Texturing method, silicon wafer and solar cell

Abstract

The invention provides a texturing method, a silicon wafer and a solar cell. The texturing method comprises the following steps: providing a first-type solution and a first-type gas; performing two-phase mixing treatment on the first-type solution and the first-type gas to obtain a gas-liquid mixed phase initial etching agent; performing atomization treatment on the initial etching agent to obtain etching spray; etching the target surface of the silicon wafer by using the etching spray to obtain a textured structure; wherein the first type solution comprises an acid solution; the first-type gas includes an acidic gas. The texturing method is used for texturing, so that the silicon wafer with lower surface reflectivity can be obtained, and the efficiency of a battery using the silicon wafer is further improved.

Description

Technical Field

[0001] The invention relates to a texturing method, in particular to a texturing method, a silicon wafer and a solar cell, and belongs to the technical field of crystalline silicon processing. Background Art

[0002] In the solar cell industry, improving the texture quality of silicon wafers is very important to ensure the light absorption efficiency of solar cells. For example, after obtaining a texture structure on the surface of a silicon wafer through a texture treatment, the efficiency of capturing incident light can be improved, surface defects can be improved, and carrier interface recombination can be reduced, thereby improving the conversion efficiency of solar cells.

[0003] In the related technology, wet texturing is usually adopted, that is, the entire silicon wafer is immersed in a corrosive solution, and the texture structure is obtained by indiscriminately corroding the surface. However, on the one hand, it is difficult to accurately control the corrosion depth, texture uniformity and surface defects of the silicon wafer; on the other hand, the wet texturing process will leave an oxide layer on the surface of the silicon wafer, and an additional pickling step is required to remove the residual etching solution, additives and surface oxide layer, which increases the process difficulty and cost. In addition, strict environmental protection measures are required to deal with the harmful waste liquid generated after etching, which further increases the manufacturing cost.

[0004] Therefore, there is an urgent need to improve the existing velvet making method in order to improve the velvet quality, reduce the process difficulty and alleviate environmental pollution. Summary of the invention

[0005] In view of the above-mentioned defects, the present invention provides a texturing method for preparing a velvet structure on the surface of a silicon wafer. Using this method to texturize silicon wafers can accurately control the velvet structure, reduce the complexity of liquid treatment and environmental pollution problems, and the method is simple to operate and easy to achieve mass production in industry.

[0006] The present invention provides a silicon wafer, which is made on the surface of the silicon wafer by the above-mentioned texturing method. The textured surface of the silicon wafer has good quality, low light reflectivity and good light trapping performance.

[0007] The present invention provides a battery, which includes a silicon wafer made by the above-mentioned texturing method or the above-mentioned silicon wafer, the silicon wafer has good light trapping performance, and using the silicon wafer to assemble a battery can improve the light absorption rate of the battery, thereby improving the battery efficiency.

[0008] One aspect of the present invention provides a texturing method, which comprises the following steps:

[0009] Providing a type of solution and a type of gas;

[0010] Performing a two-phase mixing process on the first type of solution and the first type of gas to obtain an initial etchant of a gas-liquid mixed phase;

[0011] Atomizing the initial etchant to obtain an etching spray;

[0012] Using the etching spray to perform etching on the target surface of the silicon wafer to obtain a velvet structure;

[0013] in,

[0014] The first type of solution includes an acidic solution; the first type of gas includes an acidic gas.

[0015] The texturing method as described above, wherein the first type of solution comprises: at least one of a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution;

[0016] The type one gas includes at least one of chlorine gas and bromine gas.

[0017] The texturing method as described above, wherein the mass percentage of the hydrofluoric acid aqueous solution in the first type of solution includes: 45-55wt%;

[0018] The mass percentage of the hydrochloric acid aqueous solution includes: 35wt% to 40wt%.

[0019] The texturing method as described above, wherein in the first type of solution,

[0020] The volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution includes: (4:3) to (3:2).

[0021] In the texturing method as described above, the mass concentration of the first type of gas includes: 2g / L to 4g / L.

[0022] The texturing method as described above, wherein in the etching process,

[0023] Etching temperature includes: 20℃~28℃;

[0024] The etching time ranges from 200s to 400s.

