Preparation method of silver-coated glass powder for solar cell silver paste

Abstract

The application relates to the technical field of solar cell materials, and discloses a preparation method of silver-coated glass powder for solar cell silver paste, which comprises the following steps: S1. glass powder core preparation: raw material mixing: A phase and B phase are respectively weighed, and ball milling is carried out; gradient melting; crushing and grading; S2. plasma activation treatment pretreatment: the prepared glass powder core is placed in a citric acid solution, ultrasonic cleaning is carried out, and pollutants on the surface of the glass powder are removed; fluidized bed activation; plasma treatment; passivation protection; S3. microfluidic-ultrasonic coupling coating; S4. post-treatment procedure: washing and drying; heat treatment; screening and packaging: the powder after annealing is screened through a vibrating screen to obtain the silver-coated glass powder. The preparation method of the silver-coated glass powder for the solar cell silver paste is low in cost and less polluting.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of solar cell materials, in particular to a preparation method of silver-coated glass powder for solar cell silver paste. BACKGROUND

[0002] As the core conductive material of photovoltaic cells, the performance of solar cell silver paste directly affects the photoelectric conversion efficiency and long-term reliability of the cells. The silver-coated glass powder, as a key functional component of the silver paste, plays a triple role of etching the passivation layer, promoting ohmic contact and building a conductive network during the sintering process. The current mainstream production process is based on the three-step method (roughening-activation-silver coating) developed by Hunan Weineng New Material in 2011. The technology uses a roughening liquid treatment, an activation sensitization liquid treatment, and finally reduces and deposits a silver layer in a silver nitrate solution. However, the process has three major bottlenecks:

[0003] Insufficient uniformity of coating: the fluid dynamics in the traditional stirring reaction kettle (as described in patent CN201110200609.X) is uneven, resulting in large fluctuations in the surface silver layer coverage of the glass powder (typical value 65-80%) and wide distribution of silver particle size (50-500 nm), and poor consistency of silver film migration during sintering.

[0004] Single function of glass powder: the existing glass powder is mostly a single component system (such as system), which is difficult to meet the dual requirements of TOPCON cell resistance to acetic acid corrosion (requiring mass loss rate <0.5%) and low-temperature sintering characteristics (softening point needs to be less than or equal to 550 DEG C).

[0005] Heavy pollution in the reduction process: the chemical reduction method needs to use formaldehyde or hydrazine hydrate as a toxic reducing agent, and 3-5 tons of cyanide-containing wastewater are generated per ton of product, and residual sulfur elements ( ) will catalyze the oxidation of the silver layer. SUMMARY

[0006] Technical problems solved

[0007] In view of the deficiencies of the prior art, the application provides a preparation method of silver-coated glass powder for solar cell silver paste, which has uniform coating, low cost and less pollution.

[0008] Technical scheme

[0009] To achieve the above purpose, the application provides the following technical scheme: a preparation method of silver-coated glass powder for solar cell silver paste, comprising the following steps:

[0010] S1. Glass powder core preparation:

[0011] Raw material mixing: First weigh phase A raw material, then weigh phase B raw material, and then ball mill phase A and phase B together for 2 hours (200 rpm, zirconium balls:material = 3:1).

[0012] The composition of phase A is as follows: 35 parts by weight 30 parts by weight 12 parts by weight 4.5 parts by weight 1.5 parts by weight;

[0013] The composition of phase B is as follows: 20 parts by weight 18 parts by weight 10 parts by weight 2 parts by weight;

[0014] Gradient melting: The mixed raw materials are placed in a corundum crucible and melted for 2 hours, then cooled to 800℃ and held for 30 minutes, followed by the introduction of... Protect against oxidation;

[0015] Phase separation control: with The molten material is water-quenched to room temperature at a certain rate to obtain a phase-separated glass.

