Method for realizing metallization of solar cell and crystalline silicon solar cell

Abstract

The present invention discloses a method for realizing metallization of solar cells and a crystalline silicon solar cell, the method comprising: performing interface cleaning on the electroplating area of ​​the solar cell; electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell; and performing low-temperature annealing on the electroplated solar cell. In the present invention, pulse electroplating or light-induced pulse electroplating can help form smaller crystal nuclei, reduce grain size, increase the coverage of electroplated metal on the surface of the cell, and improve cross-sectional adhesion.

Description

Technical Field

[0001] The present invention relates to the field of solar energy technology, and in particular to a method for realizing solar cell metallization and a crystalline silicon solar cell. Background Art

[0002] In order to actively respond to global climate change, the global production capacity of crystalline silicon solar panels is growing worldwide. However, the large amount of silver consumption required for solar cell metallization is rapidly becoming a challenge in terms of sustainable development. At present, the silver consumption required for each bifacial PERC solar cell is about 100 mg. According to estimates, each terawatt of PERC cell production capacity will consume about 50% of the global silver supply in 2019. Compared with PERC cells, the silver consumption per cell of the next generation TOPCon and HJT cells will increase significantly. Therefore, it is necessary to accelerate the development and deployment of silver-free or low-silver metallization and interconnection technologies.

[0003] Solar cell metallization methods based on electroplating of base metals such as copper and nickel or light-induced electroplating can be used to replace silver paste screen printing. In addition to reducing the demand for silver paste, it can also protect cell and component manufacturers from the impact of silver price fluctuations. In addition, the electroplating-based metallization method can effectively reduce the width of the sub-grid and reduce optical losses.

[0004] Currently, base metals such as copper and nickel are usually used in solar cell metallization by constant current plating or constant current light induced plating, and the current density used is determined by the dielectric used. However, the crystal nuclei formed by constant current plating or constant current light induced plating have low coverage and low cross-sectional adhesion on the surface of crystalline silicon cells. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a method for realizing solar cell metallization and a crystalline silicon solar cell. Pulse plating or light-induced pulse plating can help to form smaller crystal nuclei, reduce grain size and increase the coverage of electroplated metal on the cell surface, thereby improving cross-sectional adhesion.

[0006] In order to solve the above problems, the present invention proposes a method for realizing metallization of solar cells, the method comprising:

[0007] Interface cleaning of the electroplating area of ​​solar cells;

[0008] Electroplating the electroplating area of ​​the solar cell using a light-induced pulse plating method or a pulse plating method based on the type of solar cell;

[0009] The electroplated solar cell is subjected to low temperature annealing treatment.

[0010] The electroplating area is an area of ​​the crystalline silicon solar cell where grooves have been opened or where there is no mask coverage.

[0011] The interface cleaning of the electroplating area of ​​the solar cell comprises:

[0012] An interface cleaning agent is used to clean the electroplating area of ​​the solar cell, and the interface cleaning agent includes: H2SO4, H2O2, HCI, HF, NH4OH, and deionized water.

[0013] The method of electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell includes:

[0014] The n-type semiconductor surface of the crystalline silicon solar cell is electroplated by light-induced pulse electroplating, and the light intensity on the solar cell surface is 150-250 watts per square meter;

[0015] The p-type semiconductor surface of the crystalline silicon solar cell is electroplated by pulse electroplating under dark light conditions.

[0016] The method of electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell includes:

[0017] The metal electrode is plated on the plating area using light-induced pulse plating or pulse plating. The material of the metal electrode is one or more of nickel, copper, silver, tin, and cobalt. The thickness of the metal electrode is between 1 and 15 microns.

[0018] The forward pulse time in the light-induced pulse electroplating method or the pulse electroplating method is less than 50 milliseconds, and the forward pulse current density is greater than 70 milliamperes per square centimeter.

[0019] The reverse pulse time in the light-induced pulse plating method or the pulse plating method is less than 50 milliseconds, and the reverse pulse current density is less than 5 milliamperes per square centimeter.

[0020] The pulse duty cycle in the light-induced pulse plating method or the pulse plating method is less than 50%.