[0025] The texturing method as described above, wherein in the etching process,

[0026] The application flow rate of the etching spray includes: 5L / min to 12L / min;

[0027] The applied pressure of the etching spray includes: 300kPa ~ 800kPa.

[0028] The texturing method as described above, wherein the etching spray is applied by a spray nozzle; wherein,

[0029] The distance between the spray nozzle and the surface of the silicon wafer is 10 cm to 15 cm.

[0030] The present invention also provides a silicon wafer, which adopts the above-mentioned texturing method to prepare a velvet structure on the surface; wherein the velvet structure includes a pyramid structure; the length of the bottom side of the pyramid structure includes: 1um~2um; the formation height of the pyramid structure includes: 2um~3um.

[0031] The present invention further provides a solar cell, wherein the solar cell comprises:

[0032] A substrate, using the silicon wafer as described above; the substrate has two opposite sides;

[0033] 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;

[0034] 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;

[0035] The electrode structure is located on a side of the first functional layer and / or the second functional layer facing away from the substrate.

[0036] The texturing method provided by the present invention etches a silicon wafer by using a type of gas including an acidic solution and a type of gas including an acidic gas to prepare an etching spray, and can utilize the different etching effects of different components in the etching spray on the silicon wafer to achieve accurate etching of the silicon wafer. The etching spray used in the present invention can spray uniform droplets onto the surface of the silicon wafer, which is conducive to the precise control of the etching of the silicon wafer, and can also save reagents on the other hand. The waste gas after use is easy to handle, which is conducive to solving the environmental pollution problem caused by general waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the texturing method in Example 1 of the present invention;

[0038] Figure 2 This is a scanning electron microscope image of the surface of a silicon wafer obtained by using the texturing method provided by the present invention in Example 1 of the present invention;

[0039] Figure 3 This is a scanning electron microscope image of the surface of a silicon wafer produced by general alkali texturing in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The first aspect of the present invention provides a texturing method, comprising the following steps:

[0042] Providing a type of solution and a type of gas;

[0043] Performing a two-phase mixing process on a type of solution and a type of gas to obtain an initial etchant of a gas-liquid mixed phase;

[0044] Atomizing the initial etchant to obtain an etching spray;

[0045] Using an etching spray to perform etching on a target surface of the silicon wafer to obtain a velvet structure;

[0046] in,

[0047] Type 1 solutions include acidic solutions; Type 1 gases include acidic gases.

[0048] The present invention does not limit the type of silicon wafers, and the above-mentioned texturing method can be used to process single-crystal silicon wafers, and can also be used to process multi-crystalline silicon wafers. The present invention does not limit the type of single-crystal silicon wafers, and both N-type single-crystal silicon wafers and P-type single-crystal silicon wafers can be processed using the above-mentioned texturing method.

[0049] The present invention does not limit the shape, size, and thickness of the silicon wafer, and may be selected according to actual needs.

[0050] The present invention does not limit the mixing treatment method, as long as a type of solution and a type of gas can be mixed to form an initial etchant of a gas-liquid mixed phase. For example, a type of solution can be passed into a type of gas, or a type of gas can be passed into a type of solution.

[0051] Among them, the above-mentioned gas-liquid mixed phase is the same system including a type one solution and a type one gas, and the type one solution and the type one gas coexist in the system. The present invention can effectively improve the efficiency of texturing by performing etching treatment on the target surface of the silicon wafer after using the initial etchant of the gas-liquid mixed phase to be atomized. According to the research of the inventor of this case, on the one hand, the addition of type one gas makes the initial etchant of the gas-liquid mixed phase have higher dispersibility and rapid diffusion ability, smaller mass transfer resistance, and the reactant molecules can quickly meet and react; on the other hand, the addition of type one solution makes the initial etchant of the gas-liquid mixed phase have better heat transfer performance, which can effectively manage the heat of the texturing process. In addition, the addition of type one gas disperses the aggregation degree of type one solution, so that type one solution has more specific surface area to react with the silicon wafer, which is conducive to further improving the rate of etching treatment.

[0052] In the above texturing method, the first type of solution includes at least one of a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution; the first type of gas includes at least one of a chlorine gas and a bromine gas. The present invention can effectively texturize the surface of a silicon wafer by using the first type of solution and the first type of gas of the above components.

