Paste composition for preparing solar cell electrode, solar cell electrode, and solar cell

Abstract

The invention provides a paste composition for preparing a solar cell electrode, a solar cell electrode and a solar cell. The paste composition comprises 10 to 90 wt% of a first conductive particle; 1 to 60 wt% of second conductive particles; 0.1 to 15 wt% of an inorganic binder powder comprising a first inorganic binder powder having a glass transition temperature of between 300 DEG C and 450 DEG C and a second inorganic binder powder having a glass transition temperature of between 450 DEG C and 700 DEG C, the weight ratio of the first and second inorganic binder powders being in the range of 0.03: 1 to 25: 1; and 2 to 20 wt% of an organic vehicle, the above weight percentages being based on the total weight of the paste composition, the sum of all the components in the paste composition being 100 wt%. According to the paste composition, the solar cell electrode and the solar cell, the low contact resistance between the electrode and the silicon substrate is ensured, the electroluminescence performance of a cell piece is improved, the performance is excellent in an acetic acid stability test, and attenuation of the cell efficiency is effectively restrained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solar cells, and in particular, to a paste composition for preparing a solar cell electrode, a solar cell electrode and a solar cell. BACKGROUND

[0002] In the field of photovoltaic new energy, especially in the manufacture of solar cells, metallization as one of the key technologies is used to form electrodes to collect and transport photo-generated carriers. The current mainstream photovoltaic silver paste mainly consists of silver powder, glass powder and organic carrier, in which the silver powder accounts for about 90% of the total weight. Although silver as a conductive material has superior performance, its price fluctuates greatly, and in recent years, the price of silver has soared by more than 100%, which has brought great challenges to the cost control of solar cells.

[0003] Reducing the amount of silver in the silver paste or replacing it with a cheaper base metal (such as copper, nickel, etc.) is an effective way to reduce the cost of the cell. However, base metals differ significantly from silver in terms of electrical conductivity, stability, and contact properties with the silicon substrate, and direct replacement can lead to a decrease in the photoelectric conversion efficiency of solar cells, especially for high-efficiency solar cells such as TOPCon (tunnel oxide passivation contact layer) and HJT (intrinsic thin layer heterojunction), which can be critical.

[0004] In the case of reducing the amount of silver powder or introducing base metals, the existing technology faces many problems. In the existing technology, in order to prevent the oxidation of base metals during sintering, some technical solutions require sintering in an inert or reducing atmosphere, which is not compatible with the traditional sintering process of silver paste in air, increasing the production complexity and equipment cost. The existing technology method wraps a protective layer on the surface of the base metal particles to prevent oxidation, but this protective layer must be completely decomposed and cannot remain during sintering, otherwise it will affect the conductivity. It is very difficult to control the conditions for complete decomposition of the protective layer, which can result in a low yield. The bulk resistivity and contact resistance of the base metal paste used are usually higher than that of silver paste, which can affect the collection and transmission efficiency of the current, resulting in a decrease in cell performance. The adhesion and long-term reliability of silver paste to the surface of silicon wafer have been optimized for a long time, while the performance of base metal paste in this regard can be unstable, with weak adhesion, easy peeling, poor resistance to humidity and heat, and poor resistance to potential induced degradation (PID), etc. The sintering temperature of some base metal paste is different from that of silver paste, which may require modification or adjustment of the existing furnace, affecting production efficiency and rhythm. In order to prevent oxidation of base metals, strong reducing substances or specific glass powders may be added to the paste, but these ingredients may corrode the silicon wafer or passivation layer at high temperatures, resulting in a decrease in cell efficiency or even damage to the device.

[0005] To solve the above technical problem, there is still a need to develop a paste composition for preparing a solar cell electrode, aiming to significantly reduce the amount of silver while maintaining or even improving the conversion efficiency of the solar cell, thereby reducing the production cost, while ensuring the long-term stability and reliability of the cell. SUMMARY

[0006] The present application relates to a paste composition for preparing a solar cell electrode, a solar cell electrode, and a solar cell.

[0007] To achieve the above object, according to one aspect of the present application, there is provided a paste composition for preparing a solar cell electrode, comprising: 10 to 90 wt% of first conductive particles, the first conductive particles being silver particles; 1 to 60 wt% of second conductive particles, the second conductive particles comprising aluminum particles, nickel particles, silver-coated nickel particles, and / or silver-coated copper particles; 0.1 to 15 wt% of inorganic binder powder, the inorganic binder powder comprising first inorganic binder powder having a glass transition temperature of 300 to 450°C, and second inorganic binder powder having a glass transition temperature of 450 to 700°C, the weight ratio of the first inorganic binder powder to the second inorganic binder powder being in the range of 0.03:1 to 25:1; and 2 to 20 wt% of organic vehicle, the above weight percentages being based on the total weight of the paste composition, and the sum of all components in the paste composition being 100 wt%.

[0008] In the above paste composition, the inorganic binder powder is glass powder; preferably, the particle size distribution D 50 is in the range of 0.5 to 3 μm, D max is less than 6 μm; more preferably, D max is less than 4 μm.

