Method for removing anti-reflection layer on surface of silicon wafer of waste photovoltaic panel and recycling silicon wafer

Abstract

The invention provides a method for removing an anti-reflection layer on the surface of a silicon wafer of a waste photovoltaic panel and recycling the silicon wafer, and belongs to the technical field of solid waste recycling. The method comprises the following steps: decomposing a waste photovoltaic module laminated part, and screening out solar cells; mixing a decomposition solution with the solar cell, performing decomposition reaction, performing solid-liquid separation, and collecting a solid product; the mass concentration of the decomposition liquid is 5%-50%; the solute in the decomposition liquid is sodium phosphate, sodium hydroxide, sodium chloride and sodium carbonate in a mass ratio of 1: 1-2: 1 or sodium chloride, potassium chloride and sodium carbonate in a mass ratio of (2-3): (3-4): (4-5). According to the method provided by the invention, strong acid is not needed, the problem that the silicon wafer is damaged and the recoverability of the silicon wafer is influenced due to high-concentration acid is avoided, the process route is simple, efficient and low in energy consumption, the decomposition liquid can be recycled, and a thought is provided for green and efficient removal of the anti-reflection layer of the waste photovoltaic panel silicon wafer and recovery of the silicon wafer.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste recycling, and in particular to a method for removing an anti-reflection layer on the surface of waste photovoltaic panel silicon wafers to recycle silicon wafers. Background Art

[0002] As the scale of photovoltaic installations expands, the growth of waste crystalline silicon solar panels is becoming an increasingly prominent problem. Crystalline silicon photovoltaic modules are composed of valuable materials such as silicon wafers and silver, of which nearly 60% of the total cost of waste photovoltaic panels is attributed to silicon wafers and manufacturing costs; for this reason, green and environmentally friendly recycling methods must be developed. The photovoltaic modules that currently dominate the market have a silicon wafer structure in the photovoltaic layer that is mainly divided into three layers: a silicon nitride (SiNx) film and silver wire on the surface, a silicon wafer in the middle layer, and a metal aluminum layer on the back. In order to extract silicon wafers with higher purity, the key is how to remove the anti-reflection layer (silicon nitride) film.

[0003] At present, the research on recycling of waste photovoltaic panel silicon wafers mainly focuses on physical and chemical methods. The traditional physical method is multi-stage mechanical crushing. The waste photovoltaic panels are crushed to a certain extent. The most effective method is to use a chemical method combined with an acid-base mixed acid process to remove the anti-reflection layer (SiNx). For example, strong acids and bases such as HF, HNO3, NaOH, and KOH are used to remove SiNx and successfully recycle silicon wafers.

[0004] From the current research, it can be seen that HNO3 has been commonly used in acid leaching systems, but high concentrations of acid can cause damage to silicon wafers and affect their recyclability. From the perspective of sustainable development, silicon wafer recycling can adopt a greener and more environmentally friendly process. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers to recycle silicon wafers. The method uses a mild conventional weak base to replace the strong acid and strong base in the existing method, and the reaction time is relatively short and the removal rate is high. It has the advantages of mild reaction conditions, simple recovery process, high removal efficiency, and little impact on the environment.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recycling silicon wafers, comprising the following steps:

[0008] Decompose waste photovoltaic module laminates and screen out solar cells;

[0009] The decomposition liquid is mixed with the solar cell to perform a decomposition reaction, followed by solid-liquid separation, and a solid product is collected;

[0010] The mass concentration of the decomposition liquid is 5% to 50%; the solutes in the decomposition liquid are sodium phosphate, sodium hydroxide, sodium chloride and sodium carbonate in a mass ratio of 1:1 to 2:1 or sodium chloride, potassium chloride and sodium carbonate in a mass ratio of (2-3):(3-4):(4-5).

[0011] In some embodiments of the present invention, the mass concentration of the decomposition solution is 10% to 30%.

[0012] In some embodiments of the present invention, the mass concentration of the decomposition solution is 20%.

[0013] In some embodiments of the present invention, the mass ratio of sodium chloride to sodium carbonate is 1:1 to 1.5:1; the mass ratio of sodium chloride, potassium chloride and sodium carbonate is (2-2.5):(3-3.5):(4-4.5).

[0014] In some embodiments of the present invention, the mass ratio of sodium chloride to sodium carbonate is 5.8:4.2; the mass ratio of sodium chloride, potassium chloride and sodium carbonate is 2.5:3.3:4.2.

