Front side fine grid silver paste for N-type topcon cell and cell

Abstract

The application provides a front fine grid silver paste for N-type TOPCON cells and a cell, and the silver paste is applied in a LECO process. The high-molecular nano-silver solution in the silver paste improves the contact performance in the N-type TOPCON laser-assisted sintering process, reduces the recombination, and improves the open circuit voltage and short circuit current. Compared with the micron-sized glass powder, the nano glass powder in the silver paste reduces the single-point etching area, increases the etching distribution density, and has ultra-low contact resistance. At the same time, due to the shallow etching depth, the metal recombination is low, the open circuit voltage can be effectively improved, and the efficiency can be improved. The application solves the problem that in the process of preparing the N-type TOPCON cell by the LECO technology, the silver atoms diffuse into the surface of the silicon wafer at a slow speed, which affects the open circuit voltage and short circuit current, and results in a low photoelectric conversion efficiency. The application also provides a cell, and the cell is prepared by the LECO technology, and the raw materials include the above-mentioned silver paste for N-type TOPCon cells.

Description

TECHNICAL FIELD

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

[0002] TOPCon is a kind of tunnel oxide passivated contact (Tunne l Oxide Pass ivated Contact) solar cell technology based on the principle of selective carrier, and the cell structure is N-type silicon substrate cell. A layer of ultra-thin silicon oxide is prepared on the back of the cell, and then a layer of doped silicon thin layer is deposited, which forms a passivation contact structure together, effectively reduces the surface recombination and metal contact recombination, and provides more space for further improvement of cell conversion efficiency. Laser-assisted sintering technology, also known as laser-enhanced contact optimization (Laser-enhanced contact optimization (LECO)), is used to improve the contact between the metal electrode and the silicon wafer in the solar cell. In the LECO process, laser is 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 paste used for LECO process also shows a small increase in open-circuit voltage and short-circuit current.

[0003] In the manufacturing process of photovoltaic cells, especially for TOPCon (Tunne l Oxide Pass ivated 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 a balance point 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 micron-sized silver powder used in the conventional silver paste has a relatively high sintering activity, and the activity of the polymeric nanosilver solution is relatively low. During laser-assisted sintering, the diffusion reaction between the silver powder and the silicon substrate is slow, and it is not easy for the silver powder to enter the silicon substrate through the etched channel to form AgSi alloy by metal recombination.

[0004] In order to solve the problem that the speed of silver atoms diffusing into the surface of the silicon wafer is slow during the preparation of N-type TOPCON cells by LECO technology, which affects the open-circuit voltage and short-circuit current and leads to low photoelectric conversion efficiency, the present application provides a front fine grid silver paste for N-type TOPCON cells and a cell. SUMMARY

[0005] To solve the problem of slow diffusion of silver atoms into the surface of the silicon wafer, affecting the open-circuit voltage and short-circuit current, and resulting in low photoelectric conversion efficiency in the process of preparing N-type TOPCON cells by LECO technology, the present application provides a kind of N-type TOPCON cell with fine grid silver paste on the front side, which includes silver powder, high molecular nano silver solution, glass powder, nano glass powder, first organic carrier, second organic carrier and additive, the mass fraction of high molecular nano silver solution in the silver paste is 1% to 5%, and the mass fraction of nano glass powder is 0.1% to 1%.

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

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

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

[0009] c) Cooling and solidification: after laser processing, the sintering area begins to cool down. The metal connection between silver particles solidifies, forming a firm electrode.

[0010] Under the laser-assisted sintering process, nano glass powder compared with micron glass powder, reduces the etching area of single point, increases the etching distribution density, (for example, 1 μm glass powder is replaced by 500 nm glass powder, the number of glass powder particles increases 4 times, then the total etching area increases 4 times, effectively improves the contact area, improves the contact), realizes ultra-low contact resistance, at the same time, due to the shallow etching depth, metal complex is low, the damage to P+ layer is small, which can effectively improve the open-circuit voltage, achieves the purpose of improving efficiency.

