Silicon wafer, method for producing the same, solar cell, photovoltaic module, and power plant

Abstract

The application discloses a silicon wafer and a preparation method thereof, a solar cell, a photovoltaic module and a power station. The silicon wafer is used for preparing the solar cell, is a quadrilateral structure obtained by cutting a circular silicon rod, and comprises the following steps: at least three angles in the quadrilateral structure are from an inner region on a cross section of the circular silicon rod, wherein the inner region on the cross section is a region with a resistivity lower than a set threshold value on the cross section, and the set threshold value is determined by the resistivity of a region with a sharp increase in the resistivity of the circular silicon rod; and the resistivity of the silicon wafer is in a decreasing distribution along a specific pair of diagonals in the quadrilateral structure. The design of the silicon wafer structure is that the proportion of the high-resistivity region is reduced, and the resistivity distribution is relatively uniform.

Description

Technical Field

[0001] This invention relates to a silicon wafer and its preparation method, a solar cell, a photovoltaic module, and a power station. Background Technology

[0002] The silicon wafers used to fabricate solar cells can affect the photoelectric conversion efficiency of solar cells. Therefore, obtaining high-performance silicon wafers can help improve the photoelectric conversion efficiency of solar cells.

[0003] Currently, silicon wafers used in solar cells are obtained by squaring and slicing circular silicon rods. However, because the resistivity of a circular silicon rod is distributed in a ring shape (increasing from the center to the edge), the resistivity of the wafer obtained from slicing the rod differs significantly between the center and the four corners, resulting in an uneven resistivity distribution. This uneven resistivity distribution negatively impacts the solar cell fabrication process and hinders the improvement of photoelectric conversion efficiency. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a silicon wafer and its preparation method, a solar cell, a photovoltaic module and a power station. The design of the silicon wafer structure can reduce the proportion of high resistivity regions while effectively reducing the difference between the resistivity at the center of the silicon wafer and the resistivity at the edges and corners of the silicon wafer, so that the resistivity distribution of the silicon wafer is relatively uniform.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a silicon wafer for fabricating solar cells, which is a quadrilateral structure obtained by cutting a circular silicon rod, comprising:

[0007] At least three corners of the quadrilateral structure originate from the internal region of the cross-section of the circular silicon rod, wherein the internal region of the cross-section is a region on the cross-section with a resistivity lower than a set threshold, wherein the set threshold is determined by the resistivity of the region of the circular silicon rod with a sharp increase in resistivity;

[0008] The resistivity of the silicon wafer (10) decreases along a specific set of diagonals in the quadrilateral structure.

[0009] Secondly, embodiments of the present invention provide a method for preparing a silicon wafer, comprising:

[0010] Based on a preset grid-shaped / deformed grid structure, a circular silicon rod is cut, and each line segment of the grid-shaped / deformed grid structure is controlled to pass through the internal region of the cross-section of the circular silicon rod to obtain multiple quadrilateral silicon rods. The grid-shaped / deformed grid structure is inscribed within the cross-section of the circular silicon rod, or at least one set of diagonals of the largest quadrilateral in the grid-shaped / deformed grid structure extends out of the cross-section of the circular silicon rod. The internal region of the cross-section is the region on the cross-section with resistivity lower than a set threshold, wherein the set threshold is determined by the resistivity of the region of the circular silicon rod with a sharp increase in resistivity.

[0011] The quadrilateral silicon rod is sliced ​​to obtain silicon wafers.

[0012] Thirdly, embodiments of the present invention provide a solar cell, which is fabricated using the silicon wafer provided in the first aspect embodiment, and includes: a cell chamfer, wherein...

[0013] The chamfer of the battery is formed based on the chamfer of the silicon wafer.

[0014] Fourthly, embodiments of the present invention provide a photovoltaic module, comprising: a plurality of solar cells arranged in an array, wherein the solar cells are prepared from the solar cells provided in the third aspect embodiment.

[0015] Fifthly, embodiments of the present invention provide a power station including the photovoltaic modules provided in the fourth aspect embodiments.

[0016] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0017] The silicon wafer for fabricating solar cells provided by this invention is a quadrilateral structure obtained by cutting a circular silicon rod. Since at least three corners of the quadrilateral structure originate from the internal region of the cross-section of the circular silicon rod, and this internal region is defined as a region with resistivity below a set threshold (determined by the resistivity of a region on the circular silicon rod where resistivity increases sharply), the impact of the high resistivity at the edges of the circular silicon rod on the silicon wafer is effectively reduced or even eliminated. Furthermore, compared to existing silicon wafers where the center is the center of the circular silicon rod, this invention, through a design where the resistivity of the silicon wafer decreases along a specific set of diagonals in the quadrilateral structure, effectively reduces the difference between the resistivity at the center of the silicon wafer and the resistivity at the edges and corners, resulting in a more uniform resistivity distribution. Attached Figure Description

[0018] Figure 1 It is a resistivity distribution diagram of a single-crystal silicon wafer and one of its diagonals, which is commonly used in existing technology;

[0019] Figure 2 This is a resistivity distribution diagram along one diagonal of a first type of silicon wafer provided according to an embodiment of the present invention;

[0020] Figure 3 This is a resistivity distribution diagram along one diagonal of a second type of silicon wafer provided according to an embodiment of the present invention;

[0021] Figure 4 This is a structural schematic diagram of the cross-section of a circular silicon rod provided according to an embodiment of the present invention;

[0022] Figure 5A This is a schematic diagram of the main process of a silicon wafer fabrication method according to an embodiment of the present invention;

[0023] Figure 5B This is a schematic diagram of the main process of another silicon wafer fabrication method provided by an embodiment of the present invention;

[0024] Figure 6A This is a schematic diagram of the first type of grid-shaped / deformed grid structure provided by an embodiment of the present invention;

[0025] Figure 6B This is a schematic diagram of the second type of grid-shaped / deformed grid structure provided in the embodiments of the present invention;

[0026] Figure 6C This is a schematic diagram of the third type of grid-shaped / deformed grid structure provided in the embodiments of the present invention;

[0027] Figure 6D This is a schematic diagram of the fourth type of grid-shaped / deformed grid-shaped structure provided in the embodiments of the present invention;

[0028] Figure 7A This is a schematic diagram of the cross-section of the first type of grid-shaped / grid-shaped deformable structure provided by the present invention, which is inscribed within a circular silicon rod;

[0029] Figure 7B This is a schematic diagram of the cross-section of a second type of grid-shaped / grid-shaped deformable structure inscribed within a circular silicon rod, according to an embodiment of the present invention.

