Solar cell and photovoltaic module

Abstract

A solar cell. The solar cell comprises a first anti-reflection layer, a passivation layer, an electrode emission layer, a silicon-based bottom layer, a tunneling oxide layer, a doped polycrystalline silicon layer and a second anti-reflection layer, which are stacked, wherein a first electrode and a second electrode are respectively provided on the first anti-reflection layer and the second anti-reflection layer; a low-work-function conductive layer is provided in the doped polycrystalline silicon layer; and the low-work-function conductive layer is in direct contact with the second electrode.

Description

Solar cells and photovoltaic modules

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 24, 2023, with application number 202321970187.9 and application name “Solar Cells, Photovoltaic Modules”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of solar cells, and in particular to a solar cell and a photovoltaic module. Background Art

[0003] Solar cells are thin semiconductor wafers that directly generate electricity from sunlight. Currently, in addition to traditional crystalline silicon solar cells, solar cells with tunneling passivation contact structures are gaining market attention due to their higher photoelectric conversion efficiency. These passivation contact structures typically consist of a stacked tunneling oxide layer and a doped polysilicon layer, with the doped polysilicon layer in direct contact with a metal electrode to form a current path. Currently, metal electrodes are typically produced using a high-temperature slurry screen printing process, which can easily burn through the doped polysilicon layer, damaging the cell structure.

[0004] Summary of the Invention

[0005] In view of this, the solar cell provided in the present application adds a low work function conductive layer in the tunnel passivation contact structure, which can overcome the problem of high-temperature metal paste burn-through.

[0006] In a first aspect, the present application provides a solar cell, comprising a stacked first anti-reflection layer, a passivation layer, an electrode emission layer, a silicon base layer, a tunneling oxide layer, a doped polysilicon layer, and a second anti-reflection layer; a first electrode and a second electrode are provided on the first anti-reflection layer and the second anti-reflection layer, respectively;

[0007] Wherein, a low work function conductive layer is provided in the doped polycrystalline layer; and the low work function conductive layer is in direct contact with the second electrode.

[0008] The low work function conductive layer has a good field passivation effect and can effectively collect and transfer electrons. At the same time, the low work function conductive layer is in direct contact with the second electrode. During the preparation of the battery, it serves as the main recipient of high-temperature metal slurry and can effectively improve the problem of metal slurry burn-through.

[0009] Optionally, the material of the low work function conductive layer is selected from Ca, Mg, Ba, Ga, Li, Ce, Tb, Gd, Y, Nd, Lu, Th, Sc, La, U or Hf.

[0010] Optionally, the thickness of the doped polycrystalline layer is in the range of 10 nm to 120 nm.

[0011] Optionally, the thickness of the low work function conductive layer is smaller than the thickness of the doped polysilicon layer.

[0012] Optionally, the thickness of the low work function conductive layer is in the range of 2 nm to 100 nm.

[0013] Optionally, the projection of the second electrode along the first direction on the plane where the end face of the low work function conductive layer away from the tunneling oxide layer is located falls into the end face of the low work function conductive layer away from the tunneling oxide layer; wherein the first direction points from the second anti-reflection layer to the first anti-reflection layer.

[0014] Optionally, the projection of the second electrode along the first direction on the plane where the end face of the low work function conductive layer away from the tunneling oxide layer is located coincides with the end face of the low work function conductive layer away from the tunneling oxide layer; wherein the first direction is from the second anti-reflection layer to the first anti-reflection layer.

[0015] Optionally, the second electrode penetrates the second anti-reflection layer and protrudes relative to a surface of the second anti-reflection layer away from the doped polysilicon layer.

[0016] Optionally, the second electrode penetrates the second anti-reflection layer and extends into the doped polysilicon layer to directly contact the low work function conductive layer.

[0017] Optionally, the material of the tunnel oxide layer includes but is not limited to at least one of silicon oxide, titanium oxide, and aluminum oxide.

[0018] Optionally, the material of the passivation layer includes but is not limited to at least one of silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide.

[0019] Optionally, the material of the first anti-reflection layer includes but is not limited to at least one of silicon oxide, silicon nitride, and silicon oxynitride, and the material of the second anti-reflection layer includes but is not limited to at least one of silicon oxide, silicon nitride, and silicon oxynitride.

