CN205194713U - A silicon chip for solar cell - Google Patents

Abstract

The utility model provides a silicon wafer used for solar cells, which has a textured surface, and the textured surface has a textured structure composed of a plurality of positive pyramid structures, wherein the positive pyramids on the textured surface The distribution density is 10 ⁶ to 10 ⁸ /cm ² to form independent, complete and closely arranged positive pyramid structures ^on the surface of the silicon wafer. The silicon chip used for solar cells of the utility model can form an independent, complete and closely arranged positive pyramid texture texture structure on the surface of the silicon chip at room temperature and in a very short time, and its surface reflectance is between 10% and 25% %, which is not much different from the pyramidal textured structure on the surface of silicon wafers obtained by alkali texturing used in large-scale industrial production. The silicon chip used for the solar cell used in the utility model can reduce the production cost, reduce the reaction temperature, shorten the reaction time and increase the production capacity.

Description

A silicon wafer for solar cells

technical field

The utility model relates to the technical field of solar cell preparation, in particular to a silicon wafer used for solar cells.

Background technique

With the development of society, the demand for energy in all countries in the world has increased sharply, while non-renewable resources such as fossil energy are decreasing day by day, and fossil energy is seriously polluting the environment. As a new type of green renewable energy, solar energy is expected to become one of the main energy sources in the future. At present, crystalline silicon solar cells are one of the effective ways to utilize solar energy, and occupy a mainstream position in the photovoltaic industry. In the photovoltaic industry, solar cells have been developing towards high conversion efficiency and low cost. An important part of improving the conversion efficiency of solar cells is to reduce the reflectivity of incident light and enhance the absorption and utilization of incident light. In industrial production, chemical etching is usually used to texture the surface of silicon wafers and then deposit one or more layers of anti-reflection films to reduce the reflection loss on the surface of silicon wafers. Therefore, texturing the surface of silicon wafers is an integral part of solar cell production.

Texturing is the first process of crystalline silicon cells, also known as "surface texturing". For monocrystalline silicon, its texturing process generally uses lye (sodium hydroxide (NaOH) or potassium hydroxide (KOH)), defoaming organic solvent (which can be isopropanol (IPA) or ethanol, using IPA better effect), texturing additive (Additive) and deionized water, etc. The principle of alkaline texturing is to use alkaline solution to anisotropically corrode single crystal silicon. Alkaline solution has different corrosion rates on the surface of silicon wafers. Corrosion is faster, and finally a pyramid-structured suede is obtained. At present, in large-scale industrial production, the mass percentage concentration of dilute sodium hydroxide or potassium hydroxide solution is generally 0.5% to 3%, the mass percentage concentration of the defoaming organic solvent is 1% to 5%, and the mass percentage concentration of the texturing additive is 0.5%. 0.1% to 1%, the texture temperature is usually controlled at 75°C to 85°C, and the reaction time is 20 minutes to 30 minutes to prepare the textured surface.

In view of the above problems, in order to reduce production costs, reduce reaction temperature, shorten reaction time, and increase production capacity, a new silicon wafer for solar cells is urgently needed.

Utility model content

The purpose of this utility model is to provide a silicon wafer used for solar cells, the silicon wafer has a textured surface composed of a plurality of positive pyramid structures.

The utility model provides a silicon wafer used for solar cells, which has a textured surface, and the textured surface has a textured structure composed of a plurality of positive pyramid structures, wherein the positive pyramids on the textured surface The distribution density is 10 ⁶ to 10 ⁸ /cm ² to form independent, complete and closely arranged positive pyramid structures ^on the surface of the silicon wafer.

Optionally, the base of each of the plurality of regular pyramids is a quadrilateral.

Optionally, the side length of the quadrilateral is 1 μm˜10 μm, and the height of the regular pyramid is 1 μm˜10 μm.

Optionally, the bottom of the regular pyramid is a square.

Optionally, the average reflectance of the textured surface is 10%-25%.

The silicon chip used for solar cells of the utility model can form an independent, complete and closely arranged positive pyramid texture texture structure on the surface of the silicon chip at room temperature and in a very short time, and its surface reflectance is between 10% and 25% %, which is not much different from the pyramidal textured structure on the surface of silicon wafers obtained by alkali texturing used in large-scale industrial production. The silicon chip used for the solar cell used in the utility model can reduce the production cost, reduce the reaction temperature, shorten the reaction time and increase the production capacity.

