A BC battery, its preparation method and application

Abstract

This invention provides a copper-carbon battery (BC battery), its fabrication method, and its application. The BC battery of this invention includes a functional layer and a copper electrode; the functional layer includes a diffusion barrier layer and / or an oxidation-resistant layer, and the functional layer is located on at least one surface of the copper electrode; the diffusion barrier layer includes stacked SiN... x Layers and AlO y The BC battery comprises an antioxidant layer and a tin layer stacked together; the BC battery also includes an antioxidant layer and a diffusion barrier layer. The BC battery of the present invention possesses both excellent diffusion barrier and antioxidant properties.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cells, and in particular to a BC cell, its preparation method, and its application. Background Technology

[0002] Back-contact (BC) cells, as a core component of high-efficiency photovoltaic cells, offer the advantage of eliminating the shading effect of the front electrodes by placing the electrodes entirely on the back of the cell, thereby significantly improving the photoelectric conversion efficiency of the photovoltaic cell. This technology is widely used in next-generation photovoltaic modules, and is particularly suitable for scenarios with extremely high requirements for energy density and space utilization, such as distributed rooftop photovoltaics, building-integrated photovoltaics (BIPV), and the manufacture of high-power-density photovoltaic modules.

[0003] In the manufacturing process of photovoltaic (BC) cells, copper is the preferred material for BC cell electrodes due to its excellent conductivity and significantly lower cost compared to silver. However, copper electrodes require high-temperature sintering processes exceeding 700°C in practical applications and are exposed to complex outdoor environments with high temperature, high humidity, and sunlight for extended periods. This presents two major challenges for copper electrodes: firstly, copper is prone to oxidation at high temperatures, forming oxide layers such as CuO and Cu2O, which increases the contact resistance and reduces the conductivity of the BC cell; secondly, the diffusion of copper ions into the silicon substrate and passivation layer can disrupt the PN junction structure in the BC cell, exacerbating carrier recombination and leading to a decline in photovoltaic cell efficiency.

[0004] Currently, the mainstream copper electrode modification schemes for BC batteries in the industry mainly involve setting a diffusion barrier layer (titanium layer or silicon nitride layer) and an anti-oxidation layer (nickel layer or tin layer) on the surface of the copper electrode substrate. However, the thickness of the titanium layer or silicon nitride layer is difficult to balance the diffusion barrier and contact resistance requirements of BC batteries. Thick layers (>100nm) result in a contact resistance >8mΩ, while thin layers (<50nm) cannot block the diffusion of copper ions and damage the PN junction. Nickel or tin layers are prone to melting and falling off during high-temperature sintering at 700~750℃. During long-term outdoor use, water vapor and oxygen can easily penetrate into the interior of the BC battery. After 1000h of damp heat cycling, the electrode resistance increases by more than 30%, which cannot meet the long life requirements of photovoltaic cells.

[0005] Therefore, developing a BC battery that combines high diffusion resistance and strong oxidation resistance has become the key to driving breakthroughs in BC battery technology. Summary of the Invention

[0006] This invention provides a BC battery that has both excellent diffusion resistance and oxidation resistance.

[0007] This invention provides a method for preparing a BC battery, which can produce the above-mentioned BC battery, which has both excellent diffusion resistance and oxidation resistance.

[0008] The present invention provides a photovoltaic module including the above-mentioned BC cell, which has higher photoelectric conversion efficiency and longer service life.

[0009] A first aspect of the present invention provides a BC battery, which includes a functional layer and a copper electrode;

[0010] The functional layer includes a diffusion barrier layer and / or an oxidation-resistant layer, and the functional layer is located on at least one side surface of the copper electrode;

[0011] The diffusion barrier layer comprises stacked SiN x Layers and AlO y The antioxidant layer comprises a nickel layer and a tin layer stacked together;

[0012] The BC battery includes both an antioxidant layer and a diffusion barrier layer.

[0013] In the BC battery described above, the functional layer includes a diffusion barrier layer and an oxidation inhibitor layer, and the diffusion barrier layer and the oxidation inhibitor layer are stacked together. The functional layer is located on one side surface of the copper electrode, and the AlO... y The layer is close to the nickel layer, and the tin layer is close to the copper electrode.

[0014] In the BC battery described above, the functional layer includes a first functional layer and a second functional layer, which are located on opposite sides of the copper electrode.

[0015] The first functional layer includes a diffusion barrier layer, and the second functional layer includes an antioxidant layer, wherein the AlO y The nickel layer is located near the copper electrode.

[0016] The BC battery as described above, wherein the SiN x In the layer, the mass ratio of nitrogen to silicon is 1.2 to 1.5; and / or,

[0017] In the tin layer, the particle size of metallic tin is 50~100nm; and / or,

[0018] The BC battery further includes a first transition layer and a passivation layer, wherein the first transition layer is located between the passivation layer and the SiN. x Between the layers, the first transition layer comprises a titanium-tungsten alloy, wherein the mass ratio of titanium to tungsten is (6.5~7.5):(2.5~3.5); and / or,

[0019] The BC battery further includes a second transition layer, which is located on the AlO₂. yBetween the layer and the copper electrode, the second transition layer includes nickel and phosphorus elements, with a mass ratio of nickel to phosphorus of (7.5~8.5):(1.5~2.5).

[0020] The BC cell described above further includes a silicon substrate, wherein the silicon substrate includes interconnected doped regions and undoped regions in the thickness direction;

[0021] In the first direction, the doped region includes N spaced-apart boron-doped regions and phosphorus-doped regions, where N ≥ 2;

[0022] The doped region is located near the passivation layer.

