Back contact cell and method for manufacturing the same, photovoltaic module

Abstract

A back contact cell, a preparation method thereof and a photovoltaic module belong to the technical field of solar cells. The back contact cell comprises a silicon substrate, a first doped layer arranged on a first surface of the silicon substrate, a second doped layer arranged on the first surface of the silicon substrate and opposite in polarity to the first doped layer, an isolation structure arranged between the first doped layer and the second doped layer along a first direction and penetrating the first doped layer and the second doped layer along a second direction, a first electrode electrically connected with the first doped layer, a second electrode electrically connected with the second doped layer, a surface passivation layer arranged on a side surface of the first doped layer and the second doped layer away from the silicon substrate along the second direction and filling part of the isolation structure, and a leakage channel arranged on the side surface of the surface passivation layer away from the silicon substrate and in contact and electrical connection with the first electrode and the second electrode, which can reduce the risk caused by hot spot effect and has relatively low preparation complexity.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and more specifically, to a back contact cell and its preparation method, and a photovoltaic module. Background Technology

[0002] Back-contact solar cells are solar cells with no electrodes on the light-facing side, and both the positive and negative electrodes are located on the back-facing side of the cell. This reduces the shading of the cells by the electrodes, increases the short-circuit current, and improves the energy conversion efficiency of the cells.

[0003] In actual use, back-contact solar cells may be obstructed by objects such as leaves and dust. When these objects are obstructed, the temperature of the cells rises, causing a hot spot effect. This hot spot effect can lead to permanent damage to the photovoltaic module, such as localized burning and dark spots, melting of solder joints, and aging of encapsulation materials. This severely affects the output power and lifespan of the photovoltaic module and may even cause a fire, posing a safety hazard. Summary of the Invention

[0004] The purpose of this application is to provide a back-contact battery to reduce the risks caused by hot spot effects.

[0005] To achieve the above objectives, this application provides a back contact battery, a method for preparing the same, and a photovoltaic module.

[0006] In a first aspect, a back-contact battery is provided, comprising: a silicon substrate having opposing first and second surfaces; a first doped layer disposed on the first surface; a second doped layer disposed on the first surface and having a polarity opposite to that of the first doped layer; an isolation structure disposed between the first and second doped layers along a first direction and penetrating the first and second doped layers along a second direction, the second direction being the thickness direction of the silicon substrate, and the first direction being perpendicular to the second direction; a first electrode electrically connected to the first doped layer; a second electrode electrically connected to the second doped layer; a surface passivation layer disposed on a side surface of the first and second doped layers opposite to the silicon substrate along the second direction and filling a portion of the isolation structure; and a leakage channel disposed on the side surface of the surface passivation layer opposite to the silicon substrate and in contact with and electrically connected to the first and second electrodes.

[0007] In this embodiment, the first doped layer and the second doped layer have opposite polarities, and the first electrode is electrically connected to the first doped layer, and the second electrode is electrically connected to the second doped layer. This allows the first and second electrodes to collect majority and minority carriers, respectively. The surface passivation layer reduces carrier recombination, which is beneficial for improving the efficiency of the back-contact battery. The leakage channel is located on the surface of the passivation layer away from the silicon substrate and is in contact with and electrically connected to the first and second electrodes. On the one hand, when the back-contact battery is blocked, current can be transmitted through the first electrode, the leakage channel, and the second electrode, preventing the blocked back-contact battery from becoming a load that consumes the energy generated by other illuminated cells, thereby reducing the risk of hot spot effect. On the other hand, the positional relationship between the surface passivation layer and the leakage channel helps to reduce the fabrication complexity of the back-contact battery while maintaining a relatively simple structure; for example, it can reduce the number of laser spots during the fabrication process. Therefore, this embodiment can reduce the risk of hot spot effect while reducing the fabrication complexity of the back-contact battery.

[0008] In some embodiments, the material of the leakage channel includes metal, conductive polymer, or semiconductor. These materials possess suitable conductivity, which helps to reduce the overall resistance of the leakage channel and decrease the efficiency loss of the photovoltaic module.

[0009] In some embodiments, the resistivity of the material of the leakage channel is 1.5 × 10⁻⁶. -8 Ω·m to 10×10 -8 Ω·m. Thus, the material of the leakage channel has a low resistivity, which helps reduce the overall resistance of the leakage channel, thereby reducing the efficiency loss of the photovoltaic module.

[0010] In some embodiments, the total size of the leakage channel is 10 μm to 10000 μm along a third direction, which is perpendicular to the first direction and the second direction.

[0011] When the size of the leakage channel is greater than or equal to 10 μm along the third direction, it is beneficial to reduce the fabrication complexity of the leakage channel; when the size of the leakage channel is less than or equal to 10000 μm along the third direction, it is beneficial to reduce leakage loss, thereby reducing the efficiency loss of photovoltaic modules.

[0012] In some embodiments, the size of a single leakage channel along the third direction is 10 μm to 40 μm. This reduces the efficiency loss of the photovoltaic module while also reducing the fabrication complexity of the leakage channel.

[0013] In some embodiments, the line resistance of the leakage channel is less than or equal to 1.25Ω. This helps to reduce leakage losses, thereby helping to reduce the efficiency loss of the photovoltaic module.

[0014] In some embodiments, the size of the leakage channel along the second direction is 4 μm to 50 μm.

[0015] When the size of the leakage channel is greater than or equal to 4 μm along the second direction, it is beneficial to the fabrication of the leakage channel; when the size of the leakage channel is less than or equal to 50 μm along the second direction, the leakage channel has a suitable cross-sectional area and line resistance, which is beneficial to reducing the efficiency loss of photovoltaic modules and also beneficial to the fabrication of the leakage channel.

[0016] In some embodiments, the back contact battery includes a plurality of leakage channels, which are spaced apart along a third direction perpendicular to the first and second directions. This allows current to be transmitted more evenly through the multiple leakage channels when the back contact battery is blocked, thus reducing the risk of hot spot effects.