[0011] The micron-sized silver powder used in the conventional silver paste has a relatively high sintering activity, and the high-molecular nano silver solution has a relatively low sintering activity. In laser-assisted sintering, the diffusion reaction between the high-molecular nano silver solution and the silicon substrate is relatively slow. The high-molecular nano silver solution has a small particle size and a high activity, and can easily enter the silicon substrate through the channel etched by the nano glass to form AgSi alloy and conductive channels, so as to improve the open voltage and short-circuit current and achieve the purpose of improving the efficiency. In the silver paste formula, the high-molecular nano silver solution has good dispersibility, high silver activity, and can be easily melted to form Ag-Si alloy with the silicon substrate, so as to optimize the contact, reduce the composite, improve the open voltage and short-circuit current, and reduce the etching area of the single point compared with the micron-sized glass powder. The etching distribution density is increased, the contact is ensured, the etching depth is shallow, the metal composite is low, the damage to the P+ layer is small, the open voltage can be effectively improved, and the purpose of improving the efficiency is achieved.

[0012] Optionally, the mass fraction of the silver powder in the silver paste is 85% to 89%, the mass fraction of the 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 high-molecular nano silver solution comprises a high-molecular carrier and nano silver powder, the high-molecular carrier is a polyamidoamine dendrimer, and the D50 of the nano silver powder is 20-50 nm.

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

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

[0015] Optionally, the nano glass powder is 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, based on the total molar percentage content of the Pb-Si-B-Al-Zn glass powder being 100%, the Pb-Si-B-Al-Zn glass powder comprises 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 comprises a first resin and a first solvent, the first resin comprises one or more of styrene-diene-styrene block copolymer, hydrogenated styrene-diene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and the first solvent comprises one or more of benzyl benzoate, ethylene glycol butyl ether benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate, and the first organic carrier comprises 10-30% of the first resin and 70-90% of the first solvent, based on 100% of the mass percentage of the first organic carrier.

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

[0019] The application also provides an N-type TOPCON cell, and a raw material of a front fine grid of the N-type TOPCON cell comprises the silver paste for the N-type TOPCON cell.

[0020] Optionally, the N-type TOPCon cell is prepared by LECO technology.

[0021] The application introduces high-molecular nano-silver and nano-glass powder, which has the characteristics of good dispersibility, uniform particles, high activity, low melting temperature, etc. compared with micron and submicron silver powder, and can better match with nano-glass powder and form smaller Ag-Si spikes with the silicon substrate, cause less damage to the P-N junction, and the Ag-Si alloy formation process is mainly the diffusion of silver atoms into the surface of the silicon wafer. Smaller and better dispersed nano-silver can diffuse into the surface of the silicon wafer faster, which can optimize the contact, reduce the recombination, and improve the open-circuit voltage and short-circuit current.

[0022] The application provides a front fine grid silver paste for an N-type TOPCON cell, which is applied in the LECO processing process. The silver paste comprises silver powder, high-molecular nano-silver solution, glass powder, nano-glass powder, first organic carrier, second organic carrier and additives, the mass fraction of the high-molecular nano-silver solution in the silver paste is 1-5%, and the mass fraction of the nano-glass powder is 0.1-1%.

[0023] The high polymer nano-silver solution in the formula can improve the contact performance in the N-type TOPCON laser-assisted sintering process, reduce the recombination, and improve the open circuit voltage and short circuit current. Compared with the micron-sized glass powder, the nano glass powder reduces the single-point etching area, increases the etching distribution density, and has ultra-low contact resistance. At the same time, due to the shallower etching depth, the metal recombination is low, the damage to the P+ layer is small, the open circuit voltage can be effectively improved, and the purpose of improving the efficiency is achieved. The application also provides an N-type TOPCON battery, and the raw material of the positive fine grid of the battery comprises the silver paste for the N-type TOPCon battery. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 It is a schematic diagram of the N-type TOPCon battery structure. DETAILED DESCRIPTION

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

[0027] The N-type TOPCon battery structure is shown in Figure 1 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 (1-2 nm) and a phosphorus-doped microcrystalline and amorphous mixed Si thin film, which together form a passivation contact structure. The passivation performance is activated by an annealing process, and the Si thin film changes in crystallinity during the annealing process, from a microcrystalline and amorphous mixed phase to a polycrystalline phase. Annealing at an annealing temperature of 850 DEG C.

