Electrode slurry and preparation method thereof, photovoltaic cell

Abstract

The present invention discloses an electrode paste, a preparation method thereof and a photovoltaic cell, relating to the technical field of solar cells, and aiming to solve the problem of poor welding force between the main grid formed by the existing electrode paste and the welding strip of the component string welding. The electrode paste includes a silver conductive material and an auxiliary conductive material. The auxiliary conductive material contains nickel element. The median particle size of the auxiliary conductive material body is 5.0 μm - 10.0 μm, the specific surface area is 0.2 m² / g - 0.8 m² / g, and the melting point of the auxiliary conductive material is higher than that of the silver conductive material. The preparation method is used to prepare the electrode paste, and the photovoltaic cell uses the electrode paste. The electrode paste, the preparation method and the photovoltaic cell provided by the present invention are used to improve the welding force between the main grid line and the welding strip of the component string welding.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to an electrode slurry and a preparation method thereof, and a photovoltaic cell. Background Art

[0002] Solar photovoltaic utilization is one of the fastest-growing projects in recent years. Silicon is the most ideal solar cell material. For this reason, people have studied and developed crystalline silicon solar cells. By the end of 2020, the total installed capacity of wind and solar power in China exceeded 530 million kilowatts, and the 530 million kilowatts of wind and solar power generation capacity was completed in about 15 years. Although the current production capacity, technology, and industrial chain are more mature and complete, the difficulty of realization still exists. Improving the conversion efficiency of crystalline silicon solar cells is particularly important.

[0003] At present, crystalline silicon solar cells are mainly divided into conventional BSF, PERC, TOPCon and other cells, and the development of various cell technologies is becoming more and more mature. The electrode paste is used as the main grid of the front electrode, which adopts the step-by-step printing technology, that is, welding the electrode to print the main grid electrode paste. The function of the fine grid is mainly to collect the photoelectron flow generated by the light on the surface of the cell. It needs to have excellent ohmic contact with the silicon substrate of the cell. The main function of the main grid is to collect the current of the fine grid line and provide welding adhesion when the components are serially welded. Therefore, the main grid electrode paste needs to have excellent welding bonding strength and no ohmic contact with the welding strip of the component serial welding.

[0004] However, the existing electrode paste is mainly silver-aluminum paste. When the components are serially soldered, the silver-aluminum paste has very poor wettability with the soldering tape of the components, and even cannot be soldered, resulting in poor soldering strength of the components, which greatly reduces the reliability of long-term use. On the other hand, due to the high silver content in the existing silver-aluminum paste, the production cost is relatively high. Summary of the invention

[0005] The object of the present invention is to provide an electrode slurry and a preparation method thereof, and a photovoltaic cell, which improve the welding bonding strength between the electrode slurry and the welding strip of the component series welding when printing the main grid during the battery manufacturing process.

[0006] In a first aspect, the present invention provides an electrode slurry, comprising a silver conductive material and an auxiliary conductive material, wherein the auxiliary conductive material contains a nickel element, and the auxiliary conductive material has a median particle size of 5.0 μm-10.0 μm and a specific surface area of ​​0.2 m 2 / g-0.8m 2 / g, the melting point of the auxiliary conductive material is greater than the melting point of the silver conductive material.

[0007] Compared with the prior art, the electrode slurry provided by the present invention has the following advantages:

[0008] In the electrode slurry provided by the present invention, the median particle size of the auxiliary conductive material is controlled within the range of 5.0 μm-10.0 μm, and the specific surface area is controlled within the range of 0.2 m 2 / g-0.8m 2 / g range, so that when the main grid is formed on the battery cell, the auxiliary conductive material with a larger median particle size is easily blocked when the main grid line is narrow, and the problem of being unable to print normally is avoided. At the same time, since the electrode paste of the embodiment of the present invention also includes a silver conductive material, the auxiliary conductive material will be embedded between the silver conductive materials in the electrode after the electrode paste is printed and sintered, and will be evenly dispersed in the silver conductive material. During the welding process, since the auxiliary conductive material contains nickel elements, the melting point of the auxiliary conductive material is greater than the melting point of the silver conductive material. When the silver just starts to melt, the auxiliary conductive material has not yet begun to melt, thereby reducing the flow of molten tin in the welding strip and increasing the residual silver conductive material after welding, thereby improving the welding tension. Due to the presence of the silver conductive material, the tin on the welding strip is not easy to form a silver-tin alloy with the silver conductive material after melting, avoiding excessive resistance in the welding area, reducing the degree of over-welding, and thus improving the welding tension. At the same time, in the electrode paste of the embodiment of the present invention, a part of the silver conductive material is replaced by the auxiliary conductive material, thereby reducing the amount of silver used, thereby reducing the manufacturing cost.

[0009] It can be seen from the above that, in the process of forming a main grid on a battery cell, the electrode slurry provided by the present invention can avoid excessively high resistance in the welding area and improve the welding tension.

[0010] In a second aspect, the present invention further provides a method for preparing an electrode slurry, comprising:

[0011] At least a glass material, an auxiliary conductive material, an organic carrier and an organic additive are mixed to obtain a first blend;

[0012] A silver conductive material is added to the first blend to obtain an electrode slurry.

