Copper slurry and preparation method, copper electrode, solar cell and photovoltaic module

Abstract

The present application provides a copper slurry and preparation method, a copper electrode, a solar cell, and a photovoltaic module, belonging to the field of conductive material technology. The copper slurry includes a dispersion medium and copper particles dispersed in the dispersion medium; the copper particles include first copper particles, second copper particles, third copper particles, and fourth copper particles; the particle size of the first copper particles ranges from 1 to 10 μm, the particle size of the second copper particles ranges from 500 to 999 nm, and the particle size of the third copper particles ranges from 101 to 499 nm; the first copper particles, the second copper particles, and the third copper particles are all elemental copper particles, and the fourth copper particles are cuprous hydride nanoparticles; at least a portion of the fourth copper particles are attached to the surface of the first copper particles and / or the second copper particles and / or the third copper particles. This allows the fourth copper particles to form interconnections between the aforementioned three copper particles, providing more transmission channels, reducing line resistance, and improving conductive performance.

Description

Technical Field

[0001] The present application relates to the technical field of conductive materials. Specifically, the present application relates to a copper slurry and a preparation method thereof, a copper electrode, a solar cell and a photovoltaic module, and especially to a conductive copper slurry and a preparation method thereof, a copper electrode, a solar cell and a photovoltaic module. Background Art

[0002] In recent years, solar cell technology has developed rapidly and extensively. During the development process, related technologies have tried various ways to promote cost reduction and efficiency improvement of solar cells.

[0003] The grid lines (also called main grid and / or auxiliary grid) used in solar cells are commonly made of silver or silver-clad copper. Although silver-clad copper has a certain degree of cost reduction compared to using only silver, the reduction is relatively limited.

[0004] Copper is a base metal material with conductivity comparable to that of silver and has a lower cost. However, copper itself is highly active and the storage time of copper slurry at room temperature is short, causing the conductive performance to gradually deteriorate, making it difficult to promote and apply widely. Summary of the Invention

[0005] In view of this, in order to at least partially solve the above-mentioned technical problems, the present application provides a copper slurry and a preparation method, a copper electrode, a solar cell and a photovoltaic module.

[0006] According to an embodiment of one aspect of the present application, a copper slurry is provided, comprising a dispersion medium and copper particles dispersed in the dispersion medium; the copper particles comprise first copper particles, second copper particles, third copper particles, and fourth copper particles; the first copper particles have a particle size range of 1 to 10 μm, the second copper particles have a particle size range of 500 to 999 nm, and the third copper particles have a particle size range of 101 to 499 nm; the first copper particles, the second copper particles, and the third copper particles are all elemental copper particles, and the fourth copper particles are cuprous hydride nanoparticles; at least a portion of the fourth copper particles are attached to the surfaces of the first copper particles and / or the second copper particles and / or the third copper particles.

[0007] According to an embodiment of another aspect of the present application, a method for preparing a copper slurry is provided, comprising: mixing fourth copper particles with at least one of first copper particles, second copper particles, and third copper particles, respectively, so that at least a portion of the fourth copper particles adheres to the surface of the first copper particles and / or the second copper particles and / or the third copper particles, to obtain a plurality of or a single mixture; and stirring and mixing the plurality of or the single mixture with a dispersion medium to obtain a copper slurry; the particle size of the first copper particles is in the range of 1 to 10 μm, the particle size of the second copper particles is in the range of 500 to 999 nm, and the particle size of the third copper particles is in the range of 101 to 499 nm; the first copper particles, the second copper particles, and the third copper particles are all elemental copper particles, and the fourth copper particles are cuprous hydride nanoparticles.

[0008] According to another embodiment of the present application, a copper electrode is provided, which is prepared by sintering and solidifying the above-mentioned copper slurry.

[0009] According to another embodiment of the present application, a copper electrode is provided, comprising first copper particles, second copper particles, third copper particles, and fourth copper particles; the particle size of the first copper particles ranges from 1 to 10 μm, the particle size of the second copper particles ranges from 500 to 999 nm, the particle size of the third copper particles ranges from 101 to 499 nm, and the average particle size of the fourth copper particles is less than 100 nm; the first copper particles, the second copper particles, the third copper particles, and the fourth copper particles are all elemental copper particles, and at least a portion of the fourth copper particles is attached to the surface of the first copper particles and / or the second copper particles and / or the third copper particles.

[0010] According to an embodiment of yet another aspect of the present application, a solar cell is provided, comprising a cell body and an electrode, wherein the electrode is located on at least one surface of the cell body, and the electrode comprises the copper electrode as described above.

[0011] According to another embodiment of the present application, a photovoltaic assembly is provided, comprising the solar cell as described above, and a plurality of electrical connection lines, wherein the plurality of electrical connection lines electrically connect adjacent solar cells.

[0012] According to the copper slurry of the embodiment of the present application, the fourth copper particles (cuprous hydride nanoparticles) can decompose into metallic copper and hydrogen at a relatively low temperature (e.g., between 60 and 100°C), and the cuprous hydride nanoparticles form a reducing atmosphere during the heating process, effectively inhibiting the oxidation of all copper particles. During the subsequent heating process, the active copper particles produced by the decomposition of the fourth copper particles provide adhesion between the aforementioned copper particles. The first, second, third, and fourth copper particles, which have different particle sizes, are coordinated in size to allow copper particles of various particle sizes to be densely packed. The smallest fourth copper particles can effectively fill the tiny gaps between adjacent copper particles of different particle sizes, forming tighter and more continuous copper connections, thereby significantly reducing contact resistance, reducing obstacles to electron transmission, and effectively improving the conductivity of the copper electrode after heating and sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other objects, features and advantages of the present application will become more apparent through the following description of the embodiments of the present application with reference to the accompanying drawings.

[0014] Figure 1 shows a scanning electron microscope image of a copper electrode of the related art;

[0015] Figure 2 The scanning electron microscope image of the copper paste of the embodiment of the present application is shown;

[0016] Figure 3 A flow chart showing a method for preparing a copper slurry according to an embodiment of the present application is shown;

[0017] Figure 4 The scanning electron microscope images of the fourth copper particles of the embodiment of the present application after being mixed with copper particles of different particle sizes are shown;

[0018] Figure 5 shows a scanning electron microscope image of the copper electrode of Example 1 of the present application;

[0019] Figure 6 Shown Figure 5 A partial enlarged view of

[0020] Figure 7 The scanning electron microscope images of the copper electrodes at different scales of Example 1 of the present application are shown.

[0021] In the accompanying drawings, the meanings of the reference numerals are as follows:

[0022] A-first copper particle;

[0023] B-second copper particle;

[0024] C-third copper particle;

[0025] D-Fourth copper particle. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present application. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present application.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present application. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0028] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.). When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.).

[0029] Solar cell technology is rapidly developing. Currently, electrodes are primarily made of silver or silver-coated copper. The high cost of silver contributes to the overall high cost of solar cells. While silver-coated copper offers a lower cost than silver, the reduction is limited. Therefore, a method is needed to reduce the cost of solar cells while maintaining high electrical conductivity.

[0030] Related technologies attempt to use elemental copper particles of different particle sizes or shapes to prepare copper electrodes, but this method may cause local defects when printing electrodes. There are still gaps or resin barriers between the individual elemental copper particles, making it difficult to continuously prepare copper electrodes with stable and good conductive properties. Figure 1 FIG1 shows a scanning electron microscope image of a copper electrode of the related art. Figure 1 As shown, it can be seen that the prepared copper electrode has local defects, resulting in poor conductivity.

