Solar cell and preparation method thereof, photovoltaic module

Abstract

The present application provides a solar cell and a preparation method thereof, and a photovoltaic module, wherein the solar cell comprises a silicon substrate, a doping layer and an electrode, the doping layer is arranged on the surface of the silicon substrate, the electrode is arranged on at least one side of the solar cell, the electrode comprises a main grid line, a secondary grid line and an electrode extension; a plurality of electrode extensions are arranged in sequence along the length direction of the main grid line; at least a partial area of ​​the secondary grid line covers the electrode extension; the material of the main grid line and the electrode extension includes silver, and the material of the secondary grid line includes a base metal, thereby reducing the manufacturing cost of the electrode.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] At present, silver is widely used as an electrode material for crystalline silicon solar cells due to its high conductivity, good adhesion and stability. However, the high cost and limited resources of silver are not conducive to reducing the manufacturing cost of solar cells. In the related art, aluminum materials are used in the electrodes of solar cells to reduce production costs, but since the conductivity of aluminum is worse than that of silver, the conductivity between the electrode and its connecting parts is affected. Summary of the invention

[0003] In order to solve the above technical problems, the present application discloses a solar cell and a preparation method thereof, and a photovoltaic module, which balance the performance of the solar cell while reducing the manufacturing cost of the electrode.

[0004] In a first aspect, the present application provides a solar cell, comprising a silicon substrate, a doping layer and an electrode, wherein the doping layer is disposed on a surface of the silicon substrate, the electrode is disposed on at least one side of the solar cell, and the electrode comprises a main grid line, a secondary grid line and an electrode extension;

[0005] The plurality of electrode extensions are arranged in sequence along the length direction of the main grid line;

[0006] At least a portion of the secondary grid line covers the electrode extension portion;

[0007] The material of the main grid line and the electrode extension portion includes silver, and the material of the secondary grid line includes base metal.

[0008] In some embodiments of the present application, the auxiliary gate line includes a bottom electrode layer and a top gate line layer, the bottom electrode layer is in ohmic contact with the doping layer, the top gate line layer is located on the side of the bottom electrode layer away from the silicon substrate, the material of the bottom electrode layer contains silver, and the material of the top gate line layer contains base metal.

[0009] In some embodiments of the present application, the solar cell further includes a welding strip, which is conductively connected to the main grid line and / or the electrode extension.

[0010] In some embodiments of the present application, the top gate line layer includes a sub-gate body and a lap portion, the lap portion intersects with the sub-gate body, and at least the lap portion is conductively connected to the electrode extension portion.

[0011] In some embodiments of the present application, the overlapping portion includes a first segment and a second segment arranged along the length direction of the first segment, and the number of the second segments is at least two.

[0012] In some embodiments of the present application, the length of the first section is L1, the width is W1, 0.18 mm ≤ L1 ≤ 0.22 mm, 0.02 mm ≤ W1 ≤ 0.03 mm.

[0013] In some embodiments of the present application, the length of the second section is L2, the width is W2, 0.08 mm ≤ L2 ≤ 0.1 mm, 0.02 mm ≤ W2 ≤ 0.04 mm.

[0014] In some embodiments of the present application, the length of the electrode extension portion is L3, 0.8 mm ≤ L3 ≤ 1.2 mm.

[0015] In some embodiments of the present application, the thickness of the bottom electrode layer is H1, 1 μm≤H1≤2 μm;

[0016] And / or, the thickness of the top gate line layer is H2, 7 μm≤H2≤8 μm.

[0017] In some embodiments of the present application, the width of the electrode extension at both ends is smaller than the width in the middle.

[0018] In some embodiments of the present application, the base metal includes at least one of aluminum, copper and nickel.

[0019] In a second aspect, the present application provides a method for preparing a solar cell as described in the first aspect, comprising the following steps:

[0020] Providing an initial structure of a solar cell, the initial structure of the solar cell comprising a silicon substrate, a doping layer, and a bottom electrode layer in ohmic contact with the doping layer;

[0021] Applying a first slurry on at least one side of the initial structure of the solar cell to form a main grid line pattern and an electrode extension pattern, and forming a main grid and an electrode extension after sintering, wherein the first slurry includes silver;

[0022] A second slurry is applied on the surface of the electrode extension part and the bottom electrode layer, and after curing, a secondary gate line is formed, wherein the second slurry includes a base metal.

