CN111933752B - Solar cell and preparation method thereof - Google Patents

Abstract

The present application relates to the photovoltaic field, and provides a solar cell and a method for preparing the same, wherein the method comprises the following steps: performing boron diffusion on a textured N-type semiconductor substrate to form a boron diffusion layer; performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer; performing phosphorus diffusion on the polysilicon layer to form a phosphorus-doped polysilicon layer; forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, and forming a back passivation layer on the surface of the second oxide layer; forming a front passivation layer on the surface of the boron diffusion layer; and forming an electrode on the front passivation layer and/or the back passivation layer. The solar cell and the method for preparing the same of the present application can reduce the unsaturated defects between the doped polysilicon layer and the passivation layer, and can effectively improve the passivation effect and enhance the cell conversion efficiency.

Description

A solar cell and a method for preparing the same

Technical Field

The present application relates to the technical field of photovoltaic cells, and in particular, to a solar cell and a method for preparing the same.

Background Art

Topcon cells rely on the "tunneling effect" to achieve back passivation. The existing back structure of Topcon cells is substrate, tunneling oxide layer, doped polysilicon layer, and back passivation layer from the inside to the outside. Since the doped polysilicon layer and the back passivation layer are deposited in two different devices, some unsaturated defects will inevitably be introduced between the doped polysilicon layer and the back passivation layer, which can easily cause carrier recombination and electrical performance loss, and the passivation effect is not ideal. Therefore, it is necessary to study methods to improve the back passivation effect and further improve the battery conversion efficiency.

Summary of the invention

In view of this, the present application proposes a solar cell and a method for preparing the same, which can reduce the unsaturated defects between the doped polysilicon layer and the passivation layer (such as a silicon nitride layer), effectively improve the passivation effect, and enhance the cell conversion efficiency.

The present application provides a method for preparing a solar cell, comprising the following steps:

Diffusion of boron is performed on the textured N-type semiconductor substrate to form a boron diffusion layer;

Performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer;

Diffusion of phosphorus into the polysilicon layer to form a phosphorus-doped polysilicon layer;

forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, and forming a back passivation layer on the surface of the second oxide layer;

forming a front passivation layer on a surface of the boron diffusion layer; and

An electrode is formed on the front passivation layer and/or the back passivation layer.

In a feasible implementation manner, the thickness of the second oxide layer is 0.5 nm to 5 nm; and/or the second oxide layer includes at least one of silicon oxide, aluminum oxide, and titanium oxide.

In a feasible implementation, after phosphorus is diffused into the polysilicon layer to form a phosphorus-doped polysilicon layer and before a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, the method further includes: removing the phosphorus-silicate glass layer formed during the phosphorus diffusion process.

In a feasible embodiment, after forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer and before forming a back passivation layer on the surface of the second oxide layer, the method further includes: removing the polysilicon layer plated on the front side of the N-type semiconductor substrate; and removing the borosilicate glass layer formed during the boron diffusion process.

In a feasible embodiment, after phosphorus is diffused into the polysilicon layer to form a phosphorus-doped polysilicon layer, and before a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, the method further includes: removing the polysilicon layer plated on the front side of the N-type semiconductor substrate; removing the phosphosilicate glass layer formed during the phosphorus diffusion process and the borosilicate glass layer formed during the boron diffusion process.

In a feasible embodiment, a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, including: forming the second oxide layer on the surface of the phosphorus-doped polysilicon layer by wet chemical oxidation and/or thermal oxidation; or, depositing the second oxide layer on the surface of the phosphorus-doped polysilicon layer by any one of physical vapor deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, and atomic layer deposition.

In a feasible implementation, forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer includes: forming the second oxide layer on the surface of the phosphorus-doped polysilicon layer by thermal oxidation, the thermal oxidation temperature is 500°C to 600°C, and the thermal oxidation time is 150s to 300s.

In a feasible embodiment, a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, comprising: immersing the phosphorus-doped polysilicon layer on the back side of the N-type semiconductor substrate in an oxidizing solution for wet chemical oxidation treatment, the oxidizing solution comprising a hydrochloric acid solution and ozone, the mass concentration of the hydrochloric acid solution is 0.1% to 0.5%, the ozone concentration is 20ppm to 30ppm, and the immersion time is 30s to 60s.

