Back contact cell and processing method thereof, back contact laminated cell and photovoltaic module

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a back contact cell and a processing method thereof, a back contact laminated cell and a photovoltaic module, and the processing method comprises the step of texturing a substrate. And carrying out boron diffusion on the substrate to form a boron-doped layer and a borosilicate glass layer on the surface of the substrate. And performing laser etching on the first region and the second region of the substrate, and removing the boron-doped layer, the borosilicate glass layer and part of the substrate in the first region and the second region. And carrying out phosphorus expansion on the substrate, and forming a polycrystalline silicon layer and a phosphorosilicate glass layer on the surface of the substrate. And performing laser etching on the substrate to remove the phosphorosilicate glass layers in the second area and the third area. And texturing the substrate and removing the phosphorosilicate glass layer in the first region and the polycrystalline silicon layers in the second region and the third region to form a textured surface in the second region. And forming a passivation layer on the substrate. Electrode paste is printed in the first area and the third area and sintered. And sintering the back surface of the substrate. The design can improve the double-sided rate and the efficiency of the back contact battery.

Description

Technical Field

[0001] The present application relates to the field of photovoltaics, and in particular to back-contact stacked cells and processing methods thereof, back-contact stacked cells and photovoltaic modules. Background Art

[0002] With technological advancements, photovoltaic modules are becoming increasingly widely used. These modules can include back-contact cells. Compared to other solar cells, back-contact cells have both positive and negative electrodes on the back, resulting in a larger light absorption area and lower energy loss. Therefore, further optimization of back-contact cell processing techniques is needed to improve their efficiency and better meet actual usage requirements. Summary of the Invention

[0003] The embodiments of the present application provide a back-contact stacked cell and a processing method thereof, a back-contact stacked cell and a photovoltaic module, which are used to improve the efficiency of the back-contact cell.

[0004] An embodiment of the present application provides a method for processing a back-contact battery. The back side of a substrate includes a first region, a second region, and a third region, wherein the second region is located between the first region and the third region. The method for processing the back-contact battery includes: Texturing the base; performing boron diffusion on the substrate to form a boron-doped layer and a borosilicate glass layer on the surface of the substrate; Performing laser etching on the first and second regions of the substrate to remove the boron-doped layer, the borosilicate glass layer, and a portion of the substrate in the first and second regions; performing phosphorus diffusion on the substrate to form a polysilicon layer and a phosphorus silicon glass layer on the surface of the substrate; performing laser etching on the substrate to remove the phosphosilicate glass layer in the second region and the third region; Texturing the substrate and removing the phosphosilicate glass layer in the first region and the polysilicon layers in the second and third regions, thereby forming a textured surface in the second region; forming a passivation layer on the substrate; Printing electrode paste on the first area and the third area and sintering; The back side of the substrate is sintered.

[0005] In a possible embodiment, the step of performing boron diffusion on the substrate to form a boron-doped layer and a borosilicate glass layer on the surface of the substrate includes: The boron-doped layer and the borosilicate glass layer are formed by diffusion at a temperature of 800° C. to 1200° C. for 2 h to 5 h, with a junction depth of 1 μm to 2 μm, a square resistance of 100 Ω / sq to 500 Ω / sq, and a thickness of the borosilicate glass layer of 50 μm to 150 nm.

[0006] In a possible embodiment, the first area and the second area of the substrate are laser etched to remove the boron-doped layer, the borosilicate glass layer and part of the substrate in the first area and the second area, with a laser power of 5W to 40W and an etching width of 200um to 700um.

[0007] In a possible implementation, the step of performing phosphorus diffusion on the substrate to form a polysilicon layer and a phosphorus-silicate glass layer on the surface of the substrate includes: Diffusion is performed at a temperature of 700°C to 1000°C for 1h to 3h to form the polysilicon layer and the phosphosilicate glass layer in the first region and the second region. The polysilicon layer has a thickness of 100nm to 250nm and a junction depth of 100nm to 300nm. The phosphosilicate glass layer has a thickness of 50nm to 100nm.

[0008] In a possible implementation, the step of performing laser etching on the substrate to remove the phosphosilicate glass layer in the second region and the third region includes: The laser power for laser etching the third area is 5W to 20W; The laser power for laser etching the polysilicon layer is 10W to 30W, and the etching width is 250um to 700um.

[0009] In a possible embodiment, before the step of texturing the substrate and removing the phosphosilicate glass layer in the first region and the polysilicon layers in the second and third regions, and forming a textured surface in the second region, the method for processing the back contact cell includes: Acid etching is performed on the substrate to remove the boron-doped layer, the borosilicate glass layer, the polysilicon layer and the phosphosilicate glass layer on the front side of the substrate.

