Method for recycling crystalline silicon solar cell pieces

Abstract

The application discloses a resourceful treatment method of crystalline silicon solar cell pieces, which comprises the following steps: soaking the crystalline silicon solar cell pieces in a first treatment liquid to remove the metal layer on the surface of the crystalline silicon solar cell pieces, and obtaining first-stage cell pieces and a first recovery liquid; soaking the first-stage cell pieces in a second treatment liquid to remove the passivation layer and the emitter layer on the surface of the first-stage cell pieces, and obtaining second-stage cell pieces; the second treatment liquid is a mixed acid with a concentration of 26% to 33% of nitric acid and a concentration of 3% to 5% of hydrofluoric acid; and soaking the second-stage cell pieces in a third treatment liquid to remove the metal impurities on the surface of the second-stage cell pieces and recover the silicon in the crystalline silicon solar cell pieces. The resourceful treatment method has the advantages of simple process, short time consumption, low resourceful treatment cost and high recovery rate of elements such as silicon.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, specifically to a method for the resource recovery of crystalline silicon solar cells. Background Technology

[0002] Solar energy, with its significant advantages of being clean, inexhaustible, and readily available, has become the fastest-growing renewable energy source, playing a crucial role in adjusting the energy structure and improving the ecological environment. With the booming development of the global photovoltaic industry, photovoltaic modules, as the core component of photovoltaic power plants, are environmentally friendly "DC generators." While photovoltaic modules can achieve zero-emission green electricity during normal operation, they generate solid waste after disposal. Therefore, relevant departments consider not only the generation of photovoltaic modules but also the environmental impact of their recycling in the entire life cycle assessment of photovoltaic modules.

[0003] The recycling of waste crystalline silicon solar cells is a crucial factor affecting the entire lifecycle assessment of photovoltaic modules. However, the current recycling process for waste crystalline silicon solar cells is cumbersome.

[0004] The process is time-consuming, costly, and has low recovery rates for elements such as silicon and metals, which affects the overall lifecycle assessment results of photovoltaic modules. Summary of the Invention

[0005] Therefore, the present invention provides a resource recovery method for crystalline silicon solar cells to solve the problems of long recovery time, high cost and low recovery rate of crystalline silicon solar cells in the prior art.

[0006] To achieve the above objectives, the present invention provides a method for the resource recovery of crystalline silicon solar cells, comprising:

[0007] The crystalline silicon solar cell is immersed in a first processing solution to remove the metal layer on the surface of the crystalline silicon solar cell, thereby obtaining a first-stage solar cell and a first recycling solution.

[0008] The first-stage battery cell is immersed in a second treatment solution to remove the passivation layer and emitter layer on the surface of the first-stage battery cell, thereby obtaining the second-stage battery cell; the second treatment solution is a mixed acid of nitric acid with a concentration of 26%-33% and hydrofluoric acid with a concentration of 3%-5%.

[0009] The second-stage solar cell is immersed in a third processing solution to remove metallic impurities from the surface of the second-stage solar cell and recover silicon from the crystalline silicon solar cell.

[0010] In this process, the first-stage battery cell is immersed in the second treatment solution and ultrasonically reacted for 15-30 minutes to remove the passivation layer and emitter layer on the surface of the first-stage battery cell.

[0011] The third treatment solution includes a hydrochloric acid solution with a concentration of 8-12%;

[0012] The step of immersing the second-stage battery cell in a third treatment solution to remove metallic impurities from the surface of the second-stage battery cell includes:

[0013] The second-stage solar cells are immersed in a third treatment solution at a temperature of 40-60℃ for 20-40 minutes to remove metallic impurities from the surface of the second-stage solar cells.

[0014] Prior to removing the metallic impurities from the surface of the second-stage battery cell, the process further includes:

[0015] The second-stage battery cells are ultrasonically immersed in an 8-15% sodium hydroxide solution for 10-20 minutes to remove the second treatment solution remaining on the surface of the second-stage battery cells.

[0016] The first treatment solution is a nitric acid solution with a concentration of 20-30%.

[0017] The crystalline silicon solar cell is immersed in a first treatment solution at a temperature of 40-60°C for 25-35 minutes to remove the metal layer on the surface of the crystalline silicon solar cell.

