Silicon substrate, solar cell, and photovoltaic module

Abstract

The present application provides a silicon substrate, comprising a first surface and a second surface which are opposite to each other. A plurality of recesses are formed in the first surface. The thickness of the silicon substrate is h1, and the depth of the recesses is h2, wherein the difference Δh between h1 and h2 satisfies h1>Δh≥1 / A(λ=300 nm), wherein A(λ=300 nm) is an optical absorption coefficient of the silicon substrate at a wavelength λ=300 nm, with a unit of cm-1. The present application further provides a solar cell and photovoltaic module comprising the silicon substrate. By forming the recesses and establishing a relationship among the depth of the recesses, the thickness of the silicon substrate, and the optical absorption coefficient of the silicon substrate at a corresponding wavelength, absorption of oblique incident light by the recesses is enhanced, and the requirements for specific wavelength response are met.

Description

Silicon substrate, solar cell and photovoltaic module

[0001] The present application claims priority to the Chinese patent application No. 202411380626.X, filed on September 30, 2024, and entitled "Silicon substrate, solar cell and photovoltaic module", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of photovoltaic technology, and more particularly, to a silicon substrate, a solar cell comprising the silicon substrate, and a photovoltaic module comprising the solar cell. BACKGROUND

[0003] As a new clean photovoltaic energy, solar cells have developed rapidly in recent years, and their application scenarios have also diversified. In addition to centralized power stations and distributed power stations, building curtain walls, vehicle-mounted photovoltaics, and aerospace applications have become areas of photovoltaic application exploration. However, due to the limitation of light incidence angle, in some special application scenarios, the current crystalline silicon photovoltaic modules face the problem of insufficient power generation, which leads to the fact that the absorption of crystalline silicon cannot meet the demand of photoelectric conversion, i.e., the power generation cannot meet the differentiated scenario demand. The existing silicon substrate surface is usually provided with a textured structure light-trapping structure, which can effectively improve the absorption of small-angle incident light, but cannot improve the absorption of large-angle incident light.

[0004] SUMMARY

[0005] In view of this, the present application provides a silicon substrate of a solar cell, which has good absorption effect on large-angle incident light, thereby improving the photoelectric conversion efficiency and realizing larger power generation.

[0006] In a first aspect, the present application provides a silicon substrate, comprising:

[0007] a first surface and a second surface opposite to each other,

[0008] a plurality of pits located on the first surface; the thickness of the silicon substrate is h1, and the depth of the pit is h2, wherein the difference △h between h1 and h2 satisfies h1>△h≥1 / A (λ＝300nm) , wherein A (λ＝300nm) is the light absorption coefficient of the silicon substrate at a wavelength λ=300 nm, and the unit is cm -1 .

[0009] The application establishes a relationship between the difference △h between the thickness of the silicon substrate and the depth of the pits and the light absorption coefficient of the silicon substrate corresponding to the wavelength of light, and designs the size of the pits according to different incident light conditions by using the relationship, so as to ensure that the pit structure is in the range of the best response efficiency to the incident light, thereby improving the light absorption of the pits to the oblique incident light and enabling the pits to better play their light-trapping function, improving the light absorption of the pits to the oblique incident light and meeting the requirements of special wavelength response.

[0010] As a possible implementation manner, when 0.5×h1 (λ＝x) <h1, △h≤0.5×h1; when 1 / A (λ＝x) <0.5×h1, △h satisfies 1 / A (λ＝x) ≤△h≤0.5×h1, wherein A (λ＝x) is the light absorption coefficient of the silicon substrate at the wavelength x, x≥900nm.

[0011] As a possible implementation manner, the projection size d of the pits on the first surface is 10-200μm.

[0012] As a possible implementation manner, the pits include first pits, and the first pits include first side walls, and the included angle between the first side walls and the thickness direction of the silicon substrate is less than or equal to 15 degrees.

[0013] As a possible implementation manner, the pits include second pits, and the second pits include second side walls, and the included angle between the second side walls and the thickness direction of the silicon substrate is greater than 15 degrees and less than or equal to 60 degrees.

[0014] As a possible implementation manner, the pits further include second pits, and the second pits include second side walls, and the included angle between the second side walls and the thickness direction of the silicon substrate is greater than 15 degrees and less than or equal to 60 degrees.

[0015] The projections of the first pits and the second pits on the first surface have no overlap; and / or,

[0016] The first pits and the second pits are arranged along the thickness direction of the silicon substrate and are in communication.

[0017] As a possible implementation manner, the thickness of the silicon substrate ranges from 90-180μm; or, the thickness of the silicon substrate ranges from 110-180μm.

[0018] As a possible implementation manner, the ratio of the total projection area of the pits on the first surface to the area of the first surface is 30%-80%.

[0019] As a possible implementation manner, the interval between adjacent pits is 2-200 μm; and / or,

[0020] The plurality of pits are arranged in an array.

[0021] As a possible implementation manner, the pit comprises a bottom wall and a side wall connected to the bottom wall,

[0022] At least part of the side wall is provided with a velvet structure, or,

[0023] At least part of the side wall and at least part of the bottom wall are also provided with a velvet structure.

[0024] As a possible implementation manner, the pit has a projected size d on the first surface,

[0025] When h2 / d≥2, the velvet structure is arranged at a position of the side wall close to the opening of the pit;

[0026] When 1≤h2 / d<2, the velvet structure is arranged at a position of the side wall close to the opening of the pit or covers the side wall;

[0027] When 2 / 3≤h2 / d<1, the velvet structure is arranged at a position of the side wall close to the bottom wall or covers the side wall;

[0028] When tan(π / 12)≤h2 / d<2 / 3, the velvet structure is arranged at a position of the side wall close to the opening of the pit and covers the bottom wall, or the velvet structure covers the side wall and the bottom wall;

[0029] When h2 / d<tan(π / 12), the velvet structure is arranged at a position of the side wall close to the bottom wall and covers the bottom wall, or the velvet structure covers the side wall and the bottom wall.

