A photovoltaic nickel paste, a preparation method thereof, and an application thereof in preparing a nickel grid line of a photovoltaic cell

Abstract

The present invention provides a photovoltaic nickel paste, a preparation method thereof, and an application thereof in preparing nickel grid lines of a photovoltaic cell. The photovoltaic nickel paste comprises the following components by mass percentage: 1-5% of glass powder, 10-40% of an organic carrier, and 60-80% of nickel powder; the organic carrier comprises an organic resin and an organic solvent with a mass ratio of (3-7):(2-5). During the sintering process of the photovoltaic nickel paste of the present invention, the glass powder melts and corrodes silicon nitride at high temperature, and the nickel powder forms an alloy with the underlying silicon through infiltration to generate an ohmic contact, overcoming the problem of removing the silicon nitride layer before electroplating grid lines on a solar cell by using the existing laser grooving process and the mask / photoresist process.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and particularly to a photovoltaic nickel paste, a preparation method thereof, and an application thereof in preparing nickel grid lines of a photovoltaic cell. Background Art

[0002] The development of photovoltaic technology is rapid, and the production capacity of solar cells has maintained a growth rate of more than 25% per year in recent years. At present, the photovoltaic cell process has rapidly shifted from the PERC process to the TOPCon process, and the conversion efficiency has rapidly increased from more than 23% to more than 26%, greatly improving the power of the cells and components. However, while the efficiency of solar cells has increased, the consumption of silver paste has also increased. The silver paste consumption of Topcon of the same size is 1.5 to 2 times that of PERC, making the replacement of printed silver paste with electroplated copper grid lines a technology for reducing silver consumption and cost reduction rapidly developing among various photovoltaic companies.

[0003] Currently, for electroplating copper grid lines on TOPCon cells, the etching method mainly used is to use laser grooving to remove the insulating silicon nitride passivation layer on the surface of the cell according to the grid line pattern to form a conductive path required for electroplating. However, due to the large laser grooving area, laser thermal damage will cause damage to the cell surface, resulting in a decrease in open voltage and efficiency. Another mask / photoresist process has high requirements for materials, complex processes, high production costs, and incomplete cleaning, which will cause organic matter residues.

[0004] Therefore, it is urgent to develop a new method for removing the silicon nitride layer to overcome the defects of laser grooving and mask / photoresist processes.

[0005] In view of this, the present invention is particularly proposed. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a photovoltaic nickel paste. During the sintering process of the photovoltaic nickel paste, the glass powder melts and corrodes silicon nitride at high temperature, and the nickel powder forms an alloy with the underlying silicon through infiltration to generate an ohmic contact, overcoming the problem of removing the silicon nitride layer before electroplating the grid lines of solar cells by using the existing laser grooving process and mask / photoresist process.

[0007] Another purpose of the present invention is to provide a preparation method of a photovoltaic nickel paste. The preparation method of the photovoltaic nickel paste enables the nickel powder and the glass powder to be uniformly mixed and dispersed, with less agglomeration, reducing the generation of internal defects, and effectively improving the subsequent sintering yield and reliability.

[0008] The third purpose of the present invention is to provide an application of the photovoltaic nickel paste in preparing nickel grid lines of a photovoltaic cell; wherein, the photovoltaic cell includes a PERC cell and / or a Topcon cell.

[0009] A fourth object of the present invention is to provide a method for preparing nickel grid lines in PERC solar cells, and the preparation method includes the following steps: placing the above-mentioned photovoltaic nickel paste on the front side of the blue film, and then sintering to form nickel grid lines.

[0010] A fifth object of the present invention is to provide a method for preparing nickel grid lines in Topcon solar cells, and the preparation method includes the following steps: placing the above-mentioned photovoltaic nickel paste on the back side of the blue film and drying to form back nickel grid lines; then placing the above-mentioned photovoltaic nickel paste on the front side of the blue film and sintering to form front nickel grid lines.

[0011] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0012] In the first aspect, the present invention provides a photovoltaic nickel paste, and the photovoltaic nickel paste includes the following components by mass percentage: 1-5% of glass powder, 10-40% of organic carrier, and 60-80% of nickel powder.

[0013] Based on the total mass of the photovoltaic nickel paste being 100%, the addition amount of the glass powder is 1-5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0014] Based on the total mass of the photovoltaic nickel paste being 100%, the addition amount of the organic carrier is 10-40%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc.

[0015] Based on the total mass of the photovoltaic nickel paste being 100%, the addition amount of the nickel powder is 60-80%, for example, it can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, etc.

[0016] In the photovoltaic nickel paste, the organic carrier includes an organic resin and an organic solvent with a mass ratio of (3-7):(2-5);

[0017] Among them, "3-7" can be, for example, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, etc.;

[0018] Among them, "2-5" can be, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.

[0019] In the present invention, a photovoltaic nickel paste for preparing electroplated grid lines of a photovoltaic cell is obtained from glass powder, an organic carrier, and nickel powder with a specific ratio and composition. During the sintering process of the photovoltaic nickel paste, the organic carrier is sintered and volatilized. During the sintering process, the glass powder melts and corrodes silicon nitride at high temperature, and the nickel powder forms an alloy with the underlying silicon through infiltration to generate an ohmic contact, thus well solving the problem of removing the silicon nitride layer before electroplating the grid lines of a solar cell in the laser grooving process and the mask / photoresist process.

