Back contact solar cell structure and preparation method thereof

Abstract

The invention relates to the field of photovoltaic technology, and discloses a back contact solar cell structure and a preparation method thereof, the back contact solar cell structure comprises a silicon substrate, the back surface of the silicon substrate is provided with a p-type region and an n-type region, and the height positions of the p-type region and the n-type region on the back surface of the silicon substrate are mutually staggered. According to the invention, the spacing structure, the n-type heavily doped region and the p-type heavily doped region are arranged in the vertical longitudinal mode, so that the n-type heavily doped region and the p-type heavily doped region are separated and staggered in the longitudinal height, the width occupied by the gap region in the transverse direction is greatly reduced, the width of the transverse n-type heavily doped region and the width of the transverse p-type heavily doped region are widened to the maximum extent, and the width of the gap region is increased to the maximum extent. And meanwhile, the n-type heavily doped region and the p-type heavily doped region are isolated, so that the electric leakage of the battery is reduced, and higher battery conversion efficiency is obtained.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a back-contact solar cell structure and a preparation method thereof. Background Art

[0002] The design schemes of conventional back contact battery structures are mainly divided into the following two types. One type of back contact battery does not have a gap area (hereinafter referred to as the gap area) on the back surface of the battery, that is, only an n-type heavily doped area and a p-type heavily doped area are provided on the back surface, such as Figure 1 As shown, the n-type heavily doped region is in direct contact with the p-type heavily doped region; another type of back contact battery structure has a gap region on the back surface, but the gap region is arranged in a lateral manner, that is, the gap region is arranged parallel to the n-type heavily doped region and the p-type heavily doped region on the back surface, as shown Figure 2 shown.

[0003] The first battery structure design does not have a gap area, so the carrier recombination in the n-type and p-type heavily doped areas is serious, the leakage current is high, and it is less in practical applications. The second battery structure design has a gap area, which separates the n-type and p-type heavily doped areas from the middle, greatly reducing the leakage current of the n-type heavily doped area and the p-type heavily doped area, significantly improving the open circuit voltage and fill factor of the battery, and has a higher battery conversion efficiency. It is currently widely used.

[0004] However, since the design of the gap region of the second battery structure is parallel to the n-type heavily doped region and the p-type heavily doped region, and the width of the gap region is limited by the preparation technology, it will inevitably occupy a certain width on the back surface. At present, the width is generally greater than 50 μm, and the typical value is 50~100 μm. As a result, the width of the n-type heavily doped region and the p-type heavily doped region is shortened laterally (because the wider the width of the n-type heavily doped region or the p-type heavily doped region, the larger the carrier collection area, the easier it is to collect, and the higher conversion efficiency is obtained at the battery end), resulting in a reduction in the carrier collection area and an increase in the difficulty of collection.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] The problem with the prior art is that the gap region is currently arranged in parallel laterally between the n-type heavily doped region and the p-type heavily doped region, which shortens the width of the n-type heavily doped region and the p-type heavily doped region, resulting in a reduction in the carrier collection area and an increase in the difficulty of collection. In order to solve the above problem, the present invention provides a back-contact solar cell structure and a preparation method thereof, wherein the spacing structure and the n-type heavily doped region and the p-type heavily doped region are arranged in a vertical longitudinal manner, so that the n-type heavily doped region and the p-type heavily doped region are separated and staggered in the vertical height, which greatly narrows the lateral width occupied by the gap region, which not only maximizes the lateral width of the n-type heavily doped region and the p-type heavily doped region, but also isolates the n-type from the p-type heavily doped region, thereby reducing the leakage of the battery, thereby obtaining a higher battery conversion efficiency.

[0007] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a back-contact solar cell structure, comprising a silicon substrate, wherein a p-type region and an n-type region are arranged on the back surface of the silicon substrate, and the p-type region and the n-type region are staggered in height position on the back surface of the silicon substrate.

[0008] In a specific embodiment, a gap region is provided on the sidewall at the height misalignment between the p-type region and the n-type region; the gap region is used to isolate the p-type region from the n-type region.