[0017] In some embodiments, along the second direction, the leakage channel does not penetrate the surface passivation layer, the first doped layer, and the second doped layer. Thus, the leakage channel does not damage the surface passivation layer, the first doped layer, or the second doped layer, which is beneficial for improving the efficiency of the back-contact battery.

[0018] In some embodiments, the first electrode and the second electrode comprise silver and a first glass powder, the first glass powder comprising a burn-through oxide, the burn-through oxide comprising at least one of lead oxide, bismuth oxide, tellurium oxide, vanadium oxide, and phosphorus oxide; the leakage channel comprises silver and a second glass powder, the second glass powder not comprising the burn-through oxide.

[0019] In the above technical solution, by controlling the composition of the second glass powder in the leakage channel, the leakage channel can be prevented from penetrating the surface passivation layer.

[0020] In some embodiments, the back contact battery further includes a first interface layer and a second interface layer. Along the second direction, the first interface layer is disposed between the silicon substrate and the first doped layer, and the second interface layer is disposed between the silicon substrate and the second doped layer.

[0021] The first and second interface layers help reduce carrier recombination, thereby improving the efficiency of the back contact battery.

[0022] In a second aspect, a method for fabricating a back-contact battery is provided, comprising: fabricating a first doped layer and a second doped layer on a first surface of a silicon substrate, wherein the first doped layer and the second doped layer have opposite polarities; fabricating an isolation structure, wherein the isolation structure is disposed between the first doped layer and the second doped layer along a first direction, and the isolation structure penetrates through the first doped layer and the second doped layer along a second direction, wherein the second direction is the thickness direction of the silicon substrate, and the first direction is perpendicular to the second direction; before fabricating a first electrode and a second electrode, fabricating a surface passivation layer, wherein, along the second direction, the surface passivation layer is disposed on the side surface of the first doped layer and the second doped layer opposite to the silicon substrate and fills a portion of the isolation structure; fabricating a first electrode and a second electrode, wherein the first electrode is electrically connected to the first doped layer, and the second electrode is electrically connected to the second doped layer; and after fabricating the first electrode and the second electrode, fabricating a leakage channel, wherein the leakage channel is disposed on the side surface of the surface passivation layer opposite to the silicon substrate and contacts and is electrically connected to the first electrode and the second electrode.

[0023] The back contact battery prepared by the above preparation method can reduce the risk of hot spot effect; in addition, the embodiments of this application only require setting a leakage channel on the surface of the surface passivation layer after preparing the first electrode and the second electrode to obtain the back contact battery of this application. This preparation method has low preparation complexity and can reduce the number of laser spots in the process of preparing the back contact battery.

[0024] In some embodiments, the preparation of the leakage channel includes: applying a leakage channel paste to the side of the surface passivation layer away from the silicon substrate by printing or inkjet printing; and curing the leakage channel paste by drying, ultraviolet curing or sintering to obtain the leakage channel.

[0025] In the above technical solution, after the first electrode and the second electrode are prepared, the leakage channel paste is applied to the side of the surface passivation layer away from the silicon substrate by printing or inkjet printing, and then cured to obtain the leakage channel. This preparation method has low preparation complexity and is relatively simple.

[0026] In some embodiments, the leakage current channel paste comprises silver paste, the sintering temperature of which is 670°C to 820°C; or, the leakage current channel paste comprises copper paste, the drying temperature of which is 200°C to 300°C.

[0027] In the process of preparing the leakage channel using the above-mentioned leakage channel slurry, damage to the surface passivation layer can be avoided or prevented, which is beneficial to improving the efficiency of the back contact battery.

[0028] Thirdly, a photovoltaic module is provided, including the back contact cell of the first aspect and any embodiment thereof. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a back contact battery according to an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of the structure of a photovoltaic module according to an embodiment of this application;

[0032] Figure 3 for Figure 2 An enlarged schematic diagram of region A in the diagram;

[0033] Figure 4 This is a schematic diagram of a method for preparing a back contact battery according to an embodiment of this application;

[0034] Figure 5 This is a partial structural diagram of the back contact battery during the fabrication process of an embodiment of this application.

[0035] Reference numerals: 1: Photovoltaic module; 2: Back contact cell; 20: Silicon substrate; 21: First electrode; 22: Second electrode; 211: First doped layer; 221: Second doped layer; 212: First interface layer; 222: Second interface layer; 23: Surface passivation layer; 24: Isolation structure; 25: Leakage channel; 26: Anti-reflection layer. Detailed Implementation

[0036] The back contact battery and its preparation method, as well as embodiments of the photovoltaic module, of this application have been described in detail with reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] A photovoltaic (PV) module consists of multiple back-contact cells, which are electrically connected together in series and / or parallel. During use, bird droppings, leaves, dust, and other obstructions may fall onto the back-contact cells, causing their temperature to rise and resulting in hot spots. If the temperature of these hot spots exceeds a certain threshold, it can lead to problems such as PV module delamination, backsheet burning, and glass shattering, ultimately rendering the entire solar cell unusable and potentially posing a fire hazard.

[0042] In some approaches, bypass diodes are used to mitigate the risk of hot spot effects on the back-contact cells. For example, a photovoltaic module may include six rows of back-contact cell strings, each string containing multiple back-contact cells connected in series, with a bypass diode connected in parallel between every two rows. When a back-contact cell in a row is shaded, current can flow through the bypass diode connected in parallel, thus reducing the risk of overheating caused by the shaded cell. However, this approach leads to a decrease in the open-circuit voltage of the photovoltaic module, resulting in a significant reduction in its power and efficiency. Furthermore, this method requires additional diodes, making the module structurally more complex.

