Solar cell and photovoltaic module

Abstract

The invention discloses a solar cell and a photovoltaic module, relates to the technical field of photovoltaics, and is used for solving the problem that the preparation cost of the solar cell is relatively high. The solar cell includes: a silicon substrate having two opposite surfaces; the doped semiconductor layer is positioned on at least one surface of the silicon substrate; the passivation anti-reflection layer is located on the surface, away from the silicon substrate, of the doped semiconductor layer; the conductive layer is located on the surface of the passivation anti-reflection layer and is in electric contact with the doped semiconductor layer, the conductive layer comprises a silver alloy framework and base metal particles, the silver alloy framework is provided with holes, and the base metal particles are embedded into the holes.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a solar cell and a photovoltaic module. Background Art

[0002] Electrode preparation is a key step in the manufacturing process of crystalline silicon solar cells. Traditional crystalline silicon solar cells mainly use silver paste to prepare electrodes because silver has good electrical conductivity and chemical stability. However, the high price of silver material increases the production cost of solar cells accordingly. Summary of the Invention

[0003] The object of the present invention is to provide a solar cell, which can reduce the manufacturing cost of the solar cell while maintaining the performance of the solar cell.

[0004] In a first aspect, the present invention provides a solar cell comprising:

[0005] A silicon substrate having two oppositely disposed surfaces;

[0006] a doped semiconductor layer located on at least one side of the silicon substrate;

[0007] A passivation anti-reflection layer is located on the surface of the doped semiconductor layer away from the silicon substrate;

[0008] The conductive layer is located on the surface of the passivation anti-reflection layer and forms electrical contact with the doped semiconductor layer, wherein the conductive layer includes a silver alloy skeleton and base metal particles, the silver alloy skeleton has holes, and the base metal particles are embedded in the holes.

[0009] When adopting the above technical solution, the conductive layer of the solar cell includes a silver alloy skeleton and base metal particles, that is, the conductive layer contains base metals. Compared with the existing electrodes prepared with silver paste that does not contain base metals, the conductive layer in this application can maintain the existing conductive performance or keep it basically the same while using base metals with the same quality of electrode paste, thereby reducing the use of silver paste and reducing the cost of preparing the solar cell layer.

[0010] In some possible implementations, the base metal particles may be shaped in one or more of a spherical, blocky, or flake shape. The shape of the base metal particles can ensure sufficient contact area between the base metal particles and the silver alloy skeleton or doped semiconductor layer, thereby ensuring good electrical conductivity.

[0011] In some possible implementations, the surface of the base metal particles has wrinkles, and / or the surface of the silver alloy skeleton has a terraced structure. Due to the addition of base metal particles, the silver content is reduced, and the metal crystals formed in the conductive layer and the doped semiconductor layer will be reduced, thereby reducing the tension between the conductive layer and the surface of the doped semiconductor layer or the tension between the conductive layer and the electrical connector. In the conductive layer to which base metal particles are added, the undulating structures on the surface of the base metal particles and the silver alloy skeleton can provide bonding strength between the conductive layer, the doped semiconductor layer, the passivation anti-reflection layer, and the electrical connector, increase the tension between the conductive layer and the surface of the doped semiconductor layer and the electrical connector, and improve the bonding strength and connection reliability.

[0012] In some possible implementations, the undulation degree of the surface of the base metal particles is greater than the undulation degree of the surface of the silver alloy skeleton.

[0013] In some possible implementations, the base metal particles are in contact with the doped semiconductor layer;

[0014] and / or, the base metal particles are exposed on the surface of the conductive layer facing away from the doped semiconductor layer;

[0015] And / or, the base metal particles are located between the doped semiconductor layer and the surface of the conductive layer facing away from the doped semiconductor layer and are not in contact with both surfaces.

[0016] When the above technical solution is adopted, the base metal particles are randomly distributed in the silver alloy skeleton, such as distributed at the top, bottom and / or middle position of the silver alloy skeleton, which can make the wire performance at each position of the conductive layer uniform.

[0017] In some possible implementations, the conductive layer includes base metal particle clusters, which are formed by agglomerating base metal particles connected by oxides, and the number of base metal particles included in the base metal particle clusters is greater than or equal to 2.

[0018] In some possible implementations, the thickness of the oxide is 0.1-10 nm.

[0019] In some possible implementations, the conductive layer includes a collecting electrode and a bus electrode, and the collecting electrode and the bus electrode are connected; the collecting electrode contains base metal particles, and the bus electrode does not contain base metal particles; or, both the collecting electrode and the bus electrode contain base metal particles.

[0020] When using the above technical solution, the collector electrode forms contact with the doped semiconductor layer and is responsible for collecting carriers. The bus electrode is in electrical contact with the collector electrode and is responsible for collecting the carriers collected by the collector electrode and transmitting them to the outside of the solar cell. In addition, the bus electrode is added with base metal particles with a rougher surface than the silver alloy skeleton. This can increase the roughness of the bus electrode surface to a certain extent, and improve the bonding strength between the two when establishing an electrical connection with the conductive adhesive or electrical connector. Therefore, compared to silver paste electrodes, while reducing the amount of silver material used in the conductive layer to reduce costs, it can better ensure the reliability of solar cells when connected in series.

[0021] In some possible implementations, in the thickness direction of the silicon substrate, the height of the bus electrode is less than or equal to the height of the collector electrode.

[0022] When the above technical solution is adopted, the height of the collecting electrode is equal to or greater than that of the bus electrode, which can meet the function of collecting and transmitting carriers of the solar cell while reducing the amount of conductive layer material used and reducing costs.