[0016] Crushing and Classification: First, a jaw crusher is used to coarsely crush the phase-separated glassy phases, and then a fluidized bed air jet mill is used to further pulverize it. Finally, a cyclone classifier is used to remove the particle size. The particles were used to obtain glass powder nuclei;

[0017] S2. Plasma activation treatment

[0018] Pretreatment: The prepared glass powder nucleus is placed in In a citric acid solution, at a power of 300W and a frequency Under these conditions, ultrasonic cleaning is performed for 20 minutes to remove contaminants from the glass powder surface;

[0019] Fluidized bed activation: Pretreated glass powder is loaded into a quartz reaction chamber, and the chamber is evacuated to reduce the pressure inside the chamber to a minimum. Then pass through A 9:1 volume ratio of mixed gas was applied until the working pressure inside the reaction chamber reached [the required level]. ;

[0020] Plasma processing: Turn on the radio frequency power supply, power density The processing time is 8 minutes, which generates ≡Si• free radicals on the surface;

[0021] Passivation protection: 0.5% vinyltrimethoxysilane vapor is introduced to form a protective film on the free radical surface;

[0022] S3. Microfluidic-ultrasonic coupling coating

[0023] Preparation of silver solution: Prepare a 0.25 mol / L silver nitrate solution, then add 0.1 wt% polyvinylpyrrolidone (PVP). )and Stir well to obtain silver solution;

[0024] Preparation of reducing solution: Mix 0.3 mol / L ascorbic acid, 0.1 mol / L glucose and 0.05% sodium dodecyl sulfate evenly to prepare the reducing solution;

[0025] Microfluidic coating: Silver solution and reducing solution are pumped into the microreactor at a volume ratio of 1:3. The temperature of the reaction zone is 60℃ and the pulse period is 1s (0.3s on / 0.7s off) to carry out the microfluidic coating reaction.

[0026] Ultrasonic-enhanced deposition: Powder that has undergone preliminary microfluidic coating is transferred into an electrochemical bath, where the bath solution... concentration , apply Power density Ultrasound and duty cycle 20%, current density A pulsed current was applied for 30 minutes to achieve ultrasonic-enhanced deposition.

[0027] Membrane separation and recovery: The effluent from the electrochemical cell is filtered through a 0.1μm ceramic membrane, with a silver ion rejection rate of >99.5%. The concentrate is then returned to the silver solution preparation step to achieve the recycling of silver ions.

[0028] S4. Post-processing steps

[0029] Washing and drying: The powder coated by microfluidic-ultrasonic coupling was washed by centrifugation with an ethanol-water mixture (volume ratio 1:1). Centrifuge at 1000 rpm for 10 minutes, repeat washing, and then vacuum dry at 60°C for 3 hours;

[0030] Heat treatment: Place the dried powder in... Annealing was performed at 350°C in a 95:5 volume ratio atmosphere to eliminate internal stress in the powder.

[0031] Sieving and Packaging: The annealed powder is sieved through a 500-mesh vibrating screen to obtain a particle size of 1.5 mm. The silver-coated glass powder has a silver layer coverage of ≥95%.

[0032] Furthermore, in S1, the melting temperature during the gradient melting process is 1250°C.

[0033] Further, in S1, the crushing and classification process involves coarsely crushing the phase-separated glass body to... .

[0034] Furthermore, in S2, the fluidized bed processing chamber is made of quartz material, has a diameter of 200mm, a powder residence time of 5-10 minutes, and a temperature control of 40-45℃.

[0035] Furthermore, in step S2, plasma processing involves turning on the radio frequency power supply and adjusting the frequency... ,power Adjustable, equipped with Mixed air path and The ratio is 9:1.

[0036] Furthermore, in S3, the microreactor employs a Tesla valve structure channel (width × depth = 500). ).

[0037] Furthermore, in step S4, washing and drying: washing 3 times.

[0038] Furthermore, in step S4, the heat treatment and annealing time is 30 minutes.