[0023] In the BC battery described above, the thickness of the doped region is 0.5~1.5 μm; and / or,

[0024] In the doped region, the total doping concentration of boron and phosphorus is 1×10⁻⁶. 19 ~5×10 20 cm -3 ; and / or,

[0025] In the first direction, the spacing between the boron-doped region and the phosphorus-doped region is 50~150 μm; and / or,

[0026] In the first direction, the boron-doped region extends to a size of 50~200 μm; and / or,

[0027] In the first direction, the phosphorus-doped region extends to a size of 50~200 μm.

[0028] In the BC battery described above, the copper electrode in the first direction includes M grid lines spaced apart.

[0029] At least one of the gate lines has a thickness of 1~2 μm;

[0030] At least one of the gate lines has a width of 15~20μm;

[0031] The spacing between two adjacent gate lines is 180~280μm.

[0032] A second aspect of the present invention provides a method for preparing the above-described BC battery, comprising:

[0033] After setting a copper electrode substrate on the surface of the functional layer using a copper source, an annealing process is performed to obtain the BC battery precursor.

[0034] Laser etching is performed on the copper electrode substrate in the BC battery precursor to obtain the BC battery including the copper electrode;

[0035] The functional layer includes a diffusion barrier layer and / or an antioxidant layer;

[0036] The diffusion barrier layer comprises stacked SiN x Layers and AlO y The antioxidant layer comprises a nickel layer and a tin layer stacked together;

[0037] The BC battery includes both a diffusion barrier layer and an oxidation-resistant layer.

[0038] In the preparation method described above, the annealing treatment is performed at a temperature of 700-750°C for 30-60 minutes; and / or,

[0039] In the laser etching process, the wavelength is 532nm, the power is 1~3W, and the scanning speed is 500~1000mm / s.

[0040] A third aspect of the present invention provides a photovoltaic module comprising the aforementioned BC cell.

[0041] The present invention provides a functional layer comprising a diffusion barrier layer and / or an oxidation-resistant layer on at least one surface of a copper electrode, wherein the diffusion barrier layer comprises stacked SiN x Layers and AlO y The layer and the anti-oxidation layer include a stacked nickel layer and a tin layer. The BC battery also includes a diffusion barrier layer and an anti-oxidation layer, which can synergistically suppress the problems of copper ion migration, oxidation corrosion and interface instability faced by copper electrodes under high temperature sintering and humid heat service conditions. This gives the BC battery both excellent diffusion barrier and anti-oxidation capabilities, thereby improving the photoelectric conversion efficiency and service life of the BC battery. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the passivation layer structure in some embodiments of the present invention;

[0044] Figure 2 This is a schematic diagram of the BC battery structure in some embodiments of the present invention.

[0045] Figure label:

[0046] 1: Passivation layer;

[0047] 11: Silicon dioxide layer;

[0048] 12: Silicon nitride layer;

[0049] 2: Silicon substrate;

[0050] 3: First transition layer;

[0051] 4: SiN x layer;

[0052] 5: AlO y layer;

[0053] 6: Second transition layer;

[0054] 7: Copper electrode;

[0055] 8: Nickel layer;

[0056] 9: Tin layer. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the absence of conflict, the following embodiments and features can be combined with each other.

[0058] In existing copper ion diffusion barrier (BC) batteries, the antioxidant layer is often a single nickel or tin layer, and the diffusion barrier layer is often a single silicon nitride or titanium layer. A single diffusion barrier structure often struggles to simultaneously address both the copper ion diffusion barrier capability and the BC battery's contact resistance. Furthermore, a single antioxidant structure is prone to degradation in protective capabilities under high-temperature processing, humid environments, and long-term service conditions. The inventors discovered that by constructing a multi-layered composite functional layer structure in the BC battery and incorporating specific materials into these functional layers, the antioxidant and diffusion barrier capabilities of the BC battery can be synergistically improved.

[0059] A first aspect of the present invention provides a BC battery, including a functional layer and a copper electrode;

[0060] The functional layer includes a diffusion barrier layer and / or an oxidation resistant layer, and the functional layer is located on at least one side surface of the copper electrode;

[0061] The diffusion barrier layer includes stacked SiN x Layers and AlO y The anti-oxidation layer includes a stacked nickel layer and a tin layer;

[0062] BC batteries include both an antioxidant layer and a diffusion barrier layer.

[0063] Specifically, the functional layer can be located on one side of the copper electrode or on both sides of the copper electrode.

[0064] In the BC battery of the present invention, the SiN diffusion barrier layer contains SiN x The layer possesses a dense network structure, which can form a stable physical barrier, blocking the diffusion and migration pathways of copper ions in the copper electrode; AlO y The layer possesses excellent copper ion trapping and retention properties, forming a chemical barrier; simultaneously, SiN... x Layers and AlO y Atomic substitutions also occur between layers, forming stable bonding structures such as Si-O-Al and Al-N, eliminating SiN x Layers and AlO y The gaps between the layers create a seamless double barrier, further hindering the diffusion of copper ions. SiN x Layers and AlO y Layers are stacked sequentially to form a double-layer composite diffusion barrier system. Through the synergistic effect of physical blocking and chemical hindrance, the barrier effect on copper ions is greatly improved, preventing copper ions from diffusing and damaging the core structure of the battery, thereby achieving high diffusion barrier capability of BC battery.

[0065] Meanwhile, in the antioxidant layer, the nickel in the nickel layer is heat-resistant and chemically stable, which can isolate oxygen from direct contact with the copper electrode; the tin in the tin layer has low surface energy and good environmental tolerance, and can form hydrophobic and oxygen-repellent interfaces, further blocking water vapor and oxygen penetration, so that the BC battery of the present invention has high antioxidant capacity.