[0043] In view of this, embodiments of this application provide a back-contact battery, comprising: a silicon substrate having opposing first and second surfaces; a first doped layer disposed on the first surface; a second doped layer disposed on the first surface and having a polarity opposite to that of the first doped layer; an isolation structure disposed between the first and second doped layers along a first direction and penetrating through the first and second doped layers along a second direction, the second direction being the thickness direction of the silicon substrate, and the first direction being perpendicular to the second direction; a first electrode electrically connected to the first doped layer; a second electrode electrically connected to the second doped layer; a surface passivation layer disposed on the side of the first and second doped layers opposite to the silicon substrate along the second direction and filling part of the isolation structure; and a leakage channel disposed on the side of the surface passivation layer opposite to the silicon substrate and in contact with and electrically connected to the first and second electrodes. In this way, when the back contact cell is blocked, the current can be transmitted through the first electrode, the leakage channel, and the second electrode, preventing the blocked back contact cell from becoming a load that consumes the energy generated by other illuminated cells, thereby reducing the risk caused by hot spot effects. Furthermore, the positional relationship between the surface passivation layer and the leakage channel helps to reduce the fabrication complexity of the back contact cell while maintaining a relatively simple structure; for example, it can reduce the number of laser spots used in the fabrication process.

[0044] Figure 1 This is a schematic diagram of the structure of a back contact battery according to an embodiment of this application. For example, as... Figure 1 As shown, the back contact battery 2 includes a silicon substrate 20, a first doped layer 211, a second doped layer 221, an isolation structure 24, a first electrode 21, a second electrode 22, a surface passivation layer 23, and a leakage channel 25.

[0045] The silicon substrate 20 has opposing first and second surfaces. For example, as Figure 1 As shown, along the thickness direction of the silicon substrate 20 ( Figure 1The silicon substrate 20 has a first surface and a second surface (in the z direction).

[0046] A first doped layer 211 is disposed on a first surface, and a second doped layer 221 is disposed on the first surface with the opposite polarity to the first doped layer 211; the second surface may be provided with an antireflection layer 26. As an example, the antireflection layer 26 may be a pyramid structure with a textured surface.

[0047] The first doped layer 211 and the second doped layer 221 can be doped amorphous silicon or polycrystalline silicon. As an example, the first doped layer 211 is a P-type doped polycrystalline silicon layer, and the second doped layer 221 is an N-type doped polycrystalline silicon layer. Specifically, the first doped layer 211 can be made a P-type doped polycrystalline silicon layer by doping with elements such as boron, and the second doped layer 221 can be made an N-type doped polycrystalline silicon layer by doping with elements such as phosphorus.

[0048] An isolation structure 24 is disposed between the first doped layer 211 and the second doped layer 221 along the first direction, and the isolation structure 24 extends through the first doped layer 211 and the second doped layer 221 along the second direction.

[0049] The second direction is the thickness direction of the silicon substrate 20 (e.g., Figure 1 (in the z-direction), the first direction is perpendicular to the second direction, and the first direction can be... Figure 1 The x-direction in the middle.

[0050] The isolation structure 24 can be a groove that penetrates the first doped layer 211 and the second doped layer 221 to achieve insulation between the first doped layer 211 and the second doped layer 221.

[0051] The first electrode 21 is electrically connected to the first doped layer 211, and the second electrode 22 is electrically connected to the second doped layer 221. The first and second electrodes are used to collect majority carriers and minority carriers, respectively.

[0052] As an example, the first electrode 21 and the second electrode 22 are metal electrodes, for example, the material of the metal electrodes is silver.

[0053] Along the second direction, a surface passivation layer 23 is disposed on the side of the first doped layer 211 and the second doped layer 221 facing away from the silicon substrate 20 and fills part of the isolation structure 24.

[0054] The surface passivation layer 23 filling part of the isolation structure 24 can refer to the surface passivation layer 23 covering the surface of the isolation structure 24.

[0055] A leakage channel 25 is disposed on the side of the passivation layer 23 facing away from the silicon substrate 20 and is in contact with and electrically connected to the first electrode 21 and the second electrode 22. The leakage channel 25 can be a conductive layer disposed on the side of the passivation layer 23 facing away from the silicon substrate 20 and between the first electrode 21 and the second electrode 22. The leakage channel 25 is conductive, and an electrical connection between the first electrode 21 and the second electrode 22 can be achieved through the leakage channel 25.

[0056] The leakage channel 25 is a conductive layer that electrically connects the first electrode 21 and the second electrode 22. The shape of the leakage channel 25 can be rectangular, circular or other irregular. This application embodiment does not impose specific limitations on this, as long as it can achieve the electrical connection between the first electrode 21 and the second electrode 22.

[0057] The surface passivation layer 23 can reduce carrier recombination, which is beneficial to improving the efficiency of the back contact cell. The leakage channel 25 is disposed on the surface of the surface passivation layer 23 away from the silicon substrate 20 and is electrically connected to the first electrode 21 and the second electrode 22. In this way, the back contact cell has a lower risk of hot spot effect while having a simpler structure. The back contact cell has both good performance and a simpler manufacturing process. In addition, it is also beneficial to reduce the efficiency loss of photovoltaic modules including multiple back contact cells, which is beneficial to obtaining high-efficiency photovoltaic modules while reducing the risk of hot spot effect.

[0058] Furthermore, the leakage channel 25 is disposed on the side of the surface of the passivation layer 23 facing away from the silicon substrate 20 and is electrically connected to the first electrode 21 and the second electrode 22, which corresponds to the following method for fabricating a back contact cell. In the process of fabricating the back contact cell, after the first doped layer 211 and the second doped layer 221 are fabricated, the surface passivation layer 23, the first electrode 21, the second electrode 22, and the leakage channel 25 are fabricated sequentially.

