Laser-assisted sintering base metal slurry for TOPCon solar cell and preparation method of laser-assisted sintering base metal slurry

Abstract

The invention provides laser-assisted sintering base metal slurry for a TOPCon solar cell and a preparation method of the laser-assisted sintering base metal slurry, and relates to the technical field of photovoltaic cell manufacturing, the slurry comprises the following components: nickel powder, glass powder and an organic carrier; wherein the glass powder at least comprises two types of glass powder, one type of glass powder is corrosive glass powder, and the corrosive glass powder at least comprises one or two of lead oxide, bismuth oxide or antimony oxide; the other kind of glass powder is auxiliary promotion type glass powder, and the auxiliary promotion type glass powder takes silicon and borate as main bodies; the two kinds of glass powder do not contain first main group element oxides. The nickel powder is used for replacing silver powder, the contact defect is made up through the LECO technology, the specific glass powder formula and the high-temperature sintering technology are combined, performance balance is achieved, and verification experiments prove that the nickel paste achieves the same efficiency (gt; 24.5%), and the cost is reduced by about 30%-40%.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cell manufacturing, and particularly to a laser-assisted sintering base metal paste for TOPCon solar cells and a preparation method thereof. Background Art

[0002] According to a report by the International Renewable Energy Agency (IRENA), the newly installed capacity of global renewable energy reached 473 GW in 2023. Among them, the newly installed capacity of solar photovoltaics was 345.5 GW, accounting for 73% of the annual growth of renewable energy. According to the prediction of the International Energy Agency (IEA), the newly installed capacity of global solar photovoltaics in 2024 is about 402.3 GW. To achieve the net-zero emission target in 2030, the photovoltaic installed capacity needs to reach 6101 GW, that is, nearly 683 GW needs to be newly added every year, and the average growth rate needs to reach 14.16%. Among many solar photovoltaic power generation technologies, crystalline silicon solar cell technology is the most mature and lowest-cost mass production technology so far.

[0003] In the manufacturing process of crystalline silicon solar cells, photovoltaic conductive paste is a key auxiliary material for preparing the metal electrodes of the battery. Its quality directly affects the conversion efficiency of the battery, the output power of the module, the service life of the system, etc. Crystalline silicon solar cells are classified into BSF cells, PERC cells, TOPCon cells, HJT cells, BC cells, etc. due to their structures. BSF cells have withdrawn from the historical stage due to low efficiency; PERC cells have certain competitiveness in terms of cost performance, but are gradually being phased out due to relatively low overall efficiency; HJT cells and BC cells are still in the initial stage of mass production due to high manufacturing costs; TOPCon cells have become the market mainstream due to advantages such as high efficiency and mature mass production technology. Three kinds of conductive pastes are used in the manufacturing process of TOPCon cells, and all of them are silver pastes. Therefore, photovoltaic silver paste is one of the main non-silicon costs of photovoltaic cells. Therefore, reducing the consumption of silver paste or replacing silver powder with base metal powder has become a direction for continuous research and development of photovoltaic pastes, and great success has been achieved in reducing the consumption of silver paste. However, no breakthrough has been made in the replacement of base metals. Currently, the silver paste consumption of TOPCon cells is about 10 - 13 mg / W, and the silver paste demand in 2024 is expected to be 4000 - 5000 tons, which is still very large. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem in the prior art that the large consumption of silver paste leads to high costs of photovoltaic cells.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A laser-assisted sintered base metal paste for TOPCon solar cells, and the components of the paste are as follows: including nickel powder, glass powder and organic carrier;

[0007] Among them, the glass powder includes at least two types of glass powder, one of which is corrosive glass powder, and the composition of the corrosive glass powder contains at least one or two of lead oxide, bismuth oxide or antimony oxide;

[0008] The other glass powder is auxiliary promoting glass powder, and the auxiliary promoting glass powder is mainly composed of silicon and borate;

[0009] Neither of the two glass powders contains oxides of Group I elements.

[0010] Preferably, the corrosive glass powder is one of the systems of PbO(Bi2O3, Sb2O3)-B2O3-SiO2-x, PbO-Bi2O3(Sb2O3)-B2O3-SiO2-x or Bi2O3-PbO(Sb2O3)-B2O3-SiO2-x, where x is one or several other oxides.