[0020] In the present invention, the organic carrier includes an organic resin and an organic solvent with a mass ratio of (3 - 7):(2 - 5). The purpose is to enable the composite organic carrier to penetrate into the gaps and wet the surface of the inorganic powder particles, while weakening the adsorption between the particles, inhibiting the adsorption and agglomeration between nickel powder and / or glass powder particles, promoting the dispersion of the inorganic powder, improving the screenability of the nickel paste, reducing screen clogging, and helping to reduce the generation of printing defects such as ghosting and broken grids.

[0021] Preferably, the raw materials for preparing the glass powder include the following components by mass percentage: 20 - 50% of SiO2, 5 - 30% of Bi2O3, 1 - 10% of ZnO, 5 - 30% of PbO, 1 - 10% of Al2O3, and 3 - 30% of TeO2.

[0022] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of SiO2 is 20 - 50%, for example, it can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc.

[0023] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of Bi2O3 is 5 - 30%, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0024] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of ZnO is 1 - 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0025] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of PbO is 5 - 30%, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0026] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of Al2O3 is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0027] Based on the total mass of the raw materials for preparing the glass powder being 100%, the content of TeO2 is 3-30%, for example, it can be 3%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0028] In the present invention, by using the combination of raw materials for preparing the glass powder with specific ratios and compositions, different viscosity changes and glass phases are exhibited at low and high temperatures, which can well solve the problem of the corrosion rate and depth of silicon nitride, avoid the problems of short sintering window time and too high corrosion rate during the firing process, and make the properties such as the leveling, sagging, grid line width, and grid line height of the slurry reach an ideal balance.

[0029] Preferably, the organic resin is selected from any one or a combination of at least two of acrylic resin, butyral resin, ethyl cellulose, nitrocellulose, konjac gum, guar gum, or polyvinyl alcohol.

[0030] Preferably, the molecular weight of the organic resin is 100-500 g / mol, for example, it can be 100 g / mol, 150 g / mol, 200 g / mol, 250 g / mol, 300 g / mol, 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol, etc., and the viscosity of the organic resin is 1-20 mPa·s, for example, it can be 1 mPa·s, 2 mPa·s, 4 mPa·s, 6 mPa·s, 8 mPa·s, 10 mPa·s, 12 mPa·s, 14 mPa·s, 16 mPa·s, 18 mPa·s, 20 mPa·s, etc.

[0031] Preferably, the organic resin is a combination of butyral resin, nitrocellulose, and polyvinyl alcohol with a mass ratio of (5-6):(2-3):(1-2);

[0032] Among them, "5-6" can be, for example, 5, 5.2, 5.4, 5.6, 5.8, 6, etc.;

[0033] Among them, "2-3" can be, for example, 2, 2.2, 2.4, 2.6, 2.8, 3, etc.;

[0034] Among them, "1-2" can be, for example, 1, 1.2, 1.4, 1.6, 1.8, 2, etc.

[0035] In the present invention, the selected organic resin with the above specific formulation and composition can, in addition to having the functions of dispersion, thixotropy or anti-sagging during use, generate thermal cross-linking during the baking process, which can, to a certain extent, compensate for the viscosity reduction caused by the increase in sintering temperature and the partial or complete destruction of hydrogen bonds, and endow the nickel paste with a stable system viscosity, so as to print nickel grid lines with excellent aspect ratio.

[0036] Preferably, the organic solvent is selected from any one or a combination of at least two of methyl silicate, terpineol, castor oil, diethylene glycol monobutyl ether, ethylene glycol methyl butyl ether, isopropyl alcohol or ethylene glycol monoethyl ether.

[0037] In the present invention, the combination of a specific organic resin and an organic solvent helps to control the rheological properties of the paste, adjust the viscosity of the paste, and improve the dispersion performance of the glass powder and nickel powder.

[0038] Preferably, the purity of the nickel powder is above 99.7%, for example, it can be 99.7%, 99.8%, 99.9%, 99.95%, 99.98%, etc.

[0039] Preferably, the particle size of the nickel powder is 0.1 - 2 μm, for example, it can be 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, etc.

[0040] Furthermore, the present invention ensures no impurity entry by defining the purity and particle size of the nickel powder, and the nickel powder can better penetrate during the sintering process to form an ohmic contact with the silicon below to form an alloy.

[0041] Preferably, the photovoltaic nickel paste further includes 0.1 - 5% of additives, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0042] Preferably, the additive is selected from any one or a combination of at least two of a surfactant, a leveling agent, a thixotropic agent or a penetrant.

[0043] Preferably, the surfactant is selected from any one or a combination of at least two of glycerol fatty acid ester, sorbitan fatty acid ester, polysorbate, sodium dodecyl sulfate, sodium hexadecyl benzene sulfonate or cetyl trimethyl ammonium bromide.

[0044] Preferably, the leveling agent is selected from any one or a combination of at least two of ethylene glycol butyl ether, hydrogenated castor oil, polyacrylic acid, alkylphenol polyoxyethylene ether or polyether-modified silicone.

[0045] Preferably, the thixotropic agent is selected from any one or a combination of at least two of fumed silica, organic bentonite, polyamide wax, or dibutyl phthalate.