[0020] Optionally, the low work function conductive layer is in direct contact with the tunneling oxide layer.

[0021] Optionally, the silicon base layer is an N-type silicon base layer, and the doped polysilicon layer is a phosphorus-doped polysilicon layer.

[0022] A second aspect of the present application provides a photovoltaic assembly, which includes the solar cell provided in the first aspect of the present application.

[0023] Optionally, the photovoltaic module further includes a front cover, a back cover, a first packaging film and a second packaging film, the front cover is bonded to one side of the solar cell through the first packaging film, and the back cover is bonded to the other side of the solar cell through the second packaging film.

[0024] Due to the presence of the solar cell, the photovoltaic module has higher photoelectric conversion efficiency and higher market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] FIG1 is a schematic diagram of the cross-sectional structure of a solar cell provided in one embodiment of the present application.

[0027] FIG2 is a schematic diagram of the cross-sectional structure of a solar cell provided in another embodiment of the present application.

[0028] FIG3 is a schematic diagram of the cross-sectional structure of a solar cell provided in yet another embodiment.

[0029] FIG4 is a schematic diagram of the cross-sectional structure of a solar cell provided in yet another embodiment.

[0030] FIG5 is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of the present application.

[0031] Explanation of the accompanying numbers: 100 - solar cell; 11 - first anti-reflection layer; 12 - passivation layer; 20 - electrode emission layer; 30 - silicon base layer; 40 - tunneling oxide layer; 50 - doped polysilicon layer; 60 - second anti-reflection layer; 70 - first electrode; 80 - second electrode; 90 - low work function conductive layer; 1000 - photovoltaic module; 1002 - front cover; 1004 - back cover; 1006 - first packaging film; 1008 - second packaging film. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0033] It should be understood that, in the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0034] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected or indirectly connected through an intermediate medium, and it can be internal communication between two elements or an interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0035] The above disclosure provides many different embodiments or examples for realizing different structures of the embodiments of the present application. In order to simplify the disclosure of the embodiments of the present application, the components and settings of specific examples are described above. Of course, they are merely examples and are not intended to limit the present application. In addition, the embodiments of the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the embodiments of the present application provide examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0036] Throughout this specification, references to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" indicate that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0037] Referring to Figure 1 , an embodiment of the present application provides a solar cell 100 comprising a stacked first anti-reflection layer 11, a passivation layer 12, an electrode emitter layer 20, a silicon base layer 30, a tunneling oxide layer 40, a doped polysilicon layer 50, and a second anti-reflection layer 60. A first electrode 70 and a second electrode 80 are provided on the first anti-reflection layer 11 and the second anti-reflection layer 60, respectively. That is, the first electrode 70 is provided on the first anti-reflection layer 11, and the second electrode 80 is provided on the second anti-reflection layer 60. In this embodiment of the present application, "providing the first electrode 70 on the first anti-reflection layer 11" means that the first electrode 70 may be stacked on the surface of the first anti-reflection layer 11; or, the first electrode 70 may penetrate / partially be embedded in the first anti-reflection layer 11 but may not penetrate the first anti-reflection layer 11 and may protrude from the surface of the first anti-reflection layer 11 away from the passivation layer 12. In this embodiment of the present application, "providing the second electrode 80 on the second anti-reflection layer 60" means that the second electrode 80 penetrates the second anti-reflection layer 60 and protrudes from the surface of the second anti-reflection layer 60 away from the doped polysilicon layer 50. Furthermore, the first electrode 70 can also penetrate the first anti-reflection layer 11 and extend into the passivation layer 12. The present application does not limit the specific position where the first electrode 70 extends into the interior of the solar cell 100. Ordinary technicians in this field can make a selection based on actual needs to complete the photoelectric conversion.

