Back contact battery, preparation method thereof and photovoltaic module

Abstract

The invention discloses a back contact cell, a preparation method thereof and a photovoltaic module, and belongs to the technical field of solar cells. The back contact cell includes: a silicon substrate; the first doping layer is arranged on the first surface of the silicon substrate; the second doping layer is arranged on the first surface of the silicon substrate and is opposite to the first doping layer in polarity; the isolation structure is arranged between the first doping layer and the second doping layer along the first direction and penetrates through the first doping layer and the second doping layer along the second direction; the first electrode is electrically connected with the first doping layer; the second electrode is electrically connected with the second doping layer; the surface passivation layer is arranged on the surfaces of the sides, deviating from the silicon substrate, of the first doping layer and the second doping layer in the second direction and is filled with part of the isolation structure; the electric leakage channel is arranged on the surface of the side, away from the silicon substrate, of the surface passivation layer and makes contact with and is electrically connected with the first electrode and the second electrode, the risk caused by the hot spot effect can be reduced, and meanwhile the preparation complexity is low.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and more specifically, to a back-contact cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] A back-contact cell refers to a solar cell in which the light-facing side of the cell has no electrode, and both the positive and negative electrodes are arranged on the backlight side of the cell. This can reduce the shading of the electrode on the cell, increase the short-circuit current of the cell, and improve the energy conversion efficiency of the cell.

[0003] During actual use, back-contact solar cells may be subject to obstructions such as leaves and dust falling onto them. This can cause the cell temperature to rise, resulting in a hot spot effect. This can lead to permanent damage such as localized burns (dark spots) on the solar module, melted solder joints, and aging of the encapsulation material. This can seriously affect the module's output power and service life, and may even cause fires and pose 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 the hot spot effect.

[0005] In order to achieve the above objectives, the present application provides a back-contact cell and a preparation method thereof, and a photovoltaic module.

[0006] In a first aspect, a back-contact battery is provided, comprising: a silicon substrate, the silicon substrate having a first surface and a second surface relative to each other; a first doping layer, the first doping layer being arranged on the first surface; a second doping layer, the second doping layer being arranged on the first surface and having a polarity opposite to the first doping layer; an isolation structure, the isolation structure being arranged between the first doping layer and the second doping layer along a first direction, and the isolation structure passing through the first doping layer and the second doping layer 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, the first electrode being electrically connected to the first doping layer; a second electrode, the second electrode being electrically connected to the second doping layer; a surface passivation layer, along the second direction, the surface passivation layer being arranged on a side surface of the first doping layer and the second doping layer away from the silicon substrate and filling a portion of the isolation structure; a leakage channel, the leakage channel being arranged on a side surface of the surface passivation layer away from the silicon substrate and in contact with and electrically connected to the first electrode and the second electrode.

[0007] In an embodiment of the present application, 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. In this way, majority carriers and minority carriers can be collected by the first electrode and the second electrode, respectively. The provision of a surface passivation layer can reduce carrier recombination, which is beneficial to improving the efficiency of the back contact battery. The leakage channel is provided on the surface of the surface passivation layer away from the silicon substrate and is in contact with and electrically connected to the first electrode and the second electrode. On the one hand, when the back contact battery is blocked, the 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 and consuming 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 is conducive to reducing the complexity of the back contact battery's preparation while having a relatively simple structure. For example, it can reduce the number of laser spots during the preparation of the back contact battery. Therefore, the embodiment of the present application can reduce the risk of hot spot effect while reducing the complexity of the preparation of the back contact battery.

[0008] In some embodiments, the material of the leakage path includes metal, conductive polymer or semiconductor. The above materials have relatively suitable conductivity, which is conducive to reducing the overall resistance of the leakage path and reducing the efficiency loss of the photovoltaic module.

[0009] In some embodiments, the resistivity of the material of the leakage path is 1.5×10 -8 Ω·m to 10×10 -8 Ω·m. In this way, the material of the leakage channel has a lower resistivity, which is beneficial to reducing the overall resistance of the leakage channel, thereby helping to reduce the efficiency loss of the photovoltaic module.

[0010] In some embodiments, along a third direction, a total dimension of the leakage channel is 10 μm to 10,000 μm, and the third direction is perpendicular to the first direction and the second direction.

