Solar cell and preparation method therefor

Abstract

A solar cell and a preparation method therefor. The solar cell comprises: a silicon substrate, which silicon substrate has a front surface; and an anti-ultraviolet composite film (200), wherein the anti-ultraviolet composite film (200) is arranged on the front surface, and the anti-ultraviolet composite film (200) comprises a silicon oxide layer (10) and a single-film silicon nitride layer (20) which are arranged in a stacked mode, the silicon oxide layer (10) being located on the surface of the silicon substrate that is away from the silicon nitride layer (20), and the refractive index of the silicon nitride layer (20) gradually increasing in the direction away from the silicon oxide layer (10).

Description

Solar cell and method for preparing the same This application claims the priority of the Chinese patent application filed with the China Patent Office on September 26, 2023, with application number 202311264117.6 and invention name “Solar Cell and Its Preparation Method”, all contents of which are incorporated by reference into this application. Technical Field The present invention relates to the technical field of solar cells, and in particular to a solar cell and a preparation method thereof. Background Art In the actual application of solar cells, solar cells will be accompanied by various attenuations, such as potential induced decay (PID), conventional light-induced decay (LID), thermally assisted light-induced decay (LeTID), etc. In addition, the attenuation of the battery is more serious in high-ultraviolet application scenarios. Researchers have discovered that the ultraviolet light-induced decay (UVID) phenomenon of the battery will also seriously affect the stability of photovoltaic modules or power stations. At present, the technical solution for ultraviolet light-induced decay is mainly to use an encapsulation film with ultraviolet absorption function to encapsulate the components, which can reduce the ultraviolet light reaching the battery. However, the film is a polymer material and has the risk of degradation under long-term ultraviolet light exposure. Once the film degrades and fails, the ultraviolet light decay of the solar cell will be manifested, which will have an adverse effect on the power generation of photovoltaic modules or power stations. Summary of the invention The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, one object of the present invention is to provide a solar cell, in which the anti-ultraviolet composite film can effectively alleviate or solve the problem of ultraviolet light attenuation of the solar cell. In one aspect of the present invention, the present invention provides a solar cell. According to an embodiment of the present invention, The solar cell includes: a silicon substrate, the silicon substrate has a front side; and an anti-ultraviolet composite film, the anti-ultraviolet composite film is arranged on the front side, and the anti-ultraviolet composite film includes a stacked silicon oxide layer and a single film silicon nitride layer, the silicon oxide layer is located on the surface of the silicon substrate away from the silicon nitride layer, and the refractive index of the silicon nitride layer gradually increases in the direction away from the silicon oxide layer. Therefore, when ultraviolet light irradiates the anti-ultraviolet composite film of the solar cell, the anti-ultraviolet composite film can effectively absorb ultraviolet light to prevent the solar cell from being attenuated by ultraviolet light. Specifically: the full spectrum light is incident on the side of the silicon oxide layer away from the silicon nitride layer, as shown in Figure 1, so that the silicon oxide layer can first absorb most of the ultraviolet light to prevent most of the ultraviolet light from being incident on the solar cell, which can play a good role in protecting the solar cell. Then, after passing through the silicon oxide layer, a small part of the ultraviolet light passes through the silicon oxide layer and enters the silicon nitride layer, and the more Si-H bonds in the silicon nitride layer, the more ultraviolet light is incident on the solar cell. The better the silicon nitride layer absorbs ultraviolet light, in the silicon nitride layer of the present invention, as the refractive index of the silicon nitride layer increases, the number of Si-H bonds therein gradually increases, thereby gradually improving its absorption of ultraviolet light, thereby preventing ultraviolet light from damaging the passivation structure of the solar cell, fundamentally alleviating or solving the problem of ultraviolet light attenuation of the solar cell containing the anti-ultraviolet composite film; at the same time, the silicon nitride layer with a gradient refractive index can maintain a good visible light transmittance; in addition, the refractive index of the silicon oxide layer is lower than that of the silicon nitride layer, so that it is located on the outside of the solar cell, which can better reduce the reflection of visible light. Ensure that the light required by the solar cell enters the solar cell and improve the cell efficiency of the solar cell; further, the setting of the silicon oxide layer can further improve the potential induced decay (PID) of the solar cell. According to an embodiment of the present invention, the refractive index of the silicon nitride layer gradually increases from A to B, wherein A is 1.8 to 2.0, and B is 2.4 to 2.6. According to an embodiment of the present invention, the refractive index of the silicon nitride layer increases linearly. According to an embodiment of the present invention, the increasing rate of the refractive index of the silicon nitride layer is 0.01 / nm to 0.015 / nm. According to an embodiment of the present invention, the thickness of the silicon nitride layer is 50 nm to 60 nm. According to an embodiment of the present invention, the thickness of the silicon oxide layer is 20 nm to 25 nm. According to an embodiment of the present invention, the anti-ultraviolet composite film can be reused as an anti-reflection film. In another aspect of the present invention, the present invention provides a method for preparing the aforementioned solar cell. According to an embodiment of the present invention, the method for preparing the solar cell comprises: providing a silicon substrate; forming a silicon nitride layer on the front side of the silicon substrate by a first deposition method, adjusting the