WO2023184844A1

WO2023184844A1 - Silicon-based thin film and solar cell, and preparation methods therefor

Info

Publication number: WO2023184844A1
Application number: PCT/CN2022/115658
Authority: WO
Inventors: 张丽平; 刘正新; 蓝仕虎; 张海川; 赵晖; 李龙文; 孟凡英
Original assignee: 中威新能源(成都)有限公司
Priority date: 2022-03-29
Filing date: 2022-08-30
Publication date: 2023-10-05
Also published as: CN114823302A

Abstract

The present disclosure relates to a method for preparing a silicon-based thin film. The method comprises the following steps: preheating a substrate; and placing the preheated substrate in a deposition chamber, introducing hydrogen and an inert gas into the deposition chamber, triggering glow discharge, introducing a reaction gas into the deposition chamber, and forming a silicon-based thin film on the substrate by means of deposition. Moreover, the present disclosure relates to a corresponding silicon-based thin film, a method for preparing a solar cell, and a solar cell.

Description

Silicon-based thin film, solar cell and preparation method thereof

This application claims priority to the Chinese patent application filed with the China Patent Office on March 29, 2022, with the application number 2022103207022 and the invention name "Silicon-based thin film, solar cell and preparation method thereof", the entire content of which is incorporated by reference. in this application.

Technical field

The present application relates to the field of semiconductor photoelectric conversion technology, and in particular to a silicon-based film, a solar cell and a preparation method thereof.

Background technique

Silicon heterojunction (HJT, Heterojunction with Intrinsic Thin Film) solar cell is a high-efficiency crystalline silicon solar cell. It has attracted widespread attention in the photovoltaic industry because of its high open circuit voltage, high conversion efficiency, and low temperature coefficient. HJT cells are also bifacial cells with a high bifacial ratio. Since the backside is also a grid electrode that allows light to enter, it further contributes to power generation. Under the same conditions, its power generation output is higher than that of ordinary crystalline silicon solar cells10 %above. Therefore, this type of solar cell has a higher cost performance.

HJT cells use n-type monocrystalline silicon wafers as substrates. The basic manufacturing process includes texturing and cleaning, silicon-based film passivation layer deposition, transparent conductive oxide film deposition and metal electrode production. Compared with conventional crystalline silicon solar cells, the process is simpler and the large-scale production process is easy to control.

The deposition of silicon-based thin film passivation layer is the key to all production processes of HJT solar cells, and it is also the difficulty of HJT cell production technology. Amorphous silicon films are generally deposited using equipment such as plasma enhanced chemical vapor deposition (PECVD), catalytic chemical vapor deposition (Cat-CVD), and photochemical vapor deposition (Photo-CVD). A stack of intrinsic silicon and n-type doped silicon films is deposited on the first surface of the texturing-cleaned silicon wafer to form a first light-receiving surface; a stack of intrinsic silicon and p-type doped silicon films is deposited on the second surface to form The second light-receiving surface.

Different from traditional crystalline silicon solar cells, the intrinsic silicon film has the effect of terminating dangling bonds on the surface of n-type single crystal silicon, thereby forming good surface passivation. The abundant atomic hydrogen in the silicon film can reduce the probability of surface defects trapping photogenerated carriers, thereby greatly increasing the open circuit voltage of HJT solar cells. A built-in electric field is formed between the n-type and p-type doped silicon films and n-type single crystal silicon, which separates and collects electrons and holes to form electric power output.

Usually the reaction gases for depositing intrinsic and doped silicon-based thin film passivation layers are SiH ₄ , Si ₂ H ₆ , PH ₃ , B ₂ H ₆ , CH ₄ , CO ₂ , and the diluting gas is usually H ₂ . When forming a base film, power feed or high-temperature thermal decomposition is used to decompose the gas into the main precursors such as SiH ₃ , SiH ₂ , PH ₂ , PH, BH ₃ , BH ₂ , CH ₃ and CO groups at a temperature of 200°C. A large area of continuous and uniform silicon-based film is formed on the left and right substrates.

During the deposition process, affected by the feed power or the temperature of the hot wire, only a small part of the reaction gases such as SiH ₄ in the reaction gas is decomposed, and most of the reaction gas is discharged from the chamber because it has not had time to decompose; in addition, in terms of process technology, Low pressure and high flow are often used to reduce the residence time of reaction gases in the chamber to obtain fresh precursors to improve film quality. In view of the above reasons, the gas utilization rate of conventional processes is very low. This inefficient gas utilization brings great cost pressure to the production of large-scale high-efficiency HJT solar cells. Moreover, in actual production, methods to further reduce the utilization rate of reaction gas are often adopted to improve film quality, further increasing production costs.

Contents of the invention

According to some embodiments of the present disclosure, a method for preparing a silicon-based thin film is provided, including the following steps:

Preheating the substrate; and

The preheated substrate is placed in a deposition chamber, hydrogen and inert gas are filled into the deposition chamber to trigger glow discharge, and reactive gas is filled into the deposition chamber to deposit silicon on the substrate. base film.

In some embodiments of the present disclosure, in the mixed gas formed by hydrogen, inert gas and reactive gas in the deposition chamber, the volume ratio of hydrogen to reactive gas is (1-3000):1.

