Method for removing silicon nitride antireflection layer on surface of crystalline silicon solar cell

Abstract

The invention discloses a method for removing a silicon nitride antireflection layer on a crystalline silicon solar electric surface. A waste crystalline silicon solar cell containing a silicon nitride layer is obtained through pretreatment, the waste crystalline silicon solar cell is put into a high-pressure reaction kettle, water is added as a solution, the high-pressure reaction kettle is transferred to a high-temperature environment to start a reaction after a kettle cover is tightened, and finally a silicon nitride antireflection layer on the surface of the waste crystalline silicon solar cell is removed. According to the method, the silicon nitride antireflection layer on the surface of the crystalline silicon solar cell is effectively etched and removed in a hydrothermal environment by using pure water as a solvent and using a high-pressure reaction kettle, and the removal rate of the silicon nitride antireflection layer can reach 100%. The process is simple and efficient, does not use any chemical reagent, and is environment-friendly. The method is easy to operate, wide in applicability, environmentally friendly and free of secondary pollution. Other chemical reagents are not introduced, the reaction system is simple and environment-friendly, and effective removal of the silicon nitride antireflection layer is realized. The applicability is wide, and efficient removal of the antireflection layer can be achieved for crystalline silicon solar cells of different types and different components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste recycling, and particularly relates to a recycling method for solar cells in various types of waste crystalline silicon photovoltaic modules. TECHNICAL BACKGROUND

[0002] Under the dual driving of global fossil energy reserves decreasing and environmental pressure increasing, the transformation of traditional energy system to clean energy system has become the consensus of the international community. Photovoltaic power generation technology is in a period of rapid development due to its advantages of high efficiency, stability and green. With the large-scale installation and operation of photovoltaic modules, the amount of waste photovoltaic modules is also increasing. It is estimated that 8000 tons of photovoltaic waste will be generated worldwide by 2050. Photovoltaic modules contain harmful substances such as fluorides and heavy metals lead, as well as valuable materials such as high-purity silicon, silver, aluminum and copper, forming a double constraint of environmental risk and resource pressure. Recycling and utilization of photovoltaic module materials is of great significance to the sustainable development of the photovoltaic industry and environmental quality protection. At present, among various types of photovoltaic modules, crystalline silicon photovoltaic modules occupy the main market share

[0003] Most of the valuable materials in crystalline silicon photovoltaic modules are concentrated in crystalline silicon solar cells. Crystalline silicon solar cells mainly use crystalline silicon as the main body, and are covered with silver, aluminum and silicon nitride anti-reflection layers on the surface. Purification of crystalline silicon solar cells can obtain high-purity silicon. The silicon nitride anti-reflection layer is stable and does not react with most chemical reagents, so how to effectively remove it is a challenge. At present, hydrofluoric acid and phosphoric acid are mainly used as etchants to remove the silicon nitride anti-reflection layer. However, these two inorganic acids can pose potential risks to the health of operators and the ecological environment during use, and are prone to produce secondary pollutants. Therefore, it is urgent to develop a more environmentally friendly and low-hazard treatment process. SUMMARY

[0004] Technical problem: The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for removing the silicon nitride anti-reflection layer on the surface of crystalline silicon solar cells, which is simple in process, easy to operate, environmentally friendly and efficient.

[0005] Technical solution: To achieve the above purpose, the present application provides a method for removing the silicon nitride anti-reflection layer of crystalline silicon solar cells. The waste crystalline silicon solar cells containing silicon nitride layer are obtained by pretreatment, and then put into a high-pressure reaction kettle, water is added as a solution, the kettle cover is tightened, and then the high-pressure reaction kettle is transferred to a high-temperature environment to start the reaction, and finally the silicon nitride anti-reflection layer on the surface of the waste crystalline silicon solar cells is removed. The specific steps are as follows:

[0006] a. Crush the large piece of waste crystalline silicon solar cell so that it can be put into the inner container of the reaction kettle;

[0007] b. Put the waste crystalline silicon solar cell into the inner container, add water as the solvent, set the solid-liquid ratio and the feeding amount, then put the inner container containing the reactants into the high-pressure reaction kettle, and tighten the kettle cover;

[0008] c. Transfer the high-pressure reaction kettle to the oven or heating jacket, and perform hydrothermal reaction, adjust the heating rate, reaction temperature and stirring speed, the pressure in the system gradually increases with the temperature rising, and after reaching the set reaction temperature, keep constant temperature for a period of time;

[0009] d. After the reaction is completed, open the kettle cover after the reaction kettle is cooled to room temperature, take out the reaction, filter and separate the solid-liquid, and obtain the solar cell with the removed silicon nitride anti-reflective layer.

[0010] In step a, the large piece of waste crystalline silicon solar cell is broken to 0.5-40mm.