[0046] Preferably, the penetrant is selected from any one or a combination of at least two of polyethylene glycol, polyoxyethylene phenol ether, fatty alcohol polyoxyethylene ether phosphate, or polyoxyethylene secondary alkyl alcohol ether.

[0047] Second, the present invention provides a method for preparing the photovoltaic nickel paste as described in the first aspect. The preparation method includes the following steps:

[0048] Grind and mix the raw materials for preparing the glass powder to obtain a mixed material;

[0049] Anneal the mixed material to obtain molten glass; mix the molten glass and water, carry out a hydrothermal reaction, and then sequentially carry out filtration, drying, and grinding to obtain the glass powder;

[0050] Carry out a first mixing of the organic resin and the organic solvent, and then add the glass powder and the nickel powder for a second mixing to obtain a crude paste;

[0051] Grind and filter the crude paste in sequence to obtain the photovoltaic nickel paste.

[0052] In the present invention, the preparation method of the photovoltaic nickel paste enables the nickel powder and the glass powder to be uniformly mixed and dispersed, with less agglomeration, reducing the generation of internal defects, and having an obvious positive effect on improving the subsequent sintering yield and reliability, ensuring that a good ohmic contact cannot be formed with the silicon substrate subsequently.

[0053] Preferably, the specific grinding of the raw materials for preparing the glass powder is as follows: ball milling with a ball mill for 5 to 8 hours, such as 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, etc.

[0054] Preferably, after the ball milling, there is also a sieving step; the mesh number of the sieving is 100 to 300 meshes, such as 100 meshes, 120 meshes, 140 meshes, 160 meshes, 180 meshes, 200 meshes, 220 meshes, 240 meshes, 260 meshes, 280 meshes, 300 meshes, etc.

[0055] Preferably, after the sieving, there is also a drying step; that is, drying the sieved material to a constant weight.

[0056] Preferably, the annealing temperature is 180 to 240 °C, such as 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, etc., and the annealing time is 1 to 2 hours, such as 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, etc.

[0057] Preferably, before the annealing, a melting step is further included; that is, the mixture is loaded into a corundum crucible for melting.

[0058] Preferably, the mass ratio of the mixture to water is 1:(0.3 - 0.7), for example, it can be 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, etc.

[0059] Preferably, the temperature of the hydrothermal reaction is 180 - 240 °C, for example, it can be 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, etc., and the time of the hydrothermal reaction is 2 - 3 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0060] Preferably, the temperature of the first mixing is 20 - 30 °C, for example, it can be 20 °C, 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, etc., the rotation speed of the first mixing is 100 - 200 rpm, for example, it can be 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm, 200 rpm, etc., and the time of the first mixing is 40 - 60 min, for example, it can be 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0061] Preferably, during the process of adding the glass powder and nickel powder, the rotation speed is 200 - 500 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc.

[0062] Preferably, the temperature of the second mixing is 20 - 30 °C, for example, it can be 20 °C, 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, etc., the rotation speed of the second mixing is 50 - 100 rpm, for example, it can be 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, etc., and the time of the second mixing is 90 - 150 min, for example, it can be 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, etc.

[0063] Preferably, after the secondary mixing, it further includes: adding an additive and performing a third mixing.

[0064] Preferably, the temperature of the third mixing is 20 - 30°C, such as 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc.; the rotation speed of the third mixing is 50 - 150 rpm, such as 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, etc.; the time of the third mixing is 30 - 60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0065] Preferably, the grinding of the coarse slurry is carried out using a three - roll mill.

[0066] Preferably, the fineness of the ground slurry is 0.5 - 2 μm, such as 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, etc.

[0067] In the third aspect, the present invention provides an application of the photovoltaic nickel paste as described in the first aspect in the preparation of nickel grid lines for photovoltaic cells.

[0068] Among them, the photovoltaic cell includes a PERC cell and / or a Topcon cell.

[0069] In the fourth aspect, the present invention provides a method for preparing nickel grid lines in a PERC cell, and the preparation method includes the following steps:

[0070] Place the photovoltaic nickel paste described in the first aspect on the front of the blue film, and then sinter it to form nickel grid lines.

[0071] More specifically, the method for preparing nickel grid lines in the PERC cell includes the following steps:

[0072] S1. Sample preparation: Take the blue film before printing; the blue film includes a P - type silicon substrate, and the front of the P - type silicon substrate sequentially includes a phosphorus diffusion layer and a silicon nitride layer; the back of the P - type silicon substrate sequentially includes an alumina layer and a silicon nitride layer.

[0073] S2. Laser grooving: According to the grid line design, use a laser to remove the local alumina layer and silicon nitride layer on the back to form a groove on the back of the blue film (ensuring that the subsequent printed aluminum paste contacts the silicon substrate to form an ohmic contact).

[0074] S3. Back printing: Use the printing method to print back silver and back aluminum on the back respectively, and dry them at a temperature of 200 - 300°C.

