Solar cell and preparation method thereof, photovoltaic module

Abstract

The present invention provides a solar cell and a preparation method thereof, and a photovoltaic module, relating to the field of photovoltaic technology. The solar cell includes: a silicon substrate, and a low absorption coefficient layer arranged on the light-facing surface of the silicon substrate; the low absorption coefficient layer and the light-facing surface of the silicon substrate have the same conductivity type; in a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate; the thickness x of the low absorption coefficient layer is 15-200 nm; and the low absorption coefficient layer is in direct contact with the silicon substrate. The low absorption coefficient layer and the light-facing surface of the silicon substrate have the same conductivity type, which is conducive to the transmission of minority carriers. The low absorption coefficient layer absorbs a portion of the light in the wavelength band less than or equal to 400 nm, and the light absorbed by the silicon substrate in the wavelength band less than or equal to 400 nm is reduced, which can reduce the concentration of non-equilibrium carriers in the light-facing surface of the silicon substrate. The low absorption coefficient layer fully absorbs light in the wavelength band less than or equal to 400 nm.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Solar cells are a power generation method that directly converts light energy into electrical energy output. As a clean energy source, they have broad application prospects.

[0003] Currently, solar cells all have the problem of poor short-wave response, which can lead to reduced photoelectric conversion efficiency of solar cells. Summary of the Invention

[0004] The present invention provides a solar cell and a preparation method thereof, and a photovoltaic module, aiming to solve the problem of poor short-wave response of solar cells.

[0005] A first aspect of the present invention provides a solar cell comprising:

[0006] A silicon substrate, and a low absorption coefficient layer provided on a light-facing surface of the silicon substrate;

[0007] The low absorption coefficient layer and the light-facing surface of the silicon substrate have the same conductivity type;

[0008] In a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate;

[0009] The thickness x of the low absorption coefficient layer is 15-200 nm; the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer;

[0010] The low absorption coefficient layer is in direct contact with the silicon substrate.

[0011] In an embodiment of the present invention, the low absorption coefficient layer has the same conductivity type as the light-facing surface of the silicon substrate, which facilitates the transmission of minority carriers, allowing non-equilibrium minority carriers in the light-facing surface of the silicon substrate to be effectively conducted and collected, thereby reducing the concentration of non-equilibrium carriers in the light-facing surface of the silicon substrate, reducing recombination on the light-facing surface of the silicon substrate, and improving the photoelectric conversion efficiency of the solar cell. The low absorption coefficient layer is in direct contact with the silicon substrate, and within a wavelength band less than or equal to 400nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate. The low absorption coefficient layer absorbs a portion of the light within the wavelength band less than or equal to 400nm. The amount of light within the wavelength band less than or equal to 400nm absorbed by the silicon substrate is reduced, thereby reducing the concentration of non-equilibrium carriers in the light-facing surface of the silicon substrate and facilitating the reduction of recombination on the light-facing surface of the silicon substrate 1. Moreover, the thickness x of the low absorption coefficient layer is 15-200nm. The thickness of the low absorption coefficient layer is not too thin, and can fully absorb light in a band less than or equal to 400nm. The thickness of the low absorption coefficient layer is not too thick, and the concentration of minority carriers in the low absorption coefficient layer is not too low. The minority carriers in the silicon substrate will not be injected into the low absorption coefficient layer, which is beneficial to the transmission of unbalanced minority carriers in the silicon substrate toward the light surface, so that the unbalanced minority carriers in the silicon substrate toward the light surface can be effectively conducted and collected, which is beneficial to reducing the concentration of unbalanced carriers in the silicon substrate toward the light surface, and is beneficial to reducing the recombination of the silicon substrate toward the light surface, which can improve the photoelectric conversion efficiency of solar cells.

[0012] Optionally, the band gap of the low absorption coefficient layer is greater than or equal to the band gap of the silicon substrate.

[0013] Optionally, the thickness x of the low absorption coefficient layer is 20-100 nm.

[0014] Optionally, the thickness of the low absorption coefficient layer Among them, κ min is the minimum extinction coefficient of the low absorption coefficient layer in the 200-400nm band.

[0015] Optionally, within the wavelength range of 300-400 nm, the extinction coefficient of the low absorption coefficient layer is greater than or equal to 0.1 and less than or equal to 2.

[0016] Optionally, within the wavelength range of 300-400 nm, the integrated average extinction coefficient of the low absorption coefficient layer is greater than or equal to 0.1 and less than or equal to 2.

[0017] Optionally, the material of the low absorption coefficient layer is selected from at least one of boron carbide, zinc oxide, gallium phosphide, indium phosphide, cadmium sulfide, zinc sulfide, arsenic selenide, cadmium selenide, and zinc selenide.

[0018] Optionally, the material of the low absorption coefficient layer is selected from zinc oxide, and the solar cell further includes: a front anti-reflection layer and a front electrode located on the side of the low absorption coefficient layer away from the silicon substrate, and the front electrode penetrates the front anti-reflection layer and contacts the low absorption coefficient layer.

[0019] Optionally, the low absorption coefficient layer has a local doped region, and the local doped region is a front selective contact region; or, the low absorption coefficient layer is a whole-surface doped layer, and the low absorption coefficient layer is a front selective contact layer;

[0020] The solar cell further includes a front electrode located on a side of the low absorption coefficient layer away from the silicon substrate, wherein the front electrode is in contact with the front selective contact region or the front selective contact layer.

[0021] Optionally, the solar cell further includes: a buffer layer located between the silicon substrate and the low absorption coefficient layer; the material of the buffer layer is selected from: at least one of silicon oxide, zinc sulfide, silicon carbide, aluminum nitride, and silicon nitride.