flow rates of silane and ammonia in the step of forming the silicon nitride layer so that the flow rates of silane and nitrogen gradually change; forming a silicon oxide layer on the surface of the silicon nitride layer away from the silicon substrate by a second deposition method. Therefore, the above method can prepare an anti-ultraviolet composite film of a stacked silicon nitride layer and a silicon oxide layer, and the silicon nitride layer is a silicon nitride layer with a gradient refractive index. When ultraviolet light irradiates the anti-ultraviolet composite film of the solar cell, the anti-ultraviolet composite film can effectively absorb ultraviolet light to prevent the solar cell from being attenuated by ultraviolet light. Specifically: full-spectrum light is incident on the side of the silicon oxide layer away from the silicon nitride layer, as shown in Figure 1, so that the silicon oxide layer can first absorb most of the ultraviolet light to prevent most of the ultraviolet light from being incident on the solar cell, which can play a good role in protecting the solar cell, and then after passing through the silicon oxide layer, a small amount of ultraviolet light passes through the silicon oxide layer into the silicon nitride layer, and the more Si-H bonds there are in the silicon nitride layer, the more ultraviolet light there is in the silicon nitride layer. The better the absorption of ultraviolet light, in the silicon nitride layer of the present invention, as the refractive index of the silicon nitride layer increases, the number of Si-H bonds therein gradually increases, and thus its absorption of ultraviolet light can be gradually improved, thereby avoiding ultraviolet light from damaging the passivation structure of the solar cell, fundamentally alleviating or solving the problem of ultraviolet light attenuation of the solar cell: at the same time, the silicon nitride layer with a gradient refractive index can maintain a good visible light transmittance; in addition, the refractive index of the silicon oxide layer is lower than that of the silicon nitride layer, so that it is located on the outside of the solar cell, which can better reduce the reflection of visible light, ensure that the light required by the solar cell enters the solar cell, and improve the battery efficiency of the solar cell; further, the provision of the silicon oxide layer can further improve the potential induced decay (PID) of the solar cell. According to an embodiment of the present invention, the flow rate of the silane and the flow rate of the nitrogen both vary continuously. According to an embodiment of the present invention, the change rate of the flow rate of the silane is -1.25 sccm / s to -1.5 sccm / s, and the change rate of the flow rate of the nitrogen is 2.5 sccm / s to 3.0 sccm / s. BRIEF DESCRIPTION OF THE DRAWINGS The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: FIG1 is a schematic diagram of a partial structure of a solar cell in one embodiment of the present invention; FIG2 is a schematic diagram of a partial structure of a solar cell in Comparative Example 1; FIG3 is a schematic diagram of a partial structure of a solar cell in Comparative Example 2. DETAILED DESCRIPTION The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially. The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way. In one aspect of the present invention, a solar cell is provided. According to an embodiment of the present invention, referring to FIG1 , the solar cell comprises: a silicon substrate having a front surface; and an anti-ultraviolet composite film 200, the anti-ultraviolet composite film 200 being arranged on the front surface, and the anti-ultraviolet composite film comprises a stacked silicon oxide layer 10 and a single film silicon nitride layer 20, the silicon oxide layer 10 being located on the surface of the silicon substrate away from the silicon nitride layer 20. On the direction X away from the silicon oxide layer 10, the refractive index of the silicon nitride layer 20 gradually increases. Therefore, when ultraviolet light irradiates the anti-ultraviolet composite film of the solar cell, the anti-ultraviolet composite film can effectively absorb ultraviolet light to prevent the solar cell from being attenuated by ultraviolet light. Specifically: the full spectrum light is incident on the side of the silicon oxide layer away from the silicon nitride layer, as shown in Figure 1. In this way, the silicon oxide layer can first absorb most of the ultraviolet light to prevent most of the ultraviolet light from being incident on the solar cell, which can play a good role in protecting the solar cell. Then, after passing through the silicon oxide layer, a small amount of ultraviolet light passes through the silicon oxide layer and enters the silicon nitride layer. Moreover, the more Si-H bonds there are in the silicon nitride layer, the better the silicon nitride layer absorbs ultraviolet light. In the silicon nitride layer of the present invention, as the refractive index of the silicon nitride layer increases, the ultraviolet light absorption rate increases. The number of Si-H bonds gradually increases, thereby gradually improving its absorption of ultraviolet light, thereby preventing ultraviolet light from damaging the passivation structure of the solar cell, and fundamentally alleviating or solving the problem of ultraviolet light attenuation of the solar cell containing the anti-ultraviolet composite film; at the same time, the silicon nitride layer with a gradient refractive index can maintain a good visible light transmittance; in addition, the refractive index of the silicon oxide layer is lower than that of the silicon nitride layer, so that it is located on the outside of the solar cell, which can better reduce the reflection of visible light, ensure that the light required by the solar cell enters the solar cell, and improve the battery efficiency of the solar cell; further, the setting of the silicon oxide layer can further improve the potential induced decay (PID) of the solar cell. According to an embodiment of the present invention, as described above, the silicon nitride layer is a single-film structure, so there is no interface caused by a change in the refractive index in the single-film silicon nitride layer, and there is no stratified interface. If there is an interface in the silicon nitride layer, it will cause defects in the silicon nitride layer at the interface, and the defects can allow part of the ultraviolet