[0030] As a possible implementation manner, the velvet structure is a pyramid structure, the base size of the velvet structure is less than or equal to 7 μm, and / or the height of the pyramid of the velvet structure is less than or equal to 5 μm.

[0031] In a second aspect, the present application provides a silicon substrate comprising the silicon substrate of the first aspect.

[0032] By arranging the pit structure on the light-receiving surface of the silicon substrate of the solar cell, and establishing a relationship between the difference △h between the thickness of the silicon substrate and the depth of the pit and the light absorption coefficient of the corresponding wavelength of the silicon substrate, the absorption of the pit to the oblique incident light is improved, and the requirement for special wavelength response is met. The pit has good absorption effect on large-angle incident light.

[0033] As a possible implementation, the solar cell comprises a passivation layer disposed on the first surface, the second surface, and the bottom wall and the side wall of the recess, and the recess is not filled.

[0034] As a possible implementation, the solar cell comprises an electrode.

[0035] The electrode comprises a plurality of current collecting electrodes disposed in the regions between the recesses; or,

[0036] The electrode comprises a plurality of current collecting electrodes disposed in the regions between the recesses; or,

[0037] In a third aspect, the present application provides a photovoltaic module comprising the solar cell of the second aspect.

[0038] The above description is only a summary of the technical solutions of the present application. In order to enable one skilled in the art to better understand the technical means of the present application, and to implement the same according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more apparent and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0040] Fig. 1 is a schematic diagram of a silicon substrate according to an embodiment of the present application.

[0041] Fig. 2 is a graph of the reciprocal of the absorption coefficient of crystalline silicon material corresponding to different wavelengths.

[0042] Fig. 3 is a graph of the light absorption rate of two kinds of silicon substrates corresponding to different wavelengths.

[0043] Fig. 4 is a schematic diagram of a first recess and a second recess of a silicon substrate.

[0044] Fig. 5 is a schematic diagram of another recess of a silicon substrate.

[0045] Fig. 6 is a schematic diagram of a solar cell with a double-sided electrode.

[0046] Fig. 7 is a schematic diagram of a solar cell with a single-sided electrode.

[0047] Main element symbol explanation: silicon substrate 10, first surface 11, second surface 12, first region 20, second region 30, pit 31, first pit 31A, second pit 31B, first electrode 13, 24, first functional layer 15, second functional layer 14, second electrode 16, 26, first collector 131, second collector 132, first passivation layer 21, functional layer 28, second passivation layer 22, bottom wall 32, side wall 34, 36. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0049] In order to reduce the reflection of incident light on the surface of a solar cell, increase the absorption effect of the incident light, and improve the photoelectric conversion efficiency, a texturing structure with a pyramid structure and an inverted pyramid structure is usually designed on the surface through a texturing process. The texturing structure has a good antireflection effect for the vertically incident light or the incident light with a small incident angle, and can reduce the probability of the small-angle incident light being reflected out of the solar cell. However, the effect is not good for the incident light with a large incident angle, that is, the omnidirectionality of the solar cell is not good. The solar cell with poor omnidirectionality needs to be set at an optimal light-receiving angle or adopt a tracking support to achieve a large photoelectric conversion efficiency. The optimal light-receiving angle changes according to the geographical location and time season, so that it is difficult for a fixed support to be adjusted in real time to make the solar cell reach the optimal light-receiving angle, and the tracking support usually has a high cost. Therefore, improving the omnidirectionality of the solar cell is a relatively simple way to improve the photoelectric conversion efficiency.

[0050] In the present application, the incident light with an incident angle greater than or equal to 45 degrees is determined as large-angle incident light, and the incident light with an incident angle less than 45 degrees is determined as small-angle incident light. The incident angle is the included angle between the incident light to the surface of the silicon substrate and the normal in the thickness direction of the silicon substrate.

[0051] The large-angle incident light is irradiated on the region of the texturing structure, and under the reflection of the pyramid and / or inverted pyramid structure in the texturing structure, the large-angle incident light is shot away from the silicon substrate after one reflection. Therefore, the large-angle incident light has a very small optical path in the silicon substrate, resulting in a poor absorption effect of the solar cell on the large-angle incident light.

[0052] The small-angle incident light is irradiated on the area of the textured structure, and under the reflection of the pyramid and / or inverted-pyramid structure in the textured structure, the small-angle incident light can be reflected for multiple times in the textured structure of the solar cell, so that the small-angle incident light has a large optical path in the silicon substrate, and the solar cell has a good absorption effect on the small-angle incident light.

[0053] Therefore, the solar cell with only the textured structure has a good absorption effect on the small-angle incident light, but has a poor absorption effect on the large-angle incident light, so that the omnidirectionality of the solar cell is poor. When the photovoltaic module containing the solar cell is installed in an aircraft, a vehicle or a building, the installation position is limited because the solar cell needs to have an optimal light-receiving angle, or a tracking support needs to be used to achieve a large power generation, which is high in cost.

[0054] The application provides a silicon substrate of a solar cell, which is beneficial to improving the absorption effect of the large-angle incident light.

[0055] The silicon substrate (for example, crystalline silicon) has different light absorption coefficients at different light wavelengths. In order to ensure the front absorption when the light is vertically irradiated on the silicon substrate and take into account the absorption of the inclined incident light, the application provides a silicon substrate structure for improving the absorption of crystalline silicon.