[0011] In step b, the solid-liquid ratio is the ratio of the added crystalline silicon solar cell and water, which is 1:25-1:100 g / mL, and the feeding amount is the volume of the added crystalline silicon solar cell and water, which accounts for 30%-70% of the volume of the inner container of the reaction kettle.

[0012] In step c, the adjusted heating rate is 4-7℃ / min, the reaction temperature is 160-220℃, and the stirring speed is 0-400rpm.

[0013] In step c, the pressure in the system increases with the temperature rising, which is 0.5-1.6MPa; and the time for keeping constant temperature is 60-240min.

[0014] Beneficial effects: Since the above technical scheme is adopted, the present application is based on a high-temperature and high-pressure hydrothermal reaction system, aiming to realize green removal of the silicon nitride anti-reflective layer on the surface of the solar cell. Pure water is used as the solvent, and the high-pressure reaction kettle is used to realize effective etching and removal of the silicon nitride anti-reflective layer on the surface of the crystalline silicon solar cell in the hydrothermal environment, and the removal rate of the silicon nitride anti-reflective layer can reach 100%. The process flow of the technical scheme is simple and efficient, and no chemical reagent is used, which is environmentally friendly. The technical scheme has the advantages of simple process flow, easy operation, wide applicability, green environmental protection and no secondary pollution. Compared with the prior art, the present application has the following advantages:

[0015] (1) Pure water is used as the solvent, no other chemical reagent is introduced, the reaction system is simple, environmentally friendly, and the silicon nitride anti-reflective layer can be effectively removed.

[0016] (2) Wide applicability, different types and components of crystalline silicon solar cell can realize efficient removal of the anti-reflective layer. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1This is a schematic diagram of the technical process of the present invention.

[0018] Figure 2 This is a SEM comparison image of the surface of the crystalline silicon solar cell before and after the reaction of the present invention. Detailed Implementation

[0019] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0020] like Figure 1 As shown, the present invention discloses a method for removing the silicon nitride antireflection layer from the surface of a crystalline silicon solar cell. The method involves pre-treating the crystalline silicon solar cell to obtain a silicon nitride layer, placing it in a high-pressure reactor, adding water as a solution, tightening the reactor lid, and then transferring the reactor to a high-temperature environment to initiate the reaction. Ultimately, the silicon nitride antireflection layer on the surface of the crystalline silicon solar cell is removed. The specific steps are as follows:

[0021] a. Large pieces of waste crystalline silicon solar cells are crushed so that they can be placed into the inner container of the reactor; the large pieces of waste crystalline silicon solar cells are crushed to 0.5-40mm.

[0022] b. Place the waste crystalline silicon solar cells into the inner container, add water as a solvent, set the solid-liquid ratio and feed amount, and then place the inner container containing the reactants into the high-pressure reactor and tighten the reactor lid; the solid-liquid ratio is the ratio of the added crystalline silicon solar cells to water of 1:25 to 1:100 g / mL, and the feed amount is the volume of the added crystalline silicon solar cells and water accounting for 30% to 70% of the volume of the inner container of the reactor;

[0023] c. Transfer the high-pressure reactor to an oven or heating mantle for hydrothermal reaction. Set the heating rate, reaction temperature, and stirring speed. As the temperature rises, the pressure inside the system gradually increases. Once the set reaction temperature is reached, maintain the temperature at a constant level for a period of time. The set heating rate is 4–7 °C / min, the reaction temperature is 160–220 °C, and the stirring speed is 0–400 rpm. The system pressure as the temperature rises is 0.5–1.6 MPa. The time to maintain the constant temperature is 60–240 min.

[0024] d. After the reaction is complete, the reactor is cooled to room temperature, the reactor lid is opened, the reactants are removed, and the solid and liquid are separated by filtration to obtain a solar cell with the silicon nitride antireflection layer removed. The removal efficiency of the silicon nitride antireflection layer after the reaction is as high as 100%.

[0025] Example 1

[0026] a. Crush large pieces of waste crystalline silicon solar cells to 10-20mm so that they can be placed into the inner container of the reactor;

[0027] b. Put the waste crystalline silicon solar cell into the inner container, add water as solvent, keep the solid-liquid ratio of the added crystalline silicon solar cell and water at 1:50, the volume of the added crystalline silicon solar cell and water accounts for 50% of the inner container volume of the reaction kettle, then put the inner container with the reactants into the high-pressure reaction kettle, and tighten the kettle cover;

[0028] c. Transfer the high-pressure reaction kettle to the oven or heating jacket for hydrothermal reaction, set the heating rate at 5℃ / min, the reaction temperature at 180℃, and the stirring speed at 200rpm, maintain the constant temperature for 120min after reaching the reaction temperature, and the system pressure is 0.85-0.95MPa as the temperature rises;

[0029] d. After the reaction is completed, open the kettle cover after the reaction kettle is cooled to room temperature, take out the reaction product, and filter for solid-liquid separation to obtain the solar cell with the silicon nitride anti-reflective layer removed, and the silicon nitride anti-reflective layer removal efficiency is 100% (as shown in the SEM comparison chart of the crystalline silicon solar cell surface before and after the reaction). Figure 2

