Front fine grid silver paste for N-type TOPCON battery and battery

Abstract

The invention provides front fine grid silver paste for an N-type TOPCON battery and the battery. The silver paste is applied to an LECO treatment process. The polymer nano-silver solution in the silver paste improves the contact performance in the N-type TOPCON laser-assisted sintering process, reduces recombination, and improves open-circuit voltage and short-circuit current. Compared with micron-sized glass powder, the nano glass powder in the silver paste has the advantages that the single-point etching area is reduced, the etching distribution density is increased, the contact resistance is ultralow, meanwhile, the open-circuit voltage can be effectively improved due to the fact that the etching depth becomes shallow and the metal recombination is low, and the purpose of improving the efficiency is achieved. The problem that in the process of preparing the N-type TOPCON battery through the LECO technology, the speed that silver atoms diffuse into the surface of a silicon wafer is low, the open-circuit voltage and the short-circuit current are affected, and consequently the photoelectric conversion efficiency is low is solved. The invention further provides a battery, the battery is prepared through the LECO technology, and raw materials comprise the silver paste for the N-type TOPCon battery.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and mainly to a front fine grid silver paste and a battery for an N-type TOPCON battery. Background Art

[0002] TOPCon is a tunnel oxide passivated contact solar cell technology based on the principle of selective carriers. Its cell structure is an N-type silicon substrate cell. An ultra-thin silicon oxide layer is prepared on the back of the cell, and then a thin layer of doped silicon is deposited. The two together form a passivated contact structure, which effectively reduces surface recombination and metal contact recombination, providing more room for further improvement of cell conversion efficiency. Laser-assisted sintering technology, also known as laser-enhanced contact optimization (LECO), is used to improve the contact between metal electrodes and silicon wafers in solar cells. In LECO processing, lasers are used for non-destructive carrier injection, and the driving force of the process is the current induced by the LECO process. After LECO processing, the contact resistance of the solar cell is significantly reduced. The new slurry used for the LECO process also showed an increase in open circuit voltage and a small increase in short-circuit current.

[0003] In the manufacturing process of photovoltaic cells, especially for TOPCon (Tunnel Oxide Passivated Contact) solar cells, LECO technology can accurately destroy the passivation layer on the surface of the silicon wafer and form an optimized silver / silicon contact point in the process. For TOPCon cells, the structural design requires finding a balance between the surface passivation layer and the metal contact in order to reduce the recombination of electron-hole pairs while maintaining good current collection. The sintering activity of the micron-scale silver powder used in the current conventional silver paste is relatively low compared to the high-molecular nanosilver solution. During laser-assisted sintering, the diffusion reaction between the silver powder and the silicon substrate is slow, and it is not easy to enter the silicon substrate through the etched channel for metal recombination to form AgSi alloy.

[0004] In order to solve the problem that in the process of preparing N-type TOPCON cells using LECO technology, silver atoms diffuse slowly into the silicon wafer surface, affecting the open circuit voltage and short circuit current, resulting in low photoelectric conversion efficiency, the present application provides a front fine grid silver paste and a cell for N-type TOPCON cells. Summary of the invention

[0005] In order to solve the problem that in the process of preparing N-type TOPCON batteries by LECO technology, silver atoms diffuse into the silicon wafer surface slowly, affecting the open circuit voltage and short circuit current, resulting in low photoelectric conversion efficiency, the present application provides a front fine grid silver paste for N-type TOPCON batteries, the silver paste comprising silver powder, polymer nanosilver solution, glass powder, nano glass powder, a first organic carrier, a second organic carrier and additives, the mass fraction of the polymer nanosilver solution in the silver paste is 1% to 5%, and the mass fraction of the nano glass powder is 0.1% to 1%.

[0006] In the LECO process, the microscopic changes between the silver paste and the cell are as follows:

[0007] a) Local destruction of the passivation layer: The hot spots caused by laser heating will locally destroy the passivation layer on the silicon wafer. This is a precisely controlled physical process. The passivation layer is destroyed to enable the silver to form direct contact with the silicon wafer and establish an effective electron transmission path.

[0008] b) Silver-silicon alloy formation: Under the action of high temperature, silver particles begin to react with silicon to form silver-silicon alloy locally. This process involves the diffusion of silver atoms into the surface of the silicon wafer and the formation of good ohmic contact in the contact area.

[0009] c) Cooling and solidification: After laser treatment, the sintered area begins to cool. The metal connection between the silver particles solidifies to form a strong electrode.

