N-type ibc cell positive grid line silver-aluminum paste, n-type ibc cell and preparation method thereof

Abstract

The embodiment of the present application provides a N-type IBC battery positive electrode grid line silver-aluminum paste, a N-type IBC battery and a preparation method thereof, wherein the N-type IBC battery positive electrode grid line silver-aluminum paste provided by the embodiment of the present application comprises an organic additive, silver powder, aluminum powder, boron powder, gallium powder, an organic binder and glass powder. By adding the silver powder, the boron powder and the gallium powder in the positive electrode grid line paste, printing on the passivation layer area above the p+ doped area, and then performing high-temperature sintering, the positive electrode grid line can be in contact with the p+ doped area and formed, the step of secondary laser slotting is saved, the passivation layer is prevented from being damaged by the secondary laser slotting, the formation of metal recombination centers is reduced, and the open-circuit voltage of the battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of crystalline silicon solar cell manufacturing technology, and in particular to an N-type IBC cell positive electrode grid line silver-aluminum paste, an N-type IBC cell, and a method for preparing the same. Background Technology

[0002] Interdigitated Back Contact (IBC) batteries are a new type of battery in which the P / N junction, substrate and emitter contact electrodes are made in an interdigitated shape on the back of the battery. The core technology is to prepare high-quality p-regions and n-regions that are interdigitated and spaced apart in an interdigitated shape on the back of the battery.

[0003] Currently, N-type IBC cells use N-type silicon wafers, and the P+ region employs boron diffusion superimposed laser SE technology to reduce metal recombination and improve on-state voltage.

[0004] In the above-mentioned N-type IBC battery manufacturing process, the P+ region still needs to be laser-grooved before printing the grid lines in order to print aluminum paste to form the positive electrode grid lines. However, laser grooving not only increases the manufacturing process, but also damages the passivation layer. Furthermore, during the cooling process after sintering, aluminum elements in the aluminum paste diffuse into the PN junction, which easily forms metal composite centers, resulting in a decrease in the open circuit voltage of the battery. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an N-type IBC battery positive electrode grid line silver aluminum paste, an N-type IBC battery and its preparation method, so as to solve the problem that the existing N-type IBC battery aluminum paste requires laser grooving of the P+ region before printing into positive electrode grid lines, and is prone to forming metal composite centers, which leads to a decrease in the open circuit voltage of the battery cell.

[0006] To solve the above problems, the present invention is achieved through the following technical solution:

[0007] This invention proposes a silver-aluminum paste for the positive grid of an N-type IBC battery, wherein the components constituting the silver-aluminum paste include organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder.

[0008] Furthermore, in the N-type IBC battery silver-aluminum paste, the mass fractions of the organic additive, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder are 0.8–1.5%, 65–75%, 2–5%, 0.1–0.3%, 0.1–0.2%, 15.5–30.2%, and 1.8–2.5%, respectively.

[0009] Furthermore, in the silver-aluminum paste, the glass powder comprises 15-25% Bi2O3, 4-8% Al2O3, 6-12% SiO2, 10-29% ZnO, 15-20% Pb2O5, 4-8% TiO2, 4-10% B2O3, and 15-28% TeO3 by mass percentage.

[0010] Furthermore, in the silver-aluminum paste, the gallium powder is elemental gallium.

[0011] Furthermore, in the silver-aluminum paste, the organic additives include one or more of the following: fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, lauryl phosphate, silicone oil, diester, and a mixture of lauryl phosphate.

[0012] Furthermore, in the silver-aluminum paste, the organic binder includes a polymer resin and an organic solvent;

[0013] The polymer in the organic adhesive has a mass fraction of 8-12%;

[0014] The organic solvent has a mass fraction of 88-92% in the organic adhesive.

[0015] Furthermore, in the silver-aluminum paste, the polymer is resin-50;

[0016] The organic solvent includes at least five of the following: benzyl alcohol, diethyl phthalate, terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and ester twelve.

[0017] Furthermore, in the silver-aluminum paste, the silver powder includes micron-sized spherical silver powder and nano-sized spherical silver powder;

[0018] And / or the aluminum powder includes micron-sized spherical aluminum powder with a mass fraction of 82-92% and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a mass fraction of 8-18% and a D50 of 9-10 μm.

[0019] This invention also proposes a method for preparing an N-type IBC battery, comprising:

[0020] After forming interdigitated n+ doped regions and p+ doped regions on the back side of an N-type silicon wafer, a passivation layer is formed on the surface of the n+ doped regions and p+ doped regions.