[0030] Figure 7C This is a schematic diagram of the cross-section of a third type of grid-shaped / grid-shaped deformed structure inscribed within a circular silicon rod, according to an embodiment of the present invention.

[0031] Figure 8A This is a schematic diagram of the cross-section of at least one set of diagonally extended circular silicon rods in the largest quadrilateral in the first type of grid / grid-shaped deformed structure provided by the present invention;

[0032] Figure 8BThis is a schematic diagram of the cross-section of at least one set of diagonally extended circular silicon rods in the largest quadrilateral in the second type of grid / grid-shaped deformed structure provided by the present invention;

[0033] Figure 9 This is a top view of a first type of solar cell provided according to an embodiment of the present invention;

[0034] Figure 10 This is a top view of a second type of solar cell provided according to an embodiment of the present invention;

[0035] Figure 11 This is a cross-sectional schematic diagram of a photovoltaic module provided according to an embodiment of the present invention.

[0036] The attached figures are labeled as follows:

[0037] 10-Silicon wafer; 11-Chamfer; 12-Chamfer diagonal; 20-Solar cell; 21-Cell chamfer; 22-Fine grid line; 23-Main grid line; 30-Photovoltaic module; 31-Solar cell; 32-Cover plate; 33-Backsheet; 34-Encapsulation layer. Detailed Implementation

[0038] Improving the resistivity of silicon wafers made from circular monocrystalline silicon rods helps to increase the photoelectric conversion efficiency of solar cells. To obtain silicon wafers with improved resistivity and find methods to improve wafer resistivity, it is first necessary to understand the resistivity of commonly used monocrystalline silicon wafers in the photovoltaic field, such as resistivity distribution and high-resistivity regions. Resistivity tests on commonly used monocrystalline silicon wafers (obtained by slicing a circular monocrystalline silicon rod by taking the square root of its inscribed rectangle / square, thus the four corners of the wafer correspond to the edges of the circular rod) revealed that the resistivity is lowest at the center of the wafer, increasing further away from the center (i.e., the four corners have the highest resistivity). Furthermore, the increasing resistivity trend starts from the center of the wafer and expands outwards in a ring-like structure (i.e., regions with the same resistivity form concentric rings centered on the center of the wafer). Therefore, the resistivity distribution along any diagonal of a commonly used monocrystalline silicon wafer can comprehensively reflect the resistivity of the entire wafer. Based on this, Figure 1 An exemplary resistivity profile is shown along a diagonal of a commonly used monocrystalline silicon wafer (this profile indicates the relationship between resistivity and position on the diagonal of a commonly used monocrystalline silicon wafer). Figure 1 The dashed line in the figure represents the region where resistivity was tested (the region corresponding to one diagonal line of the single-crystal silicon wafer), and the corresponding resistivity distribution is shown as the curve in the figure. From Figure 1It can be seen that the silicon wafer exhibits a trend of low resistivity at the center and high resistivity at the periphery, and the resistivity of the silicon wafer increases in a ring-like pattern from the center to the edge. Furthermore, from... Figure 1 It can be seen that the square single-crystal silicon wafers obtained by squaring and slicing circular single-crystal silicon rods have significant differences in resistivity between the center and the four corners (the center is darker and has lower resistivity, while the four corners are brighter and have higher resistivity; the area with high resistivity accounts for more than 10% of the total area of ​​the silicon wafer), resulting in uneven resistivity. In other words, the commonly used silicon wafers currently suffer from high resistivity at the corners and poor resistivity uniformity, which negatively impacts the solar cell fabrication process and hinders the improvement of photoelectric conversion efficiency.

[0039] To address the problems existing in current silicon wafers, embodiments of the present invention provide a silicon wafer with improved resistivity obtained from a circular silicon rod, a method for preparing the silicon wafer, and a solar cell, photovoltaic module, and power station obtained based on the improved silicon wafer.

[0040] Figure 2 and Figure 3 An exemplary illustration shows a silicon wafer 10 provided in an embodiment of the present invention and a schematic diagram of the resistivity distribution curve of the silicon wafer 10. This silicon wafer 10 is used to fabricate... Figure 5A and Figure 5B The solar cell 20 shown has a quadrilateral structure obtained by cutting a circular silicon rod, comprising:

[0041] At least three corners of the quadrilateral structure originate from the internal region of the cross-section of the circular silicon rod, wherein the internal region of the cross-section is the region of the cross-section with a resistivity lower than a set threshold, and the set threshold is determined by the resistivity of the region of the circular silicon rod with a sharp increase in resistivity.

[0042] The resistivity of silicon wafer 10 decreases along a specific set of diagonals in the quadrilateral structure.

[0043] The quadrilateral structure generally refers to a quadrilateral with two pairs of parallel sides, such as a parallelogram, rhombus, rectangle, square, etc. In a preferred embodiment, the silicon wafer 10 is a rectangle or a square to facilitate cutting from a circular silicon rod, and also to facilitate the subsequent fabrication of solar cells and photovoltaic modules.

[0044] Furthermore, the aforementioned quadrilateral structure refers to the fact that when the silicon wafer is laid flat, its upper and lower surfaces are quadrilateral in shape, and the vertical distance between the upper and lower surfaces is the thickness of the silicon wafer. Since the silicon wafer is relatively thin, and the upper and lower surfaces of the silicon wafer have the same shape and structure, the entire silicon wafer can be characterized by describing the shape, angle, etc., of the upper or lower surface.