[0022] Optionally, the buffer layer has a thickness less than or equal to 4 mm; and a direction of the thickness is parallel to a direction in which the silicon substrate and the low absorption coefficient layer are arranged.

[0023] Optionally, the light-facing surface of the silicon substrate has a light-trapping structure.

[0024] A second aspect of the present invention provides a photovoltaic assembly comprising: a plurality of any of the aforementioned solar cells.

[0025] A third aspect of the present invention provides a method for preparing any of the aforementioned solar cells, comprising: providing a low absorption coefficient layer on the light-facing surface of a silicon substrate; the low absorption coefficient layer and the silicon substrate have the same conductivity type; within a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate; the thickness x of the low absorption coefficient layer is 15-200 nm; the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer; and the low absorption coefficient layer is in direct contact with the silicon substrate.

[0026] Optionally, providing a low absorption coefficient layer on the light-facing surface of the silicon substrate includes:

[0027] The low absorption coefficient layer is arranged on the light-facing surface of the silicon substrate by adopting chemical vapor deposition, evaporation deposition or molecular beam epitaxy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 shows a schematic structural diagram of a first solar cell in an embodiment of the present invention;

[0030] Figure 2 shows a schematic structural diagram of a second solar cell in an embodiment of the present invention;

[0031] Figure 3 shows a schematic structural diagram of a third solar cell in an embodiment of the present invention;

[0032] Figure 4 FIG. 4 is a schematic structural diagram of a fourth solar cell according to an embodiment of the present invention.

[0033] Description of reference numerals:

[0034] 1-silicon substrate, 2-low absorption coefficient layer, 31-front functional layer, 312-front passivation contact layer, 313-front anti-reflection layer, 32-front electrode, 41-back functional layer, 411-back passivation layer, 412-back transmission layer, 413-back anti-reflection layer, 42-back electrode. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Figure 1 A schematic structural diagram of a first solar cell in an embodiment of the present invention is shown. Figure 2 FIG. 1 is a schematic structural diagram of a second solar cell according to an embodiment of the present invention. Figure 3 FIG. 4 shows a schematic structural diagram of a third solar cell in an embodiment of the present invention. Figure 4 FIG. 4 shows a schematic structural diagram of a fourth solar cell according to an embodiment of the present invention. Figures 1 to 4 As shown, an embodiment of the present invention provides a solar cell, comprising: a silicon substrate 1, and a low absorption coefficient layer 2 arranged on the light-facing surface of the silicon substrate.

[0037] Specifically, the inventors found that in the prior art, the reason for the poor short-wave response of solar cells is that the absorption coefficient of the photosensitive surface of the silicon substrate 1 for short waves in the wavelength band less than or equal to 400nm (nanometers) is relatively high, resulting in most of the incident light being absorbed within a very shallow depth of the photosensitive surface of the silicon substrate 1. For example, the incident light in the wavelength band less than or equal to 400nm can be completely absorbed from the photosensitive surface of the silicon substrate 1 with a thickness of 10nm inside the silicon substrate. As a result, under illumination, it has a very high non-equilibrium carrier concentration, and the high concentration of non-equilibrium carriers cannot be effectively and timely extracted and collected, resulting in serious recombination on the photosensitive surface of the silicon substrate 1.

[0038] More specifically, the material absorption coefficient is directly related to the optical parameters as follows: Where α is the absorption coefficient, κ is the extinction coefficient, and λ is the wavelength. Silicon material has a peak extinction coefficient of κ = 0.387 in the 400nm band, κ = 3.014 in the 350nm band, κ = 4.639 in the 300nm band, κ = 5.395 in the 288nm band, and κ = 2.909 in the 200nm band. The extinction coefficient κ is greater than 2.9 in the 200-350nm band, and only falls below 2.9 in the 350-400nm band, but it rises sharply as the wavelength decreases. In the band less than or equal to 400nm, silicon material has the lowest absorption coefficient in the 400nm band, α = 0.0122nm. -1 , that is, through Thickness, can absorb most of the incident light in the 400nm band, however, for the 350nm band, only 10nm thickness is needed to absorb most of the incident light in the 350nm band, and for the incident light in the 200-350nm band, the silicon material only needs less than 10nm thickness to achieve most of the absorption. At the same time, the non-equilibrium carrier yield G∝∫f·α·e in the light-facing surface of the silicon substrate -αx The absorption coefficient α is directly proportional to G, and the two have a direct impact. That is, if the absorption coefficient α decreases by one order of magnitude, G can also decrease by one order of magnitude. Therefore, the light-facing surface of silicon substrate 1 has a higher absorption coefficient for short wavelengths less than or equal to 400 nm, and thus has a high non-equilibrium carrier concentration.

