A heterojunction solar cell and its preparation method

Abstract

An embodiment of the present application provides a heterojunction solar cell and a preparation method thereof, relating to the field of new energy. The preparation method of the metal seed layer includes the following steps: taking a cell wafer, wherein at least one surface of the cell wafer is provided with a transparent conductive layer, and the transparent conductive layer contains a metal oxide; the metal oxide is any one of indium oxide, tin oxide, zinc oxide, antimony oxide, and cadmium oxide; using an electrochemical method to prepare a metal nucleation layer in a partial area of the transparent conductive layer; electroplating a metal thin layer on the surface of the metal nucleation layer, and the metal thin layer of the same material combines with the metal nucleation layer to form a metal seed layer; and then, based on the metal seed layer, forming a metal grid line. In the heterojunction solar cell of the embodiment of the present application, the adhesion between the metal grid line and the cell wafer is strong, which is beneficial to increasing the service life and conversion efficiency of the heterojunction solar cell, and the preparation method of the embodiment of the present application is also relatively simple.

Description

Technical Field

[0001] This application relates to the field of new energy, and more particularly, to a heterojunction solar cell and a method for manufacturing the same. Background Art

[0002] A heterojunction solar cell is a device that uses the photovoltaic effect of semiconductor materials to convert solar energy into electrical energy. It can convert inexhaustible, clean and pollution-free solar energy into electrical energy for human use, and can partially replace fossil energy. Heterojunction solar cells include PERC (Passivated Emitter and Rear Cell) and heterojunction cells (Heterojunction with Intrinsic Thin film, HIT). Taking HIT as an example, it was first successfully developed by Sanyo Electric Co., Ltd. of Japan in 1990, and is also known as HJT, HDT, or SHJ. The main part of HIT is a special PN junction formed by amorphous silicon and crystalline silicon materials, which belongs to one of the N-type cells. It has high photoelectric conversion efficiency, great development potential, simple process and clear cost reduction route, which conforms to the development law of the photovoltaic industry and is the most promising next-generation battery technology.

[0003] In order to reduce the manufacturing cost of heterojunction cells, copper is generally used to replace low-temperature silver paste to prepare grid electrodes. Currently, there are two methods for preparing copper grid electrodes. One is to deposit a whole surface of a metal seed layer on a transparent conductive film by vacuum deposition first, and then selectively electroplate metal grid lines. After the metal grid lines are electroplated, the excess seed layer is etched away. The other is to prepare a pattern mask first, and then vacuum deposit a seed layer and metal grid lines in the maskless area, and finally remove the mask. However, both of these two methods for preparing copper grid lines are relatively complex, and both methods require vacuum deposition to form the seed layer. Vacuum deposition has high requirements for equipment and high manufacturing costs. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a heterojunction solar cell and a method for manufacturing the same, which can simplify the manufacturing difficulty of the heterojunction solar cell, reduce the manufacturing cost, and at the same time do not affect the adhesion between the metal grid line and the cell wafer.

[0005] In a first aspect, an embodiment of the present application provides a method for manufacturing a heterojunction solar cell, which includes the following steps: obtaining a cell wafer, wherein at least one surface of the cell wafer is provided with a transparent conductive layer (Transparent Conductive Oxide, TCO), and the transparent conductive layer contains metal oxides; the metal oxides are any one of indium oxide, tin oxide, zinc oxide, antimony oxide, and cadmium oxide; using an electrochemical method to reduce metal particles in the metal oxides in a partial area of the transparent conductive layer to form a metal nucleation layer; electroplating a thin metal layer on the surface of the metal nucleation layer, and the thin metal layer combines with the metal nucleation layer to form a metal seed layer, and the material of the thin metal layer is the same as that of the metal nucleation layer; sequentially electroplating a metal barrier layer and a metal conduction layer on the surface of the metal seed layer, and the metal seed layer, the metal barrier layer, and the metal conduction layer form a metal grid line.

[0006] In the above technical solution, the method of forming a metal nucleation layer by an electrochemical method and then forming a thin metal layer combined with the metal nucleation layer on the surface of the metal nucleation layer is called the "two-step method", and the two-step method can be used to prepare a metal seed layer with good adhesion and convenient for forming metal grid lines.