[0010] In one possible implementation, before performing phosphorus diffusion on the substrate to form a polysilicon layer and a phosphorus-silicate glass layer on the surface of the substrate, the processing method includes: The damage caused by laser etching is removed by alkaline etching, with a reaction time of 100s to 300s and an etching depth of 1um to 5um.

[0011] In one possible implementation, the step of sintering the back side of the substrate includes: The third region of the substrate is laser-processed by using a laser with a power of 5W to 50W.

[0012] A second aspect of the present application provides a back-contact battery, which is processed by any of the above-described back-contact battery processing methods.

[0013] In one possible embodiment, the back-contact battery includes a front surface and a back surface along the thickness direction. In a direction away from the substrate, the front surface includes a passivation layer, and the back surface includes a first region, a second region, and a third region. The second region is located between the first region and the third region. The first region and the third region are respectively provided with electrodes. The first region is provided with a polysilicon layer and a passivation layer in sequence in a direction away from the interior of the substrate; The second region is provided with a passivation layer; The third region is provided with a boron doping layer and a passivation layer in sequence in a direction away from the interior of the substrate; The junction depth of the first region is 100 nm to 300 nm, the junction depth of the third region is 1 micron to 2 microns, and the square resistance is 100 Ω / sq to 500 Ω / sq; The second region and the third region have a velvet surface, and the front surface of the battery has a velvet surface.

[0014] A third aspect of the present application is a back-contact stack cell, which includes a top cell and a bottom cell electrically connected to each other, wherein the top cell is a perovskite cell, and the bottom cell is a back-contact cell, wherein the back-contact cell is any one of the back-contact cells described above.

[0015] An embodiment of the present application further provides a photovoltaic module, which includes at least one cell string, and the cell string includes any one of the back-contact cells or the back-contact laminated cells described above.

[0016] The embodiments of the present application provide a back-contact cell and a processing method thereof, a back-contact stacked cell and a photovoltaic module. The processing method includes texturing a substrate. Boron-diffusion is performed on the substrate to form a boron-doped layer and a borosilicate glass layer on the surface of the substrate. Laser etching is performed on the first and second regions of the substrate to remove the boron-doped layer, the borosilicate glass layer and part of the substrate in the first and second regions. Phosphorus-diffusion is performed on the substrate to form a polysilicon layer and a phosphosilicate glass layer on the surface of the substrate. Laser etching is performed on the substrate to remove the phosphosilicate glass layer in the second and third regions. Texturing is performed on the substrate and the phosphosilicate glass layer in the first region and the polysilicon layer in the second and third regions are removed to form a velvet surface in the second region. A passivation layer is formed on the substrate. Electrode slurry is printed on the first and third regions and sintered. The back side of the substrate is sintered. Such a design can improve the bifaciality and efficiency of the back-contact cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flowchart of a method for processing a back-contact battery provided in an embodiment of the present application; Figure 2A schematic diagram of a textured substrate provided in an embodiment of the present application; Figure 3 A schematic diagram of a boron-diffused substrate provided in an embodiment of the present application; Figure 4 A schematic diagram of a laser-etched substrate provided in an embodiment of the present application; Figure 5 A schematic diagram of a phosphorus-expanded substrate provided in an embodiment of the present application; Figure 6 A schematic diagram of a substrate after a second laser etching according to an embodiment of the present application; Figure 7 A schematic diagram of an acid-etched substrate provided in an embodiment of the present application; Figure 8 A schematic diagram of a substrate that has undergone a second texturing process provided in an embodiment of the present application; Figure 9 A schematic diagram of a passivated substrate provided in an embodiment of the present application; Figure 10 A schematic diagram of a substrate after electrodes are provided according to an embodiment of the present application; Figure 11 A schematic diagram of a back-contact stacked battery provided in an embodiment of the present application; Figure 12 A schematic structural diagram of a back-contact stacked battery provided in an embodiment of the present application.

