Low-temperature photovoltaic slurry for full-opening screen printing, preparation method of low-temperature photovoltaic slurry and photovoltaic cell

Abstract

The invention belongs to the technical field of photovoltaic conductive paste, and provides low-temperature photovoltaic paste for full-opening screen printing, a preparation method of the low-temperature photovoltaic paste and a photovoltaic cell, and the paste comprises the following components by weight: 60-95 wt% of conductive powder, 1-20 wt% of first resin, 0.1-2.5 wt% of an auxiliary agent, 0-15 wt% of a first solvent, 0.1-2.5 wt% of a curing agent and 0.1-5 wt% of a nano carbon solution. The preparation method comprises the following steps: S1, mixing the conductive powder, the first resin, the auxiliary agent, the first solvent, the curing agent and the nanocarbon solution according to a formula proportion, and then centrifuging or stirring for fully mixing and dispersing; and S2, grinding and filtering the slurry obtained in the step S1 to obtain the low-temperature photovoltaic slurry for the full-opening screen plate. By adding the nano carbon solution, the thixotropy of the slurry can be improved by nano carbon with high specific surface area, the shaping capability of the slurry on a full-opening screen printing plate is improved, and a relatively high depth-width ratio is obtained; and the nano carbon with excellent lubricity can improve the ink passing property of the slurry, so that the photoelectric conversion efficiency of the prepared battery is better.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic conductive pastes, and in particular relates to a low-temperature photovoltaic paste for full-opening screen printing and a preparation method thereof. Background Art

[0002] With the rapid development of the photovoltaic industry, photovoltaic cell technology continues to innovate, with the main goals of improving photoelectric conversion efficiency and reducing production costs. Among them, the silver paste printing process occupies a key position in the manufacture of photovoltaic cells. The amount of silver paste used and the printing quality of the grid lines directly affect the performance and production cost of photovoltaic cells. However, as a high-cost conductive material, silver paste has a high unit consumption (the amount of silver paste consumed per unit cell), which has become an important factor limiting the further reduction of photovoltaic cell manufacturing costs.

[0003] In order to reduce the unit consumption of silver paste, narrowing the line width of the grid line has become a key technical means. The narrowing of the grid line width can not only reduce the amount of silver paste used, but also reduce the grid line from blocking light, thereby improving the photoelectric conversion efficiency of photovoltaic cells. In this context, full-opening stencil technology has been introduced into the silver paste printing process. Compared with traditional stencils, full-opening stencils have a higher aperture rate and more precise line width control capabilities, which can achieve narrower and more uniform grid line printing, thereby effectively reducing the unit consumption of silver paste and improving battery performance. Full-opening stencils have higher requirements on the rheology, thixotropy and curing properties of silver paste. Traditional silver paste is prone to problems such as grid line breakage, unstable line width and low aspect ratio during the full-opening stencil printing process, which affects the printing effect and battery performance. Therefore, a low-temperature silver paste suitable for full-opening stencils is developed to match the high-precision printing process of full-opening stencils, ensure the uniform narrowing and stable forming of the grid lines, and form a higher aspect ratio. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a low-temperature photovoltaic slurry for full-opening screen printing and a preparation method thereof. A nanocarbon solution is added to the low-temperature slurry provided by the present invention, and the nanocarbon has properties such as high conductivity, high specific surface area, and excellent lubricity. High conductivity can improve the overall conductivity of the slurry; high specific surface area can improve the thixotropy of the slurry and improve the shaping ability of the slurry on the full-opening screen; excellent lubricity can improve the ink-passing property of the slurry, thereby making the prepared battery photoelectric conversion efficiency better.

[0005] To achieve the above object, the technical solution of the present invention is: A low-temperature photovoltaic slurry for full-opening screen printing comprises, by weight, 60-95wt% of a conductive powder, 1-20wt% of a first resin, 0.1-2.5wt% of an auxiliary agent, 0-15wt% of a first solvent, 0.1-2.5wt% of a curing agent, and 0.1-5wt% of a nanocarbon solution, wherein 0.1-5wt% is the mass proportion of the nanocarbon solution in the photovoltaic slurry.

[0006] Preferably, the solid nanocarbon of the nanocarbon solution includes one or more of graphene, nanographite powder, carbon nanotubes, fullerene carbon spheres, nanocarbon black powder, and carbon quantum dots; The liquid part of the nano-carbon solution is a second solvent or a second resin; The solid content of the nano-carbon solution is 1-15wt%. When the liquid part of the nano-carbon solution is the second solvent and the content of the nano-carbon solution is relatively high, the content of the first solvent may be 0.