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

[0012] In some embodiments, along the third direction, a size of a single leakage channel is 10 μm to 40 μm. In this way, the efficiency loss of the photovoltaic module can be reduced while reducing the complexity of preparing the leakage channel.

[0013] In some embodiments, the line resistance of the leakage channel is less than or equal to 1.25Ω, which is beneficial to reducing leakage loss and thus reducing efficiency loss of the photovoltaic module.

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

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

[0016] In some embodiments, the back-contact cell includes multiple leakage channels, which are spaced apart along a third direction perpendicular to the first and second directions. This allows for more uniform current transmission through the multiple leakage channels when the back-contact cell is obscured, mitigating the risk of hot spot effects.

[0017] In some embodiments, along the second direction, the leakage path does not penetrate the surface passivation layer, the first doping layer, and the second doping layer. In this way, the leakage path does not damage the surface passivation layer and the first and second doping layers, which is beneficial for improving the efficiency of the back-contact battery.

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

[0019] In the above technical solution, by controlling the composition of the second glass powder in the leakage path, it is possible to prevent the leakage path 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 interface layer and the second interface layer are beneficial to reducing the recombination of carriers, thereby improving the efficiency of the back contact battery.

[0022] In a second aspect, a method for preparing a back-contact battery is provided, comprising: preparing a first doping layer and a second doping layer on a first surface of a silicon substrate, the first doping layer and the second doping layer having opposite polarities; preparing an isolation structure, the isolation structure being arranged between the first doping layer and the second doping layer along a first direction, and the isolation structure penetrating the first doping layer and the second doping layer 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; before preparing the first electrode and the second electrode, preparing a surface passivation layer, wherein along the second direction, the surface passivation layer is arranged on a side surface of the first doping layer and the second doping layer away from the silicon substrate and fills part of the isolation structure; preparing the first electrode and the second electrode, the first electrode being electrically connected to the first doping layer, and the second electrode being electrically connected to the second doping layer; after preparing the first electrode and the second electrode, preparing the leakage channel, the leakage channel being arranged on a side surface of the surface passivation layer away from the silicon substrate and in contact with and electrically connected to the first electrode and the second electrode.

[0023] The back-contact battery prepared by the above-mentioned preparation method can reduce the risk brought by the hot spot effect; in addition, the embodiment of the present application only needs to set 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 the present application. The preparation method has a lower preparation complexity and can reduce the number of laser spots in the process of preparing the back-contact battery.

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

[0025] In the above technical solution, it is only necessary to apply the leakage channel slurry on the surface of the surface passivation layer away from the silicon substrate by printing or inkjet after preparing the first electrode and the second electrode, and then solidify it to obtain the leakage channel. This preparation method has low preparation complexity and is relatively simple.

[0026] In some embodiments, the leakage path slurry includes silver paste, and the sintering temperature of the silver paste is 670°C to 820°C; or, the leakage path slurry includes copper paste, and the drying temperature of the copper paste is 200°C to 300°C.

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

[0028] In a third aspect, a photovoltaic module is provided, comprising the back-contact cell according to the first aspect and any embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. 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 the drawings without creative work.

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

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

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

[0033] Figure 4 A schematic diagram of a method for preparing a back-contact battery according to an embodiment of the present application;

[0034] Figure 5 This is a schematic diagram of a portion of the structure of a back-contact battery during the preparation process of one embodiment of the present application.

[0035] Figure numerals: 1: photovoltaic module; 2: back contact cell; 20: silicon substrate; 21: first electrode; 22: second electrode; 211: first doping layer; 221: second doping layer; 212: first interface layer; 222: second interface layer; 23: surface passivation layer; 24: isolation structure; 25: leakage channel; 26: anti-reflection layer. DETAILED DESCRIPTION

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

[0037] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0041] Photovoltaic modules consist of multiple back-contact cells, which are electrically connected in series and / or parallel. During use, obstructions such as bird droppings, leaves, and dust may fall onto the back-contact cells. This obstruction can cause the back-contact cells to heat up, creating a hot spot effect. If the temperature of the hot spot exceeds a certain value, it can cause problems such as delamination of the photovoltaic module, backsheet burns, and glass cracking, rendering the entire solar cell useless. In severe cases, it can even pose a fire risk.