[0013] Compared with the prior art, the beneficial effects of the method for preparing the electrode slurry provided by the present invention are the same as the beneficial effects of the electrode slurry of the first aspect, which will not be described in detail here.

[0014] In a third aspect, the present invention further provides a photovoltaic cell, wherein the surface of the photovoltaic cell has grid lines, and the material of the grid lines is the electrode slurry provided by the present invention.

[0015] Compared with the prior art, the material of the grid lines in the photovoltaic cell provided by the present invention is the electrode slurry provided by the present invention, so the beneficial effects are the same as those of the electrode slurry in the first aspect, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 This is a flow chart for preparing the electrode slurry provided by the present invention. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0020] The embodiment of the present invention provides a photovoltaic cell, the surface of the photovoltaic cell has a grid line, the material of the grid line is the electrode slurry provided by the present invention, so as to provide a photovoltaic cell with high photoelectric conversion efficiency. It should be understood that the photovoltaic cell can be a BSF cell, a Topcon cell, a PERC cell, or other photovoltaic cells, which will not be described in detail here.

[0021] An electrode slurry provided by an embodiment of the present invention includes: a silver conductive material and an auxiliary conductive material, wherein the auxiliary conductive material contains nickel. The auxiliary conductive material has a median particle size of 5.0 μm-10.0 μm and a specific surface area of ​​0.2 m 2 / g-0.8m 2 / g, the melting point of the auxiliary conductive material is greater than that of the silver conductive material. It should be understood that the silver conductive material can be in the form of powder, and the auxiliary conductive material can be in the form of powder.

[0022] In the electrode slurry provided by the present invention, the median particle size of the auxiliary conductive material is controlled within the range of 5.0 μm-10.0 μm, and the specific surface area is controlled within the range of 0.2 m 2 / g-0.8m 2 / g range, so that when the main grid is formed on the battery cell, the auxiliary conductive material with a larger median particle size is easily blocked when the main grid line is narrow, and the problem of being unable to print normally is avoided. At the same time, since the electrode paste of the embodiment of the present invention also includes a silver conductive material, the auxiliary conductive material will be embedded between the silver conductive materials in the electrode after the electrode paste is printed and sintered, and will be evenly dispersed in the silver conductive material. During the welding process, since the auxiliary conductive material contains nickel elements, the melting point of the auxiliary conductive material is greater than the melting point of the silver conductive material. When the silver just starts to melt, the auxiliary conductive material has not yet begun to melt, thereby reducing the flow of molten tin in the welding strip and increasing the residual silver conductive material after welding, thereby improving the welding tension. Due to the presence of the silver conductive material, the tin on the welding strip is not easy to form a silver-tin alloy with the silver conductive material after melting, avoiding excessive resistance in the welding area, reducing the degree of over-welding, and thus improving the welding tension. At the same time, in the electrode paste of the embodiment of the present invention, a part of the silver conductive material is replaced by the auxiliary conductive material, thereby reducing the amount of silver used, thereby reducing the manufacturing cost.

[0023] Exemplarily, the auxiliary conductive material of the embodiment of the present invention includes at least one of a nickel material or a nickel alloy material. It should be understood that the nickel alloy material can be a binary nickel alloy material or a ternary nickel alloy material. When the nickel alloy material is a binary nickel alloy material, it can be a Ni-X alloy powder, wherein X can be one of Cu, Bi, Mg, Mo, Pb, Zn, Nd, Ce, Cr, Co, Ag, Ga, Ge, In, Sb, Sn, Ti, V, W, Zr, Ta, Nb, Y, Yb, Er, Sm metal elements. When the nickel alloy material is a ternary nickel alloy material, it can be a Ni-Cu-Y alloy powder, wherein Y can be one of Mn, Si, Ag, W, Sn, La, Co elements.

[0024] In one achievable manner, a surfactant is attached to the surface of the auxiliary conductive material of the embodiment of the present invention. Among them, the surfactant can be at least one of oleic acid, oleamide, erucamide, stearic acid, and stearate. By attaching a surfactant to the auxiliary conductive material of the embodiment of the present invention, the adsorption of the auxiliary conductive material can be improved, so that the auxiliary conductive material and the silver conductive material are evenly mixed, so that the auxiliary conductive material can be evenly embedded in the silver conductive material and well adsorbed in the silver conductive material, reducing the flow of molten tin in the soldering ribbon and increasing the residual silver conductive material after soldering, thereby improving the welding tension. Effect

[0025] In an optional manner, in the electrode slurry implemented by the present invention, the silver conductive material includes a first silver conductive material and a second silver conductive material having different median particle sizes, the median particle size of the first silver conductive material is 1.15 μm-1.30 μm, the median particle size of the second silver conductive material is 0.85 μm-0.98 μm, and the specific surface area of ​​the first silver conductive material is 0.6 m 2 / g-0.9m 2 / g, tap density is 5.0g / cm 3 -6.0g / cm 3 ; The specific surface area of ​​the second silver conductive material is 1.0m 2 / g-1.5m 2 / g, tap density is 4.0g / cm 3 -5.5g / cm 3 It should be understood that the first silver conductive material may be spherical silver powder, and the second silver conductive material may be irregular silver powder.