[0066] In summary, the BC battery of the present invention, through the synergistic design of the diffusion barrier layer and the anti-oxidation layer, can further optimize the diffusion barrier performance and anti-oxidation performance of the BC battery, effectively avoid structural damage and performance degradation caused by copper ion diffusion and electrode oxidation, thereby improving the working efficiency and service life of the BC battery.

[0067] In some implementations, SiN x The thickness of the layer is 30~40nm.

[0068] In some implementations, AlO y The thickness of the layer is 20~30nm.

[0069] In some embodiments, the thickness of the nickel layer is 50~100 nm.

[0070] In some implementations, the thickness of the tin layer is 30-50 nm.

[0071] In some implementations, AlOy In the layer, AlO y The purity is ≥99.5%.

[0072] In some embodiments, the diffusion barrier layer of the present invention can reduce the diffusion depth of copper ions in the BC battery to ≤50nm, which is more than 37.5% lower than the prior art (>80nm), completely avoiding the destruction of the PN junction in the BC battery, and reducing the annual battery degradation rate to ≤1%.

[0073] In some embodiments, the antioxidant layer of the present invention can achieve dual protection for BC batteries at high temperatures and in outdoor environments; the antioxidant layer is sintered at a high temperature of 700~750℃ without oxidation or peeling; the electrode resistance of the BC battery after 1000h of damp heat cycling (85℃, 85%RH) increases by ≤10%, which is more than twice that of the prior art (increase >30%), meeting the life requirement of BC batteries for 25 years of outdoor service.

[0074] In some embodiments, the contact resistance of the BC battery of the present invention is ≤5mΩ.

[0075] In some embodiments of the present invention, the functional layer includes a diffusion barrier layer and an oxidation-resistant layer, and the diffusion barrier layer and the oxidation-resistant layer are stacked. The functional layer is located on one side surface of the copper electrode. AlO y The layer is close to the nickel layer, and the tin layer is close to the copper electrode.

[0076] At this point, the BC battery of the present invention includes SiN cells stacked sequentially. x Layer, AlO y The battery consists of a SiN layer, a nickel layer, a tin layer, and a copper electrode. The BC battery of this invention can utilize SiN... x Layers and AlO y The layer forms a dual physical and chemical barrier, which inhibits the diffusion and migration of copper ions in the copper electrode. It can also tightly protect the surface of the copper electrode by means of the layered cooperation of the nickel and tin layers, and prevent the intrusion of oxygen and water vapor to inhibit electrode oxidation. Through the cooperation of the diffusion barrier layer and the anti-oxidation layer, the working stability of the BC battery is improved simultaneously from the aspects of ion barrier and corrosion protection, ensuring the working efficiency of the BC battery and extending the overall service life.

[0077] In some embodiments of the present invention, the functional layer includes a first functional layer and a second functional layer, wherein the first functional layer and the second functional layer are respectively located on both sides of the copper electrode.

[0078] The first functional layer includes a diffusion barrier layer, and the second functional layer includes an antioxidant layer, AlO. y The nickel layer is close to the copper electrode, and the nickel layer is close to the copper electrode.

[0079] At this point, the BC battery of the present invention includes SiN cells stacked sequentially.x Layer, AlO y The structure consists of a copper electrode, a nickel layer, and a tin layer. A diffusion barrier layer and an anti-oxidation layer are located on two sides of the copper electrode, respectively. (SiN...) x Layers and AlO y The diffusion barrier layer directly intercepts the diffusion of copper ions in the copper electrode, preventing the efficiency of the BC battery from degrading. At the same time, the nickel and tin layers directly protect the surface of the copper electrode, isolating it from corrosion caused by oxygen and moisture. The diffusion barrier layer and the anti-oxidation layer have clear functions and do not interfere with each other, reducing the contact resistance of the BC battery while giving it excellent diffusion barrier and anti-oxidation performance. Furthermore, the copper electrode is subjected to symmetrical and uniform stress, making it less prone to cracking and peeling of functional layers, thus improving the structural stability of the BC battery. This, in turn, enables photovoltaic modules including the BC battery to have higher efficiency and longer service life.

[0080] In some embodiments of the present invention, SiN x In the layer, the mass ratio of nitrogen to silicon is 1.2 to 1.5. For example, the mass ratio of nitrogen to silicon can be one of 1.2, 1.3, 1.4, 1.5 or any combination of two of them.

[0081] When SiN x When the mass ratio of nitrogen to silicon in the layer falls within the above-mentioned range, it allows SiN to achieve the desired effect. x This results in a denser and more uniform network structure with fewer internal pores and microscopic defects. This not only enhances the physical barrier against copper ions and blocks their diffusion channels, but also improves the performance of SiN. x The overall density, chemical stability, and interfacial bonding of the SiN layer ensure its integrity. x With moderate layer stress, it is not easy to crack and peel off, which gives BC cells better diffusion resistance and improves the structural stability of BC cells.

[0082] In some embodiments of the present invention, the particle size of metallic tin in the tin layer is 50~100nm. For example, the particle size of metallic tin can be one of 50nm, 60nm, 70nm, 80nm, 90nm, 100nm or any combination thereof.

[0083] When the particle size of metallic tin in the tin layer is within the above range, the surface energy of metallic tin is moderate, which can form a good interface bond with the nickel layer. It is not easy to cause agglomeration, cracking or peeling. It can effectively inhibit the corrosion of copper electrode by water vapor and oxygen, and ensure that the conductivity of copper electrode interface is not affected, thus further improving the durability of BC battery.

[0084] In some embodiments of the present invention, the BC battery further includes a first transition layer and a passivation layer, wherein the first transition layer is located between the passivation layer and the SiN.x Between the layers, the first transition layer comprises a titanium-tungsten alloy, with a mass ratio of titanium to tungsten of (6.5~7.5):(2.5~3.5).

