Heterojunction solar cell and method for preparing the same

Abstract

The present application discloses a heterojunction solar cell and a preparation method thereof, belonging to the technical field of solar cells. A preparation method of a heterojunction solar cell, the method comprising: providing a semiconductor substrate, forming transparent conductive layers on both sides of the semiconductor substrate respectively; performing plasma treatment on the transparent conductive layer on at least one side by a plasma process; forming a tin oxide layer on the surface of the transparent conductive layer after the plasma treatment by atomic layer deposition; performing plasma treatment on the tin oxide layer by a plasma process, and performing annealing treatment; forming a seed layer on the surface of the tin oxide layer after the annealing treatment; and forming metal electrodes on the surface of the seed layer on both sides of the semiconductor substrate by an electroplating process. The present invention can reduce the series resistance of the battery, reduce the preparation cost of the battery, improve the bonding strength between the layers in the battery structure, and ensure the photoelectric conversion efficiency of the battery.

Description

Technical Field

[0001] The present application belongs to the technical field of solar cells, and specifically relates to a heterojunction solar cell and a preparation method thereof. Background Art

[0002] As a new type of solar cell, heterojunction solar cells have become a new hot spot in the photovoltaic field in recent years. They have many advantages, such as simple structure, wide source of raw materials, high open circuit voltage, high conversion efficiency, and low temperature coefficient. Traditional heterojunction solar cells mostly use screen printing to prepare metal electrodes during the preparation process, which consumes a large amount of silver paste and leads to high cost of solar cells. Using electroplating to prepare metal (such as copper, tin, etc.) electrodes instead of traditional screen printing to prepare electrodes is one of the important means to reduce the cost of solar cells.

[0003] However, in the existing preparation technology, the obtained heterojunction solar cell is prone to form a high resistance interface, which leads to a large contact resistance / series resistance of the cell; or the prepared metal grid electrode is easy to fall off. In addition, in the preparation process of the existing heterojunction solar cell, when the metal electrode is prepared by electroplating process, the transparent conductive oxide film is easy to be damaged, especially the transparent conductive oxide film with lower price is more likely to be completely destroyed, which affects the photoelectric conversion efficiency of the heterojunction solar cell. Summary of the invention

[0004] In view of the above problems, the present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the present invention provides a heterojunction solar cell and a preparation method thereof, which can reduce the series resistance of the cell, reduce the preparation cost of the cell, ensure the photoelectric conversion efficiency of the cell, and overcome the shortcomings of the prior art.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] According to one aspect of the present application, a method for preparing a heterojunction solar cell is provided, the method comprising: providing a semiconductor substrate, and forming a transparent conductive layer on both sides of the semiconductor substrate; performing plasma treatment on at least one side of the transparent conductive layer using a plasma process; forming a tin oxide layer on the surface of the transparent conductive layer after the plasma treatment using atomic layer deposition; performing plasma treatment on the tin oxide layer using a plasma process, and performing annealing treatment; forming a seed layer on the surface of the tin oxide layer after the annealing treatment, or forming a seed layer on the surface of the transparent conductive layer that has not been plasma treated; and forming metal electrodes on the surfaces of the seed layer on both sides of the semiconductor substrate using an electroplating process.

[0007] In some embodiments, the process conditions for plasma treatment of the transparent conductive layer on either side of the semiconductor substrate include: the plasma is oxygen plasma or argon plasma; when the oxygen plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 , the treatment time is 20 to 300 s; and / or, when the argon plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 The processing time is 20 to 300 seconds.

[0008] In some of the embodiments, the process conditions for forming the tin oxide layer on either side include: placing a sample having a transparent conductive layer treated with plasma in an atomic layer deposition device, using at least one of tetrakis(dimethylamino)tin and diethyltin dichloride as a tin source, and forming a tin oxide layer on the surface of the transparent conductive layer at a substrate temperature of 80 to 210°C.

[0009] In some embodiments, the tin oxide layer has a thickness of 0.5 nm to 20 nm.

[0010] In some embodiments, the process conditions for plasma treatment of the tin oxide layer on either side of the semiconductor substrate include: the plasma is oxygen plasma or argon plasma; when the oxygen plasma is used, the power density of the plasma treatment is 200 to 3000 W / m 2 , the treatment time is 20 to 300 s; and / or, when the argon plasma is used, the power density of the plasma treatment is 200 to 3000 W / m 2 The processing time is 20 to 300 seconds.

[0011] In some of the embodiments, the tin oxide layer after the plasma treatment is subjected to an annealing treatment, and the annealing treatment is performed using a pulse infrared laser annealing treatment; the wavelength range of the pulse infrared laser annealing is 1200 to 3000 nm.

[0012] In some embodiments, forming a transparent conductive layer on both sides of the semiconductor substrate includes: sequentially forming an intrinsic amorphous silicon layer and a doped layer on both sides of the semiconductor substrate; and forming the transparent conductive layer on the surfaces of the doped layers on both sides by a magnetron sputtering process.

[0013] In some of the embodiments, the transparent conductive layers on both sides of the semiconductor substrate respectively include at least one of an ITO (indium tin oxide) film, an IWO (tungsten-doped indium oxide) film or an AZO (aluminum-doped zinc oxide) film; and the material types of the transparent conductive layers on both sides of the semiconductor substrate are the same or different.

[0014] In some embodiments, the thickness of the transparent conductive layer on both sides of the semiconductor substrate is 50 nm to 100 nm respectively.

[0015] In some embodiments, the sum of the thicknesses of the transparent conductive layer and the tin oxide layer on either side of the semiconductor substrate is 50 nm to 120 nm, respectively.

[0016] In some embodiments, the seed layer is formed by: forming the seed layer by a magnetron sputtering process; and / or the seed layer includes a copper seed layer.

[0017] In some embodiments, the step of forming the transparent conductive layer includes: forming a first transparent conductive layer on one side of the semiconductor substrate, and forming a second transparent conductive layer on the other side of the semiconductor substrate; the step of plasma-treating the transparent conductive layer includes: plasma-treating the first transparent conductive layer and the second transparent conductive layer respectively; the step of forming the tin oxide layer includes: forming a first tin oxide layer on the surface of the first transparent conductive layer after the plasma treatment, and forming a second tin oxide layer on the surface of the second transparent conductive layer after the plasma treatment; the step of plasma-treating the tin oxide layer includes: plasma-treating the first tin oxide layer and the second tin oxide layer respectively, and performing annealing treatment; the step of forming the seed layer includes: forming a first seed layer on the surface of the first tin oxide layer after the annealing treatment, and forming a second seed layer on the surface of the second tin oxide layer after the annealing treatment.

[0018] In some embodiments, the step of forming the transparent conductive layer includes: forming a first transparent conductive layer on one side of the semiconductor substrate, and forming a second transparent conductive layer on the other side of the semiconductor substrate; the step of plasma-treating the transparent conductive layer includes: plasma-treating the first transparent conductive layer; the step of forming the tin oxide layer includes: forming a first tin oxide layer on the surface of the first transparent conductive layer after the plasma treatment; the step of plasma-treating the tin oxide layer includes: plasma-treating the first tin oxide layer and annealing; the step of forming the seed layer includes: forming a first seed layer on the surface of the first tin oxide layer after the annealing treatment, and forming a second seed layer on the surface of the second transparent conductive layer.

[0019] According to another aspect of the present application, a heterojunction solar cell is provided, which comprises: a semiconductor substrate; a first intrinsic amorphous silicon layer, a first doped layer, a first transparent conductive layer, a first tin oxide layer, a first seed layer and a first metal electrode are sequentially arranged on a surface of one side of the semiconductor substrate; a second intrinsic amorphous silicon layer, a second doped layer, a second transparent conductive layer, a second tin oxide layer, a second seed layer and a second metal electrode are sequentially arranged on the surface of the other side of the semiconductor substrate.