[0028] The structure can block the hole-electron recombination, improve the open circuit voltage and short circuit current of the battery. The ultra-thin oxide layer can make the hole-electron tunnel into the polycrystalline silicon layer while blocking the hole-electron recombination. The good passivation effect of the ultra-thin silicon oxide and the heavily doped silicon thin film makes the energy band of the silicon wafer surface curve, thereby forming a field passivation effect. The probability of electron tunneling is greatly increased, the contact resistance is reduced, the open circuit voltage and short circuit current of the battery are improved, and the conversion efficiency of the battery is improved.

[0029] In order to solve the problem of low photoelectric conversion efficiency caused by slow diffusion of silver atoms into the surface of the silicon wafer, affecting the open circuit voltage and short circuit current during the preparation of N-type TOPCON cells by LECO technology, the application provides a front fine grid silver paste for N-type TOPCON cells, which comprises silver powder, high molecular nano-silver solution, glass powder, nano glass powder, first organic carrier, second organic carrier and additive. The mass fraction of high molecular nano-silver solution in the silver paste is 1% to 5%, and the mass fraction of nano glass powder is 0.1% to 1%.

[0030] In LECO processing, the micro changes between silver paste and cell wafer are as follows:

[0031] a) Local destruction of passivation layer: hot spots caused by laser heating can locally destroy the passivation layer on the silicon wafer. This is a precisely controlled physical process. The passivation layer is destroyed to enable silver to form direct contact with the silicon wafer and establish an effective electron transport 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 processing, the sintering area begins to cool down. The metal connection between silver particles solidifies to form a firm electrode.

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

[0035] The micron-sized silver powder used in the conventional silver paste has a relatively high sintering activity, and the high polymer nano silver solution has a relatively low sintering activity. When laser-assisted sintering is performed, the diffusion reaction between the high polymer nano silver solution and the silicon substrate is relatively slow. The high polymer nano silver solution has a small particle size and a high activity, and can more easily enter the silicon substrate through the channel etched by the nano glass to form AgSi alloy and form a conductive channel, so as to improve the open voltage and short circuit current and achieve the purpose of improving the efficiency. The high polymer nano silver solution is introduced into the paste formula. The high polymer nano silver solution has good dispersibility, high silver activity, and is easy to melt and form Ag-Si alloy with the silicon substrate, so as to optimize the contact, reduce the composite, improve the open voltage and short circuit current, and reduce the etching area of the single point compared with the micron-sized glass powder. The etching distribution density is increased, the contact is ensured, the etching depth is shallow, the metal composite is low, the damage to the P+ layer is small, the open voltage can be effectively improved, and the purpose of improving the efficiency is achieved.

[0036] In some embodiments, the mass fraction of the silver powder in the silver paste is 85% to 89%, the mass fraction of the 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 high polymer nano silver solution comprises a high polymer carrier and nano silver powder. The high polymer carrier is a polyamidoamine dendrimer, and the D50 of the nano silver powder is 20-50 nm. The nano silver powder is slowly added into the high polymer carrier, and the high polymer nano silver solution is obtained by stirring at room temperature for 30 minutes.

[0038] The polyamidoamine (PAMAM) dendrimer has a precise molecular structure, a large number of surface functional groups, and a cavity in the molecule. The polyamidoamine dendrimer can be easily functionalized by core modification or surface modification, so the polyamidoamine dendrimer is a good template for preparing nano materials. The nano materials have a small size and a large surface energy, and are easy to agglomerate during preparation. The polyamidoamine dendrimer is introduced as a carrier to solve the agglomeration problem of the nano silver.