[0018] After obtaining the first recovered liquid, the process also includes:

[0019] Sodium hydroxide was added to the first recovery solution to adjust it to be alkaline, thereby obtaining a silver oxide and aluminate solution.

[0020] The silver oxide was treated with tris(hydroxymethyl)aminomethane to obtain crude silver.

[0021] When the silver oxide is treated with the tris(hydroxymethyl)aminomethane, the mass ratio of the silver oxide to the tris(hydroxymethyl)aminomethane is 1:1 to 1:2.

[0022] The crude silver is roasted to obtain pure silver.

[0023] The aluminate solution is subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0024] The resource recovery method for crystalline silicon solar cells provided by this invention involves immersing the crystalline silicon solar cells to be recovered in a first treatment solution to remove the metal layer on the surface of the crystalline silicon solar cells, obtaining a first-stage cell and a first recovery solution; then immersing the first-stage cell in a second treatment solution to remove the passivation layer and emitter layer on the surface of the first-stage cell, obtaining a second-stage cell; the second treatment solution is a mixed acid consisting of 26%-33% nitric acid and 3%-5% hydrofluoric acid; then immersing the second-stage cell in a third treatment solution to remove metal impurities on the surface of the second-stage cell, thereby recovering silicon from the crystalline silicon solar cells. This resource recovery method is simple, time-saving, low-cost, and has a high recovery rate for elements such as silicon. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0026] Figure 1 A flowchart illustrating a method for resource recovery of crystalline silicon solar cells provided in an embodiment of the present invention;

[0027] Figure 2 These are comparison images of the crystalline silicon solar cells provided in the embodiments of this application before and after resource recovery processing;

[0028] Figure 3 This is a comparison image of the silver grid side of the crystalline silicon solar cell before and after the resource recovery treatment provided in the embodiments of this application;

[0029] Figure 4 A scanning electron microscope (SEM) image of the silicon wafer surface after resource recovery processing of the crystalline silicon solar cell wafer provided in the embodiments of this application;

[0030] Figure 5 The image shows the X-ray energy dispersive spectroscopy (EDS) curve of the silicon wafer surface after resource recovery treatment of the crystalline silicon solar cell wafer provided in the embodiments of this application.

[0031] Figure 6 A photograph of silicon wafers recovered from the first stage of battery cells after being soaked in hydrofluoric acid.

[0032] Figure 7 A photograph of silicon wafers recovered from the first stage of battery cell recycling using hydrofluoric acid immersion. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] As used in this disclosure, the term "and / or" includes any and all combinations of one or more of the related enumerated entries.

[0035] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. As used in this disclosure, the singular forms “a” and “the” are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0036] When the terms “comprising” and / or “made of” are used in this disclosure, they specify the presence of the said feature, integral, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or groups thereof.

[0037] Unless otherwise specified, all terms used in this disclosure (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so specified in this disclosure.

[0038] The resource recovery process in this application refers to the recycling of valuable elements such as silicon, silver, and aluminum from crystalline silicon solar cells, turning these valuable elements from waste into treasure and allowing them to be reused, thereby achieving the goal of resource conservation.

[0039] Current resource recovery methods mainly focus on the treatment of encapsulation materials to separate the solar cells from the glass backsheet. These methods include inorganic acid dissolution, heat treatment, and a combination of organic dissolution and heat treatment. Resource recovery for solar modules primarily focuses on two directions: repairing the solar modules, i.e., inspecting and maintaining the electrical faults of the solar cells; and physical separation, mainly including breaking down and mechanically separating the solar cells.

[0040] For example, the resource recovery process of solar cells includes: sequentially removing aluminum with hydrochloric acid (HCl), removing silver with nitric acid (HNO3), removing the aluminum-silicon alloy layer with sodium hydroxide (NaOH), removing the silicon nitride layer with hydrofluoric acid (HF), removing the phosphorus diffusion layer again with sodium hydroxide, and removing surface metallic impurities with hydrochloric acid, thereby recovering silicon from the solar cells. This resource recovery process is complex, time-consuming, and costly, making it difficult to implement industrially. Moreover, considering only the recovery of silicon or precious metals (such as silver) fails to achieve the full recovery and utilization of valuable resources. In addition, using hydrochloric acid / sodium hydroxide to remove aluminum first, followed by nitric acid to remove silver, makes it easy for the silver grid to detach after aluminum removal, reducing the recovery rate of metallic silver.