[0045] in, Figure 4An exemplary schematic diagram of the cross-section of a circular silicon rod is shown. (As shown) Figure 4 As shown, the resistivity of a circular silicon rod increases outwards in a ring-like pattern from the center of its cross-section. Figure 4 The marked rings 1, 2, 3, 4, 5, and 6 gradually increase in resistance until edge 7. It's worth noting that the resistivity of a circular silicon rod increasing outwards in a ring-like pattern from the center of the cross-section is an ideal scenario. Within the same ring, the resistivity also gradually increases from the inside out, although the difference in resistivity within a single ring is smaller than the difference between different rings. For ease of explanation, the following description will only use the rings shown below. Figure 4 The circular ring shown is used as an example for illustration.

[0046] The threshold value is determined by the resistivity of the region on the circular silicon rod where a sharp increase in resistivity occurs. For example, the threshold value can be equal to the resistivity of the region with the sharp increase in resistivity. If the resistivity of the region with the sharp increase in resistivity is 0.9, then the threshold value can be 0.9; if the resistivity of the region with the sharp increase in resistivity is 0.5, then the threshold value can be 0.5. Correspondingly, the inner region is the area within the region where the sharp increase in resistivity occurs. Alternatively, the threshold value can be a certain percentage increase in resistivity relative to the center of the circular silicon rod. For example, if this certain percentage is 25%, then the threshold value is the resistivity that increases by 25% relative to the center of the circular silicon rod. That is, if the resistivity of the center of the circular silicon rod is 0.4, the threshold value can be 0.5; if the resistivity of the center of the circular silicon rod is 0.8, the threshold value can be 1, and so on.

[0047] The following is based on Figure 4 Taking the cross-section of a circular silicon rod as an example, this paper details the resistivity of the internal region and the region with a sharp increase in resistivity on the cross-section of the circular silicon rod, as well as the set threshold. For example, by testing the resistivity, it was found that... Figure 4 The resistivity of the corresponding circular silicon rod shows a slight increase from ring 1 to ring 6, but a significant increase at edge 7. Therefore, the resistivity of the region with the sharp increase can be identified as the resistivity of edge 7. Correspondingly, a threshold can be set equal to the resistivity of edge 7, and the inner region is the region within edge 7. For example, by testing the resistivity, it was found that... Figure 4 The resistivity of the corresponding circular silicon rod shows a slight increase from ring 1 to ring 5, but a sharp increase in resistivity begins from ring 6. Therefore, the region of sharp increase in resistivity is the region of ring 6, and the resistivity of this region is the resistivity of the region with the sharp increase in resistivity. Accordingly, a threshold can be set equal to the resistivity of ring 6, and the inner region is the area within ring 6 (i.e., the area occupied by rings 1 to 5). For example, by testing resistivity, it was found that... Figure 4The resistivity of the corresponding circular silicon rod does not increase significantly from ring 1 to ring 3. The resistivity increases sharply from ring 4 onwards. The region of the circular silicon rod with a sharp increase in resistivity is the region of ring 4. The resistivity of the region of ring 4 is the resistivity of the region with a sharp increase in resistivity. Accordingly, the threshold can be set to be equal to the resistivity of ring 4. The inner region is the region inside ring 4 (i.e., the region occupied by rings 1 to 3).

[0048] Due to the differences in the production process environment of different batches of round silicon rods, by determining the resistivity of the region with a sharp increase in resistivity based on the resistivity of the round silicon rod itself, setting a threshold, and the internal region, it is possible to cut the round silicon rods of different batches differently, so as to obtain silicon wafers with small high resistivity areas and uniform resistivity distribution, thereby achieving better quality control of silicon wafers and ensuring the quality stability of silicon wafers.

[0049] Since the resistivity of silicon wafer 10 decreases along a specific set of diagonals in the quadrilateral structure, it can be known that the silicon wafer spans... Figure 4 The multiple annular regions shown.

[0050] In summary, the silicon wafer for fabricating solar cells provided by this invention, which is obtained by cutting a circular silicon rod into a quadrilateral structure, effectively reduces or even eliminates the influence of the high resistivity at the edges of the circular silicon rod on the silicon wafer because at least three corners of the quadrilateral structure originate from the internal region of the cross-section of the circular silicon rod. This internal region is defined as the area with resistivity below a set threshold, determined by the resistivity of the region where the resistivity of the circular silicon rod increases sharply. Furthermore, compared to existing silicon wafers where the center is the center of the circular silicon rod, this invention, through its design where the resistivity of the silicon wafer decreases along a specific set of diagonals in the quadrilateral structure, effectively reduces the difference between the resistivity at the center of the silicon wafer and the resistivity at the edges and corners, resulting in a more uniform resistivity distribution.

[0051] In addition, such as Figure 2 and Figure 3 The silicon wafer structure shown can have four right angles, or three right angles and one chamfered angle. It's worth noting that the right angles on the silicon wafer are also rounded or chamfered to reduce the risk of corner damage.

[0052] In this embodiment of the invention, three corners of the quadrilateral structure of the silicon wafer correspond to the inner region of the circular silicon rod, and the remaining corner corresponds to the region of steep resistivity increase outside the inner region of the circular silicon rod. The corner corresponding to the region of steep resistivity increase outside the inner region of the circular silicon rod and its opposite corner form a specific pair of opposite corners. For example, Figure 2The angle A shown corresponds to the region of steep resistivity increase outside the inner region of the circular silicon rod, and it is related to... Figure 2 The angle B shown is a specific set of opposite angles. The area outside this inner region can be the edge of a circular silicon rod or the area between the edge of the circular silicon rod and the edge of the inner region. For example, Figure 4 In the cross-section of the circular silicon rod shown, rings 1 to 5 represent the inner region, while ring 6 and edge 7 represent the region outside the inner region. A corner of the quadrilateral structure can correspond to either edge 7 or the area inside ring 6. It is worth noting that the corner of the quadrilateral structure corresponding to the region outside the inner region can be a right angle or a chamfer. This structural arrangement ensures that only one corner of the entire silicon wafer has a high resistivity region, while the remaining areas are low resistivity. This maintains a relatively low proportion of high resistivity regions, ensuring silicon wafer performance while making efficient use of the high resistivity region of the circular silicon rod.