[0038] In the embodiment of the present application, a low work function conductive layer 90 is provided in the doped polysilicon layer 50. The low work function conductive layer 90 is in direct contact with the second electrode 80. In the embodiment of the present application, the low work function conductive layer 90 is provided in the doped polysilicon layer 50, including but not limited to the following: the low work function conductive layer 90 extends from the surface of the tunneling oxide layer 40 toward the second electrode 80. At the same time, the surface of the low work function conductive layer 90, except for the end surface in contact with the second electrode 80 and the end surface in contact with the tunneling oxide layer 40, is surrounded by the doped polysilicon layer 50.

[0039] The present application adds a low work function conductive layer 90 to the tunnel passivation contact structure, which has a good field passivation effect and can effectively collect free electrons, so it can ensure the smooth and efficient transmission of electrons in the solar cell and ensure the normal operation of the solar cell. In addition, in the preparation process of the existing tunnel passivation contact solar cell, a high-temperature metal paste is printed on the surface of the second anti-reflection layer 60 (that is, the back anti-reflection layer of the solar cell), and the metal paste burns through the second anti-reflection layer 60 to form a second electrode 80, and the second electrode 80 is in direct contact with the doped polysilicon layer 50 to collect electrons. However, in the above process, the problem of the metal paste burning through the doped polysilicon layer 50 often occurs. The low work function conductive layer 90 in the battery of the present application is in direct contact with the second electrode 80. In the preparation process of the battery, it serves as the main recipient of the high-temperature metal paste and can effectively improve the problem of the metal paste burning through.

[0040] Generally, during use of a solar cell, one side of the first anti-reflection layer 11 is the front side of the solar cell (facing sunlight), and the side with the tunnel passivation contact structure is the back side of the solar cell. Therefore, the first anti-reflection layer 11 is also referred to as the "front anti-reflection layer," and the second anti-reflection layer 60 is also referred to as the "back anti-reflection layer."

[0041] In addition, in the prior art, in order to avoid the problem of metal paste burning through the doped polysilicon layer, the existing process must rely on increasing the thickness of the doped polysilicon layer to solve the problem (generally, in the prior art, the thickness of the doped polysilicon layer in the tunnel passivation contact structure is greater than 120nm), which will in turn lead to an increase in the parasitic absorption phenomenon of the battery, affecting the photoelectric conversion efficiency of the battery. However, in the solar cell 100 provided in the present application, due to the presence of the low work function conductive layer 90, there is no need to increase the thickness of the doped polysilicon layer 50. In the solar cell 100 of the present application, the thickness of the doped polysilicon layer 50 can be less than or equal to 120nm, thereby reducing the parasitic absorption effect of the doped polysilicon layer 50, thereby improving the photoelectric conversion efficiency of the solar cell 100.

[0042] In some embodiments of the present application, the thickness of the doped polysilicon layer 50 is within the range of 10 nm to 120 nm. For example, the thickness of the doped polysilicon layer 50 can be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, etc. Controlling the thickness of the doped polysilicon layer 50 within the above range can effectively reduce parasitic absorption effects, promote electron tunneling, and improve the photoelectric conversion efficiency of the battery.

[0043] In some embodiments of the present application, the silicon base layer 30 is an N-type silicon base layer. The electrode emitter layer 20 is a boron-doped electrode emitter layer. The doped polysilicon layer 50 is a phosphorus-doped polysilicon layer. The material of the tunneling oxide layer 40 includes, but is not limited to, at least one of silicon oxide, titanium oxide, and aluminum oxide. The material of the passivation layer 12 includes, but is not limited to, at least one of silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide. The material of the first anti-reflection layer 11 and the second anti-reflection layer 60 are each independently selected from at least one of silicon oxide, silicon nitride, and silicon oxynitride. In some specific embodiments, the passivation layer 12 is an aluminum oxide layer. The first anti-reflection layer 11 and the second anti-reflection layer 60 are both silicon nitride layers. In some specific embodiments, the refractive index of the first anti-reflection layer 11 is different from the refractive index of the second anti-reflection layer 60. The materials of the first electrode 70 and the second electrode 80 are each independently selected from, but are not limited to, metal materials such as silver and aluminum.