[0075] S4. Formation of nickel grid lines: Place nickel paste on the front side of the blue diaphragm according to the designed pattern, and then sinter it at 300 - 700 °C to form conductive nickel grid lines;

[0076] S5. Formation of copper grid lines: Use electroplating process to electroplate copper on the front nickel grid lines to form copper grid lines;

[0077] S6. Formation of anti-oxidation layer: Use electroplating process to electroplate a metal coating layer on the outer layer of the copper grid lines to obtain an anti-oxidation layer; wherein, the metal includes any one or a combination of at least two of tin, nickel, silver, zinc or aluminum.

[0078] Preferably, the thickness of the photovoltaic nickel paste is 1 - 5 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0079] Preferably, the placement method of the photovoltaic nickel paste includes any one of printing, inkjet or laser transfer.

[0080] Preferably, the sintering temperature is 300 - 700 °C, for example, it can be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, etc.

[0081] Preferably, the width of the nickel grid lines is 5 - 15 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and the height is 1 - 5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0082] Preferably, the width of the copper grid lines is 10 - 20 μm, for example, it can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc., and the height is 5 - 15 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0083] Preferably, the thickness of the anti-oxidation layer is 0.5 - 1 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0084] Fifthly, the present invention provides a preparation method of nickel grid lines in Topcon solar cells, and the preparation method includes the following steps:

[0085] Place the photovoltaic nickel paste described in the first aspect on the back of the blue film, and dry it to form the back nickel grid line; then place the photovoltaic nickel paste described in the first aspect on the front of the blue film and sinter it to form the front nickel grid line.

[0086] More specifically, the method for preparing the nickel grid line in the Topcon solar cell includes the following steps:

[0087] S1. Sample preparation: Take the blue film before printing; the blue film includes an N-type silicon substrate, and the front of the N-type silicon substrate sequentially includes a boron diffusion layer, an alumina layer, and a silicon nitride layer; the back of the N-type silicon substrate sequentially includes a tunneling oxide layer, a poly layer, and a silicon nitride layer;

[0088] S2. Formation of the back nickel grid line: Place the nickel paste on the back of the blue film according to the designed pattern, and dry it at a temperature of 200 - 300 °C to form the back nickel grid line;

[0089] S3. Formation of the front nickel grid line: Place the nickel paste on the front of the blue film according to the designed pattern, and then sinter it at 300 - 700 °C to form the front nickel grid line;

[0090] S4. Formation of the copper grid line: Use the electroplating process to electroplate copper on the front nickel grid line to form the copper grid line;

[0091] S5. Formation of the anti-oxidation layer: Use the electroplating process to electroplate a metal coating layer on the outer layer of the copper grid line to obtain the anti-oxidation layer; wherein, the metal includes any one or a combination of at least two of tin, nickel, silver, zinc, or aluminum.

[0092] Preferably, the thickness of the photovoltaic nickel paste is 1 - 5 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0093] Preferably, the placement method of the photovoltaic nickel paste includes any one of printing, inkjet, or laser transfer.

[0094] Preferably, the drying temperature is 200 - 300 °C, for example, it can be 200 °C, 220 °C, 240 °C, 260 °C, 280 °C, 300 °C, etc.

[0095] Preferably, the sintering temperature is 300 - 700 °C, for example, it can be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, etc.

[0096] Preferably, the width of the back nickel grid line is 5 - 15 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc., and the height is 1 - 5 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0097] Preferably, the width of the front nickel grid line is 5 - 15 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc., and the height is 1 - 5 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0098] Preferably, the width of the copper grid line is 10 - 20 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc., and the height is 5 - 15 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0099] Preferably, the thickness of the anti - oxidation layer is 0.5 - 1 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0100] Compared with the prior art, the present invention has the following beneficial effects:

[0101] (1) The photovoltaic nickel paste of the present invention can be directly printed on the screen. Through high - temperature sintering at 300 - 700 °C, the organic carrier is sintered and volatilized. During the sintering process, the glass powder melts and corrodes silicon nitride at high temperature, and the nickel powder forms an alloy with the underlying silicon through infiltration to produce an ohmic contact.

[0102] (2) The process for preparing the nickel grid line of the photovoltaic cell of the present invention can be completed in the printing and sintering furnace, without the need to add other equipment and processes.

[0103] (3) The cell sheet with the nickel grid line made by the present invention grows a copper grid line on the nickel grid line through the electroplating process to improve the conductivity of the grid line; at the same time, a metal coating layer is further plated on the outer layer of the copper grid line, which well avoids the oxidation of the copper grid line. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0105] Figure 1 It is a schematic structural diagram of a PERC cell prepared with the photovoltaic nickel paste described in the present invention.

[0106] Among them, 1 is a P-type silicon substrate, 2 is a phosphorus diffusion layer, 3 is a silicon nitride layer, 4 is an alumina layer, 5 is a back aluminum layer, 6 is a back silver layer, 7 is a laser groove, 8 is a nickel grid line, 9 is a copper grid line, and 10 is an anti-oxidation layer.

[0107] Figure 2 It is a schematic structural diagram of a Topcon cell prepared with the photovoltaic nickel paste described in the present invention.

[0108] Among them, 11 is an N-type silicon substrate, 3 is a silicon nitride layer, 4 is an alumina layer, 12 is a boron diffusion layer, 13 is a tunneling oxide layer, 14 is a poly layer, 8 is a nickel grid line, 9 is a copper grid line, and 10 is an anti-oxidation layer. Specific Embodiments

[0109] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In this application, unless otherwise specified, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-restrictive.