[0023] In some embodiments of the present application, the process of forming the busbar pattern and the electrode extension pattern includes:

[0024] The first slurry is applied to at least one side of the initial structure of the solar cell to simultaneously form the busbar pattern and the electrode extension pattern.

[0025] In some embodiments of the present application, the process of forming the busbar pattern and the electrode extension pattern includes:

[0026] Applying the first slurry to at least one side of the initial structure of the solar cell to form the main grid line pattern;

[0027] The first slurry is applied on the same side as the main grid line to form the electrode extension pattern.

[0028] In some embodiments of the present application, the temperature of the sintering treatment is 800°C to 900°C, and the temperature of the curing treatment is 200°C to 400°C.

[0029] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module includes the solar cell as described in the first aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the second aspect.

[0030] Compared with the prior art, this application has at least the following beneficial effects:

[0031] The present application provides a solar cell and a preparation method thereof, and a photovoltaic module, wherein the solar cell includes a silicon substrate, a doping layer and an electrode, the doping layer is arranged on the surface of the silicon substrate, the electrode includes a main grid line, a secondary grid line and an electrode extension, a plurality of electrode extensions are arranged in sequence along the length direction of the main grid line, and the material of the main grid line and the electrode extension includes silver. On the one hand, the material of the secondary grid line includes a base metal, and the base metal can be used to replace part of the silver. Compared with the current electrode structure in which the main grid line and the secondary grid line are both made of silver material, the technical solution of the present application can effectively reduce the use of silver, thereby reducing the manufacturing cost of the electrode; on the other hand, even if the component connected to the electrode is slightly offset and does not completely cover the main grid line, the connecting component can be conductively connected to the main grid line through the silver electrode extension structure of the present application, so that it can be ensured as much as possible that the contact parts between the electrode and its connecting component are both made of silver with excellent conductive properties, so that the conductive properties between the electrode and its connecting component are not easily affected, thereby balancing the performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a schematic diagram of the structure of a solar cell in one embodiment of the present application;

[0034] Figure 2 This is a schematic diagram of the structure of a secondary grid line in an implementation scheme of the present application;

[0035] Figure 3a It is a schematic diagram of the structure of the welding strip and the main grid line in the related technology;

[0036] Figure 3b This is a schematic diagram of the structure of the welding strip and the main grid line in another embodiment of the present application;

[0037] Figure 4 This is a schematic diagram of the structure of a secondary grid line in an implementation scheme of the present application;

[0038] Figure 5 This is a structural schematic diagram of the overlap portion in one embodiment of the present application;

[0039] Figure 6 This is a schematic diagram of the initial structure of a solar cell in one embodiment of the present application;

[0040] Figure 7 This is a schematic diagram of the structure of a solar cell in another embodiment of the present application.

[0041] Explanation of the figure markings: silicon substrate-1, electrode-2, welding point-3, welding strip-4, doping layer-5, first passivation layer-6, anti-reflection layer-7, dielectric layer-8, second passivation layer-10, main gate line-21, auxiliary gate line-22, electrode extension part-23, first doping layer-51, second doping layer-52, top gate line layer-220, auxiliary gate body-221, overlapping part-222, bottom electrode layer-223, first section-2221, second section-2222. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0044] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0045] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0046] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0047] The technical solution of the present application will be further described below in conjunction with embodiments and drawings.

[0048] In the related art, aluminum is used in the electrodes of solar cells to reduce production costs. However, since aluminum has a lower conductivity than silver, the conductivity between components connected to the electrodes is affected, for example, the conductivity between welding strips connected to the electrodes is affected, thus affecting the performance of the solar cell.

[0049] In a first aspect, the present application provides a solar cell, referring to Figure 1 The solar cell comprises a silicon substrate 1, a doping layer and an electrode 2, wherein the doping layer is disposed on the surface of the silicon substrate 1, and the electrode 2 is disposed on at least one side of the solar cell. In one embodiment, the electrode 2 is disposed on the backlight side of the solar cell; in another embodiment, the electrode 2 is disposed on the light-receiving side of the solar cell; in yet another embodiment, the electrode 2 is disposed on the backlight side and the light-receiving side of the solar cell respectively.