[0039] To address the above issues, in the present invention, the low absorption coefficient layer 2 has the same conductivity type as the light-facing surface of the silicon substrate 1, which facilitates the transmission of minority carriers. This allows the non-equilibrium minority carriers on the light-facing surface of the silicon substrate 1 to be effectively conducted and collected, thereby reducing the concentration of non-equilibrium carriers on the light-facing surface of the silicon substrate 1 and reducing recombination on the light-facing surface of the silicon substrate 1, thereby improving the photoelectric conversion efficiency of the solar cell. The low absorption coefficient layer 2 is in direct contact with the silicon substrate 1, and within a wavelength band less than or equal to 400nm, the absorption coefficient of the low absorption coefficient layer 2 is less than that of the silicon substrate 1. The low absorption coefficient layer 2 absorbs a portion of the light within the wavelength band less than or equal to 400nm. The amount of light within the wavelength band less than or equal to 400nm absorbed by the silicon substrate 1 is reduced, thereby reducing the concentration of non-equilibrium carriers on the light-facing surface of the silicon substrate 1, reducing recombination on the light-facing surface of the silicon substrate 1, and improving the photoelectric conversion efficiency of the solar cell. Moreover, the thickness x of the low absorption coefficient layer 2 is 15-200nm. The thickness of the low absorption coefficient layer 2 is not too thin and can fully absorb light in a band less than or equal to 400nm. The thickness of the low absorption coefficient layer 2 is not too thick. The concentration of minority carriers in the low absorption coefficient layer 2 is not too low. The minority carriers in the silicon substrate 1 will not be injected into the low absorption coefficient layer 2, which is beneficial to the transmission of non-equilibrium minority carriers in the light-facing surface of the silicon substrate 1, so that the non-equilibrium minority carriers in the light-facing surface of the silicon substrate 1 can be effectively conducted and collected, which is beneficial to reducing the concentration of non-equilibrium carriers in the light-facing surface of the silicon substrate 1 and reducing the recombination of the light-facing surface of the silicon substrate 1.

[0040] For example, the thickness x of the low absorption coefficient layer 2 can be 15 nm, 30 nm, 50 nm, 90 nm, 110 nm, 130 nm, 170 nm, or 200 nm. The direction of the thickness is parallel to the orientation of the silicon substrate 1 and the low absorption coefficient layer 2, and the thickness direction referred to throughout the text is defined in the same manner.

[0041] The low absorption coefficient layer 2 is in direct contact with the silicon substrate 1, and the interface between the two is not specifically limited. For example, the interface between the two can be an epitaxial interface or a chemical bond interface. The epitaxial interface is a lattice-matched interface. Through a high-precision transmission electron microscope, it looks like there is almost no interface, and the low absorption coefficient layer 2 and the silicon substrate 1 can be considered as a whole. The chemical bond interface is that the low absorption coefficient layer 2 is bonded to the silicon substrate 1. The interface can be lattice-matched in some areas, while the lattice is not matched in other areas. Through a projection electron microscope, the low absorption coefficient layer 2 and the silicon substrate 1 will have a display interface. It should be noted that in the interface between the low absorption coefficient layer 2 and the silicon substrate 1, the larger the lattice adaptation area is, the more conducive it is to the conduction or transport of carriers at the interface between the two. The present invention does not limit the doping concentration, doping type, thickness, etc. of the silicon substrate 1.

[0042] The low absorption coefficient layer 2 may be made of a polycrystalline material or a single crystal material, which is not specifically limited. For example, the low absorption coefficient layer 2 may be made of a single crystal material, thereby forming an interface with the silicon substrate 1 having excellent performance.

[0043] Optionally, the band gap of the low absorption coefficient layer 2 is greater than or equal to the band gap of the silicon substrate 1, ensuring that the silicon substrate 1 is the primary absorber of light in the wavelength range greater than 400 nm. In other words, because the silicon substrate 1 has a higher absorption coefficient for wavelengths less than or equal to 400 nm, the non-equilibrium carrier concentration on the photo-facing surface of the silicon substrate 1 is higher. In the present invention, the silicon substrate 1 absorbs less light in the wavelength range less than or equal to 400 nm, thereby reducing the non-equilibrium carrier concentration on the photo-facing surface of the silicon substrate 1. Meanwhile, the silicon substrate 1 absorbs as much light in the wavelength range greater than 400 nm as possible.

[0044] Optionally, the thickness x of the low absorption coefficient layer 2 is 20-100nm. In this case, the thickness of the low absorption coefficient layer 2 is more appropriate. It can not only fully absorb light in a wavelength band less than or equal to 400nm, but also the concentration of minority carriers in the low absorption coefficient layer 2 is not too low. The minority carriers in the silicon substrate 1 will not be injected into the low absorption coefficient layer 2, which is beneficial to the transmission of non-equilibrium minority carriers in the light-facing surface of the silicon substrate 1, so that the non-equilibrium minority carriers in the light-facing surface of the silicon substrate 1 can be effectively conducted and collected, which is beneficial to reducing the concentration of non-equilibrium carriers in the light-facing surface of the silicon substrate 1, and is beneficial to reducing the recombination of the light-facing surface of the silicon substrate 1.

[0045] For example, the thickness x of the low absorption coefficient layer 2 may be 20 nm, 30 nm, 42 nm, 55 nm, 63 nm, 77 nm, 89 nm, or 100 nm.

[0046] Optionally, the thickness of the low absorption coefficient layer 2 is Among them, κ min is the minimum extinction coefficient of the low absorption coefficient layer 2 in the 200-400nm band. In this case, the thickness x of the low absorption coefficient layer 2 is more appropriate, not only fully absorbing light in the wavelength band less than or equal to 400nm, but also ensuring that the concentration of minority carriers in the low absorption coefficient layer 2 is not too low. Minority carriers in the silicon substrate 1 are not injected into the low absorption coefficient layer 2, which facilitates the transmission of non-equilibrium minority carriers on the light-facing surface of the silicon substrate 1. These non-equilibrium minority carriers on the light-facing surface of the silicon substrate 1 can be effectively conducted and collected, thereby reducing the concentration of non-equilibrium carriers on the light-facing surface of the silicon substrate 1 and reducing recombination on the light-facing surface of the silicon substrate 1.

