阅读说明：本技术 适用于太阳能电池的硅片的表面处理方法 (Surface treatment method of silicon wafer suitable for solar cell ) 是由 丁建明 袁地春 崔俊虎 崔钟亨 于 2020-06-29 设计创作，主要内容包括：本发明公开了一种适用于太阳能电池的硅片的表面处理方法,包括以下步骤：对硅片的表面进行激光处理,所述激光处理用于降低所述硅片表面的反射率；对激光处理后的硅片的正面进行刻蚀,所述刻蚀用于去除激光处理后硅片表面产生的熔融硅。本发明的一种适用于太阳能电池的硅片的表面处理方法,该表面处理方法通过激光技术在原硅片表面进行规则的打孔处理,可有效降低表面反射率,且对激光处理后的硅片进行刻蚀以去除硅片表面的复合层,通过刻蚀之后的硅片制备得到的电池片将反射率的优势进一步体现在电学性能上,硅片各项电学性能均有明显提升,在保持低反射的优势下,有效提高太阳能电池的转换效率,具有很好的应用推广前景。(The invention discloses a surface treatment method of a silicon wafer suitable for a solar cell, which comprises the following steps: carrying out laser treatment on the surface of the silicon wafer, wherein the laser treatment is used for reducing the reflectivity of the surface of the silicon wafer; and etching the front surface of the silicon wafer after the laser treatment, wherein the etching is used for removing the molten silicon generated on the surface of the silicon wafer after the laser treatment. According to the surface treatment method for the silicon wafer suitable for the solar cell, regular punching treatment is carried out on the surface of the original silicon wafer through a laser technology, the surface reflectivity can be effectively reduced, the silicon wafer after laser treatment is etched to remove a composite layer on the surface of the silicon wafer, the advantages of the reflectivity of the cell prepared through the etched silicon wafer are further reflected on the electrical performance, all the electrical performances of the silicon wafer are obviously improved, the conversion efficiency of the solar cell is effectively improved under the advantage of low reflection, and the surface treatment method has good application and popularization prospects.)

1. A surface treatment method for a silicon wafer suitable for a solar cell is characterized by comprising the following steps: carrying out laser treatment on the surface of the silicon wafer, wherein the laser treatment is used for reducing the reflectivity of the surface of the silicon wafer; and etching the front surface of the silicon wafer after the laser treatment, wherein the etching is used for removing the molten silicon generated on the surface of the silicon wafer after the laser treatment.

2. The surface treatment method according to claim 1, wherein the laser treatment is to form pits on the surface of the silicon wafer by using laser, and the laser parameters are power of 1-200W, frequency of 100-600 kHz and speed of 0.2-2 m/s.

3. The surface treatment method according to claim 2, wherein the front surface of the silicon wafer comprises a receiving area for receiving light and a grid line area for printing a grid line, and the pits are distributed in the receiving area.

4. The surface treatment method according to claim 3, wherein the pits have a diameter of 10 to 100 μm, a depth of 1 to 20 μm, and a distance between adjacent pits of 0 to 10 μm.

5. The surface treatment method according to claim 4, wherein the pits have a diameter of 20 to 40 μm and a depth of 5 to 15 μm, and adjacent pits are closely connected to each other.

6. The surface treatment method according to claim 1, wherein the etching is etching using a mixed acid solution; the mixed acid solution comprises HNO₃、HF、H₂SO₄。

7. The surface treatment method according to claim 6, wherein HNO is contained in the mixed acid solution₃The solubility of (A) is 500-700 g/L, the solubility of HF is 10-30 g/L, H₂SO₄The concentration of (b) is 60-80 g/L.

8. The surface treatment method according to claim 1, further comprising an acid etching step after etching, wherein the acid etching step is performed by using a mixed acid etching solution to perform front and back surface etching on the etched silicon wafer.

9. The surface treatment method according to claim 8, wherein the mixed acid texturing solution comprises HNO₃And HF; HNO in the mixed acid texturing solution₃The solubility of the fluorine-containing compound is 200-400 g/L, and the solubility of the HF is 50-70 g/L.