[0018] Reference numerals 1-base; 2-boron doped layer; 3- borosilicate glass layer; 4-polysilicon layer; 5-phosphosilicate glass layer; 6-passivation layer; 61-silicon nitride layer; 62-aluminum oxide layer; 7-electrode; 10-First area; 20-Second area; 30-third area; 40-back contact stacked cell; 401-Protection layer; 402-transparent conductive layer; 403 electron transport layer; 404-perovskite layer; 405-hole transport layer; 406-composite layer; 407-back contact battery; 408-Perovskite battery. DETAILED DESCRIPTION

[0019] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0020] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0021] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0022] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0023] like Figure 1 As shown, an embodiment of the present application provides a processing method for a back-contact battery 407, which is used to process the back-contact battery 407. The substrate 1 is generally a silicon substrate, and along the thickness direction of the substrate 1, the substrate 1 includes a front side and a back side. After processing, the back side of the back-contact battery 407 generally includes a phosphorus expansion area, a boron expansion area and an isolation area, and the isolation area is located between the phosphorus expansion area and the boron expansion area. During processing, the area on the back side of the substrate 1 can be divided in advance, and the back side of the substrate 1 includes a first area 10, a second area 20 and a third area 30. The second area 20 is located between the first area 10 and the third area 30. The first area 10 can correspond to the phosphorus expansion area, the second area 20 can correspond to the isolation area, and the third area 30 can correspond to the boron expansion area. The processing method includes: S1. Texturing the substrate 1.

[0024] S2. Boron diffusion is performed on the substrate 1 to form a boron-doped layer 2 and a borosilicate glass layer 3 on the surface of the substrate 1.

[0025] S3 , performing laser etching on the first region 10 and the second region 20 of the substrate 1 to remove the boron-doped layer 2 , the borosilicate glass layer 3 and a portion of the substrate 1 in the first region 10 and the second region 20 .

[0026] S4 , performing phosphorus diffusion on the substrate 1 to form a polysilicon layer 4 and a phosphorus silicon glass layer 5 on the surface of the substrate 1 .

[0027] S5 , performing laser etching on the substrate 1 to remove the phosphosilicate glass layer 5 in the second region 20 and the third region 30 .

[0028] S6 , texturing the substrate 1 and removing the phosphosilicate glass layer 5 in the first region 10 and the polysilicon layer 4 in the second region 20 and the third region 30 , thereby forming a textured surface in the second region 20 .

[0029] S7 . Form a passivation layer 6 on the substrate 1 .

[0030] S8 , printing the electrode 7 paste in the first area 10 and the third area 30 and sintering.

[0031] S9, sintering the back side of the substrate 1.

[0032] The back contact cell 407 processed by the processing method provided in the embodiment of the present application can form a velvet surface on both the front and back sides of the back contact cell 407. During the processing, the velvet surface located in the third region 30 is retained, that is, the boron expansion area located on the back side of the back contact cell 407 has a velvet structure. The velvet structure forms an uneven structure on the surface of the back contact cell 407, thereby increasing the number of reflections of light on the surface of the back contact cell 407, which is beneficial to extend the transmission path of light in the back contact cell 407 and increase the light receiving area of the back contact cell 407. Such a design can reduce the loss of light and improve the utilization rate of light, thereby improving the overall efficiency of the back contact cell 407. At the same time, the bifaciality of the back contact cell 407 is one of the important indicators for evaluating the back contact cell 407. The bifaciality of the back contact cell 407 refers to the ratio of the power generation capacity of the front and back sides of the back contact. In the related art, the bifaciality of the back contact cell 407 is usually less than 80%. By using the processing method provided in the embodiments of the present application to process the back-contact cell 407, a first region 10 and a third region 30 with different morphologies can be formed on the back side of the back-contact cell 407. Because the third region 30 has a suede surface, the back side of the back-contact cell 407 utilizes more light, thereby improving the power generation capacity of the back side of the back-contact cell 407. Testing has shown that the bifaciality of the back-contact cell 407 processed using the processing method provided in the embodiments of the present application can exceed 90%, improving the overall efficiency of the back-contact cell 407 and better meeting actual usage requirements.

[0033] Meanwhile, in related art, the boron extension region on the back side of the back-contact cell 407 is typically made of boron-doped polycrystalline silicon (poly-Si), which is subject to parasitic absorption. Parasitic absorption refers to non-ideal light absorption processes, in addition to the effective absorption that contributes to photogenerated carriers. These absorption processes not only fail to effectively generate carriers for power generation, but can also result in energy loss, reducing the efficiency of the photovoltaic cell. Specifically, while the boron extension region, formed from boron-doped polycrystalline silicon, absorbs light and converts it into photogenerated current, it also undergoes other reactions that do not generate photogenerated current. When the back-contact cell 407 absorbs the same amount of light, the more severe the parasitic absorption, the lower the efficiency of the back-contact cell 407, while the less severe the parasitic absorption, the higher the efficiency of the back-contact cell 407. The third region 30 on the back side of the back-contact cell 407, i.e., the boron extension region, obtained using the processing method provided in the embodiments of the present application, has a structure consisting, from the outside inward, of a passivation layer 6 and a boron-doped layer 2. Compared to polysilicon, the boron-doped layer 2 exhibits less parasitic absorption, thus minimizing the impact of parasitic absorption on the efficiency of the back-contact cell 407, thereby improving the overall efficiency of the back-contact cell 407. Furthermore, in related art, metal recombination is a significant phenomenon in the boron-doped regions of polysilicon, which can reduce the open-circuit voltage and photoelectric conversion efficiency of the back-contact cell 407. The back-contact cell 407 fabricated using the processing methods provided in the embodiments of the present application is less susceptible to metal recombination, thereby improving the efficiency and open-circuit voltage of the back-contact cell 407.