In some embodiments of the present disclosure, in the mixed gas formed by hydrogen, inert gas and reaction gas in the deposition chamber, the volume percentage of the inert gas is 5% to 80%.

In some embodiments of the present disclosure, during the deposition and formation of the silicon-based film, the gas pressure in the deposition chamber ranges from 1 Pa to 300 Pa.

In some embodiments of the present disclosure, after triggering the glow discharge on the substrate for 1 s to 120 s, the reaction gas is filled into the deposition chamber.

In some embodiments of the present disclosure, the silicon-based film includes an intrinsic silicon film, and the reactive gas includes at least one of CO ₂ and CH ₄ and at least one of SiH ₄ and Si ₂ H ₆ .

In some embodiments of the present disclosure, the silicon-based film includes an n-type doped silicon film, and the reaction gas includes at least one of SiH ₄ and Si ₂ H ₆ and PH ₃ .

In some embodiments of the present disclosure, the silicon-based film includes a p-type doped silicon film, and the reaction gas includes at least one of SiH ₄ and Si ₂ H ₆ and B ₂ H ₆ .

In some embodiments of the present disclosure, preheating the substrate includes the following steps:

The substrate is placed in a preheating chamber, and the substrate is preheated. During the preheating process, hydrogen and inert gas are filled into the preheating chamber.

In some embodiments of the present disclosure, nitrogen is also filled into the preheating chamber during the preheating process.

In some embodiments of the present disclosure, the preheating temperature of the substrate is 150°C to 300°C, and the preheating time is 20s to 200s.

In some embodiments of the present disclosure, in the mixed gas formed by nitrogen, hydrogen and inert gas in the preheating chamber, the volume percentage of nitrogen is 50% to 90%, and the volume percentage of hydrogen is 5% to 49%. %, the volume percentage of inert gas is 5% to 45%.

In some embodiments of the present disclosure, the air pressure in the preheating chamber during the preheating process ranges from 1 Pa to 300 Pa.

According to further embodiments of the present disclosure, a silicon-based film is provided, and the silicon-based film is prepared by the above-mentioned preparation method of the present disclosure.

In some embodiments of the present disclosure, the silicon-based film includes one or more of an intrinsic silicon film, an n-type doped silicon film, and a p-type doped silicon film.

According to further embodiments of the present disclosure, a method for preparing a solar cell is provided, including the following steps:

Texturing and cleaning the n-type monocrystalline silicon substrate;

Using the above-mentioned preparation method of the present disclosure, silicon-based thin films are respectively deposited on the two opposite surfaces of the n-type single crystal silicon substrate;

respectively deposit transparent conductive films on the silicon-based films on two opposite surfaces of the n-type single crystal silicon substrate; and

Metal electrodes are respectively made on the transparent conductive films on two opposite surfaces of the n-type single crystal silicon substrate.

In some embodiments of the present disclosure, respectively depositing silicon-based thin films on two opposite surfaces of the n-type single crystal silicon substrate includes the following steps:

sequentially depositing an intrinsic silicon film and an n-type doped silicon stack film on the first surface of the n-type single crystal silicon substrate; and

An intrinsic silicon film and a p-type doped silicon stacked film are sequentially deposited on the second surface of the n-type single crystal silicon substrate opposite to the first surface.

In some embodiments of the present disclosure, when depositing the intrinsic silicon film, the reaction gas includes at least one of CO ₂ and CH ₄ and at least one of SiH ₄ and Si ₂ H ₆ .

In some embodiments of the present disclosure, when depositing the n-type doped silicon stack film, the reaction gas includes at least one of SiH ₄ and Si ₂ H ₆ and PH ₃ .

In some embodiments of the present disclosure, when depositing the p-type doped silicon film, the reaction gas includes at least one of SiH ₄ and Si ₂ H ₆ and B ₂ H ₆ .

According to further embodiments of the present disclosure, a solar cell is provided, and the solar cell is prepared by the above-mentioned solar cell preparation method of the present disclosure.

According to further embodiments of the present disclosure, a solar cell is provided, including:

n-type single crystal silicon substrate;

A first silicon-based film is deposited on the first surface of the n-type single crystal silicon substrate. The first silicon-based film is prepared by using the silicon-based film preparation method described above in the present disclosure;

A second silicon-based film is deposited on the second surface of the n-type single crystal silicon substrate opposite to the first surface. The second silicon-based film is prepared by using the silicon-based film preparation method described above in this disclosure. ;

A transparent conductive film deposited on the first silicon-based film and the second silicon-based film; and

Metal electrodes are provided on the transparent conductive film.

In some embodiments of the present disclosure, the first silicon-based film includes:

A first intrinsic silicon film deposited on the first surface of the n-type single crystal silicon substrate; and

An n-type doped silicon film is deposited on the surface of the first intrinsic silicon film facing away from the n-type single crystal silicon substrate.

In some embodiments of the present disclosure, the second silicon-based film includes:

A second intrinsic silicon film is deposited on the second surface of the n-type single crystal silicon substrate; and

A p-type doped silicon film is deposited on the surface of the second intrinsic silicon film facing away from the n-type single crystal silicon substrate.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will become apparent from the description, drawings and claims.