According to the following detailed description of specific embodiments of the utility model in conjunction with the accompanying drawings, those skilled in the art will be more aware of the above and other objectives, advantages and features of the utility model.

Description of drawings

Hereinafter, some specific embodiments of the present utility model will be described in detail in an exemplary rather than restrictive manner with reference to the accompanying drawings. The same reference numerals in the drawings designate the same or similar parts or parts. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the attached picture:

Fig. 1 is the structural diagram of wherein a regular pyramid structure of the present utility model;

Fig. 2 is the SEM figure of the positive pyramid structure obtained on the textured surface after etching in the utility model embodiment 1;

Fig. 3 is the SEM figure of the positive pyramid structure obtained on the textured surface after etching in the utility model embodiment 2;

Fig. 4 is the SEM figure of the positive pyramid structure obtained in the texture section after etching in the utility model embodiment 2;

Fig. 5 is the SEM figure of the positive pyramid structure obtained on the textured surface after etching in the utility model embodiment 3;

Fig. 6 is the SEM figure of the positive pyramid structure obtained in the texture section after etching in the utility model embodiment 3;

Fig. 7 is the SEM picture of the positive pyramid structure obtained on the textured surface after etching in the utility model embodiment 4;

Fig. 8 is the SEM figure of the positive pyramid structure obtained in the texture section after etching in the utility model embodiment 4;

FIG. 9 shows the surface reflectance of silicon wafers etched in Examples 1, 2, 3, and 4 of the present invention.

detailed description

In order to solve the problems of complex texturing process and high reflectivity of silicon wafers in the prior art, the utility model proposes an acidic texturing liquid for pyramid texturing of silicon wafers. In one embodiment of the present invention, the acidic texturing solution includes: a copper ion source, used to provide copper ions with a concentration of 0.1mmol/L-150.0mmol/L; a fluoride ion source, used to provide a concentration of 0.5 mol/L-10.0mol/L fluoride ion; and an oxidizing agent with a concentration of 0.1mol/L-5.0mol/L, which can oxidize silicon to silicon oxide and copper to copper ion.

By immersing the silicon wafer in the acidic texturing solution, and controlling the concentration of the solution copper ion source, fluorine ion source and oxidizing agent to control the shape and depth of the etching, so that it can be formed on the surface of the silicon wafer at room temperature and in a very short time. Closely arranged positive pyramid structure. The reaction mechanism of this process is: the copper ion source containing Cu ²⁺ in the acidic ^texturing solution mainly plays a catalytic role. At the same time, the oxidant can also oxidize silicon to silicon oxide and copper to copper ions, and the fluorine ion source reacts with the oxidized silicon oxide to achieve etching. However, if there is no oxidizing agent, Cu ²⁺ will always get electrons from silicon and react to form copper particles. As the reaction progresses, it is easy to form a dense copper film on the surface of the silicon wafer, which will hinder the formation of fluorine ions on the silicon wafer. further etching. The utility model makes the excess copper nanoparticles formed on the silicon surface oxidized to form Cu ²⁺ by adding an oxidizing agent, thereby avoiding the formation of a dense copper film on the surface of a silicon chip to hinder the etching process, so the addition of an oxidizing agent can effectively control the metal The precipitation and dissolution of copper nanoparticles can effectively control the etching morphology and shorten the etching time.

The utility model controls the concentration of copper ions in the acidic texturing liquid to 0.1mmol/L-150.0mmol/L, the concentration of fluorine ions to 0.5mol/L-10.0mol/L, and at the same time controls the concentration of the oxidant to 0.1 mol/L～5.0mol/L. Among them, copper ions can obtain electrons from the surface of silicon, oxidize silicon to silicon dioxide, and at the same time be reduced to copper nanoparticles, thereby realizing catalytic etching of silicon wafers. If the concentration of copper ions is low, the precipitation of copper nanoparticles is less, and the silicon surface cannot be etched effectively. As the concentration of copper ions increases, the etching of the silicon wafer increases, and the shape of the regular pyramid on the surface will increase accordingly. The top of the regular pyramid is etched, and a relatively smooth structure is formed at the top. If the concentration of copper ions is further increased, the problem of rapid precipitation of copper nanoparticles will occur, thereby forming a dense film on the surface of the silicon wafer, which hinders the progress of etching.