[0034] like Figure 1 As shown, in one possible embodiment, before step S4, the processing method of the back contact battery 407 includes: S40, removing damage caused by laser etching.

[0035] The step of removing the laser-etched damage may be removing the laser-etched damage by alkali polishing, wherein the reaction time is 100s to 300s and the etching depth is 1 μm to 5 μm.

[0036] Laser debonding of substrate 1 can damage substrate 1 and destroy its structure, which can easily lead to reduced transmission and collection efficiency of photogenerated carriers, affecting the conversion efficiency of back-contact cell 407. It can also affect the aging resistance and reliability of back-contact cell 407, leading to a reduction in the overall performance of back-contact cell 407. Alkaline etching can remove the damage caused by laser etching to substrate 1, thereby reducing the impact of laser etching damage on the efficiency of back-contact cell 407. By setting the reaction time to 100s to 300s and the etching depth to 1um to 5um, the damage caused by laser etching can be fully removed, while reducing the impact of the damage removal step on substrate 1.

[0037] like Figure 1As shown, in a possible embodiment, before step S6, the processing method further includes: S60 , performing acid etching on the substrate 1 to remove the boron-doped layer 2 , the borosilicate glass layer 3 , the polysilicon layer 4 and the phosphosilicate glass layer 5 on the front surface of the substrate 1 .

[0038] In the solution provided in the embodiment of the present application, there is no diffusion on the front side of the back contact battery 407. Therefore, by acid etching the substrate 1, the boron doped layer 2, the boron doped layer 2, the borosilicate glass layer 3, the polysilicon layer 4 and the phosphorus silicon glass layer 5 on the front side of the substrate 1 can be removed, so that there is no diffusion on the front side of the processed back contact battery 407.

[0039] like Figure 1 As shown, in a possible implementation manner, the processing flow of the back contact cell 407 provided in the embodiment of the present application is as follows: The substrate 1 is textured to obtain Figure 2 The substrate 1 is shown. A velvet surface can be formed on the surface of the substrate 1 by texturing.

[0040] Boron diffusion is performed on the substrate 1. The surface of the substrate 1 is converted into a boron-doped layer 2 and a borosilicate glass layer 3 (BSG layer). The borosilicate glass layer 3 is located outside the boron-doped layer 2. The structure of the substrate 1 is as follows: Figure 3As shown. Diffusion is performed at a temperature of 800°C to 1200°C for 2 to 5 hours to form a boron-doped layer 2 and a borosilicate glass layer 3. The junction depth is 1 μm to 2 μm, the sheet resistance is 100 Ω / sq to 500 Ω / sq, and the thickness of the borosilicate glass layer 3 is 50 nm to 150 nm. The temperature can be 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, etc. The diffusion time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc. The junction depth can be 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, etc. The square resistance can be 100Ω / sq, 150Ω / sq, 200Ω / sq, 250Ω / sq, 300Ω / sq, 350Ω / sq, 400Ω / sq, 450Ω / sq, 500Ω / sq, etc. The thickness of the borosilicate glass layer 3 is 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, etc. By minimizing the junction depth and increasing the square resistance, the effect on the passivation of the back-contact battery 407 can be reduced, thereby increasing the open-circuit voltage of the back-contact battery 407, improving the short-circuit current of the back-contact battery 407, and enhancing the stability of the back-contact battery 407. This improves the overall performance of the back-contact battery 407.