Description of drawings

To better describe and illustrate embodiments and/or examples of the present application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be construed as limiting the scope of any of the disclosed inventions, the embodiments and/or examples presently described, and the best modes currently understood of these inventions.

Figure 1 is a diagram comparing the hydrogen content of a silicon-based film grown using the method of the present invention and a silicon-based film grown using a conventional method;

Figure 2 is a comparison diagram of the dielectric constant of a silicon-based film grown using the method of the present invention and a silicon-based film grown using a conventional method.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the accompanying drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided for the purpose of making the disclosure of the present application more thorough and comprehensive.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number or order of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

When describing positional relationships, unless otherwise specified, when an element such as a layer, film or substrate is referred to as being "on" another layer, it can be directly on the other layer or intervening layers may also be present. Furthermore, when a layer is referred to as being "under" another layer, it can be directly underneath, or one or more intervening layers may also be present. It will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

Unless mentioned to the contrary, terms in the singular may include the plural and shall not be construed as being one in number.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing specific embodiments only and is not intended to limit the application.

Some embodiments of the present invention provide a method for preparing a silicon-based thin film, including the following steps S100 and S200.

Step S100: Preheat the substrate.

The substrate used is an n-type single crystal silicon substrate. The specific steps for preheating the substrate are as follows: first place the substrate in a vacuum preheating chamber, preheat the substrate, and fill the preheating chamber with hydrogen and inert gas during the preheating process.

In the traditional silicon-based thin film deposition method, the preheating time of the n-type single crystal silicon substrate is generally long, resulting in a long production cycle time and affecting production efficiency. In the present invention, hydrogen and inert gas are filled into the preheating chamber during the substrate preheating process; the introduction of hydrogen can enhance the collision of gas molecules, thereby speeding up the preheating speed of the substrate; the introduction of inert gas can interact with the hydrogen to enhance molecular collision and stimulate More metastable atomic hydrogen can play a role in heating, cleaning and passivating the substrate surface, which is beneficial to improving the preheating speed and film quality.

In some embodiments, the preheating temperature of the substrate ranges from 150°C to 300°C. The preheating time of the substrate is 20s to 200s.

It can be understood that the preheating temperature of the substrate can be specifically, but not limited to, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, Specific values such as 270°C, 280°C, 290°C, and 300°C. The preheating time of the substrate can be, but is not limited to, specific values such as 20s, 50s, 80s, 100s, 120s, 140s, 160s, 180s, 200s, etc.

In some of the embodiments, nitrogen is also filled into the preheating chamber during the preheating process. Introducing lower-cost nitrogen into the preheating chamber to partially replace hydrogen can reduce the cost of using the higher-priced special gas (hydrogen), thereby reducing the overall production cost of silicon-based films.

In some embodiments, in the mixed gas formed by nitrogen, hydrogen and inert gas in the preheating chamber, the volume percentage of nitrogen is 50% to 90%, the volume percentage of hydrogen is 5% to 49%, and the volume percentage of the inert gas is The percentage is 5% to 45%. During the preheating process, the air pressure in the preheating chamber ranges from 1Pa to 300Pa. During the preheating process, the volume ratio and pressure of nitrogen, hydrogen and inert gas are within the above range, which can not only effectively shorten the preheating time of the substrate, shorten the production cycle time, but also reduce production costs.

It can be understood that the volume percentage of nitrogen may specifically be, but is not limited to, 50%, 60%, 70%, 80%, 90% and other specific values; the volume percentage of hydrogen may specifically be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 49% and other specific values; the volume percentage of the inert gas can be but not limited to 5%, 10%, 15%, 20%, 25%, Specific values such as 30%, 35%, 40%, 45%, etc.; the air pressure range in the preheating chamber during the preheating process may be, but is not limited to, specific values such as 1Pa, 50Pa, 100Pa, 150Pa, 200Pa, 250Pa, 300Pa, etc.

Step S200: Place the preheated substrate in a deposition chamber, fill hydrogen and inert gas into the deposition chamber, trigger glow discharge, fill the reaction gas into the deposition chamber, and deposit a silicon-based film on the substrate.

In the traditional preparation method of silicon-based thin films, only a small part of the SiH ₄ in the reaction gas is decomposed, and most of the reaction gas is discharged from the chamber because it does not have time to decompose. In addition, traditional processes often use low-pressure and high-flow reaction gases to reduce the residence time of the reaction gases in the deposition chamber, thereby obtaining fresh precursors to improve film quality. Therefore, the reaction gas utilization rate in traditional processes is very low. This inefficient utilization of reaction gas brings great cost pressure to the production of large-scale high-efficiency HJT solar cells. Moreover, in order to better improve the quality of silicon-based films, methods are often adopted to further reduce the utilization rate of reaction gases, which further increases production costs.