[0042] In some treatment methods, the risk of hot spot effect is reduced by setting a bypass diode for the back contact cell. For example, a photovoltaic module includes six columns of back contact cell strings, each back contact cell string includes a plurality of back contact cells connected in series, and a bypass diode is connected in parallel with every two columns of back contact cell strings. When a back contact cell in a column of the back contact cell string is blocked, the current can pass through the bypass diode connected in parallel with the back contact cell string, thereby reducing the risk caused by heating of the blocked back contact cell. However, this treatment method will cause the open circuit voltage of the photovoltaic module to decrease, thereby significantly reducing the power and efficiency of the photovoltaic module, and the photovoltaic module needs to be additionally provided with a diode, and the structure is relatively complex.

[0043] In view of this, an embodiment of the present application provides a back-contact battery, comprising: a silicon substrate, the silicon substrate having a first surface and a second surface relative to each other; a first doping layer, the first doping layer being arranged on the first surface; a second doping layer, the second doping layer being arranged on the first surface and having a polarity opposite to the first doping layer; an isolation structure, the isolation structure being arranged between the first doping layer and the second doping layer along a first direction, and the isolation structure passing through the first doping layer and the second doping layer 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, the first electrode being electrically connected to the first doping layer; a second electrode, the second electrode being electrically connected to the second doping layer; a surface passivation layer, along the second direction, the surface passivation layer being arranged on a side surface of the first doping layer and the second doping layer away from the silicon substrate and filling part of the isolation structure; a leakage channel, the leakage channel being arranged on a side surface of the surface passivation layer away from the silicon substrate and in contact with and electrically connected to the first electrode and the second electrode. Thus, when the back-contact cell is blocked, current can be transmitted via the first electrode, the leakage channel, and the second electrode, 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. In addition, the positional relationship between the surface passivation layer and the leakage channel is conducive to reducing the complexity of back-contact cell preparation while maintaining a relatively simple structure. For example, the number of laser spots during the preparation of the back-contact cell can be reduced.

[0044] Figure 1 This is a schematic diagram of the structure of a back contact battery according to an embodiment of the present application. Figure 1 As shown, the back contact cell 2 includes a silicon substrate 20 , a first doping layer 211 , a second doping 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 a first surface and a second surface opposite to each other. 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 opposite to each other.

[0046] The first doped layer 211 is disposed on the first surface, and the second doped layer 221 is disposed on the first surface and has a polarity opposite to that of the first doped layer 211. The second surface may be provided with an anti-reflection layer 26. As an example, the anti-reflection layer 26 may be a pyramid structure with a velvet surface.

[0047] The first doping layer 211 and the second doping layer 221 may be doped amorphous silicon or polycrystalline silicon. As an example, the first doping layer 211 is a P-type doped polycrystalline silicon layer, and the second doping layer 221 is an N-type doped polycrystalline silicon layer. The first doping layer 211 may be a P-type doped polycrystalline silicon layer by doping with an element such as B, and the second doping layer 221 may be an N-type doped polycrystalline silicon layer by doping with an element such as P.

[0048] The isolation structure 24 is disposed between the first doping layer 211 and the second doping layer 221 along the first direction, and penetrates the first doping layer 211 and the second doping layer 221 along the second direction.

[0049] The second direction is the thickness direction of the silicon substrate 20 (eg Figure 1 The first direction is perpendicular to the second direction, and the first direction can be Figure 1 The x direction in .

[0050] The isolation structure 24 may be a groove that passes through the first doping layer 211 and the second doping layer 221 to achieve insulation between the first doping layer 211 and the second doping layer 221 .

[0051] The first electrode 21 is electrically connected to the first doping layer 211, and the second electrode 22 is electrically connected to the second doping layer 221. The first electrode and the second electrode 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, the surface passivation layer 23 is disposed on the surface of the first doping layer 211 and the second doping layer 221 facing away from the silicon substrate 20 and fills a portion of the isolation structure 24 .

[0054] The surface passivation layer 23 filling a portion of the isolation structure 24 may mean that the surface passivation layer 23 covers the surface of the isolation structure 24 .

