CN112531035A

CN112531035A - Solar cell, preparation method thereof and solar cell back surface multilayer composite passivation film

Info

Publication number: CN112531035A
Application number: CN202011414696.4A
Authority: CN
Inventors: 苏荣; 谢毅; 王璞; 杨文栋; 邓明璋; 李兵川; 黄军; 李书森; 王岚; 黄艳琴
Original assignee: Tongwei Solar Chengdu Co Ltd
Current assignee: Tongwei Solar Chengdu Co Ltd
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-03-19
Anticipated expiration: 2040-12-03
Also published as: CN112531035B

Abstract

The present application relates to the field of solar cells, in particular, to a solar cell and a preparation method thereof, and a multilayer composite passivation film on the back of the solar cell. The backside compound passivation film is arranged on the backside of the silicon substrate; the backside compound passivation film includes a first silicon oxide film, a passivation layer, a first passivation film, and a reflective film that are sequentially arranged outward along the backside of the silicon substrate. , a second passivation film and a second silicon dioxide film; the reflective film is a silicon oxide film with a refractive index of 1.45-1.7; or the reflective film is a silicon oxynitride film with a refractive index of 1.7-1.9. The solar cell provided in this application can reduce the reflectivity of incident visible light on the front, and the multilayer composite film on the back can improve the reflectivity of visible light after penetrating the silicon substrate, forming secondary reflection, which can significantly improve the "hydrogen passivation" effect and the "field effect". Passivation" effect, reduce PID decay and improve battery reliability.

Description

Solar cell, preparation method thereof and solar cell back surface multilayer composite passivation film

Technical Field

The application relates to the field of solar cells, in particular to a solar cell, a preparation method thereof and a solar cell back surface multilayer composite passivation film.

Background

Photovoltaic power generation is a clean energy source and a renewable energy source by directly converting solar light energy into electric energy through a photovoltaic effect of a semiconductor, for example, a PERC (passivated Emitter and reactor cell) cell is one of solar cells, the PERC cell adopts a back passivation core technology, the PERC cell adopts an alumina passivation layer for bulk passivation, and a silicon nitride coating layer is usually adopted outside the alumina film layer as a protective layer.

The application mainly provides a solar cell back multilayer composite passivation film, aiming at improving the utilization rate of light.

Disclosure of Invention

The embodiment of the application aims to provide a solar cell, a preparation method thereof and a solar cell back surface multilayer composite passivation film, and aims to improve the light utilization rate of the solar cell.

The application provides a solar cell back surface multilayer composite passivation film, wherein the back surface composite passivation film is arranged on the back surface of a silicon substrate; the back composite passivation film comprises a first silicon oxide film, a passivation layer, a first passivation film, a reflection film, a second passivation film and a second silicon oxide film which are sequentially arranged outwards along the back of the silicon substrate;

wherein the passivation layer is made of aluminum oxide or gallium oxide; the first passivation film is made of silicon nitride or silicon carbide; the second passivation film is made of silicon nitride or amorphous silicon;

the reflecting film is a silicon oxide film with the refractive index of 1.45-1.7; or the reflecting film is a silicon oxynitride film with the refractive index of 1.7-1.9.

The reflecting film between the first passivation film and the second silicon dioxide film has a lower refractive index, so that the back composite passivation film has an enhancement effect on the reflection of long-wave-band visible light; the light with long wave band is reflected to the silicon substrate again under the action of the film system to generate carriers, so that secondary utilization of visible light is realized. The first passivation film can block plasma O generated by laughing gas in the process of preparing the reflective film⁺、O^-And the excessive etching of the passivation layer by the plasma is avoided, so that the electrical property of the solar cell is improved. The second silicon dioxide film can play a role in isolating hydrogen, so that the hydrogen generated by the second passivation film and the like can only move into the silicon substrate after high-temperature annealing and cannot overflow outwards, and the hydrogen passivation effect can be enhanced.

A second aspect of the present application provides a solar cell, comprising:

a silicon substrate;

a front electrode and a front passivation film disposed on the front surface of the silicon substrate; and

and the back electrode is arranged on the back surface of the silicon substrate, and the back composite passivation film is arranged on the back surface of the silicon substrate.

The third aspect of the present application provides a method for manufacturing the solar cell, including:

carrying out texturing treatment on the silicon substrate and then polishing the back of the silicon substrate;

sequentially preparing a first silicon oxide film, a passivation layer, a first passivation film, a reflecting film, a second passivation film and a second silicon oxide film on the back of the silicon substrate;

sequentially preparing a first silicon nitride antireflection film, a second silicon nitride antireflection film, a silicon oxynitride film and a silicon oxide film on the front surface of a silicon substrate;

optionally, after preparing the second passivation film and before preparing the second silicon oxide film, preparing a third passivation film covering the second passivation film is further included.

The preparation method enhances the passivation performance of the coating layer, and atomic hydrogen in the coating layer can enter the silicon wafer body in the subsequent rapid thermal annealing to passivate internal crystal boundaries and defects, reduce composite centers and improve open-circuit voltage and short-circuit current. And a film color bad selecting system is adopted in the back coating and front coating processes, the reverse working flow is carried out on bad pieces, and the yield of finished battery pieces is obviously improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 shows a schematic cross-sectional structure diagram of a solar cell provided in an embodiment of the present application.

Fig. 2 shows a process flow of manufacturing a solar cell provided in an embodiment of the present application.

Fig. 3 shows another manufacturing process of the solar cell provided in the embodiment of the present application.

Fig. 4 shows a cross-sectional view of a square spot and a grout groove formed using the square spot on a silicon substrate.

Fig. 5 shows a cross-sectional view of a circular spot and a grout groove formed using the circular spot on a silicon substrate.

FIG. 6 is a graph of the EQE of examples 6-8 versus comparative example 1.

FIG. 7 is a graph showing the relationship between the reflectance of examples 6 to 8 and that of comparative example 1.

FIG. 8 is an enlarged graph of the short-band EQE and the reflectivity curve of examples 6-8.

Fig. 9 shows the measurement result of the photovoltaic current-voltage characteristic of the solar cell provided in example 2.

Fig. 10 shows an I-V test curve of the solar cell provided in example 2.

Icon: 100-solar cell; 1-a silicon substrate; 2-a first silicon nitride anti-reflective film; 3-a second silicon nitride anti-reflective film; 4-silicon oxynitride film; 5-silicon oxide film; 6-front electrode; 7-first silicon oxide film; 8-a passivation layer; 9-a first passivation film; 10-a reflective film; 11-a second passivation film; 12-a third passivation film; 13-a second silicon oxide film; 14-grouting grooves; 15-aluminum back field; 16-back electrode.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following detailed description of the embodiments of the present application, presented in the figures, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the embodiments of the present application, it should be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships that the products of the application usually place when in use, or the orientations or positional relationships that the skilled person usually understands, are only for convenience of description and simplification of description, and do not indicate or imply that the indicated devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and therefore, should not be construed as limiting the application.

Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

In the description of the embodiments of the present application, it should also be noted that the terms "disposed" and "connected" are to be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, unless explicitly stated or limited otherwise; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The solar cell, the method for manufacturing the same, and the multilayer composite passivation film on the back surface of the solar cell according to the embodiments of the present application will be specifically described below.

Fig. 1 shows a schematic cross-sectional structure diagram of a solar cell 100 provided in an embodiment of the present application, please refer to fig. 1, and this embodiment provides a solar cell 100, in which the solar cell 100 may be a double-sided cell or a single-sided cell.

The solar cell 100 mainly includes a silicon substrate 1, a front surface electrode 6, a front surface passivation film, a back surface electrode 16, and a back surface composite passivation film.

The front passivation film is positioned on the front surface of the silicon substrate 1, and the back composite passivation film is positioned on the back surface of the silicon substrate 1.

In the embodiments of the present application, the material of the silicon substrate 1 may be p-type silicon or n-type silicon.

The back composite passivation film comprises a first silicon oxide film 7, a passivation layer 8, a first passivation film 9, a reflection film 10, a second passivation film 11, a third passivation film 12 and a second silicon oxide film 13 which are sequentially arranged outwards along the back of the silicon substrate 1.

A first silicon oxide film 7 is provided on the back surface of the silicon substrate 1; the first silicon oxide film 7 mainly functions to protect the silicon substrate 1, and a passivation layer 8 is provided on the surface of the first silicon oxide film 7, and the passivation layer 8 mainly functions to perform field effect passivation on the silicon substrate 1. In the embodiment of the present application, the material of the passivation layer 8 is aluminum oxide or gallium oxide.

The first passivation film 9 is provided on the surface of the passivation layer 8. The first passivation film 9 has a function of protecting the passivation layer 8.

The material of the first passivation film 9 is silicon nitride or silicon carbide. For example, the first passivation film 9 is a silicon nitride film having a film thickness of 10 to 20nm and a refractive index of 2.2 to 2.3. Alternatively, the first passivation film 9 is a silicon carbide film having a film thickness of 20 to 40nm and a refractive index of 2.35 to 2.65.

In the present embodiment, the first passivation film 9 has a film thickness of 10 to 20nm and a refractive index of 2.2 to 2.3, for example, the first passivation film 9 may have a film thickness of 10nm, 11nm, 12nm, 14nm, 17nm, 18nm, or 20 nm. The refractive index of the first passivation film 9 may be 2.2, 2.21, 2.25, 2.27, 2.28, 2.3, or the like. The material of the first passivation film 9 is silicon nitride or silicon carbide.

In the embodiment of the present application, the number of the first passivation film 9 may be one or more, and for the embodiment in which the first passivation film 9 is a plurality of layers, the thickness of the plurality of first passivation films 9 is 10 to 20nm in total, and the refractive index of the plurality of first passivation films 9 is 2.2 to 2.3 in total.

Alternatively, in some embodiments, the material of the first passivation film 9 is silicon carbide, the film thickness is 20 to 40nm, and the refractive index is 2.35 to 2.65. For example, the film thickness of the first passivation film 9 of a silicon carbide material may be 20nm, 22nm, 24nm, 26nm, 29nm, 32nm, 35nm, 37nm, 39nm, 40nm, or the like. The refractive index may be 2.35, 2.38, 2.41, 2.46, 2.51, 2.55, 2.58, 2.61, or 2.65, etc.

The reflecting film 10 is a silicon oxide film with a refractive index of 1.45-1.7; alternatively, the reflective film 10 is a silicon oxynitride film having a refractive index of 1.7 to 1.9.

For example, the reflective film 10 may be a silicon oxide film having a refractive index of 1.45, 1.5, 1.55, 1.6, 1.62, 1.65, or 1.7, etc.; alternatively, the reflective film 10 may be a silicon oxynitride film having a refractive index of 1.7, 1.72, 1.75, 1.8, 1.85, or 1.9.

For example, in some embodiments, the reflective film 10 has a film thickness of 10 to 30 nm; for example, the film thickness of the reflective film 10 may be 10nm, 14nm, 17nm, 19nm, 20nm, 23nm, or 30nm, or the like.

Visible light of a long wave band can penetrate through the silicon substrate 1, the first silicon oxide film 7 and the passivation layer 8, the reflection film 10 is located between the first passivation film 9 and the second passivation film 11, the refractive indexes of the reflection film 10 are smaller than those of the first passivation film 9 and the second passivation film 11, and a film system formed by the reflection film 10, the first passivation film 9, the second passivation film 11 and the like has an enhancement effect on reflection of the visible light of the long wave band; the light with long wave band is reflected to the silicon substrate 1 again under the action of the film system to generate carriers, so that secondary utilization of visible light is realized.

The reflective film 10 is a silicon oxynitride film or a silicon oxide film, and during the preparation of the silicon oxynitride film or the silicon oxide film, laughing gas (N) is required₂O), plasma O generated by laughing gas excitation⁺、O^-The plasma etches the surface of the aluminum oxide, which significantly degrades the electrical performance of the solar cell 100. The first passivation film 9 can reduce the plasma O⁺、O^-And (4) performing bombardment etching on the passivation layer 8, thereby improving the electrical property of the solar cell.

The material of the second passivation film 11 is silicon nitride or amorphous silicon. The second passivation film 11 is a silicon nitride film having a thickness of 30 to 70nm and a refractive index of 1.95 to 2.05, or the second passivation film 11 is an amorphous silicon film having a thickness of 5 to 20nm and a refractive index of 3.0 to 4.0.

In the embodiment of the application, the second passivation film 11 has a film thickness of 30 to 70nm and a refractive index of 1.95 to 2.05; for example, the film thickness of the second passivation film 11 may be 30nm, 35nm, 38nm, 40nm, 45nm, 50nm, 56nm, 62nm, 68nm, 70nm, or the like. The refractive index of the second passivation film 11 may be 1.95, 1.97, 2.0, 2.02, 2.05, or the like.

Alternatively, in some embodiments, the material of the second passivation film 11 is amorphous silicon, the film thickness is 5 to 20nm, and the refractive index is 3.0 to 4.0. For example, the film thickness of the second passivation film 11 of amorphous silicon material may be 5nm, 7nm, 9nm, 11nm, 13nm, 15nm, 18nm, 20nm, or the like. The refractive index may be 3.0, 3.15, 3.26, 3.37, 3.51, 3.75, 3.88, 3.91, or 4.0, among others.

In the embodiment of the present application, the surface of the second passivation film 11 is provided with the third passivation film 12.

