Solar cell, preparation method of solar cell and photovoltaic module

Abstract

The invention relates to a solar cell, a preparation method of the solar cell and a photovoltaic module. The solar cell comprises a substrate layer which is provided with a first surface and a second surface which are oppositely arranged; the tunneling layer is arranged on the first surface; the polycrystalline silicon layer is arranged on the side, away from the first face, of the tunneling layer, the polycrystalline silicon layer is provided with a first area and a second area which are arranged on the same face, the element doping concentration of the first area is larger than that of the second area, and the element doping width of the first area is smaller than that of the second area; the first region is distributed along the boundary of the second region; the electrodes comprise the first electrode and the second electrode, the first electrode is electrically connected with the second area, and the second electrode is arranged on one side of the second face. By adopting the solar cell, the passivation effect of the solar cell can be improved on the premise of ensuring the normal work of the solar cell.

Description

Technical Field

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

[0002] With the continuous development of science and 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 photoelectric effect. The electron-hole pairs are separated to generate current. In order 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, thereby reducing the recombination of photogenerated carriers on the surface.

[0003] At present, 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 the boron diffusion layer is used 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 high, which makes the passivation performance of the solar cell poor. At the same time, since the surface state of the boron diffusion layer is globally passivated, the edge effect is weakened, which easily leads to smaller edge leakage, and then there are more hot spots in the component. Therefore, the passivation effect of current solar cells is poor. Summary of the invention

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

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

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

[0007] A tunneling layer, the tunneling layer is arranged on the first surface;

[0008] 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;

[0009] The electrode includes 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.

[0010] In a second aspect, the present application also provides a method for preparing 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 tunnel oxide layer away from the first surface, and performing annealing treatment on the layer to be annealed to obtain a preliminary polysilicon layer;

[0013] 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, and the element doping width of the first region is less than the element doping width of the second region;

[0014] 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.

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

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

[0017] In the above-mentioned solar cell, method for preparing solar cell and photovoltaic module, the substrate layer has a first surface and a second surface arranged opposite to each other, and a tunneling layer is arranged on the first surface of the substrate layer, which serves as a channel for electron tunneling and can realize efficient carrier separation and transmission; the first area of ​​the polycrystalline silicon layer that is not in contact with the first electrode is doped with a high concentration of elements, and the second area that is in contact with the first electrode is doped with a low concentration of elements, so that the leakage of the first area is increased, which can reduce the operating temperature of the solar cell and reduce hot spots; the element doping width of the first area in the polycrystalline silicon layer is smaller than the element doping width of the second area, and the first area is distributed along the boundary of the second area, which effectively controls the passivation effect of the high concentration area in the polycrystalline silicon layer on the solar cell, thereby reducing the surface recombination rate of the polycrystalline silicon layer and improving the passivation performance of the solar cell. At the same time, the electrical contact formed between the first electrode of the solar cell and the second area of ​​the polycrystalline silicon layer can ensure the normal flow of current inside the battery, and the second electrode arranged on one side of the second surface can ensure the normal extraction of current; based on this, the present application can improve the passivation effect of the solar cell under 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 the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of a conventional tunnel oxide passivated contact (TOPCon) solar cell structure in one embodiment;

[0020] Figure 2 A schematic diagram of the internal structure of a solar cell provided in one embodiment;

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

[0022] Figure 4 A schematic diagram of the internal structure of another solar cell provided in one embodiment;

[0023] Figure 5 The ECV curves of the boron (B) element in the first region and the second region in one embodiment;

[0024] Figure 6 A schematic diagram of Hall mobility and carrier concentration at different positions in a polysilicon layer at different comparative ratios of a solar cell in an embodiment;

[0025] Figure 7 Schematic diagram of minority carrier lifetimes in the first sub-region and the second sub-region in one embodiment.