[0041] This invention provides a method for the resource recovery of crystalline silicon solar cells. Figure 1 This is a flowchart illustrating a method for the resource recovery of crystalline silicon solar cells provided in an embodiment of the present invention. Figure 1 As shown, the resource recovery methods for crystalline silicon solar cells include:

[0042] Step S101: Immerse the crystalline silicon solar cell in the first processing solution to remove the metal layer on the surface of the crystalline silicon solar cell, and obtain the first stage cell and the first recycling solution.

[0043] The first-stage solar cell refers to the crystalline silicon solar cell after the metal layer has been removed. The crystalline silicon solar cell is immersed in a first processing solution, where the metal layer on the surface of the crystalline silicon solar cell (such as the silver in the silver grid and the aluminum paste on the back) reacts with the first processing solution, and the metal layer is removed, leaving the first-stage solar cell.

[0044] The first recovery liquid refers to the solution containing reaction products obtained after the first treatment liquid reacts with the metal layer on the surface of the crystalline silicon solar cell. The reaction products include silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3).

[0045] In some embodiments, the first treatment solution is a nitric acid solution with a concentration of 20-30%.

[0046] In some embodiments, the crystalline silicon solar cell is immersed in a first treatment solution at a temperature of 40-60°C for 25-35 minutes to remove the metal layer on the surface of the crystalline silicon solar cell.

[0047] The metal layer includes, but is not limited to, silver in the silver grid and aluminum on the back side. In this embodiment of the invention, the metal layer is removed by a first processing solution, rather than removing aluminum first and then silver. During the aluminum removal process, no silver is lost, thereby improving the silver recovery rate.

[0048] Step S102: Immerse the first-stage battery cell in the second treatment solution to remove the passivation layer and emitter layer on the surface of the first-stage battery cell to obtain the second-stage battery cell; the second treatment solution is a mixed acid of nitric acid with a concentration of 26%-33% and hydrofluoric acid with a concentration of 3%-5%.

[0049] In some embodiments, the first-stage solar cell is immersed in a second treatment solution and ultrasonically reacted for 15-30 minutes to remove the passivation layer and emitter layer on the surface of the first-stage solar cell.

[0050] Step S103: Immerse the second-stage solar cell in the third processing solution to remove metal impurities from the surface of the second-stage solar cell and recover silicon from the crystalline silicon solar cell.

[0051] In some embodiments, the third treatment solution comprises a hydrochloric acid solution with a concentration of 8-12%.

[0052] The second-stage solar cells are immersed in a third treatment solution to remove metallic impurities from their surface. This includes immersing the second-stage solar cells in the third treatment solution at a temperature of 40-60°C for 20-40 minutes to remove metallic impurities and recover silicon from the crystalline silicon solar cells. The silicon obtained by this method has a purity of 99.93% (>99.1% for industrial grade) and a recovery rate of approximately 90%.

[0053] In some embodiments, before removing metallic impurities from the surface of the second-stage solar cell, the method further includes:

[0054] Step S103′: Soak the cells in an 8-15% sodium hydroxide solution for 10-20 minutes using ultrasonication to remove the second treatment solution remaining on the surface of the second-stage battery cells.

[0055] In some embodiments, after obtaining the first recovered liquid, the method further includes:

[0056] Step S104: Add sodium hydroxide to the first recovery liquid to adjust the first recovery liquid to be alkaline, and obtain silver oxide and aluminate solution;

[0057] Step S105: Silver oxide is treated with tris(hydroxymethyl)aminomethane to obtain crude silver.

[0058] In some embodiments, when silver oxide is treated with tris(hydroxymethyl)aminomethane, the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane is 1:1 to 1:2.

[0059] Tris(hydroxymethyl)aminomethane is a green, pollution-free, low-toxicity, and low-cost reducing agent, providing a theoretical basis for the pollution-free and low-cost recycling of silver from waste crystalline silicon solar cells.

[0060] In some embodiments, the resource recovery method for crystalline silicon solar cells further includes:

[0061] Step S106: The crude silver is roasted to obtain pure silver.

[0062] Crude silver refers to silver with a purity of less than 90%. Pure silver can have a purity of 99.9%, and the silver recovery rate can reach 90.08%.

[0063] In step S107, the aluminate solution is subjected to evaporation and concentration, cooling and crystallization, and calcination treatment in sequence to obtain alumina.

