TOPCon photovoltaic silver powder and preparation method thereof

Abstract

The invention provides TOPCon photovoltaic silver powder and a preparation method thereof, and belongs to the technical field of photovoltaic material preparation. According to the method, the regulation mechanism of coordination compound preparation-synchronous dropwise adding is combined with the double-liquid-phase flow velocity ratio, and superfine narrow distribution of the silver powder can be achieved; through modification of a silane coupling agent and stearic acid, Van der Waals force adhesion among particles is eradicated through cooperation of the silane coupling agent and the stearic acid, so that the silver powder keeps monodisperse in an organic slurry system (such as terpilenol and an ethyl cellulose system), and the problem that the slurry rheological property is poor due to the fact that superfine silver powder is prone to agglomeration is solved; meanwhile, a compact siloxane film formed by silane hydrolysis and a hydrophobic alkyl base layer of stearic acid construct a double-layer protective barrier on the surface of the silver powder, contact between air and water and the silver powder is isolated, normal-temperature oxidation of the superfine silver powder is effectively inhibited (generation of silver oxide impurities is avoided), and the storage shelf life of the silver powder is greatly prolonged.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic material preparation technology, specifically relating to a TOPCon photovoltaic silver powder and its preparation method. Background Technology

[0002] TOPCon solar cells (tunneling oxide passivated contact cells), as a new generation of high-efficiency photovoltaic technology, place stringent requirements on the conductivity, sintering activity, and morphology control of silver powder in their back electrode. Traditional silver powder preparation methods suffer from problems such as wide particle size distribution, insufficient specific surface area, and poor oxidation resistance, resulting in weak interfacial bonding between silver paste and silicon wafers and high contact resistance, thus hindering the improvement of cell conversion efficiency. In existing technologies, conventional chemical reduction methods, although cost-effective, struggle to achieve both ultrafine particle size and narrow distribution characteristics. Therefore, how to improve the preparation method to achieve ultrafine and narrow distribution has become a pressing technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a TOPCon photovoltaic silver powder and its preparation method. The preparation method provided by this invention can obtain ultra-fine, narrowly distributed TOPCon photovoltaic silver powder.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing TOPCon photovoltaic silver powder, comprising the following steps: (1) Mix the silver ion solution and the chelating agent solution to perform chelation and obtain the coordination compound; (2) A dispersant solution and a solution containing an organic reducing agent and an inorganic reducing agent are simultaneously added to the coordination compound obtained in step (1) to carry out a reduction reaction and obtain silver powder; the ratio of the rate at which the dispersant solution and the solution containing an organic reducing agent and an inorganic reducing agent are added is 1:(4~6). (3) Mix the silver powder, stearic acid, silane coupling agent and solvent obtained in step (2) and perform surface modification to obtain TOPCon photovoltaic silver powder.

[0005] Preferably, the silver ion solution in step (1) is subjected to ultrasonic treatment before use.

[0006] Preferably, the chelating agent in step (1) is at least one of citric acid, sodium citrate, tartaric acid, potassium sodium tartrate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, dimercaptopropanol, aminotrimethylenephosphonic acid, hydroxyethylidene diphosphonic acid, and catechols.

[0007] Preferably, in step (2), the organic reducing agent is at least one of ascorbic acid, formaldehyde, acetaldehyde, methylamine, ethylenediamine, glucose, sodium gluconate, and linoleic acid; the inorganic reducing agent is at least one of hydrazine hydrate, potassium iodide, ferrous sulfate, ferrous chloride, stannous chloride, sodium sulfite, and sodium thiosulfate, and the molar ratio of the organic reducing agent to the inorganic reducing agent is (2~5):1.

[0008] Preferably, the temperature of the reduction reaction in step (2) is 39.5~40.5℃, the time of the reduction reaction is 20~40min, and the reduction reaction is carried out in a protective atmosphere.

[0009] Preferably, in step (3), the mass ratio of stearic acid to silane coupling agent is (1~2):1; the total mass of stearic acid and silane coupling agent is 1~2% of the dry weight of silver powder.

[0010] Preferably, in step (3), the surface modification is carried out in a nitrogen-hydrogen mixed gas, wherein the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is (97~98):(2~3), and the temperature of the nitrogen-hydrogen mixed gas is 45~55℃.

[0011] Preferably, step (3) further includes post-processing after surface modification, which includes sequential filtration, primary centrifugation, secondary centrifugation, tertiary centrifugation and vacuum freeze drying.

[0012] Preferably, the medium used in the three-stage centrifugal separation is a dispersant.

[0013] The present invention also provides TOPCon photovoltaic silver powder prepared by the preparation method described in the above technical solution.

[0014] This invention provides a method for preparing TOPCon photovoltaic silver powder, comprising the following steps: mixing a silver ion solution and a chelating agent solution to perform chelation and obtain a coordination compound; simultaneously adding a dispersant solution and a solution containing an organic reducing agent and an inorganic reducing agent to the coordination compound to perform a reduction reaction and obtain silver powder; the ratio of the rate at which the dispersant solution and the solution containing the organic reducing agent and the inorganic reducing agent are added is 1:(4~6); mixing the silver powder, stearic acid, silane coupling agent and solvent to perform surface modification and obtain TOPCon photovoltaic silver powder. This invention utilizes a "coordination compound preparation-synchronous dropwise addition" control mechanism. A chelating agent forms a weak coordination compound with silver ions, slowly releasing free silver ions and reducing the reduction reaction rate. This allows silver atoms sufficient time to grow into orderly spherical particles. Simultaneously, the coordination effect limits excessive particle growth, achieving precise particle size control. Combined with a two-phase flow rate ratio, it enables ultra-fine, narrow distribution control of silver powder, overcoming the technical bottleneck of large particle size fluctuations in traditional chemical reduction methods. Furthermore, through the composite modification of silane coupling agents and stearic acid, one end of the silane coupling agent (e.g., alkoxy group)... The stearic acid reacts chemically with the hydroxyl groups on the surface of the silver powder to form chemical bonds. At the other end (e.g., an organic functional group), a dense organic-inorganic hybrid layer is constructed on the silver powder surface, inhibiting excessive migration and agglomeration of silver powder particles during sintering. The long-chain alkyl groups of stearic acid can form a "lubricating layer" between silver powder particles, reducing frictional resistance. Simultaneously, its carboxyl groups can weakly interact with the functional groups of the silanized layer, further regulating the particle fusion rate during sintering. This achieves good matching with the low-temperature sintering process of TOPCon batteries, reducing thermal damage to the silicon wafer and passivation layer. The results of the examples show that the TOPCon photovoltaic silver powder obtained by the preparation method provided by this invention has a spherical morphology. 50 =1.3~1.7μm. Attached Figure Description