[0007] In the two-step method, the adhesion between the metal particles reduced on the surface of the transparent conductive layer by the electrochemical method and the transparent conductive layer is relatively large, so the metal nucleation layer is not easily detached from the surface of the transparent conductive layer.

[0008] In addition, the applicant found that when using the electrochemical method to prepare a metal nucleation layer with good adhesion, the loss of metal oxides in the transparent conductive layer is relatively large, which is very unfavorable for improving the efficiency of the heterojunction solar cell and is also unfavorable for the subsequent growth of the metal grid line. At the same time, the applicant also found that when electroplating an additional thin metal layer with the same material on the surface of the metal nucleation layer, the above problems can be well improved or even solved, and since the material of the thin metal layer is the same as that of the metal nucleation layer, the combination between the two will be closer. Therefore, the adhesion of the metal seed layer obtained by the two-step method can be well guaranteed, which is also more conducive to improving the photoelectric conversion efficiency of the heterojunction solar cell; and compared with the methods of preparing the metal seed layer by physical vapor deposition, magnetron sputtering and other vacuum preparation methods, the method for preparing the metal seed layer in the embodiment of the present application is simpler and the cost is lower.

[0009] In addition, since materials such as tin oxide, indium oxide, zinc oxide, antimony oxide, and cadmium oxide have good electrical conductivity and high transparency, they are very suitable for being used as the transparent conductive layer of the heterojunction solar cell.

[0010] After forming the metal seed layer, this application uses the metal seed layer as a substrate and then electroplates structures such as a metal barrier layer and a metal conductive layer to form the metal grid lines of the heterojunction solar cell together with the metal seed layer. Among them, the metal barrier layer can prevent the substances in the metal conductive layer from diffusing into the cell, so as to prevent a serious decline in device efficiency; the metal conductive layer can collect and transmit current, collecting and transmitting the current generated in the cell outward.

[0011] In a possible implementation, the electrochemical method includes the following steps: immersing the transparent conductive layer in an electrolyte solution.

[0012] In the above technical solution, immersing the transparent conductive layer in the electrolyte solution is beneficial to accelerating the reaction rate.

[0013] In a possible implementation, the solute in the electrolyte solution includes at least one of citrate, aminosulfonate, bicarbonate, and acetate; and / or, the temperature of the electrolyte solution is 18 - 30 °C.

[0014] In the above technical solution, controlling the temperature of the electrolyte solution within the range of 18 - 30 °C is beneficial to both the stable progress of the electrochemical reaction and the acceleration of the reaction rate.

[0015] In a possible implementation, in the electrochemical method, the reaction time is 10 - 300 s; and / or, in the electrochemical method, the reaction voltage is 1 - 6 V.

[0016] In a possible implementation, the thickness of the metal thin layer is 0.1 - 10 μm; and / or, the density range of the metal particles is 2.0×10 7 ~8.0×10 9 pcs / cm 2 ; and / or, the size of the metal particles is 10 - 250 nm.

[0017] In the above technical solution, the metal thin layer that meets the above conditions is beneficial to increasing the bonding force and stability of the seed layer; the metal particles that meet the above conditions are beneficial to reducing the preparation difficulty of subsequent steps and making it easier to prepare the metal grid lines.

[0018] In a possible implementation, the thickness of the transparent conductive layer is 75 - 80 nm.

[0019] In the above technical solution, the transparent conductive layer that meets the above conditions has both good light transmittance and good conductivity, which is beneficial to improving the efficiency of the heterojunction solar cell.

[0020] In a possible implementation, when electroplating a thin metal layer, the electroplating solution is an organic sulfonate system; optionally, the organic sulfonate system contains stannous sulfamate, sulfamic acid, and dihydroxydiphenyl sulfone; and / or, the temperature of the electroplating solution is 40-60°C; and / or, the cathode current density is 10-20 A / dm 2 .

[0021] In a possible implementation, when the metal oxide is indium oxide, the metal oxide is further doped with at least one of tin, hydrogen, and tungsten; or, when the metal oxide is tin oxide, the metal oxide is further doped with at least one of fluoride ions and metal cations; optionally, the metal cations include at least one of antimony, tantalum, niobium, bismuth, tungsten, and vanadium.