[0030] Example Two,

[0031] a. Crush the large piece of waste crystalline silicon solar cell to 20-40mm so as to be able to put into the inner container of the reaction kettle;

[0032] b. Put the waste crystalline silicon solar cell into the inner container, add water as solvent, keep the solid-liquid ratio of the added crystalline silicon solar cell and water at 1:75, the volume of the added crystalline silicon solar cell and water accounts for 70% of the inner container volume of the reaction kettle, then put the inner container with the reactants into the high-pressure reaction kettle, and tighten the kettle cover;

[0033] c. Transfer the high-pressure reaction kettle to the oven or heating jacket for hydrothermal reaction, set the heating rate at 4℃ / min, the reaction temperature at 220℃, and the stirring speed at 100rpm, maintain the constant temperature for 90min after reaching the reaction temperature, and the system pressure is 1.6-1.7MPa as the temperature rises;

[0034] d. After the reaction is completed, open the kettle cover after the reaction kettle is cooled to room temperature, take out the reaction product, and filter for solid-liquid separation to obtain the solar cell with the silicon nitride anti-reflective layer removed, and the silicon nitride anti-reflective layer removal efficiency is 100%.

[0035] Example Three,

[0036] a. Crush the large piece of waste crystalline silicon solar cell to 0.5-10mm so as to be able to put into the inner container of the reaction kettle;

[0037] ​b. The waste crystalline silicon solar cell is put into the inner container, water is added as a solvent, the solid-liquid ratio of the added crystalline silicon solar cell and water is kept at 1:100, the volume of the added crystalline silicon solar cell and water accounts for 40% of the volume of the inner container of the reaction kettle, then the inner container with the reactants is put into the high-pressure reaction kettle, and the kettle cover is tightened;

[0038] c. The high-pressure reaction kettle is transferred to an oven or heating jacket for hydrothermal reaction, the temperature rising rate is set to 5 ℃ / min, the reaction temperature is 160 ℃, and the stirring speed is 300 rpm, after reaching the reaction temperature, the constant temperature time of 240 min is maintained, and the system pressure is 0.5-0.6 MPa as the temperature rises;

[0039] d. After the reaction is completed, the kettle cover is opened after the reaction kettle is cooled to room temperature, the reactants are taken out, and solid-liquid separation is performed by filtration to obtain a solar cell from which the silicon nitride anti-reflection layer is removed, and the silicon nitride anti-reflection layer removal efficiency is 100%.

Claims

1. A method for removing the silicon nitride antireflective layer from a crystalline silicon solar cell, characterized in that: Waste crystalline silicon solar cells containing a silicon nitride layer, obtained through pretreatment, are placed in a high-pressure reactor. Water is added as a solution, the reactor lid is tightened, and the reactor is transferred to a high-temperature environment to begin the reaction. Ultimately, the silicon nitride antireflection layer on the surface of the waste crystalline silicon solar cells is removed. The specific steps are as follows: a. Crush large pieces of waste crystalline silicon solar cells so that they can be placed into the inner container of the reactor; b. Place the waste crystalline silicon solar cells into the inner container, add water as a solvent, set the solid-liquid ratio and feed amount, and then place the inner container containing the reactants into the high-pressure reactor and tighten the reactor lid. c. Transfer the high-pressure reactor to an oven or heating mantle for hydrothermal reaction. Adjust the heating rate, reaction temperature, and stirring speed. As the temperature rises, the pressure inside the system gradually increases. Once the set reaction temperature is reached, maintain a constant temperature for a period of time. d. After the reaction is complete, wait for the reactor to cool to room temperature, open the lid, remove the reactants, filter to separate the solid and liquid, and obtain a solar cell with the silicon nitride antireflection layer removed.

2. The method for removing the silicon nitride antireflection layer of a crystalline silicon solar cell according to claim 1, characterized in that: In step a, the large pieces of waste crystalline silicon solar cells are crushed to 0.5-40mm.

3. The method for removing the silicon nitride antireflection layer of a crystalline silicon solar cell according to claim 1, characterized in that: In step b, the solid-liquid ratio is 1:25 to 1:100 g / mL for the added crystalline silicon solar cells and water, and the feed amount is 30% to 70% of the volume of the added crystalline silicon solar cells and water in the reactor liner.

4. The method for removing the silicon nitride antireflective layer of a crystalline silicon solar cell according to claim 1, characterized in that: In step c, the heating rate is adjusted to 4-7℃ / min, the reaction temperature to 160-220℃, and the stirring speed to 0-400rpm.

5. The method for removing the silicon nitride antireflective layer of a crystalline silicon solar cell according to claim 1, characterized in that: In step c, the system pressure increases from 0.5 to 1.6 MPa as the temperature rises; the time for maintaining a constant temperature is 60 to 240 minutes.

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