[0009] The present invention arranges the spacing structure and the n-type heavily doped region and the p-type heavily doped region in a vertical manner, so that the n-type region and the p-type region are separated and staggered in the vertical height, which greatly narrows the width occupied by the gap region in the lateral direction. It can not only maximize the width of the lateral n-type region and the p-type region, increase the carrier collection area, and reduce the collection difficulty, but also isolate the n-type and p-type regions, reduce the leakage of the battery, and significantly improve the open circuit voltage and fill factor of the battery, thereby obtaining a higher battery conversion efficiency.

[0010] In a specific embodiment, the surface of the gap region is a velvet structure. Setting the longitudinal gap structure surface as a velvet structure can control the lateral width of the gap structure to a few micrometers, which not only reduces the transmission resistance loss of the gap region, but also ensures that the width occupied in the lateral direction is small enough to avoid affecting the width of the n-type region and the p-type region.

[0011] In a specific embodiment, the height of the p-type region on the back surface of the silicon substrate is higher or lower than the height of the n-type region on the back surface of the silicon substrate.

[0012] The present invention does not limit the height of the p-type region and the n-type region. The heights of the two regions can be interchanged as long as they are separated by a height difference in the longitudinal direction.

[0013] In a specific embodiment, the longitudinal height of the gap region is 3 μm to 50 μm.

[0014] In a specific embodiment, the p-type region includes a p-type heavily doped region and a first passivation film layer on the back surface that are sequentially arranged on the back surface of the silicon substrate.

[0015] In a specific embodiment, the n-type region includes an n-type heavily doped region and a second passivation film layer on the back surface that are sequentially disposed on the back surface of the silicon substrate.

[0016] In a specific embodiment, the gap region is perpendicular to the silicon substrate, and the back surface of the silicon substrate is a step structure. The present invention sets the gap region in a vertical vertical structure, which can maximize the minimum width occupied by the gap region in the lateral direction compared to the inclined structure of the gap region.

[0017] In a specific embodiment, the gap region includes a back surface third passivation film layer disposed on the back surface of the silicon substrate.

[0018] In a specific embodiment, when the silicon substrate is an n-type silicon substrate, the height of the p-type region on the back surface of the silicon substrate is higher than the height of the n-type region on the back surface of the silicon substrate.

[0019] In a specific embodiment, when the silicon substrate is a p-type silicon substrate, the height of the p-type region on the back surface of the silicon substrate is lower than the height of the n-type region on the back surface of the silicon substrate.

[0020] In a second aspect, the present invention provides a method for preparing a back-contact solar cell structure, comprising the following steps: S1: Select an n-type or p-type silicon substrate as the substrate, and then polish the silicon substrate on both sides; S2: forming a p-type or n-type heavily doped film layer on the back surface of the silicon substrate, and retaining the BSG film layer or PSG film layer grown on the back surface after completion; S3: removing the BSG film layer or the PSG film layer on the surface of the n-type region or the p-type region reserved on the back surface of the silicon substrate; S4: removing the p-type or n-type heavily doped film layer formed on the surface of the reserved n-type region or p-type region by alkaline etching, and increasing the etching intensity to generate steps in the longitudinal direction of the reserved n-type region or p-type region as a gap region; S5: depositing a PSG film layer or a BSG film layer on the back surface of the silicon substrate; S6: a velvet structure is formed on the surface of the gap area; S7: annealing treatment activates the phosphorus source in the PSG film layer or the boron source in the BSG film layer to form an n-type heavily doped film layer or a p-type heavily doped film layer; S8: removing the BSG film layer and the PSG film layer on the surfaces of the p-type region and the n-type region.