[0039] In some embodiments, the mass ratio of the high polymer carrier to the nano silver powder in the high polymer nano silver 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 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 system glass powder, and the nano glass powder is obtained by grinding the glass 50-200 times by a sand mill to obtain a nano glass powder with a D50 size of 100-200 nm. In terms of the total molar percentage content of the Pb-Si-B-Al-Zn system glass powder being 100%, the Pb-Si-B-Al-Zn system glass powder comprises 30%-50% Pb, 10%-20% Si, 5%-30% B, 1%-10% Al, and 5%-20% Zn.

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

[0044] In some embodiments, the first organic carrier comprises one or more of a first resin and a first solvent, the first resin comprises one or more of a styrene-butadiene-styrene block copolymer, a hydrogenated styrene-butadiene block copolymer, a styrene-isoprene-styrene block copolymer, and a hydrogenated styrene-isoprene block copolymer, and the first solvent comprises one or more of benzyl benzoate, ethylene glycol butyl ether benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate, and dipropylene glycol dibenzoate, and in terms of the mass percentage of the first organic carrier being 100%, the first organic carrier comprises 10%-30% first resin and 70%-90% first solvent.

[0045] In some embodiments, the second organic carrier comprises one or more of a second resin and a second solvent, the second resin comprises one or more of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin, and polyester resin, and the second solvent comprises two or more of butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester twelve, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate, and bivalent acid ester, and in terms of the total mass percentage of the second organic carrier being 100%, the second organic carrier comprises 10%-30% second resin and 70%-90% second solvent.

[0046] The application also provides an N-type TOPCON cell, a raw material of a front fine grid of the N-type TOPCON cell comprises the above-mentioned silver paste for the N-type TOPCON cell, and the N-type TOPCON cell is prepared by LECO technology.

[0047] Embodiment one:

[0048] The embodiment provides a front fine grid silver paste for an N-type TOPCON cell, namely, a first silver paste. In terms of 100% of total mass percentage content of the first silver paste, the mass fraction of silver powder is 85%, the mass fraction of glass powder is 1.5%, the mass fraction of a first organic carrier is 3.5%, the mass fraction of a second organic carrier is 3%, the mass fraction of an additive is 1%, the mass fraction of a high-molecular nano-silver solution is 5%, and the mass fraction of nano glass powder is 1%.

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

[0050] The glass powder and the nano glass powder are Pb-Si-B-Al-Zn system glass powder, the D50 of the nano glass powder is 100 nm, and the D50 of the glass powder is 1.4 μm. In terms of 100% of total mole percentage content of the Pb-Si-B-Al-Zn system glass powder, the Pb-Si-B-Al-Zn system glass powder comprises 45% of Pb, 20% of Si, 5% of B, 10% of Al and 20% of Zn.

[0051] The N-type TOPCon cell is prepared by using the first silver paste as raw material and using the LECO technology.

[0052] Embodiment two:

[0053] The embodiment provides a front fine grid silver paste for an N-type TOPCON cell, namely, a second silver paste. In terms of 100% of total mass percentage content of the second silver paste, the mass fraction of silver powder is 89%, the mass fraction of glass powder is 1%, the mass fraction of a first organic carrier is 7.8%, the mass fraction of a second organic carrier is 1%, the mass fraction of an additive is 0.1%, the mass fraction of a high-molecular 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; and the second organic carrier includes 30% of the second resin and 70% of the second solvent. The first resin includes a styrene-butadiene-styrene block copolymer, and the first solvent includes dipropylene glycol dibenzoate. The second resin includes ethyl cellulose, an acrylic resin, and a 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 2.0 μm, the mass ratio of the polymeric carrier polyamide amine to the nano silver powder in the polymeric nano silver solution is 1:2, and the D50 of the nano silver powder is 20 nm.

[0055] The nano glass powder is a Pb-Si-B-Al-Zn glass powder, and the D50 of the nano glass powder is 200 nm. In terms of the total molar percentage content of the Pb-Si-B-Al-Zn glass powder being 100%, the Pb-Si-B-Al-Zn glass powder includes 39% of Pb, 10% of Si, 30% of B, 1% of Al, and 20% of 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. In terms of the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder being 100%, the second front glass powder includes 1% of P, 20% of Pb, 20% of Si, 25% of B, 20% of Bi, 5% of Al, and 9% of Ca.

