Low-temperature photovoltaic silver paste and preparation method and application thereof

Abstract

The invention provides low-temperature photovoltaic silver paste and a preparation method and application thereof. The low-temperature photovoltaic silver paste comprises silver conductive paste, a rheological additive and a coalescing agent, the rheological additive comprises at least one of organic silicon, acrylic acid, fluorocarbon, hydroxypropyl methyl cellulose and polyurethane; the coalescing agent comprises at least one of texanol, polyethylene glycol, acrylate, polyurethane, polyvinyl alcohol and PVP (Polyvinyl Pyrrolidone). According to the low-temperature photovoltaic silver paste disclosed by the invention, the rheological additive and the coalescing agent are added into the conventional silver conductive paste, so that the sectional area of the grid line is triangular after the silver paste is printed, the surface is smoother under the action of the coalescing agent, sunlight is irradiated on the grid line and reflected to the surface of a battery piece through the triangular grid line to be reused, and the utilization rate of the solar energy is improved. The sunlight utilization rate is increased, the shading loss is greatly reduced, and the photovoltaic power generation current is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic silver paste, and in particular relates to a low-temperature photovoltaic silver paste and a preparation method and application thereof. Background Art

[0002] Photovoltaic power generation is the process of converting solar radiation into electrical energy through solar cell modules. This process involves the photovoltaic effect of the semiconductor PN junction. Under the illumination of light, the internal electrons of the cell move in a directed manner, generating current for load use or storage. Therefore, the size of the current is directly related to the efficiency of photovoltaic power generation.

[0003] When traditional silver conductive paste is printed on the cell, the grid lines block the cell, causing shading loss and reducing the utilization rate of sunlight, thus affecting the current and final power generation efficiency of photovoltaic power generation. In addition, after printing traditional silver conductive paste, the cross section of the grid lines is trapezoidal, with an uneven and irregular surface. Most of the sunlight hitting the grid lines is reflected in all directions and cannot be used. Therefore, even if the aspect ratio of the grid lines is increased, there will still be more shading loss.

[0004] Based on the defects of the current silver conductive paste, it is necessary to improve it. Summary of the invention

[0005] In view of this, the present invention proposes a low-temperature photovoltaic silver paste and a preparation method and application thereof, so as to solve or at least partially solve the technical problems existing in the prior art.

[0006] In a first aspect, the present invention provides a low-temperature photovoltaic silver paste, comprising: a silver conductive paste, a rheological additive and a film-forming additive;

[0007] Wherein, the rheological additive includes at least one of silicone additives, acrylic additives, fluorine-containing polymers, hydroxypropyl methylcellulose, and polyurethane;

[0008] The film-forming aid includes at least one of alcohol ester dodecanedione, polyethylene glycol, acrylate, polyurethane, polyvinyl alcohol, and PVP.

[0009] Preferably, the acrylic acid ester includes at least one of hydroxyethyl acrylate, methyl acrylate, ethyl acrylate, 2-methyl methacrylate, and 2-ethyl methacrylate;

[0010] And / or, the organosilicon additive includes organosilicon bentonite;

[0011] And / or, the acrylic auxiliary agent is an acrylic ester copolymer, and the acrylic ester copolymer includes polyacrylic acid ammonium salt.

[0012] Preferably, the mass of the film-forming aid is 0.05-5% of the mass of the silver conductive paste.

[0013] And / or, the mass of the rheological additive is 0.05-5% of the mass of the silver conductive paste.

[0014] Preferably, the silver conductive paste comprises silver powder, organic resin, curing agent and solvent.

[0015] Preferably, the organic resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, alicyclic epoxy resin, and resorcinol epoxy resin;

[0016] And / or, the curing agent is a latent curing agent;

[0017] And / or, the solvent includes at least one of diethylene glycol butyl ether acetate, acetone, butanone, methyl isobutyl ketone, isophorone, ethylene glycol, propylene glycol, ethyl acetate, butyl acetate, xylene, terpineol, ethylene glycol ethyl ether, diethylene glycol butyl ether, dodecanol ester, dibutyl phthalate, dioctyl phthalate, dioctyl adipate, isopropanol, n-butanol, and cyclopentanone.

[0018] Preferably, the latent curing agent comprises:

[0019] Preferably, the silver conductive paste comprises the following components in parts by weight:

[0020] 90-120 parts of silver powder, 5-15 parts of organic resin, 2-5 parts of curing agent, and 5-10 parts of solvent.