[0022] In the above technical solution, in order to improve the conductivity of the transparent conductive layer and thus improve the photoelectric conversion efficiency of the heterojunction solar cell, other elements or ions are usually doped into the metal oxide.

[0023] In a possible implementation, the mass fraction of the metal oxide in the transparent conductive layer is not less than 85%.

[0024] In the above technical solution, for the transparent conductive layer that meets the above conditions, its conductivity and transparency are better.

[0025] In a possible implementation, the solar cell further includes a P-type amorphous silicon layer, an intrinsic amorphous silicon layer, an N-type silicon wafer, an intrinsic amorphous silicon layer, and an N-type amorphous silicon layer that are sequentially stacked, and the transparent conductive layer is stacked on the surface of the P-type amorphous silicon layer and / or the N-type amorphous silicon layer.

[0026] In the above technical solution, a PN junction can be formed between the N-type silicon wafer and the intrinsic amorphous silicon layer, and light energy can be converted into electrical energy. The above solar cell is generally used to prepare a heterojunction solar cell.

[0027] In a possible implementation, the metal barrier layer mainly contains at least one of tungsten, cobalt, nickel, and tantalum; and / or, the material of the metal conduction layer is at least one of copper, silver, aluminum, and gold.

[0028] In the above technical solution, high melting point metals such as tungsten, cobalt, nickel, and tantalum can well prevent the substances in the metal conduction layer from diffusing into the solar cell; metals such as copper, silver, aluminum, and gold have good conductivity and low resistivity. When used as the material of the metal conduction layer, they can well reduce the current loss.

[0029] In a possible implementation, the preparation method of the heterojunction solar cell further includes the following steps: after forming the metal conduction layer, an electroplated metal welding layer is further formed on the surface of the metal conduction layer; optionally, the material of the metal welding layer is tin.

[0030] In the above technical solution, on the one hand, the metal welding layer can protect the metal conduction layer and prevent the metal conduction layer from being oxidized; on the other hand, the metal welding layer can also provide welding sites to facilitate welding multiple heterojunction solar cells together to output current externally.

[0031] Secondly, the embodiment of the present application provides a heterojunction solar cell prepared by the above preparation method.

[0032] In the above technical solution, for the heterojunction solar cell prepared by the above preparation method, the adhesion between the metal seed layer and the cell is strong, the metal seed layer is not easy to fall off from the surface of the transparent conductive layer, and the entire metal grid line is not easy to fall off from the surface of the cell, so that the service life of the heterojunction solar cell can be extended and the efficiency of the heterojunction solar cell can be increased; moreover, the preparation method is relatively simple. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a process flow chart for preparing a heterojunction solar cell in an embodiment of the present application;

[0035] Figure 2 It is a structural schematic diagram of the heterojunction solar cell provided in an embodiment of the present application;

[0036] Figure 3 is Figure 2 an enlarged view of part A in

[0037] Figure 4 It is an SEM image of the tin nucleation layer in Example 1;

[0038] Figure 5 It is an SEM image of the metal seed layer in Example 1.

[0039] Icons: 001 - Heterojunction solar cell; 100 - Metal grid line; 110 - Metal seed layer; 120 - Metal barrier layer; 130 - Metal conduction layer; 140 - Metal welding layer; 200 - Transparent conductive layer; 300 - P-type amorphous silicon layer; 400 - Intrinsic amorphous silicon layer; 500 - N-type silicon wafer; 600 - N-type amorphous silicon layer. Detailed Embodiments

[0040] The applicant has found that in the current process of preparing copper grid lines for heterojunction solar cells, physical vapor deposition, magnetron sputtering and other vacuum preparation methods are used to prepare the seed layer, and then the copper grid lines are prepared. However, this preparation method is relatively complex and costly; moreover, the adhesion between the prepared seed layer and the cell is weak, and the service life and photoelectric conversion efficiency of the heterojunction solar cell will be affected.

[0041] In order to solve the problems existing in the prior art, the applicant uses an electrochemical method to reduce metal ions in the transparent conductive layer 200 of the cell into metal elements. The reduced metal elements form a metal nucleation layer, and the adhesion between the metal nucleation layer and the transparent conductive layer 200 is large and it is not easy to fall off from the surface of the transparent conductive layer 200.

