WO2022247570A1

WO2022247570A1 - Heterojunction solar cell and preparation method therefor

Info

Publication number: WO2022247570A1
Application number: PCT/CN2022/089454
Authority: WO
Inventors: 张海川; 袁强; 石建华; 孟凡英; 刘正新; 程琼; 周华
Original assignee: 中威新能源(成都)有限公司
Priority date: 2021-05-28
Filing date: 2022-04-27
Publication date: 2022-12-01
Also published as: CN113224182A

Abstract

Embodiments of the present application relate to the field of heterojunction solar cells, and provide a heterojunction solar cell and a preparation method therefor. The heterojunction solar cell comprises a silicon substrate; a front-side passivation layer, an n-type doped layer, a front-side TCO layer, and a front-side electrode are sequentially disposed on the front side of the silicon substrate in an overlapped mode; a back-side passivation layer, a p-type doped layer, a back-side TCO layer, and a back-side electrode are sequentially disposed on the back side of the silicon substrate in an overlapped mode; the front-side TCO layer and/or the back-side TCO layer comprise/comprises at least two layers of TCO thin films, the TCO thin films of some layers are low-doped TCO thin films having a doping concentration of 0wt% to 5wt%, and the TCO thin films of some layers are high-doped TCO thin films having a doping concentration of 8wt% to 15wt%. According to the heterojunction solar cell and the preparation method therefor, the reliability of the heterojunction solar cell is effectively improved and the aging attenuation of the heterojunction solar cell is slowed down while the cost and efficiency of the cell are ensured.

Description

A kind of heterojunction solar cell and its preparation method

Cross References to Related Applications

This application claims the priority of the Chinese patent application with application number 202110596804.2 and titled "A Heterojunction Solar Cell and Its Preparation Method" filed with the State Intellectual Property Office of China on May 28, 2021, the entire contents of which are incorporated by reference incorporated in this application.

technical field

The present application relates to the field of heterojunction solar cells, in particular, to a heterojunction solar cell and a preparation method thereof.

Background technique

In today's society, environmental protection is a major issue, and it is imperative to vigorously develop clean energy. Solar energy is a kind of energy with huge reserves, clean and pollution-free, and has broad application prospects. The use of solar energy is mainly to use solar cells to convert it for electrical energy. At present, crystalline silicon solar cells occupy more than 90% of the market, and crystalline silicon solar cells are mainly PERC (Passivated Emitter and Rear Cell, passivated emitter and rear passivated) cells, but the efficiency of PERC cells is already at a low level. In the bottleneck period, it is too difficult to improve efficiency. At the same time, heterojunction solar cells have the advantages of symmetrical structure, high open circuit voltage, good temperature characteristics, thin silicon wafers, and low-temperature manufacturing processes. They are entering the stage of industrialization and becoming one of the industry's target products.

The general preparation process of heterojunction solar cells is to use N-type crystalline silicon as the substrate, and form a "pyramid" light-trapping structure by cleaning and texturing, and then deposit intrinsic amorphous silicon passivation layers, A p-type doped layer, an intrinsic amorphous silicon passivation layer, and an n-type doped layer are deposited on both sides of a transparent conductive oxide (TCO, Transparent Conductive Oxide) film, and finally a silver electrode is prepared. However, the reliability of the current heterojunction solar cells is poor, which is mainly manifested in the rapid attenuation in the sodium resistance test, damp heat test (DH), and thermal cycle test (TC); if specific materials are used to improve the reliability of heterojunction solar cells The reliability will increase the cost.

Contents of the invention

The embodiment of the present application provides a heterojunction solar cell and a preparation method thereof, which can effectively improve the reliability of the heterojunction solar cell and slow down the aging attenuation of the heterojunction solar cell while ensuring the cost and efficiency of the cell.

Some embodiments of the present application provide a heterojunction solar cell, which may include a silicon substrate, and the front side of the silicon substrate is sequentially stacked with a front passivation layer, an n-type doped layer, a front TCO layer and a front electrode, The back side of the silicon substrate is successively provided with a back passivation layer, a p-type doped layer, a back TCO layer and a back electrode, and the front TCO layer and/or the back TCO layer include at least two layers of TCO films, of which some layers of TCO films It is a low-doped TCO film with a doping concentration of 0wt% to 5wt%, and some layers of the TCO film are high-doped TCO films with a doping concentration of 8wt% to 15wt%.

In the above implementation process, at least one of the transparent conductive oxide (TCO) films on the front and back of the heterojunction solar cell adopts a stacked structure in which a highly doped TCO film and a low doped TCO film are combined, which can improve The reliability and photoelectric conversion efficiency of heterojunction solar cells slow down the aging and attenuation of heterojunction solar cells, so that heterojunction solar cells take into account the cost, efficiency and reliability of heterojunction solar cells.