[0021] Preferably, the silver conductive paste comprises the following components in parts by weight:

[0022] 40 to 50 parts of spherical silver powder with a particle size of 1.15 to 1.85 μm, 40 to 50 parts of spherical silver powder with a particle size of 200 to 400 nm, 10 to 20 parts of spherical silver powder with a particle size of 20 to 80 nm, 5 to 15 parts of organic resin, 2 to 5 parts of curing agent, and 5 to 10 parts of solvent.

[0023] In a second aspect, the present invention also provides a method for preparing the low-temperature photovoltaic silver paste, comprising the following steps: adding a rheological additive and a film-forming additive to a silver conductive paste, and ball milling to obtain a low-temperature photovoltaic silver paste.

[0024] In a third aspect, the present invention also provides an application of the low-temperature photovoltaic silver paste in the preparation of solar cells.

[0025] The low-temperature photovoltaic silver paste of the present invention and its preparation method and application have the following beneficial effects compared with the prior art:

[0026] 1. The low-temperature photovoltaic silver paste of the present invention can make the cross-sectional area of ​​the grid line present a triangle after the silver paste is printed by adding a rheological additive and a film-forming additive to a conventional silver conductive paste. The surface is smoother under the action of the film-forming additive. Sunlight irradiates the grid line and is reflected by the triangular grid line to the surface of the solar cell for reuse, thereby increasing the utilization rate of sunlight, greatly reducing the shading loss, and improving the photovoltaic power generation current.

[0027] 2. The low-temperature photovoltaic silver paste of the present invention uses a combination of 40 to 50 parts of spherical silver powder with a particle size of 1.15 to 1.85 μm, 40 to 50 parts of spherical silver powder with a particle size of 200 to 400 nm, and 10 to 20 parts of spherical silver powder with a particle size of 20 to 80 nm as the silver powder. After the paste is printed, the surface of the grid line is smoother, so that the sunlight blocked by the grid line is more inclined to be reflected in the direction of the battery cell surface, thereby increasing the utilization rate of sunlight and the power generation current. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0029] In order to better understand the present invention but not to limit the scope of the present invention, all the numbers used in this application to express the amount, percentage, and other numerical values ​​should be understood as modified by the word "about" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the specification and the appended claims are approximate values, which may be changed according to the different ideal properties attempted to be obtained. Each numerical parameter should at least be regarded as obtained based on the reported significant figures and by conventional rounding methods.

[0030] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0031] The present invention provides a low-temperature photovoltaic silver paste, comprising: silver conductive paste, rheological additive and film-forming additive;

[0032] The rheological additive includes at least one of silicone additives, acrylic additives, fluorine-containing polymers, hydroxypropyl methylcellulose, and polyurethane;

[0033] The film-forming aid includes at least one of alcohol ester, polyethylene glycol, acrylate, polyurethane, polyvinyl alcohol and PVP.

[0034] The low-temperature photovoltaic silver paste of the present invention can make the cross-sectional area of ​​the grid lines present a triangle after the silver paste is printed by adding a rheological additive and a film-forming additive to a conventional silver conductive paste. The surface is smoother under the action of the film-forming additive. Sunlight irradiated on the grid lines is reflected by the triangular grid lines onto the surface of the battery cell for reuse, thereby increasing the utilization rate of sunlight, greatly reducing the shading loss, and improving the photovoltaic power generation current.

[0035] The key to the present invention is to add suitable rheological additives and film-forming additives to the silver conductive paste. The addition of the rheological additive improves the rheological properties of the paste and makes it easier to level. The addition of the rheological additive makes the paste more wire-drawn. During printing, the paste is printed on the battery cell through the screen. During the lifting process of the screen, the screen will lift the paste and then break it because the paste is relatively wire-drawn, making the top of the entire grid line very narrow. After subsequent leveling, the entire cross-section presents a triangle. Under the action of the film-forming additive, the two sides of the grid line become smoother, which plays a vital role in making the sunlight irradiate the grid line and then reflect onto the battery cell to increase the power generation current. The width of the triangular grid line is almost the same as that of the traditional grid line, that is, it does not affect the contact area with the battery cell, and does not affect the contact resistivity between the grid line and the TCO layer. Except for the leveling agent and the film-forming agent, the other components of the slurry are the same as the normal slurry components, such as metal silver powder, resin, solvent, etc. Therefore, the grid line itself has good conductivity and does not affect the transmission of current during photovoltaic power generation. However, the increase in current will greatly improve the efficiency of the battery.

