Heterojunction solar cell and manufacturing method

Abstract

The present application provides a heterojunction solar cell and a manufacturing method thereof, which comprises an n-type or p-type silicon sheet that is n-type or p-type doped and has a front and a back surface facing each other, a first passivation layer and a second passivation layer that are sequentially provided on the front surface of the n-type or p-type silicon sheet, a third passivation layer and a fourth passivation layer that are sequentially provided on the back surface of the n-type or p-type silicon sheet, and a microcrystalline or nanocrystalline silicon carbide layer that is provided on one side of the fourth passivation layer away from the n-type or p-type silicon sheet, the microcrystalline or nanocrystalline silicon carbide layer forms a pn junction with the n-type or p-type silicon sheet through n-type or p-type doping, and the atomic percentage of carbon element in the silicon carbide layer is greater than the atomic percentage of oxygen element. The heterojunction solar cell of the present application enhances the performance of the solar cell, and the carbon element and the oxygen element have a fixing effect on the hydrogen element in the silicon carbide layer, which is advantageous in reducing the loss of hydrogen element.

Description

[Technical Field]

[0001] This application relates primarily to the field of photovoltaics, and more particularly to heterojunction solar cells and methods of manufacture. [Background technology]

[0002] Silicon-based heterojunction cells are one of the current mainstream high-efficiency solar cell technologies, boasting the advantages of simple structure, high conversion efficiency, and a low temperature coefficient, making them an important direction for the development of solar cells. The structure and process of silicon-based heterojunction cells are relatively simple: they start with an n- or p-type doped silicon substrate, form an intrinsic amorphous silicon layer and a p- or n-type amorphous silicon layer on one side of the silicon substrate, and then form an intrinsic amorphous silicon layer and an n-type amorphous silicon layer on the other side of the silicon substrate. Here, the p- or n-type amorphous silicon layer forms a pn junction with the n- or p-type doped silicon substrate.

[0003] In conventional silicon-based heterojunction cells, the p-type doping layer was amorphous silicon doped with boron element, but the doping amount was limited to an upper limit, resulting in low doping efficiency of the p-type doping layer, weakening the electric field of the pn junction on the back of the cell, increasing the recombination of photocarriers, and ultimately reducing the cell efficiency.

[0004] Therefore, how to increase the upper limit of doping of dopants and improve cell efficiency is an issue that needs to be resolved urgently. Summary of the Invention [Problem to be solved by the invention]

[0005] The technical problem to be solved by the present application is to provide a heterojunction solar cell and a manufacturing method thereof that have the advantages of a high upper doping limit and high cell efficiency. [Means for solving the problem]

[0006] In order to solve the above technical problems, the present application adopts a technology for a heterojunction solar cell comprising: a silicon substrate doped with n-type or p-type doping and having opposite front and back surfaces; a first passivation layer and a second passivation layer formed sequentially on the front surface of the silicon substrate; a third passivation layer and a fourth passivation layer formed sequentially on the back surface of the silicon substrate; and a silicon carbide layer formed on one side of the fourth passivation layer facing away from the silicon substrate, wherein the silicon carbide layer is doped with n-type or p-type doping to form a pn junction with the silicon substrate, and the atomic percentage of carbon in the silicon carbide layer is greater than the atomic percentage of oxygen.

[0007] In one embodiment of the present application, the first passivation layer is hydrogenated amorphous silicon oxide and the second passivation layer is hydrogenated nanocrystalline silicon.

[0008] In one embodiment of the present application, the third passivation layer is hydrogenated amorphous silicon and the fourth passivation layer is hydrogenated nanocrystalline silicon.

[0009] In one embodiment of the present application, the silicon substrate is n-type doped and the silicon carbide layer is p-type doped.

[0010] In one embodiment of the present application, the semiconductor device further comprises a fifth passivation layer provided on a surface of the second passivation layer away from the silicon substrate, and the material of the fifth passivation layer is hydrogenated n-type microcrystalline or nanocrystalline silicon carbide.

[0011] In one embodiment of the present application, the semiconductor device further comprises a first transparent conductive oxide thin film provided on a surface of the fifth passivation layer facing away from the silicon substrate, and a second transparent conductive oxide thin film provided on a surface of the fourth passivation layer facing away from the silicon substrate.

[0012] In one embodiment of the present application, the device further comprises an anti-reflection thin film provided on one surface of the first transparent conductive oxide thin film that faces away from the silicon substrate.

