CN105040108B - The etching method of polysilicon solar cell - Google Patents

Abstract

A texturing method for polycrystalline silicon solar cells, the texturing aqueous solution includes: 5-20% hydrofluoric acid, 25-55% nitric acid, 0.5-5% silicofluoric acid, 0.1-0.5% acetic acid, 0.5-1.5% additives, and Measure water; additives are: polyvinyl alcohol 0.2-0.8%, triethanolamine 0.1-6%, hydrolyzed polymaleic anhydride 1-6%, polyvinylpyrrolidone 0.05-0.1%, balance water: texturing aqueous solution temperature 0-30 ℃, put the silicon chip in the aqueous solution for 100-300s, and perform ultrasonic vibration at the same time, the ultrasonic frequency is 40-60KHZ; take it out and wash it with 0.2-0.5% sodium hydroxide and 0.5-2% sodium dodecylbenzenesulfonate Wash in liquid, remove and blow dry. It has the advantages of good stability, easy temperature control, good light trapping effect on the polysilicon surface, high photoelectric conversion rate of the battery, uniform suede surface and low reflectivity.

Description

Texturing method for polycrystalline silicon solar cells

technical field

The invention relates to the technical field of solar cell preparation methods, in particular to a texturing method for polycrystalline silicon solar cells.

Background technique

Polycrystalline silicon is when molten elemental silicon is solidified under supercooled conditions, silicon atoms are arranged in the form of diamond lattices to form many crystal nuclei, and if these crystal nuclei grow into crystal grains with different crystal plane orientations, these crystal grains combine to form crystallization into polysilicon. Polycrystalline silicon cannot be etched with alkali like monocrystalline silicon due to the different crystal orientations of each grain; in order to obtain a good polycrystalline silicon texture, there are currently many methods, such as reactive ion etching, mechanical grooving and chemical etching. . Among them, the chemical corrosion method has been widely used in industrial production due to its convenient operation and strong repeatability. The principle is as follows: mainly adopts the acid velvet process, the system mainly includes nitric acid and hydrofluoric acid, the specific reaction equation is as follows:

_3Si +4HNO3——3SiO2 ₊ 2H2O ₊ 4NO

SiO ₂ +6HF——H ₂ (SiF ₆ )+2H ₂ O

Among them, nitric acid acts as a strong oxidizing agent, nourishes silicon into dense water-insoluble silicon dioxide and adheres to the surface of silicon wafers, preventing further reaction between nitric acid and silicon, but silicon dioxide can react with hydrofluoric acid in the solution, and the production can be The water-soluble complex H2 (SiF6) leads to the destruction of silicon dioxide. At this time, the chemical reaction between nitric acid and silicon occurs again, and the surface of the silicon wafer is continuously corroded, finally forming a continuous and dense "wormhole-like" structure. Although this method does not require specific reaction equipment, the process is relatively simple, and the manufacturing cost is low, but because this method is a pure chemical reaction, the reaction speed of the acid on the silicon wafer is fast, the stability is not easy to control, and the temperature of the reaction also affects the silicon wafer. The key factor of the texturing effect, if the control is not good, the light trapping effect on the polysilicon surface and the photoelectric conversion rate of the battery will be low, the texture of the battery will be uneven, and the reflectivity will be high.

Contents of the invention

The present invention aims at the above-mentioned deficiencies of the prior art, and provides a method for making texture of a polycrystalline silicon solar cell with good stability, easy temperature control, good light trapping effect on the surface of polycrystalline silicon, high photoelectric conversion rate of the battery, uniform textured surface and low reflectivity .