[0056] As shown in FIG. 1, the application provides a silicon substrate 10, which includes a first surface 11 and a second surface 12 opposite and parallel to each other. In the embodiment of the application, when the silicon substrate 10 is applied to a solar cell, at least one of the first surface 11 and the second surface 12 is a light-receiving surface, that is, a surface directly irradiated by incident light. FIG. 1 takes the first surface 11 as the light-receiving surface as an example for description. The first surface 11 is provided with a plurality of pits 31 recessed relative to the first surface 11.

[0057] The pit 31 is a large-angle light-trapping structure. In this way, when the light is obliquely irradiated on the light-receiving surface of the silicon substrate 10, the reflection and light-trapping effect of the pit 31 structure can be used to increase the optical path, thereby improving the absorption of the silicon substrate 10 to the oblique incident light.

[0058] Based on the response absorption of the crystalline silicon material to the light in the spectrum, the application strengthens the reflection of the silicon substrate 10 to the oblique incident light and increases the optical path by setting the pits on the surface of the silicon substrate 10 and correlating the depth of the pit 31 with the thickness of the silicon substrate 10 and the light absorption coefficient of the silicon substrate 10, thereby improving the absorption of the oblique incident light and improving the response to the spectrum.

[0059] As shown in FIG. 1, the thickness of the silicon substrate 10 is h1, the depth of the pit 31 is h2, and the difference △h between the thickness h1 of the silicon substrate 10 and the depth h2 of the pit 31 is h1-h2≥1 / λ (λ＝300nm)where A is the light absorption coefficient of the silicon substrate at wavelength λ, in cm -1 The silicon substrate 10 has different light absorption coefficients corresponding to different wavelengths of light. A (λ＝300nm) is the light absorption coefficient of the silicon substrate at wavelength λ = 300 nm. In addition, the depth h2 of the recess 31 is less than the thickness hi of the silicon substrate 10. It can be seen that the depth h2 of the recess 31 satisfies: h2≤ hi - 1 / A (λ＝300nm) .

[0060] where hi is the distance between the first surface 11 and the second surface 12 of the silicon substrate 10; and h2 is the distance between the highest point and the lowest point of the recess 31 along the thickness direction of the silicon substrate 10.

[0061] The absorption coefficient of the silicon substrate 10 can be obtained by testing and fitting the silicon substrate 10 using an ellipsometer or an ultraviolet absorption meter. In this application, the difference between the thickness of the silicon substrate 10 and the depth of the recess 31 is related to the light absorption coefficient of the silicon substrate 10 at the corresponding wavelength, and the established relationship can be used to design the size of the recess according to different incident light conditions, so as to ensure that the recess 31 structure is in the range of the best response efficiency for the incident light and increase the utilization rate of light.

[0062] The absorption coefficients of different types and different doping concentrations of crystalline silicon are also different. Generally, the wavelength response range of the crystalline silicon cell is about 600 nm-850 nm. The reciprocal 1 / A of the absorption coefficient A of the silicon substrate of crystalline silicon corresponding to different wavelengths is shown in FIG. 2. Further, in some embodiments, when 0.5 x hi < 1 / A (λ＝x) < hi, the difference Ah between the thickness hi of the silicon substrate 10 and the depth h2 of the recess 31 satisfies:

[0063] Ah≤ 0.5 x hi. That is, the difference Ah between hi and h2 is less than or equal to half of the thickness hi of the silicon substrate 10, and at this time the recess can achieve the light trapping effect on the large-angle incident light.

[0064] When 1 / A (λ＝x) < 0.5 x hi, the difference Ah between the thickness hi of the silicon substrate 10 and the depth h2 of the recess 31 satisfies: 1 / A (λ＝x) ≤ Ah≤ 0.5 x hi. That is, the difference Ah between hi and h2 is greater than or equal to 1 / A (λ＝x) and less than or equal to half of the thickness hi of the silicon substrate 10. Where A (λ＝x)The light absorption coefficient of the silicon substrate 10 at a wavelength x, for example, the light absorption coefficient at x = 900 nm, x = 1000 nm, x = 1100 nm, x = 1200 nm, or x = 1300 nm. The wavelength x can be the above example values, but is not limited to the above values. Thus, the depth h2 of the pit 31 satisfies: 0.5 x hi ≤ h2 ≤ hi - 1 / A (λ＝x) . That is, the depth h2 of the pit 31 is greater than or equal to half of the thickness hi of the silicon substrate 10, and less than or equal to the thickness hi of the silicon substrate minus 1 / A (λ＝x) .

[0065] By reasonably setting the range of the difference Ah between hi and h2, the pit 31 can better play the role of light trapping, thereby improving the absorption of light by the silicon substrate 10, and avoiding the influence of the existence of the pit 31 on the mechanical strength of the silicon substrate 10. As shown in FIG. 2, for a crystalline silicon material, for light with a wavelength λ = 900 nm, 1 / A = 2 x 10 -3 cm = 20 μm. The difference Ah between the thickness hi of the silicon substrate 10 and the depth h2 of the pit 31 is Ah ≥ 20 μm. For a silicon substrate with a certain thickness hi, the depth h2 of the pit 31 can be determined as h2 ≤ hi - 20 μm.

[0066] Suppose two identical silicon substrates (thickness 180 μm) are provided, and pits with a simple circular hole structure are set. The other conditions of the two silicon substrates are the same, and the difference is that the depths of the pits of the two silicon substrates are set to 170 μm and 80 μm, respectively. The absorption curves of the two silicon substrates are shown in FIG. 3. As can be seen, the depth h2 of the pit needs to satisfy h2 ≤ hi - 1 / A, where hi = 180 μm and 1 / A = 20 μm, that is, h2 ≤ 160 μm, and the absorption is good. Therefore, from the test results in FIG. 3, it can be seen that in the wavelength range of 600-900 nm, the absorption of the silicon substrate with a pit depth of 80 μm is indeed significantly higher than that of the silicon substrate with a pit depth of 170 μm.