[0015] Figure 1 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Example 1. Figure 2 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Example 1 is shown. Figure 3 The specific surface area test diagram of the TOPCon photovoltaic silver powder prepared in Example 1 is shown. Figure 4 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Example 2. Figure 5 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Example 2 is shown. Figure 6 The specific surface area test diagram of the TOPCon photovoltaic silver powder prepared in Example 2 is shown. Figure 7The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 1. Figure 8 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Comparative Example 1 is shown. Figure 9 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 2. Figure 10 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Comparative Example 2 is shown. Figure 11 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Comparative Example 9 is shown. Figure 12 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 10. Figure 13 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Comparative Example 10 is shown. Figure 14 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Example 4. Figure 15 The particle size distribution diagram of the TOPCon photovoltaic silver powder prepared in Example 4 is shown. Figure 16 The image shows the specific surface area of ​​the TOPCon photovoltaic silver powder prepared in Example 4. Detailed Implementation

[0016] This invention provides a method for preparing TOPCon photovoltaic silver powder, comprising the following steps: (1) Mix the silver ion solution and the chelating agent solution to perform chelation and obtain the coordination compound; (2) A dispersant solution and a solution containing an organic reducing agent and an inorganic reducing agent are simultaneously added to the coordination compound obtained in step (1) to carry out a reduction reaction and obtain silver powder; the ratio of the rate at which the dispersant solution and the solution containing an organic reducing agent and an inorganic reducing agent are added is 1:(4~6). (3) Mix the silver powder, stearic acid, silane coupling agent and solvent obtained in step (2) and perform surface modification to obtain TOPCon photovoltaic silver powder.

[0017] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.

[0018] This invention involves mixing a silver ion solution and a chelating agent solution to chelate and obtain a coordination compound.

[0019] In this invention, the concentration of the silver ion solution is preferably 1~2 mol / L; the temperature of the silver ion solution is preferably 38~42℃, more preferably 40℃.

[0020] As one embodiment, the silver ion solution can be prepared by mixing silver nitrate and deionized water to obtain a silver ion solution; the deionized water can be deionized water with an oxygen content ≤5%.

[0021] In this invention, the silver ion solution is preferably subjected to ultrasonic treatment before use; the power of the ultrasonic waves is preferably 30-40 kHz, more preferably 35 kHz. This invention does not have a specific limitation on the duration of the ultrasonic treatment, as long as air bubbles are removed. Ultrasonic treatment of the silver ion solution in this invention can eliminate air bubbles, create a uniform reaction environment, ensure stable dispersion of silver ions in the solution, prevent uneven nucleation caused by excessively high local concentrations, and further improve particle uniformity.

[0022] In this invention, the chelating agent is preferably at least one selected from citric acid, sodium citrate (Na3C6H5O7), tartaric acid, potassium sodium tartrate tetrahydrate (KNaC4H4O6·4H2O), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), dimercaptopropanol (BAL), aminotrimethylenephosphonic acid (ATMP), hydroxyethylidene diphosphonic acid (HEDP), and catechols; the catechol is preferably catechol. In this invention, the chelating agent can form a weak coordination compound with silver ions, slowly releasing free silver ions, reducing the reduction reaction rate, and allowing silver atoms sufficient time to grow into spherical particles in an orderly manner.

[0023] In this invention, the solvent used in the chelating agent solution is preferably deionized water; the concentration of the chelating agent solvent is preferably 0.4~0.6 mol / L, more preferably 0.5 mol / L; the chelating agent is formulated according to the reaction with Ag... + Coordination capacity (coordination number) and Ag + The preferred molar ratio of the substances is (0.5~1.5):1. As one embodiment, the chelating agent is prepared according to the ratio of Ag... + Coordination capacity (coordination number) and Ag + The molar ratio can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1.

[0024] The present invention does not impose any special limitation on the preparation method of the chelating agent solution; any preparation method well known to those skilled in the art can be used.

[0025] In this invention, the mixing of the silver ion solution and the chelating agent solution is preferably achieved by injecting the chelating agent solution into the silver ion solution.

[0026] This invention does not impose a specific time limit on the injection; uniform addition is acceptable. As one embodiment, the injection rate of the chelating agent solution can be 200 mL / min or 400 mL / min.

[0027] In this invention, the chelation temperature is preferably 40~60℃; the chelation time is preferably 5~20min. As one embodiment, the chelation temperature can be 45℃, 50℃, or 55℃; the chelation time can be 10min or 15min.

[0028] After obtaining the coordination compound, the present invention simultaneously adds a dispersant solution and a solution containing an organic reducing agent and an inorganic reducing agent to the coordination compound to carry out a reduction reaction and obtain silver powder.

[0029] In this invention, the dispersant is preferably any one of polyethylene glycol (PEG), polyacrylic acid (PAA), polyacrylate (PAAS), sodium dihydrogen phosphate (NaH2PO4), disodium hydrogen phosphate (Na2HPO4), sodium hexametaphosphate ((NaPO3)6), ethylene glycol (HOCH2CH2OH), and polyvinyl alcohol (PVA).

[0030] In this invention, the solvent used in the dispersant solution is preferably deionized water; the concentration of the dispersant solution is preferably 2-15 wt%. As one embodiment, the concentration of the dispersant solution can be 3 wt%, 4 wt%, 5 wt%, 5.71 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, or 14 wt%. In this invention, the dispersant ensures stable dispersion of silver ions in the solution, prevents uneven nucleation caused by excessively high local concentrations, and further improves particle uniformity.

[0031] In this invention, the preferred mass ratio of the dispersant to the silver salt in the silver ion solution is 1:(10~20). As one embodiment, the mass ratio of the dispersant to the silver salt in the silver ion solution can be 1:10.6, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, or 1:19. Limiting the mass ratio of the dispersant to the silver salt within the above range further ensures a narrow particle size of the silver powder.