The main function of fluoride ions in the acidic texturing solution is to etch the silicon dioxide formed by silicon. If the fluoride ion concentration in the acidic texturing solution is too low, the silicon wafer cannot be etched effectively, and a better positive pyramid structure cannot be obtained. If the fluoride ion concentration in the acidic texturing solution is too high, the etching speed will be too fast, and the formed positive pyramid structure will be etched twice to form nanostructures on the surface of the positive pyramid.

The function of the oxidizing agent is mainly to oxidize the excess copper nano-ions to copper ions and oxidize silicon to silicon oxide. If the concentration of the oxidizing agent is too low, there will be too much precipitation of copper nano-ions, resulting in the appearance of a dense copper film, which hinders the engraving process. erosion proceeds. If the oxidant concentration is too high and the reaction is faster, secondary etching will be formed on the top of the formed positive pyramid, and the speed of producing copper nano-ions will be accelerated, thereby reducing the etching rate and failing to obtain a positive pyramid structure.

Generally, silicon wafers prepared by metal-catalyzed chemical etching are nanostructures, which easily form a large number of dead layer structures when preparing solar emitters, resulting in increased surface recombination and Auger recombination, which hinders the improvement of solar cell conversion efficiency. . And although also adopt metal catalyzed etching method in the utility model, because the concentration of etching reagent in the acidic texturizing liquid is creatively selected and controlled in the above-mentioned range, thereby obtained and industrial production adopts alkali texturing gained similar Pyramid structure suede, while effectively inhibiting the appearance of nanostructures. Moreover, the reaction temperature and reaction time are greatly reduced, and the reduction in cost and the increase in production capacity are huge.

In order to obtain a better textured structure, make the positive pyramid volume size of the textured surface more uniform, and reduce the reflectivity of the silicon wafer better, further preferably, in the acidic textured solution, the concentration of copper ions is 2.0mmol/ L～100.0mmol/L, the concentration of fluoride ion is 3.0mol/L～7.0mol/L, and the concentration of oxidant is 0.6mol/L～3.0mol/L.

In a typical embodiment of the present utility model, the copper ion source is selected from one or more of copper chloride, copper sulfate and copper nitrate. In the present invention, the above-mentioned copper ion source is preferred, but not limited thereto, as long as freely moving copper ions can be ionized in the copper ion source.

In a typical embodiment of the present invention, the source of copper ions is copper nitrate, the source of fluoride ions is hydrofluoric acid, and nitric acid or hydrogen peroxide is used as the oxidizing agent. That is, the acidic texturing solution is composed of copper nitrate, hydrofluoric acid and nitric acid or hydrogen peroxide. In a preferred embodiment of the present invention, if nitric acid is used as the oxidizing agent, the concentration of copper nitrate is 8.0mmol/L, the concentration of hydrofluoric acid is 4.8mol/L, and the concentration of nitric acid is 1.2mol/L. If hydrogen peroxide is used as the oxidant, the concentration of copper ions is 60mmol/L, the concentration of fluoride ions is 6.5mol/L, and the concentration of hydrogen peroxide is 1.5mol/L. Using the acidic texturing solution of this preferred embodiment to texture the silicon wafer can obtain a regular pyramid structure with a more uniform volume and size, the surface of the regular pyramid is relatively smooth, and the entire volume of the regular pyramid is relatively complete.

According to another aspect of the present utility model, there is also provided an acidic texturing method for silicon wafer pyramid texturing, comprising the following steps: first preparing any of the above-mentioned acidic texturing liquids, mixing the acidic texturing liquids evenly , not limited to methods such as stirring, bubbling, etc.; then, placing the silicon wafer to be textured in an acidic texturing solution at room temperature, and etching for a predetermined time to obtain a textured silicon wafer.

The silicon chip referred to in the utility model includes single crystal silicon and quasi-single crystal, which can be suitable for both N-type single crystal silicon and P-type single crystal silicon. After the silicon wafer to be textured is placed in the acidic texturing solution, under the combined action of fluoride ions, oxidants and Cu nanoparticles, the etching rate of the Cu nanoparticles on the Si (100) and (111) surfaces is different, which can Anisotropic etching similar to alkali etching is formed on the silicon surface at room temperature and in a short period of time, so that a complete and closely arranged positive pyramid structure is simply and quickly obtained on the silicon surface.

In order to obtain the regular pyramid textured structure of the present invention, in a typical embodiment of the present invention, the temperature of the acidic texturing solution is in the room temperature range of 20° C. to 30° C., and the etching time is 1 minute to 12 minutes. Within the above specific temperature range, mainly at room temperature without external heating or cooling, the surface texture of the obtained silicon wafer is not much different. For the setting of etching time, if the etching time is less than 1 minute, it will not be able to form an effective positive pyramid texture because the etching time is too short. If the etching time is more than 12 minutes, it will damage the prepared positive pyramid. A secondary etch is formed, resulting in nanostructures.