[0007] Preferably, the conductive powder is any one of silver powder, silver-coated copper powder, silver-coated nickel powder, gold powder or alloy powder, or a mixture thereof.

[0008] Preferably, the conductive powder has a shape of flake, sphere or wire, or a mixture thereof.

[0009] Preferably, the curing agent is one or a mixture of amine curing agent, anhydride curing agent or imidazole curing agent; The auxiliary agent is a functional auxiliary agent, including one or a mixture of leveling agent, thickener, dispersant, accelerator or thixotropic agent.

[0010] Preferably, the first resin or the second resin is one or a mixture of epoxy resin, polyester resin, polyurethane resin, acrylic resin or PVB resin.

[0011] Preferably, the first solvent or the second solvent is any one of ethyl acetate, propyl acetate, butyl acetate, hexyl acetate, terpineol, DBE, diethylene glycol monobutyl ether or dodecyl alcohol ester, or a mixture of several of them.

[0012] Based on the same inventive concept, the present invention also provides a method for preparing a low-temperature photovoltaic slurry for full-opening screen printing, comprising the following steps: S1: After mixing the conductive powder, the first resin, the additive, the first solvent, the curing agent and the nanocarbon solution according to the formula ratio, centrifuging or stirring to fully mix and disperse; S2: Grind the slurry obtained in step S1 with a three-roll grinder to further mix the slurry and reduce its fineness. The fineness of the optimal slurry is controlled within 6 μm, and then filter it to remove large particles or impurities that may exist in the production process. Centrifuge or stir the filtered slurry to fully mix the filtered slurry to form a slurry with uniform components, thereby obtaining the low-temperature photovoltaic slurry for the full-opening mesh panel.

[0013] Based on the same inventive concept, the present invention further provides a photovoltaic cell, comprising a substrate and grid lines formed on the surface of the substrate, wherein the grid lines are formed by the above-mentioned low-temperature slurry through full-opening screen printing, curing or sintering.

[0014] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present invention provides a method of adding a nanocarbon solution to a slurry. The nanocarbon is an incompatible phase in the system. When the nanocarbon enters the system, the viscosity of the system increases. The nanocarbon has a large specific surface area. The addition of the nanocarbon increases the specific surface area of ​​the system as a whole, thereby increasing the oil absorption value. The increase in viscosity has a greater impact at high speed than at low speed, so that the slurry has a better shaping effect when shearing at high speed during printing, thereby improving the aspect ratio of the line type.

[0015] At the same time, nanocarbon has electrical conductivity and excellent lubricity. High electrical conductivity can improve the overall electrical conductivity of the slurry; excellent lubricity can improve the ink-passing property of the slurry, thereby making the prepared battery have better photoelectric conversion efficiency.

[0016] Adding nanocarbon in the form of a solution into the slurry system allows the nanocarbon to be better dispersed in the slurry. DETAILED DESCRIPTION

[0017] The components of the low-temperature slurry of the present invention include conductive powder, resin, solvent, auxiliary agent, curing agent and nano-carbon solution. The conductive powder / nano-carbon serves as a conductive functional phase, plays the role of conducting electrons, and determines the electrical properties of the solidified slurry. It is important that the nano-carbon solution also plays the role of adjusting the thixotropy of the slurry and improving the printing of the slurry, so that the low-temperature slurry can be suitable for full-opening screen printing; the resin, after being cured, serves as the molecular structure skeleton of the slurry, plays the role of bonding, and determines the physical properties of the solidified slurry, such as bonding strength, impact strength and mechanical properties; the main function of the solvent and other auxiliary agents is to adjust the properties of the slurry, such as bonding adhesion, leveling and castability. By adjusting and optimizing the component ratio, each component can work synergistically to obtain a low-temperature slurry with excellent conductivity.

[0018] The following is a further detailed description of a low-temperature photovoltaic paste for full-opening screen printing and a preparation method thereof proposed by the present invention in conjunction with specific embodiments. The advantages and features of the present invention will become more apparent from the following description.

[0019] Example S1 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 94wt% of silver-coated copper powder, 1wt% of a first resin, 4.2wt% of a first solvent, diethylene glycol butyl ether acetate, 0.2wt% of an auxiliary agent, 0.3wt% of a curing agent, and 0.3wt% of a graphene solution, wherein the graphene solution has a solid content of 2% and a liquid content of 98%, and the liquid content is ethyl acetate.

