Conductive paste for photovoltaic cells and preparation method thereof

Abstract

The invention discloses a conductive paste for photovoltaic cells and a preparation method thereof. The following raw materials are weighed in percentage: 40-80wt% of silver powder, 5-25wt% of a metal additive, 5-15wt% of a conductive promoter, 3-5wt% of glass powder, and the remainder is a modified carrier. The raw materials are mixed and ground evenly to prepare a conductive paste for photovoltaic cells. The conductive promoter ultrasonically treats a composite carbon tube, deionized water and silver nitrate. Under the action of ammonia water, the silver nitrate is converted into elemental silver, and micropores on the composite carbon tube are blocked, so that the copper inside is not easily contacted with air and converted into copper oxide, thereby ensuring the conductivity of the conductive paste, reducing the gold semi-contact barrier, achieving better ohmic contact, reducing the migration of anions, reducing the loss of current, and thus improving the photoelectric conversion efficiency. The modified carrier reduces the addition of organic species, prevents the conductive paste from volatilizing rapidly during sintering, makes the formed conductive film dense and uniform, and further ensures the conductivity.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic cell preparation, and in particular to a conductive paste for photovoltaic cells and a preparation method thereof. Background Art

[0002] BC is the abbreviation of Back Contact, which means back contact photovoltaic cell; there are many types of BC cells, such as PBC, IBC, HBC, etc., collectively referred to as xBC cells. Compared with existing TOPCon cells, HJT cells, etc., the biggest feature of xBC is that there is no grid line on the front, and the back is no longer a simple N area or P area, but usually a staggered P and N areas are prepared on the back of the cell, so that the positive and negative electrodes are integrated on the back of the cell. Thanks to this structure, the front of the xBC cell will not be blocked by the electrode grid line, which not only improves the power generation efficiency but also improves the aesthetics of the front, but the double-sided efficiency of the xBC cell is low, so it is necessary to further improve the conversion efficiency of the single side of the xBC cell. Summary of the invention

[0003] The purpose of the present invention is to provide a conductive paste for photovoltaic cells and a preparation method thereof, which solves the problems of large series resistance and low conversion efficiency of back-contact photovoltaic cells at the current stage.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0006] Weigh the following raw materials in percentage: 40-80wt% of silver powder, 5-25wt% of metal additives, 5-15wt% of conductive promoter, 3-5wt% of glass powder, and the remainder is a modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0007] The metal additive is silver-coated nickel powder or nickel powder.

[0008] Furthermore, the conductive promoter is prepared by the following steps:

[0009] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves are mixed evenly, and reacted for 10-15 hours at a speed of 150-200 r / min and a temperature of 60-65° C. to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid are mixed evenly, and reacted for 1-1.5 hours at a speed of 120-150 r / min and a temperature of 90-95° C., and ammonia water is added to a pH value of 8 to obtain intermediate 2;

[0010] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 200-300 r / min and a temperature of 20-25° C. for 5-7 hours, and the temperature is raised to 50-60° C., and the reaction is continued for 5-7 hours, and the pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 120-125° C. for 20-25 hours to obtain a copper organic framework;

[0011] Step A3: placing the copper organic framework in a tubular furnace, heating to 700-750°C at a heating rate of 2°C / min in an argon atmosphere, keeping warm for 4-6 hours, and cooling to room temperature to obtain a composite carbon tube, dispersing the composite carbon tube in deionized water, adding silver nitrate, ultrasonically treating for 5-10 minutes at a frequency of 20-30kHz and a temperature of 25-30°C, adding ammonia water to a pH value of 8-10, and reacting for 2-3 hours to obtain a conductive promoter.