[0053] In this embodiment of the invention, the four corners of the quadrilateral structure correspond to the internal region of the circular silicon rod. For example, Figure 4 In the cross-section of the circular silicon rod shown, rings 1 to 5 represent the inner region, while ring 6 and edge 7 represent the region outside the inner region. The four corners of the quadrilateral structure correspond to the inner regions of rings 1 to 5. This design ensures that all regions of the silicon wafer have a low resistivity level and that the resistivity distribution of the silicon wafer is relatively uniform, thereby effectively improving the performance of the solar cells fabricated from it.

[0054] In embodiments of the present invention, such as Figure 3 As shown, one corner of the aforementioned quadrilateral structure is a chamfer 11, wherein the chamfer 11 is formed by removing part or all of the edge region of the circular silicon rod where the resistivity increases sharply; the chamfer 11 and its opposite corner 12 form a specific pair of opposite corners. Figure 2 The resistivity distribution curve of the silicon wafer shown (the resistivity variation with position along the line connecting the chamfer and its diagonal 12) demonstrates how the chamfering reduces or even eliminates the impact of the steep resistivity increase region of the circular silicon rod on the entire wafer. Furthermore, the chamfer is formed by removing part or all of the steep resistivity increase region of the circular silicon rod, further removing some or all of the high resistivity areas to reduce the area of ​​high resistivity regions in the wafer, thereby reducing the proportion of high resistivity regions. Moreover, by designing the resistivity of the silicon wafer to decrease from the chamfer to its diagonal, the difference between the resistivity at the center of the wafer and the resistivity at the edges and corners can be effectively reduced, resulting in a more uniform resistivity distribution.

[0055] In this embodiment of the invention, multiple regions with the same resistivity in the silicon wafer are all arc-shaped structures; a line connecting a set of specific diagonals passes through multiple arc-shaped structures, and one of the specific diagonals is the center of the multiple arc-shaped structures. These arc-shaped structures originate from rings of different resistivity in the cross-section of a circular silicon rod; therefore, the center of the arc-shaped structure is the center of the circular silicon rod. Figure 4 The center O of the circular silicon rod shown is traversed by a line connecting a set of specific diagonals through multiple arc-shaped structures, with one of the diagonals being the center of the multiple arc-shaped structures (the center of these multiple arc-shaped structures is the center of the circular silicon rod, for example...). Figure 4 The center O of the circular silicon rod shown is designed to include as many low resistivity regions of the circular silicon rod as possible on the silicon wafer. This ensures that the resistivity of the silicon wafer is uniform while allowing as many silicon wafers as possible to be cut from the same cross-section of the circular silicon rod, thereby effectively improving the utilization rate of the circular silicon rod.

[0056] In this embodiment of the invention, in the quadrilateral structure described above, apart from chamfer 11 and its opposite corner 12, the resistivity of the other two corners is less than or equal to the resistivity of chamfer 11. Preferably, the resistivity of the other two corners is less than the resistivity of chamfer 11. This further reduces the proportion of high-resistivity regions in the silicon wafer.

[0057] In this embodiment of the invention, in order to reduce waste of circular silicon rods and minimize the proportion of high resistivity regions in the silicon wafer to improve the cost-effectiveness of the fabricated solar cell, the chamfer side length or chamfer arc length of the chamfer 11 can be designed to be greater than or equal to... Wherein, L′ represents the width of the edge region with the highest resistivity in the circular silicon rod; L and D represent the length and width of the silicon wafer, respectively.

[0058] Specifically, with Figure 4 Taking the circular silicon rod shown as an example, let's explain L′ in detail, for example... Figure 4 In the circular silicon rod shown, the ring 6 and edge 7 represent the edge region with the highest resistivity. Therefore, L′ is the sum of the width of ring 6 and the width of edge 7. For example, Figure 4 In the circular silicon rod shown, rings 5, 6, and edge 7 are the edge regions with the highest resistivity in the circular silicon rod. Therefore, L′ is the sum of the widths of rings 5, 6, and 7.

[0059] Furthermore, it can be understood that when the silicon wafer is a square wafer, the length L and width D of the wafer are equal.

[0060] Furthermore, to reduce the complexity of calculations, further research revealed that for silicon wafers with the aforementioned structure obtained from commonly used circular silicon rods, a chamfer edge length or chamfer arc length of chamfer 11 is greater than or equal to 8mm, such as 9mm, 10mm, 15mm, 20mm, or 30mm. This allows the proportion of the high-conductivity region of the silicon wafer to be below 5%, resulting in a significant improvement in the photoelectric conversion efficiency of solar cells.

[0061] In this embodiment of the invention, the side length of the silicon wafer is generally controlled within the range of 156 to 800 mm, for example, 160 mm, 166 mm, 170 mm, 178 mm, 190 mm, 200 mm, 210 mm, 230 mm, 255 mm, 275 mm, 290 mm, 300 mm, 312 mm, 322 mm, 335 mm, 350 mm, 375 mm, 396 mm, 400 mm, 450 mm, 500 mm, 525 mm, 600 mm, 630 mm, 650 mm, 700 mm, 725 mm, 750 mm, 780 mm, 800 mm, etc. This allows the silicon wafer to be obtained from most circular silicon rods, ensuring the low resistivity of the silicon wafer.

[0062] In this embodiment of the invention, the circular silicon rod used to obtain the silicon wafer is a circular single-crystal silicon rod. To obtain the silicon wafers of the above embodiments while ensuring maximum utilization of the circular silicon rod, this embodiment of the invention provides a method for preparing a silicon wafer. For example... Figure 5A As shown, the method for preparing this silicon wafer may include the following steps:

[0063] Step S501A: Based on the preset grid-shaped / grid-shaped deformed structure, the circular silicon rod is cut, and each line segment of the grid-shaped / grid-shaped deformed structure is controlled to pass through the internal area of ​​the cross-section of the circular silicon rod to obtain multiple quadrilateral silicon rods.