[0021] Silver-aluminum paste is printed in a first region of the passivation layer, and silver paste is printed in a second region of the passivation layer; the projection of the first region is within the p+ doped region, and the projection of the second region is within the n+ doped region; wherein, the components constituting the silver-aluminum paste include organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder;

[0022] An IBC cell is prepared by high-temperature sintering of an N-type silicon wafer with silver-aluminum paste printed in the first region and silver paste printed in the second region.

[0023] The present invention also proposes an N-type IBC battery, wherein the N-type IBC battery is prepared by the method described above.

[0024] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0025] In this embodiment of the invention, the provided N-type IBC battery positive electrode grid silver-aluminum paste comprises organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder. The boron in the boron powder can increase the doping of the P+ region; gallium, like aluminum, is a Group 3 element and has similar chemical properties, thus it can replace some of the aluminum powder; while the silver powder has a burn-through effect, allowing it to be directly printed onto the passivation layer above the p+ doped region after a passivation layer is formed on the back of the battery silicon wafer, followed by high-temperature sintering. This allows it to contact the p+ doped region and form the positive electrode grid, eliminating the need for a secondary laser grooving step and avoiding damage to the passivation layer caused by secondary laser grooving, thereby improving the battery open-circuit voltage; simultaneously, gallium has a higher specific gravity and decreases to the silicon surface more rapidly than aluminum during sintering. This design increases the contact probability between Ga and Si, reduces aluminum as a recombination center, lowers the contact resistance between the paste and the battery, and maintains a higher open-circuit voltage. In addition, by using gallium to replace some aluminum powder, the aluminum content is reduced, which helps to reduce the side effects of Al, weakens the Al-Si reaction, and results in shallower silver-aluminum corrosion pits and reduced recombination, thereby improving the open-circuit voltage and efficiency of the battery. Thus, it solves the problem that existing N-type IBC battery aluminum paste requires laser grooving of the P+ region before printing into positive electrode grid lines, which easily forms metal recombination centers and leads to a decrease in the open-circuit voltage of the battery cell.

[0026] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation method of silver-aluminum paste for the positive electrode grid of an N-type IBC battery provided in an embodiment of the present invention;

[0028] Figure 2This is a flowchart of the preparation method of the N-type IBC battery provided in the embodiments of the present invention. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The applicant of this invention has discovered that the metallization printing paste for N-type IBCs is mainly composed of aluminum paste. Aluminum paste can cause significant metal bonding to the cell itself, increasing the series resistance of the cell, reducing the electrical performance of the cell, resulting in low on-state voltage, high series resistance, poor filling, and easily affecting the efficiency of the cell itself.

[0031] To address the aforementioned problems, this invention provides a silver-aluminum paste for the positive grid of an N-type IBC battery. The components of the silver-aluminum paste include organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder.

[0032] The silver-aluminum paste for the positive grid line of the N-type IBC battery provided in this embodiment of the invention is used to form the positive grid line of the N-type IBC battery, specifically for forming the positive grid line of the N-type IBC battery with the P+ region formed on the back side by boron diffusion superposition laser SE technology.

[0033] Silver powder and aluminum powder are the main components. Aluminum powder mainly replaces the P+ emitter of the battery. Silver has excellent burn-through performance. Gallium and aluminum are both group 3 elements and have similar chemical properties. Gallium can not only play a doping role, but also has a larger specific gravity. During the sintering process, gallium reaches the silicon wafer surface before aluminum, reducing aluminum as a recombination center. Therefore, when printing the aluminum paste on the passivation layer on the back of the N-type silicon wafer, the silicon nitride film and silicon oxide film in the passivation layer can be burned through in sequence, and then contact the p+ doped region to form the positive electrode grid line. This eliminates the need for the secondary laser grooving step and avoids damage to the passivation layer caused by the secondary laser grooving.

[0034] Among them, boron powder can diffuse into the silicon interior for heavy doping during high-temperature sintering, which is beneficial to improving the contact performance of the slurry and reducing the reaction contact surface between aluminum and silicon.

[0035] Among them, glass powder is an inorganic binder that melts into a liquid state under high temperature conditions and solidifies when cooled, thus playing a bonding role; organic binders can ensure the overall bonding effect; and organic additives can reduce the overall viscosity of silver-aluminum paste.

[0036] Therefore, the silver-aluminum paste provided in this embodiment of the invention has better contact with the battery cell itself, lower series resistance than traditional aluminum paste, and significantly improved recombination rate and degree. The open-circuit voltage of the battery can be increased by 5 millivolts, thus solving the problem that existing N-type IBC batteries require laser grooving of the P+ region when printing the positive grid lines, and are prone to forming metal recombination centers, which leads to a decrease in the open-circuit voltage of the battery cell.