[0067] By setting a plurality of pits 31 on the light-receiving surface of the silicon substrate 10 of the solar cell, and establishing a relationship between the difference Ah between the thickness of the silicon substrate 10 and the depth of the pit 31 and the light absorption coefficient of the silicon substrate 10 at a corresponding wavelength, the pit size can be designed according to different incident light conditions using the relationship, to ensure that the pit 31 structure is within the range of optimal response efficiency for incident light, thereby improving the absorption of the pit 31 to oblique incident light. The micrometer-level pit 31 has a certain absorption effect on small-angle incident light and has a good absorption effect on large-angle incident light.

[0068] In some embodiments, the vertical projection size of the recess 31 on the light-receiving surface (the first surface 11 or the second surface 12) is 10-200 μm. The vertical projection size in the present application refers to the maximum width of the cross section of the recess 31 along the thickness direction of the silicon substrate. That is, the size of the recess 31 is in the order of microns. By limiting the projection size of the recess 31, the recess 31 has an appropriate opening size, which allows light to enter the recess 31 and does not affect the strength of the silicon substrate 10.

[0069] Compared with the light-trapping structure whose vertical projection size of the recess on the light-receiving surface is in the order of nanometers, the structure size of the recess 31 is in the order of microns, which can avoid the failure of the passivation layer to successfully form the inner wall of the light-trapping structure, thereby ensuring that a uniform passivation layer can be generated on the surface of the solar cell. Meanwhile, the recess 31 can reduce the specific surface area of the solar cell, thereby reducing the recombination rate of non-equilibrium carriers on the surface of the solar cell, without affecting the lateral transport and collection of carriers on the surface of the solar cell, and ultimately improving the photoelectric conversion efficiency of the solar cell.

[0070] FIGS. 4 and 5 show several shapes of the recess 31 as an illustration. As shown in FIG. 4, the recess 31 includes a first recess 31A. The first recess 31A includes a bottom wall 32 and a first side wall 34 connected to the bottom wall 32, wherein the first side wall 34 is connected between the light-receiving surface and the bottom wall 32. The angle between the first side wall 34 and the thickness direction of the silicon substrate 10 is less than or equal to 15 degrees. For example, the angle between the side wall 34 and the thickness direction of the silicon substrate 10 can be any one of 0 degrees, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 7 degrees, 8 degrees, 9 degrees, 10 degrees, 11 degrees, 12 degrees, 13 degrees, 14 degrees, and 15 degrees. The present embodiments do not limit the specific value of the angle. As shown in FIG. 1, the angle between the first side wall 34 of the recess 31 and the thickness direction of the silicon substrate 10 is 0 degrees, that is, the first side wall 34 of the first recess 31A is perpendicular to the first surface 11 and the second surface 12. Although not shown in the figure, when the angle between the first side wall 34 of the recess 31 and the thickness direction of the silicon substrate 10 is greater than 0 degrees, the cross section of the recess 31 along the thickness direction of the silicon substrate 10 is trapezoidal. That is, the opening size of the recess 31 along the thickness direction of the silicon substrate 10 and in the direction of the light-receiving surface is increasing or decreasing. The first side wall 34 is beneficial to absorbing incident light with a large incident angle.

[0071] In some embodiments, as shown in FIG. 4, the recesses 31 can further include second recesses 31B. The second recesses 31B include second sidewalls 36, which have an angle with the thickness direction of the silicon substrate 10 greater than 15 degrees and less than or equal to 60 degrees. For example, the angle between the two second sidewalls 36 can be any one of 16 degrees, 18 degrees, 20 degrees, 22 degrees, 24 degrees, 27 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, and 60 degrees. The embodiments of the present application do not limit the specific value of the angle. The second sidewalls 36 are beneficial to absorbing incident light with a small incident angle. When the incident angle of the incident light is small, the incident light can be projected on the second sidewalls 36 and reflected back and forth on the second sidewalls 36, increasing the optical path of the incident light, improving the absorption of the silicon substrate 10 to the incident light, and meeting the needs of photoelectric conversion. The second recesses 31B can also have a bottom wall.

[0072] In some embodiments, as shown in FIG. 4, the first recesses 31A and the second recesses 31B have no overlap in the projection on the first surface. That is, the first surface 11 or the second surface 12 is distributed with two different structures of recesses 31.

[0073] In some embodiments, as shown in FIG. 5, the first recesses 31A and the second recesses 31B are arranged and communicated along the thickness direction of the silicon substrate 10 to form a specific structure of recesses 31.

[0074] FIGS. 4 and 5 show three different structures of the recesses 31. It can be understood that the second region 20 can be provided with at least one of the above-mentioned three structures of recesses 31. In addition, the shape of the recesses 31 is not limited to that shown in FIGS. 4 and 5, and can also be other shapes as long as it can increase the absorption of light.

[0075] As known in the prior art, the silicon substrate with different thicknesses has different absorption in the visible spectrum. If the thickness of the silicon substrate is too thin, the light will not be completely absorbed, causing waste. If the thickness of the silicon substrate is too thick, the cost will be increased.

[0076] In some embodiments, the thickness of the silicon substrate 10 ranges from 90 to 180 μm. For example, the thickness of the silicon substrate can be 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, and 180 μm. Further, the thickness of the silicon substrate ranges from 110 to 180 μm.

[0077] For the incident light with a large incident angle, the plurality of pits 31 on the surface of the solar cell can reduce the probability that the large-angle incident light is reflected out of the solar cell. The large-angle incident light is reflected multiple times in the pits 31, and has a large optical path in the solar cell, thereby improving the absorption effect of the solar cell on the incident light. Meanwhile, compared with the nano-scale light-trapping structure (textured structure or pit with a small planar size), the structure size of the pit 31 is micron-level, so that it is easier to generate a uniform passivation layer on the surface of the solar cell, and the recombination rate of non-equilibrium carriers on the surface of the solar cell is reduced, thereby improving the photoelectric conversion efficiency of the solar cell.