[0031] During the implementation of the present invention, it was discovered that due to the mutual coordination of the sizes of the first, second, and third copper particles of different particle sizes, they were tightly packed to form smaller gaps. By attaching cuprous hydride nanoparticles (fourth copper particles) to the surface of at least one of the first, second, and third copper particles of different particle sizes, the copper slurry formed was subsequently used to prepare electrodes. The small-sized copper particles, especially the fourth copper particles, were able to effectively fill the smaller gaps between adjacent copper particles. This allows the copper particles of various particle sizes in the copper electrode to be compactly packed, reducing the gaps in the copper electrode, increasing the electron transmission path, and thus improving conductivity. Furthermore, since copper particles are used to completely replace silver, raw material costs are reduced, which is conducive to production and promotion.

[0032] Specifically, according to an embodiment of one aspect of the present application, Figure 2 The scanning electron microscope image of the copper paste of the embodiment of the present application is shown in FIG. Figure 2 As shown, the present application provides a copper slurry, including a dispersion medium and copper particles dispersed in the dispersion medium; the copper particles include first copper particles A, second copper particles B, third copper particles C and fourth copper particles D; the particle size of the first copper particles A ranges from 1 to 10 μm, the particle size of the second copper particles B ranges from 500 to 999 nm, and the particle size of the third copper particles C ranges from 101 to 499 nm; the first copper particles A, the second copper particles B and the third copper particles C are all elemental copper particles, and the fourth copper particles D are cuprous hydride nanoparticles; at least a portion of the fourth copper particles D are attached to the surface of the first copper particles A and / or the second copper particles B and / or the third copper particles C.

[0033] According to the embodiments of the present application, without wishing to be bound by theory, by in-situ attaching fourth copper particles D to the surface of at least one of first copper particles A, second copper particles B, and third copper particles C of different particle sizes, the reducible nature of the fourth copper particles D (cuprous hydride nanoparticles) allows them to generate highly active nano-copper particles upon subsequent thermal decomposition. The generated nano-copper particles then rapidly sinter or fuse with the surfaces of adjacent copper particles of other particle sizes, enabling the copper slurry to achieve effective connection and formation of a conductive network between copper particles of different particle sizes at relatively low temperatures (typically sintering temperatures of 200°C-300°C). Due to the coordinated sizes of the first copper particles A, second copper particles B, and third copper particles C of different particle sizes, they form a densely packed structure with relatively small gaps. The nano-copper particles generated by the decomposition of the fourth copper particles D have high surface energy and reactivity, effectively filling the tiny gaps between adjacent copper particles, forming a denser and more continuous copper connection region. This significantly reduces contact resistance and reduces obstacles to electron transfer. After subsequent sintering and solidification, the conductivity of the copper electrode can be significantly improved.

[0034] Based on the effective connection between the copper particles of different particle sizes mentioned above, not only the conductive performance is improved, but also the mechanical strength of the overall copper electrode structure is enhanced. In addition, copper particles of different particle sizes are used in this application to form a good gradient distribution of different particle sizes. Among them, the first copper particles A of large particles constitute the skeleton of the overall copper slurry, the second copper particles B and the third copper particles C of medium particles fill the gaps between the large particles, and the smaller fourth copper particles D are attached and / or fill smaller gaps. By using the above-mentioned multi-stage filling structure, the copper particles can reach a higher initial packing density before the copper slurry is subsequently sintered and solidified, providing a good basic structure for the subsequent acquisition of a highly conductive copper electrode. It can be understood that fewer gaps mean less possibility of oxidation and higher mechanical strength.

[0035] It should be noted that during the relevant experiments, it was found that cuprous hydride nanoparticles have a certain reducing property and can quickly decompose at a relatively low temperature. Compared with directly using easily oxidized nano-copper powder particles, the use of cuprous hydride in the present application provides a reducing atmosphere during the storage and processing of copper slurry (such as printing), making it less susceptible to oxidation. In addition, during the decomposition process at low temperatures (such as 60-100°C), the reaction is relatively rapid, and the generated nano-copper particles are exposed to a high-temperature oxidizing environment for a shorter time before forming effective connections (between copper particles of various particle sizes). The hydrogen generated by the decomposition forms a local instantaneous reducing atmosphere, preventing the surfaces of the first copper particles A, the second copper particles B, and the third copper particles C from being oxidized. The nano-copper particles formed after decomposition fuse and / or connect with the surrounding larger-sized copper particles and are fully filled in the tiny gaps formed by the first copper particles A, the second copper particles B, and the third copper particles C, thereby being protected within the conductive network. Compared with directly using nano-copper powder, the method of attaching cuprous hydride to the surface of copper particles of different particle sizes further improves the storage stability of the copper slurry and the oxidation resistance of the conductive network formed after low-temperature curing.

[0036] It should be noted that the first copper particles A, the second copper particles B, and the third copper particles C refer to particles whose main component is zero-valent copper.

[0037] In this embodiment, it can be understood, at least in part, that the fourth copper particles D are all attached to the surface of the first copper particles A; or the fourth copper particles D are all attached to the surface of the second copper particles B; or the fourth copper particles D are all attached to the surface of the third copper particles C; or some of the fourth copper particles D are attached to the surface of the first copper particles A, and another part of the fourth copper particles D are discretely distributed in the gaps between copper particles of different particle sizes; or all of the fourth copper particles D are attached to the surfaces of the first copper particles A and the second copper particles B; or some of the fourth copper particles D are attached to the surfaces of the first copper particles A and the second copper particles B, respectively, and another part of the fourth copper particles D is discretely distributed in the gaps between copper particles of different particle sizes. Part of the fourth copper particles D are discretely distributed in the gaps between copper particles of several different particle sizes; or part of the fourth copper particles D are respectively attached to the surfaces of the first copper particles A, the second copper particles B, and the third copper particles C; or part of the fourth copper particles D are attached to the surfaces of the first copper particles A, the second copper particles B, and the third copper particles C, and another part of the fourth copper particles are discretely distributed in the gaps between copper particles of several different particle sizes; or part of the fourth copper particles D are attached to the surfaces of the second copper particles B and the third copper particles C, and another part of the fourth copper particles are discretely distributed in the gaps between copper particles of several different particle sizes.

[0038] Preferably, the fourth copper particles D are attached to the surfaces of the first copper particles A, the second copper particles B and the third copper particles C. Therefore, since the combination of copper particles of different particle sizes can have a larger total surface area than copper particles of a single particle size, more fourth copper particles D can be attached to the surfaces of the three copper particles. With the help of the antioxidant properties of the fourth copper particles D, the surfaces of the larger particle sizes of the first copper particles A, the second copper particles B and the third copper particles C can be prevented from being oxidized.

[0039] It is understood that the copper paste of the present application does not require that the fourth copper particles D be attached to all of the first copper particles A, the second copper particles B, and the third copper particles C. The partial attachment of the fourth copper particles D can enhance the electron tunneling transmission effect between copper particles of different particle sizes. In actual testing, several samples of copper paste can be randomly sampled and examined using an electron microscope to determine whether the fourth copper particles D are attached to the surfaces of copper particles of different particle sizes.

[0040] In some embodiments, the interaction between copper particles of different particle sizes in the copper slurry allows smaller copper particles, particularly nano-copper particles produced by the decomposition of cuprous hydride (CuH), to effectively fill the gaps formed by larger particles. This results in a compact packing of copper particles of varying sizes within the copper slurry. This improves the packing density of the copper particles in the copper electrode, reduces voids within the copper electrode, increases electron transport pathways, and enhances electrical conductivity. Furthermore, the higher packing density of the copper particles helps improve the peel strength of the copper electrode, thereby increasing its durability and service life.

