Solar cell, preparation method thereof, and photovoltaic module

Abstract

The present application relates to a solar cell, a preparation method of the solar cell, and a photovoltaic module. The solar cell includes: a substrate layer having a first surface and a second surface disposed opposite to each other; a tunneling layer disposed on the first surface; a polysilicon layer disposed on a side of the tunneling layer away from the first surface, the polysilicon layer having a first region and a second region disposed on the same surface, the element doping concentration of the first region being greater than that of the second region, the element doping width of the first region being less than that of the second region, and the first region being distributed along the boundary of the second region; and electrodes including a first electrode and a second electrode, the first electrode being electrically connected to the second region, and the second electrode being disposed on one side of the second surface. By using the above solar cell, the passivation effect of the solar cell can be improved on the premise of ensuring the normal operation of the solar cell.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and particularly to a solar cell, a preparation method of the solar cell, and a photovoltaic module. Background Art

[0002] With the continuous development of technology, solar cells (photovoltaic cells) have been widely used in people's daily lives due to their environmental protection, economy, and reliability. Solar cells generate electron-hole pairs based on the photovoltaic effect, and the electron-hole pairs are separated to generate current. Among them, to improve the efficiency of solar cells, a passivation contact layer is usually formed inside the solar cell, and then a passivation layer is formed on the silicon surface to reduce the surface state density and thus reduce the recombination of photo-generated carriers on the surface.

[0003] Currently, solar cells usually use a boron diffusion process to form a PN junction on a substrate, thereby forming a high-concentration boron diffusion layer on the surface and using the boron diffusion layer as a passivation contact layer. However, due to the high impurity concentration of the boron diffusion layer, the surface recombination of the boron diffusion layer is relatively high, resulting in poor passivation performance of the solar cell. At the same time, since the surface states of the boron diffusion layer are passivated globally, the edge effect is weakened, so the edge leakage is small, and thus there are more hot spots in the module. Therefore, the current passivation effect of solar cells is poor. Summary of the Invention

[0004] Based on this, it is necessary to provide a solar cell, a preparation method of the solar cell, and a photovoltaic module that can improve the passivation effect of the solar cell on the premise of ensuring the normal operation of the solar cell for the above technical problems.

[0005] In a first aspect, the present application provides a solar cell, which includes:

[0006] A substrate layer having a first surface and a second surface disposed opposite to each other;

[0007] A tunneling layer disposed on the first surface;

[0008] A polysilicon layer disposed on a side of the tunneling layer away from the first surface. The polysilicon layer has a first region and a second region disposed on the same surface. The element doping concentration of the first region is greater than that of the second region, the element doping width of the first region is less than that of the second region, and the first region is distributed along the boundary of the second region;

[0009] An electrode including a first electrode and a second electrode. The first electrode is electrically connected to the second region, and the second electrode is disposed on one side of the second surface.

[0010] In a second aspect, the present application also provides a method for manufacturing a solar cell, the method comprising:

[0011] Depositing a tunneling oxide layer on a substrate layer, wherein the substrate layer has a first surface and a second surface disposed opposite to each other, and the tunneling oxide layer is deposited on the first surface;

[0012] Depositing a layer to be annealed on a side of the tunneling oxide layer away from the first surface, and annealing the layer to be annealed to obtain a preliminary polysilicon layer;

[0013] Dividing the preliminary polysilicon layer into a first region and a second region disposed on the same surface, and doping elements are respectively doped into the first region and the second region to form a polysilicon layer, wherein the element doping concentration of the first region is greater than the element doping concentration of the second region, and the element doping width of the first region is less than the element doping width of the second region;

[0014] Setting a first electrode on the second region, electrically connecting the first electrode and the second region, and setting a second electrode on one side of the second surface.

[0015] In a third aspect, the present application also provides a photovoltaic module, the photovoltaic module comprising a first cover plate, a first encapsulant film, a battery string, a second encapsulant film, and a second cover plate which are stacked;

[0016] The battery string includes a plurality of electrically connected solar cells, and the solar cells are the solar cells as described above.

[0017] For the above-mentioned solar cell, the method for manufacturing a solar cell, and the photovoltaic module, the substrate layer has a first surface and a second surface disposed opposite to each other, and a tunneling layer is provided on the first surface of the substrate layer, which serves as a channel for electron tunneling and can achieve efficient carrier separation and transport; the first region in the polysilicon layer that does not form contact with the first electrode is doped with high-concentration elements, and the second region that forms contact with the first electrode is doped with low-concentration elements, so that the leakage current in the first region increases, which can reduce the working temperature of the solar cell and reduce hot spots; the element doping width of the first region in the polysilicon layer is less than the element doping width of the second region, and the first region is distributed along the boundary of the second region, effectively controlling the passivation effect of the high-concentration region in the polysilicon layer on the solar cell. Therefore, the surface recombination rate of the polysilicon layer is reduced, and the passivation performance of the solar cell can be improved. At the same time, the electrical contact formed between the first electrode of the solar cell and the second region of the polysilicon layer can ensure the normal flow of current inside the battery, and the second electrode provided on one side of the second surface can ensure the normal export of current; based on this, the present application can improve the passivation effect of the solar cell on the premise of ensuring the normal operation of the solar cell. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of the structure of an existing tunnel oxide passivated contact (TOPCon) solar cell in an embodiment;

