solar cells

Abstract

An embodiment of the present application provides a solar cell, which includes a silicon substrate containing antimony, the silicon substrate having a first surface; an antimony-rich tunneling oxide layer covering the first surface; a doped conductive layer, wherein the doped conductive layer covers the surface of the antimony-rich tunneling oxide layer on a side away from the silicon substrate along the thickness direction of the solar cell, and the doped conductive layer contains antimony; the antimony concentration in the antimony-rich tunneling oxide layer is greater than the antimony concentration in the silicon substrate, and the antimony concentration in the silicon substrate is greater than the antimony concentration in the doped conductive layer, wherein a first antimony-containing layer is formed on a side of the doped conductive layer close to the antimony-rich tunneling oxide layer along the thickness direction of the solar cell, the antimony concentration in the first antimony-containing layer is greater than the antimony concentration in other parts of the doped conductive layer, which can increase the conductivity of the antimony-rich tunneling oxide layer, reduce the series resistance of the solar cell, and improve the fill factor of the solar cell, thereby improving the photoelectric conversion efficiency 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. Background Art

[0002] Solar cells can directly convert solar radiation energy into electrical energy. In order to suppress carrier recombination on the surface of the solar cell substrate, a tunneling oxide layer and a doped conductive layer are usually prepared on the substrate surface to enhance the passivation effect on the substrate.

[0003] In existing solar cells, the doped conductive layer still has the problem of poor conductivity, which leads to high series resistance of the solar cell and affects the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0004] In view of this, the present application provides a solar cell to solve the problem of low photoelectric conversion efficiency of solar cells in the prior art.

[0005] An embodiment of the present application provides a solar cell, comprising: a silicon substrate containing antimony, the silicon substrate having a first surface; an antimony-rich tunneling oxide layer covering the first surface; a doped conductive layer, wherein, along the thickness direction of the solar cell, the doped conductive layer covers the surface of the antimony-rich tunneling oxide layer on a side away from the silicon substrate, the doped conductive layer containing antimony; the antimony concentration in the antimony-rich tunneling oxide layer is greater than the antimony concentration in the silicon substrate, and the antimony concentration in the silicon substrate is greater than the antimony concentration in the doped conductive layer; wherein, along the thickness direction of the solar cell, a first antimony-containing layer is formed on a side of the doped conductive layer close to the antimony-rich tunneling oxide layer, and the antimony concentration in the first antimony-containing layer is greater than the antimony concentration in other parts of the doped conductive layer.

[0006] In one possible implementation, in the thickness direction of the solar cell, the antimony element concentration in the antimony-rich tunneling oxide layer gradually decreases in the direction away from the silicon substrate; and / or, in the thickness direction of the solar cell, the antimony element concentration in the first antimony-containing layer gradually decreases in the direction away from the silicon substrate.

[0007] In a possible implementation, the antimony concentration in the silicon substrate is 2.0×10 16 cm -3 ~8.0×10 16 cm -3 .

[0008] In a possible implementation, the antimony element concentration in the antimony-rich tunneling oxide layer is 1.0×10 18 cm -3 ~2.0×1018 cm -3 .

[0009] In a possible implementation, the antimony element concentration in the first antimony-containing layer is 1.0×10 16 cm -3 ~1.0×10 18 cm -3 .

[0010] In a possible implementation, the thickness of the first antimony-containing layer is 5 nm to 10 nm.

[0011] In one possible implementation, a second antimony-containing layer is formed on a side of the silicon substrate close to the antimony-rich tunneling oxide layer along the thickness direction of the solar cell; and along the thickness direction of the solar cell, the concentration of antimony elements in the second antimony-containing layer gradually increases in a direction close to the antimony-rich tunneling oxide layer.

[0012] In a possible implementation, the thickness of the second antimony-containing layer is 5 nm to 10 nm.

[0013] In a possible implementation, the thickness of the antimony-rich tunneling oxide layer is 1 nm to 10 nm; and / or the thickness of the doped conductive layer is 20 nm to 300 nm.

[0014] In a possible implementation, the doped conductive layer further contains phosphorus, and the concentration of phosphorus in the doped conductive layer is 1.0×10 20 cm -3 ~1.0×10 21 cm -3 .

[0015] In the present application, first, when the antimony concentration in the antimony-rich tunneling oxide layer is greater than the antimony concentration in the silicon substrate, a concentration gradient can be formed between the antimony-rich tunneling oxide layer and the silicon substrate, and antimony atoms can effectively diffuse from the antimony-rich tunneling oxide layer to the silicon substrate, which will increase the free electron concentration in the silicon substrate, thereby improving the carrier transport efficiency, which is beneficial to improving the conductivity of the silicon-rich substrate and the antimony tunneling oxide layer. Moreover, the antimony concentration on one side of the antimony-rich tunneling oxide layer is higher, which can help to better passivate the interface between the antimony-rich tunneling oxide layer and the silicon substrate, and reduce the interface defect density of the first surface by filling dangling bonds and other defects. Secondly, when the antimony concentration in the doped conductive layer is less than the antimony concentration in the silicon substrate and less than the antimony concentration in the antimony-rich tunneling oxide layer, on the one hand, the lower antimony concentration can avoid carrier concentration saturation caused by excessive doping in the doped conductive layer, and can also reduce the scattering effect and avoid a decrease in carrier mobility. On the other hand, a lower antimony concentration can ensure good ohmic contact between the first electrode and the silicon substrate while avoiding the introduction of additional interface defects or dangling bonds due to excessive antimony doping concentration, thereby reducing the contact resistance between the first electrode and the silicon substrate, improving current transmission capacity, reducing energy loss, and improving the interface passivation effect of the solar cell, thereby improving the long-term stability and durability of the solar cell. In addition, the antimony element in the doped conductive layer is mainly obtained by diffusion into the doped conductive layer through the antimony-rich tunneling oxide layer. The antimony-rich tunneling oxide layer has a certain barrier effect on the antimony element. If the antimony element concentration in the doped conductive layer is set higher, a more complex doping process is required to achieve it. Therefore, when the antimony element concentration in the doped conductive layer is less than the antimony element concentration in the silicon substrate and less than the antimony element concentration in the antimony-rich tunneling oxide layer, it is beneficial to reduce the difficulty of the doping process, save doping materials, thereby reducing the production cost and difficulty of the solar cell, and improving the production efficiency of the solar cell. Moreover, along the thickness direction of the solar cell, a first antimony-containing layer is formed on the side of the doped conductive layer close to the antimony-rich tunneling oxide layer, and the antimony element concentration in the first antimony-containing layer is greater than the antimony element concentration in other parts of the doped conductive layer. Such a concentration setting method causes the antimony element to be concentrated on the side of the doped conductive layer close to the antimony-rich tunneling oxide layer, that is, the side of the doped conductive layer close to the first surface can maintain a higher antimony element concentration, which is beneficial to improving the passivation effect of the doped conductive layer on the first surface.