In a possible implementation manner, the thickness of the low-doped TCO film may be 10 nm to 80 nm; the thickness of the highly doped TCO film may be 20 nm to 80 nm.

In a possible implementation manner, the low-doped TCO films and the highly-doped TCO films in the front TCO layer and/or the back TCO layer may be respectively arranged sequentially or alternately according to gradually changing doping concentrations.

In a possible implementation manner, the front TCO layer may include at least two layers of TCO thin films, and the doping concentration of each layer of TCO thin films decreases sequentially from the direction close to the silicon substrate to the direction away from the silicon substrate;

Alternatively, the front TCO layer includes an even number of TCO films, and all TCO films are grouped in pairs from adjacent to far away from the silicon substrate, and the doping concentration of the TCO films adjacent to the silicon substrate in each group is greater than that of the TCO films far away from the silicon substrate. doping concentration of the film.

In a possible implementation manner, the front TCO layer may include four layers of TCO thin films, and the four layers of TCO thin films are respectively arranged as a first front TCO thin film and a second front TCO thin film in a direction from adjacent to away from the silicon substrate. , the third front TCO film and the fourth front TCO film, wherein, the first front TCO film is an indium oxide-based TCO film with a thickness of 10nm and a tin doping concentration of 10wt%, and the second front TCO film has a thickness of is an indium oxide-based TCO film with a thickness of 20nm and a tin doping concentration of 3wt%, the third front TCO film is an indium oxide-based TCO film with a thickness of 30nm and a tin doping concentration of 10wt%, and the fourth front TCO The film 214 is an indium oxide-based TCO film with a thickness of 30 nm and a tin doping concentration of 3 wt%.

In the above implementation process, the high-doped TCO film has high electrical conductivity, and the low-doped TCO film has good light transmittance. The TCO film with doping concentration decreasing from high to low is arranged on the front of the light-receiving surface, which can fully Utilize the different properties of highly doped TCO thin films and low doped TCO thin films on light transmittance and electrical conductivity to improve the short-circuit current of heterojunction cells and improve the photoelectric conversion efficiency.

In a possible implementation manner, the back TCO layer includes at least two TCO thin films, and the doping concentration of each TCO thin film increases sequentially from the direction close to the silicon substrate to the direction away from the silicon substrate;

Alternatively, the back TCO layer includes an even number of TCO thin films, and all TCO thin films are grouped in pairs from adjacent to far away from the silicon substrate, and the doping concentration of the TCO thin films adjacent to the silicon substrate in each group is less than that of the TCO thin films far away from the silicon substrate. doping concentration of the film.

In a possible implementation manner, the back TCO layer may include four layers of TCO thin films, and the four layers of TCO thin films are respectively arranged as a first back TCO thin film and a second back TCO thin film in a direction adjacent to and away from the silicon substrate. , the third back TCO film and the fourth back TCO film, the first back TCO film is an indium oxide-based TCO film with a thickness of 10nm and a tin doping concentration of 3wt%, and the second back TCO film has a thickness of 20nm indium oxide-based TCO film with a tin doping concentration of 10wt%, the third back TCO film 223 is an indium oxide-based TCO film with a thickness of 30nm and a tin doping concentration of 3wt%, and the fourth back TCO film The film 224 is an indium oxide-based TCO film with a thickness of 30 nm and a tin doping concentration of 10 wt%.

In the above implementation process, the high-doped TCO film has high electrical conductivity, and the low-doped TCO film has good light transmittance. On the back of the backlight surface, TCO films with doping concentrations increasing in sequence from low to high can fully Utilizing the different performances of highly doped TCO films and low doped TCO films on light transmittance and electrical conductivity, the setting of TCO film stacks can enhance the long-wave reflection of light on the back, improve the short-circuit current of heterojunction cells, and improve photoelectric conversion efficiency. .

In a possible implementation manner, the front passivation layer and/or the back passivation layer is an intrinsic silicon passivation layer, and the thickness of the front passivation layer and/or the back passivation layer is 4 nm to 10 nm.

In a possible implementation, the n-type doped layer can be an n-type doped amorphous silicon or microcrystalline silicon layer, the doping concentration is 0.5wt% to 5wt%, and the thickness of the n-type doped layer is 5nm to 5nm. 15nm;

And/or, the p-type doped layer is a p-type doped amorphous silicon or microcrystalline silicon layer, the doping concentration is 0.5wt% to 5wt%, and the p-type doped layer has a thickness of 8nm to 20nm.

In a possible implementation manner, the front electrode and/or the back electrode may be a silver grid line electrode with a thickness of 2 μm to 50 μm.

Other embodiments of the present application provide a method for preparing a heterojunction solar cell according to some embodiments of the present application, which may include the following steps:

A front passivation layer, an n-type doped layer and a front TCO layer are sequentially deposited on the front side of the silicon substrate, and a back passivation layer, a p-type doped layer and a back TCO layer are sequentially deposited on the back side of the silicon substrate;

A front electrode is prepared on the surface of the front TCO layer, and a back electrode is prepared on the surface of the back TCO layer.