[0041] It should be noted that the average particle size of the first copper particles A, the second copper particles B, and the third copper particles C can be measured using a scanning electron microscope (SEM). 10 to 100 copper particles of any of the above different particle sizes are randomly sampled and imaged in the SEM, and their particle sizes are measured. The arithmetic mean of these particle size values ​​is then calculated. It is understood that the above method is merely exemplary, and the number of copper particles selected can be appropriately reduced or increased based on actual conditions.

[0042] Furthermore, the particle size of the first copper particles A ranges from 1 to 10 μm, the particle size of the second copper particles B ranges from 500 to 999 nm, and the particle size of the third copper particles C ranges from 101 to 499 nm. With this arrangement, the first copper particles A serve as the main framework of the copper slurry, the second copper particles B perform primary filling of the gaps between adjacent first copper particles A, and the third copper particles C perform secondary filling, which can be understood as submicron-level gap filling. The nanometer-scale fourth copper particles D are attached to the surfaces of the aforementioned copper particles of different particle sizes and further fill the tiny gaps that may exist between the copper particles of the three average particle sizes, effectively improving the density of the copper slurry. The use of copper particles of different particle sizes helps prevent nano-scale particle agglomeration, thereby maintaining the stability of the copper slurry.

[0043] In some embodiments, the fourth copper particles D are non-spherical nanoparticles. The shape of the non-spherical copper nanoparticles has a larger specific surface area and a rich angular structure, which can fit more tightly into the depressions on the surface of copper particles of different particle size ranges, thereby improving the adhesion strength of the fourth copper particles D on the surface of elemental copper particles of different average particle sizes, reducing the risk of falling off during subsequent slurry processing (such as printing and drying), and allowing the cuprous hydride nanoparticles to form a relatively stable physical anchor before subsequent thermal decomposition, providing a more uniform distribution of active sites for subsequent low-temperature sintering. Furthermore, during the thermal decomposition process of the non-spherical nanoparticles, their corners and edges have a small radius of curvature and unsaturated atomic arrangement, and their activity is much higher than that of the spherical surface. These locations can preferentially decompose to produce highly active copper atoms, which then quickly diffuse to the interface of adjacent copper particles, connecting different copper particles in a relatively short period of time to form a more continuous conductive path, further increasing the electron transmission path and improving the conductive performance.

[0044] In some embodiments, the fourth copper particles D are polyhedral copper particles or solid-of-rotation copper particles. For example, the polyhedral copper particles can be attached parallel to the surface of larger copper particles (which can be at least one of the first copper particles A, the second copper particles B, and the third copper particles C), covering the exposed areas of the copper particles. The solid-of-rotation copper particles can be interspersed in the gaps between copper particles of different sizes. At the same addition amount, the use of the aforementioned non-spherical fourth copper particles D can more effectively reduce the porosity compared to spherical copper nanoparticles, improving the sinterability of the copper slurry. This results in a higher density of the copper electrode formed after subsequent curing and sintering. This also facilitates the rapid expansion of conductive pathways during sintering, further improving electron transmission efficiency.

[0045] For example, the polyhedral copper nanoparticles may be at least one of cubes, flakes, layers, octahedrons, prisms, and pyramids. The rotating copper nanoparticles may be at least one of rods, disks, trees, needles, and truncated cones.

[0046] Alternatively, the polyhedral copper particles, such as flaky or layered copper nanoparticles, can be coated on the surface of other copper particles of varying sizes. This physically isolates oxygen from the elemental copper within the cuprous hydride before it decomposes. After the cuprous hydride decomposes, the resulting nanocopper particles preferentially cover the underlying elemental copper, reducing oxidation sites. This arrangement helps extend the storage life of the copper slurry and reduces copper oxidation during decomposition and sintering, resulting in a copper electrode with more stable conductivity.

[0047] In some embodiments, a polyhedral copper particle can be understood as a three-dimensional structure formed by multiple planar polygons, whose main components include planes, edges, and vertices. A polyhedral copper particle has at least four surfaces. When having four surfaces, the polyhedral copper particle can be, for example, a regular tetrahedron. The corners of the polyhedral copper particle (which can be understood as the intersection of multiple surfaces) have unsaturated atomic coordination and high surface energy, becoming preferential active sites for the decomposition of cuprous hydride and the diffusion of copper atoms, which helps to increase the decomposition rate of cuprous hydride nanoparticles. During the subsequent printing and drying process of the copper slurry, the contact area between the surfaces can be increased by directional stacking of the planes on the planes, reducing contact resistance and forming a more stable conductive path. A solid of rotation copper particle is formed by rotating a planar figure around an axis of rotation. Its surface includes at least one of curved and / or flat surfaces. A solid of rotation copper particle has at least two surfaces. When having two surfaces, the solid of rotation copper particle can be, for example, at least one of a cone or a rod (cylinder). The stress dispersion of the rotating copper particles enables them to improve the bending resistance and mechanical flexibility of the copper electrode. In addition, the rotating copper particles can prevent sedimentation during the subsequent shear stirring process, which facilitates the subsequent printing and preparation of copper electrodes.

[0048] For example, the number of surfaces of a polyhedral copper particle may be 4, 5, 6, 7, or 8, which is not limited in this application. The number of surfaces of a rotating copper particle may be 2, 3, or 4, which is not limited in this application.

[0049] In some embodiments, the contour line of the surface of the fourth copper particle D includes at least one of a straight line and an arc. The contour line of the surface of the fourth copper particle D can be understood as a boundary feature line that describes the geometric shape of the copper particle surface at a microscopic scale. The contour line can be observed by observing the edge of the particle using an image captured by a scanning electron microscope, or by extracting a height change curve using an atomic force microscope.

[0050] In some embodiments, the surface of the fourth copper particle D can be, for example, a triangle, a triangle with rounded corners at the vertex, a trapezoid, a trapezoid with rounded corners at the vertex, a rhombus, a rhombus with rounded corners at the vertex, a square, a square with rounded corners at the vertex, a rectangle, a rectangle with rounded corners at the vertex, an arch, an arch with rounded corners at the vertex, a hexagon, a hexagon with rounded corners at the vertex, etc., and this application does not specifically limit this.

[0051] In some embodiments, the first copper particles A, the second copper particles B, and the third copper particles C are of any shape, such as a spherical shape, an ellipsoidal shape, a rod-like shape, a pyramidal shape, a disc-like shape, a branched shape, a network shape, or any other irregular shape. From the perspective of facilitating slurry preparation and printing, the first copper particles A, the second copper particles B, and the third copper particles C are preferably spherical in shape due to their good fluidity and workability.

[0052] In some embodiments, the average particle size of the fourth copper particles D is 10 to 100 nm. It is understood that the average particle size of the fourth copper nanoparticles can be obtained by randomly sampling 100 copper nanoparticles from a scanning electron microscope image or a transmission electron microscope image, photographing the image, measuring the longest and shortest lengths of each particle, and then calculating the arithmetic mean of these lengths. Of course, a different number of copper nanoparticles can be sampled as needed, and this is not particularly limited in this application.

[0053] The longest direction can be understood as the direction of the longest geometric dimension of the fourth copper particle D in three-dimensional space, and the shortest direction can be understood as the direction of the shortest geometric dimension of the fourth copper particle D in three-dimensional space. For example, taking the fourth copper particle D as a rotating nanoparticle, such as a rod-shaped copper nanoparticle, the longest direction can be understood as the direction of its principal axis, and the shortest direction can be understood as the radial direction perpendicular to its principal axis. Taking the fourth copper particle D as a polyhedral nanoparticle, such as a cube or a cuboid, the straight-line distance between two opposite vertices can be understood as the length of the longest direction, and the straight-line distance between the two closest vertices can be understood as the length of the shortest direction.