[0013] In one embodiment of the present application, the device further comprises a first electrode and a second electrode in contact with the first transparent conductive oxide thin film and the second transparent conductive oxide thin film, respectively, and the first electrode and / or the second electrode is manufactured by electroplating or chemical plating.

[0014] In one embodiment of the present application, the atomic percentage of the carbon element in the silicon carbide layer is 7 times or more the atomic percentage of the oxygen element.

[0015] In order to solve the above technical problems, the present application further provides a method for manufacturing a heterojunction solar cell, comprising the steps of: providing an n-type or p-type silicon sheet having opposite front and back surfaces; sequentially forming a first passivation layer and a second passivation layer on the front surface of the n-type or p-type silicon sheet; sequentially forming a third passivation layer and a fourth passivation layer on the back surface of the n-type or p-type silicon sheet; and forming a silicon carbide layer on a surface of the fourth passivation layer facing away from the n-type or p-type silicon sheet, wherein the silicon carbide layer is doped n-type or p-type to form a p-n junction with the n-type or p-type silicon sheet, and the atomic percentage of carbon in the silicon carbide layer is greater than the atomic percentage of oxygen.

[0016] The heterojunction solar cell of the present invention employs a doped silicon carbide layer and an n-type or p-type silicon sheet to form a pn junction, thereby increasing the upper limit of doping of the dopant in the silicon sheet layer and thereby improving the performance of the solar cell. Carbon and oxygen elements have a fixing effect on hydrogen in the silicon carbide layer, which is advantageous in reducing hydrogen loss.

[0017] In order to make the above objects, features, and advantages of the present application more clearly understandable, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional schematic diagram of a heterojunction solar cell according to an embodiment of the present application. [Figure 2] 1 is an exemplary flowchart of a method for manufacturing a heterojunction solar cell according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to make the above objects, features, and advantages of the present application more clearly understandable, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0020] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application; however, the present application may also be practiced in other ways other than those described herein, and therefore the present application is not limited to the specific embodiments disclosed below.

[0021] As set forth in this application and the claims, unless the context clearly indicates otherwise, terms such as "a," "one," "one," "a kind," and / or "the" do not specifically refer to the singular but may also include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, and do not constitute an exclusive list of these steps and elements; a method or apparatus may include other steps or elements.

[0022] It should also be noted that the use of terms such as "first" and "second" to define components is merely to facilitate distinguishing between corresponding components, and that unless otherwise stated, the terms do not have any special meaning and therefore should not be understood as limiting the scope of protection of the present application. Furthermore, although the terms used in the present application are selected from well-known terms, some terms described in the specification of the present application have been selected by the applicant at his / her own discretion, and their detailed meanings will be explained in the relevant parts of the description of this specification. It is also required to understand the present application not only by the actual terms used but also by the meanings contained in each term.

[0023] Flowcharts are used herein to describe operations performed by systems according to embodiments of the present application. It will be understood that the operations described above or below are not necessarily intended to be performed in exact order. In contrast, various steps may be processed in reverse order or simultaneously. Concurrently, other operations may be added to these processes, or operations of one or more steps may be deleted from these processes.

[0024] The pn junction in a heterojunction solar cell consists of a doped silicon substrate and a material layer located on one side of the silicon substrate and doped with a dopant of opposite polarity to the dopant in the silicon substrate. In conventional technology, the upper doping limit in this material layer is low. The heterojunction solar cell of the present application has the advantage of a high upper doping limit.

[0025] Next, the heterojunction solar cell of the present application will be described with reference to specific embodiments.

[0026] 1 is a cross-sectional schematic diagram of a heterojunction solar cell according to one embodiment of the present application. As shown in FIG. 1, the heterojunction solar cell 100 includes a silicon substrate 110, a first passivation layer 120, a second passivation layer 130, a third passivation layer 140, a fourth passivation layer 150, and a silicon carbide layer 160.

[0027] Specifically, as shown in FIG. 1 , the silicon substrate 110 is subjected to n-type or p-type doping. The material of the silicon substrate 110 includes one or more of single crystal silicon and polycrystalline silicon. Through the doping process, the single crystal silicon may be doped with phosphorus (P) to form an n-type silicon substrate 110, or may be doped with boron (B) to form a p-type silicon substrate 110. It is understood that the doping element in the silicon substrate 110 is not limited to the above-mentioned phosphorus and boron elements, but may be other elements capable of forming n-type and p-type silicon substrates.

