Back contact solar cell, preparation method thereof and photovoltaic module

Abstract

The embodiment of the invention provides a back contact solar cell, a preparation method thereof and a photovoltaic module. The back contact solar cell comprises a substrate, the backlight surface of which comprises a first area and a second area which are distributed in an interdigital manner; the first tunneling oxide layer and the first phosphorus-doped silicon layer are sequentially stacked on the first region; the second tunneling oxide layer, the boron-doped silicon layer, the third tunneling oxide layer and the second phosphorus-doped silicon layer are sequentially arranged on the second area in a stacked mode, and the third tunneling oxide layer is located in at least part of the area, away from one side face of the substrate, of the boron-doped silicon layer. The back contact solar cell provided by the embodiment of the invention has relatively high open-circuit voltage and fill factor, so that the cell has relatively high photoelectric conversion efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a back-contact solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] With the rapid development of photovoltaic technology, the conversion efficiency of crystalline silicon solar cells has increased year by year. Among them, back contact solar cells (TBC cells) stand out with many advantages such as high conversion efficiency and high compatibility with TOPCon (tunnel passivated solar cell) cell production lines. Many manufacturers in the industry have begun to increase their investment in the research and development and production of TBC cells.

[0003] At present, the preparation process of TBC cells is as follows: alkali polishing substrate, first deposition of tunnel oxide layer and amorphous silicon layer on the back, boron diffusion doping to form mask borosilicate glass (BSG layer), first grooving and cleaning, second deposition of tunnel oxide layer and amorphous silicon layer on the back, phosphorus diffusion doping to form mask phosphorus silicon glass (PSG layer), second grooving, cleaning and double-sided texturing, post-acidification, back deposition of AlO b SiN is deposited on the back and front sides of the x Anti-reflection film, screen printing, sintering and testing and sorting. However, the TBC cells prepared by the current process still have many problems, such as low yield and photoelectric conversion efficiency.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0005] The embodiments of the present application provide a back-contact solar cell and a method for preparing the same, and a photovoltaic module to solve or alleviate one or more of the technical problems raised above.

[0006] According to a first aspect of an embodiment of the present application, a back-contact solar cell is proposed, comprising: a substrate, wherein the backlight surface of the substrate comprises a first region and a second region distributed in a finger-like manner; a first tunneling oxide layer and a first phosphorus-doped silicon layer stacked in sequence on the first region; a second tunneling oxide layer, a boron-doped silicon layer, a third tunneling oxide layer, and a second phosphorus-doped silicon layer stacked in sequence on the second region, and the third tunneling oxide layer is located in at least a portion of the boron-doped silicon layer away from a side of the substrate.

[0007] The back-contact solar cell of the embodiment of the present application has a higher open circuit voltage and fill factor, which can improve the photoelectric conversion efficiency of the cell. This is because a boron-doped silicon layer and a second phosphorus-doped silicon layer are stacked on the second region of the substrate of the solar cell of the embodiment of the present application, so that the concentration of dopants located in the second region of the substrate is improved, which is conducive to the subsequent formation of the metal electrode. The first phosphorus-doped silicon layer and the boron-doped silicon layer form a better contact with the metal paste respectively. This excellent contact effect is conducive to improving the back-contact solar cell with a higher open circuit voltage and fill factor, which can improve the photoelectric conversion efficiency of the cell. In addition, the first phosphorus-doped silicon layer and the boron-doped silicon layer form a better contact with the metal paste respectively, which is also conducive to the development of a paste with wider adaptability and lower cost, that is, it is suitable for more types of metal pastes; and for the same metal paste, it can also have a wider range of metal electrode sintering peak temperatures.

[0008] According to an embodiment of the present application, in the extension direction of the back contact solar cell, the length of the boron-doped silicon layer is M 1 , the length of the third tunnel oxide layer is M 2 , the length of the second phosphorus-doped silicon layer is M 3 , and 5≤M 1 / M 3 ≤15,0.8≤M 3 / M 2 ≤1.

[0009] According to an embodiment of the present application, the back-contact solar cell further includes a first electrode and a second electrode, wherein the first electrode contacts the first phosphorus-doped silicon layer, and the second electrode contacts the boron-doped silicon layer.

