Photovoltaic cell and back structure thereof, back structure preparation method, and laminated cell and photovoltaic module

Abstract

The application discloses a photovoltaic cell and a back structure thereof, a preparation method of the back structure, a laminated cell and a photovoltaic module, and belongs to the technical field of photovoltaics. The isolation area comprises at least two of a platform structure, a convex structure and a tapered structure, wherein: the platform structure extends in a substantially horizontal direction as a whole; the convex structure protrudes from the inner side of the semiconductor substrate to the outer side thereof; and the tapered structure is formed by recessing from the back surface of the semiconductor substrate to the inner side thereof. The structure and morphology of the isolation area are optimized by graphical design, so that the isolation area forms a combined structure comprising at least two of the platform structure, the convex structure and the tapered structure, thereby improving the light absorption rate of the back surface of the solar cell while ensuring the isolation effect.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, and more specifically, relates to a photovoltaic cell and its back structure, a method for preparing the back structure, a tandem cell, and a photovoltaic module. Background Technology

[0002] In back-contact solar cells, the positive and negative metal electrodes are arranged in an interdigitated pattern on the back surface of the cell. This design ensures that the front surface of the cell is free of any metal grid lines, maximizing the light-receiving area, reducing optical losses, and improving short-circuit current and overall photoelectric conversion efficiency. This is one of the current technological directions for fabricating high-efficiency crystalline silicon solar cells. However, since back-contact solar cells place both the positive and negative electrodes on the back of the cell, they need to be separated to prevent short circuits caused by interconnection. This requires the creation of a junction isolation region or channel region. Current channel fabrication processes typically utilize a combination of two laser overlay processes and a wet process to form a channel of a specific shape.

[0003] To ensure effective separation, current trench designs typically employ conventional laser ablation techniques to create rectangular trenches. For example, patent CN 119855305 A utilizes masking technology, employing two overlapping laser beams to create rectangular trenches. While designing the trenches as rectangular achieves the desired separation, the required width and depth are significant, which substantially impacts the efficiency of the solar cells.

[0004] For example, Chinese patent CN 120583786 A discloses a solar cell, its fabrication method, and a photovoltaic module. This method uses a laser multi-overlapping technique in the trench region to create an arched protrusion structure, thereby increasing the textured surface area of ​​the back partition region and improving the light absorption capacity of the partition region. However, a single protrusion structure and textured surface design cannot guarantee the effective utilization of the light absorption capacity of the partition region, thus limiting the improvement in the back light absorption rate of the solar cell.

[0005] Therefore, how to maximize the light absorption rate on the back of the solar cell while ensuring that the isolation effect of the isolation zone is not weakened is the key issue that should be explored in the current graphic design of solar cells. Summary of the Invention

[0006] The first objective of this invention is to provide a photovoltaic cell back structure that optimizes the structural morphology of the isolation region (or trench region) through graphical design, so that the isolation region forms a combination structure of at least two morphologies including a platform structure, a raised structure and a conical structure, thereby further improving the light absorption rate of the back of the solar cell while ensuring the isolation effect.

[0007] Another objective of this invention is to provide a method for preparing the back structure of the above-mentioned photovoltaic cell. By using a multi-line patterning method to perform laser patterning on the trench region, an isolation region structure including at least two morphologies among a platform structure, a protruding structure, and a conical structure can be prepared. Another object of the present invention is to provide a photovoltaic cell comprising the above-described backside structure; Another object of the present invention is to provide a tandem battery comprising the above-mentioned photovoltaic cells and a photovoltaic module.

[0008] To achieve the above objectives, the technical solution provided by this invention is as follows: The first aspect of the present invention provides a back structure of a photovoltaic cell, including a first doped region and a second doped region disposed alternately along a first direction on the back side of a semiconductor substrate, and an isolation region is provided between the first doped region and the second doped region. The isolation zone includes at least two of the following: platform structure, raised structure, and conical structure, wherein: The platform structure extends primarily horizontally. The protrusion structure protrudes from the inside of the semiconductor substrate toward the outside. The tapered structure is formed by a recess inward from the back side of the semiconductor substrate.

[0009] According to any of the embodiments described in the first aspect of the invention, the isolation zone includes a raised structure and at least one platform structure or a conical structure.

[0010] According to any embodiment of the first aspect of the present invention, the isolation zone includes a raised structure and two platform structures or two conical structures, the two platform structures or two conical structures being located on both sides of the raised structure.

[0011] According to any embodiment of the first aspect of the present invention, the isolation zone includes a raised structure, at least one platform structure, and at least one conical structure.

[0012] According to any embodiment of the first aspect of the present invention, the protrusion structure is located in the middle region of the isolation region along the first direction, and its two sides are respectively connected to the first doped region and the second doped region through a platform structure and / or a conical structure.

[0013] According to any of the embodiments described in the first aspect of the present invention, the isolation zone includes a protruding structure, four platform structures and two conical structures, wherein two platform structures and one conical structure are symmetrically provided on each side of the protruding structure, and the conical structure is connected between the two platform structures.

[0014] According to any of the embodiments described in the first aspect of the present invention, the platform structure, the protruding structure, and the conical structure adopt a velvety surface design or a polished surface.

[0015] According to any of the embodiments described in the first aspect of the present invention, the primary platform structures directly connected to the protruding structure all adopt a large-size velvet structure, and the secondary platform structures located on one side of the protruding structure and not directly connected to the protruding structure adopt a small-size velvet structure. The tower base size of the large-size velvet structure is larger than the tower base size of the small-size velvet structure.

[0016] According to any embodiment of the first aspect of the present invention, the base size of the small-sized velvet surface is 0.5-1.5 μm, and the base size of the large-sized velvet surface is 2-5 μm.

[0017] According to any of the embodiments described in the first aspect of the present invention, the conical structure adopts a velvet structure design, and the velvet size (tower base size) is 0.1-1μm.

[0018] According to any of the embodiments described in the first aspect of the present invention, the protruding structure adopts a velvet structure design, and the velvet size (tower base size) is 0.3-1.8μm, more preferably 0.3-1.5μm.

[0019] According to any of the embodiments described in the first aspect of the present invention, the protruding structure adopts an arc-shaped structure, a rounded rectangle structure, or a trapezoidal structure, or is formed by any combination of the above-mentioned arc-shaped structure, rounded rectangle structure, and trapezoidal structure.

[0020] According to any embodiment of the first aspect of the present invention, the width dimension of the tapered structure is less than or equal to the width dimension of the platform structure and less than or equal to the width dimension of the protruding structure.

[0021] According to any of the embodiments described in the first aspect of the present invention, there is a height gradient between the platform structure, the protruding structure and the conical structure along the second direction; And / or the width dimension L2 of the conical structure is 2~40μm, and the depth L3 along the second direction is 3~10μm; And / or the width dimension L1 of the protrusion structure is 20~200μm, and the height H1 away from the semiconductor substrate along the second direction is 0.3~2μm.

[0022] According to any embodiment of the first aspect of the present invention, the first doped region is provided with a first functional layer, the first functional layer including a first doped semiconductor layer, the second doped region is provided with a second functional layer, the second functional layer including a second doped semiconductor layer, and the first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types.