[0015] In some embodiments of the present invention, before decomposing the waste photovoltaic module laminate, the step of cutting the waste photovoltaic module laminate is also included. The present invention cuts the waste photovoltaic module laminate into suitable sizes to facilitate the subsequent decomposition reaction.

[0016] In some embodiments of the present invention, when decomposing the waste photovoltaic module laminate, the decomposition method is a pyrolysis method or a solvent method. The present invention does not specifically limit the specific steps and parameter settings of the pyrolysis method and the solvent method, and conventional technical means of those skilled in the art are selected as long as the laminate is successfully separated. After decomposing the waste photovoltaic module laminate, impurities such as glass, welding slag, and organic residues are separated, and solar cells (i.e., silicon wafers containing anti-reflection layers) are collected.

[0017] In some embodiments of the present invention, the waste photovoltaic module laminates are from photovoltaic modules that are in the scrapping period in the solid waste treatment and disposal industry. The photovoltaic modules that are in the scrapping period in the solid waste treatment and disposal industry are mainly composed of aluminum frames, glass, EVA, solar cells, back panels and junction boxes. After removing the aluminum frames and junction boxes of the waste photovoltaic modules, the waste photovoltaic module laminates can be obtained.

[0018] After decomposing the waste photovoltaic module laminates and selecting the solar cells, the steps of cleaning and drying the solar cells are also included. The present invention does not specifically limit the cleaning and drying methods, and conventional technical means of those skilled in the art can be used.

[0019] In some embodiments of the present invention, the liquid-to-solid ratio of the decomposition liquid to the solar cell is 1:50 to 1:500 g / mL.

[0020] In some embodiments of the present invention, the liquid-to-solid ratio of the decomposition liquid to the solar cell is 1:100 to 1:200 g / mL.

[0021] In some embodiments of the present invention, the decomposition reaction temperature is 50° C. to 200° C., and the time is 1 to 24 hours.

[0022] In some embodiments of the present invention, the decomposition reaction is carried out at a temperature of 120° C. to 150° C. and for a time of 1 to 3 hours.

[0023] In the present invention, if the decomposition reaction temperature is too high or the concentration of the decomposition liquid is too high, the solar cell will be severely broken and the integrity of the recovery cannot be guaranteed. If the decomposition reaction temperature is too low or the concentration of the decomposition liquid is too low, the anti-reflection layer will not react with the decomposition liquid, affecting the removal rate of the anti-reflection layer. Experimental results show that the reaction temperature is 120℃~150℃, the time is 1~3h, and the mass concentration of the decomposition liquid is 10%~30%, which has a better effect.

[0024] In the present invention, the reactor for performing the decomposition reaction can select one or more methods of relevant reaction devices involved in the reactor, such as water bath heating, oil bath heating, stirring, ultrasound, and mechanical stirring, to accelerate the reaction speed and remove the anti-reflection layer.

[0025] The solid product collected by solid-liquid separation in the present invention is the recovered silicon wafer, which can be further purified and recycled.

[0026] The present invention discloses the following technical effects:

[0027] The method provided by the present invention does not require strong acid, thus avoiding the problem that high concentration of acid may cause damage to the silicon wafer and affect its recyclability.

[0028] The process route of the invention is simple, efficient and low in energy consumption, and the decomposed liquid can be recycled, which provides a method for green and efficient removal of the anti-reflection layer of waste photovoltaic panel silicon wafers and recycling of silicon wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1The present invention is a schematic flow chart of a method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers to recycle silicon wafers. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] The present invention provides a method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recycling silicon wafers, comprising the following steps:

[0037] 1) removing the aluminum frame and junction box of the waste photovoltaic module to obtain the laminated parts of the waste photovoltaic module;

[0038] 2) cutting the waste photovoltaic module laminate into uniform sizes to obtain waste photovoltaic module laminate samples;

[0039] 3) decomposing the waste photovoltaic module laminate sample by pyrolysis or solvent method;

[0040] 4) After the decomposition is completed, the products are separated and collected into solar cells, and then cleaned and dried;

[0041] 5) Mixing the dried solar cell with the decomposition liquid to carry out a decomposition reaction, then collecting the solid product by solid-liquid separation, and then washing and drying the solid product to obtain a silicon wafer with the anti-reflection layer removed.