[0042] However, the applicant has also found that when using the electrochemical method to prepare the metal nucleation layer, the loss of metal oxides in the transparent conductive layer 200 is large, which is very unfavorable for improving the efficiency of the heterojunction solar cell 001, and is also unfavorable for the subsequent growth of the metal grid line 100; however, the thickness of the transparent conductive layer 200 cannot be too thick, otherwise it will affect the light absorption rate of the heterojunction solar cell 001 and reduce the photoelectric conversion efficiency of the heterojunction solar cell 001.

[0043] Based on this, the applicant has found that after preparing the metal nucleation layer by the electrochemical method, a metal thin layer with the same material as the metal nucleation layer is electroplated on the surface of the metal nucleation layer. In this way, even if the metal nucleation layer is formed on the surface of the transparent conductive layer 200 by the electrochemical method, it will basically not affect the efficiency of the heterojunction solar cell 001, nor will it affect the growth of the metal grid line 100.

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0045] The heterojunction solar cell 001 and its preparation method in the embodiments of the present application, and the preparation method of the metal seed layer 110 will be specifically described below.

[0046] The process flow chart for preparing the heterojunction solar cell 001 is as Figure 1 shown, and the steps are specifically as follows:

[0047] S100. Select a cell: Take at least one cell with a transparent conductive layer 200 on its surface. The transparent conductive layer 200 contains metal oxides such as indium oxide, tin oxide, zinc oxide, antimony oxide, and cadmium oxide.

[0048] Due to the good electrical conductivity and high transparency of tin oxide, indium oxide, zinc oxide, antimony oxide, and cadmium oxide, they are very suitable for use as the transparent conductive layer of heterojunction solar cells. Moreover, in the actual production and preparation process, it is generally common to use tin oxide or indium oxide to prepare the transparent conductive layer 200. Exemplarily, in the embodiments of the present application, transparent conductive layers 200 are provided on both the upper and lower surfaces of the cell wafer. The structure of the entire cell wafer includes, from top to bottom, a transparent conductive layer 200, a P-type amorphous silicon layer 300, an intrinsic amorphous silicon layer 400, an N-type silicon wafer 500, an intrinsic amorphous silicon layer 400, an N-type amorphous silicon layer 600, and a transparent conductive layer 200 stacked in sequence. The heterojunction solar cell 001 made of the cell wafer with this structure is called a heterojunction cell, in which a PN junction capable of generating current is formed between the intrinsic amorphous silicon layer 400 and the N-type silicon wafer 500. In the heterojunction cell, the thickness of the transparent conductive layer 200 needs to be in the range of 75-80 nm. If it is too thick, its own light transmittance will be poor, affecting the efficiency of the cell; if it is too thin, the conductive efficiency of the cell will be poor, which will also affect the efficiency of the cell.

[0049] In addition, during actual use, the metal oxides in the transparent conductive layer 200 are generally doped with other elements to improve the electrical conductivity of the transparent conductive layer 200. Moreover, the mass fraction of the metal oxides in the transparent conductive layer 200 is generally not less than 85%, so that the comprehensive performance of the entire transparent conductive layer 200 is better, and both the electrical conductivity and transparency are relatively good. Moreover, this is also conducive to quickly reducing the metal ions in the metal oxides subsequently.

[0050] For example, when the metal oxide is indium oxide, the metal oxide is also doped with at least one of tin and tungsten. Specifically, when indium oxide is doped with tin, ITO (Indium tin oxide) is formed; when indium oxide is doped with tungsten, IWO (Indium Tungsten oxide) is formed. These are all commonly used conductive materials in the prior art, and will not be elaborated herein.

[0051] When the metal oxide is tin oxide, the metal oxide is also doped with at least one of fluoride ions and metal cations; optionally, the metal cations include at least one of antimony, tantalum, niobium, bismuth, tungsten, and vanadium.