[0037] Optionally, in one embodiment, the mass fractions of the organic additive, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder in the above-mentioned silver-aluminum paste are 0.8-1.5%, 65-75%, 2-5%, 0.1-0.3%, 0.1-0.2%, 15.5-30.2%, and 1.8-2.5%, respectively. In the silver-aluminum paste provided in this embodiment of the invention, the aluminum content is low. When forming the aluminum-silicon alloy, the proportion of aluminum in the aluminum-silicon alloy is small. Therefore, during the cooling process, no excess aluminum diffuses into the PN junction region, causing a metal composite region.

[0038] Optionally, in one embodiment, the mass fractions of the organic additive, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder in the above-mentioned silver-aluminum paste are 1.0-1.2%, 68-72%, 3-4%, 0.15-0.25%, 0.12-0.18%, 20-25%, and 2.0-2.2%, respectively.

[0039] For example, in the above-mentioned silver-aluminum paste, the mass fractions of organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder are 0.8%, 75%, 2%, 0.3%, 0.1%, 20% and 1.8%, respectively.

[0040] For example, in the above-mentioned silver-aluminum paste, the mass fractions of organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder are 1.5%, 65%, 5%, 0.1%, 0.2%, 25.7% and 2.5%, respectively.

[0041] For example, in the above-mentioned silver-aluminum paste, the mass fractions of organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder are 1.1%, 70%, 3%, 0.2%, 0.15%, 23.45% and 2.1%, respectively.

[0042] For example, in the above-mentioned silver-aluminum paste, the mass fractions of organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder are 1.5%, 75%, 5%, 0.3%, 0.2%, 15.5% and 2.5%, respectively.

[0043] For example, in the above-mentioned silver-aluminum paste, the mass fractions of organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder are 0.8%, 65%, 2%, 0.1%, 0.1%, 30.2% and 1.8%, respectively.

[0044] Optionally, in one embodiment, the gallium powder is micron-sized elemental indium, specifically micron-sized elemental gallium with a purity of 2 nines.

[0045] Alternatively, in one embodiment, the gallium powder is a gallium-aluminum alloy.

[0046] Optionally, in one embodiment, the boron powder comprises micron-sized elemental boron. By adding this micron-sized elemental boron, the boron powder can rapidly diffuse into the silicon interior for heavy doping during high-temperature sintering, which is beneficial for improving the contact performance of the slurry.

[0047] Optionally, in one specific embodiment, the boron powder is micron-sized boron powder with a purity of 99.99%.

[0048] Optionally, in one embodiment, the aluminum powder includes micron-sized spherical aluminum powder with a mass fraction of 82-92% and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a mass fraction of 8-18% and a D50 of 9-10 μm. The different particle sizes of the aluminum powder are graded to fill and penetrate the gaps between the micron-sized particles.

[0049] Optionally, in one embodiment, the aluminum powder comprises 82-92% by mass of micron-sized spherical aluminum powder and 8-18% by mass of nano-sized spherical aluminum powder.

[0050] Optionally, in one specific embodiment, the aluminum powder includes micron-sized spherical aluminum powder with a purity of three nines, a mass fraction of 82-92%, and a D50 of 5-6 μm, and nano-spherical aluminum powder with a purity of three nines, a mass fraction of 8-18%, and a D50 of 9-10 nm.

[0051] Optionally, in one embodiment, the silver powder includes micron-sized spherical silver powder and nano-sized spherical silver powder. Since there are gaps between the micron-sized silver powder particles, the nano-sized spherical silver powder can fill and penetrate these gaps.

[0052] Optionally, in one specific embodiment, the silver powder includes 82-92% by mass of micron-sized spherical silver powder and 8-18% by mass of nano-sized spherical silver powder.

[0053] Optionally, in one specific embodiment, the silver powder includes micron-sized spherical silver powder with a purity of three nines, a mass fraction of 82-92%, and a D50 of 5-6 μm, and nano-sized spherical silver powder with a purity of three nines, a mass fraction of 8-18%, and a D50 of 9-10 nm.

[0054] Optionally, in one embodiment, the above-mentioned organic additives include one or more of fatty alcohol ether phosphates, aluminate coupling agents, silane coupling agents, zirconium aluminate coupling agents, lauryl phosphates, silicone oil, diesters, lauryl phosphate mixtures, DIG655, and BYK109.