[0078] In some embodiments, the interval between adjacent pits 31 can be 2-200 μm, so that other structures of the solar cell can be arranged in the area between adjacent pits 31 to realize the function of the solar cell. In some embodiments, the plurality of pits 31 are arranged in an array on the surface of the silicon substrate.

[0079] The shape of the pit 31 is not limited. In some embodiments, the shape of the pit 31 can be any one or more of a cylindrical shape, a conical shape, a triangular pyramid shape, a quadrangular prism shape, or an irregular shape, so that the incident light can be reflected multiple times in the micron-level pit 31 when the incident light is incident on the bottom wall and the side wall of the micron-level pit 31.

[0080] In some embodiments, the ratio of the total projected area of all pits 31 on the light-receiving surface (for example, the first surface 11) to the area of the light-receiving surface can be 30%-80%. If the projected area of the pit 31 accounts for too large a proportion, the mechanical strength of the cell piece is affected, and the cell piece is prone to breakage. If the projected area of the pit 31 accounts for too small a proportion, the absorption of the silicon substrate 10 on the oblique incident light cannot be effectively improved.

[0081] In the embodiments of the present application, the projected area proportion of the micron-level pit 31 on the light-receiving surface can be determined according to the specific application scenario of the photovoltaic module containing the solar cell. Specifically, for an application scenario in which a large proportion of the incident light is at a large angle, the projected size of the pit 31 on the light-receiving surface or the number of pits 31 can be increased, so that the ratio of the projected area of the pit 31 on the light-receiving surface to the area of the light-receiving surface is large, thereby increasing the absorption effect of the solar cell on the large-angle incident light. For an application scenario in which a small proportion of the incident light is at a large angle, the projected size of the pit 31 on the light-receiving surface or the number of pits 31 can be reduced, so that the ratio of the projected area of the pit 31 on the light-receiving surface to the surface area of the light-receiving surface is small, thereby enabling the solar cell to have a good absorption effect on the incident light.

[0082] As shown in FIG. 1, the area between the pits 31 on the first surface 11 of the silicon substrate 10 is defined as the first area 20, and the area where the pits 31 are located is defined as the second area 30. That is, the first surface 11 is divided into the first area 20 and the second area 30. The first area 20 can be provided with a textured structure or be flat. In FIG. 1, the first area 20 is flat. In addition, FIG. 6 and FIG. 7 both show that the first area 20 is provided with a textured structure.

[0083] In addition to the area between the pits 31 (the first area 20) being selectively provided with a textured structure, further, in some embodiments, at least part of the sidewall 34 of the pit 31 is provided with a textured structure, or at least part of the sidewall 34 of the pit and at least part of the bottom wall 32 are both provided with a textured structure.

[0084] In some embodiments, the pits have a projected size d on the first surface, and the pits have a depth h2. The ratio of the depth h2 to the projected size d of the pits has a certain relationship. In combination with the mechanical strength of the silicon wafer and the depth of the pits satisfying the light trapping effect, the ratio of the depth h2 to the projected size d of the pits is generally set to 0.1≤h2 / d≤2. If h2 / d is too small or too large, it will affect the probability of large-angle light entering the pit, and reduce the light trapping effect brought by the pit. h2 / d can be any one of 0.1, 0.3, 0.5, 0.7, 0.9, 1, 1.3, 1.5, 1.7, 1.9, and 2.

[0085] In the embodiments of the present application, the incident angle range of the large-angle incident light is 45°-70°. According to the ratio of h2 / d, the setting area of the textured structure includes the following cases.

[0086] (1) When h2 / d≥2, the textured structure is set at the position of the sidewall close to the opening of the pit. That is, when the pit depth and the projected size satisfy the above relationship, and the textured structure is set close to the opening of the pit, the large-angle incident light can be irradiated on the textured structure of the sidewall, the number of reflections of the incident light in the pit is increased, the possibility of the incident light being completely absorbed by the pit is improved, and the light utilization rate is improved.

[0087] (2) When 1≤h2 / d<2, the textured structure is set at the position of the sidewall close to the opening of the pit or covers the sidewall. That is, when the pit depth and the projected size satisfy the above relationship, and the textured structure is set close to the opening of the pit or covers the sidewall, the large-angle incident light can be irradiated on the textured structure of the sidewall, the number of reflections of the incident light in the pit is increased, the possibility of the incident light being completely absorbed by the pit is improved, and the light utilization rate is improved.

[0088] (3) When 2 / 3≤h2 / d<1, the rough surface structure is arranged on the side wall close to the bottom wall or covers the side wall. At this time, the large-angle incident light is more likely to irradiate the position of the side wall close to the bottom wall of the pit. Therefore, when the pit depth and the projection size satisfy the above relationship, and the rough surface structure is arranged on the side wall close to the bottom wall of the pit or covers the side wall, the large-angle incident light can be irradiated on the rough surface structure of the side wall, the number of reflections of the incident light in the pit is increased, the possibility of complete absorption of the incident light by the pit is improved, and the light utilization rate is improved.

[0089] (4) When tan(π / 12)≤h2 / d<2 / 3, the rough surface structure is arranged on the side wall close to the opening of the pit and covers the bottom wall, or the rough surface structure covers the side wall and the bottom wall. At this time, the large-angle incident light is more likely to irradiate the position of the side wall close to the opening of the pit and the bottom wall of the pit. Therefore, when the pit depth and the projection size satisfy the above relationship, and the rough surface structure is arranged on the side wall close to the opening of the pit and the bottom wall or covers the side wall and the bottom wall, the large-angle incident light can be irradiated on the rough surface structure of the side wall, the number of reflections of the incident light in the pit is increased, the possibility of complete absorption of the incident light by the pit is improved, and the light utilization rate is improved.

