A glass powder for a back silver paste of an N-type crystalline silicon solar cell and a preparation method thereof

Abstract

The application relates to the technical field of solar cells, in particular to a glass powder for a back silver paste of an N-type crystalline silicon solar cell and a preparation method thereof, and specifically comprises the following steps: 1) carrying out surface pretreatment on the glass powder to obtain pretreated glass powder, then immersing the pretreated glass powder into prepared reaction liquid, and carrying out hydrothermal reaction to obtain loaded nanosheet type glass powder; 2) taking adenosine disodium triphosphate as a phosphorus source, taking calcium oleate as a precursor and a template agent, and depositing super-long nanowires on the loaded nanosheet type glass powder through a microwave-assisted hydrothermal method, and then carrying out cleaning and drying. The glass powder for the silver paste can not only make silver powder firmly adhere to the surface of a silicon substrate, improve the bonding strength between the silver powder and the silicon substrate, but also form a plurality of nanosheet layers with a dense structure in a sintered electrode, so that the sintered electrode is improved in compactness, and the photoelectric conversion rate and service life of the solar cell are improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a glass powder for back-side silver paste in N-type crystalline silicon solar cells and its preparation method. Background Technology

[0002] Solar energy, a green energy source, is gaining increasing attention due to its advantages such as being pollution-free, inexhaustible, and not limited by geographical resources, leading to the development of solar cells. The front surface electrodes and grid lines of crystalline silicon solar cells are made from conductive silver paste through high-speed, high-precision screen printing, low-temperature drying, and high-temperature sintering processes. This conductive silver paste is typically prepared from silver powder, glass powder, and an organic carrier. The glass powder liquefies during rapid sintering, acting as a binder between the silver powder and the silicon substrate, while also penetrating the anti-reflective coating, thus creating a good ohmic contact between the silver powder and the silicon substrate. The composition, content, particle size, and softening temperature of the glass powder directly affect the contact resistance, the ability to penetrate the anti-reflective coating, the conductivity of the electrodes, and the adhesion between the electrodes and the substrate, thereby influencing the photoelectric conversion efficiency and lifespan of the solar cell.

[0003] For example, the invention patent with publication number CN102126829A discloses a lead-free glass powder and its preparation method, a silver paste containing the glass powder, and a crystalline silicon solar cell made with the silver paste. The lead-free glass powder includes Bi2O3, ZnO, Al2O3, B2O3, SiO2, and BaO. Its raw materials are simple, with low melting and softening temperatures and fine glass powder particle size. The silver paste prepared with it has excellent performance, and the crystalline silicon solar cell made with this silver paste has a high photoelectric conversion efficiency. Although the glass powder can be quickly sintered and liquefied to act as a bond between the silver powder and the silicon substrate, its bonding strength is poor. This results in low adhesion strength of the solidified silver paste on the silicon substrate, making it easy to peel off. Moreover, the density of the sintered electrode formed after sintering and liquefaction is also poor, which will affect the photoelectric conversion efficiency and service life of the solar cell. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a glass powder for back-side silver paste in N-type crystalline silicon solar cells and a method for preparing the same.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells specifically includes the following steps:

[0007] 1) The glass powder is pretreated to obtain pretreated glass powder, which is then immersed in the prepared reaction solution and subjected to hydrothermal reaction to obtain supported nanosheet glass powder.

[0008] 2) Using sodium adenosine triphosphate as the phosphorus source and calcium oleate as the precursor and template agent, ultra-long nanowires were deposited on loaded nanosheet glass powder by microwave-assisted hydrothermal method. After cleaning and drying, glass powder for silver paste was obtained.

[0009] As a further preferred embodiment of the present invention, the surface pretreatment of the glass powder is specifically performed as follows:

[0010] Glass powder is placed in sodium hydroxide solution and dispersed by ultrasonic stirring for 30-50 minutes. It is then repeatedly washed with deionized water and placed in a mixture of equal volumes of hydrogen fluoride solution and ammonium fluoride solution. The mixture is stirred for 10-20 minutes, filtered, and dried to obtain pretreated glass powder.

[0011] As a further preferred embodiment of the present invention, the sodium hydroxide solution has a mass fraction of 1-5 wt%.

[0012] In the mixed solution, the concentration of hydrogen fluoride solution is 20-28 mol / L, and the concentration of ammonium fluoride solution is 1.5-3.0 mol / L.