In a feasible implementation manner, removing the phosphosilicate glass layer formed during the phosphorus diffusion process includes:

The phosphosilicate glass layer on the back of the N-type semiconductor substrate is pickled for 30s to 60s with a prepared mixed acid, wherein the mixed acid includes a hydrofluoric acid solution with a mass concentration of 2% to 10% and a hydrochloric acid solution with a mass concentration of 2% to 10%; the back of the N-type semiconductor substrate after pickling is washed with water and dried.

An embodiment of the present application also provides a solar cell, which is obtained by the above-mentioned solar cell preparation method, and includes a first electrode, a first passivation layer, a boron diffusion layer, a semiconductor substrate, a first oxide layer, a phosphorus-doped polysilicon layer, a second oxide layer, a second passivation layer, and a second electrode arranged in sequence from top to bottom.

The technical solution of this application has at least the following beneficial effects:

By forming a multilayer structure of a first oxide layer, a doped polysilicon layer, a second oxide layer and a back passivation layer, the formation of the second oxide layer can effectively passivate the unsaturated defects between the doped polysilicon layer and the back passivation layer. The experimental results show that the solar cell prepared according to the preparation method of the present application has a 1% to 2% improvement in the monitored cell minority carrier lifetime and the implied-Voc before screen printing, indicating that the passivation effect has been enhanced. The absolute value of the cell efficiency has increased by 0.1% to 0.2%, indicating that the multilayer passivation structure can effectively improve the cell conversion efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG1 is a flow chart of a method for preparing a solar cell provided in an embodiment of the present application;

FIG. 2 is another flow chart of a method for preparing a solar cell provided in an embodiment of the present application;

FIG. 3 is a schematic diagram of the structure of a solar cell provided in an embodiment of the present application.

DETAILED DESCRIPTION

In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

It should be understood that the term "and/or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.

Topcon cells rely on the "tunneling effect" to achieve back passivation. The existing Topcon cell back structure is substrate, tunneling oxide layer, doped polysilicon layer, and back passivation layer from the inside out. Since the doped polysilicon layer and the back passivation layer are deposited in two different devices, some unsaturated defects will inevitably be introduced between the doped polysilicon layer and the back passivation layer, which can easily cause carrier recombination and electrical performance loss, and the passivation effect is not ideal.

Therefore, in order to overcome the imperfections of the prior art, the technical solution of the embodiment of the present invention provides a solar cell and a method for preparing the same, in which an oxide layer is prepared between the doped polysilicon layer and the passivation layer on the back of the cell to passivate the defects between the doped polysilicon layer and the back passivation layer, thereby improving the passivation effect on the back of the cell and enhancing the conversion efficiency of the cell.

In a first aspect, an embodiment of the present application provides a method for preparing a solar cell, comprising the following steps:

Diffusion of boron is performed on the textured N-type semiconductor substrate to form a boron diffusion layer;

Performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer;

Diffusion of phosphorus into the polysilicon layer to form a phosphorus-doped polysilicon layer;

forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, and forming a back passivation layer on the surface of the second oxide layer;

forming a front passivation layer on a surface of the boron diffusion layer; and

An electrode is formed on the front passivation layer and/or the back passivation layer.

In this solution, a first oxide layer, a phosphorus-doped polysilicon layer, a second oxide layer and a back passivation layer are arranged on the back of the battery, which can effectively improve the unsaturated defects between the doped polysilicon layer and the back passivation layer, improve the back passivation effect of the battery, and improve the conversion efficiency of the battery.

Below, the preparation method of the N-type Topcon battery will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on Embodiment 1 and Embodiment 2 of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

FIG. 1 is a flow chart of a method for preparing a solar cell provided in this embodiment. As shown in FIG. 1 , Embodiment 1 of the present application provides a method for preparing a solar cell, comprising the following steps:

Step S10, performing boron diffusion on the textured N-type semiconductor substrate to form a boron diffusion layer.

Specifically, before boron diffusion, the front and back sides of the N-type semiconductor substrate may be subjected to a texturing treatment to form a velvet surface or a surface texture structure (e.g., a pyramid structure). The texturing treatment may be performed by chemical etching, laser etching, mechanical method, plasma etching, etc., which are not limited here. Exemplarily, a NaOH solution may be used to perform a texturing treatment on the front and back sides of a silicon wafer. Since the corrosion of the NaOH solution is anisotropic, a pyramid structure velvet surface may be prepared.