[0090] (5) When h2 / d<tan(π / 12), the rough surface structure is arranged on the side wall close to the bottom wall and covers the bottom wall, or the rough surface structure covers the side wall and the bottom wall. At this time, the large-angle incident light is more likely to irradiate the position of the side wall close to the bottom wall and the bottom wall of the pit. Therefore, when the pit depth and the projection size satisfy the above relationship, and the rough surface structure is arranged on the side wall close to the bottom wall and the bottom wall or covers the side wall and the bottom wall, the large-angle incident light can be irradiated on the rough surface structure of the side wall, the number of reflections of the incident light in the pit is increased, the possibility of complete absorption of the incident light by the pit is improved, and the light utilization rate is improved.

[0091] When the rough surface structure is arranged on the side wall close to the opening of the pit, the area occupied by the rough surface structure can be equal to one half of the area of the side wall, or less than one half of the area of the side wall, or greater than one half of the area of the side wall.

[0092] When the rough surface structure is arranged on the side wall close to the bottom wall, the area occupied by the rough surface structure can be equal to one half of the area of the side wall, or less than one half of the area of the side wall, or greater than one half of the area of the side wall.

[0093] For the pits without the textured structure on the bottom wall and the side wall, when the oblique incident light enters the pit, due to the smooth wall, part of the incident light can exit the pit 31 through several reflections. When the wall has the textured structure (micro-nano pyramid structure), the oblique incident light entering the pit can increase the number of reflections of the incident light in the pit due to the synergistic effect of the pit and the textured structure, and increase the possibility of the incident light being completely captured by the pit structure. Therefore, more light energy can be converted into electrical energy, thereby increasing the power generation of the photovoltaic device / component.

[0094] In some embodiments, the textured structure is a pyramid structure, the base size of the textured structure is less than or equal to 7 μm, and / or the height of the textured structure is less than or equal to 5 μm. The base size refers to the longest distance of the length, the width or the diagonal length of the base of the pyramid structure, and the height refers to the vertical distance between the top of the pyramid and the base.

[0095] When the first region 20 is provided with the textured structure, the size of the textured structure of the first region 20 and the textured structure in the pit 31 can be the same or different.

[0096] When the first region 20 is provided with the textured structure, the crystal direction of the pyramid textured structure in the first region 20 is the same as the crystal direction of the pyramid textured structure on the bottom wall of the pit.

[0097] The crystal planes of the textured pyramid on the first surface, the textured pyramid on the bottom wall of the pit and the textured pyramid on the side wall have obvious differences. The textured pyramid on the first region 20 and the bottom wall 32 is composed of four crystal planes, which are [1, 1, 1], [-1, 1, 1], [1, -1, 1] and [-1, -1, 1]. The crystal plane of the textured pyramid on the side wall 34 of the pit 31 is [1, 1, 1], [-1, 1, 1], [1, 1, -1] and [-1, 1, -1] (or [1, 1, 1], [1, -1, 1], [1, 1, -1] and [1, -1, -1]).

[0098] The application also provides a solar cell comprising the above-mentioned silicon substrate 10.

[0099] The first region 20 can be provided with a textured structure, and the textured structure is a small-angle light-trapping structure. The textured structure has a good antireflection effect on the vertical incident light or the incident light with a small incident angle, which can reduce the probability of the small-angle incident light being reflected out of the solar cell, thereby increasing the absorption effect of the small-angle incident light.

[0100] Therefore, when the light is obliquely incident on the light-receiving surface of the bottom of the silicon substrate 10, the reflection and light-trapping effect of the textured structure and the pit 31 structure can be used to increase the optical path, thereby effectively improving the light absorption of the silicon substrate.

[0101] The first region 20 with the texture structure is composed of pyramids and / or inverted pyramids distributed on the light-receiving surface. The silicon substrate can be prepared from a single crystal silicon wafer, and the texture structure is regular or irregular pyramids and / or inverted pyramids prepared on the surface of the single crystal silicon wafer by a texturing process. The silicon substrate 10 can also be prepared from a polycrystalline silicon wafer, and the texture structure is regular or irregular pyramids and / or inverted pyramids prepared on the surface of the polycrystalline silicon wafer by a texturing process. The formation of the pits 31 can be formed by wet etching or dry etching.

[0102] By arranging a plurality of pits 31 on the light-receiving surface of the silicon substrate 10 of the solar cell, and by linking the difference △h between the thickness of the silicon substrate 10 and the depth of the pits 31 with the light absorption coefficient of the corresponding wavelength of the silicon substrate 10, the absorption of the pits 31 to the oblique incident light is improved, and the requirements for special wavelength response are met. The area between the pits 31 can be provided with a texture structure to enhance the absorption effect of small-angle incident light. The micrometer-level pits 31 have good absorption effect for large-angle incident light. Therefore, the solar cell has high omnidirectionality. When the photovoltaic module containing the solar cell is installed in an aircraft, a vehicle, and a building, the solar cell has good incident light absorption effect without the need for installation location and the use of a tracking support, thereby improving the photoelectric conversion efficiency of the photovoltaic module and achieving a large power generation capacity.

[0103] The solar cell further includes a passivation layer. The passivation layer is arranged on the bottom wall and the side wall of the first region 20 and the pits 31. Compared with the nano-level light-trapping structure, the structure size of the micrometer-level pits 31 is larger, and therefore, the passivation layer can be effectively generated on the surface of the solar cell to achieve surface passivation of the solar cell. In some embodiments, the passivation layer includes an aluminum oxide layer and an anti-reflection layer. The thickness of the aluminum oxide layer is not more than 10 nm. The material of the anti-reflection layer is Si y N x or Si z N x O y , and the thickness is usually not more than 100 nm.