[0020] According to another aspect of the present application, a heterojunction solar cell is provided, which comprises: a semiconductor substrate; a first intrinsic amorphous silicon layer, a first doped layer, a first transparent conductive layer, a first tin oxide layer, a first seed layer and a first metal electrode are sequentially arranged on a surface of one side of the semiconductor substrate; a second intrinsic amorphous silicon layer, a second doped layer, a second transparent conductive layer, a second seed layer and a second metal electrode are sequentially arranged on the surface of the other side of the semiconductor substrate.

[0021] It should be noted that the above numerical ranges all include endpoint values.

[0022] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0023] In the preparation process of heterojunction solar cells, the present application uses a plasma process to perform plasma treatment on the transparent conductive layer, which can effectively clean the dust and impurity adsorption on the surface of the transparent conductive layer, and eliminate the thin layer with poor performance on the surface of the transparent conductive layer, so that the surface activity of the transparent conductive layer is higher and the surface is cleaner, so that when the transparent conductive layer contacts other materials, there is no contact high-resistance interface layer, which is beneficial to reduce the series resistance of the battery. In addition, the tin oxide layer is formed on the surface of the transparent conductive layer by atomic layer deposition, which can alleviate the problem of poor contact between the existing transparent conductive layer and the seed layer, and can also avoid the problem of poor adhesion between the transparent conductive layer and the seed layer, which helps to improve the bonding strength between the layers in the solar cell structure, and can avoid the problem of easy detachment of the metal (grid line) electrode of the solar cell finally obtained. At the same time, the preparation method can avoid the transparent conductive layer from reacting with gases in the environment such as oxygen / water vapor in the air, and avoid damage to the transparent conductive layer during the subsequent annealing treatment and the preparation of the metal electrode by the electroplating process by means of the above-mentioned plasma treatment of the transparent conductive layer and the formation of the tin oxide layer by atomic layer deposition, so that the transparent conductive layer is not affected in any way, and various transparent conductive oxide materials including cheap transparent conductive oxide materials can be used in the preparation method of the present invention, which is beneficial to reducing the preparation cost of the heterojunction battery and improving the photoelectric conversion efficiency of the heterojunction battery.

[0024] Additional aspects and advantages of the present application will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic flow chart of a method for preparing a heterojunction solar cell provided by some embodiments of the present invention;

[0026] Figure 2 is a schematic flow chart of a method for preparing a heterojunction solar cell provided by other embodiments of the present invention;

[0027] Figure 3 is a schematic diagram of the structure of a heterojunction solar cell provided by some embodiments of the present invention;

[0028] Figure 4 It is a schematic structural diagram of an existing heterojunction solar cell provided in a comparative example of the present invention;

[0029] Figure 5 is a schematic structural diagram of a heterojunction solar cell provided by other embodiments of the present invention;

[0030] Figure 6 It is a schematic diagram of the structure of a heterojunction solar cell provided by other embodiments of the present invention.

[0031] Description of reference numerals:

[0032] 1-semiconductor substrate; 2-first intrinsic amorphous silicon layer; 3-first doping layer; 6-first transparent conductive layer; 8-first seed layer; 9-first metal electrode; 10-first tin oxide layer;

[0033] 4 - a second intrinsic amorphous silicon layer; 5 - a second doping layer; 7 - a second transparent conductive layer; 8' - a second seed layer; 9' - a second metal electrode; 10' - a second tin oxide layer. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally a class, and the number of objects is not limited. For example, the first object can be one or more. In addition, the term "and / or" used in this article is only a kind of association relationship describing associated objects, indicating that three relationships can exist, for example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone.

[0036] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges.

[0037] In the related art, in order to reduce the preparation cost of heterojunction cells, one improvement method is to reduce the amount of silver paste or use electroplating process to prepare metal electrodes (such as copper electrodes). For example, Chinese patent CN112531043A discloses a double-sided heterojunction solar cell, a manufacturing method and a module, the back of which uses a metal conductive layer as a grid-shaped metal electrode to reduce the amount of silver paste used for the back electrode of the battery. At present, the method for preparing copper electrodes on heterojunction cells mainly includes: the cell (silicon wafer) is cleaned by texturing, and amorphous silicon film is deposited by plasma enhanced vapor chemical deposition (PECVD for short), and then a transparent conductive film (such as ITO, IWO, AZO, etc., all referred to as TCO) with a thickness of 70 to 80 nm is deposited on the upper and lower surfaces of the cell by magnetron sputtering (PVD for short) or reactive plasma deposition (RPD for short). After the transparent conductive film (TCO) is deposited, in order to improve the performance of the transparent conductive film and restore the damage caused by the PVD deposited film, the cell needs to be annealed at 190°C for 15 minutes. After annealing, the sample is again subjected to the PVD process to deposit a 50-200 nm thick copper seed layer on the surface of the transparent conductive film. The sample then undergoes an electroplating process (pressing dry film / or spraying photoresist / or spraying ink, exposure, development, electroplating copper / electroplating tin), and copper and tin electrodes are electroplated on the upper and lower surfaces of the cell. The sample is then placed in an alkaline solution to remove the above-mentioned mask (dry film / photoresist / ink), and then the sample is placed in an acidic / alkaline solution to remove the copper seed layer film to obtain the final heterojunction battery structure.

[0038] It can be seen that in the current heterojunction battery preparation process, the battery cell needs to be annealed at 190°C for 15 minutes. This will result in the battery cell being placed in the atmosphere during the annealing process. Even in a dust-free workshop, impurities such as dust will inevitably be adsorbed on the surface of the battery cell. In addition, when the copper seed layer is directly deposited on the TCO film, there will be a stress effect between the TCO film and the copper seed layer, which makes the adhesion between the two materials insufficient, and easily leads to the problem of the subsequent metal grid line falling off. Moreover, in the existing annealing process, the TCO film reacts with gases in the environment such as oxygen / water vapor in the air, and it is easy to form a high-resistance interface, which leads to a large contact resistance / series resistance of the battery. Further, in the process of removing the copper seed layer, the etching solution (acid / alkali solution) needs to react with the copper film and etch the copper seed layer, and finally the corresponding etching solution will contact the TCO film. Since the TCO film is composed of many nano-scale particles, there are many pinholes, and the etching solution can easily penetrate into the TCO film, which makes it difficult to remove all the etching solution residues in subsequent cleaning, affecting the reliability of the product. In some cases, the etching solution can even etch away the entire TCO film. For example, the AZO film can be easily etched away by the etching solution in a short time, which greatly affects the conversion efficiency of the heterojunction battery.

[0039] In view of this, the technical solution of the embodiment of the present application provides a method for preparing a heterojunction solar cell and a heterojunction solar cell. The technical method of the embodiment of the present application is conducive to improving the bonding force between the layers in the battery structure, ensuring the photoelectric conversion efficiency of the battery, and is conducive to reducing the series resistance of the battery and reducing the preparation cost of the battery. The description of the specific technical solution is as follows.

[0040] See also Figure 1 or Figure 2 As shown, in some embodiments, a method for preparing a heterojunction solar cell is provided, the method comprising:

[0041] S1. providing a semiconductor substrate, and forming transparent conductive layers on both sides of the semiconductor substrate;

[0042] S2, performing plasma treatment on at least one side of the transparent conductive layer using a plasma process;

[0043] S3, forming a tin oxide layer on the surface of the transparent conductive layer after the plasma treatment by atomic layer deposition;

[0044] S4, performing plasma treatment on the tin oxide layer using a plasma process, and performing annealing treatment;

[0045] S5, forming a seed layer on the surface of the tin oxide layer after annealing, or forming a seed layer on the surface of the transparent conductive layer that has not been treated with plasma;

[0046] S6. Form metal electrodes on the surfaces of the seed layer on both sides of the semiconductor substrate respectively by using an electroplating process.

