Conductive slurry, electrode prepared therefrom, and crystalline silicon solar cell comprising electrode

Abstract

A conductive slurry, which comprises: a) conductive metal particles, b) a glass powder, c) a laser thermal promoter, and d) an organic carrier, wherein the laser thermal promoter is represented by formula (I): ZrxCuyAlmNizNbnAq(I), where x=10-90 wt%, y=5-50 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, and q=0-5 wt%; A is a metal selected from Ag, Cr, Zn and Ti; and the weight percentages are based on the weight of the laser thermal promoter. Further provided is another conductive slurry, which comprises: a) conductive metal particles, b) a glass powder, c) a reducing additive, and d) an organic carrier, wherein the reducing additive is represented by formula (I): ZrxCuyAlz (I), where x=10-90 wt%, y=5-50 wt%, z=5-20 wt%, and the weight percentages are based on the weight of the reducing additive. Also provided are an electrode formed by sintering the conductive slurry, and a crystalline silicon solar cell comprising a substrate and the electrode bonded to the substrate.

Description

Conductive paste, electrode prepared therefrom, and crystalline silicon solar cell comprising the electrode Technical Field

[0001] The present invention relates to a conductive paste, an electrode prepared from the same, and a crystalline silicon solar cell comprising the electrode. Background Art

[0002] Solar energy is an attractive green energy source because it is sustainable and produces only non-polluting by-products. Therefore, people have developed solar cells that use the photovoltaic effect to convert solar energy into electrical energy. Solar cells are usually made of semi-conductive materials, for example, usually made of appropriately doped silicon materials. When light shines on the solar cell, a portion of the incident light is reflected by the surface, while the remaining portion of the incident light is transmitted to the solar cell. The transmitted photons are absorbed by the solar cell, which in turn excites the electrons of the semi-conductive material to generate electron-hole pairs. The electrons and holes are guided through the electrodes on the front side (i.e., the side illuminated by light) and the back side (i.e., the side not illuminated by light) of the substrate to form current, thereby obtaining electrical energy.

[0003] The front electrodes of a solar cell are typically arranged as two sets of perpendicular straight lines, called "grid lines" and "bus bars." The grid lines make electrical contact with the front surface, while the bus bars connect these grid lines, allowing for efficient extraction of charge into the external circuit. This arrangement of grid lines and bus bars is typically applied in the form of a conductive paste, which is then fired to form a solid electrode body. The back electrodes of the solar cell are also typically applied in the form of a conductive paste, which is then fired to obtain a solid electrode body.

[0004] The quality of the conductive paste directly impacts the performance of the electrode material, such as contact resistance. A typical conductive paste contains conductive metal particles, glass frit, and an organic vehicle. The conductive metal particles form an ohmic metal-semiconductor contact with the underlying silicon, directly responsible for the transmission of current from the silicon emitter to the gate line. Therefore, achieving low contact resistance between the conductive paste and the silicon emitter has a significant impact on solar cell performance.

[0005] CN101609849A discloses a silver conductive paste for solar cell front electrodes and its preparation process, wherein the silver paste for solar cell front electrodes uses silver powders of different particle size ranges as the conductive functional phase. Spherical silver powders of two particle size ranges are mixed so that the small-sized silver powder fills the gaps in the large-sized silver powder. After the electrode is formed, a tighter conductive network can be formed, thereby reducing the contact resistance of the battery and improving electrical performance and conversion efficiency. In addition, by adding BaO and CaO powders, the glass phase is microcrystallized during the sintering process, the supersaturation of dissolved silver in the glass phase is increased, and more crystalline silver is precipitated at the Ag-Si interface, forming a good ohmic contact, thereby reducing the contact resistance. However, the results in Table 1 of CN101609849A show that the contact resistance of the embodiment is higher than that of the comparative example.

[0006] CN115312629A discloses a solar cell and its fabrication method, wherein the metal paste on the front surface of a silicon wafer is treated using laser-enhanced contact optimization technology to form a localized ohmic contact electrode on the front surface of the silicon wafer, thereby reducing contact resistance. However, CN115312629A does not provide corresponding experimental data to prove that the contact resistance can be reduced.

[0007] Therefore, there is still a need to further find a method for reducing the contact resistance of solar cells to improve the efficiency of solar cells. Summary of the Invention

[0008] In order to reduce the contact resistance of solar cells, the first aspect of the present invention provides a conductive paste comprising:

[0009] a) conductive metal particles,

[0010] b) glass powder,

[0011] c) laser thermal accelerator, and

[0012] d) an organic carrier,

[0013] The laser thermal accelerator is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I)

[0014] In formula (I), x=10-90 wt%, y=5-50 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, q=0-5 wt%, and A is a metal selected from Ag, Cr, Zn and Ti, and the weight percentages are based on the weight of the laser thermal accelerator.

[0015] The present invention also provides an electrode for a crystalline silicon solar cell, which is formed by sintering the conductive paste.

[0016] The present invention also provides a crystalline silicon solar cell, which includes a substrate and the electrode combined on the substrate.

[0017] The applicant has discovered that by adding a laser thermal accelerator to a conductive paste, the contact resistance of a solar cell can be reduced, and thus the efficiency of a solar cell prepared using the conductive paste can be improved.

[0018] In order to reduce the contact resistance of solar cells, the second aspect of the present invention further provides a conductive paste comprising:

[0019] a) conductive metal particles, b) glass powder, c) reducing additive, and d) organic vehicle, wherein the reducing additive is represented by formula (I): Zr x Cu y Al z (I)

[0020] In formula (I), x=10-90% by weight, y=5-50% by weight, and z=5-20% by weight, the weight percentages being based on the weight of the reducing additive.

[0021] The present invention also provides an electrode for a crystalline silicon solar cell. The electrode is formed by sintering the conductive paste.

[0022] The present invention also provides a crystalline silicon solar cell, which includes a substrate and the electrode combined on the substrate.

[0023] The applicant has discovered that the contact resistance of solar cells can be reduced by adding a reducing additive to a conductive paste, and thus the efficiency of solar cells prepared using the conductive paste can be improved. DETAILED DESCRIPTION

[0024] Conductive paste

[0025] According to a first aspect of the present invention, a conductive paste is applied to the surface of a solar cell wafer and forms a solid electrode body in electrical contact with the surface when fired. According to the first aspect of the present invention, the conductive paste comprises:

[0026] a) conductive metal particles,

[0027] b) glass powder,

[0028] c) laser thermal accelerator, and

[0029] d) an organic carrier,

[0030] The laser thermal accelerator is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I)

[0031] In formula (I), x=10-90 wt%, y=5-50 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, q=0-5 wt%, and A is a metal selected from Ag, Cr, Zn and Ti, preferably Ti, and the weight percentages are based on the weight of the laser thermal accelerator.

[0032] In a preferred embodiment, the conductive paste comprises:

[0033] a) conductive metal particles,

[0034] b) glass powder,

[0035] c) laser thermal accelerator, and

[0036] d) an organic carrier,

[0037] The laser thermal accelerator is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I)

[0038] In formula (I), x=50-90 wt%, y=5-35 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, q=0-5 wt%, and A is a metal selected from Ag, Cr, Zn and Ti, preferably Ti, and the weight percentages are based on the weight of the laser thermal accelerator.

[0039] a) Conductive metal particles

[0040] The conductive metal particles present in the conductive paste provide metallic conductivity to the solid electrode formed when the conductive paste is sintered. Metal particles that facilitate efficient sintering and result in an electrode with high conductivity and low contact resistance are preferred. All metal particles known to those skilled in the art and deemed suitable in the context of the present invention can be used as the conductive metal particles in the conductive paste.

[0041] According to the present invention, preferred conductive metal particles are metals, alloys, mixtures of at least two metals, mixtures of at least two alloys or mixtures of at least one metal and at least one alloy.

[0042] According to the present invention, the conductive metal particles may comprise Ag, Al, Cu, Zn, Pd, Ni, Pb, Au or a combination thereof, preferably Ag, Al, Cu or an alloy thereof, more preferably Ag. In a preferred embodiment of the present invention, the conductive metal particles are silver particles (silver powder).

[0043] According to the present invention, when the conductive metal particles are alloys, the conductive metal particles may be crystalline metal particles or amorphous metal particles, preferably amorphous metal particles.

[0044] According to the present invention, the conductive metal particles can have various shapes, surfaces, sizes, surface area to volume ratios, oxygen contents and oxide layers. Many shapes are known to those skilled in the art. Some examples are spherical, angular, elongated (rod-shaped or needle-shaped) and flat (flake-shaped). The metal particles can also exist as a combination of particles of different shapes. According to the present invention, metal particles having a shape or a combination of shapes that are conducive to favorable sintering, electrical contact, adhesion and conductivity of the electrode produced are preferred. Without taking into account the surface characteristics, one way to characterize such shapes is by means of the parameters length, width and thickness. For the purposes of the present invention, the length of the particle is given by the length of the longest spatial displacement vector whose two endpoints are contained within the particle. The width of the particle is given by the length of the longest spatial displacement vector perpendicular to the length vector defined above and whose two endpoints are contained within the particle. The thickness of the particle is given by the length of the longest spatial displacement vector perpendicular to the length vector and width vector defined above and whose two endpoints are contained within the particle. In one embodiment of the present invention, metal particles having a shape that is as uniform as possible, i.e., a shape in which the ratios of length, width, and thickness are as close to 1 as possible, are preferred, preferably all ratios are within the range of 0.7-1.5, more preferably 0.8-1.3, and most preferably 0.9-1.2. In one embodiment of the present invention, preferred examples of the shape of the conductive metal particles are spheres and cubes, or a combination thereof, or a combination of one or more thereof with other shapes. In one embodiment of the present invention, the conductive metal particles in the conductive paste are spherical.