[0010] Under the laser-assisted sintering process, compared with micron-level glass powder, nano-glass powder reduces the single-point etching area and increases the etching distribution density (for example, if 1μm glass powder is replaced with 500nm glass powder, the number of glass powder particles increases by 4 times, and the total etching area increases by 4 times, effectively increasing the contact area and improving the contact), achieving ultra-low contact resistance. At the same time, due to the shallower etching depth, low metal composite, and less damage to the P+ layer, the open circuit voltage can be effectively increased to achieve the purpose of improving efficiency.

[0011] The sintering activity of the micron-scale silver powder used in the current conventional silver paste is relatively low compared to that of the polymer nano-silver solution. During laser-assisted sintering, the diffusion reaction between the micron-scale silver powder and the silicon substrate is slow. Due to its small particle size and high activity, the polymer nano-silver can more easily enter the silicon substrate through the channel etched by the nano-glass for metal composite to form AgSi alloy, forming a conductive channel, thereby increasing the opening voltage and short-circuit current, and achieving the purpose of improving efficiency. The polymer nano-silver solution is introduced into the slurry formula. The polymer nano-silver solution has good dispersibility, high silver activity, and is easy to melt and form Ag-Si alloy with the silicon substrate, optimizing contact, reducing composite, and increasing the open circuit voltage and short-circuit current. Compared with the micron-scale glass powder, the nano-glass powder reduces the single-point etching area and increases the etching distribution density. While ensuring contact, due to the shallow etching depth and low metal composite, the damage to the P+ layer is small, which can effectively increase the opening voltage and achieve the purpose of improving efficiency.

[0012] Optionally, in the silver paste, the mass fraction of silver powder is 85% to 89%, the mass fraction of glass powder is 1% to 2%, the mass fraction of the first organic carrier is 2% to 10%, the mass fraction of the second organic carrier is 1% to 5%, and the mass fraction of the additive is 0.1% to 1%. Optionally, the polymer nano silver solution includes a polymer carrier and nano silver powder, the polymer carrier is a polyamide amine dendrimer, and the D50 of the nano silver powder is 20-50nm.

[0013] Optionally, the mass ratio of the polymer carrier to the nano-silver powder in the polymer nano-silver solution is 1:1 to 1:3.

[0014] Optionally, the silver powder is spherical silver powder, and D50 of the silver powder is 1.4-2.0 μm.

[0015] Optionally, the nano glass powder is a Pb-Si-B-Al-Zn glass powder, the D50 of the glass powder is 1-1.6 μm, and the D50 of the nano glass powder is 100-200 nm.

[0016] Optionally, taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al, and 5% to 20% Zn.

[0017] Optionally, the first organic carrier includes a first resin and a first solvent, the first resin includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, the first solvent includes one or more of benzyl benzoate, ethylene glycol butyl ether benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate, and based on the mass percentage of the first organic carrier as 100%, the first organic carrier includes 10% to 30% of the first resin and 70% to 90% of the first solvent.

[0018] Optionally, the second organic carrier includes a second resin and a second solvent, the second resin includes one or more of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, the second solvent includes two or more of butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodeca, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and dibasic acid esters. Taking the total mass percentage of the second organic carrier as 100%, the second organic carrier includes 10% to 30% of the second resin and 70% to 90% of the second solvent.

[0019] The present application also provides an N-type TOPCON battery, wherein the raw material of the front fine grid of the N-type TOPCon battery includes the above-mentioned silver paste for the N-type TOPCon battery.

[0020] Optionally, the N-type TOPCon battery is manufactured using LECO technology.

[0021] This application introduces polymer nano silver and nano glass powder. Compared with micron-level and submicron-level silver powder, they have the characteristics of good dispersibility, uniform particles, high activity, low melting temperature, etc., and can be better matched with nano glass powder. The Ag-Si spikes formed with the silicon substrate are smaller and the damage to the PN junction is small. At the same time, the Ag-Si alloy formation process is mainly the diffusion of silver atoms into the silicon wafer surface. Smaller and better dispersed nano silver can diffuse into the silicon wafer surface faster, which can well optimize the contact, reduce recombination, and increase the open circuit voltage and short circuit current.

[0022] The present application provides a front fine grid silver paste for an N-type TOPCON battery, and the silver paste is used in a LECO process. The silver paste comprises silver powder, a polymer nano silver solution, glass powder, nano glass powder, a first organic carrier, a second organic carrier and an additive, wherein the mass fraction of the polymer nano silver solution in the silver paste is 1% to 5%, and the mass fraction of the nano glass powder is 0.1% to 1%.