[0016] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. 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 any creative work.

[0018] Figure 1 A schematic diagram of the cross-sectional structure of the solar cell provided in this application;

[0019] Figure 2 for Figure 1 Antimony element curve of the solar cell obtained by SIMS testing;

[0020] Figure 3 for Figure 1 Enlarged view of part A.

[0021] Reference numerals:

[0022] 1-Silicon substrate;

[0023] 1a-first surface;

[0024] 1b-second surface;

[0025] 11- second antimony-containing layer;

[0026] 2-antimony-rich tunneling oxide layer;

[0027] 3- doped conductive layer;

[0028] 31- first antimony-containing layer;

[0029] 4-first electrode;

[0030] 5-first passivation layer;

[0031] 6-Emitter;

[0032] 7- second electrode;

[0033] 8- Second passivation layer. DETAILED DESCRIPTION

[0034] 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.

[0035] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" 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 otherwise.

[0037] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0038] An embodiment of the present application provides a solar cell comprising a silicon substrate 1, which is configured to receive sunlight and generate photogenerated carriers. Specifically, the silicon substrate 1 may be a single crystal silicon substrate, a polycrystalline silicon substrate, a microcrystalline silicon substrate, a nanocrystalline silicon substrate, or the like. In this embodiment, the silicon substrate 1 is an N-type silicon substrate doped with antimony (Sb). Antimony atoms replace certain silicon atoms in the silicon lattice. Because antimony atoms have five valence electrons, while silicon atoms have only four, each antimony atom contributes an additional free electron to the lattice. The free electrons provided by the antimony atoms increase the carrier concentration, thereby reducing the resistivity of the silicon substrate 1 and increasing its conductivity, thereby improving its electrical conductivity. Specifically, the silicon substrate 1 may be doped solely with antimony, or it may be doped with one or more Group V elements other than antimony, such as nitrogen (N), phosphorus (P), arsenic (As), or bismuth (Bi). That is, the silicon substrate 1 can be an N-type silicon substrate doped with pure antimony, or an N-type silicon substrate doped with antimony and other fifth main group elements. The embodiment of the present application takes the silicon substrate 1 as an N-type silicon substrate doped with phosphorus and antimony as an example.

[0039] like Figure 1 As shown, the silicon substrate 1 has a first surface 1a and a second surface 1b that are arranged opposite each other along the thickness direction Z of the solar cell. The first surface 1a is the backlight side of the silicon substrate 1, that is, the side of the silicon substrate 1 facing away from the light source and used to receive sunlight reflected from the ground. The second surface 1b is the light-facing side of the silicon substrate 1, that is, the side of the silicon substrate 1 facing the light source and used to receive direct sunlight. In other words, both the first surface 1a and the second surface 1b can absorb sunlight, allowing the solar cell to convert light energy into electrical energy.

[0040] The solar cell also includes an antimony-rich tunneling oxide layer 2 and a doped conductive layer 3. The antimony-rich tunneling oxide layer 2 covers the first surface 1a. Along the thickness direction Z of the solar cell, the doped conductive layer 3 covers the side surface of the antimony-rich tunneling oxide layer 2 away from the silicon substrate 1. The stacked antimony-rich tunneling oxide layer 2 and the doped conductive layer 3 can form a passivation contact structure, which can improve the efficiency of the doped conductive layer 3 in collecting electrons.

[0041] Specifically, the antimony-rich tunneling oxide layer 2 may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride, amorphous silicon, and polycrystalline silicon. The lattice of the antimony-rich tunneling oxide layer 2 can be well matched with the lattice of the silicon substrate 1, thereby chemically passivating the first surface 1a, reducing the interface defect density of the first surface 1a, and thereby reducing the recombination center of the first surface 1a to reduce the carrier recombination rate. In the embodiment of the present application, since the antimony-rich tunneling oxide layer 2 is rich in antimony elements, on the one hand, the antimony atoms can increase the free electron concentration in the antimony-rich tunneling oxide layer 2, which is beneficial to improving the conductivity of the antimony-rich tunneling oxide layer 2, and can also achieve the adjustment of the band structure, making it easier for electrons to pass through the antimony-rich tunneling oxide layer 2, thereby reducing the energy loss during the tunneling process. On the other hand, the antimony atoms can effectively fill the defect positions in the silicon lattice, reduce the number of dangling bonds, and thus reduce the interface defect density of the first surface 1a.