[0026] Reference numerals:

[0027] 1- Solar cell;

[0028] 11- upper electrode;

[0029] 12-front passivation layer;

[0030] 13-boron-doped polysilicon layer;

[0031] 14-silyl;

[0032] 15- oxide layer;

[0033] 16- back side passivation layer;

[0034] 17-lower electrode;

[0035] 2- Solar cells;

[0036] 21- substrate layer;

[0037] 22- tunneling layer;

[0038] 23-polysilicon layer;

[0039] 24-electrode;

[0040] 25- passivation layer;

[0041] 211-side 1;

[0042] 212-side 2;

[0043] 231-1st area;

[0044] 232-Second area;

[0045] 241- first electrode;

[0046] 242 - second electrode. DETAILED DESCRIPTION

[0047] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0048] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within 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 "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0050] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

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

[0052] First, it should be understood that the current mainstream solar cells usually use a boron diffusion process to form a PN junction on the substrate, thereby forming a high-concentration boron diffusion layer on the surface. Figure 1 , Figure 1 Schematic diagram of the existing tunnel oxide passivated contact (TOPCon) solar cell structure. The solar cell 1 is 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 in sequence from the light-facing side to the backlight side. The front side of the silicon substrate 14 can be a velvet surface, and the back side 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+ The "p+" in the poly-Si structure refers to a p-type semiconductor material with a high doping concentration. High-concentration doping can improve the conductivity of the polysilicon layer, so that the current can be more efficiently 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 high, which makes the passivation performance of the solar cell poor. At the same time, the surface state of the boron diffusion layer is fully passivated, that is, the PL (Photoluminescence) image of the solar cell has no black edges, thereby weakening the edge effect. Therefore, it is easy to cause small edge leakage, which in turn makes the component have more hot spots. Therefore, the above defects reflect the poor passivation effect of current solar cells.

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

[0054] like Figure 2 As shown, Figure 22 is a partial schematic diagram of a solar cell 2, wherein the solar cell 2 comprises a substrate layer 21, a tunneling layer 22, a polysilicon layer 23 and an electrode 24, wherein the substrate layer 21 has a first surface 211 and a second surface 212 arranged opposite to each other, the tunneling layer 22 is arranged on the first surface 211, the polysilicon layer 23 is arranged on a 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 the element doping concentration of the second region 232, and the element doping width of the first region 231 is less than the element doping width of the second region 232. The element doping width 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, and the second electrode 242 is arranged on the side of the second surface 212. For example, in an implementable manner, the first surface 211 can be a light-facing surface, and the second surface 212 can be a backlight 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 side.

[0055] It should be noted that the substrate layer 21 may be a silicon base layer, the tunneling layer 22 is disposed on the first surface 211, the material of the tunneling layer 22 may specifically be silicon oxide, and along the thickness direction of the solar cell 2, the thickness of the tunneling layer 22 may be 1 nm to 10 nm, the polycrystalline silicon layer 23 is disposed on the side of the tunneling layer 22 away from the first surface 211, and along the thickness direction of the solar cell 2, the thickness of the polycrystalline silicon layer 23 may be 50 nm to 500 nm, wherein the thickness direction of the solar cell 2 is perpendicular to the first surface 211 and the second surface 211, respectively. 2, the first surface 211 and the second surface 212 of the substrate layer 21 are arranged opposite to each other and are parallel to each other, the first electrode 241 and the second region 232 are electrically connected, and the second electrode 242 is arranged on one side of the second surface 212, wherein the first electrode 241 can be formed on the surface of the polysilicon layer 23 by screen printing, electroplating or evaporation process, and the second electrode 242 can be formed on the second surface 212 by screen printing, electroplating or evaporation process, and the materials of the first electrode 241 and the second electrode 242 can be a composite of one or more 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 and the second region 232 are electrically connected, the first region 231 and the second region 232 have conditional restrictions of different dimensions, and in terms of element doping concentration, the element doping concentration of the first region 231 is less than the element doping concentration of the second region 232. Specifically, the element doping concentration of the first region 231 is , the element doping concentration of the second region 232 is , wherein the elements that can be doped into the polysilicon layer 23 may specifically be boron (B), phosphorus (P), antimony (Sb), arsenic (As), aluminum (Al) and gallium (Ga) and the like; in terms of element doping width, the element doping width of the first region 231 is smaller than the element doping width of the second region 232, specifically, the element doping width of the first region 231 is 4nm, and the element doping width of the second region 232 is 8nm; in terms of positional relationship, the first region 231 is distributed along the boundary of the second region 232, and 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 one practicable manner, refer to Figure 3 , Figure 3 To illustrate 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 a rectangle, the positional distribution relationship between the first region and the second region can be as shown in Figure (a), where the first region is the edge region of the rectangle, and the second region is the rectangular region contained in the rectangle. The positional distribution relationship between the first region and the second region can also be as shown in Figure (b), where the first region is the four corner regions of the rectangle, and the second region is the other regions in the rectangle except the four corner regions. This embodiment only limits the first region to be distributed along the boundary of the second region, and the first region and the second region together constitute the entire region of the polysilicon layer, thereby ensuring that the region jointly constituted by the first region and the second region is continuous, and the specific shape of the first region or the second region is 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 electrically connected indirectly by other materials or structures. For example, the first electrode and the second region are electrically connected by means of a metallization layer, a conductive adhesive, a conductive film, a conductive oxide or an embedded structure. The first electrode and the second electrode are arranged on the electrodes of the solar cell, so that the solar cell can be led out and connected to an external circuit. The first electrode is electrically connected to the second region in the polysilicon layer as the negative electrode or the positive electrode of the solar cell, and the second electrode is arranged on one side of the second surface and can be connected to the substrate layer, the tunneling layer or other functional layers as the positive electrode or the negative electrode of the solar cell, thereby ensuring the normal flow of current inside the solar cell.