[0023] The polymer nanosilver solution improves the contact performance during the laser-assisted sintering of N-type TOPCON, reduces the composite, and increases the open circuit voltage and short-circuit current. Compared with micron-level glass powder, nano glass powder reduces the single-point etching area, increases the etching distribution density, and presents ultra-low contact resistance. At the same time, due to the shallower etching depth, low metal composite, and less damage to the P+ layer, the open circuit voltage can be effectively increased to achieve the purpose of improving efficiency. It solves the problem that in the process of preparing N-type TOPCON batteries with LECO technology, silver atoms diffuse into the surface of the silicon wafer slowly, affecting the open circuit voltage and short-circuit current, resulting in low photoelectric conversion efficiency. The present application also provides an N-type TOPCON battery, the raw materials of the fine grid on the front of the battery include the above-mentioned silver paste for N-type TOPCon batteries, and the N-type TOPCon battery is prepared by LECO technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 Schematic diagram of the N-type TOPCon battery structure. DETAILED DESCRIPTION

[0026] The following embodiments are described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following embodiments do not represent all implementations consistent with the present application. They are only examples of systems and methods consistent with some aspects of the present application as detailed in the claims.

[0027] N-type TOPCon battery structure Figure 1 As shown. The core technology of the battery is the back passivation contact. The back of the battery is composed of an ultra-thin silicon oxide layer (1-2nm) and a phosphorus-doped microcrystalline amorphous mixed Si film, which together form a passivation contact structure. The passivation performance is activated through the annealing process. During this annealing process, the crystallinity of the Si film changes from a microcrystalline amorphous mixed phase to a polycrystalline. Annealing is performed at an annealing temperature of 850°C.

[0028] This structure can block the recombination of minority carriers and holes, and improve the open circuit voltage and short circuit current of the battery. The ultra-thin oxide layer can allow the majority electrons to tunnel into the polysilicon layer while blocking the recombination of minority carriers and holes. The good passivation effect of ultra-thin silicon oxide and heavily doped silicon film causes the surface energy band of the silicon wafer to bend, thereby forming a field passivation effect, greatly increasing the probability of electron tunneling, reducing contact resistance, and improving the open circuit voltage and short circuit current of the battery, thereby improving the battery conversion efficiency.

[0029] In order to solve the problem that in the process of preparing N-type TOPCON batteries by LECO technology, silver atoms diffuse into the silicon wafer surface slowly, affecting the open circuit voltage and short circuit current, resulting in low photoelectric conversion efficiency, the present application provides a front fine grid silver paste for N-type TOPCON batteries, the silver paste comprising silver powder, polymer nanosilver solution, glass powder, nano glass powder, a first organic carrier, a second organic carrier and additives, the mass fraction of the polymer nanosilver solution in the silver paste is 1% to 5%, and the mass fraction of the nano glass powder is 0.1% to 1%.

[0030] In the LECO process, the microscopic changes between the silver paste and the cell are as follows:

[0031] a) Local destruction of the passivation layer: The hot spots caused by laser heating will locally destroy the passivation layer on the silicon wafer. This is a precisely controlled physical process. The passivation layer is destroyed to enable the silver to form direct contact with the silicon wafer and establish an effective electron transmission path.

[0032] b) Silver-silicon alloy formation: Under the action of high temperature, silver particles begin to react with silicon to form silver-silicon alloy locally. This process involves the diffusion of silver atoms into the surface of the silicon wafer and the formation of good ohmic contact in the contact area.

[0033] c) Cooling and solidification: After laser treatment, the sintered area begins to cool. The metal connection between the silver particles solidifies to form a strong electrode.

[0034] Under the laser-assisted sintering process, compared with micron-level glass powder, nano-glass powder reduces the single-point etching area and increases the etching distribution density (for example, if 1μm glass powder is replaced with 500nm glass powder, the number of glass powder particles increases by 4 times, and the total etching area increases by 4 times, effectively increasing the contact area and improving the contact), achieving ultra-low contact resistance. At the same time, due to the shallower etching depth, low metal composite, and less damage to the P+ layer, the open circuit voltage can be effectively increased to achieve the purpose of improving efficiency.