[0011] Preferably, the particle size D50 of the nickel powder ranges from 0.5 to 5.0 μm, and the maximum particle D100 is not greater than 8 μm.

[0012] Preferably, the particle size D50 of the nickel powder ranges from 0.5 to 2.0 μm, and the maximum particle D100 is not greater than 5 μm.

[0013] Preferably, the organic carrier: includes resin, solvent, thickener, thixotropic agent.

[0014] Preferably, the mass composition of the organic carrier is: polyvinyl butyral 5%, SEPS resin 6%, butyl carbitol 20%, butyl carbitol acetate 40%, dimethyl adipate 16%, polyamide wax 4%, methyl silicone oil 4%, and auxiliary agent 5%.

[0015] Preferably, its preparation method includes the following steps:

[0016] S1: Prepare glass powder: The glass powder is prepared by steps of batching - mixing - melting - cold extraction - crushing - grinding. Among them, the impurities of Group I elements in the raw materials used for the corrosive glass powder are controlled at the ppm level, and the crucible used for melting is made of platinum, quartz or corundum;

[0017] The melting temperature of the auxiliary promoting glass powder is 1400°C - 1600°C, the heat preservation time is 50 min, and the quartz crucible;

[0018] S2: Prepare paste: The paste preparation process is batching - mixing - three-roll - sieving - stirring - detecting;

[0019] Among them, ultrasonic dispersion is introduced during the mixing process or a planetary dispersion process is added after stirring and dispersion, and at least two passes of grinding are performed in the EKKART gap 5μm mode at the final stage of the three-roll grinding stage;

[0020] S3: Slurry performance test.

[0021] Preferably, after the glass powder is prepared in S1, it is quenched with deionized water, dried, dry-milled and crushed with Φ10mm zirconia balls, and then Φ3mm zirconia balls and Φ1mm zirconia balls are mixed in a volume ratio of 4:3, and wet-milled with deionized water as the medium. The particle size D50 of the glass powder is controlled in the range of 0.5 - 1.5μm, and the maximum particle size D100 is less than 6μm.

[0022] Preferably, the specific process for preparing the slurry is: weighing the organic carrier, glass powder and nickel powder in proportion, stirring and mixing, then performing planetary dispersion, grinding 8 times with an EKKART three-roll mill, and the gap for the last 2 passes is 5μm. The fineness of the obtained slurry is less than 5μm.

[0023] Compared with the prior art, the present application includes the following beneficial effects:

[0024] 1. In the present application, nickel powder is used as the main conductive medium, replacing traditional silver powder, which can significantly reduce the material cost;

[0025] 2. Through the two-stage laser-assisted sintering technology of forming a conductive film by co-firing + generating local high temperature by laser excitation of high current, a silicon-nickel alloy contact is formed, improving the contact quality and battery efficiency;

[0026] 3. In the present application, a design of dual-functional glass powder is adopted, among which the corrosive glass powder (containing lead / bismuth / antimony oxides) is used to corrode the silicon nitride film and form laser activation points, and the auxiliary promoting glass powder (containing silicon / borate) optimizes the sintering function of nickel powder and reduces the resistivity;

[0027] 4. In the present application, an ultrasonic dispersant planetary dispersion process is introduced to solve the problem of nickel powder agglomeration, and the gap 5μm mode is adopted during three-roll grinding to improve the slurry uniformity.

[0028] 5. Through the high-temperature sintering process, the peak temperature is maintained above 750°C and the sintering time is above 12 seconds to ensure the conductivity of the nickel film. Description of the Drawings

[0029] Figure 1 It is a physical picture of the slurry prepared in an embodiment of the present invention;

[0030] Figure 2 It is a front photo of a TOPCon battery after nickel paste printing and sintering laser in an embodiment of the present invention; Detailed Embodiments

[0031] The present invention will be further described in detail below in conjunction with specific embodiments.

[0032] The present application provides a laser-assisted sintering base metal paste for TOPCon solar cells, and its components are as follows:

[0033] It includes nickel powder (mass percentage 80%-90%), glass powder (mass percentage 1%-5%), and organic carrier (mass percentage 5%-19%);

[0034] In one embodiment, for the nickel powder: generally, the particle size D50 of the nickel powder is required to be in the range of 0.5-5.0 μm, and the maximum particle D100 is not greater than 8 μm; preferably, the particle size D50 of the nickel powder is in the range of 0.5-2.0 μm, and the maximum particle D100 is not greater than 5 μm to meet the requirements of the increasingly fine opening printing of the grid lines.