[0050] The electrode 2 includes a main grid line 21, a secondary grid line 22 and an electrode extension 23. The plurality of electrode extensions 23 are sequentially arranged along the length direction of the main grid line 21, the electrode extensions 23 are conductively connected to the main grid line 21, the electrode extensions 23 are conductively connected to the secondary grid line 22, and the length extension direction of the electrode extensions 23 is the same as the length extension direction of the secondary grid line 22.

[0051] At least a portion of the secondary grid line 22 covers the electrode extension 23, thereby being conductively connected to the electrode extension 23. In one example, the boundary area between the secondary grid line and the main grid line covers the electrode extension. The material of the main grid line 21 and the electrode extension 23 includes silver. Exemplarily, the materials of the main grid line 21 and the electrode extension 23 are both silver. The material of the secondary grid line includes base metals. Exemplarily, the surface material of the secondary grid line is a base metal material, and the bottom material of the secondary grid line is a silver material, which can reduce the use of silver. The meaning of "base metal" is the opposite of precious metals. Base metals include metals such as aluminum, copper and nickel that are lower in price than precious metals. In addition, the solar cell also includes a welding point 3, which is used to weld connecting components, such as welding strips.

[0052] In the present application, the doping layer may include a first doping layer and a second doping layer, wherein the first doping layer and the second doping layer may be respectively disposed on two sides of the silicon substrate, and the structure thereof will be shown below.

[0053] The solar cell provided by the present application, on the one hand, the material of the auxiliary grid line includes base metals, and the base metals therein can be used to replace part of the silver. According to research, compared with the current electrode structure in which the main grid line and the auxiliary grid line are both made of silver material, the technical solution of the present application can effectively reduce the use of silver, thereby reducing the manufacturing cost of the electrode; on the other hand, even if the component connected to the electrode is slightly offset and does not completely cover the main grid line, the connecting component can be conductively connected to the main grid line through the silver electrode extension structure of the present application, so that it can be ensured as much as possible that the contact parts between the electrode and its connecting component are all silver with excellent conductive properties, so that the conductive performance between the electrode and its connecting component is not easily affected, thereby balancing the performance of the solar cell.

[0054] In an optional embodiment, reference Figure 2 The auxiliary gate line 22 includes a bottom electrode layer 223 and a top gate line layer 220. The bottom electrode layer 223 is in ohmic contact with the doped layer 5. The top gate line layer 220 is located on the side of the bottom electrode layer 223 away from the silicon substrate 1. The material of the bottom electrode layer 223 includes silver, and the material of the top gate line layer 220 includes a base metal. The bottom electrode layer 223 is in ohmic contact with the doped layer 5, collects current and transmits it to the top gate line layer 220, and then the top gate line layer 220 conducts the current. This structure reduces the overall silver usage of the auxiliary gate line.

[0055] In order to further improve the conductivity of the secondary grid line, the surface of the top grid line layer of the present application may also have a silver coating layer, thereby forming a silver-coated base metal structure, such as silver-coated aluminum, silver-coated copper or silver-coated nickel.

[0056] In an optional embodiment, the solar cell further includes a welding strip, which is conductively connected to the main grid line and / or the electrode extension.

[0057] refer to Figure 3a Ideally, the welding strip 4 will completely cover the main grid line 21 to achieve a good conductive connection between the welding strip 4 and the main grid line 21. However, in actual production, Figure 3b , the welding strip 4 will inevitably have a small deviation, which makes it difficult for the welding strip 4 to completely cover the main grid line 21, and there may be a poor contact between the welding strip 4 and the main grid line 21. Based on this, the present application is provided with a silver electrode extension 23. Even if the welding strip has a small deviation and does not completely cover the main grid line, the welding strip can be electrically connected to the main grid line through the silver electrode extension, thereby improving the conductivity between the welding strip and the main grid line. It should be noted that Figure 3b The deviation of the solder strip 4 is only for illustration.

