Substrate preparation method and photovoltaic cell

Abstract

The invention provides a substrate preparation method and a photovoltaic cell. The substrate preparation method is used for preparing a substrate with a pyramid structure. The preparation method comprises the following steps: providing a substrate, wherein the substrate has two opposite sides; forming a first adjustment layer on at least one side of the substrate; forming a second adjusting layer with a preset thickness on one side, deviating from the substrate, of the first adjusting layer; the second adjusting layer is provided with a plurality of through holes penetrating through the second adjusting layer in the thickness direction; performing first type etching on the first adjusting layer by taking the second adjusting layer as a mask, removing a part of the first adjusting layer exposed by the through hole and forming an opening pattern with a preset width value; performing second type etching on the second adjusting layer and a part of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate; and removing the residual first adjusting layer, wherein the residual substrate and the pyramid structure jointly form a substrate. By using the method, the process difficulty is effectively simplified and the preparation cost is reduced while relatively high regulation and control precision of pyramid structure morphology parameters is obtained.

Description

Technical Field

[0001] The invention relates to a semiconductor substrate preparation method, and in particular to a substrate preparation method and a photovoltaic cell. Background Art

[0002] Forming texture on the surface of silicon substrate is an extremely important step in the preparation process of photovoltaic cells. It is mainly to prepare a pyramid structure on the surface of silicon substrate to reduce the reflectivity of incident light and thus improve the utilization rate of incident light. It can be understood that the morphological parameters of the aforementioned pyramid structure (such as formation width, formation height, etc.) play a vital role in ensuring and improving the conversion efficiency of photovoltaic cells.

[0003] In the related technology, metal copper-assisted chemical etching process, dual-beam interference process and plasma etching process are usually used to obtain the pyramid structure by removing part of the material in a specific area on the surface of the silicon substrate. However, in the related process, there is a lack of technical means to accurately control the morphological parameters of the pyramid structure. It often relies on the personal experience of technicians or previous experimental data to roughly control the morphological parameters of the pyramid structure by adjusting some process parameters; or, by preparing a high-precision etching mask and cooperating with multiple etchings to gradually control the morphological parameters of the pyramid structure. Obviously, this not only cannot meet the increasingly stringent performance requirements for the conversion efficiency of photovoltaic cells, but also is not conducive to improving production efficiency and reducing preparation costs.

[0004] Therefore, there is an urgent need to make technical improvements to the relevant processes and enhance the control accuracy of the pyramid structure morphology parameters, so as to ensure and improve the conversion efficiency of photovoltaic cells and further reduce the preparation cost. Summary of the invention

[0005] In view of the above-mentioned defects, the present application provides a substrate preparation method for preparing a substrate including a pyramid structure. The method improves the relevant processes, obtains a high control accuracy of the pyramid structure morphology parameters, and effectively simplifies the process difficulty and reduces the preparation cost.

[0006] On the one hand, an embodiment of the present application provides a substrate preparation method for preparing a substrate including a pyramid structure, the preparation method comprising the following steps:

[0007] providing a substrate having two opposing sides;

[0008] forming a first adjustment layer on at least one side of the substrate; the first adjustment layer and the substrate have different etching selectivities;

[0009] A second adjustment layer having a preset thickness is formed on the side of the first adjustment layer away from the substrate; the second adjustment layer and the substrate have the same etching selectivity; and the second adjustment layer has a plurality of through holes penetrating through the second adjustment layer in the thickness direction; the through holes are used to define the number of pyramid structures formed;

[0010] Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to remove a portion of the first adjustment layer exposed by the through hole and form an opening pattern with a preset width value; the opening pattern is used to define the length of the bottom side of the pyramid structure;

[0011] Performing a second type of etching simultaneously on the second adjustment layer and the portion of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define the formation height of the pyramid structure;

[0012] The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

[0013] In the preparation method described above, the step of forming a second adjustment layer on the side of the first adjustment layer away from the substrate comprises:

[0014] A silicon-based thin film is deposited by a deposition process and oxygen atoms are doped at the same time to obtain an oxygen-containing crystalline silicon film having a plurality of through holes; the oxygen-containing crystalline silicon film is used as the second adjustment layer; wherein,

[0015] The porosity of the oxygen-containing crystalline silicon film is 60-97%; the average diameter of the through hole is 2nm-1000nm.

[0016] The preparation method as described above, wherein the first adjustment layer comprises: a SiOx layer, a SiNy layer, a PSG layer or a BSG layer, wherein x and y are both positive numbers;

[0017] The second adjustment layer includes: an N-type doped oxygen-containing microcrystalline layer, a P-type doped oxygen-containing microcrystalline layer, or an oxygen-containing polycrystalline silicon layer.

[0018] The preparation method as described above, wherein

[0019] The first type of etching includes: etching the first adjustment layer for 0.2 min to 10 min using a HF solution having a mass percentage content of 0.1 wt % to 10 wt % at a reaction temperature of 25° C. to 35° C.

[0020] The preparation method as described above, wherein

[0021] The second type of etching includes: at a reaction temperature of 50°C to 85°C, using a mixed solution including 0.1wt% to 10wt% of alkali solution and 0.1wt% to 10wt% of a texturing additive by mass percentage to etch the second adjustment layer and the portion of the substrate exposed by the opening pattern for 200s to 1000s.

[0022] The preparation method as described above, wherein

[0023] The thickness of the first adjustment layer is 10nm-300nm; the thickness of the second adjustment layer is 5nm-300nm; the length of the bottom side of the pyramid structure is 10nm-100nm; the height of the pyramid structure is 2nm-200nm.

[0024] The preparation method as described above,

[0025] Forming a first adjustment layer on at least one side of the substrate, comprising:

[0026] forming a first regulating layer only on one side of the substrate;

[0027] Correspondingly, the method comprises:

[0028] A second adjustment layer having a preset thickness is formed on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction;

[0029] Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to form an opening pattern with a preset width value;

[0030] Simultaneously performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate;

[0031] The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

[0032] The preparation method as described above,

[0033] Forming a first adjustment layer on at least one side of the substrate, comprising:

[0034] forming a first regulating layer only on one side of the substrate;

[0035] Correspondingly, the method comprises:

[0036] A second adjustment layer having a preset thickness is formed on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction;

[0037] Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to form an opening pattern with a preset width value;

[0038] forming a protective layer on a side of the substrate away from the first regulating layer;

[0039] Simultaneously performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern to obtain a pyramid structure on one side of the substrate;

[0040] The remaining first adjustment layer and the protective layer are removed, and the remaining base and the pyramid structure together constitute the substrate.