[0057] The second silver paste is used as a raw material to prepare an N-type TOPCon cell by using a LECO technology.

[0058] Embodiment Three

[0059] The embodiment provides a front fine grid silver paste for an N-type TOPCon cell, namely a third silver paste. In terms of the total mass percentage content of the third silver paste being 100%, the mass fraction of the silver powder is 86%, the mass fraction of the 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 the additive is 0.3%, the mass fraction of the polymeric nano silver solution is 4%, and the mass fraction of the 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, 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 twelve, tributyl citrate.

[0061] The D50 of the silver powder is 1.8 μm, the mass ratio of the polymeric carrier polyamide amine to the nano silver powder in the polymeric 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 system glass powder, the D50 of the glass powder is 1.2 μm, and the D50 of the nano glass powder is 160 nm. The Pb-Si-B-Al-Zn system glass powder includes 50% of Pb, 15% of Si, 20% of B, 10% of Al and 5% of Zn, with the total mole percentage content of the Pb-Si-B-Al-Zn system glass powder being 100%.

[0063] The third silver paste is used as raw material to prepare the N-type TOPCon cell by using LECO technology.

[0064] Embodiment Four

[0065] The embodiment provides a front fine grid silver paste for an N-type TOPCON cell, i.e., a fourth silver paste. The mass fraction of the silver powder is 86%, the mass fraction of the 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 the additive is 0.3%, the mass fraction of the polymeric nano silver solution is 4%, and the mass fraction of the nano glass powder is 0.7%, with the total mass percentage content of the fourth silver paste being 100%.

[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, 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 twelve, tributyl citrate.

[0067] The D50 of the silver powder is 1.8 pm, the mass ratio of the polymeric carrier polyamide amine to the nano silver powder in the polymeric nano silver solution is 1:1, and the D50 of the nano silver powder is 40 nm.

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

[0069] The fourth silver paste is used as a raw material to prepare the N-type TOPCon cell by using the LECO technology.

[0070] Embodiment five:

[0071] The embodiment provides a front fine grid silver paste for an N-type TOPCon cell, namely a fifth silver paste. The mass percentage of silver powder is 85%, the mass percentage of glass powder is 1.5%, the mass percentage of a first organic carrier is 10%, the mass percentage of a second organic carrier is 1%, the mass percentage of an additive is 1%, the mass percentage of a polymeric nano silver solution is 1%, and the mass percentage of nano glass powder is 0.5%, with the total mass percentage content of the fifth silver paste being 100%.

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

[0073] The D50 of the silver powder is 1.4 pm, the mass ratio of the polymeric carrier polyamide amine to the nano silver powder in the polymeric nano silver solution is 1:3, and the D50 of the nano silver powder is 50 nm.

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

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

[0076] An N-type TOPCon cell is prepared by using the fifth silver paste as a raw material and by using a LECO technology.

[0077] Example Six

[0078] The present embodiment provides a front fine grid silver paste for an N-type TOPCON cell, i.e., a sixth silver paste. The mass fraction of the silver powder is 85%, the mass fraction of the 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 the additive is 1%, the mass fraction of the high-molecular nano-silver solution is 1%, and the mass fraction of the nano-glass powder is 0.5%, based on a total mass percentage content of the sixth silver paste being 100%.

[0079] The first organic carrier includes 30% of a first resin and 70% of a first solvent, and the second organic carrier includes 20% of a second resin and 80% of a second solvent. The first resin includes a styrene-butadiene-styrene block copolymer, and the first solvent includes benzyl benzoate, dipropylene glycol dibenzoate. The second resin includes a rosin resin and a 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 high-molecular polyamide amine carrier to the nano-silver powder in the high-molecular nano-silver solution is 1:2, and the D50 of the nano-silver powder is 25 nm.

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

[0082] An N-type TOPCon cell is prepared by using the sixth silver paste as a raw material and by using a LECO technology.