The present invention introduces hydrogen and inert gas into the deposition chamber before glow discharge, and after starting the glow discharge, the inert gas interacts with hydrogen to enhance the collision frequency of gas molecules and stimulate rich metastable atomic hydrogen. This can significantly reduce the dangling bond density and defect states in the silicon-based film, thereby improving the quality of the silicon-based film. The introduction of inert gas can, on the one hand, consume the feed power, reduce the probability of high-energy particle generation, and reduce the bombardment of the film interface; on the other hand, it can induce the production of a large amount of atomic hydrogen in the plasma and improve the quality of the film; on the other hand, the inert gas The addition of can also accelerate the decomposition of reaction gases by enhancing molecular collision, thereby improving the utilization rate of reaction gases and reducing production costs. Introducing an inert gas during deposition also reduces the power required to activate the glow, thereby reducing energy consumption.

In some embodiments, in the mixed gas formed by hydrogen, inert gas and reactive gas in the deposition chamber, the volume ratio of hydrogen to reactive gas is (1-3000):1, and the volume percentage of inert gas is 5%-80%. . During the deposition and formation of silicon-based thin films, the air pressure in the deposition chamber ranges from 1Pa to 300Pa. It can be understood that the volume ratio of hydrogen to reaction gas can be but is not limited to 1:1, 2:1, 200:1, 500:1, 800:1, 1200:1, 1500:1, 2000:1, 2500:1 , 3000:1 and other specific values; the volume percentage of the inert gas can be but not limited to 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 80% and other specific values; deposition chamber The air pressure in the room can be, but is not limited to, 1Pa, 50Pa, 100Pa, 150Pa, 200Pa, 250Pa, 300Pa and other specific values.

Glow discharges can be triggered by feeding power onto a preheated substrate or by igniting a hot filament. When the glow discharge is triggered by feeding in power, the feeding power is generally 10mW/cm ² ~ 200mW/cm ² . It can be understood that the fed-in power can be, but is not limited to, 10mW/cm ² , 50mW/cm ² , 100mW/cm ² , 150mW/cm ² , 200mW/cm ² and other specific values.

In some embodiments, after triggering the dilute gas glow discharge for 1 s to 120 s (more preferably 1 s to 20 s), the reaction gas is filled into the deposition chamber. In this way, after triggering the glow discharge, the reactive gas is filled again after a certain period of time, so that the diluted gas glow that starts first can clean, etch and nucleate the substrate surface, making the relationship between the silicon-based film and the substrate Close bonding without defects. It can be understood that after triggering the diluent gas glow discharge, the interval time for filling the reaction gas into the deposition chamber can be, but is not limited to, specific values such as 1s, 20s, 40s, 60s, 80s, 100s, 120s, etc.

The inert gas filled in the preheating chamber and the deposition chamber can be helium, argon, etc. The preheating chamber can be a separate vacuum preheating chamber, or it can be shared with the deposition chamber, that is, the preheating operation is performed directly in the deposition chamber.

The reaction gas used in the present invention is at least one of CO ₂ , CH ₄ , PH ₃ and B ₂ H ₆ and at least one of SiH ₄ and Si ₂ H ₆ . The deposited silicon-based films include intrinsic silicon films and doped silicon films, where the doped silicon films include n-type doped silicon films and p-type doped silicon films.

When the deposited silicon-based film is an intrinsic silicon film, the reaction gas is at least one of CO ₂ and CH ₄ and at least one of SiH ₄ and Si ₂ H ₆ . After triggering the glow discharge, the above-mentioned reaction gas is introduced into the deposition chamber, and a low-defect c-Si/Si:H intrinsic silicon film can be deposited on the substrate.

When the deposited silicon-based film is an n-type doped silicon film, the reaction gas is at least one of SiH ₄ and Si ₂ H ₆ and PH ₃ . After triggering the glow discharge, the above-mentioned reaction gas is introduced into the deposition chamber, and a high-quality n-type doped silicon film can be deposited on the substrate.

When the deposited silicon-based film is a p-type doped silicon film, the reaction gas is at least one of SiH ₄ and Si ₂ H ₆ and B ₂ H ₆ . After triggering the glow discharge, the above-mentioned reaction gas is introduced into the deposition chamber, and a high-quality p-type doped silicon film can be deposited on the substrate.

Some embodiments of the present invention provide a silicon-based film, which is prepared by the above-mentioned preparation method of the silicon-based film of the present invention. The silicon-based film has low production cost, good film quality and high production efficiency. The silicon-based film specifically includes one or more of an intrinsic silicon film, an n-type doped silicon film, and a p-type doped silicon film. Depending on the reaction gas used in the preparation method, different types of silicon-based films can be obtained.

Some embodiments of the present invention provide a method for manufacturing a solar cell. The preparation method includes the following steps S300 to S600.

Step S300: Texture and clean the n-type single crystal silicon substrate.

Alkaline solutions such as KOH and NaOH are used to texturize the n-type monocrystalline silicon substrate, and the anisotropic etching characteristics of monocrystalline silicon by KOH, NaOH, etc. are used to form a textured surface on the n-type monocrystalline silicon substrate; then RCA is used The n-type single crystal silicon substrate is cleaned with the solution to obtain an n-type single crystal silicon substrate with a clean surface.

Step S400: Use the above-mentioned preparation method of silicon-based thin films of the present invention to deposit silicon-based thin films on two opposite surfaces of the substrate.