[0020] Figure 2 It is a schematic diagram of the internal structure of a solar cell provided in an embodiment;

[0021] Figure 3 It is a schematic diagram of the positional relationship between a first region and a second region in an embodiment;

[0022] Figure 4 It is a schematic diagram of the internal structure of another solar cell provided in an embodiment;

[0023] Figure 5 It is the ECV curve of boron (B) element in a first region and a second region in an embodiment;

[0024] Figure 6 It is a schematic diagram of the Hall mobility and carrier concentration at different positions in the polysilicon layer under different comparative examples of a solar cell in an embodiment;

[0025] Figure 7 It is a schematic diagram of the minority carrier lifetime in a first sub-region and a second sub-region in an embodiment.

[0026] Reference Signs:

[0027] 1 - Solar cell;

[0028] 11 - Upper electrode;

[0029] 12 - Front passivation layer;

[0030] 13 - Boron-doped polysilicon layer;

[0031] 14 - Silicon substrate;

[0032] 15 - Oxide layer;

[0033] 16 - Back passivation layer;

[0034] 17 - Lower electrode;

[0035] 2 - Solar cell;

[0036] 21 - Substrate layer;

[0037] 22 - Tunneling layer;

[0038] 23 - Polysilicon layer;

[0039] 24 - Electrode;

[0040] 25 - Passivation layer;

[0041] 211 - First side;

[0042] 212 - Second side;

[0043] 231 - First region;

[0044] 232 - Second region;

[0045] 241 - First electrode;

[0046] 242 - Second electrode. Detailed implementation manners

[0047] For a better understanding of the technical solutions of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0048] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0049] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0050] It should be understood that the term " / and / " used herein is only a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0051] It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described from the angles shown in the drawings and should not be construed as limiting the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0052] First of all, it should be understood that for currently mainstream solar cells, the boron diffusion process is usually used to form a PN junction on the substrate, thereby forming a high-concentration boron diffusion layer on the surface. For example, referring to Figure 1 , Figure 1 is a schematic diagram of the structure of an existing tunnel oxide passivated contact (TOPCon) solar cell. The solar cell 1 is sequentially provided with an upper electrode 11, a front passivation layer 12, a boron-doped polysilicon layer 13, a silicon substrate 14, an oxide layer 15, a back passivation layer 16, and a lower electrode 17 from the light-facing side to the backlight side. Among them, the front surface of the silicon substrate 14 can be a textured surface, and the back surface can be a polished surface. The boron-doped polysilicon layer 13 can be a p+ poly-Si structure. It can be understood that the "p+" in the p+ poly-Si structure represents a p-type semiconductor material with a high doping concentration. By high-concentration doping, the conductivity of the polysilicon layer can be improved, so that the current can be more effectively transmitted inside the battery. However, due to the high impurity concentration of the boron diffusion layer, the surface recombination of the boron diffusion layer is likely to be high, which in turn makes the passivation performance of the solar cell poor. At the same time, since the surface states of the boron diffusion layer are passivated globally, that is, there is no black edge at the edge of the PL (Photoluminescence) picture of the solar cell, the edge effect is weakened. Therefore, the edge leakage is likely to be small, which in turn makes the component have more hot spots. Therefore, the above defects reflect the poor passivation effect of the current solar cell.

[0053] Therefore, this embodiment provides a solar cell to solve the above technical problems.

[0054] As Figure 2 shown, Figure 2Partial schematic diagram of the solar cell 2, the solar cell 2 includes a substrate layer 21, a tunneling layer 22, a polysilicon layer 23 and an electrode 24. Among them, the substrate layer 21 has a first surface 211 and a second surface 212 arranged oppositely. The tunneling layer 22 is arranged on the first surface 211. The polysilicon layer 23 is arranged on the side of the tunneling layer 22 away from the first surface 211. The polysilicon layer 23 has a first region 231 and a second region 232 arranged on the same surface. The element doping concentration of the first region 231 is greater than that of the second region 232. The element doping width of the first region 231 is less than that of the second region 232. The first region 231 is distributed along the boundary of the second region 232. The electrode 24 includes a first electrode 241 and a second electrode 242. The first electrode 241 and the second electrode 242 are electrically connected. The second electrode 242 is arranged on one side of the second surface 212. For example, in an implementable manner, the first surface 211 can be the light-facing surface, and the second surface 212 can be the backlight-facing surface. Then the tunneling layer 22 is arranged on the first surface 211, the polysilicon layer 23 is arranged on the side of the tunneling layer 22 away from the first surface 211, and the second electrode 242 is arranged on the backlight-facing surface side.