[0021] The preparation method of the present invention prepares a p-type or n-type heavily doped film layer on the back surface of the substrate as a whole first, then forms a step while reserving the n-type area or the p-type area to remove the heavily doped film by etching, and then prepares the n-type or p-type heavily doped film layer, thereby obtaining a structure in which the n-type area and the p-type area are highly misaligned to form a longitudinal gap area.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. A back-contact solar cell structure and a preparation method thereof provided in an embodiment of the present invention, wherein the spacer structure and the n-type heavily doped region and the p-type heavily doped region are arranged in a vertical manner, so that the n-type region and the p-type region are separated and staggered in the vertical height, thereby reducing the leakage of the battery, significantly improving the open circuit voltage and fill factor of the battery, and thus obtaining a higher battery conversion efficiency; 2. A back-contact solar cell structure and a preparation method thereof provided by an embodiment of the present invention greatly narrows the lateral width of the gap region by setting a longitudinal structure gap region, and can maximize the width of the lateral n-type region and the p-type region, increase the carrier collection area, reduce the collection difficulty, and improve the battery conversion efficiency; 3. A back-contact solar cell structure and a preparation method thereof provided in an embodiment of the present invention sets the surface of the longitudinal gap structure to a velvet structure, so that the lateral width of the gap structure can be controlled at the level of several microns, which not only reduces the transmission resistance loss in the gap area, but also ensures that the width occupied in the lateral direction is small enough to avoid affecting the width of the n-type area and the p-type area. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the structure of an existing back contact solar cell; Figure 2 It is a schematic diagram of the structure of an existing back contact solar cell; Figure 3 A schematic diagram of the overall structure of a back-contact solar cell provided by the present invention; Figure 4 This is a schematic diagram of the specific layer structure of the back contact solar cell provided in Example 1 of the present invention.

[0025] Drawings and parts markings: 100-front surface region, 101-front surface passivation layer, 102-anti-reflection film layer, 200-silicon substrate, 300-p-type region, 301-p-type heavily doped region, 302-back surface first passivation film layer, 400-n-type region, 401-n-type heavily doped region, 402-back surface second passivation film layer, 500-gap region, 501-back surface third passivation film layer, 600-first metal electrode, 700-second metal electrode. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0027] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details need not be employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known materials or methods are not specifically described.

[0028] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0030] At present, the design schemes of conventional back contact battery structures are mainly divided into the following two types. One type of back contact battery does not have a gap area (hereinafter referred to as a gap area) on the back surface of the battery, that is, only an n-type heavily doped area and a p-type heavily doped area are set on the back surface, such as Figure 1As shown, the n-type heavily doped region is in direct contact with the p-type heavily doped region. Since no gap region is provided, carrier recombination is serious in the n-type and p-type heavily doped regions, leakage current is high, and is less in practical applications.

[0031] Another type of back contact battery structure has a gap region on the back surface, but the gap region is arranged in a lateral manner, that is, the gap region is arranged parallel to the n-type heavily doped region and the p-type heavily doped region on the back surface, such as Figure 2 As shown in the figure, due to the provision of the gap region, the n-type and p-type heavily doped regions are separated from each other, which greatly reduces the leakage current of the n-type heavily doped region and the p-type heavily doped region, significantly improves the open circuit voltage and fill factor of the battery, has a higher battery conversion efficiency, and is currently widely used. Due to the limitations of the preparation technology, the width of the gap region will inevitably occupy a certain width on the back surface, thereby shortening the width of the n-type heavily doped region and the p-type heavily doped region laterally, resulting in a reduction in the carrier collection area and an increase in the difficulty of collection.

[0032] In order to solve the above technical problems, In a first aspect, the present invention provides a back contact solar cell structure, such as Figure 3 As shown, it is an overall structure diagram, including a silicon substrate 200, a p-type region 300 and an n-type region 400 are arranged on the back surface of the silicon substrate 200, and the height positions of the p-type region 300 and the n-type region 400 on the back surface of the silicon substrate 200 are staggered.

[0033] In a specific embodiment, a gap region 500 is disposed on the sidewalls of the height misalignment between the p-type region 300 and the n-type region 400 ; the gap region is used to isolate the p-type region 300 from the n-type region 400 .

[0034] The present invention arranges the spacing structure and the n-type heavily doped region and the p-type heavily doped region in a vertical manner, so that the n-type region and the p-type region are separated and staggered in the vertical height, which greatly narrows the width occupied by the gap region in the lateral direction. It can not only maximize the width of the lateral n-type region and the p-type region, increase the carrier collection area, and reduce the collection difficulty, but also isolate the n-type and p-type regions, reduce the leakage of the battery, and significantly improve the open circuit voltage and fill factor of the battery, thereby obtaining a higher battery conversion efficiency.