[0026] Illustratively, since the first silver conductive material and the second silver conductive material in the embodiment of the present invention have different median particle sizes, when sintering to form a main grid, the second silver conductive material with a relatively smaller median particle size will melt first, and the first silver conductive material with a relatively larger median particle size will melt later. This can reduce the pores generated during sintering and make the film layer of the electrode slurry after sintering denser, thereby reducing the series resistance of the battery, avoiding excessive resistance in the welding area, and improving the welding tension.

[0027] Exemplarily, the mass ratio of the spherical silver powder to the irregular silver powder in the embodiment of the present invention is (1-7): (3-9). Since the spherical silver powders are in point-to-point contact, the contact area is relatively small, while the irregular silver powders contain a large amount of surface-to-surface contact or surface-to-line contact, the contact area is relatively large, and the resistivity of the silver paste increases with the increase of the contact area. However, since the spherical silver powder has good printing adaptability, at this ratio, when the electrode paste is sintered to form the main grid, the resistivity of the main grid can be guaranteed to be large while ensuring printing adaptability.

[0028] In one example, the electrode slurry implemented in the present invention further includes a glass material in terms of molar percentage, and the median particle size of the glass material is not greater than 2 μm; in terms of molar percentage, the glass material includes 28 mol% to 58 mol% of SiO2, 15 mol% to 35 mol% of PbO, 6 mol% to 26 mol% of TiO2 and 1 mol% to 10 mol% of metal oxides.

[0029] For example, the metal oxide of the embodiment of the present invention includes at least one of alkali metal oxide and amphoteric oxide. For example, the metal oxide of the embodiment of the present invention includes at least one of ZnO, TeO2, Bi2O3, B2O3, MgO, CaO, BaO, Cr2O3, MoO3 and WO3.

[0030] Under the composition of the glass powder in the embodiment of the present invention and the content of each component, the PN junction matrix material will not be etched during etching. After sintering, it will only combine with the passivation layer matrix material (silicon nitride material) on the surface of the battery, providing excellent mechanical bonding force, but will not produce metallized ohmic contact with the PN junction matrix material constituting the silicon battery. This can effectively reduce metal recombination on the surface of the battery and improve the photoelectric conversion efficiency of the battery.

[0031] In an optional manner, the electrode slurry of the embodiment of the present invention also includes an organic carrier and an organic additive, and the mass ratio of the glass material, the auxiliary conductive material, the silver conductive material, the organic carrier and the organic additive is (1-5): (1-10): (60-80): (8-20): (0.5-5).

[0032] As for the organic carrier, it includes resin and organic solvent. Among them, the resin includes one or more of ethyl cellulose, cellulose acetate butyrate, rosin resin, acrylic resin, and polyvinyl butyral ester. The organic solvent includes one or more of pinene alcohol, butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, tripropylene glycol monomethyl ether, triethylene glycol butyl ether, alcohol fat twelve, and alcohol fat sixteen. The ratio of the resin content to the organic solvent content is: (5-25): (75-95).

[0033] As for the organic auxiliary agent, it includes one or more of a surface dispersant, a thixotropic agent and a leveling agent. Among them, the surface dispersant includes one or more of stearic acid, stearic acid derivatives, unsaturated fatty acids or alkylamines. The thixotropic agent includes one or more of modified hydrogenated castor oil and polyamide wax. The leveling agent includes one or more of isophorone and diacetone alcohol.

[0034] Figure 1 The preparation flow chart of the electrode slurry provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the present invention also provides a method for preparing the electrode slurry, comprising:

[0035] Step 101: at least the glass material, the auxiliary conductive material, the organic vehicle and the organic additive are mixed to obtain a first blend. For example, first, 1wt%-10wt% of auxiliary conductive powder, 1wt%-5wt% of glass powder, 8wt%-20wt% of organic vehicle, and 0.5wt%-5wt% of organic additive are mixed uniformly according to mass percentage to obtain a first blend.

[0036] Step 102: Add silver conductive material to the first blend to obtain electrode slurry. For example: 60wt%-80wt% of mixed silver powder,

[0037] The silver conductive material was added to the first blend and the mixed slurry was placed on a three-roll mill for 6 times to further disperse and homogenize. When the scraper fineness of the three-roll mill was less than 8 μm, the electrode slurry was filtered using a filter cloth to obtain a electrode slurry. At the same time, a rotational viscometer (52 rotor viscometer) was used to test the viscosity at a speed of 5 rpm at room temperature 25°C.

[0038] The electrode paste prepared according to the technical solution of the present invention includes a silver conductive material, so that the auxiliary conductive material will be embedded between the silver conductive materials in the electrode after the electrode paste is printed and sintered, and will be evenly dispersed in the silver conductive material. During the welding process, since the auxiliary conductive material contains nickel elements, the melting point of the auxiliary conductive material is greater than the melting point of the silver conductive material. When the silver begins to melt, the auxiliary conductive material has not yet begun to melt, thereby reducing the flow of molten tin in the welding strip and increasing the residual silver conductive material after welding, thereby improving the welding tension. Due to the presence of the silver conductive material, the tin on the welding strip is not easy to form a silver-tin alloy with the silver conductive material after melting, thereby avoiding excessive resistance in the welding area, reducing the degree of over-welding, and thus improving the welding tension. At the same time, the auxiliary conductive material replaces a part of the silver conductive material in the electrode paste of the embodiment of the present invention, thereby reducing the amount of silver used, thereby reducing the manufacturing cost.