[0055] It should be noted that the substrate layer 21 can be a silicon-based substrate layer. The tunneling layer 22 is arranged on the first surface 211. The material of the tunneling layer 22 can specifically be silicon oxide. Along the thickness direction of the solar cell 2, the thickness of the tunneling layer 22 can be 1 nm to 10 nm. The polysilicon layer 23 is arranged on the side of the tunneling layer 22 away from the first surface 211. Along the thickness direction of the solar cell 2, the thickness of the polysilicon layer 23 can be 50 nm to 500 nm. Among them, in the thickness direction of the solar cell 2, it is perpendicular to the first surface 211 and the second surface 212 respectively. Then the first surface 211 and the second surface 212 of the substrate layer 21 arranged oppositely are parallel to each other. The first electrode 241 is electrically connected to the second region 232. The second electrode 242 is arranged on one side of the second surface 212. Among them, the first electrode 241 can be formed on the surface of the polysilicon layer 23 by screen printing, electroplating or evaporation. The second electrode 242 can be formed on the second surface 212 by screen printing, electroplating or evaporation. The materials of the first electrode 241 and the second electrode 242 can be one or more composites of copper, silver, aluminum and nickel.

[0056] It should be noted that the polysilicon layer 23 has a first region 231 and a second region 232 arranged on the same surface. The first electrode 241 is electrically connected to the second region 232. There are conditional restrictions on the dimensions of the first region 231 and the second region 232. In terms of the element doping concentration, the element doping concentration of the first region 231 is less than that of the second region 232. Specifically, the element doping concentration of the first region 231 is , and the element doping concentration of the second region 232 is , wherein the elements that the polysilicon layer 23 can be doped with can specifically be elements such as boron (B), phosphorus (P), antimony (Sb), arsenic (As), aluminum (Al), and gallium (Ga); in terms of the element doping width, the element doping width of the first region 231 is less than that of the second region 232. Specifically, the element doping width of the first region 231 is 4 nm, and the element doping width of the second region 232 is 8 nm; in terms of the positional relationship, the first region 231 is distributed along the boundary of the second region 232. It can be understood that the second region 232 refers to the region where the first electrode 241 contacts the polysilicon layer 23, and the region in the polysilicon layer 23 other than the second region 232 is the first region 231. For example, in an implementable manner, refer to Figure 3 , Figure 3 is a schematic diagram showing the positional relationship between the first region and the second region. Assuming that the cross-section of the polysilicon layer 23 on the light-facing side is rectangular, the positional distribution relationship between the first region and the second region can be shown in Figure (a). The first region is the edge region of the rectangle, and the second region is the rectangle-containing rectangle region within the rectangle. The positional distribution relationship between the first region and the second region can also be shown in Figure (b). The first region is the four corner point regions of the rectangle, and the second region is the other region within the rectangle except for the four corner point regions. In this embodiment, it is only limited that the first region is distributed along the boundary of the second region, and the first region and the second region together form the overall region of the polysilicon layer, so as to ensure that the region formed by the first region and the second region together is continuous, and the specific shapes of the first region or the second region are not limited.

[0057] It should be noted that the first electrode and the second region are electrically connected. Specifically, the first electrode and the second region can be electrically connected by direct physical connection. For example, the first electrode and the second region are electrically connected by physical means such as welding or crimping. The first electrode and the second region can also be indirectly connected by other materials or structures to form an electrical connection. For example, the first electrode and the second region are electrically connected by means of a metallization layer, conductive adhesive, conductive film, conductive oxide, or embedded structure. When two electrodes, namely the first electrode and the second electrode, are provided in the electrodes of the solar cell, the extraction of the solar cell and the connection with the external circuit can be realized. Among them, the first electrode is electrically connected to the second region in the polysilicon layer and serves as the negative electrode or positive electrode of the solar cell, while the second electrode is provided on the second surface side and can be connected to the substrate layer, tunneling layer, or other functional layers and serves as the positive electrode or negative electrode of the solar cell, thus ensuring the normal flow of the internal current of the solar cell.

[0058] In this embodiment, a first region and a second region are formed in the polysilicon layer and arranged on the same plane. Among them, the second region is the region in the polysilicon layer that contacts the first electrode, and the first region is the region in the polysilicon layer except the second region and distributed along the boundary of the second region. In this embodiment, by setting the first region in the polysilicon layer that does not form contact with the first electrode to be doped with high-concentration elements, and the second region that forms contact with the first electrode to be doped with low-concentration elements, the leakage current of the first region is increased, which can reduce the working temperature of the solar cell and reduce hot spots. At the same time, by setting the element doping width of the first region in the polysilicon layer to be smaller than that of the second region, the leakage current conditions of different regions in the polysilicon layer can be made different, thereby effectively controlling the passivation effect of the high-concentration region in the polysilicon layer on the solar cell. Therefore, the surface recombination rate of the polysilicon layer is reduced, and the passivation performance of the solar cell can be improved. At the same time, the electrical contact formed between the first electrode of the solar cell and the second region of the polysilicon layer can ensure the normal flow of the internal current of the battery, and the second electrode arranged on one side of the second surface can ensure the normal export of the current. Based on this, this embodiment can improve the passivation effect of the solar cell on the premise of ensuring the normal operation of the solar cell.

[0059] In some embodiments, to further improve the passivation effect and stability of the solar cell, a passivation layer can also be deposited in the solar cell. The passivation layer covers the side of the polysilicon layer away from the first surface. Along the thickness direction of the solar cell, the first projection of the first electrode on the passivation layer is covered by the second projection of the second region on the passivation layer, where the thickness direction is perpendicular to the first surface and the second surface respectively. Through the setting of the passivation layer in this embodiment, the dangling bonds and interface state density on the surface of the silicon wafer can be reduced, thereby reducing the recombination rate. It can also be used as a transition layer between the polysilicon layer and the first electrode of the solar cell to improve the adhesion and stability of the first electrode.