[0064] The embodiments of this application do not limit the parameters of evaporation concentration, cooling crystallization, and calcination treatment to obtain solid alumina.

[0065] The resource recovery method for crystalline silicon solar cells provided by this invention involves immersing the crystalline silicon solar cells to be recycled in a first treatment solution to remove the metal layer on the surface of the solar cells, obtaining a first-stage cell and a first recovery solution. The first-stage cell is then immersed in a second treatment solution to remove the passivation layer and emitter layer on the surface of the first-stage cell, obtaining a second-stage cell. The second treatment solution is a mixed acid consisting of 26%-33% nitric acid and 3%-5% hydrofluoric acid. Next, the second-stage cell is immersed in a third treatment solution to remove metal impurities from its surface, thereby recovering silicon from the crystalline silicon solar cells. This resource recovery method is simple, time-efficient, and cost-effective, with a high recovery rate of silicon and other elements. Furthermore, this resource recovery method for crystalline silicon solar cells has low equipment requirements, reducing recycling costs.

[0066] Example 1

[0067] Waste crystalline silicon solar cells are immersed in a 25% nitric acid solution at 50°C, allowing the silver in the silver grids and the aluminum paste on the back to react with the nitric acid for 30 minutes. Then, they are ultrasonically treated at 53 kHz for 10 minutes to remove the silver from the silver grids and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cells can be 20 × 20 mm in size.

[0068] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution reacted with the passivation layer and emitter layer in 53kHz ultrasound for 20 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thus obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 26% nitric acid and 3% hydrofluoric acid.

[0069] The second-stage battery cells were immersed in a 10% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage battery cells with the sodium hydroxide for 15 minutes to remove the residual second treatment solution.

[0070] The second-stage solar cells were immersed in a third treatment solution at 50°C for 30 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was a 10% hydrochloric acid solution.

[0071] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0072] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:1.

[0073] The crude silver is roasted to obtain pure silver.

[0074] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0075] In Example 1, silicon and silver were analyzed by ICP-MS and their purities were 99.93% and 99.9%, respectively, with recoveries of 90.02% and 90.08%, respectively. The trace element content in the silicon wafer is shown in Table 1.

[0076] Table 1. Trace element content in silicon wafers

[0077]

[0078] Example 2

[0079] Waste crystalline silicon solar cells are immersed in a 22% nitric acid solution at 45°C, allowing the silver in the silver grid and the aluminum paste on the back to react with the nitric acid for 32 minutes. Then, they are ultrasonically treated at 53 kHz for 10 minutes to remove the silver from the silver grid and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cell can be 20 × 20 mm in size.

[0080] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution reacted with the passivation layer and emitter layer in 53kHz ultrasound for 30 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thus obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 28% nitric acid and 5% hydrofluoric acid.

[0081] The second-stage solar cells were immersed in an 8% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage solar cells with the sodium hydroxide for 18 minutes to remove the residual second treatment solution.

[0082] The second-stage solar cells were immersed in a third treatment solution at 40°C for 40 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was an 8.5% hydrochloric acid solution.

[0083] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0084] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:1.2.

[0085] The crude silver is roasted to obtain pure silver.

[0086] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0087] Example 3

[0088] Waste crystalline silicon solar cells are immersed in a 20% nitric acid solution at 40°C, allowing the silver in the silver grids and the aluminum paste on the back to react with the nitric acid for 35 minutes. Then, they are ultrasonically treated at 53 kHz for 10 minutes to remove the silver from the silver grids and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cells can be 20 × 20 mm in size.

[0089] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution reacted with the passivation layer and emitter layer in 53kHz ultrasound for 25 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thus obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 30% nitric acid and 3.8% hydrofluoric acid.

[0090] The second-stage solar cells were immersed in a 12% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage solar cells with the sodium hydroxide for 16 minutes to remove the residual second treatment solution.

[0091] The second-stage solar cells were immersed in a third treatment solution at 50°C for 40 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was a 9% hydrochloric acid solution.

[0092] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0093] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:2.

[0094] The crude silver is roasted to obtain pure silver.

[0095] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0096] In Example 3, silicon and silver were analyzed by ICP-MS and their purities were 99.93% and 99.9%, respectively, with recoveries of 90.02% and 90.05%, respectively.

