A method for manufacturing a back contact solar cell and a back contact solar cell

Abstract

The application discloses a preparation method of a back contact solar cell and the back contact solar cell. The preparation method comprises the following steps: performing double-side polishing treatment on a silicon base; a back surface of the silicon base is formed with a first tunneling oxide layer, a P+ polysilicon layer and a laser blocking layer from inside to outside in a laminated mode, and a first silicon oxide layer is synchronously formed on the P+ polysilicon layer; the laser blocking layer and the first silicon oxide layer of a first region are removed by laser, and the first region and a second region retaining the laser blocking layer are arranged alternately; the first tunneling oxide layer and the P+ polysilicon layer of the first region are removed; the second tunneling oxide layer and an N+ polysilicon layer laminated on the second tunneling oxide layer are formed in the first region in a control mode and are separated from the P+ polysilicon layer and arranged alternately, a texturing treatment is performed on an interval region adjacent to the second region in the first region and a front surface of the silicon base; and the laser blocking layer and the first silicon oxide layer on the second region are removed through acid cleaning. The preparation process stability of the back contact solar cell is improved.

Description

Technical Field

[0001] This invention relates to a method for fabricating a back-contact solar cell and the back-contact solar cell itself. Background Technology

[0002] Existing fabrication processes for back-contact solar cells with passivated contact structures are not only complex, but also involve several steps. After forming a P+-doped polysilicon layer on the passivation layer, a portion of the P+-doped polysilicon layer is removed via direct laser ablation, or a mask layer (such as photoresist or ink) is introduced onto the P+-doped polysilicon layer. This mask layer is then partially removed using photolithography, laser etching, or chemical etching. Subsequent processes use chemical cleaning to remove the unmasked P+-doped polysilicon layer, and then an N+-doped polysilicon layer is formed in the area where the P+-doped polysilicon layer was removed. Finally, the mask layer is removed again. Because it is difficult to precisely control the removal of nanometer-thick films using photolithography, laser etching, and chemical etching, the existing fabrication processes inevitably damage the passivation layer corresponding to the N+-doped polysilicon layer. This results in poor process stability, suboptimal photoelectric conversion efficiency (PEP) of the fabricated back-contact solar cells, and significant differences in PEP between different fabricated back-contact solar cells. Summary of the Invention

[0003] In view of this, the present invention provides a method for preparing a back-contact solar cell and a back-contact solar cell. The preparation method can effectively improve the stability of the preparation process of the back-contact solar cell and can ensure that the photoelectric conversion efficiency of the prepared back-contact solar cells remains consistent.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] In a first aspect, the present invention provides a method for fabricating a back-contact solar cell, comprising:

[0006] Step a: Perform double-sided polishing on the silicon substrate;

[0007] Step b: A first tunneling oxide layer, a P+ polysilicon layer, and a laser blocking layer are stacked from the inside to the outside on the back side of the silicon substrate. During the formation of the P+ polysilicon layer, a first silicon oxide layer is simultaneously formed on the P+ polysilicon layer.

[0008] Step c: Remove the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, wherein the first region is alternately arranged with the second region where the laser blocking layer and the first silicon oxide layer are retained;

[0009] Step d: Remove the first tunneling oxide layer and P+ polysilicon layer in the first region by alkaline polishing;

[0010] Step e: In a first region on the back side of the silicon substrate, a second tunneling oxide layer and an N+ polysilicon layer stacked on the second tunneling oxide layer are formed in a controlled manner, which are isolated from the first tunneling oxide layer and the P+ polysilicon layer and are alternately arranged. Simultaneously, the spacer region adjacent to the second region in the first region and the front side of the silicon substrate are texturized to form a textured structure on the spacer region and the front side of the silicon substrate. The spacer region is used to isolate the adjacent P+ polysilicon layer and N+ polysilicon layer.

[0011] Step f: Remove the laser blocking layer and the first silicon oxide layer on the second region by acid cleaning.

[0012] In a second aspect, embodiments of the present invention provide a back-contact solar cell prepared according to the first aspect embodiment described above, comprising:

[0013] Silicon substrate;

[0014] A first tunneling oxide layer and a second tunneling oxide layer are formed on the back side of a silicon substrate, are phase-isolated and alternately arranged;

[0015] A P+ polysilicon layer stacked on the first tunneling oxide layer;

[0016] An N+ polycrystalline silicon layer stacked on the second tunneling oxide layer;

[0017] A spacer region formed on the back side of the silicon substrate to isolate the adjacent first tunneling oxide layer and second tunneling oxide layer, as well as the adjacent P+ polysilicon layer and N+ polysilicon layer.

[0018] The area on the back side of the silicon substrate corresponding to the first tunneling oxide layer and the second tunneling oxide layer is a polished surface;

[0019] The silicon substrate has a textured structure formed synchronously on the front side and the spacer area. The textured structure is formed synchronously during the process of forming a second tunneling oxide layer and an N+ polysilicon layer that are isolated from and alternately arranged with the first tunneling oxide layer and the P+ polysilicon layer.

[0020] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0021] 1. The back-contact solar cell fabrication method provided by the present invention, by setting a laser blocking layer on the P+ polycrystalline silicon layer, allows the laser blocking layer to absorb laser energy and block laser energy conduction during the process of removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser. Furthermore, since there are steps after removing the laser blocking layer in the first region on the back side of the silicon substrate by laser, such as alkaline polishing to remove the first tunneling oxide layer and the P+ polycrystalline silicon layer in the first region, and controlling the formation of a second tunneling oxide layer and an N+ polycrystalline silicon layer stacked on the second tunneling oxide layer that are isolated from and alternately arranged with the first tunneling oxide layer and the P+ polycrystalline silicon layer in the first region on the back side of the silicon substrate, i.e., the step of reforming the second tunneling oxide layer located below the N+ polycrystalline silicon layer after laser treatment, there is no need to consider the damage to the first tunneling oxide layer and the P+ polycrystalline silicon layer during laser treatment, giving the laser a wider operating window. Moreover, the width of the first region can be controlled more precisely by removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser.

[0022] 2. Given the wider operating window of the laser and the fact that the laser removal process of the first region's laser blocking layer does not require consideration of damage to the first tunneling oxide layer and P+ polycrystalline silicon layer, the subsequent acid cleaning process removes the laser blocking layer in the second region. This ensures the laser blocking layer is not retained in the final cell structure. Therefore, the placement and thickness of the laser blocking layer do not affect the back-contact solar cell. Based on this, the thickness of the laser blocking layer can be adjusted as needed, resulting in better process flexibility and a wider operating window for the back-contact solar cell fabrication process.

[0023] 3. Due to the steps of removing the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region by alkaline polishing, and the steps of controlling the formation of a second tunneling oxide layer and an N+ polycrystalline silicon layer stacked on the second tunneling oxide layer in the first region on the back side of the silicon substrate, which are isolated from and alternately arranged with the first tunneling oxide layer and the P+ polycrystalline silicon layer, i.e., the second tunneling oxide layer located below the N+ polycrystalline silicon layer is re-formed after laser treatment, even if the laser damages the tunneling oxide layer corresponding to the N+ doped polycrystalline silicon layer under a wide laser operating window, it will not affect the photoelectric conversion performance of the back contact solar cell, thereby improving the stability of the back contact solar cell fabrication process and effectively improving the relative consistency of photoelectric conversion efficiency among the fabricated back contact solar cells.

[0024] 4. Removing the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region by alkaline polishing can prevent residual P+ doped elements in the first region, thereby reducing carrier recombination in the first region and effectively improving the photoelectric conversion efficiency of the back contact solar cell.

[0025] 5. Polishing is performed to ensure that the areas forming the first tunneling oxide layer and the areas forming the second tunneling oxide layer are both polished surfaces, thereby guaranteeing the flatness and uniformity of the first tunneling oxide layer, the second tunneling oxide layer, the P+ polycrystalline silicon layer, and the N+ polycrystalline silicon layer, which effectively improves the passivation effect and photoelectric conversion efficiency of the back contact solar cell.

[0026] 6. Texturing of the spacer region and the front side is completed during the process of removing N+ polycrystalline silicon and second silicon oxide from the second region and the spacer region, so that the spacer region and the front side of the prepared back contact solar cell have a textured structure, which simplifies the preparation process and ensures the light utilization rate of the back contact solar cell. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the main process of the preparation method of a back contact solar cell provided in an embodiment of the present invention;

[0028] Figure 2 This is a partial structural cross-sectional schematic diagram during the fabrication process of a back-contact solar cell according to an embodiment of the present invention;

[0029] Figure 3 This is a partial cross-sectional structural diagram obtained after step S13 processing according to an embodiment of the present invention;

[0030] Figure 4 This is a partial cross-sectional structural diagram obtained after step S14 processing according to an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the main process of implementing step S15 according to an embodiment of the present invention;

[0032] Figure 6 This is a partial cross-sectional structural diagram of the formation of multiple film layers simultaneously on the front side of the silicon substrate in step S151 according to an embodiment of the present invention.