[0047] The method for preparing a heterojunction solar cell provided in an embodiment of the present invention can effectively clean the dust and impurity adsorption on the surface of the transparent conductive layer (TCO) by performing plasma treatment on the TCO, eliminate the thin layer with loose density and poor performance on the surface of the TCO, make the surface activity of the TCO higher and the surface cleaner, so that when the TCO contacts with other materials, there is no high-resistance interface layer, which is beneficial to reducing the series resistance of the battery.

[0048] The method for preparing a heterojunction solar cell provided by an embodiment of the present invention integrates the annealing process of the cell into the atomic layer deposition (ALD) process or the post-deposition treatment process, thereby eliminating the need for a special annealing process and avoiding various problems existing in the existing annealing process.

[0049] The method for preparing a heterojunction solar cell provided by an embodiment of the present invention adopts an ALD method to prepare a tin oxide (also known as tin dioxide, SnO2) layer. The deposited tin oxide film is relatively dense, which solves the problem of poor contact between the existing TCO and the copper seed layer, avoids the problem of poor adhesion between the TCO and the copper seed layer, and can avoid the problem of easy detachment of the metal grid electrode prepared subsequently. Furthermore, since the tin oxide film deposited by ALD is relatively dense and has no defects such as pinholes and gaps, the tin oxide layer itself has good corrosion resistance. In this way, when the metal electrode is prepared by electroplating, the plating solution basically does not penetrate into the battery, which is very beneficial for TCO materials such as AZO that are not corrosion-resistant, and thus makes it possible for cheap TCO materials such as AZO to be applied to heterojunction batteries, which is beneficial to reducing the preparation cost of the battery and ensuring the photoelectric conversion efficiency of the battery.

[0050] In an embodiment of the present invention, the semiconductor substrate may be a silicon substrate, such as a single crystal silicon substrate, a polycrystalline silicon substrate, or a quasi-single crystal silicon substrate, etc. The embodiment of the present invention does not limit the specific type of the semiconductor substrate. And the semiconductor substrate may be P-type doped or N-type doped, that is, the semiconductor substrate may be a P-type semiconductor substrate or an N-type semiconductor substrate. The heterojunction solar cell of the embodiment of the present invention may be an N-type heterojunction solar cell, or may be a P-type heterojunction solar cell. Exemplarily, in some embodiments, the semiconductor substrate is an N-type single crystal silicon substrate (also referred to as an N-type single crystal silicon wafer).

[0051] In an embodiment of the present invention, the semiconductor substrate includes two oppositely arranged surfaces, namely a front side and a back side; the front side of the semiconductor substrate is the surface facing the sun, that is, the surface facing sunlight, and the back side of the semiconductor substrate is the surface facing away from the sun.

[0052] In some embodiments, step S1 includes:

[0053] S11, providing a semiconductor substrate, and sequentially forming an intrinsic amorphous silicon layer and a doping layer on both sides of the semiconductor substrate.

[0054] Specifically, in step S11, a first intrinsic amorphous silicon layer and a first doped layer are sequentially formed on the front side of the semiconductor substrate, and a second intrinsic amorphous silicon layer and a second doped layer are sequentially formed on the back side of the semiconductor substrate. The first doped layer may be a phosphorus-doped amorphous or microcrystalline silicon layer, and the second doped layer may be a boron-doped amorphous or microcrystalline silicon layer; or, the first doped layer may be a boron-doped amorphous or microcrystalline silicon layer, and the second doped layer may be a phosphorus-doped amorphous or microcrystalline silicon layer, which is not limited in the embodiments of the present application. The method for forming the intrinsic amorphous silicon layer and the doped layer may adopt the existing conventional process method for forming the intrinsic amorphous silicon layer and the doped layer. Exemplarily, the first intrinsic amorphous silicon layer and the first doped layer may be sequentially deposited on the front side of the semiconductor substrate by chemical vapor deposition, and the second intrinsic amorphous silicon layer and the second doped layer may be sequentially deposited on the back side of the semiconductor substrate by chemical vapor deposition.

[0055] More specifically, the operating conditions when performing chemical vapor deposition to prepare the first intrinsic amorphous silicon layer or the second intrinsic amorphous silicon layer may be as follows: power supply power is 500W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 9.5:1, the pressure is 50Pa, and the substrate temperature during deposition is 220°C. The operating conditions when performing chemical vapor deposition to prepare a phosphorus-doped amorphous or microcrystalline silicon layer may be as follows: power supply power is 400W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 5.5:1, the gas flow ratio of phosphine to silane (phosphorus-silicon ratio) is 1:109, the pressure is 120Pa, and the substrate temperature during deposition is 230°C. The operating conditions when implementing chemical vapor deposition to prepare boron-doped amorphous or microcrystalline silicon layers can be as follows: the power supply is 360 W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 2:1, the gas flow ratio of phosphine to silane (phosphorus to silicon ratio) is 2:98, the pressure is 55 Pa, and the temperature of the substrate during deposition is 205°C.

[0056] S12, using a magnetron sputtering process, forming transparent conductive layers on the surfaces of the doping layers on both sides, that is, using a magnetron sputtering coating device to deposit a TCO thin film.

[0057] Specifically, in step S12, a first transparent conductive layer is formed on the surface of the first doped layer, and a second transparent conductive layer is formed on the surface of the second doped layer. The process operating conditions for forming the first transparent conductive layer may be as follows: using a magnetron sputtering coating device, introducing argon and oxygen at room temperature, the gas flow ratio of argon to oxygen may be 55:1, the chamber pressure is maintained at 0.3 SPa, the sputtering power supply is turned on, the power density of the power supply is 4 KW / m, and the first transparent conductive layer is deposited on the surface of the first doped layer (such as a phosphorus-doped a-Si:H layer) by magnetron sputtering. When forming the second transparent conductive layer, the same process operating conditions as those used to form the first transparent conductive layer, that is, the same magnetron sputtering parameters are used to deposit the second transparent conductive layer on the surface of the second doped layer (such as a boron-doped a-Si:H layer).

[0058] In some embodiments, the thickness of the transparent conductive layers on both sides of the semiconductor substrate is 50 nm to 100 nm respectively.

[0059] Specifically, the thickness of the first transparent conductive layer can be recorded as x1, and the thickness of the second transparent conductive layer can be recorded as x2, and both x1 and x2 can be any value between 50nm and 100nm. For example, x1 can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc., and x2 can be 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc. The specific values ​​of x1 and x2 can be the same or different.

[0060] In some embodiments, the transparent conductive layers on both sides of the semiconductor substrate respectively include at least one of an ITO film, an IWO film, or an AZO film; the material types of the transparent conductive layers on both sides of the semiconductor substrate are the same or different. Specifically, the first transparent conductive layer may include one or more layers of an ITO film, an IWO film, or an AZO film, and the second transparent conductive layer may include one or more layers of an ITO film, an IWO film, or an AZO film; the first transparent conductive layer and the second transparent conductive layer may be made of the same material, or of course, different materials.

[0061] It should be pointed out here that the material of the transparent conductive layer of the present application can be various transparent conductive oxides commonly used in the art, including but not limited to ITO, IWO, AZO, for example, it can also be GZO (gallium-doped zinc oxide), fluorine-doped tin oxide (FTO), etc., which are not limited here.

[0062] Preferably, in the heterojunction solar cell provided by the embodiment of the present invention, the materials of the first transparent conductive layer and the second transparent conductive layer are both ITO. Alternatively, the material of one of the first transparent conductive layer and the second transparent conductive layer is ITO, and the other is AZO. Alternatively, the material of the first transparent conductive layer and the second transparent conductive layer are both AZO.