An intrinsic silicon film is deposited on the first surface and the opposite second surface of the n-type single crystal silicon substrate after texturing and cleaning, and then n-type doping is deposited on the intrinsic silicon film on the first surface. A silicon film, depositing a p-type doped silicon film on the intrinsic silicon film on the second surface. The above-mentioned intrinsic silicon film, n-type doped silicon film and p-type doped silicon film are all prepared using the preparation method of the silicon-based film of the present invention. The method of depositing the silicon-based thin film can be plasma enhanced chemical vapor deposition, metal hot wire catalyst sensitized chemical vapor deposition and photochemical vapor deposition, but is not limited thereto.

Step S500: Deposit transparent conductive films on the silicon-based films on two opposite surfaces of the substrate respectively.

After preparing the silicon-based film, the present invention deposits transparent conductive oxide (TCO) on the surface of the n-type doped silicon film away from the intrinsic silicon film and on the surface of the p-type doped silicon film away from the intrinsic silicon film, respectively. Form a transparent conductive film.

Step S600: Make metal electrodes on the transparent conductive films on the two opposite surfaces of the substrate.

Furthermore, the present invention prepares metal electrodes on the surface of the transparent conductive film facing away from the doped silicon film to form a heterojunction solar cell. Specifically, the metal electrode may be a silver grid electrode.

The solar cell preparation method of the present invention adopts the silicon-based thin film preparation method of the present invention to prepare an intrinsic silicon film, an n-type doped silicon film and a p-type doped silicon film on an n-type single crystal silicon substrate; silicon The production cost of the base film is low, the film quality is good, and the production efficiency is high.

Some embodiments of the present invention provide a solar cell, which is prepared by the above-mentioned solar cell preparation method of the present invention.

The solar cell includes an n-type monocrystalline silicon substrate, an intrinsic silicon thin film is deposited on both a first surface and an opposite second surface of the n-type single crystal silicon substrate, and an n-type silicon thin film is deposited on the intrinsic silicon thin film on the first surface. Type doped silicon film, a p-type doped silicon film is deposited on the intrinsic silicon film on the second surface, and a transparent transparent film is deposited on the surface of the n-type doped silicon film and the p-type doped silicon film away from the intrinsic silicon film. A conductive film is provided, and a metal electrode is prepared on the transparent conductive film. Among them, the intrinsic silicon film, the n-type doped silicon film and the p-type doped silicon film are all prepared by using the above-mentioned preparation method of the silicon-based film of the present invention.

The solar cell of the present invention has low production cost, good silicon-based film quality, high production efficiency, and high cell conversion efficiency.

By using the preparation method of the present invention to add nitrogen, helium or a combination of the two gases during the preheating and deposition processes, 10% to 80% of hydrogen can be saved, and 5% to 50% of silane can be saved. As shown in Figure 1, the hydrogen content of the film grown using this method is about 40% higher than that of the film grown by the ordinary method, and the Si-H content represented by the low wave number is mainly increased, proving that the density of the film increases with the increase of hydrogen content. has also been increased. A high hydrogen content represents a low density of defect states in the film, and a high density represents an enhanced ability of the film to passivate dangling bonds on the surface of crystalline silicon.

Using the preparation method of the present invention, the hydrogen gas is first glowed and then the reaction gas is introduced, and the resulting film is compared with the conventional method of growing a silicon film on a wafer with a <100> crystal orientation; two types of films were tested using an ellipsometry spectrometer. Thin film, the optical dielectric constant after fitting is shown in Figure 2. Compared with the dielectric constant of the film obtained by the conventional method, the dielectric constant intensity of the film prepared by the reaction gas is increased, which proves that the density of the film grown by the reaction gas is higher and the defect state density is relatively small.

Specific examples are provided below to further describe the solar cell of the present invention in detail.

Example 1:

This embodiment provides a method for preparing a heterojunction solar cell, which includes the following steps:

1) Texturing and cleaning n-type monocrystalline silicon substrate:

Alkaline solutions such as KOH and NaOH are used to texturize the n-type single crystal silicon substrate, and the anisotropic etching characteristics of the single crystal silicon by the alkaline solution are used to form a textured surface on the surface of the n-type single crystal silicon substrate; then RCA1 and RCA2 solutions are used The n-type single crystal silicon substrate is cleaned to obtain an n-type single crystal silicon substrate with a clean surface.

2) Deposit silicon-based thin film:

The intrinsic silicon film and the n-type doped silicon stacked film are sequentially deposited on the first surface of the n-type single crystal silicon substrate by the PECVD method; the n-type single crystal silicon substrate is sequentially deposited on the second surface opposite to the first surface. Intrinsic silicon films and p-type doped silicon laminated films.