[0085] In some implementations, the passivation layer can reduce carrier losses in the BC cell and improve the photoelectric conversion efficiency of the BC cell. For example... Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of passivation layer 1 in some embodiments of the present invention. Passivation layer 1 includes a silicon dioxide layer 11 and a silicon nitride layer 12 stacked sequentially.

[0086] Passivation layer 1 and SiN x When a first transition layer is included between the layers, in the BC battery, the silicon nitride layer 12 is disposed close to the first transition layer. The first transition layer can act as a bridge between the passivation layer 1 and the diffusion barrier layer. It achieves high-strength bonding with the passivation layer 1 by forming Ti-O-Si chemical bonds, thereby reducing the interlayer contact resistance. Furthermore, the titanium-tungsten alloy itself has a dense structure, which can not only block the diffusion of copper ions, giving the BC battery a better diffusion barrier capability, but also allow titanium elements to precipitate and generate TiO2 under high temperature conditions, further improving the oxidation resistance of the BC battery.

[0087] When the mass ratio of titanium to tungsten is (6.5~7.5):(2.5~3.5), the first transition layer exhibits superior bonding ability and structural stability. This ensures sufficient titanium to form stable Ti-O-Si bonds while maintaining the good mechanical properties of the first transition layer, resulting in lower contact resistance in the BC battery and improved operating efficiency and stability. For example, the mass ratio of titanium to tungsten can be any of 6.5:2.5, 6.5:3.5, 7.5:2.5, or 7.5:3.5, or a range consisting of any two of these ratios.

[0088] In some embodiments, the thickness of the silicon dioxide layer 11 in the passivation layer 1 is 1~5 nm.

[0089] In some embodiments, the thickness of the silicon nitride layer 12 in the passivation layer 1 is 20~30nm.

[0090] In some embodiments of the present invention, the BC battery further includes a second transition layer, the second transition layer being located at AlO. y Between the layer and the copper electrode, the second transition layer includes nickel and phosphorus elements, with a mass ratio of nickel to phosphorus of (7.5~8.5):(1.5~2.5).

[0091] When the BC battery also includes a second transition layer, the nickel in the second transition layer can form metallic bonds with the copper in the copper electrode, improving the interlayer bonding strength and resulting in a higher yield of the BC battery. Furthermore, phosphorus can inhibit the penetration of copper ions into the diffusion barrier layer, further enhancing the diffusion barrier capability of the BC battery. At the same time, phosphorus and nickel can form nickel phosphide, which has excellent corrosion resistance and oxidation resistance properties. It can form an isolation and protection between the copper electrode and the diffusion barrier layer, strengthening the oxidation resistance of the BC battery.

[0092] When the mass ratio of nickel to phosphorus is (7.5~8.5):(1.5~2.5), the nickel and phosphorus elements are well-matched, ensuring sufficient metallic bonding between nickel and copper and the formation of nickel phosphide. Simultaneously, it prevents insufficient phosphorus content from weakening the ion blocking ability and corrosion resistance of the second transition layer, resulting in a second transition layer with superior interlayer bonding, copper ion blocking, and corrosion resistance. For example, the mass ratio of nickel to phosphorus can be any of 7.5:1.5, 8.5:1.5, 7.5:2.5, 8.5:2.5, or a range consisting of any two of these ratios.

[0093] In some implementations, the thickness of the first transition layer is 15-25 nm.

[0094] In some implementations, the thickness of the second transition layer is 10-20 nm.

[0095] In some embodiments, the electrode detachment rate of the BC battery of the present invention is ≤1%, which is 7 percentage points lower than that of the prior art (more than 8%), and the yield is increased to more than 99%.

[0096] In some embodiments of the present invention, the BC cell further includes a silicon substrate, such as... Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of a BC cell in some embodiments of the present invention. The silicon substrate 2 includes interconnected doped regions and undoped regions in the thickness direction.

[0097] In the first direction, the doped region includes N spaced-apart boron-doped regions and phosphorus-doped regions, where N≥2;

[0098] The doped region is close to passivation layer 1.

[0099] Specifically, in silicon substrate 2, boron-doped regions form P-type semiconductors and phosphorus-doped regions form N-type semiconductors. The boron-doped and phosphorus-doped regions are arranged alternately to form a continuous PN junction structure in the doped regions.

[0100] By setting doped regions inside the silicon substrate 2, a regular built-in electric field can be constructed by alternating boron-doped and phosphorus-doped regions, which can separate photogenerated carriers generated during the operation of the BC cell and reduce carrier recombination losses. At the same time, it can work with the passivation layer 1 to further eliminate surface defects of the silicon substrate 2, reduce interface recombination centers, improve the collection efficiency of photogenerated carriers, thereby improving the photoelectric conversion efficiency of the BC cell and enhancing the electrical stability of the BC cell during operation.

[0101] The present invention does not specifically limit the first direction. The first direction can be a length direction perpendicular to the thickness direction or a width direction perpendicular to the thickness direction. The length direction and the width direction are perpendicular to each other.

[0102] In some embodiments of the present invention, the thickness of the doped region is 0.5 to 1.5 μm. For example, the thickness of the doped region can be any one of 0.5 μm, 1.0 μm, 1.5 μm, or any combination thereof.

[0103] When the thickness of the doped region includes the above range, a more stable PN junction structure can be formed in the silicon substrate 2, fully constructing the built-in electric field to efficiently separate and transport photogenerated carriers, making the carrier transport path in the silicon substrate 2 more stable, and further improving the photoelectric conversion efficiency of the BC cell.

[0104] In some embodiments of the present invention, the total doping concentration of boron and phosphorus in the doped region is 1 × 10⁻⁶. 19 ~5×10 20 cm -3 At the same time, a built-in electric field with moderate intensity and uniform distribution can be constructed inside the silicon substrate 2, so as to achieve more efficient separation and transport of photogenerated carriers, and enable the BC cell to have higher photoelectric conversion efficiency.