[0009] In the above paste composition, the first inorganic binder powder comprises: 5 to 50 wt% of P2O5; 0 to 50 wt% of PbO; 10 to 40 wt% of B2O3; 0 to 80 wt% of Bi2O3; 0 to 10 wt% of SiO2; 0 to 10 wt% of TeO2; 1 to 10 wt% of SnO2; and 1 to 5 wt% of SnCl2, the above weight percentages being based on the total weight of the first inorganic binder powder, and the sum of all components in the first inorganic binder powder being 100 wt%.

[0010] In the above-mentioned paste composition, the first inorganic binder powder further comprises other metal oxides, including Al2O3, ZnO, WO3, MoO3, CuO, TiO2, Nb2O5, NiO, Fe2O3, Y2O3, MgO, CaO, SrO, BaO, Li2O, Na2O or K2O, and the amount of other metal oxides is in the range of 0 wt% to 10 wt% based on the total weight of the first inorganic binder powder.

[0011] In the above paste composition, the second inorganic binder powder comprises 1 wt% to 50 wt% of La2O5; 1 wt% to 20 wt% of SiO2; 10 wt% to 40 wt% of B2O3; 0 wt% to 30 wt% of Ga2O3; 0 wt% to 10 wt% of ZrO2; 0 wt% to 30 wt% of PbO; and 0 wt% to 40 wt% of Bi2O3, all weight percentages being based on the total weight of the second inorganic binder powder, and the sum of all components in the second inorganic binder powder being 100 wt%.

[0012] In the above-mentioned paste composition, the second inorganic binder powder further comprises other metal oxides, including Al2O3, ZnO, WO3, MoO3, CuO, TiO2, Nb2O5, NiO, Fe2O3, Y2O3, MgO, CaO, SrO, BaO, Li2O, Na2O, or K2O, with the amount of other metal oxides ranging from 0 wt% to 10 wt% based on the total weight of the second inorganic binder powder.

[0013] In the above paste composition, the second conductive particle is a nickel particle, and the content of the nickel particle is from 5 wt% to 20 wt% based on the total weight of the paste composition.

[0014] In the above paste composition, the second conductive particles are silver-coated nickel particles or silver-coated copper particles, and the content of silver-coated nickel particles or silver-coated copper particles is 10 wt% to 30 wt% based on the total weight of the paste composition.

[0015] In the above paste composition, the organic carrier is selected from one or more of the group consisting of organic solvents, binders, plasticizers and surfactants.

[0016] According to another aspect of the present invention, a solar cell electrode is provided, which is prepared from the paste composition of the present invention.

[0017] According to another aspect of the present invention, a solar cell is provided, which includes the solar cell electrode of the present invention.

[0018] The paste composition, solar cell electrode, and solar cell of the present invention for preparing solar cell electrodes maintain conductivity and reliability comparable to pure silver paste, even with a significant reduction in silver content. Furthermore, it ensures low contact resistance between the electrode and the silicon substrate, improves the electroluminescence (EL) performance of the cell, and exhibits excellent performance in acetic acid stability tests, effectively suppressing the degradation of cell efficiency. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 The solar cell of Example 8 is shown before acid resistance testing.

[0021] Figure 2 The solar cell of Example 8 is shown after acid resistance testing.

[0022] Figure 3 The solar cell of Example 11 is shown before acid resistance testing.

[0023] Figure 4 The solar cell of Example 11 is shown after acid resistance testing.

[0024] Figure 5 The solar cell of Comparative Example 3 is shown before the acid resistance test.

[0025] Figure 6 The solar cell of Comparative Example 3 is shown after acid resistance testing. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0027] In existing technologies, reducing the amount of silver powder or introducing base metals cannot effectively guarantee conductivity, and problems such as weak adhesion, easy detachment, poor resistance to damp heat, and poor resistance to potential-induced degradation (PID) exist. To address the problems in the prior art, according to a typical embodiment of this application, a paste composition for preparing solar cell electrodes is provided. This paste composition comprises: 10 wt% to 90 wt% of first conductive particles, 1 wt% to 60 wt% of second conductive particles, 0.1 wt% to 15 wt% of inorganic binder powder, and 2 wt% to 20 wt% of organic carrier. All weight percentages are based on the total weight of the paste composition, and the sum of all components in the paste composition is 100 wt%. In this embodiment, the first conductive particle is a silver particle, the second conductive particle includes aluminum particles, nickel particles, silver-coated nickel particles and / or silver-coated copper particles, and the inorganic binder powder includes a first inorganic binder powder having a glass transition temperature between 300°C and 450°C, and a second inorganic binder powder having a glass transition temperature between 450°C and 700°C, wherein the weight ratio of the first inorganic binder powder to the second inorganic binder powder is in the range of 0.03:1 to 25:1.

[0028] The paste composition of this invention for improving the performance of solar cell electrodes aims to achieve a balance between high conductivity and cost-effectiveness in electrode materials through the rational proportioning of various components. The first conductive particle is silver particles, which account for 10 wt% to 90 wt% of the paste composition. Silver particles play a crucial role in solar cell electrodes due to their excellent conductivity and stability, and are key to ensuring a low-resistance ohmic contact between the electrode and the solar cell. While a high proportion of silver particles can significantly improve the conductivity of the electrode, given the impact of silver price fluctuations on production costs, this invention achieves cost control and optimized electrode performance by adjusting the proportion of silver particles and combining them with the use of other conductive particles.