[0052] Although the efficiency of the heterojunction solar cell 001 prepared with indium oxide is slightly better than that prepared with tin oxide, since the price of indium is much higher than that of tin, using indium oxide as the main raw material to prepare the transparent conductive layer 200 is not conducive to reducing the preparation cost of the heterojunction solar cell 001. Therefore, exemplarily, in this embodiment, tin oxide is used as the main raw material to prepare the transparent conductive layer 200.

[0053] S200. Prepare the metal nucleation layer: Use electrochemistry to reduce the metal particles in the metal oxide in some areas of the transparent conductive layer 200.

[0054] In this step, the transparent conductive layer 200 is generally immersed in the electrolyte solution. And usually, a mask layer is coated on some areas of the transparent conductive layer 200 before immersion. The areas without the coated mask can react and reduce to form metal particles, thus forming the metal nucleation layer. The subsequent metal grid line 100 is formed in the area where the metal nucleation layer is located. The mask is generally a photoresist and can be coated by methods such as photolithography, plasma etching, and laser etching. Moreover, after the metal grid line 100 is formed, the coated mask is removed by wet etching, photolithography lift off, heating, or laser. The techniques of coating the mask and removing the mask are common in the prior art and will not be elaborated herein.

[0055] In this step, the temperature of the electrolyte solution is 18 - 30 °C, which is beneficial to both the stable progress of the electrochemical reaction and the acceleration of the reaction rate.

[0056] In addition, the reaction time of the electrochemistry method is 10 - 300 s; and / or, the reaction voltage is 1 - 6 V. Generally, the density range of the formed metal particles is between 2.0×10 7 ~8.0×10 9 pcs / cm 2 ; and / or, the size of the metal particles is 10 - 250 nm, which is beneficial to increasing the bonding force and stability of the entire metal seed layer 110 and also beneficial to reducing the preparation difficulty of the subsequent metal grid line 100. Moreover, during the process of reducing the metal oxide by electrochemistry, either direct current electroplating or pulse electroplating can be used. Exemplarily, direct current electroplating is used in this embodiment.

[0057] In addition, in this step, the solute in the electrolyte solution includes at least one of citrate, aminosulfonate, bicarbonate, and acetate.

[0058] S300. Prepare the metal seed layer 110: Electroplate the same metal material as the metal nucleation layer on the surface of the metal nucleation layer to form a metal thin layer, and the metal thin layer combines with the metal nucleation layer to form the metal seed layer.

[0059] When electroplating another metal thin layer with the same material on the surface of the metal nucleation layer, it can compensate for the loss of metal oxide in the transparent conductive layer 200, which is beneficial to improving the efficiency of the heterojunction solar cell 001 and also beneficial to the growth of the subsequent metal grid line 100. Moreover, the combination between the metal nucleation layer and the metal thin layer with the same material will be closer.

[0060] In the embodiment of the present application, when electroplating a thin metal layer, the temperature of the electroplating solution is 40 - 60 °C, and the cathode current density is 10 - 20 A / dm 2 . Moreover, by way of example, in this embodiment, the electroplating solution is an organic sulfonate system.

[0061] The organic sulfonate system generally contains 40 - 80 g / L of stannous sulfamate, 20 - 80 g / L of sulfamic acid, and 3 - 7 g / L of dihydroxydiphenyl sulfone; specifically in this embodiment, there is 60 g / L of stannous sulfamate, 50 g / L of sulfamic acid, and 5 g / L of dihydroxydiphenyl sulfone.

[0062] Of course, in some other embodiments, the electroplating solution can also be other systems such as an alkaline stannate system or a sulfate system, which will not be elaborated herein in the present application.

[0063] The thickness of the thin metal layer obtained by the above method is generally in the range of 0.1 - 10 μm.

[0064] It should be noted that in the present application, the metal seed layer 110 is obtained by combining the S200 step and the S300 step. Among them, the metal seed layer 110 is a combination of a metal nucleation layer and a thin metal layer. This metal seed layer 110 has good adhesion, and this method is called the "two-step method" by the applicant. The metal seed layer 110 prepared by the two-step method has good adhesion to the battery chip, and can also provide a basis for the growth of the subsequent layer structure, facilitating the rapid formation of the metal grid line 100; moreover, compared with the existing methods such as vacuum deposition and magnetron sputtering, the two-step method has a relatively simple process, low requirements for equipment, and low cost.