[0097] Example 4

[0098] Waste crystalline silicon solar cells are immersed in a 28% nitric acid solution at 58°C, allowing the silver in the silver grids and the aluminum paste on the back to react with the nitric acid for 25 minutes. Then, they are ultrasonically treated at 53 kHz for 12 minutes to remove the silver from the silver grids and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cells can be 20 × 20 mm in size.

[0099] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution was subjected to ultrasonic treatment at 53 kHz to react with the passivation layer and emitter layer for 18 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thereby obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 33% nitric acid and 3% hydrofluoric acid.

[0100] The second-stage solar cells were immersed in a 12% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage solar cells with the sodium hydroxide for 12 minutes to remove the residual second treatment solution.

[0101] The second-stage solar cells were immersed in a third treatment solution at 60°C for 25 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was an 11% hydrochloric acid solution.

[0102] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0103] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:1.8.

[0104] The crude silver is roasted to obtain pure silver.

[0105] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0106] In Example 4, the purities of silicon and silver, as determined by ICP-MS, were 99.89% and 99.9%, respectively, with recoveries of 89.87% and 90.08%, respectively.

[0107] Example 5

[0108] Waste crystalline silicon solar cells are immersed in a 30% nitric acid solution at 60°C, allowing the silver in the silver grids and the aluminum paste on the back to react with the nitric acid for 25 minutes. Then, they are ultrasonically treated at 53 kHz for 8 minutes to remove the silver from the silver grids and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cells can be 20 × 20 mm in size.

[0109] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution reacted with the passivation layer and emitter layer in 53kHz ultrasound for 15 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thus obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 26% nitric acid and 5% hydrofluoric acid.

[0110] The second-stage solar cells were immersed in a 15% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage solar cells with the sodium hydroxide for 10 minutes to remove the residual second treatment solution.

[0111] The second-stage solar cells were immersed in a third treatment solution at 60°C for 20 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was a 12% hydrochloric acid solution.

[0112] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0113] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:2.

[0114] The crude silver is roasted to obtain pure silver.

[0115] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0116] In Example 5, the purities of silicon and silver, as determined by ICP-MS, were 99.92% and 99.9%, respectively, with recoveries of 86.87% and 90.08%, respectively.

[0117] Example 6

[0118] Waste crystalline silicon solar cells are immersed in a 30% nitric acid solution at 60°C, allowing the silver in the silver grids and the aluminum paste on the back to react with the nitric acid for 25 minutes. Then, they are ultrasonically treated at 53 kHz for 8 minutes to remove the silver from the silver grids and the aluminum from the back, yielding a first-stage solar cell and a first-stage recovery solution. The first-stage solar cell is the crystalline silicon solar cell from which silver and aluminum have been removed. The first-stage recovery solution comprises a solution of the reaction products of the nitric acid solution and the silver and aluminum, including silver nitrate (AgNO3) and aluminum nitrate (Al(NO3)3). The waste crystalline silicon solar cells can be 20 × 20 mm in size.

[0119] The first-stage solar cell was immersed in a second treatment solution, and the second treatment solution was subjected to ultrasonic treatment at 53 kHz to react with the passivation layer and emitter layer for 15 minutes to remove the passivation layer and emitter layer from the surface of the first-stage solar cell, thereby obtaining the second-stage solar cell. The second treatment solution was a mixed acid consisting of 33% nitric acid and 5% hydrofluoric acid.

[0120] The second-stage solar cells were immersed in a 15% sodium hydroxide solution and then ultrasonically (53 kHz) was used to react the residual second treatment solution on the surface of the second-stage solar cells with the sodium hydroxide for 10 minutes to remove the residual second treatment solution.

[0121] The second-stage solar cells were immersed in a third treatment solution at 60°C for 20 minutes to remove metallic impurities from their surface and recover silicon from the crystalline silicon solar cells. The third treatment solution was a 12% hydrochloric acid solution.

[0122] Sodium hydroxide was added to the first recovery solution to adjust it to alkaline (pH > 7), thereby obtaining silver oxide (Ag2O) and aluminate solution.

[0123] Crude silver was obtained by treating silver oxide with tris(hydroxymethyl)aminomethane, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane was 1:2.

[0124] The crude silver is roasted to obtain pure silver.