[0035] The sintering activity of the micron-scale silver powder used in the current conventional silver paste is relatively low compared to that of the polymer nano-silver solution. During laser-assisted sintering, the diffusion reaction between the micron-scale silver powder and the silicon substrate is slow. Due to its small particle size and high activity, the polymer nano-silver can more easily enter the silicon substrate through the channel etched by the nano-glass for metal composite to form AgSi alloy, forming a conductive channel, thereby increasing the opening voltage and short-circuit current, and achieving the purpose of improving efficiency. The polymer nano-silver solution is introduced into the slurry formula. The polymer nano-silver solution has good dispersibility, high silver activity, and is easy to melt and form Ag-Si alloy with the silicon substrate, optimizing contact, reducing composite, and increasing the open circuit voltage and short-circuit current. Compared with the micron-scale glass powder, the nano-glass powder reduces the single-point etching area and increases the etching distribution density. While ensuring contact, due to the shallow etching depth and low metal composite, the damage to the P+ layer is small, which can effectively increase the opening voltage and achieve the purpose of improving efficiency.

[0036] In some embodiments, the mass fraction of silver powder in the silver paste is 85% to 89%, the mass fraction of glass powder is 1% to 2%, the mass fraction of the first organic carrier is 2% to 10%, the mass fraction of the second organic carrier is 1% to 5%, and the mass fraction of the additive is 0.1% to 1%.

[0037] In some embodiments, the polymer nanosilver solution includes a polymer carrier and nanosilver powder, the polymer carrier is a polyamidoamine dendrimer, and the nanosilver powder D50 is 20-50nm. The nanosilver powder is slowly added to the polymer carrier and stirred at room temperature for 30 minutes to obtain the desired polymer nanosilver solution.

[0038] Polyamidoamine (PAMAM) dendrimers have precise molecular structures, a large number of surface functional groups, and cavities within the molecules. They can be easily functionalized through core modification or surface modification, so polyamidoamine dendrimers are good templates for preparing nanomaterials. Nanomaterials are very small in size and have large surface energy. They are easy to agglomerate during the preparation process. Polyamidoamine dendrimers are introduced as carriers to solve the problem of nanosilver agglomeration.

[0039] In some embodiments, the mass ratio of the polymer carrier to the nanosilver powder in the polymer nanosilver solution is 1:1 to 1:3.

[0040] In some embodiments, the silver powder is spherical silver powder, and the D50 of the silver powder is 1.4-2.0 μm.

[0041] In some embodiments, the nano glass powder is a Pb-Si-B-Al-Zn glass powder, the D50 of the glass powder is 1-1.6 μm, and the D50 of the nano glass powder is 100-200 nm.

[0042] In some embodiments, the glass powder is also a Pb-Si-B-Al-Zn glass powder, and the nano glass powder is a glass powder with a D50 size of 100-200 nm obtained by grinding the glass by a sand mill for 50-200 times. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al, and 5% to 20% Zn.

[0043] In some embodiments, the glass powder is a P-Pb-Si-B-Bi-Ca-Al glass powder. Taking the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder as 100%, the second front glass powder includes 1% to 10% P, 20% to 30% Pb, 10% to 20% Si, 10% to 25% B, 5% to 20% Bi, 5% to 15% Al, and 5% to 20% Ca.

[0044] In some embodiments, the first organic carrier includes a first resin and a first solvent, the first resin includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, the first solvent includes one or more of benzyl benzoate, butyl benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate, and based on the mass percentage of the first organic carrier as 100%, the first organic carrier includes 10% to 30% of the first resin and 70% to 90% of the first solvent.

[0045] In some embodiments, the second organic carrier includes a second resin and a second solvent, the second resin includes one or more of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, the second solvent includes two or more of butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodeca, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and dibasic acid esters. Taking the total mass percentage of the second organic carrier as 100%, the second organic carrier includes 10% to 30% of the second resin and 70% to 90% of the second solvent.

[0046] The present application also provides an N-type TOPCON battery, wherein the raw material of the front fine grid of the N-type TOPCon battery includes the above-mentioned silver paste for the N-type TOPCon battery, and the N-type TOPCon battery is manufactured by LECO technology.

[0047] Embodiment 1:

[0048] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely, a first silver paste. Taking the total mass percentage content of the first silver paste as 100%, the mass fraction of silver powder is 85%, the mass fraction of glass powder is 1.5%, the mass fraction of the first organic carrier is 3.5%, the mass fraction of the second organic carrier is 3%, the mass fraction of additives is 1%, the mass fraction of polymer nano silver solution is 5%, and the mass fraction of nano glass powder is 1%.