[0036] Specifically, the selection of rheological additives mainly needs to be compatible with the slurry's own resin system, and can improve the silver paste's own leveling performance and drawing performance; rheological additives can be selected from silicone additives, acrylic additives, fluoropolymers, hydroxypropyl methylcellulose, polyurethane and other thermoplastic resins; film-forming additives need to be compatible with the system and can achieve a good film-forming effect to make the surface smoother. One or more of alcohol ester dodecahydrate, polyethylene glycol, acrylate, polyurethane, polyvinyl alcohol, PVP, etc. can be selected.

[0037] In some embodiments, the acrylate includes at least one of hydroxyethyl acrylate, methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate.

[0038] In some embodiments, the organosilicon additive is organosilicon bentonite, for example, it may be HIMESTECH BENTONE 1000 solvent-based organosilicon bentonite.

[0039] In some embodiments, the acrylic auxiliary agent is an acrylic acid ester copolymer, and the acrylic acid ester copolymer may be polyacrylic acid ammonium salt.

[0040] In some embodiments, the fluorine-containing polymer is PPA5420 (a new generation of polymer processing aid developed by Shanghai Jiuwu New Materials Technology Co., Ltd.; the active ingredient of PPA5420 is fluorine polymer, which is a white powder).

[0041] In some embodiments, the mass of the rheological additive is 0.05-5% of the mass of the silver conductive paste.

[0042] In some embodiments, the mass of the film-forming aid is 0.05-5% of the mass of the silver conductive paste.

[0043] The general addition amount of rheological additives and film-forming additives is 0.05-5% of the mass of the silver conductive paste, which can be determined according to the performance of the paste itself. Adding too little will not achieve the leveling effect, and adding too much will affect the overall electrical properties of the paste, thereby affecting the final photoelectric conversion efficiency.

[0044] In some embodiments, the silver conductive paste includes silver powder, an organic resin, a curing agent, and a solvent.

[0045] In some embodiments, the organic resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, alicyclic epoxy resin, and resorcinol epoxy resin.

[0046] In some embodiments, the curing agent is a latent curing agent;

[0047] In some embodiments, the solvent includes at least one of diethylene glycol butyl ether acetate, acetone, butanone, methyl isobutyl ketone, isophorone, ethylene glycol, propylene glycol, ethyl acetate, butyl acetate, xylene, terpineol, ethylene glycol ethyl ether, diethylene glycol butyl ether, dodecanol, dibutyl phthalate, dioctyl phthalate, dioctyl adipate, isopropanol, n-butanol, and cyclopentanone.

[0048] In some embodiments, the latent curing agent includes at least one of dicyandiamide, anhydride-based latent curing agent, and isocyanate-based latent curing agent.

[0049] In some embodiments, the anhydride latent curing agent includes at least one of phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride glyceride, polyazelaic anhydride, polysebacic anhydride, tung oil anhydride, 647 anhydride, and chlorendic anhydride.

[0050] In some embodiments, the isocyanate-based latent curing agent includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

[0051] In some embodiments, the silver conductive paste includes the following components in parts by weight:

[0052] 90-120 parts of silver powder, 5-15 parts of organic resin, 2-5 parts of curing agent, and 5-10 parts of solvent.

[0053] In some embodiments, the silver conductive paste includes the following components in parts by weight:

[0054] 40 to 50 parts of spherical silver powder with a particle size of 1.15 to 1.85 μm, 40 to 50 parts of spherical silver powder with a particle size of 200 to 400 nm, 10 to 20 parts of spherical silver powder with a particle size of 20 to 80 nm, 5 to 15 parts of organic resin, 2 to 5 parts of curing agent, and 5 to 10 parts of solvent.

[0055] The silver powder is a combination of 40-50 parts of spherical silver powder with a particle size of 1.15-1.85 μm, 40-50 parts of spherical silver powder with a particle size of 200-400 nm, and 10-20 parts of spherical silver powder with a particle size of 20-80 nm. After the slurry is printed, the surface of the grid line is smoother, so that the sunlight blocked by the grid line is more inclined to be reflected in the direction of the battery cell surface, thereby increasing the utilization rate of sunlight and the power generation current.

[0056] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned low-temperature photovoltaic silver paste, comprising the following steps: adding a rheological additive and a film-forming additive to a silver conductive paste, and ball milling to obtain a low-temperature photovoltaic silver paste.