[0125] Aluminate solution was subjected to evaporation and concentration, cooling and crystallization, and calcination in sequence to obtain alumina.

[0126] In Example 6, the purities of silicon and silver, as determined by ICP-MS, were 99.78% and 99.9%, respectively, with recoveries of 92.56% and 90.08%, respectively.

[0127] Figure 2 These are comparison images showing the crystalline silicon solar cells before and after resource recovery processing according to the embodiments of this application. Figure 2In the image, (a) shows a photograph of the silver grid side of a crystalline silicon solar cell before resource recovery treatment, and (b) shows a photograph of the silver grid side of a crystalline silicon solar cell after resource recovery treatment. Figure 2 As can be seen, the silver grid was cleaned very thoroughly, with no residue.

[0128] Figure 3 This is a comparison image of the silver grid side of the crystalline silicon solar cell before and after resource recovery processing according to the embodiments of this application. Figure 3 In the image, (a) shows a photograph of the aluminum paste side of the back of a crystalline silicon solar cell before resource recovery treatment, and (b) shows a photograph of the aluminum paste side of the back of a crystalline silicon solar cell after resource recovery treatment. Figure 2 As can be seen, the aluminum paste on the back side has been cleaned very thoroughly, with no residue.

[0129] Figure 4 These are scanning electron microscope (SEM) images of the silicon wafer surface after resource recovery processing of the crystalline silicon solar cell wafers provided in this application embodiment. Figure 4 As can be seen, the surface of the silicon wafer is clean and free of metallic impurities.

[0130] Figure 5 The image shows an X-ray energy dispersive spectroscopy (EDS) curve of the silicon wafer surface after resource recovery treatment according to the embodiments of this application. Figure 5 As can be seen, the silicon wafers after resource recovery are composed entirely of silicon, without any other elements, indicating a very high purity of silicon. It should be noted that the EDS curve shows the presence of carbon, but this carbon is due to the use of conductive carbon adhesive during the EDS process.

[0131] Comparative Example 1

[0132] Waste crystalline silicon solar cells are soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, a mixed acid is used to remove the passivation layer and emitter layer, sodium hydroxide solution is used to remove residual mixed acid from the surface, and hydrochloric acid solution is used to remove metallic impurities, yielding silicon.

[0133] Sodium hydroxide is added to the first recovered liquid to adjust it to alkaline (pH > 7), yielding silver oxide (Ag₂O) and an aluminate solution. The silver oxide is then treated with tris(hydroxymethyl)aminomethane to obtain crude silver, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane is 1:0.5. The crude silver is then calcined to obtain pure silver.

[0134] In Comparative Example 1, the recovered silicon and silver were analyzed by ICP-MS and their purities were 99.93% and 92.37%, respectively, with recovery rates of 90.02% and 87.39%, respectively. The recovery rate and purity of silver decreased.

[0135] Comparative Example 2

[0136] Waste crystalline silicon solar cells are soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, a mixed acid is used to remove the passivation layer and emitter layer, sodium hydroxide solution is used to remove residual mixed acid from the surface, and hydrochloric acid solution is used to remove metallic impurities, yielding silicon.

[0137] Sodium hydroxide is added to the first recovery solution to adjust it to alkaline (pH > 7), yielding silver oxide (Ag₂O) and an aluminate solution. The silver oxide is then treated with tris(hydroxymethyl)aminomethane to obtain crude silver, wherein the mass ratio of silver oxide to tris(hydroxymethyl)aminomethane is 1:3. The crude silver is then calcined to obtain pure silver.

[0138] In Comparative Example 1, the recovered silicon and silver were analyzed by ICP-MS and found to have purities of 99.93% and 99.9%, respectively, with recovery rates of 90.08% and 90.05%. Although the recovery rate and purity of silver were basically consistent with those of this application, the addition of silver oxide to the recovered silver-containing tris(hydroxymethyl)aminomethane allowed for further reduction, indicating that excessive amounts of tris(hydroxymethyl)aminomethane were used, resulting in high costs and waste.

[0139] Comparative Example 3

[0140] Waste crystalline silicon solar cells are soaked in nitric acid solution to remove silver from the silver grid and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the passivation layer and emitter layer are removed using 5% hydrofluoric acid, residual mixed acids on the surface are removed using sodium hydroxide solution, and metallic impurities are removed using hydrochloric acid solution to obtain silicon.