[0044] In some embodiments of the present application, the thickness of the low work function conductive layer 90 is less than that of the doped polysilicon layer 50. At this time, it can be understood that the second electrode 80 passes through the second anti-reflection layer 60 and extends in the doped polysilicon layer 50 to directly contact the low work function conductive layer 90. In this way, the second electrode 80 can collect electrons from the low work function conductive layer 90 and directly collect electrons from the doped polysilicon layer 50, which is more efficient. In addition, the low work function conductive layer 90 is embedded in the doped polysilicon layer 50, which can also prevent the low work function conductive layer 90 from being oxidized and corroded, thereby extending the service life of the solar cell. Specifically, the low work function conductive layer 90 is embedded in the doped polysilicon layer 50, which means that the portion of the surface of the low work function conductive layer 90 that is not in contact with the second electrode 80 and the portion that is not in contact with the tunneling oxide layer 40 are all surrounded by the material of the doped polysilicon layer 50.

[0045] In some embodiments of the present application, the thickness of the low work function conductive layer 90 is in the range of 2nm-100nm. For example, the thickness of the low work function conductive layer 90 can be, but is not limited to, 2nm, 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, etc. Controlling the thickness of the low work function conductive layer 90 within the above range can not only fully reduce the risk of high-temperature metal paste burn-through during battery preparation, greatly improve the yield rate, but also achieve a high photoelectric conversion rate.

[0046] In some embodiments of the present application, the low-work-function conductive layer 90 is in direct contact with the tunneling oxide layer 40. That is, the low-work-function conductive layer 90 extends from the surface of the tunneling oxide layer 40 toward the second electrode 80. In some specific embodiments, the low-work-function conductive layer 90 extends from the surface of the tunneling oxide layer 40 toward the second electrode 80, and its thickness is less than the thickness of the doped polysilicon layer 50. The second electrode 80 penetrates the second anti-reflection layer 60 and extends into the doped polysilicon layer 50, directly contacting the low-work-function conductive layer 90.

[0047] In some embodiments of the present application, the orthographic projection of the second electrode 80 in the first direction falls into the low work function conductive layer 90, and the orthographic projection of the second electrode 80 in the first direction overlaps with the low work function conductive layer 90; wherein, the first direction points from the second anti-reflection layer 60 to the first anti-reflection layer 11. That is, the second electrode 80 is a patterned electrode (gate line), and the shape of the second electrode 80 is the same as the shape of the low work function conductive layer 90. In an embodiment of the present application, the projection of the second electrode 80 on the low work function conductive layer 90 along the first direction coincides with the end face of the low work function conductive layer 90 away from the tunneling oxide layer 40. In some embodiments of the present application, the sidewalls of the low work function conductive layer 90 are perpendicular to the tunneling oxide layer 40 (as shown in FIG. 1 , the cross-sectional dimensions of the low work function conductive layer 90 are equal everywhere). However, at present, the low work function conductive layer 90 is generally prepared by an etching process. Taking into account the etching accuracy, the sidewalls of the low work function conductive layer 90 are not necessarily perpendicular to the tunneling oxide layer 40. Please refer to Figure 2. In the direction from the doped polysilicon layer 50 to the tunneling oxide layer 40, the cross-sectional size of the low work function conductive layer 90 gradually increases (that is, its sidewalls are not perpendicular to the tunneling oxide layer 40, and its sidewalls can be flat or curved). It should be noted that the cross-section of the low work function conductive layer 90 refers to: the cross-section obtained by cutting the low work function conductive layer 90 with a plane parallel to the tunneling oxide layer 40. At this time, the above-mentioned orthographic projection of the second electrode 80 overlaps with the low work function conductive layer. It can be understood that the orthographic projection of the second electrode 80 overlaps with the first surface of the low work function conductive layer 90, and its first surface is the surface of the low work function conductive layer 90 facing away from the tunneling oxide layer 40. In the embodiment of the present application, the projection of the second electrode 80 on the low work function conductive layer 90 along the first direction coincides with a plane of the low work function conductive layer 90 away from the tunneling oxide layer 40 .