[0058] In an optional embodiment, reference Figure 4 The top gate line layer 220 includes a sub-gate body 221 and a lap portion 222, the lap portion 222 intersects with the sub-gate body 221, and at least the lap portion 222 is conductively connected to the electrode extension portion 23. In one embodiment, the lap portion 222 is conductively connected to the electrode extension portion 23; in another embodiment, both the sub-gate body 221 and the lap portion 222 are conductively connected to the electrode extension portion 23.

[0059] The inventor has found that, since the top grid line layer as part of the secondary grid line is inevitably slightly offset in actual production, the top grid line layer may not be able to completely cover the surface of the electrode extension, thereby affecting the current path between the main grid line and the secondary grid line. Based on this, the top grid line layer of the present application is provided with an overlap portion, and even if the top grid line layer is slightly offset, the top grid line layer can be connected to the electrode extension portion through the overlap portion, so that a current path is formed between the secondary grid line and the electrode extension, thereby ensuring the current path between the secondary grid line and the main grid line.

[0060] In an optional embodiment, reference Figure 5 The overlap portion 222 includes a first section 2221 and a second section 2222 arranged along the length direction of the first section 2221, and the number of the second sections 2222 is at least two. For example, the number of the second sections can be 2, 3 or 4. In this way, the second section can be connected to the electrode extension portion, so that a current path is formed between the auxiliary grid line and the electrode extension portion, thereby ensuring the current path between the auxiliary grid line and the main grid line.

[0061] In an optional embodiment, reference Figure 5, the length of the first segment 2221 is L1, the width is W1, 0.18mm≤L1≤0.22mm, 0.02mm≤W1≤0.03mm. For example, L1 is 0.18μm, 0.20μm or 0.22μm, and W1 is 0.02μm, 0.025μm or 0.03μm. By controlling L1 and / or W1 within the above range, it is beneficial to maintain the strength of the first segment while reducing the shading area of ​​the first segment.

[0062] In an optional embodiment, reference Figure 5 , the length of the second section 2222 is L2, the width is W2, 0.08mm≤L2≤0.1mm, 0.02mm≤W2≤0.04mm. For example, L2 is 0.08μm, 0.09μm or 0.1μm, and W2 is 0.02μm, 0.03μm or 0.04μm. By controlling L2 and / or W2 within the above range, even if the secondary grid line is slightly offset during printing, it can be connected to the electrode extension through the second section, thereby allowing a certain offset during the secondary printing of the secondary grid line (i.e., the process of forming the top grid line layer), reducing the process difficulty.

[0063] In an optional embodiment, reference Figure 4 The length of the electrode extension is L3, 0.8 mm ≤ L3 ≤ 1.2 mm. By controlling L3 within the above range, it is helpful to reduce the risk of broken welds during component end welding.

[0064] In an optional embodiment, reference Figure 2 The thickness of the bottom electrode layer 223 is H1, 1 μm ≤ H1 ≤ 2 μm; and / or the thickness of the top gate line layer 220 is H2, 7 μm ≤ H2 ≤ 8 μm. For example, H1 is 1 μm, 1.5 μm or 2 μm, and H2 is 7 μm, 7.5 μm or 8 μm.

[0065] In the present application, the thickness H1 refers to the distance between the bottom surface of the bottom electrode layer and its upper surface, and the thickness H2 refers to the distance between the bottom surface of the top gate line layer and its upper surface. By controlling H1 and / or H2 within the above range, the total thickness of the electrode will not be too small or too large, which is conducive to reducing the consumption of silver and ensuring the welding height.

[0066] In an optional embodiment, the width of the electrode extension at both ends is smaller than the width of the middle portion. Figure 3b Since the intersection point of the welding strip 4 and the electrode extension part 23 is mostly located in the middle of the electrode extension part 23, the electrode extension part is designed to be a structure with narrow ends and a wide middle. On the one hand, it is beneficial to increase the contact area between the electrode extension part and the welding strip, thereby improving the conductive effect between the two. On the other hand, the structure with narrower ends can further reduce the use of silver and thus reduce the electrode manufacturing cost.

[0067] In an optional embodiment, the base metal of the present application includes but is not limited to at least one of aluminum, copper and nickel, which is used to replace the more expensive silver, thereby reducing the manufacturing cost of the electrode and further reducing the manufacturing cost of the solar cell.