[0032] In this invention, the dispersant solution is preferably subjected to ultrasonic treatment before use; the power of the ultrasonic waves is preferably 30-40 kHz, more preferably 35 kHz. This invention does not have a specific limitation on the duration of the ultrasonic treatment, as long as it removes air bubbles. Ultrasonic treatment of the dispersant solution in this invention can eliminate air bubbles and create a uniform reaction environment.

[0033] In this invention, the organic reducing agent is preferably at least one selected from ascorbic acid, formaldehyde, acetaldehyde, methylamine, ethylenediamine, glucose, sodium gluconate, and linoleic acid; the inorganic reducing agent is preferably at least one selected from hydrazine hydrate, potassium iodide, ferrous sulfate, ferrous chloride, stannous chloride, sodium sulfite, and sodium thiosulfate; the molar ratio of the organic reducing agent to the inorganic reducing agent is preferably (2~5):1. As one embodiment, the molar ratio of the organic reducing agent to the inorganic reducing agent can be (3~4):1. This invention uses a synergistic reduction system combining organic and inorganic reducing agents to ensure controllable nucleation and directional growth of silver ions under mild conditions.

[0034] In this invention, the solvent used in the solution containing the organic and inorganic reducing agents is preferably deionized water; the concentration of the solution containing the organic and inorganic reducing agents is preferably 0.2~0.5 mol / L. As one embodiment, the concentration of the solution containing the organic and inorganic reducing agents can be 0.25 mol / L, 0.3 mol / L, 0.3336 mol / L, or 0.4 mol / L.

[0035] In this invention, the preferred volume ratio of the solution containing organic and inorganic reducing agents to the silver ion solution is (1.5~2):1. As one embodiment, the volume ratio of the solution containing organic and inorganic reducing agents to the silver ion solution can be 1.6:1, 1.7:1, 1.8:1, or 1.9:1. Limiting the volume ratio of the solution containing organic and inorganic reducing agents to the silver ion solution within the above range further enhances the degree of reduction reaction.

[0036] In this invention, the ratio of the dropwise addition rate of the dispersant solution and the solution containing both organic and inorganic reducing agents is 1:(4~6), preferably 1:5. This invention limits the flow rate ratio of the two liquid phases to the above range, enabling ultra-fine and narrow distribution control of silver powder and overcoming the technical bottleneck of large particle size fluctuations in traditional chemical reduction methods.

[0037] This invention does not impose any particular limitation on the dropping rate of the dispersant solution or the solution containing organic and inorganic reducing agents; uniform dropping is sufficient. As one embodiment, the dropping rate of the solution containing organic and inorganic reducing agents can be 300 mL / min or 400 mL / min.

[0038] In this invention, the reduction reaction is preferably carried out under stirring conditions; the stirring rate is preferably 400-500 rpm; the temperature of the reduction reaction is preferably 39.5-40.5°C, more preferably 40°C; the time of the reduction reaction is preferably 20-40 min, more preferably 30 min; the reduction reaction is preferably carried out under a protective atmosphere; the protective atmosphere is preferably nitrogen. By limiting the conditions of the reduction reaction within the above ranges, this invention ensures thorough mixing of the reactants, achieving uniform nucleation of silver nuclei and inhibiting secondary aggregation.

[0039] After the reduction reaction is completed, the present invention preferably performs solid-liquid separation and washing on the product obtained from the reduction reaction in sequence to obtain silver powder.

[0040] The present invention does not impose any particular limitation on the operation of the solid-liquid separation; any operation well known to those skilled in the art can be used to obtain the filter residue. As one embodiment, the solid-liquid separation can be vacuum filtration.

[0041] The present invention does not impose any special limitations on the washing operation; as long as the water is clean, it is acceptable. As one embodiment, the detergent used for washing can be deionized water.

[0042] After obtaining the silver powder, the present invention mixes the silver powder, stearic acid, silane coupling agent and solvent, and performs surface modification to obtain TOPCon photovoltaic silver powder.

[0043] In this invention, the preferred mass ratio of stearic acid to silane coupling agent is (1~2):1, more preferably 2:1; the preferred total mass of stearic acid and silane coupling agent is 1~2% of the dry weight of silver powder. As one embodiment, the total mass of stearic acid and silane coupling agent can be 1.33% or 1.5% of the dry weight of silver powder. In this invention, stearic acid and silane coupling agent can coat silver powder to form a 3-5 nm antioxidant layer, improving the dispersibility and chemical stability of the silver powder. The synergistic effect of stearic acid (dispersing) and silane coupling agent (dense) avoids the defects of a single coating agent, while stearic acid alone is prone to detachment, and silane coupling agent alone results in poor dispersion. Limiting the mass ratio of stearic acid and silane coupling agent within the above range can further ensure ultra-fine and narrow distribution and low sintering yield. Excess stearic acid is prone to multilayer adsorption, resulting in a slight increase in apparent particle size. Excess silane coupling agent is prone to silane self-aggregation, resulting in "bridging agglomeration" between particles, significantly increasing the apparent particle size and widening the particle size distribution.

[0044] In this invention, the silane coupling agent is preferably γ-glycidoxypropyltrimethoxysilane or γ-aminopropyltriethoxysilane. In this invention, the solvent is preferably an alcohol solvent; the alcohol solvent is preferably ethanol.

[0045] In this invention, the mixing of silver powder, stearic acid, silane coupling agent and solvent is preferably carried out by mixing stearic acid, silane coupling agent and solvent to obtain a modifier solution, which is then added to silver powder.

[0046] In this invention, the mixing of the silver powder, stearic acid, silane coupling agent and solvent is preferably carried out in a nitrogen atmosphere.

[0047] In this invention, the preferred mixing temperature for the stearic acid, silane coupling agent, and solvent is 30-40°C. This invention does not impose a specific time limit on the mixing process, as long as complete dissolution is ensured and undissolved particles are avoided from affecting the uniformity of coating.

[0048] In this invention, the mass concentration of the modifier solution is preferably 5-10%. As one embodiment, the mass concentration of the modifier solution can be 6%, 6.56%, 6.67%, 7%, 8%, or 9%.