light to pass through. That is to say, the silicon nitride layer of the present invention can avoid defects caused by the interface, and thus better prevent ultraviolet light from passing through the anti-UV composite film, that is, further improve the anti-UV effect of the anti-UV composite film, and even achieve complete transmission of ultraviolet light through the anti-UV composite film. According to some embodiments of the present invention, since ultraviolet light is usually incident on the front side of the solar cell, the anti-ultraviolet composite film can be disposed only on the front side 110 of the silicon substrate 100. In some other embodiments, the anti-ultraviolet composite film can be reused as an anti-reflection film, so the anti-ultraviolet composite film can also be set on one side of the back side 120 of the silicon substrate. In summary, those skilled in the art can flexibly choose to set the anti-ultraviolet composite film on the front side 110 of the silicon substrate 100 or set the anti-ultraviolet composite film on both the front side 110 and the back side 120 according to the specific function of the anti-ultraviolet composite film in the solar cell. In some embodiments of the present invention, the anti-ultraviolet composite film can be located at the outermost side of the solar cell. In this way, ultraviolet light can be prevented from entering the interior of the solar cell and affecting any structure such as the passivation layer and electrode inside the solar cell, thereby better protecting the solar cell from interference from ultraviolet light. In some embodiments, when the anti-ultraviolet composite film can be reused as an anti-reflection film, there is no need to further set an anti-reflection film, thereby simplifying the structure of the solar cell and reducing its production cost. In other embodiments, an anti-reflection film and an anti-ultraviolet composite film can be set at the same time. In some embodiments of the present invention, the anti-ultraviolet composite film can be located at the outermost side of the solar cell. In this way, ultraviolet light can be prevented from entering the interior of the solar cell and affecting any structure such as the passivation layer and electrode inside the solar cell, thereby better protecting the solar cell from interference from ultraviolet light. In some embodiments, when the anti-ultraviolet composite film can be reused as an anti-reflection film, there is no need to further set an anti-reflection film, thereby simplifying the structure of the solar cell and reducing its production cost. In other embodiments, an anti-reflection film and an anti-ultraviolet composite film can be set at the same time. According to an embodiment of the present invention, in the direction X, the refractive index of the silicon nitride layer 20 gradually increases from A to B, A is 1.8 to 2.0, such as 1.8, 1.85, 1.9, 1.95 or 2.0, and B is 2.4 to 2.6, such as 2.4, 2.45, 2.5, 2.55, 2.6, etc. In this way, within the above-mentioned range of refractive index variation, as the refractive index increases, the number of Si-H bonds inside it increases, which can ensure that the silicon nitride layer has a good absorption rate for ultraviolet light. At the same time, the refractive index of the silicon nitride layer gradually changes from small to large, rather than having a uniform and large refractive index, so the silicon nitride layer of the present invention also has a good transmittance to visible light. According to an embodiment of the present invention, the refractive index of the silicon nitride layer increases linearly. The change of refractive index is relatively regular. During the production process, the flow rate of nitrogen gas used to prepare the raw material silane of the silicon nitride layer can be regularly adjusted, which facilitates the control of the raw material flow rate. Moreover, the refractive index of the silicon nitride layer changes uniformly, which is conducive to maintaining good ultraviolet light absorption rate and visible light transmittance. According to an embodiment of the present invention, the increasing rate of the refractive index of the silicon nitride layer is 0.01 / nm to 0.015 / nm, such as the increasing rate of the refractive index is 0.01 / nm, 0.011 / nm, 0.012 / nm, 0.013 / nm, 0.014 / nm, 0.015 / nm, etc. Within the above-mentioned increasing rate range, the refractive index change of the silicon nitride layer will not be too large or too small, which helps to simultaneously ensure the absorption rate of the silicon nitride layer to ultraviolet light and the transmittance of visible light. It should be noted that in the actual manufacturing process, it is difficult to achieve a theoretically completely linear change, and there may be a certain error, that is, the increasing rate may be difficult to remain completely unchanged, so as long as the refractive index of the silicon nitride layer of the present invention basically shows a linear increasing trend, a certain error can be allowed to exist, such as the rate of change of the increasing rate is within 20%, and the refractive index of the silicon nitride layer of the present invention can be basically considered to change linearly. Furthermore, the thickness of the silicon nitride layer is 50 nm to 60 nm, such as 50 nm, 51 nm, 52 nm, 53 nm, 54 nm, 55 nm, 56 nm, 57 nm, 58 nm, 59 nm, 60 nm, etc. The above thickness can meet the above setting range and incremental requirement of the refractive index. According to an embodiment of the present invention, the thickness of the silicon oxide layer is 20nm to 25nm, such as 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, etc. The silicon oxide layer of the above thickness can effectively meet the good ultraviolet absorption function of the anti-ultraviolet composite film, and also has a better anti-reflection effect, effectively improving the efficiency of the solar cell; if the thickness of the silicon oxide layer is greater than 25nm, it will absorb too much light, which will relatively reduce the efficiency of the cell. In the embodiment of the present invention, the refractive index of the silicon oxide layer is uniform, which is conducive to the transmission of light. In some embodiments of the present invention, the silicon substrate may be a P-type silicon substrate or an N-type silicon substrate, and those skilled in the art may flexibly select the one according to actual needs. Those skilled in the art will appreciate that the