[0021] The low temperature annealing treatment of the electroplated solar cell comprises:

[0022] After the solar cell is subjected to pulse plating or light-induced pulse plating, low-temperature annealing is performed, wherein the annealing time is less than 5 minutes and the annealing temperature is less than 500 degrees Celsius.

[0023] Correspondingly, the present invention also provides a crystalline silicon solar cell, which is prepared based on the above method.

[0024] The present invention uses pulse plating or light-induced pulse plating, which has a higher forward pulse current density and a shorter forward pulse time, and can induce high-concentration metal ion adsorption on the surface of the solar cell. Compared with the crystal nuclei formed by constant current plating or constant current light-induced plating, pulse plating or light-induced pulse plating can help form smaller crystal nuclei, reduce grain size and increase the coverage of electroplated metal on the battery surface, while also improving the adhesion performance of metal to the solar cell surface. In addition, the electrode based on pulse plating is more compact and has good adhesion to the surface of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a flow chart of a method for realizing metallization of a solar cell in an embodiment of the present invention;

[0027] Figure 2 is a scanning electron microscope image of a textured surface of a solar cell using a metallization method based on pulse electroplating in an embodiment of the present invention;

[0028] Figure 3 This is a scanning electron microscope image of the textured surface of a solar cell using a metallization method based on constant current electroplating as an experimental control in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1

[0031] Figure 1 A flow chart of a method for realizing metallization of solar cells according to an embodiment of the present invention is shown, and the method comprises:

[0032] S11, performing interface cleaning on the electroplating area of ​​the solar cell;

[0033] It should be noted that the electroplating area is an area of ​​the crystalline silicon solar cell where grooves have been opened or where there is no mask covering.

[0034] It should be noted that an interface cleaning agent is used to clean the electroplating area of ​​the solar cell, and the interface cleaning agent includes: H2SO4, H2O2, HCI, HF, NH4OH, and deionized water.

[0035] Specifically, the solar cell metallization method of this embodiment can be applied to the grooved area on PERC and TOPCon solar cells and the area not covered by the mask layer on the HJT solar cell. In the present invention, the grooved method includes but is not limited to laser grooved and inkjet printing grooved. The mask layer can be made by inkjet printing, photolithography, thermal evaporation, electron beam evaporation, magnetron sputtering, atomic layer deposition, spin coating, scraping and the like.

[0036] Specifically, the interface cleaning of the grooved or unmasked area of ​​the crystalline silicon solar cell can be carried out by using solvents such as H2SO4, H2O2, HCI, HF, NH4OH, deionized water, etc., but is not limited to the solvents listed above. The main function of the interface cleaning is to remove surface contaminants such as impurities and dust that affect electroplating, reduce the influence of these surface contaminants on the adhesion between the metal layer and the surface of the solar cell, and improve the reliability of the solar cell metallization method of the embodiment of the present invention.

[0037] S12, electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell;

[0038] The solar cell metallization method in the embodiment of the present invention can solve the problems related to crystal nucleation and interface adhesion in the existing solar cell electroplating metallization, reduce the grain size and increase the coverage of the electroplated metal on the cell surface, and can reduce the width of the sub-grid and reduce optical losses, thereby realizing the metallization of solar cells based on base metals. It can be applied to the preparation of crystalline silicon and thin-film solar cells, reduce the dependence of the photovoltaic industry on precious metals such as silver, reduce the cost of the industrial chain and promote sustainable development.

[0039] It should be noted that the types of solar cells involve two situations: the n-type semiconductor surface of a crystalline silicon solar cell and the p-type semiconductor surface of a crystalline silicon solar cell. The n-type semiconductor surface of a crystalline silicon solar cell is electroplated by light-induced pulse plating, and the light intensity on the solar cell surface is 150-250 watts per square meter; the p-type semiconductor surface of a crystalline silicon solar cell is electroplated by pulse plating under dark light conditions. When electroplating the n-type semiconductor surface of a crystalline silicon solar cell, light-induced pulse plating is required. During the metallization process, the electrons inside the solar cell flow from the p-type semiconductor to the n-type semiconductor. The light intensity on the solar cell surface ranges from 150 to 250 watts per square meter. When electroplating the p-type semiconductor surface of a crystalline silicon solar cell, pulse plating is required under dark light conditions. During the metallization process, the electrons inside the solar cell flow from the n-type semiconductor to the p-type semiconductor. The dark light conditions here generally limit the light intensity on the solar cell surface to 10 watts per square meter (10W / m 2 ) within.

