Back contact cells and methods for processing the same, back contact stacked cells and photovoltaic modules

Abstract

The embodiment of the present application relates to the field of photovoltaics, and provides a back contact cell and a processing method thereof, a back contact laminated cell and a photovoltaic module, the processing method comprising texturing a substrate. Boron diffusion is carried out on the substrate to form a boron-doped layer and a borosilicate glass layer on the surface of the substrate. Laser etching is carried out on a first region and a second region of the substrate to remove the boron-doped layer, the borosilicate glass layer and part of the substrate in the first region and the second region. Phosphorus diffusion is carried out on the substrate to form a polysilicon layer and a phosphosilicate glass layer on the surface of the substrate. Laser etching is carried out on the substrate to remove the phosphosilicate glass layer in the second region and a third region. The substrate is textured, and the phosphosilicate glass layer in the first region, the polysilicon layer in the second region and the third region are removed, and a textured surface is formed in the second region. A passivation layer is formed on the substrate. Electrode paste is printed on the first region and the third region and sintered. The back surface of the substrate is sintered. Such a design can improve the bifacial rate and efficiency of the back contact cell.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to back-contact tandem solar cells and their processing methods, as well as back-contact tandem solar cells and photovoltaic modules. Background Technology

[0002] With technological advancements, photovoltaic (PV) modules are becoming increasingly widely used. PV modules can include back-contact solar cells. Compared to other solar cells, back-contact solar cells have both positive and negative electrodes on the back side, resulting in a larger light absorption area and lower energy loss. Therefore, further optimization of the back-contact solar cell manufacturing process and improvement of its efficiency are crucial to better meet practical application requirements. Summary of the Invention

[0003] This application provides a back-contact tandem battery and its processing method, as well as a back-contact tandem battery and a photovoltaic module, for improving the efficiency of back-contact batteries.

[0004] This application provides a method for processing a back contact battery. The back side of the substrate includes a first region, a second region, and a third region, with the second region located between the first region and the third region. The method for processing the back contact battery includes: Texturing the base material; The substrate is subjected to boron diffusion 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 a portion of the substrate in the first and second regions. The substrate is subjected to phosphorus diffusion to form a polycrystalline silicon layer and a phosphosilicate glass layer on the surface of the substrate; The substrate is laser-etched to remove the phosphosilicate glass layer in the second and third regions; The substrate is texturized and the phosphosilicate glass layer in the first region, the polycrystalline silicon layer in the second region and the third region are removed, and a textured surface is formed in the second region. A passivation layer is formed on the substrate; Electrode paste is printed in the first region and the third region and then sintered. The back side of the substrate is sintered.

[0005] In one possible implementation, 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℃ to 1200℃ for 2h to 5h, with a junction depth of 1um to 2um and a sheet resistance of 100Ω / sq to 500Ω / sq. The thickness of the borosilicate glass layer is 50um to 150nm.

[0006] In one possible implementation, in the step of laser etching 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, the laser power is 5W to 40W and the etching width is 200µm to 700µm.

[0007] In one possible implementation, the step of performing phosphorus diffusion on the substrate to form a polycrystalline silicon layer and a phosphorus silicate glass layer on the surface of the substrate includes: The polycrystalline silicon layer and the phosphosilicate glass layer are formed in the first region and the second region by diffusion at a temperature of 700°C to 1000°C for 1 to 3 hours. The polycrystalline silicon layer has a thickness of 100 nm to 250 nm and a junction depth of 100 nm to 300 nm. The phosphosilicate glass layer has a thickness of 50 nm to 100 nm.

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

[0009] In one possible implementation, prior to the step of texturing the substrate and removing the phosphosilicate glass layer in the first region, the polycrystalline silicon layer in the second region, and the third region, and forming a textured surface in the second region, the processing method of the back contact battery includes: The substrate is acid-etched 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 phosphorus diffusion of the substrate to form a polycrystalline silicon layer and a phosphosilicate glass layer on the surface of the substrate, the processing method includes: Damage from laser etching is removed by alkaline polishing, 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 using a laser with a power of 5W to 50W.