In some embodiments of the present application, the material of the third passivation film 12 is silicon nitride, the total film thickness is 30 to 70nm, and the refractive index is 1.9 to 2.3. For example, the total film thickness of the third passivation film 12 may be 30nm, 34nm, 39nm, 42nm, 47nm, 51nm, 57nm, 63nm, 69nm, 70nm, or the like. The refractive index of the third passivation film 12 may be 1.9, 1.92, 1.93, 1.95, 1.97, 2.0, or 2.3, etc.

Alternatively, in some embodiments, the material of the third passivation film 12 is amorphous silicon, the film thickness is 5 to 20nm, and the refractive index is 3.0 to 4.0. For example, the film thickness of the third passivation film 12 of amorphous silicon material may be 5nm, 7nm, 10nm, 12nm, 14nm, 16nm, 18nm, or 20nm, or the like. The refractive index may be 3.0, 3.1, 3.4, 3.5, 3.6, 3.7, or 4.0, etc.

In the embodiment of the present application, the number of layers of the third passivation film 12 may be one, two or more, and when the number of layers of the third passivation film 12 is multiple, the total film thickness of the multiple layers is 30 to 70 nm.

The first passivation film 9 is high in refractive index, the second passivation film 11 is low in refractive index, the third passivation film 12 is low in refractive index, the passivation films are compounded by the first passivation film 9, the second passivation film 11 and the third passivation film 12, and the silicon oxide film is superposed, so that the protective effect is achieved, the corrosion of sodium ions can be effectively prevented, and the PID resistance of the solar cell is improved.

In some embodiments of the present application, the third passivation film 12 is not necessary, and the third passivation film 12 may not be provided.

The second silicon oxide film 13 covers the surface of the third passivation film 12. Illustratively, the second silicon oxide film 13 has a film thickness of 5 to 100nm and a refractive index of 1.45 to 1.7; for example, the film thickness of the second silicon oxide film 13 may be 5nm, 10nm, 17nm, 26nm, 37nm, 43nm, 53nm, 57nm, 67nm, 73nm, 82nm, 92nm, 100nm, or the like. The refractive index of the second silicon oxide film 13 may be 1.45, 1.5, 1.53, 1.58, 1.62, 1.65, 1.7, or the like.

The second silicon oxide film 13 can play a role of isolating 'hydrogen', so that the 'hydrogen' generated by the second passivation film 11 can only move into the silicon substrate 1 after high-temperature annealing and cannot overflow outwards, and the 'hydrogen passivation' effect can be enhanced.

In the embodiment of the present application, the film thicknesses and refractive indices of the first passivation film 9, the second passivation film 11, and the second silicon oxide film 13 may be set to other values, and are not limited to the above example. Accordingly, the film thickness of the reflective film 10 is not limited to the above-illustrated thickness.

In the embodiment of the application, the optical length of the back composite passivation film is 180 nm-350 nm. The color of the back composite passivation film can be blue, light blue, white, grey, light yellow, orange and purple. The total thickness of the first passivation film 9, the reflection film 10, the second passivation film 11, the third passivation film 12, and the second silicon oxide film 13 multiplied by the average refractive index defines an optical path length.

Referring to fig. 1 again, the solar cell 100 is further provided with a grouting groove 14 for grouting, and the grouting groove 14 penetrates through the entire back surface composite passivation film until communicating with the silicon substrate 1.

In the embodiment of the present application, the grout groove 14 is circular arc-shaped in the cross section of the silicon substrate 1. The section of the grouting groove 14 is arc-shaped (see the lower drawing in fig. 4), and compared with conical laser grooving (see the lower drawing in fig. 5), arc-shaped laser grooving enables the screen printing to be filled with the slurry more fully, and good ohmic contact can be formed after sintering, so that the electrical property of the solar cell is improved.

In other embodiments of the present application, the grout groove 14 may have other shapes such as a conical shape in the cross section of the silicon substrate 1. The aluminum paste fills the grouting groove 14 and is sintered and cured.

An aluminum back field 15 is printed on the surface of the back composite passivation film, which is away from the silicon substrate 1, and the aluminum back field 15 is electrically connected with a back electrode 16, in this embodiment, the material of the back electrode 16 is silver.

The front passivation film comprises a first silicon nitride antireflection film 2, a second silicon nitride antireflection film 3, a silicon oxynitride film 4 and a silicon oxide film 5 which are sequentially arranged outwards along the front surface of the silicon substrate 1.

Illustratively, the first silicon nitride antireflection film 2 has a film thickness of 10 to 20nm and a refractive index of 2.2 to 2.3; for example, the refractive index of the first silicon nitride antireflection film 2 may be 2.2, 2.23, 2.26, 2.3, or the like; the film thickness of the first silicon nitride antireflection film 2 may be 10nm, 12nm, 13nm, 15nm, 17nm, 18nm, 19nm, 20nm, or the like.

In some embodiments of the present application, the second silicon nitride antireflection film 3 has a film thickness of 20 to 40nm and a refractive index of 1.9 to 2.1; for example, the refractive index of the second silicon nitride antireflection film 3 may be 1.9, 1.95, 1.98, 2.04, 2.08, or 2.1, or the like; the film thickness of the second silicon nitride antireflection film 3 may be 20nm, 26nm, 31nm, 37nm, 39nm, 40nm, or the like.

In some embodiments of the present application, the silicon oxynitride film 4 has a film thickness of 20 to 40nm and a refractive index of 1.7 to 1.9; for example, the refractive index may be 1.7, 1.72, 1.78, 1.82, 1.86, or 1.9, etc.; the film thickness of the silicon oxynitride film 4 may be 20nm, 25nm, 32nm, 36nm, 38nm, 40nm, or the like.

In some embodiments of the present application, the silicon oxide film 5 has a film thickness of 5 to 30nm and a refractive index of 1.45 to 1.7. For example, it may be 1.45, 1.50, 1.52, 1.56, 1.60, 1.65, or 1.7, etc.; the thickness of the silicon oxide film 5 may be 5nm, 8nm, 12nm, 16nm, 20nm, 28nm, or 30 nm.

In the embodiment per se, the optical length of the front passivation film is 150 nm-170 nm; the front passivation film may be light blue, and deep blue in color. The total thickness of the first silicon nitride antireflection film 2, the second silicon nitride antireflection film 3, the silicon oxynitride film 4, and the silicon oxide film 5 multiplied by the average refractive index defines an optical path length.

The refractive indexes of the first silicon nitride antireflection film 2, the second silicon nitride antireflection film 3 and the silicon oxynitride film 4 are gradually reduced, so that the reflectivity of the front passivation film can be reduced, and a better antireflection effect is achieved. The silicon oxynitride film 4 can improve the passivation effect, and the silicon oxide film 5 can enhance the "hydrogen passivation" effect. The front electrode 6 is electrically connected to the silicon substrate 1 through the front passivation film.