[0035] In a specific embodiment, the surface of the gap region is a velvet structure. Setting the longitudinal gap structure surface as a velvet structure can control the lateral width of the gap structure to a few micrometers, which not only reduces the transmission resistance loss of the gap region, but also ensures that the width occupied in the lateral direction is small enough to avoid affecting the width of the n-type region and the p-type region.

[0036] In a specific embodiment, the height of the p-type region 300 on the back surface of the silicon substrate 200 is higher or lower than the height of the n-type region 400 on the back surface of the silicon substrate 200 .

[0037] The present invention does not limit the height of the p-type region and the n-type region. The heights of the two regions can be interchanged as long as they are separated by a height difference in the longitudinal direction.

[0038] In a specific embodiment, the longitudinal height of the gap region is 3 μm to 50 μm.

[0039] In a specific embodiment, if Figure 4 As shown, the p-type region 300 includes a p-type heavily doped region 301 and a first back surface passivation film layer 302 sequentially disposed on the back surface of the silicon substrate 200 .

[0040] In a specific embodiment, the n-type region 400 includes an n-type heavily doped region 401 and a second back surface passivation film layer 402 sequentially disposed on the back surface of the silicon substrate 200 .

[0041] In a specific embodiment, the gap region 500 is perpendicular to the silicon substrate 200, and the back surface of the silicon substrate 200 is a step structure. The present invention sets the gap region in a vertical structure, which can minimize the width of the gap region in the lateral direction compared to the inclined structure of the gap region.

[0042] In a specific embodiment, the gap region 500 includes a back surface third passivation film layer 501 disposed on the back surface of the silicon substrate 200 .

[0043] In a specific embodiment, when the silicon substrate 200 is an n-type silicon substrate, the height of the p-type region 300 on the back surface of the silicon substrate 200 is higher than the height of the n-type region 400 on the back surface of the silicon substrate 200 .

[0044] In a specific embodiment, when the silicon substrate 200 is a p-type silicon substrate, the height of the p-type region 300 on the back surface of the silicon substrate 200 is lower than the height of the n-type region 400 on the back surface of the silicon substrate 200 .

[0045] In a second aspect, the present invention provides a method for preparing a back-contact solar cell structure, comprising the following steps: S1: Select an n-type or p-type silicon substrate as the substrate, and then polish the silicon substrate on both sides; S2: forming a p-type or n-type heavily doped film layer on the back surface of the silicon substrate, and retaining the BSG film layer or PSG film layer grown on the back surface after completion; S3: removing the BSG film layer or the PSG film layer on the surface of the n-type region or the p-type region reserved on the back surface of the silicon substrate; S4: removing the p-type or n-type heavily doped film layer formed on the surface of the reserved n-type region or p-type region by alkaline etching, and increasing the etching intensity to generate steps in the longitudinal direction of the reserved n-type region or p-type region as a gap region; S5: depositing a PSG film layer or a BSG film layer on the back surface of the silicon substrate; S6: a velvet structure is formed on the surface of the gap area; S7: annealing treatment activates the phosphorus source in the PSG film layer or the boron source in the BSG film layer to form an n-type heavily doped film layer or a p-type heavily doped film layer; S8: removing the BSG film layer and the PSG film layer on the surfaces of the p-type region and the n-type region.

[0046] The preparation method of the present invention prepares a p-type or n-type heavily doped film layer on the back surface of the substrate as a whole first, then forms a step while reserving the n-type area or the p-type area to remove the heavily doped film by etching, and then prepares the n-type or p-type heavily doped film layer, thereby obtaining a structure in which the n-type area and the p-type area are highly misaligned to form a longitudinal gap area.