In a possible implementation, the deposition method of the TCO film can be: radio frequency sputtering, DC sputtering or pulse sputtering; the target is a planar target or a rotating target;

In the deposition method of the TCO thin film: the process chamber pressure is 0.1Pa to 1Pa; the argon flow rate is 400sccm to 1000sccm; the oxygen flow rate is 5sccm to 50sccm; the silicon substrate temperature is 100°C to 220°C; the power is 5kW to 20kW.

In a possible implementation, the preparation methods of the front electrode and the back electrode can be: screen printing, evaporation, magnetron sputtering or inkjet printing;

And/or, the deposition methods of the front passivation layer, n-type doped layer, back passivation layer, and p-type doped layer are: PECVD, Cat.CVD or HWCVD; the temperature of the silicon substrate in the deposition method is 150°C to 250°C; the process chamber pressure is 10Pa to 100Pa.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings that need to be used in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, so It should not be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings according to these drawings without creative work.

FIG. 1 is a schematic structural diagram of a heterojunction solar cell provided in the first embodiment of the present application;

FIG. 2 is a schematic structural diagram of a heterojunction solar cell provided in the second embodiment of the present application.

Icon: 100-heterojunction solar cell; 110-silicon substrate; 120-front passivation layer; 130-n-type doped layer; 141-first front TCO film; 142-second front TCO film; 150-front Electrode; 160-back passivation layer; 170-p-type doped layer; 181-first back TCO film; 182-second back TCO film; 190-back electrode; 200-heterojunction solar cell; 211-first 212-second front TCO film; 213-third front TCO film; 214-fourth front TCO film; 221-first back TCO film; 222-second back TCO film; 223-third back TCO film Film; 224 - fourth backside TCO film.

Detailed ways

The applicant found in the process of realizing this application that the TCO thin film has the following important functions in heterojunction solar cells: 1. As a surface anti-reflection window layer, it needs to have excellent optical transmittance, low parasitic absorption and suitable optical The refractive index allows the incident light to enter the silicon absorbing layer to the maximum; 2. As a carrier collection and transport layer, it needs to have excellent lateral and vertical conductivity, effectively collect and transmit to the low-conductivity amorphous silicon thin film layer; 3. , As a protective layer, it needs to have good chemical inertness and ion barrier properties to effectively protect the amorphous silicon thin film layer.

Based on the important role of TCO thin films in heterojunction solar cells, TCO thin films in heterojunction solar cells are usually prepared by magnetron sputtering (PVD), and the widely used TCO target material has a tin doping concentration of about 10wt%. Indium oxide (referred to as 9010 target). However, the reliability of the heterojunction solar cells obtained by using the 9010 target is poor, which is mainly reflected in the severe attenuation in the sodium resistance test, damp heat test (DH), and thermal cycle test (TC). The applicant analyzed the reason and speculated that the main reason is that when the TCO target material with high tin doping concentration is prepared into a TCO film by PVD technology, there are many defects formed inside the film, and the compactness is not good, which cannot effectively block the particles that damage the battery structure. Get inside the battery. The applicant further speculates that the target material with low doping concentration has a low content of impurity ions, and when the TCO film is prepared by PVD technology, there are fewer internal defects, and the film has good compactness, which can effectively prevent particles that destroy the battery structure from entering the battery. Thereby improving the reliability of the battery and reducing the aging and attenuation of the battery. However, the preparation process of the indium oxide ceramic target with a lower tin doping concentration is more difficult, so its cost is higher, and the efficiency of the formed heterojunction solar cell will be reduced. Considering the cost, efficiency and reliability of heterojunction solar cells comprehensively, the applicant has explored a heterojunction solar cell with a new structure.

When PVD prepares TCO film, the oxygen partial pressure also has a certain influence on the reliability of the battery, mainly by adjusting the oxygen vacancy defects inside the TCO film; in general, under high oxygen conditions, the concentration of oxygen vacancies inside the TCO film is low, and the battery reliability is better ; Under low oxygen conditions, the concentration of oxygen vacancies inside the TCO film is high, and the reliability of the battery is poor.

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, not all of them. The components of the embodiments of the application generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the present application. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of this application.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer" etc. is based on the orientation or positional relationship shown in the drawings, or the The usual orientation or positional relationship of the application product when used is only for the convenience of describing the application and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, therefore It should not be construed as a limitation of the application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the term "arrangement" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application in specific situations.