[0064] Among them, the grid-shaped / deformed grid structure can be as follows: Figure 6A , 6B The 6C and 6D examples illustrate the grid-shaped or grid-shaped modified structures, and other structures based on this... Figures 6A to 6D All modifications are also within the protection scope of this invention.

[0065] Wherein, the cross-section of the circular silicon rod is inscribed within the cross-section of the grid-shaped / grid-deformed structure or at least one set of diagonals of the largest quadrilateral in the grid-shaped / grid-deformed structure extends out of the cross-section of the circular silicon rod. The internal region on the cross-section is the region on the cross-section with resistivity lower than a set threshold. The set threshold is determined by the resistivity of the region on the circular silicon rod with a sharp increase in resistivity.

[0066] Among them, the cross-section of the circular silicon rod inscribed within the grid-shaped / deformed grid structure can be as follows: Figure 7A, Figure 7B as well as Figure 7C As shown, the four vertices of the grid-shaped / grid-deformed structure are all located at the edge of the cross-section of the circular silicon rod.

[0067] The cross-section of a circular silicon rod can be derived from at least one pair of diagonals of the largest quadrilateral in a grid-shaped / deformed grid structure, as shown in the example. Figure 8A and Figure 8B As shown, at least one set of diagonals of the grid-shaped / grid-shaped deformed structure extends beyond the edge of the cross-section of the circular silicon rod.

[0068] It is worth noting that in the process of cutting a circular silicon rod based on a grid-shaped / deformed grid structure, the center of the grid-shaped / deformed grid structure (designed as the intersection of two intersecting lines within the grid-shaped / deformed grid structure) is generally controlled to be located at the center of the circular silicon rod. This ensures that the resistivity of the resulting silicon wafer at its center is between the resistivity of the center of the circular silicon rod and the resistivity of the edge or edge region of the circular silicon rod. This effectively reduces the difference in resistivity between various locations on the silicon wafer and the resistivity at the center of the silicon wafer, thereby effectively improving the uniformity of the silicon wafer's resistivity. At the same time, it ensures that the four silicon wafers cut from a cross-section of the circular silicon rod are essentially identical, maximizing the utilization rate of the circular silicon rod and reducing the production costs of silicon wafers, solar cells, and other components.

[0069] Step S502: Slice the quadrilateral silicon rod to obtain silicon wafers.

[0070] like Figure 7A The circular silicon rod shown is obtained through steps S501A and S502 as follows: Figure 2 The silicon wafer structure shown.

[0071] In the above embodiments, the circular silicon rod used in the preparation method is generally a circular single-crystal silicon rod.

[0072] In summary, the method for preparing silicon wafers by cutting circular silicon rods provided by this invention, due to the presence of a grid-shaped / deformed grid structure within the cross-section of the circular silicon rod, or at least a set of diagonals of the largest quadrilateral in the grid-shaped / deformed grid structure extending out of the cross-section of the circular silicon rod, ensures that at least three corners of the resulting silicon wafer originate from the internal region of the cross-section of the circular silicon rod. This internal region is defined as the area on the cross-section where the resistivity is below a set threshold, determined by the resistivity of the region where the resistivity of the circular silicon rod increases sharply. This effectively reduces or even eliminates the influence of the high resistivity at the edge of the circular silicon rod on the silicon wafer. Furthermore, compared to existing silicon wafers where the center is the center of the circular silicon rod, the resistivity of the silicon wafer obtained by the method provided by this invention is designed to decrease along a specific set of diagonals (corresponding to the corners at the edge of the circular silicon rod and the corners at the center of the circular silicon rod). This effectively reduces the difference between the resistivity at the center of the silicon wafer and the resistivity at the edges and corners, resulting in a more uniform resistivity distribution for the silicon wafer.

[0073] Furthermore, in order to further reduce the high resistivity regions of the silicon wafer, such as... Figure 5B As shown, after step S501A and before step S502, step S501B may be further included: removing the edge region of a specific interior corner of the quadrilateral silicon rod, wherein the specific interior corner is inherited from an interior corner of the largest quadrilateral in the grid / grid-shaped deformed structure; correspondingly, the specific implementation of slicing the quadrilateral silicon rod in step S502 may include step S502': slicing the quadrilateral silicon rod with the edge region of a specific interior corner removed to obtain a silicon wafer. Figure 7B As shown, the circular silicon rod obtained through steps S501A, S501B, and S502' is as follows: Figure 3 The silicon wafer structure shown.

[0074] By chamfering, the impact of the steep resistivity increase region of the circular silicon ingot on the entire silicon wafer can be reduced or even eliminated. Furthermore, chamfering is formed by removing part or all of the steep resistivity increase region of the circular silicon ingot, which can further remove part or all of the high resistivity region, thereby reducing the area of ​​the high resistivity region in the silicon wafer and thus reducing the proportion of high resistivity regions in the wafer. Moreover, by designing the resistivity of the silicon wafer to decrease from the chamfer to its diagonal, the difference between the resistivity at the center of the silicon wafer and the resistivity at the edges and corners can be effectively reduced, resulting in a more uniform resistivity distribution on the silicon wafer.

[0075] In this embodiment of the invention, the specific implementation of step S501 may include: cutting a circular silicon rod using three mutually parallel first cutting lines and three mutually parallel second cutting lines intersecting the first cutting lines. The orthographic projections of the three first cutting lines and the three second cutting lines form a grid / grid-shaped deformed structure. All three first cutting lines and three second cutting lines pass through the internal region of the cross-section of the circular silicon rod, and the first cutting line in the middle position and the second cutting line in the middle position both coincide with the diameter of the cross-section of the circular silicon rod. Cutting using these cutting lines ensures the integrity of the silicon wafer, especially its edges.

[0076] In this embodiment of the invention, the specific implementation of removing the edge region of a specific interior corner of a quadrilateral silicon rod may include: determining the width of the edge region with the highest resistivity in the circular silicon rod; determining the chamfer side length or chamfer arc length of the required chamfer on the silicon wafer based on the width of the edge region with high resistivity in the circular silicon rod and the size of the silicon wafer to be prepared; and cutting the edge region of a specific interior corner of the quadrilateral silicon rod based on the determined chamfer side length or chamfer arc length.