[0033] Figure 7 This is a schematic cross-sectional view of the structure obtained by removing the film layer corresponding to the second silicon oxide layer on the front side of the silicon substrate according to an embodiment of the present invention;

[0034] Figure 8 This is a partial cross-sectional structural schematic diagram obtained after step S152 processing according to an embodiment of the present invention;

[0035] Figure 9 This is a partial cross-sectional structural schematic diagram obtained after step S153 processing according to an embodiment of the present invention;

[0036] Figure 10 This is provided according to embodiments of the present invention. Figure 9The diagram shown is a partial cross-sectional view of the structure obtained by simultaneously removing the second silicon oxide layer on the N+ polysilicon layer.

[0037] Figure 11 It is provided according to the embodiments of the present invention. Figure 10 A bottom view of the back contact solar cell;

[0038] Figure 12 This is a schematic cross-sectional view of a back-contact solar cell including a passivation antireflection layer according to an embodiment of the present invention;

[0039] Figure 13 This is a schematic cross-sectional view of a back-contact solar cell after electrode formation according to an embodiment of the present invention.

[0040] The attached figures are labeled as follows:

[0041] 1-Silicon substrate; 2-First tunneling oxide layer; 2'-First film layer; 3-P+ polycrystalline silicon layer; 3'-Second film layer; 31-First silicon oxide layer; 31'-Third film layer; 4-Laser blocking layer; 4'-Fourth film layer; 5-Second tunneling oxide layer; 5'-Fifth film layer; 6-N+ polycrystalline silicon layer; 6'-Sixth film layer; 61-Second silicon oxide layer; 61'-Seventh film layer; 7-Spacer region; 8-Back passivation and antireflection layer; 9-Front passivation and antireflection layer; 101-First electrode; 102-Second electrode. Detailed Implementation

[0042] In the embodiments of this invention, the layering of multiple other structures from the inside out at a specific location of a structure (such as the back, front, side, a portion of the back, a portion of the front, etc.) means that multiple other structures are layered from the inside out, starting from the original structure and moving away from it. For example, Figures 2 to 8 The first tunneling oxide layer 2, P+ polysilicon layer 3, first silicon oxide layer 31, and laser blocking layer 4, which are sequentially stacked from the inside to the outside on the back side of the silicon substrate 1, are arranged starting from the back side of the silicon substrate 1 and moving away from the back side of the silicon substrate 1. The first tunneling oxide layer 2 is in direct contact with the silicon substrate 1, that is, the first tunneling oxide layer 2 is closest to the back side of the silicon substrate 1. The P+ polysilicon layer 3 is stacked on the first tunneling oxide layer 2, the first silicon oxide layer 31 is stacked on the P+ polysilicon layer 3, and the laser blocking layer 4 is stacked on the first silicon oxide layer 31.

[0043] The stacking / forming of one structure on one structure in the embodiments of the present invention does not specifically refer to the other structure being located on top of the structure. Rather, it generally refers to the stacking / forming of another structure on a portion or all of the main surface of the structure away from the silicon substrate, and the other structure being in direct or indirect contact with the portion or all of the main surface of the structure away from the silicon substrate.

[0044] In the embodiments of this invention, the front side of a structure generally refers to the surface facing sunlight during the use of a back-contact solar cell. Conversely, the back side of a structure generally refers to the surface facing away from sunlight during the use of a back-contact solar cell. For example, the back and front sides of a silicon substrate refer to the two relatively large, oppositely arranged main surfaces of a P-type silicon substrate, serving as the back-light surface (the side facing away from sunlight) and the light-receiving surface (the side facing sunlight) of the solar cell.

[0045] In this embodiment of the invention, "one structure penetrating another structure" means that a portion of the one structure extends from one side of the other structure to the other in the thickness direction. For example, "a second electrode penetrating the front passivation antireflection layer" means that the second electrode extends from one side of the front passivation antireflection layer to the other side. Similarly, "a first electrode penetrating the back passivation antireflection layer" means that the first electrode extends from one side of the back passivation antireflection layer to the other side.

[0046] In this invention, the simultaneous processing of one process and another generally refers to the simultaneous completion of one process and another in the same step or using the same solution in the same step. For example, simultaneously texturing the spacer region 7 adjacent to the second region and the front side of the silicon substrate 1 in the first region means that the spacer region 7 and the front side of the silicon substrate 1 are texturized using the same alkaline solution. As another example, in the acid cleaning process of step f, simultaneously removing the second silicon oxide layer on the N+ polysilicon layer in the first region means that the removal of the second silicon oxide layer on the N+ polysilicon layer in the first region is also completed through the acid cleaning process of step f.

[0047] The terms "first" and "second" used in the embodiments of the present invention are only for distinguishing the different positions, structures they are in contact with, or functions they perform. However, structures made of the same material, such as the first tunneling oxide passivation layer and the second tunneling oxide passivation layer, the first electrode and the second electrode, are not a limitation on the number or order of structures.

[0048] To address the problems of complex fabrication processes, poor process stability, significant variability in fabricated back-contact solar cells, carrier recombination on the silicon substrate surface, and difficulty in further improving the photoelectric conversion efficiency of existing back-contact solar cell fabrication methods, this invention provides a method for fabricating back-contact solar cells. Specifically, Figure 1 A schematic diagram of the main process for fabricating this back-contact solar cell is shown. Figures 2 to 4 , Figures 6 to 13 This shows a schematic diagram of the partial structures upon which each step of the preparation method depends, or the partial structures obtained by each step. For example... Figure 1 As shown, the method for fabricating a back-contact solar cell may include the following steps:

[0049] Step S11: Perform double-sided polishing on silicon substrate 1;

[0050] Step S12: A first tunneling oxide layer 2, a P+ polysilicon layer 3, and a laser blocking layer 4 are stacked from the inside to the outside on the back side of the silicon substrate 1. During the formation of the P+ polysilicon layer 3, a first silicon oxide layer 31 is simultaneously formed on the P+ polysilicon layer 3.

[0051] Step S13: Remove the laser blocking layer 4 and the first silicon oxide layer 31 from the back side of the silicon substrate 1 by laser, wherein the first region is alternately arranged with the second region where the laser blocking layer 4 and the first silicon oxide layer 31 are retained;

[0052] Step S14: Remove the first tunneling oxide layer 2 and the P+ polysilicon layer 3 in the first region by alkaline polishing;

[0053] Step S15: In the first region on the back side of the silicon substrate 1, a second tunneling oxide layer 5 and an N+ polysilicon layer 6 stacked on the second tunneling oxide layer 5 are formed in a controlled manner, which are isolated from the first tunneling oxide layer 2 and the P+ polysilicon layer 3 and are alternately arranged. Simultaneously, the spacer region 7 adjacent to the second region in the first region and the front side of the silicon substrate 1 are texturized to form a textured structure on the spacer region 7 and the front side of the silicon substrate. The spacer region 7 is used to isolate the adjacent P+ polysilicon layer 3 and N+ polysilicon layer 6.

[0054] Step S16: Remove the laser blocking layer 4 and the first silicon oxide layer 31 on the second region by acid cleaning.

[0055] The silicon substrate used in the above steps can be either a P-type silicon substrate or an N-type silicon substrate.

[0056] Step S11 mainly refers to polishing the two main surfaces of the silicon substrate to achieve flatness. This polishing can be achieved using existing polishing techniques, which will not be elaborated further. Furthermore, compared to single-sided polishing, double-sided polishing reduces the requirements for process control precision, making this step easier to control. Moreover, the polishing in step S11 ensures that the area on the silicon substrate in contact with the tunneling oxide layers (first and second tunneling oxide layers) in subsequent processing steps remains flat. This effectively improves the flatness and uniformity of the tunneling oxide layers (first and second tunneling oxide layers) and the P+ and N+ polycrystalline silicon layers stacked on them, thereby effectively improving the passivation effect of the passivation contact structure formed on the back of the back contact solar cell.

[0057] Furthermore, step S12 can be performed using one or more deposition methods selected from low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), and atomic layer deposition (ALD) to form the first tunneling oxide layer 2, the P+ polycrystalline silicon layer 3, and the laser blocking layer 4. The deposited first tunneling oxide layer 2 is generally silicon oxide, with a thickness of 0.5–3.0 nm. The formation process of the P+ polycrystalline silicon layer 3 generally involves first depositing an intrinsic amorphous silicon layer or a microcrystalline silicon layer on the first tunneling oxide layer 2, then doping the intrinsic amorphous silicon layer or microcrystalline silicon layer with boron, and finally converting the intrinsic amorphous silicon layer or microcrystalline silicon layer into a polycrystalline silicon layer through processes such as high-temperature annealing, thereby activating the doped boron.