[0023] In some possible implementations, the base metal particles are nickel particles. Nickel particles are not only much less expensive than silver, but also offer superior electrical conductivity and excellent bonding with solar cells and electrical connectors. This can reduce the cost of solar cell production while maintaining existing electrical conductivity and cell performance.

[0024] In some possible implementations, the silver content in the conductive layer is greater than the nickel content. While ensuring that the conductive layer has good conductivity, the production cost of the solar cell can be reduced by adding nickel with a content less than that of silver.

[0025] In some possible implementations, the base metal particles have a particle size of 0.5 μm to 12 μm. Compared to conventional silver particle size, this optimized base metal particle size can achieve a higher surface area to volume ratio without sacrificing conductivity, reducing the surface area per unit mass of the base metal particles, thereby reducing the probability of oxidation and improving the bonding strength and long-term stability of the conductive layer in the photovoltaic cell.

[0026] In some possible implementations, two oppositely disposed surfaces of the silicon substrate include a first surface and a second surface, the first surface is provided with a pyramid-shaped velvet structure, and the pyramid-shaped velvet structure includes a top and a plurality of side surfaces;

[0027] Part of the base metal particles in the conductive layer are close to the top of the pyramid-shaped velvet structure and / or at least one side surface of the pyramid-shaped velvet structure.

[0028] In some possible implementations, the second surface includes a doped semiconductor layer and a tunneling oxide layer, the tunneling oxide layer is located between the silicon substrate and the doped semiconductor layer, the tunneling oxide layer and the doped semiconductor layer constitute a tunneling passivation contact structure, and the tunneling passivation contact structure partially or entirely covers the second surface of the silicon substrate.

[0029] In some possible implementations, the doped semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer disposed on one surface of a silicon substrate, and the first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types; the passivation anti-reflection layer includes a first passivation anti-reflection layer located on the first doped semiconductor layer and a second passivation anti-reflection layer located on the second doped semiconductor layer.

[0030] When the above technical solution is adopted, a first doped semiconductor layer and a second doped semiconductor layer with opposite conductivity types are formed on one side of the silicon substrate, and the first doped semiconductor layer and the second doped semiconductor layer both form a tunneling passivation contact structure with the tunneling oxide layer. The solar cell is a back contact cell with a tunneling passivation contact structure, and has the advantages of both a tunneling passivation contact structure and a back contact cell. The positive and negative electrodes of the back contact cell are both located on the back, eliminating the blocking of light by the electrodes, which can increase the short-circuit current and the open-circuit voltage.

[0031] In some possible implementations, the conductive layer includes a first conductive layer and a second conductive layer, the first conductive layer is located on the surface of the first passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the first doped semiconductor layer, and the second conductive layer is located on the surface of the second passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the second doped semiconductor layer; wherein the doping type of the first doped semiconductor layer is P-type doping, and the content of base metal particles in the first conductive layer is less than the content of base metal particles in the second conductive layer.

[0032] In some possible implementations, the conductive layer includes a first conductive layer and a second conductive layer, the first conductive layer being located on a surface of the first passivation anti-reflection layer away from the silicon substrate and forming electrical contact with the first doped semiconductor layer, and the second conductive layer being located on a surface of the second passivation anti-reflection layer away from the silicon substrate and forming electrical contact with the second doped semiconductor layer; wherein the doping type of the first doped semiconductor layer is P-type doping, and along an extension direction perpendicular to the conductive layer, the width of the first conductive layer is greater than the width of the second conductive layer;

[0033] In a second aspect, the present invention further provides a photovoltaic module comprising a plurality of cell strings, wherein the cell strings comprise a plurality of solar cells and electrical connectors, wherein the solar cells are any of the solar cells described above, and the electrical connectors are electrically connected to the conductive layer.

[0034] Base metal particles are added to the conductive layer of the photovoltaic module. Compared with silver alloy, the base metal particles have greater surface roughness and better bonding force when electrically connected to the electrical connector, thereby increasing the bonding force between the electrical connector and the conductive layer, reducing the possibility of the electrical connector falling off, and increasing the reliability of the photovoltaic module.

[0035] In some possible implementations, the electrical connector and the conductive layer are electrically connected via conductive adhesive. Because the conductive adhesive has better wettability during welding, it can achieve sufficient contact between the electrical connector and the conductive layer, reducing the risk of cold solder joints and improving the reliability of the conductive connection. Furthermore, the conductive layer, due to the addition of base metal particles, has a greater surface roughness, which allows for better bonding with the conductive adhesive, thereby increasing the bonding strength between the electrical connector and the conductive layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0037] Figure 1 A schematic structural diagram of a solar cell provided by an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the microstructure of a conductive layer of a solar cell provided by an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of another microstructure of a conductive layer of a solar cell provided by an embodiment of the present invention;

[0040] Figure 4 A schematic diagram of another microstructure of a conductive layer of a solar cell provided by an embodiment of the present invention;

[0041] Figure 5 A schematic diagram of another structure of a conductive layer of a solar cell provided by an embodiment of the present invention;

[0042] Figure 6 A schematic structural diagram of another solar cell provided by an embodiment of the present invention;

[0043] Figure 7 A schematic structural diagram of another solar cell provided by an embodiment of the present invention.

[0044] Figure numerals: 1 is a silicon substrate, 2 is a doped semiconductor layer, 21 is a first doped semiconductor layer, 22 is a second doped semiconductor layer, 3 is a conductive layer, 31 is a silver alloy skeleton, 311 is a hole, 32 is a base metal particle, 4 is a passivation anti-reflection layer, 41 is a first passivation anti-reflection layer, 42 is a second passivation anti-reflection layer, and 5 is a tunneling oxide layer. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0048] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0049] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and may encompass internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0050] Electrode preparation is a key step in the manufacturing process of crystalline silicon solar cells. Traditional crystalline silicon solar cells mainly use silver paste to prepare electrodes because silver has good electrical conductivity and chemical stability. However, the high price of silver material increases the production cost of solar cells accordingly.