[0077] The specific implementation of determining the chamfer edge length or chamfer arc length of the required chamfer 11 based on the width of the edge region with higher resistivity in the circular silicon rod and the required size of the silicon wafer may include: controlling the chamfer edge length or chamfer arc length of the aforementioned chamfer 11 to be greater than or equal to Where L′ represents the width of the edge region with the highest resistivity in the circular silicon rod; L and D represent the length and width of the silicon wafer, respectively. By controlling the chamfer edge length or chamfer arc length of the aforementioned chamfer 11, it can be designed to be greater than or equal to... This can effectively reduce waste of circular silicon rods, while minimizing the proportion of high resistivity regions on the silicon wafer, thereby improving the cost-effectiveness of the fabricated solar cells.

[0078] Furthermore, the chamfer edge length or chamfer arc length of the silicon wafer determined above can also be controlled to be greater than or equal to 8mm, such as 9mm, 10mm, 15mm, 20mm, 30mm, etc. This can ensure that the proportion of the high conductivity region of the silicon wafer is less than 5%, which can significantly improve the photoelectric conversion efficiency of the solar cell.

[0079] In this embodiment of the invention, the above-described preparation method may further include: flattening each corner of the quadrilateral silicon rod to reduce the risk of the silicon wafer being damaged by impacts.

[0080] In this embodiment of the invention, the above-described preparation method may further include: flattening each side of the quadrilateral silicon rod to ensure the flatness of the silicon wafer sides.

[0081] This invention provides a solar cell. Figure 9 and Figure 10 Top views of solar cells fabricated from silicon wafers with different structures provided in the above embodiments are shown. Figure 9 Based on Figure 2 A top view of the solar cell derived from the silicon wafer shown. Figure 10 Based on Figure 2 The image shows a top view of a solar cell made from a silicon wafer.

[0082] like Figure 9 and Figure 10 As shown, the solar cell also includes fine grid lines 22, wherein the fine grid lines 22 are parallel to a set of opposite sides of the silicon wafer 10.

[0083] In addition, such as Figure 9 and Figure 10 As shown, the solar cell may further include: a main grid line 23, wherein the main grid line 23 is parallel to a set of opposite sides of the silicon wafer 10.

[0084] It is worth noting that, Figure 9 and Figure 10 The illustration only shows the case of including fine grid lines 22 and main grid lines 23; a solar cell may also include only fine grid lines.

[0085] In addition, based on Figure 3 The solar cell fabricated from the silicon wafer shown is as follows: Figure 10 The device may also include a cell chamfer 21, wherein the cell chamfer 21 is formed based on the chamfer 11 of the silicon wafer 10.

[0086] It is worth noting that the aforementioned solar cells may also include a textured surface, a passivation layer, and an anti-reflection layer. The textured surface, passivation layer, anti-reflection layer, as well as the aforementioned fine grid lines and main grid lines, can be implemented using existing technologies, and will not be elaborated further here.

[0087] This invention also provides a photovoltaic module. Figure 11 A cross-sectional schematic diagram of the photovoltaic module is shown. (As shown) Figure 11 As shown, the photovoltaic module 30 includes a plurality of solar cells 31 arranged in an array, wherein the solar cells 31 are prepared from the solar cells provided in the above embodiments. Specifically, the solar cells described above can be used directly as solar cells, or they can be cut into individual small solar cells by a cutting method.

[0088] The photovoltaic module may further include an encapsulation layer 34 for encapsulating multiple arrayed solar cells 31 between a cover plate 32 and a backplate 33. It is worth noting that the multiple arrayed solar cells 31 can collect current via solder ribbons and busbars. The connection method between the solder ribbons and busbars and the multiple arrayed solar cells 31 can be achieved using existing connection methods, and will not be elaborated further here.

[0089] This invention also provides a power station, which includes the photovoltaic module 30 provided in the above embodiments.

[0090] In summary, the technical solutions provided by the embodiments of the present invention include:

[0091] Technical Solution 1: A silicon wafer 10, said silicon wafer 10 being used to fabricate a solar cell 20, which is a quadrilateral structure obtained by cutting a circular silicon rod, comprising:

[0092] At least three corners of the quadrilateral structure originate from the internal region of the cross-section of the circular silicon rod, wherein the internal region of the cross-section is a region on the cross-section with a resistivity lower than a set threshold, and the set threshold is determined by the resistivity of the region of the circular silicon rod with a sharp increase in resistivity;

[0093] The resistivity of the silicon wafer 10 decreases along a specific set of diagonals in the quadrilateral structure.

[0094] Technical Solution 2: The silicon wafer 10 as described in Technical Solution 1,

[0095] In the quadrilateral structure, three corners correspond to the inner region of the circular silicon rod, and the remaining corner corresponds to the region outside the inner region of the circular silicon rod. The corner corresponding to the region outside the inner region of the circular silicon rod and its opposite corner form the set of specific opposite corners.

[0096] Technical Solution 3: The silicon wafer 10 according to Technical Solution 1,

[0097] The four corners of the quadrilateral structure correspond to the inner regions of the circular silicon rod.

[0098] Technical solution 4: The silicon wafer 10 according to technical solution 2 or 3,

[0099] One corner of the quadrilateral structure is a chamfer 11, wherein the chamfer 11 is formed by removing part or all of the region of sharp increase in resistivity of the circular silicon rod;

[0100] The chamfer 11 and its opposite corner 12 form the specific set of opposite corners.

[0101] Technical Solution 5: The silicon wafer according to any one of Technical Solutions 1 to 3,

[0102] The silicon wafer has multiple regions with the same resistivity that are all arc-shaped.

[0103] The line connecting the set of specific diagonals passes through the plurality of the arc structures, and one of the angles in the set of specific diagonals is the center of the plurality of the arc structures.

[0104] Technical Solution 6: The silicon wafer as described in Technical Solution 4,

[0105] In the quadrilateral structure, apart from the chamfer 11 and its opposite corner 12, the resistivity of the other two corners is less than or equal to the resistivity of the chamfer 11. Preferably, the resistivity of the other two corners is less than the resistivity of the chamfer 11.