[0054] In some embodiments, by setting the average particle size of the fourth copper particles D within the aforementioned range, combined with the aforementioned stepped arrangement of the average particle size ranges of the first copper particles A, the second copper particles B, and the third copper particles C, the fourth copper particles D can more easily adhere to the surfaces of the aforementioned three copper particles. During decomposition, the fourth copper particles D can better cover the surfaces of the underlying copper particles, providing a better anti-oxidation effect while also achieving higher and more stable electrical conductivity.

[0055] Furthermore, setting the average particle size of the fourth copper particles D within the aforementioned range sufficiently reduces their surface melting temperature, facilitating surface melting and facilitating bonding with copper particles of other sizes. Compared to copper particles, cuprous hydride nanoparticles are less susceptible to oxidation in air, making them more stable and providing excellent shelf life. Furthermore, cuprous hydride nanoparticles decompose at temperatures between 60°C and 100°C to form nanocopper particles. If the average particle size of the fourth copper particles D is too small, adhesion is difficult to achieve, limiting the improvement in conductive properties. If the average particle size of the fourth copper particles D is too large, surface melting is less likely to occur, making bonding with copper particles of other sizes more difficult.

[0056] Optionally, the average particle size of the fourth copper particles D may be, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, or a range between any two of the above values.

[0057] Optionally, the particle size range of the first copper particles A may be, for example, a range consisting of any two of the following values: 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0058] Optionally, the particle size range of the second copper particles B can be, for example, a range consisting of any two of the following values: 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm or 999 nm.

[0059] Optionally, the particle size range of the third copper particles C can be, for example, a range consisting of any two of the following values: 101 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 499 nm.

[0060] In some embodiments, based on the total number of first copper particles A, second copper particles B, and third copper particles C being 100, the number of first copper particles A is 1-3, the number of second copper particles B is 8-15, the number of third copper particles C is 80-90, and the number of fourth copper particles D is greater than 100. The number of particles can be determined, for example, by scanning electron microscopy (SEM) testing, where a specific area is selected and imaged to measure its particle size. Copper particles with these particle sizes are then counted into different size ranges, and the number of first copper particles A, second copper particles B, and third copper particles C is then counted. It will be appreciated that the above method is merely exemplary, and the size of the selected area and the number of copper particles of different sizes selected can be appropriately reduced or increased based on actual circumstances.

[0061] This arrangement, utilizing the aforementioned number of different copper particles, further enhances electrical conductivity. If the number of fourth copper particles D is too small, it will be difficult to provide a relatively continuous conductive path, thereby affecting electrical conductivity. Furthermore, utilizing a combination of first copper particles A, second copper particles B, and third copper particles C of varying particle size ranges improves the copper electrode stacking effect and increases the density of the copper electrode.

[0062] In some embodiments, the dispersion medium includes a resin. The resin, as a dispersion medium, forms a continuous phase after subsequent sintering and curing, encapsulating and bonding the aforementioned copper particles of various sizes into a whole. The addition of the resin can impart higher mechanical strength to the copper slurry, improve adhesion to the subsequent battery body, enhance peel strength, and increase the durability and service life of the copper electrode.

[0063] Alternatively, the resin can be a thermosetting resin. After curing, thermosetting resins cross-link to form a three-dimensional network structure, making it less susceptible to deformation and softening during subsequent high-temperature processes used to manufacture solar cells, such as during encapsulation. Furthermore, the curing process rarely destroys the already formed interconnected structure formed by sintering the copper particles, maintaining the integrity of the conductive pathway.

[0064] Further optionally, the resin can be at least one of phenolic resin, epoxy resin, polyester resin, vinyl resin, phthalate resin, oligonucleotide acrylate resin, xylene resin, bismuth triazine resin, polyurethane, melamine resin, silicone resin, acrylic resin, oxetane resin, oxazine resin, etc.

[0065] Furthermore, from the perspective of facilitating adhesion with the battery cell, at least one of phenolic resin, epoxy resin or unsaturated polyester resin is preferred.

[0066] In some embodiments, the mass percentage of the resin in the copper paste is 1-15 wt %. This configuration can improve the adhesion between the copper paste and the battery body while also achieving high conductivity.

[0067] Optionally, the mass percentage of the resin may be, for example, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 11 wt%, 13 wt% or 15 wt%, or a range between any two of the above values.

[0068] In some embodiments, the dispersion medium further comprises at least one of an organic coating agent and a reducing agent. The organic coating agent is used to coat the surface of the four copper particles to prevent oxidation of the surface of the cuprous hydride nanoparticles or the elemental copper particles. The end group of the organic coating agent has at least one group selected from an amino group, an amide group, a sulfhydryl group, a carboxyl group, a hydroxyl group, a carbonyl group, a sulfide group, and an ether group, and the organic coating agent has 1 to 50 carbon atoms. Among them, the organic coating agent containing an amino group or an amide group can be, for example, at least one of octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine, benzylamine, octadecylamide, oleamide, etc. The organic coating agent containing a sulfhydryl group or a sulfide group can be exemplified by at least one of decanethiol, dodecanethiol, trimethylbenzylmercaptan, butylbenzylmercaptan, dihexyl sulfide, etc. The organic capping agent containing hydroxyl, carboxyl, carbonyl and etheroxy groups can be exemplified by at least one of dodecanediol, hexadecanediol, dodecanoic acid, octadecanoic acid, oleic acid, formic acid, linoleic acid, linolenic acid, dodecanedione, dibenzoylmethane, ethylene glycol monodecyl ether, diethylene glycol monodecyl ether, triethylene glycol monodecyl ether, tetraethylene glycol monodecyl ether, ethylene glycol monododecyl ether, diethylene glycol monododecyl ether, triethylene glycol monododecyl ether, tetraethylene glycol monododecyl ether, ethylene glycol monohexadecyl ether, and diethylene glycol monohexadecyl ether.

[0069] In some embodiments, from the perspective of good reduction effect of copper ions, the reducing agent is preferably a metal hydride or hypophosphorous acid, and more preferably hypophosphorous acid. As the above-mentioned metal hydride, it can be selected from lithium aluminum hydride, lithium borohydride, sodium borohydride, lithium hydride, potassium hydride, and calcium hydride, and is preferably lithium aluminum hydride, lithium borohydride, and sodium borohydride.

[0070] In some embodiments, the mass percentage of the reducing agent in the copper slurry is 0.1-15 wt %. This configuration can enhance the reducing atmosphere, reduce the possibility of oxidation of cuprous hydride and elemental copper, and thus ensure high conductivity and stability of the prepared copper electrode.

[0071] Optionally, the mass percentage of the reducing agent can be, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, 11 wt%, 13 wt% or 15 wt%, or a range between any two of the above values.

[0072] In some embodiments, the dispersion medium further includes a solvent. The solvent may be, for example, at least one of water, an alcohol compound, an ether compound, and a ketone compound. For example, the solvent may be one or more of water, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, hexanol, cyclohexanol, cyclohexanone, cyclohexanol, terpineol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol, ethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0073] In some embodiments, as a copper paste for subsequent printing, the mass percentage of the solvent in the copper paste is 1 to 10 wt % from the viewpoint of ensuring an appropriate viscosity range.

[0074] Optionally, the mass percentage of the solvent can be, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, or a range between any two of the above values.

[0075] According to another embodiment of the present application, a method for preparing a copper slurry is provided. Figure 3 A flow chart of a method for preparing copper slurry according to an embodiment of the present application is shown, and the method includes operations S301 to S302.

[0076] In operation S301, the fourth copper particles D are mixed with at least one of the first copper particles A, the second copper particles B, and the third copper particles C, respectively, so that at least a portion of the fourth copper particles D adheres to the surface of the first copper particles A and / or the second copper particles B and / or the third copper particles C, to obtain a plurality of or a single mixture.