[0049] In this invention, the temperature at which the modifier solution is added to the silver powder is preferably 45-55°C, more preferably 50°C; the time for adding the modifier solution to the silver powder is preferably 15-30 minutes. This invention adds the modifier solution to the silver powder, allowing the long-chain alkyl groups of stearic acid to undergo initial physical adsorption on the surface of the silver powder, and the silane coupling agent to undergo a preliminary chemical reaction with the hydroxyl groups on the surface of the silver powder.

[0050] In this invention, the surface modification is preferably carried out in a nitrogen-hydrogen mixed gas; the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is preferably (97~98):(2~3), more preferably 98:2; the temperature of the nitrogen-hydrogen mixed gas is preferably 45~55℃, more preferably 50℃; the surface modification time is preferably 25~35 min, more preferably 30 min. This invention uses a nitrogen-hydrogen mixed atmosphere (protective + weak reducing) for synergistic heat treatment, which prevents secondary oxidation and repairs surface defects, ensuring the quality of the antioxidant layer and achieving a balance between "antioxidant properties, dispersibility, and conductivity." Limiting the surface modification conditions within the above range promotes the uniform spreading and cross-linking of the coating agent, enabling the silver powder to form an antioxidant layer.

[0051] This invention limits the volume ratio of nitrogen to hydrogen to 98:2, which results in weak reducing power, inhibiting the oxidation of silver powder, but unable to reduce the trace amounts of Ag2O that have already been generated. The high proportion of N2 results in extremely high safety. H2 ≥ 2% leads to strong reducing power, which can quickly reduce the oxide layer on the surface of silver powder; however, the high concentration of H2 requires strict control of the system's sealing and gas flow rate, resulting in lower safety.

[0052] In this invention, the surface modification is preferably carried out under stirring conditions. The stirring rate is not particularly limited in this invention; any operation well-known to those skilled in the art can be used.

[0053] In this invention, the surface modification preferably includes post-treatment; the post-treatment preferably includes filtration, primary centrifugation, secondary centrifugation, tertiary centrifugation and vacuum freeze drying performed sequentially.

[0054] The present invention does not impose any special limitations on the filtration operation; any operation known to those skilled in the art can be used to obtain the filter residue.

[0055] In this invention, the rotation speed of the first-stage centrifugation is preferably 900-1100 rpm, more preferably 1000 rpm; the first-stage centrifugation time is preferably 10-15 min; the first-stage centrifugation temperature is preferably 20-25℃; and the medium for the first-stage centrifugation is preferably deionized water or ethanol. In this invention, the first-stage centrifugation is a coarse separation, aimed at separating large particulate impurities (such as agglomerates and unreacted raw materials); the use of a medium can reduce surface tension and reduce agglomeration.

[0056] The present invention does not impose any special limitation on the amount of the medium used; any amount known to those skilled in the art can be used.

[0057] In this invention, the rotational speed of the secondary centrifugation is preferably 3900~4100 rpm, more preferably 4000 rpm; the secondary centrifugation time is preferably 15~20 min; the secondary centrifugation temperature is preferably 10~15℃; and the medium for the secondary centrifugation is preferably deionized water or ethanol. In this invention, the secondary centrifugation is a medium separation, the purpose of which is to enrich silver powder of the target particle size; limiting the temperature of the secondary centrifugation within the above range can reduce the Brownian motion of the particles; and the use of a medium can prevent particle aggregation.

[0058] The present invention does not impose any special limitation on the amount of the medium used; any amount known to those skilled in the art can be used.

[0059] In this invention, the preferred rotation speed of the three-stage centrifugation is 5900~6100 rpm, more preferably 6000 rpm; the preferred centrifugation time is 15~20 min; the preferred centrifugation temperature is 10~15℃; the preferred medium for the three-stage centrifugation is a dispersant; the preferred dispersant is polyvinylpyrrolidone (PVP); the preferred volume of the dispersant is 0.1~0.5% of the volume of the product obtained from the two-stage centrifugation. In this invention, the three-stage centrifugation is a fine separation, the purpose of which is to further purify fine particles and remove residual impurities; the use of a medium can prevent particle aggregation.

[0060] In this invention, the pressure of the vacuum freeze-drying is preferably <10 Pa. As one embodiment, the pressure of the vacuum freeze-drying can be 5 Pa or 8 Pa.

[0061] In this invention, the vacuum freeze drying preferably includes pre-freezing and drying performed sequentially; the pre-freezing temperature is preferably -40°C; the pre-freezing time is preferably 5 hours; the drying operation is preferably to raise the temperature to 5°C at a heating rate of 5°C / h, hold the temperature for 5 hours, and then raise the temperature to 25°C at a heating rate of 5°C / h and hold the temperature for 5 hours.

[0062] This invention employs a refined graded drying process to ensure the quality and performance of the final product. First, a three-stage centrifugal separation technique is used to effectively grade the silver powder according to particle size by gradually increasing the centrifugal speed. This step not only helps improve the purity of the silver powder but also helps ensure the uniformity of its particle size distribution. Next, vacuum freeze-drying technology is used to dry the silver powder under extremely low pressure (less than 10 Pa) with a slow heating rate. This drying method effectively avoids agglomeration of the silver powder during the drying process, thus maintaining its good dispersibility and stability. Through this graded drying process, the tap density of the silver powder can be ensured to remain stable at 3.0~3.5 g / cm³. 3 Its specific surface area is 0.3~0.6 m². 2 / g. These physical properties make silver powder a promising candidate for applications in electronic materials and catalysts. Furthermore, this refined preparation process helps improve the electrical conductivity, thermal conductivity, and oxidation resistance of silver powder, thereby further expanding its application range.

[0063] This invention utilizes a multi-stage synergistic control preparation technology to establish a synergistic control process and technical method for silver powder nucleation-growth, morphology and structure, particle size distribution, surface and interface properties, and product consistency in the actual production of photovoltaic silver powder, thereby achieving precise control of silver powder morphology, particle size, and surface properties.