[0083] Comparative Example One

[0084] The embodiment provides a front fine grid silver paste for N-type TOPCON cells, namely, seventh silver paste. 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% in the seventh silver paste, with the total mass percentage content of the seventh silver paste being 100%.

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

[0086] The D50 of the silver powder is 1.4 μm. The glass powder is Pb-Si-B-Al-Zn system glass powder, and the D50 of the glass powder is 1 μm. The Pb-Si-B-Al-Zn system glass powder comprises 50% Pb, 10% Si, 30% B, 5% Al and 5% Zn, with the total mole percentage content of the Pb-Si-B-Al-Zn system glass powder being 100%.

[0087] The seventh silver paste is used as raw material to prepare an N-type TOPCon cell by using LECO technology.

[0088] Comparative Example Two

[0089] The embodiment provides a front fine grid silver paste for N-type TOPCON cells, namely, eighth silver paste. 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 high-molecular nano-silver solution is 5% in the eighth silver paste, with the total mass percentage content of the eighth silver paste being 100%.

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

[0091] The D50 of the silver powder is 2.0 μm, the mass ratio of the polymeric carrier polyamide amine to the nano silver powder in the polymeric 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. The Pb-Si-B-Al-Zn glass powder includes 30% Pb, 20% Si, 30% B, 10% Al, and 10% Zn, with the total molar percentage content of the Pb-Si-B-Al-Zn glass powder being 100%.

[0093] The eighth silver paste is used as a raw material to prepare an N-type TOPCon cell by using the LECO technology.

[0094] Comparative Example Three

[0095] The present embodiment provides a front-side fine-grid silver paste for an N-type TOPCon cell, i.e., a ninth silver paste. The mass fraction of the silver powder is 86%, the mass fraction of the 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 the additive is 1%, and the mass fraction of the nano glass powder is 1%, with the total mass percentage content of the ninth silver paste being 100%.

[0096] The first organic carrier includes 30% first resin and 70% first solvent, and the second organic carrier includes 10% second resin and 90% second solvent. The first resin includes styrene-butadiene-styrene block copolymer and hydrogenated styrene-isoprene block copolymer, and 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. The Pb-Si-B-Al-Zn glass powder includes 35% Pb, 15% Si, 20% B, 10% Al, and 20% Zn, with the total molar percentage content of the Pb-Si-B-Al-Zn glass powder being 100%.

[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. In terms of the total molar percentage content of the P-Pb-Si-B-Bi-Ca-Al glass powder being 100%, the second front glass powder comprises 10% P, 30% Pb, 10% Si, 10% B, 20% Bi, 15% Al, and 5% Ca.

[0099] The ninth silver paste is used as a raw material to prepare an N-type TOPCon battery by using the LECO technology.

[0100] 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 are tested for photoelectric conversion efficiency, and the data are recorded. The test results are shown in Table 1.

[0101] Table 1 Battery test results 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] No nano glass powder and high molecular nano silver solution are introduced in Comparative Example 1, no nano glass powder is introduced in Comparative Example 2, and no high molecular nano silver solution is introduced in Comparative Example 3. After the introduction of the nano glass powder and the high molecular nano silver solution, the open-circuit voltage is obviously improved, the short-circuit current is also obviously improved, and the photoelectric conversion efficiency is obviously improved. Therefore, the silver paste provided in the present application can realize the improvement of the photoelectric conversion efficiency of the N-type TOPcon battery by using the LECO sintering process.

[0112] The application introduces high molecular nano silver and nano glass powder, which has the characteristics of good dispersity, uniform particles, high activity, low melting temperature, etc. compared with micron and submicron silver powder, can better match with nano glass powder, form smaller Ag-Si spikes with silicon substrate, cause less damage to P-N junction, and the Ag-Si alloy formation process is mainly the diffusion of silver atoms into the surface of the silicon wafer. Smaller and better dispersed nano silver can diffuse into the surface of the silicon wafer faster, which can optimize the contact, reduce the recombination, and improve the open circuit voltage and short circuit current.