[0047] Optionally, within the wavelength range of 300-400 nm, the extinction coefficient of the low absorption coefficient layer 2 is greater than or equal to 0.1 and less than or equal to 2. The extinction coefficient of the low absorption coefficient layer 2 is directly proportional to its absorption coefficient. Within the wavelength range of 300-400 nm, if the extinction coefficient of the low absorption coefficient layer 2 is within this range, its absorption coefficient is relatively appropriate, and the amount of light absorbed within the wavelength range of 300-400 nm is relatively appropriate. The amount of light absorbed by the silicon substrate 1 within the wavelength range of 300-400 nm is relatively appropriate, which can reduce the non-equilibrium carrier concentration on the light-facing surface of the silicon substrate 1.

[0048] For example, in the wavelength range of 300-400 nm, the extinction coefficients of the low absorption coefficient layer 2 are: 0.1, 0.3, 0.5, 0.8, 0.9, 1.1, 1.5, 1.9, and 2.

[0049] Optionally, within the wavelength range of 300-400nm, the integrated average extinction coefficient of the low absorption coefficient layer 2 is greater than or equal to 0.1 and less than or equal to 2. The integrated average extinction coefficient here is: taking the wavelength range of 300-400nm as the integration interval, taking the extinction coefficient of the low absorption coefficient layer 2 as the integrand function, integrating, and then dividing by the length of the integration interval. Within the wavelength range of 300-400nm, if the extinction coefficient of the low absorption coefficient layer 2 is within this range, then its absorption coefficient is relatively appropriate, and the amount of light absorbed within the wavelength range of 300-400nm is relatively appropriate. The amount of light absorbed by the silicon substrate 1 within the wavelength range of 300-400nm is relatively appropriate, which can reduce the non-equilibrium carrier concentration on the light-facing surface of the silicon substrate 1.

[0050] For example, in the wavelength range of 300-400 nm, the integrated average extinction coefficients of the low absorption coefficient layer 2 are: 0.1, 0.3, 0.46, 0.73, 0.92, 1.1, 1.5, 1.88, and 2.

[0051] Optionally, the material of the low absorption coefficient layer 2 is selected from at least one of boron carbide, zinc oxide, gallium phosphide, indium phosphide, cadmium sulfide, zinc sulfide, arsenic selenide, cadmium selenide, and zinc selenide. The low absorption coefficient layer 2 made of the above material has a suitable absorption coefficient within the 300-400nm wavelength band, and can reduce the non-equilibrium carrier concentration on the photo-facing surface of the silicon substrate 1. Furthermore, the lattice constants of the low absorption coefficient layer 2 and the silicon substrate 1 are relatively close, making it easy to form an epitaxial interface or a chemical bond interface at the interface between the two, which facilitates the conduction or transport of carriers at the interface between the two and helps improve the photoelectric conversion efficiency of the solar cell.

[0052] More specifically, the lattice constant of silicon in the silicon substrate 1 is (angstroms), the lattice constant of boron carbide is In the wavelength range of 300-400nm, the extinction coefficient of boron carbide ranges from 1.05 to 0.76. If boron carbide is used as the material of the low absorption coefficient layer 2, it can not only reduce the non-equilibrium carrier concentration on the light-facing surface of the silicon substrate 1. In addition, the lattice constants of the low absorption coefficient layer 2 of the boron carbide material and the silicon substrate 1 are relatively close, and it is easy to form an epitaxial interface or a chemical bond interface at the interface between the two, which is beneficial to the conduction or transportation of carriers at the interface between the two, and is beneficial to improving the photoelectric conversion efficiency of the solar cell. Similarly, the lattice constant of zinc oxide is In the 300-400nm band, the extinction coefficient of zinc oxide is roughly 0.196 to 0.254 and 0.254 to 0.109. The lattice constant of gallium phosphide is In the 300-400nm band, the extinction coefficient of gallium phosphide is roughly 2.1 to 0.275. The lattice constant of indium phosphide is In the 300-400nm band, the extinction coefficient of indium phosphide is roughly 1.7 to 2.2 and 2.2 to 1.7. The lattice constant of cadmium sulfide is In the 300-400nm band, the extinction coefficient of cadmium sulfide is approximately 0.39 to 0.34. The lattice constant of zinc sulfide is In the 300-400nm band, the extinction coefficient of zinc sulfide is roughly 0.357 to 0.008. The lattice constant of arsenic selenide is In the 300-400nm band, the extinction coefficient of arsenic selenide is roughly 1.66 to 1.86 and 1.86 to 1.65. The lattice constant of cadmium selenide is In the 300-400nm band, the extinction coefficient of cadmium selenide is roughly 1.34 to 0.56. The lattice constant of zinc selenide is In the 300-400nm band, the extinction coefficient of zinc selenide is roughly 0.79 to 0.48.

[0053] Optional, see Figure 3As shown, the material of the low absorption coefficient layer 2 is zinc oxide. The solar cell further includes a front anti-reflection layer 313 and a front electrode 32 located on the side of the low absorption coefficient layer 2 facing away from the silicon substrate 1. The front electrode 32 penetrates the front anti-reflection layer 313 and contacts the low absorption coefficient layer 2. Specifically, the low absorption coefficient layer 2 is made of zinc oxide. The low absorption coefficient layer 2 has at least two functions: one is to provide a low absorption coefficient within the 300-400 nm wavelength range, and the other is to provide front carrier transport or front selective contact. This eliminates the need for a separate front carrier transport layer, simplifying the cell structure. Since zinc oxide naturally has an N-type conductivity, there is no specific restriction on whether the zinc oxide low absorption coefficient layer 2 is doped. For example, the zinc oxide low absorption coefficient layer 2 can be undoped, and the silicon substrate 1 can also be of N-type conductivity. Alternatively, the zinc oxide low absorption coefficient layer 2 can be surface doped in whole or in part to enhance its conductivity. For example, this can be doped with elements such as aluminum, indium, and gallium. In the present invention, the doping concentration in the low absorption coefficient layer 2 is not particularly limited.