Wherein, the intrinsic silicon film and the n-type doped silicon laminated film on the first surface are prepared by the following method: placing the n-type single crystal silicon substrate in a preheating chamber and filling it with nitrogen, hydrogen and helium. The flow volume ratio of the three gases is 5:4:1, and the total gas pressure is 300Pa. Turn on the heater and raise the temperature to 150°C ~ 300°C to preheat for 80 seconds; place the preheated n-type single crystal silicon substrate in the deposition chamber. Fill the deposition chamber with hydrogen and helium, the deposition pressure is 100Pa, and feed the power density 30mW/ ^cm2 to the electrode to trigger the glow discharge. After starting the glow for 10 seconds, fill the reaction gases _SiH4 and CO into the deposition chamber. _2. The volume ratio of diluting gas (hydrogen) and reactive gas is 2:1, thereby depositing an intrinsic silicon-based film with a thickness of 10nm on the substrate; then place the sample in the same or another deposition chamber, and pass it into the deposition chamber. Fill the chamber with hydrogen and helium, keep the pressure at 50Pa, and feed 30 to 500mW/cm ² power to the electrode. Start the glow for 2s to 20s and then fill the deposition chamber with SiH ₄ and PH ₃ , hydrogen and helium. The volume ratio of the total gas flow to the reaction gas is 100 to 500, the volume ratio of PH ₃ to SiH ₄ is 1:100, and an n-type silicon film with a thickness of 5 nm to 10 nm is deposited on the substrate.

The intrinsic silicon film and the p-type doped silicon laminated film on the second surface are prepared by the following method: place the n-type single crystal silicon substrate with the first surface silicon film deposited in a preheating chamber, fill it with nitrogen, Hydrogen and helium, the flow volume ratio of the three gases is 5:3:2, the total pressure range is 50Pa ~ 300Pa, turn on the heater and raise the temperature to 150℃ ~ 300℃ to preheat for 80s; put the preheated n-type single The crystalline silicon substrate is placed in the deposition chamber, and hydrogen and helium gas with a volume ratio of 1:1 to 4:1 are filled into the deposition chamber. The deposition pressure is 100Pa, and a power density of 10 to 30mW/cm ² is fed to the electrode. Trigger the glow discharge. After starting the glow for 2 to 20 seconds, fill the reaction gas SiH ₄ and CO ₂ into the deposition chamber. The ratio of the diluting gas and the reaction gas is 1:1 to 1:4. Deposit on the substrate to form a thickness of 10nm. intrinsic silicon-based film; then place the sample in the same or another deposition chamber, fill the deposition chamber with hydrogen and helium in a ratio of 1:1 to 4:1, keep the pressure at 50Pa to 300Pa, and Feed the power of 10 to 500mW/cm ² to the electrode, start the glow for 2 seconds and then fill the deposition chamber with SiH ₄ and B ₂ H ₆ . The ratio of the total flow rate of hydrogen and helium to the reaction gas is 100 to 500, B The ratio of _2H ₆ to SiH ₄ is 1:100, and a p-type silicon film with a thickness of 10nm to 15nm is deposited on the substrate.

3) Deposit transparent conductive film:

A transparent conductive oxide is deposited on the n-type doped silicon laminated film and the p-type doped silicon laminated film respectively to form a transparent conductive film.

4) Make metal electrodes:

Silver grid electrodes are prepared on the transparent conductive films on the first and second sides of the n-type single crystal silicon substrate, respectively, to obtain a heterojunction solar cell.

In this embodiment, during the deposition process of the silicon-based film, helium gas is introduced to participate in the deposition and growth of the silicon-based film. Through Fourier transform infrared spectroscopy (FTIR) detection, the H content bonded to Si atoms in the prepared silicon-based film reached more than 15%, which was much higher than the bonded hydrogen content of the silicon-based film prepared without introducing helium. . The silicon-based film can be used to passivate the surface of an n-type single crystal silicon substrate to reduce defect states on the surface of the substrate. The recombination rate of minority carriers in the heterojunction solar cell of this embodiment is reduced to less than 5 cm/s.

In the deposition process of silicon-based thin films, the introduction of nitrogen and inert gases greatly reduces the use of hydrogen during the preheating process, reduces the use of SiH ₄ during the deposition process, improves the gas utilization rate of the deposition process, and reduces the cost of the film. The cost incurred by consuming gas during the deposition process.

Example 2:

1) Texturing and cleaning n-type monocrystalline silicon substrate:

Alkaline solutions such as KOH and NaOH are used to texturize the n-type single crystal silicon substrate. The anisotropic etching characteristics of the single crystal silicon by the alkaline solution are used to form a textured surface on the surface of the n-type single crystal silicon substrate; then ozone is used to texturize the single crystal silicon. The silicon substrate is cleaned to obtain an n-type single crystal silicon substrate with a clean surface, which is placed in an ultra-clean space to form a natural oxide layer of about 2 nm on the surface of the single crystal silicon substrate.

2) Deposit silicon thin film passivation layer:

The intrinsic silicon film and the n-type doped silicon stacked film are sequentially deposited on the first surface of the n-type single crystal silicon substrate through HWCVD (hot wire chemical vapor deposition) technology; the n-type single crystal silicon substrate is opposite to the first surface. The intrinsic silicon film and the p-type doped silicon stack film are sequentially deposited on the second surface.