[0053] As mentioned above, the acidic solution includes at least one of a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution, and the acidic gas includes chlorine gas and bromine gas. For example, the acidic solution can be a hydrofluoric acid aqueous solution or a hydrochloric acid aqueous solution, or a mixed solution of a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution.

[0054] The present invention uses an aqueous solution of hydrofluoric acid as an acidic solution to produce an isotropic corrosion effect to etch a silicon wafer, thereby preparing a silicon wafer with a uniform velvet structure. In the present invention, the silicon wafer reacts with the hydrofluoric acid to generate silicon tetrafluoride (SiF4) and hydrogen (H2). The silicon tetrafluoride is converted into a gaseous state due to a large amount of heat released in the reaction, and after the reaction, it leaves the surface of the silicon wafer to form holes, thereby completing the etching of the silicon wafer.

[0055] The present invention can promote the anisotropic corrosion of the etching reaction and form an inverted pyramid textured velvet structure on the surface of the silicon wafer by using an aqueous hydrochloric acid solution as an acidic solution, so that the reflectivity of the silicon wafer surface is reduced. The inventor speculates that it may be because hydrochloric acid does not react with the silicon wafer, and its main function is to slow down the reaction etching rate, that is, it can act as a "mask". The part covered by hydrochloric acid will not be etched by hydrofluoric acid, and the uncovered part is etched to form an inverted pyramid textured velvet structure. By forming an inverted pyramid velvet structure, the reflectivity of the silicon wafer surface can be further reduced, the light trapping performance of the silicon wafer can be improved, and the battery efficiency can be improved.

[0056] The present invention uses chlorine as an acidic gas, which can generate chlorine free radicals through photolysis and consume hydrogen, thereby accelerating the etching rate of hydrofluoric acid on the silicon wafer. At the same time, chlorine can also react with the silicon wafer to generate silicon tetrachloride, which can react with hydrogen fluoride to generate silicon tetrafluoride, which reacts with hydrofluoric acid to generate hexafluorosilicic acid, which decomposes and releases hydrofluoric acid gas. Therefore, the presence of chlorine can promote the etching effect of the entire system on the silicon wafer. The present invention can also use bromine as an acidic gas, which can also produce an etching effect similar to that of chlorine.

[0057] In addition, the present invention does not limit the method of atomization processing, as long as the initial etchant can be processed into an etching spray, for example, the following methods can be used for atomization: using a pressure nozzle to atomize the initial etchant, using ultrasonic vibration for atomization, using a vibrating diaphragm for vibration atomization, using high-speed airflow for airflow atomization, or heating the liquid phase to form a thermal spray for atomization, or using a nozzle with pores for spray atomization.

[0058] The present invention uses atomization treatment to reduce unnecessary acid liquid usage and can recycle unreacted acid liquid, thereby reducing chemical consumption. At the same time, the waste liquid generated by atomization treatment is less and more concentrated, which is convenient for subsequent treatment or purification and is beneficial to environmental protection. In addition, the use of atomization treatment can also flexibly adjust the composition, concentration and atomization conditions in the initial etchant according to the characteristics and process requirements of different silicon wafers, so as to achieve a better texturing effect.

[0059] Furthermore, the present invention does not limit the manner in which the etching spray is used to etch the silicon wafer. For example, the silicon wafer can be moved so that its surface is covered by the etching spray for etching, or the etching spray can be moved so that it is evenly distributed on the surface of the silicon wafer. The etching spray can cover every corner of the silicon wafer and effectively handle the etching of silicon wafers with complex geometric shapes.

[0060] The present invention uses etching spray to etch the surface of the silicon wafer, and can effectively utilize the different etching effects of the above-mentioned acidic solution and acidic gas on the silicon wafer to accurately control the velvet structure, so as to obtain a silicon wafer with a more uniform surface. In addition, by using a spray method to etch the silicon wafer, the droplets of the etching spray can be evenly distributed on the surface of the silicon wafer, avoiding the uneven etching caused by the local excess of etching solution on the surface of the silicon wafer, thereby forming a more uniform velvet structure on the surface of the silicon wafer. In addition, the use of etching spray can also greatly reduce the amount of reagents used, and only a small amount of etching spray can be used to complete the etching of the silicon wafer, and because the etching spray is in the gas phase, a variety of methods can be used to treat the waste gas, such as adsorption, catalysis, absorption, etc., which greatly reduces the difficulty and cost of treating waste liquid compared to using a solution to etch the silicon wafer, thereby helping to protect the environment.