[0012] Furthermore, the dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0013] Furthermore, the molar ratio of the intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0014] Furthermore, the usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0015] Further, the modified carrier is prepared by the following steps:

[0016] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed uniformly, and reacted for 2-3 hours at a speed of 120-150 r / min and a temperature of 130-135° C. to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted for 4-6 hours at a speed of 150-200 r / min and a temperature of 50-60° C. to obtain modified cyclodextrin;

[0017] Step B2: Cellulose, chloropropane, boron trifluoride etherate and DMF are mixed evenly, reacted at a speed of 120-150 r / min and a temperature of 65-70° C. for 2-3 hours, and then sodium hydroxide solution is added, the temperature is raised to 75-80° C., and the reaction is carried out for 3-5 hours to obtain pretreated cellulose. Pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF are mixed, and reacted at a speed of 120-150 r / min and a temperature of 100-110° C. for 8-10 hours to obtain modified cellulose. The following raw materials are weighed in parts by weight: 20-30 parts of modified cellulose, 60-80 parts of epoxy soybean oil and 0.1-0.5 parts of organosilicon defoaming agent, and the raw materials are ball-milled evenly to obtain a modified carrier.

[0018] Furthermore, the mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0019] Furthermore, the dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass ratio of pretreated cellulose and modified cyclodextrin is 5:1, and the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose.

[0020] Beneficial effects of the present invention: A conductive paste for photovoltaic cells prepared by the present invention comprises the following raw materials: silver powder, metal additives, conductive promoter, glass powder and modified carrier, wherein the conductive promoter is reacted with p-nitrophenylboric acid and 3,4-dihydroxybenzoic acid as raw materials, so that the boric acid group on the p-nitrophenylboric acid reacts with the catechol on the 3,4-dihydroxybenzoic acid to obtain intermediate 1, the intermediate 1 is reduced with tin powder, so that the nitro group on the intermediate 1 is converted into an amino group to obtain intermediate 2, and the intermediate 2 is reacted with ethyl dichlorophosphate The method comprises the steps of: reacting the amino group on the intermediate 2 with the chlorine atom site on the ethyl dichlorophosphate to obtain an organic ligand; reacting the organic ligand, 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate to form a copper organic framework; calcining the copper organic framework under an argon atmosphere to carbonize the organic part of the copper organic framework to form a carbon-coated copper composite carbon tube doped with boron and phosphorus; ultrasonically treating the composite carbon tube, deionized water and silver nitrate, and then converting the silver nitrate into elemental silver under the action of ammonia water, thereby blocking the micropores on the composite carbon tube to obtain a conductive promoter.

[0021] The modified carrier is made of beta-cyclodextrin and monochloroacetic acid as raw materials. Under the action of p-toluenesulfonic acid, the hydroxyl group on the beta-cyclodextrin and the carboxyl group on the monochloroacetic acid are esterified to obtain pretreated cyclodextrin. The pretreated cyclodextrin is reacted with dodecyl dimethyl tertiary amine so that the chlorine atom site on the pretreated cyclodextrin reacts with the tertiary amine on the dodecyl dimethyl tertiary amine to form a quaternary ammonium salt structure to obtain modified cyclodextrin. Cellulose is reacted with epichlorohydrin so that the epoxy group on the epichlorohydrin reacts with the carboxyl group on the cellulose, and then the ring is closed under alkaline conditions to form a new epoxy group to obtain pretreated cellulose. The modified cyclodextrin is reacted with the pretreated cellulose so that the hydroxyl group on the modified cyclodextrin reacts with the epoxy group on the pretreated cellulose to obtain modified cellulose. The modified cellulose, epoxy soybean oil and an organosilicon defoamer are mixed and ball-milled to obtain a modified carrier.