A heterojunction solar cell according to some embodiments of the present application will be described below with reference to FIG. 1 . Some embodiments of the present application provide a heterojunction solar cell 100, the heterojunction solar cell 100 includes a silicon substrate 110, and the silicon substrate 110 has two surfaces, respectively the front (direct light surface) and the back ( The surface opposite to the surface directly irradiated by light), the front side of the silicon substrate 110 is sequentially superimposed with a front passivation layer 120, an n-type doped layer 130, a front TCO layer and a front electrode 150, and the back side of the silicon substrate 110 is sequentially superimposed with a back side The passivation layer 160, the p-type doped layer 170, the back TCO layer and the back electrode 190, the front TCO layer and/or the back TCO layer include at least two stacked TCO films, wherein some layers of TCO films are low-doped TCO film, some layers of TCO film are highly doped TCO film.

In this embodiment, the silicon substrate 110 is an n-type single crystal silicon substrate.

In the embodiment of the present application, the front passivation layer 120 is an intrinsic silicon passivation layer, such as an intrinsic amorphous silicon passivation layer or an intrinsic microcrystalline silicon passivation layer, and the thickness of the front passivation layer 120 is 4nm to 10nm. The back passivation layer 160 is an intrinsic silicon passivation layer, such as an intrinsic amorphous silicon passivation layer or an intrinsic microcrystalline silicon passivation layer, and the thickness of the back passivation layer 160 is 4 nm to 10 nm. In this embodiment, the front passivation layer 120 is an intrinsic amorphous silicon passivation layer a-Si:H(i) with a thickness of 8 nm.

In the embodiment of the present application, the n-type doped layer 130 is an n-type doped amorphous silicon layer or an n-type doped microcrystalline silicon layer, the doping concentration is 0.5wt% to 5wt%, and the thickness of the n-type doped layer 130 is 5nm to 15nm. In this embodiment, the n-type doped layer 130 is an n-type doped amorphous silicon layer a-Si:H(i)<n> film with a thickness of 10 nm.

In the embodiment of the present application, the p-type doped layer 170 is a p-type doped amorphous silicon layer or a p-type doped microcrystalline silicon layer, the doping concentration is 0.5wt% to 5wt%, and the thickness of the p-type doped layer 170 is 8nm to 20nm. In this embodiment, the p-type doped layer 170 is a p-type doped amorphous silicon layer a-Si:H(i) film with a thickness of 12 nm.

In the embodiment of the present application, a combination of a highly doped TCO film with a relatively high doping concentration and a low-doped TCO film with a relatively low doping concentration is combined to take into account the cost, efficiency and reliability of the heterojunction solar cell 100 . TCO films are tin-doped or undoped indium oxide-based or zinc oxide-based films, such as tin-doped indium oxide (ITO, In ₂ O ₃ : Sn), aluminum-doped zinc oxide (AZO, ZnO: Al) , fluorine-doped tin oxide (FTO, SnO ₂ : F), antimony-doped tin oxide (ATO, Sn ₂ O: Sb), the doping concentration is 0wt% to 20wt%, and the doping of the low-doped TCO film The concentration is 0wt% to 5wt% (low doping range), and the doping concentration of the highly doped TCO thin film is 8wt% to 15wt% (high doping range). The thickness of the TCO thin film is 10nm to 80nm, wherein the thickness of the low doped TCO thin film is 10nm to 80nm, and the thickness of the high doped TCO thin film is 20nm to 80nm.

In this embodiment, the front TCO layer and the back TCO layer are respectively provided with a low-doped TCO film and a high-doped TCO film at the same time, that is, the low-doped TCO film and the high-doped TCO film in the front TCO layer and the back TCO layer respectively according to The doping concentration is gradually changed sequentially or alternately. In other embodiments, only the front TCO layer can adopt the above-mentioned design, and the back TCO layer can adopt a conventional design, that is, a single-layer TCO film, or the back TCO layer can adopt the above-mentioned design, and the front TCO layer can adopt a conventional design, that is, a single-layer TCO film. film.

For the situation that the low-doped TCO film and the high-doped TCO film of the front TCO layer are arranged in sequence according to the gradual change of doping concentration, as an implementation mode, the front TCO layer includes at least two layers of TCO films, and the doping of each layer of TCO films The concentration decreases sequentially in a direction from being close to the silicon substrate 110 to being far away from the silicon substrate 110 .

For the case where the low-doped TCO films and the high-doped TCO films of the front TCO layer are arranged alternately, as another implementation, the front TCO layer includes an even number of TCO films, and all the TCO films are arranged in a direction from adjacent to far away from the silicon substrate 110. Two by two form a group, and the doping concentration of the TCO thin films adjacent to the silicon substrate 110 in each group is greater than the doping concentration of the TCO thin films far from the silicon substrate 110 .

It should be noted that no matter which of the above-mentioned conditions is used for the front TCO layer, there must be a high-doped TCO film in the TCO film, and there must also be a low-doped TCO film. Doped TCO thin film (that is, the doping concentration is not in the high doping range, nor in the low doping range).