[0065] S400. Form the metal grid line 100: Electroplate a metal barrier layer 120, a metal conduction layer 130, and a metal welding layer 140 on the surface of the metal seed layer 110 in sequence. The metal seed layer 110, the metal barrier layer 120, the metal conduction layer 130, and the metal welding layer 140 form the metal grid line 100.

[0066] The metal conduction layer 130 can play a role in collecting and transmitting current, collecting the current generated in the battery chip and transmitting it outward; therefore, the metal conduction layer 130 needs to have good conductivity and low resistivity, and the material is usually at least one of copper, silver, aluminum, and gold; in order to save the preparation cost in this embodiment, the material of the metal conduction layer 130 is selected as copper.

[0067] The metal barrier layer 120 can prevent the substances in the metal conduction layer 130 from diffusing into the battery chip to prevent a serious roll-off of the device efficiency; therefore, the main component of the metal barrier layer 120 is generally a high-melting-point metal or alloy material, such as at least one of tungsten, cobalt, nickel, and tantalum. By way of example, the material of the metal barrier layer 120 in this embodiment is nickel.

[0068] On the one hand, the metal welding layer 140 can protect the metal conduction layer 130 and prevent the metal conduction layer 130 from being oxidized. On the other hand, it can also provide welding sites to facilitate welding multiple heterojunction solar cells 001 together for external current transmission. Therefore, by way of example, in this embodiment, the material of the metal welding layer 140 is selected as tin.

[0069] The structure of the heterojunction solar cell 001 prepared by the above preparation method is as Figure 2 shown. From top to bottom, it includes a transparent conductive layer 200, a P-type amorphous silicon layer 300, an intrinsic amorphous silicon layer 400, an N-type silicon wafer 500, an intrinsic amorphous silicon layer 400, an N-type amorphous silicon layer 600, and a transparent conductive layer 200 which are sequentially stacked. Metal grid lines 100 are provided on the surfaces of both transparent conductive layers 200. The structure of the metal grid lines 100 is as Figure 3 shown. Relative to the cell, from far to near, it includes a metal welding layer 140, a metal conduction layer 130, a metal barrier layer 120, and a metal seed layer 110 which are sequentially stacked. An ohmic contact is formed between the metal grid line 100 and the transparent conductive layer 200 through the metal seed layer 110.

[0070] In some other embodiments, after the metal grid lines 100 are formed, annealing treatment is performed in a gas atmosphere to improve the adhesion, but the annealing treatment is omitted in this application.

[0071] The features and properties of this application will be further described in detail below in conjunction with embodiments.

[0072] Embodiment 1

[0073] This embodiment provides a heterojunction solar cell 001, which is prepared by a two-step method. The specific preparation method is as follows:

[0074] (1) Select a cell. The outermost layer structure on both the upper and lower surfaces of the cell is a transparent conductive layer 200 made of FTO (FTO contains SnO2 and F, and the mass ratio of the two is 95:5). The thickness of the transparent conductive layer 200 is 80 nm.

[0075] (2) Immerse the cell with masks coated on both the upper and lower surfaces in an electrolyte. The solute in the electrolyte is sulfamate. The temperature of the electrolyte is 18 °C, the immersion time is 300 s, and the reaction voltage is 6 V. After immersion, a part of the transparent conductive layer 200 is reduced, and tin particles are precipitated to form a tin nucleation layer. Use SEM (Scanning Electron Microscope) to test the tin nucleation layer. The result is as Figure 4 shown. As can be seen from the figure, the density range of the precipitated tin particles is 1×109 per cm 2 , with the size ranging from 20 to 100 nm.

[0076] (3) Deposit a thin tin layer on the surface of the tin nucleation layer by electroplating. The temperature of the electroplating solution is 40 °C, and the cathode current density is 20 A / dm 2 . The thickness of the formed thin tin layer is 1.5 μm. The thin tin layer will combine with the tin nucleation layer to form the metal seed layer 110. Use SEM to test the morphology of the metal seed layer 110, and the results are as Figure 5 shown. As Figure 5 can be seen, the seed layer formed by electroplating a thin tin layer on the basis of the tin nucleation layer is more conducive to subsequent attachment of other layer structures such as the metal barrier layer 120.