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a method for making texture of a polycrystalline silicon solar cell, the steps comprising:

(1) First, prepare the aqueous solution for velvet making in the velvet making tank, and the preparation raw materials include: 5-20wt% hydrofluoric acid, 25-55wt% nitric acid, 0.5-5wt% silicofluoric acid, 0.1-0.5wt% acetic acid, and 0.5-5% additives. 1.5wt%, the balance is water; mix and stir the above-mentioned components;

The additives are composed of: polyvinyl alcohol 0.2-0.8wt%, triethanolamine 0.1-6wt%, hydrolyzed polymaleic anhydride 1-6wt%, polyvinylpyrrolidone 0.05-0.1wt%, and the balance is water:

(2) Maintain the temperature of the texturing aqueous solution in step (1) at 0-30°C, then place the polysilicon wafer in the above-mentioned aqueous solution for 100-300s, and perform ultrasonic vibration at the same time, with an ultrasonic frequency of 40-60KHZ; then take it out and place it in the 0.2-0.5 wt% of sodium hydroxide, 0.5-2 wt% of sodium dodecylbenzenesulfonate, and the rest in a cleaning solution composed of water for cleaning, taking out and blowing dry.

As a preference, the velvet-making aqueous solution is prepared in the velvet-making tank, and the preparation raw materials include: hydrofluoric acid 10-15wt%, nitric acid 25-45wt%, silicofluoric acid 0.5-1.5wt%, acetic acid 0.1-0.2wt%, additives 0.5-1.0wt%, the balance is water.

Preferably, the additive composition is: 0.2-0.5% of polyvinyl alcohol, 0.1-0.8% of triethanolamine, 1-2% of hydrolyzed polymaleic anhydride, 0.05-0.08% of polyvinylpyrrolidone, and the balance is water.

Advantages and excellent effects of the present invention:

1. In the above-mentioned preparation process of the present invention, fluorosilicic acid and acetic acid are added in traditional hydrofluoric acid and nitric acid texturizing liquid, both of which can play the role of corrosion inhibitor, reducing the rapid damage of hydrofluoric acid to the polycrystalline surface. Corrosion, thereby increasing the stability and controllability of the texturing liquid; especially the addition of acetic acid reduces the overall concentration of the mixed solution, thereby reducing the corrosion rate, and at the same time reduces the surface tension of the polysilicon wafer, which is beneficial to the air bubbles attached to the surface of the polysilicon Detachment, so that the texturing liquid can fully and evenly contact the surface of the polysilicon wafer, and improve the texturing effect and uniformity. In addition, ultrasonic vibration is used in the texturing process, which can also remove the air bubbles attached to the polysilicon surface during the texturing process, prevent the surface from being covered, achieve uniform corrosion at all corners, and prepare a better textured surface. In addition, the present invention also adds additives to the suede liquid, so that the prepared suede has regularity, low reflectivity and controllable reaction process.

2. The cleaning solution after texture making of the present invention has the advantages of being able to effectively remove impurities, having good surface cleaning consistency and low reflectivity.

Description of drawings

Fig. 1 is a microscopic view of the textured silicon wafer prepared in Example 1 of the present invention.

Fig. 2 is a microscopic view of the textured silicon wafer prepared in Example 2 of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the examples, but not limited thereto.

The silicon wafer used in the embodiment is a commercially available polycrystalline silicon wafer with a size of 2×2 cm, a thickness of 180-200 microns, and a resistivity of 0.5-1.5 Ω·cm.

Example 1

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a method for making texture of a polycrystalline silicon solar cell, the steps comprising:

(1) Firstly, prepare the aqueous solution of velvet in the velvet-making tank, and the preparation raw materials include: 5wt% hydrofluoric acid, 25wt% nitric acid, 0.5wt% silicofluoric acid, 0.1wt% acetic acid, 0.5wt% additive, and the balance is water; Mix the above components and stir evenly;

The additives are composed of: 0.5% polyvinyl alcohol, 0.2% triethanolamine, 3% hydrolyzed polymaleic anhydride, 0.06% polyvinylpyrrolidone, and the balance is water:

(2) Maintain the temperature of the texturing aqueous solution in step (1) at 15°C, then place the polysilicon sheet in the aqueous solution for 120s, and simultaneously perform ultrasonic vibration at an ultrasonic frequency of 40KHZ; then take it out and place it in 0.3% sodium hydroxide, Sodium dodecylbenzene sulfonate 0.8%, the rest is water in the cleaning solution for cleaning, take it out and blow dry.

As shown in Fig. 1, the suede surface prepared by the embodiment of the present invention has uniform, small and relatively uniform suede surface size.