[0041] The preparation method as described above, forming a first adjustment layer on at least one side of the substrate, comprises:

[0042] forming a first adjustment layer on both sides of the substrate;

[0043] Correspondingly, the method comprises:

[0044] A second adjustment layer having a preset thickness is formed on a side of each of the first adjustment layers away from the substrate; each of the second adjustment layers has a plurality of through holes penetrating the second adjustment layer in a thickness direction;

[0045] Using each of the second adjustment layers as a mask, respectively, a first type of etching is performed on the corresponding first adjustment layer to form an opening pattern penetrating each of the first adjustment layers;

[0046] Simultaneously performing a second type of etching on each of the second adjustment layers and a portion of the substrate exposed by each of the opening patterns, so as to obtain pyramid structures on both sides of the substrate respectively;

[0047] The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

[0048] On the other hand, the present application provides a photovoltaic cell, which includes a substrate, a first functional layer, a second functional layer and an electrode structure prepared by the preparation method as described above; wherein the substrate has two opposite sides; the first functional layer is located on one side of the substrate; the first functional layer is configured to: form a PN junction with the substrate; the second functional layer is located on the side of the substrate away from the first functional layer; the second functional layer is configured to: constitute a back surface field of the substrate; the electrode structure is located on the side of the first functional layer and / or the second functional layer away from the substrate.

[0049] The substrate preparation method and photovoltaic cell provided in the embodiment of the present application are formed by forming a first adjustment layer on at least one side of the substrate; and forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate, and the second adjustment layer has a plurality of through holes penetrating itself in the thickness direction. The first adjustment layer and the substrate are set to have different etching selectivities; the second adjustment layer and the substrate are set to have the same etching selectivity.

[0050] Based on this, the first type of etching is performed on the first adjustment layer using the second adjustment layer as a mask, and the portion of the first adjustment layer exposed by the through hole can be selectively removed to form an opening pattern, and the opening pattern can be conveniently and accurately controlled to have a preset width value by adjusting the parameters such as the etching time of the first type of etching; then, the second type of etching is synchronously performed on the second adjustment layer and the portion of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate. In this way, the length of the bottom side of the pyramid structure can be conveniently and accurately controlled by means of the opening pattern; and by setting the thickness of the second adjustment layer, it is convenient to synchronously stop etching the substrate when the etching of the second adjustment layer is finished, thereby realizing a convenient and accurate control of the formation height of the pyramid structure.

[0051] In this way, the embodiment of the present application effectively improves the control accuracy of the pyramid structure morphology parameters, reduces the reflectivity of the obtained pyramid structure to the incident light, thereby ensuring and improving the conversion efficiency of the photovoltaic cell. It also effectively simplifies the process difficulty and reduces the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of a process for preparing a substrate provided in some embodiments of the present application;

[0053] Figure 2 A schematic flow chart of another substrate preparation method provided in some embodiments of the present application;

[0054] Figure 3 A schematic flow chart of another substrate preparation method provided in some embodiments of the present application;

[0055] Figure 4 A schematic flow chart of another substrate preparation method provided in some embodiments of the present application;

[0056] Figure 5 A schematic diagram of a structure obtained after executing step S10 provided in some embodiments of the present application;

[0057] Figure 6 A schematic diagram of a structure obtained after executing step S20 and a structure obtained after executing step S20″ provided in some embodiments of the present application;

[0058] Figure 7 A schematic diagram of a structure obtained after executing step S30 and a structure obtained after executing step S30″ provided in some embodiments of the present application;

[0059] Figure 8 A schematic diagram of a structure obtained after executing step S40 and a structure obtained after executing step S40″ provided in some embodiments of the present application;

[0060] Fig. 9 for Figure 8 A magnified schematic diagram of the middle A area;

[0061] Fig.10 A schematic diagram of a structure obtained after executing step S50 and a structure obtained after executing step S50″ provided in some embodiments of the present application;

[0062] Fig.11 A schematic diagram of a structure obtained after executing step S60 and a structure obtained after executing step S60' provided in some embodiments of the present application;

[0063] Fig.12 A schematic diagram of a structure obtained after executing step S20' provided in some embodiments of the present application;

[0064] Fig.13 A schematic diagram of a structure obtained after executing step S30' provided in some embodiments of the present application;

[0065] Fig.14 A schematic diagram of a structure obtained after executing step S40' provided in some embodiments of the present application;

[0066] Fig.15 A schematic diagram of a structure obtained after executing step S50' provided in some embodiments of the present application;

[0067] Fig.16 A schematic diagram of a structure obtained after executing step S60' provided in some embodiments of the present application;

[0068] Fig.17 A schematic diagram of a structure obtained after executing step S45 provided in some embodiments of the present application;

[0069] Fig.18 A schematic diagram of a structure obtained after executing step S50″ provided in some embodiments of the present application;

[0070] Fig.19 A schematic diagram of a structure obtained after executing step S60″ provided in some embodiments of the present application;

[0071] Fig. 20 This is a schematic diagram of the structure of a photovoltaic cell provided in some embodiments of the present application.

[0072] Description of reference numerals:

[0073] 10-substrate; 20-first adjustment layer; 30-second adjustment layer; 40-protective layer; 50-first functional layer; 60-second functional layer; 70-electrode structure;

[0074] H1-through hole; H2-opening pattern; G0-pyramid structure; G1-first type pyramid structure; G2-second type pyramid structure. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in combination with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0076] like Figure 1 As shown, the present application provides a substrate preparation method for preparing a substrate including a pyramid structure, comprising the following steps:

[0077] S10, providing a substrate, wherein the substrate has two opposite sides.

[0078] S20, forming a first adjustment layer on at least one side of the substrate; the first adjustment layer and the substrate have different etching selectivities.

[0079] S30, forming a second adjustment layer with a preset thickness value on the side of the first adjustment layer away from the substrate; the second adjustment layer and the substrate have the same etching selectivity; and the second adjustment layer has a plurality of through holes penetrating through itself in the thickness direction; the through holes are used to define the number of pyramid structures formed.

[0080] S40, performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask, removing a portion of the first adjustment layer exposed by the through hole and forming an opening pattern with a preset width value; the opening pattern is used to define the length of the bottom side of the pyramid structure.

[0081] S50, performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern simultaneously to obtain a pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define the formation height of the pyramid structure.

[0082] S60, removing the remaining first adjustment layer; the remaining base and the pyramid structure together constitute a substrate.

[0083] In the present application, a first adjustment layer is formed on at least one side of a substrate; and a second adjustment layer with a preset thickness is formed on the side of the first adjustment layer away from the substrate, and the second adjustment layer has a plurality of through holes penetrating the first adjustment layer in the thickness direction. The first adjustment layer and the substrate are set to have different etching selectivities; and the second adjustment layer and the substrate are set to have the same etching selectivity.

[0084] Based on this, the first type of etching is performed on the first adjustment layer with the second adjustment layer as a mask, and the part of the first adjustment layer exposed by the through hole can be selectively removed to form an opening pattern, and the opening pattern can be accurately controlled to have a preset width value by adjusting the etching time of the first type of etching; then, the second type of etching is synchronously performed on the second adjustment layer and the part of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate. In this way, the bottom side length of the pyramid structure can be conveniently and accurately regulated by means of the opening pattern; and by means of the thickness setting of the second adjustment layer, it is convenient to synchronously stop etching the substrate when the second adjustment layer etching is finished, thereby achieving a convenient and accurate regulation of the formation height of the pyramid structure. In this way, the embodiment of the present application effectively improves the control accuracy of the pyramid structure morphology parameters, reduces the reflectivity of the incident light of the obtained pyramid structure, and thereby ensures and improves the conversion efficiency of the photovoltaic cell. It also effectively simplifies the process difficulty and reduces the preparation cost.