[0058] In this embodiment, a first region and a second region are formed in the polysilicon layer and are arranged on the same surface, wherein the second region is a region in the polysilicon layer that contacts the first electrode, and the first region is a region in the polysilicon layer that is excluding the second region and distributed along the boundary of the second region. In this embodiment, the first region in the polysilicon layer that is not in contact with the first electrode is doped with a high concentration of elements, and the second region in contact with the first electrode is doped with a low concentration of elements, so that the leakage of the first region is increased, the operating temperature of the solar cell can be reduced, and the hot spots can be reduced. In addition, the element doping width of the first region in the polysilicon layer is simultaneously set to be smaller than the element doping width of the second region, so that the leakage conditions of different regions in the polysilicon layer are different, thereby effectively controlling the passivation effect of the high-concentration region in the polysilicon layer on the solar cell, thereby reducing the surface recombination rate of the polysilicon layer and improving the passivation performance of the solar cell. 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 cell, and the second electrode arranged on one side of the second surface can ensure the normal extraction of the current. Based on this, the present embodiment can improve the passivation effect of the solar cell under the premise of ensuring the normal operation of the solar cell.

[0059] In some embodiments, in order to further improve the passivation effect and stability of the solar cell, a passivation layer can be deposited in the solar cell, and 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, wherein the thickness direction is perpendicular to the first surface and the second surface, respectively. Through the setting of the passivation layer, this embodiment can reduce the dangling bonds and interface state density on the surface of the silicon wafer, thereby reducing the recombination rate. It can also serve 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 stacks of thin films such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. The thickness of the passivation layer along the thickness direction of the solar cell can be 50nm~150nm. It can be understood that when 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 fully in contact, and by increasing the contact area between the first electrode and the second region, the transmission efficiency of electrons inside the solar cell can be improved. Figure 4 , Figure 4 The solar cell 2 is a partial schematic diagram. As shown 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. Figure 4It can be seen that the passivation layer 25 covers the side of the polysilicon layer 23 away from the first surface 211, wherein the polysilicon layer 23 has a first region 231 and a second region 232 arranged on the same surface. It can be understood that the horizontal transverse direction is the x direction, the horizontal longitudinal direction is the y direction, and the direction perpendicular to the first surface and the second surface is 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] This embodiment can improve the passivation effect and stability of the solar cell by covering the side of the polysilicon layer away from the first surface between the polysilicon layer and the tunneling layer. At the same time, 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, which 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 simultaneously improving the transmission efficiency inside the solar cell, that is, simultaneously 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 between: , , .