[0051] In view of this, if Figure 1-Figure 3As shown, an embodiment of the present invention provides a solar cell, comprising a silicon substrate 1, a doped semiconductor layer 2, a passivation anti-reflection layer 4 and a conductive layer 3; wherein the silicon substrate 1 has two oppositely arranged surfaces; the doped semiconductor layer 2 is located on at least one side of the silicon substrate 1, and on the same side of the silicon substrate 1, the doped semiconductor layer 2 can completely cover the surface of the silicon substrate 1 or partially cover the surface of the silicon substrate 1; the passivation anti-reflection layer 4 is located on the surface of the doped semiconductor layer 2 away from the silicon substrate 1; the conductive layer 3 is located on the surface of the passivation anti-reflection layer 4 and forms electrical contact with the doped semiconductor layer 2, wherein the conductive layer 3 comprises a silver alloy skeleton 31 and base metal particles 32, the silver alloy skeleton 31 has holes 311, and the base metal particles 32 are embedded in the holes 311.

[0052] It should be noted that the silver alloy skeleton 31 is as follows Figure 2 and Figure 3 As shown, it is a solidified structure formed by solidifying a slurry composed of a majority of silver and other elements, such as one or more of Si, B, Bi, Pb, Te, etc., after being melted at high temperature. There may still be parts in the silver alloy skeleton that can identify the morphology of silver particles before sintering, wherein the particle size of the silver particles ranges from 1 to 5 μm, specifically 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. The particle size refers to the distance between the two farthest points in the silver particles. The morphology of the silver alloy skeleton 31 can be characterized by testing methods such as scanning electron microscope (SEM), for example, a conductive top view of the conductive layer 3, and then the particle size is measured in the morphology image. The particle size can be the particle size of a single silver particle or the average particle size of multiple silver particles. The silver content in the silver alloy skeleton 31 is greater than 50%. After natural solidification, irregular holes 311 are formed in the silver alloy skeleton 31. Base metal particles 32 are embedded in some holes 311. One or more base metal particles 32 can be embedded in a hole 311. Part of the surface of the base metal particle 32 is metallurgically bonded to the silver alloy skeleton 31. There is a gap between the base metal particle 32 and the inner wall of the hole 311, so that the conductive layer 3 forms a non-dense alloy layer.

[0053] When adopting the above technical solution, the conductive layer 3 of the solar cell includes a silver alloy skeleton 31 and base metal particles 32, that is, the conductive layer 3 contains base metals. Compared with the existing electrodes prepared with silver paste that does not contain base metals, the conductive layer 3 in the present application can maintain the existing conductive performance or basically the same, and maintain the battery efficiency while using base metals with the same quality of electrode paste, thereby reducing the amount of silver paste used and reducing the cost of preparing the solar cell layer.

[0054] It should be noted that, in the conductive layer on the solar cell, the conductive layer in a partial area may include the silver alloy skeleton 31 and the base metal particles 32 , or the entire conductive layer may include the silver alloy skeleton 31 and the base metal particles 32 .

[0055] like Figure 2 and Figure 3 As shown, in some embodiments, the shape of the base metal particles 32 includes one or more of spherical, blocky, and flake-like. It should be noted that the spherical shape is similar to a sphere, not a standard sphere, and the surface of the base metal particles 32 is an uneven surface. Similarly, the block shape is similar to a rectangular block structure, not a standard rectangular block, and the flake shape is similar to a flat flake structure, not a standard flake structure. The base metal particles 32 can also be of any three-dimensional shape, and are not limited to the types mentioned above. The shape of the base metal particles 32 can ensure that there is sufficient contact area between the base metal particles 32 and the silver alloy skeleton 31 or the doped semiconductor layer 2, thereby ensuring good conductive properties.

[0056] In some embodiments, as Figure 2 and Figure 3 As shown, the surface of the base metal particles 32 has wrinkles, such as Figure 4 As shown, the surface of the silver alloy skeleton has a terraced structure, that is, there is a strip-shaped stepped or wavy cross-section texture structure on the surface of the silver alloy skeleton 31 (such as Figure 4 In the above technical solution, the undulating structures on the surface of the base metal particles and the silver alloy skeleton can provide bonding force between the conductive layer 3, the doped semiconductor layer, the passivation anti-reflection layer, and the electrical connector, thereby preventing the conductive layer 3 from falling off.

[0057] In some embodiments, the surface undulation of the base metal particles 32 is greater than that of the silver alloy skeleton 31. This comparison of undulations can be performed by comparing the number of protrusions and / or depressions; the degree of protrusions and / or depressions; or the degree of disorder in the arrangement of the protrusions and / or depressions. In other cases, it can be performed by comparing the height of the protrusions and / or the depth of the depressions; or the complexity of the morphology. Alternatively, the surface of the base metal particles 32 has a greater undulation than that of the silver alloy skeleton 31. In other words, the surface of the base metal particles 32 is rougher than that of the silver alloy skeleton 31. This can be determined qualitatively, for example, by comparing the depth of the depressions on the surface of the silver alloy skeleton 31 with the surface of the base metal particles 32. Compared to electrodes formed from existing silver pastes, the addition of base metal particles reduces the silver content, resulting in fewer metal crystals formed between the silver and doped semiconductor layers in the conductive layer, or a reduced contact area between the silver alloy skeleton in the conductive layer and the doped semiconductor layer. Consequently, the tensile force between the conductive layer and the surface of the doped semiconductor layer or the electrical connector is reduced. In the conductive layer 3 of the present application, in which base metal particles 32 are added, the wrinkled surface of the base metal particles 32 increases the tensile force between the conductive layer 3 and the surface of the doped semiconductor layer 2 and the electrical connector, thereby improving the bonding strength and connection reliability of the conductive layer 3, the doped semiconductor layer 2, and the electrical connector. The wrinkles on the surface of the base metal particles 32 are attached oxides, such as one or more of silicon oxide, lead oxide, bismuth oxide, nickel oxide, or aluminum oxide.