[0039] Exemplarily, the preparation method of the above-mentioned organic carrier can be: weigh 75wt%-95wt% solvent and 5wt%-25wt% organic resin by mass percentage, heat them to 70-100°C while stirring, continue stirring for 30-60 minutes after the resin is completely dissolved, and then cool to room temperature to obtain the organic carrier.

[0040] In an optional manner, at least the glass material, the auxiliary conductive material, the organic carrier and the organic additive are mixed to obtain the first blend. The preparation method of the electrode slurry of the embodiment of the present invention also includes: pre-treating the auxiliary conductive material, that is, attaching the surfactant to the surface of the auxiliary conductive material, and then processing the auxiliary conductive material into a powder. For example, the pretreatment process of the auxiliary conductive material is: first, the auxiliary conductive material is placed in an ethanol solution of the surfactant, stirred for 10-60 minutes, and then the auxiliary conductive material is filtered and dried at 80-120°C for 0.5 hours to 2 hours, and finally crushed by a gas flow mill. The maximum particle size of the auxiliary conductive material after crushing is less than 10μm. By attaching a surfactant to the auxiliary conductive material of the embodiment of the present invention, the adsorption of the auxiliary conductive material can be improved, so that the auxiliary conductive material and the silver conductive material are evenly mixed.

[0041] In an optional manner, the preparation process of the glass powder of an embodiment of the present invention is: 28mol% to 58mol% of SiO2, 15mol% to 35mol% of PbO, 6mol% to 26mol% of TiO2 and 15mol% to 19mol% of metal oxide raw materials are evenly mixed, melted at 1200℃ to 1600℃, the melting time is 10min to 60min, and then cooled and rolled into sheets, the rolled glass material is crushed, and the crushed glass material is subjected to air flow crushing treatment to obtain glass powder, and the median particle size of the glass powder is less than or equal to 2μm.

[0042] For example, a rolling mill is used to roll the glass material, and a pulverizer is used to pulverize the rolled glass sheet, and then a vibrating screener is used to screen the pulverized glass powder, and then an air flow mill is used to polish, grind and grade the screened glass powder. The rolling mill can be a double-roll rolling mill or a single-roll rolling mill, the pulverizer can be any one of a mechanical pulverizer, an air flow pulverizer, a grinder and a low-temperature pulverizer, the vibrating screener can be a fixed screener or a movable screener, and the air flow mill can be one of a flat air flow mill, a circulating air flow mill, a jet air flow mill, a target air flow mill and a fluidized jet air flow mill.

[0043] In order to verify the effect of the electrode slurry provided by the embodiment of the present invention, the embodiment of the present invention is demonstrated by comparing the embodiment with the comparative example.

[0044] Embodiment 1

[0045] The electrode slurry provided in Example 1 of the present invention includes, by mass percentage, 48% of spherical silver powder, 30% of irregular silver powder, 4.5% of Ni powder, 1.6% of glass material, 12.8% of organic carrier, 1.8% of stearic acid, 0.8% of modified hydrogenated castor oil, 0.5% of isophorone and 0.5% of oleic acid.

[0046] The method for preparing the electrode slurry provided in the first embodiment of the present invention comprises the following steps:

[0047] The first step is to prepare mixed silver powder: according to the mass percentage, 48% of spherical silver powder and 30% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.21 μm, and the specific surface area is 0.78 m 2 / g, tap density is 5.2g / cm 3 ; The median particle size of irregular silver powder is 0.92μm, and the specific surface area is 1.28m 2 / g, tap density is 4.6g / cm 3 .

[0048] The second step is the pretreatment of the auxiliary conductive powder: first, the Ni powder is placed in an oleic acid solution and stirred continuously for 30 minutes, then the powder is filtered, dried at 100°C for 1.5 hours, and finally pulverized using a jet mill. The median particle size of the pulverized nickel powder is 5μm.

[0049] The third step is to process the glass material: according to the molar percentage, take 25 mol% of PbO, 38 mol% of SiO2, 18 mol% of TiO2, 7 mol% of ZnO, 6 mol% of TeO2, 2 mol% of B2O3, and 4 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0050] Step 4: prepare an organic carrier: weigh 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve by mass percentage, mix them evenly, and obtain a mixed solvent. Then weigh 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester, add them to the mixed solvent, and then heat to 80°C while stirring. After the resin is completely dissolved, continue stirring for 60 minutes, and then cool to room temperature to obtain an organic carrier.

[0051] The fifth step is to prepare electrode slurry: first, 4.5% of auxiliary conductive powder, 1.6% of glass material, 12.8% of organic carrier, 1.8% of stearic acid, 0.8% of modified hydrogenated castor oil, and 0.5% of isophorone are mixed uniformly according to mass percentage, and then the mixed silver powder is added and stirred thoroughly. The mixed silver slurry is placed on a three-roll mill for dispersion and grinding for 8 times. The obtained electrode slurry has a fineness of less than 8μm and a viscosity of 105Pa·S / 25°C at a rotation speed of 5rmp.