[0060] It should be noted that the material of the passivation layer can be one or more laminations of thin films such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Along the thickness direction of the solar cell, the thickness of the passivation layer can be 50 nm to 150 nm. It can be understood that in the case where the first projection of the first electrode on the passivation layer is covered by the second projection of the second region on the passivation layer, the first electrode and the second region can be in full contact. By increasing the contact area between the first electrode and the second region, the electron transport efficiency inside the solar cell can be improved. Refer to Figure 4 , Figure 4 is a partial schematic diagram of the solar cell 2. As above, the solar cell 2 includes a substrate layer 21, a tunneling layer 22, a polysilicon layer 23, and an electrode 24. The solar cell also includes a passivation layer 25. Based on Figure 4It can be seen that the passivation layer 25 covers the side of the polysilicon layer 23 away from the first surface 211. Among them, the polysilicon layer 23 has a first region 231 and a second region 232 arranged on the same plane. It can be understood that taking the horizontal transverse direction as the x direction, the horizontal longitudinal direction as the y direction, and the direction perpendicular to the first surface and the second surface as the z direction, then the thickness direction is the z direction, and the thickness of the passivation layer of the solar cell in the thickness direction is the thickness of the solar cell in the z direction.

[0061] In this embodiment, by covering the side of the polysilicon layer away from the first surface between the polysilicon layer and the tunneling layer, the passivation effect and stability of the solar cell can be improved. At the same time, setting the first projection generated by the first electrode on the passivation layer to be covered by the second projection generated by the second region on the passivation layer can increase the contact area between the first electrode and the second region. Therefore, this embodiment can further improve the passivation effect of the solar cell while synchronously improving the internal transmission efficiency of the solar cell, that is, synchronously improving the conductivity of the solar cell.

[0062] In some embodiments, the total doping width of the solar cell is , the element doping width of the first region is , the element doping width of the second region is , , and satisfy the following between: , , .

[0063] It should be noted that by testing and selecting the relevant parameters of the solar cell, and controlling the prepared solar cell to meet the parameter requirement range, the passivation effect of the solar cell can be further improved. Taking the solar cell with a p+ poly-Si structure as an example, for the p+ poly-Si structure of the solar cell, its corresponding photoluminescence image has significant characteristics, that is, there will be obvious black edges in the edge region of the photoluminescence image, and in the black edge region, it usually means that the radiative recombination efficiency of electrons and holes in this region is low, thus affecting the passivation effect of the solar cell. Therefore, by controlling the element doping width of different regions in the polysilicon layer, the passivation effect of the solar cell can be further improved.

[0064] It should be noted that the total doping width of the solar cell corresponds to the overall doping region of the polysilicon layer, which specifically includes the first region and the second region. The total doping width, the doping width of the first region, and the doping width of the second region are represented as , and , exemplarily, assuming is 20 mm, then the doping width of the first region Specifically, the doping width of the second region may be 1 mm, 2 mm, 3 mm, 4 mm or 5 mm. Specifically, it can be 15mm, 16mm, 17mm, 18mm or 19mm, etc. It can be understood that in For 2mm 18mm, For 3mm 17mm, For 4mm is 16 mm, that is, .

[0065] After controlling the element doping width of the first region and the element doping width of the second region based on the above conditions, the first region of the solar cell has limited effect on passivation. At the same time, since the first region is doped with high concentration elements relative to the second region, the leakage current in the first region will increase, thereby lowering the operating temperature of the solar cell and reducing hot spots. In an practicable manner, the first region can be understood as the edge region of the p+poly-Si structure of the solar cell, and the second region can be understood as the central region of the p+poly-Si structure of the solar cell.

[0066] This embodiment characterizes the passivation performance characteristics of the solar cell by introducing the element doping width, and sets the corresponding relationship between the element doping width of different regions and the total doping width of the solar cell, while ensuring that the high-concentration element doping region has little effect on the passivation of the solar cell. At the same time, since the high-concentration element region can increase leakage current, thereby reducing the operating temperature of the solar cell, it is possible to improve the heat dissipation effect of the solar cell on the basis of ensuring the passivation performance of the solar cell, thereby further improving the passivation effect of the solar cell.

[0067] In some embodiments, 15mm, and satisfy: , , exemplary, It can be 1mm, 1.05mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.24mm, 3.8mm or 4mm, etc. It can be 11mm, 11.2mm, 11.75mm, 12mm, 12.5mm, 13mm, 13.5mm, 13.95mm and 14mm, etc.

[0068] It should be noted that when the element doping widths in the first region of the solar cell are different, the conductivity of the solar cell is different. As shown in Table 1 below, Comparative Example 1 represents the structure of the mainstream solar cell 1 in the prior art as shown in Figure 1 In the prior art, in the polysilicon layer, element doping is carried out by boron diffusion, and the entire polysilicon layer is uniformly doped with boron element at the same concentration. The structure of the solar cell 1 is as above, which will not be elaborated in this embodiment. It can be understood that in Comparative Example 1, since boron element is uniformly doped in the whole layer, the solar cell prepared in Comparative Example 1 can be understood as a "black-edge-free cell", that is, in the photoluminescence picture of this solar cell, the edge of its p+poly-Si structure does not turn black.