[0055] The leakage channel 25 is provided on the side 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. The leakage channel 25 can be a conductive layer provided on the side of the surface passivation layer 23 facing away from the silicon substrate 20 and provided between the first electrode 21 and the second electrode 22. The leakage channel 25 is conductive and can achieve electrical connection between the first electrode 21 and the second electrode 22 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 shapes. The embodiment of the present application does not impose any specific restrictions on this, as long as the electrical connection between the first electrode 21 and the second electrode 22 can be achieved.

[0057] The provision of the surface passivation layer 23 can reduce the recombination of carriers, which is beneficial to improving the efficiency of the back-contact battery; the leakage channel 25 is provided 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 battery has a lower risk of hot spot effect and a simpler structure. The back-contact battery has both good performance and a simpler preparation process; in addition, it is also beneficial to reduce the efficiency loss of photovoltaic modules including multiple back-contact cells, which is beneficial to obtain photovoltaic modules with higher efficiency while reducing the risk of hot spot effect.

[0058] Furthermore, the leakage channel 25 is disposed on the surface of the surface 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 preparing a back-contact battery. In the process of preparing a back-contact battery, after the first doped layer 211 and the second doped layer 221 are prepared, the surface passivation layer 23, the first electrode 21 and the second electrode 22, and the leakage channel 25 are sequentially prepared.

[0059] Compared to the structure in which the leakage channel is set between the surface passivation layer and the silicon substrate, the structure of the embodiment of the present application can reduce the complexity of preparing the back contact battery. For example, after preparing the first doping layer 211, it is usually necessary to use a laser or etching slurry to remove the glass (such as borosilicate glass) formed by preparing the first doping layer according to a specific pattern. In the embodiment of the present application, since the leakage channel 25 is set on the surface of the surface passivation layer 23 on the side away from the silicon substrate 20, the number of spots used for laser removal of borosilicate glass is less or the specific pattern etched by the etching slurry is more regular (for example, a rectangle), and the process for preparing the back contact battery is simpler. In the structure in which the leakage channel is set between the surface passivation layer and the silicon substrate, in order to prepare the leakage channel, the number of spots used for laser removal of borosilicate glass is more or the specific pattern etched by the etching slurry is more complex and varied, and its preparation process is more complicated.

[0060] In addition, in the embodiment of the present application, the leakage channel is in contact with and electrically connected to the first electrode and the second electrode, and does not affect the collection of carriers by the first doped layer and the second doped layer, thereby not affecting the normal use of the back contact battery.

[0061] In the embodiment of the present application, 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. Thus, majority carriers and minority carriers can be collected by the first electrode 21 and the second electrode 22, respectively. Along the second direction, a surface passivation layer 23 is disposed on the surface of the first doped layer 211 and the second doped layer 221 facing away from the silicon substrate and partially fills the isolation structure. A leakage channel 25 is disposed on the surface of the surface passivation layer 23 facing away from the silicon substrate and contacts and electrically connects to the first electrode 21 and the second electrode 22. Thus, when the back-contact cell 2 is blocked, current can be transmitted via the first electrode 21, the leakage channel 25, and the second electrode 22, preventing the blocked back-contact cell from becoming a load and consuming 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 facilitates a simpler structure for the back-contact cell while reducing the complexity of its fabrication.

[0062] In some embodiments, the material of the leakage path 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 polymer materials and polythiophene polymer materials; and the semiconductor may include doped or undoped silicon.

[0064] The above materials have relatively suitable electrical conductivity, which is beneficial to reducing the overall resistance of the leakage channel 25 and reducing the efficiency loss of the photovoltaic module.

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

[0066] The resistivity of the material of the leakage path 25 may be 1.5×10 -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 embodiment, the material of the leakage channel 25 has a relatively low resistivity, which is beneficial to reducing the overall resistance of the leakage channel 25 , thereby facilitating reduction of efficiency loss of the photovoltaic module.

[0068] Figure 2 This is a schematic structural diagram of a photovoltaic module according to an embodiment of the present application. Figure 3 for Figure 2 Schematic diagram of the enlarged area A in FIG.

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

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

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

[0072] In the above embodiment, when the back contact cell 2 is shielded, the current can be transmitted more evenly through the multiple leakage channels 25, which is beneficial to reducing the risk caused by the hot spot effect.