[0077] (4) Electroplate and form a metal barrier layer 120, a metal conduction layer 130, and a metal welding layer 140 on the surface of the metal seed layer 110 in sequence. The metal seed layer 110, the metal barrier layer 120, the metal conduction layer 130, and the metal welding layer 140 combine to form the metal grid line 100.

[0078] Example 2

[0079] This example provides a heterojunction solar cell 001. The main difference in its preparation method compared with Example 1 is that in step (1), the material of the transparent conductive layer 200 is SnO2 doped with Sb, and the mass ratio of SnO2 to Sb is 95:5.

[0080] Example 3

[0081] This example provides a heterojunction solar cell 001. The main difference in its preparation method compared with Example 1 is that in step (1), the material of the transparent conductive layer 200 is SnO2 doped with Ta, and the mass ratio of SnO2 to Ta is 95:5.

[0082] Example 4

[0083] This example provides a heterojunction solar cell 001. The main difference in its preparation method compared with Example 1 is that in step (1), the material of the transparent conductive layer 200 is SnO2 doped with F and Sb, and SnO2 accounts for 90% of the mass of the transparent conductive layer 200, F accounts for 5% of the mass of the transparent conductive layer 200, and Sb accounts for 5% of the mass of the transparent conductive layer 200.

[0084] Example 5

[0085] This example provides a heterojunction solar cell 001. The main difference in its preparation method compared with Example 1 is that the surface of the N-type silicon wafer 500 has a pyramid texture.

[0086] Comparative Example 1

[0087] This comparative example provides a heterojunction solar cell. The main difference in its preparation method compared with Example 1 is as follows:

[0088] It does not contain step (3), and directly electroplates a metal barrier layer, a metal conduction layer, and a metal welding layer on the surface of the tin nucleation layer in sequence.

[0089] Comparative Example 2

[0090] This comparative example provides a heterojunction solar cell. The main difference in its preparation method compared with Example 1 is as follows:

[0091] In the electroplating solution of step (3), indium sulfate is used to replace stannous sulfamate to form an indium thin layer on the surface of the tin nucleation layer; the concentration of indium sulfate is 50 g / L.

[0092] Comparative Example 3

[0093] This comparative example provides a heterojunction solar cell. The main difference in its preparation method compared with Example 1 is as follows:

[0094] The magnetron sputtering method is used to replace the two-step method to prepare the metal seed layer.

[0095] Application Example

[0096] Adhesion Test

[0097] The heterojunction solar cells of each example and each comparative example were tested using a tensile test to determine the adhesion between the metal grid line and the cell. The test results are shown in the following table:

[0098] Table 1 Adhesion Test Results of Each Example and Comparative Example

[0099] Group Adhesion between the metal grid line 100 and the cell Example 1 2N Example 2 1.9N Example 3 2.1N Example 4 1.9N Comparative Example 1 1.0N Comparative Example 2 0.4N Comparative Example 3 2.1N

[0100] As can be seen from Table 1, the adhesion between the metal grid line and the cell in the examples is much greater than that between the metal grid line and the cell in Comparative Example 1 and Comparative Example 2, and is comparable to that of the heterojunction solar cell obtained by magnetron sputtering; thus, it can be known that for the heterojunction solar cell prepared by the method of the present application, the combination between the metal grid line and the cell is relatively tight and can meet the existing production requirements.

[0101] Electrical Performance Test

[0102] The heterojunction solar cells of each example and each comparative example were tested for electrical performance using a Halm tester. The test results are shown in the following table:

[0103] Table 2 Electrical Performance Test Results of Each Example and Comparative Example

[0104]

[0105] As can be seen from Table 2, compared with Comparative Examples 1 and 2, the heterojunction solar cell of the embodiment of the present application has a higher photoelectric conversion efficiency E ta and better electrical performance.

[0106] In summary, when the seed layer in the heterojunction solar cell is formed by the electrochemical method and electroplating in the present application, it can ensure good adhesion between the metal grid line and the cell, and can also ensure good conversion efficiency of the heterojunction solar cell. At the same time, the preparation method of the present application is simple and the cost is low.