[0022] The conductive promoter ultrasonically treats the composite carbon tube, deionized water and silver nitrate, and then under the action of ammonia water, the silver nitrate is converted into elemental silver, which blocks the micropores on the composite carbon tube, making it difficult for the internal copper to be exposed to air and converted into copper oxide, thereby ensuring the conductivity of the conductive slurry, reducing the gold-semiconductor contact barrier, achieving better ohmic contact, reducing the migration of anions, reducing the loss of current, and thus improving the photoelectric conversion efficiency. The modified carrier reduces the addition of organic species, preventing the conductive slurry from volatilizing rapidly during sintering, making the formed conductive film dense and uniform, with small film pores and low porosity, further ensuring the conductivity. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0025] Weigh the following raw materials in percentage: 40wt% silver powder, 25wt% metal additive, 15wt% conductive promoter, 5wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0026] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is silver-coated nickel powder, and the particle size of the conductive promoter is 5μm.

[0027] The conductive promoter is prepared by the following steps:

[0028] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and reacted at a speed of 150 r / min and a temperature of 60° C. for 10 h to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and reacted at a speed of 120 r / min and a temperature of 90° C. for 1 h, and ammonia water was added to a pH value of 8 to obtain intermediate 2;

[0029] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 200 r / min and a temperature of 20° C. for 5 hours, and the temperature is raised to 50° C. and the reaction is continued for 5 hours, and the pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 120° C. for 20 hours to obtain a copper organic framework;

[0030] Step A2: Place the copper organic framework in a tubular furnace, heat to 700°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 4 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 5 minutes at a frequency of 20 kHz and a temperature of 25°C. Then, add ammonia water to a pH of 8, react for 2 hours, and obtain a conductive promoter.

[0031] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0032] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0033] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0034] The modified carrier is prepared by the following steps:

[0035] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed evenly, and reacted for 2 hours at a speed of 120 r / min and a temperature of 130° C. to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted for 4 hours at a speed of 150 r / min and a temperature of 50° C. to obtain modified cyclodextrin;

[0036] Step B2: Mix cellulose, chloropropane, boron trifluoride etherate and DMF evenly, react for 2 hours at a speed of 120 r / min and a temperature of 65°C, add sodium hydroxide solution, raise the temperature to 75°C, and react for 3 hours to obtain pretreated cellulose. Mix pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF, react for 8 hours at a speed of 120 r / min and a temperature of 100°C to obtain modified cellulose. Weigh the following raw materials in parts by weight: 20 parts of modified cellulose, 60 parts of epoxidized soybean oil and 0.1 parts of silicone defoaming agent, and ball-mill the raw materials evenly to obtain a modified carrier.

[0037] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0038] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0039] Embodiment 2 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0040] Weigh the following raw materials in percentage: 40wt% silver powder, 25wt% metal additive, 15wt% conductive promoter, 5wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0041] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is nickel powder, and the particle size of the conductive promoter is 5μm.

[0042] The conductive promoter is prepared by the following steps:

[0043] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and reacted at a speed of 150 r / min and a temperature of 60° C. for 10 h to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and reacted at a speed of 120 r / min and a temperature of 90° C. for 1 h, and ammonia water was added to a pH value of 8 to obtain intermediate 2;

[0044] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 200 r / min and a temperature of 20° C. for 5 hours, and the temperature is raised to 50° C. and the reaction is continued for 5 hours, and the pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 120° C. for 20 hours to obtain a copper organic framework;

[0045] Step A2: Place the copper organic framework in a tubular furnace, heat to 700°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 4 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 5 minutes at a frequency of 20 kHz and a temperature of 25°C. Then, add ammonia water to a pH of 8, react for 2 hours, and obtain a conductive promoter.

[0046] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0047] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0048] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0049] The modified carrier is prepared by the following steps:

[0050] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed evenly, and reacted for 2 hours at a speed of 120 r / min and a temperature of 130° C. to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted for 4 hours at a speed of 150 r / min and a temperature of 50° C. to obtain modified cyclodextrin;

[0051] Step B2: Mix cellulose, chloropropane, boron trifluoride etherate and DMF evenly, react for 2 hours at a speed of 120 r / min and a temperature of 65°C, add sodium hydroxide solution, raise the temperature to 75°C, and react for 3 hours to obtain pretreated cellulose. Mix pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF, react for 8 hours at a speed of 120 r / min and a temperature of 100°C to obtain modified cellulose. Weigh the following raw materials in parts by weight: 20 parts of modified cellulose, 60 parts of epoxidized soybean oil and 0.1 parts of silicone defoaming agent, and ball-mill the raw materials evenly to obtain a modified carrier.