[0049] The first organic carrier includes 30% of the first resin and 70% of the first solvent; the second organic carrier includes 10% of the second resin and 90% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer, and the first solvent includes benzyl benzoate, butyl benzoate, and diethylene glycol dibenzoate. The second resin includes ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester twelve, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and divalent acid ester. The D50 of the silver powder is 1.7μm, the mass ratio of the polymer carrier polyamide amine to the nano silver powder in the polymer nano silver solution is 1:3, and the D50 of the nano silver powder is 50nm.

[0050] The glass powder and the nano glass powder are Pb-Si-B-Al-Zn glass powders, the D50 of the nano glass powder is 100nm, and the D50 of the glass powder is 1.4μm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 45% Pb, 20% Si, 5% B, 10% Al, and 20% Zn.

[0051] The N-type TOPCon battery was produced using the first silver paste as raw material and LECO technology.

[0052] Embodiment 2:

[0053] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, i.e., a second silver paste. Taking the total mass percentage content of the second silver paste as 100%, the mass fraction of silver powder is 89%, the mass fraction of glass powder is 1%, the mass fraction of the first organic carrier is 7.8%, the mass fraction of the second organic carrier is 1%, the mass fraction of additives is 0.1%, the mass fraction of polymer nano silver solution is 1%, and the mass fraction of nano glass powder is 0.1%.

[0054] The first organic carrier includes 10% of the first resin and 90% of the first solvent; the second organic carrier includes 30% of the second resin and 70% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer, and the first solvent includes dipropylene glycol dibenzoate. The second resin includes ethyl cellulose, acrylic resin, polyvinyl butyral resin, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester twelve, and tributyl citrate. The D50 of the silver powder is 2.0μm, the mass ratio of the polymer carrier polyamide amine to the nano silver powder in the polymer nano silver solution is 1:2, and the D50 of the nano silver powder is 20nm.

[0055] The nano glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the nano glass powder is 200nm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 39% Pb, 10% Si, 30% B, 1% Al, and 20% Zn.

[0056] The glass powder is a P-Pb-Si-B-Bi-Ca-Al glass powder, and the D50 of the glass powder is 1 μm. Taking the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder as 100%, the second front glass powder includes 1% P, 20% Pb, 20% Si, 25% B, 20% Bi, 5% Al, and 9% Ca.

[0057] The N-type TOPCon battery was produced using the second silver paste as raw material and LECO technology.

[0058] Embodiment three:

[0059] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, i.e., a third silver paste. Taking the total mass percentage content of the third silver paste as 100%, the mass fraction of silver powder is 86%, the mass fraction of glass powder is 2%, the mass fraction of the first organic carrier is 2%, the mass fraction of the second organic carrier is 5%, the mass fraction of additives is 0.3%, the mass fraction of polymer nano silver solution is 4%, and the mass fraction of nano glass powder is 0.7%.

[0060] The first organic carrier includes 20% of the first resin and 80% of the first solvent; the second organic carrier includes 10% of the second resin and 90% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and the first solvent includes benzyl benzoate and diethylene glycol dibenzoate. The second resin includes ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodecahydrate, and tributyl citrate.

[0061] The D50 of the silver powder is 1.8 μm, the mass ratio of the polymer carrier polyamidoamine to the nano silver powder in the polymer nano silver solution is 1:1, and the D50 of the nano silver powder is 40 nm.

[0062] The glass powder and the nano glass powder are Pb-Si-B-Al-Zn glass powders, the D50 of the glass powder is 1.2 μm, and the D50 of the nano glass powder is 160 nm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 50% Pb, 15% Si, 20% B, 10% Al, and 5% Zn.

[0063] The N-type TOPCon battery is produced using the third silver paste as raw material and LECO technology.

[0064] Embodiment 4:

[0065] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, i.e., a fourth silver paste. Taking the total mass percentage content of the fourth silver paste as 100%, the mass fraction of silver powder is 86%, the mass fraction of glass powder is 2%, the mass fraction of the first organic carrier is 2%, the mass fraction of the second organic carrier is 5%, the mass fraction of additives is 0.3%, the mass fraction of polymer nano silver solution is 4%, and the mass fraction of nano glass powder is 0.7%.

[0066] The first organic carrier includes 20% of the first resin and 80% of the first solvent; the second organic carrier includes 10% of the second resin and 90% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and the first solvent includes benzyl benzoate and diethylene glycol dibenzoate. The second resin includes ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodecahydrate, and tributyl citrate.

[0067] The D50 of the silver powder is 1.8 μm, the mass ratio of the polymer carrier polyamidoamine to the nanosilver powder in the polymer nanosilver solution is 1:1, and the D50 of the nanosilver powder is 40 nm.