[0010] According to an embodiment of the present application, in the extension direction of the back contact solar cell, the length of the second electrode is M 4 , and 1.2≤M 3 / M 4 ≤2.5.

[0011] According to an embodiment of the present application, the back-contact solar cell further includes a first anti-reflection layer, a second anti-reflection layer, a first passivation layer and a second passivation layer, and the first passivation layer is provided on a side of the first phosphorus-doped silicon layer and the second phosphorus-doped silicon layer away from the substrate; the first anti-reflection layer is located on a side of the first passivation layer away from the substrate; the second passivation layer is located on the light-receiving surface of the substrate, and the second anti-reflection layer is located on a side of the second passivation layer away from the substrate.

[0012] A second aspect of an embodiment of the present application provides a method for preparing a back-contact solar cell of the first aspect, the method comprising: sequentially forming a first tunneling oxide layer and a phosphorus-doped silicon layer on the backlight surface of a cell piece, the cell piece comprising a substrate and a second tunneling oxide layer and a boron-doped silicon layer sequentially stacked in a second area on the backlight surface of the substrate; performing a first removal treatment on a product obtained after forming the phosphorus-doped silicon layer according to a first predetermined pattern to insulate the phosphorus-doped silicon layer and the boron-doped silicon layer, and retaining the first tunneling oxide layer and the phosphorus-doped silicon layer on at least a portion of the area on a side of the boron-doped silicon layer away from the substrate.

[0013] The method of the embodiment of the present application can obtain a new battery structure (the structure described in the first aspect) through the graphical adjustment of the first predetermined pattern. The back-contact solar cell of this structure not only optimizes the contact between the boron-doped layer and the metal electrode, but also reduces the cost of preparing the battery laser. This is because, in the process of performing the first removal treatment to insulate the phosphorus-doped silicon layer and the boron-doped silicon layer, the first tunneling oxide layer and the phosphorus-doped silicon layer on the boron-doped silicon layer are still retained, which simplifies the removal process and reduces the removal cost (if laser is used, the cost of using the laser can be reduced).

[0014] According to an embodiment of the present application, the first removal treatment method includes: using laser to perform the first removal treatment.

[0015] According to an embodiment of the present application, the wavelength of the laser is 500-600nm.

[0016] According to the embodiment of the present application, the energy density is 0.1-1 J / cm 2 .

[0017] According to an embodiment of the present application, the pulse width is 10-60ns.

[0018] According to an embodiment of the present application, the battery cell is prepared in the following manner: a second tunneling oxide layer and a boron-doped silicon layer are sequentially formed on the backlight side of the substrate; a second removal treatment is performed on the resultant after forming the boron-doped silicon layer according to a second predetermined pattern, retaining the phosphorus-doped silicon layer in the first area of ​​the backlight side of the substrate, so that the back side of the substrate except for the second area is exposed.

[0019] According to a third aspect of the embodiments of the present application, a photovoltaic module may be provided, wherein the photovoltaic module includes the back-contact solar cell according to the first aspect.

[0020] In some embodiments, the photovoltaic module includes a plurality of solar cells connected in series and / or in parallel, wherein at least one solar cell is a back-contact solar cell as described above. A plurality of solar cells in series form a cell string, and adjacent back-contact solar cells can be connected together by string welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0022] Figure 1 is a schematic structural diagram of a back-contact solar cell according to some embodiments.