[0041] Laser film opening is performed on the first region 10 and the second region 20 of the substrate 1, that is, the boron doped layer 2, the borosilicate glass layer 3 and part of the substrate 1 at the corresponding positions of the phosphorus diffusion region and the spacer region are removed by laser etching to obtain Figure 4 The structure shown. The substrate 1 is opened by laser etching to remove the boron diffusion layer and the borosilicate glass layer 3 of the first region 10 and the second region 20, so that the second region 20 can be used as an isolation region and subsequent phosphorus diffusion can be performed in the first region 10. Green light or purple light can be selected for laser etching, the laser power is 5W to 40W, and the etching width is 200um to 700um. The etching width can be 200um, 250um, 300um, 350um, 400um, 450um, 500um, 550um, 600um, 650um, 700um, etc. When the etching width is within the range of 200um to 700um, it can be beneficial to make the first region 10, the second region 20 and the third region 30 on the back of the back contact battery 407 within a reasonable width range, thereby helping to improve the efficiency and performance of the back contact battery 407.

[0042] After laser etching, the damage caused by laser etching is removed, and then the substrate 1 is phosphorus diffused at a temperature of 700℃ to 1000℃ for 1h to 3h, and a phosphorus-silicate glass layer 5 and a phosphorus-doped polysilicon layer 4 are formed on the surface of the substrate 1. The phosphorus-doped polysilicon layer 4 is located outside the phosphorus-doped polysilicon layer 4. The phosphorus-doped polysilicon layer 4 has a thickness of 100nm to 250nm, a junction depth of 100nm to 300nm, and a thickness of 50nm to 100nm. After phosphorus diffusion, the structure of the substrate 1 is as follows Figure 5 shown.

[0043] The phosphorus-expanded substrate 1 is opened again, and the second region 20 and the third region 30 are etched with green light or purple light to remove the phosphorus-silicon glass layer 5 in the second region 20 and the third region 30. When the second region 20 is laser-etched, the power of the laser is 10W to 30W, and when the third region 30 is laser-etched, the power of the laser is 5W to 20W. The etching width of the second laser opening of the substrate 1 is 250um to 700um, and the etching width can be 250um, 300um, 350um, 400um, 450um, 500um, 550um, 600um, 650um, 700um, etc. After the substrate 1 is laser-etched for the second time, the structure obtained is as follows Figure 6 Since the first area 10 is a flat area and the third area 30 is a suede area, the flat area has a higher reflectivity, so when the laser is opened, the power of the first area 10 is higher.

[0044] After the second laser etching, the substrate 1 is acid-etched to remove the phosphorus-silicon glass layer 5, polysilicon layer 4, borosilicate glass layer 3, and boron diffusion layer on the front surface of the substrate 1. Since there is no phosphorus diffusion area or boron diffusion area on the front surface of the back contact battery 407, the structure on the front surface of the substrate 1 is removed. Acid etching can be performed using a mixed solution of hydrofluoric acid and nitric acid. After acid etching, the structure of the substrate 1 is as follows: Figure 7 shown.

[0045] After acid etching, the substrate 1 is subjected to a second texturing process to form a velvet surface on the surface of the substrate 1. In addition, texturing can remove the damage caused by the second laser etching to the substrate 1, which is beneficial to reducing the impact of laser etching on the substrate 1, and is beneficial to improving the quality of the substrate 1 and the efficiency and performance of the processed back contact battery 407. The reaction time of the texturing process is 100s to 500s, and the etching depth is 1um to 5um. After texturing, the structure of the substrate 1 is as follows Figure 8As shown. Texturing can form an uneven textured surface structure on substrate 1, thereby increasing the number of light reflections, facilitating light absorption by back-contact cell 407, and improving the efficiency of back-contact cell 407. Simultaneously, during the texturing process, the phosphosilicate glass layer 5 in first region 10, the polysilicon layer 4 in second region 20, and the polysilicon layer 4 and borosilicate glass layer 3 in third region 30 are removed.

[0046] The substrate 1 after texturing is passivated to form an oxide layer on both the front and back sides of the substrate 1. After passivation, the structure of the substrate 1 is as follows: Figure 9 As shown. The passivation layer 6 may include a silicon nitride layer 61, an aluminum oxide layer 62, a silicon oxide layer, and the like. Figure 9 In the structure shown, from the outside to the inside, there is a silicon nitride layer 61 and an aluminum oxide layer 62. The passivation layer 6 can reduce the surface load, increase the open circuit voltage and short circuit current of the back contact battery 407, and enhance the stability of the back contact battery 407.

[0047] After passivation, the electrode 7 paste is printed on the first region 10 and the third region 30 and sintered to form the electrode 7. The structure of the substrate 1 is as follows Figure 10 shown.