[0059] Compared to structures where the leakage channel is located between the surface passivation layer and the silicon substrate, the structure of this application embodiment can reduce the fabrication complexity of the back contact battery. For example, after the first doped layer 211 is fabricated, it is usually necessary to remove the glass (e.g., borosilicate glass) formed by the first doped layer using a laser or etching paste in a specific pattern. In this application embodiment, since the leakage channel 25 is located on the side of the surface passivation layer 23 facing away from the silicon substrate 20, fewer spots are needed for laser removal of the borosilicate glass, or the specific pattern etched using the etching paste is more regular (e.g., rectangular), making the fabrication process of the back contact battery simpler. In contrast, in structures where the leakage channel is located between the surface passivation layer and the silicon substrate, more spots are needed for laser removal of the borosilicate glass, or the specific pattern etched using the etching paste is more complex and varied, making the fabrication process more complicated.

[0060] Furthermore, in this embodiment, the leakage channel is in contact with and electrically connected to the first electrode and the second electrode, which does not affect the collection of charge carriers by the first doped layer and the second doped layer, and thus does not affect the normal use of the back contact battery.

[0061] In this embodiment, the first doped layer 211 and the second doped layer 221 have opposite polarities, and the first electrode 21 is electrically connected to the first doped layer 211, and the second electrode 22 is electrically connected to the second doped layer 221. This allows the first electrode 21 and the second electrode 22 to collect majority carriers and minority carriers, respectively. Along the second direction, a surface passivation layer 23 is disposed on the side of the first doped layer 211 and the second doped layer 221 facing away from the silicon substrate and fills a partial isolation structure. A leakage channel 25 is disposed on the side of the surface passivation layer 23 facing away from the silicon substrate and contacts and is electrically connected to the first electrode 21 and the second electrode 22. Thus, when the back contact cell 2 is blocked, current can be transmitted through the first electrode 21, the leakage channel 25, and the second electrode 22, preventing the blocked back contact cell from becoming a load that consumes energy generated by other illuminated cells, thereby reducing the risk of hot spot effects. Furthermore, the positional relationship between the surface passivation layer and the leakage channel helps to reduce the fabrication complexity of the back contact cell while maintaining a relatively simple structure.

[0062] In some embodiments, the material of the leakage channel 25 includes metal, conductive polymer or semiconductor.

[0063] The metal may include at least one of copper, silver, and aluminum; the conductive polymer may include at least one of polyaniline polymers and polythiophene polymers; and the semiconductor may include doped or undoped silicon, etc.

[0064] The aforementioned materials have suitable conductivity, which helps to reduce the overall resistance of the leakage channel 25 and reduce the efficiency loss of the photovoltaic module.

[0065] In some embodiments, the resistivity of the material of the leakage channel 25 is 1.5 × 10⁻⁶. -8 Ω·m to 10×10 -8 Ω·m.

[0066] The resistivity of the material of the leakage current channel 25 can be 1.5 × 10⁻⁶. -8 Ω·m, 3×10 -8 Ω·m, 4×10 -8 Ω·m, 5×10 -8 Ω·m, 6×10 -8 Ω·m, 8×10 -8 Ω·m, 9×10 -8 Ω·m, 10×10-8 Ω·m or any value within the above range.

[0067] In the above embodiments, the material of the leakage channel 25 has a low resistivity, which is beneficial to reducing the overall resistance of the leakage channel 25, thereby helping to reduce the efficiency loss of the photovoltaic module.

[0068] Figure 2 This is a schematic diagram of the structure of a photovoltaic module according to an embodiment of this application. Figure 3 for Figure 2 An enlarged schematic diagram of region A in the image.

[0069] In some embodiments, the photovoltaic module 1 includes a plurality of back contact cells 2.

[0070] In some embodiments, for example, combined Figure 2 and Figure 3 As shown, the back contact battery 2 includes multiple leakage channels 25, which are spaced apart along a third direction, which is perpendicular to the first and second directions.

[0071] The third direction can be Figure 2 and Figure 3 y direction in .

[0072] In the above embodiments, when the back contact battery 2 is blocked, the current can be transmitted more evenly through multiple leakage channels 25, which helps to reduce the risk caused by hot spot effect.

[0073] In some embodiments, the back contact battery 2 includes a leakage channel 25 that extends in a third direction.

[0074] The projection of the leakage current channel 25 onto the xoy plane can be rectangular, circular, elliptical, T-shaped, airfoil-shaped, or other irregular shapes.

[0075] In some embodiments, the total size of the leakage channel 25 along a third direction is 10 μm to 10000 μm, and the third direction is perpendicular to the first direction and the second direction.

[0076] In the case of having multiple leakage channels 25 along a third direction, the total size of the leakage channels 25 in the third direction is the sum of the sizes of the multiple leakage channels 25 in the third direction.

[0077] In the case of having a leakage channel 25 along the third direction, the total size of the leakage channel 25 in the third direction is the size of the leakage channel 25 in the third direction.

[0078] Along the third direction, the total size of the leakage channel 25 can be 10μm, 15μm, 20μm, 22μm, 25μm, 28μm, 30μm, 35μm, 40μm, 50μm, 80μm, 100μm, 120μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 1000μm, 2000μm, 3000μm, 4000μm, 5000μm, 6000μm, 8000μm, 9000μm, 10000μm or any value within the above range.

[0079] When the size of the leakage channel 25 is greater than or equal to 10 μm along the third direction, it is beneficial to reduce the fabrication complexity of the leakage channel 25; when the size of the leakage channel 25 is less than or equal to 10000 μm along the third direction, it is beneficial to reduce leakage loss, thereby helping to reduce the efficiency loss of photovoltaic modules.

[0080] In some embodiments, the total size of a single leakage channel 25 along a third direction is 10 μm to 40 μm. This reduces the efficiency loss of the photovoltaic module while also reducing the fabrication complexity of the leakage channel 25.

[0081] In some embodiments, the line resistance of the leakage channel 25 is less than or equal to 1.25Ω. This helps to reduce leakage losses, thereby helping to reduce the efficiency loss of the photovoltaic module.