[0052] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0053] Embodiment 2

[0054] The electrode slurry provided in the second embodiment of the present invention includes, by mass percentage, 40% of spherical silver powder, 38% of irregular silver powder, 4.5% of Ni powder, 1.6% of glass material, 12.8% of organic carrier, 1.8% of polyamide wax, 0.8% of unsaturated fatty acid, 0.5% of diacetone alcohol and 0.5% of oleic acid.

[0055] The method for preparing the electrode slurry provided in the second embodiment of the present invention comprises the following steps:

[0056] The first step is to prepare mixed silver powder: according to the mass percentage, 48% of spherical silver powder and 30% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.3 μm, and the specific surface area is 0.72 m 2 / g, tap density is 5.6g / cm 3 ; The median particle size of irregular silver powder is 0.85μm, and the specific surface area is 1.34m 2 / g, tap density is 4.8g / cm 3 .

[0057] The second step is the pretreatment of the auxiliary conductive powder: first, the Ni powder is placed in an oleic acid solution and stirred continuously for 30 minutes, then the powder is filtered, dried at 100°C for 1.5 hours, and finally pulverized using a jet mill. The median particle size of the pulverized nickel powder is 7μm.

[0058] The third step is to process the glass material: according to the molar percentage, take 25 mol% of PbO, 38 mol% of SiO2, 18 mol% of TiO2, 7 mol% of ZnO, 6 mol% of TeO2, 2 mol% of B2O3, and 4 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0059] Step 4: prepare an organic carrier: weigh 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve by mass percentage, mix them evenly, and obtain a mixed solvent. Then weigh 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester, add them to the mixed solvent, and then heat to 80°C while stirring. After the resin is completely dissolved, continue stirring for 60 minutes, and then cool to room temperature to obtain an organic carrier.

[0060] The fifth step is to prepare electrode slurry: first, 4.5% of auxiliary conductive powder, 1.6% of glass material, 12.8% of organic carrier, 1.8% of polyamide wax, 0.8% of unsaturated fatty acid and 0.5% of diacetone alcohol are mixed evenly according to mass percentage, and then mixed silver powder is added and stirred thoroughly. The mixed silver paste is placed on a three-roll mill and dispersed and ground for 8 times. The obtained electrode slurry has a fineness of less than 8 μm and a viscosity of 105 Pa·S / 25°C at a speed of 5 rpm.

[0061] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0062] Embodiment 3

[0063] The electrode slurry provided in Example 3 of the present invention includes, by mass percentage, 38% of spherical silver powder, 38% of irregular silver powder, 6.0% of Ni powder and nickel alloy powder, 1.75% of glass material, 12.8% of organic carrier and 1.95% of hydrogenated castor oil, 0.9% of alkylamine, 0.6% of isophorone and 0.6% of oleic acid and oleamide.

[0064] The method for preparing the electrode slurry provided in the third embodiment of the present invention comprises the following steps:

[0065] The first step is to prepare mixed silver powder: according to the mass percentage, 38% of spherical silver powder and 38% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.15 μm, and the specific surface area is 0.85 m 2 / g, tap density is 5.3g / cm 3 ; The median particle size of irregular silver powder is 0.98μm, and the specific surface area is 1.20m 2 / g, tap density is 4.2g / cm 3 .

[0066] The second step is the pretreatment of auxiliary conductive powders: first, Ni powder, Ni-Cu alloy powder, and Ni-Ce alloy powder are placed in oleic acid and oleamide solution in a mass ratio of 6:3:1, and stirring is continued for 30 minutes. Then the powder is filtered and dried at 100°C for 1.5 hours. Finally, it is pulverized by a jet mill. The median particle size of the pulverized nickel powder is 7.5μm.

[0067] The third step is to process the glass material: according to the molar percentage, take 29 mol% of PbO, 36 mol% of SiO2, 16 mol% of TiO2, 6.5 mol% of ZnO, 5 mol% of TeO2, 4.5 mol% of B2O3, and 3 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0068] The fourth step is to prepare an organic carrier: 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve are weighed and mixed evenly to obtain a mixed solvent. Then 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester are weighed and added to the mixed solvent, and then heated to 80°C while stirring, and continued to stir for 60 minutes after the resin is completely dissolved, and then cooled to room temperature to obtain an organic carrier.

[0069] The fifth step is to prepare electrode slurry: first, 6% of auxiliary conductive powder, 1.75% of glass material, 12.8% of organic carrier, 1.95% of hydrogenated castor oil, 0.9% of alkylamine and 0.6% of isophorone are mixed uniformly according to mass percentage, and then mixed silver powder is added and stirred thoroughly. The mixed silver slurry is placed on a three-roll mill for dispersion grinding 8 times. The obtained electrode slurry has a fineness of less than 8μm and a viscosity of 98Pa·S / 25°C at a rotation speed of 5rmp.

[0070] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0071] Embodiment 4

[0072] The electrode slurry provided in Example 4 of the present invention includes, by mass percentage, 48% of spherical silver powder, 30% of irregular silver powder, 4.5% of Ni powder and nickel alloy powder, 1.6% of glass material, 12.8% of organic carrier and 1.8% of polyamide wax, 0.8% of stearic acid, 0.5% of diacetone alcohol and 0.5% of oleic acid.