[0029] The second conductive particles used in the paste composition of the present invention include aluminum, nickel, silver-coated nickel, and / or silver-coated copper particles, accounting for 1 wt% to 40 wt% of the paste composition. The introduction of these particles aims to replace some of the silver particles, thereby significantly reducing the amount of silver used. The silver-coated nickel and silver-coated copper particles employ a core-shell structure, with an inexpensive base metal core and a silver outer shell. This design not only reduces costs but also, through the protective effect of the silver shell, prevents the base metal from oxidizing during sintering, ensuring the conductivity and stability of the electrode.

[0030] The inorganic binder powder used in the paste composition of the present invention accounts for 0.1 wt% to 15 wt% of the paste composition. This inorganic binder powder consists of two systems. The first inorganic binder powder has a low glass transition temperature (Tg), typically between 300°C and 450°C, and can rapidly soften in the early stages of sintering, thus protecting the surface of the base metal particles and preventing their oxidation. The second inorganic binder powder has a Tg between 450°C and 700°C, and plays a role in the later stages of sintering, enhancing the structural stability of the electrode film and preventing excessive erosion of the passivation layer, which could damage electrode performance.

[0031] The organic carrier used in the paste composition of the present invention accounts for 2 wt% to 20 wt% of the paste composition. The organic carrier not only imparts good rheological properties to the paste composition, ensuring its continuity and uniformity during the printing process, but also provides the necessary viscosity so that the paste can maintain the desired shape after printing until the organic carrier completely volatilizes during the sintering process, leaving no residue that affects the electrode performance.

[0032] The glass powder in the paste composition of the present invention, after high-temperature sintering, can completely etch away the silicon nitride antireflection layer (SiN) on the surface of the silicon wafer. x This allows silver to form a low-resistance ohmic contact with silicon (Si). However, base metals such as nickel have a different work function than silver, and their oxides (NiO) have poor conductivity. Simply replacing silver with nickel will prevent the paste from forming the same high-quality ohmic contact, leading to a sharp increase in contact resistance. This directly reduces the battery's fill factor (FF) and conversion efficiency (Eff).

[0033] Although nickel is more stable than copper, it will still partially oxidize at the high temperatures (approximately 800°C) during silver paste sintering and under atmospheric conditions, forming NiO. NiO is a semiconductor with a resistivity much higher than metallic nickel, which severely degrades the bulk resistivity of the paste. This leads to increased series resistance and decreased battery performance. Furthermore, silver powder undergoes rearrangement and densification through the molten glass phase at high temperatures, forming excellent conductive channels. Nickel's melting point (1455°C) is much higher than silver's (961°C), and it is "rigid" at silver sintering temperatures. Adding too much nickel powder will alter the sintering kinetics of the paste, adversely affecting the electrode film, making it porous and reducing conductivity.

[0034] In terms of glass design, the inorganic binder powder (glass powder) of this invention comprises two systems. The first is a low-melting-point phosphate glass system, which also contains a small amount of etching elements. The phosphate glass has a unique [PO4] tetrahedral structure, P... 5+ The variable valence of phosphorus (P) gives phosphate glass systems reducing properties. Phosphorus (P) in glass is typically in the +5 valence state (P₂O₅). 5 +However, under high temperature and specific conditions, it can be reduced to a lower valence state (such as P). 3+ This valence change process involves the transfer of electrons. For example, when glass powder comes into contact with nickel oxide (NiO) on the surface of nickel powder, P... 5+ It can capture oxygen from oxides, reducing itself to a lower valence state, while simultaneously reducing the metal oxide, thereby preventing nickel oxidation and maintaining its conductivity. Taking advantage of the characteristics of phosphates, the inventors of this invention added lead oxide or bismuth oxide, enabling it to etch SiN during sintering. x Furthermore, it can undergo specific reactions at the nickel and silicon interface, reducing any nickel oxides that may form and promoting the formation of a low-resistance contact layer. Simultaneously, due to the lower glass transition temperature (Tg) of the first glass system (phosphate glass), it exhibits good flow and wetting properties during high-temperature sintering. Before the silver powder is fully sintered, it softens and coats the surfaces of the nickel and silver powders, preventing localized silver-to-silver bonding and avoiding nickel-to-nickel concentration. Instead, it evenly disperses silver and nickel, forming a continuous two-phase conductive path, which is beneficial for electron transport. Silver has higher conductivity than nickel, especially at the interface after sintering; silver is necessary to ensure low contact resistance at the ohmic contact points with silicon. Excessive nickel in localized areas can prevent current collection, leading to non-conductive blackening of the solar cell. The second glass system, due to its relatively high glass transition temperature (Tg),... g Therefore, during sintering, the high viscosity and slow flow of the glass can locally buffer the over-erosion of the first glass system, thus protecting the passivation film of the battery from excessive erosion. Furthermore, due to the large atomic radii of elements such as La and Ga in the second glass system, more silver can be incorporated into the glass, providing more lattice sites for the glass network and allowing for the incorporation of more atomic silver or silver ions. In this case, during the Laser-Enhanced Contact Optimization (LECO) process, more silver can migrate to the silicon interface in the TOPCon battery, forming more silver-silicon conductive alloy contact points, reducing the contact resistivity of the slurry grid lines, and thus compensating for the weakened electronic conductivity from the grid lines to the silicon emitter due to the addition of base metals such as nickel. In addition, due to the inclusion of strong covalent bonds such as La-O, Ga-O, and Si-O, the high-melting-point glass has a more stable glass network structure. Dispersing the glass system in the slurry and sintering it can build a strong skeleton network for the entire grid line, and enhance the grid line's water resistance and acetic acid resistance, ensuring the stability of TOPCon cells in high temperature and high humidity environments.