[0052] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0053] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0054] Embodiment 3 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0055] Weigh the following raw materials in percentage: 60wt% silver powder, 15wt% metal additive, 10wt% conductive promoter, 4wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0056] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is silver-coated nickel powder, and the particle size of the conductive promoter is 5μm.

[0057] The conductive promoter is prepared by the following steps:

[0058] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and the mixture was reacted at a speed of 150 r / min and a temperature of 65° C. for 10 h to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and the mixture was reacted at a speed of 150 r / min and a temperature of 93° C. for 1.3 h, and aqueous ammonia was added to a pH value of 8 to obtain intermediate 2;

[0059] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 300 r / min and a temperature of 20° C. for 6 hours, and the temperature is raised to 55° C. and the reaction is continued for 6 hours. The pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 120° C. for 25 hours to obtain a copper organic framework;

[0060] Step A2: Place the copper organic framework in a tubular furnace, heat to 730°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 5 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 10 minutes at a frequency of 25 kHz and a temperature of 28°C. Then, add ammonia water to a pH of 9, react for 2 hours, and obtain a conductive promoter.

[0061] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0062] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0063] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0064] The modified carrier is prepared by the following steps:

[0065] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed uniformly, and reacted at a speed of 120 r / min and a temperature of 135° C. for 2 h to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted at a speed of 150 r / min and a temperature of 55° C. for 5 h to obtain modified cyclodextrin;

[0066] Step B2: Mix cellulose, chloropropane, boron trifluoride etherate and DMF evenly, react for 3 hours at a speed of 120 r / min and a temperature of 68°C, add sodium hydroxide solution, raise the temperature to 78°C, and react for 4 hours to obtain pretreated cellulose. Mix pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF, react for 9 hours at a speed of 120 r / min and a temperature of 105°C to obtain modified cellulose. Weigh the following raw materials in parts by weight: 25 parts of modified cellulose, 70 parts of epoxidized soybean oil and 0.3 parts of silicone defoaming agent, and ball-mill the raw materials evenly to obtain a modified carrier.

[0067] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0068] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0069] Embodiment 4 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0070] Weigh the following raw materials in percentage: 60wt% silver powder, 15wt% metal additive, 10wt% conductive promoter, 4wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0071] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is nickel powder, and the particle size of the conductive promoter is 5μm.

[0072] The conductive promoter is prepared by the following steps:

[0073] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and the mixture was reacted at a speed of 150 r / min and a temperature of 65° C. for 10 h to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and the mixture was reacted at a speed of 150 r / min and a temperature of 93° C. for 1.3 h, and aqueous ammonia was added to a pH value of 8 to obtain intermediate 2;

[0074] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 300 r / min and a temperature of 20° C. for 6 hours, and the temperature is raised to 55° C. and the reaction is continued for 6 hours. The pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 120° C. for 25 hours to obtain a copper organic framework;

[0075] Step A2: Place the copper organic framework in a tubular furnace, heat to 730°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 5 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 10 minutes at a frequency of 25 kHz and a temperature of 28°C. Then, add ammonia water to a pH of 9, react for 2 hours, and obtain a conductive promoter.