[0045] Particle size D50 is a particle characteristic known to those skilled in the art. Determination of particle size D50 is known to those skilled in the art. According to the present invention, the conductive metal particles preferably have a particle size D50 of 0.5-10 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, preferably 1-5 μm.

[0046] In one embodiment of the present invention, the conductive metal particles are silver particles (silver powder) having a particle size D50 of 1-4 μm, preferably 2-3.5 μm, more preferably 2.8-3.2 μm.

[0047] In another embodiment of the present invention, the conductive metal particles are aluminum particles (aluminum powder) having a particle size D50 of 1-5 μm, preferably 2-4 μm, more preferably 2.5-3.5 μm.

[0048] In yet another embodiment of the present invention, the conductive metal particles are copper particles (copper powder) having a particle size D50 of 1-6 μm, preferably 2-4 μm, more preferably 2-3 μm.

[0049] In one embodiment of the present invention, the conductive metal particles are present in a proportion greater than 50 wt %, preferably greater than 70 wt %, and most preferably greater than 80 wt % of the conductive paste.

[0050] In a preferred embodiment of the present invention, the conductive metal particles are present in a proportion of 50-95 wt % of the conductive paste, for example, 50 wt %, 60 wt %, 70 wt %, 80 wt %, or 90 wt %.

[0051] b) Glass powder

[0052] According to the present invention, glass frit is present in the conductive paste to induce etching and sintering. For the purposes of the present invention, the glass frit is preferably an amorphous or partially crystalline solid with a low glass transition temperature (Tg). The glass transition temperature (Tg) is the temperature at which a rigid solid transforms into a partially fluid, undercooled melt upon heating. Methods for determining the glass transition temperature (Tg) are well known to those skilled in the art. Etching and sintering caused by the glass frit occur above the glass transition temperature (Tg) of the glass frit, and preferably, the glass transition temperature (Tg) is below the desired peak firing temperature.

[0053] All glass frits known to those skilled in the art and deemed suitable in the context of the present invention can be used as the glass frit in the conductive paste. For the purposes of the present invention, the glass frit present in the conductive paste preferably comprises an element, its oxide, a compound that produces an oxide upon heating, or a mixture thereof. In this regard, preferred elements are Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P, or combinations thereof. For the purposes of the present invention, preferred oxides that the glass frit may comprise are alkali metal oxides, alkaline earth metal oxides, rare earth oxides, oxides of Groups V and VI elements, other oxides, or combinations thereof. Further, preferred oxides include lead oxide (PbO), boron oxide (BO), silicon dioxide (SiO), zinc oxide (ZnO), aluminum oxide (AlO), tellurium oxide (TeO), bismuth oxide (BiO), phosphorus oxide (PO), and combinations thereof. Preferred oxides are also mixed oxides containing at least two of the elements listed as preferred elemental constituents of the glass frit, or mixed oxides formed by heating at least one of the above-mentioned oxides with at least one of the above-mentioned metals. Also preferred for the purposes of the present invention are mixtures of at least two of the above-mentioned oxides and mixed oxides.

[0054] In one embodiment of the present invention, the glass powder may comprise:

[0055] 30-50 mol% PbO;

[0056] 5-15 mol% B2O3; and

[0057] 40-60 mol% SiO2,

[0058] The mole percentages are based on the total moles of all oxides.

[0059] In one embodiment of the present invention, the glass powder may comprise:

[0060] 20-30 mol% PbO;

[0061] 10-20 mol% B2O3;

[0062] 40-50 mol% SiO2;

[0063] 2-8 mol% ZnO;

[0064] 2-8 mol% Al2O3; and

[0065] 2-8 mol% Bi2O3,

[0066] The mole percentages are based on the total moles of all oxides.

[0067] In one embodiment of the present invention, the glass powder may comprise:

[0068] 20-40 mol% PbO;

[0069] 2-8 mol% SiO2;

[0070] 10-20 mol% ZnO; and

[0071] 40-60 mol% TeO2,

[0072] The mole percentages are based on the total moles of all oxides.

[0073] In one embodiment of the present invention, the glass powder may comprise:

[0074] 30-50 mol% PbO;

[0075] 2-8 mol% SiO2;

[0076] 2-8 mol% ZnO; and

[0077] 40-60 mol% TeO2,

[0078] The mole percentages are based on the total moles of all oxides.

[0079] In one embodiment of the present invention, the glass powder may comprise:

[0080] 5-15 mol% B2O3;

[0081] 30-50 mol% SiO2;

[0082] 10-20 mol% ZnO;

[0083] 20-40 mol% Bi2O3; and

[0084] 1-5 mol% P2O5,

[0085] The mole percentages are based on the total moles of all oxides.

[0086] According to the present invention, the glass frit preferably has a glass transition temperature Tg lower than the desired firing temperature of the conductive paste. In one embodiment of the present invention, the glass frit preferably has a glass transition temperature Tg of 300-600°C, more preferably 300-500°C, most preferably 320-450°C.

[0087] According to the present invention, the glass powder particles can have a variety of shapes, surface properties, sizes, surface area to volume ratios, and coatings. Many shapes of glass powder particles are known to those skilled in the art. Some examples are spherical, angular, elongated (rod-like or needle-like), and flat (flake-like). Glass powder particles can also be present as a combination of particles of different shapes. According to the present invention, glass powder having a shape or combination of shapes that contributes to favorable sintering, adhesion, electrical contact, and conductivity of the resulting electrode is preferred.

[0088] According to the present invention, the particle size D50 of the glass powder is preferably 0.1-10 μm, more preferably 0.2-7 μm, and most preferably 0.5-5 μm. The determination of the particle size D50 is well known to those skilled in the art.

[0089] In one embodiment of the present invention, the glass powder has a particle size D50 of 0.1-3 μm, preferably 0.5-2 μm, more preferably 0.8-1.5 μm.

[0090] In one embodiment of the present invention, the glass powder is present in a proportion of 0.1-15 wt %, preferably 3-10 wt %, of the conductive paste.

[0091] In one embodiment of the present invention, the glass powder of the present invention can be prepared by the following method and then used to prepare the conductive paste of the present invention: all components of the glass powder are combined together to obtain a composition, the composition is melted to obtain a glass frit, and the composition is quenched in deionized water, and finally the product is made into particles with a desired particle size to obtain the glass powder of the present invention.

[0092] Preferably, the “melting” is performed by charging the composition into a crucible, placing the crucible in a muffle furnace, and melting the composition at a high temperature; the “water quenching” is performed by removing the molten glass from the muffle furnace and pouring it into a bucket filled with deionized water; and the “forming particles having a desired particle size” is performed by grinding the water-quenched glass slag with a ball mill to obtain glass powder having a desired particle size D50.

[0093] In the above method, the temperature of the muffle furnace is high enough to melt the components of the glass powder, and the melting time is long enough to uniformly mix the components.

[0094] More preferably, in the preparation of the glass powder, the temperature of the muffle furnace is 800-1500° C., preferably 900-1200° C., and the melting time of the mixture is 15 minutes to 2 hours, preferably 30 minutes to 1 hour.

[0095] In another embodiment of the present invention, the glass powder of the present invention can be prepared by the following method and then used to prepare the conductive paste of the present invention: combining part of the components of the glass powder together to obtain a first composition, melting the first composition to obtain glass, quenching it in deionized water, and finally making the product into first particles with a desired particle size; combining the remaining components of the glass powder together to obtain a second composition, melting the second composition to obtain glass, quenching it in deionized water, and finally making the product into second particles with a desired particle size; combining the first particles and the second particles together to obtain the glass powder of the present invention.

[0096] The glass powder of the present invention can be divided into more parts and the glass powder of the present invention can be obtained by corresponding methods.

[0097] For example, in yet another embodiment of the present invention, the glass powder of the present invention can be prepared by the following method and then used to prepare the conductive paste of the present invention: combining the first part of the components of the glass powder together to obtain a first composition, melting the first composition to obtain glass, quenching the first composition in deionized water, and finally making the product into first particles with a desired particle size; combining the second part of the components of the glass powder together to obtain a second composition, melting the second composition to obtain glass, quenching the second composition in deionized water, and finally making the product into second particles with a desired particle size; combining the remaining components of the glass powder together to obtain a third composition, melting the third composition to obtain glass, quenching the third composition in deionized water, and finally making the product into third particles with a desired particle size; combining the first particles, the second particles, and the third particles together to obtain the glass powder of the present invention.

[0098] Obviously, the first particles, second particles and / or third particles mentioned above can be particles that have been prepared.

[0099] c) Laser thermal accelerator

[0100] According to the present invention, the laser thermal accelerator is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I)

[0101] In formula (I), x=10-90 wt%, y=5-50 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, q=0-5 wt%, and A is a metal selected from Ag, Cr, Zn and Ti, preferably Ti, and the weight percentages are based on the weight of the laser thermal accelerator.

[0102] In one embodiment of the present invention, in formula (I), x = 10-90 weight%, for example, x = 10 weight%, 20 weight%, 30 weight%, 40 weight%, 50 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight%, preferably 50-90 weight%, more preferably 65-85 weight%, and the weight percentages are based on the weight of the laser thermal accelerator.

[0103] In one embodiment of the present invention, in formula (I), y = 5-50 weight%, for example, y = 5 weight%, 10 weight%, 15 weight%, 20 weight%, 25 weight%, 30 weight%, 35 weight%, 40 weight%, 45 weight%, 50 weight%, preferably 5-35 weight%, more preferably 10-30 weight%, and the weight percentages are based on the weight of the laser thermal accelerator.

[0104] In one embodiment of the present invention, in formula (I), m = 0.5-10 wt%, for example, m = 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, preferably 2-9 wt%, and the weight percentages are based on the weight of the laser thermal accelerator.