[0058] Furthermore, in step S12, during the formation of the P+ polycrystalline silicon layer 3, a first silicon oxide layer 31 can be simultaneously formed on the P+ polycrystalline silicon layer 3. This first silicon oxide layer 31 can include silicon oxide or boron-containing silicon oxide. It is generally formed during the conversion of intrinsic amorphous silicon or microcrystalline silicon layers to polycrystalline silicon, or during boron doping, when the surface silicon reacts with oxygen in the reaction environment. This allows the formation of the P+ polycrystalline silicon layer 3 to be completed in an atmospheric environment, eliminating the need for an inert atmosphere and reducing the control of deposition conditions and costs associated with the P+ polycrystalline silicon layer 3. Additionally, the first silicon oxide layer 31, together with the laser blocking layer 4, can prevent laser light from damaging the first tunneling oxide layer 2 and the P+ polycrystalline silicon layer 3 in the second region. Simultaneously, the laser blocking layer 4 absorbs laser energy, blocking its transmission.

[0059] The laser blocking layer 4 can be deposited from at least one of silicon oxide, silicon oxynitride, and silicon nitride. The material used to prepare the laser blocking layer 4 is commonly used in solar cell fabrication and does not increase the cost of the back-junction solar cell.

[0060] Specifically, regarding step S12, in order to further reduce the complexity and limitations of the process, and to reduce the cost of the fabrication process while ensuring its stability, multiple films are simultaneously formed on the front side of the silicon substrate 1 during the formation of the first tunneling oxide layer 2, the P+ polycrystalline silicon layer 3, the first silicon oxide layer 31, and the laser blocking layer 4. For example... Figure 2 As shown, through step S12 in Figure 2 (A) shows a silicon substrate 1 on which a first tunneling oxide layer 2, a P+ polysilicon layer 3, a first silicon oxide layer 31, and a laser blocking layer 4 are sequentially deposited from the inside to the outside on the back side. Simultaneously, during the deposition of the first tunneling oxide layer 2, a first film layer 2' corresponding to the first tunneling oxide layer 2 is deposited on the front side of the silicon substrate 1. During the formation of the P+ polysilicon layer 3, a second film layer 3' corresponding to the P+ polysilicon layer 3 and a third film layer 31' corresponding to the first silicon oxide layer 31 are formed on the first film layer 2'. During the deposition of the laser blocking layer 4, a fourth film layer 4' corresponding to the laser blocking layer 4 is formed on the third film layer 31', thus obtaining... Figure 2 The structure shown in (B) is for... Figure 2 The case shown in step S12, where multiple films are simultaneously formed on the front side of the silicon substrate 1, may further include, after step S12, the formation of the films on the front side of the silicon substrate 1 corresponding to the first silicon oxide layer 31 and the laser blocking layer 4 by acid etching or laser removal, i.e., removal by this step. Figure 2 The fourth film layer 4' and the third film layer 31' in the structure shown in (B) yield... Figure 2 The structure shown in (C) is noteworthy. It is worth noting that the step of removing the film layer on the front side of the silicon substrate 1 corresponding to the first silicon oxide layer 31 and the laser blocking layer 4 by acid etching or laser can be performed before or after step S13. In a preferred embodiment, this step of removing the film layer on the front side of the silicon substrate 1 corresponding to the first silicon oxide layer 31 and the laser blocking layer 4 by acid etching or laser is performed before step S13 to reduce the impact of this step on the back side of the silicon substrate 1. The acid used for acid etching can be any acid used in the production process of back-contact solar cells for etching film layers, such as hydrofluoric acid. The intensity of the laser used can be adjusted according to the thickness of the film layer and is not limited here.

[0061] Furthermore, with Figure 2 Taking the structure shown in (C) as an example, after processing through the above step S13, the following can be obtained: Figure 3 The structure shown. It is worth noting that... Figure 3 The widths of the first and second regions shown can be set according to actual needs. The width of the first region can be adjusted by controlling the laser width. Understandably, the laser blocking layer 4 and the first silicon oxide layer 31 are materials that can be removed by laser. However, due to their certain thickness, they can act as laser energy absorption layers, blocking the laser from reaching the first tunneling oxide layer 2 and the P+ polysilicon layer 3 for a certain period of time. In addition, since there are steps after removing the laser blocking layer in the first region on the back side of the silicon substrate by laser, such as alkaline polishing to remove the first tunneling oxide layer and the P+ polysilicon layer in the first region on the back side of the silicon substrate, and controlling the formation of a second tunneling oxide layer that is isolated from the first tunneling oxide layer and the P+ polysilicon layer and an N+ polysilicon layer stacked on the second tunneling oxide layer, that is, the step of reforming the second tunneling oxide layer below the N+ polysilicon layer after laser treatment, then there is no need to consider the damage to the first tunneling oxide layer and the P+ polysilicon layer during the laser treatment in step S13, so that the laser has a wider operating window, and the width of the first region can be controlled more precisely by removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser.

[0062] In addition, since the laser blocking layer can absorb the laser energy transmitted by the first region, it can block the thermal damage caused by the laser acting on the first region.

[0063] Furthermore, given the wider operating window of the laser and the fact that the laser does not need to be considered for damaging the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region during the removal of the laser blocking layer, the laser blocking layer in the second region is subsequently removed by acid cleaning. This ensures that the laser blocking layer is not retained in the final cell structure. Therefore, the setting and thickness of the laser blocking layer do not affect the back-contact solar cell. Based on this, the thickness of the laser blocking layer can be adjusted as needed, resulting in better process flexibility and operating window for the back-contact solar cell fabrication process, further improving the controllability of step S13 and the stability of the back-contact solar cell fabrication process. In addition, step S13, through the laser width setting combined with the use of the laser blocking layer, can effectively form the spacer between the P-region and the N-region, completing the PN region partitioning without the need for separate spacer fabrication, further simplifying the process flow.

[0064] Furthermore, step S14 above, through alkaline polishing, can simultaneously remove the film layer on the front side of the silicon substrate 1 corresponding to the first tunneling oxide layer 2 and the P+ polycrystalline silicon layer 3. Figure 3 Taking the structure shown as an example, step S14 can remove... Figure 3The first tunneling oxide layer 2 and the P+ polysilicon layer 3 in the first region are shown. Simultaneously, the second film layer 3' corresponding to the P+ polysilicon layer 3 and the first film layer 2' corresponding to the first tunneling oxide layer 2 on the front side of the silicon substrate 1 are removed, resulting in the following: Figure 4 The structure is shown. The alkaline solution can be a commonly used alkaline solution in existing solar cell fabrication processes, and its concentration and other parameters can be adjusted as needed. Furthermore, the alkaline polishing process in step S14 can remove a portion of the silicon substrate on the back side corresponding to the first region, such as... Figure 4 This allows the silicon substrate thickness in the first region to be less than that in the second region. By removing a portion of the silicon substrate corresponding to the first region, the boron element that entered the silicon substrate in the first region during the formation of the P+ polysilicon layer 3 in step S12 can be effectively removed, reducing carrier recombination in the first region. Furthermore, since step S14 can effectively remove the boron element that entered the silicon substrate in the first region, reducing carrier recombination in the first region, the conditions for forming the P+ polysilicon layer 3 in step S12 can be further relaxed to better ensure the stability of the entire process.

[0065] Furthermore, due to the combination of steps S14 and S15, a second tunneling oxide layer is re-formed below the N+ polycrystalline silicon layer after laser treatment. Therefore, even if the laser damages the tunneling oxide layer corresponding to the N+ doped polycrystalline silicon layer under a wide laser usage window, it will not affect the photoelectric conversion performance of the back contact solar cell, thereby improving the stability of the back contact solar cell fabrication process and effectively improving the relative consistency of photoelectric conversion efficiency among the fabricated back contact solar cells.

[0066] More specifically, in embodiments of the present invention, such as Figure 5 As shown, the implementation of step S15 above may include the following process steps:

[0067] Step S151: A second tunneling oxide layer 5 and an N+ polysilicon layer 6 are simultaneously formed in the first and second regions on the back side of the silicon substrate 1, wherein, during the formation of the N+ polysilicon layer 6, a second silicon oxide layer 61 is simultaneously formed on the N+ polysilicon layer 6.