[0077] In operation S302 , a plurality of or one mixture is stirred and mixed with a dispersion medium to obtain a copper slurry.

[0078] According to an embodiment of the present application, the particle size of the first copper particles A ranges from 1 to 10 μm, the particle size of the second copper particles B ranges from 500 to 999 nm, and the particle size of the third copper particles C ranges from 101 to 499 nm. The first copper particles A, the second copper particles B, and the third copper particles C are all elemental copper particles, and the fourth copper particles D are cuprous hydride nanoparticles. By first mixing copper particles of different particle sizes, since the fourth copper particles D have the smallest particle size and higher surface activity, they are easily attached to the surfaces of the first copper particles A, the second copper particles B, and / or the third copper particles C with larger particle sizes. In the specific mixing process, high-speed shearing can be used to mix the fourth copper particles D, so that the fourth copper particles D are strongly pressed into the micron- or nanometer-scale depressions on the surfaces of the first copper particles A, the second copper particles B, and the third copper particles C, thereby improving the adhesion rate of the fourth copper particles D. By pre-attaching the cuprous hydride nanoparticles before introducing the dispersion medium, the problems of copper nanoparticle agglomeration, uneven dispersion, and loss of activity of elemental copper particles that may occur in the traditional copper slurry preparation process are solved. In this way, the pre-attachment method is carried out to ensure the rheological consistency of the copper paste and reduce the disconnection rate of copper electrode printing.

[0079] In some embodiments, the aforementioned copper particles may be mixed, for example, by mechanically mixing copper particles of four different particle sizes to form fourth copper particles D that adhere to the surface of at least one of the first copper particles A, the second copper particles B, and the third copper particles C. Of course, to improve the compactness of the copper powder, a portion of the fourth copper particles D may be mixed with the first copper particles A, a portion of the fourth copper particles D may be mixed with the second copper particles B, and another portion of the fourth copper particles D may be mixed with the third copper particles C, thereby causing the fourth copper particles D to adhere to the surfaces of the first copper particles A, the second copper particles B, and the third copper particles C, respectively. Figure 4 FIG4 shows a scanning electron microscope image of the fourth copper particle of the embodiment of the present application after being mixed with copper particles of different particle sizes. Figure 4 As shown, such separate mixing makes the fourth copper particles D distributed on the surface of the copper particles more continuous and dense, which helps to provide higher conductivity and better oxidation resistance after subsequent solidification and sintering.

[0080] It should be noted that the properties and shapes of the copper particles of different particle sizes, as well as the materials and amounts of the dispersion medium used are the same as those described above and will not be described in detail here.

[0081] It can be understood that when the fourth copper particles D are mixed with any one of the first copper particles A, the second copper particles B, and the third copper particles C, a single mixture is obtained. When the fourth copper particles D are mixed with multiple types of the first copper particles A, the second copper particles B, and the third copper particles C, multiple mixtures are obtained. The content and particle size of the copper particles in the multiple mixtures can be the same or different.

[0082] In some embodiments, during the stirring and mixing process of operation S302, fourth copper particles D are additionally added. In this configuration, the fourth copper particles D are added again during the preparation of the copper slurry, so that after the copper slurry is cured, more dense conductive connection channels are formed, thereby improving the conductive performance while further increasing the peel strength of the copper electrode, thereby enhancing the durability and life of the copper electrode.

[0083] In some embodiments, the mass ratio of the fourth copper particles D added when a plurality of particles or a single mixture is stirred and mixed with the dispersion medium to the total amount of the fourth copper particles D added when the fourth copper particles D are mixed with at least one of the first copper particles A, the second copper particles B, and the third copper particles C is between 1:100 and 20:100. This configuration can further enhance the compactness of the copper slurry, thereby improving the mechanical strength and electrical conductivity of the copper electrode.

[0084] Optionally, the mass ratio of the fourth copper particles D additionally added when stirring and mixing a plurality of or a mixture with the dispersion medium to the total amount of the fourth copper particles D added when mixing the fourth copper particles D with at least one of the first copper particles A, the second copper particles B, and the third copper particles C can be 1:100, 5:100, 10:100, 15:100 or 20:100, etc., or a range between any two of the above values.

[0085] According to another embodiment of the present application, a copper electrode is provided, which is prepared by sintering and solidifying the above copper slurry.

[0086] According to the embodiments of the present application, the fourth copper particles D undergo an oxidation-reduction reaction during the sintering and solidification process, and nano-copper particles are generated in situ. The nano-copper particles are interconnected between the three copper particles of different particle sizes, thereby realizing more current transmission channels for the copper particles, reducing line resistance, and improving the binding force between the nano-copper particles and copper particles of different particle sizes. The tensile force and peeling strength of the copper electrode are improved, thereby improving the durability and stability of the copper electrode.

[0087] It should be noted that cuprous hydride nanoparticles are reducing and are less susceptible to oxidation in air than copper particles. Furthermore, cuprous hydride nanoparticles can decompose into elemental copper at temperatures between 60 and 100°C.

[0088] Optionally, the cuprous hydride nanoparticles in the fourth copper particles D may be partially or completely converted into copper alone. Preferably, the cuprous hydride nanoparticles are completely converted into copper alone.

[0089] According to another embodiment of the present application, a copper electrode is provided, comprising first copper particles A, second copper particles B, third copper particles C and fourth copper particles D; the particle size of the first copper particles A ranges from 1 to 10 μm, the particle size of the second copper particles B ranges from 500 to 999 nm, and the particle size of the third copper particles C ranges from 101 to 499 nm; the average particle size of the fourth copper particles is less than or equal to 100 nm; the first copper particles A, the second copper particles B, the third copper particles C and the fourth copper particles D are all elemental copper particles; at least a portion of the fourth copper particles D is attached to the surface of the first copper particles A and / or the second copper particles B and / or the third copper particles C.

[0090] It should be noted that after the copper slurry is sintered and solidified, the size and morphology of the fourth copper particles D may be different from those of the cuprous hydride nanoparticles in the copper slurry. If there is a difference between the size and morphology, the fourth copper particles D must meet the size requirement (≤100 nm).

[0091] In some embodiments, the fourth copper particles D are polyhedral copper particles or solid-of-rotation copper particles.

[0092] In some embodiments, polyhedral copper particles have at least 4 surfaces; solid-of-revolution copper particles have at least 2 surfaces.

[0093] In some embodiments, the contour line of the surface of the fourth copper particle D includes at least one of a straight line and an arc line.

[0094] In some embodiments, based on the total number of first copper particles A, second copper particles B, and third copper particles C being 100, the number of first copper particles A is 1 to 5, the number of second copper particles B is 8 to 15, the number of third copper particles C is 80 to 90, and the number of fourth copper particles D is greater than 100.

[0095] Since the first copper particles A, the second copper particles B, the third copper particles C and the fourth copper particles D also cooperate with each other in the above embodiment, the technical effects produced are the same or similar to those of the aforementioned copper slurry, which will not be repeated here.

[0096] According to another embodiment of the present application, a solar cell is provided, including a cell body and an electrode. The electrode is located on at least one surface of the cell body, and the electrode includes the copper electrode as described above.

[0097] According to the embodiments of the present application, the electrode is set on the battery body, and the fourth copper particle D is used in combination with the aforementioned elemental copper particles of different particle sizes, which helps to improve the contact resistance of the solar cell, reduce the current transmission loss of the copper electrode, and thus improve the current collection efficiency of the solar cell.

[0098] In some embodiments, the solar cell is selected from any one of a back contact solar cell, a heterojunction solar cell, and a tunnel oxide layer passivation contact cell.