[0105] In one embodiment of the present invention, in formula (I), z = 0-20 weight%, for example, z = 0.5 weight%, 1 weight%, 2 weight%, 3 weight%, 4 weight%, 5 weight%, 6 weight%, 7 weight%, 8 weight%, 9 weight%, 10 weight%, 11 weight%, 12 weight%, 13 weight%, 14 weight%, 15 weight%, 16 weight%, 17 weight%, 18 weight%, 19 weight%, 20 weight%, preferably 8-15 weight%, and the weight percentages are based on the weight of the laser thermal accelerator.

[0106] In one embodiment of the present invention, in formula (I), n = 0-15 weight%, for example, n = 0.5 weight%, 1 weight%, 2 weight%, 3 weight%, 4 weight%, 5 weight%, 6 weight%, 7 weight%, 8 weight%, 9 weight%, 10 weight%, 11 weight%, 12 weight%, 13 weight%, 14 weight%, 15 weight%, preferably 1-10 weight%, and the weight percentages are based on the weight of the laser thermal accelerator.

[0107] In one embodiment of the present invention, in formula (I), q = 0-5% by weight, for example, q = 0.5% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, preferably 1-5% by weight, and the weight percentages are based on the weight of the laser thermal accelerator.

[0108] In one embodiment of the present invention, the laser thermal accelerator is amorphous (non-crystalline) metal alloy particles.

[0109] In one embodiment of the present invention, the laser thermal accelerator is amorphous metal alloy particles having a particle size D50 of 0.1-8 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm. In a preferred embodiment of the present invention, the laser thermal accelerator is amorphous metal alloy particles having a particle size D50 of 1-5 μm. The determination of particle size D50 is well known to those skilled in the art.

[0110] In one embodiment of the present invention, the laser thermal accelerator is present in a proportion of 0.05-10 weight % of the conductive paste, for example, 0.05 weight %, 0.1 weight %, 0.5 weight %, 1 weight %, 2 weight %, 3 weight %, 4 weight %, 5 weight %, 6 weight %, 7 weight %, 8 weight %, 9 weight %, 10 weight %, preferably 0.1-1 weight %, more preferably 0.1-0.5 weight %.

[0111] In one embodiment of the present invention, the laser thermal accelerator is prepared by a jet powder preparation method, which includes the following steps:

[0112] (1) Mixing and uniformly dispersing the high-purity metal powders used to prepare the laser thermal accelerator according to the formula ratio;

[0113] (2) heating and melting the obtained metal powder mixture in a crucible (e.g., a copper pressure crucible lined with quartz) at a temperature greater than 1000° C. to obtain a liquid master alloy;

[0114] (3) Under the action of pressure, the liquid master alloy is directly sprayed into ice water mixed with NaCl to obtain amorphous LTP alloy powder.

[0115] According to one embodiment of the present invention, the high-purity metal powder in step (1) has a purity of, for example, 99% or more.

[0116] According to one embodiment of the present invention, the temperature of step (2) is preferably 1050-1500°C, such as 1100°C, 1200°C, 1300°C, 1400°C.

[0117] According to one embodiment of the present invention, the pressure of step (3) is preferably 20-100 PSI, such as 30 PSI, 40 PSI, 50 PSI, 60 PSI, 70 PSI, 80 PSI, 90 PSI.

[0118] According to one embodiment of the present invention, the concentration of NaCl in step (3) is preferably 1-10 wt%, such as 2-5 wt% or 6-9 wt%.

[0119] According to the present invention, LTP powders with different particle sizes and morphologies can be obtained by adjusting the temperature, pressure and injection speed.

[0120] d) Organic carrier

[0121] In one embodiment of the present invention, the conductive paste comprises an organic vehicle commonly used in the art.Preferred organic vehicles are those that provide optimal stability of the ingredients within the conductive paste and impart viscosity to the conductive paste that allows for effective printability.

[0122] In one embodiment, the amount of the organic vehicle may be 2-20 wt %, more preferably 5-15 wt %, and most preferably 6-10 wt %, based on the total weight of the conductive paste.

[0123] In one embodiment, the organic vehicle comprises a solvent, a binder (e.g., an organic binder, such as a polymer, a resin), a surfactant, an additive, or any combination thereof, preferably an organic binder and a solvent. The additives include thixotropic agents, viscosity modifiers, stabilizers, thickeners, emulsifiers, dispersants, slip agents (e.g., alkyl-modified silicone oils), or pH modifiers, and any combination thereof. For example, in one embodiment, the organic vehicle comprises one or more binders in an organic solvent.

[0124] The binder may be present in an amount of 0.1-10 wt %, preferably 0.1-8 wt %, more preferably 0.5-7 wt %, based on the total weight of the organic vehicle. Preferred binders are those that promote the formation of a conductive paste having favorable stability, printability, viscosity, and sintering properties. Preferred binders (which generally fall within the category referred to as "resins") are polymeric binders, monomeric binders, and binders that are combinations of polymers and monomers. Polymeric binders may also be copolymers.

[0125] Preferred polymeric binders include those with functional groups in the polymer backbone, those with functional groups outside the backbone, and those with functional groups both inside and outside the backbone. Preferred polymers with functional groups in the backbone include, for example, polyesters, substituted polyesters, polycarbonates, substituted polycarbonates, polymers with cyclic groups in the backbone, polysaccharides, substituted polysaccharides, polyurethanes, substituted polyurethanes, polyamides, substituted polyamides, phenolic resins, substituted phenolic resins, copolymers of one or more monomers of the above polymers (optionally with other comonomers), or combinations of at least two thereof.

[0126] Preferred polymers carrying cyclic groups in the main chain include, for example, polyvinyl butyral (PVB) and its derivatives and polyterpineol and its derivatives or mixtures thereof. Preferred polysaccharides include, for example, cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, propyl cellulose, hydroxypropyl cellulose, butyl cellulose, derivatives thereof and mixtures of at least two thereof. Other preferred polymers include, for example, cellulose ester resins, such as cellulose acetate propionate, cellulose acetate butyrate and any combination thereof. Other preferred polymers are those disclosed in U.S. Patent Application Publication No. 2013 / 0180583, which is incorporated herein by reference.

[0127] Preferred polymers carrying functional groups outside the polymer backbone are polymers carrying amide groups, polymers carrying acid and / or ester groups (commonly referred to as acrylic resins), or polymers carrying combinations of the above functional groups, or combinations thereof. Preferred polymers carrying amide groups outside the backbone include, for example, polyvinylpyrrolidone (PVP) and its derivatives. Preferred polymers carrying acid and / or ester groups outside the backbone include, for example, polyacrylic acid and its derivatives, polymethyl methacrylate (PMMA) and its derivatives, or mixtures thereof.

[0128] Preferred monomeric binders include, for example, those based on ethylene glycol. Preferred monomeric binders based on ethylene glycol are those having multiple ether groups, multiple ester groups, or one ether group and one ester group, with preferred ether groups being methyl, ethyl, propyl, butyl, pentyl, hexyl, and higher alkyl ethers, and preferred ester groups being acetates and their alkyl ether derivatives, preferably ethylene glycol monobutyl ether monoacetate or mixtures thereof.

[0129] Preferred binders in the present invention are, for example, alkylcelluloses (preferably ethylcellulose), their derivatives and mixtures thereof with other binders from the previous list of binders.

[0130] The amount of the organic solvent may be 40 to 90 wt%, more preferably 35 to 85 wt%, based on the total weight of the organic vehicle.

[0131] Preferred solvents are those that allow the formation of a conductive paste having favorable viscosity, printability, stability and sintering properties. All solvents known in the art and considered suitable for use in the present invention can be used as solvents in the organic vehicle. According to the present invention, preferred solvents are those that allow the achievement of a preferred high level of printability of the conductive paste as described above. Preferred solvents according to the present invention are solvents that exist in liquid form at standard ambient temperature and pressure (SATP) (25°C, 100 kPa), preferably solvents having a boiling point above 90°C and a glass transition temperature Tg above -20°C.

[0132] Preferred solvents are polar or nonpolar, protic or aprotic, aromatic or nonaromatic. Preferred solvents include, for example, monoalcohols, diols, polyalcohols, monoesters, diesters, polyesters, monoethers, diethers, polyethers, solvents comprising at least one or more of these classes of functional groups, optionally comprising other classes of functional groups, and mixtures of two or more of the foregoing solvents, such as diethylene glycol butyl ether acetate.

[0133] The organic vehicle may further comprise a surfactant. The amount of the surfactant may be 0-10 wt %, preferably 0-8 wt %, more preferably 0.01-6 wt %, based on the total weight of the organic vehicle. Preferred surfactants in the present invention are surfactants that promote the formation of a conductive paste having favorable stability, printability, viscosity and sintering properties. All surfactants known in the art and considered suitable for use in the present invention may be used as surfactants in the organic vehicle. Preferred surfactants may have nonionic, anionic, cationic, amphoteric or zwitterionic heads. Preferred surfactants are polymeric and monomeric or mixtures thereof.

[0134] According to the present invention, the conductive paste optionally contains additives commonly used in the art. Preferred conductive paste additives are components added to the conductive paste in addition to the ingredients already explicitly mentioned, which are used to promote higher performance of the conductive paste, the electrode produced therefrom, or the resulting crystalline silicon solar cell. All additives known in the art and considered suitable for use in the present invention can be used as conductive paste additives. Preferred additives are thixotropic agents, viscosity regulators, stabilizers, thickeners, emulsifiers, dispersants, slip agents, or pH regulators, and any combination thereof. Preferred thixotropic agents herein are carboxylic acid derivatives, preferably fatty acid derivatives, or combinations thereof. Preferred fatty acid derivatives are C9H 19 COOH (decanoic acid), C 11 H 23 COOH (lauric acid), C 13 H 27 COOH (myristic acid), C 15 H 31 COOH (palmitic acid), C 17 H 35 COOH (stearic acid), C 18 H 34 O2(oleic acid), C 18 H 32 O2 (linoleic acid), castor oil, hydrogenated castor oil, or a combination thereof.