[0110] It should be noted that specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0111] Such as Figure 1As shown in the figure, the present invention provides a PERC cell prepared by using the photovoltaic nickel paste of the present invention. Among them, take the blue film before printing. The blue film includes a P-type silicon substrate 1. The front side of the P-type silicon substrate 1 successively includes a phosphorus diffusion layer 2 and a silicon nitride layer 3. The back side of the P-type silicon substrate 1 successively includes an aluminum oxide layer 4 and a silicon nitride layer 3. And the local aluminum oxide layer and silicon nitride layer on the back side are removed by laser to form a laser groove 7 on the back side of the blue film. Then, by printing, a back aluminum layer and a back silver layer 6 are respectively printed on the back side. Then, the photovoltaic nickel paste of the present invention is placed on the front side of the blue film and sintered to form a nickel grid line 8. Finally, by using an electroplating process, copper is electroplated on the front nickel grid line to form a copper grid line 9, and a metal coating layer is electroplated on the outer layer of the copper grid line 9 to obtain an anti-oxidation layer 10.

[0112] As Figure 2 shown in the figure, the present invention provides a Topcon cell prepared by using the photovoltaic nickel paste of the present invention. Among them, take the blue film before printing. The blue film includes an N-type silicon substrate 11. The front side of the N-type silicon substrate 11 successively includes a boron diffusion layer 12, an aluminum oxide layer 4 and a silicon nitride layer 3. The back side of the N-type silicon substrate successively includes a tunneling oxide layer 13, a poly layer 14 and a silicon nitride layer 3. Then, the photovoltaic nickel paste of the present invention is respectively placed on the front side and the back side of the blue film and sintered to form a nickel grid line 8. Finally, by using an electroplating process, copper is electroplated on the front nickel grid line to form a copper grid line 9, and a metal coating layer is electroplated on the outer layer of the copper grid line 9 to obtain an anti-oxidation layer 10.

[0113] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0114] The present invention will be further described below through embodiments. Unless otherwise specified, the materials in the embodiments are prepared according to existing methods or directly purchased from the market.

[0115] Embodiment 1

[0116] This embodiment provides a photovoltaic nickel paste. The photovoltaic nickel paste includes the following components by mass percentage:

[0117]

[0118]

[0119] The photovoltaic nickel paste is prepared by the following steps:

[0120] (a) Load the raw materials of the glass powder into a ball mill according to the above ratio and ball mill for 6 h. Pass through a 200-mesh sieve, dry the sieved material to constant weight to obtain a composite powder, and mix it with a mixer.

[0121] (b) Load the mixed material into a corundum crucible and melt it at 1050 °C, then put it into an electric resistance furnace and anneal it at 480 °C for 1.5 h to obtain molten glass. Mix the molten glass and deionized water with a mass ratio of 1:0.65 and load them into a hydrothermal reaction kettle, react at 210 °C for 2.5 h, filter, dry, and ball mill after cooling to room temperature, and pass through a 300-mesh sieve to obtain glass powder.

[0122] (c) Add the organic solvent and organic resin to a blender and stir and separate at a speed of 150 rpm at 25 °C for 50 min. Then add the glass powder and nickel powder at a speed of 350 rpm, separate at a reduced speed of 80 rpm for 120 min, and finally add the above additives in proportion and stir and separate at a speed of 120 rpm for 45 min to obtain a crude slurry.

[0123] (d) Grind the crude slurry with a three-roll mill, control the fineness of the slurry to an average particle size of 1 μm, and filter it through a 400-mesh screen after completion to obtain the photovoltaic nickel paste.

[0124] Example 2

[0125] This example provides a photovoltaic nickel paste, and the photovoltaic nickel paste includes the following components by mass percentage:

[0126]

[0127]

[0128] The photovoltaic nickel paste is prepared by the following steps:

[0129] (a) Load the raw materials of the glass powder into a ball mill according to the above ratio and ball mill for 5 h. Pass through a 200-mesh sieve, dry the sieved material to constant weight to obtain a composite powder, and mix it with a mixer.

[0130] (b) Load the mixed material into a corundum crucible and melt it at 1100 °C, then put it into an electric resistance furnace and anneal it at 480 °C for 1 h to obtain molten glass. Mix the molten glass and deionized water with a mass ratio of 1:0.4 and load them into a hydrothermal reaction kettle, react at 200 °C for 2 h, filter, dry, and ball mill after cooling to room temperature, and pass through a 300-mesh sieve to obtain glass powder.

[0131] (c) Add the organic solvent and organic resin into a blender, stir and separate at 20°C at a speed of 100 rpm for 60 min. Then add the glass powder and nickel powder at a speed of 200 rpm, reduce the speed by half to 50 rpm and separate for 150 min. Finally, add the above additives in proportion and stir and separate at a speed of 50 rpm for 60 min to obtain the crude slurry;

[0132] (d) Grind the crude slurry with a three-roll mill, control the fineness of the slurry to an average particle size of 0.5 μm, and after completion, filter it through a 400-mesh screen to obtain the photovoltaic nickel paste.