[0099] According to the embodiments of the present application, the solar cell of the present application may be a bifacial cell, such as an HJT solar cell (heterojunction solar cell), a TOPCon solar cell (tunneling oxide passivation contact cell), or a back-contact solar cell. Furthermore, the back-contact solar cell may be a traditional IBC solar cell (interdigitated back-contact solar cell), or a TBC solar cell (TOPCon back-contact solar cell), an HBC solar cell (heterojunction back-contact solar cell), or a hybrid solar cell (i.e., wherein the PN passivation is a different passivation material, for example, a combination of polycrystalline silicon passivation and amorphous / microcrystalline passivation).

[0100] The solar cell comprises a cell body, which at least comprises a semiconductor substrate and a doped semiconductor layer on the semiconductor substrate, wherein the semiconductor substrate is a rectangular or square structure.

[0101] The material of the semiconductor substrate can be selected from materials such as silicon (Si) or germanium (Ge) or materials such as gallium arsenide (GaAs). Obviously, in terms of conductivity type, the semiconductor substrate can be an intrinsic semiconductor substrate, an n-type semiconductor substrate, or a p-type semiconductor substrate. Preferably, the semiconductor substrate is a p-type semiconductor substrate or an n-type semiconductor substrate. Compared with the intrinsic semiconductor substrate, the p-type semiconductor substrate or the n-type semiconductor substrate has better conductivity, so that the solar cell finally produced has a lower body resistivity, thereby improving the efficiency of the solar cell.

[0102] Furthermore, an n-type semiconductor substrate may be selected, which has the advantages of long minority carrier lifetime, no light decay, and good weak light performance.

[0103] Furthermore, the doped semiconductor layer includes a first doped semiconductor region and a second doped semiconductor region.

[0104] In some embodiments, when the solar cell provided in the present application is a back-contact solar cell, the first doped semiconductor region and the second doped semiconductor region are both located on the first surface, and the gate electrode is only formed on the first surface, a portion of the gate electrode is electrically connected to the first doped semiconductor region, and another portion of the gate electrode is electrically connected to the second doped semiconductor region, thereby facilitating the gate electrode to extract electrons or holes to form current.

[0105] In some embodiments, when the solar cell is a bifacial cell, the first doped semiconductor region and the second doped semiconductor region are respectively located on the first surface and the second surface of the cell body, and a portion of the gate electrode is formed on the first surface and electrically connected to the first doped semiconductor region, and another portion of the gate electrode is formed on the second surface and electrically connected to the second doped semiconductor region.

[0106] Of course, the solar cell may also include a transparent conductive layer, which is disposed on the side of the first doped semiconductor region or the second doped semiconductor region facing away from the semiconductor substrate. The transparent conductive layer has high electrical conductivity, allowing for timely conduction of collected carriers and reducing the carrier recombination rate. Furthermore, it is possible to select whether to dispose the transparent conductive layer on the side of the first doped semiconductor region facing away from the semiconductor substrate, as needed. For example, if the first doped semiconductor region is doped polycrystalline silicon, the side of the first doped semiconductor region facing away from the semiconductor substrate may or may not be provided with a transparent conductive layer. If the first doped semiconductor region is one or more of doped amorphous silicon, doped microcrystalline silicon, or doped nanocrystalline silicon, the side of the first doped semiconductor region facing away from the semiconductor substrate may be provided with a transparent conductive layer. Similarly, it is possible to select whether to dispose a transparent conductive layer on the side of the second doped semiconductor region facing away from the semiconductor substrate, as needed. For example, if the second doped semiconductor region is one or more of doped amorphous silicon, doped microcrystalline silicon, or doped nanocrystalline silicon, the side of the second doped semiconductor region facing away from the semiconductor substrate may be provided with a transparent conductive layer.

[0107] In some embodiments, the electrode is a collecting electrode and / or a bus electrode. The collecting electrode can be called a fine grid, a grid line electrode, a sub-grid, etc., and a plurality of collecting electrodes are located on at least one surface of the battery body. The plurality of collecting electrodes are spaced apart in a first direction (not shown in the figure) and extend along a second direction (not shown in the figure) intersecting the first direction. The bus electrode extends along the second direction, the bus electrode is in direct contact and electrically connected to the collecting electrode of the same polarity, the bus electrode is electrically isolated from the collecting electrodes of different polarities, the bus electrode is located on the side close to the battery body, and is electrically connected to the electrical connection line through a joint. The extension direction of the bus electrode intersects with the extension direction of the collecting electrode, and preferably the extension directions of the two intersect. The bus electrode or the collecting electrode is fixed to and electrically connected to the electrical connection line.

[0108] In some embodiments, setting the copper electrode as a collecting electrode and / or a bus electrode helps to improve the current collection efficiency of the collecting electrode and / or the bus electrode by combining the cuprous hydride nanoparticles with copper particles of different particle sizes, thereby improving the photoelectric conversion efficiency.

[0109] It should be noted that the solar cell of the present application may adopt a busbar-less (busbar-less, 0BB) structure, that is, the collecting electrode may be directly connected to the external electrical connection line by welding without passing through the busbar.

[0110] In the case where the solar cell of the present application further includes a transparent conductive layer, the transparent conductive layer is formed on the textured structure, and the collecting electrode is formed on the transparent conductive layer.

[0111] The embodiments of the present invention do not specifically limit the material and thickness of the transparent conductive layer. For example, the transparent conductive layer is a TCO (transparent conductive oxide) thin film layer that covers the entire surface of the pyramid. TCO thin films primarily include oxides of In, Sb, Zn, and Cb, as well as composite multi-element oxide thin films, such as ITO, GZO, and IZO, with varying doping types.

[0112] In addition, the materials of the first doped semiconductor region and the second doped semiconductor region can be silicon (Si), germanium (Ge), silicon carbide (SiCx) or gallium arsenide (GaAs), etc. Taking the example that the materials of the first doped semiconductor region and the second doped semiconductor region are both silicon (Si), the first doped semiconductor region can be one or more of doped polycrystalline silicon, doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. The second doped semiconductor region can be one or more of doped polycrystalline silicon, doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. The first doped semiconductor region can be additionally formed on the semiconductor substrate by deposition technology, or can be formed in the semiconductor substrate by diffusion, ion implantation, etc.

[0113] In some examples, the first doped semiconductor region includes a doped polysilicon layer. In this case, the doped polysilicon layer has higher carrier transport properties than the doped amorphous silicon layer. Therefore, when the first doped semiconductor region is a doped polysilicon layer, the carrier transport efficiency is higher, which is beneficial to improving the photoelectric conversion efficiency of the solar cell.

[0114] In terms of conductivity type, the first doped semiconductor region may be an n-type doped region, and the second doped semiconductor region may be a p-type doped region; or, the first doped semiconductor region may be a p-type doped region, and the second doped semiconductor region may be an n-type doped region.

[0115] In the case where the solar cell provided in the present application is a back-contact solar cell, the first surface may include a first region and a second region. The solar cell also includes a first doped semiconductor region formed at least in the first region and a second doped semiconductor region formed at least in the second region, and the first doped semiconductor region and the second doped semiconductor region have opposite conductivity types. The collector electrode includes a first collector electrode and a second collector electrode; the first collector electrode is located in the first region and is electrically connected to the first doped semiconductor region; the second collector electrode is located in the second region and is electrically connected to the second doped semiconductor region. The first region and the second region may be distributed alternately in strips or in interdigitated patterns.