[0113] The application provides a front fine grid silver paste for N-type TOPCON cells, which is applied in the LECO process. The silver paste includes silver powder, high molecular nano silver solution, glass powder, nano glass powder, first organic carrier, second organic carrier and additives, the mass fraction of the high molecular nano silver solution in the silver paste is 1-5%, and the mass fraction of the nano glass powder is 0.1-1%.

[0114] The high molecular nano silver solution in the application improves the contact performance in the N-type TOPCON laser-assisted sintering process, reduces the recombination, improves the open circuit voltage and short circuit current. The nano glass powder reduces the single-point etching area compared with micron glass powder, increases the etching distribution density, and has ultra-low contact resistance. At the same time, due to the shallow etching depth, the metal recombination is low, the damage to the P+ layer is small, the open circuit voltage can be effectively improved, and the efficiency can be improved. The application solves the problem that the speed of silver atoms diffusing into the surface of the silicon wafer is slow in the process of preparing N-type TOPCON cells by LECO technology, which affects the open circuit voltage and short circuit current and leads to low photoelectric conversion efficiency.

[0115] The application also provides an N-type TOPCON cell, and the raw material of the front fine grid of the cell includes the above-mentioned silver paste for N-type TOPCon cells, and the N-type TOPCon cell is prepared by LECO technology.

[0116] The similar parts among the embodiments provided by the application can be referred to each other, the specific embodiments provided above are only some examples under the general concept of the application, and do not limit the protection scope of the application. Any other embodiments extended according to the application scheme without creative labor belong to the protection scope of the application for those skilled in the art.

Claims

1. A front side fine grid silver paste for N-type TOPCON cells, characterized in that, The silver paste comprises silver powder, high-molecular nano-silver solution, glass powder, nano glass powder, first organic carrier, second organic carrier and additive, wherein, in terms of the total mass percentage content of the silver paste, the mass fraction of the silver powder in the silver paste is 85% to 89%, the mass fraction of the 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%; the mass fraction of the high-molecular 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%; the high-molecular nano-silver solution comprises a high-molecular carrier and nano silver powder, the high-molecular carrier is polyamidoamine dendrimer, the D50 of the silver powder is 1.4 to 2.0 microns, the D50 of the nano silver powder is 20 to 50 nanometers, the D50 of the glass powder is 1 to 1.6 microns, the D50 of the nano glass powder is 100 to 200 nanometers, and the mass ratio of the high-molecular carrier to the nano silver powder in the high-molecular nano-silver solution is 1:1 to 1:

3.

2. The silver paste according to claim 1, characterized in that, The silver powder is spherical silver powder.

3. The silver paste according to claim 1, characterized in that, The nano glass powder is Pb-Si-B-Al-Zn system glass powder.

4. The silver paste according to claim 3, characterized in that, In terms of the total mole percentage content of the Pb-Si-B-Al-Zn system glass powder, the Pb-Si-B-Al-Zn system glass powder comprises 30% to 50% Pb, 10% to 20% Si, 5% to 30% B, 1% to 10% Al and 5% to 20% Zn.

5. The silver paste according to claim 1, characterized in that, The first organic carrier comprises a first resin and a first solvent, the first resin comprises 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 comprises one or more of benzyl benzoate, ethylene glycol butyl ether benzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate and dipropylene glycol dibenzoate; in terms of the mass percentage of the first organic carrier, the first organic carrier comprises 10% to 30% first resin and 70% to 90% first solvent.

6. The silver paste according to claim 1, characterized in that, The second organic carrier comprises a second resin and a second solvent, the second resin comprises one or more of ethyl cellulose, acrylic resin, polyvinyl butyral resin, cellulose acetate butyrate, rosin resin and polyester resin, and the second solvent comprises two or more of butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, alcohol ester twelve, tributyl citrate, dimethyl adipate, dimethyl phthalate, dioctyl phthalate and divalent acid ester; in terms of the total mass percentage of the second organic carrier, the second organic carrier comprises 10% to 30% second resin and 70% to 90% second solvent.

7. An N-type TOPCON cell, characterized in that, The raw material of the N-type TOPCon cell positive surface fine grid comprises the silver paste of any one of claims 1 to 6.

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