[0061] In the above-mentioned type 1 solution, the mass percentage of the hydrofluoric acid aqueous solution includes 44-45wt%. Specifically, the mass percentage of the hydrofluoric acid aqueous solution is the mass percentage of the mass of pure hydrofluoric acid in the total mass of the hydrofluoric acid aqueous solution. For example, the mass percentage of hydrofluoric acid includes but is not limited to 45wt%, 48wt%, 50wt%, 52wt%, 55wt% or a range consisting of any two of them.

[0062] In the above-mentioned type 1 solution, the mass percentage of the hydrochloric acid aqueous solution includes 35-40wt%. Specifically, the mass percentage of the hydrochloric acid aqueous solution is the mass percentage of pure hydrochloric acid in the total mass of the hydrochloric acid aqueous solution. For example, the mass percentage of hydrochloric acid includes but is not limited to 35wt%, 36wt%, 37wt%, 38wt%, 39wt% or a range consisting of any two of them.

[0063] In a specific embodiment, the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the first type of solution is (4:3) to (3:2). Specifically, the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution is the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant.

[0064] In a specific embodiment, the mass concentration of the first type of gas includes: 2g / L to 4g / L. Specifically, the mass concentration of the acid gas in the initial etchant is 2 to 4g of acid gas per liter of the initial etchant. For example, the mass concentration of the first type of gas includes but is not limited to 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, or a range consisting of any two of them.

[0065] The present invention can control the degree of etching of the silicon wafer by controlling the concentration of the hydrofluoric acid, hydrochloric acid and type I gas, thereby preparing a silicon wafer with a better velvet structure.

[0066] In a specific embodiment, the etching temperature in the etching process includes: 20°C to 28°C; the etching time includes: 200s to 400s. For example, the etching temperature of the etching process includes but is not limited to 20°C, 23°C, 25°C, 28°C or a range consisting of any two thereof; the etching time of the etching process includes but is not limited to 200s, 250s, 300s, 350s, 400s or a range consisting of any two thereof.

[0067] The present invention controls the etching degree by controlling the temperature and duration of the etching process within the above range, thereby obtaining a silicon wafer with a better velvet structure.

[0068] In a specific embodiment, during the etching process, the applied flow rate of the etching spray is 5 to 12 L / min. For example, the applied flow rate of the etching spray includes but is not limited to 5 L / min, 7 L / min, 9 L / min, 11 L / min, 12 L / min, or a range consisting of any two thereof. The present invention can control the etching degree of the silicon wafer by limiting the flow rate of the etching spray.

[0069] The present invention does not limit the application flow rate of the etching spray, which can be selected according to actual conditions. When the application flow rate of the etching spray is high, the anisotropic etching of the silicon wafer is more obvious. The inventor speculates that the reason may be that when the application flow rate of the etching spray is high, the amount of droplets of the etching spray per unit time is large, and the local silicon wafer that receives more etching spray has a faster etching rate, while the local silicon wafer that receives less etching spray has a slower etching rate, thus producing anisotropic etching phenomenon. For example, the application flow rate can be 0.5 to 1.5 m / s.

[0070] In a specific embodiment, during the etching process, the applied pressure of the etching spray is 300 to 800 kPa. For example, the applied pressure of the etching spray includes but is not limited to 300 kPa, 400 kPa, 500 kPa, 600 kPa, 700 kPa, 800 kPa or a range consisting of any two of them. The present invention can control the rate of the etching reaction by controlling the applied pressure of the etching spray. The greater the applied pressure of the etching spray, the greater the etching rate. The inventor speculates that this may be because when the applied pressure of the etching spray is large, the droplets in the etching spray will be more strongly broken into smaller droplets, and the small droplets have a larger surface area, so the contact area with the workpiece surface is larger, increasing the contact points of the reaction. In addition, a higher spray applied pressure will cause the droplets to hit the surface of the silicon wafer at a higher speed, which can increase the contact opportunity between the droplets and the surface, and can also provide sufficient kinetic energy to destroy the chemical bonds on the surface, thereby accelerating the etching reaction. Therefore, different etching spray applied pressures can be selected according to different requirements for the silicon wafer surface.