[0055] In the N-type IBC battery positive grid silver-aluminum paste provided in this embodiment of the invention, the organic binder includes a polymer resin and an organic solvent; wherein, the polymer resin is dissolved in the organic solvent, so that the organic solvent can act as an organic binder, that is, the paste can act as a binder for powder after drying.

[0056] Optionally, in one embodiment, the polymer in the organic adhesive has a mass fraction of 8-12%; and the organic solvent in the organic adhesive has a mass fraction of 88-92%.

[0057] Optionally, in some embodiments, the polymer in the organic adhesive has a mass fraction of 9-11%, and the organic solvent in the organic adhesive has a mass fraction of 89-91%.

[0058] Optionally, in one embodiment, the above-mentioned polymer is ethyl cellulose-N20, ethyl cellulose N-50, ethyl cellulose-N100, resin-50, etc.

[0059] The aforementioned organic solvents include at least five of the following: benzyl alcohol, diethyl phthalate, terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and ester twelve.

[0060] Optionally, in one embodiment, the glass powder comprises 15-25% Bi2O3, 4-8% Al2O3, 6-12% SiO2, 10-29% ZnO, 15-20% Pb2O5, 4-8% TiO2, 4-10% B2O3, and 15-28% TeO3 by mass percentage. That is, by mass percentage, the above glass powder is obtained by sintering and pulverizing 15-25% Bi2O3, 4-8% Al2O3, 6-12% SiO2, 10-29% ZnO, 15-20% Pb2O5, 4-8% TiO2, 4-10% B2O3, and 15-28% TeO3. The glass powder has a D50 of 1.8-2.2 μm and moderate glass activity. Optionally, the D50 of the glass powder is 1.9–2.1 μm.

[0061] Among them, Bi2O3 forms the main network structure; Al2O3 can adjust the glass stability and increase the viscosity; SiO2, as a glass network forger, promotes glass stability and lowers the glass melting point; ZnO can break the network structure and promote glass crystallization; Pb2O5 reacts with silicon nitride to generate lead, nitrogen and silicon dioxide; TiO2 is used for local crystallization; B2O3 is used to provide trace amounts of boron; TeO3 is used for local microcrystallization and lowers the melting point.

[0062] This invention also provides a method for preparing silver-aluminum paste for N-type IBC batteries, wherein, as shown in the embodiments of the present invention... Figure 1 As shown, steps 101 to 102 are included:

[0063] Step 101: Mix boron powder, gallium powder and organic binder to obtain a first mixture;

[0064] Step 101: Add silver powder, aluminum powder and glass powder to the first mixture, mix well, and obtain the second mixture;

[0065] Step 102: After grinding the second mixture, add organic additives to obtain N-type IBC battery silver-aluminum paste.

[0066] In step 101 above, 0.1-0.3% of boron powder, 0.1-0.2% of gallium powder, and 15.5-30.2% of organic binder, accounting for the total mass of raw materials, are weighed, mixed, and dispersed using a disperser to obtain the first mixture mentioned above.

[0067] In step 102 above, 65-75% of silver powder, 2-5% of aluminum powder, and 1.8-2.5% of glass powder, accounting for the total mass of the raw materials, are weighed and mixed, and dispersed using a disperser to obtain the second mixture mentioned above.

[0068] In step 102 above, after grinding the second mixture, 0.8 to 1.5% of an organic additive is added according to the total mass of the raw materials. After high-speed dispersion, a positive electrode grid line that can be formed to contact the P+ region on the back of the N-type IBC battery without laser grooving is obtained, thus avoiding the damage to the passivation layer caused by laser grooving.

[0069] In this embodiment of the invention, silver powder, boron powder, and gallium powder are added to the positive electrode grid paste. The boron in the boron powder increases the doping of the P+ region. Gallium, like aluminum, is a Group 3 element and has similar chemical properties to aluminum, thus it can replace some of the aluminum powder. Silver powder has an etching effect; after forming a passivation layer on the back of the silicon wafer, it is directly printed onto the passivation layer region above the p+ doped region, and then subjected to high-temperature sintering. This allows it to contact the p+ doped region and form the positive electrode grid, eliminating the need for a secondary laser grooving step and avoiding damage to the passivation layer caused by secondary laser grooving, thereby improving the battery open-circuit voltage. Simultaneously, gallium has a higher specific gravity, which... During sintering, Ga descends to the silicon surface more rapidly than aluminum, increasing the probability of Ga-Si contact, reducing aluminum as a recombination center, lowering the contact resistance between the paste and the battery, and maintaining a higher open-circuit voltage. In addition, using gallium to replace some aluminum powder reduces the aluminum content, which helps to reduce the side effects of Al, weakens the Al-Si reaction, and results in shallower silver-aluminum corrosion pits and reduced recombination, thereby improving the open-circuit voltage and efficiency of the battery. Thus, it solves the problem that existing N-type IBC battery aluminum paste requires laser grooving of the P+ region before printing into positive electrode grid lines, which easily forms metal recombination centers and leads to a decrease in the open-circuit voltage of the battery cell.