[0068] In this step, by simultaneously forming the second silicon oxide layer 61 on the N+ polysilicon layer 6 during the formation of the N+ polysilicon layer 6, the formation of the N+ polysilicon layer 6 can be completed in an atmospheric environment without the need for an inert atmosphere. Furthermore, to further reduce the limitations of this step, multiple corresponding films can be formed simultaneously on the front side of the silicon substrate 1 during the formation of the second tunneling oxide layer 5, the N+ polysilicon layer 6, and the second silicon oxide layer 61. Figure 4 Taking the structure shown as an example, this step can yield the following result: Figure 6 The structure shown. (As illustrated) Figure 6 As shown, a stacked second tunneling oxide layer 5, an N+ polysilicon layer 6, and a second silicon oxide layer 61 are formed in both the first and second regions on the back side of the silicon substrate 1. The second tunneling oxide layer 5 in the first region is in direct contact with the back side of the silicon substrate, while the second tunneling oxide layer 5 in the second region is in direct contact with the laser blocking layer 4 in the second region. Additionally, as... Figure 6 As shown, a fifth film layer 5' corresponding to the second tunneling oxide layer 5, a sixth film layer 6' corresponding to the N+ polycrystalline silicon layer 6 stacked on the fifth film layer 5', and a seventh film layer 61' corresponding to the second silicon oxide layer 61 stacked on the sixth film layer 6' are formed on the front side of the silicon substrate 1. The second silicon oxide layer may include silicon oxide or phosphorus-containing silicon oxide.

[0069] Furthermore, targeting Figure 6 As shown, multiple films corresponding to the second tunneling oxide layer 5, the N+ polysilicon layer 6, and the second silicon oxide layer 61 are formed on the front side of the silicon substrate 1. After step S151, the process may further include: removing the films corresponding to the second silicon oxide layer 61 on the front side of the silicon substrate 1 by acid etching or laser treatment. Figure 7 As shown, compared to Figure 6 This step removes the seventh film layer 61' corresponding to the second silicon oxide layer 61. This process of removing the film layer on the front side of the silicon substrate 1 corresponding to the second silicon oxide layer 61 can be performed before or after step S152. In a preferred embodiment, this process can be performed before step S152. When using acid etching, commonly used acids for etching silicon oxide, such as hydrofluoric acid, in solar cell fabrication processes can be selected. The acid concentration, reaction time, and other parameters can be adjusted as needed. Similarly, when using laser etching, the laser intensity and other parameters can be adjusted as needed and are not limited here.

[0070] The second tunneling oxide layer 5 and the N+ polysilicon layer 6 in this step can be prepared by one or more deposition methods, including low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), and atomic layer deposition (ALD). The prepared second tunneling oxide layer 5 is generally silicon oxide, and its thickness can be 0.5–3.0 nm.

[0071] Step S152: Laser removal of the second silicon oxide layer 61 in the second region and the spacer region 7 adjacent to the second region in the first region;

[0072] by Figure 7 Taking the structure shown as an example, step S152 can yield the following result: Figure 8 The structure shown is the result of removing the second silicon oxide layer 61 of the second region and the spacer region 7 adjacent to the second region in the first region.

[0073] In step S152, when the silicon dioxide layer of the second region and the spacer region is removed by laser, a laser blocking layer exists in the second region due to the aforementioned steps. This laser blocking layer can absorb laser energy and prevent the laser energy from being conducted to the P+ polycrystalline silicon layer and the first tunnel oxide layer that need to be retained on the back contact solar cell. This avoids the laser treatment in this step from damaging or destroying the P+ polycrystalline silicon layer and the first tunnel oxide layer on the second region, thereby further ensuring the integrity of the P+ polycrystalline silicon layer and the first tunnel oxide layer of the back contact solar cell, ensuring the performance of the cell, and also contributing to the stability of the fabrication process.

[0074] This step uses laser to remove the second silicon oxide layer 61 of the second region and the spacer region 7 adjacent to the second region in the first region, so as to facilitate the completion of the subsequent step S153. At the same time, compared with other methods of removing the second silicon oxide layer 61 by means of a mask, this laser removal effectively simplifies the process operation.

[0075] Additionally, in this step, the width of the spacer region 7 or the spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 can be controlled to be 1×10. 3 nm~5×10 5 nm. The spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 refers to the distance between the side of the P+ polysilicon layer 3 closest to the N+ polysilicon layer 6 and the side of the N+ polysilicon layer 6 closest to the P+ polysilicon layer 3. This can be achieved by controlling the width of the spacing region 7 or by setting the spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 to 1 × 10⁻⁶. 3 nm~5×10 5 Any value in nm, such as 2 × 10 3 nm, 3×10 3 nm, 5×10 3 nm, 1×10 4 nm, 3×10 4 nm, 5×10 4 nm, 7×10 4 nm, 9×10 4 nm, 1×10 5 nm, 2×10 5 nm, 4×10 5 nm, 5×105 nm, etc., can effectively reduce carrier recombination while ensuring the P+ polysilicon layer 3 and N+ polysilicon layer 6.

[0076] Step S153: While removing the N+ polysilicon layer 6 and the second tunneling oxide layer 5 from the second region and the spacer region 7 with alkaline solution, the film layer on the front side of the silicon substrate 1 corresponding to the second tunneling oxide layer 5 and the N+ polysilicon layer 6 is removed simultaneously, forming a textured structure on the spacer region 7 and the front side of the silicon substrate 1.

[0077] In other words, a single alkaline treatment can remove the N+ polycrystalline silicon layer 6 and the second tunneling oxide layer 5 from the second region and spacer region 7, as well as the film layer on the front side of the silicon substrate 1 corresponding to the second tunneling oxide layer 5 and the N+ polycrystalline silicon layer 6. Simultaneously, a textured structure can be formed on the spacer region 7 and the front side of the silicon substrate 1. The textured structure of the spacer region 7 and the textured structure of the front side of the silicon substrate 1 can be completed simultaneously, simplifying the fabrication process while ensuring the light utilization rate of the battery.

[0078] by Figure 8 Taking the structure shown as an example, step S153 can yield the following result: Figure 9 The structure shown. (As illustrated) Figure 9 As shown, this step removes the sixth film layer 6' corresponding to the N+ polycrystalline silicon layer 6 and the second tunneling oxide layer 5 corresponding to the fifth film layer 5' on the front side of the silicon substrate 1, resulting in a textured structure on both the spacer region 7 and the front side of the silicon substrate 1. This step S153 effectively simplifies the fabrication process while achieving selective texturing (texturing on the spacer region 7 and the front side of the silicon substrate 1), reducing interference from back-contact solar cell fabrication conditions and improving the light utilization efficiency of the fabricated back-contact solar cell.

[0079] Furthermore, regarding such Figure 9 The structure shown is achieved by removing the laser blocking layer 4 and the first silicon oxide layer 31 on the second region and the second silicon oxide layer 61 on the N+ polycrystalline silicon layer 6 in the first region through step S16, forming a fully passivated contact structure for the back contact solar cell, resulting in the structure shown. Figure 10 The structure shown. From Figure 10 As can be seen, in the obtained back-contact solar cell, not only are the P+ polycrystalline silicon layer 3 and the N+ polycrystalline silicon layer 6 isolated by the spacer region 7, but the first tunneling oxide layer 2 corresponding to the P+ polycrystalline silicon layer 3 and the second tunneling oxide layer 5 corresponding to the N+ polycrystalline silicon layer 6 are also isolated by the spacer region 7, so as to further reduce carrier recombination and help to further improve the photoelectric conversion efficiency of the back-contact solar cell.

[0080] The result obtained through the above process Figure 10 The bottom view of the structure (i.e., the planar structure on the back of the silicon substrate) can be seen as follows: Figure 11 As shown. From Figure 11 It can be seen that the P+ polycrystalline silicon layer 3 and N+ polycrystalline silicon layer 6 formed on the back side of the silicon substrate are arranged alternately, and there is a gap 7 between adjacent P+ polycrystalline silicon layer 3 and N+ polycrystalline silicon layer 6 to isolate the P+ polycrystalline silicon layer 3 and N+ polycrystalline silicon layer 6.

[0081] Furthermore, with Figure 10 Taking the structure shown as an example, after step S16 above, it may further include: forming a back passivation antireflection layer 8 in the first and second regions on the back side of the silicon substrate 1, and forming a front passivation antireflection layer 9 on the front side of the silicon substrate 1, to obtain the structure shown above. Figure 12 The structure shown is designed to improve the light absorption performance of back-contact solar cells. The front passivation antireflection layer 9 and the back passivation antireflection layer 8 can be formed simultaneously. These layers can be fabricated using one or more deposition methods, including LPCVD, PECVD, PVD, and ALD. Both the front and back passivation antireflection layers 9 and 8 can comprise at least one of aluminum oxide, silicon oxide, gallium oxide, silicon nitride, aluminum nitride, and silicon oxynitride. The simultaneous formation of the front and back passivation antireflection layers 9 and 8 effectively simplifies the fabrication process of back-contact solar cells.