[0133] Example 3

[0134] This example provides a photovoltaic nickel paste, and the photovoltaic nickel paste comprises the following components by mass percentage:

[0135]

[0136]

[0137] The photovoltaic nickel paste is prepared by the following steps:

[0138] (a) Charge the raw materials of the glass powder into a ball mill according to the above ratio, ball mill for 8 h, pass through a 200-mesh sieve, dry the sieved material to a constant weight to obtain the composite powder, and mix it with a mixer;

[0139] (b) Charge the mixture into a corundum crucible, melt it at 1150°C, and then put it into an electric resistance furnace for annealing treatment at 500°C for 2 h to obtain the molten glass; Mix the molten glass and deionized water with a mass ratio of 1:0.6 and put them into a hydrothermal reaction kettle, react at 225°C for 3 h, filter, dry, and ball mill after cooling to room temperature, and pass through a 300-mesh sieve to obtain the glass powder;

[0140] (c) Add the organic solvent and organic resin into a blender, stir and separate at 30°C at a speed of 200 rpm for 40 min. Then add the glass powder and nickel powder at a speed of 500 rpm, reduce the speed by half to 100 rpm and separate for 90 min. Finally, add the above additives in proportion and stir and separate at a speed of 150 rpm for 30 min to obtain the crude slurry;

[0141] (d) Grind the crude slurry with a three-roll mill, control the fineness of the slurry to an average particle size of 1.5 μm, and after completion, filter it through a 400-mesh screen to obtain the photovoltaic nickel paste.

[0142] Example 4

[0143] This embodiment provides a photovoltaic nickel paste, which is only different from that of Embodiment 1 in that the raw materials for preparing the glass powder include the following components by mass percentage: 60% of SiO2, 4% of Bi2O3, 15% of ZnO, 4% of PbO, 15% of Al2O3, and 2% of TeO2; the contents of other components and the preparation method are exactly the same as those of Embodiment 1.

[0144] Embodiment 5

[0145] This embodiment provides a photovoltaic nickel paste, which is only different from that of Embodiment 1 in that the organic resin is a combination of acrylic resin, ethyl cellulose, and konjac gum with a mass ratio of 5:3:2; the contents of other components and the preparation method are exactly the same as those of Embodiment 1.

[0146] Comparative Example 1

[0147] This comparative example provides a photovoltaic nickel paste, which is only different from that of Embodiment 1 in that the addition amount of glass powder is 6%, the addition amount of organic resin is 4%, the addition amount of organic solvent is 9%, and the addition amount of nickel powder is 90%; the contents of other components and the preparation method are exactly the same as those of Embodiment 1.

[0148] Comparative Example 2

[0149] This comparative example provides a photovoltaic nickel paste, which is only different from that of Embodiment 1 in that the content of organic resin is reduced to 9% and the content of organic solvent is increased to 18%; the contents of other components and the preparation method are exactly the same as those of Embodiment 1.

[0150] Comparative Example 3

[0151] This comparative example provides a photovoltaic nickel paste, which is only different from that of Embodiment 1 in that the content of organic resin is reduced to 24% and the content of organic solvent is increased to 3%; the contents of other components and the preparation method are exactly the same as those of Embodiment 1.

[0152] Application Example 1

[0153] This application example uses the photovoltaic nickel paste provided in Embodiment 1 to prepare two types of photovoltaic cells (PERC cells and Topcon cells) respectively;

[0154] I. PERC cell wafers

[0155] S1. Sample preparation: Take the blue film before printing. The blue film is a semi-finished product of the battery produced by the normal PERC process;

[0156] S2. Laser grooving: Remove the back insulating silicon nitride and alumina layers according to the aluminum grid line design to ensure that the aluminum paste printed subsequently forms an ohmic contact with the silicon substrate;

[0157] S3. Back printing: Print back silver and back aluminum on the back respectively, and dry them at a temperature of 250°C; among them, the thickness of the back silver is 7μm, and the thickness of the back aluminum is 20μm;

[0158] S4. Nickel paste printing: By means of printing, place the nickel paste provided in Example 1 with a thickness of 2.5μm on the front of the blue film sheet according to the designed pattern, and then sinter it at a high temperature of 500°C to form conductive nickel grid lines;

[0159] S5. Electroplating: Using the electroplating process, electroplate copper with a height of 10μm on the front nickel grid lines to improve the conductivity of the grid lines, and then electroplate a 0.5μm thick tin protective layer on the outer layer of copper to prevent the copper grid lines from oxidizing, and the PERC cell is completed (as Figure 1 shown).

[0160] II. Topcon cell

[0161] S1. Sample preparation: Take the blue film sheet before printing, and the blue film sheet is a battery semi-finished product produced by the normal TOPCon process;

[0162] S2. Back printing: By means of printing, place the nickel paste provided in Example 1 with a thickness of 2.5μm on the back of the blue film sheet according to the designed pattern, and dry it at a temperature of 250°C;

[0163] S3. Front printing: Turn over the blue film sheet that has completed the back printing, and also complete the patterning of the nickel paste on the front of the blue film sheet, and then carry out / sinter it at a high temperature of 500°C to form conductive nickel grid lines.

[0164] S4. Electroplating: Using the electroplating process, electroplate copper with a height of 10μm on the front and back nickel grid lines to improve the conductivity of the grid lines, and then electroplate a 0.5μm thick tin protective layer on the outer layer of copper to prevent the copper grid lines from oxidizing. After electroplating the grid lines on both sides of the cell, the Topcon cell is completed.