In this embodiment, the front TCO layer includes two layers of TCO thin films, and the two layers of TCO thin films are arranged in the direction adjacent to and far away from the silicon substrate 110, which are respectively a first front TCO film 141 and a second front TCO film 142. The film 141 is an indium oxide-based TCO film (highly doped TCO film) with a thickness of 20 nm and a tin doping concentration of 10 wt%, and the second front TCO film 142 is an indium oxide film with a thickness of 70 nm and a tin doping concentration of 3 wt%. Base TCO film (low doped TCO film). In other embodiments, the front TCO layer includes n layers of TCO thin films, n>3, respectively marked as TCO1, TCO2, TCO3, ..., TCOn, and all the above TCO thin films are arranged in a direction from adjacent to away from the silicon substrate 110 (according to The doping concentration of TCO1 , TCO2 , TCO3 , .

For the situation that the low-doped TCO film and the high-doped TCO film of the back TCO layer are arranged in sequence according to the gradual change of the doping concentration, as an implementation mode, the back TCO layer includes at least two TCO films, and the doping of each TCO film The concentration increases sequentially in a direction from being close to the silicon substrate 110 to being far away from the silicon substrate 110 .

For the case where the low-doped TCO films and the high-doped TCO films of the back TCO layer are arranged alternately, as another implementation, the back TCO layer includes an even number of TCO films, and all the TCO films are arranged in a direction from adjacent to far away from the silicon substrate 110. The doping concentration of the TCO films adjacent to the silicon substrate 110 in each group is smaller than the doping concentration of the TCO films far away from the silicon substrate 110 .

It should be noted that no matter which of the above-mentioned conditions is used for the back TCO layer, there must be a high-doped TCO film in the TCO film, and there must also be a low-doped TCO film. Doped TCO thin film (that is, the doping concentration is not in the high doping range, nor in the low doping range).

In this embodiment, the back TCO layer includes two layers of TCO films, and the two layers of TCO films are arranged in the direction from adjacent to far away from the silicon substrate 110 and are respectively a first back TCO film 181 and a second back TCO film 182. The film 181 is an indium oxide-based TCO film (lowly doped TCO film) with a thickness of 20nm and a tin doping concentration of 3wt%, and the second back TCO film 182 is an indium oxide film with a thickness of 70nm and a tin doping concentration of 10wt%. Base TCO film (highly doped TCO film). In other embodiments, the back TCO layer may also include n layers of TCO thin films, n>3, respectively marked as TCO1, TCO2, TCO3, ..., TCOn, and all the above-mentioned TCO thin films are arranged in a direction from adjacent to away from the silicon substrate 110 (according to the deposition sequence) the doping concentration increases sequentially, and the doping concentrations of TCO1, TCO2, TCO3, . . .

In the embodiment of the present application, the front electrode 150 is a silver wire electrode with a thickness of 2 μm to 50 μm. The back electrode 190 is a silver grid line electrode with a thickness of 2 μm to 50 μm. In this embodiment, both the front electrode 150 and the back electrode 190 are metallic silver grid lines with a thickness of 20 μm.

This embodiment also provides a method for preparing a heterojunction solar cell 100, which includes the following steps:

First, the front passivation layer 120, the n-type doped layer 130 and the front TCO layer are sequentially deposited on the front side of the silicon substrate 110, and the back passivation layer 160, the p-type doped layer are sequentially deposited on the back side of the silicon substrate 110. 170 and back TCO layer.

Among them, the deposition method of TCO film is: radio frequency sputtering, DC sputtering or pulse sputtering; corresponding PVD includes vertical PVD, inclined PVD and horizontal PVD, etc.; the target is a planar target or a rotating target; TCO The chamber pressure of the film deposition process is 0.1Pa to 1Pa; the flow rate of argon is 400sccm to 1000sccm; the flow rate of oxygen is 5sccm to 50sccm; the temperature of the silicon substrate 110 is 100°C to 220°C; the power is 5kW to 20kW.

Wherein, the front passivation layer 120, the n-type doped layer 130, the back passivation layer 160, and the p-type doped layer 170 can respectively adopt PECVD or Cat.CVD, HWCVD or other chemical vapor deposition methods; the temperature of the silicon substrate 110 is 150°C to 250°C; process chamber pressure is 10Pa to 100Pa.

Next, a front electrode 150 is prepared on the surface of the front TCO layer, and a back electrode 190 is prepared on the surface of the back TCO layer.

Wherein, the preparation methods of the front electrode 150 and the back electrode 190 may be: screen printing, vapor deposition, magnetron sputtering or inkjet printing and other methods.

Specifically, the preparation method of the heterojunction solar cell 100 of this embodiment is as follows:

The n-type single crystal silicon is used as the silicon substrate 110 and cleaned and textured to form a pyramid-shaped light-trapping structure.

Then use chemical vapor deposition methods such as PECVD, Cat.CVD, HWCVD to deposit 8nm thick a-Si:H(i) on both sides as the front passivation layer 120 and the back passivation layer 160, and deposit 10nm thick a- The Si:H(i)<n> thin film serves as the n-type doped layer 130 , and the 12 nm-thick a-Si:H(i) thin film serves as the p-type doped layer 170 .