[0042] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0043] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0044] In the embodiment, the calculation formula of the silicon wafer anti-reflection layer removal rate can be expressed as (1):

[0045]

[0046] η—anti-reflection layer removal rate, %; C—nitrogen content of silicon wafer without removing the anti-reflection layer, %; C1—nitrogen content of silicon wafer after removing the anti-reflection layer, %.

[0047] Example 1

[0048] The aluminum frame and junction box of the waste photovoltaic panel are removed and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the lining of the reactor for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 2.5g:3.3g:4.2g of sodium chloride, potassium chloride, and sodium carbonate are added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 120°C and the insulation time is 2h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed. After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 86.2%.

[0049] Example 2

[0050] The aluminum frame and junction box of the waste photovoltaic panel are removed, and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the lining of the reactor for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 5.8g:4.2g of sodium chloride and sodium carbonate are added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 120°C and the insulation time is 1h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed. After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 91.5%.

[0051] Example 3

[0052] The aluminum frame and junction box of the waste photovoltaic panel are removed, and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the lining of the reactor for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 5.8g:4.2g of sodium chloride and sodium carbonate are added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 120°C and the insulation time is 2h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed (that is, the difference from Example 2 is that the decomposition reaction time is adjusted from 1h to 2h). After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 94.1%.

[0053] Example 4

[0054] The aluminum frame and junction box of the waste photovoltaic panel are removed, and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the reactor lining for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 5.8g:4.2g of sodium chloride and sodium carbonate are added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 150°C, and the insulation time is 2h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed (that is, the difference from Example 3 is that the temperature of the decomposition reaction is adjusted from 120°C to 150°C). After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 96.8%.

[0055] Example 5

[0056] The aluminum frame and junction box of the waste photovoltaic panel are removed and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the lining of the reactor for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 10g of sodium phosphate is added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 120°C and the insulation time is 2h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed. After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 87.4%.

[0057] Example 6

[0058] The aluminum frame and junction box of the waste photovoltaic panel are removed and then cut to obtain the waste photovoltaic panel sample. The waste photovoltaic panel sample is decomposed, and after the decomposition is completed, the solar cell is screened and separated, washed and dried. The decomposition liquid and the solar cell are mixed in a liquid-solid ratio of 100:1mL / g and placed in the lining of the reactor for decomposition reaction, wherein the mass concentration of the decomposition liquid is 20%wt, and 10g of sodium hydroxide is added to deionized water and stirred until transparent. The heating temperature of the decomposition reaction is set to 120°C and the insulation time is 2h. After the decomposition reaction is completed, a solid-liquid mixture is obtained. The solid-liquid mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed and dried to obtain a silicon wafer with the anti-reflection layer removed. After SEM-EDS (cold field scanning electron microscope + energy scattering spectrometer) detection, the nitrogen content is calculated by comparing the silicon wafer without removing the anti-reflection layer, and the removal rate is 92.6%.

[0059] Table 1 is the statistical results of the removal rate of the anti-reflection layer in Examples 1-5.

[0060] Table 1

[0061]

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers to recycle silicon wafers, characterized in that: The following steps are involved: Decompose waste photovoltaic module laminates and screen out solar cells; The decomposition liquid is mixed with the solar cell to perform a decomposition reaction, followed by solid-liquid separation, and a solid product is collected; The mass concentration of the decomposition liquid is 5% to 50%; the solutes in the decomposition liquid are sodium phosphate, sodium hydroxide, sodium chloride and sodium carbonate in a mass ratio of 1:1 to 2:1 or sodium chloride, potassium chloride and sodium carbonate in a mass ratio of (2-3):(3-4):(4-5).

2. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: The mass ratio of the sodium chloride to the sodium carbonate is 1:1 to 1.5:1; the mass ratio of the sodium chloride, potassium chloride and sodium carbonate is (2-2.5):(3-3.5):(4-4.5).

3. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: Before decomposing the waste photovoltaic module laminates, the method further includes cutting the waste photovoltaic module laminates.

4. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: When decomposing waste photovoltaic module laminates, the decomposition method is a thermal decomposition method or a solvent method.

5. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: The waste photovoltaic module laminates come from photovoltaic modules that are at the end of their service life in the solid waste treatment and disposal industry.

6. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: The liquid-to-solid ratio of the decomposition liquid to the solar cell is 1:50 to 1:500 g / mL.

7. The method for removing the anti-reflection layer on the surface of waste photovoltaic panel silicon wafers and recovering silicon wafers according to claim 1, characterized in that: The temperature of the decomposition reaction is 50° C. to 200° C., and the time is 1 to 24 hours.

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