[0023] Description of reference numerals: 1: substrate; 2: first tunneling oxide layer; 3: first phosphorus-doped silicon layer; 4: first passivation layer; 5: first anti-reflection layer; 6: second tunneling oxide layer; 7: boron-doped silicon layer; 8: third tunneling oxide layer; 9: second phosphorus-doped silicon layer; 10: first electrode; 11: second electrode; 12: second anti-reflection layer; 13: second passivation layer. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers and regions and their relative sizes may be exaggerated. The same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0025] It should be understood that when a layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another layer, it may be directly on, adjacent to, connected to, or coupled to the other layer, or there may be intervening layers. It should be understood that although the terms first, second, third, etc. may be used to describe various regions, layers, and / or portions, these regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one region, layer, or portion from another region, layer, or portion. Therefore, without departing from the teachings of the present application, the first region, layer, or portion discussed below may be represented as the second region, layer, or portion. When the second region, layer, or portion is discussed, it does not mean that the first region, layer, or portion necessarily exists in the present application.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0028] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0029] In a first aspect of an embodiment of the present application, a back-contact solar cell is provided. Figure 1A back-contact solar cell comprises a substrate 1, wherein the backlight surface of the substrate 1 comprises a first region and a second region distributed in a forked shape; a first tunneling oxide layer 2, a first phosphorus-doped silicon layer 3, a first passivation layer 4 and a first anti-reflection layer 5 are sequentially stacked on the first region; a second tunneling oxide layer 6, a boron-doped silicon layer 7, a third tunneling oxide layer 8, a second phosphorus-doped silicon layer 9, the first passivation layer 4 and the first anti-reflection layer 5 are sequentially stacked on the second region, and the third tunneling oxide layer 8 is located in at least a portion of the region on a side of the boron-doped silicon layer 7 away from the substrate 1.

[0030] The back-contact solar cell of the embodiment of the present application has a higher open circuit voltage and fill factor, which can improve the photoelectric conversion efficiency of the cell. This is because a boron-doped silicon layer and a second phosphorus-doped silicon layer are stacked on the second region of the substrate of the solar cell of the embodiment of the present application, so that the concentration of dopants located in the second region of the substrate is improved, which is conducive to the subsequent formation of the metal electrode. The first phosphorus-doped silicon layer and the boron-doped silicon layer form a better contact with the metal paste respectively. This excellent contact effect is conducive to improving the back-contact solar cell with a higher open circuit voltage and fill factor, which can improve the photoelectric conversion efficiency of the cell. In addition, the first phosphorus-doped silicon layer and the boron-doped silicon layer form a better contact with the metal paste respectively, which is also conducive to the development of a paste with wider adaptability and lower cost, that is, it is suitable for more types of metal pastes; and for the same metal paste, it can also have a wider range of metal electrode sintering peak temperatures.

[0031] Optionally, in the extension direction of the back contact solar cell, the length of the boron-doped silicon layer is M 1 , the length of the third tunnel oxide layer is M 2 , the length of the second phosphorus-doped silicon layer is M 3 , and 5≤M 1 / M 3 ≤15,0.8≤M 3 / M 2 ≤1.

[0032] Optionally, the length of the boron-doped silicon layer is 400-700 μm, preferably 430-500 μm.

[0033] Optionally, the length of the third tunnel oxide layer is 30-80 μm, preferably 35-75 μm.

[0034] Optionally, the length of the second phosphorus-doped silicon layer is 24-80 μm, thereby reducing the absorption of light by the second phosphorus-doped silicon layer.

[0035] Optionally, the substrate comprises a silicon wafer.

[0036] In some embodiments, the design of the second phosphorus-doped layer can effectively increase the concentration of the dopant in the second region and reduce the concentration difference between the dopant in the second region and the dopant in the first region; the second phosphorus-doped silicon layer needs to be in contact with the metal electrode to conduct current and reduce the absorption of light. The third tunneling oxide layer serves as an intermediate layer between the boron-doped silicon layer and the second phosphorus-doped silicon layer to minimize the occurrence of short circuits.

[0037] Optionally, the length of the third tunnel oxide layer should be greater than or equal to the length of the second phosphorus-doped silicon layer.

[0038] In some embodiments, reference Figure 1 The back contact solar cell further comprises a first electrode 10 and a second electrode 11. The first electrode 10 contacts the first phosphorus-doped silicon layer 3, and the second electrode 11 contacts the boron-doped silicon layer 7. In this way, the first electrode and the second electrode can gather current and conduct it outward.

[0039] In some embodiments, in the extension direction of the back contact solar cell, the length of the second electrode is M 4 , and 1.2≤M 3 / M 4 ≤2.5. Thus, the second electrode can increase the area of ​​the second phosphorus-doped silicon layer to reduce the absorption of light by the second phosphorus-doped silicon layer and improve the current collection capability of the second electrode.