[0063] In some embodiments, step S2 includes: performing plasma treatment on at least one side of the transparent conductive layer using a plasma process; that is, both the first transparent conductive layer and the second transparent conductive layer may be plasma treated, or only either one of the first transparent conductive layer and the second transparent conductive layer may be plasma treated. In actual application, the setting may be selected based on the materials of the first transparent conductive layer and the second transparent conductive layer or related actual needs; after the plasma treatment, the dust and impurity adsorption on the surface of the transparent conductive layer may be effectively cleaned, and the thin layer with poor performance on the surface of the transparent conductive layer may be removed, so that the surface activity of the transparent conductive layer is higher and the surface is cleaner. When in contact with other materials, there is no high-resistance interface layer, which is beneficial to reducing the series resistance of the battery.

[0064] The process conditions for plasma treatment of the transparent conductive layer on either side of the semiconductor substrate include: the plasma is oxygen plasma or argon plasma; when oxygen plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 The treatment time is 20 to 300 seconds. When argon plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 The processing time is 20 to 300 seconds.

[0065] Specifically, taking the plasma treatment of the first transparent conductive layer and the second transparent conductive layer as an example, the sample obtained in step S12 is placed in a plasma treatment device, and the first transparent conductive layer and the second transparent conductive layer are treated with argon or oxygen plasma, wherein oxygen plasma or argon plasma is used, and the power density of the plasma treatment can be 50 to 200 W / m 2 The processing time is 20 to 300 seconds, and the power density can be 80 to 150 W / m 2 The treatment time is 60 to 180 seconds. The time and power settings for the argon or oxygen plasma treatment of the first transparent conductive layer and the second transparent conductive layer can be the same or different.

[0066] In some embodiments, step S3 includes: forming a tin oxide layer on the surface of the transparent conductive layer after plasma treatment by atomic layer deposition. The process step of atomic layer deposition of tin oxide layer saves the special annealing process. The tin oxide deposited by ALD is relatively dense, which solves the problem of poor contact between TCO and copper seed, and also avoids the problem of poor adhesion between TCO and copper seed layer. The tin oxide film deposited by ALD is relatively dense, without defects such as pinholes and gaps, and has good corrosion resistance. During electroplating, the plating solution will not penetrate into the battery, which is very beneficial for TCO materials such as AZO that are not corrosion-resistant, so that cheap TCO materials such as AZO may be applied to heterojunction batteries. It should be understood that the above-mentioned first transparent conductive layer and the second transparent conductive layer can be selectively plasma treated. When both are plasma treated, tin oxide layers can be formed on the surfaces of the two, respectively. When one of the two is plasma treated, a tin oxide layer can be formed on the surface of the transparent conductive layer after plasma treatment, and the tin oxide layer that has not been plasma treated may not be provided. The following mainly describes the plasma treatment of both the first transparent conductive layer and the second transparent conductive layer as an example.

[0067] Specifically, the sample obtained in step S2 is placed in an atomic layer deposition device, a first tin oxide layer is deposited on the surface of the first transparent layer, and a second tin oxide layer is deposited on the surface of the second transparent layer. The process conditions for preparing the first tin oxide layer and the second tin oxide layer include: the tin source used is a combination of tetrakis(dimethylamino)tin (TDMASn) and diethyltin dichloride, or simple tetrakis(dimethylamino)tin, or diethyltin dichloride; the substrate temperature is 80 to 210°C.

[0068] In some embodiments, the thickness of the tin oxide layer is 0.5 nm to 20 nm. By controlling the thickness of the formed tin oxide layer, such as the first tin oxide layer or the second tin oxide layer, within the range of 0.5 nm to 20 nm, on the one hand, it is possible to avoid the tin oxide layer being too thin, which cannot protect the TCO, or the protective effect is extremely insignificant. In addition, it is not easy to achieve a tin oxide layer that is too thin; on the other hand, it is possible to avoid the tin oxide layer being too thick. When the thickness exceeds a certain threshold, the protective effect will not continue to increase, and the ALD deposition time will be increased, which increases the cost and reduces the production efficiency, and is not suitable for mass production.

[0069] Specifically, the thickness of the first tin oxide layer can be recorded as y1, and the thickness of the second tin oxide layer can be recorded as y2, and both y1 and y2 can be any value between 0.5nm and 20nm. For example, y1 can be 0.5nm, 0.8nm, 1nm, 2nm, 5nm, 8nm, 10nm, 12nm, 15nm, 20nm, etc., and y2 can be 0.5nm, 0.8nm, 1nm, 2nm, 5nm, 8nm, 10nm, 12nm, 15nm, 20nm, etc. The specific values ​​of the above y1 and y2 can be the same or different.

[0070] In some embodiments, the sum of the thickness of the transparent conductive layer and the tin oxide layer on either side of the semiconductor substrate is 50 nm to 120 nm, respectively. Preferably, in some embodiments, the sum of the thickness of the transparent conductive layer and the tin oxide layer on either side of the semiconductor substrate is 50 nm to 100 nm, respectively. More preferably, in some embodiments, the sum of the thickness of the transparent conductive layer and the tin oxide layer on either side of the semiconductor substrate is 55 nm to 85 nm, respectively. Specifically, x1+y1 satisfies any value between 50nm and 120nm, for example, x1+y1 can be 50nm, 52nm, 55nm, 58nm, 60nm, 68nm, 70nm, 80nm, 82nm, 85nm, 88nm, 90nm, 100nm, 110nm, 120nm, etc.; x2+y2 satisfies any value between 50nm and 120nm, for example, x2+y2 can be 50nm, 52nm, 55nm, 58nm, 60nm, 68nm, 70nm, 80nm, 82nm, 85nm, 88nm, 90nm, 100nm, 110nm, 120nm, etc. By controlling the sum of the thickness of the transparent conductive layer and the tin oxide layer to be formed within the range of 50nm to 120nm, it can be ensured that the final heterojunction battery meets certain requirements. If the sum of the thickness of the two is too thin, it will affect the bonding strength between the layers, or fail to play the corresponding protective role, or lead to poor light trapping effect of the entire heterojunction battery; and if the sum of the thickness of the two is too thick, it will not significantly improve the electrochemical performance of the battery, and will also prolong the preparation time, increase costs, and reduce production efficiency, which may also affect the light trapping effect of the entire heterojunction battery.

[0071] In some embodiments, step S4 includes: performing plasma treatment on the tin oxide layer using a plasma process, and performing annealing treatment. For example, performing plasma treatment on the first tin oxide layer and the second tin oxide layer using a plasma process, and performing annealing treatment. Due to the presence of the tin oxide layer, in the annealing process step, the TCO film is prevented from reacting with gases in the environment such as oxygen / water vapor in the air.

[0072] Specifically, the sample obtained in step S3 is placed in a plasma treatment device, and the first tin oxide layer and the second tin oxide layer are treated with argon or oxygen plasma. During or after the treatment, the sample is subjected to rapid pulse infrared laser annealing. Oxygen plasma or argon plasma is used, and the power density of the plasma treatment can be 20 to 3000 W / m 2 The processing time is 20 to 300 seconds, and the power density can be 100 to 2000 W / m 2 The treatment time is 60 to 180 seconds. The time and power settings for the argon or oxygen plasma treatment of the first tin oxide layer and the second tin oxide layer can be the same or different.

[0073] It should be understood that the above annealing treatment may be performed simultaneously with the plasma treatment or after the plasma treatment.