In this embodiment, the surface of the silicon substrate is provided with a velvet structure by texturing, thereby generating a light trapping effect, increasing the amount of light absorbed by the solar cell, and thus improving the conversion efficiency of the solar cell.

In some embodiments, the front side of the N-type semiconductor substrate is the surface facing the sun, and the back side is the surface facing away from the sun. It should also be noted that the semiconductor substrate may be a crystalline silicon substrate (silicon substrate), such as a polycrystalline silicon substrate, a single crystal silicon substrate, or a quasi-single crystal silicon substrate. The embodiments of the present invention do not limit the specific type of the semiconductor substrate.

In step S10 , a boron diffusion layer may be formed on the surface of the N-type semiconductor substrate by using any one or more methods of high temperature diffusion, slurry doping or ion implantation.

In a specific embodiment, the N-type semiconductor substrate is N-type crystalline silicon, and the boron diffusion treatment is to diffuse boron atoms through a boron source to form a boron diffusion layer. The boron source can be, for example, treated with boron tribromide diffusion, and the microcrystalline silicon phase of the crystalline silicon is transformed into a polycrystalline silicon phase. Since the surface of the semiconductor substrate has a high concentration of boron, a borosilicate glass layer (BSG) is usually formed. This borosilicate glass layer has a metal gettering effect, which will affect the normal operation of the solar cell and needs to be removed later.

Optionally, before the texturing process, a step of cleaning the semiconductor substrate may be included to remove metal and organic pollutants on the surface.

Step S20, performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer.

It should be noted that the embodiment of the present invention does not limit the specific operation method for forming the first oxide layer. Specifically, the semiconductor substrate can be etched from the back by ozone oxidation, high temperature thermal oxidation, or nitric acid oxidation, and then oxidized to form the first oxide layer. For example, the back of the semiconductor substrate is oxidized by thermal oxidation to form the first oxide layer. The first oxide layer can be a thin oxide layer or a tunneling oxide layer.

In a specific implementation, the polysilicon layer can be deposited on the surface of the first oxide layer by using any one of low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, and normal pressure chemical vapor deposition.

It can be understood that during the process of depositing polysilicon on the surface of the first oxide layer of the semiconductor substrate, the polysilicon is plated along the back side of the semiconductor substrate to the front side. Therefore, in the subsequent process, the polysilicon plated to the front side of the semiconductor substrate needs to be de-plated.

Step S30, diffusing phosphorus into the polysilicon layer to form a phosphorus-doped polysilicon layer.

Phosphorus diffusion treatment refers to the process of forming a doped polysilicon layer by diffusing pentavalent phosphorus atoms at about 900°C. After the diffusion treatment, the microcrystalline silicon phase of the crystalline silicon is transformed into a polycrystalline silicon phase, and phosphorus is deposited on the surface of the semiconductor substrate to form phosphosilicate glass (PSG).

A two-step heat treatment method can be used for diffusion, that is, the phosphorus source is first decomposed at about 1000°C and deposited on the surface of the semiconductor substrate, and then heat treated in the range of 800°C to 900°C, so that the phosphorus atoms on the surface diffuse into the polysilicon layer to form a phosphorus-doped polysilicon layer. Of course, a one-step deposition method can also be used, that is, a polysilicon layer is deposited on the surface of the first oxide layer and an in-situ doping treatment is performed at the same time to form a phosphorus-doped polysilicon layer. The phosphorus diffusion process can also use any one or more methods of high-temperature diffusion, slurry doping or ion implantation, which are not limited here.

In one embodiment, after step S30, the method further includes:

Step S31 , removing the phosphosilicate glass (PSG) layer formed during the phosphorus diffusion process.

Understandably, when phosphorus diffuses, a phosphosilicate glass layer (PSG) is usually formed due to the high concentration of phosphorus on the surface of the semiconductor substrate. This phosphosilicate glass layer has a metal gettering effect, which will affect the normal operation of the solar cell and needs to be removed.