[0040] Optionally, the second electrode has a length of 20-40 μm.

[0041] In some embodiments, reference Figure 1 , the back contact solar cell further comprises a first antireflection layer 5, a second antireflection layer 12, a first passivation layer 4 and a second passivation layer 13. The first phosphorus-doped silicon layer 3 and the second phosphorus-doped silicon layer 9 are both provided with the first passivation layer 4 on the side away from the substrate; the first antireflection layer 5 is located on the side of the first passivation layer 4 away from the substrate 1; the second passivation layer 13 is located on the light-receiving surface of the substrate 1, and the second antireflection layer 12 is located on the side of the second passivation layer 13 away from the substrate 1. The first antireflection layer and the second antireflection layer can effectively reduce the reflection of light and improve the transmittance. By controlling the thickness of the film, its reflectivity can be adjusted to achieve the desired antireflection effect.

[0042] Furthermore, the first anti-reflection layer and the second anti-reflection layer include SiN X SiN is prepared in this way X NH in the raw materials 4 H atoms will be decomposed during the reaction. At high temperatures, the H atoms will penetrate into the crystalline silicon and combine with the dangling bonds on the surface to passivate the substrate.

[0043] In some embodiments, an insulating region is provided between the first region and the second region of the substrate in an interdigitated distribution, and a first passivation layer and a first anti-reflection layer are sequentially provided in the insulating region.

[0044] In some embodiments, the substrate is an N-type silicon wafer.

[0045] In some embodiments, the thickness of the substrate is 100-300 μm, preferably 120-220 μm.

[0046] In some embodiments, the thickness of the first tunnel oxide layer and the second tunnel oxide layer are independently 1-3 nm, so that electrons can pass through the doped silicon film layer (such as a boron doped layer or a phosphorus doped layer) from the substrate by tunneling.

[0047] In some embodiments, the thickness of the boron-doped silicon layer is 100-400 nm, so as to improve the process window of boron diffusion, reduce the absorption of light by the boron-doped silicon layer, and increase production capacity.

[0048] In some embodiments, the thickness of the first phosphorus-doped silicon layer and the second phosphorus-doped silicon layer is 100-400 nm, so that the absorption of light by the first phosphorus-doped silicon layer and the second phosphorus-doped silicon layer can be reduced while the process window of phosphorus diffusion is improved, and the production capacity can be increased.

[0049] In some embodiments, the thickness of the first passivation layer and the second passivation layer is 3-10 nm.

[0050] A second aspect of an embodiment of the present application provides a method for preparing a back-contact solar cell of the first aspect, the method comprising: sequentially forming a first tunneling oxide layer and a phosphorus-doped silicon layer on the backlight surface of a cell piece, the cell piece comprising a substrate and a second tunneling oxide layer and a boron-doped silicon layer sequentially stacked in a second area on the backlight surface of the substrate; performing a first removal treatment on a product obtained after forming the phosphorus-doped silicon layer according to a first predetermined pattern, retaining the phosphorus-doped silicon layer in the first area on the backlight surface of the substrate to insulate the phosphorus-doped silicon layer and the boron-doped silicon layer, and retaining the first tunneling oxide layer and the phosphorus-doped silicon layer on at least a portion of the area on a side of the boron-doped silicon layer away from the substrate.

[0051] The method of the embodiment of the present application can prepare a new cell structure through the graphical adjustment of the first predetermined pattern. The back-contact solar cell of this structure not only optimizes the contact of the P region, but also reduces the cost of laser. This is because, in the process of performing the first removal treatment to insulate the phosphorus-doped silicon layer and the boron-doped silicon layer, the first tunneling oxide layer and the phosphorus-doped silicon layer on the boron-doped silicon layer are still retained, which simplifies the removal process and reduces the removal cost (if laser is used, the cost of using the laser can be reduced).

[0052] In some embodiments, the first removal process includes using a laser to perform the first removal process. During the first removal process, the first tunneling oxide layer and the phosphorus-doped silicon layer on the boron-doped silicon layer are still retained, so that the first removal process can be completed without much energy during the first removal process using the laser, thereby reducing the cost during the first removal process.