[0013] As a further preferred embodiment of the present invention, the specific preparation method of the supported nanosheet glass powder is as follows:

[0014] 1) Sodium molybdate dihydrate powder is placed in deionized water and stirred thoroughly until completely dissolved. Then selenium powder is added and magnetically stirred continuously to ensure that the selenium powder is fully adsorbed into the solution. Then sodium borohydride powder is weighed and added to the above solution. After stirring thoroughly, anhydrous ethanol is added and mixed evenly to obtain the reaction solution.

[0015] 2) Add the pretreated glass powder to the reaction solution, disperse it evenly by ultrasonication, transfer it to the reaction vessel, seal it, and perform a hydrothermal reaction for 30-40 hours. After the reaction is completed, cool it to room temperature, separate it by centrifugation, wash it repeatedly with deionized water, and dry it to obtain the loaded nanosheet glass powder.

[0016] As a further preferred embodiment of the present invention, the proportions of sodium molybdate dihydrate powder, deionized water, selenium powder, sodium borohydride powder, and anhydrous ethanol in the reaction solution are (96-120) mg: (20-30) mL: (62-70) mg: (60-90) mg: (25-40) mL.

[0017] As a further preferred embodiment of the present invention, the mass ratio of the pretreated glass powder to the reaction solution is 1:(20-30);

[0018] The temperature of the hydrothermal reaction is 160-200℃.

[0019] As a further preferred embodiment of the present invention, the specific preparation method of the glass powder for silver paste is as follows:

[0020] 1) Dissolve 2.5-3.2g of sodium oleate in 15-30mL of deionized water, then add 5-8mL of calcium chloride aqueous solution to the sodium oleate solution and stir magnetically for 15-25min at room temperature. Then dissolve 0.3-0.4g of disodium adenosine triphosphate in 5-8mL of deionized water and slowly add it dropwise to the reaction system. Continue stirring at room temperature for 15-30min to obtain a suspension.

[0021] 2) Add the loaded nanosheet glass powder to the suspension, disperse it by ultrasonication for 10-30 min, transfer it to the reaction vessel, seal it and place it in a microwave reactor and heat it to 180-200℃. Heat and keep it at this temperature for 1-5 h. After the reaction is completed, cool it to room temperature, wash it repeatedly with ethanol and deionized water and dry it to obtain the required glass powder for silver paste.

[0022] As a further preferred embodiment of the present invention, the concentration of the calcium chloride aqueous solution in the suspension is 2-5 wt%.

[0023] As a further preferred embodiment of the present invention, the ratio of the loaded nanosheet glass powder to the suspension is (1-5) g: (60-80) mL.

[0024] A glass powder for back-side silver paste in N-type crystalline silicon solar cells is prepared using the aforementioned preparation method.

[0025] A back-side silver paste for an N-type crystalline silicon solar cell includes the aforementioned glass powder.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] In this invention, a surface pretreatment of glass powder, including two cleaning processes (alkali washing and acid washing), is performed to obtain pretreated glass powder with high surface cleanliness and easy deposition of nanosheets. Then, a reaction solution is prepared using sodium molybdate dihydrate and selenium powder as raw materials and sodium borohydride as a reducing agent. The pretreated glass powder is added to the reaction solution, ultrasonically dispersed, and then placed in a reaction vessel for hydrothermal reaction. This allows for the deposition of a large number of nanosheets on the pretreated glass powder, forming a nanosheet-loaded glass powder. Disodium adenosine triphosphate is used as the phosphorus source, and calcium oleate is used as a precursor and template agent. Ultralong nanowires were deposited on glass powder loaded with nanosheets using a microwave-assisted hydrothermal method. The nanosheets on the surface of the glass powder increase the surface area of ​​the pretreated glass powder, facilitating the subsequent deposition of ultralong nanowires. Furthermore, the stacking of nanosheets on the pretreated glass powder surface forms a multi-layered sheet structure with small interlayer gaps. Once the deposited nanowires are embedded in these gaps, they are less likely to detach, allowing the ultralong nanowires to be firmly embedded within the nanosheets. This results in a structure where the glass powder serves as the matrix, the nanosheets as the connecting layer, and the ultralong nanowires as the... The silver paste uses glass powder with raised surfaces. The ultra-long nanowires on the surface of this glass powder can intertwine to form a network structure, which helps to disperse and transfer stress, thereby improving the strength of the sintered electrode formed after the glass powder liquefies during sintering and giving it excellent structural stability. Furthermore, the ultra-long nanowires, through their own cross-linking, can form a coated network structure on the surface of the silver powder, resulting in a larger contact area between the silver powder and the silicon substrate. This allows for a better and stronger bond between the two, creating a high bonding strength and ensuring the silver powder adheres firmly to the silicon substrate, preventing peeling. Simultaneously, the nanosheets, acting as a connecting layer, not only connect the nanowires to the surface of the glass powder, but their layered structures can also interlock to form a continuous phase of nanosheet layers. Since the nanosheet layers are formed by stacking nanosheets, they possess excellent density, allowing for the formation of multi-layered, dense nanosheet layers in the sintered electrode. This contributes to improving the density of the sintered electrode, thereby enhancing the photoelectric conversion efficiency and lifespan of the solar cell.