[0054] Optionally, the low absorption coefficient layer 2 of zinc oxide material can have a thickness of 15-100 nm. The low absorption coefficient layer 2 of zinc oxide material within this thickness range has a good low absorption coefficient effect within the wavelength range of 300-400 nm, and has a good frontal carrier transport effect or frontal selective contact effect. For example, the thickness of the low absorption coefficient layer 2 of zinc oxide material can be 15 nm, 23 nm, 36 nm, 45 nm, 58 nm, 66 nm, 79 nm, 88 nm, or 100 nm.

[0055] Optionally, the thickness of the zinc oxide low absorption coefficient layer 2 can be further 20-50 nm. The zinc oxide low absorption coefficient layer 2 having the above thickness range has a better low absorption coefficient effect within the wavelength range of 300-400 nm, and has a better frontal carrier transport effect or frontal selective contact effect. For example, the thickness of the zinc oxide low absorption coefficient layer 2 can be 20 nm, 23 nm, 29 nm, 36 nm, 38 nm, 42 nm, 47 nm, or 50 nm.

[0056] The material, structure, and thickness of the front anti-reflection layer 313 are not specifically limited. For example, the material of the front anti-reflection layer 313 can be selected from at least one of silicon nitride, magnesium fluoride, silicon oxide, zinc sulfide, silicon oxynitride, aluminum nitride, titanium nitride, aluminum oxide, and titanium oxide. For example, the front anti-reflection layer 313 can be a stacked structure of an aluminum nitride layer and a titanium nitride layer.

[0057] There are no specific limitations on the material, structure, and size of the front electrode 32. For example, the material of the front electrode 32 can be selected from at least one of silver, copper, nickel, zinc, and aluminum. The front electrode 32 can have a single layer or a stacked layer structure.

[0058] Optionally, the low absorption coefficient layer 2 has a local doped region, which is a front selective contact region. The solar cell also includes: a front electrode 32 located on the side of the low absorption coefficient layer 2 away from the silicon substrate 1, and the front electrode 32 is in contact with the front selective contact region. That is to say, the entire layer of the low absorption coefficient layer 2 plays the role of low absorption coefficient in the 300-400nm band. In addition to playing the role of low absorption coefficient in the local doped region, the low absorption coefficient layer 2 also plays the role of front carrier transport or the role of front selective contact, thereby eliminating the need to independently set up a front carrier transport layer, which can simplify the battery structure. In the present invention, there is no specific limitation on the doping concentration of the front selective contact region.

[0059] Optional, see Figure 2 As shown, the low absorption coefficient layer 2 is a fully doped layer, and the low absorption coefficient layer 2 also serves as a front selective contact layer. The solar cell further includes a front electrode 32 located on the side of the low absorption coefficient layer 2 away from the silicon substrate 1, and the front electrode 32 is in contact with the low absorption coefficient layer 2. In other words, the fully doped low absorption coefficient layer 2 has at least two functions: one is to exert a low absorption coefficient within the 300-400nm band, and the other is to transport carriers on the front side. This eliminates the need for a separate front selective contact layer, simplifying the cell structure. In the present invention, the doping concentration of the low absorption coefficient layer 2 is not specifically limited.

[0060] Optionally, the solar cell may further include a buffer layer (not shown) positioned between the silicon substrate 1 and the low absorption coefficient layer 2. The buffer layer may be made of at least one of silicon oxide, zinc sulfide, silicon carbide, aluminum nitride, and silicon nitride. The buffer layer of these materials exhibits good lattice matching with both the silicon substrate 1 and the low absorption coefficient layer 2, as well as excellent electrical properties, thereby enhancing contact between the silicon substrate 1 and the low absorption coefficient layer 2.

[0061] Optionally, the buffer layer has a thickness less than or equal to 4 mm, and the direction of the thickness is parallel to the arrangement direction of the silicon substrate 1 and the low absorption coefficient layer 2. The buffer layer thickness within this range has good lattice matching performance for the silicon substrate 1 and the low absorption coefficient layer 2.

[0062] For example, the thickness of the buffer layer may be 50 um, 150 um, 500 um, 1.2 mm, 2.4 mm, 3.2 mm, 3.7 mm, or 4 mm.

[0063] Optionally, the thickness of the buffer layer is less than or equal to 2 mm. Within this range, the thickness of the buffer layer provides good lattice matching performance between the silicon substrate 1 and the low absorption coefficient layer 2. For example, the thickness of the buffer layer can be 50 μm, 150 μm, 500 μm, 980 μm, 1.2 mm, 1.5 mm, 1.8 mm, or 2 mm.

[0064] Optionally, the light-facing surface of the silicon substrate 1 has a light-trapping structure. Since the shape of the low absorption coefficient layer 2 is adapted to the light-facing surface of the silicon substrate 1, the low absorption coefficient layer 2 also has a light-trapping structure, which can improve the light-trapping effect of the solar cell.

[0065] Reference Figure 1 As shown, the solar cell may further include: a front functional layer 31 located on the light-facing side of the low absorption coefficient layer 2. The front functional layer 31 may include one or more layers such as a front passivation layer, a front transmission layer, and a front anti-reflection layer 313. The material and structure of the front functional layer 31 are not specifically limited. For example, part of the front anti-reflection layer 313 may also have field passivation or chemical passivation functions. For example, the front transmission layer mainly plays the role of selecting and conducting the majority carriers on the light-facing side of the silicon substrate 1, and also includes a light-facing chemical passivation function. For example, the material of the front transmission layer may be selected from at least one of intrinsic amorphous silicon and doped amorphous silicon, silicon oxide and doped polycrystalline silicon, silicon oxide and indium tin oxide.