Example 2

The other steps are the same as in Example 1, the difference is that: the velvet-making aqueous solution is prepared in the velvet-making tank, and the preparation raw materials include: 10wt% hydrofluoric acid, 45wt% nitric acid, 1.5wt% silicofluoric acid, 0.2wt% acetic acid, additives 1.0 wt%, and the balance is water.

The additive is composed of: 0.5% of polyvinyl alcohol, 0.7% of triethanolamine, 1.5% of hydrolyzed polymaleic anhydride, 0.07% of polyvinylpyrrolidone, and the balance is water.

As shown in Fig. 2, the suede surface prepared in the embodiment of the present invention has uniform, small and relatively uniform suede surface size.

comparative example

(1) at first prepare the aqueous solution for making cashmere in the cashmere-making tank, preparation raw material comprises: hydrofluoric acid 5wt%, nitric acid 25wt%, silicofluoric acid 0.5wt%, additive 0.5wt%, surplus is water; Above-mentioned each component Mix and stir well;

The additives are composed of: 0.5% polyvinyl alcohol, 0.2% triethanolamine, 3% hydrolyzed polymaleic anhydride, 0.06% polyvinylpyrrolidone, and the balance is water:

(2) Maintain the temperature of the texturing aqueous solution in step (1) at 15°C, then place the polysilicon sheet in the aqueous solution for 120s, and simultaneously perform ultrasonic vibration at an ultrasonic frequency of 40KHZ; then take it out and place it in 0.3% sodium hydroxide, Sodium dodecylbenzene sulfonate 0.8%, the rest is water in the cleaning solution for cleaning, take it out and blow dry.

Observation through a microscope shows that the suede surface of the product prepared in the comparative example is uneven, and there are limited differences from the above-mentioned examples 1-2.

As shown in Fig. 1, the suede surface prepared by the embodiment of the present invention has uniform, small and relatively uniform suede surface size.

The battery performance parameters prepared by Examples 1-2 of the present invention and comparative examples are shown in Table 2:

Table 2 The battery performance parameters prepared by Examples 1-2 and Comparative Examples

It can be seen from the above parameters that the battery prepared by the method of the present invention has the advantages of low reflectivity and can effectively improve the conversion efficiency of the battery.

Claims (3)

1. a method for making texture of polycrystalline silicon solar cell, is characterized in that, step comprises: (1) First, prepare the aqueous solution for velvet making in the velvet making tank, and the preparation raw materials include: 5-20wt% hydrofluoric acid, 25-55wt% nitric acid, 0.5-5wt% silicofluoric acid, 0.1-0.5wt% acetic acid, and 0.5-5% additives. 1.5wt%, the balance is water; mix and stir the above-mentioned components; The additives are composed of: polyvinyl alcohol 0.2-0.8wt%, triethanolamine 0.1-6wt%, hydrolyzed polymaleic anhydride 1-6wt%, polyvinylpyrrolidone 0.05-0.1wt%, and the balance is water: (2) Maintain the temperature of the texturing aqueous solution in step (1) at 0-30°C, then place the polysilicon wafer in the above-mentioned aqueous solution for 100-300s, and perform ultrasonic vibration at the same time, with an ultrasonic frequency of 40-60KHZ; then take it out and place it in the 0.2-0.5 wt% of sodium hydroxide, 0.5-2 wt% of sodium dodecylbenzenesulfonate, and the rest in a cleaning solution composed of water for cleaning, taking out and blowing dry. 2. The method for making texturing of polycrystalline silicon solar cells according to claim 1, characterized in that, the texturing aqueous solution is prepared in the described texturing tank, and the preparation raw materials include: hydrofluoric acid 10-15wt%, nitric acid 25-45wt% , 0.5-1.5 wt% of silicofluoric acid, 0.1-0.2 wt% of acetic acid, 0.5-1.0 wt% of additives, and the balance is water. 3. the method for making texture of polycrystalline silicon solar cell according to claim 1, is characterized in that, described additive consists of: polyvinyl alcohol 0.2-0.5wt%, triethanolamine 0.1-0.8wt%, hydrolyzed polymaleic anhydride 1-2wt%, polyvinylpyrrolidone 0.05-0.08wt%, and the balance is water.