[0071] In a specific embodiment, during the etching process, the etching spray is applied by using a spray nozzle; wherein the distance between the spray nozzle and the surface of the silicon wafer is comprised between 10 cm and 15 cm.

[0072] The present invention does not limit the shape, nozzle aperture, and spray angle of the spray nozzle, which can be selected according to actual needs. For example, the aperture of the spray nozzle includes 9 to 15 μm, and the angle formed by the spray nozzle and the silicon wafer includes 60 to 120°. By controlling the aperture of the nozzle and the angle formed by the spray nozzle and the silicon wafer, the size of the droplets in the etching spray and the shape of the droplets after contacting the silicon wafer can be controlled, thereby controlling the uniformity of the etched velvet surface.

[0073] The distance between the spray nozzle and the silicon wafer includes 10 to 15 cm. For example, the distance between the spray nozzle and the silicon wafer includes but is not limited to 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm or a range consisting of any two of them. The present invention can control the rate of the etching reaction by controlling the distance between the spray nozzle and the silicon wafer. The closer the distance between the spray nozzle and the silicon wafer, the faster the etching reaction rate. The inventor speculates that this may be because when the distance between the spray nozzle and the silicon wafer is close, the concentration of the etching spray is higher and the spray can cover the surface of the silicon wafer more densely, increasing the contact area between the etching spray and the surface of the silicon wafer, thereby increasing the rate of the etching reaction. Therefore, the distance between the spray nozzle and the silicon wafer can be adjusted according to different requirements for the silicon wafer surface.

[0074] The second aspect of the present invention provides a silicon wafer, which adopts the above-mentioned texturing method to prepare a velvet structure on the surface; wherein the velvet structure includes a pyramid structure; the length of the bottom side of the pyramid structure includes: 1um~2um; the formation height of the pyramid structure includes: 2um~3um.

[0075] The silicon wafer has low surface reflectivity and good light trapping performance. The present invention adopts the above-mentioned texturing method, on the one hand, can prepare a controllable velvet structure by adjusting the amount of etching spray, the distance between the spray nozzle and the silicon wafer, etc., and on the other hand, it is also beneficial to save reagents and further improve industrial economy.

[0076] It should be clarified that after the surface of the silicon wafer is textured by the above-mentioned texture making method, the textured silicon wafer is also subjected to cleaning, wiping, drying and other operations in sequence. The present invention does not specifically limit the above-mentioned cleaning, wiping and drying processes, as long as a clean silicon wafer with a textured structure without etching spray residue can be obtained.

[0077] The present invention also provides a solar cell, the solar cell comprising

[0078] A substrate, using the above silicon wafer; the substrate has two opposite sides;

[0079] 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;

[0080] 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: form a back surface field of the substrate;

[0081] The electrode structure is located on the side of the first functional layer and / or the second functional layer facing away from the substrate.

[0082] Wherein, the first functional layer and the second functional layer are independently deposited in sequence with an intrinsic passivation layer, a doping layer, a transparent conductive layer and a metal electrode (which can be used).

[0083] Among them, the preparation of the intrinsic passivation layer can be prepared by chemical vapor deposition or physical deposition using at least one compound selected from amorphous silicon, silicon nitride, silicon dioxide, and aluminum oxide; the preparation of the doping layer can use at least one compound selected from phosphorus-doped polycrystalline silicon and boron-doped polycrystalline silicon through chemical vapor deposition or physical deposition; the preparation of the transparent conductive layer can use at least one compound selected from indium tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, and gallium-doped zinc oxide through chemical vapor deposition or physical deposition; the preparation of the metal electrode can use at least one substance selected from silver, copper, aluminum, nickel, and gold through processes such as screen printing and electroplating.

[0084] The cell has good light-harvesting capabilities, so the cell efficiency is high.

[0085] The texturing method provided by the present invention uses an etching spray formed by mixing and atomizing an acidic solution and an acidic gas to texturize the surface of a silicon wafer, which can quickly form a velvet surface structure with an inverted pyramid and a regular pyramid, thereby reducing the reflectivity of the silicon wafer surface and facilitating the improvement of battery efficiency. At the same time, the texturing method has simple steps, easy to control reaction conditions, and is easy to carry out industrial production.

[0086] Hereinafter, the present invention will be further described in detail through specific examples.