[0116] As another example, the solar cell provided in this application may be a TBC (Tunnel Oxide Passivated Contact-Back Contact) solar cell, in which the first doped semiconductor region is a doped polycrystalline silicon layer, and a tunnel oxide layer is provided between the first doped semiconductor region and the semiconductor substrate; the second doped semiconductor region is a doped polycrystalline silicon layer, and a tunnel oxide layer is provided between the second doped semiconductor region and the semiconductor substrate. In this technical solution, neither the first doped semiconductor region nor the second doped semiconductor region extends into the third region, which isolates the first doped semiconductor region from the second doped semiconductor region to prevent leakage. Furthermore, a passivation layer is provided on the side of the first doped semiconductor region and the second doped semiconductor region facing away from the semiconductor substrate, and a collector electrode is formed on the passivation layer. The passivation layer comprises one or more stacked layers of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer.

[0117] For another example, the solar cell provided in the present application may be a TOPCon (Tunnel Oxide Passivated Contact) solar cell, in which a first doped semiconductor region is formed on a first surface, and a second doped semiconductor region is formed on a second surface. The first doped semiconductor region includes doped polycrystalline silicon, and a tunneling oxide layer is further provided between the first doped semiconductor region and the semiconductor substrate; the second doped semiconductor region may include doped polycrystalline silicon, and a tunneling oxide layer is further provided between the second doped semiconductor region and the semiconductor substrate. In addition, a passivation layer is provided on the side of the first doped semiconductor region and the second doped semiconductor region facing away from the semiconductor substrate, and a collector electrode is formed on the passivation layer. It should be noted that when the collector electrode is located on the passivation layer, the passivation layer needs to be burned through to achieve electrical connection between the collector electrode and the doped semiconductor layer of the battery body.

[0118] The doped layer can be formed on the semiconductor substrate by deposition, and can also be formed in the semiconductor substrate by diffusion, ion implantation, etc.

[0119] It should be noted that the structure of the electrodes in the solar cell, the shapes of the copper particles of several different average particle sizes, the number on the surface, the size, etc. are the same as those described above and will not be described in detail here.

[0120] It should be noted that the copper paste of the present application is not only suitable for the above-mentioned different batteries, but can also be used in other electronic devices, and the present application does not make any special restrictions on this.

[0121] It is understood that the copper paste of this application can be directly sintered and solidified on a battery with a transparent conductive layer at a low temperature (which can be understood as curing at ≤300°C). For high-temperature batteries (which can be understood as sintering at 600-800°C), a thin isolation layer needs to be prepared. The isolation layer can be made of a metal such as silver, nickel, tin, or their alloys, and the copper paste is then sintered on the isolation layer surface. The isolation layer can be prepared by at least one of electroplating, chemical plating, printing, or inkjet printing. Since this is not the focus of this application, it will not be described in detail.

[0122] According to another embodiment of the present application, a photovoltaic assembly is provided, comprising the above-mentioned solar cell and a plurality of electrical connection lines, wherein the plurality of electrical connection lines electrically connect adjacent solar cells.

[0123] According to an embodiment of the present application, the aforementioned solar cells are connected in series to form a solar cell string; and a packaging structure is disposed around the periphery of the solar cell string.

[0124] In some embodiments, the encapsulation structure may include a backsheet or back glass, an encapsulation film, a glass panel, etc. to enhance the stability of the solar cell string. The glass panel is located on the front of the solar cell string, and the backsheet is located on the back of the solar cell string, both of which provide protection. The adhesive film is used to bond the solar cell string to the glass panel and backsheet, providing a secure bond.

[0125] In some embodiments, multiple electrical connection lines (also called welding strips or interconnecting strips, which can be metal wires, metal lines, etc.) include first electrical connection lines and second electrical connection lines extending along a first direction and alternately arranged in a second direction. The cross-section of the electrical connection line can be circular or quasi-circular, elliptical, square, triangular, other polygonal, etc. The wire diameter or width of the electrical connection line ranges from 200 to 1200 μm. For example, the circular electrical connection line is preferably 220 to 350 μm, and particularly preferably 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 300 μm, 310 μm, 320 μm, and 330 μm. The maximum width of the square or rectangular electrical connection line is preferably 500 to 800 μm, and particularly preferably 600 μm.

[0126] In a photovoltaic module, the polarity of the electrical connection line of the adjacent previous solar cell is opposite to the polarity of the electrical connection line of the connected next solar cell to achieve current transmission.

[0127] The present application will be further described below by way of examples, drawings, and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may also be implemented without these specific details. Moreover, in the absence of conflict, the details in the following embodiments may be arbitrarily combined into other feasible embodiments.

[0128] It should be noted that the following specific examples are for illustration only and the scope of protection of this application is not limited thereto. The chemicals and raw materials used in the following examples were either commercially available or prepared in-house using recognized processing methods.

[0129] Example 1:

[0130] Preparation process of copper powder:

[0131] 50 g of first elemental copper particles with an average particle size of 5 μm, 300 g of second elemental copper particles with an average particle size of 750 nm, 450 g of third elemental copper particles with an average particle size of 250 nm, and 100 g of non-spherical cuprous hydride nanoparticles with an average particle size of 50 nm were shear-mixed to form a copper powder in which cuprous hydride nanoparticles were attached to the surfaces of different elemental copper particles.

[0132] The preparation process of solar cells:

[0133] 0.4 g of bisphenol F epoxy resin, 0.15 g of curing agent dicyandiamide, 0.2 g of 2-propyl imidazole, 0.05 g of dispersant oleic acid, and 0.3 g of solvent diethylene glycol butyl ether acetate were stirred evenly in a watch glass to obtain a slurry mother liquor. 8 g of copper powder was poured into the mother liquor and stirred, and then poured into a three-roll mill for rolling and grinding to obtain a homogeneous copper slurry.

[0134] The copper paste was screen-printed onto a semiconductor substrate and then sintered and solidified at 300°C for 3 seconds to obtain a 1 cm x 1 cm square copper electrode. Figure 5 FIG1 shows a scanning electron microscope image of the copper electrode of Example 1 of the present application. Figure 5 As shown, it can be seen that the particle sizes of the first elemental copper particles, the second elemental copper particles, and the third elemental copper particles do not change significantly after sintering and solidification. Figure 6 Shown Figure 5 A partial enlarged view of the Figure 6 As shown, it can be seen that the average particle size of the fourth copper nanoparticles formed by sintering is 55 nm. Figure 7The scanning electron microscope images of the copper electrodes at different scales in Example 1 of the present application are shown. Figure 7 As shown, it can be seen that the nano-copper particles are non-spherical nano-particles.

[0135] Example 2:

[0136] The preparation process of this Example 2 is substantially the same as that of Example 1, except that 40 g of cuprous hydride nanoparticles are shear-mixed with the first elemental copper particles, 40 g of cuprous hydride nanoparticles are shear-mixed with the second elemental copper particles, and 30 g of cuprous hydride nanoparticles are shear-mixed with the third elemental copper particles, and then the three materials are shear-mixed to obtain copper powder.

[0137] A copper electrode was prepared in substantially the same manner as in Example 1.

[0138] Example 3:

[0139] The preparation process of Example 3 is substantially the same as that of Example 1, except that during the preparation of the solar cell, 10 g of cuprous hydride nanoparticles are additionally added to the slurry mother liquor. The average particle size of the cuprous hydride is the same as that of Example 1, and a copper electrode is prepared.

[0140] Comparative Example 1:

[0141] The preparation process of Comparative Example 1 is substantially the same as that of Example 1, except that the cuprous hydride nanoparticles are replaced with elemental copper particles having the same average particle size to prepare a copper electrode.

[0142] Comparative Example 2:

[0143] The preparation process of this comparative example 2 is substantially the same as that of Example 1, except that the first elemental copper particles, the second elemental copper particles, and the third elemental copper particles are not distinguished, and the cuprous hydride nanoparticles and the elemental copper particles with an average particle size of 500 nm are directly shear-mixed to prepare copper powder.