Using the pulse magnetron sputtering method, the adjusted power is 13KW, the flow rate of argon is 800sccm, and the flow rate of oxygen is 35sccm and 10sccm respectively, on a-Si:H(i), deposit 20nm thick tin-doped An indium oxide-based TCO film with a dopant concentration of 3wt% (the first back TCO film 181 ) and a 70nm-thick indium oxide-based TCO film with a tin doping concentration of 10wt% (the second back TCO film 182 ).

Then, using the pulse magnetron sputtering method, the power is adjusted to 13KW, the flow rate of argon is 800sccm, and the flow rate of oxygen is 12sccm and 30sccm respectively, and the tin doped with a thickness of 20nm is sequentially deposited on a-Si:H(i)<n> An indium oxide-based TCO film with a dopant concentration of 10wt% (the first front TCO film 141 ) and an indium oxide-based TCO film with a thickness of 70nm and a tin doping concentration of 3wt% (the second front TCO film 142 ).

Finally, 20 μm thick metal silver grid lines were printed on the second front TCO film 142 and the second back TCO film 182 as the front electrode 150 and the back electrode 190 respectively by silk printing method.

Through the sodium resistance test, damp heat test (DH), and thermal cycle test (TC), the aging attenuation of the heterojunction solar cell 100 made by the conventional process is 8% in the first test, and the aging attenuation in the second test is 8%. 9%, and the aging decay of the third test is 8%. The aging decay of the heterojunction solar cell 100 in this embodiment is 1.5% in the first test, 2.5% in the second test, and 2% in the third test.

It can be seen that, compared with the conventional heterojunction solar cell 100, the heterojunction solar cell 100 of this embodiment improves the conductivity of the TCO layer and the carrier collection efficiency, enhances current collection, and can effectively reduce aging attenuation and improve reliability. .

Heterojunction solar cells according to other embodiments of the present application will be described below with reference to FIG. 2 . Other embodiments of the present application provide a heterojunction solar cell 200. The heterojunction solar cell 200 includes a silicon substrate 110. The impurity layer 130, the front TCO layer and the front electrode 150, the back side of the silicon substrate 110 are successively provided with a back passivation layer 160, a p-type doped layer 170, a back TCO layer and a back electrode 190, a front TCO layer and a back TCO layer Including four layers of superimposed TCO films, wherein two layers of TCO films are low-doped TCO films with a doping concentration of 0wt% to 5wt%, and two layers of TCO films are high-doped TCO films with a doping concentration of 8wt% to 15wt%. film.

Specifically, the silicon substrate 110 is an n-type single crystal silicon substrate.

Both the front passivation layer 120 and the back passivation layer 160 are intrinsic amorphous silicon passivation layers a-Si:H(i) with a thickness of 8 nm.

The n-type doped layer 130 is an n-type doped amorphous silicon layer a-Si:H(i)<n> film with a thickness of 10 nm.

The p-type doped layer 170 is a p-type doped amorphous silicon layer a-Si:H(i) film with a thickness of 12 nm.

The front TCO layer includes four layers of TCO films, and these four layers of TCO films are arranged in a direction from adjacent to far away from the silicon substrate 110, respectively as a first front TCO film 211, a second front TCO film 212, a third front TCO film 213 and a fourth front TCO film. The front TCO film 214, the first front TCO film 211 is an indium oxide-based TCO film (highly doped TCO film) with a thickness of 10nm and a tin doping concentration of 10wt%, and the second front TCO film 212 is a thickness of 20nm, tin Indium oxide-based TCO film (lowly doped TCO film) with a doping concentration of 3wt% The third front TCO film 213 is an indium oxide-based TCO film (highly doped TCO film) with a thickness of 30nm and a tin doping concentration of 10wt% , the fourth front TCO film 214 is an indium oxide-based TCO film (lowly doped TCO film) with a thickness of 30 nm and a tin doping concentration of 3 wt%.

The back TCO layer includes four layers of TCO films, and these four layers of TCO films are arranged in a direction from adjacent to far away from the silicon substrate 110, respectively as a first back TCO film 221, a second back TCO film 222, a third back TCO film 223 and a fourth back TCO film. The back TCO film 224, the first back TCO film 221 is an indium oxide-based TCO film (lowly doped TCO film) with a thickness of 10 nm and a tin doping concentration of 3 wt%, and the second back TCO film 222 is a thickness of 20 nm, tin The doping concentration is an indium oxide-based TCO film (highly doped TCO film) with a doping concentration of 10wt%. ), the fourth back TCO film 224 is an indium oxide-based TCO film (highly doped TCO film) with a thickness of 30 nm and a tin doping concentration of 10 wt%.