[0068] The solar cells of the present application include but are not limited to TOPCon cells, PERC cells, HJT cells, TBC cells, etc.

[0069] In a second aspect, the present application provides a method for preparing a solar cell as described in the first aspect, comprising the following steps:

[0070] Step A, providing an initial structure of a solar cell, wherein the initial structure of the solar cell includes a silicon substrate, a doping layer, and a bottom electrode layer in ohmic contact with the doping layer;

[0071] Step B, applying a first slurry on at least one side of the initial structure of the solar cell to form a main grid line pattern and an electrode extension pattern, and forming the main grid and the electrode extension after sintering, wherein the first slurry includes silver;

[0072] Step C: applying a second slurry on the surface of the electrode extension part and the bottom electrode layer, and forming a secondary grid line after curing, wherein the second slurry includes a base metal.

[0073] In step A of the present application, the silicon substrate can be of the first conductivity type, the doping element of the second doping layer has the second conductivity type, one of the first conductivity type and the second conductivity type is N-type and the other is P-type. For example, when the first conductivity type is N-type, the second conductivity type is P-type; when the first conductivity type is P-type, the second conductivity type is N-type. The silicon substrate can be a silicon substrate after texturing, and the thickness of the silicon substrate is 100μm~200μm. As long as it can meet the purpose of the present application, the present application does not make specific restrictions. A thin layer of silver paste can be applied on the surface of the silicon substrate as a bottom electrode layer. The bottom electrode layer can be used as a part of the secondary grid line, so it also has a secondary grid line pattern. This process is a one-time printing process; further, the mutual diffusion of silver and silicon is induced by sintering treatment, and the Ag in the bottom electrode layer and the Si in the doping layer quickly reach the Ag-Si eutectic point, forming a metal silicon compound with excellent conductive properties locally, thereby realizing metal-semiconductor contact, that is, realizing ohmic contact.

[0074] The present application has no particular restrictions on the type of initial structure of the solar cell, as long as it can form the electrode of the present application. For example, the initial structure of the solar cell is as follows: Figure 6 As shown, it includes a silicon substrate 1, the light-receiving surface of the silicon substrate 1 is sequentially provided with a first doping layer 51, a first passivation layer 6 and an anti-reflection layer 7, and the backlight surface of the silicon substrate 1 is sequentially stacked with a dielectric layer 8, a second doping layer 52 and a second passivation layer 10.

[0075] In step B of the present application, the first slurry may be a commercially available silver slurry, and the materials of the prepared main grid lines and electrode extensions may both be silver;

[0076] In step C of the present application, the second slurry may be a slurry obtained by replacing the silver in the first slurry with a base metal. The second slurry may include the following components:

[0077] Base metal powder 50wt%~80wt%

[0078] Organic carrier 20wt%~50wt%

[0079] The sum of the contents of the above components is 100%. This second slurry is beneficial to reducing manufacturing costs.

[0080] Alternatively, the second slurry may include the following components:

[0081] Base metal powder 51wt%~80wt%

[0082] Organic carrier 7wt%~20wt%

[0083] Ag10wt%~30wt%

[0084] The sum of the contents of the above components is 100%. The second slurry contains a small amount of silver, which can reduce the manufacturing cost and improve the performance of the solar cell.

[0085] After applying the second slurry on the surface of the electrode extension part and the bottom electrode layer, the top gate line layer is obtained after curing. This process is a secondary printing process. The bottom electrode layer and the top gate line layer together form a secondary gate line, and the base metal therein can replace part of the silver to reduce the use of silver.

[0086] The material of the dielectric layer of the present application may include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Specifically, the dielectric layer may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation properties, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high-temperature processes. In order to better provide interface passivation for the substrate, the thickness of the dielectric layer may be 0.1nm~5nm. For example, the thickness of the dielectric layer may be 0.1nm, 0.5nm, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, etc., however, the present application is not limited thereto, and the thickness of the dielectric layer may have various values. The dielectric layer, as a barrier for electrons and holes, may be combined with a polycrystalline silicon layer to prevent minority carriers from passing through. The dielectric layer may also have a pinhole channel effect, allowing the carriers in the solar cell to move freely, and selective passage of majority carriers is generated by heavily doped polycrystalline silicon, which is conducive to reducing the recombination loss of minority carriers. In addition, the dielectric layer may serve as a diffusion barrier to prevent dopants of the doped polysilicon layer from diffusing into the semiconductor substrate.