[0106] Technical Solution 7: The silicon wafer as described in Technical Solution 4.

[0107] The chamfer side length or chamfer arc length of the chamfer (11) is greater than or equal to Wherein, L′ represents the width of the edge region with the highest resistivity in the circular silicon rod; L and D represent the length and width of the silicon wafer, respectively.

[0108] Technical Solution 8: The silicon wafer as described in Technical Solution 7.

[0109] The chamfer side length or chamfer arc length of the chamfer 11 is greater than or equal to 8mm.

[0110] Technical Solution 9: The silicon wafer according to any one of Technical Solutions 1 to 3,

[0111] The silicon wafer has a side length of 156–800 mm.

[0112] Technical Solution 10: The silicon wafer according to any one of Technical Solutions 1 to 3, 6 and 7, wherein the circular silicon rod is a circular single-crystal silicon rod.

[0113] Technical Solution 11: A method for preparing a silicon wafer according to any one of Technical Solutions 1 to 10, comprising:

[0114] Based on a preset grid-shaped / deformed grid structure, a circular silicon rod is cut, and each line segment of the grid-shaped / deformed grid structure is controlled to pass through the internal region of the cross-section of the circular silicon rod to obtain multiple quadrilateral silicon rods. The grid-shaped / deformed grid structure is inscribed within the cross-section of the circular silicon rod, or at least one set of diagonals of the largest quadrilateral in the grid-shaped / deformed grid structure extends out of the cross-section of the circular silicon rod. The internal region of the cross-section is the region on the cross-section with resistivity lower than a set threshold, wherein the set threshold is determined by the resistivity of the region of the circular silicon rod with a sharp increase in resistivity.

[0115] The quadrilateral silicon rod is sliced ​​to obtain silicon wafers.

[0116] Technical Solution 12: According to the silicon wafer preparation method described in Technical Solution 11, the step of cutting the circular silicon rod includes:

[0117] A circular silicon rod is cut by three parallel first cutting lines and three parallel second cutting lines that intersect the first cutting lines. The orthographic projections of the three first cutting lines and the three second cutting lines form the grid-shaped / deformed grid structure. All three first cutting lines and three second cutting lines pass through the internal region of the cross-section of the circular silicon rod. The first cutting line in the middle position of the three first cutting lines and the second cutting line in the middle position of the three second cutting lines coincide with the diameter of the cross-section of the circular silicon rod.

[0118] Technical Solution 13: The silicon wafer preparation method according to Technical Solution 11, after obtaining multiple quadrilateral silicon rods and before slicing the quadrilateral silicon rods, further includes:

[0119] Remove the edge region of a specific interior corner of the quadrilateral silicon rod, wherein the specific interior corner is inherited from an interior corner of the largest quadrilateral in the grid-shaped / grid-deformed structure;

[0120] The step of slicing the quadrilateral silicon rod includes slicing the quadrilateral silicon rod by removing an edge region with a specific interior corner to obtain a silicon wafer.

[0121] Technical Solution 14. According to the preparation method of Technical Solution 13, removing the edge region of a specific inner corner of the quadrilateral silicon rod includes:

[0122] Determine the width of the edge region with the highest resistivity in the circular silicon rod;

[0123] Based on the width of the edge region with higher resistivity in the circular silicon rod and the size of the silicon wafer to be produced, the chamfer side length or chamfer arc length of the required chamfer of the silicon wafer is determined;

[0124] Based on the determined chamfer side length or chamfer arc length, the edge region of a specific interior corner of the quadrilateral silicon rod is cut.

[0125] Technical Solution 15: The preparation method according to any one of technical solutions 11 to 14 further includes:

[0126] The corners of the quadrilateral silicon rod are flattened.

[0127] And / or,

[0128] The sides of the quadrilateral silicon rod are flattened.

[0129] Technical Solution 16: The preparation method according to any one of Technical Solutions 11 to 14,

[0130] The circular silicon rod is a circular single-crystal silicon rod.

[0131] Technical Solution 17: A solar cell, wherein the solar cell is prepared using any one of the silicon wafers 10 described in Technical Solutions 1 to 10.

[0132] Technical solution 18, based on the solar cell described in technical solution 17, further includes: a cell chamfer 21, wherein,

[0133] The chamfer 21 of the battery is formed based on the chamfer 11 of the silicon wafer 10.

[0134] Technical Solution 19: The solar cell according to Technical Solution 17,

[0135] The solar cell further includes: fine grid lines 22, wherein the fine grid lines 22 are parallel to a set of opposite sides of the silicon wafer 10;

[0136] And / or,

[0137] The solar cell further includes a main grid line 23, wherein the main grid line 23 is parallel to a set of opposite sides of the silicon wafer 10.

[0138] Technical solution 20: A photovoltaic module, comprising: a plurality of solar cells 31 arranged in an array, wherein the solar cells 31 are prepared from solar cells provided in any one of technical solutions 17 to 19.

[0139] Technical solution 21: A power station, comprising the photovoltaic module 30 provided in technical solution 20.

[0140] The above steps are provided only to help understand the method, structure, and core ideas of this invention. Those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A silicon wafer (10) characterized by, The silicon wafer (10) is used for preparing a solar cell (20), which is a quadrilateral structure obtained by cutting a circular silicon rod, the quadrilateral structure refers to two groups of paralleled opposite sides, including: At least three corners of the quadrilateral structure come from an inner region on a cross section of the circular silicon rod, wherein the inner region on the cross section is a region with a resistivity lower than a set threshold on the cross section, and the set threshold is determined by a resistivity of a region with a sharp increase of resistivity of the circular silicon rod; The resistivity of the silicon wafer (10) decreases along a specific pair of opposite corners of the quadrilateral structure; the remaining pair of corners of the quadrilateral structure of the silicon wafer corresponds to a region with a sharp increase of resistivity outside the inner region of the circular silicon rod, wherein the corner corresponding to the region with a sharp increase of resistivity outside the inner region of the circular silicon rod and its opposite corner form a specific pair of opposite corners.