[0035] The paste composition of this invention enables the electrode to maintain conductivity and reliability comparable to pure silver paste, even with a significant reduction in silver usage. Specifically, the use of silver-coated nickel or silver-coated copper core-shell structure particles, combined with the synergistic effect of two inorganic binder powders, not only reduces the overall silver usage (silver consumption can be reduced by 30%-50%), but also ensures low contact resistance between the electrode and the silicon substrate, improving the electroluminescence (EL) performance of the cell. Furthermore, it exhibits excellent performance in acetic acid stability tests, effectively suppressing the degradation of cell efficiency.

[0036] In some embodiments of the invention, the amount of the first conductive particles may be in the following ranges based on the total weight of the paste composition: 10 wt% to 90 wt%, 20 wt% to 80 wt%, 30 wt% to 70 wt%, 40 wt% to 60 wt%, 10 wt% to 80 wt%, 10 wt% to 70 wt%, 10 wt% to 60 wt%, 10 wt% to 50 wt%, 10 wt% to 40 wt%, 10 wt% to 30 wt%, 10 wt% to 20 wt%, 20 wt% to 90 wt%, 30 wt% to 90 wt%, 40 wt% to 90 wt%, 50 wt% to 90 wt%, 60 wt% to 90 wt%, 70 wt% to 90 wt%, or 80 wt% to 90 wt%.

[0037] Based on the total weight of the paste composition, the amount of the second conductive particles can be in the following ranges: 1 wt% to 60 wt%, 5 wt% to 50 wt%, 10 wt% to 40 wt%, 20 wt% to 30 wt%, 1 wt% to 50 wt%, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, 1 wt% to 10 wt%, 10 wt% to 60 wt%, 20 wt% to 60 wt%, 30 wt% to 60 wt%, 40 wt% to 60 wt%, or 50 wt% to 60 wt%.

[0038] Based on the total weight of the paste composition, the amount of inorganic binder powder may be in the following ranges: 0.1 wt% to 15 wt%, 1 wt% to 14 wt%, 2 wt% to 13 wt%, 3 wt% to 12 wt%, 4 wt% to 11 wt%, 5 wt% to 10 wt%, 6 wt% to 9 wt%, 7 wt% to 8 wt%, 0.1 wt% to 10 wt%, 0.1 wt% to 5 wt%, 1 wt% to 15 wt%, 5 wt% to 15 wt%, or 10 wt% to 15 wt%.

[0039] Based on the total weight of the paste composition, the amount of organic carrier may be in the following ranges: 2 wt% to 20 wt%, 3 wt% to 19 wt%, 4 wt% to 18 wt%, 5 wt% to 17 wt%, 6 wt% to 17 wt%, 7 wt% to 16 wt%, 8 wt% to 15 wt%, 9 wt% to 14 wt%, 10 wt% to 13 wt%, 11 wt% to 12 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, 15 wt% to 20 wt%, 2 wt% to 15 wt%, 2 wt% to 10 wt%, or 2 wt% to 5 wt%.

[0040] In a further embodiment, the inorganic binder powder of the present invention preferably uses glass powder. Glass powder has strong melting, flow, and bonding capabilities during sintering and can form a good bond structure in the formation of electrode structures. The particle size distribution of glass powder can ensure optimal dispersibility and sintering effect in the electrode paste composition.

[0041] The D50 particle size distribution of the glass powder is preferably controlled within the range of 0.5 μm to 3 μm. This median particle size ensures uniform dispersion of the glass powder in the paste, as well as effective melting and flow during sintering, which helps to form a dense electrode film layer, enhances the contact between the electrode and the silicon wafer, reduces contact resistance, and thus improves the conversion efficiency of the solar cell. The maximum particle size Dmax of the glass powder is less than 6 μm. This maximum particle size range avoids the agglomeration of large particles in the paste, as well as clogging or grid breakage during the printing process, ensuring the continuity of electrode printing and the high aspect ratio of the grid lines. This plays an important role in achieving stability and electrode microstructure during high-speed screen printing. In a more preferred embodiment, the maximum particle size Dmax of the glass powder is limited to less than 4 μm. By strictly controlling the particle size distribution of the glass powder, especially controlling Dmax to less than 4 μm, not only is the uniformity and density of the electrode paste promoted during printing and sintering, but the mechanical strength and reliability of the electrode are also ensured. This has a significant impact on improving the electrical performance and long-term stability of the solar cell. Precise particle size distribution control enables the paste composition to maintain or even improve the overall performance of solar cell electrodes while reducing costs, resulting in significant technical and economic advantages.