[0063] It should be noted that by testing the relevant parameters of the selected 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 using the p+ poly-Si structure as an example, the corresponding photoluminescence image has a significant feature for the p+ poly-Si structure of the solar cell, that is, there will be obvious black edges in the edge area of ​​the photoluminescence image, and the black edge area usually means that the radiation recombination efficiency of electrons and holes in this area is low, thereby affecting the passivation effect of the solar cell. Therefore, by controlling the element doping width of different areas 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 may specifically include 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 expressed as , and , for example, assuming is 20 mm, then the doping width of the first region Specifically, it can be 1 mm, 2 mm, 3 mm, 4 mm or 5 mm, etc. The doping width of the second region 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 width of the first region of the solar cell is controlled differently, the conductivity of the solar cell is different, as shown in Table 1 below. Figure 1 The structure of the mainstream solar cell 1 in the prior art is shown, wherein the polysilicon layer is doped with elements by boron diffusion, and the entire polysilicon layer is uniformly doped with boron elements at the same concentration. The structure of the solar cell 1 is as above, and this embodiment will not be repeated here. It can be understood that in comparative example 1, since the boron element is uniformly doped in the entire layer, the solar cell prepared in comparative example 1 can be understood as a "black-edge-free cell", that is, in the photoluminescence image of the solar cell, the edge of its p+poly-Si structure is not black.

[0069] Further, Comparative Example 2 represents Figure 2 The solar cell 2 structure shown in the figure, wherein different concentrations of element doping are performed in the first region and the second region of the polysilicon layer, the boron element doping concentration in the first region is greater than the boron element doping concentration in the second region, the boron doping width in the first region is less than the element doping width in the second region, and the boron doping width in the first region is controlled to be between 0 mm and 5 mm, and the boron doping width in the second region is controlled to be between 10 mm and 15 mm. The structure of the solar cell 2 is as shown in FIG. Figure 2 As shown, this embodiment will not be described in detail here. It can be understood that since the boron element is doped in different concentrations in different areas of the polysilicon layer and the width of the first area is controlled to be 0 mm~5 mm, the solar cell prepared in Comparative Example 2 can be understood as a "5 mm black-bordered cell", that is, in the photoluminescence image of the solar cell, the edge black border of its p+poly-Si structure is 5 mm.

[0070] Further, Comparative Example 3 also shows that Figure 2 The solar cell 2 structure shown in the figure, wherein different concentrations of element doping are performed in the first region and the second region of the polysilicon layer, the boron element doping concentration in the first region is greater than the boron element doping concentration in the second region, and the boron doping width in the first region is less than the boron element doping width in the second region. The difference from the comparative example 2 is that the comparative example 3 only controls the total doping width of the solar cell. , the element doping width of the first region and the element doping width of the second region Satisfy between: , , , wherein the element doping width of the first region is controlled to be 20 mm, and the total doping width of the solar cell is not limited, nor is the element doping width of the second region limited. The structure of the solar cell 2 is as follows Figure 2As shown, this embodiment will not be described in detail here. It can be understood that since the boron element is doped in different concentrations in different areas of the polysilicon layer and the width of the first area is controlled to be 20 mm, the solar cell prepared in Comparative Example 3 can be understood as a "20 mm black-bordered cell", that is, in the photoluminescence image of the solar cell, the edge black border of its p+poly-Si structure is 20 mm.

[0071]

[0072] Among them, other parameters of solar cells in different comparative examples are the same and will not be described 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 open-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 of the above comparative example, it can be known 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 the element doping width of the low-concentration doping region, compared with a solar cell in which the entire polysilicon layer is uniformly doped with the same element doping concentration, it has better electrical properties, that is, after the first region and the second region are set on the same surface in the polysilicon layer, and 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 smaller than the element doping width 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 properties than the mainstream solar cell 1 in the prior art; at the same time, by comparing comparative example 2 with comparative example 3, Ratio 3 shows 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, it has better electrical performance than 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. Therefore, when the total doping width of the solar cell is controlled to be 15 mm, 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, the photoelectric conversion efficiency of the solar cell can be further improved under the premise of improving the passivation effect of the solar cell.

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

[0075] , .