above solar cells have the following features in addition to the silicon substrate and UV protection: In addition to the composite film, it also includes the necessary structures and components of conventional solar cells, such as the back passivation layer, front electrode and back electrode structures, which will not be elaborated here. According to the embodiments of the present invention, there is no special requirement for the specific type of the solar cell, and those skilled in the art can flexibly select according to actual needs. In some embodiments, the solar cell can be a PERC cell, a passivated contact cell or a RESH cell. According to the embodiments of the present invention, there is no special requirement for the specific type of the solar cell, and those skilled in the art can flexibly select according to actual needs. In some embodiments, the solar cell can be a PERC cell, a passivated contact cell or a RESH cell. In another aspect of the present invention, the present invention provides a method for preparing the aforementioned anti-ultraviolet composite film. According to an embodiment of the present invention, the method for preparing a solar cell includes: providing a silicon substrate; forming a silicon nitride layer on the front side of the silicon substrate by a first deposition method, and adjusting the flow rates of silane and nitrogen in the step of forming the silicon nitride layer so that the flow rates of the silane and the ammonia gradually change; forming a silicon oxide layer on the surface of the silicon nitride layer away from the silicon substrate by a second deposition method. Thus, the above method can prepare an anti-ultraviolet composite film of a stacked silicon nitride layer and a silicon oxide layer, and the silicon nitride layer is a silicon nitride layer with a gradient refractive index. When ultraviolet light irradiates the anti-ultraviolet composite film of the solar cell, the anti-ultraviolet composite film can effectively absorb ultraviolet light to prevent the solar cell from being attenuated by ultraviolet light. Specifically: full spectrum light is incident on the side of the silicon oxide layer away from the silicon nitride layer, as shown in Figure 1. In this way, the silicon oxide layer can first absorb most of the ultraviolet light to prevent most of the ultraviolet light from being incident on the solar cell. In the solar cell, it can play a good role in protecting the solar cell. After passing through the silicon oxide layer, a small part of the ultraviolet light passes through the silicon oxide layer and enters the silicon nitride layer. The more Si-H bonds there are in the silicon nitride layer, the more the silicon nitride layer absorbs ultraviolet light. In the silicon nitride layer of the present invention, as the refractive index of the silicon nitride layer increases, the number of Si-H bonds therein gradually increases, and thus the absorption of ultraviolet light can be gradually improved, thereby preventing ultraviolet light from damaging the passivation structure of the solar cell, and fundamentally alleviating or solving the problem of using the anti- The problem of ultraviolet light attenuation of solar cells with ultraviolet composite films; at the same time, the silicon nitride layer with a gradient refractive index can maintain a good visible light transmittance; in addition, the refractive index of the silicon oxide layer is lower than that of the silicon nitride layer, so that it is located on the outside of the solar cell, which can better reduce the reflection of visible light, ensure that the light required by the solar cell enters the solar cell, and improve the battery efficiency of the solar cell; further, the setting of the silicon oxide layer can further improve the potential induced decay (PID) of the solar cell. According to the embodiment of the present invention, the flow rate of silane and the flow rate of the nitrogen both vary continuously. In this way, it is convenient to change the flow rate of the raw materials and obtain a silicon nitride layer with a linearly varying refractive index. Moreover, the refractive index of the silicon nitride layer varies uniformly, which is conducive to maintaining a good ultraviolet light absorption rate and visible light transmittance. According to an embodiment of the present invention, the change rate of the flow rate of silane is -1.25 sccm / s to -1.5 sccm / s, that is, as the silicon nitride layer is prepared, the flow rate of silane gradually decreases, and the change rate of the flow rate of nitrogen is 2.5 sccm / s to 3.0 sccm / s, that is, as the silicon nitride layer is prepared, the flow rate of nitrogen increases. Within the above range of change, it can help to obtain a silicon nitride layer with a suitable refractive index. The specific methods of the first deposition and the second deposition may be chemical vapor deposition or physical vapor deposition, such as magnetron sputtering. Those skilled in the art may flexibly select a suitable deposition method according to actual conditions. Furthermore, when the silicon oxide layer is formed by the second deposition, silane and nitrous oxide are deposited according to a certain flow ratio to obtain a silicon oxide layer with a uniform refractive index. Example 1 In the PERC cell, a single-film silicon nitride layer is arranged on the front side of the P-type silicon substrate, and a silicon oxide layer is arranged on the surface of the silicon nitride layer away from the silicon substrate. In the direction close to the silicon substrate, the refractive index of the single-film silicon nitride layer gradually increases linearly from 1.9 to 2.5. The thickness of the silicon nitride layer is 50nm, and the thickness of the silicon oxide layer is 20nm. Comparative Example 1 In the PERC cell, referring to FIG2 , a silicon nitride layer is disposed on the front side of a P-type silicon substrate, wherein in the direction close to the silicon substrate, the silicon nitride layer includes a first sublayer, a second sublayer and a third sublayer which are stacked in three layers, wherein the refractive index of the first sublayer is 1.9 and the thickness is 23 nm, the refractive index of the second sublayer is 2.2 and the thickness is 23 nm, and the refractive index of the third sublayer is 2.5 and the thickness is 24 nm. Comparative Example 2 The difference from Comparative Example 1 is that, referring to FIG. 3 , a film containing an ultraviolet absorber is also included.