[0048] In some embodiments, referring to FIG3 , the orthographic projection of the second electrode 80 in the first direction falls into the low work function conductive layer 90, and the edge of the orthographic projection of the second electrode 80 in the first direction is at a certain distance from the edge of the low work function conductive layer 90. The first direction points from the second anti-reflection layer 60 to the first anti-reflection layer 11. In this way, the low work function conductive layer 90 can well carry the electrode paste to prevent the doped polysilicon layer 50 from being burned through. At this time, the sidewall of the low work function conductive layer 90 may be perpendicular to the tunneling oxide layer 40 or may not be perpendicular to the tunneling oxide layer 40. In an embodiment of the present application, the edge of the projection of the second electrode 80 on the low work function conductive layer 90 along the first direction is spaced from the edge of the plane of the low work function conductive layer 90 away from the tunneling oxide layer 40.

[0049] In other specific embodiments, referring to FIG. 4 , taking into account fabrication accuracy, the low work function conductive layer 90 may fall within the orthographic projection of the second electrode 80 in the first direction, and the distance from the edge of the low work function conductive layer 90 to the edge of the orthographic projection of the second electrode 80 is less than or equal to 10 μm. In the application embodiment, the projection of the second electrode 80 along the first direction on the plane where the end face of the low work function conductive layer 90 away from the tunneling oxide layer 40 is located covers the end face of the low work function conductive layer 90 away from the tunneling oxide layer 40, and its area is larger than the end face of the low work function conductive layer 90 away from the tunneling oxide layer 40. Furthermore, the distance from the edge of the end face of the low work function conductive layer 90 away from the tunneling oxide layer 40 to the projection is less than or equal to 10 μm. For example, the above distance may be, but is not limited to, 0.1 μm, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 9.5 μm, etc. It should be noted that when the cross-sectional size of the low work function conductive layer 90 gradually increases in the direction from the doped polysilicon layer 50 toward the tunnel oxide layer 40, the above situation refers to the distance from the edge of the first surface of the low work function conductive layer 90 (the first surface is the surface of the low work function conductive layer 90 facing away from the tunnel oxide layer 40) to the edge of the orthographic projection of the second electrode 80 is less than or equal to 10 μm. When the distance from the edge of the low work function conductive layer 90 to the edge of the orthographic projection of the second electrode 80 is less than or equal to 10 μm, the risk of the high-temperature electrode slurry burning through the doped polysilicon layer 50 is extremely small during the battery manufacturing process. Therefore, the problem of the electrode paste burning through the doped polysilicon layer 50 can be effectively improved, and the second electrode 80 can also directly collect electrons from the doped polysilicon layer 50. In this case, the sidewalls of the low work function conductive layer 90 may be perpendicular to the tunneling oxide layer 40 or not.

[0050] It should be noted that in Figures 1 to 4 of the present application, the first anti-reflection layer 11, the passivation layer 12 and the electrode emission layer 20 are wavy. This is only to cater to the pyramid-shaped light-trapping structure formed on one side surface (front) of the silicon base layer due to the texturing process. It is a commonly used drawing style in the field and does not constitute any restriction on the shape of the first anti-reflection layer 11, the passivation layer 12 and the electrode emission layer 20 in the present application.

[0051] In some embodiments of the present application, the work function of the low-work-function conductive layer 90 is in the range of 2.7 eV to 3.9 eV. The work function is defined as "the minimum energy required to move an electron from the interior of a solid to the surface of the solid." For example, the work function of the low-work-function conductive layer 90 may be, but is not limited to, 2.7 eV, 2.8 eV, 2.9 eV, 3.0 eV, 3.1 eV, 3.2 eV, 3.3 eV, 3.4 eV, 3.5 eV, 3.6 eV, 3.7 eV, 3.8 eV, 3.9 eV, etc.

[0052] In some embodiments of the present application, the material of the low work function conductive layer 90 is selected from metal materials. In some specific embodiments, the material of the low work function conductive layer 90 is selected from at least one of Ca, Mg, Ba, Ga, Li, Ce, Tb, Gd, Y, Nd, Lu, Th, Sc, La, U, and Hf.

[0053] In some embodiments of the present application, the thickness of the tunnel oxide layer 40 is less than or equal to 2 nm, for example, 0.5 nm, 1.0 nm, 1.5 nm, 2.0 nm, etc.