[0040] It should be noted that the electroplating area is plated with a metal electrode using light-induced pulse plating or pulse plating. The material of the metal electrode is one or more of nickel, copper, silver, tin, and cobalt, and the thickness of the metal electrode is between 1 and 15 microns. The pulse plating or light-induced pulse plating can be used to electroplate metal electrode materials such as nickel, copper, silver, tin, and cobalt, but is not limited to the metal materials listed above. The thickness of the plated metal electrode is between 1 and 15 microns, and the thickness of the base metal will account for 80% to 100% of the total thickness. The outermost layer uses a 0.5 to 1 micron silver or tin protective layer to prevent the increase in body resistance caused by oxidation failure of the base metal.

[0041] It should be noted that the forward pulse time in the light-induced pulse plating method or the pulse plating method is less than 50 milliseconds, and the forward pulse current density is greater than 70 milliamperes per square centimeter. Using a larger forward pulse current density value can effectively increase the surface chemical potential, which is conducive to inducing high concentrations of metal ion adsorption on the surface of the solar cell, and helps to form smaller crystal nuclei, reduce grain size and increase the coverage of the electroplated metal on the battery surface.

[0042] It should be noted that the reverse pulse time in the light-induced pulse plating method or the pulse plating method is less than 50 milliseconds, and the reverse pulse current density is less than 5 milliamperes per square centimeter. In the reverse pulse, the metal ions in the double electric layer between the solar cell surface and the plating solution can be effectively replenished, otherwise it is easy to cause hydrogen evolution during the plating process, thereby making the plating electrode embrittled.

[0043] It should be noted that the pulse duty ratio of the light-induced pulse plating method or the pulse plating method is less than 50%. The pulse duty ratio of the pulse plating or light-induced pulse plating is less than 50% to prevent the embrittlement and failure of the plating electrode caused by the depletion of metal ions in the double electric layer.

[0044] S13, performing low temperature annealing treatment on the electroplated solar cell.

[0045] After pulse plating or light-induced pulse plating is performed on the solar cell, low-temperature annealing is performed, the annealing time is less than 5 minutes, and the annealing temperature is less than 500 degrees Celsius. Low-temperature annealing helps to reduce the internal stress and body resistance of the electroplating electrode.

[0046] The present invention uses pulse plating or light-induced pulse plating, which has a higher forward pulse current density and a shorter forward pulse time, and can induce high-concentration metal ion adsorption on the surface of the solar cell. Compared with the crystal nuclei formed by constant current plating or constant current light-induced plating, pulse plating or light-induced pulse plating can help form smaller crystal nuclei, reduce grain size and increase the coverage of electroplated metal on the battery surface, while also improving the adhesion performance of metal to the solar cell surface. In addition, the electrode based on pulse plating is more compact and has good adhesion to the surface of the solar cell.

[0047] Embodiment 2

[0048] Here we take the TOPCon solar cell after coating and slotting as an example to illustrate the specific preparation process as follows:

[0049] S21, using the RCA standard cleaning method (NH4OH:H2O2:H2O, 1:1:5) to remove contaminants from the surface of the TOPCon solar cell, the cleaning time is about 3 minutes;

[0050] S22, using 1% HF solvent to remove silicon oxide on the surface of the grooved TOPCon solar cell, the cleaning time is about 1 minute;

[0051] S23, cleaning the TOPCon solar cell with deionized water for about 1 minute, and drying;

[0052] S24, using pulse plating or light-induced pulse plating to deposit nickel, copper, and tin as dense layers in the grooved area on the surface of the TOPCon solar cell, with thicknesses of 1.5 μm, 11 μm, and 1 μm, respectively;

[0053] Specifically, the forward pulse time of the pulse plating or light-induced pulse plating is 15-25 milliseconds, and the forward pulse current density is 70-90 milliamperes per square centimeter.