[0042] In this embodiment of the invention, the first inorganic binder powder is designed to optimize the conductivity, stability, and cost-effectiveness of the electrode. Based on the total weight of the first inorganic binder powder, the first inorganic binder powder may contain 5 wt% to 50 wt% of P2O5; 0 wt% to 50 wt% of PbO; 10 wt% to 40 wt% of B2O3; 0 wt% to 80 wt% of Bi2O3; 0 wt% to 10 wt% of SiO2; 0 wt% to 10 wt% of TeO2; 1 wt% to 10 wt% of SnO2; and 1 wt% to 5 wt% of SnCl2, the sum of all components in the first inorganic binder powder being 100 wt%.

[0043] Phosphorus pentoxide (P2O5) exhibits reducing properties during sintering due to its unique valence variation, effectively inhibiting the oxidation of base metal particles, such as nickel and copper, thus ensuring high conductivity of the electrode. Furthermore, the introduction of phosphorus pentoxide helps form a low-resistance ohmic contact layer, promoting electron transport between the electrode and the silicon substrate. Lead oxide (PbO) is added primarily to promote the adhesion between the inorganic binder and base metal particles during sintering. Simultaneously, it can undergo specific reactions at the silver-silicon interface, strengthening the contact between the electrode and the silicon wafer, reducing contact resistance, and improving battery conversion efficiency. Boron trioxide (B2O3) is a key component in forming the glass network structure. Boron trioxide helps control the sintering kinetics of the paste, ensuring that the binder can flow sufficiently at suitable temperatures, encapsulating base metal particles and forming continuous conductive pathways. It also stabilizes the glass network structure, improving the corrosion resistance and mechanical strength of the electrode film. Bismuth oxide (Bi₂O₃) exhibits excellent thermal stability during high-temperature sintering, promoting silver rearrangement and densification to form excellent conductive channels. Simultaneously, its synergistic effect with components such as PbO and B₂O₃ helps improve the acetic acid stability and long-term reliability of the electrode. Silicon dioxide (SiO₂), tellurium dioxide (TeO₂), tin dioxide (SnO₂), and tin chloride (SnCl₂) play different roles during sintering, from promoting electrode film formation to optimizing the electrode's microstructure, thus playing an indispensable role in improving electrode performance.

[0044] In addition, the first inorganic binder powder may also contain a series of other metal oxides, such as aluminum oxide (Al₂O₃), zinc oxide (ZnO), tungsten oxide (WO₃), molybdenum oxide (MoO₃), copper oxide (CuO), titanium dioxide (TiO₂), zirconium dioxide (ZrO₂), niobium pentoxide (Nb₂O₅), nickel oxide (NiO), ferric oxide (Fe₂O₃), yttrium oxide (Y₂O₃), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), lithium oxide (Li₂O), sodium oxide (Na₂O), or potassium oxide (K₂O). Based on the total weight of the first inorganic binder powder, the amount of other metal oxides ranges from 0 wt% to 10 wt%. The addition of these metal oxides not only improves the conductivity and adhesion of the electrode to the substrate but also provides additional chemical stability, preventing performance degradation of the electrode under extreme environments, thereby enhancing the reliability of the solar cell.

[0045] The use of the second inorganic binder powder is designed to provide additional performance optimization for solar cell electrode paste compositions, particularly in improving the stability of the electrode structure and enhancing the contact performance of the silver-silicon interface. Based on the total weight of the second inorganic binder powder, it may contain 1 wt% to 50 wt% La₂O₅; 1 wt% to 20 wt% SiO₂; 10 wt% to 40 wt% B₂O₃; 0 wt% to 30 wt% Ga₂O₃; 0 wt% to 10 wt% ZrO₂; 0 wt% to 30 wt% PbO; and 0 wt% to 40 wt% Bi₂O₃. In addition, the second inorganic binder powder also contains other metal oxides including Al2O3, ZnO, WO3, MoO3, CuO, TiO2, ZrO2, Nb2O5, NiO, Fe2O3, Y2O3, MgO, CaO, SrO, BaO, Li2O, Na2O or K2O, with the amount of other metal oxides ranging from 0 wt% to 10 wt% based on the total weight of the second inorganic binder powder.

[0046] The addition of lanthanum oxide (La₂O₅) endows the second inorganic binder powder with excellent chemical stability, effectively improving the electrode's water resistance and acetic acid resistance, ensuring the long-term stability and reliability of the solar cell under harsh environments. Silicon dioxide (SiO₂) helps form a stable glass network structure during sintering, enhancing the mechanical strength of the electrode film. Simultaneously, the presence of silicon dioxide optimizes the interfacial contact between the electrode and the silicon substrate, reducing contact resistance and improving the electrode's conductivity. Boron trioxide (B₂O₃) is a crucial component in constructing the network structure of the second inorganic binder powder. It exhibits good flow properties during high-temperature sintering, forming continuous conductive pathways in the electrode film. Furthermore, B₂O₃ synergistically interacts with La₂O₅ to form a composite glass phase with a high melting point and high stability. Gallium trioxide (Ga₂O₃), zirconium dioxide (ZrO₂), lead oxide (PbO), and bismuth oxide (Bi₂O₃) exhibit different functional characteristics during sintering. The addition of gallium trioxide and zirconium dioxide can enhance the oxidation resistance and corrosion resistance of the electrode film, while the reasonable ratio of lead oxide and bismuth oxide helps to optimize the sintering temperature and kinetics, ensuring the density and conductivity of the electrode film.