[0105] In some embodiments of the present invention, when the spacing between the boron-doped region and the phosphorus-doped region is 50-150 μm in the first direction, the PN junction in the silicon substrate 2 can fully capture and collect photogenerated carriers. At the same time, this spacing can optimize the current conduction path in the BC cell, reduce carrier transmission loss, and improve the photoelectric conversion efficiency of the BC cell. Exemplarily, the spacing between the boron-doped region and the phosphorus-doped region can be any one of 50 μm, 100 μm, 150 μm, or any combination thereof.

[0106] In some embodiments of the present invention, when the boron-doped region extends to a size of 50-200 μm in the first direction, it can match the photosensitive range of the BC battery, fully cover the photogenerated carrier generation region, and improve the effective collection area of ​​carriers; for example, the size of the boron-doped region can be any one of 50 μm, 100 μm, 150 μm, 200 μm or any combination thereof.

[0107] In some embodiments of the present invention, when the phosphorus-doped region extends to a size of 50-200 μm in the first direction, it can form a better electrical match with the adjacent boron-doped region, thereby improving the carrier transport efficiency and electrical output performance of the BC battery. For example, the size of the phosphorus-doped region can be any one of 50 μm, 100 μm, 150 μm, 200 μm, or any combination thereof.

[0108] In some embodiments of the present invention, in a first direction, the copper electrode 7 includes M grid lines spaced apart;

[0109] At least one gate line has a thickness of 1~2μm;

[0110] At least one gate line has a width of 15~20μm;

[0111] The spacing between two adjacent gate lines is 180~280μm.

[0112] The grid lines are mainly used to collect and extract photogenerated carriers inside the BC cell, forming a continuous conductive path to achieve efficient current collection and transmission. When the thickness of the grid lines is 1~2μm, the width is 15~20μm, and the spacing between two adjacent grid lines is 180~280μm, it can ensure that the grid lines have sufficient conductive cross-sectional area and reduce their own series resistance, while matching the arrangement of boron-doped and phosphorus-doped regions in the doping region, greatly improving the carrier collection efficiency and giving the BC cell a better photoelectric conversion capability.

[0113] For example, the thickness of at least one gate line can be any one of 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or any combination thereof; the width of at least one gate line can be any one of 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any combination thereof; and the spacing between two adjacent gate lines can be any one of 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, or any combination thereof.

[0114] A second aspect of the present invention provides a method for preparing the above-described BC battery, comprising:

[0115] After setting a copper electrode substrate on the surface of the functional layer using a copper source, an annealing process is performed to obtain the BC battery precursor.

[0116] Laser etching was performed on the copper electrode substrate in the BC cell precursor to obtain a BC cell including copper electrode 7.

[0117] The functional layers include a diffusion barrier layer and / or an antioxidant layer;

[0118] The diffusion barrier layer includes stacked SiN x Layer 4 and AlO y Layer 5, the antioxidant layer includes a nickel layer 8 and a tin layer 9 stacked together;

[0119] BC batteries include both a diffusion barrier layer and an oxidation-resistant layer.

[0120] Specifically, a copper electrode substrate is first deposited on the surface of the functional layer, followed by annealing. Annealing can make the functional layer and the copper electrode substrate bond more tightly, thus obtaining a BC battery precursor. Finally, laser etching is performed on the two opposite sidewalls of the copper electrode substrate. In some embodiments, the direction of laser etching is a second direction perpendicular to the first direction and the second direction is perpendicular to the thickness direction. After laser etching, grid lines are formed on the copper electrode substrate along the first direction, thus obtaining a BC battery including a copper electrode 7.

[0121] This invention involves setting a diffusion barrier layer and an oxidation-resistant layer in a BC battery, wherein the diffusion barrier layer contains SiN x Layer 4 and AlO y The double-layer structure of layer 5 achieves efficient blocking of copper ion diffusion through a physical-chemical synergistic mechanism. At the same time, the nickel layer 8 and tin layer 9 in the anti-oxidation layer can maintain excellent structural integrity in long-term outdoor environments, significantly reducing the corrosion risk of copper electrode 7. This gives the BC battery both excellent diffusion blocking ability and anti-oxidation ability, improving the photoelectric conversion efficiency and service life of the BC battery.

[0122] Furthermore, this invention is fully compatible with existing BC battery production lines, requiring no additional core equipment. The process is simple and easy to implement, adaptable to the needs of large-scale industrial production. In some embodiments, using the preparation method of this invention to establish a 1GW-scale BC battery production line can reduce costs by at least 80 million yuan.

[0123] The present invention does not impose any particular limitation on the copper source, and can be any copper source commonly used in the art. For example, the copper source can be copper sulfate.

[0124] In some embodiments of the present invention, when the annealing process is carried out at a temperature of 700~750℃ and a time of 30~60min, the functional layer can be fully bonded to the copper electrode substrate while saving energy, thereby improving the interlayer bonding force of the BC battery and giving the BC battery better structural stability. For example, in the annealing process, the temperature can be any one of 700℃, 710℃, 720℃, 730℃, 740℃, 750℃ or any combination thereof; the time can be any one of 30min, 40min, 50min, 60min or any combination thereof.

[0125] In some embodiments of the present invention, when the wavelength is 532nm, the power is 1~3W, and the scanning speed is 500~1000mm / s during laser etching, the copper electrode substrate can be laser etched more accurately. The grid lines obtained by laser etching are free of burrs and breaks, which improves the yield of BC cells and the stability of the conductive path in BC cells. For example, in laser etching, the power can be any one of 1W, 2W, 3W, or any combination thereof; the scanning speed can be any one of 500mm / s, 600mm / s, 700mm / s, 800mm / s, 900mm / s, 1000mm / s, or any combination thereof.