[0087] In the present application, the first passivation layer can be formed based on the atomic layer deposition (ALD) process, and the anti-reflection layer and the second passivation layer can be formed based on the plasma enhanced chemical vapor deposition (PECVD) process, wherein the first passivation layer is an aluminum oxide layer, and the first passivation layer plays a passivation role; the anti-reflection layer is a silicon oxynitride layer, and the anti-reflection layer plays an anti-reflection role; the second passivation layer can be prepared on the backlight side of the initial structure of the solar cell, and the second passivation layer is a silicon oxynitride layer, which plays a passivation role.

[0088] The present application has no particular restrictions on the thickness of each functional layer, as long as the purpose of the present application can be achieved. For example, the thickness of the first passivation layer is 80 nm to 100 nm, the thickness of the second passivation layer is 3 nm to 7 nm, and the thickness of the anti-reflection layer is 3 nm to 7 nm.

[0089] The present application has no particular limitation on the particle size of the base metal powder, as long as the purpose of the present application can be achieved. For example, the average particle size of the base metal powder is 1 μm to 10 μm; the organic carrier includes but is not limited to epoxy resin.

[0090] After electrode preparation, refer to Figure 7 The light-receiving surface and the backlight surface of the solar cell both form electrodes 2, wherein the electrode on the light-receiving surface may be an electrode having an electrode extension portion of the present application, and / or the electrode on the backlight surface may be an electrode having an electrode extension portion of the present application.

[0091] The present application provides a method for preparing a solar cell, which prepares a main grid line and an electrode extension based on a silver material, and a secondary grid line including a base metal material, which can effectively reduce the amount of silver used, thereby reducing the manufacturing cost of the electrode.

[0092] In an optional embodiment, the process of forming the busbar pattern and the electrode extension pattern includes:

[0093] Implementation method 1:

[0094] The first slurry is applied to at least one side of the initial structure of the solar cell to form a main grid line pattern and an electrode extension pattern at the same time.

[0095] In one embodiment, the first slurry is applied to the backlight side of the solar cell initial structure; in another embodiment, the first slurry is applied to the light-receiving side of the solar cell initial structure; in yet another embodiment, the first slurry is applied to both the backlight side and the light-receiving side of the solar cell initial structure.

[0096] In the first embodiment, the first slurry can be printed on at least one side of the initial structure of the solar cell by screen printing. In this way, the main grid line pattern and the electrode extension pattern can be formed simultaneously in one process, which is beneficial to improving the preparation efficiency of the electrode. The electrode structure formed in the first embodiment helps to disperse the stress concentration that may occur in the solar cell during physical deformation or temperature change, and reduce the potential risk of cracks and fractures.

[0097] Implementation method 2:

[0098] Step a, applying a first slurry to at least one side of the initial structure of the solar cell to form a main grid line pattern;

[0099] Step b: applying the first slurry on the same side as the main grid line to form an electrode extension pattern.

[0100] In the second embodiment, the first slurry can be printed on at least one side of the initial structure of the solar cell by screen printing to form a main grid line pattern, and then the first slurry can be printed on at least one side of the initial structure of the solar cell by screen printing to form an electrode extension pattern. In this way, although the main grid line pattern and the electrode extension pattern are formed respectively through two processes, the main grid line pattern and the electrode extension pattern are printed separately. Although the printing process is increased, the wet weight of the main grid line can be controlled more accurately.

[0101] In an optional embodiment, the temperature of the sintering treatment is 800°C to 900°C, and the temperature of the curing treatment is 200°C to 400°C. By adjusting the temperature of the sintering treatment within the above range, it is beneficial to form a good conductive contact between the electrode extension and the main grid line. By adjusting the temperature of the curing treatment within the above range, the auxiliary grid line based on the base metal material can be cured at a lower temperature to transmit current, which reduces energy consumption and manufacturing costs.