[0047] In the second inorganic binder powder, the combined use of the above components produces a high-melting-point glassy phase, which ensures the stability and integrity of the electrode film structure during sintering, avoiding the negative impact on cell performance caused by excessive erosion of the passivation layer. Furthermore, the high-melting-point glassy phase provides more lattice sites, promoting silver melting and migration, optimizing the alloy contact between silver and silicon, and significantly reducing contact resistivity, thereby compensating for the weakened electronic conductivity from the electrode to the silicon emitter due to the addition of base metals. Moreover, the lanthanum oxide, silicon dioxide, boron trioxide, gallium trioxide, zirconium dioxide, lead oxide, and bismuth oxide in the second inorganic binder powder, along with possible other metal oxides, constitute a complex chemical system designed to optimize electrode performance by adjusting the proportions of these components.

[0048] In some embodiments of this application, the second conductive particle is a nickel particle, and the nickel particle content is from 5 wt% to 20 wt% based on the total weight of the paste composition. This content range ensures the effective participation of the nickel particles in the electrode structure while avoiding performance degradation or instability caused by excessive nickel content.

[0049] Nickel particles, as a stable base metal conductive material, are introduced to replace some of the expensive silver particles, thereby significantly reducing the cost of electrode materials. However, simple nickel substitution can lead to a sharp increase in contact resistance due to the difference in work function between nickel and silver, and the poor conductivity of its oxide (NiO). To address this problem, this invention successfully maintains or even improves the conversion efficiency of solar cells while reducing the amount of silver used by adjusting the ratio of the first conductive particles (silver particles) to the second conductive particles (nickel particles) and through the synergistic effect with inorganic binder powder (glass powder containing specific chemical elements). Specifically, a paste composition containing a specific proportion (5wt% to 20wt%) of nickel particles, combined with the reducing and flowability of the first and second inorganic binder powders during sintering, effectively prevents oxidation of the nickel particle surface and maintains its good conductivity. Simultaneously, the design of silver-coated nickel particles further utilizes the high conductivity of silver to form a continuous conductive network, ensuring low contact resistance and efficient electron transport between the electrode and the silicon substrate even with an increased proportion of nickel particles.

[0050] In other embodiments of the present invention, the second conductive particles are silver-coated nickel particles or silver-coated copper particles, and the content of silver-coated nickel particles or silver-coated copper particles is 10 wt% to 30 wt% based on the total weight of the paste composition. Within the above content range, the conductivity and stability of the electrode are ensured while significantly reducing the amount of pure silver used in conventional silver paste. The silver-coated nickel particles and silver-coated copper particles adopt a core-shell structure, with the core being a base metal such as nickel or copper, and the outer shell being made of silver. The advantage of this structure is that the silver outer shell can effectively isolate the core from contact with the external environment, prevent the oxidation of the base metal during sintering, and maintain its conductivity. At the same time, the high conductivity of silver can ensure that the electrode forms a continuous conductive network at the microscopic level, and even with a high base metal content, it can maintain a low contact resistance between the electrode and the silicon substrate, thereby ensuring the conversion efficiency of the solar cell. In specific implementations, the high content of silver-coated nickel particles or silver-coated copper particles in the paste, through synergistic effect with the first inorganic binder powder and the second inorganic binder powder, further optimizes the construction of the conductive network during the sintering process. The low-melting-point first inorganic binder powder can quickly soften, encapsulate and protect the silver-coated particles from oxidation, while the high-melting-point second inorganic binder powder plays a role in the later stage of sintering, enhancing the structural stability of the electrode film and preventing excessive erosion of the passivation layer, thereby ensuring the optimization of electrode performance while reducing the amount of silver used.

[0051] The organic carrier used in this invention can be any typical organic carrier used in solar cell electrode compositions, and in a preferred embodiment, the organic carrier can be selected from one or more of the group consisting of organic solvents, binders, plasticizers, and surfactants. The binder resin can be selected from acrylate resins or cellulose resins. Ethyl cellulose is typically used as the binder resin. Furthermore, the binder resin can be selected from ethyl hydroxyethyl cellulose, nitrocellulose, blends of ethyl cellulose and phenolic resins, alkyd resins, phenol, acrylates, xylene, polybutene, polyesters, urea, melamine, vinyl acetate resins, rosin, polymethyl methacrylates of alcohols, etc. The solvent can be selected from, for example, hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl carbitol (diethylene glycol monobutyl ether), dibutyl carbitol (diethylene glycol dibutyl ether), butyl carbitol acetate (monobutyl ether acetate), propylene glycol monomethyl ether, hexanediol, terpineol, methyl ethyl ketone, benzyl alcohol, γ-butyrolactone, ethyl lactate, and combinations thereof. By mechanically mixing with the inorganic components in the solar cell electrodes, the organic carrier imparts the appropriate viscosity and rheological properties to the conductive paste for the printing process.