[0082] Furthermore, with Figure 12 Taking the structure shown as an example, after forming the back passivation antireflection layer 8 and the front passivation antireflection layer 9, the above preparation method may further include: preparing a first electrode 101 that penetrates the back passivation antireflection layer 8 and is connected to the P+ polysilicon layer 3, and a second electrode 102 that is connected to the N+ polysilicon layer 6, respectively, to obtain the structure shown. Figure 13 The structure shown is such that the first electrode 101 and the second electrode 102 can be prepared simultaneously, and the first electrode 101 and the second electrode 102 can be prepared using any of the following methods for preparing metal electrodes.

[0083] The first method for preparing a metal electrode involves printing a paste for the first electrode 101 and a paste for the second electrode 102 in the regions where the P+ polysilicon layer 3 and the N+ polysilicon layer 6 are located, respectively, followed by sintering. The pastes for the first electrode 101 and the second electrode 102 are burned through the back passivation and antireflection layer 8 and come into contact with the P+ polysilicon layer 3 and the N+ polysilicon layer 6, respectively.

[0084] The second method for preparing metal electrodes involves using laser film cutting in the regions where the P+ polycrystalline silicon layer 3 and the N+ polycrystalline silicon layer are located, printing the paste for the first electrode 101 and the paste for the second electrode 102 respectively, and covering the film cutting areas. The resulting area is then sintered to obtain the first electrode 101 and the second electrode 102.

[0085] The third method for preparing metal electrodes involves using laser film cutting in the regions where the P+ polysilicon layer 3 and the N+ polysilicon layer are located, and then depositing the first electrode 101 and the second electrode 102 by electroplating.

[0086] It is worth noting that the embodiments of the present invention involve Figures 2 to 4 Appendix Figures 6 to 10 , Figure 12 as well as Figure 13 This is merely an example of a partial structure corresponding to adjacent P+ polysilicon layer 3 and N+ polysilicon layer 6. Those skilled in the art can combine this partial structure with... Figure 11 The complete structure is obtained.

[0087] The back-contact solar cell fabrication methods provided in the above embodiments, by setting a laser blocking layer on the P+ polycrystalline silicon layer, on the one hand, when removing the silicon dioxide layer of the second region and the spacer region by laser, the laser blocking layer in the second region can absorb laser energy, preventing laser energy from being conducted to the P+ polycrystalline silicon layer and the first tunnel oxide layer that need to be retained in the back-contact solar cell. This avoids damage to the P+ polycrystalline silicon layer and the first tunnel oxide layer on the second region by the laser treatment in this step, thereby further ensuring the integrity of the P+ polycrystalline silicon layer and the first tunnel oxide layer of the back-contact solar cell, ensuring cell performance, and also contributing to the stability of the fabrication process. On the other hand, during the process of removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, the laser blocking layer can absorb laser energy, blocking the conduction of laser energy, and because during the process of removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, the laser blocking layer can absorb laser energy, blocking the conduction of laser energy, and because during the process of removing the laser blocking layer and the first silicon dioxide ... second region, the laser blocking layer can absorb laser energy, blocking the conduction of After laser removal of the laser blocking layer in the first region on the back side of the silicon substrate, there are steps including alkaline polishing to remove the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region on the back side of the silicon substrate, and controlling the formation of a second tunneling oxide layer and an N+ polycrystalline silicon layer stacked on the second tunneling oxide layer, which are isolated from and alternately arranged with the first tunneling oxide layer and the P+ polycrystalline silicon layer in the first region on the back side of the silicon substrate. That is, after laser treatment, a second tunneling oxide layer located below the N+ polycrystalline silicon layer is re-formed. Therefore, during the laser treatment process, there is no need to consider the damage to the first tunneling oxide layer and the P+ polycrystalline silicon layer, which gives the laser a wider operating window. Furthermore, by removing the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, the width of the first region can be controlled more precisely, which is beneficial to reducing the production cost of back contact solar cells and promoting the commercialization of back contact solar cells.

[0088] Furthermore, given the wider operating window of the laser and the fact that the laser removal process of the first region's laser blocking layer does not require consideration of damage to the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region, the subsequent removal of the laser blocking layer in the second region via acid cleaning ensures that the laser blocking layer is not retained in the final cell structure. Therefore, the setting and thickness of the laser blocking layer do not affect the back-contact solar cell. Based on this, the thickness of the laser blocking layer can be adjusted as needed, resulting in better process flexibility and a wider operating window for the back-contact solar cell fabrication process.

[0089] Furthermore, due to the steps of removing the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region through alkaline polishing, and the controlled formation of a second tunneling oxide layer and an N+ polycrystalline silicon layer stacked on the second tunneling oxide layer in the first region on the back side of the silicon substrate, which are isolated from and alternately arranged with the first tunneling oxide layer and the P+ polycrystalline silicon layer, i.e., the second tunneling oxide layer located below the N+ polycrystalline silicon layer is re-formed after laser treatment, even if the laser damages the tunneling oxide layer corresponding to the N+ doped polycrystalline silicon layer under a wide laser operating window, it will not affect the photoelectric conversion performance of the back contact solar cell, thereby improving the stability of the back contact solar cell fabrication process and effectively improving the relative consistency of photoelectric conversion efficiency among the fabricated back contact solar cells. In addition, removing the first tunneling oxide layer and P+ polycrystalline silicon layer in the first region through alkaline polishing can avoid residual P+ doped elements in the first region, thereby reducing carrier recombination in the first region and effectively improving the photoelectric conversion efficiency of the back contact solar cell.

[0090] In addition, in the solution provided in the above embodiments, the areas where the first tunneling oxide layer is formed and the areas where the second tunneling oxide layer is formed are polished surfaces through polishing treatment, so as to ensure the flatness and uniformity of the first tunneling oxide layer, the second tunneling oxide layer, the P+ polycrystalline silicon layer and the N+ polycrystalline silicon layer, so as to effectively improve the passivation effect and photoelectric conversion efficiency of the back contact solar cell.

[0091] In addition, texturing of the spacer region and the front side is completed during the removal of N+ polycrystalline silicon and second silicon oxide from the second region and the spacer region, so that the spacer region and the front side of the fabricated back contact solar cell have a textured structure, which simplifies the fabrication process while ensuring the light utilization rate of the back contact solar cell.

[0092] The cross-sectional structure diagram and top view of the back contact solar cell obtained based on the fabrication methods provided in the above embodiments can be respectively shown in the figure. Figure 10 and Figure 11 As shown.

[0093] like Figure 10 and Figure 11As shown, the back-contact solar cell may include:

[0094] Silicon substrate 1;

[0095] A first tunneling oxide layer 2 and a second tunneling oxide layer 5 are formed on the back side of the silicon substrate 1, are phase-isolated and alternately arranged;

[0096] A P+ polysilicon layer 3 is stacked on the first tunneling oxide layer 2;

[0097] An N+ polysilicon layer 6 is stacked on the second tunneling oxide layer 5;

[0098] A spacer region 7 is formed on the back side of the silicon substrate 1 to isolate the adjacent first tunneling oxide layer 2 and second tunneling oxide layer 5 as well as the adjacent P+ polysilicon layer 3 and N+ polysilicon layer 6.

[0099] The area on the back side of the silicon substrate 1 corresponding to the first tunneling oxide layer 2 and the second tunneling oxide layer 5 is a polished surface;

[0100] The silicon substrate 1 has a textured surface structure formed synchronously on the front side and the spacer region 7. The textured surface structure is formed synchronously during the process of forming a second tunneling oxide layer 5 and an N+ polysilicon layer 6 that are isolated from and alternately arranged with the first tunneling oxide layer 2 and the P+ polysilicon layer 3.

[0101] The silicon substrate 1 can be either a P-type silicon substrate or an N-type silicon substrate.

[0102] By setting the area on the back of the silicon substrate 1 corresponding to the first tunneling oxide layer 2 and the second tunneling oxide layer 5 as a polished surface, the integrity and uniformity of the first tunneling oxide layer 2 and the second tunneling oxide layer 5 can be ensured, so as to effectively achieve a fully passivated contact structure.

[0103] In addition, the textured surface structure formed simultaneously on the front side of the silicon substrate 1 and the spacer region 7 is formed simultaneously during the process of controlling the formation of the second tunneling oxide layer 5 and the N+ polycrystalline silicon layer 6, which are isolated from the first tunneling oxide layer 2 and the P+ polycrystalline silicon layer 3 and are arranged alternately. This simplifies the fabrication process of the back contact solar cell and is conducive to the commercialization of the back contact solar cell.

[0104] Furthermore, the textured structure provided on the front side of the silicon substrate 1 and the spacer region 7 is formed during the process of removing the N+ polycrystalline silicon layer 6 and the second tunneling oxide layer 5 formed on the second region and the spacer region 7 using an alkaline solution, so as to effectively simplify the process of the back contact solar cell.