[0058] In some embodiments, as Figure 2 and Figure 3As shown, the base metal particles 32 are randomly distributed in the silver alloy skeleton 31, mainly in the following three distribution positions: the first is that the base metal particles 32 are located in the silver alloy skeleton 31 close to the doped semiconductor layer 2 and in contact with the doped semiconductor layer 2. Correspondingly, the pores 311 are located in the silver alloy skeleton 31 close to the doped semiconductor layer 2, and the openings of the pores 311 face the doped semiconductor layer 2. The second is that the base metal particles 32 are located in the silver alloy skeleton 31 away from the doped semiconductor layer 2, and the base metal particles 32 are exposed on the surface of the conductive layer 3 facing away from the doped semiconductor layer 2. The base metal particles 32 can be slightly lower than the surface of the conductive layer 3 facing away from the doped semiconductor layer 2, or be flush with or exposed from the surface of the conductive layer 3 facing away from the doped semiconductor layer 2. Correspondingly, the pores 311 are located on the surface of the conductive layer 3 facing away from the doped semiconductor layer 2, and the openings of the pores 311 face away from the doped semiconductor layer 2. The third type is that the base metal particles 32 are located between two opposing surfaces of the conductive layer 3, one adjacent to the doped semiconductor layer 2 and the other facing away from the doped semiconductor layer 2, without contacting either surface. Correspondingly, the pores 311 are located within the silver alloy skeleton 31 and are closed pores. The base metal particles 32 can be located in one or more of the three distribution positions above, in any combination, and in a random distribution.

[0059] When the above technical solution is adopted, the base metal particles 32 are randomly distributed in the conductive layer 3, such as distributed at the top, bottom and / or middle position of the conductive layer 3. The base metal particles 32 can electrically contact the silver alloy skeleton 31 at multiple positions to form carrier transmission channels, thereby making the electrical properties of each position of the conductive layer 3 uniform.

[0060] In some embodiments, the conductive layer 3 includes base metal particle clusters, which are formed by agglomerating base metal particles 32, and the number of base metal particles 32 included in the base metal particle cluster is greater than or equal to 2. The agglomerated base metal particles are composed of base metal particles at least partially connected by oxides, which can achieve dense connection, effectively reduce the interfacial contact resistance between the base metal particles while maintaining high continuity of the conductive path, and significantly improve the overall current carrying capacity of the base metal particles.

[0061] In some embodiments, the thickness of the oxide is 0.1 to 1000 nm, for example, 0.1 nm, 1 nm, 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or a range consisting of any two of the foregoing values. When the thickness is too thin, it is difficult to form continuous coverage, causing the connecting regions between the base metal particles 32 to be more easily oxidized, resulting in reduced stability. When the thickness is too thick, the interface resistance between adjacent base metal particles 32 increases, thereby degrading the conductive performance. When the oxide thickness is set within the above range, carriers can pass through the connecting regions of the thinner base metal particles 32, forming a conductive path between adjacent base metal particles 32, thereby reducing the obstruction of the base metal particles 32 on the conductive performance.

[0062] It should be noted that the thickness of the oxide can be understood as the length in the direction of any tangent perpendicular to the connection region between adjacent base metal particles 32 , where any tangent here can be understood as the tangent of any one of the adjacent base metal particles 32 .

[0063] In some embodiments, the conductive layer includes a collecting electrode and a bus electrode. The collecting electrode, also known as a fine grid, and the bus electrode, also known as a main grid, form contact with the doped semiconductor layer and are responsible for collecting carriers. The bus electrode is in electrical contact with the collecting electrode and is responsible for collecting the carriers collected by the collecting electrode and transmitting them outside the solar cell. The collecting electrode may contain base metal particles, while the bus electrode does not; alternatively, the collecting electrode does not contain base metal particles, while the bus electrode does; or both the collecting electrode and the bus electrode contain base metal particles.

[0064] When the above technical solution is adopted, for example, when base metal particles are added to the collecting electrode, the bus electrode does not contain base metal particles. The collecting electrode can maintain the existing conductive performance or basically the same, and maintain the battery efficiency, while using base metals with the same mass of electrode paste, reducing the amount of silver paste used and reducing the cost of preparing the solar cell layer. Since the bus electrode does not add base metal paste, it can still maintain the original contact performance and tensile force, especially at the overlap position of the collecting electrode and the bus electrode. For another example, the collecting electrode and the bus electrode both contain base metal particles, and the collecting electrode and the bus electrode add base metal particles with a rougher surface than the silver alloy skeleton, which can increase the roughness of the bus electrode surface to a certain extent, and improve the bonding force between the two when electrically connected with the conductive glue or electrical connector. Therefore, compared with the silver paste electrode, while reducing the cost by reducing the amount of silver material used in the conductive layer, it can better ensure the reliability of the solar cell when connected in series.

[0065] In some embodiments, the height of the busbar electrode is less than or equal to the height of the collector electrode in the thickness direction of the silicon substrate. Functionally, the busbar electrode is primarily used to collect carriers from the collector electrode and connect them to the electrical connector, while the collector electrode is primarily used to collect carriers generated in the solar cell substrate. Therefore, setting the height of the busbar electrode less than or equal to the height of the collector electrode can reduce the amount of conductive layer material used while meeting the solar cell's function of collecting and transmitting carriers, thereby reducing costs.