[0069] Furthermore, Comparative Example 2 represents the structure of the solar cell 2 as shown in Figure 2 In the polysilicon layer, different concentrations of elements are doped in the first region and the second region. The boron element doping concentration in the first region is greater than that in the second region, and the boron doping width in the first region is smaller than the element doping width in the second region. And the boron doping width in the first region is controlled between 0 mm and 5 mm, and the boron doping width in the second region is controlled between 10 mm and 15 mm. The structure of the solar cell 2 is as shown in Figure 2 In this embodiment, it will not be elaborated here. It can be understood that since boron element is doped at different concentrations in different regions of the polysilicon layer, and the width of the first region is controlled to be between 0 mm and 5 mm, the solar cell prepared in Comparative Example 2 can be understood as a "5-mm black-edge cell", that is, in the photoluminescence picture of this solar cell, the black edge of its p+poly-Si structure is 5 mm.

[0070] Furthermore, Comparative Example 3 also represents the structure of the solar cell 2 as shown in Figure 2 In the polysilicon layer, different concentrations of elements are doped in the first region and the second region. The boron element doping concentration in the first region is greater than that in the second region, and the boron doping width in the first region is smaller than the boron element doping width in the second region. The difference from Comparative Example 2 is that Comparative Example 3 only controls the total doping width of the solar cell and the element doping width in the first region and the element doping width in the second region to satisfy: wherein, the element doping width in the first region is controlled to be 20 mm, the total doping width of the solar cell is not limited, and the element doping width in the second region is not limited. The structure of the solar cell 2 is as shown in Figure 2 ​​As shown, the details of this embodiment will not be elaborated here. It can be understood that since boron elements are doped in different regions of the polysilicon layer at different concentrations, and the width of the first region is controlled to be 20 mm, the solar cell prepared in Comparative Example 3 can be understood as a "20-mm black-edge cell", that is, in the photoluminescence image of this solar cell, the black edge at the edge of its p+ poly-Si structure is 20 mm.

[0071]

[0072] Among them, the other parameters of the solar cells in different comparative examples are the same and will not be elaborated one by one here. In Table 1 above, "Eta" represents the proportion of the solar cell converting solar energy into electrical energy, "Uoc" represents the open-circuit voltage, "Isc" represents the short-circuit current, "FF" represents the fill factor, "RS" represents the series resistance, and "Rsh" represents the parallel resistance.

[0073] Combined with the test data of different parameters in the above comparative examples, it can be seen that by doping different regions of the polysilicon layer with different element doping concentrations and controlling the element doping width of the high-concentration doping region to be smaller than that of the low-concentration region, compared with the solar cell with the entire polysilicon layer uniformly doped with the same element doping concentration, it has better electrical performance. That is, after setting the first region and the second region on the same plane in the polysilicon layer, and the element doping concentration of the first region is greater than that of the second region, the element doping width of the first region is smaller than that of the second region, and the first region is distributed along the boundary of the second region, the prepared solar cell 2 has better electrical performance than the mainstream solar cell 1 in the prior art; at the same time, by comparing Comparative Example 2 and Comparative Example 3, it can be seen that in solar cell 2, if the element doping width of the first region is further controlled to be between 0 mm and 5 mm, accounting for 0% to 3% of the side length of the solar cell, compared with only controlling the element doping width of the first region to account for 0% to 3% of the total doping width of the solar cell and controlling the element doping concentration of the second region to account for 97% to 100% of the total doping concentration of the solar cell, it has better electrical performance. Therefore, when the total doping width of the solar cell is controlled to be 15 mm, and the element doping width of the first region is controlled to be between 0 mm and 5 mm, and the element doping width of the second region is controlled to be between 10 mm and 15 mm, it is possible to further improve the photoelectric conversion efficiency of the solar cell on the premise of improving the passivation effect of the solar cell.

[0074] In some embodiments, the element doping concentration of the first region is and the element doping concentration of the second region is , and satisfy:

[0075] , .

[0076] Exemplarily, specifically, it can be , , and etc. Specifically, it can be , , and It can be understood that after preparing a solar cell based on the structure shown in Figure 2 , the element doping concentration in the first region is greater than that in the second region. For example, assuming that the doping element is boron, Specifically, it can be , Specifically, it can be , that is, the boron element content concentration in the first region is greater than that in the second region. The reason is that during the preparation process of the solar cell, due to the influence of deposition, more boron source is deposited in the first region, resulting in a higher boron doping concentration in the first region. And because the boron element content in the first region of the p+ poly-Si of the solar cell is relatively high, it leads to an increase in leakage current in the first region. Therefore, it can reduce the component working temperature and reduce hot spots.

[0077] Referring to Figure 5 , Figure 5 is the ECV curve of boron (B) element representing the first region and the second region. Among them, the abscissa represents the depth, and the ordinate represents the doping concentration of boron element in the first region and the doping concentration of boron element in the second region. It can be seen from the figure that in the polysilicon layer, the doping concentration of boron element in the first region is greater than that in the second region, and in the direction from the polysilicon layer towards the tunneling layer, as the depth increases, the doping concentration of boron element in the first region and the doping concentration of boron element in the second region both gradually decrease. It should be noted that Q1 represents the ECV curve diagram of the first region, and Q2 represents the ECV curve diagram of the second region.