[0076] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0077] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0078] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0079] The modified carrier is prepared by the following steps:

[0080] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed uniformly, and reacted at a speed of 120 r / min and a temperature of 135° C. for 2 h to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted at a speed of 150 r / min and a temperature of 55° C. for 5 h to obtain modified cyclodextrin;

[0081] Step B2: Mix cellulose, chloropropane, boron trifluoride etherate and DMF evenly, react for 3 hours at a speed of 120 r / min and a temperature of 68°C, add sodium hydroxide solution, raise the temperature to 78°C, and react for 4 hours to obtain pretreated cellulose. Mix pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF, react for 9 hours at a speed of 120 r / min and a temperature of 105°C to obtain modified cellulose. Weigh the following raw materials in parts by weight: 25 parts of modified cellulose, 70 parts of epoxidized soybean oil and 0.3 parts of silicone defoaming agent, and ball-mill the raw materials evenly to obtain a modified carrier.

[0082] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0083] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0084] Embodiment 5 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0085] Weigh the following raw materials in percentage: 80wt% silver powder, 5wt% metal additive, 5wt% conductive promoter, 3wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0086] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is silver-coated nickel powder, and the particle size of the conductive promoter is 5μm.

[0087] The conductive promoter is prepared by the following steps:

[0088] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and reacted at a speed of 200 r / min and a temperature of 65° C. for 15 hours to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and reacted at a speed of 150 r / min and a temperature of 95° C. for 1.5 hours, and ammonia water was added to a pH value of 8 to obtain intermediate 2;

[0089] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 300 r / min and a temperature of 25° C. for 7 hours, and the temperature is raised to 60° C. and the reaction is continued for 7 hours. The pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 125° C. for 25 hours to obtain a copper organic framework;

[0090] Step A2: Place the copper organic framework in a tubular furnace, heat to 750°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 6 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 10 minutes at a frequency of 30 kHz and a temperature of 30°C. Then, add ammonia water to a pH of 10, react for 3 hours, and obtain a conductive promoter.

[0091] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0092] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0093] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0094] The modified carrier is prepared by the following steps:

[0095] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed evenly, and reacted at a speed of 150 r / min and a temperature of 135° C. for 3 hours to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted at a speed of 200 r / min and a temperature of 60° C. for 6 hours to obtain modified cyclodextrin;

[0096] Step B2: Cellulose, chloropropane, boron trifluoride etherate and DMF are mixed evenly, reacted at a speed of 150 r / min and a temperature of 70°C for 3 hours, and then sodium hydroxide solution is added, the temperature is raised to 80°C, and the reaction is carried out for 5 hours to obtain pretreated cellulose. The pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF are mixed, and reacted at a speed of 150 r / min and a temperature of 110°C for 10 hours to obtain modified cellulose. The following raw materials are weighed in parts by weight: 30 parts of modified cellulose, 80 parts of epoxidized soybean oil and 0.5 parts of silicone defoaming agent, and the raw materials are ball-milled evenly to obtain a modified carrier.

[0097] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0098] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0099] Embodiment 6 A method for preparing a conductive paste for photovoltaic cells comprises the following steps:

[0100] Weigh the following raw materials in percentage: 80wt% silver powder, 5wt% metal additive, 5wt% conductive promoter, 3wt% glass powder, and the remainder as modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells.

[0101] The glass powder contains 18wt% silicon dioxide, 5wt% aluminum oxide, 26wt% boron oxide, 49wt% lead oxide, 1wt% calcium oxide and 1wt% magnesium oxide. The particle size of the silver powder is 1μm, the particle size of the metal additive is 1μm, the metal additive is nickel powder, and the particle size of the conductive promoter is 5μm.

[0102] The conductive promoter is prepared by the following steps:

[0103] Step A1: p-Nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves were mixed evenly, and reacted at a speed of 200 r / min and a temperature of 65° C. for 15 hours to obtain intermediate 1; intermediate 1, tin powder and concentrated hydrochloric acid were mixed evenly, and reacted at a speed of 150 r / min and a temperature of 95° C. for 1.5 hours, and ammonia water was added to a pH value of 8 to obtain intermediate 2;