[0042] In addition, in the prior art, hydrogen passivation technology is generally used to deal with defect problems in solar cells. However, due to the limitations of hydrogen injection technology, the concentration of hydrogen atoms injected into solar cells is often lower than the defect concentration. In particular, when there are a large number of defects, the number of hydrogen atoms is insufficient to completely passivate all defects. In the embodiment of the present application, antimony atoms can effectively passivate some deep defects or high-density defect areas that are difficult to treat by hydrogen passivation to a certain extent. Moreover, antimony atoms can form stable and non-breakable covalent bonds with surrounding silicon atoms, which is conducive to maintaining a good passivation effect. That is, by providing an antimony-rich tunneling oxide layer 2, not only can the passivation effect of the solar cell be improved, thereby improving the photoelectric conversion efficiency of the solar cell, but it is also conducive to reducing the process requirements of the subsequent hydrogen injection technology, reducing resource consumption, and thus reducing the production difficulty and production cost of the solar cell.

[0043] The doped conductive layer 3 forms a field passivation layer, which reduces the concentration of minority carriers (holes) and enables the selective transport of majority carriers (free electrons). This reduces the carrier recombination rate, increases the voltage of the solar cell, and increases the short-circuit current of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell. The doped conductive layer 3 contains antimony, which enhances the long-term stability of the doped conductive layer 3, thereby improving the reliability and service life of the solar cell. Specifically, the doped conductive layer 3 can be a pure antimony-doped structure or a mixed structure doped with antimony and other Group V elements. The Group V elements can include nitrogen (N), phosphorus (P), arsenic (As), bismuth (Bi), etc.

[0044] like Figure 1 As shown, the solar cell also includes a first electrode 4 and a first passivation layer 5. Along the thickness direction Z of the solar cell, multiple first electrodes 4 are arranged on the side of the doped conductive layer 3 away from the antimony-rich tunneling oxide layer 2. The multiple first electrodes 4 are respectively electrically connected to the doped conductive layer 3. The first passivation layer 5 covers the surface of the doped conductive layer 3 on the side away from the antimony-rich tunneling oxide layer 2. The components of the first passivation layer 5 may include one or more of silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or silicon oxynitride. The first passivation layer 5 can be a single-layer structure or a multi-layer structure, and the refractive index and thickness of each layer can be designed accordingly. The first passivation layer 5 can passivate the surface in contact with it, which is used to enhance the passivation effect of the solar cell, reduce carrier recombination at the interface, improve carrier transmission efficiency, and thus improve the photoelectric conversion efficiency of the solar cell. The first passivation layer 5 also has the function of reducing or eliminating the reflection effect of the first surface 1a and increasing the light transmittance of the second surface 1b, which is conducive to further improving the photoelectric conversion efficiency of the solar cell.

[0045] The first electrode 4 is specifically the negative electrode of the solar cell. At least part of the structure of the first electrode 4 can penetrate the doped conductive layer 3 and form an electrical connection with the antimony-rich tunneling oxide layer 2. The antimony-rich tunneling oxide layer 2 can improve the electrical conductivity and ensure that a good ohmic contact is formed between the first electrode 4 and the silicon substrate 1, which is beneficial to reducing the series resistance of the solar cell and further beneficial to improving the photoelectric conversion efficiency of the solar cell.

[0046] like Figure 1 and Figure 2As shown, in the embodiment of the present application, the antimony concentration in the antimony-rich tunneling oxide layer 2 is greater than the antimony concentration in the silicon substrate 1, and the antimony concentration in the silicon substrate 1 is greater than the antimony concentration in the doped conductive layer 3. First, when the antimony concentration in the antimony-rich tunneling oxide layer 2 is greater than the antimony concentration in the silicon substrate 1, a concentration gradient can be formed between the antimony-rich tunneling oxide layer 2 and the silicon substrate 1, and antimony atoms can effectively diffuse from the antimony-rich tunneling oxide layer 2 into the silicon substrate 1, which will increase the free electron concentration in the silicon substrate 1, thereby improving the carrier transport efficiency and facilitating the improvement of the conductivity of the silicon substrate 1 and the antimony-rich tunneling oxide layer 2. Moreover, the higher antimony concentration on one side of the antimony-rich tunneling oxide layer 2 can help better passivate the interface between the antimony-rich tunneling oxide layer 2 and the silicon substrate 1, and reduce the interface defect density of the first surface 1a by filling dangling bonds and other defects.

[0047] Secondly, when the antimony concentration in the doped conductive layer 3 is lower than the antimony concentration in the silicon substrate 1 and lower than the antimony concentration in the antimony-rich tunneling oxide layer 2, on the one hand, the lower antimony concentration can avoid carrier concentration saturation in the doped conductive layer 3 due to excessive doping, and can also reduce the scattering effect and avoid a decrease in carrier mobility. On the other hand, the lower antimony concentration can ensure that the first electrode 4 forms a good ohmic contact with the silicon substrate 1 while avoiding the introduction of additional interface defects or dangling bonds due to excessive antimony doping concentration, thereby helping to reduce the contact resistance between the first electrode 4 and the silicon substrate 1, improve current transmission capacity, reduce energy loss, and improve the interface passivation effect of the solar cell, thereby helping to improve the long-term stability and durability of the solar cell. In addition, the antimony in the doped conductive layer 3 is mainly obtained by diffusion from the antimony-rich tunneling oxide layer 2 into the doped conductive layer 3. The antimony-rich tunneling oxide layer 2 has a certain barrier effect on antimony. If the antimony concentration in the doped conductive layer 3 is set higher, a more complex doping process is required to achieve it. Therefore, when the antimony element concentration in the doped conductive layer 3 is lower than the antimony element concentration in the silicon substrate 1 and lower than the antimony element concentration in the antimony-rich tunnel oxide layer 2, it is beneficial to reduce the difficulty of the doping process and save doping materials, thereby reducing the production cost and production difficulty of solar cells and improving the production efficiency of solar cells.