[0023] According to any aspect of the present invention, at least one of the first doped semiconductor layer and the second doped semiconductor layer is provided with a dielectric layer between itself and the semiconductor substrate; And / or the first doped semiconductor layer and the second doped semiconductor layer are provided with a passivation layer and / or an anti-reflection layer on the side away from the semiconductor substrate.

[0024] A second aspect of the present invention provides a method for fabricating the back structure of a photovoltaic cell as described in the first aspect, comprising: Provide semiconductor substrates; A first doped region is formed on the back side of a semiconductor substrate, and the first doped region is provided with a first functional layer; A second doped region is formed on the back side of the semiconductor substrate, and the first doped region is provided with a second functional layer; An isolation region is formed on the back side of the semiconductor substrate and between the first doped region and the second doped region.

[0025] According to any embodiment of the second aspect of the present invention, forming an isolation region on the back side of the semiconductor substrate and located between the first doped region and the second doped region includes: processing the back side of the semiconductor substrate corresponding to the isolation region by means of a laser patterning process.

[0026] According to any of the embodiments described in the second aspect of the present invention, when processing the back side of the semiconductor substrate corresponding to the isolation region using a laser patterning process, the platform structure, the bump structure, and the tapered structure are all fabricated using a multi-line splicing method, wherein: The platform structure is formed using a high-power, multi-overlapping method, with a laser power of 40-80W and an overlap rate of 50-80%. The laser power of the raised structure is 5-30W, the overlap rate is 0-50%, and the laser power and overlap rate decrease sequentially from the two edges of the raised structure to its apex. The laser power of the conical structure is 30-50W, and the overlap rate is 0-50%.

[0027] According to any of the embodiments described in the second aspect of the present invention, the method specifically includes the following steps: Provide semiconductor substrates; A first functional layer is formed on the back side of the semiconductor substrate; A portion of the first functional layer on the back side of the semiconductor substrate is removed, leaving only the first functional layer corresponding to the first doped region, so that the semiconductor substrate corresponding to the second doped region and the isolation region is exposed. A second functional layer is formed on the back side of the semiconductor substrate; Laser patterning is performed on the first doped region on the back side of the semiconductor substrate to remove the corresponding second functional layer. Laser patterning is performed on the isolation region on the back side of the semiconductor substrate to remove the corresponding second functional layer and form the corresponding isolation region morphology.

[0028] According to any embodiment of the second aspect of the present invention, after laser patterning of the first doped region and the isolation region, etching and wet texturing are performed to form a textured surface in the isolation region; the wet texturing uses an alkaline solution with a concentration of 1.5-1.8%.

[0029] A third aspect of the present invention also provides a photovoltaic cell, including a semiconductor substrate, the semiconductor substrate including a front side and a back side disposed opposite to each other, wherein the back side structure of the photovoltaic cell adopts any of the back side structures described in the first aspect of the present invention, or a back side structure prepared by any of the preparation methods described in the second aspect of the present invention.

[0030] A fourth aspect of the present invention also provides a stacked battery, comprising a top battery, an intermediate connecting layer and a bottom battery stacked sequentially, wherein the bottom battery has the back structure described in the first aspect of the present invention, or adopts the photovoltaic cell described in the third aspect of the present invention.

[0031] The fifth aspect of the present invention also provides a photovoltaic module, including the photovoltaic cell described in the third aspect of the present invention, or the tandem cell described in the fourth aspect of the present invention.

[0032] Compared with the prior art, the technical solution provided by this invention has the following advantages: (1) The present invention optimizes the design of the isolation region on the back of the photovoltaic cell. The isolation region includes at least two of the following morphologies: platform structure, protrusion structure and conical structure. This can reduce the etching of the semiconductor substrate while effectively ensuring the isolation effect, thereby greatly reducing the proportion of the area occupied by the channel on the back of the silicon substrate. This is beneficial to improving the light absorption rate on the back of the photovoltaic cell and the efficiency of the cell.

[0033] (2) Specifically, the platform structure of this invention helps to effectively isolate the PN region, ensuring that the PN region is not connected and preventing leakage failure; while the protrusion structure reduces the etching of the semiconductor substrate and reduces interference with the carrier transport path inside the semiconductor substrate; the tapered structure also helps to ensure the isolation effect of the channel region and prevent PN connection leakage failure caused by incomplete etching of the platform and / or protrusion structure; on the other hand, it can also reduce the etching depth of the platform and / or protrusion structure during the channel fabrication process, thereby further reducing the carrier transport obstruction inside the semiconductor substrate. Therefore, by combining any two of the above morphologies, the advantages of both morphologies can be obtained simultaneously, solving the problem of the large obstruction of carrier transport inside the semiconductor substrate in existing rectangular channels.

[0034] Furthermore, when the isolation region includes three morphologies—platform structure, protrusion structure, and conical structure—better results can be achieved. This can minimize the etching of the semiconductor substrate while effectively ensuring the isolation effect, and maximize the light absorption rate on the back of the solar cell and the yield of the finished solar cell.

[0035] (3) The present invention designs the platform structure, the protruding structure and the conical structure as a velvet structure, and optimizes the velvet size of different areas, which is conducive to improving the light refraction and diffuse reflection absorption effect, thus effectively improving the bifaciality of the battery cell; at the same time, it can also improve the absorption capacity of sunlight on the back side.

[0036] (4) By optimizing and controlling the preparation process of the isolation region, the first doped region, the second doped region and the channel of the semi-finished product are separated by the first laser treatment and the second laser treatment respectively. Then, the channel area is treated by the third small spot purple skin laser. Thus, under the premise of ensuring the isolation effect of the first doped region and the second doped region, the isolation region with a unique morphology can be prepared by reasonably adopting the multi-line method. This solves the problems of wide and deep etching or limited light absorption capacity of existing rectangular channel etching, and improves the performance of the solar cell. Attached Figure Description

[0037] Figure 1 A schematic diagram of the structure of an existing photovoltaic cell is shown; Figure 2 This shows a partially enlarged schematic diagram of a single rectangular partition area in an existing photovoltaic cell; Figure 3 A schematic diagram of the structure of a photovoltaic cell according to an embodiment of the present invention is shown; Figure 4 This shows a partially enlarged schematic diagram of the isolation region according to an embodiment of the present invention; Figure 5 A schematic diagram of the structure of a photovoltaic cell according to an embodiment of this application is shown; Figure 6 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 7 Showing Figure 6 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 8 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 9 Showing Figure 8 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 10 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 11 Showing Figure 10 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 12 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 13 Showing Figure 12 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 14 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 15 Showing Figure 14 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 16 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 17 Showing Figure 16 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 18 A schematic diagram of the structure of a photovoltaic cell according to another embodiment of this application is shown; Figure 19 Showing Figure 18 A partial schematic diagram of the distribution structure of the central isolation zone; Figure 20 A schematic diagram of the protrusion structure according to another embodiment of this application is shown; Figure 21 A schematic diagram of the protrusion structure according to another embodiment of this application is shown; Figure 22 A schematic diagram of the protrusion structure according to another embodiment of this application is shown; Figure 23 This shows a schematic diagram of the structure of the semiconductor substrate after double-sided polishing in Embodiment 1 of this application; Figure 24 This shows a schematic diagram of the battery cell structure after the first deposition and diffusion in Embodiment 1 of this application; Figure 25 This shows a schematic diagram of the battery cell structure after the first laser treatment and etching in Embodiment 1 of this application; Figure 26 This shows a schematic diagram of the battery cell structure after the second deposition and diffusion in Embodiment 1 of this application; Figure 27 This shows a schematic diagram of the battery cell structure after acid etching and texturing in Embodiment 1 of this application.