[0066] Reference Figure 1 As shown, the backlight side of the silicon substrate 1 may have a diffused or implanted pn junction or a heavily doped layer or region. The solar cell may also include a backside functional layer 41 located on the backlight side of the silicon substrate 1. The backside functional layer 41 may include one or more layers, such as a backside passivation layer 411, a backside transmission layer 412, and a backside anti-reflection layer 413. The materials and structure of the backside functional layer 41 are not specifically limited. The backside anti-reflection layer 413 may include one or more layers, such as silicon nitride, silicon oxide, silicon oxynitride, aluminum nitride, titanium nitride, aluminum oxide, or titanium oxide. For example, portions of the backside anti-reflection layer 413 may have field passivation or chemical passivation functions. For example, the backside transmission layer 412 primarily functions to select and conduct majority carriers on the backlight side of the silicon substrate 1. For example, the material of the backside transmission layer 412 may be selected from at least one of intrinsic amorphous silicon and doped amorphous silicon, silicon oxide and doped polycrystalline silicon, or silicon oxide and zinc oxide. The solar cell may also include a backside electrode 42, the material of which is not specifically limited. For example, the back electrode 42 may be made of a metal material, such as at least one of gold, silver, copper, aluminum, nickel, indium, and gallium.

[0067] The present invention further provides a photovoltaic module, which includes a plurality of any of the aforementioned solar cells. The photovoltaic module can achieve the same or similar beneficial effects, and to avoid repetition, the relevant parts are not described in detail.

[0068] The present invention also provides a method for preparing any of the aforementioned solar cells, the method comprising the following steps: providing a low absorption coefficient layer on the light-facing surface of a silicon substrate; the low absorption coefficient layer and the silicon substrate have the same conductivity type; within a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate; the thickness x of the low absorption coefficient layer is 15-200 nm; the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer; and the low absorption coefficient layer is in direct contact with the silicon substrate.

[0069] This preparation method can achieve the same or similar beneficial effects as any of the aforementioned solar cells. To avoid repetition, the relevant parts will not be described again.

[0070] Alternatively, a low absorption coefficient layer 2 can be formed on the light-facing surface of the silicon substrate 1 by chemical vapor deposition, evaporative deposition, or molecular beam epitaxy. The above preparation method can easily produce a low absorption coefficient layer 2 with excellent performance and a good contact interface with the silicon substrate 1.

[0071] It should be noted that the above-mentioned solar cells, photovoltaic modules, and methods for preparing solar cells can refer to each other and can achieve the same or similar beneficial effects. In order to avoid repetition, the relevant parts will not be described again.

[0072] The present application is further explained below with reference to specific embodiments.

[0073] Example 1

[0074] Reference Figure 2 As shown, the backlight surface of the solar cell adopts a TOPCon (Tunnel Oxide Passivated Contact) structure.

[0075] The silicon substrate 1 is an n-type silicon wafer with no limit on thickness and no limit on doping concentration. For example, the doping concentration of the silicon substrate 1 is 10 10 / cm 3 to 10 16 / cm 3 , the thickness can be 30-150um (micrometer), or 50-200um. For another example, for 10 10 / cm 3 to 10 14 / cm 3The low doping concentration silicon substrate 1 can be thicker, and the thickness can be 80-150um. 14 / cm 3 to 10 16 / cm 3 The high doping concentration silicon substrate 1 can be thinner, with a thickness of 30-80 μm. The light-facing surface of the silicon substrate 1 can be a flat structure or a low-roughness light-trapping structure, and the backlight surface of the silicon substrate 1 has a suede light-trapping structure.

[0076] A low absorption coefficient layer 2 is provided on the light-facing surface of a silicon substrate 1. The layer is made of gallium phosphide (GaP) or indium phosphide (InP) material, has a thickness of 20-100 nm, for example, 20-50 nm, and has n-type conductivity. The layer is formed using a chemical vapor phase epitaxial deposition method, such as chemical molecular beam epitaxy or atomic layer deposition.

[0077] A front passivation contact layer 312 is provided on the light-facing surface of the low absorption coefficient layer 2 . The front passivation contact layer 312 is made of a wide bandgap III-V material, such as AlGaAs, AlGaInP, GaInAs, etc. (the stoichiometric ratio is not limited).

[0078] A front anti-reflection layer 313 is disposed on the light-facing surface of the front passivation contact layer 312 . The material of the front anti-reflection layer 313 is silicon nitride, magnesium fluoride, silicon oxide, or the like.

[0079] The front electrode 32 penetrates the front anti-reflection layer 313 and forms electrical contact with the front passivation contact layer 312, or partially forms contact with the low absorption coefficient layer 2. The front electrode 32 is a single layer or a stacked layer structure of at least one of silver, copper, nickel, zinc, and aluminum.

[0080] The backlight side of the solar cell has a conventional TOPCon structure and is provided with a backside passivation layer 411 made of silicon oxide. The backside transmission layer 412 is doped polysilicon, and the doping type of the backside transmission layer 412 is the same as that of the backlight side of the silicon substrate 1. If the low absorption coefficient layer 2 is an n-type material, the backlight side of the silicon substrate 1 uses a p-type diffusion or injection layer. The backside transmission layer 412 uses p-type polysilicon. If the low absorption coefficient layer 2 is a p-type material, the backlight side of the silicon substrate 1 can be un-diffused or injected with an n-type heavily doped layer, and the backside transmission layer 412 uses n-type polysilicon.