[0074] In some embodiments, the annealing process is performed by pulse infrared laser annealing process; the processing wavelength of the pulse infrared laser must exceed the wavelength corresponding to the band gap of single crystal silicon, and the wavelength range can be any value between 1200 and 3000 nm.

[0075] In some embodiments, step S5 includes forming a seed layer, and the seed layer may be formed by a magnetron sputtering process. The material of the seed layer includes but is not limited to copper, that is, the seed layer may be composed of a plurality of copper films.

[0076] It should be understood that when both the first transparent conductive layer and the second transparent conductive layer are subjected to plasma treatment, the step of forming the seed layer may include: forming a first seed layer on the surface of the first tin oxide layer after annealing, and forming a second seed layer on the surface of the second tin oxide layer after annealing. When one of the first transparent conductive layer and the second transparent conductive layer, such as the first transparent conductive layer, is subjected to plasma treatment, the step of forming the seed layer may include: forming a first seed layer on the surface of the first tin oxide layer after annealing, and forming a second seed layer on the surface of the second transparent conductive layer.

[0077] Exemplarily, the sample obtained in step S4 is placed in a magnetron sputtering coating device, and a first seed layer is deposited on the surface of the first tin oxide layer, and a second seed layer is deposited on the surface of the second tin oxide layer, respectively, and the first seed layer and the second seed layer completely cover the front and back of the sample. The process conditions for preparing the seed layer may include: the chamber pressure is maintained at 0.3 Pa, and the power density of the power supply is 8 KW / m.

[0078] In some embodiments, step S6 includes forming metal electrodes, such as by using an electroplating process to form a first metal electrode and a second metal electrode on the first seed layer and the second seed layer respectively.

[0079] It should be noted that the embodiments of the present application do not limit the specific operation method and process conditions for forming the metal electrode, which can be selected and adjusted by technical personnel in this field according to actual conditions.

[0080] Exemplarily, the sample obtained in step S5 is subjected to an electroplating copper process. The operation steps of the electroplating copper process can be as follows: spraying photosensitive ink on both sides of the sample, wherein the thickness of the sprayed ink is 12 microns; then using an exposure machine to expose the ink on the front and back sides respectively, wherein the line width after exposure is 15 microns, and then the sample is developed to obtain the desired graphics, the required graphics line width is 15 microns, and the depth is 12 microns. Next, the sample enters the electroplating equipment, and a metal electrode, i.e., a copper electrode, is electroplated according to the designed image to obtain a copper electrode grid line with a plating line width of 15 microns and a height of 10 microns. Finally, the sample is placed in an ink removal solution to remove all residual ink.

[0081] Furthermore, the step of removing part of the copper seed layer is also included. Specifically, the sample after removing all residual ink is placed in a copper seed layer acidic solution, wherein the pH value of the acidic solution is 1 to 2, the reaction time is 35 seconds, and the temperature of the reaction solution is 25°C to remove part of the copper seed layer. It should be understood that due to the covering protection of the metal electrode, except for the copper seed layer directly below the metal electrode (metal electrode with micron-level thickness and width), the copper seed layer in the remaining area will be removed, and the first tin oxide layer and the second tin oxide layer will be exposed. In the process of removing the copper seed layer, the etching solution will react with the copper film and etch the copper seed layer. Due to the presence of the first tin oxide layer and the second tin oxide layer, the etching solution will not contact the TCO film and is not easy to enter the TCO film, resulting in subsequent etching solution cleaning residues, which will affect the reliability of the product. What's more, the etching solution can etch part or all of the TCO.

[0082] See also Figure 3 As shown, in some embodiments, a heterojunction solar cell is provided, which heterojunction solar cell includes: a semiconductor substrate 1; a first intrinsic amorphous silicon layer 2, a first doped layer 3, a first transparent conductive layer 6, a first tin oxide layer 10, a first seed layer 8 and a first metal electrode 9 are sequentially arranged on a surface of one side of the semiconductor substrate 1; a second intrinsic amorphous silicon layer 4, a second doped layer 5, a second transparent conductive layer 7, a second tin oxide layer 10', a second seed layer 8' and a second metal electrode 9' are sequentially arranged on the surface of the other side of the semiconductor substrate 1.

[0083] The heterojunction solar cell corresponds to the situation in which the first transparent conductive layer 6 and the second transparent conductive layer 7 are both subjected to plasma treatment during the preparation of the heterojunction solar cell, and the first tin oxide layer 10 and the second tin oxide layer 10' are formed respectively.

[0084] In some embodiments, a heterojunction solar cell is provided, such as the attached Figure 5 As shown, the heterojunction solar cell includes: a semiconductor substrate 1; a first intrinsic amorphous silicon layer 2, a first doped layer 3, a first transparent conductive layer 6, a first tin oxide layer 10, a first seed layer 8 and a first metal electrode 9 are sequentially arranged on a surface of one side of the semiconductor substrate 1; a second intrinsic amorphous silicon layer 4, a second doped layer 5, a second transparent conductive layer 7, a second seed layer 8' and a second metal electrode 9' are sequentially arranged on the surface of the other side of the semiconductor substrate 1.

[0085] Alternatively, the heterojunction solar cell, as shown in the attached Figure 6 As shown, it includes: a semiconductor substrate 1; a first intrinsic amorphous silicon layer 2, a first doped layer 3, a first transparent conductive layer 6, a first seed layer 8 and a first metal electrode 9 are sequentially arranged on one side surface of the semiconductor substrate 1; a second intrinsic amorphous silicon layer 4, a second doped layer 5, a second transparent conductive layer 7, a second tin oxide layer 10', a second seed layer 8' and a second metal electrode 9' are sequentially arranged on the other side surface of the semiconductor substrate 1.

[0086] This heterojunction solar cell corresponds to the case where one of the first transparent conductive layer 6 and the second transparent conductive layer 7 is subjected to plasma treatment during the preparation of the heterojunction solar cell, and a tin oxide layer is formed only on one side.

[0087] Those skilled in the art can understand that the heterojunction solar cell and the aforementioned method for preparing a heterojunction solar cell are based on the same inventive concept, and the features and advantages described above for the method for preparing a heterojunction solar cell are also applicable to the heterojunction solar cell. Therefore, the heterojunction solar cell has at least the same or different features and advantages as the aforementioned method for preparing a heterojunction solar cell, which will not be described in detail herein.

[0088] The present invention is further described below in conjunction with specific embodiments and comparative examples.

[0089] Example 1

[0090] S11. A first intrinsic amorphous silicon layer 2 and a first doped layer 3 (such as a phosphorus-doped amorphous or microcrystalline silicon layer) are sequentially deposited on the front side of a semiconductor substrate 1 (such as an n-type single crystal silicon wafer) by chemical vapor deposition, and a second intrinsic amorphous silicon layer 4 and a second doped layer 5 (such as a boron-doped amorphous or microcrystalline silicon layer) are sequentially deposited on the back side of the semiconductor substrate 1.

[0091] The deposition conditions of the first intrinsic amorphous silicon layer or the second intrinsic amorphous silicon layer are as follows: the power is 500W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 9.5:1, the pressure is 50Pa, and the substrate temperature is 220°C during deposition. The deposition conditions of the phosphorus-doped amorphous or microcrystalline silicon layer are as follows: the power is 400W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 5.5:1, the gas flow ratio of phosphine to silane (phosphorus-silicon ratio) is 1:109, the pressure is 120Pa, and the substrate temperature is 230°C during deposition. The deposition conditions of the boron-doped amorphous or microcrystalline silicon layer are as follows: the power is 360W, the gas flow ratio of hydrogen to silane (hydrogen dilution ratio) is 2:1, the gas flow ratio of phosphine to silane (phosphorus-silicon ratio) is 2:98, the pressure is 55Pa, and the substrate temperature is 205°C during deposition.