[0135] In one embodiment of the present invention, to form a conductive paste, glass frit can be combined with conductive metal particles, a laser thermal accelerator, an organic vehicle, and optional conductive paste additives using any method known in the art for preparing a paste. The details of the preparation method are not critical, as long as it produces a homogeneously dispersed paste. The components can be mixed, for example, using a mixer and then passed through, for example, a three-roll mill to produce a dispersed, uniform paste.

[0136] Electrodes for crystalline silicon solar cells

[0137] The electrode for the crystalline silicon solar cell of the present invention is formed by sintering the above conductive paste.

[0138] In one embodiment of the present invention, the temperature of the conductive paste sintering treatment is 700-850°C, preferably 750-800°C.

[0139] crystalline silicon solar cells

[0140] The present invention also relates to a crystalline silicon solar cell, which comprises a substrate and the electrode combined on the substrate.

[0141] In one embodiment of the present invention, a preferred crystalline silicon solar cell according to the present invention is one that has high efficiency in terms of the ratio of the total energy of incident light to electrical energy output. Lightweight and durable crystalline silicon solar cells are also preferred. A crystalline silicon solar cell comprises at least: (i) a front electrode, (ii) a front doped layer, (iii) a pn junction boundary, (iv) a back doped layer, (v) a back electrode, and (vi) a passivation layer. The crystalline silicon solar cell may also include additional layers for chemical / mechanical protection.

[0142] In one embodiment of the present invention, the crystalline silicon solar cell substrate of the present invention is a substrate for crystalline silicon solar cells well known to those skilled in the art.

[0143] The crystalline silicon solar cell of the present invention basically comprises electrodes bonded to the substrate and formed by sintering the conductive paste of the present invention.

[0144] In one embodiment of the present invention, the conductive paste of the present invention is applied to a substrate, such as a semiconductor substrate (eg, a crystalline silicon wafer), to form printed electrodes.

[0145] In one embodiment of the present invention, the electrode is optionally processed by a Laser Enhanced Contact Optimization (LECO) (also known as Laser Assisted Sintering) process.

[0146] The present invention utilizes the characteristics of the Laser Enhanced Contact Optimization (LECO) process to repair insufficiently sintered solar cells. LECO's main operating principle is to illuminate the cell with a high-intensity laser, exciting charge carriers, while simultaneously applying a reverse voltage of 10V or higher. This generates a localized current of several amperes, causing sintering at the corresponding location.

[0147] In one embodiment of the present invention, the laser enhanced contact optimization (LECO) process comprises the following steps:

[0148] (1) Each of the parallel conductive wires is crimped onto a busbar of a solar cell, and the conductive wires extend along a first direction of the solar cell, where the first direction is an extension direction of the busbar;

[0149] (2) providing a power source, electrically connecting a first end of the power source to each conductive filament, and electrically connecting a second end of the power source to the silicon substrate of the solar cell; applying a reverse voltage through the power source solar cell, and the reverse voltage is evenly distributed on the surface of the solar cell through the conductive filament;

[0150] (3) providing a strip-shaped laser spot, wherein the strip-shaped laser spot extends along a second direction of the solar cell, where the second direction is an extension direction of the secondary grid line;

[0151] (4) controlling the strip-shaped laser spot to move along a first direction, scanning and irradiating the electrodes on the surface of the solar cell, so that the generated radiation current is evenly concentrated on each main grid line covered by the strip-shaped laser spot;

[0152] (5) After the laser completes scanning the cell, remove the strip laser spot and the conductive wire, remove the cell, and proceed to the next cell.

[0153] Regarding the laser enhanced contact optimization (LECO) process, the contents of CN217485456U are incorporated herein by reference.

[0154] In one embodiment of the present invention, the laser enhanced contact optimization process is performed at a laser wavelength of 400-1500 nm (preferably 900-1100 nm, such as 1000 nm, 1050 nm), a power of 500-1100 W / cm 2 (Preferably 600-1000 nm, such as 600 W / cm 2 , 700W / cm 2 , 800W / cm 2 , 900W / cm 2 , 1000W / cm 2) and a reverse voltage of 5-40V (preferably 10-25V, for example 10V, 15V, 20V, 25V) for a time of 0.5-5s (for example 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 2s, 3s, 4s, 5s) on the entire battery cell.

[0155] The laser may be a laser of any single wavelength or multiple different wavelengths within the above range, or may be a single broad-spectrum laser covering a certain wavelength range within the above range.

[0156] In a preferred embodiment of the present invention, the laser enhanced contact optimization process is performed at a laser wavelength of 1000-1100 nm and a power of 600-1000 W / cm 2 The laser energy density and reverse voltage of 10-25V are carried out on the entire cell for 0.8-1s.

[0157] The conductive paste of the present invention can be applied to the substrate by any method known in the art and considered suitable for use in the present invention. Examples of such methods include, but are not limited to, dipping, immersing, pouring, dripping, injecting, spraying, doctor blade coating, curtain coating, brushing, or printing, or a combination of at least two thereof. Preferred printing techniques are inkjet printing, screen printing, flexographic printing, offset printing, letterpress printing, or stencil printing, or a combination of at least two thereof. It is preferred according to the present invention to apply the conductive paste of the present invention by printing, preferably by screen printing.

[0158] Firing is required to sinter the printed electrodes to form a solid conductor. Firing is well known in the art and can be achieved in any manner deemed appropriate in the present invention. It is preferred that firing be performed above the Tg of the glass frit material.

[0159] Outside the area occupied by the electrodes, the substrate of the present invention, preferably a crystalline silicon wafer, has an area where light can be absorbed efficiently, thereby generating electron-hole pairs and efficiently separating holes and electrons across the boundary, preferably across the pn junction boundary.

[0160] The pn junction boundary is located where the front-side doped layer of the wafer meets the back-side doped layer. In an n-type solar cell, the back-side doped layer is doped with an n-type dopant and the front-side doped layer is doped with a p-type dopant. In a p-type solar cell, the back-side doped layer is doped with a p-type dopant and the front-side doped layer is doped with an n-type dopant. According to a preferred embodiment of the present invention, a wafer having a pn junction boundary is prepared by first providing a doped silicon substrate and then applying a doped layer of the opposite type to one side of the substrate.

[0161] The above-mentioned dopants are preferably dopants that form a pn junction boundary by introducing electrons or holes into the band structure when added to the crystalline silicon wafer. According to the present invention, it is preferred to specifically select the type and concentration of these dopants to adjust the band structure profile of the pn junction and set the light absorptivity and conductivity profile as required. The preferred p-type dopant according to the present invention is a dopant that adds holes to the band structure of the crystalline silicon wafer. All dopants known in the art and considered suitable for use in the present invention can be used as p-type dopants. The preferred p-type dopant according to the present invention is a trivalent element, especially a trivalent element of Group 13 in the periodic table. The preferred Group 13 elements in the periodic table herein include, but are not limited to, boron, aluminum, gallium, indium, thallium or a combination of at least two thereof, with boron being particularly preferred.

[0162] Preferred n-type dopants according to the present invention are dopants that add electrons to the band structure of the crystalline silicon wafer. All dopants known in the art and considered suitable for use in the present invention can be used as n-type dopants. Preferred n-type dopants according to the present invention are elements of Group V of the Periodic Table. Preferred Group V elements herein include nitrogen, phosphorus, arsenic, antimony, bismuth, or combinations of at least two thereof, with phosphorus being particularly preferred.

[0163] In one embodiment of the present invention, an antireflection layer may be applied as an outer layer before the electrode is applied to the front face of the crystalline silicon solar cell according to the present invention. A preferred antireflection layer according to the present invention is an antireflection layer that reduces the proportion of incident light reflected by the front face and increases the proportion of incident light that will be absorbed by the wafer across the front face. Antireflection layers that produce a favorable absorptivity / reflectivity are susceptible to etching by the conductive paste. In addition, antireflection layers that are resistant to the temperatures required for firing the conductive paste and that do not promote greater recombination of electrons and holes near the electrode interface are preferred. All antireflection layers known in the art and considered suitable for use in the present invention may be used. A preferred antireflection layer according to the present invention is silicon nitride, silicon dioxide, aluminum oxide, titanium dioxide or a mixture of at least two thereof and / or a combination of at least two layers thereof. According to a preferred embodiment, the antireflection layer is silicon nitride, i.e. Si x N y , especially when using crystalline silicon wafers, where x is 2-4 and y is 3-5.

[0164] In one embodiment of the present invention, one or more passivation layers can be applied to the substrate, preferably the front side and / or back side of the crystalline silicon wafer as an outer layer. The passivation layer can be applied before forming the front electrode or before applying the anti-reflection layer (if one of them exists). Preferably, the passivation layer is a passivation layer that reduces the electron / hole recombination rate near the electrode interface. Any passivation layer known in the art and considered to be applicable in the present invention can be used. According to the present invention, the passivation layer can be silicon nitride, aluminum oxide, silicon dioxide and titanium dioxide. According to the most preferred embodiment, aluminum oxide is used. Preferably, the passivation layer has a thickness of 0.1nm to 2μm, more preferably 1nm to 1μm, and most preferably 1nm to 200nm.

[0165] In one embodiment of the present invention, in addition to the above-mentioned layers which directly contribute to the main functions of the crystalline silicon solar cell, further layers may be added for mechanical and chemical protection.

[0166] The battery can be encapsulated to provide chemical protection. Encapsulation is well known in the art and any encapsulation suitable for the present invention can be used. According to a preferred embodiment, a transparent polymer (commonly referred to as a transparent thermoplastic resin) is used as the encapsulating material, provided such an encapsulation exists. Preferred transparent polymers herein are silicone rubber and polyethylene vinyl acetate (EVA).