[0039] Beneficial technical effects

[0040] 1. Design of a two-phase separated glass core structure

[0041] Technological Breakthrough: A two-phase structure of "high-lead tellurium phase + zinc borosilicate phase" was achieved through... Interface modifiers induce the formation of a nano-interpenetrating network. Compared to single-phase glass powder (CN 119285239 A), this structure exhibits staged melting characteristics during sintering: phase A melts first at 520℃ to drive the flow of the silver film, while phase B melts at 580℃ to provide etching control.

[0042] 2. Solution Acetic acid corrosion of batteries and Layer-by-layer etching contradiction: in the B phase The network provides excellent acid resistance (acetic acid weight loss rate) Traditionally 0.8%, while phase A ensures low-temperature fluidity. After passing 3000 hours of double 85 testing, the weld pull retention rate of the battery module is >95%.

[0043] 3. Silver coverage increased from 75±8% in the traditional process to 98±1%, and the silver layer thickness fluctuation range (CV value) decreased from 25% to 8%. After sintering, the silver grain size distribution narrowed (1.5±0.3μm vs. traditional 0.8-5μm), and the contact resistance decreased to [missing value]. (Tradition ).

[0044] 4. Piezoelectric ultrasonic cavitation combined with pulsed electrochemistry to generate periodic cavitation bubble collapse (local temperature , pressure ) in 28 kHz ultrasonic field to drive silver ion directional deposition while densifying silver layer using cavitation impact effect. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0046] Embodiment 1

[0047] A preparation method of a silver-coated glass powder for silver paste of a solar cell, comprising the following steps:

[0048] S1. Glass powder core preparation:

[0049] Raw material mixing: first, A-phase raw materials are weighed, then B-phase raw materials are weighed, and then the A-phase and the B-phase are ball-mixed for 2 hours (rotation speed 200 rpm, zirconium ball: material = 3:1);

[0050] The A-phase consists of: 35 parts by weight, 30 parts by weight, 12 parts by weight, 4.5 parts by weight, 1.5 parts by weight;

[0051] The B-phase consists of: 20 parts by weight, 18 parts by weight, 10 parts by weight, 2 parts by weight;

[0052] Gradient melting: the mixed raw materials are placed in a corundum crucible and melted at 1250℃ for 2 hours, cooled to 800℃ and kept for 30 minutes, and protective gas is introduced to prevent oxidation;

[0053] Phase separation control: the melted material is water-quenched to room temperature at a rate of 50℃ / s to obtain a phase-separated glass body;

[0054] Crushing and grading: the phase-separated glass body is first coarsely crushed to by a jaw crusher, and then crushed to = 1.2 pm, and finally, a cyclone classifier was used to remove particles with a size > 3 pm to obtain the glass powder core;

[0055] S2. Plasma activation treatment

[0056] Pre-treatment: The prepared glass powder core was placed in a 0.1 mol / L citric acid solution and ultrasonically cleaned for 20 minutes at a power of 300 W and a frequency of 40 kHz to remove contaminants on the surface of the glass powder;

[0057] Fluidized bed activation: The pre-treated glass powder was loaded into a quartz reaction chamber, the reaction chamber was vacuumed to reduce the pressure in the chamber to , then a mixture of (volumetric ratio 9:1) was introduced until the working pressure in the reaction chamber reached ;

[0058] Plasma treatment: the radio frequency power was turned on, the power density was , and the treatment time was 8 minutes to generate free radicals on the surface;

[0059] Passivation protection: 0.5% vinyltrimethoxysilane vapor was introduced to form a protective film on the surface of the free radicals;

[0060] S3. Microfluidic-ultrasonic coupling coating

[0061] Silver solution preparation: a silver nitrate solution was prepared, and then polyvinylpyrrolidone and were added thereto, and the mixture was stirred uniformly to obtain a silver solution; Reduction solution preparation: ascorbic acid,

[0062] glucose, and 0.05% sodium dodecyl sulfate were mixed uniformly to prepare a reduction solution; Microfluidic coating: the silver solution and the reduction solution were pumped into a microreactor at a volumetric ratio of 1:3, the reaction zone temperature was 60°C, the pulse cycle was 1 s (on 0.3 s / off 0.7 s), and the microfluidic coating reaction was performed;