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

[0013] In one possible implementation, along the thickness direction, the back contact battery includes a front side and a back side, and along the direction away from the substrate, the front side includes a passivation layer, the back side includes a first region, a second region and a third region, the second region being located between the first region and the third region, and electrodes being disposed in the first region and the third region respectively; The first region is sequentially provided with a polycrystalline silicon layer and a passivation layer along 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 doped layer and a passivation layer in sequence along the direction away from the interior of the substrate; The junction depth of the first region is 100 nm to 300 nm, and the junction depth of the third region is 1 micrometer to 2 micrometers, with a sheet resistance of 100 Ω / sq to 500 Ω / sq. The second region and the third region have a textured surface, and the front side of the battery has a textured surface.

[0014] A third aspect of this application discloses a back-contact stacked battery, the back-contact stacked battery comprising a top battery and a bottom battery electrically connected to each other, the top battery being a perovskite battery and the bottom battery being a back-contact battery, wherein the back-contact battery is any of the back-contact batteries described above.

[0015] This application also provides a photovoltaic module, which includes at least one battery string, the battery string including any of the back contact batteries or the back contact stacked batteries described above.

[0016] This application provides a back-contact battery and its processing method, a back-contact tandem battery, 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 its surface. Laser etching is performed on a first and second region of the substrate to remove the boron-doped layer, the borosilicate glass layer, and a portion of the substrate in both regions. Phosphorus diffusion is performed on the substrate to form a polycrystalline silicon layer and a phosphosilicate glass layer on its surface. 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 to remove the phosphosilicate glass layer in the first region and the polycrystalline silicon layer in the second and third regions, forming a textured surface in the second region. A passivation layer is formed on the substrate. Electrode paste is printed in the first and third regions and sintered. The back side of the substrate is sintered. This design can improve the bifaciality and efficiency of the back-contact battery. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the processing method of the back contact battery provided in an embodiment of this application; Figure 2This is a schematic diagram of a texturing substrate provided in an embodiment of this application; Figure 3 This is a schematic diagram of a boron-expanded substrate provided in an embodiment of this application; Figure 4 This is a schematic diagram of a laser-etched substrate provided in an embodiment of this application; Figure 5 This is a schematic diagram of a phosphorus-expanded substrate provided in an embodiment of this application; Figure 6 A schematic diagram of a substrate subjected to a second laser etching, provided in an embodiment of this application; Figure 7 This is a schematic diagram of an acid-etched substrate provided in an embodiment of this application; Figure 8 A schematic diagram of a substrate that has undergone a second texturing process, provided in an embodiment of this application; Figure 9 A schematic diagram of a passivated substrate provided in an embodiment of this application; Figure 10 This is a schematic diagram of the substrate after electrodes have been applied, as provided in an embodiment of this application. Figure 11 This is a schematic diagram of a back-contact stacked battery provided in an embodiment of this application; Figure 12 This is a schematic diagram of the back-contact stacked battery provided in an embodiment of this application.

[0018] Figure Labels 1-Base; 2-Boron doped layer; 3-Borosilicate glass layer; 4-Polycrystalline silicon layer; 5-phosphosilicate glass layer; 6-Passivation layer; 61-Silicon nitride layer; 62-alumina layer; 7-electrode; 10-First Zone; 20 - Second Region; 30 - Third Region; 40-Back contact stacked battery; 401 - Protective 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 solar cell. Detailed Implementation

[0019] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0021] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0023] like Figure 1 As shown, this application embodiment provides a method for processing a back contact battery 407, used to process the back contact battery 407. The substrate 1 is typically 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 typically includes a phosphorus-expanded region, a boron-expanded region, and an isolation region, with the isolation region located between the phosphorus-expanded region and the boron-expanded region. During processing, the back side of the substrate 1 can be pre-divided. The back side of the substrate 1 includes a first region 10, a second region 20, and a third region 30, with the second region 20 located between the first region 10 and the third region 30. The first region 10 can correspond to the phosphorus-expanded region, the second region 20 can correspond to the isolation region, and the third region 30 can correspond to the boron-expanded region. The processing method includes: S1, Texturing the base 1.