[0073] In some embodiments, the back-contact cell 2 includes a leakage channel 25 extending along the third direction.

[0074] The projection of the leakage channel 25 on the xoy plane may be a rectangle, a circle, an ellipse, a T-shape, a wing-shape or other irregular shapes.

[0075] In some embodiments, along the third direction, the total size of the leakage channel 25 is 10 μm to 10,000 μm, and the third direction is perpendicular to the first direction and the second direction.

[0076] In the case where there are a plurality of leakage paths 25 along the third direction, the total size of the leakage paths 25 in the third direction is the sum of the sizes of the plurality of leakage paths 25 in the third direction.

[0077] In the case where there is one leakage path 25 along the third direction, the total size of the leakage paths 25 in the third direction is the size of one leakage path 25 in the third direction.

[0078] Along the third direction, the total size of the leakage path 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 ranges.

[0079] When the size of the leakage channel 25 along the third direction is greater than or equal to 10 μm, it is beneficial to reduce the preparation complexity of the leakage channel 25; when the size of the leakage channel 25 along the third direction is less than or equal to 10,000 μm, it is beneficial to reduce leakage loss, thereby reducing the efficiency loss of the photovoltaic module.

[0080] In some embodiments, along the third direction, the total size of a single leakage channel 25 is 10 μm to 40 μm. In this way, the efficiency loss of the photovoltaic module can be reduced while reducing the complexity of manufacturing the leakage channel 25.

[0081] In some embodiments, the line resistance of the leakage channel 25 is less than or equal to 1.25Ω, which is helpful in reducing leakage loss and thus reducing efficiency loss of the photovoltaic module.

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

[0083] The line resistance of the leakage path 25 may 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, along the second direction, the size of the leakage path 25 is 4 μm to 50 μm.

[0085] The second direction can be Figure 1 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 path 25 may be 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value within the above range.

[0087] When the size of the leakage channel 25 along the second direction is greater than or equal to 4 μm, it is beneficial to the preparation of the leakage channel 25; when the size of the leakage channel 25 along the second direction is less than or equal to 50 μm, 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 is also beneficial to the preparation of the leakage channel 25.

[0088] In some embodiments, along the second direction, the leakage path 25 does not penetrate the surface passivation layer 23, the first doping layer 211, and the second doping layer 221. Thus, the leakage path 25 does not damage the surface passivation layer 23, the first doping layer 211, and the second doping layer 221, thereby improving the efficiency of the back-contact cell.

[0089] In some embodiments, the first electrode 21 and the second electrode 22 include silver and a first glass powder, the first glass powder includes a burn-through oxide, and the burn-through oxide includes 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, and the second glass powder does not include a burn-through oxide.

[0090] Silver is conductive and helps form conductive pathways, facilitating the collection and transmission of current.

[0091] The first glass frit adjusts the sintering properties of the silver paste, promotes contact between the silver electrode and the silicon substrate, and achieves the function of burning through the surface passivation layer. The first glass frit contains a burn-through oxide. During the high-temperature sintering process, the burn-through oxide chemically reacts and physically melts, helping the 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 and promote the melting of the glass phase at a lower temperature; it can react with the surface passivation layer (such as SiNx) to destroy its structure and form a permeable glass phase channel; it can also enhance the migration ability of silver particles and help silver penetrate the surface passivation layer.

[0093] For example, bismuth oxide (Bi2O3) not only has good environmental protection effects, but also has a low melting point (about 817°C), which is suitable for low-temperature sintering processes; it can react with the passivation surface layer to form low-melting-point compounds, reducing the energy required for burn-through; it can also regulate the viscosity of the glass phase and balance 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 lower than 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; and it can also react with the silicon substrate to form a conductive interface layer (such as a Te-Si compound).

[0095] For example, vanadium oxide (V2O5) has strong oxidizing properties and high reactivity, which can combine with nitrogen or oxygen in the surface passivation layer to destroy its dense structure; it can also form a low-melting-point vanadate glass phase (such as Pb-VO or Bi-VO), which promotes 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 the silicon substrate to form phosphosilicate glass (PSG), improving contact resistance. Furthermore, when used in combination with lead oxide and bismuth oxide, phosphorus oxide can also help optimize burn-through performance.