The back composite passivation film provided by the embodiment of the application has at least the following advantages:

the reflecting film 10 positioned between the first passivation film 9 and the second silicon dioxide film 13 has a lower refractive index, so that the back composite passivation film has an enhancement effect on the reflection of long-wave-band visible light; making light in long wave band atThe film system is reflected to the silicon substrate 1 again to generate carriers under the action of the film system, and secondary utilization of visible light is realized. The first passivation film 9 can block plasma O generated from laughing gas during the preparation of the reflective film 10⁺、O^-And excessive etching of the passivation layer 8 by plasma is avoided, so that the electrical property of the solar cell is improved.

The second silicon oxide film 13 can play a role of isolating 'hydrogen', so that the 'hydrogen' generated by the second passivation film 11 and the like can only move into the silicon substrate 1 after high-temperature annealing and cannot overflow outwards, and the 'hydrogen passivation' effect can be enhanced. The first silicon oxide film 7 and the passivation layer 8 contain a large amount of fixed negative charges and are field effect passivation layers; the first passivation film 9, the second passivation film 11, and the third passivation film 12 play a role of "hydrogen passivation"; in addition, the first passivation film 9 has a protective effect of protecting the passivation layer 8 from N₂O ionized O⁺、O^-Bombardment etching of plasma; the reflection film 10 is matched with the first passivation film 9 and the second passivation film 11, and plays a role in increasing reflection; the second silicon dioxide film 13 is a compact silicon oxide layer, and can play a role of isolating hydrogen at the outermost layer of the composite passivation film, so that the hydrogen generated by the silicon nitride film coating layer can only move into the silicon wafer body after high-temperature annealing and cannot overflow outwards, and the hydrogen passivation effect can be enhanced;

in addition, the film system composed of the second passivation film 11 and the third passivation film 12 has a hydrogen passivation effect; the field effect passivation of the passivation layer 8 can be superposed to improve the passivation effect.

The solar cell 100 provided by the embodiment of the present application has the advantages of the above-mentioned back surface composite passivation film.

In addition, the first silicon nitride antireflection film 2 and the second silicon nitride antireflection film 3 can reduce the reflectivity of front incident visible light; the outermost layer of the front passivation film adopts the compact silicon oxide film 5, which can play a role in isolating hydrogen, so that the hydrogen generated by the first silicon nitride antireflection film 2 and the second silicon nitride antireflection film 3 can only move in the silicon wafer body after high-temperature annealing, cannot overflow outwards, and can enhance the hydrogen passivation effect.

The solar cell 100 provided by the embodiment of the application can reduce the reflectivity of the incident visible light on the front surface, the multilayer composite film on the back surface can improve the reflectivity of the visible light after penetrating through the silicon substrate, secondary reflection is formed, the hydrogen passivation effect and the field effect passivation effect can be obviously improved, the PID attenuation is reduced, and the cell reliability is improved.

The application also provides a preparation method of the solar cell, which mainly comprises the following steps: polishing the back of the silicon substrate after texturing treatment; preparing a back composite passivation film; and preparing a front passivation film. Fig. 2 and fig. 3 show two preparation processes of the solar cell provided in the embodiment of the present application. It should be noted that, in the embodiment of the present application, there is no precedence relationship between the two steps of preparing the back composite passivation film and preparing the front passivation film, and the steps may be adjusted according to the requirements of the product.

The process conditions of firstly plating the back composite passivation film and then plating the front passivation film are adopted, so that the pollution reject ratio of a film plating section can be reduced, and the yield of finished battery pieces is improved by 0.2%. The process conditions of firstly plating the front passivation film and then plating the back composite passivation film are adopted, so that the photoelectric conversion efficiency of the battery can be improved by 0.05-0.1%.

As an example, the preparation method comprises:

the method comprises the following steps of removing a damage layer of a silicon substrate and texturing: and (3) cleaning and drying the P-type silicon substrate after alkaline texturing, wherein the side length of the bottom edge of the pyramid textured surface is less than 3 um.

And (3) diffusion PN junction preparation: phosphorus diffusion is performed at the textured surface, the diffusion sheet resistance is 150-200 omega/□, and the depth of the PN junction is 0.1-0.3 um.

Laser SE doping: the small-spot narrow-linewidth laser process is used, high-precision localized doping is achieved, the side length of a laser spot is 60-100 um, the area proportion of an N + + SE heavily-doped region is 5-7%, and the sheet resistance of the N + + SE heavily-doped region is 70-100 omega/□.

Etching and back polishing: acid polishing or alkali polishing is adopted, the phosphorosilicate glass is removed through wet etching, and the reflectivity of the etched polished surface is 30% -45%.

Preparation of a passivation layer: the aluminum oxide passivation layer is prepared by ALD (atomic layer Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment, wherein the pulse time is 30-120 s, the Deposition temperature is 70-120 ℃, and the number of aluminum oxide turns is 20-40 turns.

In the following description, SiH will be₄、NH₃Flow rate ratio of (1) is denoted as "SiH₄/NH₃＝”，SiH₄、NH₃Flow rate ratio of (1) is denoted as "SiH₄/N₂O＝”。

And preparing the back composite passivation film by adopting PECVD equipment.

The opening of a vacuum pump butterfly valve for depositing a first passivation film 9 (silicon nitride film) is 1400-1700, the temperature is 400-₄/NH ₃1/4 to 1/6.

The opening of the vacuum pump butterfly valve for depositing the reflective film 10 (silicon oxide film) is 900-1300 deg.C, the temperature is 400-500 deg.C, the power is 4000-12000W, the duty ratio of opening and closing the microwave is (20-40): 800-1000), and the SiH₄/N₂O-1/15 to 1/40.

The opening 1300-1700 of the vacuum pump butterfly valve for depositing the reflective film 10 (silicon oxynitride film), the temperature 450-₄、NH₃、N₂The flow ratio of O is 1: (4-6): (4-6);

the opening of the butterfly valve of the vacuum pump for depositing the second passivation film 11 (silicon nitride film) is 1500-2000 deg.C, the temperature is 400-500 deg.C, the power is 10000-15000W, the duty ratio of opening and closing the microwave is 30-50 (500-800), and SiH₄、NH₃Is 1/9 to 1/12.

The degree of opening of the butterfly valve of the vacuum pump for depositing the third passivation film 12 (silicon nitride film) is 1500-2000 at 400-₄/NH ₃1/10 to 1/13.

The opening of the butterfly valve of the vacuum pump for depositing the second silicon oxide film 13 is 900-1300 deg.C, the temperature is 400-₄/N₂O-1/15 to 1/40.

The deposition time ratios of the first passivation film 9, the reflection film 10, the second passivation film 11, the third passivation film 12 and the second silicon oxide film 13 are as follows in sequence: (200-400), (100-300), (200-500) and (100-300).