Further preferably, the predetermined temperature is 22° C. to 28° C., and the predetermined time is 3 minutes to 10 minutes. Most preferably, the predetermined etching temperature is 25° C., and the predetermined time is 5 minutes.

Since it is inevitable to leave some organic impurities on the silicon wafer during the process of cutting the silicon wafer, before placing the silicon wafer to be textured in the acidic texturing solution for etching, the silicon wafer is also pre-cleaned and washed with water. A step of. Specifically include: first place the silicon chip in acetone and ethanol for ultrasonic cleaning, then place it in a mixture of sulfuric acid solution and hydrogen peroxide solution and heat to boil. Generally, after heating and boiling, keep it for 0.5 to 1 hour, and then place it in water for ultrasonic cleaning. Wherein, the concentration of the sulfuric acid solution is 70wt.%, and the concentration of the hydrogen peroxide solution is 35wt.%. The volume ratio of sulfuric acid solution to hydrogen peroxide solution is 3:1. The purpose of ultrasonic cleaning with acetone and ethanol is to remove the organic impurities remaining on the silicon wafer, and the purpose of cleaning with a mixture of sulfuric acid solution and hydrogen peroxide solution is to remove metal impurities on the surface of the silicon wafer. Finally, the purpose of ultrasonic cleaning with deionized water is to remove the chemical solution remaining on the surface of the silicon wafer after pre-cleaning. It is of great significance to improve the photoelectric conversion efficiency of the battery through pre-cleaning and water washing.

Considering the factors matching the existing solar cell preparation process, the acidic texturing method provided by the utility model also includes the step of ultrasonically cleaning the texturized silicon wafer in nitric acid or aqua regia to remove the metal covering on the texturized surface. The silicon wafer after removing the metal covering was ultrasonically cleaned with deionized water, and then dried with high-purity nitrogen gas.

Further illustrate the beneficial effect of the utility model below in conjunction with more specific embodiment:

Example 1

1) Surface cleaning steps

Take a P-type silicon wafer with a size of 156cm×156cm (resistivity 1Ω·cm～3Ω·cm), put it in acetone and ultrasonically clean it for 5 minutes, put it in ethanol for 5 minutes, and then place it in sulfuric acid solution and In the mixed liquid of hydrogen peroxide solution (the concentration of sulfuric acid solution is 70wt.%, the concentration of hydrogen peroxide solution is 35wt.%, the volume ratio of sulfuric acid solution and hydrogen peroxide solution is 3:1), heat and boil the silicon chip and keep it for 0.5 hours, and finally Clean it ultrasonically with deionized water.

2) Etching step

Immerse the pre-cleaned and water-washed silicon wafers in step 1) in the acidic texturing solution consisting of copper nitrate, hydrofluoric acid and nitric acid (wherein the concentration of copper nitrate is 8.0mmol/L, and the concentration of hydrofluoric acid is 4.8 mol/L, the concentration of nitric acid is 1.2 mol/L), at room temperature (the temperature range of 20° C. to 30° C. has little difference), etch for 8 minutes.

3) Post-processing stage

Take out the textured silicon wafer in step 2), ultrasonically clean it with nitric acid with a concentration of 69wt.% to remove the metal covered on the surface, then ultrasonically clean it with deionized water, and dry it with high-purity nitrogen to obtain a A silicon substrate with a pyramidal structure. The scanning electron microscope (SEM) image obtained by it has a regular pyramid surface structure, see FIG. 2 . It can be seen that the positive pyramid structure obtained by the acid texturing method of the present invention is independent, complete and tightly arranged, with a size of 1 μm to 10 μm.

Example 2

1) Surface cleaning steps

Take a P-type silicon wafer with a size of 156cm×156cm (resistivity 1Ω·cm～3Ω·cm), put it in acetone and ultrasonically clean it for 5 minutes, put it in ethanol for 5 minutes, and then place it in sulfuric acid solution and In the mixed liquid of hydrogen peroxide solution (the concentration of sulfuric acid solution is 70wt.%, the concentration of hydrogen peroxide solution is 35wt.%, the volume ratio of sulfuric acid solution and hydrogen peroxide solution is 3:1), heat and boil the silicon chip and keep it for 0.5 hours, and finally Clean it ultrasonically with deionized water.

