CN101540351B - A method of etching textured surface on the surface of monocrystalline silicon solar cell - Google Patents

Abstract

The invention relates to a method for etching the textured surface on the surface of a monocrystalline silicon solar cell, using sodium hypochlorite solution to corrode and etch the textured surface on the surface of a monocrystalline silicon solar cell, wherein the sodium hypochlorite content of the etching solution is 8-15 wt%, and the texture is produced The content of sodium hypochlorite and ethanol in the liquid is: sodium hypochlorite 5wt%, ethanol 10vl%. The suede on the surface of the obtained silicon wafer is a pyramid structure with moderate particle size and uniform distribution, which increases the absorption area of sunlight and reduces the reflectivity of the surface of the solar cell. The invention has simple process, does not need to add other auxiliary equipment, and can be widely used in the surface treatment of monocrystalline silicon solar cells.

Description

A method of etching textured surface on the surface of monocrystalline silicon solar cell

technical field

The process of the invention relates to a method for etching textured surfaces on the surface of monocrystalline silicon solar cells, which can be widely used in the surface etching treatment of monocrystalline silicon solar cells and belongs to the technical field of chemical etching.

Background technique

Due to the limited reserves of traditional coal, petroleum and other fossil energy sources, and the serious pollution of the environment during use, the global annual CO ₂ emission exceeds 50 billion tons, seriously restricting the sustainable development of the world economy. Solar energy has the "infinity" of reserves, inexhaustible and inexhaustible. As a main form of solar energy utilization, solar cells have become a hotspot in the research of renewable energy. Among them, the production technology of monocrystalline silicon solar cells is the most mature, and the conversion efficiency is the highest, but due to its high cost, the price is still difficult to compete with coal power, oil power, etc. Therefore, how to reduce the production cost of solar cells and increase their energy Conversion efficiency has become a common goal of solar energy researchers.

In order to increase light absorption on the surface of solar cells, suede production becomes a key step. Utilizing the principle of anisotropic etching of the alkaline solution on the surface of the silicon wafer, that is, the etching rate on the <100> plane of crystalline silicon is much higher than that on the <110> plane and the <111> plane, and a certain corrosion rate can be obtained on the silicon wafer surface. A suede structure. At present, in the industrial production of monocrystalline silicon solar cells, the commonly used texturing liquid is mainly a mixed solution of NaOH (KOH) and IPA (ethanol, isopropanol, etc.), and NaCO ₃ is also used as texturing liquid, and NaHCO ₃ Instead of IPA as the buffer, in addition, there are studies using K ₂ CO ₃ , CH ₃ COONa, etc. as the texturing solution. But there are many problems in adopting these texturing solutions: (1) the pyramidal particles obtained on the silicon chip surface after texturing are too large, about 10 μm; (2) IPA is expensive, highly volatile, and high in production cost; (3) ) The reflectivity of the surface of the silicon wafer is still high after texturing; (4) Although the price of the carbonic acid solution is relatively cheap, it is very easy to crystallize. Therefore, looking for a better and cheaper texturing solution has become an important topic for many solar cell researchers.

Contents of the invention

The purpose of the present invention is to provide a method for etching the textured surface on the surface of a monocrystalline silicon solar cell, using the texturing liquid to obtain a uniformly divided textured surface structure on the surface of a single crystal silicon wafer, and the pyramid particle size is moderate, within 1- Between 4μm, the most important thing is to get a lower reflectivity on the surface of the silicon wafer, which increases the absorption of light. The preparation method of the texturizing liquid is simple, and the process is stable and easy to control.

The invention provides a method for etching the textured surface on the surface of a monocrystalline silicon solar cell. The sodium hypochlorite solution is used to corrode the surface and make texture on the surface of a monocrystalline silicon solar cell. The process steps are:

① Put the silicon wafer into the etching solution to remove the damaged layer on the surface. The content of sodium hypochlorite in the etching solution is 8-15wt%, the temperature is controlled at 85±1°C, and the reaction time is 20-30 minutes;

② Texture the corroded silicon wafer. The texturing solution is composed of sodium hypochlorite, ethanol and deionized water, wherein the content of sodium hypochlorite is: 5wt%, the content of ethanol is: 10vl%, the temperature is controlled at 80±1°C, the reaction time 5-15 minutes.

③ Finally, the textured silicon wafer is washed with deionized water and dried to obtain a uniform textured structure on the surface of the monocrystalline silicon solar cell, and the pyramid particle size is moderate, between 1-4 μm.

The optimal content of sodium hypochlorite in the corrosive solution of the present invention is 15 wt%.

The optimum reaction time for corroding silicon wafers for texturing in the present invention is 15 minutes.

The invention uses unique chemical reagents to rationally configure the components of the texturing liquid. The active chlorine contained in sodium hypochlorite has a strong oxidizing property. While increasing the reaction rate and shortening the working hours, it can also remove the organic pollutants and metal impurity ions remaining on the surface of the silicon wafer. The textured pyramids on the surface of silicon wafers obtained by using the etching solution and texturing solution of the present invention are moderate in size (all below 4 μm), evenly distributed, and have good coverage, which increases the absorption area of sunlight and reduces the surface area of solar cells. reflectivity. The reflectance measurement carried out by spectrophotometer shows that the reflectivity of the silicon chip surface after using the corrosion solution of the present invention and the texturing solution is all lower than the silicon chip surface obtained by conventional methods in most of the wave bands of visible light and infrared. The method can be used to prepare high-quality monocrystalline silicon solar cell texture.