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

[0025] S3. 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 part of the substrate 1 in the first region 10 and the second region 20.

[0026] S4. Phosphorus diffusion is performed on substrate 1 to form a polycrystalline silicon layer 4 and a phosphorus-silicon glass layer 5 on the surface of substrate 1.

[0027] S5. Laser etching is performed on substrate 1 to remove the phosphorus-silicon glass layer 5 in the second region 20 and the third region 30.

[0028] S6. The substrate 1 is texturized and the phosphorus glass layer 5, the polysilicon layer 4 of the first region 10, the second region 20 and the third region 30 are removed, and a textured surface is formed in the second region 20.

[0029] S7. A passivation layer 6 is formed on the substrate 1.

[0030] S8. Print electrode paste 7 in the first region 10 and the third region 30 and sinter it.

[0031] S9. Sinter the back side of substrate 1.

[0032] The back contact battery 407 processed using the processing method provided in this application embodiment can form a textured surface on both the front and back sides of the back contact battery 407. During the processing, the textured surface located in the third region 30 is retained, that is, the boron-expanded region on the back side of the back contact battery 407 has a textured structure. The textured structure creates an uneven surface on the back contact battery 407, thereby increasing the number of light reflections on the surface of the back contact battery 407, which is beneficial for extending the light transmission path and increasing the light-receiving area of ​​the back contact battery 407. This design can reduce light loss and improve light utilization, thereby improving the overall efficiency of the back contact battery 407. Meanwhile, the bifaciality of the back contact battery 407 is one of the important indicators for evaluating the back contact battery 407. The bifaciality of the back contact battery 407 refers to the ratio of the power generation capacity of the front and back sides of the back contact battery. In related technologies, the bifaciality of the back contact battery 407 is typically less than 80%. By processing the back contact battery 407 using the processing method provided in this application embodiment, a first region 10 and a third region 30 with different morphologies can be formed on the back side of the back contact battery 407. Since the third region 30 has a textured surface, the utilization rate of light on the back side of the back contact battery 407 is improved, thereby increasing the power generation capacity of the back side of the back contact battery 407. Testing shows that the bifaciality of the back contact battery 407 processed using the processing method provided in this application embodiment can exceed 90%, and the overall efficiency of the back contact battery 407 is improved, better meeting practical application requirements.

[0033] Meanwhile, in related technologies, the boron-doped region on the back side of the back contact cell 407 is typically boron-doped polycrystalline silicon (poly-Si), which exhibits parasitic absorption. Parasitic absorption refers to non-ideal light absorption processes other than the effective absorption that contributes to photogenerated carriers. These absorptions not only fail to effectively generate carriers for power generation but may also lead to energy loss and reduce the efficiency of the photovoltaic cell. That is, while the boron-doped polycrystalline silicon-formed boron-doped region absorbs light and converts it into photocurrent, other reactions that do not generate photocurrent also occur. 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; the milder 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-doped region, obtained by the processing method provided in the embodiments of this application, has a structure consisting of a passivation layer 6 and a boron-doped layer 2, arranged sequentially from the outside to the inside. Compared to polycrystalline silicon, the boron-doped layer 2 exhibits less parasitic absorption. Therefore, the parasitic absorption has a smaller impact on the efficiency of the back contact cell 407, resulting in an overall improvement in the efficiency of the back contact cell 407. Furthermore, in related technologies, metal recombination in the boron-doped region of polycrystalline silicon is quite severe, leading to a decrease in the open-circuit voltage and photoelectric conversion efficiency of the back contact cell 407. The back contact cell 407 processed using the method provided in this application is less affected by metal recombination, thus contributing to improved efficiency and open-circuit voltage of the back contact cell 407.

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

[0035] The procedure for removing damage from laser etching can be alkaline polishing. The reaction time is 100 to 300 seconds, and the etching depth is 1 to 5 μm.