[0053] Optionally, the wavelength of the laser is 500-600 nm, such as 500 nm, 550 nm, 600 nm, etc. In this way, while completing the first removal process, over-etching of the back contact solar cell is reduced.

[0054] Optionally, the energy density of the laser is 0.1-1 J / cm 2 , for example 0.1 J / cm 2 , 0.5J / cm 2 , 1J / cm 2 wait.

[0055] Optionally, the pulse width of the laser is 30-100ns, such as 30ns, 50ns, 70ns, 100ns, etc.

[0056] In some embodiments, the battery cell is prepared by: sequentially forming a second tunneling oxide layer and a boron-doped silicon layer on the backlight side of the substrate; performing a second removal treatment on the resultant after forming the boron-doped silicon layer according to a second predetermined pattern, retaining the phosphorus-doped silicon layer in the first area of ​​the backlight side of the substrate, so that the back side of the substrate except the second area is exposed.

[0057] It is understandable that the above-mentioned cell refers to an intermediate product in the process of preparing a back-contact solar cell.

[0058] In some embodiments, a method of making a back-contact solar cell comprises the following steps: (1) Under high temperature conditions, oxygen is passed through the substrate to form a second tunneling oxide layer with a thickness of 1-3 nm on the backlight side of the substrate; the oxygen flow rate is 500-1000 sccm.

[0059] (2) Using a PEVCD or LPCVD device, a first intrinsic amorphous silicon layer is formed on a side of the second tunnel oxide layer away from the substrate. The thickness of the first intrinsic amorphous silicon layer is 100-400 nm.

[0060] (3) performing boron doping treatment on the first intrinsic amorphous silicon layer and annealing to form a boron doped silicon layer. The boron source in the boron diffusion process includes BH 3 or BCl 3The diffusion temperature during the boron diffusion process is 800-1100°C. The diffusion time during the boron diffusion process is 30-200 minutes. The ambient gas source during the boron diffusion process includes N 2 and O 2 At least one of .

[0061] (4) Performing a second removal treatment on the silicon wafer after the boron-doped silicon layer is completed according to the second predetermined pattern, so that the non-second area of ​​the substrate is exposed. The second removal treatment includes first removing the borosilicate glass layer, the boron-doped silicon layer and the second tunneling oxide layer by laser, and then cleaning the silicon wafer after the second removal treatment with a potassium hydroxide aqueous solution KOH with a concentration of 5-30wt%, and controlling the temperature to 50-80°C; the time is 200-400s.

[0062] (5) Forming a first tunneling oxide layer on the backlight surface of the silicon wafer obtained in step (4) by using PEVCD.

[0063] (6) forming a second intrinsic amorphous silicon layer by chemical vapor deposition on a side of the first tunnel oxide layer away from the substrate, and performing phosphorus doping and annealing on the second intrinsic amorphous silicon layer to obtain a phosphorus doped layer. The annealing temperature is 700-950° C. The thickness of the second intrinsic amorphous silicon layer is 100-400 nm.

[0064] (7) performing a first removal treatment on the product obtained after the phosphorus-doped silicon layer is completed according to a first predetermined pattern to remove the first tunneling oxide layer, the phosphorus-doped silicon layer and the phosphosilicate glass layer, so that the phosphorus-doped silicon layer and the boron-doped silicon layer are insulated, and the first tunneling oxide layer and the phosphorus-doped silicon layer are retained on a partial area of ​​the boron-doped silicon layer away from a side surface of the substrate.

[0065] (8) The silicon wafer obtained in step (7) is subjected to a second cleaning, wherein a 5-30 wt % potassium hydroxide aqueous solution (KOH) is used to clean the silicon wafer after the second removal treatment, and the temperature is controlled at 50-80° C. and the cleaning time is 20-400 s.

[0066] (9) Texturing the front and back sides of the silicon wafer that has completed the second cleaning process.

[0067] (10) Using a plate-type ALD device, a first passivation layer is deposited on the back of the silicon wafer after the texturing, and a second passivation layer is deposited on the front. The first passivation layer and the second passivation layer each independently include AlO b The thickness of the first passivation layer and the second passivation layer are independently 3-10 nm.