[0087] Example 1

[0088] like Figure 1 As shown, the texturing method provided in this embodiment includes the following steps:

[0089] 1) providing a type of solution and a type of gas; the type of solution includes an acidic solution, and the type of gas includes an acidic gas; performing a two-phase mixing process on the type of solution and the type of gas to obtain an initial etchant of a gas-liquid mixed phase;

[0090] Among them, the acidic solution is a hydrofluoric acid aqueous solution with a mass percentage of 50wt% and a hydrochloric acid aqueous solution with a mass percentage of 36wt%, and the acidic gas is chlorine gas with a mass concentration of 3g / L; the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant is 3:2.

[0091] 2) Atomizing the initial etchant to obtain an etching spray.

[0092] 3) etching the target surface of the silicon wafer using an etching spray to obtain a velvet structure;

[0093] The etching temperature of the etching process is 25°C, and the etching time of the etching process is 400s;

[0094] During the etching process, the etching spray application flow rate was 8 L / min;

[0095] During the etching process, the applied pressure of the etching spray was 600 kPa;

[0096] During the etching process, the distance between the spray nozzle and the silicon wafer was 12 cm.

[0097] The surface morphology of the silicon wafer prepared in this embodiment is as follows: Figure 2 As shown by Figure 2 It can be seen that by using the texturing method provided in this embodiment, a relatively uniform velvet structure is formed on the surface of the silicon wafer. The texturing uniformity is calculated using the 9-point test method in the velvet reflectivity uniformity test. The reflectivity uniformity of this embodiment is 2.42%, and a relatively uniform velvet structure is formed on the surface of the silicon wafer.

[0098] Example 2

[0099] The texturing method provided in this embodiment is basically the same as that in Embodiment 1, except that the acidic solution is a hydrofluoric acid aqueous solution with a mass percentage of 55wt% and a hydrochloric acid aqueous solution with a mass percentage of 36wt%, and the acidic gas is chlorine gas with a mass concentration of 3g / L; the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant is 3:2.

[0100] Example 3

[0101] The texturing method provided in this embodiment is basically the same as that in Embodiment 1, except that the acidic solution is a hydrofluoric acid aqueous solution with a mass percentage of 55wt% and a hydrochloric acid aqueous solution with a mass percentage of 38wt%, and the acidic gas is chlorine gas with a mass concentration of 3g / L; the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant is 3:2.

[0102] Example 4

[0103] The texturing method provided in this embodiment is basically the same as that in Embodiment 1, except that the acidic solution is a hydrofluoric acid aqueous solution with a mass percentage of 50wt% and a hydrochloric acid aqueous solution with a mass percentage of 38wt%), and the acidic gas is chlorine gas with a mass concentration of 3g / L; the volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant is 3:2.

[0104] Example 5

[0105] The texturing method provided in this embodiment is basically the same as that in embodiment 1, except that the acidic solution is a hydrofluoric acid aqueous solution with a mass percentage of 50wt% and a hydrochloric acid aqueous solution with a mass percentage of 36wt%, and the acidic gas is a chlorine gas with a mass concentration of 4g / L. The volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution in the initial etchant is 4:3.

[0106] Example 6

[0107] The texturing method provided in this embodiment is basically the same as that in Embodiment 1, except that the hydrochloric acid aqueous solution in the acidic solution is replaced by a sulfuric acid aqueous solution with a mass percentage of 36%.

[0108] Comparative Example 1

[0109] The texturing method provided in this comparative example is basically the same as that in Example 1, except that no acidic gas is added to the initial etchant in this comparative example.

[0110] Comparative Example 2

[0111] In this comparative example, NaOH alkali was used for texturing. The specific experimental steps were as follows: 38L of 4% NaOH solution and 4.8L of 0.5% texturing additive (Hangzhou Xiaochen TS53 series) solution were soaked in 80°C for 10 minutes to obtain a silicon wafer with a velvet structure. The surface morphology of the silicon wafer obtained in this comparative example is as follows: Figure 3 As shown by Figure 3 It can be seen that the velvet produced on the surface of the silicon wafer is not uniform when the silicon wafer is etched by soaking it in a solution containing alkali. The velvet uniformity is calculated using the 9-point test method in the velvet reflectivity uniformity test. The reflectivity uniformity of this comparative example is 4.67%. Therefore, the velvet produced by the alkali velvet method is not uniform.