[0048] Therefore, the solar cell provided in the embodiment of the present application is doped with antimony elements in the silicon substrate 1, the antimony-rich tunneling oxide layer 2 and the doped conductive layer 3, respectively, and the antimony element concentration in the antimony-rich tunneling oxide layer 2 is set to be greater than the antimony element concentration in the silicon substrate 1, and the antimony element concentration in the silicon substrate 1 is greater than the antimony element concentration in the doped conductive layer 3. This can increase the conductivity of the antimony-rich tunneling oxide layer 2, reduce the series resistance of the solar cell, and improve the fill factor of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0049] Moreover, if Figure 1 and Figure 2 As shown, along the thickness direction Z of the solar cell, a first antimony-containing layer 31 is formed on the side of the doped conductive layer 3 close to the antimony-rich tunneling oxide layer 2. The antimony concentration in the first antimony-containing layer 31 is greater than the antimony concentration in other parts of the doped conductive layer 3. This concentration setting allows the antimony element to be concentrated on the side of the doped conductive layer 3 close to the antimony-rich tunneling oxide layer 2. In other words, the side of the doped conductive layer 3 close to the first surface 1a can maintain a higher antimony concentration, which is beneficial for improving the passivation effect of the doped conductive layer 3 on the first surface 1a.

[0050] It should be noted that the antimony concentrations in the silicon substrate 1, the antimony-rich tunneling oxide layer 2, the doped conductive layer 3, and the first antimony-containing layer 31 can be detected by SIMS, ICP-MS, GDMS, and other methods, respectively. The present embodiment preferably uses the SIMS detection method. The antimony concentration of the silicon substrate 1 refers to the average antimony concentration at each point in the silicon substrate 1, the antimony concentration of the antimony-rich tunneling oxide layer 3 refers to the average antimony concentration at each point in the antimony-rich tunneling oxide layer 3, the antimony concentration of the doped conductive layer 3 refers to the average antimony concentration at each point in the doped conductive layer 3, and the antimony concentration of the first antimony-containing layer 31 refers to the average antimony concentration at each point in the first antimony-containing layer 31.

[0051] The silicon substrate 1 , the antimony-rich tunneling oxide layer 2 and the doped conductive layer 3 are described in detail below.

[0052] like Figure 3 As shown, in a specific embodiment, the thickness D1 of the antimony-rich tunneling oxide layer 2 is 1 nm to 10 nm. D1 can specifically be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm, or other values within the above range, which are not limited in this embodiment of the present application.

[0053] In this embodiment, if D1 is too small (e.g., less than 1 nm), the antimony-rich tunneling oxide layer 2 may not provide sufficient passivation, resulting in an increase in the interface defect density of the first surface 1a. If D1 is too large (e.g., greater than 10 nm), the resistance of the antimony-rich tunneling oxide layer 2 may increase, making it difficult for carriers to effectively pass through the antimony-rich tunneling oxide layer 2, resulting in a decrease in the carrier tunneling efficiency. This in turn increases the series resistance of the solar cell, affecting the solar cell's photoelectric conversion efficiency. Therefore, when D1 is between 1 nm and 10 nm, the antimony-rich tunneling oxide layer 2 can ensure that it provides an effective passivation effect for the first surface 1a while maintaining a low resistance, thereby achieving efficient carrier transport and improving the photoelectric conversion efficiency of the solar cell.

[0054] In a specific embodiment, reference Figure 2 It can be seen that the antimony concentration in the antimony-rich tunnel oxide layer 2 is 1.0×10 18 cm -3 ~2.0×10 18 cm -3 Specifically, it can be 1.0×10 18 cm -3 , 1.1×10 18 cm -3 , 1.2×10 18 cm -3 , 1.3×10 18 cm -3 , 1.4×10 18 cm -3 , 1.5×10 18 cm -3 , 1.6×10 18 cm -3 , 1.7×10 18 cm -3 , 1.8×10 18 cm -3 , 1.9×10 18 cm -3 or 2.0×10 18 cm -3 , or other values within the above range, which is not limited in the embodiments of the present application.

[0055] If the antimony concentration is too low (e.g. less than 1.0×10 18 cm -3 ), the antimony-rich tunnel oxide layer 2 may not provide sufficient passivation effect, resulting in an increase in the interface defect density of the first surface 1a, and an inability to ensure a good ohmic contact between the first electrode 4 and the silicon substrate 1, resulting in an increase in the series resistance of the solar cell; if the antimony concentration is too high (for example, higher than 2.0×1018 cm -3 ), may also lead to the introduction of more additional interface defects or dangling bonds, affecting carrier mobility and increasing the resistance of the antimony-rich tunneling oxide layer 2. Therefore, when the antimony concentration gradient in the antimony-rich tunneling oxide layer 2 meets the above range, it can achieve optimal passivation and carrier transfer efficiency without affecting other performance indicators of the solar cell, thereby improving the photoelectric conversion efficiency and long-term stability of the solar cell and increasing the service life of the solar cell. In addition, an appropriate antimony concentration can help adjust the band structure of the antimony-rich tunneling oxide layer 2, forming a favorable barrier height and shape, and promoting the effective separation and transfer of electrons and holes.

[0056] In a specific embodiment, in the thickness direction Z of the solar cell, the concentration of antimony in the antimony-rich tunneling oxide layer 2 gradually decreases in the direction away from the silicon substrate 1, that is, the distribution of antimony in the antimony-rich tunneling oxide layer 2 shows a concentration gradient change. In this embodiment, the antimony-rich tunneling oxide layer 2 maintains a higher antimony concentration on the side close to the silicon substrate 1, which can effectively fill the defects and dangling bonds in the silicon lattice, reduce the interface defect density of the first surface 1a, and help to improve the passivation effect on the first surface 1a, thereby maintaining good interface quality. Moreover, as the distance from the silicon substrate 1 gradually increases, the antimony concentration gradually decreases, reducing the possible introduction of new defects or impurity scattering centers, which is beneficial to improving the carrier mobility. Therefore, the antimony-rich tunneling oxide layer 2 can help reduce the defect density of the first surface 1a by setting an appropriate antimony concentration gradient, thereby improving the open circuit voltage of the solar cell and improving the overall performance of the solar cell.