[0102] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module includes the solar cell as described in the first aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the second aspect.

[0103] The present application also provides a photovoltaic module, which is used to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; a packaging film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the packaging film away from the battery string.

[0104] The above is a detailed introduction to a solar cell and its preparation method, and a photovoltaic module disclosed in the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for general technicians in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A solar cell, characterized in that: It comprises a silicon substrate, a doping layer and an electrode, wherein the doping layer is arranged on the surface of the silicon substrate, the electrode is arranged on at least one side of the solar cell, and the electrode comprises a main grid line, a secondary grid line and an electrode extension part; The plurality of electrode extensions are arranged in sequence along the length direction of the main grid line; The junction area between the auxiliary grid line and the main grid line covers the electrode extension part; The auxiliary gate line includes a bottom electrode layer and a top gate line layer, the bottom electrode layer is in ohmic contact with the doped layer, the top gate line layer is located on a side of the bottom electrode layer away from the silicon substrate, the material of the bottom electrode layer includes silver, the material of the top gate line layer includes a base metal, the top gate line layer includes an auxiliary gate body and a lap portion, the lap portion intersects with the auxiliary gate body, at least the lap portion is conductively connected to the electrode extension portion, the lap portion includes a first segment and a second segment arranged along the length direction of the first segment, and the number of the second segments is at least two.

2. The solar cell according to claim 1, characterized in that: The solar cell further comprises a welding strip, and the welding strip is conductively connected to the main grid line and / or the electrode extension portion.

3. The solar cell according to claim 1, characterized in that: The first section has a length of L1 and a width of W1, 0.18 mm ≤ L1 ≤ 0.22 mm, and 0.02 mm ≤ W1 ≤ 0.03 mm.

4. The solar cell according to claim 1, characterized in that: The second section has a length of L2 and a width of W2, 0.08 mm ≤ L2 ≤ 0.1 mm, and 0.02 mm ≤ W2 ≤ 0.04 mm.

5. The solar cell according to claim 1, characterized in that: The length of the electrode extension portion is L3, 0.8 mm ≤ L3 ≤ 1.2 mm.

6. The solar cell according to claim 1, characterized in that: The thickness of the bottom electrode layer is H1, 1 μm≤H1≤2 μm; And / or, the thickness of the top gate line layer is H2, 7 μm≤H2≤8 μm.

7. The solar cell according to claim 1, characterized in that: The widths of the two ends of the electrode extension portion are smaller than the width of the middle portion.

8. The solar cell according to any one of claims 1 to 7, characterized in that: The base metal includes at least one of aluminum, copper and nickel.

9. A method for preparing a solar cell according to any one of claims 1 to 8, characterized in that: The following steps are involved: Providing an initial structure of a solar cell, the initial structure of the solar cell comprising a silicon substrate, a doping layer, and a bottom electrode layer in ohmic contact with the doping layer; Applying a first slurry on at least one side of the initial structure of the solar cell to form a main grid line pattern and an electrode extension pattern, and forming a main grid and an electrode extension after sintering, wherein the first slurry includes silver; A second slurry is applied and cured to form a secondary gate line having the bottom electrode layer and the top gate line layer, wherein the second slurry includes a base metal.

10. The preparation method according to claim 9, characterized in that: The process of forming the main grid line pattern and the electrode extension pattern includes: The first slurry is applied to at least one side of the initial structure of the solar cell to simultaneously form the busbar pattern and the electrode extension pattern.

11. The preparation method according to claim 10, characterized in that: The process of forming the main grid line pattern and the electrode extension pattern includes: Applying the first slurry to at least one side of the initial structure of the solar cell to form the main grid line pattern; The first slurry is applied on the same side as the main grid line to form the electrode extension pattern.

12. The preparation method according to any one of claims 9 to 11, characterized in that: The temperature of the sintering treatment is 800°C to 900°C, and the temperature of the curing treatment is 200°C to 400°C.

13. A photovoltaic module, characterized in that: The photovoltaic module comprises the solar cell according to any one of claims 1 to 8, or the photovoltaic module comprises the solar cell prepared by the preparation method according to any one of claims 9 to 12.

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