[0052] In a further embodiment, the additive is one or more selected from the group consisting of dispersants, thixotropic agents, plasticizers, viscosity stabilizers, defoamers, pigments, UV stabilizers, antioxidants, and coupling agents.

[0053] According to another typical embodiment of the present invention, a solar cell electrode is provided. This solar cell electrode is prepared from the paste composition described above.

[0054] According to another typical embodiment of the present invention, a solar cell is provided. The solar cell includes an electrode, and the electrode is a solar cell electrode as described above. The solar cell in this invention can be a solar cell manufactured using any technology, such as solar cells manufactured using laser-enhanced contact optimization (LECO), back-contact cell (BC) technology, conventional screen printing technology, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), electrochemical deposition (ECD), nanocrystalline chemical solar cell technology, perovskite solar cell technology, thin-film solar cell technology, or concentrated photovoltaic (CPV) technology.

[0055] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0056] The formulations of the glass powders used in the examples and comparative examples are listed in Tables 1-3 below.

[0057] Table 1 Glass Formulations for the First Glass System

[0058] GA1 (wt%) GA2 (wt%) GA3 (wt%) P2O5 7 16 25 PbO 25 19 13 B2O3 18 19 13 Bi2O3 43 39 34 SiO2 0 0 4 TeO2 4 4 0 SnO 1 2 8 SnCl2 1 1 2 ZnO 1 1 1 Tg (°C) 383 381 379

[0059] Table 2 Glass Formulations for the Second Glass System

[0060] GB1 (wt%) GB2 (wt%) GB3 (wt%) La2O3 11 22 31 SiO2 26 20 14 B2O3 34 33 29 Ga2O3 21 16 10 ZrO2 0 0 5 PbO 5 5 0 Bi2O3 2 2 10 TiO2 1 1 1 Tg (°C) 495 527 560

[0061] Table 3 Glass formulations used in comparative examples

[0062] GC1 (wt%) PbO 25 B2O3 25 Bi2O3 40 SiO2 5 WO3 3 TiO2 1 Al2O3 1 Tg (°C) 515

[0063] Table 4. Formulations of the organic carriers used in the examples and comparative examples.

[0064]

[0065] Tables 5 and 6 below list the formulation composition of the paste combinations in the examples and comparative examples.

[0066] Table 5

[0067]

[0068] Table 6

[0069]

[0070] Preparation of solar cell electrode compositions

[0071] According to the composition shown in Tables 1-3 above, the raw materials used to prepare glass powder are thoroughly mixed evenly, and any clumps are broken up to obtain raw materials for high-temperature melting. The mixed raw materials are placed in a suitable high-temperature crucible, and the crucible is placed in a muffle furnace at a temperature set to 1000℃~1400℃ for 60 minutes. The crucible is then removed, and the molten glass is quenched in a roller mill with cooling water or in deionized water. Finally, the product is ground by ball milling to obtain the glass powder of the present invention. The prepared glass powder has a particle size D. 50 =2μm, D max <6μm.

[0072] Mix the components according to the weight percentages listed in Table 4, heat and stir until the polymer is completely dissolved to form a homogeneous and transparent solution.

[0073] According to the compositions shown in Tables 5 and 6 above, each component was weighed according to its corresponding weight percentage and placed in a mixer for thorough mixing and premixing. Subsequently, it was ground in a three-roll mill to prepare a paste composition.

[0074] The paste composition prepared above is deposited on the front surface of a single-crystal silicon wafer in a predetermined pattern via screen printing, followed by drying in an infrared drying oven. Then, the composition for preparing the back aluminum electrode is printed on the back side of the wafer and dried in the same manner. The solar cell treated in the above steps is then fired in a belt furnace for 40 seconds.

[0075] Test methods

[0076] The solar cells of Examples 1-11 and Comparative Examples 1-3 prepared above were tested using a HALM standard IV testing instrument. The electroluminescence (EL) results were obtained from the electroluminescence spectroscopy imaging (EL) built into the HALM IV testing instrument.

[0077] Acid resistance test

[0078] After exposing the test sample to a predetermined concentration of acetic acid for a certain period of time, the sample is removed, and the cell conversion efficiency is evaluated using the photovoltaic IV test described above. The acid resistance test results are obtained through the following calculation formula:

[0079] Acid corrosion resistance (%) = [Conversion efficiency of uncorroded solar cell (%) - Conversion efficiency of solar cell after acetic acid corrosion (%)] / Conversion efficiency of uncorroded solar cell (%)

[0080] The measurement results are shown in Tables 7 and 8.

[0081] Table 7

[0082]

[0083] Table 8

[0084]

[0085] The experimental results above show that Example 1 used the double-glass system of the present application's technical solution. With the addition of 5% nickel powder, its conversion efficiency (Eff) was basically the same as that of the comparative example, and its resistance to acetic acid (acetic acid Eta decay (%)) was also comparable to that of the comparative example. In Example 4, silver-coated nickel was used as the second conductive particle. The conductive path constructed was no different from that of pure silver. Therefore, it can be seen that its conversion efficiency was comparable to that of using pure silver particles as the second conductive particle.