[0057] like Figure 3 As shown, in a specific embodiment, the thickness D2 of the doped conductive layer 3 is 20 nm to 300 nm. D2 can specifically be 20 nm, 50 nm, 60 nm, 80 nm, 100 nm, 110 nm, 130 nm, 150 nm, 170 nm, 190 nm, 200 nm, 220 nm, 240 nm, 250 nm, 260 nm, 280 nm, or 300 nm, or other values within the above range, which is not limited in this embodiment of the present application.

[0058] In this embodiment, if D2 is too small (for example, less than 20nm), a thin layer effect may occur, resulting in an increase in the resistance of the doped conductive layer 3, affecting the carrier transmission efficiency; if D2 is too large (for example, greater than 300nm), the problem of uneven doping may cause the resistance of the local area of the doped conductive layer 3 to increase, or even form defects, which will affect the carrier transmission efficiency and increase the energy loss during the carrier transmission process. Therefore, when D2 is 20nm~300nm, it helps to improve the carrier mobility, thereby improving the conversion efficiency of the solar cell. In addition, when D2 is 20nm~300nm, the doped wire layer 3 is maintained within an appropriate thickness range, which can also reduce the light absorption ability of the doped conductive layer 3, thereby reducing the optical loss of the solar cell and improving the photoelectric conversion efficiency of the solar cell.

[0059] In a specific embodiment, the thickness D3 of the first antimony-containing layer 31 is 5 nm to 10 nm. D3 can be 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm, or other values within the above range, which are not limited in this embodiment.

[0060] In this embodiment, since the antimony element in the doped conductive layer 3 is obtained by diffusion from the antimony-rich tunneling oxide layer 2, the thickness D3 of the first antimony-containing layer 31 formed is generally not greater than 10 nm due to the diffusion effect of the diffusion process and production cost constraints. Moreover, if D3 is too large (for example, greater than 10 nm), the resistance of the local area of the first antimony-containing layer 31 may increase due to uneven doping, affecting the carrier transmission efficiency and increasing the energy loss during the carrier transmission process. If D3 is too small (for example, less than 5 nm), the passivation ability of the doped conductive layer 3 will be affected, resulting in an increase in the interface defect density of the first surface 1a, and may also shorten the carrier lifetime, affecting the overall performance of the solar cell. Moreover, an overly thin first antimony-containing layer 31 is more sensitive to the external environment (such as moisture, oxygen, etc.), and is easily affected by corrosion or other chemical reactions. In high temperature or high stress environments, it is also prone to material degradation or peeling, which reduces the service life of the solar cell. Therefore, when D3 is 5 nm to 10 nm, it can ensure that the first antimony-containing layer 31 can provide good passivation effect and electrical performance for the solar cell, and can also appropriately reduce the process difficulty and production cost of the solar cell.

[0061] In a specific embodiment, reference Figure 2 It can be seen that the antimony element concentration in the first antimony-containing layer 31 is 1.0×10 16 cm -3 ~1.0×10 18 cm -3 Specifically, it can be 1.0×1016 cm -3 , 2.0×10 16 cm -3 , 5.0×10 16 cm -3 , 8.0×10 16 cm -3 , 1.0×10 17 cm -3 , 2.0×10 17 cm -3 , 5.0×10 17 cm -3 , 7.0×10 17 cm -3 , 9.0×10 17 cm -3 or 1.0×10 18 cm -3 , or other values within the above range, which is not limited in the embodiments of the present application.

[0062] If the antimony concentration is too low (e.g. less than 1.0×10 16 cm -3 ), which will affect the passivation ability of the doped conductive layer 3 and increase the interface defect density of the first surface 1a; if the antimony concentration is too high (for example, higher than 1.0×10 18 cm -3 ), may also introduce additional interface defects or dangling bonds, affecting carrier mobility. Excessively high antimony concentrations may reduce the chemical stability of the solar cell, shortening its service life. Therefore, when the antimony concentration gradient in the doped conductive layer 3 falls within the aforementioned range, the passivation capability of the doped conductive layer 3 is maintained, thereby improving the photoelectric conversion efficiency, long-term stability, and service life of the solar cell.

[0063] In this embodiment, the antimony element is also contained in the portion of the doped conductive layer 3 other than the first antimony-containing layer 31, but the antimony element concentration is lower than the antimony element concentration in the first antimony-containing layer 31. The antimony element concentration in the portion of the doped conductive layer 3 other than the first antimony-containing layer 31 is 1.0×10 16 cm -3 ~2.0×10 16 cm -3 , specifically 1.0×10 16 cm -3 , 1.1×10 16 cm -3 , 1.2×10 16 cm -3 , 1.3×10 16 cm -3 , 1.4×1016 cm -3 , 1.5×10 16 cm -3 , 1.6×10 16 cm -3 , 1.7×10 16 cm -3 , 1.8×10 16 cm -3 , 1.9×10 16 cm -3 or 2.0×10 16 cm -3 .

[0064] If the antimony concentration is too low (e.g. less than 1.0×10 16 cm -3 ), which will affect the passivation ability of the doped conductive layer 3 and increase the interface defect density of the first surface 1a; if the antimony concentration is too high (for example, higher than 2.0×10 16 cm -3 ), which will increase the process difficulty and production cost of solar cells.

[0065] In a specific embodiment, in the thickness direction Z of the solar cell, the antimony concentration in the first antimony-containing layer 31 gradually decreases in the direction away from the silicon substrate 1, that is, the distribution of the antimony element in the first antimony-containing layer 31 presents a concentration gradient change. In this embodiment, the first antimony-containing layer 31 maintains a higher antimony concentration on the side close to the antimony-rich tunneling oxide layer 2, which is beneficial to improving the passivation effect of the first antimony-containing layer 31. Moreover, as the distance from the silicon substrate 1 gradually increases, the antimony concentration gradually decreases, reducing the possible introduction of new defects or impurity scattering centers, which is beneficial to improving the mobility of carriers. Therefore, the first antimony-containing layer 31 can help reduce the defect density of the first surface 1a by setting an appropriate antimony concentration gradient, thereby improving the open circuit voltage of the solar cell and thus improving the overall performance of the solar cell.