[0073] The method for preparing the electrode slurry provided in the fourth embodiment of the present invention comprises the following steps:

[0074] The first step is to prepare mixed silver powder: according to the mass percentage, 48% of spherical silver powder and 30% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.21 μm, and the specific surface area is 0.78 m 2 / g, tap density is 5.2g / cm 3 ; The median particle size of irregular silver powder is 0.92μm, and the specific surface area is 1.28m 2 / g, tap density is 4.6g / cm 3 .

[0075] The second step is the pretreatment of auxiliary conductive powder: first, Ni powder, Ni-Ga alloy powder, and Ni-In alloy powder are placed in an oleic acid solution in a mass ratio of 6:3:1, and stirred continuously for 30 minutes. Then the powder is filtered and dried at 100°C for 1.5 hours. Finally, it is pulverized by a jet mill. The median particle size of the pulverized nickel powder is 10μm.

[0076] The third step is to process the glass material: according to the molar percentage, take 15 mol% of PbO, 28 mol% of SiO2, 6 mol% of TiO2, 7 mol% of ZnO, 6 mol% of TeO2, 2 mol% of B2O3, and 4 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0077] Step 4: prepare an organic carrier: weigh 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve by mass percentage, mix them evenly, and obtain a mixed solvent. Then weigh 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester, add them to the mixed solvent, and then heat to 80°C while stirring. After the resin is completely dissolved, continue stirring for 60 minutes, and then cool to room temperature to obtain an organic carrier.

[0078] The fifth step is to prepare electrode slurry: first, 4.5% of auxiliary conductive powder, 1.6% of glass material, 12.8% of organic carrier, 1.8% of polyamide wax, 0.8% of stearic acid, and 0.5% of diacetone alcohol are mixed uniformly according to mass percentage, and then the mixed silver powder is added and stirred thoroughly. The mixed silver paste is placed on a three-roll mill and dispersed and ground 8 times. The obtained electrode slurry has a fineness of less than 8μm and a viscosity of 105Pa·S / 25°C at a speed of 5rmp.

[0079] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0080] Embodiment 5

[0081] The electrode slurry provided in Example 5 of the present invention includes, by mass percentage, 24% of spherical silver powder, 46% of irregular silver powder, 7.8% of Ni powder and nickel alloy powder, 2.0% of glass material, 16.5% of organic carrier and 2.4% of hydrogenated castor oil, 0.8% of alkylamine, 0.5% of isophorone and 0.5% of oleic acid and oleamide.

[0082] The method for preparing the electrode slurry provided in the fifth embodiment of the present invention comprises the following steps:

[0083] The first step is to prepare mixed silver powder: according to the mass percentage, 24% of spherical silver powder and 46% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.21 μm, and the specific surface area is 0.78 m 2 / g, tap density is 5.2g / cm 3 ; The median particle size of irregular silver powder is 0.92μm, and the specific surface area is 1.28m 2 / g, tap density is 4.6g / cm 3 .

[0084] The second step is the pretreatment of auxiliary conductive powder: first, Ni powder and Ni-Cu alloy powder are placed in oleic acid and oleamide solution in a mass ratio of 8:2, and stirring is continued for 45 minutes. Then the powder is filtered and dried at 100°C for 2 hours. Finally, it is pulverized by a jet mill. The median particle size of the pulverized nickel powder is 4.8μm.

[0085] The third step is to process the glass material: according to the molar percentage, take 25 mol% of PbO, 38 mol% of SiO2, 18 mol% of TiO2, 7 mol% of ZnO, 6 mol% of TeO2, 2 mol% of B2O3, and 4 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0086] Step 4: prepare an organic carrier: weigh 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve by mass percentage, mix them evenly, and obtain a mixed solvent. Then weigh 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester, add them to the mixed solvent, and then heat to 80°C while stirring. After the resin is completely dissolved, continue stirring for 60 minutes, and then cool to room temperature to obtain an organic carrier.

[0087] The fifth step is to prepare electrode slurry: first, 7.8% of auxiliary conductive powder, 2.0% of glass material, 16.5% of organic carrier, 2.4% of hydrogenated castor oil, 0.8% of alkylamine and 0.5% of isophorone are mixed uniformly according to mass percentage, and then mixed silver powder is added and stirred thoroughly. The mixed silver slurry is placed on a three-roll mill for dispersion grinding 8 times. The obtained electrode slurry has a fineness of less than 8 μm and a viscosity of 118 Pa·S / 25°C at a rotation speed of 5 rpm.

[0088] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0089] Embodiment 6

[0090] The electrode slurry provided in Example 6 of the present invention includes, by mass percentage, 24% of spherical silver powder, 46% of irregular silver powder, 7.8% of Ni powder and Ni alloy powder, 2.0% of glass material, 16.5% of organic carrier and 2.4% of polyamide wax, 0.8% of stearic acid, 0.5% of diacetone alcohol and 0.5% of oleic acid and oleamide.

[0091] The method for preparing the electrode slurry provided in the sixth embodiment of the present invention comprises the following steps:

[0092] The first step is to prepare mixed silver powder: according to the mass percentage, 24% of spherical silver powder and 46% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.21 μm, and the specific surface area is 0.78 m 2 / g, tap density is 5.2g / cm 3 ; The median particle size of irregular silver powder is 0.92μm, and the specific surface area is 1.28m 2 / g, tap density is 4.6g / cm 3 .