[0092] S12, using magnetron sputtering coating equipment to deposit TCO thin film, introducing argon and oxygen at room temperature, the gas flow ratio of argon to oxygen is set at 55:1, the chamber pressure is maintained at 0.35Pa, the sputtering power supply is turned on, the power density of the power supply is 4KW / m, and the first transparent conductive layer 6 is deposited on the surface of the first doped layer 3 by magnetron sputtering; on the other side of the battery, the second transparent conductive layer 7 is deposited on the surface of the second doped layer 5 using the same magnetron sputtering parameters. Among them, the thickness of the first transparent conductive layer 6 is 70nm, and the material is ITO, and the thickness of the second transparent conductive layer 7 is 60nm, and the material is ITO.

[0093] S2. Place the sample obtained after step S12 into a plasma treatment device, and perform oxygen plasma treatment on the first transparent conductive layer 6 and the second transparent conductive layer 7. When the first transparent conductive layer 6 is treated, the power density of the plasma is 100 W / m 2 , the treatment time is 50s; when the second transparent conductive layer 7 is treated, the plasma power density is 150W / m 2 , the processing time is 100s.

[0094] S3, placing the sample obtained after S2 into an atomic layer deposition (ALD) device, and depositing a first tin oxide layer 10 with a thickness of 10 nm and a second tin oxide layer 10' with a thickness of 20 nm on the first transparent conductive layer 6 and the second transparent conductive layer 7, respectively. The tin source used in the process of preparing tin oxide is diethyltin dichloride; the substrate temperature is 150°C.

[0095] S4, placing the sample obtained after S3 into a plasma treatment device, subjecting the first tin oxide layer 10 and the second tin oxide layer 10' to argon or oxygen plasma treatment, and subjecting the sample to rapid pulse infrared laser annealing during or after the plasma treatment. When the first tin oxide layer 20 is subjected to plasma treatment, the plasma power density is 500 W / m 2The treatment time is 100 s, and the gas used to generate the plasma is argon. When the second tin oxide layer 10' is treated with plasma, the power density of the plasma is 1000 W / m 2 The treatment time is 50s, and the gas used to generate plasma is argon. The wavelength of the pulsed infrared laser treatment is 1650nm.

[0096] S5. Place the sample obtained after S4 into a magnetron sputtering coating device, and deposit a first seed layer 8 on the surface of the first tin oxide layer 10, and deposit a second seed layer 8' on the surface of the second tin oxide layer 10', respectively. At this time, the seed layer copper film completely covers the front and back of the sample. The operating conditions for preparing the first seed layer 8 and the second seed layer 8' include: the chamber pressure is maintained at 0.3Pa, and the power density of the power supply is 8KW / m.

[0097] S6. The sample obtained after S5 is subjected to a copper electroplating process. The steps of the electroplating process are as follows: spray photosensitive ink on both sides of the sample, wherein the thickness of the sprayed ink is 12 microns; then use an exposure machine to expose the ink on the front and back sides respectively, wherein the line width after exposure is 15 microns, and then the sample is developed to obtain the desired graphics, wherein the required graphics line width is 15 microns and the depth is 12 microns. Next, the sample enters the electroplating equipment, and the metal electrodes, namely the first metal electrode 9 and the second metal electrode 9', are electroplated according to the designed image. Among them, a copper electrode grid line with an electroplating line width of 15 microns and a height of 10 microns is obtained. Finally, the sample is placed in an ink removal solution to remove all residual ink.

[0098] Furthermore, the sample after removing all the residual ink was placed in a copper seed layer acid solution, wherein the pH value of the acid solution was 1-2, the reaction time was 35 seconds, and the reaction solution temperature was 25°C to remove part of the copper seed layer. Due to the covering protection of the metal electrode, except for the copper seed layer directly below the metal electrode (metal electrode with micron-level thickness and width), the copper seed layer in the remaining area will be removed, and the first tin oxide layer and the second tin oxide layer will be exposed.

[0099] The transparent conductive layers of ITO material are arranged on both sides of the battery in the above-mentioned embodiment 1, and both sides are subjected to plasma treatment and atomic layer deposition tin oxide layers are performed on both sides.

[0100] Example 2

[0101] The preparation method of Example 2 is basically the same as that of Example 1, and the similarities are not repeated here. The difference is that:

[0102] In Example 2, in step S12, a magnetron sputtering coating device is used to deposit a TCO thin film, argon and oxygen are introduced at room temperature, the gas flow ratio of argon to oxygen is set at 55:1, the chamber pressure is maintained at 0.35Pa, the sputtering power supply is turned on, the power density of the power supply is 4KW / m, and the first transparent conductive layer is deposited on the surface of the first doped layer by magnetron sputtering. On the other side of the battery, argon and oxygen are introduced, the gas flow ratio of argon to oxygen is set at 30:1, the chamber pressure is maintained at 0.35Pa, the sputtering power supply is turned on, the power density of the power supply is 4KW / m, and the second transparent conductive layer is deposited on the surface of the second doped layer. Among them, the thickness of the first transparent conductive layer is 70nm, and the material is ITO, and the thickness of the second transparent conductive layer is 50nm, and the material is AZO.

[0103] S2. Place the sample obtained after step S12 into a plasma treatment device, perform argon plasma treatment on the first transparent conductive layer, and perform oxygen plasma treatment on the second transparent conductive layer, wherein the power density of the plasma is 120 W / m 2 , the treatment time is 100s; when the second transparent conductive layer is treated, the plasma power density is 150W / m 2 , the processing time is 20s.

[0104] S3, placing the sample obtained after S2 into an atomic layer deposition (ALD) device, and depositing a first tin oxide layer with a thickness of 10 nm and a second tin oxide layer with a thickness of 20 nm on the first transparent conductive layer and the second transparent conductive layer, respectively. The tin source used in the process of preparing tin oxide is a mixed gas source of tetrakis(dimethylamino)tin (TDMASn) and diethyltin dichloride; the substrate temperature is 180°C.

[0105] S4, placing the sample obtained after S3 into a plasma treatment device, subjecting the first tin oxide layer and the second tin oxide layer to argon or oxygen plasma treatment, and after the plasma treatment, subjecting the sample to rapid pulse infrared laser annealing. When the first tin oxide layer is subjected to plasma treatment, the plasma power density is 1000 W / m 2 The treatment time is 25s, and the gas used to generate the plasma is argon. When the second tin oxide layer is treated with plasma, the plasma power density is 800W / m 2 The treatment time is 20s, and the gas used to generate plasma is argon. The wavelength of the pulsed infrared laser treatment is 1550nm.

[0106] The transparent conductive layer of ITO material is disposed on one side of the battery in the above-mentioned embodiment 2, and the transparent conductive layer of AZO material is disposed on the other side. Both sides are plasma treated, and both sides are subjected to atomic layer deposition of tin oxide layer.

[0107] Example 3

[0108] The preparation method of Example 3 is basically the same as that of Example 1, and the similarities are not repeated here. The difference is that:

[0109] In Example 3, in step S12, the thickness of the first transparent conductive layer is 80 nm, and the material is ITO; the thickness of the second transparent conductive layer is 75 nm, and the material is AZO.

[0110] S2. Place the sample obtained after step S12 into a plasma treatment device, and perform argon plasma treatment on the second transparent conductive layer; when the second transparent conductive layer is treated, the power density of the plasma is 130 W / m2, the treatment time is 15 s, and the gas used to generate the plasma is argon.

[0111] S3, placing the sample obtained after S2 into an atomic layer deposition (ALD) device, and depositing a second tin oxide layer with a thickness of 10 nm on the second transparent conductive layer. The tin source used in the process of preparing tin oxide is tetrakis(dimethylamino)tin (TDMASn) gas source; the substrate temperature is 200°C.