[0068] The nano glass powder and the glass powder are both Pb-Si-B-Al-Zn glass powders, the D50 of the nano glass powder is 160nm, and the D50 of the glass powder is 1.6μm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 50% Pb, 15% Si, 20% B, 10% Al, and 5% Zn.

[0069] The fourth silver paste was used as raw material and the N-type TOPCon battery was produced using the LECO technology.

[0070] Embodiment five:

[0071] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely, the fifth silver paste. Taking the total mass percentage content of the fifth silver paste as 100%, the mass fraction of silver powder is 85%, the mass fraction of glass powder is 1.5%, the mass fraction of the first organic carrier is 10%, the mass fraction of the second organic carrier is 1%, the mass fraction of additives is 1%, the mass fraction of polymer nano silver solution is 1%, and the mass fraction of nano glass powder is 0.5%.

[0072] The first organic carrier includes 30% of the first resin and 70% of the first solvent; the second organic carrier includes 20% of the second resin and 80% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer, and the first solvent includes benzyl benzoate and dipropylene glycol dibenzoate. The second resin includes rosin resin and polyester resin, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodecahydrate, tributyl citrate, dimethyl adipate, and dimethyl phthalate.

[0073] The D50 of the silver powder is 1.4 μm, the mass ratio of the polymer carrier polyamidoamine to the nanosilver powder in the polymer nanosilver solution is 1:3, and the D50 of the nanosilver powder is 50 nm.

[0074] The nano glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the nano glass powder is 100 nm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 30% Pb, 20% Si, 30% B, 5% Al, and 15% Zn.

[0075] The glass powder is a P-Pb-Si-B-Bi-Ca-Al glass powder, and the D50 of the glass powder is 1.0 μm. Taking the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder as 100%, the second front glass powder includes 9% P, 27% Pb, 11% Si, 18% B, 17% Bi, 13% Al, and 5% Ca.

[0076] Using the fifth silver paste as raw material, N-type TOPCon batteries were produced using LECO technology.

[0077] Embodiment six:

[0078] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely, the sixth silver paste. Taking the total mass percentage content of the sixth silver paste as 100%, the mass fraction of silver powder is 85%, the mass fraction of glass powder is 1.5%, the mass fraction of the first organic carrier is 10%, the mass fraction of the second organic carrier is 1%, the mass fraction of additives is 1%, the mass fraction of polymer nano silver solution is 1%, and the mass fraction of nano glass powder is 0.5%.

[0079] The first organic carrier includes 30% of the first resin and 70% of the first solvent; the second organic carrier includes 20% of the second resin and 80% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer, and the first solvent includes benzyl benzoate and dipropylene glycol dibenzoate. The second resin includes rosin resin and polyester resin, and the second solvent includes butyl carbitol, dimethyl adipate, and dimethyl phthalate.

[0080] The D50 of the silver powder is 1.4 μm, the mass ratio of the polymer carrier polyamidoamine to the nanosilver powder in the polymer nanosilver solution is 1:2, and the D50 of the nanosilver powder is 25 nm.

[0081] The glass powder and the nano glass powder are P-Pb-Si-B-Bi-Ca-Al glass powders, the D50 of the nano glass powder is 100nm, and the D50 of the glass powder is 1.4μm. Taking the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder as 100%, the second front glass powder includes 10% P, 30% Pb, 10% Si, 10% B, 5% Bi, 15% Al, and 20% Ca.

[0082] Using the sixth silver paste as raw material, N-type TOPCon batteries were produced using LECO technology.

[0083] Comparative Example 1:

[0084] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely the seventh silver paste. Taking the total mass percentage content of the seventh silver paste as 100%, the mass fraction of silver powder is 85%, the mass fraction of glass powder is 2%, the mass fraction of the first organic carrier is 10%, the mass fraction of the second organic carrier is 2%, and the mass fraction of additives is 1%.

[0085] The first organic carrier includes 10% of the first resin and 90% of the first solvent; the second organic carrier includes 30% of the second resin and 70% of the second solvent. The first resin includes styrene-butadiene-styrene block copolymer and hydrogenated styrene-butadiene block copolymer, and the first solvent includes benzyl benzoate, butyl benzoate, and diethylene glycol dibenzoate. The second resin includes polyester resin, and the second solvent includes butyl carbitol, butyl carbitol acetate, and divalent acid ester.

[0086] The D50 of the silver powder is 1.4 μm. The glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the glass powder is 1 μm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 50% Pb, 10% Si, 30% B, 5% Al, and 5% Zn.