[0035] The glass powder includes at least two types of glass powder. The function of one type of glass powder is to corrode the silicon nitride (SINx) film during the sintering stage to form contacts that can be activated during the laser stage; the function of the other type of glass powder is to assist in promoting the sintering of the nickel powder into a film during the sintering stage.

[0036] Among them, the composition of the corrosive glass powder contains at least one or two of lead oxide, bismuth oxide, or antimony oxide, generally PbO(Bi 2 O 3 、Sb 2 O 3 )-B 2 O 3 -SiO 2 -x、PbO-Bi 2 O 3 (Sb 2 O 3 )-B 2 O 3 -SiO 2 -x or Bi 2 O 3 -PbO(Sb 2 O 3 )-B 2 O 3 -SiO 2 -x system, where x is one or several other oxides, but does not contain oxides of the first main group elements such as Li, Na, and K, and its ratio is adjusted according to the requirements of the corresponding paste formula.

[0037] The auxiliary promoting glass powder is mainly composed of silicon and borate with good wettability to nickel, and is adjusted according to the corresponding sintering properties to optimize the volume resistivity and adhesion after sintering. Similarly, the auxiliary promoting glass powder does not contain oxides of Group I elements such as Li, Na, and K.

[0038] The organic carrier: includes resin, solvent, thickener, thixotropic agent; used to ensure the storage stability and good printability of the slurry;

[0039] Preferably, the mass composition of the organic carrier is: polyvinyl butyral 5%, SEPS resin 6%, butyl carbitol 20%, butyl carbitol acetate 40%, dimethyl adipate 16%, polyamide wax 4%, methyl silicone oil 4%, and additives 5%.

[0040] Based on the above raw material composition, the present application also provides a preparation method of a laser-assisted sintered base metal paste for TOPCON solar cells, which includes the following steps:

[0041] S1: Preparation of glass powder;

[0042] In one embodiment, the preparation process of the glass powder is basically the same as that of the glass powder for traditional electronic pastes, namely batching - mixing - melting - cold extraction - crushing - grinding - classification - detection - packaging.

[0043] Among them, the impurities of Group I elements in the raw materials used for the corrosive glass powder are controlled at the ppm level, and the crucible used for melting is made of platinum, quartz or corundum.

[0044] Specifically, in one embodiment, the melting temperature of the corrosive glass powder is 900°C - 1100°C, the holding time is 30 min, and the quartz crucible is used.

[0045] The melting temperature of the auxiliary promoting glass powder is 1400°C - 1600°C, the holding time is 50 min, and the quartz crucible is used.

[0046] After preparation, quench with deionized water, dry and then dry-grind and crush with Φ10mm zirconium balls, and then mix Φ3mm zirconium balls and Φ1mm zirconium balls in a volume ratio of 4:3, and carry out wet grinding with deionized water as the medium. The particle size D50 of the glass powder is controlled in the range of 0.5 - 1.5 μm, and the maximum particle size D100 is less than 6 μm.

[0047] S2: Preparation of slurry:

[0048] The preparation process of the slurry is basically the same as that of traditional electronic pastes, namely batching - mixing - three-roll - sieving - stirring - detection - packaging.

[0049] In one embodiment, since the nickel powder is prepared by a physical method and is prone to agglomeration, the stirring time and the number of three-roll grinding passes need to be increased in the two stages of mixing and three-roll grinding. More preferably, ultrasonic dispersion is introduced during the mixing process or a planetary dispersion process is added after stirring and dispersion. In the three-roll grinding stage, the EKATO gap 5μm mode is finally used for grinding not less than twice.

[0050] Specifically, in one embodiment, the organic carrier, glass powder and nickel powder are weighed in proportion, stirred and mixed, then subjected to planetary dispersion, and ground 8 times with an EKATO three-roll mill. The gap for the last 2 passes is 5μm, and the fineness of the obtained slurry is less than 5μm.