[0063] Ultrasonic enhanced deposition: the powder coated by the microfluidic method was transferred into an electrochemical cell, the concentration of the electrolyte in the cell was , ultrasonic waves with a power density of 50 W / L and a duty cycle of 20% and pulsed current with a current density of

[0064] were applied for 30 minutes to realize ultrasonic enhanced deposition;

[0065] ​​​​​Membrane separation and recovery: The effluent from the electrochemical cell is separated by... The ceramic membrane is used for filtration, with a silver ion rejection rate of >99.5%. The concentrate is then returned to the silver solution preparation step to achieve the recycling of silver ions.

[0066] S4. Post-processing steps

[0067] Washing and drying: The powder coated by microfluidic-ultrasonic coupling was washed by centrifugation with an ethanol-water mixture (volume ratio 1:1). Centrifuge at 1000 rpm for 10 minutes, repeat washing 3 times, and then vacuum dry at 60°C for 3 hours;

[0068] Heat treatment: Place the dried powder in... Annealing at 350°C for 30 minutes in a 95:5 (volume ratio) atmosphere to eliminate internal stress in the powder;

[0069] Sieving and Packaging: The annealed powder is sieved through a 500-mesh vibrating screen to obtain silver-coated glass powder with a particle size of 1.5±0.5μm and a silver layer coverage of ≥95%.

[0070] In S2, the fluidized bed processing chamber is made of quartz material, has a diameter of 200mm, a powder residence time of 5 minutes, and a temperature control of 40℃.

[0071] In step S2, plasma processing involves turning on the radio frequency power supply and adjusting the frequency. Equipped Mixed air path (ratio 9:1).

[0072] In S3, the microreactor employs a Tesla valve structure channel (width × depth = ).

[0073] The TOPCON back silver paste prepared from the silver-coated glass powder obtained in this invention, under standard process conditions (screen printing + sintering at 780℃), reduces the open-circuit voltage of the battery cell ( Upgraded to (Tradition The fill factor (FF) reaches 83.5% (compared to 81.2% in the traditional method), and the photoelectric conversion efficiency exceeds 26.2% (compared to 25.0% in the traditional method).

[0074] Process environmental innovation: Elimination of formaldehyde use (reducing highly toxic waste liquid by 3.5 tons per ton of product), silver ion recycling rate ≥99.5%, and energy consumption reduced by 40% (plasma activation replaces high-temperature heat treatment).

[0075] Significant cost-effectiveness: Although it increases the cost of preparing duplex glass powder, the overall silver consumption is reduced and the yield is improved, resulting in a decrease in the overall cost of silver paste.

[0076] Completely replace formaldehyde and other toxic reducing agent, waste water COD reduced to (Traditional process > 1000 mg / L ). Silver layer bonding strength increased 2 times (scratch test critical load Traditional 6N), and silver utilization rate from 85% to 99.5% increase.

[0077] It should be noted that in this paper, the term "including", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0078] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0079] Those skilled in the art should understand that the above only describes several specific embodiments of the present application, not all embodiments.