[0104] The solar cell of the present application also includes an electrode. In some embodiments, the electrode includes a plurality of current collecting electrodes disposed in the regions between the plurality of pits. In other embodiments, the electrode includes a plurality of current collecting electrodes disposed in the regions between the plurality of pits and a plurality of bus electrodes disposed in the regions between the plurality of pits or partially disposed in the regions between the plurality of pits and partially disposed in the regions of the plurality of pits. In summary, the electrode cannot be completely disposed in the micrometer-level pits 31, thereby reducing the filling of the electrode in the micrometer-level pits 31 and avoiding affecting the light trapping function of the micrometer-level pits 31 for reflecting light at a large angle.

[0105] Optionally, the solar cell in the embodiments of the present application can be a solar cell with a double-sided electrode, such as a tunnel oxide passivated contact (TOPCon) cell. Referring to FIG. 6, a schematic structural diagram of a double-sided electrode solar cell is shown. As shown in FIG. 6, the solar cell includes a silicon substrate 10, a first electrode 13 and a first passivation layer 15 disposed on a first surface 11 of the silicon substrate 10, and a second passivation layer 14 and a second electrode 16 disposed on a second surface 12 of the silicon substrate 10, wherein the first surface 11 is a light-receiving surface, and the first surface 11 is provided with a first region 20 and a second region 30.

[0106] Taking a TOPCon cell as an example, the first passivation layer 15 is disposed on the bottom wall and the side wall of the pit 31 in the first region 20 and the second region 30, the first electrode 13 is located on the side of the first passivation layer 15 away from the silicon substrate 10, the second passivation layer 14 is disposed on the second surface 12 of the silicon substrate 10, and the second electrode 16 is located on the side of the second passivation layer 14 away from the silicon substrate 10.

[0107] Specifically, the silicon substrate 10 can be an n-type silicon substrate prepared from an n-type crystalline silicon wafer; the first passivation layer 15 can have a multi-layer structure, for example, the first passivation layer 15 can include silicon oxide and silicon nitride, which respectively serve the functions of surface passivation and anti-reflection on one side of the solar cell; the second passivation layer 14 can also have a multi-layer structure, for example, the second passivation layer 14 can include silicon oxide, doped polysilicon, aluminum oxide and silicon nitride, thereby achieving the functions of surface passivation and anti-reflection on the other side of the solar cell.

[0108] Further, the first electrode 13 is disposed on the first surface 11 of the silicon substrate 10, and the second electrode 16 is disposed on the second surface 12 of the silicon substrate 10, thereby forming a solar cell with a double-sided electrode. Specifically, the electrode can be prepared by screen printing, electroplating or the like, and the electrode material can include Ag, Al, Ni and other conductive materials, which are not specifically limited herein.

[0109] Optionally, referring to FIG. 6, the first electrode 13 can include a busbar electrode and a current collecting electrode, which is not shown in the figure. The current collecting electrode includes a first current collecting electrode 131 and a second current collecting electrode 132, the first current collecting electrode 131 can be disposed in the first region 20 and / or the recess 31 of the second region 30, and the second current collecting electrode 132 can be disposed in the first region 20.

[0110] It can be understood that in some embodiments, the busbar electrode can also be omitted, that is, at least the first surface of the solar cell is designed without a busbar electrode.

[0111] Optionally, the solar cell in the embodiments of the present application can be a solar cell with a single-sided electrode, for example, an interdigitated back contact cell (IBC).

[0112] Referring to FIG. 7, a structure diagram of a passivated contact back contact solar cell is shown. As shown in FIG. 7, the solar cell includes a silicon substrate 10, a first passivation layer 21 disposed on a first surface 11 of the silicon substrate 10, and a functional layer 28, a second passivation layer 22, a first electrode 24 and a second electrode 26 disposed on a second surface 12 of the silicon substrate 10. The first surface 11 is a light receiving surface, and the first surface 11 is provided with a first region 20 and a second region 30.

[0113] In some embodiments, the silicon substrate 10 can be an n-type silicon substrate prepared from an n-type crystalline silicon wafer.

[0114] The first passivation layer 21 is disposed on the area between the recesses 31 and the bottom wall and the side wall of the recesses 31. The first passivation layer 21 has a passivation and anti-reflection function for the first surface. Although not shown in the figure, the first passivation layer 21 is disposed on the area between the recesses 31 and the bottom wall and the side wall of the recesses 31 of the first surface 11, and the first passivation layer 21 does not fill the recesses 31.

[0115] Although not shown in the figure, the functional layer 28 includes a tunneling oxide layer and a doped polysilicon layer stacked thereon, wherein the doped polysilicon layer is located on the surface of the tunneling oxide layer away from the silicon substrate 10. The tunneling oxide layer is silicon oxide with a thickness of several nanometers.

[0116] The second passivation layer 22 is disposed on the surface of the functional layer 28 away from the silicon substrate 10, and has a passivation and anti-reflection function for the second surface 12. For example, the second passivation layer 22 includes an aluminum oxide layer and an anti-reflection layer stacked thereon. The first electrode 24 and the second electrode 26 are disposed on the second passivation layer 22.

[0117] The first electrode 24 can include a first busbar (not shown) and a first collector (not shown), and the second electrode 26 can include a second busbar (not shown) and a second collector (not shown). It can be understood that the first busbar and / or the second busbar can also be omitted, i.e., at least the first surface of the solar cell is designed without a busbar.