[0066] In some embodiments, the busbar can be a continuous or discontinuous busbar, a pad, a terminal wire near each end of the collector electrode, or a thickened section on the collector electrode. Any form of busbar can be used, as long as it can be electrically connected to the collector electrode and to an electrical connector, such as a soldering ribbon. These various busbar forms can increase the bonding area and strength between the conductive layer and the electrical connector.

[0067] In some embodiments, the base metal particles 32 are nickel metal particles. Nickel is not only much less expensive than silver, but also has excellent electrical conductivity and excellent bonding with solar cells and electrical connectors, comparable to silver. This allows for reduced solar cell manufacturing costs while maintaining existing electrical conductivity and cell efficiency.

[0068] The following is a comparison of the performance parameters of solar cells whose conductive layer 3 contains nickel metal particles and whose conductive layer prepared by the existing electrode slurry does not contain nickel metal particles, as shown in Table 1, Table 2 and Table 3 below:

[0069] Table 1. Performance comparison of solar cell backside collecting electrodes with and without nickel metal particles

[0070]

[0071] As can be seen from Table 1, multiple solar cells were tested in each experimental group to obtain the average value of the battery performance parameters in each experimental group. The collecting electrode (also known as the fine grid) on the back of the solar cell adopts the structure of the conductive layer in the present application, that is, it contains nickel metal particles. Compared with not containing nickel metal particles, the battery efficiency is not much different, and other battery performance remains basically unchanged. That is, the conductive layer with added nickel metal particles maintains the existing battery performance and battery efficiency or remains basically unchanged. Moreover, due to the use of base metal nickel, the cost of nickel is much lower than that of silver, thereby reducing the preparation cost of solar cells.

[0072] Table 2. Performance comparison of solar cell backside busbar electrodes containing nickel metal particles and those without nickel metal particles

[0073]

[0074] As can be seen from Table 2, multiple solar cells were tested in each experimental group to obtain the average value of the battery performance parameters in each experimental group. The busbar electrode (also known as the main grid) on the back of the solar cell adopts the structure of the conductive layer in this application, that is, it contains nickel metal particles. Compared with not containing nickel metal particles, the battery efficiency is improved, and other battery performance remains basically unchanged. That is, the conductive layer with added nickel metal particles maintains the existing battery performance and battery efficiency or remains basically unchanged, and since base metal nickel is used, the cost of nickel is much lower than the cost of silver, thereby reducing the preparation cost of solar cells.

[0075] Table 3. Performance comparison of solar cell front busbar electrodes containing nickel metal particles and those without nickel metal particles

[0076]

[0077] As can be seen from Table 3, multiple solar cells were tested in each experimental group to obtain the average value of the battery performance parameters in each experimental group. The front busbar (also known as the main grid) of the solar cell adopts the structure of the conductive layer in the present application, that is, it contains nickel metal particles. Compared with not containing nickel metal particles, the battery efficiency is improved, and other battery performance remains basically unchanged. That is, the conductive layer with added nickel metal particles maintains the existing battery performance and battery efficiency or remains basically unchanged, and since base metal nickel is used, the cost of nickel is much lower than the cost of silver, thereby reducing the preparation cost of solar cells.

[0078] In addition, it can be concluded from Tables 1, 2 and 3 that the use of the conductive layer structure of the present application in the collecting electrode or the bus electrode, i.e., containing nickel metal particles, can reduce the preparation cost of solar cells while maintaining battery performance and battery efficiency.

[0079] Of course, base metals can also include aluminum, copper, zinc, etc., which can all reduce the preparation cost of solar cells. However, compared with nickel, adding a conductive layer of nickel metal can better maintain battery performance and battery efficiency.

[0080] In some embodiments, the silver content of the conductive layer is greater than the nickel content. Specifically, the mass fraction of silver in the conductive layer is greater than the mass fraction of nickel. By adding less nickel than silver, the production cost of the solar cell can be reduced while ensuring good cell performance and efficiency in the conductive layer.

[0081] It should be noted that the content of silver and nickel in the conductive layer can be measured by technical means commonly used by those skilled in the art, for example, by performing point scanning, line scanning or surface scanning of the conductive layer using a scanning electron microscope (SEM) combined with an energy dispersive spectrometer to perform elemental testing to display the spatial distribution of each element. The element distribution is tested in a cross-sectional view including the conductive layer. The cross-sectional view can be an SEM test image obtained by cutting the solar cell at a certain angle to the extension direction of the conductive layer, such as 90° (i.e., parallel to the width of the conductive layer) or 120°. A single sub-region is taken in the corresponding area of ​​the conductive layer, and then the element distribution in the sub-region is characterized by an EDS surface scan test to obtain the proportion of the metal element in the sub-region to the element distribution in the sub-region, and the metal element content in the corresponding area of ​​the conductive layer is obtained. Alternatively, multiple sub-regions of the same area are taken in the corresponding area of ​​the conductive layer, and then the element distribution in each sub-region of the same area is tested and characterized by EDS surface scanning to obtain the proportion of metal elements in each sub-region to the element distribution in the sub-region, and then the average value is taken to obtain the metal element content in the corresponding area of ​​the conductive layer. The multiple here can be 2, 3, 4, 5, 6, etc.