[0028] Furthermore, the silicon substrate 110 is not limited to a particular size or shape. The silicon substrate 110 may be a circular substrate having other diameters, such as a 200 mm diameter, a 300 mm diameter, or a 450 mm diameter. If desired, the silicon substrate 110 may be a polygonal, square, rectangular, curved, or other non-circular workpiece, such as a polygonal workpiece.

[0029] As shown in FIG. 1, the silicon substrate 110 has a front surface 110a and a back surface 110b that face each other along a thickness direction D1, and the front surface 110a refers to the surface of the silicon substrate 110 facing upward in FIG.

[0030] In one embodiment, the silicon substrate 110 is an n-type doped silicon substrate. For convenience of explanation, unless otherwise specified, all silicon substrates 110 described below are n-type doped silicon substrates.

[0031] 1 , the first passivation layer 120 is disposed on the front surface 111a of the silicon substrate 110, and the second passivation layer 130 is disposed on one surface away from the silicon substrate 110 along the thickness direction D1 of the first passivation layer 120. That is, the first passivation layer 120 and the second passivation layer 130 are sequentially disposed on the front surface 110a of the silicon substrate 110. The method for sequentially forming the first passivation layer 120 and the second passivation layer 130 on the front surface 110a of the silicon substrate 110 is to use VHF plasma enhanced chemical vapor deposition (VHF-PECVD) to sequentially form the first passivation layer 120 and the second passivation layer 130 on the front surface 110a of the silicon substrate 110, where the thickness of the first passivation layer 120 is 0.8 to 1.5 nm, and the thickness of the second passivation layer 130 is 3 to 4 nm. In some embodiments, the method further includes performing a damage removal cleaning and flocking process on the silicon substrate 110 before forming the first passivation layer 120, where the damage removal cleaning can remove damage on the front surface 110a and back surface 110b of the silicon substrate 110, and the flocking process can form pyramid piles to reduce the reflectivity of the silicon substrate 110 to light.

[0032] In one embodiment, the first passivation layer is hydrogenated amorphous silicon oxide, and the second passivation layer is hydrogenated nanocrystalline silicon. Compared with monocrystalline silicon oxide and amorphous silicon oxide, using hydrogenated amorphous silicon oxide for the first passivation layer is advantageous in that it increases the hydrogen content in the first passivation layer, thereby improving the passivation performance of the first passivation layer and reducing the probability of interfacial epitaxial crystal growth, thereby increasing the photocurrent density of the battery. Furthermore, oxygen atoms in the first passivation layer can form hydrogen bonds with hydrogen atoms, thereby preventing hydrogen atoms from diffusing from the first passivation layer. The conductivity of the second passivation layer using nanocrystalline silicon is superior to that of the second passivation layer using amorphous silicon, thereby reducing the resistivity of the second passivation layer and increasing the fill factor (FF) of the battery. The combination of the first and second passivation layers provides excellent passivation while ensuring that the conductivity of the passivation layer meets requirements. In some embodiments, the size of the nanocrystalline silicon in the second passivation layer is 2-5 nm, and the crystallinity of the second passivation layer is 10%-70%. Here, "hydrogenation" refers to the introduction of hydrogen atoms (H) into a material layer (e.g., the first passivation layer, the second passivation layer). These hydrogen atoms can neutralize dangling bonds and defects in the material layer, thereby reducing carrier recombination and ultimately improving battery efficiency. Unless otherwise specified, the above explanation of "hydrogenation" also applies to the following description and will not be repeated.

[0033] In another embodiment, as shown in FIG. 1 , the solar cell 100 further includes a fifth passivation layer 170 disposed on the surface of the second passivation layer 130 away from the silicon substrate 110. The fifth passivation layer 170 is made of hydrogenated n-type microcrystalline or nanocrystalline silicon carbide. When the silicon carbide in the fifth passivation layer 170 is microcrystalline silicon carbide, its crystal grain size is 10 to 100 nm. The atomic percentage of oxygen in the fifth passivation layer can be greater than, equal to, or less than the atomic percentage of carbon. The fifth passivation layer 170 serves the roles of electron transport and electric field passivation, thereby improving the performance of the cell.

[0034] In some embodiments, the method for manufacturing the fifth passivation layer 170 comprises depositing the fifth passivation layer 170 on a surface of the second passivation layer 130 facing away from the silicon substrate 110 using VHF plasma enhanced chemical vapor deposition (VHF-PECVD), where the thickness of the fifth passivation layer 170 is 10-20 nm. In the previous embodiment, the second passivation layer 130 uses hydrogenated nanocrystalline silicon, and the hydrogenated nanocrystalline silicon at the interface between the second passivation layer 130 and the fifth passivation layer 170 can be a seed layer for n-type microcrystalline or nanocrystalline silicon carbide in the fifth passivation layer, which is advantageous for increasing the crystallinity of the fifth passivation layer.