[0054] Specifically, the reverse pulse time of the pulse plating or light-induced pulse plating is 20-30 milliseconds, and the reverse pulse current density is less than 5 mA per square centimeter.

[0055] Specifically, the pulse duty cycle of the pulse plating or light-induced pulse plating is 30%.

[0056] S25, using low temperature annealing, the annealing time is about 1-4 minutes, and the annealing temperature is 400-500 degrees Celsius.

[0057] After pulse plating or light-induced pulse plating, low-temperature annealing is performed, the annealing time is less than 5 minutes, and the annealing temperature is less than 500 degrees Celsius. Here, low-temperature annealing helps to reduce the internal stress and body resistance of the electroplating electrode.

[0058] By using a pulse electroplating-based solar cell metallization method, it helps to form smaller crystal nuclei on the surface of solar cells, reduce grain size and increase the coverage of electroplated metal on the cell surface. Figure 1 and Figure 2 As shown in the figure, at the same coulomb density, pulse plating can effectively reduce the grain size and increase the uniform coverage of the electroplated metal on the surface of the solar cell textured surface compared to traditional constant current plating. In addition, pulse plating also helps to reduce the aggregation of the electroplated metal at the tip of the textured pyramid. Figure 1 The metal nuclei shown in the figure are nickel, and in all cases the charge density delivered to the grooved silicon surface is 0.025 coulombs per square centimeter.

[0059] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for realizing metallization of solar cells, characterized in that: The method comprises: Interface cleaning of the electroplating area of ​​solar cells; Electroplating the electroplating area of ​​the solar cell using a light-induced pulse plating method or a pulse plating method based on the type of solar cell; Performing low temperature annealing on the electroplated solar cell; The method of electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell includes: The n-type semiconductor surface of the crystalline silicon solar cell is electroplated by light-induced pulse electroplating, and the light intensity on the solar cell surface is 150-250 watts per square meter; The p-type semiconductor surface of the crystalline silicon solar cell is electroplated by pulse electroplating under dark light conditions, wherein the dark light conditions limit the light intensity on the surface of the solar cell to 10 watts per square meter (10W / m 2 ) within; The method of electroplating the electroplating area of ​​the solar cell using a light-induced pulse electroplating method or a pulse electroplating method based on the type of the solar cell includes: Electroplating the electroplating area with a metal electrode by light-induced pulse electroplating or pulse electroplating, wherein the material of the metal electrode is one or more of nickel, copper, silver, tin, and cobalt, the thickness of the metal electrode is between 1 and 15 microns, the thickness of the base metal will account for 80% to 100% of the total thickness, and the outermost layer is a 0.5 to 1 micron silver or tin protective layer; The forward pulse time in the light-induced pulse plating method or the pulse plating method is less than 50 milliseconds, and the forward pulse current density is greater than 70 milliamperes per square centimeter; The reverse pulse time in the light-induced pulse plating method or the pulse plating method is less than 50 milliseconds, and the reverse pulse current density is less than 5 mA per square centimeter.

2. The method for realizing metallization of solar cells according to claim 1, characterized in that: The electroplating area is an area of ​​the crystalline silicon solar cell where grooves have been opened or where there is no mask coverage.

3. The method for realizing metallization of solar cells according to claim 1, characterized in that: The interface cleaning of the electroplating area of ​​the solar cell comprises: An interface cleaning agent is used to clean the electroplating area of ​​the solar cell. The interface cleaning agent includes: H2SO4, H2O2, HCI, HF, NH4OH, and deionized water.

4. The method for realizing metallization of solar cells according to claim 1, characterized in that: The pulse duty cycle in the light-induced pulse plating method or the pulse plating method is less than 50%.

5. The method for realizing metallization of a solar cell according to any one of claims 1 to 4, characterized in that: The low temperature annealing treatment of the electroplated solar cell comprises: After the solar cell is subjected to pulse plating or light-induced pulse plating, low-temperature annealing is performed, wherein the annealing time is less than 5 minutes and the annealing temperature is less than 500 degrees Celsius.

6. A crystalline silicon solar cell, characterized in that: The crystalline silicon solar cell is prepared based on the method according to any one of claims 1 to 3.

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