10. The surface treatment method according to any one of claims 1 to 9, further comprising a diffusion step for forming a PN junction on the silicon wafer after the acid texturing.

Technical Field

The invention relates to the technical field of solar cells, in particular to a surface treatment method of a silicon wafer suitable for a solar cell.

Background

The solar power generation technology is a new energy technology for converting light into electricity based on a semiconductor photovoltaic effect, and is favored due to the characteristics of cleanness, reproducibility, wide application range and the like, and a solar cell is a core component of the whole power generation system.

The principle of the solar cell is the photovoltaic effect, the output efficiency of the cell is directly influenced by the proportion of incident light, so that the reduction of the reflectivity of the surface of the cell is the most direct method for improving the conversion efficiency of the cell, and the conventional antireflection process is a method for texturing the surface of a silicon wafer through chemical corrosion, but the process is mature at present and basically has no space for further reducing the reflectivity.

Disclosure of Invention

In view of the above, in order to overcome the defects of the prior art, the present invention aims to provide an improved surface treatment method for a silicon wafer suitable for a solar cell, which can not only reduce the reflectivity of the surface of the silicon wafer, but also has high photoelectric conversion efficiency.

In order to achieve the purpose, the invention adopts the following technical scheme:

a surface treatment method of a silicon wafer suitable for a solar cell comprises the following steps:

carrying out laser treatment on the surface of the silicon wafer, wherein the laser treatment is used for reducing the reflectivity of the surface of the silicon wafer;

and etching the front surface of the silicon wafer after the laser treatment, wherein the etching is used for removing the molten silicon generated on the surface of the silicon wafer after the laser treatment.

Regular punching treatment is carried out on the surface of the original silicon wafer through a laser technology, so that the surface reflectivity can be effectively reduced, but a composite layer is generated due to serious recombination caused by molten silicon remaining on the surface after laser treatment. The low reflectivity for a cell sheet treated by laser alone does not lead to high conversion efficiency, since the light reception and conversion is severely affected by the presence of a composite layer of molten silicon. In contrast, the laser-treated silicon wafer is etched to remove the composite layer on the surface of the silicon wafer, the battery piece prepared from the etched silicon wafer further reflects the advantage of reflectivity on electrical properties, and all the electrical properties of the silicon wafer are obviously improved.

According to some preferred embodiments of the invention, the laser treatment is to form pits on the surface of the silicon wafer by using laser, and the laser parameters are power of 1-200W, frequency of 100-600 kHz and speed of 0.2-2 m/s. The reflectivity is reduced by forming pits in the surface of the silicon wafer. In some embodiments, the preferred laser parameters are 100W power, 300kHz frequency, and 1m/s speed.

According to some preferred embodiments of the present invention, the front surface of the silicon wafer includes a receiving area for receiving light and a gate line area for printing a gate line, the pits are distributed in the receiving area, and the pits are regularly distributed. If all areas on the front surface of the silicon wafer are formed into pits by laser, when the height difference between the top and the bottom of each pit is too large, the width and the thickness of a metalized grid line manufactured on the surface of each pit are uneven, so that the metal consumption is increased, the resistance of the grid line is increased, and the current conduction is influenced. Therefore, the invention selects local laser processing on the surface of the silicon chip to form pits at the positions needing to receive light so as to reduce the reflectivity, and simultaneously does not carry out laser processing on the positions on the silicon chip corresponding to the subsequent grid lines needing to be printed, so that the surface of the battery piece obtained by the subsequent preparation of the silicon chip has two textured structures with different depths, the textured structure comprises a large textured area with the pits to ensure the antireflection effect, and the textured area is small so as to be beneficial to forming uniform metalized grid lines.

According to some preferred embodiments of the present invention, the pits have a diameter of 10 to 100 μm, a depth of 1 to 20 μm, and a distance between adjacent pits is 0 to 10 μm.