[0082] In some embodiments, the particle size of the base metal particles is 0.5 μm to 12 μm, and the particle size here can be the particle size D in the conductive layer. 90 The base metal particle size ranges from 0.5μm to 12μm, specifically 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, etc. It should be noted that the particle size of base metal particles does not refer only to spherical particles; block and flake particles can also be expressed by particle size. The particle size of block and flake particles refers to the distance between the two farthest points in the particle. Compared with conventional silver particle size, this optimized base metal particle size can achieve a higher surface area to volume ratio without sacrificing conductivity, reducing the surface area per unit mass of base metal particles, thereby reducing the probability of oxidation and improving the bonding strength and long-term stability of the conductive layer in the photovoltaic cell. In addition, the relatively small base metal particle size of this size enables the preparation of fine and precise electrode patterns, improving the accuracy of electrode line width and spacing. Conductive layers with smaller base metal particles can avoid interruptions and irregularities in the conductive path, thereby reducing electrode resistance and improving current collection efficiency. Conductive layers with smaller base metal particles have less stress concentration, which can reduce electrode cracking caused by stress concentration during solar cell packaging and subsequent use. Particle size can be measured using a laser particle size analyzer.

[0083] In some embodiments, the solar cell may be a back-contact cell, a bifacial cell, or the like. The back-contact cell may be an interdigitated back-contact cell, a heterojunction back-contact cell, a tunneling passivation back-contact cell, or a hybrid tunneling passivation and heterojunction back-contact cell. The bifacial cell may be a heterojunction cell, a tunneling passivation cell, or the like. The conductive layer may be applicable to any of the above solar cells. Different cell types employ different materials and structures for the doped semiconductor layer.

[0084] For example, the silicon substrate 1 may be made of N-type or P-type single crystal silicon, polycrystalline silicon, microcrystalline silicon, or other materials. The material of the doped semiconductor layer 2 may include doped single crystal silicon, doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, or doped amorphous silicon. The material of the passivation anti-reflection layer 4 may include silicon oxide, silicon carbide, aluminum oxide, silicon nitride, silicon oxynitride, or titanium oxide, and the passivation anti-reflection layer 4 may be a single layer or a stacked structure composed of one or more of the above materials. The materials and doping type of the silicon substrate 1 and the doped semiconductor layer 2 are appropriately selected based on the cell type. For example, when the doped semiconductor layer 2 is doped polycrystalline silicon, it can form a tunneling passivation contact structure with the tunneling oxide layer. When the doped semiconductor layer 2 is doped amorphous silicon, it can form a heterojunction contact structure with intrinsic amorphous silicon. The resulting solar cell may be a back-contact solar cell or a bifacial solar cell with a tunneling passivation contact structure and / or a heterojunction contact structure, without specific limitation herein.

[0085] like Figure 5 and Figure 7 As shown, in some embodiments, when the doped semiconductor layer 2 includes one or more of doped polycrystalline silicon, doped microcrystalline silicon, and doped nanocrystalline silicon, the solar cell further includes a tunneling oxide layer 5, and the tunneling oxide layer 5 is located between the silicon substrate 1 and the doped semiconductor layer 2. The tunneling oxide layer 5 and the doped semiconductor layer 2 constitute a tunneling passivation contact structure, and the tunneling passivation contact structure partially or entirely covers the surface of the silicon substrate 1. The solar cell is a tunneling passivation contact solar cell.

[0086] like Figure 5As shown, for a bifacial solar cell, the two opposing sides of a silicon substrate 1 include a first side and a second side. A pyramid-shaped velvet structure is provided on the first side of the silicon substrate 1. The pyramid-shaped velvet structure, including a spire and multiple side surfaces, enables incident light to be reflected and refracted multiple times on the surface of the silicon substrate 1, creating a light trapping effect. Conductive layers 3 are provided on both sides of the silicon substrate 1, with the conductive layers 3 on each side having opposite polarities. The doped semiconductor layers 2 on the same side of the silicon substrate 1 have the same conductivity type, and can be either a P-type or an N-type doped semiconductor layer. Doped semiconductor layers of different doping types are located on the opposing first and second sides of the silicon substrate 1, forming a bifacial solar cell with a tunneling passivation contact mechanism. Some of the base metal particles 32 in the conductive layer 3 are close to the top of the pyramid-shaped velvet structure and / or at least one side of the pyramid-shaped velvet structure. At this time, compared with the polished surface of the silicon substrate, the silicon substrate surface with the pyramid-shaped velvet structure can provide more contact area with the conductive layer. The positional relationship between the base metal particles distributed on the surface of the conductive layer close to the silicon substrate and the pyramid-shaped velvet structure is close to the top of the pyramid-shaped velvet structure and / or at least one side, or in contact with the top of the pyramid-shaped velvet structure and / or at least one side, rather than directly in contact with the bottom of the pyramid-shaped velvet structure. Such a distribution setting will not excessively block the contact between the silver alloy skeleton and the pyramid-shaped velvet structure, reduce the ohmic contact formed by the silver alloy skeleton, and ensure the contact performance between the conductive layer and the surface with the pyramid-shaped velvet structure.

[0087] In some embodiments, as Figure 6 As shown, the tunneling passivation contact structure on the same surface of the silicon substrate 1 can partially cover the surface, forming a certain pattern, such as a pattern of spaced stripes or a cross-shaped pattern. Alternatively, the tunneling passivation contact structure on the same surface of the silicon substrate 1 can cover the entire surface. In a bifacial solar cell, a tunneling oxide layer 5, a doped semiconductor layer 2, a passivation anti-reflection layer 4, and a conductive layer 3 are sequentially stacked on the first surface of the silicon substrate 1, and a diffusion layer (not shown), a passivation anti-reflection layer 4, and a conductive layer 3 are sequentially stacked on the second surface of the silicon substrate 1.

[0088] In a solar cell with a tunneling passivation contact structure, the tunneling oxide layer 5 located between the silicon substrate 1 and the doped semiconductor layer 2 allows electrons to pass through while blocking hole transport, thereby achieving efficient charge separation, reducing interfacial recombination losses, and improving interfacial passivation, thereby increasing photoelectric conversion efficiency. Furthermore, the tunneling oxide layer 5 prevents metal crystals from piercing the doped semiconductor layer 2 and entering the silicon substrate 1, preventing damage to the passivation on the solar cell surface and thus loss of cell efficiency.