[0081] A back anti-reflection layer 413 is provided on the backlight surface of the back transmission layer 412 and is made of at least one of silicon nitride, magnesium fluoride and silicon oxide.

[0082] The back electrode 42 penetrates the back anti-reflection layer 413 to form an electrical contact with the back transmission layer 412, or partially penetrates the back transmission layer 412 and the back passivation layer 411 to form contact with the backlight side of the silicon substrate 1. The material of the back electrode 42 is selected from at least one of silver, copper, nickel, zinc, and aluminum, forming a single layer structure or a stacked layer structure.

[0083] Example 2

[0084] Reference Figure 3 As shown, the silicon substrate 1 is an n-type silicon wafer with no limit on thickness and no limit on doping concentration. For example, the doping concentration is 10 10 / cm 3 to 10 16 / cm 3 , thickness is 30-150um. For example, for 10 10 / cm 3 to 10 14 / cm 3 The low doping concentration silicon substrate 1 can be thicker, and the thickness can be 80-150um. 14 / cm 3 to 10 16 / cm 3 The high doping concentration silicon substrate 1 can be thinner, with a thickness of 30-80 μm. The light-facing surface of the silicon substrate 1 can be a flat structure or a low-roughness light-trapping structure, and the backlight surface of the silicon substrate 1 has a suede light-trapping structure.

[0085] A low absorption coefficient layer 2 is provided on the light-facing surface of the silicon substrate 1, and is made of zinc oxide with a thickness of 15-100 nm, for example, 20-50 nm. Zinc oxide naturally has an n-type conductivity type, and zinc oxide can be doped to improve conductivity or enhance the conductivity type, for example, by doping with elements such as aluminum, indium, and gallium. The low absorption coefficient layer 2 can be prepared by processes such as chemical vapor deposition, evaporative deposition, and molecular beam epitaxy. A buffer layer can be present between the low absorption coefficient layer 2 and the silicon substrate 1. The material of the buffer layer can be selected from silicon oxide, zinc sulfide, silicon carbide, aluminum nitride, silicon nitride, etc. The thickness of the buffer layer does not exceed 4 nm. Optionally, the thickness of the buffer layer does not exceed 2 nm.

[0086] A front anti-reflection layer 313 is provided on the light-facing surface of the low absorption coefficient layer 2 and is made of at least one of silicon nitride, magnesium fluoride, silicon oxide, and zinc sulfide.

[0087] The front electrode 32 penetrates the front anti-reflection layer 313 and forms electrical contact with the low absorption coefficient layer 2. The material of the front electrode 32 is selected from at least one of silver, copper, nickel, zinc, and aluminum to form a single layer structure or a stacked layer structure.

[0088] The backlight side of the solar cell is a conventional HJT (Hetero-Junction with Intrinsic Thin-layer) structure. A back passivation layer 411 is provided on the backlight side of the silicon substrate 1, and the material is intrinsic amorphous silicon. A back transmission layer 412 is provided on the surface of the back passivation layer 411. When the silicon substrate 1 is an n-type or p-type silicon wafer, the back transmission layer 412 is a multilayer structure of p-type amorphous silicon or nanocrystalline silicon and a transparent conductive film. A back anti-reflection layer 413 is provided on the backlight side of the back transmission layer 412, and is made of silicon nitride material, or silicon nitride, magnesium fluoride material, or silicon oxide, silicon nitride, magnesium fluoride material, etc.

[0089] The back electrode 42 penetrates the back anti-reflection layer 413 and forms electrical contact with the back transmission layer 412. The back electrode 42 is made of at least one material selected from silver, copper, nickel, zinc, and aluminum to form a single layer structure or a stacked layer structure.

[0090] Example 3

[0091] Reference Figure 4 As shown, the backlight surface adopts DASH structure. The silicon substrate 1 adopts p-type silicon wafer. For example, the doping concentration is 10 10 / cm 3 to 10 16 / cm 3 , thickness is 30-150um. For example, for 10 10 / cm 3 to 10 14 / cm 3 The low doping concentration silicon substrate 1 can be thicker, and the thickness can be 80-150um. 14 / cm 3 to 10 16 / cm 3 The high doping concentration silicon substrate 1 can be thinner, with a thickness of 30-80 μm. The light-facing surface of the silicon substrate 1 can be a flat structure or a low-roughness light-trapping structure, and the backlight surface of the silicon substrate 1 has a suede light-trapping structure.

[0092] A low absorption coefficient layer 2 is applied to the light-facing surface of the silicon substrate 1. It is made of zinc sulfide or zinc selenide and has a thickness of 15-100 nm, for example, 20-50 nm. Low absorption coefficient layer 2 has p-type conductivity. The zinc sulfide or zinc selenide can be doped with elements such as aluminum, indium, and gallium to increase conductivity or enhance conductivity. This layer is fabricated using processes such as chemical vapor deposition, evaporative deposition, and molecular beam epitaxy. Alternatively, zinc oxide or other aforementioned materials can be used.

[0093] A front passivation contact layer 312 is provided on the low absorption coefficient layer 2 and is made of a transparent conductive film such as zinc oxide (which may be doped with aluminum, indium, gallium, etc.) or indium tin oxide.

[0094] A front anti-reflection layer 313 is provided on the front passivation contact layer 312 and is made of silicon nitride material, or silicon nitride and magnesium fluoride material, or silicon oxide, silicon nitride, magnesium fluoride material, etc.