[0035] 1 , the third passivation layer 140 is located on the back surface 110b of the silicon substrate 110, and the fourth passivation layer 150 is formed on one side of the third passivation layer 140 facing away from the silicon substrate 110, i.e., the third passivation layer 140 and the fourth passivation layer 150 are sequentially formed on the back surface 110b of the silicon substrate 110. In some embodiments, the manufacturing methods for the third passivation layer 140 having a thickness of 5 to 10 nm and the fourth passivation layer 150 having a thickness of 3 to 4 nm may be the same as those for the first passivation layer 120 and the second passivation layer 130.

[0036] In one embodiment, the third passivation layer is hydrogenated amorphous silicon, and the fourth passivation layer is hydrogenated nanocrystalline silicon. Using amorphous silicon as the third passivation layer material helps increase the hydrogen content in the third passivation layer compared to using hydrogenated nanocrystalline silicon, thereby improving the passivation effect. Because the high-concentration hydrogen plasma during processing has an etching effect on amorphous silicon, the thickness of the third passivation layer may be smaller than the designed thickness. Therefore, nanocrystalline silicon is used as the fourth passivation layer material, thus serving as an auxiliary passivation layer and thereby ensuring the passivation effect. In some embodiments, the size of the nanocrystalline silicon in the fourth passivation layer is 2-5 nm, and the crystallinity of the fourth passivation layer is 10%-70%.

[0037] Continuing with FIG. 1 , a silicon carbide layer 160 is provided on one side of the fourth passivation layer 150 away from the silicon substrate 110. Here, the silicon carbide layer is n-type or p-type doped to form a p-n junction with the silicon substrate 110, and the atomic percentage of carbon in the silicon carbide layer is greater than the atomic percentage of oxygen. As described above, the silicon substrate 110 may be either an n-type silicon substrate or a p-type silicon substrate. When the silicon substrate 110 is an n-type silicon substrate, the silicon carbide layer 160 is a p-type doped silicon carbide layer that forms a p-n junction with the silicon substrate 110. Conversely, the silicon carbide layer 160 is an n-type doped silicon carbide layer. The silicon carbide layer 160 described below is p-type doped for ease of explanation. In some embodiments, the silicon carbide layer 160 is formed using the same method as the fourth passivation layer, the silicon carbide layer 160 has a thickness of 5 to 10 nm, and the silicon carbide may be microcrystalline silicon carbide or nanocrystalline silicon carbide. If the silicon carbide is microcrystalline silicon carbide, its particle size is 10 to 100 nm, and if the silicon carbide is nanocrystalline silicon carbide, its particle size is 2 to 5 nm.

[0038] In conventional technology, a p-type doped layer is typically obtained by doping amorphous silicon with boron. However, due to the low doping activation rate, the doping amount must be increased to increase the doping activation rate, which can result in overdoping and the formation of a dead layer. Furthermore, when microcrystalline silicon is doped with boron to obtain a p-type doped layer, the upper limit of the boron doping level in the microcrystalline silicon is low. The present application effectively solves this problem by doping silicon carbide. Because carbon is a chemical element of the same group as silicon, it can be efficiently incorporated into the silicon thin film structure during the manufacturing process, forming a stable carbon-silicon compound and improving the optical bandgap of solar cells. Furthermore, adding oxygen can further improve the optical bandgap, and because both oxygen and carbon have the ability to fix hydrogen, it can reduce the increase in internal defect density in the silicon carbide layer 160 due to the loss of hydrogen. At the same time, silicon carbide has a high doping limit, is less likely to form a dead layer, and can be microcrystallized to increase the doping activation concentration, so using p-type hydrogenated microcrystalline silicon carbide can improve the performance of silicon-based heterojunction batteries. In addition to using silicon carbide as the p-type layer, the present application further restricts the carbon content in the silicon carbide layer to be greater than the oxygen content, thereby allowing for the formation of more carbon-silicon bonds in the silicon carbide layer. On the one hand, compared with silicon oxide, silicon carbide has a wider band gap and a higher doping limit, thereby improving the doping amount and solar cell performance. On the other hand, when the doping element in the silicon carbide layer is boron, the oxygen in the silicon carbide layer can bond with boron to form boron-oxygen pairs, which can cause attenuation in the solar cell. Therefore, reducing the oxygen content is advantageous for reducing the boron-oxygen bonds.In some other embodiments, the atomic percentage of carbon element in the silicon carbon oxide layer is 7 times or more than the atomic percentage of oxygen element, which ensures that the doping amount in the silicon carbon oxide layer meets the requirements.