[0089] like Figure 7As shown, for a back-contact solar cell, the doped semiconductor layer 2 includes a first doped semiconductor layer 21 and a second doped semiconductor layer 22 disposed on one surface of a silicon substrate 1. The first doped semiconductor layer 21 and the second doped semiconductor layer 22 have opposite conductivity types. The passivation anti-reflection layer 4 includes a first passivation anti-reflection layer 41 disposed on the first doped semiconductor layer 21 and a second passivation anti-reflection layer 42 disposed on the second doped semiconductor layer 22. It should be noted that the first passivation anti-reflection layer 41 and the second passivation anti-reflection layer 42 can be formed in the same layer structure, a single layer, or cover the isolation trench between the first doped semiconductor layer 21 and the second doped semiconductor layer 22, and can be formed in the same step. Alternatively, the first passivation anti-reflection layer 41 and the second passivation anti-reflection layer 42 can be separate layers, or only cover the corresponding first doped semiconductor layer 21 and second doped semiconductor layer 22. The tunneling oxide layer 2 between the silicon substrate 1 and the doped semiconductor layer 2 can be a single layer structure, or can correspond to the first doped semiconductor layer 21 and the second doped semiconductor layer 22, with a break at the isolation trench. A passivation anti-reflection layer 4 is provided on the other side (ie, the front side) of the silicon substrate 1 .

[0090] When the above technical solution is adopted, a first doped semiconductor layer 21 and a second doped semiconductor layer 22 with opposite conductivity types are formed on one surface of the silicon substrate 1, and the first doped semiconductor layer 21 and the second doped semiconductor layer 22 both form a tunneling passivation contact structure with the tunneling oxide layer 5. The solar cell is a back contact cell with a tunneling passivation contact structure, and has the advantages of both a tunneling passivation contact structure and a back contact cell. The positive and negative electrodes of the back contact cell are both located on the back, eliminating the blocking of light by the electrodes, which can increase the short-circuit current and the open-circuit voltage.

[0091] In some embodiments, as Figure 7 As shown, the conductive layer 3 includes a first conductive layer and a second conductive layer. The first conductive layer is located on the surface of the first passivation anti-reflection layer 41 away from the silicon substrate 1 and forms an electrical contact with the first doped semiconductor layer 21. The second conductive layer is located on the surface of the second passivation anti-reflection layer 42 away from the silicon substrate 1 and forms an electrical contact with the second doped semiconductor layer 22. The first doped semiconductor layer 21 and the second doped semiconductor layer 22 have opposite doping types, with the first doped semiconductor layer 21 being P-type doped. The content of base metal particles in the first conductive layer is less than that in the second conductive layer. Therefore, while the P-type first doped semiconductor layer 21 generally has a lower doping concentration than the N-type second doped semiconductor layer 22, resulting in poor contact performance between the first doped semiconductor layer 21 and the first conductive layer structure, by controlling the content of base metal particles in the first conductive layer to be less than that in the second conductive layer, the difference in contact performance between the P-region and the N-region can be reduced, thereby achieving balanced carrier transport between the N-region and the P-region.

[0092] It should be noted that the content of base metal particles can be compared by the number of base metal particles in the conductive layer per unit length or per unit volume. For example, a unit volume of the conductive layer is taken, and the base metal particles exposed on the surface or cross-section of the conductive layer away from the silicon substrate are counted; or multiple unit volumes of the conductive layer are taken, and the base metal particles exposed on the surface or cross-section of the conductive layer away from the silicon substrate are counted and the average value is taken to compare the content of the base metal particles.

[0093] In some embodiments, the conductive layer 3 includes a first conductive layer and a second conductive layer. The first conductive layer is located on a surface of the first passivation anti-reflection layer 41 away from the silicon substrate 1 and forms electrical contact with the first doped semiconductor layer 21. The second conductive layer is located on a surface of the second passivation anti-reflection layer 42 away from the silicon substrate 1 and forms electrical contact with the second doped semiconductor layer 22. The first doped semiconductor layer 21 and the second doped semiconductor layer 22 have opposite doping types, with the first doped semiconductor layer 21 being P-type doped. Along a direction perpendicular to the conductive layer, the width of the first conductive layer is greater than the width of the second conductive layer. Therefore, in the case where the P-type first doped semiconductor layer 21 generally has a lower doping concentration than the N-type second doped semiconductor layer 22, resulting in poor contact performance between the first doped semiconductor layer 21 and the first conductive layer structure, by adjusting the width of the first conductive layer to be greater than the width of the second conductive layer, the contact area between the first conductive layer and the first doped semiconductor layer 21 can be increased, thereby increasing the carrier transmission channel and improving the contact performance. This can further help reduce the difference in contact performance between the P region and the N region, thereby achieving balanced carrier transmission between the N region and the P region.

[0094] Based on the solar cell described in any of the above embodiments, an embodiment of the present invention further provides a photovoltaic module, which includes multiple cell strings, and the cell strings include multiple solar cells and electrical connectors. The solar cell is a solar cell as described in any of the above embodiments, and the electrical connector is electrically connected to the conductive layer. Specifically, the electrical connector is electrically connected to the electrical junction of the conductive layer.

[0095] Because this photovoltaic module utilizes the solar cell described in any of the above embodiments, it has the same beneficial effects as any of the above embodiments. Base metal particles are added to the conductive layer of this photovoltaic module. Compared to silver alloys, the base metal particles have a greater surface roughness, resulting in better bonding strength when electrically connected to electrical connectors. This increases the bonding strength between the electrical connectors and the conductive layer, reduces the likelihood of the electrical connectors falling off, and improves the reliability of the photovoltaic module. Furthermore, the base metal particles reduce the manufacturing cost of the photovoltaic module.