[0078] In some embodiments, in the polysilicon layer, the Hall mobility decreases along the direction from the center position of the second region to the first region. The Hall mobility of the first region is , and the Hall mobility of the second region is , and satisfy:

[0079] , .

[0080] It should be noted that for the characteristics of the black edge at the edge of the p+poly-Si of the solar cell, in addition to being characterized by the element doping widths of the first region and the second region, the Hall mobility can also be introduced for characterization. Among them, the Hall mobility is used to describe the migration rate of carriers in a semiconductor material under a unit electric field. It can be understood that the Hall mobility decreases along the direction from the central position of the second region to the first region, that is, the Hall mobility of the first region is lower than that of the second region. For example, the Hall mobility of the first region Specifically, it can be , , , and etc., and the Hall mobility of the second region Specifically, it can be , , , and etc. The central position of the second region can be understood as the geometric center position.

[0081] In some embodiments, in the polysilicon layer, the surface carrier concentration increases along the direction from the central position of the second region to the first region. The surface carrier concentration of the first region is , and the surface carrier concentration of the second region is , and Satisfy:

[0082] , .

[0083] It should be noted that for the characteristics of the black edge at the edge of the p+poly-Si of the solar cell, in addition to being characterized by the element doping widths of the first region and the second region, the surface carrier concentration can also be introduced for characterization. Among them, the surface carrier concentration is the number of carriers per unit area and unit height, which can determine the electrical performance of the solar cell. It can be understood that the surface carrier concentration increases along the direction from the central position of the second region to the first region, that is, the surface carrier concentration of the first region is greater than that of the second region. For example, the surface carrier concentration of the first region Specifically, it can be , , , and etc., and the surface carrier concentration of the second region Specifically, it can be , , , and etc., the central position of the second region can be understood as the geometric center position.

[0084] It should be noted that when the element doping widths in the first region of the solar cell are different, the Hall mobilities and carrier concentrations at different positions in the polysilicon layer are also different. As shown in Table 2 below, Comparative Example 4 represents the Hall mobility and surface carrier concentration at the central position of the second region of the solar cell, numbered 1, Comparative Example 5 represents the Hall mobility and surface carrier concentration 30 mm away from the central position of the second region of the solar cell, numbered 2, Comparative Example 6 represents the Hall mobility and surface carrier concentration 60 mm away from the central position of the second region of the solar cell, and Comparative Example 7 represents the Hall mobility and surface carrier concentration in the first region (edge) of the solar cell.

[0085]

[0086] Based on the test data of different parameters in the above comparative examples, when different regions of the polysilicon layer are doped with elements at different doping concentrations and the element doping width in the high-concentration doping region is controlled to be smaller than that in the low-concentration region, the Hall mobility decreases along the direction from the central position of the second region to the first region, and the surface carrier concentration increases along the direction from the central position of the second region to the first region. That is, by controlling different relevant parameters reflecting the black-edge characteristics of the p+ poly-Si structure of the solar cell within their respective corresponding conditions, the passivation effect of the solar cell can be further improved on the premise.

[0087] Referring to Figure 6 , Figure 6 is a schematic diagram showing the Hall mobilities and carrier concentrations at different positions in the polysilicon layer under different comparative examples of the solar cell. Among them, number 1 corresponds to Comparative Example 4, number 2 corresponds to Comparative Example 5, number 3 corresponds to Comparative Example 6, and number 4 corresponds to Comparative Example 7. As can be seen from the figure, the Hall mobility decreases along the direction from the central position of the second region to the first region, and the surface carrier concentration increases along the direction from the central position of the second region to the first region.

[0088] In some embodiments, the minority carrier lifetime in the first region is , and the minority carrier lifetime in the second region is , and satisfy: .

[0089] It should be noted that for the characteristic of the black edge at the edge of the p+ poly-Si in the solar cell, in addition to being characterized by the element doping widths of the first region and the second region, the minority carrier lifetime can also be introduced for characterization. The minority carrier lifetimes in different regions of the polysilicon layer are different. Among them, the minority carrier lifetime refers to the time from the generation of photo-generated electrons and holes in the semiconductor until they disappear. By controlling the minority carrier lifetime of the first region and the minority carrier lifetime of the second region to satisfy , the overall performance of the solar cell can be further improved.

[0090] In some embodiments, the first region includes a first sub-region and a second sub-region. The element doping width of the first sub-region is less than that of the second sub-region. The minority carrier lifetime of the first sub-region under the first light injection dose is , and the minority carrier lifetime of the first sub-region under the second light injection dose is , and satisfy: , and the minority carrier lifetime of the second sub-region under the first light injection dose is , and the minority carrier lifetime of the second sub-region under the second light injection dose is , and satisfy: , where the first light injection dose is less than the second light injection dose.