[0036] Laser etching of substrate 1 causes damage to the substrate, disrupting its structure and potentially reducing the efficiency of photogenerated carrier transport and collection, thus affecting the conversion efficiency of the back contact cell 407. It may also impact the aging resistance and reliability of the back contact cell 407, leading to a decrease in its overall performance. Alkaline polishing can remove the damage caused by laser etching to the substrate 1, thereby reducing the impact of laser etching damage on the efficiency of the back contact cell 407. By setting the reaction time to 100s to 300s and the etching depth to 1µm to 5µm, the damage caused by laser etching can be effectively removed while minimizing the impact of the damage removal step on the substrate 1.

[0037] like Figure 1As shown, in one possible implementation, before step S6, the processing method further includes: S60. Acid etching is performed on substrate 1 to remove the boron doped layer 2, borosilicate glass layer 3, polysilicon layer 4 and phosphosilicate glass layer 5 on the front side of substrate 1.

[0038] In the solution provided in this application embodiment, 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, borosilicate glass layer 3, polysilicon layer 4 and phosphosilicate 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 one possible implementation, the processing flow of the back contact battery 407 provided in this application embodiment is as follows: Texturing of substrate 1 yields the following result: Figure 2 The substrate 1 shown. A velvety surface can be formed on the surface of the substrate 1 by velveting.

[0040] The substrate 1 is subjected to boron diffusion, which transforms the surface of the substrate 1 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. At temperatures ranging from 800℃ to 1200℃, diffusion occurs for 2 to 5 hours to form a boron-doped layer 2 and a borosilicate glass layer 3. The junction depth is 1µm to 2µm, the sheet resistance is 100Ω / sq to 500Ω / sq, and the thickness of the borosilicate glass layer 3 is 50nm to 150nm. Temperatures can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, etc. Diffusion times can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc. Junction depths can be 1.0µm, 1.1µm, 1.2µm, 1.3µm, 1.4µm, 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2.0µm, etc. The sheet 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 sheet resistance, the impact on the passivation of the back contact battery 407 can be reduced, thereby increasing the open-circuit voltage of the back contact battery 407, increasing 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 etching is performed on the first region 10 and the second region 20 of substrate 1. This involves removing the boron-doped layer 2, the borosilicate glass layer 3, and part of substrate 1 at corresponding positions in the phosphorus expansion region and the spacer region using laser etching. Figure 4 The structure is shown. The substrate 1 is laser-etched to remove the boron diffusion layer and borosilicate glass layer 3 from the first region 10 and the second region 20, so that the second region 20 can serve as an isolation region and for subsequent phosphorus diffusion in the first region 10. The laser etching can use green or violet light, with a laser power of 5W to 40W and an etching width of 200µm to 700µm. The etching width can be 200µm, 250µm, 300µm, 350µm, 400µm, 450µm, 500µm, 550µm, 600µm, 650µm, 700µm, etc. By keeping the etching width within the range of 200µm to 700µm, it is beneficial to ensure that the first region 10, the second region 20, and the third region 30 on the back of the back contact battery 407 are within a reasonable width range, thereby improving the efficiency and performance of the back contact battery 407.

[0042] After laser etching, the damage caused by the laser etching is removed. Then, phosphorus diffusion is performed on substrate 1 at a temperature of 700℃ to 1000℃ for 1 to 3 hours, forming a phosphorus-silicon glass layer 5 and a phosphorus-doped polycrystalline silicon layer 4 on the surface of substrate 1. The phosphorus-silicon glass layer 5 is located outside the phosphorus-doped polycrystalline silicon layer 4. The phosphorus-doped polycrystalline silicon layer 4 has a thickness of 100 nm to 250 nm and a junction depth of 100 nm to 300 nm. The thickness of the phosphorus-silicon glass layer 5 is 50 nm to 100 nm. After phosphorus diffusion, the structure of substrate 1 is as follows: Figure 5 As shown.

[0043] The phosphorus-diffused substrate 1 is subjected to a second laser etching process. Green or violet light is used to etch the second region 20 and the third region 30, removing the phosphorosilicon glass layer 5 from these regions. The laser power is 10W to 30W for etching the second region 20 and 5W to 20W for etching the third region 30. The etching width for the second laser etching of substrate 1 is 250µm to 700µm, and can be 250µm, 300µm, 350µm, 400µm, 450µm, 500µm, 550µm, 600µm, 650µm, or 700µm. The structure obtained after the second laser etching of substrate 1 is as follows: Figure 6 As shown. Since the first region 10 is a planar region and the third region 30 is a textured region, the planar region has a higher reflectivity, so the power of the first region 10 is greater during laser delamination.