[0141] Figure 6 These are photographs of silicon wafers recovered from the first stage of solar cell recycling using hydrofluoric acid immersion. (a) shows the silver grid side of the crystalline silicon solar cell after resource recovery treatment, and (b) shows the aluminum paste side of the back of the crystalline silicon solar cell after resource recovery treatment. Figure 6 It can be seen that there are residues on both the silver grid side and the aluminum paste side on the back, indicating that there are many impurities.

[0142] Comparative Example 4

[0143] Waste crystalline silicon solar cells are soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the passivation layer and emitter layer are removed using 25% hydrofluoric acid, residual mixed acids on the surface are removed using sodium hydroxide solution, and metallic impurities are removed using hydrochloric acid solution to obtain silicon.

[0144] Figure 7 These are photographs of silicon wafers recovered from the first stage of solar cell recycling using hydrofluoric acid immersion. (a) shows the silver grid side of the crystalline silicon solar cell after resource recovery treatment, and (b) shows the aluminum paste side of the back of the crystalline silicon solar cell after resource recovery treatment. Figure 7 It can be seen that there is no residue on either the silver grid side or the aluminum paste side on the back, indicating that there are no impurities.

[0145] The recovered silicon wafers, analyzed by ICP-MS, had a purity of 99.36% and a recovery rate of 80.87%. Although the purity of silicon was basically consistent with that of the embodiments in this application, the recovery rate was significantly lower. There was no impact on the recovery rate or purity of silver and aluminum.

[0146] Comparative Example 5

[0147] Waste crystalline silicon solar cells were soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the first-stage solar cell was soaked for 10 minutes in a second treatment solution (a mixture of 26% nitric acid and 3% hydrofluoric acid) to remove the passivation layer and emitter layer. Sodium hydroxide solution was used to remove any remaining mixed acid from the surface, and hydrochloric acid solution was used to remove metallic impurities, yielding silicon.

[0148] The recovered silicon wafers, analyzed by ICP-MS, had a purity of 82.81% and a recovery rate of 90.32%. Although the silicon recovery rate was basically consistent with that of the embodiments in this application, the silicon purity was significantly reduced. This indicates that the soaking time in the second treatment solution affects the purity of silicon, but has no effect on the recovery rate and purity of silver and aluminum.

[0149] Comparative Example 6

[0150] Waste crystalline silicon solar cells were soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the first-stage solar cell was soaked for 30 minutes in a second treatment solution (a mixture of 26% nitric acid and 3% hydrofluoric acid) to remove the passivation layer and emitter layer. Sodium hydroxide solution was used to remove any remaining mixed acid from the surface, and hydrochloric acid solution was used to remove metallic impurities, yielding silicon.

[0151] The recovered silicon wafers were tested by ICP-MS and found to have a purity of 99.98% and a recovery rate of 81.39%. Although the purity of silicon was basically the same as in the embodiments of this application, the silicon recovery rate was significantly lower. This indicates that prolonged soaking time in the second treatment solution reduces the silicon recovery rate, but has no effect on the recovery rate and purity of silver and aluminum.

[0152] Comparative Example 7

[0153] Waste crystalline silicon solar cells were soaked in a nitric acid solution to remove silver from the silver grid and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the first-stage solar cell was soaked for 30 minutes in a second treatment solution (a mixture of 40% nitric acid and 3% hydrofluoric acid) to remove the passivation layer and emitter layer. Sodium hydroxide solution was used to remove any remaining mixed acid from the surface, and hydrochloric acid solution was used to remove metallic impurities, yielding silicon.

[0154] The recovered silicon wafers were tested by ICP-MS and found to have a purity of 99.98% and a recovery rate of 81.02%. Although the purity of silicon was basically consistent with that of the embodiments in this application, the recovery rate of silicon was low. This indicates that a higher concentration of nitric acid in the second processing solution reduces the recovery rate of silicon, but has no effect on the recovery rate and purity of silver and aluminum.

[0155] Comparative Example 8

[0156] Waste crystalline silicon solar cells were soaked in nitric acid solution to remove silver from the silver grids and aluminum from the back side, yielding the first-stage solar cell and the first recycling solution. Then, the first-stage solar cell was soaked for 30 minutes in a second treatment solution (a mixture of 26% nitric acid and 8% hydrofluoric acid) to remove the passivation layer and emitter layer. Sodium hydroxide solution was used to remove any remaining mixed acid from the surface, and hydrochloric acid solution was used to remove metallic impurities, yielding silicon.