[0104] Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed evenly, and the reaction is carried out at a speed of 300 r / min and a temperature of 25° C. for 7 hours, and the temperature is raised to 60° C. and the reaction is continued for 7 hours. The pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed evenly, and the reaction is carried out at a temperature of 125° C. for 25 hours to obtain a copper organic framework;

[0105] Step A2: Place the copper organic framework in a tubular furnace, heat to 750°C at a heating rate of 2°C / min in an argon atmosphere, keep warm for 6 hours, and then cool to room temperature to obtain a composite carbon tube. Disperse the composite carbon tube in deionized water, add silver nitrate, and ultrasonically treat for 10 minutes at a frequency of 30 kHz and a temperature of 30°C. Then, add ammonia water to a pH of 10, react for 3 hours, and obtain a conductive promoter.

[0106] The dosage ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, the dosage ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0107] The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

[0108] The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

[0109] The modified carrier is prepared by the following steps:

[0110] Step B1: β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide are mixed evenly, and reacted at a speed of 150 r / min and a temperature of 135° C. for 3 hours to obtain pretreated cyclodextrin; pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide are mixed, and reacted at a speed of 200 r / min and a temperature of 60° C. for 6 hours to obtain modified cyclodextrin;

[0111] Step B2: Cellulose, chloropropane, boron trifluoride etherate and DMF are mixed evenly, reacted at a speed of 150 r / min and a temperature of 70°C for 3 hours, and then sodium hydroxide solution is added, the temperature is raised to 80°C, and the reaction is carried out for 5 hours to obtain pretreated cellulose. The pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF are mixed, and reacted at a speed of 150 r / min and a temperature of 110°C for 10 hours to obtain modified cellulose. The following raw materials are weighed in parts by weight: 30 parts of modified cellulose, 80 parts of epoxidized soybean oil and 0.5 parts of silicone defoaming agent, and the raw materials are ball-milled evenly to obtain a modified carrier.

[0112] The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, the amount of p-toluenesulfonic acid is 1% of the mass of monochloroacetic acid, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.5.

[0113] The dosage ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, the mass fraction of sodium hydroxide solution is 25%, the mass of pretreated cellulose and modified cyclodextrin is 5:1, the dosage of triphenylphosphine is 1‰ of the mass of pretreated cellulose, and the model of the silicone defoamer is KS-66.

[0114] Comparative Example 1: Compared with Example 1, this comparative example uses silver-coated copper instead of the conductive promoter, and the other steps are the same.

[0115] Comparative Example 2: Compared with Example 1, no organic ligand was added in this comparative example, and the remaining steps were the same.

[0116] Comparative Example 3: Compared with Example 1, this comparative example uses β-cyclodextrin instead of modified cyclodextrin, and the other steps are the same.

[0117] Comparative Example 4: Compared with Example 1, this comparative example uses cellulose instead of modified cellulose, and the other steps are the same.

[0118] Boron diffusion is performed on the back side of an N-type silicon wafer with a thickness of 150 μm, and a mask SiNx layer is deposited on the back surface of the boron diffusion. The mask of the N+ type area on the back side is removed by laser etching, and phosphorus is implanted on the front surface of the N-type silicon wafer by an ion implantation method. Phosphorus is ion implanted in the laser opening area on the back surface by an ion implantation method. Annealing is performed for 1 h at a temperature of 1000° C., and an oxide layer with a thickness of 10 nm is formed on the front and back sides of the N-type silicon wafer. A passivation SiNx layer is deposited on both sides of the N-type silicon wafer, and the conductive pastes prepared in Examples 1-3 and Comparative Examples 1-4 are respectively printed on the P+ layer on the back side of the N-type silicon wafer. Finally, a battery sample is sintered, and its series resistance, contact resistivity and conversion efficiency are tested by a German Berger tester PSS10-HE. The test results are shown in Table 1 below.

[0119] Table 1

[0120]

[0121] From Table 1 above, it can be seen that the series resistance of the photovoltaic cell prepared by the conductive paste prepared in this application is 0.8-1.2 mΩ, and the contact resistivity is 1.03-1.31 mΩ·cm 2 , the conversion efficiency is 25.8-26.9%.