[0093] The second step is the pretreatment of auxiliary conductive powder: first, Ni powder, Ni-Cu alloy powder, and Ni-Cu-Mn alloy powder are placed in oleic acid and oleamide solution in a mass ratio of 6:3:1, and stirring is continued for 45 minutes. Then the powder is filtered and dried at 100°C for 2 hours. Finally, it is pulverized by a jet mill. The median particle size of the pulverized nickel powder is 4.8μm.

[0094] The third step is to process the glass material: according to the molar percentage, take 35 mol% of PbO, 58 mol% of SiO2, 26 mol% of TiO2, 4 mol% of ZnO, 4 mol% of TeO2, 2 mol% of B2O3 and 3 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0095] The fourth step is to prepare an organic carrier: 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve are weighed and mixed evenly to obtain a mixed solvent. Then 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester are weighed and added to the mixed solvent, and then heated to 80°C while stirring, and continued to stir for 60 minutes after the resin is completely dissolved, and then cooled to room temperature to obtain an organic carrier.

[0096] The fifth step is to prepare electrode slurry: first, 7.8% of auxiliary conductive powder, 2.0% of glass material, 16.5% of organic carrier, 2.4% of polyamide wax, 0.8% of stearic acid, and 0.5% of diacetone alcohol are mixed uniformly according to mass percentage, and then the mixed silver powder is added and stirred thoroughly. The mixed silver paste is placed on a three-roll mill and dispersed and ground 8 times. The obtained electrode slurry has a fineness of less than 8μm and a viscosity of 118Pa·S / 25°C at a speed of 5rmp.

[0097] The performance test results of the main grid printed by the electrode paste provided in this embodiment are shown in Table 1 below.

[0098] Comparative Example 1

[0099] Comparative Example 1 of the present invention uses commercially available main grid electrode slurry as comparative electrode slurry, wherein the silver content is 84%, and the glass powder used is Pb-Si-Ti glass.

[0100] Comparative Example 2

[0101] The electrode slurry provided in Comparative Example 2 of the present invention comprises, by mass percentage, 40% of spherical silver powder, 40% of irregular silver powder, 2.0% of glass material, 16.5% of organic carrier, 2.4% of polyamide wax, 0.8% of stearic acid, 0.5% of diacetone alcohol, and 0.5% of oleic acid and oleamide. It does not contain the auxiliary conductive powder in the electrode slurry of the present invention.

[0102] The preparation method of the electrode slurry provided in Comparative Example 2 of the present invention comprises the following steps:

[0103] The first step is to prepare mixed silver powder: according to the mass percentage, 40% of spherical silver powder and 40% of irregular silver powder are mixed evenly to obtain mixed silver powder; the median particle size of the spherical silver powder is 1.21 μm, and the specific surface area is 0.78 m 2 / g, tap density is 5.2g / cm 3 ; The median particle size of irregular silver powder is 0.92μm, and the specific surface area is 1.28m 2 / g, tap density is 4.6g / cm 3 .

[0104] The second step is to process the glass material: according to the molar percentage, take 25 mol% of PbO, 38 mol% of SiO2, 18 mol% of TiO2, 7 mol% of ZnO, 6 mol% of TeO2, 2 mol% of B2O3, and 4 mol% of MoO3, mix the components evenly in a mixer, heat them into a high-temperature furnace to 1450°C, keep them warm and melt for 60 minutes, then cool and roll them into sheets, crush the rolled glass material, and use a jet mill to polish, grind and grade the glass powder to obtain the required glass material, whose average particle size is less than or equal to 2μm.

[0105] The third step is to prepare an organic carrier: 7.5% of butyl carbitol, 32% of butyl carbitol acetate, 12.5% ​​of diethylene glycol dibutyl ether, 20.5% of tripropylene glycol monomethyl ether, and 6% of alcohol lipid twelve are weighed and mixed evenly to obtain a mixed solvent. Then 7.2% of ethyl cellulose resin, 2.5% of cellulose acetate butyrate resin, 2.8% of rosin resin, 4.0% of acrylic resin, and 5% of polyvinyl butyral ester are weighed and added to the mixed solvent, and then heated to 80°C while stirring. After the resin is completely dissolved, continue stirring for 60 minutes, and then cool to room temperature to obtain an organic carrier.

[0106] The fourth step is to prepare the electrode slurry: first, 2.0% of the glass material, 16.5% of the organic carrier, 2.4% of the polyamide wax, 0.8% of the dispersant, and 0.5% of the leveling agent are mixed evenly according to the mass percentage, and then the mixed silver powder is added and stirred thoroughly. The mixed silver paste is placed on a three-roll mill and dispersed and ground for 8 times. The obtained electrode slurry has a fineness of less than 8μm.