[0047] Example 1 like Figure 4 As shown, an embodiment of the present invention provides a method for preparing a back contact solar cell structure, comprising the following steps: S1: Selecting an n-type silicon substrate 200 as a substrate, and then performing double-sided polishing on the silicon substrate 200; S2: A p-type heavily doped film layer is made on the back surface by boron diffusion. After the diffusion, the BSG layer grown on the back surface is retained to serve as a mask layer for the next step. S3: laser patterning to remove the BSG film layer on the surface of the reserved n-type heavily doped region 401 on the back surface; S4: removing the BSG film layer introduced in step S2 of the front surface region 100 by chain etching, and then removing the p-type heavily doped film layer expanded at the edge of the front surface in step S2 of the front surface by alkali etching, and removing the p-type heavily doped film layer formed on the surface of the reserved n-type heavily doped region 401 at the same time; and increasing the etching intensity so that an obvious step region is generated vertically between the reserved n-type heavily doped region 401 and the p-type heavily doped region 301 to serve as the gap region 500; S5: depositing a PSG film layer on the back surface by PVD; S6: performing a texturing process so that a suede structure is formed on the surface of the front surface area 100 and the gap area 500 of the battery; S7: annealing treatment activates the phosphorus source in the PSG film layer, thereby forming an n-type heavily doped film layer; S8: removing the BSG film layer on the surface of the p-type heavily doped region and the PSG film layer on the surface of the n-type heavily doped region by wet cleaning; S9: depositing a first passivation film layer 302 , a third passivation film layer 501 , and a second passivation film layer 402 on the back surface by PECVD; S10: a front surface passivation layer 101 and an anti-reflection film layer 102 are sequentially deposited on the front surface region 100; S11: printing the first metal electrode 600 and the second metal electrode 700, and then drying and sintering them so that the first metal electrode 600 forms an ohmic contact with the p-type heavily doped region 301, and the second metal electrode 700 forms an ohmic contact with the n-type heavily doped region 401.

[0048] The longitudinal height of the gap region 500 is 5 μm.

[0049] Example 2 The preparation method of the embodiment of the present invention is the same as that of the embodiment 1, except that the longitudinal height of the gap region 500 is 25 μm.

[0050] Example 3 The preparation method of the embodiment of the present invention is the same as that of the embodiment 1, except that the longitudinal height of the gap region 500 is 50 μm.

[0051] Example 4 An embodiment of the present invention provides a method for preparing a back-contact solar cell structure, comprising the following steps: S1: Select a p-type silicon substrate 200 as a substrate, and then perform double-sided polishing on the silicon substrate 200; S2: The n-type heavily doped film layer is made on the back surface by phosphorus diffusion. After diffusion, the PSG layer grown on the back surface is retained to serve as a mask layer for the next step; S3: laser patterning to remove the PSG film layer on the surface of the reserved p-type heavily doped region 301 on the back surface; S4: removing the PSG film layer introduced in step S2 of the front surface region 100 by chain etching, and then removing the n-type heavily doped film layer expanded around the edge of the front surface in step S2 of the front surface by alkali etching, and removing the n-type heavily doped film layer formed on the surface of the reserved p-type heavily doped region 301 at the same time; and increasing the etching intensity so that an obvious step is generated vertically between the reserved p-type heavily doped region 301 and the n-type heavily doped region 401 to serve as a gap region 500; S5: depositing a BSG film layer on the back surface by PVD; S6: Texturing treatment is performed so that the front surface area 100 and the gap area 500 of the battery form a suede structure; S7: Annealing treatment activates the boron source in the BSG film layer, thereby forming a p-type heavily doped region; S8: wet cleaning to remove the PSG mask layer on the surface of the p-type heavily doped region 301 and the BSG film layer on the surface of the n-type heavily doped region; S9: depositing a first passivation film layer 302 , a third passivation film layer 501 , and a second passivation film layer 402 on the back surface by PECVD; S10: a front surface passivation layer 101 and an anti-reflection film layer 102 are sequentially deposited on the front surface region 100; S11: printing the first metal electrode 600 and the second metal electrode 700, and then drying and sintering them so that the first metal electrode 600 forms an ohmic contact with the n-type heavily doped region 401, and the second metal electrode 700 forms an ohmic contact with the p-type heavily doped region 301.

[0052] Comparative Example This comparative example provides a back contact solar cell structure, such as Figure 2 As shown, the width of the gap region is 100 μm.

[0053] The battery structures prepared in Examples 1-3 and the comparative example were tested for performance parameters, and the results are shown in Table 1 below.

[0054] Table 1 Gap area vertical height (μm) Battery efficiency (%) Open circuit voltage(mV) Short circuit current density(A) Fill factor(%) Example 1 5 25.27 725.83 13.79 83.51 Example 2 25 25.24 726.26 13.77 83.50 Example 3 50 25.19 726.38 13.74 83.48 Figure 2 Battery structure (comparative example) 100 25.04 726.27 13.67 83.44 It can be seen from Table 1 that the present invention can improve the conversion efficiency of the battery by vertically arranging the gap structure in the longitudinal direction compared with the existing lateral gap area.