Preparing a grouting groove 14 by back laser grooving: in the embodiment of the application, the laser grooving adopts square light spot laser, the diameter of the laser light spot is 30-40 um, and the laser power is 15-25W. The laser film opening process can fill aluminum paste, the diameter of a light spot and the laser power can be matched with the back surface multilayer composite passivation films with different film thicknesses of the double-sided PERC battery and the single-sided PERC battery, the appearance of the film opening light spot of laser on a film coating layer is good, and ablation or insufficient film opening can not occur.

It should be noted that in other embodiments of the present application, the back laser grooving preparation grouting groove 14 may use a round spot.

Referring to fig. 4 and 5, fig. 4 is a cross-sectional view of a square spot and a grout groove 14 formed using the square spot on a silicon substrate 1. The upper diagram in fig. 4 shows the square spot and below a cross-sectional view of the grout groove 14 on the silicon substrate 1. It can be seen that the laser grooving uses square spot laser, and an arc groove recessed from the front surface to the back surface can be formed on the silicon substrate 1, and the arc groove can increase the holding amount of the slurry.

Fig. 5 shows a cross-sectional view of a circular light spot and a grout groove 14 formed using the circular light spot on a silicon substrate 1. The upper diagram in fig. 5 shows a circular light spot, and the lower is a cross-sectional view of the grout groove 14 on the silicon substrate 1. It can be seen that the laser grooving uses a circular spot laser, and a tapered groove recessed from the front surface to the back surface can be formed on the silicon substrate 1.

And preparing the front passivation film by adopting PECVD equipment.

The degree of opening 1300-1700 of the vacuum pump butterfly valve for depositing the first silicon nitride antireflection film 2, the temperature of 450-₄/NH ₃1/3 to 1/5.

The opening of a vacuum pump butterfly valve for depositing the second silicon nitride antireflection film 3 is 1400-2000 ℃, the temperature is 450-530 ℃, the power is 10000-15000W, and the microwave opening and closing dutyThe ratio of (30-50) to (500-800) SiH₄/NH ₃1/8 to 1/12.

The opening of a vacuum pump butterfly valve for depositing the silicon oxynitride film 4 is 1300-1700, the temperature is 450-₄：NH₃：N₂The flow ratio of O is 1: (4-6): (4-6).

The opening of the butterfly valve of the vacuum pump for depositing the silicon oxide film 5 is 900-1200 deg.C, the temperature is 450-530 deg.C, the power is 8000-12000W, the duty ratio of the microwave on/off is (20-40): 800-1100), and the SiH₄And N₂The flow rate ratio of O is 1/10 to 1/14.

The deposition time ratios of the first silicon nitride antireflection film 2, the second silicon nitride antireflection film 3, the silicon oxynitride film 4 and the silicon oxide film 5 are as follows in sequence: (100-200), (200-400) and (200-400).

Aluminum back surface field 15: the aluminum paste should fill the grouting grooves 14 as full as possible when printing the aluminum back field. And forming an aluminum back surface field through high-temperature sintering after printing.

Front electrode 6: and a screen printing process is adopted, high-temperature silver paste is adopted to perform screen printing on screen printing equipment, and a silver grid line needs to be aligned to the N + + SE heavily-doped region during printing.

Back electrode 16: and (3) performing screen printing on screen printing equipment by adopting high-temperature silver-aluminum paste.

And (3) sintering: the sintering furnace temperature was set as follows: the temperature of the upper temperature zone eleven is 750-790 ℃, the temperature of the upper temperature zone twelve is 750-790 ℃, the temperature of the upper temperature zone thirteen is 750-790 ℃, and the temperature of the upper temperature zone fourteen is 720-760 ℃.

An electric injection process: each station is divided into an upper temperature area, a middle temperature area and a lower temperature area, each temperature area adopts 5-point temperature control, and the set temperature is 100-220 ℃; the electrical injection adopts a multi-point temperature control technology, for example, 4-8 temperature control points, and the temperature control points are uniformly distributed at different height positions of the stacked battery pieces in the battery box. The temperature difference generated by different height positions of the stacked battery pieces can be reduced by multi-point temperature control, and the uniformity of the electric injection effect is improved;

the preparation method of the solar cell provided by the embodiment of the application can be used for preparing the solar cell, and the preparation method at least has the following advantages:

The features and properties of the present application are described in further detail below with reference to examples.

Example 1

This example provides a single-sided PERC cell, made essentially by the following method:

and sequentially carrying out texturing, diffusion, laser SE, etching and annealing on the P-type silicon wafer. The method is characterized in that ALD equipment and a low-temperature process are adopted to prepare aluminum oxide, ozone and trimethylaluminum are adopted as reaction raw materials, the pulse time is 30s, the deposition temperature is 70 ℃, the number of aluminum oxide turns is 25, and the thickness of a passivation layer is 2-7 nm.

And plating a front composite passivation film by adopting PECVD equipment after the aluminum oxide film plating is finished.

The deposition time of the first silicon nitride antireflection film 2 is 150s, the opening of a butterfly valve of a vacuum pump is 1350, the temperature is 470 ℃, the power is 12000W, the duty ratio of opening and closing microwaves is 350:650, and SiH is added₄/NH₃＝1/4.2。

The deposition time of the second silicon nitride antireflection film 3 is 250s, the butterfly valve opening of the vacuum pump is 1600 ℃, the temperature is 480 ℃, the power is 12500W, the microwave opening and closing duty ratio is 42:680, and SiH₄/NH₃＝1/10.5。

The deposition time of depositing the silicon oxynitride film 4 is 250s, the butterfly valve opening of a vacuum pump is 1500, the temperature is 485 ℃, the power is 13000W, the duty ratio of opening and closing the microwave is 38:720, and SiH₄：NH₃：N₂The volume ratio of O is 1:4.8: 4.6.

The deposition time of the silicon oxide film 5 is 320s, the butterfly valve opening 1050 of the vacuum pump is carried out at the temperature of 500 ℃, the power is 10050W, the duty ratio of opening and closing the microwave is 32:780, and SiH is added₄/N₂O＝1/12。

And plating the back multilayer composite film by adopting PECVD equipment.

The deposition time of the first passivation film 9 (silicon nitride film) is 250s, the butterfly valve opening of the vacuum pump is 1500 ℃, the temperature is 430 ℃, the power is 12000W, the microwave opening and closing duty ratio is 35:680, and SiH₄/NH₃＝1/4.5。

The deposition time of the deposited reflection film 10 (silicon oxide film) is 200s, the butterfly valve opening of the vacuum pump is 1100 ℃, the temperature is 440 ℃, the power is 9000W, the microwave opening and closing duty ratio is 28:880, and SiH₄/N₂O＝1/20。

The deposition time of the second passivation film 11 (silicon nitride film) is 200s, the butterfly valve opening of the vacuum pump is 1700, the temperature is 450 ℃, the power is 12000W, the microwave on-off duty ratio is 40:700, and SiH₄/NH₃＝1/10。

The deposition time for depositing the third passivation film 12 (silicon nitride film) is 350s, the opening of a butterfly valve of a vacuum pump is 1800 ℃, the temperature is 470 ℃, the power is 12500W, the duty ratio of opening and closing the microwave is 42:800, and SiH₄/NH₃＝1/11。

The deposition time of the second silicon oxide film 13 is 200s, the butterfly valve opening of the vacuum pump is 1250, the temperature is 443 ℃, the power is 6000W, the microwave opening and closing duty ratio is 35:880, and SiH₄/N₂O-1/20; the back coating layer is light yellow or yellow.