[0068] (11) Using PECVD equipment, deposit a first anti-reflection layer on the back side of the silicon wafer obtained in step (10), and deposit a second anti-reflection layer on the front side, so as to obtain the solar cell. The first anti-reflection layer and the second anti-reflection layer independently include SiN x The thickness of the first anti-reflection layer and the second anti-reflection layer are independently 30-100 nm.

[0069] (12) The first electrode and the second electrode are formed by screen printing and sintering. The first electrode and the second electrode are independently made of silver.

[0070] According to a third aspect of the embodiments of the present application, a photovoltaic module may be provided, wherein the photovoltaic module includes the back-contact solar cell according to the first aspect.

[0071] In some embodiments, the photovoltaic module includes a plurality of solar cells connected in series and / or in parallel, wherein at least one solar cell is a back-contact solar cell as described above. A plurality of solar cells in series form a cell string, and adjacent back-contact solar cells can be connected together by string welding.

[0072] A fourth aspect of the embodiments of the present application provides a photovoltaic system, comprising the photovoltaic assembly of the third aspect. The photovoltaic system also has the advantages of the above photovoltaic assembly, which will not be described in detail here.

[0073] The above-mentioned photovoltaic system has a wide range of applications, not only limited to photovoltaic power stations, such as ground power stations, rooftop power stations and water power stations, but also includes various equipment and devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars and solar buildings. Of course, it is understandable that the application scenarios of photovoltaic systems are not limited to this, that is to say, photovoltaic systems can be used 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 may be an array combination of multiple photovoltaic components. For example, multiple photovoltaic components 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 and is converted into the alternating current required by the mains power grid. After that, it is connected to the mains network to realize solar power supply. Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0074] Example 1 S1: Polishing is performed on an N-type bare silicon wafer with a length and width (210×182mm).

[0075] S2: Under high temperature conditions, the substrate is oxygenated to form a second tunneling oxide layer (silicon dioxide) on the backlight side of the substrate, and the oxygen flow rate is 1000sccm. Then, LPCVD is used to deposit the first intrinsic amorphous silicon layer, wherein: the first tunneling oxide layer has a thickness of 2nm and the first intrinsic amorphous silicon layer has a thickness of 100nm.

[0076] S3: Put the product obtained in step S2 into a boron diffusion furnace for boron diffusion. The boron diffusion process is carried out in a nitrogen atmosphere, and the boron source is BH 3 , diffusion temperature is 1000° C., time is 40 min, at which time a borosilicate glass layer is also formed on the first tunneling oxide layer and the boron-doped layer.

[0077] S4: Perform a second removal treatment on the silicon wafer after the boron diffusion is completed and the boron-doped silicon layer is completed according to the second predetermined pattern, so that the non-second area of ​​the substrate is exposed, and the length of the boron-doped silicon layer in the extension direction of the back contact solar cell is 500mm. The second removal treatment includes first removing the borosilicate glass layer, the boron-doped silicon layer and the second tunneling oxide layer by laser, and then cleaning the silicon wafer after the second removal treatment with KOH of potassium hydroxide aqueous solution with a concentration of 30wt%, and controlling the temperature to 80°C; time 200s.

[0078] S5: Under high temperature conditions, the substrate is oxygenated to form a first tunneling oxide layer (silicon dioxide) with a thickness of 2 nm on the backlight side of the substrate.

[0079] S6: forming a second intrinsic amorphous silicon layer by chemical vapor deposition on a side of the first tunnel oxide layer away from the substrate, and performing phosphorus doping and annealing on the second intrinsic amorphous silicon layer to obtain a phosphorus doped layer. The annealing temperature is 800° C. The thickness of the second intrinsic amorphous silicon layer is 100 nm.