In a specific embodiment, the semiconductor substrate can be placed on a chain pickling device with its back side facing downward (the belt speed of the chain pickling device is 1.0 m/min to 2.0 m/min, and the semiconductor substrate enters an acid tank to etch off the phosphosilicate glass layer (PSG) formed by the back phosphorus diffusion. A prepared mixed acid is provided in the acid tank, wherein the mixed acid comprises a hydrofluoric acid solution having a mass concentration of 2% to 10% and a hydrochloric acid solution having a mass concentration of 2% to 10%, the pickling temperature is 15° C. to 25° C., the pickling time is about 30s to 60s, the semiconductor substrate front side is covered with a water film, and the borosilicate glass layer (BSG) on the semiconductor substrate front side can also be used as a protective layer, and in the process of removing the phosphosilicate glass layer (PSG), the semiconductor substrate front side is prevented from reacting with the mixed acid.

It should be noted that water washing is required after acid washing, the water washing time is 10 to 20 seconds, and the water washing temperature can be 15° C. to 25° C.; of course, the semiconductor substrate can also be dried after water washing.

Step S40, forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, and forming a back passivation layer on the surface of the second oxide layer.

The thickness of the second oxide layer is 0.5 nm to 5 nm, for example, 0.5 nm, 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm. The second oxide layer not only plays a passivation role on the surface of the semiconductor substrate, but also needs to allow carriers to tunnel through. When the thickness of the second oxide layer is too small, it cannot play a passivation role. When the thickness of the second oxide layer is too large, carriers cannot effectively pass through.

Optionally, the material of the second oxide layer includes at least one of silicon oxide, aluminum oxide, titanium oxide, silicon carbide, and hydrogenated amorphous silicon. For example, the second oxide layer includes a silicon oxide layer or a titanium oxide layer.

Specifically, step S40 includes:

Step S41, forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer;

Step S42, removing the polysilicon layer plated on the front side of the N-type semiconductor substrate;

Step S43, removing the borosilicate glass layer (BSG) formed during the boron diffusion process;

Step S44, forming a back passivation layer on the surface of the second oxide layer.

Optionally, in step S41, a second oxide layer may be formed on the surface of the phosphorus-doped polysilicon layer by wet chemical oxidation and/or thermal oxidation, and the second oxide layer may be, for example, silicon oxide. Alternatively, any one of physical vapor deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, and atomic layer deposition may be used to deposit and form the second oxide layer on the surface of the phosphorus-doped polysilicon layer, and the second oxide layer may be, for example, silicon carbide, titanium oxide, etc.

Exemplarily, a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer by a thermal oxidation method, and the steps include: arranging the front sides of two semiconductor substrates opposite to each other and inserting them into a tubular heating device, the thermal oxidation temperature is 500° C. to 600° C., and the thermal oxidation time is 150s to 300s. It should be noted that when the second oxide layer is formed by a thermal oxidation method, an oxide layer may also be formed on the front side of the semiconductor substrate during the thermal oxidation process.

Exemplarily, a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer by a wet chemical oxidation method, and the steps include: immersing the phosphorus-doped polysilicon layer on the back of the N-type semiconductor substrate in an oxidizing solution for wet chemical oxidation treatment, the oxidizing solution includes a hydrochloric acid solution and ozone, the mass concentration of the hydrochloric acid solution is 0.1% to 0.5%, the ozone concentration is 20ppm to 30ppm, and the immersion time is 30s to 60s. During immersion, the temperature is controlled to be 15°C to 25°C, the front of the semiconductor substrate is covered with a water film, and the borosilicate glass layer (BSG) on the front of the semiconductor substrate can also be used as a protective layer to prevent the front of the semiconductor substrate from reacting with the oxidizing solution when the second oxide layer is formed.

It should be noted that after the second oxide layer is formed by the wet chemical oxidation method, the semiconductor substrate may be washed with water and dried.

Specifically, in step S42, the prepared solution can be used to clean the polysilicon layer plated on the front side of the semiconductor substrate for 100 to 120 seconds. By way of example, the de-plating solution can be prepared by mixing 10 ml of 36% hydrofluoric acid, 50 ml of 70% concentrated nitric acid, 10 ml of 98% concentrated sulfuric acid and 30 ml of water. This preparation method is only for illustration and is not limited here.

Furthermore, in step S43, the borosilicate glass layer (BSG) formed during the boron diffusion process is removed, and liquid etching, laser etching and other processes may also be used, which are not limited here.