The laser grooving light spot on the back adopts a circular light spot, the proper laser light spot is adjusted, the diameter of the laser light spot is 35um, and the laser power is 20W. After back laser grooving, printing a back electrode, a back electric field and a front electrode by adopting proper slurry, wherein the total wet weight of the back electrode silver paste is 0.034g, the wet weight of the aluminum back field slurry is 0.85g, and the total wet weight of the front electrode silver paste is 0.088g, each time of printing is carried out, the back electrode, the back electric field and the front electrode are formed by drying in a curing furnace and finally sintering and curing at high temperature in a sintering furnace; the temperature of the sintering process is set as follows: the eleven upper temperature zone is 780 ℃, the twelve upper temperature zone is 780 ℃, the thirteen upper temperature zone is 770 ℃ and the fourteen upper temperature zone is 750 ℃; and starting an electrical injection process after sintering, wherein an electrical injection furnace with nine stations is adopted, each station is divided into an upper temperature area, a middle temperature area and a lower temperature area, each temperature area adopts 5-point temperature control, and the set temperature is 100-220 ℃.

Example 2

Embodiment 2 provides a solar cell, and the difference between embodiment 2 and embodiment 1 is that a PECVD apparatus is used to plate a back multilayer composite film, and then a PECVD apparatus is used to plate a front composite passivation film.

Example 3

Example 3 provides a bifacial solar cell, please refer to example 1, and the difference between example 3 and example 1 is:

and plating a back composite passivation film by adopting PECVD equipment.

The deposition time of the first passivation film 9 (silicon nitride film) is 190s, the butterfly valve opening of the vacuum pump is 1700, the temperature is 470 ℃, the power is 13500W, the microwave opening and closing duty ratio is 38:620, and SiH is₄/NH₃＝1/5.5。

The deposition time of the deposited reflection film 10 (silicon oxide film) is 150s, the butterfly valve opening 1550 of the vacuum pump, the temperature 470 ℃, the power 12500W, the microwave on-off duty ratio is 28:880, and SiH₄/N₂O＝1/22。

The deposition time of the second passivation film 11 (silicon nitride film) is 190s, the butterfly valve opening of the vacuum pump is 1750, the temperature is 450 ℃, the power is 13600W, the duty ratio of opening and closing the microwave is 40:630, and SiH₄/NH₃＝1/10。

The deposition time of the third passivation film 12 (silicon nitride film) is 210s, the butterfly valve opening of the vacuum pump is 1680, the temperature is 470 ℃, the power is 12580W, the microwave on-off duty ratio is 42:780, and SiH is added₄/NH₃＝1/11。

The deposition time of the second silicon oxide film 13 is 125s, the butterfly valve opening 1550 of the vacuum pump, the temperature is 483 ℃, the power is 10000W, the microwave opening and closing duty ratio is 35:880, and SiH₄/N₂And O1/20. The back coating layer is blue or light blue.

After plating the front multilayer composite film, performing laser back grooving, printing (adopting a double-sided battery screen printing plate, printing a pattern by a local aluminum back field) and sintering.

Example 4

Example 4 provides a single-sided solar cell, please refer to example 1, and example 4 differs from example 1 in that: and the laser grooving light spot on the back adopts a square light spot.

Example 5

Example 5 provides a bifacial solar cell, please refer to example 3, and the difference between example 5 and example 3 is: and the laser grooving light spot on the back adopts a square light spot.

Example 6

Example 6 provides a bifacial solar cell, please refer to example 3, and example 6 differs from example 3 in that: the film thicknesses of the silicon oxynitride film 4 and the silicon oxide film 5 in the front passivation film were changed.

In example 6:

the deposition time of depositing the silicon oxynitride film 4 is 120s, the butterfly valve opening of the vacuum pump is 1500, the temperature is 485 ℃, the power is 12500W, the microwave opening and closing duty ratio is 38:780, and SiH₄：NH₃：N₂O＝1：4.8：4.5。

The deposition time of the silicon oxide film 5 is 220s, the butterfly valve opening of the vacuum pump is 1200, the temperature is 500 ℃, the power is 10050W, the duty ratio of opening and closing the microwave is 32:900, and SiH is₄/N₂O＝1：11。

Example 7

Example 7 provides a bifacial solar cell, please refer to example 3, and the difference between example 7 and example 3 is: the film thicknesses of the silicon oxynitride film 4 and the silicon oxide film 5 in the front passivation film were changed.

In example 7:

the deposition time of depositing the silicon oxynitride film 4 is 135s, the butterfly valve opening of a vacuum pump is 1700, the temperature is 485 ℃, the power is 12500W, the microwave opening and closing duty ratio is 38:780, and SiH₄：NH₃：N₂O＝1：4.8：4.5。

The deposition time of the silicon oxide film 5 is 200s, the butterfly valve opening of the vacuum pump is 1500, the temperature is 500 ℃, the power is 10050W, the microwave opening and closing duty ratio is 32:900, and SiH₄/N₂O＝1/11。

Example 8

Example 8 provides a bifacial solar cell, please refer to example 3, and example 8 differs from example 3 in that: the film thicknesses of the silicon oxynitride film 4 and the silicon oxide film 5 in the front passivation film were changed.

In example 8:

the deposition time of depositing the silicon oxynitride film 4 is 155s, the butterfly valve opening of the vacuum pump is 1500, the temperature is 485 ℃, the power is 12500W, the microwave opening and closing duty ratio is 38:780, and SiH₄/NH₃/N₂O is 1:4.8: 4.5; the deposition time of the silicon oxide film 5 is 180s, the butterfly valve opening of the vacuum pump is 1500, the temperature is 500 ℃, the power is 10050W, the microwave opening and closing duty ratio is 32:900, and SiH₄/N₂O＝1/11。

Example 9

Example 9 provides a bifacial solar cell, please refer to example 3, and example 9 differs from example 3 in that: the reflective film 10 is a silicon oxynitride film having a refractive index of 1.7 to 1.9.