[0080] S7: Performing a first removal treatment with laser on the product after the phosphorus-doped silicon layer is completed according to a first predetermined pattern to remove the first tunneling oxide layer, the phosphorus-doped silicon layer and the phosphorus-silicate glass layer, so that the phosphorus-doped silicon layer and the boron-doped silicon layer are insulated, and the first tunneling oxide layer (third tunneling oxide layer) and the phosphorus-doped silicon layer (second phosphorus-doped silicon layer) on the partial area of ​​the boron-doped silicon layer away from one side of the substrate are retained. The wavelength of the laser is 355nm, and the energy density of the laser is 3J / cm 2 , the pulse width of the laser is 80ns. In the extension direction of the back contact solar cell, the length of the third tunnel oxide layer is 50mm, and the length of the second phosphorus-doped silicon layer is 45mm.

[0081] S8: Clean the grooved area of ​​the silicon wafer obtained in S7 and texturize both sides at the same time, wherein the concentration of KOH is 55wt%; the temperature is 80°C; the time is 180s; and then use HF with a concentration of 60wt% to remove the surface phosphosilicate glass layer; the time is 120s.

[0082] S9: The cleaned silicon wafer is placed in a plate-type ALD device, and AlO with a film thickness of 8 nm is deposited on the front and other surfaces of the wafer obtained in step S8. b .

[0083] S10: Place the product obtained after step S9 into a tubular PECVD device, and first deposit a SiN layer on the back of the silicon wafer. x Anti-reflection film, film thickness 100nm.

[0084] Then a layer of SiN is deposited on the front side of the silicon wafer. x Anti-reflection film, film thickness 80nm.

[0085] S11: Screen printing is performed on the silicon wafer obtained in step S10 to form a first electrode and a second electrode, and sintering and testing and sorting are performed to obtain a back-contact solar cell. In the extension direction of the back-contact solar cell, the length of the second electrode is 22 mm.

[0086] Example 2 A back-contact solar cell is prepared according to the method of Example 1, except that in the extension direction of the back-contact solar cell, the length of the second phosphorus-doped silicon layer is 40 μm.

[0087] Example 3 A back-contact solar cell was prepared according to the method of Example 1, except that, in the extension direction of the back-contact solar cell, the length of the second phosphorus-doped silicon layer was 50 μm.

[0088] Embodiment 4-5 A back-contact solar cell was prepared according to the method of Example 1, except that in the extension direction of the back-contact solar cell, the lengths of the second electrode were 20 μm and 40 μm respectively.

[0089] Embodiment 6-8 The back contact solar cell was prepared according to the method of Example 1, except that the laser energy was 0.7 J / cm 2 , 2J / cm 2 , 5J / cm 2 .

[0090] Comparative Example 1 A back-contact solar cell is prepared in the manner of Example 1, except that in step S7, a first removal treatment is performed on the resultant after the phosphorus-doped silicon layer is completed using a laser according to a first predetermined pattern to remove the first tunneling oxide layer, the phosphorus-doped silicon layer and the phosphosilicate glass layer, so that the phosphorus-doped silicon layer and the boron-doped silicon layer are insulated, and the first tunneling oxide layer (third tunneling oxide layer) and the phosphorus-doped silicon layer (second phosphorus-doped silicon layer) on a partial area of ​​the boron-doped silicon layer away from a side surface of the substrate are not retained.

[0091] Test Example The above-mentioned battery was subjected to the following performance tests, and the results are shown in Table 1.

[0092] Tests of photoelectric conversion efficiency, short-circuit current, open-circuit voltage, and fill factor: The specific test method is to place the battery under simulated sunlight with a light source of 100 mW / cm2 AM 1.5G at 25°C and connect it to a source meter using the four-wire method to obtain the test results.

[0093] Yield test: The yield test is to study the quality and performance of the batteries prepared in the above embodiments and comparative examples on a PL tester. 2000 sets of parallel samples are made for each embodiment and comparative example, and then their yields are sorted and counted.

[0094] Table 1

[0095] As can be seen from Table 1 above, by comparing Examples 1-8 with Comparative Example 1, it can be seen that the back-contact solar cell of the embodiment of the present application has a higher open circuit voltage and fill factor, and the photoelectric conversion efficiency of the cell is also higher. This is because a second phosphorus-doped silicon layer is also present in some areas on the boron-doped silicon layer of the back-contact solar cell of the present application, so that the concentration of the dopant located in the second area of ​​the substrate is increased, which is conducive to the subsequent formation of the metal electrode. The first phosphorus-doped silicon layer and the boron-doped silicon layer form a better contact with the metal slurry, which is conducive to the development of a slurry with wider adaptability and lower cost, that is, it is suitable for more types of metal slurries; at the same time, for the same metal slurry, it can also have a wider range of metal electrode sintering peak temperatures.