[0082] The line resistance of a leakage current path is R = ρ × L / S, where ρ is the resistivity, L is the length of the leakage current path, and S is the cross-sectional area of ​​the leakage current path. As an example, the cross-sectional area of ​​the leakage current path is the dimension of the leakage current path in the second direction (…). Figure 1 (z-direction) and third direction ( Figure 3 The product of the dimensions in the y-direction, the length of the leakage channel is the product of the dimensions in the first direction (in the y-direction), and the length of the leakage channel is the product of the dimensions in the y-direction. Figure 1 The dimension in the x-direction.

[0083] The line resistance of the leakage current channel 25 can be 1.25Ω, 1.0Ω, 0.8Ω, 0.5Ω, 0.3Ω, 0.1Ω, 0.01Ω or any value within the above range.

[0084] In some embodiments, the size of the leakage channel 25 along the second direction is 4 μm to 50 μm.

[0085] The second direction can be Figure 1 The z-direction in the middle. The dimension of the leakage channel 25 along the second direction refers to the height of the leakage channel 25 protruding from the surface passivation layer 23 along the second direction.

[0086] Along the second direction, the size of the leakage channel 25 can be 4μm, 5μm, 6μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm or any value within the above range.

[0087] When the size of the leakage channel 25 is greater than or equal to 4 μm along the second direction, it is beneficial to the fabrication of the leakage channel 25; when the size of the leakage channel 25 is less than or equal to 50 μm along the second direction, the leakage channel 25 has a suitable cross-sectional area and line resistance, which is beneficial to reducing the efficiency loss of the photovoltaic module and also beneficial to the fabrication of the leakage channel 25.

[0088] In some embodiments, along the second direction, the leakage channel 25 does not penetrate the surface passivation layer 23, the first doped layer 211, and the second doped layer 221. Thus, the leakage channel 25 does not damage the surface passivation layer 23, the first doped layer 211, and the second doped layer 221, which is beneficial for improving the efficiency of the back-contact battery.

[0089] In some embodiments, the first electrode 21 and the second electrode 22 comprise silver and a first glass powder, the first glass powder comprising a burn-through oxide, the burn-through oxide comprising at least one of lead oxide, bismuth oxide, tellurium oxide, vanadium oxide, and phosphorus oxide; the leakage channel 25 comprises silver and a second glass powder, the second glass powder not comprising a burn-through oxide.

[0090] Silver is conductive, which facilitates the formation of conductive channels, making it easier to collect and transmit current.

[0091] The first glass powder can adjust the sintering characteristics of silver paste, promote the contact between the silver-containing electrode and the silicon substrate, and achieve the function of burning through the surface passivation layer. The first glass powder contains burn-through oxides, which, through chemical reaction and physical melting during high-temperature sintering, help silver particles penetrate the surface passivation layer (such as SiNx or AlOx) and form an ohmic contact with the silicon substrate.

[0092] For example, lead oxide (PbO) can lower the softening temperature of the first glass powder, promoting the melting of the glass phase at a lower temperature; it can react with the surface passivation layer (such as SiNx), destroying its structure and forming a permeable glass phase channel; it can also enhance the migration ability of silver particles, helping silver to penetrate the surface passivation layer.

[0093] For example, bismuth oxide (Bi2O3) not only has good environmental protection properties, but also has a low melting point (about 817℃), making it suitable for low-temperature sintering processes; it can react with the passivation layer to generate low-melting-point compounds, reducing the energy required for burn-through; and it can also regulate the viscosity of the glass phase, balancing fluidity and penetration ability.

[0094] For example, tellurium oxide (TeO2) can significantly reduce the melting temperature of the first glass powder (the softening point of TeO2-based glass can be below 400°C); it can improve the fluidity of the glass phase, accelerate the dissolution of the surface passivation layer and the penetration of silver particles; it can also react with silicon substrates to form conductive interface layers (such as Te-Si compounds).

[0095] For example, vanadium oxide (V2O5) has strong oxidizing properties and high reactivity. It can combine with nitrogen or oxygen in the surface passivation layer, destroying its dense structure. It can also form a low-melting-point vanadate glass phase (such as Pb-VO or Bi-VO), promoting burn-through.

[0096] For example, phosphorus oxide (P2O5) can modulate the glass network structure and enhance the chemical stability of the glass phase; it can also react with silicon substrates to form phosphosilicate glass (PSG), improving contact resistance. Furthermore, the combined use of phosphorus oxide with lead oxide and bismuth oxide is beneficial for optimizing burn-through performance.

[0097] The first and second glass powders have different compositions. The second glass powder contains almost no burn-through oxides, which can prevent leakage channels from passing through the surface passivation layer and help reduce the efficiency loss of the back contact battery.

[0098] In some embodiments, in addition to burn-through oxides, the first and second glass powders may also include auxiliary oxides, such as zinc oxide (ZnO), boron oxide (B2O3), and silicon oxide (SiO2). Zinc oxide can adjust the coefficient of thermal expansion and reduce sintering stress; boron oxide can enhance the heat resistance and chemical stability of the glass phase; and silicon oxide can act as a glass network forger, controlling viscosity and mechanical strength.

[0099] In some embodiments, the first electrode and the second electrode comprise silver, with the silver content being 80% to 90% based on the total mass of the first electrode, and further, 85% to 90% based on the total mass of the second electrode.

[0100] In some embodiments, the mass content of the first glass powder in the first electrode is 1% to 5%, which is beneficial to enhancing the adhesion of the slurry of the first electrode during the preparation process; the mass content of the first glass powder in the second electrode is 1% to 5%, which is beneficial to enhancing the adhesion of the slurry of the second electrode during the preparation process.

[0101] In some embodiments, the first electrode, the second electrode, and the leakage channel further include an organic carrier, wherein the organic carrier has a mass content of 5% to 15%. The organic carrier is composed of resin, solvent, and additives, and can adjust the viscosity and flowability of the paste of the first electrode, the second electrode, and the leakage channel to facilitate printing.