[0020] A method for preparing a low-temperature slurry for solar cells comprises the following steps: S1: After adding the powder, the first resin, the additive, diethylene glycol butyl ether acetate, the curing agent and the nanocarbon solution according to the formula ratio, they are fully mixed and dispersed by centrifugation or stirring; S2: Grind the slurry obtained in step S1 with a three-roll grinder to further mix the slurry and reduce the fineness to within 6 μm, and then filter to remove large particles or impurities that may exist in the production process, centrifuge or stir the filtered slurry to fully mix the filtered slurry to form a slurry with uniform components.

[0021] Example S2 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 94wt% of silver-coated copper powder, 1wt% of a first resin, 4.2wt% of a first solvent, diethylene glycol butyl ether acetate, 0.2wt% of an auxiliary agent, 0.3wt% of a curing agent, and 0.3wt% of a carbon nanotube solution, wherein the carbon nanotube solution has a solid content of 2% and a liquid content of 98%, and the liquid content is diethylene glycol butyl ether acetate.

[0022] The preparation method is the same as Example L1.

[0023] Example S3 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 94wt% of silver-coated copper powder, 1wt% of a first resin, 4.4wt% of a first solvent, diethylene glycol butyl ether acetate, 0.1wt% of an auxiliary agent, 0.2wt% of a curing agent, and 0.3wt% of a nanographite powder solution, wherein the nanographite powder solution has a solid content of 2% and a liquid content of 98%, and the liquid content is pinene alcohol.

[0024] The preparation method is the same as Example L1.

[0025] Example S4 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 92.6 wt% of conductive silver powder, 1 wt% of silver-coated copper powder, 1 wt% of a first resin, 4.5 wt% of a first solvent, diethylene glycol butyl ether acetate, 0.1 wt% of an auxiliary agent, 0.2 wt% of a curing agent, 0.3 wt% of a graphene solution, and 0.3 wt% of a carbon nanotube solution, wherein the solid content of the graphene solution and the carbon nanotube solution are both 2%, the liquid content is 98%, and the liquid content is both dodecanol ester.

[0026] The preparation method is the same as Example L1.

[0027] Example S5 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 92.6 wt% of conductive silver powder, 1 wt% of silver-coated copper powder, 1 wt% of a first resin, 4.5 wt% of a first solvent, diethylene glycol butyl ether acetate, 0.1 wt% of an auxiliary agent, 0.2 wt% of a curing agent, 0.2 wt% of a graphene solution, 0.2 wt% of a carbon nanotube solution, and 0.2 wt% of a nanographite powder solution, wherein the solid content of the graphene solution, the carbon nanotube solution, and the nanographite powder solution are all 2%, and the liquid content is all 98%, and the liquid content is all dodecanol ester.

[0028] The preparation method is the same as Example L1.

[0029] Example S6 A low-temperature slurry for solar cells comprises, calculated by mass fraction, 40wt% of conductive silver powder, 54wt% of silver-coated copper powder, 1wt% of a first resin, 4.2wt% of a first solvent, diethylene glycol butyl ether acetate, 0.1wt% of an auxiliary agent, 0.4wt% of a curing agent, 0.1wt% of a graphene solution, 0.1wt% of a carbon nanotube solution, and 0.1wt% of a nanographite powder solution, wherein the solid content of the graphene solution, the carbon nanotube solution, and the nanographite powder solution are all 2%, the liquid content is all 98%, and the liquid content is all dodecanol ester.

[0030] Example S7 A low-temperature slurry for solar cells comprises, by mass fraction, 40 wt% of conductive silver powder, 53.5 wt% of silver-coated copper powder, 1 wt% of a first resin, 0.1 wt% of an auxiliary agent, 0.4 wt% of a curing agent, and 5 wt% of a graphene solution, wherein the solid content of the graphene solution is 2%, the liquid content is 98%, and the liquid content is diethylene glycol butyl ether acetate.

[0031] The preparation method is the same as Example L1.

[0032] Comparative Example B1 A low-temperature paste for solar cells comprises, calculated by mass fraction, 94 wt% of silver-coated copper powder, 1 wt% of a first resin, 4.5 wt% of a first solvent, diethylene glycol butyl ether acetate, 0.2 wt% of an auxiliary agent, and 0.3 wt% of a curing agent.

[0033] The preparation method is the same as Example L1.

[0034] Comparative Example B2 A low-temperature slurry for solar cells comprises, by mass fraction, 47 wt% of conductive silver powder, 45.5 wt% of silver-coated copper powder, 1 wt% of a first resin, 0.2 wt% of an auxiliary agent, 0.3 wt% of a curing agent, and 6 wt% of a carbon nanotube solution, wherein the solid content of the carbon nanotube solution is 2%, the liquid content is 98%, and the liquid content is diethylene glycol butyl ether acetate.