[0066] In a specific embodiment, the antimony concentration in the silicon substrate 1 is 2.0×10 16 cm -3 ~8.0×10 16 cm -3 , specifically 2.0×10 16 cm -3 , 2.5×10 16 cm -3 , 3.0×10 16 cm -3 , 3.5×10 16 cm -3 , 4.0×10 16 cm -3, 4.5×10 16 cm -3 , 5.0×10 16 cm -3 , 5.5×10 16 cm -3 , 6.0×10 16 cm -3 , 6.5×10 16 cm -3 , 7.0×10 16 cm -3 , 7.5×10 16 cm -3 or 8.0×10 16 cm -3 , or other values within the above range, which is not limited in the embodiments of the present application.

[0067] If the antimony concentration is too low (e.g. less than 2.0×10 16 cm -3 ), which will lead to insufficient number of free electrons in the silicon substrate 1, resulting in increased conductivity of the silicon substrate 1 and limiting the current transmission efficiency; if the antimony concentration is too high (for example, higher than 8.0×10 16 cm -3 ), may introduce more defects, affecting the photovoltaic conversion efficiency of the solar cell. It may also cause the chemical stability of the silicon substrate 1 to decrease. It may also cause the diffusion of antimony atoms under high temperature conditions, resulting in structural changes in the silicon substrate 1 or the formation of new defects, affecting the service life and long-term stability of the solar cell. Therefore, when the antimony concentration gradient in the silicon substrate 1 meets the above range, the photovoltaic conversion efficiency of the solar cell can be improved without affecting the stability and service life of the solar cell.

[0068] Furthermore, along the thickness direction Z of the solar cell, a second antimony-containing layer 11 having a relatively high antimony concentration is formed on the side of the silicon substrate 1 near the antimony-rich tunneling oxide layer 2. The second antimony-containing layer 11 has a thickness D4 of 5 nm to 10 nm. Specifically, D4 may be 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm, or other values within the foregoing range, which is not limited in this embodiment of the present application.

[0069] In this embodiment, by providing a second antimony-containing layer 11 with a high antimony concentration near the first surface 1a of the silicon substrate 1, dangling bonds and other defects in the silicon lattice can be effectively filled, reducing the interface defect density of the first surface 1a, thereby enhancing the passivation effect of the first surface 1a. Furthermore, this facilitates the diffusion of antimony from the second antimony-containing layer 11 into the antimony-rich tunneling oxide layer 2, reducing the process difficulty of preparing the antimony-rich tunneling oxide layer 2. If D4 is too small (e.g., less than 5nm), the number of free carriers may be insufficient to meet the requirements for efficient current transmission. It may also cause uneven doping in local areas within the second antimony-containing layer 11, affecting the photovoltaic conversion efficiency of the solar cell. If D4 is too large (e.g., greater than 10nm), it may introduce new interface defects, destroying the passivation effect of the first surface 1a. It may also increase the resistance of the second antimony-containing layer 11 and increase energy loss in carrier transmission. Therefore, when D4 is between 5nm and 10nm, it is beneficial to improve the electrical performance of the solar cell.

[0070] In a specific embodiment, in the thickness direction Z of the solar cell, the antimony concentration in the second antimony-containing layer 11 gradually increases in the direction approaching the antimony-rich tunneling oxide layer 2, that is, the distribution of the antimony element in the second antimony-containing layer 11 exhibits a concentration gradient. In this embodiment, the antimony concentration is higher on the side of the second antimony-containing layer 11 closer to the antimony-rich tunneling oxide layer 2, which can provide more free electrons, effectively fill defect sites in the silicon lattice, reduce the number of dangling bonds, and further reduce the interface defect density of the first surface 1a. The antimony concentration is lower on the side of the second antimony-containing layer 11 farther from the antimony-rich tunneling oxide layer 2, which is beneficial for reducing the resistivity of the silicon substrate 1 and improving the conductivity of the silicon substrate 1, thereby improving the electrical conductivity of the silicon substrate 1.

[0071] The doping elements in the silicon substrate 1 in the embodiment of the present application are mixed doping of phosphorus and antimony. Phosphorus is an efficient shallow energy level dopant, which is easily activated at low temperatures and can provide a large number of free carriers. Antimony has a high activation energy and is usually fully activated at higher temperatures. By mixing these two doping elements, the silicon substrate 1 can maintain a high free carrier concentration in different temperature ranges, and the silicon substrate 1 can maintain stable electrical properties in a wide temperature range. Phosphorus doping can provide more free carriers, while antimony doping helps to reduce impurity scattering. This combination can better balance the carrier concentration and mobility and improve the overall electrical performance. Therefore, when phosphorus and antimony are mixed doped, the carrier concentration and mobility in the silicon substrate 1 can be better balanced to improve the electrical performance of the solar cell as a whole.

[0072] In a specific embodiment, the phosphorus concentration in the silicon substrate 1 is 1.804×10 15 cm -3~4.798×10 16 cm -3 , specifically 1.804×10 15 cm -3 , 2.0×10 15 cm -3 , 3.0×10 15 cm -3 , 4.0×10 15 cm -3 , 5.0×10 15 cm -3 , 6.0×10 15 cm -3 , 7.0×10 15 cm -3 , 8.0×10 15 cm -3 , 9.0×10 15 cm -3 , 1.0×10 16 cm -3 , 2.0×10 16 cm -3 , 3.0×10 16 cm -3 , 4.0×10 16 cm -3 or 4.798×10 16 cm -3 , or other values within the above range, which is not limited in the embodiments of the present application.