[0165] Application Example 2

[0166] In this application example, two kinds of photovoltaic cells are prepared respectively using the photovoltaic nickel paste provided in Example 2, and the preparation process flow is completely the same as that of Application Example 1, only replacing the nickel paste provided in Example 1 with the nickel paste provided in Example 2.

[0167] Application Example 3

[0168] In this application example, two kinds of photovoltaic cells are prepared respectively using the photovoltaic nickel paste provided in Example 3, and the preparation process flow is completely the same as that of Application Example 1, only replacing the nickel paste provided in Example 1 with the nickel paste provided in Example 3.

[0169] Application Example 4

[0170] In this application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Example 4. The preparation process flow was exactly the same as that in Application Example 1, except that the nickel paste provided in Example 1 was replaced with the nickel paste provided in Example 4.

[0171] Application Example 5

[0172] In this application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Example 5. The preparation process flow was exactly the same as that in Application Example 1, except that the nickel paste provided in Example 1 was replaced with the nickel paste provided in Example 5.

[0173] Comparative Application Example 1

[0174] In this comparative application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Comparative Example 1. The preparation process flow was exactly the same as that in Application Example 1, except that the nickel paste provided in Example 1 was replaced with the nickel paste provided in Comparative Example 1.

[0175] Comparative Application Example 2

[0176] In this comparative application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Comparative Example 2. The preparation process flow was exactly the same as that in Application Example 1, except that the nickel paste provided in Example 1 was replaced with the nickel paste provided in Comparative Example 2.

[0177] Comparative Application Example 3

[0178] In this comparative application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Comparative Example 3. The preparation process flow was exactly the same as that in Application Example 1, except that the nickel paste provided in Example 1 was replaced with the nickel paste provided in Comparative Example 3.

[0179] Comparative Application Example 4

[0180] In this comparative application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Example 1. The difference in the preparation process flow from Application Example 1 was only that the step of S4 copper plating was not carried out.

[0181] Comparative Application Example 5

[0182] In this comparative application example, two photovoltaic cells were prepared using the photovoltaic nickel paste provided in Example 1. The difference in the preparation process flow from Application Example 1 was only that the step of S4 tin plating protective layer was not carried out.

[0183] Test Example

[0184] Test samples: Photovoltaic cells prepared in Application Examples 1 - 5, and photovoltaic cells prepared in Comparative Application Examples 1 - 5;

[0185] Test method:

[0186] (1) Corrosion depth of the silicon nitride layer: The cell with printed and sintered nickel grid lines is cut into small pieces, and the cross-section with nickel grid lines is observed through an electron microscope to confirm the corrosion depth of the nickel paste;

[0187] (2) Aspect ratio of the nickel grid line: Through an electron microscope, measure the grid line width and grid line height of the electrode's linear shape to confirm the aspect ratio data;

[0188] (3) Photoelectric conversion efficiency: Through I-V testing.

[0189] The test results of PERC cells are shown in Table 1 below:

[0190] Table 1

[0191]

[0192]

[0193] The test results of Topcon cells are shown in Table 2 below:

[0194] Table 2

[0195]

[0196] As shown in Table 1 and Table 2 above, the nickel paste of the present invention can be directly printed on the screen, and through high-temperature sintering at 300-700 °C, the organic carrier is sintered and volatilized. During the sintering process, the glass powder melts and corrodes the silicon nitride at high temperature, and the nickel powder forms an alloy with the underlying silicon to generate an ohmic contact. It can be completed with the current production line's printing and sintering furnace, without the need to add other equipment and processes.

[0197] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic nickel paste, characterized in that, The photovoltaic nickel paste comprises the following components by mass percentage: 1-5% of glass powder, 10-40% of organic carrier, and 60-80% of nickel powder; The organic carrier comprises an organic resin and an organic solvent with a mass ratio of (3-7):(2-5); The organic resin is a combination of butyral resin, nitrocellulose, and polyvinyl alcohol with a mass ratio of (5-6):(2-3):(1-2); The organic solvent is selected from any one or a combination of at least two of methyl silicate, terpineol, castor oil, diethylene glycol monobutyl ether, ethylene glycol methyl butyl ether, isopropanol, or ethylene glycol monoethyl ether; The preparation raw materials of the glass powder are composed of the following components by mass percentage: 20-50% of SiO2, 5-30% of Bi2O3, 1-10% of ZnO, 5-30% of PbO, 1-10% of Al2O3, and 3-30% of TeO2; The photovoltaic nickel paste further comprises 0.1-5% of additives; The additives are selected from a combination of surfactants, leveling agents, thixotropic agents, and penetrants; The surfactant is selected from any one of sodium dodecyl sulfate, sodium hexadecyl benzene sulfonate, or cetyl trimethyl ammonium bromide; The leveling agent is selected from any one of ethylene glycol butyl ether, hydrogenated castor oil, or alkylphenol polyoxyethylene ether; The thixotropic agent is selected from any one of fumed silica, organic bentonite, or polyamide wax; The penetrant is selected from any one of polyethylene glycol, polyoxyethylene phenolic ether, or polyoxyethylene secondary alkyl alcohol ether.