[0064] The multi-parameter synergistic control technology of this invention employs a triple regulation mechanism of "coordination compound preparation - synchronous dropping - ultrasonic assistance." Through a chelating agent, weak coordination compounds are formed with silver ions, slowly releasing free silver ions and reducing the reduction reaction rate. This allows silver atoms sufficient time to grow into orderly spherical particles. Simultaneously, coordination restricts excessive particle growth, achieving precise particle size control. Combined with the two-phase flow rate ratio and ultrasonic cavitation effect, this technology achieves D-type silver powder... 50 The ultra-fine, narrow particle size distribution of 1.5±0.2μm overcomes the technical bottleneck of large particle size fluctuations in traditional chemical reduction methods; Surface silanization treatment: Silane coupling agents (such as aminosilanes and epoxysilanes) are used to coat and modify the surface of silver powder. Key function: From the perspective of "particle-interface interaction," this reduces the driving force of sintering shrinkage and decreases the volume shrinkage of the silver layer at high temperatures; Stearic acid lubricant composite: An appropriate amount of stearic acid (C...) is added... 18 H 36O2), key role: optimizes sintering fluidity from the perspective of "particle movement resistance" and avoids silver layer cracking caused by excessive local shrinkage.

[0065] The present invention also provides TOPCon photovoltaic silver powder prepared by the preparation method described in the above technical solution.

[0066] The TOPCon photovoltaic silver powder provided by this invention has a spherical morphology, D 50 =1.5±0.2μm, tap density is 3.0~3.5g / cm³ 3 Its specific surface area is 0.3~0.8 m². 2 / g.

[0067] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0068] Example 1 A method for preparing TOPCon photovoltaic silver powder is as follows: Dissolve 170g of silver nitrate crystals with a purity of 99.9% in 1L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤5%) to prepare a 1mol / L silver nitrate (AgNO3) solution, and keep the temperature constant to 40℃. 104 g of hydroxyethylidene diphosphonic acid was dissolved in 2 L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤ 5%) to prepare a 0.5 mol / L chelating agent solution; wherein, hydroxyethylidene diphosphonic acid was reacted with Ag... + Coordination ability and Ag + The molar ratio of the substances is 0.5:1; 70.5g of ascorbic acid and 5g of hydrazine hydrate were mixed and dissolved in 2L of deoxygenated water (deionized water with oxygen content ≤5%) to obtain a 0.25mol / L solution containing organic and inorganic reducing agents; wherein the molar ratio of ascorbic acid to hydrazine hydrate was 4:1, and the volume ratio of the solution containing organic and inorganic reducing agents to silver nitrate solution was 2:1. Mix 17g of polyethylene glycol 400 with 408g of deoxygenated water to prepare a 4wt% dispersant solution; wherein the mass ratio of polyethylene glycol to silver nitrate is 1:10. Silver nitrate solution was injected into the reaction vessel, the stirring speed was adjusted to 200 rpm, and the temperature was kept constant at 40℃. Then, it was pretreated by ultrasonic treatment at 35 kHz. The chelating agent solution was pumped into the inlet on the side of the vessel through a metering pump and added at a constant rate of 400 mL / min. After chelation for 5 minutes, the solution first changed from colorless to light yellow and then to yellow turbid liquid. A dual-channel metering pump was used for precise control. The solutions containing organic and inorganic reducing agents were added dropwise to the dispersant solution at a rate of 5:1. The solutions containing organic and inorganic reducing agents were added uniformly at a rate of 400 mL / min. The reduction reaction was carried out at a constant temperature of 40℃ and a stirring rate of 400 rpm for 30 min. Then, solid-liquid separation was performed by vacuum filtration, and the mixture was washed with deionized water to remove impurities, yielding silver powder. Weigh 0.72g of stearic acid and 0.36g of silane coupling agent γ-glycidoxypropyltrimethoxysilane, mix them, add 20.52g of anhydrous ethanol, heat to 40℃ and stir to dissolve, to obtain a modifier solution with a mass concentration of 5%; wherein, the mass ratio of stearic acid to silane coupling agent is 2:1; the total mass of stearic acid and silane coupling agent is 1% of the dry weight of silver powder; Silver powder was placed in a new reactor, and under a nitrogen atmosphere, it was stirred at a constant temperature of 50°C for 15 minutes. The modifier solution was then poured into the reactor at a uniform rate. The gas flow was switched to a nitrogen-hydrogen mixture (N2:H2 volume ratio of 98:2). Surface modification was performed under stirring for 30 minutes. After surface treatment, the filter residue was collected. First, the residue was mixed with ethanol, and the centrifuge speed was adjusted to 1000 rpm for 10 minutes at 25°C for primary centrifugation. Then, the centrifuge speed was adjusted to 4000 rpm for 20 minutes at 15°C for secondary centrifugation. Finally, 0.1% of the volume of PVP obtained from the secondary centrifugation was added, and the centrifuge speed was adjusted to 6000 rpm for 20 minutes at 15°C for tertiary centrifugation. Finally, the filtered silver powder is evenly spread into the freeze-drying tray, without compaction, and kept loose. It is pre-frozen at -40℃ for 5 hours under 5 Pa conditions, then heated to 5℃ at a rate of 5℃ / h and held at that temperature for 5 hours, and then heated to 25℃ at a rate of 5℃ / h and held at that temperature for 5 hours to obtain TOPCon photovoltaic silver powder.

[0069] The morphology of the TOPCon photovoltaic silver powder prepared in Example 1 is shown in the figure below. Figure 1 As shown.

[0070] The particle size distribution of the TOPCon photovoltaic silver powder prepared in Example 1 is shown in the figure below. Figure 2 As shown.

[0071] The specific surface area of ​​the TOPCon photovoltaic silver powder prepared in Example 1 was determined as follows: Figure 3 As shown.

[0072] The TOPCon photovoltaic silver powder prepared in Example 1 had a tap density of 3.22 g / cm³, as determined by GB / T 5162. 3 .

[0073] from Figure 1 It can be seen that the particles are generally spherical or nearly spherical with smooth surfaces and no obvious sharp edges, burrs or irregular shapes; the particles are basically monodisperse with no obvious hard agglomeration or sintering necks; the high sphericity and good dispersibility mean that they have excellent rheological properties in the slurry and are more likely to form a continuous and dense conductive network after printing into a film.

[0074] from Figure 2 It can be seen that the D of TOPCon photovoltaic silver powder 50 =1.568μm.

[0075] from Figure 3 It can be seen that the specific surface area of ​​TOPCon photovoltaic silver powder is 0.5512 m². 2 / g.