[0070] Optionally, in the preparation method provided in the embodiments of the present invention, the boron powder is a micron-sized boron-aluminum alloy and / or a micron-sized elemental boron. Micron-sized boron-aluminum alloy and micron-sized elemental boron have the characteristics of high tap density, low oxygen content, and high activity. By adding this micron-sized boron-aluminum alloy powder and / or micron-sized elemental boron, the aluminum paste can quickly form a good alloy with silicon under relatively low sintering temperature conditions, reducing the contact resistivity between the front-side aluminum grid and the battery.

[0071] Optionally, in the preparation method provided in the embodiments of the present invention, the organic additive includes two or more of the following: fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, lauryl phosphate, silicone oil, diester, and lauryl phosphate.

[0072] Optionally, in the preparation method provided in the embodiments of the present invention, the silver powder includes micron-sized spherical silver powder and nano-sized spherical silver powder;

[0073] And / or the aluminum powder includes micron-sized spherical aluminum powder with a mass fraction of 82-92% and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a mass fraction of 8-18% and a D50 of 9-10 μm.

[0074] Optionally, in one specific embodiment, the silver powder includes 82-92% by mass of micron-sized spherical silver powder and 8-18% by mass of nano-sized spherical silver powder.

[0075] Optionally, in the preparation method provided in the embodiments of the present invention, the glass powder is obtained by sintering and pulverizing 15-25% Bi2O3, 4-8% Al2O3, 6-12% SiO2, 10-29% ZnO, 15-20% Pb2O5, 4-8% TiO2, 4-10% B2O3 and 15-28% TeO3 by mass percentage.

[0076] Optionally, in the preparation method provided in the embodiments of the present invention, the gallium powder is micron-sized elemental gallium or gallium-aluminum alloy.

[0077] Optionally, in the preparation method provided in the embodiments of the present invention, the organic additives include one or more of fatty alcohol ether phosphates, aluminate coupling agents, silane coupling agents, zirconium aluminate coupling agents, lauryl phosphates, silicone oil, diesters, and mixtures of lauryl phosphates.

[0078] Optionally, in the preparation method provided in the embodiments of the present invention, the organic binder includes a polymer resin and an organic solvent;

[0079] The polymer in the organic adhesive has a mass fraction of 8-12%;

[0080] The organic solvent has a mass fraction of 88-92% in the organic adhesive.

[0081] Optionally, in the preparation method provided in the embodiments of the present invention, the polymer is resin-50;

[0082] The organic solvent includes at least five of the following: benzyl alcohol, diethyl phthalate, terpineol, butylcarbiol, butylcarbiol acetate, tributyl citrate, Span 85, and ester twelve.

[0083] This invention also proposes a method for preparing an N-type IBC battery, wherein, as... Figure 2 As shown, steps 201 to 203 are included:

[0084] Step 201: After forming interdigitated n+ doped regions and p+ doped regions on the back side of the N-type silicon wafer, a passivation layer is formed on the surface of the n+ doped regions and p+ doped regions.

[0085] Step 202: Print silver-aluminum paste in the first region of the passivation layer and print silver paste in the second region of the passivation layer; the projection of the first region is within the p+ doped region and the projection of the second region is within the n+ doped region; wherein, the components constituting the silver-aluminum paste include organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder and glass powder;

[0086] Step 203: The N-type silicon wafer with silver-aluminum paste printed in the first region and silver paste printed in the second region is subjected to high-temperature sintering to obtain an IBC battery.

[0087] In step 201 above, the silicon wafer is first texturized with an alkaline agent, and then interdigitated n+ doped regions and p+ doped regions are formed on the back side of the silicon wafer. Then, a silicon oxide layer or silicon nitride layer is deposited to cover the entire back side of the silicon wafer as the passivation layer.

[0088] Among them, a P+ doped region is formed by superimposing a laser SE process on a boron-doped N-type silicon wafer to further reduce metal recombination and improve the turn-on voltage.