[0085] See also Figure 1 S10 and Figure 5 In step S10, a substrate 10 is provided, and the substrate 10 has two opposite sides. The present application does not specifically limit the type of the substrate 10, for example, the substrate 10 may include a single crystal silicon substrate, a polycrystalline silicon substrate, a silicon epitaxial substrate, etc.

[0086] The present application does not impose any special restrictions on the shape, size, and thickness of the substrate 10, which can be selected according to actual needs.

[0087] In the reference Figure 1 S20 and Figure 6 In step S20 , a first adjustment layer 20 is formed on at least one side of the substrate 10 ; the first adjustment layer 20 and the substrate 10 have different etching selectivities.

[0088] Here, the first adjustment layer 20 and the substrate 10 may have different acid and alkali corrosion selectivities. For example, the first adjustment layer 20 may be acid-resistant but not alkali-resistant, and the substrate 10 may be alkali-resistant but not acid-resistant; or the first adjustment layer 20 may be alkali-resistant but not acid-resistant, and the substrate 10 may be acid-resistant but not alkali-resistant. The present application does not limit the specific acid and alkali corrosion selectivities of the first adjustment layer 20 and the substrate 10.

[0089] In a specific embodiment, the first adjustment layer 20 includes SiO x Layer, SiN y At least one of a layer, a PSG layer, and a BSG layer, wherein x and y are both positive numbers. For example, the present application can use one of the above substances to prepare the first adjustment layer 20, or can use two or more of the above substances to prepare the first adjustment layer 20. SiO x Including at least one of silicon dioxide (SiO2) and silicon tetraoxide (Si3O4); SiN y Including silicon nitride (Si3N4).

[0090] The present application does not limit the method for preparing the first adjustment layer 20, which can be selected according to the actual situation. For example, the first adjustment layer 20 can be prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD). By using the above-mentioned material as the first adjustment layer 20, the present application can act as a "mask" in the subsequent etching process.

[0091] See also Figure 1 S30 and Figure 7 In step S30, a second adjustment layer 30 having a preset thickness is formed on the side of the first adjustment layer 20 away from the substrate 10; the second adjustment layer 30 has the same etching selectivity as the substrate 10; and the second adjustment layer 30 has a plurality of through holes H1 penetrating through the second adjustment layer 30 in the thickness direction; the through holes H1 are used to define the number of pyramid structures formed.

[0092] Here, the obtained through hole H1 is used in the subsequent step, and the pyramid structure is prepared by patterning and etching the relevant film layer through the through hole H1. Therefore, based on the adjustment of the formation density (i.e., porosity) of the through hole H1 in this step, the number of pyramid structures formed in the subsequent step can be defined.

[0093] In a specific embodiment, the step of forming the second adjustment layer 30 on the side of the first adjustment layer 20 facing away from the substrate 10 includes:

[0094] A silicon-based thin film is deposited by a deposition process while oxygen atoms are doped to obtain an oxygen-containing crystalline silicon film having a plurality of through holes H1; the oxygen-containing crystalline silicon film serves as a second adjustment layer; wherein the porosity of the oxygen-containing crystalline silicon film is 60-97%; and the average diameter of the through hole H1 is 2nm-1000nm.

[0095] The present application does not impose any special limitation on the deposition process, as long as it can be used to form an oxygen-containing crystalline silicon film. For example, the oxygen-containing crystalline silicon film can be prepared by chemical vapor deposition, physical vapor deposition, etc.

[0096] After research, the inventors found that the silicon-based film obtained by the deposition process has pinhole characteristics, and by adjusting the relevant process parameters, the formation density (i.e., porosity) of the relevant pinholes can be controlled. In addition, by doping oxygen atoms while depositing the silicon-based film using the deposition process, the average diameter of the pores in the oxygen-containing crystalline silicon film can be further controlled to ensure that the relevant etching solution can pass through the pores. In this way, the present application uses the aforementioned oxygen-containing crystalline silicon film as the second adjustment layer 30, and by adjusting the porosity of the second adjustment layer 30 and the average diameter of the through hole H1, it is possible to conveniently and accurately control the etching process in the subsequent steps, thereby controlling the number of pyramid structures formed.

[0097] In some embodiments, the porosity of the oxygen-containing crystalline silicon film includes: 60~97%. For example, the porosity of the oxygen-containing crystalline silicon film includes but is not limited to 60%, 70%, 80%, 90%, 97% or a range consisting of any two thereof.

[0098] In some embodiments, the average diameter of the through hole H1 includes: 2nm-1000nm. For example, the average diameter of the through hole includes but is not limited to 2nm, 10nm, 50nm, 100nm, 200nm, 400nm, 600nm, 800nm, 1000nm or a range consisting of any two of them. By further limiting the porosity of the oxygen-containing crystalline silicon film and the average diameter of the through hole H1, it is beneficial to prepare a substrate with low reflectivity.

[0099] See also Figure 1 S40 and Figure 8 In step S40, the first adjustment layer 20 is etched using the second adjustment layer 30 as a mask to remove the portion of the first adjustment layer 20 exposed by the through hole H1 and form an opening pattern H2 with a preset width value; the opening pattern H2 is used to define the length of the bottom side of the pyramid structure.

[0100] It can be understood that based on the setting that the second adjustment layer 30 has the same etching selectivity as the substrate 10 and the first adjustment layer 20 has different etching selectivity from the substrate 10, the second adjustment layer 30 can be used as a mask to selectively etch the first adjustment layer 20 (for example, first type etching) to obtain an opening pattern H2 corresponding to the formation density (i.e., porosity) of the through hole H1.

[0101] Please combine Fig. 9Here, the opening width w2 of the opening pattern H2 is different from the opening width w1 of the through hole H1. For example, by adjusting the process parameters such as the first type etching time, the opening width w2 of the opening pattern H2 can be conveniently and accurately controlled to reach its preset width value. Furthermore, in the subsequent steps, the pyramid structure can be obtained by patterning etching based on the film layer related to the opening pattern H2. In this way, the opening width w2 of the opening pattern H2 can define the length of the bottom side of the pyramid structure in the subsequent steps.

[0102] Specifically, the first type of etching is to immerse the Figure 7 The structure shown includes a first adjustment layer 20 and a second adjustment layer 30. During the etching process, the acidic etching solution can penetrate through the through hole H1 in the second adjustment layer 30, and react with the first adjustment layer 20 exposed by the through hole H1, so that the portion of the first adjustment layer 20 exposed by the through hole H1 is corroded and dissolved by the acidic etching solution, thereby forming an opening pattern H2 running through the first adjustment layer 20, providing a position for etching for forming an inverted pyramid pit in the subsequent steps. In addition, by adjusting the process parameters such as the etching time, the etching continues in a direction perpendicular to the thickness of the first adjustment layer 20, ensuring that the opening width w2 of the opening pattern H2 reaches its preset width value.