[0057] In some embodiments, a method for preparing low-temperature photovoltaic silver paste comprises the following steps:

[0058] The rheological additive and the film-forming additive are added to the silver conductive paste, and the paste is ground in a three-roll grinder until the particle size is less than 10 μm to obtain a low-temperature photovoltaic silver paste.

[0059] Based on the same inventive concept, the present invention also provides an application of the low-temperature photovoltaic silver paste in the preparation of solar cells.

[0060] Specifically, a solar cell usually includes an N-type crystalline silicon wafer, an intrinsic amorphous silicon layer, a P-type amorphous silicon thin film layer, an n-type amorphous silicon thin film layer, and a TCO conductive layer. When used, the low-temperature photovoltaic silver paste of the present invention is brushed on the TCO conductive layer, dried and cured at 200°C for 30 minutes to form a cathode; photovoltaic silver paste can be divided into high-temperature sintering type and low-temperature curing type. The high-temperature sintering temperature is generally greater than 500°C, and the low-temperature curing temperature is generally 180-250°C. The curing temperature of the photovoltaic silver paste of the present invention is 180-250°C, so it is a low-temperature photovoltaic silver paste.

[0061] The low-temperature photovoltaic silver paste of the present invention is printed onto the battery cell through the screen during printing. Under the action of the film-forming aid, both sides of the grid line become smoother, the grid line cross section is triangular, and the surface is smoother, so that the sunlight that would have been lost by the grid line is reflected back onto the battery cell for use, thereby increasing the power generation current and improving the photovoltaic power generation efficiency. Since the reflected light is reduced, the battery cell is more inclined to have a completely black effect after being prepared into a component.

[0062] The following further illustrates the low-temperature photovoltaic silver paste of the present application and its preparation method and application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as a limitation of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0063] Example 1

[0064] The embodiment of the present application provides a low-temperature photovoltaic silver paste, including: silver conductive paste, rheological additive and film-forming additive;

[0065] The silver conductive paste includes the following components in parts by weight:

[0066] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0067] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0068] The rheological additive is hydroxypropyl methylcellulose;

[0069] The film-forming aid is alcohol ester dodecahydrate (chemical formula C 12 H 24 O3);

[0070] The mass of the rheological additive is 0.3% of the mass of the silver conductive paste;

[0071] The mass of the film-forming aid is 0.3% of the mass of the silver conductive paste.

[0072] The method for preparing the low-temperature photovoltaic silver paste comprises the following steps:

[0073] The rheological additive and the film-forming additive are added into the silver conductive paste, and the paste is ground in a three-roll grinder to obtain a low-temperature photovoltaic silver paste.

[0074] Example 2

[0075] The embodiment of the present application provides a low-temperature photovoltaic silver paste, including: silver conductive paste, rheological additive and film-forming additive;

[0076] The silver conductive paste includes the following components in parts by weight:

[0077] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0078] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0079] The rheological additive is silicone bentonite (specifically, HIMESTECH BENTONE 1000 solvent-based silicone bentonite);

[0080] The film-forming aid is polyethylene glycol (specifically polyethylene glycol 2000 (PEG-2000));

[0081] The mass of the rheological additive is 1% of the mass of the silver conductive paste;

[0082] The mass of the film-forming aid is 0.5% of the mass of the silver conductive paste.

[0083] The method for preparing the low-temperature photovoltaic silver paste comprises the following steps:

[0084] The rheological additive and the film-forming additive are added into the silver conductive paste, and the paste is ground in a three-roll grinder to obtain a low-temperature photovoltaic silver paste.

[0085] Example 3

[0086] The embodiment of the present application provides a low-temperature photovoltaic silver paste, including: silver conductive paste, rheological additive and film-forming additive;

[0087] The silver conductive paste includes the following components in parts by weight:

[0088] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0089] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0090] The rheological additive is ammonium polyacrylate (specifically ammonium polyacrylate dispersant, model: Mowiplus XW, brand: Archroma);

[0091] The film-forming aid is PVP (polyvinyl pyrrolidone);

[0092] The mass of the rheological additive is 0.5% of the mass of the silver conductive paste;

[0093] The mass of the film-forming aid is 0.5% of the mass of the silver conductive paste.

[0094] The method for preparing the low-temperature photovoltaic silver paste comprises the following steps:

[0095] The rheological additive and the film-forming additive are added into the silver conductive paste, and the paste is ground in a three-roll grinder to obtain a low-temperature photovoltaic silver paste.