[0102] In some embodiments, the back contact battery 2 further includes a first interface layer 212 and a second interface layer 222. Along the second direction, the first interface layer 212 is disposed between the silicon substrate 20 and the first doped layer 211, and the second interface layer 222 is disposed between the silicon substrate 20 and the second doped layer 221.

[0103] The first interface layer 212 and the second interface layer 222 can be tunneling oxide layers. As an example, the material of the tunneling oxide layer includes SiO2.

[0104] The first interface layer 212 and the second interface layer 222 help reduce carrier recombination, thereby improving the efficiency of the back contact battery.

[0105] In some embodiments, the distance between the first doped layer 211 and the second doped layer 221 along the first direction is greater than 0.5 mm, and the dimension of the leakage channel 25 along the first direction is greater than or equal to the distance between the first doped layer 211 and the second doped layer 221. This facilitates the electrical connection of the leakage channel 25 to the first electrode 21 and the second electrode 22.

[0106] This application provides a photovoltaic module 1, which includes the back contact battery 2 in any of the above embodiments.

[0107] Figure 4 This is a schematic diagram illustrating a method for fabricating a back contact battery according to an embodiment of this application. This application provides a method for fabricating a back contact battery, for example, as... Figure 4 As shown, the method 300 for preparing a back contact battery includes the following steps.

[0108] Step 310: A first doped layer 211 and a second doped layer 221 are prepared on the first surface of the silicon substrate 20, wherein the polarities of the first doped layer 211 and the second doped layer 221 are opposite.

[0109] As an example, prior to step 310, the silicon wafer is processed to obtain a silicon substrate. Specifically, the silicon wafer is polished using an alkaline solution to remove the damaged layer and form a flat planar structure.

[0110] In step 310, a polycrystalline silicon layer can be deposited on the first surface of the silicon substrate using a low-pressure chemical vapor deposition (LPCVD) device, and then the polycrystalline silicon layer can be doped by thermal diffusion to obtain a first doped layer 211 and a second doped layer 221.

[0111] Step 320: Prepare an isolation structure 24, wherein the isolation structure 24 is disposed between the first doped layer 211 and the second doped layer 221 along the first direction, and the isolation structure 24 penetrates through the first doped layer 211 and the second doped layer 221 along the second direction, the second direction being the thickness direction of the silicon substrate 20, and the first direction being perpendicular to the second direction.

[0112] As an example, in step 320, the region between the first doped layer 211 and the second doped layer 221 is processed (e.g., etched or laser-processed) to create a groove to obtain the isolation structure 24.

[0113] Step 330: Before fabricating the first electrode 21 and the second electrode 22, a surface passivation layer 23 is fabricated, wherein, along the second direction, the surface passivation layer 23 is disposed on the side surface of the first doped layer 211 and the second doped layer 221 facing away from the silicon substrate 20 and fills part of the isolation structure 24.

[0114] As an example, the material of the surface passivation layer 23 includes at least one of aluminum oxide, silicon nitride, silicon oxynitride, or silicon oxide.

[0115] Step 340: Prepare a first electrode 21 and a second electrode 22, wherein the first electrode 21 is electrically connected to the first doped layer 211 and the second electrode 22 is electrically connected to the second doped layer 221.

[0116] As an example, the first electrode 21 and the second electrode 22 penetrate the first doped layer 211 and the second doped layer 221, respectively. The first electrode 21 and the second electrode 22 are made of silver.

[0117] Step 350: After preparing the first electrode 21 and the second electrode 22, a leakage channel 25 is prepared, wherein the leakage channel 25 is disposed on the side surface of the surface passivation layer 23 facing away from the silicon substrate 20 and is in contact with and electrically connected to the first electrode 21 and the second electrode 22.

[0118] The back contact battery prepared by the above method can reduce the risk of hot spot effect. In the above technical solution, the back contact battery of this application can be obtained by simply setting a leakage channel 25 on the surface of the passivation layer 23 after preparing the first electrode 21 and the second electrode 22. This preparation method has low preparation complexity and can reduce the number of laser spots in the process of preparing the back contact battery.

[0119] In some embodiments, the back contact battery can be prepared by the following method: (1): Polishing the silicon wafer with an alkaline solution to remove the damaged layer and form a flat planar structure to obtain a silicon substrate; (2): Depositing a first interface layer (SiO2) and a polycrystalline silicon layer on the first surface of the silicon substrate using an LPCVD device; (3): Doping the silicon substrate after the polycrystalline silicon layer has been deposited by thermal diffusion to form a P-type doped region with a certain borosilicate glass BSG; (4): Removing the formed BSG according to a specific pattern using a laser or etching paste to expose the P-type doped region; (5): Removing the P-type doped region exposed in step (4). (6) The silicon substrate after step (5) is deposited with a second interface layer (SiO2) and a polycrystalline silicon layer using an LPCVD device; (7) The silicon substrate after step (6) is placed in a diffusion furnace with POCl3 as the diffusion source. After diffusion, an N-type doped region with a certain thickness of phosphorus silicate glass PSG is formed; (8) The PSG on the P-type doped region and part of the N-type doped region is removed by laser; (9) Chain-type film removal and post-texturing; (10) The surface passivation layer, the first electrode and the second electrode, and the leakage channel are prepared in sequence.

[0120] In the above preparation method, laser or etching processes are required at least twice, as shown in steps (4) and (8). Figure 5 This is a partial structural diagram of the back contact battery during the fabrication process of an embodiment of this application. (Combined with...) Figure 5 As shown, the back contact battery obtained after step (3) can be obtained by laser or paste etching of a portion of the first doped layer 211 after step (3). The laser spots have a small number or the mold used for paste etching has a regular shape and does not require special settings, which helps to simplify the preparation process.

[0121] In some embodiments, the preparation of the leakage channel 25 includes: applying a leakage channel 25 paste to the side of the surface passivation layer 23 away from the silicon substrate 20 by printing or inkjet printing; and curing the leakage channel 25 paste by drying, ultraviolet curing or sintering to obtain the leakage channel 25.