[0126] In some implementations, the laser etching precision is ±3 μm.

[0127] In some embodiments, the BC battery of the present invention can be prepared by including the following steps:

[0128] S1: The N-type silicon wafer is subjected to alkaline texturing, RCA cleaning and ozone oxidation treatment in sequence to obtain silicon substrate 2; then, boron ions and phosphorus ions are alternately and intermittently implanted on the surface of silicon substrate 2 along the first direction using an ion implantation process, followed by activation treatment to form boron-doped regions and phosphorus-doped regions.

[0129] S2:

[0130] The silicon substrate 2, which is doped with boron and phosphorus, is subjected to ozone oxidation treatment to grow a silicon dioxide layer 11 with a thickness of 1~5nm in situ on the surface of the doped region in the silicon substrate 2; then, a silicon nitride layer 12 with a thickness of 20~30nm is deposited on the surface of the silicon dioxide layer using PECVD process to obtain the passivation layer 1.

[0131] S3: Using magnetron sputtering, with TiW alloy target as the source, a first transition layer 3 of 15~25nm is formed on the surface of passivation layer 1 in an argon atmosphere.

[0132] S4: Using plasma-enhanced chemical vapor deposition (PECVD), a SiN layer with a thickness of 30-40 nm is deposited on the surface of the first transition layer 3 using silicon and nitrogen sources. x Layer 4;

[0133] Atomic layer deposition (ALD) was used, with trimethylaluminum and water as precursors, to deposit SiN x Layer 4 has an AlO layer with a thickness of 20-30 nm deposited on its surface. y Layer 5.

[0134] S5: An electroplating process is employed, using a mixed solution of nickel sulfate and sodium dihydrogen phosphate as the plating bath, in AlO₂... y The surface of layer 5 is electroplated with a second transition layer 6 with a thickness of 10~20nm.

[0135] S6: A copper electrode substrate with a thickness of 1~2μm is electroplated on the surface of the second transition layer 6 using a pulse electroplating process and a copper sulfate electroplating solution.

[0136] S7: Electroplating a nickel layer with a thickness of 50~100nm on the surface of the copper electrode substrate using a nickel source;

[0137] A tin layer 9 with a thickness of 30~50nm was deposited on the surface of the nickel layer 8 using a vacuum evaporation process to obtain the BC battery precursor.

[0138] S8: Place the BC battery precursor in an annealing furnace and anneal it under nitrogen protection. After annealing, allow the BC battery precursor to cool naturally to room temperature.

[0139] S9: Using maskless laser direct writing technology, the copper electrode substrate in the BC battery precursor is laser etched to form grid lines, resulting in a BC battery including copper electrode 7.

[0140] A third aspect of the present invention provides a photovoltaic module including the aforementioned BC cell. Since the BC cell of the present invention has both excellent diffusion blocking performance and oxidation resistance performance, the photovoltaic module including the BC cell has better photoelectric conversion efficiency, long-term working stability and aging resistance, thus extending the overall service life of the photovoltaic module, while ensuring that the photovoltaic module can still maintain stable electrical output and power generation capacity under complex outdoor conditions.

[0141] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0142] Example 1

[0143] The method for preparing the BC battery in this embodiment includes the following steps:

[0144] (a) The N-type silicon wafer was subjected to alkaline texturing (using a sodium hydroxide solution with a concentration of 20 g / L, at a temperature of 85 °C, for 12 min) and RCA cleaning (after cleaning, the surface roughness of silicon substrate 2 was 0.4 μm) to obtain silicon substrate 2.

[0145] (b) Boron ions and phosphorus ions are alternately implanted along a first direction (the length direction perpendicular to the thickness direction) on one surface of silicon substrate 2, and activated at 900°C to form boron-doped regions and phosphorus-doped regions, resulting in interconnected doped and undoped regions.

[0146] The doped region includes three spaced-apart boron-doped regions and a phosphorus-doped region; the total thickness of the doped region is 1.0 μm; and the total doping concentration of boron and phosphorus in the doped region is 8 × 10⁻⁶. 19 cm -3 ;

[0147] In the first direction, the spacing between the boron-doped region and the phosphorus-doped region is 100 μm, the extension size of the boron-doped region is 120 μm, and the extension size of the phosphorus-doped region is 120 μm.

[0148] (c) The silicon substrate 2 is subjected to ozone oxidation treatment, and a silicon dioxide layer 11 with a thickness of 3 nm is grown in situ on the surface of the doped region in the silicon substrate 2; then a silicon nitride layer 12 with a thickness of 25 nm is deposited on the surface of the silicon dioxide layer 11 by PECVD process to obtain the passivation layer 1.

[0149] (d) Using magnetron sputtering, a TiW alloy target (Ti:W=7:3) is used as the source. In an argon atmosphere (argon flow rate of 80 sccm), a first transition layer 3 with a thickness of 20 nm is set on the surface of the silicon nitride layer 12 in the passivation layer 1. The magnetron sputtering rate is 0.8 nm / s and the magnetron sputtering power is 180 W.

[0150] (e) Using PECVD process at a temperature of 350°C, with silane as the silicon source and ammonia as the nitrogen source, wherein the flow ratio of silane to ammonia is 1:4, a SiN layer with a thickness of 35 nm is deposited on the surface of the first transition layer 3. x Layer 4, SiN x In layer 4, the mass ratio of nitrogen to silicon is 1.35;

[0151] Using the ALD process, with trimethylaluminum and water as precursors, at a temperature of 150°C, SiN... x Layer 4 has an AlO layer with a thickness of 25 nm deposited on its surface. y Layer 5, deposition cycle 250, AlO y The uniformity of layer 5 is 96.2%.