[0089] In step 202 above, the silicon wafer after the passivation layer is formed is screen-printed to prepare electrode gate lines. Specifically, the silver-aluminum paste is printed in the first region of the passivation layer on the back of the silicon wafer. The projection of this first region is within the p+ doped region to form a positive gate line that is connected to the p+ doped region. At the same time, silver paste is also printed in the second region of the back passivation layer. The projection of this second region is within the n+ doped region to form a negative gate line that is spaced apart from the positive gate line. The silver paste can be a conventional silver paste.

[0090] In step 203 above, silver powder and gallium powder are added to the silver-aluminum paste. Gallium, like aluminum, is a Group 3 element and has similar chemical properties to aluminum, so it can replace some of the aluminum powder. Silver powder has a burn-through effect. After the passivation layer is formed on the back of the silicon wafer, it is directly printed on the passivation layer area above the p+ doped region. Then, high-temperature sintering is performed, which allows it to contact the p+ doped region and form the positive electrode grid line. This eliminates the need for a secondary laser grooving step, avoiding damage to the passivation layer caused by secondary laser grooving and improving the open-circuit voltage of the battery. At the same time, gallium has a higher specific gravity and descends to the silicon surface faster than aluminum during sintering, increasing the probability of Ga-Si contact, reducing aluminum as a recombination center, lowering the contact resistance between the paste and the battery, and maintaining a high open-circuit voltage. In addition, using gallium to replace some of the aluminum powder reduces the aluminum content, which helps to reduce the side effects of Al, weakens the Al-Si reaction, and results in shallower silver-aluminum corrosion pits and reduced recombination, thereby improving the open-circuit voltage and efficiency of the battery.

[0091] The present invention will be described in detail below through embodiments.

[0092] Example 1

[0093] (1) Provide silver-aluminum paste: by weight, the silver-aluminum paste consists of 1.2 parts organic additives, 70 parts silver powder, 3 parts aluminum powder, 0.1 parts boron powder, 0.1 parts gallium powder, 23.6 parts organic binder and 2 parts glass powder;

[0094] The organic additives include three of the following: silane coupling agent, silicone oil, and a mixture of lauryl phosphate; the silver powder includes micron-sized spherical silver powder with a purity of 90% by mass and a purity of 99.99% by mass, and nano-spherical silver powder with a purity of 99.99% by mass and a purity of 10% by mass; the aluminum powder includes micron-sized spherical aluminum powder with a purity of 85% by mass and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a purity of 15% by mass and a D50 of 9-10 μm; the organic binder includes 10% by mass of resin-50 and 90% by mass of organic solvent, the organic solvent including benzyl alcohol, diethyl phthalate, terpineol, butylcarbiol, butylcarbiol acetate, and tributyl citrate;

[0095] The glass powder is obtained by sintering and pulverizing 20% ​​Bi2O3, 7% Al2O3, 10% SiO2, 10% ZnO, 20% Sb2O5, 8% TiO2, 6% B2O3 and 19% TeO3 by mass percentage.

[0096] (2) After forming a silicon oxide layer and a polycrystalline silicon layer on the back side of an N-type silicon wafer with a specification of 182mm×182mm, the polycrystalline silicon layer on the back side is subjected to boron diffusion and laser SE treatment.

[0097] (3) Laser grooving is performed on the back side of the phosphorus-doped N-type silicon wafer to form interdigitated n+ doped regions and p+ doped regions, and the front polycrystalline silicon layer is removed.

[0098] (4) After removing the front polysilicon layer and sequentially forming a double-sided aluminum oxide layer, a front silicon nitride layer, and a back silicon nitride layer, the above silver-aluminum paste is printed on the back silicon nitride opposite the p+ doped region using a 480-mesh screen, and silver paste is printed on the back silicon nitride opposite the n+ doped region.

[0099] (5) The silicon wafer is sintered at high temperature in a sintering furnace. The peak sintering temperature is 778°C to obtain an N-type IBC cell.

[0100] Example 2

[0101] The difference between Example 2 and Example 1 is that, in step (1), the silver-aluminum paste is composed of 0.8 parts organic additives, 75 parts silver powder, 2 parts aluminum powder, 0.3 parts boron powder, 0.1 parts gallium powder, 20 parts organic binder and 1.8 parts glass powder by mass.

[0102] Example 3

[0103] The difference between Example 3 and Example 1 is that, in step (1), the silver-aluminum paste is composed of 1.5 parts organic additives, 65 parts silver powder, 5 parts aluminum powder, 0.1 parts boron powder, 0.2 parts gallium powder, 25.7 parts organic binder and 2.5 parts glass powder by mass.