[0103] Further, the thickness of the first adjustment layer 20 includes: 10nm~300nm; correspondingly, the first type etching includes: etching the first adjustment layer 20 for 0.2min~10min at a reaction temperature of 25°C~35°C using an HF solution with a mass percentage content of 0.1~10wt%.

[0104] For example, the thickness of the first adjustment layer 20 includes but is not limited to 10nm, 20nm, 100nm, 150nm, 200nm, 250 nm, 300nm or a range consisting of any two thereof; at 25~35°C, the temperature of the first type of etching includes but is not limited to 25°C, 26°C, 29°C, 32°C, 35°C or a range consisting of any two thereof; the time of the first type of etching is 0.2~10min, and the above time includes but is not limited to 0.2min, 1min, 3min, 5min, 7min, 9min, 10min or a range consisting of any two thereof.

[0105] By using HF within the above concentration range for the first type of etching, the present application can selectively etch the first adjustment layer 20 without etching the second adjustment layer 30, which is beneficial for preparing a substrate with a pyramid structure in the subsequent steps. By limiting the reaction temperature and time of the first type of etching and the thickness of the first adjustment layer within the above range, a pyramid structure with a suitable morphology can be prepared, which is beneficial for reducing the reflectivity of the substrate.

[0106] See also Figure 1 S50 and Fig.10 In step S50, a second type of etching is simultaneously performed on the second adjustment layer 30 and a portion of the substrate 10 exposed by the opening pattern H2 to obtain a pyramid structure G0 on the substrate 10; wherein the thickness of the second adjustment layer 30 is used to define the formation height of the pyramid structure G0.

[0107] Here, based on the setting that the second adjustment layer 30 and the substrate 10 have the same etching selectivity, the second adjustment layer 30 can be used as a reference for etching the substrate 10, that is, the second type of etching is performed on the second adjustment layer 30 and the portion of the substrate 10 exposed by the opening pattern H2 simultaneously, and the first adjustment layer 20 with different etching selectivity is used as an etching stop layer to end the second type of etching when the second adjustment layer 30 is consumed. In this way, by adjusting the thickness of the second adjustment layer 30 in step S30, the formation height of the pyramid structure G0 can be conveniently and accurately controlled.

[0108] Specifically, the second type of etching is to use a mixed solution including an alkali solution and a texturing additive to soak the Figure 8 As shown in: a structure including a first adjustment layer 20 and a second adjustment layer 30. Fig.10 As shown, during the etching process, the second adjustment layer 30 and the substrate 10 are resistant to alkalinity but not acid. Therefore, the mixed solution including the alkali solution and the texturing additive corrodes and removes the second adjustment layer 30, and the mixed solution also etches the substrate 10 through the opening pattern H2 to form the pyramid structure G0, while the first adjustment layer 20 with different etching selectivity is retained as a "mask", and the platform part of the pyramid structure G0 is formed by the corrosion of the mixed solution including the alkali solution and the texturing additive under the mask. In addition, by setting the thickness of the second adjustment layer 30 and the etching parameters of the second type of etching, the second type of etching is stopped after the second adjustment layer 30 is etched, and the height of the obtained pyramid structure G0 can be controlled.

[0109] In addition, the thickness of the second adjustment layer 30 includes: 5~300nm; correspondingly, the second type etching includes: at a reaction temperature of 50℃~85℃, using a mixed solution with a mass percentage of 0.1~10wt% of alkali solution and 0.1~10wt% of a texturing additive to etch the second adjustment layer 30 and the portion of the substrate 10 exposed by the opening pattern H2 for 200s~1000s.

[0110] The alkali in the alkali solution includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, and potassium carbonate. For example, the mass percentage content of the alkali solution includes but is not limited to 0.1wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 10wt% or a range consisting of any two of them.

[0111] The texturing additives include at least one of inhibitors, surfactants, buffers, metal particles, fluorides, complexing agents, and chelating agents. Among them, the inhibitor includes at least one of ethanol, isopropanol, ethylenediamine, and triethylamine alcohol; the surfactant includes at least one of sodium dodecyl sulfate, polyethylene glycol, and polyvinyl alcohol; the buffer includes at least one of sodium carbonate and sodium phosphate; the metal particles include at least one of tin ions and zinc ions; the fluoride includes at least one of hydrofluoric acid and sodium fluoride; the complexing agent includes at least one of citric acid and EDTA; the chelating agent can be tartaric acid. For example, the mass percentage content of the texturing additive includes but is not limited to 0.1wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 10wt% or a range consisting of any two of them.

[0112] For example, the thickness of the second adjustment layer 30 includes but is not limited to 5nm, 10nm, 20nm, 100nm, 150nm, 200nm, 250nm, 300nm or a range consisting of any two thereof; at 50~85°C, the reaction temperature of the second type of etching includes but is not limited to 50°C, 60°C, 70°C, 80°C, 85°C or a range consisting of any two thereof; the reaction time of the second type of etching is 200~1000s, and the above time includes but is not limited to 200s, 300s, 400s, 500s, 600s, 700s, 800s, 900s, 1000s or a range consisting of any two thereof.

[0113] The present application uses the mixed solution including the alkali solution and the texturing additive to perform the second type of etching, which can selectively etch the second adjustment layer without etching the first adjustment layer, which is beneficial to preparing a substrate including a pyramid structure. By limiting the reaction temperature and time of the second type of etching and the thickness of the second adjustment layer within the above range, a pyramid structure with a suitable height can be prepared, which is beneficial to reducing the reflectivity of the substrate.

[0114] In the present application, the formation width of the pyramid structure G0 prepared by the above preparation method includes: 10nm~100nm; the formation height of the pyramid structure G0 includes: 2nm~200nm. For example, the formation width includes but is not limited to 10nm, 50nm, 100nm or a range consisting of any two thereof; the thickness of the second adjustment layer includes but is not limited to 2nm, 10nm, 20nm, 100nm, 150nm, 200nm or a range consisting of any two thereof. The above formation width and formation height are caused by controlling the opening width w2 of the opening pattern H2 and the thickness of the second adjustment layer 30. The pyramid structure G0 with the above formation width and formation height can make the substrate have good light trapping efficiency.

[0115] See also Figure 1 S60 and Fig.11 In step S60, the remaining first adjustment layer 20 is removed; the remaining base 10 and the pyramid structure G0 together constitute a substrate.

[0116] For example, a first type of etching (eg, acid etching) is performed on the structure obtained after step S50 to remove the remaining first adjustment layer 20 to fully expose the pyramid structure G0.

[0117] The present application does not impose any particular limitation on the acid solution, as long as the first adjustment layer 20 can be removed. For example, a 0.1-10wt% HF solution can be used for treatment at 25-35°C for 0.2-10 minutes. By using the above acid solution for pickling, it is beneficial to remove the residual acid-corroded medium layer (i.e., the first adjustment layer 20) and reduce damage to the base having a pyramid structure.