[0038] Label Explanation: 1. First antireflection layer; 2. First passivation layer; 3. Semiconductor substrate; 4. First dielectric layer; 5. First doped semiconductor layer; 6. BSG layer; 7. Isolation region; 8. Second doped semiconductor layer; 9. Second antireflection layer; 10. Second passivation layer; 11. First electrode; 12. Second electrode; 13. Second dielectric layer; 14. Platform structure; 15. PSG layer; 16. Protrusion structure; 17. Conical structure. Detailed Implementation

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate for the embodiments of this application described herein.

[0040] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances.

[0041] Furthermore, it should be understood that when the parameters in this application involve numerical ranges, it means that the parameter can take any value within the aforementioned numerical range, or any specific value within the aforementioned numerical range. For example, 0.5-1.5μm can take values ​​within the ranges of 0.5-1.5μm, 0.5-0.7μm, 0.6-0.9μm, 1.0-1.3μm, 1.1-1.5μm, etc., or specific values ​​such as 0.5μm, 0.6μm, 0.8μm, 0.9μm, 1.2μm, 1.4μm, 1.5μm, etc.

[0042] In addition, in this application, the horizontal direction refers to the direction parallel to the front and back sides of the semiconductor substrate; the first direction refers to the lateral direction along the horizontal direction; the second direction refers to the thickness direction of the semiconductor substrate; the inner side of the semiconductor substrate refers to the side extending from the front / back side of the semiconductor substrate into the semiconductor substrate, that is, the direction from the front / back side of the semiconductor substrate towards the side closer to the semiconductor substrate; the outer side of the semiconductor substrate refers to the direction from the front / back side of the semiconductor substrate towards the side farther away from the semiconductor substrate.

[0043] The present invention provides a back structure of a photovoltaic cell, including a first doped region A and a second doped region C arranged alternately along a first direction on the back of a semiconductor substrate 3, and an isolation region (i.e., a channel region) B is provided between the first doped region A and the second doped region C, and the first doped region A and the second doped region C are insulated and isolated by the isolation region B.

[0044] Specifically, the isolation zone includes at least two of the following: platform structure 14, protruding structure 16, and conical structure 17, and there is a height gradient between adjacent structures along the second direction, wherein: The platform structure 14 extends generally in the horizontal direction. Here, "extends generally in the horizontal direction" means that the angle of inclination between it and the horizontal direction is ≤10°. The protrusion structure 16 protrudes from the inside of the semiconductor substrate toward the outside. The conical structure 17 is formed by a recess from the back side of the semiconductor substrate toward its inner side, and the whole is a conical structure (or a sloping groove).

[0045] Combination Figure 1 , Figure 2 As shown, in current technologies, rectangular isolation regions are typically used to insulate and isolate the first and second doped regions. However, in order to ensure the isolation effect, the required width and depth of the channel are large, i.e., the etching is deep, which greatly obstructs the transport of charge carriers inside the semiconductor substrate, thus significantly affecting the efficiency of the solar cell and causing the yield of the finished solar cell to remain low.

[0046] Based on the above, this application optimizes the structural morphology of the isolation region. The platform structure effectively isolates the PN region, ensuring it remains unconnected and preventing leakage failure. The protruding structure reduces etching of the semiconductor substrate, minimizing interference with the carrier transport path within the substrate, and thus significantly improves the yield of the finished solar cell. The tapered structure (or inclined trench) is also primarily used to separate the PN doped regions. On one hand, it helps ensure the isolation effect of the channel region, preventing PN connection leakage failure caused by incomplete etching of the platform and / or protruding structures. On the other hand, during channel fabrication, the tapered structure (or inclined trench) can reduce the etching depth of the platform and / or protruding structures, further reducing carrier transport obstruction within the semiconductor substrate.

[0047] Therefore, this application, through the combination and synergistic effect of at least two of the following morphological structures—platform, protrusion, and conical—can simultaneously obtain the advantages of different morphological structures. This allows for a reduction in the overall etching depth of the semiconductor substrate and the obstruction of carrier transport within the semiconductor substrate while ensuring the best possible isolation effect. This, in turn, is beneficial for improving the efficiency of the solar cells and the yield of the finished cells. Furthermore, the diverse morphological designs of the trench can also better utilize reflected and scattered sunlight, further enhancing the efficiency of back-contact solar cells.

[0048] Specifically, in this application, the isolation region 7 can be a combination of a platform structure and a raised structure, a combination of a platform structure and a conical structure, a combination of a raised structure and a conical structure, or a combination of a platform structure, a raised structure, and a conical structure. The best effect is achieved when the isolation region simultaneously includes a platform structure, a raised structure, and a conical structure. This effectively ensures the isolation effect while minimizing etching of the semiconductor substrate and maximizing the light absorption rate on the back of the solar cell and the yield of the finished solar cell.

[0049] In the various combinations mentioned above, the specific number and relative distribution of the platform structure, protrusion structure, and cone structure can be set according to actual needs. However, when both sides of the protrusion structure are directly connected to the PN doped region, the protrusion is etched relatively little due to its shape, and its isolation effect cannot be fully guaranteed. Therefore, this application preferably connects at least one side of the protrusion structure to the PN doped region through a platform structure and / or a cone structure. More preferably, both sides of the protrusion structure are connected to the PN doped region through a platform structure and / or a cone structure. That is, the central region of the isolation region is provided with a protrusion structure, and both sides of the protrusion structure are provided with a platform structure and / or a cone structure.

[0050] That is, the isolation zone 7 of this application can adopt different combinations such as one platform + one protrusion, two platforms + one protrusion, one protrusion + one cone, one protrusion + two cones, one platform + one cone, one platform + two cones, one protrusion + one platform + one cone, one protrusion + two platforms + one cone, one protrusion + two platforms + two cones, one protrusion + three platforms + one cone, one protrusion + three platforms + two cones, one protrusion + four platforms + two cones, as long as the protrusion structure is located in the middle of the isolation zone and at least one side of the protrusion structure is provided with a platform structure and / or a cone structure.

[0051] Specifically, in some embodiments, combined with Figure 5 As shown, the isolation zone 7 includes a platform structure 14 and a protruding structure 16, but does not have a conical structure 17.

[0052] In other embodiments, combined with Figure 4 , Figure 6As shown, the isolation zone 7 includes two platform structures 14 and one protruding structure 16, but does not have a conical structure 17. The two platform structures 14 are located on opposite sides of the protruding structure 16. Figure 7 As shown, the widths of the platform structures 14 on both sides of the protruding structure 16 can be the same (symmetrical distribution) or different (asymmetrical).

[0053] In other embodiments, combined with Figure 8 , Figure 9 As shown, the isolation region includes a platform structure 14, a protrusion structure 16, and a conical structure 17. Preferably, the platform structure 14 and the conical structure 17 are respectively located on both sides of the protrusion structure 16, but they can also be located on the same side of the protrusion structure 16. For example, the platform structure 14 can be located on the side closer to the first doped region A, or it can be located on the side closer to the second doped region C.