[0048] After sintering to form the electrode 7, the back side of the substrate 1 or the third region 30 can be laser treated and then sintered again to achieve a secondary sintering of the electrode 7 in the third region 30. In this explanation, the positive and negative poles are reversed, that is, the electrode 7 in the third region 30 is supplied with a negative voltage from an external power supply, while the electrode 7 in the first region 10 is supplied with an external power supply. The voltage is 10V to 20V, and the laser treatment is performed while the power is applied. The laser treatment can use laser-assisted sintering (LECO). The laser can be red or green light, with a laser power of 5W to 50W. The entire back side of the substrate 1 is laser treated, or the third region 30 is laser treated. The laser direction is incident from the front or back side of the substrate 1. After conventional sintering, the third region 30 is laser-assisted sintered again, so that after two sinterings, the slurry in the third region 30 can have good metal contact, forming the positive electrode 7. Laser-assisted sintering of the third region 30, i.e., the boron expansion region, can help reduce the contact resistance and form a good ohmic contact between the boron expansion region and the electrode 7, thereby reducing the contact resistance, which is beneficial to reducing the energy loss during current transmission, improving the fill factor of the battery, and thus improving the photoelectric conversion efficiency of the battery.

[0049] Based on the processing methods of the back-contact battery 407 provided in the above embodiments, the embodiment of the present application further provides a back-contact battery 407 sheet, and the back-contact battery 407 sheet is processed by the above processing methods.

[0050] Along the thickness direction of the back-contact cell 407, the back-contact cell 407 includes a front side and a back side. The front side of the back-contact cell 407, as viewed away from the substrate 1, includes a passivation layer 6. The back side of the back-contact cell 407 includes a first region 10, a second region 20, and a third region 30. The second region 20 is located between the first and third regions 10, 30. The first region 10 is a phosphorus-expanded region, the third region 30 is a boron-expanded region, and the second region 20 is an isolation region. Electrodes 7 are provided in each of the first and third regions 10, 30. A polysilicon layer 4 and a passivation layer 6 are provided in the first region 10, in that order, away from the interior of the substrate 1. The second region 20 is provided with a passivation layer 6. The third region 30, in that order, away from the interior of the substrate 1, includes a boron-doped layer 2 and a passivation layer 6. The junction depth of the first region 10 is 100 nm to 300 nm. The junction depth of the third region 30 is 1 micron to 2 microns, and the sheet resistance is 100 Ω / sq to 500 Ω / sq. The second area 20 and the third area 30 both have a velvet surface, and the first area 10 is a flat surface. Meanwhile, the front side of the battery has a velvet surface.

[0051] The back contact cell 407 obtained by the processing method provided in the embodiment of the present application can form a velvet surface in the second region 20 and the third region 30, that is, the boron expansion region and the isolation region of the back contact cell 407 have a velvet surface. Such a design is beneficial for increasing the light-receiving area of the back contact cell 407 and increasing the number of light reflections, which is beneficial for improving the light absorption efficiency of the back contact cell 407. At the same time, the boron expansion region of the back contact cell 407 is a boron-doped layer 2 instead of a polysilicon layer 4, which is beneficial for reducing parasitic absorption and metal recombination of the back contact cell 407, thereby improving the efficiency and bifaciality of the back contact cell 407, which is more in line with actual usage requirements.

[0052] like Figure 11 and Figure 12As shown, an embodiment of the present application also provides a back-contact stack cell, and the back-contact stack cell 40 includes a top cell and a bottom cell electrically connected to each other. The top cell is a perovskite cell 408, and the bottom cell is a back-contact cell 407, wherein the back-contact cell 407 can be the back-contact cell 407 involved in any of the above embodiments. The back-contact stack cell 40 can be a three-terminal stack cell. When processing the back-contact stack cell 400, the top cell and the bottom cell can be connected by directly depositing the perovskite top cell on the bottom cell. Compared with single-crystal silicon solar cells, the back-contact stack cell 40 has higher efficiency and power generation. Moreover, the back-contact stack bottom cell using the back-contact cell 407 as the bottom cell has the advantages of no current mismatch, high process tolerance, and a wide range of application scenarios. At the same time, compared to the two-terminal stacked cell, the three-terminal stacked cell formed by the perovskite cell 408 and the back contact cell 407 can have an extra end electrode 7 to output the mismatch current, which is beneficial to ensure that the back contact stacked cell 40 can operate at a relatively higher power, and the required voltage matching is less affected by the change in the solar spectrum than the current. When the back contact cell 407 is used as the bottom cell, a two-terminal series structure can be constructed by contacting the electrode 7 with opposite polarity, which can realize the conversion from three ends to two ends. The back contact cell 407 has a velvet surface, and conformal deposition and growth of perovskite are carried out on the velvet surface, which can improve the utilization rate of incident light. The back contact stacked cell 40 made of the perovskite cell 408 and the back contact cell 407 does not need to consider current matching, and has a high tolerance for the band gap and thickness of the perovskite. The application scenarios of the three-terminal back contact stacked cell 40 are more extensive, and high-power operation can be achieved in different outdoor environments, which is more in line with actual usage needs.