[0054] In some embodiments of the present application, the thickness of the first anti-reflection layer 11 and the second anti-reflection layer 60 are each independently within the range of 10 nm to 120 nm. Controlling the thickness of the first anti-reflection layer 11 and the second anti-reflection layer 60 within the above range can not only ensure the performance of the cell, but also control the total thickness of the solar cell to a relatively thin thickness. For example, the thickness of the first anti-reflection layer 11 and the second anti-reflection layer 60 can each independently be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, etc.

[0055] In some embodiments of the present application, the thickness of the passivation layer 12 is within the range of 5 nm to 20 nm. Controlling the thickness of the passivation layer 12 within this range can ensure a good passivation effect while keeping the total thickness of the solar cell within a smaller range. For example, the thickness of the passivation layer 12 can be 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, etc.

[0056] In a specific embodiment, the solar cell includes a first anti-reflection layer 11 (specifically a silicon nitride layer with a thickness of 80 nm), a passivation layer 12 (specifically an aluminum oxide layer with a thickness of 12 nm), an electrode emission layer 20, a silicon base layer 30 (specifically an N-type silicon base layer with a thickness of 130 μm), a tunneling oxide layer 40 (specifically a silicon oxide layer with a thickness of 1.6 nm), a doped polysilicon layer 50 (specifically a phosphorus-doped polysilicon layer with a thickness of 100 nm and a square resistance of 40 Ω / sqr), and the like. A second anti-reflection layer 60 (specifically, a silicon nitride layer with a thickness of 80 nm) is provided, wherein a low work function conductive layer 90 with a thickness of 50 nm is provided in the doped polysilicon layer 50, which extends from the surface of the tunneling oxide layer 40 toward the second anti-reflection layer 60; a first electrode 70 and a second electrode 80 are provided on the first anti-reflection layer 11 and the second anti-reflection layer 60, respectively, the second electrode 80 penetrates the second anti-reflection layer 60 and is in direct contact with the low work function conductive layer 90, and the pattern of the second electrode 80 is the same as the shape of the low work function conductive layer 90.

[0057] In some embodiments of the present application, the preparation of a solar cell may include the following steps:

[0058] S01, pre-treating the silicon wafer raw material;

[0059] S02, forming an electrode emission layer on one surface (front side) of the silicon wafer, and polishing the back side of the silicon wafer to obtain the electrode emission layer and the silicon base layer;

[0060] S03, depositing a tunnel oxide layer on the back side of the silicon wafer;

[0061] S04, depositing a low work function conductive pre-layer on the tunneling oxide layer;

[0062] S05. Preparing a mask on the low-work-function conductive prefabricated layer, etching the low-work-function metal layer in the non-masked area, and removing the mask layer to obtain a low-work-function conductive layer. In some specific embodiments, the pattern of the mask is consistent with the pattern of the preset second electrode.

[0063] S06, continuing to form a doped amorphous silicon thin film, and then performing high-temperature crystallization annealing to obtain a doped polysilicon layer; in some specific embodiments, the doped polysilicon layer is a phosphorus-doped polysilicon layer;

[0064] S07, preparing a passivation layer on the surface of the electrode emission layer;

[0065] S08, forming a first anti-reflection layer on the surface of the passivation layer; and forming a second anti-reflection layer on the surface of the doped polysilicon stacked structure away from the tunneling oxide layer;

[0066] S09. Prepare the first electrode and the second electrode separately by a printing process to obtain a solar cell. Electrode paste is printed on the surfaces of the first anti-reflection layer and the second anti-reflection layer respectively by printing, and then sintered at a high temperature to prepare the first electrode and the second electrode. In some specific embodiments, the printing is screen printing.

[0067] The present application also provides a photovoltaic module 1000, comprising the solar cell provided in the present application. As shown in FIG5 , the photovoltaic module 1000 further comprises a front cover 1002, a rear cover 1004, a first encapsulation film 1006, and a second encapsulation film 1008. The front cover 1002 is bonded to one side of the solar cell 100 via the first encapsulation film 1006. The rear cover 1004 is bonded to the other side of the solar cell 100 via the second encapsulation film 1008. Due to the inclusion of the solar cell provided in the present application, the photovoltaic module 1000 has good market competitiveness.