[0118] In the above embodiments, the pyramid structure is prepared on at least one side of the substrate 10 by using the first adjustment layer 20 and the second adjustment layer 30 with different sensitivities to acid and alkali. This method does not introduce any metal particles, thus avoiding the pollution of the environment by heavy metals. Compared with the related art, it is necessary to prepare the initial mask layer multiple times, and then prepare a high-precision photolithography mask to expose and develop the initial mask layer to obtain the mask layer, and then etch the substrate with the help of the mask layer to obtain the pyramid structure. The method provided in the embodiment of the present application can prepare a substrate having a pyramid structure by using simple acid corrosion and alkali corrosion, and the steps are simple and easy to mass produce in industry.

[0119] In addition, in some of the following embodiments of the present application, the formation positions of the first adjustment layer 20 and the second adjustment layer 30 are flexibly adjusted to adjust the formation positions of the pyramid structure accordingly. For example, after both surfaces of the substrate 10 are processed by the above-mentioned preparation method, a substrate with a double-sided pyramid structure can be obtained; or, after only one surface of the substrate 10 is processed by the above-mentioned treatment, a pyramid structure is formed only on the surface; or, different process parameters are respectively performed on the two surfaces of the substrate 10 to obtain pyramid structures with different morphological characteristics. The following is a corresponding explanation in conjunction with the accompanying drawings.

[0120] See also Figure 2 In one embodiment, a first adjustment layer 20 is formed on at least one side of a substrate, comprising:

[0121] S20', forming a first adjustment layer only on one side of the substrate.

[0122] S30', forming a second adjustment layer with a preset thickness on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction.

[0123] S40 ′, performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to form an opening pattern with a preset width value.

[0124] S50 ′, performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern simultaneously to obtain a pyramid structure on the substrate.

[0125] S60 ′, removing the remaining first adjustment layer, and the remaining base and the pyramid structure together constitute a substrate.

[0126] In the present embodiment, since the first adjustment layer 20 and the second adjustment layer 30 are prepared only on one side of the substrate, when etching is performed using a mixed solution including an alkali solution and a texturing additive, the pyramid structures formed on both sides of the substrate will present different morphological features. For example, the side with the first adjustment layer 20 and the second adjustment layer 30 forms a first-type pyramid structure (inverted pyramid); the side without the first adjustment layer 20 and the second adjustment layer 30 forms a second-type pyramid structure (positive pyramid), thereby meeting the morphological requirements of different batteries for the pyramid structure.

[0127] See also Fig.12 In step S20 ′, the first adjustment layer 20 is formed only on one side of the substrate 10 .

[0128] For example, the method for forming the first adjustment layer 20 may be performed with reference to the aforementioned step S20 .

[0129] See also Fig.13 In step S30 ′, a second adjustment layer 30 having a preset thickness is formed on the side of the first adjustment layer 20 away from the substrate 10 ; the second adjustment layer 30 has a plurality of through holes H1 penetrating the second adjustment layer 30 in the thickness direction.

[0130] For example, the method for forming the second adjustment layer 30 may be performed with reference to the aforementioned step S30 .

[0131] See also Fig.14 In step S40 ′, the first type etching is performed on the first adjustment layer 20 using the second adjustment layer 30 as a mask to form an opening pattern H2 having a preset width value.

[0132] For example, the method for forming the opening pattern H2 may be performed with reference to the aforementioned step S40 .

[0133] See also Fig.15 In step S50 ′, a second type of etching is performed on the second adjustment layer 30 and a portion of the substrate 10 exposed by the opening pattern H2 to obtain a pyramid structure on the substrate 10 .

[0134] For example, the second type of etching can be performed with reference to the aforementioned step S50. Here, based on the difference in the etching environment of the second type of etching, for example, on the side of the substrate 10 where the first adjustment layer 20 and the second adjustment layer 30 are formed, the etching solution needs to penetrate and pass through the through hole H1 and the opening pattern H2 to etch the limited area of ​​the substrate 10; and on the side of the substrate 10 where the first adjustment layer 20 and the second adjustment layer 30 are not formed, the etching solution can perform etching on the entire surface. In this way, the pyramid structure obtained based on the etching characteristics (such as anisotropy) of the etching solution has different morphological characteristics. For example, it includes: a first type pyramid structure G1 (inverted pyramid) and a second type pyramid structure G2 (positive pyramid).

[0135] See also Fig.16 In step S60 ′, the remaining first adjustment layer 20 is removed, and the remaining base 10 and the pyramid structure together constitute a substrate.

[0136] For example, the step of removing the first adjustment layer 20 may be performed with reference to the aforementioned step S60 .

[0137] See also Figure 3 In another embodiment, a first adjustment layer 20 is formed on at least one side of the substrate, comprising:

[0138] S20 ′, forming a first adjustment layer with a preset thickness value only on one side of the substrate.

[0139] S30', forming a second adjustment layer with a preset thickness on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction.

[0140] S40 ′, performing a first type of etching on the first adjustment layer with a second adjustment layer mask to form an opening pattern with a preset width value.

[0141] S45, forming a protective layer on a side of the substrate away from the first regulating layer.

[0142] S50 ′, performing a second type of etching simultaneously on the second adjustment layer and a portion of the substrate exposed by the opening pattern to obtain a pyramid structure on one side of the substrate.

[0143] S60'', removing the remaining first adjustment layer and the protective layer, and the remaining base and the pyramid structure together constitute a substrate.

[0144] In this embodiment, a substrate having only one side with the pyramid structure G0, that is, a single-sided pyramid structure substrate, can be prepared to meet the morphology requirements of different batteries for the pyramid structure.

[0145] See also Figure 12 to Figure 14, performing steps S20 ′, S30 ′ and S40 ′ in sequence to obtain a structure including the first adjustment layer 20 , the second adjustment layer 30 , the through hole H1 and the opening pattern H2 .

[0146] For example, the above steps may be performed with reference to the aforementioned steps S20, S30 and S40.

[0147] See also Fig.17 In step S45 , a protective layer 40 is formed on a side of the substrate 10 away from the first adjustment layer 20 .

[0148] In a specific embodiment, the protective layer 40 includes SiO x Layer, SiN y At least one of a layer, a PSG layer, and a BSG layer, wherein x and y are both positive numbers. For example, the present application may use one of the above materials to prepare the protective layer 40, or may use two or more of the above materials to prepare the protective layer 40. SiO x Including at least one of silicon dioxide (SiO2) and silicon tetraoxide (Si3O4); SiN y Including silicon nitride (Si3N4).

[0149] The present application does not limit the method for preparing the protective layer 40, which can be selected according to the actual situation. For example, the protective layer 40 can be prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD). By using the above-mentioned material as the protective layer 40, the present application can act as a "protective layer" in the subsequent etching process.

[0150] The present application does not impose any special limitation on the thickness of the protective layer 40, as long as it can cover and fill the surface and pores of the above-mentioned second adjustment layer 30, so that the surface of the substrate 10 is not corroded by the mixed solution including alkali solution and texturing additives. For example, a protective layer 40 of 200~500nm can be set on the above-mentioned non-one side.

[0151] See also Fig.18 In step S50 ′, a second type of etching is performed on the second adjustment layer 30 and a portion of the substrate 10 exposed by the opening pattern H2 to obtain a pyramid structure G0 on one side of the substrate 10 .