[0096] In some embodiments, the electrical connector and the conductive layer are electrically connected via a bonding material. The bonding material can be a material such as a conductive adhesive that can achieve an electrically conductive connection between the electrical connector and the conductive layer. Because the conductive adhesive has better wettability during the welding process, it can achieve sufficient contact between the electrical connector and the conductive layer, reducing the risk of cold solder joints and improving the reliability of the conductive connection. Furthermore, the conductive layer, due to the addition of base metal particles, has a greater surface roughness, which can improve the bonding strength when in contact with the conductive adhesive, thereby increasing the bonding strength between the electrical connector and the conductive layer.

[0097] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0098] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A solar cell, characterized in that: include: A silicon substrate having two oppositely disposed surfaces; a doped semiconductor layer, located on at least one side of the silicon substrate; a passivation anti-reflection layer, located on a surface of the doped semiconductor layer away from the silicon substrate; A conductive layer is located on the surface of the passivation anti-reflection layer and forms an electrical contact with the doped semiconductor layer, wherein the conductive layer includes a silver alloy skeleton and base metal particles, the silver alloy skeleton has holes, and the base metal particles are embedded in the holes.

2. The solar cell according to claim 1, wherein The base metal particles may be in one or more shapes including spherical, blocky, and flake-like.

3. The solar cell according to claim 1, wherein The surface of the base metal particles has wrinkles, and / or the surface of the silver alloy skeleton has a terraced structure.

4. The solar cell according to claim 3, characterized in that The undulation degree of the surface of the base metal particles is greater than the undulation degree of the surface of the silver alloy skeleton.

5. The solar cell according to claim 1, wherein The base metal particles are in contact with the doped semiconductor layer; And / or, the base metal particles are exposed on a surface of the conductive layer facing away from the doped semiconductor layer; And / or, the base metal particles are located between the doped semiconductor layer and the surface of the conductive layer facing away from the doped semiconductor layer and are not in contact with both surfaces.

6. The solar cell according to claim 1, wherein The conductive layer includes base metal particle clusters, wherein the base metal particle clusters are formed by agglomerating the base metal particles connected by oxides, and the number of the base metal particles included in the base metal particle clusters is greater than or equal to 2.

7. The solar cell according to claim 6, characterized in that The thickness of the oxide is 0.1 to 10 nm.

8. The solar cell according to claim 1, wherein The conductive layer includes a collector electrode and a bus electrode, and the collector electrode and the bus electrode are connected; The current collecting electrode contains the base metal particles, and the bus electrode does not contain the base metal particles; Alternatively, both the current collecting electrode and the bus electrode contain base metal particles.

9. The solar cell according to claim 8, characterized in that In the thickness direction of the silicon substrate, the height of the bus electrode is less than or equal to the height of the collector electrode.

10. The solar cell according to claim 1, wherein The base metal particles are nickel metal particles.

11. The solar cell according to claim 10, characterized in that The content of silver in the conductive layer is greater than that of nickel.

12. The solar cell according to claim 1, wherein The base metal particles have a particle size of 0.5 μm to 12 μm.

13. The solar cell according to any one of claims 1 to 12, characterized in that: The two opposite sides of the silicon substrate include a first side and a second side, the first side is provided with a pyramid-shaped velvet structure, and the pyramid-shaped velvet structure includes a top and multiple side surfaces; Part of the base metal particles in the conductive layer are close to the top of the pyramid-shaped velvet structure and / or at least one side surface of the pyramid-shaped velvet structure.

14. The solar cell according to claim 13, characterized in that The second surface includes the doped semiconductor layer and the tunneling oxide layer, the tunneling oxide layer is located between the silicon substrate and the doped semiconductor layer, the tunneling oxide layer and the doped semiconductor layer constitute a tunneling passivation contact structure, and the tunneling passivation contact structure partially or entirely covers the second surface of the silicon substrate.

15. The solar cell according to any one of claims 1 to 12, characterized in that: The doped semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer provided on one surface of the silicon substrate, wherein the first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types; The passivation anti-reflection layer includes a first passivation anti-reflection layer located on the first doped semiconductor layer and a second passivation anti-reflection layer located on the second doped semiconductor layer.

16. The solar cell according to claim 15, characterized in that The conductive layer includes a first conductive layer and a second conductive layer, the first conductive layer is located on a surface of the first passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the first doped semiconductor layer, and the second conductive layer is located on a surface of the second passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the second doped semiconductor layer; The doping type of the first doped semiconductor layer is P-type doping, and the content of the base metal particles in the first conductive layer is less than the content of the base metal particles in the second conductive layer.

17. The solar cell according to claim 15, characterized in that The conductive layer includes a first conductive layer and a second conductive layer, the first conductive layer is located on a surface of the first passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the first doped semiconductor layer, and the second conductive layer is located on a surface of the second passivation anti-reflection layer away from the silicon substrate, and forms an electrical contact with the second doped semiconductor layer; The doping type of the first doped semiconductor layer is P-type doping, and along an extension direction perpendicular to the conductive layer, the width of the first conductive layer is greater than the width of the second conductive layer.

18. A photovoltaic assembly comprising a plurality of cell strings, each cell string comprising a plurality of solar cells and electrical connectors, characterized in that: The solar cell is the solar cell according to any one of claims 1 to 17, and the electrical connector is electrically connected to the conductive layer.

19. The photovoltaic module according to claim 18, characterized in that: The electrical connector is electrically connected to the conductive layer via a bonding material.

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