[0051] S3: Slurry performance test:

[0052] The slurry performance test conditions are as follows: The screen plate parameters are 500 mesh, wire diameter 9μm, yarn thickness 15μm, film thickness 3.5μm, opening 12μm, and 148 sub-grid non-knotted main and sub-integrated stainless steel wire mesh; the silicon wafer is a 182mm×182mm semi-finished TOPCon blue film from a certain manufacturer, with a front sheet resistance of 300±15 ohms per square, a front alumina thickness of 3 - 5nm, a silicon nitride thickness of 79 - 83nm, and a silicon nitride refractive index of 2.05 - 2.15; the back fine grid slurry uses the mainstream model used by the silicon wafer manufacturer; a belt-type sintering furnace, the sintering furnace temperature is adjusted, the actual peak temperature is 760℃, and the sintering time above 650℃ is 13.5 seconds; the laser light source is green, the laser power is 50%, a bias voltage of 17mV is applied, and the laser scanning method is area scanning. After the laser is completed, the battery conversion efficiency is tested, and the result is the average value of 5 pieces.

[0053] Based on the preparation method of the laser-assisted sintering base metal slurry for TOPCON solar cells, the present application also provides the printing and sintering of the slurry. Among them, the printing can adopt the same printing process as the existing front LECO silver paste.

[0054] Sintering: Since the sintering activity of the nickel powder is lower than that of the silver powder, higher sintering temperature and longer sintering time are required to ensure the sintering film formation of the nickel powder and the resistivity of the nickel film. Preferably, the actual peak temperature of the sintering process reaches 750℃ and above, and the sintering time above 650℃ reaches 12 seconds and above.

[0055] Laser: The laser power and the applied bias voltage can be adjusted according to the actual situation. Preferably, the applied bias voltage is adjusted to 16mV and above.

[0056] The above content is elaborated below with specific examples:

[0057] Example 1:

[0058] The mass composition of the corrosive glass powder: lead oxide 75%, boron oxide 10%, silicon oxide 8%, zinc oxide 4%, aluminum oxide 3%.

[0059] The mass composition of the auxiliary promoting glass powder: 5% silicon oxide, 35% boron oxide, 10% tellurium oxide, 15% calcium oxide, 10% aluminum oxide, 20% bismuth oxide, 5% molybdenum oxide.

[0060] The specifications of the nickel powder: The particle size D50 of nickel powder 1 is 1.2 μm and D100 is 4.7 μm

[0061] The mass composition of the slurry: 85% nickel powder, 0.5% corrosive glass powder, 2.5% auxiliary promoting glass powder, 12% organic carrier.

[0062] Example 2:

[0063] The mass composition of the corrosive glass powder: 65% lead oxide, 10% bismuth oxide, 10% boron oxide, 8% silicon oxide, 4% zinc oxide, 3% aluminum oxide.

[0064] The mass composition of the auxiliary promoting glass powder is the same as that in Example 1.

[0065] The specifications of the nickel powder: The particle size D50 of nickel powder 1 is 1.2 μm and D100 is 4.7 μm

[0066] The mass composition of the slurry: 83% nickel powder, 0.6% corrosive glass powder, 3.0% auxiliary promoting glass powder, 13.4% organic carrier.

[0067] Example 3:

[0068] The mass composition of the corrosive glass powder: 70% bismuth oxide, 5% antimony oxide, 8% boron oxide, 10% silicon oxide, 7% molybdenum oxide.

[0069] The mass composition of the auxiliary promoting glass powder is the same as that in Example 1.

[0070] The specifications of the nickel powder: The particle size D50 of nickel powder 2 is 0.7 μm and D100 is 4.2 μm

[0071] The mass composition of the slurry: 80% nickel powder, 0.5% corrosive glass powder, 2.5% auxiliary promoting glass powder, 17% organic carrier.

[0072] Example 4:

[0073] The mass composition of the corrosive glass powder: 35% lead oxide, 35% bismuth oxide, 15% boron oxide, 5% silicon oxide, 5% molybdenum oxide, 5% aluminum oxide.

[0074] The mass composition of the auxiliary promoting glass powder: 20% lead oxide, 10% silicon oxide, 30% boron oxide, 5% tellurium oxide, 15% magnesium oxide, 15% aluminum oxide, 5% tungsten oxide.

[0075] Nickel powder specifications: For nickel powder 3, D50 is 1.8 μm and D100 is 5.5 μm.

[0076] Slurry mass composition: 90% nickel powder, 0.3% corrosive glass powder, 2.2% auxiliary promoting glass powder, 7.5% organic carrier.