[0076] For example, Specifically, it can be , , and wait, Specifically, it can be , , and It is understandable that based on Figure 2 After the solar cell is prepared with the structure shown, the element doping concentration of the first region is greater than the element doping concentration of the second region. For example, assuming that the doping element is boron, Specifically, it can be , Specifically, it can be That is, the boron 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, the boron source in the first region is deposited more due to the influence of deposition, thereby making the boron doping concentration in the first region higher. Since the boron content in the first region of the p+ poly-Si of the solar cell is higher, the leakage current in the first region increases. Therefore, the operating temperature of the component can be reduced and hot spots can be reduced.

[0077] Reference Figure 5 , Figure 5 To represent the ECV curve of the boron (B) element in the first region and the second region, wherein the horizontal axis represents the depth, and the vertical axis represents the concentration of the boron element doping in the first region and the doping concentration of the boron element in the second region. It can be seen from the figure that in the polysilicon layer, the doping concentration of the boron element in the first region is greater than the doping concentration of the boron element in the second region, and from the polysilicon layer toward the tunneling layer, as the depth increases, the doping concentration of the boron element in the first region and the doping concentration of the boron element in the second region are gradually smaller. It should be noted that Q1 represents the ECV curve graph of the first region, and Q2 represents the ECV curve graph of the second region.

[0078] In some embodiments, 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:

[0079] , .

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

[0081] In some embodiments, in the polysilicon layer, the surface carrier concentration increases in a direction from the center of the second region to the first region, and the surface carrier concentration of the first region is , the surface carrier concentration in the second region is , and satisfy:

[0082] , .

[0083] It should be noted that, in addition to characterizing the characteristics of the black edge of the p+poly-Si edge of the solar cell by the width of the element doping in the first region and the second region, the surface carrier concentration can also be introduced for characterization, wherein 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 in the direction from the center position of the second region to the first region, that is, the surface carrier concentration of the first region is greater than the surface carrier concentration of the second region, for example, the surface carrier concentration of the first region Specifically, it can be , , , and etc., the surface carrier concentration in the second region Specifically, it can be , , , and Etc., the center position of the second area can be understood as the geometric center position.

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

[0085]

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

[0087] Reference Figure 6 , Figure 6 The figure is a schematic diagram of the Hall mobility and carrier concentration at different positions in the polysilicon layer under different comparative examples of solar cells, wherein No. 1 corresponds to comparative example 4, No. 2 corresponds to comparative example 5, No. 3 corresponds to comparative example 6, and No. 4 corresponds to comparative example 7. It can be seen from the figure that the Hall mobility decreases in the direction from the center position of the second region to the first region, and the surface carrier concentration increases in the direction from the center position of the second region to the first region.

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

[0089] It should be noted that, for the characteristics of the black edge of the p+poly-Si edge of the solar cell, in addition to the characterization of the element doping width 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, where the minority carrier lifetime is the minority carrier lifetime, which refers to the time from the generation of photogenerated electrons and holes in the semiconductor until they disappear. By controlling the minority carrier lifetime in the first region and the minority carrier lifetime in the second region satisfy , which can further improve the overall performance of solar cells.

[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 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 in the first sub-region under the second light injection dose is , and satisfy: , the minority carrier lifetime in the second sub-region under the first light injection dose is , the minority carrier lifetime in 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.

[0091] It should be noted that the first region includes a first sub-region and a second sub-region, and the first sub-region and the second sub-region are used to represent different types of sub-regions in the first region. Specifically, the first sub-region may be a narrow black-border region, and the second sub-region may be a wide black-border 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 border feature of the sub-region increases, the relationship between the minority carrier lifetimes of the sub-regions under different light injection doses decreases accordingly. Refer to Figure 7 , Figure 7Schematic diagram of minority carrier lifetimes in the first sub-region and the second sub-region, wherein the horizontal axis is the light injection dose, the vertical axis is the minority carrier lifetime, Q3 is a minority carrier lifetime curve diagram for the first sub-region, and Q4 is a minority carrier lifetime curve diagram for the second sub-region. Specifically, the first sub-region may be a region with a 5mm black border of the p+ poly-Si solar cell, and the second sub-region may be a region with a 5mm black border of the p+ poly-Si solar cell. It can be seen from the figure that the minority carrier lifetime in the first sub-region presents a decreasing trend as a whole, and the minority carrier lifetime in the second sub-region has a critical value, which presents an increasing trend before the critical value and a decreasing trend after the critical value. By controlling the minority carrier lifetime in the first sub-region under the first light injection dose: , the minority carrier lifetime in the first sub-region under the second light injection dose is , and satisfy: , the minority carrier lifetime in the second sub-region under the first light injection dose is , the minority carrier lifetime in 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, which can further enhance the passivation effect of the solar cell through the parameter dimension of minority carrier lifetime.