[0112] S4, placing the sample obtained after S3 into a plasma treatment device, subjecting the second tin oxide layer to argon plasma treatment, and after the plasma treatment, subjecting the sample to rapid pulse infrared laser annealing. When the second tin oxide layer is subjected to plasma treatment, the plasma power density is 750 W / m 2 The treatment time is 35s, and the gas used to generate the plasma is argon. The wavelength of the pulsed infrared laser treatment is 1650nm.

[0113] S5. Place the sample obtained after S4 into a magnetron sputtering coating device, deposit a first seed layer on the surface of the first transparent conductive layer, and deposit a second seed layer on the surface of the second tin oxide layer, respectively. At this time, the copper film of the seed layer completely covers the front and back of the sample. The operating conditions for preparing the first seed layer and the second seed layer include: the chamber pressure is maintained at 0.3 Pa, and the power density of the power supply is 8 KW / m.

[0114] The battery of Example 3 has a transparent conductive layer of ITO material on one side and a transparent conductive layer of AZO material on the other side. One side is plasma treated and one side is atomic layer deposited with tin oxide.

[0115] The structural schematic diagram of the existing heterojunction solar cell provided in the following comparative example 1 or 2 is as follows Figure 4 As shown. Figure 4As shown, a heterojunction solar cell prepared by conventional electroplating includes a semiconductor substrate 1, and a first intrinsic amorphous silicon layer 2, a first doped layer 3, a first transparent conductive layer 6, a first seed layer 8 and a first metal electrode 9 are sequentially arranged on a surface of one side of the semiconductor substrate 1; a second intrinsic amorphous silicon layer 4, a second doped layer 5, a second transparent conductive layer 7, a second seed layer 8' and a second metal electrode 9' are sequentially arranged on a surface of the other side of the semiconductor substrate 1.

[0116] Comparative Example 1

[0117] S11. A first intrinsic amorphous silicon layer and a first doped layer (such as a phosphorus-doped amorphous or microcrystalline silicon layer) are sequentially deposited on the front side of a semiconductor substrate (such as an n-type single crystal silicon wafer) by chemical vapor deposition, and a second intrinsic amorphous silicon layer and a second doped layer (such as a boron-doped amorphous or microcrystalline silicon layer) are sequentially deposited on the back side of the semiconductor substrate. The deposition conditions of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer, the deposition conditions of the phosphorus-doped amorphous or microcrystalline silicon layer, and the deposition conditions of the boron-doped amorphous or microcrystalline silicon layer are the same as those in Example 1.

[0118] S12. Use magnetron sputtering coating equipment to deposit TCO thin film. At room temperature, introduce argon and oxygen. The gas flow ratio of argon to oxygen is set at 55:1. The chamber pressure is maintained at 0.35Pa. Turn on the sputtering power supply. The power density of the power supply is 4KW / m. Use magnetron sputtering to deposit the first transparent conductive layer on the surface of the first doped layer. On the other side of the battery, use the same magnetron sputtering parameters to deposit the second transparent conductive layer on the surface of the second doped layer. The thickness of the first transparent conductive layer and the second transparent conductive layer are both 80nm, and the material is ITO.

[0119] S2. Anneal the sample obtained after step S12 in an atmospheric environment at 190° C. for 20 min.

[0120] S3, placing the sample obtained after S2 into a magnetron sputtering coating device, depositing a first seed layer on the surface of the first transparent conductive layer, and depositing a second seed layer on the surface of the second transparent conductive layer, respectively, at which time the seed layer copper film completely covers the front and back of the sample. The operating conditions for preparing the first seed layer and the second seed layer include: the chamber pressure is maintained at 0.3Pa, and the power density of the power supply is 8KW / m.

[0121] S4, subjecting the sample obtained after S3 to a copper electroplating process. The steps of the electroplating process are as follows: spraying photosensitive ink on both sides of the sample, wherein the thickness of the sprayed ink is 12 microns; then using an exposure machine to expose the ink on the front and back sides respectively, wherein the line width after exposure is 15 microns, and then the sample is developed to obtain the desired graphics, wherein the required graphics line width is 15 microns and the depth is 12 microns. Next, the sample enters the electroplating equipment, and electroplating generates metal electrodes, namely the first metal electrode and the second metal electrode, according to the designed image. Among them, a copper electrode grid line with an electroplating line width of 15 microns and a height of 10 microns is obtained. Finally, the sample is placed in an ink removal solution to remove all residual ink.

[0122] Furthermore, the sample after removing all the residual ink was placed in a copper seed layer acid solution, wherein the pH value of the acid solution was 1-2, the reaction time was 35 seconds, and the reaction solution temperature was 25°C, to remove part of the copper seed layer. Due to the covering protection of the metal electrode, except for the copper seed layer directly below the metal electrode (the metal electrode with micron-level thickness and width), the copper seed layer in the remaining area will be removed, and the first transparent conductive layer and the second transparent conductive layer will be exposed.

[0123] Comparative Example 2

[0124] The preparation method of Comparative Example 2 is basically the same as that of Comparative Example 1, and the similarities are not repeated here. The difference is that:

[0125] In comparative example 2, in S12, a TCO film is deposited using a magnetron sputtering coating device, argon and oxygen are introduced at room temperature, the gas flow ratio of argon to oxygen is set at 55:1, the cavity pressure is maintained at 0.35Pa, the sputtering power supply is turned on, the power density of the power supply is 4KW / m, and the first transparent conductive layer is deposited on the surface of the first doped layer by magnetron sputtering; on the other side of the battery, argon and oxygen are introduced, the gas flow ratio of argon to oxygen is set at 30:1, the cavity pressure is maintained at 0.35Pa, the sputtering power supply is turned on, the power density of the power supply is 4KW / m, and the second transparent conductive layer is deposited on the surface of the second doped layer. Wherein, the thickness of the first transparent conductive layer and the second transparent conductive layer are both 80nm, the material of the first transparent conductive layer is ITO, and the material of the second transparent conductive layer is AZO.

[0126] In the step of removing the seed layer in Comparative Example 2, the film layer completely fell off on the back side of the battery because AZO was extremely corrosion-resistant.

[0127] The heterojunction cells of the above-mentioned embodiments 1-3 and comparative examples 1-2 were subjected to performance tests, and the test results are shown in Table 1 below.

[0128] Table 1

[0129] project Battery efficiency (%) Open circuit voltage (%) Short circuit current (%) Fill factor (%) Example 1 102.52 100.00 102.55 99.98 Example 2 100.92 100.00 100.11 100.81 Example 3 100.18 100.00 99.97 100.21 Comparative Example 1 100.00 100.00 100.00 100.00 Comparative Example 2 0 0 0 0

[0130] From the data in Table 1, it can be seen that Comparative Example 2 uses AZO as the transparent conductive layer, which is destroyed by the acidic solution during the experiment, resulting in the failure of the experiment. Compared with Comparative Example 1, the battery efficiency of Examples 1 and 2 is improved. Examples 2 and 3 adopt the preparation method of the present invention, replace the ITO material with the cheap AZO material, realize the AZO battery electroplating, and the battery efficiency is not affected, which is of great significance for the cost reduction of heterojunction batteries.

[0131] In addition, it can be seen from the above embodiments and comparative examples that the embodiment of the present invention can increase the roughness and improve the bonding force between the tin oxide layer and the copper seed layer by setting step S4, that is, by performing plasma treatment and annealing treatment on the tin oxide layer. Moreover, through the optimization of the process parameters of the plasma treatment, it is found that if the parameter setting is too small, the technical effect of increasing the roughness cannot be achieved, and if the parameter setting is too large, the tin oxide layer will be damaged. For example, the wavelength range used in the pulsed infrared laser annealing is 1200 to 3000 nm. After being treated with the process parameters of the plasma treatment described in the embodiment of the present invention, the pull-off force of the obtained heterojunction battery copper grid line increased from 1.2N to 2.5N.