[0044] After the second laser etching, substrate 1 is subjected to acid etching to remove the phosphorus-silicon glass layer 5, polysilicon layer 4, borosilicate glass layer 3, and boron diffusion layer on the front side of substrate 1. Since there are no phosphorus or boron diffusion regions on the front side of the back contact cell 407, the structure on the front side of 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 substrate 1 is as follows: Figure 7 As shown.

[0045] After acid etching, substrate 1 undergoes a second texturing process to form a textured surface. Texturing removes damage caused by the second laser etching, reducing its impact and improving substrate quality, as well as the efficiency and performance of the resulting back contact battery 407. The texturing process has a reaction time of 100 to 500 seconds and an etching depth of 1 to 5 μm. After texturing, the structure of substrate 1 is as follows: Figure 8As shown. Texturing creates an uneven, textured surface on the substrate 1, which increases the number of light reflections, facilitating light absorption by the back contact cell 407 and improving its efficiency. Simultaneously, during texturing, the phosphosilicate glass layer 5 in the first region 10, the polycrystalline silicon layer 4 in the second region 20, the polycrystalline silicon layer 4 in the third region 30, and the borosilicate glass layer 3 are removed.

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

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

[0048] After sintering to form electrode 7, the back side of substrate 1 or the third region 30 can be laser-treated, followed by secondary sintering to achieve a second sintering of electrode 7 in the third region 30. In some cases, reverse polarity is applied, i.e., a negative current from an external power source is applied to electrode 7 in the third region 30, and a positive current from an external power source is applied to electrode 7 in the first region 10. The voltage is 10V to 20V, and laser treatment is performed simultaneously with the current application. Laser treatment can be performed using laser-assisted sintering (LECO), with the laser being red or green light, and a laser power of 5W to 50W. Laser treatment can be applied to the entire back side of substrate 1, or to the third region 30. The laser direction is from the front or back side of substrate 1. After conventional sintering, laser-assisted sintering is performed on the third region 30, allowing the slurry in the third region 30 to achieve good metal-to-metal contact after two sintering processes, forming the positive electrode 7. Laser-assisted sintering of the third region 30, i.e. the boron expansion region, can help reduce contact resistance and form a good ohmic contact between the boron expansion region and the electrode 7. This reduces contact resistance, helps reduce energy loss during current transmission, increases the fill factor of the battery, and thus improves the photoelectric conversion efficiency of the battery.

[0049] Based on the processing methods of the back contact battery 407 provided in the above embodiments, this application embodiment also provides a back contact battery 407 piece, which 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. Along the direction away from the substrate 1, the front side of the back contact cell 407 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 region 10 and the third region 30. The first region 10 is a phosphorus-doped region, the third region 30 is a boron-doped region, and the second region 20 is an isolation region. Electrodes 7 are respectively disposed in the first region 10 and the third region 30. A polycrystalline silicon layer 4 and a passivation layer 6 are sequentially disposed in the first region 10 along the direction away from the interior of the substrate 1. A passivation layer 6 is disposed in the second region 20. A boron-doped layer 2 and a passivation layer 6 are sequentially disposed in the third region 30 along the 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 μm to 2 μm, and the sheet resistance is 100 Ω / sq to 500 Ω / sq. The second region 20 and the third region 30 both have a textured surface, while the first region 10 is flat. The front of the battery also has a textured surface.

[0051] The back contact battery 407 processed using the processing method provided in this application embodiment can form a textured surface in the second region 20 and the third region 30, that is, the boron-doped region and the isolation region of the back contact battery 407 have a textured surface. This design is beneficial for increasing the light-receiving area of ​​the back contact battery 407 and increasing the number of light reflections, which is beneficial for improving the light absorption efficiency of the back contact battery 407. At the same time, the boron-doped region of the back contact battery 407 is a boron-doped layer 2 instead of a polycrystalline silicon layer 4, which is beneficial for reducing parasitic absorption and metal recombination of the back contact battery 407, thereby improving the efficiency and bifaciality of the back contact battery 407, which is more in line with actual application requirements.