[0092] This embodiment also provides a method for preparing a solar cell, and the method for preparing a solar cell includes:

[0093] A tunneling oxide layer is deposited on a substrate layer, wherein 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; a layer to be annealed is deposited on a side of the tunneling oxide layer away from the first surface, and the layer to be annealed is annealed to obtain a preliminary polysilicon layer; the preliminary polysilicon layer is divided into a first region and a second region arranged 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 smaller than the element doping width of the second region; a first electrode is arranged on the second region, and the first electrode and the second region are electrically connected, and a second electrode is arranged on one side of the second surface.

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

[0095] 1) Deposition of tunnel oxide layer ( ): Using LP (may refer to a specific deposition equipment or technology) machine, the deposition temperature is in the range of 400℃-900℃, and the oxide layer thickness is controlled between 1nm-10nm to achieve an ultra-thin tunneling effect; 2) Deposition of polycrystalline silicon (poly-Si) layer: Continue to deposit a layer of 50nm-500nm thick polycrystalline silicon on the tunneling oxide layer. The deposition temperature is relatively low, 300℃-700℃, to avoid thermal damage to the tunneling oxide layer below; 3) Annealing treatment: the deposited polysilicon layer is annealed and crystallized in an annealing furnace, and the annealing temperature is relatively high, 900℃-1400℃, 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 (boron diffusion): the annealed polysilicon layer is subjected to boron diffusion treatment, and the boron diffusion deposition temperature and advancement temperature are in the range of 700℃-900℃ and 800℃-1000℃ respectively. Through boron diffusion, a p+ type polysilicon layer is formed, and the boron 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: a passivation layer can be further deposited on the polysilicon layer, wherein the passivation layer can reduce surface recombination and improve the passivation of the device.

[0096] In the above-mentioned method for preparing the solar cell, the substrate layer has a first surface and a second surface that are relatively arranged, and a tunneling layer is arranged on the first surface of the substrate layer, which serves as a channel for electron tunneling and can achieve efficient carrier separation and transmission; the first area of ​​the polycrystalline silicon layer that is not in contact with the first electrode is doped with a high concentration of elements, and the second area that is in contact with the first electrode is doped with a low concentration of elements, so that the leakage of the first area is increased, which can reduce the operating temperature of the solar cell and reduce hot spots; the element doping width of the first area in the polycrystalline silicon layer is smaller than the element doping width of the second area, and the first area is distributed along the boundary of the second area, which effectively controls the passivation effect of the high-concentration area in the polycrystalline silicon layer on the solar cell, thereby reducing the surface recombination rate of the polycrystalline silicon layer and improving the passivation performance of the solar cell. At the same time, the electrical contact formed between the first electrode of the solar cell and the second area of ​​the polycrystalline silicon layer can ensure the normal flow of current inside the battery, and the second electrode arranged on one side of the second surface can ensure the normal extraction of current; based on this, the present application can improve the passivation effect of the solar cell under the premise of ensuring the normal operation of the solar cell.

[0097] This embodiment further provides a photovoltaic module, which includes a first cover plate, a first adhesive film, a battery string, a second adhesive film, and a second cover plate which are stacked, and 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 and is used to transmit sunlight and to improve the waterproof and moisture-proof capabilities of the photovoltaic module, and to seal the battery string together with the second cover plate; during the lamination process of the photovoltaic module, the first adhesive film and the second adhesive 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 can also bond the first cover plate, the battery string and the second cover plate into a whole.

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

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

[0101] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. 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 includes 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.

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 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: , , .

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

5. 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: ， 。 6. 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: ， 。 7. 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: ， 。 8. 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: .

9. The solar cell according to claim 8, 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.

10. 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, and the element doping width of the first region is less than the element doping width 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.

11. 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 9.

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