The deposition time of the deposited reflection film 10 (silicon oxynitride film) is 140s, the butterfly valve opening of the vacuum pump is 1650, the temperature is 485 ℃, the power is 12500W, the microwave opening and closing duty ratio is 40:800, and SiH₄：NH₃：N₂O＝1：5：4.5。

Example 10

Example 10 provides a single-sided solar cell, please refer to example 1, and the difference between example 10 and example 1 is: the first passivation film 9 is a silicon carbide film.

The deposition time of the first passivation film 9 (silicon carbide film) is 200s, the opening of a butterfly valve of a vacuum pump is 1500 ℃, the temperature is 250 ℃, the power is 6000W, the duty ratio of opening and closing microwaves is 40:720, and SiH₄/CH₄＝1/3。

Example 11

Example 11 provides a single-sided solar cell, referring to example 1, the difference between example 11 and example 1 is: the second passivation film 11 is an amorphous silicon film.

The deposition time of the second passivation film 11 (amorphous silicon film) is 200s, the butterfly valve opening of the vacuum pump is 900 ℃, the temperature is 300 ℃, the power is 10000W, and the microwave opening and closing duty ratio is30:600，B₂H₆/SiH₄/H₂＝20/60/300。

Comparative example 1

Comparative example 1 provides a conventional method for manufacturing a single-sided solar cell, referring to example 1, the comparative example 1 is different from example 1 in that: the back surface is free of the first passivation film 9 and the reflection film 10, the second passivation film 11 is a silicon nitride film having a refractive index of 1.9 to 2.1, and the third passivation film 12 is a silicon nitride film having a refractive index of 2.0 to 2.3.

The deposition time of the second passivation film 11 (silicon nitride film) was 430s, the butterfly valve opening of the vacuum pump 1650, the temperature was 450 ℃, the power was 13500W, the microwave on/off duty ratio was 40:700, and SiH was₄/NH₃＝1/10.5。

The deposition time of the third passivation film 12 (silicon nitride film) is 550s, the butterfly valve opening of the vacuum pump is 1700, the temperature is 480 ℃, the power is 13500W, the microwave opening and closing duty ratio is 40:600, and SiH₄/NH₃＝1/6。

And a laser grooving light spot on the back adopts a circular light spot, and a proper laser light spot is adjusted, wherein the diameter of the laser light spot is 38um, and the laser power is 22W. The temperature of the sintering process is set as follows: eleven upper temperature zone is 750 ℃, twelve upper temperature zone is 750 ℃, thirteen upper temperature zone is 740 ℃, and fourteen upper temperature zone is 720 ℃;

test example 1

The solar cells provided in examples 1 to 5, 9 and comparative example 1 were subjected to online appearance inspection, electrical property test and EL test to obtain electrical property data and yield data, the electrical property and yield test results are shown in table 1, the PID attenuation results are shown in table 2, and the CTM results are shown in table 3.

TABLE 1

TABLE 2

TABLE 3

As can be seen from tables 1-3: example 1 provides a solar cell with better electrical performance than comparative example 1. The method has the advantages that the coating sequence is changed in the embodiment 2, the back composite passivation film is coated firstly, then the front composite passivation antireflection film is coated, the conversion efficiency is lower than that of the embodiment 1 by 0.061%, the yield is higher than that of the embodiment 1 by 0.021%, and the yield of the PERC battery can be improved by adopting the preparation method in the embodiment 2; example 3 provides a double-sided PERC cell, the passivation effect of which is poorer than that of a single-sided cell, and the conversion efficiency of example 3 is 0.216% lower than that of example 1; in the method of embodiment 4, the back laser grooving adopts square light spots, and the conversion efficiency is 0.042% higher than that of embodiment 1; similarly, the square light spot is adopted in the example 5, and the conversion efficiency is 0.033% higher than that of the example 3; the comparative example 1 is a conventional process scheme, and compared with the examples 1 to 11, the reflective film 10 and the first passivation film 9 are not provided, the conversion efficiency of the example 1 is 0.115% higher than that of the comparative example, and the reflection increasing effect of the visible reflective film 10 can more fully utilize the long-wavelength band sunlight, thereby improving the photoelectric conversion efficiency.

Test example 2

The short band EQE and reflectance of examples 6, 7, 8 were tested; FIG. 6 is a graph of the EQE of examples 6-8 versus comparative example 1; FIG. 7 is a graph showing the relationship between the reflectance of examples 6 to 8 and comparative example 1, and FIG. 8 is an enlarged graph showing the short-band EQE and reflectance curve of examples 6 to 8. In the figure, BL represents comparative example 1.

As can be seen from fig. 6 to 8, the short-band quantum efficiency of embodiment 6 is the highest, and the short-band quantum efficiency of

embodiments

7 and 8 is lower, which indicates that the film matching structure of embodiment 6 is better; with the increase of the thickness of the silicon oxynitride film 4, the thickness of the silicon oxide film 5 is reduced, and the short-band reflectivity is increased, but the short-band reflectivity is obviously lower than that of a production line coating process, and compared with the three examples of examples 6, 7 and 8, the short-band reflectivity of the front film layer of example 6 is the lowest, and the matching effect of the front multilayer film of example 6 is the best.

Test example 3

The photovoltaic current-voltage characteristics of the solar cell provided in example 2 were measured, and the measurement results are shown in fig. 9; the I-V test curve is shown in FIG. 10. In fig. 10, the abscissa represents the open circuit voltage in volts (V) and the ordinate represents the short circuit current in amps (a).

As can be seen from fig. 9 and 10, the solar cell provided in example 2 has better electrical properties.

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

Claims

1. The multilayer composite passivation film for the back of the solar cell is characterized in that the composite passivation film for the back is arranged on the back of a silicon substrate (1); the back composite passivation film comprises a first silicon oxide film (7), a passivation layer (8), a first passivation film (9), a reflection film (10), a second passivation film (11) and a second silicon oxide film (13) which are sequentially arranged outwards along the back of the silicon substrate (1);

wherein the material of the passivation layer (8) is aluminum oxide or gallium oxide;

the first passivation film (9) is made of silicon nitride or silicon carbide;

the second passivation film (11) is made of silicon nitride or amorphous silicon;

the reflecting film (10) is a silicon oxide film with the refractive index of 1.45-1.7; or the reflecting film (10) is a silicon oxynitride film with the refractive index of 1.7-1.9.

2. The solar cell backside multilayer composite passivation film according to claim 1, further comprising at least one third passivation film (12) disposed between the second passivation film (11) and the second silicon oxide film (13); the material of the third passivation film (12) is silicon nitride or amorphous silicon;

optionally, the first passivation film (9) is a multilayer structure;

optionally, the third passivation film (12) is made of silicon nitride, the total film thickness of the third passivation film (12) is 30-70 nm, and the total refractive index is 1.9-2.3;

optionally, the third passivation film (12) is made of amorphous silicon, the total film thickness of the third passivation film (12) is 5-20nm, and the total refractive index is 3.0-4.0.