Wherein, the intrinsic silicon film and the n-type doped silicon laminated film on the first surface are prepared by the following method: placing the n-type single crystal silicon substrate in a preheating chamber and filling it with nitrogen, hydrogen and helium. The flow volume ratio of the three gases is 6:1:1, and the total gas pressure is 100Pa. Turn on the infrared lamp heater and raise the temperature to 150°C to preheat for 50s to 150s; place the preheated n-type single crystal silicon substrate in the deposition chamber In the room, the deposition chamber is filled with hydrogen and helium with a volume ratio of 1:1, the deposition pressure is 1Pa, and a current of 20A is passed through the hot wire. The heated wire rapidly heats up and decomposes the gas to produce a glow. After 1s Fill the deposition chamber with reactive gases SiH ₄ and CH _4. The volume ratio of diluting gas (hydrogen) and reactive gas is 2:1, thereby depositing an intrinsic silicon-based film with a thickness of 6nm to 8nm on the substrate; then Place the sample in the same or another deposition chamber, fill the deposition chamber with hydrogen and helium with a volume ratio of 1:1, keep the pressure at 1Pa, and pass a current of 30A to the hot wire, and start the glow for 2 seconds. Fill the deposition chamber with SiH ₄ , CH ₄ and PH ₃ . The ratio of the total flow rate of hydrogen and helium to the reaction gas is 5:1, and the volume ratio of PH ₃ to SiH ₄ is 1:50. Deposit on the substrate to form An n-type wide bandgap silicon carbon film with a thickness of 6nm.

The intrinsic silicon film and the p-type doped silicon laminated film on the second surface are prepared by the following method: place the n-type single crystal silicon substrate with the first surface silicon film deposited in a preheating chamber, fill it with nitrogen, Hydrogen and helium, the flow volume ratio of the three gases is 2:1:1, the total pressure range is 2Pa, turn on the heater and raise the temperature to 150℃~300℃ to preheat for 80s; heat the preheated n-type single crystal silicon The substrate is placed in the deposition chamber, and hydrogen and helium gases with a volume ratio of 1:1 are filled into the deposition chamber, and the deposition pressure is 1.2Pa, and a 20A current is passed through the hot wire to decompose the reaction gas, and the glow is started for 2 seconds. Fill the deposition chamber with the reactive gas SiH ₄ . The volume ratio of the diluting gas and the reactive gas is 1:1. Deposit an intrinsic silicon-based film with a thickness of 10nm on the substrate; then place the sample in the same or another deposition chamber. In the room, fill the deposition chamber with hydrogen and helium in a ratio of 4:1, keep the pressure at 1.8Pa, and pass a 25A current through the hot wire. After decomposing the gas for 2 seconds, fill the deposition chamber with SiH ₄ and B. ₂ H ₆ , the total flow rate of hydrogen and helium to the volume ratio of the reaction gas is 5:1, the volume ratio of B ₂ H ₆ to SiH ₄ is 1:100~1:10, and is deposited on the substrate to form a thickness of 10nm~ 20nm p-type silicon film.

3) Deposit transparent conductive film:

Deposit 90nm to 120nm indium tin oxide transparent conductive oxide on the n-type doped silicon carbon laminated film and the p-type doped silicon laminated film respectively to form a transparent conductive film.

4) Make metal electrodes:

Silver grid electrodes are respectively prepared on the first and second transparent conductive films of the n-type single crystal silicon substrate to obtain a silicon heterojunction solar cell.

In this embodiment, during the deposition process of the silicon-based film, nitrogen and helium are introduced to participate in the preheating of the substrate, and helium is introduced to participate in the deposition of the silicon-based film by the hot wire method. On the one hand, the usage of gas can be saved, and on the other hand, the gas usage can be saved. Increase the density of the film. Through spectroscopic ellipsometry (SE) detection, the imaginary part of the dielectric constant of the prepared silicon-based film can reach about 30, while ordinary silicon films are only about 20.

In summary, during the preheating and deposition process of silicon-based films, the introduction of nitrogen and inert gas helium can greatly reduce the use of hydrogen during the preheating process, reduce the use of SiH ₄ during the deposition process, and improve the efficiency of the deposition process. The gas utilization rate reduces the cost of gas consumption during the film deposition process. At the same time, the reduction of the dissociation rate of helium on the reaction gas and diluent gas increases the hydrogen content in the plasma region and improves the quality of the silicon film.

The technical features of the above-described embodiments can be combined in any way. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, All should be considered to be within the scope of this manual.

The above-described embodiments only express several implementation modes of the present invention, and their descriptions are relatively specific and detailed, but they should not be understood as limiting the scope of the invention patent. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the patent of the present invention should be determined by the appended claims.