[0028] In this invention, glass powder is pretreated and then deposited with nanosheets and ultralong nanowires via a hydrothermal method to form a silver paste glass powder with glass powder as the matrix, nanosheets as the connecting layer, and ultralong nanowires as surface protrusions. This silver paste glass powder not only enables the silver powder to adhere firmly to the silicon substrate surface, improving the bonding strength between the two, but also forms a multi-layered nanosheet layer with a dense structure in the sintered electrode, thereby helping to improve the density of the sintered electrode and thus helping to improve the photoelectric conversion efficiency and lifespan of the solar cell. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the embodiments described below, the glass powder includes oxides of lead, tellurium, bismuth, zinc, boron, and silicon. In other embodiments, the specific components of the glass powder can be selected according to product requirements; this application does not limit the specific components of the glass powder or the content of each component. Furthermore, the silver powder prepared by this invention can be further supplemented with typical additives as needed to enhance flow properties, processing performance, and stability, including but not limited to dispersants, thixotropic agents, plasticizers, viscosity stabilizers, etc. These additives can be used alone or in combination.

[0031] Example 1

[0032] A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells specifically includes the following steps:

[0033] 1) Place the glass powder in a 1 wt% sodium hydroxide solution, disperse it by ultrasonic stirring for 30 min, wash it repeatedly with deionized water, and then place it in an equal volume mixture of a 20 mol / L hydrogen fluoride solution and a 1.5 mol / L ammonium fluoride solution. Stir for 10 min, filter and dry to obtain pretreated glass powder.

[0034] 2) Add 96 mg of sodium molybdate dihydrate powder to 20 mL of deionized water and stir thoroughly until completely dissolved. Then add 62 mg of selenium powder and stir continuously with magnetic force to ensure that the selenium powder is fully adsorbed into the solution. Then weigh 60 mg of sodium borohydride powder and add it to the above solution. Stir thoroughly and mix well. Then add 25 mL of anhydrous ethanol and mix evenly to obtain the reaction solution.

[0035] 3) Add the pretreated glass powder to the reaction solution at a mass ratio of 1:20. After ultrasonic dispersion, transfer it to the reaction vessel, seal it, and perform hydrothermal reaction at 160℃ for 30 hours. After the reaction is completed, cool it to room temperature, separate it by centrifugation, wash it repeatedly with deionized water, and dry it to obtain the loaded nanosheet glass powder.

[0036] 4) Dissolve 2.5g of sodium oleate in 15mL of deionized water, then add 5mL of 2wt% calcium chloride aqueous solution to the sodium oleate solution, stir magnetically for 15min at room temperature, then dissolve 0.3g of disodium adenosine triphosphate in 5mL of deionized water, and slowly add it dropwise to the reaction system, continue stirring at room temperature for 15min to obtain a suspension;

[0037] 5) Add 1g of loaded nanosheet glass powder to 60mL of suspension, disperse by ultrasonication at 100W for 10min, transfer to a reaction vessel, seal and place in a microwave reactor and heat to 180℃. Heat and keep at this temperature for 1h. After the reaction is completed, cool to room temperature, wash repeatedly with ethanol and deionized water, and dry in a vacuum oven at 60℃ for 20h to obtain the required glass powder for silver paste.

[0038] Example 2

[0039] A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells specifically includes the following steps:

[0040] 1) The glass powder was placed in a 3 wt% sodium hydroxide solution and dispersed by ultrasonic stirring for 40 min. After repeated washing with deionized water, it was placed in an equal volume mixture of a 25 mol / L hydrogen fluoride solution and a 2.3 mol / L ammonium fluoride solution and stirred for 15 min. After filtration and drying, the pretreated glass powder was obtained.

[0041] 2) Add 110 mg of sodium molybdate dihydrate powder to 25 mL of deionized water and stir thoroughly until completely dissolved. Then add 68 mg of selenium powder and stir continuously with magnetic force to ensure that the selenium powder is fully adsorbed into the solution. Then weigh 80 mg of sodium borohydride powder and add it to the above solution. Stir thoroughly and mix well. Then add 35 mL of anhydrous ethanol and mix evenly to obtain the reaction solution.

