℃. The pretreatment time of H2O on the substrate 110 surface is 3~10s. The gasification time of trimethylaluminum (TMA) in each cycle is 5~10s, and the TMA purging time is 10~20s. The H2O gasification time is 5~10s, and the H2O purging time is 10~20s. After 20~30 cycles, a full-surface AlO2 with a thickness ≥3.5nm on both the front and back sides is obtained. x .

[0111] Selective removal of AlO2 over the P-region was achieved using spin-coating photoresist and ultraviolet exposure techniques. x A first passivation layer 410 (AlO) was deposited on the back side of substrate 110 by ALD deposition. x The thickness of the first passivation layer 410 is ≥2nm, and the first passivation layer 410 above the N region is selectively removed by spin-coating photoresist and ultraviolet exposure technology, thereby obtaining AlO with different thicknesses on the back N region and P region. x AlO in the Gap region x The thickness is the sum of the thicknesses of the two depositions.

[0112] Annealing and preparation of front-side SiN using PECVD x Annealing was performed at 500℃~550℃ for 10min~30min to further release H, resulting in the deposition of SiN with a thickness of 70nm~90nm. x .

[0113] The 520 (ultrathin SiO2) oxide layer on the back side was prepared by PECVD. xTo prepare ultrathin SiO₂ sheets with a thickness of 0.5 nm to 3 nm, nitrous oxide and silane were introduced at a temperature of 500℃ to 550℃ for 5 to 15 seconds. x To alleviate interfacial stress between film layers, further release H, and improve film bursting, an antireflection layer 510 (SiN) on the back side was prepared by PECVD. x The antireflective layer 510 has a thickness of 70-80 nm. Finally, conductive electrodes are printed onto the corresponding positions on the back side to complete the process. Figure 2 Fabrication of the back-contact solar cell 100 shown.

[0114] This application also provides a photovoltaic module, which includes the back-contact solar cell 100 as described above.

[0115] According to the photovoltaic module provided in the embodiments of this application, the area where the first conductive layer 310 is located in the back contact solar cell 100 of the photovoltaic module is more prone to film explosion. By appropriately reducing the thickness of the first passivation layer 410 deposited on the surface of the first conductive layer 310 without affecting the thickness of the second passivation layer 420 deposited on the surface of the second conductive layer 320, the probability of film explosion in the back contact solar cell 100 can be reduced while achieving a good passivation effect, thereby improving the yield and efficiency of the back contact solar cell 100.

[0116] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0117] In the description of this application, it should be understood that the terms "width", "thickness", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0118] In the description of this application, "first feature" and "second feature" may include one or more of the features.

[0119] In the description of this application, "multiple" means two or more.

[0120] In the description of this application, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features being in contact through another feature between them.

[0121] In the description of this application, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature.

[0122] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," 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 this application. In this specification, the 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.

[0123] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A back-contact solar cell, characterized in that, include: A substrate, the back side of which has a plurality of alternating first and second regions; A first dielectric layer is disposed in the first region; A first conductive layer is disposed on the surface of the first dielectric layer away from the substrate, and the first conductive layer and the substrate are doped with dopants of different conductivity types. A second dielectric layer is disposed in the second region; A second conductive layer is disposed on the surface of the second dielectric layer away from the substrate, and the second conductive layer has doping elements of the same conductivity type as the substrate; A first passivation layer is disposed on the side of the first conductive layer away from the substrate. A second passivation layer is disposed on the side of the second conductive layer away from the substrate; The thickness of the first passivation layer is less than the thickness of the second passivation layer.

2. The back-contact solar cell according to claim 1, characterized in that, The absolute value of the thickness difference between the first passivation layer and the second passivation layer is greater than or equal to 0.5 nm.

3. The back-contact solar cell according to claim 1 or 2, characterized in that, The first passivation layer and / or the second passivation layer comprise aluminum oxide.

4. The back-contact solar cell according to claim 3, characterized in that, The thickness of the first passivation layer is greater than or equal to 2 nm, and / or the thickness of the second passivation layer is greater than or equal to 3.5 nm.

5. The back-contact solar cell according to claim 1, characterized in that, An isolation region exists between the first region and the second region, and the first passivation layer and / or the second passivation layer cover the isolation region.

6. The back-contact solar cell according to claim 1 or 5, characterized in that, Also includes: An anti-reflection layer that simultaneously covers both the first passivation layer and the second passivation layer.

7. The back-contact solar cell according to claim 6, characterized in that, The antireflection layer is a single-layer film or a multilayer film of silicon nitride, silicon oxynitride, or silicon oxide.

8. The back-contact solar cell according to claim 6, characterized in that, Also includes: An oxide layer is disposed between the first passivation layer and the antireflection layer, and / or the oxide layer is disposed between the second passivation layer and the antireflection layer.

9. The back-contact solar cell according to claim 8, characterized in that, The oxide layer comprises silicon oxide.

10. The back-contact solar cell according to claim 8, characterized in that, The thickness of the oxide layer is 0.5nm-3nm.

11. The back-contact solar cell according to claim 1, characterized in that, The material of the first dielectric layer includes one of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the material of the second dielectric layer includes one of silicon oxide, silicon carbide, silicon nitride, and silicon oxynitride; and / or, the first conductive layer is a doped polycrystalline silicon layer; and / or, the second conductive layer is a doped polycrystalline silicon layer.

12. The back-contact solar cell according to claim 11, characterized in that, The thickness of the first dielectric layer is 0.5 nm to 3 nm; and / or the thickness of the second dielectric layer is 0.5 nm to 3 nm; and / or the thickness of the first conductive layer is 30 nm to 300 nm; and / or the thickness of the second conductive layer is 30 nm to 300 nm.

13. A photovoltaic module, characterized in that, include: The back-contact solar cell as described in any one of claims 1-12.

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