[0039] In one embodiment, the solar cell further comprises a first transparent conductive oxide thin film and a second transparent conductive oxide thin film. As shown in FIG. 1 , the first transparent conductive oxide thin film 180 is disposed on a side of the fifth passivation layer 170 facing away from the silicon substrate 110, and the second transparent conductive oxide thin film 190 is disposed on a side of the silicon carbide layer 160 facing away from the silicon substrate 110. In some embodiments, the method for manufacturing the transparent conductive oxide thin film comprises using physical vapor deposition (PVD) and reactive plasma deposition (RPD), wherein the first transparent conductive oxide thin film 180 and the second transparent conductive oxide thin film 190 have a thickness of 60-80 nm. It should be noted that the thicknesses of the first transparent conductive oxide thin film 180 and the second transparent conductive oxide thin film 190 may or may not be equal.

[0040] 1 , in another embodiment, the solar cell 100 further includes a first electrode 211 and a second electrode 212. Here, the first electrode 211 and the second electrode 212 are in contact with a first transparent conductive oxide thin film 180 and a second transparent conductive oxide thin film 190, respectively. The first transparent conductive oxide thin film 180 can prevent the first electrode 211 from directly contacting the fifth passivation layer 170, and the second transparent conductive oxide thin film 190 can prevent the second electrode 212 from directly contacting the silicon carbide layer 160, thereby avoiding a significant increase in resistance.

[0041] In some embodiments, the method for manufacturing the first and second electrodes comprises an electroplating or chemical plating method, and the material of the first and second electrodes comprises one or more of metallic copper, metallic aluminum, metallic nickel, and metallic tin. Compared to using screen-printed silver electrodes, manufacturing non-silver electrodes by electroplating or chemical plating has the advantage of lower cost.

[0042] As shown in FIG. 1 , in one embodiment, the solar cell 100 further includes an anti-reflective thin film 220 provided on one side of the first transparent conductive oxide thin film 180 away from the silicon substrate 110. In some embodiments, the number of anti-reflective thin films is not limited to one layer as shown in FIG. 1 , but may be any number, such as two or three layers. Materials for the anti-reflective thin film include, but are not limited to, one or more of silicon nitride, silicon oxide, magnesium fluoride, and titanium oxide. The anti-reflective thin film 220 can reduce the reflection of incident light from the solar cell and improve the cell's utilization rate of incident light.

[0043] The solar cell in the above embodiment employs a doped silicon carbide layer and a silicon substrate to form a pn junction. The atomic percentage of carbon in the silicon carbide layer is greater than the atomic percentage of oxygen, thereby increasing the upper limit of doping in the silicon carbide layer and thereby improving the performance of the solar cell. The carbon and oxygen elements have a fixing effect on the hydrogen in the silicon carbide layer, which is advantageous in reducing the loss of hydrogen.

[0044] Another aspect of the present application also proposes a method for manufacturing a heterojunction solar cell. Referring to an exemplary flowchart of the method for manufacturing a heterojunction solar cell in one embodiment of the present application shown in Figure 2, as shown in Figure 1, the manufacturing method includes the following steps:

[0045] Step S110: An n-type or p-type silicon sheet 110 having an opposing front surface 110a and a back surface 110b is provided.

[0046] Step S120: A first passivation layer 120 and a second passivation layer 130 are sequentially formed on the front surface 110a of the n-type or p-type silicon sheet 110.

[0047] Step S130: A third passivation layer 140 and a fourth passivation layer 150 are sequentially formed on the rear surface 110b of the n-type or p-type silicon sheet 110.

[0048] Step S140: On one side of the fourth passivation layer 150 away from the n-type or p-type silicon sheet 110, a silicon carbide layer 160 is formed which is doped with n-type or p-type doping to form a pn junction with the n-type or p-type silicon sheet 110, and in which the atomic percentage of carbon elements in the silicon carbide layer 160 is greater than the atomic percentage of oxygen elements.

[0049] For other details of the method for manufacturing the heterojunction solar cell of the present application, reference can be made to the above related descriptions, and a detailed description will not be given here.