[0053] like Figure 11 As shown in FIG. 1 , in one possible embodiment, a back-contact stacked cell 40 comprises, from top to bottom, a protective layer 401, a transparent conductive layer 402, a cell transport layer, a perovskite layer 404, a hole transport layer 405, a recombination layer 406, and a back-contact cell 407. The transparent conductive oxide (TCO) layer 402 may be an indium tin oxide layer.

[0054] The embodiments of the present application further provide a photovoltaic module, which includes at least one cell string, and the cell string includes the back-contact cell 407 or the back-contact stacked cell 40 in any of the above embodiments.

[0055] The photovoltaic module may also include structures such as a first cover plate, a second cover plate, a first adhesive film, and a second adhesive film. A plurality of back-contact cells 407 or back-contact laminated cells 40 are electrically connected to form a cell string, and a plurality of cell strings are electrically connected to form a cell array. Along the thickness direction of the photovoltaic module, the first adhesive film and the second adhesive film are located on opposite sides of the cell array. The first cover plate is located on the side of the first adhesive film away from the cell array, and the second cover plate is located on the side of the second adhesive film away from the cell array. The first cover plate and the second cover plate are located on the surface of the photovoltaic module and can protect the photovoltaic module. The first adhesive film and the second adhesive film can act as a buffer to reduce the possibility of hidden cracks in the back-contact cell 407 or the back-contact laminated cell 40 during lamination and collision, thereby helping to increase the service life of the photovoltaic module.

[0056] The embodiments of the present application provide a back-contact cell 407 and a processing method thereof, a back-contact stacked cell 40, and a photovoltaic module. The processing method includes texturing a substrate 1. Boron-diffusion is performed on the substrate 1 to form a boron-doped layer 2 and a borosilicate glass layer 3 on the surface of the substrate 1. Laser etching is performed on the first region 10 and the second region 20 of the substrate 1 to remove the boron-doped layer 2, the borosilicate glass layer 3, and a portion of the substrate 1 in the first region 10 and the second region 20. Phosphorus-diffusion is performed on the substrate 1 to form a polysilicon layer 4 and a phosphosilicate glass layer 5 on the surface of the substrate 1. Laser etching is performed on the substrate 1 to remove the phosphosilicate glass layer 5 in the second region 20 and the third region 30. The substrate 1 is texturized and the phosphosilicate glass layer 5 in the first region 10 and the polysilicon layer 4 in the second region 20 and the third region 30 are removed, forming a velvet surface in the second region 20. A passivation layer 6 is formed on the substrate 1. Electrode 7 slurry is printed on the first region 10 and the third region 30 and sintered. The back side of the back-contact cell 407 is sintered. This design can improve the bifaciality and efficiency of the back contact battery 407.

[0057] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for processing a back contact battery, characterized in that: The back side of the substrate (1) comprises a first region (10), a second region (20) and a third region (30), wherein the second region (20) is located between the first region (10) and the third region (30), and the processing method of the back contact battery (407) comprises: (1) making a velvet on the substrate; Boron diffusion is performed on the substrate (1) to form a boron-doped layer (2) and a borosilicate glass layer (3) on the surface of the substrate (1); Laser etching is performed on the first region (10) and the second region (20) of the substrate (1) to remove the boron-doped layer (2), the borosilicate glass layer (3) and a portion of the substrate (1) in the first region (10) and the second region (20); Phosphorus diffusion is performed on the substrate (1) to form a polysilicon layer (4) and a phosphorus silicon glass layer (5) on the surface of the substrate (1); Laser etching the substrate (1) to remove the phosphosilicate glass layer (5) in the second region (20) and the third region (30); The substrate (1) is textured and the phosphorus silicon glass layer (5) in the first region (10) and the polysilicon layer (4) in the second region (20) and the third region (30) are removed, thereby forming a textured surface in the second region (20); forming a passivation layer (6) on the substrate (1); Printing electrode paste in the first region (10) and the third region (30) and sintering (7); The back side of the substrate (1) is sintered.