[0054] In other embodiments, combined with Figure 10 , Figure 11 As shown, the isolation region includes two platform structures 14, a protrusion structure 16, and a conical structure 17, and preferably one of the platform structures 14 is located on one side of the protrusion structure 16 (it can be the side closer to the first doped region A or the side closer to the second doped region C), and the other platform structure 14 and the conical structure 17 are located on the other side of the protrusion structure 16.

[0055] In other embodiments, combined with Figure 12 , Figure 13 As shown, the isolation zone includes three platform structures 14, one protruding structure 16, and one conical structure 17. One platform structure 14 is located on one side of the protruding structure 16, and the other two platform structures 14 and the conical structure 17 are located on the other side of the protruding structure 16, with the conical structure 17 located between the two platform structures 14.

[0056] In other embodiments, combined with Figure 14 , Figure 15 As shown, the isolation zone includes two platform structures 14, one protruding structure 16, and two conical structures 17, but the specific distribution of each morphological structure is not limited, for example... Figure 15 The document lists some possible distribution forms, but it should be noted that... Figure 15 The method does not involve exhaustive search, therefore it can also be used. Figure 15 Other combinations not listed in the document.

[0057] In other embodiments, combined with Figure 16 , Figure 17As shown, the isolation zone includes three platform structures 14, one protruding structure 16, and two conical structures 17.

[0058] In a further preferred embodiment, combined with Figure 18 , Figure 19 As shown, the isolation zone includes four platform structures 14, one protruding structure 16, and two conical structures 17. More preferably, each side of the protruding structure 16 is respectively provided with one conical structure 17 and two platform structures 16, and the conical structure is located between the two platform structures, thereby maximizing the absorption capacity of sunlight from the back while ensuring the isolation effect; similarly, Figure 19 Only some feasible distribution forms are shown.

[0059] It should be noted that when multiple platform structures or multiple conical structures are located on the same side of the protruding structure, adjacent platform structures can be connected by conical structures. Similarly, multiple adjacent conical structures can be connected by platform structures, but they can also be connected by other structural shapes, such as ramp structures. That is, the isolation zone is not limited to only platform structures, protruding structures, and conical structures; other structural shapes can also be provided as needed.

[0060] It should also be understood that this application does not limit the specific shape of the protrusion structure, as long as it protrudes from the inside to the outside of the semiconductor substrate. For example, it can be an arc-shaped structure (or a fan-shaped structure), or a rounded rectangular structure (such as...). Figure 20 (as shown) or trapezoidal structure (such as) Figure 21 As shown), the protruding structure can also be formed by any combination of arc-shaped structures, rounded rectangular structures, and trapezoidal structures, such as multiple different arc-shaped structures (e.g., Figure 22 It is formed by connecting the following structures in sequence: (as shown), or rounded rectangles or trapezoids.

[0061] Furthermore, the platform structure and / or the raised structure and / or the conical structure can adopt a velvet surface design or a polished surface, preferably both of which adopt a velvet surface design.

[0062] When a velvet structure design is adopted, the velvet dimensions corresponding to the platform structure, protrusion structure and conical structure in different areas of the isolation zone can be the same or different.

[0063] Optionally, the textured surface dimension (radial dimension of the tower base) of the conical structure is 0.1-1 μm. For example, the textured surface dimension of the conical structure can be 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, or 1 μm, etc.

[0064] Optionally, the textured surface size of the raised structure is 0.3-1.8 μm. For example, the textured surface size of the raised structure can be 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.5 μm, or 1.8 μm, etc.

[0065] Optionally, the texture size of the platform structure is 0.5-5μm. For example, the texture size of the platform structure can be 0.5μm, 0.8μm, 1.0μm, 1.5μm, 1.7μm, 2μm, 2.5μm, 3μm, 4μm, or 5μm, etc.

[0066] As a further preferred embodiment, based on the location of the platform structure, it can be divided into a primary platform directly connected to the raised structure, and a secondary platform (located on one side of the raised structure and not directly connected to it) used to create the conical structure. The primary platform can be designed with a large-sized textured surface, and the secondary platform can be designed with a small-sized textured surface. The base size of the large-sized textured surface structure is larger than that of the small-sized textured surface structure. This differentiated design of textured surface sizes helps to improve the refraction and diffuse reflection absorption of light, thus effectively increasing the bifaciality of the solar cells; it also further enhances the absorption capacity of sunlight from the back side.

[0067] For example, the base size (radial dimension) of the small-sized velvet surface is preferably 0.5-1.5μm, specifically 0.5μm, 0.6μm, 0.7μm, 0.9μm, 1.0μm, 1.2μm, 1.4μm or 1.5μm, etc.; the base size (radial dimension) of the large-sized velvet surface is preferably 2-5μm, specifically 2μm, 2.2μm, 2.5μm, 3μm, 3.5μm, 4μm or 5μm, etc.

[0068] As a further preferred embodiment, the width of the conical structure is less than or equal to the width of the platform structure and less than or equal to the width of the protruding structure. Here, the width refers to the total extension dimension of the various structures with different morphologies along the first direction; for example, when multiple different platform structures are included, it refers to the sum of the widths of all platform structures. Among them, the protruding structure has the largest width, which can retain the semiconductor substrate portion to the greatest extent possible, minimizing the transmission interference of photogenerated carriers inside the semiconductor substrate, while requiring less etching. Therefore, it can reduce the dependence of the solar cell on the silicon wafer thickness and effectively improve the yield of the solar cell. It should be noted that the specific width dimensions of the conical structure, platform structure, and protruding structure in this application can be adjusted accordingly based on the design width of the isolation region, and no specific limitations are imposed here.

[0069] In some embodiments, the width L2 of the conical structure is 2~40μm, and the depth L3 along the second direction is 3~10μm. For example, the width L2 of the conical structure can be 2μm, 3μm, 4μm, 5μm, 9μm, 15μm, 20μm, 25μm, 30μm, or 40μm, etc., and its depth L3 along the second direction can be 3μm, 4μm, 5μm, 7μm, 9μm, or 10μm, etc.

[0070] Here, combined Figure 8 As shown, the width of the conical structure refers to the horizontal distance between the horizontal plane where the apex of the protruding structure is located and the two intersection points of the conical structure, with the horizontal plane being the reference. Its depth along the second direction is the dimension of the indentation or extension into the semiconductor substrate with the first or second doped region on its side as the reference.

[0071] In some embodiments, the width dimension L1 of the protrusion structure is 20~200μm, and the height H1 away from the semiconductor substrate along the second direction is 0.3~2μm. Here, the width dimension of the protrusion structure refers to the horizontal distance between the two edge vertices of the protrusion structure (where the protrusion structure intersects with the semiconductor substrate) along the first direction. For example, the width dimension L1 of the protrusion structure can be 20μm, 40μm, 60μm, 80μm, 100μm, 120μm, 160μm, 175μm, 185μm, or 200μm, etc., and the height H1 away from the semiconductor substrate along the second direction can be 0.3μm, 0.5μm, 0.7μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.7μm, or 2μm, etc.

[0072] It should be noted that this application does not specifically limit the material and conductivity type of the semiconductor substrate. The material can be a silicon substrate, a germanium substrate, or a gallium arsenide substrate, etc. Optionally, the conductivity type of the semiconductor substrate can be an N-type semiconductor substrate (e.g., an N-type single-crystal silicon substrate) or a P-type semiconductor substrate (e.g., a P-type single-crystal silicon substrate).