[0052] like Figure 11 and Figure 12As shown in the illustration, this application also provides a back-contact tandem solar cell 40, which 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 any of the back-contact cell 407 involved in the above embodiments. The back-contact tandem solar cell 40 can be a three-terminal tandem solar cell. When processing the back-contact tandem solar cell 40, the top cell and the bottom cell can be connected by directly depositing a perovskite top cell on the bottom cell. Compared with single-crystal silicon solar cells, the back-contact tandem solar cell 40 has higher efficiency and power generation. Moreover, the back-contact tandem bottom cell using the back-contact cell 407 as the bottom cell has advantages such as no current mismatch, high process tolerance, and wide application scenarios. Meanwhile, compared to two-terminal stacked cells, the three-terminal stacked cell formed by the perovskite cell 408 and the back contact cell 407 can have an additional electrode 7 to output mismatch current, which is beneficial to ensure that the back contact stacked cell 40 can operate at relatively higher power. Moreover, the voltage matching requirement is less affected by changes 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 connecting electrodes 7 with opposite polarities, realizing the conversion from three-terminal to two-terminal. The back contact cell 407 has a textured surface, and conformal deposition and growth of perovskite on the textured surface can improve the utilization rate of incident light. The back contact stacked cell 40 made of perovskite cell 408 and back contact cell 407 does not need to consider current matching and has high tolerance for the band gap and thickness of perovskite. The three-terminal back contact stacked cell 40 has a wider range of applications and can achieve high-power operation in different outdoor environments, which is more in line with practical use needs.

[0053] like Figure 11 As shown, in one possible embodiment, the back contact stacked battery 40 consists of, from top to bottom, a protective layer 401, a transparent conductive layer 402, a battery transport layer, a perovskite layer 404, a hole transport layer 405, a composite layer 406, and a back contact battery 407. The transparent conductive layer 402 (transparent conductive oxide, TCO) can be an indium tin oxide layer.

[0054] This application also provides a photovoltaic module, which includes at least one battery string, and the battery string includes a back contact battery 407 or a back contact tandem battery 40 in any of the above embodiments.

[0055] Photovoltaic modules may also include structures such as a first cover plate, a second cover plate, a first encapsulant film, and a second encapsulant film. Multiple back-contact cells 407 or back-contact stacked cells 40 are electrically connected to form a cell string, and multiple cell strings are electrically connected to form a cell array. Along the thickness direction of the photovoltaic module, the first encapsulant film and the second encapsulant film are located on opposite sides of the cell array. The first cover plate is located on the side of the first encapsulant film furthest from the cell array, and the second cover plate is located on the side of the second encapsulant film furthest from the cell array. The first and second cover plates are located on the surface of the photovoltaic module and can protect the photovoltaic module. The first and second encapsulant films can act as buffers to reduce the possibility of microcracks appearing in the back-contact cells 407 or back-contact stacked cells 40 during lamination and impact, thereby helping to improve the service life of the photovoltaic module.

[0056] This application provides a back contact cell 407 and its processing method, a back contact tandem 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 a first region 10 and a 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 and second regions 10 and 20. Phosphorus diffusion is performed on the substrate 1 to form a polycrystalline silicon 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 polycrystalline silicon layer 4 in the second region 20 and the third region 30 are removed, forming a textured surface in the second region 20. A passivation layer 6 is formed on the substrate 1. Electrode 7 paste is printed in the first region 10 and the third region 30 and sintered. The back side of the back contact cell 407 is sintered. This design improves the bifaciality and efficiency of the back-contact battery 407.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for processing a back-contact battery, characterized in that, The back side of the substrate (1) includes 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) includes: Texturing of the 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 part of the substrate (1) in the first region (10) and the second region (20). The substrate (1) is subjected to phosphorus diffusion to form a polycrystalline silicon layer (4) and a phosphorus-silicon 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) of the first region (10), the polycrystalline silicon layer (4) of the second region (20) and the third region (30) are removed, and a textured surface is formed in the second region (20); A passivation layer (6) is formed on the substrate (1); Electrode paste is printed and sintered in the first region (10) and the third region (30); The back side of the substrate (1) is sintered; 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) includes: The boron doped layer (2) and the borosilicate glass layer (3) are formed by diffusion at a temperature of 800℃ to 1200℃ for 2h to 5h, with a junction depth of 1um to 2um and a sheet resistance of 100Ω / sq to 500Ω / sq. The thickness of the borosilicate glass layer (3) is 50nm to 150nm.