[0086] In the solar cell prepared in Example 8, the dual-glass system combined with 10% nickel powder achieved the same conversion efficiency as conventional pure silver paste (comparative example), while its acetic acid resistance was superior to that of the comparative example. In the solar cell prepared in Example 11, the excessive amount of the second glass system resulted in insufficient passivation layer etching, leading to a significant difference in conductive contact. Furthermore, insufficient etching of the interface glass resulted in weak bonding between the grid lines and the silicon interface, causing a substantial decrease in efficiency after the acetic acid test.

[0087] In addition, the attached diagram Figures 1 to 6 The image shows EL images of Examples 8, 11, and Comparative Example 3 before and after acid resistance testing.

[0088] pass Figure 1 and Figure 2 The comparison shows that after the acid resistance test, only the left edge area turned black and failed, resulting in a degradation rate of 12.2% for the solar cell of Example 8.

[0089] pass Figure 3 and Figure 4 The comparison shows that after the acid resistance test, the area that was corroded by acetic acid and turned black and failed was larger, resulting in a degradation rate of 38.4% for the solar cell of Example 11.

[0090] pass Figure 4 and Figure 5 The comparison shows that after acid resistance testing, the edge area of ​​Comparative Example 3 turned black and failed, with a decay rate of 15.3%.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A paste composition for preparing solar cell electrodes, characterized in that, Include: 10 wt% to 90 wt% of first conductive particles, wherein the first conductive particles are silver particles; 1 wt% to 60 wt% of a second conductive particle, wherein the second conductive particle comprises aluminum particles, nickel particles, silver-coated nickel particles and / or silver-coated copper particles; 0.1 wt% to 15 wt% of an inorganic binder powder, said inorganic binder powder comprising a first inorganic binder powder having a glass transition temperature between 300°C and 450°C, and a second inorganic binder powder having a glass transition temperature between 450°C and 700°C, wherein the weight ratio of the first inorganic binder powder to the second inorganic binder powder is in the range of 0.03:1 to 25:1; and 2 wt% to 20 wt% organic carrier, The weight percentages mentioned above are based on the total weight of the paste composition, where the sum of all components in the paste composition is 100 wt%.

2. The paste composition according to claim 1, characterized in that, The inorganic binder powder is glass powder; preferably, the particle size distribution D of the inorganic binder powder is... 50 Within the range of 0.5μm to 3μm, D max Less than 6 μm; more preferably, the D max Less than 4μm.

3. The paste composition according to claim 1, characterized in that, The first inorganic binder powder comprises: 5 wt% to 50 wt% P2O5; 0 wt% to 50 wt% PbO; 10 wt% to 40 wt% B2O3; 0 wt% to 80 wt% Bi2O3; 0 wt% to 10 wt% SiO2; 0 wt% to 10 wt% TeO2; 1 wt% to 10 wt% SnO2; and 1 wt% to 5 wt% SnCl2, The above weight percentages are all based on the total weight of the first inorganic binder powder, and the sum of all components in the first inorganic binder powder is 100 wt%.

4. The paste composition according to claim 3, characterized in that, The first inorganic binder powder also contains other metal oxides. The other metal oxides include Al₂O₃, ZnO, WO₃, MoO₃, CuO, TiO₂, Nb₂O₅, NiO, Fe₂O₃, Y₂O₃, MgO, CaO, SrO, BaO, Li₂O, Na₂O, or K₂O. Based on the total weight of the first inorganic binder powder, the amount of the other metal oxides is in the range of 0 wt% to 10 wt%.

5. The paste composition according to claim 1, characterized in that, The second inorganic binder powder comprises: 1 wt% to 50 wt% of La2O5; 1 wt% to 20 wt% SiO2; 10 wt% to 40 wt% B2O3; 0 wt% to 30 wt% Ga2O3; 0 wt% to 10 wt% ZrO2; 0 wt% to 30 wt% PbO; and 0 wt% to 40 wt% Bi2O3, The above weight percentages are all based on the total weight of the second inorganic binder powder, and the sum of all components in the second inorganic binder powder is 100 wt%.

6. The paste composition according to claim 5, characterized in that, The second inorganic binder powder also contains other metal oxides. The other metal oxides include Al₂O₃, ZnO, WO₃, MoO₃, CuO, TiO₂, Nb₂O₅, NiO, Fe₂O₃, Y₂O₃, MgO, CaO, SrO, BaO, Li₂O, Na₂O, or K₂O. Based on the total weight of the second inorganic binder powder, the amount of the other metal oxides is in the range of 0 wt% to 10 wt%.

7. The paste composition according to claim 1, characterized in that, The second conductive particle is a nickel particle, and the content of the nickel particle is from 5 wt% to 20 wt% based on the total weight of the paste composition.

8. The paste composition according to claim 1, characterized in that, The second conductive particle is a silver-coated nickel particle or a silver-coated copper particle, and the content of the silver-coated nickel particle or the silver-coated copper particle is 10 wt% to 30 wt% based on the total weight of the paste composition.

9. The paste composition according to claim 1, characterized in that, The organic carrier is selected from one or more of the group consisting of organic solvents, adhesives, plasticizers and surfactants.

10. A solar cell electrode, characterized in that, It is prepared from the paste composition according to any one of claims 1 to 9.

11. A solar cell, characterized in that, Includes the solar cell electrode according to claim 10.

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