[0087] Using the seventh silver paste as raw material, N-type TOPCon batteries were produced using LECO technology.

[0088] Comparative Example 2:

[0089] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely, the eighth silver paste. Taking the total mass percentage content of the eighth silver paste as 100%, the mass fraction of silver powder is 89%, the mass fraction of glass powder is 1%, the mass fraction of the first organic carrier is 2%, the mass fraction of the second organic carrier is 2%, the mass fraction of additives is 1%, and the mass fraction of polymer nano silver solution is 5%.

[0090] The first organic carrier includes 20% of the first resin and 80% of the first solvent; the second organic carrier includes 10% of the second resin and 90% of the second solvent. The first resin includes styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and the first solvent includes triethylene glycol dibenzoate and dipropylene glycol dibenzoate. The second resin includes polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, and the second solvent includes butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester twelve, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and divalent acid ester.

[0091] The D50 of the silver powder is 2.0 μm, the mass ratio of the polymer carrier polyamidoamine to the nano silver powder in the polymer nano silver solution is 1:1, and the D50 of the nano silver powder is 50 nm.

[0092] The glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the glass powder is 1.6 μm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 30% Pb, 20% Si, 30% B, 10% Al, and 10% Zn.

[0093] The N-type TOPCon battery was produced using the eighth silver paste as raw material and LECO technology.

[0094] Comparative Example 3:

[0095] This embodiment provides a front fine grid silver paste for an N-type TOPCON battery, namely, the ninth silver paste. Taking the total mass percentage content of the ninth silver paste as 100%, the mass fraction of silver powder is 86%, the mass fraction of glass powder is 2%, the mass fraction of the first organic carrier is 6%, the mass fraction of the second organic carrier is 4%, the mass fraction of additives is 1%, and the mass fraction of nano glass powder is 1%.

[0096] The first organic carrier includes 30% of a first resin and 70% of a first solvent; the second organic carrier includes 10% of a second resin and 90% of a second solvent. The first resin includes styrene-butadiene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, the first solvent includes benzyl benzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate. The second resin includes ethyl cellulose, and the second solvent includes butyl carbitol and butyl carbitol acetate.

[0097] The D50 of the silver powder is 1.7 μm. The nano glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the nano glass powder is 150 nm. The glass powder is also a Pb-Si-B-Al-Zn glass powder, and the D50 of the glass powder is 1.5 μm. Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 35% Pb, 15% Si, 20% B, 10% Al, and 20% Zn.

[0098] The glass powder is a P-Pb-Si-B-Bi-Ca-Al glass powder, and the D50 of the glass powder is 1-1.6 μm. Taking the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder as 100%, the second front glass powder includes 10% P, 30% Pb, 10% Si, 10% B, 20% Bi, 15% Al, and 5% Ca.

[0099] Using the ninth silver paste as raw material, N-type TOPCon batteries were produced using LECO technology.

[0100] The photoelectric conversion efficiency of the batteries prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was tested, and the data was recorded. The test results are shown in Table 1.

[0101] Table 1 Cell test results Cell open circuit voltage V Short circuit current A Photoelectric conversion efficiency %

[0102] Example 1 0.7194 13.673 25.72

[0103] Example 2 0.7202 13.680 25.67

[0104] Example 3 0.7212 13.679 25.77

[0105] Example 4 0.7198 13.678 25.65

[0106] Example 5 0.7189 13.712 25.69

[0107] Example 6 0.7192 13.682 25.75

[0108] Comparative Example 1 0.7102 13.644 25.24

[0109] Comparative Example 2 0.7157 13.649 25.35

[0110] Comparative Example 3 0.7175 13.654 25.40

[0111] In Comparative Example 1, nano glass powder and polymer nano silver solution were not introduced, in Comparative Example 2, nano glass powder was not introduced, and in Comparative Example 3, polymer nano silver solution was not introduced. After the introduction of nano glass powder and polymer nano silver solution, the open circuit voltage was significantly improved, the short circuit current was also significantly improved, and the photoelectric conversion efficiency was significantly improved. Therefore, the silver paste provided in this application is combined with the LECO technology sintering process to achieve an improvement in the photoelectric conversion efficiency of the N-type TOPcon battery.