[0132] In summary, the heterojunction solar cell and its preparation method provided by the embodiment of the present invention have added plasma treatment between TCO / tin oxide layer / copper seed layer; it can effectively clean the dust and adsorption on the surface of TCO, making the surface activity of TCO higher and the surface cleaner; by increasing the roughness of the tin oxide layer through plasma treatment, the bonding force between the tin oxide layer and the copper seed layer can be improved. In the existing electroplating process, the TCO is directly in contact with the copper seed layer; and the TCO / tin oxide structure is applied to the electroplating of heterojunction batteries. Since the tin oxide deposited by ALD technology is relatively dense, it has good contact with TCO, and the electrical performance of the TCO / tin oxide layer / copper seed layer structure is more reliable. Rapid laser annealing is added, and the TCO film layer is annealed while the plasma treatment is performed, which can improve the performance of the material and increase the conductivity of the TCO film.

[0133] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A method for preparing a heterojunction solar cell, the heterojunction solar cell comprising: Semiconductor substrate; A first intrinsic amorphous silicon layer and a first doped layer are sequentially disposed on a surface of one side of the semiconductor substrate; A second intrinsic amorphous silicon layer and a second doped layer are sequentially disposed on the other side surface of the semiconductor substrate; and a transparent conductive layer located on the first doped layer and the second doped layer, the transparent conductive layer comprising a first transparent conductive layer located on the first doped layer and a second transparent conductive layer located on the second doped layer; Characterized in that the method comprises: Depositing the transparent conductive layer using a magnetron sputtering coating device; Performing plasma treatment on the transparent conductive layer on at least one side of the semiconductor substrate using a plasma process; forming a tin oxide layer on the surface of the transparent conductive layer after plasma treatment by atomic layer deposition; Performing plasma treatment on the tin oxide layer by using a plasma process, and performing annealing treatment; Using a magnetron sputtering coating device to deposit on the surface of the tin oxide layer after annealing to form a seed layer, or using a magnetron sputtering coating device to deposit on the surface of the transparent conductive layer that has not been plasma treated to form a seed layer; Forming metal electrodes on the surfaces of the seed layer on both sides of the semiconductor substrate respectively by using an electroplating process; The method further comprises removing at least a portion of the seed layer using an etching solution; The sum of the thickness of the transparent conductive layer and the tin oxide layer is 50 nm to 120 nm.

2. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The process conditions for plasma treatment of the transparent conductive layer on either side of the semiconductor substrate include: The plasma is oxygen plasma or argon plasma; When the oxygen plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 , the processing time is 20 to 300 seconds; And / or, when the argon plasma is used, the power density of the plasma treatment is 50 to 200 W / m 2 The processing time is 20 to 300 seconds.

3. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The process conditions for forming the tin oxide layer on either side include: A sample having a transparent conductive layer after plasma treatment is placed in an atomic layer deposition device, and at least one of tetrakis(dimethylamino)tin and diethyltin dichloride is used as a tin source. A tin oxide layer is formed on the surface of the transparent conductive layer at a substrate temperature of 80 to 210°C.

4. The method for preparing a heterojunction solar cell according to claim 3, characterized in that: The thickness of the tin oxide layer is 0.5 nm to 20 nm.

5. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The process conditions for plasma treatment of the tin oxide layer on either side of the semiconductor substrate include: The plasma is oxygen plasma or argon plasma; When the oxygen plasma is used, the power density of the plasma treatment is 200 to 3000 W / m 2 , the processing time is 20 to 300 seconds; And / or, when the argon plasma is used, the power density of the plasma treatment is 200 to 3000 W / m 2 The processing time is 20 to 300 seconds.

6. The method for preparing a heterojunction solar cell according to claim 5, characterized in that: Annealing the tin oxide layer after the plasma treatment, wherein the annealing is performed by pulse infrared laser annealing; The wavelength range of the pulse infrared laser annealing is 1200-3000nm.

7. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The forming of transparent conductive layers on both sides of the semiconductor substrate comprises: An intrinsic amorphous silicon layer and a doping layer are sequentially formed on both sides of the semiconductor substrate; The transparent conductive layer is formed on the surface of the doping layer on both sides respectively by using a magnetron sputtering process.

8. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The transparent conductive layers on both sides of the semiconductor substrate respectively include at least one of an ITO film, an IWO film or an AZO film; The transparent conductive layers on both sides of the semiconductor substrate are made of the same or different materials.

9. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The thickness of the transparent conductive layers on both sides of the semiconductor substrate is 50 nm to 100 nm respectively.

10. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The method of forming the seed layer includes: forming the seed layer by a magnetron sputtering process; And / or, the seed layer includes a copper seed layer.

11. The method for preparing a heterojunction solar cell according to any one of claims 1 to 10, characterized in that: forming a first transparent conductive layer on one side of the semiconductor substrate, and forming a second transparent conductive layer on the other side of the semiconductor substrate; The step of performing plasma treatment on the transparent conductive layer comprises: performing plasma treatment on the first transparent conductive layer and the second transparent conductive layer respectively; The step of forming the tin oxide layer comprises: forming a first tin oxide layer on the surface of the first transparent conductive layer after the plasma treatment, and forming a second tin oxide layer on the surface of the second transparent conductive layer after the plasma treatment; The step of plasma treating the tin oxide layer comprises: plasma treating the first tin oxide layer and the second tin oxide layer respectively, and performing annealing treatment; The step of forming the seed layer includes: forming a first seed layer on the surface of the first tin oxide layer after annealing, and forming a second seed layer on the surface of the second tin oxide layer after annealing.

12. The method for preparing a heterojunction solar cell according to any one of claims 1 to 10, characterized in that: forming a first transparent conductive layer on one side of the semiconductor substrate, and forming a second transparent conductive layer on the other side of the semiconductor substrate; The step of performing plasma treatment on the transparent conductive layer comprises: performing plasma treatment on the first transparent conductive layer; The step of forming the tin oxide layer includes: forming a first tin oxide layer on the surface of the first transparent conductive layer after the plasma treatment; The step of plasma treating the tin oxide layer comprises: plasma treating the first tin oxide layer and performing annealing treatment; The step of forming the seed layer includes: forming a first seed layer on the surface of the first tin oxide layer after annealing, and forming a second seed layer on the surface of the second transparent conductive layer.

13. A heterojunction solar cell, prepared by the method for preparing a heterojunction solar cell according to any one of claims 1 to 12, characterized in that: The heterojunction solar cell comprises: Semiconductor substrate; A first intrinsic amorphous silicon layer, a first doping layer, a first transparent conductive layer, a first tin oxide layer, a first seed layer and a first metal electrode are sequentially arranged on one side surface of the semiconductor substrate; A second intrinsic amorphous silicon layer, a second doping layer, a second transparent conductive layer, a second tin oxide layer, a second seed layer and a second metal electrode are sequentially arranged on the other side surface of the semiconductor substrate.

14. A heterojunction solar cell, prepared by the method for preparing a heterojunction solar cell according to any one of claims 1 to 12, characterized in that: The heterojunction solar cell comprises: Semiconductor substrate; A first intrinsic amorphous silicon layer, a first doping layer, a first transparent conductive layer, a first tin oxide layer, a first seed layer and a first metal electrode are sequentially arranged on one side surface of the semiconductor substrate; A second intrinsic amorphous silicon layer, a second doping layer, a second transparent conductive layer, a second seed layer and a second metal electrode are sequentially arranged on the other side surface of the semiconductor substrate.

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