The salient features of the technical solution of the present invention are mainly manifested in:

1. the present invention has utilized a kind of novel chemical reagent sodium hypochlorite as the suede-making liquid, and ethanol is used as the buffer solution, has guaranteed that the size of the suede pyramid particle can all be in an ideal range (1-4 μ m), and arranges tightly, coverage rate high.

②Using the texturing liquid can generate a uniformly distributed pyramid structure on the surface of the solar cell, increasing the absorption area of sunlight, thereby reducing the reflection loss of sunlight.

③ The reflectance of the textured surface prepared on the silicon wafer surface by this texturing solution is lower than that of the textured surface prepared on the silicon wafer surface by conventional methods.

④ Sodium hypochlorite is the main component of industrial bleach, its production process is quite mature, and its price is very cheap.

Description of drawings:

Fig. 1: use the scanning electron micrograph (10000 *) of the suede structure on the silicon chip surface of the present invention.

Fig. 2: Scanning electron micrograph (2500×) of the suede structure on the silicon wafer surface of the mixed solution of NaOH+ethanol by conventional method.

Fig. 3: Comparison of the reflectance of the textured structure on the surface of the silicon wafer of the present invention and the reflectance of the textured structure on the silicon surface obtained by conventional methods.

Detailed ways:

Below in conjunction with accompanying drawing, technical solution of the present invention is described further:

Example 1

Clean the P-type <100> crystal plane Czochralski single crystal silicon wafer with a resistivity of 1Ωcm by conventional methods, and then put the silicon wafer into a sodium hypochlorite (NaClO) solution with a temperature of 85±1°C and a concentration of 10wt% for etching 25 minutes to remove the silicon surface damage layer. Then put the corroded silicon chip into 80±1°C texturing solution (sodium hypochlorite 5wt%, ethanol 10vl%), react for 5-10 minutes, take out the silicon chip, clean it with deionized water, and dry it.

Example 2

According to the method of Example 1, the silicon wafer was put into the etching solution to remove the damaged surface layer. The proportion of the etching solution was 15 wt% sodium hypochlorite, the temperature was controlled at 85±1° C., and the reaction time was 30 minutes. The corroded silicon chip is put into the texturing solution composed of 5wt% sodium hypochlorite, 10vl% ethanol and deionized water. The reaction time is 15 minutes, and the temperature is controlled at 80±1°C. Finally, the wafers were rinsed with deionized water and dried. As shown in Figure 1, under the scanning electron microscope, it can be seen that a dense pyramid structure is formed on the surface of the silicon wafer. The size of the pyramid particles is about 1-4 μm, and the distribution is uniform and the coverage is high.

Embodiment 3 (comparative example)

This scheme uses a conventional corrosion solution, its components are: sodium hydroxide, ethanol and deionized water, the respective percentages are NaOH2wt%, CH3COOH 10vl%. Clean the P-type <100> crystal plane Czochralski silicon wafer with a resistivity of 1Ωcm by conventional methods, and then put it into a sodium hydroxide (NaOH) solution with a temperature of 85±1°C and a concentration of 15wt% for 10 minutes to remove the surface damage layer. Then put the corroded silicon chip into the prepared etching solution, texture it at 80±1°C for 15 minutes, take out the textured silicon chip, wash it with deionized water, and dry it. As shown in Figure 2, it can be seen under the scanning electron microscope that the pyramid structure formed on the surface of the silicon wafer is relatively large in shape.

The main technical performance indicators of the texturing reagent of the present invention are shown in Table 1.

Table 1

Test items Example 1 Example 1 Example 2 Embodiment 3 Comparative example Pyramid base length 0.8-1.5μm 1.2-2.5μm 2.0-4.0μm 8-10μm Pyramid distribution uneven, messy uneven, messy uniform, tidy uniform, regular time 5 minutes 10 minutes 15 minutes 15 minutes

Claims (3)

1. the method for an etching matte on the monocrystaline silicon solar cell surface is characterized in that adopting the liquor natrii hypochloritis to corrode and making herbs into wool on the monocrystaline silicon solar cell surface, and processing step is:

1. silicon chip is put in the corrosive liquid, removed surface damage layer, the content of clorox is 8-15wt% in the corrosive liquid, and temperature is controlled at 85 ± 1 ℃, and the reaction time is 20-30 minute;

2. will corrode good silicon chip and carry out making herbs into wool, Woolen-making liquid is made up of clorox, ethanol and deionized water, and wherein clorox content is: 5wt%, and ethanol content is: 10vl%, temperature is controlled at 80 ± 1 ℃, reaction time 5-15 minute;

3. last with the silicon chip washed with de-ionized water after the making herbs into wool, drying obtains single crystal silicon solar cell surface suede structure uniformly, and matte pyramid granular size is moderate, and matte pyramid bottom side length is between 1-4 μ m.

2. according to claim 1 on the monocrystaline silicon solar cell surface method of etching matte, the content that it is characterized in that clorox in the corrosive liquid is 15wt%.

3. according to claim 1 on the monocrystaline silicon solar cell surface method of etching matte, the reaction time that it is characterized in that the silicon chip after the corrosion is carried out making herbs into wool is 15 minutes.

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