[0157] The recovered silicon wafers were tested by ICP-MS and found to have a purity of 99.98% and a recovery rate of 80.11%. Although the purity of silicon was basically consistent with that of the embodiments in this application, the recovery rate of silicon was low. This indicates that a higher concentration of hydrofluoric acid in the second processing solution will reduce the recovery rate of silicon, but will not affect the recovery rate and purity of silver and aluminum.

[0158] As shown in Comparative Examples 1-8, for silicon recovery, the combined second treatment solution of nitric acid and hydrofluoric acid is more effective than hydrofluoric acid alone. However, different concentrations of nitric acid and hydrofluoric acid, as well as the treatment time, all have a certain impact on the purity and recovery rate of silicon. Excessive nitric acid concentration leads to an overly rapid, violent, and uncontrollable reaction; excessive hydrofluoric acid concentration causes excessive corrosion of the silicon wafer, reducing the silicon recovery rate. Silicon purity is positively correlated with treatment time, but the recovery rate is negatively correlated; the recovery rate decreases significantly with prolonged treatment time. For silver recovery, the use of an appropriate amount of tris(hydroxymethyl)aminomethane can effectively reduce silver oxide.

[0159] Those skilled in the art will understand that although some embodiments described herein include certain features that are included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of this embodiment and form different embodiments.

[0160] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for resourceful processing of crystalline silicon solar cell pieces, characterized in that, The application relates to a method for recycling crystalline silicon solar cell pieces. The crystalline silicon solar cell pieces are soaked in a nitric acid solution with a concentration of 20-30% to remove the metal layer on the surface of the crystalline silicon solar cell pieces, and first-stage cell pieces and a first recovery liquid are obtained; sodium hydroxide is added to the first recovery liquid to obtain a silver oxide and a partial aluminate solution, and the silver oxide is treated by using tris(hydroxymethyl) aminomethane to obtain crude silver; The first-stage cell pieces are soaked in a second treatment liquid to remove the passivation layer and the emitter layer on the surface of the first-stage cell pieces, and second-stage cell pieces are obtained; the second treatment liquid is a mixed acid of nitric acid with a concentration of 26%-33% and hydrofluoric acid with a concentration of 3%-5%; The second-stage cell pieces are soaked in a third treatment liquid to remove the metal impurities on the surface of the second-stage cell pieces, and the silicon in the crystalline silicon solar cell pieces is recovered.

2. The method of claim 1, wherein, The first-stage cell pieces are soaked in the second treatment liquid for ultrasonic reaction for 15-30 min to remove the passivation layer and the emitter layer on the surface of the first-stage cell pieces.

3. The method of claim 1, wherein, The third treatment liquid is a hydrochloric acid solution with a concentration of 8-12%; The step of soaking the second-stage cell pieces in the third treatment liquid to remove the metal impurities on the surface of the second-stage cell pieces comprises the following steps: The second-stage cell pieces are soaked in the third treatment liquid at a temperature of 40-60 DEG C for 20-40 min to remove the metal impurities on the surface of the second-stage cell pieces.

4. The method of claim 1, wherein, Before the step of removing the metal impurities on the surface of the second-stage cell pieces, the following step is further included: The second-stage cell pieces are ultrasonically soaked in a sodium hydroxide solution with a concentration of 8-15% for 10-20 min to remove the second treatment liquid remaining on the surface of the second-stage cell pieces.

5. The method of claim 1, wherein, The crystalline silicon solar cell pieces are soaked in a first treatment liquid at a temperature of 40-60 DEG C for 25-35 min to remove the metal layer on the surface of the crystalline silicon solar cell pieces.

6. The method of claim 1, wherein, When the silver oxide is treated by using the tris(hydroxymethyl) aminomethane, the mass ratio of the silver oxide to the tris(hydroxymethyl) aminomethane is 1:1-1:

2.

7. The method of claim 1, wherein, The crude silver is subjected to roasting treatment to obtain pure silver.

8. The method of claim 1, wherein, The partial aluminate solution is subjected to evaporation concentration, cooling crystallization and roasting treatment in sequence to obtain alumina.

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