[0104] Example 4

[0105] The difference between Example 4 and Example 1 is that, in step (1), the silver-aluminum paste is composed of 1.5 parts organic additives, 75 parts silver powder, 5 parts aluminum powder, 0.3 parts boron powder, 0.2 parts gallium powder, 15.5 parts organic binder and 2.5 parts glass powder by mass.

[0106] Example 5

[0107] The difference between Example 3 and Example 1 is that, in step (1), the silver-aluminum paste is composed of 0.8 parts organic additives, 65 parts silver powder, 2 parts aluminum powder, 0.1 parts boron powder, 0.1 parts gallium powder, 30.2 parts organic binder and 1.8 parts glass powder by mass.

[0108] Example 6

[0109] The difference between Example 6 and Example 1 is that, in step (1), the silver-aluminum paste is composed of 1.1 parts organic additives, 70 parts silver powder, 3 parts aluminum powder, 0.2 parts boron powder, 0.15 parts gallium powder, 23.45 parts organic binder and 2.1 parts glass powder by mass.

[0110] Comparative Example 1

[0111] The difference between Comparative Example 1 and Example 1 is that, in step (1), the silver-aluminum paste, by mass, consists of 1.1 parts organic additives, 70 parts silver powder, 3.35 parts aluminum powder, 23.45 parts organic binder and 2.1 parts glass powder.

[0112] Comparative Example 2

[0113] (1) Provide silver-aluminum paste: by weight, the silver-aluminum paste consists of 1.2 parts organic additives, 73.35 parts aluminum powder, 23.6 parts organic binder and 2 parts glass powder;

[0114] The organic additives include three of the following: silane coupling agent, silicone oil, and a mixture of lauryl phosphate; the silver powder includes micron-sized spherical silver powder with a purity of 90% by mass and a purity of 99.99% by mass, and nano-spherical silver powder with a purity of 99.99% by mass and a purity of 10% by mass; the aluminum powder includes micron-sized spherical aluminum powder with a purity of 85% by mass and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a purity of 15% by mass and a D50 of 9-10 μm; the organic binder includes 10% by mass of resin-50 and 90% by mass of organic solvent, the organic solvent including benzyl alcohol, diethyl phthalate, terpineol, butylcarbiol, butylcarbiol acetate, and tributyl citrate;

[0115] The glass powder is obtained by sintering and pulverizing 20% ​​Bi2O3, 7% Al2O3, 10% SiO2, 10% ZnO, 20% Sb2O5, 8% TiO, 6% B2O3 and 19% TeO3 by mass percentage.

[0116] (2) After forming a silicon oxide layer and a polycrystalline silicon layer on the back side of an N-type silicon wafer with a specification of 182mm×182mm, the polycrystalline silicon layer on the back side is subjected to boron diffusion and laser SE treatment.

[0117] (3) Laser grooving is performed on the back side of the phosphorus-doped N-type silicon wafer to form interdigitated n+ doped regions and p+ doped regions, and the front polycrystalline silicon layer is removed.

[0118] (4) After removing the front polysilicon layer and sequentially forming a double-sided aluminum oxide layer, a front silicon nitride layer, and a back silicon nitride layer, laser grooving is performed on the back area opposite the p+ doped region to form a first opening that is connected to the p+ doped region. The silver-aluminum paste is printed at the first opening by 480 mesh screen printing, and silver paste is printed on the back silicon nitride opposite the n+ doped region.

[0119] (5) The silicon wafer was sintered at high temperature in a sintering furnace, with a peak sintering temperature of 778°C, to obtain an N-type IBC cell.

[0120] The electrical performance of the N-type IBC batteries prepared in the above embodiments and comparative examples was tested, and the results are shown in Table 1 below:

[0121] Table 1

[0122]

[0123] Comparing Examples 1 to 6 with Comparative Examples 1 and 2, it can be seen that using silver-aluminum paste doped with indium and boron to form the P+ emitter not only eliminates the need for laser grooving to form the back grid line, but also greatly improves the recombination rate and degree of recombination in the battery, resulting in a 0.35% increase in battery efficiency and an 8mV increase in open voltage.