[0035] The preparation method is the same as Example L1.

[0036] Comparative Example B3 A low-temperature paste for solar cells comprises, by mass fraction, 30 wt% of conductive silver powder, 65.5 wt% of silver-coated copper powder, 1 wt% of a first resin, 3.2 wt% of a first solvent, diethylene glycol butyl ether acetate, 0.1 wt% of an auxiliary agent, and 0.2 wt% of a curing agent.

[0037] The preparation method is the same as Example L1.

[0038] The conductive powder, silver-coated copper powder, first resin, first solvent, additive, curing agent and nano-carbon solution used in the above embodiments and comparative examples are all commercially available. The morphology of the silver-coated copper powder and the conductive silver powder is flake, spherical or linear, or a mixture thereof.

[0039] The above embodiments and comparative examples only have a variable in the ratio of components, and the other components are prepared using the same reagents, the same preparation conditions, and the batteries are prepared under the same conditions.

[0040] The components of Examples S1-S7 and Comparative Examples B1-B3 are summarized in Table 1 below, as shown in Table 1: Table 1 The above 10 slurries were made into solar cells, and the wet weight and aspect ratio were tested. The results are shown in Table 2: Table 2 As shown in Table 2, by comparing the embodiments with Comparative Examples B1 and B3 that do not use nanocarbon solution and Comparative Example B2 that is not within the appropriate ratio range, the aspect ratio of the line type obtained by the slurry through full-opening screen printing is significantly improved, which directly illustrates that the use of nanocarbon solution and the addition of a suitable nanocarbon solution can help increase the line height, narrow the line width, and achieve the purpose of improving the line type. Further, when nanocarbon is a mixture of graphene, nanographite powder, and carbon nanotubes, the aspect ratio is improved more significantly, and the mixed use has a further gain effect.

[0041] The above is a detailed description of the implementation of the present invention in conjunction with the specific embodiments, but the present invention is not limited to the above implementation. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A low-temperature photovoltaic slurry for full-opening screen printing, characterized in that: The composition comprises, by weight, 60-95 wt% of conductive powder, 1-20 wt% of a first resin, 0.1-2.5 wt% of an auxiliary agent, 0-15 wt% of a first solvent, 0.1-2.5 wt% of a curing agent, and 0.1-5 wt% of a nano-carbon solution.

2. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 1, characterized in that: The solid nanocarbon of the nanocarbon solution includes one or more of graphene, nanographite powder, carbon nanotubes, fullerene carbon spheres, nanocarbon black powder, and carbon quantum dots; The liquid part of the nano-carbon solution is a second solvent or a second resin; The solid content of the nano-carbon solution is 1-15wt%.

3. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 1, characterized in that: The conductive powder is any one of silver powder, silver-coated copper powder, silver-coated nickel powder, gold powder or alloy powder or a mixture thereof.

4. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 1, characterized in that: The morphology of the conductive powder is any one of flake, spherical or linear or a mixture thereof.

5. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 1, characterized in that: The curing agent is one or a mixture of amine curing agents, anhydride curing agents or imidazole curing agents; The auxiliary agent is a functional auxiliary agent, including one or a mixture of leveling agent, thickener, dispersant, accelerator or thixotropic agent.

6. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 2, characterized in that: The first resin or the second resin is one of epoxy resin, polyester resin, polyurethane resin, acrylic resin or PVB resin, or a mixture of several of them.

7. The low-temperature photovoltaic slurry for full-opening screen printing according to claim 2, characterized in that: The first solvent or the second solvent is any one of ethyl acetate, propyl acetate, butyl acetate, hexyl acetate, terpineol, DBE, diethylene glycol monobutyl ether or dodecyl alcohol ester or a mixture of several of them.

8. A method for preparing a low-temperature photovoltaic slurry for full-opening screen printing according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: After mixing the conductive powder, the first resin, the additive, the first solvent, the curing agent and the nanocarbon solution according to the formula ratio, centrifuging or stirring to fully mix and disperse; S2: Grind and filter the slurry obtained in step S1 to obtain the low-temperature photovoltaic slurry for the full-opening mesh panel.

9. A photovoltaic cell, characterized in that: The invention comprises a substrate and grid lines formed on the surface of the substrate, wherein the grid lines are formed by the low-temperature slurry according to any one of claims 1 to 7 through full-opening screen printing, curing or sintering.

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