[0122] In the above technical solution, after preparing the first electrode 21 and the second electrode 22, the leakage channel 25 paste is applied to the side of the surface passivation layer 23 facing away from the silicon substrate 20 by printing or inkjet printing, and then cured to obtain the leakage channel 25. This preparation method has low preparation complexity and is relatively simple.

[0123] In some embodiments, the leakage channel 25 slurry comprises silver paste, the sintering temperature of which is 670°C to 820°C; or, the leakage channel 25 slurry comprises copper paste, the drying temperature of which is 200°C to 300°C.

[0124] In the process of preparing the leakage channel 25 using the above-mentioned leakage channel 25 slurry, damage to the surface passivation layer 23 can be avoided or prevented, which is beneficial to improving the efficiency of the back contact battery.

[0125] As an example, the leakage current channel paste is silver paste.

[0126] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0127] In Example 1, the back contact battery is prepared as follows.

[0128] (1) Polishing: The silicon wafer is polished with alkaline solution to remove the damaged layer and form a flat planar structure to obtain the silicon substrate;

[0129] (2) Polycrystalline silicon layer deposition: A first interface layer (SiO2) and a polycrystalline silicon layer are deposited on the first surface of a silicon substrate using an LPCVD device. The thickness of the first interface layer is 1 nm and the deposition temperature is 600 °C. The thickness of the polycrystalline silicon layer is 300 nm and the deposition temperature is 610 °C.

[0130] (3) Boron diffusion: The silicon substrate after the polycrystalline silicon layer has been deposited is doped by thermal diffusion to form a P-type doped region with a certain borosilicate glass (BSG). The diffusion source is BCl3 and the diffusion temperature is 900 to 1000℃.

[0131] (4) Patterning 1: Use a laser or etching paste to remove the BSG formed in step 3 in a specific pattern to expose the P-type doped region (first doped layer);

[0132] (5) Alkali polishing: Remove the P-type doped region exposed in step 4 to form a polished morphology;

[0133] (6) Polycrystalline silicon layer deposition: The silicon substrate after step 5 is deposited with a second interface layer (SiO2) and a polycrystalline silicon layer using an LPCVD device. The thickness of the second interface layer is 1 nm and the deposition temperature is 600 °C. The thickness of the polycrystalline silicon layer is 250 nm and the deposition temperature is 610 °C.

[0134] (7) Phosphorus diffusion: The silicon substrate from step 6 is placed in a diffusion furnace with POCl3 as the diffusion source. After diffusion, an N-type doped region (second doped layer) with a certain thickness of phosphorus silicon glass PSG is formed. The diffusion temperature is 850 to 950°C.

[0135] (8) Patterning 2: Using laser to remove PSG on P-type doped regions and part of N-type doped regions;

[0136] (9) Chain-type film removal and post-texturing: The winding plating on the second surface of the silicon substrate is removed by a chain machine, and then placed in a groove-type texturing tank to complete the texturing, so that a pyramid-shaped textured surface is formed on the front side. In addition, the N-type doped layer on the P-type doped region on the second surface of the silicon substrate is also removed simultaneously, and a groove (isolation structure) is formed between the P-type doped region and the N-type doped region.

[0137] (10) Passivation: A passivation film is deposited on the second surface to prepare a surface passivation layer. The material of the surface passivation layer is SiNx.

[0138] (11) Electrode preparation: Electrode paste is printed on the surface of the passivation layer at the positions corresponding to the P-type doped region and the N-type doped region, respectively, and sintered to obtain the first electrode and the second electrode. The electrode paste includes silver, organic carrier and first glass powder. The first glass powder includes burn-through oxide. Based on the total mass of the electrode paste, the mass content of silver is 85% to 90%.

[0139] (12) Preparation of leakage channel: Leakage channel paste is printed on the surface of the passivation layer and then dried to obtain the leakage channel. The leakage channel paste includes silver, an organic carrier, and a second glass powder. The second glass powder does not include burn-through oxides. Based on the total mass of the leakage channel paste, the silver content is 80%–85%. The leakage channel does not penetrate the surface passivation layer; along the third direction ( Figure 3 In the y-direction, 200 leakage channels were set up, each with a size of 20μm.

[0140] The difference between Example 2-3 and Example 1 is that the number of leakage current channels is different.

[0141] The difference between Example 4 and Example 3 is that the resistivity of the leakage current channel is different.

[0142] In Example 4, the resistivity of the material of the leakage channel is 10 × 10⁻⁶. -8 Ω·m.

[0143] The difference between Comparative Example 1 and Example 1 is that no leakage current path was provided.

[0144] Performance tests were conducted on the back contact batteries of the examples and comparative examples. The test conditions and results are as follows.

[0145] Specifically, at 25±2℃ under standard simulated sunlight (AM1.5G, 1000W / m²) 2Under illumination, the performance of the back-contact battery was tested to obtain the IV curve. Based on the IV curve and data from the testing equipment, the short-circuit current Isc, open-circuit voltage Voc, maximum light output voltage Vmpp, and maximum power point current Impp were obtained. The fill factor FF of the back-contact battery was calculated using the formula FF = (Impp × Vmpp) / (Isc × Voc). The conversion efficiency Eff of the back-contact battery was calculated using the formula Eff = Jsc × Voc × FF / Pin, where Pin is the input power.

[0146] In Table 1, Rsh is the parallel resistance of the back contact battery, and IRev2 is the leakage current under reverse bias. In Tables 1 and 2, the maximum power point current Impp is 15.2A.