Claims

1. A method for producing a glass powder coated with silver for silver paste of a solar cell, characterized by, The method comprises the following steps: S1. Glass powder core preparation: Raw material mixing: first, weigh the A phase raw materials, then weigh the B phase raw materials, and then ball mill mix the A phase and the B phase; The A phase consists of: PbO 35 parts by weight, parts by weight, parts by weight, parts by weight, parts by weight; The B phase consists of: ZnO 20 parts by weight, parts by weight, parts by weight, parts by weight; Gradient melting: The mixed raw materials were put into a corundum crucible to be melted, cooled, and nitrogen was introduced Protection against oxidation; Phase separation control: quench the molten material to room temperature by water to obtain a phase separation glass body; Crushing and Classification: First, a jaw crusher is used to coarsely crush the phase-separated glassy phases, then a fluidized bed jet mill is used to pulverize it, and finally a cyclone classifier is used to remove particle size. The particles were used to obtain glass powder nuclei; S2. Plasma activation treatment Pre-treatment: place the prepared glass powder core in a citric acid solution and ultrasonically clean to remove contaminants on the surface of the glass powder; Fluidized bed activation: The pretreated glass powder was loaded into a quartz reaction chamber, the chamber was vacuumized to reduce the pressure, and then mixed gas was introduced until the working pressure in the chamber reached 100 Pa. Mixed gas was introduced until the working pressure in the chamber reached 100 Pa. Plasma treatment: turn on the radio frequency power source to generate ≡Si• free radicals on the surface of the glass powder; Passivation protection: introduce vinyltrimethoxysilane vapor to form a protective film on the surface of the free radicals; S3. Microfluidic-ultrasonic coupling coating Silver solution preparation: A silver nitrate solution was prepared and polyvinylpyrrolidone and were added thereto, and stirred to obtain a silver solution; Reducing liquid preparation: mix ascorbic acid, glucose and sodium dodecyl sulfate uniformly to prepare a reducing liquid; Microfluidic coating: pump the silver liquid and the reducing liquid into a microreactor to perform a microfluidic coating reaction on the glass powder; Ultrasonic enhanced deposition: transfer the microfluidically coated powder into an electrochemical cell, apply ultrasonic and pulse current treatment to achieve ultrasonic enhanced deposition; Membrane separation and recovery: filter the discharge liquid in the electrochemical cell through a ceramic membrane, return the concentrated liquid to the silver liquid preparation step to realize the recycling of silver ions; S4. Post-processing procedure Washing and drying: centrifugally wash the microfluidic-ultrasonic coupling coated powder with an ethanol-water mixture, and then vacuum dry; Heat treatment: The dried powder was annealed in an atmosphere to relieve internal stress of the powder. Heat treatment: The dried powder was annealed in an atmosphere to relieve internal stress of the powder. Screening and packaging: screen the annealed powder through a vibrating screen to obtain silver-coated glass powder.

2. The method for preparing a silver glass powder for a silver paste of a solar cell according to claim 1, characterized in that, In the S1, the melting temperature in the gradient melting process is 1250°C.

3. The method of claim 1, wherein the glass powder is prepared by the steps of: preparing a glass frit by mixing a glass material and a fluxing agent; melting the glass frit; and pulverizing the melted glass frit. In the S1, the pulverization and classification: the phase separation glass is coarsely crushed to .

4. The method of claim 1, wherein the silver glass powder is prepared by the steps of: preparing a silver glass powder by a method according to any one of claims 1 to 3; and adding a fluxing agent to the silver glass powder. In the S2, the fluidized bed type treatment chamber is made of quartz with a diameter of 200 mm, the powder residence time is 5-10 minutes, and the temperature is controlled at 40-45°C.

5. The method of claim 1, wherein the silver glass frit is prepared by mixing the silver glass frit with a glass powder, a binder, a dispersant, and a solvent. In the S2, the plasma treatment: open radio frequency power, frequency 13.56MHz, power 0-500W adjustable, equipped with Mixed gas path, And The ratio of 9:

1.

6. The method of claim 1, wherein the silver glass frit is prepared by mixing the silver glass frit with a glass powder, a binder, a solvent, and a dispersant. In the S3, the microreactor adopts a Tesla valve structure channel, and the Tesla valve structure channel is wide x deep .

7. The method of claim 1, wherein the glass powder is prepared by the steps of: preparing a glass frit by mixing a glass material and a fluxing agent; melting the glass frit; and pulverizing the melted glass frit. In the S4, the washing and drying is performed for 3 times.

8. The method of claim 1, wherein the silver glass frit is prepared by mixing the silver glass frit with a solvent, and then adding a dispersant to the mixture. In the S4, the heat treatment is performed for 30 minutes.

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