[0112] This application introduces polymer nano silver and nano glass powder. Compared with micron-level and submicron-level silver powder, they have the characteristics of good dispersibility, uniform particles, high activity, low melting temperature, etc., and can be better matched with nano glass powder. The Ag-Si spikes formed with the silicon substrate are smaller and the damage to the PN junction is small. At the same time, the Ag-Si alloy formation process is mainly the diffusion of silver atoms into the silicon wafer surface. Smaller and better dispersed nano silver can diffuse into the silicon wafer surface faster, which can well optimize the contact, reduce recombination, and increase the open circuit voltage and short circuit current.

[0113] The present application provides a front fine grid silver paste for an N-type TOPCON battery, and the silver paste is used in a LECO process. The silver paste comprises silver powder, a polymer nano silver solution, glass powder, nano glass powder, a first organic carrier, a second organic carrier and an additive, wherein the mass fraction of the polymer nano silver solution in the silver paste is 1% to 5%, and the mass fraction of the nano glass powder is 0.1% to 1%.

[0114] The polymer nanosilver solution improves the contact performance during the N-type TOPCON laser-assisted sintering process, reduces the composite, and increases the open circuit voltage and short circuit current. Compared with micron-level glass powder, nano glass powder reduces the single-point etching area, increases the etching distribution density, and achieves ultra-low contact resistance. At the same time, due to the shallower etching depth, low metal composite, and less damage to the P+ layer, it can effectively increase the open circuit voltage and achieve the purpose of improving efficiency. It solves the problem that in the process of preparing N-type TOPCON batteries with LECO technology, the silver atoms diffuse slowly into the silicon wafer surface, affecting the open circuit voltage and short circuit current, resulting in low photoelectric conversion efficiency.

[0115] The present application also provides an N-type TOPCON battery, wherein the raw material of the fine grid on the front side of the battery includes the above-mentioned silver paste for the N-type TOPCon battery, and the N-type TOPCon battery is manufactured by LECO technology.

[0116] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the general concept of this application and do not constitute a limitation on the protection scope of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without creative work belong to the protection scope of this application.

Claims

1. A front fine grid silver paste for N-type TOPCON battery, characterized in that: The silver paste comprises silver powder, polymer nano silver solution, glass powder, nano glass powder, a first organic carrier, a second organic carrier and additives. The mass fraction of the polymer nano silver solution in the silver paste is 1% to 5%, and the mass fraction of the nano glass powder is 0.1% to 1%.

2. The silver paste according to claim 1, characterized in that In the silver paste, the mass fraction of silver powder is 85% to 89%, the mass fraction of glass powder is 1% to 2%, the mass fraction of the first organic carrier is 2% to 10%, the mass fraction of the second organic carrier is 1% to 5%, and the mass fraction of additives is 0.1% to 1%.

3. The silver paste according to claim 1, characterized in that The polymer nano silver solution comprises a polymer carrier and nano silver powder, wherein the polymer carrier is a polyamidoamine dendrimer, and the D50 of the nano silver powder is 20-50 nm.

4. The silver paste according to claim 3, characterized in that The mass ratio of the polymer carrier to the nano silver powder in the polymer nano silver solution is 1:1 to 1:

3.

5. The silver paste according to claim 1, characterized in that The silver powder is spherical silver powder, and the D50 of the silver powder is 1.4-2.0 μm.

6. The silver paste according to claim 1, characterized in that The nano glass powder is a Pb-Si-B-Al-Zn glass powder, the D50 of the glass powder is 1-1.6 μm, and the D50 of the nano glass powder is 100-200 nm.

7. The silver paste according to claim 6, characterized in that Taking the total molar percentage content of the Pb-Si-B-Al-Zn glass powder as 100%, the Pb-Si-B-Al-Zn glass powder includes 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al, and 5% to 20% Zn.

8. The silver paste according to claim 1, characterized in that The first organic carrier includes a first resin and a first solvent, wherein the first resin includes one or more of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and the first solvent includes one or more of benzyl benzoate, ethylene glycol butyl ether benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate. Taking the mass percentage of the first organic carrier as 100%, the first organic carrier includes 10% to 30% of the first resin and 70% to 90% of the first solvent.

9. The silver paste according to claim 1, characterized in that: The second organic carrier includes a second resin and a second solvent, the second resin includes one or more of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, the second solvent includes two or more of butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester dodecahydrate, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and dibasic acid esters, and based on the total mass percentage of the second organic carrier as 100%, the second organic carrier includes 10% to 30% of the second resin and 70% to 90% of the second solvent.

10. An N-type TOPCON battery, characterized in that: The raw material of the N-type TOPCon battery front fine grid includes the silver paste for N-type TOPCon battery according to any one of claims 1 to 9.

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