2. The photovoltaic nickel paste according to claim 1, wherein the molecular weight of the organic resin is 100-500 g / mol, and the viscosity of the organic resin is 1-20 mPa·s.

3. The photovoltaic nickel paste according to claim 1, wherein The purity of the nickel powder is above 99.7%.

4. The photovoltaic nickel paste according to claim 1, characterized in that, The particle size of the nickel powder is 0.1-2 μm.

5. A method for preparing a photovoltaic nickel paste according to any one of claims 1 to 4, characterized in that, The preparation method comprises the following steps: Grind and mix the preparation raw materials of the glass powder to obtain a mixture; Anneal the mixture to obtain molten glass; Mix the molten glass and water, carry out a hydrothermal reaction, and then filter, dry, and grind in sequence to obtain the glass powder; Carry out a first mixing of the organic resin and the organic solvent, then add the glass powder and the nickel powder, carry out a second mixing, and add the additives to carry out a third mixing to obtain a crude paste; Grind and filter the crude paste in sequence to obtain the photovoltaic nickel paste.

6. The preparation method of the photovoltaic nickel paste according to claim 5, wherein, The specific grinding of the preparation raw materials of the glass powder is: ball milling with a ball mill for 5-8 h.

7. The preparation method of the photovoltaic nickel paste according to claim 5, wherein, The temperature of the annealing is 450-550 °C, and the time of the annealing is 1-2 h.

8. The preparation method of the photovoltaic nickel paste according to claim 5, wherein, The mass ratio of the mixture and water is 1:(0.3-0.7).

9. The preparation method of the photovoltaic nickel paste according to claim 5, characterized in that, The temperature of the hydrothermal reaction is 180-240 °C, and the time of the hydrothermal reaction is 2-3 h.

10. The preparation method of the photovoltaic nickel paste according to claim 5, characterized in that, The temperature of the first mixing is 20-30 °C, the rotation speed of the first mixing is 100-200 rpm, and the time of the first mixing is 40-60 min.

11. The preparation method of the photovoltaic nickel paste according to claim 5, characterized in that, During the process of adding the glass powder and the nickel powder, the rotation speed is 200-500 rpm.

12. The preparation method of the photovoltaic nickel paste according to claim 5, characterized in that, The temperature of the second mixing is 20~30°C, the rotation speed of the second mixing is 50~100 rpm, and the time of the second mixing is 90~150 min.

13. The preparation method of the photovoltaic nickel paste according to claim 5, wherein, The temperature of the third mixing is 20~30°C, the rotation speed of the third mixing is 50~150 rpm, and the time of the third mixing is 30~60 min.

14. The preparation method of the photovoltaic nickel paste according to claim 5, wherein, The grinding of the coarse slurry is carried out by a three-roll mill.

15. The preparation method of the photovoltaic nickel paste according to claim 5, wherein The fineness of the ground slurry is 0.5~2 μm.

16. Use of the photovoltaic nickel paste according to any one of claims 1 to 4 in preparing nickel grid lines of a photovoltaic cell; wherein, The photovoltaic cell includes a PERC cell and / or a Topcon cell.

17. A preparation method of nickel grid lines in a PERC cell, characterized in that, The preparation method includes the following steps: Place the photovoltaic nickel paste according to any one of claims 1~4 on the front side of the blue film, and then sinter it to form a nickel grid line.

18. The method for preparing nickel grid lines in a PERC solar cell according to claim 17, characterized in that, The thickness of the photovoltaic nickel paste is 1~5 μm.

19. The method for preparing the nickel grid line in the PERC solar cell according to claim 17, characterized in that, The placement method of the photovoltaic nickel paste includes any one of printing, inkjet or laser transfer printing.

20. The method for preparing nickel grid lines in a PERC solar cell according to claim 17, characterized in that, The sintering temperature is 300~700°C.

21. The method for preparing nickel grid lines in a PERC solar cell according to claim 17, wherein The width of the nickel grid line is 5~15 μm, and the height is 1~5 μm.

22. A preparation method of nickel grid lines in a Topcon solar cell, characterized in that, The preparation method includes the following steps: Place the photovoltaic nickel paste according to any one of claims 1~4 on the back side of the blue film, dry it to form a back nickel grid line; then place the photovoltaic nickel paste according to any one of claims 1~4 on the front side of the blue film and sinter it to form a front nickel grid line.

23. The method for preparing nickel grid lines in Topcon solar cells according to claim 22, wherein, The thickness of the photovoltaic nickel paste is 1~5 μm.

24. The preparation method of the nickel grid line in the Topcon cell according to claim 22, characterized in that, The placement method of the photovoltaic nickel paste includes any one of printing, inkjet or laser transfer printing.

25. The preparation method of the nickel grid line in the Topcon cell according to claim 22, characterized in that, The drying temperature is 200~300°C.

26. The preparation method of nickel grid lines in Topcon solar cells according to claim 22, characterized in that, The sintering temperature is 300~700°C.

27. The preparation method of nickel grid lines in a Topcon solar cell according to claim 22, characterized in that, The width of the back nickel grid line is 5~15 nm, and the height is 1~5 μm.

28. The method for preparing nickel grid lines in a Topcon solar cell according to claim 22, wherein The width of the front nickel grid line is 5~15 nm, and the height is 1~5 μm.

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