[0167] A transparent glass sheet may also be added to the front side of the crystalline silicon solar cell to provide mechanical protection thereto. Transparent glass sheets are well known in the art, and any transparent glass sheet suitable for use in the present invention may be employed.

[0168] A back protective material can be added to the back of the crystalline silicon solar cell to provide mechanical protection. Back protective materials are well known in the art and any back protective material considered suitable in the present invention can be used. A preferred back protective material according to the present invention is a back protective material with good mechanical properties and weather resistance. A preferred back protective material according to the present invention is polyethylene terephthalate with a polyvinyl fluoride layer (e.g., a PTFE layer). It is preferred according to the present invention that the back protective material is present below the encapsulation layer (in the presence of a back protective layer and an encapsulation).

[0169] Frame materials can be added to the outside of the crystalline silicon solar cell to provide mechanical support. Frame materials are well known in the art and any frame material deemed suitable for use in the present invention can be used. A preferred frame structure according to the present invention is aluminum.

[0170] In a preferred embodiment of the present invention, the conductive paste of the present invention is used to prepare an N-type solar cell, in particular a TOPCon solar cell, and the conductive paste comprises:

[0171] a) 50-95% by weight of conductive metal particles,

[0172] b) 1-15% by weight of glass powder,

[0173] c) 0.1-10 wt% of a laser thermal accelerator, and

[0174] d) 2-20 wt % of an organic vehicle, wherein the weight percentage is based on the total weight of the conductive paste.

[0175] Those skilled in the art can more easily understand the first aspect of the present invention according to the following embodiments:

[0176] Embodiment 1-1. A conductive paste comprising:

[0177] a) conductive metal particles, b) glass powder, c) laser thermal accelerator, and d) organic vehicle, wherein the laser thermal accelerator is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I)

[0178] In formula (I), x=10-90 wt%, y=5-50 wt%, m=0.5-10 wt%, z=0-20 wt%, n=0-15 wt%, q=0-5 wt%, and A is a metal selected from Ag, Cr, Zn and Ti, and the weight percentages are based on the weight of the laser thermal accelerator.

[0179] Embodiment 1-2. The conductive paste according to embodiment 1-1, wherein in formula (I), x=50-90 wt % and y=5-35 wt %.

[0180] Embodiment 1-3. The conductive paste according to embodiment 1-1 or 1-2, wherein the laser thermal accelerator is amorphous metal alloy particles.

[0181] Embodiment 1-4. The conductive paste according to any one of embodiments 1-1 to 1-3, wherein the laser thermal accelerator has a particle size D50 of 0.1-8 μm, preferably 1-5 μm.

[0182] Embodiment 1-5. The conductive paste according to any one of embodiments 1-1 to 1-4, wherein the conductive metal particles comprise Ag, Al, Cu, Zn, Pd, Ni, Pb, Au or a combination thereof, preferably Ag, Al, Cu or an alloy thereof, more preferably Ag.

[0183] Embodiment 1-6. The conductive paste according to any one of Embodiments 1-1 to 1-5, wherein the conductive metal particles have a particle size D50 of 0.5-10 μm, preferably 1-5 μm.

[0184] Embodiment 1-7. A conductive paste according to any one of Embodiments 1-1 to 1-6, wherein the glass powder contains oxides of elements selected from Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P, and combinations thereof, preferably containing PbO, B2O3, SiO2, ZnO, Al2O3, TeO2, Bi2O3, P2O5, or a combination of any two or more thereof.

[0185] Embodiment 1-8. The conductive paste according to any one of Embodiments 1-1 to 1-7, wherein the glass frit has a glass transition temperature Tg of 300-600°C, preferably 300-500°C.

[0186] Embodiment 1-9. The conductive paste according to any one of Embodiments 1-1 to 1-8, wherein the glass frit has a particle size D50 of 0.1-10 μm, preferably 0.2-7 μm, more preferably 0.5-5 μm.

[0187] Embodiment 1-10. The conductive paste according to any one of Embodiments 1-1 to 1-9, wherein in formula (I),

[0188] (1) n = 1-10% by weight, or

[0189] (2) n = 1-10 wt% and z = 8-15 wt%, or

[0190] (3) z = 8-15 wt%, q = 1-5% and A is Ti.

[0191] Embodiment 1-11. The conductive paste according to any one of embodiments 1-1 to 1-10, wherein the conductive paste comprises:

[0192] a) 50-95 wt % of conductive metal particles, b) 0.1-15 wt % of glass powder, c) 0.1-10 wt % of laser thermal accelerator, and d) 2-20 wt % of organic vehicle, the weight percentages being based on the total weight of the conductive paste.

[0193] Embodiment 1-12. An electrode for a crystalline silicon solar cell, the electrode being formed by sintering the conductive paste described in any one of Embodiments 1-1 to 1-11.

[0194] Embodiment 1-13. The electrode according to embodiment 1-12 is processed by a laser enhanced contact optimization process, wherein the laser enhanced contact optimization process is processed at a laser wavelength of 400-1500nm, 500-1100W / cm 2 The laser energy density and reverse voltage are 5-40V.

[0195] Embodiment 1-14. An electrode according to embodiment 1-13, wherein the reverse voltage is 10-25V.

[0196] Embodiment 1-15. A crystalline silicon solar cell comprising a substrate and the electrode described in any one of Embodiments 1-12 to 1-14 bonded to the substrate, wherein the crystalline silicon solar cell is an N-type crystalline silicon solar cell, preferably a TOPCon solar cell.

[0197] Embodiments according to the first aspect of the present invention

[0198] The present invention is illustrated below by way of examples, but it should be understood that the following examples are non-limiting and are not intended to limit the scope of protection of the present invention.

[0199] raw material

[0200] PbO, B2O3, SiO2, ZnO, Al2O3, TeO2, Bi2O3, and P2O5 are 4N grade chemical reagents.

[0201] Silver powder (Ag) and aluminum powder (Al) are spherical powders with a particle size D50 of 2 μm.

[0202] The silicon wafer is an N-type silicon wafer with a size of 182mm and a silicon nitride and aluminum oxide passivation layer.

[0203] The organic carrier (V1-1) is composed as follows:

[0204] Diethylene glycol butyl ether acetate: 5.6 parts by weight;

[0205] Cellulose acetate butyrate: 0.6 parts by weight;

[0206] Oleic acid: 0.6 parts by weight;

[0207] Hydrogenated castor oil: 0.6 parts by weight;

[0208] Alkyl-modified silicone oil: 0.6 parts by weight.

[0209] The compositions of the glass powders (G1-1 to G1-5) are shown in Table 1-1 below:

[0210] Table 1-1 Composition of glass powder

[0211] The compositions of the laser thermal accelerators (LTP) (AM1-01 to AM1-04) are shown in Table 1-2 below:

[0212] Table 1-2 Composition of laser thermal accelerator (LTP)

[0213] Test Method

[0214] The commercial IV tester “cetisPV-Celltest4-BF” from Halm Elektronik GmbH was used to perform IV tests on the cells to measure the cell conversion efficiency (Eta), open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and series resistance (Rs).

[0215] Preparation of glass powder

[0216] Weigh the components of glass powders G1-1 to G1-5 according to the ratios shown in Table 1-1, and combine them to obtain compositions corresponding to the glass powders G1-1 to G1-5;

[0217] The obtained compositions were respectively loaded into alumina crucibles, placed in a muffle furnace and kept at 1100°C for 60 minutes;

[0218] The alumina crucibles containing the molten glass were removed from the muffle furnace, and the molten glass was poured into a bucket filled with deionized water for water quenching;

[0219] The water-quenched glass slag was respectively ground into a particle size D50 of about 1.5 μm using a ball mill, thereby obtaining glass powders G1-1 to G1-5.

[0220] Preparation of Laser Thermal Promoter (LTP)

[0221] The laser thermal accelerator is prepared by a jet powder preparation method, which includes the following steps:

[0222] (1) The high-purity metal powders (purity 99%) used to prepare the laser thermal accelerator were mixed and dispersed uniformly according to the formula ratio in Table 1-2;

[0223] (2) heating and melting the obtained metal powder mixture in a quartz-lined copper pressure crucible at a temperature of 1100° C. to obtain a liquid master alloy;

[0224] (3) The liquid master alloy was directly sprayed into ice water mixed with 2 wt% NaCl under a pressure of 50 PSI to prepare amorphous LTP alloy powder.

[0225] Preparation of Conductive Paste (Examples 1-1 to 1-4 / Comparative Example 1-1)

[0226] Silver powder, laser thermal accelerator (LTP) or aluminum powder, glass powder and organic carrier were weighed respectively according to the ratio shown in Table 1-3, combined, mixed with a planetary mixer, and then mixed with a three-roll mill to prepare the conductive pastes of Examples 1-1 to 1-4 / Comparative Example 1-1.

[0227] Table 1-3 Composition of conductive paste

[0228] Preparation of Solar Cell Substrates with Electrodes (Inventive Samples 1-1 to 1-4 / Comparative Sample 1-1)

[0229] The conductive pastes of Examples 1-1 to 1-4 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered at a peak temperature of 750°C and a time from room temperature to peak temperature of 16 seconds. The laser enhanced contact optimization (LECO) process was then performed (laser wavelength of 1064 nm, laser energy density of 800 W / cm 2 , LECO reverse voltage is 14V, laser processing time is 0.8s), solar cell substrates with electrodes (samples 1-1 to 1-4 of the present invention) were prepared, and the electrical properties were tested. The results are shown in Table 1-4.

[0230] The conductive paste of comparative example 1-1 was printed onto an N-type silicon wafer by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered (conventional sintering) under the conditions of a peak temperature of 800°C and a time from room temperature to peak temperature of 16 seconds to produce a solar cell substrate with electrodes (comparative sample 1-1). The electrical properties were tested, and the results are shown in Table 1-4.