2. The silicon wafer (10) according to claim 1, wherein: The four corners of the quadrilateral structure correspond to the inner region of the circular silicon rod.

3. The silicon wafer (10) according to claim 1 or 2, wherein: One corner of the quadrilateral structure is a chamfered corner (11), and the remaining three corners are right angles corresponding to the inner region of the circular silicon rod, wherein the chamfered corner (11) is formed by removing part or all of the region with a sharp increase of resistivity of the circular silicon rod; The chamfered corner (11) and its opposite corner (12) form the specific pair of opposite corners.

4. The silicon wafer according to claim 1 or 2, wherein: The regions with the same resistivity in the silicon wafer are all in an arc structure; The line connecting the specific pair of opposite corners passes through a plurality of the arc structures, and one corner of the specific pair of opposite corners is the center of the plurality of the arc structures.

5. The silicon wafer according to claim 3, wherein: The chamfer (11) has a chamfer edge length or a chamfer arc length greater than or equal to L' represents the width of the edge region with the maximum resistivity in the circular silicon rod; L and D represent the length and the width of the silicon wafer, respectively.

6. The silicon wafer according to claim 3, wherein: In the quadrilateral structure, the resistivities of the other two corners except the chamfered corner (11) and its opposite corner (12) are less than or equal to the resistivity of the chamfered corner (11).

7. The silicon wafer according to claim 5, wherein: The length of the chamfered side or the arc length of the chamfered corner (11) is greater than or equal to 8 mm.

8. The silicon wafer according to claim 1 or 2, wherein: The side length of the silicon wafer is 156-800 mm.

9. The silicon wafer according to any one of claims 1, 2, 5 and 6, wherein: The circular silicon rod is a circular single crystal silicon rod.

10. The silicon wafer according to claim 6, wherein: The resistivities of the other two corners are less than the resistivity of the chamfered corner (11).

11. A method of producing a silicon wafer as claimed in any one of claims 1 to 10, characterized in that including: The circular silicon rod is cut based on a preset ploughshare shape / ploughshare deformation structure, and each line segment of the ploughshare shape / ploughshare deformation structure passes through an inner region on a cross section of the circular silicon rod, to obtain a plurality of quadrilateral silicon rods, wherein the ploughshare shape / ploughshare deformation structure is inscribed in the cross section of the circular silicon rod, or at least one group of opposite angles of the largest quadrilateral in the ploughshare shape / ploughshare deformation structure extends out of the cross section of the circular silicon rod, and the inner region on the cross section is a region with a resistivity lower than a set threshold on the cross section, wherein the set threshold is determined by the resistivity of a region with a sharp increase in resistivity of the circular silicon rod; The quadrilateral silicon rods are sliced to obtain silicon wafers.

12. The method of claim 11, wherein the silicon wafer is prepared by a method comprising: The cutting of the circular silicon rod comprises: ​ The circular silicon rod is cut by three mutually parallel first cutting lines and three mutually parallel second cutting lines intersecting the first cutting lines, wherein the orthogonal projections of the three first cutting lines and the orthogonal projections of the three second cutting lines form the ploughshare shape / ploughshare deformation structure, the three first cutting lines and the three second cutting lines all pass through the inner region of the cross section of the circular silicon rod, and the first cutting line in the middle position of the three first cutting lines and the second cutting line in the middle position of the three second cutting lines both coincide with the diameter of the cross section of the circular silicon rod.

13. The method for preparing a silicon wafer according to claim 11, characterized in that, After the plurality of quadrilateral silicon rods are obtained, before the quadrilateral silicon rods are sliced, the method further comprises: Removing an edge region of a specific interior angle in the quadrilateral silicon rod, wherein the specific interior angle corresponds to an interior angle of the largest quadrilateral in the ploughshare shape / ploughshare deformation structure, and the specific interior angle is an angle corresponding to the edge of the circular silicon rod; The slicing of the quadrilateral silicon rod comprises slicing the quadrilateral silicon rod from which the edge region of the specific interior angle is removed to obtain a silicon wafer.

14. The method of claim 13, wherein, The removing of the edge region of the specific interior angle in the quadrilateral silicon rod comprises: Determining the width of the edge region with the largest resistivity in the circular silicon rod; According to the width of the edge region with greater resistivity in the circular silicon rod and the size of the silicon wafer to be prepared, the length of the chamfer edge or the arc length of the chamfer required by the silicon wafer specifically comprises: controlling the length of the chamfer edge or the arc length of the chamfer to be greater than or equal to wherein L' represents the width of the edge region with the greatest resistivity in the circular silicon rod; L and D respectively represent the length and width of the silicon wafer; Based on the determined chamfer edge length or chamfer arc length, the edge region of the specific interior angle in the quadrilateral silicon rod is cut.

15. The production method according to any one of claims 11 to 14, characterized by, Further comprising: Each corner of the quadrilateral silicon rod is flattened; And / or, Each side surface of the quadrilateral silicon rod is flattened.

16. The preparation method according to any one of claims 12 to 14, wherein The circular silicon rod is a circular single crystal silicon rod.

17. The preparation method according to claim 15, wherein The circular silicon rod is a circular single crystal silicon rod.

18. A solar cell, characterized by, The solar cell is prepared by using the silicon wafer (10) according to any one of claims 1 to 10.

19. The solar cell of claim 18, wherein, Further comprising: A cell chamfer (21), wherein The cell chamfer (21) is formed based on the chamfer (11) of the silicon wafer (10).

20. The solar cell according to claim 18, wherein The solar cell further comprises a fine grid line (22), wherein the fine grid line (22) is parallel to a group of opposite sides of the silicon wafer (10). and / or, The solar cell further comprises: a main grid line (23), wherein the main grid line (23) is parallel to a pair of opposite edges of the silicon wafer (10).

21. A photovoltaic module, characterized by, Comprising: An array of a plurality of cell pieces (31), wherein the cell pieces (31) are prepared from the solar cell provided in any one of claims 18 to 20.

22. A power plant characterized by Comprising the photovoltaic module (30) provided in claim 21.

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