[0055] In addition, the present invention also uses software simulation calculation, if Figure 2 If the width of the gap area is reduced from 100 μm to 50 μm, and the reduced width of the gap area is increased to the width of the emitter area, the battery end efficiency gain can reach 0.1%.

[0056] The longitudinal height of the gap region provided by the present invention is obtained by wet etching, which has high control accuracy and can reduce the width of the gap region to 3 μm. Therefore, the battery structures of Examples 1 and 2 of the present invention are superior to those of the prior art. Figure 2 The battery structure can achieve at least 0.1% improvement in battery conversion efficiency.

[0057] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A back-contact solar cell structure, comprising a silicon substrate (200), wherein a p-type region (300) and an n-type region (400) are provided on the back surface of the silicon substrate (200), characterized in that: The height positions of the p-type region (300) and the n-type region (400) on the back surface of the silicon substrate (200) are staggered with each other.

2. A back contact solar cell structure according to claim 1, characterized in that: A gap region (500) is provided on the side wall at the height misalignment between the p-type region (300) and the n-type region (400); The gap region is used to isolate the p-type region (300) and the n-type region (400).

3. A back contact solar cell structure according to claim 2, characterized in that: The surface of the gap area is a suede structure.

4. The back contact solar cell structure according to claim 2, characterized in that: The height of the p-type region (300) on the back surface of the silicon substrate (200) is higher or lower than the height of the n-type region (400) on the back surface of the silicon substrate (200).

5. A back contact solar cell structure according to claim 2, characterized in that: The longitudinal height of the gap region is 3 μm to 50 μm.

6. The back contact solar cell structure according to claim 2, characterized in that: The p-type region (300) comprises a p-type heavily doped region (301) and a first back surface passivation film layer (302) sequentially arranged on the back surface of the silicon substrate (200); the n-type region (400) comprises an n-type heavily doped region (401) and a second back surface passivation film layer (402) sequentially arranged on the back surface of the silicon substrate (200).

7. The back contact solar cell structure according to claim 2, characterized in that: The gap region (500) is perpendicular to the silicon substrate (200), and the back surface of the silicon substrate (200) presents a step structure.

8. The back contact solar cell structure according to claim 7, characterized in that: The gap region (500) comprises a back surface third passivation film layer (501) arranged on the back surface of the silicon substrate (200).

9. The back contact solar cell structure according to claim 4, characterized in that: When the silicon substrate (200) is an n-type silicon substrate, the height of the p-type region (300) on the back surface of the silicon substrate (200) is higher than the height of the n-type region (400) on the back surface of the silicon substrate (200); when the silicon substrate (200) is a p-type silicon substrate, the height of the p-type region (300) on the back surface of the silicon substrate (200) is lower than the height of the n-type region (400) on the back surface of the silicon substrate (200).

10. The method for preparing a back contact solar cell structure according to any one of claims 1 to 9, characterized in that: The steps include: S1: Select an n-type or p-type silicon substrate as the substrate, and then polish the silicon substrate on both sides; S2: forming a p-type heavily doped film layer or an n-type heavily doped film layer on the back surface of the silicon substrate, and retaining the BSG film layer or PSG film layer grown on the back surface after completion; S3: removing the BSG film layer or the PSG film layer on the surface of the n-type region or the p-type region reserved on the back surface of the silicon substrate; S4: removing the p-type heavily doped film layer or the n-type heavily doped film layer formed on the surface of the reserved n-type region or the p-type region by alkaline etching, and increasing the etching intensity to generate steps in the longitudinal direction of the reserved n-type region or the p-type region as a gap region; S5: depositing a PSG film layer or a BSG film layer on the back surface of the silicon substrate; S6: a velvet structure is formed on the surface of the gap area; S7: annealing treatment activates the phosphorus source in the PSG film layer or the boron source in the BSG film layer in S5 to form an n-type heavily doped film layer or a p-type heavily doped film layer; S8: removing the BSG film layer and the PSG film layer on the surfaces of the p-type region and the n-type region.

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