[0073] Furthermore, the first doped region is provided with a first functional layer, which includes a first doped semiconductor layer, and the second doped region is provided with a second functional layer, which includes a second doped semiconductor layer, wherein the conductivity types of the first and second doped semiconductor layers are opposite. Exemplarily, in some embodiments, the semiconductor substrate is an N-type single-crystal semiconductor, and the first doped semiconductor layer is P-type doped, with the doping element selected from one or more of boron, aluminum, gallium, and indium; exemplarily, the P-type doping element is boron. The second doped semiconductor layer is N-type doped, with the doping element selected from one or more of phosphorus, arsenic, antimony, and bismuth; exemplarily, the N-type doping element is phosphorus.

[0074] In some optional embodiments, a dielectric layer (corresponding to the first dielectric layer and the second dielectric layer, respectively) is provided between at least one of the first doped semiconductor layer and the semiconductor substrate. The dielectric layer and the first or second doped semiconductor layer together form a passivation contact structure, thereby effectively reducing carrier recombination and improving the performance of the back-contact solar cell. The dielectric layer may include at least one of various dielectric materials, such as silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Exemplarily, both the first and second dielectric layers are silicon oxide layers containing silicon oxide. In a further preferred embodiment, the thicknesses of the first dielectric layer and the first doped semiconductor layer are 1-3 nm and 200-500 nm, respectively, and the thicknesses of the second dielectric layer and the second doped semiconductor layer are 1-3 nm and 100-300 nm, respectively.

[0075] In some optional embodiments, both the first doped semiconductor layer and the second doped semiconductor layer have a passivation layer and / or an antireflection layer on the side facing away from the semiconductor substrate. The passivation layer can passivate the defect structure on the back surface, further reducing carrier recombination and improving the photoelectric conversion efficiency of the solar cell; while the antireflection layer can reduce the reflection of incident light, which is beneficial to further improve the light utilization rate of the solar cell.

[0076] It should be noted that the first and second functional layers of this application may also be provided with other membrane layers as needed.

[0077] This invention also provides a method for fabricating the back structure of a photovoltaic cell, comprising the following steps: Provide semiconductor substrates; A first doped region is formed on the back side of a semiconductor substrate, the first doped region having a first functional layer, the first functional layer including a first doped semiconductor layer; A second doped region is formed on the back side of a semiconductor substrate, and the first doped region is provided with a second functional layer, the second functional layer including a second doped semiconductor layer; An isolation region is formed on the back side of the semiconductor substrate and between the first doped region and the second doped region to insulate and isolate the first doped semiconductor layer and the second doped semiconductor layer.

[0078] In some alternative embodiments, forming an isolation region on the back side of the semiconductor substrate and located between the first doped region and the second doped region includes: processing the back side of the semiconductor substrate corresponding to the isolation region using a laser patterning process.

[0079] A further preferred method is to use a purple laser to process the isolation area using a multi-line method, wherein: The platform area adopts a high-power multi-overlapping method, with a laser power of 40-80W and an overlap rate of 50-80%. For example, the laser power of the platform area can be 40W, 50W, 60W, 65W, 70W or 80W, and the overlap rate can be 50%, 60%, 70%, 75% or 80%, etc. The laser power of the raised structure is 5-30W, and the overlap rate is 0-50%, with both the laser power and overlap rate decreasing sequentially from the two edges of the raised structure to its apex. For example, the laser powers of the raised structures are 30W, 25W, 20W, 15W, 10W, and 5W; and the overlap rates are 50%, 40%, 30%, 20%, 10%, and 0%. The parameters can be selected from the above range based on the number of laser stitching lines. The laser power of the conical structure is 30-50W, and the overlap rate is 0-50%. For example, the conical structure adopts a multi-line, multi-overlapping method, wherein the laser power is 50W, 45W, and 40W respectively; the overlap rate is 30%, 20%, and 10% respectively. The parameters can be selected from the above range according to the number of laser lines.

[0080] For example, the purple laser is a small spot ((5~100)×(5~100)) purple (355nm) laser.

[0081] This application utilizes a purple laser to process the isolation zone using a multi-line method, and controls process parameters such as laser processing power and overlap rate as needed, thereby forming a specific combination of morphological structures in the isolation zone.

[0082] In some optional embodiments, the method for fabricating the back structure of the photovoltaic cell specifically includes the following steps: Provide semiconductor substrates; A first functional layer is formed on the back side of a semiconductor substrate, the first functional layer including a first doped semiconductor layer; The first laser patterning process removes part of the first functional layer on the back side of the semiconductor substrate, leaving only the first functional layer corresponding to the first doped region A, so that the semiconductor substrate corresponding to the second doped region C and the isolation region B is exposed. A second functional layer is formed on the back side of a semiconductor substrate, the second functional layer including a second doped semiconductor layer; The first doped region A on the back side of the semiconductor substrate is processed by a second laser patterning process to remove the second functional layer corresponding to the region. The isolation region B on the back side of the semiconductor substrate is processed by a third laser patterning process to remove the corresponding second functional layer and form the corresponding isolation region morphology.

[0083] Furthermore, the laser parameters for the first laser patterning process are: wavelength 500-1200nm, frequency 500-1000kHz, scanning speed 40-150m / s, and power 80-150W.

[0084] Furthermore, the laser parameters for the second laser patterning process are: wavelength 200-1000nm, frequency 200-800kHz, scanning speed 10-80m / s, and power 40-70W.

[0085] Furthermore, the third laser patterning process employs a multi-line splicing method, selecting different numbers of laser lines to splice together based on the shape and width of different morphological channels.

[0086] Furthermore, the doping concentration of the first doped semiconductor layer is (4.8-5.8)E+19, and the doping concentration of the second doped semiconductor layer is (3.8-4.4)E+20.

[0087] In some alternative embodiments, forming the first functional layer on the back side of the semiconductor substrate includes: depositing a first semiconductor layer (a first polysilicon layer in this embodiment) on the back side of the semiconductor substrate, then performing boron diffusion to form an integral P+poly layer (i.e., the first doped semiconductor layer), and forming a BSG layer on its surface; furthermore, before depositing the first semiconductor layer, a first dielectric layer may be deposited on the back side of the semiconductor substrate as needed.

[0088] In some alternative embodiments, the removal of a portion of the first functional layer on the back side of the semiconductor substrate by the first laser patterning process includes: First laser processing: According to the division of the back side region of the semiconductor substrate in the pre-designed pattern, the second doped region C and the channel region B on the back side of the semiconductor substrate are processed by laser to excavate the second doped region and the channel region. Etching process: using alkaline solution to etch the back side of the semiconductor substrate.

[0089] In some alternative embodiments, forming a second functional layer on the back side of the semiconductor substrate includes: depositing a second semiconductor layer (a second polysilicon layer in this embodiment) on the back side of the semiconductor substrate, then performing phosphorus diffusion to form an integral N+poly (i.e., a second doped semiconductor layer), and forming a PSG layer on its surface; furthermore, a second dielectric layer may be deposited as needed before depositing the second semiconductor layer.