[0091] It should be noted that the first region includes a first sub-region and a second sub-region. The first sub-region and the second sub-region are used to represent different types of sub-regions within the first region. Specifically, the first sub-region can be a narrow black edge region, and the second sub-region is a wide black edge region. It can be understood that due to the different element doping widths of the first sub-region and the second sub-region, their minority carrier lifetimes under different light injection doses are different. As the light injection dose increases, for any sub-region of the first region, its minority carrier lifetime will increase. And as the black edge characteristic of the sub-region increases, the relationship between the minority carrier lifetimes of the sub-region under different light injection doses decreases. Refer to Figure 7 , Figure 7Schematic diagram of minority carrier lifetime representing the first sub-region and the second sub-region, where the abscissa is the optical injection dose and the ordinate is the minority carrier lifetime. Q3 is the minority carrier lifetime curve of the first sub-region, and Q4 is the minority carrier lifetime curve of the second sub-region. Specifically, the first sub-region can be the region of 5 mm of the p+ poly-Si black edge of the solar cell, and the second sub-region can be the region of 5 mm of the p+ poly-Si black edge of the solar cell. As can be seen from the figure, the minority carrier lifetime of the first sub-region shows a decreasing trend as a whole, and the minority carrier lifetime of the second sub-region has a critical value, showing an increasing trend before the critical value and a decreasing trend after the critical value. By controlling the minority carrier lifetime of the first sub-region at the first optical injection dose to be and the minority carrier lifetime of the first sub-region at the second optical injection dose to be , and satisfy: The minority carrier lifetime of the second sub-region at the first optical injection dose is , and the minority carrier lifetime of the second sub-region at the second optical injection dose is , and satisfy: where the first optical injection dose is less than the second optical injection dose, and the passivation effect of the solar cell can be further improved through the parameter dimension of the minority carrier lifetime.

[0092] This embodiment also provides a preparation method of a solar cell. The preparation method of the solar cell includes:

[0093] Deposit a tunneling oxide layer on the substrate layer. The substrate layer has a first surface and a second surface arranged opposite to each other, and the tunneling oxide layer is deposited on the first surface; deposit a layer to be annealed on the side of the tunneling oxide layer away from the first surface, and perform an annealing treatment on the layer to be annealed to obtain a preliminary polysilicon layer; divide the preliminary polysilicon layer into a first region and a second region arranged on the same plane, and dope doping elements into the first region and the second region respectively to form a polysilicon layer, where the element doping concentration of the first region is greater than that of the second region, and the element doping width of the first region is less than that of the second region; set a first electrode on the second region, electrically connect the first electrode and the second region, and set a second electrode on the side of the second surface.

[0094] It should be noted that the preparation process of preparing the above solar cell 2 can be specifically as follows:

[0095] 1) Deposit a tunneling oxide layer ( 1) Using an LP (presumably referring to a specific deposition equipment or technology) machine, deposit at a temperature in the range of 400°C - 900°C, and control the thickness of the oxide layer between 1nm - 10nm to achieve an ultra-thin tunneling effect; 2) Deposit a polysilicon (poly-Si) layer: Continuously deposit a polysilicon layer with a thickness of 50nm - 500nm on the tunneling oxide layer. The deposition temperature is relatively low, at 300°C - 700°C, to avoid thermal damage to the underlying tunneling oxide layer; 3) Annealing treatment: Anneal and crystallize the deposited polysilicon layer in an annealing furnace. The annealing temperature is relatively high, at 900°C - 1400°C, to promote the crystallization of polysilicon and reduce defects. The annealing time is usually between 5min - 100min, depending on the required crystallization quality and process efficiency; 4) Boron diffusion: Perform boron diffusion treatment on the annealed polysilicon layer. The boron diffusion deposition temperature and push temperature are in the ranges of 700°C - 900°C and 800°C - 1000°C respectively. Through boron diffusion, a p+-type polysilicon layer is formed, and the boron element content reaches 1E17 - 1E21 atom / cm³ to improve conductivity and form a good ohmic contact; 5) A passivation layer can also be formed on the polysilicon layer: Above the polysilicon layer, a passivation layer can be further deposited, and the passivation layer can reduce surface recombination and improve the passivation of the device.

[0096] For the preparation method of the above solar cell, the substrate layer has a first surface and a second surface arranged opposite to each other, and a tunneling layer is provided on the first surface of the substrate layer. As a channel for electron tunneling, it can achieve efficient carrier separation and transmission; the first region in the polysilicon layer that does not form contact with the first electrode is doped with a high-concentration element, and the second region that forms contact with the first electrode is doped with a low-concentration element, so that the leakage current in the first region increases, which can reduce the working temperature of the solar cell and reduce hot spots; the element doping width of the first region in the polysilicon layer is less than that of the second region, and the first region is distributed along the boundary of the second region, effectively controlling the passivation effect of the high-concentration region in the polysilicon layer on the solar cell. Therefore, the surface recombination rate of the polysilicon layer is reduced, and the passivation performance of the solar cell can be improved. At the same time, the electrical contact formed between the first electrode of the solar cell and the second region of the polysilicon layer can ensure the normal flow of current inside the battery, and the second electrode provided on one side of the second surface can ensure the normal export of current; based on this, the present application can improve the passivation effect of the solar cell on the premise of ensuring the normal operation of the solar cell.