In this embodiment, the de-plating process and the BSG removal process are located after the process of forming the second oxide layer, and the borosilicate glass layer on the front side of the semiconductor substrate can effectively prevent the front side of the semiconductor substrate from reacting with the oxidizing solution in the wet chemical oxidation process, so that the borosilicate glass layer protects the front side of the semiconductor substrate. In addition, the de-plating process and the BSG removal process are located after the process of forming the second oxide layer, and the oxide layer formed on the front side of the semiconductor substrate in the thermal oxidation process can also be removed synchronously by the BSG removal process. In this embodiment, a multilayer structure of a first oxide layer, a phosphorus-doped polysilicon layer, a second oxide layer, and a back passivation layer is provided on the back side of the battery, which can effectively improve the unsaturated defects introduced between the doped polysilicon layer and the back passivation layer, and effectively improve the passivation effect.

Step S44, forming a back passivation layer on the surface of the second oxide layer. The back passivation layer may include but is not limited to a single layer or a stacked layer structure of silicon nitride, silicon oxynitride, aluminum oxide, etc.

For example, the back passivation layer is composed of silicon nitride. The silicon nitride film layer can play the role of an anti-reflection film, and the silicon nitride film has good insulation, compactness, stability and shielding ability for impurity ions. The silicon nitride film layer can passivate the silicon wafer and significantly improve the photoelectric conversion efficiency of the solar cell.

Step S50, forming a front passivation layer on the surface of the boron diffusion layer.

In some embodiments, the front passivation layer may include but is not limited to a single layer or a stacked structure of silicon nitride, silicon oxynitride, aluminum oxide, etc. Of course, the front passivation layer may also use other types of passivation layers, and the present invention does not limit the specific material of the front passivation layer. For example, in other embodiments, the front passivation layer may also be a stack of silicon dioxide and silicon nitride. The above-mentioned front passivation layer can produce a good passivation effect on the semiconductor substrate, which helps to improve the conversion efficiency of the battery.

Step S60, forming an electrode on the front passivation layer and/or the back passivation layer.

In some embodiments, a back main grid and a back sub-grid can be printed on the back of a semiconductor substrate using silver paste and dried, and a front main grid and a front sub-grid can be printed on the front of the semiconductor using aluminum-doped silver paste and dried, and finally sintered to produce a solar cell.

It should be noted that the front electrode passes through the front passivation layer to form an ohmic contact with the boron diffusion layer; the back electrode passes through the back passivation layer and the second oxide layer, and then forms an ohmic contact with the phosphorus-doped polysilicon layer. The phosphorus-doped polysilicon layer and the first oxide layer form a TopCon structure.

FIG. 2 is another flow chart of a method for preparing a solar cell provided in an embodiment of the present application. As shown in FIG. 2 , Embodiment 2 of the present application provides a method for preparing a solar cell, comprising the following steps:

Step S10, performing boron diffusion on the textured N-type semiconductor substrate to form a boron diffusion layer;

Step S20, performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer;

Step S30, diffusing phosphorus into the polysilicon layer to form a phosphorus-doped polysilicon layer;

Step S40, forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, and forming a back passivation layer on the surface of the second oxide layer;

Step S50, forming a front passivation layer on the surface of the boron diffusion layer; and

Step S60, forming an electrode on the front passivation layer and/or the back passivation layer.

Different from the first embodiment, after step S30 and before step S40, the method further includes:

Step S310, removing the polysilicon layer plated on the front side of the N-type semiconductor substrate;

Step S320 , removing the phosphosilicate glass layer formed during the phosphorus diffusion process and the borosilicate glass layer formed during the boron diffusion process.

In this embodiment, after the de-plating process, the PSG and BSG removal process, a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer. Compared with the existing Topcon battery preparation process, only one second oxide layer formation process is added, which can effectively improve the unsaturated defects introduced between the doped polysilicon layer and the back passivation layer, effectively improve the passivation effect, and only slightly change the original generation process, thereby improving the battery mass production yield and reducing production costs.

In some embodiments, the solar cell may be a solar cell with a Topcon structure, as shown in FIG3 , the solar cell includes a first electrode 13, a first passivation layer 12, a boron diffusion layer 11, a semiconductor substrate 10, a first oxide layer 14, a phosphorus-doped polysilicon layer 15, a second oxide layer 16, a second passivation layer 17, and a second electrode 18 stacked sequentially from top to bottom. It should be noted that the first electrode 13 forms an ohmic contact with the boron diffusion layer 11 through the first passivation layer 12, the second electrode 18 forms an ohmic contact with the phosphorus-doped polysilicon layer 15 through the second passivation layer 17 and the second oxide layer 16, and the phosphorus-doped polysilicon layer 15 and the first oxide layer 14 form a TopCon structure.