[0105] In addition, the textured surface structure can effectively improve the light utilization rate of back-contact solar cells.

[0106] Furthermore, in order to effectively reduce carrier recombination in the back-contact solar cell and improve its isolation effect, the P+ polycrystalline silicon layer 3 and the N+ polycrystalline silicon layer 6, as well as the first tunneling oxide layer 2 and the second tunneling oxide layer 5, are separated by a spacer region 7. Generally, the width of the spacer region 7, or the spacing between adjacent P+ polycrystalline silicon layers 3 and N+ polycrystalline silicon layers 6, is 1 × 10⁻⁶. 3 nm~5×10 5 nm. The spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 refers to the distance between the side of the P+ polysilicon layer 3 closest to the N+ polysilicon layer 6 and the side of the N+ polysilicon layer 6 closest to the P+ polysilicon layer 3. This can be achieved by controlling the width of the spacing region 7 or by setting the spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 to 1 × 10⁻⁶. 3 nm~5×10 5 Any value in nm, such as 2 × 10 3 nm, 3×10 3 nm, 5×10 3 nm, 1×10 4 nm, 3×10 4 nm, 5×10 4 nm, 7×10 4 nm, 9×10 4 nm, 1×10 5 nm, 2×10 5 nm, 4×10 5 nm, 5×10 5 nm, etc., can effectively reduce carrier recombination while ensuring the P+ polysilicon layer 3 and N+ polysilicon layer 6.

[0107] The thickness of the first tunneling oxide layer 2 can be 0.5 nm to 3.0 nm.

[0108] In addition, the thickness of the second tunneling oxide layer 5 is 0.5 nm to 3.0 nm.

[0109] In addition, such as Figure 12 As shown, the aforementioned back-contact solar cell may further include: a back passivation and antireflection layer 8 formed on the back side of the silicon substrate 1, consisting of a P+ polycrystalline silicon layer 3, an N+ polycrystalline silicon layer 9, and a spacer region 7, and a front passivation and antireflection layer 9 formed on the front side of the silicon substrate 1, so as to effectively improve the light absorption effect of the back-contact solar cell.

[0110] Furthermore, such as Figure 13 As shown, the aforementioned back-contact solar cell may further include: a first electrode 101 connected to the back passivation and antireflection layer 8, a P+ polycrystalline silicon layer 3, and a second electrode 102 connected to the N+ polycrystalline silicon layer 6.

[0111] This invention also provides a photovoltaic module, which may include: a cell made of a back-contact solar cell as described above.

[0112] This invention also provides a power station, which may include the photovoltaic modules provided in the above embodiments.

[0113] The preparation method described above is explained in detail below with two specific examples.

[0114] Example 1:

[0115] Step A1: Perform double-sided polishing on the P-type silicon substrate;

[0116] Step B1: Using atomic deposition technology, at a deposition temperature of 100°C to 500°C, a first silicon dioxide tunneling oxide layer with a thickness of 1 nm is deposited on one main surface of a P-type silicon substrate (which serves as the back side of the silicon substrate), and a first film layer corresponding to the first silicon dioxide tunneling oxide layer is deposited on the other main surface of the P-type silicon substrate (which serves as the front side of the silicon substrate). The thickness of the first film layer is generally less than the thickness of the first silicon dioxide tunneling oxide layer.

[0117] Step C1: Using LPCVD (Low Pressure Chemical Vapor Deposition) equipment, an intrinsic amorphous silicon layer is grown on the first silicon dioxide tunneling oxide layer; then, using ion implantation equipment, boron is implanted into the intrinsic amorphous silicon layer, and high-temperature annealing is performed, wherein the annealing temperature is 800-950℃. After annealing, the boron-implanted amorphous silicon layer forms a 100-200nm P+ polycrystalline silicon layer, and a first silicon oxide layer is simultaneously formed on the P+ polycrystalline silicon layer, and a second film layer corresponding to the P+ polycrystalline silicon layer and a third film layer corresponding to the first silicon oxide layer are simultaneously formed on the first film layer.

[0118] Step D1: Deposit a 2×10⁻⁶ thick silicon oxide layer on the first silicon oxide layer using PVD. 5 A laser blocking layer of nm is formed, and a fourth film layer corresponding to the laser blocking layer is simultaneously formed on the third film layer;

[0119] Step E1: Remove the fourth and third films on the front side of the silicon substrate by acid etching;

[0120] Step F1: Remove the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, wherein the first region is alternately arranged with the second region where the laser blocking layer and the first silicon oxide layer are retained;

[0121] Step G1: Remove the first tunneling oxide layer and P+ polysilicon layer in the first region by alkaline polishing, and the front side of the silicon substrate corresponds to the second film layer and the first film layer, while simultaneously removing part of the silicon substrate in the first region;

[0122] Step H1: Using atomic deposition technology, at a deposition temperature of 100°C to 500°C, a second silicon dioxide tunneling oxide layer with a thickness of 1.5 nm is simultaneously deposited on the silicon substrate in the first region and the laser blocking layer in the second region. A fifth film layer corresponding to the second silicon dioxide tunneling oxide layer is deposited on another main surface of the P-type silicon substrate (this other main surface is regarded as the front side of the silicon substrate). The thickness of the fifth film layer is generally smaller than the thickness of the second silicon dioxide tunneling oxide layer.

[0123] Step I1: Using LPCVD (Low Pressure Chemical Vapor Deposition) equipment, an intrinsic amorphous silicon layer is grown on the second silicon dioxide tunneling oxide layer; then, using ion implantation equipment, phosphorus is implanted into the intrinsic amorphous silicon layer, followed by high-temperature annealing. After annealing, the phosphorus-implanted amorphous silicon layer forms an N+ polycrystalline silicon layer of 100-200 nm, and a second silicon oxide layer is simultaneously formed on the N+ polycrystalline silicon layer, as well as a sixth film layer corresponding to the N+ polycrystalline silicon layer and a seventh film layer corresponding to the second silicon oxide layer on the fifth film layer.

[0124] Step J1: Laser removal of the seventh film layer on the front side of the silicon substrate, as well as the second silicon oxide layer in the spacer region adjacent to the second region in the second region and the first region;

[0125] Step K1: Remove the N+ polysilicon layer and the second tunneling oxide layer in the second region and the spacer region by alkaline solution, as well as the second silicon oxide layer on the N+ polysilicon layer and the sixth and fifth films on the front side of the silicon substrate, and simultaneously form a textured structure in the spacer region and the front side of the silicon substrate.

[0126] Step L1: Deposit a back passivation antireflection layer in the first and second regions on the back side of the silicon substrate, and simultaneously deposit a front passivation antireflection layer on the front side of the silicon substrate;

[0127] Step M1: Print the first electrode paste and the second electrode paste in the regions where the P+ polysilicon layer and the N+ polysilicon layer are located, respectively, and sinter them. The first electrode paste and the second electrode paste burn through the back passivation antireflection layer and come into contact with the P+ polysilicon layer and the N+ polysilicon layer, respectively.

[0128] Example 2:

[0129] Step A2: Perform double-sided polishing on the N-type silicon substrate;

[0130] Step B2: Using an LPCVD device, deposit a first silicon dioxide tunneling oxide layer with a thickness of 2.5 nm on one main surface of a P-type silicon substrate (which serves as the back side of the silicon substrate), and deposit a first film layer corresponding to the first silicon dioxide tunneling oxide layer on the other main surface of the P-type silicon substrate (which serves as the front side of the silicon substrate). The thickness of the first film layer is generally less than the thickness of the first silicon dioxide tunneling oxide layer.

[0131] Step C2: Using a PECVD device, an intrinsic amorphous silicon layer is grown on the first silicon dioxide tunneling oxide layer; then, using an ion implantation device, boron is implanted into the intrinsic amorphous silicon layer, and high-temperature annealing is performed, wherein the annealing temperature is 800-950℃. After annealing, the boron-implanted amorphous silicon layer forms a 100-200nm P+ polycrystalline silicon layer, and a first silicon oxide layer is simultaneously formed on the P+ polycrystalline silicon layer, and a second film layer corresponding to the P+ polycrystalline silicon layer and a third film layer corresponding to the first silicon oxide layer are simultaneously formed on the first film layer.