[0095] The front electrode 32 and the front antireflection layer 313 form an electrical contact with the front passivation contact layer 312, or partially form a contact with the low absorption coefficient layer 2. The front electrode 32 is a single layer or a stacked layer structure of at least one of silver, copper, nickel, zinc, and aluminum.

[0096] The backlight surface of the solar cell has a DASH structure. A back passivation layer 411 is provided on the backlight surface of the silicon substrate 1, which is made of silicon oxide. A back transmission layer 412 is provided on the surface of the back passivation layer 411, which is made of a wide-bandgap transition metal oxide and a transparent conductive film stacked material. The wide-bandgap transition metal oxide has an opposite conductivity type to the low-absorption coefficient layer 2. The p-type material can be selected with a high work function, and the n-type material can be selected from molybdenum oxide, tungsten oxide, vanadium oxide, etc. The p-type material can also be selected from a p-type oxide such as nickel oxide. The n-type material can be selected from an n-type oxide such as zinc oxide, tin oxide, titanium oxide, etc. A back anti-reflection layer 413 is provided on the backlight surface, which is made of silicon nitride material, or silicon nitride, magnesium fluoride material, or silicon oxide, silicon nitride, magnesium fluoride material, etc.

[0097] The back electrode 42 penetrates the back anti-reflection layer 413 and forms electrical contact with the back transmission layer 412. The back electrode 42 is made of at least one material selected from silver, copper, nickel, zinc, and aluminum to form a single layer structure or a stacked layer structure.

[0098] It should be noted that, for the sake of simplicity, the method embodiments are described as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the order of the actions described, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0099] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0100] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A solar cell, characterized in that: The method comprises: a silicon substrate, and a low absorption coefficient layer arranged on the light-facing surface of the silicon substrate; The low absorption coefficient layer and the light-facing surface of the silicon substrate have the same conductivity type; In a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate; The thickness x of the low absorption coefficient layer is 15-200 nm; the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer; The low absorption coefficient layer is in direct contact with the silicon substrate; or the solar cell further comprises: a buffer layer located between the silicon substrate and the low absorption coefficient layer; the material of the buffer layer is selected from: at least one of silicon oxide, zinc sulfide, silicon carbide, aluminum nitride, and silicon nitride; The thickness of the low absorption coefficient layer ;in, is the minimum extinction coefficient of the low absorption coefficient layer in the 200-400nm band.

2. The solar cell according to claim 1, wherein The band gap of the low absorption coefficient layer is greater than or equal to the band gap of the silicon substrate.

3. The solar cell according to claim 1, wherein The thickness x of the low absorption coefficient layer is 20-100 nm.

4. The solar cell according to any one of claims 1 to 3, characterized in that: In the wavelength range of 300-400 nm, the extinction coefficient of the low absorption coefficient layer is greater than or equal to 0.1 and less than or equal to 2.

5. The solar cell according to any one of claims 1 to 3, characterized in that: In the wavelength range of 300-400 nm, the integrated average extinction coefficient of the low absorption coefficient layer is greater than or equal to 0.1 and less than or equal to 2.

6. The solar cell according to claim 1, wherein The material of the low absorption coefficient layer is selected from at least one of boron carbide, zinc oxide, gallium phosphide, indium phosphide, cadmium sulfide, zinc sulfide, arsenic selenide, cadmium selenide, and zinc selenide.

7. The solar cell according to claim 6, characterized in that The material of the low absorption coefficient layer is selected from zinc oxide. The solar cell further comprises: a front anti-reflection layer and a front electrode located on a side of the low absorption coefficient layer away from the silicon substrate. The front electrode penetrates the front anti-reflection layer and contacts the low absorption coefficient layer.

8. The solar cell according to any one of claims 1 to 3, characterized in that: The low absorption coefficient layer has a local doping region, and the local doping region is a front selective contact region; or the low absorption coefficient layer is a full-surface doping layer, and the low absorption coefficient layer is a front selective contact layer; The solar cell further includes a front electrode located on a side of the low absorption coefficient layer away from the silicon substrate, wherein the front electrode is in contact with the front selective contact region or the front selective contact layer.

9. The solar cell according to claim 1, wherein The thickness of the buffer layer is less than or equal to 4 mm; the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer.

10. The solar cell according to any one of claims 1 to 3, characterized in that: The light-facing surface of the silicon substrate has a light-trapping structure.

11. A photovoltaic module, characterized in that: include: Several solar cells according to any one of claims 1 to 10.

12. A method for preparing the solar cell according to any one of claims 1 to 10, characterized in that: include: A low absorption coefficient layer is provided on the light-facing surface of the silicon substrate; The low absorption coefficient layer and the silicon substrate have the same conductivity type; In a wavelength band less than or equal to 400 nm, the absorption coefficient of the low absorption coefficient layer is less than the absorption coefficient of the silicon substrate; the thickness x of the low absorption coefficient layer is 15-200 nm; and the direction of the thickness is parallel to the arrangement direction of the silicon substrate and the low absorption coefficient layer; The low absorption coefficient layer is in direct contact with the silicon substrate; or the solar cell further comprises: a buffer layer located between the silicon substrate and the low absorption coefficient layer; the material of the buffer layer is selected from at least one of silicon oxide, zinc sulfide, silicon carbide, aluminum nitride, and silicon nitride; the thickness of the low absorption coefficient layer is ;in, is the minimum extinction coefficient of the low absorption coefficient layer in the 200-400nm band.

13. The method for preparing a solar cell according to claim 12, wherein: The method of providing a low absorption coefficient layer on the light-facing surface of the silicon substrate comprises: The low absorption coefficient layer is arranged on the light-facing surface of the silicon substrate by adopting chemical vapor deposition, evaporative deposition or molecular beam epitaxy.

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