[0118] The present application, by arranging a plurality of pits 31 on the light-receiving surface of the silicon substrate of the solar cell, and by establishing a relationship between the difference Δh between the thickness of the silicon substrate and the depth of the pits 31 and the light absorption coefficient of the corresponding wavelength of the silicon substrate, etc., the established relationship can be used to design the pit size according to different incident light conditions, to ensure that the pit 31 structure is within the range of optimal response efficiency for incident light, to increase the utilization of light and improve the absorption of the pit 31 for oblique incident light. The micron-level pits 31 have good absorption effect for large-angle incident light. In addition, a textured structure can be arranged in the area between the pits 31 to enhance the absorption effect for small-angle incident light. Therefore, the solar cell has high omnidirectionality, and when the photovoltaic module containing the solar cell is installed in an aircraft, a vehicle, and a building, the solar cell can have good incident light absorption effect without the need for installation location and the use of tracking supports, thereby improving the photoelectric conversion efficiency of the photovoltaic module and achieving a larger power generation capacity.

[0119] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced without departing from the spirit and scope of the present application.

Claims

1. A silicon substrate, characterized by, Comprising: opposite first and second surfaces; A plurality of pits are located on the first surface; the thickness of the silicon substrate is h1, the depth of the pits is h2, wherein the difference △h between h1 and h2 satisfies h1>△h≥1 / A (λ＝300nm) , wherein A (λ＝300nm) is the light absorption coefficient of the silicon substrate at a wavelength λ=300nm, with the unit of cm -1 .

2. The silicon substrate according to claim 1, wherein when 0.5 x hi < 1 / A (λ＝x) < hi, then Ah < 0.5 x hi; when 1 / A (λ＝x) when 1 / A (λ＝x) when 1 / A (λ＝x) is the optical absorption coefficient of the silicon substrate at a wavelength x, x > 900 nm.

3. The silicon substrate of claim 1, wherein a projected size d of the pits on the first surface is 10-200 μm.

4. The silicon substrate of claim 1, wherein The pits comprise first pits, the first pits comprising first sidewalls, the first sidewalls having an angle with a thickness direction of the silicon substrate less than or equal to 15 degrees.

5. The silicon substrate according to claim 1 or 4, wherein The pits comprise second pits, the second pits comprising second sidewalls, the second sidewalls having an angle with the thickness direction of the silicon substrate greater than 15 degrees, less than or equal to 60 degrees.

6. The silicon substrate of claim 4, wherein The pits further comprise second pits, the second pits comprising second sidewalls, the second sidewalls having an angle with the thickness direction of the silicon substrate greater than 15 degrees, less than or equal to 60 degrees; the first pits and the second pits are projected on the first surface without overlapping; and / or, the first pits and the second pits are arranged along the thickness direction of the silicon substrate and are communicated.

7. The silicon substrate of claim 1, wherein The thickness of the silicon substrate ranges from 90-180 μm; or, The thickness of the silicon substrate ranges from 110-180 μm.

8. The silicon substrate of claim 1, wherein A ratio of a total projected area of the pits on the first surface to an area of the first surface is 30%-80%.

9. The silicon substrate of claim 1, wherein The interval between adjacent pits is 2-200 μm; and / or, The pits are arranged in an array.

10. The silicon substrate of claim 1, wherein The pits comprise a bottom wall and sidewalls connecting the bottom wall, At least part of the sidewalls is provided with a textured structure, or, At least part of the sidewalls and at least part of the bottom wall are also provided with a textured structure.

11. The silicon substrate of claim 10, wherein A projected size of the pits on the first surface is d, When h2 / d≥2, the textured structure is arranged at a position of the sidewall close to an opening of the pit; When 1≤h2 / d<2, the textured structure is arranged at a position of the sidewall close to the opening of the pit or covers the sidewall; When 2 / 3≤h2 / d<1, the textured structure is arranged at a position of the sidewall close to the bottom wall or covers the sidewall; When tan(π / 12)≤h2 / d<2 / 3, the textured structure is arranged at a position of the sidewall close to the opening of the pit and covers the bottom wall, or the textured structure covers the sidewall and the bottom wall; When h2 / d<tan(π / 12), the textured structure is arranged at a position of the sidewall close to the bottom wall and covers the bottom wall, or the textured structure covers the sidewall and the bottom wall.

12. The silicon substrate of claim 10, wherein The textured structure is a pyramid structure, a base size of the pyramid structure is less than or equal to 7 μm, and / or a height of the pyramid structure is less than or equal to 5 μm.

13. The silicon substrate of claim 1, wherein The shape of the pits is one or more of a cylindrical shape, a conical shape, a triangular pyramid shape, a quadrangular prism shape, or an irregular shape.

14. A solar cell, characterized by, The silicon substrate in any one of claims 1-13.

15. The solar cell of claim 14, wherein, The solar cell comprises a passivation layer, the passivation layer being arranged on the first surface, the second surface, and the bottom wall and sidewalls of the pits, and not filling the pits.

16. The solar cell of claim 15, wherein, The passivation layer comprises an aluminum oxide layer and an anti-reflection layer.

17. The solar cell of claim 16, wherein, The thickness of the aluminum oxide layer is less than or equal to 10 nm, and the thickness of the anti-reflection layer is less than or equal to 100 nm.

18. The solar cell of claim 14, wherein, The solar cell comprises an electrode; The electrode includes a plurality of collector electrodes disposed in the areas between the pits. Alternatively, the electrode includes a plurality of collector electrodes and a plurality of collector electrodes, the collector electrodes are disposed in the areas between the pits, the collector electrodes are disposed in the areas between the pits, or part of the collector electrodes are disposed in part of the areas of the pits, and the other part is disposed in the areas between the pits.

19. A photovoltaic module, characterized by: A solar cell comprising any one of claims 14 to 18.

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