[0152] For example, the step of performing the second type etching may be performed with reference to the aforementioned step S50 .

[0153] See also Fig.19 In step S60 ″, the remaining first adjustment layer 20 and the protective layer 40 are removed, and the remaining base 10 and the pyramid structure G0 together constitute a substrate.

[0154] For example, the step of removing the first adjustment layer 20 and the protective layer 40 may be performed with reference to the aforementioned step S60 .

[0155] In the above preparation method, because the first adjustment layer 20 and the second adjustment layer 30 are sequentially arranged on only one side of the substrate 10, the first type of etching will only occur on the side with the first adjustment layer 20 and the second adjustment layer 30, without affecting the other side. After the first type of etching is completed, a protective layer 40 is arranged on the other side to protect the side from being corroded in the second type of etching, so that the side can be used as the backlight surface of the photovoltaic cell to maintain a high reflectivity of the surface, realize the secondary utilization of the incident spectrum, and further improve the conversion efficiency of the photovoltaic cell.

[0156] See also Figure 4 In another embodiment, a first adjustment layer 20 is formed on at least one side of the substrate 10, comprising:

[0157] S20'', forming a first adjustment layer on both sides of the substrate.

[0158] S30 ″, forming a second adjustment layer with a preset thickness on a side of each first adjustment layer 20 away from the substrate; each second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction.

[0159] S40 ″, performing first-type etching on the corresponding first adjustment layers using each second adjustment layer as a mask, so as to form an opening pattern penetrating each first adjustment layer.

[0160] S50 ″, performing a second type of etching simultaneously on each second adjustment layer and a portion of the substrate exposed by each opening pattern, so as to obtain pyramid structures on both sides of the substrate respectively.

[0161] S60', removing the remaining first adjustment layer; the remaining base and the pyramid structure together constitute a substrate.

[0162] In this embodiment, a substrate having a pyramid structure G0 on both sides, that is, a double-sided pyramid structure substrate, can be prepared to meet the morphology requirements of different batteries for the pyramid structure.

[0163] See also Figure 6 In step S20 ″, a first adjustment layer 20 is formed on both sides of the substrate 10 .

[0164] For example, this step may be performed with reference to the aforementioned step S20.

[0165] See also Figure 7In step S30 ″, a second adjustment layer 30 having a preset thickness is formed on the side of each first adjustment layer 20 away from the substrate 10 ; each second adjustment layer 30 has a plurality of through holes H1 penetrating the second adjustment layer 30 in the thickness direction.

[0166] For example, this step may be performed with reference to the aforementioned step S30.

[0167] See also Figures 8 to 9 In step S40 ″, the first type etching is performed on the corresponding first adjustment layer 20 using each second adjustment layer 30 as a mask to form an opening pattern penetrating each first adjustment layer 20 .

[0168] For example, this step may be performed with reference to the aforementioned step S40.

[0169] See also Fig.10 In step S50 ″, the second type etching is simultaneously performed on each second adjustment layer 30 and a portion of the substrate 10 exposed by each opening pattern to obtain pyramid structures on both sides of the substrate 10 .

[0170] For example, this step may be performed with reference to the aforementioned step S50.

[0171] See also Fig.11 In step S60 ′, the remaining first adjustment layer 20 is removed; the remaining base 10 and the pyramid structure G0 together constitute a substrate.

[0172] For example, this step may be performed with reference to the aforementioned step S60 , and the pyramid structures G0 obtained in this step are all first-type pyramid structures (inverted pyramid structures).

[0173] In some specific embodiments, a substrate with a double inverted pyramid structure can be prepared by the above-mentioned preparation method to meet the morphology requirements of different batteries for the substrate pyramid structure.

[0174] In addition, the substrate preparation method of the present application also includes:

[0175] Before forming the first adjustment layer, performing a first type cleaning process on the substrate; and,

[0176] After obtaining the pyramid structure, a second type cleaning process is performed on the substrate.

[0177] The first type of cleaning process is not particularly limited in the present application. For example, a NaOH or KOH solution with a mass percentage of 0.5-5 wt% can be used for cleaning at 80-85° C. for 2-15 minutes. The cleaning process can also include drying the substrate.

[0178] The present application cleans the substrate through a first type of cleaning treatment, which can remove impurities on the substrate surface and remove damage to the substrate surface, thereby obtaining a clean substrate, which is conducive to the deposition of a uniform first adjustment layer 20 and a second adjustment layer 30, and further conducive to the preparation of an inverted pyramid structure.

[0179] The present application does not make any special limitation on the second type of cleaning process, which can be selected according to actual needs. For example, it can be a standard RCA cleaning process.

[0180] The present application can obtain a clean substrate including a pyramid structure through the second type cleaning process.

[0181] See also Fig. 20 In a second aspect, the present application provides a photovoltaic cell for practical application of the substrate preparation method provided in some of the above embodiments. The photovoltaic cell comprises:

[0182] A substrate 10, wherein the substrate 10 is obtained by the above substrate preparation method; the substrate 10 has two opposite sides;

[0183] The first functional layer 50 is located on one side of the substrate 10; the first functional layer 50 is configured to form a PN junction with the substrate 10;

[0184] The second functional layer 60 is located on the side of the substrate 10 away from the first functional layer 50; the second functional layer 60 is configured to: constitute a back surface field of the substrate 10;

[0185] The electrode structure 70 is located on the side of the first functional layer 60 and the second functional layer 70 facing away from the substrate 10 .

[0186] By way of example, the first functional layer 50 includes: a first intrinsic semiconductor layer, a first doped semiconductor layer, and a first transparent conductive layer stacked in sequence.

[0187] By way of example, the second functional layer 60 includes: a second intrinsic semiconductor layer, a second doped semiconductor layer, and a second transparent conductive layer stacked in sequence.

[0188] For example, the first transparent conductive layer and / or the second transparent conductive layer includes: at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum zinc oxide (AZO).

[0189] For example, the first doped semiconductor layer and / or the second doped semiconductor layer includes at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, an organic semiconductor material, copper indium gallium selenide, and nanoporous titanium dioxide.

[0190] Illustratively, the electrode structure 70 includes at least one of silver (Ag), copper (Cu), and aluminum (Al).

[0191] In another embodiment, the electrode structure 70 is located on the side of the first functional layer 60 or the second functional layer 70 facing away from the substrate.

[0192] Hereinafter, the present application will be further described in detail through specific embodiments.

[0193] Example 1

[0194] The method for preparing a substrate having a pyramid structure provided in this embodiment comprises the following steps:

[0195] 1) Performing a first type of cleaning and drying on the substrate, wherein the reagent used for the first type of cleaning is a mixed solution of 5wt% alkali and 5wt% hydrogen peroxide, and the cleaning time is 180s at a temperature of 70°C to remove oil stains on the surface of the substrate, and then using a 5wt% alkali solution at a temperature of 83°C for 180s to remove the mechanical damage layer of the substrate; then performing RCA cleaning and drying; the alkali solution includes a potassium hydroxide solution;

[0196] 2) A first adjustment layer and a second adjustment layer are respectively provided on both sides of the substrate, and the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in the thickness direction; wherein,

[0197] The first adjustment layer is a SiNx layer with a thickness of 300 nm;

[0198] The second adjustment layer is a doped microcrystalline P layer with a thickness of 20 nm. The maximum size of the through holes in this layer is 500 nm, and the porosity is 80%.