3. The solar cell back multilayer composite passivation film according to claim 1, wherein the back composite passivation film is provided with a grouting groove (14) communicated with the silicon substrate, and the section of the grouting groove (14) in the thickness direction of the silicon substrate (1) is arc-shaped.

4. The solar cell back surface multilayer composite passivation film according to any one of claims 1 to 3, wherein the first passivation film (9) is made of silicon nitride, and has a film thickness of 10 to 20nm and a refractive index of 2.2 to 2.3; the second passivation film (11) is made of silicon nitride, the film thickness is 30-70 nm, and the refractive index is 1.95-2.05; the second silicon dioxide film (13) has a film thickness of 5-100 nm and a refractive index of 1.45-1.7;

or the first passivation film (9) is made of silicon carbide, the film thickness is 20-40 nm, and the refractive index is 2.35-2.65; the second passivation film (11) is made of amorphous silicon, the film thickness is 5-20nm, and the refractive index is 3.0-4.0; the second silicon dioxide film (13) has a film thickness of 5-100 nm and a refractive index of 1.45-1.7;

optionally, the thickness of the reflecting film (10) is 10-30 nm.

5. A solar cell, comprising:

a silicon substrate (1);

a front electrode (6) and a front passivation film arranged on the front surface of the silicon substrate (1); and

a back electrode (16) disposed on the back surface of the silicon substrate (1) and the back composite passivation film according to any one of claims 1 to 4.

6. The solar cell according to claim 5, wherein the front passivation film comprises a first silicon nitride anti-reflection film (2), a second silicon nitride anti-reflection film (3), a silicon oxynitride film (4) and a silicon oxide film (5) which are sequentially arranged outwards along the front surface of the silicon substrate (1).

7. The solar cell according to claim 6,

the first silicon nitride antireflection film (2) has a film thickness of 10-20 nm and a refractive index of 2.2-2.3;

the second silicon nitride antireflection film (3) has a film thickness of 20-40 nm and a refractive index of 1.9-2.1;

the silicon oxynitride film (4) has a film thickness of 20 to 40nm and a refractive index of 1.7 to 1.9;

the silicon oxide film (5) has a film thickness of 5 to 30nm and a refractive index of 1.45 to 1.7.

8. The method of any one of claims 5 to 7, comprising:

texturing, diffusing and carrying out laser SE doping treatment on a silicon substrate (1) and then polishing the back surface of the silicon substrate;

sequentially preparing a first silicon oxide film (7), a passivation layer (8), a first passivation film (9), a reflection film (10), a second passivation film (11) and a second silicon oxide film (13) on the back surface of a silicon substrate (1);

sequentially preparing a first silicon nitride antireflection film (2), a second silicon nitride antireflection film (3), a silicon oxynitride film (4) and a silicon oxide film (5) on the front surface of a silicon substrate (1);

optionally, after the second passivation film (11) is prepared and before the second silicon oxide film (13) is prepared, a third passivation film (12) covering the second passivation film (11) is further prepared.

9. The method for manufacturing a solar cell according to claim 8,

in the laser SE doping step, the side length of a laser spot is 60-100 um, the area percentage of an N + + SE heavily doped region is 5-7%, and the sheet resistance of the N + + SE heavily doped region is 70-100 omega/□;

optionally, preparing the first passivation film (9) by adopting PECVD equipment; 1400-1700 degree of butterfly valve opening of vacuum pump, 400-500 degree of butterfly valve opening, 10000-15000W of power, 30-50 duty ratio of opening and closing microwave (500-800), SiH₄、NH₃The flow ratio of (a) is from 1/4 to 1/6;

optionally, PECVD equipment is adopted to prepare the reflecting film (10), and the reflecting film is a silicon oxide film with the refractive index of 1.45-1.7; 900-1300 degrees of opening of the butterfly valve of the vacuum pump, 400-500 degrees of temperature, 4000-12000W of power, 20-40 duty ratio of opening and closing of the microwave (800-1000), SiH₄、NH₃The flow ratio of (a) is from 1/15 to 1/40;

optionally, preparing the second passivation film (11) by using PECVD equipment; 1500-2000 degree of butterfly valve opening of vacuum pump, 400-500 degree of butterfly valve opening, 10000-15000W of power, 30-50 duty ratio of opening and closing microwave (500-800), SiH₄、NH₃The flow ratio of (a) is from 1/9 to 1/12;

optionally, preparing the third passivation film (12) by adopting PECVD equipment; 1500-2000 degree of butterfly valve opening of vacuum pump, 400-500 degree of butterfly valve opening, 10000-15000W of power, 30-50 duty ratio of opening and closing microwave (600-900), SiH₄、NH₃The flow ratio of (a) is from 1/10 to 1/13;

optionally, preparing the second silicon oxide film (13) by adopting PECVD equipment; 900-1300 degrees of opening of the butterfly valve of the vacuum pump, 400-500 degrees of temperature, 4000-12000W of power, 20-40 duty ratio of opening and closing of the microwave (800-1000), SiH₄、NH₃The flow ratio of (a) is from 1/15 to 1/40;

optionally, a PECVD device is adopted to prepare the first silicon nitride antireflection film (2); 1300-1700 degree of butterfly valve opening of vacuum pump, 450-530 degree of butterfly valve opening, 10000-15000W of power, 30-50 duty ratio of opening and closing microwave (500-800), SiH₄、NH₃Flow rate ratio of1/3 to 1/5;

optionally, a PECVD device is adopted to prepare the second silicon nitride antireflection film (3); 1400-2000 degree of butterfly valve opening of vacuum pump, 450-530 degree of butterfly valve opening, 10000-15000W of power, 30-50 duty ratio of opening and closing microwave (500-800), SiH₄、NH₃The flow ratio of (a) is from 1/8 to 1/12;

optionally, preparing the silicon oxynitride film (4) by adopting PECVD equipment; 1300-1700 degree of butterfly valve opening of vacuum pump, 450-530 degree of butterfly valve opening, 14000W of power 10000-50 degree of butterfly valve opening and closing duty ratio of microwave opening and closing (700-1000), SiH₄、NH₃、N₂The flow ratio of O is 1: (4-6): (4-6);

optionally, preparing the silicon oxide film (5) by adopting PECVD equipment; 900-1200 degree of butterfly valve opening of vacuum pump, 450-530 degree of butterfly valve opening, 8000-12000W of power, 20-40 duty ratio of opening and closing microwave (800-1100), SiH₄、N₂The flow ratio of O is 1/10 to 1/14.

10. The method for manufacturing a solar cell according to claim 8 or 9, wherein, after the second silicon oxide film (13) is manufactured,

preparing a grouting groove (14) communicated with the silicon substrate in a laser grooving mode; wherein the laser is square spot laser;

optionally, the diameter of a light spot of the laser is 30-40 um, and the laser power is 15-25W.