[0132] Step D2: Deposit a 1×10⁻⁶ thickness on the first silicon oxide layer using a PECVD device. 4 A laser blocking layer of nm is formed, and a fourth film layer corresponding to the laser blocking layer is simultaneously formed on the third film layer;

[0133] Step E2: Remove the fourth and third films on the front side of the silicon substrate by acid etching;

[0134] Step F2: Remove the laser blocking layer and the first silicon oxide layer in the first region on the back side of the silicon substrate by laser, wherein the first region is alternately arranged with the second region where the laser blocking layer and the first silicon oxide layer are retained;

[0135] Step G2: Remove the first tunneling oxide layer and P+ polysilicon layer in the first region by alkaline polishing, and the front side of the silicon substrate corresponds to the second film layer and the first film layer, while simultaneously removing part of the silicon substrate in the first region;

[0136] Step H2: Using a PECVD device, a second silicon dioxide tunneling oxide layer with a thickness of 2nm is simultaneously deposited on the silicon substrate in the first region and the laser blocking layer in the second region. A fifth film layer corresponding to the second silicon dioxide tunneling oxide layer is deposited on another main surface of the P-type silicon substrate (this other main surface is the front side of the silicon substrate). The thickness of the fifth film layer is generally less than the thickness of the second silicon dioxide tunneling oxide layer.

[0137] Step I2: Using a PECVD device, an intrinsic amorphous silicon layer is grown on the second silicon dioxide tunneling oxide layer; then, using an ion implantation device, phosphorus is implanted into the intrinsic amorphous silicon layer, and high-temperature annealing is performed. After annealing, the phosphorus-implanted amorphous silicon layer forms an N+ polycrystalline silicon layer of 100-200 nm, and a second silicon oxide layer is simultaneously formed on the N+ polycrystalline silicon layer, as well as a sixth film layer corresponding to the N+ polycrystalline silicon layer and a seventh film layer corresponding to the second silicon oxide layer are simultaneously formed on the fifth film layer.

[0138] Step J2: Laser removal of the seventh film layer on the front side of the silicon substrate, as well as the second silicon oxide layer in the spacer region adjacent to the second region in the second region and the first region;

[0139] Step K2: Remove the N+ polysilicon layer and the second tunneling oxide layer in the second region and the spacer region by alkaline solution, as well as the second silicon oxide layer on the N+ polysilicon layer and the sixth and fifth films on the front side of the silicon substrate, and simultaneously form a textured structure in the spacer region and the front side of the silicon substrate.

[0140] Step L2: Deposit a back passivation antireflection layer in the first and second regions on the back side of the silicon substrate, and simultaneously deposit a front passivation antireflection layer on the front side of the silicon substrate;

[0141] Step M2: Laser film opening is performed in the regions where the P+ polysilicon layer and the N+ polysilicon layer are located. The paste for the first electrode and the paste for the second electrode are printed and covered in the film opening regions, and then sintered to obtain the first electrode and the second electrode.

[0142] In summary, the technical solutions provided by the various embodiments of the present invention are as follows:

[0143] Technical Solution 1: A method for fabricating a back-contact solar cell, comprising:

[0144] Step a: Perform double-sided polishing on silicon substrate 1;

[0145] Step b: A first tunneling oxide layer 2, a P+ polysilicon layer 3, and a laser blocking layer 4 are stacked from the inside to the outside on the back side of the silicon substrate 1. During the formation of the P+ polysilicon layer 3, a first silicon oxide layer 31 is simultaneously formed on the P+ polysilicon layer 3.

[0146] Step c: Remove the laser blocking layer 4 and the first silicon oxide layer 31 in the first region on the back side of the silicon substrate 1 by laser, wherein the first region is alternately arranged with a second region in which the laser blocking layer 4 and the first silicon oxide layer 31 are retained;

[0147] Step d: Remove the first tunneling oxide layer 2 and the P+ polysilicon layer 3 in the first region by alkaline polishing;

[0148] Step e: In a first region on the back side of the silicon substrate 1, a second tunneling oxide layer 5 and an N+ polysilicon layer 6 are formed in a controlled manner, which are isolated from the first tunneling oxide layer 2 and the P+ polysilicon layer 3 and are arranged alternately. Simultaneously, a texturing process is performed on the spacer region 7 adjacent to the second region in the first region and the front side of the silicon substrate 1, so that the spacer region 7 and the front side of the silicon substrate form a texturing structure. The spacer region 7 is used to isolate the adjacent P+ polysilicon layer 3 and the N+ polysilicon layer 6.

[0149] Step f: Remove the laser blocking layer 4 and the first silicon oxide layer 31 on the second region by acid cleaning.

[0150] Technical Solution 2: The method for fabricating a back-contact solar cell according to Technical Solution 1.

[0151] Regarding step b, in the process of forming the first tunneling oxide layer 2, the P+ polycrystalline silicon layer 3, the first silicon oxide layer 31, and the laser blocking layer 4, if multiple films are simultaneously formed on the front side of the silicon substrate 1,

[0152] Step b is followed by:

[0153] Step c': Remove the film layer on the front side of the silicon substrate 1 corresponding to the first silicon oxide layer 31 and the laser blocking layer 4 by acid etching or laser.

[0154] Technical Solution 3: The method for fabricating a back-contact solar cell according to Technical Solution 2 further includes:

[0155] During the alkaline polishing process in step d, the film layer on the front side of the silicon substrate 1 corresponding to the first tunneling oxide layer 2 and the P+ polycrystalline silicon layer 3 is removed simultaneously.

[0156] Technical Solution 4: The method for fabricating a back-contact solar cell according to any one of Technical Solutions 1 to 3, step e includes:

[0157] Step e1: A second tunneling oxide layer 5 and an N+ polysilicon layer 6 are simultaneously formed in the first region and the second region on the back side of the silicon substrate 1, wherein, during the formation of the N+ polysilicon layer 6, a second silicon oxide layer 61 is simultaneously formed on the N+ polysilicon layer 6.

[0158] Step e2: Laser removal of the second silicon oxide layer 61 in the second region and the spacer region 7 adjacent to the second region in the first region;

[0159] Step e3: While removing the N+ polysilicon layer 6 and the second tunneling oxide layer 5 from the second region and the spacer region 7 with an alkaline solution, a textured structure is formed on the front side of the spacer region 7 and the silicon substrate 1.

[0160] Technical Solution 5: The method for fabricating a back-contact solar cell according to Technical Solution 4.

[0161] In the case where multiple films are simultaneously formed on the front side of the silicon substrate 1 during the formation of the second tunneling oxide layer 5, the N+ polysilicon layer 6, and the second silicon oxide layer 61 in step e1, the method further includes step e2' after step e1: removing the film layer on the front side of the silicon substrate 1 corresponding to the second silicon oxide layer 61 by acid etching or laser.

[0162] And / or,

[0163] The back-contact solar cell fabrication method further includes: during the acid cleaning process in step f, simultaneously removing the second silicon oxide layer 61 on the N+ polycrystalline silicon layer 6 in the first region.

[0164] Technical Solution 6: The method for fabricating a back-contact solar cell according to Technical Solution 5 further includes:

[0165] In step e3, during the alkaline treatment, the film layer on the front side of the silicon substrate 1 corresponding to the second tunneling oxide layer 5 and the N+ polycrystalline silicon layer 6 is simultaneously removed.

[0166] Technical Solution 7: The method for fabricating a back-contact solar cell according to Technical Solution 1 or 5, further comprising, after step f:

[0167] Step g: A back passivation antireflection layer 8 is formed on the first and second regions on the back side of the silicon substrate 1, and a front passivation antireflection layer 9 is formed on the front side of the silicon substrate 1.

[0168] Technical Solution 8: The method for fabricating a back-contact solar cell according to Technical Solution 7, further comprising, after step g:

[0169] Step h: Prepare a first electrode 101 that penetrates the back passivation antireflection layer 8 and is connected to the P+ polysilicon layer 3, and a second electrode 102 that is connected to the N+ polysilicon layer 6.

[0170] Technical Solution 9: The method for fabricating a back-contact solar cell according to Technical Solution 1.

[0171] The thickness of the first tunneling oxide layer 2 is 0.5 nm to 3.0 nm;

[0172] And / or,

[0173] The thickness of the second tunneling oxide layer 5 is 0.5 nm to 3.0 nm.

[0174] Technical Solution 10: The method for fabricating a back-contact solar cell according to Technical Solution 1.

[0175] Step e further includes: controlling the width of the spacing region 7 or the spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6 to be 1×10. 3 nm~5×10 5 nm.

[0176] Technical Solution 11: According to the back contact solar cell fabrication method of Technical Solution 1, the laser blocking layer 4 is deposited from at least one of the following materials:

[0177] Silicon oxide, silicon oxynitride, and silicon nitride.

[0178] Technical Solution 12: A back-contact solar cell prepared by any one of the preparation methods described in Technical Solutions 1 to 11, comprising:

[0179] Silicon substrate 1;

[0180] A first tunneling oxide layer 2 and a second tunneling oxide layer 5 are formed on the back side of the silicon substrate 1, are phase-isolated and alternately arranged;

[0181] A P+ polysilicon layer 3 is stacked on the first tunneling oxide layer 2;

[0182] An N+ polysilicon layer 6 is stacked on the second tunneling oxide layer 5;

[0183] A spacer region 7 is formed on the back side of the silicon substrate 1 to isolate the adjacent first tunneling oxide layer 2 and second tunneling oxide layer 5, as well as the adjacent P+ polysilicon layer 3 and N+ polysilicon layer (6).