2) Etching step

Immerse the pre-cleaned and water-washed silicon wafers in step 1) in an acidic texturing solution consisting of copper nitrate, hydrofluoric acid and nitric acid (wherein the concentration of copper nitrate is 10mmol/L, and the concentration of hydrofluoric acid is 4.8mol /L, the concentration of nitric acid is 1.2mol/L), at room temperature (the temperature range of 20°C to 30°C has little difference), etch for 5 minutes.

3) Post-processing stage

Take out the textured silicon wafer in step 2), ultrasonically clean it with nitric acid with a concentration of 69wt.% to remove the metal covered on the surface, then ultrasonically clean it with deionized water, and dry it with high-purity nitrogen to obtain a A silicon substrate with a pyramidal structure.

Compared with Example 1, the concentration of copper nitrate and the etching time are different. Since the concentration of copper nitrate in Example 2 increases, the catalytic ability of copper increases, making the reaction faster, so a positive pyramid can be formed in a shorter time. Suede construction. Due to the increased concentration of copper nitrate, secondary etching will be formed on the top of the pyramid when the pyramid is formed (copper nanoparticles will be preferentially deposited at the tip and the kink, so that the reaction can proceed). The SEM image of the surface is shown in Figure 3, and the SEM image of its cross-section is shown in Figure 4. It can be seen that the positive pyramid structures obtained by the acidic texturing method of the present invention are independent and closely arranged, with a size of 1 μm to 10 μm. It can be seen that the height of the regular pyramid is between 1 μm and 5 μm.

Example 3

1) Surface cleaning steps

Take a P-type silicon wafer with a size of 156cm×156cm (resistivity 1Ω·cm～3Ω·cm), put it in acetone and ultrasonically clean it for 5 minutes, put it in ethanol for 5 minutes, and then place it in sulfur solution and In the mixed liquid of hydrogen peroxide solution (the concentration of sulfuric acid solution is 70wt.%, the concentration of hydrogen peroxide solution is 35wt.%, the volume ratio of sulfuric acid solution and hydrogen peroxide solution is 3:1), heat and boil the silicon chip and keep it for 0.5 hours, and finally Clean it ultrasonically with deionized water.

2) Etching step

Immerse the pre-cleaned and water-washed silicon wafers in step 1) in an acidic texturing solution consisting of copper nitrate, hydrofluoric acid and nitric acid (wherein the concentration of copper nitrate is 10mmol/L, and the concentration of hydrofluoric acid is 4.8mol /L, the concentration of nitric acid is 1.8mol/L), at room temperature (the temperature range of 20°C to 30°C has little difference), etch for 5 minutes.

3) Post-processing stage

Take out the textured silicon wafer in step 2), ultrasonically clean it with nitric acid with a concentration of 69wt.% to remove the metal covered on the surface, then ultrasonically clean it with deionized water, and dry it with high-purity nitrogen to obtain a A silicon substrate with a pyramidal structure.

Compared with Example 1, Example 3 has different concentrations of nitric acid and copper nitrate, and different etching times. Because the concentration of nitric acid and copper nitrate in Example 3 increases, the reaction is faster, so the suede structure can be formed in a shorter time. Due to the high concentration of copper nitrate and nitric acid, a secondary etching will be formed on the top of the pyramid when forming the pyramid (copper nanoparticles will be preferentially deposited at the tip and kink, so that the reaction can proceed), and due to the concentration of nitric acid The increase of will increase the ability of the deposited metal copper nanoparticles to oxidize into copper ions, hindering the further deposition of copper particles. Its surface SEM image is shown in FIG. 5 , and its cross-sectional SEM image is shown in FIG. 6 . It can be seen that the positive pyramid structures obtained by the acidic texturing method of the present invention are independent and closely arranged, with a size of 1 μm to 10 μm. It can be seen that the height of the regular pyramid is also 1 μm to 10 μm.

Example 4

1) Surface cleaning steps

Take a P-type silicon wafer with a size of 156cm×156cm (resistivity 1Ω·cm～3Ω·cm), put it in acetone and ultrasonically clean it for 5 minutes, put it in ethanol for 5 minutes, and then place it in sulfur solution and In the mixed liquid of hydrogen peroxide solution (the concentration of sulfuric acid solution is 70wt.%, the concentration of hydrogen peroxide solution is 35wt.%, the volume ratio of sulfuric acid solution and hydrogen peroxide solution is 3:1), heat and boil the silicon chip and keep it for 0.5 hours, and finally Clean it ultrasonically with deionized water.