[0097] The first glass powder and the second glass powder have different components. The second glass powder hardly includes burn-through oxide, so that leakage channels can be prevented from penetrating the surface passivation layer, which is beneficial to reducing efficiency loss of the back contact battery.

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

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

[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 path further comprise an organic vehicle, wherein the weight content of the organic vehicle is 5% to 15%. The organic vehicle is composed of a resin, a solvent, and an additive, and can adjust the viscosity and fluidity of the slurry of the first electrode, the second electrode, and the leakage path to facilitate printing.

[0102] In some embodiments, the back contact cell 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 may be tunneling oxide layers. As an example, the material of the tunneling oxide layer includes SiO 2 .

[0104] The first interface layer 212 and the second interface layer 222 are beneficial to reducing the recombination of carriers, thereby improving the efficiency of the back contact battery.

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

[0106] An embodiment of the present application provides a photovoltaic module 1 , which includes the back-contact cell 2 in any of the above embodiments.

[0107] Figure 4 Schematic diagram of a method for preparing a back-contact battery according to an embodiment of the present application. The present application provides a method for preparing a back-contact battery, for example, Figure 4 As shown, the method 300 for preparing a back contact cell includes the following steps.

[0108] Step 310 : Forming a first doping layer 211 and a second doping layer 221 on a first surface of a silicon substrate 20 , wherein the first doping layer 211 and the second doping layer 221 have opposite polarities.

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

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

[0111] In step 320, an isolation structure 24 is prepared, wherein the isolation structure 24 is arranged between the first doping layer 211 and the second doping layer 221 along a first direction, and penetrates the first doping layer 211 and the second doping layer 221 along a second direction. The second direction is the thickness direction of the silicon substrate 20, and the first direction is perpendicular to the second direction.

[0112] As an example, in step 320 , the region between the first doping layer 211 and the second doping layer 221 is processed (eg, etched or laser processed) to form a groove, thereby obtaining the isolation structure 24 .

[0113] Step 330 , before preparing the first electrode 21 and the second electrode 22 , prepare a surface passivation layer 23 , wherein along the second direction, the surface passivation layer 23 is arranged on the surface of the first doping layer 211 and the second doping layer 221 facing away from the silicon substrate 20 and fills a portion 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 , preparing a first electrode 21 and a second electrode 22 , wherein the first electrode 21 is electrically connected to the first doping layer 211 , and the second electrode 22 is electrically connected to the second doping layer 221 .

[0116] As an example, the first electrode 21 and the second electrode 22 respectively penetrate the first doping layer 211 and the second doping layer 221. 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 , prepare a leakage channel 25 , wherein the leakage channel 25 is provided on a surface of the surface passivation layer 23 facing away from the silicon substrate 20 and contacts and is electrically connected to the first electrode 21 and the second electrode 22 .

[0118] The back-contact cell fabricated by the above-described method can reduce the risk of hot spot effects. In the above-described technical solution, the back-contact cell of the present application can be obtained by simply providing a leakage path 25 on the surface of the surface passivation layer 23 after fabricating the first electrode 21 and the second electrode 22. This method has low fabrication complexity and can reduce the number of laser spots during the fabrication of the back-contact cell.

[0119] In some embodiments, a back contact cell can be prepared by the following method: (1): polishing a 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 polysilicon layer on the first surface of the silicon substrate using an LPCVD device; (3): doping the silicon substrate on which the polysilicon layer has been deposited by thermal diffusion to form a P-type doped region with a certain amount of borosilicate glass (BSG); (4): removing the formed BSG according to a specific pattern using a laser or etching slurry to expose the P-type doped region; (5): removing the P-type exposed in step (4). doped area to form a polished morphology; (6): using LPCVD equipment to deposit a second interface layer (SiO2) and a polysilicon layer on the silicon substrate after step (5); (7): placing the silicon substrate of step (6) in a diffusion furnace, with POCl3 as the diffusion source, and forming an N-type doped area with a certain thickness of phosphorus silicon glass PSG after diffusion; (8): using laser to remove PSG on the P-type doped area and part of the N-type doped area; (9): chain stripping and post-texturing; (10): sequentially preparing a surface passivation layer, a first electrode, a second electrode, and a leakage channel.