[0097] This embodiment also provides a photovoltaic module, which includes a first cover plate, a first encapsulant, a battery string, a second encapsulant, and a second cover plate arranged in a stacked manner. The battery string includes a plurality of electrically connected solar cells.

[0098] It should be noted that the first cover plate is located on the light-facing side of the battery string, which is used to transmit sunlight and improve the waterproof and moisture-proof capabilities of the photovoltaic module, and jointly seals the battery string with the second cover plate; during the lamination process of the photovoltaic module, the first encapsulant film and the second encapsulant film are used to encapsulate the battery string to prevent the external environment from affecting the performance of the battery string, and at the same time, they can also bond the first cover plate, the battery string, and the second cover plate into a whole.

[0099] Among them, the materials of the first encapsulant film and the second encapsulant film can be one of materials such as ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), polyvinyl butyral (PVB), etc., and can also be an EPE encapsulant film (EVA-POE-EVA co-extrusion structure) or an EP encapsulant film (EVA-EP co-extrusion structure).

[0100] This embodiment also provides a tandem battery, which includes a top cell, an intermediate connection layer, and a bottom cell, and the intermediate connection layer is connected between the bottom cell and the top cell. The top cell is one of a perovskite cell, a cadmium telluride solar cell, a copper indium gallium selenide solar cell, or a gallium arsenide solar cell, and the bottom cell is the above-mentioned solar cell 2.

[0101] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A solar cell, characterized in that: The solar cell comprises: A substrate layer, the substrate layer having a first surface and a second surface arranged opposite to each other; A tunneling layer, the tunneling layer is arranged on the first surface; a polysilicon layer, the polysilicon layer being arranged on a side of the tunneling layer away from the first surface, the polysilicon layer having a first region and a second region arranged on the same surface, the element doping concentration of the first region being greater than the element doping concentration of the second region, the element doping width of the first region being less than the element doping width of the second region, and the first region being distributed along a boundary of the second region; The electrode comprises a first electrode and a second electrode, the first electrode is electrically connected to the second region, and the second electrode is arranged on one side of the second surface, wherein the total doping width of the solar cell is , the element doping width of the first region is , the element doping width of the second region is , , and Satisfy between: , , .

2. The solar cell according to claim 1, characterized in that: The solar cell also includes a passivation layer, which covers a side of the polysilicon layer away from the first surface. Along the thickness direction of the solar cell, a first projection of the first electrode on the passivation layer is covered by a second projection of the second region on the passivation layer, wherein the thickness direction is perpendicular to the first surface and the second surface, respectively.

3. The solar cell according to claim 1, characterized in that 15mm, and satisfy: , .

4. The solar cell according to claim 1, characterized in that The element doping concentration of the first region is , the element doping concentration of the second region is , and satisfy: ， 。 5. The solar cell according to claim 1, characterized in that: In the polysilicon layer, the Hall mobility decreases in a direction from the center of the second region to the first region, and the Hall mobility of the first region is , the Hall mobility of the second region is , and satisfy: ， 。 6. The solar cell according to claim 1, characterized in that In the polysilicon layer, the surface carrier concentration increases in a direction from the center position of the second region to the first region, and the surface carrier concentration of the first region is , the surface carrier concentration of the second region is , and satisfy: ， 。 7. The solar cell according to claim 1, characterized in that The minority carrier lifetime in the first region is , the minority carrier lifetime in the second region is , and satisfy: .

8. The solar cell according to claim 7, characterized in that: The first region includes a first sub-region and a second sub-region, the element doping width of the first sub-region is smaller than the element doping width of the second sub-region, and the minority carrier lifetime of the first sub-region under the first light injection dose is , the minority carrier lifetime of the first sub-region under the second light injection dose is , and satisfy: , the minority carrier lifetime of the second sub-region under the first light injection dose is , the minority carrier lifetime of the second sub-region under the second light injection dose is , and satisfy: , wherein the first light injection dose is less than the second light injection dose.

9. A method for preparing a solar cell, characterized in that: The method comprises: Depositing a tunneling oxide layer on a substrate layer, wherein the substrate layer has a first surface and a second surface disposed opposite to each other, and the tunneling oxide layer is deposited on the first surface; Depositing a layer to be annealed on a side of the tunnel oxide layer away from the first surface, and performing annealing treatment on the layer to be annealed to obtain a preliminary polysilicon layer; The preliminary polysilicon layer is divided into a first region and a second region disposed on the same surface, and doping elements are respectively doped into the first region and the second region to form a polysilicon layer, wherein the element doping concentration of the first region is greater than the element doping concentration of the second region, the element doping width of the first region is less than the element doping width of the second region, and the first region is distributed along a boundary of the second region; A first electrode is disposed on the second region, and the first electrode and the second region are electrically connected, and a second electrode is disposed on one side of the second surface, wherein the total doping width of the solar cell is , the element doping width of the first region is , the element doping width of the second region is , , and Satisfy between: , , .

10. A photovoltaic module, characterized in that: The photovoltaic module comprises a first cover plate, a first adhesive film, a battery string, a second adhesive film and a second cover plate which are stacked; The cell string includes a plurality of electrically connected solar cells, and the solar cell is the solar cell according to any one of claims 1 to 8.

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