According to some preferred embodiments of the present invention, the diameter of the pits is 20 to 40 μm, the depth of the pits is 5 to 15 μm, and adjacent pits are tightly connected, i.e. there is no space between the pits, so as to form more pits, further ensuring the reduction and uniformity of the reflectivity. The highest conversion efficiency can be obtained by matching the parameters of the pits with the concentration of the etching solution in the invention.

According to some preferred implementation aspects of the invention, the etching is etching with a mixed acid solution; the mixed acid solution comprises HNO₃、HF、H₂SO₄。

Preferably, the mixed acid solution contains HNO₃The solubility of (A) is 500-700 g/L, the solubility of HF is 10-30 g/L, H₂SO₄The concentration of (b) is 60-80 g/L. In some specific embodiments of the invention, the HNO is in the mixed acid solution₃Has a solubility of 600g/L, HF has a solubility of 20g/L, H₂SO₄The concentration of (2) was 70 g/L.

According to some preferred embodiments of the present invention, the surface treatment method further includes an acid etching step after etching, wherein the acid etching step is to perform front and back etching on the etched silicon wafer by using a mixed acid etching solution.

Preferably, the mixed acid texturing solution comprises HNO₃And HF; HNO in the mixed acid texturing solution₃The solubility of the fluorine-containing compound is 200-400 g/L, and the solubility of the HF is 50-70 g/L. In some embodiments of the invention, the mixed acid texturing solution comprises HNO₃And HF, wherein, HNO₃Has a solubility of 300g/L and a solubility of 60g/L for HF.

The laser parameters, the pit parameters, the mixed acid etching solution and the mixed acid texturing solution are matched with each other to achieve the best effect, and the battery piece obtained by subsequent preparation can obtain the optimal conversion efficiency.

According to some preferred embodiment aspects of the present invention, the surface treatment method further includes a diffusion step after the acid texturing, the diffusion step being for forming a PN junction on the silicon wafer. The specific operation in the diffusion step is a conventional technical means in the field, but in the invention, the original silicon wafer is firstly subjected to laser treatment to reduce the reflectivity of the silicon wafer, then the composite layer of the silicon wafer is removed by etching, and then the silicon wafer is subjected to texturing by using mixed acid and diffusion after the treatment steps. The method has the advantages that after the silicon wafer is subjected to laser treatment, the reflectivity of the surface is obviously reduced, then the composite layer is removed through etching, the residual molten silicon on the surface of the silicon wafer after laser can be effectively removed, then texturing and diffusion are carried out, through the sequence of the steps, the reflectivity of the surface of the silicon wafer can be effectively reduced, and various electrical properties of the battery piece obtained through subsequent preparation can be effectively improved.

A preparation method of a solar cell comprises the surface treatment method of the silicon wafer suitable for the solar cell and subsequent conventional treatment steps such as etching, removing junctions, polishing, depositing, coating, silk-screen printing, sintering and the like.

Compared with the prior art, the invention has the advantages that: according to the surface treatment method for the silicon wafer suitable for the solar cell, provided by the invention, regular pit-making treatment is carried out on the surface of the original silicon wafer through a laser technology, so that the surface reflectivity can be effectively reduced, the silicon wafer after laser treatment is etched to remove a composite layer on the surface of the silicon wafer, the advantages of the reflectivity are further reflected on the electrical properties of the cell prepared through the etched silicon wafer, all the electrical properties of the silicon wafer are obviously improved, the conversion efficiency of the solar cell is effectively improved under the advantage of low reflection, and the surface treatment method has a good application and popularization prospect.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a block flow diagram of a method for surface treatment of a silicon wafer suitable for use in a solar cell according to a preferred embodiment of the present invention;

FIG. 2 is a scanning electron microscope image of the front side of a silicon wafer after laser treatment;

FIG. 3 is a scanning electron microscope image of a silicon wafer after laser processing according to a preferred embodiment of the present invention;

FIG. 4 is a scanning electron microscope image of an etched silicon wafer after texturing in a preferred embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not a whole embodiment. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.