[0096] Example 4

[0097] The embodiment of the present application provides a low-temperature photovoltaic silver paste, including: silver conductive paste, rheological additive and film-forming additive;

[0098] The silver conductive paste includes the following components in parts by weight:

[0099] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0100] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0101] The rheological additive is fluoropolymer PPA5420;

[0102] The film-forming aid is acrylate, and the acrylate is hydroxyethyl acrylate;

[0103] The mass of the rheological additive is 1% of the mass of the silver conductive paste;

[0104] The mass of the film-forming aid is 1% of the mass of the silver conductive paste.

[0105] The method for preparing the low-temperature photovoltaic silver paste comprises the following steps:

[0106] The rheological additive and the film-forming additive are added into the silver conductive paste, and the paste is ground in a three-roll grinder to obtain a low-temperature photovoltaic silver paste.

[0107] Comparative Example 1

[0108] This comparative example provides a low-temperature photovoltaic silver paste, which is the same as Example 1, but does not contain a rheological additive or a film-forming additive; specifically, it includes the following components in parts by weight:

[0109] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0110] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate.

[0111] Comparative Example 2

[0112] This comparative example provides a low-temperature photovoltaic silver paste, which is the same as Example 1, but does not contain a film-forming aid; specifically, it includes: a silver conductive paste, a rheological aid;

[0113] The silver conductive paste includes the following components in parts by weight:

[0114] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0115] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0116] The rheological additive is hydroxypropyl methylcellulose;

[0117] The mass of the rheological additive is 0.3% of the mass of the silver conductive paste.

[0118] Comparative Example 3

[0119] This comparative example provides a low-temperature photovoltaic silver paste, which is the same as Example 1, but does not contain a rheological additive; specifically, it includes: a silver conductive paste, a film-forming additive;

[0120] The silver conductive paste includes the following components in parts by weight:

[0121] 40 parts of spherical silver powder with a particle size of 1.5 μm, 40 parts of spherical silver powder with a particle size of 300 nm, 10 parts of spherical silver powder with a particle size of 50 nm, 8 parts of organic resin, 2 parts of curing agent, and 5 parts of solvent;

[0122] The organic resin is bisphenol F epoxy resin, the curing agent is dicyandiamide, and the solvent is diethylene glycol butyl ether acetate;

[0123] The film-forming aid is alcohol ester dodecahydrate (chemical formula C 12 H 24 O3);

[0124] The mass of the film-forming aid is 0.3% of the mass of the silver conductive paste.

[0125] The low-temperature photovoltaic silver paste in the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 3 was screen-printed on the TCO conductive layer of the battery cell, and then dried and cured at 200°C for 30 minutes. The performance of the battery cell (specifically resistivity, ohmic contact, battery conversion efficiency Eta, short-circuit current Isc, fill factor FF) was tested, and the results are shown in Table 1 below.

[0126] Table 1 - Cell performance after printing low-temperature photovoltaic silver paste in different embodiments

[0127]

[0128]

[0129] Furthermore, the differences in Eta, battery conversion efficiency Eta, short-circuit current Isc, and fill factor FF of the cells printed with low-temperature photovoltaic silver paste in Examples 1 to 4 and Comparative Examples 2 to 3 compared to the cells printed with low-temperature photovoltaic silver paste in Comparative Example 1 are shown in Table 2 below.

[0130] Table 2 - Performance difference of the solar cells after printing with low-temperature photovoltaic silver paste in different embodiments compared with the solar cells after printing with low-temperature photovoltaic silver paste in comparative example 1.

[0131] Example Eta(%) Isc(A) FF Example 1 0.15 0.030 0.26 Example 2 0.03 0.021 -0.17 Example 3 0.05 0.033 -0.31 Example 4 -0.07 0.040 -0.53 Comparative Example 1 25.06 8.697 84.54 Comparative Example 2 0.01 0.005 -0.15 Comparative Example 3 0.01 -0.010 0.1

[0132] It can be seen from Tables 1 and 2 that in Example 1, by adding hydroxypropyl methylcellulose rheological additive and alcohol ester twelve film-forming additive, the cross-section of the gate line after the paste printing is made triangular without affecting the electrical properties of the silver paste. The triangular surface can be used for secondary reflection, thereby reducing the shading loss of the battery cell and improving Isc.

[0133] In Example 2, Isc can be improved to a certain extent by adding an organosilicon bentonite rheological additive and a polyethylene glycol film-forming additive. However, the organosilicon leveling additive has poor conductivity and will affect the volume resistivity and contact resistance.