[0050] The manufacturing method in the above embodiment employs a doped carbon dioxide layer and an n-type or p-type silicon sheet to form a pn junction. The atomic percentage of carbon atoms in the silicon carbide layer is greater than the atomic percentage of oxygen atoms, thereby increasing the upper limit of doping of dopants in the silicon carbide layer and thereby improving the performance of the solar cell. Carbon and oxygen elements have a fixing effect on hydrogen atoms in the silicon carbide layer, which is advantageous in reducing hydrogen loss.

[0051] While the basic concepts have been described above, it will be apparent to those skilled in the art that the above disclosure is merely illustrative and not limiting of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and amendments to the present application. Such modifications, improvements, and amendments are proposed herein and therefore fall within the spirit and scope of the exemplary embodiments of the present application.

[0052] At the same time, the present application uses specific terms to describe embodiments of the present application. For example, "one embodiment," "one embodiment," and / or "some embodiments" refer to features, configurations, or characteristics associated with at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment," "one embodiment," or "one alternative embodiment" mentioned more than once in different places in this specification do not necessarily refer to the same embodiment. Furthermore, some features, configurations, or characteristics of one or more embodiments of the present application may be combined as appropriate.

[0053] In some embodiments, numbers describing the number of components or attributes are used; however, it should be understood that the numbers describing such embodiments are, in some instances, modified using the modifiers "about," "approximately," or "approximately." Unless otherwise specified, "about," "approximately," or "approximately" means that the numerical value can vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations, and these approximations may vary depending on the characteristics required for particular embodiments. In some embodiments, the numerical parameters should be calculated using a given number of significant digits and ordinary methods of conserving digits. In some embodiments, the numerical fields and parameters used to determine the breadth of their ranges are approximations; however, in certain embodiments, such numerical values ​​are set as precisely as possible within the limits of their possible values.

Claims

1. A silicon substrate that is n-type doped and has opposing front and back surfaces; a first passivation layer and a second passivation layer sequentially disposed on the front surface of the silicon substrate; a third passivation layer and a fourth passivation layer sequentially provided on the back surface of the silicon substrate; a silicon carbide layer provided on one surface of the fourth passivation layer away from the silicon substrate; a second transparent conductive oxide thin film provided on one surface of the silicon carbide layer away from the silicon substrate, the thickness of the silicon carbide layer is 5 to 10 nm; a silicon carbide layer that is p-type doped to form a p-n junction with the silicon substrate, and an atomic percentage of carbon atoms in the silicon carbide layer that is 7 times or more the atomic percentage of oxygen atoms.

2. 2. The solar cell of claim 1, wherein the first passivation layer is hydrogenated amorphous silicon oxide and the second passivation layer is hydrogenated nanocrystalline silicon.

3. 2. The solar cell of claim 1, wherein the third passivation layer is hydrogenated amorphous silicon and the fourth passivation layer is hydrogenated nanocrystalline silicon.

4. 2. The solar cell of claim 1, further comprising a fifth passivation layer provided on a surface of the second passivation layer away from the silicon substrate, the material of the fifth passivation layer being hydrogenated n-type microcrystalline or nanocrystalline silicon carbide.

5. The solar cell according to claim 4 , further comprising a first transparent conductive oxide thin film provided on a surface of the fifth passivation layer away from the silicon substrate.

6. The solar cell according to claim 5 , further comprising an anti-reflection thin film provided on a surface of the first transparent conductive oxide thin film that faces away from the silicon substrate.

7. The solar cell of claim 5 , further comprising a first electrode and a second electrode in contact with the first transparent conductive oxide thin film and the second transparent conductive oxide thin film, respectively.

8. providing an n-type silicon sheet having opposing front and back surfaces; sequentially forming a first passivation layer and a second passivation layer on a front surface of the n-type silicon sheet; Sequentially forming a third passivation layer and a fourth passivation layer on the back surface of the n-type silicon sheet; forming a silicon carbide layer on a surface of the fourth passivation layer away from the n-type silicon sheet; forming a second transparent conductive oxide thin film on a surface of the silicon carbide layer away from the n-type silicon sheet; the thickness of the silicon carbide layer is 5 to 10 nm; a silicon carbide layer that is p-type doped to form a p-n junction with the n-type silicon sheet, and an atomic percentage of carbon atoms in the silicon carbide layer that is 7 times or more the atomic percentage of oxygen atoms.

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