[0144] A copper electrode was prepared in substantially the same manner as in Example 1.

[0145] Comparative Example 3:

[0146] The preparation process of Comparative Example 3 is substantially the same as that of Example 1, except that the added cuprous hydride nanoparticles are spherical, and a copper electrode is prepared.

[0147] The copper pastes of Examples 1-3 and Comparative Examples 1-3 were screen-printed and heated in a curing device at 300°C for 3 seconds to form copper films, yielding copper film blocks. Electrical performance testing was performed on the copper electrodes and copper film blocks prepared from Examples 1-3 and Comparative Examples 1-3.

[0148] Resistivity (ρ) testing method: The square resistance R (mΩ) of the copper film was measured using a four-probe square resistance meter, and the film thickness t (μm) was measured using a micrometer. The resistivity ρ = R × t / 10. The copper electrode contact resistance was measured using the transmission line mode (TLM) test. The DH5 contact resistance represents the contact resistance of the cured battery after 5 hours of storage at 85% humidity and 85°C. Table 1 below shows the relevant performance parameters of the copper electrodes for Examples 1-3 and Comparative Examples 1-3.

[0149] Table 1

[0150]

[0151] As shown in Table 1, Examples 1 to 3 have relatively lower resistivity than Comparative Examples 1-3, thereby improving the conductive efficiency of the copper electrode. Further comparisons are made between Examples 1 to 3. In Example 2, cuprous hydride particles are shear-mixed with different elemental copper particles, respectively, so that the resistivity of the resulting copper electrode is further reduced compared to Example 1. Example 3 is based on the additional addition of cuprous hydride nanoparticles to the slurry mother liquor, which correspondingly reduces the resistivity of the copper electrode, thereby further improving the conductive efficiency of the copper electrode. Comparing Example 1 and Comparative Example 3, it can be seen that when the cuprous hydride nanoparticles used are non-spherical, the non-spherical cuprous hydride nanoparticles have a greater improvement in the conductive efficiency of the copper electrode than the spherical cuprous hydride nanoparticles. Accordingly, it can be seen that while Examples 1 to 3 improve the conductive efficiency, the initial resistance and DH5 contact resistance are also greatly reduced. This shows that the use of non-spherical cuprous hydride nanoparticles can not only improve the conductive efficiency, but also reduce the initial resistance and DH5 contact resistance due to the reducing property provided by the cuprous hydride nanoparticles, thereby improving the stability of the copper electrode and promoting the widespread application of base metalization in the solar cell industry.

[0152] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above is only a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A copper slurry, characterized in that: The method comprises a dispersion medium and copper particles dispersed in the dispersion medium; the copper particles comprise first copper particles, second copper particles, third copper particles and fourth copper particles; The particle size of the first copper particles is in the range of 1 to 10 μm, the particle size of the second copper particles is in the range of 500 to 999 nm, and the particle size of the third copper particles is in the range of 101 to 499 nm. Wherein, the first copper particles, the second copper particles and the third copper particles are all elemental copper particles, and the fourth copper particles are cuprous hydride nanoparticles; At least a portion of the fourth copper particles is attached to the surface of the first copper particles and / or the second copper particles and / or the third copper particles.

2. The copper paste according to claim 1, characterized in that The fourth copper particles are non-spherical nanoparticles.

3. The copper slurry according to claim 2, characterized in that The fourth copper particles are polyhedral copper particles or rotating copper particles.

4. The copper slurry according to claim 3, characterized in that The polyhedral copper particles have at least four surfaces; the rotating copper particles have at least two surfaces.

5. The copper paste according to claim 4, characterized in that The contour line of the surface of the fourth copper particle includes at least one of a straight line and an arc line.

6. The copper paste according to claim 4, characterized in that The average particle size of the fourth copper particles is 10-100 nm.

7. The copper paste according to any one of claims 1 to 6, characterized in that Based on the total number of the first copper particles, the second copper particles, and the third copper particles being 100, the number of the first copper particles is 1 to 5, the number of the second copper particles is 8 to 15, and the number of the third copper particles is 80 to 90; The number of the fourth copper particles is greater than 100.

8. The copper paste according to any one of claims 1 to 6, characterized in that The dispersion medium includes a resin.

9. A method for preparing a copper slurry, characterized in that: include: mixing the fourth copper particles with at least one of the first copper particles, the second copper particles, and the third copper particles, respectively, so that at least a portion of the fourth copper particles adheres to the surface of the first copper particles and / or the second copper particles and / or the third copper particles, to obtain a plurality of particles or a single mixture; Stirring and mixing the plurality of or one mixture with a dispersion medium to obtain the copper slurry; Among them, the particle size range of the first copper particles is 1~10μm, the particle size range of the second copper particles is 500~999nm, and the particle size range of the third copper particles is 101~499nm; the first copper particles, the second copper particles and the third copper particles are all elemental copper particles, and the fourth copper particles are cuprous hydride nanoparticles.

10. The preparation method according to claim 9, characterized in that When the plurality of particles or the mixture are stirred and mixed with the dispersion medium, the fourth copper particles are additionally added.

11. The preparation method according to claim 10, characterized in that: The mass ratio of the total amount of the fourth copper particles additionally added when stirring and mixing the multiple or one mixture with the dispersion medium to the total amount of the fourth copper particles added when mixing the fourth copper particles with at least one of the first copper particles, the second copper particles, and the third copper particles is between 1:100 and 20:

100.

12. A copper electrode, characterized in that: The copper paste according to any one of claims 1 to 8 is prepared by sintering and solidifying.

13. A copper electrode, characterized in that: comprising a first copper particle, a second copper particle, a third copper particle and a fourth copper particle; The particle size of the first copper particles is in the range of 1 to 10 μm, the particle size of the second copper particles is in the range of 500 to 999 nm, the particle size of the third copper particles is in the range of 101 to 499 nm, and the average particle size of the fourth copper particles is less than or equal to 100 nm; The first copper particles, the second copper particles, the third copper particles and the fourth copper particles are all elemental copper particles, and at least part of the fourth copper particles is attached to the surface of the first copper particles and / or the second copper particles and / or the third copper particles.

14. The copper electrode according to claim 13, characterized in that The fourth copper particles are polyhedral copper particles or rotating copper particles.

15. The copper electrode according to claim 14, characterized in that The polyhedral copper particles have at least four surfaces; the rotating copper particles have at least two surfaces.

16. The copper electrode according to claim 14 or 15, characterized in that The contour line of the surface of the fourth copper particle includes at least one of a straight line and an arc line.

17. The copper electrode according to any one of claims 13 to 15, characterized in that Taking the total number of the first copper particles, the second copper particles and the third copper particles as 100, the number of the first copper particles is 1 to 5, the number of the second copper particles is 8 to 15, the number of the third copper particles is 80 to 90, and the number of the fourth copper particles is greater than 100.

18. A solar cell, characterized in that: The invention comprises a battery body and an electrode, wherein the electrode is located on at least one surface of the battery body, and the electrode comprises the copper electrode according to any one of claims 12 to 17.

19. The solar cell according to claim 18, characterized in that The electrodes are current collecting electrodes and / or bus electrodes.

20. The solar cell according to claim 18 or 19, characterized in that The solar cell is selected from any one of a back contact solar cell, a heterojunction solar cell, and a tunnel oxide layer passivation contact cell.

21. A photovoltaic module, characterized in that: The solar cell comprises the solar cell according to any one of claims 18 to 20, and a plurality of electrical connection lines, wherein the plurality of electrical connection lines electrically connect adjacent solar cells.

Images