[0096] Compared with Example 1, it can be seen that the performance of the batteries of Examples 6-8 and Example 1 is slightly different, which means that when the back-contact solar cells are prepared using the method of the present application, a lower energy laser can be used for the first removal treatment to reduce the cost of the laser for preparing the battery.

[0097] It should also be noted that the "some embodiments", "other embodiments", "embodiments", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure or characteristic is described in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0098] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0099] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A back contact solar cell, characterized in that: include: A substrate, wherein a backlight surface of the substrate includes a first region and a second region distributed in an interdigitated shape; A first tunneling oxide layer and a first phosphorus-doped silicon layer are sequentially stacked on the first region; A second tunneling oxide layer, a boron-doped silicon layer, a third tunneling oxide layer, and a second phosphorus-doped silicon layer are sequentially stacked on the second region, and the third tunneling oxide layer is located in at least a portion of the boron-doped silicon layer away from a side of the substrate.

2. The back contact solar cell according to claim 1, characterized in that: In the extension direction of the back contact solar cell, the length of the boron-doped silicon layer is M1, the length of the third tunneling oxide layer is M2, the length of the second phosphorus-doped silicon layer is M3, and 5≤M1 / M3≤15, 0.8≤M3 / M2≤1.

3. The back contact solar cell according to claim 2, characterized in that: The back-contact solar cell further includes a first electrode and a second electrode, the first electrode being in contact with the first phosphorus-doped silicon layer, and the second electrode being in contact with the boron-doped silicon layer.

4. The back contact solar cell according to claim 3, characterized in that: In the extension direction of the back contact solar cell, the length of the second electrode is M4, and 1.2≤M3 / M4≤2.

5.

5. The back contact solar cell according to any one of claims 1 to 4, characterized in that: The back contact solar cell further comprises a first anti-reflection layer, a second anti-reflection layer, a first passivation layer and a second passivation layer. The first passivation layer is disposed on a side of the first phosphorus-doped silicon layer and the second phosphorus-doped silicon layer away from the substrate; The first anti-reflection layer is located on a side of the first passivation layer away from the substrate; The second passivation layer is located on the light-receiving surface of the substrate, and the second anti-reflection layer is located on a side of the second passivation layer away from the substrate.

6. A method for preparing a back contact solar cell according to any one of claims 1 to 5, characterized in that: include: A first tunneling oxide layer and a phosphorus-doped silicon layer are sequentially formed on the backlight surface of the cell, wherein the cell comprises a substrate and a second tunneling oxide layer and a boron-doped silicon layer which are sequentially stacked and arranged in a second region of the backlight surface of the substrate; A first removal treatment is performed on the product after forming the phosphorus-doped silicon layer according to a first predetermined pattern, retaining the phosphorus-doped silicon layer in the first area of ​​the backlight surface of the substrate to insulate the phosphorus-doped silicon layer and the boron-doped silicon layer, and retaining the first tunneling oxide layer and the phosphorus-doped silicon layer on at least a portion of the area of ​​the boron-doped silicon layer away from one side of the substrate.

7. The method according to claim 6, characterized in that The first removal treatment method includes: using laser to perform the first removal treatment; The wavelength of the laser is 500-600nm; Energy density is 0.1-1J / cm 2 ; The pulse width is 10-60ns.

8. The method according to claim 6 or 7, characterized in that: The battery cell is prepared by the following method: forming a second tunneling oxide layer and a boron-doped silicon layer in sequence on the backlight surface of the substrate; A second removal treatment is performed on the resultant after forming the boron-doped silicon layer according to a second predetermined pattern, so that the back surface of the substrate except the second region is exposed.

9. A photovoltaic module, characterized in that: The photovoltaic module comprises the back-contact solar cell according to any one of claims 1 to 5.

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