[0107] The performance test results of the main grid printed by the electrode slurry provided in this embodiment are shown in Table 1 below. The present invention tests the performance of the electrode slurry prepared in the embodiment and the comparative example. First, by using PERC and Topcon silicon wafers with consistent square resistance, the prepared electrode slurry and the same main grid silver paste are respectively printed on the front and back fine grids and the front and back main grids of the battery by screen printing process, and the back side is printed with the same electrode slurry once, and the PERC and Topcon battery cells are obtained by drying-sintering-cooling to room temperature. Secondly, the IV electrical performance test of the TOPCon battery cell is carried out by IV tester, and the main grid electrode on the front of the battery is welded at 360°C using 0.35mm tin-coated solder strip, and the tensile test is carried out by tensile testing machine.

[0108] The test results of the embodiments of the present invention and the comparative examples are shown in the following table:

[0109]

[0110] As can be seen from the above table, in Examples 1, 2, 3, and 5, the physical properties of the mixed silver powder are adjusted, the amount of silver powder is reduced, and an appropriate amount of auxiliary conductive powder nickel powder or nickel alloy powder is added. The photoelectric conversion efficiency of the battery printed with the main grid silver paste is not lower than the commercially available electrode paste purchased in Comparative Example 1, and the welding tension is higher than that of Comparative Example 1. In Examples 1, 3, 4, 5, and 6, the types and mass ratios of the auxiliary conductive powders are adjusted, and the welding tension of the battery printed with the main grid silver paste is also higher than that of Comparative Example 1 and Comparative Example 2. At the same time, it can be seen that the median particle size of the auxiliary conductive powder in Examples 1 to 4 is between 5μm-10μm, while the median particle size of the auxiliary conductive powder in Examples 5 and 6 is 4.8μm. Therefore, in the electrode paste of the embodiment of the present invention, the median particle size of the auxiliary conductive powder is controlled between 5μm-10μm, and the welding tension of the battery made of the printed main grid is significantly greater than the welding tension of the battery with a median particle size less than 5μm in Examples 5 and 6.

[0111] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An electrode slurry, characterized in that: Applied to photovoltaic cells, comprising silver conductive material and auxiliary conductive material, wherein the auxiliary conductive material contains nickel element, the median particle size of the auxiliary conductive material is 5.0 μm-10.0 μm, and the specific surface area is 0.2 m 2 / g-0.8m 2 / g, the melting point of the auxiliary conductive material is greater than the melting point of the silver conductive material; The auxiliary conductive material includes a nickel alloy material, and the nickel alloy material includes a binary nickel alloy material and a ternary nickel alloy material; the binary nickel alloy material includes a Ni-X alloy material, wherein X includes at least one of Cu, Bi, Mg, Mo, Pb, Zn, Nd, Ce, Cr, Co, Ag, Ga, Ge, In, Sb, Sn, Ti, V, W, Zr, Ta, Nb, Y, Yb, Er, and Sm; the ternary nickel alloy material includes a Ni-Cu-Y alloy material, wherein Y includes at least one of Mn, Si, Ag, W, Sn, La, and Co; The electrode slurry further comprises a glass material, wherein the median particle size of the glass material is not greater than 2 μm; in terms of molar percentage, the glass material comprises 28 mol% to 58 mol% of SiO2, 15 mol% to 35 mol% of PbO, 6 mol% to 26 mol% of TiO2 and 15 mol% to 19 mol% of a metal oxide, wherein the metal oxide comprises at least one of an alkali metal oxide and an amphoteric oxide; A surfactant is attached to the surface of the auxiliary conductive material.

2. The electrode slurry according to claim 1, characterized in that: The silver conductive material comprises a first silver conductive material and a second silver conductive material having different median particle sizes. The median particle size of the first silver conductive material is 1.15 μm-1.30 μm, and the median particle size of the second silver conductive material is 0.85 μm-0.98 μm.

3. The electrode slurry according to claim 2, characterized in that: The specific surface area of ​​the first silver conductive material is 0.6 m 2 / g-0.9m 2 / g, tap density is 5.0g / cm 3 -6.0g / cm 3 The specific surface area of ​​the second silver conductive material is 1.0m 2 / g-1.5m 2 / g, tap density is 4.0g / cm 3 -5.5g / cm 3 ; The first silver conductive material is spherical silver powder, and the second silver conductive material is irregular silver powder. The mass ratio of the spherical silver powder to the irregular silver powder is (1-7):(3-9).

4. The electrode slurry according to any one of claims 1 to 3, characterized in that: The electrode slurry also includes an organic carrier and an organic additive. The mass ratio of the glass material, the auxiliary conductive material, the silver conductive material, the organic carrier and the organic additive is (1-5): (1-10): (60-80): (8-20): (0.5-5).

5. A method for preparing an electrode slurry according to any one of claims 1 to 4, characterized in that: include: At least a glass material, an auxiliary conductive material, an organic carrier and an organic additive are mixed to obtain a first blend; The silver conductive material is added to the first blend to obtain an electrode slurry.

6. The method for preparing the electrode slurry according to claim 5, characterized in that: Before at least mixing the glass material, the auxiliary conductive material, the organic carrier and the organic additive to obtain the first blend, the method for preparing the electrode slurry further comprises: A surfactant is attached to the surface of the auxiliary conductive material, and then the auxiliary conductive material is processed into a powder.

7. A photovoltaic cell, characterized in that: The photovoltaic cell has grid lines on its surface, and the material of the grid lines is the electrode slurry according to any one of claims 1 to 4.

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