[0124] In summary, in this embodiment, silver powder, boron powder, and gallium powder are added to the positive electrode grid paste. The boron in the boron powder increases the doping of the P+ region. Gallium, like aluminum, is a Group 3 element and has similar chemical properties, thus it can replace some of the aluminum powder. Silver powder has an etching effect; after forming a passivation layer on the back of the silicon wafer, it is directly printed onto the passivation layer region above the p+ doped region, followed by high-temperature sintering. This allows it to contact the p+ doped region and form the positive electrode grid, eliminating the need for a secondary laser grooving step and avoiding damage to the passivation layer caused by secondary laser grooving, thereby improving the battery's open-circuit voltage. Simultaneously, gallium has a higher specific gravity than... In addition, gallium, compared to aluminum, descends to the silicon surface more rapidly during sintering, increasing the probability of Ga-Si contact, reducing aluminum as a recombination center, lowering the contact resistance between the paste and the battery, and maintaining a higher open-circuit voltage. Furthermore, by using gallium to replace some aluminum powder, the aluminum content is reduced, which helps to reduce the side effects of Al, weakening the Al-Si reaction, resulting in shallower silver-aluminum corrosion pits and reduced recombination, thereby improving the open-circuit voltage and efficiency of the battery. Thus, it solves the problem that existing N-type IBC battery aluminum paste requires laser grooving of the P+ region before printing into positive electrode grid lines, and is prone to forming metal recombination centers, leading to a decrease in the open-circuit voltage of the battery cell.

[0125] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0126] The foregoing has provided a detailed description of the silver-aluminum paste for the positive electrode grid of an N-type IBC battery, the N-type IBC battery itself, and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A silver-aluminum paste for the positive electrode grid of an N-type IBC battery, characterized in that, The silver-aluminum paste comprises organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder; the mass fraction of the silver powder is 65-75%; and the mass fractions of the organic additives, aluminum powder, boron powder, gallium powder, organic binder, and glass powder are 0.8-1.5%, 2-5%, 0.1-0.3%, 0.1-0.2%, 15.5-30.2%, and 1.8-2.5%, respectively. The glass powder comprises 15-25% Bi2O3, 4-8% Al2O3, 6-12% SiO2, 10-29% ZnO, 15-20% Pb2O5, 4-8% TiO2, 4-10% B2O3 and 15-28% TeO3 by mass.

2. The silver-aluminum paste according to claim 1, characterized in that, The gallium powder is elemental gallium.

3. The silver-aluminum paste according to claim 1, characterized in that, The organic additives include one or more of the following: fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, silicone oil, diester, and a mixture of lauryl phosphate.

4. The silver-aluminum paste according to claim 1, characterized in that, The organic adhesive comprises a polymer resin and an organic solvent; The polymer in the organic adhesive has a mass fraction of 8-12%; The organic solvent has a mass fraction of 88-92% in the organic adhesive.

5. The silver-aluminum paste according to claim 4, characterized in that, The organic solvent includes at least five of the following: benzyl alcohol, diethyl phthalate, terpineol, butyl carbiol, butyl carbiol acetate, tributyl citrate, Span 85, and ester twelve.

6. The silver-aluminum paste according to claim 1, characterized in that, The silver powder includes micron-sized spherical silver powder and nano-sized spherical silver powder; And / or the aluminum powder includes micron-sized spherical aluminum powder with a mass fraction of 82-92% and a D50 of 5-6 μm, and micron-sized spherical aluminum powder with a mass fraction of 8-18% and a D50 of 9-10 μm.

7. A method for preparing an N-type IBC battery, characterized in that, include: After forming interdigitated n+ doped regions and p+ doped regions on the back side of an N-type silicon wafer, a passivation layer is formed on the surface of the n+ doped regions and p+ doped regions. Silver-aluminum paste is printed in the first region of the passivation layer, and silver paste is printed in the second region of the passivation layer; The projection of the first region is within the p+ doped region, and the projection of the second region is within the n+ doped region; wherein, the components constituting the silver-aluminum paste include organic additives, silver powder, aluminum powder, boron powder, gallium powder, organic binder, and glass powder; the mass fraction of the silver powder is 65~75%; the mass fractions of the organic additives, aluminum powder, boron powder, gallium powder, organic binder, and glass powder are 0.8~1.5%, 2~5%, 0.1~0.3%, 0.1~0.2%, 15.5~30.2%, and 1.8~2.5%, respectively; the glass powder includes 15~25% Bi2O3, 4~8% Al2O3, 6~12% SiO2, 10~29% ZnO, 15~20% Pb2O5, 4~8% TiO2, 4~10% B2O3, and 15~28% TeO3 by mass percentage; An IBC cell is prepared by high-temperature sintering of an N-type silicon wafer with silver-aluminum paste printed in the first region and silver paste printed in the second region.

8. An N-type IBC battery, characterized in that, It is prepared by the method described in claim 7.

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