[0231] Table 1-4 Performance of solar cells

[0232] The results in Tables 1-4 show that the cell conversion efficiency (Eta), fill factor (FF) and resistance (Rs) of the solar cell of the present invention are improved in the samples of the present invention using the laser thermal accelerator of the present invention compared to the control samples using aluminum powder. The reduction in Rs indicates a reduction in the contact resistance of the solar cell of the present invention.

[0233] Preparation of Conductive Paste (Examples 1-5 to 1-8)

[0234] Silver powder, laser thermal accelerator (LTP), glass powder and organic vehicle were weighed according to the ratios shown in Tables 1-5, combined, mixed with a planetary mixer, and then mixed with a three-roll mill to prepare conductive pastes of Examples 1-5 to 1-8.

[0235] Table 1-5 Composition of conductive paste

[0236] Preparation of Solar Cell Substrates with Electrodes (Samples 1-5 to 1-8 of the Present Invention)

[0237] The conductive pastes of Examples 1-5 to 1-8 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered at a peak temperature of 750°C and a time from room temperature to peak temperature of 16 seconds. The laser enhanced contact optimization (LECO) process was then performed (laser wavelength of 1064 nm, laser energy density of 800 W / cm 2 , LECO reverse voltage is 14V, laser processing time is 0.8s), solar cell substrates with electrodes (samples 1-5 to 1-8 of the present invention) were prepared, and the electrical properties were tested. The results are shown in Table 1-6.

[0238] Table 1-6 Performance of solar cells

[0239] The results in Tables 1-6 show that the cell conversion efficiency (Eta), fill factor (FF) and resistance (Rs) of the solar cell of the present invention are improved in the samples of the present invention using the laser thermal accelerator of the present invention and glass powder of different compositions compared with the control samples using aluminum powder. The reduction in Rs indicates a reduction in the contact resistance of the solar cell of the present invention.

[0240] Preparation of conductive paste (Comparative Example 1-2)

[0241] The conductive paste of Comparative Example 1-2 was prepared in the same manner as that of Example 1-2, except that aluminum powder was used instead of the laser thermal accelerator in Example 1-2.

[0242] Preparation of Solar Cell Substrates with Electrodes (Inventive Samples 1-9 to 1-12 / Comparative Sample 1-2)

[0243] The conductive paste of Example 1-2 was printed onto four N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered under the conditions of a peak temperature of 750°C and a time from room temperature to peak temperature of 16 seconds. The four sintered N-type silicon wafers were then subjected to different laser enhanced contact optimization (LECO) processes (as shown in Table 1-7) to obtain solar cell substrates with electrodes (samples 1-9 to 1-12 of the present invention).

[0244] The conductive paste of comparative example 1-2 was printed onto an N-type silicon wafer by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered under the conditions of a peak temperature of 750°C and a time from room temperature to peak temperature of 16 seconds. The sintered N-type silicon wafer was then subjected to a laser enhanced contact optimization (LECO) process (as shown in Table 1-7) to obtain a solar cell substrate with an electrode (comparative sample 1-2).

[0245] Table 1-7 Manufacturing conditions of solar cells

[0246] The electrical performance test results of samples 1-9 to 1-12 of the present invention and comparative samples 1-1 to 1-2 are shown in Table 1-8.

[0247] Table 1-8 Performance of solar cells

[0248] The results in Tables 1-8 show that the samples of the present invention using the laser thermal accelerator of the present invention have improved cell conversion efficiency (Eta), fill factor (FF), and resistance (Rs) of the solar cells of the present invention compared to Comparative Sample 1-1 using aluminum powder (not subjected to the LECO process). The reduction in Rs indicates a reduction in the contact resistance of the solar cells of the present invention. The samples of the present invention using the laser thermal accelerator of the present invention have higher cell conversion efficiency (Eta) than Comparative Sample 1-2 using aluminum powder (treated with the LECO process).

[0249] According to a second aspect of the present invention, a conductive paste is applied to a surface of a solar cell wafer and forms a solid electrode body in electrical contact with the surface when fired. According to the second aspect of the present invention, the conductive paste comprises:

[0250] a) conductive metal particles, b) glass powder, c) reducing additive, and d) organic vehicle, wherein the reducing additive is represented by formula (I): Zr x Cu y Al z (I)

[0251] In formula (I), x=10-90% by weight, y=5-50% by weight, and z=5-20% by weight, the weight percentages being based on the weight of the reducing additive.

[0252] In a preferred embodiment, the conductive paste comprises:

[0253] a) conductive metal particles, b) glass powder, c) reducing additive, and d) organic vehicle, wherein the reducing additive is represented by formula (I): Zr x Cu y Al z (I)

[0254] In formula (I), x=40-90% by weight, y=5-20% by weight, and z=5-20% by weight, the weight percentages being based on the weight of the reducing additive.

[0255] The conductive metal particles can be fully described with reference to the first aspect of the present invention, and will not be described in detail here.

[0256] b) Glass powder

[0257] According to the present invention, glass frit is present in the conductive paste to induce etching and sintering. For the purposes of the present invention, the glass frit is preferably an amorphous or partially crystalline solid with a low glass transition temperature (Tg). The glass transition temperature (Tg) is the temperature at which a rigid solid transforms into a partially fluid, undercooled melt upon heating. Methods for determining the glass transition temperature (Tg) are well known to those skilled in the art. Etching and sintering caused by the glass frit occur above the glass transition temperature (Tg) of the glass frit, and preferably, the glass transition temperature (Tg) is below the desired peak firing temperature.

[0258] Any glass frit known to those skilled in the art and deemed suitable in the context of the present invention can be used as the glass frit in the conductive paste. For the purposes of the present invention, the glass frit present in the conductive paste preferably comprises an element, its oxide, a compound that produces an oxide upon heating, or a mixture thereof. Preferred elements in this regard are Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, or combinations thereof. For the purposes of the present invention, preferred oxides that the glass frit may comprise are alkali metal oxides, alkaline earth metal oxides, rare earth oxides, oxides of Groups V and VI elements, other oxides, or combinations thereof. Preferred alkali metal oxides in this regard are sodium oxide, lithium oxide, potassium oxide, rubidium oxide, cesium oxide, or combinations thereof. Preferred alkaline earth metal oxides in this regard are beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, or combinations thereof. In this regard, preferred oxides of Group V elements are phosphorus oxides, such as P2O5; bismuth oxides, such as Bi2O3; or combinations thereof. Preferred oxides of Group VI elements are tellurium oxides, such as TeO2 or TeO3; selenium oxides, such as SeO2; or combinations thereof. Preferred rare earth oxides are cerium oxides, such as CeO2; and lanthanum oxides, such as La2O3. Other preferred oxides in this regard are silicon oxides, such as SiO2; zinc oxides, such as ZnO; aluminum oxides, such as Al2O3; germanium oxides, such as GeO2; vanadium oxides, such as V2O5; niobium oxides, such as Nb2O5; boron oxides, such as B2O3; tungsten oxides, such as WO3; molybdenum oxides, such as MoO3; indium oxides, such as In2O3; other oxides of those elements listed above as preferred elements; or combinations thereof. Preferred oxides are also mixed oxides containing at least two of the elements listed as preferred elemental constituents of the glass frit, or mixed oxides formed by heating at least one of the above-mentioned oxides with at least one of the above-mentioned metals. Also preferred for the purposes of the present invention are mixtures of at least two of the above-mentioned oxides and mixed oxides.

[0259] In one embodiment of the present invention, the glass powder comprises oxides of elements selected from the group consisting of Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P, and combinations thereof, preferably lead oxide, boron oxide, and silicon oxide.

[0260] In one embodiment of the present invention, the glass frit may comprise: 30-50 mol % PbO; 5-15 mol % B 2 O 3 ; and 40-60 mol % SiO 2 , wherein the molar percentages are based on the total moles of all oxides.

[0261] The glass transition temperature, morphology, particle size, weight ratio in the conductive paste and preparation method of the glass powder can be found in detail in the first aspect of the present invention and will not be described in detail here.

[0262] c) Reducing additives

[0263] According to the present invention, the reducing additive is represented by formula (I): Zr x Cu y Al z (I)

[0264] In formula (I), x=10-90% by weight, y=5-50% by weight, and z=5-20% by weight, the weight percentages being based on the weight of the reducing additive.

[0265] In one embodiment of the present invention, in formula (I), x=10-90 wt %, preferably 40-90 wt %, more preferably 60-80 wt %, the weight percentages being based on the weight of the reducing additive.

[0266] In one embodiment of the present invention, in formula (I), y=5-50% by weight, preferably 5-20% by weight or 10-30% by weight, the weight percentages being based on the weight of the reducing additive.

[0267] In one embodiment of the present invention, in formula (I), z=5-20 wt %, preferably 5-20 wt %, more preferably 5-15 wt %, the weight percentages being based on the weight of the reducing additive.

[0268] In one embodiment of the present invention, the reducing additive is amorphous (non-crystalline) metal alloy particles.

[0269] In one embodiment of the present invention, the reducing additive is amorphous metal alloy particles having a particle size D50 of 0.1-8 μm. In a preferred embodiment of the present invention, the reducing additive is amorphous metal alloy particles having a particle size D50 of 1-5 μm. The determination of the particle size D50 is well known to those skilled in the art.

[0270] In one embodiment of the present invention, the reducing additive is present in a proportion of 0.1-10 wt %, preferably 0.1-5 wt %, more preferably 0.1-1 wt % of the conductive paste.

[0271] In one embodiment of the present invention, the reducing additive is prepared by a jet powder preparation method, which comprises the following steps:

[0272] (1) mixing and uniformly dispersing the high-purity metal powders used to prepare the reducing additive according to the formula ratio;

[0273] (2) heating and melting the obtained metal powder mixture in a crucible (e.g., a copper pressure crucible lined with quartz) at a temperature greater than 1000° C. to obtain a liquid master alloy;

[0274] (3) Under the action of pressure, the liquid master alloy is directly sprayed into ice water mixed with NaCl to obtain amorphous LTP alloy powder.