[0120] In the above preparation method, laser or etching process needs to be used at least twice, such as shown in step (4) and step (8). Figure 5 This is a partial structural diagram of a back contact battery during the preparation process of an embodiment of the present application. Figure 5 As shown, it is a back contact battery obtained after step (3), wherein, after step (3), a partial area of the first doping layer 211 can be etched by laser or slurry, wherein the laser spots have a smaller number or the mold used for slurry etching has a more regular shape, and no special setting is required, which is conducive to simplifying the preparation process.

[0121] In some embodiments, preparing the leakage channel 25 includes: applying the leakage channel 25 slurry on the surface of the surface passivation layer 23 facing away from the silicon substrate 20 by printing or inkjet; and curing the leakage channel 25 slurry by drying, UV curing or sintering to obtain the leakage channel 25.

[0122] In the above technical solution, it is only necessary to apply the leakage channel 25 slurry on the side of the surface passivation layer 23 away from the silicon substrate 20 by printing or inkjet after preparing the first electrode 21 and the second electrode 22, and then solidify it 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 paste includes silver paste, and the sintering temperature of the silver paste is 670° C. to 820° C.; or, the leakage channel 25 paste includes copper paste, and the drying temperature of the copper paste is 200° C. to 300° C.

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

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

[0126] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0127] In Example 1, the back contact cell was prepared as follows.

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

[0129] (2) Polysilicon layer deposition: using LPCVD equipment to deposit a first interface layer (SiO2) and a polysilicon layer on the first surface of the silicon substrate, wherein the thickness of the first interface layer is 1 nm and the deposition temperature is 600°C, and the thickness of the polysilicon layer is 300 nm and the deposition temperature is 610°C;

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

[0131] (4) Patterning 1: Using laser or etching slurry to remove the BSG formed in step 3 according to a specific pattern, exposing the P-type doped region (first doped layer);

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

[0133] (6) Polysilicon layer deposition: The silicon substrate after step 5 is deposited with a second interface layer (SiO2) and a polysilicon layer using an LPCVD device, wherein the thickness of the second interface layer is 1 nm and the deposition temperature is 600°C, and the thickness of the polysilicon 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. The diffusion source is POCl3. After diffusion, an N-type doping region (second doping layer) with a certain thickness of phosphorus silicate glass (PSG) is formed. The diffusion temperature is 850 to 950°C.

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

[0136] (9) Chain stripping and post-texturing: A chain machine is used to remove the wrap-around plating on the second surface of the silicon substrate, and then the substrate is placed in a slot-type texturing tank to complete the texturing. At the same time, a pyramid-shaped velvet surface is formed on the front side. In addition, the N-type doped layer on the P-type doped area on the second surface of the silicon substrate is also removed simultaneously, and a groove (isolation structure) is formed between the P-type doped area and the N-type doped area.

[0137] (10) Passivation: Depositing a passivation film on the second surface to prepare a surface passivation layer, wherein the material of the surface passivation layer is SiNx;

[0138] (11) preparing electrodes: printing electrode paste on the surface of the surface passivation layer at positions corresponding to the P-type doping region and the N-type doping region, and sintering to obtain a first electrode and a second electrode, wherein the electrode paste comprises silver, an organic carrier, and a first glass powder, the first glass powder comprises a burn-through oxide, and the mass content of silver is 85% to 90% based on the total mass of the electrode paste;

[0139] (12) Preparing a leakage channel: printing a leakage channel paste on the surface of the surface passivation layer, and then drying to obtain a leakage channel. The leakage channel paste includes silver, an organic carrier, and a second glass powder, the second glass powder does not include a burn-through oxide, and the mass content of silver is 80% to 85% based on the total mass of the leakage channel paste. The leakage channel does not penetrate the surface passivation layer; along the third direction ( Figure 3 In the y direction), 200 leakage channels are set, and the size of each leakage channel is 20μm.