[0068] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A solar cell (100), characterized in that: The invention comprises a first anti-reflection layer (11), a passivation layer (12), an electrode emission layer (20), a silicon base layer (30), a tunneling oxide layer (40), a doped polysilicon layer (50) and a second anti-reflection layer (60) which are stacked; a first electrode (70) and a second electrode (80) are respectively provided on the first anti-reflection layer (11) and the second anti-reflection layer (60); Wherein, a low work function conductive layer (90) is provided in the doped polysilicon layer (50), and the low work function conductive layer (90) is in direct contact with the second electrode (80).

2. The solar cell (100) according to claim 1, characterized in that The thickness of the doped polysilicon layer (50) is in the range of 10nm-120nm.

3. The solar cell (100) according to claim 1, characterized in that The thickness of the low work function conductive layer (90) is smaller than the thickness of the doped polysilicon layer (50).

4. The solar cell (100) according to any one of claims 1 to 3, characterized in that: The thickness of the low work function conductive layer (90) is in the range of 2nm-100nm.

5. The solar cell (100) according to any one of claims 1 to 3, characterized in that: The projection of the second electrode (80) along the first direction on the plane where the end surface of the low work function conductive layer (90) away from the tunneling oxide layer (40) is located falls into the end surface of the low work function conductive layer (90) away from the tunneling oxide layer (40); Wherein, the first direction points from the second anti-reflection layer (60) to the first anti-reflection layer (11).

6. The solar cell (100) according to claim 5, characterized in that: A projection of the second electrode (80) along the first direction on a plane where an end face of the low work function conductive layer (90) away from the tunneling oxide layer (40) is located coincides with the end face of the low work function conductive layer (90) away from the tunneling oxide layer (40).

7. The solar cell (100) according to any one of claims 1 to 6, characterized in that: The low work function conductive layer (90) is in direct contact with the tunneling oxide layer (40).

8. The solar cell (100) according to any one of claims 1 to 7, characterized in that: The material of the low work function conductive layer (90) is selected from Ca, Mg, Ba, Ga, Li, Ce, Tb, Gd, Y, Nd, Lu, Th, Sc, La, U or Hf.

9. The solar cell (100) according to any one of claims 1 to 8, characterized in that: The silicon base layer (30) is an N-type silicon base layer, and the doped polysilicon layer (50) is a phosphorus-doped polysilicon layer.

10. The solar cell (100) according to any one of claims 1 to 9, characterized in that: The second electrode (80) penetrates the second anti-reflection layer (60) and protrudes from a surface of the second anti-reflection layer (60) that is away from the doped polysilicon layer (50).

11. The solar cell (100) according to any one of claims 1 to 10, characterized in that: The second electrode (80) penetrates the second anti-reflection layer (60) and extends into the doped polysilicon layer (50) to directly contact the low work function conductive layer (90).

12. The solar cell (100) according to any one of claims 1 to 11, characterized in that: The material of the tunnel oxide layer (40) includes but is not limited to at least one of silicon oxide, titanium oxide and aluminum oxide.

13. The solar cell (100) according to any one of claims 1 to 12, characterized in that: The material of the passivation layer (12) includes but is not limited to at least one of silicon oxide, silicon nitride, silicon oxynitride and aluminum oxide.

14. The solar cell (100) according to any one of claims 1 to 13, characterized in that: The material of the first anti-reflection layer (11) includes but is not limited to at least one of silicon oxide, silicon nitride and silicon oxynitride, and the material of the second anti-reflection layer (60) includes but is not limited to at least one of silicon oxide, silicon nitride and silicon oxynitride.

15. A photovoltaic module (1000), characterized in that: The photovoltaic module (1000) comprises the solar cell (100) according to any one of claims 1 to 14.

16. The photovoltaic assembly (1000) according to claim 15, characterized in that: The photovoltaic module (1000) further comprises a front cover plate (1002), a rear cover plate (1004), a first packaging film (1006) and a second packaging film (1008); the front cover plate (1002) is bonded to one side of the solar cell (100) via the first packaging film (1006), and the rear cover plate (1004) is bonded to the other side of the solar cell (100) via the second packaging film (1008).

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