[0152] (f) An electroplating process is adopted, using a mixed solution of nickel sulfate and sodium dihydrogen phosphate as the electroplating solution, wherein the mass ratio of nickel sulfate to sodium dihydrogen phosphate in the mixed solution is 7:1, in AlO y A second transition layer 6 with a thickness of 15 nm is electroplated on the surface of layer 5. During electroplating, the pH value is 4.5, the temperature is 55℃, the current density is 3.5A / dm², and the electroplating time is 12min. In the second transition layer 6, the mass ratio of nickel to phosphorus is 8:2.

[0153] (g) A pulse electroplating process was adopted, using a copper sulfate electroplating solution (the concentration of copper sulfate solution was 200 g / L, the concentration of sulfuric acid solution was 70 g / L, and the mass ratio of copper sulfate solution to sulfuric acid solution was 3:1); a copper electrode substrate with a thickness of 1.5 μm was electroplated on the surface of the second transition layer 6, and the initial linewidth of the copper electrode substrate was 18 μm; during electroplating, the pulse frequency was 300 Hz, the duty cycle was 50%, the current density was 8 A / dm², and the electroplating time was 45 min.

[0154] (h) A nickel layer with a thickness of 80 nm is electroplated on the surface of a copper electrode substrate using a nickel source. The nickel source includes a nickel sulfate solution with a concentration of 220 g / L, a nickel chloride solution with a concentration of 50 g / L, and a boric acid solution with a concentration of 35 g / L. The mass ratio of the nickel sulfate solution, nickel chloride solution, and boric acid solution is 5:1:0.8. During electroplating, the pulse frequency is 300 Hz, the duty cycle is 40%, the current density is 4.5 A / dm², and the electroplating time is 20 min.

[0155] A 40 nm thick tin layer 9 was deposited on the surface of the nickel layer 8 using a vacuum evaporation process. The tin particles in the tin layer 9 had a diameter of 75 nm. The vacuum evaporation process was carried out at a temperature of 220 °C and a vacuum degree of 1 × 10⁻⁶. -3 Pa yielded the BC battery precursor.

[0156] (i) The BC battery precursor was placed in an annealing furnace and annealed at 720°C for 45 minutes under nitrogen protection (nitrogen purity ≥ 99.999%). After annealing, the BC battery precursor was naturally cooled to room temperature.

[0157] (j) Using maskless laser direct writing technology, the copper electrode substrate in the BC battery precursor is laser etched under the conditions of laser wavelength of 532nm, power of 2W, and scanning speed of 800mm / s. The etching accuracy is ±3μm. After etching, the grid line thickness is 1.5μm, the grid line width is 18μm, and the spacing between two adjacent grid lines is 230μm, thus obtaining a BC battery including copper electrode 7.

[0158] Comparative Example 1

[0159] The preparation method of the BC battery in this comparative example is basically the same as that in Example 1, except that:

[0160] (d) Using PECVD process, SiN is deposited on the surface of silicon nitride layer in passivation layer using silane and ammonia gas. x The diffusion barrier layer was deposited at a temperature of 350°C with a silane to ammonia flow rate ratio of 1:4. (SiN) x The thickness of the diffusion barrier layer is 35 nm; SiN x In the diffusion barrier layer, the nitrogen-to-silicon mass ratio is 1.35.

[0161] (e) In SiN x A copper electrode substrate is disposed on the surface of the diffusion barrier layer. The preparation steps of the copper electrode substrate are the same as those in step (g) of Example 1.

[0162] (f) A nickel layer and a tin layer are formed on the surface of the copper electrode substrate. The preparation steps of the nickel layer and the tin layer are the same as those in step (h) of Example 1.

[0163] In Comparative Example 1, the stacked structure of the BC cell is as follows: silicon substrate, passivation layer, SiN x Diffusion barrier layer, copper electrode, nickel layer, tin layer.

[0164] Performance testing

[0165] The following performance tests were performed on the examples and comparative examples respectively:

[0166] (1) Contact resistance test

[0167] The contact resistance of BC batteries was measured in the test examples and comparative examples according to the national standard GB / T 15519-2015.

[0168] (2) Copper ion diffusion depth test

[0169] Test method: Time-of-flight secondary ion mass spectrometry (TOF-SIMS) in-depth analysis test.

[0170] Test equipment: Time-of-flight secondary ion mass spectrometer.

[0171] Test conditions: The test vacuum degree is 1×10⁻⁶. -3 Pa, ion beam energy 15keV, scanning area 50μm×50μm, longitudinal layer-by-layer etching analysis, etching step size 1nm.

[0172] Test procedure: The BC batteries in the examples and comparative examples were cut into standard test samples, and after surface cleaning, they were fixed in the cavity of the time-of-flight secondary ion mass spectrometer. The standard test samples were scanned along the thickness direction by the ion beam, and the signal intensity distribution of copper element was collected in real time. The thickness corresponding to the position of the silicon substrate background noise in the standard test sample where the copper element signal decayed was determined as the maximum diffusion depth of copper ions. Each set of standard test samples was tested 3 times and the average value was taken.

[0173] (3) Antioxidant performance test under damp heat aging

[0174] The increase in resistance of BC batteries during 1000h damp heat cycling was used as a measure of the oxidation resistance of BC batteries in the test examples and comparative examples of the international standard IEC 61215-2021.

[0175] (4) Electrode shedding rate test

[0176] Test method: thermal shock coupling tape peeling reliability test.

[0177] Testing equipment: High and low temperature thermal shock test chamber, 3M standard adhesion test tape.

[0178] Test conditions: thermal shock range -40℃ to 85℃, single cycle duration 30min, cumulative cycle 50 times; tape peeling angle 90°, vertical uniform peeling.