[0073] If the phosphorus concentration is too low (for example, less than 1.804×10 15 cm -3 ), which will lead to insufficient free electrons in the silicon substrate 1, thereby increasing the resistance of the silicon substrate 1, limiting the current transmission efficiency and affecting the photoelectric conversion efficiency of the solar cell; if the phosphorus concentration is too high (for example, higher than 4.798×10 16 cm -3 ), may also lead to the introduction of more defects, affecting the mobility of carriers. Therefore, when the phosphorus concentration gradient in the silicon substrate 1 meets the above range, the photoelectric conversion efficiency of the solar cell can be improved.

[0074] In the embodiment of the present application, the doped conductive layer 3 is also doped with phosphorus, that is, the doping elements in the doped conductive layer 3 are a mixed doping of phosphorus and antimony. Phosphorus is a highly efficient shallow-level dopant that is easily activated at low temperatures and can provide a large number of free carriers. Antimony, on the other hand, has a higher activation energy and is generally only fully activated at higher temperatures. By combining these two doping elements, the doped conductive layer 3 can maintain a high free carrier concentration across different temperature ranges and maintain stable electrical properties over a wide temperature range. Furthermore, using a single dopant (such as phosphorus or antimony) at a high concentration alone may introduce excessive defects, reducing carrier mobility. By mixing phosphorus and antimony in the embodiment of the present application, carrier concentration can be increased without significantly increasing defects, thereby optimizing carrier mobility. Phosphorus doping provides more free carriers, while antimony doping helps reduce impurity scattering. This combination achieves a better balance between carrier concentration and mobility in the doped conductive layer 3, thereby improving the overall electrical performance of the solar cell.

[0075] In a specific embodiment, the concentration of phosphorus in the doped conductive layer 3 is 1.0×10 20 cm -3 ~1.0×10 21 cm -3 , specifically 1.0×10 20 cm -3 , 2.0×10 20 cm -3 , 3.0×10 20 cm -3 , 4.0×10 20 cm -3 , 5.0×10 20 cm -3 , 6.0×10 20 cm -3 , 7.0×10 20 cm -3 , 8.0×10 20 cm -3 , 9.0×10 20 cm -3 or 1.0×10 21 cm -3 , or other values within the above range, which is not limited in the embodiments of the present application.

[0076] If the phosphorus concentration is too low (for example, less than 1.0×10 20 cm -3 ), which will lead to insufficient free electrons in the doped conductive layer 3, thereby increasing the resistance of the doped conductive layer 3 and limiting the transmission of current, affecting the photoelectric conversion efficiency of the solar cell; if the phosphorus concentration is too high (for example, higher than 1.0×1021 cm -3 ), may also lead to the introduction of more defects, affecting the mobility of carriers. Therefore, when the phosphorus concentration gradient in the silicon substrate 1 meets the above range, the photoelectric conversion efficiency of the solar cell can be improved.

[0077] In the embodiment of the present application, the phosphorus concentration in the doped conductive layer 3 is greater than the phosphorus concentration in the silicon substrate 1. The doped conductive layer 3 with a high concentration of phosphorus doping can produce a larger band bending at the first surface 1a, which helps to block minority carriers and promote the transmission of majority carriers, thereby improving the electrical performance of the solar cell.

[0078] In the embodiments of the present application, the method for preparing the antimony-rich tunneling oxide layer 2 can be one of wet oxidation, thermal oxidation, PECVD ionization, and ozone oxidation, or a combination of multiple methods. Specifically, the antimony concentration in the antimony-rich tunneling oxide layer 2 can be controlled by changing the preparation temperature or time during the process of preparing the antimony-rich tunneling oxide layer 2, or by changing the doping ratio of the antimony element in the silicon substrate 1.

[0079] In one specific embodiment, a method for preparing a solar cell is as follows: a silicon wafer is prepared as a silicon substrate 1. After the silicon substrate 1 is subjected to a texturing treatment, a front-side boron doping treatment, and a back-side cleaning treatment, a tunneling oxide layer and an intrinsic amorphous silicon layer are formed on the back side of the silicon wafer (the aforementioned first surface 1a) using a low-pressure chemical vapor deposition (LPCVD) process. A phosphorus diffusion process is then performed. During the phosphorus diffusion process, the antimony element in the silicon substrate 1, driven by the high temperature, diffuses outward from the silicon substrate 1 into the tunneling oxide layer and the intrinsic amorphous silicon layer, thereby forming an antimony-rich tunneling oxide layer 2 in the tunneling oxide layer and a doped conductive layer 3 in the intrinsic amorphous silicon layer.

[0080] Specifically, the deposition temperature during deposition of the tunnel oxide layer is 400°C to 700°C, specifically 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or 700°C; the processing time is 400s to 700s, specifically 400s, 450s, 500s, 550s, 600s, 650s or 700s, and oxygen and water vapor are introduced. The deposition temperature during deposition of the intrinsic amorphous silicon layer is 400° C. to 700° C., specifically 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., or 700° C. The processing time is 1000s to 2000s, specifically 1000s, 1100s, 1200s, 1300s, 1400s, 1500s, 1600s, 1700s, 1800s, 1900s, or 2000s, and a silicon source gas (such as silane) is introduced.

[0081] In the embodiment of the present application, during the process of preparing the tunneling oxide layer, antimony diffuses into the tunneling oxide layer, forming an antimony-rich tunneling oxide layer 2. The antimony in this layer occupies more vacancies in the oxide layer, forming more stable chemical bonds, thereby achieving better interface passivation effect on the first surface 1a. The above preparation method can not only reduce the diffusion depth of phosphorus atoms in the existing phosphorus diffusion process, widen the process window, but also improve the passivation effect of the first surface 1a.