[0076] Example 2 Dissolve 170g of silver nitrate crystals with a purity of 99.9% in 1L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤5%) to prepare a 1mol / L silver nitrate solution, and keep the temperature constant to 40℃. Dissolve 96.1 g of citric acid in 1 L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤ 5%) to prepare a 0.5 mol / L chelating agent solution; wherein, the citric acid is reacted with Ag... + Coordination ability and Ag + The molar ratio of the substances is 0.5:1; 15g of formaldehyde and 5g of hydrazine hydrate were mixed and dissolved in 2L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤5%) to obtain a 0.3mol / L solution containing organic and inorganic reducing agents; wherein the molar ratio of formaldehyde to hydrazine hydrate was 5:1, and the volume ratio of the solution containing organic and inorganic reducing agents to silver nitrate solution was 2:1. 17g of polyvinyl alcohol (PVA) 0588 was mixed with 408g of deoxygenated water to prepare a 4wt% dispersant solution; wherein the mass ratio of polyvinyl alcohol to silver nitrate was 1:10. Silver nitrate solution was injected into the reaction vessel, the stirring speed was adjusted to 200 rpm, and the temperature was kept constant at 40℃. Then, it was pretreated by ultrasonic treatment at 35 kHz. The chelating agent solution was pumped into the inlet on the side of the vessel through a metering pump at a constant rate of 200 mL / min. After chelation for 5 minutes, the solution first changed from colorless to light yellow and then to dark brown. A dual-channel metering pump was used for precise control. The solutions containing organic and inorganic reducing agents were added dropwise to the dispersant solution at a rate ratio of 5:1. The solutions containing organic and inorganic reducing agents were added uniformly at a rate of 400 mL / min. The reduction reaction was carried out at a constant temperature of 40℃ and a stirring rate of 400 rpm for 30 min. Then, solid-liquid separation was performed by vacuum filtration, and the mixture was washed with deionized water to remove impurities, thus obtaining silver powder. Weigh 0.72g of stearic acid and 0.36g of silane coupling agent (γ-aminopropyltriethoxysilane), mix them, add 20.52g of anhydrous ethanol, heat to 40℃ and stir to dissolve, to obtain a modifier solution with a mass concentration of 5%; wherein, the mass ratio of stearic acid to silane coupling agent is 2:1; the total mass of stearic acid and silane coupling agent is 1% of the dry weight of silver powder; Silver powder was placed in a new reactor, and under a nitrogen atmosphere, it was stirred at a constant temperature of 50°C for 15 minutes. The modifier solution was then poured into the reactor at a uniform rate. The gas flow was switched to a nitrogen-hydrogen mixture (N2:H2 volume ratio of 98:2). Surface modification was performed under stirring for 30 minutes. After surface treatment, the filter residue was collected. First, the residue was mixed with ethanol, and the centrifuge speed was adjusted to 1000 rpm for 10 minutes at 25°C for primary centrifugation. Then, the centrifuge speed was adjusted to 4000 rpm for 15 minutes at 15°C for secondary centrifugation. Finally, 0.1% of the volume of PVP obtained from the secondary centrifugation was added, and the centrifuge speed was adjusted to 6000 rpm for 15 minutes at 15°C for tertiary centrifugation. Finally, the filtered silver powder is evenly spread into the freeze-drying tray, without compaction, and kept loose. It is pre-frozen at -40℃ for 5 hours under 5 Pa conditions, then heated to 5℃ at a rate of 5℃ / h and held at that temperature for 5 hours, and then heated to 25℃ at a rate of 5℃ / h and held at that temperature for 5 hours to obtain TOPCon photovoltaic silver powder.

[0077] The morphology of the TOPCon photovoltaic silver powder prepared in Example 2 is shown in the figure below. Figure 4 As shown.

[0078] The particle size distribution of the TOPCon photovoltaic silver powder prepared in Example 2 is shown in the figure below. Figure 5 As shown.

[0079] The specific surface area of ​​the TOPCon photovoltaic silver powder prepared in Example 2 was determined as follows: Figure 6 As shown.

[0080] The TOPCon photovoltaic silver powder prepared in Example 2 had a tap density of 3.19 g / cm³, as determined by GB / T 5162. 3 .

[0081] from Figure 4It can be seen that the particles have a high degree of sphericity and a smooth and rounded surface; the particles are basically monodisperse, with no obvious hard agglomerates or sintering necks, and only a small amount of slight soft agglomerates.

[0082] from Figure 5 It can be seen that the D of TOPCon photovoltaic silver powder 50 =1.327μm.

[0083] from Figure 6 It can be seen that the specific surface area of ​​TOPCon photovoltaic silver powder is 0.4292 m². 2 / g.

[0084] Comparative Example 1 Based on Example 2, the mass ratio of stearic acid to silane coupling agent was changed to 3:1, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0085] The morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 1 is shown in the figure below. Figure 7 As shown, the particle size distribution diagram is as follows: Figure 8 As shown.

[0086] from Figure 7 It can be seen that when stearic acid is in excess, it is easy to undergo multi-layer physical adsorption on the surface of silver powder, forming an excessively thick non-covalently bonded organic layer, which leads to a slight increase in the apparent particle size of silver powder; there is no chemical adhesion between particles, and the particle size distribution does not deteriorate significantly, which is a mild and reversible effect.

[0087] from Figure 8 It can be seen that D 50 =1.449μm, with a slight increase in particle size.

[0088] Comparative Example 2 Based on Example 2, the mass ratio of stearic acid to silane coupling agent was changed to 1:3, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0089] The morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 2 is shown in the figure below. Figure 9 As shown, the particle size distribution diagram is as follows: Figure 10 As shown.

[0090] from Figure 9 It can be seen that when the silane coupling agent is in excess, the excess molecules undergo a self-condensation reaction in the liquid phase to generate siloxane oligomers, which produce interparticle bridging effects and trigger irreversible bridging and agglomeration of silver powder; ultimately, this results in a significant increase in apparent particle size and a markedly wider particle size distribution.

[0091] from Figure 10 It can be seen that D 50 =2.968μm, the apparent particle size is significantly increased, and the particle size distribution is widened.

[0092] Comparative Example 3 Based on Example 2, the ratio of the rate at which the dispersant solution and the solution containing organic and inorganic reducing agents were added was modified to 1:7, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0093] TOPCon photovoltaic silver powder D prepared in Comparative Example 3 50 =2.117μm, specific surface area is 0.51m² 2 / g, tap density is 2.76g / cm³ 3 .