2. The method for processing a back contact battery according to claim 1, wherein: The step of performing boron diffusion on the substrate (1) to form a boron doped layer (2) and a borosilicate glass layer (3) on the surface of the substrate (1) comprises: The boron doping layer (2) and the borosilicate glass layer (3) are formed by diffusion at a temperature of 800° C. to 1200° C. for 2 h to 5 h, with a junction depth of 1 μm to 2 μm, a square resistance of 100 Ω / sq to 500 Ω / sq, and a thickness of 50 μm to 150 nm.

3. The method for processing a back contact battery according to claim 1, wherein: Laser etching is performed on the first region (10) and the second region (20) of the substrate (1) to remove the boron-doped layer (2), the borosilicate glass layer (3) and a portion of the substrate (1) in the first region (10) and the second region (20), with a laser power of 5W to 40W and an etching width of 200um to 700um.

4. The method for processing a back contact battery according to claim 1, wherein: The step of performing phosphorus diffusion on the substrate (1) to form a polysilicon layer (4) and a phosphorus silicon glass layer (5) on the surface of the substrate (1) comprises: Diffusion is performed at a temperature of 700° C. to 1000° C. for 1 h to 3 h to form the polysilicon layer (4) and the phosphosilicate glass layer (5) in the first region (10) and the second region (20). The polysilicon layer (4) has a thickness of 100 nm to 250 nm and a junction depth of 100 nm to 300 nm, and the phosphosilicate glass layer (5) has a thickness of 50 nm to 100 nm.

5. The method for processing a back contact battery according to claim 1, wherein: The step of laser etching the substrate (1) to remove the phosphosilicate glass layer (5) in the second region (20) and the third region (30) comprises: The laser power for laser etching the third region (30) is 5W to 20W; The laser power for laser etching the polysilicon layer (4) is 10W to 30W, and the etching width is 250um to 700um.

6. The method for processing a back contact battery according to any one of claims 1 to 5, characterized in that: Before the step of texturing the substrate (1) and removing the phosphorus silicon glass layer (5) of the first region (10) and the polysilicon layer (4) of the second region (20) and the third region (30), and forming a textured surface in the second region (20), the processing method of the back contact cell (407) comprises: The substrate (1) is acid-etched to remove the boron-doped layer (2), the borosilicate glass layer (3), the polysilicon layer (4), and the phosphorus-silicon glass layer (5) on the front surface of the substrate (1).

7. The method for processing a back contact battery according to any one of claims 1 to 5, characterized in that: Before the substrate (1) is phosphorus-doped and a polysilicon layer (4) and a phosphorus-silicon glass layer (5) are formed on the surface of the substrate (1), the processing method comprises: The damage caused by laser etching is removed by alkaline etching, with a reaction time of 100s to 300s and an etching depth of 1um to 5um.

8. The method for processing a back contact battery according to any one of claims 1 to 5, characterized in that: The step of sintering the back side of the substrate (1) comprises: The third area (30) of the substrate (1) is laser-processed by using a laser with a power of 5W to 50W.

9. A back contact battery, characterized in that: The back contact cell (407) is processed by the processing method of the back contact cell (407) according to any one of claims 1 to 8.

10. The back contact battery according to claim 9, characterized in that Along the thickness direction, the back contact battery (407) includes a front surface and a back surface. Along the direction away from the substrate (1), the front surface includes a passivation layer (6), and the back surface includes a first region (10), a second region (20), and a third region (30). The second region (20) is located between the first region (10) and the third region (30). The first region (10) and the third region (30) are respectively provided with electrodes (7). The first region (10) is provided with a polysilicon layer (4) and a passivation layer (6) in sequence in a direction away from the interior of the substrate (1); The second region (20) is provided with a passivation layer (6); The third region (30) is provided with a boron doping layer (2) and a passivation layer (6) in sequence along a direction away from the interior of the substrate (1); The junction depth of the first region (10) is 100 nm to 300 nm, the junction depth of the third region (30) is 1 micron to 2 microns, and the square resistance is 100 Ω / sq to 500 Ω / sq; The second region (20) and the third region (30) have a velvet surface, and the front surface of the battery has a velvet surface.

11. A back contact stacked battery, characterized in that: The back-contact stack cell (40) comprises a top cell and a bottom cell electrically connected to each other, the top cell is a perovskite cell (408), and the bottom cell is a back-contact cell (407), wherein the back-contact cell (407) is the back-contact cell (407) according to any one of claims 9 to 10.

12. A photovoltaic module, characterized in that: The photovoltaic module comprises at least one cell string, wherein the cell string comprises the back-contact cell (407) according to any one of claims 9 to 10 or the back-contact stacked cell (40) according to claim 11.

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