[0134] In Example 3, by adding polyacrylate ammonium salt rheological additive and PVP film-forming additive, Isc can be improved well, but it will lead to a significant increase in volume resistivity and contact resistance.

[0135] In Example 4, by adding more fluoropolymer PPA5420 rheological additive and hydroxyethyl acrylate film-forming additive, Isc can be significantly improved. However, when the amount is large, the volume resistivity and contact resistance will be significantly increased.

[0136] In Comparative Example 2, only the rheological additive was added. After the grid line was pulled up, there was no film-forming additive involved, resulting in no obvious improvement in Isc.

[0137] In Comparative Example 3, only the film-forming aid was added, and the line width widened after the slurry was printed, resulting in a loss of Isc.

[0138] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-temperature photovoltaic silver paste, characterized in that: include: Silver conductive paste, rheological additives and film-forming additives; Wherein, the rheological additive includes at least one of silicone additives, acrylic additives, fluorine-containing polymers, hydroxypropyl methylcellulose, and polyurethane; The film-forming aid includes at least one of alcohol ester dodecanedione, polyethylene glycol, acrylate, polyurethane, polyvinyl alcohol, and PVP.

2. The low-temperature photovoltaic silver paste according to claim 1, characterized in that: The acrylic acid ester includes at least one of hydroxyethyl acrylate, methyl acrylate, ethyl acrylate, 2-methyl methacrylate, and 2-ethyl methacrylate; And / or, the organosilicon additive includes organosilicon bentonite; And / or, the acrylic auxiliary agent is an acrylic ester copolymer, and the acrylic ester copolymer includes polyacrylic acid ammonium salt.

3. The low-temperature photovoltaic silver paste according to claim 1, characterized in that: The mass of the film-forming aid is 0.05-5% of the mass of the silver conductive paste. And / or, the mass of the rheological additive is 0.05-5% of the mass of the silver conductive paste.

4. The low-temperature photovoltaic silver paste according to any one of claims 1 to 3, characterized in that: The silver conductive paste comprises silver powder, organic resin, curing agent and solvent.

5. The low-temperature photovoltaic silver paste according to claim 4, characterized in that: The organic resin comprises at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, alicyclic epoxy resin, and resorcinol epoxy resin; And / or, the curing agent is a latent curing agent; And / or, the solvent includes at least one of diethylene glycol butyl ether acetate, acetone, butanone, methyl isobutyl ketone, isophorone, ethylene glycol, propylene glycol, ethyl acetate, butyl acetate, xylene, terpineol, ethylene glycol ethyl ether, diethylene glycol butyl ether, dodecanol ester, dibutyl phthalate, dioctyl phthalate, dioctyl adipate, isopropanol, n-butanol, and cyclopentanone.

6. The low-temperature photovoltaic silver paste according to claim 5, characterized in that: The latent curing agent includes at least one of dicyandiamide, anhydride latent curing agent, and isocyanate latent curing agent; The acid anhydride latent curing agent includes at least one of phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride glyceride, polyazelaic anhydride, polysebacic anhydride, tung oil anhydride, 647 anhydride, and chlorendic anhydride; The isocyanate latent curing agent includes at least one of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

7. The low-temperature photovoltaic silver paste according to claim 4, characterized in that: The silver conductive paste comprises the following components in parts by weight: 90-120 parts of silver powder, 5-15 parts of organic resin, 2-5 parts of curing agent, and 5-10 parts of solvent.

8. The low-temperature photovoltaic silver paste according to claim 7, characterized in that: The silver conductive paste comprises the following components in parts by weight: 40 to 50 parts of spherical silver powder with a particle size of 1.15 to 1.85 μm, 40 to 50 parts of spherical silver powder with a particle size of 200 to 400 nm, 10 to 20 parts of spherical silver powder with a particle size of 20 to 80 nm, 5 to 15 parts of organic resin, 2 to 5 parts of curing agent, and 5 to 10 parts of solvent.

9. A method for preparing a low-temperature photovoltaic silver paste as claimed in any one of claims 1 to 8, characterized in that: The method comprises the following steps: adding a rheological additive and a film-forming additive into a silver conductive paste, and ball milling to obtain a low-temperature photovoltaic silver paste.

10. Use of the low-temperature photovoltaic silver paste according to any one of claims 1 to 8 in preparing solar cells.

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