[0090] Furthermore, after performing a second laser patterning process on the first doped region A on the back side of the semiconductor substrate, and a third laser patterning process on the isolation region B on the back side of the semiconductor substrate, acid etching and texturing are performed on the back side of the battery to remove the PSG layer, N+poly layer, second dielectric layer, and BSG layer in the first doped region, the PSG layer in the second doped region, and the polysilicon layer in the channel region, and to fabricate a textured structure in the channel region. Exemplarily, the acid etching uses HF with a mass concentration of 10-40%. Exemplarily, the mass concentration of the HF can be 10%, 20%, 25%, 30%, or 40%, etc.

[0091] Furthermore, the texturing process employs a wet texturing method using an alkaline solution, with the alkaline concentration reduced from the conventional 2-3% to 1.5-1.8%. Simultaneously, the type of additive is changed to ensure that the etched pyramid sizes vary depending on the laser power and overlap rate. For example, the alkaline concentration in the texturing process can be 1.5%, 1.6%, 1.7%, or 1.8%, etc.

[0092] Furthermore, in some alternative embodiments, the method further includes: depositing a passivation layer and / or an antireflection layer on the back side of the semiconductor substrate, and performing post-processing operations such as screen printing electrodes.

[0093] Optionally, the preparation method of the present invention further includes: pretreating the semiconductor substrate before the first deposition and diffusion; exemplaryly, performing double-sided polishing on the semiconductor substrate in an alkaline solution.

[0094] The present invention also provides a photovoltaic cell, including a semiconductor substrate, the semiconductor substrate including a front side and a back side disposed opposite to each other, the back side structure of the photovoltaic cell adopts the back side structure described above, which will not be described in detail here.

[0095] Furthermore, the front side of the photovoltaic cell is provided with a passivation layer and / or an anti-reflection layer; exemplarily, the passivation layer on the front side of the photovoltaic cell is made of AlO. x The passivation layer and antireflection layer are made of SiN. x Anti-reflective layer.

[0096] The present invention also provides a stacked battery, comprising a top battery, an intermediate connecting layer and a bottom battery stacked in sequence, wherein the bottom battery is a photovoltaic cell as described above.

[0097] The present invention also provides a photovoltaic module, which includes the above-described photovoltaic cell or the above-described stacked cell.

[0098] Embodiments of the present disclosure will now be described with reference to the accompanying drawings and specific examples. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0099] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0100] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0101] Example 1 like Figure 3 As shown, the photovoltaic cell of this embodiment includes a semiconductor substrate 3, which has a front side and a back side disposed opposite to each other. The front side is provided with a first passivation layer 2 and a first antireflection layer 1 from the inside to the outside. The back side is provided with a first doped region A and a second doped region C alternately disposed along a first direction. An isolation region B is provided between the first doped region A and the second doped region C. The isolation region B provides insulation and isolation between the first doped region A and the second doped region C.

[0102] In this embodiment, the first doped region A has a first functional layer, which includes a first dielectric layer 4, a first doped semiconductor layer 5, a second antireflection layer 9, and a second passivation layer 10 arranged sequentially from the inside out. The second doped region C has a second functional layer, which includes a second dielectric layer 13, a second doped semiconductor layer 8, a second antireflection layer 9, and a second passivation layer 10 arranged sequentially from the inside out. In this embodiment, the semiconductor substrate 3 is an N-type single-crystal silicon substrate, the first doped semiconductor layer 5 is a P-type doped semiconductor layer with boron as the dopant element, and the second doped semiconductor layer 8 is an N-type doped semiconductor layer with p-type dopant element.

[0103] Specifically, the photovoltaic cell preparation method described in this embodiment includes the following steps: Step 1) Substrate pretreatment: The semiconductor substrate 3 is polished on both sides in an alkaline solution. The polished semiconductor substrate 3 is as follows: Figure 23 As shown; Step 2) First Deposition and Diffusion: A first dielectric layer 4 and a first polysilicon layer are sequentially deposited on the back side of the semiconductor substrate 3. Then, boron diffusion is performed to form an integral P+poly layer (i.e., the first doped semiconductor layer 5), and a BSG layer 6 is formed on its surface, as shown below. Figure 24 As shown; Step 3) First laser processing: According to the division of the back surface region of semiconductor substrate 3 in the pre-designed pattern, a laser is used to process the second doped region C and the channel region B on the back surface of semiconductor substrate 3 to excavate the second doped region and the channel region; the first laser processing can use the following laser parameters: wavelength 500-1200nm, frequency 500-1000kHz, scanning speed 40-150m / s, power 80-150W. Specifically, in this embodiment, the laser parameters for the first laser processing are: wavelength 532nm, frequency 700kHz, scanning speed 70m / s, power 90W; Step 4) Etching: The back side of the semiconductor substrate 3 is etched using an alkaline solution. The etched cell structure is as follows: Figure 25 As shown; Step 5) Second Deposition and Diffusion: A second dielectric layer 13 and a second polysilicon layer are sequentially deposited on the back side of the semiconductor substrate 3. Then, phosphorus diffusion is performed to form an integral N+poly (i.e., the second doped semiconductor layer 8), and a PSG layer 15 is formed on its surface, as shown below. Figure 26 As shown; Step 6) Second laser processing: The first doped region A on the back side of the semiconductor substrate 3 is processed using a laser to excavate the first doped region; the second laser processing can use the following laser parameters: wavelength 200-1000nm, frequency 200-800kHz, scanning speed 10-80m / s, power 40-70W. Specifically, in this embodiment, the laser parameters for the second laser processing are: wavelength 532nm, frequency 500kHz, scanning speed 70m / s, power 50W; Step 7) Third laser processing: A small-spot (40×40nm) purple-skin (355nm) laser is used to process the channel region B through a multi-line method, constructing a platform + a fan-shaped raised channel. Specifically, in this embodiment, the platform region uses a high-power 80W multi-overlap method (overlap rate 50%) for the line stitching. The power and overlap rate of the fan-shaped raised region decrease sequentially from the edge to the apex of the fan, with laser powers of 30W, 25W, 20W, 15W, 10W, and 5W respectively; and overlap rates of 50%, 40%, 30%, 20%, 10%, and 0% respectively. The parameters can be directly selected from the above range according to the number of laser lines. Step 8) Acid etching and texturing: The PSG layer, N+ poly layer, second dielectric layer, and BSG layer in the first doped region, the PSG layer in the second doped region, and the polysilicon layer in the channel region are removed using HF. A textured structure is then fabricated in the channel region, resulting in a cell structure as shown below. Figure 27 As shown; In the wet texturing process, the alkali concentration was reduced from 3% to 1.8%, and the type of additives was changed to ensure that the textured pyramids etched in different laser power and overlap areas have different sizes. The textured pyramids in the platform area and the fan-shaped protrusion area are 3μm and 0.7μm, respectively. The width of the platform area is 40μm, and the width (L1) and depth (H1) of the fan-shaped protrusion area are 120μm and 2μm, respectively. Step 9) Post-processing: Passivation layers and antireflection layers are deposited on the surface (front and back) of semiconductor substrate 3, followed by screen printing of electrodes (first electrode 11 and second electrode 12), sintering, and light injection testing. The resulting cell structure is as follows. Figure 3 As shown.