[0275] According to one embodiment of the present invention, the high-purity metal powder in step (1) has a purity of, for example, 99% or more.

[0276] According to one embodiment of the present invention, the temperature in step (2) is preferably 1050-1500°C, such as 1100°C, 1200°C, 1300°C, 1400°C.

[0277] According to one embodiment of the present invention, the pressure in step (3) is preferably 20-100 PSI, such as 30 PSI, 40 PSI, 50 PSI, 60 PSI, 70 PSI, 80 PSI, 90 PSI.

[0278] According to one embodiment of the present invention, the concentration of NaCl in step (3) is preferably 1-10 wt%, such as 2-5 wt% or 6-9 wt%.

[0279] According to the present invention, LTP powders with different particle sizes and morphologies can be obtained by adjusting the temperature, pressure and injection speed.

[0280] d) Organic carrier

[0281] In one embodiment of the present invention, the conductive paste comprises an organic vehicle commonly used in the art.Preferred organic vehicles are those that provide optimal stability of the ingredients within the conductive paste and impart viscosity to the conductive paste that allows for effective printability.

[0282] For the relevant introduction of the organic carrier, reference may be made to the organic carrier in the first aspect of the present invention.

[0283] Electrodes for crystalline silicon solar cells

[0284] The electrode for the crystalline silicon solar cell of the present invention is formed by sintering the above conductive paste.

[0285] In one embodiment of the present invention, the temperature of the conductive paste sintering treatment is 700-850°C, preferably 750-800°C.

[0286] crystalline silicon solar cells

[0287] The present invention also relates to a crystalline silicon solar cell, which comprises a substrate and the electrode combined on the substrate.

[0288] In one embodiment of the present invention, a preferred crystalline silicon solar cell according to the present invention is one that has high efficiency in terms of the ratio of the total energy of incident light to electrical energy output. Lightweight and durable crystalline silicon solar cells are also preferred. A crystalline silicon solar cell comprises at least: (i) a front electrode, (ii) a front doped layer, (iii) a pn junction boundary, (iv) a back doped layer, (v) a back electrode, and (vi) a passivation layer. The crystalline silicon solar cell may also include additional layers for chemical / mechanical protection.

[0289] In one embodiment of the present invention, the crystalline silicon solar cell substrate of the present invention is a substrate for crystalline silicon solar cells well known to those skilled in the art.

[0290] The crystalline silicon solar cell of the present invention basically comprises electrodes bonded to the substrate and formed by sintering the conductive paste of the present invention.

[0291] In one embodiment of the present invention, the conductive paste of the present invention is applied to a substrate, such as a semiconductor substrate (eg, a crystalline silicon wafer), to form printed electrodes.

[0292] The manner of applying the conductive paste to the substrate and the material selection of the substrate have been described in detail in the first aspect of the present invention. For details, please refer to the relevant content and will not be repeated here.

[0293] In a preferred embodiment of the present invention, the conductive paste of the present invention is used to prepare N-type solar cells, in particular TOPCon solar cells, the conductive paste comprising: a) 50-95 wt % of conductive metal particles, b) 0.1-15 wt % of glass powder, c) 0.1-10 wt % of a reducing additive, and d) 2-20 wt % of an organic vehicle, wherein the weight percentages are based on the total weight of the conductive paste.

[0294] Those skilled in the art can more easily understand the second aspect of the present invention according to the following embodiments:

[0295] Embodiment 2-1. A conductive paste comprising: a) conductive metal particles, b) glass powder, c) a reducing additive, and d) an organic vehicle, wherein the reducing additive is represented by formula (I): Zr x Cu y Al z (I)

[0296] In formula (I), x=10-90% by weight, y=5-50% by weight, and z=5-20% by weight, the weight percentages being based on the weight of the reducing additive.

[0297] Embodiment 2-2. The conductive paste according to Embodiment 2-1, wherein in formula (I), x=40-90 wt % and y=5-20 wt %.

[0298] Embodiment 2-3. The conductive paste according to embodiment 2-1 or 2-2, wherein the reducing additive is amorphous metal alloy particles.

[0299] Embodiment 2-4. The conductive paste according to any one of embodiments 2-1 to 2-3, wherein the reducing additive has a particle size D50 of 0.1-8 μm, preferably 1-5 μm.

[0300] Embodiment 2-5. The conductive paste according to any one of embodiments 2-1 to 2-4, wherein the conductive metal particles comprise Ag, Al, Cu, Zn, Pd, Ni, Pb, Au or a combination thereof, preferably Ag, Al, Cu or an alloy thereof, more preferably Ag.

[0301] Embodiment 2-6. The conductive paste according to any one of Embodiments 2-1 to 2-5, wherein the conductive metal particles have a particle size D50 of 0.5-10 μm, preferably 1-5 μm.

[0302] Embodiment 2-7. A conductive paste according to any one of Embodiments 2-1 to 2-6, wherein the glass powder contains oxides of elements selected from Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P and combinations thereof, preferably lead oxide, boron oxide and silicon oxide.

[0303] Embodiment 2-8. The conductive paste according to any one of Embodiments 2-1 to 2-7, wherein the glass frit has a glass transition temperature Tg of 300-600°C, preferably 300-500°C.

[0304] Embodiment 2-9. The conductive paste according to any one of Embodiments 2-1 to 2-8, wherein the glass frit has a particle size D50 of 0.1-10 μm, preferably 0.2-7 μm, more preferably 0.5-5 μm.

[0305] Embodiment 2-10. The conductive paste according to any one of Embodiments 2-1 to 2-9, wherein the conductive paste comprises: a) 50-95 wt % of conductive metal particles, b) 0.1-15 wt % of glass powder, c) 0.1-10 wt % of a reducing additive, and d) 2-20 wt % of an organic vehicle, the weight percentages being based on the total weight of the conductive paste.

[0306] Embodiment 2-11. An electrode for a crystalline silicon solar cell, the electrode being formed by sintering the conductive paste described in any one of Embodiments 2-1 to 2-10.

[0307] Embodiment 2-12. The electrode according to embodiment 2-11, wherein the sintering treatment is performed at a temperature of 700-850°C, preferably 750-800°C.

[0308] Embodiment 2-13. A crystalline silicon solar cell comprising a substrate and the electrode described in any one of Embodiments 2-11 to 2-12 bonded to the substrate, wherein the crystalline silicon solar cell is an N-type crystalline silicon solar cell, preferably a TOPCon solar cell.

[0309] Embodiments according to the second aspect of the present invention

[0310] The present invention is illustrated below by way of examples, but it should be understood that the following examples are non-limiting and are not intended to limit the scope of protection of the present invention.

[0311] raw material

[0312] PbO, B2O3, and SiO2 are 4N grade chemical reagents.

[0313] Silver powder (Ag) and aluminum powder (Al) are spherical powders with a particle size D50 of 2 μm.

[0314] The silicon wafer is an N-type silicon wafer with a size of 182mm and a silicon nitride and aluminum oxide passivation layer.

[0315] The organic carrier (V2-1) is composed as follows:

[0316] Diethylene glycol butyl ether acetate: 5.6 parts by weight;

[0317] Cellulose acetate butyrate: 0.6 parts by weight;

[0318] Oleic acid: 0.6 parts by weight;

[0319] Hydrogenated castor oil: 0.6 parts by weight;

[0320] Alkyl-modified silicone oil: 0.6 parts by weight.

[0321] The glass powder (G2-1) consists of 40 mol% PbO, 10 mol% B2O3 and 50 mol% SiO2.

[0322] The compositions of the reducing additives (AM2-01 to AM2-03) are shown in Table 2-1 below:

[0323] Table 2-1 Composition of reducing additives

[0324] Test Method

[0325] The commercial IV tester “cetisPV-Celltest4-BF” from Halm Elektronik GmbH was used to perform IV tests on the cells to measure the cell conversion efficiency (Eta), open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and series resistance (Rs).

[0326] Preparation of glass powder

[0327] Weigh the components of glass powder G2-1 and combine them to obtain a composition corresponding to glass powder G2-1;

[0328] The resulting composition was placed in an alumina crucible, placed in a muffle furnace and kept at 1100°C for 60 minutes;

[0329] The alumina crucible containing the molten glass was removed from the muffle furnace, and the molten glass was poured into a bucket containing deionized water for water quenching;

[0330] The water-quenched glass slag was ground into a particle size D50 of about 1.5 μm using a ball mill, thereby obtaining glass powder G2-1.

[0331] Preparation of reducing additives

[0332] The reducing additive is prepared by a jet powder preparation method, which includes the following steps:

[0333] (1) The high-purity metal powders (purity 99%) used to prepare the reducing additive were mixed and dispersed uniformly according to the formula ratio in Table 2-1;

[0334] (2) heating and melting the obtained metal powder mixture in a quartz-lined copper pressure crucible at a temperature of 1100° C. to obtain a liquid master alloy;

[0335] (3) The liquid master alloy was directly sprayed into ice water mixed with 2 wt% NaCl under a pressure of 50 PSI to prepare amorphous LTP alloy powder.

[0336] Preparation of Conductive Paste (Examples 2-1 to 2-3 / Comparative Examples 2-1 to 2-2)

[0337] Silver powder, reducing additive or aluminum powder, glass powder and organic vehicle were weighed respectively according to the ratio shown in Table 2-2, combined, mixed with a planetary mixer, and then mixed with a three-roll mill to prepare the conductive pastes of Examples 2-1 to 2-3 / Comparative Examples 2-1 to 2-2.