2. The processing method for a back contact battery according to claim 1, characterized in that, In the step of laser etching 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 part of the substrate (1) in the first region (10) and the second region (20), the laser power is 5W to 40W and the etching width is 200um to 700um.

3. The processing method for a back contact battery according to claim 1, characterized in that, The steps of performing phosphorus diffusion on the substrate (1) to form a polycrystalline silicon layer (4) and a phosphorus-silicon glass layer (5) on the surface of the substrate (1) include: The polycrystalline silicon layer (4) and the phosphorus silica glass layer (5) are formed in the first region (10) and the second region (20) by diffusion at a temperature of 700°C to 1000°C for 1 to 3 hours. The polycrystalline silicon layer (4) has a thickness of 100 nm to 250 nm and a junction depth of 100 nm to 300 nm. The phosphorus silica glass layer (5) has a thickness of 50 nm to 100 nm.

4. The processing method of the back contact battery according to claim 1, characterized in that, 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) includes: The laser power for laser etching the third region (30) is 5W to 20W; The laser power for laser etching of the polycrystalline silicon layer (4) is 10W to 30W, and the etching width is 250um to 700um.

5. The processing method of the back contact battery according to any one of claims 1 to 4, characterized in that, The processing method of the back contact battery (407) includes the following steps prior to texturing the substrate (1) and removing the phosphosilicate glass layer (5), the polycrystalline silicon layer (4) of the first region (10), the second region (20), and the third region (30) of the polycrystalline silicon layer (4), and forming the textured surface in the second region (20): The substrate (1) is acid-etched 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 side of the substrate (1).

6. The method for processing a back contact battery according to any one of claims 1 to 4, characterized in that, Before phosphorus diffusion of the substrate (1) and forming a polycrystalline silicon layer (4) and a phosphorus-silicon glass layer (5) on the surface of the substrate (1), the processing method includes: Damage from laser etching is removed by alkaline polishing, with a reaction time of 100s to 300s and an etching depth of 1um to 5um.

7. The method for processing a back contact battery according to any one of claims 1 to 4, characterized in that, The step of sintering the back side of the substrate (1) includes: The third region (30) of the substrate (1) is laser-processed using a laser with a power of 5W to 50W.

8. A back-contact battery, characterized in that, The back contact battery (407) is processed by the processing method of the back contact battery (407) according to any one of claims 1 to 7.

9. The back contact battery according to claim 8, characterized in that, Along the thickness direction, the back contact battery (407) includes a front side and a back side. Along the direction away from the substrate (1), the front side includes a passivation layer (6), and the back side 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). Electrodes (7) are respectively provided in the first region (10) and the third region (30). The first region (10) is provided with a polysilicon layer (4) and a passivation layer (6) 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 doped layer (2) and a passivation layer (6) in a direction away from the interior of the substrate (1); The junction depth of the first region (10) is 100 nm to 300 nm, and the junction depth of the third region (30) is 1 micrometer to 2 micrometers, with a sheet resistance of 100 Ω / sq to 500 Ω / sq. The second region (20) and the third region (30) have a textured surface, and the front side of the battery has a textured surface.

10. A back-contact stacked battery, characterized in that, The back contact stacked battery (40) includes a top battery and a bottom battery that are electrically connected to each other. The top battery is a perovskite battery (408), and the bottom battery is a back contact battery (407). The back contact battery (407) is the back contact battery (407) according to any one of claims 8 to 9.

11. A photovoltaic module, characterized in that, The photovoltaic module includes at least one battery string, the battery string including the back contact battery (407) of any one of claims 8 to 9 or the back contact tandem battery (40) of claim 10.

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