[0104] Example 2 The method for preparing photovoltaic cells in this embodiment includes the following steps: Step 1) Substrate pretreatment: The semiconductor substrate 3 is polished on both sides in an alkaline solution. The polished semiconductor substrate 3 is as follows: Figure 23 As shown; Step 2) First Deposition and Diffusion: A first dielectric layer 4 and a first polysilicon layer are sequentially deposited on the back side of the semiconductor substrate 3. Then, boron diffusion is performed to form an integral P+poly layer (i.e., the first doped semiconductor layer 5), and a BSG layer 6 is formed on its surface, as shown below. Figure 24 As shown; Step 3) First laser processing: According to the division of the back surface region of semiconductor substrate 3 in the pre-designed pattern, the second doped region C and the channel region B on the back surface of semiconductor substrate 3 are processed by laser to excavate the second doped region and the channel region; In this embodiment, the laser parameters for the first laser processing are: wavelength 532nm, frequency 700kHz, scanning speed 70m / s, and power 90W. Step 4) Etching: The back side of the semiconductor substrate 3 is etched using an alkaline solution. The etched cell structure is as follows: Figure 25 As shown; Step 5) Second Deposition and Diffusion: A second dielectric layer 13 and a second polysilicon layer are sequentially deposited on the back side of the semiconductor substrate 3. Then, phosphorus diffusion is performed to form an integral N+poly (i.e., the second doped semiconductor layer 8), and a PSG layer 15 is formed on its surface, as shown below. Figure 26 As shown; Step 6) Second laser processing: The first doped region A on the back side of the semiconductor substrate 3 is processed by laser to excavate the first doped region; In this embodiment, the parameters of the laser for the second laser processing are: wavelength 532nm, frequency 500kHz, scanning speed 70m / s, and power 50W. Step 7) Third laser processing: A small-spot (40×40nm) purple-skin (355nm) laser is used to process the channel region B through a multi-line method, constructing a conical + fan-shaped protruding channel. Specifically, in this embodiment, the conical region adopts a multi-line, multi-overlap method, with laser powers of 50W, 45W, and 40W respectively; and overlap rates of 30%, 20%, and 10% respectively. The power and overlap rate of the fan-shaped protruding region decrease sequentially from the edge to the apex of the fan, with laser powers of 30W, 25W, 20W, 15W, 10W, and 5W respectively; and overlap rates of 50%, 40%, 30%, 20%, 10%, and 0% respectively. The parameters can be selected from this range according to the number of laser lines. Step 8) Acid etching and texturing: The PSG layer, N+ poly layer, second dielectric layer, and BSG layer in the first doped region, the PSG layer in the second doped region, and the polysilicon layer in the channel region are removed using HF. A textured structure is then fabricated in the channel region, resulting in a cell structure as shown below. Figure 27 As shown; In the wet texturing process, the alkali concentration was reduced from 3% to 1.8%, and the type of additives was changed to ensure that the textured pyramids etched in different laser power and overlap areas have different sizes. The textured pyramids in the conical region and the fan-shaped protrusion region are 0.5μm and 0.7μm, respectively. The width (L2) of the conical region is 40μm, and the width (L1) and depth (H1) of the fan-shaped protrusion region are 120μm and 2μm, respectively. Step 9) Post-processing: Passivation layers and antireflection layers are deposited on the surface (front and back) of semiconductor substrate 3, followed by screen printing of electrodes (first electrode 11 and second electrode 12), sintering, and light injection testing. The resulting cell structure is as follows. Figure 3 As shown.

[0105] Example 3 The photovoltaic cell preparation method in this embodiment is basically the same as that in Example 1, with the main difference being: Step 7) Third laser processing: A small-spot (40×40nm) purple-skin (355nm) laser is used to process channel region B through a multi-line method, constructing a platform + a conical channel. Specifically, in this embodiment, the platform region uses a high-power 80W multi-overlap method with an overlap rate of 50%; the conical region uses a multi-line, multi-overlap method, with laser powers of 50W, 45W, and 40W respectively; and overlap rates of 30%, 20%, and 10% respectively. The pyramidal dimensions of the platform region and the conical region are 3μm and 0.5μm respectively; the width of the platform region is 120μm, and the width (L2) and height (L3) of the conical region are 40μm and 5μm respectively.

[0106] Example 4 The photovoltaic cell preparation method in this embodiment is basically the same as that in Example 1, with the main difference being: Step 7) Third laser processing: A small spot (40×40nm) purple (355nm) laser is used to process the channel region B through a multi-line method, constructing a platform + a cone + a fan-shaped protruding channel (the platform is a primary platform; in this embodiment, the platform and the cone structure are located on both sides of the fan-shaped protruding structure). Specifically, in this embodiment, the platform region uses a high-power 80W multi-overlap method with an overlap rate of 50%; the cone region uses a multi-line, multi-overlap method, with laser powers of 50W, 45W, and 40W respectively; and overlap rates of 30%, 20%, and 10% respectively; the power and overlap rate of the fan-shaped protruding region decrease sequentially from the edge to the apex of the fan, with laser powers of 30W, 25W, 20W, 15W, 10W, and 5W respectively; and overlap rates of 50%, 40%, 30%, 20%, 10%, and 0% respectively. The dimensions of the velvet pyramid in the platform region, cone region, and fan-shaped protrusion region are 3μm, 0.5μm, and 0.7μm, respectively. The width of the platform region is 20μm, the width (L2) of the cone region is 20μm and the height (L3) is 5μm, and the width (L1) of the fan-shaped protrusion region is 120μm and the depth (H1) is 2μm.

[0107] Example 5 This embodiment is identical to Embodiment 4 in its preparation process, except for step 7) of the laser grooving section, which forms a four-platform + two-conical + one-fan-shaped raised channel structure (isolation zone). The other parts are the same. The specific diagram of the channel structure combination is shown below. Figure 18As shown. The dimensions of the felt pyramid of the primary platform, secondary platform, conical region, and fan-shaped protrusion region are 3μm, 0.5μm, 0.5μm, and 0.7μm, respectively; the width of the platform region is 20μm (including a single primary platform with a width of 8μm and a single secondary platform with a width of 2μm), the width (L2) of the conical region is 20μm (the width of a single cone is 10μm) and the height (L3) is 5μm, and the width (L1) of the fan-shaped protrusion region is 120μm and the depth (H1) is 2μm.

[0108] Comparative Example 1 The preparation method of this comparative example is similar to that of Example 1, except that in the laser grooving step 7), only the platform channel is constructed.

[0109] Comparative Example 2 The preparation method of this comparative example is similar to that of Example 1, except that in the laser grooving step 7), only a tapered channel is constructed.

[0110] Comparative Example 3 The preparation method of this comparative example is similar to that of Example 1, except that in the laser grooving step 7), only a fan-shaped raised groove is constructed.

[0111] The performance of all solar cells prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was tested, and the test data are shown in Table 1.

[0112] Table 1. Solar cell performance test data

[0113] As can be seen from the test results in Table 1 above, the test results of Example 5 are significantly better than those of Examples 1-3. This is because the channel structure formed by the combination of platform + conical + fan-shaped protrusion structure has the best P / N zone separation effect. At the same time, the combination of multiple textured surface sizes makes the solar cell more efficient in utilizing sunlight. The test performance of Example 5 is better than that of Example 4 because the structure of four platforms + two conical + one fan-shaped protrusion structure has more features, resulting in more variations in textured surface size and better absorption capacity of sunlight.