[0045] The PERC cells of Example 1 and Comparative Examples 1 and 2 were subjected to a cell efficiency attenuation test, and the test results are shown in the following table. Table 1 In Table 1, the test conditions 280nm~400nm refer to the wavelength range of ultraviolet light, that is, the solar cell is placed under light of this wavelength range for attenuation test; 60kWh / m 2 and 600kWh / m 2 Refers to the unit of ultraviolet radiation. As can be seen from Table 1, compared with Comparative Examples 1 and 2, the anti-ultraviolet composite film of the present invention can more effectively alleviate the problem of ultraviolet light attenuation of solar cells. In the structure of Comparative Example 2, since the refractive index of the first sublayer, the second sublayer and the third sublayer changes in a step-by-step manner rather than a gradual linear change, there is an interface between the adjacent two-layer structures of the first sublayer, the second sublayer and the third sublayer. Compared with the silicon nitride layer structure in Example 1, the existence of this interface allows more ultraviolet light to pass through the anti-ultraviolet composite film, that is, ultraviolet light that destroys the Si-H passivation structure inside the battery enters the battery, which will eventually cause the battery's ultraviolet light attenuation. As can be seen from the second set of test data, although the provision of an adhesive film that can absorb ultraviolet light can alleviate the problem of ultraviolet light attenuation of solar cells, However, since the film is a polymer material, it is easy to degrade under long-term ultraviolet light. Therefore, the ultraviolet light attenuation of the battery may increase with the extension of illumination time. The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory. Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A solar cell comprising: A silicon substrate having a front side; and An anti-ultraviolet composite film is arranged on the front side, and the anti-ultraviolet composite film includes a stacked silicon oxide layer and a single-film silicon nitride layer, the silicon oxide layer is located on the surface of the silicon substrate away from the silicon nitride layer, and the refractive index of the silicon nitride layer gradually increases in the direction away from the silicon oxide layer.