[0042] 3) Add the pretreated glass powder to the reaction solution at a mass ratio of 1:25. After ultrasonic dispersion, transfer it to the reaction vessel, seal it, and perform hydrothermal reaction at 180℃ for 35 hours. After the reaction is completed, cool it to room temperature, separate it by centrifugation, wash it repeatedly with deionized water, and dry it to obtain the loaded nanosheet glass powder.

[0043] 4) Dissolve 2.8g of sodium oleate in 26mL of deionized water, then add 7mL of 3wt% calcium chloride aqueous solution to the sodium oleate solution, stir magnetically for 20min at room temperature, then dissolve 0.4g of disodium adenosine triphosphate in 6mL of deionized water, and slowly add it dropwise to the reaction system, continue stirring at room temperature for 25min to obtain a suspension;

[0044] 5) Add 3g of loaded nanosheet glass powder to 70mL of suspension, disperse by ultrasonication at 150W for 20min, transfer to a reaction vessel, seal and place in a microwave reactor and heat to 190℃. Heat and keep at this temperature for 3h. After the reaction is completed, cool to room temperature, wash repeatedly with ethanol and deionized water, and dry in a vacuum oven at 65℃ for 23h to obtain the required glass powder for silver paste.

[0045] Example 3

[0046] A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells specifically includes the following steps:

[0047] 1) Place the glass powder in a 5 wt% sodium hydroxide solution, disperse it by ultrasonic stirring for 50 min, wash it repeatedly with deionized water, and then place it in an equal volume mixture of a 28 mol / L hydrogen fluoride solution and a 3 mol / L ammonium fluoride solution. Stir for 20 min, filter and dry to obtain pretreated glass powder.

[0048] 2) Add 120mg of sodium molybdate dihydrate powder to 30mL of deionized water and stir thoroughly until completely dissolved. Then add 70mg of selenium powder and stir continuously with magnetic force to ensure that the selenium powder is fully adsorbed into the solution. Then weigh 90mg of sodium borohydride powder and add it to the above solution. Stir thoroughly and mix well. Then add 40mL of anhydrous ethanol and mix evenly to obtain the reaction solution.

[0049] 3) Add the pretreated glass powder to the reaction solution at a mass ratio of 1:30. After ultrasonic dispersion, transfer it to the reaction vessel, seal it, and perform hydrothermal reaction at 200℃ for 40 hours. After the reaction is completed, cool it to room temperature, separate it by centrifugation, wash it repeatedly with deionized water, and dry it to obtain the loaded nanosheet glass powder.

[0050] 4) Dissolve 3.2g of sodium oleate in 30mL of deionized water, then add 8mL of 5wt% calcium chloride aqueous solution to the sodium oleate solution, stir magnetically for 25min at room temperature, then dissolve 0.4g of disodium adenosine triphosphate in 8mL of deionized water, and slowly add it dropwise to the reaction system, continue stirring at room temperature for 30min to obtain a suspension;

[0051] 5) Add 5g of loaded nanosheet glass powder to 80mL of suspension, disperse by ultrasonication at 200W for 30min, transfer to a reaction vessel, seal and place in a microwave reactor and heat to 200℃. Heat and keep at this temperature for 5h. After the reaction is completed, cool to room temperature, wash repeatedly with ethanol and deionized water, and dry in a vacuum oven at 70℃ for 25h to obtain the required glass powder for silver paste.

[0052] Comparative Example 1: This comparative example is basically the same as Example 1, except that ordinary lead-free glass powder is used instead of the glass powder used for the back silver paste.

[0053] Comparative Example 2: This comparative example is basically the same as Example 1, except that pretreated glass powder is used instead of the glass powder used for the back silver paste.

[0054] Comparative Example 3: This comparative example is basically the same as Example 1, except that a loaded nanosheet glass powder is used instead of the glass powder used for the back silver paste.

[0055] Comparative Example 4: This comparative example is basically the same as Example 1, except that step 1 is omitted in the preparation process of the glass powder for the silver paste.

[0056] Comparative Example 5: This comparative example is basically the same as Example 1, except that steps 2)-3) are omitted in the preparation process of the glass powder for silver paste.

[0057] The silver paste was prepared in the same manner as the glass powders used in Examples 1-3 and Comparative Examples 1-5. The formula was as follows: by weight, it included 85 parts silver powder, 3 parts glass powder, 6.5 parts ethyl cellulose, 1.5 parts diethylene glycol acetate and 2.5 parts phosphate dispersant.