[0077] Example 5:

[0078] Mass composition of corrosive glass powder: 70% bismuth oxide, 15% boron oxide, 5% silicon oxide, 5% molybdenum oxide, 5% zinc oxide.

[0079] The mass composition of the auxiliary promoting glass powder is the same as that in Example 4.

[0080] Nickel powder specifications: Nickel powder 1, nickel powder 2, and nickel powder 3 in Examples 1 - 3 are mixed in a mass ratio of 2:5:3.

[0081] Slurry mass composition: 86% nickel powder, 0.5% corrosive glass powder, 2.5% auxiliary promoting glass powder, 11% organic carrier.

[0082] The following are the electrical properties of the slurry prepared according to the above examples:

[0083]

[0084]

[0085] In this application, nickel powder is used instead of silver powder, and the contact defects are compensated by LECO technology. Combining a specific glass powder formula (to avoid contamination by Group I elements) and a high - temperature sintering process, performance balance is achieved. Moreover, through verification experiments, it is proved that the nickel paste can achieve the same efficiency (>24.5%) as the silver paste in TOPCon cells, with a cost reduction of about 30% - 40%.

Claims

1. A base metal slurry for laser-assisted sintering of TOPCON solar cells, characterized in that: The slurry comprises the following components: nickel powder, glass powder and an organic carrier; The glass powder comprises at least two types of glass powder, one of which is a corrosive glass powder, and the composition of the corrosive glass powder contains at least one or two of lead oxide, bismuth oxide or antimony oxide; Another type of glass powder is an auxiliary-promoting glass powder, wherein the auxiliary-promoting glass powder is mainly composed of silicon and borate; Both of the glass powders do not contain oxides of the first main group elements.

2. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 1, characterized in that: The corrosive glass powder is one of the PbO(Bi2O3, Sb2O3)-B2O3-SiO2-x, PbO-Bi2O3(Sb2O3)-B2O3-SiO2-x or Bi2O3-PbO(Sb2O3)-B2O3-SiO2-x systems, wherein x is one or more other oxides.

3. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 2, characterized in that: The nickel powder has a particle size D50 ranging from 0.5 to 5.0 μm, and a maximum particle size D100 not greater than 8 μm.

4. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 3, characterized in that: The particle size D50 of nickel powder ranges from 0.5 to 2.0 μm, and the maximum particle D100 is no greater than 5 μm.

5. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 3, characterized in that: The organic carrier includes resin, solvent, thickener and thixotropic agent.

6. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 5, characterized in that: The mass composition of the organic carrier is: 5% of polyvinyl butyral, 6% of SEPS resin, 20% of butyl carbitol, 40% of butyl carbitol acetate, 16% of dimethyl diacid, 4% of polyamide wax, 4% of methyl silicone oil and 5% of auxiliary agent.

7. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 1, characterized in that: The preparation method comprises the following steps: S1: preparing glass powder: the glass powder is prepared by batching-mixing-melting-cold extraction-crushing-grinding steps, wherein the impurities of the first main group elements of the raw materials used for the corrosive glass powder are controlled at the ppm level, and the crucible used for melting is made of platinum, quartz or corundum; The auxiliary accelerated glass powder has a melting temperature of 1400°C-1600°C, a heat preservation time of 50 minutes, and a quartz crucible; S2: Slurry preparation: The slurry preparation process is batching-mixing-three-roller-screening-stirring-detection; In the mixing process, ultrasonic dispersion is introduced or a planetary dispersion process is added after stirring dispersion, and the three-roll grinding stage is finally ground with Eckart gap 5μm mode for no less than two times; S3: Slurry performance test.

8. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 7, characterized in that: After the glass powder in S1 is prepared, it is quenched with deionized water, dried, and dry-milled with Φ10mm zirconium balls. Then, Φ3mm zirconium balls and Φ1mm zirconium balls are mixed in a volume ratio of 4:3 and wet-milled with deionized water as the medium. The particle size D50 of the glass powder is controlled in the range of 0.5-1.5μm, and the maximum particle size D100 is less than 6μm.

9. The laser-assisted sintering base metal slurry for TOPCON solar cells according to claim 7, characterized in that: The specific process for preparing the slurry is: weighing the organic carrier, glass powder and nickel powder in proportion, stirring and mixing, and then planetary dispersing, grinding with Eckart three-roller for 8 times, with the gap of the last 2 times being 5 μm, and the fineness of the obtained slurry is less than 5 μm.

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