[0112] Test example

[0113] The surface reflectivity of the silicon wafers prepared in Examples 1-6 and Comparative Examples 1-2 was tested by a D8 surface reflectivity tester. The test results are shown in Table 1.

[0114] Silicon wafers were prepared by combining Examples 1-6 and Comparative Examples 1-2, and intrinsic amorphous silicon passivation films were deposited on both sides of the silicon wafers using CVD. Doped amorphous functional layers were then deposited on both sides. A transparent conductive film was then deposited by double-sided sputtering using PVD. Finally, double-sided silver electrodes were screen-printed to assemble the electrodes into intrinsic thin-film heterogeneous cells. The cell efficiency (eff), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) parameters of the cells were tested using a solar cell IV test system under standard solar illumination AM1.5 with a light intensity of 1000W / m^2. The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] According to the results in the table, compared with Comparative Examples 1-2, Examples 1-6:

[0119] 1. The silicon wafers prepared by the texturing method provided by the present invention in Examples 1-6 have a higher quality velvet structure than that prepared in Comparative Example 1, and the velvet structure has a lower surface reflectivity, thus improving the efficiency of the battery. However, the silicon wafer prepared in Comparative Example 1 has a higher surface reflectivity than the silicon wafers in Examples 1-6, and the battery efficiency is also lower.

[0120] 2. The total amount of reagents used in the acid etching system texturing method used in Examples 1-6 to prepare 100 silicon wafers is about 2L, while the total amount of reagents required in the texturing method containing alkaline solution used in Comparative Example 2 to prepare 100 silicon wafers is 42.8L. Therefore, the present invention can greatly reduce the consumption of reagents in the texturing process, which is conducive to reducing the difficulty of waste liquid treatment, and further conducive to solving the problem of environmental pollution.

[0121] 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 texturing method for preparing a velvet structure on the surface of a silicon wafer, characterized in that: The following steps are involved: Providing a type of solution and a type of gas; Performing a two-phase mixing process on the first type of solution and the first type of gas to obtain an initial etchant of a gas-liquid mixed phase; Atomizing the initial etchant to obtain an etching spray; Using the etching spray to perform etching on the target surface of the silicon wafer to obtain a velvet structure; in, The first type of solution includes an acidic solution; the first type of gas includes an acidic gas.

2. The texturing method according to claim 1, characterized in that: The first type of solution comprises: at least one of a hydrofluoric acid aqueous solution and a hydrochloric acid aqueous solution; The type one gas includes at least one of chlorine gas and bromine gas.

3. The texturing method according to claim 2, characterized in that: In the type 1 solution, The mass percentage of the hydrofluoric acid aqueous solution includes: 45wt% to 55wt%; The mass percentage of the hydrochloric acid aqueous solution includes: 35wt% to 40wt%.

4. The texturing method according to claim 3, characterized in that: In the type 1 solution, The volume ratio of the hydrofluoric acid aqueous solution to the hydrochloric acid aqueous solution includes: (4:3) to (3:2).

5. The texturing method according to any one of claims 1 to 4, characterized in that: The mass concentration of the type 1 gas includes: 2g / L to 4g / L.

6. The texturing method according to any one of claims 1 to 4, characterized in that: During etching process, Etching temperature includes: 20℃~28℃; The etching time ranges from 200s to 400s.

7. The texturing method according to any one of claims 1 to 4, characterized in that: During etching process, The application flow rate of the etching spray includes: 5L / min to 12L / min; The applied pressure of the etching spray includes: 300kPa ~ 800kPa.

8. The texturing method according to claim 7, characterized in that: The etching spray is applied by a spray nozzle; wherein, The distance between the spray nozzle and the surface of the silicon wafer is 10 cm to 15 cm.

9. A silicon wafer, characterized in that: The velvet structure is prepared on the surface by using the velvet making method described in any one of claims 1 to 8; wherein: The velvet structure includes a pyramid structure; The length of the bottom side of the pyramid structure includes: 1um to 2um; The formation height of the pyramid structure includes: 2um to 3um.

10. A solar cell, characterized in that: include: A substrate, comprising the silicon wafer as claimed in claim 9; the substrate having two opposite sides; A first functional layer, 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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