2) Etching step

Immerse the pre-cleaned and water-washed silicon wafers in step 1) in the acidic texturing solution consisting of copper nitrate, hydrofluoric acid and hydrogen peroxide (wherein the concentration of copper nitrate is 60mmol/L, and the concentration of hydrofluoric acid is 4.8mol /L, the concentration of hydrogen peroxide is 1.5mol/L), at room temperature (the temperature range from 20°C to 30°C has little difference), etch for 5 minutes.

3) Post-processing stage

Take out the textured silicon wafer in step 2), ultrasonically clean it with nitric acid with a concentration of 69wt.% to remove the metal covered on the surface, then ultrasonically clean it with deionized water, and dry it with high-purity nitrogen to obtain a A silicon substrate with a pyramidal structure.

Compared with Example 1, Example 2 and Example 3, the concentration of copper nitrate in Example 4 is different and the oxidizing agent is hydrogen peroxide, and the etching time is also different. Due to the different redox potentials of hydrogen peroxide and nitric acid, the concentration of the acidic texturing solution was adjusted accordingly in specific experiments. The concentration of copper nitrate in Example 4 increases, so that the reaction is faster, so the suede structure can be formed in a shorter time. Its surface SEM image is shown in FIG. 7 , and its cross-sectional SEM image is shown in FIG. 8 . It can be seen that the positive pyramid structures obtained by the acid texturing method of the present invention are independent and closely arranged, with a size of 1 μm to 10 μm. It can be seen that the height of the regular pyramid is also 1 μm to 10 μm.

The utility model adopts a VarianCary5000 total reflection integrating sphere to test the surface reflectance of the above-mentioned samples. As shown in Figure 9. Its average reflectance is between 10% and 16%.

The monocrystalline silicon wafers after texturing in Examples 1-4 were prepared into solar cells by conventional methods, including sequentially performing diffusion junction, phosphorus-silicate glass removal, etching and edge removal, anti-reflection coating coating, electrode preparation, and characteristic testing. . The square resistance of the diffused silicon wafer is 80Ω/sq, and the deposited silicon nitride antireflection film is 80nm. The Uoc, Jsc, _FF , and Eff of the solar cells were measured with a halm tester, and the specific properties are shown in Table 1.

Table 1

As can be seen from Table 1, adopt the technical scheme of the present invention among the embodiment 1-4, by controlling the concentration, etching temperature and time of copper ion salt solution, fluorine-containing ion and nitric acid or hydrogen peroxide in the acidic texturing liquid, The shape and depth of the etching are well controlled, so the textured surface can be etched at room temperature and in a short period of time, so as to obtain an independent, complete and closely arranged positive pyramid structure texture, which is different from conventional Compared with the reflectivity of alkali textured pyramid structure, the time and temperature of texturing process are greatly reduced, which is huge for the reduction of cost and the improvement of production capacity.

Therefore, the acidic texturing liquid and the texturing method of the present invention have the advantages of simple process, low cost, convenient operation and wide application conditions, and can obtain positive pyramid structures on silicon wafers in a very short period of time in one step at room temperature.

So far, those skilled in the art should recognize that, although a number of exemplary embodiments of the present invention have been illustrated and described in detail herein, they can still be used according to the present invention without departing from the spirit and scope of the present invention. The disclosed content of the utility model directly determines or deduces many other variations or modifications that conform to the principle of the utility model. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (5)

1. A silicon wafer for solar cells has a textured surface, characterized in that, the textured surface has a textured structure made of a plurality of positive pyramid structures, wherein the textured surface on the textured surface The distribution density of the pyramids is 10 ⁶ -10 ⁸ /cm ² to form independent, complete and closely arranged regular pyramid structures ^on the surface of the silicon wafer. 2 . The silicon wafer according to claim 1 , wherein the base of each of the plurality of regular pyramids is a quadrilateral. 3 . 3 . The silicon wafer according to claim 2 , wherein the side length of the quadrilateral is 1 μm˜10 μm, and the height of the regular pyramid is 1 μm˜10 μm. 4 . 4. The silicon wafer according to claim 1, wherein the bottom of the regular pyramid is a square. 5. The silicon wafer according to any one of claims 1-4, characterized in that, the average reflectance of the textured surface is 10%-25%.