[0199] 3) performing a first type of etching on one side of the first intermediate substrate layer using an acidic etching solution to remove the first adjustment layer exposed through the through hole;

[0200] Wherein, the acidic etching solution is HF with a mass percentage of 2%;

[0201] The temperature of the first type of etching is 25°C and the time is 2 minutes.

[0202] 4) using a mixed solution including an alkali solution and a texturing additive to perform a second type of etching treatment on both sides of the structure obtained after performing step 3 above;

[0203] The mixed solution including the alkali solution and the texturing additive includes 1wt% of the alkali solution and 0.5wt% of the texturing additive, the alkali solution is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0204] The temperature of the second type etching process is 80° C. and the time is 420 s.

[0205] 5) The structure obtained after performing step 4 is pickled to remove the remaining first adjustment layer, thereby obtaining a substrate having a pyramid structure.

[0206] The pickling treatment is to use HF with a mass percentage of 5wt% at 25°C for 2min.

[0207] 6) Performing an RCA cleaning procedure on the above-mentioned substrate including the pyramid structure.

[0208] The substrate including the pyramid structure prepared in this embodiment is as follows Fig.11 shown.

[0209] Example 2

[0210] The method for preparing a substrate having a pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that the first adjustment layer and the second adjustment layer are sequentially arranged only on one side of the substrate.

[0211] The subsequent preparation steps are the same as those in Example 1.

[0212] Step 2) also includes providing a protective layer with a thickness of 300 nm on the other side of the substrate.

[0213] The substrate with a single-sided pyramid structure prepared in this embodiment is as follows Fig.19 As shown by Fig.19 It can be seen that one side of the substrate prepared by the method of this embodiment has a pyramid structure, while the other side surface has no pyramid structure.

[0214] Example 3

[0215] The method for preparing a substrate having a pyramid structure provided in this embodiment is basically the same as that in embodiment 1, except that in step 2), the first adjustment layer and the second adjustment layer are not deposited on one side of the substrate, and the subsequent processing conditions are the same as those in embodiment 1.

[0216] The subsequent preparation steps are the same as those in Example 1.

[0217] The substrate prepared in this embodiment has a first type pyramid structure (i.e., an inverted pyramid structure) on one side and a second type pyramid structure (i.e., a normal pyramid structure) on the other side. Fig.16 shown.

[0218] Example 4

[0219] The method for preparing a substrate having a pyramid structure provided in this embodiment is basically the same as that in embodiment 1, except that in step 2):

[0220] The first adjustment layer is a BSG layer with a thickness of 300 nm;

[0221] The second adjustment layer is a microcrystalline N layer with a thickness of 30 nm. The maximum pore size of the through holes in this layer is 200 nm, and the porosity is 85%.

[0222] In step 3):

[0223] The acidic etching solution is HF with a mass percentage of 5%;

[0224] The temperature of the first type of etching is 25°C and the time is 3 minutes.

[0225] In step 4):

[0226] The mixed solution including alkali solution and texturing additive includes 1wt% alkali solution and 0.5wt% texturing additive, the alkali solution is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0227] The temperature of the second type etching process is 80° C. and the time is 300 s.

[0228] In step 5):

[0229] The method is to use 5wt% HF at 30°C for 2 to 4 minutes.

[0230] Example 5

[0231] The method for preparing a substrate having a pyramid structure provided in this embodiment is basically the same as that in embodiment 1, except that in step 2):

[0232] The first adjustment layer is a SiOx layer with a thickness of 200 nm;

[0233] The second adjustment layer is a 60 nm intrinsic amorphous silicon layer, the maximum size of the through holes in this layer is 400 nm, and the porosity is 65%.

[0234] In step 3):

[0235] The acidic etching solution is HF with a mass percentage of 3%;

[0236] The temperature of the first type of etching is 30°C and the time is 1 min.

[0237] In step 4):

[0238] The mixed solution including alkali solution and texturing additive includes 1wt% alkali solution and 1wt% texturing additive, the alkali solution is potassium hydroxide, and the texturing additive is a conventional texturing additive;

[0239] The temperature of the second type of etching process is 85° C. and the time is 500 s.

[0240] In step 5):

[0241] The reaction mixture was treated with 5 wt% HF at 30°C for 4 min.

[0242] Example 6

[0243] The method for preparing a substrate having a pyramid structure provided in this embodiment is basically the same as that in Embodiment 1, except that, in this embodiment, the maximum pore size of the through holes of the second adjustment layer is 500 nm, and the porosity is 90%.

[0244] Comparative Example 1

[0245] This comparative example adopts a substrate having a pyramid structure prepared in the invention patent CN107611226B. The preparation method thereof comprises the following steps:

[0246] 1) Providing a substrate, and performing metal-assisted chemical etching on the substrate to form raised spots.

[0247] Metal assisted chemical etching specifically includes the following steps:

[0248] HF / HNO3 / DIW (deionized water) solution is used for cleaning, the solution ratio is 1:4-6:1-6, the cleaning temperature is 0℃-8℃; the cleaning time is 10s-120s; deionized water is used for cleaning at room temperature for 60s-180s; HF / H2O2 / DIW / additives are used for metal-assisted chemical etching, wherein the additives may be nitrates of metals such as Ag, Cu, and Au; the solution ratio is 1:1-7:1-7 (additive 100-1000mL), the etching temperature is 15℃-65℃; the etching time is 20s-240s; then deionized water is used for cleaning for 60s-180s; then HNO3 with a concentration of 69% is used twice for etching at room temperature for 60s-180s to fully remove metal ions; then deionized water is used for cleaning at room temperature for 60s-180s; then 1 %-20% HF is etched at room temperature for 60s-180s; deionized water is used for cleaning at room temperature for 60s-180s; KOH with a concentration of 0.1%-10% is used alone for etching at room temperature for 60s-180s; deionized water is used for cleaning at room temperature for 60s-180s; HCL / H2O2 / DIW is used for etching, wherein the solution ratio is 1:1-10:1-10, and the etching temperature is 25℃-75℃; The etching time is 60s-180s; the deionized water is used for cleaning at room temperature for 60s-180s; HF / HCl / DIW is used for etching, wherein the solution ratio is 1:1-10:1-10, and the etching temperature is room temperature; the etching time is 60s-180s; the deionized water is used for cleaning at room temperature for 60s-180s; then the hot water with a temperature of 60℃-90℃ is used for cleaning, and then drying is performed for 300s-600s.