[0082] In a specific embodiment, Figure 1 As shown, the solar cell further includes an emitter 6, a second electrode 7, and a second passivation layer 8. The emitter 6 is disposed on the second surface 1b. Along the thickness direction Z of the solar cell, multiple second electrodes 7 are disposed on the side of the emitter 6 facing away from the silicon substrate 1. Each of the multiple second electrodes 7 is electrically connected to the emitter 6. The second passivation layer 8 covers the surface of the emitter 6 facing away from the silicon substrate 1. The emitter 6 contains one or more Group III elements, such as boron (B), aluminum (Al), gallium (Ga), and indium (In). This means that the emitter 6 is a P-type emitter and can form a PN junction with the N-type silicon substrate 1. This reduces parasitic absorption of incident light by the second surface 1b, increases the absorptivity of incident light by the second surface 1b, and improves the injection efficiency of photogenerated minority carriers. This improves the open-circuit voltage and short-circuit current of the solar cell, thereby increasing the photoelectric conversion efficiency of the solar cell.

[0083] The components of the second passivation layer 8 may include one or more of silicon oxide, silicon nitride, titanium oxide, aluminum oxide or silicon oxynitride. The second passivation layer 8 may be a single-layer structure or a multi-layer structure, and the refractive index and thickness of each layer may be designed accordingly. The second passivation layer 8 is close to the function and effect of the first passivation layer 5, that is, it plays the role of passivating the surface in contact with it, thereby reducing the recombination of carriers at the interface, improving the transmission efficiency of carriers, and then improving the photoelectric conversion efficiency of the solar cell. The second passivation layer 8 also has the function of reducing or eliminating the reflection effect of the second surface 1b and increasing the light transmittance of the second surface 1b, which is conducive to further improving the photoelectric conversion efficiency of the solar cell.

[0084] The second electrode 7 is specifically the positive electrode of the solar cell. At least part of the structure of the second electrode 7 can penetrate the second passivation layer 8 and form an electrical connection with the emitter 6. The emitter 6 is used to form a good ohmic contact between the second electrode 7 and the silicon substrate 1, which is beneficial to reducing the series resistance of the solar cell, and thus beneficial to improving the photoelectric conversion efficiency of the solar cell.

[0085] In addition, if Figure 1 As shown, the second surface 1b of the silicon substrate 1 can be configured as a pyramid velvet structure to reduce the reflectivity of the second surface 1b to incident light and increase the absorption and utilization rate of light, thereby increasing the light transmittance of the second surface 1b and further improving the photoelectric conversion efficiency of the solar cell. The first surface 1a of the silicon substrate 1 can be configured as a non-pyramid velvet structure, such as a stacked step morphology, so that the antimony-rich tunneling oxide layer 2 located on the first surface 1a has a high density and uniformity, so that the antimony-rich tunneling oxide layer 2 has a good passivation effect on the silicon substrate 1.

[0086] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A solar cell, characterized in that: include: A silicon substrate (1) containing antimony elements, wherein the silicon substrate (1) has a first surface (1a); an antimony-rich tunneling oxide layer (2) covering the first surface (1a); A doped conductive layer (3), along the thickness direction of the solar cell, the doped conductive layer (3) covers a surface of the antimony-rich tunneling oxide layer (2) on a side away from the silicon substrate (1), and the doped conductive layer (3) contains antimony elements; The antimony element concentration in the antimony-rich tunneling oxide layer (2) is greater than the antimony element concentration in the silicon substrate (1), and the antimony element concentration in the silicon substrate (1) is greater than the antimony element concentration in the doped conductive layer (3); Wherein, along the thickness direction of the solar cell, a first antimony-containing layer (31) is formed on a side of the doped conductive layer (3) close to the antimony-rich tunneling oxide layer (2), and the antimony element concentration in the first antimony-containing layer (31) is greater than the antimony element concentration in other parts of the doped conductive layer (3).

2. The solar cell according to claim 1, wherein In the thickness direction of the solar cell, the concentration of the antimony element in the antimony-rich tunneling oxide layer (2) gradually decreases in a direction away from the silicon substrate (1); And / or, in the thickness direction of the solar cell, the concentration of the antimony element in the first antimony-containing layer (31) gradually decreases in a direction away from the silicon substrate (1).

3. The solar cell according to claim 1, wherein The antimony element concentration in the silicon substrate (1) is 2.0×10 16 cm -3 ~8.0×10 16 cm -3 .

4. The solar cell according to claim 1, wherein The antimony element concentration in the antimony-rich tunneling oxide layer (2) is 1.0×10 18 cm -3 ~2.0×10 18 cm -3 .

5. The solar cell according to claim 1, wherein The antimony element concentration in the first antimony-containing layer (31) is 1.0×10 16 cm -3 ~1.0×10 18 cm -3 .

6. The solar cell according to claim 1, wherein The thickness of the first antimony-containing layer (31) is 5 nm to 10 nm.

7. The solar cell according to claim 1, wherein Along the thickness direction of the solar cell, a second antimony-containing layer (11) is formed on a side of the silicon substrate (1) close to the antimony-rich tunneling oxide layer (2); In the thickness direction of the solar cell, the concentration of the antimony element in the second antimony-containing layer (11) gradually increases in a direction approaching the antimony-rich tunneling oxide layer (2).

8. The solar cell according to claim 7, characterized in that The thickness of the second antimony-containing layer (11) is 5 nm to 10 nm.

9. The solar cell according to any one of claims 1 to 8, characterized in that The thickness of the antimony-rich tunneling oxide layer (2) is 1 nm to 10 nm; And / or, the thickness of the doped conductive layer (3) is 20 nm to 300 nm.

10. The solar cell according to any one of claims 1 to 8, characterized in that The doped conductive layer (3) also contains phosphorus, and the concentration of phosphorus in the doped conductive layer (3) is 1.0×10 20 cm -3 ~1.0×10 21 cm -3 .

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