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

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

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

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

[0144] Performance tests were performed on the back-contact cells 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 / m 2) irradiation, the back-contact cell was tested for performance and an IV curve was obtained. Based on the IV curve and data from the test 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 cell was calculated using the formula FF = (Impp × Vmpp) / (Isc × Voc). The conversion efficiency (Eff) of the back-contact cell 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 providing a leakage channel, the reverse bias leakage current is greater than the maximum power point current, indicating that the risk of hot spot effect can be suppressed by providing a leakage channel. In addition, as shown in Examples 1-3, by setting the number of leakage channels to 200 to 400, the efficiency loss can be controlled to within 0.25% while suppressing the risk of hot spot effect. Furthermore, setting the number of leakage channels to approximately 200 can further reduce the efficiency loss to within 0.05%.

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

[0152]

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

[0154] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A back contact battery, characterized in that: include: A silicon substrate (20) having a first surface and a second surface opposite to each other; A first doping layer (211), the first doping layer (211) being disposed on the first surface; a second doping layer (221), the second doping layer (221) being disposed on the first surface and having a polarity opposite to that of the first doping layer (211); an isolation structure (24), the isolation structure (24) being arranged between the first doping layer (211) and the second doping layer (221) along a first direction, and the isolation structure (24) penetrating the first doping layer (211) and the second doping layer (221) along a second direction, the second direction being a thickness direction of the silicon substrate (20), and the first direction being perpendicular to the second direction; a first electrode (21), the first electrode (21) being electrically connected to the first doping layer (211); a second electrode (22), the second electrode (22) being electrically connected to the second doping layer (221); a surface passivation layer (23), wherein along the second direction, the surface passivation layer (23) is provided on a surface of the first doping layer (211) and the second doping layer (221) on a side facing away from the silicon substrate (20) and fills a portion of the isolation structure (24); A leakage channel (25) is provided on a 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).

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 -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, a total size of the leakage channel (25) is 10 μm to 10,000 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 size of the leakage channel (25) is 4 μm to 50 μm.

8. The back contact battery according to claim 1, characterized in that The back contact battery comprises a plurality of leakage channels (25), wherein the plurality of leakage channels (25) are arranged at intervals along a third direction, and the third direction 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 doping layer (211) and the second doping 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, 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 path (25) includes silver and a second glass frit, and the second glass frit does not include the burn-through oxide.

11. The back contact battery according to claim 1, characterized in that The back contact battery further comprises a first interface layer (212) and a second interface layer (222); along the second direction, the first interface layer (212) is arranged between the silicon substrate (20) and the first doping layer (211), and the second interface layer (222) is arranged between the silicon substrate (20) and the second doping layer (221).

12. A method for preparing a back contact battery, characterized in that: include: A first doping layer (211) and a second doping layer (221) are prepared on a first surface of a silicon substrate (20), wherein the first doping layer (211) and the second doping layer (221) have opposite polarities; An isolation structure (24) is prepared, wherein the isolation structure (24) is disposed between the first doping layer (211) and the second doping layer (221) along a first direction, and the isolation structure (24) penetrates the first doping layer (211) and the second doping layer (221) along a second direction, wherein the second direction is a thickness direction of the silicon substrate (20), and the first direction is perpendicular to the second direction; Before preparing the first electrode (21) and the second electrode (22), a surface passivation layer (23) is prepared, wherein, along the second direction, the surface passivation layer (23) is provided on a surface of the first doping layer (211) and the second doping layer (221) on a side facing away from the silicon substrate (20) and fills a portion of the isolation structure (24); preparing the first electrode (21) and the second electrode (22), wherein the first electrode (21) is electrically connected to the first doping layer (211), and the second electrode (22) is electrically connected to the second doping layer (221); After preparing the first electrode (21) and the second electrode (22), a leakage channel (25) is prepared. The leakage channel (25) is arranged on a surface of the surface passivation layer (23) that is away from 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, wherein: The preparation of the leakage channel (25) comprises: Applying leakage channel (25) slurry to the surface of the surface passivation layer (23) on the side away from the silicon substrate (20) by printing or inkjet; The leakage path (25) slurry is solidified by drying, ultraviolet curing or sintering to obtain the leakage path (25).

14. The method for preparing a back contact battery according to claim 13, wherein: The leakage path (25) slurry comprises silver paste, and the sintering temperature of the silver paste is 670° C. to 820° C.; or, The leakage channel (25) slurry comprises copper slurry, and the drying temperature of the copper slurry is 200° C. to 300° C.

15. A photovoltaic module, characterized in that: Comprising a back contact cell according to any one of claims 1-11.

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