[0249] 2) Dry ion etching is performed on the substrate after metal-assisted chemical etching to obtain an inverted pyramid structure;

[0250] The dry ion etching comprises the following steps: adopting an etching time of 120s-300s; a reaction chamber pressure of 24Pa-100Pa; an incoming chlorine gas flow rate of 400sccm-4000sccm; an incoming oxygen gas flow rate of 1000sccm-3000sccm; an incoming SF6 gas flow rate of 700sccm-3000sccm; an outgoing chlorine gas flow rate of 700sccm-4000sccm; an outgoing oxygen gas flow rate of 1800sccm-5000sccm; an outgoing SF6 gas flow rate of 650sccm-4000sccm; and performing reactive ion etching at a radio frequency power of 24000W-100000W to obtain an inverted pyramid structure.

[0251] 3) Clean the substrate after dry ion etching using the RCA cleaning process.

[0252] Test example

[0253] The surface reflectivity of the substrates having pyramid structures prepared in Examples 1-6 and Comparative Example 1 was measured by a reflectivity testing device. The results are shown in Table 1.

[0254] Table 1 - Reflectivity measurement results

[0255] One side reflectivity / % Reflectivity of the other side / % Example 1 3.87% 3.87% Example 2 3.87% 35.77% Example 3 3.87% 10.62% Example 4 4.5% 4.5% Example 5 4.5% 4.5% Example 6 3.03% 3.03% Comparative Example 1 3％～8％ 3％～8％

[0256] According to Table 1, the surface reflectivity of the substrate including the pyramid structure prepared by the metal-assisted chemical etching process in Comparative Example 1 is 3-8%. Based on its process characteristics, metal particle impurities need to be introduced, which inevitably causes environmental pollution. In addition, in its preparation process, it is necessary to accurately adjust multiple process parameters such as gas flow, RF power, etching solution concentration, component ratio, etc., which significantly increases the difficulty of preparation.

[0257] In Examples 1-6 of the present application, a substrate having a pyramid structure is prepared by a relatively simple process, and its reflectivity is only 3-5.12%, which has good light trapping performance. In addition, compared with the method provided in Comparative Example 1, Examples 1-6 do not introduce metal particle impurities and are more environmentally friendly.

[0258] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A substrate preparation method for preparing a substrate including a pyramid structure; characterized in that: include: providing a substrate having two opposing sides; forming a first adjustment layer on at least one side of the substrate; The first adjustment layer and the substrate have different etching selectivities; A second adjustment layer having a preset thickness is formed on the side of the first adjustment layer away from the substrate; the second adjustment layer and the substrate have the same etching selectivity; and the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction; The through holes are used to define the number of pyramid structures formed; Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to remove a portion of the first adjustment layer exposed by the through hole and form an opening pattern with a preset width value; The opening pattern is used to define the length of the base side of the pyramid structure; Performing a second type of etching simultaneously on the second adjustment layer and the portion of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate; wherein the thickness of the second adjustment layer is used to define the formation height of the pyramid structure; The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

2. The substrate preparation method according to claim 1, characterized in that: The step of forming a second adjustment layer on a side of the first adjustment layer away from the substrate comprises: A silicon-based thin film is deposited by a deposition process and oxygen atoms are doped at the same time to obtain an oxygen-containing crystalline silicon film having a plurality of through holes; the oxygen-containing crystalline silicon film is used as the second adjustment layer; wherein, The porosity of the oxygen-containing crystalline silicon film is 60-97%; the average diameter of the through hole is 2nm-1000nm.

3. The substrate preparation method according to claim 1, characterized in that: The first adjustment layer includes: a SiOx layer, a SiNy layer, a PSG layer or a BSG layer, wherein x and y are both positive numbers; The second adjustment layer includes: an N-type doped oxygen-containing microcrystalline layer, a P-type doped oxygen-containing microcrystalline layer or an oxygen-containing polycrystalline silicon layer.

4. The substrate preparation method according to claim 1, characterized in that: The first type of etching includes: etching the first adjustment layer for 0.2 min to 10 min using a HF solution having a mass percentage content of 0.1 to 10 wt % at a reaction temperature of 25° C. to 35° C.

5. The substrate preparation method according to claim 1, characterized in that: The second type of etching includes: at a reaction temperature of 50°C to 85°C, using a mixed solution including 0.1wt% to 10wt% of alkali solution and 0.1wt% to 10wt% of a texturing additive by mass percentage to simultaneously etch the second adjustment layer and the portion of the substrate exposed by the opening pattern for 200s to 1000s.

6. The method for preparing a substrate according to any one of claims 1 to 5, characterized in that: The thickness of the first adjustment layer includes: 10nm~300nm; The thickness of the second adjustment layer includes: 5nm~300nm; The length of the bottom side of the pyramid structure includes: 10nm~100nm; The formation height of the pyramid structure includes: 2nm~200nm.

7. The method for preparing a substrate according to any one of claims 1 to 5, characterized in that: Forming a first adjustment layer on at least one side of the substrate, comprising: forming a first regulating layer only on one side of the substrate; Correspondingly, the method comprises: A second adjustment layer having a preset thickness is formed on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction; Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to form an opening pattern with a preset width value; Simultaneously performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern to obtain a pyramid structure on the substrate; The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

8. The method for preparing a substrate according to any one of claims 1 to 5, characterized in that: Forming a first adjustment layer on at least one side of the substrate, comprising: forming a first regulating layer only on one side of the substrate; Correspondingly, the method comprises: A second adjustment layer having a preset thickness is formed on a side of the first adjustment layer away from the substrate; the second adjustment layer has a plurality of through holes penetrating the second adjustment layer in a thickness direction; Performing a first type of etching on the first adjustment layer using the second adjustment layer as a mask to form an opening pattern with a preset width value; forming a protective layer on a side of the substrate away from the first regulating layer; Simultaneously performing a second type of etching on the second adjustment layer and a portion of the substrate exposed by the opening pattern to obtain a pyramid structure on one side of the substrate; The remaining first adjustment layer and the protective layer are removed, and the remaining base and the pyramid structure together constitute the substrate.

9. The method for preparing a substrate according to any one of claims 1 to 5, characterized in that: Forming a first adjustment layer on at least one side of the substrate, comprising: forming a first adjustment layer on both sides of the substrate; Correspondingly, the method comprises: A second adjustment layer having a preset thickness is formed on a side of each of the first adjustment layers away from the substrate; each of the second adjustment layers has a plurality of through holes penetrating the second adjustment layer in a thickness direction; Using each of the second adjustment layers as a mask, respectively, a first type of etching is performed on the corresponding first adjustment layer to form an opening pattern penetrating each of the first adjustment layers; Simultaneously performing a second type of etching on each of the second adjustment layers and a portion of the substrate exposed by each of the opening patterns, so as to obtain pyramid structures on both sides of the substrate respectively; The remaining first adjustment layer is removed; the remaining base and the pyramid structure together constitute the substrate.

10. A photovoltaic cell comprising: A substrate, obtained by the substrate preparation method according to any one of claims 1 to 9; the substrate has two opposite sides; A first functional layer is located on one side of the substrate; the first functional layer is configured to: form a PN junction with the substrate; A second functional layer is located on a side of the substrate away from the first functional layer; the second functional layer is configured to: constitute a back surface field of the substrate; The electrode structure is located on a side of the first functional layer and / or the second functional layer facing away from the substrate.

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