Optionally, the first oxide layer 14 is a tunneling oxide layer, such as an ultra-thin silicon oxide layer.

Optionally, the second oxide layer 16 is an ultra-thin oxide layer similar to the first oxide layer 14. For example, the second oxide layer 16 is a silicon oxide layer. For another example, the second oxide layer 16 is a titanium oxide layer. The thickness of the second oxide layer 16 is in the range of 0.5 nm to 5 nm.

For the specific structure of the solar cell, such as the specific type of each layer, etc., reference may be made to the related description of the aforementioned solar cell preparation method, and will not be described in detail here.

The embodiment of the present invention does not limit the specific materials of the first electrode 13 and the second electrode 18. For example, the first electrode 13 is a silver electrode or a silver/aluminum electrode, and the second electrode 18 is a silver electrode.

The specific types of the first passivation layer 12 and the second passivation layer 17 are not limited in the embodiment of the present invention, and they may be, for example, a silicon nitride layer, a silicon oxynitride layer, an aluminum oxide/silicon nitride stacked structure, and the like.

It should also be noted that the embodiment of the present invention does not limit the thickness of each layer structure in the above solar cell, which can be adjusted by those skilled in the art according to actual conditions.

The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any technical personnel in this field may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims (7)

1. A method for preparing a solar cell, characterized in that it comprises the following steps: Diffusion of boron is performed on the textured N-type semiconductor substrate to form a boron diffusion layer; Performing back etching and oxidation on the semiconductor substrate to form a first oxide layer, and depositing a polysilicon layer on the surface of the first oxide layer; Diffusion of phosphorus into the polysilicon layer to form a phosphorus-doped polysilicon layer; Forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer, the second oxide layer is titanium oxide, the thickness of the second oxide layer is 0.5nm to 5nm, and forming a back passivation layer on the surface of the second oxide layer, the back passivation layer is aluminum oxide/silicon nitride stacked layer; forming a front passivation layer on a surface of the boron diffusion layer; and An electrode is formed on the front passivation layer and/or the back passivation layer. 2. The method for preparing a solar cell according to claim 1, characterized in that after the polysilicon layer is subjected to phosphorus diffusion to form a phosphorus-doped polysilicon layer and before a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, the method further comprises: The phosphosilicate glass layer formed during the phosphorus diffusion process is removed. 3. The method for preparing a solar cell according to claim 2, characterized in that after forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer and before forming a back passivation layer on the surface of the second oxide layer, the method further comprises: Removing the polysilicon layer deposited on the front side of the N-type semiconductor substrate; The borosilicate glass layer formed during the boron diffusion process is removed. 4. The method for preparing a solar cell according to claim 1, characterized in that after phosphorus is diffused into the polysilicon layer to form a phosphorus-doped polysilicon layer and before a second oxide layer is formed on the surface of the phosphorus-doped polysilicon layer, the method further comprises: Removing the polysilicon layer deposited on the front side of the N-type semiconductor substrate; The phosphosilicate glass layer formed during the phosphorus diffusion process and the borosilicate glass layer formed during the boron diffusion process are removed. 5. The method for preparing a solar cell according to claim 1, characterized in that forming a second oxide layer on the surface of the phosphorus-doped polysilicon layer comprises: A second oxide layer is formed by deposition on the surface of the phosphorus-doped polysilicon layer using any one of physical vapor deposition and chemical vapor deposition methods. 6. The method for preparing a solar cell according to claim 2 or 4, characterized in that the removing of the phosphosilicate glass layer formed during the phosphorus diffusion process comprises: Pickling the phosphosilicate glass layer on the back of the N-type semiconductor substrate with a prepared mixed acid for 30s to 60s, wherein the mixed acid comprises a hydrofluoric acid solution with a mass concentration of 2% to 10% and a hydrochloric acid solution with a mass concentration of 2% to 10%; The back side of the N-type semiconductor substrate after pickling is washed with water and dried. 7. A solar cell, characterized in that the solar cell is obtained by the solar cell preparation method according to any one of claims 1 to 6, and the solar cell comprises a first electrode, a first passivation layer, a boron diffusion layer, a semiconductor substrate, a first oxide layer, a phosphorus-doped polysilicon layer, a second oxide layer, a second passivation layer, and a second electrode arranged in sequence from top to bottom.