[0094] Comparative Example 4 Based on Example 2, the ratio of the rate at which the dispersant solution and the solution containing organic and inorganic reducing agents were added was modified to 1:3, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0095] Comparative Example 4: TOPCon photovoltaic silver powder D 50 =1.717μm, specific surface area is 0.62m² 2 / g, tap density is 2.93g / cm³ 3 .

[0096] Comparative Example 5 Based on Example 2, a dispersion solution was first added, followed by a solution containing organic and inorganic reducing agents (i.e., added dropwise at different times), while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0097] Comparative Example 5: TOPCon photovoltaic silver powder D 50 =1.018μm, specific surface area is 0.43m² 2 / g, tap density is 1.33g / cm³ 3 Compared to Example 2, although the particle size is smaller, the tap density is too low, failing to meet the high tap density requirements of the current market. The core problem of low tap density is that "the degradation of various performance characteristics caused by looseness" leads to a decrease in the photoelectric conversion efficiency of the solar cell and an increase in mass production costs. Therefore, tap density is a core indicator that must be strictly controlled within the optimal range during the factory inspection of photovoltaic silver powder.

[0098] Comparative Example 6 Based on Example 2, a solution containing organic and inorganic reducing agents was first added, followed by the addition of a dispersion solution (i.e., not added dropwise), while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0099] Comparative Example 6 prepared TOPCon photovoltaic silver powder D 50 =3.862μm, specific surface area is 0.51m² 2 / g, tap density is 0.97g / cm³ 3 .

[0100] Comparative Example 7 Based on Example 2, the ultrasonic pretreatment of silver nitrate solution was omitted, and other conditions remained unchanged to obtain TOPCon photovoltaic silver powder.

[0101] Comparative Example 7 prepared TOPCon photovoltaic silver powder D 50 =1.815μm, specific surface area is 0.63m² 2 / g, tap density is 3.16g / cm³ 3 .

[0102] Example 3 Based on Example 2, the volume ratio of nitrogen to hydrogen was modified to 97:3, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0103] TOPCon photovoltaic silver powder D prepared in Example 3 50 =1.315μm, specific surface area is 0.43m² 2 / g, tap density is 3.16g / cm³ 3 The powder properties are not significantly different from those in Example 2, and the presence of 1% more hydrogen slightly enhances the system's deoxygenation and anti-oxidation capabilities. However, for continuous production using a reducing protective gas, the safe threshold for the volume fraction of H2 should be ≤2%, and 3% is close to the lower explosive limit of hydrogen, thus increasing the safety risk level.

[0104] Comparative Example 8 Based on Example 2, the volume ratio of nitrogen to hydrogen was modified to 99:1, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0105] Comparative Example 8: TOPCon photovoltaic silver powder D 50 =1.445μm, specific surface area is 0.47m² 2 / g, tap density is 3.06g / cm³ 3 The powder properties are not significantly different from those in Example 2, but the core of this atmosphere is inert protection + trace deoxidation to prevent the silver powder from oxidizing during the modification process at 50°C; although the deoxidation capacity of 1% H2 is slightly lower than 2%.

[0106] Comparative Example 9 Based on Example 2, only primary and secondary centrifugal separation were set up, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0107] Figure 11 The particle size distribution diagram is shown for the TOPCon photovoltaic silver powder prepared in Comparative Example 9.

[0108] from Figure 11 It can be seen that the TOPCon photovoltaic silver powder D prepared in Comparative Example 9... 50 =1.660μm, its specific surface area is 0.58m². 2 / g, tap density is 3.06g / cm³ 3 Although within the target parameter range, there may be residual impurities, resulting in a slight decrease in performance. While omitting three-stage centrifugation may meet low-end requirements, it leads to insufficient stability in mass production. Large-scale mass production necessitates adherence to three-stage centrifugation to ensure batch consistency.

[0109] Comparative Example 10 Based on Example 2, the medium for the three-stage centrifugation was changed to ethanol, while other conditions remained unchanged, to obtain TOPCon photovoltaic silver powder.

[0110] Figure 12 The image shows the morphology of the TOPCon photovoltaic silver powder prepared in Comparative Example 10.

[0111] from Figure 12 It can be seen that the core function of PVP is to provide steric hindrance dispersion during centrifugation to prevent particle collision and agglomeration under high-speed centrifugation; ethanol has no dispersing effect, and three-stage high-speed centrifugation may cause slight soft agglomeration of ultrafine silver powder.

[0112] Figure 13 The particle size distribution diagram is shown for the TOPCon photovoltaic silver powder prepared in Comparative Example 10.

[0113] from Figure 13 It can be seen that D 50 =1.919μm, with a significantly increased apparent particle size.

