CN105845785B - A kind of method for preparing crystal silicon nanostructured anti-reflection layer - Google Patents

Abstract

The invention proposes a method for preparing an anti-reflection layer by chemically etching a silicon substrate under the condition of energization. The method of the invention can conveniently prepare the crystalline silicon anti-reflection layer on the p-type silicon substrate with low resistivity, and the preparation cost is low. The size and structure of the anti-reflection layer obtained by the method of the present invention is relatively large, the anti-reflection effect is obvious, the surface composite is small, and the compatibility with the existing industrial production process is good. After the solar cell is made, the conversion efficiency of the cell can be improved About 0.2%.

Description

A method for preparing crystalline silicon nanostructure anti-reflection layer

technical field

The invention relates to the field of semiconductors, in particular to a method for preparing a crystalline silicon nanostructure anti-reflection layer.

Background technique

At present, in the production process of solar cells, the textured structure on the surface of silicon wafers can effectively reduce the surface reflectance of solar cells, which is one of the important factors affecting the photoelectric conversion efficiency of solar cells. In order to obtain a good textured structure on the surface of crystalline silicon solar cells to achieve a better anti-reflection effect, many methods have been tried, including mechanical grooving, laser etching, and reactive ion etching (RIE). , chemical etching (ie wet etching), etc. Among them, the mechanical groove method can obtain lower surface reflectivity, but this method causes serious mechanical damage to the surface of the silicon wafer, and its yield is relatively low, so it is rarely used in industrial production. For the laser etching method, lasers are used to make different groove patterns. Striped and inverted pyramid-shaped surfaces have been produced. The reflectivity can be as low as 8.3%, but the efficiency of the cells made by it is relatively high. Low and cannot be effectively used in production. The RIE method can use different templates for etching. The etching is generally dry etching, and the so-called "black silicon" structure can be formed on the surface of the silicon wafer, and its reflectivity can be as low as 7.9%, or even 4%. However, due to expensive equipment and high production costs, it is less used in industrial production. The chemical etching method has the characteristics of simple process, low cost and high quality, and good compatibility with existing processes, and has become the most used method in the existing industry. However, the reflectivity of the suede surface obtained by conventional alkali texturing is usually above 10%. There is still room for further reduction.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the existing chemical etching technology on the silicon substrate, and propose a method for preparing the anti-reflection layer by chemically etching the silicon substrate under the condition of energization. The method of the invention can conveniently prepare the crystalline silicon nanostructure anti-reflection layer on the p-type silicon substrate with low resistivity, and the preparation cost is low.

The preparation method of the present invention is as follows:

Select a low-resistivity p-type silicon substrate, immerse it in a solution containing oxidants and silver ions for galvanic corrosion, and adjust the process parameters of each step to obtain anti-reflection of crystalline silicon nanostructures with a microstructure of hundreds of nanometers to microns Floor;

Specifically, the low resistivity means that the resistivity of the p-type silicon substrate is less than 5Ω·cm. The corrosion solution contains hydrofluoric acid, silver nitrate, hydrogen peroxide and deionized water, the concentrations of which are respectively HF=0.5mol/L, AgNO ₃ =1*10 ^-4 mol/L, H ₂ O ₂ =3mol/L . The ratio of the above various solutions can be adjusted according to the size of the desired anti-reflection structure

The method for preparing the crystalline silicon nanostructure anti-reflection layer is characterized in that the galvanic corrosion is to apply a uniform electric field on the front surface of the crystalline silicon, the back surface of the crystalline silicon does not contact the above-mentioned etching solution, and the current density of the galvanic corrosion is: 30mA/cm ² , the galvanic corrosion time is 30 minutes. The size and corrosion time of the aforementioned energized current can also be adjusted according to the desired size and depth of the anti-reflection structure.