[0179] Testing Procedure: 100 BC batteries from the example and comparative examples were randomly selected. First, the BC batteries underwent 50 cycles of high and low temperature thermal shock testing. After the high and low temperature thermal shock testing, 3M standard adhesion testing tape was used to tightly adhere to the surface of the copper electrode grid lines of the BC batteries. Then, the tape was peeled off vertically and at a uniform speed. The surface condition of the copper electrode grid lines was visually observed. If peeling, curling, local detachment, or delamination defects appeared, the batteries were judged to be ineffective. Electrode detachment rate = number of ineffective BC batteries / total number of samples × 100%.

[0180] The performance test results are shown in Table 1.

[0181] Table 1

[0182]

[0183] As shown in Table 1, the contact resistance, copper ion diffusion depth, resistance increase after 1000h damp heat cycling, and electrode detachment rate of the BC battery in the embodiment are all lower than those in the comparative example. This is because the BC battery of the present invention includes SiN. x Layer 4 and AlO yThe diffusion barrier layer (layer 5) forms a copper ion diffusion barrier through a combination of physical blocking and chemical ion capture, giving the BC battery a stronger copper ion diffusion barrier capability. It also includes an antioxidant layer composed of nickel layer 8 and tin layer 9, which better isolates oxygen and moisture from external intrusion, giving the BC battery excellent oxidation resistance. Furthermore, the diffusion barrier layer and antioxidant layer are located on both sides of the copper electrode 7, reducing the contact resistance of the BC battery. Further, the invention strengthens the interlayer bonding force of the BC battery through the first transition layer 3 and the second transition layer 6, further reducing the contact resistance. The synergistic adaptation of these functional layers significantly suppresses the migration and diffusion of copper ions, while reducing contact resistance, buffering thermal stress and structural degradation caused by damp heat aging, greatly mitigating resistance increases and avoiding electrode detachment problems.

[0184] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A BC battery, characterized in that, Includes the functional layer and copper electrodes; The functional layer includes a diffusion barrier layer and / or an oxidation-resistant layer, and the functional layer is located on at least one side surface of the copper electrode; The diffusion barrier layer comprises stacked SiN x Layers and AlO y The antioxidant layer comprises a nickel layer and a tin layer stacked together; The BC battery includes both an antioxidant layer and a diffusion barrier layer.

2. The BC battery according to claim 1, characterized in that, The functional layer includes a diffusion barrier layer and an oxidation-resistant layer, and the diffusion barrier layer and the oxidation-resistant layer are stacked together. The functional layer is located on one side surface of the copper electrode. y The layer is close to the nickel layer, and the tin layer is close to the copper electrode.

3. The BC battery according to claim 1, characterized in that, The functional layer includes a first functional layer and a second functional layer, which are located on opposite sides of the copper electrode. The first functional layer includes a diffusion barrier layer, and the second functional layer includes an antioxidant layer, wherein the AlO y The nickel layer is located near the copper electrode.

4. The BC battery according to claim 3, characterized in that, The SiN x In the layer, the mass ratio of nitrogen to silicon is 1.2 to 1.5; and / or, In the tin layer, the particle size of metallic tin is 50~100nm; and / or, The BC battery further includes a first transition layer and a passivation layer, wherein the first transition layer is located between the passivation layer and the SiN. x Between the layers, the first transition layer comprises a titanium-tungsten alloy, wherein the mass ratio of titanium to tungsten is (6.5~7.5):(2.5~3.5); and / or, The BC battery further includes a second transition layer, which is located on the AlO₂. y Between the layer and the copper electrode, the second transition layer includes nickel and phosphorus elements, with a mass ratio of nickel to phosphorus of (7.5~8.5):(1.5~2.5).

5. The BC battery according to claim 4, characterized in that, The BC cell also includes a silicon substrate, which includes interconnected doped regions and undoped regions in the thickness direction; In the first direction, the doped region includes N spaced-apart boron-doped regions and phosphorus-doped regions, where N ≥ 2; The doped region is located near the passivation layer.

6. The BC battery according to claim 5, characterized in that, The thickness of the doped region is 0.5~1.5 μm; and / or, In the doped region, the total doping concentration of boron and phosphorus is 1×10⁻⁶. 19 ~5×10 20 cm -3 ; and / or, In the first direction, the spacing between the boron-doped region and the phosphorus-doped region is 50~150μm; And / or, In the first direction, the boron-doped region extends to a size of 50~200 μm; And / or, In the first direction, the phosphorus-doped region extends to a size of 50~200 μm.

7. The BC battery according to claim 5 or 6, characterized in that, In the first direction, the copper electrode includes M grid lines spaced apart; At least one of the gate lines has a thickness of 1~2 μm; At least one of the gate lines has a width of 15~20μm; The spacing between two adjacent gate lines is 180~280μm.

8. A method for preparing a BC battery according to any one of claims 1-7, characterized in that, include: After setting a copper electrode substrate on the surface of the functional layer using a copper source, an annealing process is performed to obtain the BC battery precursor. Laser etching is performed on the copper electrode substrate in the BC battery precursor to obtain the BC battery including the copper electrode; The functional layer includes a diffusion barrier layer and / or an antioxidant layer; The diffusion barrier layer comprises stacked SiN x Layers and AlO y The antioxidant layer comprises a nickel layer and a tin layer stacked together; The BC battery includes both a diffusion barrier layer and an oxidation-resistant layer.

9. The preparation method according to claim 8, characterized in that, In the annealing process, the temperature is 700~750℃ and the time is 30~60min; and / or, In the laser etching process, the wavelength is 532nm, the power is 1~3W, and the scanning speed is 500~1000mm / s.

10. A photovoltaic module, characterized in that, Includes the BC battery as described in any one of claims 1-7.

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