[0114] The test results of Comparative Examples 1 to 3 show that the test results of Comparative Example 3 are significantly better than those of Comparative Examples 1 and 2. This is because the presence of the fan-shaped protrusions results in less etching of the semiconductor substrate, which is beneficial to improving the yield of solar cells. At the same time, it reduces the transmission of photogenerated carriers inside the semiconductor substrate, resulting in a higher short-circuit current for photoelectric conversion. Examples 1 to 5 are all better than Comparative Example 3. This is because the combination of platform, cone, and fan-shaped protrusion structures has greater advantages in terms of isolation effect and absorption and utilization of sunlight compared to a single fan-shaped protrusion structure. In summary, the channel structure formed by the combination of platform + cone + fan-shaped protrusion structure has better performance than other channel structures, among which the four-platform + two-cone + one-fan-shaped protrusion structure is the most superior.

[0115] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A photovoltaic cell backside structure, comprising a first doped region and a second doped region alternately disposed along a first direction on the backside of a semiconductor substrate, wherein an isolation region is provided between the first doped region and the second doped region, characterized in that, The isolation zone includes at least two of the following: platform structure, raised structure, and conical structure, wherein: The platform structure extends primarily horizontally. The protrusion structure protrudes from the inside of the semiconductor substrate toward the outside. The tapered structure is formed by a recess inward from the back side of the semiconductor substrate.

2. The photovoltaic cell back structure according to claim 1, characterized in that, The isolation zone includes a raised structure and at least one platform structure or a conical structure.

3. The photovoltaic cell back structure according to claim 2, characterized in that, The isolation zone includes a raised structure and two platform structures or two conical structures, with the two platform structures or two conical structures located on both sides of the raised structure.

4. The photovoltaic cell back structure according to claim 1, characterized in that, The isolation zone includes a raised structure, at least one platform structure, and at least one conical structure.

5. The photovoltaic cell back structure according to claim 4, characterized in that, The protruding structure is located in the middle region of the isolation region along the first direction, and its two sides are connected to the first doped region and the second doped region through a platform structure and / or a conical structure, respectively.

6. The photovoltaic cell back structure according to claim 5, characterized in that, The isolation zone includes a raised structure, four platform structures and two conical structures. The two sides of the raised structure are symmetrically provided with two platform structures and one conical structure, and the conical structure is connected between the two platform structures.

7. The photovoltaic cell back structure according to any one of claims 1-6, characterized in that, The platform structure, raised structure, and conical structure adopt a velvet surface design or a polished surface.

8. The photovoltaic cell back structure according to claim 7, characterized in that, The primary platform structures directly connected to the raised structure all adopt large-size velvet structures, while the secondary platform structures located on one side of the raised structure and not directly connected to it adopt small-size velvet structures. The tower base size of the large-size velvet structure is larger than that of the small-size velvet structure.

9. The back structure of the photovoltaic cell according to claim 8, characterized in that, The base size of the small-sized velvet surface is 0.5-1.5μm, and the base size of the large-sized velvet surface is 2-5μm; And / or the conical structure adopts a velvet structure design with a velvet size of 0.1-1μm; And / or the raised structure adopts a velvet structure design with a velvet size of 0.3-1.8μm.

10. The photovoltaic cell back structure according to any one of claims 1-6, characterized in that, The protruding structure can be an arc-shaped structure, a rounded rectangle structure, or a trapezoidal structure, or can be any combination of the above arc-shaped structure, rounded rectangle structure, or trapezoidal structure.

11. The back structure of the photovoltaic cell according to any one of claims 1-6, characterized in that, The width of the tapered structure is less than or equal to the width of the platform structure and less than or equal to the width of the protruding structure.

12. The photovoltaic cell back structure according to any one of claims 1-6, characterized in that, There is a height gradient between the platform structure, the protruding structure, and the conical structure along the second direction; And / or the width dimension L2 of the conical structure is 2~40μm, and the depth L3 along the second direction is 3~10μm; And / or the width dimension L1 of the protrusion structure is 20~200μm, and the height H1 away from the semiconductor substrate along the second direction is 0.3~2μm.

13. The photovoltaic cell back structure according to any one of claims 1-6, characterized in that, The first doped region is provided with a first functional layer, which includes a first doped semiconductor layer. The second doped region is provided with a second functional layer, which includes a second doped semiconductor layer. The conductivity types of the first doped semiconductor layer and the second doped semiconductor layer are opposite.

14. The photovoltaic cell back structure according to claim 13, characterized in that, A dielectric layer is provided between at least one of the first doped semiconductor layer and the second doped semiconductor layer and the semiconductor substrate; And / or the first doped semiconductor layer and the second doped semiconductor layer are provided with a passivation layer and / or an anti-reflection layer on the side away from the semiconductor substrate.

15. A method for preparing the back structure of a photovoltaic cell as described in any one of claims 1-14, characterized in that, include: Provide semiconductor substrates; A first doped region is formed on the back side of a semiconductor substrate, and the first doped region is provided with a first functional layer; A second doped region is formed on the back side of the semiconductor substrate, and the first doped region is provided with a second functional layer; An isolation region is formed on the back side of the semiconductor substrate and between the first doped region and the second doped region.

16. The preparation method according to claim 15, characterized in that, The method of forming an isolation region on the back side of a semiconductor substrate and located between the first doped region and the second doped region includes: processing the back side of the semiconductor substrate corresponding to the isolation region using a laser patterning process.

17. The preparation method according to claim 16, characterized in that, When processing the back side of the semiconductor substrate corresponding to the isolation region using laser patterning, the platform structure, bump structure, and tapered structure are all fabricated using purple laser and multi-line splicing methods, among which: The platform structure is formed using a high-power, multi-overlapping method, with a laser power of 40-80W and an overlap rate of 50-80%. The laser power of the raised structure is 5-30W, the overlap rate is 0-50%, and the laser power and overlap rate decrease sequentially from the two edges of the raised structure to its apex. The laser power of the conical structure is 30-50W, and the overlap rate is 0-50%.

18. The preparation method according to any one of claims 15-17, characterized in that, Specifically, the following steps are included: Provide semiconductor substrates; A first functional layer is formed on the back side of the semiconductor substrate; A portion of the first functional layer on the back side of the semiconductor substrate is removed, leaving only the first functional layer corresponding to the first doped region, so that the semiconductor substrate corresponding to the second doped region and the isolation region is exposed. A second functional layer is formed on the back side of the semiconductor substrate; The first doped region is patterned using laser technology to remove the corresponding second functional layer. The isolation area is laser-graphically processed to remove the corresponding second functional layer and form the corresponding partition area shape.

19. The preparation method according to claim 18, characterized in that, After laser patterning of the first doped region and the isolation region, etching and wet texturing are performed to form a textured surface in the isolation region; the wet texturing uses an alkaline solution with a concentration of 1.5-1.8%.

20. A photovoltaic cell, comprising a semiconductor substrate, the semiconductor substrate including a front side and a back side disposed opposite to each other, characterized in that, The back structure of the photovoltaic cell adopts the back structure of any one of claims 1-14, or is prepared by the method of any one of claims 15-19.

21. A stacked battery, comprising a top battery, an intermediate connecting layer, and a bottom battery stacked sequentially, characterized in that, The bottom battery has the back structure as described in any one of claims 1-14, or adopts the photovoltaic cell as described in claim 20.

22. A photovoltaic module, characterized in that, This includes the photovoltaic cell of claim 20, or the stacked cell of claim 21.

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