2. The solar cell according to claim 1, wherein: The refractive index of the silicon nitride layer gradually increases from A to B, where A is 1.8-2.0 and B is 2.4-2.

6.

3. The solar cell according to claim 1, wherein: The refractive index of the silicon nitride layer increases linearly.

4. The solar cell according to claim 3, wherein: The increasing rate of the refractive index of the silicon nitride layer is 0.01 / nm to 0.015 / nm.

5. The solar cell according to any one of claims 1 to 4, wherein The thickness of the silicon nitride layer is 50nm-60nm.

6. The solar cell according to any one of claims 1 to 4, wherein The thickness of the silicon oxide layer is 20nm-25nm.

7. The solar cell according to any one of claims 1 to 4, wherein The anti-ultraviolet composite film can be reused as an anti-reflection film.

8. A method for preparing the solar cell according to any one of claims 1 to 7, comprising: providing a silicon substrate; A silicon nitride layer is formed on the front side of the silicon substrate by a first deposition method, and in the step of forming the silicon nitride layer, the flow rates of silane and nitrogen are adjusted so that the flow rate of the silane and the flow rate of the nitrogen are Gradual change; A silicon oxide layer is formed on the surface of the silicon nitride layer away from the silicon substrate by using a second deposition method.

9. The method according to claim 8, wherein: The flow rates of the silane and the nitrogen both vary continuously.

10. The method according to claim 9, wherein: The change rate of the flow rate of the silane is -1.25 sccm / s to -1.5 sccm / s, and the change rate of the flow rate of the ammonia is 2.5 sccm / s to 3.0 sccm / s.

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