[0058] Test experiment:

[0059] Silver paste prepared using the glass powder samples for silver paste provided in Examples 1-3 and Comparative Examples 1-5 was printed and sintered on a silicon substrate to form gate electrodes. The adhesion between the gate electrodes and the silicon substrate was tested using a tensile tester, and the test results are shown in Table 1.

[0060] Table 1

[0061]

[0062]

[0063] As shown in Table 1, the gate electrode prepared by the silver paste using glass powder in this invention has a high adhesion to the silicon substrate, which allows the silver powder to adhere better and more firmly to the silicon substrate.

[0064] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells, characterized in that, Specifically, the steps include the following: 1) The glass powder is pretreated to obtain pretreated glass powder, which is then immersed in the prepared reaction solution and subjected to hydrothermal reaction to obtain supported nanosheet glass powder; 2) Using sodium adenosine triphosphate as the phosphorus source and calcium oleate as the precursor and template agent, ultra-long nanowires were deposited on loaded nanosheet glass powder by microwave-assisted hydrothermal method. After cleaning and drying, glass powder for silver paste was obtained. The specific preparation method of the supported nanosheet glass powder is as follows: 1) Sodium molybdate dihydrate powder is placed in deionized water and stirred thoroughly until completely dissolved. Then selenium powder is added and magnetically stirred continuously to ensure that the selenium powder is fully adsorbed into the solution. Then sodium borohydride powder is weighed and added to the above solution. After stirring thoroughly, anhydrous ethanol is added and mixed evenly to obtain the reaction solution. 2) Add the pretreated glass powder to the reaction solution, disperse it evenly by ultrasonication, transfer it to the reaction vessel, seal it, and perform a hydrothermal reaction for 30-40 hours. After the reaction is completed, cool it to room temperature, separate it by centrifugation, wash it repeatedly with deionized water, and dry it to obtain the loaded nanosheet glass powder.

2. The method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 1, characterized in that, The specific steps for surface pretreatment of the glass powder are as follows: Glass powder is placed in sodium hydroxide solution and dispersed by ultrasonic stirring for 30-50 minutes. It is then repeatedly washed with deionized water and placed in a mixture of equal volumes of hydrogen fluoride solution and ammonium fluoride solution. The mixture is stirred for 10-20 minutes, filtered, and dried to obtain pretreated glass powder.

3. The method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 2, characterized in that, The sodium hydroxide solution has a mass fraction of 1-5 wt%. In the mixed solution, the concentration of hydrogen fluoride solution is 20-28 mol / L, and the concentration of ammonium fluoride solution is 1.5-3.0 mol / L.

4. The method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 1, characterized in that, In the reaction solution, the ratio of sodium molybdate dihydrate powder, deionized water, selenium powder, sodium borohydride powder, and anhydrous ethanol is (96-120) mg: (20-30) mL: (62-70) mg: (60-90) mg: (25-40) mL.

5. The method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 1, characterized in that, The mass ratio of the pretreated glass powder to the reaction solution is 1:(20-30). The temperature of the hydrothermal reaction is 160-200℃.

6. The method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 1, characterized in that, The specific preparation method of the glass powder for the silver paste is as follows: 1) Dissolve 2.5-3.2g of sodium oleate in 15-30mL of deionized water, then add 5-8mL of calcium chloride aqueous solution to the sodium oleate solution. Stir magnetically for 15-25min at room temperature. Then dissolve 0.3-0.4g of disodium adenosine triphosphate in 5-8mL of deionized water and slowly add it dropwise to the reaction system. Continue stirring at room temperature for 15-30min to obtain a suspension. 2) Add the loaded nanosheet glass powder to the suspension, disperse it by ultrasonication for 10-30 min, transfer it to the reaction vessel, seal it and place it in a microwave reactor and heat it to 180-200℃. Heat and keep it at this temperature for 1-5 h. After the reaction is completed, cool it to room temperature, wash it repeatedly with ethanol and deionized water and dry it to obtain the required glass powder for silver paste.

7. A method for preparing glass powder for back-side silver paste in N-type crystalline silicon solar cells according to claim 6, characterized in that, The ratio of the loaded nanosheet glass powder to the suspension is (1-5) g: (60-80) mL.

8. A glass powder for back-side silver paste in N-type crystalline silicon solar cells, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A back-side silver paste for an N-type crystalline silicon solar cell, characterized in that, Includes the glass powder described in claim 8.

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