Both the front electrode 150 and the back electrode 190 are metallic silver grid lines with a thickness of 20 μm.

The preparation method of the heterojunction solar cell 200 is as follows:

Then use chemical vapor deposition methods such as PECVD, Cat.CVD, HWCVD to deposit 8nm thick a-Si:H(i) on both sides as the front passivation layer 120 and the back passivation layer 160, and deposit 10nm thick a- Si:H(i)<n> serves as the n-type doped layer 130 , and a 12 nm-thick a-Si:H(i) thin film serves as the p-type doped layer 170 .

Using the pulsed magnetron sputtering method, the power is adjusted to 13KW, the flow rate of argon gas is 800 sccm, and the flow rate of oxygen gas is 35 sccm, 20 sccm, 10 sccm, and 5 sccm respectively, and 10 nm is sequentially deposited on a-Si:H(i) The indium oxide-based TCO film (the first front TCO film 211) with a tin doping concentration of 3wt%, the indium oxide-based TCO film (the second front TCO film 212) with a 20nm tin doping concentration of 10wt%, and the 30nm tin doping concentration 3wt% indium oxide-based TCO thin film (third front TCO thin film 213 ), 30nm indium oxide-based TCO thin film with tin doping concentration of 10wt% (fourth front TCO thin film 214 ).

Then use the pulsed magnetron sputtering method, adjust the power to 13KW, argon gas flow to 800sccm, and oxygen flow to 5sccm, 10sccm, 15sccm, and 25sccm respectively to deposit 10nm on a-Si:H(i)<n> The indium oxide-based TCO film (the first back TCO film 221) with a tin doping concentration of 10wt%, the indium oxide-based TCO film (the second back TCO film 222) with a 20nm tin doping concentration of 3wt%, and the 30nm tin doping concentration 10wt% indium oxide-based TCO film (third back TCO film 223 ), 30nm indium oxide-based TCO film with tin doping concentration of 3wt% (fourth back TCO film 224 ).

Finally, 20 μm thick metal silver grid lines were printed on the fourth front TCO film 214 and the fourth back TCO film 224 respectively by silk printing method as the front electrode 150 and the back electrode 190 .

To sum up, the heterojunction solar cell 200 and its preparation method according to the embodiment of the present application can effectively improve the reliability of the heterojunction solar cell 200 and slow down the aging of the heterojunction solar cell 200 while ensuring the cost and efficiency of the cell. attenuation.

The above descriptions are only examples of the present application, and are not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and changes may be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Industrial Applicability

The application provides a heterojunction solar cell and a preparation method thereof, relating to the field of heterojunction solar cells. The heterojunction solar cell includes a silicon substrate, the front side of the silicon substrate is sequentially provided with a front passivation layer, an n-type doped layer, a front TCO layer and a front electrode, and the back side of the silicon substrate is sequentially provided with a rear passivation layer. layer, p-type doped layer, back TCO layer and back electrode, the front TCO layer and/or the back TCO layer include at least two layers of TCO films, wherein the TCO films of some layers are low-doped TCO films with a doping concentration of 0wt% to 5wt%. The doped TCO thin film, the TCO thin film of some layers is a highly doped TCO thin film with a doping concentration of 8wt% to 15wt%. The heterojunction solar cell and the preparation method thereof effectively improve the reliability of the heterojunction solar cell and slow down the aging attenuation of the heterojunction solar cell while ensuring the cost and efficiency of the cell. .

In addition, it is understood that the heterojunction solar cell of the present application and its fabrication method are reproducible and can be used in various industrial applications. For example, the heterojunction solar cell and its preparation method of the present application can be used in the field of heterojunction solar cells.

Claims

A heterojunction solar cell is characterized in that it includes a silicon substrate, and the front of the silicon substrate is sequentially stacked with a front passivation layer, an n-type doped layer, a front TCO layer and a front electrode, and the silicon The back side of the substrate is successively provided with a back passivation layer, a p-type doped layer, a back TCO layer and a back electrode, and the front TCO layer and/or the back TCO layer include at least two TCO thin films, wherein some layers The TCO film is a low-doped TCO film with a doping concentration of 0wt% to 5wt%, and some of the TCO films in the layers are highly doped TCO films with a doping concentration of 8wt% to 15wt%.
The heterojunction solar cell according to claim 1, wherein the thickness of the low-doped TCO thin film is 10 nm to 80 nm; the thickness of the highly doped TCO thin film is 20 nm to 80 nm.
The heterojunction solar cell according to claim 1 or 2, characterized in that the low-doped TCO film and the high-doped TCO film in the front TCO layer and/or the back TCO layer are respectively adjusted according to the doping concentration Gradual changes are set sequentially or alternately.
The heterojunction solar cell according to any one of claims 1 to 3, characterized in that, the front TCO layer comprises at least two TCO thin films, and the doping concentration of each TCO thin film is in accordance with the order of being adjacent to far from all The direction of the silicon substrate decreases in turn;