[0114] Example 4 Dissolve 170g of silver nitrate crystals with a purity of 99.9% in 1L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤5%) to prepare a 1mol / L silver nitrate solution, and keep the temperature constant to 40℃. Dissolve 141g of potassium sodium tartrate tetrahydrate in 1L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤5%) to prepare a 0.5mol / L chelating agent solution; wherein, the citric acid is reacted with Ag... + Coordination ability and Ag + The molar ratio of the substances is 0.5:1; 16.5 g of acetaldehyde and 15.8 g of sodium sulfite were mixed and dissolved in 1.5 L of deoxygenated water (a deionized aqueous solution with an oxygen content ≤ 5%) to obtain a 0.3336 mol / L solution containing organic and inorganic reducing agents; wherein the molar ratio of acetaldehyde to sodium sulfite was 3:1, and the volume ratio of the solution containing organic and inorganic reducing agents to silver nitrate solution was 1.5:1. 16g of ethylene glycol was mixed with 264g of deoxygenated water to prepare a 5.71wt% dispersant solution; wherein the mass ratio of ethylene glycol to silver nitrate was 1:10.6. Silver nitrate solution was injected into the reaction vessel, the stirring speed was adjusted to 200 rpm, and the temperature was kept constant at 40℃. Then, it was pretreated by ultrasonic treatment at 35 kHz. The chelating agent solution was pumped into the inlet on the side of the vessel at a constant rate of 200 mL / min using a metering pump. After chelation for 5 minutes, the solution first changed from colorless to milky white and then back to colorless. A dual-channel metering pump was used for precise control. The solutions containing organic and inorganic reducing agents were added dropwise to the dispersant solution at a rate of 5:1. The solutions containing organic and inorganic reducing agents were added uniformly at a rate of 300 mL / min. After the addition was completed, the reduction reaction was carried out at a constant temperature of 40℃ and a stirring rate of 400 rpm for 30 min. Then, solid-liquid separation was performed by vacuum filtration, and the mixture was washed with deionized water to remove impurities, thus obtaining silver powder. Weigh 0.72g of stearic acid and 0.72g of silane coupling agent (γ-glycidoxypropyltrimethoxysilane), mix, add 20.52g of anhydrous ethanol, heat to 40℃ and stir to dissolve, to obtain a modifier solution with a mass concentration of 6.56%; wherein, the mass ratio of stearic acid to silane coupling agent is 1:1; the total mass of stearic acid and silane coupling agent is 1.33% of the dry weight of silver powder; Silver powder was placed in a new reactor, and under a nitrogen atmosphere, it was stirred at a constant temperature of 50°C for 20 minutes. The modifier solution was then poured into the reactor at a uniform rate. The gas flow was switched to a nitrogen-hydrogen mixture (N2:H2 volume ratio of 98:2), and surface modification was performed for 30 minutes under stirring. After surface treatment, the filter residue was collected. First, the filter residue was mixed with ethanol, and the centrifuge speed was adjusted to 1000 rpm for 10 minutes at 25°C for primary centrifugation. Then, the centrifuge speed was adjusted to 4000 rpm for 20 minutes at 15°C for secondary centrifugation. Finally, 0.1% of the volume of PVP obtained from the secondary centrifugation was added, and the centrifuge speed was adjusted to 6000 rpm for 20 minutes at 15°C for tertiary centrifugation. Finally, the filtered silver powder is evenly spread into the freeze-drying tray, without compaction, and kept loose. It is pre-frozen at -40℃ for 5 hours under 5 Pa conditions, then heated to 5℃ at a rate of 5℃ / h and held at that temperature for 5 hours, and then heated to 25℃ at a rate of 5℃ / h and held at that temperature for 5 hours to obtain TOPCon photovoltaic silver powder.

[0115] The morphology of the TOPCon photovoltaic silver powder prepared in Example 4 is shown in the figure below. Figure 14 As shown.

[0116] The particle size distribution of the TOPCon photovoltaic silver powder prepared in Example 4 is shown in the figure below. Figure 15 As shown.

[0117] The specific surface area of ​​the TOPCon photovoltaic silver powder prepared in Example 4 was determined as follows: Figure 16 As shown.

[0118] from Figure 14 It can be seen that the particles are basically in a monodisperse state, with no obvious hard agglomerates or sintering necks, and only a small amount of slight soft agglomerates. This indicates that the dispersion was properly controlled during the preparation process, which effectively prevented the adhesion between particles and ensured the dispersibility of the powder. High sphericity is beneficial to improving the flowability, filling density and printing performance of the slurry.

[0119] from Figure 15 It can be seen that the D of TOPCon photovoltaic silver powder 50 =1.649μm.

[0120] from Figure 16 It can be seen that the specific surface area of ​​TOPCon photovoltaic silver powder is 0.3581 m². 2 / g.

[0121] The TOPCon photovoltaic silver powder prepared in Example 3 had a tap density of 3.35 g / cm³, as determined by GB / T 5162. 3 .

[0122] As can be seen from the above embodiments and comparative examples, the preparation method provided by the present invention can obtain TOPCon photovoltaic silver powder with ultra-fine narrow distribution, high sphericity, and good dispersibility.

[0123] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing TOPCon photovoltaic silver powder, comprising the following steps: (1) Mix the silver ion solution and the chelating agent solution to perform chelation and obtain the coordination compound; (2) A dispersant solution and a solution containing an organic reducing agent and an inorganic reducing agent are simultaneously added to the coordination compound obtained in step (1) to carry out a reduction reaction and obtain silver powder; the ratio of the rate at which the dispersant solution and the solution containing an organic reducing agent and an inorganic reducing agent are added is 1:(4~6). (3) Mix the silver powder, stearic acid, silane coupling agent and solvent obtained in step (2) and perform surface modification to obtain TOPCon photovoltaic silver powder.

2. The preparation method according to claim 1, characterized in that, In step (1), the silver ion solution is subjected to ultrasonic treatment before use.

3. The preparation method according to claim 1, characterized in that, The chelating agent in step (1) is at least one of citric acid, sodium citrate, tartaric acid, potassium sodium tartrate, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, dimercaptopropanol, aminotrimethylenephosphonic acid, hydroxyethylidene diphosphonic acid, and catechols.

4. The preparation method according to claim 1, characterized in that, In step (2), the organic reducing agent is at least one of ascorbic acid, formaldehyde, acetaldehyde, methylamine, ethylenediamine, glucose, sodium gluconate, and linoleic acid; the inorganic reducing agent is at least one of hydrazine hydrate, potassium iodide, ferrous sulfate, ferrous chloride, stannous chloride, sodium sulfite, and sodium thiosulfate, and the molar ratio of the organic reducing agent to the inorganic reducing agent is (2~5):

1.

5. The preparation method according to claim 1, characterized in that, In step (2), the reduction reaction temperature is 39.5~40.5℃, the reduction reaction time is 20~40min, and the reduction reaction is carried out in a protective atmosphere.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of stearic acid to silane coupling agent is (1~2):1; the total mass of stearic acid and silane coupling agent is 1~2% of the dry weight of silver powder.

7. The preparation method according to claim 1, characterized in that, In step (3), the surface modification is carried out in a nitrogen-hydrogen mixed gas, wherein the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed gas is (97~98):(2~3), and the temperature of the nitrogen-hydrogen mixed gas is 45~55℃.

8. The preparation method according to claim 1, characterized in that, The surface modification in step (3) also includes post-processing, which includes filtration, primary centrifugation, secondary centrifugation, tertiary centrifugation and vacuum freeze drying in sequence.

9. The preparation method according to claim 8, characterized in that, The medium used in the three-stage centrifugal separation is a dispersant.

10. TOPCon photovoltaic silver powder prepared by the preparation method according to any one of claims 1 to 9.

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