[0147] Table 1. Test results of Examples 1-3 and Comparative Example 1

[0148]

[0149]

[0150] As shown in Examples 1-3 and Comparative Example 1, by setting a leakage current channel, the leakage current under reverse bias is greater than the maximum power point current, indicating that setting a leakage current channel can suppress the risk caused by the hot spot effect. Furthermore, as shown in Examples 1-3, by setting the number of leakage current channels to 200-400, the efficiency loss can be controlled within 0.25% while suppressing the risk of the hot spot effect; furthermore, setting the number of leakage current channels to around 200 can further reduce the efficiency loss to within 0.05%.

[0151] Table 2 Test results of Examples 1 and 4

[0152]

[0153] In conjunction with Examples 1 and 4, the resistivity of the leakage current channel is set to be less than or equal to 10 × 10⁻⁶. -8 The reverse bias leakage current is greater than the maximum power point current, which can effectively suppress the risk caused by hot spot effect; furthermore, the resistivity of the leakage channel is set to 5×10 Ω·m. -8 Ω·m can further reduce efficiency loss.

[0154] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A back-contact battery, characterized in that, include: A silicon substrate (20) having opposing first and second surfaces; A first doped layer (211) is disposed on the first surface; A second doped layer (221) is disposed on the first surface and has the opposite polarity to the first doped layer (211); An isolation structure (24) is disposed between the first doped layer (211) and the second doped layer (221) along a first direction, and the isolation structure (24) penetrates the first doped layer (211) and the second doped layer (221) along a second direction, the second direction being the thickness direction of the silicon substrate (20), and the first direction being perpendicular to the second direction; The first electrode (21) is electrically connected to the first doped layer (211); The second electrode (22) is electrically connected to the second doped layer (221); A surface passivation layer (23) is disposed on the side surface of the first doped layer (211) and the second doped layer (221) opposite to the silicon substrate (20) along the second direction and fills part of the isolation structure (24); A leakage channel (25) is disposed on the side surface of the surface passivation layer (23) away from the silicon substrate (20) and is in contact with and electrically connected to the first electrode (21) and the second electrode (22).

2. The back contact battery according to claim 1, characterized in that, The material of the leakage channel (25) includes metal, conductive polymer or semiconductor.

3. The back contact battery according to claim 2, characterized in that, The resistivity of the material of the leakage channel (25) is 1.5 × 10⁻⁶. -8 Ω·m to 10×10 -8 Ω·m.

4. The back contact battery according to claim 1, characterized in that, Along a third direction, the total size of the leakage channel (25) is 10 μm to 10000 μm, and the third direction is perpendicular to the first direction and the second direction.

5. The back contact battery according to claim 4, characterized in that, Along the third direction, the size of a single leakage channel (25) is 10 μm to 40 μm.

6. The back contact battery according to claim 1, characterized in that, The line resistance of the leakage channel (25) is less than or equal to 1.25Ω.

7. The back contact battery according to claim 1, characterized in that, Along the second direction, the leakage channel (25) has a size of 4 μm to 50 μm.

8. The back contact battery according to claim 1, characterized in that, The back contact battery includes a plurality of leakage channels (25), which are spaced apart along a third direction, which is perpendicular to the first direction and the second direction.

9. The back contact battery according to claim 1, characterized in that, Along the second direction, the leakage channel (25) does not penetrate the surface passivation layer (23), the first doped layer (211), and the second doped layer (221).

10. The back contact battery according to claim 1, characterized in that, The first electrode (21) and the second electrode (22) comprise silver and a first glass powder, wherein the first glass powder comprises a burn-through oxide, and the burn-through oxide comprises at least one of lead oxide, bismuth oxide, tellurium oxide, vanadium oxide, and phosphorus oxide. The leakage channel (25) includes silver and a second glass powder, wherein the second glass powder does not include the burn-through oxide.

11. The back contact battery according to claim 1, characterized in that, The back contact battery further includes a first interface layer (212) and a second interface layer (222). Along the second direction, the first interface layer (212) is disposed between the silicon substrate (20) and the first doped layer (211), and the second interface layer (222) is disposed between the silicon substrate (20) and the second doped layer (221).

12. A method for preparing a back contact battery, characterized in that, include: A first doped layer (211) and a second doped layer (221) are prepared on the first surface of a silicon substrate (20), wherein the polarities of the first doped layer (211) and the second doped layer (221) are opposite. An isolation structure (24) is prepared, wherein the isolation structure (24) is disposed between the first doped layer (211) and the second doped layer (221) along a first direction, and the isolation structure (24) penetrates the first doped layer (211) and the second doped layer (221) along a second direction, wherein the second direction is the thickness direction of the silicon substrate (20), and the first direction is perpendicular to the second direction; Before fabricating the first electrode (21) and the second electrode (22), a surface passivation layer (23) is fabricated, wherein, along the second direction, the surface passivation layer (23) is disposed on the side surface of the first doped layer (211) and the second doped layer (221) facing away from the silicon substrate (20) and fills part of the isolation structure (24); The first electrode (21) and the second electrode (22) are prepared, wherein the first electrode (21) is electrically connected to the first doped layer (211) and the second electrode (22) is electrically connected to the second doped layer (221); After the first electrode (21) and the second electrode (22) are prepared, a leakage channel (25) is prepared, which is disposed on the side surface of the surface passivation layer (23) opposite to the silicon substrate (20) and is in contact with and electrically connected to the first electrode (21) and the second electrode (22).

13. The method for preparing a back contact battery according to claim 12, characterized in that, The preparation of the leakage channel (25) includes: The leakage channel (25) paste is applied to the surface of the surface passivation layer (23) away from the silicon substrate (20) by printing or inkjet printing. The leakage channel (25) slurry is cured by drying, ultraviolet curing or sintering to obtain the leakage channel (25).

14. The method for preparing a back contact battery according to claim 13, characterized in that, The leakage channel (25) slurry includes silver paste, the sintering temperature of which is 670°C to 820°C; or, The leakage channel (25) slurry includes copper paste, which is dried at a temperature of 200°C to 300°C.

15. A photovoltaic module, characterized in that, Includes the back contact battery according to any one of claims 1-11.

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