Alternatively, the front TCO layer includes an even number of TCO films, and all the TCO films are grouped in pairs from adjacent to far away from the silicon substrate, and the TCO films adjacent to the silicon substrate in each group are The doping concentration is greater than that of the TCO thin film far away from the silicon substrate.
The heterojunction solar cell according to any one of claims 1 to 4, characterized in that, the front TCO layer comprises four layers of TCO films, and the four layers of TCO films are arranged in a direction from adjacent to away from the silicon substrate They are the first front TCO film, the second front TCO film, the third front TCO film and the fourth front TCO film, wherein the first front TCO film is indium oxide with a thickness of 10nm and a tin doping concentration of 10wt%. base TCO film, the second front TCO film is an indium oxide-based TCO film with a thickness of 20nm and a tin doping concentration of 3wt%, and the third front TCO film is 30nm in thickness and a tin doping concentration of 10wt%. Indium oxide-based TCO film, the fourth front TCO film 214 is an indium oxide-based TCO film with a thickness of 30 nm and a tin doping concentration of 3 wt%.
The heterojunction solar cell according to any one of claims 1 to 5, characterized in that the back TCO layer comprises at least two layers of TCO thin films, and the doping concentration of each layer of the TCO thin films is in accordance with the order of being adjacent to far from all The direction of the silicon substrate increases sequentially;

Alternatively, the back TCO layer includes an even number of TCO thin films, and all the TCO thin films are grouped in pairs from adjacent to far away from the silicon substrate, and the TCO thin films adjacent to the silicon substrate in each group are The doping concentration is smaller than that of the TCO thin film far away from the silicon substrate.
The heterojunction solar cell according to any one of claims 1 to 6, characterized in that, the back TCO layer comprises four layers of TCO films, and the four layers of TCO films are arranged in a direction from adjacent to away from the silicon substrate Respectively, the first back TCO film, the second back TCO film, the third back TCO film and the fourth back TCO film, the first back TCO film is an indium oxide-based film with a thickness of 10nm and a tin doping concentration of 3wt%. TCO film, the second back TCO film is an indium oxide-based TCO film with a thickness of 20nm and a tin doping concentration of 10wt%, and the third back TCO film 223 has a thickness of 30nm and a tin doping concentration of 3wt%. Indium oxide-based TCO film, the fourth back TCO film 224 is an indium oxide-based TCO film with a thickness of 30 nm and a tin doping concentration of 10 wt%.
The heterojunction solar cell according to any one of claims 1 to 7, characterized in that, the front passivation layer and/or the back passivation layer are intrinsic silicon passivation layers, and the front passivation layer The thickness of the passivation layer and/or the back passivation layer is 4nm to 10nm.
The heterojunction solar cell according to any one of claims 1 to 8, wherein the n-type doped layer is an n-type doped amorphous silicon or microcrystalline silicon layer, and the doping concentration is 0.5wt % to 5wt%, the thickness of the n-type doped layer is 5nm to 15nm;

And/or, the p-type doped layer is a p-type doped amorphous silicon or microcrystalline silicon layer, the doping concentration is 0.5wt% to 5wt%, and the thickness of the p-type doped layer is 8nm to 20nm.
The heterojunction solar cell according to any one of claims 1 to 9, characterized in that the front electrode and/or the back electrode are silver grid wire electrodes with a thickness of 2 μm to 50 μm.
A method for preparing a heterojunction solar cell according to any one of claims 1 to 10, characterized in that it comprises the following steps:

Depositing the front passivation layer, the n-type doped layer and the front TCO layer sequentially on the front side of the silicon substrate, depositing the rear passivation layer, the front TCO layer on the back side of the silicon substrate in sequence the p-type doped layer and the back TCO layer;

The front electrode is prepared on the surface of the front TCO layer, and the back electrode is prepared on the surface of the back TCO layer.
The method for preparing a heterojunction solar cell according to claim 11, wherein the deposition method of the TCO thin film is: radio frequency sputtering, direct current sputtering or pulse sputtering; the target is a planar target or a rotating target material;

In the deposition method of the TCO thin film: the process chamber pressure is 0.1Pa to 1Pa; the argon flow rate is 400sccm to 1000sccm; the oxygen flow rate is 5sccm to 50sccm; the silicon substrate temperature is 100°C to 220°C; and the power is 5kW to 20kW.
The preparation method of heterojunction solar cells according to claim 11 or 12, characterized in that the preparation methods of the front electrode and the back electrode are respectively: screen printing, evaporation, magnetron sputtering or spraying ink printing;

And/or, the deposition methods of the front passivation layer, the n-type doped layer, the back passivation layer, and the p-type doped layer are respectively: PECVD, Cat.CVD or HWCVD; in the deposition method The silicon substrate temperature is 150°C to 250°C; the process chamber pressure is 10Pa to 100Pa.