Through the method of the present invention, relatively regular silicon holes can be obtained on the p-type silicon substrate with low resistivity. The silicon holes have a large inverted pyramid structure at the top and a small bottom at the bottom, and have a good light-trapping effect. This is an additional The result of the synergistic effect of electric field and metal particle catalysis. If only an external electric field is used for galvanic corrosion, porous silicon can only be formed on the surface of the silicon substrate with low resistivity, the silicon pores are small in size and shallow in depth, and the anti-reflection effect is not good. If only the metal particles are catalyzed to corrode in the corrosion solution without an external electric field, silicon nanowires can only be placed on the surface of such a silicon substrate, which has good anti-reflection effect, but the surface recombination is serious, which is not conducive to the preparation of solar cells. In the present invention, a small amount of silver ions are added to the corrosion solution for galvanic corrosion. During the reaction process, the silver ions are continuously nucleated and precipitated on the surface of the corroded porous silicon, and then a plurality of tiny electrodes are formed to catalyze the corrosion reaction, thereby forming a better The anti-reflection structure has a reflectivity below 10%. The anti-reflection layer obtained by the method of the present invention has a large size and structure, obvious anti-reflection effect, small surface recombination, and good compatibility with the existing industrial production process. After the solar cell is made, the conversion efficiency of the cell can be improved About 0.2%. Therefore, the present invention provides an effective method for obtaining a crystalline silicon nanostructure anti-reflection layer on a low-resistivity p-type silicon substrate.

Description of drawings

Fig. 1 is the front SEM figure of the anti-reflection layer structure prepared by the embodiment of the present invention, Fig. 2 is the cross-sectional SEM figure of the anti-reflection layer prepared by the embodiment of the present invention, Fig. 3 is the embodiment of the present invention and only galvanic corrosion ( Corrosion solution does not contain silver ions) reflectance spectrum comparison chart.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the technical scheme is further described as follows:

Select a p-type silicon substrate with low resistivity, and immerse it in a solution containing oxidant and silver ions for galvanic corrosion. Specifically, the low resistivity means that the resistivity of the p-type silicon substrate is less than 5Ω cm. The corrosion solution contains hydrofluoric acid, silver nitrate, hydrogen peroxide and deionized water, the concentrations of which are respectively HF=0.5mol/L, AgNO ₃ =1*10 ^{- 4} mol/L, H ₂ O ₂ =3mol/L . The galvanic corrosion is to apply a uniform electric field on the front surface of the crystalline silicon, the back surface of the crystalline silicon is not in contact with the above-mentioned etching solution, the current density of the galvanic corrosion is 30mA/cm ² , and the time of the galvanic corrosion is 30 minutes. The reflectance of the prepared anti-reflection layer is lower than 10% in all visible light bands, and the reflectance in short wavelength bands and long wavelength bands is even lower. Fig. 3 is the reflectance that the sample is tested under the wavelength of 300-1200nm, as can be seen from this figure, the embodiment of the present invention compares with the reflectance spectrum that only carries out electrification corrosion (does not contain silver ion in the corrosion solution), at full wavelength The segmental reflectance is significantly reduced. After it is made into a solar cell by the traditional method, the conversion efficiency of the cell sheet can be increased by about 0.2%.

Claims (1)

1. A method for preparing crystalline silicon nanostructure anti-reflection layer, is characterized in that, selects the p-type silicon substrate of low resistivity, immerses it in the solution that contains oxidizer and silver ion and carries out galvanic corrosion, by adjusting each step Process parameters, to obtain a crystalline silicon nanostructure anti-reflection layer with a microstructure of hundreds of nanometers to microns; wherein, the low resistivity means that the resistivity of the p-type silicon substrate is less than 5Ω·cm, and the corrosion The solution contains hydrofluoric acid, silver nitrate, hydrogen peroxide and deionized water, the concentrations of which are HF=0.5mol/L, AgNO ₃ =1*10-4mol/L, H ₂ O ₂ =3mol/L; The galvanic corrosion is to apply a uniform electric field on the front surface of the crystalline silicon, the back surface of the crystalline silicon is not in contact with the etching solution, the current density of the galvanic corrosion is 30mA/cm ² , and the time of the galvanic corrosion is 30 minutes. By this method , Obtain regular silicon holes on a low-resistivity p-type silicon substrate, and the silicon holes have an inverted pyramid structure with a large upper part and a smaller lower part.