[0107] The above are only the embodiments of the present application and are not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a heterojunction solar cell, characterized in that, It includes the following steps: Take a battery cell, wherein at least one surface of the battery cell is provided with a transparent conductive layer, and the transparent conductive layer contains a metal oxide; the metal oxide is any one of indium oxide, tin oxide, zinc oxide, antimony oxide, cadmium oxide; Use an electrochemical method to reduce metal particles in the metal oxide in a partial area of the transparent conductive layer to form a metal nucleation layer; Electroplate a metal thin layer on the surface of the metal nucleation layer, and the metal thin layer combines with the metal nucleation layer to form a metal seed layer, and the material of the metal thin layer is the same as that of the metal nucleation layer; Electroplate a metal barrier layer and a metal conduction layer on the surface of the metal seed layer in sequence, and the metal seed layer, the metal barrier layer, and the metal conduction layer form a metal grid line.

2. The preparation method of the heterojunction solar cell according to claim 1, wherein The electrochemical method includes the following steps: Immerse the transparent conductive layer in an electrolyte.

3. The preparation method of the heterojunction solar cell according to claim 2, characterized in that, The solute in the electrolyte includes at least one of citrate, sulfamate, bicarbonate, acetate; And / or, the temperature of the electrolyte is 18 - 30 °C.

4. The preparation method of the heterojunction solar cell according to claim 2, characterized in that, In the electrochemical method, the reaction time is 10 - 300 s; And / or, in the electrochemical method, the reaction voltage is 1 - 6 V.

5. The manufacturing method of the heterojunction solar cell according to claim 1, characterized in that, The thickness of the metal thin layer is 0.1 - 10 μm; and / or, the density range of the metal particles is 2.0×10 7 ~8.0×10 9 pieces / cm 2 ; And / or, the size of the metal particles is 10 - 250 nm.

6. The preparation method of the heterojunction solar cell according to claim 1, characterized in that, The thickness of the transparent conductive layer is 75 - 80 nm.

7. The preparation method of the heterojunction solar cell according to claim 1, wherein, When electroplating the metal thin layer, the electroplating solution is an organic sulfonate system; And / or, the temperature of the electroplating solution is 40 - 60 °C; and / or, the cathode current density is 10 to 20 A / dm 2 .

8. The preparation method of the heterojunction solar cell according to claim 7, wherein, The organic sulfonate system contains stannous sulfamate, sulfamic acid, and dihydroxydiphenyl sulfone.

9. The preparation method of the heterojunction solar cell according to claim 1, wherein When the metal oxide is indium oxide, at least one of tin and tungsten is further doped in the metal oxide; Or, when the metal oxide is tin oxide, at least one of fluoride ions and metal cations is further doped in the metal oxide.

10. The preparation method of the heterojunction solar cell according to claim 9, wherein The metal cations include at least one of antimony, tantalum, niobium, bismuth, tungsten, and vanadium.

11. The preparation method of the heterojunction solar cell according to claim 1 or 9, characterized in that, The mass fraction of the metal oxide in the transparent conductive layer is not less than 85%.

12. The preparation method of the heterojunction solar cell according to claim 1, characterized in that, The battery cell further includes a P-type amorphous silicon layer, an intrinsic amorphous silicon layer, an N-type silicon wafer, an intrinsic amorphous silicon layer, and an N-type amorphous silicon layer stacked in sequence, and the transparent conductive layer is stacked on the surface of the P-type amorphous silicon layer and / or the N-type amorphous silicon layer.

13. The preparation method of the heterojunction solar cell according to claim 1, characterized in that, The metal barrier layer mainly contains at least one of tungsten, cobalt, nickel, and tantalum; And / or, the material of the metal conduction layer is at least one of copper, silver, aluminum, and gold.

14. The manufacturing method of the heterojunction solar cell according to claim 1, characterized in that, It further includes the following step: after forming the metal conduction layer, electroplate a metal welding layer on the surface of the metal conduction layer.

15. The method for preparing a heterojunction solar cell according to claim 14, wherein The material of the metal welding layer is tin.

16. A heterojunction solar cell, characterized in that, It is obtained by using the preparation method of the heterojunction solar cell according to any one of claims 1 - 15.

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