Claims

A method for preparing a silicon-based thin film, including the following steps:

Preheating the substrate; and

The preheated substrate is placed in a deposition chamber, hydrogen and inert gas are filled into the deposition chamber to trigger glow discharge, and reactive gas is filled into the deposition chamber to deposit silicon on the substrate. base film.
The method for preparing a silicon-based thin film according to claim 1, in the mixed gas formed by hydrogen, inert gas and reactive gas in the deposition chamber, the volume ratio of hydrogen to reactive gas is (1-3000):1.
According to the preparation method of a silicon-based thin film according to claim 1, in the mixed gas formed by hydrogen, inert gas and reaction gas in the deposition chamber, the volume percentage of the inert gas is 5% to 80%.
According to the method for preparing a silicon-based thin film according to claim 1, during the deposition and formation of the silicon-based thin film, the air pressure in the deposition chamber ranges from 1 Pa to 300 Pa.
The method for preparing a silicon-based thin film according to claim 1, after triggering a glow discharge on the substrate for 1 to 120 s, the reaction gas is filled into the deposition chamber.
The preparation method of a silicon-based film according to any one of claims 1 to 5, wherein the silicon-based film includes an intrinsic silicon film, and the reaction gas includes at least one of CO 2 and CH 4 and SiH 4 and At least one of Si 2 H 6 .
The method for preparing a silicon-based film according to any one of claims 1 to 5, wherein the silicon-based film includes an n-type doped silicon film, and the reaction gas includes at least one of SiH 4 and Si 2 H 6 and PH 3 .
The method for preparing a silicon-based film according to any one of claims 1 to 5, wherein the silicon-based film includes a p-type doped silicon film, and the reaction gas includes at least one of SiH 4 and Si 2 H 6 and B 2 H 6 .
The method for preparing a silicon-based thin film according to any one of claims 1 to 8, wherein preheating the substrate includes the following steps:

The substrate is placed in a preheating chamber, and the substrate is preheated. During the preheating process, hydrogen and inert gas are filled into the preheating chamber.
According to the method for preparing a silicon-based film according to claim 9, nitrogen gas is also filled into the preheating chamber during the preheating process.
According to the preparation method of a silicon-based thin film according to claim 10, the preheating temperature of the substrate is 150°C to 300°C, and the preheating time is 20s to 200s.
The method for preparing a silicon-based film according to claim 10 or 11, in the mixed gas formed of nitrogen, hydrogen and inert gas in the preheating chamber, the volume percentage of nitrogen is 50% to 90%, and the volume percentage of hydrogen is The percentage is 5% to 49%, and the volume percentage of inert gas is 5% to 45%.
According to the method for preparing a silicon-based film according to claim 10 or 11, the air pressure in the preheating chamber during the preheating process ranges from 1 Pa to 300 Pa.
A silicon-based film prepared by the method for preparing a silicon-based film according to any one of claims 1 to 13.
The silicon-based film according to claim 14, which includes one or more of an intrinsic silicon film, an n-type doped silicon film, and a p-type doped silicon film.
A method for preparing a solar cell, including the following steps:

Texturing and cleaning the n-type monocrystalline silicon substrate;

Using the method for preparing a silicon-based thin film according to any one of claims 1 to 13, silicon-based thin films are respectively deposited on two opposite surfaces of the n-type single crystal silicon substrate;

respectively deposit transparent conductive films on the silicon-based films on two opposite surfaces of the n-type single crystal silicon substrate; and

Metal electrodes are respectively made on the transparent conductive films on two opposite surfaces of the n-type single crystal silicon substrate.
The method for preparing a solar cell according to claim 16, depositing silicon-based thin films on two opposite surfaces of the n-type single crystal silicon substrate, including the following steps:

sequentially depositing an intrinsic silicon film and an n-type doped silicon stack film on the first surface of the n-type single crystal silicon substrate; and

An intrinsic silicon film and a p-type doped silicon stacked film are sequentially deposited on the second surface of the n-type single crystal silicon substrate opposite to the first surface.
The method for preparing a solar cell according to claim 17, when depositing the intrinsic silicon film, the reaction gas includes at least one of CO 2 and CH 4 and at least one of SiH 4 and Si 2 H 6 .
According to the method of manufacturing a solar cell according to claim 17, when depositing the n-type doped silicon stack film, the reaction gas includes at least one of SiH 4 and Si 2 H 6 and PH 3 .
According to the method of manufacturing a solar cell according to claim 17, when depositing the p-type doped silicon film, the reaction gas includes at least one of SiH 4 and Si 2 H 6 and B 2 H 6 .
A solar cell prepared by the method for producing a solar cell according to any one of claims 16 to 20.
A solar cell including:

n-type single crystal silicon substrate;

A first silicon-based film is deposited on the first surface of the n-type single crystal silicon substrate. The first silicon-based film is prepared by using the method for preparing a silicon-based film according to any one of claims 1 to 13. get;

A second silicon-based thin film is deposited on the second surface of the n-type single crystal silicon substrate opposite to the first surface. The second silicon-based thin film adopts the method as described in any one of claims 1 to 13. Preparation method of silicon-based thin film;

A transparent conductive film deposited on the first silicon-based film and the second silicon-based film; and

Metal electrodes are provided on the transparent conductive film.
The solar cell according to claim 22, the first silicon-based film includes:

A first intrinsic silicon film deposited on the first surface of the n-type single crystal silicon substrate; and

An n-type doped silicon film is deposited on the surface of the first intrinsic silicon film facing away from the n-type single crystal silicon substrate.
The solar cell according to claim 22, the second silicon-based film includes:

A second intrinsic silicon film is deposited on the second surface of the n-type single crystal silicon substrate; and

A p-type doped silicon film is deposited on the surface of the second intrinsic silicon film facing away from the n-type single crystal silicon substrate.