[0122] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a conductive paste for photovoltaic cells, characterized in that: The specific steps include: Weigh the following raw materials in percentage: 40-80wt% silver powder, 5-25wt% metal additive, 5-15wt% conductive promoter, 3-5wt% glass powder, and the remainder is a modified carrier, mix and grind the raw materials evenly to prepare a conductive slurry for photovoltaic cells; The conductive promoter is prepared by the following steps: Step A1: p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid, chloroform and 5A molecular sieves are mixed to react to obtain intermediate 1, intermediate 1, tin powder and concentrated hydrochloric acid are mixed to react, and ammonia water is added to a pH value of 8 to obtain intermediate 2; Step A2: The intermediate 2, ethyl dichlorophosphate, pyridine and DMF are mixed for reaction, and the pH value is adjusted to 5 to obtain an organic ligand, and the organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF are mixed for reaction to obtain a copper organic framework; Step A3: placing the copper organic framework in a tube furnace and heating it, then cooling it to room temperature to obtain a composite carbon tube, dispersing the composite carbon tube in deionized water, adding silver nitrate, ultrasonically treating it, and then adding ammonia water to a pH value of 8-10 to react and obtain a conductive promoter; The modified carrier is prepared by the following steps: Step B1: mixing β-cyclodextrin, monochloroacetic acid, p-toluenesulfonic acid and dimethyl sulfoxide to obtain pretreated cyclodextrin, and mixing the pretreated cyclodextrin, dodecyldimethyl tertiary amine and dimethyl sulfoxide to obtain modified cyclodextrin; Step B2: After cellulose, chloropropane, boron trifluoride etherate and DMF are mixed for reaction, sodium hydroxide solution is added, and the temperature is increased to react to obtain pretreated cellulose. The pretreated cellulose, modified cyclodextrin, triphenylphosphine and DMF are mixed for reaction to obtain modified cellulose. The following raw materials are weighed in parts by weight: 20-30 parts of modified cellulose, 60-80 parts of epoxy soybean oil and 0.1-0.5 parts of silicone defoaming agent, and the raw materials are ball-milled to obtain a modified carrier.

2. The method for preparing a conductive paste for photovoltaic cells according to claim 1, characterized in that: The amount ratio of p-nitrophenylboric acid, 3,4-dihydroxybenzoic acid and 5A molecular sieve described in step A1 is 15.2mmol:15mmol:2g, and the amount ratio of intermediate 1, tin powder and concentrated hydrochloric acid is 6mmol:2g:5mL.

3. The method for preparing a conductive paste for photovoltaic cells according to claim 1, characterized in that: The molar ratio of intermediate 2, ethyl dichlorophosphate and pyridine described in step A2 is 2:1:2.1, and the amount ratio of organic ligand, 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate, ethanol and DMF is 3g:1g:6g:20mL:10mL.

4. The method for preparing a conductive paste for photovoltaic cells according to claim 1, characterized in that: The usage ratio of the composite carbon tube, deionized water and silver nitrate in step A3 is 2g:20mL:1g.

5. The method for preparing a conductive paste for photovoltaic cells according to claim 1, characterized in that: The mass ratio of β-cyclodextrin and monochloroacetic acid in step B1 is 1:1, and the mass ratio of pretreated cyclodextrin and dodecyldimethyl tertiary amine is 1:1.

5.

6. The method for preparing a conductive paste for photovoltaic cells according to claim 1, characterized in that: The amount ratio of cellulose, oxychloropropane, boron trifluoride etherate and sodium hydroxide solution in step B2 is 2g:1g:0.9g:15mL, and the mass ratio of pretreated cellulose to modified cyclodextrin is 5:

1.

7. A conductive paste for photovoltaic cells, characterized in that: Prepared according to any one of claims 1 to 6.

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