[0184] The area on the back side of the silicon substrate 1 corresponding to the first tunneling oxide layer 2 and the second tunneling oxide layer 5 is a polished surface;

[0185] The silicon substrate 1 and the spacer region 7 are provided with a textured surface structure formed simultaneously. The textured surface structure is formed simultaneously during the process of forming a second tunneling oxide layer 5 and an N+ polysilicon layer 6 that are isolated from and alternately arranged with the first tunneling oxide layer 2 and the P+ polysilicon layer 3.

[0186] Technical Solution 13: The back-contact solar cell according to Technical Solution 12,

[0187] The textured surface of the silicon substrate 1 and the spacer region 7 is formed during the process of removing the N+ polysilicon layer 6 and the second tunneling oxide layer 5 formed on the spacer region 7 using an alkaline solution.

[0188] Technical Solution 14: The back-contact solar cell according to Technical Solution 11 or 12,

[0189] The width of the spacer region 7, or the spacing between adjacent P+ polysilicon layers 3 and N+ polysilicon layers 6, is 1×10. 3 nm~5×10 5 nm;

[0190] And / or,

[0191] The thickness of the first tunneling oxide layer 2 is 0.5 nm to 3.0 nm;

[0192] And / or,

[0193] The thickness of the second tunneling oxide layer 5 is 0.5 nm to 3.0 nm.

[0194] The above steps are provided only to help understand the method, structure, and core ideas of this invention. Those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A method for fabricating a back-contact solar cell, characterized in that, include: Step a: Perform double-sided polishing on the silicon substrate (1); Step b: A first tunneling oxide layer (2), a P+ polysilicon layer (3) and a laser blocking layer (4) are stacked from the inside to the outside on the back side of the silicon substrate (1). During the formation of the P+ polysilicon layer (3), a first silicon oxide layer (31) is formed simultaneously on the P+ polysilicon layer (3). Step c: Remove the laser blocking layer (4) and the first silicon oxide layer (31) in the first region on the back side of the silicon substrate (1) by laser, wherein the first region is alternately arranged with the second region where the laser blocking layer (4) and the first silicon oxide layer (31) are retained; Step d: Remove the first tunneling oxide layer (2) and the P+ polysilicon layer (3) in the first region by alkaline polishing; Step e: In the first region on the back side of the silicon substrate (1), a second tunneling oxide layer (5) and an N+ polysilicon layer (6) stacked on the second tunneling oxide layer (5) are formed in a controlled manner, which are isolated from the first tunneling oxide layer (2) and the P+ polysilicon layer (3) and are alternately arranged. At the same time, the spacer region (7) adjacent to the second region in the first region and the front side of the silicon substrate (1) are texturized so that the spacer region (7) and the front side of the silicon substrate form a textured structure. The spacer region (7) is used to isolate the adjacent P+ polysilicon layer (3) and the N+ polysilicon layer (6). Step f: Remove the laser blocking layer (4) and the first silicon oxide layer (31) on the second region by acid cleaning.

2. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, In step b, during the formation of the first tunneling oxide layer (2), the P+ polycrystalline silicon layer (3), the first silicon oxide layer (31), and the laser blocking layer (4), multiple films are simultaneously formed on the front side of the silicon substrate (1). Step b is followed by: Step c': Remove the film layer on the front side of the silicon substrate (1) corresponding to the first silicon oxide layer (31) and the laser blocking layer (4) by acid etching or laser.

3. The method for fabricating a back-contact solar cell according to claim 2, characterized in that, Also includes: During the alkaline polishing process in step d, the film layer on the front side of the silicon substrate (1) corresponding to the first tunneling oxide layer (2) and the P+ polycrystalline silicon layer (3) is removed simultaneously.

4. The method for fabricating a back-contact solar cell according to any one of claims 1 to 3, characterized in that, Step e includes: Step e1: A second tunneling oxide layer (5) and an N+ polysilicon layer (6) are simultaneously formed in the first region and the second region on the back side of the silicon substrate (1), wherein, during the formation of the N+ polysilicon layer (6), a second silicon oxide layer (61) is simultaneously formed on the N+ polysilicon layer (6); Step e2: Laser removal of the second silicon oxide layer (61) in the second region and the spacer region (7) adjacent to the second region in the first region; Step e3: While removing the N+ polysilicon layer (6) and the second tunneling oxide layer (5) of the second region and the spacer region (7) by alkaline solution, a textured structure is formed on the front side of the spacer region (7) and the silicon substrate (1).

5. The method for fabricating a back-contact solar cell according to claim 4, characterized in that, In response to the situation where multiple films are simultaneously formed on the front side of the silicon substrate (1) during the formation of the second tunneling oxide layer (5), the N+ polysilicon layer (6) and the second silicon oxide layer (61) in step e1, the method further includes step e2' after step e1: removing the film layer on the front side of the silicon substrate (1) corresponding to the second silicon oxide layer (61) by acid etching or laser. And / or, The back contact solar cell fabrication method further includes: during the acid cleaning process in step f, simultaneously removing the second silicon oxide layer (61) on the N+ polycrystalline silicon layer (6) in the first region.

6. The method for fabricating a back-contact solar cell according to claim 5, characterized in that, Also includes: In step e3, during the alkaline treatment, the film layer on the front side of the silicon substrate (1) corresponding to the second tunneling oxide layer (5) and the N+ polycrystalline silicon layer (6) is simultaneously removed.

7. The method for fabricating a back-contact solar cell according to claim 1 or 5, characterized in that, Following step f, the method further includes: Step g: A back passivation antireflection layer (8) is formed on the first and second regions on the back side of the silicon substrate (1), and a front passivation antireflection layer (9) is formed on the front side of the silicon substrate (1).

8. The method for fabricating a back-contact solar cell according to claim 7, characterized in that, Following step g, the method further includes: Step h: Prepare a first electrode (101) that penetrates the back passivation antireflection layer (8) and is connected to the P+ polysilicon layer (3) and a second electrode (102) that is connected to the N+ polysilicon layer (6).

9. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, The thickness of the first tunneling oxide layer (2) is 0.5 nm to 3.0 nm; And / or, The thickness of the second tunneling oxide layer (5) is 0.5 nm to 3.0 nm.

10. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, Step e further includes: controlling the width of the spacing region (7) or the spacing between adjacent P+ polysilicon layers (3) and N+ polysilicon layers (6) to be 1×10. 3 nm~5×10 5 nm.

11. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, The laser blocking layer (4) is deposited from at least one of the following materials: Silicon oxide, silicon oxynitride, and silicon nitride.

12. A back-contact solar cell prepared by any one of the preparation methods according to claims 1 to 11, characterized in that, include: Silicon substrate (1); A first tunneling oxide layer (2) and a second tunneling oxide layer (5) are formed on the back side of the silicon substrate (1), are phase-isolated and alternately arranged; A P+ polycrystalline silicon layer (3) is stacked on the first tunneling oxide layer (2); An N+ polysilicon layer (6) is stacked on the second tunneling oxide layer (5); A spacer region (7) formed on the back side of the silicon substrate (1) for isolating the adjacent first tunneling oxide layer (2) and second tunneling oxide layer (5) as well as the adjacent P+ polysilicon layer (3) and N+ polysilicon layer (6); The area on the back side of the silicon substrate (1) corresponding to the first tunneling oxide layer (2) and the second tunneling oxide layer (5) is a polished surface; The silicon substrate (1) and the spacer region (7) are provided with a textured surface structure formed simultaneously. The textured surface structure is formed simultaneously during the process of controlling the formation of a second tunneling oxide layer (5) and an N+ polysilicon layer (6) that are isolated from and alternately arranged with the first tunneling oxide layer (2) and the P+ polysilicon layer (3).

13. The back-contact solar cell according to claim 12, characterized in that, The textured surface of the silicon substrate (1) and the spacer region (7) is formed during the process of removing the N+ polysilicon layer (6) and the second tunneling oxide layer (5) formed on the spacer region (7) using an alkaline solution.

14. The back-contact solar cell according to claim 11 or 12, characterized in that, The width of the spacer region (7) or the spacing between adjacent P+ polysilicon layers (3) and N+ polysilicon layers (6) is 1×10. 3 nm~5×10 5 nm; And / or, The thickness of the first tunneling oxide layer (2) is 0.5 nm to 3.0 nm; And / or, The thickness of the second tunneling oxide layer (5) is 0.5 nm to 3.0 nm.

Images