[0338] Table 2-2 Composition of conductive paste

[0339] Preparation of Solar Cell Substrates with Electrodes (Inventive Samples 2-1 to 2-3 / Comparative Samples 2-1 to 2-2)

[0340] The conductive pastes of Examples 2-1 to 2-3 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered under the conditions of a peak temperature of 800°C and a time from room temperature to peak temperature of 16 seconds to produce solar cell substrates with electrodes (Samples 2-1 to 2-3 of the present invention), and the electrical properties were tested. The results are shown in Table 2-3.

[0341] The conductive pastes of comparative examples 2-1 to 2-2 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered under the conditions of a peak temperature of 800°C and a time from room temperature to peak temperature of 16 seconds to produce solar cell substrates with electrodes (comparative samples 2-1 to 2-2), and the electrical properties were tested. The results are shown in Table 2-3.

[0342] Table 2-3 Performance of solar cells

[0343] The results in Tables 2-3 show that the cell conversion efficiency (Eta), fill factor (FF) and resistance (Rs) of the solar cell of the present invention are improved in the samples of the present invention using the reducing additive of the present invention compared to the control samples using aluminum powder. The reduction in Rs indicates a reduction in the contact resistance of the solar cell of the present invention.

[0344] Preparation of Conductive Paste (Examples 2-4 to 2-6)

[0345] Silver powder, reducing additive, glass powder and organic vehicle were weighed according to the ratio shown in Table 2-4, combined, mixed with a planetary mixer, and then mixed with a three-roll mill to prepare the conductive pastes of Examples 2-4 to 2-6.

[0346] Table 2-4 Composition of conductive paste

[0347] Preparation of Solar Cell Substrates with Electrodes (Samples 2-4 to 2-6 of the Present Invention)

[0348] The conductive pastes of Examples 2-4 to 2-6 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered at a peak temperature of 800°C and a time from room temperature to peak temperature of 16 seconds to produce solar cell substrates with electrodes (samples 2-4 to 2-6 of the present invention). The electrical properties were tested, and the results are shown in Table 2-5.

[0349] Table 2-5 Performance of solar cells

[0350] The results in Tables 2-5 show that the cell conversion efficiency (Eta), fill factor (FF) and resistance (Rs) of the solar cell of the present invention are improved for the samples of the present invention using different contents of the reducing additive of the present invention compared to the control samples using aluminum powder. The reduction in Rs indicates a reduction in the contact resistance of the solar cell of the present invention.

[0351] Preparation of Conductive Paste (Examples 2-7 to 2-9)

[0352] Silver powder, reducing additive, glass powder and organic vehicle were weighed according to the ratio shown in Table 2-6, combined, mixed with a planetary mixer, and then mixed with a three-roll mill to prepare the conductive pastes of Examples 2-7 to 2-9.

[0353] Table 2-6 Composition of conductive paste

[0354] Preparation of Solar Cell Substrates with Electrodes (Samples 2-7 to 2-9 of the Present Invention)

[0355] The conductive pastes of Examples 2-7 to 2-9 were respectively printed onto N-type silicon wafers by screen printing (430-11-15-3.5-14-9BB screen), and then rapidly sintered at peak temperatures of 780°C, 770°C, and 750°C, respectively, and a time from room temperature to peak temperature of 16 seconds to obtain solar cell substrates with electrodes (samples 2-7 to 2-9 of the present invention), and their electrical properties were tested.

[0356] The results of performance tests show that, compared with the control samples using aluminum powder, the samples of the present invention using different contents of the reducing additive of the present invention and different sintering temperatures have improved the cell conversion efficiency (Eta), fill factor (FF) and resistance (Rs) of the solar cell of the present invention. The cell conversion efficiency (Eta) is increased by at least 0.04%, even up to 0.12%, the fill factor (FF) is increased by at least 0.03%, even up to 0.12%, and the resistance (Rs) is also reduced. The reduction in Rs indicates a reduction in the contact resistance of the solar cell of the present invention.

Claims

1. A conductive paste, comprising: a) Conductive metal particles, b) Glass powder, c) Laser thermal promoter, and d) Organic carrier, wherein the laser thermal promoter is represented by formula (I): Zr x Cu y Al m Ni z Nb n A q (I) In formula (I), x = 10 - 90 wt%, y = 5 - 50 wt%, m = 0.5 - 10 wt%, z = 0 - 20 wt%, n = 0 - 15 wt%, q = 0 - 5 wt%, and A is a metal selected from Ag, Cr, Zn, and Ti, and the weight percentages are based on the weight of the laser thermal promoter.

2. The conductive paste according to claim 1, wherein in formula (I), x = 50 - 90 wt% and y = 5 - 35 wt%.

3. The conductive paste according to claim 1 or 2, wherein the laser thermal promoter is amorphous metal alloy particles.

4. The conductive paste according to any one of claims 1 - 3, wherein the laser thermal promoter has a particle size D50 of 0.1 - 8 μm, preferably 1 - 5 μm.

5. The conductive paste according to any one of claims 1 - 4, wherein the conductive metal particles comprise Ag, Al, Cu, Zn, Pd, Ni, Pb, Au, or a combination thereof, preferably Ag, Al, Cu, or an alloy thereof, more preferably Ag.

6. The conductive paste according to any one of claims 1 - 5, wherein the conductive metal particles have a particle size D50 of 0.5 - 10 μm, preferably 1 - 5 μm.

7. The conductive paste according to any one of claims 1 - 6, wherein the glass powder comprises oxides of elements selected from Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P, and combinations thereof, preferably comprising PbO, B2O3, SiO2, ZnO, Al2O3, TeO2, Bi2O3, P2O5, or any combination of two or more thereof.

8. The conductive paste according to any one of claims 1 - 7, wherein the glass powder has a glass transition temperature Tg of 300 - 600 °C, preferably 300 - 500 °C.

9. The conductive paste according to any one of claims 1 - 8, wherein the glass powder has a particle size D50 of 0.1 - 10 μm, preferably 0.2 - 7 μm, more preferably 0.5 - 5 μm.

10. The conductive paste according to any one of claims 1 - 9, wherein in formula (I), (1) n = 1 - 10 wt%, or (2) n = 1 - 10 wt% and z = 8 - 15 wt%, or (3) z = 8 - 15 wt%, q = 1 - 5 wt% and A is Ti.

11. The conductive paste according to any one of claims 1 - 10, wherein the conductive paste comprises: a) 50 - 95 wt% of conductive metal particles, b) 0.1 - 15 wt% of glass powder, c) 0.1 - 10 wt% of laser thermal promoter, and d) 2 - 20 wt% of organic carrier, the weight percentages being based on the total weight of the conductive paste.

12. An electrode for a crystalline silicon solar cell, wherein the electrode is formed by sintering the conductive paste according to any one of claims 1-11.

13. The electrode according to claim 12, wherein the electrode is processed by a laser enhanced contact optimization process, and the laser enhanced contact optimization process is carried out at a laser wavelength of 400 - 1500 nm, a laser energy density of 500 - 1100 W / cm 2 and a reverse voltage of 5 - 40 V.

14. The electrode according to claim 13, wherein the reverse voltage is 10-25V.

15. A crystalline silicon solar cell, comprising a substrate and the electrode according to any one of claims 12-14 bonded to the substrate, wherein the crystalline silicon solar cell is an N-type crystalline silicon solar cell, preferably a TOPCon solar cell.

16. A conductive paste, comprising: a) Conductive metal particles, b) Glass powder, c) Reducing additive, and d) Organic carrier, wherein the reducing additive is represented by formula (I): Zr x Cu y Al z (I) In formula (I), x = 10-90 wt%, y = 5-50 wt%, z = 5-20 wt%, and the weight percentages are based on the weight of the reducing additive.

17. The conductive paste according to claim 16, wherein in formula (I), x = 40-90 wt% and y = 5-20 wt%.

18. The conductive paste according to claim 16 or 17, wherein the reducing additive is amorphous metal alloy particles.

19. The conductive paste according to any one of claims 16-18, wherein the reducing additive has a particle size D50 of 0.1-8μm, preferably 1-5μm.

20. The conductive paste according to any one of claims 16-19, wherein the conductive metal particles comprise Ag, Al, Cu, Zn, Pd, Ni, Pb, Au or a combination thereof, preferably Ag, Al, Cu or an alloy thereof, more preferably Ag.

21. The conductive paste according to any one of claims 16-20, wherein the conductive metal particles have a particle size D50 of 0.5-10μm, preferably 1-5μm.

22. The conductive paste according to any one of claims 16-21, wherein the glass powder comprises oxides of elements selected from Si, B, Al, Bi, Li, Na, K, Mg, Pb, Zn, Gd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Ba, Cr, Te, P and combinations thereof, preferably comprising lead oxide, boron oxide and silicon oxide.

23. The conductive paste according to any one of claims 16-22, wherein the glass powder has a glass transition temperature Tg of 300-600°C, preferably 300-500°C.

24. The conductive paste according to any one of claims 16-23, wherein the glass powder has a particle size D50 of 0.1-10μm, preferably 0.2-7μm, more preferably 0.5-5μm.

25. The conductive paste according to any one of claims 16-24, wherein the conductive paste comprises: a) 50-95 wt% of conductive metal particles, b) 0.1-15 wt% of glass powder, c) 0.1-10 wt% of reducing additive, and d) 2-20 wt% of organic carrier, The weight percentages are based on the total weight of the conductive paste.

26. An electrode for a crystalline silicon solar cell, which is formed by sintering the conductive paste according to any one of claims 16-25.

27. The electrode according to claim 26, wherein the sintering treatment is carried out at a temperature of 700-850 °C, preferably 750-800 °C.

28. A crystalline silicon solar cell, which comprises a substrate and the electrode according to any one of claims 26-27 bonded to the substrate, wherein the crystalline silicon solar cell is an N-type crystalline silicon solar cell, preferably a TOPCon solar cell.

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